THREE-DIMENSIONAL MEMORY DEVICE CONTAINING THROUGH-ARRAY CONTACT VIA STRUCTURES BETWEEN DIELECTRIC BARRIER WALLS AND METHODS OF MAKING THE SAME
An alternating layer stack of insulating layers and sacrificial material layers is formed over a semiconductor substrate, and memory stack structures are formed through the vertically-alternating layer stack. A pair of unconnected barrier trenches or a moat trench is formed through the alternating stack concurrently with formation of backside trenches. Backside recesses are formed by isotropically etching the sacrificial material layers selective to the insulating layers while a dielectric liner covers the barrier trenches or the moat trench. A vertically alternating sequence of the insulating plates and the dielectric spacer plates is provided between the pair of barrier trenches or inside the moat trench. Electrically conductive layers are formed in the backside recesses. A first conductive via structure is formed through the vertically alternating sequence concurrently with formation of a second conductive via structure through a dielectric material portion adjacent to the alternating stack.
The present disclosure relates generally to the field of semiconductor devices and specifically to a three-dimensional memory device containing through-array contact via structures between dielectric barrier walls and methods of making the same.
BACKGROUNDRecently, ultra-high-density storage devices using three-dimensional (3D) memory stack structures have been proposed. The memory stack structures overlie a substrate and extend through an alternating stack of insulating layers and electrically conductive layers. The memory stack structures include vertical stacks of memory elements provided at levels of the electrically conductive layers. Peripheral devices may be provided on the substrate underneath the alternating stack and the memory stack structures. A method is desired for providing interconnect via structures through the alternating stack without incurring high processing cost or long processing time.
SUMMARYAccording to an embodiment of the present disclosure, a three-dimensional memory device is provided, which comprises: field effect transistors located over a semiconductor substrate; lower-level metal interconnect structures formed within lower-level dielectric material layers that overlie the field effect transistors; an alternating stack of insulating layers and composite layers located over the lower-level metal interconnect structures and between a pair of backside trenches that laterally extend along a first horizontal direction, wherein each of the composite layers comprises a respective electrically conductive layer and a respective dielectric spacer plate, and a vertically alternating sequence of the insulating plates and the dielectric spacer plates is provided within a region including the dielectric spacer plates; memory stack structures vertically extending through the alternating stack; a pair of dielectric wall structures vertically extending through each layer within the alternating stack and which do not contact other through another dielectric wall structure, wherein a vertically alternating sequence of the insulating plates and the dielectric spacer plates is located between the pair of dielectric wall structures; and at least one conductive via structure vertically extending through the vertically alternating sequence and contacting a top surface of a respective one of the lower-level metal interconnect structures.
According to another embodiment of the present disclosure, a method for forming a three-dimensional memory device is provided, which comprises: forming an alternating stack of insulating layers and sacrificial material layers over a semiconductor substrate, wherein the sacrificial material layers comprise a dielectric material; forming memory stack structures through the alternating stack; patterning the alternating stack by performing an anisotropic etch process using a patterned mask layer, wherein the alternating stack is divided into a plurality of alternating stacks of respective insulating layers and respective sacrificial material layers by backside trenches, and wherein a pair of unconnected barrier trenches is formed through each of the plurality of alternating stacks; forming backside recesses by isotropically etching portions of the sacrificial material layers of the plurality of alternating stacks selective to the insulating layers of the plurality of alternating stacks by introducing an isotropic etchant into the backside trenches while the barrier trenches are covered by a respective dielectric liner that blocks access of the isotropic etchant to adjacent portions of the sacrificial material layers, wherein remaining portions of the sacrificial material layers between each neighboring pair of barrier trenches constitute dielectric spacer plates, and a vertically alternating sequence of the insulating plates and the dielectric spacer plates is provided between the pair of barrier trenches; forming electrically conductive layers in the backside recesses; and forming at least one conductive via structure through the vertically alternating sequence.
According to yet another aspect of the present disclosure, a method for forming a three-dimensional memory device is provided, which comprises: forming an alternating stack of insulating layers and sacrificial material layers over a substrate, wherein the sacrificial material layers comprise a dielectric material; forming a dielectric material portion adjacent to the alternating stack and over the substrate; forming memory stack structures through the alternating stack; forming backside trenches and a moat trench through the alternating stack, wherein the moat trench has a continuous outer periphery and a continuous inner periphery, portions of the insulating layers surrounded by the moat trench constitute insulating plates, portions of the sacrificial material layers surrounded by the moat trench constitute dielectric spacer plates, and a vertically alternating sequence of the insulating plates and the dielectric spacer plates is provided surrounded by the moat trench; replacing portions of the sacrificial material layers outside the moat trench with electrically conductive layers without replacing the vertically alternating sequence of the insulating plates and the dielectric spacer plates; and simultaneously forming a first through-memory-level interconnection via structure extending through the vertically alternating sequence surrounded by the moat trench and a second through-memory-level interconnection via structure extending through the dielectric material portion.
The embodiments of the present disclosure provide a three-dimensional memory device using liner-less through-array contact via structures and methods of making the same, the various embodiments of which are described herein in detail. The drawings are not drawn to scale. Multiple instances of an element may be duplicated where a single instance of the element is illustrated, unless absence of duplication of elements is expressly described or clearly indicated otherwise.
Ordinals such as “first,” “second,” and “third” are used merely to identify similar elements, and different ordinals may be used across the specification and the claims of the instant disclosure. The same reference numerals refer to the same element or similar element. Unless otherwise indicated, elements having the same reference numerals are presumed to have the same composition and the same function. Unless otherwise indicated, a “contact” between elements refers to a direct contact between elements that provides an edge or a surface shared by the elements. As used herein, a first element located “on” a second element may be located on the exterior side of a surface of the second element or on the interior side of the second element. As used herein, a first element is located “directly on” a second element if there exist a physical contact between a surface of the first element and a surface of the second element. As used herein, a “prototype” structure or an “in-process” structure refers to a transient structure that is subsequently modified in the shape or composition of at least one component therein.
As used herein, a “layer” refers to a material portion including a region having a thickness. A layer may extend over the entirety of an underlying or overlying structure, or may have an extent less than the extent of an underlying or overlying structure. Further, a layer may be a region of a homogeneous or inhomogeneous continuous structure that has a thickness less than the thickness of the continuous structure. For example, a layer may be located between any pair of horizontal planes between or at a top surface and a bottom surface of the continuous structure. A layer may extend horizontally, vertically, and/or along a tapered surface. A substrate may be a layer, may include one or more layers therein, and/or may have one or more layer thereupon, thereabove, and/or therebelow.
As used herein, a first surface and a second surface are “vertically coincident” with each other if the second surface overlies or underlies the first surface and there exists a vertical plane or a substantially vertical plane that includes the first surface and the second surface. A substantially vertical plane is a plane that extends straight along a direction that deviates from a vertical direction by an angle less than 5 degrees. A vertical plane or a substantially vertical plane is straight along a vertical direction or a substantially vertical direction, and may, or may not, include a curvature along a direction that is perpendicular to the vertical direction or the substantially vertical direction.
As used herein, a “memory level” or a “memory array level” refers to the level corresponding to a general region between a first horizontal plane (i.e., a plane parallel to the top surface of the substrate) including topmost surfaces of an array of memory elements and a second horizontal plane including bottommost surfaces of the array of memory elements. As used herein, a “through-stack” element refers to an element that vertically extends through a memory level.
As used herein, a “semiconducting material” refers to a material having electrical conductivity in the range from 1.0×10−5 S/m to 1.0×105 S/m. As used herein, a “semiconductor material” refers to a material having electrical conductivity in the range from 1.0×10−5 S/m to 1.0 S/m in the absence of electrical dopants therein, and is capable of producing a doped material having electrical conductivity in a range from 1.0 S/m to 1.0×107 S/m upon suitable doping with an electrical dopant. As used herein, an “electrical dopant” refers to a p-type dopant that adds a hole to a valence band within a band structure, or an n-type dopant that adds an electron to a conduction band within a band structure. As used herein, a “conductive material” refers to a material having electrical conductivity greater than 1.0×105 S/m. As used herein, an “insulator material” or a “dielectric material” refers to a material having electrical conductivity less than 1.0×10−5 S/m. As used herein, a “heavily doped semiconductor material” refers to a semiconductor material that is doped with electrical dopant at a sufficiently high atomic concentration to become a conductive material either as formed as a crystalline material or if converted into a crystalline material through an anneal process (for example, from an initial amorphous state), i.e., to provide electrical conductivity greater than 1.0×105 S/m. A “doped semiconductor material” may be a heavily doped semiconductor material, or may be a semiconductor material that includes electrical dopants (i.e., p-type dopants and/or n-type dopants) at a concentration that provides electrical conductivity in the range from 1.0×10−5 S/m to 1.0×107 S/m. An “intrinsic semiconductor material” refers to a semiconductor material that is not doped with electrical dopants. Thus, a semiconductor material may be semiconducting or conductive, and may be an intrinsic semiconductor material or a doped semiconductor material. A doped semiconductor material may be semiconducting or conductive depending on the atomic concentration of electrical dopants therein. As used herein, a “metallic material” refers to a conductive material including at least one metallic element therein. All measurements for electrical conductivities are made at the standard condition.
A monolithic three-dimensional memory array is a memory array in which multiple memory levels are formed above a single substrate, such as a semiconductor wafer, with no intervening substrates. The term “monolithic” means that layers of each level of the array are directly deposited on the layers of each underlying level of the array. In contrast, two dimensional arrays may be formed separately and then packaged together to form a non-monolithic memory device. For example, non-monolithic stacked memories have been constructed by forming memory levels on separate substrates and vertically stacking the memory levels, as described in U.S. Pat. No. 5,915,167 titled “Three-dimensional Structure Memory.” The substrates may be thinned or removed from the memory levels before bonding, but as the memory levels are initially formed over separate substrates, such memories are not true monolithic three-dimensional memory arrays. The various three-dimensional memory devices of the present disclosure include a monolithic three-dimensional NAND string memory device, and may be fabricated using the various embodiments described herein.
The various three-dimensional memory devices of the present disclosure include a monolithic three-dimensional NAND string memory device, and may be fabricated using the various embodiments described herein. The monolithic three-dimensional NAND string is located in a monolithic, three-dimensional array of NAND strings located over the substrate. At least one memory cell in the first device level of the three-dimensional array of NAND strings is located over another memory cell in the second device level of the three-dimensional array of NAND strings.
Generally, a semiconductor package (or a “package”) refers to a unit semiconductor device that may be attached to a circuit board through a set of pins or solder balls. A semiconductor package may include a semiconductor chip (or a “chip”) or a plurality of semiconductor chips that are bonded throughout, for example, by flip-chip bonding or another chip-to-chip bonding. A package or a chip may include a single semiconductor die (or a “die”) or a plurality of semiconductor dies. A die is the smallest unit that may independently execute external commands or report status. Typically, a package or a chip with multiple dies is capable of simultaneously executing as many external commands as the total number of dies therein. Each die includes one or more planes. Identical concurrent operations may be executed in each plane within a same die, although there may be some restrictions. In case a die is a memory die, i.e., a die including memory elements, concurrent read operations, concurrent write operations, or concurrent erase operations may be performed in each plane within a same memory die. In a memory die, each plane contains a number of memory blocks (or “blocks”), which are the smallest unit that may be erased by in a single erase operation. Each memory block contains a number of pages, which are the smallest units that may be selected for programming. A page is also the smallest unit that may be selected to a read operation.
Referring to
Dielectric material layers may be formed over the semiconductor devices, which are herein referred to as lower-level dielectric material layers 760. The lower-level dielectric material layers 760 may include, for example, a dielectric liner 762 (such as a silicon nitride liner that blocks diffusion of mobile ions and/or apply appropriate stress to underlying structures), first dielectric material layers 764 that overlie the dielectric liner 762, a silicon nitride layer (e.g., hydrogen diffusion barrier) 766 that overlies the first dielectric material layers 764, and at least one second dielectric layer 768. The dielectric layer stack including the lower-level dielectric material layers 760 may function as a matrix for lower-level metal interconnect structures 780 that provide electrical wiring to and from the various nodes of the semiconductor devices and landing pads for through-memory-level interconnection via structures to be subsequently formed. The lower-level metal interconnect structures 780 may be formed within the dielectric layer stack of the lower-level dielectric material layers 760 and overlies the field effect transistors. The lower-level metal interconnect structures 780 may comprise a lower-level metal line structure located under and optionally contacting a bottom surface of the silicon nitride layer 766.
For example, the lower-level metal interconnect structures 780 may be formed within the first dielectric material layers 764. The first dielectric material layers 764 may be a plurality of dielectric material layers in which various elements of the lower-level metal interconnect structures 780 are sequentially formed. Each dielectric material layer selected from the first dielectric material layers 764 may include any of doped silicate glass, undoped silicate glass, organosilicate glass, silicon nitride, silicon oxynitride, and dielectric metal oxides (such as aluminum oxide). In one embodiment, the first dielectric material layers 764 may comprise, or consist essentially of, dielectric material layers having dielectric constants that do not exceed the dielectric constant of undoped silicate glass (silicon oxide) of 3.9. The lower-level metal interconnect structures 780 may include various device contact via structures 782 (e.g., source and drain electrodes which contact the respective source and drain nodes of the device or gate electrode contacts), intermediate lower-level metal line structures 784, lower-level metal via structures 786, and landing-pad-level metal line structures 788 that are configured to function as landing pads for through-memory-level interconnection via structures to be subsequently formed.
The landing-pad-level metal line structures 788 may be formed within a topmost dielectric material layer of the first dielectric material layers 764 (which may be a plurality of dielectric material layers). Each of the lower-level metal interconnect structures 780 may include a metallic nitride liner and a metal fill structure. Top surfaces of the landing-pad-level metal line structures 788 and the topmost surface of the first dielectric material layers 764 may be planarized by a planarization process, such as chemical mechanical planarization. The silicon nitride layer 766 may be formed directly on the top surfaces of the landing-pad-level metal line structures 788 and the topmost surface of the first dielectric material layers 764.
The at least one second dielectric material layer 768 may include a single dielectric material layer or a plurality of dielectric material layers. Each dielectric material layer selected from the at least one second dielectric material layer 768 may include any of doped silicate glass, undoped silicate glass, and organosilicate glass. In one embodiment, the at least one first second material layer 768 may comprise, or consist essentially of, dielectric material layers having dielectric constants that do not exceed the dielectric constant of undoped silicate glass (silicon oxide) of 3.9.
An optional layer of a metallic material and a layer of a semiconductor material may be deposited over, or within patterned recesses of, the at least one second dielectric material layer 768, and is lithographically patterned to provide an optional conductive plate layer 6 and in-process source-level material layers 10′. The optional conductive plate layer 6, if present, provides a high conductivity conduction path for electrical current that flows into, or out of, the in-process source-level material layers 10′. The optional conductive plate layer 6 includes a conductive material such as a metal or a heavily doped semiconductor material. The optional conductive plate layer 6, for example, may include a tungsten layer having a thickness in a range from 3 nm to 100 nm, although lesser and greater thicknesses may also be used. A metal nitride layer (not shown) may be provided as a diffusion barrier layer on top of the conductive plate layer 6. The conductive plate layer 6 may function as a special source line in the completed device. In addition, the conductive plate layer 6 may comprise an etch stop layer and may comprise any suitable conductive, semiconductor or insulating layer. The optional conductive plate layer 6 may include a metallic compound material such as a conductive metallic nitride (e.g., TiN) and/or a metal (e.g., W). The thickness of the optional conductive plate layer 6 may be in a range from 5 nm to 100 nm, although lesser and greater thicknesses may also be used.
The in-process source-level material layers 10′ may include various layers that are subsequently modified to form source-level material layers. The source-level material layers, upon formation, include a source contact layer that functions as a common source region for vertical field effect transistors of a three-dimensional memory device. In one embodiment, the in-process source-level material layers 10′ may include, from bottom to top, a lower source-level material layer 112, a lower sacrificial liner 103, a source-level sacrificial layer 104, an upper sacrificial liner 105, an upper source-level semiconductor layer 116, a source-level insulating layer 117, and an optional source-select-level conductive layer 118.
The lower source-level material layer 112 and the upper source-level semiconductor layer 116 may include a doped semiconductor material such as doped polysilicon or doped amorphous silicon. The conductivity type of the lower source-level material layer 112 and the upper source-level semiconductor layer 116 may be the opposite of the conductivity of vertical semiconductor channels to be subsequently formed. For example, if the vertical semiconductor channels to be subsequently formed have a doping of a first conductivity type, the lower source-level material layer 112 and the upper source-level semiconductor layer 116 have a doping of a second conductivity type that is the opposite of the first conductivity type. The thickness of each of the lower source-level material layer 112 and the upper source-level semiconductor layer 116 may be in a range from 10 nm to 300 nm, such as from 20 nm to 150 nm, although lesser and greater thicknesses may also be used.
The source-level sacrificial layer 104 includes a sacrificial material that may be removed selective to the lower sacrificial liner 103 and the upper sacrificial liner 105. In one embodiment, the source-level sacrificial layer 104 may include a semiconductor material such as undoped amorphous silicon or a silicon-germanium alloy with an atomic concentration of germanium greater than 20%. The thickness of the source-level sacrificial layer 104 may be in a range from 30 nm to 400 nm, such as from 60 nm to 200 nm, although lesser and greater thicknesses may also be used.
The lower sacrificial liner 103 and the upper sacrificial liner 105 include materials that may function as an etch stop material during removal of the source-level sacrificial layer 104. For example, the lower sacrificial liner 103 and the upper sacrificial liner 105 may include silicon oxide, silicon nitride, and/or a dielectric metal oxide. In one embodiment, each of the lower sacrificial liner 103 and the upper sacrificial liner 105 may include a silicon oxide layer having a thickness in a range from 2 nm to 30 nm, although lesser and greater thicknesses may also be used.
The source-level insulating layer 117 includes a dielectric material such as silicon oxide. The thickness of the source-level insulating layer 117 may be in a range from 20 nm to 400 nm, such as from 40 nm to 200 nm, although lesser and greater thicknesses may also be used. The optional source-select-level conductive layer 118 may include a conductive material that may be used as a source-select-level gate electrode. For example, the optional source-select-level conductive layer 118 may include a doped semiconductor material such as doped polysilicon or doped amorphous silicon that may be subsequently converted into doped polysilicon by an anneal process. The thickness of the optional source-select-level conductive layer 118 may be in a range from 30 nm to 200 nm, such as from 60 nm to 100 nm, although lesser and greater thicknesses may also be used.
The in-process source-level material layers 10′ may be formed directly above a subset of the semiconductor devices on the semiconductor substrate 8 (e.g., silicon wafer). As used herein, a first element is located “directly above” a second element if the first element is located above a horizontal plane including a topmost surface of the second element and an area of the first element and an area of the second element has an areal overlap in a plan view (i.e., along a vertical plane or direction perpendicular to the top surface of the semiconductor substrate 8.
The optional conductive plate layer 6 and the in-process source-level material layers 10′ may be patterned to provide openings in areas in which through-memory-level interconnection via structures and through-dielectric contact via structures are to be subsequently formed. Patterned portions of the stack of the conductive plate layer 6 and the in-process source-level material layers 10′ are present in each memory array region 100 in which three-dimensional memory stack structures are to be subsequently formed.
The optional conductive plate layer 6 and the in-process source-level material layers 10′ may be patterned such that an opening extends over a staircase region 200 in which contact via structures contacting word line electrically conductive layers are to be subsequently formed. In one embodiment, the staircase region 200 may be laterally spaced from the memory array region 100 along a first horizontal direction hd1. A horizontal direction that is perpendicular to the first horizontal direction hd1 is herein referred to as a second horizontal direction hd2. In one embodiment, additional openings in the optional conductive plate layer 6 and the in-process source-level material layers 10′ may be formed within the area of a memory array region 100, in which a three-dimensional memory array including memory stack structures is to be subsequently formed. A peripheral device region 400 that may be subsequently filled with a field dielectric material portion may be provided adjacent to the staircase region 200.
The region of the semiconductor devices 710 and the combination of the lower-level dielectric material layers 760 and the lower-level metal interconnect structures 780 is herein referred to an underlying peripheral device region 700, which is located underneath a memory-level assembly to be subsequently formed and includes peripheral devices for the memory-level assembly. The lower-level metal interconnect structures 780 may be formed in the lower-level dielectric material layers 760.
The lower-level metal interconnect structures 780 may be electrically connected to active nodes (e.g., transistor active regions 742 or gate electrodes 754) of the semiconductor devices 710 (e.g., CMOS devices), and may be located at the level of the lower-level dielectric material layers 760. Through-memory-level interconnection via structures may be subsequently formed directly on the lower-level metal interconnect structures 780 to provide electrical connection to memory devices that are also to be subsequently formed. In one embodiment, the pattern of the lower-level metal interconnect structures 780 may be selected such that the landing-pad-level metal line structures 788 (which are a subset of the lower-level metal interconnect structures 780 located at the topmost portion of the lower-level metal interconnect structures 780) may provide landing pad structures for the through-memory-level interconnection via structures to be subsequently formed.
Referring to
The first-tier alternating stack may include first insulating layers 132 as the first material layers, and first spacer material layers as the second material layers. In one embodiment, the first spacer material layers may be sacrificial material layers that are subsequently replaced with electrically conductive layers. In another embodiment, the first spacer material layers may be electrically conductive layers that are not subsequently replaced with other layers. While the present disclosure is described using embodiments in which sacrificial material layers are replaced with electrically conductive layers, embodiments in which the spacer material layers are formed as electrically conductive layers (thereby obviating the need to perform replacement processes) are expressly contemplated herein.
In one embodiment, the first material layers and the second material layers may be first insulating layers 132 and first sacrificial material layers 142, respectively. In one embodiment, each first insulating layer 132 may include a first insulating material, and each first sacrificial material layer 142 may include a first sacrificial material. An alternating plurality of first insulating layers 132 and first sacrificial material layers 142 is formed over the in-process source-level material layers 10′. As used herein, a “sacrificial material” refers to a material that is removed during a subsequent processing step.
As used herein, an alternating stack of first elements and second elements refers to a structure in which instances of the first elements and instances of the second elements alternate. Each instance of the first elements that is not an end element of the alternating plurality is adjoined by two instances of the second elements on both sides, and each instance of the second elements that is not an end element of the alternating plurality is adjoined by two instances of the first elements on both ends. The first elements may have the same thickness throughout, or may have different thicknesses. The second elements may have the same thickness throughout, or may have different thicknesses. The alternating plurality of first material layers and second material layers may begin with an instance of the first material layers or with an instance of the second material layers, and may end with an instance of the first material layers or with an instance of the second material layers. In one embodiment, an instance of the first elements and an instance of the second elements may form a unit that is repeated with periodicity within the alternating plurality.
The first-tier alternating stack (132, 142) may include first insulating layers 132 composed of the first material, and first sacrificial material layers 142 composed of the second material, which is different from the first material. The first material of the first insulating layers 132 may be at least one insulating material. Insulating materials that may be used for the first insulating layers 132 include, but are not limited to silicon oxide (including doped or undoped silicate glass), silicon nitride, silicon oxynitride, organosilicate glass (OSG), spin-on dielectric materials, dielectric metal oxides that are commonly known as high dielectric constant (high-k) dielectric oxides (e.g., aluminum oxide, hafnium oxide, etc.) and silicates thereof, dielectric metal oxynitrides and silicates thereof, and organic insulating materials. In one embodiment, the first material of the first insulating layers 132 may be silicon oxide.
The second material of the first sacrificial material layers 142 may be a sacrificial material that may be removed selective to the first material of the first insulating layers 132. As used herein, a removal of a first material is “selective to” a second material if the removal process removes the first material at a rate that is at least twice the rate of removal of the second material. The ratio of the rate of removal of the first material to the rate of removal of the second material is herein referred to as a “selectivity” of the removal process for the first material with respect to the second material.
The first sacrificial material layers 142 may comprise an insulating material, a semiconductor material, or a conductive material. The second material of the first sacrificial material layers 142 may be subsequently replaced with electrically conductive electrodes which may function, for example, as control gate electrodes of a vertical NAND device. In one embodiment, the first sacrificial material layers 142 may be material layers that comprise silicon nitride.
In one embodiment, the first insulating layers 132 may include silicon oxide, and sacrificial material layers may include silicon nitride sacrificial material layers. The first material of the first insulating layers 132 may be deposited, for example, by chemical vapor deposition (CVD). For example, if silicon oxide is used for the first insulating layers 132, tetraethylorthosilicate (TEOS) may be used as the precursor material for the CVD process. The second material of the first sacrificial material layers 142 may be formed, for example, CVD or atomic layer deposition (ALD).
The thicknesses of the first insulating layers 132 and the first sacrificial material layers 142 may be in a range from 20 nm to 50 nm, although lesser and greater thicknesses may be used for each first insulating layer 132 and for each first sacrificial material layer 142. The number of repetitions of the pairs of a first insulating layer 132 and a first sacrificial material layer 142 may be in a range from 2 to 1,024, and typically from 8 to 256, although a greater number of repetitions may also be used. In one embodiment, each first sacrificial material layer 142 in the first-tier alternating stack (132, 142) may have a uniform thickness that is substantially invariant within each respective first sacrificial material layer 142.
A first insulating cap layer 170 may be subsequently formed over the first-tier alternating stack (132, 142). The first insulating cap layer 170 includes a dielectric material, which may be any dielectric material that may be used for the first insulating layers 132. In one embodiment, the first insulating cap layer 170 includes the same dielectric material as the first insulating layers 132. The thickness of the first insulating cap layer 170 may be in a range from 20 nm to 300 nm, although lesser and greater thicknesses may also be used.
Referring to
A dielectric fill material (such as undoped silicate glass or doped silicate glass) may be deposited to fill the first stepped cavity. Excess portions of the dielectric fill material may be removed from above the horizontal plane including the top surface of the first insulating cap layer 170. A remaining portion of the dielectric fill material that fills the region overlying the first stepped surfaces constitute a first retro-stepped dielectric material portion 165. As used herein, a “retro-stepped” element refers to an element that has stepped surfaces and a horizontal cross-sectional area that increases monotonically as a function of a vertical distance from a top surface of a substrate on which the element is present. The first-tier alternating stack (132, 142) and the first retro-stepped dielectric material portion 165 collectively constitute a first-tier structure, which is an in-process structure that is subsequently modified.
An inter-tier dielectric layer 180 may be optionally deposited over the first-tier structure (132, 142, 170, 165). The inter-tier dielectric layer 180 includes a dielectric material such as silicon oxide. In one embodiment, the inter-tier dielectric layer 180 may include a doped silicate glass having a greater etch rate than the material of the first insulating layers 132 (which may include an undoped silicate glass). For example, the inter-tier dielectric layer 180 may include phosphosilicate glass. The thickness of the inter-tier dielectric layer 180 may be in a range from 30 nm to 300 nm, although lesser and greater thicknesses may also be used.
Referring to
The first-tier memory openings 149 may be openings that are formed in the memory array region 100 through each layer within the first-tier alternating stack (132, 142) and are subsequently used to form memory stack structures therein. The first-tier memory openings 149 may be formed in clusters 319 of first-tier memory openings 149 that are laterally spaced apart along the second horizontal direction hd2. Each cluster 319 of first-tier memory openings 149 may be formed as a two-dimensional array of first-tier memory openings 149.
A subset of the first-tier support openings 129 may be formed in sections of the memory array region 100 that are not filled with the first-tier memory openings 149. The sections of the memory array region 100 that are not filled with the first-tier memory openings 149 may be distributed over multiple areas within the memory array region 100. The first-tier support openings 129 may include a first subset of first-tier support openings 129 that are formed in the staircase region 200, and a second subset of first-tier support openings 129 that are formed between clusters of first-tier memory openings 149 which are laterally spaced apart along the first horizontal direction hd1 in the memory array region 100. A first subset of the first-tier support openings 129 that is formed through the first retro-stepped dielectric material portion 165 may be formed through a respective horizontal surface of the first stepped surfaces. Further, each of the first subset of the first-tier support openings 129 may be formed directly above (i.e., above, and with an areal overlap with) a respective one of the lower-level metal interconnect structure 780.
The second subset of the first-tier support openings 129 may be formed between a respective pair of clusters 319 of first-tier memory openings 149 that are laterally spaced apart along the first horizontal direction hd1. In one embodiment, some of the first-tier support openings 129 within the second subset of the first-tier support openings 129 may be arranged in rows that extend along the first direction hd1. Additional first-tier support openings may be provided outside the rows of the first-tier support openings 129. Generally, a unit pattern UP of a combination of first-tier memory openings 149 and first-tier support openings 129 may be repeated along the second horizontal direction hd2. Each unit pattern UP includes a plurality of clusters 419 of first-tier memory openings 149 that are laterally spaced apart along the second horizontal direction hd2 and/or laterally spaced apart along the first horizontal direction hd1.
Discrete areas free of first-tier memory openings 149 and first-tier support openings 129 may be provided in the memory array region 100. First-tier support openings 129 between two groups 339 of clusters 319 of first-tier support openings 129 may be arranged such that an opening-free area (OFA) that is free of first-tier memory openings 149 and free of first-tier support openings 129 may be provided within each unit pattern (UP). In one embodiment, the OFA includes a pair of rectangular areas that laterally extend along the first horizontal direction hd1 and a connecting rectangular area that connects the pair of rectangular areas and has a lesser lateral extent along the first horizontal direction hd1 than the pair of rectangular areas.
In one embodiment, the first anisotropic etch process may include an initial step in which the materials of the first-tier alternating stack (132, 142) are etched concurrently with the material of the first retro-stepped dielectric material portion 165. The chemistry of the initial etch step may alternate to optimize etching of the first and second materials in the first-tier alternating stack (132, 142) while providing a comparable average etch rate to the material of the first retro-stepped dielectric material portion 165. The first anisotropic etch process may use, for example, a series of reactive ion etch processes or a single reaction etch process (e.g., CF4/O2/Ar etch). The sidewalls of the various first-tier openings (149, 129) may be substantially vertical, or may be tapered.
After etching through the alternating stack (132, 142) and the first retro-stepped dielectric material portion 165, the chemistry of a terminal portion of the first anisotropic etch process may be selected to etch through the dielectric material(s) of the at least one second dielectric layer 768 with a higher etch rate than an average etch rate for the in-process source-level material layers 10′. For example, the terminal portion of the anisotropic etch process may include a step that etches the dielectric material(s) of the at least one second dielectric layer 768 selective to a semiconductor material within a component layer in the in-process source-level material layers 10′. In one embodiment, the terminal portion of the first anisotropic etch process may etch through the source-select-level conductive layer 118, the source-level insulating layer 117, the upper source-level semiconductor layer 116, the upper sacrificial liner 105, the source-level sacrificial layer 104, and the lower sacrificial liner 103, and at least partly into the lower source-level semiconductor layer 112. The terminal portion of the first anisotropic etch process may include at least one etch chemistry for etching the various semiconductor materials of the in-process source-level material layers 10′. The photoresist layer may be subsequently removed, for example, by ashing.
Optionally, the portions of the first-tier memory openings 149 and the first-tier support openings 129 at the level of the inter-tier dielectric layer 180 may be laterally expanded by an isotropic etch. In this case, the inter-tier dielectric layer 180 may comprise a dielectric material (such as borosilicate glass) having a greater etch rate than the first insulating layers 132 (that may include undoped silicate glass) in dilute hydrofluoric acid. An isotropic etch (such as a wet etch using HF) may be used to expand the lateral dimensions of the first-tier memory openings 149 at the level of the inter-tier dielectric layer 180. The portions of the first-tier memory openings 149 located at the level of the inter-tier dielectric layer 180 may be optionally widened to provide a larger landing pad for second-tier memory openings to be subsequently formed through a second-tier alternating stack (to be subsequently formed prior to formation of the second-tier memory openings).
Referring to
In one embodiment, the sacrificial first-tier fill material may include a semiconductor material such as silicon (e.g., a-Si or polysilicon), a silicon-germanium alloy, germanium, a III-V compound semiconductor material, or a combination thereof. Optionally, a thin etch stop liner (such as a silicon oxide layer or a silicon nitride layer having a thickness in a range from 1 nm to 3 nm) may be used prior to depositing the sacrificial first-tier fill material. The sacrificial first-tier fill material may be formed by a non-conformal deposition or a conformal deposition method.
In another embodiment, the sacrificial first-tier fill material may include a silicon oxide material having a higher etch rate than the materials of the first insulating layers 132, the first insulating cap layer 170, and the inter-tier dielectric layer 180. For example, the sacrificial first-tier fill material may include borosilicate glass or porous or non-porous organosilicate glass having an etch rate that is at least 100 times higher than the etch rate of densified TEOS oxide (i.e., a silicon oxide material formed by decomposition of tetraethylorthosilicate glass in a chemical vapor deposition process and subsequently densified in an anneal process) in a 100:1 dilute hydrofluoric acid. In this case, a thin etch stop liner (such as a silicon nitride layer having a thickness in a range from 1 nm to 3 nm) may be used prior to depositing the sacrificial first-tier fill material. The sacrificial first-tier fill material may be formed by a non-conformal deposition or a conformal deposition method.
In yet another embodiment, the sacrificial first-tier fill material may include amorphous silicon or a carbon-containing material (such as amorphous carbon or diamond-like carbon) that may be subsequently removed by ashing, or a silicon-based polymer that may be subsequently removed selective to the materials of the first-tier alternating stack (132, 142).
Portions of the deposited sacrificial material may be removed from above the topmost layer of the first-tier alternating stack (132, 142), such as from above the inter-tier dielectric layer 180. For example, the sacrificial first-tier fill material may be recessed to a top surface of the inter-tier dielectric layer 180 using a planarization process. The planarization process may include a recess etch, chemical mechanical planarization (CMP), or a combination thereof. The top surface of the inter-tier dielectric layer 180 may be used as an etch stop layer or a planarization stop layer.
Remaining portions of the sacrificial first-tier fill material comprise sacrificial first-tier opening fill portions (148, 128). Specifically, each remaining portion of the sacrificial material in a first-tier memory opening 149 constitutes a sacrificial first-tier memory opening fill portion 148. Each remaining portion of the sacrificial material in a first-tier support opening 129 constitutes a sacrificial first-tier support opening fill portion 128. The various sacrificial first-tier opening fill portions (148, 128) are concurrently formed, i.e., during a same set of processes including the deposition process that deposits the sacrificial first-tier fill material and the planarization process that removes the first-tier deposition process from above the first-tier alternating stack (132, 142) (such as from above the top surface of the inter-tier dielectric layer 180). The top surfaces of the sacrificial first-tier opening fill portions (148, 128) may be coplanar with the top surface of the inter-tier dielectric layer 180. Each of the sacrificial first-tier opening fill portions (148, 128) may, or may not, include cavities therein.
Referring to
In one embodiment, the third material layers may be second insulating layers 232 and the fourth material layers may be second spacer material layers that provide vertical spacing between each vertically neighboring pair of the second insulating layers 232. In one embodiment, the third material layers and the fourth material layers may be second insulating layers 232 and second sacrificial material layers 242, respectively. The third material of the second insulating layers 232 may be at least one insulating material. The fourth material of the second sacrificial material layers 242 may be a sacrificial material that may be removed selective to the third material of the second insulating layers 232. The second sacrificial material layers 242 may comprise an insulating material, a semiconductor material, or a conductive material. The fourth material of the second sacrificial material layers 242 may be subsequently replaced with electrically conductive electrodes which may function, for example, as control gate electrodes of a vertical NAND device.
In one embodiment, each second insulating layer 232 may include a second insulating material, and each second sacrificial material layer 242 may include a second sacrificial material. In this case, the second-tier alternating stack (232, 242) may include an alternating plurality of second insulating layers 232 and second sacrificial material layers 242. The third material of the second insulating layers 232 may be deposited, for example, by chemical vapor deposition (CVD). The fourth material of the second sacrificial material layers 242 may be formed, for example, CVD or atomic layer deposition (ALD).
The third material of the second insulating layers 232 may be at least one insulating material. Insulating materials that may be used for the second insulating layers 232 may be any material that may be used for the first insulating layers 132. The fourth material of the second sacrificial material layers 242 is a sacrificial material that may be removed selective to the third material of the second insulating layers 232. Sacrificial materials that may be used for the second sacrificial material layers 242 may be any material that may be used for the first sacrificial material layers 142. In one embodiment, the second insulating material may be the same as the first insulating material, and the second sacrificial material may be the same as the first sacrificial material.
The thicknesses of the second insulating layers 232 and the second sacrificial material layers 242 may be in a range from 20 nm to 50 nm, although lesser and greater thicknesses may be used for each second insulating layer 232 and for each second sacrificial material layer 242. The number of repetitions of the pairs of a second insulating layer 232 and a second sacrificial material layer 242 may be in a range from 2 to 1,024, and typically from 8 to 256, although a greater number of repetitions may also be used. In one embodiment, each second sacrificial material layer 242 in the second-tier alternating stack (232, 242) may have a uniform thickness that is substantially invariant within each respective second sacrificial material layer 242.
Second stepped surfaces in the second stepped area may be formed in the staircase region 200 using a same set of processing steps as the processing steps used to form the first stepped surfaces in the first stepped area with suitable adjustment to the pattern of at least one masking layer. A second retro-stepped dielectric material portion 265 may be formed over the second stepped surfaces in the staircase region 200.
A second insulating cap layer 270 may be subsequently formed over the second-tier alternating stack (232, 242). The second insulating cap layer 270 includes a dielectric material that is different from the material of the second sacrificial material layers 242. In one embodiment, the second insulating cap layer 270 may include silicon oxide. In one embodiment, the first and second sacrificial material layers (142, 242) may comprise silicon nitride.
Generally speaking, at least one alternating stack of insulating layers (132, 232) and spacer material layers (such as sacrificial material layers (142, 242)) may be formed over the in-process source-level material layers 10′, and at least one retro-stepped dielectric material portion (165, 265) may be formed over the staircase regions on the at least one alternating stack (132, 142, 232, 242).
Referring to
The pattern of openings in the photoresist layer may be transferred through the second-tier structure (232, 242, 265, 270) by a second anisotropic etch process to form various second-tier openings (249, 229) concurrently, i.e., during the second anisotropic etch process. The various second-tier openings (249, 229) may include second-tier memory openings 249 and second-tier support openings 229.
The second-tier memory openings 249 may be formed directly on a top surface of a respective one of the sacrificial first-tier memory opening fill portions 148. The second-tier support openings 229 may be formed directly on a top surface of a respective one of the sacrificial first-tier support opening fill portions 128. Further, each second-tier support openings 229 may be formed through a horizontal surface within the second stepped surfaces, which include the interfacial surfaces between the second-tier alternating stack (232, 242) and the second retro-stepped dielectric material portion 265. Locations of steps S in the first-tier alternating stack (132, 142) and the second-tier alternating stack (232, 242) are illustrated as dotted lines in
The second anisotropic etch process may include an etch step in which the materials of the second-tier alternating stack (232, 242) are etched concurrently with the material of the second retro-stepped dielectric material portion 265. The chemistry of the etch step may alternate to optimize etching of the materials in the second-tier alternating stack (232, 242) while providing a comparable average etch rate to the material of the second retro-stepped dielectric material portion 265. The second anisotropic etch process may use, for example, a series of reactive ion etch processes or a single reaction etch process (e.g., CF4/O2/Ar etch). The sidewalls of the various second-tier openings (249, 229) may be substantially vertical, or may be tapered. A bottom periphery of each second-tier opening (249, 229) may be laterally offset, and/or may be located entirely within, a periphery of a top surface of an underlying sacrificial first-tier opening fill portion (148, 128). The photoresist layer may be subsequently removed, for example, by ashing.
A subset of the second-tier support openings 229 may be formed in sections of the memory array region 100 that are not filled with the second-tier memory openings 249. The sections of the memory array region 100 that are not filled with the second-tier memory openings 249 may be distributed over multiple areas within the memory array region 100. The second-tier support openings 229 may include a first subset of second-tier support openings 229 that are formed in the staircase region 200, and a second subset of second-tier support openings 229 that may be formed between clusters of second-tier memory openings 249 which are laterally spaced apart along the first horizontal direction hd1 in the memory array region 100. A first subset of the second-tier support openings 229 that is formed through the first retro-stepped dielectric material portion 165 may be formed through a respective horizontal surface of the first stepped surfaces. Further, each of the first subset of the second-tier support openings 229 may be formed directly above (i.e., above, and with an areal overlap with) a respective one of the lower-level metal interconnect structure 780.
The second subset of the second-tier support openings 229 may be formed between a respective pair of clusters 419 of second-tier memory openings 249 that are laterally spaced apart along the first horizontal direction hd1. In one embodiment, some of the second-tier support openings 229 within the second subset of the second-tier support openings 229 may be arranged in rows that extend along the first direction hd1. Additional first-tier support openings may be provided outside the rows of the second-tier support openings 229. Generally, a unit pattern UP of a combination of second-tier memory openings 249 and second-tier support openings 229 may be repeated along the second horizontal direction hd2. Each unit pattern UP includes a plurality of clusters 419 of second-tier memory openings 249 that are laterally spaced apart along the second horizontal direction hd2 and/or laterally spaced apart along the first horizontal direction hd1.
Discrete areas free of second-tier memory openings 249 and second-tier support openings 229 are provided in the memory array region 100. Second-tier support openings 229 between two groups 439 of clusters 419 of second-tier support openings 229 may be arranged such that an opening-free area (OFA) that is free of second-tier memory openings 249 and free of second-tier support openings 229 is provided within each unit pattern (UP). In one embodiment, the OFA includes a pair of rectangular areas that laterally extend along the first horizontal direction hd1 and a connecting rectangular area that connects the pair of rectangular areas and has a lesser lateral extent along the first horizontal direction hd1 than the pair of rectangular areas.
Referring to
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Subsequently, the charge storage layer 54 may be formed. In one embodiment, the charge storage layer 54 may be a continuous layer or patterned discrete portions of a charge trapping material including a dielectric charge trapping material, which may be, for example, silicon nitride. Alternatively, the charge storage layer 54 may include a continuous layer or patterned discrete portions of a conductive material such as doped polysilicon or a metallic material that is patterned into multiple electrically isolated portions (e.g., floating gates), for example, by being formed within lateral recesses into sacrificial material layers (142, 242). In one embodiment, the charge storage layer 54 includes a silicon nitride layer. In one embodiment, the sacrificial material layers (142, 242) and the insulating layers (132, 232) may have vertically coincident sidewalls, and the charge storage layer 54 may be formed as a single continuous layer. Alternatively, the sacrificial material layers (142, 242) may be laterally recessed with respect to the sidewalls of the insulating layers (132, 232), and a combination of a deposition process and an anisotropic etch process may be used to form the charge storage layer 54 as a plurality of memory material portions that are vertically spaced apart. The thickness of the charge storage layer 54 may be in a range from 2 nm to 20 nm, although lesser and greater thicknesses may also be used.
The tunneling dielectric layer 56 includes a dielectric material through which charge tunneling may be performed under suitable electrical bias conditions. The charge tunneling may be performed through hot-carrier injection or by Fowler-Nordheim tunneling induced charge transfer depending on the mode of operation of the monolithic three-dimensional NAND string memory device to be formed. The tunneling dielectric layer 56 may include silicon oxide, silicon nitride, silicon oxynitride, dielectric metal oxides (such as aluminum oxide and hafnium oxide), dielectric metal oxynitride, dielectric metal silicates, alloys thereof, and/or combinations thereof. In one embodiment, the tunneling dielectric layer 56 may include a stack of a first silicon oxide layer, a silicon oxynitride layer, and a second silicon oxide layer, which is commonly known as an ONO stack. In one embodiment, the tunneling dielectric layer 56 may include a silicon oxide layer that is substantially free of carbon or a silicon oxynitride layer that is substantially free of carbon. The thickness of the tunneling dielectric layer 56 may be in a range from 2 nm to 20 nm, although lesser and greater thicknesses may also be used. The stack of the blocking dielectric layer 52, the charge storage layer 54, and the tunneling dielectric layer 56 constitutes a memory film 50 that stores memory bits.
The semiconductor channel material layer 60L may include a doped semiconductor material such as at least one elemental semiconductor material, at least one III-V compound semiconductor material, at least one II-VI compound semiconductor material, at least one organic semiconductor material, or other semiconductor materials known in the art. The conductivity type of dopants in the semiconductor channel material layer 60L is herein referred to as a first conductivity type, which may be p-type or n-type. In one embodiment, the semiconductor channel material layer 60L has a p-type doping in which p-type dopants (such as boron atoms) are present at an atomic concentration in a range from 1.0×1012/cm3 to 1.0×1018/cm3, such as from 1.0×1014/cm3 to 1.0×1017/cm3. In one embodiment, the semiconductor channel material layer 60L includes, and/or consists essentially of, boron-doped amorphous silicon or boron-doped polysilicon. In another embodiment, the semiconductor channel material layer 60L has an n-type doping in which n-type dopants (such as phosphor atoms or arsenic atoms) are present at an atomic concentration in a range from 1.0×1012/cm3 to 1.0×1018/cm3, such as from 1.0×1014/cm3 to 1.0×1017/cm3. The semiconductor channel material layer 60L may be formed by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD). The thickness of the semiconductor channel material layer 60L may be in a range from 2 nm to 10 nm, although lesser and greater thicknesses may also be used. A cavity 49′ is formed in the volume of each memory opening 49 that is not filled with the deposited material layers (52, 54, 56, 60L).
Referring to
Referring to
Each remaining portion of the doped semiconductor material-constitutes a drain region 63. The dopant concentration in the drain regions 63 may be in a range from 5.0×1019/cm3 to 2.0×1021/cm3, although lesser and greater dopant concentrations may also be used. The doped semiconductor material may be, for example, doped polysilicon.
Each remaining portion of the semiconductor channel material layer 60L constitutes a vertical semiconductor channel 60 through which electrical current may flow when a vertical NAND device including the vertical semiconductor channel 60 is turned on. A tunneling dielectric layer 56 may be surrounded by a charge storage layer 54, and laterally surrounds a vertical semiconductor channel 60. Each adjoining set of a blocking dielectric layer 52, a charge storage layer 54, and a tunneling dielectric layer 56 collectively constitute a memory film 50, which may store electrical charges with a macroscopic retention time. In some embodiments, a blocking dielectric layer 52 may not be present in the memory film 50 at this step, and a blocking dielectric layer may be subsequently formed after formation of backside recesses. As used herein, a macroscopic retention time refers to a retention time suitable for operation of a memory device as a permanent memory device such as a retention time in excess of 24 hours.
Each combination of a memory film 50 and a vertical semiconductor channel 60 (which is a vertical semiconductor channel) within a memory opening 49 constitutes a memory stack structure 55. The memory stack structure 55 may be a combination of a vertical semiconductor channel 60, a tunneling dielectric layer 56, a plurality of memory elements comprising portions of the charge storage layer 54, and an optional blocking dielectric layer 52. Each combination of a memory stack structure 55, a dielectric core 62, and a drain region 63 within a memory opening 49 constitutes a memory opening fill structure 58. Each drain region 63 in a memory opening fill structure 58 is electrically connected to an upper end of a respective one of the vertical semiconductor channels 60. The in-process source-level material layers 10′, the first-tier structure (132, 142, 170, 165), the second-tier structure (232, 242, 270, 265), the inter-tier dielectric layer 180, and the memory opening fill structures 58 collectively constitute a memory-level assembly.
Referring to
Referring to
A photoresist layer (not shown) may be applied over the first contact level dielectric layer 280, and may be lithographically patterned to form various openings in the memory array region 100 and the staircase region 200. The openings in the photoresist layer include first elongated openings that laterally extend along the first horizontal direction hd1 through the entire lateral extent of the memory array region 100 and the staircase region 200 along the first horizontal direction hd1. The first elongated openings laterally extend between groups of memory opening fill structures 58 and support pillar structures 20. Further, the openings in the photoresist layer may include second elongated openings that extend along the first horizontal direction hd1 between clusters of memory opening fill structures 58 that are laterally spaced apart along the first horizontal direction hd1 and located between a neighboring pair of first elongated openings. Each second elongated opening has a lesser lateral extent that the lateral extent of the memory array region 100 along the first horizontal direction hd1. Optionally, the openings in the photoresist layer may include discrete openings located between end regions of a neighboring pair of second elongated openings.
An anisotropic etch may be performed to transfer the pattern in the photoresist layer through underlying material portions including the alternating stacks {(132, 142), (232, 242)} and an upper portion of the in-process source-level material layers 10′. Backside trenches 79 may be formed underneath the first elongated openings in the photoresist layer through the first contact level dielectric layer 280, the second-tier structure (232, 242, 270, 265), and the first-tier structure (132, 142, 170, 165), and into the in-process source-level material layers 10′. Portions of the first contact level dielectric layer 280, the second-tier structure (232, 242, 270, 265), the first-tier structure (132, 142, 170, 165), and the in-process source-level material layers 10′ that underlie the first elongated openings in the photoresist layer may be removed to form the backside trenches 79. In one embodiment, the backside trenches 79 may be formed between groups of memory stack structures 55 that are laterally spaced apart along the second horizontal direction. A top surface of a source-level sacrificial layer 104 may be physically exposed at the bottom of each backside trench 79.
The anisotropic etch forms barrier trenches 179 which are not connected to each other concurrently with formation of the backside trenches 79. The barrier trenches 179 may be formed between neighboring pairs of backside trenches 79 within the memory array region 100 underneath the second elongated openings in the photoresist layer. The barrier trenches 179 may be formed through the first contact level dielectric layer 280, the second-tier structure (232, 242, 270, 265), the first-tier structure (132, 142, 170, 165), and into the in-process source-level material layers 10′. Each barrier trench 179 laterally extends along the first horizontal direction hd1. Each pair of barrier trenches 179 may be laterally spaced apart from each other by a uniform separation distance. Each barrier trench 179 may have a pair of vertical sidewalls that laterally extend along the first horizontal direction hd1.
In case the photoresist layer includes discrete openings between end regions of each neighboring pair of second elongated openings, the anisotropic etch process forms discrete via openings 279 concurrently with formation of the backside trenches 79 and the barrier trenches 179. The discrete via openings 279 may be formed between neighboring pairs of end regions of the barrier trenches 179 within the memory array region 100 underneath the discrete openings in the photoresist layer. The discrete via openings 279 may be formed through the first contact level dielectric layer 280, the second-tier structure (232, 242, 270, 265), the first-tier structure (132, 142, 170, 165), and into the in-process source-level material layers 10′.
Each of the barrier trenches 179 may include a respective pair of lengthwise sidewalls that extend along the first horizontal direction hd1. In one embodiment, the barrier trenches 179 may have rectangular horizontal cross-sectional shapes. In one embodiment, a pair of barrier trenches 179 may extend along the first horizontal direction hd1 by a same lateral extension distance, i.e., by the same length measured along the first horizontal direction hd1, as illustrated in
Generally, an alternating stack {(132, 232), (142, 242)} of insulating layers 132 and sacrificial material layers (142, 242) may be formed over a semiconductor substrate 8 including the substrate semiconductor layer 9. The sacrificial material layers (142, 242) may comprise a dielectric material such as silicon nitride. The alternating stack {(132, 232), (142, 242)} may be etched by performing an anisotropic etch process using a patterned mask layer (such as a photoresist layer). The alternating stack {(132, 232), (142, 242)} may be divided into a plurality of alternating stacks {(132, 232), (142, 242)} of respective insulating layers (132, 232) and respective sacrificial material layers (142, 242) by backside trenches 79. A pair of barrier trenches 179 may be formed through each of the plurality of alternating stacks {(132, 232), (142, 242)}.
In one embodiment, each of the barrier trenches 179 may include a respective uniform-width region that laterally extends along the first horizontal direction hd1 with a respective uniform width along a second horizontal direction hd2 that is perpendicular to the first horizontal direction hd1. In one embodiment, the pair of backside trenches 179 may have a same lateral extent along the first horizontal direction hd1. In one embodiment, the pair of barrier trenches 179 may be laterally offset along the second horizontal direction hd2 from a respective proximal backside trench 79 selected from the pair of backside trenches 79 by unequal lateral trench-to-dielectric spacings; and a barrier trench 179 of the pair of barrier trenches 179 having a greater trench-to-sidewall spacing may have a lateral extent along the first horizontal direction hd1 that is less than a lateral extent along the first horizontal direction hd1 for a barrier trench 179 of the pair of barrier trenches 179 having a lesser trench-to-sidewall spacing.
In one embodiment, each of the pair of barrier trenches 179 may comprise angled sidewalls located within a respective vertical plane that is at an angle in a range from 15 degrees to 75 degrees with respect to a vertical plane including the first horizontal direction hd1. In one embodiment, each barrier trench 179 may be an elongated trench that vertically extends through each layer of an alternating stack {(132, 232), (142, 242)} and has a greater lateral dimension along the first horizontal direction hd1 than along the second horizontal direction hd2.
Referring to
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Wet etch chemicals such as hot TMY and TMAH are selective to the doped semiconductor materials of the upper source-level semiconductor layer 116 and the lower source-level semiconductor layer 112. Thus, use of selective wet etch chemicals such as hot TMY and TMAH for the wet etch process that forms the source cavity 109 provides a large process window against etch depth variation during formation of the backside trenches 79. Specifically, in embodiments in which sidewalls of the upper source-level semiconductor layer 116 are physically exposed or in other embodiments in which a surface of the lower source-level semiconductor layer 112 is physically exposed upon formation of the source cavity 109, collateral etching of the upper source-level semiconductor layer 116 and/or the lower source-level semiconductor layer 112 is minimal, and the structural change to the first exemplary structure caused by accidental physical exposure of the surfaces of the upper source-level semiconductor layer 116 and/or the lower source-level semiconductor layer 112 during manufacturing steps do not result in device failures. Each of the memory opening fill structures 58 may be physically exposed to the source cavity 109. Specifically, each of the memory opening fill structures 58 may include a sidewall and a bottom surface that are physically exposed to the source cavity 109.
Referring to
Referring to
In one embodiment, the doped semiconductor material of the second conductivity type may be deposited on the physically exposed semiconductor surfaces around the source cavity 109 by a selective semiconductor deposition process. A semiconductor precursor gas, an etchant, and an n-type dopant precursor gas may flow concurrently into a process chamber including the first exemplary structure during the selective semiconductor deposition process. For example, the semiconductor precursor gas may include silane, disilane, or dichlorosilane, the etchant gas may include gaseous hydrogen chloride, and the n-type dopant precursor gas such as phosphine, arsine, or stibine. In this case, the selective semiconductor deposition process grows an in-situ doped semiconductor material from physically exposed semiconductor surfaces around the source cavity 109. The deposited doped semiconductor material forms a source contact layer 114, which may contact sidewalls of the vertical semiconductor channels 60. The atomic concentration of the dopants of the second conductivity type in the deposited semiconductor material may be in a range from 1.0×1020/cm3 to 2.0×1021/cm3, such as from 2.0×1020/cm3 to 8.0×1020/cm3. The source contact layer 114 as initially formed may consist essentially of semiconductor atoms and the dopant atoms of the second conductivity type. Alternatively, at least one non-selective doped semiconductor material deposition process may be used to form the source contact layer 114. Optionally, one or more etch back processes may be used in combination with a plurality of selective or non-selective deposition processes to provide a seamless and/or voidless source contact layer 114.
The duration of the selective semiconductor deposition process may be selected such that the source cavity 109 is filled with the source contact layer 114. In one embodiment, the source contact layer 114 may be formed by selectively depositing a doped semiconductor material from semiconductor surfaces around the source cavity 109. In one embodiment, the doped semiconductor material may include doped polysilicon. Thus, the source-level sacrificial layer 104 may be replaced with the source contact layer 114.
The layer stack including the lower source-level semiconductor layer 112, the source contact layer 114, and the upper source-level semiconductor layer 116 constitutes a source region (112, 114, 116). The source region (112, 114, 116) is electrically connected to a first end (such as a bottom end) of each of the vertical semiconductor channels 60. The set of layers including the source region (112, 114, 116), the source-level insulating layer 117, and the source-select-level conductive layer 118 constitutes source-level material layers 10, which replaces the in-process source-level material layers 10′.
Referring to
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The isotropic etch process may be a wet etch process using a wet etch solution, or may be a gas phase (dry) etch process in which the etchant is introduced in a vapor phase into the backside trench 79. For example, if the sacrificial material layers (142, 242) include silicon nitride, the etch process may be a wet etch process in which the first exemplary structure is immersed within a wet etch tank including phosphoric acid, which etches silicon nitride selective to silicon oxide, silicon, and various other materials used in the art. The duration of the isotropic etch process may be selected such that portions of the sacrificial material layers 42 outside areas between neighboring pairs of backside trenches 179 are removed. Further, portions of the sacrificial material layers 42 located near end regions of the backside trenches 179 may be removed.
Backside recesses (143, 243) may be formed in volumes from which the sacrificial material layers (142, 242) are removed. The backside recesses (143, 243) include first backside recesses 143 that may be formed in volumes from which the first sacrificial material layers 142 are removed and second backside recesses 243 that may be formed in volumes from which the second sacrificial material layers 242 are removed. Each of the backside recesses (143, 243) may be a laterally extending cavity having a lateral dimension that is greater than the vertical extent of the cavity. In other words, the lateral dimension of each of the backside recesses (143, 243) may be greater than the height of the respective backside recess (143, 243). A plurality of backside recesses (143, 243) may be formed in the volumes from which the material of the sacrificial material layers (142, 242) is removed. Each of the backside recesses (143, 243) may extend substantially parallel to the top surface of the substrate semiconductor layer 9. A backside recess (143, 243) may be vertically bounded by a top surface of an underlying insulating layer (132, 232) and a bottom surface of an overlying insulating layer (132, 232). In one embodiment, each of the backside recesses (143, 243) may have a uniform height throughout.
The barrier trenches 179 may be covered by a respective dielectric liner 274 that blocks access of the isotropic etchant to adjacent portions of the sacrificial material layers 142, 242 during the isotropic etch process. Remaining portions of the sacrificial material layers 142, 242 between each neighboring pair of barrier trenches 179 constitute dielectric spacer plates (142′, 242′). Portions of the insulating layers (132, 232) located within the areas of the dielectric spacer plates (142′, 242′) constitute insulating plates (132′, 232′). The dielectric spacer plates (142′, 232′) may include first dielectric spacer plates 142′ adjoining a respective one of the first backside recesses 143, and second dielectric spacer plates 242′ adjoining a respective one of the second backside recesses 243. The insulating plates (132′, 232′) may include first insulating plates 132′ that are portions of the first insulating layers 132 and second insulating plates 232′ that are portions of the second insulating layers 232. Thus, the first insulating layers 132 and the second insulating layers 232 within each alternating stack {(132, 232), (142, 242)} continuously extend between vertically neighboring pairs of dielectric spacer plates (142′, 242′). A vertically alternating sequence of the insulating plates (132′, 232′) and the dielectric spacer plates (142′, 242′) is provided between each neighboring pair of barrier trenches 179. A dielectric liner 274 and a barrier cavity 179′ is present within each barrier trench 179. A dielectric liner 274 and a discrete via cavity 279′ is present within each discrete via opening 279.
Referring to
At least one conductive material may be deposited in the plurality of backside recesses (243, 243), on the sidewalls of the backside trenches 79, and over the first contact level dielectric layer 280. The at least one conductive material may be deposited by a conformal deposition method, which may be, for example, chemical vapor deposition (CVD), atomic layer deposition (ALD), electroless plating, electroplating, or a combination thereof. The at least one conductive material may include an elemental metal, an intermetallic alloy of at least two elemental metals, a conductive nitride of at least one elemental metal, a conductive metal oxide, a conductive doped semiconductor material, a conductive metal-semiconductor alloy such as a metal silicide, alloys thereof, and combinations or stacks thereof.
In one embodiment, the at least one conductive material may include at least one metallic material, i.e., an electrically conductive material that includes at least one metallic element. Non-limiting exemplary metallic materials that may be deposited in the backside recesses (143, 243) include tungsten, tungsten nitride, titanium, titanium nitride, tantalum, tantalum nitride, cobalt, and ruthenium. For example, the at least one conductive material may include a conductive metallic nitride liner that includes a conductive metallic nitride material such as TiN, TaN, WN, or a combination thereof, and a conductive fill material such as W, Co, Ru, Mo, Cu, or combinations thereof. In one embodiment, the at least one conductive material for filling the backside recesses (143, 243) may be a combination of titanium nitride layer and a tungsten fill material.
Electrically conductive layers (146, 246) may be formed in the backside recesses (143, 243) by deposition of the at least one conductive material. A plurality of first electrically conductive layers 146 may be formed in the plurality of first backside recesses 143, a plurality of second electrically conductive layers 246 may be formed in the plurality of second backside recesses 243, and a continuous metallic material layer (not shown) may be formed on the sidewalls of each backside trench 79 and over the first contact level dielectric layer 280. Each of the first electrically conductive layers 146 and the second electrically conductive layers 246 may include a respective conductive metallic nitride liner and a respective conductive fill material. Thus, the first and second sacrificial material layers (142, 242) may be replaced with the first and second electrically conductive layers (146, 246), respectively. Specifically, each first sacrificial material layer 142 may be replaced with an optional portion of the backside blocking dielectric layer and a first electrically conductive layer 146, and each second sacrificial material layer 242 may be replaced with an optional portion of the backside blocking dielectric layer and a second electrically conductive layer 246. A backside cavity is present in the portion of each backside trench 79 that is not filled with the continuous metallic material layer.
Residual conductive material may be removed from inside the backside trenches 79. Specifically, the deposited metallic material of the continuous metallic material layer may be etched back from the sidewalls of each backside trench 79 and from above the first contact level dielectric layer 280, for example, by an anisotropic or isotropic etch. Each remaining portion of the deposited metallic material in the first backside recesses constitutes a first electrically conductive layer 146. Each remaining portion of the deposited metallic material in the second backside recesses constitutes a second electrically conductive layer 246. Sidewalls of the first electrically conductive material layers 146 and the second electrically conductive layers may be physically exposed to a respective backside trench 79.
Each combination of an electrically conductive layer (146, 246) and a dielectric space plate (142′, 242′) located at the same level constitutes a composite layer {(146, 142′), (246, 242′). Each of the composite layers {(146, 142′), (246, 242′) comprises a respective electrically conductive layer (146 or 246) and a respective dielectric spacer plate (142′, 242′). A vertically alternating sequence of the insulating plates (132′, 232′) and the dielectric spacer plates (142′, 242′) is provided within a region including the dielectric spacer plates (142′, 242′).
Each electrically conductive layer (146, 246) may be a conductive sheet including openings therein. A first subset of the openings through each electrically conductive layer (146, 246) may be filled with memory opening fill structures 58. A second subset of the openings through each electrically conductive layer (146, 246) may be filled with the support pillar structures 20. Each electrically conductive layer (146, 246) may have a lesser area than any underlying electrically conductive layer (146, 246) because of the first and second stepped surfaces. Each electrically conductive layer (146, 246) may have a greater area than any overlying electrically conductive layer (146, 246) because of the first and second stepped surfaces.
Each of the memory stack structures 55 comprises a vertical stack of memory elements located at each level of the electrically conductive layers (146, 246). A subset of the electrically conductive layers (146, 246) may comprise word lines for the memory elements. The semiconductor devices in the underlying peripheral device region 700 may comprise word line switch devices configured to control a bias voltage to respective word lines. The memory-level assembly is located over the substrate semiconductor layer 9. The memory-level assembly includes at least one alternating stack (132, 146, 232, 246) and memory stack structures 55 vertically extending through the at least one alternating stack (132, 146, 232, 246).
Referring to
A dielectric fill material may be conformally deposited in the backside trenches 79, the barrier cavities 179′, the discrete via cavities 279′, and the drain-select-level trenches. The dielectric fill material may include a conformal dielectric material and/or a reflowable dielectric material. For example, the dielectric fill material may include silicon oxide. Excess portions of the dielectric fill material overlying the first contact level dielectric layer 280 may be removed by a planarization process, which may include chemical mechanical planarization (CMP) and/or a recess etch.
Each remaining portion of the dielectric fill material that fills a backside trench 79 constitutes a dielectric backside trench fill structure 76, which laterally extends extending along the first horizontal direction hd1 and vertically extends through each layer within a neighboring pair of alternating stacks {(132, 146), (232, 246)} of insulating layers (132, 232) and electrically conductive layers (146, 246). Each remaining portion of the dielectric fill material that fills a barrier trench 179 constitutes a dielectric fill material portion 176, which laterally extends extending along the first horizontal direction hd1 and vertically extends through each layer within an alternating stack {(132, 146), (232, 246)} of insulating layers (132, 232) and electrically conductive layers (146, 246). Each set of a dielectric fill material portion 176 and a dielectric liner that fills a barrier trench constitutes a dielectric wall structure (274, 176). Each pair of dielectric wall structures (274, 176) has a greater lateral extent a pair of lengthwise sidewalls of dielectric spacer plates (142′, 242′) within an adjoining vertically alternating sequence of insulating layers (132, 232) and the dielectric spacer plates (142′, 242′).
Each remaining portion of the dielectric fill material that fills a discrete via cavity 279′ constitutes a dielectric pillar structure 276, which vertically extends through each layer within an alternating stack {(132, 146), (232, 246)} of insulating layers (132, 232) and electrically conductive layers (146, 246). Each remaining portion of the dielectric fill material that fills the drain-select-level trenches constitutes a drain-select-level isolation structure 72. The drain-select-level isolation structures 72 vertically extend through a subset of layers within the alternating stack of insulating layers (132, 232) and composite layers (146, 142′, 246, 242′). The subset of layers that the drain-select-level isolation structures 72 extend through includes a topmost one of the composite layers (146, 142′, 246, 242′).
The drain-select-level isolation structures 72 divide each second electrically conductive layer 246 at the drain select levels into multiple electrically conductive strips that are electrically isolated from one another. Thus, the drain-select-level isolation structures 72 divide an electrically conductive layer 246 within the topmost one of the composite layers (146, 142′, 246, 242′) into multiple electrically conductive strips that are electrically isolated from one another. In one embodiment, each of the multiple electrically conductive strips of the second electrically conductive layer(s) 246 at the drain select level(s) laterally extends continuously from a first side (“Side 1”) of the vertically alternating sequence of insulating layers (132, 232) and dielectric spacer plates (142′, 242′), between a respective backside trench 179 and a respective one of the dielectric wall structures (274, 176), and to a second side (“Side 2”) of the vertically alternating sequence that is laterally spaced from the first side along the first horizontal direction hd1. The drain-select-level trenches generally extend along the first horizontal direction hd1 with a contour or lateral shift around the dielectric wall structures (274, 176) and the vertically alternating sequence of insulating layers (132, 232) and the dielectric spacer plates (142′, 242′).
At least one of the drain-select-level isolation structures 72 comprises a first dielectric material segment 721 that has a uniform width and extends along the first horizontal direction hd1, a second dielectric material segment 722 that extends along the first horizontal direction hd1 and is laterally offset from the first dielectric material segment 721 by a lateral offset distance, and a connection dielectric material segment 723 connecting the first dielectric material segment 721 and the second dielectric material segment 722 and extending horizontally along a horizontal direction that is at an angle in a range from 15 degrees to 75 degrees with respect to the first horizontal direction hd1. In some embodiments, each of the pair of dielectric wall structures (274, 176) comprises angled sidewalls located within a respective vertical plane that is at an angle in a range from 15 degrees to 75 degrees with respect to a vertical plane including the first horizontal direction hd1 as illustrated in
Memory stack structures 55 vertically extend through a respective alternating stack {(132, 146) and/or (232, 246)} of insulating layers (132, 232) and electrically conductive layers (146, 246). Each of the memory stack structures 55 comprises a respective memory film 50 and a respective vertical semiconductor channel 60. A source region (112, 114, 116) is electrically connected to a first end of each of the vertical semiconductor channels 60, and drain regions is electrically connected to a second end of a respective one of the vertical semiconductor channels 60.
Referring to
Referring to
If the barrier trenches 179 described above with respect to
Referring to
A photoresist layer (not shown) may be applied over the second contact level dielectric layer 282, and may be lithographically patterned to form various contact via openings. For example, openings for forming drain contact via structures may be formed in the memory array region 100, and openings for forming staircase region contact via structures may be formed in the staircase region 200. An anisotropic etch process is performed to transfer the pattern in the photoresist layer through the second and first contact level dielectric layers (282, 280) and underlying dielectric material portions. The drain regions 63 and the electrically conductive layers (146, 246) may be used as etch stop structures. Drain contact via cavities may be formed over each drain region 63, and staircase-region contact via cavities may be formed over each electrically conductive layer (146, 246) at the stepped surfaces underlying the first and second retro-stepped dielectric material portions (165, 265). The photoresist layer may be subsequently removed, for example, by ashing.
Drain contact via structures 88 are formed in the drain contact via cavities and on a top surface of a respective one of the drain regions 63. Staircase-region contact via structures 86 are formed in the staircase-region contact via cavities and on a top surface of a respective one of the electrically conductive layers (146, 246). The staircase-region contact via structures 86 may include drain select level contact via structures that contact a subset of the second electrically conductive layers 246 that function as drain select level gate electrodes. Further, the staircase-region contact via structures 86 may include word line contact via structures that contact electrically conductive layers (146, 246) that underlie the drain select level gate electrodes and function as word lines for the memory stack structures 55. Interconnection via structures 286 may be formed on top of a respective one of the through-memory-level interconnection via structures (488, 588).
At least one additional dielectric layer may be formed over the contact level dielectric layers (280, 282), and additional metal interconnect structures (herein referred to as upper-level metal interconnect structures) may be formed in the at least one additional dielectric layer. For example, the at least one additional dielectric layer may include a line-level dielectric layer 290 that is formed over the contact level dielectric layers (280, 282). The upper-level metal interconnect structures may include bit lines 98 contacting a respective one of the drain contact via structures 88. Further, the upper-level metal interconnect structures may include interconnection line structures 96 contacting, and/or electrically connected to, at least one of the staircase-region contact via structures 86 or the interconnection via structures 286. he bit lines 98 may be electrically connected to a respective subset of the drain regions 63. In one embodiment, the electrically conductive layers (146, 246) may laterally extend along the first horizontal direction hd1 and may have a uniform width along the second horizontal direction hd2. The bit lines 98 may laterally extend along the second horizontal direction hd2.
In one embodiment, the three-dimensional memory device comprises a monolithic three-dimensional NAND memory device, the electrically conductive strips (146, 246) comprise, or are electrically connected to, a respective word line of the monolithic three-dimensional NAND memory device, the semiconductor substrate 8 comprises a silicon substrate, the monolithic three-dimensional NAND memory device comprises an array of monolithic three-dimensional NAND strings over the silicon substrate, and at least one memory cell in a first device level of the array of monolithic three-dimensional NAND strings is located over another memory cell in a second device level of the array of monolithic three-dimensional NAND strings. The silicon substrate may contain an integrated circuit comprising a driver circuit for the memory device located thereon, the electrically conductive strips (146, 246) comprise a plurality of control gate electrodes having a strip shape extending substantially parallel to the top surface of the semiconductor substrate 8, the plurality of control gate electrodes comprise at least a first control gate electrode located in the first device level and a second control gate electrode located in the second device level. The array of monolithic three-dimensional NAND strings comprises a plurality of vertical semiconductor channels 60, wherein at least one end portion of each of the plurality of vertical semiconductor channels 60 extends substantially perpendicular to a top surface of the semiconductor substrate 8, and one of the plurality of semiconductor channels including the vertical semiconductor channel 60. The array of monolithic three-dimensional NAND strings comprises a plurality of charge storage elements (comprising portions of the memory films 50), each charge storage element located adjacent to a respective one of the plurality of vertical semiconductor channels 60.
Referring to all drawings and according to various embodiments of the present disclosure, a three-dimensional memory device is provided, which comprises: field effect transistors located over a semiconductor substrate 8 including the substrate semiconductor layer 9; lower-level metal interconnect structures 780 formed within lower-level dielectric material layers 760 that overlie the field effect transistors; an alternating stack of insulating layers (132, 232) and composite layers {(146, 142′), (246, 242′)} located over the lower-level metal interconnect structures 780 and between a pair of backside trenches 79 that laterally extend along a first horizontal direction hd1, wherein each of the composite layers {(146, 142′), (246, 242′)} comprises a respective electrically conductive layer (146, 246) and a respective dielectric spacer plate (142′, 242′), and a vertically alternating sequence of the insulating plates (132′, 232′) and the dielectric spacer plates (142′, 242′) is provided within a region including the dielectric spacer plates (142′, 242′); memory stack structures 55 vertically extending through the alternating stack {132, 232, (146, 142′), (246, 242′)}; a pair of dielectric wall structures (274, 176) vertically extending through each layer within the alternating stack {132, 232, (146, 142′), (246, 242′)} which do not contact other through another dielectric wall structure, wherein a vertically alternating sequence of the insulating plates (132′, 232′) and the dielectric spacer plates (142′, 242′) is located between the pair of dielectric wall structures (274, 176); and at least one conductive via structure 588 vertically extending through the vertically alternating sequence {132, 232, 142′, 242′)} and contacting a top surface of a respective one of the lower-level metal interconnect structures 780.
In one embodiment, the pair of dielectric wall structures (274, 176) are discrete and unconnected, which means that there is no path from one dielectric wall structure of the pair to the other dielectric wall structure of the pair through another dielectric wall structure. In other words, the pair of dielectric wall structures do not completely surround the alternating sequence of the insulating plates (132′, 232′) and the dielectric spacer plates (142′, 242′), and the alternating sequence of the insulating plates (132′, 232′) and the dielectric spacer plates (142′, 242′) are not completely surrounded by dielectric wall structures (176, 274).
In one embodiment, each of the dielectric wall structures (274, 176) includes a respective uniform-width region that laterally extend along the first horizontal direction hd1 with a respective uniform width along a second horizontal direction hd2 that is perpendicular to the first horizontal direction hd1. In one embodiment, each of the dielectric spacer plates (142′, 242′) comprises lengthwise sidewalls that extend along the first horizontal direction hd1 and contacts a respective one of the pair of dielectric wall structures (274, 176). In one embodiment, each of the pair of dielectric wall structures (274, 176) has a greater lateral extent than the pair of lengthwise sidewalls of the dielectric spacer plates (142′, 242′).
In one embodiment, the pair of dielectric wall structures (274, 176) has a same lateral extent along the first horizontal direction hd1. In one embodiment, the pair of dielectric wall structures (274, 176) are laterally offset along the second horizontal direction hd2 from a respective proximal backside trench 79 selected from the pair of backside trenches 79 by unequal lateral trench-to-dielectric spacings (as illustrated in
In one embodiment, each of the pair of dielectric wall structures (274, 176) comprises angled sidewalls located within a respective vertical plane that is at an angle in a range from 15 degrees to 75 degrees with respect to a vertical plane including the first horizontal direction hd1.
In one embodiment, each of the pair of dielectric wall structures (274, 176) is located within a respective elongated trench that vertically extends through each layer of the alternating stack {132, 232, (146, 142′), (246, 242′)} and having a greater lateral dimension along the first horizontal direction hd1 than along the second horizontal direction hd2.
In one embodiment, each of the dielectric wall structures (274, 176) comprises: a respective dielectric liner 274 comprising a dielectric material having a different material composition than the dielectric spacer plates (142′, 242′); and a dielectric fill material formed within the respective dielectric liner 274 and constituting a dielectric fill material portion 176. In one embodiment, the insulating layers (132, 232) comprise a silicon oxide material; the dielectric liner 274 comprises a material selected from silicon oxide and a dielectric metal oxide; and the dielectric spacer plates (142′, 242′) comprise silicon nitride.
In one embodiment, drain-select-level isolation structures 72 may vertically extend through a subset of layers within the alternating stack {132, 232, (146, 142′), (246, 242′)} including a topmost one of the composite layers {(146, 142′), (246, 242′)}, wherein the drain-select-level isolation structures 72 divide an electrically conductive layer 246 within the topmost one of the composite layers {(146, 142′), (246, 242′)} into multiple electrically conductive strips that are electrically isolated from one another. In one embodiment, each of the multiple electrically conductive strips laterally extends continuously from a first side of the vertically alternating sequence {132, 232, 142′, 242′)}, between a respective one of the pair of backside trenches 79 and a respective one of the dielectric wall structures (274, 176), and to a second side of the vertically alternating sequence {132, 232, 142′, 242′)} that is laterally spaced from the first side along the first horizontal direction hd1.
A semiconductor material layer (such as a source contact layer 114) may be located between the lower-level dielectric material layers 760 and the alternating stack {132, 232, (146, 142′), (246, 242′)}, wherein: each of the memory stack structures 55 comprises a vertical semiconductor channel 60 and a memory film 50; and each sidewall of the pair of dielectric wall structures (274, 176) vertically extend straight from a topmost layer of the alternating stack {132, 232, (146, 142′), (246, 242′)} to a bottommost layer of the alternating stack {132, 232, (146, 142′), (246, 242′)}.
In one embodiment, the semiconductor material layer comprises an opening that underlies the vertically alternating sequence {132, 232, 142′, 242′)}; and the at least one conductive via structure 588 vertically extends through, and contacts, a dielectric material located within the opening in the semiconductor material layer.
The various embodiments of the present disclosure may be used to provide a liner-less contact via structure that extends through the memory levels within the memory array region 100. Specifically, the first through-memory-level interconnection via structure 588 do not utilize a dielectric liner because the vertically alternating sequence {132, 232, 142′, 242′)} functions as an insulating matrix that electrically isolates each of the first through-memory-level interconnection via structure 588 from the electrically conductive layers (146, 246). The first through-memory-level interconnection via structure 588 may be formed with minimal modifications to a process flow for forming a three-dimensional memory device, while providing higher areal efficiency and reduced process cost. By providing the liner-less contact via structure, the wiring connections to semiconductor devices 710 in the underlying peripheral device region 700 may be formed at a lower cost, simplifying the fabrication process and providing the ability to reduce the pitch of the structures. Furthermore, since the alternating sequence of the insulating plates (132′, 232′) and the dielectric spacer plates (142′, 242′) are not completely surrounded by dielectric wall structures, more space is available to form memory stack structures 55, there is less likelihood of pattern collapse and over etching at the corners of the barrier trenches. Furthermore, stress is mitigated, which can reduce or prevent insulating layer 32 deflection.
Referring to
Because the second exemplary structure is derived from the first exemplary structure, the processing steps of
Generally, the substrate 8 (shown, for example, in
The backside trenches 79 and the moat trench 379 can be formed through the alternating stack {(132, 142), (232, 242)} of insulating layers (132, 232) and sacrificial material layers (142, 242) that include a dielectric material (such as silicon nitride). For example, a photoresist layer (not shown) can be applied over the second insulating cap layer 270 and can be lithographically patterned with patterns of the backside trenches 79 and the moat trenches 379, and the pattern in the photoresist layer can be transferred through the alternating stack {(132, 142), (232, 242)}, the optional source-select-level conductive layer 118, the source-level insulating layer 117, the upper source-level semiconductor layer 116, and the upper sacrificial liner 105 such that the source-level sacrificial layer 104 is physically exposed at the bottom of each backside trench 79. A top surface of the source-level sacrificial layer 104 may be physically exposed at the bottom of each moat trench 379.
Each moat trench 379 has a continuous outer periphery and a continuous inner periphery. The continuous outer periphery of each moat trench 379 can have a first rectangular shape or a first rounded rectangular shape. The continuous inner periphery of each moat trench 379 can have a second rectangular shape or a second rounded rectangular shape that is located entirely within the first rectangular shape or the first rounded rectangular shape. Portions of the insulating layers (132, 232) surrounded by each moat trench constitute insulating plates (132′, 232′). The insulating plates (132′, 232′) include first insulating plates 132′ formed by remaining portions of the first insulating layers 132 and second insulating plates 232′ formed by remaining portions of the second insulating layers 232. Portions of the sacrificial material layers (142, 242) surrounded by each moat trench 379 constitute dielectric spacer plates (142′, 242′). The dielectric spacer plates (142′, 242′) include first dielectric spacer plates 142′ formed by remaining portions of the first sacrificial material layers 142 and second dielectric spacer plates 242′ formed by remaining portions of the second sacrificial material layers 242. A vertically alternating sequence of the insulating plates (132′, 232′) and the dielectric spacer plates (142′, 242′) is provided surrounded by each moat trench 379.
The moat trenches 379 can be formed in the memory array region 100 as illustrated in the first configuration of
In case a moat trench 379 is formed in the staircase region 200 as illustrated in
In one embodiment, the backside trenches 79 can laterally extend along a first horizontal direction (e.g., word line direction) hd1, and the backside trenches 79 can be laterally spaced apart along a second horizontal direction (e.g., bit line direction) hd2 that is perpendicular to the first horizontal direction hd1. In one embodiment, a moat trench 379 can comprise a pair of lengthwise outer sidewalls that extend along the first horizontal direction hd1, a pair of lengthwise inner sidewalls that extend along the first horizontal direction hd1, a pair of widthwise outer sidewalls that extend along the second horizontal direction hd2, and a pair of widthwise inner sidewalls that extend along the second horizontal direction hd2.
Referring to
Referring to
Referring to
Referring to
Subsequently, processing steps of
Referring to
Referring to
Referring to
Referring to
The vie cavities (587A, 587B, 487) can include device-region interconnection via cavities 587A vertically extending through a respective vertically alternating sequence of insulating plates (132′, 232′) and dielectric spacer plates (142′, 242′), through an upper portion of the lower-level dielectric material layers 760 located within an opening in the source-level material layers 10, and down to a top surface of a lower-level metal interconnect structures 780 (such as landing-pad-level metal line structures 788). Alternatively or additionally, the via cavities (587A, 587B, 487) can include source contact via cavities 587B vertically extending through a respective vertically alternating sequence of insulating plates (132′, 232′) and dielectric spacer plates (142′, 242′) and into the source-level material layers 10. A surface of the source-level material layers 10 (such as a surface of a source contact layer 114) can be physically exposed at the bottom of each source contact via cavity 587B. The via cavities (587A, 587B, 487) can include peripheral-region interconnection via cavities 487 that are formed in the peripheral region 400. The device-region interconnection via cavities 587A and the source contact via cavities 587B are herein referred to as first through-memory-level via cavities (587A, 587B). As used herein, a “through-memory-level via cavity” refers to a via cavity that extends through layers of the memory levels, i.e., through layers located at levels that contain memory cells comprising charge storage elements within the charge storage layers 54.
The peripheral-region interconnection via cavities 487 vertically extend through the first contact level dielectric layer 280, the second insulating cap layer 270, the second retro-stepped dielectric material portion 265, the first retro-stepped dielectric material portion 165, and an upper portion of the lower-level dielectric material layers 760. Each peripheral-region interconnection via cavities 487 can vertically extend down to a top surface of a lower-level metal interconnect structures 780 (such as landing-pad-level metal line structures 788). The peripheral-region interconnection via cavities 487 are herein referred to as second through-memory-level via cavities.
Referring to
Each portion of the at least one conductive material deposited in a first through-memory-level via cavity (587A, 587B) constitutes a first through-memory-level interconnection via structure (588A, 588B). The first through-memory-level interconnection via structures (588A, 588B) include device-region through-memory-level interconnection via structures 588A that are formed in the device-region interconnection via cavities 587A and source contact through-memory-level interconnection via structures 588B that are formed in the source contact via cavities 587B. Each portion of the at least one conductive material deposited in a second through-memory-level via cavity 487 constitutes a second through-memory-level interconnection via structure, which is also referred to as a peripheral through-memory-level interconnection via structure 488. Thus, the first through-memory-level interconnection via structures (588A, 588B) extending through a vertically alternating sequence {(132′, 142′), (232′, 242′)} inside a respective moat trench 379 and second through-memory-level interconnection via structures (i.e., the peripheral through-memory-level interconnection via structure 488) extending through the dielectric material portion(s) (such as the second and first retro-stepped dielectric material portions (265, 165)) can be simultaneously formed employing a same conductive material deposition process and a same planarization process.
In one embodiment, a subset of the first through-memory-level interconnection via structures (588A, 588B) (such as the device-region through-memory-level interconnection via structures 588A) and the second through-memory-level interconnection via structures (i.e., the peripheral through-memory-level interconnection via structure 488) can be formed on a respective one of the lower-level metal interconnect structures 788.
Subsequently, upper-level metal interconnect structures embedded within upper-level dielectric material layers can be formed over the first through-memory-level interconnection via structures (588A, 588B) and the second through-memory-level interconnection via structures (i.e., the peripheral through-memory-level interconnection via structure 488), for example, by performing the processing steps of
Simultaneous formation of the first through-memory-level interconnection via structures (588A, 588B) and the second through-memory-level interconnection via structures (i.e., the peripheral through-memory-level interconnection via structure 488) reduce the processing cost for forming the three-dimensional memory device of the embodiments of the present disclosure by reducing the total number of processing steps. Formation of an insulating liner around any through-memory-level interconnection via structure (588A, 588B, 488) is not necessary because the dielectric material portions in the peripheral region 400 and the vertically alternating sequences of insulating plates (132′, 232′) and dielectric spacer plates (142′, 242′) in the memory array region 100 consist of dielectric materials. Thus, the processing sequences of embodiments of the present disclosure can provide a low cost manufacturing solution for three-dimensional memory devices employing various through-memory-level interconnection via structures.
Although the foregoing refers to particular embodiments, it will be understood that the disclosure is not so limited. It will occur to those of ordinary skill in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the disclosure. Compatibility is presumed among all embodiments that are not alternatives of one another. The word “comprise” or “include” contemplates all embodiments in which the word “consist essentially of” or the word “consists of” replaces the word “comprise” or “include,” unless explicitly stated otherwise. Where an embodiment using a particular structure and/or configuration is illustrated in the present disclosure, it is understood that the present disclosure may be practiced with any other compatible structures and/or configurations that are functionally equivalent provided that such substitutions are not explicitly forbidden or otherwise known to be impossible to one of ordinary skill in the art. All of the publications, patent applications and patents cited herein are incorporated herein by reference in their entirety.
Claims
1. A three-dimensional memory device, comprising:
- field effect transistors located over a semiconductor substrate;
- lower-level metal interconnect structures formed within lower-level dielectric material layers that overlie the field effect transistors;
- an alternating stack of insulating layers and composite layers located over the lower-level metal interconnect structures and between a pair of backside trenches that laterally extend along a first horizontal direction, wherein each of the composite layers comprises a respective electrically conductive layer and a respective dielectric spacer plate, and a vertically alternating sequence of the insulating plates and the dielectric spacer plates is provided within a region including the dielectric spacer plates;
- memory stack structures vertically extending through the alternating stack;
- a pair of dielectric wall structures vertically extending through each layer within the alternating stack which do not contact other through another dielectric wall structure, wherein a vertically alternating sequence of the insulating plates and the dielectric spacer plates is located between the pair of dielectric wall structures; and
- at least one conductive via structure vertically extending through the vertically alternating sequence and contacting a top surface of a respective one of the lower-level metal interconnect structures.
2. The three-dimensional memory device of claim 1, wherein the dielectric spacer plates are not completely surrounded by dielectric wall structures.
3. The three-dimensional memory device of claim 1, wherein each of the dielectric wall structures includes a respective uniform-width region that laterally extend along the first horizontal direction with a respective uniform width along a second horizontal direction that is perpendicular to the first horizontal direction.
4. The three-dimensional memory device of claim 3, wherein:
- each of the dielectric spacer plates comprises lengthwise sidewalls that extend along the first horizontal direction and contacts a respective one of the pair of dielectric wall structures; and
- each of the pair of dielectric wall structures has a greater lateral extent than the pair of lengthwise sidewalls of the dielectric spacer plates.
5. The three-dimensional memory device of claim 4, wherein the pair of dielectric wall structures has a same lateral extent along the first horizontal direction.
6. The three-dimensional memory device of claim 4, wherein:
- the pair of dielectric wall structures are laterally offset along the second horizontal direction from a respective proximal backside trench selected from the pair of backside trenches by unequal lateral trench-to-dielectric spacings; and
- a dielectric wall structure of the pair of dielectric wall structures having a greater trench-to-sidewall spacing has a lateral extent along the first horizontal direction that is less than a lateral extent along the first horizontal direction for a dielectric wall structure of the pair of dielectric wall structures having a lesser trench-to-sidewall spacing.
7. The three-dimensional memory device of claim 4, wherein each of the pair of dielectric wall structures comprises angled sidewalls located within a respective vertical plane that is at an angle in a range from 15 degrees to 75 degrees with respect to a vertical plane including the first horizontal direction.
8. The three-dimensional memory device of claim 2, wherein each of the pair of dielectric wall structures is located within a respective elongated trench that vertically extends through each layer of the alternating stack and has a greater lateral dimension along the first horizontal direction than along the second horizontal direction.
9. The three-dimensional memory device of claim 1, wherein each of the dielectric wall structures comprises:
- a respective dielectric liner comprising a dielectric material having a different material composition than the dielectric spacer plates; and
- a dielectric fill material formed within the respective dielectric liner.
10. The three-dimensional memory device of claim 9, wherein:
- the insulating layers comprise a silicon oxide material;
- the dielectric liner comprises a material selected from silicon oxide and a dielectric metal oxide; and
- the dielectric spacer plates comprise silicon nitride.
11. The three-dimensional memory device of claim 1, further comprising drain-select-level isolation structures that vertically extend through a subset of layers within the alternating stack including a topmost one of the composite layers, wherein the drain-select-level isolation structures divide an electrically conductive layer within the topmost one of the composite layers into multiple electrically conductive strips that are electrically isolated from one another.
12. The three-dimensional memory device of claim 11, wherein each of the multiple electrically conductive strips laterally extends continuously from a first side of the vertically alternating sequence, between a respective one of the pair of backside trenches and a respective one of the dielectric wall structures, and to a second side of the vertically alternating sequence that is laterally spaced from the first side along the first horizontal direction.
13. The three-dimensional memory device of claim 11, wherein at least one of the drain-select-level isolation structures comprises a first dielectric material segment that has a uniform width and extends along the first horizontal direction, a second dielectric material segment that extends along the first horizontal direction and is laterally offset from the first dielectric material segment by a lateral offset distance, and a connection dielectric material segment connecting the first dielectric material segment and the second dielectric material segment and extending horizontally along a horizontal direction that is at an angle in a range from 15 degrees to 75 degrees with respect to the first horizontal direction.
14. The three-dimensional memory device of claim 1, further comprising a semiconductor material layer located between the lower-level dielectric material layers and the alternating stack, wherein:
- each of the memory stack structures comprises a vertical semiconductor channel and a memory film; and
- each sidewall of the pair of dielectric wall structures vertically extend straight from a topmost layer of the alternating stack to a bottommost layer of the alternating stack.
15. The three-dimensional memory device of claim 14, wherein:
- the semiconductor material layer comprises an opening that underlies the vertically alternating sequence; and
- the at least one conductive via structure vertically extends through, and contacts, a dielectric material located within the opening in the semiconductor material layer.
16. A method for forming a three-dimensional memory device, comprising:
- forming an alternating stack of insulating layers and sacrificial material layers over a semiconductor substrate, wherein the sacrificial material layers comprise a dielectric material;
- forming memory stack structures through the alternating stack;
- patterning the alternating stack by performing an anisotropic etch process using a patterned mask layer, wherein the alternating stack is divided into a plurality of alternating stacks of respective insulating layers and respective sacrificial material layers by backside trenches, and wherein a pair of unconnected barrier trenches is formed through each of the plurality of alternating stacks;
- forming backside recesses by isotropically etching portions of the sacrificial material layers of the plurality of alternating stacks selective to the insulating layers of the plurality of alternating stacks by introducing an isotropic etchant into the backside trenches while the barrier trenches are covered by a respective dielectric liner that blocks access of the isotropic etchant to adjacent portions of the sacrificial material layers, wherein remaining portions of the sacrificial material layers between each neighboring pair of barrier trenches constitute dielectric spacer plates, and a vertically alternating sequence of the insulating plates and the dielectric spacer plates is provided between the pair of barrier trenches;
- forming electrically conductive layers in the backside recesses; and
- forming at least one conductive via structure through the vertically alternating sequence.
17. The method of claim 16, further comprising:
- forming field effect transistors on the semiconductor substrate; and
- forming lower-level metal interconnect structures formed within lower-level dielectric material layers that overlie the field effect transistors,
- wherein:
- the vertically-alternating layer stack is formed over the lower-level dielectric material layers; and
- the at least one conductive via structure is formed on a respective one of the lower-level metal interconnect structures.
18. The method of claim 16, further comprising: depositing a dielectric fill material on each of the dielectric liners after formation of the electrically conductive materials, wherein each material portion of the dielectric fill material and a dielectric liner that fills a respective one of the barrier trenches constitutes a dielectric wall structure.
19. The method of claim 18, wherein each pair of dielectric wall structures formed in a respective pair of barrier trenches has a greater lateral extent than the pair of lengthwise sidewalls of the dielectric spacer plates.
20. The method of claim 18, wherein each pair of dielectric wall structures formed in a respective pair of barrier trenches comprises angled sidewalls located within a respective vertical plane that is at an angle in a range from 15 degrees to 75 degrees with respect to a vertical plane including the first horizontal direction.
Type: Application
Filed: Jun 18, 2019
Publication Date: Dec 24, 2020
Inventors: Yoshitaka OTSU (Yokkaichi), Kei NOZAWA (Nagoya), Naoto HOJO (Yokkaichi), Hirofumi TOKITA (Yokkaichi), Eiji HAYASHI (Nagoya), Masanori TERAHARA (Yokkaichi)
Application Number: 16/444,186
