HETEROGENEOUS METALLIZATION USING SOLID DIFFUSION REMOVAL OF METAL INTERCONNECTS
A method for forming trenches of an interconnect network in a substrate. The method includes forming a first trench in the substrate, which has a first width. The method also includes forming a second trench in the substrate, which has a second width that is greater than the first width. The method also includes depositing a metal layer into the trenches, applying a dielectric over the metal, and diffusing metal atoms from the trenches to the dielectric. The dielectric absorbs a majority of the metal atoms from the first trench while simultaneously absorbing only a minority of metal atoms from the second trench.
This application is a divisional of U.S. application Ser. No. 15/280,518, entitled “HETEROGENEOUS METALLIZATION USING SOLID DIFFUSION REMOVAL OF METAL INTERCONNECTS”, filed Sep. 29, 2016, which is incorporated herein by reference in its entirety.
The present invention relates in general to the field of semiconductor fabrication methodologies and resulting device structures. More specifically, the present invention relates to fabrication methodologies and resulting structures for a semiconductor device having a heterogeneous metal interconnect structure containing both narrow and wide trenches or lines that can be formed simultaneously.
Semiconductor devices and components, which are referred to collectively herein as integrated circuit (IC) components, include a plurality of circuit elements (e.g., transistors, resistors, diodes, capacitors, etc.) communicatively connected together on a semiconductor substrate (i.e., a wafer or a chip). IC components are coupled to one another by providing a network of interconnected metallization layers and conductive trenches formed in the wafer/chip. Metallization layers and trenches are often formed using copper (Cu), which facilitates the development of smaller metal components, reduced energy usage, and higher-performance processors. Efficient routing of these metallization layers and trenches through multi-layered chip designs requires the formation of multi-level or multi-layered metallization layer and trench patterning schemes.
Embodiments are directed to a device with an interconnect network of trenches in a substrate. The device includes a first trench having a first width dimension and a second trench having a second width dimension that is greater than the first width dimension. The device also includes a first metal layer in the second trench and a second metal layer in the first and second trenches, with the second metal layer located over any first metal present in the trenches. The device also includes a hybrid interconnection structure of first and second trenches containing the first and second metals, where the hybrid interconnection structure is formed simultaneously, and a dielectric layer.
Additional features and advantages are realized through techniques described herein. Other embodiments and aspects are described in detail herein. For a better understanding, refer to the description and to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter which is regarded as embodiments is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the embodiments are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The drawings are not necessarily to scale. The drawings, some of which are merely pictorial and schematic representations, are not intended to portray specific parameters of the invention. The drawings are intended to depict only typical embodiments of the invention, and therefore should not be considered as limiting. In the drawings, like numbering represents like elements.
Various embodiments of the present invention will now be described with reference to the related drawings. Alternate embodiments can be devised without departing from the scope of this invention. Various connections might be set forth between elements in the following description and in the drawings. These connections, unless specified otherwise, can be direct or indirect, and the present invention is not intended to be limiting in this respect. Accordingly, a coupling of entities can refer to either a direct or an indirect connection.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this invention. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, the use of the terms “a”, “an”, etc., do not denote a limitation of quantity, but rather denote the presence of one or more of the referenced items. It will be further understood that the terms “comprises” and/or “comprising”, or “includes” and/or “including”, when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.
In addition, it will be understood that when an element as a layer, region, or substrate is referred to as being “on” or “over”, or “disposed on” another element, it can be directly on the other element or intervening elements can also be present. In contrast, when an element is referred to as being “directly on”, “directly over”, or “disposed proximately to” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or directly coupled to the other element, or intervening elements can be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.
For the sake of brevity, conventional techniques related to semiconductor device and integrated circuit fabrication can be described in detail herein. Moreover, the various tasks and process steps described herein can be incorporated into a more comprehensive procedure or process having additional steps or functionality not described in detail herein. In particular, various steps in the manufacture of semiconductor devices and semiconductor-based integrated circuits are well-known and so, in the interest of brevity, many conventional steps will only be mentioned briefly herein or will be omitted entirely without providing the well-known process details.
By way of background, however, a more general description of the semiconductor device fabrication processes that can be utilized in implementing one or more embodiments of the present invention will now be provided. Although specific fabrication operations used in implementing one or more embodiments of the present invention can be individually known, the described combination of operations and/or resulting structures of the present invention are unique. Thus, the unique combination of the operations described in connection with the fabrication of semiconductor devices according to the present invention utilize a variety of individually known physical and chemical processes performed on a semiconductor (e.g., silicon) substrate, some of which are described in the following immediately following paragraphs.
In general, the various processes used to form a micro-chip that will be packaged into an integrated circuit fall into four general categories, namely, film deposition, removal/etching, semiconductor doping and patterning/lithography. Deposition is any process that grows, coats, or otherwise transfers a material onto the wafer. Available technologies include physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition (ECD), molecular beam epitaxy (MBE) and more recently, atomic layer deposition (ALD) among others. Removal/etching is any process that removes material from the wafer. Examples include etch processes (either wet or dry), and chemical-mechanical planarization (CMP), and the like. Semiconductor doping is the modification of electrical properties by doping, for example, transistor sources and drains, generally by diffusion and/or by ion implantation. These doping processes are followed by furnace annealing or by rapid thermal annealing (RTA). Annealing serves to activate the implanted dopants. Films of both conductors (e.g., poly-silicon, aluminum, copper, etc.) and insulators (e.g., various forms of silicon dioxide, silicon nitride, etc.) are used to connect and isolate transistors and their components. Selective doping of various regions of the semiconductor substrate allows the conductivity of the substrate to be changed with the application of voltage. By creating structures of these various components, millions or even billions of transistors can be built and wired together to form the complex circuitry of a modern microelectronic device.
Fundamental to the above-described fabrication processes is semiconductor lithography, i.e., the formation of three-dimensional relief images or patterns on the semiconductor substrate for subsequent transfer of the pattern to the substrate. In semiconductor lithography, the patterns are on a light sensitive polymer called a photo-resist. To build the complex structures that make up a transistor and the many wires that connect the millions of transistors of a circuit, lithography and etch pattern transfer steps are repeated multiple times. Each pattern being printed on the wafer is aligned to the previously formed patterns and slowly the conductors, insulators and selectively doped regions are built up to form the final device.
Turning now to a description of technologies that are more specifically relevant to embodiments of the present invention, an interconnect network includes a configuration of metallization layers/lines and metal trenches. The metal trenches are disposed in trenches and run perpendicular to the semiconductor substrate. The trenches are formed in a dielectric material. The metal trenches are communicatively connected to the metallization layers/lines. The metal trenches can also run parallel to the semiconductor substrate.
An interconnect network that is copper based, when compared with an aluminum (Al) based interconnect network, can allow higher speed signal transmissions between large numbers of transistors on a complex semiconductor chip. Accordingly, when fabricating an IC, a metal conductor such as copper is typically used for forming the interconnect network because copper has a low resistivity and high current carrying capacity as compared to aluminum.
Resistivity is the measure of how much a material opposes electric current caused by a voltage being placed across the material as a function of length. However, when copper is utilized to form an interconnect network, electromigration can occur when using copper in trenches with very small dimensions. In the present description, electromigration effects become significant as trenches become smaller in width, and are referred to as “narrow” or “first” trenches with a first width of less than 30 nm. Trenches with a width of greater than 30 nm are termed “wide” or “second” trenches. Electromigration is the gradual displacement of atoms of a metal conductor due to the high density of current passing through the metal conductor.
For high-speed and low-power operation, the resistivity of copper trenches should be relatively low as compared to other materials. In addition, the ability of the materials used to form the trenches to minimize electromigration should be pronounced. A material such as Tantalum Nitride (TaN) can be used as a barrier layer at the bottom of the trenches. When the TaN barrier layer is thinned down at the trench bottom, the trench resistivity becomes low. However, this adversely affects the electromigration performance of the trench due to the “short length effect” or the “blech length effect.” The short length effect occurs when the copper trench with electromigration blocking boundaries is of a sufficiently short length (e.g., between 1 and 10 micrometers) that the migrating copper atoms impinge on the blocking boundary creating a backwards stress gradient that prevents further migration of copper. It is desirable for the material to have a blocking boundary layer that provides both low resistivity and a high ability to block electromigration.
With continued reduction in sizing of IC components, copper trenches and trenches faces several technical challenges. The limited volume of copper in a trench necessarily limits the current-carrying capability of the trenches. Also, electromigration lifetimes for narrow trenches are reduced. Finally, copper resistivity values increase with a reduction in wire width.
Turning now to an overview of aspects of the present invention, embodiments described herein includes forming an interconnect network of copper, and then replacing the copper in the narrow trenches with another metal, such as a pure metal and/or a metal silicide. These materials provide improved electromigration behavior, are able to carry large current densities, and are less affected by surface scattering effects as compared to copper, which can result in a lower total line resistance than a copper line assuming the same correctional area.
Embodiments of the present invention utilizes a single process to replace the existing copper in narrow trenches of an interconnect network while maintaining the copper in wide trenches. In embodiments, a double-layered copper interconnect structure is used with different formation methods. The copper interconnect network can include two different conductive materials, a first of which is copper in embodiments, and a second of which is not copper. The second conductive (non-copper) layer material functions as a barrier layer, which obviates the need for a barrier layer between two conductive materials. In embodiments, the second conductive layer is cobalt (Co). Other materials that can be used for the second conductive layer include ruthenium (Ru), tungsten (W), molybdenum (Mo), gold (Au), silver (Ag), aluminum (Al), and various alloys thereof. In addition to copper (Cu), other materials can be used for the first conductive material, including copper alloys, cobalt (Co), ruthenium (Ru), tungsten (W), molybdenum (Mo), gold (Au), silver (Ag), aluminum (Al), and various alloys thereof.
Turning now to a more detailed description of embodiments of the present invention,
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of embodiments of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form described. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
1. A device having trenches in a substrate, the device comprising:
- a first trench of the trenches in the substrate, wherein the first trench comprises a first width dimension;
- a second trench of the trenches in the substrate, wherein the second trench comprises a second width dimension that is greater than the first width dimension;
- a first metal layer in first trench and the second trench, wherein the first metal layer comprises first metal atoms in which the first trench devoid of significantly all of the first metal atoms;
- a second metal layer in the first trench and the second trench, wherein the second metal layer is located over the first metal present in the first and second trenches; and
- a hybrid interconnection structure including the first trench and the second trench, comprised of the first metal layer and the second metal layer, wherein the hybrid interconnection structure is formed simultaneously.
2. The device of claim 1, wherein the first width dimension is less than 30 nm.
3. The device of claim 1, wherein the second width dimension is greater than 30 nm.
4. The device of claim 1, wherein the first trench and the second trench are formed at a same layer or level.
5. The device of claim 1, wherein the first metal layer is comprised of copper or a copper alloy or metal including silver, gold, aluminum, rhodium, iridium, tungsten, molybdenum, cobalt, nickel, ruthenium or metal silicide including tungsten silicide, titanium silicide, nickel silicide, or cobalt silicide.
6. The device of claim 1, wherein the second metal layer is comprised of metal including silver, gold, aluminum, rhodium, iridium, tungsten, molybdenum, cobalt, nickel, ruthenium or metal silicide including tungsten silicide, titanium silicide, nickel silicide, or cobalt silicide.
7. The device of claim 1, further comprising a planarized surface of the hybrid interconnection structure to remove any metal overburden.
10. The device of claim 1, further comprising a protective layer over the first trench and the second trench.
11. The device of claim 1, further comprising a first barrier layer located at a bottom of the first and second trenches.
12. The device of claim 11, wherein the first barrier layer is comprised of tantalum nitride.
15. The device of claim 1, wherein the substrate is comprised of a first conductive layer, a diffusion barrier layer, and a second conductive layer.
16. The device of claim 15, wherein a copper-manganese seed is used for a deposition of the first conductive layer.
17. The device of claim 15, wherein the first conductive layer is comprised of copper or a copper alloy.
18. The device of claim 15, wherein the diffusion barrier layer is comprised of tantalum nitride, titanium nitride, pyroxmangite, or tantalum manganese oxide.
19. The device of claim 15, wherein the second conductive layer is comprised of cobalt or a cobalt alloy.
20. The device of claim 1, wherein a dielectric layer is used to absorb the first metal atoms from the first trench.
Filed: Feb 16, 2017
Publication Date: Mar 29, 2018
Inventors: Benjamin D. Briggs (Waterford, NY), Lawrence A. Clevenger (LaGrangeville, NY), Bartlet H. DeProspo (Goshen, NY), Huai Huang (Saratoga, NY), Christopher J. Penny (Saratoga Springs, NY), Michael Rizzolo (Albany, NY)
Application Number: 15/434,335