METHOD AND STRUCTURE OF FORMING SELF-ALIGNED RMG GATE FOR VFET
An intermediate semiconductor structure in fabrication includes a silicon semiconductor substrate, a hard mask of silicon nitride (SiN) over the substrate and a sacrificial layer of polysilicon or amorphous silicon over the hard mask. The sacrificial layer is patterned into sidewall spacers, each of the sidewall spacers having vertically tapered inner and outer sidewalls providing a rough triangular shape. The rough triangular sidewall spacers are used as a temporary hard mask to pattern the SiN hard mask.
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This application is a continuation application of U.S. patent application Ser. No. 15/212,755, filed Jul. 18, 2016, and entitled “METHOD AND STRUCTURE OF FORMING SELF-ALIGNED RMG GATE FOR VFET,” the entirety of which is hereby incorporated herein by reference.
TECHNICAL FIELDThis invention relates to vertical field effect transistors (VFET) and more particularly to forming self-aligned replacement metal gates therefor.
BACKGROUND INFORMATIONCurrently, the fabrication of VFETs utilize a gate first fabrication technique. Gate first fabrication techniques refer to a situation where the gate is patterned prior to the annealing step used to activate the source and drain. However, in gate last techniques, a dummy gate is used to occupy the gate space during the annealing process and a replacement metal gate is inserted into the dummy gate area after the anneal. The gate last technique and the use of replacement metal gates avoids the difficult thermal issues normally encountered with use of the gate first technique.
Accordingly, it is desirable to provide a self-aligned replacement metal gate method and structure for forming self-aligned replacement metal gates for vertical field effect transistors to provide desired thermal characteristics and effective area scaling.
SUMMARY OF THE INVENTIONIn accordance with one aspect of the invention, a method of providing a fin structure is disclosed. The fin structure includes a fin with sacrificial material above and adjacent the fin, with the fin structure being above a substrate adjacent a source or drain. The method includes removing a first portion of the sacrificial material above the fin to form an opening within the sacrificial material on top of the fin, forming a top source or drain within the opening on top of the fin, removing a second portion of the sacrificial material adjacent the top source or drain, depositing a spacer above and adjacent the top source or drain, depositing a gate material above the spacer and below the spacer to the sides of the fin, and removing the gate material above the bottom portion of the spacer to form a self aligned gate around the fin and a vertical field effect transistor.
The sacrificial material includes a first sacrificial material. A top portion of the first sacrificial material located above and adjacent said fin structure is removed to allow a remaining portion of the first sacrificial material to remain adjacent said fin. A second sacrificial material may be deposited above the remaining first sacrificial material so that the sacrificial material includes a first sacrificial material, the second sacrificial material, and a hard mask on the top of the fin.
The first sacrificial material may be a thin oxide surrounding the fin structure and an amorphous silicon deposited on top of the thin oxide. The second sacrificial material may be an oxide. The removing of a first portion of the sacrificial material above the fin to form an opening within the sacrificial material on top of the fin may include removing the hard mask above or on top of said fin. The self-aligned contact (SAC) cap may be deposited above the top source or drain within the oxide. The method may also include removing the oxide prior to depositing a spacer above and adjacent the top source or drain. Also, removing a third portion of the sacrificial material adjacent the fin may include removing the amorphous silicon.
The method may further include removing the thin oxide, which may be a silicon oxide. The method may also include providing a bottom spacer above the source or drain and substrate adjacent the fin. And, may include depositing a high K dielectric material on the bottom spacer, where the spacer and the fin form an intermediate structure, and annealing the intermediate structure.
The method may also include depositing a work function metal as part of the gate material and a metal over the work function metal as part of the gate material.
Removing the gate material above the bottom portion of the spacer may include removing the work function metal and the metal.
The method may further include removing annealed high K material above the spacer above and adjacent the top source or drain, depositing a second lithography stack over the barrier stack, performing a second lithography to pattern the at least one via opening, and etching to form at least one via opening.
The method may also include providing multiple fin structures, multiple top sources or drains to form multiple vertical field effect transistors. The fin structures may be parallel spaced with at least two vertical field effect transistors spaced apart and aligned along lengths thereof and forming at least one additional gate connecting aligned on parallel spaced vertical field effect transistors.
In another aspect of the invention, the method includes providing a fin structure having a fin with a hard mask on top of the fin. The fin structure is above a substrate adjacent a source or drain. The method includes depositing one or more sacrificial materials above and along sides of the fin structure, removing a top portion of the one or more sacrificial materials above a top of the fin to form an opening within the one or more sacrificial materials, forming a top source or drain within the opening on the top of said fin, removing a portion of the one or more sacrificial materials above and adjacent the top source or drain, depositing a spacer above the top source or drain, removing additional portions of the one or more sacrificial materials surrounding sides of the fin, depositing gate material above the spacer and below the spacer to the sides of the fin, and removing the gate material above the bottom portion of the spacer to form a self aligned gate around the fin and vertical field effort transistor.
In another aspect of the invention, the invention includes an intermediate semiconductor structure having a fin structure. The fin structure includes a fin above a substrate adjacent a bottom source or drain, a top source or drain located on the top of the fin, a spacer located above and surrounding the top source or drain and adjacent a top portion of the fin, a self-aligned gate structure located below the top spacer and above a bottom spacer located above said substrate and source or drain, and one or more work function layers located between the bottom spacer and side walls of the fin and top spacer.
One or more aspects of the present invention are particularly pointed out and distinctly claimed as examples in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Aspects of the present invention and certain features, advantages, and details thereof, are explained more fully below with reference to the non-limiting examples illustrated in the accompanying drawings. Descriptions of well-known materials, fabrication tools, processing techniques, etc., are omitted so as not to unnecessarily obscure the invention in detail. It should be understood, however, that the detailed description and the specific examples, while indicating aspects of the invention, are given by way of illustration only, and are not by way of limitation. Various substitutions, modifications, additions, and/or arrangements, within the spirit and/or scope of the underlying inventive concepts will be apparent to those skilled in the art from this disclosure.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” is not limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the 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 “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include (and any form of include, such as “includes” and “including”)”, and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a method or device that “comprises,” “has,” “includes” or “contains” one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more steps or elements. Likewise, a step of a method or an element of a device that “comprises,” “has,” “includes” or “contains” one or more features possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances the modified term may sometimes not be appropriate, capable or suitable. For example, in some circumstances, an event or capacity can be expected, while in other circumstances the event or capacity cannot occur—this distinction is captured by the terms “may” and “may be.”
As used herein, “depositing” may include any now known or later developed techniques appropriate for the material to be deposited including but not limited to, for example: chemical vapor deposition (CVD), low-pressure CVD (LPCVD), plasma-enhanced CVD (PECVD), semi-atmosphere CVD (SACVD) and high density plasma CVD (HDPCVD), rapid thermal CVD (RTCVD), ultra-high vacuum CVD (UHVCVD), limited reaction processing CVD (LRPCVD), metal-organic CVD (MOCVD), sputtering deposition, ion beam deposition, electron beam deposition, laser assisted deposition, thermal oxidation, thermal nitridation, spin-on methods, physical vapor deposition (PVD), atomic layer deposition (ALD), chemical oxidation, molecular beam epitaxy (MBE), plating, evaporation.
Reference is made below to the drawings, which are not drawn to scale for ease of understanding, wherein the same reference numbers are used throughout different figures designate the same or similar components.
In accordance with one aspect of this invention, the following describes a method for manufacturing a fin structure, wherein this fin structure includes a fin with a sacrificial material above and/or adjacent to the fin. The fin structure also being above a substrate while being adjacent to a source or drain. The figures referenced are numbered and are labeled (A) and (B) to show the corresponding method for a negative channel field-effect transistor on the figures labeled with (A) and the corresponding method for a positive channel field-effect transistor on the figures labeled with (B).
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Following these steps, device 10 may be further processed following a known set of steps for conventional VFINFET device flow to form a connecting wire to bottom S/D, gate, and top S/D, followed by a back-end-of build.
Thus, as described above, methods according to certain embodiments allow for an RMG gate that has been self-aligned to a vertical fin using the above patterning techniques. The whole high-k/metal gate formation is after bottom and top S/D formation, thus, the high-k and WFM won't see any thermal impact due to the thermal budget during S/D formation. Also, due to the unique shape of the structure, different metal gate 78 materials can be used to vary the threshold voltage (Vt) without concern for how to recess the different metals in order to define the gate length, since the unique shape of the high K dielectric layer 70 allows for self-patterning. Additionally, in recessing the gate, this also allows for protection from any plasma damage to the gate during the recessing.
Claims
1. An intermediate semiconductor structure comprising a fin structure comprising a fin above a substrate adjacent a bottom source or drain;
- a top source or drain located on the top of the fin;
- a top spacer located above and surrounding said top source or drain and adjacent a top portion of said fin;
- a self-aligned gate structure located below said top spacer and above a bottom spacer located above said substrate and source or drain; and
- one or more work function layers located between said bottom spacer and side walls of said fin and top spacer.
2. The intermediate semiconductor structure of claim 1, wherein the top source or drain comprises a phosphorus doped silicon material or a boron doped SiGe material.
3. The intermediate semiconductor structure of claim 1, wherein the top spacer and the bottom spacer each comprise a nitride material.
4. The intermediate semiconductor structure of claim 1, wherein the self-aligned gate structure comprises a high-k dielectric layer adjacent the fin, the one or more work function layers, and a gate metal adjacent the one or more work function layers.
5. The intermediate semiconductor structure of claim 4, wherein the high-k dielectric layer comprises HfO2, ZrO2, Al2O3, TiO2, Ta2O5, lanthanide oxides and mixtures thereof, silicates, YSZ (yttria-stabilized zirconia), BST, BT, ST, or SBT.
6. The intermediate semiconductor structure of claim 4, wherein the one or more work function layers comprise cobalt, titanium, aluminum, TiN, TaN, TiC, or TiAl.
7. The intermediate semiconductor structure of claim 4, wherein the gate metal comprises tungsten.
8. The intermediate semiconductor structure of claim 1, wherein the fin comprises a doped semiconductor material.
9. The intermediate semiconductor structure of claim 8, wherein the structure is an NFET and the fin is doped with phosphorous.
10. The intermediate semiconductor structure of claim 1, wherein the structure is a PFET and the fin is doped with boron.
11. The intermediate semiconductor structure of claim 8, wherein the semiconductor material comprises a type material.
12. The intermediate semiconductor structure of claim 8, wherein the semiconductor material comprises silicon or silicon germanium.
13. The intermediate semiconductor structure of claim 1, wherein the bottom source or drain comprises silicon or silicon germanium.
Type: Application
Filed: Aug 22, 2017
Publication Date: Jan 18, 2018
Applicant: GLOBALFOUNDRIES Inc. (Grand Cayman)
Inventors: Ruilong XIE (Schenectady, NY), Chanro PARK (Clifton Park, NY), Min Gyu SUNG (Latham, NY), Hoon KIM (Halfmoon, NY)
Application Number: 15/683,228