# US 6,297,152 B1 · CVD process for DCS-based tungsten silicide

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- Number: US 6,297,152 B1
- Document ID: US6297152B1
- Status: Granted
- Kind: B1
- Application number: 08/764,471
- Filed: 1996-12-12
- Granted: 2001-10-02
- Earliest claimed: 1996-12-12
- Assignees: Applied Materials, Inc.
- Inventors: Toshio Itoh; Mei Chang
- Web page: https://patentgrep.com/patent/US6297152B1

## CPC

- H10P 14/43: Chemical deposition, e.g. chemical vapour deposition [CVD]
- C23C 16/0281: {of metallic sub-layers (C23C16/029 takes precedence)}
- C23C 16/42: Silicides
- H10D 64/0112: {using conductive layers comprising silicides}
- H10D 64/01312: {the additional layer comprising a metal or metal silicide formed by deposition, i.e. without a silicidation reaction, e.g. sputter deposition}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A multiple step chemical vapor deposition process for depositing a tungsten silicide layer on a substrate. A first step of the deposition process includes a pretreatment step in which WF6 is introduced into a deposition chamber. Next, the introduction of WF6 is stopped and a silicon-containing gas, e.g., SiH4, is introduced into the chamber. Finally, during a third step, the SiH4 flow is stopped and DCS and WF6 are introduced into the chamber to deposit a tungsten silicide layer on the substrate.

## Claims

### Claim 1

A process for forming a layer on a substrate, said process comprising:
(a) forming a polysilicon layer over said substrate;
(b) thereafter, depositing a tungsten silicide layer on said polysilicon layer in a chemical vapor deposition process by:
(i) during a first process stage, introducing a tungsten-containing gas into a substrate processing chamber in an amount less than 5 cubic centimeters without flowing a silicon-containing source into said chamber;
(ii) during a second process stage after said first stage, flowing a silicon-containing gas into said chamber without flowing a tungsten-containing gas; and
(iii) during a third process stage after said second stage, flowing a process gas comprising said tungsten-containing gas and dichlorosilane into the chamber to deposit said tungsten silicide layer, wherein an average bulk ratio of silicon to tungsten in said tungsten silicide layer is between 2.0 to 2.8.

### Claim 2 (depends on 1)

The process of claim 1 further comprising:
(d) during a fourth process stage, between said first and second stages flowing an inert gas into said chamber to purge said chamber of said tungsten-containing gas.

### Claim 3 (depends on 1)

The process of claim 1 wherein said tungsten-containing gas introduced during said first process stage is selected from the group consisting of WF6, WCl6, WOF4, WOCl4 and W(CO)6.

### Claim 4 (depends on 1)

The process of claim 1 wherein said third process stage comprises nucleation and deposition steps, wherein in said nucleation step pressure in said chamber is at a first pressure level and in said deposition step pressure in said chamber is at a second pressure that is less than said first pressure.

### Claim 5 (depends on 1)

The process of claim 1 wherein said silicon-containing gas comprises SiH4 or DCS.

### Claim 6 (depends on 1)

The process of claim 1 wherein said first process stage limits an amount of tungsten incorporated into said tungsten silicide layer at an interface between said tungsten silicide layer and said substrate.

### Claim 7 (depends on 1)

The process of claim 1 wherein said polysilicon layer is doped with phosphorus.

### Claim 8 (depends on 1)

The process of claim 1 wherein said average bulk ratio of silicon to tungsten is between 2.2 and 2.6.

### Claim 9 (depends on 1)

The process of claim 1 wherein said tungsten silicide layer exhibits a substantially uniform silicon to tungsten ratio throughout the entire thickness of said layer such that the average silicon to tungsten ratio within each strata of said layer is between ±10 percent of said average bulk ratio of silicon to tungsten.

### Claim 10 (depends on 1)

The process of claim 1 wherein the flow of said tungsten-containing gas is diluted in a flow of argon at a ratio of at least 20:1 and introduced at a rate between 0.01 and 5.0 sccm.

### Claim 11 (depends on 10)

The process of claim 10 wherein said tungsten-containing gas consists of WF6.

### Claim 12 (depends on 1)

The process of claim 1 wherein said amount of tungsten-containing gas introduced into said chamber during said first process stage is between 0.000167 and 5.0 cubic centimeters.

### Claim 13 (depends on 12)

The process of claim 12 wherein said tungsten-containing gas consists of WF6.

### Claim 14 (depends on 1)

The process of claim 1 wherein said amount of tungsten-containing gas introduced into said chamber during said first process stage is between 0.0005 and 0.8333 cubic centimeters.

### Claim 15 (depends on 14)

The process of claim 14 wherein said tungsten-containing gas consists of WF6.

### Claim 16 (depends on 1)

The process of claim 1 wherein said tungsten-containing gas consists of WF6.

### Claim 17 (depends on 1)

The process of claim 1 wherein said amount of tungsten-containing gas introduced into said chamber during said first process stage is less than 0.01 cubic centimeters.

### Claim 18 (depends on 17)

The process of claim 17 wherein said tungsten-containing gas consists of WF6.

### Claim 19

A process for forming a layer on a substrate, said process comprising:
(a) forming a polysilicon layer over said substrate;
(b) thereafter, depositing a tungsten silicide layer on said polysilicon layer in a chemical vapor deposition process by:
(i) during a first process stage, introducing a tungsten-containing gas into a substrate processing chamber without flowing a silicon-containing source into said chamber, wherein said first process stage introduces said tungsten-containing gas by:
flowing said tungsten-containing gas and an inert gas into a source line that leads to said chamber while diverting said gases away from said chamber into an exhaust line; then stopping the flow of said tungsten-containing gas while maintaining said flow of said inert gas into said source line; and directing said inert gas into said chamber so that a residual amount of said tungsten-containing source within said source line is directed into said chamber;
(ii) during a second process stage after said first stage, flowing a silicon-containing gas into said chamber without flowing a tungsten-containing gas; and
(iii) during a third process stage after said second stage, flowing a process gas comprising said tungsten-containing gas and dichlorosilane into the chamber to deposit said tungsten silicide layer, wherein an average bulk ratio of silicon to tungsten in said tungsten silicide layer is between 2.0 to 2.8.

### Claim 20 (depends on 19)

The process of claim 19 wherein said tungsten-containing gas introduced during said first process stage is flowed into said source line at a rate of about 5 sccm or less.

### Claim 21 (depends on 19)

The process of claim 19 wherein said first process stage limits an amount of tungsten incorporated into said tungsten silicide layer at an interface between said tungsten silicide layer and said substrate.

### Claim 22 (depends on 19)

The process of claim 19 wherein said polysilicon layer is doped with phosphorus.

### Claim 23 (depends on 19)

The process of claim 19 wherein said average bulk ratio of silicon to tungsten is between 2.2 and 2.6.

### Claim 24 (depends on 19)

The process of claim 19 wherein said tungsten silicide layer exhibits a substantially uniform silicon to tungsten ratio throughout the entire thickness of said layer such that the average silicon to tungsten ratio within each strata of said layer is between ±10 percent of said average bulk ratio of silicon to tungsten.

### Claim 25 (depends on 19)

The process of claim 19 wherein said silicon-containing gas consists of SiH4 or DCS.

### Claim 26 (depends on 19)

The process of claim 19 wherein said residual amount is between 1 and 100 ppm in volume of the substrate processing chamber.

### Claim 27 (depends on 26)

The process of claim 26 wherein said tungsten-containing gas consists of WF6.

### Claim 28 (depends on 19)

The process of claim 19 wherein said residual amount is between 7 and 50 ppm in volume of the substrate processing chamber.

### Claim 29 (depends on 28)

The process of claim 28 wherein said tungsten-containing gas consists of WF6.

### Claim 30 (depends on 19)

The process of claim 19 wherein said tungsten-containing gas introduced during said first process stage is selected from the group consisting of WF6, WCl6, WOF4, WOCl4 and W(CO)6.

### Claim 31 (depends on 19)

The process of claim 19 wherein said residual amount is less than 0.01 cubic centimeters.

### Claim 32 (depends on 31)

The process of claim 31 wherein said tungsten-containing gas consists of WF6.

### Claim 33 (depends on 19)

The process of claim 19 wherein said flow of said tungsten-containing gas and said inert gas is directed into said chamber for 2 seconds or less before stopping said flow of said tungsten-containing gas.

### Claim 34

A process for forming a layer on a substrate, said process comprising:
(a) forming a polysilicon layer over said substrate;
(b) thereafter, depositing a tungsten silicide layer on said polysilicon layer in a chemical vapor deposition process by:
(i) during a first process stage, introducing a tungsten-containing gas into a substrate processing chamber in an amount that provides a partial layer of tungsten atoms less than one atom thick at the film surface without flowing a silicon-containing source into said chamber;
(ii) during a second process stage after said first stage, flowing a silicon-containing gas into said chamber without flowing a tungsten-containing gas; and
(iii) during a third process stage after said second stage, flowing a process gas comprising said tungsten-containing gas and dichlorosilane into the chamber to deposit said tungsten silicide layer, wherein an average bulk ratio of silicon to tungsten in said tungsten silicide layer is between 2.0 to 2.8.

### Claim 35 (depends on 34)

The process of claim 34 wherein said polysilicon layer is doped with phosphorus.

### Claim 36 (depends on 35)

The process of claim 35 wherein said amount of tungsten-containing gas is less than 100 parts per million in chamber volume.

### Claim 37 (depends on 36)

The process of claim 36 wherein said tungsten-containing gas consists of WF6.