# US 5,710,454 A · Tungsten silicide polycide gate electrode formed through stacked amorphous silicon (SAS) multi-layer structure.

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- Number: US 5,710,454 A
- Document ID: US5710454A
- Status: Granted
- Kind: A
- Application number: 08/638,671
- Filed: 1996-04-29
- Granted: 1998-01-20
- Earliest claimed: 1996-04-29
- Assignees: Vanguard International Semiconductor Corporation
- Inventors: Shye Lin Wu
- Web page: https://patentgrep.com/patent/US5710454A

## CPC

- H10D 64/662: {the conductor further comprising additional layers, e.g. multiple silicon layers having different crystal structures}
- 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}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A method for forming a tungsten silicide polycide gate electrode within a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), and the tungsten silicide polycide gate electrode which is formed through the method. Formed upon a semiconductor substrate is a gate oxide layer. Formed upon the gate oxide layer is a first polysilicon layer which is formed through annealing a first amorphous silicon layer. Formed upon the first polysilicon layer is a second polysilicon layer which is formed through annealing a second amorphous silicon layer. Formed upon the second polysilicon layer is a tungsten silicide layer formed through a Chemical Vapor Deposition (CVD) method. The first polysilicon layer and the second polysilicon layer have a crystallite size no greater than about 0.3 microns, and the first polysilicon layer and the second polysilicon layer have a dopant concentration larger than about 1E16 atoms per cubic centimeter. Optionally, at least a third polysilicon layer may be added through annealing at least a third amorphous silicon layer between the second polysilicon layer and the tungsten silicide layer. Optionally, an fourth amorphous silicon layer may be added directly beneath the tungsten silicide layer.

## Claims

### Claim 1

A method for forming a tungsten silicide polycide gate electrode within a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) comprising:
forming upon a semiconductor substrate a gate oxide layer;
forming upon the gate oxide layer a first polysilicon layer through annealing a first amorphous silicon layer;
forming upon the first polysilicon layer a second polysilicon layer through annealing a second amorphous silicon layer;
forming upon the second polysilicon layer a tungsten silicide layer through a Chemical Vapor Deposition method, wherein the first polysilicon layer and the second polysilicon layer each have a crystallite size of no greater than about 0.3 microns, and the first polysilicon layer and the second polysilicon layer each have a dopant concentration of larger than about 1E16 atoms per cubic centimeter.

### Claim 2 (depends on 1)

The method of claim 1 wherein the thickness of the gate oxide layer is from about 30 to about 200 angstroms.

### Claim 3 (depends on 1)

The method of claim 1 wherein the thickness of the first polysilicon layer and the second polysilicon layer is from about 200 to about 2000 angstroms each.

### Claim 4 (depends on 1)

The method of claim 1 wherein the first amorphous silicon layer and the second amorphous silicon layer are formed through a Low Pressure Chemical Vapor Deposition (LPCVD) method employing silane as a silicon source material.

### Claim 5 (depends on 1)

The method of claim 1 wherein the first amorphous silicon layer and the second amorphous silicon layer are annealed at a temperature of from about 700 to about 950 degrees centigrade for a time period of from about 10 to about 100 minutes in an inert atmosphere.

### Claim 6 (depends on 5)

The method of claim 5 wherein the inert atmosphere is a nitrogen inert atmosphere at a pressure of about 200 to about 760 mtorr.

### Claim 7 (depends on 1)

The method of claim 1 wherein the first amorphous silicon layer and the second amorphous silicon layer are annealed sequentially to form the first polysilicon layer and the second polysilicon layer, respectively.

### Claim 8 (depends on 1)

The method of claim 1 wherein the first amorphous silicon layer and the second amorphous silicon layer are annealed concurrently to form the first polysilicon layer and the second polysilicon layer, respectively.

### Claim 9 (depends on 1)

The method of claim 1 wherein the thickness of the tungsten silicide layer is from about 100 to about 2000 angstroms.

### Claim 10 (depends on 1)

The method of claim 1 wherein the tungsten silicide layer is formed through a Chemical Vapor Deposition (CVD) co-deposition method employing tungsten hexafluoride and a silicon source material chosen from the group of silicon source materials consisting of silane and dichlorosilane.

### Claim 11 (depends on 1)

The method of claim 1 further comprising forming at least a third polysilicon layer through annealing at least a third amorphous silicon layer, the third polysilicon layer and any additional polysilicon layers so formed residing between the second polysilicon layer and the tungsten silicide layer, the third polysilicon layer and any additional polysilicon layers each having a crystallite size no greater than about 0.3 microns, a dopant concentration larger than about 1E16 atoms per cubic centimeter and a thickness of from about 200 to about 2000 angstroms.

### Claim 12 (depends on 1)

The method of claim 1 further comprising forming a fourth amorphous silicon layer directly beneath the tungsten silicide layer, the fourth amorphous silicon layer having a dopant concentration of larger than about 1E16 atoms per cubic centimeter and a thickness of from about 200 to about 2000 angstroms.

### Claim 13 (depends on 1)

The method of claim 1 further comprising forming a pair of source/drain electrodes adjoining a pair of opposite edges of the first polysilicon layer, the second polysilicon layer and the tungsten silicide layer, thus forming a Metal Oxide Semiconductor Field Effect Transistor (MOSFET).

### Claim 14 (depends on 13)

The method of claim 13 further comprising forming at least a patterned first insulator layer and a patterned conductor layer upon the Metal Oxide Semiconductor Field Effect Transistor (MOSFET), thus forming the Metal Oxide Semiconductor Field Effect Transistor (MOSFET) within an integrated circuit.

### Claim 15

A gate electrode within a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) comprising:
a semiconductor substrate having a gate oxide layer formed thereupon;
a first polysilicon layer formed upon the gate oxide layer;
a second polysilicon layer formed upon the first polysilicon layer; and,
a tungsten silicide layer formed through a Chemical Vapor Deposition (CVD) method upon the second polysilicon layer, wherein the first polysilicon layer and the second polysilicon layer each have a crystallite size of no greater than about 0.3 microns and the first polysilicon layer and the second polysilicon layer each have a dopant concentration of larger than about 1E16 atoms per cubic centimeter.

### Claim 16 (depends on 15)

The gate electrode of claim 15 wherein the thickness of the gate oxide layer is from about 30 to about 200 angstroms.

### Claim 17 (depends on 15)

The gate electrode of claim 15 wherein the thickness of the first polysilicon layer and the second polysilicon layer is from about 200 to about 2000 angstroms each.

### Claim 18 (depends on 15)

The gate electrode of claim 15 wherein the thickness of the tungsten silicide layer is from about 100 to about 2000 angstroms.

### Claim 19 (depends on 15)

The gate electrode of claim 15 further comprising at least a third polysilicon layer between the second polysilicon layer and the tungsten silicide layer, the third polysilicon layer and any additional polysilicon layers having a crystallite size of no greater than about 0.3 microns, a dopant concentration of larger than about 1E16 atoms per cubic centimeter and a thickness of from about 200 to about 2000 angstroms.

### Claim 20 (depends on 15)

The gate electrode of claim 15 further comprising an amorphous silicon layer directly beneath the tungsten silicide layer, the amorphous silicon layer having a dopant concentration of larger than about 1E16 atoms per cubic centimeter and a thickness of from about 200 to about 2000 angstroms.

### Claim 21 (depends on 15)

The gate electrode of claim 15 further comprising a pair of source/drain electrodes within the semiconductor substrate adjoining a pair of opposite edges of the first polysilicon layer, the second polysilicon layer and the tungsten silicide layer, thus yielding a Metal Oxide Semiconductor Field Effect Transistor (MOSFET).

### Claim 22 (depends on 21)

The gate electrode of claim 21 further comprising at least a patterned first insulator layer and a patterned conductor layer upon the Metal Oxide Semiconductor Field Effect Transistor (MOSFET), thus yielding the Metal Oxide Semiconductor Field Effect Transistor (MOSFET) within an integrated circuit.