# US 6,294,442 B1 · Method for the formation of a polysilicon layer with a controlled, small silicon grain size during semiconductor device fabrication

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 6,294,442 B1
- Document ID: US6294442B1
- Status: Granted
- Kind: B1
- Application number: 09/459,135
- Filed: 1999-12-10
- Granted: 2001-09-25
- Earliest claimed: 1999-12-10
- Assignees: National Semiconductor Corporation
- Inventors: Abu-Hena Mostafa Kamal
- Web page: https://patentgrep.com/patent/US6294442B1

## CPC

- H10P 14/24: using chemical vapour deposition [CVD]
- H10D 64/01306: {the conductor comprising a layer of silicon contacting the insulator, e.g. polysilicon}
- H10P 14/2905: {Silicon, silicon germanium or germanium}
- H10P 14/3238: {being insulating materials}
- H10P 14/3411: {Silicon, silicon germanium or germanium}
- H10P 14/3456: {Polycrystalline}
- H10P 14/3802: {Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

Process for the formation of a polysilicon layer with a controlled, small silicon grain size that includes first providing a semiconductor substrate (such as a silicon wafer), followed by the formation of a silicon dioxide layer (such as a gate silicon dioxide layer) on the semiconductor substrate. Next, an amorphous silicon layer is deposited on the silicon dioxide layer. The amorphous silicon layer can be deposited using LPCVD at a temperature in the range of 520° C. to 560° C. and a pressure in the range of 150 mTorr to 250 mTorr. Next, a plurality of silicon crystallites are formed in the amorphous silicon layer by subjecting it to a first RTA cycle at a temperature in the range of 750° C. to 850° C. for a time period of 30 seconds to 90 seconds and a temperature ramp rate of at least 50° C. per second. Finally, the amorphous silicon layer with silicon crystallites is subjected to at least one additional thermal cycle, thereby growing the silicon crystallites into small silicon grains and forming a polysilicon layer with controlled, small silicon grain size.

## Claims

### Claim 1

A polysilicon layer forming method for formation of a polysilicon layer with controlled silicon grain size during a semiconductor device fabrication operation including semiconductor device fabrication steps, the polysilicon layer forming method comprising the steps of:
(a) providing a semiconductor substrate;
(b) forming a silicon dioxide layer on the surface of the semiconductor substrate;
(c) depositing an amorphous silicon layer having a thickness in the range of 1000 angstroms to 2500 angstroms on the silicon dioxide layer;
(d) forming a plurality of silicon crystallites in the amorphous silicon layer by subjecting the amorphous silicon layer to a first thermal cycle; and
(e) after forming the silicon crystallites, performing one of the semiconductor device fabrication steps in a manner subjecting the amorphous silicon layer and the silicon crystallites to at least one additional thermal cycle, thereby growing the silicon crystallites into silicon grains having silicon grain size not greater than 50 nm and forming a polysilicon layer with controlled silicon grain size not greater than 50 nm.

### Claim 2 (depends on 1)

The method of claim 1 wherein the depositing step deposits the amorphous silicon layer using a low pressure chemical vapor deposition technique at a temperature of less than 580° C. and a pressure in the range of 150 mTorr to 250 mTorr.

### Claim 3 (depends on 2)

The method of claim 2 wherein the depositing step deposits the amorphous silicon layer at a temperature in the range of 520° C. to 560° C.

### Claim 4 (depends on 3)

The method of claim 3 wherein the depositing step deposits the amorphous silicon layer at a temperature of 550° C.

### Claim 5 (depends on 2)

The method of claim 2 wherein the first thermal cycle has a temperature ramp rate of at least 50° C. per second and includes an annealing step at a temperature in the range of 750° C. to 850° C. for a time period in the range of 30 seconds to 90 seconds.

### Claim 6 (depends on 2)

The method of claim 2 wherein the first thermal cycle has a temperature ramp rate of at least 50° C. per second and includes an annealing step at a temperature in the range of 740° C. to 760° C. for a time period in the range of 54 seconds to 60 seconds.

### Claim 7 (depends on 2)

The method of claim 2 wherein the depositing step deposits an amorphous silicon layer with an rms surface roughness of less than 15 angstroms.

### Claim 8 (depends on 2)

The method of claim 2 wherein the depositing step deposits an amorphous silicon layer with a surface roughness of less than 1% of the thickness of the amorphous silicon layer.

### Claim 9 (depends on 1)

The method of claim 1 wherein the silicon grains grown during step (e) have silicon grain size in the range from 20 nm to 50 nm.

### Claim 10 (depends on 1)

The method of claim 1 wherein the silicon grains grown during step (e) have silicon grain size in the range from 20 nm to 30 nm.

### Claim 11 (depends on 1)

The method of claim 1, further including the step of patterning the amorphous silicon layer after step (c) but prior to step (d).

### Claim 12 (depends on 1)

The method of claim 1, further including the step of patterning the amorphous silicon layer with the silicon crystallites after step (d) but prior to step (e).

### Claim 13

A polysilicon layer forming method for formation of a polysilicon layer with controlled silicon grain size during a semiconductor device fabrication operation including semiconductor device fabrication steps, the polysilicon layer forming method comprising the steps of:
(a) providing a semiconductor substrate;
(b) forming a silicon dioxide layer on the surface of the semiconductor substrate;
(c) depositing an amorphous silicon layer on the silicon dioxide layer;
(d) forming a plurality of silicon crystallites in the amorphous silicon layer by subjecting the amorphous silicon layer to a first thermal cycle; and
(e) after forming the silicon crystallites, performing one of the semiconductor device fabrication steps in a manner subjecting the amorphous silicon layer and the silicon crystallites to at least one additional thermal cycle, thereby growing the silicon crystallites into silicon grains having silicon grain size not greater than 50 nm and forming a polysilicon layer with controlled silicon grain size not greater than 50 nm, wherein said one of the semiconductor device fabrication steps performed during step (e) is a step associated with the formation of silicon dioxide/silicon nitride sidewall spacers during the semiconductor device fabrication.

### Claim 14

A polysilicon layer forming method for the formation of a polysilicon layer with a controlled silicon grain size during a semiconductor device fabrication operation including semiconductor device fabrication steps, the polysilicon layer forming method comprising the steps of:
(a) providing a semiconductor substrate;
(b) forming a gate silicon dioxide layer on the surface of the semiconductor substrate;
(c) depositing an amorphous silicon layer on the gate silicon dioxide layer using a low pressure chemical vapor deposition technique at a temperature in the range of 520° C. to 560° C. and a pressure in the range of 150 mTorr to 250 mTorr, the amorphous silicon layer having a thickness in the range of 1000 angstroms to 2500 angstroms;
(d) forming a plurality of silicon crystallites in the amorphous silicon layer by subjecting the amorphous silicon layer to a first thermal cycle that includes a temperature ramp rate of at least 50° C. per second and an annealing step at a temperature in the range of 740° C. to 760° C. for a time period of 30 seconds to 90 seconds;
(e) patterning the amorphous silicon layer with the silicon crystallites therein to form a patterned amorphous silicon layer with said silicon crystallites therein, the patterned amorphous silicon layer including silicon gate electrodes with a width in the range of 0.10 μm to 0.25 μm ; and
(f) after step (e), performing one of the semiconductor device fabrication steps in such a manner as to subject the patterned amorphous silicon layer with said silicon crystallites to at least one additional thermal cycle, thereby converting said patterned amorphous silicon layer with said silicon crystallites into a patterned polysilicon layer with silicon grains of controlled size, wherein said silicon grains have grain size not greater than 50 nm.

### Claim 15 (depends on 14)

The method of claim 14, wherein said silicon grains of controlled size have grain size in the range from 20 nm to 50 nm.

### Claim 16 (depends on 15)

The method of claim 15, wherein said silicon grains of controlled size have grain size in the range from 20 nm to 30 nm.