# US 7,608,475 B2 · Buffer layer for promoting electron mobility and thin film transistor having the same

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

- Number: US 7,608,475 B2
- Document ID: US7608475B2
- Status: Granted
- Kind: B2
- Application number: 11/254,303
- Filed: 2005-10-19
- Published: 2006-02-23
- Granted: 2009-10-27
- Earliest claimed: 2003-01-07
- Assignees: Au Optronics Corporation
- Inventors: Long-Sheng Liao; Kun-Chih Lin; Chia-Tien Peng
- Web page: https://patentgrep.com/patent/US7608475B2

## CPC

- H10P 14/24: using chemical vapour deposition [CVD]
- H10D 30/0314: {of lateral top-gate TFTs comprising only a single gate}
- H10D 30/0321: {comprising silicon, e.g. amorphous silicon or polysilicon}
- H10D 30/6731: {Top-gate only TFTs}
- H10D 30/6745: {Polycrystalline or microcrystalline silicon}
- H10D 30/6758: {characterised by the insulating substrates}
- H10P 14/2922: {being non-crystalline insulating materials, e.g. glass or polymers}
- H10P 14/3211: {Silicon, silicon germanium or germanium}
- H10P 14/3238: {being insulating materials}
- H10P 14/3248: {consisting of two layers}
- H10P 14/3256: {Microstructure}
- H10P 14/3411: {Silicon, silicon germanium or germanium}
- H10P 14/3816: {Pulsed laser beam}
- H10P 32/15: {from the substrate during epitaxy, e.g. autodoping; Preventing or using autodoping}
- H10P 34/42: with electromagnetic radiation, e.g. laser annealing (laser cutting H10P54/20)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A buffer layer for promoting electron mobility. The buffer layer comprises amorphous silicon layer (a-Si) and an oxide-containing layer. The a-Si has high enough density that the particles in the substrate are prevented by the a-Si buffer layer from diffusing into the active layer. As well, the buffer, having thermal conductivity, provides a good path for thermal diffusion during the amorphous active layer's recrystallization by excimer laser annealing (ELA). Thus, the uniformity of the grain size of the crystallized silicon is improved, and electron mobility of the TFT is enhanced.

## Claims

### Claim 1

A method for forming a thin film transistor, comprising:
providing a substrate;
forming a buffer layer on the substrate, wherein the buffer layer comprises an amorphous silicon layer on the substrate, and a buffer dielectric layer on the amorphous silicon layer;
forming a amorphous silicon active layer on the buffer layer;
performing a excimer laser annealing (ELA) process to crystallize the amorphous silicon active layer to a polysilicon active layer;
forming a gate dielectric layer at least covering the polysilicon active layer; forming a gate electrode on the gate dielectric layer; and
doping the polysilicon active layer uncovered by the gate electrode to form a source region and a drain region using the gate electrode as a mask.

### Claim 2 (depends on 1)

The method for forming a thin film transistor as claimed in claim 1, wherein the grain size of the polysilicon active layer is enlarged and uniform during crystallizing the amorphous silicon active layer with excimer laser annealing (ELA) according to formation of the buffer comprising the amorphous silicon layer.