# US 7,608,869 B2 · Thin film transistor and method of fabricating the same

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- Number: US 7,608,869 B2
- Document ID: US7608869B2
- Status: Granted
- Kind: B2
- Application number: 11/509,863
- Filed: 2006-08-24
- Published: 2007-03-08
- Granted: 2009-10-27
- Earliest claimed: 2005-08-25
- Assignees: Samsung Mobile Display Co., Ltd.
- Inventors: Tae-Hoon Yang; Ki-Yong Lee; Jin-Wook Seo; Byoung-Keon Park
- Web page: https://patentgrep.com/patent/US7608869B2

## CPC

- H10P 14/2922: {being non-crystalline insulating materials, e.g. glass or polymers}
- H10D 30/0314: {of lateral top-gate TFTs comprising only a single gate}
- H10D 30/0321: {comprising silicon, e.g. amorphous silicon or polysilicon}
- H10P 14/3238: {being insulating materials}
- H10P 14/3411: {Silicon, silicon germanium or germanium}
- H10P 14/3806: {using crystallisation-enhancing elements}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A thin film transistor and a method of fabricating the same are disclosed. The method includes: sequentially depositing an amorphous silicon layer, a capping layer, and a metal catalyst layer; annealing the entire layer to crystallize the amorphous silicon layer into a polysilicon layer; removing the capping layer; and, when the capping layer is perfectly removed to make a contact angle of the polysilicon layer within a range of about 40 to about 80°, forming a semiconductor layer using the polysilicon layer.

## Claims

### Claim 1

A thin film transistor comprising:
a substrate;
a semiconductor layer containing a polysilicon material crystallized by an super grain silicon (SGS) crystallization method and disposed over the substrate, wherein the polysilicon material is defined as having a contact angle with a liquid droplet of about 40 to about 80 degrees when the liquid droplet is placed onto a flat surface made of the polysilicon material; and
a gate insulating layer, a gate electrode, an interlayer insulating layer, and source and drain electrode, which are disposed over the semiconductor layer.

### Claim 2 (depends on 1)

The thin film transistor according to claim 1, wherein the liquid droplet has a diameter between about 2 mm and about 5 mm.

### Claim 3 (depends on 1)

The thin film transistor according to claim 1, wherein the liquid droplet comprises a water droplet.

### Claim 4 (depends on 1)

The thin film transistor according to claim 1, wherein the polysilicon material contains a metal catalyst, the metal catalyst having a concentration of about 1013 atoms/cm2 or less.

### Claim 5

A method of making a thin film transistor, the method comprising:
forming a semiconductor layer over a substrate, the semiconductor layer comprising amorphous silicon;
forming a capping layer over the semiconductor layer;
forming a metal catalyst layer over the capping layer, the metal catalyst layer comprising a metal catalyst;
annealing the substrate, the semiconductor layer, the capping layer, and the metal catalyst layer, such that at least a portion of the metal catalyst diffuses into the semiconductor layer, and such that the amorphous silicon is crystallized into polysilicon;
removing the metal catalyst layer; and
removing the capping layer from over the semiconductor layer, to an extent that, when a liquid droplet is placed over the semiconductor layer, a contact angle between the semiconductor layer and the liquid droplet is from about 40 degrees to about 80 degrees.

### Claim 6 (depends on 5)

The method of claim 5, further comprising measuring the contact angle after removing the capping layer.

### Claim 7 (depends on 5)

The method of claim 5, wherein the capping layer is single-layered.

### Claim 8 (depends on 5)

The method of claim 5, wherein the capping layer comprises multiple layers.

### Claim 9 (depends on 5)

The method of claim 5, wherein the capping layer comprises one or more materials selected from the group consisting of silicon oxide and silicon nitride.

### Claim 10 (depends on 9)

The method of claim 9, wherein the polysilicon is more hydrophobic than the capping layer.

### Claim 11 (depends on 9)

The method of claim 9, wherein, after removing the catalyst layer and before removing the capping layer, the capping layer has a contact angle of about 40 degrees or less when a liquid droplet is placed on the capping layer.

### Claim 12 (depends on 5)

The method of claim 5, further comprising patterning the semiconductor layer after removing the capping layer.

### Claim 13 (depends on 5)

The method of claim 5, wherein the liquid droplet has a diameter between about 2 mm and about 5 mm.

### Claim 14 (depends on 5)

The method of claim 5, wherein the liquid droplet comprises a water droplet.

### Claim 15 (depends on 5)

The method of claim 5, wherein the contact angle is an acute angle formed between a baseline of the liquid droplet and a tangential line at a droplet boundary.

### Claim 16

A method of making a display device comprising a thin film transistor (TFT), the method comprising:
providing an intermediate device comprising a substrate, a polysilicon layer over the substrate, a capping layer over the polysilicon layer;
removing the capping layer from over the polysilicon layer; and
determining whether the capping layer has been substantially completely removed from over the polysilicon layer, wherein the determining comprises: placing a liquid droplet over the polysilicon layer; and measuring a contact angle between a baseline of the liquid droplet and a tangential line at a droplet boundary.

### Claim 17 (depends on 16)

The method of claim 16, further comprising, after measuring the contact angle, patterning the semiconductor layer if the measured contact angle is from about 40 degrees to about 80 degrees.