# US 7,410,839 B2 · Thin film transistor and manufacturing method thereof

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- Number: US 7,410,839 B2
- Document ID: US7410839B2
- Status: Granted
- Kind: B2
- Application number: 11/410,071
- Filed: 2006-04-25
- Published: 2006-11-02
- Granted: 2008-08-12
- Earliest claimed: 2005-04-28
- Assignees: Semiconductor Energy Laboratory Co., Ltd.
- Inventors: Atsuo Isobe; Shunpei Yamazaki
- Web page: https://patentgrep.com/patent/US7410839B2

## CPC

- H10D 86/0214: {using temporary substrates}
- H10D 30/6739: {Conductor-insulator-semiconductor electrodes}
- H10D 86/40: characterised by multiple TFTs
- H10D 86/60: wherein the TFTs are in active matrices
- H10K 59/12: Active-matrix OLED [AMOLED] displays
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES

## Abstract

The present invention provides a thin film transistor in which a substantial length of a channel is shortened to miniaturize a semiconductor device and a manufacturing method thereof. In addition, the present invention provides a semiconductor device which realizes high-speed operation and high-performance of the semiconductor device and a manufacturing method thereof. Further in addition, it is an object of the present invention to provide a manufacturing method in which a manufacturing process is simplified. The semiconductor device of the present invention has an island-shaped semiconductor film formed over a substrate having an insulating surface and a gate electrode formed over the island-shaped semiconductor film, in which the gate electrode is oxidized its surface by high-density plasma to be slimmed and the substantial length of a channel is shortened.

## Claims

### Claim 1

A method for manufacturing a thin film transistor comprising the steps of:
forming an amorphous semiconductor film over a substrate having an insulating surface;
forming a crystalline semiconductor film by crystallizing the amorphous semiconductor film;
forming an island-shaped semiconductor film by etching the crystalline semiconductor film;
forming a gate insulating film over the island-shaped semiconductor film;
forming a conductive film over the gate insulating film;
forming a gate electrode by etching the conductive film; and
slimming the gate electrode by oxidizing a surface of the gate electrode using high-density plasma.

### Claim 2 (depends on 1)

The method according to claim 1, wherein a high electron density of the high-density plasma is 1.0×1011 cm−3 to 1.0×1013 cm−3 and an electron temperature is 0.5 to 1.5 eV.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the surface of the gate electrode is oxidized using a mixed gas of oxygen, hydrogen, and argon in the slimming step.

### Claim 4 (depends on 1)

The method according to claim 1, wherein an oxide film formed on the surface of the gate electrode contains a rare gas element.

### Claim 5

A method for manufacturing a thin film transistor comprising the steps of:
forming an amorphous semiconductor film over a substrate having an insulating surface;
forming a crystalline semiconductor film by crystallizing the amorphous semiconductor film;
forming an island-shaped semiconductor film by etching the crystalline semiconductor film;
forming a gate insulating film over the island-shaped semiconductor film;
forming a conductive film over the gate insulating film;
forming a gate electrode by etching the conductive film;
slimming the gate electrode by oxidizing a surface of the gate electrode using high-density plasma; and
removing an oxide film formed over the surface of the gate electrode.

### Claim 6 (depends on 5)

The method according to claim 5, wherein a high electron density of the high-density plasma is 1.0×1011 cm−3 to 1.0×1013 cm−3 and an electron temperature is 0.5 to 1.5 eV.

### Claim 7 (depends on 5)

The method according to claim 5, wherein the surface of the gate electrode is oxidized using a mixed gas of oxygen, hydrogen, and argon in the slimming step.

### Claim 8

A method for manufacturing a thin film transistor comprising the steps of:
forming an amorphous semiconductor film over a substrate having an insulating surface;
forming a crystalline semiconductor film by crystallizing the amorphous semiconductor film;
forming an island-shaped semiconductor film by etching the crystalline semiconductor film;
forming a gate insulating film over the island-shaped semiconductor film;
forming a conductive film over the gate insulating film;
forming a gate electrode by etching the conductive film;
slimming the gate electrode by oxidizing a surface of the gate electrode using high-density plasma;
doping the island-shaped semiconductor film with first impurity ion using the gate electrode as a mask;
forming a sidewall on a side surface of the gate electrode; and
doping the island-shaped semiconductor film with second impurity ion to have a higher concentration of that of the first impurity ion, using the gate electrode and the sidewall as a mask.

### Claim 9 (depends on 8)

The method according to claim 8, wherein a high electron density of the high-density plasma is 1.0×1011 cm−3 to 1.0×1013 cm−3 and an electron temperature is 0.5 to 1.5 eV.

### Claim 10 (depends on 8)

The method according to claim 8, wherein the first impurity ion and the second impurity ion are a same impurity ion.

### Claim 11 (depends on 8)

The method according to claim 8, wherein the surface of the gate electrode is oxidized using a mixed gas of oxygen, hydrogen, and argon in the slimming step.

### Claim 12 (depends on 8)

The method according to claim 8, wherein an oxide film formed on the surface of the gate electrode contains a rare gas element.

### Claim 13

A method for manufacturing a thin film transistor comprising the steps of:
forming an amorphous semiconductor film over a substrate having an insulating surface;
forming a crystalline semiconductor film by crystallizing the amorphous semiconductor film;
forming an island-shaped semiconductor film by etching the crystalline semiconductor film;
forming a gate insulating film over the island-shaped semiconductor film;
forming a conductive film over the gate insulating film;
forming a gate electrode by etching the conductive film;
slimming the gate electrode by oxidizing a surface of the gate electrode using high-density plasma;
removing an oxide film formed over the surface of the gate electrode;
doping the island-shaped semiconductor film with first impurity ion using the gate electrode as a mask;
forming a sidewall on a side surface of the gate electrode; and
doping the island-shaped semiconductor film with second impurity ion to have a higher concentration of that of the first impurity ion, using the gate electrode and the sidewall as a mask.

### Claim 14 (depends on 13)

The method according to claim 13, wherein a high electron density of the high-density plasma is 1.0×1011 cm−3 to 1.0×1013 cm−3 and an electron temperature is 0.5 to 1.5 eV.

### Claim 15 (depends on 13)

The method according to claim 13, wherein the first impurity ion and the second impurity ion are a same impurity ion.

### Claim 16 (depends on 13)

The method according to claim 13, wherein the surface of the gate electrode is oxidized using a mixed gas of oxygen, hydrogen, and argon in the slimming step.