# US 5,705,411 A · Reactive ion etching to physically etch thin film semiconductor

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- Number: US 5,705,411 A
- Document ID: US5705411A
- Status: Granted
- Kind: A
- Application number: 08/476,026
- Filed: 1995-06-07
- Granted: 1998-01-06
- Earliest claimed: 1990-03-27
- Assignees: Canon Kabushiki Kaisha
- Inventors: Masato Yamanobe; Takayuki Ishii
- Web page: https://patentgrep.com/patent/US5705411A

## CPC

- H10F 30/282: Insulated-gate field-effect transistors [IGFET], e.g. MISFET [metal-insulator-semiconductor field-effect transistor] phototransistors
- H10D 30/6732: {Bottom-gate only TFTs}
- H10D 30/6746: {Amorphous silicon}
- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A thin film semiconductor device includes a gate electrode, a gate insulating electrode, a thin film semiconductor layer, an ohmic layer, source and drain electrodes, and a protective layer. The protective layer contains an impurity for controlling conductivity.

## Claims

### Claim 1

A method for producing a thin film semiconductor device which comprises a transistor having a thin film semiconductor layer, a gate electrode provided under said thin film semiconductor layer through an insulating layer, and source and drain electrodes electrically connected to said thin film semiconductor layer comprising:
after forming said thin film semiconductor layer, subjecting to reactive ion etching a surface of said thin film semiconductor layer between said source and drain electrodes employing high frequency power of at least 250 W and a pressure not greater than 10 Pa to conduct physical etching and thereby electronically depleting a surface section of a channel area between said source and drain electrodes.

### Claim 2 (depends on 1)

The method according to claim 1, further comprising the steps for (a) forming an n-layer on said thin film semiconductor layer before forming said source and drain electrodes thereon, and (b) etching said n-layer formed on said thin film semiconductor layer by reactive ion etching.

### Claim 3 (depends on 1)

The method according to claim 1, wherein said thin film semiconductor layer comprises amorphous silicon including hydrogen.

### Claim 4 (depends on 1)

The method according to claim 1, including conducting said reactive ion etching with CF.sub.4 gas.

### Claim 5

A method for producing a thin film semiconductor device comprising the steps of:
providing a gate electrode on a substrate;
providing an insulating layer covering said gate electrode on said substrate;
providing a thin film semiconductor layer on said insulating layer;
providing an n-layer on said thin film semiconductor layer;
providing a conductive layer operating as a source or drain electrode on said n-layer; and
removing said n-layer formed between said source or drain electrode;
wherein said step of removing said n-layer includes a reactive ion etching step conducted under conditions to perform mainly a physical etching to deplete a surface side of said thin film semiconductor layer from which said n-layer is removed.

### Claim 6 (depends on 5)

A method according to claim 5, wherein the physical etching is conducted employing a high frequency power of at least 250 W and a pressure not higher than 10 Pa.

### Claim 7 (depends on 5)

A method according to claim 5, including employing an amorphous silicon including hydrogen as said thin film semiconductor layer.