# US 10,121,903 B2 · Semiconductor device

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- Number: US 10,121,903 B2
- Document ID: US10121903B2
- Status: Granted
- Kind: B2
- Application number: 15/439,997
- Filed: 2017-02-23
- Published: 2017-06-08
- Granted: 2018-11-06
- Earliest claimed: 2012-11-30
- Assignees: Semiconductor Energy Laboratory Co., Ltd.
- Applicants: Semiconductor Energy Laboratory Co., Ltd.
- Inventors: Shunpei Yamazaki; Yasutaka Nakazawa; Masami Jintyou; Junichi Koezuka; Kenichi Okazaki; Takuya Hirohashi; Shunsuke Adachi
- Web page: https://patentgrep.com/patent/US10121903B2

## CPC

- H10D 30/6757: {characterised by the structure of the channel, e.g. transverse or longitudinal shape or doping profile (TFTs having channel structures for preventing kink or snapback effects H10D30/6708; TFTs having lightly-doped source or drain extensions H10D30/6715)}
- H10D 30/6713: {characterised by the properties of the source or drain regions, e.g. compositions or sectional shapes}
- H10D 30/6755: {Oxide semiconductors, e.g. zinc oxide, copper aluminium oxide or cadmium stannate}
- H10D 86/423: {comprising semiconductor materials not belonging to the Group IV, e.g. InGaZnO}
- H10D 86/60: wherein the TFTs are in active matrices
- H10D 99/00: Subject matter not provided for in other groups of this subclass
- H10P 14/412: {Deposition of metallic or metal-silicide materials}
- H10P 14/692: composed of oxides, glassy oxides or oxide-based glasses
- H10P 50/00: Etching of wafers, substrates or parts of devices
- H10P 50/28: of insulating materials
- H10K 59/1213: {the pixel elements being TFTs}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES

## Abstract

A semiconductor device including a transistor having a reduced number of oxygen vacancies in a channel formation region of an oxide semiconductor with stable electrical characteristics or high reliability is provided. A gate insulating film is formed over a gate electrode; an oxide semiconductor layer is formed over the gate insulating film; an oxide layer is formed over the oxide semiconductor layer by a sputtering method to form an stacked-layer oxide film including the oxide semiconductor layer and the oxide layer; the stacked-layer oxide film is processed into a predetermined shape; a conductive film containing Ti as a main component is formed over the stacked-layer oxide film; the conductive film is etched to form source and drain electrodes and a depression portion on a back channel side; and portions of the stacked-layer oxide film in contact with the source and drain electrodes are changed to an n-type by heat treatment.

## Claims

### Claim 1

A semiconductor device comprising:
a gate electrode;
a gate insulating film over the gate electrode;
a stacked-layer oxide film over the gate insulating film, the stacked-layer oxide film including a channel formation region; and
a source electrode and a drain electrode each over and in contact with the stacked-layer oxide film,
wherein:
the stacked-layer oxide film comprises a first layer and a second layer over the first layer,
the first layer and the second layer each contains In, Ga, Zn, and oxygen,
the second layer comprises:
a first region between the source electrode and the drain electrode;
a second region in contact with the source electrode; and
a third region in contact with the drain electrode,
the second region contains a metal element included in the source electrode,
the third region contains a metal element included in the drain electrode, and
the second region and the third region each have a lower resistivity than the channel formation region and comprise an n+ region by diffusion of the metal elements included in the source electrode and the drain electrode, respectively.

### Claim 2 (depends on 1)

The semiconductor device according to claim 1, wherein the gate electrode comprises a first layer containing Ta, and a second layer containing W over the first layer.

### Claim 3 (depends on 1)

The semiconductor device according to claim 1, wherein the source electrode and the drain electrode each comprise a first layer containing Ti, a second layer containing Cu over the first layer, and a third layer containing Ti over the second layer.

### Claim 4 (depends on 1)

The semiconductor device according to claim 1, wherein the first region has a smaller thickness than the second region and the third region.

### Claim 5 (depends on 1)

The semiconductor device according to claim 1, wherein the metal elements included in the source electrode and the drain electrode are Ti.

### Claim 6 (depends on 1)

The semiconductor device according to claim 1, wherein in the stacked-layer oxide film:
the first layer comprises a region of a first oxide semiconductor, and
the first oxide semiconductor includes a crystal part of which a c-axis is aligned in a direction of 80-100° with respect to a surface where the first layer is formed.

### Claim 7 (depends on 1)

The semiconductor device according to claim 1, wherein the first layer of the stacked-layer oxide film includes an In—Ga—Zn oxide with an atomic ratio between In, Ga, and Zn of 1:1:1.

### Claim 8 (depends on 1)

The semiconductor device according to claim 1, wherein in the stacked-layer oxide film:
the second layer comprises a region of a second oxide semiconductor, and
the second oxide semiconductor includes a crystal part with a size of 1-10 nm.

### Claim 9 (depends on 1)

The semiconductor device according to claim 1, wherein the second layer of the stacked-layer oxide film includes an In—Ga—Zn oxide with an atomic ratio between In, Ga, and Zn of 1:3:2.

### Claim 10

A semiconductor device comprising:
a gate electrode;
a gate insulating film over the gate electrode;
a stacked-layer oxide film over the gate insulating film, the stacked-layer oxide film including a channel formation region; and
a source electrode and a drain electrode each over and in contact with the stacked-layer oxide film,
wherein:
the stacked-layer oxide film comprises a first layer, a second layer over the first layer, and a depression portion between the source electrode and the drain electrode,
the first layer and the second layer each contains In, Ga, Zn, and oxygen,
the second layer comprises:
a first region in contact with the source electrode; and
a second region in contact with the drain electrode,
each of the first region and the second region is in contact with part of side surfaces of the depression portion,
the first region contains a metal element included in the source electrode,
the second region contains a metal element included in the drain electrode, and
the first region and the second region each have a lower resistivity than the channel formation region and comprise an n+ region by diffusion of the metal elements included in the source electrode and the drain electrode, respectively.

### Claim 11 (depends on 10)

The semiconductor device according to claim 10, wherein the gate electrode comprises a first layer containing Ta, and a second layer containing W over the first layer.

### Claim 12 (depends on 10)

The semiconductor device according to claim 10, wherein the source electrode and the drain electrode each comprise a first layer containing Ti, a second layer containing Cu over the first layer, and a third layer containing Ti over the second layer.

### Claim 13 (depends on 10)

The semiconductor device according to claim 10, wherein in the stacked-layer oxide film, a depth of the depression portion is larger than a thickness of each of the first region and the second region.

### Claim 14 (depends on 10)

The semiconductor device according to claim 10, wherein the metal elements included in the source electrode and the drain electrode are Ti.

### Claim 15 (depends on 10)

The semiconductor device according to claim 10, wherein in the stacked-layer oxide film:
the first layer comprises a region of a first oxide semiconductor, and
the first oxide semiconductor includes a crystal part of which a c-axis is aligned in a direction of 80-100° with respect to a surface where the first layer is formed.

### Claim 16 (depends on 10)

The semiconductor device according to claim 10, wherein the first layer of the stacked-layer oxide film includes an In—Ga—Zn oxide with an atomic ratio between In, Ga, and Zn of 1:1:1.

### Claim 17 (depends on 10)

The semiconductor device according to claim 10, wherein in the stacked-layer oxide film:
the second layer comprises a region of a second oxide semiconductor, and
the second oxide semiconductor includes a crystal part with a size of 1-10 nm.

### Claim 18 (depends on 10)

The semiconductor device according to claim 10, wherein the second layer of the stacked-layer oxide film includes an In—Ga—Zn oxide with an atomic ratio between In, Ga, and Zn of 1:3:2.