# US 8,785,925 B2 · Thin film device

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- Number: US 8,785,925 B2
- Document ID: US8785925B2
- Status: Granted
- Kind: B2
- Application number: 13/571,966
- Filed: 2012-08-10
- Published: 2013-02-14
- Granted: 2014-07-22
- Earliest claimed: 2011-08-12
- Assignees: NLT Technologies, Ltd.
- Applicants: Kazushige Takechi
- Inventors: Kazushige Takechi
- Web page: https://patentgrep.com/patent/US8785925B2

## CPC

- H10D 30/6755: {Oxide semiconductors, e.g. zinc oxide, copper aluminium oxide or cadmium stannate}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

There is such an issue with a TFT using an oxide semiconductor film that oxygen deficit is generated in a surface region of the oxide semiconductor film after performing plasma etching of a source-drain electrode, and the off-current becomes increased. Disclosed is the TFT which includes: a gate electrode on an insulating substrate as a substrate; a gate insulating film on the gate electrode; an oxide semiconductor film on the gate insulating film; and a source/drain electrode on the oxide semiconductor film. It is the characteristic of the TFT that a surface layer containing at least either fluorine or chlorine exists in a part of the oxide semiconductor film where the source/drain electrode is not superimposed.

## Claims

### Claim 1

A thin film device, comprising a gate electrode on a substrate, a gate insulating film on the gate electrode, an oxide semiconductor film on the gate insulating film, and a source/drain electrode on the oxide semiconductor film, wherein
a surface layer contains a composition element of the oxide semiconductor film, a composition element of a part of the source/drain electrode in contact with the oxide semiconductor film, and at least either fluorine or chlorine exist in a part of the oxide semiconductor film where the source/drain electrode is not superimposed.

### Claim 2

A thin film device, comprising a gate electrode on a substrate, a gate insulating film on the gate electrode, an oxide semiconductor film on the gate insulating film, and a source/drain electrode on the oxide semiconductor film, wherein
a surface layer containing at least either fluorine or chlorine exists in a part of the oxide semiconductor film where the source/drain electrode is not superimposed, and
a mixed layer containing a mixture of the composition element of the oxide semiconductor film and the composition element of the part of the source/drain electrode in contact with the oxide semiconductor film exists in an interface between the oxide semiconductor film and the source/drain electrode.

### Claim 3

A thin film device, comprising a gate electrode on a substrate, a gate insulating film on the gate electrode, an oxide semiconductor film on the gate insulating film, and a source/drain electrode on the oxide semiconductor film, wherein
a surface layer containing at least either fluorine or chlorine exists in a part of the oxide semiconductor film where the source/drain electrode is not superimposed,
the thin film device further comprises a channel protection insulating film on the surface layer, and
the surface layer also exists in a part of the oxide semiconductor film where the source/drain electrode is superimposed.

### Claim 4 (depends on 3)

The thin film device as claimed in claim 3, wherein
a mixed layer constituted with a mixture of the composition element of the oxide semiconductor film, the composition element of the part of the source/drain electrode in contact with the oxide semiconductor film, and at least either fluorine or chlorine exists in an interface between the oxide semiconductor film and the source/drain electrode.

### Claim 5

A thin film device, comprising a gate electrode on a substrate, a gate insulating film on the gate electrode, an oxide semiconductor film on the gate insulating film, and a source/drain electrode on the oxide semiconductor film, wherein:
a mixed layer containing a mixture of a first composition element of the oxide semiconductor film and a second composition element of a part of the source/drain electrode in contact with the oxide semiconductor film exists in an interface between the oxide semiconductor film and the source/drain electrode; and
a quantity of atoms of the first and second composition elements of the mixed layer changes from the source/drain electrode side towards the oxide semiconductor film side.

### Claim 6 (depends on 2)

The thin film device as claimed in claim 2, wherein:
the surface layer contains indium, gallium, zinc, oxygen, titanium, and at least either fluorine or chlorine; and
the mixed layer contains indium, gallium, zinc, oxygen, and titanium.

### Claim 7 (depends on 4)

The thin film device as claimed in claim 4, wherein:
the surface layer contains indium, gallium, zinc, oxygen, and at least either fluorine or chlorine; and
the mixed layer contains indium, gallium, zinc, oxygen, titanium, and at least either fluorine or chlorine.

### Claim 8 (depends on 2)

The thin film device as claimed in claim 2, wherein:
the surface layer contains indium, gallium, zinc, oxygen, molybdenum, and at least either fluorine or chlorine; and
the mixed layer contains indium, gallium, zinc, oxygen, and molybdenum.

### Claim 9 (depends on 4)

The thin film device as claimed in claim 4, wherein:
the surface layer contains indium, gallium, zinc, oxygen, and at least either fluorine or chlorine; and
the mixed layer contains indium, gallium, zinc, oxygen, molybdenum, and at least either fluorine or chlorine.

### Claim 10 (depends on 5)

The thin film device as claimed in claim 5, wherein:
the mixed layer contains indium, gallium, zinc, oxygen, and titanium; and
a quantity of atoms of titanium of the mixed layer decreases from the source/drain electrode side towards the oxide semiconductor film side, and a quantity of atoms of indium or zinc of the mixed layer increases from the source/drain electrode side towards the oxide semiconductor film side.

### Claim 11 (depends on 5)

The thin film device as claimed in claim 5, wherein:
the mixed layer contains indium, gallium, zinc, oxygen, and molybdenum; and
a quantity of atoms of molybdenum of the mixed layer decreases from the source/drain electrode side towards the oxide semiconductor film side, and a quantity of atoms of indium or zinc of the mixed layer increases from the source/drain electrode side towards the oxide semiconductor film side.

### Claim 12 (depends on 1)

The thin film device as claimed in claim 1, wherein the oxide semiconductor film contains at least either indium or zinc.

### Claim 13 (depends on 1)

The thin film device as claimed in claim 1, wherein a proportion of the number of atoms of fluorine or the number of atoms of chlorine of the surface layer is between 0.1% and 73%, inclusive.

### Claim 14 (depends on 1)

The thin film device as claimed in claim 1, wherein the part of the source/drain electrode in contact with the oxide semiconductor film contains at least titanium or molybdenum.