Method for manufacturing semiconductor device

• US 8,878,178 B2
• Filed: 12/06/2012
• Issued: 11/04/2014
• Est. Priority Date: 10/24/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Ito, Shunichi, Hosoba, Miyuki
• Primary Examiner(s): Luu, Chuong A
• Application Number:
  US13/706,569
• Publication Number:
  US 20130105793A1
• Time in Patent Office: 698 Days
• Field of Search: 257/43, 257/72, 257/57, 257/288, 257/347, 257/368
• US Class Current: 257/43
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 27/1288 employing particular masking sequences or specially adapted masks, e.g. half-tone mask
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H01L 29/78693 the semiconducting oxide being amorphous

Abstract

An object is to manufacture a semiconductor device including an oxide semiconductor at low cost with high productivity in such a manner that a photolithography process is simplified by reducing the number of light-exposure masks. In a method for manufacturing a semiconductor device including a channel-etched inverted-stagger thin film transistor, an oxide semiconductor film and a conductive film are etched using a mask layer formed with the use of a multi-tone mask which is a light-exposure mask through which light is transmitted so as to have a plurality of intensities. The etching step is performed by wet etching in which an etching solution is used.

Claims

1. A semiconductor device comprising:

a substrate having an insulating surface;

a gate electrode layer over the substrate;

a gate insulating layer over the gate electrode layer;

an oxide semiconductor layer over the gate insulating layer;

a source electrode layer and a drain electrode layer electrically connected to the oxide semiconductor layer;

an insulating layer over and in contact with the oxide semiconductor layer, the source electrode layer, and the drain electrode layer;

a light-transmitting conductive layer over the insulating layer, the light-transmitting conductive layer being electrically connected to one of the source electrode layer and the drain electrode layer; and

a cathode of a light-emitting element over and in contact with the light-transmitting conductive layer,

wherein the oxide semiconductor layer comprises a region with a smaller thickness than a region overlapping with the source electrode layer or the drain electrode layer, and

wherein an end portion of the oxide semiconductor layer has a curved surface.

2. The semiconductor device according to claim 1, wherein the oxide semiconductor layer includes indium, gallium, and zinc.

3. The semiconductor device according to claim 1, wherein the insulating layer comprises one selected from a silicon nitride film, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, and a tantalum oxide film.

4. The semiconductor device according to claim 1, wherein the semiconductor device is included in a pixel portion.

5. The semiconductor device according to claim 1, wherein the semiconductor device is included in a driver circuit.

6. A semiconductor device comprising:

a substrate having an insulating surface;

a gate electrode layer over the substrate;

a gate insulating layer over the gate electrode layer;

a first oxide semiconductor layer over the gate insulating layer;

a source electrode layer electrically connected to the first oxide semiconductor layer with a second oxide semiconductor layer interposed therebetween;

a drain electrode layer electrically connected to the first oxide semiconductor layer with a third oxide semiconductor layer interposed therebetween;

an insulating layer over and in contact with the first oxide semiconductor layer, the source electrode layer, and the drain electrode layer;

a light-transmitting conductive layer over the insulating layer, the light-transmitting conductive layer being electrically connected to one of the source electrode layer and the drain electrode layer; and

a cathode of a light-emitting element over and in contact with the light-transmitting conductive layer,

wherein the first oxide semiconductor layer comprises a region with a smaller thickness than a region overlapping with the source electrode layer or the drain electrode layer, and

wherein an end portion of the first oxide semiconductor layer has a curved surface.

7. The semiconductor device according to claim 6, wherein the first oxide semiconductor layer includes indium, gallium, and zinc.

8. The semiconductor device according to claim 6, wherein each of the second oxide semiconductor layer and the third oxide semiconductor layer includes a crystal grain in an amorphous structure.

9. The semiconductor device according to claim 6, wherein the insulating layer comprises one selected from a silicon nitride film, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, and a tantalum oxide film.

10. The semiconductor device according to claim 6, wherein the semiconductor device is included in a pixel portion.

11. The semiconductor device according to claim 6, wherein the semiconductor device is included in a driver circuit.