Method for manufacturing thin film transistor using multi-tone mask

• US 8,980,685 B2
• Filed: 02/27/2014
• Issued: 03/17/2015
• Est. Priority Date: 10/24/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Suzawa, Hideomi, Sasagawa, Shinya, Muraoka, Taiga, Ito, Shunichi, Hosoba, Miyuki
• Primary Examiner(s): Le, Thao X
• Assistant Examiner(s): ZHU, SHENG-BAI
• Application Number:
  US14/191,853
• Publication Number:
  US 20140179058A1
• Time in Patent Office: 383 Days
• Field of Search: 257/43, 257/57, 257/72, 438/104, 438/151, 438/148, 438/149
• US Class Current: 438/104
• 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 29/66742 Thin film unipolar transistors
• CPC Class Codes: H01L 29/66969 of devices having semiconductor bodies not comprising group 14 or group 13/15 materials comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials, comprising cuprous oxide or cuprous iodide H01L21/02365
• CPC Class Codes: H01L 29/78621 with LDD structure or an extension or an offset region or characterised by the doping profile
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate

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-staggered 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. In etching steps, a first etching step is performed by wet etching in which an etchant is used, and a second etching step is performed by dry etching in which an etching gas is used.

Claims

1. A method for manufacturing a semiconductor device, comprising:

forming a gate electrode layer over an insulating surface, wherein the gate electrode layer comprises a stack of a first layer comprising Ti and a second layer comprising Cu;

forming a gate insulating layer over the gate electrode layer, wherein the gate insulating layer comprises a stack of a silicon nitride layer and a first silicon oxide layer, and the silicon nitride layer covers the second layer;

forming an oxide semiconductor film over the gate electrode layer;

forming a conductive film over the gate electrode layer;

forming a first mask layer over the gate insulating layer, the oxide semiconductor film, and the conductive film;

forming an oxide semiconductor layer and a conductive layer by etching the oxide semiconductor film and the conductive film with the use of the first mask layer in a first etching step;

forming a second mask layer by ashing the first mask layer;

forming an oxide semiconductor layer having a depression, a source electrode layer, and a drain electrode layer by etching the oxide semiconductor layer and the conductive layer with the use of the second mask layer in a second etching step; and

performing an oxygen radical treatment on the oxide semiconductor layer having the depression,

wherein the first mask layer is formed using a light-exposure mask,

wherein wet etching in which an etchant is used is employed in the first etching step,

wherein dry etching in which an etching gas is used is employed in the second etching step, and

wherein the oxide semiconductor layer having the depression includes a region with a smaller thickness than a region overlapping with the source electrode layer or the drain electrode layer.

2. The method for manufacturing a semiconductor device, according to claim 1, wherein the oxide semiconductor film includes indium, gallium, and zinc.

3. The method for manufacturing a semiconductor device, according to claim 1, wherein the etching gas includes chlorine.

4. The method for manufacturing a semiconductor device, according to claim 1, wherein the etching gas includes oxygen.

5. The method for manufacturing a semiconductor device, according to claim 1, wherein a mixed solution of phosphoric acid, acetic acid, and nitric acid is used as the etchant in the first etching step.

6. The method for manufacturing a semiconductor device, according to claim 1, wherein a half-tone mask or a gray-tone mask is used as the light-exposure mask.

7. The method for manufacturing a semiconductor device, according to claim 1, wherein the first layer comprising Ti is stacked over the second layer comprising Cu.

8. The method for manufacturing a semiconductor device, according to claim 1, wherein the oxygen radical treatment is performed in an atmosphere of O₂or N₂O.

9. The method for manufacturing a semiconductor device, according to claim 1, wherein the oxygen radical treatment is performed with no bias voltage applied to the substrate side.

10. A method for manufacturing a semiconductor device, comprising:

forming a gate electrode layer over an insulating surface, wherein the gate electrode layer comprises a stack of a first layer comprising Ti and a second layer comprising Cu;

forming a gate insulating layer over the gate electrode layer, wherein the gate insulating layer comprises a stack of a silicon nitride layer and a first silicon oxide layer, and the silicon nitride layer covers the second layer;

forming a first oxide semiconductor film and a second oxide semiconductor film over the gate electrode layer;

forming a conductive film over the gate electrode layer;

forming a first mask layer over the gate insulating layer, the first oxide semiconductor film, the second oxide semiconductor film, and the conductive film;

forming a first oxide semiconductor layer, a second oxide semiconductor layer, and a conductive layer by etching the first oxide semiconductor film, the second oxide semiconductor film, and the conductive film with the use of the first mask layer in a first etching step;

forming a second mask layer by ashing the first mask layer;

forming an oxide semiconductor layer having a depression, a source region, a drain region, a source electrode layer, and a drain electrode layer by etching the first oxide semiconductor layer, the second oxide semiconductor layer, and the conductive layer with the use of the second mask layer in a second etching step; and

performing an oxygen radical treatment on the oxide semiconductor layer having the depression,

wherein the first mask layer is formed using a light-exposure mask,

wherein wet etching in which an etchant is used is employed in the first etching step,

wherein dry etching in which an etching gas is used is employed in the second etching step, and

wherein the oxide semiconductor layer having the depression includes a region with a smaller thickness than a region overlapping with the source region or the drain region.

11. The method for manufacturing a semiconductor device, according to claim 10, wherein each of the first oxide semiconductor film and the second oxide semiconductor film includes indium, gallium, and zinc.

12. The method for manufacturing a semiconductor device, according to claim 10, wherein the first oxide semiconductor film has lower electrical conductivity than the second oxide semiconductor film.

13. The method for manufacturing a semiconductor device, according to claim 10, wherein the etching gas includes chlorine.

14. The method for manufacturing a semiconductor device, according to claim 10, wherein the etching gas includes oxygen.

15. The method for manufacturing a semiconductor device, according to claim 10, wherein a mixed solution of phosphoric acid, acetic acid, and nitric acid is used as the etchant in the first etching step.

16. The method for manufacturing a semiconductor device, according to claim 10, wherein a half-tone mask or a gray-tone mask is used as the light-exposure mask.

17. The method for manufacturing a semiconductor device, according to claim 10, wherein the first layer comprising Ti is stacked over the second layer comprising Cu.

18. The method for manufacturing a semiconductor device, according to claim 10, wherein the oxygen radical treatment is performed in an atmosphere of O₂or N₂O.

19. The method for manufacturing a semiconductor device, according to claim 10, wherein the oxygen radical treatment is performed with no bias voltage applied to the substrate side.