Method for manufacturing semiconductor device

Patent metadata

Field	Value
Publication number	US-9450080-B2
Application number	US-201414570422-A
Country	US
Kind code	B2
Filing date	Dec 15, 2014
Priority date	Dec 20, 2013
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

The semiconductor device is manufactured by the following method. A first oxide semiconductor film is formed over a first gate electrode and a first insulating film, oxygen is added to the first oxide semiconductor film, and then a second oxide semiconductor film is formed over the first oxide semiconductor film. Then, heat treatment is performed. Next, part of the first insulating film, part of the first oxide semiconductor film, and part of the second oxide semiconductor film are etched to form a first gate insulating film having a projection. Next, a pair of electrodes is formed over the second oxide semiconductor film, and a third oxide semiconductor film is formed over the second oxide semiconductor film and the pair of electrodes. Then, a second gate insulating film is formed over the third oxide semiconductor film, and a second gate electrode is formed over the second gate insulating film.

First claim

What is claimed is:

1. A method for manufacturing a semiconductor device, comprising the steps of:
forming a first gate electrode;
forming a first insulating film over the first gate electrode;
forming a first oxide semiconductor film over the first insulating film;
adding oxygen to the first oxide semiconductor film;
forming a second oxide semiconductor film over the first oxide semiconductor film after adding the oxygen;
performing a heat treatment on the first oxide semiconductor film and the second oxide semiconductor film;
etching a part of the first insulating film, a part of the first oxide semiconductor film, and a part of the second oxide semiconductor film to form a first gate insulating film having a projection after performing the heat treatment;
forming a pair of electrodes in contact with the second oxide semiconductor film after etching the part of the second oxide semiconductor film;
forming a third oxide semiconductor film over the second oxide semiconductor film and the pair of electrodes;
forming a second gate insulating film over the third oxide semiconductor film; and
forming a second gate electrode over the second gate insulating film.

2. The method for manufacturing a semiconductor device according to claim 1 , wherein the oxygen is added to the first oxide semiconductor film by an ion implantation method, an ion doping method, or plasma treatment.

3. The method for manufacturing a semiconductor device according to claim 1 , wherein the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film include indium or gallium.

4. The method for manufacturing a semiconductor device according to claim 1 , wherein conduction band minimums of the first oxide semiconductor film and the third oxide semiconductor film are closer to a vacuum level than a conduction band minimum of the second oxide semiconductor film is.

5. The method for manufacturing a semiconductor device according to claim 1 , wherein a difference in energy level between a conduction band minimum of the second oxide semiconductor film and each of conduction band minimums of the first oxide semiconductor film and the third oxide semiconductor film is greater than or equal to 0.05 eV and less than or equal to 2 eV.

6. The method for manufacturing a semiconductor device according to claim 1 , further comprising a step of forming a second insulating film under the first gate electrode and the first insulating film,
wherein the second insulating film is in contact with the pair of electrodes.

7. The method for manufacturing a semiconductor device according to claim 1 ,
wherein the second oxide semiconductor film includes a low resistance region, and
wherein each of the pair of electrodes includes a region having high oxygen concentration.

8. A method for manufacturing a semiconductor device, comprising the steps of:
forming a first gate electrode;
forming a first insulating film over the first gate electrode;
forming a first oxide semiconductor film over the first insulating film;
forming a second oxide semiconductor film over the first oxide semiconductor film;
etching a part of the first insulating film, a part of the first oxide semiconductor film, and a part of the second oxide semiconductor film to form a first gate insulating film having a projection;
forming a pair of electrodes in contact with the second oxide semiconductor film after etching the part of the second oxide semiconductor film;
forming a third oxide semiconductor film over the second oxide semiconductor film and the pair of electrodes;
adding oxygen to the third oxide semiconductor film;
performing a heat treatment on the third oxide semiconductor film after adding the oxygen;
forming a second gate insulating film over the third oxide semiconductor film after performing the heat treatment; and
forming a second gate electrode over the second gate insulating film.

9. The method for manufacturing a semiconductor device according to claim 8 , wherein the oxygen is added to the third oxide semiconductor film by an ion implantation method, an ion doping method, or plasma treatment.

10. The method for manufacturing a semiconductor device according to claim 8 , wherein the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film include indium or gallium.

11. The method for manufacturing a semiconductor device according to claim 8 , wherein conduction band minimums of the first oxide semiconductor film and the third oxide semiconductor film are closer to a vacuum level than a conduction band minimum of the second oxide semiconductor film is.

12. The method for manufacturing a semiconductor device according to claim 8 , wherein a difference in energy level between a conduction band minimum of the second oxide semiconductor film and each of conduction band minimums of the first oxide semiconductor film and the third oxide semiconductor film is greater than or equal to 0.05 eV and less than or equal to 2 eV.

13. The method for manufacturing a semiconductor device according to claim 8 , further comprising a step of forming a second insulating film under the first gate electrode and the first insulating film,
wherein the second insulating film is in contact with the pair of electrodes.

14. The method for manufacturing a semiconductor device according to claim 8 ,
wherein the second oxide semiconductor film includes a low resistance region, and
wherein each of the pair of electrodes includes a region having high oxygen concentration.

15. A method for manufacturing a semiconductor device, comprising the steps of:
forming a first gate electrode;
forming a first insulating film over the first gate electrode;
forming a first oxide semiconductor film over the first insulating film;
adding oxygen to the first oxide semiconductor film;
forming a second oxide semiconductor film over the first oxide semiconductor film after adding the oxygen to the first oxide semiconductor film;
performing a first heat treatment on the first oxide semiconductor film and the second oxide semiconductor film;
etching a part of the first insulating film, a part of the first oxide semiconductor film, and a part of the second oxide semiconductor film to form a first gate insulating film having a projection after performing the first heat treatment;
forming a pair of electrodes in contact with the second oxide semiconductor film after etching the part of the second oxide semiconductor film;
forming a third oxide semiconductor film over the second oxide semiconductor film and the pair of electrodes;
adding oxygen to the third oxide semiconductor film;
performing a second heat treatment on the third oxide semiconductor film after adding the oxygen to the third oxide semiconductor film;
forming a second gate insulating film over the third oxide semiconductor film after performing the second heat treatment; and
forming a second gate electrode over the second gate insulating film.

16. The method for manufacturing a semiconductor device according to claim 15 , wherein the oxygen is added to the first oxide semiconductor film and the third oxide semiconductor film by an ion implantation method, an ion doping method, or plasma treatment.

17. The method for manufacturing a semiconductor device according to claim 15 , wherein the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film include indium or gallium.

18. The method for manufacturing a semiconductor de

Assignees

• Semiconductor Energy Lab

Inventors

• Yamazaki Shunpei
• Yamade Naoto
• Yamamoto Yoshitaka
• Suzawa Hideomi
• Sakakura Masayuki
• Sato Yuhei
• Yamane Yasumasa

Classifications

• H10P95/90

  Thermal treatments, e.g. annealing or sintering · CPC title

• H10P95/70

  Chemical treatments · CPC title

• H10P52/00

  Grinding, lapping or polishing of wafers, substrates or parts of devices · CPC title

• H10P50/20

  Dry etching; Plasma etching; Reactive-ion etching · CPC title

• H10P32/17

  characterised by the semiconductor material · CPC title