Semiconductor device and method for manufacturing the same

• US 9,245,958 B2
• Filed: 08/06/2013
• Issued: 01/26/2016
• Est. Priority Date: 08/10/2012
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): Lee, Calvin
• Application Number:
  US13/959,878
• Publication Number:
  US 20140042435A1
• Time in Patent Office: 903 Days
• Field of Search: 257/324, 257/411, 257/615, 257/637, 257E29132-E29162, 438/216, 438/591
• US Class Current: 1/1
• CPC Class Codes: H01L 27/11807 CMOS gate arrays
• CPC Class Codes: H01L 29/26 including, apart from doping materials or other impurities, elements provided for in two or more of the groups H01L29/16, H01L29/18, H01L29/20, H01L29/22, H01L29/24 , e.g. alloys
• 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 29/78696 characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621
• CPC Class Codes: H10K 30/152 the wide bandgap semiconductor comprising zinc oxide, e.g. ZnO
• CPC Class Codes: Y02E 10/549 Organic PV cells

Abstract

A highly reliable semiconductor device exhibiting stable electrical characteristics is provided. Further, a highly reliable semiconductor device is provided. Oxide semiconductor films are stacked so that the conduction band has a well-shaped structure. A second oxide semiconductor film having a crystalline structure is provided over the first oxide semiconductor film and a third oxide semiconductor film is provided over the second oxide semiconductor film. The bottom of a conduction band in the second oxide semiconductor film is deeper from a vacuum level than the bottom of a conduction band in the first oxide semiconductor film and the bottom of a conduction band in the third oxide semiconductor film.

Claims

1. A semiconductor device comprising:

a gate electrode;

a gate insulating film over the gate electrode;

a first oxide semiconductor film over the gate insulating film;

a second oxide semiconductor film having a crystalline structure over the first oxide semiconductor film; and

a third oxide semiconductor film over the second oxide semiconductor film,

wherein a bottom of a conduction band in the second oxide semiconductor film is deeper from a vacuum level than a bottom of a conduction band in the first oxide semiconductor film and a bottom of a conduction band in the third oxide semiconductor film.

2. The semiconductor device according to claim 1, wherein a concentration of Si contained in each of the first oxide semiconductor film and the third oxide semiconductor film is lower than or equal to 3×

10¹⁸/cm³.

3. The semiconductor device according to claim 1, wherein a concentration of carbon contained in each of the first oxide semiconductor film and the third oxide semiconductor film is lower than or equal to 3×

10¹⁸/cm³.

4. The semiconductor device according to claim 1, wherein the second oxide semiconductor film includes a crystal region which is c-axis-aligned in a direction substantially perpendicular to a surface of the second oxide semiconductor film.

5. The semiconductor device according to claim 1, wherein the first oxide semiconductor film and the third oxide semiconductor film each have an indium content of higher than or equal to 1×

10¹⁹/cm³.

6. The semiconductor device according to claim 1, wherein the second oxide semiconductor film has a higher indium content than the first oxide semiconductor film and the third oxide semiconductor film.

7. The semiconductor device according to claim 1, wherein the first oxide semiconductor film and the third oxide semiconductor film contain indium, zinc, and gallium.

8. The semiconductor device according to claim 1, wherein the second oxide semiconductor film has an absorption coefficient due to a localized state of less than or equal to 3×

10<sup>−

3</sup>/cm.

9. The semiconductor device according to claim 1, wherein the third oxide semiconductor film has a lower degree of crystallinity than the second oxide semiconductor film.

10. The semiconductor device according to claim 1, wherein the first oxide semiconductor film has a lower degree of crystallinity than the second oxide semiconductor film.

11. The semiconductor device according to claim 1,

wherein the first oxide semiconductor film has a thickness greater than or equal to 10 nm and less than or equal to 40 nm,

wherein the second oxide semiconductor film has a thickness greater than or equal to 5 nm and less than or equal to 10 nm, and

wherein the third oxide semiconductor film has a thickness greater than or equal to 10 nm and less than or equal to 40 nm.

12. The semiconductor device according to claim 1, further comprising an oxide insulating film over and in contact with the third oxide semiconductor film.

13. The semiconductor device according to claim 1, further comprising an electrode layer over the gate insulating film and in contact with the third oxide semiconductor film.

14. The semiconductor device according to claim 13, wherein a portion of the electrode layer is overlapped with the gate electrode.

15. A semiconductor device comprising:

a first nitride insulating film;

a first oxide semiconductor film over the first nitride insulating film;

a second oxide semiconductor film having a crystalline structure over the first oxide semiconductor film;

a third oxide semiconductor film over the second oxide semiconductor film; and

a second nitride insulating film over the third oxide semiconductor film,

wherein a bottom of a conduction band in the second oxide semiconductor film is deeper from a vacuum level than a bottom of a conduction band in the first oxide semiconductor film and a bottom of a conduction band in the third oxide semiconductor film.

16. The semiconductor device according to claim 15, wherein a concentration of Si contained in each of the first oxide semiconductor film and the third oxide semiconductor film is lower than or equal to 3×

10¹⁸/cm³.

17. The semiconductor device according to claim 15, wherein a concentration of carbon contained in each of the first oxide semiconductor film and the third oxide semiconductor film is lower than or equal to 3×

10¹⁸/cm³.

18. The semiconductor device according to claim 15, wherein the second oxide semiconductor film includes a crystal region which is c-axis-aligned in a direction substantially perpendicular to a surface of the second oxide semiconductor film.

19. The semiconductor device according to claim 15, wherein the first oxide semiconductor film and the third oxide semiconductor film each have an indium content of higher than or equal to 1×

10¹⁹/cm³.

20. The semiconductor device according to claim 15, wherein the second oxide semiconductor film has a higher indium content than the first oxide semiconductor film and the third oxide semiconductor film.

21. The semiconductor device according to claim 15, wherein the first oxide semiconductor film and the third oxide semiconductor film contain indium, zinc, and gallium.

22. The semiconductor device according to claim 15, wherein the second oxide semiconductor film has an absorption coefficient due to a localized state of less than or equal to 3×

10<sup>−

3</sup>/cm.

23. The semiconductor device according to claim 15, wherein the third oxide semiconductor film has a lower degree of crystallinity than the second oxide semiconductor film.

24. The semiconductor device according to claim 15, wherein the first oxide semiconductor film has a lower degree of crystallinity than the second oxide semiconductor film.

25. The semiconductor device according to claim 15,

wherein the first oxide semiconductor film has a thickness greater than or equal to 10 nm and less than or equal to 40 nm,

wherein the second oxide semiconductor film has a thickness greater than or equal to 5 nm and less than or equal to 10 nm, and

wherein the third oxide semiconductor film has a thickness greater than or equal to 10 nm and less than or equal to 40 nm.

26. The semiconductor device according to claim 15, further comprising an oxide insulating film over and in contact with the third oxide semiconductor film.

27. The semiconductor device according to claim 15, further comprising a gate electrode, a gate insulating film including the first nitride insulating film over the gate electrode, and an electrode layer over the gate insulating film and in contact with the third oxide semiconductor film.

28. The semiconductor device according to claim 27, wherein a portion of the electrode layer is overlapped with the gate electrode.

29. A semiconductor device comprising:

a gate electrode;

a gate insulating film over the gate electrode;

a first oxide semiconductor film over the gate insulating film;

a second oxide semiconductor film having a crystalline structure over the first oxide semiconductor film;

a third oxide semiconductor film over the second oxide semiconductor film; and

a source electrode and a drain electrode over the third oxide semiconductor film,

wherein the third oxide semiconductor film is in contact with a side surface of the first oxide semiconductor film and a side surface of the second oxide semiconductor film, and

wherein a bottom of a conduction band in the second oxide semiconductor film is deeper from a vacuum level than a bottom of a conduction band in the first oxide semiconductor film and a bottom of a conduction band in the third oxide semiconductor film.

30. The semiconductor device according to claim 29, wherein the second oxide semiconductor film includes a crystal region which is c-axis-aligned in a direction substantially perpendicular to a surface of the second oxide semiconductor film.

31. The semiconductor device according to claim 29, wherein the second oxide semiconductor film has a higher indium content than the first oxide semiconductor film and the third oxide semiconductor film.

32. The semiconductor device according to claim 29, wherein the first oxide semiconductor film and the third oxide semiconductor film contain indium, zinc, and gallium.

33. The semiconductor device according to claim 29, wherein a portion of the source electrode and a portion of the drain electrode are overlapped with the gate electrode.

34. A semiconductor device comprising:

a gate electrode;

a gate insulating film over the gate electrode;

a first oxide semiconductor film over the gate insulating film;

a second oxide semiconductor film having a crystalline structure over the first oxide semiconductor film;

a third oxide semiconductor film over the second oxide semiconductor film; and

a source electrode and a drain electrode over the third oxide semiconductor film,

wherein each of the first oxide semiconductor film and the second oxide semiconductor film has tapered side surfaces,

wherein the third oxide semiconductor film is in contact with the tapered side surfaces of the first oxide semiconductor film and the tapered side surfaces of the second oxide semiconductor film, and

wherein a bottom of a conduction band in the second oxide semiconductor film is deeper from a vacuum level than a bottom of a conduction band in the first oxide semiconductor film and a bottom of a conduction band in the third oxide semiconductor film.

35. The semiconductor device according to claim 34, wherein the second oxide semiconductor film includes a crystal region which is c-axis-aligned in a direction substantially perpendicular to a surface of the second oxide semiconductor film.

36. The semiconductor device according to claim 34, wherein the second oxide semiconductor film has a higher indium content than the first oxide semiconductor film and the third oxide semiconductor film.

37. The semiconductor device according to claim 34, wherein the first oxide semiconductor film and the third oxide semiconductor film contain indium, zinc, and gallium.

38. The semiconductor device according to claim 34, wherein a portion of the source electrode and a portion of the drain electrode are overlapped with the gate electrode.