Semiconductor device

• US 9,490,369 B2
• Filed: 12/01/2014
• Issued: 11/08/2016
• Est. Priority Date: 06/15/2012
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): Schoenholtz, Joseph
• Application Number:
  US14/556,371
• Publication Number:
  US 20150187949A1
• Time in Patent Office: 708 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/04886 by partitioning the display area of the touch-screen or the surface of the digitising tablet into independently controllable areas, e.g. virtual keyboards or menus
• CPC Class Codes: H01L 27/14612 involving a transistor
• CPC Class Codes: H01L 27/14616 characterised by the channel of the transistor, e.g. channel having a doping gradient
• CPC Class Codes: H01L 29/267 in different semiconductor regions , e.g. heterojunctions H01L29/263 takes precedence
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/512 the variation being parallel to the channel plane
• CPC Class Codes: H01L 29/518 the insulating material containing nitrogen, e.g. nitride, oxynitride, nitrogen-doped material
• CPC Class Codes: H01L 29/78693 the semiconducting oxide being amorphous
• 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: H01L 31/03762 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/103 the potential barrier being of the PN homojunction type
• CPC Class Codes: H10K 59/40 OLEDs integrated with touch screens
• CPC Class Codes: H10K 59/65 OLEDs integrated with inorganic image sensors

Abstract

High field-effect mobility is provided for a transistor including an oxide semiconductor. Further, a highly reliable semiconductor device including the transistor is provided. In a bottom-gate transistor including an oxide semiconductor layer, an oxide semiconductor layer functioning as a current path (channel) of the transistor is sandwiched between oxide semiconductor layers having lower carrier densities than the oxide semiconductor layer. In such a structure, the channel is formed away from the interface of the oxide semiconductor stacked layer with an insulating layer in contact with the oxide semiconductor stacked layer, i.e., a buried channel is formed.

Claims

1. A semiconductor device comprising:

a first oxide semiconductor film;

a second oxide semiconductor film on and in contact with the first oxide semiconductor film;

a third oxide semiconductor film on and in contact with the second oxide semiconductor film;

a first oxide insulating film and a second oxide insulating film between which the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film are positioned;

a gate electrode overlapping with the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film with the first oxide insulating film interposed therebetween;

a source electrode and a drain electrode each electrically connected to at least one of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film,

wherein a difference between a Fermi level and a bottom of a conduction band in the second oxide semiconductor film is smaller than those in the first oxide semiconductor film and the third oxide semiconductor film.

2. The semiconductor device according to claim 1, wherein the second oxide semiconductor film comprises an impurity imparting an n-type conductivity.

3. The semiconductor device according to claim 2, wherein the impurity is at least any one of boron, nitrogen, and phosphorus.

4. The semiconductor device according to claim 1, wherein each of the first oxide semiconductor film and the third oxide semiconductor film is an i-type oxide semiconductor film.

5. The semiconductor device according to claim 1, wherein the second oxide semiconductor film has a carrier density higher than the first oxide semiconductor film and the third oxide semiconductor film.

6. The semiconductor device according to claim 1, wherein the bottom of the conduction band of the second oxide semiconductor film is lower than those of the first oxide semiconductor film and the third oxide semiconductor film.

7. The semiconductor device according to claim 1, wherein each of the first oxide, insulating film and the second oxide insulating film is a silicon oxide film.

8. The semiconductor device according to claim 1, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises indium, gallium, and zinc.

9. The semiconductor device according to claim 1, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film is positioned over the gate electrode.

10. The semiconductor device according to claim 1, wherein each of the source electrode and the drain electrode is on and in contact with the third oxide semiconductor film.

31. The semiconductor device according to claim 1, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises a crystal part.

32. The semiconductor device according to claim 1, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film is a c-axis aligned crystalline oxide semiconductor (CAAC-OS) film.

11. A semiconductor device comprising:

a first oxide semiconductor film;

a second oxide semiconductor film on and in contact with the first oxide semiconductor film;

a third oxide semiconductor film on and in contact with the second oxide semiconductor film;

a first oxide insulating film and a second oxide insulating film between which the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film are positioned;

a first nitride insulating film and a second nitride insulating film between which the first oxide insulating film, the first oxide semiconductor film, the second oxide semiconductor film, the third oxide semiconductor film and the second oxide insulating film are positioned;

a gate electrode overlapping with the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film with the first oxide insulating film and the first nitride insulating film interposed therebetween;

a source electrode and a drain electrode each electrically connected to at least one of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film,

wherein a difference between a Fermi level and a bottom of a conduction band in the second oxide semiconductor film is smaller than those in the first oxide semiconductor film and the third oxide semiconductor film.

12. The semiconductor device according to claim 11, wherein the second oxide semiconductor film comprises an impurity imparting an n-type conductivity.

13. The semiconductor device according to claim 12, wherein the impurity is at least any one of boron, nitrogen, and phosphorus.

14. The semiconductor device according to claim 11, wherein each of the first oxide semiconductor film and the third oxide semiconductor film is an i-type oxide semiconductor film.

15. The semiconductor device according to claim 11, wherein the second oxide semiconductor film has a carrier density higher than the first oxide semiconductor film and the third oxide semiconductor film.

16. The semiconductor device according to claim 11, wherein the bottom of the conduction band of the second oxide semiconductor film is lower than those of the first oxide semiconductor film and the third oxide semiconductor film.

17. The semiconductor device according to claim 11, wherein each of the first oxide insulating film and the second oxide insulating film is a silicon oxide film.

18. The semiconductor device according to claim 11, wherein each of the first nitride insulating film and the second nitride insulating film is a silicon nitride film.

19. The semiconductor device according to claim 11, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises indium, gallium, and zinc.

20. The semiconductor device according to claim 11, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film is positioned over the gate electrode.

21. The semiconductor device according to claim 11, wherein each of the source electrode and the drain electrode is on and in contact with the third oxide semiconductor film.

33. The semiconductor device according to claim 11, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises a crystal part.

34. The semiconductor device according to claim 11, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film is a c-axis aligned crystalline oxide semiconductor (CAAC-OS) film.

22. A semiconductor device comprising:

a gate electrode;

a first gate insulating film over the gate electrode;

a second gate insulating film over the first gate insulating film;

a first oxide semiconductor film on and in contact with the second gate insulating film;

a second oxide semiconductor film on and in contact with the first oxide semiconductor film;

a third oxide semiconductor film on and in contact with the second oxide semiconductor film;

a source electrode and a drain electrode on and in contact with a top surface of the third oxide semiconductor film and in contact with side surfaces of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film;

an oxide insulating film on and in contact with the third oxide semiconductor film, the source electrode, and the drain electrode; and

a nitride insulating film over the oxide insulating film,

wherein a difference between a Fermi level and a bottom of a conduction band in the second oxide semiconductor film is smaller than those in the first oxide semiconductor film and the third oxide semiconductor film.

23. The semiconductor device according to claim 22, wherein the second oxide semiconductor film comprises an impurity imparting an n-type conductivity.

24. The semiconductor device according to claim 23, wherein the impurity is at least any one of boron, nitrogen, and phosphorus.

25. The semiconductor device according to claim 22, wherein each of the first oxide semiconductor film and the third oxide semiconductor film is an i-type oxide semiconductor film.

26. The semiconductor device according to claim 22, wherein the second oxide semiconductor film has a carrier density higher than the first oxide semiconductor film and the third oxide semiconductor film.

27. The semiconductor device according to claim 22, wherein the bottom of the conduction band of the second oxide semiconductor film is lower than those of the first oxide semiconductor film and the third oxide semiconductor film.

28. The semiconductor device according to claim 22, wherein each of the second gate insulating film and the oxide insulating film is a silicon oxide film.

29. The semiconductor device according to claim 22, wherein each of the first gate insulating film and the nitride insulating film is a silicon nitride film.

30. The semiconductor device according to claim 22, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises indium, gallium, and zinc.

35. The semiconductor device according to claim 22, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises a crystal part.

36. The semiconductor device according to claim 22, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film is a c-axis aligned crystalline oxide semiconductor (CAAC-OS) film.

37. A semiconductor device comprising:

a first oxide semiconductor film;

a second oxide semiconductor film on and in contact with the first oxide semiconductor film;

a third oxide semiconductor film on and in contact with the second oxide semiconductor film;

a first oxide insulating film and a second oxide insulating film between which the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film are positioned;

a gate electrode overlapping with the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film with the first oxide insulating film interposed therebetween;

a source electrode and a drain electrode each electrically connected to at least one of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film,

wherein a difference between a Fermi level and a bottom of a conduction band in the second oxide semiconductor film is smaller than those in the first oxide semiconductor film and the third oxide semiconductor film, and

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

38. The semiconductor device according to claim 37, wherein the second oxide semiconductor film comprises an impurity imparting an n-type conductivity.

39. The semiconductor device according to claim 38, wherein the impurity is at least any one of boron, nitrogen, and phosphorus.

40. The semiconductor device according to claim 37, wherein each of the first oxide semiconductor film and the third oxide semiconductor film is an i-type oxide semiconductor film.

41. The semiconductor device according to claim 37, wherein the second oxide semiconductor film has a carrier density higher than the first oxide semiconductor film and the third oxide semiconductor film.

42. The semiconductor device according to claim 37, wherein the bottom of the conduction band of the second oxide semiconductor film is lower than those of the first oxide semiconductor film and the third oxide semiconductor film.

43. The semiconductor device according to claim 37, wherein each of the first oxide insulating film and the second oxide insulating film is a silicon oxide film.

44. The semiconductor device according to claim 37, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises indium, gallium, and zinc.

45. The semiconductor device according to claim 37, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film is positioned over the gate electrode.

46. The semiconductor device according to claim 37, wherein each of the source electrode and the drain electrode is on and in contact with the third oxide semiconductor film.

47. The semiconductor device according to claim 37, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises a crystal part.

48. The semiconductor device according to claim 37, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film is a c-axis aligned crystalline oxide semiconductor (CAAC-OS) film.

50. The semiconductor device according to claim 37, wherein the second oxide semiconductor film comprises an impurity imparting an n-type conductivity.

51. The semiconductor device according to claim 50, wherein the impurity is at least any one of boron, nitrogen, and phosphorus.

49. A semiconductor device comprising:

a first oxide semiconductor film;

a second oxide semiconductor film on and in contact with the first oxide semiconductor film;

a third oxide semiconductor film on and in contact with the second oxide semiconductor film;

a first oxide insulating film and a second oxide insulating film between which the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film are positioned;

a gate electrode overlapping with the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film with the first oxide insulating film interposed therebetween;

a source electrode and a drain electrode each electrically connected to at least one of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film,

wherein a difference between a Fermi level and a bottom of a conduction band in the second oxide semiconductor film is smaller than those in the first oxide semiconductor film and the third oxide semiconductor film, and

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

52. The semiconductor device according to claim 49, wherein each of the first oxide semiconductor film and the third oxide semiconductor film is an i-type oxide semiconductor film.

53. The semiconductor device according to claim 49, wherein the second oxide semiconductor film has a carrier density higher than the first oxide semiconductor film and the third oxide semiconductor film.

54. The semiconductor device according to claim 49, wherein the bottom of the conduction band of the second oxide semiconductor film is lower than those of the first oxide semiconductor film and the third oxide semiconductor film.

55. The semiconductor device according to claim 49, wherein each of the first oxide insulating film and the second oxide insulating film is a silicon oxide film.

56. The semiconductor device according to claim 49, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises indium, gallium, and zinc.

57. The semiconductor device according to claim 49, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film is positioned over the gate electrode.

58. The semiconductor device according to claim 49, wherein each of the source electrode and the drain electrode is on and in contact with the third oxide semiconductor film.

59. The semiconductor device according to claim 49, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film comprises a crystal part.

60. The semiconductor device according to claim 49, wherein each of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film is a c-axis aligned crystalline oxide semiconductor (CAAC-OS) film.