SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SAME

• US 20120132906A1
• Filed: 11/16/2011
• Published: 05/31/2012
• Est. Priority Date: 11/30/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: YAMAZAKI, Shunpei
• Granted Patent: US 8,816,425 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• CPC Class Codes: H01L 21/02439 Materials
• CPC Class Codes: H01L 21/02513 Microstructure
• CPC Class Codes: H01L 21/02554 Oxides
• CPC Class Codes: H01L 21/02565 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/0259 Microstructure
• CPC Class Codes: H01L 21/02667 Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth
• CPC Class Codes: H01L 29/1033 with insulated gate, e.g. characterised by the length, the width, the geometric contour or the doping structure with channel and gate aligned in the lengthwise direction H01L29/42376; with buried channel H01L29/7838
• 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

A transistor in which the state of an interface between an oxide semiconductor layer and an insulating film in contact with the oxide semiconductor layer is favorable and a method for manufacturing the transistor are provided. Nitrogen is added to the vicinity of the interface between the oxide semiconductor layer and the insulating film (gate insulating layer) in contact with the oxide semiconductor layer so that the state of the interface of the oxide semiconductor layer becomes favorable. Specifically, the oxide semiconductor layer has a concentration gradient of nitrogen, and a region containing much nitrogen is provided at the interface with the gate insulating layer. A region having high crystallinity can be formed in the vicinity of the interface with the oxide semiconductor layer by addition of nitrogen, whereby the interface state can be stable.

Claims

1. A semiconductor device comprising:

a gate electrode layer;

a first insulating layer in contact with the gate electrode layer;

an oxide semiconductor layer in contact with the first insulating layer; and

a second insulating layer in contact with the oxide semiconductor layer,

wherein the oxide semiconductor layer has a peak of a nitrogen concentration at an interface with the first insulating layer, and

wherein the first insulating layer contains nitrogen and has a peak of a nitrogen concentration at an interface with the oxide semiconductor layer.

2. The semiconductor device according to claim 1, wherein the oxide semiconductor layer has a concentration gradient of nitrogen, which becomes higher as closer to the first insulating layer, and has a concentration gradient of oxygen, which becomes higher as closer to the second insulating layer.

3. The semiconductor device according to claim 1, wherein a region of the oxide semiconductor layer, which is in the vicinity of the interface with the first insulating layer, has higher crystallinity than other regions.

4. The semiconductor device according to claim 1, wherein a nitrogen concentration of the oxide semiconductor layer in the vicinity of the interface with the first insulating layer is higher than or equal to 5×

10¹⁹/cm³.

5. The semiconductor device according to claim 1, wherein a nitrogen concentration of the oxide semiconductor layer in the vicinity of the interface with the second insulating layer is lower than or equal to 5×

10¹⁹/cm³.

6. The semiconductor device according to claim 1,

wherein the oxide semiconductor layer has a peak of an oxygen concentration at an interface with the second insulating layer, and

wherein the second insulating layer contains oxygen and has a peak of an oxygen concentration at an interface with the oxide semiconductor layer.

7. The semiconductor device according to claim 1, wherein at least part of the oxide semiconductor layer is crystallized to have c-axis alignment.

8. The semiconductor device according to claim 1, wherein the oxide semiconductor layer comprises indium and zinc.

9. The semiconductor device according to claim 1, wherein the oxide semiconductor layer comprises at least a hexagonal wurtzite crystal structure.

10. A method for manufacturing a semiconductor device comprising the steps of:

forming an oxide semiconductor layer;

forming a source electrode layer and a drain electrode layer over the oxide semiconductor layer;

adding nitrogen to part of the oxide semiconductor layer by plasma treatment with a gas comprising nitrogen;

forming a gate insulating layer over the oxide semiconductor layer, the source electrode layer, and the drain electrode layer after the plasma treatment; and

forming a gate electrode layer in a position overlapping a region of the oxide semiconductor layer, to which nitrogen is added, through the gate insulating layer.

11. The method for manufacturing a semiconductor device according to claim 10, wherein the plasma treatment with a gas comprising nitrogen is performed by a sputtering apparatus.

12. The method for manufacturing a semiconductor device according to claim 10, wherein the plasma treatment with a gas comprising nitrogen is performed by a plasma CVD apparatus.

13. The method for manufacturing a semiconductor device according to claim 10, the step of adding nitrogen to part of the oxide semiconductor layer is performed after heating the oxide semiconductor layer under a reduced pressure.

14. The method for manufacturing a semiconductor device according to claim 10, further comprising the step of:

forming an insulating layer under an atmosphere containing oxygen by a sputtering method before forming the oxide semiconductor layer.

15. The method for manufacturing a semiconductor device according to claim 10, wherein the plasma treatment with a gas comprising nitrogen is performed before or after forming a source electrode layer and a drain electrode.

16. The method for manufacturing a semiconductor device according to claim 10, wherein the gas comprising nitrogen is a N₂ gas.

17. The method for manufacturing a semiconductor device according to claim 10, wherein the gas comprising nitrogen is a N₂O gas.

18. A method for manufacturing a semiconductor device comprising the steps of:

forming a gate electrode layer;

forming a gate insulating layer over the gate electrode layer;

adding nitrogen to part of the gate insulating layer by plasma treatment with a gas comprising nitrogen;

forming an oxide semiconductor layer in a position overlapping the gate electrode layer through the gate insulating layer;

forming a source electrode layer and a drain electrode layer over the oxide semiconductor layer;

adding oxygen to part of the oxide semiconductor layer by plasma treatment with a gas comprising oxygen; and

forming an insulating layer covering the oxide semiconductor layer, the source electrode layer, and the drain electrode layer under an atmosphere containing oxygen by a sputtering method.

19. The method for manufacturing a semiconductor device according to claim 18, wherein the plasma treatment with a gas comprising nitrogen is performed by a sputtering apparatus.

20. The method for manufacturing a semiconductor device according to claim 18, wherein the plasma treatment with a gas comprising nitrogen is performed by a plasma CVD apparatus.

21. The method for manufacturing a semiconductor device according to claim 18, the step of adding oxygen to part of the oxide semiconductor layer is performed after heating the oxide semiconductor layer under a reduced pressure.

23. The method for manufacturing a semiconductor device according to claim 18, wherein the gas comprising oxygen is an O₂ gas.

24. The method for manufacturing a semiconductor device according to claim 18, wherein the gas comprising nitrogen is a N₂ gas.

25. The method for manufacturing a semiconductor device according to claim 18, wherein the gas comprising nitrogen is a N₂O gas.

22. (canceled)