Semiconductor device and method for manufacturing the same

• US 8,298,858 B2
• Filed: 11/09/2011
• Issued: 10/30/2012
• Est. Priority Date: 11/13/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kuwabara, Hideaki, Akimoto, Kengo, Sasaki, Toshinari
• Primary Examiner(s): Pham, Long
• Application Number:
  US13/292,207
• Publication Number:
  US 20120058600A1
• Time in Patent Office: 356 Days
• Field of Search: 438/104, 438/149, 438/30
• 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 29/04 characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes characterised by physical imperfections H01L29/30
• CPC Class Codes: H01L 29/24 including, apart from doping materials or other impurities, only semiconductor materials not provided for in groups H01L29/16, H01L29/18, H01L29/20, H01L29/22 including organic materials H10K99/00
• CPC Class Codes: H01L 29/458 for thin film silicon, e.g. source or drain electrode
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• 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

Abstract

An object is to increase field effect mobility of a thin film transistor including an oxide semiconductor. Another object is to stabilize electrical characteristics of the thin film transistor. In a thin film transistor including an oxide semiconductor layer, a semiconductor layer or a conductive layer having higher electrical conductivity than the oxide semiconductor is formed over the oxide semiconductor layer, whereby field effect mobility of the thin film transistor can be increased. Further, by forming a semiconductor layer or a conductive layer having higher electrical conductivity than the oxide semiconductor between the oxide semiconductor layer and a protective insulating layer of the thin film transistor, change in composition or deterioration in film quality of the oxide semiconductor layer is prevented, so that electrical characteristics of the thin film transistor can be stabilized.

Claims

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

forming a gate electrode layer over a substrate;

forming a gate insulating layer over the gate electrode layer;

forming a conductive film over the gate insulating layer;

etching the conductive film to form source and drain electrode layers;

forming a first oxide semiconductor film over the gate insulating layer and the source and drain electrode layers by a sputtering method;

forming a second oxide semiconductor film over the first oxide semiconductor film by a sputtering method; and

etching the first oxide semiconductor film and the second oxide semiconductor film to form an oxide semiconductor layer and a semiconductor layer,

wherein the oxide semiconductor layer is provided to be in contact with the gate insulating layer and side face portions of the source and drain electrode layers,

wherein the semiconductor layer is provided over the oxide semiconductor layer, and

wherein a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the second oxide semiconductor film is made lower than a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the first oxide semiconductor film.

2. The method for manufacturing a semiconductor device according to claim 1, wherein the proportion of the flow rate of the oxygen gas for forming the first oxide semiconductor film is 10 vol. % or higher, and the proportion of the flow rate of the oxygen gas for forming the second oxide semiconductor film is lower than 10 vol. %.

3. The method for manufacturing a semiconductor device according to claim 1,

wherein the first oxide semiconductor film is formed in an atmosphere of an argon gas and an oxygen gas, and

wherein the second oxide semiconductor film is formed in an atmosphere of an argon gas.

4. The method for manufacturing a semiconductor device according to claim 1, wherein each of the first oxide semiconductor film and the second oxide semiconductor film includes at least one of indium, gallium, and zinc.

5. The method for manufacturing a semiconductor device according to claim 1, further comprising the step of forming a conductive layer over the semiconductor layer,

wherein the conductive layer is formed using a metal material such as indium, gallium, or zinc;

an alloy material containing any of the metal materials as a main component;

or an oxide or a nitride containing any of the metal materials.

12. The method for manufacturing a semiconductor device according to claim 1, wherein a concentration of sodium in the oxide semiconductor layer is lower than 1.0×

10¹⁸/cm³.

13. The method for manufacturing a semiconductor device according to claim 1, further comprising the steps of:

forming a protective film over the semiconductor layer; and

performing a heat treatment after forming the protective film.

14. The method for manufacturing a semiconductor device according to claim 13,

wherein at least one of the gate insulating layer and the protective film is formed by an oxynitride film.

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

forming a gate electrode layer over a substrate;

forming a gate insulating layer over the gate electrode layer;

forming a conductive film over the gate insulating layer;

etching the conductive film to form source and drain electrode layers;

forming an oxide semiconductor layer over the gate insulating layer and the source and drain electrode layers; and

forming a semiconductor layer over the oxide semiconductor layer,

wherein the oxide semiconductor layer is provided to be in contact with the gate insulating layer and side face portions of the source and drain electrode layers, and

wherein electrical conductivity of the semiconductor layer is higher than electrical conductivity of the oxide semiconductor layer.

7. The method for manufacturing a semiconductor device according to claim 6,

wherein the oxide semiconductor layer is a first oxide semiconductor film and the semiconductor layer is a second oxide semiconductor film, and

wherein a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the second oxide semiconductor film is made lower than a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the first oxide semiconductor film.

8. The method for manufacturing a semiconductor device according to claim 7, wherein the proportion of the flow rate of the oxygen gas for forming the first oxide semiconductor film is 10 vol. % or higher, and the proportion of the flow rate of the oxygen gas for forming the second oxide semiconductor film is lower than 10 vol. %.

9. The method for manufacturing a semiconductor device according to claim 7,

wherein the first oxide semiconductor film is formed in an atmosphere of an argon gas and an oxygen gas, and

wherein the second oxide semiconductor film is formed in an atmosphere of an argon gas.

10. The method for manufacturing a semiconductor device according to claim 7, wherein each of the first oxide semiconductor film and the second oxide semiconductor film includes at least one of indium, gallium, and zinc.

11. The method for manufacturing a semiconductor device according to claim 7, further comprising the step of forming a conductive layer over the semiconductor layer,

wherein the conductive layer is formed using a metal material such as indium, gallium, or zinc;

an alloy material containing any of the metal materials as a main component;

or an oxide or a nitride containing any of the metal materials.

15. The method for manufacturing a semiconductor device according to claim 6, wherein a concentration of sodium in the oxide semiconductor layer is lower than 1.0×

10¹⁸/cm³.

16. The method for manufacturing a semiconductor device according to claim 6, further comprising the steps of:

forming a protective film over the semiconductor layer; and

performing a heat treatment after forming the protective film.

17. The method for manufacturing a semiconductor device according to claim 16,

wherein at least one of the gate insulating layer and the protective film is formed by an oxynitride film.

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

forming a gate electrode layer over a substrate;

forming a gate insulating layer over the gate electrode layer;

forming a conductive film over the gate insulating layer;

etching the conductive film to form source and drain electrode layers;

forming an oxide semiconductor layer over the gate insulating layer and the source and drain electrode layers;

forming a semiconductor layer over the oxide semiconductor layer;

performing a heat treatment after forming the oxide semiconductor layer; and

forming a protective film over the semiconductor layer,

wherein the oxide semiconductor layer is provided to be in contact with the gate insulating layer and side face portions of the source and drain electrode layers, and

wherein electrical conductivity of the semiconductor layer is higher than electrical conductivity of the oxide semiconductor layer.

19. The method for manufacturing a semiconductor device according to claim 18,

wherein the oxide semiconductor layer is a first oxide semiconductor film and the semiconductor layer is a second oxide semiconductor film, and

wherein a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the second oxide semiconductor film is made lower than a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the first oxide semiconductor film.

20. The method for manufacturing a semiconductor device according to claim 19, wherein the proportion of the flow rate of the oxygen gas for forming the first oxide semiconductor film is 10 vol. % or higher, and the proportion of the flow rate of the oxygen gas for forming the second oxide semiconductor film is lower than 10 vol. %.

21. The method for manufacturing a semiconductor device according to claim 19,

wherein the first oxide semiconductor film is formed in an atmosphere of an argon gas and an oxygen gas, and

wherein the second oxide semiconductor film is formed in an atmosphere of an argon gas.

22. The method for manufacturing a semiconductor device according to claim 19, wherein each of the first oxide semiconductor film and the second oxide semiconductor film includes at least one of indium, gallium, and zinc.

23. The method for manufacturing a semiconductor device according to claim 18, further comprising the step of forming a conductive layer over the semiconductor layer,

wherein the conductive layer is formed using a metal material such as indium, gallium, or zinc;

an alloy material containing any of the metal materials as a main component;

or an oxide or a nitride containing any of the metal materials.

24. The method for manufacturing a semiconductor device according to claim 18, wherein a concentration of sodium in the oxide semiconductor layer is lower than 1.0×

10¹⁸/cm³.

25. The method for manufacturing a semiconductor device according to claim 18, further comprising the step of performing a heat treatment after forming the protective film.

26. The method for manufacturing a semiconductor device according to claim 25,

wherein at least one of the gate insulating layer and the protective film is formed by an oxynitride film.