Semiconductor device and method for manufacturing semiconductor device

• US 8,546,892 B2
• Filed: 10/17/2011
• Issued: 10/01/2013
• Est. Priority Date: 10/20/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Imoto, Yuki, Maruyama, Tetsunori, Omata, Takatsugu, Honda, Tatsuya, Miyanaga, Akiharu, Nonaka, Yusuke
• Primary Examiner(s): Rodela, Eduardo A
• Application Number:
  US13/274,512
• Publication Number:
  US 20120097942A1
• Time in Patent Office: 715 Days
• Field of Search: 257/49, 257/57, 257/66, 257/69, 257/288, 257/368, 257/391, 257/392, 257/402, 257/405, 257/407, 257/E29.151, 257/E29.15, 257/E29.158, 257/E29.16, 257/E21.533, 257/E21.535, 257/E21.621, 257/E21.623, 257/43, 257/E21.15, 257/E21.195, 257/E21.205, 257/E29.293, 257/E29.294, 438/85, 438/104, 438/608, 438/151, 438/157, 438/197, 438/585, 438/592
• US Class Current: 257/407
• 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 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• 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

Abstract

It is an object of an embodiment of the present invention to reduce leakage current between a source and a drain in a transistor including an oxide semiconductor. As a first gate film in contact with a gate insulating film, a compound conductor which includes indium and nitrogen and whose band gap is less than 2.8 eV is used. Since this compound conductor has a work function of greater than or equal to 5 eV, preferably greater than or equal to 5.5 eV, the electron concentration in an oxide semiconductor film can be maintained extremely low. As a result, the leakage current between the source and the drain is reduced.

Claims

1. A semiconductor device comprising:

an oxide semiconductor film comprising indium;

a first gate electrode comprising a compound conductor;

a second gate electrode in contact with the first gate electrode; and

an insulating film between the oxide semiconductor film and the first gate electrode,

wherein the compound conductor comprises indium and nitrogen,

wherein a band gap of the compound conductor is less than 2.8 eV, and

wherein a side edge of the first gate electrode is aligned with a side edge of the second gate electrode.

2. The semiconductor device according to claim 1, wherein a work function of the compound conductor is greater than or equal to 5 eV.

3. The semiconductor device according to claim 1, wherein an ionization potential of the compound conductor is greater than or equal to 7 eV.

4. The semiconductor device according to claim 1,

wherein a percentage of nitrogen in the compound conductor is greater than or equal to 10 at. % and less than or equal to 50 at. %, and

wherein a percentage of indium in the compound conductor is greater than or equal to 10 at. % and less than or equal to 50 at. %.

5. The semiconductor device according to claim 1, wherein a concentration of a donor or an acceptor in the oxide semiconductor film is lower than or equal to 1×

10¹² cm<sup>−

3</sup>.

6. The semiconductor device according to claim 1,

wherein the oxide semiconductor film comprises a crystalline structure, and

wherein the oxide semiconductor film is provided over a surface with an average surface roughness of less than or equal to 1 nm.

7. A semiconductor device comprising:

an oxide semiconductor film comprising indium;

an insulating film over the oxide semiconductor film;

a first gate electrode comprising a compound conductor over the insulating film; and

a second gate electrode over and in contact with the first gate electrode,

wherein the compound conductor comprises indium and nitrogen,

wherein a band gap of the compound conductor is less than 2.8 eV, and

wherein a side edge of the first gate electrode is aligned with a side edge of the second gate electrode.

8. The semiconductor device according to claim 7, wherein a work function of the compound conductor is greater than or equal to 5 eV.

9. The semiconductor device according to claim 7, wherein an ionization potential of the compound conductor is greater than or equal to 7 eV.

10. The semiconductor device according to claim 7,

wherein a percentage of nitrogen in the compound conductor is greater than or equal to 10 at. % and less than or equal to 50 at. %, and

wherein a percentage of indium in the compound conductor is greater than or equal to 10 at. % and less than or equal to 50 at. %.

11. The semiconductor device according to claim 7, wherein a concentration of a donor or an acceptor in the oxide semiconductor film is lower than or equal to 1×

10¹² cm<sup>−

3</sup>.

12. The semiconductor device according to claim 7,

wherein the oxide semiconductor film comprises a crystalline structure, and

wherein the oxide semiconductor film is provided over a surface with an average surface roughness of less than or equal to 1 nm.

13. A semiconductor device comprising:

a first gate electrode;

a second gate electrode comprising a compound conductor;

an insulating film over the second gate electrode; and

an oxide semiconductor film comprising indium over the insulating film,

wherein the compound conductor comprises indium and nitrogen,

wherein a band gap of the compound conductor is less than 2.8 eV,

wherein the second gate electrode is provided over and in contact with the first gate electrode, and

wherein a side edge of the first gate electrode is aligned with a side edge of the second gate electrode.

14. The semiconductor device according to claim 13, wherein a work function of the compound conductor is greater than or equal to 5 eV.

15. The semiconductor device according to claim 13, wherein an ionization potential of the compound conductor is greater than or equal to 7 eV.

16. The semiconductor device according to claim 13,

wherein a percentage of nitrogen in the compound conductor is greater than or equal to 10 at. % and less than or equal to 50 at. %, and

wherein a percentage of indium in the compound conductor is greater than or equal to 10 at. % and less than or equal to 50 at. %.

17. The semiconductor device according to claim 13, wherein a concentration of a donor or an acceptor in the oxide semiconductor film is lower than or equal to 1×

10¹² cm<sup>−

3</sup>.

18. The semiconductor device according to claim 13,

wherein the oxide semiconductor film comprises a crystalline structure, and

wherein the oxide semiconductor film is provided over a surface with an average surface roughness of less or equal to 1 nm.

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

providing a first gate electrode;

providing a second gate electrode comprising a compound conductor over and in contact with the first gate electrode;

providing an insulating film over and in contact with the second gate electrode; and

providing an oxide semiconductor film comprising indium over the insulating film,

wherein the compound conductor comprises indium and nitrogen,

wherein a band gap of the compound conductor is less than 2.8 eV, and

wherein a side edge of the first gate electrode is aligned with a side edge of the second gate electrode.

20. The method for manufacturing a semiconductor device, according to claim 19, wherein the compound conductor is formed by a sputtering method in an atmosphere comprising nitrogen.

21. The method for manufacturing a semiconductor device, according to claim 19, wherein the compound conductor is formed by a sputtering method in an atmosphere comprising oxygen at lower than or equal to 5%.

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

wherein the oxide semiconductor film comprises a crystalline structure, and

wherein the oxide semiconductor film is provided over a surface with an average surface roughness of less than or equal to 1 nm.

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

providing an oxide semiconductor film comprising indium;

providing an insulating film over the oxide semiconductor film;

providing a first gate electrode comprising a compound conductor over and in contact with the insulating film; and

providing a second gate electrode over and in contact with the first gate electrode,

wherein the compound conductor comprises indium and nitrogen,

wherein a band gap of the compound conductor is less than 2.8 eV, and

wherein a side edge of the first gate electrode is aligned with a side edge of the second gate electrode.

24. The method for manufacturing a semiconductor device, according to claim 23, wherein the compound conductor is formed by a sputtering method in an atmosphere comprising nitrogen.

25. The method for manufacturing a semiconductor device, according to claim 23, wherein the compound conductor is formed by a sputtering method in an atmosphere comprising oxygen at lower than or equal to 5%.

26. The method for manufacturing a semiconductor device, according to claim 23,

wherein the oxide semiconductor film comprises a crystalline structure, and

wherein the oxide semiconductor film is provided over a surface with an average surface roughness of less than or equal to 1 nm.