Semiconductor device with metal oxide film

• US 8,461,584 B2
• Filed: 03/25/2011
• Issued: 06/11/2013
• Est. Priority Date: 03/26/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): YUSHIN, NIKOLAY K
• Application Number:
  US13/071,802
• Publication Number:
  US 20110233540A1
• Time in Patent Office: 809 Days
• Field of Search: 257/43, 257/389, 257/E29.273
• US Class Current: 257/43
• 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 29/42356 Disposition, e.g. buried gate electrode H01L29/42324 and H01L29/4234 take precedence
• CPC Class Codes: H01L 29/66969 of devices having semiconductor bodies not comprising group 14 or group 13/15 materials comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials, comprising cuprous oxide or cuprous iodide H01L21/02365
• CPC Class Codes: H01L 29/78606 with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device H01L29/78642, H01L29/78645 take precedence
• 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 29/78693 the semiconducting oxide being amorphous

Abstract

In a transistor including an oxide semiconductor film, a metal oxide film which has a function of preventing electrification and covers a source electrode and a drain electrode is formed in contact with the oxide semiconductor film, and then, heat treatment is performed. Through the heat treatment, impurities such as hydrogen, moisture, a hydroxyl group, or hydride are intentionally removed from the oxide semiconductor film, whereby the oxide semiconductor film is highly purified. By providing the metal oxide film, generation of a parasitic channel on the back channel side of the oxide semiconductor film in the transistor is prevented.

Claims

1. A semiconductor device comprising:

a gate electrode;

a gate insulating film over the gate electrode;

an oxide semiconductor film over the gate insulating film and overlapping with the gate electrode;

a source electrode and a drain electrode in contact with the oxide semiconductor film; and

a metal oxide film in contact with the oxide semiconductor film,

wherein the metal oxide film comprises gallium oxide,

wherein a hydrogen concentration of the oxide semiconductor film is less than or equal to 5×

10¹⁸ atoms/cm³,

wherein the metal oxide film contains indium or zinc at 0.01 at. % to 5 at. %, and

wherein the metal oxide film is over the source electrode and the drain electrode.

2. The semiconductor device according to claim 1, wherein the oxide semiconductor film comprises indium and gallium.

3. The semiconductor device according to claim 1, wherein the source electrode and the drain electrode comprise a conductive material whose work function is 3.9 eV or more.

4. The semiconductor device according to claim 3, wherein the conductive material whose work function is 3.9 eV or more is tungsten nitride or titanium nitride.

5. The semiconductor device according to claim 1, wherein a thickness of the metal oxide film is larger than a thickness of the oxide semiconductor film.

6. The semiconductor device according to claim 1, wherein a carrier concentration of the oxide semiconductor film is less than 1×

10¹¹/cm³.

7. A display device comprising the semiconductor device according to claim 1.

8. A semiconductor device comprising:

a gate electrode over a substrate;

a gate insulating film over the gate electrode;

an oxide semiconductor film over the gate insulating film and overlapping with the gate electrode;

a source electrode and a drain electrode in contact with the oxide semiconductor film; and

a metal oxide film in contact with the oxide semiconductor film,

wherein a hydrogen concentration of the oxide semiconductor film is less than or equal to 5×

10¹⁸ atoms/cm³,

wherein the metal oxide film comprises gallium oxide,

wherein the metal oxide film contains indium or zinc at 0.01 at. % to 5 at. %,

wherein the metal oxide film is over the source electrode and the drain electrode, and

wherein a difference between a band gap of the metal oxide film and a band gap of the oxide semiconductor film is less than 3.0 eV.

9. The semiconductor device according to claim 8, wherein the oxide semiconductor film comprises indium and gallium.

10. The semiconductor device according to claim 8, wherein the source electrode and the drain electrode comprise a conductive material whose work function is 3.9 eV or more.

11. The semiconductor device according to claim 10, wherein the conductive material whose work function is 3.9 eV or more is tungsten nitride or titanium nitride.

12. The semiconductor device according to claim 8, wherein a thickness of the metal oxide film is larger than a thickness of the oxide semiconductor film.

13. The semiconductor device according to claim 8, wherein a carrier concentration of the oxide semiconductor film is less than 1×

10¹¹/cm³.

14. A display device comprising the semiconductor device according to claim 8.

15. A semiconductor device comprising:

a gate electrode;

a gate insulating film over the gate electrode;

an oxide semiconductor film over the gate insulating film and overlapping with the gate electrode;

a source electrode and a drain electrode in contact with the oxide semiconductor film; and

a metal oxide film in contact with the oxide semiconductor film,

wherein the metal oxide film comprises gallium oxide,

wherein a hydrogen concentration of the oxide semiconductor film is less than or equal to 5×

10¹⁸ atoms/cm³, and

wherein the metal oxide film is over the source electrode and the drain electrode.

16. The semiconductor device according to claim 15, wherein the oxide semiconductor film comprises indium and gallium.

17. The semiconductor device according to claim 15, wherein the source electrode and the drain electrode comprise a conductive material whose work function is 3.9 eV or more.

18. The semiconductor device according to claim 15, wherein the conductive material whose work function is 3.9 eV or more is tungsten nitride or titanium nitride.

19. The semiconductor device according to claim 15, wherein a thickness of the metal oxide film is larger than a thickness of the oxide semiconductor film.