Semiconductor device, method for manufacturing semiconductor device, and method for forming oxide film

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

forming a gate electrode over a substrate;

forming a gate insulating film in contact with the gate electrode;

forming an oxide semiconductor film in contact with the gate insulating film; and

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

wherein the step of forming the oxide semiconductor film comprises:

providing the substrate on a stage of a reaction chamber, wherein the stage is electrically connected to a first power source;

supplying a gas containing oxygen;

generating oxygen plasma in the reaction chamber by using a second power source, wherein the second power source is electrically connected to an electrode;

supplying RF power from the first power source to the stage so as to generate a self-bias voltage between the oxygen plasma and the substrate so that the oxide semiconductor film is formed, wherein the substrate has a negative potential with respect to a potential of the oxygen plasma; and

heating the oxide semiconductor film so that a spin density of the oxide semiconductor film is lower than 9.3×10 16 spins/cm 3 , the spin density corresponding to a peak of a signal detected at a g-value of around 1.93 by electron spin resonance spectroscopy.

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

wherein the step of forming the gate insulating film comprises:

providing the substrate on the stage of the reaction chamber, wherein the stage is electrically connected to the first power source;

supplying a gas containing oxygen;

generating oxygen plasma in the reaction chamber by using the second power source, wherein the second power source is electrically connected to the electrode; and

supplying RF power from the first power source to the stage.

3. The method for manufacturing a semiconductor device according to claim 2 , further comprising the step of performing heat treatment after the gate insulating film is formed,

wherein the heat treatment is performed at a temperature higher than or equal to 300° C. and lower than or equal to 700° C. under reduced pressure, a nitrogen atmosphere, an oxygen atmosphere, or a rare gas atmosphere.

4. The method for manufacturing a semiconductor device according to claim 1 , wherein the self-bias voltage is higher than or equal to 400 V.

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

wherein the step of heating the oxide semiconductor film is performed at a temperature higher than or equal to 300° C. and lower than or equal to 700° C. under reduced pressure, a nitrogen atmosphere, an oxygen atmosphere, or a rare gas atmosphere.

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

wherein a carrier density of the oxide semiconductor film is lower than 1×10 15 /cm 3 , and

wherein the peak of the signal detected by electron spin resonance spectroscopy is due to oxygen vacancies in the oxide semiconductor film.

7. The method for manufacturing a semiconductor device according to claim 1 , wherein the gate electrode is formed in contact with an upper surface of the gate insulating film.

8. The method for manufacturing a semiconductor device according to claim 1 , wherein the gate electrode is formed in contact with a lower surface of the gate insulating film.

9. The method for manufacturing a semiconductor device according to claim 1 , wherein the oxide semiconductor film comprises two or more metal elements.

10. The method for manufacturing a semiconductor device according to claim 1 , wherein the oxide semiconductor film comprises indium, gallium, and zinc.

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

forming a first insulating film over a substrate;

forming an oxide semiconductor film over the first insulating film;

forming a gate insulating film over the oxide semiconductor film;

forming a gate electrode over the gate insulating film;

forming a second insulating film over the gate electrode; and

forming a source electrode and a drain electrode over the second insulating film,

wherein the step of forming the oxide semiconductor film comprises:

providing the substrate on a stage of a reaction chamber, wherein the stage is electrically connected to a first power source;

supplying a gas containing oxygen;

generating oxygen plasma in the reaction chamber by using a second power source, wherein the second power source is electrically connected to an electrode;

supplying RF power from the first power source to the stage so as to generate a self-bias voltage between the oxygen plasma and the substrate so that the oxide semiconductor film is formed, wherein the substrate has a negative potential with respect to a potential of the oxygen plasma; and

heating the oxide semiconductor film to remove hydrogen from the oxide semiconductor film so that a spin density of the oxide semiconductor film is lower than 9.3×10 16 spins/cm 3 , the spin density corresponding to a peak of a signal detected at a g-value of around 1.93 by electron spin resonance spectroscopy.

12. The method for manufacturing a semiconductor device according to claim 11 ,

wherein the step of forming the gate insulating film comprises:

providing the substrate on the stage of the reaction chamber, wherein the stage is electrically connected to the first power source;

supplying a gas containing oxygen;

generating oxygen plasma in the reaction chamber by using the second power source, wherein the second power source is electrically connected to the electrode; and

supplying RF power from the first power source to the stage.

13. The method for manufacturing a semiconductor device according to claim 12 , further comprising the step of performing heat treatment after the gate insulating film is formed,

wherein the heat treatment is performed at a temperature higher than or equal to 300° C. and lower than or equal to 700° C. under reduced pressure, a nitrogen atmosphere, an oxygen atmosphere, or a rare gas atmosphere.

14. The method for manufacturing a semiconductor device according to claim 11 , wherein the self-bias voltage is higher than or equal to 400 V.

15. The method for manufacturing a semiconductor device according to claim 11 ,

wherein the step of heating the oxide semiconductor film is performed at a temperature higher than or equal to 300° C. and lower than or equal to 700° C. under reduced pressure, a nitrogen atmosphere, an oxygen atmosphere, or a rare gas atmosphere.

16. The method for manufacturing a semiconductor device according to claim 11 ,

wherein a carrier density of the oxide semiconductor film is lower than 1×10 15 /cm 3 , and

wherein the peak of the signal detected by electron spin resonance spectroscopy is due to oxygen vacancies in the oxide semiconductor film.

17. The method for manufacturing a semiconductor device according to claim 11 , wherein the oxide semiconductor film comprises indium, gallium, and zinc.

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

forming a first insulating film over a substrate;

forming an oxide semiconductor film over the first insulating film;

forming a gate insulating film over the oxide semiconductor film;

forming a gate electrode over the gate insulating film;

etching the gate insulating film and the gate electrode;

adding a dopant into the oxide semiconductor film by using the gate electrode as a mask;

forming a second insulating film over the gate electrode; and

forming a source electrode and a drain electrode over the second insulating film,

wherein the step of forming the oxide semiconductor film comprises:

providing the substrate on a stage of a reaction chamber, wherein the stage is electrically connected to a first power source;

supplying a gas containing oxygen;

generating oxygen plasma in the reaction chamber by using a second power source, wherein the second power source is electrically connected to an electrode;

supplying RF power from the first power source to the stage so as to generate a self-bias voltage between the oxygen plasma and the substrate so that the oxide semiconductor film is formed, wherein the substrate has a negative potential with respect to a potential of the oxygen plasma; and

heating the oxide semiconductor film to remove hydrogen from the oxide semiconductor film so that a spin density of the oxide semiconductor film is lower than 9.3×10 16 spins/cm 3 and a carrier density of the oxide semiconductor film is lower than 1×10 15 /cm 3 , the spin density corresponding to a peak of a signal detected at a g-value of around 1.93 by electron spin resonance spectroscopy.

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

wherein the step of forming the gate insulating film comprises:

providing the substrate on the stage of the reaction chamber, wherein the stage is electrically connected to the first power source;

supplying a gas containing oxygen;

generating oxygen plasma in the reaction chamber by using the second power source, wherein the second power source is electrically connected to the electrode; and

supplying RF power from the first power source to the stage.

20. The method for manufacturing a semiconductor device according to claim 19 , further comprising the step of performing heat treatment after the gate insulating film is formed,

wherein the heat treatment is performed at a temperature higher than or equal to 300° C. and lower than or equal to 700° C. under reduced pressure, a nitrogen atmosphere, an oxygen atmosphere, or a rare gas atmosphere.

21. The method for manufacturing a semiconductor device according to claim 18 , wherein the self-bias voltage is higher than or equal to 400 V.

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

wherein the step of heating the oxide semiconductor film is performed at a temperature higher than or equal to 300° C. and lower than or equal to 700° C. under reduced pressure, a nitrogen atmosphere, an oxygen atmosphere, or a rare gas atmosphere.

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

wherein the peak of the signal detected by electron spin resonance spectroscopy is due to oxygen vacancies in the oxide semiconductor film.

24. The method for manufacturing a semiconductor device according to claim 18 , wherein the oxide semiconductor film comprises indium, gallium, and zinc.