Method for manufacturing semiconductor device including exposure of oxide semiconductor to reducing atmosphere
View Patent ↗A highly reliable semiconductor device having stable electric characteristics is provided by suppressing, in a transistor including an oxide semiconductor film, diffusion of indium into an insulating film in contact with the oxide semiconductor film and improving the characteristics of the interface between the oxide semiconductor film and the insulating film. In an oxide semiconductor film containing indium, the indium concentration at a surface is decreased, thereby preventing diffusion of indium into an insulating film on and in contact with the oxide semiconductor film. By decreasing the indium concentration at the surface of the oxide semiconductor film, a layer which does not substantially contain indium can be formed at the surface. By using this layer as part of the insulating film, the characteristics of the interface between the oxide semiconductor film and the insulating film in contact with the oxide semiconductor film are improved.
1. A method for manufacturing a semiconductor device, comprising the steps of:
forming a first oxide semiconductor film containing indium over an insulating surface;
exposing the first oxide semiconductor film to a reducing atmosphere;
forming a gate insulating film over the first oxide semiconductor film after exposing the first oxide semiconductor film;
forming a gate electrode over the first oxide semiconductor film with the gate insulating film interposed therebetween; and
forming source and drain electrodes electrically connected to the first oxide semiconductor film,
wherein the source and drain electrodes are provided between the first oxide semiconductor film and the gate insulating film,
wherein a first region and a second region in contact with a top surface of the first region are formed in the first oxide semiconductor film by exposing the first oxide semiconductor film to the reducing atmosphere,
wherein the second region is a region exposed to the reducing atmosphere, and
wherein a concentration of indium in the second region is lower than a concentration of indium in the first region.
2. The method for manufacturing a semiconductor device, according to claim 1 ,
wherein the step of forming source and drain electrodes over the first oxide semiconductor film is performed before exposing the first oxide semiconductor film.
3. The method for manufacturing a semiconductor device, according to claim 1 , wherein the first oxide semiconductor film further contains Ga and Zn.
4. The method for manufacturing a semiconductor device, according to claim 1 , wherein the reducing atmosphere is one of a silane atmosphere and a hydrogen atmosphere.
5. The method for manufacturing a semiconductor device, according to claim 1 , wherein the reducing atmosphere is formed by using a plasma CVD apparatus.
6. The method for manufacturing a semiconductor device, according to claim 1 , wherein a second oxide semiconductor film and an oxide insulating film in contact with a top surface of the second oxide semiconductor film are formed by exposing the first oxide semiconductor film.
7. The method for manufacturing a semiconductor device, according to claim 1 , wherein a concentration of indium in the first oxide semiconductor film is higher than or equal to 10 atomic % and lower than or equal to 25 atomic %.
8. The method for manufacturing a semiconductor device, according to claim 1 , wherein the concentration of indium in the first region is higher than or equal to 10 atomic % and lower than or equal to 25 atomic %.
9. The method for manufacturing a semiconductor device, according to claim 1 , wherein the concentration of indium in the second region is higher than or equal to 0 atomic % and lower than 13 atomic %.
10. The method for manufacturing a semiconductor device, according to claim 1 , wherein the source and drain electrodes are in contact with a top surface of the first oxide semiconductor film.
11. A method for manufacturing a semiconductor device, comprising the steps of:
forming a gate electrode over an insulating surface;
forming a gate insulating film covering the gate electrode;
forming a first oxide semiconductor film containing indium over the gate insulating film;
exposing the first oxide semiconductor film to a reducing atmosphere, and
forming source and drain electrodes electrically connected to the first oxide semiconductor film,
wherein a first region and a second region in contact with a top surface of the first region are formed in the first oxide semiconductor film by exposing the first oxide semiconductor film to the reducing atmosphere,
wherein the second region is a region exposed to the reducing atmosphere, and
wherein a concentration of indium in the second region is lower than a concentration of indium in the first region.
12. The method for manufacturing a semiconductor device, according to claim 11 ,
wherein the step of forming source and drain electrodes over the first oxide semiconductor film is performed before exposing the first oxide semiconductor film.
13. The method for manufacturing a semiconductor device, according to claim 11 , wherein the step of forming source and drain electrodes over the gate insulating film is performed before forming the first oxide semiconductor film.
14. The method for manufacturing a semiconductor device, according to claim 11 , wherein the first oxide semiconductor film further contains Ga and Zn.
15. The method for manufacturing a semiconductor device, according to claim 11 , wherein the reducing atmosphere is one of a silane atmosphere and a hydrogen atmosphere.
16. The method for manufacturing a semiconductor device, according to claim 11 , wherein the reducing atmosphere is formed by using a plasma CVD apparatus.
17. The method for manufacturing a semiconductor device, according to claim 11 , wherein a second oxide semiconductor film and an oxide insulating film in contact with a top surface of the second oxide semiconductor film are formed by exposing the first oxide semiconductor film.
18. The method for manufacturing a semiconductor device, according to claim 11 , wherein a concentration of indium in the first oxide semiconductor film is higher than or equal to 10 atomic % and lower than or equal to 25 atomic %.
19. The method for manufacturing a semiconductor device, according to claim 11 , wherein the concentration of indium in the first region is higher than or equal to 10 atomic % and lower than or equal to 25 atomic %.
20. The method for manufacturing a semiconductor device, according to claim 11 , wherein the concentration of indium in the second region is higher than or equal to 0 atomic % and lower than 13 atomic %.
21. A method for manufacturing a semiconductor device, comprising the steps of:
forming an oxide semiconductor film containing indium over an insulating surface;
exposing the oxide semiconductor film to a reducing atmosphere,
forming a gate insulating film over the oxide semiconductor film after exposing the oxide semiconductor film; and
forming source and drain electrodes electrically connected to the oxide semiconductor film,
wherein the source and drain electrodes are provided between the oxide semiconductor film and the gate insulating film,
wherein a first region and a second region in contact with a top surface of the first region are formed in the oxide semiconductor film by exposing the oxide semiconductor film to the reducing atmosphere,
wherein the second region is a region exposed to the reducing atmosphere, and
wherein a concentration of indium in the second region is lower than a concentration of indium in the first region.
22. The method for manufacturing a semiconductor device, according to claim 21 , wherein the source and drain electrodes are in contact with a top surface of the oxide semiconductor film.