Method for manufacturing semiconductor device
An object is to provide a semiconductor device having stable electric characteristics in which an oxide semiconductor is used. An oxide semiconductor layer is subjected to heat treatment for dehydration or dehydrogenation treatment in a nitrogen gas or an inert gas atmosphere such as a rare gas (e.g., argon or helium) or under reduced pressure and to a cooling step for treatment for supplying oxygen in an atmosphere of oxygen, an atmosphere of oxygen and nitrogen, or the air (having a dew point of preferably lower than or equal to −40° C., still preferably lower than or equal to −50° C.) atmosphere. The oxide semiconductor layer is thus highly purified, whereby an i-type oxide semiconductor layer is formed. A semiconductor device including a thin film transistor having the oxide semiconductor layer is manufactured.
1. A method for manufacturing a semiconductor device, comprising the steps of:
forming a gate electrode over a substrate;
forming a gate insulating film over the substrate and the gate electrode;
forming an oxide semiconductor layer over the gate insulating film by sputtering;
performing a first heat treatment on the oxide semiconductor layer to reduce a hydrogen concentration of the oxide semiconductor layer;
supplying oxygen into the oxide semiconductor layer during cooling after performing the first heat treatment and before forming a source electrode and a drain electrode over the oxide semiconductor layer;
forming an insulating film over the oxide semiconductor layer, the source electrode, and the drain electrode; and
performing a second heat treatment after forming the insulating film.
2. The method of claim 1 , wherein the first heat treatment is performed at a first temperature of greater than 300° C.
3. The method of claim 1 , wherein the supplying oxygen is performed at a second temperature of greater than 350° C.
4. The method of claim 1 , wherein the oxide semiconductor layer is formed during removal of moisture from a deposition chamber.
5. The method of claim 4 , wherein moisture is removed by a vacuum pump.
6. The method of claim 1 , wherein the first heat treatment is performed in a first treatment chamber and the supplying oxygen is performed in a second treatment chamber.
7. The method of claim 1 , further comprising:
performing a plasma treatment after forming the source electrode and the drain electrode.
8. The method of claim 1 , wherein a proportion of an oxygen flow rate is 100% in the step of forming the oxide semiconductor layer.
9. A method for manufacturing a semiconductor device, comprising the steps of:
forming a gate electrode over a substrate;
forming a gate insulating film over the substrate and the gate electrode;
forming an oxide semiconductor layer over the gate insulating film by sputtering;
performing a first heat treatment on the oxide semiconductor layer to reduce a hydrogen concentration of the oxide semiconductor layer;
supplying oxygen into the oxide semiconductor layer by performing a cooling treatment after performing the first heat treatment;
forming a source electrode and a drain electrode over the oxide semiconductor layer;
forming an insulating film over the oxide semiconductor laver, the source electrode, and the drain electrode; and
performing a second heat treatment after forming the insulating film.
10. The method of claim 9 , wherein the first heat treatment is performed at a first temperature of greater than 300° C.
11. The method of claim 9 , wherein the cooling treatment is performed in an atmosphere of oxygen.
12. The method of claim 9 , wherein the cooling treatment is performed in an atmosphere of oxygen and nitrogen.
13. The method of claim 9 , wherein the cooling treatment is performed in an atmosphere of air with dew point of lower than or equal to −40° C.
14. The method of claim 9 , wherein the oxide semiconductor layer is formed during removal of moisture from a deposition chamber.
15. The method of claim 14 , wherein moisture is removed by a vacuum pump.
16. The method of claim 9 , wherein the first heat treatment is performed in a first treatment chamber and the supplying oxygen is performed in a second treatment chamber.
17. The method of claim 9 , further comprising:
performing a plasma treatment after forming the source electrode and the drain electrode.
18. The method of claim 9 , wherein a proportion of an oxygen flow rate is 100% in the step of forming the oxide semiconductor layer.