Semiconductor device and method for manufacturing semiconductor device
View Patent ↗Provided is a method for manufacturing a transistor by which the defective shape of a semiconductor device is prevented in the case where a source electrode layer and a drain electrode layer are formed on an oxide semiconductor film. A source electrode layer and a drain electrode layer are formed each having a cross-sectional shape with which disconnection of a gate insulating film is unlikely to occur even when the gate insulating film over the source electrode layer and the drain electrode layer has a small thickness. An oxide semiconductor film having a crystal structure over an insulating surface is formed; an electrode layer on the oxide semiconductor film is formed; and a thickness of an exposed portion of the oxide semiconductor film is reduced by exposing the oxide semiconductor film to dilute hydrofluoric acid with a concentration higher than 0.0001% and lower than or equal to 0.25%.
1. A method for manufacturing a semiconductor device, comprising the steps of:
forming an oxide semiconductor layer;
forming a source electrode layer and a drain electrode layer over the oxide semiconductor layer; and
exposing a part of the oxide semiconductor layer to diluted hydrofluoric acid after the formation of the source electrode layer and the drain electrode layer,
wherein a concentration of the diluted hydrofluoric acid is higher than 0.0001% and lower than or equal to 0.25%.
2. The method according to claim 1 , wherein the oxide semiconductor layer has a crystal structure.
3. The method according to claim 1 , wherein the step of forming the oxide semiconductor layer comprises the steps of:
forming a first oxide semiconductor layer;
forming a second oxide semiconductor layer over the first oxide semiconductor layer; and
forming a third oxide semiconductor layer over the second oxide semiconductor layer.
4. The method according to claim 1 , wherein the oxide semiconductor layer comprises indium, gallium, and zinc.
5. The method according to claim 1 , further comprising the step of:
forming a gate electrode layer before the formation of the oxide semiconductor layer.
6. A method for manufacturing a semiconductor device, comprising the steps of:
forming an oxide semiconductor layer over an insulating surface;
forming a source electrode layer and a drain electrode layer over the oxide semiconductor layer;
exposing a part of the oxide semiconductor layer to diluted hydrofluoric acid after the formation of the source electrode layer and the drain electrode layer;
forming an insulating layer over the oxide semiconductor layer, the source electrode layer, and the drain electrode layer; and
forming a gate electrode layer over the insulating layer, the gate electrode layer overlapping with the oxide semiconductor layer,
wherein a concentration of the diluted hydrofluoric acid is higher than 0.0001% and lower than or equal to 0.25%.
7. The method according to claim 6 , wherein the oxide semiconductor layer has a crystal structure.
8. The method according to claim 6 , wherein the step of forming the oxide semiconductor layer comprises the steps of:
forming a first oxide semiconductor layer;
forming a second oxide semiconductor layer over the first oxide semiconductor layer; and
forming a third oxide semiconductor layer over the second oxide semiconductor layer.
9. The method according to claim 6 , wherein the oxide semiconductor layer comprises indium, gallium, and zinc.
10. The method according to claim 6 , wherein the step of forming the gate electrode layer comprises the steps of:
forming a first gate electrode layer; and
forming a second gate electrode layer over the first gate electrode layer.
11. The method according to claim 6 , further comprising the step of:
forming a wiring electrically connected to one of the source electrode layer and the drain electrode layer,
wherein the wiring comprises copper.
12. A method for manufacturing a semiconductor device, comprising the steps of:
forming a first electrode layer over an insulating surface;
forming a first insulating layer over the first electrode layer;
forming an oxide semiconductor layer over the first insulating layer;
forming a source electrode layer and a drain electrode layer over the oxide semiconductor layer;
exposing a part of the oxide semiconductor layer to diluted hydrofluoric acid after the formation of the source electrode layer and the drain electrode layer;
forming a second insulating layer over the oxide semiconductor layer, the source electrode layer, and the drain electrode layer; and
forming a second electrode layer over the second insulating layer, the second electrode layer overlapping with the oxide semiconductor layer,
wherein a concentration of the diluted hydrofluoric acid is higher than 0.0001% and lower than or equal to 0.25%.
13. The method according to claim 12 wherein the oxide semiconductor layer has a crystal structure.
14. The method according to claim 12 , wherein the step of forming the oxide semiconductor layer comprises the steps of:
forming a first oxide semiconductor layer;
forming a second oxide semiconductor layer over the first oxide semiconductor layer; and
forming a third oxide semiconductor layer over the second oxide semiconductor layer.
15. The method according to claim 12 , wherein the oxide semiconductor layer comprises indium, gallium, and zinc.
16. The method according to claim 12 , wherein the step of forming the second electrode layer comprises the steps of:
forming a first gate electrode layer; and
forming a second gate electrode layer over the first gate electrode layer.
17. The method according to claim 12 , further comprising the step of:
forming a wiring electrically connected to one of the source electrode layer and the drain electrode layer,
wherein the wiring comprises copper.
18. The method according to claim 12 , wherein the first electrode layer is a back gate electrode layer.
19. The method according to claim 12 , wherein the first electrode layer overlaps with the oxide semiconductor layer.
20. The method according to claim 12 , further comprising the step of:
adding oxygen to the first insulating layer.