Semiconductor device and method for manufacturing the same
A highly reliable semiconductor device and a method for manufacturing the semiconductor device are provided. In a semiconductor device including a bottom-gate transistor in which an insulating layer functioning as a channel protective film is provided over an oxide semiconductor film, elements contained in an etching gas can be prevented from remaining as impurities on a surface of the oxide semiconductor film by performing impurity-removing process after formation of an insulating layer provided over and in contact with the oxide semiconductor film and/or formation of source and drain electrode layers. The impurity concentration in the surface of the oxide semiconductor film is lower than or equal to 5×10 18 atoms/cm 3 , preferably lower than or equal to 1×10 18 atoms/cm 3 .
1. A method for manufacturing a semiconductor device, comprising the steps of:
forming a gate electrode layer over an insulating surface;
forming a gate insulating film over the gate electrode layer;
forming an oxide semiconductor film over the gate insulating film;
forming an insulating layer over the oxide semiconductor film, the insulating layer overlapping with the gate electrode layer;
forming a conductive film over the oxide semiconductor film and the insulating layer;
etching the conductive film with an etching gas containing a halogen element to form a source electrode layer and a drain electrode layer; and
removing the halogen element from the oxide semiconductor film,
wherein a concentration of the halogen element in the oxide semiconductor film subjected to the removing step is lower than or equal to 5×10 18 atoms/cm 3 .
2. The method for manufacturing a semiconductor device, according to claim 1 , wherein the halogen element comprises chlorine.
3. The method for manufacturing a semiconductor device, according to claim 1 , wherein the oxide semiconductor film comprises indium and zinc.
4. The method for manufacturing a semiconductor device, according to claim 1 , wherein the insulating layer is in direct contact with the oxide semiconductor film.
5. The method for manufacturing a semiconductor device, according to claim 1 , wherein a plasma treatment is performed as the removing step.
6. The method for manufacturing a semiconductor device, according to claim 1 , wherein a cleaning treatment with a diluted hydrofluoric acid solution is performed as the removing step.
7. The method for manufacturing a semiconductor device, according to claim 1 , wherein a length of the oxide semiconductor film in a channel width direction is larger than a length of each of the source electrode layer and the drain electrode layer in the channel width direction.
8. The method for manufacturing a semiconductor device, according to claim 1 , wherein each of the source electrode layer and the drain electrode layer overlaps with the gate electrode layer.
9. The method for manufacturing a semiconductor device, according to claim 1 , wherein a part of the oxide semiconductor film is exposed at the step of etching the conductive film.
10. A method for manufacturing a semiconductor device, comprising the steps of:
forming a gate electrode layer over an insulating surface;
forming a gate insulating film over the gate electrode layer;
forming an oxide semiconductor film over the gate insulating film;
forming an insulating layer over the oxide semiconductor film;
etching the insulating layer with an etching gas containing a halogen element to form a channel protective film in a position overlapping with the gate electrode layer;
removing the halogen element from the oxide semiconductor film;
forming a conductive film over the oxide semiconductor film and the channel protective film; and
etching the conductive film to form a source electrode layer and a drain electrode layer,
wherein a concentration of the halogen element in the oxide semiconductor film subjected to the removing step is lower than or equal to 5×10 18 atoms/cm 3 .
11. The method for manufacturing a semiconductor device, according to claim 10 , wherein the halogen element comprises chlorine.
12. The method for manufacturing a semiconductor device, according to claim 10 , wherein the oxide semiconductor film comprises indium and zinc.
13. The method for manufacturing a semiconductor device, according to claim 10 , wherein the insulating layer is in direct contact with the oxide semiconductor film.
14. The method for manufacturing a semiconductor device, according to claim 10 , wherein a plasma treatment is performed as the removing step.
15. The method for manufacturing a semiconductor device, according to claim 10 , wherein a cleaning treatment with a diluted hydrofluoric acid solution is performed as the removing step.
16. The method for manufacturing a semiconductor device, according to claim 10 , wherein a length of the oxide semiconductor film in a channel width direction is larger than a length of each of the source electrode layer and the drain electrode layer in the channel width direction.
17. The method for manufacturing a semiconductor device, according to claim 10 , wherein each of the source electrode layer and the drain electrode layer overlaps with the gate electrode layer.
18. The method for manufacturing a semiconductor device, according to claim 10 , wherein a part of the oxide semiconductor film is exposed at the step of etching the conductive film.