Thin film transistor having oxide semiconductor layer and manufacturing method thereof
A thin film transistor has a semiconductor thin film including zinc oxide, a protection film formed on entirely the upper surface of the semiconductor thin film, a gate insulating film formed on the protection film, a gate electrode formed on the gate insulating film above the semiconductor thin film, and a source electrode and drain electrode formed under the semiconductor thin film so as to be electrically connected to the semiconductor thin film.
1. A method of manufacturing a thin film transistor, comprising:
continuously forming a semiconductor thin film forming film including zinc oxide and a protection film forming film;
forming a protection film by etching the protection film forming film;
forming a semiconductor thin film having a substantially same plan-view shape as the protection film, by etching the semiconductor thin film forming film by using the protection film as a mask;
forming a gate insulating film which covers the protection film; and
forming a gate electrode on the gate insulating film.
2. The method according to claim 1 ,
wherein etching of the protection film forming film is reactive plasma etching.
3. The method according to claim 2 ,
wherein the reactive plasma etching is performed by using a reaction gas containing sulferhexafluoride.
4. The method according to claim 1 ,
wherein etching of the semiconductor thin film forming film is performed by using an etching liquid containing sodium hydroxide aqueous solution.
5. The method according to claim 1 ,
wherein a source electrode and a drain electrode are formed before the semiconductor thin film forming film containing zinc oxide and the protection film forming film are continuously formed.
6. The method according to claim 5 ,
wherein a plurality of ohmic contact layer forming layers made of a material including zinc oxide are formed on the source electrode and the drain electrode.
7. The method according to claim 6 ,
wherein the ohmic contact layer forming layers are etched using an etching liquid including an alkaline aqueous solution.
8. The method according to claim 6 ,
wherein after the semiconductor thin film having the plan-view shape is formed, a plurality of ohmic contact layers are formed by etching the ohmic contact layer forming layers by using the protection film as a mask.
9. The method according to claim 8 ,
wherein etching of the ohmic contact layer forming layers is performed by using an etching liquid containing sodium hydroxide aqueous solution.
10. The method according to claim 1 ,
wherein an upper insulating film is formed on the gate electrode.
11. The method according to claim 10 ,
wherein an auxiliary capacitor electrode is formed on the upper insulating film.
12. The method according to claim 11 ,
wherein the auxiliary capacitor electrode is formed so as to substantially entirely cover the semiconductor thin film.
13. The method according to claim 12 ,
wherein an overcoat film is formed on the auxiliary capacitor electrode.
14. The method according to claim 13 ,
wherein a pixel electrode electrically connected to the source electrode is formed on the overcoat film.
15. The method according to claim 14 ,
wherein forming the pixel electrode comprises forming a contact hole that penetrates through the overcoat film, the upper insulating film, and the gate insulating film to expose a part of the source electrode.
16. The method according to claim 1 ,
wherein an auxiliary capacitor electrode electrically insulated from the gate electrode is formed on the gate insulating film.
17. The method according to claim 16 ,
wherein an overcoat film is formed on the gate insulating film and the gate electrode.
18. The method according to claim 17 ,
wherein a pixel electrode connected to the source electrode is formed on the overcoat film.
19. The method according to claim 18 ,
wherein forming the pixel electrode comprises exposing a part of the source electrode by penetrating the gate electrode and the overcoat film.