Thin film transistor having oxide semiconductor layer and manufacturing method thereof

• US 20060284172A1
• Filed: 06/07/2006
• Published: 12/21/2006
• Est. Priority Date: 06/10/2005
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Casio Computer Company Limited
• Inventors: Ishii, Hiromitsu
• Granted Patent: US 7,566,904 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 29/66969 of devices having semiconductor bodies not comprising group 14 or group 13/15 materials comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials, comprising cuprous oxide or cuprous iodide H01L21/02365
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate

Abstract

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.

Claims

1. A thin film transistor, comprising:

a semiconductor thin film including zinc oxide;

a protection film formed on entirely an 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 a drain electrode formed under the semiconductor thin film so as to be electrically connected to the semiconductor thin film.

2. The thin film transistor according to claim 1,

wherein ohmic contact layers made of n type zinc oxide are formed respectively on upper surfaces of the source electrode and the drain electrode under the semiconductor thin film, so as to have their end surfaces, which face each other, formed in a same shape as that of end surfaces of the source electrode and the drain electrode that face each other.

3. The thin film transistor according to claim 1,

wherein ohmic contact layers made of n type zinc oxide are formed respectively on upper surfaces of the source electrode and the drain electrode under the semiconductor thin film, so as to have their end surfaces, which face each other, protrude from end surfaces of the source electrode and the drain electrode that face each other.

4. The thin film transistor according to claim 1, comprising an overcoat film which covers the gate electrode.

5. The thin film transistor according to claim 4,

wherein a pixel electrode is formed on an upper surface of the overcoat film so as to be connected to the source electrode.

6. The thin film transistor according to claim 5,

wherein an auxiliary capacitor electrode is formed between the gate insulating film and the overcoat film.

7. The thin film transistor according to claim 6,

wherein a data line connected to the drain electrode is formed on a same layer as that of the drain electrode, the auxiliary capacitor electrode comprises a portion which includes a region overlapping the data line via the gate insulating film, and a width of the portion of the auxiliary capacitor electrode including the region overlapping the data line is larger than a width of the data line.

8. The thin film transistor according to claim 7,

wherein the auxiliary capacitor electrode overlaps all peripheral edges of the pixel electrode.

9. The thin film transistor according to claim 8, further comprising an insulating film which covers the gate electrode,

wherein the auxiliary capacitor electrode is formed on an upper surface of the insulating film.

10. The thin film transistor according to claim 9,

wherein a scanning line connected to the gate electrode is formed on a same layer as that of the gate electrode, the auxiliary capacitor electrode comprises a portion that overlaps the scanning line via the insulating film, and a width of the portion of the auxiliary capacitor electrode overlapping the scanning line is larger than a width of the data line.

11. The thin film transistor according to claim 9,

wherein the auxiliary capacitor electrode is formed on an upper surface of the gate insulating film.

12. A manufacturing method of 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 plan-view shape substantially same as that of 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.

13. The manufacturing method of the thin film transistor according to claim 12,

wherein etching of the protection film forming film is reactive plasma etching.

14. The manufacturing method of the thin film transistor according to claim 13,

wherein the reactive plasma etching is performed by using a reaction gas containing sulferhexafluoride.

15. The manufacturing method of the thin film transistor according to claim 12,

wherein etching of the semiconductor thin film forming film is performed by using an etching liquid containing sodium hydroxide aqueous solution.

16. The manufacturing method of the thin film transistor according to claim 12,

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.

17. The manufacturing method of the thin film transistor according to claim 16,

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.

18. The manufacturing method of the thin film transistor according to claim 17,

wherein a step of forming the ohmic contact layer forming layers is performed by forming an ohmic contact layer forming layer on the source electrode and the drain electrode, and by etching the ohmic contact layer forming layer by using an etching liquid including an alkaline aqueous solution.

19. The manufacturing method of the thin film transistor according to claim 17,

wherein after the semiconductor thin film having the plan-view shape substantially same as that of the protection film 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.

20. The manufacturing method of the thin film transistor according to claim 19,

wherein etching of the ohmic contact layer forming layers is performed by using an etching liquid containing sodium hydroxide aqueous solution.

21. The manufacturing method of the thin film transistor according to claim 12,

wherein an upper insulating film is formed on the gate electrode.

22. The manufacturing method of the thin film transistor according to claim 21,

wherein an auxiliary capacitor electrode is formed on the upper insulating film.

23. The manufacturing method of the thin film transistor according to claim 22,

wherein the auxiliary capacitor electrode is formed so as to substantially entirely cover the semiconductor thin film.

24. The manufacturing method of the thin film transistor according to claim 23,

wherein an overcoat film is formed on the auxiliary capacitor electrode.

25. The manufacturing method of the thin film transistor according to claim 24,

wherein a pixel electrode electrically connected to the source electrode is formed on the overcoat film.

26. The manufacturing method of the thin film transistor according to claim 25,

wherein forming of the pixel electrode includes a step of 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.

27. The manufacturing method of the thin film transistor according to claim 12,

wherein an auxiliary capacitor electrode electrically insulated from the gate electrode is formed on the gate insulating film.

28. The manufacturing method of the thin film transistor according to claim 27,

wherein an overcoat film is formed on the gate insulating film and the gate electrode.

29. The manufacturing method of the thin film transistor according to claim 28,

wherein a pixel electrode connected to the source electrode is formed on the overcoat film.

30. The manufacturing method of the thin film transistor according to claim 29,

wherein forming of the pixel electrode includes a step of exposing a part of the source electrode by penetrating the gate electrode and the overcoat film.