THIN FILM TRANSISTOR

• US 20110121289A1
• Filed: 11/19/2010
• Published: 05/26/2011
• Est. Priority Date: 11/20/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: TAKAHASHI, Masahiro, MIYANAGA, Akiharu, YAMAZAKI, Shunpei, SAKAKURA, Masayuki, SAKATA, Junichiro, KISHIDA, Hideyuki
• Granted Patent: US 8,766,250 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• CPC Class Codes: H01L 29/10 with semiconductor regions connected to an electrode not carrying current to be rectified, amplified or switched and such electrode being part of a semiconductor device which comprises three or more electrodes
• CPC Class Codes: H01L 29/41733 for thin film transistors with insulated gate
• 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 including an oxide semiconductor with favorable electrical characteristics is provided. The thin film transistor includes a gate electrode provided over a substrate, a gate insulating film provided over the gate electrode, an oxide semiconductor film provided over the gate electrode and on the gate insulating film, a metal oxide film provided on the oxide semiconductor film, and a metal film provided on the metal oxide film. The oxide semiconductor film is in contact with the metal oxide film, and includes a region whose concentration of metal is higher than that of any other region in the oxide semiconductor film (a high metal concentration region). In the high metal concentration region, the metal contained in the oxide semiconductor film may be present as a crystal grain or a microcrystal.

Claims

1. A transistor comprising:

a gate electrode;

a gate insulating film adjacent to the gate electrode;

an oxide semiconductor film adjacent to the gate electrode with the gate insulating film interposed therebetween;

a titanium oxide film formed on the oxide semiconductor film; and

a titanium film formed on the titanium oxide film,

wherein the oxide semiconductor film contains at least one of indium, gallium, and zinc.

2. The transistor according to claim 1, wherein a type of the transistor is a bottom gate type.

3. The transistor according to claim 1, wherein the oxide semiconductor film comprises In—

Ga—

Zn—

O-based oxide semiconductor.

4. The transistor according to claim 1, wherein a concentration of hydrogen in the oxide semiconductor film is less than 5×

10¹⁶/cm³.

5. The transistor according to claim 1, wherein a carrier density of the oxide semiconductor film is 5×

10¹⁰/cm³ or less.

6. The transistor according to claim 1, wherein the titanium oxide film is formed by a heat treatment, and

wherein the heat treatment is performed after the titanium film is formed.

7. A transistor comprising:

a gate electrode;

a gate insulating film adjacent to the gate electrode;

an oxide semiconductor film adjacent to the gate electrode with the gate insulating film interposed therebetween; and

a titanium film formed over the oxide semiconductor film,

wherein the oxide semiconductor film contains at least one of indium, gallium, and zinc,

wherein the oxide semiconductor film includes a high metal concentration region, and

wherein a concentration of any one of indium, gallium and zinc in the high metal concentration region is higher than a concentration thereof in any other region in the oxide semiconductor film.

8. The transistor according to claim 7, wherein a type of the transistor is a bottom gate type.

9. The transistor according to claim 7, wherein the oxide semiconductor film comprises In—

Ga—

Zn—

O-based oxide semiconductor.

10. The transistor according to claim 7, wherein indium in the high metal concentration region is present as a crystal grain or a microcrystal.

11. The transistor according to claim 7, wherein a concentration of hydrogen in the oxide semiconductor film is less than 5×

10¹⁶/cm³.

12. The transistor according to claim 7, wherein a carrier density of the oxide semiconductor film is 5×

10³⁰/cm³ or less.

13. The transistor according to claim 7, wherein the high metal concentration region is formed by a heat treatment, and

wherein the heat treatment is performed after the titanium film is formed.

14. A transistor comprising:

a gate electrode;

a gate insulating film adjacent to the gate electrode;

an oxide semiconductor film adjacent to the gate electrode with the gate insulating film interposed therebetween;

a titanium oxide film formed on the oxide semiconductor film; and

a titanium film formed on the titanium oxide film,

wherein the oxide semiconductor film contains at least one of indium, gallium, and zinc,

wherein the oxide semiconductor film includes a high metal concentration region,

wherein the high metal concentration region is in contact with the titanium oxide film, and

wherein a concentration of any one of indium, gallium and zinc in the high metal concentration region is higher than a concentration thereof in any other region in the oxide semiconductor film.

15. The transistor according to claim 14, wherein a type of the transistor is a bottom gate type.

16. The transistor according to claim 14, wherein the oxide semiconductor film comprises In—

Ga—

Zn—

O-based oxide semiconductor.

17. The transistor according to claim 14, wherein indium in the high metal concentration region is present as a crystal grain or a microcrystal.

18. The transistor according to claim 14, wherein a concentration of hydrogen in the oxide semiconductor film is less than 5×

10¹⁶/cm³.

19. The transistor according to claim 14, wherein a carrier density of the oxide semiconductor film is 5×

10¹⁰/cm³ or less.

20. The transistor according to claim 14, wherein the high metal concentration region is formed by a heat treatment, and

wherein the heat treatment is performed after the titanium film is formed.

21. The transistor according to claim 14, wherein the titanium oxide film is formed by a heat treatment, and

wherein the heat treatment is performed after the titanium film is formed.