OXIDE THIN FILM TRANSISTOR AND METHOD OF FABRICATING THE SAME

• US 20100084649A1
• Filed: 08/27/2009
• Published: 04/08/2010
• Est. Priority Date: 10/08/2008
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Seo, Hyun-Sik, Bae, Jong-Uk, Kim, Dae-Hwan
• Granted Patent: US 8,187,919 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• CPC Class Codes: H01L 29/45 Ohmic electrodes
• 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

An oxide thin film transistor (TFT) and its fabrication method are disclosed. In a TFT of a bottom gate structure using amorphous zinc oxide (ZnO)-based semiconductor as an active layer, source and drain electrodes are formed, on which the active layer made of oxide semiconductor is formed to thus prevent degeneration of the oxide semiconductor in etching the source and drain electrodes. The oxide TFT includes: a gate electrode form on a substrate; a gate insulating layer formed on the gate electrode; source and drain electrodes formed on the gate insulating layer and having a multi-layer structure of two or more layers; and an active layer formed on the source and drain electrodes and formed of amorphous zinc oxide-based semiconductor, wherein a metal layer such as indium-tin-oxide, molybdenum, and the like, having good ohmic-contact characteristics with titanium and a titanium alloy having good bonding force with oxygen or the oxide-based semiconductor is formed at an uppermost portion of the source and drain electrodes. In a method for fabricating an oxide TFT, a silicon nitride film is deposited with a sputter equipment without the necessity of H₂ gas so as to be used as a protection layer of oxide semiconductor to thus prevent degradation of the characteristics of the oxide semiconductor.

Claims

1. A method for fabricating an oxide thin film transistor, the method comprising:

forming a gate electrode on a substrate;

forming a gate insulating layer on the substrate;

forming source and drain electrodes on the gate insulating layer; and

forming an active layer made of amorphous zinc oxide-based semiconductor at an upper portion of the source and drain electrodes.

2. The method of claim 1, wherein the substrate is formed as a glass substrate or a plastic substrate.

3. The method of claim 1, wherein the active layer is made of amorphous zinc oxide (ZnO)-based semiconductor.

4. The method of claim 1, wherein the active layer is formed with a thickness of 500Å

to 1000Å

containing an oxygen density of about 1% to about 20% in a reactive gas during sputtering.

5. The method of claim 1, wherein the source and drain electrodes comprise first source and drain electrodes formed on the gate insulating layer and second source and drain electrodes formed on the first source and drain electrodes and electrically connecting with the upper active layer.

6. The method of claim 5, wherein the second source and drain electrodes are made of titanium or titanium alloy having good bonding force with oxygen or metal such as indium tin oxide or molybdenum having good ohmic-contact characteristics with the oxide-based semiconductor.

7. An oxide thin film transistor (TFT) comprising:

a gate electrode on a substrate;

a gate insulating layer on the gate electrode;

source and drain electrodes on the gate insulating layer and having a multi-layer structure of two or more layers; and

an active layer on the source and drain electrodes comprised of amorphous zinc oxide-based semiconductor,

wherein a metal layer such as indium-tin-oxide, molybdenum, and the like, having good ohmic-contact characteristics with titanium and a titanium alloy having good bonding force with oxygen or the oxide-based semiconductor is formed at an uppermost portion of the source and drain electrodes.

8. The TFT of claim 7, wherein the substrate is formed as a glass substrate or a plastic substrate.

9. The TFT of claim 7, wherein the active layer comprises amorphous zinc oxide (ZnO)-based semiconductor.

10. The TFT of claim 7, wherein the active layer has a thickness of about 500Å

to about 1000Å

containing an oxygen density of about 1% to about 20% in a reactive gas during sputtering.

11. A method for fabricating an oxide thin film transistor, the method comprising:

forming a gate electrode on a substrate;

forming a gate insulating layer on the gate electrode;

forming an active layer made of amorphous zinc oxide-based semiconductor on the gate insulating layer;

forming source and drain electrodes electrically connecting with a certain region of the active layer on the substrate with the active layer formed thereon;

forming a first protection layer formed of silicon nitride film by injecting only N₂ gas by using a stopper equipment on the substrate with the source and drain electrodes formed thereon, the first protection layer having a thickness of about 1000Å

to about 400Å

; and

forming a second protection layer on the first protection layer.

12. The method of claim 11, wherein the active layer is made of a-IGZO semiconductor.

13. The method of claim 11, wherein the first protection layer is formed by jetting N₂ gas to a wall surface of a sputter chamber so as to be reflected and introduced to a cathode.

14. The method of claim 11, wherein the second protection layer is formed by additionally injecting an inert gas such as Ar gas in a sputtering process of the first protection layer.

15. The method of claim 11, wherein the second protection layer is formed of an organic insulating layer or a high dielectric oxide film such as hafnium oxide or aluminum oxide.

16. The method of claim 11, further comprising:

forming a third protection layer comprising an inorganic insulating layer or an organic insulating layer on the second protection layer.