METHOD OF FABRICATING OXIDE THIN FILM TRANSISTOR

• US 20100304528A1
• Filed: 12/29/2009
• Published: 12/02/2010
• Est. Priority Date: 06/02/2009
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Kim, Dae-Won, Bae, Jong-Uk
• Granted Patent: US 7,981,720 B2
• Time in Patent Office: Days
• US Class Current: 438/104
• CPC Class Codes: H01L 21/02554 Oxides
• CPC Class Codes: H01L 21/02565 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/02592 amorphous
• CPC Class Codes: H01L 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• 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 27/1288 employing particular masking sequences or specially adapted masks, e.g. half-tone mask
• 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

According to a method of fabricating an oxide thin-film transistor, when a thin-film transistor is fabricated by using an amorphous zinc oxide (ZnO)-based semiconductor as an active layer, it may be possible to reduce a tact time as well as attain an enhanced element characteristic by depositing an insulation layer having an oxide characteristic in-situ through controlling oxygen (O₂) flow subsequent to depositing an oxide semiconductor using a sputter, and the method may include the steps of forming a gate electrode on a substrate; forming a gate insulation layer on the substrate; depositing an amorphous zinc oxide-based semiconductor layer made of an amorphous zinc oxide-based semiconductor and an amorphous zinc oxide-based insulation layer having an oxide characteristic in-situ on the gate insulation layer; forming an active layer made of the amorphous zinc oxide-based semiconductor over the gate electrode while at the same time forming a channel protection layer made of the amorphous zinc oxide-based insulation layer on a channel region of the active layer; and forming a source electrode and a drain electrode electrically connected to a source region and a drain region of the active layer over the active layer.

Claims

1. A method of fabricating an oxide thin-film transistor, comprising:

forming a gate electrode on a substrate;

forming a gate insulation layer on the substrate;

depositing an amorphous zinc oxide-based semiconductor layer made of an amorphous zinc oxide-based semiconductor and an amorphous zinc oxide-based insulation layer having an oxide characteristic in-situ on the gate insulation layer;

forming an active layer made of the amorphous zinc oxide-based semiconductor over the gate electrode while at the same time forming a channel protection layer made of the amorphous zinc oxide-based insulation layer on a channel region of the active layer; and

forming a source electrode and a drain electrode electrically connected to a source region and a drain region of the active layer over the active layer.

2. The method of fabricating an oxide thin-film transistor of claim 1, wherein the gate electrode, the source electrode, and the drain electrode are formed of a transparent conductive material such as indium-tin-oxide, and indium-zinc-oxide.

3. The method of fabricating an oxide thin-film transistor of claim 1, wherein the active layer is formed of an a-IGZO semiconductor.

4. The method of fabricating an oxide thin-film transistor of claim 1, wherein the substrate is formed of a glass substrate or a plastic substrate.

5. The method of fabricating an oxide thin-film transistor of claim 1, wherein the amorphous zinc oxide-based semiconductor layer and the amorphous zinc oxide-based insulation layer are formed in-situ by controlling oxygen flow within the same sputtering system.

6. The method of fabricating an oxide thin-film transistor of claim 1, wherein the amorphous zinc oxide-based semiconductor layer may be formed at a deposition speed within the range of 1-200 Å

/sec for a DC or RF sputtering and at an oxygen concentration of 1-40% in the reaction gas during a sputtering, though they may be varied more or less based on the process conditions.

7. The method of fabricating an oxide thin-film transistor of claim 1, wherein the amorphous zinc oxide-based insulation layer may be formed at a deposition speed within the range of 1-200 Å

/sec for a DC or RF sputtering and at an oxygen concentration of 30-70% in the reaction gas during a sputtering, though they may be varied more or less based on the process conditions.

8. The method of fabricating an oxide thin-film transistor of claim 1, wherein the step of forming the active layer and channel protection layer comprises,

forming a predetermined first photoresist film pattern on a substrate formed with the amorphous zinc oxide-based semiconductor layer and the amorphous zinc oxide-based insulation layer;

selectively removing the amorphous zinc oxide-based semiconductor layer and insulation layer formed under the first photoresist film pattern using the first photoresist film pattern as a mask to form an active layer made of the amorphous zinc oxide-based semiconductor over the gate electrode, and forming an insulation film pattern made of the insulation pattern over the active layer;

performing an ashing process for removing part of the first photoresist film pattern to form a predetermined second photoresist film pattern on the insulation film pattern; and

selectively removing part of the insulation film pattern using the second photoresist film pattern as a mask to form a channel protection layer made of the insulation layer on the substrate.

9. The method of fabricating an oxide thin-film transistor of claim 1, wherein the step of forming the active layer and channel protection layer comprises,

forming a first photoresist film pattern having a first thickness and a second photoresist film pattern and a third photoresist film pattern having a second thickness on the substrate using a diffraction mask for which a diffraction pattern is applied to the source/drain regions of the active layer;

selectively patterning the amorphous zinc oxide-based semiconductor layer using the first photoresist film pattern through third photoresist film pattern as a mask to form an active layer made of the amorphous zinc oxide-based semiconductor over the gate electrode;

removing the second photoresist film pattern and third photoresist film pattern while at the same time removing part of the thickness of the first photoresist film pattern to form a fourth photoresist film pattern having a third thickness; and

selectively patterning the insulation layer using the fourth photoresist film pattern as a mask to form a channel protection layer on a channel region of the active layer.

10. The method of fabricating an oxide thin-film transistor of claim 1, wherein the active layer and channel protection layer are etched at the same time and the source/drain electrodes thereon are brought into contact with a lateral surface of the active layer.