Method for fabricating organic thin film transistor and method for fabricating liquid crystal display device using the same

• US 7,754,523 B2
• Filed: 06/09/2005
• Issued: 07/13/2010
• Est. Priority Date: 08/30/2004
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Nam, Dae-Hyun, Choi, Nack-Bong, Seo, Hyun-Sik
• Primary Examiner(s): Stark; Jarrett J
• Application Number:
  US11/148,293
• Publication Number:
  US 20060046339A1
• Time in Patent Office: 1,860 Days
• Field of Search: 438/99, 438/30, 438/149, 257/E51.005
• US Class Current: 438/99
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: H10K 10/466 Lateral bottom-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 10/468 characterised by the gate dielectrics
• CPC Class Codes: H10K 10/471 the gate dielectric comprising only organic materials
• CPC Class Codes: H10K 10/472 the gate dielectric comprising only inorganic materials
• CPC Class Codes: H10K 10/88 Passivation; Containers; Encapsulations
• CPC Class Codes: H10K 71/231 by etching of existing layers
• CPC Class Codes: H10K 71/233 by photolithographic etching
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene

Abstract

A method for fabricating an organic thin film transistor includes forming a gate electrode on a substrate, forming a gate insulating layer on the substrate including the gate electrode, forming an organic active pattern on the gate insulating layer using a rear exposing process, and forming source and drain electrodes on the organic active pattern.

Claims

1. A method for fabricating an organic thin film transistor comprising:

forming a gate electrode on a substrate;

forming a gate insulating layer on the substrate including the gate electrode;

forming an organic film and an inorganic film on the gate insulating layer;

coating a first photoresist film on the inorganic film;

exposing the first photoresist film by irradiating light through a rear surface of the substrate;

developing the exposed first photoresist film to form a first photoresist pattern at a region corresponding to the gate electrode; and

etching the organic film and the inorganic film by using the first photoresist pattern as a first mask to form an organic active pattern including a thin film transistor channel;

ashing the first photoresist pattern to form a second photoresist pattern having a width smaller than that of the first photoreist pattern;

etching a part of the etched inorganic film using the ashed second photoresist pattern so that the area of upper surface of the inorganic film is smaller than that of the etched organic active pattern to expose a part of upper surface of the etched organic active pattern at the both end sides of the inorganic film;

forming source and drain electrodes on the inorganic film and the exposed part of the organic active pattern;

forming a passivation film on the entire surface of the substrate including the source and drain electrodes;

forming a contact hole in the passivation film, the contact hole exposing a portion of the drain electrode; and

forming a pixel electrode on the passivation film,

wherein the source and drain electrodes are respectively formed of a single layer made of an opaque metal selected from the group consisting of Cu, Mo, Ta, Al, Cr, Ti, Al alloy, the opaque metal being contacted directly with the side surfaces of organic active pattern and the exposed part of the organic active pattern and the pixel electrode is electrically connected to the opaque metal to be directly contacted with the side surface of the organic active pattern through the contact hole.

2. The method of claim 1, wherein a stacking of the organic film includes depositing one of pentacene and polyacrylamine (PAA) on the gate insulating layer.

3. The method of claim 1, wherein a stacking of the inorganic film includes depositing one of silicon nitride (SiNx), silicon oxide (SiOx), and indium oxide (InOx) on the organic film.

4. The method of claim 1, wherein etching a part of the inorganic film comprises:

removing a portion of the first photoresist pattern to form a second photoresist pattern, the second photoresist pattern exposing portions of the etched inorganic film; and

etching the exposed portions of the etched inorganic film using the second photoresist pattern as a mask.

5. The method of claim 1, wherein forming the gate electrode includes:

depositing a metal material; and

patterning the metal material using a photolithography process.

6. The method of claim 1, wherein forming the gate electrode includes printing Ag past on the substrate.

7. The method of claim 1, wherein forming the gate insulating layer includes coating an organic material on the substrate.

8. The method of claim 7, wherein the organic material of the gate insulating layer includes one of polyvinylPyrrolidone (PVP) and polymethylmethacrylate (PMMA).

9. The method of claim 1, wherein forming the source and drain electrodes includes printing or coating a conductive polymer on the organic active pattern.

10. The method of claim 1, wherein the passivation film includes an organic material.

11. The method of claim 10, wherein the organic material of the passivation film includes one of acryl and benzocyclobutene (BCB).

12. The method of claim 1, wherein the pixel electrode includes an organic material.

13. The method of claim 12, wherein the organic material of the pixel electrode includes polyelyene dioxy thiospnene (PEDOT).

15. The method of claim 12, wherein a stacking of the organic film includes depositing one of pentacene and polyacylamine (PAA) on the gate insulating layer.

16. The method of claim 12, wherein the etching a part of the inorganic film comprises:

removing a portion of the first photoresist pattern to form a second photoresist pattern, the second photoresist pattern exposing portions of the etched inorganic film; and

etching the exposed portions of the etched inorganic film using the second photoresist pattern as a mask.

17. The method of claim 12, further comprising:

forming a black matrix on the second substrate;

forming a color filter on the black matrix; and

forming a common electrode on the color filter.

14. A method of fabricating a liquid crystal display device comprising:

forming a gate electrode on a first substrate;

forming a gate insulating layer on the first substrate including the gate electrode;

forming an organic film and an inorganic film on the gate insulating layer;

coating a first photoresist film on the inorganic film;

exposing the first photoresist film by irradiating light through a rear surface of the first substrate;

developing the exposed first photoresist film to form a first photoresist pattern at a region corresponding to the gate electrode;

etching the organic film and the inorganic film by using the first photoresist pattern as a mask to form an organic active pattern including a thin film transistor channel;

ashing the first photoresist pattern to form a second photoresist pattern having a width smaller that that of the first photoreist pattern;

etching a part of the etched inorganic film using the ashed second photoresist pattern so that the area of upper surface of the inorganic film is smaller than that of the etched organic active pattern to expose a part of upper surface of the organic active pattern at the both end sides of the inorganic film;

forming source and drain electrodes on the inorganic film and the exposed part of the organic active pattern;

forming a passivation film on the entire surface of the substrate including the source and drain electrodes;

forming a contact hole in the passivation film, the contact hole exposing a portion of the drain electrode; and

forming a pixel electrode on the passivation film;

attaching the first substrate to a second substrate with a space therebetween; and

forming a liquid crystal layer in the space between the first and second substrates,

wherein the source and drain electrodes are respectively formed of a single layer made of an opaque metal selected from the group consisting of Cu, Mo, Ta, Al, Cr, Ti, Al alloy, the opaque metal being contacted directly with the side surfaces of organic active pattern and the exposed part of the organic active pattern and the pixel electrode is electrically connected to the opaque metal to be directly contacted with the side surface of the organic active pattern through the contact hole.