Simplified process for forming thin film transistor matrix for liquid crystal display

• US 6,372,560 B1
• Filed: 03/31/2000
• Issued: 04/16/2002
• Est. Priority Date: 04/01/1999
• Status: Expired due to Term

• Current Assignee: HannStar Display Corporation
• Original Assignee: HannStar Display Corporation
• Inventors: Jen, Tean-Sen, Cheng, Jia-Shyong
• Primary Examiner(s): Pham, Long
• Assistant Examiner(s): COLEMAN, WILLIAM D
• Application Number:
  US09/540,593
• Time in Patent Office: 746 Days
• Field of Search: 438/160, 438/158, 438/162, 257/57, 257/72, 257/59, 257/749, 349/79, 349/87, 349/156, 349/153
• US Class Current: 438/160
• CPC Class Codes: G02F 1/136231 for reducing the number of lithographic steps
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/1288 employing particular masking sequences or specially adapted masks, e.g. half-tone mask

Abstract

A simplified process for forming a thin film transistor matrix for a liquid crystal display is disclosed. By forming and patterning a conductive layer overlying a TFT unit, a data line, a first connection line between the TFT unit and the data line, and a second connection line between the TFT unit and a pixel electrode can be simultaneously formed in the forming and patterning step. Furthermore, after a passivation layer is applied to protect the TFT matrix, an isolation window area, a contact hole and a TAB window can be created in a single patterning step. Therefore, masking steps can be reduced so as to simplify the process. On the other hand, owing to the first connection line for connecting the TFT unit and the scan line is of the same material as the scan line, the resistivity of the connection line is inherently low. Therefore, a TFTLCD of a large area can be made according to this process.

Claims

1. A process for forming a thin film transistor (TFT) matrix for a liquid crystal display (LCD), comprising steps of:

providing a substrate made of an insulating material;

forming a first conductive layer on a first side of said substrate, and using a first masking and patterning procedure to form a scan line and a gate electrode of a TFT unit;

successively forming an insulation layer, a semiconductor layer, a doped semiconductor layer, and a photoresist layer on said substrate with said scan line and said gate electrode;

providing an exposing source from a second side of said substrate opposite to said first side by using said scan line and said gate electrode as shields to form an exposed area and an unexposed area;

removing said photoresist, said doped semiconductor layer, and said semiconductor layer of said exposed area so that the remaining portion of said semiconductor and said doped semiconductor layers in said unexposed area has a specific shape substantially identical to the shape of said scan line together with said gate electrode;

forming a second conductive layer on said substrate with said semiconductor and said doped semiconductor layer of said specific shape, and using a second masking and patterning procedure to integrally form a data line, a first connection line between said TFT unit and said data line, and a second connection line connecting to said TFT unit;

removing a portion of said doped semiconductor layer with said data line, and said first and said second connection lines as shields; and

forming a transparent conductive layer on said substrate with said data line, and said first and said second connection lines, and using a third masking and patterning procedure to form a pixel electrode which is connected to said TFT unit through said second connection line.

2. The method according to claim 1 wherein said insulating material is a light-transmitting material, and said exposing source is a light radiation.

3. The method according to claim 2 wherein said light-transmitting material is glass.

4. The method according to claim 1 wherein said first conductive layer is formed of a material selected from a group consisting of chromium, tungsten molybdenum, tantalum, aluminum and copper.

5. The method according to claim 1 wherein said insulation layer is formed of a material selected from a group consisting of silicon nitride, silicon oxide, silicon oxynitride, tantalum oxide and aluminum oxide.

6. The method according to claim 1 wherein said semiconductor layer is formed of a material selected from a group consisting of amorphous silicon, micro-crystalline silicon and polysilicon.

7. The method according to claim 1 wherein said doped semiconductor layer is formed of a material selected from a group consisting of n⁺ amorphous silicon, n⁺ micro-crystalline silicon and n⁺ polysilicon.

8. The method according to claim 1 wherein said second conductive layer is one selected from a group consisting of a chromium/aluminum and a molybdenum/aluminum/molybdenum composite layers.

9. The method according to claim 1 wherein said transparent conductive layer is formed of a material selected from a group consisting of indium tin oxide, indium zinc oxide and indium lead oxide.

10. The method according to claim 9 wherein said transparent conductive layer is formed by sputtering.

11. The method according to claim 1 wherein said patterned transparent conductive layer is located by a single side of said TFT unit.

12. The method according to claim 1 further comprising a step of forming a passivation layer on said substrate with said data line, and said first and said second connection lines after said step of removing said portion of said doped semiconductor layer with said data line, and said first and said second connection lines as shields, and using a fourth masking and patterning procedure to define an isolation window area, and create a contact hole.

13. The method according to claim 12 wherein said passivation layer is formed of a material selected from a group consisting of silicon nitride and silicon oxynitride.

14. The method according to claim 12 further comprising a step of removing a portion of said semiconductor layer in said isolation window area with said patterned passivation layer as a shield to form an isolation window for cutting off the connection of said TFT unit with said data line through said semiconductor layer.

15. The method according to claim 12 wherein said transparent conductive layer extends into said contact hole to connect to said second connection line.

16. A process for forming a thin film transistor (TFT) matrix for a liquid crystal display (LCD), comprising steps of:

providing a light-emitting substrate;

forming a first conductive layer on said substrate at a first side hereof;

using a first photo-mask to pattern said first conductive layer as a scan line and a gate electrode of a TFT unit;

sequentially forming an insulation layer, a semiconductor layer, and a doped semiconductor layer over said substrate with said scan line and said gate electrode;

using said scan line and said gate electrode as shields, and a radiation light from a second side of said substrate opposite to said first side as an exposing source to pattern said semiconductor and said doped semiconductor layers to define source/drain electrodes of said TFT unit;

forming a second conductive layer over said substrate with said patterned semiconductor and doped semiconductor layers;

using a second photo-mask to pattern said second conductive layer as a data line, a first connection line between said TFT unit and said data line, and a second connection line connecting to said TFT unit;

using said data line, and said first and said second connection lines as shields to remove a portion of said doped semiconductor layer to define an isolation window area;

forming a passivation layer over said substrate with said patterned second conductive layer;

using a third photo-mask to pattern said passivation layer to simultaneously uncover said isolation window area, create a contact hole for exposing a portion of said second connection line, and create a tape automated bonding (TAB) window for exposing a portion of said scan line and said data line; and

using said patterned passivation layer as a shield to remove a portion of said semiconductor layer in said isolation window area to form an isolation window;

forming a transparent conductive layer on said substrate with said patterned passivation layer; and

using a fourth photo-mask to pattern said transparent conductive layer as a pixel electrode which extends into said contact hole to connect with said TFT unit through said second connection line.

17. The method according to claim 16 wherein said insulating material is glass.

18. The method according to claim 16 wherein said first conductive layer is one selected from a group consisting of a chromium, a tungsten molybdenum, a tantalum, a aluminum and a copper layers, and said second conductive layer is one selected from a group consisting of a chromium/aluminum and a molybdenum/aluminum/molybdenum composite layers.

19. The method according to claim 16 wherein said insulation layer is formed of a material selected from a group consisting of silicon nitride, silicon oxide, silicon oxynitride, tantalum oxide and aluminum oxide.

20. The method according to claim 16 wherein said semiconductor layer is formed of a material selected from a group consisting of amorphous silicon, micro-crystalline silicon and polysilicon, and said doped semiconductor layer is formed of a material selected from a group consisting of highly doped amorphous silicon, micro-crystalline silicon and polysilicon.

21. The method according to claim 16 wherein said passivation layer is formed of a material selected from a group consisting of silicon nitride and silicon oxynitride.

22. The method according to claim 16 wherein said transparent conductive layer is formed of a material selected from a group consisting of indium tin oxide, indium zinc oxide and indium lead oxide.

23. A process for forming a thin film transistor (TFT) matrix for a liquid crystal display (LCD), comprising steps of:

providing a substrate made of an insulating material;

forming a first conductive layer of a first pattern on a first side of said substrate as a scan line and a gate electrode of a TFT unit;

forming an insulation layer over said scan line and said gate electrode;

forming a semiconductor and a doped semiconductor layers of a second pattern substantially identical to said first pattern on said insulation layer for defining a source and a drain electrodes of said TFT unit;

forming a second conductive layer of a third pattern over said semiconductor and said doped semiconductor layers of said second pattern as a data line, a first connection line between said TFT unit and said data line, and a second connection line connecting to said TFT unit;

removing a portion of said semiconductor and said doped semiconductor layers to create an isolation window for cutting off the connection of said TFT unit with said data line through said semiconductor and said doped semiconductor layers;

removing another portion of said doped semiconductor layer to isolate said source electrode from said drain electrode of said TFT unit;

forming a passivation layer of a fourth pattern over said second conductive layer which includes a contact hole to expose a portion of said second connection line; and

forming a transparent conductive layer of a fifth pattern over said passivation layer as a pixel electrode, which further extends into said contact hole to connect with said second connection line.