Method of fabricating polysilicon film by excimer laser crystallization process

• US 6,964,831 B2
• Filed: 07/25/2003
• Issued: 11/15/2005
• Est. Priority Date: 05/02/2003
• Status: Active Grant

• Current Assignee: China Star Optoelectronics International (HK) Limited (TCL Technology Group Corp.)
• Original Assignee: AU Optronics Corporation
• Inventors: Lin, Kun-chih
• Primary Examiner(s): Young, Christopher G.
• Application Number:
  US10/604,485
• Publication Number:
  US 20040222187A1
• Time in Patent Office: 844 Days
• Field of Search: 430/22, 430/313, 430/314, 430/316, 430/317, 430/330, 430/945, 438/166, 438/482, 438/486, 438/487, 438/488, 216/65
• US Class Current: 430/22
• CPC Class Codes: G03F 9/708 Mark formation
• CPC Class Codes: G03F 9/7084 Position of mark on substrate, i.e. position in (x, y, z) of mark, e.g. buried or resist covered mark, mark on rearside, at the substrate edge, in the circuit area, latent image mark, marks in plural levels
• CPC Class Codes: H01L 21/02422 Non-crystalline insulating materials, e.g. glass, polymers
• CPC Class Codes: H01L 21/02488 Insulating materials
• CPC Class Codes: H01L 21/02502 consisting of two layers
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02595 polycrystalline
• CPC Class Codes: H01L 21/02686 Pulsed laser beam
• CPC Class Codes: H01L 2223/54453 for use prior to dicing
• CPC Class Codes: H01L 23/544 Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps test patterns for characterising or monitoring manufacturing processes H01L22/00
• CPC Class Codes: H01L 29/6675 Amorphous silicon or polysilicon transistors
• CPC Class Codes: H01L 29/78672 Polycrystalline or microcrystalline silicon transistor
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: Y10S 430/146 Laser beam

Abstract

A method of fabricating a polysilicon film by an excimer laser crystallization process is disclosed. First, a substrate with a first region, a second region surrounding the first region, and a third region is provided. An amorphous silicon film is formed on the substrate. A photo-etching process is performed to remove parts of amorphous silicon film in the third region to form an alignment mark. Then, a mask layer is formed on the amorphous silicon film and a second photo-etching process is performed to remove the mask layer in the first region to expose the amorphous silicon film in the first region. After that, an excimer laser irradiation process is performed so that the amorphous silicon film in the first region is crystallized and becomes a polysilicon film.

Claims

1. A method of fabricating a polysilicon film by an excimer laser crystallization (ELC) process comprising following steps:

providing a substrate, the substrate surface defined with a first region, a second region surrounding the first region, and a third region;

forming an amorphous silicon film on the silicon substrate;

performing a first photo-etching process to remove parts of the amorphous silicon film in the third region to form an alignment mark in the third region;

forming a mask layer on the amorphous silicon film;

performing a second photo-etching process to remove the mask layer on the amorphous film in the first region; and

performing the excimer laser crystallization process with an excimer laser to make the amorphous film in the first region crystallize to a polysilicon film.

2. The method of claim 1 wherein the substrate further comprises a buffer layer and the amorphous silicon film is formed on the surface of the buffer layer.

3. The method of claim 1 wherein the method further comprises a step of removing the mask layer after forming the polysilicon film.

4. The method of claim 1 wherein the polysilicon film functions as an active area of a thin film transistor.

5. The method of claim 1 wherein the alignment mark is used to increase the alignment ability of photo masks in latter processes.

6. The method of claim 1 wherein the mask layer comprises a silicon oxide layer, a silicon nitride layer, or a silicon-oxy nitride layer.

7. The method of claim 1 wherein the excimer laser excimer crystallization process uses an excimer laser to irradiate the amorphous film to make the amorphous silicon film in the second region, which is covered with the mask layer, become partially melted and make the amorphous film in the first region, which is not covered with the mask layer, become completely melted, and grains are grown laterally toward the first region from the interface between the first region and the second region so as to form a polysilicon film in the first region.

8. The method of claim 1 wherein the excimer laser comprises a long pulse duration laser.

9. The method of claim 8 wherein the period of the long pulse duration laser is in a range of 150 to 250 ns.

10. The method of claim 1 wherein the method further comprises a step of forming a heat-retaining capping layer on the mask layer and the amorphous silicon layer before performing the excimer laser crystallization process to increase the size of the grains in the polysilicon film.

11. A method of forming a polysilicon film by an excimer laser crystallization process, the method comprising following steps:

providing a substrate, the substrate surface defined with a first region, a second region surrounding the first region, and a third region;

forming an amorphous silicon film on the substrate;

performing a first photo-etching process to remove parts of the amorphous silicon film in the third region to form an alignment mark in the third region;

forming a heat-retaining capping layer covering the amorphous silicon film and the substrate;

forming a mask layer on the heat-retaining capping layer;

performing a second photo-etching process to remove the mask layer in the first region; and

performing the excimer laser crystallization process with an excimer laser to make the amorphous film in the first region crystallize to a polysilicon film.

12. The method of claim 11 wherein the substrate comprises a buffer layer and the amorphous silicon film is formed on the buffer layer.

13. The method of claim 11 wherein the method further comprises a step of removing the mask layer and the heat-retaining capping layer alter forming the polysilicon film.

14. The method of claim 11 wherein the polysilicon film functions as an active area of a thin film transistor.

15. The method of claim 11 wherein the alignment mark is used to increase the alignment ability of photo masks in latter processes.

16. The method of claim 11 wherein the mask layer comprises a silicon oxide layer, a silicon nitride layer, or a silicon-oxy nitride layer.

17. The method of claim 11 wherein the heat-retaining capping layer comprises a silicon oxide layer, a silicon nitride layer, or a silicon-oxy nitride layer.

18. The method of claim 11 wherein the excimer laser crystallization process uses an excimer laser to irradiate the amorphous film to make the amorphous silicon film in the second region, which is covered with the mask layer, become partially melted and make the amorphous film in the first region, which is not covered with the mask layer, become completely melted, and grains are grown laterally toward the first region from the interface between the first region and the second region so as to form a polysilicon film in the first region.

19. The method of claim 11 wherein the excimer laser comprises a long pulse duration laser.

20. The method of claim 19 wherein the period of the long pulse duration laser is in a range of 150 to 250 ns.