Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2002-06-03
2004-05-04
Chowdhury, Tarifor R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C438S030000
Reexamination Certificate
active
06731352
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a liquid crystal display fabrication method. More particularly, the present invention relates to decrease the number of the mask used in the fabrication process, such that only six mask steps are required for completing the manufacture of the drive area and pixel area.
2. Description of Related Art
A low temperature polycrystalline silicon (LTPS) manufacturing process is used to fabricate thin film transistor liquid crystal display (TFT-LCD). Because the electron migration rate in polysilicon is faster than in amorphous silicon, the resolution of the LTPS TFT-LCD increases and quality is better. There are two parts of a TFT-LCD; one is the driving area and the other is the pixel area. The driving ICs are located on the driving area and the driving ICs must be made from polysilicon. In traditional amorphous TFT-LCD manufacture processes, only the pixel electrodes on the pixel area are formed. The driving ICs are bought and plastered on the driving area. The low temperature polycrystalline silicon manufacture process makes forming the pixel electrode and driving ICs simultaneously possible.
Use of the low temperature polycrystalline silicon manufacturing process to form the pixel electrode and driving ICs simultaneously is disclosed in U.S. Pat. No. 6,140,162, but twelve masks are employed in this manufacture process. More mask steps mean that the fabrication cost is higher. In fact, the cost of the twelve mask-process will be several times higher than the cost of the amorphous TFT-LCD manufacture process. The competitivity of the LTPS TFT-LCD will decrease. Therefore, the present invention provides a method of decreasing the number of the mask used in the fabrication process. Only six mask steps are required for completing the manufacture of the drive are and pixel area. The cost for producing an LTPS TFT-LCD will decrease and the competitivity of the LTPS TFT-LCD will increase.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a liquid crystal display fabrication method in which only six mask steps are used in the fabrication process.
It is another an objective of the present invention to provide a liquid crystal display fabrication method to lower the cost for producing an LTPS TFT-LCD and raise the competitivity of the LTPS TFT-LCD.
It is still another an objective of the present invention to provide a liquid crystal display fabrication method in which a self-aligned process is used to define the source/drain region and channel region to lower the number of masks used in the manufacturing process.
In accordance with the foregoing and other objectives of the present invention, a method for decreasing the mask number of the manufacture process for producing an LTPS TFT-LCD is provided. An insulation substrate is provided and a buffer layer is formed on the insulation substrate. Then, a polysilicon layer is formed on the buffer layer. The polysilicon layer is defined and a driving area and a pixel area are formed. A first insulation layer is formed and covers the polysilicon layer. A patterned conductive layer is formed on the driving area and the pixel area in which the patterned conductive layer serves as gates and upper electrodes of capacitors.
Thereafter, using the patterned conductive layer as a mask, a source/drain, channel region and lower electrode are formed in the polysilicon layer by an ion-doping process. A second insulation layer is formed and covers the insulation substrate. A plurality of first openings is formed and the gate and the source/drain are exposed. A second conductive layer is formed and covers the second insulation layer and the first opening is filled. Then, the second conductive layer is patterned, and a source/drain line is formed and contacts electrically with the source/drain. A dielectric layer is formed and covers the second insulation layer and the second conductive layer; the dielectric layer has a planar surface. A second opening is formed and the drain line on the pixel area is exposed. Finally, a pixel electrode is formed and contacts electrically with the drain line.
In conclusion, the invention allows only six mask steps are needed in the manufacture process of the LTPS TFT-LCD. The cost for producing an LTPS TFT-LCD decreases and competitivity of the LTPS TFT-LCD will increase.
It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5580801 (1996-12-01), Maegawa et al.
patent: 5595923 (1997-01-01), Zhang et al.
patent: 5614426 (1997-03-01), Funada et al.
patent: 5783468 (1998-07-01), Zhang et al.
patent: 6576504 (2003-06-01), Ohtani et al.
Lin Gwo-Long
Lu I-Min
Shih Chu-Jung
Wu I-Wei
Chowdhury Tarifor R.
Chung David Y
Toppoly Optoelectronics Corp.
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