Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Patent
1998-02-13
1999-11-23
Bowers, Charles
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
438608, 438609, 438626, 257 72, 257 59, 257 64, 257347, 428 1, 428447, 346140R, 4274192, H01L 2904, G02F 1136, G02F 11333, B05C 502
Patent
active
059899450
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film device including a thin film laminate structure such as a thin film transistor (hereinafter referred to as a TFT) and a method for making the same, and in particular relates to a thin film device capable of low cost production due to a decreased initial investment and a method for making the same. Also, the present invention relates to a liquid crystal panel and an electronic device using the thin film device.
2. Background Art
In recent years, liquid crystal display devices using such types of thin film devices have been used in notebook-type personal computers, car navigation systems, video cameras and various portable information devices, and their range of applications and production is drastically increasing. Such phenomena are due to improved performance including reduced price of the liquid crystal display devices, enlarged screen size, improved image resolution and low electrical power consumption. Further cost reduction is, however, required for further expansion of the market and range of applications.
The mainstream of the liquid crystal devices is active matrix liquid crystal devices using TFTs as switching elements for pixels. Each liquid crystal device includes TFTs, a TFT substrate on which a matrix of pixel electrodes connected to the TFTs are formed, a counter substrate provided with a common electrode, and a liquid crystal encapsulated between these two substrates. FIG. 17 shows the main section of a TFT substrate 60. In FIG. 17, TFTs 61 are formed at pixel positions near the intersections of a plurality of source or data signal lines S1, S2, . . . Sn arranged in columns with a plurality of gate or scanning signal lines G1, G2, . . . Gm arranged in rows. Source electrodes of the TFTs 61 are connected to their respective data lines, and drain electrodes are connected to their respective pixel electrodes 62. The data signal supplied from a data line is applied to a pixel electrode 62 through its corresponding TFT 61 based on the scanning timing signals supplied through the corresponding gate line. The state of the liquid crystal is changed and driven for displaying by an electric field between the pixel electrode 62 and the common electrode, not shown in the drawing.
The liquid crystal display device is fabricated by panel assembling including encapsulation of the liquid crystal between the TFT substrate 60 and the counter electrode, and packaging of driving circuits for driving the data lines and the gate lines. The cost of the liquid crystal display device greatly depends on the cost of the TFT substrate 60. The cost of the TFT substrate 60 depends on the manufacturing method of the TFTs. A part of driving circuits may be formed on the TFT substrate 60 by forming the active elements with the TFTs, and in this case, the cost of the TFT substrate represents a high proportion of the cost of the liquid crystal display device.
A TFT has a thin film monolithic structure including a plurality of thin films which include at least a silicon semiconductor layer having an insulating layer, a conductive layer, a source, a drain and a channel region. The cost of the TFT greatly depends on the production cost of the thin film monolithic structure.
The insulation layer in the thin film monolithic structure is formed by a low pressure chemical vapor deposition (LPCVD) process or a plasma enhanced CVD (PECVD) process, because a normal pressure CVD (NPCVD) process results in low uniformity of the film thickness. The conductive layer, or typically the metal layer, is formed by a sputtering process. The silicon film for forming the silicon semiconductor layer is also formed by the PECVD or LPCVD process. Further, a method for implanting an impurity into the silicon film by an ion implanting process or an ion doping process is used. Alternatively, the high concentration impurity region which functions as a source-drain region is formed of an impurity-doped silicon film in a CVD system.
The CVD systems and the s
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Kanbe Sadao
Miyazawa Wakao
Shimoda Tatsuya
Yudasaka Ichio
Bowers Charles
Seiko Epson Corporation
Sulsky Martin
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