Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Patent
1998-05-21
2000-12-19
Smith, Matthew
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
349106, 349110, 349 43, H01L 2100, G02F 11335, G02F 11333, G02F 1136
Patent
active
061626546
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a display apparatus and to a method of manufacturing the same.
In recent years, a liquid crystal display (LCD) of an active matrix system using a thin film transistor (TFT) has become attractive as a high quality display apparatus.
In a dot matrix LCD for displaying by dots arranged in a matrix manner, there are a simple matrix system and the active matrix system.
The simple matrix system is a system for directly driving a liquid crystal of each pixel arranged in a matrix manner synchronously with a scan signal from the outside. A pixel portion (liquid crystal panel) is configured as a LCD display portion by only display electrodes and liquid crystal. Therefore, when the number of scanning lines increases, a driving time (duty) which is allocated to one pixel is reduced, so that contrast is deteriorated.
On the other hand, the active matrix system is a system for integrating a pixel driving element (active element) and a charge holding element (pixel capacitance) onto each pixel arranged in a matrix manner, enabling each pixel to execute memory functions, and quasi-statically driving the liquid crystal. That is, the pixel driving element functions as a switch whose turn-on and turn-off states are switched by the scan signal. A data signal (display signal) is transmitted to the display electrode through the pixel driving element in the turn-on state, thereby driving the crystal liquid. After that, when the pixel driving element is turned off, the data signal voltage supplied to the display electrode is held in a state of charges into the charge holding element and the driving of the liquid crystal is continuously executed until the pixel driving element is turned on again. Consequently, even when the number of scanning lines increases and the driving time allocated to one pixel is decreased, the driving of the liquid crystal is not influenced and the contrast is not deteriorated. According to the active matrix system, therefore, a display having a picture quality that is much higher than that of the simple matrix system is realized.
The active matrix system is mainly classified into a transistor type (3-terminal type) and a diode type (2-terminal type) depending on a difference of the pixel driving elements. The transistor type has characteristics such that, as compared with the diode type, it is difficult to manufacture but it is easy to raise the contrast or resolution, so that the LCD having a high quality that is equivalent to that of a CRT can be realized. The foregoing explanation of the operating principle of the active matrix system mainly corresponds to that of the transistor type.
As a pixel driving element of the transistor type, the TFT is generally used. In the TFT, a semiconductor thin film formed on an insulating substrate is used as an active layer. As an active layer, an amorphous silicon film and a polysilicon film are generally used, although research in which cadmium selenide (CdSe), tellurium (Te), or the like is used has been made. The TFT in which the amorphous silicon film is used as an active layer is called an amorphous silicon TFT. The TFT using the polysilicon film is called a polysilicon TFT. The polysilicon TFT has advantages such that the mobility is larger and the driving ability is higher than those of the amorphous silicon TFT. Accordingly, the polysilicon TFT can be used as not only the pixel driving element but also an element for constructing a logic circuit. Therefore, when the polysilicon TFT is used, not only the pixel portion but also a peripheral driving circuit portion arranged around it can be integrally formed on the same substrate. That is, the polysilicon TFT serving as a pixel driving element arranged on the pixel portion and the polysilicon TFT constructing the peripheral driving circuit portion are formed by the same process.
In order to display a color image in the LCD, it is necessary to provide color filters of red, green, and blue (RGB) serving as three primary colors of light.
For example, in
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Malsawma Lex H.
Ross P.C. Sheridan
Sanyo Electric Co,. Ltd.
Smith Matthew
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