The TFT liquid crystal display is characterized by good brightness, high contrast, strong layering, and bright colors, but it also has the disadvantages of relatively power consumption and high cost. TFT LCD technology has accelerated the development of mobile phone color screens. Many of the new generation of color-screen mobile phones support 65536 color displays, and some even support 160,000 color displays. At this time, the advantages of TFT's high contrast and rich colors are very important.
TFT technology was developed in the 1990s. It uses new materials and new processes for large-scale semiconductor all-integrated circuit manufacturing technology. It is used for liquid crystal (LC), inorganic and organic thin-film electroluminescence (EL and OEL) flat panel displays. basis. TFT is a non-single wafer such as a glass or plastic substrate (of course, it can also be on a wafer) through sputtering, chemical deposition processes to form various films necessary for manufacturing circuits, and large-scale semiconductor integrated circuits (LSIC) are manufactured through film processing . The use of non-single crystal substrates can greatly reduce costs, and is an extension of traditional large-scale integrated circuits to large-area, multi-function, and low-cost directions. It is more technically difficult to manufacture TFTs that control the switching performance of pixels (LC or OLED) on large-area glass or plastic substrates than on silicon wafers. The requirements for the production environment (purification degree is 100), the requirements for the purity of raw materials (the purity of electronic special gas is 99.999985%), and the requirements for production equipment and production technology exceed the large-scale integration of semiconductors, which is the top of modern mass production. technology. Its main features are:
(1) Large area: The first generation of large-area glass substrate (300mm×400mm) TFT-LCD production line was put into production in the early 1990s. By the first half of 2000, the area of the glass substrate had been expanded to 680mm×880mm), and 950mm×1200mm The glass substrate will also be put into operation. In principle, there is no area limitation.
(2) High integration: The 1.3-inch TFT chip used for liquid crystal projection has a resolution of XGA containing millions of pixels. The film thickness of the 16.1-inch TFT array amorphous silicon with a resolution of SXGA (1280×1024) is only 50nm, and the TAB ON GLASS and SYSTEM ON GLASS technologies, the integration of its IC, the requirements for equipment and supply technology, and the technical difficulty All exceed the traditional LSI.
(3) Powerful functions: TFT was first used as a matrix location circuit to improve the light valve characteristics of liquid crystals. For high-resolution displays, through voltage regulation in the range of 0-6V (typically 0.2 to 4V), precise control of the object elements is achieved, making it possible for LCDs to achieve high-quality high-resolution displays. TFT-LCD is the first flat panel display in human history that exceeds CRT in display quality. And people begin to integrate the driver IC on the glass substrate, and the function of the entire TFT will be more powerful, which is unmatched by traditional large-scale semiconductor integrated circuits.
(4) Low cost: Glass substrates and plastic substrates fundamentally solve the cost problem of large-scale semiconductor integrated circuits and open up a broad application space for the application of large-scale semiconductor integrated circuits.
(5) Flexible process: In addition to sputtering, CVD (Chemical Vapor Deposition), MCVD (Molecular Chemical Vapor Deposition) and other traditional processes for film formation, laser annealing technology has also begun to be applied, which can produce amorphous films, polycrystalline films, and Single crystal films can be manufactured. Not only can the production of silicon films, but also other group II-VI and III-V semiconductor films.
(6) The application field is wide. The LCD flat panel display based on TFT technology is the pillar industry of the information society, and the technology can also be applied to the rapidly growing thin film transistor organic electroluminescence (TFT-OLED) flat panel display. Growing.