What is TFT-LCD?
Author:abc Time:2021-07-20 16:48 Browse(192)
TFT LCD is actually a kind of LCD at the bottom. It was used in notebook computers in the early days, and now it is widely used in mobile phones ~ MP3 ~ MP4 ~ and other electronic products ~<
TFT LCD technology is a high and new technology combining microelectronic technology with LCD technology.

What is TFT-LCD?

the technology of growing Si material and TFT planar array on large area glass substrate is developed by using microelectronic fine processing technology and Si material processing technology.
combining with the increasingly mature LCD manufacturing technology, the display quality of products is continuously improved, and the automatic large-scale production capacity is enhanced, The performance / price ratio is close to CRT.
-- in terms of display quality.
taking resolution as an example, CGA (320 × 200)、VGA(640 × 480)、SVGA(800 × 600)、XGA(1024 × 768)、SXGA(1280 × 1024) to uxga (1600) × Figure 1 shows the resolution development speed of TFT LCD.
it basically conforms to Moore's law.
it shows that the development speed of TFT LCD is consistent with that of computer chip.
this is the synchronicity of the adaptability and development speed of TFT LCD and computer.
--- Table 1 various lead technologies.
minimum gap( μ m) Resolution (line / inch) cost (USD / block).
cob 280 100 380.
tab 170 150 190.
cog 60 400 110.
integrated technology 25 1000 30.
the cost of resolution (line / inch) cost (USD / block)
cob 280 100 380.
tab 170 150 190.
cog 60 400 110
--- in order to further improve the resolution of TFT LCD.
to reduce the size of TFT and ensure the opening rate, the limitation of lead technology is also involved.
Table 1 lists the lead density of various lead technologies currently used.
in order to solve the problem of high resolution display, p-Si material has to be used, The peripheral driving circuit is integrated into the LCD screen.
high temperature polysilicon technology has realized the peripheral driving circuit integration into the LCD screen.
it is applied to the projection display.
however, the polysilicon production temperature is higher than 1000 ℃.
the cost of the quartz plate is high.
people have researched and developed the low-temperature p-Si growth technology on the glass substrate, and the low-pressure PECVD technology can grow p-Si on the glass substrate, At present, XeCl excimer laser annealing (ELA) technology is mainly used in the large-scale production of p-Si TFT LCD at low temperature.
PECVD method is used in the production of p-Si TFT LCD at 400 ℃ × A-Si film with thickness of 50nm was grown on 500mm2 glass substrate.
p-Si grains [1] as shown in Fig. 2 were obtained by laser annealing and recrystallization. The photos in the figure show the SEM morphology of different grain sizes.
the grains are less than 0.3 μ The mobility is closely related to the grain size, which is greater than 0.3 M μ In order to obtain uniform switching characteristics of TFT, the grain size of p-Si is controlled at 1 μ
--- Fig. 3 shows the cross-sectional view of n-channel and p-channel p-Si TFTs of C-MOS peripheral drive integrated circuits.
a sin / SiO2 layer is coated on the glass substrate.
alkali metals in the glass are prevented from immersing into the Si active layer, The low resistance alloy is used as gate and gate line.
to prevent the a-Si layer from melting during ELA.
the H concentration in a-Si is controlled at about 1 atom%.
the light doped drain (LDD) structure is used in n-channel TFT to improve the reliability and reduce the dark current.
Fig. 4 shows the I-V characteristics of n-channel and p-channel TFT.
the width (W) and length (L) of channel are 9 μ 5 m and 4 μ m.
the electron and hole mobility are respectively 0 μ N=236cm2 / VS and μ P=120cm2 / VS, threshold
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