What is TFT LCD manufacturing process?

- Oct 21, 2020-

The manufacturing process of tft-lcd has the following parts: forming a tft array on a tft substrate; forming a color filter pattern and an ito conductive layer on a color filter substrate; using two substrates to form a liquid crystal cell; installing peripheral circuits and assembling a backlight Source and other module assembly. 

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1. The process of forming a tft array on a tft substrate has realized industrialization of tft types including: amorphous silicon tft (a-si tft), polysilicon tft (p-si tft), monocrystalline silicon tft (c-si tft) ) Several. Currently the most used is still a-si tft. The manufacturing process of a-si tft is to sputter the gate material film on the borosilicate glass substrate, and form the gate wiring pattern after mask exposure, development, and dry etching. Stepper exposure machine is generally used for mask exposure. The second step is to use the pecvd method for continuous film formation to form a sinx film, an undoped a-si film, and a phosphorus-doped n+a-si film. Then mask exposure and dry etching are performed to form the a-si pattern of the tft part. The third step is to form a transparent electrode (ito film) by a sputtering film forming method, and then form a display electrode pattern through mask exposure and wet etching. The fourth step is to form the contact hole pattern of the insulating film at the gate end using mask exposure and dry etching. The fifth step is to sputter Al, etc. into a film, expose and etch with a mask to form the source, drain and signal line patterns of tft. Finally, a protective insulating film is formed by the pecvd method, and then the insulating film is etched and formed by mask exposure and dry etching (the protective film is used to protect the gate, the end of the signal line electrode and the display electrode). At this point, the entire process is completed. The tft array process is the key to the tft-lcd manufacturing process, and it is also the part with the most equipment investment. The entire process requires very high purification conditions (for example, level 10). 2. The process of forming the color filter pattern on the color filter (cf) substrate. The methods for forming the colored part of the color filter include dye method, pigment dispersion method, printing method, electrolytic deposition method, and inkjet method. The pigment dispersion method is currently the main method. The first step of the pigment dispersion method is to disperse fine pigments with uniform particles (average particle size less than 0.1 μm) (r, g, b three colors) in a transparent photosensitive resin. Then they are sequentially applied, exposed, and developed to form r. g. b three-color patterns. Photoetching technology is used in manufacturing, and the equipment used is mainly coating, exposure, and development equipment. In order to prevent light leakage, a black matrix (bm) is generally added at the junction of the RGB three colors. In the past, sputtering was often used to form a single-layer metal chromium film, but now there are also metal chromium and chromium oxide composite bm films or resin mixed carbon resin bm. In addition, it is necessary to make a protective film on bm and form it0 electrode, because the substrate with color filter is used as the front substrate of the liquid crystal screen and the rear substrate with tft to form a liquid crystal cell. Therefore, we must pay attention to the positioning problem, so that each unit of the color filter corresponds to each pixel of the tft substrate. 3. The manufacturing process of the liquid crystal cell. The first is to coat polyimide films on the upper and lower substrate surfaces respectively and through a rubbing process to form an orientation film that can induce the molecules to be arranged as required. After that, a sealant material is spread around the tft array substrate, and gaskets are sprayed on the substrate. At the same time, silver paste is applied to the end of the transparent electrode of the cf substrate. Then the two substrates are aligned and bonded so that the cf pattern and the tft pixel pattern are aligned, and the sealing material is cured by heat treatment. When printing the sealing material, it is necessary to leave the injection port so that the liquid crystal can be filled with a vacuum. In recent years, with technological progress and the continuous increase of substrate size, there have also been great improvements in the manufacturing process of the box. The more representative one is the change in the method of crystal filling, which is changed from the original box after filling to odf Method, that is, the crystal filling and box forming are performed simultaneously. In addition, the padding method no longer uses the traditional spraying method, but directly uses the photolithography method on the array. 4. Module assembly process for peripheral circuits, assembling backlight sources, etc. After the liquid crystal cell manufacturing process is completed, peripheral drive circuits need to be installed on the panel, and then polarizers are pasted on the surfaces of the two substrates. If it is a transmissive LCD. Backlight should be installed. LED folding screen