1. Structure of liquid crystal display
Generally, a TFT-LCD is composed of an upper substrate assembly, a lower substrate assembly, a liquid crystal, a driving circuit unit, a backlight module, and other accessories, wherein: the lower substrate assembly mainly includes a lower glass substrate and a TFT array, and the upper substrate assembly is composed of an upper glass. The substrate, the polarizing plate, and the film structure covering the upper glass substrate are filled with liquid crystal in the gap formed by the upper and lower substrates.
On the inner side of the lower glass substrate, a series of conductive glass micro-plates corresponding to the pixels of the display, TFT semiconductor switching devices, and vertical and horizontal lines connecting the semiconductor switching devices are filled, which are all fabricated by microelectronics such as photolithography and etching. Form a TFT with each pixel.
On the inner side of the upper glass substrate, a transparent conductive glass plate, generally made of indium tin oxide (ITO) material, is formed as a common electrode to form a series of electric fields with a plurality of conductive microplates on the lower substrate. If the LCD is colored, three common color (red, green, blue) filter units and black dots are filled between the common conductive plate and the glass substrate, wherein the black dots prevent the light from leaking from the gap between the pixels. It is made of opaque material and is called a matrix of black dots because it is distributed in a matrix.
2. Manufacturing process of liquid crystal display
The color TFT-LCD manufacturing process mainly includes four sub-processes: TFT processing technology, color filter processing technology, unit assembly process and module assembly process.
2.1TFT processing technology
The role of the TFT processing process is to form a TFT and an electrode array on the lower glass substrate. For the TFT and electrode layer structures, a five mask process is usually employed.
The pattern transfer product process consists of deposition, photolithography, etching, cleaning, and inspection. The specific process is as follows:
Start glass substrate inspection, film deposition, cleaning, and photoresist coating
Exposure, development, etching, photoresist removal, inspection, end
The etching methods include dry etching and wet etching. The processing principle of the above various processes is similar to the processing method of the corresponding process used in the integrated circuit manufacturing process, but the process parameters and device parameters of the processing method used in the TFT processing process are large due to the large glass substrate area in the liquid crystal display. It has its particularity.
2.2 filter processing technology
(a) Glass substrate (b) Light blocker processing (c) Filter processing
(d) Filter processing (e) Filter processing (f) ITO deposition
The function of the filter processing process is to process the film structure on the substrate. The flow is as follows:
Beginning of light blocker processing, filter processing, protective cleaning, detection, ITO deposition, detection, finishing of a series of black dots made of opaque material and distributed in a matrix shape disposed on the filter substrate, It is processed by a corresponding pattern transfer process (also called a light blocker process) and arranged at the beginning of the filter process, which in turn comprises the following processes: sputter deposition, cleaning, photolithography Glue coating, exposure, development, wet etching, and photoresist removal.
(a) Sputter deposition (b) Cleaning (c) Photoresist coating (d) Exposure
(e) development (f) wet etching (g) removal of photoresist
After the optical blocker is processed, it enters the filter processing stage, and the three filters (red, green, and blue) are processed by three-way pattern transfer process, respectively, because the three filters are directly made of photoresist of different colors. The pattern transfer process is different from the above-described pattern transfer process, and it does not include etching and photoresist removal processes. The specific process is: color photoresist coating, exposure, development, inspection.