1. The structure of the 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. The lower substrate assembly mainly includes a lower glass substrate and a TFT array, and the upper substrate assembly includes upper layers. The glass substrate, the polarizing plate, and the film structure covering the upper glass substrate are filled with the liquid crystal in the gap formed by the upper and lower substrates. Figure 1.1 shows the typical structure of a color TFT-LCD. Figure 1.2 shows the structure of the backlight module and the driving circuit unit.
The inner surface of the lower glass substrate is covered with a series of conductive glass micro-plates corresponding to pixel points of the display, TFT semiconductor switching devices, and vertical and horizontal lines connecting the semiconductor switching devices. These are all fabricated by microelectronics such as photolithography and etching. The cross-sectional structure of the TFT semiconductor device in which each pixel is formed is shown in FIG. 1.3.
On the inner surface of the upper glass substrate, a transparent conductive glass plate is applied, generally made of Indium Tin Oxide (ITO) material, which serves as a common electrode and forms a plurality of conductive micro plates on the lower substrate. Series electric field. As shown in Figure 1.4. If the LCD is color, three primary colors (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 materials, because it is distributed in a matrix, it is called the black matrix.
2 LCD manufacturing process
The color TFT-LCD manufacturing process includes four sub-processes: a TFT process, a color filter process, a cell process, and a module process. ]. Color TFT-LCD processing process
The role of the TFT processing process is to form TFTs and electrode arrays on the lower glass substrate. For the TFT and electrode layered structures shown in Fig. 1.3, a five-mask process is generally used. That is, five masks are used to complete the processing of a layered structure as shown in Fig. 1.3 by five identical pattern transfer processes . The results of the processing of the road pattern transfer process.
(a) No. 1 pattern transfer process (b) No. 2 pattern transfer process (c) No. 3 pattern transfer process
(d) No. 4 pattern transfer process (e) No. 5 pattern transfer process
Process results of each pattern transfer process
The pattern transfer product process consists of deposition, photolithography, etching, cleaning, and inspection. The specific flow is as follows :
Started with glass substrate inspection, film deposition, cleaning, and coating photoresist.
Exposure - development - etching - removal of photoresist - inspection
The etching methods include dry etching and wet etching. The processing principles of the above processes are similar to those of the corresponding processes used in the integrated circuit manufacturing process. However, due to the large area of the glass substrate in the liquid crystal display, the process parameters and equipment parameters used in the TFT processing technology are described. There are particularities.
2.2 filter plate processing technology
(a) Glass substrate (b) Light blocker processing (c) Filter processing
(d) Filter processing (e) Filter processing (f) ITO deposition
Figure 2.3 Formation of filter assembly
The function of the filter plate processing process is to process the thin film structure shown in Fig. 1.4 on the substrate. The flow is as follows:
The beginning of ??blocker processing? ??filter processing?? protection and cleaning of the detection of ITO deposition?
The main process or process described above shows the processing effect.
A series of black dots made of opaque material and distributed in a matrix shape are arranged on the filter substrate, and they are processed by a corresponding pattern transfer process (also called a light blocker process) and arranged on the filter. At the beginning of the photofabrication process, the pattern transfer process sequentially includes the following steps: sputter deposition, cleaning, photoresist coating, exposure, development, wet etching, and removal of photoresist, the basic principles of each process.
(a) Sputter deposition (b) Cleaning (c) Photoresist coating (d) Exposure
(e) Developing (f) Wet etching (g) Removing photoresist
Light-blocker pattern transfer process
After the light blocker is finished, it enters the filter processing stage. The three types of filters (red, green, and blue) are respectively processed through three pattern transfer processes, since the three types of filters are directly made of different color resists. Made, the pattern transfer process is different from the aforementioned pattern transfer process, it does not include the process of etching and removing photoresist. The specific process is: color resist coating, exposure, development and inspection, and the principle of each process.
After the light blocker is processed, after the cleaning and detection process, the ITO deposition process is performed. Finally, a layer of conductive glass indium tin oxide (ITO) is coated on the filter layer to form a common electrode of the filter plate. .
(a) Color resist coating (b) Exposure (c) Development (d) inspection
Color filter pattern transfer process
3 typical manufacturing process of liquid crystal display
The manufacturing process of the liquid crystal display is basically similar to that of the integrated circuit. The difference is that the TFT layer structure in the liquid crystal display is fabricated on the glass substrate instead of the silicon wafer. In addition, the temperature range required by the TFT processing technology is 300~. 500oC, while the integrated circuit fabrication process requires a temperature range of 1000 oC.
3.1 deposition process
There are mainly two kinds of deposition methods used in liquid crystal display manufacturing processes: one is ion-enhanced chemical vapor deposition, and the other is sputter deposition. The basic principle of ion-enhanced chemical vapor deposition is that the glass substrate is placed in a vacuum chamber and heated to a certain temperature, and then a mixed gas is introduced, and an RF voltage is applied to the chamber electrode, and the mixed gas is converted into an ion state. Thus, a solid film or coating of a metal or compound is formed on the substrate. The substrate principle of the sputter deposition method is that in the vacuum chamber, the target is bombarded with the charge energy particles, and the atom obtains enough energy to splash into the gas phase, and then a film of the same material as the target is deposited on the surface of the workpiece. In general, the energetic particles are helium ions and argon ions so as not to change the chemical properties of the target. The sputter deposition method includes a DC sputtering method, a radio frequency sputtering method, and the like.
A photolithography process is a process of transferring a pattern on a mask to a glass substrate. Since the quality of the reticle on the LCD panel depends on the lithography process, it is one of the most important processes in the LCD process. The lithography process is very sensitive to dust particles in the environment, so it must be done in a highly clean room.
3.3 etching process
The etching process is divided into a wet etching process and a dry etching process. The wet etching process chemically removes the material on the surface of the substrate using a liquid chemical reagent. The advantages thereof are short time, low cost, and simple operation. The dry etching process is a process in which a thin film line is etched by a plasma. According to the reaction mechanism, plasma etching, reactive ion etching, magnetically enhanced reactive ion etching, and high-density plasma etching can be divided into types. Form can be divided into cylindrical, parallel flat type. The advantages of the dry etching process are low lateral corrosion, high control accuracy, and good uniformity of etching over a large area. ICP technology can also etch mirrors with very good verticality and finish. Therefore, dry etching is used to make micrometers. Deep submicron, nano-scale geometry processing, there are obvious advantages.
4 Development trend of liquid crystal display manufacturing process
4.1 TFT-LCD Development Trend
Since the size of the glass substrate determines the maximum size of the LCD that can be processed in the production line and the difficulty of processing, the LCD industry divides the production line according to the maximum size of the glass substrate that the production line can process. For example, the highest level of the 5th generation line. The size of the backplane is 1200X1300mm. It can cut up to 6 substrates for 27-inch widescreen LCD-TV. The size of the 6th generation backplane is 1500X1800mm. Cutting 32-inch substrates can cut 8 pieces and 37 inches can cut 6 pieces. The size of the 7th generation line is 1800X2100mm. Cutting 42 inches of the substrate can cut 8 pieces, 46 inches can cut 6 pieces. Figure 4.1 shows the size definition of glass substrates for the 1st to 7th generations. At present, the global scope has entered the stage of production of the 6th and 7th generation products, and it is expected that in the next two years, the increase in production capacity before the 5th and 5th generation will gradually decrease, while the 6th and the 7th generation The production capacity of the 7th generation will accelerate the growth in the past two years. At present, major equipment manufacturers have also introduced devices that can be used with 6th generation or higher production lines, such as Nikon’s stepper-type flat panel display aligners for 6th, 7th, and 8th generation line applications. FX -63S, FX-71S and FX-81S.