Structure of LCD
Author:Shen Chao Time:2021-07-19 16:52 Browse(141)
1. Structure of LCD
1. Structure of liquid crystal display.

Structure of LCD

TFT-LCD consists of upper substrate assembly, lower substrate assembly, liquid crystal, driving circuit unit, backlight module and other accessories. The lower substrate assembly mainly includes lower glass substrate and TFT array, while the upper substrate assembly consists of upper glass substrate, polarizing plate and film structure covered on the upper glass substrate, and liquid crystal is filled on the upper and lower glass substrates Figure 1.1 shows the typical structure of color TFT-LCD.
Figure 1.2 further shows the structure of backlight module and driving circuit unit.
on the inner side of the lower glass substrate.
there are a series of conductive glass microplates corresponding to display pixels, TFT semiconductor switching devices and vertical and horizontal lines connecting semiconductor switching devices, They are all formed by microelectronic manufacturing processes such as lithography and etching. The sectional structure of TFT semiconductor devices for each pixel is shown in Fig. 1.3.
a transparent conductive glass plate is coated on the inner surface of the upper glass substrate, which is generally made of indium tin oxide (ITO), As a common electrode, it forms a series of electric fields with many conductive microplates on the lower substrate.
as shown in Fig. 1.4.
if the LCD is color.
there are three primary color (red, green, blue) filter units and black spots between the common conductive plate and the glass substrate, in which the black spot is used to prevent light from leaking from the gap between the pixel points. It is made of opaque material, Therefore, it is called black matrix.
2 the manufacturing process of LCD.
the manufacturing process of color TFT-LCD mainly includes four sub processes: TFT process, color filter process, cell process and module process [1] [2].
2The relationship between the sub processes is shown in Fig. 2.1.
Fig. 2.1 color TFT-LCD processing process.
TFT processing process is used to form TFT and electrode array on the lower glass substrate.
for TFT and electrode layer structure shown in Fig. 1.3.
five mask process is usually used, that is, using five masks, The processing of TFT layered structure as shown in Fig. 1.3 is completed through five identical pattern transfer processes, The processing results of each pattern transfer process are shown in Fig. 2.2.
(a) the first pattern transfer process (b) the second pattern transfer process (c) the third pattern transfer process.
(d) the fourth pattern transfer process (E) the fifth pattern transfer process.
Fig. 2.2 processing results of each pattern transfer process.
the pattern transfer deposition process consists of deposition, lithography, etching Cleaning The specific process is as follows [1]:
start  glass substrate inspection  film deposition  cleaning  photoresist coating 
exposure  development  etching  photoresist removal  inspection  end.
the etching methods include dry etching method and wet etching method.
the processing principle of the above processes is the same as the corresponding processes used in IC manufacturing process However, due to the large area of the glass substrate in the LCD, the process parameters and equipment parameters of the processing method used in the TFT processing have their own particularity.
2.2 filter processing.
(a) glass substrate (b) light barrier processing (c) filter processing.
2.2 filter processing technology
(d) filter processing (E) filter processing (f) ITO deposition.
Fig. 2.3 formation process of filter assembly.
the function of filter processing process is to process the film structure as shown in Fig. 1.4 on the substrate.
the process flow is as follows:.
start  light stop processing  filter processing  protection cleaning  detection  ITO deposition  detection  end.
the process is as follows: The processing effect of the above main processes or processes is shown in Fig. 2.3.
a series of black spots made of opaque materials and distributed in matrix shape are set on the filter substrate.
they are processed by the corresponding pattern transfer process (also known as light blocking process) and arranged at the beginning of the filter processing process, The pattern transfer process successively includes the following processes: sputtering deposition, cleaning, photoresist coating, exposure, development, wet etching and photoresist removal, The basic principles of each process are shown in Fig. 2.4 (a) - (g).
(a) sputter deposition (b) cleaning (c) photoresist coating (d) exposure.
(E) development (f) wet etching (g) photoresist removal.
Fig. 2.4 photoresist pattern transfer process.
after the photoresist is processed.
in the filter processing stage, three kinds of filters (red, black and white) are used Green and blue) are processed by three-way pattern transfer process. Because the three filters are directly made of photoresist with different colors, the pattern transfer process is different from the previous pattern transfer process,It does not include etching and photoresist removal processes.
the specific process is as follows: color photoresist coating  exposure  development  inspection.
the principle of each process is shown in Figure 2.5.
after the photoresist processing is completed.
after cleaning and detection processes, it enters the ITO deposition process, and finally applies a layer of conductive glass indium tin oxide (ITO) on the filter layer, The common electrode forming the filter.
(a) color photoresist coating (b) exposure (c) development (d) inspection.
Fig. 2.5 color filter pattern transfer process.
3 typical manufacturing process of liquid crystal display.
the manufacturing process of liquid crystal display is basically similar to that of integrated circuit.
the difference is the TFT layered structure in liquid crystal display In addition, the temperature range required for TFT processing is 300 ~ 500oC, The temperature range of IC manufacturing process is 1000 OC.
3.1 deposition process.
there are two deposition methods applied to LCD manufacturing process: one is ion enhanced chemical vapor deposition, and the other is sputtering deposition.
the basic principle of ion enhanced chemical vapor deposition is to place the glass substrate in the vacuum chamber.
After heating to a certain temperature, the mixed gas is introduced, and the RF voltage is applied to the chamber electrode. The mixed gas is transformed into ionic state, and then a solid film or coating of metal or compound is formed on the substrateThe substrate principle of sputter deposition method is: bombard the target with charged particles in vacuum chamber, so that its atoms can obtain enough energy to splash into the gas phase, and then deposit a thin film of the same material as the target on the surface of the workpiece.
in order not to change the chemical properties of the target, the charged particles are helium ion and argon ion.
sputter deposition methods include DC sputtering method, DC sputtering method and DC sputtering method
3.2 lithography process is the process of transferring the pattern on the mask to the glass substrate.
because the quality of the line on the LCD board depends on the lithography process.
therefore, it is one of the most important processes in the LCD processing.
lithography process is very sensitive to the dust particles in the environment.
therefore, it must be placed on the glass substrate The etching process is divided into wet etching process and dry etching process.
the wet etching process uses liquid chemical reagent to remove the material on the substrate surface in a chemical way, which has the advantages of short time, low cost and low cost It is easy to operate.
dry etching process is a kind of plasma etching process for thin film lines.
according to the reaction mechanism, it can be divided into plasma etching, reactive ion etching, magnetically enhanced reactive ion etching and high-density plasma etching, and according to the structure form, it can be divided into cylinder type and parallel plate type.
the advantage of dry etching process is small transverse corrosion.
high control precision, The uniformity of large area etching is good, and the mirror with good perpendicularity and finish can be etched by ICP technology. Therefore, dry etching has obvious advantages in manufacturing micron, deep submicron and nano scale geometric graphics.
4 the development trend of LCD manufacturing technology.
44.1 development trend of TFT-LCD.
since the size of glass bottom plate determines the maximum size of LCD that can be processed by the production line and the difficulty of processing, the LCD industry divides the generation of the production line according to the maximum size of glass bottom plate that can be processed by the production line. For example, the maximum size of bottom plate of generation 5 line is 1200x1300mm, It can cut up to six 27 inch wide screen LCD-TV substrates; The size of the bottom plate of the 6th generation line is 1500x1800mm, 8 pieces can be cut when cutting 32 inch base plate, and 6 pieces can be cut when cutting 37 Inch base plate.
the size of the bottom plate of the 7th generation line is 1800x2100mm.
8 pieces can be cut when cutting 42 inch base plate, and 6 pieces can be cut when cutting 46 inch base plate.
figure 4.1 shows the size definition of the glass bottom plate of the 1st to 7th generation.
at present.
the 6th and 7th generation products have been produced worldwide, It is estimated that in the next two years, the increase rate of the production capacity of the 5th generation and before the 5th generation will gradually decrease, while the production capacity of the 6th generation and the 7th generation will form a trend of accelerating growth in the past two years.
at present.
major equipment manufacturers have also launched equipment that can match the 6th generation and above production lines, such as Nikon's equipment for the 6th generation and the 7th generation The stepper projection flat panel display lithography machines fx-63s, fx-71s and fx-81s used in the 7th and 8th generation production lines.
are introduced
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