_Semiconductor_Pre-processing Phase_Pre-processing PhaseA
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- Circuit Design
- Using CAD(Computer Aided Design) system, an electronic circuit and a circuit pattern actually drawn on a real wafer.
- Mask Manufacturing
- This is a process to draw a designed circuit pattern on a glass plate. A photomask used as an important raw material in manufacturing semiconductor and LCD is to shape a micro circuit of semiconductor on a glass board. In other words, it is referred to a product drawing a semiconductor integrated circuit and LCD pattern to 1-5 time lager than its real size using chrome film applied on the upper layer of a transparent quartz board. It seems that it plays a role similar to the film of photo at the point that because it is a negative of photo describing a circuit designed by a circuit designer using advanced MEBES (Manufacturing Electronic Beam Exposure System), it is possible to describe a pattern on a photo sensitive material coated board.
- Oxidation Process
- Through chemical reaction between oxygen or steam and a wafer surface at high temperature, 800~1200℃, a thin and even silicon oxide membrane (SiO2) is formed. This oxide membrane distinguishes electric wirings each to be drawn on the wafer other avoiding short circuit. Because space between the wirings is minute, short circuits often occur.
- Photo Resist Coating
- PR Coating is referred to a process to make sprayed liquid photo sensitive solution firm by rotating it at high rpm to make it applied to the whole board in a shape of even and thin membrane, and then baking it at certain temperature. The PR indicates is a kind of photosensitive polymer that reacts when being exposed to a light within specific wavelength band (Photo Exposure). At this time, the reaction means that the photo exposed polymer chain is disconnected or combined more strongly when a part of PR is exposed to light. Generally, the PR of which polymer chain in the photo-exposed part is disconnected is referred as Positive PR and the contrary case is referred as Negative PR. In addition, it is divided into liquid type and film type according to the shape of PR.
- Exposure Process
- This is a process to take a picture of circuit pattern on a wafer where photo sensitive membrane is formed by passing light through a circuit board drawn on a mask using a stepper. Exposure indicates a process to transcribe a micro circuit pattern formed on a mask to a coated PR by irradiating a light within UV range through photo mask. The mask pattern is formed with thin Cr membrane. The light irradiated on Cr pattern is reflected and can not sensitize PR and the light on the part without Cr can sensitize PR. Through this process, the micro circuit pattern is transcribed on the PR. According to the types of PR, the mask is also divided into Negative or Positive. When using positive mask on positive PR or negative mask on negative PR, the original image is formed on the PR and otherwise, the reverse image is formed. In this produces of exposure, an exposure equipment named to Mask Aligner is used, where the reason that it is called as Aligner is because it is important to control location of microcircuit pattern precisely.
- Development Process
- This develops the photo exposed membrane on a wafer surface