After the semiconductor stripper is etched or ion implanted, the photoresist is no longer needed as a protective layer, so the photoresist can be removed from the surface of the silicon wafer. This step is referred to as stripping for short. In the integrated circuit process, the methods of degumming include wet degumming and dry degumming. The wet degumming is divided into organic solvent degumming and inorganic solvent degumming.
The dry method uses plasma to remove the photoresist. Taking oxygen plasma as an example, the photoresist on the silicon wafer undergoes a chemical reaction in the oxygen plasma to generate gaseous CO, CO2 and H2O. The vacuum system can be pumped away. The vacuum is an oil-free screw vacuum pump. 0.1pa. Compared with wet degumming, dry degumming has a better effect, but because dry degumming has the problem of contamination of reaction residues, dry degumming and wet degumming are often used in combination.
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Screw vacuum pump of cryogenic plate and adsorption surface of design
During the entire working process of the screw vacuum pump, as the operating time increases, the temperature around the mechanical equipment also continues to rise.
Install the ultra-low temperature board and the suction surface to reduce the temperature around the machine and equipment in accordance with the heat absorption and discharge method.
The selection of raw materials for cryogenic plates must meet the requirements of high thermal conductivity, high impact toughness, low emissivity and low cost. At this stage, aluminum and copper are generally used, and the copper is galvanized or gold-plated. Silver is the raw material that causes the saturated vapor pressure of hydrogen to be low. Immediately fix the ultra-low temperature board firmly on the top of the cold head of the refrigeration unit. In order to make the two contact each other well, an indium washer was attached to each other.
The surface of the ultra-low temperature plate of the screw vacuum pump needs to be polished, and the actual effect of the polished surface is better than other electro-polished surfaces.
The overall design of the freezing plate must meet the following requirements:
(1) The steam entering the partition will immediately hit the ultra-low temperature plate.
(2) Condensable gas cannot open the suction surface immediately, so as not to occupy the suction position of the absorbent and endanger the suction efficiency of non-condensable gas.
(3) The non-condensable gas should be evenly distributed on the surface of the absorbent so as not to damage the pump efficiency and suction volume.
The choice of absorbent for screw vacuum pumps should be considered from many aspects such as large external economic area, good thermal conductivity, large suction volume, and good remanufacturing characteristics. At this stage, it is generally believed that activated carbon, especially coconut shell activated carbon, has a large external economic area and high suction capacity, making it an ideal absorbent for cryogenic pumps in refrigeration units.
The adhesive processing technology of the absorbent is very detrimental to the suction characteristics of the pump. At this stage, there are roughly three bonding processes: one is clamping by mechanical equipment, the other is bonding with adhesives, and the third is plasma spraying.
Bonding will not only block a part of the microporous absorbent sheet, but also a layer of adhesive between the absorbent and the metal sheet will increase the temperature difference between the absorbent surface and the metal sheet. Some people abroad use 3.5% Ag=Zn aluminum alloy to bond activated carbon and ultra-low temperature board surface. Activated carbon is embedded in the cast aluminum alloy to produce a 3 mm thick plan view. This method will not block the micropores on the surface of activated carbon, and the surface temperature of activated carbon is lower than epoxy glue or ultra-low temperature glue.
The ultra-low temperature plate and water absorption surface of the screw vacuum pump must be considered in all aspects during the design process to ensure that the steam can touch it. When selecting the absorbent, be careful not to block the absorbent microporous plate. It can have a good real effect of lowering the temperature, thereby increasing the service life of mechanical equipment.