Why is fluoro plastics PFA irreplaceable in the semiconductor industry?

At present, all countries in the world have set the development of 5G technology as a strategic development goal. Under the support of 5G, “artificial intelligence” and “virtual reality”, the computing and data transmission rates will be greatly improved. With the development of communication technology, the rapid development of the semiconductor industry, the emerging discipline of the chemical industry - electronic chemicals also came into being, the fluorine-containing special gas is one of them. In addition to being used as a raw material, the role of fluoroplastic products in the semiconductor industry is also irreplaceable.

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What is PFA?

In 1972, DuPont of the United States developed a copolymer of tetrafluoroethylene (TFE) and perfluoropropyl vinyl ether (PPVE) under the trade name Teflon PFA, a perfluoroalkoxy copolymer. Since then, Japan's Novoflon PFA, Flon PFA, and Dyneon PFA have all developed their own PFA products and have a certain share in the market.

PFA is usually present in the form of granules or powders, and its properties are similar to those of polytetrafluoroethylene (PTFE), but it can be processed by a thermoplastic resin, so it is also called meltable polytetrafluoroethylene.

In many respects, PFA is very similar to polyperfluoroethylene propylene (FEP), but at higher temperatures it exhibits better mechanical properties. Because PFA has many advantages of PTFE and FEP, it is widely considered to be the best soluble fluorinated copolymer that can replace them. Its basic characteristics can be summarized as follows:

1) It has good flexibility and improves the melt viscosity of the polymer, so that it can be processed by a general processing process;

2) The physical and mechanical properties of PFA at room temperature are similar to those of PTFE and can be used within the temperature range in which it is applied;

3) PFA resistance to stress cracking is significantly better than FEP;

4) PFA is almost inert to all chemical reagents and solvents. It has almost no change in contact with common acids, strong bases, redox agents, halogens or solvents, but like other perfluorocarbon polymers, it will react with molten alkali. Metal, fluorine reaction;

5) PFA has good permeability. When the thickness is large, it is translucent. The sheet is transparent. It has good weather resistance and weather resistance. It can be used outdoors for a long time.

6) PFA has excellent dielectric properties, which usually appear as a constant with temperature, but sometimes lower than PTFE and FEP.

PFA application in the semiconductor industry

We know that the purity requirements of chemicals in the semiconductor industry are very demanding. From the birth of PFA in 1970, the target node size of the semiconductor industry has been gradually reduced from 10μm to 7nm or even 5nm. This means that the purity requirements for electronic chemicals are also rising.

Whether it is wet etching or chemical mechanical polishing (CMP), even a small amount of impurities in the entire integrated circuit manufacturing process will have a huge impact on the final product, so electronic component manufacturers on raw materials, transportation pipelines and reactions The requirements for containers and the like are very high. It is not easy to find an extreme chemical environment that can withstand strong acids and alkalis, high temperature and high pressure, and can be processed into various shapes of materials. Fortunately, scientists have discovered PFA.

Transportation and storage: Due to its strong chemical stability, PFA fluororesin can withstand extreme environments such as high temperatures and strong acids, and does not react with solvents, making it a good material for storage containers and transportation pipes. It guarantees the high purity of the electronic chemicals in the manufacturing process, avoids the contamination of the electronic chemicals caused by the dissolution and erosion of the reaction vessel, thereby reducing the defect rate of the wafer.

Chemical Distribution System (BCD): BCD is a system that accurately dispenses chemicals, reducing the cost of removing the right amount of chemicals from large containers. This system typically includes fully automated instruments for blending and diluting chemicals and is used in a wide range of electronic chemical plants. Fluororesin is widely used in BCD infrastructure, including the production of ventilation pipes, valves, sinks and so on.

Wet Etching and Cleaning: In the wet process, the wafer is first cleaned, then etched, and then the photoresist and the residue of the etch process are cleaned. In this process, PFA fluororesin is made into various tools, such as flow meters, to ensure high purity of the etching solution and cleaning solution; and PFA is not easy to crack during use, thereby ensuring high efficiency of production.

Chemical mechanical polishing (CMP): The CMP process smoothes the surface of the wafer before vapor deposition. The liquid used is a fine liquid containing slurry. If the particles in the slurry are too large, they will remain on the surface of the wafer. The traces are left, which leads to flaws in the product. The filter made of PFA prevents the impurities of the slurry from contacting the wafer to some extent.

Bracket: The wafer is placed on a bracket of a particular shape throughout the wet process. Since PFA can be melt processed, it is fabricated into stents of various shapes and used in the entire wafer processing.