From its onset, the semiconductor industry has relied on fluoropolymers for wet processing equipment, fluid transport systems, and wafer handling tools. Semiconductor manufacturing processes are extremely intolerant of particulate and chemical contamination which, even in trace amounts, can cause a severe decrease in yields. Fluoropolymers’ purity and resistance to chemical attack are, therefore, important attributes. Carriers are devices that carry silicon wafers through various chemical processes.
They were first made from PTFE which is still used for some carriers, usually small ones. The necessary machining to fabricate carriers was PTFE and material loss has rendered high-purity grades of PFA as the preferred material of construction. PFA can be efficiently fabricated in the required configurations by injection molding technique without costly secondary machining operations. Aggressive ultrapure acids, solvents, and water are required for silicon wafer cleaning/etching. To maintain their purity, these fluids are transported from fluoropolymer-lined storage containers to consumption points through fluoropolymer tubing, usually high-purity PFA, while flow is managed wit valves, pumps, and pressure regulators made from PFA, PTFE, and occasionally other fluoropolymers.
These fluid handling components are nearly always solid fluoropolymer constructions. These designs are possible because sizes are relatively small compared with functionally similar but far larger components used in the CPI. Therefore, mechanical properties and material cost are not particularly sensitive issues. In addition, semiconductor processes are easily compromised by the presence of tiny amounts of metallic ions, so manufacturers avoid having metal components in the vicinity of process fluids. The designers of these all-fluoropolymer components employ unusual features such as machined PTFE bellows for valves actuated by air pressure and rods incorporating carbon fiber that provides stiffness for wafer carriers.
Wet benches, the facilities in semiconductor plants where wet processes are carried out, are typically made of fluoropolymers where surfaces can affect fluid purity. Storage containers and sinks, along with all other plumbing, are constructed from fluoropolymers. Flame resistance of fluoropolymers is a major advantage in insuring Semicon fabs short for fabrication plant (also called foundry).
