Semiconductor process fluids

Particle Ramoval (Semiconductor Process Fluids). The fluids that come in contact with photo masks and wafers during integrated circuit (IC) production are often contaminated with particles which, if not eliminated, can cause defects and reduce production yields. 

Kern, F. W, Jr., Fluid Purity Requirements for Semiconductor Processing Fluids, IBM Microelectronics, Essex Junction, VT. 

Kuhn M, Bachmann P (1987) Selection and analytical monitoring of backing pump fluids in semiconductor processes. J Vac Sci Technol A5 2534-253... 

The semiconductor processing industry is one of the more recent applications for KYNAR resins. It is used for fluid handling systems for ultra-pure fluids used in the production of microchips. Resin purity and inertness, and the total absence of any additives in the fabrication process, are absolute essentials for components handling the chemicals, etchants, and rinse waters used in the making of today s state of the art integrated circuits. 

Materials suppliers produce extensive tables showing resistance to chemicals at various temperatures and stress levels. As etherketones, PARK have superb resistance to hydrolysis - in contrast to many polymers based on hydrolysable groups, such as esters, amides and imides. There are extensive data for important classes of environment. These include automotive fluids, oilfield environments, jet fuel, hydraulic fluids, refrigerants and materials used in semiconductor processing. However, these tables often provide little or no explanation of the underlying mechanisms. There are several important classes of chemical which will attack PARK. These include the following. 

Analyses of process fluid composition, determination of particulate and bacterial levels and other laboratory procedures are the critical steps in semiconductor manufacture. Fluid chemistries must be analyzed and kept on specification to maintain yields. For accuracy and repeatability, labware and equipment must not react with or contaminate the samples being studied. Reagents for analytical work as well as the process fluids are held in containers of PFA for protection against contamination. Because PFA is unaffected by virtually all chemicals and solvents, containers may be reused multiple times. Apparatus for wet analytical analyses may be interconnected with tubing made from PFA [23]. Laboratory apparatus including beakers and other lab equipment may also be made from PFA to help maintain chemical purity and prevent inaccurate analyses. 

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. 

Polymers should be tested for extractables before use. The amount of extractable material is determined by the formulation of the polymer mix. Molded plastics often have a high plasticizer content to make them more fluid for molding. These low molecular weight plasticizers migrate to and contaminate the surface. In semiconductor processing, a relatively inert fluoropolymer (perfluoroalkoxy (PFA), e.g. Teflon or Neoflon ) is often used for containers and holders but they can hberate corrosive fluorine compounds. Special treatments are used to reduce the extractable fluoride compounds from these materials. Many polymers can absorb water vapor and corrosive gases from the environment. 

Thermal Mass Flowmeters The trend in the chemical process industries is toward increased usage of mass flowmeters that are independent of changes in pressure, temperature, viscosity, and density. Thermal mass meters are widely used in semiconductor manufacturing and in bioprocessing for control of low flow rates (called mass flow controllers, or MFCs). MFCs measure the heat loss from a heated element, which varies with flow rate, with an accuracy of 1 percent. Capacitance probes measure the dielectric constant of the fluid and are useful for flow measurements of slurries and other two-phase flows. 

Modifed PTFE can be used in practically all applications, where the conventional polymer is used. In addition to that, new applications are possible because of its improved flow and overall performance. In the chemical process industry, it is used for equipment linings, seals, gaskets, and other parts, where its improved resistance to creep is an asset. In semiconductor manufacturing, modified PTFE is used in fluid handling components and in wafer processing components. Typical applications in electrical and electronic industries are connectors and capacitor films. Other applications are in unlubricated bearings, laboratory equipment, seal rings for hydraulic systems, and antistick components.103... 

Liquid-phase carbonization occurs for some precursors, such as pitches, which become viscous fluids before carbonization. This process has been used to produce various polycrystalline graphite blocks for steel refining and electrical discharge machining, jigs for the growth of semiconductor crystals, structural components of nuclear reactor, etc. 

One sign of progress is the extent to which sophisticated research on transport phenomena, particularly mass transfer, has penetrated several other fields, including those described in later papers of this volume. Examples include fundamental work on the mechanics of trickle beds [17] within reactor engineering studies of dispersion in laminar flows [18] in the context of separations important to biotechnology coupling between fluid flows and mass transfer in chemical vapor deposition processes for fabrication of semiconductor devices [19] and optical fiber preforms [20] and the simulation of flows in mixers, extruders, and other unit operations for processing polymers. 

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