PURGE GASES FOR THE REMOVAL OF AIRBORNE　MOLECULAR CONTAMINATION DURING THE STORAGE　AND TRANSPORT OF SILICON WAFERS

摘要

A method was developed to measure total hydrocarbons (THCs) to 1 part-per-trillion (ppt) concentration levels with a gas chromatograph with a flame ionization detector (GC/FID). This method was applied to measure THCs in a front opening universal pod (FOUP) under static and purge conditions. XCDA? purge gas was used for this experiment.XCDA gas is clean dry air (CDA) purified with Aeronex? purification technology to remove moisture to less than 1 part-per-billion (ppb) and hydrocarbon, sulfur, and siloxane contaminants to less than lppt. The result from this experiment was that the FOUP's environment contained ppb concentration levels of THCs under static conditions and ppt concentration levels of THCs under purge conditions. The following test involved a FOUP and a load port. The result from this test ensured that XCDA purge gas could be delivered to the FOUP from the load port with THC contaminants kept at ppt concentration levels. The final test involved exposing a silicon wafer to the FOUP's environment under static and purge conditions. The wafer's hydrocarbon contamination was less with the presence of a XCDA purge gas.