Investigation of Effects of Sulfuric Acid in Single Wafer Cleaning Process Using Isopropyl Alcohol

Abstract

Isopropyl alcohol (IPA) was used in the drying process to remove the contamination after the wet cleaning process. Regardless of the types of chemical solutions, the IPA is more strictly controlled because it is used. However, when the IPA was exposed to low acid concentration, the IPA polymers were generated to the di-isopropyl ether, isopropyl acetate, and di-isopropoxy methane. And the pH of IPA rapidly changed by about 1.99 in ppm level concentration. Generated IPA polymers were adsorbed on the wafer surface. These polymers can occur defects, and the probability increases as the concentration increases. Scanning mobility particle sizer (SMPS) measurement system can be measured the impurity in IPA solution. The total impurity concentration was increased by the concentration of H2SO4 with the same results in both gas chromatography mass spectrometry (GCMS) and time of flight secondary ion mass spectrometry (ToF-SIMS). SMPS results can be correlated with the concentration of impurities. In this paper, IPA polymers were defined by acid contamination, and these polymers have affected the Si wafer surface. In addition, the SMPS measurement system was introduced for the detection of impurities in IPA solutions.