Estimation of contamination levels in a chemical recirculationsystem for semiconductor wafer processing

摘要

A theoretical analysis is presented of the contamination buildupnin a generic chemical recirculation system used in semiconductor wafernprocessing. Mathematical expressions are derived for useful quantities,nsuch as the maximum possible concentration of contaminant in thenrecirculation tank and the number of processes required to reach anynparticular concentration level. Recirculation systems are analyzednwherein the amount of chemical used and the amount of contaminant pickednup per process cycle are either constant or process dependent. Samplencalculations are presented for the two cases. The mathematical equationsnderived in the study are presented in a form that can be easily extendednto the analysis of more complex recirculation systems and thenoptimization of chemical supplies and processes for maximum performance