Mechanism of Plasma-Enhanced Deposition of Silicon Dioxide from Teos/O2 Mixtures

Abstract

ABSTRACTThe deposition rate of silicon dioxide from TEOS/02 capacitively-coupled plasmas increases with increasing applied rf power, increasing total pressure and decreasing wafer temperature. These dependences can be explained by a mechanism in which deposition occurs through both an ionassisted and an oxygen atom initiated pathway. The ion-induced deposition rate increases with increasing rf power density and decreasing total pressure, and is independent of wafer temperature. Assuming a well-mixed plasma, and using literature values for reaction rate parameters and rate forms for oxygen plasma reactions, the rate of atom-induced deposition was found to be independent of temperature and TEOS concentration and directly proportional to oxygen atom concentration. The model suggests that the apparent negative activation energy for deposition results from competition between deposition and thermally-activated atomic oxygen surface recombination. The derived deposition rate form is consistent with an Eley-Rideal mechanism in which the rate determining step for film deposition is oxidative attack of adsorbed TEOS or TEOS fragments by a activated oxygen.