Deposition of SiO2 in a SiH4/O2 inductively coupled plasma

Abstract

Plasma enhanced chemical vapour deposition (PECVD) process in a SiH4/O2 inductively coupled plasma (ICP) is studied in this paper. The detailed chemical reactions in plasma and surface reactions on the wafer are included in the simulation using finite element method (FEM), so that the formation of bulk species of SiO2 is examined. The study is performed for 10% SiH4/90% O2 gas mixtures operating at the rf frequency of 13.56 MHz and the total gas pressure of 25 mTorr with the variation of gas flow rate from 20 to 500 sccm. The gas temperature is 300 K and the input power is 700 W. It is found that the deposition rate near the rim of wafer is much lower than that in the centre. The deposited film thickness near the rim of wafer is 70% of that in the centre after the discharge of 0.2 sec. The study shows that the oxygen atom density, which directly contributes to the deposition of SiO2, decreases when the gas flow rate increases. The deposition rate on the wafer is reduced by around one order and the deposited film thickness is reduced to 12% of the original when the gas flow rate is increased from 20 to 500 sccm.