Dependence of Driving Frequency on Capacitively Coupled Plasma in CF₄

Abstract

A radio-frequency CF 4 plasma in reactive-ion etcher with parallel plate geometry is investigated in one dimension at a position space using the relaxation continuum model. The discharge with negative ions has the double layer similar in appearance to O 2 ; the structure and mechanism are markedly changed as a function of driving frequency. The effect of driving frequency is numerically studied between 13.56 MHz and 200 MHz for 200 mTorr and 50 mTorr. In these studies, the plasma density is kept constant at ∼10 11 cm -3 , considering the charged species CF 3 + , CF 2 + , CF + , C + , F + , F - , and electrons. The mean energy of charged particles is also discussed.