Influence of the wafer biasing frequency upon etching of polyimide

Summary Form only given, as follows. In electrodeless high-frequency (HF)-produced plasmas, it is possible to set the biasing voltage at a frequency different from that of the HF field sustaining the plasma. It has been shown that biasing the wafer at 13.56 MHz in a 2.45-GHz microwave sustained plasma can lead to a substantial increase in the etch rate. The authors have examined the influence on etch rate of biasing the wafer at frequencies f that are below and above the ion plasma frequency f/sub pi/. They have studied the etch rate of polyimide in an O/sub 2/-CF/sub 4/ discharge sustained at a fixed frequency of 200 MHz. The plasma density was in the range approximately=2.5-8.0*10/sup 9/ cm/sup -3/. The value of f/sub pi/ corresponding to the average mass for 85% O/sub 2/ and 15% CF/sub 4/ was 4.3 MHz. A sine-wave biasing signal was applied in the frequency range 500 kHz>