Influence of the applied field frequency (27-2450 MHz) in high-frequency sustained plasmas used to etch polyimide

The effect of the plasma stimulating frequency upon the etching of polyimide is reported. For the first time, a system has been developed which generates, over a large frequency domain (27-2450 MHz), a high-frequency (HF) produced plasma by identical means (surface wave propagation) in a fixed plasma volume. It is found that the addition of CF4 to an O2 plasma affects the etch rate of polyimide in a manner which depends upon the operating frequency of the HF plasma. In particular, a maximum of etch rate per watt is observed around 50 MHz.