Angular dependences of SiO2 etch rates in C4F6/O2/Ar and C4F6/CH2F2/O2/Ar plasmas

Abstract

The angular dependences of SiO2 etch rates for C4F6/O2/Ar and C4F6/CH2F2/O2/Ar plasmas were investigated using a Faraday cage system. In the absence of CH2F2, the steady-state fluorocarbon film that formed on the SiO2 surface was thin enough (<10 Å) for ions to penetrate through the film. The normalized etch yield (NEY) curve in this case showed a maximum value of 1.74 at an ion-incident angle of 70°, illustrating that physical sputtering was a major contributor to the SiO2 etching. The addition of CH2F2 to C4F6/O2/Ar plasmas produced thicker and more etch-resistant fluorocarbon films, leading to a decrease in the ion energy transfer depth through the steady-state films. This implies that physical sputtering was suppressed when CH2F2 was present in the plasma, demonstrated by a decrease in the maximum NEY and the ion-incident angle at the maximum NEY.