Profile Control with D‐C Bias in Plasma Etching

Positive tapered profiles can be achieved on single crystal silicon in a parallel plate reactor by the application of a bias potential to a discharge of Cl 2 gas sustained at 13.56 MHz. Without the bias, vertical profiles are obtained. Bias dramatically increases etch rates but in a complex manner which depends to some extent on feature size. No silicon crystallographic orientation dependence has been observed. The observations can be explained by a model where the masking layer becomes charged and hence provides a horizontal component to the electric field which affects the charged particle bombardment of the surface.