Dry etching of n- and p-type polysilicon: Parameters affecting the etch rate

The etch rate of doped polycrystalline silicon films (polysilicon) was studied as a function of dopant concentration, degree of dopant activation, and dopant type, in a parallel-plate reactor, using a CFCl3 plasma. The significant difference in etch rate between n-doped and p- or undoped polysilicon observed indicates that the electrical activity of the bulk (and surface) plays an important role when etching at a plasma frequency of 13.56 MHz. However, at lower frequencies this difference in etch rate for n- and p-doped polysilicon is less pronounced.