Effect of Photoresist on Plasma Etching

Abstract

Etching characteristics of polysilicon and silicon dioxide with various photoresist coverages have been investigated to reveal the role played by the photoresist in chlorinated plasma. The etch rate of oxide decreases with decreasing coverage of photoresist on the wafer. Although the nominal etch rate of polysilicon is not sensitive to the photoresist coverage, the etch rate of polysilicon patterned with oxide mask is higher than that with photoresist mask. Chlorocarbon species originated from the photoresist erosion are speculated to be responsible for these behaviors. Furthermore, we have observed that there is a strong loading effect in polysilicon etching with chlorinated plasma if a nonerodible mask is used, but this effect is suppressed by the presence of a photoresist.