Irregular film thickness distribution in C4F8 inductively coupled plasma polymer deposition

Under certain process conditions, plasma polymerization of fluoro-carbons on structured silicon samples shows two distinctive effects: First, the growth rate at a certain depth inside the trenches is considerably larger than at the shoulders, the trench bottom or other areas of the sidewall. Second, an initial sidewall texture is enlarged in the shape of the deposited polymer film. Profile simulations support the hypothesis that these effects are caused by ion-enhancement of the deposition rate in conjunction with geometrical shadowing of ion flux to concave areas of the rippled sidewalls.