Plasma etching of organic low-dielectric-constant polymers: comparative analysis

The etch characteristics of the low-k dielectrics DVS BCB (BCB hereafter) and SILK in oxygen/fluorine plasmas are studied. In an O 2 /NF 3 plasma afterglow, the etch rate of both polymers first increase linearly with increasing NF 3 concentration, then decreases monotonously. A fluorine plasma afterglow does not etch either BCB nor SILK but strongly changes their chemical and optical properties. Reactive ion etching (RIE) of the polymers shows a different behaviour. The etch rate of SILK in a pure oxygen plasma is maximal, but BCB is etched slowly. The fluorine additives increase the etch rate of BCB. The etch rate of SILK decreases with increasing fluorine concentration. RIE in a pure SF 6 plasma shows good etch characteristics and can be used for some practical applications. Mechanisms of the reactions are discussed.