The feasibility of controlling the sidewall angle of thick benzocyclobutene (BCB) etched in a CF4/O-2 plasma using thick photoresist as an etch mask has been investigated. Sidewall angle, BCB etch rate, and BCB to photoresist. selectivity as functions of chamber pressure and CF4 to O-2 ratios are reported. Through the use of postdeveloped reflown photoresist, an optimum sidewall angle of less than 60degrees was achieved at 33 mT chamber pressure. and a 19% CF4/O-2 ratio. The method presented here achieves deep, residue-free etching of thick BCB with a sidewall profile suitable for e-beam evaporated and lifted metal for use in vertical interconnects. (C) 2005 American Vacuum Society.