Novel oxide planarization for integrated high-speed Si/SiGe heterojunction bipolar transistors

A straightforward oxide planarization for double mesa Si/SiGe heterojunction bipolar transistors (HBTs) is presented. The starting point is a bias-sputtered SiO/sub 2/ film covering a mesa with an auxiliary layer on top. The following planarization is performed only by wet chemical etching. A planarized multiplexer circuit resulted in bit rates up to 18 Gbit/s.