48 GHz digital ICs using transferred-substrate HBTs

Using substrate transfer processes, we have fabricated heterojunction bipolar transistors with submicron emitter-base and collector-base junctions, minimizing RC parasitics and increasing f/sub max/ to 500 GHz. The process also provides a microstrip wiring environment on a low-/spl epsiv//sub r/ dielectric substrate. First design iterations of ECL master-slave flip-flops exhibit 48 GHz maximum clock frequency when connected as static frequency dividers.