A >400 GHz fmax transferred-substrate heterojunction bipolar transistor IC technology

We report transferred-substrate AlInAs/GaInAs heterojunction bipolar transistors. A device having 0.6 mu m x 25 mu m emitter and a 0.8 mu m x29 mu m collector exhibited f(tau) = 134 GHz and f(max) > 400 GHz. A device with a 0.6 mu m x 25 mu m emitter and a 1.8 mu m x 29 mu m collector exhibited 400 GHz f(max) and 164 GHz f(tau). The improvement in f(max) over previous transferred-substrate HBT's is due to improved base Ohmic contacts, narrower emitter-base and collector-base junction areas, and slightly reduced transit times. The transferred-substrate fabrication process provides electroplated gold thermal vias for transistor heat-sinking and a microstrip wiring environment on a low dielectric constant polymer substrate.