FABRICATION OF SMALL ALGAAS GAAS HBTS FOR INTEGRATED-CIRCUITS USING NEW BRIDGED BASE ELECTRODE TECHNOLOGY/

This paper describes small AlGaAs/GaAs HBT's for low-power and high-sp eed integrated circuits. The device fabrication is based on a new brid ged base electrode technology that permits emitter width to be defined down to 1 mum. The new technology features oxygen-ion implantation fo r emitter-base junction isolation and zinc diffusion for extrinsic bas e formation. The oxygen-ion implanted emitter-based junction edge has been shown to provide a periphery recombination current much lower tha n that for the previous proton implanted edge, the result being a much higher current gain particularly in small devices. The zinc diffusion offers high device yield and good uniformity in device characteristic s even for a very thin (0.04 mum) base structure. An HBT with emitter dimensions of 1 x 2.4 mum2 yields an f(T) of 103 GHz and an f(max) of 62 GHz, demonstrating that the new technology has a significant advant age in reducing the parasitic elements of small devices. Fabricated on e-by-eight static frequency dividers and one-by-four/one-by-five two-m odulus prescalers operate at frequencies over 10 GHz. The emitters of HBT's used in the divider are 1 x 2.4 mum2 in size, which is the small est ever reported for AlGaAs/GaAs HBT IC's. These results indicate tha t the bridged base electrode technology is promising for developing a variety of high-speed HBT IC's.