SELF-ALIGNED Si BJT/SiGe HBT TECHNOLOGY AND ITS APPLICATION TO HIGH-SPEED CIRCUITS

Abstract

In a Si bipolar transistor (BJT) and a SiGe heterojunction bipolar transistor (HBT), self-aligned structures help to improve high-speed and high-frequency characteristics. These structures are used to reduce parasitic capacitance and resistance, and thus maximize the transistor's intrinsic performance. In addition to generally used process technology, selective metal deposition to form electrodes and selective epitaxial growth of Si/SiGe multilayers are applied in the fabrication process. To improve the intrinsic speed, the cutoff frequency, a shallow diffusion process for Si BJTs and a graded-Ge profile SiGe-base layer for SiGe HBTs are used. These also enable a high maximum oscillation frequency and a small gate delay in the emitter-coupled logic through the synergistic effect of the self-aligned structure. Both high-speed digital circuits — frequency dividers up to millimeter-wave bands and a multiplexer/demultiplexer for optical-fiber-links — and high-frequency analog circuits for optical-fiber-links — a preamplifier, an automatic gain control amplifier. a limiting amplifier, and a decision circuit — have been implemented by applying the self-aligned Si BJTs and/or SiGe HBTs.