Self-aligned metal/IDP Si bipolar technology with 12-ps ECL and 45-GHz dynamic frequency divider

Ultra-high-speed operation using a self-aligned stacked metal/in situ doped poly-Si (IDP) (referred to as SMI) Si bipolar transistor technology that offers low base resistance while keeping collector capacitance low is demonstrated. This SMI technology provides a base electrode consisting of metal and in situ boron-doped poly-Si (IBDP). Here, metal is fully stacked on the IBDP by using selective tungsten CVD in the self-aligned manner, which means that the structure has low sheet resistance and the fabrication process has a small thermal budget. Thus, low base resistance and low collector capacitance can be achieved. Three types of base electrode, an IBDP, a partially stacked SMI, and a fully stacked SMI, were fabricated to investigate the usefulness of this SMI technology and the importance of the low base resistance. Using the SMI technology, the base resistance was reduced to about 40% and the maximum oscillation frequency was raised by about 30% with respect to the conventional poly-Si base electrode. This technology makes it possible to obtain ultra-high-speed operation with a 12-ps gate-delay emitter-coupled logic (ECL) circuit, and with 45-GHz-dynamic and 28-GHz-static frequency dividers, even when using a conventional ion-implanted base