12-PS ECL USING LOW-BASE-RESISTANCE SI BIPOLAR-TRANSISTOR BY SELF-ALIGNED METAL IDP TECHNOLOGY/

A self-aligned metal/IDP (SMI) technology is proposed to reduce the ex ternal base resistance and to enable fabrication of high-speed bipolar transistors. This SMI technology produces a self-aligned base electro de of stacked layers of metal and in situ-doped poly-Si (IDP) with a s mall thermal budget by selective tungsten CVD. It provides the low bas e resistance and a shallow link base for the small-collector capacitan ce and the high-cutoff frequency, The base resistance is reduced to a half that in a transistor having a conventional poly-Si base electrode . A maximum oscillation frequency of 81 GHz and a 12.2-ps gate delay t ime in an ECL ring oscillator at a voltage swing of 250 mV were achiev ed by using the SMI technology even with an ion-implanted base.