SDX: a novel self-aligned technique and its application to high-speed bipolar LSIs

A novel polysilicon selective-deposition method named selective deposition by exdiffusion (SDX) and a self-aligned bipolar LSI process using the SDX process are presented. The SDX process makes it possible to selectively form polysilicon patterns on silicon oxide patterns but not on silicon nitride patterns, where these patterns are formed on a silicon substrate surface. Bipolar transistor self-alignment between the isolation pattern and the entire transistor active region can be achieved in a 0.85-μm silicon island by the SDX process. A transistor with a 12-GHz cutoff frequency, an LCML gate with a propagation delay time of 59 ps/gate, and a 1-kb ECL (emitter-coupled logic) memory with an access time of 0.95 ns have been achieved