A novel base emitter self-alignment process for high speed bipolar LSIs

A novel base-emitter self-alignment process is described. It produces a transistor which has a cutoff frequency of 12 GHz. It provides 88 ps of propagation delay for an ECL (emitter-coupled logic) gate. The process is characterized by its extensive use of S i/sub 3/N/sub 4/. Utilizing Si/sub 3/N/sub 4/ as a multipurpose layer, the main structures (active region of transistor and resistor) are defined by self-alignment from a single photomask. In addition, constituent materials are chosen to have enough mutual selectivity under conventional etching processes. Therefore, the process has an excellent reproducibility with less strict requirements than standard etching technology.<
>