SATURN: Device technology for high‐speed bipolar LSIs

Abstract

A new self‐alignment process technology SATURN (self alignment technology utilizing reserved nitride) has been developed in which the selective oxidation of polysilicon and the nitride films in this oxidation process are used for a number of objectives with a view to improve the operating speed of the bipolar devices. This method is characterized by the control of the emitter stripe width by the side wall spacer film thickness and the control of the distance between the emitter and the external base by the selective oxide film thickness are carried out independently. A process of optimization based on the forementioned control was carried out so that the small transistor with an emitter stripe width of 0.5 μm and a distance of 0.35 μm between the emitter contact and the base contact was realized. This resulted in a current gain of 66 and a cutoff frequency of 12 GHz. Further, this transistor was applied in the ECL circuit which resulted in the performance with the minimum propagation delay time of 88 ps in an inverter gate and the maximum dividing frequency of 3.5 GHz in a 1/8 divider.