Bipolar trends

Device and technology issues are discussed that have led to the present deep-trench-isolated self-aligned bipolar structures, examining the problems in scalig these devices down to submicron dimensions. Self-aligned structure and deep-trench isolation both allow advanced bipolar devices to have much higher circuit density and lower power-delay product than otherwise possible. The polysilicon emitter contact allows bipolar devices to be scaled down vertically without suffering from problems of insufficient current gain or low emitter-collector punchthrough voltage. One promising and yet relatively unexplored direction is to increase the integration level by taking advantage of circuits with much lower power-delay product than the ECL (such as NTL, TTL, CML, and MTL) to improve the functional throughput.