Bipolar trends

The development of bipolar technology in recent years is reviewed, and trends for future development are projected. The developments clearly point to three salient features of today´s advanced bipolar transistors, namely i) self-aligned structure, ii) deeptrench isolation, and iii) polysilicon emitter contact. Both i) and ii) allow advanced bipolar devices to have much higher circuit density and lower power-delay product than without these features. 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. It is clear that while progress will continue in scaling the familiar high-speed ECL logic and memory, the integration level of these very-high-speed chips is severely limited by the accompanied power dissipation. One seemingly promising and yet relatively unexplored direction is to increase the integration level by taking advantage of circuits with much lower power-delay product than ECL, such as NTL, TTL, CIVIL, and MTL to improve the functional throughput. The technology challenges as well as the potential of submicrometer bipolar technology are also discussed.