Fully ion-implanted bipolar transistors

Abstract
Technology for the fabrication of fully ion-implanted bipolar transistors with arsenic emitters and boron bases is described. This technology results in extremely uniform distributions of electrical parameters, e.g,, hFE= 113 with a standard deviation of 1.3 across a wafer. In addition, it can produce a wide range of doping profiles and hence, a wide range of device performance. Using very similar processing schedules, transistors with hFEfrom 20 to >5000 and with fT's from 1.5 to 8.1 GHz have been made. The features of implanted arsenic which make it an excellent emitter are: 1) it can be implanted to high doses with only a small deep side tail which has a negligible effect on the typical transistor base; 2) because of the concentration dependence of its diffusion constant, it forms a very abrupt profile after diffusion; and 3) when diffused a short distance (∼1000 Å) away from the implanted region, high-lifetime material can be incorporated into the emitter and hence, high-gain low-leakage transistors can be made. When the arsenic emitter is combined with a double-peaked boron-implanted base, precise independent control of the active and inactive base properties of the device can be achieved. This independence allows considerable latitude in the choice of device parameters for fully implanted bipolar transistors.

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