A new sub-micron emitter formation with reduced base resistance for ultra high speed devices

A new self-aligning method has been developed to control the emitter width of bipolar transistors in sub-micron sizes. This permits accurate control of distance between the emitter and the base contact region, namely, the outer base region. Desired emitter widths less than the 0.5 μm range, suitable for use in IC production, are routinely achieved. By applying the 3μm wide mask pattern, which is an easy photolithographic technique this method permits control of the emitter width to 0.5μm and the distance of the outer base region to 0.3μm. Since the outer base resistance is remarkably reduced by this method, the base resistance rbb´, can be easily reduced to less than 1/4 of that of conventional methods. Application of this method to fabrication of transistors have been shown to improve the noise figure in the very high frequency range as shown in Fig. 1. When the new method was applied to the monolithic CML IC, an excellent tpd value of 0.25ns was obtained, suggesting that the tpd value can be further improved by selecting suitable conditions for the fabrication of IC.