Inverse current gain improvement of bipolar transistors by double-base diffusion

The double-base diffusion process is introduced and is experimentally shown to significantly improve the inverse or upward current gain of the n-p-n bipolar transistor. The technique consists of a deep p⁺diffusion into an external base region of multicollector transistors forming a close-in collar around the intrinsic base of each transistor. This technique, together with the use of deep diffusion n⁺guard rings around the complete unit cell, is shown to improve the inverse current gain significantly.