The effect of isolation regions on the current gain of inverse NPN-transistors used in Integrated Injection Logic (I2L)

In Integrated Injection Logic it is desirable to separate the base regions of the common emitter inverse npn transistors from each other. An n⁺-diffusion isolation or oxide isolation minimizes the loss in gain due to hole currents from the base to the emitter. We analyzed the case of n⁺ isolation with different unicollector structures of different geometries. Experimental results are presented based on the following comparison; A: no n⁺ isolation; B: shallow n⁺ isolation and C: deep n⁺ isolation.