Impact of Interstitial Carbon on Base Current Ideality in SiGe:C Heterojunction Bipolar Transistors

We show that the incorporation of interstitial C impacts the base current ideality in SiGe:C HBTs fabricated in 0.18mum SiGe BiCMOS process. SiGe:C epi layers with the same structural and processing parameters but with less interstitial C obtained by adjusting growth conditions have better base current ideality. It is observed that the interstitial C in the emitter/base depletion region, rather than that in the neutral base region, leads to the base current non-ideality. Optimization of C substitution and profile leads to less recombination as well as good B diffusion control thus good device performance