Arsenic-spike epilayer technology applied to bipolar transistors

For the first time, epilayers with an arsenic-doped spike of 50 nm width have been grown and used in silicon bipolar junction transistors (BJTs). The epilayer has been optimized such that the collector-base junction of the BJT is formed within the arsenic spike. The counterdoping of boron out-diffusion by arsenic strongly reduces the basewidth. The portion of the spike that is not counterdoped increases the total amount of n-type doping in the collector without reducing BV_ceo. The increased collector-doping allows a 60% higher collector current prior to f_T fall-off. Arsenic has a low diffusivity so very few constraints are put on the thermal budget of the final process. This high flexibility makes the presented epilayer technology a promising candidate to enhance a bipolar process significantly.