Current gain recovery in silicon nitride passivated planar transistors by hydrogen implantation

During deposition of silicon nitride, the low-current hFEof silicon planar transistors decreases. When the nitride layer completely seals the oxide from the ambient, the initial value of hFEcannot be restored by annealing at 500°C in forming gas. To eliminate this difficulty, hydrogen ions have been implanted at an energy of 70 keV and at doses varying from 1.10¹³to 1.10¹⁶cm^-2through the nitride into the oxide. Optimum hFErecovery has been obtained with implantation at a dose of 3.10¹⁵cm^-2followed by a radiation damage annealing at 400-500°C in dry nitrogen.