The Oxidation Inhibition in Nitrogen‐Implanted Silicon

Abstract

In order to reveal the mechanism of oxidation inhibition in nitrogen‐implanted silicon, the 15N(p, αγ)12C resonant nuclear reaction has been applied to obtain detailed information on nitrogen concentration profiles in silicon. It appears that the oxidation resistance is caused by an extremely thin (<3 nm) nitrogen‐rich layer at the interface. The formation of this interfacial nitride‐like layer is the result of complicated redistributions of the nitrogen which take place during annealing and oxidation. It is shown that implantation of nitrogen ions into source and drain areas of an MOS transistor can be used to inhibit further growth of the gate oxide in these areas during a subsequent oxidation and thus allows a selective oxidation of polysilicon gates. This provides a novel technique for obtaining self‐aligned contact windows to the source and drain regions. Finally reverse current measurements on gate‐controlled diodes show that the bulk and surface generation currents in the nitrogen‐implanted layer are as low as for unimplanted reference wafers, provided adequate experimental conditions are applied.