Boron emitters: Defects at the silicon - silicon dioxide interface

An investigation of defects caused by boron diffusion into silicon is presented, using two techniques to directly compare the defects at an undiffused and lightly boron diffused Si-SiO2 interface. The first technique uses field effect passivation induced by a MOS structure; the second uses Electron Paramagnetic Resonance measurements to determine the concentration of unpassivated Pb centers on <111> oriented surfaces. It is found that additional defects introduced by the boron diffusion account for a relatively small proportion of total recombination at a well passivated <100> interface, while for more at <111> interfaces, as both the defect density and recombination increase by a factor of more than 2. The effect of the addition of LPCVD nitride on top of oxide layers is also explored. We show that exposure of samples to hot phosphoric acid (used to selectively remove silicon nitride) leads to significant changes to the Si-SiO2 interface, so that this treatment cannot be considered noninvasive.