Deep trench structures in silicon for sensitivity enhancement of Si/SiO₂ interface studies

The measurement of defects at the silicon-insulator interface by most spectroscopic techniques is difficult because of their low concentration. A novel structure has been fabricated by etching a dense array of deep trenches through a silicon wafer. All the sidewalls in this structure are {111} surfaces, and the surface area is greatly enhanced compared to that of a polished wafer of equivalent size. We have grown an oxide on this structure and have achieved better than an order of magnitude increase in the sensitivity of electron paramagnetic resonance measurements of Pb defects at the SiO 2-Si(111) interface.