ELECTRON PARAMAGNETIC RESONANCE INVESTIGATION OF SI-SIO2 INTERFACE

Unoxidized and oxidized (in dry oxygen or steam) p-type, 70 Ω cm silicon samples bounded with (100) planes were investigated for EPR absorption at 77°K. Heat treatment at 1100°C in H2 or He results in paramagnetic centers (g = 1.999, ΔH = ~1 G) at the surface of unoxidized silicon; their density is a few times 1012 cm.-2 Oxidation with or without subsequent He-treatment does not give rise to EPR absorption, but post-oxidation H2-treatment does (g = 1.999, ΔH = ~1 G). These centers (probably trivalent Si atoms) are in the oxide; they are associated with electrons. Except for the He-treated dry-oxide sample (no absorption), irradiation by 1 MeV electrons produced defects mainly at the silicon surface. The absorption is broad (8 ≤ ΔH ≤ 19 G), the g varies from 2.001 to 2.004. These centers differ from K-centers produced in bulk silicon under comparable conditions. After dissolving the oxide, those irradiated oxidized samples which were He-annealed did not show EPR absorption, but all the others did. Our observations indicate that post-oxidation heat treatment in He results in a very stable silicon surface. © 1969.