Octahedral Void Defects Causing Gate-Oxide Defects In Moslsis

We found oxide defects originating in standard Czochralski silicon and proposed the sacrificial oxidation method to eliminate these defects in about 1979. Later, N2 annealing and H2 annealing methods were proposed successively, and these three elimination methods have been successfully introduced into actual fabrication lines for highly reliable integrated circuits. However, the origin of the defect was not clarified until recently. We combined copper decoration and TEM in order to observe the origin of the oxide defects and for the first time, observed octahedral void defects systematically at the oxide defects with standard Czochralski silicon. The sizes of the defects are typically 0.1–0.2 microns. These Si-crystalline defects are the origin of oxide defects and, at the same time, may be the origin of crystal originated particles. Recently, we have observed octahedral void defects in the bulk of the standard Czochralski silicon too. Some experimental findings suggest that some impurities on the side wall of the octahedral void defect induce dielectric breakdown of the gate-oxides.