Theory of defects and defect processes in silicon dioxide

摘要

Defects and defect processes are of particular importance in the thin SiO2 films that form an integral part of silicon-based metal-oxide-semiconductor (MOS) electronic systems. To understand such effects, we have carried out total-energy electronic structure calculations on large clusters of atoms chosen to simulate particular defects and their reactions. Here we consider two examples. (1) Electrical switching experiments in thin oxides have been interpreted by a model in which a metastable state of the oxygen vacancy has a longer lifetime than seems theoretically reasonable. We suggest that this might be explained by different time scales for local and longer-range atomic relaxations. (2) A serious problem occurs if boron diffuses from the polysilicon gate through the oxide in MOS devices. It has been found that hydrogen enhances and nitrogen inhibits the boron diffusion. We use the results of our calculations to discuss several possible explanations for these effects. (C) 1997 Elsevier Science B.V.