OXIDE DEFECTS ORIGINATING FROM CZOCHRALSKI SILICON SUBSTRATES

Oxide defects originating from Czochralski silicon substrates are characterized. It is shown that oxide defect density is significantly large for the oxide thickness range of 20-200 nm. This noteworthy feature is valid for dry oxidation and HCl oxidation alike. It is considered that small defects in the silicon substrate surface layer are introduced into the growing oxides during thermal oxidation and that the small defects in oxides provide conductive paths across the oxides. The origin of the small defects is not known at present. A simple model is proposed in an effort to show the relation between the size and density of the small defects. The oxide thickness dependence data of oxide defect density are characterized in terms of the small-defect behaviors. The relationship between the small-defect size L and the density rho in the Cz-Si substrates is shown as rho = rho-0 exp(-L/L0), where rho-0 = 10(7) cm-3 and L0 = 48 nm. In addition, oxide surface etching of thick oxides followed by oxide defect evaluation of the thinned oxides reveals that even thick oxides with seemingly low oxide density contain many small defects. The small defect density in 130 nm oxides is estimated as 120 cm-2.