Effects of iron contamination in silicon on thin oxide breakdown and reliability characteristics

Abstract

Effects of iron contamination on the breakdown and reliability characteristics of thin silicon gate oxides are discussed. Gate oxide integrity is measured for thermal oxides of 8, 10, 13 and 20 nm grown on silicon wafers intentionally contaminated with 10 10–10 14 cm −3 of iron. Iron concentration in silicon is measured using surface photovoltage (SPV) minority carrier lifetime analysis. The density of gate oxide weak spots as a function of iron concentration for the various oxide thicknesses is reported. For 10 nm oxides, iron concentration cannot exceed 8 × 10 10 cm −3 without severe degradation in oxide quality. The threshold contamination level for 20 nm oxides is 200 times higher