Degradation of n⁺/p junction characteristics by aluminum contamination

This paper discusses the effects of Al contamination on n⁺/p junction characteristics. The Al contamination occurs during ion implantation and the level can be as high as one tenth of the implanted dose. The Al contamination leads to an increase in the n⁺/p junction leakage current and a decrease in breakdown voltage. This is due to the increase of SiO₂/Si interface state density and fixed negative charge in SiO₂ film. The contaminating Al is segregated in the SiO₂ film and remains very close to the oxide surface even in nm-order SiO₂ (less than 10 nm), and the influence of Al becomes greater as SiO₂ thickness decreases. Since Al is, and will continue to be, the most widely used material for process equipment, Al contamination control might become one of the key issues in achieving highly reliable future giga-scale ULSIs.