Optimization of amorphous layer thickness and junction depth on the pre-amorphization method for forming shallow-junction in silicon

A 0.1- mu m-deep p/sup +/-n junction was formed by Si/sup +/ and Ge/sup +/ preamorphization methods. Both the thickness of the preamorphized layer and the junction depth were optimized systematically. It is found that channeling of 15-keV, 2*10/sup 15/-cm/sup -2/ dose BF/sub 2//sup +/ implantation is eliminated by a 40-nm-thick preamorphized layer formed by Si/sup +/ implantation and that the junction must be formed 70-90 nm deeper than the amorphous-crystal (a-c) interface for the Si/sup +/ case and 20 nm for the Ge/sup +/ case in order to reduce leakage current density J/sub 1/ to less than 1*10/sup -8/ A/cm/sup -2/. The advantage of the Ge/sup +/ case over the Si/sup +/ case is confirmed. The dependence of J/sub 1/ on the distance between the junction and a-c interface (x/sub j/-x/sub a/) was also investigated. It is confirmed that the preamorphized layer thickness influences the dependence of J/sub 1/ on x/sub j/-x/sub a/ for both Si/sup +/ and Ge/sup +/ preamorphizations.<
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