Formation of Shallow p+n Junction by Low Temperature Annealing

Abstract
The formation of shallow p+n junction with B+ implantation in silicon was investigated. A rapid diffusion of implanted borons was observed in the initial stage of the annealing for activation (in 10 sec), and it was independent of the annealing temperature (600∼1000°C) and determined the shallower limit of B+ implanted p+n junction depth, 0.25 and 0.4 microns for the B+ acceleration of 10 and 20 KV, respectively. Appropriate Si+ implantation subsequent to B+ implantation enabled the annealing temperature reduction to about 600°C with activation (sheet resistivity) and crystallinity (junction quality) comparable to those of high temperature annealing (900∼1000°C). It is suggested that the rapid diffusion and the reduction in the annealing temperature resulted from the excess configuration entropy in the ion implanted layer which corresponded to high temperature situation in effect.

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