Probes for Monitoring Low Dose Silicon Ion Implants for Process Yield Enhancement

A newly developed optical densitometry probe, and existing thermal wave, eddy current sheet resistance, and four-point GaAs sheet resistance probes were used to measure low dose Si+ ion implams. The four probes were evaluated for their ability to detect implant dose uniformity, their sensitivity to low doses, and their repeatability for multiple measurements on a single wafer, and on several wafers implamed with the same dose. The new optical densitometry probe was found to be highly sensitive (S = 0.5 0.6) to low doses (Si+, 100 keV, 0.75E12 5E12 cm-2). The thermal wave probe was found to be relatively insensitive (S = 0.1 0.15) in the same low dose region (Si+, 100 keV,2E124E12) and moderately sensitive (S = 0.40) at higher doses (Si+, 150 keV, 6E13 9E13). The eddy current sheet resistance probe was found to be about four times more precise as the GaAs four point probe. By providing precise information about low Si+ dose uniformity, all four techniques can be applied to yield improvement of GaAs devices made with ion implantation.