VACANCY CONCENTRATION WAFER MAPPING IN SILICON

A method is described, which for the first time allows the fast determination of the concentration of vacancies and the visualization of their inhomogeneity in silicon wafers. The vacancy concentration wafer mapping is suggested as a means for the determination of the quality of silicon wafers. The concentration of vacancies is determined via the measurement of the concentration of fast diffusing elements, especially platinum or gold, which occupy silicon vacancies. Platinum and gold introduce deep energy levels in the bandgap, which act as recombination centers for excess carriers, whether excess electrons or holes, and the platinum or gold concentration can be obtained from excess carrier lifetime measurements. Several important applications of this method are suggested such as the optimization of the crystal growth manufacturing process, wafer quality control, and the selection of wafers for the fabrication of specific devices.