Test Methods for Measuring Bulk Copper and Nickel in Heavily Doped p-Type Silicon Wafers

Abstract

The goal of this work was to optimize the existing test methods for measuring bulk copper and nickel impurities in the heavily doped p-type silicon wafers and to assess their sensitivity, recovery rate, and correlation. Three test methods were studied; low-temperature out-diffusion, polysilicon ultratrace profiling, and wafer digestion. The bulk copper and nickel recovery rates of low-temperature out-diffusion were improved by one order of magnitude in the concentration around . Among the three test methods, polysilicon ultratrace profiling and wafer digestion were found to be most sensitive and the method detection limit of or better was achieved after optimization. The optimized wafer digestion and polysilicon ultraprofiling also correlated well across six laboratories with a bias less than for both bulk copper and nickel.