Sputtered depth profile resolution on some samples can be improved by sputtering from the backside of the wafer; utilizing the lower profile broadening of a leading edge measurement, as opposed to the trailing edge. This work develops a technique for simple and accurate backside thinning using a silicon-on-insulator substrate. A combination of backside grinding and selective wet etching results in a planar and smooth surface for accurate measurements. Using 800 eV oxygen sputtering, the measured slope due to the sputter broadening is 1.6 nm/decade of concentration for a phosphorus distribution. The technique is used to evaluate shallow phosphorus diffusion from doped polysilicon to provide calibration for diffusion modeling.