For small angles that are
near critical angle, a primary incident X-
ray beam has excellent depth resolution. A series of X-
ray fluorescence measurements are performed at varying small angles and analyzed for depth profiling of elements within a substrate. One highly useful application of the X-
ray fluorescence measurements is depth profiling of a
dopant used in
semiconductor manufacturing such as
arsenic,
phosphorus, and
boron. In one example, angles are be varied from 0.01° to 0.20° and measurements made to profile
arsenic distribution within a
semiconductor wafer. In one embodiment, measurements are acquired using a total reflection X-ray
fluorescence (TXRF)
type system for both known and unknown profile distribution samples. The fluorescence measurements are denominated in counts / second terms and formed as ratios comparing the known and unknown sample results. The count ratios are compared to ratios of known to unknown samples that are acquired using a control analytical measurement technique. In one example the control technique is secondary
ion mass spectroscopy (SIMS) so that the count ratios from the TXRF-type measurements are compared to ratios of integrals of SIMS profiles. In another example, the TXRF-type measurement ratios are compared to
simulation profiles of known samples. Integrals of the SIMS profile that vary as a function of depth into the substrate correspond to the
grazing incidence angles of the TXRF-like measurement and respective count rates.