standard handling procedures and methods associated with the type of epitaxial reactor being monitored the substrate wafer is placed on the susceptor such that the bare silicon substrate surface is facing toward and in contact with the susceptor and the surface containing the protective layer is facing away from the susceptor as shown at 230 the substrate wafer is then processed through an epitaxial deposition cycle representative of the thermal cycle used during standard deposition for that particular epitaxial reactor and process used during normal operating procedures as shown in 240 it is preferred that gas flows used in epitaxial deposition are incorportated into step 240 to more closely simulate standard processing but gas flows and constituents may be changed if so desired multiple substrate wafers can be singularly processed sequentially through steps 230 and 240 if desired to obtain a statistically valid sampling in accordance with known statistical process control techniques the substrate wafer s can optionally have the protective layer stripped as demonstrated in 250 more preferably however the protective layer would not be stripped from the substrate wafer thereby prohibiting impurities from migrating through the protective layer and thereby increasing the sensitivity to impurity concentration measurements as previously explained as indicated in 260 a gettering layer is then formed on the substrate wafer using any standard technique such as deposition of a polycrystalline silicon layer by lpcvd if the protective layer is stripped as indicated in 250 the gettering layer must be formed on both sides of the substrate wafer alternatively if the.