Accurate Junction-Depth Measurements Using Chemical Staining

The techniques of chemical staining, spreading resistance, and secondary-ion mass spectrometry (SIMS) have been used in the determination of the depth of diffused and ion-implanted junctions in an effort to estimate the accuracy of the staining method. Computer simulations were also used to study the behaviour of charge carriers in the semiconductor under illumination, and the accuracy of the junction depth obtained from raw spreading resistance data. It was observed that it is possible to measure junction depth reproducibly, to within 200 Å of the metallurgical junction depth, by carefully controlling the surface preparation of the sample and the lighting conditions under which the staining takes place.