Mesa sample preparation for secondary ion mass spectrometry depth profiling using an automated dicing saw

摘要

The use of secondary ion mass spectrometry to verify dopant profiles, either for process control or for simulation modeling, is an established practice in semiconductor fabrication, where precise dopant concentrations are integral to device performance. Of the many understood secondary ion mass spectrometry (SIMS) artifacts, the crater edge effect is one that can limit critical detection limits under conventional SIMS profiling of high dose samples. The use of a mesa structure to eliminate crater sidewall contribution is a proven remedial method, although with practical limitations associated with each iteration of the approach. This work explored a method of constructing a mesa structure using an automated dicing saw. The mesa structures were prepared relatively quickly, taking only about 20 min to construct a six mesa array per sample. Scanning electron microscopy images of cross sectioned mesa structures indicating excellent slope was achieved, without erosion of the mesa surface. Depth profiles from two examples of high dose samples were collected by both standard SIMS and mesa SIMS. Analogous mesa profiles demonstrated between 20 and 5 times gains in detection limits compared to the standard SIMS profiles, comparable to gains achieved in other mesa work. Mesa profiles appeared to be accurate, void of mesa induced artifacts, and repeatable, based on examinations of matrix intensities and peak shapes compared to the standard profiles.