The D‐C MOSFET Dopant Profile Method

Dopant profiles can be determined from d‐c measurements on a four‐terminal surface‐channel MOSFET. The region from about three Debye lengths from the oxide‐silicon interface to a maximum depth, limited by the avalanche breakdown in silicon, can be profiled by this method. Within three Debye lengths of the surface, the depletion approximation fails, and in this region the profile has a characteristic dip which is easily recognized. Other limitations include effects due to the field dependence of the channel mobility, short channel enects, and the lack of parallelism of the depletion edge with the interface. The method is illustrated by dopant profiles of bulk wafers, implanted layers, and a diffused layer. The dopant densities covered by these profiles vary from to .