Method and apparatus for high resolution profiling in semiconductor structures

Abstract

A method for determining the characteristics of a doped semiconductor substrate is disclosed, wherein a scanning probe microscope, preferably an atomic force microscope, is used to move a probe across a sample surface gathering electrical measurements at many locations. The probe tip is conductive and is connected to a control circuit that applies a voltage to the probe and to an electrode fixed to the semiconductor substrate. Preferably, the current that flows through the sample is measured and saved, together with the position of the probe on the surface of the sample. In this manner, the characteristics of the doped sample can be determined at many different locations with many different degrees of doping. The sample is prepared by doping its top surface, then machining off the top surface to provide access to the sample at different doping depths. By driving the probe back and forth across the surface and taking readings of the sample at many different locations, a map of the electrical,characteristics at various doping depths below the top surface can be developed. By using a single scanning probe, that probe can be manufactured to have an extremely small radius of curvature, and hence a much smaller contact spot on the surface of the sample.