Carrier distribution in silicon devices by atomic force microscopy on etched surfaces

The selective chemical etching of silicon containing an impurity profile was used to obtain surface topography related to the local carrier concentration. Atomic force microscopy (AFM) was then used to image this topography. Through a calibration curve of etched depth versus carrier concentration, established by etching uniformly doped epitaxial silicon layers, it is possible to convert the AFM topographical data into carrier concentration. The technique was applied to measure directly the carrier distribution in submicron devices.