Direct comparison of two-dimensional dopant profiles by scanning capacitance microscopy with TSUPREM4 process simulation

Abstract

Quantitative two-dimensional (2D) dopant profiling of a gatelike structure is achieved by scanning capacitance microscopy (SCM) on a cross-sectioned polished silicon wafer. The gatelike structures consist of heavily implanted n+ regions separated by a lighter doped n region underneath a 0.56 μm gate. The SCM is operated in the constant change capacitance mode while scanning with a 37 nm radius tip. The 2D SCM data are converted to dopant density through a physical model of the SCM/silicon interaction. The model parameters are adjusted so that the SCM dopant profile far from the gate edge fits the vertical secondary ion mass spectrometry (SIMS) profile. A 15% error in average accuracy is found between SCM and SIMS profiles evaluated over the dopant range of 1020–1017 cm−3. The same model parameters are used for all points in converting the 2D SCM data, indicating that the accuracy of the full 2D result should be comparable to that of the vertical profile. A direct comparison of the 2D SCM and 2D TSUPREM4 results is made for the first time. The agreement is generally good, but there are some notable differences.