Comparison of scanning capacitance microscopy and scanning Kelvin probe microscopy in determining two-dimensional doping profiles of Si homostructures

Abstract

Two-dimensional (2D) doping profiles of layered, differently doped, n-step Si homostructures were measured by scanning capacitance microscopy (SCM) and scanning Kelvin probe microscopy (SKPM). The calibrated doping concentration of the n-type Si layers was in the range of 4.2×1014cm−3to1.7×1019cm−3. For the SCM images, the measured ΔC∕ΔV signals were converted to 2D doping concentrations using the NIST FASTC2D program. To compare the SCM-based 2D dopant profiles with those obtained by SKPM, a contact potential difference (CPD) between a probe tip and the Si sample surface was measured with SKPM. Using the relation between a work function and a doping concentration of Si, the doping concentrations were extracted from the measured CPD. The SCM results had good agreements with the calibrated data, but the SKPM results showed some differences due to the presence of the top native oxide layer.