Dopant profiling on semiconducting sample by scanning capacitance force microscopy

Scanning capacitance force microscopy (SCFM) capable of mapping differential capacitance $\mathrm{(\partial C/\partial V)}$ on semiconducting sample based on atomic force microscopy (AFM) without an external capacitance sensor is introduced. While an electric field alternating at an angular frequency ω is applied between the tip and the sample, an induced electrostatic force (ESF) oscillating at its third harmonic frequency (3ω) is detected by a lock-in amplifier. Owing to the fact that the magnitude of the induced ESF is proportional to the square of the magnitude of the applied electric field and the fact that the capacitance of the semiconducting sample is also modulated at ω, the amplitude and the phase of the induced ESF oscillating at 3ω contain information on $\mathrm{\partial C/\partial V.}$ We present $\mathrm{\partial C/\partial V}$ images on a Si test sample obtained by SCFM using both contact-mode AFM and dynamic-mode AFM, showing clear contrasts depending on species and density of dopants.