The use of Atomic Force Microscopy (AFM) electrical measurement modes is a critical tool for the study of semiconductor devices and process development. A relatively new electrical mode, scanning microwave impedance microscopy (sMIM), measures a material’s change in permittivity and conductivity at the scale of an AFM probe tip [1]. sMIM provides the real and imaginary impedance (Re(Z) and Im(Z)) of the probe-sample interface. By measuring the reflected microwave signal as a sample of interest is imaged with an AFM, we can in parallel capture the variations in permittivity and conductivity and, for doped semiconductors, variations in the depletion-layer geometry. An existing technique for characterizing doped semiconductors, scanning capacitance microscopy, modulates the tip-sample bias and detects the tip-sample capacitance with a lock-in amplifier. A previous study compares sMIM to SCM and highlights the additional capabilities of sMIM [2], including examples of nano-scale capacitance-voltage curves. In this paper we focus on the detailed mechanisms and capabilities of the nano-scale C-V curves and the ability to extract semiconductor properties from them. This study includes analytical and finite element modeling of tip bias dependent depletion-layer geometry and impedance. These are compared to experimental results on reference samples for both doped Si and GaN doped staircases to validate the systematic response of the sMIM-C (capacitive) channel to the doping concentration.

Dielectric film quality is one of the most important factors that will greatly impact device performance and reliability. Device level electrical analysis techniques for dielectric quality monitoring are highly needed. In this paper we present results using a new electrical AFM mode, scanning Microwave Impedance Microscopy (sMIM), for characterization of device oxide quality and for fault isolation. Devices with poor oxide quality show sMIM nano C-V and dC/dV hysteresis behavior during forward and reverse bias sweep. The sMIM capacitance sensitivity is below 1 aF allowing one to capture C-V spectra from the MOS structure formed by the gate and gate oxide with excellent signal/noise ratio and observe subtle variations between different sites.

Scanning microwave impedance microscopy was used to analyze a CMOS image sensor sample to reveal details of the dopant profiling in planar and cross-sectional samples. Sitespecific capacitance-voltage spectroscopy was performed on different regions of the samples.