Carrier concentration dependence of the scanning capacitance microscopy signal in the vicinity of p–n junctions

Abstract

Scanning capacitance microscopy (SCM) was used to image (1) boron dopant gradients in p-type silicon and (2) identical boron dopant gradients in n-type silicon. The bias voltage dependence of the apparent p–n junction location in the (SCM) images was measured. The theoretical bias voltage dependence of the apparent p–n junction location of the same structures was determined using a two-dimensional, numerical Poisson equation solver. The simulations confirm that, for symmetric step p–n junctions, the apparent junction coincides with the electrical junction when the bias voltage is midway between the voltage that produces the peak SCM response on the p-type side and the voltage that produces the peak response on the n-type side. This rule is only approximately true for asymmetrically doped junctions. We also specify the extent of the region on the junction high and low sides from which valid carrier profiles may be extracted with a simple model.

Modeling mobility degradation in scanning capacitance microscopy for semiconductor dopant profile measurement

“…The peak dC / dV of the known n-type substrate is used as the reference to normalize the raw dC / dV data obtained from the instrumentation. The p-n junction is estimated to be at x = 1.9 µm according to Kopanski et al [13]. The plot displays the results as we expect from standard theory, positive and negative peaks of dC / dV are observed in the n and p + regions, respectively.…”

Influence of Interface Traps and Surface Mobility Degradation on Scanning Capacitance Microscopy Measurement

“…The versus data at each spatial position from the SCM instrumentation has been normalized by the peak of the known n-type substrate. Following Kopanski et al [15], the junction is estimated to be at m. As expected from MOS C-V theory, shows positive and negative peaks in the n and p regions respectively at the accumulation-to-depletion transition of the surface. Within the space charge region (approximately m m), shows both negative and positive peaks similar to what is observed in a low-frequency MOS C-V curve but measured at 915-MHz, indicating both are accumulation-to-depletion transitions.…”

Scanning capacitance spectroscopy of an AlxGa1−xN/GaN heterostructure field-effect transistor structure: Analysis of probe tip effects

“…thicknesses and dopant concentrations, and a low density of trap states to avoid additional changes in the dC/dV spectra, could be used to obtain an approximate tip shape by fitting simulated dC/dV spectra for a set of possible tip shapes to dC/dV data recorded on the calibration sample. While this method has been demonstrated successfully for Si dopant profiling, 15 it is more difficult to obtain good calibration samples in the Al x Ga 1Ϫx N/GaN system due to higher densities of trap states that can affect dC/dV spectra significantly. To be able to use this approach, measurements on the calibration sample should be performed before and after the actual experiment to check if the tip shape has changed in the course of the experiment.…”