Factors influencing the capacitance–voltage characteristics measured by the scanning capacitance microscope

Abstract

A scanning capacitance microscope (SCM) can measure the local capacitance–voltage (C–V) characteristics of a metal-oxide-semiconductor structure formed by the SCM probe tip and a doped semiconductor sample. A common realization of the SCM depends on a parallel atomic force microscope, which includes a laser focused on the end of the cantilever to monitor the position of the probe tip. In this configuration, it is found that the stray light from the laser can dramatically affect the measured C–V curve. The difference between the SCM C–V curves measured in this high stray light condition and those measured in the true dark condition are shown and discussed. Also discussed is the distortion of the measured C–V curves caused by the SCM method of measuring the differential capacitance using a capacitance-modulating ac voltage and a lock-in amplifier. After reducing and accounting for these effects, the SCM C–V curves show markedly different behavior from that of conventional one-dimensional C–V curves. The measured C–V curves are stretched out in voltage and have a larger |dC/dV| signal in the depletion and the inversion regions, as compared to the conventional one-dimensional C–V curve. The measured C–V curves are compared with the results of three-dimensional calculations for different values of the probe-tip size.

Scanning capacitance spectroscopy on n+-p asymmetrical junctions in multicrystalline Si solar cells

“…Indeed, when the laser was turned off using the "dark lift" mode, we did not observe any measureable affect on the SCM images, which is different from the literature 10,11 and is likely a result of a different sample setup. Intentionally connecting the contacts of a live device so that every local area of the front and back contacts are shorted could result in a different sample condition from an unintentionally, and unevenly, shorted device.…”

Halo Ion Implantation Effect on Extension Profile Studied by Scanning Capacitance Microscopy Using All-Metal Probe under FM Control

“…7) To overcome these drawbacks, we have applied an all-metal probe under frequency modulation (FM) control that requires no optical detection technique. Figure 1 is a schematic of the FM-SCM setup.…”

Contrast distortion induced by modulation voltage in scanning capacitance microscopy

“…16,17 The SCS investigations by Buh et al indicated that both the AFM laser beam and the modulation voltage (MV) may distort SCS profiles of a metal-oxide-semiconductor (MOS) capacitor. 18 Moreover, the humidity-induced hysteretic behavior of SCS was studied, exploring the importance of environmental control for SCM measurements. 19 Since SCM is equipped with a lock-in amplifier to measure the dC/dV signals, it is necessary to apply a MV during SCM measurements.…”