profilingcapacitancevoltage

Profiling capacitance-voltage, often abbreviated as C-V profiling, is a semiconductor characterization technique used to determine how dopant concentration varies with depth in a semiconductor. It relies on measuring the capacitance of a structure such as a metal-oxide-semiconductor (MOS) capacitor or a p-n junction as an external bias is swept. The depletion width in the semiconductor changes with voltage, altering the structure’s capacitance. By analyzing how the capacitance changes with voltage, researchers extract information about the dopant distribution beneath the surface.

In practice, a C-V profile is obtained by performing capacitance measurements at appropriate frequencies, typically comparing low-frequency and high-frequency responses to separate effects from interface traps and minority-carrier contributions. For uniform doping, a simple relation links the inverse square of capacitance to the applied voltage; for nonuniform or graded doping, the derivative of 1/C^2 with respect to voltage provides a means to reconstruct the dopant concentration as a function of depth, often through solving an inverse problem based on Poisson’s equation.

C-V profiling can be used to verify dopant profiles in device fabrication, assess implant depth and diffusion, and evaluate oxide thickness or fixed charges in MOS structures. Its limitations include sensitivity to oxide thickness, interface states, and series resistance, as well as resolution limits set by depletion width and measurement conditions. It complements other profiling methods such as secondary ion mass spectrometry and spreading resistance profiling, offering a nondestructive means to gauge near-surface dopant distributions.