A Signal-Processing-Assisted Instrumentation System for Nondestructive Characterization of Semiconductor Wafers

A signal-processing-assisted instrumentation system has been developed for nondestructive resistivity mapping in semiconductor wafers. With the recent performance improvement and market expansion on power electronic devices with gallium nitride (GaN) and silicon carbide (SiC), there is a strong demand for ultra-high-resolution resistivity mapping based on measurement informatics by combining narrow-pitch scanning and super resolution techniques, but it was still difficult to realize narrow-pitch scanning with high measurement stability. The developed system combined a special technique of signal processing with a conventional resistivity-measurement technique based on frequency response of metal-insulator-semiconductor-metal (MISM) structure consisting of two electrodes, air gap and semiconductor. This system enabled us to obtain the gap-dependent and resistivity-dependent components by straightforward peak estimation instead of parametric model fitting from the measured frequency response of the MISM structure to a square wave, which improves the reproducibility of gap control and stability of resistivity evaluation. The system performance was examined with commercial 6-inch \(\phi\) GaAs wafers and it exhibited good reproducibility in gap control finer than the minimum translation step of 4 μm, and a small coefficient of variation of 1.7% for 100 repeated measurement of resistivity at the order of 108 Ωcm, which demonstrates a high applicability of the system in narrow-pitch scanning much finer than the probe diameter of 2 mm required for further study on ultra-high-resolution mapping with super resolution technique for GaN and SiC wafers.