Detection of defects on the surface of a semiconductor by terahertz surface plasmon polaritons

We propose a new method for detecting small defects on the surface of a semiconductor by analyzing the transmission spectrum of terahertz surface plasmon polaritons. The field distributions caused by the detection of defects of different sizes are simulated. Experimentally, using a terahertz time domain spectrometer, we measure the transmission spectrum of terahertz surface plasmon polaritons passing through particles on the surface of an intrinsic InSb wafer. Our results show that the measured temporal waveform and frequency spectra are distinctly changed due to the presence of the particles, thereby confirming the effectiveness of this method for detecting defects. For increased detection efficiency, the frequency of the surface plasmon polaritons has to be slightly lower than the plasma frequency of the semiconductor. In comparison with traditional methods, our approach offers the merits of detecting both on-surface and subsurface defects, which is critical in monitoring the quality of semiconductor wafers.