Observation of MOSFETs without bias voltage using a laser-THz emission microscope

For inspecting electrical failures in large-scale integration circuits (LSI), we developed a laser-THz emission microscope (LTEM), which records the map of the THZ emission amplitude in a sample upon excitation with fs laser pulses. We successfully obtained the THz emission image of MOSFETs fabricated in a test element group without bias voltage. We also measured MOSFETs in which the connection lines from the electrodes to the p-n junctions were interrupted, and found that the polarity of the temporal waveform of the THz emission from the p-n junction in damaged MOSFETs has the opposite sign compared to that in normal MOSFETs. This result indicates that the LTEM is a potential tool for the inspection of MOSFETs without bias voltage, which is the advantage for the failure analysis of semiconductor devices during the manufacturing process.