Abstract
Monitoring electrical properties in semiconductor integration processes is crucial in identifying electrical defects that determine the reliability and performance of metal oxide semiconductor field-effect transistors. A non-destructive in-line metrology technique using terahertz (THz) waves was developed to observe electrical properties between semiconductor integration processes. By combining near-field microprobes with THz time-domain spectroscopy (TDS), sub-10 μm resolution was achieved, enabling the measurement of on-chip micro-patterns. The system was integrated into a memory production line and demonstrated consistent results with conventional destructive methods. The TDS signal correction method effectively suppressed signal variations in unwanted layers. The results of non-invasive THz TDS measurements of tungsten films deposited by three different processes were consistent with those obtained by four- point probe method. We also non-destructively detected differences in THz transmission at the gate-oxide/Si-substrate interface due to the infiltration of nitrogen species after the thermal nitridation process at nitridation temperatures ranging from 670 to 730 °C, which were consistent with the results of secondary ion mass spectrometry. Our in-line near-field THz TDS will predict electrical performance immediately after the process, allowing for rapid correction of production conditions.