2018 Volume 67 Issue 7 Pages 700-707
Stress/strains in silicon-based devices play important roles in controlling the performance and the reliability, therefore it is recently very important to grasp stress/strain states in these devices. In this study, stress/strain components in (111) single crystal silicon wafers were determined by polarized micro-Raman spectroscopy. The polarized micro-Raman spectroscope equips with the devices for independently controlling the polarization direction of irradiation and scattering lights and achieves the sub-micro spatial resolution. The silicon belongs to the Oh point group with A1g, Eg and F2g vibration mode, but the measured active Raman line is the only triply-degenerate single peak with F2g mode. First, the polarization condition to decompose the triply-degenerate Raman line into three independent Raman peaks was determined by the theoretical and experimental polarization analysis of backscattered Raman spectrum for (001), (110) and (111) single crystal Si wafers. Based on the determined polarization condition, Raman shift change in (111) single crystal Si wafers under equi-biaxial stress condition was measured. The relationships between Raman shift change and applied strain were linear function, and the obtained values were good agreement with theoretical values. Therefore, three independent Raman peaks were able to be detected by polarized micro-Raman spectroscopy. Finally, the stress components around indentation-induced crack in (111) single crystal Si wafer were measured by polarized micro-Raman spectroscopy. The measured stresses around a crack tip asymptotically approached the values dominated by the stress intensity factor calculated from the empirical equations proposed by Newman and Raju. Therefore, the applicability of polarized micro-Raman spectroscopy to the measurement of stresses/strains components in (111) single crystal Si was confirmed.
