| A new characterization technique, called polarized off-axis Raman spectroscopy, was developed for measuring the complete tensor nature of stress fields in semiconductors. By combining incident light tilted away from the normal axis with polarization of the incident and scattered beams, any Raman-active optical phonon mode can be selectively studied. Once the frequencies and intensities of these phonons are known, the complete stress tensor can be uniquely determined. Using this concept, a general, systematic methodology for implementing polarized off-axis Raman spectroscopy was developed that took into account realistic effects which would be encountered in an actual experiment. In order to establish its validity, this technique was applied macroscopically to mechanically deformed silicon wafers subjected to a variety of bending configurations. The results using this new approach compared favorably both with the stress calculated by means of the theory of elasticity and with an independent characterization method based upon directly measuring the wafer curvature using laser beam deflection. |
