Polarized off-axis Raman spectroscopy: A technique for measuring stress tensors in semiconductors

A characterization technique was developed for measuring the complete tenso r nature of stress fields in semiconductors. By combining incident light ti lted away from the normal axis with polarization of the incident and scatte red beams, any Raman-active optical phonon mode can be selectively studied. Once the frequencies and intensities of these phonons are known, the compl ete stress tensor can be determined. Using this concept, a general, systema tic theory and methodology for implementing polarized off-axis Raman spectr oscopy was developed that took into account realistic effects which would b e encountered in an actual experiment. This methodology was applied to mech anically deformed silicon wafers. By applying loads in different configurat ions across the wafer, various types of stress were created including tensi on, compression, and shear. The polarized off-axis Raman technique was vali dated by comparing its results to both analytic calculations based upon the theory of elasticity and to direct measurements of the wafer curvature usi ng a laser deflection method. (C) 1999 American Institute of Physics. [S002 1-8979(99)02922-9].