Real Time Measurement of Epilayer Strain Using a Simplified Wafer Curvature Technique

We describe a technique for measuring thin film stress using wafer curvature that is robust, compact, easy to setup, and sufficiently sensitive to serve as a routine diagnostic of semiconductor epilayer strain in real time during MBE or CVD growth. We demonstrate, using growth of SiGe alloys on Si, that the critical thickness for misfit dislocation can clearly be resolved, and that the subsequent strain relaxation kinetics during growth or post-growth annealing are readily obtained.