Crystallization of Thin-Film Si Monitored in Real Time by In-situ Spectroscopic Techniques

We have developed optical techniques for real-time, in-situ monitoring of crystallization and epitaxial growth of silicon. Real-time spectroscopic ellipsometry is used for evaluating epitaxial growth during hot-wire CVD (HWCVD) reveals the thickness at which epitaxy fails and amorphous cones start to nucleate. To distinguish the various processes related to solid phase crystallization of amorphous silicon, we employ, instead, an in-situ real-time reflectance spectroscopy technique, which is simpler and less expensive. Here, we demonstrate the sensitivity of reflectivity spectroscopy to key changes in materials properties. By analyzing reflectance in strongly absorbing UV and transparent IR spectral regions, we distinguish and study the: (1) crystallization mode (random crystallization or solid-phase epitaxy); (2) nucleation location (uniformly in bulk, near film-substrate interface, or film surface); and (3) hydrogen effusion prior to crystallization.