In Situ Monitoring of Crystallinily and Temperature during Rapid Thermal Crystallization of Silicon on Glass

A novel technique is presented for simultaneously measuring temperature and crystallinity in situ during the rapid thermal annealing of thin Si films on transparent substrates for active matrix liquid crystal display applications. This technique makes use of acoustic waves to monitor temperature by measuring changes in Lamb wave velocity with temperature. Since this technique is independent of emissivity, it enables accurate tracking of crystalline phase transitions along with temperature, based on changes in the optical absorption properties of the film. This provides a methodology for closed-loop control and end-point detection. The experiments on thin amorphous Si on fused silica demonstrate temperature repeatability of 2%. Also, the technique proved sensitive enough to detect the onset of nucleation, as evidenced by transmission electron microscopy.