Crystallization of semiconductor films by laser

Abstract

To study the dynamics of laser annealing, the time-resolved refectivety measurement are performed, We observe that the initial reflectivity of 150Kev, $1.0\times1015/cm^2$ phosphorous implanted $<100>$ Si rises abruptly to that of liquid silicon by pulse laser irradiation. This is the evidence that the melting phenomena happens. We estimate the regrowth velocity as 2m/s from the reflectivity fall time. The hydrogenated amorhpous silicon (a-Si:H) films deposited by grow discharge method on Corning glass are transformed from the amorphous to the crystalline state by the ruby laser irradiation. By laser irradiation, the Si melts, agglomerates on the roughened on the roughened glass surface, and forms nonepitaxially the small crystallites with the random crystal orientaion. Raman scattering, X-ray diffraction, and Normarski optical microscopy are carried out on the laser irradiated Si films. raman scattering of the laser irradiated $S_1$ films have the peak at 520cm-1 just like single or polycrystalline Si. From X-ray diffraction linewidths and Nomarski micrograph of the irradiated Si films, the estimated grain size is 1$\mu$ m. GaAs epitaxial layers were grown by metalorganic chemical vapor deposition (MOCVD) on exact $<100>$ Si substrates by using two-step growth method. The effects of pulsed ruby laser annealing (PLA) on GaAs-on-Si were characterized by Raman spectroscopy and double crystal X-ray diffraction measurement. The laser-annealed surface with 0.4J/$cm^2$ laser energy density had cracks of a rectangular mosaic type. The cause of theses cracks was attributed to the stress which came from epictxial regrowth process on the strained unmelted layer near GaAa/Si interface or the large thermal gradient that developed during the melting and resolidifying process by pulse laser annealing. The annealing with 0. 6J/$cm^2$ laser energy density made these cracks dim. Raman spectra and X-ray diffraction measurement showed that there were substantial improvement in th...