Solid phase epitaxy on N-type polysilicon films formed by aluminium induced crystallization of amorphous silicon

In this work, undoped amorphous silicon layers were deposited on n-type AIC seed films and then annealed at different temperatures for epitaxial growth. The epitaxy was carried out using halogen lamps (rapid thermal process or RTP) or a tube conventional furnace (CTP). We investigated the morphology of the resulting 2 μm thick epi-layers by means of optical microscopy. An average grain size of about 40 μm is formed after 90 s annealing at 1000 oC in RTP. The stress and degree of crystallinity of the epi-layers were studied by micro-Raman Spectroscopy and UV-visible spectrometer as a function of annealing time. The presence of compressive stress is observed from the peak position which shifts from 520.0 cm-1 to 521.0 cm-1 and 522.3 cm-1 after CTP annealing for 10 min and 90 min, respectively. It is shown that the full width at half maximum (FWHM) varies from 9.8 cm-1 to 15.6 cm-1, and the magnitude of stress is changing from 325 MPa to 650 MPa. Finally, the highest crystallinity is achieved after annealing at 1000 oC for 90 min in a tube furnace exhibiting a crystalline fraction of 81.5%. X-ray diffraction technique was used to determine the preferential orientation of the poly-Si thin films formed by SPE technique on n+ type AIC layer. The preferential orientation is <100> for all annealing times at 1000 oC.