Comparative solid-phase crystallisation of Si thin-films on glass deposited by electron-beam evaporation and plasma-enhanced CVD

Abstract

Solid-phase crystallisation (SPC) of hydrogenated (H + ) and dehydrogenated (H - ) Si thin films on glass deposited by electron-beam (e-beam) evaporation (EVA) and plasma-enhanced chemical vapor deposition (PECVD) is compared. Four independent film characterisation methods, optical transmission microscopy (OTM), UV reflectance spectroscopy (UV-R), X-ray diffraction (XRD) and Raman spectroscopy, reveal that for the SPC process at 600oC the evaporated films have similar incubation and nucleation times as the PECVD films but the number of initial crystal grains is less and their growth rate is faster in the evaporated films. The scanning electron microscopy (SEM) images of fully crystallised polycrystalline Si film (poly-Si) samples after Secco etching show that the average grain size is larger in the evaporated film. The resulting quality of evaporated poly-Si appears to be at least as good as the quality of poly-Si made by PECVD promising similar cell efficiencies. Hydrogen is not responsible for the observed differences between SPC of the films from two different deposition methods. Keywords: 1. Poly-Si 1. Solid Phase Crystallisation 2. Si e-beam evaporation 3. a-Si:H PECVD