Preparation of high quality polycrystalline silicon thin films by aluminum induced crystallization

Abstract

In this paper, high-quality polycrystalline silicon (poly-Si) thin films on glass substrates are formed by Aluminum-induced crystallization (AIC). In AIC processes, bi-layer structures of amorphous silicon (a-Si) / Al are transformed into ones of (Al+ residual Si)/ poly-Si after simply annealing at 500°C in vacuum furnace. After Al chemical etchings, it isobserved that the obtained structures are poly-Si thinfilms on glasses with some amount of residual Si as“ islands”scattered on theirsurfaces. The number of these “Si islands” remarkedly reduced by choosing an appropriate thickness ratio of pre-annealled Al and Si layers that prepared by magnetron dc sputtering. In this study, at initial Al/a-Si thickness ratio of 110/230 nm, the high-quality poly-Si thin films are formed with very few“Si islands” on the surfaces after AIC processes. Theobtained smooth surfaces are not appearing “dendritic” in optical transmission microscopy (OTM ) images, have large grain size of tens of nanometers in SEM images and have average surface roughness of about 2.8 nm in AFM images. In addition, XRD Ө -2Ө measurements show a strong Si (111) peak at the 2Ө angle of 28.5°, presenting good crystalline phases. The films also reveal good p-type electrical conductivityin that their high carrier concentration and mobility in Hall effect measurements are 1018 cm-3 and 48 cm2/Vs, respectively.