Large-grained polycrystalline silicon films on glass by argon-assisted ECRCVD epitaxial thickening of seed layers

Abstract

This work reports on the low temperature ( ⩽ 550 ∘ C ) epitaxial growth of Si films on polycrystalline seed layers made by aluminium-induced crystallisation (AIC) on glass. The seed layers were chemically mechanically polished before use and electron–cyclotron resonance chemical vapour deposition (ECRCVD) was used to deposit the Si films. The quality of the deposited films depends strongly on the addition of Ar to the hydrogen rich silane growth environment. With Ar, epitaxial growth has been achieved to a thickness of ∼ 2.7 μ m . Electron backscatter diffraction (EBSD) analysis shows a similar grain structure to the starting seed layers with a preferred (1 0 0) orientation and grain sizes approaching ∼ 10 μ m for samples up to ∼ 1.7 μ m thick. Thicker films ( 2.7 μ m ) show a more mixed orientation with an increase in the density of smaller grains. Nevertheless, more than 95% of the film surface can be indexed suggesting large grained crystal growth has occurred on all grain orientations present in the seed layer. Similar behaviour is also exhibited by the films grown without Ar but these films are more defective and the deterioration in the EBSD orientation maps occurs at a significantly lower thickness. The role of Ar in the growth process is briefly discussed.