Crystallographic analysis of polysilicon films formed on foreign substrates by aluminium induced crystallisation and epitaxy

Abstract

The crystallographic quality of poly-Si films formed by aluminium-induced-crystallisation (AIC) is characterised by electron backscattering diffraction (EBSD). EBSD gives a detailed analysis of the inner-grain structure, the grain boundaries and the grain orientation. The AIC and epitaxy are carried out on either silicon dioxide, glass, oxide coated alumina or mullite ceramics. Average grain sizes of about 8, 11 and 20 μm for respectively flowable oxide coated ceramics, th-SiO 2 and glass substrates are obtained and a strong correlation between the average grain size and the size distribution is found. Furthermore, the grains contain subgrain-structures and numerous defects. The crystallographic defects in the AIC layers are mainly low angle boundaries and CSL boundaries (Σ3 and Σ9) for all substrates. Most grain orientations deviate by 5–20° from to the (100) surface plane. High temperature vapour phase epitaxy on the AIC seed layer resulted in a polysilicon layer of similar crystallographic properties than the seed layer although deviations in orientation and additional twin formations were observed.