Fabrication of high-quality poly-Si thin films combined with in situ real-time spectroscopic ellipsometry

Abstract

Polysilicon thin films, exhibiting both high crystallinity and photoconductivity, have been successfully fabricated on glass substrate at 360°C from fluorinated precursors SiF n H m ( n + m = 3). Direct nucleation of Si crystals on glass substrate was promoted by the layer-by-layer (LBL) technique wherein deposition of thin layer (∼ 4 nm) and exposure to atomic hydrogen were alternately repeated. In situ real-time spectroscopic ellipsometry revealed that atomic-hydrogen-induced crystallization occurs within the sub-surface of the growing film during the LBL growth. Atomic hydrogen permeating to the sub-surface promotes structural relaxation by breaking some SiSi bonds. Excessive exposure to atomic hydrogen, however, causes both degradation of the crystalline structure and the formation of surface roughness.