50-NM-THICK SILICON-ON-INSULATOR FABRICATION BY ADVANCED EPITAXIAL LATERAL OVERGROWTH - TUNNEL EPITAXY

An advanced epitaxial lateral overgrowth (ELO) technique, called tunne l epitaxy is presented, in which the lateral epitaxy is grown in a sma ll gap between the upper and lower layers of SiO2. Therefore, the fabr icated silicon on insulator (SOI) thickness can be controlled precisel y by the gap height. Thin SOI films with thicknesses of 50-150 nm are fabricated successfully using this technique. The fabricated SOI areas were 5-10 mum in length and 10-750 mum in width. Due to gas heating t hrough a narrow SiO2 tunnel, the optimal growth conditions for the tun nel epitaxy using ultrahigh vacuum chemical vapor deposition (UHV/CVD) depends on the tunnel length, distance between the gas injection wind ow and the seed. A defect-free area within 2-3 mum from the seed was o btained. An n-channel metal oxide semiconductor field effect transisto r (MOSFET) fabricated in this area shows good characteristics. Possibl e mechanisms for defect generation after 2-3 mum growth are discussed.