Ultra thin silicon films directly bonded onto silicon wafers

Ultra thin film of silicon bonded on 4 in. (001) silicon wafers have been o btained by combining a direct hydrophobic silicon bonded technique with a l ayer transfer. The twist angle between the ultra thin Si film and the Si su bstrate was varied from 0 to 15 degrees. X-ray reflectivity measured the th ickness and the roughness of the ultra thin films. Complementary results co ncerning the interface structure were obtained with high resolution transmi ssion electronic microscopy. It is shown that an ultra thin film (a few nm) can be reproductively prepared upon the full 4 in. wafers. Moreover, this process gives very small thickness fluctuations and a small surface roughne ss. The bonding interface has a low concentration of oxide precipitates and presents two arrays dislocations respectively, due to the twist (screw dis locations) and a residual tilt angle (mixed dislocations) of the crystals. Dissociation of the screw dislocations is also observed on the lowest twist angle sample. (C) 2000 Elsevier Science S.A. All rights reserved.