X-ray reflectivity of ultrathin twist-bonded silicon wafers

Ultrathin Si (001) layers (< 15 nm) are hydrophobic bonded to a full 4 in. Si (001) wafer. The interface quality and surface roughness, checked by spe cular x-ray reflectivity, are very good. This technique, well suited to mea sure the homogeneity thickness, shows that the samples have very small thic kness fluctuations, and no extended defects. Quantitative analysis proves t hat the interfacial layer resulting from the bonding is very thin (about 8 Angstrom). Its atomic density is significantly different from bulk Si only for large bonding twist angles (> 5 degrees). (C) 1999 American Institute o f Physics. [S0003-6951(99)01448-5].