Ultra high precision of the tilt/twist misorientation angles in silicon/silicon direct wafer bonding

An original direct wafer bonding process has been developed to accurately control the bonding interface twist and tilt angles between a mono-crystalline layer and a bare mono-crystalline wafer. This process is based on the bonding of twin surfaces resulting from a single wafer separation, using for instance the Smart Cut® process. A targeted control of ±0.005° is obtained for the twist angle without any crystallographic measurement; leading to a pure twist-bonded interface between two (001) silicon surfaces. Then, by chemical etching, the interfacial dislocation network is used to nanopattern the silicon surface which periodicity is exactly related to the dislocation network one. This periodicity is tunable between few angstroms to few tenths microns. Moreover, this nanopattern is shown to give a long range organization of flat Ge islands.