Ultra-thin (001) Si films bonded onto (001) Si wafers, which form so-called surfacial grain boundaries, were analyzed by transmission electron microscopy and X-ray diffraction. The aim of this study was to find a way of controlling precisely, before direct wafer bonding, the structure of the Si/Si (001) interface. Two kinds of dislocation networks were found at the bonded interface. A square array of screw dislocations accommodates the twist between the 2 crystals, whereas a linear network of mixed dislocations accommodates the tilt resulting from the residual vicinality of the initial surfaces. A theoretical study showed that knowing and choosing before bonding the characteristics of these interfacial dislocations depend on the control of the ‘twist' angle during the hydrophobic molecular bonding process. Recently, a new bonding method permitted the achievement of an accuracy of ±0.005° for the so-called twist angle from patterned grooves, without any crystallographic measurement. The precision of this technique was compared with 3 different measurements of the misorientation between the 2 grains; taken after bonding. The first one was deduced from the periodicity of the dislocation networks located at the interface. The second one was estimated from large-angle convergent beam electron diffraction patterns. The final one was obtained by using synchrotron X-ray diffraction. The possibility of choosing the precise characteristics of so-called Si (001) surfacial grain boundaries before direct wafer bonding was considered.

(001) Silicon Surface Grain Boundaries Obtained by Direct Wafer Bonding Process - Accurate Control of the Structure before Bonding. K.Rousseau, J.Eymery, F.Fournel, J.P.Morniroli, J.L.Rouvière: Philosophical Magazine, 2005, 85[21], 2415-48