STRUCTURAL QUALITY OF DIRECTLY BONDED SILICON-WAFERS WITH REGULARLY GROOVED INTERFACES

The role of a regularly grooved pattern on a silicon wafer surface to be bonded was studied from the viewpoint of interfacial properties and structural quality of directly bonded silicon wafers by using x-ray t opography and scanning electron microscope techniques. The presence of the grooves resulted in a decrease in the dislocation density at the interface as well as in the crystal bulk, which can be explained by th e dislocation-collection capability of the grooves. Successful bonding , not only between strongly misoriented silicon wafers, but even betwe en (001) and (111) wafers could be achieved. The grooves were eventual ly flattened during a suitable annealing by the aid of the dislocation migration to their free surfaces. Large voids, originating from disbo nded boundaries and provoked by entrap gases, could also be removed by annealing. Measured I-V characteristics of p-n diodes verified the re liability of the modified structures.