An investigation was made, of the interface of Si/Si directly bonded wafers, by using X-ray topographic, spreading resistance, and secondary ion mass spectroscopic methods. The residual stress which was induced at the interface of the bonded wafer was revealed as ring-like patterns by X-ray topography when the 2 wafers, flat and convex, were bonded. It appeared that the residual stress enhanced the diffusion of B atoms and caused them to aggregate near to the bonded interface. Self-interstitials which were ejected during the formation of an amorphous SiOx (where x was between 0.2 and 0.3) layer at the bonded interface led to an increased diffusion length of B on the substrate side (which was under tensile stress) than in the active layer. The resistivity increased in the region under compressive stress; in spite of the aggregation of B.

S.Ishigami, Y.Kawai, H.Furuya, T.Shingyouji: Japanese Journal of Applied Physics 1, 1993, 32[10], 4408-12