STRESS-ENHANCED DIFFUSION OF BORON AT THE INTERFACE OF A DIRECTLY BONDED SILICON-WAFER

We have investigated the interface of Si/Si directly bonded wafers usi ng X-ray topography (XRT), spreading resistance (SR), and secondary io n mass spectroscopy (SIMS). The residual stress induced at the interfa ce of the bonded wafer was observed as ring patterns by XRT when the t wo wafers, flat and convex, were bonded. It appears that the residual stress enhanced the diffusion of boron atoms and aggregated them near the bonded interface. However, the resistivity increased in the region under the compressive stress in spite of the aggregation of boron.