Stress-Enhanced Diffusion of Boron at the Interface of a Directly Bonded Silicon Wafer

Abstract
We have investigated the interface of Si/Si directly bonded wafers using X-ray topography (XRT), spreading resistance (SR), and secondary ion mass spectroscopy (SIMS). The residual stress induced at the interface of the bonded wafer was observed as ring patterns by XRT when the two 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.