Observation of lattice spacing fluctuation and strain undulation around through-Si vias in wafer-on-wafer structures using X-ray microbeam diffraction

Abstract

Spatial fluctuations of the Si 004 lattice spacing, strain, and lattice tilt around through-Si vias (TSVs) in wafer-on-wafer (WOW) structures annealed at different temperatures were quantitatively investigated using X-ray microbeam diffraction. The TSVs were found to induce spatial fluctuations in the base and bonded wafers, and a strain of approximately 0.1% and lattice tilt with a long undulation period of 40 µm were clearly observed. Furthermore, annealing at approximately 100 °C effectively reduced the spatial fluctuation, strain, and lattice tilt in the WOW structure.