Quantitative model-based interpretation of experimentally measured nanoscale stress sources at wafer bonded interfaces

Nanoscale surface features at the interface of bonded silicon wafers are critical to achieving high yield wafer bonding processes. Interfacial features such as surface patterning, trapped particles and gasses, and wafer surface nanotopography can generate residual stresses that may affect subsequent device lifetimes, processing and performance. This paper presents a numerical model that captures a more complete description of bonding physics and mechanics than extensions of closed form thin-plate solutions. The model is verified by experimentally measuring residual stresses arising from patterned nanoscale surface features using an infrared grey-field polariscope. The proposed numerical model captures the functional form of the observed residual stress fields arising from interfacial defects and is in good agreement with experiments. These simulations indicate that high bond energies may produce debonds around small defects that are not possible to detect using infrared transmission inspection techniques, yet the associated residual stresses are increasingly large in magnitude. copyright The Electrochemical Society.