The density of microvoids with dimensions from several to a few tens of microns at the interface of bonded silicon wafers formed during annealing at different temperatures was investigated by using a submicron resolution scanning infrared microscope (SERM). For low temperature heat-treatment (400°C), the density and size (i.e., area) of micro voids have been found to be much larger in the case of bonding with hydrophilic wafers (2.5 X 104/cm2 and up to 400 µm2, respectively) than for the hydrophobic one (3 X 103/cm2 and up to 20 µm2). By increasing the annealing temperature to 1150°C, the density and size of microvoids decreased in both cases, but more significantly for hydrophobic wafer bonding (90% and <4 µm2 compared to 66% and <100 µm2). The cause of the different annealing behavior of microvoids between hydrophilic and hydrophobic samples is believed to be the native oxide forming only on the surface of the hydrophilic wafers during storage and surface treatment.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry