Silicon Multilayer Stacking Based on Copper Wafer Bonding

Using copper wafer bonding and silicon substrate thinning, a novel face-to-face silicon bilayer stacking method was successfully demonstrated. Silicon-on-insulator donor wafer was bonded to a substrate wafer using low temperature Cu wafer bonding. Donor wafer was ground and etched back to the buried oxide layer in selective tetraethylammonium hydroxide solution. It was also possible to thin the silicon substrate using hydrogen-induced layer splitting. A progression to silicon multilayer stack was also demonstrated. Cross-sectional scanning electron microscopy confirmed this type of silicon layers transfer and stacking. This method can potentially be used in three-dimensional integration.