3-Layer Stacking Technology with Pixel-Wise Interconnections for Image Sensors Using Hybrid Bonding of Silicon-on-Insulator Wafers Mediated by Thin Si Layers

We report a 3-layer stacking technology with pixel-wise interconnections suitable for image sensors. Au/SiO
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hybrid bonding of silicon-on-insulator wafers allows face-to-back as well as face-to-face bonding for multilayer stacking with pixel-wise interconnections. Thin Si layer is introduced as a bonding medium to enhance bonding strength. We have developed 3-layer stacked wafers without delamination thanks to adhesive thin Si layers with 3-layered pixel-parallel image sensors aligned at accuracy of 1 μm or better.