Next Generation Image Sensor Via Direct Hybrid Bonding

We report wafer level assembly of an advanced image sensor with control logic units and memories. The stack includes all back-end levels of a 0.13 mu m double damascene technology. The back-side imaging structure consists of 12 metal levels connected via direct hybrid copper-copper and oxide-oxide bonding. Thanks to a 3 step Chemical Mechanical Polishing (CMP) process applied at the bonding level and a proper wafer conditioning, the bonding was achieved at room temperature (RT) and under atmospheric pressure, with an x-y alignment precision below 400nm. The annealed structure has a pure copper metal connection with excellent mechanical and electrical properties. Beyond the next generation image sensors and hybrid integration, this demonstration appears as a good omen for a general three-dimensional (3D) IC integration via direct bonding.