In the fabrication of advanced stacked CMOS image sensors, the Image Signal Processor (ISP) wafer must be intimately bonded to the sensing wafer via Cu-dielectric hybrid bonding P3.Following post-CMP cleaning, the RF surface activation of the ISP wafer serves as the critical preparatory step immediately preceding wafer alignment and thermocompression bonding P1.This step is designed to modify the surface chemistry of the top dielectric and exposed Cu pads specifically on the ISP logic wafer P1.J