Development of low temperature dielectrics down to 150°C for multiple TSVs structure with Wafer-on-Wafer (WOW) technology

With evaluation of various dense silicon-oxy-nitride (SiON) films, a critical density and thickness against to Cu diffusion into Si substrate has been evaluated. Density of SiON films varied with deposition temperature using Plasma-Enhanced Chemical-Vapor-Deposition (PECVD) was ranged from 56% to 69% for bulk film. Cu diffusion increased with decreasing the film density, resulting in 3.5 × 10¹⁰ cm²/s at 63% density. In case of 100-nm thick of SiON film with 63% density formed at 150°C, leakage current and breakdown voltage were <;1 × 10⁸ A/cm² and >4.5 MV/cm, respectively. There is no change of electrical resistance after 1000 cycles of thermal stress for stacked wafers with multiple Through-Silicon-Vias (TSVs). Therefore, the SiON formed at 150°C enables as barrier layer providing enough reliability for TSV interconnects in the Wafer-on-Wafer (WOW) technology.