Development of Backside Buried Metal Layer Technology for 3D-ICs

Abstract

Abstract In this study, we developed backside buried metal (BBM) layer technology for three-dimensional integrated circuits (3D-ICs). In this technology, a BBM layer for global power routing is introduced in the large vacant area on the backside of each chip and is parallelly connected with the frontside routing of the chip. The resistances of the power supply (VDD) and ground (VSS) lines consequently decrease. In addition, the BBM structure acts as a decoupling capacitor because it is buried in the Si substrate and has metal–insulator–silicon structure. Therefore, the impedance of power delivery network can be reduced by introducing the BBM layer. The fabrication process of the BBM layer for 3D-ICs was simple and compatible with the via-last through-silicon via (TSV) process. With this process, it was possible to fabricate the BBM layer consisting of electroplated Cu (thickness: approximately 10 μm) buried in the backside of the CMOS chip (thickness: 43 μm), which was connected with the frontside routing of the chip using 9 μm-diameter TSVs.