Opportunities of Chip Power Integrity and Performance Improvement through Wafer Backside (BS) Connection: Invited Paper.

Technology node scaling is driven by the need to increase system performance, but it also leads to a significant power integrity bottleneck, due to the associated back-end-of-line (BEOL) scaling. Power integrity degradation induced by on-chip Power Delivery Network (PDN) IR drop is a result of increased power density and number of metal layers in the BEOL and their resistivity. Meanwhile, signal routing limits the SoC performance improvements due to increased routing congestion and delays. To conquer these issues, we introduce a disruptive technology: wafer backside (BS) connection to realize chip BS PDN (BSPDN) and BS signal routing. We first provide some key wafer processes features that were developed at imec to enable this technology. Further, we show benefits of this technology by demonstrating a large improvement in chip power integrity and performance after applying this technology to BSPDN and BS routing with a sub-2nm technology node design rule. Challenges and outlook of the BS technology are also discussed before conclusion of this paper.