A Si-Backside Protection Circuits Against Physical Security Attacks on Flip-Chip Devices
Takuji Miki, Makoto Nagata, Hiroki Sonoda, Noriyuki Miura, Takaaki Okidono, Yuuki Araga, Naoya Watanabe, Haruo Shimamoto, Katsuya Kikuchi · 2019
Flip-chip semiconductor packaging reduces the footprint of IC chips while leads to serious vulnerabilities against emerging backside physical security attacks. The proposed backside buried metal (BBM) structure forming a meander wire pattern on the Si backside detects unexpected disconnection of the meander wire and warns malicious attempts. Besides prevention is also achieved against both passive probing attacks and active laser fault injection as well. Unlike other conventional laminate-based protection, this backside monolithic approach does not require frontside wiring resources or additional packaging layers, resulting in only 0.0025 % area-overhead. The BBM meander was formed on the backside of a 0.13 μn CMOS cryptographic chip by wafer-level via-last backside buried metal processing.