From IC debug to hardware security risk: The power of backside access and optical interaction

IC debug and diagnosis techniques like photon emission and FIB circuit edit are well established as powerful ways to attack secret codes in security ICs through chip frontside. But protective additions like interconnect meshes serve as countermeasures. This work shows examples how the risk assessment of contactless fault isolation (CFI) techniques through chip backside has indicated a drastic increase of vulnerability. Acclaimed unclonable functions and keys have been successfully challenged. There is no low-cost electronic backside protection concept available like the frontside meshes, because alignment and contact of backside structures to active IC layers cannot be handled without expensive through-silicon-via (TSV) technologies. But optical interaction can also be used to create backside protection concepts: Such concepts based on electro-optical properties are presented and proven to be operational.