Infra-Red, In-Situ (IRIS) Inspection of Silicon

This paper introduces the Infra-Red, In Situ (IRIS) inspection method, which uses short-wave IR (SWIR) light to non-destructively "see through" the backside of chips and image them with lightly modified conventional digital CMOS cameras. With a ~1050 nm light source, IRIS is capable of constraining macro- and meso-scale features of a chip. This hardens existing micro-scale self-test verification techniques by ruling out the existence of extra circuitry that can hide a hardware trojan with a test bypass. Thus, self-test techniques used in conjunction with IRIS can ensure the correct construction of security-critical hardware at all size scales.