Generation and Tracking of Optical Signals inside the IC to Improve Device Security and Failure Analysis

Abstract

Optical signal tracking techniques accessing the IC through the chip backside have become the most successful methods in hardware attacks. On the other hand, tracking the optical signal can be employed to protect the IC against such attacks. Furthermore, this technique is an advantageous method for failure analysis. Tracking the optical signal reflected from, or transmitted through a surface, reveals some information about this surface that can be used to monitor the surface. Thus, detection of the light reflected from the silicon chip back surface discloses any harms and violations to the backside. For this purpose, we need to generate light inside the IC, which is possible by applying forward bias to a p-n junction. However, in most ICs, silicon is the base material, and the light generated by silicon LED is weak. Furthermore, this application may lead to degradation of the silicon LED. Therefore, an externally produced a stronger light source mounted onto the chip is desirable. This paper considers possible ways to generate and track optical signals inside the silicon to achieve a proper protection structure that prevents attacks from being carried out through the silicon back surface. We describe how an efficient LED can be integrated into an IC to illuminate light in the demanded directions, as well as which kind of LED is favorable for this target.