Critical timing analysis in microprocessors using near-ir laser assisted device alteration (lada)

Abstract

A scalable laser-based timing analysis technique we call laser assisted device alteration (LADA) is introduced for the rapid isolation and analysis of defect-free performance limiting circuits in advanced flip-chip packaged microprocessors and other complex IC’s. The technique, which has been demonstrated to be widely applicable to production level as well as motherboardhystem level testing, uses a laser incident f iom the backside to perturb the timing of internal nodes by means of temporary alteration of transistor characteristics primarily by means of localized photocurrent injection. The relevant physics describing the effects of near-IR laser sources on modern day CMOS FET devices and circuits is discussed in this paper in the context of achieving precision picosecondscale timing adjustment. A selected case study where this technique was used to isolate a critical path circuit in a leading edge 130 nm generation product is provided. Scaling trends for LADA and other relevant issues are discussed.