Resumen de Exploitation of Laser Voltage techniques for identification and complete characterization of a scan chain transition fail issue using the second harmonic approach
Emanuele Villa, Audrey Garnier, Antoine Reverdy
This work presents a Failure Analysis case study related to a scan chain integrity issue. By using Laser Voltage Imaging and Probing (LVx) approaches, we have been able to localize a defect that was inducing a transition failure, detected during scan chain integrity test flow. Laser Voltage Imaging (LVI) and Laser Voltage Probing (LVP) techniques were applied with the aim of both identifying and characterizing the first failing flip-flop of the chain, in order to understand the failure mechanism. The relatively simple Design For Test (DFT) structure of the device, made of a single scan chain to address a large area of the digital logic, and the nature of the electrical behaviour did not allow the ATPG Scan Chain diagnostic to be accurate, leaving the failure identification task to the FA engineer with the help of classical optical techniques. In this work we specially focused on the application of the two fault isolation techniques, to first, identify the failing flip-flop through dichotomy approach, investigating the macro failure mode through a second harmonic LVI analysis and finally characterizing this failure using LVP.
