The Application of 2nd Harmonic Laser Voltage Imaging for Timing Failure, Re-Thinning Techniques for Effective Dislocation Identification

Laser voltage imaging (LVI) and laser voltage probing (LVP) are laser stimulation techniques to verify a device under test (DUT) and have been widely used for circuit debugging and various frequency-dependent failure modes [1] [2]. In this paper, a scan chain with timing failure study was demonstrated by using LVI and LVP techniques, and further physical failure analysis (PFA) found dislocations in bulk silicon by plan view transmission electron microscopy (TEM). However, on checking the depth of dislocations by 3D-TEM, only deep dislocations were found, and it was hard to explain the phenomenon of channel leakage.In this paper, it is not to introduce the methods for dislocation inspection. The major idea is how to distinguish the dislocations those would induce channel leakage. In this work, we presented a re-thinning technique for shallow dislocation inspection by using EasyLift [5]. The EasyLift system allowed operators to extract the lamella and attach it to a TEM grid, all within the dual beam FIB chamber. Because the lamella had attached to TEM grid, lamella re-thinning and acquisition of TEM images could be performed repeatedly [6]. Using this method makes it possible to partially remove the deep dislocations from bulk silicon and then perform 3D-TEM to acquire the actual depth of target of interest.