Near Infra-Red (NIR) techniques such as Laser Voltage Probing/Imaging (LVP/I), Dynamic Laser Stimulation (DLS), and Photon Emission Microscopy (PEM) are indispensable for Electrical Fault Isolation/Electrical Failure Analysis (EFI/EFA) of silicon Integrated Circuit (IC) devices. However, upcoming IC architectures based on Buried Power Rails (BPR) with Backside Power Delivery (BPD) networks will greatly reduce the usefulness of these techniques due to the presence of NIR-opaque layers that block access to the transistor active layer. Alternative techniques capable of penetrating these opaque layers are therefore of great interest. Recent developments in intense, focused X-ray microbeams for micro X-Ray Fluorescence (μXRF) microscopy open the possibility to using X-rays for targeted and intentional device alteration. In this paper, we will present results from our preliminary investigations into X-ray Device Alteration (XDA) of flip-chip packaged FinFET devices and discuss some implications of our findings for EFI/EFA.

High core-Vdd overvoltage latchup margins in CMOS ICs are required to enable many reliability screens (e.g., DVS and HTOL testing). We introduce an efficient way to isolate defects that degrade these margins using PEM and 1064/1340 nm CW laser-stimulation. Current pulses from a current amplifier are used to rapidly charge and discharge the DUT power rail to repetitively ramp Vdd to (or near) the latchup threshold. The characteristic drop in Vdd when latchup is induced is used to generate a latchup flag for laser-stimulation mapping. Latchup events are automatically terminated and latchup durations are minimized, leading to high stability/repeatability of the technique. Isolations down to the cell level were successfully performed in sub-14 nm FinFET test vehicles. This level of isolation is unmatched and this is the first reported use of thermal laser stimulation for latchup investigations. In one provided example, the latchup trigger was isolated to FET based decoupling capacitors (decaps) widely used as fill.

Using a laser to purposely damage (or zap) a static random-access memory (SRAM) bitcell for bitmap validation purposes is a well-established technique. However, the absence of visible damage in FinFET SRAM cells, amongst other things, makes precision zapping in these devices more difficult. In this paper, we describe system enhancements and a modified workflow for bitmap validation of these devices using precision, near-infrared (NIR) laser-induced damage. We also explore the use of laser perturbation and non-precision zapping options. Examples are provided.

A variety of EFA techniques have been deployed to improve scan chain failure isolation. In contrast to other laser techniques, modulation mapping (MM) does not require electrically perturbing of the device. Beginning with a review of MM and continuous-wave (CW) probing as well as shift debug using MM, this paper presents three case studies involving scan chains with subtle resistive and leakage failure mechanisms, including transition, bridge, and slow-to-rise/fall failures, using a combination of these techniques. Combining modulation mapping with laser probing has proven to be a very effective and efficient methodology for isolating shift defects, even challenging timing-related shift defects. So far, every device submitted for physical failure analysis using this workflow has led to successful root cause identification. The techniques are sufficiently non-invasive and straightforward that they can be successfully applied at wafer level for volume, yield-oriented EFA.

Yield on specific designs often falls far short of predicted yield, especially at new technology nodes. Product-specific yield ramp is particularly challenging because the defects are, by definition, specific to the design, and often require some degree of design knowledge to isolate the failure. Despite the wide variety of advanced electrical failure analysis (EFA) techniques available today, they are not routinely applied during yield ramp. EFA techniques typically require a significant amount of test pattern customization, fixturing modification, or design knowledge. Unless the problem is critical, there is usually not time to apply advanced EFA techniques during yield ramp, despite the potential of EFA to provide valuable defect insight. We present a volume-oriented workflow integrating a limited set of electrical failure analysis (EFA) techniques. We believe this workflow will provide significant benefit by improving defect localization and identification beyond what is available using test-based techniques.