A Manual Diagnosis Approach Using Targeted Fault Injection and Fault Simulation to Extend ATPG Diagnostic Resolution in Localizing Faults

This paper discusses a creative manual diagnosis approach, a complementary technique that provides the possibility to extend Automatic Test Pattern Generation (ATPG) beyond its own limits. The authors will discuss this approach in detail using an actual case – a test coverage issue where user-generated ATPG patterns and the resulting ATPG diagnosis isolated the fault to a small part of the digital core. However, traditional fault localization techniques was unable to isolate the fault further. Using the defect candidates from ATPG diagnosis as a starting point, manual diagnosis through fault Injection and fault simulation was performed. Further fault localization was performed using the ‘not detected’ (ND) and/or ‘detected’ (DT) fault classes for each of the available patterns. The result has successfully deduced the defect candidates until the exact faulty net causing the electrical failure was identified. The ability of the FA lab to maximize the use of ATPG in combination with other tools/techniques to investigate failures in detail; is crucial in the fast root cause determination and, in case of a test coverage, aid in having effective test screen method implemented.

LADA Synchronization for Symmetric and Asymmetric ATE Test Program Cycles

Laser Assisted Device Alteration (LADA) or Soft Defect Localization (SDL) is commonly used to root cause device marginality due to functional or structural failures. At a high level, LADA involves setting the device under test (DUT) at its marginal state and using focused near infra-red laser beams to perturb sensitive circuitry [1]. Scanning the focused laser beam over the die can be a long and time-consuming process. In this paper, two LADA cases are presented, which involve a parametric measurement failure while running a dynamic ATE test. Using LADA technique, these two cases were root caused. These two cases also explain how a parametric measurement-based LADA can be setup on ATE, as well as a synchronization method independent of vectors in a pattern. Synchronization was necessitated in the 2nd case due to the asymmetric test program loop, as well as the long test program cycle time. There are many factors which impact LADA turnaround time and it can take anywhere between few seconds to one day. The two major factors are the size of the Area of Interest (AOI) and test program cycle time. Test program cycle time influences the laser “dwell time” for LADA. Dwell time, in simple terms, is the total time the laser is parked at each pixel. The laser can also be synchronized with the test program cycle, keeping the two always in phase. This is explained in Case 2, where LADA synchronization was implemented, and the analysis was successfully completed in time, even though the test cycle time was very long.

NanoProbing on 7 nm FinFET Devices in an SRAM Array: Challenges and Solutions

Nanoprobing systems have evolved to meet the challenges from recent innovations in the semiconductor manufacturing process. This is demonstrated through an exhibition of standard SRAM measurements on TSMC 7 nm FinFET technology. SEM based nanoprober is shown to meet or exceed the requirements for measuring 7nm technology and beyond. This paper discusses in detail of the best-known methods for nanoprobing on 7nm technology.

Submicron Simultaneous IR and Raman Spectroscopy (IR+Raman): Breakthrough Developments in Optical Photothermal IR (O-PTIR) Combined for Enhanced Failure Analysis

Failure analysis of organics at the microscopic scale is an increasingly important requirement, with traditional analytical tools such as FTIR and Raman microscopy, having significant limitations in either spatial resolution or data quality. We introduce here a new method of obtaining Infrared microspectroscopic information, at the submicron level in reflection (far-field) mode, called Optical-Photothermal Infrared (O-PTIR) spectroscopy, that can also generate simultaneous Raman spectra, from the same spot, at the same time and with the same spatial resolution. This novel combination of these two correlative techniques can be considered to be complimentary and confirmatory, in which the IR confirms the Raman result and vice-versa, to yield more accurate and therefore more confident organic unknowns analysis.

Analysis of Voltage Contrast in Secondary Electron Images Using a High-Energy Electron Spectrometer

Voltage contrast (VC) observation using a scanning electron microscope (SEM) or a focused ion beam (FIB) is a common failure analysis technique for semiconductor devices.[1] The VC information allows understanding of failure localization issues. In general, VC images are acquired using secondary electrons (SEs) from a sample surface at an acceleration voltage of 0.8–2.0 kV in SEM. In this study, we aimed to find an optimized electron energy range for VC acquisition using Auger electron spectroscopy (AES) for quantitative understanding.

Nanoprobe Characterization of Soft SRAM bit Fails in Advanced Technologies

Nanoprobing is one of the key characterization techniques for soft defect localization in SRAM. DC transistor performance metrics could be used to identify the root cause of the fail mode. One such case report where nanoprobing was applied to a wafer impacted by significant SRAM yield loss is presented in this paper where standard FIB cross-section on hard fail sites and top down delayered inspection did not reveal any obvious defects. The authors performed nanoprobing DC characterization measurements followed by capacitance-voltage (CV) measurements. Two probe CV measurement was then performed between the gate and drain of the device with source and bulk floating. The authors identified valuable process marginality at the gate to lightly doped drain overlap region. Physical characterization on an inline split wafer identified residual deposits on the BL contacts potentially blocking the implant. Enhanced cleans for resist removal was implemented as a fix for the fail mode.

A Review on Automatic Bill of Material Generation and Visual Inspection on PCBs

Globalization and complexity of the PCB supply chain has made hardware assurance a challenging task. An automated system to extract the Bill of Materials (BoM) can save time and resources during the authentication process, however, there are numerous imaging modalities and image analysis techniques that can be used to create such a system. In this paper we review different imaging modalities and their pros and cons for automatic PCB inspection. In addition, image analysis techniques commonly used for such images are reviewed in a systematic way to provide a direction for future research in this area. Index Terms—Component Detection, PCB, Authentication, Image Analysis, Machine Learning

FIB Enhancement of Mechanically Polished Cross-sections

On mechanically polished cross-sections, getting a surface adequate for high-resolution imaging is sometimes beyond the analyst’s ability, due to material smearing, chipping, polishing media chemical attack, etc.. A method has been developed to enable the focused ion beam (FIB) to re-face the section block and achieve a surface that can be imaged at high resolution in the scanning electron microscope (SEM).

Applying a Significant Protection Layer on Double Ex Situ Lift-out TEM Specimens to Protect Against Ion Beam Impact

Protection layers on double ex situ lift-out TEM specimens were investigate in this paper and two protection layer approaches for double INLO or double EXLO were introduced. The improved protection methods greatly decreased the damage layer on the top surface from 90 nm to 5 nm (or lower) during FIB milling. According to the property of different sample and its preliminary treatment in the FIB, we have the satisfactory approaches to be applied. Using this improved protection method, we demonstrate the structures within the TEM lamella can be observed without ion beam damage/implantation during FIB

Interpreting Laser-Based Fault Localization Results: Case Studies

Laser-based dynamic analysis has become a very important tool for analyzing advanced process technology and complex circuit design. Thus, many good reference papers discuss high resolution, high sensitivity, and useful applications. However, proper interpretation of the measurement is important as well to understand the failure behavior and find the root cause. This paper demonstrates this importance by describing two insightful case studies with unique observations from laser voltage imaging/laser voltage probing (LVP), optical beam induced resistance change, and soft defect localization (SDL) analysis, which required an in-depth interpretation of the failure analysis (FA) results. The first case is a sawtooth LVP signal induced by a metal short. The second case, a mismatched result between an LVP and SDL analysis, is a good case of unusual LVP data induced by a very sensitive response to laser light. The two cases provide a good reference on how to properly explain FA results.