Recent improvements in giant magnetoresistance sensors have increased the achievable spatial resolution of magnetic current imaging on packaged devices without a significant compromise in magnetic field sensitivity. Front and backside current imaging examples show the utility of these new sensors for die-level failure analysis.

This column provides a ten-year retrospective on laser-based fault isolation techniques and the important role of laser signal injection microscopes.

Electro optical terahertz pulse reflectometry (EOTPR) is a nondestructive fault isolation technique that is well suited for today’s ICs. This article provides examples of how EOTPR is being used to investigate 2.5D and 3D packages, wafer level fanout packages, and MEMS devices. It also discusses recent advancements in EOTPR systems and software.

This article discusses the failure analysis challenges associated with large overmolded 2.5D packages and explains how laser decapsulation followed by microwave-induced plasma (MIP) spot etching removes overmold while keeping everything else intact. It also describes a defect isolation procedure in which the sample is analyzed in a large chamber environmental SEM with its ball grid array directly wired to an EBAC amplifier.

Technologies relatively new to failure analysis, like time-correlated photon counting, electro-optical probing, antireflective (AR) coating, Schlieren microscopy, and superconducting quantum interference (SQUID) devices are being leveraged to create faster, more powerful tools to meet increasingly difficult challenges in failure analysis. This article reviews recent advances and research in fault isolation and circuit repair.

Recent work with a commercial instrument based on a SQUID sensor shows that magnetic field imaging can be very effective in isolating defect shorts in packages and dies. This technique is especially beneficial when the defect is buried under layers of metal, Si, or encapsulation materials. Many of these defects can be imaged for coarse localization without any deprocessing of the sample. SQUID sensors can produce weak current images even in the presence of background current five orders of magnitude stronger. This high sensitivity also enables effective imaging with much lower currents than thermal techniques.

Conventional backside imaging takes advantage of silicon’s transmission of light which, based on the Plank relation ( E g = hc/ λ ), occurs at wavelengths greater than 1 µm. Because of diffraction, the lateral spatial resolution of backside imaging techniques is limited to about half the wavelength of the light source used, which is far too coarse to isolate faults in a typical IC. In this article, the authors explain how they overcome this limitation by reprofiling the backside of the silicon, forming spherically shaped domes. The raised convex surfaces act as solid immersion lenses that are shown to improve spatial resolution by nearly an order of magnitude. The degree of improvement is evaluated using backside emission microscopy (EMS), optical beam induced current (OBIC) imaging, and laser voltage probing (LVP) and the results are presented in the article.

A review of the 2001 edition of the International Technology Roadmap for Semiconductors indicates major obstacles ahead. Of the three basic failure analysis steps—inspection, deprocessing, and fault isolation—the latter is the most at risk, especially physical fault isolation.

Selecting a fault isolation technique for a particular type of SRAM logic failure requires an understanding of available methods. In this article, the authors review common fault isolation techniques and present several case studies, explaining how they determined which technique to use.

This is a case study of an illumination-sensitive failure. Due to the unavailability of a scanning optical microscope, fault isolation was performed using a different approach based on available equipment. Through a combination of emission microscopy, FIB isolation, mechanical probing, and in-depth circuit analysis, the root cause and failure mechanism were determined.

The Product Analysis Forum (PAF), sponsored by the Quality Council of SEMATECH, has been chartered to facilitate the ongoing development of tools and techniques for semiconductor characterization and failure analysis. Drawing on input from industry experts, universities, and national laboratories, the PAF has identified critical needs in three areas: software fault isolation, backside fault isolation, and deprocessing & inspection. This article discusses the current state of deprocessing and inspection technology and provides insights into how some of the future challenges will be addressed.

Magnetic current imaging provides electrical fault isolation for shorts, leakage currents, resistive opens, and complete opens. In addition, it can be performed nondestructively from either side a die, wafer, packaged IC, or PCB. This article reviews the basic theory and attributes of MCI, describes the types of sensors used, and discusses general measurement procedures. It also presents application examples demonstrating recent advancements and improvements in MCI.

The EDFAS Die-Level Roadmap Committee was formed to identify forthcoming challenges related to electrical fault isolation within the next five years and collaborate with various stakeholders, including industry, academia, and tool vendors, to devise practical solutions. To that end, the team has pinpointed five critical areas of focus: (1) laser-based, photon emission, and thermal; (2) 2D/2.5D/3D packaging; (3) product yield, test, and diagnostics; (4) general (leading edge technologies); and (5) system level, analog/RF, and digital functional.

Over the last few years, new challenges increased the pressure on packaging and assembly analytical resources. Reduced product development cycle time, increased market segmentation, new package and die level materials, ever shrinking device geometries, and fully enabled technologies (i.e. with thermal, retention, and EMI solutions) created these new pressures on fault isolation/failure analysis efforts and package development.

The Package Innovation Roadmap Council (PIRC) was established as part of the Failure Analysis Technology Roadmap activity at the direction of the EDFAS Board. This column provides an overview of a technical paper by the PIRC that highlights recent innovations, technology gaps, and future development trends in package fault isolation and failure analysis. The paper focuses on three main categories: 1) Artificial intelligence (AI) applications, 2) Sample handling, and 3) FA tool robustness.

The 40th International Symposium for Testing and Failure Analysis (ISTFA 2014) was held November 8 to 14, 2014, at the George R. Brown Convention Center in Houston, Texas. “Exploring the Many Facets of Failure Analysis,” the theme of ISTFA 2014, emphasized the diverse nature of semiconductor failure analysis in the 21st century. The technical sessions, keynotes, and tutorials at ISTFA 2014 covered a wide range of topics from fault isolation and sample prep to extreme environment failures and the birth of the digital signal processor.

This article summarizes major discussion points from four User’s Group meetings held at the ISTFA 2009 conference. The topics addressed are "Optical Techniques: Growth and Limitations," "Resolution of Nanoprobing for 45 nm and Beyond: New Challenges," "FIB," and "Fast ASIC Fault Isolation: Efficiency and Accurate Resolution of Software-Based Fault Isolation."

This article explains how laser voltage probing (LVP) can be used to analyze combinational logic circuits. The authors describe how the technique is aided by the development and use of a waveform library and a corresponding truth table. They also present a case study in which the new technique is used to isolate faults in a combinational logic circuit consisting of multiple gates.

Magnetic current imaging is a proven fault-isolation technique. Its unsurpassed sensitivity and resolution coupled with the fact that magnetic fields are unaffected by packaging and die materials make it a valuable FA tool for a wide variety of ICs and devices. This article reviews the basic measurement physics of magnetic current imaging, describes the general implementation, and presents several practical examples of its use.

This article compiles summaries of User Group meetings held at ISTFA 2013, including the Contactless Fault Isolation User’s Group, the Focused Ion Beam User’s Group, the Sample Prep/3D Package User’s Group, and the Nanoprobing User’s Group. For each meeting, a brief synopsis of the presentations and subsequent dialog is provided.