Search Results for scanning laser-SQUID microscopy

Scanning laser-SQUID microscopy is a new electrical inspection and failure analysis technique that can detect open, high-resistance, and shorted interconnects without electrical contact in areas ranging in size from a few square microns to an entire die. This article describes the setup of a prototype laser-SQUID system, explaining how it works and how it compares to other nondestructive defect localization techniques. It presents application examples in which laser-SQUID microscopy is used to locate gate oxide shorts to within 1.3 μm and detect IC defects prior to bond-pad pattering and after bonding and packaging. It also includes a series of images acquired from a board-mounted chip with fields of view ranging from 5 x 5 mm down to 50 x 50 μm.

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.

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.

This article provides a high-level review of the tools and techniques used for backside analysis. It discusses the use of laser scanning and conventional microscopy, liquid and solid immersion lenses, photon emission microscopy (PEM), and laser-based fault isolation methods with emphasis on light-induced voltage alteration (LIVA). It explains how laser voltage probing is used for backside waveform acquisition and describes backside sample preparation and deprocessing techniques including parallel polishing and milling, laser chemical etching, and FIB circuit edit and modification.

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.

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 22nd European Symposium on Reliability of Electron Devices, Failure Physics and Analysis (ESREF 2011) was held October 3 to 7, 2011, in Bordeaux, France. The conference concentrated on two main areas in electronics that concern designers, manufacturers, and users: (1) strategy for quality and reliability assessment of electronic circuits and systems, and (2) advanced analysis techniques for technology and product evaluation. This article reports on highlights of the technical program.

Failure analysis labs are fairly well equipped for dealing with shorts and leakages in stacked-die packages, but are at a disadvantage when it comes to opens, particularly those at the die or die interconnect level. This article presents a new FA technique that has the potential to make up for this shortcoming. The new method, called space domain reflectometry (SDR), is based on radio-frequency magnetic current imaging, and as the authors show, is capable of accurately locating a dead open in a double-stacked BGA package, even when the full stack is encapsulated in molding compound.

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.

This article presents a failure analysis workflow tailored for complex ICs and device packages. The FA flow determines the root cause of failures using nondestructive analysis and advanced sample preparation techniques. The nondestructive tests typically used are X-ray radiography, scanning acoustic microscopy, time domain reflectometry, and magnetic current imaging. To gain access to interconnect failures, laser ablation is used, typically in combination with chemical etching to finish the decapsulation process. Repackaging is also part of the FA flow and is briefly discussed.

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.

Magnetic field imaging is proving to be a valuable tool for semiconductor failure analysts and test engineers. One of its main advantages is that it does not require sample preparation or deprocessing because magnetic fields pass through most materials used in ICs and device packages. This article discusses the theory and practical limitations of magnetic field imaging and demonstrates its use in mapping current density and determining the location and depth of current-carrying conductors.

Photon emission microscopy (PEM) has proven to be a powerful tool for fault isolation and has adapted well to ongoing changes in technology and emerging needs. In this tutorial, the authors describe the fundamentals of photon emission, the essential elements of a typical PEM system, and the procedures involved in diagnosing various types of failures. They also classify a wide range of photon-emitting defects and explain how PEM is used for backside analysis of flip-chip packaged devices and for timing diagnostics.

Researchers have developed an imaging technique that reveals wiring defects in packaged ICs without requiring decapsulation. The sensing mechanism is based on resistance changes, similar to IR-OBIRCH, but instead of an IR beam, the metal conductors in the chip are heated by ultrasonic waves. This article describes the basic principles of ultrasonic beam induced resistance change (SOBIRCH) imaging and demonstrates its effectiveness in a wide range of applications, including multilayer metal stacks.

Quantum diamond microscopy is an innovative nondestructive tool. This article describes detailed operations from a failure analyst's perspective, showing how the technique integrates into standard workflows. Case histories are included comparing its performance to established FA methods and highlighting QDM's specific advantages.

The complexity of sample preparation and deprocessing has risen exponentially with the emergence of 2.5-D and 3D packages. This article provides answers and insights on how to deal with the challenges of increasingly complex semiconductor packages. After identifying pressing issues and potential bottlenecks with state-of-the-art FA flows, the authors present two case studies demonstrating the capabilities of electro-optical terahertz pulse reflectometry (EOTPR), plasma FIB milling, and 3D X-ray imaging. The FA results confirm the potential of all three techniques and indicate that a fully nondestructive integration flow for 3D packages may be achievable with further development and optimization.

Passive voltage contrast (PVC) has traditionally been used by semiconductor engineers for end-of-line post-mortem analysis. PVC distinguishes between open and short structures and is both nondestructive and noncontact. When applied during process development for in-line characterization, it allows wafers to be examined at multiple points, where electrical probing might not be feasible. This provides feedback on the cumulative effect of the process on critical parameters such as oxide integrity and can reduce development cycle times because wafers do not have to be deprocessed in order to determine the exact location of failures. Two case studies are presented in this article, demonstrating the use of PVC in a process development environment.