Search Results for copper compounds

FIB milling is difficult if not impossible with III-V compound semiconductors and certain interconnect metals because the materials do not react well with the gallium used in most FIB systems. This article discusses the nature of the problem and explains how cryogenic FIB-SEM techniques provide a solution. It describes the basic setup of a FIB-SEM system and provides examples of its use on InN nanocrystals, GaN films, and copper-containing multilayer photovoltaic materials.

A detailed analysis based on FIB etching and SEM image capture was conducted on a flip-chip solder joint deep inside a tablet PC. 3D views reconstructed from SEM images show what appears to be a copper pillar with a solder cap connected to a copper trace on the substrate. The investigators believe the joint was formed by thermal compression bonding with a preapplied underfill. The analysis also revealed the presence of voids and intermetallic compounds along with signs of filler entrapment.

This article describes two accelerated reliability tests that can help shorten product development cycles for power semiconductor packages. One test simulates the effects of temperature cycling by applying a series of thermal shocks to the test sample. The other test assesses the bond between metals and molding compounds as a measure of thermal cycle resistance. A button shear test is used to measure changes in adhesion strength as a function of time and temperature.

The presence of copper layers separated by low-k dielectrics in today’s ICs is a major problem for circuit edit engineers. This article explains why and presents a solution that addresses the challenges CE engineers face. According to the authors, the difficulties are primarily due to the interaction of the ion beam with variations in copper grain orientation, the effects of halogen corrosion, and the presence of CuF. As a result, copper milling tends to be uneven and edit times tend to be quite long. The solution presented is based on a chemically-assisted milling and etching process that quickly and uniformly removes copper and dielectric layers while maintaining planarity.

Chip-scale packages (CSPs) make efficient use of space on PCBs, but their small size, multilevel stacking arrangements, and complex interconnects present serious challenges when it comes to testing and failure analysis. This article describes some of the problems encountered when dealing with various types of CSPs and provides practical solutions based on the tools and techniques available in most FA labs. It discusses the causes and effects of package and die related failures and walks readers through the steps involved in decapsulating plastic FBGA packages using conventional etching, polishing, and milling techniques. It also includes a case study involving a failure caused by improper laser marking.

IBM engineers recently conducted a study to better understand and control the reliability of copper pillar solder joints in 2.5-D packages. Here they describe their approach and the results they obtained. They explain how they created test samples to evaluate different solder compositions, pillar geometries, and thermal histories and assess their effect on microstructure, precipitate morphology, intermetallic layer thickness, and shear strength. They also present thermal cycling test results comparing the performance of silicon and glass interposers.

Several failure analysis case studies have been conducted over the past few years, illustrating the importance of preserving root-cause evidence by means of artifact-free decapsulation. The findings from three of those studies are presented in this article. In one case, the root cause of failure is chlorine contamination. In another, it is a combination of corrosion and metal migration. The third case involves an EOS failure, the evidence of which was hidden under a layer of carbonized mold compound. In addition to case studies, the article also includes images that compare the results of different decapsulation methods.

This article presents two case histories that shed light on the role of gold in lead-free solder joint failures and the damage mechanisms involved. One of the failures, a brittle fracture of the solder joint, is attributed to the synergistic effects of voids, intermetallic compounds, and CTE mismatch. The investigation of the other failure revealed evidence of tin-whisker formation. As the author explains, the growth of tin whiskers is due to compressive stress in the tin solder material caused by diffusion of end-cap metals (Ni and Cu) and the formation of Sn-Ni-Au intermetallics. In both cases, the failures can be prevented by limiting the thickness of gold on all components.

Copper wires are susceptible to damage during acid decapsulation and must be protected by stopping the process at the right moment. This article describes the development and evaluation of a method that uses polarization current measurements for end-of-etch detection and subsequent rinse.

The scribe-and-cleave method is a widely used sample preparation technique, although numerous challenges make it less than ideal. A new indent-and-cleave approach described in this article provides improved results, even on samples previously considered uncleavable. Several case studies are presented to demonstrate the capabilities of the new technique.

Failure analysis is becoming increasingly difficult with the emergence of 3D integrated packages due to their complex layouts, diverse materials, shrinking dimensions, and tight fits. This article demonstrates several FA techniques, including high-frequency scanning acoustic microscopy, lock-in thermography, and FIB cross-sectioning in combination with plasma ion etching or laser ablation. Detailed case studies show how the various methods can be used to analyze bonding integrity between different materials, chip-to-chip interface structures, buried interconnect defects, and through-silicon vias at either the device or package level.

This article discusses the latest trends in wire bonding and examines common failure mechanisms.

Optical second-harmonic generation (SHG) is a noninvasive technique that provides information about interface properties and crystal defects. This article demonstrates the use of SGH in the study of high-k dielectrics, silicon-on-insulator structures, compound semiconductors, and through-silicon vias.

This is the second article in a two-part series on the causes of failure in electromechanical relays. Part I, in the February 2018 issue of EDFA , examines a variety of failures caused by the formation of oxide on contact surfaces. As the author explains, electric arcing in the presence of silicon oil or vapor creates SiO 2 deposits in the contact region that build up over time. Here in Part II, the author presents examples of failures caused by nitrous gases, phosphoric acid crystals, and wax, which is often found on enameled copper wires.

FIB circuit edit tools and techniques have thus far kept pace with the evolution of interconnect materials in ICs and downward scaling of device dimensions. This article assesses the coming challenges for FIB circuit edit technology and the changes that will be necessary to keep FIB-based etching, milling, and deposition viable in the future.

Packaging integration continues to increase in complexity, driving more samples into FA labs for development support and analysis. For many of the jobs, there is also a need for larger removal volumes, compounding the demand for tool time and throughput. Focused ion beam (FIB) and dual-beam FIB/SEM systems are helping to relieve the pressure with their ability to create site-specific cross sections and to facilitate gate-level circuit rewire and debug. This article reviews the impact of packaging trends on failure analysis along with recent improvements in FIB technology. It also presents examples that illustrate how these new FIB techniques are being applied to solve emerging packaging challenges.

Interposers play an important role in 2.5D and 3D packages, routing power and communication signals between dies while maintaining electrical contact with I/O pins. This role and their relatively simple construction makes interposers a target for malicious attacks. In this article, the authors assess the vulnerabilities inherent in the fabrication of interposers and describe various types of optical attacks along with practical countermeasures.

Microelectronics failure analysis is based on several approaches to study and understand the origin of failure. In addition to “classic” elemental methods (SIMS, ESCA, etc.), there are a number of less-common techniques that can be valuable but require significant equipment investment, specialized operators, and administrative infrastructure to make them available to analysts, if needed. Ion beam analysis methods (RBS, PIXE, NRA), found at the Bordeaux Nuclear Research Center (France), are examples of these specialized tool sets. The capabilities and improved sensitivities of this site for device examination are demonstrated by several examples.

Tin whiskers are single-crystal filaments that can grow from tin-plated copper or nickel components. This article discusses the effect of plating thickness, composition, and grain size on tin whisker formation and explains how to assess damage potential based on microanalysis, whisker length distribution models, and metal vapor arc risk factors. The authors also present and analyze several examples of failures caused by tin whisker formation in space systems.

Further development of SEM-based feature extraction tools for design validation and failure analysis is contingent on reliable sample preparation methods. This article describes how a delayering framework for 130 nm technology was adapted and used on a 45 nm SPI module consisting of 11 metal layers, 10 via layers, two layers of polysilicon, and an active silicon layer. It explains how different polishing and etching methods are used to expose each layer with sufficient contrast for SEM imaging and subsequent feature extraction. By combining polygon sets representing each layer, the full design of the device was reconstructed as shown in one of the images.