Recent demonstrations of high-repetition-rate, high-brightness soft X-ray lasers are opening new possibilities for the development of compact imaging systems with spatial resolution approaching the illumination wavelength. This article examines some of configurations that have been used in these extreme ultraviolet (EUV) imaging systems and their general capabilities. One of the systems discussed uses the output from a 46.9 nm argon laser to render transmission and reflection-mode images with a spatial resolution of 120 to 150 nm. Another uses a 13 nm AgCd laser with Fresnel zone plate optics, producing transmission-mode images with a spatial resolution of 38 nm.

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.

This article provides an introduction to scanning ion microscopy, explaining how it overcomes one of the biggest limitations of SEMs, namely the tradeoff between spatial resolution and depth of field, while also providing significantly more surface detail, a wide range of novel and familiar contrast mechanisms, and the potential for new microanalytical techniques that combine nanometer spatial resolution and single monolayer sensitivity. In addition to describing the capabilities of scanning ion microscopes, the article also addresses the issue of sample charging and the potential for physical damage that can result from ion beam irradiation.

This article discusses the setup and use of thermoreflectance imaging, a thermal mapping technique with a spatial resolution in the submicron range and a time resolution down to tens of nanoseconds. It describes the basic physics of thermoreflectance measurements and the advantages and limitations of the approach. It also provides examples showing how thermoreflectance imaging is used for thermal characterization, design optimization, and reliability analysis of high-power transistors, electrostatic discharge devices, and copper vias.

Engineers at IBM’s Watson Research Center are contending with one of the most fundamental limitations of imaging technology: the tradeoff between spatial resolution and field of view. In this article, they explain how they created tool interfaces, control and automation software, and image analysis and stitching algorithms, enabling photon emission and laser scanning microscopes to produce high-resolution mosaic images of advanced processor cores and other large-area ICs. They describe some of the challenges they faced and explain how their technology can be used to create images based on reflected light, induced voltage, photon emission, and laser stimulation signatures. In one of the latest demonstrations, the technology was used to land and focus a SIL more than 4000 times, acquiring some 16,000 images that were composed into stitched mosaics of several hundred images each.

X-ray computed tomography is a noninvasive technique that can reveal the internal structure of objects in three dimensions with spatial resolution down to 50 nm. This article discusses the basic principles of this increasingly important imaging technology and presents examples of its use on various types of defects in semiconductor packages.

One of the pioneering developers of induced voltage alteration (IVA) measurement techniques assesses the current state of the technology, the impact of major advancements, and the potential for further improvements. The assessment pays particular attention to biasing approaches, phase-locked loop detection techniques, the effect of solid immersion lenses on spatial resolution, and the emergence of production-type sample preparation methods.

Improved X-ray detector technology continues to be a critical need in the semiconductor industry, particularly for high-spatial-resolution X-ray microanalysis using lowbeam-voltage field-emission scanning electron microscopes (FE-SEMs). In response to this need, a prototype microcalorimeter energy-dispersive spectrometer has been developed. This article discusses the capabilities of the new tool and demonstrates its use in thin-film and particle analysis. It also discusses ongoing development efforts and potential future advancements.

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.

Localizing defects in one-of-a-kind failures can take days, weeks, or even months, after which a detailed physical analysis is conducted to determine the root cause. TEM and STEM play complimentary roles in this process; TEM because of its superior spatial resolution and STEM because it produces images that are easier to interpret and is less susceptible to chromatic aberrations that can occur in thicker samples. In the past, the use of STEM in FA has been limited due to the time required to switch between imaging modes, but with the emergence of TEM/STEM microscopes with computer controlled lenses, the use of STEM is increasing. This article provides an overview of STEM techniques and present examples showing how it is used to characterize subtle and complex defects in ICs.

The best spatial resolution that can be achieved with far-field optical fault localization techniques is around 20 times larger than the critical defect size at the 45 nm technology node. There is also a limit on the laser power that can be safely used on 45 nm devices, which further compromises fault localization precision. In this article, the authors explain how they overcome these limitations using pulsed laser-induced imaging techniques and a refractive solid immersion lens. Two case studies show how the combination of pulsed-laser scanning optical microscopy and a solid immersion lens improves localization precision and detection sensitivity.

Acoustic microimaging has advanced over the past few years in response to the growing use of thinner silicon die and innovative packaging designs. This article reviews the basic principles of acoustic imaging technology and describes some of the applications made possible by improvements in spatial resolution, focal length, F-number, and water couplant temperature control. It also discusses common imaging challenges and explains how they can be resolved.

IBM engineers have developed a holographic imaging technique, called dual-lens electron holography, that provides high spatial resolution and field of view without compromising signal-to-noise ratio. This article reviews the basic principles of the new method and provides several examples of its use. The first few examples demonstrate the junction profiling capabilities of the new method which, in one case, helps to explain why shallow junction devices are made with raised source-drain regions. In the other examples, dual-lens holography is used for strain mapping, in one case, to study strain distributions in sigma-shaped SiGe devices, and in another, to provide evidence that stress memorization occurs in dislocations in the source-drain region of nFET devices.

Laser stimulation is widely used to reveal defects in ICs through either heating or photonic effects. The standard approach is to use lasers with wavelengths above the bandgap wavelength of silicon to create localized heating and below it to generate photocurrent. In practice, most FAs use 1340 nm (IR) lasers for TIVA measurements and either 532 nm (visible) or 1064 nm (near IR) lasers for LIVA analysis. However, as this article demonstrates, visible and near IR lasers can also be used for TIVA analysis and, in some cases, may be preferrable based on signal strength and spatial resolution.

Scanning acoustic tomography (SAT) is widely used to detect defects such as voids and delamination in electronic devices. In this article, the authors explain how they improved the spatial resolution and detection sensitivity of SAT by switching from a conventional piezoelectric probe to a capacitive micromachined ultrasound transducer (CMUT) and by using pulse compression signal processing. They also present examples showing how the improvement makes it possible to detect very small defects in multilayer stacks and BGA packages whether in through-transmission or reflection imaging mode.

Backside optical analysis is often aided by solid immersion lenses (SILs), but as the authors of this article explain, SILs improve the resolution of front side thermography as well. The authors describe the physics behind solid immersion lenses and provide examples that demonstrate the advantages and limitations of their use from the font side.

Scanning electron microscopes (SEMs) are the dominant tool for electronic device testing, failure analysis, and characterization. This status was not apparent, however, when the first commercial SEM, the Cambridge Stereoscan, appeared in 1963. A market survey by the manufacturer at that time predicted total sales of six to ten units worldwide. For the last four decades, SEMs have sold at an average rate of one unit every 24 hours, with two out of every three instruments destined for the semiconductor industry.

This article provides a practical overview of energy-dispersive spectroscopy (EDS) and its various uses in semiconductor device manufacturing and failure analysis. It explains how EDS techniques are typically implemented, compares and contrasts different methods, and discusses the factors that determine spatial and energy resolution, measurement depth, sensitivity, signal-to-noise ratio, and ease of use.

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.

This article discusses the development of resonance-enhanced AFM-IR spectroscopy and demonstrates its effectiveness on silicon test wafers with nanoscale skin particles and polyester contaminants.