While 3D X-ray Tools or X-ray Microscopes (XRM) have been the traditional nondestructive imaging tools in Failure Analysis (FA) labs, they normally involve smaller packages or small sections cut out of a package or PCB if high resolution better than 1 um is desired. They are seldom used for intact board level FA nor is a tool of choice for inline metrology for defect inspection in wafer level integration. As sample size increases to several cm, such as 2.5D/3D Packages, Multi Chiplet Modules (MCM), PCBs or a 300 mm wafer, high resolution (< 1 um) imaging is not practical nor in many cases achievable. The acquisition time takes too long (typically hours); images are noisy and are filled with beam hardening artifacts (with bands and streaks). In this paper we will revisit the use of X-rays for high resolution (sub-micron) board level FA and in line metrology for next generation wafer level integration using a novel 3D X-ray system that can achieve sub-micron resolution on large PCBs to 300 mm wafers in as little as a few minutes to evaluate failures or defects in 3D.

The emerging era of 3D Heterogeneous Integration (3DHI) in Advanced Packages and Wafer level packaging of ICs introduce significant challenges for inline defect inspection and offline failure analysis techniques. Primarily, 3D stacking and wafer bonding result in optically opaque systems that require approaches such as X-rays to see through multiple layers of buried structures for defect detection. However, with the continual shrinkage in device features in 3DHI (e.g., microbumps are scheduled to shrink to <10 μm diameter and TSVs interconnects are scaling to single digit micrometers), non-destructive techniques are facing a technological brick wall.This includes 3D X-ray approaches, which need to have higher resolution than currently available in order to meet the evolving requirements. Furthermore, the acquisition time for sub-one micron imaging using conventional X-ray tomography even at a single location within a large 300 mm wafer may take hours or is outright impossible. To address these metrology gaps, we have developed two complementary groundbreaking 3D X-ray inspection tools:1.High throughput (3D data in minutes): The first tool is designed for rapid inspection of 300 mm wafers during wafer level packaging and bonding which can resolve various 3D defects to 0.5 μm resolution automatically and in minutes. This tool will also address board level FA, such as PCB at high resolution.2.High resolution (300 nm): The other complementary tool is designed to address the limits of resolution of the existing leading high resolution 3D X-ray and X-ray Microscopes (XRM) in Failure Analysis of Advanced Heterogeneous Packages. The system delivers true 300 nm spatial resolution (<50 nm voxel) for characterizing submicron defects in microbumps, delamination, voids interfacial cracks and RDL that cannot be seen and measured by existing XRMs.

Reverse engineering of electronics is a rapidly growing field that is limited primarily by the tools available for performing inspection & data processing. 3D X-ray Computed Tomography (CT) is a popular choice for electronics & semiconductor Failure Analysis (FA) applications, but has faced challenges such as metallic noise and artifacts limiting the reverse engineering community. Here, we present a novel high-resolution 3D X-ray imaging system, utilizing the technique of Angled CT. We demonstrate how this innovative imaging approach provides fast, sub-micron data volumes that overcome the beam hardening, inspection time, and sample size limitations imposed by conventional CT. The analysis is demonstrated using the reverse engineering of a commercially-available Xilinx Spartan-3 FPGA Printed Circuit Board (PCB) as the case study.

Rechargeable battery research often involves improving electrodes to electrolyte materials with new chemistry with the end goals to lower cost, extend cycle life, higher energy densities and better safety. Advancements in battery and fuel cell research require the understanding of the complex interplay of several components and factors in a battery ecosystem. It calls for an integrated and multimodality approach involving several new analytical techniques which have to be capable of probing the batteries electrochemistry, structures and composition at different length and time scales, several of which have to be performed non destructively (ex-situ, in situ and in operando). Because of the need to study these in operando or at higher resolution or sensitivity, conventional lab based x-ray techniques are often inadequate. Most of this research is currently performed through synchrotron X-ray techniques. These include: X-ray Absorption Spectroscopy (XAS) to probe changes in oxidation states, bond lengths and coordination numbers of electrochemistry during charge-discharge cycles. XAS comprise XANES (X-ray absorption near edge spectroscopy) & EXAFS (Extended X-ray Absorption Fine Structure). They provide information on element-specific changes in oxidation state and local atomic structure. Such microscopic descriptors are crucial for elucidating charge transfer and structural changes associated with bonding or site mixing, two key factors in evaluating state of charge and modes of cell failure or catalytic efficiency. Another major technique is synchrotron X-ray Imaging at multiple lengthscales, from micrometers to 10s of nanometers through 3D X-ray Microscopy (XRM) to determine structural changes and degradation over time of the complex system, from the electrodes, separators, current collectors to binders. Trace level elemental composition at the ppm or sub-ppm level can be studied through high sensitivity synchrotron X-ray fluorescence spectroscopy (s-XRF)- to track the migration of metallic ions from cathode to anode during charge-discharge cycle or to investigate cross contamination during manufacturing. Unfortunately, many of these X-ray techniques such as XAS has to be performed almost exclusively at synchrotron X-ray light sources, where beamtime is infrequent and experiment time-frames are limited. As a consequence, high level battery, fuel cell or catalyst research in many research institutions have been largely curtailed. In this talk, we will discuss the advancements made in high flux, tunable lab x-ray sources and high efficiency optics for enabling novel synchrotron-equivalent XAS, XRM and XRF techniques in the laboratory. Breakthrough correlative applications through these suite of tools in the field of battery research and catalysts are now feasible in your own laboratory 24/7, without the constraint of limited access nor the research continuity challenges at synchrotron beamlines. Measurements results (including in operando) will be illustrated for conventional NMC batteries to novel solid-state lithium air batteries and next generation battery materials.

X-ray imaging (2D & 3D) has been one of the primary non-destructive analysis methods for electronic packages and printed circuit boards (PCB) for over three decades. The continually shrinking features and growth of heterogeneous packaging and wafer-level packaging drive urgent demand for even higher resolution but on larger samples, including larger packages and on wafers. Currently, gaps in non-destructive 2D and 3D imaging in failure analysis exist due to lack of resolution to resolve sub-micron defects typically found in most cracks or voids in microbumps less than 30 microns in diameter and on low contrast materials such as defects in organic substrates. The larger form factors of samples including modern heterogeneous packages, PCB, wafers adds yet another layer of difficulty, and submicron lengthscale defects on such samples are far beyond the resolution power of most existing 2D or 3D X-ray tools. Conventional, high resolution 3D X-ray tools are designed to inspect small packages, but as sample size increases, the time to detect small defects in large packages or PCB may run into several hours or days, rendering this application impractical. We describe a novel 3D X-ray tool that overcome the sample size and speed limitation of traditional X-ray imaging systems. Time to obtain a sub-micron resolution imaging on a region of interest in a package, pcb or 300 mm can be completed within a few minutes. The rapid multiresolution capabilities are also well suited for construction analysis or reverse engineering from packages to pcbs.

This article provides an overview of a commercial 3D X-ray system, explaining how it acquires high-resolution images of submicron defects in large intact samples. It presents examples in which the system is used to reveal cracks in thin redistribution layers, voids in organic substrates, and variations in TSV metallization on 300-mm wafers. As the authors explain, each scan can be done in as little as a few minutes regardless of sample size, and the resulting images are clear of the beam hardening artifacts that often cause problems in failure analysis and reverse engineering.

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Currently gaps in non-destructive 2D and 3D imaging in PFA for advanced packages and MEMS exist due to lack of resolution to resolve sub-micron defects and the lack of contrast to image defects within the low Z materials. These low Z defects in advanced packages include sidewall delamination between Si die and underfill, bulk cracks in the underfill, in organic substrates, Redistribution Layer, RDL; Si die cracks; voids within the underfill and in the epoxy. Similarly, failure modes in MEMS are often within low Z materials, such as Si and polymers. Many of these are a result of mechanical shock resulting in cracks in structures, packaging fractures, die adhesion issues or particles movements into critical locations. Most of these categories of defects cannot be detected non-destructively by existing techniques such as C-SAM or microCT (micro x-ray computed tomography) and XRM (X-ray microscope). We describe a novel lab-based X-ray Phase contrast and Dark-field/Scattering Contrast system with the potential to resolve these types of defects. This novel X-ray microscopy has spatial resolution of 0.5 um in absorption contrast and with the added capability of Talbot interferometry to resolve failure issues which are related to defects within organic and low Z components.

Modified Talbot X-ray interferometry provides three contrast modes simultaneously: absorption, phase, and dark field/scattering. This article describes the powerful new imaging technique and shows how it is used to characterize various types of defects in advanced semiconductor packages.

The past decade has witnessed tremendous growth in both interest and available techniques for laboratory X-ray analysis. From the progression of commercially-available micro- and nano-CT scanners to the resolution and sensitivity enhancements of x-ray fluorescence spectrometers, the scientific community is benefiting from a rapid expansion of laboratory-based x-ray techniques. In our work, we have developed a suite of advanced x-ray instrumentation providing a wide range of enhanced capabilities for specimen characterization. The key enabling technology lies in the X-ray source, which features a microstructured target capable of providing 5-10x higher brightness than conventional sealed-tube x-ray sources and offering power flux densities that rival rotating anode sources. The target array can be custom-designed to incorporate a variety of materials, facilitating fast & easy switching between characteristic emission lines and radiation spectra. This source has been subsequently integrated with state-of-the-art X-ray focusing optics, such as ellipsoidal/paraboloidal capillary lenses and finely-structured Fresnel zone plate imaging objective lenses, and sensitive scintillator-coupled CCD detection systems, opening up new opportunities for advancing laboratory x-ray inspection equipment. Here, we will describe the system geometries in detail and demonstrate how these new advancements have led us to the development of laboratory micro-XRF, nano-XRM, and XAS instrumentation. We will also briefly introduce the image-centric software workspace, which facilitates novice users to collect data quickly and reliably with minimal training overhead.

Modern X-ray microscopy (XRM) has grown in popularity in recent years [1]. Owing to the high penetrating power of X-ray radiation and the promising resolution levels that can be achieved, XRM is now an established technique at many synchrotrons and become more commonplace in laboratory settings as well. Nano-XRM, in particular, is of interest due to its abilities to provide spatial resolutions in the 10s to 100s of nanometers [2]. While this technique is of considerable interest, still many researchers rely on precious synchrotron time in order to characterize their material systems.

Both laboratory and synchrotron-based microanalytical techniques (e.g. microXRF, microXRD, x-ray microscopy, SAXS, etc.) have made substantial advances in the past decades, including improved algorithms and faster, higher sensitivity detectors. However, laboratory performance remains comparatively limited in performance (e.g. sensitivity and resolution), primarily due to limited laboratory x-ray source brightness and narrow selection of usable x-ray optics. Here we present our patented x-ray source concept. Coupled with our proprietary high efficiency x-ray optics, the system provides over 50X brightness over a conventional x-ray illumination beam system comprised of a microfocus source and polycapillary optic. The brightness is enabled by the design of the x-ray targets, which are comprised of microstructured x-ray emitters in thermal contact with a diamond substrate. Utilization of a diamond substrate enables highly localized and large thermal gradients that rapidly cool the metal as x-rays and heat are generated under the bombardment of electrons. In addition to brightness, the spectral output of the x-ray source, particularly the characteristic lines, is sometimes indeed more important than brightness alone. For example, fluorescence cross-sections can vary by several orders of magnitude depending on the characteristic energy employed. Throughput and contrast of x-ray imaging and microscopy are also highly dependent on x-ray energy. Because characteristic lines can be the dominant spectral output for some metals, the ability to select and change metal types within an x-ray source provides substantial performance advantages. Sigray’s x-ray source incorporates several choices of metals on its x-ray target for push-button energy selectability within the x-ray source. A turret of Sigray’s interchangeable x-ray optics that are optimized for highest efficiencies at these energies can be coupled to provide the optimal flux and spectrum for each application.

New heterogeneous 3D integration schemes and continuing miniaturization of semiconductor packaging components, such as micropillars, are driving demand for substantive changes to conventional PFA (physical failure analysis). In particular, desired performance capabilities include the ability to nondestructively determine failures within seconds to minutes. New tools should be quantitative, have sufficient resolution to determine sub-micron sized defects and voids in TSVs at the wafer or package level. It should also measure thickness and their material composition of multilayer structures above the wafer surface, such as microbumps, or those below the surface including UBM and RDL. In this paper we are introducing a novel x-ray fluorescence microscope technique capable of solving the above applications in advanced packaging for PFA and process development. The same technique can also be applied in the front end metrology of new gate materials, 3D FinFET structures within test structures in patterned wafers. Characterization of sub nanoscopic changes (sensitivity of sub-angstrom) in film and dopants deposited in 3D structures will also be shown. With its high sensitivity for trace materials, contamination analysis of post hard mask residue, post metal etch residue especially in high aspect ratio structures is also possible.

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An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the 'Save PDF' action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Sigray's axially symmetric x-ray optics enable advanced microanalytical capabilities for focusing x-rays to microns-scale to submicron spot sizes, which can potentially unlock many avenues for laboratory micro-analysis. The design of these optics allows submicron spot sizes even at low x-ray energies, enabling research into low atomic number elements and allows increased sensitivity of grazing incidence measurements and surface analysis. We will discuss advances made in the fabrication of these double paraboloidal mirror lenses designed for use in laboratory x-ray applications. We will additionally present results from as-built paraboloids, including surface figure error and focal spot size achieved to-date.