Article

# Magnetic Field Imaging for non destructive 3D IC testing

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## Abstract

Due to magnetic fields ability to penetrate through all materials used by the semiconductor industry, a unique ability not found in any other techniques, it has become an important technique for detecting shorts, leakages and opens in multi stacked Through Silicon Via samples. We show in this paper how Magnetic Field Imaging is being used to image the current in a TSV stacked silicon device with a new 3D analysis algorithm of the distance from the top of the stacked device to the current path.

## No full-text available

... In general, the resulting integrated-circuit magnetic fields pass through many standard integrated circuit materials, and will vary spatially and temporally in ways that correlate with both integratedcircuit architecture and operational state. Thus, combined high-resolution and wide-field-of-view mapping of magnetic fields may yield simultaneous structural and functional information, and may be suitable for identification of malicious circuitry or Trojans [6,7], counterfeit detection [8], fault detection [9][10][11], and manufacturing flaws [12]. However, leveraging magnetic field emanations is challenging due to the tremendous complexity of circuits integrating billions of transistors of minimum feature sizes down to tens of nanometers, with interconnects distributed across multiple levels of metallization [13]. ...
... To date, the QDM's unique combination of magnetic field sensitivity, spatial resolution, field of view, and ease of use has allowed it to be used to measure microscopic current and magnetization distributions from a wide variety of sources in both the physical and life sciences [21][22][23][24][25][26][27][28]. Complementary to scanning techniques for characterizing integrated-circuit magnetic field emanations, which include wire loops [29], probe antennas [30], magnetic force microscopy [11], superconducting quantum interference device magnetometers [7], and vapor cell magnetometers [31], the QDM employs a nonscanning imaging modality [15] that provides simultaneous highresolution (micron-scale) and wide-field (millimeter-scale) vector magnetic imaging, while operating under ambient conditions. This capability allows for monitoring of transient behavior over sequential measurements of a magnetic field, providing a means to study correlations in signal patterns that can evolve more quickly than a single-sensor scan time. ...
Article
Current density distributions in active integrated circuits result in patterns of magnetic fields that contain structural and functional information about the integrated circuit. Magnetic fields pass through standard materials used by the semiconductor industry and provide a powerful means to fingerprint integrated-circuit activity for security and failure analysis applications. Here, we demonstrate high spatial resolution, wide field-of-view, vector magnetic field imaging of static magnetic field emanations from an integrated circuit in different active states using a quantum diamond microscope (QDM). The QDM employs a dense layer of fluorescent nitrogen-vacancy (N-V) quantum defects near the surface of a transparent diamond substrate placed on the integrated circuit to image magnetic fields. We show that QDM imaging achieves a resolution of approximately 10μm simultaneously for all three vector magnetic field components over the 3.7×3.7mm2 field of view of the diamond. We study activity arising from spatially dependent current flow in both intact and decapsulated field-programmable gate arrays, and find that QDM images can determine preprogrammed integrated-circuit active states with high fidelity using machine learning classification methods.
... In general, the resulting IC magnetic fields pass through many standard IC materials, and will vary spatially and temporally in ways that correlate with both IC architecture and operational state. Thus, combined high-resolution and wide-field-of-view mapping of magnetic fields may yield simultaneous structural and functional information, and may be suitable for identification of malicious circuitry or Trojans [6,7], counterfeit detection [8], fault detection [9,10], and manufacturing flaws [11]. However, leveraging magnetic field emanations is challenging due to the tremendous complexity of circuits integrating billions of transistors of minimum feature sizes down to tens of nanometers, with interconnects distributed across multiple levels of metallization [12]. ...
... To date, QDM magnetic field imaging has been used to measure microscopic current and magnetization distributions from a wide variety of sources in both the physical and life sciences [17][18][19][20][21][22][23]. Complementary to existing scanning techniques for characterizing IC magnetic field emanations, which include wire loops [24], probe antennas [25], magnetic force microscopy [10], SQUID magnetometers [7], and vapor cell magnetometers [26], the QDM provides simultaneous high-resolution (micron-scale) and wide-field (millimeter-scale) vector magnetic imaging. This capability allows for monitoring of transient behavior over sequential measurements of a magnetic field, providing a means to study correlations in signal patterns that can evolve more quickly than a single-sensor scan time. ...
Preprint
Current density distributions in active integrated circuits (ICs) result in patterns of magnetic fields that contain structural and functional information about the IC. Magnetic fields pass through standard materials used by the semiconductor industry and provide a powerful means to fingerprint IC activity for security and failure analysis applications. Here, we demonstrate high spatial resolution, wide field-of-view, vector magnetic field imaging of static (DC) magnetic field emanations from an IC in different active states using a Quantum Diamond Microscope (QDM). The QDM employs a dense layer of fluorescent nitrogen-vacancy (NV) quantum defects near the surface of a transparent diamond substrate placed on the IC to image magnetic fields. We show that QDM imaging achieves simultaneous $\sim10$ $\mu$m resolution of all three vector magnetic field components over the 3.7 mm $\times$ 3.7 mm field-of-view of the diamond. We study activity arising from spatially-dependent current flow in both intact and decapsulated field-programmable gate arrays (FPGAs); and find that QDM images can determine pre-programmed IC active states with high fidelity using machine-learning classification methods.
... Many scholars have conducted research on the reliability of TSV. Related research includes TSV thermal stress distribution analysis [2][3][4][5][6][7], copper pumping [8][9][10][11], stress testing and failure analysis [12][13][14][15][16][17][18], fatigue and fracture [19][20][21][22][23][24][25][26][27][28][29][30], radiation [31], electromigration [32][33][34][35][36], dielectric failure(TDDB) [37], reliability test [38], and structural optimization design [22,39], etc. However, the research on the reliability of TSV is still in the preliminary stage, and there are still many issues that require in-depth systematic research. ...
Article
Three-dimensional (3D) integrated packaging technology is gradually moving from the laboratory to the market. Through silicon via (TSV) is the most critical structural unit in 3D integrated packaging. However, during the TSV manufacturing process flow and its service process, many micro cracks will be generated in the TSV microstructure. The multi-cracks seriously threaten the reliability of the TSV and affect the device performance and service life. The existing literature often focus on a single crack under thermal load alone, which obviously does not match the actual situation and leads to larger analysis errors. Based on the theory of elastoplastic fracture mechanics and multi-physics coupling analysis, this paper explored the effects of multi-cracks and thermal-mechanical coupled load on the reliability of TSVs using numerical analysis. Using the J integral value as the indicator, the effects of crack numbers, crack locations, crack lengths, crack propagation directions and thermal-mechanical coupled load on the crack propagation of TSV structures were studied. Based on the research results, suggestions were made for TSV structure design and manufacturing process optimization. The main goal of this paper is to explore the influence of cracks and thermal-mechanical coupled loads on TSV microstructure through numerical analysis. Due to the micro-scale of the TSV structure, the above targets are difficult to obtain through experimental tests. The research methods and results of this paper can provide important references for the reliability evaluation and optimization design of TSV microstructures.
Article
We report laser-based fault isolation methodologies for the localization of open and short failures in 1x5 μm via-last through-silicon via (TSV) structures for three-dimensional (3D) system-on-chip (SoC) integration. Thanks to the photosensitive TSV interconnect capacitance, observation of the photocapacitance response enables non-destructive localization of metallization ruptures. A light-induced capacitance alteration (LICA) measurement is demonstrated on an open failed 1×5 μm TSV chain structure with a manufacturing defect. We validate our measurements with active voltage contrast imaging in the scanning electron microscope (SEM) and focused-ion beam (FIB) cross-sectioning. Secondly, TSV dielectric defects generating leakage current between TSV and substrate (i.e. short defects) are detected and localized by sensing the laser induced TSV photocurrent. An optical beam induced current (OBIC) measurement is demonstrated on electrically overstressed TSV array structures whereby multiple TSVs are configured in a parallel arrangement. By applying a selective substrate removal process, we can expose the full TSV array and perform optical and tilted SEM inspection and reveal pinhole defects in the TSV liner. We further investigate the effect of breakdown energy on the pinhole formation, relate electrical measurements to SEM inspection, and confirm our results by FIB cross-sectioning.
Article
Full-text available
Magnetic current imaging (MCI) is found to image open defects in a fully assembled double-stacked dice inside a mold compound package with ball grid array (BGA) by increasing the bandwidth of the SQUID electronics up to 200 MHz. By imaging the magnetic field of a standing wave in the vicinity of the open, the RF MCI microscope Magma recovers the standing wave current profile and locates the open. In a continuity analysis, a BGA sample containing double-stacked dice revealed that High 1 (H1) was open to Ground 1 (G1) and Ground 2 (G2), showing infinite resistance when this connection pair should have shown 400 kω. Comparison of the physical failure analysis (FA) result confirms that space domain reflectometry (SDR) found the defect accurately. The crack are caused by the through-silicon vias (TSV) manufacturing process. This type of open failure has been a rather common failure in this specific TSV process.
Conference Paper
Full-text available
Magnetic field based techniques have shown great capabilities for investigation of current flows in ICs. After reviewing the performances of SQUID, GMR (hard disk head technologies) and MTJ existing sensors, we present results obtained on various case studies. This comparison shows the benefit of each approach according to each case study (packaged devices, flip-chip circuits,...). Finally we discuss the obtained results to classify current techniques, optimal domain of applications and advantages.
Conference Paper
With the arrival of flip-chip packaging, present tools and techniques are having increasing difficulty meeting failure-analysis needs. Recently a magneticfield imaging system has been used to localize shorts in buried layers of both packages and dies. Until now, these shorts have been powered directly through simple connections at the package. Power shorts are examples of direct shorts that can be powered through connections to Vdd and Vss at the package level. While power shorts are common types of failure, equally important are defects such as logic shorts, which cannot be powered through simple package connections. These defects must be indirectly activated by driving the part through a set of vectors. This makes the magnetic-field imaging process more complicated due to the large background currents present along with the defect current. Magnetic-field imaging is made possible through the use of a SQUID (Superconducting Quantum Interference Device), which is a very sensitive magnetic sensor that can image magnetic fields generated by magnetic materials or currents (such as those in an integrated circuit). The current-density distribution in the sample can then be calculated from the magnetic-field image revealing the locations of shorts and other current anomalies. Presented here is the application of a SQUID-based magnetic-field imaging system for isolation of indirect shorts. This system has been used to investigate shorts in two flip-chip-packaged SRAMs. Defect currents as small as 38 ìA were imaged in a background of 1 A. The measurements were made using a lock-in thechnique and image subtraction. The magnetic-field image from one sample is compared with the results from a corresponding infrared-microscope image.
Article
The need to miniaturize in the electronics industry is driving smaller form factors, and resulting in complex packaging innovations such as structures with multiple devices stacked inside a three dimensional package. These structures present a challenge for non-destructive fault isolation. Two such modules recently exhibited failures on the NASA Goddard Space Flight Center Solar Dynamic Observatory (SDO) during board-level testing. Each module consisted of eight vertically-stacked mini-boards, each mini-board with a single EEPROM microcircuit and capacitor, and connected by external gold metallization to module pins. Both failed modules exhibited low-resistance shorts between multiple pins. The orthogonal structure of the module prompted the use of magnetic current imaging (MCI) in three planes in order to construct an internal three-dimensional current path for each of the failed modules. Magnetic current imaging is able to "look through" non-magnetic, or de-gaussed packaging materials, allowing global imaging without physical deprocessing of the stacked EEPROM modules, in order to construct the internal current path and localize defects. To our knowledge, this is the first time that this has been done. Following global isolation of the defects, two types of magnetic sensors were used in parallel with limited deprocessing in order to more precisely characterize suspect failure locations before actually physically exposing the defects. This paper will show the process for using magnetic current imaging with both SQUID and magnetoresistive (GMR) sensors to isolate defects in two stacked EEPROM packages along with the final physical analysis of the defects. The failure analysis found that these devices were damaged by external heat, possibly during oven pre-conditioning or hot air soldering onto the board. The manufacturer, 3-D Plus, was not implicated in the failure.
Article
Superconducting quantum interference device (SQUID) is a device developed in 1964 to convert minute changes in current or magnetic field into a measurable room-temperature voltage. Over the past decades, the SQUID technology has undergone several major innovations. At present, commercial companies are extending the application of these devices to a variety of emerging markets such as magnetocardiology, nondestructive evaluation, explosives detection, and geophysics.
Conference Paper
Lock-in thermography and magnetic current imaging are emerging as the two image-based fault isolation methods most capable of meeting the challenges of short and open defect localization in thick, opaque assemblies. Such devices are rapidly becoming prevalent as 3D integration begins to ramp up production. This paper expands on previously published work with a qualitative comparison of the techniques on single chip and stacked die packages with known designed-in or FIB-created defects.
Conference Paper
The relative effectiveness of lock-in thermography and magnetic current imaging for identifying defects in packaged ICs was studied by directly comparing results on the same three devices. One known (in-lab fabricated) and two unknown (field return) defects were studied in organic flip-chip and wirebond configurations. Both methods succeeded in identifying the defective area but significant differences were observed in the qualitative nature of the signals, XY localization resolution, and sensitivity. Depth estimates were obtained where possible which aided in localization.
Conference Paper
Space Domain Reflectometry (SDR) is a new technique that has already shown to be a reliable non-destructive method to image open failures in semiconductor chips by pumping a high frequency signal into the open trace. We show in this paper that SDR can be used to accurately find a breakage location in copper wire bond that failed during stress test.
Conference Paper
Space Domain Reflectometry (SDR) is a newly developed non-destructive failure analysis (FA) technique for localizing open defects through the imaging of magnetic field produced by a radio frequency (RF) current induced in the sample. The technique employs a Scanning Superconducting Quantum Interference Device (SQUID) RF Microscope and is capable of locating open failures with 30μm accuracy. Here we present a theory of SDR and show examples of locating opens in various integrated circuit (IC) package samples.
Conference Paper
Magnetic Field Imaging (MFI) technology is capable of localize shorts using Magnetic Current Imaging (MCI) technique with a very high spatial resolution [1]. In this paper we demonstrate that a Giant Magneto Resistance (GMR) sensor positioned in close proximity to the front side of a die sample enables MFI to achieve sub micron resolution.
Article
Space Domain Reflectometry is a newly developed non-destructive failure analysis technique for localizing open defects by imaging the magnetic field generated by a radio frequency (RF) current induced in the sample. The technique was used to locate a cracked microbump in a daisy chain between two full 725-μm-thick dies.
Article
DOI:https://doi.org/10.1103/PhysRevLett.12.159
Article
I have designed, built and tested a cryo-cooled scanning SQUID microscope for imaging room-temperature samples, which uses a commercially available closed-cycle refrigerator to cool a high-Tc YBa2Cu 3O7-delta dc SQUID to 76 K. The system uses a custom dewar design for a minimum SQUID-sample separation of 50 mum. The flux white noise is 10.5 muphi0/Hz1/2 above 1 kHz. Below 1 kHz, 1/f noise is dominant, reaching 160 muphi0/HZ 1/2 at 10 Hz. I used the microscope to perform non-destructive fault isolation on short circuits in modern microelectronic chips. Through a 120 mum thick silicon die, I isolated a power to ground plane short to within +/-100 mum at a SQUID-sample separation of 200 mum. In a multi-chip module package, I isolated a trace-to-trace short to within +/-18.5 mum at a SQUID-sample separation of 340 mum. These results helped lead to the successful commercialization of a SQUID microscope based upon my system. Using one of these commercial systems, I trained technical personnel and performed short-circuit fault isolation research at a major microelectronic manufacturer. I also used the microscope for non-destructive evaluation of defects in low-Tc NbTi wires, comparing injected current vs. eddy current techniques. I found that the phase of the eddy currents was much less sensitive to geometry effects of both the sample and the defect when imaging fabricated test samples. I discovered that imaging injected currents with a SQUID oriented to detect the x-component of magnetic field produced a strong response to a defect in a NbTi wire, while the z-oriented SQUID produced no observable response to this defect. I developed analysis techniques for calculating the magnetic pole density rho M, magnetic field H⃗ and magnetization M⃗ from images of Bz from in-plane magnetized samples. I used these techniques to screen sputtered magnetic combinatorial libraries of rare earth compounds. I found at least one interesting new compound, Fe11 Nd10Bx, which exhibited anisotropic characteristics and a remanent magnetization of at least 416 emu/cc. Finally, I developed a technique for making zero-applied-field non-remanent magnetization measurements, which would be useful to screen for the highest energy product (B*H) max of samples in magnetic combinatorial libraries.
Article
A point‐contact (SQUID) magnetometer was used inside a shielded room to record the magnetic field of the human heart, without noise‐averaging. The resulting magnetocardiograms, with the peak signal at about 3 × 10<sup>-7</sup> G had a noise level of about 1 × 10<sup>-9</sup> G (rms, per root cycle). They approach good medical electrocardiograms in clarity, and are an order‐of‐magnitude improvement in sensitivity over previous magnetic detectors of the heart. These results suggest new medical uses for this magnetometer.
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As microelectronic technologies continue to develop according to the More than Moore’s law, so that full systems can be confined inside one assembly, failure analysis must take this into account. Magnetic microscopy has achieved successful failure analysis of standard ICs but now it faces new challenges related to the lack of resolution triggered by the long working distances necessary when working on complex 3D architectures. Our new approach can push the present scope of the technique further by using a simulation approach, and by measuring not only the z component of the magnetic field but also the x and the y by tilting the sample. We will show how we can map and localize defects with an increased resolution taking into account three-dimensional geometries.
Article
The future of integrated electronics is the future of electronics itself. Integrated circuits will lead to such wonders as home computers, automatic controls for automobiles, and personal portable communications equipment. But the biggest potential lies in the production of large systems. In telephone communications, integrated circuits in digital filters will separate channels on multiplex equipment. Integrated circuits will also switch telephone circuits and perform data processing. In addition, the improved reliability made possible by integrated circuits will allow the construction of larger processing units. Machines similar to those in existence today will be built at lower costs and with faster turnaround.
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