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Gigahertz (GHz) scanning acoustic microscopy (SAM) employed for high-resolution acoustical imaging at 1 GHz for inspecting microbumps and through silicon vias (TSVs). (a) photograph of the scanner unit including a 1-GHz acoustical lens. (b) schematics of the GHz-SAM for generation, transmission, and reception of 1-GHz acoustic signals, including analog signal preprocessing for noise reduction and signal acquisition.
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Current trends in microelectronics focus on three-dimensionally integrating different components to
allow for increasing density and functionality of integrated systems. Concepts pursued involve vertical stacking
and interconnecting technologies that employ micro bumping, wafer bonding, and through silicon vias (TSVs).
Both the increasing complexit...
Context in source publication
Context 1
... microscope was equipped with a 1-GHz acous- tical lens (opening angle: 100 deg; focal length 80 μm in water). Figure 1 contains a photograph and a schematic of the working principle of the GHz SAM. The scan range of this microscope can be defined freely between 50 μm and 2 mm, while the line repetition frequency can be adjusted between 10 and 50 Hz, allowing fast acquisition of the GHz micrographs. ...
Citations
... Scanning acoustic microscopy (SAM) is of increasing interest because it can non-destructively derive depth-specific information of specimens combined with a lateral resolution in the micron range [71]. It has been effectively applied to the detection of flip-chip solder joints [72,73], voids [74], delamination defects [75,76] and micro-bubbles [77,78]. SAM has been used over the past decade as a successful nondestructive technique to detect discontinuities within materials and interconnects [73]. ...
... It has been effectively applied to the detection of flip-chip solder joints [72,73], voids [74], delamination defects [75,76] and micro-bubbles [77,78]. SAM has been used over the past decade as a successful nondestructive technique to detect discontinuities within materials and interconnects [73]. SAM uses a piezoelectric transducer to produce an ultrasonic pulse, which is incident into the specimen through the acoustic lens and coupling medium (usually deionized water). ...
Flip chip technology has been widely used in integrated circuit packages due to its superiority of performance in various aspects. The solder joints sandwiched between chips and organic substrates, act as the mechanical and electrical connections in flip chips. However, with the trend of flip chips towards ultra-fine pitch and high density, and the new requirements of encapsulation materials, the solder joints are more likely to suffer from the defects of cracks, voids, balls missing. These defects affect the performance and service life of flip chips and result in false alarms. Solder joint defects can be detected using both contact and non-contact ways, and non-contact testing methods have proven to be more successful than contact methods for detecting the solder joint defects. This review emphasizes the main results of research in the field of solder joints defect inspection approaches and clarifies the principle of the methods as well as the corresponding advantages and disadvantages.
... although they may not cause great damage to the performance of these devices in the initial phase, and some also sweep through electrical or logic performance test, in the use, subject to ambient temperature and humidity, these defects keep evolving and expanding under thermal and electromagnetic effects formed by thermal cycle, electromagnetic and stress fields. In this case, the thermal diffusion that further gets weak in the micro devices makes the internal structure fracture in different degrees, ultimately leading the micro devices to failure [1][2][3][4][5][6]. In order to improve the reliability of micro devices, we should identify and eliminate various defects that possibly appear on these devices in a timely manner, if necessary, they should be replaced. ...
... The high surface quality and the monocrystalline material structure result in the reduction of artefacts enabling a comparatively high imaging resolution. Combined with the near absolute reflectance of delamination and voids such defects can still be detected even if their lateral dimension is below the resolution limit of the acoustic imaging system (Briggs 1992;Brand et al. 2014aBrand et al. , 2015, however, such features will appear larger than their actual size. This should not be accounted for as a disadvantage, since it enables imaging of features with dimensions below the resolution limit. ...
... This technique provides lateral resolution in the 1 lm regime and allows for the application of wave modes that propagate in the surface and in interfaces providing an additional contrast mechanism. GHz-SAM also offers an extended surface and sub-surface sensitivity valuable for the non-destructive inspection of thin layers (Briggs 1992;Brand et al. 2014a). Even though acoustic imaging in the GHz-band may require destructive or semidestructive preparation, the method itself still operates nondestructively giving access to the analysis of metal interfaces in mono-metallic single interconnects like Cu to Cu wire-or Cu-pillar bonding (Vogg et al. 2015). ...
... The bonded wafer pair consisted of a Si and a sapphire wafer acoustic data to also enable parametric and spectral imaging to further increase the lateral resolution and detectability of structures with further reduced spatial dimensions. Another highly pursued topic is the inspection of through silicon vias by acoustic GHz-microscopy for detecting rim-delaminations and voids in the conductive fillings (Brand et al. 2014aDe Wolf et al. 2015;Phommahaxay et al. 2013Phommahaxay et al. , 2014. Springer Nature journal content, brought to you courtesy of Springer Nature Customer Service Center GmbH ("Springer Nature"). ...
Link to pdf: http://rdcu.be/voAK
Ongoing trends in microelectronics aim at continuously increasing the integration rate and complexity of microelectronic systems and devices. Novel integration technologies that arise from these demands need to be addressed from a reliability and quality assurance perspective. As a consequence, novel and adapted inspection techniques are strongly required, including non- or semi-destructive testing during development and manufacturing. Within this context non-destructively operating scanning acoustic microscopy is an already widely used and established inspection method that provides even more potential if the corresponding performance parameters can be further improved. Currently, conventional scanning acoustic imaging is performed based on pure amplitude imaging thereby neglecting most of the information contained in the acoustic signals. The current paper exemplarily presents novel and extended approaches for addressing current limitations in conventional acoustic microscopy, including the detection and evaluation of void defects in small electrical interconnects, increasing detectability of delaminations in bonded wafers, but also the use of acoustic GHz-microscopy for increasing the spatial resolution and sub-surface sensitivity. An improved detectability and sensitivity for crack assessment using shear and mixed acoustic mode inspection is presented.
... The most commonly used methods in nondestructive evaluation for micro defect detection are acoustic micro imaging (AMI), X-ray [1,2], and infrared thermography [3]. AMI, also known as scanning acoustic microscopy, has been proven to be sufficiently sensitive for detecting micro defects and features, such as delamination [4,5], voids in the interfaces [6], microbubbles [7,8], stress distributions [9], solder bumps in flip chip [10,11], etc. The general working modes of AMI include A-scan, B-scan, and C-scan, obtaining time-domain signal, time-spatial image, and spatial image, respectively. ...
... Till now, little work has been involved in research on sparse reconstruction for C-scan images of AMI. Actually, C-scan can provide more effective results than A/B-scan for detecting micro defects, and the transducer is a focusing transducer whose central frequency can be as high as 230 MHz [10,11] or even GHz [6]. The acoustic field distribution of the focusing transducer is completely different from the planar transducer, and the formation of the C-scan image is also different from that of the B-scan image. ...
Acoustic micro imaging has been proven to be sufficiently sensitive for micro defect detection. In this study, we propose a sparse reconstruction method for acoustic micro imaging. A finite element model with a micro defect is developed to emulate the physical scanning. Then we obtain the point spread function, a blur kernel for sparse reconstruction. We reconstruct deblurred images from the oversampled C-scan images based on l1-norm regularization, which can enhance the signal-to-noise ratio and improve the accuracy of micro defect detection. The method is further verified by experimental data. The results demonstrate that the sparse reconstruction is effective for micro defect detection in acoustic micro imaging.
... GHz-SAM [2,3] inspection applied in the current study was performed at 1 GHz acoustic frequency employing a highly focused acoustic lens with 80 μm focal length (in water) and a semi-aperture angle of 50°. For coupling the acoustic waves into the sample, deionized and degassed water was used and experiments were performed at 21°C. ...
... In contrast to conventional SAM excitation of the acoustic lens is performed in burst-mode to provide sufficient energy in the acoustic pulse to overcome the increased acoustic attenuation. Also the GHz-SAM contains an analogue pre-processor unit which allows for a high degree of lateral oversampling in order to increase the signal-to-noise ratio of the received data without the need of sequential averaging [8]. ...
... However, as sample structures decrease in size inspection becomes challenging with tradeoffs made in lateral resolution and depth resolution of defects. With advances in GHz range SAM, studies have shown an improved capability for void detection in TSVs, but these techniques still require the presence of a coupling medium and the ability to detect voids at the bottom 10- 20µm of a 10:1 aspect ratio via is yet to be demonstrated [4,5]. ...
Advanced interconnect technologies such as Through Silicon Vias (TSV) have become an integral part of 3-D integration. International Technology Roadmap for Semiconductors (ITRS) has identified a need for an in-line metrology for characterizing voids in TSV structures. In this paper, we describe a laser-based acoustic technique in which a short laser pulse generates broadband acoustic waves that propagate in the TSV structure. An optical interferometer detects the surface displacement caused by the acoustic waves reflecting within the structure as well as other acoustic waves traveling near the surface that has information about the structure dimensions and irregularities. Sensitivity of the technique to detect various types of voids has been confirmed by performing cross-section microscopy. Measurements typically take few seconds per site and can be easily adopted for in-line process monitoring. The technique has also demonstrated capability for measuring copper pillar stacks, characterizing bonding voids and delamination. INTRODUCTION Microelectronics industry trends have continued to move rapidly towards 3-D integration of semiconductor devices and the driving force remains the need for smaller, faster devices with optimized performance, enhanced data transfer speeds, minimum transmission loss, while maintaining reliability and meeting cost targets. TSV technology has entered the mainstream for 3D ICs as they support heterogeneous integration of logic and memory devices resulting in significant improvements in performance. Depending on the application, a " Via-first " or " Via-last " approach may be used in manufacturing. Nevertheless, the process is complex and filling the high aspect ratio vias with copper is one of the most challenging and expensive steps of the fabrication process. Achieving void-free copper fill is critical to avoiding reliability problems and improving yield. Void formation may occur at the bottom of the vias, along the seamline and at the top of the vias and are dependent on the plating chemistry and approach used [1].
More than Moore technology is driving semiconductor devices towards higher complexity and further miniaturization. Device miniaturization strongly impacts failure analysis (FA), since it triggers the need for non-destructive approaches with high resolution in combination with cost and time efficient execution. Conventional scanning acoustic microscopy (SAM) is an indispensable tool for failure analysis in the semiconductor industry, however resolution and penetration capabilities are strongly limited by the transducer frequency. In this work, we conduct an acoustic interferometry approach, based on a SAM-setup utilizing 100 MHz lenses and enabling not only sufficient penetration depth but also high resolution for efficient in-line FA of Through Silicon Vias (TSVs). Accompanied elastodynamic finite integration technique-based simulations, provide an in-depth understanding concerning the acoustic wave excitation and propagation. We show that the controlled excitation of surface acoustic waves extends the contingency towards the detection of nm-sized cracks, an essential accomplishment for modern FA of 3D-integration technologies.
Failure analysis (FA) could provide timely feedback to process optimization and solution paths for system failures; thus, it is critical for the development of advanced driver assistance systems (ADAS). In this chapter, failure analysis flows starting from systems or boards until components or packages and dice are introduced. Electrical fault isolation (FI) techniques designed to locate subtle defects inside complicated semiconductor devices are reviewed. Physical failure analysis approaches adopted to provide artifact free nanometer scale analysis are discussed. Material analysis methods assisting in thorough root cause investigation are presented. Non-destructive and high-resolution imaging tools with the potential of significantly shortening failure analysis through put time are demonstrated. Case studies are used to illustrate strategies and methodologies in ADAS failure analysis.
