Experimental verification of super-resolution optical inspection for semiconductor defect by using standing wave illumination shift

Semiconductor design rules and process windows continue to shrink, so we face many challenges in developing new processes such as the less 100-nm design rule and the 300-mm wafer. The challenges have become more difficult, and the next generation of defect inspections is urgently needed. Optics and electron beams have been primarily used for the detection of critical defects, but both technologies have disadvantages. The optical inspection is generally not sensitive enough for defects at 100 nm or less, while the scanning electron microscopy inspection has low throughput because it takes a long time to scan 300 mm. To find a solution to these problems, we have proposed a novel optical inspection method for the critical defects on the semiconductor wafer. First, we carried out theoretical examinations and computer simulations. As a result, the proposed method makes it possible to observe a structure with robustness and higher resolution beyond the Rayleigh limit. Second, we developed an apparatus for the basic experiment and carried out the super-resolution experiment using a line and space sample. As a result, the sample structures were clearly resolved beyond the Rayleigh limit and defects on the sample surface were detected with super-resolution.     

Low cost digital radiography system for weld joints and castings testing

A low cost digital radiography system (DRS) for testing weld joints and castings in laboratory was assembled. The DRS is composed from X-ray source, scintillator, first surface mirror with Aluminum coating, charged coupled device (CCD) camera and lens. The DRS was used to test flawed carbon steel welded plates with thicknesses up to 12 mm. The comparison between the digital radio-graphs of the plates weldments and the radiographs of the same plates weldments using medium speed film type had shown that, the detection capability of the weld flaws are nearly identical for the two radiography techniques, while the sensitivity achieved in digital radiography of the plates weldments was one Image Qualits Indicator (IQI) wire less than the sensitivity achieved by conventional radiography of the same plates weldments according to EN 462-1. Further, the DRS was also successfully used to test (100 × 100 × 100) mm³ Aluminum casting with artificial flaws of varied dimensions and orientations. The resulted digital radiographs of the casting show that, all the flaws had been detected and their dimensions can be measured accurately, this confirm that. The proposed DRS can be used to detect and measure the flaws in the Aluminum and others light metals castings accurately.     

有序金纳米棒阵列的超分辨成像

显微成像技术受限于光学成像系统的衍射极限，无法分辨亚波长尺度的结构。通过饱和散射抑制成像技术已经实现了单个纳米颗粒的超分辨成像，但是涉及到纳米颗粒集合，需要考虑纳米颗粒间的耦合作用。利用超越衍射极限的双光束方法，可以在有序金纳米棒阵列上实现远场超分辨光学成像。本文设计了纳米棒长径比为2的5×5金纳米棒阵列，通过矢量光场理论和热扩散理论计算了金纳米棒阵列在连续波激光下的热分布，并模拟了双光束激光即脉冲激发光和连续波抑制光下的散射成像。仿真结果显示，连续波激光能够有效抑制金纳米棒阵列对脉冲激光的散射，双光束方法实现了80 nm横向特征尺寸的超分辨成像。     

Digital radiography of aluminum castings by fluoroscopy

Digital fluoroscope was used as digital industrial radiography system to test three flawed Aluminum castings with dimension of (100 × 100 × 100) mm³. The digital radiographs show that, all the flaws in the three aluminum castings had been detected and their dimensions can be measured accurately. The comparison between the digital radiographs of the three aluminum castings and the digitized medium speed films radiographs of the same castings had shown that; the detection capability of flaws in the castings for the two radiography techniques were nearly identical. The sensitivity achieved by digital radiographs and by digitized films radiographs, using wire (IQI) according to EN 462-1, were W5 and W6 respectively, while the image definition achieved by digital radiographs and by digitized films, using duplex wire IQI according to EN 462-5, were 5D and 7D respectively. The results confirm that digital fluoroscopy can be applied to detect and measure flaws in relatively thick Aluminum and others light metal castings according to the requirements of the EN 444, EN 13068 and ISO 17636 class A testing.     

Computer analysis of the configurations of magnetic fields of subsurface discontinuities of finite dimensions and arbitrary shapes in tested objects of finite length by the method of spatial integral equations

Using software developed by the authors and based on the method of spatial integral equations, the spatial configurations of the magnetic fields of tested objects of finite length that contain subsurface discontinuity flaws of finite dimensions and arbitrary shapes are studied. It is possible to take into account the influence of both uniform and nonuniform magnetizing fields, including real sources; an arbitrary geometry of tested objects; and a nonlinear character of the magnetic properties of materials. It is shown that software can be used in studies of the influence of the geometrical parameters of a defect on the topography of the informative magnetic field in the testing zone.     

Obtaining flaw images by the SAFT method taking the variable velocity of sound in a test object into account

A modification of the SAFT method for obtaining flaw images in test objects containing three regions with different velocities of sound (SV) is proposed. Complex composite welded joints and repair welds are classified as objects in which the SV in a welded joint may differ from the velocity in a parent metal by >5%; therefore, a high-quality image of flaws can be obtained by taking different SVs into account. To solve this problem, a method for obtaining a test object with three regions with different SVs is proposed. The delays of propagating ultrasonic pulses were calculated using the Fermat principle. The results of reconstructing flaw images in a 300 welded joint from echo signals obtained as a result of numerical simulation by the finite-element method are presented. The images obtained by the SAFT method without taking different SVs into account are displaced from their true position, thus they do not allow determination of their coordinates and location. Consideration of different SVs allows one to obtain unshifted reflections of flaw images and, hence, evaluate the types and dimensions of flaws more accurately.     

Single image super-resolution using self-optimizing mask via fractional-order gradient interpolation and reconstruction

Image super-resolution using self-optimizing mask via fractional-order gradient interpolation and reconstruction aims to recover detailed information from low-resolution images and reconstruct them into high-resolution images. Due to the limited amount of data and information retrieved from low-resolution images, it is difficult to restore clear, artifact-free images, while still preserving enough structure of the image such as the texture. This paper presents a new single image super-resolution method which is based on adaptive fractional-order gradient interpolation and reconstruction. The interpolated image gradient via optimal fractional-order gradient is first constructed according to the image similarity and afterwards the minimum energy function is employed to reconstruct the final high-resolution image. Fractional-order gradient based interpolation methods provide an additional degree of freedom which helps optimize the implementation quality due to the fact that an extra free parameter α-order is being used. The proposed method is able to produce a rich texture detail while still being able to maintain structural similarity even under large zoom conditions. Experimental results show that the proposed method performs better than current single image super-resolution techniques.     

航空发动机叶片X射线数字图像分析的一种新方法

以某型号航空发动机叶片为研究对象，介绍并分析了基于分区域自适应中值滤波的X射线数字图像特征提取和基于曲面函数和阈值分割的X射线数字图像特征提取两种方法，提出了一种新型的数学形态学滤波与计算机视觉算法相结合的缺陷自动提取方法。试验结果表明，提出的方法可行，能有效减小缺陷的误判率。     

A method for improving the accuracy of evaluating the dimensions of flaws in walls of tubular elements of structures

An algorithm for evaluating the real accuracy of the basic measuring instrument (exterior or in-tube flaw detector) in measuring parameters of flaws of a particular inspected tube was proposed on condition that the basic measuring equipment has no systematic error, while a verification instrument is considered as “absolutely” precise or “reference.” A statistical method of increasing the accuracy of evaluating the dimensions of flaws in thin-walled tube elements was developed on the basis of a correlation between the dimensions of flaw parameters. It can be taken as a basis for finding real values of parameters of flaws and for performing reliable calculations of the residual strength and residual life, for scheduling optimal periods for the next inspection of pipelines, and for ranging segments of a pipeline by a risk criterion, thus providing optimal scheduling of repairs.     

飞机多层结构中裂纹的定量检测及分类识别

对飞机机身多层结构中的缺陷进行定量检测是无损检测领域的一个难点,脉冲涡流是目前有效的能对这种类型缺陷进行定量检测的技术。采用时频分析的方法实现了对飞机结构中出现的裂纹的定量检测。针对脉冲涡流在裂纹分类中存在的识别正确率较低的问题,提出一种新的称为频谱分离点的缺陷识别方法,提高了缺陷分类识别的正确率,理论分析与试验结果相一致,验证了所采用方法的正确性。     

A decrease in the error of the statistical method for estimating the parameters of flaws in magnetic flaw detection

A method for increasing the accuracy of evaluating the dimensions of flaws during magnetic flaw detection in steel sheets and pipes, which is based on the division of a set of flaws into subclasses using a certain generalized parameter in accordance with the criterion of minimization of an appropriate estimate, is described. The results of applicability of this method to the evaluation of the depths of flaws of the metal loss type are presented.     

Use of the Harmonic Analysis of an Induction Probe's Signal for Increasing the Information Content of Test Results

The harmonic content of a probe's electromotive force when magnetic testing is conducted with the use of alternating fields is significantly affected by the possible presence of a flaw in the specimen. Magnetic biasing of the specimen with a static field enables identification of internal flaws in addition to surface flaws. The electromotive force's harmonic content depends on the flaw's dimensions and depth. This circumstance can be used to determine these parameters in a separate way. The effect of a gap between the surface of a tested specimen and the probe is significantly weaker on the topography and amplitude of higher harmonics than on the corresponding parameters of the first harmonic. This observation, which holds for both internal and surface flaws, enables testing of larger gaps.     

Effect of fuzzy C means technique in failure mode discrimination of glass/epoxy laminates using acoustic emission monitoring

Acoustic emission is one of the powerful techniques that can be used for in situ structural health monitoring of composite laminates. One of the main issues of AE is to characterize the different damage mechanisms from the detected AE signals. Unsupervised Pattern recognition has been one of the techniques used for the identification of a specific failure mode in composites from Acoustic emission data. Cross ply composite laminate of size 300 × 300 mm is fabricated using Vacuum bag molding. ASTM D3039 Standard tensile specimens are cut from the laminate and these specimens are subjected to uni axial tensile test under Acoustic Emission monitoring. Fast Fourier transform analysis (FFT) and Short Time Fast Fourier Transform (STFFT) analysis are performed on the Wave forms of the AE hit data obtained during the conduct of tensile test to characterize the failure modes in crossply specimens. Fast Fourier Transform enabled calculating the frequency content of each damage mechanism. In this paper Fuzzy C Mean clustering is performed for the AE parameters obtained from the test and the efficiency of this technique is being investigated using FFT AND STFFT analysis.     

A polyaniline based intrinsically conducting coating for corrosion protection of structural steels

Among the various corrosion protection strategies for structural steels, coating techniques provide the most cost‐effective protection and have been used as the primary mode of corrosion protection. Existing coating techniques however have been used mainly for their barrier capability and therefore all have a limited service life due to oxidation aging, electrolytic degradation, or various inadvertent defects and flaws occurred in and after coating applications. This work investigated the anti‐corrosion potential of a π‐conjugated polymer—polyaniline (PANi), which was doped into an intrinsically conducting polymer and then included in a two‐layer coating system as a primer layer. To achieve a long service life, the primer layer was made by mixing the conductive PANi in a waterborne poly‐vinyl butyral solution to provide strong adhesion to steel surface, and then topcoated with a layer of elastomer‐modified polyethylene to obtain extra mechanical and barrier protections. Two ASTM standard tests were conducted to evaluate the corrosion durability and tensile adhesion of the two‐layer system, in which the system demonstrated superior performance. The Scanning Kelvin Probe Force Microscopy (SKPFM) was used to provide the microscopic evidences for the outstanding performance. Microsc. Res. Tech. 76:1186–1195, 2013. © 2013 Wiley Periodicals, Inc.     

Direct versus iterative structure retrieval for a Cu/Ti misfit dislocation: a comparison of various 1Å HREM technologies

Using an interface between Cu/Ti as an example, two HREM-based image analysis techniques, strain mapping and iterative digital image matching, are compared. The validity limit of these techniques is discussed as a function of specimen thickness and microscope technology. Two criteria are used to assess the limits: (i) the difference between two geometric phase maps, one calculated in image plane and one in object plane, and (ii) a difference image from two HREM simulations of two structure models differing in one atomic column. The latter displays the overall delocalisation of information by the microscope due to diffraction and imaging. It is outlined how far images and strain maps, obtained for high-voltage microscopy at 1250 kV and C _S correction at 200 kV, are identical. Both techniques exhibit a significantly increased regime of applicability of strain mapping near defect cores. Simulations for a 400 kV HREM and a 300 kV FEGTEM with and without focal series reconstruction complement the study.     

Features of ultrasonic shadow testing of foam plastics based on time-amplitude parameters. Part II

Features of ultrasonic shadow testing of hard foam plastics are discussed. Foam plastics are very difficult objects of testing because of their highly inhomogeneous structure depending on the processes of foaming and solidification of polymers. The main conclusion of the reported study is that shadow techniques based on the amplitude and temporal characteristics present a particular case of the more complex time-amplitude ultrasonic shadow testing technique. At low frequencies, flaws can be treated as entities transparent to acoustic waves. With due account of this fact, both the flaw extension and its thickness can be estimated. In addition, variations in the ultrasound velocity due to anisotropy and dominant orientations of cells in foam plastics should be taken into consideration.     

Dependence of the magnetic field of a flaw on the distance to the surface of a tested article

The dependence of the magnetic field of a flaw on the distance to the surface of a tested article has been studied for rectangular slot-type flaws. For flaws with a small opening width, it can be considered that their magnetic field decreases in inverse proportion to this distance, but with an increase in the flaw width, the field decreases more slowly.     

Time reversal method for guided wave inspection in pipes

The application of the time reversal method in pipe-like structures based on finite element method (FEM) is investigated. A steel pipe model measuring 70 mm x 3.5 mm is used to analyze the reflection coefficient of the L(0,2) mode with the time reversal process. Simulation results show that the time reversal array method is beneficial to the improvement of the signalto-noise ratio of a guided wave inspection system. As the intercepting window is widened, more energy is included in re-emitted signals, which leads to a large reflection coefficient of the L(0,2) mode. In parallel, a circumferential locating method based on the time reversal method is described. The time reversal process used for guided wave inspection leads to the temporal and spatial focusing. When the time reversal signals are re-emitted, the angular profile obtained at the axial location of the defect can be used to determine the circumferential location of the defect. Except for a pipe with one defect, the circumferential locating method has been verified on another pipe model with two defects. Meanwhile, the elements number of the time reversal array has been discussed for enhancing the discrimination of the defect circumferential location.     

Comparison of single‐particle analysis and electron tomography approaches: an overview

Three‐dimensional structure of a wide range of biological specimens can be computed from images collected by transmission electron microscopy. This information integrated with structural data obtained with other techniques (e.g., X‐ray crystallography) helps structural biologists to understand the function of macromolecular complexes and organelles within cells. In this paper, we compare two three‐dimensional transmission electron microscopy techniques that are becoming more and more related (at the image acquisition level as well as the image processing one): electron tomography and single‐particle analysis. The first one is currently used to elucidate the three‐dimensional structure of cellular components or smaller entire cells, whereas the second one has been traditionally applied to structural studies of macromolecules and macromolecular complexes. Also, we discuss possibilities for their integration with other structural biology techniques for an integrative study of living matter from proteins to whole cells.     

Non-Contact Subsurface Defects Characterization by Microwave and Millimeter Wave Techniques

In this paper, a characterization technique for Non-Destructive Evaluation of dielectric materials by microwave and millimeter wave techniques is presented. The proposed method is based on the use of systems that allow the determination of the reflection coefficient S ₁₁ of the material under test and an artificial neural network (ANN) treatment. The systems that are considered in this study are on one hand a commercial vector network analyzer that operates in that frequency band [0.05–18 GHz] and on the other hand two systems, named S-Parameter Measurement Systems, that have been developed in our laboratory. The first one permits measurements between 1 and 4 GHz whereas the second operates at the frequency of 35 GHz. The investigation concerns dielectric materials that contain a defect of different nature. The defect width and burial depth vary from a few centimeters to a few microns so that a width ratio of more than one thousand is obtained between the biggest and the smallest defects considered. Characterization techniques and results are discussed through measurements and simulations, main benefits and drawbacks of each method are also analyzed in this paper.