The development of an inspection system for defects in silicon crystal growth

This study presents an inspection system to detect the growth defects of silicon crystals that comprise a CCD camera, an LED light source, and power modulation. The defects on multicrystalline silicon can be observed clearly while the silicon wafer were irradiated by the red LED light at a small lighting angle (i.e., 20–30°). However, the growth defects on monocrystalline silicon wafer were difficult to observe because of it low image intensity. And then, the growth defects image was significantly enhanced when the wafer was illuminated by a white LED (WLED) and rotated at a specific angle (i.e., 23°). The experimental results showed that the WLED illumination system made the growth defects more easily observable than did other LED sources (i.e., red, blue, and green LEDs). In addition, the proposed inspection system can be used for on-line fast detection for quality control of monocrystalline silicon wafer.     

Measuring principle of vertical target density based on single linear array CCD camera

In consideration of the complexity and the high cost of the dual CCD intersection vertical target when it is used indoor. A novel measuring principle of one linear array CCD camera vertical target is presented. One low-power semiconductor sector-like laser with projection board is used to be the lamp-house of the CCD camera. The detection light screen of the CCD camera and the laser lamp-house are adjusted to same plane. When the projectile through the detection light screen, it blocks the part light of the laser and leaves a shadow of projectile on the board. The shadow and its coordinate are acquired and calculated by the CCD camera and computer, and the projectile coordinate of X and Y can be gotten through image processing and further calculation. The measuring principle and the formulas are given, and the measuring error is analyzed. The result indicates that the coordinate error of X and Y less than 1.5 and 2.2 mm, respectively, when the detection light screens is 1 m × 1 m, The principle presented has the advantages that measurement principle is simple, low cost and easy engineering.     

On-line conveyor belts inspection based on machine vision

Under the background that mining conveyor belts are prone to failure in operation, the on-line fault detection technique based on machine vision for conveyor belts is investigated. High-brightness linear light sources arranged to a vaulted shape provide light for a line-array CCD camera to capture high-quality belt images. A fast image segmentation algorithm is proposed to deal belt images on-line. The algorithm for detecting longitudinal rip and belt deviation which are serious threat to the mine safety production from binary belt images is presented. Then, an on-line visual belt inspection system is developed. The laboratory testing results testify the validity of the visual inspection system.     

An automatic optical inspection system for the detection of three parallel lines in solar panel end face

This study inspected and tracked the location state of a test object in the telemetry monitoring of a wafer or solar panel, and the relevant optoelectronic devices. A CCD camera, triggered by the proposed system, captures the test target image in real time, which is transferred to the system for low-pass filtering, image binarization, spatial masking, boundary tracing, and other means of image processing. The new edge point detection algorithm is then applied to identify the edge points of three parallel lines. Three different group edge points are determined using the edge point detection algorithm, and the three groups are computed using a single linear regression equation. Multiple-linear regression is conducted to obtain the sections of straight lines of the groups that can best satisfy the expected requirements. Finally, whether the detection results are consistent with the expected requirements is determined to inspect whether the test object is consistent with the process specifications in order to reduce undesirable losses, as caused by inappropriate placement angle in subsequent manufacturing, thus, enhancing subsequent manufacturing to achieve high yield.     

A study of the impact on telecentricity to the illumination system based on CCD imaging

One of the important properties of the illumination system is of determining telecentricity for the realization of the place of wafer in the optical lithography. In this paper, we present numerical simulations of the optical imaging using four different illumination models and based on CCD imaging. We simulate the imaging of light source for different illumination pupil distributions and determine the energy centroid through the imaging of the conventional illumination which exist telecentricity of 11 mrad. Furthermore, we discuss the influencing factors of two aspects on telecentricity. One is the non-uniformity of light intensity distribution, and the other is pinhole defocus in the wafer. The range between the non-uniformity of light intensity distribution and pinhole defocus are quantified by computing the allowed telecentricity error in the illumination system. Finally, experiments have verified telecentricity measurement feasibility and validity. The presented scheme that with CCD imaging instead the actual wafer which saves cost and improves the accuracy in the optical lithography. In comparison with the measurement methods of convention the CCD imaging has a series of advantages such as fast response, high sensibility, high precision and the measurement is carried out on-line.     

Real-time defect detection on highly reflective curved surfaces

This paper presents an automated defect detection system for coated plastic components for the automotive industry. This research activity came up as an evolution of a previous study which employed a non-flat mirror to illuminate and inspect high reflective curved surfaces. According to this method, the rays emitted from a light source are conveyed on the surface under investigation by means of a suitably curved mirror. After the reflection on the surface, the light rays are collected by a CCD camera, in which the coating defects appear as shadows of various shapes and dimensions. In this paper we present an evolution of the above-mentioned method, introducing a simplified mirror set-up in order to reduce the costs and the complexity of the defect detection system. In fact, a set of plane mirrors is employed instead of the curved one. Moreover, the inspection of multiple bend radius parts is investigated. A prototype of the machine vision system has been developed in order to test this simplified method. This device is made up of a light projector, a set of plane mirrors for light rays reflection, a conveyor belt for handling components, a CCD camera and a desktop PC which performs image acquisition and processing. Like in the previous system, the defects are identified as shadows inside a high brightness image. At the end of the paper, first experimental results are presented.     

Ultrathin Wafer Pre-Assembly and Assembly Process Technologies: A Review

Ultrathin silicon wafer technology is reviewed in terms of the semiconductor applications, critical challenges, and wafer pre-assembly and assembly process technologies and their underlying mechanisms. Mechanical backgrinding has been the standard process for wafer thinning in the semiconductor industry owing to its low cost and productivity. As the thickness requirement of wafers is reduced to below 100 μm, many challenges are being faced due to wafer/die bow, mechanical strength, wafer handling, total thickness variation (TTV), dicing, and packaging assembly. Various ultrathin wafer processing and assembly technologies have been developed to address these challenges. These include wafer carrier systems to handle ultrathin wafers; backgrinding subsurface damage and surface roughness reduction, and post-grinding treatment to increase wafer/die strength; improved wafer carrier flatness and backgrinding auto-TTV control to improve TTV; wafer dicing technologies to reduce die sidewall damage to increase die strength; and assembly methods for die pick-up, die transfer, die attachment, and wire bonding. Where applicable, current process issues and limitations, and future work needed are highlighted.     

Photographic diagnosis of crystalline silicon solar cells utilizing electroluminescence

The photographic surveying of electroluminescence (EL) under forward bias was proved to be a powerful diagnostic tool for investigating not only the material properties but also process induced deficiencies visually in silicon (Si) solar cells. Under forward bias condition, solar cells emit infrared light (wavelength around 1000 to 1200 nm) whose intensity reflects the number of minority carriers in base layers. Thus, all the causes that affect the carrier density can be detected, i.e., the minority carrier diffusion length (or in other words, lifetime), recombination velocity at surfaces and interfaces, etc. (intrinsic material properties), and wafer breakage and electrode breakdown, etc. (extrinsic defects). The EL intensity distribution can be captured by Si CCD camera in less than 1 s, and the detection area simply depends upon the optical lens system suitable to the wide range of 1 cm–1.5 m. This fast and precise technique is superior to the conventional scanning method such as the laser beam induced current (LBIC) method. The EL images are displayed as grayscale, which leads to the difficulty of distinguishing the sorts of those deficient areas. Since the intrinsic deficiency is more sensitive to temperature than the extrinsic deficiency, the change in solar cell temperature can offer the difference in EL intensity contrasts. These effects upon the measurement temperature can be applied to categorize the types of deficiency in the crystalline Si solar cell.     

Ultrasound-assisted handling force reduction during the solar silicon wafers production

Surface adhesion between wet wafers poses great challenges for silicon wafer handling. It has been shown that both the shear and normal handling forces of the solar silicon wafers can be dramatically reduced by using the ultrasound energy. Approximately 20 and 5 times reduction in horizontal and vertical forces were achieved by as low power as 10 W, and a good agreement was found between the measured values and the predictions of a simple model for the effect of longitudinal vibration we developed.     

脆性断裂统计理论

本文试图用统计方法,将金属脆性断裂的微观过程与宏观过程结合起来,把断裂理论建立于微裂纹发展动力学的统计基础上。脆性断裂实质上是在小的范性变形过程中微裂纹成核长大的非平衡统计过程和单个主裂纹的传播过程。本文导出了描述这种非平衡统计过程的微分积分方程,并从位错机理出发研究了微裂纹动力学,从而解出了微裂纹的分布函数,求出了金属试样的断裂几率,进而导出了延伸率、断裂强度、范性功、裂纹扩展力、断裂韧性、临界裂纹长度、范性-脆性转变温度以及它们的统计偏差与其它有关物理量之间的函数关系。 关键词：     

Dazzling effect of repetitive short pulse laser on TDI CCD camera

A dazzling experiment was performed on a 64-stage TDI CCD camera using a 20 Hz repetition frequency picoseconds pulse laser, during which we found a new dazzling effect in which the fringes appeared in the video of the camera beside the saturation spot induced by the laser. We considered it to be the scattered light of the repetition frequency laser pulse to have induced the phenomenon. Width and visibility of the fringes recorded the information of the scattered light, such as repetitive frequency, pulse width and intensity distribution. With the assumption that the laser pulse width is less than one stage integral time of TDI CCD, width expressions for the fringes and space between the fringes were given using the repetitive frequency of laser pulse, row output frequency and integral stage number of the TDI CCD camera.     

Optical three-dimensional sensing by phase measuring profilometry

The technique of phase-measuring profilometry is reviewed, whereby a sinusoidal grating structure is projected onto a diffuse three-dimensional surface, and the resulting deformed grating image is detected by a solid state array camera and processed by a microcomputer using interferometric phase measuring algorithms. The approach permits parallel acquisition and processing of large amounts of data with high accuracy and speed.Several systems are described, configured with telecentric laser light illumination or general white light diverging illumination, and capable of measurement from a single point of view or over full 360°. Each system consists of an optical projection assembly with phase-shifter, an imaging assembly with high density CCD camera and an IBM AT microcomputer with buffer and control cards.Applications to industrial inspection and medical diagnostics are presented.     

Laser ablation of toluene liquid for surface micro-structuring of silica glass

Microstructures with well-defined micropatterns were fabricated on the surfaces of silica glass using a laser-induced backside wet etching (LIBWE) method by diode-pumped solid state (DPSS) UV laser at the repetition rate of 10 kHz. For a demonstration of flexible rapid prototyping as mask-less exposure system, the focused laser beam was directed to the sample by galvanometer-based point scanning system. Additionally, a diagnostics study of plume propagation in the ablated products of toluene solid film was carried out with an intensified CCD (ICCD) camera.     

单线阵CCD相机立靶测量原理

针对现有双CCD交汇立靶在室内使用时存在的光源复杂的问题,提出一种单线阵CCD相机立靶测量原理.采用一台线阵CCD相机,配合两个小功率半导体扇形一字线状激光器和投影板作为光源,将CCD相机的探测光幕面和激光光源的光幕面调整在同一个面内,当弹丸穿越探测光幕面时,档住了两个激光器投射在投影板上的部分光线,并在投影板上留下对...     

硅片及其太阳电池的光衰规律研究

采用氙灯模拟太阳光源,将光强调至1000 W/m2,研究常规太阳能级单晶硅片、多晶硅片和物理提纯硅片的原片、去损减薄片、热氧化钝化片、双面镀氮化硅(SiN x:H)膜钝化片、碘酒钝化片以及太阳电池的光衰规律.利用WT-2000少子寿命测试仪以及太阳电池I-V特性测试仪分别对硅片的少子寿命和太阳电池的I-V特性参数随光照时间的变化进行了测试.结果表明:所有硅片以及太阳电池在光照的最初60 min内衰减很快随后衰减变慢,180 min之后光衰速率变得很小,几乎趋于零.     

A very short vertical directional coupler with polarization-insensitive high extinction ratios

We propose a very short vertical directional coupler with polarization-insensitive high extinction ratios. The structure of the coupler has two deep-ridge waveguide structures in the upper and lower parts which can be implemented using a double-sided wafer process. The coupling length and extinction ratios of the vertical directional coupler with symmetric structures decrease as the thicknesses of the inner cladding layer and core layer decrease. The extinction ratio is improved using a slight asymmetry in the refractive indices of two core layers. As the thicknesses of the inner cladding layer and core layer decrease, the length of the vertical directional coupler for extinction ratios greater than 30 dB of both TE and TM modes decreases. A vertical directional coupler with a very short length less than 100 μm and polarization-insensitive high extinction ratios greater than 30 dB can be implemented using the structure proposed in this paper.     

Quadrature fringes wide-field optical coherence tomography and its applications to biological tissues

We propose and demonstrate quadrature fringes wide-field optical coherence tomography (QF WF OCT) to expand an optical Hilbert transformation to two-dimensions. This OCT simultaneously measures two quadrature interference images using a single InGaAs CCD camera to obtain en face OCT images. The axial and lateral resolutions are measured at 29 μm in air and 70 μm limited by a pixel size of camera using a superluminescent diode with a wavelength of 1.3 μm as the light source; the system sensitivity is determined to be −90 dB. The area of the en face OCT images is 4.0 mm × 4.0 mm (160 × 160  pixels). The OCT images are measured axially with steps of 10 μm. The en face OCT images of a in vivo human fingertip and a in situ rat brain are three-dimensionally measured up to the depth of about 3 mm with some degradations of a lateral resolution.     

探月光学

介绍了我国首次绕月探测嫦娥一号卫星的主载荷CCD立体相机与干涉成像光谱仪的原理、设计思想、技术措施与特色、设计结果以及在轨图像质量评估与检测. CCD立体相机采用一个广角物镜加一块面阵CCD的独特技术方案,从而使立体相机具有结构紧凑、小型轻量、配准精度高、航天环境适应性强等优点. 4种曝光时间与4种电子学增益共16组合,可以实现同轨不同纬度的曝光量调整. 干涉成像光谱仪采用了大比尺缩小的图像传递、2×2像元合并、矩形孔径光阑、2种曝光时间与3种电子学增益共6种组合的在轨曝光量调整等技术措施. 在轨运行表明,各项技术措施有效,达到了预期目标.     

Audible vibration diagnostics of thermo-elastic residual stress in multi-crystalline silicon wafers

This paper presents audible vibratory mode data obtained by mechanically exciting acoustic modes in multi-crystalline silicon wafers with various levels and distributions of residual stress. Natural frequency data from the silicon wafers is found to correlate with residual stress optical polariscopy measurements. The data is fit with both linear and quadratic models with correlation coefficients of 0.8. The results reveal a dependence of wafer audible mode frequencies on residual stress level that may be useful for solar cell mechanical quality control and breakage inspection.     

Flat-top beam profile generated using a fiber-bundle prism-coupled beam shaper

In this paper, an optical beam shaping system is theoretically and experimentally investigated. The optical system design software ZEMAX is used to simulate and analyze the reported beam shaping design. By using this software ray tracing diagrams are presented with the aim of studying the direct beam propagation, total reflection rays, and the lost rays. The prism duct output beam shape and radiance profiles in both position space and angle space are also studied. For experimental investigation, a two-stage beam shaping design including a fiber-bundle and a prism duct is used. A source light is used for the fiber-bundle illumination and the photograph image of the output beam is taken by a digital camera. The fiber-bundle output beam cross section is a rectangular shape with a dimension of 25.65 mm width and 2.44 mm height. In another experiment, the prism output beam is captured by a CCD camera. The prism output beam shape depends on the prism exit face, which is a rectangle (4.15 mm × 3.55 mm) for this case. The image date of the prism output beam is converted to a response curve, which is approximately a flat-top profile. The experimental image profiles are compared with the simulated image profiles and there is a good agreement between the observed results.