大型硅晶片平面度精密纳米计量技术

描述了一种基于斜率传感器的大型硅晶片平面度扫描测量系统．采用二维斜率传感器对晶片表面扫描，以获得表面绕X和Y轴的倾斜度．斜率传感器装在X向滑板上，而晶片固定在可绕Z轴转动的主轴上．对斜率传感器Y向的输出积分，得到晶片表面各个同心圆上轮廓截面高度．对斜率传感器X向的输出积分，得到晶片表面沿X向的截面轮廓，从而获得各同心圆轮廓之间的关系．构建了一个包括基于自准直原理的小型斜率传感器、气浮主轴、气浮导轨的实验系统，提出一种斜率传感器现场标定方法，用此系统测量了直径300mm的硅晶片平面度。     

薄/厚膜压电参数测量方法的研究进展

介绍了当前测量薄/厚压电参数的2大类方法:直接测量法(包括Berlincourt法、圆片弯曲技术、激光干涉法、扫描激光多普勒振动法、原子力显微镜法)和间接测量法(包括体声波响应和表面声波响应法、复合谐振法).详细分析了这些方法的基本原理、测试表征、应用状况和存在的问题,比较了这些方法的优缺点.结果表明,高分辨率的双束激光干涉和表面扫描振动相结合的方法将是评估压电参数方便、准确和可靠的方法,有望成为将来表征薄/厚膜压电特性的标准方法.     

Catalyst-free synthesis of ZnO nanorod arrays on InP (001) substrate by pulsed laser deposition

High-density well-aligned ZnO nanorod arrays were successfully fabricated on ZnO a seed-layer coated InP (001) substrate by using pulsed laser deposition (PLD) technique without metal catalyst. SEM image showed that uniformly distributed droplet-like ZnO seed-layer was formed on the InP wafer. Well-oriented ZnO nanorods were formed perpendicular to the seed-layer coated substrate and well-separated from each other. X-ray diffraction θ-2θ scanning measurements demonstrated that the ZnO nanorods exhibited a strong c-axis orientation with high crystalline quality. The photoluminescence (PL) spectrum measurement illuminated that the ZnO nanorods produced in this work had well optical quality. The well-aligned and separated ZnO nanorods fabricated by this comparatively simple technique shed light on further applications for nanodevices.     

Using concentric circles and wedge grating for camera calibration

This paper presents a method for camera calibration based on the orthogonal vanishing point calibration using concentric circles grating and wedge grating. This method, which we believe is new, uses the high-precision characteristics of phase extraction to obtain the feature points, thus decreasing the calibration errors caused by the traditional marker extraction errors of gray pattern. According to the simulation experiment analysis results, the concentric circles grating was designed with seven periods and the wedge grating was designed with four periods. In the real measuring experiment, the grating target and the similar gray concentric circles target were used to calibrate the camera, respectively. Through comparing the reprojective errors of the two methods, the method proposed is proven to improve the calibration accuracy and robustness for the vanishing point calibration algorithm.     

采用金-金键合工艺制备垂直结构氮化镓发光二极管(英文)

本文在采用键合工艺制备以硅为衬底的氮化镓发光二极管的工艺过程中分别尝试采用金-金,金-硅,铝-铝,铝-硅键合对。研究发现金-金键合对得到了100%的键合面积。键合工艺结束后,采用KrF激光分离氮化镓发光二极管的器件层和原蓝宝石衬底。通过超声波造影仪(SAM)和扫描电子显微镜(SEM)研究了金属键合工艺过程中相应的键合机制。     

Optimization of selective emitter fabrication method for solar cells using a laser grooving

In this paper, screen-printing laser grooved buried contact (LGBC) method was applied, which is compatible with the existing screen-printed solar cell equipment and facilities. Experiments were performed in order to optimize short circuit current (I(sc)), open circuit voltage (V(oc)) and fill factor of high efficiency solar cells. To enhance I(sc), V(oc) and efficiency, heavy doping was performed at low sheet resistance in the laser grooved region of the cell. In contrast, light doping was carried out at a high sheet resistance in the non-laser grooved region. To increase fill factor, porous silicon found on the wafer after dipping in an HF solution to remove SiN(x), was cleared. The fabricated screen-printing LGBC solar cell using a 125 mm x 125 mm single crystalline silicon wafer exhibited an efficiency of 17.2%. The results show that screen-printing LGBC method can be applied for high efficiency solar cells.     

Measurement of profiles along a circle on two flat surfaces by use of a Fizeau interferometer with no standard

A method for measuring profiles along a circle on a flat surface with no standard is described. For the measurement, two unknown surfaces are placed almost parallel, and the distance between them is measured many times along a circle by rotation of one of the surfaces. Profiles of the two surfaces can be determined from the distance data. In this study the measuring method is explained: The space between two surfaces measured with a Fizeau interferometer. Four measuring experiments are carried out for determining the profile of a precision-grade half-mirror; in each experiment a different ordinary mirror with unknown profile is used as the second mirror. Profiles of the precise mirrors obtained by these experiments agree closely, with deviations of approximately 2 nm. A similar experiment with many concentric circles was carried out with a precise half-mirror and another precise mirror. Although the profiles of many concentric circles were independent of one another, the result shows that the high-frequency component of a whole plane can be estimated.     

Computer-generated microcooled reflection holograms in silicon for material processing with a CO(2) laser

We report on the design, fabrication, and testing of multilevel computer-generated reflection holograms in Si for CO(2) laser material processing for laser intensities of <2 kW/cm(2). The holograms are designed with an iterative method based on scalar diffraction theory. In this case the reconstructed intensity distribution is independent of the incident high-power laser mode. For achieving high diffraction efficiencies, multilevel staircase surface topologies are fabricated by multimask and reactive ion-etching technology on the front side of a polished Si wafer. For efficient hologram cooling, a gratinglike structure of microchannels is chemically etched on the back side of the Si wafer. Absorption and deformation measurements have been carried out on both a microcooled flat mirror and a reflection hologram. The maximum deformation amounts to 200 nm and is 10 times smaller than comparable conventional uncoated Cu mirrors. A diffraction efficiency of 88% is achieved with an eight-level reflection hologram and a 30-mm-diameter CO(2) laser beam with a power of 5 kW.     

Fabrication of high aspect ratio metal nanotips by nanosecond pulse laser melting

The authors have developed an approach to fabricate sharp and high aspect ratio metal tips using nanosecond pulse laser melting. A quartz wafer covered with a thin chromium (Cr) film was placed on top of a second wafer with a sub-micrometer gap between them and the Cr film facing the second wafer. Then an excimer laser pulse (308?nm wavelength, 20?ns pulse duration) was shone from the back of the quartz wafer and melted the Cr film momentarily (several hundred nanoseconds). It is found that the molten Cr films can self-form discrete metal pillars connecting the two wafers. After separating the two wafers, nanotips were formed at the broken pillar necks. The sharpest tip achieved has an apex diameter 10?nm and height 180?nm. The self-formation of Cr pillars between the two wafers was attributed to the attractive electrostatic force caused by the work function difference of two wafers that were in close proximity. This technique could be extended to other metals, and a periodic uniform tip array could be obtained by pre-patterning the metal into identical isolated mesas and precisely controlling the gap between the two wafers.     

碳化硅粒径分布对单晶硅线切割的影响

研究不同粒度分布的碳化硅磨料对线切割硅片表面损伤的影响,利用激光粒度仪和扫描电镜对切割前后碳化硅粒径的变化及切割后硅片的形貌进行表征,通过实际切割过程分析,指出粒度分布不均引起的局部切割堵塞而导致的垂直于切割方向的左右侧滑振动,是导致表面损伤的主要原因。结果表明:当碳化硅的粒度分布窄时,线切割硅片表面损伤层浅,表面粗糙度小。     

Screen-printed single-walled carbon nanotube networks and their use for dimethyl methylphosphonate detection

Single-walled carbon nanotube (SWNT) films were prepared on silicon/silica substrates by screen-printed technique at a wafer scale, and their sensing properties to dimethyl methylphosphonate (DMMP) were studied. The SWNT networks were characterized by field-emission scanning electron microscope. The resistance responses to different concentrations of DMMP vapors were investigated at room temperature. The results showed that the resistance changes of the screen-printed SWNT films increased rapidly in varying concentrations ranging from 20 to 200?ppm. The sensor exhibited high resistance responses, good reproducibility and excellent long-term stability for DMMP vapor detection. The screen-printed SWNT networks would be potentially extended to large-scale, low cost and simple manufacturing sensor applications.     

Performance of GaN vertical light emitting diodes using wafer bonding process with Al-alloyed graphite substrate

We report on the vertical-structure light emitting diodes (VLEDs) fabricated with wafer bonding method using Al-alloyed graphite and Si supporter. VLEDs with Al-alloyed graphite produced no crack during/after laser lift-off (LLO) techniques while the wafer crack took place using Si supporter because of the difference of thermal expansion coefficients between Si and sapphire. The performance of VLEDs with wafer bonding method using Al-alloyed graphite supporter was compared to those fabricated by Cu plating methods. The output power of the chips with wafer bonding method was nearly same as the one with Cu-plating method. However, the forward voltage of VLEDs with wafer bonding method was higher than those with Cu-plating method. In the terms of reliabilities the wafer bonding process is more preferable to Cu-plating and our report proposes that Al-alloyed graphite could be one of promising candidates for the supporters in wafer bonding process.     

Band-edge photoluminescence degradation in GaAs

This paper reports on the degradation of the band-edge photoluminescence (PL) signal seen in various types of GaAs samples during low-power argon laser irradiation. This degradation was observed to take place over a period of minutes and was found to be a function of the position on the wafer as well as the temperature of the wafer and laser power. The decrease in PL intensity did not recover after several hours with the laser off. Surface, thermal and system parameters were eliminated as possible sources of the PL degradation seen. We propose that the observed PL degradation is partly due to a bulk material parameter, and that the method of measuring PL degradation could be used as a more reliable and reproducible method of whole-wafer characterization than the current procedure of mapping PL intensities.     

A Simple Optical Reader for Upconverting Phosphor Particles Captured on Lateral Flow Strip

A simple optical reader was developed for rapid and sensitive quantification of lateral flow (LF) strip with upconverting phosphor (UCP) particles as reporters. The excitation beam from a 980 nm laser diode (LD) was focused to a 4 mm (length) $,times,$0.02 mm (width) rectangular spot on LF strip. A rectangular slit with 4 mm $,times,$0.02 mm before the photomultiplier tube (PMT) which was selected as receiver was introduced as field diaphragm to prevent stray light from entering the PMT. The scanning resolution was 20 $mu$m, and the scanning speed was 0.75 mm/s, and the scanning range was 10 mm. With the above optical reader, serial dilutions of Yersinia pestis F1 antigen were detected to achieve the test sensitivity was 5 ng/ml, and the dynamic range reached 150 ng/ml. The algorithms of the low-pass filter and the first derivative were used to search the boundaries of T line and C line from the original data acquired by the reader. A four-parameter logistic mathematical model was used to deduce the quantitative equation for determination of unknown F1 antigen concentration. Our 1-D optical reader possessed the following characteristics: high 1-D testing resolution, high sensitivity, simple structure, simple data processing method, high testing efficiency, and small total volume.      

Coupled and forced patterns in reaction-diffusion systems

Several reaction-diffusion systems that exhibit temporal periodicity when well mixed also display spatio-temporal pattern formation in a spatially distributed, unstirred configuration. These patterns can be travelling (e.g. spirals, concentric circles, plane waves) or stationary in space (Turing structures, standing waves). The behaviour of coupled and forced temporal oscillators has been well studied, but much less is known about the phenomenology of forced and coupled patterns. We present experimental results focusing primarily on coupled patterns in two chemical systems, the chlorine dioxide-iodine-malonic acid reaction and the Belousov-Zhabotinsky reaction. The observed behaviour can be simulated with simple chemically plausible models.     

An experimental approach for growth rate determination of LCVD-written aluminium stripes

A new experimental approach for growth rate determination of microdimensional aluminium stripes written by laser-induced chemical vapour deposition (LCVD) was developed. The aluminium lines were obtained by pyrolysis of trimethylaluminium (TMA) on (100) silicon monocrystalline wafer using the focused beam of a copper bromide vapour laser. Quantitative determination of the deposit was performed by its chemical removal from the substrate into a solution and further analysis performed using inductively coupled plasma atomic emission spectroscopy. Using this analytical method, dependences of the aluminium quantity on the partial pressure of TMA and the laser power were obtained. The growth rate at direct writing with a pulsed visible laser was calculated on the basis of aluminium quantity determinations. It is demonstrated that the proposed experimental approach could be successfully used for kinetic studies of LCVD processes.     

Optimisation of GaAs nanocrystals synthesis by laser ablation in water

Laser ablation of a gallium arsenide (GaAs) wafer immersed in distilled water was carried out using the fundamental wavelength of a high frequency Nd:YAG laser with 240?ns pulse duration. Rate of nanoparticles generation through laser ablation for various amounts of laser pulse energies (0.4–0.94?mJ) and repetition rates (400–2000?Hz) were studied and a maximum ablation rate of 19.6?µgr/s was obtained. Formation of the pure GaAs nanocrystals (NCs) is confirmed using TEM micrograph and X-ray diffraction analysis. Band-gap energy of generated GaAs NCs is calculated by Tauc method to be between 2.48 and 2.60?eV which is larger than the band-gap energy of bulk GaAs. The band-gap energy of NCs is increased by increasing the energy of laser pulses and is decreased by increasing the pulse repetition rate.     

Influence of liquid environments on femtosecond laser ablation of silicon

Liquid-assisted ablation of solids by femtosecond laser pulses has proved to be an efficient tool for highly precise microfabrication, which evokes numerous research interests in recent years. In this paper, we systematically investigate the interaction of femtosecond laser pulses with silicon wafer in water, alcohol, and as a comparison, in air. After producing a series of multiple-shot craters on a silicon wafer in the three types of environments, surface morphologies and femtosecond laser-induced periodic surface structures are comparatively studied via the scanning electron microscope investigations. Meanwhile, the influence of liquid mediums on ablation threshold fluence and ablation depth is also numerically analyzed. The experimental results indicate that the ablation threshold fluences of silicon are reduced by the presence of liquids (water/alcohol) and ablation depths of craters are deepened in ambient water. Furthermore, smoother surfaces tend to be obtained in alcohol-mediated ablation at smaller shot numbers. Finally, the evolution of the femtosecond laser-induced periodic surface structures in air, water and alcohol is also discussed.     

基于机器视觉的鞋楦数字化及类似方法对比

介绍了机器视觉的原理和目前主流的鞋楦数字化方法,讨论了机器视觉的研究发展现状、优缺点及技术上的瓶颈;重点将接触式测量、激光扫描和立体视觉这三种方法进行了对比。接触式测量可靠性高,但是精度低。激光扫描法测量精度相当高,可测量柔软易脆对象,不必作测头半径补偿,工作距离大、范围广,但是容易受物件表面光学性质影响,设备精密,价格昂贵。立体视觉方法也可测量柔软易脆对象,速度快,硬件简单,价格低廉,并且不会抹平模型上的尖点。立体视觉方法是目前正在发展的一种图像测量方法,同样能完成鞋楦数字化,与前两种方法相比,在鞋模的定制方面更为合适。     

Simultaneous wavenumber measurement and coherence detection using temporal phase unwrapping

Wavelength scanning interferometry and swept-source optical coherence tomography require accurate measurement of time-varying laser wavenumber changes. We describe here a method based on recording interferograms of multiple wedges to provide simultaneously high wavenumber resolution and immunity to the ambiguities caused by large wavenumber jumps. All the data required to compute a wavenumber shift are provided in a single image, thereby allowing dynamic wavenumber monitoring. In addition, loss of coherence of the laser light is detected automatically. The paper gives details of the analysis algorithms that are based on phase detection by a two-dimensional Fourier transform method followed by temporal phase unwrapping and correction for optical dispersion in the wedges. A simple but robust method to determine the wedge thicknesses, which allows the use of low-cost optical components, is also described. The method is illustrated with experimental data from a Ti:sapphire tunable laser, including independent wavenumber measurements with a commercial wavemeter. A root mean square (rms) difference in measured wavenumber shift between the two of ~4 m?1 has been achieved, equivalent to an rms wavelength shift error of ~0.4 pm.