离子束螺旋扫描方式修正光学镜面方法

研究基于螺旋扫描方式的光学镜面离子束修正方法.根据离子束去除函数的特性,将螺旋扫描加工过程简化成线性过程并建立工艺过程模型,采用基于Bayesian原理的改进Richard-Lucy迭代法求解驻留时间.在分析驻留时间的连续速度实现基础上,给出螺旋路径参数的确定准则.建立螺旋扫描加工方式的工艺流程并进行试验验证研究.试验研究对φ100平面镜和φ200非球面镜修形加工得到了面形方均根误差均优于0.01λ.研究结果表明:极轴加工与普通的全口径加工一样是一种高效率、高确定性的加工方法,能够对镜面进行精确修形,同时可以节约加工成本.     

Optimization strategy for the velocity distribution based on tool influence function non-linearity in atmospheric pressure plasma processing

Atmospheric pressure plasma processing (APPP) is proved to be potential in the fabrication of optical elements with high efficiency and near-zero damage. However, high convergence rate in the figuring process is hard to achieve because of the tool influence function (TIF) non-linearity. Directly solved dwell time map by conventional deconvolution methods does not consider the non-linear thermal effect, which leads to significant figuring error. In this paper, the optimization strategy for TIF non-linearity based on the velocity distribution in APPP is presented. The exponential model of TIF with non-linearity is established by trench experiments. A series of simulations are also conducted to analyze the thermal effect of non-linearity on the figuring process, indicating the TIF constantly changes with velocity distribution. Two evaluation parameters, relative balance factor and velocity concentration factor, are proposed to investigate the figuring capacity of calculated velocity distribution. With two evaluation parameters, the optimization strategy of velocity distribution based on TIF selection is proposed to suppress the non-linearity. Verification experiments are carried out to validate the two optimized TIFs. The results show that high convergence is achieved to be 72.41% and 82.81% for root-mean-square value respectively, which proves the feasibility of the proposed optimization strategy.     

光学平面镜面离子束修形中速度模式的实现

针对光学平面镜面离子束修形工艺中,目前采用的位置加工模式额外加工时间长、精度不高的缺点,提出离子束修形工艺中的速度加工模式,并给出速度加工模式中如何根据驻留时间计算加工中进给速度的方法。使用速度模式在自研的离子束加工机床KDIFS-500上进行了验证试验,对一块直径98 mm的微晶玻璃平面样镜进行修形,加工时间为17.5 min,样镜经过一次加工后,其面形误差的方均根值由初始的33.2 nm提高到了3.1 nm,面形收敛比高达10.7。试验结果表明,速度模式加工比位置模式加工可以缩短加工时间,提高加工精度,获得更大的面形收敛比。     

基于Bayesian原理的低陡度光学镜面面形误差离子束修正驻留时间算法

离子束修形是一种高效修除镜面误差的技术,驻留时间求解算法是此技术的关键问题之一。以光学镜面计算机控制成型原理为基础,建立基于Bayesian原理的平面镜面驻留时间算法,对数据边缘进行Gaussian延拓以消除边缘效应。分析驻留时间近似速度实现方式的实现误差与工艺参数的关系,通过在算法中引入附加光滑修正因子以提高驻留时间实现精度。在适当的路径规划下,将低陡度非球面修形过程近似用平面修形过程线性模型来描述,最终形成低陡度光学镜面面形误差离子束修正中驻留时间的快速近似算法。利用此算法对 100平面镜和 200球面镜进行修形加工,加工收敛率均可达9。研究结果表明：线性化近似模型是合理的,速度近似计算是可行的,基于Bayesian原理的低陡度非球面驻留时间求解算法是一种快速高效面形控制技术,可对镜面进行确定性精确修形。     

Time of flight secondary ion mass spectrometry: a powerful high throughput screening tool

Combinatorial materials libraries are becoming more complicated; successful screening of these libraries requires the development of new high throughput screening methodologies. Time of flight secondary ion mass spectrometry (ToF-SIMS) is a surface analytical technique that is able to detect and image all elements (including hydrogen which is problematic for many other analysis instruments) and molecular fragments, with high mass resolution, during a single measurement. Commercial ToF-SIMS instruments can image 500 microm areas by rastering the primary ion beam over the region of interest. In this work, we will show that large area analysis can be performed, in one single measurement, by rastering the sample under the ion beam. We show that an entire 70 mm diameter wafer can be imaged in less than 90 min using ToF-SIMS stage (macro)rastering techniques. ToF-SIMS data sets contain a wealth of information since an entire high mass resolution mass spectrum is saved at each pixel in an ion image. Multivariate statistical analysis (MVSA) tools are being used in the ToF-SIMS community to assist with data interpretation; we will demonstrate that MVSA tools provide details that were not obtained using manual (univariate) analysis.     

光学镜面离子束加工材料去除效率

分析了离子束加工材料去除效率、不同材料之间的相对去除效率与工艺参数的关系。基于Sigmund溅射理论,建立表征去除效率的指标－法向去除率、体积去除率和溅射产额与束能、束流以及入射角度之间的关系模型。以石英、微晶和K4等为样件,实验分析了去除效率与工艺参数的关系,验证了模型的正确性。分析结果表明材料去除效率随束流线性增大;约与束能平方根呈线性关系;随着入射角度先缓慢增大,约在60~80°达到最大值,尔后迅速降为零。不同材料之间的相对去除效率与束流无关;与束能的关系较弱,可以忽略;随角度变化较为明显。     

A study on an object transport system using ultrasonic wave excitation

The development of information and telecommunication industries leads to the development of semiconductor and optical industries. In recent years, the demand of optical components is growing due to the demand of faster network. On the other hand, conventional transport systems are not adequate for transporting precision optical components and semiconductors. Because the conveyor belt can damage precision optical components with contact force and a magnetic system would destroy the inner structure of semiconductor with magnetic field, a new system for transporting optical components and semiconductors is required. One of the alternatives to the existing systems is a transport system using ultrasonic wave excitation since it can transport precision components such as semiconductors and optical components without damage. In this paper, a transport system using 2-mode ultrasonic wave excitation was developed for transporting optical components and semiconductor, and its performance was evaluated. The relationship between transporting characteristics and flexural beam shapes were evaluated.     

光学镜面离子束加工的可达性

提出了离子束加工可达性问题的理论描述和定义,分析了驻留函数解的存在条件,进而分析了采用不同直径的离子束去除不同频率面形误差时额外去除量的大小,最后进行了仿真验证。分析结果表明,对于高斯型的束函数,驻留函数解总是存在的。但是面形误差频率越高,驻留函数解越大,去除面形误差时去除的额外材料越多。额外的材料去除量随着离子束径和空间误差波长之比(d/λ)的增加而指数增加。当d/λ=0.5时,额外材料去除量为15%,还是可以接受的;当d/λ=1时,额外材料去除量迅速上升到73%,该值即很难被接受。理论分析和仿真结果表明,为了优化加工过程,d/λ应该＜0.5。     

光学非球面离子束加工模型及误差控制

摘要：通过对离子束加工系统的分析,给出了加工非球面光学元件的离子源子系统运动模型公式,并将驻留时间求解的反卷积过程转化为求解线性矩阵方程模型,便于进一步优化求解;对加工过程中不可避免的离子源定位误差过程进行了分析,指出其对最终面形精度的影响可归结为一个系数因子的控制上,并提出了综合考虑离子束材料去除函数和定位误差的方法来控制系数因子,降低对定位系统的苛刻精度要求,保证过程稳定的同时降低设备成本。     

Matrix based algorithm for ion-beam figuring of optical elements

An algorithm for solving the problem of local shape errors of optical surfaces correcting by a small-sized ion beam, based on the matrix representation is presented. The algorithm involves searching for points that rise relative to the average height on the surface, where exposure to an ion beam of a given shape will lead to a decrease in the RMS deviation of the surface shape from the calculated one. It is shown that the new approach makes it possible to significantly expand the range of spatial frequencies, in which the height of relief can be reduced using the given ion beam size, and provides better results than the method of minimizing the functional of convolution of the ion beam and the surface map. Moreover, the new approach does not lead to appearance of shape errors (concentric structure) defined by the ion beam size and scanning step. An experiment for minimizing of local surface shape errors based on an etching map calculated using new approach was done. Matrix algorithm allowed in one procedure to reduce surface shape errors for a concave spherical optical element made of fused silica with a diameter D = 100 mm and a radius of curvature R = −137.5 mm in the RMS by more than 3 times. The initial RMS was 4.5 nm, RMS after treatment is 1.36 nm.     

多模式组合抛光技术在光学加工中的应用

介绍了将经典抛光方法与数控加工技术有机结合的多模式组合抛光技术.描述了多模式组合抛光的关键技术之一,材料去除率仿真模型的建立方法.通过设置抛光盘因子和元件因子,多模式组合抛光的材料去除模型不仅包含抛光模式、速度等加工参数,还将抛光模形状、边角效应、元件面形误差等因素对材料去除的影响一并考虑入内,可以根据抛光阶段的不同,...     

Surface damage induced by FIB milling and imaging of biological samples is controllable

Focused ion beam (FIB) techniques are among the most important tools for the nanostructuring of surfaces. We used the FIB/SEM (scanning electron microscope) for milling and imaging of digestive gland cells. The aim of our study was to document the interactions of FIB with the surface of the biological sample during FIB investigation, to identify the classes of artifacts, and to test procedures that could induce the quality of FIB milled sections by reducing the artifacts. The digestive gland cells were prepared for conventional SEM. During FIB/SEM operation we induced and enhanced artifacts. The results show that FIB operation on biological tissue affected the area of the sample where ion beam was rastering. We describe the FIB-induced surface major artifacts as a melting-like effect, sweating-like effect, morphological deformations, and gallium (Ga(+)) implantation. The FIB induced surface artifacts caused by incident Ga(+) ions were reduced by the application of a protective platinum strip on the surface exposed to the beam and by a suitable selection of operation protocol. We recommend the same sample preparation methods, FIB protocol for milling and imaging to be used also for other biological samples.     

离子束抛光去除函数计算与抛光实验

由于传统的离子抛光工艺采用的确定去除函数的方法操作复杂且成本很高,本文提出了利用法拉第杯对离子束流空间分布进行测量、标定的方法,并计算得到不同离子源工作参数对应的去除函数。首先,基于离子束抛光材料去除原理,研究了离子束抛光过程中束流分布与能量对去除函数的影响,并提出简化的离子束抛光去除函数模型。然后,设计实验并得出离子束流空间分布与去除函数相关参数间的关系,计算得到了不同离子源工作参数产生的离子束流对应的去除函数。对硅和融石英玻璃的相关实验表明:利用法拉第杯扫描结果计算相同材料的去除函数的单位时间体积去除率与实际测量值误差小于2%。结合抛光实验,对Φ800mm碳化硅表面硅改性层平面镜进行抛光,得到的初始面形误差均方根(RMS)值为57.886nm,两次抛光后RMS值为11.837nm,收敛率达到4.89,满足精密光学加工对去除函数的确定性及精度的要求,并大大提升了确定去除函数的效率。     

Nano-abrasion machining of brittle materials and its application to corrective figuring

A method of ultraprecision abrasion machining named “Nano-abrasion machining” is proposed for optical finishing of brittle materials. The fundamental characteristics and its applicability for corrective figuring to improve form accuracy of optics of brittle materials are investigated. It is experimentally ascertained that the material removal rate and surface roughness are suitable for optical finishing. However, the cross-sectional profile of the machined spot that is dependent on the collision angle is a combination of V- and W-shape, which is unsuitable for the corrective figuring. Therefore, circular motion machining is introduced and a preferable profile with an axis-symmetric V-shape is realized. The machining method is applied to corrective figuring of optical glass of BK7. The NC program is generated with a computer program developed by modifying the scanning motion and the form accuracy is predicted. According to the simulation results, corrective figuring is performed. The flatness is improved from PV = 151 to 29 nm. From the experimental results, it is clarified that the nano-abrasion machining is applicable to corrective figuring of brittle materials.     

Deconvolution improves colocalization analysis of multiple fluorochromes in 3D confocal data sets more than filtering techniques

Background and noise impair image quality by affecting resolution and obscuring image detail in the low intensity range. Because background levels in unprocessed confocal images are frequently at about 30% maximum intensity, colocalization analysis, a typical segmentation process, is limited to high intensity signal and prone to noise‐induced, false‐positive events. This makes suppression or removal of background crucial for this kind of image analysis. This paper examines the effects of median filtering and deconvolution, two image‐processing techniques enhancing the signal‐to‐noise ratio (SNR), on the results of colocalization analysis in confocal data sets of biological specimens. The data show that median filtering can improve the SNR by a factor of 2. The technique eliminates noise‐induced colocalization events successfully. However, because filtering recovers voxel values from the local neighbourhood false‐negative (‘dissipation’ of signal intensity below threshold value) as well as false‐positive (‘fusion’ of noise with low intensity signal resulting in above threshold intensities), results can be generated. In addition, filtering involves the convolution of an image with a kernel, a procedure that inherently impairs resolution. Image restoration by deconvolution avoids both of these disadvantages. Such routines calculate a model of the object considering various parameters that impair image formation and are able to suppress background down to very low levels (< 10% maximum intensity, resulting in a SNR improved by a factor 3 as compared to raw images). This makes additional objects in the low intensity but high frequency range available to analysis. In addition, removal of noise and distortions induced by the optical system results in improved resolution, which is of critical importance in cases involving objects of near resolution size. The technique is, however, sensitive to overestimation of the background level. In conclusion, colocalization analysis will be improved by deconvolution more than by filtering. This applies especially to specimens characterized by small object size and/or low intensities.     

全频段亚纳米精度氟化钙材料加工

考虑用CaF_2材料制作投影光刻物镜可以明显提高其性能指标,本文研究了CaF_2材料加工工艺的全流程,以实现CaF_2材料的全频段高精度加工。首先,利用沥青抛光膜和金刚石微粉使CaF_2元件有较好的面形和表面质量。然后,优化转速、抛光盘移动范围、压力等加工工艺参数,并使用硅溶胶溶液抛光进一步降低CaF_2元件的高频误差,逐渐去除加工中产生的划痕并且获得极小中频误差(Zernike残差)和高频粗糙度。最后,在不改变CaF_2元件高频误差的同时利用离子束加工精修元件面形。对100mm口径氟化钙材料平面进行了加工和测试。结果表明:其Zernike 37项拟合面形误差RMS值可达0.39nm,Zernike残差RMS值为0.43nm,高频粗糙度均值为0.31nm,实现了对CaF_2元件的亚纳米精度加工,为研发高性能深紫外投影光刻物镜奠定了良好基础。     

Observation of the ion-mirror effect during microscopy of insulating materials

Utilizing the ion beam of a focused ion beam (FIB)/scanning electron microscope (SEM) microscope to investigate non‐conductive samples, we observe a mirror image very much similar to the one that is commonly obtained with the electron beam and the same samples. To our knowledge this is the first observation of what can be called ‘Ion‐Mirror Effect’. This effect is produced by a positive charging of the sample obtained by rastering with high‐energy ions (30 kV) and a subsequent imaging with low energy ones (5 kV). The proposed explanation is that first a positive charge is trapped within the sample and eventually the lower energy ions are deflected back by the latter, and hit the surface of the microscope chamber very similar to what happens in the ‘Electron‐Mirror Effect’. The mirror image is produced after detection of the electrons produced by the interaction between ions and the chamber materials.     

Dual-beam stealth laser dicing based on electrically tunable lens

In this paper, we present the development of a high-speed dual-beam stealth laser dicing (D-SLD) method for processing semiconductor wafers based on electrically tunable lenses (ETLs). An SLD system utilizes a laser beam to dice a wafer by inducing interior defects without modifying the surface characteristics of a wafer, thereby presenting significant advantages over conventional dicing methods, e.g., blade dicing or laser ablation. Currently, the throughput of SLD is limited by the serial scanning process; in addition, wafer misalignment and the warpage effects together deteriorate the dicing quality and yield and demand high-cost multi-axis precision stages. To address the issue, we parallelize the dicing process by splitting the laser focus into two foci, where the laser intensity at different depths are automatically adjusted to achieve optimal dicing condition. By combining the height sensor and ETLs, each laser focus, i.e., laser scan lines, can be rapidly controlled axially to compensate the wafer curvature and misalignment errors in real time, leading to substantially improved precision (kerf width < 2 μm) and speed, demonstrated by our experimental results. The new dual-beam laser dicing system presents an effective solution for high-speed wafer dicing as well as other important engineering applications, e.g., fabrication of micro-devices and optical components.     

A swing arm method for profile measurement of large optical concave surfaces in the lapping process

Generally, optical components are fabricated by grinding, lapping, and polishing. Usually, these processes take a long time to obtain high surface quality. Therefore, in the case of large optical components, on-machine inspection (OMI) is essential, because the workpiece is fragile and difficult to set up for fabricating and measuring. This paper describes a swing arm method for measuring the surface profile of large optical concave mirrors. The measuring accuracy and uncertainty for the method are studied. Experimental results show that this method is especially useful in the lapping process, where an accuracy of 3–5 μm is obtained. Inspection data is also provided to correct the residual figuring error in lapping or polishing processes .     

Tool removal function modeling and processing parameters optimization for bonnet polishing

Since computer controlled optical surfacing (CCOS) processes were proposed in the 1960s, many processes were developed for precision optics successfully. In this present work, a novel approach, the precessions process, is proposed and used for large segments fabrication. The removal function of the bonnet polisher based on velocity and pressure distribution, which are obtained from the geometry of the process tool-motion and Hertzian contact theory respectively, are simulated. A finite element analysis (FEA) model is constructed to optimize process parameters. At last, detailed experimental studies are carried out to verify the optimal parameters.