X射线干涉光刻光束线偏转镜系统的设计与测试

介绍了上海光源X射线干涉光刻（XIL）光束线的基本情况。为实现光束线的光束偏转和光路切换,完成了其偏转镜系统的研制。分析了偏转镜系统的功能,设计了偏转镜的调节机构、切换机构和冷却结构。论述了调节机构的关键运动,即镜箱外直线运动转化为超高真空内旋转运动的实现过程;讨论了切换机构重复精度与承载能力之间的关系,并完成了精密丝杆的校核。采用镜子支撑方式和冷却方式集成的方案设计了冷却结构,并通过数值模拟分析了冷却结构和冷却效果。模拟结果表明镜子子午面形误差和弧矢面形误差分别约为6.5rad和7rad。应用激光干涉仪和光电自准直仪对调节机构和切换机构进行了测试,结果表明：调节机构的线性分辨力可达0.2μm,切换机构的重复精度满足设计要求。     

X射线干涉光刻光束线关键光学元件热-结构耦合分析

为了保证上海光源X射线干涉光刻光束线的稳定性,减小热变形对实验结果的影响,对X射线干涉光刻光束线的3个关键光学元件——偏转镜、聚焦镜和精密四刀狭缝进行热-结构耦合分析。首先,计算偏转镜、聚焦镜和精密四刀狭缝所承载的功率密度;然后,建立其有限元模型;最后,获得光学元件的温度场和热变形的结果。结果表明,偏转镜和聚焦镜采用间接水冷方式可有效抑制热变形,冷却后的最大面形误差分别为7.2μrad和9.2μrad。精密四刀狭缝未冷却时,刀片组件温度介于271.56~273.27℃,刀口热变形为0.19 mm,直线导轨热变形为0.08 mm;经过铜辫子冷却后,刀片组件温度降至22.24~23.94℃,刀口热变形降至0.2μm,直线导轨热变形降至0.1μm;采用影像法和接触探头法测试后,刀口直线度、平行度和重复精度均满足技术要求。偏转镜、聚焦镜和精密四刀狭缝的热变形通过间接水冷和铜辫子的冷却方式可以得到很大程度的抑制,进而保证光斑质量。     

类镍钽软X射线激光用多层膜反射镜的研制

设计并制备了工作波长为4.48 nm类镍钽软X射线激光用多层膜反射镜。选择C r/C、C r/Sc为多层膜材料对,模拟了多层膜非理想界面对多层膜反射率的影响。采用直流磁控溅射技术在超光滑硅基片上制备了C r/C、C r/Sc多层膜。利用X射线衍射仪测量了多层膜结构,在德国Bessy II同步辐射上测量了多层膜的反射率,C r/C,C r/Sc多层膜峰值反射率分别为7.50%,6.12%。     

聚甲基丙烯酸甲酯材质硬X射线组合Kinoform透镜的制作

为提高硬X射线聚焦元件的聚焦性能,利用LIGA(Lithographie,Galvanoformung,Abformung)技术,制备了深度为60μm的聚甲基丙烯酸甲酯(PMMA)材质硬X射线组合Kinoform透镜(CKL),并获得了良好的面形。制备的CKL以宽度为几个微米的细窄线条为主要结构,包括曲面和直角面形,线条最窄宽度为2μm。为保证CKL良好的曲面及直角结构,样品制备分为三部分:过渡掩模板的制备,LIGA掩模板的制备,以及最终样品的硬X射线曝光制备。在LIGA掩模板制备过程中,采用制备有纳米柱阵列的硅衬底有效解决了光刻胶脱胶的问题。在最终样品制备过程中,选用分子量较高的PMMA片作衬底,提高了PMMA刚度,有效缓解了细窄线条的倒塌黏连问题,保证了CKL的良好面形。在北京同步辐射光源(BSRF)成像站测试了CKL透镜的性能,结果显示其对于8keV的X射线,聚焦焦斑的半高全宽(FWHM)为440nm。     

掠入射X射线散射法测量超光滑表面

介绍了掠入射X射线散射法(GXRS)测量超光滑表面的原理及商业用X射线衍射仪改造而成的实验装置。选择微晶玻璃、蓝宝石以及三片不同粗糙度的硅片作为实验样品。根据一级矢量微扰理论对各个样品所测量的散射分布进行处理。结果表明：GXRS法得到的样品功率谱密度函数(PSD)与使用原子力显微镜(AFM)所测量的结果基本相符。分析了探测器接收狭缝的宽度和入射光发散度对实验结果的影响。分析结果表明：当其他实验条件理想的情况下,探测器接收狭缝宽度小于0.02mm和入射光发散度小于43\"时,在空间频率大于0.03μm-1的范围内,由其引起的PSD函数测量误差都小于2%。随着探测器接收狭缝宽度和入射光发散度的减小,测量误差呈指数迅速减小。在所测量的空间频率范围内,PSD函数的误差随频率的增加而减小。     

X射线诱导俄歇电子能谱(XAES)的应用

简要介绍X射线诱导俄歇电子能谱(XAES)用于化学分析的一般性理论。XAES可与X射线光电子能谱(XPS)一起用于元素化学态分析。但是XAES分析有其优势,(1)俄歇参数与荷电位移无关,结果无需荷电校准就可用于价态分析;(2)在一些涉及过渡元素和重元素物质的价态分析时,XAES峰化学位移大于XPS峰;(3)对于分析一些轻元素(如K、Mg、Al等),XAES峰比某些XPS峰有更高的灵敏度。因而,XAES可弥补XPS分析的某些不足,可方便、有效地表征元素价态。通过实例,介绍XAES在这3个方面的实际应用。     

基于多层膜的软X射线偏振测量

综述了过去10年中德国BESSY同步辐射装置在软X射线偏振测量方面所做的工作。在BESSY同步辐射装置中,有10条椭圆波动器光束线,这可使同步加速器辐射的偏振态从线偏振光(水平或者垂直)转变为左旋或右旋圆偏振光。由于很多偏振敏感实验(例如,MCD光谱测量)需要归一化量,因此对偏振度进行量化非常重要。对于偏振实验,即对光的偏振态测量来说,需要两个光学元件分别起相位片和检偏器作用。因此,专门研制了在软X射线区有透射和反射功能的多层膜,并对其做了优化。通过使多层膜参数(周期,厚度比)与构成材料的吸收边相匹配,即可获得共振加强的偏振灵敏度。由此可知,基于多层膜的偏振测量与这些偏振光学元件工作波长处性能测量密切相关,文中对仪器的设置和测试结果做了介绍,同时给出了磁性薄膜或光活化物质的磁光光谱测量和偏振测量的示例(法拉第和克尔效应)。     

新型X光成像系统及其性能分析

本文设计了新型的X光成像系统，它的核心部件X光影像增强器是一个混合型器件。该成像系统具有数字化、大视野成像和可移动的优点，成像视野在6-15英寸连续可调。在文中，对这种新型成像系统的成像性能进行了定量的评价，并给出了系统所成的图像。结果表明新型X光成像系统的性价比高，可以广泛应用在机场安检、工业探伤、无损检测等领域。     

用X射线晶片分析器同时测定硅片上薄膜的厚度及组成

晶片专用X射线荧光分析装置在半导体工业中被用于多种工程的评价。在半导体分析中XRF法的显著特征是能分析各种薄膜(氧化膜、硅化物膜、金属膜等);能同时分析晶片上同一部位的膜厚及组成;XRF法是非破坏分析,因受化学键的影响不大,同一个试样可以反复使用。 厚度在400nm以上的掺硼磷硅玻璃(BPSG)膜的分析结果已做报道。近年,随着对半导体器件的高度集成化、高性能化(64 Mbit以上)要求的提高,希望能更准确地分析。作为有代表性的氧化膜——BPSG膜,为改善其在工程中的热处理特性,B_2O_3、P_2O_5的浓度控制是不可缺少的。为了满足这些要求,必须分析更薄的薄膜(300nm以下),在薄膜分析中的关键问题是B Kα背底的变动。 B分析的新光学系统改善了声噪比(S/N),使250nm以上的BPSG膜的分析成为可能。为了提高晶片分析器的性能,在装置上做了一些改良:真空度的稳定化;减轻污染的特制真空泵;分光室部分的恒温化。新的晶体分析器无论在短期或长期的测定,对10％B_2O_3的测定能做到1％的相对精度。 对在硅晶片上的钨硅化物的分析,不能使用W Lα及Si Kα两种谱线,而应使用W的两种谱线(浓度分析用W-N线,膜厚分析对用W-Lα线)。 膜厚测定的相对精度在0.2％以下,对于Si/W=2.5,摩尔比精度约0.015％(相对精度约为0.56％)。     

X-ray microscopy: experimental results with the Göttingen X-ray microscope at the electron storage ring BESSY in Berlin

An X-ray microscope and X-ray microscopy experiments with biological specimens are described. The experiments have been performed with a resolution of about 0.05 μm using the synchrotron radiation of the electron storage ring BESSY.     

Soft X-ray contact imaging of nucleolar chromatin using synchrotron radiation: a comparative scanning and transmission electron microscope study

Contact images (CI) of dehydrated, nucleolar chromatin from amphibian oocytes have been produced by soft X-rays from a synchrotron radiation source. These CI have been compared with the morphology of the original chromatin as seen in scanning and transmission electron microscopes. The quality and informational content of the CI depend very much on certain preparative procedures. The following factors have a marked effect on image quality and need to be carefully controlled: the total X-ray dose, the time and nature of development and the distance of the specimen from the photoresist. The preparation of the chromatin itself, providing that it is critically point dried, is less important. By following a regime of high X-ray dose, sufficient for penetration of the rather thick chromatin rings, and gentle development so that fine detail is not dissolved from the resist surface, it has been possible to obtain images which closely resemble the original chromatin, although the detailed resolution of the CI is not as clear. The smallest biological structures clearly resolved in the CI are ribonucleoprotein granules, which vary in size from 200 to 800 nm. However, by further refinement of preparative conditions it should be possible to improve on the informational content of these images.     

Optimization of a Wolter type I mirror for a soft X-ray microscope

The demand for an X-ray microscope has received much attention because of the desire to study living cells under high resolution. A Wolter type I mirror used for soft X-ray microscope optics has a number of advantages. Although much progress has been made, it is still not easy to fabricate this mirror and satisfy the surface roughness and figure error requirements. From the mirror fabrication point of view, it is necessary to see the mirror design and the tolerance budget, especially with respect to the surface roughness and the figure errors. This paper deals with the design and optimization of a Wolter type I microscope mirror. The optimization was carried out by choosing an optimum central grazing incidence angle for which a merit function had the maximum value. The image quality of the mirror was also examined. A smaller diameter gave better image quality because of the Abbe sine condition. Finally, the figure errors for the axial and the radial directions were simulated by sinusoidal deformation waves, and the figure tolerance was obtained.     

Soft X-ray microscopy with a cryo scanning transmission X-ray microscope: II. Tomography

Using a cryo scanning transmission X-ray microscope ( Maser, et al . (2000 ) Soft X-ray microscopy with a cryo scanning transmission X-ray microscope: I. Instrumentation, imaging and spectroscopy. J. Microsc . 197, 68–79), we have obtained tomographic data-sets of frozen hydrated mouse 3T3 fibroblasts. The ice thickess was several micrometres throughout the reconstruction volume, precluding cryo electron tomography. Projections were acquired within the depth of focus of the focusing optics, and the three-dimensional reconstruction was obtained using an algebraic reconstruction technique. In this first demonstration, 100 nm lateral and 250 nm longitudinal resolution was obtained in images of unlabelled cells, with potential for substantial further gains in resolution. Future efforts towards tomography of spectroscopically highlighted subcellular components in whole cells are discussed.     

Soft X-ray microscopy with a cryo scanning transmission X-ray microscope: I. Instrumentation, imaging and spectroscopy

We have developed a cryo scanning transmission X-ray microscope which uses soft X-rays from the National Synchrotron Light Source. The system is capable of imaging frozen hydrated specimens with a thickness of up to 10 μm at temperatures of around 100 K. We show images and spectra from frozen hydrated eukaryotic cells, and a demonstration that biological specimens do not suffer mass loss or morphological changes at radiation doses up to about 10¹⁰ Gray. This makes possible studies where multiple images of the same specimen area are needed, such as tomography ( Wang et al. (2000 ) Soft X-ray microscopy with a cryo scanning transmission X-ray microscope: II. Tomography. J. Microsc . 197, 80–93) or spectroscopic analysis.     

大型X射线光学仪器:单层镜和多层镜的制造与表征

150~500 mm长度的各种X射线光学元件可用于光束导引,光束调整,以及单色化。本文介绍了两种不同的大型X射线反射镜。第一种为单层反射镜,这种反射镜以2°掠入射角在软X射线区(50~200 eV)起全反射镜作用,可用于自由电子激光器,如德国汉堡的FLASH。第二种是多层镜,由于它的布喇格反射特性,适于作为反射镜以0.4~1°的入射角用于硬X射线区(20~50 keV),如层析光束线的同步辐射存储环中。两种反射镜都用最新物理汽相淀积法制备,并用磁控溅射来实现X射线光学应用所需要的优良光学品质。这一淀积工艺使不同批次的镀膜稳定性良好,有利于实际反射镜在优质衬底上的最后淀积。单层镜和多层镜在它们的相关能量范围内都有很高的反射率,表面粗糙度也很低,且在整个光学波长区这些特性表现均匀。文中所叙相关研究都是借助X射线反射计量(XRR)法,透射电子显微镜(TEM)、光学轮廓仪(OP),以及原子力显微镜(AFM)完成的。     

Measurement of potential distribution function on object surface by using an electron microscope in the mirror operation mode

The quantitative theory of image contrast in an electron microscope in the mirror operation mode is given in this paper. This theory permits us to calculate the potential distribution on the object surface from the current density distribution on the microscope screen. The potential distribution results in image formation on the screen. Local electric fields existing on the object surface lead to a perturbation of electron trajectories above the object and to a redistribution of the current density on the screen, causing image contrast. Using the quantitative correlation between these fields and the function of current density distribution on the screen, it is possible to calculate the magnitude of these microfields as well. As illustration, a measured potential distribution on an object surface with spiral structures of adsorbates was analysed. These structures are formed during reaction of CO oxidation on Pt(110). The value of the measured contact potential difference comprised a few hundredths of volt.     

多种材料软X光平面镜反射率标定

利用北京同步辐射装置(BSRF) 3W1B束线及反射率计靶室,在束流强度40～120mA、贮存环电子能量2GeV专用光运行模式下,做了不同材料掠入射平面镜反射率标定实验。标定过程用高灵敏度无死层的硅光二极管代替X射线二极管(XRD)作探测器,使输出信号提高2～3个量级,可标定能区从150～270eV拓展为50～1500eV能区,对C,Si和Ni材料平面镜给出完整的反射率标定曲线,最终把实验数据与理论计算比对并分析。     

A synchrotron X-ray study of the changes occurring in the corneal stroma during processing for electron microscopy

Using a high-intensity synchrotron X-ray source, the structural changes occurring in the corneal stroma were monitored during each stage of several different processing runs for the transmission electron microscope (TEM) and scanning electron microscope (SEM). The parameters studied were interfibrillar spacing, intermolecular spacing, D-periodicity and fibril diameter. The processing schedule that produced the least changes in spacings for TEM specimens involved extended fixation in glutaraldehyde followed by low-temperature embedding in Lowicryl K4M resin. However, interfibrillar material was better preserved after embedding in LR White resin or Nanoplast. Almost every processing stage for electron microscopy produced significant changes in one or more structural parameters in the cornea. Glutaraldehyde fixation significantly increased the intermolecular spacings, while resin infiltration and resin polymerization each resulted in shrinkage of all the spacings monitored. Critical-point drying for SEM specimens resulted in considerable shrinkage in all three spacings, but was still preferable to air drying, which caused reduction in the order of the fibril packing, resulting in loss of the interfibrillar X-ray pattern. Perhaps the most drastic effect was caused by post-fixation in osmium tetroxide, which resulted in loss of the intermolecular pattern, and also increased the amount of shrinkage in the interfibrillar spacings and the D-periodicity which occurred during later stages of processing.     

Backscattered electron imaging of cultured cells: application to electron probe X-ray microanalysis using a scanning electron microscope

We report a simple method to study the elemental content in cultured human adherent cells by electron probe X-ray microanalysis with scanning electron microscopy. Cells were adapted to grow on polycarbonate tissue culture cell inserts, washed with distilled water, plunge-frozen with liquid nitrogen and freeze-dried. Unstained, freeze-dried cultured cells were visualized in the secondary and backscattered electron imaging modes of scanning electron microscopy. With backscattered electron imaging it was possible to identify unequivocally major subcellular compartments, i.e. the nucleus, nucleoli and cytoplasm. X-ray microanalysis was used simultaneously to determine the elemental content in cultured cells at the cellular level. In addition, we propose some improvements to optimize backscattered electron and X-ray signal collection. Our findings demonstrate that backscattered electron imaging offers a powerful method to examine whole, freeze-dried cultured cells for scanning electron probe X-ray microanalysis.