Calculation of the high-frequency diffraction by two nearby edges illuminated at grazing incidence

The uniform geometrical theory of diffraction (UTD) together with a generalized spectral extension arc applied to calculate the high-frequency scattering by two nearby edges illuminated at grazing incidence. Several examples arc considered which involve the diffraction by a pair of parallel edges where one edge is illuminated by the shadow boundary field of the other. Expressions for the diffracted field have been obtained for plane, cylindrical, and spherical wave illumination with either the electric or magnetic field perpendicular to the edges. Extensive numerical results are given for a pair of staggered parallel half-planes, a thick screen, and a rectangular cylinder. Comparisons with the results calculated by other techniques are also presented to demonstrate the accuracy of the method.     

Characterization of a photoresist with wavelength selected tone

The line edge profile simulation of a tone-switching resist system, obtained from the dissolution model of dual-sensitized, novolak-based resist in aqueous developer, is described. The model incorporates the actinic response of both a positive and a negative sensitizer in a two-pattern lithographic process that simultaneously exposes the same resist film. These response data are combined with dissolution rate measurements to establish a model for the resist and carry out SAMPLE simulation of resist line edge profiles for contact and projection printing. The model predictions are compared with SEM micrographs of exposed resist features     

Preparation of Metallic Films on Elastomeric Stamps and Their Application for Contact Processing and Contact Printing

The formation of permanent or reversible metallic patterns on a substrate has applications in microfabrication and analytical techniques. Here, we investigate how to metallize an elastomeric stamp, either for processing of a substrate mediated by the proximity between the metal on the stamp and an active layer on the substrate, or for contact printing of the metal from a stamp to a substrate. The stamps were made from poly(dimethylsiloxane) (PDMS) and were modified before metallizing them with Au by adding to or removing from their bulk mobile silicone residues, by oxidizing their surface with an O₂‐plasma, by surface‐fluorination via silanization, or by priming them with a Ti layer. The interplay between the adhesion of the different layers defines two categories of application: contact processing and contact printing. Contact processing corresponds to keeping the metal on the stamp after contacting a substrate; it is reversible and nondestructive, and useful to define transient electrical contacts or quench fluorescence on a surface, for example. Contact printing occurs when the metal on the stamp adheres to the printed surface. Contact printing can transfer a metal, layers of metals, or an oxide onto a substrate with submicrometer lateral resolution. The transfer can be total or localized to the regions of contact, depending on the morphology of the metal on the stamp and/or the surface chemistry of the substrate.     

Diffraction of cylindrical and plane waves by an array of absorbinghalf-screens

Multiple forward diffraction past an array of many absorbing half-screens whose separation is large compared to wavelength is examined. Starting with the physical optics approximation for half-planes that are equally spaced and of equal height, the field incident on successive edges is represented by a multidimensional Fresnel integral, which is then expanded into a series of functions studied by Boersma (1978). When the angle of incidence with respect to the plane containing the edges is small, each edge is in the transition region of the previous edge, which precludes the use of the geometrical theory of diffraction and related asymptotic theories. The solution obtained applies for incidence either from above or below the plane containing the edges, and is especially suited to the case of near-grazing incidence. This method of solution allows for numerical evaluation of a large number of half-screens and shows how the multiple diffracted fields are influenced by the physical parameters. Both incident plane waves and incident cylindrical waves can be treated     

Ohmic contacts formation of silicon schottky diodes by screen printing and rapid isothermal processing

Rapid isothermal processing based on incoherent radiation as the source of optical and thermal energy is playing a major role in flexible fast-cycle time integrated circuits manufacturing. In this paper, we present the dark and illuminated current-voltage characteristics of silicon Schottky barrier diodes where the ohmic contacts are formed by screen printing and rapid isothermal annealing. These results are compared with evaporated contacts followed by furnace annealing or rapid isothermal annealing. In this paper, we have shown that the ohmic contacts formed by screen printing and rapid isothermal annealing are compatible with the contacts formed by evaporation process. The processing time of the screen printed ohmic contacts is significantly lower than the contacts formed by evaporation process.     

Coherent optical processing

The principles of communication theory were applied in the 1950's to optical imaging systems and to the analysis of images. Optical systems were analyzed in much the same way as linear systems (modulation transfer functions and channel capacities) and images were characterized in ways analogous to time signals (space-bandwidth products, spatial frequency content, etc.). Both coherently and incoherently illuminated optical systems can be treated using these concepts. Coherently illuminated systems are most useful for performing operation such as convolution, cross correlation, and spectral analysis because the Fourier transform of an optical signal physically exists and can, therefore, be measured or modified. The basic Fourier transform relationship for coherently illuminated systems is developed in this paper. It can be detected directly and used to estimate the distribution of spatial frequencies contained in the signal. Methods for constructing complex-valued spatial filters are described; these filters can be used to realize such operations as convolution or cross correlation, addition or subtraction, and differentiation or integration. Experimental results are given to illustrate the concepts and to susgest potential applications. To extend the range of applications, interface devices are needed to allow optical processing of two-dimensional raster-scanned time signals, wide bandwidth electrical signals, and incoherent optical signals. Interface devices are often needed to convert the output optical signal to an electrical signal for post-processing by a digital computer. For some applications, interface devices are needed to construct spatial filters in real time, so different operations can be performed on a given signal. The desired characteristics of these three interface devices and the current state of their development are briefly reviewed.     

Shorter-wavelength lithography utilizing MRS-type negative resists

New negative photoresists, called MRS-type resists, are successfully applied to deep-UV 1:1 projection printing and 365 nm 10:1 reduction projection printing. The MRS-type resists are characterized by intense absorption of exposure light and absence of swelling in aqueous developer solutions. They resolve steep profile submicron images in a 1.0 μ thick film. They are not adversely affected by reflected light from water surfaces. In order to use MRS-type resists with broader development latitude, optimizing the extent of light absorption is important because the resist profiles strongly depend on development conditions due to increasing solubility towards the resist bottom.     

三维物体菲涅耳计算全息图的研究

介绍一种用计算全息显示三维物体的方法.记录三维物体在非相干白光照明条件下两个正交方向上不同视角的一系列连续二维像,根据计算机断层成像原理,由这些二维像计算出物体的三维傅立叶频谱,从中提取出一特征傅立叶频谱,用卷积算法计算出在一定传播距离处的菲涅耳衍射分布,用计算全息编码方法制出一张菲涅耳计算全息图,并进行模拟再现,给出了不同再现距离处的再现像.     

Pathways in device lithography

A brief review is given of approaches to lithography for microdevice fabrication. Exposure systems in common use, as well as those in development, are described and assessed. These include contact and proximity printing, stationary and scanning projection printing, step-and-repeat reduction printing, scanning electron beam systems, electron imaging systems, and X-ray systems.     

秩和非参数检测器在杂波边缘中的性能

人们常用Rohling教授提出的3种典型背景即均匀背景、多目标和杂波边缘来对检测器的恒虚警率(CFAR)性能进行衡量,但在现有的文献中缺乏秩和(RS)非参数检测器在杂波边缘中虚警概率的解析表达式,缺乏RS检测器与经典的参量型恒虚警率(CFAR)检测器在杂波边缘中虚警控制能力的比较,这在理论研究上是不完整、不全面的。该文给出了RS检测器在杂波边缘中虚警概率的解析表达式,并比较了它与非相干积累单元平均(CA),选大(GO)和有序统计(OS)恒虚警方法在杂波边缘中的虚警控制能力。可以看出,在强、弱杂波均为瑞利分布的情况下,RS检测器在杂波边缘的虚警控制能力处于非相干积累CA方法和非相干积累OS方法之间。但是当长拖尾分布的非高斯杂波进入参考滑窗时,非相干积累CA, GO和OS参量型检测方法的虚警概率都产生了3个以上数量级的上升,且不能回到原始设定的虚警概率。而RS检测器显示出了非参量检测器的优势,即当杂波背景的分布类型发生变化后,它仍然可以保持虚警概率的恒定。     

Detection of edges from projections

In a number of applications of computerized tomography, the ultimate goal is to detect and characterize objects within a cross section. Detection of edges of different contrast regions yields the required information. The problem of detecting edges from projection data is addressed. It is shown that the class of linear edge detection operators used on images can be used for detection of edges directly from projection data. This not only reduces the computational burden but also avoids the difficulties of postprocessing a reconstructed image. This is accomplished by a convolution backprojection operation. For example, with the Marr-Hildreth edge detection operator, the filtering function that is to be used on the projection data is the Radon transform of the Laplacian of the 2-D Gaussian function which is combined with the reconstruction filter. Simulation results showing the efficacy of the proposed method and a comparison with edges detected from the reconstructed image are presented.     

Inkjet printed dielectrics for electronic packaging of chip embedding modules

The inkjet printing of a dielectric layer as part of an assembling process for a semiconductor device was evaluated. This layer embeds a chip so that a space-saving package with surface conformal conductive paths instead of wire bonds can be designed. Three different polymer solutions were tested whereas the polyimide ink is favored due to the high thermal stability and dielectric strength of the printed layer. By multiple printing of dielectric layers on top of each other a sufficient layer thickness and cover of the chip edges as well as accurate contact holes can be realized.     

一种基于t图的多尺度边缘检测方法

在多尺度边缘检测方法中，滤波器的滤波尺度的选取是关键，本文通过检验一给定像素邻域的灰度分布来判断此像素是否位于平滑区，并产生一幅五维向量图－t图，然后根据t图自适应地选取小波变换的尺度。实验结果表明，应用这种方法进行多尺度小波边缘检测具有较强的抗噪能力。     

一种成倒像投影关系的非相干光相关器

提出了一种新型成倒像投影关系的非相干光相关器,这种相关器具有便于校准输出平面位置的优点.使用傅里叶光学理论对这种相关器相关输出图样进行了仿真实验.结果表明,这种相关器和其他非相干光相关器的相关输出质量相同.对于相关峰展宽的仿真分析表明,虽然这种相关器具有低通特性,它的适用范围仍然比较广泛.     

On the cascade of incoherent discrete-time microwave photonic filters

In this study, a theoretical analysis leading to the derivation of the overall incoherent transfer function of a microwave photonic filter composed of the cascade of two optical structures is developed. Two cases that are more common in practice are considered, i.e., 1) a filter illuminated by a single optical source and 2) a compound filter illuminated by an optical source array. In both cases, the conditions on which the overall incoherent transfer function can be expressed as the product of the individual incoherent transfer functions of each of the optical structures that compose the filter are investigated. In other words, the conditions where the end-to-end electrical linearity is preserved when cascading incoherent optical structures are studied. These results are of importance for the design of complex incoherent filter structures aiming to provide high Q or single resonance performance.     

Corner diffraction coefficients for the quarter plane

The current near a right-angled corner on a perfectly conducting flat scatterer illuminated by a plane wave is expressed as a sum of three currents. The first is the physical optics current, which describes the surface effect. The second is the fringe wave current, which is found from the half-plane solution and accounts for the distortion of the current caused by the edges. The third is the corner current, which is found from the numerical solution to the electric-field integral equation applied to the square plate, and accounts for the distortion of the current caused by the corner. It is found that the corner current for the right-angled corner, illuminated from a forward direction, consists mainly of two edge waves propagating along the edges forming the corner. Analytical expressions for these edge wave currents are constructed from the numerical results. A corner diffracted field is calculated by evaluating the asymptotic corner contributions to the radiation integral over the sum of the three currents. It is found that the corner contribution from the edge wave currents in some cases is of the same size as the corner contributions from the physical optics current and the fringe wave current     

Improved Physical Theory of Diffraction: Removal of the Grazing Singularity

Physical theory of diffraction based on the concept of elementary edge waves [P. Ya. Ufimtsev, Electromagnetics, vol. 11, no. 2, pp. 125–160, 1991] is well suited for analysis of backscattering from perfectly conducting objects with edges. However, it needs to be improved for the investigation of forward scattering, especially in the directions grazing to the edge faces, where it predicts infinite values. The present paper removes this singularity by introducing a new definition for the uniform component of the surface current. This component is defined here as the current induced on the half-plane tangential to the illuminated face of the scattering edge (and to the edge itself). The improved theory of elementary edge waves is developed, which is valid for all scattering directions, including forward scattering.     

Reflector antenna radiation pattern analysis by equivalent edge currents

Equivalent edge currents, derived from the edge diffraction theory for a half-plane, are used to obtain the radiation patterns of a parabeloidal reflector antenna when illuminated by a source at the focus. Cylindrical wave diffraction coefficients are used. The method avoids infinities at caustics and shadow boundaries thus giving solutions which are finite everywhere. A slope-wave equivalent current correction term is applied when the illumination is tapered towards the edge of the reflector. Comparisons are given with the physical optics approach and experimental results.     

Plates and edges

The backscattering from a rectangular plate at edge-on incidence is due essentially to the individual contributions from the front and trailing edges. The contribution of the front edge is analogous to that of a wire illuminated by a plane wave, but the rear edge excitation is almost wholly determined by current waves along the side edges of the plate.