Ultrafast Direct Ablative Patterning of HOPG by Single Laser Pulses to Produce Graphene Ribbons

Ultrafast, single step and direct patterning of highly oriented pyrolytic graphite (HOPG) is achieved through pulsed laser interference ablation using a near field transmitting phase mask. Periodic arrays of lines are patterned on the HOPG surface over large areas by spatially modulating the laser intensity through the mask. Thus patterned surface serve as a source for multi and few layer graphene ribbons for transferring onto desired substrates using polydimethylsiloxane as transferring agent. The transferred regions are contained with few layer graphene (5–6 layers) ribbons as well as thick graphitic ribbons (30–40 nm), with widths ～1 μm and lengths of several micrometers. Raman, TEM and electrical measurements have confirmed that the transferred ribbons are highly crystalline in nature. Using combinations of shadow and transmitting phase masks, other patterns such as checker boards and diamond‐shaped pits are produced.     

248 nm KrF准分子激光零级抑制石英相位掩模器的研制

实验研制了针对波长２４８ｎｍＫｒＦ准分子激光的零级抑制石英相位掩模器。用双层掩蔽和图形转移技术，在双面抛光的石英基片上以ＣＨＦ３／Ｏ２为反应气体，用反应离子刻蚀技术制作了具有良好完整性、周期１．０８５μｍ的石英相位掩模器。实际测量表明其零级衍射效率被抑制到５．９７％。     

A new approach for eliminating unwanted patterns in attenuated phase shift masks

A new approach is identified to eliminate unwanted patterns in high transmission phase shift masks to achieve useful patterning across pitch. A sub-resolution structure is added to the reticle where the propensity of unwanted pattern is found to be maximum. This sub-resolution feature is fully transmitting and has a phase opposite to that of the background. Simulations prove that the light from this feature is successful in nullifying the background intensity responsible for producing the unwanted patterns, while the radiation coming out of the added feature itself gets cancelled and there is no resulting aerial image intensity at the location of the main feature. This technique will help patterning at dense (side lobe prone) pitches even for high transmission masks. Also, the mask-making process will be lot simpler than that of a ternary mask.     

Single mask dual damascene processes

Single mask dual damascene processes are described. The unique mask merges via and modified trench patterns. We design the mask’s trench area to have partial transmission using thin chromium or add phase shifted gratings in the trench area to achieve destructive interference for lowering the intensity. Optical proximity correction is used to obtain the desired lithography process window. Upon exposure, the trench results in a partial exposure while the via is fully exposed and a dual damascene (DD) photoresist profile is created within specifications. Following with an integrated etch can complete the DD image transfer into the underneath dielectric. A single mask DD process eliminates via/trench misalignment issues, can save up to one half of metal mask cost, and 50% of other processing costs. It is expected to also boost yield and improve product reliability.     

涡旋光用于物体面内位移变形测量的模拟

提出了一种利用涡旋光进行面内位移测 量的新方法。将传统的电子散斑干涉测量技术与液晶空间光调制器(SLM)相结合,把 利用SLM所 获得的涡旋光应用于双光路电子散斑干涉,从而测量变形物体的面内位移。推导出了以平面 光为物光、涡 旋光为参考光以及涡旋光为参考光、物光时物体发生面内变形前后的干涉强度公式, 模拟了变形前 后的干涉图样,分析了干涉变形图样的特征。运用四步相移方法求出了物体的变形相位公式 ,通过解包裹得 到了物体的变形相位。模拟结果与利用传统电子散斑干涉测量系统结合傅里叶变换法 获得面内位 移的变形相位分布是一致的,表明涡旋光可以应用于物体的变形测量,为物体面内位移变 形测量提供了一种新途径。     

64×64点阵达曼光栅的设计与实现

分析了偶数点阵达曼光栅的设计原理与特性。利用数值优化方法 ,获得了一组 6 4× 6 4点阵达曼光栅解。光栅模版用电子束制版法制成 ,其最细线宽为 2 .5 μm。用光刻法实现了这一位相光栅 ,并比较了不同位相光栅制作法的优缺点。原子力显微镜测得的光栅深度曲线与 6 4× 6 4点阵实验结果表明 ,此光栅结果接近理论值。     

Position-only planar hexagonal array antenna pattern nulling with simultaneous side lobe reduction at multiple azimuth planes

This article presents a study on the placement of multiple nulls as well as minimization of side lobe level in the radiation pattern using a planar hexagonal antenna array structure in two different vertical planes. The desired null depth is achieved to suppress the interference signal by the position-only control of the uniformly excited isotropic antennas in the array structure. The immediate solution to the mentioned computational problem is reached by various meta-heuristic optimization algorithms such as teaching learning-based optimization (TLBO), symbiotic organism search (SOS), and moth fly optimization (MFO) within a considerably reduced processing time with a control over the design constrains. Various examples for diversified scenarios are demonstrated to place multiple deep nulls in the radiation pattern without compromising the pattern constraints and all other radiation pattern characteristics. This experiment sought to illustrate and quantify the unique benefits and limitations of proposed technique using three considered meta-heuristic optimization algorithm.     

248 nm imaging photolithography assisted by surface plasmon polariton interference

A new photolithography technique for 248 nm based on the interference of surface plasmon waves is proposed and demonstrated by using computer simulations.The basic structure consists of surface plasmon polariton（SPP）interference mask and multi-layer film superlens.Using the amplification effect of superlens on evanescent wave,the near field SPP interference pattern is imaged to the far field,and then is exposed on photo resist（PR）.The simulation results based on finite difference time domain（FDTD）method show that the full width at half maximum（FWHM）of the interference pattern is about 19 nm when the p-polarization light from 248 nm source is vertically incident to the structure.Meanwhile,the focal depth is 150 nm for negative PR and 60 nm for positive PR,which is much greater than that in usual SPP photolithography.     

电子束图形分割程序FDEB

电子束图形分割程序FDEB将CAD系统产生的原始图形分割成不相交的几种基本图形,以适应电子束曝光机制作细线条IC版的需要。本文介绍了图形分割的主要算法以及场划分和曝光路径优化的方法。     

Double-dipole mask-synthesis using inverse lithography technology

Double-dipole lithography (DDL) uses two orthogonal dipole illuminations and one or two masks to print the desired wafer pattern. The main challenge of using such IC-manufacturing technique remains how to properly synthesize the proper mask patterns for the arbitrarily given target pattern. This paper presents a gradient-based inverse lithography technology (ILT) addressing the problem above. This approach properly models the partially coherent imaging system by employing the double-dipole lithography, and then uses the steepest descent method to automatically synthesize the masks required to print the desired wafer pattern. We also present results for various kinds of masks for printing 45-nm critical dimension (CD) features. The results show that our algorithm automatically generates the synthesized masks and that the synthesized masks reduce the pattern distortion error (PDE) by 85-90%. The comparison with a single-exposure case indicates a superior improvement.     

利用背面曝光技术制造大高宽比SU8结构的一种新方法

提出了一种解决大高宽比SU 8结构的新方法.该方法是将SU 8胶涂在一块掩模上,紫外光从掩模的背面照射,这样SU 8胶的曝光将从底部开始,不需要进行过曝光来保证底部胶的曝光剂量,从而很容易控制曝光剂量和SU 8胶结构的内应力.实验结果表明,该方法能够得到高宽比为32的SU 8结构,而文献报道的SU 8胶结构的高宽比最大仅为18     

Patterning and Conductivity Modulation of Conductive Polymers by UV Light Exposure

A novel patterning technique of conductive polymers produced by vapor phase polymerization is demonstrated. The method involves exposing an oxidant film to UV light which changes the local chemical environment of the oxidant and subsequently the polymerization kinetics. This procedure is used to control the conductivity in the conjugated polymer poly(3,4‐ethylenedioxythiophene):tosylate by more than six orders of magnitude in addition to producing high‐resolution patterns and optical gradients. The mechanism behind the modulation in the polymerization kinetics by UV light irradiation as well as the properties of the resulting polymer are investigated.     

利用背面曝光技术制造大高宽比SU8结构的一种新方法

提出了一种解决大高宽比SU8结构的新方法.该方法是将SU8胶涂在一块掩模上,紫外光从掩模的背面照射,这样SU8胶的曝光将从底部开始,不需要进行过曝光来保证底部胶的曝光剂量,从而很容易控制曝光剂量和SU8胶结构的内应力.实验结果表明,该方法能够得到高宽比为32的SU8结构,而文献报道的SU8胶结构的高宽比最大仅为18.     

期望主瓣响应下任意阵方向图综合方法

为实现任意阵列天线的方向图综合,特别是考虑到不同空间指向对阵列方向图的影响,提出自适应原理与凸优化理论相结合的方向图综合法.该方法首先利用自适应原理综合法得到所需阵列方向图的旁瓣特性;而后,选择零度角的方向图主瓣作为期望主瓣;最后,在该期望主瓣响应下,将阵列方向图综合问题转化为二阶锥规划问题.采用凸优化循环迭代算法,完成对非凸优化问题的求解,从而保证方向图在满足期望主瓣响应的同时,使旁瓣特性与自适应方向图综合方法得到的结果最接近.理论分析与仿真结果表明,综合后阵列方向图在不同空间指向上具有与期望主瓣一致的主瓣特性,且其旁瓣也能够很好地保持对动态干扰的抑制特性.     

基于凸投影算法的多相位掩模设计原理研究

根据所需光刻图形的分布,反推掩模结构的思路,提出了一种基于交替投影算法的掩模设计方法。该方法设计出的掩模为振幅和相位连续。并给出了一个设计实例和量化方法。实验结果表明该方法对复杂相移掩模的设计有效,可以减小邻近效应。     

A hybrid computational model for ultrasound phased-array heating inpresence of strongly scattering obstacles

A computationally efficient hybrid ray-physical optics (HRPO) model is presented for the analysis and synthesis of multiple-focus ultrasound heating patterns through the human rib cage. In particular, a ray method is used to propagate the ultrasound fields from the source to the frontal plane of the rib cage. The physical-optics integration method is then employed to obtain the intensity pattern inside the rib cage. The solution of the matrix system is carried out by using the pseudo inverse technique to synthesize the desired heating pattern. The proposed technique guides the fields through the intercostal spacings between the solid ribs and, thus, minimal intensity levels are observed over the solid ribs. This simulation model allows for the design and optimization of large-aperture phased-array applicator systems for noninvasive ablative thermal surgery in the heart and liver through the rib cage     

Investigation of the Photoresist Pattern Profile Contrast Improvement in Interference Lithography Technique Using 488-nm Laser

The interference lithography technique at 488 nm is explored theoretically and experimentally, and the effect of photoresist pattern profile contrast improvement is presented. In order to produce high contrast photoresist patterns using interference lithography, the system setup and process have to be optimized strictly, and process optimization can be facilitated by simulation. In the proposed simulation method, the absorption coefficient of photoresist varying with wavelength is considered by using photoresists with lower absorption coefficients, or, for the same photoresist, using laser sources with longer wavelengths. The visibility of aerial fringe patterns of the photoresist can be improved greatly. However, after developing, the contrast of photoresist patterns was not improved. The reason is that the photo sensitivity and etching rate V of photoresist decrease at 488 nm. This offsets the effect of lower absorption coefficients even though a 488-nm argon ion laser source is useable for some photoresists. This opens up a new window for the interference lithography technique.      

Optimization of photomask design for reducing aberration-induced placement error

In semiconductor manufacturing, the accurate placement of circuit components ensures the proper functioning of microelectronic circuits. This is often subject to photolithography, an optical technique that transfers circuit patterns from photomasks to silicon wafers. Sources of placement error include aberration and misalignment between different levels, and we focus on the former. Aberration is an optical phenomenon that often degrades imaging system performance. Since aberration differs from one imaging system to another, a photomask design that minimizes the aberration-induced placement error is desired. In this paper, we discuss the optimization process of a general one-dimensional mask pattern under a general illumination condition. The constraint is a known population mean of the root mean square aberrations for the imaging systems under consideration. To apply the theory, we search for the optimal parameters for two common mask designs: alternating phase-shifting masks (PSMs) and attenuated PSMs. The theoretical results are compared with those from a Monte Carlo analysis on a large set of imaging systems. These results are indicative to mask manufacturers and circuit designers of increasing manufacturability of circuits.     

Generation of a single-lobe radiation pattern from a phased-array laser using a near-contact variable phase-shift zone plate

A very simple and practical technique to generate a stable, narrow-angle single-lobe far-field radiation pattern from an ordinary twin-lobe phase-locked laser diode array is demonstrated. A variable phase-shift zone plate mounted close to the laser output facet is used to readjust the phase distribution of the array into an all-in-phase distribution producing the desired single narrow-lobe far-field pattern.     

A flexible array synthesis method using quadratic programming

A highly flexible synthesis method for an arbitrary array is proposed to best approximate a desired array pattern in a minimum-mean-square-error sense. The basic idea of the technique is to form a quadratic program with its cost function given by the mean-square error between the array response and a properly selected pattern described by a known mathematical function. This quadratic program can be a constrained or unconstrained optimization problem depending on the requirements of the desired array pattern. In formulating the quadratic program, no assumption has been made on the gain/phase response or characteristics of the individual array elements. Therefore, one can synthesize an array of arbitrary shape to any appropriate pattern with the characteristic of the array elements taken into consideration as long as one is able to model the array accurately. The proposed method is used to synthesize arrays of different shapes, linear as well as planar arrays (including rectangular and circular planar arrays), using a Chebyshev polynomial or zero function as a design template, to illustrate the feasibility of the proposed method