Real-time generation of circular patterns in electron beam lithography

Electron beam lithography(EBL)involves the transfer of a pattern onto the surface of a substrate byfirst scanning a thin layer of organicfilm(called resist)on the surface by a tightly focused and precisely controlled electron beam(exposure)and then selectively removing the exposed or nonexposed regions of the resist in a solvent(developing).It is widely used for fabrication of integrated cir-cuits,mask manufacturing,photoelectric device processing,and otherfields.The key to drawing circular patterns by EBL is the graphics production and control.In an EBL system,an embedded processor calculates and generates the trajectory coordinates for movement of the electron beam,and outputs the corresponding voltage signal through a digital-to-analog converter(DAC)to control a deflector that changes the position of the electron beam.Through this procedure,it is possible to guarantee the accuracy and real-time con-trol of electron beam scanning deflection.Existing EBL systems mostly use the method of polygonal approximation to expose circles.A circle is divided into several polygons,and the smaller the segmentation,the higher is the precision of the splicing circle.However,owing to the need to generate and scan each polygon separately,an increase in the number of segments will lead to a decrease in the overall lithography speed.In this paper,based on Bresenham’s circle algorithm and exploiting the capabilities of afield-programmable gate array and DAC,an improved real-time circle-producing algorithm is designed for EBL.The algorithm can directly generate cir-cular graphics coordinates such as those for a single circle,solid circle,solid ring,or concentric ring,and is able to effectively realizes deflection and scanning of the electron beam for circular graphics lithography.Compared with the polygonal approximation method,the improved algorithm exhibits improved precision and speed.At the same time,the point generation strategy is optimized to solve the blank pixel and pseudo-pixel problems that arise with Bresenham’s circle algorithm.A complete electron beam deflection system is established to carry out lithography experiments,the results of which show that the error between the exposure results and the preset pat-terns is at the nanometer level,indicating that the improved algorithm meets the requirements for real-time control and high precision of EBL.

A New Method to Retrieve Proximity Effect Parameters in Electron-Beam Lithography

A new method for determining proximity parameters α,β ,and η in electron beam lithography is introduced on the assumption that the point exposure spread function is composed of two Gaussians.A single line is used as test pattern to determine proximity effect parameters and the normalization approach is adopted in experimental data transaction in order to eliminate the need of measuring exposure clearing dose of the resist.Furthermore,the parameters acquired by this method are successfully used for proximity effect correction in electron beam lithography on the same experimental conditions.

Nano-Level Electron Beam Lithography

The JEOL JBX-5000LS is a vector type machine.The system hardware features an ion-pumped column,a LaB 6 electron emitter,25kV and 50kV accelerating voltage,and a turbo-pumped sample chamber.The resolution,stability,stitching and overlay of this system are evaluated.The system can write complex patterns at dimensions down to 30nm.The demonstrated overlay accuracy of this system is better than 40nm.

ELECTRON OPTICS OF VARIABLE RECTANGULAR SHAPED BEAM LITHOGRAPHY SYSTEM D J-2

The electron optical column for the variable rectangular-shaped beam lithographysystem DJ-2 is described,with emphasis on the analysis of the optical configuration and theshaping deflection compensation.In this column the variable spot shaping is performed with aminimum number of lenses by a more reasonable optical scheme.A high-sensitivity electrostaticshaping deflector with sequential parallel-plates is implemented for high-speed spot shaping.With a precise linear and rotational approach,the spot current density,the edge resolution aswell as the position of spot origin remain unchanged when the spot size varies.Experiments showthat the spot current density of over 0.4 A/cm^2 is obtained with a tungsten hairpin cathode,andthe edge resolution is better than 0.2μm within a 2×2 mm^2 field size.

DESIGN AND PERFORMANCE OF SHAPING DEFLECTORS FOR VARIABLY SHAPED ELECTRON BEAM LITHOGRAPHY

In order to obtain uniform exposure in variably shaped electron beam lithography,the beam current density and edge resolution on the target must not change for different spotshapes and sizes.The key to the goal is the appropriate design of shaping deflectors.A linearand rotation compensation approach is presented.Values of linear and rotation compensationfactors versus the distances between electron source image and centers of deflectors are measuredon an experimental electron beam column with variable spot shaping.The experimental resultsare in good agreement with the calculated ones.

Effects of electron beam lithography process parameters on structure of silicon optical waveguide based on SOI

Electron beam lithography(EBL) is a key technology in the fabrication of nanoscale silicon optical waveguide. The influence of exposure dose, the main process parameter of EBL, on the structure profile of poly-methyl methacrylate(PMMA) after development was studied using a silicon on insulator(SOI) wafer with 220 nm top silicon as the substrate. The relationship between exposure dose and structure pattern width after development was analyzed according to the measurement results. The optimum exposure dose of 220 μC/cm^(2) was found to obtain a final structure consistent with the designed mask value through subsequent processes. At the same time, according to the image segmentation curve tracking technology, the contour extraction process of the dose test results was carried out, and the relationship among mask design value, exposure dose and two-dimensional roughness of boundary contour was analyzed, which can provide reference for the subsequent electron beam lithography of the same substrate material.

Nanofabrication of 50 nm zone plates through e-beam lithography with local proximity effect correction for x-ray imaging

High resolution Fresnel zone plates for nanoscale three-dimensional imaging of materials by both soft and hard x-rays are increasingly needed by the broad applications in nanoscience and nanotechnology.When the outmost zone-width is shrinking down to 50 nm or even below,patterning the zone plates with high aspect ratio by electron beam lithography still remains a challenge because of the proximity effect.The uneven charge distribution in the exposed resist is still frequently observed even after standard proximity effect correction(PEC),because of the large variety in the line width.This work develops a new strategy,nicknamed as local proximity effect correction(LPEC),efficiently modifying the deposited energy over the whole zone plate on the top of proximity effect correction.By this way,50 nm zone plates with the aspect ratio from 4:1 up to 15:1 and the duty cycle close to 0.5 have been fabricated.Their imaging capability in soft(1.3 keV)and hard(9 keV)x-ray,respectively,has been demonstrated in Shanghai Synchrotron Radiation Facility(SSRF)with the resolution of 50 nm.The local proximity effect correction developed in this work should also be generally significant for the generation of zone plates with high resolutions beyond 50 nm.

POLYMETHYLMETHACRYLATE LANGMUIR-BLODGETT FILMS FOR HIGH RESOLUTION ELECTRON BEAM RESIST

Ultra-thin (20-100nm) polymethylmethacrylate(PMMA) films prepared by Langmuir-Blodgett techniques have been explored as high resolution electron beam resists. A Hitachi S-450 Scanning Electron Microscope (SEM) has been refitted for a high resolution electron beam exposure system. The lithographic properties and exposure conditions of LB PMMA films were investigated. 0.15μm lines-and-spaces patterns were achieved by using the SEM as the exposure tool. The results demonstrate that the etch resistance of such films is sufficiently good to allow patterning of a 20 nm aluminum film suitable for mask fabrication.

Fabrication and Characteristics of a Si-Based Single Electron Transistor

Si based single electron transistor (SET) is fabricated successfully on p type SIMOX substrate,based on electron beam (EB) lithography,reactive ion etching (RIE) and thermal oxidation.In particular,using thermal oxidation and etching off the oxide layer,a one dimensional Si quantum wire can be converted into several quantum dots inside quantum wire in connection with the source and drain regions.The differential conductance (d I ds /d V ds ) oscillations and the Coulomb staircases in the source drain current ( I ds ) are shown clearly dependent on the source drain voltage at 5 3K.The I ds V gs (gate voltage) oscillations are observed from the I ds V gs characteristics as a function of V gs at different temperatures and various values of V ds .For a SET whose total capacitance is about 9 16aF,the I ds V gs oscillations can be observed at 77K.

Fabrication of a 256-bits organic memory by soft x-ray lithography

This paper reports a procedure of soft x-ray lithography for the fabrication of an organic crossbar structure. Electron beam lithography is employed to fabricate the mask for soft x-ray lithography, with direct writing technology to the lithograph positive resist and polymethyl methacrylate on the polyimide film. Then Au is electroplated on the polyimide film. Hard contact mode exposure is used in x-ray lithography to transfer the graph from the mask to the wafer. The 256-bits organic memory is achieved with the critical dimension of 250 nm.

电子束光刻“自主可控”EDA软件HNU-EBL

为模拟和优化电子束光刻(Electron Beam Lithography,EBL)工艺过程,提高电子束光刻版图加工质量,依托湖南大学(Hunan University,HNU)开发了一套电子束光刻的“自主可控”国产电子设计自动化(Electronic Design Automation,EDA)软件HNU-EBL.该软件实现了以下主要功能:1)基于Monte Carlo方法计算电子束在光刻胶和衬底中的散射过程与运动轨迹;2)基于多高斯加指数函数模型计算拟合出电子束散射的点扩散函数;3)基于GDSII光刻版图文件矩阵化,进行邻近效应、雾效应等校正计算,优化电子束曝光剂量;4)基于卷积计算,计算出给定曝光剂量下的能量沉积密度,并计算出边缘放置误差等光刻加工质量关键指标.基于该软件,通过异或门(Exclusive OR,XOR)集成电路的光刻版图算例,计算在聚甲基丙烯酸甲酯(Polymethyl Methacrylate,PMMA)光刻胶和硅衬底中10 kV电子束的光刻工艺过程.通过对比电子束邻近效应校正前后的显影版图,验证了该软件的有效性.在完全相同的计算硬件和算例条件下,与主流同类进口EDA软件进行了对比,证实了在同等精度下,本软件具有更高的计算效率.已建立http://www.ebeam.com.cn网站,将HNU-EBL软件免费授权给EBL用户使用.

Electron Moirémethod

It is very important to measure local deformations for an in-depth understanding of mechanical properties and fracture mechanism of structural and functional materials. In this paper, different types of model grid fabrication methods and many types of electron Moire methods using an electron beam drawing system, a scanning electron microscope or a focus ion beam are reported, together with their applications in the measurement of deformations occurring in various engineerings and materials science research.

Power Law Nature in Electron Solid Interaction

Monte Carlo simulation of paths of a large number of impinging electrons in a multi-layered solid allows defining area of spreading electrons (A) to capture overall behavior of the solid. This parameter “A” follows power law with electron energy. Furthermore, change in critical energies, which are minimum energies loses corresponding to various electrons, as a function of variation in lateral distance also follows power law nature. This power law behavior could be an indicator of how strong self-organization a solid has which may be used in monitoring efficiency of device fabrication.

微型阵列束闸设计与实验

微型阵列束闸是多束电子束曝光系统的关键部件,用于控制多束电子束的开/关,实现复杂图形的快速曝光。对3×3微型阵列束闸进行了设计与制作,并进行了多束电子束偏转实验研究。对阵列束闸结构进行了优化设计,并基于MEMS加工工艺成功制备了阵列束闸。针对阵列束闸的控制要求,设计了可单独控制的阵列束闸控制器。将控制器与阵列束闸进行连接,验证了控制器的偏转速度与功能完整性。最后,在多束电子束测试平台对阵列束闸进行了偏转实验,研究串扰对电子束偏转的影响。实验结果表明:阵列束闸控制器的偏转速度达到43.5 MHz,大于设计值10 MHz;阵列束闸成功实现了单独控制电子束开和关,束闸的偏转距离在25~30μm之间,小于计算值43.29μm;串扰程度均小于3%。该阵列束闸已经具备多束电子束开/关控制功能,但在偏转精度,设计和加工工艺等方面还需进一步优化和完善。

具有双重显影特性的多用途单分子树脂化学放大光刻胶

化学放大光刻胶(CARs)由于其在分辨率和灵敏度方面的出色性能而广泛应用于光刻领域。本文报道了一种基于单分子树脂的多用途化学放大光刻胶SP8-PAG_(AN),可同时用于365 nm光刻和电子束光刻。该体系主要由螺二芴结构的单分子树脂主体材料(SP-8Boc)和N-(三氟甲基磺酸酯基)蒽-1,9-二羧酰亚胺非离子型光致产酸剂(PAGAn)组成。测试了产酸剂PAGAN在365 nm紫外光激发下的光致产酸效率ΦH+为23%。研究了SP8-PAG_(AN)光刻胶的365 nm光刻和电子束光刻性能。365 nm光刻中,分别利用四甲基氢氧化胺(TMAH,质量分数2.38%)水溶液和正己烷作为显影液,可实现1μm正性和负性光刻图案。电子束光刻中,可实现50 nm Line/Space(L/S)的正性密集线条图案(曝光剂量110μC/cm^(2)),32 nm L/S的负性密集线条图案(曝光剂量40μC/cm^(2))以及19 nm L/3S负性半密集线条图案(曝光剂量96μC/cm^(2))。本研究工作提供了一种具有双重显影特性的多用途单分子树脂化学放大光刻胶的新范例。

基于101.6 mm晶圆35 nm InP HEMT工艺的340 GHz低噪声放大器芯片研制

实现了在101.6 mm InP晶圆上制备35 nm的增强型InP高电子迁移率晶体管。通过InAs复合沟道外延结构设计,使得室温二维电子气迁移率面密度乘积达到4.2×10^(16)/(V·s)。采用了铂钛铂金埋栅工艺技术,典型器件最大跨导达到2900 mS/mm,电流增益截止频率达到460 GHz,最高振荡频率为720 GHz。同时研制出340 GHz低噪声放大器芯片,在310~350 GHz内小信号增益22~27 dB,噪声系数在8 dB以下。建立了340 GHz InP低噪声放大器芯片技术平台,为太赫兹低噪声单片微波集成电路的发展奠定基础。

新型锑氧簇光刻胶的性能与机理研究

随着半导体行业集成度越来越高,对光刻材料提出了更高的要求。近年来,金属氧簇光刻胶由于尺寸小、结构设计灵活,得到了广泛的研究。目前锑基金属光刻胶仅局限于含锑配合物。开发出新型锑氧簇光刻胶,通过对比金属有机组装Sb_(4)O-1与自组装Sb_(4)O-2的溶解度差异说明自组装策略优势。原子力显微镜证实Sb_(4)O-2光刻胶可形成光滑薄膜,并获得低粗糙度值(均方根粗糙度<0.3 nm)。电子束光刻(EBL)证明Sb_(4)O-2光刻胶优异的图案化能力(线宽<50 nm),理论计算支持X射线光电子能谱(XPS)分析的新型自组装Sb_(4)O-2“配体解离”机制。

Large area mold fabrication for the nanoimprint lithography using electron beam lithography

The mold fabrication is a critical issue for the development of nanoimprint lithography as an effective low-cost and mass production process.This paper describes the fabrication process developed to fabricate the large area nanoimprint molds on the silicon wafers.The optimization of e-beam exposure dose and pattern design is presented.The overlayer process is developed to improve the field stitching accuracy of e-beam exposure,and around 10 nm field stitching accuracy is obtained.By means of the optimization of the e-beam exposure dose,pattern design and overlayer process,large area nanoimprint molds having dense line structures with around 10 nm field stitching accuracy have been fabricated.The fabricated mold was used to imprint commercial imprinting resist.

Development of massively parallel electron beam direct write lithography using active-matrix nanocrystalline-silicon electron emitter arrays

Nanoscale lithographic technologies have been intensively studied for the development of the next generation of semiconductor manufacturing practices.While mask-less/direct-write electron beam(EB)lithography methods serve as a candidate for the upcoming 10-nm node approaches and beyond,it remains difficult to achieve an appropriate level of throughput.Several innovative features of the multiple EB system that involve the use of a thermionic source have been proposed.However,a blanking array mechanism is required for the individual control of multiple beamlets whereby each beamlet is deflected onto a blanking object or passed through an array.This paper reviews the recent developments of our application studies on the development of a high-speed massively parallel electron beam direct write(MPEBDW)lithography.The emitter array used in our study includes nanocrystalline-Si(nc-Si)ballistic electron emitters.Electrons are drifted via multiple tunnelling cascade transport and are emitted as hot electrons.The transport mechanism allows one to quickly turn electron beamlets on or off.The emitter array is a micro-electro-mechanical system(MEMS)that is hetero-integrated with a separately fabricated active-matrix-driving complementary metal-oxide semiconductor(CMOS)large-scale integration(LSI)system that controls each emitter individually.The basic function of the LSI was confirmed to receive external writing bitmap data and generate driving signals for turning beamlets on or off.Each emitted beamlet(10×10μm^(2))is converged to 10×10 nm^(2) on a target via the reduction electron optic system under development.This paper presents an overview of the system and characteristic evaluations of the nc-Si emitter array.We examine beamlets and their electron emission characteristics via a 1:1 exposure test.