Spectral Efficiency of Extreme Ultraviolet Emission from CO_2 Laser-Produced Tin Plasma Using a Grazing Incidence Flat-Field Spectrograph

A grazing incidence flat-field spectrograph using a concave grating was constructed to measure extreme ultraviolet （EUV） emission from a CO 2 laser-produced tin plasma throughout the wavelength region of 5 nm to 20 nm for lithography. Spectral efficiency of the EUV emission around 13.5 nm from plate, cavity, and thin foil tin targets was studied. By translating the focusing lens along the laser axis, the dependence of EUV spectra on the amount of defocus was investigated. The results showed that the spectral efficiency was higher for the cavity target in comparison to the plate or foil target, while it decreased with an increase in the defocus distance. The source＇s spectra and the EUV emission intensity normalized to the incident pulse energy at 45 from the target normal were characterized for the in-band （2% of bandwidth） region as a function of laser energy spanning from 46 mJ to 600 mJ for the pure tin plate target. The energy normalized EUV emission was found to increase with the increasing incident pulse energy. It reached the optimum value for the laser energy of around 343 mJ, after which it dropped rapidly.

Spectral purity systems applied for laser-produced plasma extreme ultraviolet lithography sources:a review

With the development of high-volume manufacturing for very-large-scale integrated circuits,the purity of the light source in the extreme ultraviolet lithography(EUVL)system needs to fulfil extreme requirements in order to avoid thermal effect,optical distortion and critical dimension errors caused by out-of-band radiations.This paper reviews the key technologies and developments of the spectral purity systems for both a free-standing system and a built-in system integrated with the collector.The main challenges and developing trends are also discussed,with a view towards practical applications for further improvement.Designing and manufacturing spectral purity systems for EUVL is not a single task;rather,it requires systematic considerations for all relevant modules.Moreover,the requirement of spectral purity filters drives the innovation in filtering technologies,optical micromachining and advanced metrology.

基于宽带高次谐波的掩模版缺陷检测(特邀)

使用严格的时域有限差分法研究高次谐波光源的检测能力,探索不同波长光源的检测潜力。在综合考虑散射光效率和入射光光强的前提下,与光化波长检测相比,较长波长的光源如38 nm对直径小于10 nm的表面缺陷具有更好的检测能力。此外,38 nm波长光源对极紫外掩模版具有较好的穿透能力,可用于相位缺陷的检测。特别是对于具有特定高度和宽度的缺陷,如高度为7~20 nm,宽度为20~80 nm的浅层缺陷,38 nm波长光源具有较为可观的检测能力。该研究可为掩模版缺陷检测装置检测能力的提升提供指导。

极紫外光刻量产良率的保障:掩模版保护膜

当前信息技术的快速发展,需要不断扩大高端芯片的产能和良率,以满足当下及未来对电子产品持续增长的需求。在高端芯片制造环节中的极紫外光刻过程中,任何落在掩模版上的纳米尺度的颗粒污染,都会使曝光成像的图案产生缺陷而降低光刻制程的良率,最终导致芯片制造成本的激增。因此,通过在掩模版上安装“保护膜”这一物理屏障,可有效阻挡任何尺度的污染颗粒进入成像的焦平面内,避免其对极紫外曝光成像质量的不利影响,从而极大地提高芯片制造的良品率。本综述从极紫外光刻掩模版保护膜的材料选择、结构设计、保护膜的制备工艺,以及表征手段等方面进行了详细的介绍。本综述将为我国从事先进光刻以及自支撑薄膜器件研究的学者、工程师等提供有益的参考。

All-reflective optical system design for extreme ultraviolet lithography

All-reflective optical systems,due to their material absorption and low refractive index,are used to create the most suitable devices in extreme ultraviolet lithography （EUVL）.In this letter,we present a design for an all-reflective lithographic projection lens.We also discuss its design idea and structural system.After analysis of the four-mirror optical system,the initial structural parameters are determined,the optical system is optimized,and the tolerances of the system are analyzed.We also show the implementation of optimal layout and desired imaging performance.

Development of an Experimental EUVL System

The authors have developed an experimental system for the studies of extreme ultraviolet projection lithography at 13.0nm wavelength, which includes a laser plasma source, an ellipsoidal condenser, a transmission mask and a Schwarzschild optics. The optical system is optimized to achieve 0.1μm resolution over a 0.1mm diameter image field of view and the mirrors of the objective were coated with Mo/Si multilayer to provide 60% reflectance at near normal incidence angle for 13.0nm radiation.

Developments at SSRF in soft X-ray interference lithography

The soft X-ray interference lithography(XIL) branch beamline at Shanghai Synchrotron Radiation Facility(SSRF) is briefly introduced in this article. It is designed for obtaining 1D(line/space) and 2D(dot/hole)periodic nanostructures by using two or more coherent extreme ultraviolet(EUV) beams from an undulator source. A transmission-diffraction-grating type of interferometer is used at the end station. Initial results reveal high performance of the beamline, with 50 nm half-pitch 1D and 2D patterns from a single exposure area of400 μm× 400 μm. XIL is used in a growing number of areas, such as EUV resist test, surface enhanced Raman scattering(SERS) and color filter plasmonic devices. By using highly coherent EUV beam, broadband coherent diffractive imaging can be performed on the XIL beamline. Well reconstructed pinhole of φ20 μm has been realized.

A compact electron storage ring for lithographical applications

The physical design for a novel low-energy compact-storage-ring-based extreme ultraviolet(EUV)light source was systemically studied.The design process considers the linear and nonlinear beam optics,including transverse matching and the optimization of the dynamic aperture,momentum aperture,and beam lifetime.With a total circumference of 36.7 m and a beam energy of 400 MeV,the storage ring can operate with an average beam current of up to 1 A.With the undulator as the radiator,this facility has the potential to emit EUV radia-tion at 13.5 nm with an average power exceeding 10 W within the bandwidth.In addition,the collective instabili-ties of the lattice at high beam current were analyzed;it was found that the typical instabilities which may occur in an electron storage ring can be reasonably controlled in our design.With the advantages of variable beam energy and current,this design exhibits great promise as a new can-didate for various EUV lithographical applications requir-ing tunable radiation power.

从极紫外光刻发展看全球范围内的技术合作

在针对芯片的“卡脖子”技术中,极紫外(EUV)光刻是最重要的一环。EUV光刻技术已经被广泛应用于最先进工艺节点的集成电路芯片制造之中。它的研发交叉融合了光学、机械、电子、控制、软件、材料、数学、物理等多个学科的知识。EUV光刻的发展反映了世界范围内联合研发的演变过程,开放和合作是发展过程中的主旋律。回顾了EUV光刻的发展历史及所涉及的重大项目和机构,讨论了全球唯一的EUV光刻机制造商——ASML公司的灵活多变的国际化合作路线,分析了自1997年以来世界各代表性研发机构的研发趋势以及与EUV光刻发展的关系,详叙了各参与机构在世界范围内的合作对EUV光刻发展的影响。该研究为研发先进光刻机等类似高端装备提供了一些启示和参考。

Latest developments in EUV photoresist evaluation capability at Shanghai Synchrotron Radiation Facility

Evaluating the comprehensive characteristics of extreme ultraviolet(EUV)photoresists is crucial for their application in EUV lithography,a key process in modern technology.This paper highlights the capabilities of the Shanghai Synchrotron Radiation Facility(SSRF)08U1B beamline in advancing this field.Specifically,it demonstrates how this beamline can create fringe patterns with a 15-nm half-pitch on a resist using synchrotron-based EUV lithography.This achievement is vital for evaluating EUV photoresists at the advanced 5-nm node.We provide a detailed introduction to the methods and experimental setup used at the SSRF 08U1B beamline to assess an EUV photoresist.A significant part of this research involved the fabrication of high-resolution hydrogen silsesquioxane mask gratings.These gratings,with an aspect ratio of approximately 3,were created using electron beam lithography on an innovative mask framework.This framework was crucial in eliminating the impact of zeroth-order light on interference patterns.The proposed framework propose offers a new approach to mask fabrication,particularly beneficial for achromatic Talbot lithography and multicoherent-beam interference applications.

MAPDST单体在EUV光刻胶制备过程中的应用

极紫外(EUV)光刻胶的研发作为适配未来光刻技术的发展方向,现已成为超高精度集成电路制造的最高效工艺技术。其中,(4-(甲基丙烯酰氧基)苯基)二甲基锍三氟甲磺酸盐(MAPDST)作为一种含辐射敏感锍基功能的关键单体,现已广泛应用于极紫外(EUV)光刻胶的研发生产过程中。首先,简要阐述在制约光刻胶性能提升过程中存在的分辨率(R)、线边缘粗糙度(LER)、曝光灵敏度(S)之间的平衡制约关系,即RLS平衡制约关系;随后,对MAPDST单体的优越性能以及在推动光刻胶朝着高分辨率方向发展的应用现状进行综述;最后,对EUV光刻胶材料及MAPDST单体的未来发展做出展望。

Heterometallic Ti-Zr oxo nanocluster photoresists for advanced lithography

Extreme ultraviolet lithography(EUVL)and electron beam lithography(EBL)are considered to be crucial lithography techniques utilized in the fabrication of nanoscale semiconductor devices.However,the industry currently faces a scarcity of EUV photoresists that meet the increasingly challenging standards in terms of resolution,sensitivity and roughness.Metal oxo nanoclusters have garnered significant interest in the field of EUV photoresist due to their relatively stronger absorption cross-section for extreme ultraviolet light and lower dimensions.In this study,we utilize a heterometallic nanocluster strategy by a combination of titanium and zirconium metals to investigate their solubility,assess the suitability of various developers,and evaluate their performance in electron-beam and EUVL,as well as study their etch resistance for pattern transfer.We demonstrate that R-4 is able to get a critical dimension(CD)of 25 nm at low doses under EBL,as well as 50 nm resolution at EUVL with a remarkable sensitivity of 19.7 mJ cm−2.This study offers an efficient heterometallic method for optimizing the lithographic performance of metal oxo nanocluster photoresists,which can benefit the development of commercially viable next-generation EUV photoresists.

A Model for Extreme Ultraviolet Radiation Conversion Efficiency From Laser Produced Mass-Limited Tin-Based Droplet Target Plasmas

Simple arguments are used to construct a model to explain the extreme ultraviolet radiation conversion efficiency(EUV-CE) of a tin-based droplet target laser produced plasmas by calculating the laser absorption efficiency,radiation efficiency,and spectral efficiency.The dependence of drive laser pulse duration and laser intensity on EUV-CE is investigated.The results show that at some appropriate laser intensity,where the sum energy of the thermal conduction,out-off band radiation and plasma plume kinetic losses is at a minimum,the EUV-CE should reach a maximum.The EUV-CE predicted by the present simple model is also compared with the available experimental and simulation data and a fair agreement between them is found.

激光等离子体13.5 nm极紫外光刻光源进展

半导体产业是高科技、信息化时代的支柱。光刻技术,作为半导体产业的核心技术之一,已成为世界各国科研人员的重点研究对象。本文综述了激光等离子体13.5 nm极紫外光刻的原理和国内外研究发展概况,重点介绍了其激光源、辐射靶材和多层膜反射镜等关键系统组成部分。同时,指出了在提高激光等离子体13.5 nm极紫外光源输出功率的研究进程中所存在的主要问题,包括提高转换效率和减少光源碎屑。特别分析了目前已实现百瓦级输出的日本Gigaphoton公司和荷兰的ASML公司的极紫外光源装置。最后对该项技术的发展前景进行了总结与展望。

激光等离子体极紫外光刻光源

研究并讨论了下一代光刻的核心技术之一—激光等离子体极紫外光刻光源。简要介绍了欧美和日本等国极紫外光刻技术的发展概况,分析了新兴的下一代13.5 nm极紫外光刻光源的现状,特别讨论了国内外激光等离子体极紫外光刻光源的现状,指出目前其存在的主要问题是如何提高光源的转化效率和减少光源的碎屑。文中同时概述了6.x nm(6.5～6.7 nm)极紫外光刻光源的最新研究工作。最后,介绍了作者所在研究小组近年来在极紫外光源和极紫外光刻掩模缺陷检测方面开展的研究工作。

应用于极紫外光刻系统多层膜的研究进展

极紫外光刻是采用波长为13.5 nm的极紫外光作为光源,实现半导体集成电路工艺22 nm以及更窄线宽节点的主要候选光刻技术。性能优越稳定的多层膜技术是构建整个极紫外光刻系统的重要技术之一、从高反射率、波长匹配、控制面形以及稳定性和寿命方面总结了极紫外光刻系统中多层膜的性能要求和最新的研究进展,叙述了制备高性能多层膜的方法和沉积设备,讨论了多层膜制备技术存在的问题和发展的方向。

Gd靶激光等离子体6.7nm光源的实验研究

本文对Gd靶激光等离子体极紫外光源进行了实验研究,在6.7 nm附近获得了较强的辐射,并研究了6.7nm附近光辐射随打靶激光功率密度变化的规律以及收集角度对极紫外辐射的影响.同时,对平面Gd靶激光等离子光源的离子碎屑角分布进行了测量,发现从靶面的法线到沿着靶面平行方向上Gd离子数量依次减少.进一步研究结果表明采用0.9 T外加磁场的条件下可取得较好的Gd离子碎屑阻挡效果.

现代光刻技术

作为当前集成电路制造的主流技术,光学光刻在趋近其分辨力极限的同时,面临着越来越大的挑战,即便在波前工程和分辨力增强技术的帮助下,光学光刻的分辨力也难以满足快速发展的半导体产业的技术需求。接近式 X 射线光刻技术(XRL)、散射角限制电子束投影光刻技术(SCALPEL)、电子束直写光刻技术(EBDW)、极紫外线即软 X 射线投影光刻技术(EUVL)、离子投影光刻技术(IPL)等下一代光刻技术(NGL)将会在特征线宽为 100—70 nm 的技术节点介入集成电路制造的主流技术中。从目前 NGL 技术发展的趋势和市场需求的多元化来看,竞争的结果很可能是各种 NGL 技术并存。当特征尺寸进入纳米尺度(≤100 nm)以后,最终只有那些原子级的成像技术才能成为胜者。

极紫外光刻机真空材料放气分率的单质谱测试方法研究

水蒸气(H_2O)和碳氢化合物(C_xH_y)的放气分率是评价极紫外光刻机(EUVL)真空材料的重要参数。研究材料放气分率的传统方法一般需要2个完全相同的四极质谱计,这不仅大大增加了测试设备造价,而且会导致测试结果存在误差。为解决这一问题,本文仅采用1个四极质谱计,设计了一种EUVL真空材料评价装置。采用该装置测试了碳纤维增强树脂基复合材料层压板(CFRP板)和玻璃陶瓷板(GC板)在不同时间的放气组分、总放气率和放气分率。结果表明,CFRP板放出大量的H_2O和C_xH_y;虽然C_xH_y放气分率比H_2O下降快,但经10h抽真空后,CFRP板仍可放出大量C_xH_y,且其总放气率高于经验阈值;GC板置于真空1h后就不再放出C_xH_y,且其总放气率低于经验阈值;因此GC板比CFRP板更适用于极紫外光刻机真空系统。基于单质谱的放气分率测试方法可用于指导极紫外光刻机真空材料的选择。

极紫外光刻机多层膜反射镜表面碳污染的清洗

针对极紫外(EUV)光刻机工作过程中,多层膜反射镜表面沉积碳污染造成的反射率下降问题展开研究,讨论了多层膜反射镜表面碳污染清洗方法。首先描述了在EUV曝光过程中多层膜表面的碳污染形成过程,简单阐述了碳污染对多层膜反射镜的危害。然后从清洗机理、速率以及效果等方面详细描述了多种EUV多层膜表面碳污染清洗方法,分析对比了各清洗技术在清洗速率和效果等方面的优缺点。分析表明:离子体氧和活化氧清洗速率相差不多,可达到2nm/min,但清洗过程中容易造成表面氧化;等离子体氢和原子氢的清洗速率相对较慢,一般在0.37nm/min左右,但清洗过程中不易产生氧化。最后针对不同方法应用于在线清洗EUV多层膜反射镜过程中将遇到的问题和难点进行了讨论。