厚胶光刻中曝光光强对光化学反应速率的影响

针对用于厚层光刻的重氮萘醌类正性光刻胶,利用动力学模型,分析了光化学反应速率的影响因素;给出了光化学反应速率明显受光强变化的影响以致互易律失效的原因。对厚度24μm的光刻胶AZP4620在相同曝光量而光强分别为3.2mW/cm2和0.63mW/cm2的条件下进行了数值模拟和实验。当曝光光强为3.2mW/cm2时仅需300s,即可显影完全,而当曝光光强为0.63mW/cm2时需要的时间长达2400s,才显影完全,且面形轮廓差异较大。因此,在厚胶光刻中,当曝光光强较大时应适当减小曝光量,反之,应适当增加曝光量。     

亚波长分辨光刻介质特性研究

利用365nm波段光源、扫描电镜、台阶仪、原子力显微镜和椭偏仪,研究了亚波长分辨光刻介质X AR-N 7700/30型光刻胶的显影速度、对比度、薄膜厚度和折射率等化学、物理特性参数。光刻胶未曝光部分显影速度为23.15nm/s,曝光部分为1.85nm/s,光刻胶的对比度高达2.5,稀释至30%的质量浓度时,光刻胶可旋涂成45nm厚的薄膜。     

应用于纳米制造的新型电子束抗蚀剂Calixarene的工艺研究

为了满足电子束光刻（EBL）对高分辨率、性能优秀抗蚀剂的需求,研究了将Calixarene衍生物作为电子束抗蚀剂在胶液配制、电子束曝光及显影等工艺过程中的相关技术.其中电子束曝光实验在JEOL JBX-5000LS系统上进行.实验结果表明,在入射电子能量50 keV、束流50 pA的条件下,Calixarene可以方便地形成50 nm的单线、50nm等线宽与间距的图形结构.通过与常用电子束抗蚀剂的对比,总结了Calixarene在电子束光刻性能上的优缺点,并分析了其成因.作为一种新型的高分辨率电子束光刻抗蚀剂,Calixarene有望应用在纳米结构制造、纳米尺寸器件及电路的研制等领域.     

基于硅与非硅复合方法的异平面空心微针制作

为了解决制备空心微针工艺复杂且成本高的问题,本文提出了采用湿法刻蚀、光刻和电镀结合的方法制备低成本空心金属微针.首先采用湿法刻蚀硅,得到280μm深的倒四棱锥锥坑;然后在锥坑上甩200μm厚的负胶SU-8填充锥坑,并通过曝光显影负胶形成微针的形貌;最后在曝光显影后的负胶上电镀50μm厚的镍得到所需形状的空心金属微针.用此方法制备的空心微针高度为350μm、壁厚为50μm,其针尖形状为三棱锥和四棱锥.通过有限元仿真分析微针强度与微针结构尺寸的关系.用此方法加工出的微针具有锥形尖,改善了刺入皮肤的效果.     

冷压印光刻中斜纹光栅对准信号计算模型

采用傅里叶光学的方法,分析了冷压印光刻中新型斜纹光栅对准标记的透光特性。分析表明,对准信号与光栅副相对位移之间是正弦变化关系,且对准位置附近是一个陡直的线性区。该区对准信号的灵敏度很高,适合于多层套刻对准,根据信号和位移的线性关系,给出初步的对准信号计算模型。由于抗蚀剂的存在,使晶片表面反射率随位移而变化,提出用反射率因子进行修正的方案。反射率因子中包含有位移信息,将其与初步对准信号模型相乘,得到修正的计算模型。由新模型,研究了抗蚀剂平均厚度不同对对准信号的影响,说明要获得高灵敏度的信号,抗蚀剂厚度应取满足压印条件的最小值。     

使用激态准分子激光的超快速高分辨率接触光刻术

本文叙述并用实验验证了使用大功率脉冲激态准分子激光器的新技术。它是一种无光斑、细线高速光刻术。使用激励喇曼偏侈,任一种抗蚀剂都获得了最理想的光谱线。这种技术(目前还是第一次)容许某一已知抗蚀剂的曝光波最佳化。在 AX—2400和 DNN 系列的重氮系光致抗蚀剂上膜厚1微米,使用波长为308nm 的 XeCl 激光和波长为248nm 的 KrF 的激光接触曝光,得到了优质图形。1000对线/毫米的分辨率己被实验证明。这些图形比得上使用普通光源而代表目前工艺水平的接触光刻术所获得的图形。上述两种光刻术的主要不同之点是:激态准分子激光光刻术的速度大约快两个数量级。实验表明,尽管在激光曝光中所用的功率强度要大10~8左右,但几种抗蚀剂互换时其灵敏度衰减仅仅减少到三分之一。根据上述实验结果,讨论了光化反应与普通光源曝光中所发生的反应不相同的地方。     

光热敏微胶囊的感光特性研究

采用界面聚合技术制备了新型光信息记录材料光热敏微胶囊.利用红外光谱技术及热显影技术对光热敏微胶囊的感光特性进行了研究.在傅里叶红外光谱中根据C=C键在1634cm~(-1)处振动吸收峰强度的变化,研究了囊内预聚物TMPTA单体在光引发剂184作用下随曝光时间改变的光固化特性.实验结果表明预聚物TMPTA聚合时,C=C键在1634cm~(-1)处振动吸收峰随曝光时间的延长逐渐变小,即预聚物的固化程度随曝光时间延长逐渐增大.利用热显影技术研究了光热敏微胶囊影密度随曝光时间的变化,研究结果发现随曝光时间的延长显影密度逐渐降低,说明囊内预聚物固化程度的增大加强了对染料前体的包裹作用,从而降低了显影剂与染料前体的结合机会.     

基于DMD光刻制作微柱透镜阵列分模曝光的研究

针对无掩模光刻技术制作微柱透镜阵列的面形精度问题,对曝光方式和掩模设计进行研究,采用一种分模曝光方法,包括图形分层,掩模设计,分层掩模灰度调制,分层曝光四个步骤。在曝光前,需要对二维掩模版图按设计结构高度进行分层,以实现单层掩模在抗蚀剂上的投影成像高度不超过物镜的焦深范围。基于数字微镜阵列对灰度掩模的空间调制原理,设计出匹配的分层掩模版图,给出了图形分层原则和方法以及模板设计的原理。实验结果表明:采用该方法制作微柱透镜阵列,面形平均误差为0.54μm,相比以往单模曝光平均误差值0.79μm,平均误差减小了0.25μm,该方法弥补了由物镜焦深限制所造成的技术问题,提高了曝光质量。     

下世纪的抗蚀刻材料

半导体大规模集成电路的集成度以相当快的速度逐年提高。现已大量生产4M DRAM(最小线宽0.8μm),1991～1992年将大量生产16M DRAM(最小线宽0.5μm)的产品。集成度之所以能如此急剧地提高是与光刻技术的发展分不开的,而该技术则依赖于抗蚀刻材料的开发。表1是短波长抗蚀技术中对抗蚀剂特性的要求,而下世纪在64M和256M DRAM的制作中,对抗蚀剂特性的要求将更高。在此就短波长紫外线光刻,技术中所用抗蚀剂的开发动向     

采用双向偏置曝光的成像干涉光刻技术

成像干涉光刻技术(IIL)具有干涉光刻技术(IL)的高分辨力和光学光刻技术(OL)产生任意形状集成电路特征图形的能力。在IIL中,按掩模图形的不同空间频率成份分区曝光,并使其在抗蚀剂基片上非相干叠加,得到高分辨抗蚀剂图形。本文在研究一般三次曝光IIL原理基础上,提出采用沿X轴正、负方向以及沿Y轴正、负方向偏置的双向偏置照明,分别曝光 X方向、-X方向、 Y方向、-Y方向的高空间频率分量并与垂直于掩模方向的低空间频率分量曝光相结合的五次曝光IIL。理论和计算模拟表明,该方法可以提高图形对比度和分辨力,并减小因调焦误差引起的图形横向位移误差,有利于改善抗蚀剂图形质量。     

Surfaces that resist bioadhesion

The search for surfaces that resist bioadhesion has continued with the pursuit of a number of avenues. A large part of the studies has investigated PEG coatings. Nevertheless, there is still controversy about what exactly the properties and modes of action of an ‘ideal’ PEG coating should be. While some studies have reported no irreversible protein adsorption, other, very similar coatings appear less able to resist bioadhesion. Of great interest are results showing that PEG surfaces with very short chains are capable of rejecting proteins. As it is very difficult to obtain direct information about the microstructure of the coatings, studies typically employ plausible models to interpret observations. New analytical techniques and the direct measurement of interfacial forces between proteins and surfaces open up the possibility of improved, guided design and feedback in the optimization of surfaces intended to resist bioadhesion.     

Ion-implanted resist removal using atomic hydrogen

We removed B-, P-, and As-ion-implanted positive-tone novolak resists with an implantation dose of 5 × 10¹² to 5 × 10¹⁵ atoms/cm² at 70 keV, using atomic hydrogen. Though the removal rate decreased with increase in the implantation dose, all of the ion-implanted resists were removed. The rates of thickness of the surface-hardened layer/all resist layer of B, P, and As implanted resists were 0.38, 0.26, and 0.16, respectively, by SEM observation. The removal rate decreased with increasing the rate of the surface-hardened layer. The energy supplied from the ions to the resist concentrated on the surface side in the increasing order of B-P-As.     

Barnacles resist removal by crack trapping

We study the mechanics of pull-off of a barnacle adhering to a thin elastic layer which is bonded to a rigid substrate. We address the case of barnacles having acorn shell geometry and hard, calcarious base plates. Pull-off is initiated by the propagation of an interface edge crack between the base plate and the layer. We compute the energy release rate of this crack as it grows along the interface using a finite element method. We also develop an approximate analytical model to interpret our numerical results and to give a closed-form expression for the energy release rate. Our result shows that the resistance of barnacles to interfacial failure arises from a crack-trapping mechanism.     

A new composite designed to resist wear

Nacre is known for its superior mechanical properties due to its uniquely interlocked-layered structures. In this study, a new composite containing nacre in an Al matrix was fabricated. The composite was produced using powder metallurgy method followed by a heat treatment. Mechanical properties were tested using SEM, micro hardness tester and profilometer. Results showed that the hardness of the composites increased as the concentration of nacre increased in the composite. The hardness of a composite containing 20 wt% of nacre increased by 40% compared to pure Al. Tribological evaluation indicates that samples with 1 wt% and 5 wt% of nacre exhibited the best wear resistance. The wear mechanism changed from adhesive to abrasive wear with varying concentration of nacre. This research demonstrates that the design of mechanical properties and the control of wear mechanisms is possible through the optimization of hybrid configuration. This approach can be adapted to most conventional materials.     

A chemically amplified fullerene-derivative molecular electron-beam resist

Current lithographic resists depend on large polymeric materials, which are starting to limit further improvements in line-width roughness and feature size. Fullerene molecular resists use much smaller molecules to avoid this problem. However, such resists have poor radiation sensitivity. Chemical amplification of a fullerene derivative using an epoxy crosslinker and a photoacid generator is demonstrated. The sensitivity of the material is increased by two orders of magnitude, and 20-nm line widths are patterned.     

Selecting aluminum alloys to resist failure by fracture mechanisms

Useful information and guidelines are presented for engineers who wish to minimize fracture problems in aluminum engineering structures through better application of materials knowledge and optimum alloy choice. Consideration is given to methods and examples of characterizing fracture resistance of aluminum alloys including interpretations of data addressing basic design approaches. Specific attention is given to trade-offs among properties of strength, fracture toughness, corrosion, stress corrosion cracking, and fatigue in structural aluminum materials.