微光刻中的驻波效应研究

本文阐述了驻波效应的成因及其对微细图形光刻，特别是对深亚微米和亚半微米光刻的影响；分析了驻波强度分布；根据抗蚀剂的物理和化学机制，建立了抗蚀剂显影过程的数学和物理模型，并开展了计算机模拟和光刻曝光实验；研究了减小驻波效应的方法；给出了部分模拟和实验结果。     

减小光刻中驻波效应的新方法研究

光刻过程中，抗蚀剂内部光敏混合物（PAC）浓度受光场的影响呈驻波分布，导致抗蚀剂显影后的侧壁轮廓成锯齿状。分析了后烘（PEB）对PAC浓度分布的影响，模拟了不同后烘扩散长度下的抗蚀剂显影轮廓，从模拟结果可知利用后烘可明显减小驻波效应，得到平滑的抗蚀剂显影轮廓，提高光刻质量。     

厚层抗蚀剂曝光模型及其参数测量

针对厚层抗蚀剂曝光过程中存在诸非线性因素的影响,更新Dill曝光参数的定义,建立了适合描述厚层抗蚀剂曝光过程的增强Dill模型.光刻过程模拟的准确性与曝光参数的测量精度有很大关系,为此,建立了实时曝光监测实验装置,测量了不同工艺条件、不同厚度抗蚀剂的曝光透过率曲线,并演绎计算出曝光参数随抗蚀剂厚度和工艺条件的变化规律.最后给出了采用增强Dill模型进行曝光过程的模拟和实验结果的分析.     

厚层抗蚀剂曝光模型及其参数测量

针对厚层抗蚀剂曝光过程中存在诸非线性因素的影响，更新Dill曝光参数的定义，建立了适合描述厚层抗蚀剂曝光过程的增强Dill模型．光刻过程模拟的准确性与曝光参数的测量精度有很大关系，为此，建立了实时曝光监测实验装置，测量了不同工艺条件、不同厚度抗蚀剂的曝光透过率曲线，并演绎计算出曝光参数随抗蚀剂厚度和工艺条件的变化规律．最后给出了采用增强Dill模型进行曝光过程的模拟和实验结果的分析．     

光学光刻工艺中邻近效应的定量分析

随着超大规模集成电路 (VLSI)图形密度的增大 ,邻近效应已成为光学光刻的关键问题之一。通常在平整硅片上对 0 5 μm图形采用 0 5 4NA和传统的单层i线抗蚀工艺时 ,密集图形和孤立图形间的线宽差异大约为 0 0 8μm。然而 ,这一线宽差异已严重地影响了实际生产的工艺稳定性。阐述了邻近效应对图形尺寸、线条与间隙占空比、衬底膜种类、曝光过程的散焦效应、与抗蚀剂厚度变化有关的抗蚀工艺条件和显影时间的依赖性。同时 ,采用 2种不同抗蚀剂实验监测了不同潜像对比度引起的关键尺寸 (CD)偏差。为减小实际图形因抗蚀剂厚度变化引起的CD差异 ,获得最佳抗蚀剂厚度 ,进行了一种模拟研究。     

电子束零宽度线曝光及其应用

为了提高电子束光刻的图形质量及光刻分辨率,从入射束能和束流密度等方面探讨了克服邻近效应影响的途径,在制备亚30 nm结构图形时采用零宽度线曝光的方法。该方法把版图上线条的宽度设为零,因此该线条的光刻尺寸取决于电子束束斑大小、曝光剂量与显影条件。在400 nm厚HSQ抗蚀剂层上通过零宽度线曝光技术制作出了线宽20 nm网状结构的抗蚀剂图形,实验证明采用零宽度线曝光技术可以比较容易地制作出密集线以及高深宽比的抗蚀剂图形。将该技术应用到扫描电镜放大倍率校准标准样品的制备,取得了较好的效果。零宽度线曝光技术是实现电子束直写曝光极限分辨率的有效方法。     

各种光致抗蚀剂的无显影刻蚀特性

继A抗蚀剂成功地实现无显影光刻之后,为了进一步扩大该技术的实用范围,并了解其它光刻胶是否同样存在这种效应,我们对不同的光刻胶(包括正性胶和负性胶)进行了研究.通过大量实验发现,在一定条件下它们都具有无显影刻蚀效应.有趣的是负性胶     

连续微浮雕面形控制的新方法

建立了抗蚀剂表面曝光量分布与抗蚀剂内部PAC浓度分布之间的关系,通过分析抗蚀剂内部PAC浓度分布特点,发现了抗蚀剂显影过程中的壁垒效应。在此基础上,提出一种新颖的微浮雕面形控制方法——等PAC浓度曲线面形控制技术。该方法克服了抗蚀剂显影模型精度以及显影不稳定性对浮雕面形的影响,使光刻胶上微结构浮雕深度超过100μm,面形均方根误差小于1μm。     

各种光致抗蚀剂的无显影刻蚀特性,

<正> 继A抗蚀剂成功地实现无显影光刻之后,为了进一步扩大该技术的实用范围,并了解其它光刻胶是否同样存在这种效应,我们对不同的光刻胶(包括正性胶和负性胶)进行了研究.通过大量实验发现,在一定条件下它们都具有无显影刻蚀效应.有趣的是负性胶     

新型抗蚀剂的电子束曝光性能研究

为了满足越来越多的特殊结构纳米电子器件的制作要求,亟需进一步提高电子束光刻的分辨率与质量,选择适合的高分辨率电子束抗蚀剂材料显得尤为重要。从曝光剂量以及显影与烘烤过程中具体工艺条件的影响等方面对三种新型抗蚀剂材料HSQ,Calixarene和ARN7520进行了电子束曝光性能的研究,同时也对三者的优缺点进行了讨论。通过实验可知,三种新型抗蚀剂均有小于50 nm的高曝光分辨率。HSQ与衬底有更好的附着力,具有较高的机械强度和对比度,在小面积密集图形的制作中具有较好的性能。而ARN7520具有较高的灵敏度,受电子束邻近效应的影响较小,更适合复杂版图的制作。Calixarene虽然也具有较高的曝光分辨率,但过低的灵敏度严重限制了其实用性。     

Simulation and analysis for microstructure profile of optical lithography based on SU-8 thick resist

Profile simulation of optical lithography is very useful for micro-fabrication of microstructure with high sidewall quality. In this paper the light wave propagation, exposure and development process were analyzed, and modeling for thick film lithography was developed to accurately and rapidly obtain simulated results. The effect of exposure dose on the profile quality after development were simulated and discussed, which show that these process parameters have a great impact on the profile quality of microstructure. With guidance of the simulation and analysis, the micro-gear and micro-piston of micro-motor fabricated by SU-8 thick resist were presented.     

电子束光刻三维仿真研究

本文利用Monte Carlo方法及优化的散射模型,对电子束光刻中电子在抗蚀剂中的散射过程进行了模拟,通过分层的方法,对厚层抗蚀剂不同深度处的能量沉积密度进行了计算,建立了电子束光刻厚层抗蚀剂的三维能量沉积模型。根据建立的三维能量沉积模型,采用重复增量扫描策略对正梯锥三维微结构进行了光刻仿真。理论分析和仿真结果表明,利用分层的三维能量沉积分布模型能更精确地实现电子束光刻的三维仿真。     

A model for the thermal degeneration of a positive opticalphotoresist

Positive optical photoresists have been used extensively in the semiconductor industry and in the manufacture of thin-film disk- and tape-drive heads. Mathematical models for the exposure and development phases of the lithography process have been well defined, but scant information on modeling of the pre-bake phase is available. A pre-bake model which describes the deterioration of the photoactive component in a positive optical resist is derived. A mass balance and the kinetics of the situation are used to describe the change in the Dill exposure model parameters. Experimental verification of the model is shown with three photoresists whose parameters are calculated for different wavelengths of light. The effect of the resist solvent on the exposure model parameters is discussed     

Lithography scaling issues associated with III–V MOSFETs

In this work we investigate fabrication issues associated with scaling down the gate length and source drain contact separation of a III–V MOSFET. We used high resolution electron-beam lithography and lift-off for gate and ohmic contact patterning to fabricate gate-last lithographically-aligned MOSFETs. This work considers the effect of variations in resist thickness on gate lengths and also the fabrication of long narrow gaps using electron-beam lithography. The study showed that the effect of resist thickness variation on metal linewidth is insignificant. A difference of around 2–3 nm was found between PtAu linewidths fabricated using 150 and 280 nm thick resist. A VB6 lithography tool was found to be useful for linewidth measurements. We showed that the choice of resist is critical to gap formation, and that PMMA is not well suited to this task.     

Actinic inspection of EUVL mask blank defects by photoemission electron microscopy: Effect of inspection wavelength variation

Extreme ultraviolet (EUV) photoemission electron microscopy (PEEM), which employs standing wave field illumination of a sample, is a potential tool for at-wavelength inspection of phase defects on extreme ultraviolet lithography (EUVL) mask blank. In this paper, we will demonstrate that the contrast of an underneath multilayer programmed defect in EUV-PEEM image is strongly dependent on the inspection wavelength. The observed contrast variation at different inspection wavelengths is in good agreement with the simulation result of a standing wave field on surface of multilayer stack in the mask blank sample. We also observed some native defects on the programmed defect sample, and found that some of them reverse their contrast with varying inspection wavelengths while others do not.     

Fabrication of hp 32 nm resist patterns using near-field lithography

Near-field lithography (NFL) has no fundamental limit such as the diffraction limit of light. However, in order to fabricate resist patterns with hp 32 nm, thorough optimization of various processes are indispensable. Previously, we reported on the use of fine and ultra-thin top-layer resist, and designs and fabrication of our special masks. In this paper, the effect of the total resist thickness on the near-field distribution is analyzed by the finite-difference time domain analyses and compared with our experiments. For the fabrication of hp 32 nm patterns, the total resist thickness as well as the tri-layer resist process are accordingly optimized. By the near-field exposure using an i-line mercury lamp and the dry-etching process for thin top-layer photo-resist, we have successfully fabricated the hp 32 nm resist pattern of 120 nm height.     

Low energy electron proximity printing using a self-assembled monolayer resist

A simple method for high resolution (<100nm) lithography is reported. We use electrons with energies ranging from 100–300eV emitted by tungsten field emission tips for proximity printing of stencil masks. A comparison with other parallel fine line techniques, like proximity printing and projection lithography with x-rays, high energy electrons or ions, reveals the specific advantages and restrictions of our method.

The masks are made of ≈ 100nm thick silicon membranes structured by e-beam lithography and reactive ion etching (RIE). Free standing gratings with periods down to 100nm serve as test patterns for proximity printing with gaps of ≈15μm. due to the short penetration depth of the low energy electrons, ultrathin resist systems are needed. We have chosen self-assembled monolayers (SAMs) of hexadecane thiol on gold. The monolayer resist is degraded by the exposure, the structures can be transferred by wet chemical etching. Periodic gold structures below 100nm lines and spaces have been generated this way. It was found, that the SAM resist of hexadecane thiol can be used as a positive or negative tone resist depending on the exposure dose.