对胶体球光刻中单层胶体晶体曝光特性的研究

对胶体球光刻中单层胶体晶体(MCC)的曝光特性进行了研究。利用磁控溅射的方法在蓝宝石衬底上生长SiO2薄膜并旋涂光刻胶,通过固液界面自组装的方法在光刻胶上制备了单层胶体晶体。胶体球光刻利用单层胶体晶体作为微透镜阵列,通过紫外曝光的方法在光刻胶上制备微孔阵列。光刻胶上图形的周期性与胶体球的直径有关,并且大直径的胶体球的聚光性能要强于小直径胶体球,在曝光过程中随着曝光时间的增加,由于曝光量的增加以及光刻胶的漂白现象,光刻胶上微孔的尺寸也在增加。最后以曝光后的光刻胶为掩膜,将感应耦合等离子体刻蚀技术(ICP)以及湿法腐蚀相结合,制备出了图形化蓝宝石(PSS)衬底。     

丙烯酸酯干膜光刻胶曝光特性及其应用

对一种新型的丙烯酸酯干膜光刻胶(DFP)的曝光及显影特性进行了研究,采用该干胶制作出微沟道结构,进行微流道实验研究。在4英寸(1英寸=2.54cm)硅片上实现了厚度为50μm的干胶完好贴敷,从而解决了干胶在硅衬底上的贴敷问题。利用改变曝光时间设定曝光剂量梯度的方法,研究了干胶的曝光特性。采用不同质量分数的显影液,研究干胶的显影特性,获得了优化的结果。采用干胶系统进行了微流体沟道制作,得到了侧壁陡直的微沟道结构。实验发现,65mJ/cm2及以上的曝光剂量可使厚度为50μm的干膜光刻胶充分曝光并获得形貌效果良好的微结构,质量分数为5%的显影液具有最快的显影速度。     

The Control of Shrinkage and Thermal Instability in SU‐8 Photoresists for Holographic Lithography

The negative‐tone epoxy photoresist, SU‐8, expands ≈1% by volume after postexposure baking. However, if the maximum optical fluence is comparable to that at the insolubility threshold, as in a holographic exposure, the developed resist shrinks (≈35% by volume) due to the removal of light oligomers not incorporated into the polymeric network. IR spectroscopy shows that, at this level of exposure, only 15% of the epoxy groups in the insoluble polymer have reacted; consequently microstructural elements soften and collapse at >100 °C. When the light oligomers are removed, the sensitivity of the resist is unchanged, provided that 5% (w/w) of a high‐molecular‐weight reactive plasticizer (glycidoxy‐terminated polyethylene glycol) is added, but it shrinks less on development and, when used as a photonic crystal template, shows improved uniformity with less cracking and buckling. Reinforcing the polymer network by reaction with the polyfunctional amine (bis‐N,N′‐(3‐aminopropyl)ethylenediamine) increases the extent of cross‐linking and the thermal stability, allowing inverse replicas of photonic crystal templates to be fabricated from both Al:ZnO and Zr₃N₄ using atomic layer deposition at temperatures up to 200 °C.     

Optical lithography

This is the first in a series of papers describing a theoretical process model for positive photoresist. This model, based upon a set of measurable parameters, can be used to calculate the response of photoresist to exposure and development in terms of image surface profiles. The model and its parameters are useful in many ways, from measuring quantitative differences between different resist materials to establishment of process sensitivities and optimization of the resist process within a manufacturing system. In this paper, the concepts of photoresist modeling are introduced by following the exposure and development of a photoresist film on silicon exposed by a uniform monochromatic light flux. This very simple example provides insight into the complex nature of the photoresist process for reflective substrates. The accompanying paper, "Characterization of Positive Photoresists," gives detail about measurement of the new photoresist parameters. It is supported by "In-Situ Measurement of Dielectric Thickness During Etching or Developing Processes" which discusses automated experimental techniques needed to establish photoresist development rates. These resist parameters provide a complete quantitative specification of the exposure and development properties of the resist. They also allow quantitative comparisons: lot to lot, material to material, and processing condition to processing condition. The fourth paper, "Modeling Projection Printing of Positive Photoresists," applies the process model to one technique of photoresist exposure. This paper contains the detailed mathematics of the model. The model is then used to calculate line-edge profiles For developed resist images.     

抗蚀剂AZ4562曝光参数的变化趋势分析

针对厚胶曝光参数随不同光刻胶厚度及工艺条件变化的特点,在原有Dill曝光模型基础上,建立了适合于描述厚胶曝光过程的增强Dill模型,并将统计分析的趋势面法引入到厚胶曝光参数变化规律的研究中,给出了厚胶AZ4562曝光参数随胶厚及工艺条件的变化趋势,为开展厚胶光刻实验研究和曝光过程模拟提供指导性依据。     

基于UV-LIGA技术的双层微齿轮模具镶块工艺

以氧化铟锡(ITO)玻璃作为基底,采用UV-LIGA技术制作了双层微齿轮型腔模具的镶块。首先,采用正胶(RZJ-304)进行光刻,在ITO玻璃表面电镀镍掩模,通过镍掩模对第一层SU-8光刻胶进行背面曝光。再利用正面套刻的方法对第二层SU-8光刻胶进行曝光,显影得到双层微齿轮的胶模。最后,进行微电铸得到双层微齿轮型腔镶块。通过实验验证了双层微齿轮模具镶块制作的工艺流程,优化了其工艺参数,克服了底部曝光不足引起的问题,并对制作工艺过程中产生的涂胶不平整、前烘时胶层不稳定、热板加热不均以及接触式曝光破坏胶层表面等问题进行了研究。所制得的双层微齿轮胶模垂直度高,表面质量好,且套刻精度高。     

High aspect ratio electrodeposited Ni/Au contacts for GaAs‐based III–V concentrator solar cells

We report on a photolithographic and electro‐deposition process that results in an optimized front grid structure for high efficiency multi‐junction III–V concentrator solar cells operating under flux concentrations up to 1000 suns. Two different thick photoresists were investigated to achieve a 6 µm wide grid line with an aspect ratio of 1:1. A positive photoresist, SPR220 manufactured by Rohm and Haas was compared with a negative photoresist, nXT15 manufactured by AZ. A gold sulfite electrolyte was employed to prevent underplating as well as for environmental and safety considerations. An initial layer of nickel was discovered to be necessary to prevent delamination of the fingers during the removal of the contact layer. When deposited on a purpose grown, heavily doped GaAs contact layer, this Ni/Au contact exhibits an acceptable specific contact resistance in the low 10⁻⁴ to mid 10⁻⁵ Ohm cm² range along with excellent adhesion without sintering. Copyright © 2014 John Wiley & Sons, Ltd.     

Direct Growth of Nanocrystalline Graphene/Graphite Transparent Electrodes on Si/SiO2 for Metal‐Free Schottky Junction Photodetectors

Conventional methods to produce graphene/silicon Schottky junctions inevitably involve graphene transfer and metal deposition, which leads to the techniques being complicated, high‐cost, and environmentally unfriendly. It is possible to directly grow hybrid nanocrystalline graphene/graphite transparent electrodes from photoresist on quartz without any catalyst. Due to the source material being photoresist, nanographene/graphite patterns can easily be made on Si/SiO₂ structures to form nanographene/silicon Schottky junctions via commercial photolithography and silicon techniques. The obtained Schottky junctions exhibit excellent properties with respect to photodetection, with photovoltage responsivity of 300 V W^‐1 at a light power of 0.2 μW and photovoltage response time of less than 0.5 s. The devices also exhibit an excellent reliability with the photovoltage deviating less than 1% when cycled over 200 times.     

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．     

Photolithographic linewidth control

A simple model for the image formation process in photoresist is proposed based on Fresnel diffraction from the edge of a mask feature. It is shown theoretically and verified experimentally that the dimensional difference between a clear mask feature and its image in photoresist is given by aL^½[ ln (Ei) - ln (ET) + ln (K) ] where a and K are constants peculiar to the exposure optics, L is the separation between mask and silicon wafer, Eiis the exposure energy, and ETis the effective exposure energy threshold of the photoresist. The model is used to show the existence of "optimum" exposure ratios Ei/ETwhich minimize image variability in hard-, soft-, and near-contact printing. Control of this exposure ratio is found to be the key to successful use of off-contact printing. Based on this model, a photolithographic process control system is outlined in which exposure tool operation and photoresist processing parameters are characterized and monitored with a single silicon wafer. The system is equally applicable to photomask fabrication.     

Photolithography of thick photoresist coating for electrically controlled liquid crystal photonic bandgap fibre devices

Thick photoresist coating for electrode patterning in an anisotropically etched V-groove is investigated for electrically controlled liquid crystal photonic bandgap fibre devices. The photoresist step coverage at the convex corners is compared with and without soft baking after photoresist spin coating. Two-step UV exposure is applied to achieve a complete exposure for the thick photoresist layer at the bottom of the V-groove, and minimise the reduction in resolution and image distortion. The resolution reduction of the different open window width for electrode pattern transfer is also experimentally found.     

表面传导电子发射显示器微细结构光刻工艺的优化

研究了旋涂和光刻工艺对制备表面传导发射显示器(SED)微细结构的影响,分析正性光刻胶和旋涂工艺的作用机理,探讨光刻胶的平面旋涂工艺、曝光剂量、前烘对光刻图形的影响.借助旋涂技术将光刻胶转移在附有金属薄膜的玻璃基片上,利用紫外光对其进行曝光,通过视频显微镜、台阶仪对实验结果分析,优化实验工艺参数.结果表明,光刻胶留膜率随旋转速度增大而减少,随光刻胶的粘度增大而增大,光刻图形宽度随曝光剂量的增大而变窄,曝光剂量40～50 mJ/cm2,前烘110 ℃保温25 min条件下光刻图形边缘平整,为研制SED微细结构奠定了基础.     

Multicomponent Physical Vapor Deposited Films with Homogeneous Molecular Material Distribution Featuring Improved Resist Sensitivity

Each film preparation technique affects the physical properties of the resulting coating and thus defines its applicability in modern device construction. In this context solvent based spin coated and solvent‐free physical vapor deposited molecular glass photoresist films are systematically investigated for their dissolution behavior, sensitivity, and overall lithographic performance. These investigations demonstrate that the solvent‐free physical vapor deposition leads to a marked increase in sensitivity. This could be explained by the individual molecule by molecule deposition step producing a more homogeneous distribution of the multicomponent resist system, especially the photoacid generator. In addition, this assumption is supported by former published simulations focusing on aggregate formation within thin films. This work demonstrates that the lithographic sensitivity of multicomponent resist system is an intrinsic parameter to investigate molecular material distribution and indicates that the applied film preparation technique is crucial for the corresponding performance and applicability.     

Soft‐Contact Optical Lithography Using Transparent Elastomeric Stamps and Application to Nanopatterned Organic Light‐Emitting Devices

Conventional photolithography uses rigid photomasks of fused quartz and high‐purity silica glass plates covered with patterned microstructures of an opaque material. We introduce new, transparent, elastomeric molds (or stamps) of poly(dimethylsiloxane) (PDMS) that can be employed as photomasks to produce the same resist pattern as the pattern of the recessed (or non‐contact) regions of the stamps, in contrast to other reports in the literature^[1] of using PDMS masks to generate edge patterns. The exposure dose of the non‐contact regions with the photoresist through the PDMS is lower than that of the contact regions. Therefore, we employ a difference in the effective exposure dose between the contact and the non‐contact regions through the PDMS stamp to generate the same pattern as the PDMS photomask. The photomasking capability of the PDMS stamps, which is similar to rigid photomasks in conventional photolithography, widens the application boundaries of soft‐contact optical lithography and makes the photolithography process and equipment very simple. This soft‐contact optical lithography process can be widely used to perform photolithography on flexible substrates, avoiding metal or resist cracks, as it uses soft, conformable, intimate contact with the photoresist without any external pressure. To this end, we demonstrate soft‐contact optical lithography on a gold‐coated PDMS substrate and utilized the patterned Au/PDMS substrate with feature sizes into the nanometer regime as a top electrode in organic light‐emitting diodes that are formed by soft‐contact lamination.     

Linewidth variations in photoresist patterns on profiled surfaces

Photoresist thickness nonuniformities in the vicinity of profile steps on substrate surfaces lead to linewidth variations of AZ 1350 photoresist geometries. The effect increases with increasing reflectivity of the substrate, decreasing photoresist layer thickness, and decreasing contrast transfer of the exposure system. It is shown that the photoresist linewidth is maximum when the resist thickness is a multiple of half the exposure wavelength in the resist.     

Calcination‐ and Etching‐Free Photolithography of Inorganic Phosphor Films Consisting of Rare Earth Ion Doped Nanoparticles on Plastic Sheets

It is demonstrated that patterned inorganic phosphor films consisting of rare earth ion doped nanoparticles (RE‐NPs) can be fabricated on plastic sheets using calcination‐ and etching‐free photolithography. Green up‐conversion luminescence and near‐infrared (NIR) fluorescence appears from the RE‐NPs that are prepared from Y₂O₃ doped with 1 mol% Er³⁺ and 0.85 mol% Yb³⁺. The diameter of the RE‐NPs is estimated to be about 300 nm using dynamic light scattering. Visible transmittance of the RE‐NP film fabricated by dip‐coating is more than 90%. Patterned RE‐NP films are obtained by dip‐coating the RE‐NPs on patterned photoresist films fabricated by UV exposure through a photomask, followed by selective removal of the photoresist. Optical, fluorescence, scanning electron, atomic force, and Kelvin probe force microscopies are used for the characterization of the patterned RE‐NP films. The present methodology enables fabrication of patterned RE‐NP films, not only on inorganic substrates but also on plastic sheets, with low cost and material consumption.     

基于背向曝光的GaN基脊型LD制备工艺改进

GaN基脊型激光二极管（LD）的制备工艺中,面临的一个主要困难是p电极和窄脊结构的制备受到光刻对准精度的严重制约。设计和验证了一种基于背向曝光技术的激光器制备工艺。通过预先沉积一层200nm的铝作为挡光掩模和牺牲层,利用ICP蚀刻制备出宽为2.5μm的脊型结构,并使用PECVD沉积SiO2绝缘层。随后采用背向曝光实现二次光刻,将脊型图形精确地转移到电极窗口,继而采用湿法腐蚀SiO2绝缘层打开窗口,借助对的铝掩模腐蚀实现对残余绝缘层的辅助剥离,从而同时解决了目前脊型激光器电极窗口对准困难和绝缘层侧向腐蚀条件难于把握的问题。     

微柱透镜阵列的全息-光刻胶热熔制作技术

为改善微柱透镜阵列的制作技术、消除光刻工艺对光刻掩模版的依赖,研究了利用全息-热熔技术制作微柱透镜阵列的新方法,即首先采用了全息技术进行曝光,然后利用光刻胶热熔技术在K9玻璃基底上制作出了面形良好的微柱透镜阵列。实验结果表明,进行全息曝光并显影后,能够在光刻胶表面产生良好的正弦阵列表面结构,之后采用光刻胶热熔技术可将光刻胶的正弦阵列结构转变为微柱透镜阵列,且实验结果良好。     

GaAs(100)面光栅皱折的形成

使用光致抗蚀剂的全息干涉曝光、显影方法在GaAs(100)面衬底上形成光致抗蚀剂光栅图形.采用选择化学腐蚀将光致抗蚀剂光栅浮雕图形转换到GaAs(100)面衬底上.已成功地在GaAs(100)面衬底上制作了周期为0.33微米的光栅皱折.在GaAs(100)面上的光栅皱折具有良好的V-形沟槽轮廓.