电子束曝光中能量沉积过程及沉积能分布规律

电子束曝光是研制亚微米线宽VLSI的重要手段,虽然电子束机本身可达100(?)或更高的分辩率,但入射电子在胶和衬底中的散射却使曝光分辨率降低到微米级,这说明电子束入射后的能沉过程及沉积能的分布是影响曝光分辨率的关键因素。本文利用多层介质中电子散射的Monte-Carlo计算模型计算了不同条件下的能沉过程,提示并使用了三维接近函数来描述胶中沉积能的分布规律,研究了曝光条件对沉积能分布的影响,文中并给出表示电子空间输运过程的矩阵递推式,使散射过程描述更加完善和简化,以便能更好的应用于电子束曝光的邻近效应校正和曝光条件的优化中。     

低能电子束散射模拟在邻近效应修正中的应用

文章运用Monte Carlo方法模拟具有高斯分布特征的低能入射电子束斑在PMMA-村底中的复杂散射过程，分别得到了电子束在抗蚀剂中的穿透深度和能量沉积分布圈，并利用模拟结果进行邻近效应的修正．得到修正后的剂量数据文件。结果表明：采用修正后的剂量曝光，光刺胶中的能量沉积比较均匀．曝光分辨率有较大幅度的提高。该研究将对低能电子束曝光技术的定量研究和邻近效应修正技术的探索具有较高的理论指导意义。     

微型彩色显示管校正透镜的设计与加工技术

曝光透镜是彩管曝光台中的一个光学零件，它主要用于彩色CRT荧光屏制造过程中模拟电子束进行光学曝学涂屏。就是要使电子束都能一一对应地落在由光线曝光所制出的荧光粉点上，以得到满屏正确的色纯。     

电沉积法制备彩色滤光膜

介绍了电沉积法制备彩色滤光膜的基本原理和电沉积涂料的主要组分,着重介绍了两种不需将透明电极排列成图案的改进的电沉积法——多次曝光法和一次曝光法,这两种工艺通过采用光刻技术克服了传统电沉积法中像素排列的缺点。     

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．     

低能电子束对抗蚀剂曝光的Monte Carlo模拟

考虑二次电子的产生和散射，利用Monte Carlo方法模拟了具有高斯分布特征的低能入射电子束斑在抗蚀剂中的散射过程，分别得到了电子束在抗蚀剂中的穿透深度和能量沉积的分布图。发现在能量小于2．5keV范围内的模拟结果与实验结果相吻合，这比用传统的不考虑二次电子的Bethe公式得到的模拟结果更加符合实际的电子散射过程，精度更高。另外还发现电子束能量越低，曝光的分辨率和效率越高，这一结果也与实验相吻合。结果表明，二次电子的产生和散射对电子束曝光起了重要的作用，需考虑它们的影响。     

非线性曲线拟合法确定邻近效应参数

为了更精确地确定邻近效应参数,借助优化的电子散射模型,利用改进的Monte Carlo算法模拟了电子束在固体中的散射过程,得到了不同曝光条件下抗蚀剂中的能量沉积分布。利用最小二乘非线性曲线拟合法对该分布进行了双高斯拟合,得到了邻近效应参数α,β和η的值,并与实验结果进行了比较发现,最小二乘非线性曲线拟合法可以用于邻近效应参数的确定。对不同曝光条件的参数拟合显示,增加入射电子束能量,α减小,β增大,而η几乎不变;增加抗蚀剂厚度,α增大,β和η变化不明显;增大衬底材料原子序数,β减小,η增大,而α几乎不变。所得结果不但能为电子束曝光条件的优化、邻近效应的降低提供理论指导,而且还能为邻近效应校正快速地提供精确的参数。     

低能电子束光刻过程的Monte Carlo模拟分析研究

对低能电子在光刻胶和衬底中的复杂散射过程进行分析和物理建模,采用Monte Carlo方法进行模拟研究。利用Browning拟合公式来解决Mott弹性散射截面计算速度慢的问题,采用D.C.Joy和S.Luo修正的Bethe能量损耗公式计算低能电子在固体中的能量损耗。通过跟踪电子的散射轨迹、计算电子的能量沉积密度、结合显影阈值模型,模拟出了电子束光刻的三维显影轮廓图。据此研究了入射电子束能量、剂量、光刻胶厚度、衬底材料、衬底和光刻胶形貌等不同条件下电子束曝光邻近效应的影响。此外,还将具有高斯分布特征的低能电子束入射产生的沉积能量密度进行移动处理,模拟一个以"T"字型为代表的较为复杂图形的电子束曝光过程,通过三维显影轮廓模拟图比较直观地显示了邻近效应的影响,并演示了采用电子束曝光剂量补偿的方法实现邻近效应校正的效果。     

激光诱导普通玻璃表面局域液相化学沉积铜的研究

利用CO2激光（λ=10.6μm）作为诱导光源，普通玻璃作为衬底，研究了影响激光沉积质量和速率的因素，探讨了激光诱导液相化学沉积技术的反应机制，反应产物及其沉积模型等。采用光学显微镜对其沉积过程和沉积铜的微观形貌进行了观察。结果表明：激光诱导液相化学沉积技术能沉积出表面平整，颗粒大小均匀、规则，分布致密的铜镀层，且沉积速率比起普通化学镀也要高出几个数量级。     

电子束曝光UV3正性抗蚀剂的工艺研究

为了在体硅CMOSFinFET中用等离子体腐蚀精细凹槽图形，研究了将电子束直写曝光用于原为深紫外光学曝光的UV3正性抗蚀剂的工艺技术；详细分析了包括膜厚、曝光能量、曝光剂量、显影时间、设计尺寸和衬底材料等在内的各类工艺参数与实际曝光图形效果的关系；特别指出了曝光过程中特有的延迟效应及解决办法。采用最终的优化工艺条件，得到了合适的图形效果。     

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。     

Monte Carlo simulation of the energy dissipation profiles of 30, 50 and 100 keV incident beams in a layered structure in electron beam lithography

This paper presents a Monte Carlo simulation of the energy dissipation profiles of 30, 50 and 100 keV incident beams in thin film (0.4μm) of electron resist, polymethyl methacrylate (PMMA), on thick silicon substrate in electron beam lithography. The radial scattering and the energy loss of incident electrons (including backscattered electrons from the substrate) are simulated under the illumination of ideal point source and Gaussian round beam spot source, and the histories of 30000–50000 electrons are computed.     

Computer-controlled resist exposure in the scanning electron microscope

In modern microelectronics, complicated structures with very small dimensions must be fabricated on active-device materials. This task has been traditionally accomplished by photolithographic techniques, but electron-beam exposure of resist materials has recently been explored [1]-[3]. Submicron electron devices have been fabricated in several laboratories, often featuring a flying-spot scanner to generate the pattern being exposed [4]-[7]. Paper tape drives have been used for repetitive patterns [8], and computer control of the electron beam has been reported also [1], [9]. The electron resist that has shown the highest resolution to date appears to be poly-(methyl methacrylate) (PMM). We have used this material in a resist form for microelectronic device fabrication, and in bulk form to determine energy dissipation profiles. The exposure is performed with a computer-controlled scanning electron microscope (CCSEM). In this paper, we describe the electron beam system briefly, discuss the processes involved in resist exposure and development, describe our exposure procedures using the CCSEM, and show results of fabricated devices and energy dissipation studies.     

蒙特卡罗模拟电子束光刻中30、50和100keV电子束入射在层结构样品中的能量耗散剖面

本文利用蒙特卡罗模拟给出了电子束光刻中 30、50、100 keV 电子束垂直入射到厚衬底硅上的薄膜(0.4m)电子抗蚀剂聚甲基丙烯酸甲酯聚合物(PMMA)中的能量耗散剖面,模拟了理想点源和高斯圆束点源电子束情况下的膜中的径向散射和能耗,包括来自衬底的背散射,计算的电子数为三万到五万个。     

Monte Carlo方法模拟低能电子束曝光电子散射轨迹

建立了一个适用于描述低能电子散射的物理模型 ,利用 Monte Carlo方法对低能电子在多元多层介质中的散射过程进行模拟 .低能电子弹性散射采用较严格的 Mott截面描述 ,为了节约机时 ,利用查表与线性插值方法获得 Mott截面值 ;低能电子非弹性散射能量损失采用 Joy修正的 Bethe公式计算 ,并对其加以改进 ,引入多元介质平均电离电位、平均原子序数、平均原子量概念 ,利用线性插值方法给出光刻胶 PMMA对应的 k值 .对电子穿越多层介质提出一种新的边界处理方法 .在此基础上运用 Monte Carlo方法模拟高斯分布低能电子束在 PMMA-衬底中的复杂散射过程 .     

电子束曝光中低能电子散射的模拟

介绍了Pendry弹性散射截面,描述了电子在固体中的散射过程,包括散射步长、散射角、方位角和散射点处能量的确定,并将Pendry截面和Monte Carlo计算方法应用到电子散射过程中。分别改变入射电子束能量、抗蚀剂厚度和衬底材料,模拟了能量不超过5keV的低能电子束在PMMA抗蚀剂中的散射轨迹。模拟结果表明,低能电子束曝光同样可应用于较高分辨率的表面成像技术工艺。通过对模拟结果和电子束曝光实验比较分析,可以进一步完善散射模型,为更深入开展电子束曝光技术的应用研究创造有利条件,同时也为开发低成本的低能电子束曝光系统提供了理论依据。     

Modeling and simulation development of electron beam resist based on cellular automata

This paper presents a robust Cellular Automata model which predicts the two dimensional development profile as a function of development time, exposure dose and electron beam resist type.The main advantage of CA model is that they exhibit high efficiency and accuracy when handling arbitrarily complex system. In the CA method, A resist is represented by an array of discrete cells that reside in a crystalline lattice. Development of the resist is represented by removal and of individual cell according to development rules. During development, the decision to remove or retain a particular cell is based on the link status of its lattice neighbors according to cell-removal rules, The link status is categorized by number of neighboring cells and their relative positions. The modeling approach also uses Monte-Carlo simulation of electron scattering and energy dissipation and a simple development rate versus dose model for the resist. An absolute quantitative evaluation of the simulation accuracy is made based on resist exposure-development measurement and comparisons with SEM micrographs of experimental profiles of PMMA, SAL601 and ZEP520.The comparisons show good quantitative agreement and indicate the model based on CA can be used as a quantitative processing aid. Simulation results illustrate the importance of resist, beam and dose.     

An exposure model for electron-sensitive resists

We present a mathematical model for the exposure of electron-sensitive resists where an electron beam is incident normal to a substrate coated with a thin layer of resist. We include both the scattering of the incident electrons as they penetrate the resist and the electrons backscattered from within the resist and from the substrate. The calculations yield contours of equal absorbed energy density, and these are interpreted as the contours which bound the resist after development. The absorbed energy density is found as the sum, for all electrons, of the product of the energy absorbed per unit length of trajectory and the flux density of electrons at the point in question. We first calculate the absorbed energy density for an electron beam of vanishingly small cross section (an incident delta function) and then convolve that result with a beam of Gaussian current-density distribution to obtain the reSult for a single beam location. For poly(methyl methacrylate) resist, we study the achievable dot resolution, as a function of the incident charge, for various incident energies-and substrates. Since our main interest is in computer-controlled resist exposures in which patterns are generated as a succession of dots, we calculate the absorbed energy density contours for a line generated in that manner. Detailed comparison is made with the experimental results of Wolf et al., by fitting a single point on one contour at one beam energy to account for the unknown developer sensitivity. The resulting contours predict the undercutting effect experimentally observed for the 5-20-keV beam energies studied. The developed shape and linewidth are found to be nonlinear functions of the incident charge per unit length. Experimental data for the linewidth at 20 keV are presented and compared with theory.