A Study of the Particle Transport and Surface Reactions in Microstructures on Substrates during Plasma Processing

了解衬底微结构中的粒子输运和表面反应是控制先进等离子体工艺制造0.1 μm以下器件的必要条件。我们开发了粒子输运和表面反应的原子尺度模型，以模拟等离子体蚀刻过程中纳米尺度的轮廓和关键尺寸控制的特征轮廓演变。该模型是介于分子动力学模拟和连续体模型之间的一种中间尺度的现象学模型。该模型考虑了微结构中离子和中性离子的输运，离子增强蚀刻的多层表面反应，以及由此产生的特征剖面演变，其中通过基于具有三个速度分量的连续注入单粒子轨迹的粒子模拟来分析输运。为了将原子图像纳入模型，基底由大量小的c…组成，在整个感兴趣的计算域中有更多的细胞或晶格，并且使用细胞去除方法对进化界面进行建模；衬底原子被分配在各自的原子尺度的方阵中。此外，还采用蒙特卡罗方法计算了入射高能离子穿透基底的轨迹。该模型具有现象学模拟多层表面反应、表面粗糙度和刻蚀过程中特征轮廓演变的突出特点。为了验证该模型的有效性，对平面硅衬底的氯化学蚀刻进行了模拟，显示了表面反应层的结构、Cl原子在其中的分布以及与入射中性离子通量比和离子能量有关的表面粗糙度。不同离子能量下，蚀刻产率随中性离子通量比的变化趋势与已知实验数据相似，表明本模型较好地反映了离子增强蚀刻中中性反应物与高能离子之间的协同效应。考虑化学蚀刻、钝化层形成（表面氧化和缓蚀剂沉积）和表面充电的影响，模拟了低于0.1 μm的Si线空模式在蚀刻过程中的特征轮廓演变。数值结果显示了反应性离子蚀刻（RIE）滞后的发生取决于中性离子通量比和离子能量，并与蚀刻和等离子体和表面诊断实验进行了比较。在较高的通量比和较高的能量下，RIE滞后的程度更为显著，这与特征底部表面氯化程度的差异有关；实际上，对于小于0.1 μm量级的窄图案特征，由于几何阴影的严重影响，底表面本质上倾向于缺乏中性反应物。此外，基于这些结果，我们开发了新型栅极介质和电极材料的先进栅极蚀刻工艺。少

An understanding of the particle transport and surface reactions in microstructures on substrates are indispensable for the control of advanced plasma processing for the fabrication of sub-0.1 μm devices. We have developed an atomic scale model of the particle transport and surface reactions, to simulate the feature profile evolution for nanometer-scale control of the profile and critical dimensions during plasma etching. The model is a phenomenological one at an intermediate scale between molecular dynamics simulation and continuum models. The model takes into account the transport of ions and neutrals in microstructures, multilayer surface reactions through ion-enhanced etching, and the resulting feature profile evolution, where the transport is analyzed by a particle simulation based on successively injected single-particle trajectories with three velocity components. To incorporate an atomistic picture into the model, the substrates are taken to consist of a large number of small c … More ells or lattices in the entire computational domain of interest, and the evolving interfaces are modeled by using the cell removal method ; the substrate atoms are allocated in the respective square lattices of atomic scale. Moreover, the Monte Carlo calculation is employed for the trajectory of incident energetic ions that penetrate into substrates. The present model has a prominent feature to phenomenologically simulate the multilayer surface reaction, the surface roughness, and also the feature profile evolution during etching. The etching of planar Si substrates with chlorine chemistries was simulated for a test of validity of the present model, showing the structure of surface reaction layers, the distribution of Cl atoms therein, and the surface roughness that depend on incident neutral-to-ion flux ratio and ion energy. The etch yield as a function of neutral-to-ion flux ratio for different ion energies gave a similar tendency to the known experimental data, indicating that the present model properly reflects synergistic effects between neutral reactants and energetic ions in the ion-enhanced etching.The feature profile evolution during etching was then simulated for sub-0.1 μm line-and-space patterns of Si, taking into account also the effects of chemical etching, passivation layer formation (surface oxidation and inhibitor deposition), and surface charging. The numerical results exhibited the reactive ion etching (RIE) lag that occurs depending on neutral-to-ion flux ratio and ion energy, being compared with the experiments of etching and plasma and surface diagnostics. The degree of RIE lag was found to be more significant at higher flux ratios and higher energies, being associated with the difference in surface chlorination at the feature bottom ; in effect, for narrow pattern features of the order of sub-0.1 μm, the bottom surfaces tend to intrinsically starve for neutral reactants owing to severe effects of the geometrical shadowing. Moreover, based on these results, we developed the fabrication processes for advanced gate etch processes of new gate dielectric and electrode materials. Less