Career: Silicon Etching: Gas-Surface Dynamics and Profile Evolution

职业：硅蚀刻：气体表面动力学和轮廓演化

• 批准号: 9623450
• 负责人: Konstantinos Giapis
• 金额: $ 31万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-01 至 2000-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9623450&HistoricalAwards=false
• 关键词: Career; Silicon; Etching; Gas; Surface

ABSTRACT CTS-9623450 This project addresses the importance of inelastic and reactive scattering in the etching of semiconductors. Experiments are proposed with a recently invented hypersonic neutral beam of fluorine atoms with translational energies in the 3-25 eV regime for fundamental studies of the gas-surface dynamics occurring during steady-state etching of silicon and etching studies of submicron features in silicon in order to understand how neutral beams etch. The effort is based on recent results from profile evolution modeling and experiments with flourine atom beams with translational energies between 3 and 18 eV. Anisotropic etching of silicon at room temperature with fluorine chemistry (no sidewall deposition) is demonstrated as a proof of the capabilities of such beams. This has been possible because of direct reactions occurring at the high translational energies employed. Collision-induced desorption (CID) has been implicated as the mechanism responsible for the increased desorption rate of fluorinated silicon moieties from the SiFx layer at the higher energies. Rapid removal of the SiF3 product in the CID mode enables rapid fluorination of the exposed surface, which increases fluorine utilization and, in turn, results in a reduction of the thermally desorbing unreacted fluorine-atom flux. Reduction of scattered fluorine to the sidewalls dramatically improves anisotropy. Fundamental measurements of the energy and flux of unreacted F atoms and reaction products (SixFy) leaving the SiFx layer during etching are made. Moreover, similar measurements are performed on the silicon dioxide surface. Silicon dioxide is ubiquitous on today's wafers (e.g., as a hard mask, gate oxide, etc.) and scattering on its surface will also affect profile evolution. Besides improving fundamental understanding of gas-surface dynamics, these measurements provide for a description of the physics and chemistry of the interaction, which is incorporated into a Monte Carlo simulator of profile evolution. Preliminary calculations based on detailed scattering experiments on SiFx are shown to capture profile peculiarities such as the so-called "microtrenching", that is, the appearance of grooves at the bottom of etched features. The model is improved to describe pattern-dependent etching, three-dimensional effects, and the roughness appearing on etched surfaces. By including microstructure charging and ion deflection effects, the applicability of the profile simulator is enhanced, enabling its combination with plasma reactor models (developed by others) for designing the etch tools for the next generation of ultrahigh-density semiconductor devices. Etching experiments are also performed to support the model and verify predictions of profile peculiarities. Understanding the origin of predicted and observed deviations from the ideal anisotropic profile is expected to enable control over the final profile. Electrical damage studies on gate oxides of MOS devices are done as a demonstration of the potential of the technique. Finally, upon perfection of the technique, fabrication of quantum-confined and photonic bandgap structures is attempted. In order to integrate research with education in chemical engineering, the relation between classical chemical engineering concepts and modern electronic material processing techniques is exposed. As an example, special topics are offered in the undergraduate thermodynamics class, such as equilibrium in plasmas and surface thermodynamics, which are not traditionally covered. An introductory plasma experiment is planned for the undergraduate laboratory with hands-on experience in diagnostics. Extended research projects are also offered to undergraduates in the P.I.'s laboratory to enhance their appreciation of experimental science. At the graduate level, in addition to a course on electronic materials processing, plans are made to offer a new course on beam modification of surfaces, which is based on results and understanding obtained from this proposed research. ***

摘要CTS-9623450 本计画探讨半导体蚀刻过程中非弹性及反应性散射的重要性。 实验提出了一个最近发明的高超音速中性束的氟原子的平移能量在3-25 eV的制度的气体表面动力学的基础研究，在硅的稳态蚀刻和硅中的亚微米功能的蚀刻研究，以了解如何中性束蚀刻。 这项工作是基于最近的结果，从档案演变建模和实验与氟原子束的平移能量在3和18 eV之间。 硅在室温下的氟化学各向异性蚀刻（无侧壁沉积）被证明是这种光束的能力的证明。 这是可能的，因为直接反应发生在高平移能量。 碰撞诱导脱附（CID）已被牵连的机制，负责从SiFx层在较高的能量的氟化硅部分的脱附速率增加。 在CID模式下快速去除SiF 3产物能够快速去除暴露表面，这增加了氟利用率，并且进而导致热解吸的未反应的氟原子通量的减少。散射到侧壁的氟的减少显著地改善了各向异性。 未反应的F原子和反应产物（SixFy）的能量和通量的基本测量在蚀刻过程中离开SiFx层。 此外，在二氧化硅表面上进行类似的测量。 二氧化硅在当今的晶片上无处不在（例如，作为硬掩模、栅极氧化物等）。并且在其表面上的散射也将影响轮廓演化。 除了提高气体表面动力学的基本理解，这些测量提供了一个描述的物理和化学的相互作用，这是纳入Monte Carlo模拟器的轮廓演变。 初步计算的基础上详细的散射实验SiFx捕获轮廓的特点，如所谓的“微沟槽”，即在蚀刻功能的底部的凹槽的外观。 该模型进行了改进，以描述图案相关的蚀刻，三维效果，和出现在蚀刻表面上的粗糙度。 通过包括微结构充电和离子偏转效应，轮廓模拟器的适用性得到增强，使其与等离子体反应器模型（由他人开发）相结合，用于设计下一代超高密度半导体器件的蚀刻工具。 蚀刻实验也进行了支持模型和验证预测的轮廓特性。 了解预测和观察到的偏离理想的各向异性配置文件的起源，预计能够控制最终的配置文件。对MOS器件栅氧化层的电损伤研究表明了该技术的潜力。 最后，在技术完善的基础上，尝试制作量子限制和光子带隙结构。 为了使化学工程的研究与教育相结合，阐述了经典化学工程概念与现代电子材料加工技术之间的关系。 作为一个例子，在本科热力学课程中提供了特殊的主题，如等离子体和表面热力学的平衡，这是传统上不包括在内。 计划为具有诊断学实践经验的本科实验室进行介绍性血浆实验。 扩展的研究项目也提供给P.I.的本科生。的实验室，以提高他们对实验科学的欣赏。 在研究生阶段，除了电子材料加工课程外，还计划提供一门关于表面束改性的新课程，这是基于从这项拟议研究中获得的结果和理解。 ***