Collaborative Research: GOALI - Non-Equilibrium Processes, Stability, Design and Control of Pulsed Plasmas for Materials Processing

该项目的目标是研究半导体晶圆脉冲等离子体加工的科学和技术，旨在建立一个知识库，使脉冲等离子体能够优化材料改性。等离子体辅助材料加工在很大程度上是在微电子设备生产中不断取得令人印象深刻的进步的主要原因。等离子体蚀刻是唯一已知的，工业上可实现的方法来制造纳米尺寸的逻辑和存储芯片。在等离子体蚀刻过程中，离子和中性粒子的通量被指向被加工的晶圆。粒子撞击晶圆表面的能量和角度是制备微电子器件、纳米结构和生物相容性材料的关键参数。控制这些参数可以更好地控制表面成分，在微电子制造中，蚀刻速率。低温等离子体加工等离子体材料传统上采用连续激发等离子体。然而，所有主要的半导体芯片和设备制造商都预测脉冲等离子体将成为实现10纳米以下特征尺寸的使能技术。这项研究最直接的影响是解决对高性能微电子、纳米结构和生物相容性材料的等离子体处理至关重要的基础科学问题。除了更广泛的技术影响外，该项目还将高度关注教育推广。Gekelman教授是LAPTAG（洛杉矶物理教师联盟小组）的创始人之一，他和LAPTAG的几名学生将参与这些等离子体处理研究。库什纳教授是密歇根等离子体科学与工程研究所的主任，他将利用这些资源推出“每日等离子体图片”网站，目的是提供等离子体的信息图像，以教育公众和学生关于等离子体的知识。缺乏对脉冲等离子体系统动力学的基本理解是目前广泛采用的障碍。例如，在脉冲等离子体中，特别是在电负性等离子体中，几乎普遍观察到不稳定性和波动，这有时会妨碍在理想的参数空间中运行。人们不了解这些不稳定的根源和防止它们的手段。脉冲等离子体处理可以任意复杂。例如，现代电容耦合等离子体蚀刻工具可以由多达3个不同频率的独立电源驱动，这些电源可以以不同的重复率和不同的占空比独立脉冲。参数的组合可以达到数百万。这个非常大的参数空间对脉冲等离子体处理的基本理解有很大的好处，因此能够预测等离子体的性能。在这个研究项目中，一个高度合作的实验建模工作将研究用于材料加工的脉冲等离子体的基本特性，重点是不稳定性和波，诊断和建模从脉冲余辉到动力等离子体的转变动力学，以及通过脉冲提高均匀性的方法。激光诱导荧光将用于表征离子的轨迹，因为它们被加速通过脉冲等离子体产生的瞬态鞘；并将与朗缪尔探测器对等离子体特性的测量相关联。多维计算机建模将通过这些测量得到验证，并将进一步用于阐明与脉冲系统中等离子体输运相关的基本问题。

The goal of this project is to investigate the science and technology of pulsed plasma processing of semiconductor wafers aimed towards developing a knowledge base that will enable pulsed plasmas to be optimized for materials modification. Plasma assisted materials processing is largely responsible for the impressive progress that continues to be made in production of microelectronics devices of ever increasing capability. Plasma etching is the only known, industrially implementable method to fabricate the nanometer sized features in logic and memory chips. During plasma etching, fluxes of ions and neutral particles are directed towards the wafer being processed. The energy and angle of impact of the particles onto the surface of wafers are the critical parameters for the fabrication of microelectronic devices, as well as nanostructured and biocompatible materials. Control of these parameters allows for finer control of the surface composition and, in microelectronics fabrication, etch rate. Low temperature plasmas for plasma materials processing have traditionally used continuously excited plasmas. However, all major semiconductor chip and equipment manufacturers are predicting that pulsed plasmas will be the enabling technology for achieving sub-10 nanometer feature sizes. The most direct impact of this research is addressing fundamental science issues that are of paramount importance to the plasma processing of high performance microelectronics, nanostructures and biocompatible materials. In addition to the technological broader impacts, this project will be highly focused on educational outreach. Prof. Gekelman is one of the founders of LAPTAG (Los Angeles Physics Teachers Alliance Group) and several LAPTAG students and will be involved in these plasma processing studies. Prof. Kushner, director of the Michigan Institute of Plasma Science and Engineering, will leverage those resources to launch the Plasma Picture of the Day website with the goal of providing informative images of plasmas to educate the general public and school children about plasmas.The lack of fundamental understanding of the dynamics of pulsed plasma systems is the current impediment to widespread adoption. For example, instabilities and waves are nearly universally observed in pulsed plasmas, and particularly in electronegative plasmas, which sometimes prevents operation in desirable parameters spaces. The sources of these instabilities and the means to prevent them are not understood. Pulsed plasma processing can be arbitrarily complex. For example, modern capacitively coupled plasma etching tools may be driven by up to 3 separate power supplies at different frequencies which can be pulsed independently at different repetition rates and different duty cycles. The combinations of parameters can number into the millions. This extremely large parameter space places a large premium on having a fundamental understanding of pulsed plasma processing and so be able to predict plasma performance. In this research project, a highly collaborative experimental-modeling effort will investigate the fundamental properties of pulsed plasmas as used in materials processing, with an emphasis on instabilities and waves, diagnosing and modeling the dynamics of the transition from interpulse afterglow to powered plasma, and the means to improve uniformity through pulsing. Laser induced fluorescence will be used to characterize the trajectory of ions as they are accelerated through the transient sheaths produced by pulsed plasmas; and will be correlated with Langmuir probe measurements of plasma properties. Multi-dimensional computer modeling will be validated by these measurements and will be further used to illuminate fundamental issues related to plasma transport in pulsed systems.