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的脉冲等离子体加工的科学和技术，旨在开发一个知识库，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推动了能力不断增强的微电子设备的生产不断取得令人印象深刻的进步。等离子体刻蚀是唯一已知的、在工业上可实现的在逻辑和存储芯片中制造纳米级特征的方法。在等离子体刻蚀过程中，离子和中性粒子的通量直接流向正在加工的晶片。粒子在晶片表面的能量和入射角是制造微电子器件以及纳米结构和生物相容性材料的关键参数。这些参数的控制允许更精细地控制表面成分以及在微电子制造中的蚀刻速率。用于等离子体材料加工的低温等离子体传统上使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低于10纳米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、纳米结构和生物兼容材料的等离子加工至关重要的基础科学问题。除了更广泛的技术影响外，该项目还将高度侧重于教育宣传。Gekelman教授是LAPTAG(洛杉矶物理教师联盟组织)和几名LAPTAG学生的创始人之一，他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所长，他将利用这些资源推出每日等离子体图片网站，目的是提供丰富的等离子体图像，教育普通公众和学童关于等离子体的知识。对脉冲等离子体系统动力学的基本了解是目前广泛采用的障碍。例如，在脉冲等离子体中几乎普遍观察到不稳定性和波，特别是在电负性等离子体中，这有时会阻止在理想的参数空间中运行。这些不稳定的来源和防止它们的方法尚不清楚。脉冲等离子体处理可以是任意复杂的。例如，现代电容耦合等离子刻蚀工具可以由多达3个不同频率的独立电源驱动，这些电源可以在不同的重复率和不同的占空比下独立地脉冲。参数的组合可以数以百万计。这一极大的参数空间非常重视对脉冲等离子体处理的基本了解，因此能够预测等离子体性能。在这项研究项目中，一项高度协作的实验模拟工作将研究材料加工中使用的脉冲等离子体的基本性质，重点是不稳定性和波动，诊断和模拟从脉冲间余辉到带电等离子体的转变的动力学，以及通过脉冲提高均匀性的方法。激光诱导荧光将被用来表征离子通过脉冲等离子体产生的瞬变鞘加速时的轨迹；并将与朗缪尔探针测量的等离子体性质相关联。多维计算机模型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传输有关的基本问题。

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.