Measurement of Electron Concentrations in Low Frequency Glow Discharges by High-Frequency (4-15MHz) Impedance Analysis: Research Initiation Award

射频等离子体用于各种工艺，包括 在半导体工业中用于等离子沉积和等离子 蚀刻 等离子体可以被看作是至少 三个过程： (1)电压施加到一个电极，而另一个电极 接地，在 电极; (2)电场将电子加速到很高的速度 能量（1至20 eV）; (3)在这些高能量下， 带电分子形成更多的电子、离子、自由基 物种和激发分子。 (4)自由基彼此、其他气相发生反应 分子，或与固体表面上的分子 反应堆;以及 (5)离子通过等离子体鞘层被加速， 产生高能量轰击（高达几百eV）的 影响表面反应发生的固体表面 那里 目前，大多数蚀刻和蚀刻工艺的开发和控制， 沉积过程主要由经验方法控制， 检查所产生的最终效果（例如蚀刻速率、均匀性 横跨晶片、定向蚀刻等）作为过程的函数， 条件（功率、压力、气体成分、频率）， 特殊反应堆 一个更基本的理解一个特定的 这将加快发展进程（特别是新的 或基本上不同的等离子体工艺），并有助于理解 控制这些过程。 为了获得这样的基础 理解并最终建模整个系统， 对每个人的定量理解和/或测量 过程是需要的。 本研究项目的目标是建立和使用一个 确定电子浓度随时间变化的新方法 低频（40 - 400 Hz）放电。 高频 放电产生更快的蚀刻和沉积速率， 频率放电产生更高的离子轰击能量， 固体表面，其导致改进的表面效果， 更好的蚀刻方向性。 PI的方法包括 高频扰动低频放电 信号，然后测量和分析高频 在低频周期内，阻抗作为时间的函数。 这些阻抗将根据等离子体解释为 电路给出电子浓度在 放电作为时间的函数。 这项技术将允许 实验者定量测定电子 在特定蚀刻或沉积中出现的浓度 放电。 电子浓度测量将有助于 预测电子分子反应发生的速率， 等离子体反应器 这些测量可以与 确定对蚀刻的最终影响的其他信息，或 沉积速率和特性。

Radio-frequency plasmas are used for a variety of processes including uses in the semiconductor industry for plasma deposition and plasma etching. The plasma can be viewed as the combination of at least three processes: (1) a voltage is applied to one electrode while another one is grounded creating an electric field between the electrodes; (2) the electric field accelerates electrons to very high energies (1 to 20 eV); (3) at those high energies, electrons react with neutrally charged molecules to form more electrons, ions, free radical species, and excited molecules. (4) the free radicals react with each other, other gas phase molecules, or with the molecules on solid surfaces of the reactor; and (5) ions are accelerated through the plasma sheathes to produce high energy bombardment (up to several hundred eV) of the solid surfaces which influence the surface reactions occurring there. At the present time the development and control of most etch and deposition processes is mainly governed by empirical approaches that examine the final effect created (such as etching rate, uniformity across a wafer, etch directionally, etc.) as a function of the process conditions (power, pressure, gas composition, frequency) for a particular reactor. A more fundamental understanding of a particular process would speed up the development process (especially of new orsubstantially different plasma processes) and aid in understanding the control of these processes. To obtain such a fundamental understanding and to ultimately model the whole system, a quantitative understanding and/or measurement of each individual process occurring is needed. The objectives of this research project are to establish and use a new method to determine electron concentrations as function of time in low frequency (40 - 400 Hz) discharges. High frequency discharges produce faster etch and deposition rates while low frequency discharges produce higher ion bombardment energies of solid surfaces which leads to improved surface effect such as better etching directionality. The PI's method involves perturbing the low frequency discharge with high frequency signals, and then measuring and analyzing the high-frequency impedance as a function of time within the low frequency cycle. These impedances will be interpreted in terms of the plasma as an electrical circuit to give the electron concentrations in the discharge as a function of time. The technique will allow experimenters to determine quantitatively the electron concentrations occurring in specific etching or deposition discharges. Electron concentration measurements will help in predicting rates of the electron-molecule reactions occurring in the plasma reactor. These measurements can be combined with other information to determine the ultimate effects on etching or deposition rates and characteristics.