Microplasma for Dry Etching: New Approaches for Micro and Nano Systems

等离子体加工通常用于半导体加工应用，是硅蚀刻的主要技术。传统蚀刻机的目标是在硅晶圆所在的工艺室中产生均匀的等离子体。然而，在微机械加工和纳米技术的应用中，替代范例可能被证明是有用的。例如，目前的制造技术对于制造100个不同深度的沟槽阵列是不实用的，这将需要100个光刻步骤。这种阵列在生物细胞分选等应用中可能很有用。本提案解决了有关空间受限反应等离子体（微等离子体）的科学和技术及其在硅和其他材料刻蚀中的应用的问题。特别地，它聚焦于原位微等离子体，这是由在硅片上图案的电极产生的。这一概念的可行性与最近在微等离子体方面的其他工作截然不同，已经通过初步实验证明了这一概念的可行性，在初步实验中，原位直流微等离子体在不到一小时的时间内完全蚀刻通过硅片。提出的努力将探索物理，技术和诊断反应微等离子体蚀刻硅和其他材料。许多蚀刻结构将被检查它们对等离子体约束、蚀刻速率、各向异性、掩膜选择性和电极磨损的影响。有前途的电极结构将被探索，包括选择离子通量是静电控制，以局部调整蚀刻速率和侧壁轮廓。各种电极材料，供电方案和气体化学将被评估。将开发和使用原位和非原位诊断工具（包括薄膜Langmuir探针）。将进行光谱分析。研究了Paschen击穿曲线、周围气体的分子行为、电离速率和电子能量的依赖关系，以及这些参数与蚀刻速率和刻蚀谱的关系。通过改进全球等离子体分析，将建立反应性微等离子体的理论模型。这包括结合实际的基本数据和考虑放电几何形状和电极材料。理论模型将用于缩放研究，以确定等离子体是否可以缩小到纳米尺寸。我们将进行配套实验来探索尺度限制并验证理论。所提出的反应性微等离子体不仅有潜力为传统的蚀刻应用做出贡献，而且还促进了以前不可行的微结构的制造。利用微等离子体，只需两个掩蔽步骤，就可以建立一个由100个不同深度的沟槽组成的阵列。此外，如果研究成功，不仅可以单独指定阵列中每个沟槽的轮廓，还可以借助二次电极控制的局部电场来倾斜蚀刻方向。从长远来看，拟议的研究可能会导致其他研究途径，包括通过溅射或等离子体增强化学气相沉积（PECVD）的局部沉积。

0100366GianchandaniPlasma processing is routinely used in semiconductor processing applications, and is the dominant technique for silicon etching. Conventional etchers aim to create a uniform plasma across the process chamber in which the silicon wafers are located. However, there are applications in micromachining and nanotechnology in which alternative paradigms may prove useful. For example, present fabrication techniques are not practical for manufacturing an array of trenches with 100 different depths, which would require 100 lithography steps. Such a array could be useful for applications like biological cell sorting.This proposal addresses questions pertaining to the science and technology of spatially confined reactive plasmas (microplasmas) and their application to the etching of silicon and other materials. In particular, it focuses on in-situ microplasmas, which are generated by electrodes patterned on the silicon wafer itself. The viability of this concept, which differs radically from other recent work in microplasmas, has been demonstrated by preliminary experiments in which in-situ DC microplasmas were used to etch completely through a silicon wafer in less than one hour. The proposed effort will explore the physics, technology, and diagnostics for reactive microplasmas for etching silicon and other materials.A number of etching configurations will be examined for their impact on plasma confinement, etch rates, anisotropy, mask selectivities, and electrode wear. Promising electrode structures will be explored, including options in which the ion flux is electrostatically controlled to locally adjust the etch rate and sidewall profile. Various electrode materials, powering schemes, and gas chemistries will be evaluated. Both in-situ and ex-situ diagnostic tools (including thin-film Langmuir probes) will be developed and used. Spectroscopic analysis will be performed. The dependencies of the Paschen breakdown curve, the molecular behavior of the ambient gas, the ionization rates and the electron energies, as well as the relationship of these parameters to the etch rates and profiles will be explored.Theoretical models will be developed for the reactive microplasmas by refining global plasma analysis. This includes the incorporation of realistic basic data and consideration of discharge geometry and electrode material. The theoretical models will be used for scaling studies to determine if the plasmas can be reduced to nanometer dimensions. Supporting experiments will be carried out to explore the scaling limits and validate the theory.The proposed reactive microplasmas have the potential not only for making a contribution to traditional etching applications, but also facilitating the fabrication of microstructures that were previously infeasible. Using microplasmas, an array of 100 trenches with different depths could be built with just two masking steps. In addition, if the proposed research is successful, not only will it be possible to individually specify the profile of every trench in the array, but also to skew the direction of the etch with the help of local electric fields controlled by secondary electrodes. In the longer term, the proposed research could lead to other avenues of research, including localized deposition by sputtering or plasma enhanced chemical vapor deposition (PECVD).