An etching system based on the interaction of electrons extracted from a direct current hollow cathode (HC) Ar plasma and injected toward an Si3N4 covered silicon substrate located in the downstream reactive environment created by an additional remote CF4/O2 plasma source was developed and evaluated. By controlling the properties of the injected beam electrons, this approach allows to deliver energy to a surface functionalized by exposure to reactive species and initiate surface etching. The energy of the primary beam electrons is controlled by the acceleration voltage relative to the HC discharge. Ar atoms flow from the high-pressure HC discharge into the low pressure downstream reactive environment in the process chamber. For an acceleration voltage greater than the ionization potential of Ar and/or process gas species, the energetic primary beam electrons produce a secondary plasma in the process chamber and can also cause additional dissociation. The authors have characterized the properties of the secondary plasma and also surface etching of Si3N4 as a function of process parameters, including acceleration voltage (0–80 V), discharge current of the HC discharge (1–2 A), pressure (3.5–20 mTorr), source to substrate distance (1.5–5 cm), and feed gas composition (20% and 80% O2 in CF4/O2). The electron energy probability function measured with a Langmuir probe about 2.5 cm below the extraction ring suggests several major groups of electrons for this situation, including high energy primary beam electrons with an energy that varies as the acceleration voltage is changed and low-energy electrons produced by beam electron-induced ionization of the Ar gas in the process chamber. When a remote CF4/O2 plasma is additionally coupled to the process chamber, Si3N4 surfaces can be functionalized, and by varying the energy of the beam electrons, Si3N4 etching can be induced by electron-neutral synergy effect with plasma-surface interaction. For conditions without beam electron injection, the remote plasma etching rate of Si3N4 depends strongly on the O2 concentration in the CF4/O2 processing gas mixture and can be suppressed for O2-rich process conditions by the formation of an SiONF passivation layer on the Si3N4 surface. The combination of the HC electron beam (HCEB) source with the remote plasma source makes it possible to induce Si3N4 etching for O2-rich remote plasma conditions where remote plasma by itself produces negligible Si3N4 etching. The electron enhanced etching of Si3N4 depends strongly on the O2/CF4 mixing ratio reflecting changing arrival rates of O and F species at the surface. Optical emission spectroscopy was used to estimate the ratio of gas phase F and O densities and found to be controlled by the gas mixing ratio and independent of HCEB operating conditions. At this time, the detailed sequence of events operative in the etching mechanism is unclear. While the increase of the electron energy is ultimately responsible for initiating surface etching, presently, the authors cannot rule out a role of ions from the simultaneously produced secondary plasma in plasma-surface interaction mechanisms.

中文翻译：

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在下游反应环境中由空心阴极等离子体中的电子束等离子体诱导的 Si3N4 蚀刻

开发并评估了一种蚀刻系统，该蚀刻系统基于从直流空心阴极 (HC) Ar 等离子体中提取的电子，并注入位于下游反应环境中的 Si3N4 覆盖的硅衬底，该反应环境由额外的远程 CF4/O2 等离子体源产生。通过控制注入束电子的特性，这种方法允许将能量传递到通过暴露于活性物质而功能化的表面并启动表面蚀刻。初级束电子的能量由相对于 HC 放电的加速电压控制。Ar 原子从高压 HC 放电流入处理室中的低压下游反应环境。对于大于 Ar 和/或工艺气体种类的电离电位的加速电压，高能初级束电子在处理室中产生次级等离子体，也可能引起额外的离解。作者将二次等离子体的特性和 Si3N4 的表面蚀刻特性描述为工艺参数的函数，包括加速电压 (0–80 V)、HC 放电的放电电流 (1–2 A)、压力 (3.5– 20 mTorr)、源到基板的距离 (1.5–5 cm) 和原料气组成（CF4/O2 中的 O2 为 20% 和 80%）。用朗缪尔探针在提取环下方约 2.5 厘米处测量的电子能量概率函数表明在这种情况下有几个主要的电子群，包括能量随着加速电压变化而变化的高能初级束电子和由束电子诱导处理室中的 Ar 气体电离产生的低能电子。当远程 CF4/O2 等离子体额外耦合到处理室时，Si3N4 表面可以被功能化，并且通过改变束电子的能量，Si3N4 蚀刻可以通过电子中性协同效应与等离子体表面相互作用引起。对于没有电子束注入的条件，Si3N4 的远程等离子体蚀刻速率很大程度上取决于 CF4/O2 处理气体混合物中的 O2 浓度，并且可以通过在 Si3N4 表面上形成 SiONF 钝化层来抑制富氧工艺条件. HC 电子束 (HCEB) 源与远程等离子体源的组合使得在富氧远程等离子体条件下诱导 Si3N4 蚀刻成为可能，其中远程等离子体本身产生的 Si3N4 蚀刻可忽略不计。Si3N4 的电子增强蚀刻很大程度上取决于 O2/CF4 混合比，反映了 O 和 F 物种在表面的变化到达率。光学发射光谱用于估计气相 F 和 O 密度的比率，发现它受气体混合比控制并且与 HCEB 操作条件无关。目前，蚀刻机制中运行的详细事件序列尚不清楚。虽然电子能量的增加最终是引发表面蚀刻的原因，但目前，