In the ideal case, plasma-enhanced atomic layer etching enables the ability to not only remove one monolayer of material but also leave adjacent layers undamaged. This dual mandate requires fine control over the flux of species to ensure efficacy, while maintaining an often arduously low ion energy. Electron beam-generated plasmas are well-suited for etching at low ion energies as they are generally characterized by highly charged particle densities (10¹⁰–10¹¹ cm⁻³) and low electron temperatures (<1.0 eV), which provide the ability to deliver a large flux of ions whose energies are <5 eV. Raising the ion energy with substrate biasing thus enables process control over an energy range that extends down to values commensurate with the bond strength of most material systems. In this work, we discuss silicon nitride etching using pulsed, electron beam-generated plasmas produced in argon-SF₆ backgrounds. We pay particular attention to the etch rates and selectivity versus oxidized silicon nitride and polycrystalline silicon as a function of ion energy from a few eV up to 50 eV. We find the blanket etch rate of Si₃N₄ to be in the range of 1 A/s, with selectivities (versus SiO₂ and poly-Si) greater than 10:1 when ion energies are below 30 eV.

中文翻译：

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用电子束产生的等离子体蚀刻：硅基薄膜的选择性与离子能量的关系

在理想情况下，等离子体增强的原子层刻蚀不仅能够去除材料的一个单层，而且还能使相邻层不受损坏。这种双重要求要求对物质的通量进行精细控制，以确保功效，同时保持通常非常低的离子能量。电子束产生的等离子体非常适合在低离子能量下进行蚀刻，因为它们通常具有高电荷粒子密度（10 ¹⁰ –10 ¹¹  cm ^-3）和较低的电子温度（<1.0 eV），这提供了传递能量<5 eV的大离子通量的能力。因此，通过衬底偏置来提高离子能量可实现对能量范围的过程控制，该能量范围向下扩展至与大多数材料系统的键合强度相称的值。在这项工作中，我们讨论使用在氩气-SF ₆背景下产生的脉冲，电子束产生的等离子体进行氮化硅蚀刻。我们特别注意相对于氧化氮化硅和多晶硅的蚀刻速率和选择性，它是从几eV到最高50 eV的离子能量的函数。我们发现，Si ₃ N ₄的毯式蚀刻速率在1 A / s的范围内，具有选择性（相对于SiO ₂ 当离子能量低于30 eV时，多晶硅（Poly-Si）和多晶硅（Poly-Si）大于10：1。