Feature profiles of Si etched in HBr-containing plasmas have been analyzed through a comparison between experiments and simulations. The emphasis was placed on a mechanistic understanding of the difference in the evolution of profile anomalies (such as tapering, footing, and microtrenching) during Si etching between HBr- and Cl₂-based plasmas. Experiments were made with Cl₂/O₂/HBr chemistry by varying the HBr mixing ratio, using a commercial ultrahigh-frequency electron cyclotron resonance plasma etching reactor, where HCl/O₂ chemistry was also employed to compare with that of Cl₂/O₂ and HBr/O₂. Numerical simulations of feature profile evolution were made using a semiempirical atomic-scale cellular model based on the Monte Carlo method that we developed for Si etching in Br₂, HBr, and Cl₂ plasmas, where surface chemistry and kinetics include the effects of ion reflection from and/or penetration into feature surfaces on incidence. The experiments showed more vertical sidewalls with less footing and microtrenching with HBr; concretely, with increasing HBr mixing ratio in Cl₂/O₂/HBr plasmas, the tapering is reduced and minimized at 80% HBr where slight lateral or side etching tends to occur, the footing is reduced gradually, and the microtrenching fades away at more than 20% HBr. A comparison with simulations, with the help of separate analyses of ion reflection from surfaces on incidence, indicated that the smaller reflection probability and reflected energy fraction of Br⁺ on tapered sidewalls (compared to Cl⁺) are responsible for reduced tapering, footing, and microtrenching in HBr-containing plasmas; moreover, chemical etching effects of neutral H atoms at the feature bottom and sidewalls, arising from the larger reaction probability of H (compared to Cl), are also responsible for reduced microtrenching and for reduced tapering (and the lateral or side etching induced) therein.

中文翻译：

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含 HBr 等离子体中 Si 蚀刻过程中特征轮廓演变的模型分析

通过实验和模拟之间的比较，分析了在含 HBr 等离子体中蚀刻的 Si 的特征轮廓。重点放在对基于HBr 和 Cl ₂的等离子体之间的 Si 蚀刻过程中轮廓异常（例如锥形、基脚和微沟槽）演变差异的机械理解上。使用商用超高频电子回旋共振等离子体蚀刻反应器，通过改变 HBr 混合比对 Cl ₂ /O ₂ /HBr 化学进行了实验，其中还使用了HCl/O ₂化学与 Cl ₂ /O进行了比较₂和 HBr/O ₂. 使用基于我们为 Br ₂、HBr 和 Cl ₂等离子体中的Si 蚀刻开发的蒙特卡罗方法的半经验原子尺度细胞模型对特征轮廓演化进行了数值模拟，其中表面化学和动力学包括离子反射的影响在入射时从和/或穿透到特征表面。实验显示了更多的垂直侧壁，更少的基脚和使用 HBr 的微沟槽；具体而言，随着 HBr 在 Cl ₂ /O _{2 中}混合比的增加/HBr 等离子体，在 80% HBr 时锥度减小并最小化，其中容易发生轻微的横向或侧面蚀刻，基脚逐渐减小，微沟槽在超过 20% HBr 时逐渐消失。借助对入射表面离子反射的单独分析，与模拟的比较表明，在锥形侧壁上Br ^{+ 的}反射概率和反射能量分数较小（与 Cl ⁺相比）) 负责减少含 HBr 等离子体中的锥度、基脚和微沟槽；此外，中性氢原子在特征底部和侧壁的化学蚀刻效应，源于 H 的较大反应概率（与 Cl 相比），也是减少微沟槽和减少锥度（以及诱导的横向或侧面蚀刻）的原因.