Recently, the electrical asymmetry effect (EAE) has been proven effective not only in separate control of the ion energy and ion flux, but also in modulation of the plasma radial uniformity. Since no major change in reactor constructions is required, this method is promising and of significant importance in the plasma industry. In this work, a two-dimensional electromagnetic fluid model is employed to investigate the influence of the EAE on the plasma density distribution under various voltages (i.e., the peak-to-peak voltage V0 equals to 33 V, 56 V and 100 V) and pressures (i.e., 50 mTorr, 200 mTorr and 750 mTorr), in H2 capacitively coupled plasma (CCP) discharges sustained by multiple consecutive harmonics. The results indicate that at V0=33 V or 750 mTorr, the plasma density is characterized by a broad maximum at the radial center, and the effectiveness of the EAE on the modulation of the plasma radial uniformity is limited. When V0 becomes higher, the plasma distribution varies obviously by adjusting the phase shift of the fundamental frequency θ1. For instance, when θ1 increases from 0 to 2π at V0=56 V, the plasma density shifts from uniform over center-high to uniform. Moreover, at V0=100 V, the best uniformity is observed at θ1=π. When the pressure decreases to 50 mTorr, although the uniformity varies significantly with θ1, the plasma density stays low, which may be not welcomed in the plasma processing. Different influences of the EAE on the plasma radial uniformity can be understood by examining the electron heating induced by the sheath expansion and the electric field reversal under various discharge conditions. The results obtained in this work could help us to have a better understanding of the EAE on the plasma radial uniformity, which would be useful to improve the plasma processing in large area CCP reactors.

中文翻译：

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如何解决大面积电容耦合等离子体的均匀性问题？建模调查

最近，电不对称效应 (EAE) 已被证明不仅在单独控制离子能量和离子通量方面有效，而且在调制等离子体径向均匀性方面也是有效的。由于不需要对反应器结构进行重大更改，因此该方法很有前途，并且在等离子体工业中具有重要意义。在这项工作中，采用二维电磁流体模型研究了EAE在各种电压下（即峰峰值电压V0等于33 V、56 V和100 V）对等离子体密度分布的影响和压力（即 50 mTorr、200 mTorr 和 750 mTorr），在由多个连续谐波维持的 H2 电容耦合等离子体 (CCP) 放电中。结果表明，在 V0=33 V 或 750 mTorr 时，等离子体密度的特点是在径向中心有一个广泛的最大值，并且EAE对等离子体径向均匀性调制的有效性是有限的。当 V0 变高时，通过调整基频 θ1 的相移，等离子体分布发生明显变化。例如，当 θ1 在 V0=56V 时从 0 增加到 2π，等离子体密度从中心高处的均匀转变为均匀。此外，在 V0=100 V 时，在 θ1=π 处观察到最佳均匀性。当压力降低到 50 mTorr 时，虽然均匀性随 θ1 变化很大，但等离子体密度保持较低，这在等离子体处理中可能不受欢迎。通过检查不同放电条件下鞘层膨胀和电场反转引起的电子加热，可以理解 EAE 对等离子体径向均匀性的不同影响。