Spherical shell model of an asymmetric rf discharge
Spherical shell model of an asymmetric rf discharge
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非对称射频放电的球壳模型
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
M. Lieberman
中科院分区：
文献类型：
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作者：
M. Lieberman
采用球壳模型研究了非对称电容性射频放电中离子输运和偏置电压的形成，这种放电在通电(A)和接地(b)电极处具有不相等的面积A和辉光对电极电压V。离子由热电子电离产生，并在辉光中因双极性扩散而丢失。假设具有恒定横截面的共振电荷转移主导离子输运。我们得到密度比尺度为na/nb∝(Ab/Aa)7/24，其中n为辉光鞘边缘的密度。考虑了三种电极鞘模型：无碰撞离子，碰撞（恒定迁移率）离子和恒定离子截面碰撞定律。利用这些和射频电流的连续性，我们得到了电极电压比与电极面积比的比例关系：Va/Vb∝(Ab/Aa)q。对于典型的射频材料加工放电，恒定的截面定律产生q 2.21。研究了鞘层附近二次电子电离和局部电子电离的影响。
A spherical shell model is used to study ion transport and bias voltage formation in asymmetric, capacitive rf discharges, which have unequal areas A and glow‐to‐electrode voltages V at the powered (a) and grounded (b) electrodes. Ions are generated by thermal electron ionization and are lost by ambipolar diffusion in the glow. Resonant charge transfer with a constant cross section is assumed to dominate the ion transport. We obtain the density ratio scaling na/nb∝(Ab/Aa )7/24, where n is the density at the glow‐sheath edge. Three electrode sheath models are considered: collisionless ions, collisional (constant mobility) ions, and a constant‐ion cross‐section collisional law. Using these and the continuity of the rf current flow, we obtain the scaling of the electrode voltage ratio with the electrode area ratio: Va/Vb∝(Ab/Aa )q. For typical rf materials processing discharges, the constant cross section law yields q≊2.21. The effects of secondary electron ionization and local ionization near the sheaths du...