Changing the RF bias is widely used to control the ion energy in inductively coupled plasma (ICP). Here, the plasma densities were measured using the floating harmonic method at various ICP powers and RF bias power frequencies. It is observed that there is an RF bias power (PB,min) that minimizes the plasma density. With increasing ICP power, PB,min is increased. When the frequency is changed from 12.5 MHz to 2 MHz, PB,min is decreased. To understand this phenomenon, the relative variation of the plasma density (δn) with the RF bias power is considered based on a power balance equation. PB,min is determined by δn, and δn changes based on the self-bias voltage caused by the RF bias power. Because the self-bias voltages change depending on the ICP power and frequency of the RF bias power, PB,min is shifted by altering the ICP power and the RF bias power frequency. The results are in good agreement with the experimental results.

中文翻译：

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射频偏压对氩电感耦合等离子体中等离子体密度的影响

改变射频偏置被广泛用于控制电感耦合等离子体 (ICP) 中的离子能量。在这里，等离子体密度是使用浮动谐波方法在各种 ICP 功率和 RF 偏置功率频率下测量的。据观察，存在使等离子体密度最小化的 RF 偏置功率 (PB,min)。随着ICP功率的增加，PB,min增加。当频率从 12.5 MHz 变为 2 MHz 时，PB,min 减小。为了理解这种现象，基于功率平衡方程考虑等离子体密度 (δn) 与 RF 偏置功率的相对变化。PB,min 由δn 决定，δn 根据射频偏置功率引起的自偏置电压而变化。因为自偏置电压根据 ICP 功率和射频偏置功率 PB 的频率而变化，min 是通过改变 ICP 功率和 RF 偏置功率频率来改变的。结果与实验结果非常吻合。