射频等离子系统中微弧放电的解析模型

A Simple Model of micro arcing in RF plasma capacitive discharge systems

最近我们在实验中发现:射频等离子体系统中的高电位可以引发微弧放电,这种微弧放电现象不是发生在射频系统的输入极上而是发生在接地极上。这种相对于电极呈非对称分布的微弧放电现象不是我们期待的结果,也不能用现有的理论来解释它。本文在Ch ild-L angm u ir鞘层模型理论和电流连续性理论的基础上,推导建立了一个用于表述射频等离子体系统中的这种非对称型微弧放电现象的解析模型。从我们的推导过程可以发现鞘层内外的电位差取决于接地极鞘层面积与输入极鞘层面积之比。当接地极的鞘层面积大于输入极鞘层面积时,接地极鞘层电位差的最小值成为高电位,从而引发电弧放电。而输入极鞘层电位差的最小值不发生变化。这个模型和推导结果与实验现象和P IC仿真数据有较好的一致性。

A simple model is developed to explain why the micro arcing in radio frequency （RF） capacitive discharge systems occurs on grounded electrode other than on RF powered electrode when high plasma potential is present, which was unable to interpret via existing theories. This model is simply based on the time-dependent Child-Langmuir sheath model and the current continuity equation. It is found that the minimum potential difference across a grounded chamber sheath depends on the areal ratio of the grounded electrode sheath to the powered electrode sheath. When the ratio is larger than unity, the minimum potential difference across the grounded electrode sheath is higher than that across the powered electrode sheath, thus resulting in micro arcing. The analytical model is supported by both experiment and particle-in-cell simulation.