Sustaining mechanism and spatial structure of high-density ring-shaped hollow cuspate magnetized rf plasma for low-pressure plasma processing
Sustaining mechanism and spatial structure of high-density ring-shaped hollow cuspate magnetized rf plasma for low-pressure plasma processing
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DOI：
10.1088/0963-0252/24/3/034005
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发表时间：
2015-05
影响因子：
3.8
通讯作者：
Y. Ohtsu;T. Yanagise
中科院分区：
文献类型：
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作者：
Y. Ohtsu;T. Yanagise
为了改善传统空心阴极放电的低密度问题，在1 Pa左右的低气压下，研制了一种带有空心沟槽和磁体的环形空心尖形磁化射频等离子体。从维持机制的观点出发，研究了等离子体粒子（如电子和离子）的磁特性。在存在磁场的情况下，有效的电子-中性碰撞频率具有THz的幅度，其比没有磁场的碰撞频率高大约100 000倍。在磁场存在下的有效电子平均自由程小于一微米，使得电子可以在环形槽中更频繁地与中性原子碰撞。发现在功率密度为0.14W cm-2和氩气压力为1 Pa时，在中空槽下方5 mm距离处的等离子体密度达到2.5 × 1011 cm-3以上。其维持机制是基于巨大的有效电子碰撞频率和空心槽出口处横向磁场对电子的强磁约束。等离子体密度的空间分布在距电极表面70 mm处变得均匀，并且均匀性和平均等离子体密度为18%和6 × 1010 cm-3。结果表明，等离子体密度的均匀性受气压控制。
The ring-shaped hollow cuspate magnetized rf plasma with the hollow trench and magnets has been developed to improve the low-density of conventional hollow cathode discharge under a low-pressure, around 1 Pa. From the point of view of the sustaining mechanism, magnetic characteristics of plasma particles such as electrons and ions have been investigated. The effective electron–neutral collision frequency in the presence of a magnetic field has the magnitude of THz, which is approximately 100 000 times higher than the collision frequency without the magnetic field. The effective electron mean free path in the presence of the magnetic field is less than a micrometer, so that the electrons can collide with neutral atoms more frequently in the ring-shaped groove. It is found that the plasma density at the distance of 5 mm under the hollow groove attains more than 2.5 × 1011 cm−3 at a power density of 0.14 W cm−2 and an argon pressure of 1 Pa. The sustaining mechanism is based both on the huge effective electron collision frequency and the strong magnetic confinement of electrons across the transverse magnetic field in the exit of the hollow groove. The spatial distribution of the plasma density has become uniform at the distance of 70 mm from the electrode surface and the uniformity and the averaged plasma density are 18% and 6 × 1010cm−3. It is indicated that the uniformity of the plasma density is controlled by gas pressure.