Characteristics of Ultrahigh-Frequency Surface-Wave Plasmas Excited at 915 MHz
Characteristics of Ultrahigh-Frequency Surface-Wave Plasmas Excited at 915 MHz
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DOI：
10.1143/jjap.38.l679
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发表时间：
1999-06
影响因子：
1.5
通讯作者：
M. Nagatsu;A. Ito;N. Toyoda;H. Sugai
中科院分区：
文献类型：
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作者：
M. Nagatsu;A. Ito;N. Toyoda;H. Sugai
研究了在 Ar 和 O2 气体中使用各种类型的缝隙天线在 915 MHz 下激发的 40 厘米大小的平面等离子体的特性。波电场和电子密度的轴向分布清楚地表明，即使在相对较低的功率下也很容易产生高密度表面波等离子体：电子密度从5×1010 cm-3（纯表面波模式激发的临界密度）线性增加到6×1011 cm-3，在Ar中80 mTorr时净入射功率从100 W到1 kW。因此，915 MHz 放电使人们能够控制等离子体，即使在低密度下，传统的 2.45 GHz 表面波放电会出现不稳定的密度跳跃。此外，目前的结果表明，在三种类型的缝隙天线中获得了几乎线性的等离子体产生特性，即一个倾斜缝隙、一对横向缝隙以及两个横向缝隙和两个纵向缝隙的组合。 915 MHz 激励的这些优点是由于临界密度比 2.45 GHz 激励低七倍。在距离狭缝天线正下方的顶部石英板 z=23 cm 的轴向位置处，Ar 和 O2 放电在约 20 cm 的水平长度上获得均匀度为 ±5% 的大面积均匀等离子体。
Characteristics of 40-cm-sized planar plasmas excited at 915 MHz using various types of slot antennas in Ar and O2 gases are investigated. Axial profiles of the wave electric field and the electron density clearly reveal that high-density surface-wave plasmas are easily produced even at relatively low powers: the electron density increases linearly from 5×1010 cm-3 (the critical density for pure surface-wave mode excitation) to 6×1011 cm-3 with the net incident power from 100 W to 1 kW at 80 mTorr in Ar. Thus, the 915 MHz discharge enables one to control the plasma, even at low densities where a conventional 2.45 GHz surface-wave discharge suffers from unstable density jumps. In addition, the present results indicate that almost linear plasma production characteristics are obtained in three types of slot antennas, that is, one inclined slot, a pair of transverse slots and a combination of two transverse slots and two longitudinal slots. These advantages of the 915 MHz excitation are due to the critical density being lower than that of the 2.45 GHz excitation by a factor of seven. A large-area uniform plasma with a homogeneity of ±5% is obtained for both Ar and O2 discharges over a horizontal length of about 20 cm at an axial position of z=23 cm away from the top quartz plate just below the slot antennas.