The evolution of the plasma potential in a HiPIMS discharge and its relationship to deposition rate
The evolution of the plasma potential in a HiPIMS discharge and its relationship to deposition rate
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DOI：
10.1088/0963-0252/19/4/045014
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发表时间：
2010-08
影响因子：
3.8
通讯作者：
A. Mishra;P. Kelly;J. Bradley
中科院分区：
文献类型：
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作者：
A. Mishra;P. Kelly;J. Bradley
用电子发射探头测量了在脉冲频率为100 Hz的高功率脉冲磁控溅射放电中，等离子体电势Vp沿赛道上方靶(Ti)到衬底的时间演化。探头的时间分辨率为20 ns，使我们能够观察到随着放电电压波形的发展，Vp的高度动态特性，在前6~8µS的磁陷区存在较大的负Vp值(−210V)和强烈的电位梯度。在55~60µS之后，Vp升高到地电位(0V)，体电场崩塌。在磁场陷阱外，即在开场线上，Vp的轴向和时间变化要小得多，类似于在常规脉冲直流磁控管中观察到的变化。在标准条件下(Ar气压0.54Pa，平均功率650W)，结果表明，在100uM的S等离子体中，Vp的空间结构为溅射的后电离物种提供了一个很大的势垒，阻碍了它们在衬底上的传输和沉积。通过小幅降低磁场强度(靶处的磁场强度为33%)，使衬底的典型位置(z=100 mm)的沉积速率提高到原来的6倍，从而使该势垒显著降低(50%)。VP的结构对压力的变化(0.54至1.08Pa.)有轻微的敏感性，但对外加功率(650至950W)的依赖性更强。
An electron-emitting probe has been used to measure the temporal evolution of the plasma potential Vp along a line from target (Ti) to substrate above the racetrack in a high-power impulse magnetron sputtering discharge pulsed at 100 Hz. The 20 ns time-resolution of the probe allowed us to observe the highly dynamic nature of Vp as the discharge voltage waveform develops, with large negative Vp values (−210 V) and strong potential gradients existing in the magnetic trap region in the first 6 to 8 µs. After 55 to 60 µs, Vp is elevated towards ground potential (0 V) and the bulk electric field collapses. Outside the magnetic trap, i.e. on the open field lines, Vp reveals much smaller axial and temporal variations, similar to those observed in conventional pulsed dc magnetrons. At standard conditions (Ar pressure of 0.54 Pa and 650 W average power), the results show that for over 50% of the 100 µs plasma ‘on-time’ the spatial structure of Vp provides a large potential barrier for the sputtered post-ionized species so impeding their transport and deposition at the substrate. This barrier is reduced markedly (by 50%) through a small reduction in the magnetic field strength (33% at the target) so increasing the deposition rate by a factor of 6 at a typical position of the substrate (z = 100 mm). The structure of Vp is marginally sensitive to changes in pressure (over the range 0.54 to 1.08 Pa), but more strongly dependent on the applied power (over the range 650 to 950 W).