The effect of changing the magnetic field strength on HiPIMS deposition rates
The effect of changing the magnetic field strength on HiPIMS deposition rates
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DOI：
10.1088/0022-3727/48/21/215202
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发表时间：
2015-04
期刊：
影响因子：
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通讯作者：
J. Bradley;A. Mishra;P. Kelly
中科院分区：
文献类型：
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作者：
J. Bradley;A. Mishra;P. Kelly
随着磁场强度的变化，HiPIMS和传统的直流或脉冲直流磁控溅射放电在行为上的显著差异通过沉积速率的测量得到了证明。在平均功率为680 W、压力为0.54 Pa的条件下，采用三种激励方式对同一圆形磁控管进行了非反应溅射实验。在跑道中间的阴极表面的总磁场强度B在195 ~ 380 g之间变化，脉冲直流放电显示出预期的行为，即沉积速率随着B的减小而下降（这里约为25-40%）。然而，在HiPIMS中观察到相反的趋势，沉积速率上升了2倍，而在b中同样下降。这些观察结果是从不同技术之间沉积金属通量的不同组成和输送过程的角度来理解的。在HiPIMS中，这种通量主要是离子的，缓慢的后电离溅射粒子受到前方延迟等离子体势结构对目标的强烈反向吸引。根据溅射粒子通量的简单现象学模型，并使用不同技术测量的沉积速率作为输入，计算了HiPIMS中金属物种的电离α和反吸引β的组合概率。随着b场强度的降低，αβ明显下降（从~0.9降至~0.7），我们认为这主要是由于静电离子反向吸引力的减弱，从而导致沉积速率的提高。结果表明，为了优化HiPIMS的沉积速率，需要仔细设计磁控管场强。
The marked difference in behaviour between HiPIMS and conventional dc or pulsed-dc magnetron sputtering discharges with changing magnetic field strengths is demonstrated through measurements of deposition rate. To provide a comparison between techniques the same circular magnetron was operated in the three excitation modes at a fixed average power of 680 W and a pressure of 0.54 Pa in the non-reactive sputtering of titanium. The total magnetic field strength B at the cathode surface in the middle of the racetrack was varied from 195 to 380 G. DC and pulsed-dc discharges show the expected behaviour that deposition rates fall with decreasing B (here by ~25–40%), however the opposite trend is observed in HiPIMS with deposition rates rising by a factor of 2 over the same decrease in B. These observations are understood from the stand point of the different composition and transport processes of the depositing metal flux between the techniques. In HiPIMS, this flux is largely ionic and slow post-ionized sputtered particles are subject to strong back attraction to the target by a retarding plasma potential structure ahead of them. The height of this potential barrier is known to increase with increasing B. From a simple phenomenological model of the sputtered particles fluxes, and using the measured deposition rates from the different techniques as inputs, the combined probabilities of ionization, α, and back attraction, β, of the metal species in HiPIMS has been calculated. There is a clear fall in αβ (from ~0.9 to ~0.7) with decreasing B-field strengths, we argue primarily due to a weakening of electrostatic ion back attraction, so leading to higher deposition rates. The results indicate that careful design of magnetron field strengths should be considered to optimise HiPIMS deposition rates.