闭合磁场的作用原理与布局逻辑

Working principle and layout logic of closed magnetic field in sputtering

采用非平衡磁控溅射阴极在镀膜区间构建闭合磁场已经成为设计开发磁控溅射真空镀膜系统的通用手段,然而闭合磁场具体的作用对象、作用机制、闭合条件、布局逻辑以及作用效果等仍没有定量的判定标准或设计依据.本文从带电粒子在磁场中的运动出发,推导了真空室内电子与离子运动行为,得出闭合磁场的作用机制,并依此研究了磁控溅射阴极和离子源布局方式对电子约束效果和沉积效率的影响.结果表明,闭合磁场在真空室中主要通过约束电子来约束等离子体,进而减少系统内电子损失;阴极数量和真空室尺寸对闭合磁场的作用效果有重要影响.提出在真空室中央增加对偶离子源,研究了闭合磁场中阴极类型、旋转角度和磁场方向对电子的约束作用,发现当离子源正对阴极相斥或相吸时,真空室内分别形成了局部高密度和均匀连续的两种等离子体分布特征,边缘电子溢出比均低于3%,镀膜区的电子占比相对无对偶离子源时分别提高到53.41%和42.25%.

Closed magnetic field constructed by unbalanced magnetron sputtering(MS)cathodes has been a general means of developing the MS coating system.However,owing to the difficulties in characterizing the complex plasma behaviors,there are still no quantitative criteria or design bases for some critical points,such as the effective object,the working mechanism,the closure condition,the layout logic and the effectivity of the closed magnetic field.Here in this work,out of the movements of charged particles in magnetic field,the motion behaviors of electrons and ions in the vacuum chamber are studied and it is also revealed that the closed magnetic field can affect mainly the electrons and further control the distributions of ions.A Monte-Carlo collision(MCC)model of the closed magnetic field MS coating system is established by test-electron to characterize the plasma transport characteristics,and the electron constraint and coating deposition efficiency are studied by different layouts of the magnetron cathodes and the ion sources.The simulation results show that the cathode numbers and vacuum chamber size determine the constraint effect on electrons in closed magnetic field.By 8 MS cathodes and the chamber radius of 0.5 m,the proportion of the overflow electrons can decrease to 1.77%.To increase the proportion of the electrons in the coating region,four coupled magnetic fields are introduced in the center of vacuum chamber.The studies of cathode type,rotation angle and magnetic field direction reveal that the proportion of the overflow electrons is less than 3%.A local dense plasma distribution and a continuous uniform plasma distribution can be observed in the vacuum chamber,corresponding to the same and opposite layout in magnetic poles of the MS cathodes and the ion sources,and the proportion of the electrons in the coating region significantly increases to 53.41%and 42.25%,respectively.