Studies of Electron Behavior in Magnetic Neutral-Loop Discharge (NLD) Plasmas for Processing Applications

本课题从理论和实验上研究了磁中性回路放电(NLD)等离子体的形成机理。利用二维电磁场构型对NLD等离子体中的电子行为进行了理论模拟。该模型预测，在无碰撞的低压区，电子在中性环(NL)周围的运动变得混沌，电子可以被射频电场有效地加热。然后，对其电子行为进行了实验研究。实验结果表明，NL附近的电子能量沉积对NLD等离子体的形成起着至关重要的作用。这一结果与二维模型的预测结果一致。然而，等离子体产生效率与磁场强度梯度的关系与实验结果不一致。该模型预测了…更重要的是，磁场梯度越小，等离子体的生产效率就越高。另一方面，实验结果表明，磁场梯度存在一个最佳值。为了改善这种情况，提出了一种新的模型，该模型考虑了三维电磁场构型、空间变化的射频电场以及电子与中性粒子的碰撞。该模型给出了给定放电条件下磁场强度的最佳值，预测结果与实验结果吻合较好。该模型为NLD等离子体器件的设计提供了指导，成功地将NLD等离子体应用于高速刻蚀工艺中，获得了满意的均匀性。在SiO_2刻蚀工艺中，获得了大约1微米/分钟的刻蚀速率。当刻蚀孔图案时，刻蚀的轮廓几乎是垂直的。这些结果被发现优于使用感应耦合等离子体的刻蚀结果。为了开放溅射应用，提出了一种基于电容耦合的NLD等离子体，并设计了原型装置。较少

In this project, the formation mechanism of a magnetic neutral-loop discharge (NLD) plasma was studied theoretically and experimentally. Also, application possibilities of the NLD plasma were studied.Electron behavior in the NLD plasma was theoretically modeled using a two-dimensional electromagnetic field configuration. The model predicted that the electron motion around the neutral loop (NL) became chaotic, and electrons could be effectively heated by the rf electric field in the collisionless low pressure regime. Then, the electron behavior was examined experimentally. The experimental results showed that the energy deposition to electrons in the vicinity of the NL played an essential role in the formation of the NLD plasma. This result was consistent with the prediction of the two-dimensional model. However, the dependence of the plasma production efficiency on the gradient of the magnetic field strength showed disagreement between the experiment and the model. The model predicted … More that plasma production became more efficient for a smaller magnetic field gradient. On the other hand, the experimental results showed the existence of an optimum value of the magnetic field gradient. In order to improve the situation, a new model which included effects of the three-dimensional electromagnetic field configuration, a spatially varied rf electric field and electron collisions with neutral particles was proposed. The model gave optimum values of the magnetic field strength for given discharge conditions, and those predictions were found to be consistent with experimental results. In conclusion, the model gives a guideline for the design of NLD plasma devices.NLD plasmas were successfully applied to a high-rate etch process with satisfactory uniformity. In the application to the SiO_2 etch process, an etch rate of about 1 mum/min was obtained. When the hole pattern was etched, the etched profile was almost vertical. These results were found to be superior to the etching results using an inductively coupled plasma. In order to open sputtering applications, an NLD plasma based on capacitive coupling was proposed and a prototype device was designed. Less