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1、 【关键词】等离子体浸没离子注入 充电效应 PIC-MCC模型 混合PIC 圆柱形介质圆管【英文关键词】Plasma Immersion Ion Implantation Charging effects Particle In Cellplus Monte Carlo Collision(PIC/MCC)model Hybrid PIC Cylindrical dielectric tube等离子体浸没离子注入论文：等离子体浸没离子注入介质靶鞘层特性的粒子模拟研究【中文摘要】等离子体浸没离子注入(plasma immersion ion implantation,简称P)是在传统的束线离子注
2、入(PB)的基础上提出的一种新的离子注入技术,由于其具有成本低、设备简单、易操作、适合处理复杂形状样品等诸多优点,在材料表面改性、半导体和微电子材料加工等方面得到广泛的应用。然而,由于介质材料的导电性能较差,在对介质材料进行表面改性时容易出现注入离子电荷在表面积累的现象,出现充电效应,从而导致注入离子能量达不到预期负脉冲电压幅值,严重影响注入效果；同时,对于空心圆柱形介质圆管的内表面的离子注入过程,除了充电效应,随着离子注入过程的进行,介质圆管内的鞘层不断向圆管中心扩展,鞘层在圆管中心会出现重叠现象,导致离子的注入剂量和注入能量降低。为了解决上述问题,对介质靶P过程中鞘层演化特性进行理论上的深
3、入研究就显得尤为必要。因为注入材料表面的离子主要是在鞘层中获得加速,鞘层特性直接影响被加工材料的离子注入效果,同时,理论研究的结果可以揭示离子注入过程的物理机理,为实际离子注入工艺的优化提供一定的参考。本文主要采用粒子模拟(particle in cell,简称PIC)方法,对介质靶材料等离子体浸没离子注入过程中的鞘层演化规律和靶表面的离子注入特性进行了模拟研究,分析讨论了各种参数对P过程中鞘层演化和注入特性的影响。本论文的具体安排如下：第一章,介绍了P技术的特点及其发展应用、P技术在平板介质靶和圆管介质靶的应用研究现状及意义,综述了对P过程进行计算机模拟时常用到的模拟方法。第二章,对等离子体
4、模拟中使用的PIC/MCC模拟方法进行了详细的介绍,把PIC/MCC分成PIC和MCC两个部分进行讲述。同时,结合本文要用到的算法,在讨论模型时对一维平板模型和柱坐标下的二维模型都做了相应的推导。第三章,采用二维混合PIC(Hybrid PIC)的方法对介质圆管内表面的P过程进行了数值模拟,得到了空间鞘层演化的规律,并且对离子注入剂量和注入能量均匀性的进行了讨论。结果显示：在介质圆管内表面P过程中,随着积累电荷的增多,充电效应越来越明显,导致介质表面的电势降低,注入能量减小；其次,离子注入剂量在介质圆管内表面的分布不均匀,在介质圆管管口附近位置注入剂量明显偏大。当介质圆管内离子完全注入到介质内
5、表面后,由于管口外端离子还会继续注入到管口内表面,随着注入时间的增加,这种不均匀性变得越来越严重。因此,在介质圆管内离子完全注入到内壁前结束一个脉冲周期就变得尤为必要；最后,适当延长金属电极的长度,可以有效的提高介质圆管内表面离子注入剂量和离子注入能量的均匀性。第四章,我们针对混合PIC在处理短脉冲P中的不足(假设电子满足波尔兹曼分布,从而忽略了电子的运动和效应对离子注入的影响),采用完全自洽的一维PIC/MCC模型对一维平板介质靶P过程进行了模拟。该模型完全跟踪电子和离子的运动轨迹,对带电粒子运动过程中与中性气体间的碰撞过程及介质表面的二次电子发射过程进行了全面的考虑；同时讨论了介质厚度和气
6、体压强对注入过程的影响。结果表明,为了获得较好的注入效果,应该尽量采用较薄的介质、短的脉冲上升时间和低的放电气压。【英文摘要】Plasma immersion ion implantation (P) is a new ion implantation technology based upon the traditional ion-beam ion implantation (PBII) technology, as P has many advantages such as low costs, simple equipment, easily operation and is capa
7、ble to process the work-piece with complex shape. Presently, P technology has been widely used in the modification of materials, semiconductor treatment, and microelectronic materials processing, etc. However, when treating the dielectric substrate with P, the implanted ions can accumulate at the di
8、electric surface owing to the low electric conductivity of the dielectric materials, and this result in the charging effects. So the implanted ions cant get the full acceleration with the same amplitude of the applied negative pulse. Whats more, with the time extend, the converging plasma sheaths fr
9、om the inner surfaces of the cylindrical dielectric tube could get overlapping in the central axis, the implanted dose and energy decrease further. In order to solve these problems, it is necessary to sduty theoretically the sheath evolution near the inner of the cylindrical dielectric tube during t
10、he P processing. Because the implanted ions mainly get acceleration from the plasma sheath, the characteristics of the plasma sheath directly affect the final properties of the target materials after P process. With the theoretical investigation, the physical mechanism of ion implantation can be rev
11、ealed, and the results can give some guidance for the optimization of an actual P process.In this thesis, we adopt the particle-in-cell method to study the principles of the sheath expansion and implantation characteristics in P process with a dielectric target. The influences of many parameters on
12、the P are discussed. The thesis is organized as:In Chapter1, we briefly introduce the characteristics and applications of P technology, the current research state and significance of the P in flat and cylindrical dielectric materials, and also review the investigation methods of computer simulation
13、for P.In Chapter2, we give a detailed description about the Particle-In-Cell plus Monte Carlo Collision (PIC/MCC) method which is used in plasma computer simulation. We divide the PIC/MCC method into two parts, and introduce the PIC and MCC method, respectively. At the same time, we also make a corr
14、esponding derivation of the one-dimension flat plate model and two-dimension cylindrical model.In Chapter3, the sheath expansion near the inner surface of a cylindrical dielectric tube is investigated by using a two-dimension hybrid PIC model. The influence of experimental parameters (such as the me
15、tal electrode length and dielectric thickness) on the uniformity of implanted ions dose and energy along the inner surface of the dielectric tube is analyzed and discussed. It finds that during the P process, as there are increasingly amount of charges accumulate on the dielectric surface, the charg
16、ing effect become much more significant, leading a lower surface potential and lower implanted energy. Secondly, with a finite length cylindrical dielectric tube, the distribution of the implanted ion dose along the inner surface is nonuniform, the implanted dose near the top of the bore is much bigger than the other region. When all the ions inner the tube get implanted, ma
