【作者】 戴华；

【导师】 蔡珣； 潘健生； 沈耀；

【作者基本信息】 上海交通大学 ， 材料学， 2009， 博士

【摘要】 真空阴极电弧离子源具有离化率高(90%以上)、离子能量可控、沉积速率高等优点,广泛应用于等离子体表面改性领域。然而弧源在提供镀膜离子的同时,也会产生直径约为0.1至数百微米的宏观颗粒,这些颗粒大大降低了膜层的表面光洁度,增加了膜层性能的不均匀性,甚至成为贯穿缺陷而严重破坏膜层性能。所以宏观颗粒的存在制约了电弧离子镀工艺在精密镀膜领域的应用。为了去除宏观颗粒,本文提出使用脉冲(叠加直流)电源作为电弧电源,初步降低了弧源发射的宏观颗粒的数量和尺寸;进而设计一种直流可调开放式电磁线圈过滤器,在传输过程中将颗粒过滤掉,获得了较好的颗粒去除效果。使用脉冲电源作为弧电源可以调节阴极斑点处的能量输入,从而降低宏观颗粒污染。计算表明阴极斑点处场致发射电流密度及其加热效应导致的局部区域的最高温度均很高,如Ti靶可达1012A/m2和5000K以上。极高的能量输入使得液态颗粒的产生几乎不可避免(大尺寸液态颗粒凝固即成为宏观颗粒),同时也启示调低能量输入或可降低颗粒数量和尺寸。本文使用脉冲电源作为弧电源进行了这样的尝试。试验结果显示调节脉冲参数可以从一定程度上调节能量输入从而影响到宏观颗粒的数量和尺寸,使用相对小的占空比,高的脉冲频率,小的直流电流分量,阴极产生的宏观颗粒数量下降了约9%到39%,从而获得了一定程度的宏观颗粒去除效果。同时该方法无需添加额外装置,仅将电弧主电源替换为脉冲电源就可实现一定的宏观颗粒去除效果,实施较方便。进一步,本文提出了一种直流可调开放式电磁线圈过滤器,在传输过程中去除绝大部分宏观颗粒。该过滤器继承了管道式过滤器利用电磁场改变离子运动轨迹的特点,能较好地过滤掉宏观颗粒,并且其开放式结构可以避免宏观颗粒通过器壁反弹导致的膜层污染,获得了更好的颗粒去除效果;该过滤器自身具有的电场可吸引更多离子到达过滤器入口,并降低离子在器壁的损失,增强了过滤效率;该过滤器可实现过滤通道曲率可调,从而可以在过滤效率和过滤效果之间取得平衡。试验结果显示,在遮挡良好、无直接视线连接的镀膜区域(也就是具有直线运动轨迹的宏观颗粒无法到达的区域),每平方毫米范围宏观颗粒数量接近于0,相比而言传统管道式过滤器由于存在颗粒反弹,即使无视线连接的镀膜区域,每平方毫米范围宏观颗粒数量的典型值也在103数量级。同时,饱和离子电流探针试验结果显示当线圈电流在50 A到250 A范围内时,过滤器效率随线圈电流单调增大,最高过滤效率可达2%左右,优于大部分文献报道的90°管道式过滤器的过滤效率(低于1%)。另外,针对复合成分和多层结构膜的镀制,本文还提出了具有公用混合通道的双通道线圈过滤器,利用混合通道磁场对离子的聚焦效应,达到离子混合、均化的效果,从而获得较好的镀膜均匀性;利用双靶并调节弧电流可以方便地在一定范围内调节复合膜的成分比。为了检验线圈过滤器在实际镀膜中的应用效果,本文使用单通道和双通道的过滤器镀制了AlN、TiAlN复合成分膜和TiN/AlN多层膜。单通道过滤器镀制AlN薄膜的表面光洁度得到了大幅提高,这表明了过滤器的过滤效果良好。双通道过滤器镀制TiAlN薄膜的抗高温氧化性能得到了较大程度提高,相比较未经过滤的TiAlN薄膜来说,700℃保温1小时的氧化增重下降了54%。双通道线圈过滤器制备TiN/AlN多层膜的分析结果显示,该过滤器可以成功用于制备多层膜,其多层结构特征经由X射线光电子谱仪(XPS)的离子束溅射深度剖析测试和低角度X射线衍射(LAXRD)测试结果得到了证明。更多还原

【Abstract】 Vacuum cathodic arc deposition is widely adopted in surface modification industry for its merits of high ionization rate (90% above), easily controlling for ions energy, high depositing speed, etc. However, macroparticles, which are emitted along with ions from the cathode to the sample, contaminate sample surface and decrease key properties of deposited films. Therefore, steps must be taken to remove the macroparticles. In this work, power input for cathodic arc source was theoretically analyzed, and pulsed power was adopted for lessening of macroparticle emission. We also designed a new type of flexible electromagnetic filter which could filter most of particles during their flight. And the filter effiency of this type of flexible filter can be enhanced greatly by its magnetic and electric fields.Very high current of field emission in vicinity close to the cathodic spot is the source for locally arc heating, which whereafter leads to high ionization rate and the generation of liquid droplets (liquid form of macroparticles). This process implies two points: one is that the emission is inevitable, the other is that energy adjustment could be a method to lessen the emission of macroparticles. We tried to theoretically and experimentally study the effect of pulsing parameters of arc source on the emission of macroparticles. Results show that we could decrease the amount of macroparticles to about 9% to 39% of the original case by adopting relatively small duty cycle, high pulsing frequencies, and small d.c. current.A new type of flexbile electromagnetic filter was designed according to detailed analyzing of common 1/4 torus duct filter. Good points are remained and some shortcomings are overcomed. Our filters have good performance with macroparticles removal and transportation efficiency for ions. Experimental results show that the amount of macroparticles is almost close to 0 per square milimeter in the none-line-of-sight zone, while the quantity for 1/4 torus duct filter with the same experimental condition was about 103 order of magnitude. The measurement for saturation ion current revealed that the system efficiency of the flexible filter reached to 2% at 250 A filter current, and kept increasing trend with higher filter current. This efficiency already surpass most reported efficiency of 1/4 torus duct filter (low than 1%). The flexible filter also characterized with its electric field which enhanced filtering efficiency. For dual channel filter, a shared mixing channel was adopted to get better uniformity for deposited films.Furthermore, application of flexible filters for fabrication of thin films were also conducted. The fabrication of AlN films was conducted by single channel flexible filter. Experimental results show that surface roughness of AlN was greatly improved comparing with 1/4 torus filter and no filter cases. The fabrication of TiAlN and TiN/AlN films were conducted by dual channel flexible filter. The oxidation resistance at high temperature of TiAlN sample was much better than samples fabricated by two cathode without filters. Experiments of XPS sputtering and low angle XRD both show that the TiN/AlN samples had obvious multilayered characteristics.更多还原