Study On Macroparticles Reduction For Vacuum Cathodic Arc Source

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.