Plasma Etching Enhance CVD Diamond Films Polishing

Diamond has been well recognized as a strategic engineering material for its many attractive properties. Because of these excellent properties of diamond, CVD diamond is a promising material for numerous mechanic, thermal, optical, electrical and electronic applications. But in general, these applications require a finished and smooth surface. It is well know that the columnar growth nature of CVD diamond results in a non-uniform thickness, a non-uniform grain size, randomly oriented crystals and the high surface roughness. These are limitations on the application of diamond film. To overcome some of these limitations, depending on the applications, the CVD diamond surface polishing and planarizing technology become a vital part of diamond applications.In this paper, in order to improve the polishing efficiency and reduce the polishing cost, CVD diamond films are polished using a combination technology of ECR plasma etching and mechanical polishing, for full using of the advantages of both technology as low-cost, convenience of mechanical polishing and high efficiency, low damage of ECR plasma etching. The mainly works are as follows:1. CVD diamond films are polished using a combination technology of ECR plasma etching and mechanical polishing and the effect of plasma etching on the following mechanical polishing is studied. The results show that the content of non-diamond phase in the diamond film decreases with mechanical polishing. The loose structure produced by the plasma etching is useful for the mechanical polishing. The comparison experiments show that the plasma etching is more helpful for increasing the efficient of the earlier stage mechanical polishing.2. Several CVD diamond films are etched by ECR plasma in different magnetic fields, sample stages and sample stage bias. The influence of these parameters on CVD diamond films polishing is also investigated. Results show that:(1) Compared with the divergence field, the convergence field has constraints and focusing effect on plasma. The ions in convergence field are more concentrated and have higher energy to produce strong bombardment on diamond surface, which leads to a thicker defect layer. Then the polishing efficiency is obviously improved.(2)When we use small sample stage to etch diamond films, the self bias and field emission result in a stronger etching effect. Compared with the large sample stage, more ions with high energy bombard on the diamond surface, producing a thicker defect layer. Because of the thicker defect layer, the mechanical polishing has higher efficiency.(3)With the changing of bias voltage loaded on the samples, DC plasma sheath and the micro electric field work together to influence the etching effect, what product a selective etching. When the bias voltage is-30 V, the beam bombardment focuses on the high area, and then the defect layer in high area is wider and thicker. Since the high area is more easily removed, a faster decreasing rate of the surface roughness is appeared.3. Based on the early research on the combination technology, the influence of the copper film is investigated. The performances of before and after etched diamond surface are tested. Results show that:(1)With higher polishing rate, the copper film has a limiting effect on the loss of diamond, decreases the production costs. So it is a polishing technology with high polishing efficiency, low cost and low loss.(2)Compared with the non polishing diamond films, the polished surface is finished and smooth and the quality of diamond surface is improved. The wetting angle is increased.