An Experimental Study Of The Polishing Process For MgO Single Crystal Substrate

MgO single crystal has been widely used as the substrate in the field of various thin films. The MgO single crystal substrate is not only demanded extreme low surface roughness, but also high accuracy of flatness. Up to now, there are few papers dealing with the ultra polishing technology of MgO single crystal substrate, by which the final surface quality of the substrate is achieved, because the ultra-precision machining technology of large size MgO substrate with the high accurancy and quality is the business secret or know-how related to the high technology and national defence field ,.In this thesis, a systematic experimental study is presented on the polishing mechanism and process for MgO single crystal substrate. The main studied contents and conclusions are as follows:The mechanical polishing process of MgO single crystal is investigated by using SiO₂ abrasive with the size of 10-20 nm. The effects of polishing pressure, polishing plate rotational speed, slurry flow rate and abrasive concentration on surface roughness and material removal rate (MRR) are analyzed. The results show that there are the suitable polishing process parameters by which the low surface roughness and the high MRR can be achieved concurrently.On the basis of the physical and chemical properties of the MgO single crystal, the different kinds of abrasive free polishing fluid containing different concentration of magnesium chloride, ammonium nitrate, ammonium chloride, hydrochloric acid, ammonium monoacid phosphate, and phosphoric acid are prepared. And the abrasive free polishing experiments are performed. From the solubility of the reactive products of MgO in polishing, chemical action mechanism of the polishing fluid are analyzed, and the effects of surface roughness and MRR in using the different kinds of polishing fluids are investigated. It is shown that an ideal polishing fluid to efficiently achieve high surface quality of MgO substrate should have two characteristics: the resultant of reaction on the MgO substrate must be insoluble; then, the generation and removal speed of the resultant of reaction should be correspond.By using the polishing slurry containing SiO₂ abrasive with size of 10-20 nm and phosphoric acid, the systematic experiments on chemical mechanical polishing (CMP) process of MgO substrate are performed, a suitable polishing process and a kind of polishing slurry for MgO substrate are developed. The results show that the CMP is an applied...