Papers by Author: Qiu Sheng Yan

Abstract: For subsurface crack detection of single crystal SiC wafer, this paper proposed a cross-sectional cleavage detection method and compared with traditional cross-sectional sample preparation method. The characteristics and detection results of two cross-sectional sample preparation methods were compared and the subsurface crack characteristics in SiC wafer grinding were researched. The results show that the configurations and depth of subsurface cracks measured by two cross-sectional sample preparation methods were similar. The cross-sectional cleavage sample preparation method is simpler and more rapid in subsurface crack detection. The subsurface crack system of single crystal SiC wafer grinding mainly includes lateral crack and median crack.

Abstract: Chemical reaction rate of SiC wafer surface usually determines the material removal rate (MRR) in chemical mechanical polishing (CMP). In this paper, systemic experiments are carried out to discover the relationship between Fe catalyst with different forms or valence and chemical reaction rate based on Fenton reaction. Experimental results show that the MRR changes little using Fe powder or hydrogen peroxide (H₂O₂) alone, but the MRR of SiC will increase largely by adding them both that will produce Fenton reaction. The MRR continues to increase slightly when Fe²⁺ ions is employ as catalyst, but that is much lower when utilizing Fe³⁺ ions. Moreover, SiC wafer with a smaller surface roughness and better quality can be obtained when using Fe powder as catalyst in Fenton reaction. The results indicate that the Fenton reaction can effectively improve the polishing efficiency of SiC substrate and Fe powder is more suitable for polishing of SiC than ferrous or ferric salt in CMP based on Fenton reaction.

Abstract: Based on the principle of disc slitting process, a 3D model of the disc slitting process for galvanized sheet was established by using DEFORM-3D software, and the deformation, fracture and material effective stress of galvanized sheet were analyzed. The surface morphology of numerical simulation is in good agreement with the actual result. The curve of shearing force was obtained and well matched with the change rule of slitting process. Compared with the theoretical calculation result, the simulation result is reliable and can provide a reference for the calculation of shearing force.

Abstract: The growth of epitaxial layer of SiC wafer requires the surface of SiC substrate to reach an atomic scale accuracy. To solve the problems of low machining efficiency and low surface accuracy in the polishing process of SiC wafer, a novel ultra-precision machining method based on the synergistic effect of chemical reaction and flexible mechanical removal of the magnetorheological (MR) effect, the MR-chemical mechanical polishing (MRCMP) is proposed. In this technique, magnetic particles, abrasives and chemical additives are used as MR-chemical polishing fluid to form a cluster MR-effect flexible polishing platen under an applied magnetic field, and it is expected to realize an atomic scale ultra-smooth surface planarization with good controllability and high material removal rate by using the flexible polishing platen. Polishing experimental results of C surface of 6H-SiC crystal substrate indicate that an atomic scale zero-defect surface can be obtained. The surface roughness of C surface of SiC wafer decreased from 50.86nm to 0.42nm and the material removal rate was 98nm/min when SiC wafer was polished for 60 minutes.

Abstract: A new planarization polishing method, based on the cluster magnetorheological (MR) effect and using MR fluid to form the flexible polishing pad, is presented in this paper to polish optical glass. To explore the machining characteristic of the viscid and flexible polishing pad based on the cluster MR-effect, some process experiments were conducted to reveal the influence of the machining gap, the speed of the polishing disc and the polishing time on the machining effect. The results indicate that the viscid and flexible polishing pad based on the cluster MR-effect under a strong magnetic field can reduce surface roughness effectively. When the strength of the magnetic field is 2000Gs, and the content of the carbonyl iron is 12%, the surface roughness can be reduced rapidly from the original Ra0.27μm to Ra1.4nm based on the cluster MR-effect.

Abstract: It is an important method to machine revolution aspheric with Arc Envelope Grinding Method（AEGM）. In this article, the relationship between the grinding point of the wheel and its position is analyzed, and motion law of the grinding point is discussed in grinding aspheric. According to motion velocity of the grinding point , the concrete position of severe wear for the wheel can be calculated out theoretically. It is possible to achieve even angular velocity of the grinding point by adjusting the wheel feed rate, so the angular velocity of wheel movement is optimized, which provide confirm base for improving the precision of grinding aspheric.

Abstract: A new planarization grinding method based on the cluster magnetorheological (MR) effect is presented to grind optical glass in this paper. Some process experiments were conducted to reveal the influence of the speed of the grinding disc and grinding time and grinding pressure during the machining process. The results indicate that the speed of the grinding disc influences definitively on grinding effect of this planarization grinding method based on the cluster MR-effect. When the speed of the grinding disc is 110r/min, better machining effect can be achieved. Furthermore, the influence of the grinding time on machining effect is obviously, and the proper machining time is 6mins. However, under the experiment condition in this paper, the influence of grinding pressure on machining effect is unobvious.

Abstract: A new planarization grinding method based on the cluster magnetorheological (MR) effect is presented to grind optical glass in this paper. Some process experiments were conducted to reveal the influence of the species and granularity and content of the abrasive materials in the MR fluid on the machining effect, furthermore, the machining characteristic of grinded surface was studied. The results indicate that the abrasive influences definitively on machining effect of this planarization grinding method based on the cluster MR-effect. Under the certain experiment condition, with the content of the abrasive 10% and grain size 800# of SiC, best machining effect can be achieved. The difference species of abrasive results in various machining effects. As for the removal rate of K9 optical glass: abrasive CeO2 is the best, the Al2O₃ is the second and the SiC is the worst. While the surface roughness: abrasive SiC is the lowest，the Al2O₃ is the second and CeO2 is the highest.

Abstract: Based on the principle of MR polishing processing, cluster MR-effect polishing method which formed by cluster distributed magnetic body has been put forward in this article. The author analyzed the principle of the cluster MR-effect plane polishing, developed experimental device and conducted processing experiment to K9 optical glass and silicon slice. Results show that the method is feasible and can realize high precision polishing. The surface roughness of K9 glass and silicon slice can achieve respectively Ra0.005µm and Ra0.016µm finally after processed. It has high efficiency at the same time, the surface roughness can decrease 1 order of magnitude after processed 10 minutes, the surface roughness of K9 glass and silicon slice can realize respectively decrease 3 orders of magnitude and 1 order of magnitude after processed 50 minutes.

Abstract: Method of compound machining is used to process single crystal silicon and SrTiO3 ceramic substrates, and the factors on effects of compound machining are studied such as magnetic field intensity, processing time, rotating speed of lapping plate and lapping pressure. The results show that the roughness of work pieces processed by compound machining are smaller than that by lapping based on cluster MR effect and polyurethane pad polishing process, while the material removal rate is higher than polyurethane pad polishing process, therefore, compound machining shows its synergistic effect between lapping based on cluster MR effect and polyurethane pad polishing process. The type and properties of workpiece material, and machining parameters both have a significant impact on the roughness and material removal rate of compound machining process of polyurethane polishing pad and cluster abrasive brush based on MR effect.