Advanced Materials Research Vol. 497

Abstract: We proposed a novel polishing technique named plasma assisted polishing (PAP) which combined atmospheric pressure water vapor plasma irradiation and soft abrasive polishing. Plasma irradiation oxidized the surface of workpiece and made it easier to be polished. PAP was applied to 4H-SiC, and an automatic flat surface without any scratches was obtained. In this study, we observed the processed surfaces using cross-sectional transmission electron microscopy (XTEM). The XTEM images showed us that an oxide layer with a thickness of about 20 nm was generated after plasma irradiation for 1 h, which proved the strong oxidation potential of OH radical in water vapor plasma. The surfaces processed by PAP were next observed, oxide layer was completely removed and no surface damages were introduced as the crystal structure of 4H-SiC was clearly observed and well ordered.

Abstract: Silicon carbide (SiC) power devices have received much attention in recent years because they enable the fabrication of devices with a low power consumption. To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin a SiC wafer with a high removal rate by conventional mechanical machining because its high hardness and brittleness cause cracking and chipping during thinning. We have attempted to thin a SiC wafer by plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. In this paper, we describe a machining property using a newly developed flat-bar electrode with multiple gas nozzles for thinning a SiC wafer.

Abstract: Although Single Point Diamond Turning (SPDT) can do pretty well in optical surfacing of large scale KDP crystal, both the surface accuracy and integrity are considerably high; meanwhile as the defects of micro-waveness and stress are inevitable, the laser-induced damage threshold of KDP optical elements after SPDT still cannot be satisfied. Because of the characters of deliquescent and water-soluble, the process of computer controlled Micro-nano deliquescence is attempted to remove the residual micro-waveness on KDP surface after SPDT. Based on the assumption of Preston and the characters of Micro-nano deliquescence, the model of material removal ratio is suggested, the dwell time for ascertained KDP surface is solved, the processing of computer controlled Micro-nano deliquescence is simulated and the processed surface condition on theory is obtained. Besides, the influences of different parameters on the surfacing efficiency and accuracy are analyzed. Finally, three polishing tracks are comparatively analyzed. The simulation results are quite important in guiding the experimental polishing of large scale KDP by computer controlled Micro-nano deliquescence

Abstract: Stainless steel; Aspheric mould; Ultra-precision turning; Magnetorheological polishing The ultra precision turning and the inclined-axis type of magnetorheological polishing were introduced for the small aspheric mould of stainless steel. The method was based on the principle of two kinds of processing methods, and the processing feature of stainless steel material. Firstly, the ultra-precision turning was employed to shape aspheric surface rapidly and obtain a relatively good surface. And then, the inclined-axis type of magnetorheological polishing as the final finishing was used to decrease sub-surface damage to obtain better precision. Several of experiments were carried out, the experimental results show that surface roughness can be achieved for Ra 0.0073μm.

Abstract: Stainless steel; Aspheric mould; Ultra-precision turning; Magnetorheological polishing Abstract. The ultra precision turning and the inclined-axis type of magnetorheological polishing were introduced for the small aspheric mould of stainless steel. The method was based on the principle of two kinds of processing methods, and the processing feature of stainless steel material. Firstly, the ultra-precision turning was employed to shape aspheric surface rapidly and obtain a relatively good surface. And then, the inclined-axis type of magnetorheological polishing as the final finishing was used to decrease sub-surface damage to obtain better precision. Several of experiments were carried out, the experimental results show that surface roughness can be achieved for Ra 0.0073μm.

Abstract: Semi-fixed abrasive plate (SFAP) lapping is an effective ultra-precision lapping method. It can efficiently obtain good surface quality in ductile regime machining. Probability density function of abrasive grains cutting depth is the key factor to control removing mode. This paper verified the function by analyzing and comparing simulation results and detection results. It showed the simulation results were consistent with the detection results. The more fine grits SFAP could result in the more consistent cutting depth on workpiece surface, and standard deviation of cutting depth distribution of 4000# SFAP was only 0.0754, compared with 1000# SFAP (0.1527).

Abstract: CVD diamond has become the mainstream trend for the development of diamond. Its ultra precision machining is one of the key technologies for expanding the application of CVD diamond film. The efficient polishing method is studied, called accelerant polishing technology, which can lower the activation energy needed in diamond graphitization by the accelerant action of transition metal. It accelerates reaction rates of graphitization and promotes the implementation of diamond’s removal mechanism. Experimentation results indicate that the polishing method is one new type of precision polishing technology with low cost and high efficiency.

Abstract: in order to improve the polishing efficiency to high hardness and high resistance free-form surface of mold, the paper present a new method based on soft-consolidation abrasive pneumatic wheel. The abrasive group is bond to the rubber matrix by the polymer binder. In this way, a flexible pneumatic wheel is formed to get copying contact with the free-form surface for efficient cutting. Combined with the elastic system theory, mechanics model of polishing is found. Scidic silicone sealant is used as the polymer binder, because of its excellent effect of adhesion. The result of experiment shows its wild prospects in the process of polishing.

Abstract: As sapphire is an important substrate material, stringent surface quality requirements (i.e., surface finish and flatness) are required. In order to acquire the higher material removal rate and the better surface quality of sapphire, the solid state-reaction were introduced in this paper; abrasive of SiO2 and SiO2 with mixing the MgF2 power were compared to polish sapphire. The result showed that abrasive of SiO2 with mixing the MgF2 can obtain higher material removal rate and better surface quality. The result of the pr

Abstract: GaAs are one of the most important semiconductor followed silicon, GaAs wafers are the mostly used substrates for fabricating integrated circuits (ICs). So the quality of ICs depends directly on the quality of GaAs wafers. A series of processes are required to manufacture high quality GaAs wafers. This paper reviews the literature on polishing technology of GaAs wafers, covering the history, summarizes the effects of slurry’s chemical and physical characters such as pH, oxidants, abrasive grit, velocity, and temperature in the polishing process. It also discusses some possible topics for future research.