Papers by Keyword: Sapphire Substrate

Abstract: Technologies of TaN thin-film resistors were studied, the thin films were prepared by the D.C. sputtering system, and the trimming methods of the resistor were anodic oxidation and autoxidation. We laid emphasis on the study of power capability of TaN thin film resistor in this paper. We acquired the resistors with the average power capability of 13W/mm².

Abstract: Sapphire (α-Al₂O₃) single crystal combines many good mechanical and optical properties that make it become the material of choice in a variety of modern Hi-Tech applications The use of CMP technique can produce high quality surface finishes at low cost and with fast material removal rates. In CMP process, nanoabrasive is very important parameters in determining the removal rate. In this paper, the influence mechanism of nanoabrasive on sapphire substrate CMP was analyzed deeply. The main kinetics processing was discussed in detail. According to sapphire substrate properties, alkali slurry was chosen and the mix of SiO₂ and Al₂O₃ sol was selected as nanoabrasive, and the particle size was 20~30nm. The results show that adding nanoalumina with the concentration of 20ml / L in the main abrasive can make the chemical action balance with the mechanical action in the CMP process, so that the substrate removal rate is well improved, and the surface roughness can be reduced to 0.236nm by adjusting the process parameters and slurry ratio. Such data meets the super smooth requirement and the optimal sapphire surface can be gotten. So such slurry with mixed abrasive can be as rough polishing slurry and can improve the polishing efficiency.

Abstract: Using the ring-belt magnetorheological polishing equipment to do polishing experiments on sapphire substrate, analyzed the influence of the main process parameters on polishing, focus on the influence of the polishing liquid PH value on material removal. Experimental results show that, with the increase of the PH value of the polishing liquid, sapphire substrate material removal rate increased, the roughness value was convergence trend, roughness will increases when the PH value is greater than 12.5. In optimal conditions, the maximum material removal rate of sapphire substrate was 5.6μm/h, after polishing the original surface roughness was decreased from 11nm to 0. 84nm. The ring-belt magnetorheological finishing applicable to sapphire efficient and ultra-smooth processing.

Abstract: The three-dimensional quasi-steady molecular statics nanocutting model developed by this paper carries out simulation analysis of nanocutting of sapphire substrate in order to explore the effects of tools with the same tip radii of probe and straight-line cutting at different cutting depths, on cutting force. The three-dimensional quasi-steady molecular statics nanocutting sapphire workpiece model first assumes the trajectory of each atom of the sapphire workpiecs being cut whenever the diamond cutter goes forward one step. It then uses the optimization search method to solve the force equilibrium equation of the Morse force in the X, Y and Z directions when each atom moves a small distance, so as to find the new movement position of each atom, and step by step calculates the behavior during cutting. And from the simulation results of cutting force, down force and side force, it is found that under the actions of cutting tools with the same tip radius of probe, cutting force enlarges with the increase of cutting depth. This result is identical to the actual experimental phenomena of nanocutting. From this, it is known that the simulation model developed in this study is reasonable.

Abstract: In order to improve the surface quality of sapphire substrates ground by diamond wheel, the chemo-mechanical grinding (CMG) tools for sapphire grinding was investigated in this paper. According to the processing principle of CMG, three CMG tools with different abrasives of SiO2, Fe2O3 and MgO were developed respectively. The compositions of the CMG tools were designed and optimized based on the physicochemical characteristics of sapphire. The grinding experiments were performed with the developed CMG tools and the grinding performance of three kind of tools were evaluated by comparing the surface roughness and the MRR of sapphire. The experiment results show that the grinding performance of SiO2 CMG tool was worst. The surface roughness and MRR corresponding to SiO2 CMG tool were all significantly poorer than Fe2O3 and MgO CMG tools. The highest MRR could be obtained by Fe2O3 CMG tool, but the best surface quality was obtained by MgO CMG tool.

Abstract: Sapphire (α-Al2O3) single crystal, as an important photoconducting device substrate material, stringent surface quality requirements, i.e. surface finish and flatness, are required. The use of chemical mechanical polishing (CMP) technique can produce high quality surface finishes at low cost and with fast material removal rates. The polishing mechanism was studied in this paper, and it was pointed that there were chemical and mechanical kinetics process respectively. The chosen polishing temperature was 40 oC. SiO2 sol was chosen as abrasive and the particle size is 40nm. The pH value was determined at 11.5~12. During CMP process C6382I-W/YJ single side polisher and SUBA 600 pad were used. After polishing and cleaning of sapphire surface, the measured removal rate was above 183.3nm /min and the surface roughness by using AFM was lower than Ra 0.3 nm. From the results, it was found that using such method, the optimal sapphire surface can be gotten, which is advantaged for epitaxial growth and device making-up.

Abstract: This paper proposed a new approach to control the micro-quality of sapphire substrate, in order to grow GaN on substrate. The main factors that influence macro-quality are the method of slicing, grinding and polishing. Thread speed of slicing is less than 0.5m/s. Ductile mode grinding of substrate is achieved by #3000 diamond wheel and feed of 1μm/r. The suitable polishing conditions are that the SiO2 grain size is less than 10nm, the concentration SiO2 is 3％, pH value of polishing liquid is 10.5 and polishing stress is 190Pa. The undamaged substrates have been obtained steadily. The surface roughness RMS is less than 0.4 nm.