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Patterned sapphire substrate (PSS) was fabricated by wet etching solutions with different mixture ratios of H2SO4 to H3PO4 and different temperatures to investigate the fabrication mechanisms. It was found that the mixture ratio and temperature of the etching solutions affect the ratio of the pattern diameter to the pattern depth. In addition, the observed pattern shape was strongly affected by the mixture ratio. To discuss the reaction mechanisms of sapphire with H2SO4 and H3PO4 separately, we estimated the activation energies and reaction frequency factors for each reaction. By the estimated results, the behavior of the observed pattern shape for the etching conditions was well explained. To confirm the fabrication mechanism of pattern shape in the microscopic scale, the electron probe microanalysis (EPMA) inspection of the sapphire surface after H2SO4 and H3PO4 etching were carried out. As a result, it was indicated that the pattern shape is controlled by the step flow reaction with and without impurities in the etching solutions. From the observation of the pattern shape, the estimation of the activation energies and reaction frequency factors, and EPMA inspection of the reaction products for each reaction, a schematic model of the fabrication mechanisms for the wet etching of a PSS was established.

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In chemical mechanical polishing (CMP) process, the removal rate is affected by the actual contact conditions between the wafer and the polishing pad. Further, the free abrasives in the slurry attack the wafer at the regions of actual contact. The polishing pad is one of the most important consumable materials in CMP since the pad surface texture changes during wafer polishing and substantially influences the actual contact conditions. Therefore, methods for quantitative evaluation of the pad surface texture have been proposed by various research institutes. We have developed a novel method for the quantitative evaluation of the polishing pad surface texture; this method is based on contact image analysis using an image rotation prism. We have proposed the use of four effective evaluation parameters: the number of contact points, the contact ratio, the maximum value of the minimum spacing of the contact points, and the half-width of the peak of the spatial fast Fourier transform (FFT) of a contact image. We determine the changes in the polishing pad surface texture on the basis of the proposed evaluation parameters in serial batch polishing tests. In particular, we focus on the relationships between the proposed evaluation parameters and the removal rate, which changes with an increase in the number of batch polishing tests. The evaluation parameters are linearly correlated with the removal rate. Hence, the removal rate is improved not only with an increase of the number of contact points and the contact ratio but also with a decrease in the size of the cohesion regions and the spacing between the contact points.Progress in science and technology depends substantially on innovations in the semiconductor industry. For example, silicon wafers used for semiconductor device fabrication should have highly flat surfaces, and because of the continuous downsizing of such devices, 1 nanometer-scale planarization becomes important. Therefore, there is an increasing demand for chemical mechanical polishing (CMP) techniques.Recently, it was found that the material removal rate in wafer polishing is affected by the actual contact conditions between the wafer and the polishing pad. 2, 3 The actual contact conditions affect both the mix effects of chemical mechanical factors of the slurry and the viscoelastic deformation of the pad. Additionally, the free abrasives in the slurry attack the wafer at the regions of actual contact. 3 Therefore, it is important to identify the optimum contact conditions under which the slurry can effectively act on the wafer and the removal rate can be improved.The polishing pad is one of the most important consumable materials used in CMP since its surface texture has a substantial influence on the actual contact conditions. 4 Therefore, it is extremely important to develop methods for the quantitative evaluation of the actual contact conditions between the wafer and the polishing pad and to examine the effects of these conditions on the CMP characteristics.With this background, we have developed ...