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Research paper : The aerosol deposition method (J. Akedo et al.)−123 Synthesiology - English edition Vol.1 No.2 (2008) 6. Film formation is possible even at low vacuum (several hundred Pa ~ atmospheric pressure).During the film formation by RTIC using the AD method, absolutely no increase in substrate temperature due to collision was observed. Macroscopically, ceramic material was consolidated at room temperature. Since it did not undergo firing process, AD consolidation process could be considered as binderless, ultra high-density ceramic green fabrication process.3 Comparison with current thin film technologies and energy conservation3.1 Difference in principle with conventional thin film technologiesIf ceramic film with high density and good crystallization can be formed accurately at low temperature, at low cost, and at high speed, the issue of mass production discussed in Chapter 1 can be solved. The AD method is a non-heat equilibrium process, and unlike thermal spraying, the material powder is bonded and a thin film is formed in solid state at room temperature. Compared to the conventional thin film method, the coating speed is extremely fast since it is a build up process at a particle level, and the crystal structure of material powder is almost completely preserved in the film coat. Therefore, one major characteristic of AD method is that it can be used for film coating on any substrate material, and film coatings from powders with complex compositions such as composite oxides can be formed. Due to the characteristics of the AD method, drastic reduction in process temperature can be expected compared to other coating technologies. Moreover, the AD method is also readily applicable for compounding and integration of different ceramic, metal, and polymer materials, as well as for development of nanostructure compound materials.From the perspective of process energy conservation, coating with conventional technologies is normally possible only in vacuum environment of several hundred Pa or less, while, with AD method, coating can be done in atmospheric pressure depending on the material and use. In conventional thin film technology, material is broken down to atomic and molecular levels, and then crystallized on the substrate. Therefore, to obtain highly pure crystal formation without defects and with high-performance film properties, it is necessary to maintain ultra high vacuum to control adhesion and bonding of contaminating atoms before reaching the substrate. As shown in Figure 3, in the AD method raw powder material is already in crystallized form. AD method has a fast powder supply speed to the substrate and, because the surface of material powder is inactive before collision with the substrate or the coated film and the activation for bond formation occurs only due to collision with the substrate, the need of ultra high vacuum is not necessary to control inclusion of impurities during the coating process. Since adhesion of impurities can occur on the surface of material powder, it is necessary to clean the surface before use to obtain ultra pure crystals. However, in the NEDO Nanotechnology Program / Low Temperature Formation and Integration Technology of Nano level Electronic Ceramics Material Project (FY2002~FY2006)[4], film property equivalent or better than that achieved with current vacuum thin film technology was demonstrated in many electronic ceramic materials without the cleaning process.For industrial application, the innovative point added by AD method is that although high performance material is involved, coating can be accomplished in low vacuum. Compared to the conventional vacuum thin film process, it is expected to reduce cost of building manufacturing facility, energy consumption, and environment load.3.2 Energy conservation by using the AD method in electrostatic chuck manufacturing processInvestigation has been conducted on how much energy could be conserved in the whole product manufacturing process and to what degree product function would be improved by employing the AD method in the NEDO Energy Research and Development Project for Core Technology for Efficient Energy Use (Leading Energy Conservation Research FY2001~FY2003)[5] through joint research with a private corporation. The subject of investigation was electrostatic chuck, which is currently used to lift up wafers by adsorption in semiconductor manufacturing, and product with high adsorptivity is in demand to support large wide size Si wafers or heavy components such as flat panels. Electrostatic chuck has a structure consisting of a ceramic thin plate added on as isolator to generate static electricity on a metal jacket that acts as radiator and electrode, as shown in Figure 4. The thinner the ceramic plate is, the higher the adsorptivity per applied voltage. Aluminum nitride material with good heat conductivity is generally used due to its radiation property. In Fig. 3 Difference between the processes of AD method and conventional thin film method.(Conventional thin film method)(AD method, Process)Atoms and molecules of raw material (highly active)・Low vacuum process・High-speed low-temperature coating・Any substrateCrystallization・Substrate: crystalline・Heating necessarySurface defectCoating (particle collision, particle destruction, defect introduced)AD film: polycrystal 20 nm or lessGrain growth, defect recoveryGrain boundary defectHigh vacuumHeat treatment (200~900 °C, dependent on material and purpose)Raw material powder: 100 nm or more (low activity) (Use of temporary chamotte, change due to preliminary treatment)Internal defect, distortion (structural defect, incomplete structure, etc.)Easily contaminated(51)−

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