Development of ultra-precision processing technology of novel semiconductor substrate applied to devices with nano-structure

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The research target in this project is to develop the ultra-precision machining technology of novel semiconductor substrates, such as GaAs, silicon carbide and diamond single crystal, applied to future devices with nano-structure. The basic concept of the technology is application of solid catalysis and ultra-violet rays in polishing technology. The results obtained are as follows.(1)Ultra-precision polishing of GaAs substrateUltra-violet rays was irradiated on the GaAs wafer on which TiO_2 photocatalyst powder was dispersed for ten minutes. It is found that oxide film composed from Ga_2O_3 and As_2O_3 was detected by evaluation method of XPS. It is possible to polish GaAs by means of removing the oxide film with safety and high quality. On the other hand, hydroxyl-radical generated from H_2O_2 is also available for GaAs polishing.(2)Ultra-precision polishing of silicon carbide substrateSilicon terminated surface of SiC single crystal is polished with Cr_2O_3-grinding wheel to high quality and high efficiency. The stock removal rate of it achieves to 3 micrometer per hour and the surface roughness polished is below Ra 0.3nm. It was found that there is no sub-surface damage from the evaluation by CAICISS method.It was found that SiC single crystal can be polished with quartz disk under ultra-violet rays irradiation. The polishing mechanism of this based on photochemical reaction of SiC semiconductor.(3)Ultra-precision polishing of diamond single crystalThe (100) surface of diamond single crystal can be polished with quartz disk under ultra-violet rays irradiation. The stock removal rate is achieved to 2 micrometers per hour under the condition of polishing pressure of 70 MPa. The surface roughness of the surface polished is below Ra 0.5nm.