Papers by Author: Junji Watanabe

Abstract: The ultra-precision polishing assisted by the ultraviolet rays irradiation was performed to achieve the atomic-scale planarization of the single crystal diamond substrates. This polishing method is a novel and simple polishing method characterizing by a quartz disk and an ultraviolet irradiation device. The principle three crystal planes of the diamond substrate were polished by this method. The polished surfaces were evaluated by an optical interferometric profilers (Wyko), an atom force microscope (AFM) and LEED (low-energy electron diffraction). The surface roughness of the polished diamond substrates was evaluated as 0.2 ~ 0.4 nmRa in (100), (110) and (111) crystal planes. The LEED (low-energy electron diffraction) patterns indicated the almost perfect crystallographic structure without the residual processed strain beneath the polished surface. In this paper, the optimum polishing condition to achieve the atomic-scale planarization of the diamond substrates has been investigated by the evaluation of LEED patterns, Wyko and AFM images. The mechanismof the ultraviolet rays assisted polishing is discussed in detail.

Abstract: Silicon carbide (SiC) single crystal has many advantages comparing with silicon single crystal, such as wide band-gap, hardness and various stable physical properties at high temperature and severe chemical environments. SiC semiconductor substrate is expected to be applied to high power devices and sensor devices in the severe environments. The polishing process under ultraviolet-ray irradiation has been developed in our laboratory to achieve the mirror-finish process of single-crystal SiC. In this paper, after the confirmation of the elastic deformation behavior of SiC single crystal using the nano-indentation tester, pre-processings of SiC by lapping and constant-pressure grinding were performed to obtain good surface without brittle fracture region. The indentation tests indicate the single-crystal SiC shows a very high elastic recovery rate. SiC substrate was processed by the lapping and the constant-pressure grinding using the constant-pressure processing to avoid the cumulative residual stock removal. As many experimental results, the constant-pressure grinding is found to be suitable for the pre-processing of SiC substrates. Additionally, it is clarified that good surface roughness on the ground surface is achieved by using a diamond wheel with the same protrusion height of abrasive grains.

Abstract: Polycrystalline diamond (PCD) has been widely used for various cutting tools and die components making use of its hardness and wear resistance properties. The polishing method of a single crystal diamond substrate and SiC using ultraviolet irradiation was newly developed to obtain mirror-finished surfaces. Due to the long polishing time in this method, a better pre-machined surface is required to shorten the total processing time. In this work, the constant-pressure grinding was performed using a cup type metal-bonded diamond wheel and a constant pressure device. After the good constant-pressure grinding, the PCD was finished by the polishing under the ultraviolet irradiation, and the microroughness was reached to be 0.71 nmRa.

Abstract: The ultraviolet irradiation-assisted ultra precision polishing was performed on single crystal diamond substrates. This polishing method has been newly developed in our laboratory. The change of polishing performances was investigated by the presence of the UV irradiation. The polished surfaces were evaluated by the observation with WYKO. The experimental results are as follows; Surface roughness of diamond substrates polished under UV irradiation has become clearly smoother than that without UV irradiation. The surface roughness by this polishing method was reached to be 0.19 nm Ra on (100) surface of single crystal diamond. The equivalent surface was obtained on (110) surface by the UV-polishing.

Abstract: Recently, the research of the gene using the transgenic mouse has been performed for the development of new medicines. However, 600,000 kinds of mice are produced for the elucidation of each gene function. For this reason, the intelligent microchips have been developed to obtain an individual identification and biological information. The ventricular rate of a mouse can be monitored by the micro pressure sensor mounted on the intelligent microchip. In this research, the detailed structure and functions of the micro pressure sensor were investigated by the FEM analysis, and the sensor-chips were manufactured on 6-inch silicon wafer. The wafer thickness had to be reduced owing to the size restriction of the intelligent microchip. The grinding of the 6-inch silicon wafer with 560 µm in thickness with 19200 sensor-chips was carried out by the newly developed thinning technology. After the basic characteristics of a sensor-chip were evaluated, the output profile containing small peaks corresponding to the heartbeat of a transgenic mouse was finally detected using a mounted sensor-chip.

Abstract: The GaAs wafer is widely applied to semiconductor element related to telecommunication and semiconductor laser. In this research, novel fine polishing technology of GaAs wafer was investigated using TiO2-H2O2-H2O slurry system instead of NaOCl which is conventionally used as polishing slurry. And then the ultraviolet ray was applied in order to investigate the effect of TiO2 photocatalyst. The polishing characteristics were estimated by optical microscope and WYKO optical profiler. It was found that the slurry system was available for GaAs wafer polishing although the polishing rate was lower than NaOCl. Moreover, the effect of the photocatalyst of TiO2 including in slurry was investigated. In this polishing system, the effect of the photocatalyst on GaAs wafer CMP mechanism has not been confirmed yet.