Development of Ultra Thinning Technology of Multifunctional Device Substrates by Abrasive Processing

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This research was performed to develop the ultra thinning technology of three kinds of multifunctional device substrates, and finally this technology is aimed to establish as the mass production technology. The device substrates used in this research were quartz substrate, barium titanate (BaTiO_3), and lithium niobate (LiNbO_3). First of all, the slight waviness generated in the quartz substrate during the polishing can be difficulties in making the ultra thin substrates. The waviness generated in the substrate was induced by the compressive force from the protective-plating film, confirmed by the computer simulation calculated by Dr. Sakamoto ; this can make the correction of the plating formation condition. As experimental results, it has been understood that there is the optimum value of the plating thickness to suppress these compressive forces. The plating formation conditions (plating voltage, plating liquid temperature, and electric current density) were clarified. Moreover, th … More e cylindrical column implant processing was newly developed to achieve the mass production. It finally succeeded in the establishment of the mass production technology of ultra thin quartz substrate with 4 μm in thickness and 5.2 mm in diameter. The barium titanate substrate (BaTiO_3) was also achieved in the processing up to 13 μm in the final thickness by applying the improved technique of the above-mentioned plating method. The lithium niobate (LiNbO_3) was processed from the original shape with 3-inch wafer and 350 μm in thickness. Ultra thin wafer with 20 μm in thickness with an excellent flatness within 1 μm in the entire substrate were achieved. Finally, these wafers were cut into about 500 chips of 2.0 mm×0.4 mm using the precision dicing machine. In addition, the thinning of 6-inch silicon wafer was performed by the precision grinding machine using newly developed fine diamond wheels including comparative large pores. By supplying the grinding fluid to superimpose the ultrasonic vibration to the grinding process, silicon wafer with 50 μm in the final thickness can be obtained, and the micro chip with 1.0 mm×1.0 mm were obtained for the micro-pressure sensor. These sensors will be incorporate into a "smart microchip" to monitor the biological information of the transgenic mouse or the knock-out mouse. Less