| Summary: | 碩士 === 國立彰化師範大學 === 機電工程學系所 === 104 === In recent years, the need of consumer electronics increases because of industrial demand, and furthermore, effects the requirement of oscillators. Quartz crystal oscillator can get accurate clock signal with the piezoelectric effect oscillation. The range of oscillation frequency, which is made by quartz wafer, is from MHz to several hundred MHz, and the mode of oscillation is TSM (Thickness Shear Mode). However, in a traditional fabrication was based on mechanical cutting and polishing process, which is difficult to increase the oscillation frequency anymore. Therefore, a novel process was propose in this research. In this research, using the chemical wet etching and polishing process to reduce the thickness to reach the ideal oscillation frequency, 60MHz, and discussed the surface roughness of AT-cut quartz wafer for depicting the frequency response characteristics.
In his research, a novel notion of etching and polish was proposed. In the process of etching and polish, the ultrasound was used to enhance the effect of etching and the fluidity of polish solution. Compared the process with stirring magnet, we used the conditions, first soaked the wafer in mixed solution of HF (49%) and NH4F (40%) or 36℃ HF (23%) for two hours, and then soaked in the solution of 36℃ HF (11.5%) for one hour. After the polishing process, we use the WYKO NT-2000 non-contact optical profiler to measure the surface roughness of AT-cut quartz wafer, and using the ViTiny UM06 electron microscope to measure the thickness. Form the measurement data, the etching rate and oscillation frequency can be clearly explain. Finally, use the HP AgilentE5100B high speed network analyzer to measure the oscillation frequency and frequency characteristics.
After the process of polishing and chemical wet etching, we can find the best experimental parameters, which is using 36 ℃ HF (23%) for etching with ultrasonic vibration and 36 ℃ HF (11.5%) for polishing. The surface roughness can reach 53.1 nm, and the transparency is relatively better. In the Frequency response characteristics, the main frequency is more obvious, and the least parasitic frequency. The real oscillation frequency is 33.38 MHz, it has 3.98MHz error with the formula. We can have the AT-cut quartz wafer with better roughness, transparency, and less spurious by adjusted the experimental and theoretical parameters.
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