A micro-pressure sensor with a circular diaphragm has been studied. The diaphragm has a layered structure consisting of five thin films and is fixed along its circumference and at its center. Sensor characteristics strongly depend on the mechanical properties such as the Young's modulus, internal stress and Poisson's ratio of thin films utilized as the constructional material of a diaphragm. If the influence of the mechanical properties of the thin films on sensor characteristics is analyzed, an optimum design is realized to improve the sensitivity. In this study, theoretical expressions to calculate the strain on a circular diaphragm fixed along the circumference and at the center has been derived to predict the sensitivity of a micro-pressure sensor. The Young's modulus and internal stress of each thin film and the layered thin film structures were measured, and the validity of a composite law to calculate the sensor properties were confirmed. Two types of micro-pressure sensors having diaphragms of different layered thin film structures were prepared, and their sensitivities were measured and calculated. The measured sensitivity ratio was 0.80, whereas the calculated sensitivity ratio was 0.78. Consequently, it is concluded that the influence of the mechanical properties of the diaphragm on the pressure sensitivity of the micro-pressure sensor is analyzed using these expressions and measurement techniques.
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