Development of Capacitive Ultrasonic Sensor with Parylene Diaphragm Using Micromachining Technique

Abstract

In this paper, we reports the development of a miniaturized capacitive ultrasonic sensor with a Parylene diaphragm using a micromachining technique. Since the polymer diaphragm is flexible and nonbrittle, good sensitivity and durability are expected. Moreover, Parylene has good complementary metal oxide semiconductor (CMOS) compatibility, since it can be deposited at room temperature. Practical sensor devices were fabricated, and their performance was characterized. They can receive an impulsive ultrasonic pulse transmitted by a spark discharge with an open-circuit sensitivity of 0.3 mV/Pa. A well-damped waveform was obtained by setting appropriate acoustic holes. The ranging system using this sensor can detect distances up to 1 m with an error of less than 1 mm. The developed sensor can receive ultrasound from a wide area. The wide directivity could be effective for realizing the omni-directional characteristics of the future arrayed sensor, which contains many of the developed sensors.

Miniature Ultrasonic and Tactile Sensors for Dexterous Robot

“…Microfabricated ultrasonic sensors have been realized on cantilevers and diaphragms using the detection principles of the capacitive [6][7][8], piezoresistive [9,10] and piezoelectric [11][12][13] sensing techniques. Piezoelectric-type microsensors have several advantages: they are simple structures; they have a simple fabrication process because, unlike the capacitive-type, a narrow gap structure is not required; and they potentially have lower power-consumption owing to their nature of self energyconversion [14] than the capacitive-and piezoresistive-types.…”

Highly sensitive structures for ultrasonic microsensors by buckling control of diaphragms through intrinsic stress of PZT films

“…Microfabricated ultrasonic sensors for these applications have been increasingly investigated in a capacitive type [1], [2] and a piezoelectric type [3], [4]. Owing to its nature of self-generating charge, the piezoelectric microsensors have advantages [5] such that no need of biasing voltage and simple readout circuit, low cost with easy microfabrication process, especially being freed from sticking issue because of backplate-less configuration, and potential to fully batteryless operation with energy harvesting nature.…”

Buckling control of silicon dioxide diaphragms by lateral stress enhancement for sensitivity improvement of piezoelectric ultrasonic microsensors

“…Microfabricated ultrasonic sensors have been realized on cantilevers and diaphragms using detection principle of capacitive [1][2][3], piezoresistive [4,5] and piezoelectric [6][7][8] sensing technique. Piezoelectric-type microsensors have advantages from the viewpoints of simple structure and simple fabrication process because no narrow gap structure is required over the capacitive-type, and potentially low power-consumption owing to self energy-conversion nature [9] over the capacitive-and piezoresistive-type.…”