A kind of Cmuts fluid density sensor and preparation method thereof

Abstract

The invention discloses a CMUTs fluid density sensor and a preparation method thereof. A CMUTs unit structure comprises a substrate, a lower electrode, a silica thermal stress matching layer, a silicapillar, a silica vibration thin film layer, an annular metal upper electrode, a silica insulating layer, an acoustic resistance anti-matching layer, and a sound insulation wall. An annular thin filmis taken as a vibration structure, compared with conventional circular thin film, the advantages are that: the resonant frequency and density detection sensitivity are increased; the sound insulationwall is capable of reducing ultrasonic mutual radiation among CMUTs arrays, and increasing sensor precision; the acoustic resistance anti-matching layer is adopted to increase CMUTs detection signal intensity effectively; the CMUTs upper electrode and lower electrode are coated with insulation silica low in thermal expansion coefficient, so that the CMUTs fluid density sensor can be used in high temperature, electric conductive, and corrosive fluid measuring environment.

Description

technical field [0001] The invention belongs to the technical field of micro-electro-mechanical systems (Micro Electro-Mechanical Systems, MEMS) and fluid physical parameter testing, and specifically relates to a fluid density sensor based on capacitive micromachined ultrasonic transducers (Capacitive Micromachined Ultrasonic Transducers, CMUTs) and a preparation method thereof. Background technique [0002] Density is an important physical parameter of fluid, which plays an extremely important role in many fields such as petroleum, chemical industry, medical treatment, food, etc. Therefore, a high-precision fluid density sensor has important application value. At present, in industrial sites and laboratories, the traditional method is mainly used to obtain the density data of the fluid, that is, to extract the sample first and then measure the density value off-line. However, due to the large difference between the test environment and the actual working environment, the de...

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Problems solved by technology

Traditional CMUTs metal electrodes are located on the uppermost layer and cannot work in conductive or corrosive fluids; and there are acoustic impedance mismatch problems between the layers of the film and between the film and the fluid, resulting in a large loss of acoustic energy converted by CMUTs, which will The test signal of the fluid density is weak; for CMUTs working in the form of an array, the interaction of ultrasonic radiation in the array seriously affects the resonance consistency of each unit, so it is necessary to design a new CMUTs structure for the measurement of fluid density

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