Capacitance-type ultrasonic sensor of integrated full-vibration conductive film structure and manufacturing method thereof

Abstract

The invention relates to a capacitance-type ultrasonic sensor of an integrated full-vibration conductive film structure. The capacitance-type ultrasonic sensor of the integrated full-vibration conductive film structure resolves the problems that an existing sensor is large in frequency deviation, low in normalization displacement, low in sensitivity and the like. The capacitance-type ultrasonic sensor comprises a silicon substrate provided with a plurality of cylindrical micro structure cavities in a curved mode and a full-vibration film bonded on the silicon substrate through the bonding technology, wherein a vacuum sub-vibration cavity is formed by the full-vibration film and the cylindrical micro structure cavities, and the cylindrical micro structure cavities are mutually connected through a first groove to form a regionalization bottom electrode. The capacitance-type ultrasonic sensor is novel in design, simple in structure, low in frequency deviation, high in normalization displacement, and obvious in improvement of sensitivity. Additional electrodes are not needed to deposit on the full-vibration film in a separated mode, and the film is good in uniformity, high in thickness controllability, high in response sensitivity, and low in frequency deviation. The regionalization bottom electrode of the sensor largely reduces the unnecessary stray capacitance. Meanwhile, the capacitance-type ultrasonic sensor is simple in manufacturing process, is high in integration degree, and has certain application prospects.

Description

technical field [0001] The invention relates to an ultrasonic sensor in the field of MEMS sensors, in particular to a capacitive ultrasonic sensor with an integrated full-vibration conductive film structure and a manufacturing method thereof. Background technique [0002] Capacitive ultrasonic sensor is a widely used electrostatic sensor, which can work in various media such as liquid, solid and gas. Capacitive ultrasonic sensors have been widely used in medical diagnosis and treatment, non-destructive material testing, sonar, communication, flow measurement, real-time process control, and ultrasonic microscopy. [0003] However, the existing capacitive ultrasonic sensors also have disadvantages: 1) Due to the fact that there are not many researches on capacitive ultrasonic sensors in underwater ultrasonic imaging at home and abroad, the working frequency is mostly concentrated in the megahertz and above frequency bands, so it cannot satisfy Long-distance underwater imaging...

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Problems solved by technology

[0003] However, the existing capacitive ultrasonic sensors also have disadvantages: 1) Due to the fact that there are not many researches on capacitive ultrasonic sensors in underwater ultrasonic imaging at home and abroad, the working frequency is mostly concentrated in the megahertz and above frequency bands, so it cannot satisfy Long-distance underwater imaging application requirements; 2) The uniformity and controllability of the diaphragm thickness of the existing capacitive ultrasonic sensor is not high, and the surface roughness of the diaphragm is large, which directly affects the deformation uniformity of the diaphragm, resulting in the normalization of the diaphragm The displacement (that is, the ratio of the average displacement to the maximum displacement of the diaphragm everywhere is used to reflect the uniformity of the deformation of the diaphragm.

The closer it is to 1, the better the acoustic-electric conversion capability of the structure to ultrasonic waves) becomes smaller, and the sensor’s ability to transmit and receive ultrasonic waves decreases; 3) Since the diaphragms of existing capacitive ultrasonic sensors are mostly insulating materials such as silicon nitride, the surface Inevitably, the deposition of discrete metal electrodes is required, which leads to an increase in the frequency of the sensing diaphragm and deviations, which is not conducive to the realization of the required sub-megahertz sensor; 4) The existing capacitive ultrasonic sensors are mostly prepared by surface sacrificial processes, resulting in thin film Difficult to release, unstable device yield

In addition, the limitations of the existing capacitive ultrasonic sensor fabrication process and the deposition of discrete electrodes on the surface of the structure limit the improvement of sensor sensitivity.

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