A pmut unit driven by an embedded arched film and its preparation method

Abstract

The invention discloses a PMUT unit driven by embedded arch thin films and a preparation method thereof. The PMUT unit comprises vibration thin films, a driving layer and a substrate sequentially arranged from top to bottom, wherein the driving layer comprises a supporting structure and a driving structure, the substrate comprises a back cavity and a base, and the back cavity is formed by the driving layer and the base in an enclosing mode; and the driving structure is provided with a horizontal part and a plurality of arch parts, the arch parts are marked as the embedded arch driving films, the embedded arch driving films are located right above the back cavity, and the lower end surface of the horizontal part is connected with the upper end surface of the base. According to the PMUT unit, the purpose of improving the resonant frequency under the condition of the same area of the vibration thin films is achieved, electrodes and the driving layer are sealed in the back cavity, only thevibration thin films playing a role in vibration and support make contact with the outside, and the direct contact between the sensitive element part of a PMUT chip and the outside is completely isolated, so that PMUT is more durable.

Description

technical field [0001] The invention belongs to the technical field of ultrasonic transducers, in particular to a PMUT unit driven by an embedded arched film and a preparation method thereof. Background technique [0002] In view of the advantages of MEMS technology, in the 1990s, researchers began to use MEMS technology to design and manufacture ultrasonic transducers. This kind of ultrasonic transducer designed and manufactured using MEMS technology is called a micromachined ultrasonic transducer (Micromachined Ultrasonic Transducer, MUT). Compared with the ultrasonic transducer made of traditional piezoelectric thick film, MUT has the advantages of miniaturization, mass production, low power consumption, flexible frequency control, high receiving sensitivity, easy two-dimensional array processing, and easy integration with ICs And the advantages of realizing intelligence; it has great application potential in cutting-edge application fields such as real-time ultrasonic i...

AI Technical Summary

Problems solved by technology

[0005] 1) The shape of the PMUT vibrating film is usually circular, rectangular or polygonal. Taking the circular vibrating film as an example, its structural parameters and its resonance frequency follow a functional relationship where f n is the resonant frequency of the vibrating film, h is the thickness of the vibrating film, and a is the radius of the vibrating film. Therefore, to obtain a PMUT with a high resonant frequency, the only way to obtain a PMUT with a high resonant frequency is to reduce the radius a of the vibrating film or increase the thickness h of the supporting layer of the vibrating film, but by The membrane vibration amplitude of the high-frequency PMUT obtained by these methods will become smaller, resulting in a greatly reduced emission sound pressure and receiving sensitivity, which restricts the development of PMUTs to ultra-high frequencies.

[0006] 2) The application environment of the PMUT chip is usually immersed in a liquid environment, but currently the PMUT chip processed mainly by the MEMS surface deposition process is very fragile, and the sensitive part of its excitation and receiving signals is usually in direct contact with the external environment, which is easy to Cause PMUT chip damage and failure

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