Film bulk acoustic resonator based on phase change actuation effect of anti-ferroelectric material

Abstract

The invention belongs to the technical fields of intelligent micro-nano devices and systems and provides a film bulk acoustic resonator (FBAR) based on a phase change actuation effect of an anti-ferroelectric material. The film bulk acoustic resonator comprises a silicon substrate (5), wherein a front oxide layer (4) and a back oxide layer (6) cover the top and the bottom of the silicon substrate (5). The film bulk acoustic resonator is characterized in that a bottom electrode layer (3) is grown on the front oxide layer (4); a PLZT film layer (2) made from the anti-ferroelectric material is grown on the upper surface of the bottom electrode layer (3); and a top electrode layer (1) is grown on the PLZT film layer (2). According to the film bulk acoustic resonator, the anti-ferroelectric PLZT film material is taken as a function layer of the FBAR, and the phase change strain effect of the anti-ferroelectric PLZT film material is utilized as a resonant device mechanism, so that the high resonant efficiency can be obtained; and meanwhile, the larger transverse strain of the material has an important significance on improvement of a Q value in a liquid state of the device.

Description

technical field [0001] The invention belongs to the technical field of intelligent micro-nano devices and systems, and specifically relates to a novel thin-film bulk acoustic resonator (FBAR) based on a phase change actuation effect. The resonator has the characteristics of high Q value and high resonance frequency. Background technique [0002] FBAR is a kind of electromechanical conversion effect of functional thin film, through the acoustic bulk wave resonance method, the electrical energy is converted into sound waves to form resonance. Due to the characteristics of high Q value, high resonance frequency, low loss and small size, FBAR is the core device of modern intelligent wireless communication systems (such as mobile phones, GPS, etc.); on the other hand, sensor devices based on FBAR (such as quality sensors, temperature Sensors, radiation sensors, etc.) have higher sensitivity and accuracy than traditional devices. As the front-end components of information collect...

AI Technical Summary

Problems solved by technology

However, for the piezoelectric materials ZnO and AlN mainly used in FBAR, although they have high energy gaps, they still belong to the category of semiconductors. As the film thickness decreases, the leakage phenomenon is obvious.

Piezoelectric materials such as PZT and BST have superior dielectric properties than ZnO and AlN at low thickness, but their inherently high internal loss will increase sharply as the thickness decreases, which limits the increase in frequency

On the other hand, when the thickness of the film is constant, the rise of the resonance frequency is largely related to the response speed of the material itself (that is, the speed of sound in the material), and the best response speed that can be obtained in piezoelectric materials can only reach µs level, it is difficult to further improve, which has become a major obstacle to the increase of FBAR frequency

[0004] In addition, since the liquid does not support the transmission of longitudinal waves, the Q value of FBAR in the liquid phase environment will drop significantly (the Q value will drop from hundreds to tens)

Although partial shear modes can be formed by the method of oblique growth of the piezoelectric film, in the actual preparation process, it is difficult to precisely control the oblique growth of the piezoelectric film, and the repeatability is poor; if the method of lateral field excitation is used, high-quality The interdigitated electrodes not only make the process more complicated, but also increase the lateral size of the device, which is not conducive to its miniaturization and integration

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