CN-121972390-A - Piezoelectric micromechanical ultrasonic transducer, control method and array

CN121972390ACN 121972390 ACN121972390 ACN 121972390ACN-121972390-A

Abstract

The invention provides a piezoelectric micromachined ultrasonic transducer, a control method and an array. The piezoelectric micromachined ultrasonic transducer (100) comprises a substrate (101) provided with a back cavity (102), a composite vibrating diaphragm structure arranged above the back cavity and comprising a piezoelectric film layer (105) used for transmitting and receiving ultrasonic waves based on a piezoelectric effect, a phase change tuning layer (110) mechanically coupled with the piezoelectric film layer and made of a nonvolatile material with reversible change of mechanical properties, wherein the nonvolatile material has at least two stable phase forms under external excitation, the different phase forms correspond to different mechanical properties, the change of the mechanical properties causes the integral effective rigidity of the composite vibrating diaphragm structure to change, and an excitation structure (108) coupled with the phase change tuning layer is used for applying external excitation to the phase change tuning layer so as to drive the nonvolatile material to carry out nonvolatile switching between the different phase forms and realize frequency tuning of the piezoelectric micromachined ultrasonic transducer.

Inventors

DU LIDONG
ZHANG CHENGCHEN
FANG ZHEN
CHEN XIANXIANG
LI ZHENFENG
WANG PENG
WU PANG

Assignees

中国科学院空天信息创新研究院

Dates

Publication Date: 20260505
Application Date: 20260324

Claims (10)

1. A piezoelectric micromachined ultrasonic transducer, comprising: The substrate is provided with a back cavity; The compound vibrating diaphragm structure is arranged above the back cavity, and the compound vibrating diaphragm structure comprises: the piezoelectric film layer is used for transmitting and receiving ultrasonic waves based on a piezoelectric effect; The phase change tuning layer is mechanically coupled with the piezoelectric film layer and is prepared from a nonvolatile material with reversible change of mechanical properties, at least two stable phase forms exist in the nonvolatile material under external excitation, and the different phase forms correspond to different mechanical properties, and the change of the mechanical properties leads to the change of the integral effective rigidity of the composite diaphragm structure; And the excitation structure is coupled with the phase-change tuning layer and is used for applying the external excitation to the phase-change tuning layer so as to drive the nonvolatile material to perform nonvolatile switching between different phase forms, thereby realizing the frequency tuning of the piezoelectric micromachined ultrasonic transducer.
2. The piezoelectric micromachined ultrasonic transducer of claim 1, wherein the at least two stable phase morphologies include an amorphous state and a crystalline state, and the amorphous state corresponds to a macroscopic mechanical stiffness that is less than the crystalline state corresponds to a macroscopic mechanical stiffness.
3. The piezoelectric micromachined ultrasonic transducer of claim 2, wherein the non-volatile material is a germanium-antimony-tellurium alloy material.
4. The piezoelectric micromachined ultrasonic transducer of claim 2, wherein the excitation structure comprises a micro-heater for providing the external excitation to the phase-change tuning layer by joule heating to drive the nonvolatile material to non-volatile switch between the amorphous state and the crystalline state.
5. The piezoelectric micromachined ultrasonic transducer of claim 4, wherein the micro-heater is a patterned resistive metal layer, a projection of the resistive metal layer onto a plane at least partially covering the phase change tuning layer.
6. The piezoelectric micromachined ultrasonic transducer of claim 4, wherein the piezoelectric thin film layer is made of aluminum nitride or aluminum scandium nitride.
7. The piezoelectric micromachined ultrasonic transducer of claim 1, wherein the excitation structure is located below the phase change tuning layer, the piezoelectric micromachined ultrasonic transducer further comprising: a bottom electrode between the piezoelectric thin film layer and the substrate; A top electrode located on a side of the piezoelectric thin film layer away from the substrate; A first dielectric layer covering the top electrode and located between the top electrode and the excitation structure; A second dielectric layer between the excitation structure and the phase change tuning layer; And a third dielectric layer covering the phase change tuning layer.
8. A method for controlling a piezoelectric micromachined ultrasonic transducer according to any one of claims 1 to 7, comprising: Applying a first control signal to the excitation structure to drive the non-volatile material to transition to a first phase morphology, thereby tuning the piezoelectric micromachined ultrasonic transducer to a first resonant frequency; A second control signal is applied to the excitation structure to drive the non-volatile material to transition to a second phase morphology to tune the piezoelectric micromechanical ultrasound transducer to a second resonant frequency different from the first resonant frequency.
9. The method of claim 8, wherein the first phase morphology is amorphous and the second phase morphology is crystalline, the first control signal is a first electrical pulse, and the second control signal is a second electrical pulse; Wherein the amplitude of the first electric pulse is greater than the amplitude of the second electric pulse, and the pulse width of the first electric pulse is smaller than the pulse width of the second electric pulse.
10. A piezoelectric micromachined ultrasonic transducer array comprising a plurality of piezoelectric micromachined ultrasonic transducers according to any one of claims 1 to 7, the plurality of piezoelectric micromachined ultrasonic transducers being arranged in a two-dimensional array.

Description

Piezoelectric micromechanical ultrasonic transducer, control method and array Technical Field The invention relates to the fields of ultrasonic imaging and micro-electromechanical systems, in particular to a piezoelectric micro-mechanical ultrasonic transducer, a control method and an array. Background Piezoelectric materials have become the focus of industry attention as a new generation of smart materials by virtue of excellent mechanical-electrical energy conversion characteristics. In recent years, with the rapid development of Micro-Electro-MECHANICAL SYSTEM, MEMS technology, the MEMS sensor chip prepared from the piezoelectric film has the outstanding advantages of miniaturization, low power consumption and the like, and the application field is continuously expanded. The piezoelectric micromachined ultrasonic transducer (Piezoelectric Micromachined Ultrasonic Transducer, PMUT) is used as a core ultrasonic device, and has been widely applied in the fields of ranging, imaging, fingerprint identification and the like. Although PMUTs have made significant progress in miniaturized research, practical application scenarios place higher demands on them, medical ultrasound imaging requires larger-scale PMUT arrays to improve image clarity, and fingerprint identification imaging relies on more PMUT units to guarantee high resolution. It is worth noting that the traditional PMUT belongs to a single-frequency narrow-band device, the narrow bandwidth not only causes lower axial resolution of the device, but also cannot adapt to advanced technologies such as harmonic imaging, resonance imaging and the like, and the limitation has severely restricted further expansion of the PMUT in the imaging field. Disclosure of Invention In view of the above, the invention provides a piezoelectric micromachined ultrasonic transducer, a control method and an array. The invention provides a piezoelectric micromechanical ultrasonic transducer which comprises a substrate, a composite vibrating diaphragm structure, a phase change tuning layer and an excitation structure, wherein a back cavity is arranged on the substrate, the composite vibrating diaphragm structure is arranged above the back cavity and comprises a piezoelectric film layer used for transmitting and receiving ultrasonic waves based on a piezoelectric effect, the phase change tuning layer is mechanically coupled with the piezoelectric film layer and is prepared from a nonvolatile material with reversible change of mechanical properties, the nonvolatile material has at least two stable phase forms under external excitation, the different phase forms correspond to different mechanical properties, the change of the mechanical properties causes the change of the integral effective rigidity of the composite vibrating diaphragm structure, and the excitation structure is coupled with the phase change tuning layer and is used for applying external excitation to the phase change tuning layer so as to drive the nonvolatile material to carry out nonvolatile switching between the different phase forms, so that the frequency tuning of the piezoelectric micromechanical ultrasonic transducer is realized. According to an embodiment of the invention, the at least two stable phase morphologies include an amorphous state and a crystalline state, and the macroscopic mechanical stiffness corresponding to the amorphous state is smaller than the macroscopic mechanical stiffness corresponding to the crystalline state. According to an embodiment of the invention, the non-volatile material is a germanium antimony tellurium alloy material. According to an embodiment of the invention, the actuation structure comprises a micro-heater for providing an external actuation to the phase change tuning layer by means of joule heating to drive the non-volatile material to switch between the amorphous and crystalline states. According to an embodiment of the invention, the micro-heater is a patterned resistive metal layer, the projection of which onto a plane at least partially covers the phase change tuning layer. According to the embodiment of the invention, the piezoelectric film layer is prepared from aluminum nitride or scandium aluminum nitride. According to the embodiment of the invention, the excitation structure is positioned below the phase-change tuning layer, and the piezoelectric micromechanical ultrasonic transducer further comprises a bottom electrode positioned between the piezoelectric film layer and the substrate, a top electrode positioned on one side of the piezoelectric film layer away from the substrate, a first dielectric layer covering the top electrode and positioned between the top electrode and the excitation structure, a second dielectric layer positioned between the excitation structure and the phase-change tuning layer, and a third dielectric layer covering the phase-change tuning layer. A second aspect of the present invention provides a method for controlling a piezoelectri