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CN-122001329-A - Acoustic resonator based on periodically polarized piezoelectric film and preparation method thereof

CN122001329ACN 122001329 ACN122001329 ACN 122001329ACN-122001329-A

Abstract

The invention provides an acoustic resonator based on a periodically polarized piezoelectric film and a preparation method thereof, wherein a piezoelectric film layer is locally polarized to form alternately arranged polarized areas and non-polarized areas in a material crystal forming the piezoelectric film layer, and interdigital electrodes are arranged in the centers of the polarized areas and the non-polarized areas to regulate and control equivalent stiffness constants in an acoustic wave propagation path, so that remarkable improvement of resonant frequency is realized, and excellent electromechanical coupling coefficient and passband bandwidth can be maintained without changing the physical size (physical thickness or electrode size) of a device, and in addition, the frequency is improved without reducing the finger width of the interdigital electrodes and carrying out extreme thinning on the piezoelectric film, thereby reducing the dependence and process complexity of high-end photoetching equipment, and eliminating the problems of difficult thickness uniformity control, mechanical strength reduction, poor process consistency and low yield caused by preparing an ultrathin film, thereby reducing the production cost.

Inventors

  • WANG CHENGLI
  • ZHOU WEIRAN
  • CHEN BOWEN
  • OU XIN

Assignees

  • 中国科学院上海微系统与信息技术研究所

Dates

Publication Date
20260508
Application Date
20260113

Claims (11)

  1. 1. An acoustic resonator based on a periodically poled piezoelectric film, comprising: a substrate and a sacrificial layer positioned on the substrate, wherein a cavity is arranged in the sacrificial layer; The piezoelectric film layer is arranged on the sacrificial layer, and comprises a polarized region and a non-polarized region, wherein a plurality of etching through holes are formed in the non-polarized region; The interdigital transducer is arranged on the piezoelectric film layer and comprises a first interdigital transducer and a second interdigital transducer, wherein the first interdigital transducer and the second interdigital transducer both comprise a plurality of even pairs of interdigital electrodes, the plurality of even pairs of interdigital electrodes of the first interdigital transducer are arranged in the polarized region, and the plurality of even pairs of interdigital electrodes of the second interdigital transducer are arranged in the unpolarized region.
  2. 2. The acoustic resonator based on the periodically poled piezoelectric film according to claim 1, wherein the piezoelectric film layer comprises one of lithium niobate, lithium tantalate, barium titanate, strontium titanate, aluminum nitride or gallium nitride, and the thickness of the piezoelectric film layer is 100-1000 nm.
  3. 3. The acoustic resonator based on the periodically poled piezoelectric film according to claim 1, wherein the substrate comprises one of a silicon substrate, a silicon carbide substrate, a quartz substrate or a sapphire substrate, and the thickness of the substrate is 200-550 μm.
  4. 4. The acoustic resonator based on the periodically poled piezoelectric film according to claim 1, wherein the finger width of each of the interdigital electrodes is 0.1-10 μm, and the distance between two adjacent interdigital electrodes is 0.1-10 μm.
  5. 5. The acoustic resonator based on a periodically poled piezoelectric film according to claim 1, characterized in that the poled regions and the unpolarized regions are alternately arranged and the poled regions are disposed only directly above the cavity.
  6. 6. The acoustic resonator based on the periodically poled piezoelectric film according to claim 5, wherein the width between any two adjacent polarized regions and the non-polarized region is 0.2 to 20 μm.
  7. 7. The acoustic resonator based on the periodically poled piezoelectric film according to claim 1, wherein the sacrificial layer comprises one of a silicon dioxide layer and a polysilicon layer, and the thickness of the sacrificial layer is 0.5-5 μm.
  8. 8. The acoustic resonator according to claim 1, wherein the interdigital electrode material comprises at least one of titanium, gold, silver, copper, niobium, aluminum, and chromium.
  9. 9. A method for preparing an acoustic resonator based on a periodically poled piezoelectric film, which is used for preparing the acoustic resonator based on the periodically poled piezoelectric film according to any one of claims 1 to 8, and is characterized by comprising the following steps: Providing a substrate, and sequentially forming a sacrificial layer and a piezoelectric film layer on the substrate; Spin-coating photoresist on one side surface of the piezoelectric film layer to form a first photoresist layer, and exposing and developing the first photoresist layer to obtain a first patterned photoresist layer; Depositing metal on the first patterned photoresist layer to form interdigital polarized electrodes, and applying high-power alternating voltage to the interdigital polarized electrodes to form polarized areas and unpolarized areas in the piezoelectric film layer; Removing the interdigital polarized electrode through an etching process, spin-coating photoresist on one side of the piezoelectric film layer again to form a second photoresist layer, and exposing and developing the second photoresist layer to obtain a second patterned photoresist layer; Redeposit metal on the second patterned photoresist layer to form a first interdigital transducer and a second interdigital transducer, wherein the first interdigital transducer and the second interdigital transducer both comprise a plurality of even pairs of interdigital electrodes; Spin coating photoresist on one side of the piezoelectric film layer again to form a third photoresist layer, and exposing and developing the third photoresist layer to obtain a third patterned photoresist layer; performing dry etching on the piezoelectric film layer based on the third patterned photoresist layer to form a plurality of etched through holes; And carrying out wet etching on the sacrificial layer based on the etched through holes so as to form cavities in the sacrificial layer.
  10. 10. The method for manufacturing an acoustic resonator based on a periodically poled piezoelectric film according to claim 9, wherein the thickness of the piezoelectric film layer is 100-1000 nm, and the depth of the etched through hole is equal to the thickness of the piezoelectric film layer.
  11. 11. The method of manufacturing an acoustic resonator based on a periodically poled piezoelectric film according to claim 9, wherein the poled regions and the unpolarized regions are alternately arranged and the poled regions are disposed only directly above the cavity.

Description

Acoustic resonator based on periodically polarized piezoelectric film and preparation method thereof Technical Field The invention relates to the field of film radio frequency acoustic wave filters, in particular to an acoustic resonator based on a periodically polarized piezoelectric film and a preparation method thereof. Background With the full commercialization of the fifth generation mobile communication technology (5G) and the initiation of future sixth generation mobile communication satellite internet research, modern wireless communication systems are rapidly evolving toward higher frequency bands, greater bandwidths, higher data throughput, and higher density integration. As a key passive device in the radio frequency front-end module, the performance of the filter directly determines the signal quality, anti-interference capability and overall efficiency of the communication system. In order to meet the application requirements of 5G/6G systems, modern radio frequency filters are required to meet multiple indexes such as low insertion loss, wide stop band suppression, small integration, high power capacity and the like. Among them, the acoustic filter based on piezoelectric effect has the advantages of excellent frequency selectivity, potential compatibility with CMOS process, suitability for integration, etc., and is a hot spot for current research. Acoustic filters achieve filtering functions by exciting and manipulating acoustic resonances in piezoelectric materials, whose core always extends around three challenges of how to boost operating frequency, expand bandwidth, and improve temperature stability. In the initial Surface Acoustic Wave (SAW) filter, the acoustic wave propagation characteristics are controlled by optimally designing the pattern of an interdigital transducer on a piezoelectric substrate such as lithium niobate (LiNbO 3) or quartz. However, as the frequency requirement enters the 5G millimeter wave band and the 6G terahertz exploration band, the frequency and bandwidth of the conventional SAW filter gradually cannot meet the system requirement. In order to break through the frequency limitation, the main process paths for realizing the high-frequency acoustic resonance in the industry can be divided into two types, one is to shorten the sound wave wavelength by reducing the finger width of the interdigital electrode depending on the high-precision photoetching process, so as to improve the resonance frequency, and the other is to improve the resonance frequency by reducing the thickness of the piezoelectric film. However, excessive thinning of the thickness of the piezoelectric film can cause significant reduction of the electromechanical coupling coefficient, so that the bandwidth of the filter is narrowed, and the communication requirement of a 5G/6G system is difficult to meet. In addition, the preparation process of thinning the piezoelectric film is complex, the control difficulty of thickness uniformity and consistency is high, and the performance stability and mass production feasibility of the device are possibly affected. Disclosure of Invention In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide an acoustic resonator based on a periodically poled piezoelectric film and a method for manufacturing the same, so that a high-frequency acoustic resonance mode can be effectively excited without relying on a high-precision photolithography process or excessively reducing the thickness of the piezoelectric film, and at the same time, an excellent electromechanical coupling coefficient and passband bandwidth are maintained, and finally a high-performance, high-reliability and low-cost filter solution is provided for the rf front end of a 5G/6G system. To achieve the above and other related objects, the present invention provides an acoustic resonator based on a periodically poled piezoelectric film, comprising: a substrate and a sacrificial layer positioned on the substrate, wherein a cavity is arranged in the sacrificial layer; The piezoelectric film layer is arranged on the sacrificial layer, and comprises a polarized region and a non-polarized region, wherein a plurality of etching through holes are formed in the non-polarized region; The interdigital transducer is arranged on the piezoelectric film layer and comprises a first interdigital transducer and a second interdigital transducer, wherein the first interdigital transducer and the second interdigital transducer both comprise a plurality of even pairs of interdigital electrodes, the plurality of even pairs of interdigital electrodes of the first interdigital transducer are arranged in the polarized region, and the plurality of even pairs of interdigital electrodes of the second interdigital transducer are arranged in the unpolarized region. Optionally, the piezoelectric film layer includes one of lithium niobate, lithium tantalate, barium titanate, strontium tit