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JP-7855867-B2 - Device and method for manufacturing the device

JP7855867B2JP 7855867 B2JP7855867 B2JP 7855867B2JP-7855867-B2

Inventors

  • ガルシア ブライアント
  • イリエヴ フィリップ

Assignees

  • 株式会社村田製作所

Dates

Publication Date
20260511
Application Date
20220210
Priority Date
20210803

Claims (20)

  1. An acoustic resonator device having a narrow gap between the busbar and the end of the interdigital transducer (IDT) finger, A substrate having a surface, A piezoelectric plate having a front surface and a rear surface attached to the surface of the substrate, excluding the portion of the piezoelectric plate that forms a diaphragm spanning the cavity of the substrate, An interdigital transducer (IDT) formed on the front surface of the piezoelectric plate, wherein alternating fingers are arranged on the diaphragm at an overlap distance of the alternating fingers that defines the aperture of the acoustic resonator device, and the interdigital transducer (IDT) includes The alternatingly arranged fingers include a first set of parallel fingers extending from the first busbar of the IDT and a second set of parallel fingers extending from the second busbar of the IDT. The distance between the alternating fingers defines the IDT pitch. The IDT includes the gap distance between the ends of the first plurality of parallel fingers and the second busbar, and between the ends of the second plurality of parallel fingers and the first busbar. The device wherein the gap distance is 1/2 to 2/3 times the IDT pitch.
  2. The device according to claim 1, wherein the acoustic resonator device is a shunt resonator of a ladder-type filter that includes a plurality of series resonators and a plurality of shunt resonators including the acoustic resonator device.
  3. The device according to claim 1, wherein the IDT pitch is 2 to 20 times the width of the alternating fingers of the IDT.
  4. The device according to claim 1, wherein the gap distance is 1.0 to 5 μm.
  5. The device according to claim 1, wherein the gap distance is 1.5 μm to 5.0 μm, and the IDT pitch is 3 μm to 7.5 μm.
  6. The device according to claim 1, wherein the IDT pitch is the center-to-center distance between adjacent fingers of the first and second plurality of parallel fingers, and the first and second plurality of parallel fingers are attached to the first and second busbars, respectively.
  7. The device according to claim 1, wherein a radio frequency signal applied to the IDT excites a primary shear acoustic mode above the cavity in the piezoelectric plate, and the thickness of the piezoelectric plate is selected to adjust the primary shear acoustic mode in the piezoelectric plate.
  8. The piezoelectric plate is a lithium Y-cut niobate piezoelectric material. The radio frequency signal applied to the IDT excites a spurious mode in the gap region between the end of the IDT finger and the adjacent busbar, which causes spurious signals undesirable to the admittance of the XBAR. The device according to claim 7 , wherein the gap distance is a predetermined gap distance that suppresses spurious modes by up to 10 or 20 dB at a specific frequency in use.
  9. An acoustic resonator device having a narrow gap between the busbar and the end of the interdigital transducer (IDT) finger, A substrate having a surface, A piezoelectric plate having a front surface and a rear surface attached to the surface of the substrate, excluding the portion of the piezoelectric plate that forms a diaphragm spanning the cavity of the substrate, An interdigital transducer (IDT) formed on the front surface of the piezoelectric plate, wherein alternating fingers are arranged on the diaphragm at an overlap distance of the alternating fingers that defines the aperture of the acoustic resonator device, and the interdigital transducer (IDT) includes The alternatingly arranged fingers include a first set of parallel fingers extending from the first busbar of the IDT and a second set of parallel fingers extending from the second busbar of the IDT. The alternatingly arranged fingers have an IDT finger pitch between adjacent fingers of the first and second parallel fingers. The IDT includes the gap distance between the ends of the first plurality of parallel fingers and the second busbar, and between the ends of the second plurality of parallel fingers and the first busbar. The device wherein the gap distance is 1/2 to 2/3 times the IDT finger pitch.
  10. The device according to claim 9, wherein the acoustic resonator device is a shunt resonator of a ladder filter comprising a plurality of series resonators and a plurality of shunt resonators including the acoustic resonator device.
  11. The device according to claim 9, wherein the IDT finger pitch is 2 to 20 times the width of the alternating fingers of the IDT.
  12. The device according to claim 9 , wherein the gap distance is 5 μm to 1.0 μm.
  13. The device according to claim 12 , wherein the IDT finger pitch is 3 μm to 7.5 μm.
  14. The device according to claim 9, wherein the IDT finger pitch is the center-to-center distance between directly adjacent fingers of the first and second plurality of parallel fingers, and the first and second plurality of parallel fingers are attached to the first and second busbars, respectively.
  15. The device according to claim 9, wherein a radio frequency signal applied to the IDT excites a primary shear acoustic mode above the cavity in the piezoelectric plate, and the thickness of the piezoelectric plate is selected to adjust the primary shear acoustic mode in the piezoelectric plate .
  16. The piezoelectric plate is a lithium Y-cut niobate piezoelectric material. The radio frequency signal applied to the IDT excites a spurious mode in the gap region between the end of the IDT finger and the adjacent busbar, which causes spurious signals undesirable to the admittance of the XBAR. The device according to claim 15 , wherein the gap distance is a predetermined gap distance that suppresses spurious modes by up to 10 or 20 dB at a specific frequency in use.
  17. A method for manufacturing an acoustic resonator device, The rear surface of the piezoelectric plate is bonded to the substrate such that a portion of the piezoelectric plate forms a diaphragm that spans the cavity of the substrate, The interdigital transducer (IDT) is formed on the front surface of the piezoelectric plate, wherein the alternating fingers are positioned on the diaphragm at an overlap distance of the alternating fingers that defines the aperture of the acoustic resonator device. The piezoelectric plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm. The alternatingly arranged fingers include a first set of parallel fingers extending from the first busbar of the IDT and a second set of parallel fingers extending from the second busbar of the IDT. The distance between the alternating fingers defines the IDT finger pitch. The IDT includes the gap distance between the ends of the first plurality of parallel fingers and the second busbar, and between the ends of the second plurality of parallel fingers and the first busbar. The method wherein the gap distance is 1/2 to 2/3 times the IDT finger pitch.
  18. The method according to claim 17, wherein the acoustic resonator device is a shunt resonator of a ladder filter comprising a plurality of series resonators and a plurality of shunt resonators including the acoustic resonator device.
  19. The method according to claim 17, wherein the IDT finger pitch is 2 to 20 times the width of the alternating fingers of the IDT.
  20. The method according to claim 17 , wherein the gap distance is 1.0 to 5 μm.

Description

This disclosure relates to radio frequency filters using acoustic wave resonators, particularly filters for communication devices. Some disclosures in this patent document include material protected by copyright. This patent document may indicate and/or describe matters that are or may be the owner's trade dress. The owners of the copyrights and trade dress will not object to anyone reproducing the patent disclosures so that they appear in the patent files or records of the Patent and Trademark Office, but otherwise, all rights to the copyrights and trade dress are reserved. Related Application Information This patent claims priority to concurrently pending U.S. Provisional Patent Application No. 63/148,803, entitled “Narrow Busbar-Electrode Gap XBAR,” filed on 12 February 2021. A radio frequency (RF) filter is a two-port device configured to pass certain frequencies and block others. "Passing" means transmitting with relatively low signal loss, while "blocking" means blocking or substantially attenuating the signal. The range of frequencies passed through a filter is called the filter's "passband." The range of frequencies blocked by such a filter is called the filter's "stopband." A typical RF filter has at least one passband and at least one stopband. The specific requirements for the passband or stopband depend on the particular application. For example, the "passband" may be defined as a frequency range where the filter's insertion loss is better than a specified value such as 1 dB, 2 dB, or 3 dB. The "stopband" may be defined as a frequency range where the filter's rejection ratio exceeds a specified value such as 20 dB, 30 dB, or 40 dB, or a larger frequency range depending on the application. RF filters are used in communication systems where information is transmitted over a radio link. For example, RF filters are found in cellular base stations, mobile phones and computing devices, satellite transceivers and ground stations, IoT (Internet of Things) devices, laptop computers and tablets, fixed-point radio links, and the RF front-end of other communication systems. RF filters are also used in radar, electronic warfare systems, and information warfare systems. RF filters typically require numerous design trade-offs to achieve the best compromise between performance parameters such as insertion loss, rejection ratio, isolation, power handling, linearity, size, and cost, depending on the specific application. Specific designs, manufacturing methods, and enhancements can simultaneously benefit from one or more of these requirements. Improving the performance of RF filters in wireless systems can have a wide-ranging impact on system performance. Leveraging improvements in RF filters can enable system performance enhancements such as increased cell size, extended battery life, higher data rates, expanded network capacity, reduced costs, enhanced security, and improved reliability. These improvements can be implemented individually or in combination at various levels of the wireless system, such as RF modules, RF transceivers, and mobile or fixed subsystems, or at the network level. High-performance RF filters for current communication systems typically incorporate acoustic wave resonators, including surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, film bulk acoustic wave resonators (FBARs), and other types of acoustic resonators. However, these existing technologies are not suitable for use at the higher frequencies and bandwidths proposed for future communication networks. The demand for wider communication channel bandwidth inevitably leads to the use of higher frequency communication bands. Radio access technologies for mobile networks are standardized by the 3GPP (Third Generation Partnership Project). Radio access technologies for fifth-generation mobile networks are defined by the 5G NR (New Radio) standard. The 5G NR standard defines several new communication bands. Two of these new communication bands are n77, which uses the frequency range of 3300 MHz to 4200 MHz, and n79, which uses the frequency range of 4400 MHz to 5000 MHz. Since both band n77 and band n79 use time-division duplexing (TDD), communication devices operating in band n77 and/or band n79 use the same frequency for both uplink and downlink transmissions. The bandpass filters for bands n77 and n79 must be able to handle the transmit power of the communication devices. High frequencies and wide bandwidths are also required for the 5GHz and 6GHz Wi-Fi bands. The 5G NR standard also defines a millimeter-wave communication band with frequencies ranging from 24.25GHz to 40GHz. A Transversely-Excited Film Bulk Acoustic Resonator (XBAR) is an acoustic resonator structure for microwave filters. The XBAR is described in US Patent 10,491,291, entitled “Transversely-Excited Film Bulk Acoustic Resonator”. The XBAR resonator includes an interdigital transducer (IDT) formed of a single-crystal piezoelectric material,