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CN-122026855-A - Acoustic surface filter and preparation method thereof

CN122026855ACN 122026855 ACN122026855 ACN 122026855ACN-122026855-A

Abstract

The invention relates to the technical field of SAW device design, in particular to an acoustic surface filter and a preparation method thereof, wherein the filter comprises a piezoelectric substrate; the IDT electrode is arranged on one side surface of the piezoelectric substrate and comprises a plurality of metal interdigital bars, a plurality of inner side artificial fingers, a plurality of outer side artificial fingers and a pair of bus bars, wherein the metal interdigital bars are uniformly distributed on the inner sides of the pair of bus bars and form an interdigital structure, the inner side artificial fingers are positioned on the inner sides of the bus bars, the end parts of the inner side artificial fingers are opposite to the end parts of the metal interdigital bars, the outer side artificial fingers are arranged on the outer sides of the bus bars, each conductive bar is arranged on the outer sides of one bus bar and is opposite to the end parts of the plurality of outer side artificial fingers on the outer sides of the bus bars, and the distance between the end parts of the outer side artificial fingers and the opposite conductive bars is smaller than the distance between the end parts of the inner side artificial fingers and the end parts of the metal interdigital bars opposite to the inner side artificial fingers, so that the effect of ESD protection is improved.

Inventors

  • PENG YANJUN
  • Jiang Pinfang

Assignees

  • 唯捷创芯(天津)电子技术股份有限公司

Dates

Publication Date
20260512
Application Date
20260109

Claims (14)

  1. 1. An acoustic surface filter, comprising: A piezoelectric substrate for acoustic-electric transduction; An IDT electrode arranged on one side surface of the piezoelectric substrate and comprising a plurality of metal interdigital bars, a plurality of inner side false fingers, a plurality of outer side false fingers and a pair of bus bars, wherein the plurality of metal interdigital bars are uniformly distributed on the inner sides of the pair of bus bars and form an interdigital structure, the plurality of inner side false fingers are uniformly distributed on the inner sides of the pair of bus bars and the end parts of the inner side false fingers are opposite to the end parts of the metal interdigital bars, and the plurality of outer side false fingers are arranged on the outer sides of the pair of bus bars; And the pair of conductive strips are arranged outside the pair of bus bars and are opposite to the plurality of outer fake finger ends, and the distance between the outer fake finger end and one conductive strip opposite to the outer fake finger end is smaller than the distance between the inner fake finger end and the metal interdigital finger end opposite to the inner fake finger end.
  2. 2. The filter of claim 1, further comprising: The plurality of ground wire pins are uniformly distributed on the periphery of the IDT electrode, and at least one ground wire pin is connected to the pair of conductive strips through a conductive circuit.
  3. 3. The filter of claim 1, wherein the outer finger has a protruding end profile.
  4. 4. A filter according to claim 3, wherein the protrusion is a triangular protrusion.
  5. 5. The filter of claim 1, wherein the outer finger width is less than the widths of the metal interdigital bars and inner fingers.
  6. 6. The filter of claim 5, wherein the pair of conductive strips are provided with a plurality of conductor fingers and a distance between the outer finger end and the opposite conductor finger end is less than a distance between the inner finger end and the opposite metal finger end.
  7. 7. The filter of claim 1, wherein the outer finger overlaps the inner finger in a lateral direction of the bus bar.
  8. 8. The filter of claim 7, wherein the outer side of the bus bar corresponding to the inner side dummy finger is provided with an outer side dummy finger, and the outer side corresponding to the at least one metal interdigital finger is not provided with an outer side dummy finger.
  9. 9. The filter of claim 8, wherein the metal interdigital bars are provided with no outer dummy fingers on the corresponding outer sides.
  10. 10. A method of manufacturing a filter according to any one of claims 1 to 9, comprising: providing a piezoelectric substrate; Forming an IDT electrode and a pair of conductive strips on one side surface of the piezoelectric substrate in the same layer; A plurality of metal interdigital bars, a plurality of inner side artificial fingers, a plurality of outer side artificial fingers and a pair of bus bars are arranged on the IDT electrode, the metal interdigital bars are uniformly distributed on the inner sides of the pair of bus bars to form an interdigital structure, the inner side artificial fingers are arranged on the inner sides of the bus bars, the end parts of the inner side artificial fingers are opposite to the end parts of the metal interdigital bars, and the outer side artificial fingers are arranged on the outer sides of the bus bars; The conductive strips are arranged outside the bus bars and are opposite to the outer fake finger end parts, and the distance between the outer fake finger end parts and the conductive strips opposite to the outer fake finger end parts is smaller than the distance between the inner fake finger end parts and the metal interdigital finger strip end parts opposite to the inner fake finger end parts.
  11. 11. The method of manufacturing according to claim 10, further comprising: Coating, exposing and developing photoresist on one side surface of a piezoelectric substrate around the IDT electrode in sequence to obtain a conductive circuit layer and a position pattern of metal pads of a plurality of ground wire pins uniformly distributed on the periphery of the IDT electrode, and then carrying out metal evaporation; connecting a pair of conductive strips to at least one ground pin by a conductive line in a vicinity according to the distance between the IDT electrode and the plurality of ground pins; Disposing each of the lateral prostheses in a protrusion-like manner; The width of the outer artificial finger is smaller than the width of the metal interdigital finger strip and the width of the inner artificial finger; Arranging a plurality of conductor false fingers on one side of the conducting bar, wherein the conductor false fingers correspond to outer false finger end parts, and the distance between the outer false finger end parts and the conductor false finger end parts opposite to the outer false finger end parts is smaller than the distance between the inner false finger end parts and the metal interdigital finger bar end parts opposite to the inner false finger end parts; arranging outer false fingers on the outer sides of the bus bars corresponding to the inner false fingers, wherein the outer sides corresponding to at least one metal interdigital finger bar are not provided with outer false fingers; The outer dummy fingers are disposed to overlap the inner dummy fingers in a lateral direction of the bus bar.
  12. 12. The method of manufacturing according to claim 11, wherein the protrusion shape is a triangular protrusion; and outer false fingers are not arranged on the outer sides corresponding to the metal interdigital finger strips.
  13. 13. The method of manufacturing according to claim 11, wherein an outer dummy finger is provided outside the bus bar corresponding to the inner dummy finger.
  14. 14. The method of claim 10, wherein the IDT electrode is formed of Al or Cu, and the process is a dry etching or a metal lift-off process; The material used for metal evaporation is metal Ti or Al or Cu.

Description

Acoustic surface filter and preparation method thereof Technical Field The invention relates to the technical field of SAW device design, in particular to an acoustic surface filter and a preparation method thereof. Background Currently, a plurality of SAW (Surface Acoustic wave) filters are generally provided in many electronic devices having a communication function. In practical packaging, the problem that ESD breakdown damages a filter often occurs, and typically, the electrode size of the filter IDT (INTERDIGITAL TRANSDUCER interdigital transducer) is small, which makes it easy for local electric field strength to rise sharply when facing ESD (Electro-STATIC DISCHARGE electrostatic discharge), and when the electric field strength exceeds the breakdown field strength of the material, insulation breakdown is caused. IDTs are generally small in electrode spacing, and high voltages generated by ESD tend to form arcing between the electrodes, resulting in breakdown. Patent application CN118413206a discloses a surface acoustic wave filter and an electronic device, at least one free end of an electrode structure is covered with an electrostatic protection stacked layer, the electrostatic protection stacked layer comprises at least two passivation layers covering the free end, and the ESD breakdown resistance of the surface acoustic wave filter can be improved through the electrostatic protection stacked layer, so that the performance and reliability of the surface acoustic wave filter can be improved, and further, the performance and reliability of the electronic device adopting the surface acoustic wave filter can be improved. Although the ESD protection stack layer can improve the ESD breakdown resistance of the saw filter to some extent, the ESD protection stack layer does not form an effective conductive path, and the discharge structure is not precisely dimensioned, so that the improvement of the ESD breakdown resistance is limited. The invention provides an acoustic surface filter and a preparation method thereof. Disclosure of Invention In order to overcome the defects of the prior art, the invention provides the acoustic surface filter and the preparation method thereof, and the filter ensures that static charges collected on an IDT electrode are released preferentially through the connection of a pair of conductive strips by arranging that the distance between the end part of each outer side false finger and one conductive strip opposite to the end part of each outer side false finger is smaller than the distance between the end part of each inner side false finger and the end part of one metal interdigital finger opposite to the end part of each inner side false finger, thereby improving the damage of the IDT electrode caused by the ESD problem and improving the ESD protection effect. To achieve the above object, a first aspect of the present invention provides an acoustic surface filter comprising: A piezoelectric substrate for acoustic-electric transduction; An IDT electrode arranged on one side surface of the piezoelectric substrate and comprising a plurality of metal interdigital bars, a plurality of inner side false fingers, a plurality of outer side false fingers and a pair of bus bars, wherein the plurality of metal interdigital bars are uniformly distributed on the inner sides of the pair of bus bars and form an interdigital structure, the plurality of inner side false fingers are uniformly distributed on the inner sides of the pair of bus bars and the end parts of the inner side false fingers are opposite to the end parts of the metal interdigital bars, and the plurality of outer side false fingers are arranged on the outer sides of the pair of bus bars; And the pair of conductive strips are arranged outside the pair of bus bars and are opposite to the plurality of outer fake finger ends, and the distance between the outer fake finger end and one conductive strip opposite to the outer fake finger end is smaller than the distance between the inner fake finger end and the metal interdigital finger end opposite to the inner fake finger end. The second aspect of the present invention provides a method for manufacturing the above filter, including: providing a piezoelectric substrate; Forming an IDT electrode and a pair of conductive strips on one side surface of the piezoelectric substrate in the same layer; A plurality of metal interdigital bars, a plurality of inner side artificial fingers, a plurality of outer side artificial fingers and a pair of bus bars are arranged on the IDT electrode, the metal interdigital bars are uniformly distributed on the inner sides of the pair of bus bars to form an interdigital structure, the inner side artificial fingers are arranged on the inner sides of the bus bars, the end parts of the inner side artificial fingers are opposite to the end parts of the metal interdigital bars, and the outer side artificial fingers are arranged on the outer sides of the bus