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JP-7857171-B2 - Elastic wave device and method for manufacturing the same, filter and multiplexer

JP7857171B2JP 7857171 B2JP7857171 B2JP 7857171B2JP-7857171-B2

Inventors

  • 浅田 稔
  • 西澤 年雄
  • 岡村 龍一

Assignees

  • 太陽誘電株式会社

Dates

Publication Date
20260512
Application Date
20220620

Claims (12)

  1. circuit board and The upper electrode provided on the substrate, A piezoelectric film is provided between the substrate and the upper electrode, A resonant region is provided between the substrate and the piezoelectric film, and is defined by a region that sandwiches at least a portion of the piezoelectric film and overlaps with the upper electrode. A first conductive film mainly composed of the first element, A second conductive film is provided between the first conductive film and the piezoelectric film, and the second conductive film is mainly composed of a second element different from the first element. An interlayer provided between the first conductive film and the second conductive film, A third conductive film is provided between the second conductive film and the piezoelectric film, and the third conductive film mainly consists of a third element different from the second element, Equipped with, The interlayer is provided in a first region including the center of the resonance region, and is not provided in a second region that surrounds at least a part of the outer periphery of the first region and includes at least a part of the outer periphery of the resonance region. The lower electrode, wherein the concentration of the second element in the first conductive film in the second region is higher than the concentration of the second element in the first conductive film in the first region, and/or the concentration of the first element in the second conductive film in the second region is higher than the concentration of the first element in the second conductive film in the first region. A wave-based elastic device equipped with the following features.
  2. The elastic wave device according to claim 1, wherein the first conductive film and the second conductive film are in contact in the second region.
  3. The elastic wave device according to claim 1 , wherein the acoustic impedance of the third conductive film is higher than the acoustic impedance of the second conductive film.
  4. The acoustic wave device according to any one of claims 1 to 3 , wherein the surface roughness of the upper surface of the piezoelectric film in the second region is greater than the surface roughness of the upper surface of the piezoelectric film in the first region.
  5. The elastic wave device according to any one of claims 1 to 3 , wherein the orientation of the crystal orientation of the piezoelectric film in the second region is lower than the orientation of the crystal orientation of the piezoelectric film in the first region.
  6. The elastic wave device according to any one of claims 1 to 3 , wherein the resistivity of the first element that is the main component of the first conductive film is lower than the resistivity of the second element that is the main component of the second conductive film.
  7. The elastic wave device according to any one of claims 1 to 3, wherein the concentration of the second element in the first conductive film in the second region is at least twice the concentration of the second element in the first conductive film in the first region, and/or the concentration of the first element in the second conductive film in the second region is at least twice the concentration of the first element in the second conductive film in the first region.
  8. The elastic wave device according to any one of claims 1 to 3 , wherein the thickness of the interlayer is smaller than the thickness of the first conductive film and the thickness of the second conductive film.
  9. The elastic wave device according to any one of claims 1 to 3 , wherein the first element is aluminum, the second element is chromium, and the main component of the interlayer is titanium or titanium nitride.
  10. A filter comprising an elastic wave device according to any one of claims 1 to 3 .
  11. A multiplexer comprising the filter described in claim 10 .
  12. A step of forming a lower electrode comprising: a first conductive film mainly composed of a first element on a substrate; a second conductive film mainly composed of a second element different from the first element and provided on the first conductive film; an intermediate film provided between the first conductive film and the second conductive film in a first region including the center of the resonance region, surrounding at least a part of the outer periphery of the first region and not provided in a second region including at least a part of the outer periphery of the resonance region ; and a third conductive film provided between the second conductive film and the piezoelectric film and mainly composed of a third element different from the second element ; A step of heat-treating the lower electrode to make the concentration of the second element in the first conductive film in the second region higher than the concentration of the second element in the first conductive film in the first region, and/or making the concentration of the first element in the second conductive film in the second region higher than the concentration of the first element in the second conductive film in the first region, The steps include forming the piezoelectric film on the lower electrode, A step of forming the upper electrode on the piezoelectric film such that the resonance region is formed by the region in which the upper electrode and the lower electrode overlap, with at least a portion of the piezoelectric film sandwiched between them; A method for manufacturing elastic wave devices, including

Description

This invention relates to an elastic wave device, a method for manufacturing the same, a filter, and a multiplexer. Filters and multiplexers with piezoelectric thin-film resonators are used in high-frequency circuits of wireless terminals such as mobile phones. A piezoelectric thin-film resonator has a laminated film in which a lower electrode, a piezoelectric film, and an upper electrode are stacked. The region where the lower electrode and upper electrode face each other, with at least a portion of the piezoelectric film in between, is the resonance region where elastic waves are excited. It is known that an insertion film is provided within the piezoelectric film in the outer peripheral region of the resonance region, while the insertion film is not provided in the central region of the resonance region (for example, Patent Documents 1 and 2). It is known that providing a piezoelectric film on a substrate with a large surface roughness on its upper surface reduces the crystallinity of the piezoelectric film (for example, Patent Documents 3 to 5). Japanese Patent Publication No. 2014-161001Japanese Patent Publication No. 2017-158161Japanese Patent Publication No. 2005-94735Japanese Patent Publication No. 2015-119249Japanese Patent Publication No. 2013-34130 Figure 1 is a plan view of the piezoelectric thin-film resonator according to Example 1.Figure 2 is a cross-sectional view taken along line A-A in Figure 1.Figures 3(a) to 3(d) are cross-sectional views showing a method for manufacturing a piezoelectric thin-film resonator according to Example 1.Figures 4(a) and 4(b) are cross-sectional views showing a method for manufacturing a piezoelectric thin-film resonator according to Example 1.Figures 5(a) and 5(b) are cross-sectional views showing a method for manufacturing a piezoelectric thin-film resonator according to Example 1.Figure 6 is a cross-sectional view of a piezoelectric thin-film resonator according to Comparative Example 1.Figure 7 is a cross-sectional view of a piezoelectric thin-film resonator according to Modification 1 of Example 1.Figures 8(a) to 8(c) are cross-sectional views of samples A to C, respectively, from the experiment.Figures 9(a) and 9(b) show the EDX spectra of sample B.Figures 10(a) and 10(b) show the EDX spectra of sample C.Figures 11(a) and 11(b) are cross-sectional views of piezoelectric thin-film resonators according to modified examples 2 and 3 of Example 1.Figure 12 is a cross-sectional view of a piezoelectric thin-film resonator according to a modified example 4 of Example 1.Figure 13(a) is a circuit diagram of the filter according to Example 2, and Figure 13(b) is a circuit diagram of the duplexer according to Modification 1 of Example 2. The following describes an embodiment with reference to the drawings.