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CN-114665840-B - Elastic wave device

CN114665840BCN 114665840 BCN114665840 BCN 114665840BCN-114665840-B

Abstract

The invention provides an elastic wave device which is not easy to generate variation of SH wave stray size even when the film thickness of a frequency adjusting film is changed. An elastic wave device (1) is provided with an IDT electrode (3), a dielectric film (6), and a frequency adjustment film (7) on a LiNbO 3 substrate (2). The Euler angle of the LiNbO 3 substrate (2) is (within the range of 0 DEG + -5 DEG, within the range of theta + -1.5 DEG, within the range of 0 DEG + -10 DEG), the IDT electrode (3) has a main electrode which is Cu or an alloy mainly composed of Cu, and when the film thickness of the main electrode normalized by the wavelength lambda determined by the electrode finger pitch of the IDT electrode (3) is T and the density ratio of the material of the main electrode to Pt is r, the film thickness T of the main electrode and the theta of the Euler angle satisfy the formula (1). Formula (1) θ= -0.05 °/(T/r-0.04) +3135°.

Inventors

  • MIMURA MASAKAZU

Assignees

  • 株式会社村田制作所
  • 株式会社村田制作所

Dates

Publication Date
20260421
Application Date
20160808
Priority Date
20160808

Claims (10)

  1. 1. An elastic wave device is provided with: a LiNbO 3 substrate; an IDT electrode arranged on the LiNbO 3 substrate; A dielectric film disposed on the LiNbO 3 substrate so as to cover the IDT electrode, and A frequency adjustment film provided on the dielectric film, The Euler angle of the LiNbO 3 substrate is (within a range of 0 DEG + -5 DEG, within a range of theta + -1.5 DEG, and within a range of 0 DEG + -10 DEG), the IDT electrode has a main electrode, and when the film thickness of the main electrode normalized by a wavelength lambda determined by the electrode finger pitch of the IDT electrode is T and the density ratio of the material of the main electrode to Pt is r, The main electrode is Cu or an alloy mainly comprising Cu, The film thickness T of the main electrode and the Euler angle θ satisfy the following formula (1), Formula (1) θ= -0.05 °/(T/r-0.04) +31.35°.
  2. 2. The elastic wave device according to claim 1, wherein, The θ is in a range of 25 ° or more and 31 ° or less.
  3. 3. The elastic wave device according to claim 1 or 2, wherein, The film thickness of the frequency adjustment film is more than 0 and less than 0.025 lambda.
  4. 4. The elastic wave device according to claim 3, wherein, The film thickness of the frequency adjustment film is 0.005 lambda or less.
  5. 5. The elastic wave device according to claim 1 or 2, wherein, The dielectric film comprises silicon oxide.
  6. 6. The elastic wave device according to claim 1 or 2, wherein, The frequency adjustment film comprises silicon nitride.
  7. 7. The elastic wave device according to claim 1 or 2, wherein, The IDT electrode has the main electrode and another electrode layer containing a metal other than the main electrode.
  8. 8. The elastic wave device according to claim 1 or 2, wherein, The elastic wave device is a band-pass filter having the IDT electrode.
  9. 9. The elastic wave device according to claim 1 or 2, wherein, The total film thickness of the IDT electrode is less than or equal to 0.25λ.
  10. 10. The elastic wave device according to claim 5, wherein, The silicon oxide has a thickness thicker than the IDT electrode.

Description

Elastic wave device The application is a divisional application of an application patent application with the application date of 2016, 08 and 08, the application number of 201680059542.3 and the name of an elastic wave device. Technical Field The present invention relates to an elastic wave device in which an IDT electrode, a dielectric film, and a frequency adjustment film are laminated on a LiNbO 3 substrate. Background Patent document 1 below discloses an elastic wave device using rayleigh waves. In this elastic wave device, an SiO 2 film is laminated on a LiNbO 3 substrate so as to cover IDT electrodes. Further, a SiN film for adjusting frequency is provided on the SiO 2 film. By adjusting the thickness of the SiN film, the frequency of the elastic wave device can be adjusted. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2012-186808 Disclosure of Invention Problems to be solved by the invention In the elastic wave device described in patent document 1, if the film thickness of the SiN film varies, the response of SH wave that becomes stray (Spurious) changes. Therefore, when the film thickness of the SiN film is changed for frequency adjustment, SH wave spurious generation may be greatly suppressed. The invention aims to provide an elastic wave device which is not easy to generate variation of SH wave stray size even if the film thickness of a frequency adjusting film is changed. Means for solving the problems An elastic wave device according to the present invention includes a LiNbO 3 substrate, an IDT electrode provided on the LiNbO 3 substrate, a dielectric film provided on the LiNbO 3 substrate so as to cover the IDT electrode, and a frequency adjustment film provided on the dielectric film, wherein the Euler angle of the LiNbO 3 substrate is (within a range of 0 DEG + -5 DEG, within a range of θ + -1.5 DEG, and within a range of 0 DEG + -10 DEG), the IDT electrode has a main electrode, and when the film thickness of the main electrode normalized by a wavelength lambda determined by the electrode finger pitch of the IDT electrode is T and the density ratio of the material of the main electrode to Pt is r, the film thickness T of the main electrode and θ of the Euler angle satisfy the following formula (1). Formula (1) θ= -0.05 °/(T/r-0.04) +31.35° In a specific aspect of the elastic wave device according to the present invention, θ is in a range of 25 ° or more and 31 ° or less. In this case, even when the film thickness of the frequency adjustment film is thin, variation in SH wave spurious can be more effectively suppressed. In another specific aspect of the elastic wave device according to the present invention, the main electrode is a metal selected from the group consisting of Pt, au, W, ta, mo and Cu, or an alloy mainly composed of the metal. In still another specific aspect of the elastic wave device according to the present invention, the film thickness of the frequency adjustment film is greater than 0 and equal to or less than 0.025 λ. In this case, a region with high frequency adjustment sensitivity can be used. Therefore, the cost of the frequency adjustment process can be reduced. In still another specific aspect of the elastic wave device according to the present invention, the film thickness of the frequency adjustment film is 0.005 λ or less. In another specific aspect of the elastic wave device according to the present invention, the dielectric film includes silicon oxide such as SiO 2. In this case, the absolute value of the frequency temperature coefficient TCF can be reduced. In still another specific aspect of the elastic wave device according to the present invention, the frequency adjustment film includes silicon nitride such as SiN. In another specific aspect of the elastic wave device according to the present invention, the IDT electrode includes the main electrode and another electrode layer containing a metal other than the main electrode. In another specific aspect of the elastic wave device according to the present invention, the elastic wave device is a band-pass filter having the IDT electrode. In still another specific aspect of the elastic wave device according to the present invention, the total film thickness of the IDT electrode is 0.25λ or less. In another specific aspect of the elastic wave device according to the present invention, the silicon oxide has a thickness thicker than the IDT electrode. Effects of the invention In the elastic wave device according to the present invention, even when the film thickness of the frequency adjustment film is changed, fluctuation in the magnitude of the spurious caused by the SH wave is less likely to occur. Drawings Fig. 1 (a) and 1 (b) are a plan view and a partially enlarged front cross-sectional view of an elastic wave device according to an embodiment of the present invention, the main portion of which is enlarged. Fig. 2 is a cross-sectional view showing an electr