JP2015076653A - Piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and reliably realize heightening in frequency by excitation in double-wave mode using parallel electric fields.SOLUTION: A piezoelectric device is provided with a piezoelectric vibration piece 100 created by a rotary Y plate of crystal system 32 in which each of the Z' axis and the X axis is in a planar direction, and the Y' axis is in a thickness direction. The piezoelectric vibration piece 100 has, on a surface 10a, a plurality of first excitation electrodes (first electrodes) 21, 22 extending in the X direction together in a row of direction Z', and has, on a reverse side 10b, a plurality of second excitation electrodes (second electrodes) 51, 52 arranged in the Y' direction with respect to the first excitation electrodes 21, 22 and extending in the X direction together in a row of direction Z'. The first excitation electrodes 21, 22 and the second excitation electrodes 51, 52 adjoining each other in the Z' direction are set to have different potentials, and those corresponding to each other in the Y' direction across a vibration part 10 of the piezoelectric vibration piece 100 are set to have different potentials, excitation being caused between the first excitation electrodes 21, 22 and between the second excitation electrodes 51, 52 including at least a double-wave mode.

Description

  The present invention relates to a piezoelectric device.

  Electronic devices such as mobile terminals and mobile phones are equipped with piezoelectric devices such as crystal resonators and crystal oscillators. Such a piezoelectric device is manufactured by mounting a piezoelectric vibrating piece such as a quartz vibrating piece in a cavity in a package constituted by a lid and a base. Such a piezoelectric device is required to have excellent long-term stability in order to improve the reliability of electronic equipment. In order to improve the long-term stability of the piezoelectric device, for example, as described in Patent Document 1, a pair of electrodes are arranged so as to sandwich a predetermined portion of the piezoelectric vibrating piece in the Z (Z ′) direction. A configuration is known in which a predetermined portion of a piezoelectric vibrating piece is vibrated by applying an electric field in the Z (Z ′) direction between the electrodes. According to this configuration, since no electrode is provided in the vibration part, it is difficult to be affected by changes in the electrode over time, and long-term stability can be ensured.

US Pat. No. 4,625,138

  However, in the configuration of the parallel electric field excitation type as described in Patent Document 1, the electric field efficiency is worse than the configuration (vertical electric field excitation type) in which the electrode is provided on the Y (Y ′) side surface of the vibration part. There is a problem that the CI value becomes high. In recent years, there has been a demand for higher frequencies for piezoelectric devices, but in the case of the vertical electric field excitation type, the thickness of the vibrating part has to be reduced. However, not only is it extremely difficult to process a piezoelectric vibrating piece such as a quartz piece, but it is also difficult to control its thickness.

  In view of the circumstances as described above, an object of the present invention is to provide a piezoelectric device that can easily and surely realize a high frequency by exciting in a second harmonic mode using a parallel electric field.

  According to the present invention, there is provided a piezoelectric device including a piezoelectric vibrating piece formed by a rotating Y plate of a crystal system 32 in which the Z ′ axis and the X axis are each in a plane direction and the Y ′ axis is a thickness direction, Has a plurality of first electrodes arranged in the Z ′ direction and extending in the X direction. The back surface of the piezoelectric vibrating piece is arranged in the Y ′ direction with respect to the first electrode and arranged in the Z ′ direction. The first electrode and the second electrode correspond to the Y ′ direction across the piezoelectric vibrating piece while the adjacent electrodes in the Z ′ direction are set to different potentials. The electrodes to be driven are set to different potentials, and are excited between the first electrode and the second electrode of the piezoelectric vibrating piece including at least the second harmonic mode.

  The piezoelectric vibrating piece may be formed with a thick mesa between at least one of the first electrodes or between the second electrodes. The ratio of the thickness of the piezoelectric vibrating piece in the portion where the mesa is formed to the step difference of the mesa with respect to the portion other than the mesa may be set to 0.05 to 0.15. In addition, when three or more first electrodes and second electrodes are formed, the first electrodes and the second electrodes may be arranged at regular intervals in the Z ′ direction. Further, an AT cut plate or a BT cut plate may be used as the rotating Y plate of the crystal system 32.

  According to the present invention, by exciting in the second harmonic mode using a parallel electric field, there is no need to create a very thin thickness of the vibrating part when exciting by a vertical electric field, and high frequency can be achieved easily and reliably. Can be realized.

An example of the piezoelectric vibrating piece used in the piezoelectric device according to the first embodiment is shown, (a) is a plan view of the front surface, and (b) is a plan view of the back surface when viewed through the surface. (A) is sectional drawing along the AA line of Fig.1 (a), (b) is sectional drawing which shows the mode of a vibration. Sectional drawing which shows an example of the piezoelectric vibrating piece used for the piezoelectric device which concerns on 2nd Embodiment, (b) is sectional drawing which shows an example of the piezoelectric vibrating piece which concerns on the modification. It is sectional drawing which shows an example of the piezoelectric vibrating piece used for the piezoelectric device which concerns on 3rd Embodiment. It is sectional drawing which shows an example of the piezoelectric vibrating piece used for the piezoelectric device which concerns on 4th Embodiment. An example of the piezoelectric vibrating piece used for the piezoelectric device which concerns on 5th Embodiment is shown, (a) is a top view, (b) is sectional drawing along the BB line. It is sectional drawing which shows an example of embodiment of a piezoelectric device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to this. Further, in the drawings, in order to describe the embodiment, the scale is appropriately changed and expressed, for example, partly enlarged or emphasized. The hatched portion in the drawing represents a metal film.

<First Embodiment>
1 and 2 show an example of an embodiment of a piezoelectric vibrating piece 100 used in a piezoelectric device. A piezoelectric device using the piezoelectric vibrating piece 100 will be described later. The same applies to other embodiments and modifications. The piezoelectric vibrating piece 100 is a rotating Y plate formed using a material belonging to the crystal system 32. As a material belonging to the crystal system 32 (belonging to the point group 32) in the piezoelectric vibrating piece, quartz, GaPO4 (gallium phosphate), langasite (LGS, LGN, LGT), quartz, and the like are known. A rotating Y plate formed using a material belonging to the crystal system 32 generates both thickness-shear vibration and contour-slip vibration.

  Piezoelectric vibrating pieces using thickness-shear vibration are AT-cut and BT-cutting, and piezoelectric vibrating pieces using contour-slip vibration are CT-cut and DT-cutting, and both have temperature characteristics. Is excellent. The thickness-shear vibration and the contour-slip vibration are coupled to each other to disturb the temperature characteristics and the like, but the coupling of both vibrations can be eliminated by inclining the end face of the vibration piece at a predetermined angle.

  As the piezoelectric vibrating piece 100, for example, an AT-cut quartz crystal vibrating piece that vibrates in a thickness manner is used. The AT cut has the advantage that a good frequency characteristic can be obtained when a piezoelectric device such as a crystal resonator is used near room temperature. The electrical axis (X axis), which is the three crystal axes of artificial quartz, and the mechanical axis This is a processing method of cutting out at an angle of 35 ° 15 ′ around the X axis with respect to the Z axis, among the (Y axis) and the optical axis (Z axis). However, a BT cut quartz plate may be used instead of the AT cut. The BT cut is a processing method of cutting at an angle inclined by −49 ° around the X axis with respect to the Z axis.

  In the present embodiment, directions in the drawings will be described using the XY′Z ′ coordinate system in the following drawings. In the XY′Z ′ coordinate system, the X axis coincides with the crystal axis of the crystal, and the Y ′ axis and the Z ′ axis correspond to the cutting direction when cutting the piezoelectric vibrating piece 100. In this embodiment, since the piezoelectric vibrating piece 100 is an AT-cut crystal piece, the Y ′ axis and the Z ′ axis are inclined by 35 ° 15 ′ from the mechanical axis (Y axis) and the optical axis (Z axis) of the crystal axis, respectively. Matches the axis. In this XY′Z ′ coordinate system, the plane parallel to the surface of the piezoelectric vibrating piece is the XZ ′ plane. In the XZ ′ plane, the longitudinal direction of the piezoelectric vibrating piece is denoted as the X direction, and the direction orthogonal to the X direction is denoted as the Z ′ direction. A direction perpendicular to the XZ ′ plane is denoted as a Y ′ direction. In each of the X direction, the Y ′ direction, and the Z ′ direction, the direction of the arrow in the figure is the + direction, and the direction opposite to the arrow direction is the − direction.

  The piezoelectric vibrating piece 100 is formed in a rectangular plate shape as shown in FIG. The piezoelectric vibrating piece 100 is formed to be long in the X direction and short in the Z ′ direction. In the piezoelectric vibrating piece 100, the Y ′ direction is the thickness direction. The piezoelectric vibrating piece 100 includes a vibrating unit 10 and a holding unit 20. The vibration unit 10 is a part that generates vibration of a predetermined wavelength (λ). The vibration unit 10 is disposed on the + X side of the piezoelectric vibrating piece 100 that is separated from the holding unit 20 (bonding side) in the X-axis direction. The thickness of the vibration part 10 in the Y ′ direction is adjusted according to a desired frequency.

  First excitation electrodes (first electrodes) 21 and 22 are provided on the surface (+ Y side surface) 10 a of the vibration unit 10. The first excitation electrodes 21 and 22 each extend along the X direction and are arranged side by side in the Z ′ direction. The vibration unit 10 has a vibration region W sandwiched between the first excitation electrodes 21 and 22. The first excitation electrode 21 is disposed on the −Z ′ side of the vibration unit 10. The first excitation electrode 22 is disposed on the + Z ′ side of the vibration unit 10 so as to be separated in the Z ′ direction. The length and width of each of the first excitation electrodes 21 and 22 are arbitrarily set. Moreover, although the 1st excitation electrodes 21 and 22 are formed in the same length and width, they may differ.

  The holding unit 20 is disposed on the −X side of the piezoelectric vibrating piece 100. Lead electrodes 31 and 32 are formed on the surface of the holding portion 20 (the surface on the + Y ′ side). The extraction electrode 31 is formed by being extracted from the first excitation electrode 21 in the −X direction and then bent to the + Z ′ side. The extraction electrode 32 is formed by being extracted from the first excitation electrode 22 in the −X direction and then bent to the −Z ′ side. In the holding part 20, through electrodes 41 and 42 penetrating in the Y ′ direction are formed corresponding to the extraction electrodes 31 and 32, respectively.

  As shown in FIG. 1B, second excitation electrodes (second electrodes) 51 and 52 are provided on the back surface (the surface on the −Y side) 10 b of the vibration unit 10. The second excitation electrodes 51 and 52 extend along the X direction similarly to the first excitation electrode 21 and the like, and are arranged side by side in the Z ′ direction. The second excitation electrode 51 is disposed on the + Z ′ side of the vibration unit 10. The second excitation electrode 52 is arranged on the −Z ′ side of the vibration unit 10 so as to be separated in the Z ′ direction. The length and width of each of the second excitation electrodes 51 and 52 are arbitrarily set. The second excitation electrodes 51 and 52 are formed to have the same length and width, but may be different.

  Lead electrodes 61 and 62 are formed on the back surface (the surface on the −Y ′ side) of the holding unit 20. The extraction electrode 61 is extracted from the second excitation electrode 51 in the −X direction and is extracted to the −X side and + Z ′ side corners of the holding unit 20. Furthermore, the extraction electrode 61 is also extracted to a region corresponding to the through electrode 41. The extraction electrode 62 is extracted from the second excitation electrode 52 in the −X direction, and is extracted to the −X side and −Z ′ side corners of the holding unit 20. Furthermore, the extraction electrode 62 is also extracted to a region corresponding to the through electrode 42.

  The extraction electrode 31 and the extraction electrode 61 are electrically connected by the through electrode 41. As a result, the first excitation electrode 21 and the second excitation electrode 51 have the same polarity. Further, the extraction electrode 32 and the extraction electrode 62 are electrically connected by the through electrode 42. Thereby, the first excitation electrode 22 and the second excitation electrode 52 have the same polarity. Note that the connection between the extraction electrode 31 and the extraction electrode 61 and the connection between the extraction electrode 32 and the extraction electrode 62 are not limited to the use of the through electrodes 41 and 42, but a metal film via the side surface of the piezoelectric vibrating piece 100. You may connect by.

  As shown in FIG. 2A, the first excitation electrodes 21 and 22 and the second excitation electrodes 51 and 52 are arranged with the vibration region W interposed therebetween so as to overlap each other in the Y ′ direction. Therefore, as shown in FIG. 2A, the first excitation electrodes 21 and 22 and the second excitation electrodes 51 and 52 are arranged in a square when the cross section of the piezoelectric vibrating piece 100 is viewed. . Further, the first excitation electrode 21 and the second excitation electrode 51 arranged in the Y ′ direction, and the first excitation electrode 22 and the second excitation electrode 52 are set to have different potentials.

  The first excitation electrodes 21 and 22, the second excitation electrodes 51 and 52, and the extraction electrodes 31, 32, 61, and 62 are made of conductive metal films. As the metal film, for example, chromium (Cr), titanium (Ti), nickel (Ni), nickel chromium (NiCr), nickel titanium as a base layer having a role of improving the adhesion of each electrode to a crystal material A laminated structure such as two or three layers in which (NiTi) or nickel tungsten (NiW) alloy is formed and gold (Au) or silver (Ag) is formed thereon is employed. The through electrodes 41 and 42 are formed by being filled with copper plating or conductive paste.

  In the present embodiment, no electrode is disposed in the vibration region W of the vibration unit 10. When an electrode is disposed in the vibration region W, if the electrode changes due to deterioration with time or the like, the vibration frequency may be affected, and thus it may be difficult to obtain stable vibration over the long term. On the other hand, in the piezoelectric vibrating piece 100, since no electrode is provided in the vibration region W, it is difficult to be affected by deterioration of the electrode with time, and long-term stability can be ensured.

  As shown in FIG. 2A, the first excitation electrode 21 and the second excitation electrode 51 have the same polarity (electrode in), and the first excitation electrode 22 and the second excitation electrode 52 have the same polarity. It is electrically connected so as to be a pole (electrode out). As a result, an electric field E1 substantially parallel to the XZ ′ plane is generated from the first excitation electrode 21 toward the first excitation electrode 22, and the XZ ′ plane is approximately parallel from the second excitation electrode 51 toward the second excitation electrode 52. A parallel electric field E2 is generated. The direction of the electric field differs between the electric field E1 and the electric field E2. Thereby, the vibration region W of the piezoelectric vibrating piece 100 vibrates in the S0 mode of the second harmonic as shown in FIG. Although vibrations in other modes such as a fundamental wave are included, it is possible to extract the second harmonic mode by filtering the extracted signal.

  As described above, according to the first embodiment, by exciting in the second harmonic mode, a high frequency can be easily extracted without reducing the thickness of the vibration part as in the vertical electric field excitation type. Therefore, it becomes easy to control the thickness of the vibration part, and a piezoelectric device corresponding to a high frequency can be easily manufactured.

Second Embodiment
A second embodiment will be described with reference to FIG. FIG. 3A is a plan view illustrating an example of the piezoelectric vibrating piece 200 according to the second embodiment. FIG. 3A is a Y′Z ′ cross-sectional view of the piezoelectric vibrating piece 200 and corresponds to FIG. 2A of the first embodiment. In the following description, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified. The piezoelectric vibrating piece 200 is an AT-cut crystal piece.

  As shown in FIG. 3A, the piezoelectric vibrating piece 200 has a first mesa (mesa) 71 on the surface 10 a of the vibrating unit 10. The first mesa 71 is formed, for example, by projecting a portion corresponding to the vibration region W (see FIG. 1A) in the + Y ′ direction. The first mesa 71 is formed in a rectangular shape when viewed from the Y ′ direction. The first excitation electrodes 21 and 22 are arranged so as to sandwich the first mesa 71 in the Z ′ direction. The extraction electrodes 31 and 32 are arranged so as to avoid the first mesa 71. The portion of the vibrating portion 10 where the first mesa 71 is formed has a larger vibration wavelength (lower frequency) than the peripheral portion. As a result, the energy of vibration generated in the first mesa 71 is confined in the first mesa 71 and is difficult to diffuse to the peripheral portion. Thereby, since the attenuation of the vibration generated in the first mesa 71 is suppressed, it is possible to efficiently generate the vibration in the vibration unit 10.

Further, the portion where the first mesa 71 is formed is thicker than the thickness H of the other portion, and has a thickness H1. Thereby, the level | step difference D1 of the surface of the 1st mesa 71 and the other surface 10a is formed. The ratio (D1 / H1) between the thickness H1 and the step D1 is
0.05-0.15
Set to If it is less than 0.05, the vibration confinement effect becomes small. On the other hand, if it is larger than 0.15, the confinement of the vibration is improved, but the secondary vibration such as the bending system is increased, so that the equivalent series capacitance C1 is small and the equivalent series resistance CI is large, and the vibration characteristics are deteriorated. The first mesa 71 desirably has a uniform thickness throughout, but may have a partially different thickness.

  Similar to the piezoelectric vibrating piece 100 of the first embodiment, the piezoelectric vibrating piece 200 generates a parallel electric field such as the electric fields E1 and E2 by applying a voltage to the first excitation electrode 21 and the like, thereby generating a double wave S0 mode. Vibrate. As described above, according to the second embodiment, since the excitation is performed in the second harmonic mode similarly to the first embodiment, a high frequency can be easily extracted. Furthermore, since the vibration is confined in the first mesa 71 by the first mesa 71, the attenuation of the vibration is suppressed and the vibration can be efficiently performed.

<Modification>
A modification of the second embodiment will be described with reference to FIG. FIG. 3B is a plan view illustrating an example of the piezoelectric vibrating piece 300 according to the modification. FIG. 3B is a Y′Z ′ cross-sectional view of the piezoelectric vibrating piece 300 and corresponds to FIG. 2A of the first embodiment. In the following description, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified. The piezoelectric vibrating piece 300 is an AT-cut crystal piece.

  As shown in FIG. 3B, in the piezoelectric vibrating piece 300, not only the first mesa (mesa) 71 is formed on the surface 10 a of the vibrating unit 10, but also the second mesa 72 on the back surface 10 b of the vibrating unit 10. Is formed. Similar to the first mesa 71, the second mesa 72 is formed, for example, by projecting a portion corresponding to the vibration region W (see FIG. 1A) in the −Y ′ direction. The second mesa 72 is formed in a rectangular shape when viewed from the Y direction. Therefore, the first mesa 71 and the second mesa 72 have the same shape and arrangement when viewed from the Y direction. The second excitation electrodes 51 and 52 are arranged so as to sandwich the second mesa 72 in the Z ′ direction. The extraction electrodes 61 and 62 are arranged so as to avoid the second mesa 72.

  The portion of the vibration unit 10 where the first mesa 71 and the second mesa 72 are formed has a larger vibration wavelength (smaller frequency) than the peripheral portion. As a result, the energy of vibration generated in the first mesa 71 and the second mesa 72 is confined in the first mesa 71 and the second mesa 72, and is more difficult to diffuse to the peripheral portion as compared with the second embodiment. . Thereby, since the attenuation of the vibration generated in the first mesa 71 and the second mesa 72 is suppressed, it is possible to efficiently generate the vibration in the vibration unit 10.

Further, the portion where the first mesa 71 and the second mesa 72 are formed is larger than the thickness H of the other portion, and has a thickness H2. Thereby, in addition to the step D1 on the surface of the first mesa 71, a step D2 is formed on the back surface 10b of the vibration unit 10. The ratio ((D1 + D2) / H2) between the thickness H2 and the step D1 + D2 is the same as in the first embodiment.
0.05-0.15
Set to If it is less than 0.05, the vibration confinement effect becomes small. On the other hand, if it is larger than 0.15, the confinement of the vibration is improved, but the secondary vibration such as the bending system is increased, so that the equivalent series capacitance C1 is small and the equivalent series resistance CI is large, and the vibration characteristics are deteriorated.

  However, since two steps D1 and D2 are added, it is possible to set one step small. The second mesa 72 desirably has a uniform thickness throughout, but may have a partially different thickness. Also, by making the first mesa 71 and the second mesa 72 have the same step (D1 = D2), it is possible to maintain the symmetry around the X axis (two-fold symmetry axis) and reduce spurious. Can do. However, the steps are not limited to the same step and may be different.

  Similar to the piezoelectric vibrating reeds 100 and 200 of the first and second embodiments, the piezoelectric vibrating reed 300 generates a parallel electric field such as electric fields E1 and E2 by applying a voltage to the first excitation electrode 21 and the like. It vibrates in the S0 mode of the double wave. As described above, according to the modification, since the excitation is performed in the second harmonic mode similarly to the first embodiment, a high frequency can be easily extracted. Furthermore, since the vibration is confined in the first mesa 71 and the second mesa 72 by the first mesa 71 and the second mesa 72, the attenuation of the vibration is suppressed, and the vibration can be efficiently performed. In addition, since mesas are formed on the front surface 10a and the back surface 10b of the vibration unit 10, vibration can be confined in the same manner as in the first embodiment even if the steps of each mesa are reduced. In addition, the formation of mesas on both sides of the vibration unit 10 increases man-hours compared to the formation of mesas on one side, but it maintains the symmetry around the X axis (two-fold symmetry axis) and generates spurious. Can be reduced.

<Third Embodiment>
A third embodiment will be described with reference to FIG. FIG. 4 is a plan view illustrating an example of the piezoelectric vibrating piece 400 according to the third embodiment. In the following description, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified. 4 is a Y′Z ′ cross-sectional view of the piezoelectric vibrating piece 400 and corresponds to FIG. The piezoelectric vibrating piece 400 uses an AT-cut crystal piece.

  As shown in FIG. 4, in the piezoelectric vibrating piece 400, three first excitation electrodes 121, 122, 123 are formed on the front surface 10a of the vibration unit 10, and three second excitation electrodes 151, 152 are similarly formed on the back surface 10b. , 153 are formed. The first excitation electrodes 121 to 123 and the second excitation electrodes 151 to 153 extend along the X direction, respectively, similarly to the first and second excitation electrodes 21 and 51 shown in FIG. It arrange | positions along with the space | interval L1. The lengths and widths of the first excitation electrodes 121 to 123 and the second excitation electrodes 151 to 153 are arbitrarily set. In FIG. 4, the first excitation electrodes 121 to 123 and the second excitation electrodes 151 to 153 are formed to have the same length and width, but may be different.

  Further, the first excitation electrodes 121 to 123 and the second excitation electrodes 151 to 153 are arranged to overlap each other in the Y ′ direction. The first excitation electrodes 121 to 123 and the second excitation electrodes 151 to 153 are connected so as to have different potentials in the Y ′ direction. Moreover, each of the 1st excitation electrodes 121-123 and the 2nd excitation electrodes 151-153 is set so that it may become a different electric potential from the electrode adjacent to a Z 'direction. That is, the first excitation electrodes 121 and 123 and the second excitation electrode 152 are connected to the in side, and the first excitation electrode 122 and the second excitation electrodes 151 and 153 are connected to the out side.

  As a result, as shown in FIG. 4, an electric field E <b> 11 is generated between the first excitation electrodes 121 and 122, and an electric field E <b> 12 is generated between the first excitation electrodes 122 and 123. An electric field E21 is generated between the second excitation electrodes 151 and 152, and an electric field E22 is generated between the second excitation electrodes 152 and 153. The electric fields E11 to E21 are generated substantially parallel to the XZ ′ plane. The direction of the electric field differs between the electric field E11 and the electric field E12. Similarly, the electric field E21 and the electric field E22 have different electric field directions. As a result, the piezoelectric vibrating piece 400 vibrates in the second wave A0 mode.

  Thus, according to the piezoelectric vibrating piece 400, as in the above-described piezoelectric vibrating piece 100 and the like, excitation is performed in the second harmonic mode, so that a high frequency can be easily extracted. In FIG. 4, each of the three first excitation electrodes 121 to 123 and the second excitation electrodes 151 to 153 is used to vibrate in the second harmonic A0 mode, but the first excitation electrode and the second excitation electrode are used. May be vibrated in a double wave A1 mode, A2 mode,... Moreover, the 1st mesa 71 as shown to Fig.3 (a) may be formed in one or all between the 1st excitation electrodes 121-123, and the 2nd mesa as shown in FIG.3 (b). 72 may be formed at any or all between the second excitation electrodes 151 to 153.

<Fourth embodiment>
A fourth embodiment will be described with reference to FIG. FIG. 5 is a plan view illustrating an example of the piezoelectric vibrating piece 500 according to the fourth embodiment. In the following description, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified. FIG. 5 is a Y′Z ′ cross-sectional view of the piezoelectric vibrating piece 500 and corresponds to FIG. The piezoelectric vibrating piece 500 is an AT-cut crystal piece.

  As shown in FIG. 5, the piezoelectric vibrating piece 500 includes four first excitation electrodes 221, 222, 223, and 224 formed on the front surface 10 a of the vibration unit 10, and the same four second excitation electrodes 251 on the back surface 10 b. , 252, 253, 254 are formed. The first excitation electrodes 221 to 224 and the second excitation electrodes 251 to 254 extend along the X direction in the same manner as the first and second excitation electrodes 21 and 51 shown in FIG. It arrange | positions along with the space | interval L2. The lengths and widths of the first excitation electrodes 221 to 224 and the second excitation electrodes 251 to 254 are arbitrarily set. In FIG. 5, the first excitation electrodes 221 to 224 and the second excitation electrodes 251 to 254 are formed to have the same length and width, but may be different.

  Further, the first excitation electrodes 221 to 224 and the second excitation electrodes 251 to 254 are arranged so as to overlap each other in the Y ′ direction. The first excitation electrodes 221 to 224 and the second excitation electrodes 251 to 254 are connected so as to have different potentials in the Y ′ direction. In addition, each of the first excitation electrodes 221 to 224 and the second excitation electrodes 251 to 254 is set to have a different potential from the electrodes adjacent in the Z ′ direction. That is, the first excitation electrodes 221 and 223 and the second excitation electrodes 251 and 253 are connected to the in side, and the first excitation electrodes 222 and 224 and the second excitation electrodes 252 and 254 are connected to the out side.

  As a result, as shown in FIG. 5, an electric field E31 is generated between the first excitation electrodes 221 and 222, an electric field E32 is generated between the first excitation electrodes 222 and 223, and between the first excitation electrodes 223 and 224. An electric field E33 is generated. An electric field E41 is generated between the second excitation electrodes 251 and 252, an electric field E42 is generated between the second excitation electrodes 252 and 253, and an electric field E43 is generated between the second excitation electrodes 253 and 254. The electric fields E31 to E33 and E41 to E43 are generated almost in parallel with the XZ ′ plane. The electric fields E31 and E33 have the same electric field direction, and these electric fields E32 and E32 have different electric field directions. The electric fields E41 and E43 have the same electric field direction, and these electric fields E42 and E42 have different electric field directions. Thereby, the piezoelectric vibrating piece 500 vibrates in the S1 mode of the second harmonic.

  As described above, according to the piezoelectric vibrating piece 500, as in the piezoelectric vibrating piece 100 and the like described above, excitation is performed in the second harmonic mode, so that a high frequency can be easily extracted. In FIG. 5, the four first excitation electrodes 221 to 224 and the second excitation electrodes 251 to 254 are used to vibrate in the S1 mode of the second harmonic, but the first excitation electrode and the second excitation electrode are used. May be vibrated in the second harmonic S2 mode, S3 mode,... Moreover, the 1st mesa 71 as shown to Fig.3 (a) may be formed in any or all between the 1st excitation electrodes 221-224, and the 2nd mesa as shown in FIG.3 (b). 72 may be formed in any or all between the second excitation electrodes 251 to 254.

<Fifth Embodiment>
A fifth embodiment will be described with reference to FIG. FIG. 6 is a plan view illustrating an example of a piezoelectric vibrating piece 600 according to the fifth embodiment. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. FIG. 6A is a plan view of the piezoelectric vibrating piece 600 and corresponds to FIG. 6B is a Y′Z ′ cross-sectional view of the piezoelectric vibrating piece 600 taken along the line BB in FIG. 6A, and corresponds to FIG. The piezoelectric vibrating piece 600 is an AT-cut crystal piece.

  As shown in FIG. 6A, in the piezoelectric vibrating piece 600, two first excitation electrodes 321 and 322 are formed on the front surface 10a of the vibration unit 10 with the first mesa 71 interposed therebetween, and two pieces are similarly formed on the back surface 10b. The second excitation electrodes 351 and 352 are formed. The first excitation electrodes 321 and 322 and the second excitation electrodes 351 and 352 extend along the X direction, respectively, similarly to the first and second excitation electrodes 21 and 51 shown in FIG. They are arranged side by side. The first excitation electrodes 321 and 322 and the second excitation electrodes 351 and 352 are arranged so as to overlap each other in the Y ′ direction, and are connected to have different potentials in the Y ′ direction. The first excitation electrode 321 and the second excitation electrode 351 are connected to the in side, and the first excitation electrode 322 and the second excitation electrode 352 are connected to the out side.

  In addition, the extraction electrode 361 is formed so as to be extracted from the + X side end of the second excitation electrode 351 in the −Z ′ direction and overlap with a part of the first excitation electrode 321 in the Y ′ direction. The extraction electrode 361 is electrically connected to the first excitation electrode 321 through the side surface of the piezoelectric vibrating piece 600. This connecting portion is used as an adhesive region 371. In addition, the extraction electrode 362 is formed so as to be extracted from the −X side end of the second excitation electrode 352 in the + Z ′ direction and overlap with a part of the first excitation electrode 322 in the Y ′ direction. The extraction electrode 362 is electrically connected to the first excitation electrode 322 through the side surface of the piezoelectric vibrating piece 600. This connecting portion is used as an adhesive region 372.

  As shown in FIG. 6B, an electric field E51 is generated between the first excitation electrodes 321 and 322, and an electric field E52 is generated between the second excitation electrodes 351 and 352. The electric fields E51 and E52 are generated substantially parallel to the XZ ′ plane. Further, the electric fields E51 and E52 have different electric field directions. As a result, the piezoelectric vibrating piece 600 vibrates in the double wave S0 mode.

  As described above, according to the piezoelectric vibrating piece 600, as in the piezoelectric vibrating piece 100 and the like described above, excitation is performed in the second harmonic mode, so that a high frequency can be easily extracted. Moreover, although the 1st mesa 71 is formed in FIG. 6, it does not need to be formed. A second mesa 72 as shown in FIG. 3B may be formed between the second excitation electrodes 351 and 352. Unlike the piezoelectric vibrating piece 100 illustrated in FIG. 1, the piezoelectric vibrating piece 600 does not use the through electrode 41 or the like for connection between the first excitation electrode 321 and the second excitation electrode 351 or the like. Therefore, it is not necessary to form a through hole in the piezoelectric vibrating piece, and the manufacturing cost can be suppressed.

<Piezoelectric device>
Next, an embodiment of a piezoelectric device will be described. As shown in FIG. 7, the piezoelectric device 700 includes a piezoelectric vibrating piece 100, a base 110 on which the piezoelectric vibrating piece 100 is mounted, and a lid 120 that seals the piezoelectric vibrating piece 100 between the base 110. doing. As the piezoelectric vibrating piece 100, the piezoelectric vibrating piece 100 shown in FIG. 1 is used. For the base 110 and the lid 120, for example, a material such as glass or ceramics is used. Further, a metal plate may be used as the lid 120.

  The base 110 is formed in a rectangular plate shape, and includes a concave portion 111 formed on the surface (+ Y ′ side surface) and a joint surface 112 surrounding the concave portion 111. The joint surface 112 faces the lid 120. The lid 120 is also formed in a rectangular plate shape, and a part of the back surface (the surface on the −Y ′ side) faces the bonding surface 112 of the base 110. The base 110 and the lid 120 are bonded via, for example, a bonding material, but may be directly bonded without using the bonding material. By joining the base 110 and the lid 120, a cavity 140 for accommodating the piezoelectric vibrating piece 100 is formed. The inside of the cavity 140 is set to, for example, a vacuum atmosphere or an inert gas atmosphere such as nitrogen gas or argon gas.

  In the concave portion 111 of the base 110, connection electrodes 114 connected to the extraction electrodes 61 and 62 of the piezoelectric vibrating piece 100 are formed. Further, a through electrode 115 penetrating the base portion 110 in the Y ′ direction is formed. On the back surface (the surface at the −Y ′ side) of the base 110, rectangular external electrodes 116 and dummy electrodes 116a are formed at the four corners. The external electrode 116 is used as a mounting terminal when mounted on the substrate. Note that the dummy electrode 116a is not electrically connected to other electrodes. The connection electrode 114 and the external electrode 116 are electrically connected by the through electrode 115.

  For the connection electrode 114, the external electrode 116, and the dummy electrode 116a, a conductive metal film is used. As the metal film, for example, chromium (Cr), titanium (Ti), nickel (Ni), nickel chromium (NiCr), nickel titanium (NiTi), nickel tungsten (NiW) alloy is formed as an underlayer. A laminated structure in which gold (Au) or silver (Ag) is formed thereon is employed. The through electrode 115 is formed by filling the through hole of the base 110 with copper plating, conductive paste, or the like.

  The piezoelectric vibrating piece 100 is held on the base 110 by a conductive adhesive 130. Further, the connection electrode 114 of the base 110 and the extraction electrodes 61 and 62 of the piezoelectric vibrating piece 100 are electrically connected to each other through the conductive adhesive 130. In this piezoelectric device 700, the piezoelectric vibrating piece 100 shown in FIG. 1 is used. Instead, for example, the piezoelectric vibrating pieces 200, 300, 400, 500, and 600 described above may be used. When the piezoelectric vibrating piece 600 is used, the connection electrode 114 of the base 110 is formed at a position corresponding to the piezoelectric vibrating piece 600 and the conductive adhesive 130 applied to the bonding regions 371 and 372 (see FIG. 6) is applied. Connected through.

  Next, a method for manufacturing the piezoelectric device 700 will be described. The piezoelectric device 700 is manufactured by a so-called wafer level packaging method. First, the piezoelectric vibrating piece 100 is created. The piezoelectric vibrating piece 100 is subjected to multiple chamfering for extracting individual piezoelectric vibrating pieces 100 from the piezoelectric wafer. The piezoelectric wafer is cut out from the crystal body with a predetermined thickness by AT cut, and the surface is cleaned after the thickness is adjusted by etching or polishing. In addition, through holes for forming the through electrodes 41 and 42 are formed in the piezoelectric wafer. In the piezoelectric vibrating piece 600 shown in FIG. 6, it is not necessary to form a through hole.

  Subsequently, through electrodes 41 and 42 are formed in the through holes of the piezoelectric wafer by copper plating or the like. Next, the first excitation electrodes 21 and 22 and the second excitation electrodes 51 and 52 are formed on the front surface 10 a and the back surface 10 b of the vibration unit 10. The extraction electrodes 31, 32, 61, and 62 are formed simultaneously with the first excitation electrode 21 and the like. The first excitation electrode 21 and the extraction electrode 31 and the like are formed of a conductive metal film. The metal film is formed by forming a base layer such as nickel chrome by sputtering using a metal mask or vacuum deposition, and then forming a main electrode layer such as gold. Instead of using a metal mask or the like, patterning may be performed by a photolithography method, etching, or the like. After the formation of the first excitation electrode 21 and the like, each piezoelectric vibrating piece 100 is completed by dicing the piezoelectric wafer along the scribe line.

  Similarly to the piezoelectric vibrating piece 100, the base 110 and the lid 120 are subjected to multi-cavity cutting out from the lid wafer and the base wafer. As these lid wafer and base wafer, for example, borosilicate glass or ceramics is used. Further, similarly to the piezoelectric vibrating piece 100, an AT-cut crystal material may be used.

  In the base wafer, the recess 111 for forming the cavity 140 is formed by sandblasting or wet etching. Further, a through hole for forming the through electrode 115 is formed in the base wafer by sand blasting or wet etching. The base wafer is filled with through holes by, for example, copper plating, and the through electrodes 115 are formed. A connection electrode 114 is formed in the recess 111 and an external electrode 116 is formed on the back surface so as to be electrically connected to the through electrode 115. At the same time, a dummy electrode 116a is also formed. The connection electrode 114 and the external electrode 116 are formed by depositing gold or silver on a base layer such as nickel tungsten by sputtering or vacuum deposition using a metal mask or the like, for example.

  Next, the individual piezoelectric vibrating reeds 100 are transported to the concave portion 111 of the base wafer by a chip mounter or the like and held by the conductive adhesive 130. By the conductive adhesive 130, the first excitation electrodes 21 and 22 and the second excitation electrodes 51 and 52 of the piezoelectric vibrating piece 100 and the external electrode 116 are electrically connected to each other. Next, the lid wafer is bonded to the base wafer through a bonding material in a vacuum atmosphere. In addition, you may join directly, for example using a plasma activated joining method, an ion beam activated joining method, etc., without using a joining material. Thereafter, the bonded wafers are diced along a scribe line to complete individual piezoelectric devices 700.

  The embodiment has been described above, but the present invention is not limited to the above description, and various modifications can be made without departing from the gist of the present invention. In the above-described embodiment, a crystal resonator (piezoelectric resonator) is shown as the piezoelectric device, but an oscillator may be used. In the case of an oscillator, an IC or the like is mounted on the base 110, and the piezoelectric vibrating piece 100 and the external electrode 116 of the base 110 are connected to the IC or the like.

  Further, in each of the above-described embodiments and modifications, a rectangular vibration piece is used, but the present invention is not limited to this. For example, as the piezoelectric vibrating piece, for example, an AT-cut piezoelectric vibrating piece configured by a vibrating portion, a frame portion surrounding the vibrating portion, and an anchor portion that connects the vibrating portion and the frame portion may be used. . In this case, the first excitation electrode and the second excitation electrode are formed on the front surface and the back surface of the vibration part, respectively. Further, a mesa may be formed on one or both of the front surface and the back surface of the vibration part.

  Even when this framed piezoelectric vibrating piece is used, it is manufactured by a wafer level packaging technique. First, a lid, a base, and a piezoelectric vibrating piece are formed on each wafer. Next, the lid wafer is bonded to the surface of the piezoelectric wafer in a vacuum atmosphere, and the base wafer is bonded to the back surface of the piezoelectric wafer. The bonded wafer is diced along a scribe line to complete individual piezoelectric devices.

H, H1, H2 ... Thickness D1, D2 ... Steps L1, L2 ... Interval 10 ... Vibrating part 10a ... Front 10b ... Back 21, 22, 121, 122, 123, 221, 222, 223, 224, 321, 322 ... First excitation electrode (first electrode)
51, 52, 151, 152, 153, 251, 252, 253, 254, 351, 352 ... second excitation electrode (second electrode)
71 ... 1st mesa (mesa)
72 ... Second mesa (mesa)
100 to 600 ... piezoelectric vibrating piece 700 ... piezoelectric device

Claims (5)

A piezoelectric device including a piezoelectric vibrating piece formed by a rotating Y plate of a crystal system 32 in which each of a Z ′ axis and an X axis is a planar direction and a Y ′ axis is a thickness direction,
The surface of the piezoelectric vibrating piece has a plurality of first electrodes extending in the X direction side by side in the Z ′ direction,
The back surface of the piezoelectric vibrating piece has a plurality of second electrodes arranged in the Y ′ direction with respect to the first electrode and extending in the X direction side by side in the Z ′ direction,
The electrodes adjacent to the Z ′ direction are set to different potentials, and the electrodes corresponding to the Y ′ direction are set to different potentials across the piezoelectric vibrating piece.
A piezoelectric device that excites between the first electrode and the second electrode of the piezoelectric vibrating piece including at least a second harmonic mode.   2. The piezoelectric device according to claim 1, wherein the piezoelectric vibrating reed is formed with a thick mesa between at least one of the first electrodes and between the second electrodes. The ratio of the thickness of the piezoelectric vibrating piece in the portion where the mesa is formed and the step difference of the mesa to the portion other than the mesa
0.05-0.15
The piezoelectric device according to claim 2, which is set as follows.   The said 1st electrode and the said 2nd electrode are arrange | positioned at a fixed space | interval in the said Z 'direction, when the said 1st electrode and the said 2nd electrode are formed in three or more places. The piezoelectric device according to claim 1.   The piezoelectric device according to any one of claims 1 to 4, wherein an AT cut plate or a BT cut plate is used as the rotating Y plate of the crystal system 32.

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