JP2014192832A - Piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high quality piezoelectric device by reducing a CI value of a piezoelectric vibration piece.SOLUTION: Disclosed is a piezoelectric device which includes a piezoelectric vibration piece 100 made of a rotary Y plate of a crystal system 32 whose Z' axis and X-axis are in the plane direction, respectively and Y' axis is in the thickness direction and whose at least one of the surface 100a or the rear surface 100b of the piezoelectric vibration piece 100 is equipped with a mesa 11 having a thicker thickness than a peripheral part 12. A pair of electrodes 13, 14 holding the mesa 11 in the Z' direction is formed, and a width 2a in the Z' direction of the mesa 11 is set in 1.62λ≤2a≤1.98λ with respect to a wavelength λ of vibration of the piezoelectric vibration piece 100.

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.

  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. On the other hand, since the piezoelectric vibrating piece uses thickness-shear vibration, a mesa whose vibrating part is thicker than the peripheral part is formed, and the vibration energy is confined in this mesa to increase the electric field efficiency of the vibrating part. Can be considered.

US Pat. No. 4,625,138

  However, the structure in which a mesa is provided on a parallel electric field excitation type piezoelectric vibrating piece has not been sufficiently studied so far, and a clear value has not been obtained for the CI value. Therefore, using a piezoelectric vibrating piece made of a rotating Y plate of a crystal system 32 in which the Z ′ axis and the X axis are each in the plane direction and the Y ′ axis is in the thickness direction, When a thick mesa is provided from the periphery, it is required to find a mesa shape having good vibration characteristics when a parallel electric field excitation type electrode arrangement is adopted.

  In view of the circumstances as described above, an object of the present invention is to provide a high-quality piezoelectric device in which the CI value is reduced by specifying the shape of the mesa.

  In the present invention, the piezoelectric vibrating piece is formed by a rotating Y plate of a crystal system 32 in which the Z′-axis and the X-axis are each a planar direction and the Y′-axis is a thickness direction. A piezoelectric device having a mesa thicker than the peripheral portion is formed on at least one of the electrodes, and a pair of electrodes sandwiching the mesa in the Z ′ direction is formed. The width 2a of the mesa in the Z ′ direction is the vibration of the piezoelectric vibrating piece. Is set to 1.62λ ≦ 2a ≦ 1.98λ.

  The mesa width 2a may be set to 1.80λ. Further, the ratio between the thickness H ′ of the piezoelectric vibrating piece in the portion where the mesa is formed and the step d of the mesa with respect to the peripheral portion may be set to 0.05 ≦ d / H ′ ≦ 0.15. . 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, in the configuration in which the mesa is provided on at least one of the front surface and the back surface of the piezoelectric vibrating piece formed by the rotating Y plate of the crystal system 32, the mesa width 2a sandwiched between the electrodes is vibrated. By setting 1.62λ ≦ 2a ≦ 1.98λ with respect to the wavelength λ, the CI value of the piezoelectric vibrating piece can be reduced, and a high-quality piezoelectric device can be provided.

Embodiment of the piezoelectric vibrating piece used for a piezoelectric device is shown, (a) is a top view, (b) is sectional drawing along the AA of (a). The vibration characteristics of the piezoelectric vibrating piece when the width 2a of the mesa in the Z ′ direction is changed are shown, (a) is a graph showing the R1 (CI) value, and (b) is a graph showing the Q value. The vibration characteristics of the piezoelectric vibrating piece when the ratio between the thickness H ′ of the piezoelectric vibrating piece and the step difference d of the mesa with respect to the peripheral portion is changed are shown, (a) is a graph showing the C1 value, and (b) is Q It is a graph which shows a value. It is sectional drawing which shows 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. In order to describe the following embodiments, the drawings are expressed by appropriately changing the scale, for example, by partially enlarging or emphasizing them. The hatched portion in the drawing represents a metal film.

<Piezoelectric vibrating piece>
FIG. 1 shows an embodiment of a piezoelectric vibrating piece 100 used in a piezoelectric device. 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.

  As shown in FIGS. 1A and 1B, the piezoelectric vibrating piece 100 is formed in a rectangular plate shape. 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. The vibrating unit 10 is formed with a mesa 11 that protrudes toward the surface 100 a side of the piezoelectric vibrating piece 100. As shown in FIG. 1B, the mesa 11 is formed to have a thickness H ′ that is larger than the thickness H of the peripheral portion 12 in the Y ′ direction. The mesa 11 is uniformly formed throughout. The mesa 11 is not limited to being formed on the surface 100 a side of the piezoelectric vibrating piece 100. For example, the mesa 11 may be formed on the back surface 100b of the piezoelectric vibrating piece 100, or may be formed on both the front surface 100a and the back surface 100b.

The ratio of the thickness H ′ of the mesa 11 to the step d of the mesa 11 with respect to the peripheral portion 12 is
d / H ′ ≧ 0.05
It is set to become.

The mesa 11 is formed in a rectangular shape in a plan view (when viewed from the Y ′ direction), and is disposed at the center in the Z ′ direction. The mesa 11 is formed so as to be long in the X direction and short in the Z ′ direction. The width (2a) in the Z ′ direction of the mesa 11 is relative to the wavelength λ of the vibration of the piezoelectric vibrating piece 100.
1.62λ ≦ 2a ≦ 1.98λ
It is set to become.

  The portion of the vibrating portion 10 where the mesa 11 is formed has a larger vibration wavelength (lower frequency) than the peripheral portion 12. In this case, the energy of vibration generated in the mesa 11 is confined in the mesa 11 and hardly diffuses to the peripheral portion 12. Thereby, since attenuation | damping of the vibration generate | occur | produced in the mesa 11 is suppressed, it becomes possible to generate a vibration efficiently in the vibration part 10. FIG.

  An excitation electrode 13 is disposed on the surface of the vibration unit 10 (the surface 100 a of the piezoelectric vibrating piece 100) and on the + Z ′ side of the mesa 11. The excitation electrode 14 is disposed on the −Z ′ side of the mesa 11. The excitation electrodes 13 and 14 extend along the longitudinal direction (X direction) of the mesa 11 and are arranged over the entire mesa 11 in the X direction. In this way, the excitation electrodes 13 and 14 are arranged so as to sandwich the mesa 11 in the Z ′ direction.

  Therefore, this piezoelectric vibrating piece 100 is configured such that no electrode is disposed on the surface of the mesa 11 (the surface on the + Y ′ side). When an electrode is disposed on the surface of the mesa 11, if the electrode changes due to deterioration with time or the like, the frequency of vibration generated in the mesa 11 is affected, so that it may be difficult to obtain stable vibration in the long term. On the other hand, in the piezoelectric vibrating piece 100, no electrode is provided on the surface of the mesa 11, so that the piezoelectric vibrating piece 100 is less affected by the deterioration of the electrode with time and the like, and the long-term stability can be ensured.

  The holding unit 20 is disposed on the −X side portion of the piezoelectric vibrating piece 100. Lead electrodes 15 and 16 are formed on the surface of the holding portion 20 (the surface on the + Y ′ side). The extraction electrode 15 is extracted from the excitation electrode 13 in the −X direction, and is extracted to the −X side and −Z ′ side corners of the holding unit 20. The extraction electrode 16 is extracted in the −X direction from the excitation electrode 14 and is extracted to the −X side and + Z ′ side corners of the holding unit 20. The extraction electrodes 15 and 16 may be extracted over the side surface and the back surface of the holding unit 20.

  For the excitation electrodes 13 and 14 and the extraction electrodes 15 and 16, conductive metal films are used. 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.

  FIG. 2 is a graph showing the vibration characteristics of the piezoelectric vibrating piece 100 configured as described above. FIG. 2A is a graph showing the CI value when the width 2a of the mesa 11 is changed. In FIG. 2A, the horizontal axis is the width 2 a (unit μm) of the mesa 11, and the vertical axis is the CI value (unit Ω) of the piezoelectric vibrating piece 100. FIG. 2B is a graph showing the Q value when the width 2a of the mesa 11 is changed. In FIG. 2B, the horizontal axis is the width 2 a (unit μm) of the mesa 11, and the vertical axis is the Q value of the piezoelectric vibrating piece 100. 2A and 2B, the piezoelectric vibrating piece 100 in which the thickness H ′ of the mesa 11 is 83.5 μm and the vibration wavelength λ is 167 (μm) is used.

  As shown in FIG. 2A, when the mesa width 2a is 100 μm, the CI value (R1 value) is about 260 kΩ. The CI value decreases as the width 2a increases from 100 μm. For example, when 2a = 300 (μm), the CI value is as small as 22.8 kΩ. The CI value increases as the width 2a increases from 300 μm. Although not shown, the equivalent series capacitance C1 value also shows the maximum value when the width 2a is 300 μm.

  As shown in FIG. 2B, when the width 2a is 100 μm, the Q value is about 3500 to 4000. The Q value increases as the width 2a increases from 100 μm. For example, when 2a = 300 (μm), the maximum value is Q = 16500 (value in the atmosphere). Further, the Q value decreases (or fluctuates) as the width 2a increases from 300 μm.

  From the graph of FIG. 2A, in the relationship between the width 2a of the mesa 11 and the CI value (R1), it is confirmed that the CI value changes by changing the value of the width 2a and has a predetermined extreme value. Is done. In the present embodiment, for example, when 2a = 300, the CI value is an extreme value (minimum value) of 22.8 kΩ. Further, from the graph of FIG. 2B, it is confirmed that the Q value is changed by changing the width 2a and has a predetermined extreme value in the relationship between the width 2a of the mesa 11 and the Q value. In this embodiment, for example, the Q value is an extreme value (maximum value) 16500 at 2a = 300.

  Thus, it was confirmed that good vibration characteristics could be obtained when the width 2a was in the range of 270 μm to 330 μm with 300 μm as the center. 300 μm is 1.80λ in relation to the wavelength (λ) of 167 μm. Similarly, 270 μm is 1.62λ in relation to the wavelength of 167 μm, and 330 μm is 1.98λ.

Therefore, in the present embodiment, the width 2a in the Z ′ direction of the mesa 11 is set to the wavelength λ of the vibration of the piezoelectric vibrating piece.
1.62λ ≦ 2a ≦ 1.98λ
Thus, the piezoelectric vibrating piece 100 having a low CI value (or a high Q value) can be obtained. That is, if the width (2a) of the mesa 11 is smaller than 1.62λ, the CI value becomes large and the vibration characteristics deteriorate, and if the width (2a) is larger than 1.98λ, the CI value becomes large and the vibration characteristics are the same. Will get worse.

  2A and 2B show the results when the vibration wavelength λ is 167 μm, but similar results can be obtained even when the wavelengths are different. Specifically, good vibration characteristics can be obtained when the width 2a is a value obtained by multiplying the wavelength λ by a predetermined constant (eg, 1.62 to 1.98).

  FIG. 3A is a graph showing the equivalent series capacitance value (C1) when d / H ′, which is the ratio between the step d of the mesa 11 and the thickness H ′ of the mesa 11, is changed. In FIG. 3A, the horizontal axis is the value of d / H (unit%), and the vertical axis is the equivalent series capacitance (unit is fF). FIG. 3B is a graph showing the Q value when d / H ′ is changed. In FIG. 3B, the horizontal axis is the value of d / H ′ (unit%), and the vertical axis is the Q value of the piezoelectric vibrating piece 100. In FIGS. 3A and 3B, the width 2a of the mesa 11 is 300 μm, and the vibration wavelength λ is 167 μm.

  As shown in FIG. 3A, when d / H ′ is 0 (when the mesa 11 is not formed), the C1 value is about 0.021 fF. Further, as d / H ′ increases from 0, the C1 value increases rapidly. When d / H ′ is 5%, the value is 0.034 fF, which is close to the maximum value, and thereafter, d / H ′ is 7.5%. The maximum value is 0.035 fF. When d / H ′ increases from 7.5%, the C1 value gradually decreases between 0.030 and 0.035 fF, and when d / H ′ is 20%, the C1 value decreases to 0.030 fF. Although not shown, the equivalent series resistance CI value also decreases in the range where d / H ′ is 5% to 15%.

  Further, as shown in FIG. 3B, when the value of d / H ′ is 0 to 25%, the Q value fluctuates in the range of 98000 to 100,000, and the Q value greatly fluctuates. Absent. However, when d / H ′ is 20% or more, the Q value is close to 9800. According to the graphs of FIGS. 3A and 3B, when d / H ′ is in the range of 5% (0.05) to 15% (0.15), the C1 value increases. It is confirmed that the value does not deteriorate. That is, if d / H ′ is smaller than 5% (0.05), the equivalent series capacitance C1 is lowered and the vibration characteristics are deteriorated. If d / H ′ exceeds 15% (0.15), spurious such as contour vibration and bending vibration in the mesa 11 increases.

Therefore, in the present embodiment, the ratio between the thickness H ′ of the mesa 11 and the step difference d of the mesa with respect to the peripheral portion 12 is
0.05 ≦ d / H ′ ≦ 0.15
Thus, the piezoelectric vibrating piece 100 having a high C1 value (low CI value) and excellent vibration characteristics can be obtained. This relationship is represented by the ratio of d and H ′ and does not depend on the wavelength λ of vibration. 3A and 3B show the results when the vibration wavelength λ is 167 μm, but similar results can be obtained even when the wavelengths are different.

Next, a method for manufacturing the piezoelectric vibrating piece 100 will be described.
First, the piezoelectric vibrating piece 100 is subjected to multi-sided drawing in which individual piezoelectric vibrating pieces 100 are taken out 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. Next, a part of the surface 100a of the piezoelectric vibrating piece 100 is removed by a photolithography technique, etching, sandblasting, or the like, and the mesa 11 is formed.

  Next, excitation electrodes 13 and 14 are formed on the surface 100 a of the piezoelectric vibrating piece 100 so as to sandwich the mesa 11. Simultaneously with the excitation electrodes 13 and 14, extraction electrodes 21 and 22 are formed. These excitation electrodes 13 and 14 and extraction electrodes 15 and 16 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 excitation electrodes 13 and 14 are formed, the piezoelectric wafer 100 is completed by dicing the piezoelectric wafer along the scribe line.

  As described above, according to the piezoelectric vibrating piece 100, the mesa 11 is sandwiched between the excitation electrodes 13 and 14, so that not only the influence of the vibration characteristics due to the change with time of the electrode is small but also the Z ′ direction of the mesa 11. Is set to 1.62λ ≦ 2a ≦ 1.98λ with respect to the wavelength λ of the vibration of the piezoelectric vibrating piece 100, so that the parallel electric field excitation can be efficiently realized and the piezoelectric vibrating piece 100 having good vibration characteristics can be obtained. Can be provided. Further, by setting d / H ′, which is the ratio of the height H ′ of the mesa 11 to the step d, in the range of 5% (0.05) to 15% (0.15), the C1 value is increased. Vibration characteristics can be improved.

  The piezoelectric vibrating piece 100 is not limited to that shown in FIG. For example, a piezoelectric vibrating piece that includes a vibrating part, a frame part that surrounds the vibrating part, and an anchor part that connects the vibrating part and the frame part may be used. In this case, a mesa is formed in the vibrating portion, and a pair of excitation electrodes is formed so as to sandwich the mesa in the Z ′ direction. The width of the mesa formed in the vibration part is set to 1.62λ ≦ 2a ≦ 1.98λ with respect to the vibration wavelength λ of the piezoelectric vibrating piece, as described above. Similarly to the above, the ratio of the mesa level difference to the mesa thickness is set to 0.05 or more.

<Piezoelectric device>
Next, an embodiment of a piezoelectric device will be described. As shown in FIG. 4, the piezoelectric device 200 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 has 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) 121 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.

  In the recess 111 of the base 110, connection electrodes 114 connected to the extraction electrodes 15 and 16 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 on the −Y ′ side) of the base 110, rectangular external electrodes 116 and dummy electrodes 116a are formed at the four corners. The external electrodes 116 are used as a pair of mounting terminals 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.

  The connection electrode 114 and the external electrodes 116 and 116a are made of conductive metal films. 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 or the like.

  The piezoelectric vibrating piece 100 is mounted on the base 110 via a conductive adhesive 130. Via the conductive adhesive 130, the connection electrode 114 of the base 110 and the extraction electrodes 15 and 16 of the piezoelectric vibrating piece 100 are electrically connected. Further, the piezoelectric vibrating piece 100 is held on the base 110 by the conductive adhesive 130 and is accommodated in the cavity 140.

  Next, a method for manufacturing the piezoelectric device 200 will be described. The piezoelectric device 200 is manufactured by a so-called wafer level packaging method. The piezoelectric vibrating piece 100 is created by the method described above. 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.

  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 this conductive adhesive 130, the excitation electrodes 13 and 14 of the piezoelectric vibrating piece 100 and the external electrode 116 are electrically connected. 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 200.

  As described above, according to the present embodiment, the mesa 11 thicker than the peripheral portion 12 is formed on the piezoelectric vibrating piece 100 made of the rotating Y plate of the crystal system 32, and the mesa 11 is moved in the Z ′ direction. In the configuration in which the pair of sandwiched excitation electrodes 13 and 14 are formed, the CI value is lowered because the width 2a of the mesa in the Z ′ direction is set to 1.62λ ≦ 2a ≦ 1.98λ with respect to the vibration wavelength λ. Therefore, the high-quality piezoelectric device 200 having good vibration characteristics can be obtained.

  In addition, the manufacturing method in the case of using the type which has a frame part as a piezoelectric vibrating piece is as follows. Similar to the piezoelectric device 200 described above, 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.

  While the embodiments of the piezoelectric device have been described above, 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 the oscillator, an IC or the like is mounted on the base 110, and the extraction electrodes 15 and 16 of the piezoelectric vibrating piece 100 and the external electrodes 116 and 116a of the base 110 are connected to the IC or the like, respectively.

DESCRIPTION OF SYMBOLS 10 ... Vibrating part 11 ... Mesa 12 ... Peripheral part 13, 14 ... Excitation electrode (electrode)
DESCRIPTION OF SYMBOLS 15, 16 ... Extraction electrode 20 ... Holding part 100 ... Piezoelectric vibrating piece 100a ... Front surface 100b ... Back surface 110 ... Base 120 ... Lid 200 ... Piezoelectric device

Claims (4)

It has a piezoelectric vibrating piece made of a rotating Y plate of a crystal system 32 in which each of the Z ′ axis and the X axis is a planar direction and the Y ′ axis is a thickness direction, and at least one of the front and back surfaces of the piezoelectric vibrating piece In addition, a piezoelectric device having a thicker mesa than the periphery,
A pair of electrodes sandwiching the mesa in the Z ′ direction is formed,
The width 2a in the Z ′ direction of the mesa is relative to the wavelength λ of the vibration of the piezoelectric vibrating piece.
1.62λ ≦ 2a ≦ 1.98λ
Piezoelectric device set to.   The piezoelectric device according to claim 1, wherein the width 2a of the mesa is set to 1.80λ. The ratio between the thickness H ′ of the piezoelectric vibrating piece in the portion where the mesa is formed and the step difference d of the mesa with respect to the peripheral portion is as follows:
0.05 ≦ d / H ′ ≦ 0.15
The piezoelectric device according to claim 1, wherein the piezoelectric device is set to The piezoelectric device according to claim 1, 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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