JP2007006375A - Piezoelectric resonator and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of a conventional piezoelectric resonator that the equivalent series resistance R is increased because the dimension of its electrodes is decreased and the electric field gets smaller due to downsizing of the piezoelectric resonator. <P>SOLUTION: A piezoelectric resonator 1 comprises vibration arms 2, 3 and a base part 4. The vibration arms 2, 3 are respectively formed with through-holes 5, 6 and an electrode is respectively formed to inner walls of the through-holes 5, 6. Then the through-holes 5, 6 are formed with embedded members 27, 28. Through the structure, even when the width W1 of the vibration arms 2, 3 is narrowed due to downsizing of the piezoelectric resonator 1, the thickness of the vibration arms 2, 3 is utilized to surely secure electrode forming regions. Further, the mechanical strength of the vibration arms 2, 3 can be maintained. As a result, the equivalent series resistance R can be decreased while downsizing of the piezoelectric resonator 1 is attained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a miniaturized piezoelectric vibrator incorporated in an electronic apparatus and a manufacturing method thereof.

  A conventional piezoelectric vibrator having a bending vibration mode is formed by processing a crystal piece. And the piezoelectric vibrator is planarly mounted on the mounting board | substrate with which the mount electrode was formed (for example, refer patent document 1).

  As shown in FIG. 11, the piezoelectric vibrator 101 is integrally formed by a pair of vibrating arm portions 102, a base portion 103 that connects the vibrating arm portions 102, and a support arm portion 104 that extends from the base portion 103 in a predetermined direction. The vibrating arm portion 102 has a thickness of 50 to 200 (μm), and the length and width are set according to the vibration frequency. For example, when the vibration frequency is designed at 32.768 (KHz), the width W10 of the vibrating arm portion 102 is 100 (μm) and the length L6 is 1650 (μm). The width W10 and the length L6 of the vibrating arm unit 102 are changed in design according to the vibration frequency.

  The support arm portion 104 is formed in parallel along the outer surface of the vibrating arm portion 102 from an L-shaped bent portion 105 protruding in the left-right direction of the base portion 103. The size of the support arm portion 104 is approximately half the length of the vibrating arm portion 102 and the width is equal to or greater than that of the vibrating arm portion 102. A terminal electrode 106 is formed at the tip of the support arm 104, and the terminal electrode 106 is fixed to a mount electrode (not shown) on a mounting substrate (not shown) with a conductive adhesive.

  A conventional piezoelectric vibrator having a bending vibration mode includes a vibrating arm and a base. Grooves are formed on the upper and lower surfaces of the vibrating arm, and electrodes are formed using the side surfaces of the grooves (see, for example, Patent Document 2).

As shown in FIG. 12A, the piezoelectric vibrator is a quartz crystal vibrator 111, and the quartz crystal vibrator 111 includes a pair of vibrating arm portions 112 and a base portion 113, and one end portion of the vibrating arm portion 112 is formed on the base portion 113. It is connected. The vibrating arm portion 112 has an upper surface, a lower surface, and side surfaces, and a groove 115 is formed on the upper and lower surfaces so as to sandwich the neutral line 114. The width W13 of the groove 115 is designed so that the relationship (W13 / W12) between the width W12 of the vibrating arm portion 112 and the width W13 of the groove 115 is in the range of 0.35 to 0.95. . FIG. 12B is a cross-sectional view taken along the line CC ′ in FIG. As illustrated, the thickness T2 of the groove 115 is designed so that the relationship (T2 / T1) between the thickness T1 of the vibrating arm portion 112 and the thickness T2 of the groove 115 is within a range of 0.01 to 0.79. Has been. Electrodes 116 and 117 are formed in the groove 115. With this structure, the electromechanical conversion efficiency is improved, the equivalent series resistance R is small, the quality factor value Q is high, and a quartz resonator having a small capacitance ratio is configured.
JP 2004-357178 A (page 4-5, Fig. 1-2) Japanese Patent Laying-Open No. 2005-39767 (page 5-8, FIG. 1)

  As described above, the piezoelectric vibrator is supported on the mounting substrate by fixing the terminal electrode of the piezoelectric vibrator and the mount electrode on the mounting substrate. The piezoelectric vibrator supported on the mounting substrate is accommodated in the package. With the recent miniaturization of electronic devices such as mobile phones, the package in which the piezoelectric vibrator is housed is downsized, and the piezoelectric vibrator is also downsized.

  The piezoelectric vibrator 101 is supported on the mounting substrate via a terminal electrode 106 formed at the tip of the support arm 104. The width W10 of the vibrating arm portion 102 is constant, and electrodes are arranged using the upper and lower surfaces and the side surfaces of the vibrating arm portion 102. With this structure, the electric field that vibrates the vibrating arm portion 102 does not work linearly with respect to the vibration direction (the width direction of the vibrating arm portion). Therefore, in order to reduce the equivalent series resistance R, it is necessary to increase the electric field by increasing the width of the vibrating arm 102 and forming a larger electrode. As a result, there is a problem that it is difficult to reduce the size of the piezoelectric vibrator 101 in the width direction and it is difficult to reduce the size of the package. In order to reduce the size of the piezoelectric vibrator 101 in the width direction, it is necessary to reduce the width of the vibrating arm portion 102. In this case, there is a problem that the equivalent series resistance R becomes large because the electrode becomes small and the electric field becomes small.

  In the piezoelectric vibrator 111, the vibrating arm portion 112 has an upper surface, a lower surface, and side surfaces, and grooves 115 are formed on the upper and lower surfaces. In order to obtain a desired equivalent series resistance R and quality factor value Q, the groove 115 is designed in a desired width and thickness range with respect to the width and thickness of the vibrating arm portion. However, it is difficult to form the groove 115 with high accuracy due to variations in etching conditions such as the etching time and the amount of the etching solution when forming the groove 115 in the vibrating arm portion 112. As a result, there is a problem that electrical characteristics vary due to variations in the shape and the like of the groove 115, making it difficult to obtain a desired vibration frequency.

  In view of the above circumstances, the piezoelectric vibrator of the present invention is configured to vibrate in a bending mode and has a pair of vibrating arm portions having an upper surface, a lower surface, and side surfaces, and one end side of the vibrating arm portion. A base portion formed integrally, and a through-hole penetrating between the upper and lower surfaces is formed in the vibrating arm portion, and an electrode is formed on an inner wall of the through-hole facing the side surface of the vibrating arm portion. An embedded member is formed in the through hole. Therefore, in the present invention, a through hole is formed in the vibrating arm portion, and an electrode is formed using the through hole. An embedded member is formed in the through hole. With this structure, the piezoelectric vibrator can be reduced in size while maintaining the mechanical strength of the vibrating arm, and the equivalent series resistance R can also be reduced.

  The present invention further includes a pair of vibrating arm portions that vibrate in a bending mode and have an upper surface, a lower surface, and a side surface, and a base portion that is formed integrally with one end side of the vibrating arm portion, In the extending direction, a plurality of through-holes penetrating between the upper and lower surfaces are formed, an electrode is formed on the inner wall of the through-hole facing the side surface of the vibrating arm portion, and embedded in the through-hole A member is formed. Therefore, in the present invention, the embedded member is formed in the through hole even in the vibrating arm portion formed in the ladder shape by the through hole. With this structure, it is possible to reduce the equivalent series resistance R while improving the mechanical strength of the vibrating arm portion.

  In the piezoelectric vibrator of the present invention, the embedded member is Ni, Sn—Au alloy, glass, or silicon. Therefore, in the present invention, by using a material whose rigidity is equal to or higher than that of the crystal that is the raw material of the piezoelectric vibrator as the embedded member, it is possible to prevent a reduction in electromechanical conversion efficiency at the vibrating arm portion and to increase the equivalent series resistance R. Can be prevented.

  In the piezoelectric vibrator of the present invention, an electrode having a polarity different from that of the electrode of the through hole is formed on a side surface of the vibrating arm portion facing the inner wall of the through hole. Therefore, in this invention, the electrode is efficiently arrange | positioned on the side surface of the vibrating arm part. With this structure, a piezoelectric vibrator having a small equivalent series resistance R can be realized.

  In the piezoelectric vibrator according to the aspect of the invention, the vibrating arm portion may extend from the one end side with a certain width, and may have a step portion that is wider than the certain width near the other end side of the vibrating arm portion. It is characterized by. Therefore, in the present invention, the vibrating arm portion is formed so that the width on the other end side of the vibrating arm portion is widened. With this structure, when supported on the mounting substrate, the center of gravity of the piezoelectric vibrator is located near the center of the vibrating arm portion, and the piezoelectric vibrator is supported in a stable state.

  In the piezoelectric vibrator of the present invention, the piezoelectric vibrator includes a pair of side bases that are formed integrally with the base and extend along a side surface of the vibration arm, and the width of the side base is the vibration arm. It is characterized by being narrower than a certain width. Therefore, in the present invention, the center of gravity of the piezoelectric vibrator is located in the vicinity of the center portion of the vibrating arm portion, so that the mechanical strength burden on the side base portion can be reduced and the width of the side base portion can be reduced.

  In the piezoelectric vibrator manufacturing method of the present invention, the crystal wafer is prepared by etching the crystal wafer to form a piezoelectric vibrator including a vibrating arm portion and a base portion. Forming a first metal layer on both sides of the wafer, selectively removing the first metal layer, etching from both sides of the quartz wafer using the first metal layer as an etching mask, and And forming the through-hole of the vibrating arm portion, and removing the first metal layer, forming a second metal layer on the quartz wafer, and selectively forming the second metal layer An electrode is formed on the inner wall of the through hole facing the extending side surface of the vibrating arm portion, and the electrode of the through hole is polar on the side surface of the vibrating arm portion facing the inner wall of the through hole. Forming different electrodes, and Characterized by a step of forming a buried member embedding the hole. Therefore, in the present invention, it is possible to form a through hole with little variation in shape in the vibrating arm portion and to form an embedded member in the through hole. By this manufacturing method, a piezoelectric vibrator having a small equivalent series resistance R can be formed while maintaining the mechanical strength of the vibrating arm portion.

  In the present invention, a through hole is formed in the vibrating arm portion, and an embedded member is formed in the through hole. With this structure, the mechanical strength of the vibrating arm portion is maintained, and the decrease in electromechanical conversion efficiency at the vibrating arm portion is prevented.

  In the present invention, a through hole is formed in the vibrating arm portion, and an electrode is formed on the inner wall of the through hole. The electrode in the through hole and the electrode on the side surface of the vibrating arm portion are formed to face each other. With this structure, the electrodes can be efficiently formed on the vibrating arm portion, and the equivalent series resistance R can be reduced while realizing miniaturization of the piezoelectric vibrator.

  In the present invention, a through hole is formed in the vibrating arm portion, and an electrode is formed on the inner wall of the through hole. With this structure, variations in electrode formation positions can be prevented, and variations in electrical characteristics can be prevented.

  In the present invention, the vibrating arm portion is formed to have at least two widths. One end side of the vibrating arm portion is formed integrally with the base portion, and there is a widely formed region on the other end side. With this structure, the center of gravity of the piezoelectric vibrator supported on the mounting substrate is positioned at the center, and the piezoelectric vibrator is supported in a stable state.

  In the present invention, since the piezoelectric vibrator is supported on the mounting substrate in a stable state, the mechanical strength to the support portion is reduced, and the width of the support portion can be reduced. With this structure, the piezoelectric vibrator can be downsized in the width direction.

  In the present invention, through holes are formed by etching from the upper and lower surfaces of the vibrating arm portion. By this manufacturing method, it is possible to reduce variations in the size and shape of the openings of the through holes on the upper and lower surfaces.

  Hereinafter, a piezoelectric vibrator according to an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1A is a plan view for explaining the piezoelectric vibrator according to the present embodiment. FIG. 1B is a cross-sectional view of the piezoelectric vibrator shown in FIG. 1A taken along the line A-A ′, and is a view for explaining an electrode structure of the piezoelectric vibrator. FIG. 2 is a diagram for explaining the relationship between the equivalent series resistance value R of the piezoelectric vibrator according to the present embodiment and the Young's modulus of the material constituting the embedded member. FIG. 3 is a plan view for explaining the piezoelectric vibrator according to the present embodiment. FIG. 4A is a plan view for explaining the piezoelectric vibrator of the present embodiment. FIG. 4B is a plan view for explaining the piezoelectric vibrator of the present embodiment. FIG. 5 is a diagram for explaining the relationship between the side base width and the base length with less frequency dependency in the piezoelectric vibrator according to the present embodiment.

  The piezoelectric vibrator of the first embodiment will be described with reference to FIGS. The piezoelectric vibrator 1 mainly includes a pair of vibrating arm portions 2 and 3 and a base portion 4. The piezoelectric vibrator 1 is, for example, a cut angle that is rotated in the X-axis direction by 1 ° from the Z-axis plane in a rectangular crystal orthogonal coordinate system in which the electrical axis is the X axis, the mechanical axis is the Y axis, and the optical axis is the Z axis. This is formed by processing a crystal wafer thinly sliced into a plate shape. Therefore, the piezoelectric vibrator 1 is formed with a constant thickness of about 100 to 150 (μm), for example.

  The vibrating arm portions 2 and 3 are integrally formed with the base portion 4 at one end side and have a tuning fork shape. The vibrating arm portions 2 and 3 are designed with a width W1 and a length L1. Specifically, the width and length of the vibrating arm portion 2 are determined according to a desired vibration frequency based on the following relational expression.

ここで、Ｆは振動周波数（Ｈｚ）、Ｌは振動腕部の長さ（ｍ）、Ｗは振動腕部の幅（ｍ）、Ｃ‘_２２は弾性スチフネス定数（Ｎ／ｍ^２）、ρは水晶の密度（ｋｇ／ｍ^３）を示している。

Where F is the vibration frequency (Hz), L is the length of the vibrating arm (m), W is the width of the vibrating arm (m), C ′ ₂₂ is the elastic stiffness constant (N / m ² ), and ρ is The density (kg / m ³ ) of quartz is shown.

  The vibrating arms 2 and 3 are formed with through holes 5 and 6 having a width W2. The through holes 5 and 6 are formed in the vibrating arm 2 so as to be symmetric with respect to a neutral line indicated by a dotted line.

  The base portion 4 has a region having a length L2 and a width W3, and the vibrating arm portions 2 and 3 and a part thereof are integrally formed. The base 4 is designed to have a region that attenuates mechanical vibration energy generated in the vibrating arm 2 and prevents vibration leakage to the package.

  As shown in FIG. 1B, the vibrating arm portions 2 and 3 are separated in the width direction (X-axis direction) by the through holes 5 and 6 in the cross section along the line A-A ′.

  In the vibrating arm portion 2, electrodes 9 and 10 having the same polarity are formed so as to cover the inner walls 7 and 8 formed by the through holes 5. Part of the electrodes 9 and 10 is formed up to the upper and lower surfaces 11 and 12 of the vibrating arm portion 2. Electrodes 15 and 16 having polarities different from those of the electrodes 9 and 10 are formed on the side surfaces 13 and 14 of the vibrating arm portion 2 facing the inner walls 7 and 8.

  Similarly, in the vibrating arm portion 3, electrodes 19 and 20 having the same polarity are formed so as to cover the inner walls 17 and 18 formed by the through holes 6. Part of the electrodes 19 and 20 is formed up to the upper and lower surfaces 21 and 22 of the vibrating arm portion 3. Electrodes 25 and 26 having polarities different from those of the electrodes 19 and 20 are formed on the side surfaces 23 and 24 of the vibrating arm portion 3 facing the inner walls 17 and 18.

  Each electrode is connected to the same polarity via wires formed on the vibrating arm portions 2 and 3 and the base portion 4. The electrodes and wirings are formed in a desired shape by sputtering gold (Au) after sputtering chromium (Cr) on a quartz wafer, for example.

Specifically, when electrodes 9, 10, 25, 26 are positive electrodes, electrodes 15, 16, 19, 20 are negative electrodes and a DC voltage is applied between the electrodes, an electric field is formed in the direction of the arrow (X width direction) shown in the figure. E _X occurs. Then, the vibrating arms 2 and 3, elastic stresses across the neutral line (see FIG. 1 (A)) acts by the electric field E _X, the vibrating arms 2 and 3 are vibrated by the bending mode. As described above, by forming the through holes 5 and 6, the electrodes 9, 10, 19, and 20 are formed on the entire surface of the vibrating arms 2 and 3 in the thickness direction (a plane perpendicular to the X-axis direction). With this structure, the electrode forming area in the vibrating arm portions 2 and 3 is increased as compared with the groove structure, and the vibrating arm portions 2 and 3 are bent in the direction in which the vibrating arm portions 2 and 3 are bent (X width direction). a large electric field _{E X} occurs. That is, even when the width W1 of the vibrating arm portions 2 and 3 is reduced due to the miniaturization of the piezoelectric vibrator 1, the electric field E _{X is} obtained by forming the through holes and effectively using the thickness of the vibrating arm portions 2 and 3. To generate efficiently. Then, it is possible to prevent the electromechanical conversion efficiency from being deteriorated and to form the piezoelectric vibrator 1 having a small equivalent series resistance R.

  As shown in the figure, in the through holes 5 and 6, embedded members 27 and 28 made of Ni, Sn—Au alloy, low melting point glass, silicon or the like are formed between the electrodes formed in the through holes 5 and 6. . With this structure, the embedded members 27 and 28 are formed in the through holes 5 and 6 of the vibrating arm portions 2 and 3, so that the bending mode vibration of the vibrating arm portions 2 and 3 is disturbed and the equivalent series resistance R is increased. Can be prevented. Specifically, when Ni or Sn—Au alloy having higher rigidity than quartz is used as the embedding members 27 and 28, the equivalent series resistance R is smaller than when the embedding member is made of quartz. On the other hand, when low melting point glass or silicon having rigidity lower than that of quartz is used as the embedding members 27 and 28, the equivalent series resistance R is larger than when the embedding member is made of quartz. For example, when comparing vibration arm parts having the same structure, the equivalent series resistance R is 21.4 (kΩ) for Ni, 33.8 (kΩ) for Sn—Au alloy, and 47.5 for quartz. (KΩ), in the case of silicon, it is 79.3 (kΩ). That is, the equivalent series resistance R can be reduced by using the embedded members 27 and 28 having rigidity substantially equal to or higher than that of quartz. However, the embedding members 27 and 28 take into account various factors such as the handling property in the liquid state when filling the through holes 5 and 6 and the cured shape in the through holes 5 and 6. Can be selected.

As shown in FIG. 2, the equivalent series resistance R of the piezoelectric vibrator can be compared with the Young's modulus E (10 ¹⁰ Pa) of the material constituting the embedded members 27 and 28 formed in the through holes 5 and 6. . As described above, when the embedded members 27 and 28 are made of Ni, the equivalent series resistance R is 21.4 (kΩ), and the Young's modulus E is 21.92 (10 ¹⁰ Pa). That is, as shown by the curves in the figure, the material having the embedded members 27 and 28 having a higher Young's modulus E does not hinder the bending mode vibration of the vibrating arms 2 and 3 and the equivalent series resistance R is small. can do.

  As shown in FIG. 3, three through holes 32 to 37 are formed in each of the vibrating arm portions 30 and 31 of the piezoelectric vibrator 29. The widths of the through holes 32 to 37 are W2, and are formed in the vibrating arm portions 30 and 31 so as to be symmetric with respect to a neutral line indicated by a dotted line. 1A, electrodes are formed on the inner walls of the through holes 32-37, and embedded members are formed in the through holes 32-37. Examples of the embedded member include Ni, Sn—Au alloy, low-melting glass, and silicon. In the structure in which the plurality of through-holes 32 to 37 are formed in the vibrating arm portions 30 and 31, each through-hole 32 to 37 is longer in the extending direction than the through-holes 5 and 6 shown in FIG. It gets shorter. And in the area | region in which the through-holes 32-37 of the vibration arm parts 30 and 31 are formed, it has the crystal | crystallization integrated area | regions 38-41 between the through-holes 32-37, and the vibration arm parts 30 and 31 become a ladder shape. . That is, in the vibrating arm portions 30 and 31, the integrated regions 38 to 41 are arranged at regular intervals, and the embedded members are formed at regular intervals. With this structure, the electrode formation region at the vibrating arm portions 30 and 31 is increased as compared with the groove structure, while the mechanical strength at the vibrating arm portions 30 and 31 is compared with the structure of FIG. Further improvement can be achieved.

  The structure of the piezoelectric vibrator 29 shown in FIG. 3 is the same as that of the piezoelectric vibrator 1 shown in FIG. 1A except for the number of through holes 32 to 37 formed in the vibrating arm portions 30 and 31. Therefore, for the description of other structures, refer to the description of FIG. 1A, and the description is omitted here.

  The piezoelectric vibrator of the second embodiment will be described with reference to FIGS.

  As shown in FIG. 4A, the piezoelectric vibrator 51 is mainly composed of a pair of vibrating arm portions 52 and 53, a base portion 54, and a pair of side base portions 55 and 56. The piezoelectric vibrator 51 is, for example, a cut angle that is rotated in the X-axis direction by 1 ° from the Z-axis plane in a quartz crystal orthogonal coordinate system in which the electrical axis is the X-axis, the mechanical axis is the Y-axis, and the optical axis is the Z-axis. This is formed by processing a crystal wafer thinly sliced into a plate shape. Therefore, the piezoelectric vibrator 51 is formed with a constant thickness of about 100 to 150 (μm), for example.

  The vibrating arm portions 52 and 53 are integrally formed with the base portion 54 at one end side and have a tuning fork shape. Since the structures of the vibrating arm portions 52 and 53 are the same, the following description will be made using the vibrating arm portion 52.

  The vibrating arm portion 52 extends in parallel with the vibrating arm portion 53 from one end side integrated with the base portion 54. The vibrating arm portion 52 has a stepped portion 57, which is formed with a width W4 from one end side to the stepped portion 57 of the vibrating arm portion 52, and formed with a width W5 from the stepped portion 57 to the other end side. The step portion 57 is formed so as to be symmetric about the neutral line indicated by the dotted line in the vibrating arm portion 52. That is, the vibrating arm 52 is formed from two types of widths W4 and W5, and is designed to satisfy the relationship of W4 <W5. The position of the stepped portion 57 formed on the vibrating arm portion 52 can be arbitrarily determined according to various design conditions such as the length L3, width W4, and W5 of the vibrating arm portion 52 according to a desired vibration frequency. Design changes are possible.

  Specifically, the length L3, the width W4, and W5 of the vibrating arm portion 52 corresponding to a desired vibration frequency are determined for the vibrating arm portion 52 based on the above relational expression.

  The vibration frequency F of the piezoelectric vibrator 51 is proportional to the width W of the vibrating arm portion and inversely proportional to the square of the length L of the vibrating arm portion. As described above, the vibrating arm portion 52 of the piezoelectric vibrator 51 has the width W5 of the other end portion from the stepped portion 57, and the width W of the vibrating arm portion in the above relational expression becomes wide. Therefore, in order to obtain the desired vibration frequency F, it is necessary to shorten the length L of the vibrating arm portion. As a result, the length of the vibrating arm portion 52 is shortened, and the piezoelectric vibrator 51 can be downsized in the length direction.

  A through hole 58 is formed in the vibrating arm portion 52. The through hole 58 is formed in the vibrating arm 52 so as to be symmetric about a neutral line indicated by a dotted line. Note that the electrode structure and the effect of the vibrating arm portions 52 and 53 shown in the direction of the line BB ′ shown in FIG. 4A are the same as the electrode structure and the effect described with reference to FIG. Therefore, the description of FIG. 1B is referred to and the description is omitted here.

  The base portion 54 has a region of length L4 and width W6, and the vibrating arm portions 52 and 53 and the side base portions 55 and 56 and a part thereof are integrally formed. In the base portion 54, a region for attenuating mechanical vibration energy generated in the vibrating arm portion 52 and preventing vibration leakage through the side base portions 55 and 56 is necessary.

  The side base portions 55 and 56 are formed integrally with the base portion 54 at one end side. The side base portions 55 and 56 are formed so as to be parallel to the vibrating arm portions 52 and 53 so that the vibrating arm portions 52 and 53 are sandwiched therebetween. On the other end side of the side base portions 55 and 56, a terminal electrode (not shown) is formed in a region indicated by a circle, and the terminal electrode is mounted on the mounting substrate via a conductive adhesive, for example, silver paste. It is connected to the electrode. The piezoelectric vibrator 51 is supported on the mounting substrate in a state of being fixed to the mounting substrate only under the side base portions 55 and 56 indicated by circles.

  As described above, one end side of the vibrating arm portions 52 and 53 is formed integrally with the base portion 54, and a region having a width W5 is formed on the other end side of the vibrating arm portions 52 and 53. With this structure, the balance of the weights at both ends of the vibrating arm portions 52 and 53 is adjusted, and when the piezoelectric vibrator 51 is supported on the mounting substrate, the center of gravity of the piezoelectric vibrator 51 is the vibration arm portions 52 and 53. Located near the center. As a result, the piezoelectric vibrator 51 is supported on the mounting substrate in a stable state. And the influence by the mechanical strength by the weight of the piezoelectric vibrator 51 itself, a vibration, etc. with respect to the side base parts 55 and 56 reduces. That is, the width W7 of the side base portions 55 and 56 can be designed so as to satisfy the relationship of W7 <W4, and the piezoelectric vibrator 51 can be downsized in the width direction.

  As illustrated, the base 54 and the side base 55 are separated by a width W8. The vibrating arm portion 52 and the side base portion 55 are separated by a width (W8 + W9). That is, the width W8 is the minimum width that allows the quartz wafer to be etched through, and the separation width between the base 54 and the side base 55 is reduced. A base 54 having a desired width W6 is formed without expanding the width direction of the piezoelectric vibrator 51. With this structure, vibration leakage from the base 54 can be prevented.

  On the other hand, the separation width between the vibrating arm portion 52 and the side base portion 55 is further expanded by the width W9 to the minimum width W8 that can be etched through, and an appropriate separation width is secured between the vibrating arm portion 52 and the side base portion 55. . It is difficult to form the vibrating arm 52 with a minimum width that can be etched through due to mask displacement, etching conditions, and the like. That is, by having an appropriate separation width (W8 + W9) between the vibrating arm portion 52 and the side base portion 55, when the vibrating arm portion 52 is formed, the outer dimensions thereof are less likely to vary. As a result, the vibration frequency F of the vibration arm portions 52 and 53 is affected by the width W of the vibration arm portions 52 and 53, but the vibration frequency F is less likely to be distorted, and the piezoelectric vibrator 51 having a high quality factor Q value is formed. Is done.

  The minimum width W8 capable of penetrating the quartz wafer is a width that can be penetrated by wet etching using, for example, hydrofluoric acid using a known photolithography technique. The width W8 is about 25 (μm), and the width W9 is about 50 (μm).

  As shown in FIG. 4B, three through-holes 62 to 67 are formed in the vibrating arm portions 60 and 61 of the piezoelectric vibrator 59. The through holes 62 to 67 are formed so as to be symmetrical about the neutral line indicated by the dotted line in the vibrating arm portions 60 and 61. As in the case of FIG. 4A, electrodes are formed on the inner walls of the through holes 62 to 67, and embedded members are formed in the through holes 62 to 67. Examples of the embedded member include Ni, Sn—Au alloy, low-melting glass, and silicon. In the structure in which the plurality of through holes 62 to 67 are formed in the vibrating arm portions 60 and 61, the length of each through hole 62 to 67 is longer than the through hole 58 shown in FIG. Shorter. And in the area | region where the through-holes 62-67 of the vibrating arm parts 60 and 61 are formed, it has the integrated area | regions 68-71 of the crystal | crystallization between the through-holes 62-67, and the vibrating arm parts 60 and 61 become ladder shape. . That is, in the vibrating arm portions 60 and 61, the integrated regions 68 to 71 are arranged at regular intervals, and the embedded members are formed at regular intervals. With this structure, the electrode formation region in the vibrating arm portions 60 and 61 is increased as compared with the groove structure, while the mechanical strength in the vibrating arm portions 60 and 61 is compared with the structure in FIG. Further improvement can be achieved.

  The structure of the piezoelectric vibrator 59 shown in FIG. 4B is the same as that of the piezoelectric vibrator 51 shown in FIG. 4A except for the number of through holes 62 to 67 formed in the vibrating arm portions 60 and 61. Therefore, for the description of other structures, refer to the description of FIG. 4A, and the description thereof is omitted here.

  In FIG. 5, the horizontal axis indicates the base length L4 (μm). The vertical axis shows the frequency deviation (ppm) between the frequency when the piezoelectric vibrator is completely floating in the air and the frequency when the piezoelectric vibrator is fixed on the mounting board in order to be housed in the package. Is shown. A solid line indicates a case where the length L5 in which the base 54 and the side bases 55 and 56 are integrated is 240 (μm). On the other hand, the dotted line shows the case where the length L5 is 190 (μm).

  As shown in the figure, both the solid line and the dotted line are downwardly convex curves, and the frequency deviation is the smallest at the lower limit value. Specifically, as indicated by the solid line, when the length L5 is 240 (μm), the base length L4 needs to be about 320 to 350 (μm). On the other hand, when the length L5 is 190 (μm), the base length L4 needs to be about 250 to 300 (μm). That is, the length L4 increases as the length L5 increases, and the length L4 decreases as the length L5 decreases.

  Here, as described above, the piezoelectric vibrator 51 is supported on the mounting substrate by the terminal electrodes (not shown) on the other end side of the side base portions 55 and 56 indicated by circles (see FIG. 4A). Has been. The minimum value of the length L5 is determined in relation to the frequency deviation while taking into account the length necessary for continuing to support the piezoelectric vibrator 51 in the hollow portion, that is, the length for securing the mechanical strength. . On the other hand, the maximum value of the length L5 is determined in relation to the package size in which the piezoelectric vibrator is accommodated. In other words, in the present embodiment, for example, the length L4 of the base 54 is designed in the range of 250 to 350 (μm) while considering the reduction of the package size, so that the side bases 55 and 56 have vibration leakage. It can be formed with a width W7 having a small frequency dependency.

  In the present embodiment, the structure in which the vibrating arm portion has two widths has been described. However, the present invention is not limited to this case. For example, the vibrating arm portion may be formed so as to have a plurality of widths, for example, the vibrating arm portion is formed in a stepped manner as the vibrating arm portion is separated from the base portion. In addition, various modifications can be made without departing from the scope of the present invention.

  Next, a method for manufacturing a piezoelectric vibrator according to an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 6A is a cross-sectional view for explaining the method of manufacturing the piezoelectric vibrator according to the present embodiment. FIG. 6B is a plan view for explaining the method for manufacturing the piezoelectric vibrator according to the present embodiment. 7A and 7B are cross-sectional views for explaining the method of manufacturing the piezoelectric vibrator according to the present embodiment. 8A and 8B are cross-sectional views for explaining the method for manufacturing the piezoelectric vibrator according to the present embodiment. 9A to 9C are cross-sectional views for explaining the method for manufacturing the piezoelectric vibrator according to the present embodiment. FIG. 10A is a plan view for explaining the manufacturing method of the piezoelectric vibrator according to the present embodiment. FIG. 10B is a cross-sectional view for explaining the method for manufacturing the piezoelectric vibrator according to the present embodiment. The cross-sectional view for explaining the method for manufacturing the piezoelectric vibrator is a cross-sectional view of a region where the through-hole of the vibrating arm portion is formed.

  First, a first embodiment of a method for manufacturing a piezoelectric vibrator will be described with reference to FIGS.

  As shown in FIG. 6A, in a rectangular crystal orthogonal coordinate system in which the electrical axis is the X axis, the mechanical axis is the Y axis, and the optical axis is the Z axis, the cut is rotated by 1 ° from the Z axis plane in the X axis direction. A crystal wafer 71 sliced thinly into a plate shape at a corner is prepared. After chromium (Cr) 72 is sputtered on both surfaces of the quartz wafer 71, gold (Au) 73 is sputtered to form a metal layer 74 used as an etching mask. Thereafter, the metal layer 74 is selectively removed by a known photolithography technique so that the opening is provided in a region where the opening and the through hole are formed along the outer shape of the piezoelectric vibrator.

  As shown in FIG. 6B, the outer shape of the piezoelectric vibrator 75 and the through hole 76 are formed from both surfaces of the crystal wafer 71 by wet etching using, for example, hydrofluoric acid using the metal layer 74 as an etching mask. Thereafter, the metal layer 74 is removed. By this etching process, a support bar 77 is formed on the crystal wafer 71, and the plurality of piezoelectric vibrators 75 are integrated with the support bar 77, so that the piezoelectric vibrator 75 is supported on the crystal wafer 71.

  Further, in the present embodiment, since the through hole 76 is used, as compared with the case where the groove is formed from the upper and lower surfaces of the crystal wafer 71, the groove shape shift (due to variations in etching conditions such as etching time and the amount of etching solution) ( (Groove width, groove depth) need not be considered. Further, by etching from both sides of the quartz wafer 71, the opening sizes of the through holes 76 can be made equal. As a result, the piezoelectric vibrator 75 has a structure in which variation in electrical characteristics due to the displacement of the through-hole shape hardly occurs. And the piezoelectric vibrator 75 which has a desired vibration frequency can be formed with an easy manufacturing method, and a yield can also be improved.

  As shown in FIG. 7A, after chromium (Cr) 78 is sputtered on both sides of the quartz wafer 71, in the through holes 76, and on the side surfaces of the piezoelectric vibrator 75, gold (Au) 79 is sputtered to form the metal layer 80. Form. Thereafter, the metal layer 80 is selectively removed by a known photolithography technique to form electrodes, wiring (not shown), and terminal electrodes (not shown).

  As shown in FIG. 7B, an embedded member 81 is formed in the through hole 76. The embedded member 81 is made of, for example, Ni, Sn—Au alloy, low melting point glass, or silicon. Here, when forming the embedded member 81 made of low-melting glass, the low-melting glass in the liquid state is filled between the through holes 76 by utilizing the surface tension of the liquid. Then, after the low melting point glass is solidified between the through holes 76, the low melting point glass is cured in a substantially constant shape in the through holes 76 by performing heat treatment. In addition, silicon also embeds the through-hole 76 by the same method as the low melting point glass. In the case of Ni or Sn—Au alloy, the through hole 76 is embedded by plating using the electrode on the inner wall of the through hole 76.

  Finally, the piezoelectric vibrator 75 is detached from the crystal wafer 71, and the piezoelectric vibrator 75 is completed. At this time, as shown in FIG. 6B, the piezoelectric vibrator 75 is supported by the quartz wafer 71 with the portion extending from the inside of the recess 83 formed in the base 82 connected to the support bar 77. . With this structure, when the piezoelectric vibrator 75 is detached from the crystal wafer 71, it is possible to prevent the notched portion from being accommodated in the recess 83 and protruding from the base portion 82. As a result, even when the package size is reduced, it is possible to form the piezoelectric vibrator 75 in which the notched portion is not caught by the package.

  In the above-described first embodiment, the case where the outer shape of the piezoelectric vibrator 75 and the through hole 76 are formed by one etching process has been described. However, the present invention is not limited to this case. For example, the outer shape of the piezoelectric vibrator 75 may be formed by changing the etching mask after forming the through hole 76 by two etching steps. Similarly, the through hole may be formed after the outer shape of the piezoelectric vibrator 75 is formed.

  Next, a second embodiment of the piezoelectric vibrator manufacturing method will be described with reference to FIG. In the second embodiment, the step of forming the piezoelectric vibrator and the through hole in the quartz wafer and the step of removing the piezoelectric vibrator from the quartz wafer are the same as those in the first embodiment. Therefore, for the same steps as those in the first embodiment, the description of the first embodiment is referred to and the description thereof is omitted here.

  As shown in FIG. 8A, after forming the outer shape of the piezoelectric vibrator 85 and the through hole 86 in the crystal wafer 84, chromium (Cr) is formed on both sides of the crystal wafer 84, in the through hole 86, and on the side surface of the piezoelectric vibrator 85. After sputtering 87, gold (Au) 88 is sputtered to form a metal layer 89. Thereafter, the metal layer 89 is selectively removed by a known photolithography technique, and an electrode is formed in the through hole 86.

  As shown in FIG. 8B, an embedded member 90 is formed in the through hole 86. The embedded member 90 is made of, for example, Ni, Sn—Au alloy, low melting point glass, or silicon. The method for forming the embedded member 90 is the same as the method described with reference to FIG. Thereafter, chromium (Cr) 91 is sputtered on both surfaces of the quartz wafer 84, and then gold (Au) 92 is sputtered to form the metal layer 93. Then, the metal layer 93 is selectively removed by a known photolithography technique to form electrodes and wirings. Finally, the piezoelectric vibrator 85 is detached from the crystal wafer 84, and the piezoelectric vibrator 85 is completed.

  In the second embodiment described above, the outer shape of the piezoelectric vibrator 85 and the formation process of the through-hole 86 are performed twice even in the case of a single etching process as in the first embodiment. It may be an etching process.

  Next, a third embodiment of the piezoelectric vibrator manufacturing method will be described with reference to FIGS.

  As shown in FIG. 9A, in a rectangular crystal orthogonal coordinate system in which the electrical axis is the X axis, the mechanical axis is the Y axis, and the optical axis is the Z axis, the cut is rotated by 1 ° from the Z axis plane in the X axis direction. A quartz wafer 94 is prepared by thinly slicing it into a plate shape at a corner. Then, after sputtering chromium (Cr) 95 on both sides of the quartz wafer 94, gold (Au) 96 is sputtered to form a metal layer 97 used as an etching mask. Thereafter, the metal layer 97 is selectively removed by a known photolithography technique so that an opening is provided in a region where the through hole 98 is formed.

  As shown in FIG. 9B, through holes 98 are formed from both sides of the quartz wafer by wet etching using the metal layer 97 as an etching mask and using, for example, hydrofluoric acid. After chromium (Cr) 99 is sputtered on both sides of the quartz wafer 94 and in the through holes 98, gold (Au) 100 is sputtered to form the metal layer 101. Thereafter, the metal layer 101 is selectively removed by a known photolithography technique, and an electrode is formed in the through hole 98. Then, after removing the metal layer 101, the embedded member 102 is formed in the through hole 98. The embedded member 102 is made of, for example, Ni, Sn—Au alloy, low-melting glass, or silicon. The method for forming the embedded member 102 is similar to the method described with reference to FIG.

  As shown in FIG. 9C, after chromium (Cr) 103 is sputtered on both sides of the quartz wafer 94, gold (Au) 104 is sputtered to form a metal layer 105. Thereafter, the metal layer 105 is selectively removed by a known photolithography technique so that an opening along the outer shape of the piezoelectric vibrator is formed.

  As shown in FIG. 10A, the outer shape of the piezoelectric vibrator 106 is formed from both surfaces of the crystal wafer 94 by wet etching using, for example, hydrofluoric acid, using the metal layer 105 as an etching mask. Thereafter, the metal layer 105 is removed. By this etching process, the support bar 107 is formed on the crystal wafer 94, and the plurality of piezoelectric vibrators 106 are integrated with the support bar 107, so that the piezoelectric vibrator 106 is supported on the crystal wafer 94.

  As shown in FIG. 10B, after chromium (Cr) 108 is sputtered on both surfaces of the quartz wafer 94, gold (Au) 109 is sputtered to form the metal layer 110. Thereafter, the metal layer 110 is selectively removed by a known photolithography technique to form electrodes and wirings. Finally, the piezoelectric vibrator 106 is detached from the crystal wafer 94, and the piezoelectric vibrator 106 is completed. The shape of the concave portion 112 of the base 111 when the piezoelectric vibrator 106 is detached is as described above.

  In this embodiment, the case where the same metal layer as the metal layer that forms the electrode is used as an etching mask when the quartz wafer is etched is not necessarily limited to this case. For example, another metal layer used as an etching mask, a photoresist, or the like may be used. In addition, various modifications can be made without departing from the scope of the present invention.

(A) It is a top view for demonstrating a piezoelectric vibrator in embodiment of this invention, (B) It is sectional drawing along the A-A 'line | wire of the piezoelectric vibrator shown to (A). It is a figure for demonstrating the relationship between the equivalent series resistance value R of the piezoelectric vibrator in embodiment of this invention, and the Young's modulus of the material which comprises an embedding member. It is a top view for demonstrating the piezoelectric vibrator in embodiment of this invention. It is a top view for demonstrating the (A) piezoelectric vibrator in embodiment of this invention, (B) It is a top view for demonstrating a piezoelectric vibrator. In the piezoelectric vibrator in the embodiment of the present invention, it is a diagram for explaining the relationship between the side base width and the base length with less frequency dependency. It is (A) sectional drawing and (B) top view for demonstrating the manufacturing method of the piezoelectric vibrator in embodiment of this invention. FIG. 4A is a cross-sectional view for explaining a method of manufacturing a piezoelectric vibrator in the embodiment of the present invention, and FIG. FIG. 4A is a cross-sectional view for explaining a method of manufacturing a piezoelectric vibrator in the embodiment of the present invention, and FIG. FIG. 4A is a cross-sectional view, FIG. 4B is a cross-sectional view, and FIG. 3C is a cross-sectional view for explaining a method of manufacturing a piezoelectric vibrator according to an embodiment of the present invention. It is (A) top view and (B) sectional drawing for demonstrating the manufacturing method of the piezoelectric vibrator in embodiment of this invention. It is a top view for demonstrating the conventional piezoelectric vibrator. It is a top view for demonstrating the conventional (A) piezoelectric vibrator, (B) It is sectional drawing along the C-C 'line | wire of the piezoelectric vibrator shown to (A).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrator 2, 3 Vibrating arm part 4 Base part 5, 6 Through-hole 9, 10, 15, 16, 19, 20, 25, 26 Electrode 27, 28 Embedded member

Claims (9)

A pair of vibrating arms that vibrate in a bending mode and have upper, lower and side surfaces;
A base portion formed integrally with one end side of the vibrating arm portion;
A through hole penetrating between the upper and lower surfaces is formed in the vibrating arm portion, an electrode is formed on an inner wall of the through hole facing the side surface of the vibrating arm portion, and an embedded member is formed in the through hole A piezoelectric vibrator characterized by being formed. A pair of vibrating arms that vibrate in a bending mode and have upper, lower and side surfaces;
A base portion formed integrally with one end side of the vibrating arm portion;
A plurality of through holes penetrating between the upper and lower surfaces are formed in the extending direction of the vibrating arm portion, an electrode is formed on an inner wall of the through hole facing the side surface of the vibrating arm portion, and the through hole A piezoelectric vibrator characterized in that an embedded member is formed in the hole. The piezoelectric vibrator according to claim 1, wherein the embedded member is made of Ni, Sn—Au alloy, glass, or silicon. 3. The piezoelectric vibrator according to claim 1, wherein an electrode having a polarity different from that of the electrode of the through hole is formed on a side surface of the vibrating arm portion facing the inner wall of the through hole. . 2. The vibrating arm portion extends from the one end side with a constant width, and has a step portion having a width wider than the constant width near the other end side of the vibrating arm portion. The piezoelectric vibrator according to claim 4. A pair of side bases formed integrally with the base and extending along a side surface of the vibrating arm, wherein the width of the side base is narrower than a certain width of the vibrating arm. The piezoelectric vibrator according to claim 5. In a method for manufacturing a piezoelectric vibrator that etches a quartz wafer and forms a piezoelectric vibrator composed of a vibrating arm and a base,
After preparing the crystal wafer and forming a first metal layer on both sides of the crystal wafer, the first metal layer is selectively removed, and the crystal wafer is formed using the first metal layer as an etching mask. Etching from both sides, forming the outer shape of the piezoelectric vibrator and the through-hole of the vibrating arm,
After removing the first metal layer, a second metal layer is formed on the quartz wafer, the second metal layer is selectively removed, and faces the side surface in the extending direction of the vibrating arm portion. Forming an electrode on the inner wall of the through hole, and forming an electrode having a polarity different from that of the electrode of the through hole on a side surface of the vibrating arm portion facing the inner wall of the through hole;
And a step of forming an embedded member for embedding the through hole. In a method for manufacturing a piezoelectric vibrator that etches a quartz wafer and forms a piezoelectric vibrator composed of a vibrating arm and a base,
After preparing the crystal wafer and forming a first metal layer on both sides of the crystal wafer, the first metal layer is selectively removed, and the crystal wafer is formed using the first metal layer as an etching mask. Etching from both sides, forming the outer shape of the piezoelectric vibrator and the through-hole of the vibrating arm,
After removing the first metal layer, a second metal layer is formed on the quartz wafer, the second metal layer is selectively removed, and faces the side surface in the extending direction of the vibrating arm portion. Forming an embedding member for embedding the through hole after forming an electrode on the inner wall of the through hole;
A third metal layer is formed on the quartz wafer, the third metal layer is selectively removed, and the polarity of the electrode of the through hole is different from the side surface of the vibrating arm portion facing the inner wall of the through hole. A method of manufacturing a piezoelectric vibrator, comprising: forming an electrode. In a method for manufacturing a piezoelectric vibrator that etches a quartz wafer and forms a piezoelectric vibrator composed of a vibrating arm and a base,
After preparing the crystal wafer and forming a first metal layer on both sides of the crystal wafer, the first metal layer is selectively removed, and the crystal wafer is formed using the first metal layer as an etching mask. Etching from both sides, forming a through-hole of the vibrating arm part,
After removing the first metal layer, a second metal layer is formed on the quartz wafer, the second metal layer is selectively removed, and faces the side surface in the extending direction of the vibrating arm portion. Forming an embedding member for embedding the through hole after forming an electrode on the inner wall of the through hole;
Forming a third metal layer on the quartz wafer, selectively removing the third metal layer, etching from both sides of the quartz wafer using the third metal layer as an etching mask, and Forming the outer shape;
After removing the third metal layer, a fourth metal layer is formed on the quartz wafer, the fourth metal layer is selectively removed, and the vibrating arm portion facing the inner wall of the through hole is formed. Forming a electrode having a polarity different from that of the electrode of the through hole on a side surface.

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