JP2008022378A - Crystal vibration piece and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverted mesa type crystal vibration piece and a method of manufacturing the same that can suitably be made practical by suppressing a leak of vibration from an excitation part to increase an energy confinement effect and make a CI value small, securing mechanical strength, and improving shock resistance. <P>SOLUTION: The crystal vibration piece 21 has: a crystal element piece comprising a thin excitation part 22, a thick reinforced frame 23 disposed across a through groove 24, and support parts 25 and 26 which are formed on the same plane as the excitation part with the same thickness and couple the excitation part and the reinforced frame together in one body; excitation electrodes 27a and 27b provided on top and reverse surfaces of the excitation part; connection electrodes 28 and 29 provided at the reinforced frame; and lead-out electrodes 30 and 31 which connect the respective excitation electrodes to the corresponding connection electrodes. The support parts are heated at a temperature higher than the αβ transition point of a crystal by irradiating metal thin films formed on their surfaces with laser light to form a twin crystal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a so-called inverted mesa type crystal vibrating piece in which an excitation electrode is formed on a thin vibrating part and a manufacturing method thereof.

  Recently, in the field of information communication equipment such as mobile phones, piezoelectric devices such as vibrators, resonators, and oscillators have been required to have higher frequencies in response to an increase in capacity and speed of information transmission. In particular, in the thickness-shear vibration mode piezoelectric vibrator, it is necessary to reduce the thickness of the excitation portion of the piezoelectric vibrating piece in order to increase the frequency. Therefore, in order to improve mechanical strength while realizing high frequency, an inverted mesa type piezoelectric vibrator having a structure in which a piezoelectric vibrating piece is integrated with a thin excitation part and a thick reinforcing frame around it is provided. Well known. Furthermore, a crystal resonator has been proposed in which a slit or groove is formed between the thin-walled excitation portion and the reinforcement frame to make it difficult for external force to be transmitted from the reinforcement frame to the excitation portion (for example, patents). References 1 and 2).

  4A and 4B show typical examples of such an inverted mesa type crystal vibrating piece. The crystal resonator element 1 is an AT-cut rectangular crystal thin plate that is frequently used for a thickness-shear vibration mode crystal resonator. The quartz crystal resonator element 1 is composed of a quartz element piece having a rectangular thin excitation portion 2 in the center and a rectangular thick reinforcement frame portion 3 around the excitation portion 2. The excitation portion 2 and the reinforcing frame portion 3 are separated by a through groove 4 having a predetermined width, and are integrally coupled by support portions 5 and 6 in the vicinity of the center of both longitudinal sides of the excitation portion. The excitation portion 2 has a pair of excitation electrodes 7a and 7b formed on the front and back main surfaces, and the reinforcing frame portion 3 has a pair of left and right connection electrodes 8 and 9 formed on one longitudinal end. Yes. Each of the excitation electrodes is electrically connected to the corresponding connection electrodes 8 and 9 via the extraction electrodes 10 and 11 extracted from the support portions 5 and 6 to the reinforcing frame portion 3, respectively.

  In the inverted mesa crystal vibrating piece 1 of this typical example, the support portions 5 and 6 are flush with the excitation portion 2 and have the same thickness. Therefore, as can be seen from the vibration distribution shown in the upper part of FIG. 4B, the vibration of the excitation part 2 leaks from the support parts 5 and 6 to the reinforcing frame part 3, resulting in a problem that the CI value increases. Therefore, as shown in FIGS. 5A and 5B, each of the support portions 5 and 6 is thinned by providing steps 5a, 5b, 6a, and 6b between the support portions 5 and the excitation portion 2 and the reinforcing frame portion 3. An inverted mesa type crystal vibrating piece has been proposed (see, for example, Patent Document 1). Thereby, as shown in the vibration distribution in the upper part of FIG. 5B, the leakage of vibration from the support parts 5 and 6 to the reinforcing frame part 3 is greatly reduced, and an energy confinement effect that does not deteriorate the CI characteristics can be obtained.

  In addition, a reverse mesa type quartz vibrating piece has been proposed in which inverted mesa portions are provided on a quartz plate and excitation electrodes are formed on both sides thereof, and twin portions are formed around the excitation electrode portions (for example, , See Patent Document 3). According to Patent Document 3, since the resonance frequency increases when the crystal is twinned, the same effect as when the crystal is thinned is obtained, and the energy confinement effect is obtained while ensuring the strength of the crystal vibrating piece. Can do.

  Quartz twinning is possible by heating the quartz to a temperature above its αβ transition point and reversing the electrical axis of the quartz, ie the X axis. In particular, in order to cope with the twinning of fine portions and the miniaturization of elements in a quartz resonator, the heating method by laser light irradiation is advantageous because it has excellent controllability and can be heated extremely locally. It is known (see, for example, Patent Document 4 and Non-Patent Documents 1 and 2).

  Further, when the X axis of the AT-cut quartz plate is inverted, it has been reported that the cutoff frequency in the X axis inversion region is 1.47 times higher than that in the non-inversion region (for example, non-patent document). 2). Therefore, the vibration is greatly attenuated in the inversion region of the X axis. In Non-Patent Document 2, the inversion region of the X axis is used as a separation wall between adjacent vibrators to experimentally verify that elastic coupling does not occur.

Satoru Noge, Takehiko Uno, “Artificial Twin Formation Using Laser Light Irradiation”, Proceedings of the 19th Symposium on Basics and Applications of Ultrasonic Electronics, November 1998, Vol. 19, p. 187-188 Satoru Noge, “Research on crystal resonator integration technology and its application to sensor systems”, Graduate School of Engineering, Tokyo Metropolitan University, Public Dissertation Thesis, December 3, 2004 JP-A 61-189715 JP-A-10-32456 JP 2004-48717 A Japanese Patent Laid-Open No. 11-346136

  However, when the support part which couple | bonds an excitation part and a reinforcement frame part is made thin like the reverse mesa type | mold crystal vibrating piece of patent document 1, the problem that mechanical strength falls arises. In order to sufficiently suppress the leakage of vibration, the support portion must be made very thin, and particularly the impact resistance against dropping or the like is lowered, which becomes a great obstacle when put to practical use.

  Further, as in the case of the inverted mesa type crystal vibrating piece described in Patent Document 4, when the twin portion is formed around the excitation electrode forming portion, the processing region is controlled with high accuracy even in the case of the heat treatment by laser light irradiation. Difficult to do. In addition, since the excitation electrode forming portion is adjacent to the laser light irradiation region over the entire circumference, there is a possibility that the high temperature of the laser light acts on the quartz crystal in the excitation electrode forming portion and adversely affects the vibration characteristics.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an excitation in an inverted mesa type crystal vibrating piece in which a thin-walled excitation part and a thick-walled reinforcement part are integrally coupled by a support part. Effectively suppresses leakage of vibration from the part to the reinforcement frame, enhances the energy confinement effect, stabilizes the vibration characteristics, reduces the CI value, achieves high performance, and secures its mechanical strength Thus, the impact resistance against dropping or the like is improved to be put to practical use.

  It is another object of the present invention to provide a practical method capable of manufacturing such a quartz crystal vibrating piece with high accuracy and stability without affecting its vibration characteristics.

  According to the present invention, in order to achieve the above object, a thin excitation part, a thick reinforcing frame part arranged with a through groove around it, and a through groove with the same plane and the same thickness as the excitation part A crystal element piece formed of a support part integrally connecting the excitation part and the reinforcement frame part, excitation electrodes provided on the front and back surfaces of the excitation part, connection electrodes provided on the reinforcement frame part, In order to connect the excitation electrode to the connection electrode, there is provided a quartz crystal vibrating piece having a reinforcing frame portion and an extraction electrode provided on the support portion, the support portion being twinned.

  In this way, by twining the support part with the same thickness as the excitation part, vibration leakage to the reinforcement frame part is effectively suppressed by damping the vibration in the support part while ensuring its mechanical strength. can do. Therefore, the CI value can be reduced and the energy confinement effect can be enhanced, and a high-performance and high-stability inverted mesa crystal resonator element can be put to practical use.

  In one embodiment, the quartz element piece is formed of an AT-cut quartz sheet. As described above in relation to the prior art, a twinned AT-cut quartz can obtain a frequency as high as 1.47 times, so that vibrations can be greatly damped in the support portion, and an excellent energy confinement effect can be obtained. can get.

  According to another aspect of the present invention, in order to form the quartz crystal resonator element of the present invention described above, the quartz wafer is half-etched to the thickness of the excitation unit to correspond to the shapes of the excitation unit, the through groove, and the support unit. A step of forming a thin portion, a step of etching through the thin portion to form a through groove and defining a reinforcing frame portion, an excitation portion and a supporting portion, a step of heating the supporting portion to form a twinning, and a reinforcing frame And a step of patterning the excitation electrode, the connection electrode, and the extraction electrode on the excitation portion, the excitation portion, and the support portion.

  In this way, the quartz crystal resonator element of the present invention can be manufactured easily and at low cost by simply using the conventional manufacturing process as it is and adding the twinning process of the support portion by heating.

  In one embodiment, the twinning of the support part is performed by forming a metal thin film on the surface of the support part, irradiating the metal thin film with a laser beam, and selectively supporting only the support part above the αβ transition point of the crystal. It is carried out by heating to a temperature of Heating by laser light irradiation is easy to control as well as the excitation part and the reinforcing frame part are physically separated by the through groove, so that only the support part is heated to the desired temperature. It is very easy to do.

  In this case, in one embodiment, the through groove is formed by forming a corrosion resistant film of a metal material on the surface of the quartz wafer after forming the thin portion, and patterning the corrosion resistant film by photoetching to form the through groove. The surface of the crystal wafer to be exposed is exposed, and the exposed surface of the crystal wafer is etched. After the through groove is formed, the portion of the anticorrosion film formed on the surface of the support portion is left, so that the support portion is doubled. A metal thin film for crystallization is formed. Since the corrosion-resistant film formed in the conventional manufacturing process is used as it is, an additional film-forming process is unnecessary, and the support portion can be twinned efficiently at low cost.

  In another embodiment, patterning of the excitation electrode, the connection electrode, and the extraction electrode is performed by forming an electrode film on the surface of the quartz wafer after forming the through groove, and photoetching the electrode film. When photoetching is performed, a portion of the electrode film formed on the surface of the support portion is left to form a metal thin film for twinning the support portion. In this case as well, since the electrode film formed in the conventional manufacturing process is used as it is, an additional film forming process is unnecessary, and the twinning of the support portion can be efficiently performed at low cost. .

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIGS. 1A and 1B schematically show a preferred embodiment of an inverted mesa type quartz vibrating piece in a thickness-shear vibration mode to which the present invention is applied. The quartz crystal resonator element 21 of the present embodiment is formed of an AT-cut rectangular quartz crystal plate that has been conventionally used in a thickness-shear vibration mode quartz crystal resonator. The AT-cut quartz plate is obtained by cutting a quartz crystal around the X axis at a predetermined cut angle of about 35 degrees from the Z axis. The crystal vibrating piece 21 has two opposite longitudinal sides on the X axis direction of the quartz crystal. And two opposite sides in the width direction are oriented so as to extend in the Z ′ direction forming the predetermined angle with respect to the Z axis of the crystal. Both main surfaces of the crystal vibrating piece 21 are inclined at the predetermined angle with respect to the Y ′ direction that forms the predetermined angle with respect to the Y axis of the crystal, in other words, with respect to the plane orthogonal to the Y axis.

  The quartz crystal vibrating piece 21 has a quartz crystal element piece including a rectangular thin-walled excitation portion 22 at the center and a rectangular thick-walled reinforcing frame portion 23 arranged around the excitation portion 22. The excitation portion 22 and the reinforcing frame portion 23 are separated by a through groove 24 having a predetermined width provided therebetween, and the support portion 25 is disposed in the longitudinal direction of the excitation portion 22, that is, near the center of each side in the X-axis direction. , 26 are connected together. Both support parts 25 and 26 have the same thickness as the excitation part 22 and are formed so as to be flush with the excitation part 22. In another embodiment, the support part can be provided at a position other than the center of each side in the longitudinal direction of the excitation part 22, and two or more support parts can be provided.

  A pair of excitation electrodes 27a and 27b having the same rectangular pattern are formed on the front and back main surfaces of the excitation unit 22, respectively. A pair of left and right connection electrodes 28 and 29 for connecting the excitation electrode to the outside are formed on the front and back main surfaces of one end portion in the longitudinal direction of the reinforcing frame portion 23. Further, an extraction electrode 30 connected to one connection electrode 28 is formed on the front side main surface of the reinforcing frame portion 23, and an extraction electrode 31 connected to the other connection electrode 9 is formed on the back side main surface thereof. Has been.

  The extraction electrode 30 extends from the connection electrode 28 along one adjacent side in the X-axis direction, bends near the center of the side, passes through the front main surface of the support portion 25, and the surface of the excitation portion 22. The excitation electrode 27a is connected. The extraction electrode 31 extends from the connection electrode 29 along the other side in the X-axis direction, bends near the center of the side, passes through the back side main surface of the support portion 26, and the back surface of the excitation unit 22 The excitation electrode 27b is connected. Furthermore, the extraction electrode 31 is connected to the connection electrode 9 on the front side main surface of the reinforcing frame 23 by an electrode film 31a formed on the side surface of the longitudinal end portion.

  In addition, the etching rate of crystal differs depending on the crystal orientation, and is large in the Z-axis direction (inclination of about 35 degrees with respect to the width direction Z ′ of the crystal vibrating piece 21) and in the X-axis direction (longitudinal direction of the crystal vibrating piece 21). ) And the crystal axis dependence of the etching rate, which is further smaller in the Y-axis direction (inclination of about 35 degrees with respect to the surface direction Y ′ of the crystal vibrating piece 21). For this reason, the step between the thin excitation portion 22 and the thick reinforcement frame portion 23 is inclined relatively gently toward the inner side of the + Z ′ side of the two opposing sides extending in the X-axis direction, The −Z ′ side is etched substantially vertically. The opposite two sides extending in the Z ′ direction perpendicular to these are slightly steeply inclined on the −X side, whereas the + X side is etched more steeply.

  The entire thickness of the support portions 25 and 26 is twinned. As will be described later, twinning of the support can be performed by irradiating laser light to a temperature equal to or higher than the αβ transition point of the crystal and inverting the electric axis of the crystal, that is, the X axis. Since the support portions 25 and 26 have the same thickness as the excitation portion 22, the resonance frequency is 1.47 times higher than other portions that are not twinned while ensuring mechanical strength. Thereby, as shown in the vibration distribution in the upper part of FIG. 1B, the vibration by the excitation part 22 is greatly attenuated by the support part, and the leakage of vibration to the reinforcing frame part 23 is greatly reduced. Therefore, the CI value can be reduced and a high energy confinement effect can be obtained.

  As will be described below, the quartz crystal resonator element 21 of the present invention can be formed by using a conventional method in which the front and back main surfaces of an AT-cut quartz plate are anisotropically etched using a photolithography technique. Specifically, a quartz wafer having a predetermined thickness is first prepared and both surfaces thereof are finished by mirror polishing, and then a hydrofluoric acid-resistant corrosion-resistant film made of, for example, a Cr / Au thin film is formed on the entire surface by sputtering or vapor deposition. A resist film is applied to both surfaces of the quartz wafer, and the resist film is exposed to ultraviolet rays using a photomask in which a mesa shape including the through groove 24 inside the reinforcing frame portion 23 is patterned.

  The exposed portion of the resist film is removed, and the exposed portion of the corrosion-resistant film is removed with an appropriate etching solution to pattern the mesa shape. As a result, the surface of the quartz wafer is exposed, and the exposed surface is half-etched to a desired thickness of the excitation unit 22 using, for example, a quartz etching solution mainly containing hydrofluoric acid. The remaining resist film is completely removed with an appropriate stripping solution or oxygen plasma, and the remaining corrosion-resistant film is completely removed with a stripping solution.

  Next, in the same manner, a corrosion-resistant film is formed on both surfaces of the quartz wafer, a resist film is applied, and the resist film is exposed with ultraviolet rays using a photomask in which the shape of the through groove 24 is patterned. The exposed portion of the resist film is removed, and the exposed portion of the corrosion-resistant film is removed with an appropriate etching solution to expose the surface of the quartz wafer. Then, the exposed surface of the crystal wafer is similarly etched with a crystal etching solution containing hydrofluoric acid as a main component to form the through grooves 4. The remaining resist film and corrosion resistant film are completely removed in the same manner. Thereby, the crystal element piece which processed the external shape including the thickness direction of the crystal vibrating piece 1 is obtained.

  As shown in FIG. 2, metal thin films 32 and 33 made of, for example, a Cr film or a Ni film are formed on the front or back surfaces of the support portions 25 and 26 of the crystal element pieces obtained in this way. Using a laser device such as a YAG laser, the metal thin film is focused and irradiated with laser light, and only the support is heated to a temperature equal to or higher than the αβ transition point of quartz. Since the laser beam irradiation can be controlled so as to locally heat a desired portion, each support portion 25 and 26 can be selectively twinned by reversing the X axis of the crystal. Particularly in the present invention, since the excitation part 22 is physically separated from the reinforcing frame part 23 by the through groove 24 around the support parts 25 and 26, control is performed so that only the support part is heated to a desired temperature. It is very easy.

  In this case, when peeling off the corrosion-resistant film remaining after the formation of the through-groove 24, the metal thin film for twinning by leaving the Cr film of the corrosion-resistant film formed on one surface of the support portion. It can be. Thus, if the corrosion resistant film formed in the conventional manufacturing process is used as it is, an additional film forming process is not required for the metal thin films 32 and 33, so that the twin of the supporting portion can be efficiently produced at low cost. Can be made. The metal thin films 32 and 33 after the laser beam irradiation are completely removed from the surface of the support part.

  Next, an electrode film made of, for example, a Cr / Au thin film is formed on the entire surface of the crystal element piece by sputtering or vapor deposition, and a resist film is applied. The resist film is exposed with ultraviolet rays using a photomask in which the shapes of the excitation electrodes 27a and 27b, the extraction electrodes 30 and 31 and the connection electrodes 28 and 29 are patterned. The exposed portion of the resist film is removed, and the exposed portion of the electrode film is removed with an appropriate etching solution, and the excitation electrode, the extraction electrode, and the connection electrode are patterned. Finally, when the remaining resist film is completely removed, the crystal vibrating piece 21 of the present invention is completed. Furthermore, when this crystal resonator element is mounted on a known package, the inverted mesa AT-cut crystal resonator of the present invention is obtained.

  In another embodiment, in order to pattern the excitation electrodes 27a and 27b, the extraction electrodes 30 and 31, and the connection electrodes 28 and 29, the electrode film formed on the surface of the crystal element piece after the outer shape processing is used. The metal thin film for twinning can be formed. As shown in FIG. 3, electrode films 34 and 35 are formed on the surface of the crystal element piece, and patterning is performed so that the metal thin films 32 and 33 are left on the surfaces of the support portions 25 and 26 where the extraction electrodes are not formed. . At this time, the metal thin films 32 and 33 may be only the Cr thin film under the electrode film. The laser light is applied to the metal thin films 32 and 33 from the opposite side so as not to affect the electrode films 34 and 35 on the opposite side. The metal thin films 32 and 33 after the laser light irradiation may not be removed. In this case as well, an additional film forming process is not required for the metal thin films 32 and 33, and the support portion can be twinned efficiently at low cost.

  Further, a large number of crystal vibrating pieces 21 can be formed at a time using a large crystal wafer. A large-sized quartz wafer having a predetermined thickness with both surfaces mirror-finished is prepared, and a large number of quartz vibrating pieces 21 are continuously formed in the vertical and horizontal directions according to the manufacturing process described above. The quartz wafer can be divided into individual vibrating pieces by dicing.

  In the above embodiment, the case where the present invention is applied to the quartz-crystal vibrating piece in the thickness-shear vibration mode has been described, but if it is an inverted mesa type quartz-crystal vibrating piece having a thin-walled excitation portion and a thick reinforcing frame portion, The present invention can also be applied to a crystal vibrating piece of a monolithic crystal filter. In this case, the thin excitation portion is provided with a plurality of excitation electrodes separated on one main surface thereof. The connection electrode and the extraction electrode can be formed on the main surface on the same side as the excitation electrode of the reinforcing frame portion and the support portion.

  The preferred embodiments of the present invention have been described in detail above. However, as will be apparent to those skilled in the art, the present invention can be carried out with various modifications and changes made to the above embodiments within the technical scope thereof. . For example, the mesa shape of the crystal vibrating piece can be formed by dry etching or a mechanical processing method other than anisotropic wet etching. Further, when individual vibrating pieces are separated from the quartz wafer, mechanical processing other than dicing or wet etching can be used. Further, the present invention can be similarly applied to a crystal vibrating piece made of a crystal other than the AT cut.

(A) is a plan view showing an embodiment of an AT-cut quartz crystal resonator element to which the present invention is applied, and (B) is a cross-sectional view taken along the line II and a vibration distribution diagram in the cross-section. The partial expanded sectional view in the II line of Drawing 1 (A) explaining the process of twining a support part. The partial expanded sectional view similar to FIG. 2 explaining another process of twinning a support part. FIG. 4A is a plan view showing a typical example of a conventional AT-cut quartz crystal vibrating piece, and FIG. 4B is a sectional view taken along line IV-IV and a distribution diagram of vibrations in the section. (A) is a plan view showing another AT-cut quartz crystal resonator element according to the prior art, and (B) is a cross-sectional view taken along line VV and a vibration distribution diagram in the cross-section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,21 ... Crystal vibrating piece, 2,22 ... Excitation part, 3,23 ... Reinforcement frame part, 4,24 ... Through groove, 5, 6, 25, 26 ... Support part, 5a, 5b, 6a, 6b ... Step 7a, 7b, 27a, 27b ... excitation electrodes, 8, 9, 28, 29 ... connection electrodes, 10, 11, 30, 31 ... extraction electrodes, 11a, 31a ... electrode films, 32, 33 ... metal thin films, 34, 35 ... Electrode film.

Claims (6)

  A thin-walled excitation part, a thick reinforcing frame part arranged with a through-groove sandwiched around it, and the excitation part and the reinforcing frame part formed in the through-groove in the same plane and the same thickness as the excitation part A crystal element piece composed of a support unit coupled integrally, an excitation electrode provided on each surface of the excitation unit, a connection electrode provided on the reinforcing frame, and the excitation electrode connected to the connection electrode For this purpose, the quartz crystal vibrating piece includes the reinforcing frame part and an extraction electrode provided on the support part, wherein the support part is twinned.   The quartz crystal resonator element according to claim 1, wherein the quartz element piece is made of an AT-cut quartz thin plate.   To form the quartz crystal resonator element according to claim 1 or 2, a quartz wafer is half-etched to a thickness of the excitation part, and a thin part corresponding to the shape of the excitation part, the through groove, and the support part Forming the through-groove by etching the thin portion and defining the reinforcing frame portion, the excitation portion and the support portion, and heating and twinning the support portion And a step of patterning the excitation electrode, the connection electrode, and the extraction electrode on the reinforcement frame portion, the excitation portion, and the support portion.   The twinning of the support part forms a metal thin film on the surface of the support part, irradiates the metal thin film with laser light, and selectively heats only the support part to a temperature equal to or higher than the αβ transition point of the crystal. The method for manufacturing a quartz crystal vibrating piece according to claim 3, wherein the method is performed.   The through-groove is formed by forming a corrosion-resistant film of a metal material on the surface of the crystal wafer after forming the thin-walled portion, and patterning the corrosion-resistant film by photoetching to form the through-groove. It is performed by exposing the wafer surface and etching the exposed surface of the quartz wafer, and after forming the through groove, leaving the portion of the corrosion-resistant film formed on the surface of the support portion, The method for manufacturing a quartz crystal vibrating piece according to claim 4, wherein the metal thin film for twinning is formed.   The excitation electrode, the connection electrode, and the extraction electrode are patterned by forming an electrode film on the surface of the crystal wafer after the formation of the through groove and photoetching the electrode film. 5. The metal thin film for twinning the support part is formed by leaving a part of the electrode film formed on the surface of the support part when performing the process. A method of manufacturing a quartz crystal vibrating piece.

Images