JP6373669B2 - Crystal oscillator - Google Patents

Description

  The present invention relates to a crystal resonator having good vibration characteristics and high reliability used as a reference signal source for electronic devices such as mobile communication devices and smart meters and watches, and a method for manufacturing the same. Specifically, the present invention relates to a tuning fork type crystal resonator having a groove formed in a vibration leg and having an island-shaped wall inside the groove, and a method of manufacturing the same.

  Piezoelectric vibration devices such as vibrators and oscillators are widely used as reference signal sources for watches and mobile communication devices. Among such piezoelectric vibration devices, crystal oscillators and crystal oscillators that use quartz as a piezoelectric material are in great demand because of their good temperature characteristics and high accuracy.

  Among crystal resonators, tuning fork type crystal resonators utilizing bending vibration and torsional vibration used in a low frequency band (several hundred kHz or less) are widely used in many products. Bending vibration is one of the vibration modes, and refers to a vibration mode in which the outer shape of the vibrating body is bent. On the other hand, torsional vibration is a vibration mode in which the outer shape of the vibrating body is twisted.

  The structure of the most common tuning-fork type crystal resonator will be described below as a resonator using bending vibration. FIG. 10 is a perspective view of a crystal resonator having two grooves on the main surface of a conventional vibration leg.

  As shown in FIG. 10, a tuning fork type crystal resonator 13 having two grooves on the main surface of a conventional vibrating leg has a vibrating piece comprising a base 33 and two vibrating legs 160 and 170 protruding from the base 33. 23, electrodes 56 and 57 having different potentials are formed by patterning in a desired shape.

  Further, in order to keep the crystal impedance value (generally abbreviated as CI value for short) of the crystal resonator 13, as shown in FIG. 10, two grooves 43 are formed on the main surfaces of the vibration legs 160 and 170. A structure in which electrodes 56 and 57 are also formed on the inner side wall of the groove 43 is widely known (see, for example, Patent Document 1). By applying a voltage between the inner side wall of the groove 43 and the outer side walls of the vibrating legs 160 and 170 and alternately switching the potential, the vibrating legs 160 and 170 made of quartz, which is a piezoelectric material, vibrate by electrostriction. To do. Incidentally, the CI value is a value that serves as an index of the ease of oscillation of the crystal resonator, and the smaller the CI value, the easier the oscillation and the better the vibration characteristics.

  Patent Document 1 also discloses a structure in which three grooves are formed on the main surface.

  Moreover, since the shape of the groove formed on the vibrating leg greatly affects the CI value and the rigidity of the vibrating leg, various shapes have been proposed so far. FIG. 11 is a perspective view of a crystal resonator in which a plurality of small grooves are arranged in the longitudinal direction of a conventional vibration leg.

  As shown in FIG. 11, a tuning fork type quartz crystal vibrator 14 in which a plurality of small grooves 44 are arranged in the longitudinal direction of a conventional vibrating leg has a vibration composed of a base 34 and two vibrating legs 180 and 190 protruding from the base 34. On the piece 24, electrodes 58 and 59 having different potentials are formed by patterning in a desired shape. Further, a plurality of small grooves 44 are formed on the main surface of the vibrating legs 180 and 190 side by side in the two-dimensional direction of the vibrating legs 180 and 190 in the width direction and the longitudinal direction (see, for example, Patent Document 2).

  By arranging the small grooves 44 in this manner, it becomes easier to control the groove depth than the groove 43 as shown in FIG. 10 formed long in the longitudinal direction, the yield is improved, and good and stable electric field efficiency is obtained. It is done.

  FIG. 12 is a perspective view of a crystal resonator in which a plurality of conventional small grooves are arranged in a staggered arrangement. As shown in FIG. 12, a tuning fork type crystal resonator 14 in which a plurality of small grooves 44 disclosed in the prior art are arranged in a staggered arrangement includes a base portion 34 and two vibrating legs 180 and 190 protruding from the base portion 34. Electrodes 58 and 59 having different potentials are formed on the resonator element 24 by patterning in a desired shape. Furthermore, a plurality of small grooves 44 are formed on the main surfaces of the vibrating legs 180 and 190 in a staggered arrangement in the two-dimensional direction of the vibrating legs 180 and 190 in the width direction and the longitudinal direction (for example, Patent Document 2 and Patent Document 3). reference).

  By arranging the small grooves 44 in a staggered arrangement on the main surfaces of the vibrating legs 180 and 190 in this way, the effective area of the electrodes 58 and 59 formed in the small grooves 44 is the electrode 58 formed on the crystal resonator shown in FIG. , 59, and the electric field efficiency is improved.

JP 2012-156873 A JP 2006-060727 A JP 2004-260249 A

  As described above, it has been conventionally known that by forming a plurality of grooves on the main surface of the vibrating leg, the electric field efficiency can be improved and the crystal impedance value (CI value) can be kept low. However, in recent years, the area of the main surface of the vibrating leg becomes narrower as the size of the quartz crystal resonator becomes smaller and accordingly the vibrating leg becomes thinner. Becomes narrower.

  The electrode must be formed with a predetermined thickness on the inner side wall of the groove, but the electrode is formed by a vacuum film forming method such as a vapor deposition method or a sputtering method. When it narrows, it becomes difficult for the electrode film material to enter deeply into the groove, and as a result, many defects that the electrode is not formed on the inner side wall of the groove have occurred. If the electrode is not formed, good electric field efficiency cannot be obtained no matter how the groove shape is optimized.

  In particular, in the case of a small groove as shown in FIG. 11 and FIG. 12, the opening is further narrowed, so that it is very difficult to form an electrode on the inner side wall of the small groove.

  As a result, the smaller the size of the conventional crystal unit, the worse the electric field efficiency and the CI value, resulting in poor crystal characteristics and low reliability.

In order to solve the above problems, a crystal resonator according to the present invention is a crystal resonator in which an electrode is formed on a resonator element having a groove on a vibration leg, and the crystal resonator is adjacent to the center leg and the center leg. A vibrating leg , a connecting portion connecting the one end of the central leg and the vibrating leg, and a supporting portion formed at the other end of the central leg. The vibrating leg is fixed by the supporting portion and the central leg. Is provided with a first vibrating leg portion that is reduced in width in the projecting direction from the connecting portion with the central leg, and a second vibrating leg portion having a certain width, and at least one island-like shape formed inside the groove. It is assumed that the inner wall has a crystal resonator formed at a boundary portion between the first vibrating leg and the second vibrating leg.

  In the crystal resonator of the present invention, by providing island-like protrusions (inner walls) on the inner side of the groove, a groove shape having excellent electric field efficiency can be obtained in the same manner as when a plurality of grooves are formed, and in an island shape By forming, a wide opening area can be obtained at the time of electrode formation, so that the electrode material can be formed deep into the groove, so that a continuous electrode film can be formed, and a further improvement in electric field efficiency can be obtained. It is done. As a result, a CI value can be reduced, and a crystal resonator having good vibration characteristics and high reliability can be provided.

  Furthermore, since it becomes easy to form an electrode deeply in the groove, defective electrode formation is reduced and productivity is improved.

The perspective view of the crystal oscillator which has the inner wall arranged in a line in the shape of an island inside the groove | channel of this invention Sectional drawing of the crystal oscillator which has the inner wall arranged in a line in the shape of an island of this invention The figure which showed the electrode formation process of the crystal oscillator of this invention The perspective view of the crystal oscillator which has the inner wall arranged in a line in the shape of an island inside the groove | channel of this invention The perspective view of the crystal oscillator which has an island-like protrusion inside the groove | channel of this invention The front view of the crystal oscillator which has an island-shaped protrusion inside the groove | channel of this invention The perspective view of the crystal oscillator which has the inner wall arranged in a line in the shape of an island inside the groove | channel of this invention The top view of the crystal oscillator provided with the center leg which has the inner wall arranged in two rows in the shape of an island inside the groove | channel of this invention Sectional drawing of the crystal oscillator provided with the center leg which has the inner wall arranged in two rows in the shape of an island of this invention A perspective view of a crystal unit having two grooves on the main surface of a conventional vibrating leg A perspective view of a crystal resonator in which a plurality of small grooves are arranged in the longitudinal direction of a conventional vibration leg. Perspective view of a crystal unit with a plurality of conventional small grooves arranged in a staggered arrangement

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of a crystal resonator having inner walls arranged in a row in an island shape inside a groove according to the present invention. As shown in FIG. 1, the crystal resonator 10 of the present invention has different potentials patterned in a desired shape on a vibrating piece 20 including a base 30 and two vibrating legs 100 and 110 protruding from the base 30. It has a structure in which the electrodes 50 and 51 are formed. Further, the vibration legs 100 and 110 have grooves 40 formed on the front and back main surfaces along the longitudinal direction of the vibration legs. Inside the groove 40, an inner wall 70 that partitions the grooves 40 in the width direction is provided. It is formed in a row in an island shape along the longitudinal direction of the leg.

  An electrode 50 is formed on the inner side surface of the groove 40 of the vibrating leg 100, and an electrode 51 having a potential different from that of the electrode 50 is formed on the outer side surface of the vibrating leg 100. On the other hand, an electrode 51 is formed on the inner side surface of the groove 40 of the vibration leg 110, and an electrode 50 having a potential different from that of the electrode 51 is formed on the outer side surface of the vibration leg 110. In this way, by applying a voltage between the outer side surface of the vibrating legs 100 and 110 and the inner side surface of the groove 40 and alternately switching the potential, the vibrating legs 100 and 110 made of quartz, which is a piezoelectric material, Vibrates due to electrostrictive action.

  FIG. 2 is a cross-sectional view of a crystal resonator having inner walls arranged in a row in an island shape according to the present invention. 2A is a view showing a cross section (AA cross section) of the groove 40 in the region where the inner wall 70 is present in FIG. 1, and FIG. 2B is a groove in the region where the inner wall 70 is not present in FIG. It is the figure which showed the cross section (BB cross section) of 40. In addition, in order to explain the content of the present invention in an easy-to-understand manner, the electrodes 50 and 51 are not shown.

  As shown in FIG. 2A, in the AA cross section where the inner wall 70 exists, the groove 40a is divided into two by the inner wall 70 in the width direction of the vibration legs 100a and 110a, and the cross section is similar to the two grooves. It has a shape. As a result, the groove 40a is formed in a shape having a narrow groove width and a deep depth, so that the side wall 400a inside the groove 40a is formed in a shape close to vertical.

  Thus, the side wall 400a on the inner side of the groove 40a is formed in a nearly vertical shape, so that the distance between the vibrating legs 100a and 110a and the side wall 300 is from the opening side of the groove 40a to the bottom side of the groove 40a. The distance can be almost constant, and a potential can be applied between the side wall 300 and the side wall 400a without waste. Thereby, very good electric field efficiency can be obtained.

  On the other hand, as shown in FIG. 2B, in the BB cross section where the inner wall 70 does not exist, the groove 40b has the same shape as the cross section of one groove. As a result, the groove 40b has a wide groove width and a very large opening area.

  As described above, the inner wall 70 is partially removed and the opening area of the groove 40b is widened, so that the electrode material reaches deep inside the groove 40b in the step of forming the electrode material by sputtering or vapor deposition. It is possible to form a film thickness necessary to obtain a sufficient electric field efficiency deep into the groove 40b. As a result, good electric field efficiency can be obtained.

  When the electrode material is formed by forming island-shaped inner walls 70 inside the grooves 40 at predetermined intervals as in the present invention, the electrode material wraps around the gap between the inner wall 70 and the inner wall 70 to form the film. Therefore, even in the region where the inner wall 70 exists (the region in FIG. 2A), it is possible to form a film thickness necessary to obtain good electric field efficiency deep into the groove 40a.

  Therefore, in the present invention, in the region where the inner wall 70 exists, the effect of improving the electric field efficiency by optimizing the groove shape and the improvement of the electric field efficiency by forming the electrodes 50 and 51 with a required film thickness deep into the groove 40a. Both effects can be obtained.

  The present invention also has an advantage that a highly reliable crystal resonator 10 can be manufactured while suppressing the occurrence of defects in the manufacturing process. FIG. 3 is a view showing an electrode forming process of the crystal resonator according to the present invention. In FIG. 3, the cross section of the region where the inner wall 70 of one vibration leg 100 exists is described. However, the electrodes 50 and 51 are formed by the same manufacturing method even in the region where the inner wall 70 does not exist. Further, the electrodes 50 and 51 are also formed on the other vibrating leg 110 by the same manufacturing method.

  First, the crystal resonator 10 of the present invention in FIG. 1 uses a vacuum film formation method such as a sputtering method or a vapor deposition method as shown in FIG. Then, the electrode film 500 is formed on the entire surface of the vibration leg 100a. As shown in FIG. 3A, the inner walls 70 are arranged in an island shape inside the groove 40 and a gap is provided between the inner walls 70 as in the configuration of the present invention shown in FIG. The electrode film 500 can be formed on the side wall 40a with a desired film thickness.

  Next, as shown in FIG. 3B, a resist 200 is formed on the electrode film 500 by electrodeposition. The electrodeposition method is a method in which a resist can be coated only on a surface where current flows. If electricity is applied to the conductive electrode film 500 as in the present manufacturing method, the resist is easily coated on the electrode film 500. Because it can, production efficiency is very good.

  On the other hand, when the conductive film on the surface through which the current flows has a non-uniform film thickness or is insulated, the resistance value between the two points across these defects is It is often worse than the intermembrane resistance. When a resist is formed on the conductive film having such a defect by an electrodeposition method, there is a drawback that the resist 200 cannot be formed to a desired thickness in a portion where current is difficult to flow. Accordingly, the electrode film 500 is thinly formed inside the groove 43 shown in FIG. 7 or the groove 44 shown in FIG. 8, and the resist 200 cannot be coated with a uniform thickness.

  However, in the crystal resonator 10 having the structure of the present invention, the electrode film 500 is formed with a film thickness sufficient to allow current to flow also on the inner side wall of the groove 40a. A resist 200 can be formed.

  Next, as shown in FIG. 3C, the resist 200 is patterned into the same shape as the electrodes 50 and 51 by photolithography.

  Thereafter, as shown in FIG. 3D, the exposed portion of the electrode film 500 not covered with the resist 200 is removed by etching, and the electrode film 500 is patterned into the shape of the electrodes 50 and 51.

  Finally, as shown in FIG. 3E, the resist 200 is peeled off to complete the formation of the electrodes 50 and 51.

  As described above, according to the present invention, since the resist 200 can be uniformly and firmly formed inside the groove 40a, the electrode 50 inside the groove 40a can be stably patterned in a desired shape. it can. As a result, the occurrence of defective patterning of the electrode 50 can be reduced, and the productivity is improved.

  FIG. 4 is a perspective view of a modified example of the crystal resonator shown in the first embodiment. As shown in FIG. 4, one end of the groove 40 may be formed from a boundary portion between the vibration legs 100 and 110 protruding from the base 30 and the base 30, or one end of the groove may be formed in the base. The boundary portion shown here is a place where the vibrating legs 100 and 110 extend from the base 30 and is indicated by a line segment CC in FIG.

  FIG. 5 is a perspective view of a crystal resonator having an island-shaped inner wall according to the present invention. FIG. 6 is a top view of the crystal resonator (electrode not shown). The groove 41 has one island-like inner wall 71 in the groove 41. The vibration legs 120 and 130 extended from the base 31 perform flexural vibration due to electrostriction due to an applied voltage. The vibration legs 120, 130 include a first vibration leg portion that is reduced in width in the extending direction of the vibration leg from a boundary portion with the base portion 31, and a second vibration leg portion having a certain width, and the first vibration leg An inflection point is generated in the vicinity of the boundary between the first and second vibrating legs, that is, in the vicinity of the line segment DD shown in FIG.

  As shown in FIG. 6, by providing the inner wall 71 in the groove 41 formed in the vibrating legs 120 and 130 on the boundary line DD, the groove 41 is uniform in the depth direction between the side wall of the groove 41 and the inner wall 71. Thickness is obtained, and the shape of the electric field efficiency is the best in the vicinity of the inflection point of the bending vibration by the vibrating legs 120 and 130, and the uniformity of the electrode film formed in the groove 41 is further improved in the direction in which the vibrating legs extend. Can be prioritized.

  FIG. 7 is a further modified perspective view of the crystal resonator shown in the third embodiment. As shown in FIG. 7, an inner wall 71 arranged in a row in an island shape is formed inside the groove 41.

  Further, the inner wall may be formed in a plurality of rows, and FIG. 8 is a plan view of a crystal resonator provided with a central leg having inner walls arranged in two rows in an island shape inside the groove of the present invention. This embodiment is an example in which the present invention is applied to a crystal resonator 12 having a central leg 81 suitable for miniaturization.

  As shown in FIG. 8, the crystal resonator 12 shown in the present embodiment has a center leg 81 disposed between two vibrating legs 140 and 150, and a support portion 80 at the tip of the center leg 81. The crystal unit 11 is fixed by 80 and the center leg 81. By adopting such a structure, the overall length can be shortened compared to the crystal resonator 10 having the structure in which the vibrating legs 100 and 110 protrude from the base 30 as shown in FIG. Yes.

  For this reason, the crystal resonator 12 including the central leg 81 is often used for the purpose of downsizing. However, it is known that the smaller the crystal resonator 12 is, the higher the CI value becomes and the worse it is. As a result, the vibration characteristic is generally deteriorated.

  The form of the present invention shown in the present embodiment is advantageous in that even if the crystal resonator 12 is downsized, the CI value is low and the vibration characteristics are good.

  The crystal resonator 12 including the central leg 81 according to the present invention has electrodes 54 and 55 having different potentials patterned in a desired shape on the vibration piece 22 including the vibration legs 140 and 150 arranged on both sides of the central leg 81. Is formed. Further, the vibrating legs 140 and 150 have grooves 42 formed on the front and back main surfaces along the longitudinal direction of the vibrating legs. Inside the grooves 42, an inner wall 72 that partitions the grooves 42 in the width direction is provided. It is formed in two rows in an island shape along the longitudinal direction of the leg.

  An electrode 54 is formed on the inner side surface of the groove 42 of the vibration leg 140, and an electrode 55 having a potential different from that of the electrode 54 is formed on the outer side surface of the vibration leg 140. On the other hand, an electrode 55 is formed on the inner side surface of the groove 42 of the vibration leg 150, and an electrode 54 having a potential different from that of the electrode 55 is formed on the outer side surface of the vibration leg 150. In this way, by applying a voltage between the outer side surface of the vibrating legs 140 and 150 and the inner side surface of the groove 42, and alternately switching the potential, the vibrating legs 140 and 150 made of quartz, which is a piezoelectric material, Vibrates due to electrostrictive action.

  FIG. 9 is a cross-sectional view of a crystal resonator having a central leg having inner walls arranged in two rows in an island shape according to the present invention. 9A is a view showing a cross section (EE cross section) of the groove 42 in the region where the inner wall 72 is present in FIG. 8, and FIG. 9B is a groove in the region where the inner wall 72 is not present in FIG. It is the figure which showed the cross section of 42 (FF cross section). In addition, in order to explain the content of the present invention in an easy-to-understand manner, the electrodes 54 and 55 are not shown.

  As shown in FIG. 9A, in the EE cross section in which the inner wall 72 exists, the groove 42a is divided into three in the width direction of the vibrating legs 140a and 150a by the inner wall 72, and the cross section is similar to the three grooves. It has a shape. As a result, since the groove 42a has a narrow groove width and a deep depth, the side wall 420a on the inner side of the groove 42a is formed in a shape close to vertical.

  As described above, the inner side wall 420a of the groove 42a is formed in a shape that is nearly vertical, so that the distance (wall thickness) between the outer side wall 320 and the inner side wall 420a of the vibrating legs 140a, 150a is the groove. The distance from the opening side of 42a to the bottom side of the groove 42a can be set to a substantially constant distance, and a potential can be applied between the side wall 320 and the side wall 420a without waste. Thereby, very good electric field efficiency can be obtained.

  Furthermore, the vibration legs 140a and 150a are divided into three parts in the width direction by the inner wall 72 to make the vibration legs 140a and 150a more flexible and easy to vibrate because they have the same cross-sectional shape as the three grooves. The CI value can be further reduced than in the case.

  On the other hand, as shown in FIG. 9B, in the FF cross section where the inner wall 72 does not exist, the groove 42b has the same shape as the cross section of one groove. As a result, the groove 42b has a wide groove width and a very large opening area.

  As described above, the inner wall 72 is partially removed and the opening area of the groove 42b is increased, so that the electrode material reaches deep into the groove 42b in the step of forming the electrode material by sputtering or vapor deposition. It is possible to form a film thickness necessary to obtain a sufficient electric field efficiency deep into the groove 42b. As a result, good electric field efficiency can be obtained.

  Note that when the inner wall 72 is partially formed at regular intervals as in the present invention and the electrode material is deposited, the electrode material wraps around from the gap between the inner wall 72 and the inner wall 72. Even in the region where 72 is present (the region of FIG. 9A), it is possible to form a film thickness necessary to obtain good electric field efficiency deep into the groove 42b.

  Therefore, in the present invention, in the region where the inner wall 72 exists, the electric field efficiency is improved by optimizing the groove shape, and the electric field efficiency is improved by forming the electrodes 54 and 55 with the required film thickness deep into the groove 42a. Both effects can be obtained.

  As described above, the present invention can reduce the CI value even if the crystal resonator 12 includes the center leg 81 suitable for miniaturization. Therefore, the crystal resonator 12 having a small size and excellent vibration characteristics can be obtained. Can be provided.

10, 11, 12, 13, 14 Crystal resonator 20, 21, 22, 23, 24 Vibrating piece 30, 31, 32, 33, 34 Base 40, 41, 42, 43 Groove 44 Small groove 50, 51, 52, 53 , 54, 55, 56, 57, 58, 59 Electrode 70, 71, 72 Inner wall 80 Support portion 81 Central leg 100, 110, 120, 130, 140, 150 Vibrating leg 160, 170, 180, 190 Vibrating leg 200 Resist 300 320, 400a, 400b, 420a, 420b Side wall 500 Electrode film

Claims (1)

A crystal resonator in which an electrode is formed on a resonator element having a groove on a vibration leg, wherein the crystal resonator includes a center leg, the vibration leg disposed on both sides of the center leg, and one end of the center leg. And a support part formed at the other end of the center leg, and is fixed by the support part and the center leg, and the vibration leg is connected to the center leg. A first vibrating leg portion having a reduced width from the connecting portion in the protruding direction and a second vibrating leg portion having a constant width, wherein at least one island-shaped inner wall formed inside the groove includes the first vibrating leg portion; A crystal resonator, wherein the crystal resonator is formed at a boundary portion between one vibration leg and the second vibration leg.

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