JP2011120226A - Elastic-wave device, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further suppress occurrence of trouble caused by heating, in an elastic-wave device composed, by sticking a piezoelectric substrate onto a support substrate via an adhesive layer. <P>SOLUTION: The elastic-wave device 30 includes the piezoelectric substrate 42 formed with electrodes; the support substrate 44; and the adhesive layer 46 for sticking the piezoelectric substrate 42 to the support substrate 44, wherein a swollen part 43 is formed on the piezoelectric substrate 42 to be formed into a projecting shape from the piezoelectric substrate 42 side toward the support substrate 44 side. The elastic-wave device 30 is formed with bent parts 48 on the support substrate 44, and is formed so as to have the outer peripheries from a surface 41 of the piezoelectric substrate 42 reduce, toward the bent parts 48 of the support substrate 44 and to set the sizes of the outer peripheries equal to one another from the bent parts 48 toward the back face 45. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an acoustic wave device and a manufacturing method thereof.

  Conventionally, as a method for manufacturing an acoustic wave device, in a division process of a joined body in which a piezoelectric substrate and a support substrate that supports the piezoelectric substrate are joined, cutting is performed so that the width of the divided piezoelectric substrate is smaller than the width of the support substrate. The thing is proposed (for example, refer patent document 1). In this manufacturing method, first, only the piezoelectric substrate is divided from the surface side of the piezoelectric substrate with a rotary blade made of a material suitable for cutting the piezoelectric substrate, and then the piezoelectric substrate rotary blade is made of a material suitable for dividing the support substrate. The elastic wave device is manufactured by dividing only the support substrate from the back surface side of the support substrate with a narrow rotary blade.

JP 2009-94661 A

  By the way, such an acoustic wave device may be subjected to a high-temperature process step after being cut. However, in the acoustic wave device described in Patent Document 1, the width of the piezoelectric substrate is smaller than the width of the support substrate. However, cracks and the like are generated at the end of the piezoelectric substrate due to the expansion and contraction due to heating. There was something to do.

  The present invention has been made in view of such problems, and an acoustic wave device that can further suppress the occurrence of defects caused by heating in the case where a piezoelectric substrate and a support substrate are bonded together via an adhesive layer. And a manufacturing method thereof.

  As a result of diligent research to achieve the above-described main object, the present inventors formed a bulging portion on the piezoelectric substrate so as to have a convex shape from the piezoelectric substrate side toward the support substrate side. It has been found that the occurrence of the above can be further suppressed, and the present invention has been completed.

That is, the acoustic wave device of the present invention is
A piezoelectric substrate on which electrodes are formed;
A support substrate bonded directly or indirectly to the piezoelectric substrate,
A bulging portion is formed on the piezoelectric substrate so as to have a convex shape from the piezoelectric substrate side toward the support substrate side.

The method for producing an acoustic wave device of the present invention includes:
An acoustic wave device manufacturing method using a composite substrate comprising: a piezoelectric substrate on which an electrode is formed; and a support substrate bonded directly or indirectly to the piezoelectric substrate,
A cutting step of cutting out the acoustic wave device from the composite substrate using a cutting member capable of obtaining a cut surface that forms a bulging portion in which the acoustic wave device has a convex shape from the piezoelectric substrate side toward the support substrate side , Including.

  In this method of manufacturing an acoustic wave device, the bulging portion is formed on the piezoelectric substrate so as to have a convex shape from the piezoelectric substrate side toward the support substrate side. In such an acoustic wave device and a manufacturing method thereof according to the present invention, it is possible to further suppress the occurrence of problems caused by heating. The reason is presumed as follows. For example, a bulging portion is formed on the piezoelectric substrate, and the surface side of the unbonded piezoelectric substrate is formed larger than the surface of the piezoelectric substrate bonded to the support substrate by the adhesive layer. The volume on the surface side with a high degree of freedom is relatively large. Due to the presence of the bulging portion, it is presumed that the stress at the end caused by the expansion / contraction of the support substrate and the piezoelectric substrate, such as when heated, can be relieved.

FIG. 3 is an explanatory diagram showing an outline of the configuration of a composite substrate 10 and an acoustic wave device 30. FIG. 3 is a cross-sectional view schematically showing an example of a manufacturing process of the acoustic wave device 30. FIG. 3 is a cross-sectional view schematically showing an example of a manufacturing process of the acoustic wave device 30. Sectional drawing which shows typically an example of the manufacturing process of the elastic wave device 30B. FIG. 2 is a configuration diagram showing an outline of the configuration of an acoustic wave device 30. The block diagram which shows the outline of a structure of the elastic wave device 30C. Sectional drawing which shows the outline of a structure of the elastic wave device 130 of the comparative example 1. FIG. Sectional drawing which shows the outline of a structure of the elastic wave device 230 of the comparative example 2. FIG. The schematic diagram of the evaluation result of Examples 1-3 and Comparative Examples 1-3.

  Next, modes for carrying out the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of the configuration of a composite substrate 10 and an acoustic wave device 30 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of the manufacturing process of the acoustic wave device 30. The method for manufacturing the acoustic wave device 30 of the present invention includes: (a) a composite substrate manufacturing step of manufacturing a composite substrate in which a piezoelectric substrate and a support substrate are bonded together to form an electrode; and (b) from the piezoelectric substrate side to the support substrate side. A cutting step of cutting out the acoustic wave device from the composite substrate using a cutting member from which a cut surface that forms a bulging portion in which the elastic wave device has a convex shape may be obtained. The acoustic wave device 30 of the present invention may be a surface acoustic wave device, a Lamb wave element, a thin film resonator (FBAR), or the like. For example, a surface acoustic wave device has an IDT (Interdigital Transducer) electrode (also referred to as a comb-shaped electrode or an interdigital electrode) for exciting surface acoustic waves and an IDT on the output side for receiving surface acoustic waves on the surface of a piezoelectric substrate. And an electrode. When a high frequency signal is applied to the IDT electrode on the input side, an electric field is generated between the electrodes, and a surface acoustic wave is excited and propagates on the piezoelectric substrate. Then, the propagated surface acoustic wave can be taken out as an electric signal from the IDT electrode on the output side provided in the propagation direction.

(A) Composite substrate manufacturing step First, in this step, the piezoelectric substrate 12 and the support substrate 14 are bonded together to form a bonded substrate, the outer peripheral surface of the bonded substrate is ground, and the thickness of the piezoelectric substrate is reduced. The surface of the piezoelectric substrate may be mirror-polished. Here, the piezoelectric substrate 12 and the support substrate 14 may be directly bonded, or may be indirectly bonded, for example, via the adhesive layer 16. Here, as shown in FIG. 2, a case where bonding is performed through the bonding layer 16 will be mainly described. As the piezoelectric substrate 12, for example, one or more of lithium tantalate, lithium niobate, lithium niobate-lithium tantalate solid solution, lithium borate, langasite, crystal, and the like can be used. As the support substrate 14, a silicon substrate can be used. The support substrate 14 preferably has a thermal expansion coefficient of 2 to 7 ppm / K when the piezoelectric substrate 12 has a thermal expansion coefficient of 13 to 20 ppm / K. The adhesive layer 16 is preferably formed of an organic adhesive having heat resistance, and for example, an epoxy adhesive or an acrylic adhesive can be used. Next, an electrode is formed on the surface of the piezoelectric substrate 12. The electrodes may be formed by, for example, forming the IDT electrodes 32 and 34 and the reflective electrode 36 on the surface of the piezoelectric substrate 12 as shown in FIG.

(B) Cutting process In this process, as shown in FIG. 2, the composite substrate 10 which is an aggregate | assembly of many surface acoustic wave devices is diced, and the process cut | disconnected to each elastic wave device 30 is performed. Here, those before dicing are referred to as the piezoelectric substrate 12, the support substrate 14, and the adhesive layer 16, respectively, and those after dicing are referred to as the piezoelectric substrate 42, the support substrate 44, and the adhesive layer 46, respectively. In this step, it is assumed that the cutting member 50 is used which provides a cut surface for forming the bulging portion 43 on the piezoelectric substrate 42 in which the elastic wave device has a convex shape from the piezoelectric substrate 12 side toward the support substrate 14 side. Here, the convex shape includes, for example, a shape in which the outer shape becomes smaller from the front surface 41 to the back surface 45 of the acoustic wave device 30. In this cutting process, as shown in FIG. 2, a cutting member 50 which is a rotary blade having a sharp shape toward the tip side is used, and the tip of the cutting member 50 is arranged on the surface 11 side of the piezoelectric substrate. The acoustic wave device 30 may be cut out from the composite substrate 10. In this way, the bulging portion 43 can be formed on the piezoelectric substrate 42 relatively easily by using the tapered tip end side. In this cutting process, as shown in FIG. 2, the acoustic wave device may be cut out from the composite substrate 10 using one cutting member that cuts the support substrate 14 and the piezoelectric substrate 12. By doing so, the support substrate 14 and the piezoelectric substrate 12 can be cut by a single cutting treatment, and thus the work efficiency is good. Alternatively, in this cutting process, as shown in FIG. 3, after the support substrate 14 is cut using the support substrate cutting member 52 capable of cutting the support substrate 14, the piezoelectric substrate cutting member 54 that cuts the piezoelectric substrate 12 is used. The piezoelectric substrate 12 may be cut from the cut support substrate 14 side. In this case, although the cutting process is required twice, damage to the end portions of the support substrate 14 and the piezoelectric substrate 12 can be further suppressed. Further, damage to the support substrate and the piezoelectric substrate can be further suppressed. In the cutting process by the support substrate cutting member 52, the adhesive layer 46 may be cut, or the support substrate 44 may be cut to the vicinity of the surface. As a material of the cutting member, for example, one or more of an electroforming grindstone and a resin grindstone can be used. Moreover, as shown in FIG. 4, it is good also as what uses the cutting member 50B which provided the flat plate part 51B which was a pointed shape toward the front end side, and the thickness does not change at the front end. The tip of the cutting member 50B may be disposed on the surface 11 side of the piezoelectric substrate, and the acoustic wave device 30B may be cut out from the composite substrate 10. In this case, dicing can be performed, and the end portion of the bulging portion 43B can be formed in a flat surface, and damage to the end portion of the piezoelectric substrate 42B can be further suppressed. As described above, when the composite substrate 10 is cut at a predetermined interval using the cutting member, the bulging portion 43 is formed, and the elastic wave device 30 having a convex shape from the piezoelectric substrate 42 side toward the support substrate 44 side. Can be produced. 2 to 6, the electrodes formed on the piezoelectric substrate 42 are omitted.

  Next, the acoustic wave device 30 manufactured in this way will be described. FIG. 5 is a configuration diagram showing an outline of the configuration of the acoustic wave device 30, and FIG. 6 is a configuration diagram showing an outline of the configuration of the acoustic wave device 30C. An acoustic wave device of the present invention includes a piezoelectric substrate on which electrodes are formed, a support substrate, and an adhesive layer that bonds the piezoelectric substrate and the support substrate, and has a convex shape from the piezoelectric substrate side toward the support substrate side. Thus, the piezoelectric substrate is formed with a bulging portion that bulges to the outer peripheral side. As shown in FIG. 5, the elastic wave device 30 has a bent portion 48 formed on the support substrate 44, and the outer periphery decreases from the surface 41 of the piezoelectric substrate 42 toward the bent portion 48 of the support substrate 44. The outer periphery is formed so as to have the same size from the bent portion 48 toward the back surface 45. The acoustic wave device 30 has a continuous outer peripheral surface from the piezoelectric substrate 42 to the support substrate 44 through the adhesive layer 46. In this way, peeling of the adhesive layer on the outer peripheral side can be further suppressed. In the acoustic wave device 30, the piezoelectric substrate 42 has the bonding surface 49 as the surface 41 when the bonding surface 49 is the bonding surface 49 and the surface 41 is the surface opposite to the bonding surface 49. The bulging portion 43 may be formed so that the adhesive surface 49 enters the inside of the surface 41 when projected onto the surface 41 in a direction perpendicular to the surface. If it carries out like this, generation | occurrence | production of the malfunction (for example, crack etc.) which arises when it heats with the bulging part 43 can be suppressed more. In the acoustic wave device 30, an angle θ that is the maximum angle formed by the extended surface of the adhesive surface 49 and the surface of the bulging portion 43 in a cross section that is perpendicular to the adhesive surface 49 and passes through the center of the acoustic wave device 30. May be an acute angle. This is preferable because the bulging portion 43 having a relatively large volume can be formed on the piezoelectric substrate 42. This angle θ is less than 90 °, more preferably 80 ° or less, and further preferably 75 ° or less. Further, the angle θ is preferably more than 0 °, more preferably 20 ° or more, and further preferably 45 ° or more. When the angle θ is 75 ° or less and 45 ° or more, it is preferable because the mechanical strength at the end of the piezoelectric substrate 42 can be further secured. In addition, when the angle θ is set to 45 ° or more, the bulging portion 43 is reduced and the production efficiency is increased.

  Further, as shown in FIG. 6, a bent portion 48C may be formed on the piezoelectric substrate 42C. The elastic wave device 30C can be manufactured by cutting out the composite substrate 10 with the tip of the cutting member 50 described above at a deeper position. The acoustic wave device 30C also has a continuous outer peripheral surface from the piezoelectric substrate 42C through the adhesive layer 46C to the support substrate 44C. The adhesive layer may be formed with a bent portion, or may not have a continuous outer peripheral surface from the piezoelectric substrate through the adhesive layer to the support substrate. Moreover, as shown in FIG. 4, it is good also as the elastic wave device 30B by which the edge part of the bulging part 43B is formed in the plane. The acoustic wave device 30B also has a continuous outer peripheral surface from the piezoelectric substrate 42B through the adhesive layer 46B to the support substrate 44B.

  According to the acoustic wave device and the manufacturing method thereof according to the embodiments described above, the bulging portion is formed on the piezoelectric substrate so as to have a convex shape from the piezoelectric substrate side toward the support substrate side. Can be further suppressed. The reason is presumed as follows. For example, the surface side of the non-bonded piezoelectric substrate is formed larger than the surface of the piezoelectric substrate bonded to the support substrate by the adhesive layer, and the volume on the surface side with a high degree of freedom is relatively high. It is getting bigger. Due to the presence of the bulging portion, it is presumed that the stress at the end caused by the expansion / contraction of the support substrate and the piezoelectric substrate, such as when heated, can be relieved.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the above-described embodiment, the composite substrate manufacturing process is included. However, the composite substrate 10 that has been manufactured may be prepared and the composite substrate manufacturing process may be omitted.

  Hereinafter, an example in which an acoustic wave device is specifically manufactured will be described as an example.

[Production of composite substrate]
First, a lithium tantalate substrate (LT substrate) having an orientation flat part (OF part), a diameter of 100 mm, and a thickness of 250 μm was prepared as a piezoelectric substrate. In addition, a silicon substrate was prepared as a support substrate having an OF portion, a diameter of 100 mm, and a thickness of 350 μm. Here, as the LT substrate, a 42 ° Y-cut X-propagation LT substrate in which the propagation direction of the surface acoustic wave (SAW) is X and the cutting angle is a rotating Y-cut plate is used. Next, an epoxy adhesive is applied to the silicon substrate by spin coating, the LT substrate is attached, heated to 180 ° C., and an adhesive layer (layer in which the epoxy adhesive is solidified) has a thickness of 0.3 μm. Formed. Subsequently, it grind | polished until the thickness of LT board was set to 30 micrometers with the grinder. As the polishing machine, a machine that performs mirror polishing after reducing the thickness as follows was used. That is, when reducing the thickness, a bonded substrate is sandwiched between a polishing platen and a pressure plate, and a slurry containing abrasive grains is supplied between the substrate and the polishing platen. A pressure plate that rotates while pressing the substrate against the surface plate was used. Subsequently, when performing mirror polishing, the polishing surface plate is assumed to have a pad attached to the surface and the abrasive grains are changed to a high count, and by giving rotation and revolution motion to the pressure plate, A piezoelectric substrate whose surface was mirror-polished was used. First, the surface of the LT substrate after grinding was pressed against the surface of the platen, and the rotation speed of the rotation motion was 100 rpm, and polishing was continued for 60 minutes. Subsequently, the polishing surface plate is assumed to have a pad attached to the surface and the abrasive grains are changed to a higher one, the pressure for pressing the substrate against the surface plate after grinding is 0.2 MPa, the rotational speed of the rotation motion Was polished at 100 rpm, the revolution speed was 100 rpm, and the polishing time was 60 minutes. In this embodiment, the step of forming electrodes on the surface of the piezoelectric substrate is omitted.

[Example 1]
The composite substrate produced above was diced to produce an acoustic wave device. Dicing was performed using a cutting member 50 having a sharp tip as shown in FIG. The dicing was carried out at the same speed with a cutting member width of 0.5 mm and a rotational speed of 29000 rpm. As the cutting member 50, one having an angle θ formed by a tangent line from the outer periphery of the bonding surface 49 toward the bulging portion 43 of the piezoelectric substrate 42 and an extension line of the bonding surface 49 is 45 °. The obtained acoustic wave device was defined as Example 1. 1600 elastic wave devices 30 of Example 1 were produced.

[Examples 2 and 3]
Example in which the cutting member 50 is such that the angle θ formed by the tangent line from the outer periphery of the bonding surface 49 toward the bulging portion 43 of the piezoelectric substrate 42 and the extension line of the bonding surface 49 is 60 ° or 75 °. The elastic wave devices obtained through the same steps as in Example 1 were referred to as Examples 2 and 3, respectively. Fifty acoustic wave devices 30 of Examples 2 and 3 were produced.

[Comparative Example 1]
An elastic wave device obtained by dicing the composite substrate produced as described above into a shape shown in FIG. FIG. 7 is a cross-sectional view schematically illustrating the configuration of the acoustic wave device 130 of the first comparative example. In dicing, the width of the cutting member was 0.5 mm, the piezoelectric substrate 142 was cut from the front surface 141 side at a rotation speed of 29000 rpm, and then the support substrate 144 was cut from the back surface 145 side at a rotation speed of 29000 rpm. Here, the piezoelectric substrate 142 was cut so that the angle θ formed by the tangent line from the outer periphery of the adhesive surface 149 of the piezoelectric substrate 142 to the outer peripheral surface of the piezoelectric substrate 142 and the extended line of the adhesive surface 149 was 135 °. 1600 acoustic wave devices 130 of Comparative Example 1 were produced.

[Comparative Example 2]
Comparative Example 1 except that the piezoelectric substrate 142 was cut so that the angle θ formed by the tangent line from the outer periphery of the adhesive surface 149 of the piezoelectric substrate 142 to the outer peripheral surface of the piezoelectric substrate 142 and the extended line of the adhesive surface 149 was 120 °. The elastic wave device obtained through the same steps as in Example 2 was designated as Comparative Example 2. Fifty acoustic wave devices 130 of Comparative Example 2 were produced.

[Comparative Example 3]
An elastic wave device obtained by dicing the composite substrate produced above into a shape shown in FIG. 8, that is, an area on the front surface side and an area on the back surface side, was used as Comparative Example 3. FIG. 8 is a cross-sectional view illustrating a schematic configuration of the acoustic wave device 230 of the third comparative example. In dicing, the piezoelectric substrate 242 was cut from the front surface 241 side under the same conditions as in Comparative Example 1, and then the support substrate 244 was cut from the back surface 245 side. Here, the piezoelectric substrate 242 was cut so that the angle θ formed by the tangent line from the outer periphery of the adhesive surface 249 of the piezoelectric substrate 242 to the outer peripheral surface of the piezoelectric substrate 242 and the extended line of the adhesive surface 249 was 90 °. 1600 elastic wave devices 230 of Comparative Example 3 were produced.

  Next, the chip | tip of the obtained composite substrate of Examples 1-3 and Comparative Examples 1-3 was heat-processed at 260 degreeC in the air. FIG. 9 is a schematic diagram of evaluation results of the acoustic wave devices of Examples 1 to 3 and Comparative Examples 1 to 3 after the heat treatment. Table 1 shows the evaluation results of the heat treatment experiment. As shown in FIG. 9 and Table 1, in Examples 1 to 3, defects such as chipping and cracks at the end of the acoustic wave device were not observed after the heat treatment. On the other hand, in Comparative Examples 1 and 2, it was confirmed that fine cracks were generated on the surface of the piezoelectric substrate after heat treatment in 90% and 84% of the fabricated ones, respectively. Further, in Comparative Example 3, it was confirmed that fine cracks were generated on the surface of the piezoelectric substrate after heat treatment in 70% of the manufactured ones. Therefore, it has been clarified that when the bulging portion is formed on the piezoelectric substrate so as to have a convex shape from the piezoelectric substrate side toward the support substrate side, it is possible to further suppress the occurrence of problems caused by heating.

DESCRIPTION OF SYMBOLS 10 Composite substrate, 12 Piezoelectric substrate, 14 Support substrate, 16 Adhesive layer, 30, 30B, 30C, 130, 230 Elastic wave device, 32, 34 IDT electrode, 36 Reflective electrode, 41, 141, 241 Surface, 42, 42B, 42C, 142, 242 Piezoelectric substrate, 43, 43B, 43C bulge, 44, 44B, 44C, 144, 244 Support substrate, 45, 145, 245 Back surface, 46, 46B, 46C, 146, 246 Adhesive layer, 48, 48B, 48C, 148 Bent part, 49, 149, 249 Adhesive surface, 50, 50B Cutting member, 51B Flat plate part, 52 Support substrate cutting member, 54 Piezoelectric substrate cutting member.

Claims (9)

A piezoelectric substrate on which electrodes are formed;
A support substrate bonded directly or indirectly to the piezoelectric substrate,
An elastic wave device in which a bulging portion is formed in the piezoelectric substrate so as to have a convex shape from the piezoelectric substrate side toward the support substrate side.   The piezoelectric substrate is projected onto the surface in a direction perpendicular to the surface when the side bonded to the support substrate is an adhesive surface and the surface opposite to the adhesive surface is the surface. The elastic wave device according to claim 1, wherein the bulging portion is formed so that the adhesive surface enters the inside of the surface.   The angle θ, which is the maximum angle formed by the extended surface of the adhesive surface and the surface of the bulging portion, is an acute angle in a cross section perpendicular to the adhesive surface and passing through the center of the acoustic wave device. 2. The acoustic wave device according to 2.   The acoustic wave device according to claim 3, wherein the angle θ is in a range of 45 ° ≦ θ ≦ 75 °. It is an elastic wave device given in any 1 paragraph of Claims 1-4,
An acoustic wave device comprising: an adhesive layer that bonds the piezoelectric substrate and the support substrate. An acoustic wave device manufacturing method using a composite substrate comprising: a piezoelectric substrate on which an electrode is formed; and a support substrate bonded directly or indirectly to the piezoelectric substrate,
A cutting step of cutting out the acoustic wave device from the composite substrate using a cutting member capable of obtaining a cut surface that forms a bulging portion in which the acoustic wave device has a convex shape from the piezoelectric substrate side toward the support substrate side A method for manufacturing an acoustic wave device.   In the cutting step, the cutting member having a sharp shape toward the tip side is used, the tip of the cutting member is disposed on the surface side of the piezoelectric substrate, and the acoustic wave device is cut out from the composite substrate. A method for manufacturing an acoustic wave device according to claim 6.   8. The acoustic wave device according to claim 6, wherein, in the cutting step, the acoustic wave device is cut out from the composite substrate using one cutting member that cuts the support substrate and the piezoelectric substrate. Method.   In the cutting step, the support substrate cutting member capable of cutting the support substrate is used to cut the support substrate, and then the piezoelectric substrate cutting member that cuts the piezoelectric substrate is used to cut the piezoelectric substrate from the cut support substrate side. The method for manufacturing an acoustic wave device according to any one of claims 6 to 8, wherein the substrate is cut.

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