JP2019201334A - Method for manufacturing acoustic wave device - Google Patents

Abstract

To suppress chipping and cracking when dividing an acoustic wave device into individual pieces.SOLUTION: An acoustic wave device 10 includes: a piezoelectric substrate 11 having a first region 17a; a support substrate 12, formed on the piezoelectric substrate 11, having a second region 17b; and a comb-like electrode 13 provided on the piezoelectric substrate 11. The support substrate 12 is a polycrystalline substrate. Chipping and cracking are suppressed by forming the first region 17a and the second region 17b using a laser.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for manufacturing an acoustic wave device, and more particularly to a technique for individualizing an acoustic wave device.

  As a filter of a portable communication terminal, an acoustic wave device such as a surface acoustic wave (SAW) device in which a comb-like electrode (IDT: Interdigital Transducer) is provided on a piezoelectric substrate is used.

  A substrate obtained by bonding a piezoelectric substrate and a support substrate may be used for the acoustic wave device. Patent Document 1 describes a technique for joining by activating the surfaces of a piezoelectric substrate and a support substrate.

  As a technique for individualizing a wafer provided with an acoustic wave device such as a comb-like electrode, Patent Document 2 irradiates a laser to form a plurality of modified regions in a support substrate, and then cleaves and separates the wafer. The technology to do is described. Patent Document 3 describes a technique for preventing separation of the piezoelectric substrate and the support substrate by forming a modified region in the vicinity of the bonding interface between the piezoelectric substrate and the support substrate.

JP 2004-343359 A JP 2014-22966 A JP 2004-336503 A

  By setting the thickness of the piezoelectric substrate of the SAW device to be equal to or less than the wavelength of the surface acoustic wave, it is possible to suppress generation of leaky bulk waves and reduce insertion loss. A leaky bulk wave is a bulk wave that is generated from a surface acoustic wave, propagates into the piezoelectric substrate, and repeats reflection at the bonding interface between the piezoelectric substrate and the support substrate and the surface of the piezoelectric substrate.

  However, a filter using an acoustic wave device in which a single crystal support substrate is bonded to a piezoelectric substrate having the above thickness has a high frequency around 1.1 to 1.5 times the passband of the filter. There was a problem that spurious was generated. This is probably because when the piezoelectric substrate is thin, Lamb waves propagating below the surface of the piezoelectric substrate are reflected at the bonding interface of the support substrate.

  One method for solving the above problem is to use a polycrystalline substrate such as spinel or polycrystalline silicon as the supporting substrate. Since a polycrystalline substrate has non-uniform crystal grain boundaries, it can scatter elastic waves reflected at the bonding interface of the support substrate and suppress spurious generation.

  When the polycrystalline support substrate is separated into pieces by the technique described in Patent Document 2, the support substrate has a problem that chipping is likely to occur because the support substrate is easily broken along the crystal grain boundary. Further, in the technique described in Patent Document 2, since only the support substrate is modified, there is a possibility that the piezoelectric substrate and the support substrate are separated from the end portion of the bonding interface. In Patent Document 3, peeling is prevented by forming a modified region at the bonding interface, but chipping near the surface of the piezoelectric substrate is not considered because the modified region is not formed on the surface of the piezoelectric substrate.

  In view of the above problems, the present invention provides an acoustic wave device and a method for manufacturing an acoustic wave device that can prevent peeling between a piezoelectric substrate and a support substrate and can suppress chipping when a polycrystalline support substrate is separated. For the purpose.

  The acoustic wave device according to the present invention includes a pair of comb-like electrodes and a piezoelectric substrate having a first region on a side surface provided with the pair of comb-like electrodes and having a crystal structure different from a region overlapping with the comb-like electrodes. And a support substrate that is bonded to the opposite side of the comb-shaped electrode via the piezoelectric substrate and has a second region on the side surface that has a structure different from the crystal structure of the region overlapping the comb-shaped electrode.

  In the above configuration, the first region may be configured to overlap the second region.

  In the above structure, the first region may be amorphous.

  In the above configuration, the first region may be formed on the entire side surface of the piezoelectric substrate.

  In the above structure, the second region may be amorphous.

  The said structure WHEREIN: The said 2nd area | region can be set as the structure currently formed in a part at the side of the said piezoelectric substrate of the side surface of the said support substrate.

  In the above structure, the support substrate may be a polycrystalline substrate.

  The said structure WHEREIN: The said support substrate can be set as the structure which uses a polycrystalline spinel or a polycrystalline silicon as a main material.

  In the above structure, the support substrate may be formed using a single crystal spinel, sapphire, single crystal silicon, or quartz as a main material.

  The said structure WHEREIN: The said support substrate and the said piezoelectric substrate can be set as the structure joined through a thin film layer.

  The said structure WHEREIN: The said thin film layer can be set as the structure which uses silicon dioxide or aluminum nitride as a main material.

  In the method for manufacturing an acoustic wave device of the present invention, a laser beam is applied to a substrate on which a piezoelectric substrate and a support substrate are bonded, and a part of the piezoelectric substrate and a part of the support substrate are joined from the surface of the piezoelectric substrate. A laser irradiation step for forming a region having a structure different from the crystal structure of the support substrate and the piezoelectric substrate, a groove forming step for forming a groove smaller than the region in the support substrate overlapping the region, and the support substrate; And a cleaving step of cleaving the piezoelectric substrate from the groove.

  Further, in the laser irradiation step, the region reaches below the bonding surface from the surface of the piezoelectric substrate and does not reach a surface opposite to the bonding surface of the support substrate.

  Furthermore, in the laser irradiation step, the laser is irradiated from the piezoelectric substrate side.

  Furthermore, in the groove forming step, the groove is formed by irradiating a laser.

  Furthermore, in the groove forming step, the groove is formed by removing a part of the region.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of an elastic wave device and an elastic wave device which can suppress generation | occurrence | production of a chipping and a crack can be provided.

FIG. 1A to FIG. 1C are cross-sectional views illustrating a process of separating a conventional acoustic wave device. FIG. 2A is a perspective view illustrating the acoustic wave device according to the first embodiment. FIG.2 (b) is sectional drawing in the AA line of Fig.2 (a). FIG. 3A to FIG. 3C are cross-sectional views illustrating a method (part 1) for manufacturing an acoustic wave device according to the first embodiment. FIG. 4A to FIG. 4C are cross-sectional views illustrating a method (part 2) for manufacturing an acoustic wave device according to the first embodiment. FIG. 5A and FIG. 5B are cross-sectional views illustrating a method (part 3) for manufacturing an acoustic wave device according to the first embodiment. FIG. 6A to FIG. 6C are cross-sectional views illustrating another manufacturing method (No. 1) of the acoustic wave device according to the first embodiment. FIG. 7A to FIG. 7C are cross-sectional views illustrating another method (part 2) for producing the acoustic wave device according to the first embodiment. FIG. 8 is a cross-sectional view illustrating another method (part 3) for producing the acoustic wave device according to the first embodiment. FIG. 9A is a perspective view illustrating the acoustic wave device according to the second embodiment. FIG. 9B is a cross-sectional view taken along line AA in FIG. FIG. 10A to FIG. 10C are cross-sectional views illustrating a method (part 1) for manufacturing an acoustic wave device according to the second embodiment. FIG. 11A and FIG. 11B are cross-sectional views illustrating a second method for manufacturing an acoustic wave device according to the second embodiment. 12A and 12B are cross-sectional views illustrating a method (part 3) for manufacturing an acoustic wave device according to the second embodiment. FIG. 13A and FIG. 13B are cross-sectional views illustrating a method (part 4) for manufacturing an acoustic wave device according to the second embodiment. FIG. 14 is a cross-sectional view illustrating the method (part 5) for manufacturing the acoustic wave device according to the second embodiment.

  First, a conventional technique for separating an acoustic wave device will be described. FIG. 1A to FIG. 1C are cross-sectional views showing the steps of a conventional singulation method. Hereinafter, the upper side in the figure is the upper side and the lower side is the lower side.

  As shown in FIG. 1A, a piezoelectric substrate 31 and a support substrate 32 are bonded together. An IDT 33 is formed on the surface of the piezoelectric substrate 31. The piezoelectric substrate 31 is a LiTaO3 (lithium tantalate) wafer, and the support substrate 32 is a sapphire wafer.

  As shown in FIG. 1B, a laser 35 is irradiated from the upper surface of the piezoelectric substrate 31 using a laser device 34. Since the laser 35 is irradiated so that the focal point is located in the support substrate 32, the laser 35 passes through the piezoelectric substrate 31 and forms a plurality of regions 36 in the support substrate 32. The region 36 is a region where the support substrate 32 is solidified again after being melted by the laser 35.

  As shown in FIG. 1C, the piezoelectric substrate 31 and the support substrate 32 are cleaved by applying stress. The elastic wave device 30 can be singulated by the above process. The acoustic wave device 30 is, for example, a surface acoustic wave (SAW) device. However, when a polycrystalline substrate is used as the support substrate 32, the surface 37 that cleaves the acoustic wave device 30 does not crack straight because the crystal grains are irregular, and chipping of the support substrate 32 and oblique cracking of the piezoelectric substrate 31 occur. Likely to happen. In addition, when a stress is applied to the piezoelectric substrate 31 and the support substrate 32 at the time of cleaving, a crack 38 may be generated from the interface where the piezoelectric substrate 31 and the support substrate 32 on the surface 37 side are joined.

Embodiment 1 of the present invention will be described below.

  FIG. 2A is a perspective view illustrating the acoustic wave device 10 according to the first embodiment, and FIG. 2B is a cross-sectional view taken along the line AA in FIG. The acoustic wave device 10 is a SAW device used for a filter, for example. As shown in FIGS. 2A and 2B, the configuration of the acoustic wave device 10 includes an IDT 13 formed on a piezoelectric substrate 11. The support substrate 12 is bonded to the surface of the piezoelectric substrate 11 opposite to the surface on which the IDT 13 is formed. A first region 17 a different from the crystal structure of the piezoelectric substrate 11 is formed on the side surface side of the piezoelectric substrate 11. A second region 17 b different from the crystal structure of the support substrate 12 is formed in a part of the upper side surface of the support substrate 12. The region 17a overlaps the region 17b. The region 17a and the region 17b are regions where the piezoelectric substrate 11 and the support substrate 12 are melted and solidified again to become amorphous.

  The members and dimensions of each part of the acoustic wave device 10 will be described. The piezoelectric substrate 11 is mainly composed of, for example, LiTaO3 (lithium tantalate) or LiNbO3 (lithium niobate). The thickness of the piezoelectric substrate 11 is 1.0 to 5.0 μm, and is preferably equal to or less than the wavelength λ of the surface acoustic wave generated in the acoustic wave device 10. When the acoustic wave device 10 is used for a 2.4 GHz band filter, λ = 1.6 μm. The support substrate 12 is a polycrystalline substrate whose main material is, for example, polycrystalline spinel or polycrystalline silicon. The thickness of the support substrate 12 is, for example, 50 μm to 500 μm. The width of the region 17a and the region 17b when viewed from the upper surface side of the piezoelectric substrate 11 is 8 μm. The IDT 13 is, for example, Al (aluminum), Cu (copper), or an Al—Cu alloy. A grating reflector may be provided so as to sandwich the IDT 13.

  By providing the amorphized region 17a and region 17b at the end of the bonding interface between the piezoelectric substrate 11 and the support substrate 12 of the acoustic wave device 10, the mechanical strength at the end of the bonding interface increases, and the piezoelectric substrate 11 and the support substrate 12 can be expected to be difficult to peel off. Since the amorphous region 17 a reaches the surface of the piezoelectric substrate 11, the amorphous material does not have a cleavage directionality. Therefore, when microcracks are generated at the end of the piezoelectric substrate 11, It is possible to prevent the piezoelectric substrate 11 from being damaged along the cleavage direction starting from the crack.

  3A to FIG. 3C, FIG. 4A to FIG. 4C, FIG. 5A, and FIG. 5B show a method for manufacturing an acoustic wave device according to the first embodiment. It is sectional drawing.

  As shown in FIG. 3A, a piezoelectric substrate 11 and a support substrate 12 are prepared. The piezoelectric substrate 11 is a LiTaO3 wafer, and the support substrate 12 is a polycrystalline spinel wafer.

  Next, as shown in FIG. 3B, the piezoelectric substrate 11 and the support substrate 12 are bonded together. As a bonding method, for example, there is a method described in Patent Document 1.

  Next, as shown in FIG. 3C, the IDT 13 is formed on the piezoelectric substrate 11. The IDT 13 is formed by sputtering or vapor deposition, and is patterned by photolithography.

  Next, as shown in FIG. 4A, the protective tape 14 is attached to the lower surface of the support substrate 12. The laser device 15 is used to irradiate the laser 16 from the piezoelectric substrate 11 side, and the second region 17 b is formed in the support substrate 12 through the piezoelectric substrate 11. The depth of the region 17b, that is, the width in the vertical direction of the drawing is substantially the same as that of the piezoelectric substrate 11, and is 1.0 to 5.0 μm. The region 17b does not reach the lower surface. The width of the region 17b in the horizontal direction of the drawing is 26 μm. The laser 16 is, for example, an Nd (neodymium): YAG laser. The output of the laser 16 is preferably 0.8 W. The spot diameter of the laser 16 is 26 μm.

  Next, as shown in FIG. 4B, the laser device 15 is used to irradiate the piezoelectric substrate 11 with the laser 16 to form the first region 17 a in the piezoelectric substrate 11. The region 17 a reaches from the surface of the piezoelectric substrate 11 to the bonding interface with the support substrate 12. The width of the region 17a in the vertical direction of the drawing is the same as the thickness of the piezoelectric substrate 11 and is 1.0 to 5.0 μm. The width in the horizontal direction of the area 17a is 26 μm, which is the same as the area 17b. The region 17a and the region 17b are continuously formed from the front side to the back side of the drawing.

  Next, as shown in FIG. 4C, the laser 18 is irradiated with the laser 18. By performing laser ablation processing using the laser 18, the region 17 a, the region 17 b, and a part of the support substrate 12 are removed, and a groove 19 is formed in the support substrate 12. The laser 18 is, for example, an Nd: YAG laser. The output of the laser 18 is preferably 1.2 W which is stronger than the laser 16 shown in FIG. The spot diameter of the laser 18 is 10 μm. The width of the groove 19 in the horizontal direction of the paper surface is 10 μm. The depth of the groove 19 from the bonding interface between the support substrate 12 and the piezoelectric substrate 11 is about one-tenth of the thickness of the support substrate 12 and is preferably deeper than the depth of the second region. The groove 19 may have a tapered shape in which the width of the side wall becomes narrower as it becomes deeper in the thickness direction of the support substrate 12. Although omitted in the figure for convenience of explanation, when the groove 19 is formed by a laser, the side wall and the bottom of the groove 19 are also made amorphous.

  Next, as shown in FIG. 5A, the piezoelectric substrate 11 and the support substrate 12 are cleaved along the grooves 19 formed in FIG. The cleaving method includes, for example, a chocolate break method in which bending stress is applied to the piezoelectric substrate 11 and the support substrate 12 from the groove 19 to cleave the piezoelectric substrate 11, and a tape expand method in which the protective tape 14 is extended to apply stress. At this time, since the region 17a and the region 17b have a homogeneous structure, the mechanical strength is strong and generation of cracks and chipping can be suppressed. Furthermore, since the groove 19 is formed in the support substrate, the support substrate 12 can be easily cut straight, and chipping can be suppressed.

  Through the above steps, the wafer can be separated into acoustic wave devices 10 as shown in FIG.

[Modification of Example 1]
6A to FIG. 6C, FIG. 7A to FIG. 7C, and FIG. 8 are cross-sectional views showing another method for manufacturing the acoustic wave device according to the first embodiment.

  The step of bonding the piezoelectric substrate 11 and the support substrate 12 and the step of forming the IDT 13 on the piezoelectric substrate 11 are the same as the steps shown in FIGS.

  As shown in FIG. 6A, a protective tape 14a is affixed on the piezoelectric substrate 11 and the IDT 13.

  Next, as shown in FIG. 6 (b), the support substrate 12 is irradiated with a laser 18 from the laser device 15. As a result, a part of the support substrate 12 is removed to form the groove 19. The width of the groove 19 in the horizontal direction of the paper surface is 10 μm. The shape of the groove 19 may be a tapered shape in which the width of the side wall becomes narrower as the groove 19 becomes deeper in the thickness direction of the support substrate 12.

  As shown in FIG. 6C, the above-described protective tape 14 a is peeled off from the piezoelectric substrate 11 and the IDT 13. A protective tape 14b is affixed to the surface of the support substrate 12 where the grooves 19 are formed.

  As shown in FIG. 7A, the laser beam 16 is irradiated from the laser device 15 to the support substrate 12. The laser beam 16 forms a region 17 b in the support substrate 12.

  As shown in FIG. 7B, the laser beam 16 is irradiated from the laser device 15 to the piezoelectric substrate 11. The laser beam 16 forms a region 17 a in the piezoelectric substrate 11.

  Next, as shown in FIG. 7C, the piezoelectric substrate 11 and the support substrate 12 are cleaved by applying stress. The cleaving method is a chocolate break method in which stress is applied to the groove 19 to cleave the piezoelectric substrate 11 and the support substrate 12, or a tape expanding method in which the protective tape 14b is extended.

  As shown in FIG. 8, the acoustic wave device 10 can be singulated by the above steps.

  Compared to the first embodiment, the method for manufacturing the acoustic wave device 10 according to the modification of the first embodiment can reduce the number of times of laser irradiation to the piezoelectric substrate 11 and can prevent the piezoelectric substrate 11 from being damaged. .

  An acoustic wave device according to Example 2 will be described below. The dimensions and materials of the elements denoted by the same reference numerals as in the first embodiment are the same as those in the first embodiment, and the description thereof is omitted.

  FIG. 9A is a perspective view illustrating an acoustic wave device according to the second embodiment, and FIG. 9B is a cross-sectional view taken along line AA of FIG. 9A. As shown in FIGS. 9A and 9B, the piezoelectric substrate 11 and the support substrate 12 are bonded to each other with the thin film layer 20 interposed therebetween. The thin film layer 20 is, for example, a silicon compound such as SiO 2 (silicon dioxide) or AlN (aluminum nitride), and the thickness is preferably 0.1 μm to 5.0 μm. An IDT 13 is formed on the piezoelectric substrate 11. A first region 17 a is formed on a part of the upper surface and the side surface of the piezoelectric substrate 11. A second region 17 b is formed in part of the upper side surface of the support substrate 12. An altered region 21 is formed on the side surface of the thin film layer 20.

  Compared to the first embodiment, the acoustic wave device 50 according to the second embodiment has a structure in which the piezoelectric substrate 11 and the support substrate 12 are bonded via the thin film layer 20. If the thin film layer 20 is made of SiO2, the absolute value of the frequency temperature coefficient can be lowered, and an improvement in temperature characteristics can be expected.

  FIG. 10A to FIG. 10C are cross-sectional views illustrating a method for manufacturing an acoustic wave device according to the second embodiment. As shown in FIG. 10A, a thin film layer 20a and a thin film layer 20b are formed on the piezoelectric substrate 11 and the support substrate 12, respectively. The forming method is, for example, a sputtering method. The thickness of the thin film layer 20a and the thin film layer 20b is 0.05 μm to 2.5 μm.

  As shown in FIG. 10B, the piezoelectric substrate 11 and the support substrate 12 are bonded to each other on the surfaces on which the thin film layer 20a and the thin film layer 20b shown in FIG. 10A are formed. The thin film layer 20 is formed by bonding the thin film layer 20a and the thin film layer 20b.

  As shown in FIG. 10C, the IDT 13 is formed on the piezoelectric substrate 11. The IDT 13 is formed by a sputtering method, a vapor deposition method, or the like, and is patterned by a photolithography technique.

  As shown in FIG. 11A, a protective tape 14 is attached to the support substrate 12.

  As shown in FIG. 11B, a laser beam 16 is irradiated from the upper surface side of the piezoelectric substrate 11 using a laser device 15 to form a region 17 b in the support substrate 12.

  As shown in FIG. 12A, the thin film layer 20 is irradiated with a laser 16 to form an altered region 21 in the thin film layer 20. The altered region 21 is a region where the thin film layer 20 is melted by the laser 16 and solidified again. The width of the altered region 21 in the vertical direction on the paper surface is the same as the thickness of the thin film layer 20 and is 0.1 to 5.0 μm, and the horizontal width on the paper surface is 26 μm.

  As shown in FIG. 12B, the piezoelectric substrate 11 is irradiated with a laser 16 to form a region 17 a in the piezoelectric substrate 11.

  As shown in FIG. 13A, a laser 18 is irradiated from above the piezoelectric substrate 11 using a laser device 15. The laser 18 removes the regions 17 a and 17 b, the altered region 21, and a part of the support substrate 12 to form a groove 19 in the support substrate 12. The depth of the groove 19 from the interface between the thin film layer 20 and the support substrate 12 is preferably about one-tenth of the thickness of the support substrate 12.

  As shown in FIG. 13B, the piezoelectric substrate 11 and the support substrate 12 are cleaved. Examples of the cleaving method include the chocolate break method and the tape expanding method described above.

  The elastic wave device 50 can be separated into individual pieces as shown in FIG.

  The acoustic wave device of the present invention is assumed to use a polycrystalline substrate as a support substrate, but is applied to an acoustic wave device using a single crystal substrate such as single crystal spinel, single crystal silicon, or sapphire. May be.

10, 50 Elastic wave device 11 Piezoelectric substrate 12 Support substrate 13 IDT
17a 1st area | region 17b 2nd area | region 21 Alteration area | region

Claims (16)

A pair of comb-like electrodes;
A piezoelectric substrate provided with the pair of comb-like electrodes and having a first region on a side surface having a crystal structure different from a region overlapping with the comb-like electrodes;
An elastic wave device comprising: a support substrate provided on a side opposite to the comb-like electrode through the piezoelectric substrate and having a second region on a side surface having a crystal structure different from a region overlapping with the comb-like electrode.   The acoustic wave device according to claim 1, wherein the first region overlaps the second region.   The acoustic wave device according to claim 1, wherein the first region is amorphous.   4. The acoustic wave device according to claim 1, wherein the first region is formed on the entire side surface of the piezoelectric substrate. 5.   The elastic device according to claim 1, wherein the second region is amorphous.   6. The acoustic wave device according to claim 1, wherein the second region is formed on a part of the side surface of the support substrate on the piezoelectric substrate side.   The acoustic wave device according to claim 1, wherein the support substrate is a polycrystalline substrate.   The acoustic wave device according to claim 1, wherein the support substrate is mainly made of polycrystalline spinel or polycrystalline silicon.   The acoustic wave device according to any one of claims 1 to 6, wherein the support substrate is mainly composed of single crystal spinel, sapphire, single crystal silicon, or quartz.   The elastic wave device according to claim 1, wherein the support substrate and the piezoelectric substrate are bonded via a thin film layer.   The acoustic wave device according to claim 10, wherein the thin film layer is mainly made of silicon dioxide or aluminum nitride. What is the support substrate and the piezoelectric substrate by irradiating a laser on the substrate on which the piezoelectric substrate and the support substrate are bonded together so that a part of the piezoelectric substrate and a part of the support substrate extend from the surface of the piezoelectric substrate to below the bonding surface? A laser irradiation process for forming regions having different crystal structures;
Forming a groove smaller than the region in a portion overlapping the region in the support substrate; and
And a cleaving step of cleaving the support substrate and the piezoelectric substrate from the groove.   The method of manufacturing a substrate according to claim 12, wherein, in the laser irradiation step, the region reaches from the surface of the piezoelectric substrate below a bonding surface and does not reach a surface opposite to the bonding surface of the support substrate.   14. The method for manufacturing a substrate according to claim 12, wherein in the laser irradiation step, the laser is irradiated from the piezoelectric substrate side.   The substrate manufacturing method according to claim 12, wherein in the groove forming step, the groove is formed by irradiating a laser.   The substrate manufacturing method according to claim 12, wherein in the groove forming step, the groove is formed by removing a part of the region.

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