JP7382707B2 - Manufacturing method of acoustic wave device - Google Patents

Description

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

As a filter for a mobile communication terminal, an acoustic wave device such as a surface acoustic wave (SAW) device in which an interdigital transducer (IDT) is provided on a piezoelectric substrate is used.

A substrate in which a piezoelectric substrate and a support substrate are bonded together is sometimes used in an acoustic wave device. Patent Document 1 describes a technique for joining a piezoelectric substrate and a supporting substrate by activating their surfaces.

As a technique for dividing a wafer provided with an acoustic wave device such as a comb-shaped electrode into pieces, Patent Document 2 discloses a technique in which a plurality of modified regions are formed in a support substrate by irradiation with a laser, and then the wafer is cut into pieces. The technology to do so is described. Further, Patent Document 3 describes a technique for preventing separation between the piezoelectric substrate and the support substrate by forming a modified region near the bonding interface between the piezoelectric substrate and the support substrate.

Japanese Patent Application Publication No. 2004-343359 JP2014-22966A Japanese Patent Application Publication No. 2004-336503

By making the thickness of the piezoelectric substrate of the SAW device less than or equal to the wavelength of the surface acoustic wave, it is possible to suppress the 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 is repeatedly reflected at the bonding interface between the piezoelectric substrate and the support substrate and the surface of the piezoelectric substrate.

However, a filter that uses an acoustic wave device in which a single-crystal support substrate is bonded to a piezoelectric substrate of the thickness described above has a high frequency band around a frequency of 1.1 to 1.5 times the passband of the filter. There was a problem in which spurious signals were generated. This is thought to be because when the piezoelectric substrate is thin, Lamb waves propagating under 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 the grain boundaries of a polycrystalline substrate are not uniform, the elastic waves reflected at the bonding interface of the support substrate can be scattered, thereby suppressing the generation of spurious waves.

When dividing a polycrystalline support substrate into pieces using the technique described in Patent Document 2, there is a problem in that the support substrate is easily cracked along grain boundaries and is therefore prone to chipping. Furthermore, since the technique described in Patent Document 2 modifies only the support substrate, there is a possibility that the piezoelectric substrate and the support substrate will separate from the edge of the bonding interface. In Patent Document 3, peeling is prevented by forming a modified region at the bonding interface, but since the modified region is not formed on the surface of the piezoelectric substrate, chipping near the surface of the piezoelectric substrate is not taken into account.

In view of the above-mentioned problems, the present invention provides an acoustic wave device and a method for manufacturing an acoustic wave device that can prevent separation between a piezoelectric substrate and a support substrate and suppress chipping when dividing a polycrystalline support substrate into individual pieces. The purpose is to

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

In the above structure, the second region may be formed in a part of a side surface of the support substrate on the piezoelectric substrate side.

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

In the above structure, the supporting substrate may be mainly made of polycrystalline spinel or polycrystalline silicon.

In the above structure, the supporting substrate may be mainly made of single crystal spinel, sapphire, single crystal silicon, or quartz.

In the above structure, the support substrate and the piezoelectric substrate may be bonded to each other via a thin film layer.

In the above structure, the thin film layer may be mainly made of silicon dioxide or aluminum nitride.

The method for manufacturing an acoustic wave device of the present invention includes irradiating a laser onto a substrate in which a piezoelectric substrate and a supporting substrate are bonded together, and applying a laser beam to a part of the piezoelectric substrate and a part of the supporting substrate from the surface of the piezoelectric substrate to the bonded surface. a laser irradiation step of forming a region having a structure different from the crystal structure of the supporting substrate and the piezoelectric substrate downwardly; a groove forming step of forming a groove smaller than the region in the supporting substrate overlapping with the region; and a cutting step of cutting the piezoelectric substrate from the groove.

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

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.

According to the present invention, it is possible to provide an acoustic wave device and a method for manufacturing an acoustic wave device that can suppress the occurrence of chipping and cracking.

FIGS. 1(a) to 1(c) are cross-sectional views showing the process of singulating a conventional acoustic wave device. FIG. 2(a) is a perspective view showing the acoustic wave device according to the first embodiment. FIG. 2(b) is a cross-sectional view taken along line AA in FIG. 2(a). 3(a) to 3(c) are cross-sectional views showing a method (part 1) for manufacturing an acoustic wave device according to Example 1. FIG. FIGS. 4(a) to 4(c) are cross-sectional views showing the method (part 2) for manufacturing the acoustic wave device according to the first embodiment. FIGS. 5A and 5B are cross-sectional views showing the method for manufacturing an acoustic wave device according to Example 1 (part 3). FIGS. 6(a) to 6(c) are cross-sectional views showing another method (part 1) of manufacturing the acoustic wave device according to the first embodiment. FIGS. 7(a) to 7(c) are cross-sectional views showing another method (part 2) of manufacturing the acoustic wave device according to the first embodiment. FIG. 8 is a cross-sectional view showing another method (Part 3) of manufacturing the acoustic wave device according to Example 1. FIG. 9(a) is a perspective view showing an acoustic wave device according to Example 2. FIG. 9(b) is a cross-sectional view taken along line AA in FIG. 9(a). FIGS. 10(a) to 10(c) are cross-sectional views showing a method for manufacturing an acoustic wave device according to Example 2 (part 1). FIGS. 11(a) and 11(b) are cross-sectional views showing the method (part 2) of manufacturing an acoustic wave device according to the second embodiment. FIGS. 12(a) and 12(b) are cross-sectional views showing the method (part 3) for manufacturing an acoustic wave device according to the second embodiment. FIGS. 13(a) and 13(b) are cross-sectional views showing the method for manufacturing an acoustic wave device according to the second embodiment (Part 4). FIG. 14 is a cross-sectional view showing a method for manufacturing an acoustic wave device according to Example 2 (Part 5).

First, a conventional technique for singulating acoustic wave devices will be explained. FIGS. 1(a) to 1(c) are cross-sectional views showing steps of a conventional singulation method. Hereinafter, the upper side of the figure will be referred to as the top, and the lower side will be referred to as the bottom.

As shown in FIG. 1(a), 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 top surface of the piezoelectric substrate 31 using a laser device 34. As shown in FIG. The laser beam 35 is irradiated so that its focal point is located within the support substrate 32, so that it passes through the piezoelectric substrate 31 and forms a plurality of regions 36 within the support substrate 32. The region 36 is a region where the support substrate 32 is melted by the laser 35 and then solidified again.

As shown in FIG. 1(c), the piezoelectric substrate 31 and the support substrate 32 are cut by applying stress. The acoustic wave device 30 can be separated into individual pieces through the above steps. 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, since the crystal grains are irregular, the surface 37 for cutting the acoustic wave device 30 is not cut straight, resulting in chipping of the support substrate 32 and diagonal cracking of the piezoelectric substrate 31. Likely to happen. Further, by applying stress to the piezoelectric substrate 31 and the support substrate 32 during cutting, cracks 38 may occur from the interface where the piezoelectric substrate 31 and the support substrate 32 are joined on the surface 37 side.

Example 1 of the present invention will be described below.

FIG. 2(a) is a perspective view showing the acoustic wave device 10 according to Example 1, and FIG. 2(b) is a sectional view taken along line AA in FIG. 2(a). The elastic wave device 10 is, for example, a SAW device used for a filter. 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. As shown in FIGS. A 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 17a having a crystal structure different from that of the piezoelectric substrate 11 is formed on the side surface of the piezoelectric substrate 11. A second region 17b having a different crystal structure from that of the support substrate 12 is formed on a part of the upper side of the support substrate 12. Region 17a overlaps region 17b. The regions 17a and 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 made 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 less than the wavelength λ of the surface acoustic wave generated in the acoustic wave device 10. When the elastic wave device 10 is used as a 2.4 GHz band filter, λ=1.6 μm. The support substrate 12 is a polycrystalline substrate mainly made of, 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 top surface side of the piezoelectric substrate 11 is 8 μm. The IDT 13 is, for example, Al (aluminum), Cu (copper), or Al--Cu alloy. Grating reflectors may be provided to sandwich the IDT 13.

By providing the amorphous regions 17a and 17b at the ends of the bonding interface between the piezoelectric substrate 11 and the support substrate 12 of the acoustic wave device 10, the mechanical strength of the edges of the bonding interface is increased, and the piezoelectric substrate 11 and the supporting substrate 12 can be expected to have the effect of being difficult to separate from each other. Since the amorphous region 17a reaches the surface of the piezoelectric substrate 11, the amorphous material does not have a cleavage direction, so if microcracks occur at the edge of the piezoelectric substrate 11, the microcracks This prevents the piezoelectric substrate 11 from being damaged along the direction of cleavage starting from the crack.

3(a) to 3(c), FIG. 4(a) to FIG. 4(c), FIG. 5(a), and FIG. 5(b) show a method for manufacturing an acoustic wave device according to Example 1. FIG.

As shown in FIG. 3(a), 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. 3(b), 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. 3(c), an IDT 13 is formed on the piezoelectric substrate 11. The IDT 13 is formed by sputtering or vapor deposition, and patterned by photolithography.

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

Next, as shown in FIG. 4B, the piezoelectric substrate 11 is irradiated with a laser 16 using the laser device 15 to form a first region 17a in the piezoelectric substrate 11. The region 17a 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 in the drawing is the same as the thickness of the piezoelectric substrate 11, and is 1.0 to 5.0 μm. The width of the region 17a in the horizontal direction on the paper is 26 μm, which is the same as the region 17b. The region 17a and the region 17b are formed continuously from the front to the back of the paper.

Next, as shown in FIG. 4(c), a laser 18 is irradiated from the laser device 15. By performing laser ablation processing using the laser 18, the region 17a, the region 17b, 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, a Nd:YAG laser. The output of laser 18 is preferably 1.2 W, which is stronger than laser 16 shown in FIG. 4(b). The spot diameter of the laser 18 is 10 μm. The width of the groove 19 in the horizontal direction of the paper is 10 μm. The depth of the groove 19 from the bonding interface between the support substrate 12 and the piezoelectric substrate 11 is approximately one-tenth of the thickness of the support substrate 12, and is preferably deeper than the depth of the second region. Note that 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 not shown in the drawing for convenience of explanation, when the groove 19 is formed using a laser, the side walls and 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 cut along the grooves 19 formed in FIG. 4C. The cutting method is, 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 as a starting point to cut the piezoelectric substrate 11, or a tape expansion method in which stress is applied by stretching the protective tape 14. At this time, since the regions 17a and 17b have a homogeneous structure, their mechanical strength is strong and cracking and chipping can be suppressed. Furthermore, since the grooves 19 are 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 diced into acoustic wave devices 10 as shown in FIG. 5(b).

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

The process of bonding the piezoelectric substrate 11 and the support substrate 12 together and the process of forming the IDT 13 on the piezoelectric substrate 11 are the same as the processes shown in FIGS. 4(a) to 4(c) of Example 1, and therefore their description will be omitted.

As shown in FIG. 6(a), a protective tape 14a is pasted 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 portion of the support substrate 12 is removed to form a groove 19. The width of the groove 19 in the horizontal direction of the paper 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. 6(c), the above-mentioned protective tape 14a is peeled off from the piezoelectric substrate 11 and IDT 13. A protective tape 14b is attached to the surface of the support substrate 12 on which the groove 19 is formed.

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

As shown in FIG. 7(b), the piezoelectric substrate 11 is irradiated with laser light 16 from the laser device 15. Laser light 16 forms region 17a within piezoelectric substrate 11.

Next, as shown in FIG. 7(c), stress is applied to the piezoelectric substrate 11 and the support substrate 12 to break them. The cutting method is a chocolate break method in which the piezoelectric substrate 11 and the support substrate 12 are cut by applying stress to the grooves 19, or a tape expansion method in which the protective tape 14b is stretched.

Through the above steps, the acoustic wave device 10 can be separated into individual pieces as shown in FIG.

Compared to Example 1, the method for manufacturing the acoustic wave device 10 according to the modified example of Example 1 can reduce the number of laser irradiations to the piezoelectric substrate 11, and can prevent damage to the piezoelectric substrate 11. .

An elastic wave device according to Example 2 will be described below. The dimensions and materials of elements with the same reference numerals as in Example 1 are the same as in Example 1, and their explanations will be omitted.

9(a) is a perspective view showing an acoustic wave device according to Example 2, and FIG. 9(b) is a sectional view taken along line AA in FIG. 9(a). As shown in FIGS. 9A and 9B, a piezoelectric substrate 11 and a support substrate 12 are bonded together with a thin film layer 20 interposed therebetween. The thin film layer 20 is preferably a silicon compound such as SiO2 (silicon dioxide) or AlN (aluminum nitride), and has a thickness of 0.1 μm to 5.0 μm. An IDT 13 is formed on the piezoelectric substrate 11. A first region 17a is formed on a portion of the top surface and side surfaces of the piezoelectric substrate 11. A second region 17b is formed in a part of the upper side of the support substrate 12. An altered region 21 is formed on the side surface of the thin film layer 20 .

In comparison with Example 1, the acoustic wave device 50 according to Example 2 has a structure in which a piezoelectric substrate 11 and a support substrate 12 are joined via a 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.

10(a) to 10(c) are cross-sectional views showing a method for manufacturing an acoustic wave device according to Example 2. FIG. As shown in FIG. 10(a), 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. 10(b), the piezoelectric substrate 11 and the support substrate 12 are bonded to each other at the surfaces on which the thin film layers 20a and 20b shown in FIG. 10(a) are formed. The thin film layer 20 is formed by joining the thin film layer 20a and the thin film layer 20b.

As shown in FIG. 10(c), an IDT 13 is formed on the piezoelectric substrate 11. The IDT 13 is formed by sputtering, vapor deposition, or the like, and patterned by photolithography.

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

As shown in FIG. 11(b), a laser 16 is irradiated from the upper surface side of the piezoelectric substrate 11 using a laser device 15 to form a region 17b 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 within the thin film layer 20. As shown in FIG. 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 in the paper is the same as the thickness of the thin film layer 20, which is 0.1 to 5.0 μm, and the width in the horizontal direction in the paper is 26 μm.

As shown in FIG. 12(b), the piezoelectric substrate 11 is irradiated with a laser 16 to form a region 17a within 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 17a, 17b, the altered region 21, and a portion of the support substrate 12, forming 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. 13(b), the piezoelectric substrate 11 and the support substrate 12 are cut. The cutting method is, for example, the above-mentioned chocolate breaking method or tape expanding method.

Through the above steps, the acoustic wave device 50 can be separated into individual pieces as shown in FIG.

Although the acoustic wave device of the present invention is intended to use a polycrystalline substrate as a support substrate, it is not applicable to an acoustic wave device using a single crystal substrate such as single crystal spinel, single crystal silicon, or sapphire. It's okay.

10, 50 Acoustic wave device 11 Piezoelectric substrate 12 Support substrate 13 IDT
17a First region 17b Second region 21 Altered region

Claims (5)

A laser beam is irradiated onto a substrate on which a piezoelectric substrate and a support substrate are bonded together, and a portion of the piezoelectric substrate and a portion of the support substrate are exposed from the surface of the piezoelectric substrate to the bottom of the bonding surface. a laser irradiation process to form regions with different crystal structures;

After the laser irradiation step, a groove forming step of forming a groove smaller than the region in the supporting substrate in a portion overlapping with the region;

A method for manufacturing an acoustic wave device, including a cutting step of cutting the supporting substrate and the piezoelectric substrate from the groove. 2. The method of manufacturing an acoustic wave device according to claim 1 , wherein the supporting substrate is polycrystalline spinel or polycrystalline silicon. 3. The method for manufacturing an acoustic wave device according to claim 1, wherein in the laser irradiation step, the laser is irradiated from the piezoelectric substrate side. 4. The method of manufacturing an acoustic wave device according to claim 3, wherein in the groove forming step, the groove is formed by irradiating a laser with a spot diameter smaller than the spot diameter in the laser irradiation step. 5. The method for manufacturing an acoustic wave device according to claim 1, wherein in the groove forming step, the groove is formed by removing a part of the region.

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