Elastic wave device, filter and multiplexer

Abstract

To provide electronic components with reduced cracking to a piezoelectric film.SOLUTION: An elastic wave device 100 comprises a substrate 10, a lower electrode 12 provided on the substrate 10 with a void 30 between it and the substrate 10, a piezoelectric film 14 provided on the lower electrode 12, an upper electrode 16 provided on the piezoelectric film 14 to form a resonance region 50 opposite the lower electrode 12 with the piezoelectric film 14 sandwiched over the void 30, and a perimeter 20 having a side contacted by the piezoelectric film 14 around the tip 13 of the lower electrode 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an elastic wave device, a filter, and a multiplexer.

Background Art

[0002] Piezoelectric thin film resonators are used in filters and duplexers for high-frequency circuits of wireless terminals such as mobile terminals. As one of the piezoelectric thin film resonators, FBAR (Film Bulk Acoustic Resonator) is known. The FBAR has a lower electrode, a piezoelectric film, and an upper electrode on a substrate, and a gap is formed between the substrate and the lower electrode in a resonance region where the lower electrode and the upper electrode face each other with the piezoelectric film interposed therebetween. In order to suppress deterioration in the quality of the piezoelectric film, a piezoelectric thin film resonator provided with an additional film on the lower electrode in the peripheral portion of the resonance region is known (for example, Patent Document 1). In order to suppress the generation of cracks in the piezoelectric film, the tip of the lower electrode is positioned above the gap, and the piezoelectric film located between the tip of the lower electrode and the substrate is made to be continuously connected to the surface of the lower electrode on the gap side (for example, Patent Document 2), and further, it is known to provide an additional film in which the end on the lower electrode side is located inside the gap and the opposite end is located outside the gap between the substrate and the piezoelectric film (for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, there is still room for improvement in suppressing the generation of cracks in the piezoelectric film.

[0005] The present invention has been made in view of the above problems, and an object thereof is to suppress the generation of cracks in a piezoelectric film.

Means for Solving the Problems

[0006] The present invention provides an elastic wave device including a substrate, a lower electrode provided on the substrate with a gap therebetween, a piezoelectric film provided on the lower electrode, an upper electrode provided on the piezoelectric film and forming a resonance region sandwiching the piezoelectric film and facing the lower electrode above the gap, and a peripheral portion having a side surface in contact with the piezoelectric film around the tip of the lower electrode.

[0007] In the above configuration, the shortest distance between the tip of the lower electrode and the peripheral portion can be configured to be 2 times or less the thickness of the lower electrode.

[0008] In the above configuration, the piezoelectric film can be configured to be in contact with the gap between the tip of the lower electrode and the peripheral portion.

[0009] In the above configuration, the side surface can be tapered, and the angle formed by the side surface and the substrate can be configured to be 45° or more and 80° or less.

[0010] In the above configuration, the tip surface of the lower electrode can be tapered, and the angle formed by the tip surface of the lower electrode and the surface of the lower electrode on the substrate side can be configured to be 30° or more and 80° or less.

[0011] In the above configuration, the gap can be configured to have an arch shape in a cross-sectional view in which the height of the gap from the substrate is higher at the center than at the peripheral portion of the gap.

[0012] In the above configuration, the peripheral portion is made of an insulating material, provided on all of the outer periphery of the resonance region, the piezoelectric film is provided in a region inside the peripheral portion, and the lower electrode can be configured to be drawn from the inside region to the surface of the peripheral portion opposite to the substrate.

[0013] In the above configuration, the peripheral portion has a first portion containing a metal material and a second portion containing a metal material electrically insulated from the first portion, the piezoelectric film is provided in a region inside the first portion and the second portion, the lower electrode is provided only in the inside region, contacts the side surface of the first portion, and the upper electrode can be configured to contact the surface of the second portion opposite to the substrate.

[0014] The present invention is a filter including the elastic wave device described above.

[0015] The present invention is a multiplexer including the filter described above.

Advantages of the Invention

[0016] According to the present invention, generation of cracks in the piezoelectric film can be suppressed.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Best Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Examples

[0019] Fig. 1(a) is a cross-sectional view of the elastic wave device 100 according to Example 1, and Fig. 1(b) is a cross-sectional view taken along line A-A of Fig. 1(a). The directions orthogonal to each other in the plane direction of the flat surface 11 of the substrate 10 are defined as the X direction and the Y direction, and the normal direction of the flat surface 11 is defined as the Z direction. As shown in Figs. 1(a) and 1(b), the elastic wave device 100 according to Example 1 is a piezoelectric thin film resonator including a lower electrode 12, a piezoelectric film 14, and an upper electrode 16.

[0020] The lower electrode 12 is provided on the flat surface 11 of the substrate 10. A gap 30 is formed between the flat surface 11 of the substrate 10 and the lower electrode 12. The gap 30 has, for example, a dome-shaped bulge. The dome-shaped bulge is a bulge with a shape such that the height of the gap 30 is small around the periphery of the gap 30 and the height of the gap 30 becomes larger toward the inside of the gap 30. Therefore, it can also be said that the gap 30 is arch-shaped in cross-section. The substrate 10 is, for example, a silicon (Si) substrate and has a thickness of, for example, 100 μm to 1000 μm. The lower electrode 12 is, for example, a laminated film of a lower layer that is a chromium (Cr) film and an upper layer that is a ruthenium (Ru) film, and has a thickness of, for example, 30 nm to 400 nm.

[0021] A piezoelectric film 14 is provided on the lower electrode 12. The piezoelectric film 14 is, for example, an aluminum nitride (AlN) film mainly composed of aluminum nitride having the (0001) direction as the main axis (that is, having C-axis orientation). Being mainly composed means that the total of aluminum atoms and nitrogen atoms may be 50 atomic% or more, or may be 80 atomic% or more. The thickness of the piezoelectric film 14 is, for example, 400 nm to 1500 nm. Note that the piezoelectric film 14 may be other than AlN.

[0022] An upper electrode 16 is provided on the piezoelectric film 14. The upper electrode 16 is provided on the piezoelectric film 14 and has a region that sandwiches the piezoelectric film 14 and faces the lower electrode 12 above the gap 30. The region where the lower electrode 12 and the upper electrode 16 face each other with the piezoelectric film 14 sandwiched therebetween is the resonance region 50. The resonance region 50 is a region where elastic waves in the thickness longitudinal vibration mode resonate. The resonance region 50 has, for example, an elliptical shape in plan view. In plan view, the size of the gap 30 is larger than that of the resonance region 50. Note that the resonance region 50 may have a polygonal shape such as a square or a pentagon in plan view. The upper electrode 16 is, for example, a laminated film of a lower layer that is a Ru film and an upper layer that is a Cr film, and has a thickness of 30 nm to 400 nm.

[0023] On the flat surface 11 of the substrate 10, a peripheral portion 20 that completely surrounds the resonance region 50 is provided. The peripheral portion 20 has an upper surface 21, an inner side surface 22, and an outer side surface 23. The peripheral portion 20 has a region having a trapezoidal shape, for example, in a cross-sectional view. Note that the peripheral portion 20 may have a region having another shape such as a semi-elliptical shape, a triangular shape, or an oval shape in addition to the trapezoidal shape.

[0024] The gap 30 is formed on the entire surface of the inner region 24 of the peripheral portion 20. The tip 13 of the lower electrode 12 is separated from the side surface 22 of the peripheral portion 20 and is located above the gap 30. The lower electrode 12 does not contact the flat surface 11 of the substrate 10 due to the gap 30. The lower electrode 12 is drawn out from the inner region 24 of the peripheral portion 20 to the upper surface 21 via the side surface 22. The region where the lower electrode 12 is drawn out from the resonance region 50 is the lead-out region 54. The piezoelectric film 14 is provided in the inner region 24 of the peripheral portion 20. The piezoelectric film 14 contacts the side surface 22 of the peripheral portion 20 around the tip 13 of the lower electrode 12. The piezoelectric film 14 contacts the gap 30 between the tip 13 of the lower electrode 12 and the side surface 22 of the peripheral portion 20. The lower surface of the piezoelectric film 14 is continuously connected to the lower surface of the lower electrode 12. The piezoelectric film 14 does not contact the flat surface 11 of the substrate 10 due to the gap 30. Note that the piezoelectric film 14 may not contact the gap 30 between the tip 13 of the lower electrode 12 and the side surface 22 of the peripheral portion 20. The upper electrode 16 is drawn out from the resonance region 50 to the upper surface 21 of the peripheral portion 20. The region where the upper electrode 16 is drawn out from the resonance region 50 is the lead-out region 52. The peripheral portion 20 is formed of, for example, silicon oxide (SiO2).

[0025] FIG. 2 is an enlarged cross-sectional view of the vicinity of the tip 13 of the lower electrode 12 in Example 1. As shown in FIG. 2, the shortest distance L between the tip 13 of the lower electrode 12 and the side surface 22 of the peripheral portion 20 is, for example, not more than twice the thickness of the lower electrode 12. The side surface 22 of the peripheral portion 20 is tapered, and the angle α formed by the flat surface 11 of the substrate 10 and the side surface 22 of the peripheral portion 20 is, for example, 45° or more and 80° or less. The tip surface 15 of the lower electrode 12 is tapered, and the angle β formed by the surface of the lower electrode 12 on the substrate 10 side and the tip surface 15 of the lower electrode 12 is 30° or more and 80° or less. The angle γ formed by the normal line 27 of the side surface 22 of the peripheral portion 20 and the normal line 17 of the tip surface 15 of the lower electrode 12 is 20° or more and 90° or less.

[0026] As the substrate 10, in addition to a silicon substrate, for example, an insulating substrate or a semiconductor substrate such as a sapphire substrate, a spinel substrate, an alumina substrate, a quartz substrate, a glass substrate, a quartz crystal substrate, a ceramic substrate, or a gallium arsenide substrate can be used. As the lower electrode 12 and the upper electrode 16, in addition to Ru and Cr, for example, a single-layer film of aluminum (Al), titanium (Ti), copper (Cu), molybdenum (Mo), tungsten (W), tantalum (Ta), platinum (Pt), rhodium (Rh), or iridium (Ir), or a laminated film thereof can be used.

[0027] The piezoelectric film 14 mainly contains aluminum nitride and may contain other elements for improving resonance characteristics or piezoelectricity. The additive element is, for example, a combination of a group 3 element, a group 2 element, or a group 12 element and a group 4 element, or a combination of a group 2 element or a group 12 element and a group 5 element. Thereby, the piezoelectricity of the piezoelectric film 14 can be improved, and the effective electromechanical coupling coefficient can be improved. The group 2 element is, for example, magnesium (Mg), calcium (Ca), or strontium (Sr). The group 12 element is, for example, zinc (Zn). The group 4 element is, for example, titanium (Ti), zirconium (Zr), or hafnium (Hf). The group 5 element is, for example, vanadium (V), niobium (Nb), or tantalum (Ta). The group 3 element is, for example, scandium (Sc). Further, the piezoelectric film 14 mainly contains aluminum nitride and may contain fluorine (F) or boron (B).

[0028] In addition to silicon oxide, the peripheral portion 20 may be formed of an insulating material such as silicon nitride (SiN).

[0029] An insulating film such as a silicon oxide film may be provided as a frequency adjustment film and / or a protective film on the upper electrode 16 within the resonance region 50. A frequency adjustment film may be provided within the resonance region 50. An insertion film provided in the outer peripheral region within the resonance region 50 and not provided in the central region may be inserted into the piezoelectric film 14. The insertion film may be a film made of a material having a Young's modulus and / or an acoustic impedance smaller than that of the piezoelectric film 14.

[0030] [Manufacturing Method of Example 1] FIGS. 3(a) to 3(e) are cross-sectional views showing a manufacturing method of the elastic wave device 100 according to Example 1. As shown in FIG. 3(a), the peripheral portion 20 is formed on the flat surface 11 of the substrate 10. The peripheral portion 20 is formed by forming an insulating film such as silicon oxide using a sputtering method, a vacuum evaporation method, or a CVD (Chemical Vapor Deposition) method, and then patterning using a photolithography method and an etching method. The peripheral portion 20 may be formed by a lift-off method.

[0031] As shown in FIG. 3(b), a sacrificial layer 60 for forming a void 30 is formed on the flat surface 11 of the substrate 10 in the region 24 inside the peripheral portion 20. The thickness of the sacrificial layer 60 is, for example, 10 nm to 100 nm. The sacrificial layer 60 is selected from materials that are easily dissolved in an etching solution such as magnesium oxide, zinc oxide, germanium, or silicon oxide. The sacrificial layer 60 is formed by forming a film using a sputtering method, a vacuum evaporation method, or a CVD method, and then patterning using a photolithography method and an etching method. The sacrificial layer 60 may be formed by a lift-off method. The sacrificial layer 60 is formed, for example, over the entire surface of the region 24 inside the peripheral portion 20.

[0032] Next, the lower electrode 12 is formed from above the sacrificial layer 60 to the upper surface 21 of the peripheral portion 20. The lower electrode 12 is formed by depositing a film using a sputtering method, a vacuum evaporation method, or a CVD method, and then patterning it using a photolithography method and an etching method. The lower electrode 12 may be formed by a lift-off method.

[0033] As shown in FIG. 3(c), a piezoelectric film 14 is formed in the region 24 inside the peripheral portion 20. The piezoelectric film 14 is formed by depositing a film using a sputtering method, a CVD method, or an ALD (Atomic Layer Deposition) method, and then removing it using, for example, a CMP (Chemical Mechanical Polishing) method until the upper surface 21 of the peripheral portion 20 is exposed. Instead of the CMP method, the upper surface 21 may be etched using a photolithography method and an etching method until it is exposed. A portion of the lower electrode 12 formed on the upper surface 21 of the peripheral portion 20 is temporarily removed.

[0034] As shown in FIG. 3(d), the upper electrode 16 is formed from above the piezoelectric film 14 to the upper surface 21 of the peripheral portion 20. The upper electrode 16 is formed by depositing a film using a sputtering method, a vacuum evaporation method, or a CVD method, and then patterning it using a photolithography method and an etching method. The upper electrode 16 may be formed by a lift-off method. Simultaneously with the formation of the upper electrode 16, a metal film connected to the lower electrode 12 is formed on the upper surface 21 of the peripheral portion 20. As a result, the lower electrode 12 returns to a shape extending from above the sacrificial layer 60 to the upper surface 21 of the peripheral portion 20.

[0035] As shown in FIG. 3(e), an etching solution is introduced into the sacrificial layer 60 through an introduction path (not shown) formed in advance so as to be connected to the sacrificial layer 60, and the sacrificial layer 60 is removed. The stress of the laminated film of the lower electrode 12, the piezoelectric film 14, and the upper electrode 16 is set to be compressive stress. Thus, when the sacrificial layer 60 is removed, the laminated film bulges away from the substrate 10 on the opposite side of the substrate 10. A gap 30 having a dome-shaped bulge is formed between the flat surface 11 of the substrate 10 and the lower electrode 12.

[0036] [Comparative Example] FIG. 4(a) is a plan view of the elastic wave device 1000 according to the comparative example, and FIG. 4(b) is a cross-sectional view taken along the line A-A of FIG. 4(a). As shown in FIGS. 4(a) and 4(b), in the comparative example, the peripheral portion 20 is not provided on the flat surface 11 of the substrate 10. The tip 13 of the lower electrode 12 is located on the void 30, similar to Example 1. The piezoelectric film 14 is in contact with the void 30 between the tip 13 of the lower electrode 12 and the flat surface 11 of the substrate 10. Since the other configurations are the same as those in Example 1, the description thereof is omitted.

[0037] [Manufacturing Method of Comparative Example] FIGS. 5(a) to 5(e) are cross-sectional views showing the manufacturing method of the elastic wave device 1000 according to the comparative example. As shown in FIG. 5(a), a sacrificial layer 60 for forming the void 30 is formed on the flat surface 11 of the substrate 10. The shape of the sacrificial layer 60 corresponds to the planar shape of the void 30. As shown in FIG. 5(b), the lower electrode 12 is formed on the sacrificial layer 60 and the substrate 10.

[0038] As shown in FIG. 5(c), the piezoelectric film 14 is formed on the lower electrode 12 and the substrate 10. As shown in FIG. 5(d), the upper electrode 16 is formed on the piezoelectric film 14. As shown in FIG. 5(e), the etching solution is introduced into the sacrificial layer 60 through an introduction path (not shown) formed in advance so as to connect to the sacrificial layer 60 to remove the sacrificial layer 60. By setting the stress of the laminated film of the lower electrode 12, the piezoelectric film 14, and the upper electrode 16 to be compressive stress, when the sacrificial layer 60 is removed, the laminated film bulges away from the substrate 10 on the opposite side of the substrate 10, and a dome-shaped bulge void 30 is formed between the flat surface 11 of the substrate 10 and the lower electrode 12.

[0039] Figs. 6(a) and 6(b) are cross-sectional views for explaining problems occurring in the comparative example. Fig. 6(a) is a cross-sectional view before removing the sacrificial layer 60, and Fig. 6(b) is a cross-sectional view after removing the sacrificial layer 60. As shown in Fig. 6(a), the crystal axis 70 of the piezoelectric film 14 formed on the substrate 10 covering the lower electrode 12 and the sacrificial layer 60 extends in the normal direction of the upper surface of the lower electrode 12, the tip surface of the lower electrode 12, the side surface of the sacrificial layer 60, and the upper surface of the substrate 10, respectively. As shown in Fig. 6(b), when the sacrificial layer 60 is removed and the void 30 is formed, cracks 72 along the crystal axis 70 may occur at the locations where the piezoelectric film 14 contacts the void 30 of the piezoelectric film 14. In particular, cracks 72 are likely to occur when the stress of the stacked film of the lower electrode 12, the piezoelectric film 14, and the upper electrode 16 is compressive stress.

[0040] Figs. 7(a) and 7(b) are cross-sectional views for explaining the effects according to Example 1. Fig. 7(a) is a cross-sectional view before removing the sacrificial layer 60, and Fig. 7(b) is a cross-sectional view after removing the sacrificial layer 60. As shown in Fig. 7(a), in Example 1, a peripheral portion 20 is provided around the tip 13 of the lower electrode 12. The piezoelectric film 14 is provided in the region 24 inside the peripheral portion 20 in contact with the side surface 22 of the peripheral portion 20. Therefore, in the region A of the piezoelectric film 14 that contacts the sacrificial layer 60 between the tip 13 of the lower electrode 12 and the side surface 22 of the peripheral portion 20, it is considered that the crystal axes 70 along the normal directions of the tip surface 15 of the lower electrode 12, the upper surface of the sacrificial layer 60, and the side surface 22 of the peripheral portion 20 are mixed. That is, in the region A, it is considered that the piezoelectric film 14 does not become columnar crystals. Therefore, as shown in Fig. 7(b), even when the sacrificial layer 60 is removed and the void 30 is formed, the occurrence of cracks in the piezoelectric film 14 is suppressed.

[0041] [Modification Example] FIG. 8(a) is a plan view of the elastic wave device 110 according to a modified example of Example 1, and FIG. 8(b) is a cross-sectional view taken along line A-A of FIG. 8(a). As shown in FIGS. 8(a) and 8(b), in the modified example of Example 1, the peripheral portion 20 is provided over the entire periphery of the resonance region 50 except for the lead-out region 54 from which the lower electrode 12 is led out, that is, around the tip 13 of the lower electrode 12 (thick line portion). Since the other configurations are the same as those in Example 1, the description thereof is omitted.

[0042] According to Example 1 and its modified example, the peripheral portion 20 is provided around at least the tip 13 of the lower electrode 12 among the periphery of the resonance region 50. The piezoelectric film 14 is in contact with the side surface 22 of the peripheral portion 20 around the tip 13 of the lower electrode 12. Thereby, as shown in FIGS. 7(a) and 7(b), in the region A of the piezoelectric film 14 near the tip 13 of the lower electrode 12, the crystal axes 70 along the normal directions of the tip surface 15 of the lower electrode 12, the upper surface of the sacrificial layer 60, and the side surface 22 of the peripheral portion 20 are mixed. For this reason, even when the sacrificial layer 60 is removed and the void 30 is formed, it is possible to suppress the occurrence of cracks in the piezoelectric film 14.

[0043] Note that the peripheral portion 20 is not limited to being provided over the entire periphery of the tip 13 of the lower electrode 12, and it may be provided at least in a part around the tip 13 of the lower electrode 12. It is preferably provided in 50% or more, more preferably provided in 70% or more, and still more preferably provided in 90% or more.

[0044] Also, in Example 1 and its modification, as shown in FIG. 2, the shortest distance L between the tip 13 of the lower electrode 12 and the peripheral portion 20 is equal to or less than twice the thickness of the lower electrode 12. Thereby, in the region A of the piezoelectric film 14 near the tip 13 of the lower electrode 12, the crystal axes 70 of the piezoelectric film 14 are mixed, making it difficult for cracks to occur in the piezoelectric film 14. From the viewpoint of suppressing crack generation, the shortest distance L is preferably equal to or less than 1.5 times the thickness of the lower electrode 12, more preferably equal to or less than 1.0 times, and even more preferably equal to or less than 0.7 times. It is considered that the characteristics deteriorate when the lower electrode 12 contacts the side surface 22 of the peripheral portion 20. Therefore, it is preferable that the lower electrode 12 does not contact the side surface 22 of the peripheral portion 20.

[0045] Also, in Example 1 and its modification, the piezoelectric film 14 is in contact with the gap 30 between the tip 13 of the lower electrode 12 and the peripheral portion 20. As described in the comparative examples of FIGS. 6(a) and 6(b), when the piezoelectric film 14 is in contact with the gap 30, cracks 72 are likely to occur. However, as in Example 1 and its modification, by providing the peripheral portion 20, the generation of cracks can be suppressed even when the piezoelectric film 14 is in contact with the gap 30. Note that the piezoelectric film 14 may not be in contact with the gap 30 between the tip 13 of the lower electrode 12 and the peripheral portion 20.

[0046] Also, in Example 1 and its modification, as shown in FIG. 2, the side surface 22 of the peripheral portion 20 is tapered, and the angle α formed between the side surface 22 and the substrate 10 is 45° or more and 80° or less. Thereby, in the region A of the piezoelectric film 14 near the tip 13 of the lower electrode 12, the crystal axes 70 of the piezoelectric film 14 are mixed, making it difficult for cracks to occur in the piezoelectric film 14. From the viewpoint of suppressing crack generation, the angle α is preferably 50° or more, more preferably 55° or more, and even more preferably 60° or more.

[0047] In addition, in Example 1 and its modified examples, as shown in FIG. 2, the tip surface 15 of the lower electrode 12 is tapered, and the angle β formed between the tip surface 15 of the lower electrode 12 and the surface on the substrate side is 30° or more and 80° or less. Thereby, in the region A of the piezoelectric film 14 near the tip 13 of the lower electrode 12, the crystal axes 70 of the piezoelectric film 14 are mixed, making it difficult for cracks to occur in the piezoelectric film 14. From the viewpoint of suppressing the occurrence of cracks, the angle β is preferably 35° or more, more preferably 45° or more, and even more preferably 55° or more.

[0048] In addition, in Example 1 and its modified examples, the void 30 has an arch shape in a cross-sectional view where the height of the void 30 from the substrate 10 is higher at the center than at the peripheral portion of the void 30. In the case of the void 30 having such a shape, cracks 72 are likely to occur in the piezoelectric film 14 as described in the comparative examples of FIGS. 6(a) and 6(b). However, the occurrence of cracks can be suppressed by providing the peripheral portion 20 as in Example 1 and its modified examples.

[0049] In addition, in Example 1, the peripheral portion 20 is made of an insulating material and is provided on the entire outer periphery of the resonance region 50. The piezoelectric film 14 is provided in the region 24 inside the peripheral portion 20. The lower electrode 12 is drawn out from the region 24 inside the peripheral portion 20 to the upper surface 21 (the surface opposite to the substrate 10) of the peripheral portion 20. Thereby, since the tip 13 of the lower electrode 12 can be arranged near the peripheral portion 20, in the region A of the piezoelectric film 14 near the tip 13 of the lower electrode 12, the crystal axes 70 of the piezoelectric film 14 are mixed, making it difficult for cracks to occur in the piezoelectric film 14.

Example

[0050] FIG. 9(a) is a plan view of the elastic wave device 200 according to Embodiment 2, and FIG. 9(b) is a cross-sectional view taken along the line A-A of FIG. 9(a). As shown in FIGS. 9(a) and 9(b), in Embodiment 2, the peripheral portion 20a is formed of a metal material such as gold (Au), aluminum (Al), titanium (Ti), chromium (Cr), or copper (Cu). The peripheral portion 20a is divided into a first portion 25 to which the lower electrode 12 is connected and a second portion 26 to which the upper electrode 16 is connected, and an insulator 34 is provided between the first portion 25 and the second portion 26. Therefore, the first portion 25 and the second portion 26 are electrically insulated from each other. The lower electrode 12 contacts the side surface 22 of the first portion 25, and the upper electrode 16 contacts the upper surface 21 of the second portion 26. The insulator 34 may be a void or an insulating film such as a silicon oxide film or a silicon nitride film. Since the other configurations are the same as those in Embodiment 1, the description thereof is omitted.

[0051] According to Embodiment 2, the peripheral portion 20a has a first portion 25 and a second portion 26 each made of a metal material. The first portion 25 and the second portion 26 are electrically insulated from each other by the insulator 34. The lower electrode 12 is provided only in the inner region 24 of the first portion 25 and the second portion 26 and contacts the side surface 22 of the first portion 25. The upper electrode 16 contacts the upper surface 21 (the surface opposite to the substrate 10) of the second portion 26. Thereby, the first portion 25 and the second portion 26 of the peripheral portion 20a can be used as wirings, and the lower electrode 12 does not have to be drawn out to the upper surface 21 of the peripheral portion 20a. Further, the first portion 25 and the second portion 26 can also be used as pads.

Embodiment

[0052] FIG. 10(a) is a plan view of the elastic wave device 300 according to Example 3, and FIG. 10(b) is a cross-sectional view taken along line A-A of FIG. 10(a). As shown in FIGS. 10(a) and 10(b), in Example 3, similar to Example 2, the peripheral portion 20b has a first portion 25a and a second portion 26a that are electrically insulated from each other by an insulator 34. The first portion 25a and the second portion 26a have an insulating portion 62 and a metal film 63 provided on the surface of the insulating portion 62. The lower electrode 12 is in contact with the metal film 63 of the first portion 25a, and the upper electrode 16 is in contact with the metal film 63 of the second portion 26a. The insulating portion 62 is formed of, for example, silicon oxide or silicon nitride. The metal film 63 is formed of, for example, Au, Al, Ti, Cr, or Cu. Since the other configurations are the same as those in Example 1, the description thereof is omitted.

[0053] According to Example 3, the peripheral portion 20b has a first portion 25a and a second portion 26a each including an insulating portion 62 and a metal film 63 provided on the surface of the insulating portion 62. The lower electrode 12 is in contact with the metal film 63 of the first portion 25a, and the upper electrode 16 is in contact with the metal film 63 of the second portion 26a. Even in this case, similar to Example 2, the first portion 25a and the second portion 26a of the peripheral portion 20b can be used as wirings, and the lower electrode 12 does not have to be drawn out to the upper surface 21 of the peripheral portion 20b. Also, the first portion 25a and the second portion 26a can be used as pads. Further, compared with Example 2, the amount of metal material used can be reduced, so that the cost can be reduced particularly when a noble metal is used. Also, compared with Example 1, the adhesion between the peripheral portion 20b and the substrate 10 can be improved.

Example

[0054] FIG. 11(a) is a plan view of the elastic wave device 400 according to Example 4, and FIG. 11(b) is a cross-sectional view taken along line A-A of FIG. 11(a). As shown in FIGS. 11(a) and 11(b), in Example 4, the peripheral portion 20c has a first portion 25b and a second portion 26b that are electrically insulated from each other by an insulator 34, similar to Example 2. The first portion 25b is formed of a metal material. The second portion 26b has a metal portion 64 and an insulating film 65 provided on the side surface of the metal portion 64. The lower electrode 12 is in contact with the side surface 22 of the first portion 25b, and the upper electrode 16 is in contact with the upper surface of the metal portion 64 of the second portion 26b. The metal portion 64 is formed of, for example, Au, Al, Ti, Cr, or Cu. The insulating film 65 is formed of, for example, silicon oxide or silicon nitride. Since the other configurations are the same as those in Example 1, the description thereof is omitted.

[0055] According to Example 4, the peripheral portion 20c is formed only of a metal material, includes a first portion 25b with which the lower electrode 12 is in contact, a metal portion 64, and an insulating film 65 provided on the side surface thereof, and has a second portion 26b with which the upper electrode 16 is in contact with the metal portion 64. Even in this case, similar to Example 2, the first portion 25b and the second portion 26b of the peripheral portion 20c can be used as wirings, and it is not necessary to draw out the lower electrode 12 to the upper surface 21 of the peripheral portion 20c. Also, the first portion 25b and the second portion 26b can be used as pads. Further, since the insulating film 65 exists between the metal portion 64 of the second portion 26b and the lower electrode 12, a short circuit between the metal portion 64 and the lower electrode 12 can be suppressed. For example, even if the lower electrode 12 is arranged closer to the second portion 26b to suppress the generation of cracks in the piezoelectric film 14, a short circuit between the metal portion 64 and the lower electrode 12 can be suppressed.

Example

[0056] Example 5 is an example in which the configuration of the voids is changed. FIG. 12(a) is a cross-sectional view of the elastic wave device according to Example 5. As shown in FIG. 12(a), in the elastic wave device 500 of Example 5, a depression is formed on the upper surface of the substrate 10. The lower electrode 12 is formed flat on the substrate 10. As a result, the void 30 is formed by the depression of the substrate 10. Other configurations are the same as those of Example 1 and the description thereof is omitted. The void 30 may be formed so as to penetrate the substrate 10.

Example

[0057] FIG. 12(b) is a circuit diagram of the filter 600 according to Example 6. As shown in FIG. 12(b), one or more series resonators S1 to S4 are connected in series between the input terminal Tin and the output terminal Tout. One or more parallel resonators P1 to P3 are connected in parallel between the input terminal Tin and the output terminal Tout. The parallel resonators P1 to P3 are connected between the path between the input terminal Tin and the output terminal Tout and the ground terminal. The elastic wave devices according to Example 1, the modified example of Example 1, and Examples 2 to 5 can be used for at least one resonator of the series resonators S1 to S4 and the parallel resonators P1 to P3. The number of resonators of the ladder-type filter can be set as appropriate.

[0058] FIG. 12(c) is a circuit diagram of the duplexer 610 according to a modified example of Example 6. As shown in FIG. 12(c), a transmission filter 80 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 82 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 80 passes the signal in the transmission band among the signals input from the transmission terminal Tx as a transmission signal to the common terminal Ant and suppresses signals of other frequencies. The reception filter 82 passes the signal in the reception band among the signals input from the common terminal Ant as a reception signal to the reception terminal Rx and suppresses signals of other frequencies. At least one of the transmission filter 80 and the reception filter 82 can be the filter according to Example 5. Although the duplexer has been described as an example of the multiplexer, a triplexer or a quadruplexer may be used.

[0059] Note that the elastic wave device is not limited to the above case, and it may also be a MEMS or a sensor.

[0060] As described above in detail are the embodiments of the present invention. However, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0061] 10... substrate, 11... flat surface, 12... lower electrode, 13... tip, 14... piezoelectric film, 15... tip surface, 16... upper electrode, 17... normal line, 20, 20a... peripheral part, 21... upper surface, 22... side surface, 23... side surface, 24... inner region, 25, 25a, 25b... first part, 26, 26a, 26b... second part, 27... normal line, 30... gap, 50... resonance region, 52... lead-out region, 54... lead-out region, 60... sacrificial layer, 62... insulating part, 63... metal film, 64... metal part, 65... insulating film, 70... crystal axis, 72... crack, 80... transmitting filter, 82... receiving filter, 100, 110, 200, 300, 400, 500, 1000... elastic wave device, 600... filter, 610... duplexer

Claims

1. A substrate, a lower electrode provided on the substrate with a gap therebetween, a piezoelectric film provided on the lower electrode, an upper electrode provided on the piezoelectric film and forming a resonance region that sandwiches the piezoelectric film over the gap and faces the lower electrode, and a peripheral portion having a side surface in contact with the piezoelectric film around a tip of the lower electrode, the elastic wave device comprising the same.

2. The elastic wave device according to claim 1, wherein a shortest distance between a tip of the lower electrode and the peripheral portion is not more than twice a thickness of the lower electrode.

3. The elastic wave device according to claim 1 or 2, wherein the piezoelectric film is in contact with the gap between a tip of the lower electrode and the peripheral portion.

4. The elastic wave device according to claim 1 or 2, wherein the side surface is tapered, and an angle formed between the side surface and the substrate is 45° or more and 80° or less.

5. The elastic wave device according to claim 4, wherein a tip surface of the lower electrode is tapered, and an angle formed between the tip surface of the lower electrode and a surface of the lower electrode on the substrate side is 30° or more and 80° or less.

6. The elastic wave device according to claim 1 or 2, wherein the gap has an arch shape in a cross-sectional view in which a height of the gap from the substrate is higher at a central portion than at a peripheral portion thereof.

7. The peripheral portion is made of an insulating material and is provided over an entire outer periphery of the resonance region, the piezoelectric film is provided in a region inside the peripheral portion, and the lower electrode is drawn out from the inside region to a surface of the peripheral portion opposite to the substrate. The elastic wave device according to claim 1 or 2.

8. The peripheral portion has a first portion containing a metal material and a second portion containing a metal material electrically insulated from the first portion, the piezoelectric film is provided in a region inside the first portion and the second portion, the lower electrode is provided only in the inside region and is in contact with a side surface of the first portion, and the upper electrode is in contact with a surface of the second portion opposite to the substrate. The elastic wave device according to claim 1 or 2.

9. A filter including the elastic wave device according to claim 1 or 2.

10. A multiplexer including the filter according to claim 9.

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