Piezoelectric thin film resonators, filters, and multiplexers

Abstract

To provide a piezoelectric thin film resonator capable of suppressing an ESD destroy between a lower electrode and an upper electrode.SOLUTION: A piezoelectric thin film resonator comprises: a substrate 10; a piezoelectric film 14 that is provided on the substrate 10; an upper electrode 16 that is provided on the piezoelectric film 14; a lower electrode 12 which is provided between the substrate 10 and the piezoelectric film 14, forms a resonance region 50 that is overlapped with the upper electrode 16 across the piezoelectric film 14 on a gap 30 formed in a space between itself and the substrate 10, and in which an end surface 11 on a leading region 52 side where the upper electrode 16 is led from the resonance region 50 is positioned on the gap 30 separated from a peripheral edge 31 of the gap 30; and an insulation film 18 which is provided between the gap 30 and the piezoelectric film 14, and in which a lower end 19 of an end surface 17 on the side where the upper electrode 16 is led from the resonance region 50 in the leading region 52 is in contact with the peripheral edge 31 of the gap 30 and the piezoelectric film 14 is in contact with the end surface 17 in a manner to cover it.SELECTED DRAWING: Figure 2

Description

Technical Field

[0004] ,

[0001] The present invention relates to a piezoelectric thin film resonator, a filter, and a multiplexer.

Background Art

[0002] Elastic wave devices using piezoelectric thin film resonators are used, for example, as filters and duplexers for wireless devices such as mobile phones. A piezoelectric thin film resonator has a laminated film in which a piezoelectric film is sandwiched and a lower electrode and an upper electrode face each other. It is known that a dome-shaped void is formed between a substrate and a lower electrode by applying a compressive stress to the laminated film (for example, Patent Documents 1-3). It is also known that changes in film quality are suppressed by covering the lower surface of the lower electrode and the upper surface of the upper electrode with a protective film (for example, Patent Document 4). Furthermore, it is known that an additional film is provided from the inside to the outside of the void in order to suppress deterioration of the piezoelectric film due to stress concentration in the piezoelectric film (for example, Patent Document 5).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] When stress concentrates at the edge of a void, cracks may form from the edge of the void into the piezoelectric film. When cracks occur in the piezoelectric film, ESD (Electrostatic Discharge) failure may occur between the lower electrode and the upper electrode at the site of the crack.

[0005] This invention has been made in view of the above problems, and aims to suppress ESD damage between the lower electrode and the upper electrode. [Means for solving the problem]

[0006] The present invention relates to a substrate, a piezoelectric film provided on the substrate, an upper electrode provided on the piezoelectric film, a lower electrode provided between the substrate and the piezoelectric film, which forms a resonant region overlapping with the upper electrode on the gap formed between the substrate and the piezoelectric film, with the piezoelectric film in between, and whose first end face on the side of the withdrawal region where the upper electrode is drawn out from the resonant region is located on the gap away from the periphery of the gap, and a lower electrode provided between the gap and the piezoelectric film, wherein the lower end of the second end face on the side where the upper electrode is drawn out from the resonant region in the withdrawal region is in contact with the periphery of the gap, or the second end face is located on the gap closer to the periphery of the gap than the first end face of the lower electrode. A facility is provided extending from the periphery of the gap and the first end face of the lower electrode to the lower electrode, so as to cover the first end face of the lower electrode, A piezoelectric thin-film resonator comprising an insulating film that contacts the piezoelectric film so as to cover the second end face. The present invention relates to a substrate, a piezoelectric film provided on the substrate, an upper electrode provided on the piezoelectric film, a lower electrode provided between the substrate and the piezoelectric film, which forms a resonant region overlapping with the upper electrode on the gap formed between the substrate and the piezoelectric film, with the piezoelectric film sandwiched between them, and the first end face on the side of the withdrawal region where the upper electrode is drawn out from the resonant region is located on the gap away from the periphery of the gap, and a lower electrode provided between the gap and the piezoelectric film, which in the withdrawal region is on the side where the upper electrode is drawn out from the resonant region A piezoelectric thin-film resonator comprising: an insulating film in contact with the second end face such that the lower end of the second end face is in contact with the periphery of the gap, or the second end face is located on the gap closer to the periphery of the gap than the first end face of the lower electrode, and the piezoelectric film is in contact with the second end face such that the piezoelectric film covers the second end face, wherein the insulating film is provided between the first end face of the lower electrode and the periphery of the gap such that the third end face opposite to the second end face is located between the first end face of the lower electrode and the periphery of the gap, and the third end face of the insulating film is in contact with the first end face of the lower electrode.

[0007] In the above configuration, the angle between the first end face of the lower electrode and the gap-side face of the lower electrode can be smaller than the angle between the second end face of the insulating film and the gap-side face of the insulating film.

[0008] In the above configuration, the insulating film may not be provided in the central region of the resonance region.

[0011] In the above configuration, the void can have a dome-shaped configuration.

[0012] In the above configuration, the thickness of the insulating film can be set to be 1 / 2 or more of the thickness of the lower electrode.

[0013] In the above configuration, the insulating film can be made of a material with a Young's modulus greater than that of the piezoelectric film.

[0014] The present invention is a filter that includes the piezoelectric thin-film resonator described above.

[0015] The present invention is a multiplexer comprising the filter described above. [Effects of the Invention]

[0016] According to the present invention, ESD damage between the lower electrode and the upper electrode can be suppressed. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1(a) is a plan view of the piezoelectric thin-film resonator according to Example 1, and Figure 1(b) is a cross-sectional view AA of Figure 1(a). [Figure 2] Figure 2(a) is a cross-sectional view of the vicinity of the boundary between the resonance region and the extraction region in Example 1, and Figure 2(b) is an enlarged cross-sectional view of the vicinity of the end of the lower electrode and the end of the insulating film in Figure 2(a). [Figure 3] Figures 3(a) to 3(c) are cross-sectional views (part 1) showing the method for manufacturing a piezoelectric thin-film resonator according to Example 1. [Figure 4] Figures 4(a) to 4(c) are cross-sectional views (part 2) showing the method for manufacturing a piezoelectric thin-film resonator according to Example 1. [Figure 5] Figures 5(a) and 5(b) are cross-sectional views illustrating the problems that arise in the piezoelectric thin-film resonator according to the comparative example. [Figure 6] Figure 6 is a cross-sectional view illustrating the effect of the piezoelectric thin-film resonator according to Example 1. [Figure 7] Figure 7 is a cross-sectional view of a piezoelectric thin-film resonator according to Modification 1 of Example 1. [Figure 8] FIG. 8(a) is a cross-sectional view near the boundary between the resonance region and the lead-out region of the piezoelectric thin-film resonator according to Modification 2 of Example 1, and FIG. 8(b) is an enlarged cross-sectional view near the end face of the insulating film in FIG. 8(a). [Figure 9] FIG. 9(a) is a plan view of the piezoelectric thin-film resonator according to Example 2, and FIG. 9(b) is a cross-sectional view near the boundary between the resonance region and the lead-out region in Example 2. [Figure 10] FIG. 10(a) is a plan view of the piezoelectric thin-film resonator according to Example 3, and FIG. 10(b) is a cross-sectional view near the boundary between the resonance region and the lead-out region in Example 3. [Figure 11] FIG. 11 is a circuit diagram of the filter according to Example 4. [Figure 12] FIG. 12 is a block diagram of the duplexer according to Example 5.

BEST MODE FOR CARRYING OUT THE INVENTION

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

EXAMPLE

[0019] FIG. 1(a) is a plan view of the piezoelectric thin-film resonator 100 according to Example 1, and FIG. 1(b) is a cross-sectional view taken along the line A-A in FIG. 1(a). In FIG. 1(a), the lower electrode 12, the upper electrode 16, the insulating film 18, and the gap 30 are mainly shown. In FIG. 1(a), the contour of the insulating film 18 is shown by a thick line, and the region where the insulating film 18 is provided is hatched. Also, the contour of the gap 30 is shown by a broken line. The plane directions of the substrate 10 are defined as the X direction and the Y direction, and the stacking direction of the stacked film 20 is defined as the Z direction.

[0020] As shown in Figures 1(a) and 1(b), an insulating film 18 is provided on the substrate 10. A dome-shaped void 30 is formed between the flat main surface of the substrate 10 and the insulating film 18. The dome-shaped void 30 is a bulge in which the height of the void 30 is small at the periphery and larger towards the interior of the void 30. The substrate 10 is, for example, a silicon substrate. The insulating film 18 is, for example, silicon nitride (Si3N4).

[0021] A lower electrode 12 is provided on the insulating film 18. The lower electrode 12 is a metal film in which a chromium (Cr) film and a ruthenium (Ru) film are laminated from the substrate 10 side. A piezoelectric film 14 is provided on the lower electrode 12. The piezoelectric film 14 is an aluminum nitride film mainly composed of aluminum nitride (AlN) with the (0001) direction as its principal axis (i.e., having C-axis orientation).

[0022] An upper electrode 16 is provided on the piezoelectric film 14. The upper electrode 16 is a metal film, for example, in which a ruthenium film and a chromium film are laminated from the piezoelectric film 14 side. The region on the gap 30 in which the lower electrode 12 and the upper electrode 16 face each other with at least a portion of the piezoelectric film 14 in between is the resonance region 50. The resonance region 50 is the region in which elastic waves of the thickness longitudinal vibration mode resonate. The planar shape of the resonance region 50 is, for example, approximately elliptical. In a plan view, the size of the gap 30 is larger than the resonance region 50. Note that the planar shape of the resonance region 50 may be a polygon such as a square or pentagon, or other shapes.

[0023] An insertion film 28 is provided within the piezoelectric film 14. The insertion film 28 is provided in the outer peripheral region of the resonance region 50, but not in the central region. The outer peripheral region is a region within the resonance region 50, including the outer periphery of the resonance region 50 and extending along the outer periphery. The central region is a region within the resonance region 50, including the center of the resonance region 50. The central region does not necessarily have to be the geometric center. The insertion film 28 is provided, for example, continuously in the outer peripheral region and the region surrounding the resonance region 50, but it may also be provided only within the resonance region 50. The insertion film 28 is, for example, a silicon oxide film. The insertion film 28 is provided to suppress the leakage of elastic wave energy from the resonance region 50 to the outside.

[0024] A cover film 24 is provided on the upper electrode 16 and the piezoelectric film 14. The cover film 24 may function as a frequency adjustment film and / or protective film. The cover film 24 is an insulating film, such as a silicon oxide film. The laminated film 20 includes an insulating film 18, a lower electrode 12, a piezoelectric film 14, an insertion film 28, an upper electrode 16, and a cover film 24.

[0025] The region to which the upper electrode 16 is drawn out from the resonant region 50 is the extraction region 52. The extraction region 52 is located in the -X direction of the resonant region 50. The planar shape of the piezoelectric film 14 is larger than that of the upper electrode 16. The piezoelectric film 14 is provided in at least the resonant region 50 and the extraction region 52. Note that the wiring is not shown in Figures 1(a) and 1(b).

[0026] Figure 2(a) is a cross-sectional view of the vicinity of the boundary between the resonance region 50 and the extraction region 52 in Example 1, and Figure 2(b) is an enlarged cross-sectional view of the vicinity of the end of the lower electrode 12 and the end of the insulating film 18 in Figure 2(a). As shown in Figures 2(a) and 2(b), the end face 11 of the lower electrode 12 between the resonance region 50 and the extraction region 52 is located on the air gap 30, away from the periphery 31 of the air gap 30 and inward from the air gap 30. The end face 11 of the lower electrode 12 is tapered, and the angle θ1 between the end face 11 and the air gap 30 side surface 25 of the lower electrode 12 is, for example, 60° or less, but may also be 45° or less, or 30° or less.

[0027] The insulating film 18 is provided between the air gap 30 and the piezoelectric film 14. The insulating film 18 is provided between the air gap 30 and the piezoelectric film 14, for example, so as to cover the entire air gap 30. In the withdrawal region 52, the lower end 19 of the end face 17 of the insulating film 18 on the side where the upper electrode 16 is withdrawn from the resonance region 50 is in contact with the periphery 31 of the air gap 30. The distance X between the end face 11 of the lower electrode 12 and the end face 17 of the insulating film 18 is, for example, 1 μm or more. The distance X is, for example, greater than the thickness of the lower electrode 12 and the insulating film 18, and may be, for example, more than twice, more than five times, or more than ten times the thickness of the thicker of the lower electrode 12 and the insulating film 18. The end face 17 of the insulating film 18 is covered by the piezoelectric film 14 and is in contact with the piezoelectric film 14. Therefore, the end of the insulating film 18 is embedded in the piezoelectric film 14. The angle θ2 between the end face 17 of the insulating film 18 and the face 27 of the insulating film 18 on the side of the gap 30 is greater than the angle θ1, for example, 70° or more and 90° or less, and may also be 75° or more and 90° or less, or 80° or more and 90° or less. The thickness of the insulating film 18 is, for example, 1 / 2 or more of the thickness of the lower electrode 12.

[0028] In the extraction region 52, a metal wiring 26 is provided on the upper electrode 16. The metal wiring 26 is made of, for example, gold.

[0029] In addition to a silicon substrate, the substrate 10 can be a sapphire substrate, alumina substrate, spinel substrate, quartz substrate, crystal substrate, glass substrate, ceramic substrate, or GaAs substrate, etc.

[0030] In addition to ruthenium and chromium, the lower electrode 12 and upper electrode 16 can be single-layer films or multilayer films of aluminum (Al), titanium (Ti), copper (Cu), molybdenum (Mo), tungsten (W), tantalum (Ta), platinum (Pt), rhodium (Rh), or iridium (Ir).

[0031] In addition to aluminum nitride, the piezoelectric film 14 can also be made of zinc oxide (ZnO), lead zirconate titanate (PZT), or lead titanate (PbTiO3). Furthermore, the piezoelectric film 14 may primarily consist of aluminum nitride and may contain other elements to improve resonance characteristics or piezoelectricity. The piezoelectricity of the piezoelectric film 14 can be improved by using, for example, scandium (Sc), two elements from group 2 and group 4, or two elements from group 2 and group 5 as additive elements. This improves the effective electromechanical coupling coefficient of the piezoelectric thin-film resonator. Examples of group 2 elements include calcium (Ca), magnesium (Mg), strontium (Sr), or zinc (Zn). Examples of group 4 elements include titanium (Ti), zirconium (Zr), or hafnium (Hf). Examples of group 5 elements include tantalum (Ta), niobium (Nb), or vanadium (V). Furthermore, the piezoelectric film 14 may have aluminum nitride as its main component and may also contain fluorine (F) or boron (B).

[0032] The insulating film 18 is preferably formed from a material with a Young's modulus greater than that of the piezoelectric film 14. Besides silicon nitride, aluminum oxide (Al2O3) or beryllium oxide (BeO) can also be used as the insulating film 18.

[0033] The insertion film 28 is preferably formed from a material with a Young's modulus and / or acoustic impedance lower than that of the piezoelectric film 14. This improves the Q value. In addition to silicon oxide, the insertion film 28 can be a single layer or a multilayer of aluminum (Al), gold (Au), copper (Cu), titanium (Ti), platinum (Pt), tantalum (Ta), or chromium (Cr).

[0034] [Manufacturing method] Figures 3(a) to 4(c) are cross-sectional views showing a method for manufacturing a piezoelectric thin-film resonator 100 according to Example 1. As shown in Figure 3(a), a sacrificial layer 38 is formed on a substrate 10 having a flat main surface to form a void 30. The thickness of the sacrificial layer 38 is, for example, 10 nm to 100 nm. The sacrificial layer 38 is selected from materials that readily dissolve in etching solutions or etching gases, such as magnesium oxide (MgO), zinc oxide, germanium (Ge), or silicon oxide. The sacrificial layer 38 is deposited using, for example, sputtering, vacuum deposition, or CVD (Chemical Vapor Deposition). The sacrificial layer 38 is patterned into a desired shape using photolithography and etching. The sacrificial layer 38 may also be formed by the lift-off method. The shape of the sacrificial layer 38 corresponds to the planar shape of the void 30. Next, an insulating film 18 is formed on the sacrificial layer 38 and the substrate 10. The insulating film 18 is deposited using, for example, sputtering, vacuum deposition, or CVD. The insulating film 18 is patterned into a desired shape using photolithography and etching techniques. At this time, the patterning is done so that the end face 17 of the insulating film 18, which will be located in the extraction region 52 (see Figures 1(a) to 2(a)), substantially coincides with the end face of the sacrificial layer 38. The insulating film 18 may also be formed by the lift-off method.

[0035] As shown in Figure 3(b), a lower electrode 12 is formed on the insulating film 18. The lower electrode 12 is deposited using, for example, sputtering, vacuum deposition, or CVD. The lower electrode 12 is patterned into a desired shape using photolithography and etching techniques. At this time, the patterning is done so that the end face 11 of the lower electrode 12, which will be located on the extraction region 52 side (see Figures 1(a) to 2(a)), is located inward from the end face of the sacrificial layer 38. Furthermore, by adjusting the etching conditions, the patterning is done so that the end face 11 of the lower electrode 12 becomes tapered. The lower electrode 12 may also be formed by the lift-off method.

[0036] As shown in Figure 3(c), the lower piezoelectric film 14a and the insertion film 28 are deposited on the lower electrode 12 and the substrate 10 using, for example, sputtering, vacuum deposition, or CVD. The insertion film 28 is patterned into a desired shape using photolithography and etching techniques. The insertion film 28 may also be formed by the lift-off method.

[0037] As shown in Figure 4(a), the upper piezoelectric film 14b and the upper electrode 16 are deposited on the lower piezoelectric film 14a using, for example, sputtering, vacuum deposition, or CVD. A piezoelectric film 14 is formed from the lower piezoelectric film 14a and the upper piezoelectric film 14b. The upper electrode 16 is patterned into a desired shape using photolithography and etching techniques. The upper electrode 16 may also be formed by the lift-off method.

[0038] As shown in Figure 4(b), the piezoelectric film 14 is patterned into a desired shape using photolithography and etching techniques. Next, the cover film 24 is deposited using, for example, sputtering, vacuum deposition, or CVD, and then patterned into a desired shape using photolithography and etching techniques. The laminated film 20 is formed by the insulating film 18, the lower electrode 12, the piezoelectric film 14, the insertion film 28, the upper electrode 16, and the cover film 24.

[0039] As shown in Figure 4(c), the etching solution for the sacrificial layer 38 is introduced into the sacrificial layer 38 beneath the insulating film 18 via a pre-formed introduction path (not shown) that connects to the sacrificial layer 38. This removes the sacrificial layer 38. The stress of the laminated film 20 is set to compressive stress. As a result, when the sacrificial layer 38 is removed, the laminated film 20 bulges away from the substrate 10 on the opposite side of the substrate 10. A dome-shaped void 30 is formed between the substrate 10 and the insulating film 18. The end face 11 of the lower electrode 12 is located on the void 30, away from the periphery 31 of the void 30 and inward from the void 30, and the lower end 19 of the end face 17 of the insulating film 18 comes into contact with the periphery 31 of the void 30. Thus, the piezoelectric thin film resonator 100 according to Embodiment 1 is formed.

[0040] [Comparative Example] Figures 5(a) and 5(b) are cross-sectional views illustrating the problems that arise in the piezoelectric thin-film resonator according to the comparative example. Figure 5(a) is a cross-sectional view showing the state during the manufacturing process corresponding to Figure 4(b) in the comparative example, and Figure 5(b) is a cross-sectional view showing the state during the manufacturing process corresponding to Figure 4(c). As shown in Figure 5(a), in the comparative example, an insulating film 18 is not provided between the substrate 10 and the lower electrode 12. Also, the lower end of the end face 11 of the lower electrode 12 is formed to substantially coincide with the end of the sacrificial layer 38.

[0041] As shown in Figure 5(b), removing the sacrificial layer 38 forms a dome-shaped void 30 between the substrate 10 and the lower electrode 12. The periphery 31 of the void 30 contacts the substrate 10 at point 40. The lower electrode 12 and the piezoelectric film 14 also contact point 40. As a result, stress tends to concentrate at point 40. For example, if the laminated film 20 is subjected to compressive stress to form the dome-shaped void 30, stress will concentrate at point 40. Also, when the temperature changes, stress caused by the difference in thermal expansion coefficients will concentrate at point 40. The piezoelectric film 14 is brittle because it is formed by sputtering, vacuum deposition, or CVD. For example, when an aluminum nitride film is formed on the substrate 10 using the sputtering method, the aluminum nitride film has a columnar crystalline structure that extends perpendicular to the surface of the substrate 10. As a result, the aluminum nitride film is easily cleaved and prone to cracking. Consequently, cracks 42 originating near the end face 11 of the lower electrode 12 may occur within the piezoelectric film 14. Furthermore, since the substrate 10 is formed from a strong material to support the laminated film 20, it is less prone to cracking. The lower electrode 12 is a metal film, and therefore has high ductility and malleability, making it less prone to cracking.

[0042] If a crack 42 occurs in the piezoelectric film 14, starting near the end face 11 of the lower electrode 12, ESD (Electro-Static Discharge) failure will occur between the lower electrode 12 and the upper electrode 16, leading to defects in performance and other issues.

[0043] [Effects of Example 1] Figure 6 is a cross-sectional view illustrating the effect of the piezoelectric thin-film resonator 100 according to Example 1. As shown in Figure 6, in Example 1, the end face 11 of the lower electrode 12 is located on the air gap 30, away from the periphery 31 of the air gap 30. The end face 17 of the insulating film 18 is located closer to the periphery 31 of the air gap 30 than the end face 11 of the lower electrode 12. As a result, cracks 42 are more likely to occur in the piezoelectric film 14, starting near the end face 17 of the insulating film 18. Therefore, cracks 42 are formed between the insulating film 18 and the upper electrode 16. Thus, ESD fracture between the lower electrode 12 and the upper electrode 16 is suppressed.

[0044] [Differentiation] Figure 7 is a cross-sectional view of the piezoelectric thin-film resonator 110 according to Modification 1 of Example 1. As shown in Figure 7, in Modification 1 of Example 1, a depression is formed on the upper surface of the substrate 10. The insulating film 18 is formed flat on the substrate 10. As a result, a gap 30 is formed by the depression formed on the upper surface of the substrate 10. The other configurations are the same as in Example 1, so their description is omitted.

[0045] Figure 8(a) is a cross-sectional view of the vicinity of the boundary between the resonance region 50 and the extraction region 52 of the piezoelectric thin film resonator 120 according to Modification 2 of Example 1, and Figure 8(b) is an enlarged cross-sectional view of the vicinity of the end face 17 of the insulating film 18a in Figure 8(a). As shown in Figures 8(a) and 8(b), in Modification 2 of Example 1, the end face 17 of the insulating film 18a is located on the air gap 30, away from the periphery 31 of the air gap 30, and closer to the periphery 31 of the air gap 30 than the end face 11 of the lower electrode 12. The distance X1 between the periphery 31 of the air gap 30 and the end face 17 of the insulating film 18a is, for example, 0.1 μm or more and 2 μm or less. The distance X2 between the end face 17 of the insulating film 18a and the end face 11 of the lower electrode 12 is, for example, 1 μm or more and 5 μm or less. The distance X2 is greater than, for example, the thickness of the lower electrode 12 and the insulating film 18, and may be more than twice, five times, or ten times the thickness of the thicker of the two. The distance X1 is shorter than the distance X2, and may be less than or equal to half or one-third of the distance X2. The distance X1 may be less than the thickness of the thicker of the two, and may be less than or equal to half or one-third of that thickness. The other configurations are the same as in Example 1, so their description is omitted.

[0046] In the modified examples 1 and 2 of Example 1, as in Figure 6 of Example 1, cracks 42 tend to originate near the end faces 17 of the insulating films 18 and 18a and form within the piezoelectric film 14. Therefore, since cracks 42 are formed between the insulating films 18 and 18a and the upper electrode 16, ESD fracture between the lower electrode 12 and the upper electrode 16 is suppressed.

[0047] In Example 1 and its modified form, the lower electrode 12 has an end face 11 (first end face) on the extraction region 52 side that is located on the gap 30, away from the periphery 31 of the gap 30. The insulating films 18, 18a have an end face 17 (second end face) on the side where the upper electrode 16 is extracted from the resonance region 50 in the extraction region 52, with the lower end 19 of the end face 17 in contact with the periphery 31 of the gap 30, or the end face 17 is located on the gap 30, closer to the periphery 31 of the gap 30 than the end face 11 of the lower electrode 12. The end faces 17 of the insulating films 18, 18a are covered by the piezoelectric film 14 and are in contact with the piezoelectric film 14. As a result, cracks 42 that occur in the piezoelectric film 14 are more likely to originate near the end faces 17 of the insulating films 18, 18a. Therefore, cracks 42 are formed between the insulating films 18, 18a and the upper electrode 16, and ESD fracture between the lower electrode 12 and the upper electrode 16 can be suppressed.

[0048] Furthermore, according to Example 1 and its modified form, as shown in Figure 2(b), the angle θ1 between the end face 11 of the lower electrode 12 and the surface 25 on the gap 30 side is smaller than the angle θ2 between the end face 17 of the insulating films 18, 18a and the surface 27 on the gap 30 side. In this way, the tapered inclination of the end face 11 of the lower electrode 12 makes it less likely for cracks to originate near the end face 11 of the lower electrode 12 to occur within the piezoelectric film 14. Therefore, ESD fracture between the lower electrode 12 and the upper electrode 16 can be suppressed.

[0049] Furthermore, according to Example 1 and its modified form, the void 30 has a dome shape. In this case, the laminated film 20 is subjected to compressive stress, and stress tends to concentrate at location 40 in Figure 6, making it easier for cracks 42 to occur in the piezoelectric film 14 near location 40. Therefore, it is preferable to keep the end face 11 of the lower electrode 12 away from the periphery 31 of the void 30, and to position the end faces 17 of the insulating films 18, 18a closer to the periphery 31 of the void 30 than the end face 11 of the lower electrode 12.

[0050] Furthermore, according to Example 1 and its modifications, the thickness of the insulating films 18 and 18a is 1 / 2 or more of the thickness of the lower electrode 12. As a result, cracks 42 that occur in the piezoelectric film 14 are more likely to originate near the end faces 17 of the insulating films 18 and 18a, and less likely to originate near the end face 11 of the lower electrode 12. Therefore, ESD failure between the lower electrode 12 and the upper electrode 16 can be suppressed. In order to cause cracks 42 to originate near the end faces 17 of the insulating films 18 and 18a, the thickness of the insulating films 18 and 18a is preferably 2 / 3 or more of the thickness of the lower electrode 12, more preferably 3 / 4 or more, and even more preferably 4 / 5 or more. If the insulating films 18 and 18a are too thick, there is a concern that the piezoelectric thin film resonator 100 will become larger and its characteristics will deteriorate, so the thickness of the insulating films 18 and 18a is preferably 2 times or less of the thickness of the lower electrode 12, more preferably 1.5 times or less, and even more preferably 1 time or less.

[0051] Furthermore, according to Example 1 and its modifications, the insulating films 18 and 18a are formed from a material with a higher Young's modulus than the piezoelectric film 14. As a result, cracks 42 that occur in the piezoelectric film 14 are more likely to originate near the end faces 17 of the insulating films 18 and 18a. [Examples]

[0052] Figure 9(a) is a plan view of the piezoelectric thin-film resonator 200 according to Example 2, and Figure 9(b) is a cross-sectional view of the vicinity of the boundary between the resonance region 50 and the extraction region 52 in Example 2. In Figure 9(a), as in Figure 1(a), the outline of the insulating film 18b is shown with a thick line, and the area where the insulating film 18b is provided is hatched. The outline of the air gap 30 is shown with a dashed line. As shown in Figures 9(a) and 9(b), in the piezoelectric thin-film resonator 200 of Example 2, the insulating film 18b is provided on the air gap 30 between the periphery 31 of the air gap 30 and the end face 11 of the lower electrode 12, and is not provided in the resonance region 50. Therefore, the end face 23 of the insulating film 18b on the lower electrode 12 side is located closer to the periphery 31 of the air gap 30 than to the end face 11 of the lower electrode 12. For example, at least a portion of the end face 23 of the insulating film 18a is in contact with the end face 11 of the lower electrode 12, for example, more than half or all of it is in contact with the end face 11 of the lower electrode 12. Alternatively, a piezoelectric film 14 may be provided between the end face 23 of the insulating film 18b and the end face 11 of the lower electrode 12, so the end face 23 of the insulating film 18b and the end face 11 of the lower electrode 12 are not in contact. The other configurations are the same as in Example 1, so their description is omitted.

[0053] In Example 2, the end face 11 of the lower electrode 12 is located on the gap 30, away from the periphery 31 of the gap 30. The end face 17 of the insulating film 18b is located closer to the periphery 31 of the gap 30 than the end face 11 of the lower electrode 12, and its lower end 19 is in contact with the periphery 31 of the gap 30. The end face 17 of the insulating film 18b is covered by the piezoelectric film 14 and is in contact with the piezoelectric film 14. As a result, as in Example 1, cracks 42 that occur in the piezoelectric film 14 are more likely to start near the end face 17 of the insulating film 18b, and ESD fracture between the lower electrode 12 and the upper electrode 16 can be suppressed.

[0054] Furthermore, according to Example 2, the insulating film 18b is provided between the end face 11 of the lower electrode 12 and the periphery 31 of the air gap 30, such that the end face 23 (third end face) opposite to the end face 17 is located between the end face 11 of the lower electrode 12 and the periphery 31 of the air gap 30. Therefore, the insulating film 18b is not provided in the resonance region 50. This makes it possible to suppress the deterioration of the characteristics of the piezoelectric thin film resonator 200.

[0055] Furthermore, according to Example 2, the end face 23 of the insulating film 18b is in contact with the end face 11 of the lower electrode 12. This makes it possible to suppress the occurrence of cracks in the piezoelectric film 14 from the vicinity of the end face 11 of the lower electrode 12. [Examples]

[0056] Figure 10(a) is a plan view of the piezoelectric thin-film resonator 300 according to Example 3, and Figure 10(b) is a cross-sectional view of the vicinity of the boundary between the resonance region 50 and the extraction region 52 in Example 3. In Figure 10(a), as in Figure 1(a), the outline of the insulating film 18c is shown with a thick line, and the area where the insulating film 18c is provided is hatched. The outline of the air gap 30 is shown with a dashed line. As shown in Figures 10(a) and 10(b), in the piezoelectric thin-film resonator 300 of Example 3, the insulating film 18c is provided extending onto the lower electrode 12 from between the periphery 31 of the air gap 30 and the end face 11 of the lower electrode 12. That is, the insulating film 18c covers the end face 11 of the lower electrode 12 from above. The insulating film 18c is provided in the outer peripheral region 54 of the resonance region 50, but not in the central region 56. The outer peripheral region 54 is a region within the resonant region 50, including the outer periphery of the resonant region 50 and extending along its outer periphery. The central region 56 is a region within the resonant region 50, including the center of the resonant region 50. The central region does not have to be the geometric center. The distance X between the end face 11 of the lower electrode 12 and the end face 23 of the insulating film 18c is, for example, 1 μm or more and 5 μm or less. The distance X is, for example, greater than the thickness of the lower electrode 12 and the insulating film 18, and may be, for example, more than twice, more than three times, or more than five times the thickness of the thicker of the lower electrode 12 and the insulating film 18. The other configurations are the same as in Example 1, so their description is omitted.

[0057] In Example 3, the end face 11 of the lower electrode 12 is located on the gap 30, away from the periphery 31 of the gap 30. The end face 17 of the insulating film 18c is located closer to the periphery 31 of the gap 30 than the end face 11 of the lower electrode 12, and its lower end 19 is in contact with the periphery 31 of the gap 30. The end face 17 of the insulating film 18c is covered by the piezoelectric film 14 and is in contact with the piezoelectric film 14. As a result, as in Example 1, cracks 42 that occur in the piezoelectric film 14 are more likely to originate near the end face 17 of the insulating film 18c, thereby suppressing ESD failure between the lower electrode 12 and the upper electrode 16.

[0058] Furthermore, according to Example 3, the insulating film 18c is not provided in the central region 56 of the resonant region 50. This suppresses the degradation of the characteristics of the piezoelectric thin-film resonator 200.

[0059] Furthermore, according to Example 3, the insulating film 18c is provided extending over the lower electrode 12, from between the periphery 31 of the gap 30 and the end face 11 of the lower electrode 12, so as to cover the end face 11 of the lower electrode 12. This suppresses the occurrence of cracks in the piezoelectric film 14 from the vicinity of the end face 11 of the lower electrode 12. [Examples]

[0060] Figure 11 is a circuit diagram of the filter 400 according to Embodiment 4. As shown in Figure 11, the filter 400 has one or more series resonators S1 to S3 connected in series between the input terminal Tin and the output terminal Tout. One or more parallel resonators P1 and P2 are connected in parallel between the input terminal Tin and the output terminal Tout. The parallel resonators P1 and P2 are connected between the path between the input terminal Tin and the output terminal Tout and the ground terminal. Piezoelectric thin-film resonators according to Embodiments 1 to 3 can be used for one or more series resonators S1 to S3 and at least one of the one or more parallel resonators P1 and P2. The number of resonators in the ladder-type filter can be set as appropriate. [Examples]

[0061] Figure 12 is a block diagram of the duplexer 500 according to Embodiment 5. As shown in Figure 12, the duplexer 500 has a transmit filter 60 connected between the common terminal Ant and the transmit terminal Tx. A receive filter 62 is connected between the common terminal Ant and the receive terminal Rx. The transmit filter 60 allows the transmit band signal from the high-frequency signal input from the transmit terminal Tx to pass to the common terminal Ant as the transmit signal, and suppresses signals of other frequencies. The receive filter 62 allows the receive band signal from the high-frequency signal input from the common terminal Ant to pass to the receive terminal Rx as the receive signal, and suppresses signals of other frequencies. At least one of the transmit filter 60 and the receive filter 62 can be the filter of Embodiment 4. Although a duplexer has been described as an example of a multiplexer, a triplexer or quadplexer may also be used.

[0062] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0063] 10 circuit boards 11 End face of the lower electrode 12 Lower electrode 14 Piezoelectric film 16 Upper electrode 17 End face of insulating film 18, 18a, 18b, 18c insulating film 19 Lower end of the end face of the insulating film 20 Multilayer film 23 End face of insulating film 24 Cover film 25 The side of the gap of the lower electrode 26 Metal wiring 27 The side of the void in the insulating film 28 Insertion membrane 30 void 31 Periphery of the void 38 layers of victims 40 locations 42 Cracks 50 resonance area 52 Drawer area 54 Outer area 56 Central area 60 Sending Filters 62 Receiving Filter 100, 110, 120, 200, 300 piezoelectric thin film resonators 400 filters 500 Duplexa S1, S2, S3 series resonators P1, P2 parallel resonator

Claims

1. circuit board and A piezoelectric film provided on the substrate, An upper electrode provided on the piezoelectric film, A lower electrode is provided between the substrate and the piezoelectric film, forming a resonant region that overlaps with the upper electrode on the gap formed between the substrate and the piezoelectric film, with the upper electrode having a first end face on the side of the withdrawal region where the upper electrode is drawn out from the resonant region, away from the periphery of the gap and located on the gap. A piezoelectric thin film resonator comprising: an insulating film provided between the air gap and the piezoelectric film, wherein in the extraction region, the lower end of the second end face on the side where the upper electrode is extracted from the resonant region is in contact with the periphery of the air gap, or the second end face is located on the air gap closer to the periphery of the air gap than the first end face of the lower electrode, and the insulating film is provided from between the periphery of the air gap and the first end face of the lower electrode to cover the first end face of the lower electrode, and the piezoelectric film is in contact with the second end face.

2. A substrate and A piezoelectric film provided on the substrate, An upper electrode provided on the piezoelectric film, A lower electrode is provided between the substrate and the piezoelectric film, forming a resonant region that overlaps with the upper electrode on the gap formed between the substrate and the piezoelectric film, with the upper electrode having a first end face on the side of the withdrawal region where the upper electrode is drawn out from the resonant region, away from the periphery of the gap and located on the gap. An insulating film is provided between the gap and the piezoelectric film, wherein in the extraction region, the lower end of the second end face on the side where the upper electrode is extracted from the resonance region is in contact with the periphery of the gap, or the second end face is located on the gap closer to the periphery of the gap than the first end face of the lower electrode, and the piezoelectric film is in contact with the second end face so as to cover it. The insulating film is provided between the first end face of the lower electrode and the periphery of the gap, such that the third end face opposite to the second end face is located between the first end face of the lower electrode and the periphery of the gap. The piezoelectric thin-film resonator is such that the third end face of the insulating film is in contact with the first end face of the lower electrode.

3. The piezoelectric thin film resonator according to claim 1 or 2, wherein the angle between the first end face of the lower electrode and the gap-side face of the lower electrode is smaller than the angle between the second end face of the insulating film and the gap-side face of the insulating film.

4. The piezoelectric thin-film resonator according to claim 2, wherein the insulating film is not provided in the central region of the resonant region.

5. The piezoelectric thin-film resonator according to any one of claims 1 to 4, wherein the gap has a dome shape.

6. The piezoelectric thin-film resonator according to any one of claims 1 to 5, wherein the thickness of the insulating film is 1 / 2 or more of the thickness of the lower electrode.

7. The piezoelectric thin-film resonator according to any one of claims 1 to 6, wherein the insulating film is formed of a material with a Young's modulus greater than that of the piezoelectric film.

8. A filter comprising a piezoelectric thin-film resonator according to any one of claims 1 to 7.

9. A multiplexer comprising the filter described in claim 8.

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