JP7027144B2 - Elastic wave devices and their manufacturing methods and multiplexers - Google Patents

Description

The present invention relates to an elastic wave device, a method for manufacturing the same, and a multiplexer, for example, an elastic wave device having a piezoelectric thin film resonator, a method for manufacturing the same, and a multiplexer.

Elastic wave devices using piezoelectric thin film resonators are used as filters and duplexers for wireless devices such as mobile phones. The piezoelectric thin film resonator has a laminated structure in which a lower electrode and an upper electrode face each other with a piezoelectric film interposed therebetween. The region where the lower electrode and the upper electrode face each other across the piezoelectric film is the resonance region. It is known that the film thickness of the piezoelectric film is different in a plurality of piezoelectric thin film resonators using a single piezoelectric film (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-24995

In order to make the resonance frequency different in the piezoelectric thin film resonator using a single piezoelectric film, the thickness of the piezoelectric film is made different as in Patent Document 1, or a mass addition film is provided in some of the piezoelectric thin film resonators. Do that. Therefore, the manufacturing method becomes complicated. When piezoelectric thin film resonators having different resonance frequencies are formed of different piezoelectric films, miniaturization becomes difficult.

The present invention has been made in view of the above problems, and an object of the present invention is to facilitate manufacturing or to reduce the size.

INDUSTRIAL APPLICABILITY The present invention is provided on a substrate and a surface of the substrate, and becomes continuously thicker from one of the first directions parallel to the surface of the substrate to the other , and is parallel to the surface and said to the first. The rate of change in the thickness of the piezoelectric film along the second direction intersecting in one direction is smaller than the rate of change in the thickness of the piezoelectric film along the first direction . A plurality of first lower electrodes provided between the substrate and the piezoelectric film, and a first upper electrode facing the first lower electrode with a part of the piezoelectric film interposed therebetween. A plurality of first piezoelectric thin film resonators are provided along the second direction on the other side of the first piezoelectric thin film resonator from the plurality of first piezoelectric thin film resonators, and are provided between the substrate and the piezoelectric film. It is an elastic wave device including a plurality of second piezoelectric thin film resonators having a second lower electrode and a second upper electrode facing the second lower electrode with a part of the piezoelectric film interposed therebetween.

In the above configuration, a plurality of first series resonators provided in the first path from the first input terminal to the first output terminal, each of which is the plurality of first piezoelectric thin film resonators, and one end of which is electrically connected to the first path. A first ladder type filter having a plurality of first parallel resonators, each of which is electrically connected to the ground and the other end thereof is electrically connected to the ground, can be configured.

In the above configuration, a plurality of third lower portions are provided along the second direction on the other side of the first direction with respect to the plurality of second piezoelectric thin film resonators, and are provided between the substrate and the piezoelectric film. A plurality of third piezoelectric thin-film resonators having an electrode and a third upper electrode having an electrode and a third upper electrode facing the third lower electrode with a part of the piezoelectric film sandwiched therein, and the first more than the plurality of third piezoelectric thin-film resonators. A plurality of fourth lower electrodes provided along the second direction on the other side of one direction and provided between the substrate and the piezoelectric film, and the fourth lower electrode sandwiching a part of the piezoelectric film. A plurality of fourth piezoelectric thin film resonators having facing fourth upper electrodes, and the plurality of third piezoelectric thin film resonators connected in series to a second path from the second input terminal to the second output terminal, respectively. A plurality of second series resonators, one end of which is electrically connected to the second path and the other end of which is electrically connected to the ground, and a plurality of second parallel resonators, each of which is the plurality of fourth piezoelectric thin film resonators. It can be configured to include a second rudder type filter having a device and having a passing band lower than the passing band of the first rudder type filter.

In the above configuration, the thickness of the piezoelectric film can be substantially constant along the second direction.

The present invention is a multiplexer including the elastic wave device.

INDUSTRIAL APPLICABILITY The present invention is provided on a substrate and a surface of the substrate, and becomes continuously thicker from one of the first directions parallel to the surface of the substrate to the other, and is parallel to the surface and the first. The rate of change in the thickness of the piezoelectric film along the second direction intersecting the directions is smaller than the rate of change in the thickness of the piezoelectric film along the first direction with a single piezoelectric film and along the second direction. A plurality of the first lower electrodes are provided, which are provided in the first path from the common terminal to the first terminal, and the first lower electrode provided between the substrate and the piezoelectric film, and a part of the piezoelectric film are sandwiched between the first lower electrode. A plurality of first series resonators having a first upper electrode facing the electrode, one end electrically connected to the first path and the other end electrically connected to the ground, said the plurality of first series. A plurality of second lower electrodes provided along the second direction on the other side of the first direction with respect to the resonator, and a second lower electrode provided between the substrate and the piezoelectric film, and a part of the piezoelectric film are sandwiched. A first ladder type filter comprising a plurality of first parallel resonators having a second upper electrode facing the second lower electrode and a second path from the common terminal to the second terminal. A plurality of third lower electrodes provided along the second direction on the other side of the first direction than the plurality of first parallel resonators and provided between the substrate and the piezoelectric film, and the piezoelectric. A plurality of second series resonators having a third upper electrode facing the third lower electrode with a part of the film sandwiched between them, one end of which is electrically connected to the second path and the other end of which is electrically connected to the ground. A fourth lower electrode, which is connected to the plurality of second series resonators and is provided on the other side of the first direction along the second direction and is provided between the substrate and the piezoelectric film. And a plurality of second parallel resonators having a fourth upper electrode facing the fourth lower electrode with a part of the piezoelectric film interposed therebetween, and passing through lower than the passing band of the first ladder type filter. A multiplexer comprising a second ladder type filter having a band.

According to the present invention, the production can be facilitated or miniaturized.

FIG. 1 is a plan view of the elastic wave device according to the first embodiment. 2 (a) and 2 (b) are a sectional view taken along the line AA and a sectional view taken along the line BB of FIG. 1, respectively. 3 (a) and 3 (b) are cross-sectional views showing a piezoelectric film according to the first embodiment. 4 (a) to 4 (d) are cross-sectional views (No. 1) showing a method of manufacturing the elastic wave device of the first embodiment. 5 (a) to 5 (c) are cross-sectional views (No. 2) showing a method of manufacturing the elastic wave device of the first embodiment. FIG. 6 is a circuit diagram of the duplexer according to the second embodiment. FIG. 7 is a plan view of the duplexer according to the second embodiment. FIG. 8 is another plan view of the duplexer according to the second embodiment. 9 (a) to 9 (c) are cross-sectional views of the elastic wave device according to the first modification of Examples 1 and 2. 10 (a) to 10 (c) are cross-sectional views of the elastic wave device according to the first modification of Examples 1 and 2. FIG. 11 is a cross-sectional view of the elastic wave device according to the second modification of Examples 1 and 2.

Hereinafter, examples of the present invention will be described with reference to the drawings.

1 is a plan view of the elastic wave device according to the first embodiment, and FIGS. 2 (a) and 2 (b) are a sectional view taken along the line AA and a sectional view taken along the line BB of FIG. 1, respectively. In FIG. 1, the gap 30 is shown through the piezoelectric film 14. The directions parallel to the upper surface of the substrate 10 and orthogonal to each other are the X direction and the Y direction, and the normal direction of the upper surface of the substrate 10 is the Z direction.

As shown in FIGS. 1 to 2 (b), the piezoelectric thin film resonators 11a to 11d are arranged in the X direction and the Y direction. Lower electrodes 12a to 12d are provided on the substrate 10 via the gap 30. A single piezoelectric film 14 is provided on the lower electrodes 12a to 12d. The piezoelectric film 14 becomes thicker along the + X direction and has substantially the same thickness along the Y direction. That is, the upper surface of the piezoelectric film 14 is inclined along the X direction and not along the Y direction.

Upper electrodes 16a to 16d are provided on the piezoelectric film 14. The regions where the lower electrodes 12a to 12d and the upper electrodes 16a to 16d face each other with at least a part of the piezoelectric film 14 interposed therebetween are resonance regions 50a to 50d corresponding to the piezoelectric thin film resonators 11a to 11d. The planar shape of the resonance regions 50a to 50d is a substantially elliptical shape.

As the substrate 10, an insulating substrate such as a silicon substrate, an alumina substrate, a quartz substrate, a spinel substrate, a glass substrate, or a crystal substrate can be used. The lower electrodes 12a to 12d and the upper electrodes 16a to 16d include Ru (ruthenium), Cr (chromium), Al (aluminum), Ti (tantalum), Cu (copper), Mo (molybdenum), W (tungsten), and Ta. A single-layer film such as (tantalum), Pt (platinum), Rh (rhodium) or Ir (iridium) or a laminated film thereof can be used.

As the piezoelectric film 14, aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lead titanate (PbTiO ₃ ), etc., whose main axis is in the (002) direction can be used. Further, for example, the piezoelectric film 14 may contain aluminum nitride as a main component and may contain other elements for improving resonance characteristics or piezoelectricity. For example, by using Sc (scandium), two elements of a group 2 element or a group 12 element and a group 4 element, or two elements of a group 2 element or a group 12 element and a group 5 element, as an additive element, The piezoelectricity of the piezoelectric film 14 is improved. Therefore, the effective electromechanical coupling coefficient of the piezoelectric thin film resonator can be improved. Group 2 elements are, for example, Ca (calcium), Mg (magnesium) or Sr (strontium). The Group 12 element is, for example, Zn (zinc). Group 4 elements are, for example, Ti, Zr (zirconium) or Hf (hafnium). Group 5 elements are, for example, Ta, Nb (niobium) or V (vanadium). Further, the piezoelectric film 14 contains aluminum nitride as a main component and may contain B (boron).

A mass load film for adjusting the frequency may be provided in at least a part of the resonance regions 50a to 50d. As the mass addition film, an insulating film such as a silicon oxide film or a silicon nitride film, or a metal film exemplified as a lower electrode and an upper electrode can be used.

3 (a) and 3 (b) are cross-sectional views showing a piezoelectric film according to the first embodiment. As shown in FIG. 3A, the film thicknesses T1 to T4 of the piezoelectric film 14 in the resonance regions 50a to 50d of the piezoelectric thin film resonators 11a to 11d along the X direction increase in the + X direction. The thickness T1 to T4 of the piezoelectric film 14 in the resonance regions 50a to 50d is a value obtained by dividing the volume of the piezoelectric film 14 in the resonance regions 50a to 50d by the area of the XY plane of the resonance regions 50a to 50d. The film thickness T1 <T2 <T3 <T4. When the film thicknesses T1 to T4 are large, the resonance frequencies fr1 to fr4 of the piezoelectric thin film resonators 11a to 11d become low. Therefore, fr1> fr2> fr3> fr4.

As shown in FIG. 3B, the film thickness T4 of the piezoelectric film 14 in the resonance region 50d of the piezoelectric thin film resonator 11d along the Y direction is substantially constant. Therefore, the resonance frequency fr4 of the piezoelectric thin film resonator 11d is almost constant.

In the case of a piezoelectric thin film resonator of about 2 GHz, the lower electrodes 12a to 12d are, for example, a Cr film having a film thickness of 100 nm and a Ru film having a film thickness of 200 nm from the substrate 10 side. The piezoelectric film 14 is, for example, an aluminum nitride film having a film thickness of 1200 nm to 1300 nm. The upper electrodes 16a to 16d are, for example, a Ru film having a film thickness of 230 nm and a Cr film having a film thickness of 50 nm from the piezoelectric film 14 side. An insertion film may be provided between the lower electrodes 12a to 12d and the upper electrodes 16a to 16d in the resonance regions 50a to 50d. The insert film is provided in each outer peripheral region of the resonance regions 50a to 50d, and is not provided in the central region. The insertion membrane is, for example, a silicon oxide film having a film thickness of 150 nm. When 12 piezoelectric thin film resonators 11a to 11d are provided, the sizes of the voids 30 in the X direction and the Y direction are, for example, 850 μm to 1000 μm and 450 μm to 550 μm, respectively. The material, film thickness and size of each layer can be appropriately set in order to obtain desired resonance characteristics.

[Manufacturing method of Example 1]
4 (a) to 5 (c) are cross-sectional views showing a method of manufacturing the elastic wave device of the first embodiment. As shown in FIG. 4A, a recess 39 is formed on the upper surface of the substrate 10. The recess 39 is formed by using a photolithography method, an etching method, or the like. The sacrificial layer 38 is embedded in the recess. The sacrificial layer 38 is formed into a film by using, for example, a sputtering method, a vacuum deposition method, or a CVD (Chemical Vapor Deposition) method. The thickness of the sacrificial layer 38 is, for example, 10 to 100 nm, and is selected from materials that can be easily dissolved in an etching solution or an etching gas such as magnesium oxide (MgO), zinc oxide, germanium (Ge), or silicon oxide.

As shown in FIG. 4B, the lower electrodes 12a to 12d are formed on the sacrificial layer 38 by using, for example, a sputtering method, a vacuum vapor deposition method, or a CVD method. The lower electrodes 12a to 12d are patterned into a desired shape using a photolithography method and an etching method. The lower electrodes 12a to 12d may be formed by a lift-off method.

As shown in FIG. 4C, a piezoelectric film 14 is formed on the lower electrodes 12a to 12d and the substrate 10 by using, for example, a sputtering method, a vacuum vapor deposition method, or a CVD method. The film thickness of the piezoelectric film 14 is almost constant.

As shown in FIG. 4D, the mask layer 36 is formed on the piezoelectric film 14. The mask layer 36 is a photosensitive material, for example, a positive photoresist. The film thickness of the mask layer 36 is almost constant.

As shown in FIG. 5A, the mask 37 is arranged on the mask layer 36. The mask 37 is a grayscale mask. The gray scale mask is a mask in which the transmittance changes in three or more steps or continuously with respect to light having a wavelength used for exposure. As the mask 37 goes in the + X direction, the transmittance of light used for exposure decreases, and the transmittance is substantially constant along the Y direction. When the mask layer 36, which is a positive photoresist, is exposed and developed using the mask 37, the film thickness of the mask layer 36 increases in the + X direction and is substantially constant along the Y direction. When a negative photoresist is used as the mask layer 36, the transmittance of light used for exposure increases in the + X direction, and the mask 37 having a substantially constant transmittance in the Y direction is used.

As shown in FIG. 5B, the piezoelectric film 14 is etched using the mask layer 36 as a mask. The upper surface of the piezoelectric film 14 is inclined according to the ratio of the piezoelectric film 14, the mask layer 36, and the etching rate. As the etching, dry etching such as an ion milling method may be used, or a wet etching method using phosphoric acid or the like may be used. For example, if the ratio of the etching rates of the piezoelectric film 14 and the mask layer 36 is approximately 1: 1, the upper surface of the piezoelectric film 14 is inclined at substantially the same angle as the inclination of the upper surface of the mask layer 36 in FIG. 5 (a). The piezoelectric film 14 on the outer side of the sacrificial layer 38 is patterned into a desired shape by using a photography method and an etching method.

As shown in FIG. 5 (c), the upper electrodes 16a to 16d are formed on the piezoelectric film 14 by using, for example, a sputtering method, a vacuum vapor deposition method, or a CVD method. The upper electrodes 16a to 16d are patterned into a desired shape by using a photolithography method and an etching method. The upper electrodes 16a to 16d may be formed by a lift-off method.

Then, the sacrificial layer 38 is etched to form the void 30. As a result, the piezoelectric thin film resonators 11a to 11d shown in FIG. 2A are formed. In FIG. 4A, the recess 39 is not formed, and the sacrificial layer 38 is formed on the flat upper surface of the substrate 10. The stress of the piezoelectric film 14 or the like is set to be a compressive stress. Thereby, the void 30 can be formed into a shape having a dome-shaped bulge in the Z direction.

According to the first embodiment, as shown in FIGS. 2A and 3A, the single piezoelectric film 14 is provided on the upper surface of the substrate 10 and is the first in the + X direction (parallel to the upper surface of the substrate 10). It gets thicker as you go from one direction to the other. The one or a plurality of piezoelectric thin film resonators 11a (first piezoelectric thin film resonator) includes a lower electrode 12a (first lower electrode) provided between the substrate 10 and the piezoelectric film 14, and a part of the piezoelectric film 14. It has an upper electrode 16a (first upper electrode) facing the sandwiched lower electrode 12a. One or a plurality of piezoelectric thin film resonators 11b (second piezoelectric thin film resonators) are provided on the + X direction (the other side of the first direction) side of the piezoelectric thin film resonator 11a, and are provided between the substrate 10 and the piezoelectric film 14. It has a provided lower electrode 12b (second lower electrode) and an upper electrode 16b (second upper electrode) that faces the lower electrode 12b with a part of the piezoelectric film 14 sandwiched therein.

In this way, the thickness of the piezoelectric film 14 increases as it goes in the + X direction. Therefore, the resonance frequency changes according to the position in the X direction. For example, the piezoelectric film 14 continuously thickens as it goes in the + X direction. As a result, when manufacturing the piezoelectric thin film resonators 11a and 11b, it is not necessary to perform the step of differentiating the film thicknesses T1 and T2 of the piezoelectric film 14 for different resonance frequencies fr1 and fr2. Further, it is not necessary to perform the step of providing the mass addition film for each of the different resonance frequencies fr1 and fr2. Therefore, the manufacturing of elastic wave devices becomes easy. The thickness of the piezoelectric film 14 may be increased in the + X direction within the range of the region where the piezoelectric thin film resonators 11a to 11d are formed.

Further, the rate of change in the thickness of the piezoelectric film 14 along the Y direction (the second direction parallel to the upper surface of the substrate 10 and intersecting the first direction) is the rate of change in the thickness of the piezoelectric film 14 along the X direction. Make it smaller. As a result, the difference in resonance frequency of the piezoelectric thin film resonator provided in the Y direction can be reduced. The rate of change in the thickness of the piezoelectric film 14 along the Y direction is preferably 1/5 or less, more preferably 1/10 or less of the rate of change in the thickness of the piezoelectric film 14 along the X direction. The rate of change in the thickness of the piezoelectric film 14 in the X direction is ΔT / ΔX, where X is the X coordinate and T is the thickness of the piezoelectric film 14. The rate of change in the thickness of the piezoelectric film 14 in the Y direction is ΔT / ΔY, where Y is the Y coordinate and T is the thickness of the piezoelectric film 14. When the rate of change of the film thickness of the piezoelectric film 14 in the X direction and / or the rate of change in the Y direction is not constant, the thickness of the piezoelectric film 14 along the Y direction in the region where the piezoelectric thin film resonators 11a to 11d are formed. It suffices if the maximum rate of change of the shaving is smaller than the minimum rate of change in the thickness of the piezoelectric film 14 along the X direction.

The thickness of the piezoelectric film 14 is substantially constant along the Y direction to the extent of manufacturing error. As a result, the resonance frequencies of the plurality of piezoelectric thin film resonators along the Y direction can be made substantially the same as each other.

A plurality of piezoelectric thin film resonators 11a are provided along the Y direction, and a plurality of piezoelectric thin film resonators 11b are provided along the Y direction. Thereby, the difference in the resonance frequency in the piezoelectric thin film resonator 11a and the difference in the resonance frequency in the piezoelectric thin film resonator 11b can be made smaller than the difference in the resonance frequencies fr1 and fr2 between the piezoelectric thin film resonators 11a and 11b. Further, by making the positions in the X direction different in the plurality of piezoelectric thin film resonators 11a, the resonance frequencies of the plurality of piezoelectric thin film resonators 11a can be finely set.

One or a plurality of piezoelectric thin film resonators 11c (third piezoelectric thin film resonators) are provided on the + X direction side of the piezoelectric thin film resonator 11b, and lower electrodes 12c (third) provided between the substrate 10 and the piezoelectric film 14. 3 Lower electrode) and an upper electrode 16c (third upper electrode) facing the lower electrode 12c with a part of the piezoelectric film 14 interposed therebetween. The one or more piezoelectric thin film resonators 11d (fourth piezoelectric thin film resonator) are provided on the + X direction side of the piezoelectric thin film resonator 11c, and the lower electrode 12d (third) provided between the substrate 10 and the piezoelectric film 14. 4 lower electrode) and an upper electrode 16d (fourth upper electrode) facing the lower electrode 12d with a part of the piezoelectric film 14 interposed therebetween. Thereby, a plurality of piezoelectric thin film resonators 11a to 11d having different resonance frequencies of 3 or more can be easily manufactured.

As a method for manufacturing such an elastic wave device, as shown in FIG. 5A, the mask layer 36 is exposed through a gray scale mask to make the thickness of the mask layer 36 different. As shown in FIG. 5B, by etching the piezoelectric film 14 with the mask layer 36 having a different film thickness as a mask, the piezoelectric film 14 on at least two lower electrodes 12a to 12d of the plurality of lower electrodes 12a to 12d can be formed. Different film thickness. As shown in FIG. 5C, in the region where the plurality of piezoelectric thin film resonators 11a to 11d are formed, the plurality of lower electrodes 12a to 12d and the plurality of upper electrodes 16a to 16d face each other with the piezoelectric film 14 interposed therebetween. As described above, a plurality of upper electrodes 16a to 16b are formed on the piezoelectric film 14. As a result, it is not necessary to perform the step of making the film thicknesses T1 and T2 of the piezoelectric film 14 different or the step of providing the mass addition film. Therefore, the manufacturing of elastic wave devices becomes easy.

FIG. 6 is a circuit diagram of the duplexer according to the second embodiment. As shown in FIG. 6, the duplexer includes a receive filter 40 and a transmit filter 42. The reception filter 40 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 42 is connected between the common terminal Ant and the transmission terminal Tx. The reception filter 40 passes a signal in the reception band among the high frequency signals input from the common terminal Ant to the reception terminal Rx as a reception signal, and suppresses signals of other frequencies. The transmission filter 42 passes a signal in the transmission band among the high frequency signals input from the transmission terminal Tx to the common terminal Ant as a transmission signal, and suppresses signals of other frequencies.

The reception filter 40 and the transmission filter 42 are ladder type filters. In the reception filter 40, one or a plurality of series resonators S11 to S13 are connected in series between the common terminal Ant and the reception terminal Rx. One or more parallel resonators P11 to P13 are connected in parallel between the common terminal Ant and the receiving terminal Rx. In the transmission filter 42, one or a plurality of series resonators S21 to S23 are connected in series between the common terminal Ant and the transmission terminal Tx. One or more parallel resonators P21 to P23 are connected in parallel between the common terminal Ant and the transmission terminal Tx. The number of series resonators and parallel resonators in the receive filter 40 and the transmit filter 42 can be appropriately set.

FIG. 7 is a plan view of the duplexer according to the second embodiment. As shown in FIG. 7, the series resonators S11 to S13 are formed by the piezoelectric thin film resonator 11a. The parallel resonators P11 to P13 are formed by the piezoelectric thin film resonator 11b. The series resonators S21 to S23 are formed by the piezoelectric thin film resonator 11c. The parallel resonators P21 to P23 are formed by the piezoelectric thin film resonator 11d.

The piezoelectric thin film resonators 11a to 11d are electrically connected via the lower electrode 12 and / or the upper electrode 16 as wiring. The wiring may have a low resistance layer laminated on the lower electrode 12 and / or the upper electrode 16. The low resistivity layer is a layer having a lower resistivity than the lower electrode 12 and / or the upper electrode 16 such as a gold layer or a copper layer. At the location 32 where the wiring is switched between the lower electrode 12 and the upper electrode 16 (for example, between S11 and S12), a through hole is provided in the piezoelectric film 14, and the lower electrode 12 and the upper electrode 16 are electrically connected to each other through the through hole. Is connected. The common terminal Ant is electrically connected to the piezoelectric thin film resonators 11a to 11d via the upper electrode 16. The receiving terminal Rx, the transmitting terminal Tx, and the ground terminal GND are electrically connected to the piezoelectric thin film resonators 11a to 11d via the lower electrode 12. The common terminal Ant is provided on the piezoelectric film 14, and the receiving terminal Rx, the transmitting terminal Tx, and the ground terminal GND are provided on the substrate 10 in the region where the piezoelectric film 14 is not provided. Other configurations are the same as those in the first embodiment, and the description thereof will be omitted.

FIG. 8 is another plan view of the duplexer according to the second embodiment. As shown in FIG. 8, the common terminal Ant and the ground terminal GND are electrically connected to the piezoelectric thin film resonators 11a to 11d via the upper electrode 16. The transmission terminal Tx and the reception terminal Rx are electrically connected to the piezoelectric thin film resonators 11a to 11d via the lower electrode 12. The common terminal Ant and the ground terminal GND are provided on the piezoelectric film 14, and the receiving terminal Rx and the transmitting terminal Tx are provided on the substrate 10 in the opening 35 of the piezoelectric film 14. Other configurations are the same as those in FIG. 7, and the description thereof will be omitted.

For example, in the LTE (Long Term Evolution) band 25, the transmission band is 185 MHz to 1915 MHz, and the reception band is 1930 MHz to 1995 MHz. For example, consider a case where a duplexer of band 25 is manufactured by using a piezoelectric thin film resonator having a resonance frequency of 2000 MHz when the thickness of the piezoelectric film 14 is 1200 nm. In this case, the film thicknesses T1 to T4 of the piezoelectric film 14 are set to, for example, 1203 nm, 1244 nm, 1253 nm and 1297 nm, respectively.

According to the second embodiment, as shown in FIGS. 6 to 8, in the receiving filter 40 (first ladder type filter), from the common terminal Ant (first input terminal) to the receiving terminal Rx (first output terminal, first terminal). ) Is the first route. The plurality of series resonators S11 to S13 (first series resonators) are electrically connected in series to the first path, and each is a piezoelectric thin film resonator 11a. The plurality of parallel resonators P11 to P13 (first parallel resonators) have one end electrically connected to the first path and the other end electrically connected to the ground, each of which is a piezoelectric thin film resonator 11b.

Since the series resonators S11 to S13 are provided along the Y direction, the piezoelectric film 14 in the resonance region 50a of the series resonators S11 to S13 can have substantially the same thickness. As a result, the resonance frequencies of the series resonators S11 to S13 can be made substantially the same as each other. Since the parallel resonators P11 to P13 are provided along the Y direction, the piezoelectric films 14 in the resonance region 50b in the parallel resonators P11 to P13 can have substantially the same thickness. As a result, the resonance frequencies of the parallel resonators P11 to P13 can be made substantially the same.

Since the parallel resonators P11 to P13 are provided on the + X direction side of the series resonators S11 to S13, the piezoelectric film 14 in the resonance region 50a (first resonance region) of the series resonators S11 to S13 is formed from the parallel resonator P11. It can be made thinner than the piezoelectric film 14 in the resonance region 50b (second resonance region) of P13. As a result, the resonance frequency of the parallel resonators P11 to P13 can be made lower than that of the series resonators S11 to S13.

In the transmission filter 42 (second ladder type filter), the path from the transmission terminal Tx (second input terminal, second terminal) to the common terminal Ant (second output terminal) is set as the second path. The plurality of series resonators S21 to S23 (second series resonators) are electrically connected in series to the second path, and each is a piezoelectric thin film resonator 11c. The parallel resonators P21 to P23 (second parallel resonator) are piezoelectric thin film resonators 11d, one end of which is electrically connected to the second path and the other end of which is electrically connected to the ground.

The piezoelectric film 14 in the resonance region 50c of the series resonators S21 to S23 can be made to have substantially the same thickness, and the piezoelectric film 14 in the resonance region 50d of the parallel resonators P21 to P23 can be made to have substantially the same thickness. As a result, the resonance frequencies of the series resonators S21 to S23 can be made substantially the same as each other, and the resonance frequencies of the parallel resonators P21 to P23 can be made substantially the same as each other.

Since the series resonators S21 to S23 are provided on the + X direction side of the parallel resonators P11 to P13, the piezoelectric film 14 in the resonance region 50c (third resonance region) of the series resonators S21 to S23 is piezoelectric in the resonance region 50b. Can be thicker than the membrane. As a result, the resonance frequency of the series resonators S21 to S23 can be made lower than that of the parallel resonators P11 to P13.

Since the parallel resonators P21 to P23 are provided on the + X direction side of the series resonators S21 to S23, the piezoelectric film 14 in the resonance region 50d (fourth resonance region) of the parallel resonators P21 to P23 is piezoelectric in the resonance region 50c. Can be thicker than the membrane. As a result, the resonance frequency of the parallel resonators P21 to P23 can be made lower than that of the series resonators S21 to S23.

As a result, the transmission filter 42 having a pass band lower than the pass band of the reception filter 40 can be easily manufactured.

In a duplexer having a plurality of ladder type filters, piezoelectric thin film resonators 11a to 11d having at least four resonance frequencies will be provided. In order to reduce the size of the duplexer, it is preferable to provide the piezoelectric thin film resonators 11a to 11d on a single piezoelectric film 14. However, if it is attempted to form 11d from the piezoelectric thin film resonators 11a having four resonance frequencies by making the film thickness of the piezoelectric film 14 and / or the film thickness of the mass addition film different, the manufacturing process becomes complicated. Therefore, it is difficult to form the piezoelectric thin film resonators 11a to 11d on the single piezoelectric film 14. Therefore, a gray scale mask is used as shown in FIG. 5 (a). Thereby, a duplexer having a plurality of ladder type filters can be formed on a single piezoelectric film 14. Therefore, the duplexer can be downsized.

Although the duplexer has been described as an example of the multiplexer, the multiplexer may be, for example, a triplexer or a quadplexer.

[Modification 1 of Examples 1 and 2]
9 (a) to 10 (c) are cross-sectional views of the elastic wave device according to the first modification of Examples 1 and 2. As shown in FIG. 9A, the thickness of the piezoelectric film 14 changes stepwise, and the thickness of each of the piezoelectric films 14 within the resonance regions 50a to 50d may be substantially constant. As shown in FIG. 9B, in some of the piezoelectric thin film resonators 11a and 11c, the thickness of the piezoelectric film 14 in the resonance regions 50a and 50c changes continuously, and the piezoelectric thin film resonators 11b and 11d resonate. Within the regions 50b and 50d, the thickness of the piezoelectric film 14 may be substantially constant, respectively. As shown in FIG. 9 (c), the rate of change of the thickness of the piezoelectric film 14 in the resonance region 50a to 50d along X may be different.

As shown in FIG. 10A, the thickness of the piezoelectric film 14 changes stepwise, and the thickness of each of the piezoelectric films 14 within the resonance regions 50a to 50d changes continuously, and the resonance regions 50a to 50d. The rate of change of the thickness of the piezoelectric film 14 in X with respect to X may be substantially the same. As shown in FIG. 10B, the thickness of the piezoelectric film 14 may change stepwise, and the thickness of each of the piezoelectric films 14 within the resonance regions 50a to 50d may change continuously. As shown in FIG. 10 (c), the thickness of the piezoelectric film 14 along the X direction may change continuously, and the rate of change of the thickness of the piezoelectric film 14 with respect to X may change continuously. 9 (a) to 10 (c), the other configurations are the same as those of the first and second embodiments, and the description thereof will be omitted.

As shown in FIGS. 2 (a) and 10 (c) of the first embodiment, the piezoelectric film 14 becomes thicker in the + X direction, and the position in the X direction is adjusted by adjusting the position in the X direction from the piezoelectric thin film resonator 11a. The resonance frequency of 11d can be set to any value.

Piezoelectric thin film resonators having different thicknesses of the piezoelectric film 14 in the resonance regions 50a to 50d as shown in FIGS. 9 (a) to 10 (c) by using a gray scale mask as shown in FIG. 5 (a). 11a to 11d can be formed using a single patterning and etching. Therefore, the manufacturing process can be simplified.

[Modified Examples 2 of Examples 1 and 2]
FIG. 11 is a cross-sectional view of the elastic wave device according to the second modification of Examples 1 and 2. As shown in FIG. 11, the acoustic reflection film 31 is formed below the lower electrodes 12a to 12d in the resonance regions 50a to 50d. The acoustic reflection film 31 is provided with a film 31a having a low acoustic impedance and a film 31b having a high acoustic impedance alternately. The film thicknesses of the films 31a and 31b are, for example, approximately λ / 4 (λ is the wavelength of the elastic wave), respectively. The number of layers of the film 31a and the film 31b can be arbitrarily set. The acoustic reflection film 31 may be formed by laminating at least two types of layers having different acoustic characteristics at intervals. Further, the substrate 10 may be one of at least two types of layers having different acoustic characteristics of the acoustic reflection film 31. For example, the acoustic reflection film 31 may be configured such that a film having a different acoustic impedance is further provided in the substrate 10. Other configurations are the same as those of Examples 1 and 2, and the description thereof will be omitted.

In Examples 1 and 2 and the modified example 1 thereof, the acoustic reflection film 31 may be formed instead of the void 30 in the same manner as in the modified examples 2 of the first and second embodiments.

The piezoelectric thin film resonators 11a to 11d may be an FBAR (Film Bulk Acoustic Resonator) in which a gap 30 is formed between the substrate 10 and the lower electrodes 12a to 12d in the resonance regions 50a to 50d. Further, the piezoelectric thin film resonators 11a to 11d may be an SMR (Solidly Mounted Resonator) provided with an acoustic reflection film 31 that reflects elastic waves propagating in the piezoelectric film 14 under the lower electrodes 12a to 12d in the resonance regions 50a to 50d.

Although the example in which the voids 30 are provided in common to the plurality of piezoelectric thin film resonators 11a to 11d has been described, the voids 30 may be provided for each of the piezoelectric thin film resonators 11a to 11d. Although the elliptical shape has been described as an example of the planar shape of the resonance regions 50a to 50d, a polygonal shape such as a quadrangular shape or a pentagonal shape may be used.

Although the examples of the present invention have been described in detail above, the present invention is not limited to such specific examples, and various modifications and variations are made within the scope of the gist of the present invention described in the claims. It can be changed.

10 Substrate 11a-11d Piezoelectric thin film resonator 12a-12d Lower electrode 14 Piezoelectric membrane 16a-16d Upper electrode 30 Void 40 Reception filter 42 Transmission filter 50a-50d Resonance region

Claims (7)

With the board
A second that is provided on the surface of the substrate and is continuously thickened from one of the first directions parallel to the surface of the substrate to the other , parallel to the surface and intersecting the first direction. The rate of change in the thickness of the piezoelectric film along the direction is smaller than the rate of change in the thickness of the piezoelectric film along the first direction .
A plurality of first lower electrodes provided along the second direction, which are provided between the substrate and the piezoelectric film, and a first upper electrode which sandwiches a part of the piezoelectric film and faces the first lower electrode. With a plurality of first piezoelectric thin film resonators,
A plurality of second lower electrodes provided along the second direction on the other side of the first direction with respect to the plurality of first piezoelectric thin film resonators, and the second lower electrode provided between the substrate and the piezoelectric film, and the said. A plurality of second piezoelectric thin film resonators having a second upper electrode facing the second lower electrode with a part of the piezoelectric film interposed therebetween.
An elastic wave device equipped with. A plurality of first series resonators provided in the first path from the first input terminal to the first output terminal, each of which is the plurality of first piezoelectric thin film resonators, and one end thereof are electrically connected to the first path. The elastic wave device according to claim 1 , further comprising a first ladder type filter having a plurality of first parallel resonators, each of which is electrically connected to the ground at the other end and is the plurality of second piezoelectric thin-film resonators. A plurality of third lower electrodes provided along the second direction on the other side of the first direction with respect to the plurality of second piezoelectric thin film resonators, and the third lower electrode provided between the substrate and the piezoelectric film, and the said. A plurality of third piezoelectric thin film resonators having a third upper electrode facing the third lower electrode with a part of the piezoelectric film interposed therebetween.
A plurality of fourth lower electrodes provided along the second direction on the other side of the first direction with respect to the plurality of third piezoelectric thin film resonators, and the fourth lower electrode provided between the substrate and the piezoelectric film, and the said. A plurality of fourth piezoelectric thin film resonators having a fourth upper electrode facing the fourth lower electrode with a part of the piezoelectric film interposed therebetween.
A plurality of second series resonators, each of which is connected in series to a second path from the second input terminal to the second output terminal and is the plurality of third piezoelectric thin film resonators, and one end of which is electrically connected to the second path. The other end is connected and electrically connected to the ground, each having a plurality of second parallel resonators, which are the plurality of fourth piezoelectric thin-film resonators, and has a pass band lower than the pass band of the first ladder type filter. The second ladder type filter and
2. The elastic wave device according to claim 2 . The elastic wave device according to any one of claims 1 to 3 , wherein the thickness of the piezoelectric film is substantially constant along the second direction. A multiplexer including the elastic wave device according to any one of claims 1 to 4 . With the board
A second direction provided on the surface of the substrate, which is continuously thickened from one of the first directions parallel to the surface of the substrate to the other, parallel to the surface and intersecting the first direction. The rate of change in the thickness of the piezoelectric film along the first direction is smaller than the rate of change in the thickness of the piezoelectric film along the first direction .
A plurality of the first lower electrodes provided along the second direction, provided in the first path from the common terminal to the first terminal, and provided between the substrate and the piezoelectric film, and one of the piezoelectric films. A plurality of first series resonators having a first upper electrode facing the first lower electrode with a portion interposed therebetween.
One end is electrically connected to the first path and the other end is electrically connected to the ground, and a plurality of the first series resonators are provided on the other side of the first direction along the second direction. A plurality of first parallel electrodes having a second lower electrode provided between the substrate and the piezoelectric film and a second upper electrode facing the second lower electrode with a part of the piezoelectric film interposed therebetween. Resonator and
With a first ladder type filter,
A plurality of portions are provided along the second direction on the other side of the first direction from the plurality of first parallel resonators, which are provided in the second path from the common terminal to the second terminal, and the substrate and the piezoelectric. A plurality of second series resonators having a third lower electrode provided between the film and a third upper electrode having a part of the piezoelectric film sandwiched between the third lower electrode and the third lower electrode facing the third lower electrode.
One end is electrically connected to the second path and the other end is electrically connected to the ground, and a plurality of the second series resonators are provided on the other side of the first direction along the second direction. A plurality of second parallel electrodes having a fourth lower electrode provided between the substrate and the piezoelectric film and a fourth upper electrode facing the fourth lower electrode with a part of the piezoelectric film interposed therebetween. Resonator and
A second ladder type filter having a pass band lower than the pass band of the first ladder type filter.
A multiplexer equipped with. The multiplexer according to claim 6, wherein the thickness of the piezoelectric film is substantially constant along the second direction.

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