JP2009124695A - Resonance device and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resonance device capable of improving the Q-value and the electromechanical coupling coefficient, at low cast, and to provide a method of manufacturing the resonance device. <P>SOLUTION: The resonance device comprises a resonator 3, having a lower electrode 31 constituted of a first conductive thin film and a upper electrode 33 constituted of a piezoelectric film 32 and a second conductive thin film, on one surface side of a support substrate 1. In the resonator 3, a piezoelectric layer 32 is formed cylindrically, and the respective lower and upper electrodes 31, 33 are formed into a coil-spring shape (conical-coil shaped) of spring shape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a resonance device including a resonator having a laminated structure of a lower electrode, a piezoelectric layer, and an upper electrode, and a manufacturing method thereof.

  Conventionally, with the widespread use of high-frequency devices such as mobile phones and UWB (Ultra Wide Band) devices, and the strong need for their high performance and low loss, the electromechanical coupling coefficient is large in the high frequency band of 1 GHz and higher. As a resonance device having a high Q value, a BAW (Bulk Acoustic Wave) resonator has attracted attention. In particular, since a UWB filter requires a wide bandwidth, research and development of a BAW resonator having a larger electromechanical coupling coefficient has been performed in various places.

  Here, as the BAW resonator, for example, as shown in FIG. 5, the support substrate 1 ′, the acoustic mirror 2 ′ formed on the one surface side of the support substrate 1 ′, and the acoustic mirror 2 ′ are formed. An SMR (Solidly Mounted Resonator) including a resonator 3 ′ has been proposed (see, for example, Patent Document 1). Here, the acoustic mirror 2 ′ has a laminated structure in which low acoustic impedance layers 21 ′ and high acoustic impedance layers 22 ′ are alternately laminated, and the resonator 3 ′ includes a lower electrode 31 ′ and a piezoelectric layer 32 ′. AlN, ZnO, PZT (lead zirconate titanate), or the like is used as the material of the piezoelectric layer 32 ′. In the BAW resonator, the resonance frequency is inversely proportional to the film thickness of the piezoelectric layer 32 ′, and the resonance frequency can be increased as the film thickness of the piezoelectric layer 32 ′ is decreased.

  In Patent Document 1, SMR is described as a BAW resonator, but as a BAW resonator, FBAR (Film Bulk Acoustic Resonator) or the like is known in addition to SMR.

  By the way, it can be said that the electromechanical coupling coefficient of a BAW resonator is determined by the piezoelectric material of the piezoelectric layer. It is known that it has a large electromechanical coupling coefficient compared to a typical piezoelectric material. Further, it is known that the BAW resonator can maximize the electromechanical coupling coefficient by optimizing the film thickness of the piezoelectric layer.

Conventionally, in the field of SAW (Surface Acoustic Wave) filters, an admittance element near the resonance frequency is added by adding an inductance element (for example, a bonding wire, a microstrip line, etc.) connected in series to the SAW resonator. It is known that the difference between the local maximum value and the local minimum value increases, and the apparent electromechanical coupling coefficient increases (see Patent Document 2), and the inductance element described in Patent Document 2 is added. Can be applied to BAW resonators and BAW filters to which BAW resonators are applied.
Japanese Patent Laying-Open No. 2005-260964 (paragraphs [0002]-[0006] and FIG. 1) Japanese Patent No. 2800905 (paragraphs [0044]-[0048] and FIG. 7, and claim 5-7)

  In the BAW resonator having the configuration shown in FIG. 5, the piezoelectric layer 32 ′ cannot obtain a high Q value (mechanical quality factor Qm). In addition, when a configuration in which an inductance element is added in order to increase the electromechanical coupling coefficient is applied to a BAW resonator or a BAW filter, the number of parts increases, resulting in an increase in size and manufacturing cost. .

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a resonance apparatus capable of improving the Q value and improving the electromechanical coupling coefficient at a low cost, and a method for manufacturing the same. is there.

  According to a first aspect of the present invention, there is provided a resonator including a resonator having a laminated structure of a lower electrode made of a first conductive thin film, a piezoelectric layer and an upper electrode made of a second conductive thin film on one surface side of a support substrate. The apparatus is characterized in that each of the lower electrode and the upper electrode is formed in a spring shape.

  According to the present invention, since each of the lower electrode and the upper electrode is formed in a spring shape, the resonator can easily vibrate in the film thickness direction of the piezoelectric layer, and the Q value can be improved. Since each of the upper electrodes can have an inductance component and it is not necessary to add an inductance element separately, the electromechanical coupling coefficient can be improved at low cost.

  According to a second aspect of the present invention, in the first aspect of the present invention, the lower electrode and the upper electrode are characterized in that the spring shape is a coil spring shape.

  According to the present invention, the inductance components of the lower electrode and the upper electrode can be increased, and the electromechanical coupling coefficient can be further increased.

  A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the piezoelectric material of the piezoelectric layer is KNN.

  According to the present invention, the piezoelectric material of the lead layer such as PZT which can increase the electromechanical coupling coefficient compared to the case where the piezoelectric material of the piezoelectric layer is AlN and has a larger electromechanical coupling coefficient than AlN. The environmental burden can be reduced compared to the case.

  A fourth aspect of the present invention is the method of manufacturing a resonance device according to any one of the first to third aspects, wherein the lower electrode made of the first conductive thin film is formed on one surface side of the support substrate. A lower electrode forming step, a piezoelectric material layer forming step for forming a piezoelectric material layer as a basis of the piezoelectric layer on the entire surface of the one surface side of the support substrate after the lower electrode forming step, and an upper electrode on the piezoelectric material layer A sacrificial layer forming step for forming a sacrificial layer as a base of the substrate, an upper electrode forming step for forming an upper electrode made of a second conductive thin film on the one surface side of the support substrate after the sacrificial layer forming step, and an upper portion A sacrificial layer removing step for etching away the sacrificial layer after the electrode forming step, and a patterning step for patterning the piezoelectric material layer after the sacrificial layer removing step to form a piezoelectric layer made of a part of the piezoelectric material layer. It is characterized by providing.

  According to the present invention, a resonance device can be manufactured by using general semiconductor manufacturing technology and micromachining technology, the Q value can be improved, and the electromechanical coupling coefficient can be improved at low cost. An apparatus can be provided.

  In the invention of claim 1, there is an effect that the Q value can be improved and the electromechanical coupling coefficient can be improved at a low cost.

  According to the invention of claim 4, there is an effect that it is possible to provide a resonance device capable of improving the Q value and improving the electromechanical coupling coefficient at a low cost.

  As shown in FIG. 1, the resonance device of the present embodiment is a BAW resonator including a support substrate 1 and a resonator 3 formed on one surface side of the support substrate 1. A lower electrode 31 made of a first conductive thin film (for example, a Pt film) formed on the one surface side of the substrate 1 and a piezoelectric layer 32 formed on the opposite side of the lower electrode 31 to the support substrate 1 side. And an upper electrode 33 made of a second conductive thin film (for example, a Pt film) formed on the opposite side of the piezoelectric layer 32 from the lower electrode 31 side. In the resonance device of the present embodiment, the recess 1a is formed on the one surface of the support substrate 1, and the support substrate 1 is increased by increasing the acoustic impedance ratio between the lower electrode 31 and the medium immediately below the lower electrode 31. The FBAR is configured to suppress propagation of elastic wave energy to the side.

Here, the resonance device of the present embodiment employs PZT as the piezoelectric material of the piezoelectric layer 32, and the support substrate 1 uses the MgO substrate whose main surface is the (100) plane. The support substrate 1 is not limited to the MgO substrate, and an STO (SrTiO ₃ ) substrate having a main surface of (100) plane and an insulating film made of a silicon oxide film on the main surface having a main surface of (100) plane. A silicon substrate or the like may be used. Here, in this embodiment, since PZT is adopted as the piezoelectric material of the piezoelectric layer 32, the electromechanical coupling coefficient can be increased as compared with the case where the piezoelectric material is AlN. However, the piezoelectric material of the piezoelectric layer 32 is not limited to PZT, and other lead oxide-based piezoelectric materials (for example, PZT-PMT or PZT added with appropriate impurities) may be employed. In addition, lead-free KNN (potassium sodium diobate) may be adopted as the piezoelectric material of the piezoelectric layer 32. If KNN is adopted, the electromechanical coupling coefficient is increased as compared with the case where the piezoelectric material is AlN. In addition, the environmental load can be reduced as compared with the case of using a lead oxide piezoelectric material. The composition of KNN is represented by the chemical formula K _x Na _1-x NbO ₃ , and for example, x = 0.5 may be used, but this value is an example and is not particularly limited. For KNN, for example, impurities such as Li, Nb, Ta, Sb, and Cu may be added.

  In this embodiment, Pt is used as the material of the lower electrode 31 and Pt is used as the material of the upper electrode 33. However, these materials are not particularly limited, and as will be apparent from the manufacturing method described later, the piezoelectric layer When the piezoelectric material 32 is PZT, any metal material having etching resistance to hydrofluoric acid may be used.

  In the resonance device of this embodiment, the resonance frequency of the resonator 3 is set to 4 GHz, the thickness of the lower electrode 31 is set to 100 nm, the thickness of the piezoelectric layer 32 is set to 300 nm, and the thickness of the upper electrode 33 is set to 100 nm. However, these numerical values are examples and are not particularly limited. Moreover, when designing the resonance frequency in the range of 3 GHz to 5 GHz, the thickness of the piezoelectric layer 32 may be set as appropriate in the range of 200 nm to 600 nm.

  By the way, the upper electrode 33 and the lower electrode 31 of the resonator 3 are each formed in a spring shape of a coil spring shape (in this embodiment, a conical coil spring shape). Here, the upper electrode 33 and the lower electrode 31 are wound in opposite directions in plan view. The upper electrode 33 and the lower electrode 31 are not limited to the conical coil spring shape, but may be any spring shape, for example, a leaf spring shape or a wire spring shape.

  In the resonator 3, the piezoelectric layer 32 is formed in a columnar shape whose axial direction is the thickness direction, and one end portion on the center side of each of the lower electrode 31 and the upper electrode 33 is coupled to the piezoelectric layer 32. Here, the other end of the lower electrode 31 is formed on the peripheral portion of the recess 1 a on the one surface of the support substrate 1, and the other end of the upper electrode 33 is the same as the piezoelectric layer 32 on the support substrate 1. It is formed on an insulating layer 44 made of a silicon oxide film on a piezoelectric material film 34 formed of a piezoelectric material. In short, the upper electrode 33 is supported on the support substrate 1 via a laminated film of the piezoelectric material film 34 and the insulating layer 44 on the support substrate 1.

  In the resonance device of the present embodiment described above, each of the lower electrode 31 and the upper electrode 33 is formed in a spring shape, so that the resonator 3 easily vibrates in the film thickness direction of the piezoelectric layer 32 and the Q value is improved. In addition, each of the lower electrode 31 and the upper electrode 33 can have an inductance component, and it is not necessary to add an inductance element separately. Therefore, the electromechanical coupling coefficient can be improved at low cost. Become. Further, in the resonance device of the present embodiment, since the spring shape of each of the lower electrode 31 and the upper electrode 33 is a coil spring shape, the inductance component of each of the lower electrode 31 and the upper electrode 33 can be increased, and the electromechanical coupling coefficient can be further increased. It becomes possible to enlarge.

  Hereinafter, the manufacturing method of the resonance device according to the present embodiment will be described with reference to FIGS. 2 to 4. FIGS. 2 (a) to (c), FIGS. 3 (a) to (c), and FIG. 4 (a). , (B), the upper drawing shows a schematic plane, and the lower drawing shows a schematic cross section AA ′ of the upper drawing.

  First, a lower electrode is formed to form a lower electrode 31 made of a first conductive thin film (Pt film) patterned in a predetermined shape (here, a planar coil shape) on the one surface side of the support substrate 1 made of an MgO substrate. By performing the process, the structure shown in FIG. Here, in the lower electrode forming step, a first conductive thin film is formed on the entire surface of the support substrate 1 on the one surface side by a sputtering method or the like, and then a photolithography technique and an etching technique (for example, ion milling technique, reaction, etc.). The lower electrode 31 having a predetermined shape is formed by patterning the first conductive thin film using a reactive ion etching technique or the like. Note that the method for forming the first conductive thin film is not limited to the sputtering method, and for example, an EB vapor deposition method may be employed.

  After the lower electrode forming step, a piezoelectric material layer forming step for forming a piezoelectric material layer 30a made of a PZT layer serving as a basis of the piezoelectric layer 32 on the entire surface of the support substrate 1 on the one surface side is performed, whereby FIG. ) Is obtained. In the piezoelectric material layer forming step, the piezoelectric material layer 30a is formed by sputtering. However, the method is not limited to sputtering, and may be formed by, for example, CVD or sol-gel. Further, in the piezoelectric material layer forming step, in order to control the orientation of the piezoelectric material layer 30a made of the PZT layer, the piezoelectric material layer 30a is formed after forming the seed layer made of the PLT layer, the SRO layer, or the like. Also good.

  After the piezoelectric material layer forming step, the sacrificial layer forming step of forming the sacrificial layer 4 made of a silicon oxide film as a base of the upper electrode 33 on the piezoelectric material layer 30a is performed, whereby the structure shown in FIG. obtain. Here, in the sacrificial layer forming step, the sacrificial layer 4 having a circular aperture 4a that exposes a portion to be the piezoelectric layer 32 of the piezoelectric material layer 30a is formed. In forming the sacrificial layer 4, a resist layer is formed on a portion of the piezoelectric material layer 30 a that becomes the piezoelectric layer 32, and then a silicon oxide film is sputtered on the exposed portion of the piezoelectric material layer 30 a and on the resist layer. Then, the resist layer and the silicon oxide film on the resist layer are removed. In short, in the sacrificial layer forming step, the sacrificial layer 4 is formed using a lift-off method.

  After the sacrificial layer forming step, upper electrode formation for forming an upper electrode made of a second conductive thin film (Pt film) patterned in a predetermined shape (here, planar coil shape) on the one surface side of the support substrate 1 By performing the steps, the structure shown in FIG. Here, in the upper electrode formation step, a second conductive thin film is formed on the entire surface of the one surface side of the support substrate 1 by sputtering or the like, and then a photolithography technique and an etching technique (for example, ion milling technique, reaction, etc.). The upper electrode 33 having a predetermined shape is formed by patterning the second conductive thin film using a reactive ion etching technique or the like. Note that the method for forming the second conductive thin film is not limited to the sputtering method, and for example, an EB vapor deposition method may be employed.

  After the upper electrode forming step, the resist layer 5 as a mask for patterning the sacrificial layer 4 and the piezoelectric material layer 30a to form the laminated film of the piezoelectric material film 34 and the insulating layer 44 described above is used for the support substrate 1 described above. The structure shown in FIG. 3B is obtained by performing a mask forming process for forming a laminated film formed on one surface side.

  Thereafter, a sacrificial layer removing step of etching and removing the sacrificial layer 4 while leaving the portion to become the insulating layer 44 using the resist layer 5 as a mask, and patterning the piezoelectric material layer 30a using the resist layer 5 as a mask, respectively. The patterning process for forming the piezoelectric layer 32 and the piezoelectric material film 34, which are part of 30a, is continuously performed, and then the resist removing process for removing the resist layer 5 is performed, whereby the structure shown in FIG. Get. Here, hydrofluoric acid is used as an etchant in the sacrificial layer removing step and the patterning step, but the etchant may be appropriately selected according to the materials of the sacrificial layer 4 and the piezoelectric layer 32. By performing the sacrificial layer removal step and the patterning step, the upper electrode 33 becomes a conical coil spring-like spring shape due to the internal stress of the upper electrode 33.

  After the patterning step described above, a recess forming mask forming step for forming a resist layer 6 on the one surface side of the support substrate 1 as a mask for forming the recess 1a on the one surface of the support substrate 1 is performed. Thus, the structure shown in FIG.

  After the recess forming mask forming step, the recess forming step of removing the resist layer 6 after forming the recess 1a on the one surface of the support substrate 1 using the resist layer 6 as a mask is performed as shown in FIG. A resonance device having the structure shown in b) is obtained. Here, phosphoric acid is used as the etchant for forming the recess 1a. However, the etchant may be appropriately selected according to the material of the support substrate 1. By performing the recess forming step, the lower electrode 31 becomes a conical coil spring-like spring shape due to the internal stress of the lower electrode 31.

  According to the above-described method for manufacturing a resonance device, the resonance device can be manufactured using general semiconductor manufacturing technology and micromachining technology, the Q value can be improved, and the electromechanical coupling coefficient can be improved at low cost. It is possible to provide a resonance device that can perform the above-described operation.

  By the way, when the above-described resonance device is applied as a filter having a sharp cutoff characteristic and a wide bandwidth in a high frequency band of 3 GHz or more, for example, a UWB filter, a plurality of (for example, eight) resonators. 3 is formed on the one surface side of the support substrate 1 and the plurality of resonators 3 are connected to form a ladder type filter, the cost and size of the UWB filter can be reduced.

The resonance apparatus of embodiment is shown, (a) is a schematic plan view, (b) is A-A 'schematic sectional drawing of (a). It is explanatory drawing of the manufacturing method of a resonance apparatus same as the above. It is explanatory drawing of the manufacturing method of a resonance apparatus same as the above. It is explanatory drawing of the manufacturing method of a resonance apparatus same as the above. It is a schematic sectional drawing of the resonance apparatus which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support substrate 1a Recess 3 Resonator 4 Sacrificial layer 30a Piezoelectric material layer 31 Lower electrode 32 Piezoelectric layer 33 Upper electrode

Claims (4)

  A resonance device comprising a resonator having a laminated structure of a lower electrode made of a first conductive thin film, a piezoelectric layer and an upper electrode made of a second conductive thin film on one surface side of a support substrate, the lower electrode Each of the upper electrode and the upper electrode is formed in a spring shape.   The resonance device according to claim 1, wherein the lower electrode and the upper electrode have a coil spring shape as the spring shape.   3. The resonance apparatus according to claim 1, wherein the piezoelectric material of the piezoelectric layer is KNN.   A method of manufacturing a resonance device according to any one of claims 1 to 3, wherein a lower electrode forming step of forming a lower electrode made of a first conductive thin film on one surface side of a support substrate; After the lower electrode forming step, a piezoelectric material layer forming step for forming a piezoelectric material layer serving as a basis of the piezoelectric layer on the entire surface of the one surface side of the support substrate, and a sacrificial layer serving as a base for the upper electrode on the piezoelectric material layer A sacrificial layer forming step to be formed; an upper electrode forming step for forming an upper electrode made of a second conductive thin film on the one surface side of the support substrate after the sacrificial layer forming step; and a sacrificial after the upper electrode forming step. A resonance layer comprising: a sacrificial layer removing step for etching away the layer; and a patterning step for patterning the piezoelectric material layer after the sacrificial layer removing step to form a piezoelectric layer made of a part of the piezoelectric material layer. Device manufacturing method.

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