JP2008048040A - Piezoelectric thin film resonator and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-loss piezoelectric thin-film resonator that is excellent in manufacturability while avoiding crystallinity deterioration of a piezoelectric body caused by a step for pattern-forming a lower electrode. <P>SOLUTION: The piezoelectric thin-film resonator is provided with a substrate 1, the lower electrode 2 formed on one main face of the substrate so as to have a prescribed planar shape, the piezoelectric body 3 provided in a planar region at the upper part of the lower electrode, and an upper electrode 4 provided in a planar region at the upper part of the piezoelectric body. A function part of a resonator is composed by the lower electrode, piezoelectric body, and upper electrode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piezoelectric thin film resonator used in portable electronic devices having a wireless communication function typified by a mobile phone and used as an antenna duplexer, a high frequency filter, a transmitter, and the like, and a method of manufacturing the same.

  With the diversification of wireless communication systems, parts built into portable electronic devices are required to have higher performance. For example, a filter or duplexer for selecting a high-frequency signal used in a mobile phone is required to be small and have a small insertion loss. As one of filters that satisfy these requirements, a piezoelectric thin film resonator (FBAR) is known.

  FIG. 12 shows a cross-sectional view of a conventional piezoelectric thin film resonator. In FIG. 12, reference numeral 51 denotes a substrate, which is provided with a cavity 51a on its upper surface. A lower electrode 52 is provided on the upper portion of the substrate 51 so as to straddle the cavity 51a, and a piezoelectric body 53 and an upper electrode 54 are sequentially provided on the lower electrode 52 to form a piezoelectric thin film resonator 55. The manufacturing process is as follows.

  Although the substrate 51 is made of silicon and is not shown in the drawing, an insulating layer such as a thermal oxide film is usually formed on the upper surface, and a recess is formed in the portion to become the cavity 51a using anisotropic etching of silicon or the like. To do. Next, the formed depression is filled with a readily soluble oxide film or glass which is a sacrificial layer material, and is flattened. Thereafter, a metal layer such as molybdenum (Mo) is deposited as a lower electrode layer to a predetermined thickness by sputtering or the like, and a pattern is formed by a normal photolithography technique to form the lower electrode 52.

Next, a piezoelectric layer made of aluminum nitride (AlN) or the like is formed, and similarly, a piezoelectric body 53 is formed by pattern formation. Further, like the lower electrode 52, the upper electrode 54 made of a metal such as molybdenum (Mo) is patterned. Finally, the cavity 51a is formed by melting and removing the sacrificial layer material filled in the depressions through the etching holes (not shown) previously formed in the upper electrode 54, the piezoelectric body 53, and the lower electrode 52. Then, the piezoelectric thin film resonator 55 is completed. (For example, see Patent Document 1)
FIG. 13 is a sectional view of a piezoelectric thin film resonator having another conventional configuration. A filter (SCF: Stacked Crystal Filter) is configured by stacking two stages of piezoelectric resonators. In this piezoelectric thin film resonator, an acoustic mirror 56 in which materials 56 a and 56 b having different acoustic impedances are alternately stacked is formed on a substrate 51. A lower electrode 52 is provided above the acoustic mirror 56, and further, a lower piezoelectric body 53a, an intermediate electrode 57, an upper piezoelectric body 53b, and an upper electrode 54 are provided to form a piezoelectric thin film resonator filter 58.

The piezoelectric thin film resonator filter 58 uses an acoustic mirror 56 instead of a cavity in order to effectively confine piezoelectric vibration, and is deposited on the substrate 51 by sputtering, CVD (Chemical Vapor Deposition), or the like. . Usually, a material such as tungsten (W) or molybdenum (Mo) is used for the high acoustic impedance layer. On the other hand, silicon oxide (SiO ₂ ), Si (silicon), or the like is used for the low acoustic impedance layer.

In the manufacturing process, after an insulating layer (not shown) is formed on the acoustic mirror 56 as necessary, the lower electrode 52 made of Mo or the like is patterned, and the lower piezoelectric body 53a made of AlN or the like is deposited. . Next, the intermediate electrode 57 made of Mo, the upper piezoelectric body 53b, and the upper electrode 54 are sequentially formed to complete the piezoelectric thin film resonator filter 58. (For example, see Patent Document 2)
As described above, an electrode and a piezoelectric layer, which are constituent elements of a piezoelectric thin film resonator, are sequentially formed on a substrate to realize a piezoelectric thin film resonator that is easy to manufacture.
JP 2002-314368 A US Pat. No. 5,821,833

  However, in the conventional configuration shown in FIGS. 12 and 13, since the piezoelectric body is deposited after the patterning of the lower electrode, it is introduced at the time of patterning the lower electrode, that is, in the etching of the lower electrode, the resist removal process, or the like. In addition, there has been a problem that the crystallinity of the piezoelectric body is deteriorated due to the influence of oxidation or roughening of the electrode surface.

  The present invention solves the above-described conventional problems, and provides a piezoelectric thin film resonator excellent in manufacturability with low loss, avoiding deterioration of crystallinity of a piezoelectric body caused by a patterning process of a lower electrode. For the purpose.

  In order to solve the above problems, a piezoelectric thin film resonator according to the present invention includes a substrate, a lower electrode formed in a predetermined planar shape on one main surface of the substrate, and an upper portion of the lower electrode. A piezoelectric body provided in a planar region of the lower electrode; and an upper electrode disposed on the upper side of the piezoelectric body, and a functional portion of a resonator is formed by the lower electrode, the piezoelectric body, and the upper electrode. Composed.

  The method for manufacturing a piezoelectric thin film resonator of the present invention includes a step of forming a lower electrode layer on one main surface of a substrate, a step of forming a piezoelectric layer on the lower electrode layer, and a step of forming on the piezoelectric layer. A step of forming an upper electrode layer, a step of patterning the upper electrode layer into a predetermined shape after completion of the above steps, and forming an upper electrode; and a patterning of the piezoelectric layer into a predetermined shape to form a piezoelectric body And a step of patterning the lower electrode layer into a predetermined shape to form a lower electrode.

  According to the piezoelectric thin film resonator of the present invention, since the piezoelectric body is formed by the piezoelectric film formed on the lower electrode that has not been processed after film formation, the crystallinity of the piezoelectric body is good and the Q value is good. A resonator having a high (resonance sharpness) can be obtained. Further, the surface oxidation of the electrode material can be prevented, the electrical resistance is not deteriorated, the contact resistance with other wiring is small, and a low-loss piezoelectric thin film resonator can be obtained.

  According to the method for manufacturing an electronic component of the present invention, the lower electrode, the piezoelectric body, and the upper electrode are collectively formed, so that the manufacturing period is greatly shortened, and a piezoelectric body having excellent crystallinity is obtained. Thus, a piezoelectric thin film resonator having excellent high frequency characteristics can be obtained.

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

  FIG. 1 is a cross-sectional view schematically showing the basic structure of a piezoelectric thin film resonator according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a substrate, and a lower electrode 2 is formed in a predetermined shape on one main surface thereof. A cavity 1 a is provided below the lower electrode 2 in the substrate 1. A piezoelectric body 3 and an upper electrode 4 are sequentially provided on the lower electrode 2 to constitute a piezoelectric thin film resonator 5.

  The piezoelectric body 3 is provided in the region of the lower electrode 2 in a planar shape. The planar shape means a projected shape on the main surface of the substrate 1, that is, a shape of a surface parallel to the main surface of the substrate 1. The upper electrode 4 is provided in a planar area of the piezoelectric body 3. The lower electrode 2, the piezoelectric body 3, and the upper electrode 4 constitute a functional part of the resonator. According to this structure, as will be described later, the piezoelectric body 3 having good crystallinity can be formed, and a piezoelectric thin film resonator having excellent resonance characteristics can be obtained.

  FIG. 2 is a cross-sectional view schematically showing a modification of the structure of the piezoelectric thin film resonator of FIG. In this structure, an insulating layer 6 is provided between the lower electrode 2 and the substrate 1. By providing the insulating layer 6, even when a semiconductor such as silicon is used for the substrate 1, a piezoelectric thin film resonator having good high-frequency characteristics can be obtained.

  Next, a method for manufacturing the piezoelectric thin film resonator in the present embodiment will be described in detail with reference to FIG. FIG. 3 is a schematic cross-sectional view of the manufacturing process. The piezoelectric thin film resonator including the insulator layer 6 as shown in FIG. 2 sequentially shows the manufacturing process including the wiring electrodes. FIG. 4 is a top view showing a schematic configuration of the piezoelectric thin film resonator formed in the step shown in FIG. A sectional view taken along line A-A ′ in FIG. 4 corresponds to FIG.

  First, as shown in FIG. 3A, a recess is formed in a silicon substrate 1 provided with an insulating film 6 made of a silicon thermal oxide film or silicon nitride by using an anisotropic etching technique. Further, the sacrificial layer 1ax is formed by filling the recess with a material made of easily soluble phosphosilicate glass (PSG). After the sacrificial layer 1ax is planarized, a lower electrode layer 2x made of molybdenum (Mo) or the like is formed by sputtering.

  Next, as shown in FIG. 3B, without subjecting the lower electrode layer 2x to processing such as pattern formation, the piezoelectric layer 3x made of aluminum nitride or the like is continuously sputtered in the same manner as the lower electrode. Form.

  Next, as shown in FIG. 3 (c), the upper electrode layer 4x made of Mo is placed on the piezoelectric layer 3x as in the lower electrode layer 2x without performing processing such as pattern formation on the piezoelectric layer 3x. The film is formed.

  Next, a device forming process is started. First, the upper electrode layer 4x is patterned by a normal photolithography technique to form the upper electrode 4 as shown in FIG. Next, the piezoelectric layer 3x is similarly patterned to form the piezoelectric body 3 as shown in FIG. 3 (e), and the lower electrode layer 2x is similarly patterned to obtain FIG. 3 (f). As shown, the lower electrode 2 is formed.

  Next, as shown in FIG. 3G, an insulator 7 is formed in order to insulate the lower electrode 2 and perform wiring for the upper electrode 4. The insulator 7 is preferably made of silicon nitride, silicon oxide, TEOS (Tetraethyl orthosilicate) film, aluminum nitride, or the like.

  Next, as shown in FIG. 3H, the wiring electrode 8 is formed on the insulator 7. At the same time, the wiring electrode 9 for the lower electrode 2 can be formed. The material of the wiring electrodes 8 and 9 is not limited at all, but is preferably set to be thicker than the upper and lower electrodes 4 and 2. Thereby, in the peripheral part of the thin film layer which comprises a piezoelectric thin film resonator, the disconnection by the lack of coverage does not generate | occur | produce, but a highly reliable piezoelectric thin film resonator can be obtained.

  Finally, the sacrificial layer 1ax is dissolved and removed with a suitable solvent to form the cavity 1a as shown in FIG. 3 (i), and the piezoelectric thin film resonator 5 is obtained. In addition, an insulator layer for protecting the functional unit, a trimming layer for frequency adjustment, and the like may be provided.

  As described above, in the steps of FIGS. 3A and 3B, the lower electrode layer 2x is not subjected to processing such as pattern formation, so that the surface roughness of the lower electrode layer 2x does not deteriorate. . Therefore, the crystallinity of the piezoelectric layer 3x to be subsequently formed is not impaired. Similarly, since the piezoelectric layer 3x is formed without undergoing many wet processes such as a normal etching process, a resist removing process, and a cleaning process, the piezoelectric layer 3x can be obtained in a state of excellent crystallinity.

  Unlike the present embodiment, when the piezoelectric body 3 is formed after patterning the lower electrode 2, the half-value width of the rocking curve of X-ray diffraction, which is an index indicating the crystallinity of the piezoelectric layer 3x, is 1. Whereas it was about 3 °, when the piezoelectric layer 3x was continuously formed as in the present embodiment, the value improved to about 1.1 °. Further, if the same vacuum film forming apparatus is used, the piezoelectric layer 3x can be formed without being exposed to the atmosphere, so that the surface oxidation of the lower electrode layer 3x can be prevented and the resistivity of the lower electrode 2 is increased. Can be prevented.

  Further, as shown in the steps of FIGS. 3B and 3C, since the upper electrode layer 4x is formed on the piezoelectric layer 3x without forming any pattern, a high quality upper electrode layer 4x is obtained. Can do. Further, since the step portion is not formed by the piezoelectric layer 3x, even if the thickness of the upper electrode layer 4x is thin, there is no problem such as coverage of the electrode film, which can be said to be a highly reliable manufacturing method.

  Further, through the steps up to FIG. 3C, a substrate in which the lower electrode layer 2x, the piezoelectric layer 3x, and the upper electrode layer 4x are continuously formed on the substrate 1 can be obtained. Since a process such as pattern formation does not enter midway, film formation can be performed in a single film formation apparatus without being exposed to the atmosphere. Therefore, the manufacturing process can be greatly shortened, and a high-quality multilayer film can be obtained without the introduction of foreign foreign matters.

  As described above, since the pattern is sequentially formed from the upper electrode 4, each pattern shape is formed so as to spread outside the range of the pattern shape located above. In other words, each pattern shape is arranged within the range of the pattern shape located below. Therefore, for example, it is possible to prevent a problem that the upper electrode 4 and the lower electrode 2 are electrically connected to intersect with a step formed by the piezoelectric body 3. Even when the upper electrode 4 is thinner than the piezoelectric body 3 or when the cross-sectional shape of the piezoelectric body 3 is steep, problems such as insufficient coverage can be avoided.

  In the present embodiment, an example in which aluminum nitride (AlN) is used as the piezoelectric body 3 has been shown, but the same thing can be achieved by using other piezoelectric thin films such as zinc oxide (ZnO) and lead zirconate titanate (PZT). A device can be realized. Moreover, although the example which used molybdenum (Mo) as the upper-and-lower part electrodes 2 and 4 was shown, it does not restrict to this. Moreover, although the example which used the silicon substrate as the board | substrate 1 was shown, you may use a sapphire board | substrate, a glass substrate, etc., and when using such an insulation board | substrate, the insulation between the board | substrate 1 and the lower electrode 2 is used. The body layer 6 is not always necessary.

  Further, in the above configuration, the resonator including the cavity 1a formed by the sacrificial layer etching is shown. However, as shown in FIG. May be etched to form the cavity 1b. In this case, the vertical cavity 1b can be formed by using a technique such as Deep-RIE. Moreover, as shown in FIG. 6, it is needless to say that the acoustic mirror 10 in which the materials 10a and 10b having different acoustic impedances are alternately laminated may be formed, and the functional unit similar to that in FIG. 1 may be formed thereon. Yes.

  The piezoelectric thin film resonator in the present embodiment can be manufactured by the manufacturing method shown in FIGS. 7A to 7C instead of the manufacturing method shown in FIG. In the manufacturing method shown in FIGS. 7A to 7C, as shown in FIG. 1, the piezoelectric body 3 is formed in the area of the lower electrode 2 in the planar shape, and the upper electrode 4 is formed in the area of the planar shape of the piezoelectric body 3. This is a method for manufacturing a piezoelectric thin film resonator having the above-described structure by using a substrate bonding technique.

  First, as shown in FIG. 7A (a), a sacrificial layer 12 is laminated on a sacrificial substrate 11. Next, as shown in FIG. 7A (b), a piezoelectric thin film 13 x is formed on the sacrificial layer 12. Here, the sacrificial substrate 11 is a substrate temporarily used in the process of forming the piezoelectric thin film resonator, and is a component not included in the manufactured piezoelectric thin film resonator. For example, sapphire is used as the sacrificial substrate 11. The sacrificial layer 12 is a buffer layer provided to peel the sacrificial substrate 11 from the piezoelectric thin film 13x after a bonding process described later. As the sacrificial layer 12, for example, gallium nitride (GaN) is used.

  The piezoelectric thin film 13x is made of aluminum nitride (AlN), and is formed on the sacrificial layer 12 by MOCVD. Thus, by using the MOCVD method, a piezoelectric layer having excellent film quality can be formed. Note that the MOCVD method is performed at a high temperature of 1050 ° C. However, in this manufacturing method, gallium nitride, which is a high melting point material, is used as the sacrificial layer 12, so that it can sufficiently withstand a high temperature of 1050 ° C. Therefore, using the MOCVD method for forming the piezoelectric thin film 13x causes no problem in the manufacturing process. The sacrificial layer 12 may be made of molybdenum other than gallium nitride.

  Next, as shown in FIG. 7A (c), an electrode layer 14x as a conductor is laminated on the piezoelectric thin film 13x. Next, the laminated electrode layer 14x is patterned to form the lower electrode 14 as shown in FIG. 7A (d). Next, as shown in FIG. 7A (e), a sacrificial layer 15x is laminated on the molded lower electrode 14 and piezoelectric thin film 13x. At this time, the sacrificial layer 15x is laminated thicker than the lower electrode. Then, the laminated sacrificial layer 15x is patterned to form a sacrificial portion 15y as shown in FIG. 7A (f). The sacrificial part 15y is a part that is removed in a cavity part forming step, which will be described later, and forms a cavity part of the piezoelectric thin film resonator by being removed. As a material of the sacrificial layer 15x, for example, a glass-based material such as molybdenum, tungsten silicide, silicon oxide, or PSG can be used. When molybdenum is used as the material for the sacrificial layer 15x, aluminum other than molybdenum is used as the material for the lower electrode.

  Next, as shown in FIG. 7B (g), the holding layer 16 is laminated on the sacrifice portion 15y, the lower electrode 14, and the piezoelectric thin film 13x. As the holding layer 16, an insulator such as silicon oxide (SiO2) or silicon nitride (Si3N4) is desirable. Then, as shown in FIG. 7B (h), a flattening process is performed so that there is no step on the surface of the stacked holding layer 16. This flattening process is performed in order to make it possible to uniformly bond the semiconductor substrates over the entire surface in a bonding process described later. CMP or the like can be used for the planarization treatment, and uniform bonding can be performed by setting the surface roughness to RMS 2000A or less.

Next, as shown in FIG. 7B (i), a semiconductor substrate 17 made of, for example, silicon is formed with a bonding layer 18 made of a gold-tin alloy, and the holding layer 16 is formed on the surface of the bonding layer 18. And paste together. In this example, a gold-tin alloy film is formed as the bonding layer 18 to perform bonding using gold-tin eutectic bonding. Specifically, the sacrificial substrate 11 and the semiconductor substrate 17 are bonded to each other by applying the temperature of 375 ° C. for 10 minutes with the holding layer 16 and the bonding layer 18 facing each other and applying a pressure of 15 N / cm ^2. Match. In addition, if it is a material which can be eutectic-bonded, the same effect can be acquired with alloys other than gold tin. Note that an insulator layer made of silicon oxide, silicon nitride, or the like can be formed between the semiconductor substrate 17 and the bonding layer 18.

  Next, irradiation with yttrium, aluminum, garnet (YAG), and laser is performed from the back surface of the sacrificial substrate 11 to cut the junction of the sacrificial layer 12 made of gallium nitride having a small band gap as shown in FIG. 7B (j). Then, the sacrificial substrate 11 is separated from the semiconductor substrate 17 by peeling between the sacrificial layer 12 and the piezoelectric thin film 13x. As a result, the piezoelectric thin film 13 x, the lower electrode 14, the sacrificial portion 15 y, and the holding layer 16 formed above the sacrificial layer 12 are transferred to the semiconductor substrate 17. Note that the YAG laser used for the peeling is selected by changing the laser wavelength according to the film thickness and type of the sacrificial substrate 11 and the sacrificial layer 12 to be used. It is possible to cope with the case where a material is selected.

  Next, as shown in FIG. 7C (k), an electrode layer 19x that is a conductor is laminated on the surface of the piezoelectric thin film 13x that has been peeled and appears on the surface. Thereafter, the stacked electrode layer 19x is patterned to form the upper electrode 19 as shown in FIG. 7C (l). Further, as shown in FIG. 7C (m), the piezoelectric thin film 13x is patterned to form the piezoelectric body 13. The patterning of the piezoelectric body 13 is performed such that the piezoelectric body 13 is disposed in the region of the lower electrode 14 in a planar shape, and the upper electrode 19 is disposed in the region of the piezoelectric body 13 in a planar shape. Finally, the sacrificial part 15y is removed by etching or the like to form the cavity part 15 as shown in FIG. 7C (n). In this way, a piezoelectric thin film resonator having the same configuration as that shown in FIG. 1 is completed.

  As the sacrificial substrate, a silicon substrate may be used instead of the sapphire substrate. In this case, the sacrificial substrate may be removed by a normal wet etching or dry etching technique. Further, when silicon is used as the sacrificial substrate, silicon oxide, aluminum nitride, or the like can be used as the sacrificial layer 12 in addition to gallium nitride, and the sacrificial substrate can be etched away without forming the sacrificial layer. Needless to say.

  In the present embodiment, the substrates are bonded together using gold-tin eutectic, but instead of forming the sacrificial layer 15y, it is patterned on the lower electrode and around the vibrating portion. A gold tin layer may be formed, and a bonded cavity may be formed in the semiconductor substrate. In this case, steps such as formation and planarization of the holding layer 16 can be omitted, and the manufacturing period can be greatly shortened.

  FIG. 8 is a schematic cross-sectional view of a filter in which the piezoelectric thin film resonators 5 having the above configuration are connected in cascade. The piezoelectric thin film resonators 5 having the above-described configuration are formed on the left and right sides of the substrate 1, respectively, and are cascade-connected by wiring electrodes 8.

  As shown in FIG. 8, the individual piezoelectric thin film resonators 5 developed in the plane direction are formed separately from each other, and the piezoelectric vibration does not leak to each other, and the filter has excellent high frequency characteristics. Can be obtained. In this embodiment, there is no influence of unnecessary spurious, the characteristics of the piezoelectric thin film resonator are improved, and there is no deterioration of the low efficiency of the wiring electrode, so that the filter passing loss is improved by 0.3 dB at 2 GHz. It was.

  As a connection form of the piezoelectric thin film resonator, those shown in the circuit diagrams of FIGS. 9A and 9B are known, and a band-pass filter is configured by appropriately selecting the resonance frequency of the series arm and the parallel arm. be able to. In the filter of FIG. 9A, the piezoelectric thin film resonators 22a, 22b, and 22c are connected to the series arm between the input / output terminals 21a and 21b, the piezoelectric thin film resonators 23a and 23b are connected to the parallel arm, and the inductor 24a is connected to the ground. , 24b. 9B, the piezoelectric thin film resonator 22 is connected to the series arm between the input / output terminals 21a and 21b, the piezoelectric thin film resonators 23a and 23b are connected to the parallel arm, and the inductors 24a and 24b are connected to the ground. It is connected with the intervening. Further, a piezoelectric thin film resonator 25 is inserted between a node between the piezoelectric thin film resonator 23a and the inductor 24a and between a node between the piezoelectric thin film resonator 23b and the inductor 24b. However, the connection method of the resonator is not limited to this.

  FIG. 10 is a block diagram showing a duplexer using these filters. An antenna terminal 32 is connected between the transmission terminal 30 and the reception terminal 31, a transmission filter 33 is interposed between the antenna terminal 32 and the transmission terminal 30, and a phase shift circuit is interposed between the antenna terminal 32 and the reception terminal 31. 34 and the reception filter 35 are inserted to constitute a duplexer 36.

  Such a duplexer is used as a high-frequency component of the wireless device 49 as shown in FIG. In the wireless device 49, a signal from the transmission terminal 40 is transmitted via the duplexer 46 connected to the antenna 48, and a reception signal is transmitted to the reception terminal 41. The duplexer 46 includes a transmission filter 44 and a reception filter 45. A signal from the transmission terminal 40 is supplied to the transmission filter 44 through the baseband unit 42 and the power amplifier 43. The reception signal passes through the reception filter 45 and is output from the reception terminal 41 through the low noise amplifier 47 and the baseband unit 42.

  The configuration of the piezoelectric thin film resonator can also be applied to the case of the conventional piezoelectric thin film resonator filter (configuration in which resonators are stacked) shown in FIG.

  As described above, the piezoelectric thin film resonator of the basic configuration of the present invention includes a substrate, a lower electrode formed in a predetermined planar shape on one main surface of the substrate, and an upper portion of the lower electrode, A piezoelectric body provided in a planar region of the lower electrode; and an upper electrode disposed on the upper side of the piezoelectric body, and a functional portion of a resonator is formed by the lower electrode, the piezoelectric body, and the upper electrode. Composed. As a result, since the piezoelectric body is formed by the piezoelectric film formed on the lower electrode that has not been processed after film formation, a piezoelectric thin film resonator having excellent crystallinity and excellent resonance characteristics of the piezoelectric body is obtained. Obtainable.

  It is preferable that the upper electrode is disposed in a planar area of the piezoelectric body. Thereby, since the upper electrode is not disposed at the end of each thin film layer, a conduction failure due to insufficient coverage can be prevented, and a piezoelectric thin film resonator having excellent reliability can be obtained. In the conventional structure, the problem of coverage could be overcome by actually performing etching with a tapered portion at the end of the lower electrode, but according to the present embodiment, the upper electrode and the lower electrode In both cases, the shape of the electrode end can be freely selected without changing the process conditions.

  In addition, an insulator is provided between any of the substrate, the lower electrode, the piezoelectric body, and the upper electrode, and the lower electrode, the piezoelectric body, or the upper electrode formed on the insulator is It is preferable that the insulator is disposed in a planar area. Thereby, even when a semiconductor such as silicon is used for the substrate, a piezoelectric thin film resonator having good high-frequency characteristics can be obtained.

  Further, the substrate may be configured such that a cavity portion is provided in contact with the main surface of the substrate where the functional portion is formed. Thereby, a piezoelectric thin film resonator having good resonance characteristics can be obtained without inhibiting the piezoelectric vibration.

  In addition, an acoustic mirror layer formed by alternately stacking materials having different acoustic impedances on the main surface of the substrate on which the functional unit is formed is provided, and the functional unit is formed on the acoustic mirror layer. Can be configured. Thereby, piezoelectric vibration can be effectively confined and a piezoelectric thin film resonator having excellent resonance characteristics can be obtained.

  Moreover, it can be set as the structure provided with the insulator formed on the said function part, and the wiring electrode formed on the said insulator and electrically connected with the said upper electrode. Accordingly, the wiring electrode can be separately formed in a region other than the functional part, and an electrode that is sufficiently thicker than the upper electrode and the lower electrode can be formed. Therefore, even when the end of each thin film layer is processed perpendicularly to the substrate, the problem of coverage can be overcome, and a piezoelectric thin film resonator with excellent reliability and high manufacturing yield can be obtained.

  In the method of manufacturing a piezoelectric thin film resonator according to the present invention, in order to obtain the piezoelectric thin film resonator, a step of forming a lower electrode layer on one main surface of a substrate and a piezoelectric layer on the lower electrode layer are formed. A step, a step of forming an upper electrode layer on the piezoelectric layer, a step of patterning the upper electrode layer into a predetermined shape after completion of the above steps, and forming an upper electrode; and a step of forming the piezoelectric layer Patterning to form a piezoelectric body, and patterning the lower electrode layer to a predetermined shape to form a lower electrode. Accordingly, a manufacturing method with high reliability and high process yield can be provided. That is, since the crystallinity of the piezoelectric body is high and the electrode resistance is not deteriorated, a method for manufacturing a piezoelectric thin film resonator excellent in high frequency characteristics and resonance characteristics can be provided. Furthermore, there is no generation of resist residue or the like in the photolithography process, and a piezoelectric thin film resonator excellent in process yield and reliability can be obtained.

  The manufacturing method includes a step of alternately stacking materials having different acoustic impedances on one main surface of the substrate to form an acoustic mirror layer, and forming the lower electrode layer on the acoustic mirror layer. be able to. Accordingly, the manufacturing cost can be reduced, and a thin film layer having good crystallinity and orientation can be obtained, and a method for manufacturing a piezoelectric thin film resonator having excellent resonance characteristics can be provided.

  Further, the material forming the acoustic mirror layer can be an insulator. Thereby, even when a piezoelectric thin film resonator is connected to form a filter, electrical coupling in the acoustic mirror layer can be prevented, and a method for manufacturing a piezoelectric thin film resonator having excellent high frequency characteristics is provided. be able to.

  The piezoelectric thin-film resonator of the present invention is excellent in the crystallinity of a piezoelectric material, excellent in resonance characteristics and high-frequency characteristics, and in low-loss and small piezoelectric vibration devices, filters, antenna duplexers, actuators, mechanical switches, and other functional devices. Useful.

Schematic cross-sectional view showing the structure of a piezoelectric thin film resonator in an embodiment of the present invention Cross-sectional schematic diagram showing a modification of the structure of the piezoelectric thin film resonator of FIG. Sectional schematic diagram showing a method of manufacturing a piezoelectric thin film resonator according to an embodiment of the present invention Schematic top view showing the planar structure of a piezoelectric thin film resonator manufactured by the same manufacturing method Cross-sectional schematic diagram showing the structure of another piezoelectric thin film resonator according to an embodiment of the present invention Sectional schematic diagram showing the structure of still another piezoelectric thin film resonator according to the embodiment of the present invention. Sectional schematic diagram showing another method of manufacturing a piezoelectric thin film resonator according to an embodiment of the present invention Sectional schematic diagram showing the process following FIG. 7A of the manufacturing method Sectional schematic diagram showing the process following FIG. 7B of the manufacturing method Sectional schematic diagram showing the structure of a filter in which piezoelectric thin film resonators in cascade according to an embodiment of the present invention are connected Circuit diagram of a filter using a piezoelectric thin film resonator in an embodiment of the present invention Circuit diagram of another filter using a piezoelectric thin film resonator in an embodiment of the present invention Block diagram of duplexer using piezoelectric thin film resonator in an embodiment of the present invention 1 is a block diagram of a communication device using a piezoelectric thin film resonator according to an embodiment of the present invention. Cross-sectional schematic diagram showing the structure of a conventional piezoelectric thin film resonator Cross-sectional schematic diagram showing the structure of another conventional piezoelectric thin film resonator

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 1a, 1b Cavity 2 Lower electrode 2x Lower electrode layer 3 Piezoelectric body 3x Piezoelectric layer 4 Upper electrode 4x Upper electrode layer 5 Piezoelectric thin film resonator 6 Insulator layer 7 Insulator 8, 9 Wiring electrode 10 Acoustic mirror 10a Low acoustic Impedance layer 10b high acoustic impedance layer 11 sacrificial substrate 12 sacrificial layer 13 piezoelectric body 13x piezoelectric thin film 14 lower electrode 14x electrode layer 15 cavity 15x sacrificial layer 15y sacrificial portion 16 holding layer 17 semiconductor substrate 18 bonding layer 19 upper electrode 19x electrode layer 21a, 21b Input / output terminals 22, 22a, 22b, 22c Piezoelectric thin film resonators 23a, 23b Piezoelectric thin film resonators 24a, 24b Inductors 25 Piezoelectric thin film resonators 30 Transmitting terminals 31 Receiving terminals 32 Antenna terminals 33 Transmitting filters 34 Phase shift circuit 35 Receive filter 36 Duplexer 40 Send Terminal 41 Reception terminal 42 Baseband part 43 Power amplifier 44 Transmission filter 45 Reception filter 46 Duplexer 47 Low noise amplifier 48 Antenna 49 Wireless device 51 Substrate 51a Cavity 52 Lower electrode 53 Piezoelectric element 54 Upper electrode 55 Piezoelectric thin film resonator 56 Acoustic mirror 56a Low acoustic impedance layer 56b High acoustic impedance layer 57 Intermediate electrode 58 Piezoelectric thin film resonator filter

Claims (9)

A substrate,
A lower electrode formed in a predetermined planar shape on one main surface of the substrate;
A piezoelectric body provided in an upper portion of the lower electrode and in a planar shape region of the lower electrode;
An upper electrode disposed on the piezoelectric body;
A piezoelectric thin film resonator in which a functional portion of a resonator is constituted by the lower electrode, the piezoelectric body, and the upper electrode.   The piezoelectric thin film resonator according to claim 1, wherein the upper electrode is disposed in a planar area of the piezoelectric body. An insulator is provided between any layers of the substrate, the lower electrode, the piezoelectric body, and the upper electrode,
2. The piezoelectric thin film resonator according to claim 1, wherein the lower electrode, the piezoelectric body, or the upper electrode formed on an upper portion of the insulator is disposed in a planar area of the insulator.   2. The piezoelectric thin film resonator according to claim 1, wherein a cavity portion is provided in the substrate in contact with a main surface of the substrate on which the functional portion is formed.   An acoustic mirror layer formed by alternately laminating materials having different acoustic impedances on a main surface of the substrate on which the functional part is formed, wherein the functional part is formed on the acoustic mirror layer. Item 2. The piezoelectric thin film resonator according to Item 1.   2. The piezoelectric thin film resonator according to claim 1, further comprising: an insulator formed on the functional unit; and a wiring electrode formed on the insulator and electrically connected to the upper electrode. Forming a lower electrode layer on one main surface of the substrate;
Forming a piezoelectric layer on the lower electrode layer;
Forming an upper electrode layer on the piezoelectric layer;
After completing the above steps, patterning the upper electrode layer into a predetermined shape to form an upper electrode;
Patterning the piezoelectric layer into a predetermined shape to form a piezoelectric body;
And a step of patterning the lower electrode layer into a predetermined shape to form a lower electrode.   8. The method according to claim 7, further comprising forming an acoustic mirror layer by alternately laminating materials having different acoustic impedances on one main surface of the substrate, and forming the lower electrode layer on the acoustic mirror layer. Manufacturing method of the piezoelectric thin film resonator according to the present invention.   The method for manufacturing a piezoelectric thin film resonator according to claim 8, wherein a material forming the acoustic mirror layer is an insulator.

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