JPWO2007119643A1 - Piezoelectric thin film resonator, piezoelectric thin film device, and manufacturing method thereof - Google Patents

Abstract

The piezoelectric thin film resonator (10) includes a substrate (11, 12) having a vibration space (20), and a piezoelectric laminated structure (14) disposed so as to face the vibration space (20). The piezoelectric laminated structure (14) has at least a lower electrode (15), a piezoelectric thin film (16), and an upper electrode (17) arranged in this order from the side close to the vibration space (20). A lower insulating layer (13) is formed in contact with the lower surface of the lower electrode (15), and an upper insulating layer (23) is formed in contact with the lower surface of the upper electrode (17). Side spacers (26) made of a different material from the electrodes are disposed around the outer periphery of the lower electrode (15) and the upper electrode (17). The step at the interface between the side spacer (26) and the electrodes (15, 17) is less than 25 nm. The piezoelectric thin film (16) is made of aluminum nitride. The acoustic impedance of the side spacer (26) is larger than the acoustic impedance of the electrodes (15, 17).

Description

  The present invention relates to a piezoelectric thin film resonator used in a wide range of fields such as a thin film resonator, a thin film VCO (voltage controlled oscillator), a thin film filter, a transmission / reception switch, and various sensors used in mobile communication devices, etc. The present invention relates to a piezoelectric thin film device that is an element to which is applied.

  Devices applying the piezoelectric phenomenon are used in a wide range of fields. With the progress of miniaturization and labor saving of portable devices, the use of surface acoustic wave (SAW) elements as RF and IF filters is expanding. SAW filters have been able to meet the strict requirements of users by improving design and production technology. However, as the frequency of use increases, it approaches the limit of improvement in characteristics, and it is a major technology in terms of both miniaturization of electrode formation and ensuring stable output. Innovation is needed. On the other hand, a thin film bulk acoustic wave resonator (Thin Film Bulk Acoustic Resonator: hereinafter referred to as FBAR, Solid Mounted Bulk Acoustic Resonator: hereinafter referred to as SMR), a stacked thin film bulk acoustic wave resonator and a filter (Stack) using thickness vibration of a piezoelectric thin film. Thin Film Bulk Wave Acoustic Resonators and Filters (hereinafter referred to as SBAR) is a thin support film provided on a substrate on which a thin film mainly composed of a piezoelectric material and an electrode for driving the thin film are formed. Basic resonance is possible. If the filter is configured with FBAR, SMR, or SBAR, it can be remarkably miniaturized, and can be operated with low loss and wideband, and can be integrated with a semiconductor integrated circuit. Is expected.

  Piezoelectric thin film elements such as FBAR, SMR, and SBAR, which are applied to resonators and filters using elastic waves, are manufactured as follows. A dielectric thin film, a conductive thin film, or a laminate of these is formed on a substrate made of a semiconductor single crystal such as silicon and a substrate formed of polycrystalline diamond on a silicon wafer by various thin film forming methods. Forms a basement film. A piezoelectric thin film is formed on the base film, and an upper structure is formed if necessary. After each layer is formed or after all layers are formed, each film is subjected to physical processing or chemical processing to perform fine processing or patterning. A substrate portion located below the vibration region is removed by anisotropic etching to produce a floating structure, and finally, a piezoelectric thin film element is obtained by separating into one element unit.

For example, in a piezoelectric thin film element (FBAR) described in Patent Document 1, a base film, a lower electrode, a piezoelectric thin film, and an upper electrode are formed on a substrate, and then a substrate portion under a portion that becomes a vibration region is formed on the substrate. It is manufactured by removing from the back side to form a vibration space. Piezoelectric materials for piezoelectric thin film elements include aluminum nitride (AlN), zinc oxide (ZnO), cadmium sulfide (CdS), lead titanate (PT (PbTiO ₃ )), and lead zirconate titanate (PZT (Pb ( Zr, Ti) O ₃ )) and the like can be used. In particular, AlN is suitable as a piezoelectric material for a thin film resonator and a thin film filter that have a high propagation speed of elastic waves and operate in a high frequency band.

Patent Document 2 describes the configuration and manufacturing method of an air bridge type FBAR / SBAR device. According to the publication, first, phosphor quartz glass (PSG) is deposited on a silicon wafer as a sacrificial layer, and after CMP, a piezoelectric resonator is fabricated on the sacrificial layer. PSG can be deposited at relatively low temperatures and is etched with dilute H ₂ O: HF solution at very high etch rates. Therefore, the sacrificial layer is removed by etching near or at the end point of the process to form a vibration region. Because all processing is done on the front side of the wafer, this method does not require pattern alignment on both sides of the wafer and large area wafer backside openings.

  An alternative to providing an air / crystal interface is to provide a suitable acoustic mirror. In this method, as described in Patent Document 3, for example, a large acoustic impedance composed of an acoustic Bragg reflector is created under a sandwich structure composed of a lower electrode, a piezoelectric thin film, and an upper electrode. The Bragg reflector is made by alternately laminating layers of a material having a high acoustic impedance and layers of a material having a low acoustic impedance. The thickness of each layer is fixed to 1/4 of the wavelength of the resonance frequency. By forming a laminated film having a sufficient number of layers, the effective impedance at the piezoelectric body / electrode interface can be made much higher than the acoustic impedance of the element, and therefore, the acoustic wave in the piezoelectric body can be effectively confined. . The low acoustic impedance layer can be composed of silicon oxide or aluminum, and the high acoustic impedance layer can be composed of tungsten, platinum, molybdenum or gold. The acoustic resonator obtained by this method is called a solid acoustic mirror mounted resonator (SMR) because there is no air gap under the sandwich structure.

  In any of the piezoelectric thin film resonator structures and manufacturing methods described above, the lower electrode, the piezoelectric thin film, and the upper electrode are still formed in this order. It is also possible to provide an insulator layer on the lower side of the lower electrode and the upper side of the upper electrode and realize a five-layer structure comprising an insulator layer / lower electrode / piezoelectric thin film / upper electrode / insulator layer on the semiconductor substrate. Generally adopted. Furthermore, it is also known that an insulator layer provided below the lower electrode is used as a seed layer for crystal growth, and an insulator layer provided above the upper electrode is used as a protective layer.

  Various improvements have been made to methods for forming thin films such as AlN and ZnO that are used as piezoelectric thin films, and the piezoelectric properties such as electromechanical coupling coefficient, acoustic quality factor (Q value), and frequency temperature coefficient have been improved. It is desired to form an excellent, highly oriented and homogeneous piezoelectric thin film. It is known that the quality of an AlN thin film formed by a thin film forming method such as reactive sputtering is strongly influenced by the properties of the underlying layer on which AlN is deposited. According to Patent Document 4 by the present inventors, in forming an AlN thin film, the RMS fluctuation of the height of the surface of the lower electrode serving as the underlayer is controlled to 50 nm or less, preferably 20 nm or less, and the surface of the lower electrode is remarkably increased. By making it flat, a highly oriented AlN thin film can be deposited. According to the X-ray diffraction measurement of the obtained AlN thin film, the rocking curve full width at half maximum (FWHM) of the (0002) diffraction peak is less than 3.0 °, indicating good piezoelectric characteristics.

  Patent Document 4 describes that the pattern of the lower electrode is formed by a lift-off method. Accordingly, a gradual inclination, for example, an inclination having a taper angle of less than 10 ° is generated on the outer peripheral portion of the lower electrode. Here, the taper angle is an angle (inclination angle) between the upper surface of the lower electrode outer peripheral portion and the lower surface (that is, a surface in contact with the base insulating layer and parallel to the silicon substrate).

  On the other hand, when the electrode pattern is formed by wet etching, the outer periphery thereof has a steep inclination with a taper angle of 70 ° or more. An example of a piezoelectric thin film resonator in which the inclination angle of the electrode outer peripheral portion is steep is shown in FIGS. 1A is a schematic plan view showing an example of a piezoelectric thin film resonator, FIG. 1B is an XX cross-sectional view thereof, and FIG. 1C is an enlarged view of a portion surrounded by a dotted line in FIG. 1B. In these drawings, the piezoelectric thin film resonator 10 includes a substrate 11, insulator layers 12 and 13 formed on the upper surface of the substrate 11, and a vibration space 20 formed by removing a part of the insulator layer 12. It has the piezoelectric laminated structure 14 formed so that it might straddle. The piezoelectric laminated structure 14 includes a lower electrode 15 formed on the upper surface of the insulator layer 13, a piezoelectric thin film 16 formed on the upper surface of the insulator layer 13 so as to cover a part of the lower electrode 15, and the piezoelectric thin film 16 The upper electrode 17 is formed on the upper surface of the piezoelectric thin film 16. A cavity 20 that forms a vibration space is formed on the substrate 11. A part of the insulator layer 13 is exposed toward the vibration space 20.

  When the inclination angle of the lower electrode outer periphery exceeds 45 degrees and becomes steep, as shown in FIG. 1C, abnormal growth (separated growth) of AlN as a piezoelectric thin film occurs at the edge of the lower electrode outer periphery, and adjacent columnar AlN Deep crater-like defects 30 are generated between the particles. This crater-like defect causes destruction of the AlN film, and the reliability of the piezoelectric thin film resonator is impaired.

  Similarly, abnormal growth of AlN used as the upper insulator layer also occurs from the edge of the outer periphery of the upper electrode whose inclination angle is approximately 90 °, and deep crater-like defects 31 are generated between adjacent columnar AlN grains.

  2A is a schematic plan view showing an example of another piezoelectric thin film resonator different from the above, and FIGS. 2B and 2C are an XX sectional view and a YY sectional view, respectively. In these drawings, members having the same functions as those in FIGS. 1A to 1C are denoted by the same reference numerals.

  In these drawings, the piezoelectric thin film resonator 10 includes a substrate 11, an insulator layer 13 formed on the upper surface of the substrate 11, and a piezoelectric laminated structure 14 formed on the upper surface of the insulator layer 13. . The piezoelectric laminated structure 14 includes a lower electrode 15 formed on the upper surface of the insulator layer 13, a piezoelectric thin film 16 formed on the upper surface of the insulator layer 13 so as to cover a part of the lower electrode 15, and the piezoelectric thin film 16 The upper electrode 17 is formed on the upper surface of the piezoelectric thin film 16.

  Since the inclination angle of the outer periphery of the lower electrode is a steepness close to 90 ° (vertical), abnormal growth of AlN occurs at the edge of the outer periphery of the lower electrode as shown in FIG. 2C, and between adjacent columnar AlN particles. A deep crater-like defect 30 is produced. This crater-like defect causes destruction of the AlN film, and the reliability of the piezoelectric thin film resonator is impaired.

In Patent Document 5 by Ruby et al., The end of the lower electrode is inclined by a dry etching method using oxygen (O ₂ ) and sulfur hexafluoride (SF ₆ ) as an etching gas so that the taper angle is 60 ° or less. A method of controlling is disclosed. According to the publication, by controlling the taper angle to 60 ° or less, it is possible to suppress the occurrence of voids and discontinuous boundaries in the vicinity of the edge (lower electrode end) of the AlN thin film deposited and grown thereon. ing. However, in this publication, as an effect of reducing voids and discontinuous boundaries in the AlN thin film, improvement in dielectric strength, power handling capacity, and electrostatic discharge (ESD) is improved. The effect is only mentioned.

  Similarly, Patent Document 6 by Ginsburg et al. Discloses a method in which a taper angle is controlled to 30 ° or less by providing a slope at a lower electrode end by a dry etching method. According to the publication, it is described that by controlling the taper angle to 30 ° or less, the generation of cracks in the vicinity of the edge of the AlN thin film deposited and grown thereon can be suppressed. However, this publication only reports that the production yield of a die that becomes a piezoelectric thin film resonator is improved by 15 to 80% as an effect of reducing cracks in the AlN thin film.

  As is clear from the above-mentioned known literatures and the like, in the manufacture of a piezoelectric thin film resonator, it is possible to prevent the occurrence of crater-like defects due to the separate growth of the piezoelectric thin film by providing a gentle slope on the outer periphery of the lower electrode. is important.

  In the piezoelectric thin film resonator shown in FIGS. 2A to 2C, the cross-sectional shape of the outer periphery of the lower electrode is changed to provide a gentle inclination to prevent crater-like separated growth that occurs from the edge of the outer periphery of the electrode during AlN thin film growth. An example is shown in FIG. By making the inclination angle θ with respect to the lower surface of the upper surface at the outer peripheral portion of the lower electrode 15 equal to or less than 30 °, crater-like separation growth is prevented. 2A to 2C and FIG. 3, the membrane 21 has an inclination angle of the upper electrode end portion close to about 90 ° and an outer peripheral portion of the upper electrode above the vibration space 20. It spreads outside beyond the outer peripheral edge, and is in a position supported by the thick substrate 11 via the insulator layer 13.

JP 60-142607 A JP 2000-69594 A JP-A-6-295181 JP 2005-236337 A US Patent Application Publication No. 20030141946 US Patent Application Publication No. 20040263287

  Until now, various studies have been made to apply an AlN thin film to FBAR, SMR, or SBAR. However, piezoelectric thin film resonators and piezoelectric thin film filters that exhibit sufficient performance in the gigahertz band have not yet been obtained, and improvements in the acoustic quality factor (Q value) and insertion loss of the resonators are desired. In order to improve the acoustic quality factor (Q value), it is necessary to form a highly oriented and uniform AlN thin film. For this reason, a method has been adopted in which a gradual slope is provided on the outer periphery of the lower electrode formed on the substrate to prevent crater-like separation growth in the growth of the AlN thin film.

  However, providing the outer peripheral portion of the lower electrode with an inclination means that the vibration state of the elastic wave is slightly different between the central portion and the outer peripheral portion of the resonator. As a result, when the inclination of the outer peripheral portion of the lower electrode becomes excessively gentle, the horizontal distance of the inclined portion becomes too long, and there is a problem that the acoustic quality factor (Q value) of the piezoelectric thin film resonator is remarkably reduced. In addition, many noises are generated near the resonance peak in the impedance characteristic. As described above, various effects are caused on the piezoelectric characteristics, which is not preferable. Further, the same influence is observed on the inclination of the outer periphery of the upper electrode.

  Therefore, the present invention solves the above-mentioned characteristic problems associated with the provision of the slopes on the outer periphery of the lower electrode or the upper electrode, thereby taking advantage of the characteristics of the AlN thin film and reducing the electromechanical coupling coefficient. An object of the present invention is to provide a piezoelectric thin film resonator that is large, excellent in acoustic quality factor (Q value), and extremely high in performance in terms of characteristics such as insertion loss, and a piezoelectric thin film device using the same.

  The present inventors have intensively studied how the properties of an aluminum nitride thin film that greatly affects the resonance characteristics of FBAR, SMR, or SBAR are affected by the shape and material of the outer periphery of the lower electrode or upper electrode. went. As a result, a side spacer made of a material different from that of the lower electrode or the upper electrode is provided adjacent to the outer peripheral portion of the lower electrode or the upper electrode, and a step at the interface between the side spacer and the outer periphery of the lower electrode or the upper electrode is provided. By setting the thickness to less than 25 nm, the aluminum nitride thin film formed between the lower electrode and the upper electrode has a high crystallinity and no rocking curve half-width (FWHM) of 2.0 ° or less without crater-like separation growth. It has been found that a negative c-axis oriented aluminum nitride thin film can be obtained, and the adverse effect on the piezoelectric characteristics due to the inclination of the outer peripheral portion of the lower electrode or the upper electrode can be eliminated. Furthermore, by preparing the metal thin film constituting the lower electrode or the upper electrode to have a specific material, structure and crystal phase, the rocking curve half-width (FWHM) is 0.8 to 1.6 °, It has been found that a c-axis oriented aluminum nitride thin film having excellent orientation and crystallinity can be obtained. By using such a highly oriented and highly crystalline c-axis oriented aluminum nitride thin film, the electromechanical coupling coefficient is large, the acoustic quality factor (Q value) is large, the loss is low, and the performance is high. The present inventors have found that FBAR, SMR or SBAR can be realized and have reached the present invention.

According to the present invention, the above object is achieved as follows:
A substrate having a vibration space or an acoustic reflection layer; and a piezoelectric multilayer structure disposed so as to face the vibration space or the acoustic reflection layer, the piezoelectric multilayer structure being close to the vibration space or the acoustic reflection layer A piezoelectric thin film resonator having at least a lower electrode, a piezoelectric thin film and an upper electrode arranged in order from the side,
A side spacer made of a material different from that of the electrode is disposed around an outer peripheral portion of at least one of the lower electrode and the upper electrode, and a step at an interface between the side spacer and the electrode is less than 25 nm. A piezoelectric thin film resonator characterized by
Is provided.

  In one aspect of the present invention, the piezoelectric thin film is made of aluminum nitride (AlN). In one aspect of the present invention, the piezoelectric thin film made of aluminum nitride has a rocking curve half-width (FWHM) of a (0002) diffraction peak of 0.8 to 1.6 °.

  In one aspect of the present invention, the step at the interface between the side spacer and the electrode is less than 3 nm. In one aspect of the present invention, the side spacer has an upper surface formed in a slope shape with respect to the lower surface. In one aspect of the present invention, the side spacer has an inclination angle of the upper surface with respect to the lower surface of 3 to 45 degrees. In one aspect of the present invention, the acoustic impedance of the side spacer is larger than the acoustic impedance of the electrode.

In one aspect of the present invention, the side spacer is made of an insulator. In one embodiment of the present invention, the side spacer includes silicon dioxide (SiO ₂ ), silicon nitride (SiN _x ), silicon oxynitride (Si ₂ ON ₂ ), aluminum nitride (AlN), and aluminum oxynitride (AlO _x N). _y ), an insulator mainly composed of at least one material selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

In one aspect of the present invention, the side spacer is made of a conductor. In one aspect of the present invention, the side spacer is made of a conductor whose main component is at least one material selected from the group consisting of tungsten (W), tungsten silicide (WSi _x ), and iridium (Ir).

  In one aspect of the present invention, at least one of the upper electrode and the lower electrode is made of molybdenum. In one aspect of the present invention, at least one of the upper electrode and the lower electrode is composed of a laminate of two kinds of metals selected from the group consisting of molybdenum, ruthenium, aluminum, iridium, cobalt, nickel, platinum, and copper. ing.

  In one embodiment of the present invention, the lower electrode is a laminate of a lower metal layer having a thickness d1 and an upper metal layer having a thickness d2, where d1 / d2> 1 and 150 nm <(d1 + d2) <450 nm. It is. In one embodiment of the present invention, the upper electrode is a laminate of a lower metal layer having a thickness d3 and an upper metal layer having a thickness d4, d4 / d3> 1, and 150 nm <(d3 + d4) <450 nm. It is.

  In one aspect of the present invention, the vibration region defined as a region where the lower electrode and the upper electrode overlap with each other when viewed in the thickness direction of the piezoelectric multilayer structure is inside the vibration space or the outer peripheral edge of the acoustic reflection layer. Located in. In one aspect of the present invention, the distance w between the end of the vibration region and the outer periphery of the vibration space or the acoustic reflection layer, as viewed in the thickness direction of the piezoelectric multilayer structure, and the piezoelectric in the vibration region The total t of the thickness of the laminated structure and the thickness of the insulating layer satisfies the relational expression 0 <w / t ≦ 2.

In one aspect of the present invention, an insulating layer is attached to the upper surface or the lower surface of the piezoelectric multilayer structure. In one aspect of the present invention, the insulating layer is formed in contact with the lower surface of the lower electrode. In one aspect of the present invention, the insulating layer is formed in contact with the upper surface of the upper electrode. In one embodiment of the present invention, the insulating layer includes aluminum nitride (AlN), aluminum oxynitride (AlO _x N _y ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (SiN _x ), silicon oxynitride (Si ₂ ON ₂ ), zirconium oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ) as a main component.

  In one embodiment of the present invention, the thickness d5 of the lower insulating layer formed in contact with the lower surface of the lower electrode is 25 to 300 nm. In one embodiment of the present invention, the thickness d6 of the upper insulating layer formed in contact with the upper surface of the upper electrode is 40 to 600 nm. In one embodiment of the present invention, the ratio d6 / d5 between the thickness d6 of the insulating portion and the thickness d5 of the lower insulating layer satisfies the relational expression 1 ≦ d6 / d5 <4.

  Furthermore, in one aspect of the present invention, the piezoelectric thin film resonator has an anti-resonance peak acoustic quality factor (Q value) of 1000 or more in an impedance curve.

  The present invention also provides a piezoelectric thin film device configured by combining a plurality of the above-described piezoelectric thin film resonators. The piezoelectric thin film resonator includes a stacked piezoelectric thin film resonator. Examples of the piezoelectric thin film device include, but are not limited to, a VCO (Voltage Controlled Oscillator), a filter, and a transmission / reception switch configured using the piezoelectric thin film resonator and the laminated piezoelectric thin film resonator as described above. is not. In such a piezoelectric thin film device, characteristics at a high frequency of 1 GHz or more can be remarkably improved.

Furthermore, according to the present invention, the above object is achieved as follows:
A method of manufacturing the above piezoelectric thin film resonator,
A first step of forming a lower insulating layer on the substrate;
A second step of forming the lower electrode on the lower insulating layer;
After depositing an insulator or a conductor having a different material from that of the lower electrode on the exposed surfaces of the lower electrode and the lower insulating layer, the upper surface of the lower electrode is exposed by etch back, and the periphery of the outer periphery of the lower electrode A third step of forming the side spacer for the lower electrode in
A fourth step of forming a piezoelectric material layer on the exposed surfaces of the lower electrode, the lower electrode side spacer and the lower insulating layer;
A fifth step of forming the upper electrode on the piezoelectric material layer;
A sixth step of patterning the piezoelectric material layer to form the piezoelectric thin film;
A method for manufacturing a piezoelectric thin film resonator, comprising: a seventh step of forming an upper insulating layer on the piezoelectric thin film and the upper electrode;
Is provided.

  In one embodiment of the present invention, an insulator or a conductor having a different material from that of the upper electrode is deposited on the exposed surfaces of the upper electrode and the piezoelectric material layer between the fifth step and the sixth step. Thereafter, an upper surface of the upper electrode is exposed by etch back, and a step of forming the side spacer for the upper electrode around the outer peripheral portion of the upper electrode is interposed.

Furthermore, according to the present invention, the above object is achieved as follows:
A method of manufacturing the above piezoelectric thin film resonator,
A first step of forming a lower insulating layer on the substrate;
A second step of forming the lower electrode on the lower insulating layer so that the end thereof has a slope shape;
A third step of forming a piezoelectric material layer on the exposed surfaces of the lower electrode and the lower insulating layer;
A fourth step of forming the upper electrode on the piezoelectric material layer;
A fifth step of patterning the piezoelectric material layer to form the piezoelectric thin film;
After depositing an insulator or a conductor having a different material from that of the upper electrode on the exposed surfaces of the upper electrode and the piezoelectric thin film, the upper surface of the upper electrode is exposed by etch back, and around the outer periphery of the upper electrode. A sixth step of forming the side spacer for the upper electrode;
A method for manufacturing a piezoelectric thin film resonator, comprising: a seventh step of forming an upper insulating layer on the piezoelectric thin film and the upper electrode;
Is provided.

  In a piezoelectric thin film resonator having at least a lower electrode, a piezoelectric thin film, and an upper electrode disposed on a substrate, a side spacer made of a material different from the electrode is provided on the outer periphery of at least one of the lower electrode and the upper electrode. By forming an aluminum nitride thin film between the upper and lower electrodes produced by controlling the processing method so that the step at the interface between the side spacer and the electrode is less than 25 nm, a high crater-like separation and growth can be achieved. An oriented and highly crystalline c-axis oriented aluminum nitride thin film is obtained. Furthermore, by preparing the metal thin film constituting the electrode to have a specific material, structure or crystal phase, the rocking curve half-width (FWHM) of the (0002) diffraction peak is 2.0 ° or less, preferably A highly oriented and highly crystalline c-axis oriented aluminum nitride thin film of 0.8 to 1.6 ° can be formed.

  Here, the side spacer is formed around the electrode in contact with the side wall of the outer periphery of the electrode.

By providing the side spacer, the adverse effect on the piezoelectric characteristics caused by the inclination of the lower electrode or the upper electrode end, which has been a problem in the conventional piezoelectric thin film resonator, can be eliminated, and the electromechanical coupling coefficient k _t ² And a high-performance and high-reliability piezoelectric thin film resonator excellent in acoustic quality factor (Q value). Therefore, characteristics at a high frequency of 1 GHz or more can be remarkably improved in piezoelectric thin film devices such as a VCO (Voltage Controlled Oscillator), a filter, and a transmission / reception switch configured using the same.

1 is a schematic plan view showing an example of a piezoelectric thin film resonator. It is XX sectional drawing of FIG. 1A. It is an enlarged view of the part enclosed with the dotted line in FIG. 1B. 1 is a schematic plan view showing an example of a piezoelectric thin film resonator. It is XX sectional drawing of FIG. 2A. It is YY sectional drawing of FIG. 2A. 2A to 2C are cross-sectional views showing an example in which a gentle slope is provided by changing the cross-sectional shape of the outer peripheral portion of the lower electrode in the piezoelectric thin film resonator of FIGS. 1 is a schematic plan view showing an embodiment of a piezoelectric thin film resonator according to the present invention. It is XX sectional drawing of FIG. 4A. FIG. 4B is an enlarged view of a portion surrounded by a dotted line in FIG. 4B. It is typical sectional drawing for demonstrating the process of forming a side spacer around the side wall of a lower electrode. It is typical sectional drawing for demonstrating the process of forming a side spacer around the side wall of a lower electrode. It is typical sectional drawing for demonstrating the process of forming a side spacer around the side wall of a lower electrode. It is typical sectional drawing for demonstrating the process of forming a side spacer around the side wall of a lower electrode. 1 is a schematic plan view showing an embodiment of a piezoelectric thin film resonator according to the present invention. It is XX sectional drawing of FIG. 7A. It is YY sectional drawing of FIG. 7A. It is an enlarged view of the part enclosed with the dotted line in FIG. 7C. 1 is a schematic plan view showing an embodiment of a laminated piezoelectric thin film resonator according to the present invention. It is XX sectional drawing of FIG. 8A. It is a typical top view of the thin film piezoelectric filter as one embodiment of the piezoelectric thin film device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Piezoelectric thin film resonator 11 Substrate 12 made of single crystal or polycrystal Substrate insulating layer 13 Lower insulating layer (lower insulating layer)
DESCRIPTION OF SYMBOLS 14 Piezoelectric laminated structure 15 Lower electrode 15a Lower electrode main-body part 15b Lower electrode terminal part 16, 16-1, 16-2 Piezoelectric thin film (piezoelectric thin film)
17 Upper electrode 17a Upper electrode main part 17b Upper electrode terminal part 17 'Internal electrode 18 Upper electrode 18a in laminated piezoelectric thin film resonator Upper electrode main part 18b in laminated piezoelectric thin film resonator Upper electrode in laminated piezoelectric thin film resonator Terminal part 19 of etching via hole 20 vibration space 21 formed in substrate by etching membrane 23 located above vibration space upper insulator layer (upper insulation layer)
25 Thin film deposited for side spacer formation 26 Side spacer formed adjacent to electrode outer periphery

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 4A is a schematic plan view showing an embodiment of a piezoelectric thin film resonator according to the present invention, and FIG. 4B is an XX sectional view thereof. FIG. 4C is an enlarged view of a portion surrounded by a dotted line in FIG. 4B. In these drawings, the piezoelectric thin film resonator 10 includes a substrate 11, an insulating layer 12 formed on the upper surface of the substrate 11, a lower insulating layer 13, and a cavity formed by removing a part of the insulating layer 12. The piezoelectric laminated structure 14 is formed so as to straddle the vibration space 20. In addition, it can be considered that the board | substrate said by this invention is comprised by the member which consists of the board | substrate 11 and the insulating layer 12. FIG. In this sense, the insulating layer 12 is referred to as a substrate insulating layer. Thus, the vibration space 20 is formed on the substrate referred to in the present invention. The piezoelectric laminated structure 14 includes a lower electrode 15 formed on the upper surface of the lower insulating layer 13, a piezoelectric thin film 16 formed on the upper surface of the lower insulating layer 13 so as to cover a part of the lower electrode 15, and An upper electrode 17 formed on the upper surface of the piezoelectric thin film 16 is included. A part of the lower insulating layer 13 is exposed toward the vibration space 20. The exposed portion of the lower insulating layer 13 and the portion of the piezoelectric laminated structure 14 corresponding thereto constitute a membrane (vibrating membrane) 21. As described above, the lower insulating layer 13 is interposed between the piezoelectric multilayer structure 14 and the vibration space 20. The piezoelectric multilayer structure 14 is included in the vibration space 20 including such a configuration. It shall be facing. The lower electrode 15 and the upper electrode 17 include main portions 15a and 17a formed in a region corresponding to the membrane 21, and terminal portions 15b and 17b for connecting the main portions 15a and 17a to an external circuit. Have. The terminal portions 15 b and 17 b are located outside the region corresponding to the membrane 21.

  As the substrate 11, a single crystal such as Si (100) single crystal or a substrate in which a polycrystalline film such as silicon, diamond or the like is formed on the surface of a base material such as Si single crystal can be used. As the substrate 11, it is possible to use other semiconductors or those made of an insulator. The specific resistance value of the substrate 11 is, for example, 3 kΩ · cm or more, preferably 5 kΩ · cm or more, and more preferably 7 kΩ · cm or more. As a method for forming the vibration space 20, a via hole 19 penetrating each layer of the piezoelectric multilayer structure and the lower insulating layer 13 is opened, and an etching solution such as a hydrofluoric acid aqueous solution is injected from the via hole 19 to form one of the substrate insulating layers 12. And a method of removing a part of the lower region of the piezoelectric laminated structure including the portion by wet etching. As will be described later, the vibration space may be formed by deep etching from the lower surface side of the substrate 11 (Deep RIE). The vibration space may be any shape of cavity or recess as long as it allows vibration of the membrane 21. Furthermore, instead of forming the vibration space as described above to form an air gap-type piezoelectric thin film resonator, an acoustic reflection layer (acoustic layer) is formed by alternately stacking a high acoustic impedance material layer and a low high acoustic impedance material layer. It is also possible to form an acoustic mirror type piezoelectric thin film resonator by forming an optical Bragg reflector. In the case where the substrate 11 made of silicon is used, a silicon oxide film formed by thermal oxidation of the surface of the substrate 11 can be used as the substrate insulating layer 12.

The lower insulating layer 13 is preferably made of a material having a high elastic modulus. Examples of the lower insulating layer 13 include a dielectric film mainly composed of silicon nitride (SiN _x ), a dielectric film mainly composed of silicon oxynitride (Si ₂ ON ₂ ), and aluminum nitride (AlN) as a main component. A dielectric film containing aluminum oxynitride (AlO _x N _y ) as a main component, a dielectric film containing aluminum oxide (Al ₂ O ₃ ) as a main component, and zirconium oxide (ZrO ₂ ) as a main component And a dielectric film mainly composed of tantalum oxide (Ta ₂ O ₅ ), and a laminated film in which these dielectric films are stacked can be used. Regarding the material of the lower insulating layer 13, the main component refers to a component whose content in the dielectric film is 50 equivalent% or more. The dielectric film may be a single layer or a laminate. Further, it may be composed of a plurality of layers to which a layer for improving adhesion is added.

  Examples of the method for forming the lower insulating layer 13 include sputtering, vacuum deposition, and CVD. In the present invention, the lower insulating layer 13 in the region corresponding to the membrane 21 is completely removed by etching, and the lower electrode 15 is exposed toward the vibration space 20 (that is, the membrane removes the lower insulating layer 13). A piezoelectric thin film resonator having a structure not included) can also be employed. Thus, removing all the insulating layer 13 in the region corresponding to the membrane 21 has an advantage that the electromechanical coupling coefficient is improved, although the temperature characteristic of the resonance frequency is slightly deteriorated.

  The lower electrode 15 is, for example, a metal thin film containing molybdenum (Mo) as a main component, a metal thin film containing ruthenium (Ru) as a main component, a metal thin film containing aluminum (Al) as a main component, or iridium (Ir) as a main component. A metal thin film containing cobalt (Co) as a main component, a metal thin film containing nickel (Ir) as a main component, a metal thin film containing platinum (Pt) as a main component, and copper (Cu) as a main component. At least one metal thin film selected from metal thin films, a metal thin film mainly composed of molybdenum, and at least one metal selected from the group consisting of ruthenium, aluminum, iridium, cobalt, nickel, platinum and copper as a main component It consists of a laminate with a metal thin film. Here, for example, a metal thin film mainly composed of molybdenum means that 90% or more of molybdenum is contained. The lower electrode 15 may be formed by laminating an adhesive metal layer (adhesive layer) formed between the metal thin film and the lower insulating layer 13 as necessary. The portion of the lower electrode other than the adhesion metal layer is referred to as a lower electrode main layer. The thickness of the lower electrode 15 is preferably 150 to 450 nm.

  In the present invention, the lower electrode 15 is a laminate of a metal thin film (second metal layer: upper metal layer) having a thickness d2 and a metal thin film (first metal layer: lower metal layer) having a thickness d1. Can be used. As the upper metal layer or the lower metal layer, a metal thin film mainly composed of molybdenum, or a metal mainly composed of one kind of metal selected from the group consisting of ruthenium, aluminum, iridium, cobalt, nickel, platinum or copper A thin film can be exemplified. Here, when an adhesion layer is provided between the lower metal layer and the lower insulating layer 13, the thickness d1 is a value including the thickness of the adhesion layer. As a relationship between the thickness d2 of the upper metal layer and the thickness d1 of the lower metal layer, it is preferable to adopt a film thickness configuration such that d1 / d2> 1 and 150 nm <(d1 + d2) <450 nm. This is particularly because the upper metal layer with high acoustic impedance and high orientation between the lower metal layer (for example, a metal thin film mainly composed of aluminum) and the piezoelectric thin film (for example, a metal thin film mainly composed of molybdenum). It is preferable when intervening. Thereby, the electrode loss [insertion loss] (IL) and the acoustic quality factor (Q value) of the obtained piezoelectric thin film resonator can be improved. In particular, the acoustic quality factor (Q value) of the anti-resonance peak in the impedance characteristic is improved, and the roll-off characteristic on the high band side of the pass band of the piezoelectric thin film filter manufactured by combining a plurality of piezoelectric thin film resonators is improved. .

  The piezoelectric thin film 16 is preferably made of aluminum nitride (AlN), and the thickness thereof is, for example, 0.5 to 3.0 μm. When used at a frequency of about 1 GHz, the film thickness is increased. When used at a high frequency near 5 GHz, the film thickness is decreased.

  Similar to the lower electrode 15, the upper electrode 17 has a metal thin film mainly composed of ruthenium, a metal thin film mainly composed of aluminum, and a metal thin film mainly composed of iridium in addition to a metal thin film mainly composed of molybdenum. A metal thin film containing cobalt as a main component, a metal thin film containing nickel as a main component, a metal thin film containing platinum as a main component, a metal thin film containing copper as a main component, and molybdenum as a main component. A laminate of a metal thin film as a component and a metal thin film containing as a main component at least one metal selected from the group consisting of ruthenium, aluminum, iridium, cobalt, nickel, platinum, and copper can be used. Further, the upper electrode 17 may be formed by laminating an adhesion metal layer (adhesion layer) formed between the metal thin film and the piezoelectric thin film 16 as described above. The portion of the upper electrode other than the adhesion metal layer is referred to as an upper electrode main layer. The thickness of the upper electrode 17 is preferably 150 to 450 nm.

  In the present invention, the upper electrode 17 is a laminate of a metal thin film having a thickness d3 (third metal layer: lower metal layer) and a metal thin film having a thickness d4 (fourth metal layer: upper metal layer). Can be used. As the lower metal layer or the upper metal layer, a metal thin film mainly composed of molybdenum, or a metal mainly composed of one kind of metal selected from the group consisting of ruthenium, aluminum, iridium, cobalt, nickel, platinum or copper A thin film can be exemplified. Here, when an adhesion layer is provided between the lower metal layer and the piezoelectric thin film 16, the thickness d3 is a value including the thickness of the adhesion layer. Moreover, when the adhesion layer is attached to the upper metal layer, the thickness d4 is a value including the thickness of the adhesion layer. As the relationship between the thickness d3 of the lower metal layer and the thickness d4 of the upper metal layer, it is preferable to adopt a film thickness configuration in which d4 / d3> 1 and 150 nm <(d3 + d4) <450 nm. This is particularly because the lower metal layer (for example, a metal thin film mainly composed of molybdenum) having high acoustic impedance and high orientation between the upper metal layer (for example, a metal thin film mainly composed of aluminum) and the piezoelectric thin film. It is preferable when intervening. Thereby, the electrode loss [insertion loss] (IL) and the acoustic quality factor (Q value) of the obtained piezoelectric thin film resonator can be improved. In particular, the acoustic quality factor (Q value) of the anti-resonance peak in the impedance characteristic is improved, and the roll-off characteristic on the high band side of the pass band of the piezoelectric thin film filter manufactured by combining a plurality of piezoelectric thin film resonators is improved. .

In the present invention, aluminum nitride (AlN), aluminum oxynitride (AlO _x N _y ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (SiN _x ), oxynitride is formed on the upper electrode 17 as necessary. An upper insulating layer 23 mainly composed of at least one material selected from the group consisting of silicon (Si ₂ ON ₂ ), zirconium oxide (ZrO ₂ ) and tantalum oxide (Ta ₂ O ₅ ) is laminated. In this case, the membrane 21 is composed of an exposed portion of the lower insulating layer 13 and portions corresponding to the piezoelectric laminated structure 14 and the upper electrode layer 23 corresponding thereto.

  In the piezoelectric thin film resonator having the configuration shown in these drawings, the present inventors determine how the resonance characteristics depend on the material, shape and crystallinity of the lower electrode, or the properties such as the orientation and crystallinity of the AlN thin film. It was examined whether it depends on.

In the present invention, the piezoelectric laminated structure 14 is formed around the outer periphery of at least one of the lower electrode 15 and the upper electrode 17 and has a side spacer 26 made of a material different from that of the electrode. Yes. The side spacer 26 is made of an insulator or a conductor and has a slope shape. The insulator or conductor used for the side spacer 26 preferably has a bulk density of 1.6 g / cm ³ or more, and preferably uses a material other than resin.

  As a method of forming the side spacers 26 made of the insulator or the conductor as described above, it is general to form a gate electrode of a MOS (Metal-Oxide-Semiconductor) type transistor and a sidewall layer of a gate insulating film (gate oxide film). The side wall spacer technology applied to the can be adopted. An outline of a method of forming a side spacer made of an insulator around the outer peripheral portion of the electrode by the side wall spacer technique is as follows.

5A and 5B are schematic cross-sectional views for explaining a step of forming a side spacer around the outer peripheral portion (side wall) of the lower electrode. In forming the side spacer, first, as shown in FIG. 5A, silicon oxide (SiO ₂ ) (LP-TEOS) is formed on the entire surface of the lower insulating layer 13 by low-pressure CVD so as to cover the patterned lower electrode 15. Is deposited to a thickness of 300 to 900 nm. Other methods for forming the insulating film include SiN _x (LP-SiN _x ) film formation by low-pressure CVD, BPSG (Boron Phosphorate Silicate Glass) film formation by low-pressure CVD, and LP-SiN _x on the LP-SiN _x film. Examples thereof include formation of a SiO ₂ / SiN _x laminated film in which TEOS films are laminated.

Thereafter, as shown in FIG. 5B, until the upper surface of the lower electrode 15 is exposed and the upper surface of the lower electrode 15 is smoothly connected to the surface of the SiO ₂ film by anisotropic dry etching using ICP plasma. By etching back, the side spacers 26 are formed leaving the SiO ₂ film only around the side walls of the lower electrode 15. In order to make the inclination angle of the side spacer 26 gentle, anisotropic dry etching and surface polishing (CMP) can be used in combination.

6A and 6B are also schematic cross-sectional views for explaining the process of forming the side spacer around the side wall of the lower electrode. In forming the side spacer, first, as shown in FIG. 6A, the entire surface of the lower insulating layer 13 is covered with tungsten (W) (LT-W) by a low temperature CVD method so as to cover the patterned lower electrode 15. A conductive film 25 to be formed is deposited to a thickness of 300 to 900 nm. As another method of forming the conductive film, a monosilane-based WSi _x (LT-WSi _x ) film formation by a low temperature CVD method can be exemplified.

Thereafter, as shown in FIG. 6B, the upper surface of the lower electrode 15 is exposed by using an anisotropic dry etching method using ECR plasma or a combination of a surface polishing method (CMP) and a dry etching method. Etching back is performed until the surface of the SiO ₂ film is smoothly connected, thereby forming the side spacer 26 leaving the W film only around the side wall of the lower electrode 15.

  What is important in the formation of the side spacer is to control the etch back conditions so that the step at the interface between the electrode and the side spacer is less than 25 nm, preferably less than 10 nm, and more preferably less than 3 nm. When the level difference between the two interfaces is 25 nm or more, abnormal growth of AlN due to the level difference tends to occur, and a deep crater-like defect may occur between adjacent columnar AlN particles. This crater is not preferable because it causes destruction of the AlN film and impairs reliability as a piezoelectric thin film resonator.

  The thickness d5 of the lower insulating layer 13 formed in contact with the lower surface of the lower electrode is 25 to 300 nm, preferably 30 to 200 nm. When the thickness of the lower insulating layer 13 is less than 25 nm, the crystal orientation of the metal thin film mainly composed of molybdenum, ruthenium, aluminum, iridium, cobalt, nickel, platinum, copper, etc. deposited thereon is likely to deteriorate. The half-width of the rocking curve of the corresponding X-ray diffraction peak tends to be wide. The widening of the full width at half maximum of the rocking curve of the metal thin film serving as the lower electrode brings about a decrease in the crystal orientation of the AlN thin film deposited on the upper surface thereof. When the thickness of the lower insulating layer 13 exceeds 300 nm, the electromechanical coupling coefficient of the obtained piezoelectric thin film resonator tends to decrease, and the piezoelectric characteristics tend to deteriorate.

  The thickness d6 of the upper insulating layer 23 formed in contact with the upper surface of the upper electrode is preferably 40 to 600 nm. Further, the ratio d6 / d5 between the thickness d5 of the lower insulating layer 13 formed in contact with the lower surface of the lower electrode and the thickness d6 of the upper insulating layer 23 formed in contact with the upper surface of the upper electrode is 1 ≦ d6. It is preferable to control the thickness d5 and the thickness d6 so that the relationship / d5 ≦ 4 is satisfied.

  By forming the upper insulating layer 23 in contact with the upper surface of the upper electrode, spurious near the resonance peak of the obtained piezoelectric thin film resonator is reduced. In particular, when d6 / d5 satisfies the relationship 1 ≦ d6 / d5 ≦ 4, the spurious reduction effect is great. When the thickness d6 of the upper insulating layer 23 is less than 40 nm, the spurious suppressing effect tends to be remarkably reduced. Conversely, when the thickness d6 of the upper insulating layer 23 exceeds 600 nm, the piezoelectric characteristics such as the electromechanical coupling coefficient and the acoustic quality factor (Q value) of the obtained piezoelectric thin film resonator tend to deteriorate. Further, the upper insulating layer 23 is made of a chemically stable material, and there is an effect that the environmental resistance of the obtained piezoelectric thin film resonator is improved. In order to enhance the spurious reduction effect and the environmental resistance improvement effect as described above, it is important to improve the crystal orientation of the upper insulating layer 23 formed in contact with the upper surface of the upper electrode. In the present invention, by controlling the half-width of the rocking curve of a metal thin film such as molybdenum constituting the upper electrode 17 to be 3 ° or less, a highly oriented upper insulating layer is formed and good spurious A reduction effect and excellent environmental resistance can be realized.

The vibration space 20 can be formed as follows. That is, after forming the substrate insulating layer 12 on the upper surface of the substrate 11, a patterned sacrificial layer is formed on the vibration space forming region of the substrate insulating layer 12. A lower insulating layer 13 and a piezoelectric laminated structure 14 (and an upper insulating layer 23) are formed thereon. The via hole 19 penetrates through the layers constituting the piezoelectric laminated structure 14 and the insulator layer 13 from the upper side in the drawing (Deep RIE (Reactive Ion Etching)) into the sacrificial layer. An etching solution is injected from the via hole 19 to remove the sacrificial layer and the substrate insulating layer 12 in the vibration space forming region, thereby forming a vibration space 20 including a cavity. A thin film laminated on the vibration space 20 constitutes the membrane 21. In this piezoelectric thin film resonator, the AlN thin film 16 on the vibration space 20, the lower electrode 15 and the upper electrode 17 sandwiching the AlN thin film constitute a piezoelectric laminated structure 14, and as described above, the piezoelectric laminated structure 14 At least one of aluminum nitride (AlN), aluminum oxynitride (AlO _x N _y ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (SiN _x ), silicon oxynitride (Si ₂ ON ₂ ), zirconium oxide ( Insulating layers 13 and 23 mainly containing at least one material selected from ZrO ₂ ) and tantalum oxide (Ta ₂ O ₅ ) are present.

  Molybdenum (Mo), ruthenium (Ru), aluminum (Al), iridium (Ir), cobalt (Co), nickel (Ni), platinum (Pt) and copper (Cu) used for the lower electrode 15 and the upper electrode 17 Examples of the method for forming a metal thin film containing as a main component at least one metal selected from the group consisting of: sputtering and vacuum deposition.

  A thin film containing these metals as a main component can be easily formed usually by a DC magnetron sputtering method or an RF magnetron sputtering method. However, when the vacuum deposition method is used, molybdenum (Mo), ruthenium (Ru), and iridium (Ir) have high melting points (ruthenium melting point 2310 ° C., molybdenum melting point 2620 ° C., tungsten melting point 3410 ° C.). Since it is difficult to produce a thin film by resistance heating vapor deposition, it is necessary to use electron beam vapor deposition. As the crystal phase, ruthenium is known to be hexagonal, and molybdenum, aluminum, iridium, cobalt, nickel, platinum and copper are known to be cubic. When thin films of these metal crystal phases are formed by conventional techniques, a highly oriented metal crystal film having a rocking curve half-width (FWHM) of an X-ray diffraction peak of 3.0 ° or less is deposited. Was difficult.

In the present invention, paying attention to the material, thickness and crystal orientation of the lower electrode, the correlation with the crystal orientation of the aluminum nitride thin film formed on the metal thin film was examined in detail. As a result, the thickness and fine structure (crystal orientation, surface roughness) of the insulating film serving as the base layer are controlled, and an ultra-high vacuum sputtering apparatus (degree of ultimate vacuum: 10 ⁻⁶ Pa or less, preferably 4 × 10 ⁻⁷⁾ It is possible to deposit a highly oriented metal crystal film by optimizing film formation conditions such as film formation pressure, film formation temperature, DC output or RF output. In addition, the crystal orientation can be improved by performing pretreatment such as heat treatment or soft etching before film formation.

  Furthermore, the present inventors controlled the film forming conditions of the metal thin film used as the lower electrode 15 to improve the crystal orientation, and then placed the aluminum nitride thin film on the metal thin film or metal thin film laminate. It has been found that a highly oriented and highly crystalline c-axis oriented aluminum nitride thin film having a rocking curve half width (FWHM) of a (0002) diffraction peak of 0.8 to 1.6 ° can be obtained by forming the film. It was. By using a highly oriented and highly crystalline c-axis oriented aluminum nitride thin film, it is possible to realize a high performance FBAR, SMR or SBAR with low loss and excellent bandwidth and frequency temperature characteristics.

  The lower electrode 15 is formed by forming a metal thin film mainly composed of at least one kind of metal selected from the group consisting of an adhesion metal layer deposited as necessary and the above-mentioned various metals in this order. It is formed by patterning these metal thin films into a predetermined shape. The AlN thin film 16 can be formed by reactive sputtering on the upper surface of the lower insulating layer 13 on which the lower electrode 15 is formed. The upper electrode 17 is formed by forming a metal thin film mainly composed of at least one kind of metal selected from the group consisting of the various metals described above, and then using the photolithography technique in the same manner as the lower electrode 15. It is formed by patterning into a predetermined shape (for example, a shape close to a circle). After the patterning of the upper electrode, the AlN thin film 16 is patterned into a predetermined shape by etching away a part of the region excluding the part on the vibration space 20 of the AlN thin film 16 using a photolithography technique.

  When the inclination angle of the end portion of the lower electrode 15 becomes steep, as shown in FIG. 2C, abnormal growth of AlN occurs at the edge portion of the lower electrode end portion, and deep crater-like defects are formed between adjacent columnar AlN particles. Arise. This crater causes destruction of the AlN film and impairs reliability as a piezoelectric thin film resonator. Therefore, as shown in FIG. 3, it is necessary to make the inclination of the surface of the lower electrode end where the metal thin film and the aluminum nitride thin film are in contact with the substrate gentle to prevent crater-like separation growth. However, when the tilt angle of the lower electrode end becomes gentle, the horizontal distance of the tilted portion becomes too long, and the acoustic quality factor (Q value) of the piezoelectric thin film resonator decreases, and the vicinity of the resonance peak in the impedance characteristics There is a problem that many noises are generated.

  As shown in FIGS. 4B and 4C, the present inventors provide a side spacer 26 made of a material different from the electrode around the outer periphery of the lower electrode 15 or the upper electrode 17, and the side spacer 26 has a slope shape. And forming an aluminum nitride thin film between the upper and lower electrodes produced by controlling the processing method so that the step at the interface between the electrode and the side spacer 26 is less than 25 nm. It has been found that a highly oriented and highly crystalline c-axis oriented aluminum nitride thin film having no separate growth can be obtained, and that adverse effects on the piezoelectric characteristics due to the inclination of the end of the lower electrode or the upper electrode can be eliminated.

The side spacer 26 is formed of an insulator or a conductor. The side spacers 26 made of an insulator include, for example, silicon dioxide (SiO ₂ ), silicon nitride (SiN _x ), silicon oxynitride (Si ₂ ON ₂ ), aluminum nitride (AlN), and aluminum oxynitride (AlO _x N _y ). Further, it can be formed of an insulator mainly composed of at least one material selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

The side spacer 26 made of a conductor can be formed of a conductor whose main component is at least one material selected from the group consisting of tungsten (W), tungsten silicide (WSi _x ), and iridium (Ir).

  The side spacer 26 made of an insulator or a conductor is formed in a slope shape, and the inclination angle with respect to the lower surface of the upper surface of the slope is preferably 3 to 45 °. When the inclination angle is smaller than 3 °, the slope length becomes too long, and it becomes difficult to ensure the dimensional accuracy of each layer constituting the piezoelectric thin film resonator in the plane direction, and the electromechanical coupling coefficient of the obtained piezoelectric thin film resonator In addition, piezoelectric characteristics such as acoustic quality factor (Q value) tend to deteriorate. When the inclination angle exceeds 45 °, crater-like separation growth of the aluminum nitride thin film tends to occur from the boundary between the electrode and the side spacer 26 or the outer peripheral edge of the side spacer 26.

  In addition, regarding the shape of the electrode end portion in contact with the side spacer 26, it is preferable that the inclination angle of the electrode side wall surface with respect to the electrode lower surface is 70 to 90 ° (that is, substantially vertical). By setting the tilt angle to 70 to 90 °, the acoustic quality factor (Q value) of the obtained piezoelectric thin film resonator is improved, and the characteristics such as insertion loss, roll-off steepness and cut-off characteristics are excellent. A high performance piezoelectric thin film resonator can be manufactured.

  That is, the piezoelectric thin film resonator of the present invention is a resonator as described above, and is a substrate made of a semiconductor or an insulator having a vibration space or an acoustic reflection layer, and a position of the substrate facing the vibration space or the acoustic reflection layer. In addition, in the piezoelectric thin film resonator having at least a lower electrode, an aluminum nitride piezoelectric thin film, and an upper electrode arranged in order, at least one of the lower electrode and the upper electrode has another material made of a different material on the outer periphery thereof. It has a layer, and the step of the interface between the electrode (electrode body) and the side spacer disposed therearound is less than 25 nm.

  Such a piezoelectric laminated structure has excellent piezoelectric characteristics and high reliability, and a piezoelectric thin film resonator using the piezoelectric laminated structure has excellent frequency characteristics with low loss.

  In addition, the piezoelectric multilayer structure 14 of the piezoelectric thin film resonator of the present invention is defined as a region where the lower electrode 15 and the upper electrode 17 overlap each other in the thickness direction (that is, when viewed in the thickness direction of the piezoelectric multilayer structure 14). It is preferable that the vibration region to be located is inside the edge of the membrane 21 (that is, the outer peripheral edge of the vibration space 20). By maintaining such a positional relationship, the Q value of the piezoelectric thin film resonator can be increased. When the vibration region spreads outside the membrane edge, the Q value of the piezoelectric thin film resonator tends to decrease.

  Further, the distance between the edge (edge) of the vibration region and the membrane edge (corresponding to the outer periphery of the vibration space) is w, and the thickness of the piezoelectric laminated structure 14 in the vibration region and the insulating layer (lower insulation) When the total thickness of the layer and the upper insulating layer is t, the value of w / t is set within the range of 0 <w / t ≦ 2, thereby increasing the electromechanical coupling coefficient and increasing the Q value. A piezoelectric thin film resonator can be realized. Moreover, in the piezoelectric thin film resonator having such a positional relationship, spurious generation in the passband is suppressed. In the range of w / t> 2, spurious due to unnecessary lateral acoustic mode tends to occur.

  The resistance of the lower electrode 15 and the upper electrode 17 affects the loss of resonance characteristics. Therefore, in the present invention, it is preferable to control the formation conditions of the metal thin film so that the specific resistance of the lower electrode and the upper electrode, which cause the loss of the input signal, becomes a sufficiently small value. For example, the specific resistance of the electrode is controlled to be 5 to 20 μΩ · cm. By setting the specific resistance to a value in this range, it is possible to reduce the loss of the input high-frequency signal and realize good resonance characteristics.

  In the piezoelectric thin film resonator having the configuration shown in FIGS. 4A and 4B, a bulk acoustic wave is excited by applying a voltage to the upper and lower electrodes 15 and 17 of the piezoelectric thin film 16. For this reason, it is necessary to expose the lower electrode 15 as a terminal electrode. In order to configure a filter using a resonator having this configuration, it is necessary to connect two or more resonators in combination. In this case, when the electric resistance of the metal thin film is large, a loss due to the connection wiring occurs. For this reason, in the present invention, the conditions for forming the metal thin film are controlled so that the specific resistances of the lower electrode 15 and the upper electrode 17 that cause the loss of the input signal have a sufficiently small value. For example, by controlling the specific resistance of the electrode to be 5 to 20 μΩ · cm, it is possible to reduce the loss of the input high-frequency signal and realize good filter performance.

  FIG. 7A is a schematic plan view showing another embodiment of the piezoelectric thin film resonator according to the present invention, and FIGS. 7B and 7C are an XX sectional view and a YY sectional view, respectively. FIG. 7D is an enlarged view of a portion surrounded by a dotted line in FIG. 7C. In these drawings, members having the same functions as those in FIGS. 4A, 4B, and 4C are given the same reference numerals.

  In this embodiment, the piezoelectric thin film resonator 10 includes a substrate 11, a lower insulating layer 13 formed on the upper surface of the substrate 11, a piezoelectric laminated structure 14 formed on the upper surface of the lower insulating layer 13, and the An upper insulating layer 23 is formed on the upper surface of the piezoelectric laminated structure 14. The piezoelectric laminated structure 14 includes a lower electrode 15 formed on the upper surface of the insulator layer 13, a piezoelectric thin film 16 formed on the upper surface of the lower insulating layer 13 so as to cover a part of the lower electrode 15, and the piezoelectric thin film 16 An upper electrode 17 formed on the upper surface of the piezoelectric thin film 16 is included. The lower electrode 15 has a shape close to a rectangle, and includes a main portion 15a and a terminal portion 15b for connecting the main portion 15a to an external circuit.

  The upper electrode 17 includes a main body portion 17a formed in a region corresponding to the vibration space 20, and a terminal portion 17b for connecting the main body portion 17a and an external circuit. The terminal portions 15 b and 17 b are located outside the region corresponding to the vibration space 20.

At least one of the lower electrode 15 and the upper electrode 17 is formed of a metal thin film having a thickness of 150 nm to 450 nm including a layer mainly composed of molybdenum. For example, the lower electrode 15 is made of a metal thin film mainly composed of molybdenum and has a thickness of 150 to 450 nm. The upper electrode 17 is a laminate of a metal thin film having a thickness of d3 containing molybdenum as a main component and a metal thin film having a thickness of d4 containing aluminum as a main component, and the thicknesses d3 and d4 of the respective metal thin films are d4. / D3> 1 and 150 nm <(d3 + d4) <450 nm are satisfied. A metal thin film having a high acoustic impedance and a thickness d3 mainly composed of a highly oriented molybdenum thin film is preferably interposed between the metal thin film having a thickness d4 mainly composed of aluminum and the piezoelectric thin film. In addition, aluminum nitride (AlN), aluminum oxynitride (AlO _x N _y ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (SiN _x ), silicon oxynitride (Si ₂ ON ₂ ), zirconium oxide (ZrO ₂ ) And a lower insulating layer 13 mainly composed of at least one material selected from the group consisting of tantalum oxide (Ta ₂ O ₅ ) is formed in contact with the lower surface of the lower electrode, and similarly, if necessary, aluminum nitride (AlN), aluminum oxynitride (AlO _x N _y ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (SiN _x ), silicon oxynitride (Si ₂ ON ₂ ), zirconium oxide (ZrO ₂ ) and tantalum oxide ( An upper insulating layer 23 mainly composed of at least one material selected from the group consisting of Ta ₂ O ₅ ) is in contact with the upper surface of the upper electrode. Is formed.

The SiO ₂ layer on the lower surface of the substrate 11 on which the piezoelectric multilayer structure 14 is formed as described above is patterned into a predetermined shape by photolithography, and if necessary, a photoresist for micromachining is further applied, by photolithography to form a lower surface of the substrate SiO ₂ resist mask mask the same shape. The substrate 11 on which the mask is formed is loaded into a deep etching reactive ion etching (DEEP RIE) specification dry etching apparatus, and SF ₆ gas and C ₄ F ₈ gas are alternately introduced into the apparatus to etch and sidewalls. By repeating the protection, the etching rate ratio between the side surface and the bottom surface is controlled to form a deep prismatic or columnar vibration space 20 with the side walls standing vertically. As a result, as shown in FIGS. 7B and 7C, it is possible to obtain a vibration space in which the membrane 21 and the opening on the back surface of the substrate have substantially the same planar shape and dimensions.

  In the present invention, a side spacer made of a material different from the electrode is provided around the outer periphery of the lower electrode or the upper electrode, the side spacer is formed in a slope shape, and the interface between the electrode and the side spacer By forming the aluminum nitride piezoelectric thin film between the upper and lower electrodes produced by controlling the processing method so that the step in the layer is less than 25 nm, high orientation and high crystallinity without crater-like separation growth A c-axis oriented aluminum nitride thin film can be obtained, and the adverse effect on the piezoelectric characteristics due to the inclination of the end of the lower electrode or the upper electrode can be eliminated.

  As shown in FIG. 7D, an inclination angle with respect to the lower surface of the upper surface at the end portion of the electrode body is defined as θ2, and an inclination angle with respect to the lower surface of the upper surface of the slope in the side spacer formed in a slope shape is defined as θ1. The inclination angle θ1 of the side spacer with respect to the lower surface of the slope upper surface is 3 to 45 °. When the inclination angle θ1 is smaller than 3 °, the slope length becomes too long, and it becomes difficult to ensure the dimensional accuracy in the plane direction of each layer constituting the piezoelectric thin film resonator, and the resulting electromechanical coupling of the piezoelectric thin film resonator Piezoelectric properties such as coefficient and acoustic quality factor (Q value) deteriorate. When the inclination angle θ1 exceeds 45 °, crater-like separation growth of the aluminum nitride piezoelectric thin film tends to occur easily from the boundary portion between the electrode body and the side spacer or the end portion of the side spacer.

  Regarding the shape of the end of the electrode main body in contact with the side spacer, the inclination angle θ2 with respect to the lower surface of the upper surface of the electrode main body is preferably 70 to 90 ° (ie vertical). By setting the tilt angle θ2 to 70 to 90 °, the acoustic quality factor (Q value) of the obtained piezoelectric thin film resonator is improved, and characteristics such as insertion loss, roll-off steepness, and cutoff characteristics are excellent. A high-performance piezoelectric thin film resonator can be manufactured.

  Using the structure of the piezoelectric thin film resonator of the present invention, a multilayer piezoelectric thin film resonator having the piezoelectric thin film resonator of the present invention can be manufactured. That is, as shown in FIGS. 8A and 8B, the multilayer piezoelectric thin film resonator of the present invention has a substrate 11 made of a semiconductor or an insulator having a vibration space 20 and a surface facing at least the vibration space 20 on the substrate. The lower insulating layer 13 and the piezoelectric laminated structure are sequentially arranged in a region including the region to be processed. The piezoelectric multilayer structure includes a lower electrode 15, a first aluminum nitride piezoelectric thin film 16-1, an internal electrode 17 ′, a second aluminum nitride piezoelectric thin film 16-2, and an upper electrode 18. At least one of the lower electrode 15, the internal electrode 17 ′, and the upper electrode 18 has a side spacer 26, which is another layer made of a different material, around the outer periphery thereof. The level difference at the interface is less than 25 nm.

  The present embodiment is an SBAR having a piezoelectric multilayer structure corresponding to a laminate of two piezoelectric multilayer structures according to the embodiments described in FIGS. 7 to 7D. That is, the lower electrode 15, the first piezoelectric thin film 16-1, the internal electrode 17 ', the second piezoelectric thin film 16-2, and the upper electrode 18 are formed on the lower insulating layer 13 in this order. The internal electrode 17 'has a function as an upper electrode for the first piezoelectric thin film 16-1 and a function as a lower electrode for the second piezoelectric thin film 16-2. That is, the multilayer piezoelectric thin film resonator (SBAR) of the present invention has a structure including the configuration of the lower electrode, the piezoelectric layer, and the upper electrode of the present invention, and is one of the piezoelectric thin film resonators of the present invention. It is an embodiment.

  In the present embodiment, an input voltage is applied between the lower electrode 15 and the internal electrode 17 ′, and a voltage between the internal electrode 17 ′ and the upper electrode 18 can be taken out as an output voltage. It can be used as a multipole filter. By using the multipole filter having such a configuration as a constituent element of the pass band filter, the attenuation characteristic of the stop band is improved and the frequency response as the filter is improved.

In the piezoelectric thin-film resonator as described above, between the resonance frequency f _r and the antiresonance frequency f _a and the electromechanical coupling coefficient k _t ² in the impedance characteristic measured by using microwave prober, the following relationship is there.
k _t ² = φ _r / Tan (φ _r )
φ _r = (π / 2) (f _r / f _a )
For simplicity, the electromechanical coupling coefficient k _t ² was calculated from the following equation.
^{_{k t 2 = 4.8 (f a}} -f r) / (f a + f r)

Measurement of resonance frequency and anti-resonance frequency in the range of 1.5 to 2.5 GHz in the piezoelectric thin film resonator or laminated piezoelectric thin film resonator having the configuration shown in FIGS. 4A to 4C, FIGS. 7A to 7D, and FIGS. 8A and 8B. The electromechanical coupling coefficient k _t ² obtained from the value is 6.0% or more. When the electromechanical coupling coefficient k _t ² is less than 6.0%, the bandwidth of the piezoelectric thin film filter manufactured by combining these piezoelectric thin film resonators is reduced, and is practically used as a piezoelectric thin film device used in a high frequency range. Tend to be difficult.

  According to the present invention, a piezoelectric thin film resonator such as a VCO (Voltage Controlled Oscillator), a filter, and a duplexer is used by using the piezoelectric thin film resonator of the present invention and a laminated piezoelectric thin film resonator which is one form thereof. An excellent piezoelectric thin film device can be provided.

  FIG. 9 shows a schematic plan view of a thin film piezoelectric filter as an embodiment of the piezoelectric thin film device of the present invention. In the present embodiment, five piezoelectric thin film resonators 210, 220, 230, 240, 250 are formed using a common substrate. These piezoelectric thin film resonators are all of the embodiment shown in FIGS. 7A and 7B. The lower electrode terminal portions 15b of the piezoelectric thin film resonators 210, 220, and 240 are connected to each other, and the upper electrode terminal portions 17b of the piezoelectric thin film resonators 220, 230, and 250 are connected to each other. The upper electrode terminal portion of the piezoelectric thin film resonator 210 and the lower electrode terminal portion of the piezoelectric thin film resonator 230 are input / output terminals, and the upper electrode terminal portion of the piezoelectric thin film resonator 240 and the lower electrode terminal portion of the piezoelectric thin film resonator 250 are Grounded. In FIG. 9, the piezoelectric multilayer structure 14 is shown only for the piezoelectric thin film resonator 220, but the same applies to other piezoelectric thin film resonators. Further, although the side spacers are not shown in FIG. 9, side spacers for the upper electrode and the lower electrode as described with reference to FIGS. 7A and 7B are provided.

  The piezoelectric thin film device of the present invention is not particularly limited to the above device as long as it has a piezoelectric thin film resonator and a laminated piezoelectric thin film resonator which is one form thereof.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following examples and comparative examples, an air gap type piezoelectric thin film resonator is manufactured, but an acoustic mirror type piezoelectric thin film resonator can also be manufactured by the same technique.

(Example 1)
In this example, a piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B and 4C was produced as follows.

That is, after forming a 1500 nm thick SiO ₂ layer on both sides of a 625 μm thick Si wafer by thermal oxidation, a 50 nm thick Ti thin film serving as a sacrificial layer is formed on the SiO ₂ layer on the upper surface of the Si wafer. Deposited and patterned by photolithography into the desired air bridge shape (ie, the shape corresponding to the desired vibration space). Next, an Al ₂ O ₃ thin film serving as a lower insulating layer (lower insulating layer) having the thickness shown in Table 1 was formed on the exposed surfaces of the sacrificial layer and the SiO ₂ layer by reactive sputtering. On this lower insulating layer, a Mo thin film having a thickness shown in Table 1 is deposited by DC magnetron sputtering to form a lower electrode (lower electrode layer: lower electrode body), and further patterned by photolithography. did. Subsequently, a silicon oxide (SiO ₂ ) film was deposited to a thickness of 300 to 900 nm on the exposed surfaces of the lower electrode and the lower insulating layer by low pressure CVD using TEOS (Tera-ethoxy silane) as a raw material. By etching back until the surface of the lower electrode is exposed by anisotropic dry etching using ICP plasma and the surface of the SiO ₂ film in contact with the side wall of the lower electrode is smoothly connected to the surface of the lower electrode, the patterned lower portion Side spacers having a desired structure were formed by leaving the SiO ₂ film only around the side walls of the electrodes.

As a result of evaluating the crystal orientation of the lower electrode with an X-ray diffractometer, as shown in Table 1, the rocking curve FWHM of the Mo (110) plane was 2.3 deg. A piezoelectric thin film (piezoelectric material) was formed by reactive RF magnetron sputtering using an Al target with a purity of 99.999% on the exposed surfaces of the lower Mo electrode, the side spacer, and the Al ₂ O ₃ thin film under the conditions shown in Table 3. An AlN thin film having a thickness of 1.0 μm was formed as a thin film. As a result of evaluating the crystallinity of the AlN thin film by the X-ray diffraction method, only peaks corresponding to the c-plane including the (0002) plane were observed. As shown in Table 3, the rocking curve half-width (FWHM) was 1 It was 6 °. Next, a Mo thin film having a thickness described in Table 2 is deposited on the piezoelectric thin film by DC magnetron sputtering to form an upper electrode (upper electrode layer: upper electrode main body). As shown, it was patterned into a shape close to a rectangle with a plane size of 150 × 170 μm (the opposite side was slightly non-parallel). Next, the piezoelectric thin film was patterned into a predetermined shape by dry etching. On the exposed surfaces of the lower electrode and its side spacers, the piezoelectric thin film, the upper electrode, and the lower insulating layer, an Al ₂ O ₃ thin film having the thickness described in Table 2 serving as the upper insulating layer (upper insulating layer) is deposited. Then, a pattern was formed. Next, a photoresist is applied on the exposed surface of the lower electrode and its side spacer, piezoelectric thin film, upper electrode, upper insulating layer, and lower insulating layer, and a via hole for forming the vibration space shown in FIG. 4B. A via hole pattern was formed at a position corresponding to 1 and a via hole was opened by dry etching using a mixed gas of Cl ₂ and Ar. The SiO ₂ layer on the lower surface side of the Si wafer was also covered with the photoresist without peeling off the photoresist. A dilute hydrofluoric acid aqueous solution was used as an etching solution, and the Ti sacrificial layer and the 1500 nm thick SiO ₂ layer located therebelow were removed by etching by circulation of the etching solution through the via hole. The resist was removed by ashing in oxygen plasma to produce the vibration space 20 shown in FIG. 4B. The piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B and 4C was manufactured by the above manufacturing process. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

  Tables 1 and 2 list the inclination angle θ1 of the end face of the side spacer and the inclination angle θ2 of the end face of the electrode body. These are angles formed by the end surface (end surface or upper surface) and the lower surface of each layer shown in FIG. 7D.

Further, using a cascade microtech GSG micro prober and a network analyzer, the impedance characteristic between the electrode terminals 15b and 17b of the piezoelectric thin film resonator is measured to obtain a scattering parameter, and the resonance frequency _fr and from the measured values of the anti-resonance frequency f _a, the electromechanical coupling coefficient k and _t ^2, the resonance peak and anti-resonance peak from the resonance peak in the impedance characteristic and the anti-resonance peak of the peak waveform (peak width at a position away 3dB from the peak top) The acoustic quality factor Q was determined. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Example 2)
In this example, a piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B and 4C was produced as follows. That is, the material and thickness of the lower insulating layer and the upper insulating layer, the formation condition and thickness of the lower electrode, the material and inclination angle of the side spacer, the formation condition and thickness of the AlN piezoelectric thin film, and the material and thickness of the upper electrode The piezoelectric thin film resonator shown in FIGS. 4A, 4B, and 4C was manufactured using the same method as in Example 1 except that was changed. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, using a cascade microtech GSG micro prober and a network analyzer, the impedance characteristic between the electrode terminals 15b and 17b of the piezoelectric thin film resonator is measured to obtain a scattering parameter, and the resonance frequency _fr and from the measured values of the anti-resonance frequency f _a, the electromechanical coupling coefficient k and _t ^2, the resonance peak and anti-resonance peak from the resonance peak in the impedance characteristic and the anti-resonance peak of the peak waveform (peak width at a position away 3dB from the peak top) The acoustic quality factor Q was determined. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Example 3)
In this example, a piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B and 4C was produced as follows. That is, by forming a 1000 nm thick SiO ₂ layer on both sides of a 625 μm thick Si wafer by thermal oxidation, an 80 nm thick Ti thin film serving as a sacrificial layer is formed on the SiO ₂ layer on the upper surface of the Si wafer. It was deposited and patterned into the desired air bridge shape by photolithography. Next, a lower insulating layer having the material and thickness described in Table 1 was formed on the exposed surfaces of the sacrificial layer and the SiO ₂ layer by reactive sputtering. On this lower insulating layer, a Mo thin film having a thickness shown in Table 1 was deposited by DC magnetron sputtering to form a lower electrode, and further patterned by photolithography. When forming the pattern, the resist was exposed to ultraviolet light that was intentionally defocused and developed to form a gentle saddle shape. Focusing on controlling the inclination angle θ2 of the electrode pattern end face (side wall) during dry etching by giving the resist end face a gentle inclination.

  As a result of evaluating the crystal orientation of the lower electrode with an X-ray diffractometer, as shown in Table 1, the rocking curve FWHM of the Mo (110) plane was 1.5 deg. An AlN thin film as a piezoelectric thin film is formed on the exposed surfaces of the lower Mo electrode and the lower insulating layer by reactive RF magnetron sputtering using an Al target having a purity of 99.999% under the conditions shown in Table 3. did. As a result of evaluating the crystallinity of the AlN piezoelectric thin film by the X-ray diffraction method, only peaks corresponding to the c-plane including the (0002) plane were observed, and as shown in Table 3, the rocking curve half-width (FWHM) was It was 1.0 °. Next, a Mo thin film having a thickness shown in Table 2 is deposited on the piezoelectric thin film by DC magnetron sputtering to form an upper electrode, and a rectangular shape having a plane size of 150 × 170 μm is formed by photolithography as shown in FIG. 4A. It was patterned into a shape close to (the opposite side is slightly non-parallel).

Subsequently, a silicon oxynitride (Si ₂ ON ₂ ) film having a thickness of 300 to 900 nm was deposited on the exposed surfaces of the lower electrode, the piezoelectric thin film, the upper electrode, and the lower insulating layer by a low pressure CVD method. By anisotropic dry etching using ICP plasma, patterning is performed by etching back until the surface of the upper electrode is exposed and the surface of the Si ₂ ON ₂ film in contact with the side wall of the upper electrode is smoothly connected to the surface of the upper electrode. A side spacer having a desired structure was formed by leaving the Si ₂ ON ₂ film only around the side wall of the upper electrode.

Next, the piezoelectric thin film was patterned into a predetermined shape by dry etching and subsequent wet etching. On the exposed surface of the lower electrode, the piezoelectric thin film, the upper electrode and its side spacers, and the lower insulating layer, a thin film having the material and thickness described in Table 2 serving as the upper insulating layer was deposited to form a pattern. Next, a photoresist is applied on the exposed surfaces of the lower electrode, the piezoelectric thin film, the upper electrode and its side spacer, the upper insulating layer, and the lower insulating layer, and a via hole for forming the vibration space shown in FIG. 4B. A via hole pattern was formed at a position corresponding to 1 and a via hole was opened by dry etching using a mixed gas of Cl ₂ and Ar. The SiO ₂ layer on the lower surface side of the Si wafer was also covered with the photoresist without peeling off the photoresist. Diluted hydrofluoric acid aqueous solution was used as an etching solution, and the Ti sacrificial layer and the 1000 nm thick SiO ₂ layer located therebelow were removed by etching by circulation of the etching solution through the via hole. The resist was removed by ashing in oxygen plasma to produce the vibration space 20 shown in FIG. 4B. The piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B and 4C was manufactured by the above manufacturing process. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Example 4)
In this example, a piezoelectric thin film resonator having the structure shown in FIGS. 7A and 7B was produced as follows.
That is, after a SiO ₂ layer having a thickness of 1000 nm is formed on both surfaces of a (100) Si substrate having a thickness of 300 μm by a thermal oxidation method, a desired vibration space 20 is formed on the SiO ₂ layer on the lower surface of the Si substrate. A corresponding mask pattern was formed, and the SiO ₂ layer in the region corresponding to the pattern was removed by etching. At the same time, the entire SiO ₂ layer on the upper surface of the Si substrate was removed by etching. Next, a lower insulating layer having the material and thickness shown in Table 1 was formed on the SiO ₂ layer on the upper surface of the Si substrate by reactive sputtering. On this lower insulating layer, the lower electrode was formed by sequentially depositing the Cr adhesion layer and the Mo thin film having the materials and thicknesses shown in Table 1 by the DC magnetron sputtering method, and patterning by photolithography. . When forming the pattern, the resist was exposed to ultraviolet light that was intentionally defocused and developed to form a gentle saddle shape. Focusing on controlling the inclination angle θ2 of the electrode pattern end face (side wall) during dry etching by giving the resist end face a gentle inclination.

  As a result of evaluating the crystal orientation of the lower electrode using an X-ray diffractometer, as shown in Table 1, the rocking curve FWHM of the Mo (110) plane was 1.8 deg. An AlN thin film as a piezoelectric thin film was formed on the exposed surfaces of the lower Mo electrode and the lower insulating layer by reactive RF magnetron sputtering using an Al target having a purity of 99.999% under the conditions shown in Table 3. . As a result of evaluating the crystallinity of the AlN piezoelectric thin film by the X-ray diffraction method, only peaks corresponding to the c-plane including the (0002) plane were observed. As shown in Table 3, the rocking curve half-width (FWHM) Was 1.3 °.

Next, an upper electrode is formed by sequentially depositing a Mo thin film and an Al thin film having the thicknesses shown in Table 2 on the piezoelectric thin film by DC magnetron sputtering, and a planar dimension is formed by photolithography as shown in FIG. 7A. It was patterned into a shape close to a 140 × 160 μm rectangle (the opposite side was slightly non-parallel). Subsequently, a silicon oxide (SiO ₂ ) film was deposited to 300 to 900 nm on the exposed surfaces of the lower electrode, the piezoelectric thin film, the upper electrode, and the lower insulating layer by a plasma CVD method. By etching back until the surface of the upper electrode is exposed by anisotropic dry etching using ICP plasma and the surface of the SiO ₂ film in contact with the side wall of the upper electrode is smoothly connected to the surface of the lower electrode, the patterned lower electrode is obtained. Side spacers were formed by leaving the SiO ₂ film only around the periphery of the outer peripheral portion. Next, the piezoelectric thin film was patterned into a predetermined shape by dry etching.

  Further, a thin film having the material and thickness described in Table 2 is deposited on the exposed surface of the lower electrode, the piezoelectric thin film, the upper electrode and its side spacers, and the lower insulating layer by reactive sputtering. Then, a pattern was formed by a lift-off method.

Lower electrode, a piezoelectric thin film, the upper electrode and the side spacers, the upper insulating layer, and the exposed surface of the lower insulating layer, coated in protected wax, a SiO ₂ layer is patterned on a Si substrate lower surface as masks, SF ₆ A deep space etching is performed by using a deep RIE (Reactive Ion Etching) method in which a gas and a C ₄ F ₈ gas are alternately used to etch and remove a Si substrate in a region corresponding to a membrane, thereby forming a vibration space. Piezoelectric thin film resonators having the structure described in 7B and 7C were manufactured. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the rocking curve half-width (FWHM) of the lower Mo / Cr laminated electrode, and Table 3 shows the formation conditions and rocking curve of the AlN piezoelectric thin film. Crystal properties such as half width (FWHM) are described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Examples 5 and 6)
In this example, a piezoelectric thin film resonator having the structure shown in FIGS. 7A, 7B and 7C was produced as follows. That is, changing the material and thickness of the lower and upper insulator layers, the material and forming conditions and thickness of the lower and upper electrodes, and the forming conditions of the AlN piezoelectric thin film, A piezoelectric thin film resonator shown in FIGS. 7A, 7B and 7C was manufactured using the same method as in Example 4 except that side spacers were provided around the part. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Example 7)
In this example, a piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B and 4C was produced as follows. That is, the SiN _x layer formed by the low pressure CVD method is used as the lower insulator layer, and the material and thickness of the upper and lower insulator layers, the formation condition and material and thickness of the lower electrode and the upper electrode, and the formation condition of the AlN piezoelectric thin film are as follows. The piezoelectric thin film resonator shown in FIGS. 4A, 4B, and 4C was manufactured by using the same method as in Example 3 except that side spacers were provided around the outer peripheral edge for both the lower electrode and the upper electrode. . Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Examples 8 and 9)
In this example, a piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B and 4C was produced as follows. That is, the material and thickness of the lower insulator layer and the upper insulator layer, the formation condition and material and thickness of the lower electrode and the upper electrode, the material and inclination angle of the side spacer, and the formation condition of the AlN piezoelectric thin film are changed. A piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B, and 4C was manufactured in the same manner as in Example 3 except that side spacers were provided around the outer peripheral edge for both the upper electrode and the upper electrode. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Examples 10 and 11)
In this example, a piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B and 4C was produced as follows. That is, in the same manner as in Example 3, except that both the lower electrode and the upper electrode were provided with side spacers around the outer peripheral edge, and the lower insulator layer, the lower electrode, the side spacer, and the AlN thin film were formed and patterned. Thereafter, the piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B, and 4C was manufactured by forming an upper electrode, a side spacer, and an upper insulator layer. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Examples 12 to 14)
In this example, a piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B and 4C was produced as follows. That is, the material and thickness of the lower insulator layer and the upper insulator layer, the material of the lower electrode, the formation condition and thickness, the material and inclination angle of the side spacer, the formation condition of the AlN piezoelectric thin film, and the material and thickness of the upper electrode The piezoelectric thin film resonator shown in FIGS. 4A, 4B and 4C was changed using the same method as in Example 3 except that side spacers were provided around the outer peripheral edge for both the lower electrode and the upper electrode. Manufactured. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Comparative Example 1)
In this comparative example, a piezoelectric thin film resonator for comparison with the structure shown in FIGS. 4A, 4B, and 4C was produced as follows. That is, the material and thickness of the lower insulator layer and the upper insulator layer, such as using a SiN _x layer by a low pressure CVD method as the lower insulator layer, using Cr as the lower electrode adhesion layer, and Mo as the lower electrode main layer, A piezoelectric thin film resonator having a structure similar to that shown in FIGS. 4A, 4B and 4C is manufactured by the method described in Example 3 except that the material and thickness of the lower electrode and the upper electrode are changed and no side spacer is provided. did. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Comparative Example 2)
In this comparative example, a piezoelectric thin film resonator for comparison with the structure shown in FIGS. 4A, 4B, and 4C was produced as follows. 4A, 4B and 4C in the same manner as in Comparative Example 1 except that the material and thickness of the lower insulator layer and the upper insulator layer and the material and thickness of the lower electrode and the upper electrode were changed. A piezoelectric thin film resonator having a structure similar to that of the above was manufactured. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Comparative Examples 3-6)
In this comparative example, a piezoelectric thin film resonator for comparison with the structure shown in FIGS. 4A, 4B, and 4C was produced as follows. 4A, 4B and 4C in the same manner as in Comparative Example 1 except that the material and thickness of the lower insulator layer and the upper insulator layer and the material and thickness of the lower electrode and the upper electrode were changed. A piezoelectric thin film resonator having a structure similar to that of the above was manufactured. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

(Comparative Example 7)
In this comparative example, a piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B, and 4C was manufactured as follows. That is, in addition to changing the material and thickness of the lower insulator layer and the upper insulator layer, the material and thickness of the lower electrode and the upper electrode, side spacers formed around the lower electrode main body and its outer peripheral edge A piezoelectric thin film resonator having the structure shown in FIGS. 4A, 4B, and 4C was manufactured by the method described in Example 1 except that the step at the interface with the substrate had a large value of 30 nm. Tables 1 to 3 show the material and thickness of each layer in the vibration region, Table 1 shows the bottom electrode rocking curve half width (FWHM), and Table 3 shows the piezoelectric thin film formation conditions and rocking curve half width (FWHM). Etc. were described.

Further, the high frequency characteristics and resonance characteristics of the piezoelectric thin film resonator were evaluated by the same impedance characteristic measurement as in Example 1. The thickness frequency fundamental frequency, electromechanical coupling coefficient k _t ² , acoustic quality factor Q, insertion loss minimum value (forward transmission coefficient, value at the resonance point of S ₂₁ ) and spurious characteristics of the obtained piezoelectric thin film resonator are: It was as shown in Table 3.

Claims (27)

A substrate having a vibration space or an acoustic reflection layer; and a piezoelectric multilayer structure disposed so as to face the vibration space or the acoustic reflection layer, the piezoelectric multilayer structure being close to the vibration space or the acoustic reflection layer A piezoelectric thin film resonator having at least a lower electrode, a piezoelectric thin film and an upper electrode arranged in order from the side,
A side spacer made of a material different from that of the electrode is disposed around an outer peripheral portion of at least one of the lower electrode and the upper electrode, and a step at an interface between the side spacer and the electrode is less than 25 nm. A piezoelectric thin film resonator. The piezoelectric thin film resonator according to claim 1, wherein the piezoelectric thin film is made of aluminum nitride (AlN). The piezoelectric thin film resonator according to claim 2, wherein a rocking curve half-width (FWHM) of a (0002) diffraction peak of the piezoelectric thin film made of aluminum nitride is 0.8 to 1.6 °. The piezoelectric thin film resonator according to claim 1, wherein a step at an interface between the side spacer and the electrode is less than 3 nm. 2. The piezoelectric thin film resonator according to claim 1, wherein the side spacer has an upper surface formed in a slope shape with respect to a lower surface. 2. The piezoelectric thin film resonator according to claim 1, wherein the side spacer has an inclination angle of an upper surface with respect to the lower surface of 3 to 45 degrees. 2. The piezoelectric thin film resonator according to claim 1, wherein an acoustic impedance of the side spacer is larger than an acoustic impedance of the electrode. The piezoelectric thin film resonator according to claim 1, wherein the side spacer is made of an insulator. The side spacer includes silicon dioxide (SiO ₂ ), silicon nitride (SiN _x ), silicon oxynitride (Si ₂ ON ₂ ), aluminum nitride (AlN), aluminum oxynitride (AlO _x N _y ), and aluminum oxide (Al ₂ The insulator according to claim 8, comprising an insulator mainly composed of at least one material selected from the group consisting of O ₃ ), zirconium oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ). Piezoelectric thin film resonator. The piezoelectric thin film resonator according to claim 1, wherein the side spacer is made of a conductor. The side spacer is made of a conductor mainly composed of at least one material selected from the group consisting of tungsten (W), tungsten silicide (WSi _x ), and iridium (Ir). The piezoelectric thin film resonator as described. The piezoelectric thin film resonator according to claim 1, wherein at least one of the upper electrode and the lower electrode is made of molybdenum. At least one of the upper electrode and the lower electrode is composed of a laminate of two kinds of metals selected from the group consisting of molybdenum, ruthenium, aluminum, iridium, cobalt, nickel, platinum and copper, The piezoelectric thin film resonator according to claim 1. The lower electrode is a laminate of a lower metal layer having a thickness d1 and an upper metal layer having a thickness d2, wherein d1 / d2> 1 and 150 nm <(d1 + d2) <450 nm. The piezoelectric thin film resonator according to claim 1. The lower metal layer having a thickness d1 of the lower electrode is a metal thin film mainly containing aluminum, and the upper metal layer having a thickness d2 of the lower electrode is a metal thin film mainly containing molybdenum. The piezoelectric thin film resonator according to claim 14. The upper electrode is a laminate of a lower metal layer having a thickness of d3 and an upper metal layer having a thickness of d4, wherein d4 / d3> 1 and 150 nm <(d3 + d4) <450 nm. The piezoelectric thin film resonator according to claim 1. The lower metal layer having a thickness d3 of the upper electrode is a metal thin film containing molybdenum as a main component, and the upper metal layer having a thickness d4 of the upper electrode is a metal thin film containing aluminum as a main component. The piezoelectric thin film resonator according to claim 16. A vibration region defined as a region where the lower electrode and the upper electrode overlap each other when viewed in the thickness direction of the piezoelectric multilayer structure is located inside the vibration space or the outer peripheral edge of the acoustic reflection layer. The piezoelectric thin film resonator according to claim 1. The distance w between the end of the vibration region and the outer periphery of the vibration space or the acoustic reflection layer as viewed in the thickness direction of the piezoelectric multilayer structure, and the thickness of the piezoelectric multilayer structure and the insulating layer in the vibration region 19. The piezoelectric thin film resonator according to claim 18, wherein a total t with the thickness satisfies a relational expression 0 <w / t ≦ 2. The piezoelectric thin film resonator according to claim 1, wherein an insulating layer is attached to an upper surface or a lower surface of the piezoelectric multilayer structure. The piezoelectric thin film resonator according to claim 20, wherein the insulating layer is formed in contact with a lower surface of the lower electrode. The piezoelectric thin film resonator according to claim 20, wherein the insulating layer is formed in contact with an upper surface of the upper electrode. The insulating layer includes aluminum nitride (AlN), aluminum oxynitride (AlO _x N _y ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (SiN _x ), silicon oxynitride (Si ₂ ON ₂ ), zirconium oxide ( The piezoelectric thin film resonator according to claim 20, wherein the piezoelectric thin film resonator is mainly composed of at least one material selected from the group consisting of ZrO ₂ ) and tantalum oxide (Ta ₂ O ₅ ). A piezoelectric thin film device configured by combining a plurality of piezoelectric thin film resonators according to any one of claims 1 to 23. A method for manufacturing the piezoelectric thin film resonator according to claim 1, comprising:
A first step of forming a lower insulating layer on the substrate;
A second step of forming the lower electrode on the lower insulating layer;
After depositing an insulator or a conductor having a different material from that of the lower electrode on the exposed surfaces of the lower electrode and the lower insulating layer, the upper surface of the lower electrode is exposed by etch back, and the periphery of the outer periphery of the lower electrode A third step of forming the side spacer for the lower electrode in
A fourth step of forming a piezoelectric material layer on the exposed surfaces of the lower electrode, the lower electrode side spacer and the lower insulating layer;
A fifth step of forming the upper electrode on the piezoelectric material layer;
A sixth step of patterning the piezoelectric material layer to form the piezoelectric thin film;
And a seventh step of forming an upper insulating layer on the piezoelectric thin film and the upper electrode. Between the fifth step and the sixth step, an insulator or a conductor having a different material from that of the upper electrode is deposited on the exposed surfaces of the upper electrode and the piezoelectric material layer, and then the upper portion is etched back. 26. The method of manufacturing a piezoelectric thin film resonator according to claim 25, wherein an upper surface of the electrode is exposed and a step of forming the side spacer for the upper electrode is provided around the outer periphery of the upper electrode. A method for manufacturing the piezoelectric thin film resonator according to claim 1, comprising:
A first step of forming a lower insulating layer on the substrate;
A second step of forming the lower electrode on the lower insulating layer so that the end thereof has a slope shape;
A third step of forming a piezoelectric material layer on the exposed surfaces of the lower electrode and the lower insulating layer;
A fourth step of forming the upper electrode on the piezoelectric material layer;
A fifth step of patterning the piezoelectric material layer to form the piezoelectric thin film;
After depositing an insulator or a conductor having a different material from that of the upper electrode on the exposed surfaces of the upper electrode and the piezoelectric thin film, the upper surface of the upper electrode is exposed by etch back, and around the outer periphery of the upper electrode. A sixth step of forming the side spacer for the upper electrode;
And a seventh step of forming an upper insulating layer on the piezoelectric thin film and the upper electrode.

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