JP2013004707A - Piezoelectric film element and piezoelectric film device - Google Patents

Abstract

A piezoelectric film element and a piezoelectric film device having excellent piezoelectric characteristics and high reliability are provided.
In a piezoelectric film element having at least a lower electrode layer and a lead-free alkali niobium oxide-based piezoelectric film disposed on a substrate, the lower electrode layer is made of cubic or tetragonal crystals. An orthorhombic, hexagonal, monoclinic, triclinic, or trigonal crystal structure, or a state in which two or more of these crystal structures coexist, In the X-ray diffraction intensity distribution of a crystal plane that is preferentially oriented to a specific crystal axis that is not more than two of the axes and that is normal to at least one of the crystal axes on the substrate 1, The relative standard deviation of the X-ray diffraction intensity of the surface is 57% or less.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric film element and a piezoelectric film device using a lead-free alkali niobium oxide-based piezoelectric film.

Piezoelectric materials are processed into various piezoelectric elements according to various purposes. In particular, they are widely used as functional electronic parts such as actuators that generate deformation by applying voltage and conversely sensors that generate voltage from deformation of the element. ing. As a piezoelectric material used for actuators and sensors, a lead-based material dielectric material having excellent piezoelectric characteristics, particularly a Pb (Zr _1-x Ti _x ) O ₃ -based perovskite ferroelectric material called PZT However, it has been widely used so far. A piezoelectric material such as PZT is usually formed by sintering an oxide of a piezoelectric material.

In recent years, the development of a piezoelectric material containing no lead has been eagerly desired for environmental considerations, and potassium sodium niobate (general formula: (Na _x K _y ) NbO ₃ (0 <X <1, 0 <y <1, x + y + z = 1)), lithium potassium sodium niobate (general formula: (Na _x K _y Li _z ) NbO ₃ (0 <x <1, 0 <y <1, 0 <Z <1, x + y + z = 1)) and the like are under development. Since potassium sodium niobate has piezoelectric characteristics comparable to PZT, it is expected as a promising candidate for lead-free piezoelectric materials.

  On the other hand, as various types of electronic components have become smaller and higher in performance, there has been a strong demand for smaller and higher performance piezoelectric elements. However, as the thickness of the piezoelectric film produced by the conventional manufacturing method centered on the sintering method is reduced, the size of the crystal grains constituting the piezoelectric material particularly as the thickness approaches 10 μm. Therefore, there arises a problem that variation and deterioration of characteristics become remarkable. In order to avoid this, a method for forming a piezoelectric film using a thin film technique or the like instead of the sintering method has been recently studied.

  In recent years, PZT thin films formed by RF sputtering have been put to practical use as high-definition high-speed inkjet printer head actuators, small-sized and low-cost angular velocity sensors, or gyro sensors (see, for example, Patent Document 1). A piezoelectric thin film element using a piezoelectric thin film of lithium potassium sodium niobate that does not use lead has also been proposed (see, for example, Patent Document 2).

  In order to drive these piezoelectric elements, an electric field (voltage) must be applied to the piezoelectric film. For this purpose, it is necessary to dispose conductive materials called electrodes above and below the piezoelectric film. In general, platinum (Pt) having excellent environmental resistance is often used for electrodes such as piezoelectric films, high dielectric constant films, and ferroelectric thin films. In addition, the electrode layer is composed of Ru (ruthenium), Ir (iridium), Sn (tin), In (indium) or their oxides, or a compound with an element contained in the piezoelectric film. Single layer, or a laminate including these layers.

Japanese Patent Laid-Open No. 10-286953 JP 2007-19302 A

  By forming a lead-free piezoelectric film as the piezoelectric film, it is possible to manufacture a high-definition high-speed inkjet printer head with reduced environmental load, and a small and inexpensive angular velocity sensor or gyro sensor. For this reason, basic research on piezoelectric films such as lithium potassium sodium niobate is underway. In order to reduce the cost in application, it is indispensable to establish a technique for forming a piezoelectric film on a Si substrate or a glass substrate with good control.

  In the case of manufacturing actuators and sensors, in the conventional technology, the atomic level structure such as crystal orientation of the electrode material, which is one of the peripheral materials of the lead-free piezoelectric film, which is the basic part of the piezoelectric film element, is quantitatively determined. In addition, no precise control or management was performed. For this reason, a lead-free device having a long life and a high piezoelectric constant could not be stably produced. In addition, since the electrode structure of a large number of piezoelectric film elements formed on the substrate may differ depending on the formation site on the substrate, the piezoelectric constant of the piezoelectric film element becomes non-uniform, which is one of the causes of manufacturing yield reduction. It was.

  An object of the present invention is to provide a piezoelectric film element and a piezoelectric film device having excellent piezoelectric characteristics and high reliability.

  According to a first aspect of the present invention, there is provided a piezoelectric film element in which at least a lower electrode layer and a lead-free alkali niobium oxide-based piezoelectric film are disposed on a substrate, wherein the lower electrode layer includes a cubic crystal and a tetragonal crystal. An orthorhombic, hexagonal, monoclinic, triclinic, or trigonal crystal structure, or a state in which two or more of these crystal structures coexist, In the X-ray diffraction intensity distribution of the crystal plane that is preferentially oriented to a specific crystal axis that is two or less of the axes, and that is normal to at least one of the crystal axes on the substrate, the crystal plane The piezoelectric film element has a relative standard deviation of X-ray diffraction intensity of 57% or less.

  According to a second aspect of the present invention, there is provided a piezoelectric film element in which at least a lower electrode layer and a lead-free alkali niobium oxide-based piezoelectric film are disposed on a substrate, wherein the lower electrode layer includes a cubic crystal and a tetragonal crystal. An orthorhombic, hexagonal, monoclinic, triclinic, or trigonal crystal structure, or a state in which two or more of these crystal structures coexist, In the distribution of the X-ray diffraction intensity of the crystal plane that is preferentially oriented to a specific axis that is two or less of the axes and that is normal to at least one of the crystal axes on the substrate, This is a piezoelectric film element in which the maximum peak intensity relative to the minimum peak intensity of the X-ray diffraction intensity is in the range of 7 times or less.

  According to a third aspect of the present invention, in the piezoelectric film element according to the first or second aspect, the piezoelectric constant distribution of the piezoelectric film on the substrate has a relative standard deviation of 10% or less.

  According to a fourth aspect of the present invention, in the piezoelectric film element according to any one of the first to third aspects, the lower electrode layer has a texture composed of particles having a columnar structure.

  According to a fifth aspect of the present invention, in the piezoelectric film element according to any one of the first to fourth aspects, the lower electrode layer includes (001) preferentially oriented crystal grains, (110) preferentially oriented crystal grains, and ( 111) Of the preferentially oriented crystal grains, a structure mainly composed of one preferentially oriented crystal grain or a structure in which two or more preferentially oriented crystal grains coexist.

  According to a sixth aspect of the present invention, in the piezoelectric film element according to any one of the first to fifth aspects, the lower electrode layer has a single-layer structure including a Pt layer or an alloy layer containing Pt as a main component, Or it is a laminated structure containing the alloy layer which has Pt layer or Pt as a main component.

  According to a seventh aspect of the present invention, in the piezoelectric film element according to any one of the first to sixth aspects, the lower electrode layer includes Ru, Ir, Sn, In, an oxide thereof, or Pt and A single layer structure of a layer made of a compound with an element contained in the piezoelectric film, or a laminated structure including the layer.

  According to an eighth aspect of the present invention, in the piezoelectric film element according to any one of the first to seventh aspects, an upper electrode layer is provided on the piezoelectric film, and the upper electrode layer includes a Pt layer or a Pt layer. It is a single layer structure made of an alloy layer containing as a main component, or a laminated structure including a Pt layer or an alloy layer containing Pt as a main component.

  According to a ninth aspect of the present invention, in the piezoelectric film element according to the eighth aspect, the upper electrode layer is contained in Ru, Ir, Sn, In, an oxide thereof, or Pt and the piezoelectric film. It is a single layer structure of a layer made of a compound with an element or a laminated structure including the layer.

According to a tenth aspect of the present invention, in the piezoelectric film element according to any one of the first to fourth aspects, the substrate is a Si substrate, a MgO substrate, a ZnO substrate, a SrTiO ₃ substrate, a SrRuO ₃ substrate, or a glass substrate. A quartz glass substrate, a GaAs substrate, a GaN substrate, a sapphire substrate, a Ge substrate, or a stainless steel substrate.

  An eleventh aspect of the present invention is a piezoelectric film device comprising the piezoelectric film element according to any one of the first to tenth aspects.

  According to the present invention, a piezoelectric film element and a piezoelectric film device having excellent piezoelectric characteristics and high reliability can be provided by precisely controlling the lower electrode layer structure of the piezoelectric film element.

It is sectional drawing of the piezoelectric film element which concerns on one Embodiment and one Example of this invention. It is sectional drawing of the piezoelectric film element which concerns on other embodiment of this invention. It is sectional drawing of the piezoelectric film device which concerns on one Embodiment of this invention. It is a schematic block diagram which shows the sputtering device used for sputtering film-forming of the lower electrode layer in the Example of this invention. It is the surface shape image which measured the Pt lower electrode layer surface in the piezoelectric film element which concerns on one Example of this invention with the atomic force microscope. It is a figure which shows the crystal structure of Pt. 2 is an X-ray diffraction pattern of 2θ / θ scan of a Pt lower electrode layer according to an embodiment of the present invention. 2 is an X-ray diffraction pattern of 2θ / θ scan in a piezoelectric film element according to an embodiment of the present invention. (A) is a correlation diagram of 111 X-ray diffraction intensity of the Pt lower electrode layer at the wafer center of the example and 001 diffraction intensity of the KNN piezoelectric film, and (b) is a position 30 mm away from the wafer center of the example. FIG. 4 is a correlation diagram between 111 X-ray diffraction intensity of a Pt lower electrode layer and 001 diffraction intensity of a KNN piezoelectric film. (A) is a correlation diagram between the film formation temperature of the Pt lower electrode layer and 111 X-ray diffraction intensity when measured along the top side facing from the orientation flat of the wafer of the example, and (b) of FIG. It is a correlation diagram of the film-forming temperature of a Pt lower electrode layer, and 111 X-ray diffraction intensity when it measures along the right side from the left when the orientation flat of a wafer is arrange | positioned under. (A) is a correlation diagram between power (sputtering input power) of the Pt lower electrode layer and 111 X-ray diffraction intensity when measured along the top side facing from the orientation flat of the wafer of Example, (b) It is a correlation diagram of power (sputtering input power) of a Pt lower electrode layer and 111 X-ray diffraction intensity when measured along the right side from the left when the orientation flat of the wafer of the example is disposed below. It is explanatory drawing of distribution of (111) preferential orientation on the wafer (substrate) surface of the Pt lower electrode layer concerning the Example of this invention, Comprising: (a) is non-uniform (111) preferential orientation on a substrate surface. (B) is an example of a uniform (111) preferred orientation distribution in the embodiment of the present invention. It is explanatory drawing of the lattice distortion distribution of the KNN piezoelectric film on the wafer (substrate | substrate) surface of the Pt lower electrode layer based on the Example of this invention, Comprising: (a) is Pt which has distribution of non-uniform (111) priority orientation. FIG. 4B is a distribution of lattice strain of a KNN piezoelectric film formed on a lower electrode layer, and FIG. 5B is a KNN piezoelectric film formed on a Pt lower electrode layer having a uniform (111) preferred orientation according to an embodiment of the present invention. This is the distribution of lattice strain. It is a correlation diagram of the dispersion | variation in 111 diffraction intensity of the Pt lower electrode layer on the board | substrate of an Example, and the dispersion | variation in the lattice distortion c / a of a KNN piezoelectric film. It is explanatory drawing of the piezoelectric constant distribution of the KNN piezoelectric film on the wafer (substrate | substrate) surface of the Pt lower electrode layer based on the Example of this invention, Comprising: (a) is Pt which has distribution of non-uniform (111) priority orientation. FIG. 4B is a distribution of piezoelectric constants of a KNN piezoelectric film formed on the lower electrode layer, and FIG. 5B is a KNN piezoelectric film formed on a Pt lower electrode layer having a uniform (111) preferred orientation according to an embodiment of the present invention. This is a distribution of piezoelectric constants. FIG. 4 is a correlation diagram between a relative standard deviation of 111 diffraction intensities of a Pt lower electrode layer on a substrate according to an embodiment of the present invention and a relative standard deviation of a piezoelectric constant of a KNN piezoelectric film. And the magnification of the X-ray diffraction intensity of the (111) plane of the Pt lower electrode layer on a substrate according to an embodiment of the present invention, is a diagram showing the relationship between the piezoelectric constant -d ₃₁ of the KNN piezoelectric film.

  The present inventor has appropriately selected the substrate, the lower electrode layer, and the piezoelectric film, which are constituent materials of the piezoelectric film element, and has optimized the manufacturing conditions of these materials. Focusing on the relationship between the characteristics and the lower electrode structure, a precise and detailed analysis was quantitatively performed in order to clarify the correlation between the piezoelectric characteristics and the lower electrode structure. As a result, by strictly controlling the crystal orientation of the lower electrode layer, the piezoelectric characteristics of the lead-free piezoelectric film element can be improved and the performance of the piezoelectric film device can be improved. We found that the manufacturing yield of devices can be improved.

The piezoelectric film element of one embodiment of the present invention is a piezoelectric film element in which at least a lower electrode layer and a lead-free alkali niobium oxide-based piezoelectric film are arranged on a substrate, wherein the lower electrode layer includes a cubic crystal, A crystal structure of any one of tetragonal, orthorhombic, hexagonal, monoclinic, triclinic, and trigonal crystals, or a state in which two or more of these crystal structures coexist, and the crystal structure In the X-ray diffraction intensity distribution of the crystal plane that is preferentially oriented to a specific crystal axis of two or less of the crystal axes, and at least one of the crystal axes on the substrate is normal. The relative standard deviation of the X-ray diffraction intensity of the crystal plane is 57% or less.
For example, as shown in Table 2 of an example described later and FIG. 16, the relative standard deviation of the (111) X-ray diffraction intensity, which is an index of the (111) preferred orientation distribution of the lower electrode layer on the substrate, is 57% or less, More preferably, the relative standard deviation of the piezoelectric constant, which is an index of the piezoelectric constant distribution on the substrate, is set to 10% or less, or 7% or less (the relative standard deviation of 111 X-ray diffraction intensity is 44 by setting the range to 44% or less. % Or less), the piezoelectric characteristics on the substrate can be realized uniformly and stably.

According to another aspect of the present invention, there is provided a piezoelectric film element in which at least a lower electrode layer and a lead-free alkali niobium oxide-based piezoelectric film are arranged on a substrate, wherein the lower electrode layer has a cubic crystal structure. A crystal structure of any one of tetragonal, orthorhombic, hexagonal, monoclinic, triclinic, and trigonal crystals, or a state in which two or more of these crystal structures coexist, In the distribution of the X-ray diffraction intensity of the crystal plane that is preferentially oriented to a specific axis of two or less of the crystal axes of the structure, and that is normal to at least one of the crystal axes on the substrate, The magnitude of the maximum peak intensity relative to the minimum peak intensity of the X-ray diffraction intensity of the crystal plane is in the range of 7 times or less, more preferably 6 times or less.
For example, as shown in Table 3 of an example described later and FIG. 17, the maximum peak intensity with respect to the minimum peak intensity of the (111) X-ray diffraction intensity, which is an index of the (111) preferred orientation distribution of the lower electrode layer on the substrate. By precisely setting the size within a range of 7 times or less, the piezoelectric characteristics of the lead-free piezoelectric body can be freely controlled or improved. More preferably, by setting the magnitude of the X-ray diffraction intensity to about 6 times or less, the piezoelectric constant can be controlled to 70 or more, a level that can be widely applied to various devices. The piezoelectric constant at this time is expressed in arbitrary units because the Young's modulus of the KNN piezoelectric film is assumed in bulk, but in one embodiment of the present invention, the expansion and contraction in the direction along the electrode surface is described. a _{d 31} is the change amount.

In the piezoelectric film element of the above aspect, a Pt layer or a Pt alloy layer is used as the lower electrode layer, and the lower electrode layer made of the Pt layer or the Pt alloy layer is (111) preferentially oriented in a direction perpendicular to the substrate surface. By doing so, the orientation of the piezoelectric film formed on the substrate can be improved. Thereby, the piezoelectric characteristics of the piezoelectric film element can be further improved.
In addition, by using Ru, Ir, Sn, In, an oxide thereof, or a compound of Pt and an element contained in the piezoelectric film as the material of the lower electrode layer, the piezoelectric film is similarly formed. The orientation and the piezoelectric characteristics of the piezoelectric film element can be improved.
In addition, for the substrate, a Si substrate, MgO substrate, ZnO substrate, SrTiO ₃ substrate, SrRuO ₃ substrate, glass substrate, quartz glass substrate, GaAs substrate, GaN substrate, sapphire substrate, Ge substrate, or stainless steel substrate should be used. Thus, the crystal orientation of the piezoelectric film formed thereon can be controlled, and the piezoelectric characteristics can be improved.

  Hereinafter, an embodiment of a piezoelectric film element and a piezoelectric film device according to the present invention will be described with reference to the drawings.

(One Embodiment of Piezoelectric Film Element)
FIG. 1 shows an embodiment of a piezoelectric film element according to the present invention.
As shown in FIG. 1, the piezoelectric film element 10 of the present embodiment includes a substrate 1 having an oxide film on the surface, a lower electrode layer 3 formed on the substrate 1 with an adhesive layer 2 interposed therebetween, and a lower electrode layer 3. And a piezoelectric film 4 having a perovskite structure formed thereon. The piezoelectric film 4 is (Na _x K _y Li _z ) NbO ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 0.2, x + y + z = 1), and is formed by being oriented in a predetermined direction. The piezoelectric film 4 is preferentially oriented in a predetermined direction with respect to the lower electrode layer 3 to be formed.

Examples of the substrate 1 include a Si substrate, MgO substrate, ZnO substrate, SrTiO ₃ substrate, SrRuO ₃ substrate, glass substrate, quartz glass substrate, GaAs substrate, GaN substrate, sapphire substrate, Ge substrate, and stainless steel substrate. In particular, an Si substrate that is inexpensive and has an industrial record is desirable. Examples of the oxide film formed on the surface of a Si substrate and the like include a thermal oxide film formed by thermal oxidation and a Si oxide film formed by a CVD (Chemical Vapor Deposition) method. The lower electrode layer 3 such as a Pt electrode may be directly formed on an oxide substrate such as quartz glass, MgO, SrTiO ₃ , or SrRuO ₃ without forming the oxide film.

  The lower electrode layer 3 is desirably a single-layer electrode layer made of Pt or a Pt alloy containing Pt as a main component, or an electrode layer having a laminated structure including these layers. Further, the lower electrode layer 3 is preferably formed so as to be oriented in the (111) plane direction (the direction of the [111] axis), and between the substrate 1 and the lower electrode layer 3 made of a Pt layer or a Pt alloy layer. As shown in FIG. 1, it is preferable to provide an adhesive layer 2 made of Ti or the like for improving the adhesion to the substrate 1.

In this embodiment, the crystal orientation of the lower electrode layer 3 is the (111) plane preferential orientation. For example, in the distribution on the 4-inch Si wafer as the substrate 1, the lower electrode layer 3 has the (111) orientation. The relative standard deviation of the X-ray diffraction intensity of the (111) plane, which is a variation in degree, is 15%, and the X-ray diffraction intensity of the (111) plane used as an index of the (111) plane preferred orientation is (111) The magnitude of the maximum peak intensity with respect to the minimum peak intensity in the surface X-ray diffraction intensity distribution was controlled to 7 times. Further, in evaluating the (111) preferential orientation of the lower electrode layer 3 of Pt, the X-ray diffraction pattern of the lower electrode layer 3 can be easily measured before and after the KNN piezoelectric film is formed. It is possible to evaluate the Pt lower electrode layer 3 having (111) preferential orientation even before and after the modification treatment after the formation of the piezoelectric film. Focusing on the degree of orientation of the lower electrode layer 3 preferentially oriented in a predetermined direction such as the (111) plane, an X-ray diffraction method or the like (structural analysis method capable of estimating other orientation directions, for example, a scanning electron microscope The crystal orientation analysis method applying electron beam diffraction by the above-mentioned method is used to optimize the manufacturing conditions of the lower electrode layer 3 having an appropriate crystal orientation.

  In general, for an electrode layer such as Pt, in order to control the atomic level structure such as crystal orientation and lattice strain of a dielectric film or a piezoelectric film formed on the upper side, the electrode layer is formed as described above. In many cases, the crystal orientation is preferentially oriented in a specific axis direction. However, in addition to the film quality of the lower electrode layer, there are many factors that determine the film quality of the upper piezoelectric film, and it is difficult to form the film quality of the lower electrode layer uniformly on a large-diameter substrate. As a result, it is not easy to stably produce a high-performance piezoelectric film. Also in the (111) preferentially oriented Pt electrode layer which is one of the embodiments of the present invention, for the above reasons, the precision of the crystal orientation of the Pt lower electrode layer, which is one of the characteristics determining factors of the lead-free piezoelectric film, Therefore, it has been difficult to stably produce a small lead-free piezoelectric element having a desired high piezoelectric constant.

Therefore, in order to strictly control the piezoelectric characteristics of the lithium potassium sodium niobate film that is a lead-free piezoelectric film, the Pt lower electrode layer that determines the initial crystal growth state in this piezoelectric film is the crystal of the Pt lower electrode layer. In order to manufacture the structure accurately and stably, optimization is performed according to the manufacturing conditions described below.
In this embodiment, the Pt lower electrode layer was prototyped using a sputtering method, which is a film forming method that has generally been proven in mass production. First, with regard to sputtering power (Power) at the time of film formation, which is one of the control parameters, by increasing the sputtering power, many sputtered particles are forced to be applied by the impact of energetic particles such as Ar ions. As a result, a Pt lower electrode layer having an optimum high orientation is produced. The film forming temperature is also noted as a control parameter for crystal orientation, and is optimal (111) in the range of room temperature to 800 ° C., more preferably in the range of room temperature to 300 ° C., so that the (111) preferred orientation is uniformly obtained. A preferentially oriented Pt lower electrode layer is prepared. Furthermore, in order to improve the smoothness of the lower electrode layer surface and the adhesion with the substrate, Ti or TiO _x having a film thickness of 0.1 to several nm is formed on the substrate before the lower electrode layer is formed. By forming a Pt lower electrode layer on the substrate, it was possible to stably produce a highly oriented Pt lower electrode layer having strong adhesion to the substrate.

Further, the candidate for the substrate 1 is preferably Si, MgO, ZnO, SrTiO ₃ , SrRuO ₃ , glass, quartz glass, GaAs, GaN, sapphire, Ge, stainless steel, or the like, or a composite thereof. , Comparing the crystal orientation of the lithium potassium sodium niobate film in detail with respect to the piezoelectric film element in which the adhesion layer and the lower electrode layer are formed on those substrates and the lithium potassium sodium niobate film is formed on the upper layer. In fact, we proceeded with the selection of substrates that can strictly control the preferred orientation. Further, in order to more surely realize the preferential orientation of the lithium potassium sodium niobate film, in the above embodiment, the temperature when forming the lithium potassium sodium niobate film, the type of sputtering operation gas, the operation gas The conditions such as pressure, degree of vacuum, input power, and heat treatment after film formation were optimized to produce a piezoelectric film having crystal orientation that improves the piezoelectric characteristics.

The polycrystal or epitaxially grown single crystal Pt lower electrode layer in this embodiment is (111) preferentially oriented, and (111) X-rays are expressed as variations in the degree of (111) orientation on the substrate (eg, Si wafer). It is precisely controlled so that the relative standard deviation of the diffraction intensity falls within a certain range. The relative standard deviation of the (111) X-ray diffraction intensity is a structural parameter that quantitatively represents the crystal orientation of the Pt lower electrode layer preferentially oriented on the (111) plane, and the characteristics of the piezoelectric film formed on the upper part. It is a control parameter that is the key to improvement.
Actually, in order to make the (111) preferential orientation distribution of the Pt lower electrode layer uniform, film formation is performed by using thermal radiation by an infrared lamp, heat conduction by laser irradiation or heater heating through a heat transfer plate, or the like. The temperature and heat treatment temperature are controlled to be within a certain range. In addition, the input power value during the sputtering film formation of Pt is optimally controlled, the shape of the target material is changed, the distance between the substrate on which the film is formed and the sputtering target of the raw material, and the rotation relative to the sputtering target is achieved. The crystal orientation of the Pt lower electrode layer on the substrate (wafer) having a large area, that is, the (111) preferential orientation degree is made uniform by appropriately controlling the speed on the side of the substrate that has been rotated or revolved. Can be expected. Furthermore, in addition to the above setting and control conditions, the sputtering input power of the piezoelectric film, the gas pressure and flow rate introduced into the film forming apparatus are controlled, and the sputtering operation gases such as He, Ar, Kr, and Xe are controlled. 0.1
By selecting an appropriate gas type, such as containing O ₂ , N ₂ , H ₂ O or the like, a piezoelectric film element having a lithium potassium sodium niobate film exhibiting a high piezoelectric constant can be obtained stably and with a high yield. It is done. Further, the same effect can be expected by adjusting or controlling the strength and rotation speed of the magnet arranged on the sputtering target side mounted on the magnetron sputtering apparatus.

(Other Embodiments of Piezoelectric Film Element)
The piezoelectric film element (or the substrate with the piezoelectric film) 10 of the embodiment shown in FIG. 1 manufactured by accurately quantifying the crystal orientation of the lower electrode layer and strictly controlling and managing the lower electrode layer is shown in FIG. As shown in FIG. 2, by forming the upper electrode layer 5 on the piezoelectric film 4, the piezoelectric film element 20 exhibiting a high piezoelectric constant can be produced.
Further, by forming an electrode having a predetermined pattern on the piezoelectric film 4 of the piezoelectric film element 10 shown in FIG. 1, a piezoelectric film element (filter device) using surface acoustic waves can be formed. The lower electrode layer 3 is used as a base layer of the piezoelectric film 4 when a lower electrode is not required, such as a piezoelectric film element (filter device) using surface acoustic waves.

(Piezoelectric device)
By forming the piezoelectric film element 20 of the embodiment shown in FIG. 2 into a predetermined shape and providing a voltage application means or a voltage detection means between the lower electrode layer 3 and the upper electrode layer 5 of the molded piezoelectric film element, Piezoelectric film devices such as various actuators or sensors can be manufactured. By stably controlling the crystal orientation of the lower electrode layer and the piezoelectric film in these devices, it is possible to improve and stabilize the piezoelectric characteristics of the piezoelectric film elements and piezoelectric film devices, and to provide high-performance microdevices at low cost. It becomes possible. In addition, since the piezoelectric film element of the present invention is a piezoelectric film element including a piezoelectric film that does not use lead, by mounting the piezoelectric film element of the present invention, the environmental load is reduced and a high-performance small motor is provided. In addition, small system devices such as sensors and actuators, such as MEMS (Micro Electro Mechanical System), can be realized.

FIG. 3 is a cross-sectional view showing a schematic configuration of a piezoelectric film device according to another embodiment. The piezoelectric film device 30 of this embodiment shows a case where the piezoelectric film element 20 of the embodiment shown in FIG. 2 is applied to a variable capacitor.
The piezoelectric film device 30 includes a device substrate 31, an insulating layer 32 formed on the device substrate 31, and a piezoelectric film element 20 formed on the insulating layer 32 and having a structure similar to that shown in FIG. The device substrate 31 and the insulating layer 32 function as a support member that supports one end of the piezoelectric film element 20. The piezoelectric film element 20 includes an adhesion layer 2, a lower electrode layer 3, and a piezoelectric film 4 on the substrate 1.
The upper electrode layer 5 is formed, and the other end portion (free end portion) of the piezoelectric film element 20 is extended from the substrate 1. The extended portion of the substrate 1 is provided with an upper capacitor electrode 36. Protrusively provided. On the device substrate 31, a lower capacitor electrode 34 is formed below the upper capacitor electrode 36 via a gap 33, and an insulating layer 35 made of SiN or the like is formed on the surface of the lower capacitor electrode 34.
When a voltage is applied to the upper electrode layer 5 and the lower electrode layer 3 via the bonding wires 18A and 18B, respectively, the tip of the piezoelectric film element 20 is displaced, and accordingly, the upper capacitor electrode 36 is displaced in the vertical direction. To do. The displacement between the upper capacitor electrode 36 changes the capacitor between the upper capacitor electrode 36 and the lower capacitor electrode 34, and the piezoelectric film device 30 of this embodiment operates as a variable capacitor.

  Examples of the present invention will be specifically described below.

(Piezoelectric membrane element)
In this example, a piezoelectric film element (substrate with a piezoelectric film) having a cross-sectional structure similar to that of the above-described embodiment shown in FIG. 1 was produced.

  In this example, first, a substrate with a lower electrode in which the Pt lower electrode layer 3 was formed on the upper portion of the Si substrate 1 having an oxide film on which the adhesive layer 2 was formed was fabricated. At this time, the Pt lower electrode layer 3 has a structure of a face-centered cubic lattice which is one of cubic crystals as a crystal system, as shown in FIG. The lower electrode layer 3 may be made of Au instead of Pt, or may be a Pt alloy, an alloy containing Ir, Ru, or Au, or a conductive oxide containing In or Sn. Each manufacturing method will be described below.

First, a thermal oxide film was formed on the surface of the Si substrate 1, and an adhesive layer 2 and a lower electrode layer 3 were formed thereon. The substrate 1 may be an MgO substrate, a ZnO substrate, a SrTiO ₃ plate, a SrRuO ₃ substrate, a glass substrate, a quartz glass substrate, a GaAs substrate, a GaN substrate, a sapphire substrate, a Ge substrate, or a stainless steel substrate instead of the Si substrate. . The lower electrode is made of a 100 nm thick Pt thin film formed as the Pt lower electrode layer 3 on the 2 nm thick Ti film (or a compound film containing Ti) formed as the adhesive layer 2. A sputtering method was used to form the adhesive layer 2 and the Pt lower electrode layer 3.

In the embodiment of the present invention, the RF magnetron sputtering apparatus shown in FIG. 4 is used to form the adhesive layer 2, the lower electrode layer 3, and the piezoelectric film 4, and the sputtering target 42 is placed in the film forming container 41 of the sputtering apparatus. The Si substrate 1 was placed facing each other. A metal target having a diameter of 100 mm is used as the sputtering target 42 for the Ti film and the Pt film, the sputtering input power at the time of film formation is 100 W, and the sputtering gas is 100% Ar gas or a mixed gas of Ar and O ₂ , or A gas in which at least one inert gas such as He, Ne, Kr, or N ₂ was mixed was used. In forming the Pt film, the substrate temperature was set to 300 ° C. to form a polycrystalline Pt film. In addition, after film formation, heat treatment was performed in oxygen, an inert gas, a mixed gas of both, or in the air or in vacuum.

FIG. 5 shows a surface shape image of the Pt film as the lower electrode layer 3 measured with an atomic force microscope. As shown in FIG. 5, it can be seen that a texture of fine crystal particles is seen on the surface, and each particle has a shape close to an equilateral triangle. Considering that Pt is a face-centered cubic lattice, it is considered that the (111) crystal plane faces the substrate surface side, as can be inferred from the crystal structure of Pt in FIG. As a result of examining the crystal structure with a general X-ray diffractometer, the Pt lower electrode layer has a (111) plane, (22) as shown in the X-ray diffraction pattern (2θ / θ scan measurement) of FIG.
2) Only diffraction peaks on the plane were observed, and diffraction peaks on the other (200) plane, (220) plane, and (311) plane could not be confirmed. That is, it became clear that a Pt thin film with (111) preferential orientation with respect to the substrate surface was formed.

Next, a potassium sodium niobate (hereinafter referred to as KNN) film having a perovskite structure was formed as the piezoelectric film 4 on the Pt lower electrode layer 3. A KNN film was also formed by sputtering. When the KNN film is formed, the substrate temperature is in the range of 400 to 500 ° C., and a 5: 5 mixed gas of Ar and O ₂ or Ar gas or He or Ne or Kr or N ₂ is used. Sputtering film formation was performed by plasma with mixed gas. Further, the target was a ceramic target _{(Na x K 1-x)} NbO 3 (x = 0.5). The KNN film was formed until the film thickness became 3 μm. In addition, after film formation, heat treatment was performed in oxygen, an inert gas, a mixed gas of both, or in the air or in vacuum.

At this time, the KNN piezoelectric film is a pseudo cubic crystal, a tetragonal crystal or an orthorhombic crystal as a crystal system, and at least a part thereof includes an ABO ₃ crystal, an amorphous material or a mixture of both. good. Here, A is at least one element from Li, Na, K, La, Sr, Nd, Ba, and Bi, and B is from Zr, Ti, Mn, Mg, Nb, Sn, Sb, Ta, and In. At least one element selected and O is oxygen. The state of crystal orientation of the piezoelectric film changes depending on the manufacturing conditions, and the internal stress (strain) of the piezoelectric film may change to compressive stress or tensile stress. In some cases, there is no stress, that is, no strain.

  When the cross-sectional shape of the KNN film thus produced was observed with a scanning electron microscope or the like, the structure was composed of a columnar structure. Further, when the crystal structure was examined with a general X-ray diffractometer, as shown in the X-ray diffraction pattern (2θ / θ scan measurement) in FIG. 8, the KNN film was formed on the Pt film preferentially oriented to (111). As a result of the formation, the produced KNN film was found to be a polycrystalline film having a pseudo cubic perovskite crystal structure. Further, as can be seen from the X-ray diffraction pattern of FIG. 8, since only the diffraction peaks of the (001) plane, (002) plane, and (003) plane can be confirmed, the KNN piezoelectric film is generally preferentially oriented in the (001) plane. You can see that

In order to evaluate the orientation of the KNN film in detail and precisely, a pole figure was measured, and it was revealed that it was the (001) preferred orientation. For details, see References 1 and 2 below. Further, from FIG. 8, in the X-ray diffraction measurement with the KNN film formed on the upper part of the Pt lower electrode layer of the example, the (111) diffraction peak of the Pt lower electrode layer that is the base of the KNN film and (222) A diffraction peak could be confirmed simultaneously. That is, the (111) preferred orientation of the Pt lower electrode layer can be found even after the KNN film is formed. Regarding the evaluation of the orientation of the lower electrode layer in the piezoelectric film element of the example, the X-ray diffraction apparatus as an evaluation apparatus uses an MRD manufactured by Panasonic, and the output of the X-ray source at the time of measurement is 1.8 kW (45 kW, 40 mA), a CuKa line was used as the characteristic X-ray source, and a slit of 10 mm × 0.1 mm was used as the line focus. A scintillation counter was used as the diffraction X-ray detector. A high-power X-ray diffractometer equipped with a two-dimensional detector with a large area X-ray detection castle ("D8 DISCOVER with Hi STAR, VANTEC2000 ° manufactured by Bruker AXS"). )).
Reference 1: Book written by Karity, New Edition X-ray diffraction theory, Agne, 1980 Reference 2: Guide to Rigaku Denki, X-ray diffraction, 4th revised edition, Rigaku Denki, 1986

(Correlation between (111) preferred orientation of Pt lower electrode layer and (001) preferred orientation of KNN film)
In this example, for the (111) preferential orientation of the Pt lower electrode layer, the Pt111 diffraction peak intensity of the X-ray diffraction pattern described in FIG. 8 was referred to. In addition, regarding the (001) preferential orientation of the KNN film, which is closely related to the improvement of the piezoelectric characteristics, the KNN001 diffraction peak intensity of the X-ray diffraction pattern was referred to. FIG. 9 shows the change in the KNN001 diffraction intensity of the KNN film with respect to the Pt111 diffraction intensity of the lower electrode layer in one example.
As shown in FIG. 9A, the 001 diffraction intensity of the KNN film increases from about 100 counts to 650 counts as the 111 diffraction intensity of the Pt lower electrode layer increases at the center of the wafer, which is a Si substrate. It turns out that it increases to (counts). In addition, even at a position 30 mm away from the center of the wafer as the Si substrate, as shown in FIG. 9B, the 001 diffraction intensity of the KNN piezoelectric film increases as the 111 diffraction intensity of the Pt lower electrode layer increases. Yes. That is, the higher the (111) preferred orientation degree of the Pt lower electrode layer, the higher the (001) preferred orientation degree of the KNN piezoelectric film. In order to improve the piezoelectric properties correlated with the (001) preferential orientation of the KNN piezoelectric film, it was found that it is important to control the (111) preferential orientation degree of the lower electrode layer that is the base of the KNN piezoelectric film. .

(Control of (111) preferred orientation degree of Pt lower electrode layer)
One method for controlling the (111) preferential orientation degree of the Pt lower electrode layer is temperature control during sputtering film formation. FIG. 10 shows the change in 111 diffraction intensity of the Pt lower electrode layer with respect to the film formation temperature (substrate temperature). FIG. 10A shows the result of measuring five points from the orientation flat side to the top side of the wafer for a sample having a relatively uniform distribution of 111 diffraction intensity on the wafer. It can be seen that the Pt111 diffraction intensity increases as the deposition temperature of the Pt lower electrode layer increases. FIG. 10B shows the result of measuring five points from the left to the right with the orientation flat side facing down for the sample wafer. Similar to FIG. 10A, the temperature dependence is shown in which the Pt111 diffraction intensity increases as the film formation temperature increases. That is, there is a positive correlation between the film formation temperature and the Pt111 diffraction intensity over the entire wafer. This shows that appropriate control of the deposition temperature improves the (111) preferred orientation degree of the Pt lower electrode layer, and as a result, the (001) preferred orientation degree of the KNN piezoelectric film can be optimized.

As another method for controlling the (111) preferential orientation degree of the Pt lower electrode layer, there is a sputtering input power (Power) at the time of sputtering film formation. FIG. 11 shows a change in 111 diffraction intensity of the Pt lower electrode layer with respect to power. FIG. 11 shows changes in 111 diffraction intensity with respect to power at different film formation temperatures (non-heating, 150 ° C. heating). FIG. 11A shows the result of measuring five points from the orientation flat side to the top side of the wafer, and FIG. 11B shows the result of measuring five points from the left to the right with the orientation flat side facing down. As shown in FIG. 11, it can be seen that the 111 diffraction intensity increases as the power increases from 300 W to 500 W. On the wafer surface, the 111 diffraction intensity increases almost uniformly as the power increases. Further, it can be understood that the diffraction intensity of Pt111 is higher when heated at 150 ° C. during film formation than when not heated regardless of the magnitude of power (sputtering input power). In other words, Power is also considered to be a parameter for controlling the (111) preferred orientation of the Pt lower electrode layer, as is the film formation temperature.

(Distribution of (111) preferred orientation degree of Pt lower electrode layer on substrate (wafer))
Here, the distribution of the (111) preferential orientation degree of the Pt lower electrode layer on the substrate, for example, a Si wafer, will be described with respect to an embodiment of the present invention. FIG. 12 shows the distribution of the (111) preferred orientation degree of the Pt lower electrode layer on the Si wafer. The horizontal axis represents the X-ray diffraction measurement position when multipoint measurement is performed from the orientation flat side to the top side, and the vertical axis represents the 111 X-ray diffraction intensity of the Pt lower electrode layer. FIG. 12A is a diagram showing a state where the 111 diffraction intensity distribution of the Pt lower electrode layer formed on the 4-inch Si wafer is not uniform. In the case of FIG. 12A, the relative standard deviation of 111 diffraction intensity on the Si wafer, which is a distribution index of 111 diffraction intensity, is about 59%. On the other hand, FIG. 12B is a diagram showing a state in which the 111 diffraction intensity distribution of the Pt lower electrode layer has a uniform distribution. Comparing FIG. 12B and FIG. 12A, it can be seen that the convex distribution of 111 diffraction intensity in FIG. 12A is flattened in FIG. In the case of FIG. 12B, the relative standard deviation of the 111 diffraction intensity on the Si wafer is 14%, and the size of the (111) preferential orientation distribution of the Pt lower electrode layer on the wafer is reduced to about ¼. It shows that it can be improved.

(Relationship between (111) preferred orientation of Pt lower electrode layer and lattice strain of KNN piezoelectric film)
Next, KNN piezoelectric films are formed on substrates having different (111) preferred orientation distributions of the Pt lower electrode layer, and the lattice strain distributions of these KNN piezoelectric films are compared, and the uniformity of the orientation distribution of the lower electrode layer is compared. The uniformity of the lattice strain distribution of the KNN piezoelectric film was examined. FIG. 13 shows the distribution on the wafer of the lattice strain c / a of the KNN piezoelectric film. Here, the lattice strain c / a is the ratio of the lattice constant c in the normal direction perpendicular to the substrate surface of the KNN piezoelectric film and the lattice constant a in the direction parallel to the substrate surface. When c / a <1, the interstitial distance in the direction parallel to the substrate surface is longer than the interstitial distance in the normal direction, and the KNN piezoelectric film is in a tensile state in the plane, and c / a> When 1, the interstitial distance in the direction parallel to the substrate surface is shorter than the interstitial distance in the normal direction, indicating that the KNN piezoelectric film is in a compressed state in the plane.

  FIG. 13A shows the lattice strain c / a distribution of the KNN piezoelectric film formed on the Pt lower electrode layer in which the distribution of the (111) preferred orientation shown in FIG. 12A is not uniform. FIG. When the distribution of the (111) preferred orientation of the Pt lower electrode layer is non-uniform, it can be seen that the lattice strain c / a distribution of the KNN piezoelectric film is non-uniform. At this time, the relative standard deviation of the lattice strain c / a is about 31%. On the other hand, FIG. 13B shows the lattice strain c / a distribution of the KNN piezoelectric film formed on the Pt lower electrode layer in which the distribution of the (111) preferred orientation shown in FIG. It is a figure. As a result of uniformly controlling the distribution of the (111) preferential orientation of the Pt lower electrode layer, the lattice strain c / a distribution of the KNN piezoelectric film laminated thereon is made uniform. At this time, the relative standard deviation of c / a is about 5%. By realizing uniform (111) preferred orientation of the Pt lower electrode layer, the relative standard deviation of the lattice strain distribution on the wafer of the KNN piezoelectric film can be reduced to about 1/6.

Table 1 also shows the relative standard deviation of 111 diffraction intensities of the Pt lower electrode layer and the corresponding KNN for KNN piezoelectric films formed on substrates with different uniformity of (111) preferred orientation of the Pt lower electrode layer. The relative standard deviation of the lattice strain c / a of the piezoelectric film is summarized. Table 1 was used to examine the correlation between the variation in the (111) preferred orientation of the Pt lower electrode layer and the variation in the lattice strain c / a of the KNN piezoelectric film. FIG. 14 shows the result. The horizontal axis represents the 111 diffraction intensity variation of the Pt lower electrode layer representing the uniformity of the (111) preferential orientation of the Pt lower electrode layer, and the vertical axis represents the variation of the lattice strain c / a of the KNN piezoelectric film. It can be seen that the variation of the lattice strain c / a on the substrate of the KNN piezoelectric film increases as the variation of the Pt lower electrode layer on the (111) preferential orientation substrate increases. From the above, it is possible to stably produce a KNN piezoelectric film having a uniform lattice strain c / a on a Si wafer by making the (111) preferential orientation distribution of the lower electrode layer of Pt uniform. Further, since the lattice strain c / a is closely related to the piezoelectric characteristics, a high-performance KNN piezoelectric film can be manufactured with a high yield.
The 111 diffraction intensity variation of the Pt lower electrode layer is measured at multiple points on the wafer by moving the wafer or moving the X-ray source in the Pt lower electrode-formed wafer before forming the KNN piezoelectric film. The standard deviation of the 111 X-ray diffraction intensity of the Pt lower electrode layer, which is a percentage obtained by dividing the standard deviation by the average value, that is, the relative standard deviation. Next, in order to clarify the correlation between the KNN piezoelectric film and the lattice strain distribution on the wafer, the KNN piezoelectric film was formed on the wafer for which the 111 diffraction intensity variation of the Pt lower electrode layer was obtained. A wafer was produced. The arbitrary position of the KNN piezoelectric film on the wafer is measured in the out-of-plane (film thickness) direction of the KNN piezoelectric film by the out-of-plane X-ray diffraction method and the in-plane X-ray diffraction method. The lattice constant c and the lattice constant a in the in-plane direction were measured at many points, and the lattice strain amount c / a at an arbitrary position on the wafer was obtained. The variation of the lattice strain c / a of the KNN piezoelectric film described in the examples is the standard deviation of c / a obtained by measuring multiple points on the wafer described above, and is a percentage obtained by dividing the standard deviation by the average value. That is, the relative standard deviation. Note that the variation in 111 X-ray diffraction intensity of the Pt lower electrode layer and the variation of the lattice strain c / a of the KNN piezoelectric film are caused by a standard deviation or a relative standard deviation based on uniformity or non-uniformity of variation on a single wafer. Is not limited, and the standard deviation based on the difference between different wafers or lots regarding the 111 X-ray diffraction intensity of the Pt lower electrode layer obtained by measuring an arbitrary point on the wafer and the lattice strain c / a of the KNN piezoelectric film It may be a relative standard deviation.

(Relationship between (111) preferred orientation distribution of Pt lower electrode layer and piezoelectric constant distribution of KNN piezoelectric film)
FIG. 15 shows the results of evaluating the distribution of piezoelectric constants for KNN piezoelectric films actually formed on substrates (4-inch Si wafers) having different (111) preferred orientation distribution states of the Pt lower electrode layer. FIG. 15A is a diagram showing a distribution of piezoelectric constants of the KNN piezoelectric film formed on the Pt lower electrode layer in a state where the distribution of the (111) preferential orientation shown in FIG. . When the distribution of the (111) preferential orientation of the Pt lower electrode is nonuniform, it can be seen that the piezoelectric constant of the KNN piezoelectric film is nonuniform. At this time, the piezoelectric constant had a distribution from about 70 to 110 (arbitrary unit) on the wafer, and the relative standard deviation was about 14.3%. On the other hand, FIG. 15B shows the distribution of the piezoelectric constant of the KNN piezoelectric film formed on the Pt lower electrode in which the distribution of the (111) preferred orientation shown in FIG. When the distribution of the (111) preferred orientation of the Pt lower electrode was controlled uniformly, the distribution of the piezoelectric constant of the KNN piezoelectric film formed on the upper part was made uniform. The relative standard deviation of the piezoelectric constant distribution is about 4.1%, and it can be seen that the variation of the piezoelectric constant on the wafer can be reduced to about 1/4. That is, it is possible to achieve both high performance and stable production of the KNN piezoelectric film by controlling the structure of the Pt lower electrode layer that is the base of the KNN piezoelectric film, specifically, precise control of the (111) preferential orientation.

As shown in FIG. 15, the unit of the piezoelectric constant in this embodiment is an arbitrary unit. In order to obtain the piezoelectric constant, numerical values such as the Young's modulus and Poisson's ratio of the piezoelectric film are required, but it is difficult to obtain the numerical values of the Young's modulus and Poisson's ratio of the piezoelectric material in the thin film form. It is. In the case of a thin piezoelectric film, unlike the bulk material, it is affected by the substrate used during film formation (restraint, etc.), so the absolute value (true value) of the Young's modulus and Poisson's ratio (constant) of the piezoelectric thin film itself is determined. It cannot be obtained in principle. Therefore, the piezoelectric constant was calculated using the estimated values of the Young's modulus and Poisson's ratio of the KNN film known so far. Accordingly, since the obtained piezoelectric constant value is an estimated value, it is set as a relative arbitrary unit in order to provide objectivity. However, although the values of the Young's modulus and Poisson's ratio of KNN used for calculating the piezoelectric constant are estimated values, they are reliable to some extent, and the piezoelectric constant of about 100 (arbitrary unit) is the piezoelectric constant-d. ₃₁ is considered to be approximately 100 (pm / V).

Table 2 also shows the relative standard deviation of the (111) X-ray diffraction intensity of the Pt lower electrode and the corresponding values for the KNN piezoelectric films formed on the substrates with different uniformity of the (111) preferred orientation of the Pt lower electrode layer. The relative standard deviation of the piezoelectric constant of the obtained KNN piezoelectric film is shown together. Based on Table 2,
FIG. 16 shows the result of examining the variation of the piezoelectric constant variation of the KNN piezoelectric film with respect to the variation of the (111) preferred orientation of the Pt lower electrode layer. The horizontal axis in FIG. 16 is the relative standard deviation of (111) X-ray diffraction intensity corresponding to the variation in (111) preferred orientation of the Pt lower electrode layer, and the vertical axis is the piezoelectric constant corresponding to the variation in piezoelectric constant of the KNN piezoelectric film. Relative standard deviation. It can be seen that the variation of the piezoelectric constant on the substrate of the KNN piezoelectric film increases as the variation of the Pt lower electrode layer on the (111) preferred orientation substrate increases. That is, by homogenizing the (111) preferential orientation distribution of the Pt lower electrode, a KNN piezoelectric film having uniform piezoelectric characteristics on the Si wafer can be manufactured.

(Relationship between the maximum peak intensity with respect to the minimum peak intensity of the (111) plane of the (111) plane of the Pt lower electrode layer and the piezoelectric constant −d ₃₁ of the KNN piezoelectric film)
Table 3 shows the maximum relative to the minimum peak intensity of the X-ray diffraction intensity of the (111) plane of the Pt lower electrode layer for KNN piezoelectric films formed on substrates with different uniformity of the (111) preferred orientation of the Pt lower electrode layer. The magnitude of the peak intensity (the magnitude of the maximum peak intensity with respect to the minimum peak intensity of the X-ray diffraction intensity is simply referred to as “magnification of X-ray diffraction intensity”), and the corresponding piezoelectric constant −d ₃₁ of the KNN piezoelectric film It is summarized. FIG. 17 created based on Table 3 illustrates the relationship between the magnification of the X-ray diffraction intensity of the (111) plane of the Pt lower electrode layer and the piezoelectric constant −d ₃₁ of the KNN piezoelectric film. As the magnification (variation) of the X-ray diffraction intensity of the (111) plane of the Pt lower electrode layer increases, the piezoelectric constant −d ₃₁ of the KNN piezoelectric film decreases, and the X-ray diffraction of the (111) plane of the Pt lower electrode layer It can be seen that the piezoelectric constant −d ₃₁ can be controlled to 70 or more, which is a level widely applicable to various devices, by setting the strength magnification to 6 times or less.

1 Substrate (Si substrate)
2 Adhesive layer 3 Lower electrode layer (Pt lower electrode layer)
4 Piezoelectric film (KNN film)
5 Upper Electrode Layer 10 Piezoelectric Film Element 20 Piezoelectric Film Element 30 Piezoelectric Film Device 41 Film Formation Container 42 Sputtering Target

Claims (11)

In a piezoelectric film element in which at least a lower electrode layer and a lead-free alkaline niobium oxide-based piezoelectric film are arranged on a substrate,
The lower electrode layer is
Cubic, tetragonal, orthorhombic, hexagonal, monoclinic, triclinic, trigonal crystal structure, or a state in which two or more of these crystal structures coexist, X-ray diffraction intensity of a crystal plane that is preferentially oriented to a specific crystal axis that is two or less of the crystal axes of the crystal structure and that is normal to at least one of the crystal axes on the substrate. The piezoelectric film element according to the distribution, wherein a relative standard deviation of X-ray diffraction intensity of the crystal plane is 57% or less. In a piezoelectric film element in which at least a lower electrode layer and a lead-free alkaline niobium oxide-based piezoelectric film are arranged on a substrate,
The lower electrode layer is
Cubic, tetragonal, orthorhombic, hexagonal, monoclinic, triclinic, trigonal crystal structure, or a state in which two or more of these crystal structures coexist, X-ray diffraction intensity distribution of a crystal plane that is preferentially oriented to a specific crystal axis of two or less of the crystal axes of the crystal structure and that has at least one crystal axis as a normal line on the substrate Wherein the maximum peak intensity relative to the minimum peak intensity of the X-ray diffraction intensity of the crystal plane is in the range of 7 times or less.   3. The piezoelectric film element according to claim 1, wherein the piezoelectric constant distribution of the piezoelectric film on the substrate has a relative standard deviation of 10% or less.   4. The piezoelectric film element according to claim 1, wherein the lower electrode layer has a texture composed of particles having a columnar structure.   5. The piezoelectric film element according to claim 1, wherein the lower electrode layer is mainly composed of (001) preferentially oriented crystal grains, (110) preferentially oriented crystal grains, and (111) preferentially oriented crystal grains. A piezoelectric film element having a structure composed of one preferentially oriented crystal grain or a structure in which two or more preferentially oriented crystal grains coexist.   6. The piezoelectric film element according to claim 1, wherein the lower electrode layer is a single layer structure made of a Pt layer or an alloy layer containing Pt as a main component, or a Pt layer or an alloy containing Pt as a main component. A piezoelectric film element having a laminated structure including layers.   7. The piezoelectric film element according to claim 1, wherein the lower electrode layer is made of Ru, Ir, Sn, In, an oxide thereof, or a compound of Pt and an element contained in the piezoelectric film. A piezoelectric film element having a single layer structure of a layer or a laminated structure including the layer.   8. The piezoelectric film element according to claim 1, wherein an upper electrode layer is provided on the piezoelectric film, and the upper electrode layer is a single layer made of a Pt layer or an alloy layer containing Pt as a main component. A piezoelectric film element having a structure or a laminated structure including a Pt layer or an alloy layer containing Pt as a main component.   9. The piezoelectric film element according to claim 8, wherein the upper electrode layer is a single layer made of Ru, Ir, Sn, In, an oxide thereof, or a compound of Pt and an element contained in the piezoelectric film. A piezoelectric film element having a structure or a laminated structure including the layers. 10. The piezoelectric film element according to claim 1, wherein the substrate is a Si substrate, a MgO substrate, a ZnO substrate, a SrTiO ₃ substrate, a SrRuO ₃ substrate, a glass substrate, a quartz glass substrate, a GaAs substrate, a GaN substrate, A piezoelectric film element, which is a sapphire substrate, a Ge substrate, or a stainless steel substrate.   A piezoelectric film device comprising the piezoelectric film element according to claim 1.