JP3996594B2 - Piezoelectric element, inkjet head, and inkjet recording apparatus - Google Patents

Description

The present invention relates to a piezoelectric element, an ink jet head, and an ink jet recording apparatus .

Piezoelectric materials are materials that convert mechanical energy into electrical energy or convert electrical energy into mechanical energy. A typical example of the piezoelectric material is lead zirconate titanate (Pb (Zr, Ti) O ₃ , hereinafter referred to as PZT), which is an oxide having a perovskite crystal structure. In PZT having a perovskite tetragonal crystal structure, the largest piezoelectric displacement can be obtained in the <001> axial direction (c-axis direction). However, many piezoelectric materials are polycrystalline bodies composed of aggregates of crystal grains, and the crystal axes of the crystal grains are directed in various directions, and the spontaneous polarization Ps is also arranged in various ways.

  By the way, with the recent miniaturization of electronic devices, there is a strong demand for miniaturization of piezoelectric elements. And in order to satisfy | fill the request | requirement, the piezoelectric element is being used in the form of a thin film whose volume is remarkably small compared with the sintered compact conventionally used frequently. For this reason, research and development for thinning piezoelectric elements has become active.

  For example, since PZT has spontaneous polarization Ps oriented in the <001> axis direction, in order to realize a PZT thin film having high piezoelectric characteristics (piezoelectric displacement characteristics), the <001> axis of the crystal constituting the PZT thin film is used as the substrate. It is necessary to make the direction perpendicular to the surface on one side. Conventionally, in order to realize this, on a single crystal substrate made of magnesium oxide (MgO) having a rock salt type crystal structure with a crystal orientation (001) surface on the surface, on one surface thereof On the other hand, a PZT thin film having good crystallinity and oriented in the direction perpendicular to the <001> axis was directly formed by a sputtering method at a temperature of 600 to 700 ° C. and using PZT as a target (for example, Patent Document 1). See). A feature of this method is that a MgO single crystal substrate is used, and this makes it possible to realize a piezoelectric thin film having high piezoelectric characteristics and preferentially oriented in the crystal direction.

  However, since this MgO single crystal is a very expensive material, the above method is not preferable from the viewpoint of cost when mass-producing industrial products such as piezoelectric elements using piezoelectric thin films.

  On the other hand, as a method for forming a (001) plane or (100) plane crystal orientation film of a perovskite type piezoelectric material such as PZT on an inexpensive substrate such as silicon, the following is known. That is, for example, in Patent Document 2, PZT or a lanthanum-containing PZT precursor solution is applied onto a Pt electrode oriented in the (111) plane, and before the precursor solution is crystallized, first, 450 to 550 is applied. It has been shown that a (100) plane crystal orientation film of PZT can be produced by thermal decomposition at 0 ° C., followed by heat treatment at 550 to 800 ° C. for crystallization (sol-gel method).

  However, when mass-producing piezoelectric elements by this sol-gel method, the crystal changes in the process of removing organic matter and the process of crystallizing the amorphous piezoelectric precursor thin film at a high temperature, so that cracks and lower electrodes and piezoelectric There is a problem that film peeling from the body thin film is likely to occur.

On the other hand, as a method for forming a crystal orientation film on an inexpensive substrate, a method that does not require a sol-gel method, for example, a method that uses a sputtering method is known (see, for example, Patent Document 3). Hereinafter, the process of forming the crystal orientation film by this method will be described. First, an electrode thin film made of a noble metal alloy such as Pt or Ir containing Co, Ni, Mn, Fe, or Cu is formed on a substrate as a base electrode by sputtering. Next, a PZT thin film having a (001) crystal orientation can be obtained by forming PZT on the electrode thin film by sputtering.
JP-A-10-209517 Japanese Patent No. 3021930 JP 2004-79991 A

  The piezoelectric thin film obtained as described above has a high piezoelectric constant, and a large piezoelectric displacement occurs even when the applied voltage is small. Therefore, it is expected to be used as an actuator in various fields. Further, a larger voltage can be generated by applying a large voltage to the piezoelectric thin film.

  However, when a voltage is applied for a long time in an atmosphere of high temperature and high humidity (temperature of 50 ° C. and humidity of 50%) to the actuator in which the PZT thin film is formed by the sputtering method, the amount of displacement decreases and the electrode thin film turns black. As a result, there is a problem that the actuator deteriorates. This is presumably because excess Pb of the PZT thin film reacts with moisture at the interface between the electrode thin film and the PZT thin film.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a piezoelectric element with low cost, high piezoelectric characteristics, and high moisture resistance, an inkjet head including the piezoelectric element, and inkjet recording. To provide an apparatus.

  In order to solve the above problems, a piezoelectric element of the present invention includes a first electrode film, a first piezoelectric film formed on the first electrode film, the first piezoelectric film, and the first piezoelectric film. 1. A piezoelectric element comprising: a piezoelectric laminated film comprising a second piezoelectric film whose crystal orientation is controlled by one piezoelectric film; and a second electrode film formed on the second piezoelectric film. The first and second piezoelectric films are aggregates of columnar particles whose crystal growth direction is directed from one side to the other side in the thickness direction of the piezoelectric multilayer film, and the first piezoelectric film contains Pb. The amount is less than the Pb content of the second piezoelectric film, the average cross-sectional diameter of the columnar particles of the second piezoelectric film is larger than the average cross-sectional diameter of the columnar particles of the first piezoelectric film, and the second The ratio of the thickness of the piezoelectric laminated film to the average cross-sectional diameter of the columnar particles of the piezoelectric film is 20 or more and 60 or less. It is an.

  As a result, the Pb content of the first piezoelectric film is less than the Pb content of the second piezoelectric film, so that even when a voltage is applied to the piezoelectric element in a high-temperature and high-humidity atmosphere, The deterioration of the piezoelectric element due to the excess Pb of the first piezoelectric film reacting with moisture at the interface with the one piezoelectric film does not occur. Therefore, it is possible to provide a piezoelectric element with low cost, high piezoelectric characteristics, and high moisture resistance.

  Another piezoelectric element of the present invention includes a first electrode film, an alignment control film formed on the first electrode film, a first piezoelectric film formed on the alignment control film, and the first A piezoelectric laminate film formed on the piezoelectric film and comprising a second piezoelectric film whose crystal orientation is controlled by the first piezoelectric film, and a second electrode formed on the second piezoelectric film The first and second piezoelectric films are aggregates of columnar particles whose crystal growth direction is directed from one side to the other side in the thickness direction of the piezoelectric multilayer film. The Pb content of the first piezoelectric film is less than the Pb content of the second piezoelectric film, and the average cross-sectional diameter of the columnar particles of the second piezoelectric film is smaller than that of the columnar particles of the first piezoelectric film. The ratio of the thickness of the piezoelectric laminated film to the average sectional diameter of the columnar particles of the second piezoelectric film is 2 which is larger than the average sectional diameter. It is characterized in that at 60 or less.

  As a result, the Pb content of the first piezoelectric film is less than the Pb content of the second piezoelectric film, so that even if a voltage is applied to the piezoelectric element in a high-temperature and high-humidity atmosphere, Deterioration of the piezoelectric element caused by excess Pb of the first piezoelectric film at the interface with the piezoelectric film reacting with moisture that permeates through the first electrode film and the orientation control film does not occur. Therefore, it is possible to provide a piezoelectric element with low cost, high piezoelectric characteristics, and high moisture resistance.

  In addition, by forming the orientation control film on the first electrode film, the crystal orientation of the first piezoelectric film can be improved, and further, the crystal orientation of the second piezoelectric film can be improved. . Therefore, a piezoelectric element with higher piezoelectric characteristics can be provided.

  The columnar particles of the first piezoelectric film preferably have an average cross-sectional diameter of 40 nm to 70 nm and a length of 5 nm to 100 nm.

  Thereby, the first piezoelectric film can surely control the crystal orientation of the second piezoelectric film.

  The columnar particles of the second piezoelectric film preferably have an average cross-sectional diameter of 60 nm to 200 nm and a length of 2500 nm to 5000 nm.

  By the way, when the length of the columnar particles of the second piezoelectric film is smaller than 2500 nm, an electric field applied to the piezoelectric laminated film when a voltage is applied between the first and second electrode films is increased, so that cracks are not generated. It is more likely to occur.

  Here, according to the present invention, since the length of the columnar particles of the second piezoelectric film is 2500 nm or more, occurrence of cracks can be prevented.

  The first and second piezoelectric films contain at least Pb, Zr, and Ti, the chemical composition ratio is represented by Pb: Zr: Ti = (1 + a): b: 1-b, and the first and second The value of b of the piezoelectric film is the same value of 0.50 to 0.60, the value of a of the first piezoelectric film is −0.05 to 0.05, and the second The value a of the piezoelectric film is preferably 0 or more and 0.1 or less.

  Thereby, the moisture resistance of a piezoelectric element can be improved reliably.

  The first and second piezoelectric films are preferably preferentially oriented in the (001) plane.

  The first electrode film includes at least one noble metal selected from Pt, Ir, Pd and Ru, or the noble metal and Ti, Co, Ni, Al, Fe, Mn, Cu, Mg, Ca, Sr and Ba. It is preferably an aggregate of columnar particles made of an alloy with at least one selected metal or oxide thereof and having an average cross-sectional diameter of 20 nm to 30 nm.

  As a result, the first electrode film can activate the function of the first piezoelectric film as the orientation control film, so that the first piezoelectric film can reliably control the crystal orientation of the second piezoelectric film.

  The alignment control film is preferably made of lead lanthanum titanate.

  As a result, the piezoelectric laminated film can be reliably oriented in the (001) plane.

The ink jet head of the present invention is provided such that a head main body portion in which a nozzle and a pressure chamber communicating with the nozzle and containing ink are formed, and a part of a surface on one side in the thickness direction face the pressure chamber. And a piezoelectric element that is formed on the other surface in the thickness direction of the diaphragm film and applies pressure to the ink in the pressure chamber to eject the ink from the nozzle. The piezoelectric element is characterized by comprising any one of the piezoelectric elements of the present invention.

The ink jet recording apparatus of the present invention is an ink jet recording apparatus provided with an ink jet head and a moving means for relatively moving the ink jet head and the recording medium. The ink jet head is composed of the ink jet head of the present invention. It is characterized by this.

  The piezoelectric element of the present invention can also be applied to devices other than ink jet heads and ink jet recording apparatuses, such as electronic components such as gyro elements and acceleration sensors.

  According to the present invention, since a piezoelectric element does not deteriorate even when a voltage is applied to the piezoelectric element in a high-temperature and high-humidity atmosphere, the piezoelectric element is low in cost, has high piezoelectric characteristics, and has high moisture resistance. An ink jet head and an ink jet recording apparatus can be provided. In addition, a piezoelectric element with low cost, high piezoelectric characteristics, and high moisture resistance can be easily manufactured. Furthermore, it is possible to provide an ink jet head having a small variation in ink discharge capability and high reliability, and an ink jet recording apparatus including the ink jet head.

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

(Embodiment 1)
As shown in FIG. 1, a piezoelectric element (piezoelectric element) 20 according to an embodiment of the present invention includes a strip-like substrate 1 (thickness 0.3 mm, width 3.0 mm, length 15.0 mm), And a laminated body 11 formed on the substrate 1. The width of the piezoelectric element 20 is 3.0 mm. One end portion (left end portion in FIG. 1) of the piezoelectric element 20 is fixed on a stainless support substrate 6 (thickness 1.0 mm, width 3.0 mm, length 10.0 mm) via an epoxy adhesive 7. Yes. This one end portion is a portion having a length up to 3.0 mm from one end (left end in FIG. 1) of the piezoelectric element 20. The longitudinal direction of the piezoelectric element 20 and the longitudinal direction of the stainless steel support substrate 6 are almost orthogonal. From the above, the piezoelectric element 20 forms a cantilever.

  The substrate 1 also serves as a diaphragm film (diaphragm layer) that inhibits the expansion and contraction of the multilayer body 11 due to the piezoelectric effect. The stacked body 11 includes a first electrode film 2 formed on the substrate 1, a piezoelectric stacked film 10 formed on the first electrode film 2, and a second formed on the piezoelectric stacked film 10. And an electrode film 5.

  The first electrode film 2 is provided on the entire surface on one side in the thickness direction of the substrate 1. The piezoelectric laminated film 10 is provided on a portion other than the one end portion of the first electrode film 2. That is, the piezoelectric laminated film 10 has a width of 3.0 mm and a length of 12.0 mm. The piezoelectric laminated film 10 is made of a lead oxide zirconate titanate oxide (hereinafter referred to as a PZT oxide) having a perovskite crystal structure with a (001) preferential crystal orientation. The PZT-based oxide is an oxide containing at least Pb, Zr and Ti. Specifically, the piezoelectric laminated film 10 includes a first piezoelectric thin film 3 formed on the first electrode film 2 and a second piezoelectric thin film 4 formed on the first piezoelectric thin film 3. It is configured. The first piezoelectric thin film 3 functions as an orientation control film that controls the crystal orientation of the second piezoelectric thin film 4.

  The second electrode film 5 is made of platinum having a thickness of 100 nm. Gold lead wires 8 and 9 are connected to the first and second electrode films 2 and 5, respectively.

  As a feature of the present invention, the first and second piezoelectric thin films 3 and 4 have a crystal growth direction from one direction side to the other side in the thickness direction of the piezoelectric laminated film 10 (first and second piezoelectric thin films 3 and 4). It is an aggregate of columnar particles that face (see FIG. 3). In other words, the first and second piezoelectric thin films 3 and 4 are aggregates of columnar particles grown in a direction perpendicular to the surface on one side in the thickness direction of the substrate 1 (first electrode film 2). The columnar particles of the first and second piezoelectric thin films 3 and 4 are continuously connected. The Pb content of the first piezoelectric thin film 3 is smaller than the Pb content of the second piezoelectric thin film 4. The average cross-sectional diameter (particle diameter) of the columnar particles of the second piezoelectric thin film 4 is larger than the average cross-sectional diameter (particle diameter) of the columnar particles of the first piezoelectric thin film 3. The ratio of the thickness of the piezoelectric laminate film 10 (the length of the columnar particles of the piezoelectric laminate film 10) to the average cross-sectional diameter (particle diameter) of the columnar particles of the second piezoelectric thin film 4 is 20 or more and 60 or less. Here, when the ratio of the thickness of the piezoelectric multilayer film 10 to the average cross-sectional diameter of the columnar particles of the second piezoelectric thin film 4 is less than 20, a crack occurs in the piezoelectric multilayer film 10 due to stress generated during the film formation, On the other hand, if the ratio exceeds 60, the power consumption during driving increases and the responsiveness decreases, which is not desirable in either case.

  The columnar particles of the first piezoelectric thin film 3 have an average cross-sectional diameter (particle diameter) of 40 nm to 70 nm and a length of 5 nm to 100 nm. The columnar particles of the second piezoelectric thin film 4 have an average cross-sectional diameter (particle diameter) of 60 nm to 200 nm and a length of 2500 nm to 5000 nm.

  The chemical composition ratio of the first and second piezoelectric thin films 3 and 4 is represented by Pb: Zr: Ti = (1 + a): b: 1−b. The value of b of the first and second piezoelectric thin films 3 and 4 is the same value between 0.50 and 0.60. The value of a of the first piezoelectric thin film 3 is −0.05 or more and 0.05 or less. The value of a of the second piezoelectric thin film 4 is 0 or more and 0.10 or less.

  The first electrode film 2 is made of at least one kind of noble metal selected from Pt, Ir, Pd and Ru, or the noble metal and Ti, Co, Ni, Al, Fe, Mn, Cu, Mg, Ca, Sr and Ba. Is an aggregate of columnar particles having an average cross-sectional diameter of 20 nm or more and 30 nm or less.

Here, when a voltage is applied between the first and second electrode films 2 and 5 of the piezoelectric element 20 via the lead wires 8 and 9, the piezoelectric laminated film 10 extends in the X-axis direction. Here, the applied voltage is E (V), the length of the piezoelectric laminate film 10 is L (m), the thickness of the piezoelectric laminate film 10 is t (m), and the piezoelectric constant of the piezoelectric laminate film 10 is d _31. Assuming that (pm / V), the amount of change ΔL (m) in the X-axis direction of the piezoelectric laminated film 10 can be obtained by the following equation (1).
ΔL = d ₃₁ × L × E / t (1)

  The upper portion of the piezoelectric laminate film 10 bonded to the second electrode film 5 extends in the X-axis direction, while the lower portion of the piezoelectric laminate film 10 bonded to the first electrode film 2 has a thickness. Elongation is suppressed by the large substrate 1. As a result, the other end of the piezoelectric element 20 opposite to the one end (the right end in FIG. 1; hereinafter referred to as the tip) is displaced in the −Z direction of the Z axis (the lower side in FIG. 1). Therefore, when voltage application is repeated at a constant period, the tip of the piezoelectric element 20 is displaced in the Z-axis direction by a predetermined displacement amount. The displacement characteristics of the piezoelectric element 20 can be evaluated by examining the relationship between the applied voltage and the magnitude of the displacement amount at the tip of the piezoelectric element 20.

-Piezoelectric element manufacturing method-
Hereinafter, the manufacturing method of the piezoelectric element 20 will be described with reference to FIG. First, as shown in FIG. 2A, a rectangular opening having a width of 5.0 mm and a length of 18.0 mm was formed on the surface of a substrate 101 having a length of 20 mm, a width of 20 mm, and a thickness of 0.3 mm. The first electrode film 102 is formed by RF magnetron sputtering using a stainless mask (thickness 0.2 mm).

  Next, using a stainless steel mask (thickness: 0.2 mm) in which a rectangular opening having a width of 5.0 mm and a length of 12.0 mm is formed on the surface of the first electrode film 102, a piezoelectric laminated film 110 is accurately formed by RF magnetron sputtering. Specifically, the piezoelectric laminated film 110 is produced as follows. First, a first piezoelectric thin film 103 is formed on the first electrode film 102 by RF magnetron sputtering using a sintered body of PZT oxide as a predetermined target and under predetermined film forming conditions. Then, the RF magnetron sputtering method is used in the RF magnetron sputtering method using the same predetermined target as that for forming the first piezoelectric thin film 103 and under a film forming condition different from the predetermined film forming condition for forming the first piezoelectric thin film 103. A second piezoelectric thin film 104 is continuously formed on the piezoelectric thin film 103.

  Next, the second electrode film 105 is formed on the surface of the piezoelectric multilayer film 110 by the RF magnetron sputtering method using the same mask as described above. As a result, as shown in FIG. 2B, a structure body 121 including a substrate 101 and a stacked body 111 formed on the substrate 101 and including the piezoelectric stacked film 110 can be obtained.

  Next, as shown in FIG. 2C, the substrate 1 has a strip shape having a width of 3.0 mm and a length of 15.0 mm, and from one end of the first electrode film 2 (the left end in FIG. 2C). The structure 121 is cut with a dicing saw so that a portion up to a length of 3.0 mm is exposed. As a result, a piezoelectric element structure component 22 in which the substrate 1, the first electrode film 2, the first piezoelectric thin film 3, the second piezoelectric thin film 4, and the second electrode film 5 are laminated in that order can be obtained.

  Next, as shown in FIG. 2 (d), the exposed portion (the left end portion in FIG. 2 (d)) side of the first electrode film 2 on the substrate 1 is replaced with the epoxy adhesive 7 on the stainless steel support substrate 6. Use to join.

  Next, as shown in FIG. 2E, the lead wire 8 is connected to the exposed portion of the first electrode film 2 using a conductive adhesive (silver paste), and the first electrode in the second electrode film 5 is connected. By connecting the lead wire 9 to the exposed portion side portion of the film 2 by wire bonding, the piezoelectric element 20 shown in FIG. 1 can be obtained. FIG. 3 is a schematic diagram showing the film structure of the piezoelectric element 20.

  Hereinafter, specific examples will be described.

Example 1
In this example, a silicon substrate was used as the substrate 101, and a Pt thin film with a thickness of 100 nm was used as the first electrode film 102. This Pt thin film was formed by a ternary RF magnetron sputtering apparatus. Specifically, the silicon substrate 101 was heated to 400 ° C. and kept at that temperature. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 15/1) was used as the sputtering gas, and the total gas pressure was kept at 0.25 Pa. A target made of Pt was used as the first target of the ternary RF magnetron sputtering apparatus. Then, a Pt thin film was formed by applying high-frequency power of 200 W and sputtering for 1200 seconds.

  The film thickness of the piezoelectric laminate film 110 was 3100 nm. A piezoelectric laminated film 110 was formed on a first piezoelectric thin film 103 having a thickness of 100 nm made of lead zirconate titanate (hereinafter referred to as PZT) having a (001) preferential orientation, and the first piezoelectric thin film 103. (001) A second piezoelectric thin film 104 having a thickness of 3000 nm made of PZT having a preferential orientation.

The first and second piezoelectric thin films 103 and 104 were produced using an RF magnetron sputtering apparatus (see FIG. 2B). At this time, a 6-inch diameter sintered compact of lead zirconate titanate (PZT) having a stoichiometric composition prepared by adding about 20 mol% PbO in excess (composition molar ratio Pb: Zr: Ti = 1.20). : 0.53: 0.47) was used as the target. The film forming conditions were as shown below. That is, the silicon substrate 101 having the first electrode film 102 formed on one surface was heated to 580 ° C. and kept at that temperature in the film formation chamber to which the target was attached. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 79/1) was used as the sputtering gas, the gas pressure was 0.2 Pa, and the gas flow rate was 40 ml per minute. Then, the plasma generation power was set to 3 kW, and the first piezoelectric thin film 103 was formed for 50 seconds. Thereafter, the film formation is temporarily stopped, and only the gas volume ratio of the sputtering gas is changed to Ar / O ₂ = 38/2 among the above film formation conditions, and the other film formation conditions are not changed, and the second piezoelectric thin film is not changed. 104 was deposited for 3000 seconds.

  Here, in order to accurately obtain the composition, film thickness, and cross-sectional structure of the first piezoelectric thin film 103 shown in FIG. Produced. The surface of this sample was observed with a scanning electron microscope, and composition analysis was performed using an X-ray microanalyzer. Thereafter, the sample was broken, and the broken surface was observed with a scanning electron microscope.

  In addition, in order to accurately obtain the composition, film thickness, and cross-sectional structure of the second piezoelectric film 104 shown in FIG. 2B, a laminated film was formed in which the film formation was stopped after the second piezoelectric film 104 was formed. . The surface of this sample was observed with a scanning electron microscope, and composition analysis was performed using an X-ray microanalyzer. Thereafter, the sample was broken, and the broken surface was observed with a scanning electron microscope.

  Further, using the structure 121 shown in FIG. 2B as a sample, composition analysis in the thickness direction of the piezoelectric multilayer film 110 was performed by Auger spectroscopic analysis. Furthermore, the fracture surface of the piezoelectric laminated film 110 was observed with a scanning electron microscope.

  As a result of the above analysis and observation, it was found that the Pt electrode as the first electrode film 102 is an aggregate of columnar particles (columnar crystals) having an average particle diameter (average diameter) of 20 nm. The first and second piezoelectric thin films 103 and 104 existed as an aggregate of columnar structured particles that were continuously connected to each other. The first piezoelectric thin film 103 had a thickness of 100 nm, and the average particle diameter (average diameter) of the columnar particles was 40 nm. The second piezoelectric thin film 104 had a thickness of 3000 nm, and the average particle diameter (average diameter) of the columnar particles was 100 nm. The ratio of the thickness of the piezoelectric multilayer film 110 to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film 104 was 31.

Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films 103 and 104 have a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film 103 was 55%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film 104 was 75%. Here, the (001) crystal orientation ratio α is defined by the following formula (2).
α = I (001) / ΣI (hkl) (2)
Σ (hkl) is the sum of the total diffraction intensities of the perovskite oxide when 2θ is 10 ° to 70 ° when using Cu-Kα rays in the X-ray diffraction method.

  The composition of the first piezoelectric thin film 103 is Pb: Zr: Ti = 0.95: 0.53: 0.47 as a result of the composition analysis of the cations by the X-ray microanalyzer. The second piezoelectric thin film The composition of 104 was Pb: Zr: Ti = 1.00: 0.53: 0.47. That is, the first and second piezoelectric thin films 103 and 104 are PZT films having a perovskite crystal structure, with the (001) axis preferentially grown in a direction perpendicular to the upper surface of the substrate 101. The composition of Ti was the same in the first and second piezoelectric thin films 103 and 104, and the composition of Pb was found to be less in the first piezoelectric thin film 103 than in the second piezoelectric thin film 104.

  Further, a triangular wave voltage of 0 V to −50 V is applied between the first and second electrode films 2 and 5 via the lead wires 8 and 9, and the displacement amount in the Z-axis direction of the tip of the piezoelectric element 20 is laser Doppler oscillated. It measured using the displacement measuring device. FIG. 4 shows the amount of displacement in the Z-axis direction of the tip of the piezoelectric element 20 when a triangular wave voltage with a frequency of 2 kHz is applied. As a result of the measurement, it was found that the tip of the piezoelectric element 20 was displaced by a maximum of 19.0 μm.

  Further, after driving the piezoelectric element 20 continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) by this triangular wave voltage, the driving state of the piezoelectric element 20 is examined and the appearance of the piezoelectric element 20 is observed by an optical microscope. I investigated. As a result, even after the piezoelectric element 20 is continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the maximum displacement is 19.0 μm, and no decrease in the displacement is observed. There was no discoloration.

(Example 2)
In this example, a silicon substrate was used as the substrate 101, and an Ir—Ti alloy thin film having a thickness of 120 nm was used as the first electrode film 102. This Ir-Ti film was formed by a ternary RF magnetron sputtering apparatus. Specifically, the silicon substrate 101 was heated to 400 ° C. and kept at that temperature. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 15/1) was used as the sputtering gas, and the total gas pressure was kept at 0.25 Pa. A target made of Ir was used as the first target of the ternary RF magnetron sputtering apparatus, and a target made of titanium was used as the second target. Then, Ir-Ti alloy thin films were formed by applying high-frequency power of 200 W and 60 W to the first and second targets, respectively, and performing sputtering for 1200 seconds.

  The film thickness of the piezoelectric laminated film 110 was 2550 nm. The piezoelectric laminated film 110 is formed of a first piezoelectric thin film 103 having a thickness of 50 nm made of (001) preferentially oriented PZT, and a thickness made of (001) preferentially oriented PZT formed on the first piezoelectric thin film 103. And a second piezoelectric thin film 104 having a thickness of 2500 nm.

The first and second piezoelectric thin films 103 and 104 were produced using an RF magnetron sputtering apparatus (see FIG. 2B). At this time, a 6-inch diameter sintered compact of lead zirconate titanate (PZT) having a stoichiometric composition prepared by adding about 20 mol% PbO in excess (composition molar ratio Pb: Zr: Ti = 1.20). : 0.50: 0.50) was used as the target. The film forming conditions were as shown below. That is, the silicon substrate 101 having the first electrode film 102 formed on one surface was heated to 580 ° C. and kept at that temperature in the film formation chamber to which the target was attached. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 79/1) was used as the sputtering gas, the gas pressure was 0.2 Pa, and the gas flow rate was 40 ml per minute. Then, the plasma generation power was set to 3 kW, and the first piezoelectric thin film 103 was formed for 40 seconds. Thereafter, the film formation is temporarily stopped, and only the gas volume ratio of the sputtering gas is changed to Ar / O ₂ = 38/2 among the above film formation conditions, and the other film formation conditions are not changed, and the second piezoelectric thin film is not changed. 104 was deposited for 2400 seconds.

  As a result of the same analysis and observation as in Example 1, the Ir-Ti electrode as the first electrode film 102 is an Ir thin film containing titanium having a composition of 3%, and columnar particles having an average particle diameter (average diameter) of 30 nm. It was found to be an aggregate of (columnar crystals). The first and second piezoelectric thin films 103 and 104 existed as an aggregate of columnar structured particles that were continuously connected to each other. The first piezoelectric thin film 103 had a thickness of 50 nm, and the average particle diameter (average diameter) of the columnar particles was 40 nm. The second piezoelectric thin film 104 had a thickness of 2500 nm, and the average particle diameter (average diameter) of the columnar particles was 80 nm. The ratio of the thickness of the piezoelectric multilayer film 110 to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film 104 was 31.9.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films 103 and 104 have a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film 103 was 60%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film 104 was 80%.

  The composition of the first piezoelectric thin film 103 is Pb: Zr: Ti = 1.00: 0.50: 0.50 as a result of the cation composition analysis by the X-ray microanalyzer, and the second piezoelectric thin film The composition of 104 was Pb: Zr: Ti = 1.10: 0.50: 0.50. That is, the first and second piezoelectric thin films 103 and 104 are PZT films having a perovskite crystal structure, with the (001) axis preferentially grown in a direction perpendicular to the upper surface of the substrate 101. The composition of Ti was the same in the first and second piezoelectric thin films 103 and 104, and the composition of Pb was found to be less in the first piezoelectric thin film 103 than in the second piezoelectric thin film 104.

  Similarly to the first embodiment, a triangular wave voltage of 0 V to −50 V is applied between the first and second electrode films 2 and 5 via the lead wires 8 and 9, and the Z-axis direction of the tip of the piezoelectric element 20 is applied. The amount of displacement of was measured using a laser Doppler vibration displacement measuring device. As a result of the measurement, it was found that the tip of the piezoelectric element 20 was displaced by a maximum of 23.9 μm.

  Further, after driving the piezoelectric element 20 continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) by this triangular wave voltage, the driving state of the piezoelectric element 20 is examined and the appearance of the piezoelectric element 20 is observed by an optical microscope. I investigated. As a result, even after the piezoelectric element 20 is continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the displacement amount is 23.9 μm at the maximum, and the displacement amount is not reduced. There was no discoloration.

(Example 3)
In this example, a silicon substrate was used as the substrate 101, and a Pd thin film with a thickness of 150 nm was used as the first electrode film 102. This Pd film was formed by a ternary RF magnetron sputtering apparatus. Specifically, the silicon substrate 101 was heated to 400 ° C. and kept at that temperature. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 15/1) was used as the sputtering gas, and the total gas pressure was kept at 0.25 Pa. A target made of Pd was used as the first target of the ternary RF magnetron sputtering apparatus. Then, a Pd thin film was formed as the first electrode film 102 by applying high-frequency power of 200 W to the first target and performing sputtering for 1200 seconds.

  The film thickness of the piezoelectric laminate film 110 was 3100 nm. The piezoelectric multilayer film 110 is formed of a first piezoelectric thin film 103 having a thickness of 100 nm made of (001) preferentially oriented PZT, and a thickness made of (001) preferentially oriented PZT formed on the first piezoelectric thin film 103. And a second piezoelectric thin film 104 having a thickness of 3000 nm.

The first and second piezoelectric thin films 103 and 104 were produced using an RF magnetron sputtering apparatus (see FIG. 2B). At this time, a 6-inch-diameter sintered body of a lead zirconate titanate (PZT) having a stoichiometric composition prepared by adding about 20 mol% PbO in excess (composition molar ratio Pb: Zr: Ti = 1.20). : 0.60: 0.40) was used as the target. The film forming conditions were as shown below. That is, the silicon substrate 101 having the first electrode film 102 formed on one surface thereof was heated to 580 ° C. and kept at that temperature in the deposition chamber in which the target was attached. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 79/1) was used as the sputtering gas, the gas pressure was 0.2 Pa, and the gas flow rate was 40 ml per minute. Then, the plasma generation power was set to 3 kW, and the first piezoelectric thin film 103 was formed for 50 seconds. Thereafter, the film formation is temporarily stopped, and only the gas volume ratio of the sputtering gas among the above film formation conditions is changed to Ar / O ₂ = 38/2, and other film formation conditions are not changed. 104 was deposited for 2800 seconds.

  As a result of the same analysis and observation as in Example 1, it was found that the Pd electrode as the first electrode film 102 was an aggregate of columnar particles (columnar crystals) having an average particle diameter (average diameter) of 20 nm. The first and second piezoelectric thin films 103 and 104 existed as an aggregate of columnar structured particles that were continuously connected to each other. The first piezoelectric thin film 103 had a thickness of 100 nm, and the average particle diameter (average diameter) of the columnar particles was 70 nm. The second piezoelectric thin film 104 had a thickness of 3000 nm, and the average particle diameter (average diameter) of the columnar particles was 150 nm. The ratio of the thickness of the piezoelectric multilayer film 110 to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film 104 was 20.7.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films 103 and 104 have a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film 103 was 50%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film 104 was 75%.

  The composition of the first piezoelectric thin film 103 is Pb: Zr: Ti = 1.05: 0.60: 0.40 as a result of the cation composition analysis by the X-ray microanalyzer. The composition of 104 was Pb: Zr: Ti = 1.10: 0.60: 0.40. In other words, the first and second piezoelectric thin films 103 and 104 are PZT films having a perovskite crystal structure grown with a (001) axis preferentially oriented in a direction perpendicular to the upper surface of the substrate 1. The composition of Ti was the same in the first and second piezoelectric thin films 103 and 104, and the composition of Pb was found to be less in the first piezoelectric thin film 103 than in the second piezoelectric thin film 104.

  Similarly to the first embodiment, a triangular wave voltage of 0 V to −50 V is applied between the first and second electrode films 2 and 5 via the lead wires 8 and 9, and the Z-axis direction of the tip of the piezoelectric element 20 is applied. The amount of displacement of was measured using a laser Doppler vibration displacement measuring device. As a result of the measurement, it was found that the tip of the piezoelectric element 20 was displaced by a maximum of 20.2 μm.

  Further, after driving the piezoelectric element 20 continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) by this triangular wave voltage, the driving state of the piezoelectric element 20 is examined and the appearance of the piezoelectric element 20 is observed by an optical microscope. I investigated. As a result, even after the piezoelectric element 20 is continuously driven for 120 hours in a high-temperature and high-humidity atmosphere, the displacement is a maximum of 20.2 μm, and no decrease in the displacement is observed. There was no discoloration.

(Example 4)
In this embodiment, a silicon substrate is used as the substrate 101, and a Ru thin film having a thickness of 110 nm is used as the first electrode film 102. This Ru film was formed by a ternary RF magnetron sputtering apparatus. Specifically, the silicon substrate 101 was heated to 400 ° C. and kept at that temperature. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 15/1) was used as the sputtering gas, and the total gas pressure was kept at 0.25 Pa. A Ru target was used as the first target of the ternary RF magnetron sputtering apparatus. Then, a Ru thin film was formed by applying high-frequency power of 200 W to the first target and performing sputtering for 1200 seconds.

  The film thickness of the piezoelectric laminated film 110 was 4505 nm. A piezoelectric multilayer film 110 is formed of a first piezoelectric thin film 103 having a thickness of 5 nm made of (001) preferentially oriented PZT and a thickness made of (001) preferentially oriented PZT formed on the first piezoelectric thin film 103. And a second piezoelectric thin film 104 having a thickness of 4500 nm.

The first and second piezoelectric thin films 103 and 104 were produced using an RF magnetron sputtering apparatus (see FIG. 2B). At this time, a 6-inch diameter sintered compact of lead zirconate titanate (PZT) having a stoichiometric composition prepared by adding about 20 mol% PbO in excess (composition molar ratio Pb: Zr: Ti = 1.20). : 0.53: 0.47) was used as the target. The film forming conditions were as shown below. That is, the silicon substrate 101 having the first electrode film 102 formed on one surface was heated to 580 ° C. and kept at that temperature in the film formation chamber to which the target was attached. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 79/1) was used as the sputtering gas, the gas pressure was 0.2 Pa, and the gas flow rate was 40 ml per minute. Then, the plasma generation power was set to 3 kW, and the first piezoelectric thin film 103 was formed for 10 seconds. Thereafter, the film formation is temporarily stopped, and only the gas volume ratio of the sputtering gas is changed to Ar / O ₂ = 38/2 among the above film formation conditions, and the other film formation conditions are not changed, and the second piezoelectric thin film is not changed. 104 was deposited for 3600 seconds.

  As a result of the same analysis and observation as in Example 1, it was found that the Ru electrode as the first electrode film 102 was an aggregate of columnar particles (columnar crystals) having an average particle diameter (average diameter) of 25 nm. The first and second piezoelectric thin films 103 and 104 existed as an aggregate of columnar structured particles that were continuously connected to each other. The first piezoelectric thin film 103 had a thickness of 5 nm, and the average particle diameter (average diameter) of the columnar particles was 50 nm. The second piezoelectric thin film 104 had a thickness of 4500 nm, and the average particle diameter (average diameter) of the columnar particles was 150 nm. The ratio of the thickness of the piezoelectric laminated film 110 to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film 104 was 30.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films 103 and 104 have a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film 103 was 60%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film 104 was 85%.

  The composition of the first piezoelectric thin film 103 is Pb: Zr: Ti = 0.95: 0.53: 0.47 as a result of the composition analysis of the cations by the X-ray microanalyzer. The second piezoelectric thin film The composition of 104 was Pb: Zr: Ti = 1.10: 0.53: 0.47. That is, the first and second piezoelectric thin films 103 and 104 are PZT films having a perovskite crystal structure, with the (001) axis preferentially grown in a direction perpendicular to the upper surface of the substrate 101. The composition of Ti was the same in the first and second piezoelectric thin films 103 and 104, and the composition of Pb was found to be less in the first piezoelectric thin film 103 than in the second piezoelectric thin film 104.

  Similarly to the first embodiment, a triangular wave voltage of 0 V to −50 V is applied between the first and second electrode films 2 and 5 via the lead wires 8 and 9, and the Z-axis direction of the tip of the piezoelectric element 20 is applied. The amount of displacement of was measured using a laser Doppler vibration displacement measuring device. As a result of the measurement, it was found that the tip of the piezoelectric element 20 was displaced by a maximum of 18.8 μm.

  Further, after driving the piezoelectric element 20 continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) by this triangular wave voltage, the driving state of the piezoelectric element 20 is examined and the appearance of the piezoelectric element 20 is observed by an optical microscope. I investigated. As a result, even after the piezoelectric element 20 is continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the maximum displacement is 18.8 μm, and no decrease in the displacement is observed. There was no discoloration.

(Example 5)
In this example, a silicon substrate was used as the substrate 101, and an Ir—Co alloy thin film having a thickness of 130 nm was used as the first electrode film 102. This Ir—Co film was formed by a ternary RF magnetron sputtering apparatus. Specifically, the silicon substrate 101 was heated to 400 ° C. and kept at that temperature. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 15/1) was used as the sputtering gas, and the total gas pressure was kept at 0.25 Pa. A target made of Ir was used as the first target of the ternary RF magnetron sputtering apparatus, and a target made of Co was used as the second target. Then, Ir-Co alloy thin film as the first electrode film 102 was formed by applying high-frequency power of 200 W and 60 W to the first and second targets and sputtering for 1200 seconds.

  The film thickness of the piezoelectric laminate film 110 was set to 3030 nm. The piezoelectric laminated film 110 is formed of a first piezoelectric thin film 103 having a thickness of 30 nm made of (001) preferentially oriented PZT, and a thickness made of (001) preferentially oriented PZT formed on the first piezoelectric thin film 103. And a second piezoelectric thin film 104 having a thickness of 3000 nm.

The first and second piezoelectric thin films 103 and 104 were produced using an RF magnetron sputtering apparatus (see FIG. 2B). At this time, a 6-inch diameter sintered compact of lead zirconate titanate (PZT) having a stoichiometric composition prepared by adding about 20 mol% PbO in excess (composition molar ratio Pb: Zr: Ti = 1.20). : 0.50: 0.50) was used as the target. The film forming conditions were as shown below. That is, in the film formation chamber to which the target was attached, the silicon substrate 101 having the first electrode film 102 formed on one surface was preheated to 580 ° C. and kept at that temperature. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 79/1) was used as the sputtering gas, the gas pressure was 0.2 Pa, and the gas flow rate was 40 ml per minute. The plasma generation power was 3 kW, and the first piezoelectric thin film 103 was formed for 30 seconds. Thereafter, the film formation is temporarily stopped, and only the gas volume ratio of the sputtering gas is changed to Ar / O ₂ = 38/2 among the above film formation conditions, and the other film formation conditions are not changed, and the second piezoelectric thin film is not changed. 104 was deposited for 3000 seconds.

  As a result of the same analysis and observation as in Example 1, the Ir—Co electrode as the first electrode film 102 is an Ir thin film containing Co having a composition of 4%, and columnar particles having an average particle diameter (average diameter) of 20 nm. It was found to be an aggregate of (columnar crystals). The first and second piezoelectric thin films 103 and 104 existed as an aggregate of columnar structured particles that were continuously connected to each other. The first piezoelectric thin film 103 had a film thickness of 30 nm, and the average particle diameter (average diameter) of the columnar particles was 40 nm. The second piezoelectric thin film 104 had a thickness of 3000 nm, and the average particle diameter (average diameter) of the columnar particles was 60 nm. The ratio of the thickness of the piezoelectric multilayer film 110 to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film 104 was 50.5.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films 103 and 104 have a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film 103 was 65%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film 104 was 80%.

  The composition of the first piezoelectric thin film 103 is Pb: Zr: Ti = 1.00: 0.50: 0.50 as a result of the cation composition analysis by the X-ray microanalyzer, and the second piezoelectric thin film The composition of 104 was Pb: Zr: Ti = 1.10: 0.50: 0.50. That is, the first and second piezoelectric thin films 103 and 104 are PZT films having a perovskite crystal structure, with the (001) axis preferentially grown in a direction perpendicular to the upper surface of the substrate 101. The composition of Ti was the same in the first and second piezoelectric thin films 103 and 104, and the composition of Pb was found to be less in the first piezoelectric thin film 103 than in the second piezoelectric thin film 104.

  Similarly to the first embodiment, a triangular wave voltage of 0 V to −50 V is applied between the first and second electrode films 2 and 5 via the lead wires 8 and 9, and the Z-axis direction of the tip of the piezoelectric element 20 is applied. The amount of displacement of was measured using a laser Doppler vibration displacement measuring device. As a result of the measurement, it was found that the tip of the piezoelectric element 20 was displaced by a maximum of 26.7 μm.

  Further, after driving the piezoelectric element 20 continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) by this triangular wave voltage, the driving state of the piezoelectric element 20 is examined and the appearance of the piezoelectric element 20 is observed by an optical microscope. I investigated. As a result, even after the piezoelectric element 20 is continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the displacement is a maximum of 26.7 μm, and no decrease in the displacement is observed. There was no discoloration.

(Comparative Example 1)
In order to compare with the piezoelectric element of each of the above examples, the following piezoelectric element of Comparative Example 1 was produced. That is, unlike the first example, the comparative example has a Pb composition of the piezoelectric laminated film that is greater in the first piezoelectric thin film than in the second piezoelectric thin film. The method for forming the piezoelectric laminated film is the same as that in the first embodiment, and the film forming conditions are different from those in the first embodiment. The other points are exactly the same as in the first embodiment.

  As a result of the same analysis and observation as in Example 1, the first and second piezoelectric thin films of this comparative example existed as an aggregate of columnar particles that were continuously connected to each other. The first piezoelectric thin film had a thickness of 100 nm, and the average particle diameter (average diameter) of the columnar particles was 60 nm. The second piezoelectric thin film had a thickness of 3000 nm, and the average particle diameter (average diameter) of the columnar particles was 180 nm. The ratio of the thickness of the piezoelectric laminated film to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film was 17.2.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films had a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film was 70%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film was 88%.

  Further, as a result of the composition analysis of the cation by the X-ray microanalyzer, the composition of the first piezoelectric thin film is Pb: Zr: Ti = 1.15: 0.53: 0.47, The composition was Pb: Zr: Ti = 1.10: 0.53: 0.47. In other words, the first and second piezoelectric thin films are PZT films having a perovskite crystal structure with a (001) axis preferentially grown in a direction perpendicular to the upper surface of the substrate, and the compositions of Zr and Ti are It was found that the first and second piezoelectric thin films were the same, and the composition of Pb was greater in the first piezoelectric thin film than in the second piezoelectric thin film.

  Further, when a triangular wave voltage of 0 V to −50 V was applied to this piezoelectric element in the same manner as in Example 1, it was found that the tip of the piezoelectric element was displaced by a maximum of 22.3 μm.

  Moreover, after driving the piezoelectric element continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) with this triangular wave voltage, the driving state of the piezoelectric element was examined and the appearance of the piezoelectric element was examined with an optical microscope. . As a result, after the piezoelectric element was continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the amount of displacement decreased (0 μm), and the first electrode film turned black. That is, the piezoelectric element was deteriorated.

(Comparative Example 2)
In order to compare with the piezoelectric elements of the above examples, the following piezoelectric element of Comparative Example 2 was produced. That is, unlike the second example, the comparative example has a higher Pb composition in the piezoelectric laminated film in the first piezoelectric thin film than in the second piezoelectric thin film. The method for forming the piezoelectric laminated film is the same as that in Example 2, and the film forming conditions are different from those in Example 2. The other points are exactly the same as in the second embodiment.

  As a result of the same analysis and observation as in Example 1, the first and second piezoelectric thin films of this comparative example existed as an aggregate of columnar particles that were continuously connected to each other. The first piezoelectric thin film had a thickness of 50 nm, and the average particle diameter (average diameter) of the columnar particles was 70 nm. The second piezoelectric thin film had a thickness of 2500 nm, and the average particle diameter (average diameter) of the columnar particles was 140 nm. The ratio of the thickness of the piezoelectric laminated film to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film was 18.2.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films had a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film was 65%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film was 85%.

  In addition, as a result of the composition analysis of the cation by the X-ray microanalyzer, the composition of the first piezoelectric thin film is Pb: Zr: Ti = 1.10: 0.50: 0.50, The composition was Pb: Zr: Ti = 1.05: 0.50: 0.50. In other words, the first and second piezoelectric thin films are PZT films having a perovskite crystal structure with a (001) axis preferentially grown in a direction perpendicular to the upper surface of the substrate, and the compositions of Zr and Ti are It was found that the first and second piezoelectric thin films were the same, and the composition of Pb was greater in the first piezoelectric thin film than in the second piezoelectric thin film.

  Further, when a triangular wave voltage of 0 V to −50 V was applied to this piezoelectric element as in Example 2, it was found that the tip of the piezoelectric element was displaced up to 18.0 μm.

  Moreover, after driving the piezoelectric element continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) with this triangular wave voltage, the driving state of the piezoelectric element was examined and the appearance of the piezoelectric element was examined with an optical microscope. . As a result, after the piezoelectric element was continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the amount of displacement decreased (0 μm), and the first electrode film turned black. That is, the piezoelectric element was deteriorated.

-Effect-
As described above, according to the present embodiment, since the Pb composition of the first piezoelectric thin film 3 is smaller than the Pb composition of the second piezoelectric thin film 4, the piezoelectric element 20 is heated to high temperature and high humidity (temperature 50 ° C., humidity 50%). Degradation of the piezoelectric element 20 caused by excess Pb of the first piezoelectric thin film 3 reacting with moisture at the interface between the first electrode film 2 and the first piezoelectric thin film 3 even when driven in an atmosphere of Will not occur. Therefore, the piezoelectric element 20 with low cost, high piezoelectric characteristics, and high moisture resistance can be realized.

(Embodiment 2)
As shown in FIG. 5, the piezoelectric element 21 according to this embodiment has an orientation control film 12 disposed between the first electrode film 2 and the first piezoelectric thin film 3. The configuration is substantially the same as that of the piezoelectric element 20 of the first embodiment.

  The piezoelectric element 21 according to the present embodiment has a shape similar to that of the piezoelectric element 20 according to the first embodiment, and is a rectangular plate-like substrate 1 (thickness 0.3 mm, width 3.0 mm, length 15.0 mm) and And a laminated body 11 formed on the substrate 1. The width of the piezoelectric element 21 is 3.0 mm. One end portion (left end portion in FIG. 5) of the piezoelectric element 21 is fixed on a stainless support substrate 6 (thickness 1.0 mm, width 3.0 mm, length 10.0 mm) via an epoxy adhesive 7. Yes. This one end is a portion up to 3.0 mm from one end (left end in FIG. 5) of the piezoelectric element 21. The longitudinal direction of the piezoelectric element 21 and the longitudinal direction of the stainless steel support substrate 6 are almost orthogonal. From the above, the piezoelectric element 21 forms a cantilever.

  The substrate 1 also serves as a diaphragm film (diaphragm layer) that inhibits the expansion and contraction of the multilayer body 11 due to the piezoelectric effect. The laminate 11 includes a first electrode film 2 formed on the substrate 1, an orientation control film 12 formed on the first electrode film 2, and a piezoelectric laminate film formed on the orientation control film 12. 10 and a second electrode film 5 formed on the piezoelectric laminated film 10.

  The first electrode film 2 is provided on the entire surface on one side in the thickness direction of the substrate 1. The orientation control film 12 is provided on a portion other than the one end portion of the first electrode film 2. That is, the alignment control film 12 has a width of 3.0 mm and a length of 12.0 mm. The piezoelectric laminated film 10 is provided on the orientation control film 12. Specifically, the piezoelectric laminated film 10 includes a first piezoelectric thin film 3 formed on the orientation control film 12 and a second piezoelectric thin film 4 formed on the first piezoelectric thin film 3. Has been. The first piezoelectric thin film 3 functions as an orientation control film that controls the crystal orientation of the second piezoelectric thin film 4.

  The second electrode film 5 is made of platinum having a thickness of 100 nm. Gold lead wires 8 and 9 are connected to the first and second electrode films 2 and 5, respectively.

  As a feature of the present invention, the first and second piezoelectric thin films 3 and 4 have a crystal growth direction from one direction side to the other side in the thickness direction of the piezoelectric laminated film 10 (first and second piezoelectric thin films 3 and 4). It is an aggregate of columnar particles that face the surface. The Pb content of the first piezoelectric thin film 3 is smaller than the Pb content of the second piezoelectric thin film 4. The ratio of the thickness of the piezoelectric laminated film to the average cross-sectional diameter of the columnar particles of the second piezoelectric film 4 is 20 or more and 60 or less. Here, when the ratio of the thickness of the piezoelectric multilayer film 10 to the average cross-sectional diameter of the columnar particles of the second piezoelectric film 4 is less than 20, a crack occurs in the piezoelectric multilayer film 10 due to the stress generated during the film formation, On the other hand, if the ratio exceeds 60, the power consumption during driving increases and the responsiveness decreases, which is not desirable in either case.

  The columnar particles of the first piezoelectric thin film 3 have an average cross-sectional diameter (particle diameter) of 40 nm to 70 nm and a length of 5 nm to 100 nm. The columnar particles of the second piezoelectric thin film 4 have an average cross-sectional diameter (particle diameter) of 60 nm to 200 nm and a length of 2500 nm to 5000 nm.

  The chemical composition ratio of the first and second piezoelectric thin films 3 and 4 is represented by Pb: Zr: Ti = (1 + a): b: 1−b. The value of b of the first and second piezoelectric thin films 3 and 4 is the same value between 0.50 and 0.60. The value of a of the first piezoelectric thin film 3 is −0.05 or more and 0.05 or less. The value of a of the second piezoelectric thin film 4 is 0 or more and 0.10 or less.

  The orientation control film 12 is made of lead lanthanum titanate.

  The first electrode film 2 is made of at least one kind of noble metal selected from Pt, Ir, Pd and Ru, or the noble metal and Ti, Co, Ni, Al, Fe, Mn, Cu, Mg, Ca, Sr and Ba. Is an aggregate of columnar particles having an average cross-sectional diameter of 20 nm or more and 30 nm or less.

  Here, as in the first embodiment, when a voltage is applied to the piezoelectric element 21 via the lead wires 8 and 9, the tip of the piezoelectric element 21 is displaced in the -Z direction of the Z axis. Therefore, when voltage application is repeated at a constant period, the tip of the piezoelectric element 21 is displaced by a predetermined displacement amount in the Z-axis direction, and as a result, the displacement characteristics of the piezoelectric element 21 can be evaluated.

-Piezoelectric element manufacturing method-
Hereinafter, a method for manufacturing the piezoelectric element 21 will be described with reference to FIG. First, as shown in FIG. 6A, a rectangular opening having a width of 5.0 mm and a length of 18.0 mm was formed on the surface of a substrate 101 having a length of 20 mm, a width of 20 mm, and a thickness of 0.3 mm. The first electrode film 102 is formed by RF magnetron sputtering using a stainless mask (thickness 0.2 mm).

  Next, using a stainless steel mask (thickness 0.2 mm) in which a rectangular opening having a width of 5.0 mm and a length of 12.0 mm is formed on the surface of the first electrode film 102, lanthanum titanate is used. The alignment control film 112 is formed by RF magnetron sputtering using a lead sintered body as a target and under the first film-forming conditions.

  Next, the piezoelectric laminated film 110 is accurately formed on the orientation control film 112 by the RF magnetron sputtering method using the same mask as described above. Specifically, the piezoelectric laminated film 110 is produced as follows. First, the first piezoelectric thin film 103 is formed on the orientation control film 112 by RF magnetron sputtering using a sintered body of PZT oxide as a target and under a second film forming condition different from the first film forming condition. . Then, the first piezoelectric body is formed by RF magnetron sputtering using the same target as that for forming the first piezoelectric thin film 103 and under a film forming condition different from the second film forming condition for forming the first piezoelectric thin film 103. A second piezoelectric thin film 104 is continuously formed on the thin film 103.

  Next, the second electrode film 105 is formed on the surface of the piezoelectric multilayer film 110 by the RF magnetron sputtering method using the same mask as described above. As a result, as shown in FIG. 6B, a structure body 121 including a substrate 101 and a stacked body 111 formed on the substrate 101 and including the piezoelectric stacked film 110 can be obtained.

  Next, as shown in FIG. 6C, the substrate 1 has a strip shape having a width of 3.0 mm and a length of 15.0 mm, and from one end (the left end in FIG. 6C) of the first electrode film 2. The structure 121 is cut with a dicing saw so that a portion up to a length of 3.0 mm is exposed. As a result, the piezoelectric element structure component 22 in which the substrate 1, the first electrode film 2, the orientation control film 12, the first piezoelectric thin film 3, the second piezoelectric thin film 4, and the second electrode film 5 are laminated in this order is obtained. Obtainable.

  Next, as shown in FIG. 6 (d), the exposed portion (left end portion in FIG. 6 (d)) side of the first electrode film 2 on the substrate 1 is replaced with the epoxy adhesive 7 on the stainless steel supporting substrate 6. Use to join.

  Next, as shown in FIG. 6E, the lead wire 8 is connected to the exposed portion of the first electrode film 2 using a conductive adhesive (silver paste), and the first electrode in the second electrode film 5 is connected. By connecting the lead wire 9 to the exposed portion side portion of the film 2 by wire bonding, the piezoelectric element 21 shown in FIG. 5 can be obtained. FIG. 7 is a schematic diagram showing the film structure of the piezoelectric element 21.

  Hereinafter, specific examples will be described.

(Example 6)
In this example, a silicon substrate was used as the substrate 101, a Pt thin film having a thickness of 100 nm was used as the first electrode film 102, and these were formed in exactly the same manner as in Example 1.

Using a sintering target prepared by adding 15 mol% of lead oxide (PbO) to PLT containing 10 mol% of lanthanum for the alignment control film 112, a substrate gas temperature of 600 ° C. and a mixed gas atmosphere of argon and oxygen The film was formed for 12 minutes under the conditions of medium (gas volume ratio Ar / O ₂ = 19/1), vacuum degree of 0.8 Pa, and high-frequency power of 300 W.

The piezoelectric laminated film 110 was produced using the RF magnetron sputtering apparatus of Example 1. A 6-inch diameter sintered body (composition molar ratio Pb: Zr: Ti = 1.20: 0.53: 0.47) of stoichiometric lead zirconate titanate (PZT) was used as a target. The film formation conditions were as shown below. That is, the silicon substrate 101 having the first electrode film 102 formed on one surface was heated to 580 ° C. and kept at that temperature in the film formation chamber to which the target was attached. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 79/1) was used as the sputtering gas, the gas pressure was 0.2 Pa, and the gas flow rate was 40 ml per minute. Then, the plasma generation power was set to 3 kW, and the first piezoelectric thin film 103 was formed for 50 seconds. Thereafter, the film formation is temporarily stopped, and only the gas volume ratio of the sputtering gas is changed to Ar / O ₂ = 38/2 among the above film formation conditions, and the other film formation conditions are not changed, and the second piezoelectric thin film is not changed. 104 was deposited for 2500 seconds.

  The composition, thickness, cross-sectional structure, and crystal orientation of the first electrode film 102, the orientation control film 112, and the piezoelectric laminate film 110 were examined by the same method as in Example 1.

  The Pt electrode as the first electrode film 102 was found to be an aggregate of columnar particles (columnar crystals) having an average particle diameter (average diameter) of 20 nm.

  The orientation control film 112 had a perovskite crystal structure containing 10 mol% lanthanum and containing 10% of lead in excess of the stoichiometric composition.

  The first piezoelectric thin film 103 had a thickness of 100 nm, and the average particle diameter (average diameter) of the columnar particles was 40 nm. The second piezoelectric thin film 104 had a thickness of 2800 nm, and the average particle diameter (average diameter) of the columnar particles was 100 nm. The ratio of the thickness of the piezoelectric laminated film 110 to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film 104 was 29.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films 103 and 104 have a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film 103 was 78%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film 104 was 95%.

  Further, as a result of the composition analysis of the cation by the X-ray microanalyzer, the composition of the first piezoelectric thin film 103 is Pb: Zr: Ti = 1.00: 0.53: 0.47, and the second piezoelectric thin film The composition of 104 was Pb: Zr: Ti = 1.05: 0.53: 0.47. That is, the first and second piezoelectric thin films 103 and 104 are PZT films having a perovskite crystal structure, with the (001) axis preferentially grown in a direction perpendicular to the upper surface of the substrate 101. The composition of Ti was the same in the first and second piezoelectric thin films 103 and 104, and the composition of Pb was found to be less in the first piezoelectric thin film 103 than in the second piezoelectric thin film 104.

  Further, the amount of displacement in the Z-axis direction at the tip of the piezoelectric element 21 was measured using the same evaluation apparatus as in Example 1. That is, a triangular wave voltage of 0 V to −50 V is applied between the first and second electrode films 2 and 5 via the lead wires 8 and 9, and the displacement amount in the Z-axis direction of the tip of the piezoelectric element 21 is laser Doppler oscillated. It measured using the displacement measuring device. As a result of the measurement, it was found that the tip of the piezoelectric element 21 was displaced by a maximum of 28.3 μm.

  Further, after driving the piezoelectric element 21 continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) by this triangular wave voltage, the driving state of the piezoelectric element 21 is examined and the appearance of the piezoelectric element 21 is observed by an optical microscope. I investigated. As a result, even after the piezoelectric element 21 is continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the maximum displacement is 28.3 μm, and no decrease in the displacement is observed. There was no discoloration.

(Example 7)
In this example, a silicon substrate was used as the substrate 101, an Ir—Ti alloy thin film having a thickness of 120 nm was used as the first electrode film 102, and these were formed in the same manner as in Example 2.

  The orientation control film 112 was formed under the same target and film formation conditions as in Example 6.

The piezoelectric laminated film 110 was produced using the RF magnetron sputtering apparatus of Example 1. A 6-inch diameter sintered body (composition molar ratio Pb: Zr: Ti = 1.20: 0.50: 0.50) of lead zirconate titanate (PZT) having a stoichiometric composition was used as a target. The film formation conditions were as shown below. That is, the silicon substrate 101 having the first electrode film 102 formed on one surface was heated to 580 ° C. and kept at that temperature in the film formation chamber to which the target was attached. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 79/1) was used as the sputtering gas, the gas pressure was 0.2 Pa, and the gas flow rate was 40 ml per minute. Then, the plasma generation power was set to 3 kW, and the first piezoelectric thin film 103 was formed for 50 seconds. Thereafter, the film formation is temporarily stopped, and only the gas volume ratio of the sputtering gas is changed to Ar / O ₂ = 38/2 among the above film formation conditions, and the other film formation conditions are not changed, and the second piezoelectric thin film is not changed. 104 was deposited for 3000 seconds.

  The composition, thickness, cross-sectional structure, and crystal orientation of the first electrode film 102, the orientation control film 112, and the piezoelectric laminate film 110 were examined by the same method as in Example 1.

  The Ir—Ti alloy electrode as the first electrode film 102 is an Ir film containing 3% titanium, and is an aggregate of columnar particles (columnar crystals) having an average particle diameter (average diameter) of 30 nm. It was.

  The orientation control film 112 had a perovskite crystal structure containing 10 mol% lanthanum and containing 10% of lead in excess of the stoichiometric composition.

  The first piezoelectric thin film 103 had a thickness of 100 nm, and the average particle diameter (average diameter) of the columnar particles was 40 nm. The second piezoelectric thin film 104 had a thickness of 3800 nm, and the average particle diameter (average diameter) of the columnar particles was 170 nm. The ratio of the thickness of the piezoelectric laminated film 110 to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film 104 was 22.9.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films 103 and 104 have a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film 103 was 80%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film 104 was 98%.

  The composition of the first piezoelectric thin film 103 was found to be Pb: Zr: Ti = 1.05: 0.50: 0.50 as a result of the composition analysis of the cations by the X-ray microanalyzer. The composition of 104 was Pb: Zr: Ti = 1.10: 0.50: 0.50. That is, the first and second piezoelectric thin films 103 and 104 are PZT films having a perovskite crystal structure, with the (001) axis preferentially grown in a direction perpendicular to the upper surface of the substrate 101. The composition of Ti was the same in the first and second piezoelectric thin films 103 and 104, and the composition of Pb was found to be less in the first piezoelectric thin film 103 than in the second piezoelectric thin film 104.

  Further, the amount of displacement in the Z-axis direction at the tip of the piezoelectric element 21 was measured using the same evaluation apparatus as in Example 1. That is, a triangular wave voltage of 0 V to −50 V is applied between the first and second electrode films 2 and 5 via the lead wires 8 and 9, and the displacement amount in the Z-axis direction of the tip of the piezoelectric element 21 is laser Doppler oscillated. It measured using the displacement measuring device. As a result of the measurement, it was found that the tip of the piezoelectric element 21 was displaced by a maximum of 26.5 μm.

  Further, after driving the piezoelectric element 21 continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) by this triangular wave voltage, the driving state of the piezoelectric element 21 is examined and the appearance of the piezoelectric element 21 is observed by an optical microscope. I investigated. As a result, even after the piezoelectric element 21 is continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the maximum displacement is 26.5 μm, and no decrease in the displacement is observed. There was no discoloration.

(Example 8)
In this example, a silicon substrate was used as the substrate 1, a Ru thin film having a thickness of 110 nm was used as the first electrode film 102, and these were formed in exactly the same manner as in Example 2.

  The orientation control film 112 was formed under the same target and film formation conditions as in Example 6.

The piezoelectric laminated film 110 was produced using the RF magnetron sputtering apparatus of Example 1. A 6-inch diameter sintered body (composition molar ratio Pb: Zr: Ti = 1.20: 0.53: 0.47) of stoichiometric lead zirconate titanate (PZT) was used as a target. The film formation conditions were as shown below. That is, the silicon substrate 101 having the first electrode film 102 formed on one surface was heated to 580 ° C. and kept at that temperature in the film formation chamber to which the target was attached. A mixed gas of argon and oxygen (gas volume ratio Ar / O ₂ = 79/1) was used as the sputtering gas, the gas pressure was 0.2 Pa, and the gas flow rate was 40 ml per minute. The plasma generation power was 3 kW, and the first piezoelectric thin film 103 was formed for 30 seconds. Thereafter, the film formation is temporarily stopped, and only the gas volume ratio of the sputtering gas is changed to Ar / O ₂ = 38/2 among the above film formation conditions, and the other film formation conditions are not changed, and the second piezoelectric thin film is not changed. 104 was deposited for 3500 seconds.

  The composition, thickness, cross-sectional structure, and crystal orientation of the first electrode film 102, the orientation control film 112, and the piezoelectric laminate film 110 were examined by the same method as in Example 1.

  The Ru electrode as the first electrode film 102 was found to be an aggregate of columnar particles (columnar crystals) having an average particle diameter (average diameter) of 20 nm.

  The orientation control film 112 had a perovskite crystal structure containing 10 mol% lanthanum and containing 10% of lead in excess of the stoichiometric composition.

  The first piezoelectric thin film 103 had a thickness of 50 nm, and the average particle diameter (average diameter) of the columnar particles was 50 nm. The second piezoelectric thin film 104 had a thickness of 3500 nm, and the average particle diameter (average diameter) of the columnar particles was 150 nm. The ratio of the thickness of the piezoelectric multilayer film 110 to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film 104 was 28.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films 103 and 104 have a perovskite crystal structure. The (001) crystal orientation ratio of the formation surface of the first piezoelectric film 103 was 75%, and the (001) crystal orientation ratio of the formation surface of the second piezoelectric film 104 was 93%.

  Further, as a result of the composition analysis of the cation by the X-ray microanalyzer, the composition of the first piezoelectric thin film 103 is Pb: Zr: Ti = 1.00: 0.53: 0.47, and the second piezoelectric thin film The composition of 104 was Pb: Zr: Ti = 1.10: 0.53: 0.47. The composition of Zr and Ti was the same in the first and second piezoelectric thin films 103 and 104, and the composition of Pb was less in the first piezoelectric thin film 103 than in the second piezoelectric thin film 104.

  Further, the amount of displacement in the Z-axis direction at the tip of the piezoelectric element 21 was measured using the same evaluation apparatus as in Example 1. That is, a triangular wave voltage of 0 V to −50 V is applied between the first and second electrode films 2 and 5 via the lead wires 8 and 9, and the displacement amount in the Z-axis direction of the tip of the piezoelectric element 21 is laser Doppler oscillated. It measured using the displacement measuring device. As a result of the measurement, it was found that the tip of the piezoelectric element 21 was displaced by a maximum of 29.7 μm.

  Further, after driving the piezoelectric element 21 continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) by this triangular wave voltage, the driving state of the piezoelectric element 21 is examined and the appearance of the piezoelectric element 21 is observed by an optical microscope. I investigated. As a result, even after the piezoelectric element 21 is continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the displacement is a maximum of 29.7 μm, and no decrease in the displacement is observed. There was no discoloration.

(Comparative Example 3)
In order to compare with the piezoelectric elements of the above examples, a piezoelectric element of Comparative Example 3 as described below was produced. That is, in the comparative example, unlike Example 6, the Pb composition of the piezoelectric laminated film was larger in the first piezoelectric thin film than in the second piezoelectric thin film. The method for forming the piezoelectric laminated film is the same as in Example 6, and the film forming conditions are different from those in Example 6. The other points are exactly the same as in the sixth embodiment.

  The composition, thickness, cross-sectional structure, and crystal orientation of the first electrode film, the orientation control film, and the piezoelectric laminate film were examined by the same method as in Example 1.

  The orientation control film had a perovskite-type crystal structure containing 10 mol% lanthanum and containing 10% of lead in excess of the stoichiometric composition.

  The first piezoelectric thin film had a thickness of 100 nm, and the average particle diameter (average diameter) of the columnar particles was 70 nm. The second piezoelectric thin film had a thickness of 2800 nm, and the average particle diameter (average diameter) of the columnar particles was 180 nm. The ratio of the thickness of the piezoelectric laminated film to the average particle diameter (average diameter) of the columnar particles of the second piezoelectric thin film was 16.1.

  Further, as a result of analysis by the X-ray diffraction method, it was found that the first and second piezoelectric films had a perovskite crystal structure. The formation surface (001) crystal orientation of the first piezoelectric film was 80%, and the (001) crystal orientation of the second piezoelectric film formation surface was 98%.

  Further, as a result of the composition analysis of the cation by the X-ray microanalyzer, the composition of the first piezoelectric thin film is Pb: Zr: Ti = 1.15: 0.53: 0.47, The composition was Pb: Zr: Ti = 1.10: 0.53: 0.47. In other words, the first and second piezoelectric thin films are PZT films having a perovskite crystal structure with a (001) axis preferentially grown in a direction perpendicular to the upper surface of the substrate, and the compositions of Zr and Ti are It was found that the first and second piezoelectric thin films were the same, and the composition of Pb was greater in the first piezoelectric thin film than in the second piezoelectric thin film.

  In addition, the driving endurance test of the piezoelectric displacement of the piezoelectric element was performed using the same evaluation apparatus as in Example 1. That is, a triangular wave voltage of 0 V to −50 V is applied between the first and second electrode films via a lead wire, and the displacement amount in the Z-axis direction of the tip of the piezoelectric element is measured using a laser Doppler vibration displacement measuring device. did. As a result of the measurement, it was found that the tip of the piezoelectric element was displaced by a maximum of 26.0 μm.

  Moreover, after driving the piezoelectric element continuously for 120 hours in an atmosphere of high temperature and high humidity (temperature 50 ° C., humidity 50%) with this triangular wave voltage, the driving state of the piezoelectric element was examined and the appearance of the piezoelectric element was examined with an optical microscope. . As a result, after the piezoelectric element was continuously driven in a high-temperature and high-humidity atmosphere for 120 hours, the amount of displacement decreased (0 μm), and the first electrode film turned black. That is, the piezoelectric element was deteriorated.

-Effect-
As described above, according to the present embodiment, since the Pb composition of the first piezoelectric thin film 3 is smaller than the Pb composition of the second piezoelectric thin film 4, the piezoelectric element 21 is heated and humidified (temperature 50 ° C., humidity 50%). Even when driven in the atmosphere, excess Pb of the first piezoelectric thin film 3 permeates through the first electrode film 2 and the alignment control film 12 at the interface between the alignment control film 12 and the first piezoelectric thin film 3. Deterioration of the piezoelectric element 21 due to reaction with moisture does not occur. Therefore, the piezoelectric element 21 having high piezoelectric characteristics and high moisture resistance can be realized at low cost.

  Further, by providing the orientation control film 12 between the first electrode film 2 and the first piezoelectric thin film 3, the crystal orientation of the first piezoelectric thin film 3 is improved, and further, the second piezoelectric thin film is further improved. The crystal orientation of 4 is improved. Therefore, the piezoelectric element 21 having higher piezoelectric characteristics can be realized.

(Embodiment 3)
In this embodiment, the piezoelectric element of the present invention is applied to an inkjet head. As shown in FIG. 8, the inkjet head 201 according to this embodiment includes ten ink ejection elements 202,... Having the same shape and arranged in a row, and individual electrodes 33 ( And a driving power source element 203 for driving the ink ejection element 202.

  As shown in FIG. 9, the ink ejection element 202 is formed by laminating a nozzle plate D, an ink liquid flow path component C, a pressure chamber component A, and an actuator portion B in order. These parts A to D are bonded and fixed to each other with an adhesive.

  A pressure chamber opening 31 is formed in the pressure chamber component A. The actuator portion B is disposed so as to cover the upper end opening surface of the pressure chamber opening 31. That is, the actuator portion B is provided so that a part of the surface on one side in the thickness direction faces the pressure chamber opening 31. The ink liquid flow path component C is disposed so as to cover the lower end opening surface of the pressure chamber opening 31. That is, the pressure chamber opening 31 is partitioned by the actuator portion B and the ink liquid flow path component C respectively disposed above and below the pressure chamber opening 31, and the partitioned space is a pressure chamber 32 (thickness 0.2 mm) for containing the ink liquid. ). The shape of the upper opening surface is an ellipse having a minor axis of 200 μm and a major axis of 400 μm.

  The ink liquid flow path component C includes a common liquid chamber 35 shared by a plurality of pressure chambers 32 arranged in a row, and a supply port 36 that communicates the common liquid chamber 35 and the pressure chamber 32. An ink flow path 37 that communicates the pressure chamber 32 and a nozzle hole 38 to be described later is formed. The nozzle plate D is provided with a nozzle hole 38 having a diameter of 30 μm.

  The drive power supply element 203 supplies a voltage to the individual electrode 33 of each ink ejection element 202 via a bonding wire. The head main body of the present invention corresponds to the nozzle plate D, the ink liquid flow path component C, and the pressure chamber component A.

  Hereinafter, specific examples will be described.

Example 9
10 is a cross-sectional view taken along line XX of FIG. The actuator part B has a 100 nm thick individual electrode 33 made of a Pt film, and a 100 nm thick made of PZT, which is located immediately below the individual electrode 33 and is represented by Pb _1.00 Zr _0.53 Ti _0.47. First piezoelectric thin film 41 and a second piezoelectric thin film having a thickness of 2800 nm, which is made of PZT, which is located immediately below the first piezoelectric thin film 41 and represented by Pb _1.05 Zr _0.53 Ti _0.47 42, a second electrode film (common electrode) 43 having a thickness of 100 nm and made of Pt, which is located immediately below the second piezoelectric thin film 42, and a thickness which is made of chromium and is located immediately below the second electrode film 43. And a diaphragm film 44 having a thickness of 3500 nm. The individual electrode 33 is individually provided so as to correspond to the position of the pressure chamber 32. The diaphragm film 44 is displaced and vibrates due to the piezoelectric effect of the piezoelectric thin films 41 and 42. The second electrode film 43 and the diaphragm film 44 are shared between the pressure chambers 32. In portions other than the laminated film on the second electrode film 43 (the laminated film will be described later), an electrically insulating organic film 45 made of polyimide resin is formed to the same height as the upper surface of the individual electrode 33. A lead wire 46 made of gold and having a thickness of 100 nm connected to the individual electrode 33 is formed on the upper surface of the electrically insulating organic film 45. The diaphragm film and the piezoelectric element of the present invention correspond to the actuator part B.

-Manufacturing method of ink ejection element-
Hereinafter, a method for manufacturing the ink ejection element 202 will be described with reference to FIGS. 11 and 12. First, as in Example 1, the first electrode film 52, the first piezoelectric thin film 53, the second piezoelectric thin film 54, and the second electrode film are formed on a silicon substrate 51 having a length of 20 mm, a width of 20 mm, and a thickness of 0.3 mm. 43 are laminated in order. Thereby, the structure 55 shown in FIG. 11A can be obtained.

  Next, as shown in FIG. 11B, a diaphragm film 44 is formed on the second electrode film 43 by RF magnetron sputtering at room temperature.

  Next, as shown in FIG. 11C, a glass pressure chamber component 57 is bonded onto the diaphragm film 44 using an adhesive (acrylic resin) 56.

Next, as shown in FIG. 11D, the silicon substrate 51 is removed by a dry etching method using SF ₆ gas using a plasma reaction etching apparatus.

  Next, as shown in FIG. 11E, a photoresist 58 is formed on the first electrode film 52, and then the photoresist 58 is patterned so as to correspond to the position of the pressure chamber 32.

  Next, as shown in FIG. 12A, the first electrode film 52 and the first piezoelectric thin film 53 are patterned by a dry etching method so as to correspond to the position of the pressure chamber 32 and to have the same shape. Then, the photoresist 58 is removed. In the step of patterning the first electrode film 52 and the first piezoelectric thin film, patterning is performed by a dry etching method using a gas containing a halogen element or a mixed gas composed of a gas containing a halogen element and an inert gas. Is desirable.

  Next, using the same photoresist as described above, the second piezoelectric thin film 54 is patterned by a wet etching method so as to have a size larger than that of the individual electrode 33. Thereby, as shown in FIG. 12B, the laminated film composed of the first electrode film 52, the first piezoelectric thin film 53, and the second piezoelectric thin film 54 is individualized, and an actuator structure can be obtained. In the step of patterning the second piezoelectric thin film 54, it is desirable to pattern by a wet etching method using an etchant mainly containing hydrofluoric acid.

  Next, as shown in FIG. 12C, an electrically insulating organic film 45 is formed on the second electrode film 43 in a portion other than the laminated film by a printing method. Thereafter, as shown in FIG. 12D, lead wires 46 are formed on the upper surface of the electrically insulating organic film 45 by DC sputtering. Thus, the actuator part B shown in FIG. 9 can be obtained.

  30 ink ejection elements 202,... Having the same shape and size were produced by the manufacturing method as described above. Then, a sine waveform voltage (200 Hz) of 0 V to −50 V is applied between the individual electrode 33 and the second electrode film 43 of each ink ejection element 202,. It was driven in an atmosphere (temperature 50 ° C., humidity 50%). As a result, all the ink ejection elements 202,... Were driven for a long time without failure.

  The ink jet head 201 shown in FIG. 8 was manufactured using ten ink discharge elements 202 manufactured by the manufacturing method described above.

-Operation of inkjet head-
Hereinafter, the operation of the inkjet head 201 will be described. In the inkjet head 201 shown in FIG. 8, voltages are respectively supplied from the drive power supply element 203 to the individual electrodes 33 of the ten ink ejection elements 202,. Then, due to the piezoelectric effect of the piezoelectric thin films 41 and 42, the diaphragm film 44 is displaced and vibrates, whereby the ink liquid in the common liquid chamber 35 passes through the supply port 36, the pressure chamber 32, and the ink flow path 37. Then, it is discharged from the nozzle hole 38. At this time, in the inkjet head 201, the crystal orientations of the film surfaces of the piezoelectric thin films 41 and 42 are aligned with the (001) plane, and the piezoelectric characteristics of the piezoelectric thin films 41 and 42 are also aligned. Therefore, according to the inkjet head 201, a large piezoelectric displacement (displacement amount) can be obtained.

  Further, since the ink discharge element 202 has a large piezoelectric displacement, that is, has a high ink discharge capability, a large margin can be taken in the adjustment range of the power supply voltage. Therefore, the ink discharge capability of each ink discharge element 202 can be easily controlled. Therefore, the variation in the ink discharge capability between the ink discharge elements 202 can be reduced.

(Example 10)
As shown in FIG. 13, the inkjet head according to the present embodiment is different from the ninth embodiment in that an orientation control film 59 is disposed between the individual electrode 33 and the first piezoelectric thin film 41. The points are almost the same as in the ninth embodiment. The orientation control film 59 is made of the same lead lanthanum titanate as in the sixth embodiment.

  In the method of manufacturing the ink ejection element 202, the orientation control film 59 is formed between the first electrode film 52 and the first piezoelectric thin film 53, and the orientation control film 59 is replaced with the first electrode film 52 and the first piezoelectric film. Unlike the ninth embodiment, patterning is performed by the dry etching method so as to correspond to the position of the pressure chamber 32 together with the body thin film 53, and the other points are substantially the same as those of the ninth embodiment. This alignment control film 59 is produced by the same method as the alignment control film of Example 6.

  An ink jet head 201 was manufactured using the ink ejection element 202 manufactured by the manufacturing method described above.

-Effect-
As described above, according to the present embodiment, in the ink jet head 201 in which a plurality of ink discharge elements 202 are arranged, it is possible to reduce variations in the ink liquid discharge capability between the ink discharge elements 202. Therefore, the inkjet head 201 with high reliability can be realized.

  The first electrode film 52, the orientation control film 59, the first piezoelectric thin film 53, the second piezoelectric thin film 54, and the second electrode film 43 that constitute the actuator part B are the piezoelectric element 20 according to the first and second embodiments. As long as it is made of the material used in the above, 21, the actuator part B having high characteristics can be realized by using any material.

  In this embodiment, the diaphragm film 44 is made of chromium, but may be made of silicon, glass, a ceramic material, or a metal material other than chromium.

  In the present embodiment, the diaphragm film 44 is formed on the surface of the second electrode film 43 opposite to the second piezoelectric thin film 42, but the first piezoelectric thin film 41 (orientation) in the individual electrode 33 is formed. The diaphragm 44 may be formed on the surface opposite to the control film 59).

(Embodiment 4)
In this embodiment, the piezoelectric element of the present invention is applied to an ink jet recording apparatus. As shown in FIG. 14, the ink jet recording apparatus 81 according to the present embodiment includes the ink jet head 201 according to the third embodiment that performs recording using the piezoelectric effect of the piezoelectric thin films 41 and 42. Recording can be performed on the recording medium 82 by causing the ink droplets ejected from the head 201 to land on the recording medium 82 such as paper. The ink-jet head 201 is mounted on a carriage 84 attached to a carriage shaft 83 arranged so as to extend in the main scanning direction (X direction in FIG. 14). As the carriage 84 reciprocates along the carriage shaft 83, the inkjet head 201 reciprocates in the main scanning direction X. The ink jet recording apparatus 81 further includes a plurality of rollers 85 that move the recording medium 82 in the sub-scanning direction Y substantially perpendicular to the main scanning direction X. The moving means according to the present invention corresponds to the carriage shaft 83, the carriage 84, and the roller 85.

-Effect-
As described above, according to the present embodiment, since the ink jet recording apparatus 81 is configured using the ink jet head 201 having a small variation in ink discharge ability between the ink discharge elements 202, uneven printing during recording is performed. Therefore, it is possible to realize an ink jet recording apparatus 81 with a low reliability and a high reliability.

  In this embodiment, the ink jet head 201 is applied to the so-called serial type ink jet recording apparatus 81, but may be applied to a so-called line type ink jet recording apparatus.

  As described above, the present invention is useful not only for an ink jet head but also for a gyro element and the like. The present invention can also be applied to a micromachine device or the like.

1 is a perspective view of a piezoelectric element according to an embodiment of the present invention. It is a figure which shows the manufacturing process of a piezoelectric element. It is a schematic diagram which shows the film | membrane structure of a piezoelectric element. It is a figure which shows the displacement amount of the Z-axis direction of the front-end | tip of a piezoelectric element at the time of applying the triangular wave voltage of frequency 2kHz. It is a perspective view of a piezoelectric element. It is a figure which shows the manufacturing process of a piezoelectric element. It is a schematic diagram which shows the film | membrane structure of a piezoelectric element. It is a schematic block diagram of an inkjet head. FIG. 3 is an exploded perspective view in which a part of the ink ejection element is broken. It is sectional drawing of the XX line of FIG. It is a figure which shows a part of manufacturing process of an actuator part. It is a figure which shows a part of manufacturing process of an actuator part. It is a figure equivalent to FIG. 10 of the modification of an ink discharge element. 1 is a schematic perspective view of an ink jet recording apparatus.

Explanation of symbols

1,101 Substrate 2,52,102 First electrode film 3,41,53,103 First piezoelectric thin film 4,42,54,104 Second piezoelectric thin film 5,43,105 Second electrode film 20,21 Piezoelectric Element 44 Diaphragm film 81 Inkjet recording device 83 Carriage shaft (moving means)
84 Carriage (moving means)
85 Roller (moving means)
201 Inkjet head 12, 59, 112 orientation control film

Claims (10)

A first piezoelectric film; a first piezoelectric film formed on the first electrode film; and a second piezoelectric film formed on the first piezoelectric film and controlled in crystal orientation by the first piezoelectric film. A piezoelectric element comprising a piezoelectric laminate film comprising a body film and a second electrode film formed on the second piezoelectric film,
The first and second piezoelectric films are aggregates of columnar particles whose crystal growth direction is directed from one side to the other side in the thickness direction of the piezoelectric multilayer film,
The Pb content of the first piezoelectric film is less than the Pb content of the second piezoelectric film;
The average cross-sectional diameter of the columnar particles of the second piezoelectric film is larger than the average cross-sectional diameter of the columnar particles of the first piezoelectric film,
A piezoelectric element, wherein a ratio of the thickness of the piezoelectric laminated film to the average cross-sectional diameter of the columnar particles of the second piezoelectric film is 20 or more and 60 or less. A first electrode film; an alignment control film formed on the first electrode film; a first piezoelectric film formed on the alignment control film; and the first piezoelectric film formed on the first piezoelectric film. A piezoelectric element comprising: a piezoelectric laminated film comprising a second piezoelectric film whose crystal orientation is controlled by a piezoelectric film; and a second electrode film formed on the second piezoelectric film,
The first and second piezoelectric films are aggregates of columnar particles whose crystal growth direction is directed from one side to the other side in the thickness direction of the piezoelectric multilayer film,
The Pb content of the first piezoelectric film is less than the Pb content of the second piezoelectric film;
The average cross-sectional diameter of the columnar particles of the second piezoelectric film is larger than the average cross-sectional diameter of the columnar particles of the first piezoelectric film,
A piezoelectric element, wherein a ratio of the thickness of the piezoelectric laminated film to the average cross-sectional diameter of the columnar particles of the second piezoelectric film is 20 or more and 60 or less.   3. The piezoelectric element according to claim 1, wherein the columnar particles of the first piezoelectric film have an average cross-sectional diameter of 40 nm to 70 nm and a length of 5 nm to 100 nm.   3. The piezoelectric element according to claim 1, wherein the columnar particles of the second piezoelectric film have an average cross-sectional diameter of 60 nm to 200 nm and a length of 2500 nm to 5000 nm. The first and second piezoelectric films contain at least Pb, Zr and Ti, and the chemical composition ratio is represented by Pb: Zr: Ti = (1 + a): b: 1-b,
The value of b of the first and second piezoelectric films is the same value between 0.50 and 0.60,
The value of a in the first piezoelectric film is −0.05 or more and 0.05 or less,
3. The piezoelectric element according to claim 1, wherein the value a of the second piezoelectric film is 0 or more and 0.1 or less.   2. The piezoelectric element according to claim 1, wherein the first and second piezoelectric films are preferentially oriented in a (001) plane.   The first electrode film includes at least one noble metal selected from Pt, Ir, Pd and Ru, or the noble metal and Ti, Co, Ni, Al, Fe, Mn, Cu, Mg, Ca, Sr and Ba. 3. The piezoelectric element according to claim 1, wherein the piezoelectric element is an aggregate of columnar particles having an average cross-sectional diameter of 20 nm or more and 30 nm or less, which is made of an alloy with at least one selected metal or oxide thereof. .   The piezoelectric element according to claim 2, wherein the orientation control film is made of lead lanthanum titanate. A head main body formed with a nozzle and a pressure chamber communicating with the nozzle and containing ink;
A diaphragm film provided so that a part of the surface on one side in the thickness direction faces the pressure chamber;
An inkjet head including a piezoelectric element that is formed on a surface on the other side in the thickness direction of the diaphragm film and that applies pressure to the ink in the pressure chamber to discharge the ink from the nozzle;
An inkjet head comprising the piezoelectric element according to any one of claims 1 to 8. An inkjet head;
An ink jet recording apparatus comprising a moving means for relatively moving the ink jet head and the recording medium,
An ink jet recording apparatus comprising the ink jet head according to claim 9 .

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