JP2018148113A - Piezoelectric body film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric body film capable of improving piezoelectric properties by reducing the full width at half maximum of diffraction peaks derived from a given crystal plane measured by X-ray diffraction by improving crystallinity and orientation of a piezoelectric body film.SOLUTION: Disclosed piezoelectric body film has a PZT-based or PT-based perovskite structure formed on a substrate. The half value width of the diffraction peak derived from the (100) plane measured by X-ray diffraction is 0.15 degree or less, and the half value width of the diffraction peak derived from the (200) plane is 0.40 degree or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric film having a perovskite structure of lead zirconate titanate (PZT) or lead titanate (PT) based, which is used in vibration power generation elements, sensors, actuators, ink jet heads, autofocus, and the like. is there.

  Conventionally, since the characteristics of a piezoelectric device are determined by the characteristics of the piezoelectric body and the device structure, development of a material having high piezoelectric characteristics is eagerly desired. In the wet film formation typified by the sol-gel method, a high-quality film can be obtained by a simple method and has been widely used.

  For example, a ferroelectric thin film forming composition is applied on a lower electrode of a substrate having a lower electrode whose crystal plane is oriented in the (111) axial direction, calcined, and then fired to crystallize the lower electrode. A method of manufacturing a ferroelectric thin film on an electrode is disclosed (for example, see Patent Document 1). In this method of manufacturing a ferroelectric thin film, a composition for forming a ferroelectric thin film is applied on a lower electrode, calcined, and baked to form an orientation control layer, and the amount of the composition for forming a ferroelectric thin film is adjusted. The preferential crystal orientation of the orientation control layer is set to the (100) plane by setting the layer thickness after crystallization of the orientation control layer to be in the range of 35 to 150 nm. In Patent Document 1, since it is difficult to distinguish between tetragonal crystals and rhombohedral crystals in a ferroelectric thin film, all of them are treated as tetragonal crystals and expressed as (100) / (001) planes. . In addition, a part of the composition for forming a ferroelectric thin film is applied on the lower electrode, calcined, and baked to form an orientation control layer, and then the remainder of the composition for forming a ferroelectric thin film is placed on the orientation control layer. Coating, calcining, and baking are performed to form a film thickness adjusting layer having the same crystal orientation as that of the orientation control layer. Furthermore, the calcining temperature for forming the film thickness adjusting layer after applying the remainder of the composition for forming a ferroelectric thin film is in the range of 200 ° C to 450 ° C. For example, by repeating the steps of coating and calcining the composition for film thickness adjusting layer four times and then performing crystallization by heating at 700 ° C. for 1 minute in an oxygen atmosphere at a temperature rising rate of 10 ° C./sec. A film thickness adjusting layer having a layer thickness of 300 nm is obtained.

  In the manufacturing method of the ferroelectric thin film configured as described above, the thickness of the orientation control layer after crystallization is within the range of 35 to 150 nm, so that the crystal is preferentially formed on the (100) / (001) plane. A ferroelectric thin film with controlled orientation can be easily obtained without providing a seed layer or a buffer layer. In addition, by forming a film thickness adjusting layer on the orientation control layer, a crystal orientation surface having the same tendency as the orientation control layer is formed following the preferential alignment surface of the orientation control layer. Thus, the film thickness of the ferroelectric thin film whose crystal orientation is preferentially controlled in the (100) / (001) plane by the orientation control layer can be arbitrarily adjusted according to the application.

JP 2012-256850 A (Claims 1, 4 and 5, paragraphs [0017], [0056], [0076])

  However, in the manufactured ferroelectric thin film shown in the above-mentioned conventional patent document 1, when the film thickness adjusting layer is formed thickly for each firing, the ferroelectric thin film is cracked or peeled off, or has a high crystal orientation. There is a problem that the piezoelectric characteristics are deteriorated due to problems such as large composition unevenness in the film thickness direction resulting from firing in which the film cannot be obtained.

  A first object of the present invention is to provide a piezoelectric film that can improve the piezoelectric characteristics by improving the crystallinity and orientation of the piezoelectric film. A second object of the present invention is to provide a piezoelectric film that can improve the piezoelectric characteristics by increasing the film thickness that can be fired at one time. A third object of the present invention is to provide a piezoelectric film that can contribute to the improvement of piezoelectric characteristics by relaxing the composition gradient of Zr / Ti in the film thickness direction. A fourth object of the present invention is to provide a piezoelectric film that can prevent the deterioration of the piezoelectric characteristics due to the fact that the perovskite structure does not include a piacroa layer.

  A first aspect of the present invention is a piezoelectric film formed on a substrate and having a PZT-based or PT-based perovskite structure, and a half-value width of a diffraction peak derived from a (100) plane measured by X-ray diffraction Is 0.15 degrees or less, and the half width of the diffraction peak derived from the (200) plane is 0.40 degrees or less. In the present invention, since the piezoelectric film is a thin film, it is difficult to distinguish between tetragonal crystals and rhombohedral crystals. Therefore, all of them are treated as tetragonal crystals, and the (100) plane includes the (001) plane. It shall be. Similarly, it is assumed that the (200) plane includes the (002) plane.

  The second aspect of the present invention is an invention based on the first aspect, and when the number of firings is one, when the entire film thickness is 500 nm or more, and the number of firings is two or more, The film thickness at each firing interface is 500 nm or more.

  A third aspect of the present invention is an invention based on the first aspect, wherein the perovskite structure is a PZT system, and when the Zr / Ti concentration ratio is analyzed in the film thickness direction, the Zr / Ti One or two or more layers gradually increase as the concentration ratio increases from the substrate, and the thickness of each layer is 500 to 1000 nm.

  In the piezoelectric film according to the first aspect of the present invention, since the crystallinity and orientation of the piezoelectric film are extremely high, the half-value width of a diffraction peak derived from a predetermined crystal plane measured by X-ray diffraction is small. Since the compositional variation in the thickness direction of the piezoelectric film is small, the piezoelectric characteristics can be improved.

  In the piezoelectric film according to the second aspect of the present invention, when the number of firings is 1, the total film thickness is 500 nm or more, and when the number of firings is 2 or more, the film thickness for each firing interface is 500 nm or more. That is, since the film thickness that can be fired once is increased, the piezoelectric characteristics can be further improved.

  In the piezoelectric film according to the third aspect of the present invention, the Zr / Ti concentration ratio has one or more layers that gradually increase with distance from the substrate, and the thickness of each layer is increased to 500 to 1000 nm. The composition gradient of Zr / Ti in the thickness direction becomes gentle. As a result, it can contribute to the improvement of piezoelectric characteristics.

6 is a diagram showing X-ray diffraction patterns of piezoelectric films of Example 1 and Comparative Example 1. FIG. It is a figure which shows the X-ray-diffraction pattern of the piezoelectric material film of Example 1 and Comparative Example 1 which expanded and overlapped the A section of FIG. It is a figure which shows the X-ray-diffraction pattern of the piezoelectric material film of Example 1 and the comparative example 1 which expanded and overlapped the B section of FIG.

  Next, the form for implementing this invention is demonstrated. The piezoelectric film is a piezoelectric film formed on a substrate and having a PZT-based or PT-based perovskite structure. Examples of the PZT system include PZT (lead zirconate titanate), PNbZT (niobium-doped lead zirconate titanate), PLZT (lanthanum-doped lead zirconate titanate), and the PT system includes PT (lead titanate). ), PLT (lanthanum-doped lead titanate), PNbT (niobium-doped lead titanate), and the like.

  The piezoelectric film has a half-value width of a diffraction peak derived from the (100) plane measured by X-ray diffraction of 0.15 degrees or less, preferably 0.135 degrees or less, and diffraction derived from the (200) plane. The full width at half maximum of the peak is 0.40 degrees or less, preferably 0.38 degrees or less. Here, the half width of the diffraction peak derived from the (100) plane is limited to 0.15 degrees or less, and the half width of the diffraction peak derived from the (200) plane is limited to 0.40 degrees or less. This is because the piezoelectric characteristics of the piezoelectric film deteriorate if the above range is exceeded. In addition, it is preferable to use a CuKα ray as the X-ray of the X-ray diffraction. Further, when the piezoelectric film is a PZT film, when the angle of the diffraction peak measured by X-ray diffraction is θ, the (100) plane is 2θ = 21.7 ± 0.2 degrees, and the (200) plane Is 2θ = 45 ± 1 degrees. These values are not constant because the piezoelectric film is a thin film and is strongly influenced by residual stress. Therefore, in the present invention, the peak within the range of 2θ = 21.7 ± 0.2 degrees is the peak of the (100) plane, and the peak within the range of 2θ = 45 ± 1 degrees is the peak of the (200) plane. To do.

  When the number of firings of the piezoelectric film is 1, the total film thickness is preferably 500 nm or more, and when the number of firings is 2 or more, the film thickness at each firing interface is preferably 500 nm or more. . Here, the reason why the film thickness of the piezoelectric film is limited to the above range is that sufficient piezoelectric characteristics cannot be obtained if the film thickness is less than 500 nm.

  In addition, when the perovskite structure is a PZT system and the Zr / Ti concentration ratio is analyzed in the film thickness direction, the Zr / Ti concentration ratio gradually increases as the distance from the substrate increases, that is, the composition of Zr / Ti. It is preferable to have one or more inclined layers, and the thickness of each layer is 500 to 1000 nm. Here, the reason why the thickness of the gradient layer of the Zr / Ti composition is limited to the range of 500 to 1000 nm is that if the thickness is less than 500 nm, sufficient piezoelectric characteristics cannot be obtained, and if the thickness exceeds 1000 nm, cracks occur in the piezoelectric film. It will occur. The perovskite structure contains almost no piacroa phase or zirconia. This is because the pyrochlore phase and zirconia are usually generated near the surface of the film after baking, so the amount of generation increases as the number of baking increases, but in the present invention, the film thickness per baking is made thicker than before. This is because the number of firings can be reduced. Furthermore, the total thickness of the piezoelectric film is preferably 500 to 5000 nm. Here, the reason why the total thickness of the piezoelectric film is limited to the range of 500 to 5000 nm is that if it is less than 500 nm, it is difficult to use it as a piezoelectric element, and if it exceeds 5000 nm, the productivity of the piezoelectric film decreases. It is.

A method of manufacturing the piezoelectric film thus configured will be described.
[Preparation of base substrate] (when the piezoelectric film is a PZT film)
A silicon substrate, a stainless steel substrate, an alumina substrate, or the like is prepared as a substrate. When using a silicon substrate, it is desirable to form an oxide film by thermal oxidation in order to suppress lead diffusion. Next, after forming a titanium film on the substrate by a sputtering method, a titanium oxide film is formed by baking at a temperature of 700 to 800 ° C. for 1 to 3 minutes in an oxygen atmosphere by rapid heating treatment (RTA) or the like. . Here, titanium does not necessarily need to be oxidized, and titanium alone can be used as an adhesion layer. Next, a (111) -oriented Pt lower electrode is formed on the titanium oxide film or the titanium film by sputtering. Further, a (100) -oriented alignment control layer is formed on the (111) -oriented Pt lower electrode. Thereby, a substrate is produced.

  The orientation control layer is preferably formed on the Pt lower electrode by the following method. First, Zr tetra n-butoxide (Z source), Ti isopropoxide (Ti source), and acetylacetone (stabilizer) are placed in a reaction vessel and refluxed in a nitrogen atmosphere. Next, lead acetate trihydrate (Pb source) is added to this compound, and propylene glycol (solvent) is added, refluxed in a nitrogen atmosphere, and distilled under reduced pressure to remove by-products. Propylene glycol was added to adjust the concentration, and diluted alcohol was further added to adjust the concentration to a predetermined concentration. Each metal ratio in terms of oxide was Pb / Zr / Ti = 110/52/48. A composition for an orientation control layer containing the compound is obtained. Next, the composition for orientation control layer is applied onto the Pt lower electrode by spin coating while dropping the composition for orientation control layer on the Pt lower electrode. Subsequently, drying and calcination are performed by a hot plate or the like in an air atmosphere at a temperature of 285 to 315 ° C. for 3 to 5 minutes. Furthermore, after performing the application | coating of the said composition for orientation control layers, drying, and calcining once, it heated to 650-750 degreeC with the temperature increase rate of 7-13 degrees C / second in oxygen atmosphere, and this temperature The orientation control layer having a predetermined thickness can be obtained by crystallization by performing baking for 1 to 3 minutes.

[Preparation of piezoelectric film]
First, a single sol-gel solution (metal composition ratio, Pb / Zr / Ti = 115/52/48) is dropped onto the base substrate, and the sol-gel liquid is applied onto the base substrate by spin coating or the like. A substrate with a film is prepared. Next, this coated substrate is calcined for 2 to 5 minutes using a hot plate or the like at 275 to 325 ° C. and then heated to a temperature of 525 to 550 ° C. in an oxygen atmosphere by rapid heating treatment (RTA) or the like. An intermediate heat treatment for 3 minutes is performed to manufacture a substrate with an intermediate heat treatment film. Further, after repeating the operations of spin coating, calcining, and intermediate heat treatment of the sol-gel solution a plurality of times, baking is performed by holding at a temperature of 650 to 750 ° C. for 1 to 5 minutes in an oxygen atmosphere by rapid heating treatment (RTA) or the like. By doing so, a substrate with a piezoelectric film is obtained. Here, the firing temperature was limited to the range of 650 to 750 ° C., and the crystallization was insufficient at less than 650 ° C., and sufficient piezoelectric characteristics could not be obtained. This is because diffusion proceeds and the lower electrode and the oxide film deteriorate. In addition, the firing time was limited to the range of 1 to 5 minutes because the crystallization did not proceed sufficiently in less than 1 minute and the leakage current density was increased, or sufficient piezoelectric characteristics were not obtained, and 5 minutes. It is because productivity will fall when it exceeds. Depending on the required film thickness of the piezoelectric film, the step of firing after repeating coating film formation by spin coating or the like, calcination and intermediate heat treatment a plurality of times is repeated a plurality of times.

  Here, the calcining temperature was limited to the range of 275 to 325 ° C., and if it was less than 275 ° C., the thermal decomposition of the precursor contained in the sol-gel liquid did not proceed sufficiently and a large amount of carbon remained in the film. When the temperature exceeds 325 ° C., the surface of the piezoelectric film changes before the carbon inside the piezoelectric film is discharged out of the piezoelectric film, and the void is generated when the coating film is thickened. It is because it becomes easy to do. The calcining time is limited to the range of 2 to 5 minutes. If the calcining time is less than 2 minutes, the precursor contained in the sol-gel solution is not sufficiently decomposed and voids are easily generated due to residual carbon. It is because productivity will fall when it exceeds a minute. Moreover, the intermediate heat treatment temperature is limited to the range of 525 to 550 ° C. If the temperature is lower than 525 ° C., the piezoelectric film is cracked or peeled off, or is derived from the (100) plane measured by X-ray diffraction. The half-width of the peak and the half-width of the diffraction peak derived from the (200) plane are increased and the piezoelectric characteristics are lowered. When the temperature exceeds 550 ° C., half of the diffraction peak derived from the (100) plane measured by X-ray diffraction This is because the full width at half maximum of the value width and the diffraction peak derived from the (200) plane is increased and the piezoelectric characteristics are deteriorated. Furthermore, the intermediate heat treatment time is limited to the range of 0.5 to 3 minutes because if the time is less than 0.5 minutes, the piezoelectric film is not sufficiently densified and cracks and voids are generated. It is because productivity will fall if it exceeds.

  In the piezoelectric film thus manufactured, the crystallinity and orientation are extremely high, the half width of the diffraction peak derived from a predetermined crystal plane measured by X-ray diffraction is reduced, and the film thickness direction of the piezoelectric film is reduced. Therefore, the piezoelectric characteristics can be improved. That is, by using one kind of sol-gel solution, the composition unevenness of the piezoelectric film can be reduced, and as a result, the piezoelectric characteristics can be improved. In addition, since the intermediate heat treatment is performed at a temperature close to the crystallization temperature of the piezoelectric film (525 to 550 ° C. when the piezoelectric film is a PZT film), the firing limit film thickness can be improved. As a result, the film thickness for each baking is conventionally about 200 to 300 nm, whereas in the present invention, the film thickness for each baking can be increased up to 1000 nm. Thereby, the composition gradient in the film thickness direction of the piezoelectric film is reduced, and the piezoelectric characteristics are improved. For example, when the piezoelectric film is a PZT film, the composition gradient of Zr / Ti in the film thickness direction is reduced, and the piezoelectric characteristics are improved.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
[Preparation of base substrate]
A 4-inch silicon substrate was prepared as the substrate. First, a 500 nm oxide film was formed on the surface of the silicon substrate by thermal oxidation. Next, after forming a titanium film having a thickness of 20 nm on the oxide film by sputtering, the titanium oxide film is formed by baking at a temperature of 700 ° C. for 1 minute in an oxygen atmosphere by rapid heating treatment (RTA). did. Next, a (111) -oriented Pt lower electrode having a thickness of 100 nm was formed on the titanium oxide film by sputtering. Further, a (100) -oriented 60 nm thick orientation control layer was formed on the (111) -oriented Pt lower electrode. This substrate was used as a base substrate.

  The orientation control layer was formed on the Pt lower electrode by the following method. First, Zr tetra n-butoxide (Z source), Ti isopropoxide (Ti source), and acetylacetone (stabilizer) were placed in a reaction vessel and refluxed in a nitrogen atmosphere. Next, lead acetate trihydrate (Pb source) is added to this compound, and propylene glycol (solvent) is added, refluxed in a nitrogen atmosphere, and distilled under reduced pressure to remove by-products. Propylene glycol was added to adjust the concentration, and diluted alcohol was further added to adjust the concentration to 12% by mass. Each metal ratio in terms of oxide was Pb / Zr / Ti = 110/52/48. The composition for orientation control layers containing the metal compound of this was obtained. Next, the composition for orientation control layer was applied onto the Pt lower electrode by spin coating at 500 rpm for 3 seconds and then 3000 rpm for 15 seconds while dropping the composition for orientation control layer on the Pt lower electrode. . Subsequently, using a hot plate, drying and calcination were performed in an air atmosphere at a temperature of 150 ° C. for 5 minutes. Furthermore, after performing the application | coating of the said composition for orientation control layers, drying, and calcining once, it heated to 700 degreeC with the temperature increase rate of 10 degree-C / sec in oxygen atmosphere, and hold | maintained at this temperature for 1 minute An orientation control layer having a thickness of 60 nm was obtained by performing calcination and crystallization.

[Preparation of piezoelectric film]
First, 1 drop (500 μL) of sol-gel solution (Mitsubishi Materials Corporation: 25 mass% PZT-N solution (metal composition ratio, Pb / Zr / Ti = 115/52/48)) per second on the base substrate. While dropping dropwise, spin coating was performed at a rotational speed of 3500 rpm for 30 seconds to apply a sol-gel solution on the base substrate to produce a substrate with a coating film. Next, this coated substrate was calcined on a hot plate at 285 ° C. for 3 minutes, and then subjected to an intermediate heat treatment in which rapid heat treatment (RTA) was held at a temperature of 575 ° C. for 1 minute in an oxygen atmosphere. A substrate with a film was prepared. Furthermore, after repeating the operations of spin coating, calcination and intermediate heat treatment of the sol-gel solution four times, firing was performed by holding at a temperature of 700 ° C. for 1 minute in an oxygen atmosphere by rapid heating treatment (RTA), and piezoelectric material A substrate with a film was obtained. This substrate with a piezoelectric film was referred to as Example 1.

<Examples 2 to 10>
As shown in Table 1, PZT films were produced in the same manner as in Example 1 except that the spin coating conditions, the temperature of the intermediate heat treatment, the number of laminations / firing, or the number of firings were varied. These PZT films were designated as Examples 2 to 10. In Table 1, “25% PZT” of the sol-gel liquid is a 25 mass% PZT-N liquid (metal composition ratio, Pb / Zr / Ti = 115/52/48) manufactured by Mitsubishi Materials Corporation. Moreover, in Table 1, “25% PLZT” of the sol-gel liquid is a 25 mass% PLZT-N liquid manufactured by Mitsubishi Materials Corporation (metal composition ratio, Pb / La / Zr / Ti = 115/2/52/48). It is. Further, in Table 1, “25% PNbZT” of the sol-gel liquid is a 25 mass% PNbZT-N liquid manufactured by Mitsubishi Materials Corporation (metal composition ratio, Pb / Nb / Zr / Ti = 115/2/52/48). It is. Furthermore, in Table 1, “the number of laminations / firing” is the number of laminations of the intermediate heat treatment film for each firing.

<Comparative Examples 1-12>
As shown in Table 1, a 1000 nm thick PZT film was obtained in the same manner as in Example 1 except that the temperature of the intermediate heat treatment was changed from 375 ° C. to 700 ° C. These PZT films were referred to as Comparative Examples 1-12.

<Comparative test 1 and evaluation>
The film thickness, presence / absence of cracks, presence / absence of peeling, crystallinity, and voltage constant of the piezoelectric films of Examples 1 to 10 and Comparative Examples 1 to 12 were measured.
(1) Film thickness of piezoelectric film The total film thickness of the piezoelectric film was measured by SEM observation. The film thickness for each firing of the piezoelectric film was determined by dividing the total film thickness by the number of firings.
(2) Presence / absence of cracks in the piezoelectric film and presence / absence of peeling The presence / absence of cracks in the piezoelectric film and the presence / absence of peeling were visually evaluated.
(3) Crystallinity of the piezoelectric film The crystallinity of the piezoelectric film is evaluated by performing an XRD analysis of the piezoelectric film by a concentration method using an X-ray diffraction (XRD) apparatus (Spectris, model: EMPYREAN). did. Specifically, the half-value width of the diffraction peak derived from the (100) plane of the PZT film and the half-value width of the diffraction peak derived from the (200) plane of the PZT film are measured. Crystallinity was evaluated. CuKα rays were used as characteristic X-rays.
(4) Piezoelectric Constant of Piezoelectric Film After forming a Pt upper electrode on the surface of the substrate with the piezoelectric film of Examples 1 to 10 and Comparative Examples 1 to 12 by sputtering, the Pt lower electrode is exposed by etching, and further Evaluation samples of Examples 1 to 10 and Comparative Examples 1 to 12 were produced by heat treatment for 1 minute in an oxygen atmosphere. The electrode was formed in a circular shape having a thickness of 150 nm and an area of 3 mm ² . The piezoelectric constant d ₃₃ of the piezoelectric film was measured using a DBLI system (manufactured by aix ACCT) for these piezoelectric elements. The DBLI system, the piezoelectric film to ± 25V (Frequency: 1 kHz) was measured mechanical displacement ratio of 33 direction per field when an AC voltage is applied as a piezoelectric constant d _33. These results are shown in Table 2 and FIGS.

  As is clear from Table 2, in Comparative Examples 1 to 6 where the intermediate heat treatment temperature is as low as 375 to 500 ° C., cracks and peeling occurred in the piezoelectric film, whereas the intermediate heat treatment temperature was appropriate as 525 to 550 ° C. In certain Examples 1 to 10 and Comparative Examples 7 to 12 having a high intermediate heat treatment temperature of 575 to 700 ° C., cracks and peeling did not occur in the piezoelectric film.

  As is clear from Table 2 and FIGS. 1 to 3, the piezoelectric film of Comparative Examples 1 to 6 having a low intermediate heat treatment temperature of 375 to 500 ° C., and Comparative Examples 7 to 12 having a high intermediate heat treatment temperature of 575 to 700 ° C. In the piezoelectric film of Example 1, the half-value width of the diffraction peak derived from the (100) plane was as large as 0.155 to 0.199 degrees, whereas the intermediate heat treatment temperature was suitable as 525 to 550 ° C. 10 to 10, the half-value width of the diffraction peak derived from the (100) plane was as small as 0.128 to 0.150 degrees. It is clear from FIG. 2 that the piezoelectric film of Example 1 has a smaller half-value width of the diffraction peak derived from the (100) plane as compared with the piezoelectric film of Comparative Example 1. Further, the piezoelectric films of Comparative Examples 1 to 6 having a low intermediate heat treatment temperature of 375 to 500 ° C. and the piezoelectric films of Comparative Examples 7 to 12 having a high intermediate heat treatment temperature of 575 to 700 ° C. are derived from the (200) plane. In the piezoelectric films of Examples 1 to 10, in which the half-value width of the diffraction peak to be increased is as large as 0.412 to 0.599 degrees, but the intermediate heat treatment temperature is appropriate as 525 to 550 ° C., the (200) plane The full width at half maximum of the diffraction peak derived from was reduced to 0.345 to 0.396 degrees. It is clear from FIG. 3 that the piezoelectric film of Example 1 has a smaller half-value width of the diffraction peak derived from the (200) plane as compared with the piezoelectric film of Comparative Example 1.

Further, in the piezoelectric films of Comparative Examples 1 to 6 having a low intermediate heat treatment temperature of 375 to 500 ° C. and the piezoelectric films of Comparative Examples 7 to 12 having a high intermediate heat treatment temperature of 575 to 700 ° C., the piezoelectric constant d ₃₃ is 142. The piezoelectric constant d ₃₃ was as high as 210 to 282 pm / V in the piezoelectric films of Examples 1 to 10 where the intermediate heat treatment temperature was appropriate as 525 to 550 ° C., whereas it was as low as ˜192 pm / V. In Comparative Examples 1 to 12, when the film thickness for each firing was increased to 1000 nm, cracks or peeling occurred, the half-value width increased, or the piezoelectric constant d ₃₃ decreased. In 2 and 7 to 10, even when the film thickness for each firing was increased to 1000 nm, cracks and peeling did not occur, the full width at half maximum was reduced, and the piezoelectric constant d ₃₃ was increased.

  The piezoelectric film of the present invention can be used for vibration power generation elements, sensors, actuators, inkjet heads, autofocus, and the like.

Claims (3)

A piezoelectric film formed on a substrate and having a PZT-based or PT-based perovskite structure,
The half-value width of the diffraction peak derived from the (100) plane measured by X-ray diffraction is 0.15 degrees or less, and the half-value width of the diffraction peak derived from the (200) plane is 0.40 degrees or less. A characteristic piezoelectric film.   2. The piezoelectric film according to claim 1, wherein when the number of firings is one, the total film thickness is 500 nm or more, and when the number of firings is two or more, the film thickness at each firing interface is 500 nm or more.   When the perovskite structure is a PZT system and the Zr / Ti concentration ratio is analyzed in the film thickness direction, the Zr / Ti concentration ratio has one or more layers that gradually increase as the distance from the substrate increases. The piezoelectric film according to claim 1, wherein each layer has a thickness of 500 to 1000 nm.

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