JP6237152B2 - Thin film piezoelectric element, thin film piezoelectric actuator, thin film piezoelectric sensor, hard disk drive, and ink jet printer apparatus - Google Patents

Description

  The present invention relates to a thin film piezoelectric element using a thin film piezoelectric material, a thin film piezoelectric actuator using the thin film piezoelectric element, a thin film piezoelectric sensor, a hard disk drive including the thin film piezoelectric actuator, and an ink jet printer apparatus.

In recent years, thin film piezoelectric elements using thin film piezoelectric materials instead of bulk piezoelectric materials have been put into practical use. For example, a gyro sensor, a pressure sensor, a pulse wave sensor, a shock sensor, a microphone, or the like using a piezoelectric effect that converts a force applied to the piezoelectric thin film into a voltage, or a piezoelectric thin film when a voltage is applied to the piezoelectric thin film. Examples include an actuator, an inkjet head, a speaker, a buzzer, and a resonator using a deformed inverse piezoelectric effect.

When the piezoelectric material is made thin, the element can be miniaturized, and the applicable fields are widened, and a large number of elements can be manufactured on the substrate at once, so that mass productivity is increased. There are also many advantages in terms of performance, such as improved sensitivity when used as a sensor.

In a piezoelectric element, if the dielectric loss of a piezoelectric material is large, heat is generated during operation, which often causes a problem in reliability. However, a material having a dielectric loss as low as that of a bulk piezoelectric material has not been found in a thin film piezoelectric material. Therefore, the design of a piezoelectric thin film with a low dielectric loss is an important issue.

In addition, lead zirconate titanate (PZT) is well known as an excellent piezoelectric material, but because it contains lead, consideration has been given to alternative (non-lead) materials in consideration of the environment and the human body. ing. However, an alternative material having piezoelectric properties equivalent to PZT has not appeared.

JP 2011-204887 A JP 2011-109037 A

One of the important elements in piezoelectric properties is dielectric loss. Due to the presence of the dielectric loss, a part of the electric field applied to the piezoelectric material is consumed as thermal energy. In general, D = ε · ε ₀ · E (D is the electric flux density, E is the electric field, ε is the relative permittivity, and ε ₀ is the relative permittivity of vacuum) is established in the piezoelectric material. When the electric field E is an alternating current, the dielectric constant ε is a real number when there is no dielectric loss, but becomes a complex number (= ε′−j · ε ″) when there is a dielectric loss. Here, the real part ε ′. Is usually called the dielectric constant, and the imaginary part ε ″ corresponds to the dielectric loss. Tan δ = ε ″ / ε ′ is called the dielectric loss tangent, and δ is called the loss angle. The dielectric loss is that the electric flux density D of the dielectric cannot immediately follow the electric field E, and the phase of D is greater than the phase of E. This is caused by a delay of δ, the smaller the dielectric loss of the dielectric material, the better.

As a technique for reducing dielectric loss, there is a technique (Patent Document 1) in which carbon or hydrogen is mixed in a piezoelectric material. In many cases, it is necessary to review the conditions.

In addition, as a technique for improving the piezoelectric characteristic D31, there is a technique (Patent Document 2) in which the piezoelectric material is deviated from the stoichiometric composition. It cannot be fully used.

The present invention has been made in view of the above-mentioned problems of the prior art, and can obtain a larger displacement while reducing the dielectric loss of a piezoelectric thin film made of a lead-free piezoelectric material constituting the thin film piezoelectric element. An object of the present invention is to provide a thin film piezoelectric element.

In order to achieve the above object, a thin film piezoelectric element according to the present invention is a thin film piezoelectric element having a piezoelectric thin film and a pair of electrode films disposed so as to sandwich the piezoelectric thin film. has a composition formula _{(K 1-w-x Na} w Sr x) m (Nb 1-y Zr y) alkali niobate oxide of perovskite structure represented by _{O 3,} preferentially oriented in the (001) The thin film piezoelectric element is characterized in that 0.95 ≦ m <1.05 and 0.6 ≦ (m · x / y) ≦ 0.8.

When m is less than 0.95, the dielectric loss cannot be reduced. Moreover, when m is 1.05 or more, it is impossible to prevent the dielectric loss from increasing.

On the other hand, when m · x / y is less than 0.6, the dielectric loss cannot be sufficiently reduced in the vicinity of the stoichiometric composition where m is close to 1. Further, when m · x / y exceeds 0.8, it is impossible to prevent the dielectric loss from increasing near the stoichiometric composition. When these two composition regions are satisfied, a sufficiently small dielectric loss is realized.

When the piezoelectric thin film used for the thin film piezoelectric element has a composition in the vicinity of the stoichiometric composition, lattice defects are hardly formed in the perovskite structure, and more stable piezoelectric and dielectric characteristics can be obtained.

Since the piezoelectric thin film has a perovskite structure and is preferentially oriented to (001), the piezoelectric characteristics can be increased while suppressing the dielectric loss of the thin film piezoelectric element. When the piezoelectric thin film is preferentially oriented in a direction other than (001), dielectric loss cannot be reduced, and sufficient piezoelectric characteristics cannot be obtained.

Here, the preferential orientation means that the ratio of the main orientation obtained by X-ray diffraction measurement, that is, the intensity of the strongest signal, to the total peak intensity is 50% or more. The (001) degree of orientation refers to (001) peak intensity / total peak intensity and is expressed in (%).

The composition of the piezoelectric thin film preferably has a Na (sodium) / (Na + K (potassium)) ratio of 0.5 or more and 0.75 or less. By setting the Na / (Na + K) ratio to 0.5 or more, the leakage current density when a voltage is applied to the electrode film is further reduced. Moreover, the piezoelectric characteristics are further improved by setting the Na / (Na + K) ratio to 0.75 or less.

If the leakage current density of the piezoelectric element is 1 × 10 ⁻⁵ A / cm ² or less, it is practical, but more preferably 1 × 10 ⁻⁷ A / cm ² or less.

In the thin film piezoelectric element according to the present invention, it is preferable to have a strontium ruthenate thin film between the piezoelectric thin film and at least one of the pair of electrode films. By using a strontium ruthenate thin film as an intermediate film and forming it before forming the piezoelectric thin film, the piezoelectric thin film is easily preferentially oriented to (001).

The thin film piezoelectric actuator according to the present invention has a thin film piezoelectric element having an alkali niobium oxide-based perovskite structure represented by the above composition formula and preferentially oriented to (001). Specific examples of the thin film piezoelectric actuator include a head assembly of a hard disk drive and a piezoelectric actuator of an ink jet printer head.

The thin film piezoelectric sensor according to the present invention includes a thin film piezoelectric element having an alkali niobium oxide perovskite structure represented by the above composition formula and preferentially oriented to (001). Specific examples of the thin film piezoelectric sensor include a gyro sensor, a pressure sensor, and a pulse wave sensor.

The thin film piezoelectric actuator is used in the hard disk drive and the ink jet printer apparatus according to the present invention.

Since the thin film piezoelectric element according to the present invention can have a smaller dielectric loss than the conventional thin film piezoelectric element, the thin film piezoelectric element, the thin film piezoelectric actuator, the thin film piezoelectric sensor, the hard disk drive, and the ink jet printer apparatus according to the present invention. In the operation, the operation abnormality due to heat generation does not occur during the operation, and the reliability can be improved.

In addition, the thin film piezoelectric element according to the present invention can be applied to a high frequency element because the dielectric loss in the high frequency band is kept low.

Since the piezoelectric thin film according to the present invention is a lead-free piezoelectric material, its influence on the environment and the human body is kept low. Therefore, the thin film piezoelectric element, the thin film piezoelectric actuator, the thin film piezoelectric sensor, the hard disk drive, and the ink jet printer apparatus according to the present invention can be applied to applications that have been difficult to use.

It is a correlation graph of Tanδ-measurement frequency of a conventional lead-free piezoelectric thin film. 1 is a structural diagram of a thin film piezoelectric element according to the present invention. 1 is a structural diagram of an example of a thin film piezoelectric actuator according to the present invention. FIG. 6 is a structural diagram of another example of a thin film piezoelectric actuator according to the present invention. 1 is a structural diagram of an example of a thin film piezoelectric sensor according to the present invention. It is a structural diagram of the 2nd example of the thin film piezoelectric sensor concerning this invention. FIG. 4 is a structural diagram of a third example of a thin film piezoelectric sensor according to the present invention. 1 is a structural diagram of a hard disk drive according to the present invention. 1 is a structural diagram of an ink jet printer apparatus according to the present invention. It is a correlation graph of Tanδ-measurement frequency of the lead-free piezoelectric thin film according to the present invention. It is a figure which shows the relationship between (001) orientation degree of a lead-free piezoelectric thin film, and Tan (delta).

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals. Also, the positional relationship between the top, bottom, left and right is as shown in the drawing. Further, when the description overlaps, the description is omitted.

(Thin film piezoelectric element)
FIG. 1 shows a correlation graph of dielectric tangent Tan δ-measurement frequency of a conventional lead-free piezoelectric thin film. It can be seen that Tan δ increases with increasing frequency.

FIG. 2 shows a thin film piezoelectric element 100 according to this embodiment. The thin film piezoelectric element 100 includes a substrate 7, a first electrode film 5 provided on the substrate 7, an intermediate film 4 formed on the first electrode film 5, and a piezoelectric thin film 3 formed on the intermediate film 4. And a second electrode film 1 formed on the piezoelectric thin film 3.

As the substrate 7, for example, a silicon substrate having a (100) plane orientation can be used. As an example, the substrate 7 has a thickness of 100 μm or more and 1000 μm or less. Further, as the substrate 7, in addition to a silicon substrate having a plane orientation different from the (100) plane, a silicon insulator (SOI) substrate, a quartz glass substrate, a compound semiconductor substrate made of GaAs, a sapphire substrate, a metal made of stainless steel, etc. A substrate, a MgO substrate, a SrTiO ₃ substrate, or the like can also be used.

As an example, the first electrode film 5 is formed of Pt (platinum). The first electrode film 5 preferably has a thickness of 0.02 μm or more and 1.0 μm or less. If the thickness is less than 0.02 μm, the function as an electrode becomes insufficient, and if it exceeds 1.0 μm, there is a problem that the displacement characteristics of the piezoelectric material are hindered. When a Pt film is formed by sputtering on a silicon substrate having a (100) plane orientation heated to about 400 to 500 ° C., it becomes a highly oriented film oriented to (100), and the piezoelectric thin film 3 formed thereafter is also high. It can be set as the piezoelectric thin film 3 which has orientation.

The piezoelectric thin film 3, also referred to as formula _{(K 1-w-x Na} w Sr x) m (Nb 1-y Zr y) O 3 potassium sodium niobate is potassium sodium niobate compound represented by (hereinafter KNN ) Is used. In this case, m is the range of the formula (1), and m · x / y corresponding to the Sr / Zr composition ratio is the range of the formula (2).
0.95 ≦ m <1.05 (1)
0.6 ≦ (m · x / y) ≦ 0.8 Expression (2)
When these two composition regions are satisfied, a sufficiently small dielectric loss is realized. In addition, elements such as Ta (tantalum), Li (lithium), Ba (barium), and Mn (manganese) can be added to improve the Curie point and reduce the leakage current density. The thickness of the piezoelectric thin film 3 is not specifically limited, For example, it can be set as about 0.5-5 micrometers.

The piezoelectric thin film 3 is formed by heating the substrate 7 on which the first electrode film 5 is formed to about 400 to 600 ° C., and by sputtering or vapor deposition.

In this piezoelectric thin film 3, the Na / (Na + K) ratio can be 0.5 or more and 0.75 or less. Leakage current density becomes small by setting it as 0.5 or more. A piezoelectric characteristic improves by setting it as 0.75 or less.

The piezoelectric thin film 3 may contain a small amount of elements and compounds other than the above composition as long as the structure and characteristics are not greatly affected.

The piezoelectric thin film 3 preferably has a dielectric loss tangent Tan δ 100 of 0.05 or less at a measurement frequency of 100 Hz. This prevents problems such as heat generation during operation of the piezoelectric thin film 3.

Needless to say, it is preferable that the dielectric loss tangent Tan δ 100 is small, but the lower limit that can be actually realized is about 0.01.

The piezoelectric thin film 3 preferably has a ratio Tanδ10000 / Tanδ100 of a dielectric loss tangent Tanδ100 at a measurement frequency of 100 Hz and a dielectric loss tangent Tanδ10000 at a measurement frequency of 10 KHz of 1.5 or less. This makes it possible to use a thin film piezoelectric element even in a high frequency range.

Since the dielectric loss tangent generally increases as the measurement frequency increases, the value of Tanδ10000 / Tanδ100 is usually 1.0 or more.

As an example, the second electrode film 1 is made of Pt (platinum). As an example, the second electrode film 1 has a thickness of 0.02 μm or more and 1.0 μm or less. The second electrode film 1 is formed by the sputtering method in the same manner as the first electrode film 5.

As shown in FIG. 2, an intermediate film 4 can be provided between the first electrode film 5 and the piezoelectric thin film 3. The material of the intermediate film 4 is preferably strontium ruthenate: SrRuO ₃ which is a conductive oxide. Thereby, the piezoelectric thin film 3 is easily preferentially oriented to (001), and as a result, the piezoelectric characteristics and dielectric loss can be improved.

It is preferable that the intermediate film 4 has a thickness of 0.01 μm or more and 0.1 μm or less. By setting the thickness to 0.01 μm or more and 1 μm or less, the crystallinity of the intermediate film 4 can be increased, and the crystallinity of the piezoelectric thin film 3 can be increased accordingly. As a result, the effect of improving piezoelectric characteristics and reducing dielectric loss is increased.

In the thin film piezoelectric element 100, the substrate 7 may be removed. In the case of a device that requires a displacement amount of the element, the displacement amount can be increased by removing the substrate 7. Various protective films may be formed on the thin film piezoelectric element 100.

(Thin film piezoelectric actuator)
FIG. 3 is a configuration diagram of a head assembly mounted on a hard disk drive as an example of a thin film piezoelectric actuator using these thin film piezoelectric elements. As shown in this figure, the head assembly 200 includes a base plate 10, a load beam 11, a flexure 12, first and second thin film piezoelectric elements 13 as drive elements, and a head element 14a as main components. The slider 14 is provided.

The load beam 11 includes a base end portion 11b fixed to the base plate 10 by beam welding or the like, and first and second plate spring portions 11c and 11d extending in a tapered manner from the base end portion 11b. And an opening portion 11e formed between the first and second leaf spring portions 11c and 11d, and the first and second leaf spring portions 11c and 11d extending linearly and in a tapered manner. A beam main portion 11f.

The first and second thin film piezoelectric elements 13 are respectively arranged on a wiring flexible substrate 15 that is a part of the flexure 12 with a predetermined distance therebetween. The slider 14 is fixed to the tip portion of the flexure 12 and rotates with the expansion and contraction of the first and second thin film piezoelectric elements 13.

The first and second thin film piezoelectric elements 13 are composed of a piezoelectric thin film and a pair of electrode films sandwiching the piezoelectric thin film. As this piezoelectric thin film, an alkali niobic acid based piezoelectric thin film according to the present invention having a small dielectric loss is used. Thus, heat generation during operation can be suppressed and a sufficient amount of displacement can be obtained.

FIG. 4 is a configuration diagram of a piezoelectric actuator of an ink jet printer head as another example of a thin film piezoelectric actuator using the above thin film piezoelectric element.

The piezoelectric actuator 300 is configured by laminating an insulating film 23, a lower electrode film 24, a piezoelectric thin film 25, and an upper electrode film 26 on a base material 20.

When a predetermined ejection signal is not supplied and no voltage is applied between the lower electrode film 24 and the upper electrode film 26, the piezoelectric thin film 25 is not deformed. No pressure change occurs in the pressure chamber 21 provided with the thin film piezoelectric element to which no ejection signal is supplied, and no ink droplet is ejected from the nozzle 27.

On the other hand, when a predetermined discharge signal is supplied and a constant voltage is applied between the lower electrode film 24 and the upper electrode film 26, the piezoelectric thin film 25 is deformed. In the pressure chamber 21 provided with the thin film piezoelectric element to which the ejection signal is supplied, the insulating film 23 is greatly bent. For this reason, the pressure in the pressure chamber 21 increases instantaneously, and ink droplets are ejected from the nozzles 27.

Here, by using an alkali niobic acid-based piezoelectric thin film having a small dielectric loss according to the present invention as the piezoelectric thin film, heat generation during operation can be suppressed and a sufficient amount of displacement can be obtained.

(Thin film piezoelectric sensor)
FIG. 5A is a configuration diagram (plan view) of a gyro sensor as an example of a thin film piezoelectric sensor using the above thin film piezoelectric element, and FIG. 5B is an AA line in FIG. 5A. It is arrow sectional drawing.

The gyro sensor 400 is a tuning fork vibrator type angular velocity detecting element including a base 110 and two arms 120 and 130 connected to one surface of the base 110. The gyro sensor 400 is obtained by finely processing the piezoelectric thin film 30, the upper electrode film 31, and the lower electrode film 32 constituting the thin film piezoelectric element according to the shape of the tuning fork vibrator, Each part (base part 110 and arms 120 and 130) is integrally formed of a thin film piezoelectric element.

Drive electrode films 31 a and 31 b and a detection electrode film 31 d are respectively formed on the first main surface of one arm 120. Similarly, drive electrode films 31a and 31b and a detection electrode film 31c are formed on the first main surface of the other arm 130, respectively. Each of these electrode films 31a, 31b, 31c, and 31d is obtained by etching the upper electrode film 31 into a predetermined electrode shape.

The lower electrode film 32 formed on the second main surface of each of the base 110 and the arms 120 and 130 (the main surface on the back side of the first main surface) is a ground electrode of the gyro sensor 400. Function as.

Here, the longitudinal direction of each of the arms 120 and 130 is defined as the Z direction, and the plane including the principal surfaces of the two arms 120 and 130 is defined as the XZ plane, and the XYZ orthogonal coordinate system is defined.

When a drive signal is supplied to the drive electrode films 31a and 31b, the two arms 120 and 130 are excited in the in-plane vibration mode. The in-plane vibration mode refers to a vibration mode in which the two arms 120 and 130 are excited in a direction parallel to the main surfaces of the two arms 120 and 130. For example, when one arm 120 is excited at the speed V1 in the −X direction, the other arm 130 is excited at the speed V2 in the + X direction.

In this state, when rotation of the angular velocity ω is applied to the gyro sensor 400 with the Z axis as the rotation axis, Coriolis force acts in the direction perpendicular to the velocity direction for each of the two arms 120 and 130 to excite in the out-of-plane vibration mode. start. The out-of-plane vibration mode refers to a vibration mode in which the two arms 120 and 130 are excited in a direction orthogonal to the main surfaces of the two arms 120 and 130. For example, when the Coriolis force F1 acting on one arm 120 is in the −Y direction, the Coriolis force F2 acting on the other arm 130 is in the + Y direction.

Since the magnitude of the Coriolis forces F1 and F2 is proportional to the angular velocity ω, mechanical distortion of the arms 120 and 130 caused by the Coriolis forces F1 and F2 is converted into an electric signal (detection signal) by the piezoelectric thin film 30, and this is detected. The angular velocity ω can be obtained by taking out from the electrode films 31c and 31d.

By using an alkali niobic acid type piezoelectric thin film having a small dielectric loss according to the present invention as this piezoelectric thin film, heat generation during operation can be suppressed and sufficient detection sensitivity can be obtained.

FIG. 6 is a configuration diagram of a pressure sensor as a second example of a thin film piezoelectric sensor using the above thin film piezoelectric element.

The pressure sensor 500 has a cavity 45 for responding to pressure, and includes a support body 44 that supports the thin film piezoelectric element 40, a current amplifier 46, and a voltage measuring instrument 47. The thin film piezoelectric element 40 includes a common electrode film 41, a piezoelectric thin film 42, and an individual electrode film 43, which are stacked on a support 44 in this order. Here, when an external force is applied, the thin film piezoelectric element 40 bends, and a voltage is detected by the voltage measuring device 47.

By using an alkali niobic acid type piezoelectric thin film having a small dielectric loss according to the present invention as this piezoelectric thin film, heat generation during operation can be suppressed and sufficient detection sensitivity can be obtained.

FIG. 7 is a configuration diagram of a pulse wave sensor as a third example of a thin film piezoelectric sensor using the above thin film piezoelectric element.

The pulse wave sensor 600 has a configuration in which a transmitting piezoelectric element and a receiving piezoelectric element are mounted on a base material 51. Here, in the transmitting piezoelectric element, electrode films 54a and 55a are formed on both surfaces in the thickness direction of the transmitting piezoelectric thin film 52, and in the receiving piezoelectric element, electrode films are also formed on both surfaces in the thickness direction of the receiving piezoelectric thin film 53. 54b and 55b are formed. In addition, the substrate 51 is provided with an electrode 56 and an upper surface electrode 57, and the electrode films 54 a and 54 b and the upper surface electrode 57 are electrically connected to each other by a wiring 58.

In order to detect the pulse of the living body, first, the back surface of the substrate of the pulse wave sensor 600 (the surface on which the piezoelectric element is not mounted) is brought into contact with the living body. When the pulse is detected, a specific driving voltage signal is output to both electrode films 54a and 55a of the transmitting piezoelectric element. The transmitting piezoelectric element is excited according to the driving voltage signal input to both electrode films 54a and 55a to generate an ultrasonic wave, and transmits the ultrasonic wave into the living body. The ultrasonic wave transmitted into the living body is reflected by the blood flow and received by the receiving piezoelectric element. The receiving piezoelectric element converts the received ultrasonic wave into a voltage signal and outputs it from both electrode films 54b and 55b.

By using an alkali niobic acid-based piezoelectric thin film having a low dielectric loss according to the present invention as both the piezoelectric thin films, heat generation during operation can be suppressed and sufficient detection sensitivity can be obtained.

(Hard disk drive)
FIG. 8 is a configuration diagram of a hard disk drive on which the head assembly shown in FIG. 3 is mounted.

The hard disk drive 700 includes a hard disk 61 as a recording medium and a head stack assembly 62 that records and reproduces magnetic information on the hard disk 61 in a housing 60. The hard disk 61 is rotated by a motor (not shown).

The head stack assembly 62 is an assembly composed of an actuator arm 64 rotatably supported around a spindle by a voice coil motor 63 and a head assembly 65 connected to the actuator arm 64 in the depth direction of the figure. A plurality of layers are stacked. A head slider 14 is attached to the tip of the head assembly 65 so as to face the hard disk 61 (see FIG. 3A).

The head assembly 65 (200) employs a form in which the head element 14a (see FIG. 3) is changed in two stages. The relatively large movement of the head element 14 a is controlled by driving the entire head assembly 65 and actuator arm 64 by the voice coil motor 63, and the minute movement is controlled by driving the head slider 14 by the tip of the head assembly 65.

In the thin film piezoelectric element used in the head assembly 65, the use of an alkali niobic acid type piezoelectric thin film having a small dielectric loss according to the present invention as the piezoelectric thin film suppresses heat generation during operation and obtains a sufficient amount of displacement. Can do.

(Inkjet printer device)
FIG. 9 is a configuration diagram of an ink jet printer apparatus on which the piezoelectric actuator 300 of the ink jet printer head shown in FIG. 4 is mounted.

The ink jet printer apparatus 800 mainly includes an ink jet printer head 70, a main body 71, a tray 72, and a head driving mechanism 73. The piezoelectric actuator 300 in FIG. 4 is mounted on the ink jet printer head 70.

The ink jet printer apparatus 800 includes a total of four ink cartridges, yellow, magenta, cyan, and black, and is configured to be capable of full color printing. The ink jet printer apparatus 800 includes a dedicated controller board and the like, and controls ink ejection timing of the ink jet printer head 70 and scanning of the head drive mechanism 73. The main body 71 has a tray 72 on the back and an auto sheet feeder (automatic continuous paper feed mechanism) 76 inside the main body 71 to automatically feed out the recording paper 75 and eject the recording paper 75 from the front discharge port 74. Make paper.

In the thin film piezoelectric element used for the piezoelectric actuator of the ink jet printer head 70, the use of the alkali niobic acid type piezoelectric thin film having a small dielectric loss according to the present invention as the piezoelectric thin film provides high safety and low heat generation during operation. An ink jet printer apparatus can be provided.

(Thin film piezoelectric element)
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
The thin film piezoelectric element 100 of Example 1 was produced as follows.

A silicon substrate 7 having a (100) plane orientation was heated to 400 ° C., and Pt was formed on the silicon substrate 7 as a first electrode film 5 by a 200 nm sputtering method while epitaxially growing in the plane orientation of the silicon substrate 7. The film formation rate at this time is 0.2 nm / sec.

Next, the silicon substrate 7 was heated to 550 ° C., and the piezoelectric thin film 3 was epitaxially grown by a 2000 nm sputtering method to form a film. As a sputtering target of the piezoelectric thin film 3 at this time, a sintered body having a composition of (K _0.17 Na _0.76 Sr _0.07 ) _0.96 (Nb _0.9 Zr _0.1 ) O ₃ was used. . The film composition of the piezoelectric thin film 3 is substantially the same as this target composition.

Next, Pt: 200 nm was formed by sputtering as the second electrode film 1 at room temperature.

Then, the laminated body containing the piezoelectric thin film 3 was patterned using photolithography, etched by RIE, and the silicon substrate 7 was diced to produce a thin film piezoelectric element 100 having a shape of 2 mm × 20 mm.

(Examples 2-9, Comparative Examples 1-5)
A thin film piezoelectric element 100 was produced in the same manner as in Example 1 except that the piezoelectric thin film 3 was formed using the material shown in Table 1 as a sputtering target as the sputtering target of the piezoelectric thin film 3.

(Examples 10 to 12)
As in Example 1, the silicon substrate 7 was heated to 400 ° C., and Pt was formed on the silicon substrate 7 by the 200 nm sputtering method as the first electrode film 5 while being epitaxially grown in the plane direction of the silicon substrate 7. On the first electrode film 5, strontium ruthenate: SrRuO ₃ was formed as an intermediate film 4 by a 35 nm sputtering method.

As the sputtering target of the piezoelectric thin film 3, the materials shown in Table 1 were used in Example 10. In Example 11, as shown in Table 1, Ba was further added at 0.11 at% and Ta at 6.5 at%. In Example 12, as shown in Table 1, 0.11 at% Ba, 6.5 at% Ta, and 0.35 at% Mn were used. At this time, each element was contained so as to be 100 at% in the entire piezoelectric thin film containing each element. Thereafter, a thin film piezoelectric element 100 was produced in the same manner as in Example 1.

(Evaluation of thin film piezoelectric element)
About each thin film piezoelectric element 100 of Examples 1-12 and Comparative Examples 1-6, the displacement amount when a voltage of 20V was applied was measured using the laser Doppler vibrometer (made by a Graphtec company). Further, the dielectric loss tangent of each thin film piezoelectric element 100 was measured with an impedance analyzer (manufactured by Agilent Technologies) 4294A at a measurement voltage of 0.5 mV and a measurement frequency of 100 to 10,000 Hz. Next, the leakage current density was evaluated using a ferroelectric evaluation system TF-1000 (manufactured by aixACCT) at a measurement voltage of ± 20 V and a measurement frequency of 100 Hz. Table 1 shows the measured values.

Table 1 shows the value of Tan δ 100 at a measurement frequency of 100 Hz and the ratio of Tan δ 100 at a measurement frequency of 100 Hz and Tan δ 10000 at a measurement frequency of 10 KHz (Tan δ 10000 / Tan δ 100). Tan δ100 of Comparative Examples 1 to 6 was a high value of 0.071 or more, but Tan δ100 of Examples 1 to 12 was a value of 0.059 or less. In many examples, a value of 0.05 or less was shown. Similarly, Tanδ10000 / Tanδ100 was a high value of 1.64 or more in Comparative Examples 1 to 6, but the values of Examples 1 to 12 were 1.4 or less.

Thus, having a composition formula _{(K 1-w-x Na} w Sr x) m (Nb 1-y Zr y) alkali niobate oxide of perovskite structure represented by _{O 3} (0.95 ≦ m <1.05, 0.6 ≦ (m · x / y) ≦ 0.8), in a thin film piezoelectric element using a piezoelectric thin film preferentially oriented to (001), sufficiently small Tanδ100 and Tanδ10000 / Tanδ100 Can be realized.

When Tan δ 100 is 0.05 or less, the piezoelectric thin film element does not generate heat during operation. When Tan δ 10000 / Tan δ 100 is 1.5 or less, the piezoelectric thin film element is operating even in the high frequency region. Never generate heat.

FIG. 10 shows a correlation graph of Tan δ-measurement frequency of the lead-free piezoelectric thin film in Example 12. It can be seen that the Tan δ of the lead-free piezoelectric thin film of the present invention is smaller than that of FIG. 1, which is the Tan δ-measurement frequency of the conventional lead-free piezoelectric thin film, in the entire frequency region where the measurement was performed.

FIG. 11 shows the (001) orientation degree and the measurement frequency of 100 Hz of the piezoelectric thin film 3 produced with various piezoelectric thin film compositions including Examples 2, 3, 11, 12 and Comparative Examples 1, 3, 5, 6 described above. The relationship between Tan δ and Tan δ 100 is shown. From this figure, it can be seen that when the piezoelectric thin film 3 is preferentially oriented to (001), that is, when the XRD peak intensity ratio exceeds 50%, Tan δ100 is as small as 0.05 or less.

Among the piezoelectric thin films having an alkali niobium oxide-based perovskite structure satisfying the above composition range, that is, 0.95 ≦ m <1.05, 0.6 ≦ (m · x / y) ≦ 0.8, Na / When the (Na + K) ratio was 0.5 or more and 0.75 or less, the leakage current and the piezoelectric characteristics were particularly good.

Regarding the leakage current density, in Example 5 in which the Na / (Na + K) ratio was less than 0.5, the leakage current density showed a value of 10 ⁻⁶ A / cm ² or more, whereas Na / ( In Examples 6 to 8 in which the Na + K) ratio was 0.5 or more and 0.75 or less, a leakage current density of 10 ⁻⁷ A / cm ² was obtained. Further, in Examples 1 to 4 and 9, where the Na / (Na + K) ratio exceeded 0.75, the displacement amount was slightly small, but the Na / (Na + K) ratio was 0.5 or more and 0.75 or less. In Examples 6 to 8, displacements exceeding 10 μm were shown.

As shown in Table 1, the displacement amounts of the thin film piezoelectric elements of Comparative Examples 1 to 6 were 4.2 to 6.6 μm, while the displacement amounts of Examples 1 to 12 were 6.5 to 11. A value of 2 μm was obtained. With regard to the piezoelectric characteristics of the thin film piezoelectric element, in the element shape of the present embodiment, if it is 5 μm or more, it is practical, but more preferably 10 μm or more.

In Comparative Examples 4 to 6, the displacement amount was 5 μm or more, but the leakage current density was high. This is considered to be because the number of lattice defects of the piezoelectric thin film 3 increased because the value of m was out of the preferred range or (Sr / Zr) was out of range. In Comparative Example 3 in which the piezoelectric thin film 3 is preferentially oriented in a direction other than (001), the leakage current density was a good value, but as described above, the dielectric loss could not be reduced, and Sufficient piezoelectric characteristics could not be obtained.

As described above, the thin film of Examples 10 to 12 having the intermediate layer 4 between the first electrode film 5 and the piezoelectric thin film 3 and adding Ba, Ta, and Mn to the sputtering target for the piezoelectric thin film. The piezoelectric element 100 had a displacement of 11.0 to 11.2 μm and Tanδ: Tanδ100 at a measurement frequency of 100 Hz of 0.018 to 0.024, and good results were obtained. In addition, a value of 10 ⁻⁸ A / cm ² was also obtained for the leakage current density. Therefore, the orientation of the piezoelectric thin film 3 is improved by inserting the intermediate layer 4, the displacement is increased by improving the piezoelectric characteristics, and the piezoelectric thin film having an alkali niobium oxide perovskite structure. It is apparent that a piezoelectric thin film element with a reduced leakage current density can also be obtained by adding Ba, Ta, and Mn.

A thin film piezoelectric element according to the present invention is in a predetermined composition range and has a perovskite structure having a perovskite structure preferentially oriented to (001), and a pair of electrodes arranged with the piezoelectric thin film interposed therebetween. This dielectric loss is small as the piezoelectric thin film of the piezoelectric actuator. By using a large displacement piezoelectric thin film, a sufficient displacement can be obtained without generating heat during driving.

Further, by using the piezoelectric thin film having a small dielectric loss according to the present invention as the piezoelectric thin film of the piezoelectric sensor and having a large displacement, sufficient detection sensitivity can be obtained without generating heat during operation.

In a thin film piezoelectric element used in a head assembly of a hard disk drive, a dielectric loss according to the present invention is small as a piezoelectric thin film, and sufficient accessibility is obtained without generating heat during driving by using a piezoelectric thin film with a large displacement. Can do.

In a thin film piezoelectric element used for a piezoelectric actuator of an ink jet printer head, the dielectric loss according to the present invention is small as a piezoelectric thin film, and a large displacement amount of the piezoelectric thin film provides high safety without generating heat during printing. An inkjet printer apparatus can be provided.

DESCRIPTION OF SYMBOLS 1 Second electrode film 3, 25, 30, 42 Piezoelectric thin film 4 Intermediate film 5 First electrode film 7 Substrate 10 Base plate 11 Load beam 12 Flexures 13, 40, 100 Thin film piezoelectric element 14 Slider 14a Head element 15 Flexible substrate 20 for wiring , 51 Base material 21 Pressure chamber 23 Insulating film 24, 32 Lower electrode film 26, 31 Upper electrode film 27 Nozzle 41 Common electrode film 43 Individual electrode film 44 Support body 45 Cavity 46 Current amplifier 47 Voltage measuring device 52 Transmitting piezoelectric film 53 Piezoelectric films 54a, 54b, 55a, 55b for reception Electrode film 56 Electrode 57 Upper electrode 58 Wiring 60 Housing 61 Hard disk 62 Head stack assembly 63 Voice coil motor 64 Actuator arm 65, 200 Head assembly 70 Inkjet printer head 71 Main body 72 g Lee 73 head driving mechanism 110 base 120, 130 arms 300 piezoelectric actuators 400 gyro sensor 500 pressure sensor 600 pulse wave sensor 700 hard disk drive 800 inkjet printer

Claims (7)

A thin film piezoelectric element having a piezoelectric thin film and a pair of electrode films arranged with the piezoelectric thin film interposed therebetween,
The piezoelectric thin film has a composition formula _{(K 1-w-x Na} w Sr x) m (Nb 1-y Zr y) alkali niobate oxide of perovskite structure represented by _{O 3,} the (001) A thin film piezoelectric element characterized by being preferentially oriented.
here,
0.95 ≦ m <1.05, 0.6 ≦ (m · x / y) ≦ 0.8 2. The thin film piezoelectric element according to claim 1, wherein the piezoelectric thin film has a Na (sodium) / (Na + K (potassium)) ratio of 0.5 or more and 0.75 or less. The thin film piezoelectric element according to claim 1, further comprising a strontium ruthenate thin film between the piezoelectric thin film and at least one of the pair of electrode films. A thin film piezoelectric actuator using the thin film piezoelectric element according to any one of claims 1 to 3. The thin film piezoelectric sensor using the thin film piezoelectric element of any one of Claims 1 thru | or 3. A hard disk drive comprising the thin film piezoelectric actuator according to claim 4. An inkjet printer apparatus comprising the thin film piezoelectric actuator according to claim 4.