JP6934746B2 - A method for manufacturing a laminated substrate having a piezoelectric film, an element having a piezoelectric film, and a laminated substrate having a piezoelectric film. - Google Patents

Description

The present invention relates to a laminated substrate having a piezoelectric film, an element having a piezoelectric film, and a method for manufacturing a laminated substrate having a piezoelectric film.

Piezoelectric bodies are widely used in functional electronic components such as sensors and actuators. As the material of the piezoelectric material, for example, sodium potassium niobate (KNN) is used (see, for example, Patent Documents 1 and 2). In recent years, there has been a strong demand for more versatile piezoelectric materials.

JP-A-2007-184513 Japanese Unexamined Patent Publication No. 2008-159807

An object of the present invention is to provide a piezoelectric membrane having enhanced versatility and related techniques thereof.

According to one aspect of the invention
A substrate, an electrode film formed on the substrate, and a piezoelectric film formed on the electrode film are provided.
The piezoelectric film is
The first piezoelectric thin film and the second piezoelectric thin film formed of a material different from the first piezoelectric thin film are laminated.
Provided are a laminated substrate having a piezoelectric film having a relative permittivity between the relative permittivity of the first piezoelectric thin film and the relative permittivity of the second piezoelectric thin film, and related techniques thereof.

According to the present invention, it is possible to provide a piezoelectric membrane having enhanced versatility and related technology.

It is a figure which shows an example of the cross-sectional structure of the laminated substrate 10 which concerns on one Embodiment of this invention. It is a figure which shows the modification of the cross-sectional structure of the laminated substrate 10 which concerns on one Embodiment of this invention. It is a schematic block diagram of the piezoelectric membrane device 30 which concerns on one Embodiment of this invention.

<One Embodiment of the present invention>
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(1) Configuration of Laminated Substrate As shown in FIG. 1, the laminated substrate 10 according to the present embodiment has a substrate 1, a lower electrode film 2 formed on the substrate 1, and a film formed on the lower electrode film 2. It is configured as a laminate including the piezoelectric film (piezoelectric thin film) 3 formed and the upper electrode film 4 formed on the piezoelectric film 3.

_{The substrate 1 is a single crystal silicon (Si) substrate 1a on which a surface oxide film (SiO 2} film) 1b such as a thermal oxide film or a CVD (Chemical Vapor Deposition) oxide film is formed, that is, a Si substrate having a surface oxide film. Can be preferably used. Further, as the substrate 1, as shown in FIG. 2, a Si substrate 1a having an insulating film 1d formed of an insulating material other than _{SiO 2 on its surface can also be used.} Further, as the substrate 1, a Si substrate 1a in which a Si (100) surface, a Si (111) surface, or the like is exposed on the surface, that is, a Si substrate having no surface oxide film 1b or insulating film 1d can also be used. The substrate 1 is formed of a metal material such as an SOI (Silicon On Insulator) substrate, a quartz glass (SiO ₂ ) substrate, a gallium arsenide (GaAs) substrate, a sapphire (Al ₂ O ₃ ) substrate, and stainless steel (SUS). It is also possible to use a metal substrate. The thickness of the single crystal Si substrate 1a can be, for example, 300 to 1000 μm, and the thickness of the surface oxide film 1b can be, for example, 5 to 3000 nm.

The lower electrode film 2 can be formed by using, for example, platinum (Pt). The lower electrode film 2 is a single crystal film or a polycrystalline film (hereinafter, these are also referred to as Pt films). The crystals constituting the Pt film are preferably preferentially oriented in the (111) plane orientation with respect to the surface of the substrate 1. That is, it is preferable that the surface of the Pt film (the surface serving as the base of the piezoelectric film 3) is mainly composed of the Pt (111) surface. The Pt film can be formed by using a method such as a sputtering method or a vapor deposition method. In addition to Pt, the lower electrode film 2 includes various metals such as gold (Au), ruthenium (Ru), and iridium (Ir), alloys containing these as main components, strontium ruthenate (SrRuO ₃ ), and lanthanum nickelate (LaNiO). It is also possible to form a film using a metal oxide such as _3). In order to improve the adhesion between the substrate 1 and the lower electrode film 2, for example, titanium (Ti), tantalum (Ta), titanium oxide (TIO ₂ ), nickel (Ni) and the like are the main components. The adhesion layer 6 is provided. The adhesion layer 6 can be formed into a film by using a method such as a sputtering method or a vapor deposition method. The thickness of the lower electrode film 2 can be, for example, 100 to 400 nm, and the thickness of the adhesion layer 6 can be, for example, 1 to 200 nm.

The piezoelectric film 3 is a laminate (composite film) in which a first piezoelectric thin film 3a formed of a piezoelectric material and a second piezoelectric thin film 3b formed of a piezoelectric material different from the first piezoelectric thin film 3a are laminated. Is. In the present embodiment, the piezoelectric film 3 is formed so that the lowermost layer is the first piezoelectric thin film 3a. That is, the first piezoelectric thin film 3a is arranged on the lower electrode film 2. Further, in the present embodiment, the first piezoelectric thin film 3a, the second piezoelectric thin film 3b, and the first piezoelectric thin film 3a are laminated in this order from the side of the lower electrode film 2 (substrate 1). That is, in the piezoelectric film 3, the second piezoelectric thin film 3b (above and below) is sandwiched between the first piezoelectric thin films 3a. The thickness of the piezoelectric film 3 (total thickness of the first piezoelectric thin film 3a and the second piezoelectric thin film 3b) can be, for example, 0.5 to 5 μm.

The first piezoelectric thin film 3a can be formed by using, for example, aluminum nitride (AlN). The first piezoelectric thin film 3a is an AlN single crystal film or a polycrystalline film (hereinafter, these are also referred to as an AlN film 3a). The AlN film 3a has a relative permittivity of, for example, about 10 when measured by applying a voltage of ± 1 V under the condition of a frequency of 1 kHz, and an absolute value | d ₃₁ | of the piezoelectric constant is, for example, about 5 pm / V. .. Hereinafter, in the present specification, the "relative permittivity when measured by applying a voltage of ± 1 V under the condition of a frequency of 1 kHz" is also simply referred to as "relative permittivity".

The crystals constituting the AlN film 3a are preferably preferentially oriented in the (001) plane orientation with respect to the surface of the substrate 1. That is, it is preferable that the surface of the AlN film 3a (the surface serving as the base of the second piezoelectric thin film 3b and the upper electrode film 4) is mainly composed of the AlN (001) surface. KNN on the Pt film (lower electrode film 2) preferentially oriented in the (111) plane orientation with respect to the surface of the substrate 1 and in the (001) plane orientation preferentially oriented with respect to the surface of the substrate 1 as described later. By directly forming the AlN film 3a on the film 3b, it becomes easy to preferentially orient the crystals constituting the AlN film 3a in the (001) plane direction with respect to the surface of the substrate 1. The AlN film 3a can be formed by using a method such as a sputtering method.

The thickness of the AlN film 3a can be, for example, 5 to 500 nm. When the piezoelectric film 3 has a plurality of AlN films 3a, the thickness of each AlN film 3a may be the same or different. In the following, in the piezoelectric film 3, the AlN film 3a arranged on the lower surface (lower electrode film 2 side) of the KNN film 3b is also referred to as a lower AlN film, and is arranged on the upper surface (upper electrode film 4 side) of the KNN film 3b. The AlN film 3a is also referred to as an upper AlN film.

The second piezoelectric thin film 3b contains, for example, potassium (K), sodium (Na), and niobium (Nb), and is an alkaline niobium oxide represented by _{the composition formula (K 1-x} Na _x ) NbO _{3, that is, niobium.} A film can be formed using sodium potassium acid (KNN). The coefficient x [= Na / (K + Na)] in the above composition formula has a magnitude within the range of 0 <x <1, preferably 0.4 ≦ x ≦ 0.7. The second piezoelectric thin film 3b becomes a KNN polycrystalline film (hereinafter, also referred to as a KNN film 3b). The crystal structure of KNN is a perovskite structure. The KNN film 3b has a relative permittivity of, for example, about 350 to 2000 when measured by applying a voltage of ± 1 V under the condition of a frequency of 1 kHz, and an absolute value | d ₃₁ | of the piezoelectric constant is, for example, 100 to 200 pm /. It is about V.

The KNN film 3b may contain elements other than K, Na, Nb such as copper (Cu), manganese (Mn), lithium (Li), Ta, and antimony (Sb) within a range of 5 at% or less. ..

The crystals constituting the KNN film 3b are preferably preferentially oriented in the (001) plane orientation with respect to the surface of the substrate 1. That is, it is preferable that the surface of the KNN film 3b (the surface serving as the base of the AlN film 3a (upper AlN film)) is mainly composed of the KNN (001) surface. By directly forming the KNN film 3b on the AlN film 3a (lower AlN film) which is preferentially oriented in the (001) plane direction with respect to the surface of the substrate 1, the crystals constituting the KNN film 3b are formed on the substrate 1. It becomes easy to preferentially orient the surface in the (001) plane direction. For example, 80% or more of the crystals constituting the KNN film 3b are oriented in the (001) plane orientation with respect to the surface of the substrate 1, and 80% or more of the surface of the KNN film 3b is KNN (001). ) It becomes possible to make a surface. The KNN film 3b is prepared by a sputtering method, a PLD (Pulsed Laser Deposition) method, or the like.
The film can be formed by using a method such as the sol-gel method.

As described above, the piezoelectric film 3 is a laminate of the AlN film 3a and the KNN film 3b. Therefore, the entire piezoelectric film 3 has a characteristic between the characteristics of the AlN film 3a and the characteristics of the KNN film 3b (intermediate band).

Specifically, the piezoelectric film 3 is within the range between the relative permittivity of the AlN film 3a and the relative permittivity of the KNN film 3b according to the respective film thickness ratios of the AlN film 3a and the KNN film 3b ( It has a predetermined relative permittivity (intermediate band). That is, the piezoelectric film 3 has a predetermined relative permittivity in the range of, for example, 10 or more and 2000 or less.

Further, the piezoelectric film 3 has an absolute value of the piezoelectric constant of the AlN film 3a | d ₃₁ | and an absolute value of the piezoelectric constant of the KNN film 3b | d according to the respective film thickness ratios of the AlN film 3a and the KNN film 3b. _{It has an absolute value | d 31} | of a predetermined piezoelectric constant within a range (intermediate band) between 31 |. That is, the absolute value | d ₃₁ | of the piezoelectric constant of the piezoelectric film 3 is, for example, a predetermined value within the range of 5 pm / V or more and 200 pm / V or less.

Since the piezoelectric constant of the piezoelectric film 3 is derived using the relative permittivity of the piezoelectric film 3, there is a certain correlation between the piezoelectric constant and the relative permittivity. For example, when the specific dielectric constant of the piezoelectric film 3 is high, the absolute value | d ₃₁ | of the piezoelectric constant of the piezoelectric film 3 is also high, and when the specific dielectric constant of the piezoelectric film 3 is low, the absolute value of the piezoelectric constant of the piezoelectric film 3 is high. There is a correlation that | d _{31 | is also low.}

The upper electrode film 4 can be formed by using various metals such as Pt, Au, aluminum (Al), and Cu, and alloys thereof. The upper electrode film 4 can be formed by using a method such as a sputtering method, a vapor deposition method, a plating method, or a metal paste method. The upper electrode film 4 does not have a great influence on the crystal structure of the piezoelectric film 3 like the lower electrode film 2. Therefore, the material, crystal structure, and film forming method of the upper electrode film 4 are not particularly limited. In addition, in order to enhance the adhesion between the piezoelectric film 3 and the upper electrode film 4, for example, _{an adhesion layer containing Ti, Ta, TiO 2} , Ni or the like as a main component may be provided. The thickness of the upper electrode film 4 can be, for example, 100 to 5000 nm, and when the adhesion layer is provided, the thickness can be, for example, 1 to 200 nm.

(2) Configuration of Piezoelectric Membrane Device FIG. 3 shows a schematic configuration diagram of a device 30 having a piezoelectric membrane (hereinafter, also referred to as a piezoelectric membrane device 30) in the present embodiment. The piezoelectric film device 30 includes an element 20 having a piezoelectric film obtained by molding the above-mentioned laminated substrate 10 into a predetermined shape (hereinafter, also referred to as a piezoelectric film element 20) and a voltage detecting means connected to the piezoelectric film element 20. It is configured to include at least 11a or a voltage applying means 11b.

By connecting the voltage detecting means 11a between the lower electrode film 2 and the upper electrode film 4 of the piezoelectric film element 20, the piezoelectric film device 30 can function as a sensor. When the piezoelectric film 3 is deformed due to some change in physical quantity, a voltage is generated between the lower electrode film 2 and the upper electrode film 4 due to the deformation. By detecting this voltage with the voltage detecting means 11a, the magnitude of the physical quantity applied to the piezoelectric film 3 can be measured. In this case, applications of the piezoelectric film device 30 include, for example, an angular velocity sensor, an ultrasonic sensor, a pressure sensor, an acceleration sensor, and the like.

By connecting the voltage applying means 11b between the lower electrode film 2 and the upper electrode film 4 of the piezoelectric film element 20, the piezoelectric film device 30 can function as an actuator. The piezoelectric film 3 can be deformed by applying a voltage between the lower electrode film 2 and the upper electrode film 4 by the voltage applying means 11b. By this deformation operation, various members connected to the piezoelectric film device 30 can be operated. In this case, applications of the piezoelectric film device 30 include, for example, a head for an inkjet printer, a MEMS mirror for a scanner, a vibrator for an ultrasonic generator, and the like.

(3) Manufacturing Method of Laminated Substrate, Piezoelectric Film Element, and Piezoelectric Film Device Next, the manufacturing method of the above-mentioned laminated substrate 10 will be described. First, the lower electrode film 2 is formed on one of the main surfaces of the substrate 1. A substrate 1 in which the lower electrode film 2 is formed in advance on any of the main surfaces may be prepared. Subsequently, the AlN film 3a (lower AlN film), the KNN film 3b, and the AlN film 3a (upper AlN film) are formed on the lower electrode film 2 in this order by, for example, a sputtering method, and the AlN film is formed. A piezoelectric film 3 formed by laminating 3a and a KNN film 3b is formed. By adjusting the ratio of the thickness T1 of the AlN film 3a to the thickness T2 of the KNN film 3b (T1 / T2), the relative permittivity of the piezoelectric film 3 and the absolute value of the piezoelectric constant of the piezoelectric film 3 | d ₃₁ | Can be set to a predetermined value. When the piezoelectric film 3 has a plurality of AlN films 3a as in the present embodiment, the thickness T1 of the AlN film 3a means the total thickness of all the AlN films 3a of the piezoelectric film 3. After that, the laminated substrate 10 is obtained by forming the upper electrode film 4 on the piezoelectric film 3 (upper AlN film). Then, the piezoelectric film element 20 is obtained by molding the laminated substrate 10 into a predetermined shape, and the piezoelectric film device 30 is obtained by connecting the voltage detecting means 11a or the voltage applying means 11b to the piezoelectric film element 20. Be done.

(4) Effects obtained by the present embodiment According to the present embodiment, one or more of the following effects can be obtained.

(A) In the present embodiment, the AlN film 3a and the KNN film 3b are laminated to form the piezoelectric film 3, and the piezoelectric film 3 has characteristics between the characteristics of the AlN film 3a and the characteristics of the KNN film 3b. It is a film. Specifically, the piezoelectric film 3 is applied with a film having a relative permittivity between the relative permittivity of the AlN film 3a and the relative permittivity of the KNN film 3b, for example, a voltage of ± 1 V under the condition of a frequency of 1 kHz. The film has a relative permittivity of 10 or more and 2000 or less, which is a predetermined value. Further, the piezoelectric film 3 is a film having a piezoelectric constant between the piezoelectric constant of the AlN film 3a and the piezoelectric constant of the KNN film 3b, for example, the piezoelectric film 3 has an absolute value | d ₃₁ | of the piezoelectric constant of 5 pm / V. The film has a predetermined value within the range of 200 pm / V. Therefore, the versatility of the piezoelectric film device 30 produced by processing the above-mentioned laminated substrate 10 can be enhanced. For example, the piezoelectric membrane device 30 manufactured by using the above-mentioned laminated substrate 10 can be applied to a wide range of applications such as sensors, filters, and actuators.

(B) The piezoelectric film 3 is composed of a composite film of an AlN film 3a and a KNN film 3b, that is, the piezoelectric film 3 does not have a film containing lead (Pb), so that from the viewpoint of pollution prevention. It is advantageous. In the present embodiment, the versatility of the piezoelectric film device 30 can be enhanced while achieving the piezoelectric film (lead-free piezoelectric film) containing no Pb in this way.

(C) By providing the AlN film 3a on the lower electrode film 2, it becomes easy to preferentially orient the KNN film 3b in the (001) plane orientation. This is because the AlN film 3a has a (001) plane orientation even when the film forming conditions such as the underlying surface and the film forming temperature are looser than the film forming conditions of the KNN film 3b. It can be preferentially oriented. For example, the AlN film 3a can be preferentially oriented in the (001) plane orientation even when the film is formed on the surface of SUS or the like or under room temperature conditions. Therefore, as in the present embodiment, an AlN film 3a (lower AlN film) is provided on the lower electrode film 2, and the AlN film 3a also functions as a base (seed layer) for the KNN film 3b, thereby causing the lower electrode. It becomes easier to preferentially orient the KNN film 3b in the (001) plane orientation than when the KNN film 3b is directly formed on the film 2.

(D) By sandwiching the upper and lower parts of the KNN film 3b with the AlN film 3a, the withstand voltage of the piezoelectric film 3 including the KNN film 3b can be increased, and the insulating property (leak resistance) of the piezoelectric film 3 can be increased. By improving the insulating property of the piezoelectric film 3, the performance of the piezoelectric film device 30 can be enhanced, and the versatility can be further enhanced.

In the present embodiment, for example, the leakage current density when an electric field of 300 kV / cm is applied to the piezoelectric film in the thickness direction can be set ^{to, for example, 1 μA / cm 2 or less.} Therefore, the laminated substrate 10 according to the present embodiment can be particularly preferably used for applications such as actuators that require high withstand voltage.

(E) By adjusting the ratio (T1 / T2) of the thickness T1 of the AlN film 3a to the thickness T2 of the KNN film 3b, the relative permittivity and the piezoelectric constant of the piezoelectric film 3 are determined while obtaining the above effects. It is possible to set the value of. For example, by reducing the above ratio (T1 / T2), that is, by increasing the thickness of the KNN film 3b, the piezoelectric constant of the piezoelectric film 3 can be increased. Further, the relative permittivity of the piezoelectric film 3 can be lowered by increasing the above-mentioned ratio, that is, by increasing the thickness of the AlN film 3a.

When the piezoelectric film device 30 is operated as an actuator, it is preferable to adjust the thickness T1 of the AlN film 3a and the thickness T2 of the KNN film 3b so that the above ratio is 0.2 or less. This is because when the above ratio exceeds 0.2, that is, when the thickness T1 of the AlN film 3a becomes thicker, the absolute value | d ₃₁ | of the piezoelectric constant of the piezoelectric film 3 becomes lower, which makes it difficult to drive the actuator at high speed. This is because it may become.

(F) Both the AlN film 3a and the KNN film 3b are films that can be formed by a sputtering method using a general sputtering device. Therefore, when the piezoelectric film 3 according to the present embodiment is formed, the AlN film 3a and the KNN film 3b are combined by setting (installing) the AlN target and the KNN target in the film forming chamber of one sputtering apparatus. The film can be continuously formed in one device. As a result, the productivity of the piezoelectric film 3 can be improved.

(G) As described above, the piezoelectric film device 30 produced by using the laminated substrate 10 according to the present embodiment can be suitably used for a wide range of applications such as actuators that require high piezoelectric constants and high withstand voltage.

Here, in contrast to the method of the present embodiment described above, the second piezoelectric thin film is subjected to lead zirconate titanate (PZT) represented by _{the composition formula Pb (Zr x} Ti _1-x ) O _{3 (0 <x <1).} ) Can be used to form a film. However, since the piezoelectric film (PZT film) formed by this method contains about 60 to 70 wt% of lead, there is a problem that it is not preferable from the viewpoint of pollution prevention.

Further, a method of forming a second piezoelectric thin film using zinc oxide (ZnO) is also conceivable. However, the piezoelectric film (ZnO film) formed by this method _{has a low absolute value | d 31} | of the piezoelectric constant, for example, about 10 pm / V. As described above, since the absolute value | d _{31 | of the piezoelectric constant of the ZnO film is almost the same as the absolute value | d 31} | of the AlN film as the first piezoelectric thin film, the piezoelectric film can be the AlN film and ZnO. There is almost no merit of forming a laminated body with a film.

(5) Modification Example This embodiment is not limited to the above-described embodiment, and can be modified as follows, for example.

(Modification example 1)
The AlN film 3a as the first piezoelectric thin film may be provided on at least one of the lower surface or the upper surface of the KNN film 3b. That is, the piezoelectric film 3 may have at least one of an upper AlN film and a lower AlN film. Also by this, the above-mentioned effects such as at least (a) and (b) can be obtained. However, it is preferable to provide the AlN film 3a on at least the lower surface of the KNN film 3b in that the above-mentioned effect (c) can be obtained. Further, it is preferable to provide the AlN film 3a above and below the KNN film 3b, respectively, in that the above-mentioned effect (d) can be obtained.

(Modification 2)
The lowermost layer of the piezoelectric film 3 may be a second piezoelectric thin film (that is, KNN film 3b). That is, the KNN film 3b may be formed on the lower electrode film 2, and the AlN film 3a as the first piezoelectric thin film may be formed on the KNN film 3b. By tightening the conditions for forming the KNN film 3b, it is possible to form the KNN film 3b preferentially oriented in the (001) plane direction on the lower electrode film 2, which also causes at least the above-mentioned at least. The effects of (a) and (b) can be obtained. However, the effect of (c) described above can be obtained by forming the lowermost layer of the piezoelectric film 3 as the AlN film 3a and forming the KNN film on the AlN film 3a as in the above-described embodiment. ,preferable.

(Modification example 3)
The first piezoelectric thin film may be formed using quartz, lithium niobate (LiNbO ₃ ), or lithium tantalate (LiTaO _3). This also has almost the same effect as that of the above-described embodiment. However, unlike the _{AlN film 3a, it is difficult to form a film made of quartz, LiNbO 3} and LiTaO ₃ by a sputtering method, and the film is often formed by a method such as bonding. Therefore, as the thickness of the first piezoelectric thin film increases, problems such as an increase in the thickness of the piezoelectric film may occur. Further, the film formation of the first piezoelectric thin film and the film formation of the second piezoelectric thin film cannot be continuously performed in the same apparatus, and the productivity of the piezoelectric film may decrease. Therefore, it is preferable to form an AlN film as the first piezoelectric thin film from the viewpoints of simplification of the film forming process, thinning of the piezoelectric film (miniaturization of the piezoelectric film element 20), and the like.

(Modification example 4)
The second piezoelectric thin film may be formed using PZT. This also provides at least an effect other than the above-mentioned (b). However, as described above, it is preferable to form a KNN film as the second piezoelectric thin film from the viewpoints of preventing pollution, simplifying the film forming process, improving the productivity of the piezoelectric film, and the like.

(Modification 5)
When molding the above-mentioned laminated substrate 10 into the piezoelectric film element 20, as long as the piezoelectric film device 30 manufactured by using the laminated substrate 10 (piezoelectric film element 20) can be applied to a desired application such as a sensor or an actuator. The substrate 1 may be removed from the laminated substrate 10.

<Other embodiments>
The embodiment of the present invention has been specifically described above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof.

<Preferable Aspect of the Present Invention>
Hereinafter, preferred embodiments of the present invention will be added.

(Appendix 1)
According to one aspect of the invention
A substrate, an electrode film formed on the substrate, and a piezoelectric film formed on the electrode film are provided.
The piezoelectric film is
The first piezoelectric thin film and the second piezoelectric thin film formed of a material different from the first piezoelectric thin film are laminated.
Provided is a laminated substrate having a piezoelectric film having a relative permittivity between the relative permittivity of the first piezoelectric thin film and the relative permittivity of the second piezoelectric thin film.

(Appendix 2)
According to another aspect of the invention
A substrate, an electrode film formed on the substrate, and a piezoelectric film formed on the electrode film are provided.
The piezoelectric film is
The first piezoelectric thin film and the second piezoelectric thin film formed of a material different from the first piezoelectric thin film are laminated.
The having the piezoelectric film _| absolute value of the first piezoelectric thin film of the piezoelectric constant | d _{31 |} and the absolute value of the second piezoelectric thin film of the piezoelectric constant | d _{31 |} and the absolute value of the piezoelectric constant between | d ₃₁ A laminated substrate having a structure is provided.

(Appendix 3)
The substrate of Appendix 1 or 2, preferably
The first piezoelectric thin film is a film having a higher withstand voltage than the second piezoelectric thin film.

(Appendix 4)
The substrate is any of the above-mentioned appendices 1 to 3, preferably the substrate.
The first piezoelectric thin film is a film made of AlN.
The second piezoelectric thin film is a film made of an alkaline niobium oxide having a perovskite structure represented by _{the composition formula (K 1-x} Na _x ) NbO _{3 (0 <x <1).}

(Appendix 5)
The substrate according to any one of Supplementary note 1 to 4, preferably.
The piezoelectric film is formed by disposing the first piezoelectric thin film on the electrode film.

(Appendix 6)
The substrate according to any one of Supplementary note 1 to 5, preferably.
The piezoelectric film is
From the side of the electrode film (substrate), the first piezoelectric thin film, the second piezoelectric thin film, and the first piezoelectric thin film are laminated in this order.

(Appendix 7)
The substrate according to any one of Supplementary note 1 to 6, preferably.
The piezoelectric film has a predetermined value within a range of 10 or more and 2000 or less in relative permittivity when measured by applying a voltage of ± 1 V under the condition of a frequency of 1 kHz.
_{The absolute value | d 31} | of the piezoelectric constant of the piezoelectric film is a predetermined value within the range of 5 pm / V or more and 200 pm / V or less.

(Appendix 8)
According to another aspect of the invention
A lower electrode film, a piezoelectric film formed on the lower electrode film, and an upper electrode film formed on the piezoelectric film are provided.
The piezoelectric film is
The first piezoelectric thin film and the second piezoelectric thin film formed of a material different from the first piezoelectric thin film are laminated.
The relative permittivity between the relative permittivity of the first piezoelectric thin film (or the absolute value of the piezoelectric constant | d ₃₁ |) and the relative permittivity of the second piezoelectric thin film (or the absolute value of the piezoelectric constant | d ₃₁ |). An element having a piezoelectric film having (or an absolute value of the piezoelectric constant | d _{31 |) is provided.}

(Appendix 9)
According to another aspect of the invention
A substrate, a lower electrode film formed on the substrate, a piezoelectric film formed on the lower electrode film, and an upper electrode film formed on the piezoelectric film are provided.
The piezoelectric film is
The first piezoelectric thin film and the second piezoelectric thin film formed of a material different from the first piezoelectric thin film are laminated.
The relative permittivity between the relative permittivity of the first piezoelectric thin film (or the absolute value of the piezoelectric constant | d ₃₁ |) and the relative permittivity of the second piezoelectric thin film (or the absolute value of the piezoelectric constant | d ₃₁ |). An element having a piezoelectric film having (or an absolute value of the piezoelectric constant | d _{31 |) is provided.}

(Appendix 10)
According to yet another aspect of the invention.
A substrate having an electrode film formed on one of the main surfaces is prepared, and a first piezoelectric thin film and a second piezoelectric thin film formed of a material different from the first piezoelectric thin film are provided on the electrode film. Between the specific dielectric constant of the first piezoelectric thin film (or the absolute value of the piezoelectric constant | d ₃₁ |) and the specific dielectric constant of the second piezoelectric thin film (or the absolute value of the piezoelectric constant | d ₃₁ |). Provided is a method for manufacturing a laminated substrate having a piezoelectric film, which comprises a step of forming a piezoelectric film having a specific dielectric constant (or an absolute value of a piezoelectric constant | d _{31 |).}

(Appendix 11)
The method of Appendix 10, preferably
In the step of forming the piezoelectric film,
By adjusting the ratio (T1 / T2) of the thickness (T1) of the first piezoelectric thin film to the thickness (T2) of the second piezoelectric thin film, the relative permittivity (or absolute value of the piezoelectric constant) of the piezoelectric film is adjusted. | D ₃₁ |) is adjusted.

(Appendix 12)
According to yet another aspect of the invention.
The first piezoelectric thin film and the second piezoelectric thin film formed of a material different from the first piezoelectric thin film are laminated, and the specific dielectric constant of the first piezoelectric thin film (or the absolute value of the piezoelectric constant | d ₃₁ |). A laminated substrate provided with a piezoelectric film having a specific dielectric constant (or absolute value of the piezoelectric constant | d ₃₁ |) between and the specific dielectric constant (or absolute value of the piezoelectric constant | d _{31 |) of the second piezoelectric thin film.} Provided is a method of manufacturing an element having a piezoelectric film, which comprises a step of preparing.

1 Substrate 2 Lower electrode film 3 Piezoelectric film 10 Laminated substrate

Claims (7)

A substrate, an electrode film formed on the substrate, and a piezoelectric film formed on the electrode film are provided.
The piezoelectric film is
A first piezoelectric thin film made of AlN and a second piezoelectric thin film made of an alkali niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1) are continuous. And are laminated
A laminated substrate having a piezoelectric film having a relative permittivity between the relative permittivity of the first piezoelectric thin film and the relative permittivity of the second piezoelectric thin film. The laminated substrate having the piezoelectric film according to claim 1, wherein the thickness of the first piezoelectric thin film is 5 to 500 nm. The piezoelectric film is a laminated substrate having the piezoelectric film according to claim 1 or 2, wherein the first piezoelectric thin film is arranged on the electrode film. The piezoelectric film according to any one of claims 1 to 3, wherein the first piezoelectric thin film, the second piezoelectric thin film, and the first piezoelectric thin film are laminated in this order from the side of the electrode film. Laminated substrate having a piezoelectric film of. A lower electrode film, a piezoelectric film formed on the lower electrode film, and an upper electrode film formed on the piezoelectric film are provided.
The piezoelectric film is
A first piezoelectric thin film made of AlN and a second piezoelectric thin film made of an alkali niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1) are continuous. And are laminated
An element having a piezoelectric film having a relative permittivity between the relative permittivity of the first piezoelectric thin film and the relative permittivity of the second piezoelectric thin film. A substrate having an electrode film formed on one of the main surfaces is prepared, and a first piezoelectric thin film made of AlN and a composition formula (K _1-x Na _x ) NbO ₃ (0 <x) are prepared on the electrode film. A second piezoelectric thin film made of an alkaliniobium oxide having a perovskite structure represented by <1) is continuously laminated, and the specific dielectric constant of the first piezoelectric thin film and the specific dielectric constant of the second piezoelectric thin film. A method for manufacturing a laminated substrate having a piezoelectric film, which comprises a step of forming a piezoelectric film having a specific dielectric constant between the two. In the step of forming the piezoelectric film,
The method for manufacturing a laminated substrate having a piezoelectric film according to claim 6, wherein the relative permittivity of the piezoelectric film is adjusted by adjusting the ratio of the thickness of the first piezoelectric thin film to the thickness of the second piezoelectric thin film. ..

Images