JP6804615B2 - 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 (devices) 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, when used in devices, there is a strong demand for piezoelectric materials having a longer time to dielectric breakdown, that is, a longer life.

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

An object of the present invention is to provide a laminated substrate having a piezoelectric film having a longer time until dielectric breakdown when used in a device, and related techniques thereof.

According to one aspect of the invention
A laminated substrate having a piezoelectric film, comprising a substrate, a first electrode film formed on the substrate, and a piezoelectric film formed on the first electrode film.
Provided are a laminated substrate having a piezoelectric film and a related technique thereof, wherein an oxide film made of an oxide represented by the composition formula RuO _x or IrO _x is formed on the piezoelectric film.

According to the present invention, it is possible to provide a laminated substrate having a piezoelectric film having a long time until dielectric breakdown when used in a device, and related techniques thereof.

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 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. (A) to (f) are diagrams showing the evaluation results regarding the ferroelectricity of the KNN film, respectively. (A) and (b) are diagrams showing the evaluation results regarding the ferroelectricity of the KNN film, respectively.

<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 includes a substrate 1, a lower electrode film 2 as a first electrode film formed on the substrate 1, and a lower electrode. It is configured as a laminate including a piezoelectric film (piezoelectric thin film) 3 formed on the film 2 and an upper electrode film 4 as a second electrode film formed on the piezoelectric film 3 via an adhesion layer. Has been done.

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 includes 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 a metal substrate formed of a metal material such as stainless steel. Can also be used. 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 thin film 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 thin film 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 contains, for example, potassium (K), sodium (Na), and niobium (Nb), and is an alkaline niobium oxide represented by the composition formula (K _1-y N _y ) NbO ₃ , that is, potassium niobate. A film can be formed using sodium (KNN). The coefficient y [= Na / (K + Na)] in the above composition formula has a magnitude within the range of 0 <y <1, preferably 0.4 ≦ y ≦ 0.7. The piezoelectric film 3 is a KNN polycrystalline film (hereinafter, also referred to as KNN film 3). The crystal structure of KNN is a perovskite structure.

The crystals constituting the KNN film 3 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 3 (the surface serving as the base of the RuO _x film 7a described later) is mainly composed of the KNN (001) surface. By directly forming the KNN film 3 on the Pt film (lower electrode film 2) preferentially oriented in the (111) plane direction with respect to the surface of the substrate 1, the crystals constituting the KNN film 3 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 3 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 3 is KNN (001). ) It becomes possible to make a surface.

The KNN film 3 can be formed by using a method such as a sputtering method, a PLD (Pulsed Laser Deposition) method, or a sol-gel method. The thickness of the KNN film 3 can be, for example, 0.5 to 5 μm. The composition ratio of the KNN film 3 can be adjusted, for example, by controlling the composition of the target material used during sputtering film formation. The target material can be produced, for example, by mixing K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder and the like and firing them. In this case, the composition of the target material can be controlled by adjusting the mixing ratio of K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder and the like.

The KNN film 3 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 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 KNN 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. The thickness of the upper electrode film 4 can be, for example, 100 to 5000 nm.

Between the KNN layer 3 and the upper electrode film 4, i.e. on the KNN layer 3, as an adhesion layer to improve the adhesion between them, made of an oxide represented by the composition formula RuO _x film (oxide film) 7a (Hereinafter, also referred to as RuO _x film 7a) is formed. Further, as this adhesion layer, as shown in FIG. 3, a film 7b made of an oxide represented by the composition formula IrO _x (hereinafter, also referred to as IrO _x film 7b) may be formed.

The RuO _x film 7a can be formed by using a method such as a sputtering method, a chemical vapor deposition (CVD) method, or a thin film deposition method. The RuO _x film 7a does not have a great influence on the crystal structure of the KNN film 3 like the lower electrode film 2. Therefore, the crystal structure of the RuO _x film 7a and the film forming method are not particularly limited. The composition ratio of the RuO _x film 7a, that is, the value of the coefficient x in the above composition formula is the atmospheric gas at the time of sputtering film formation, for example, a mixed gas (Ar / O) of an argon (Ar) gas and an oxygen (O ₂ ) gas. _It can be adjusted by controlling the O ₂ gas ratio in ( ₂ mixed gas). The higher the O ₂ gas ratio described above, the larger the value of the coefficient x, and the smaller the O ₂ gas ratio, the smaller the value of the coefficient x tends to be. Further, as the target material used for sputtering film formation, when the RuO _x film 7a having a coefficient x within the range of 0 <x <2 is formed, a target material formed of a ruthenium (Ru) metal material is used. It is preferable to use a target material prepared by firing RuO ₂ powder or the like when forming a RuO _x film 7a having a coefficient x in the range of 2 ≦ x, preferably 2 <x. .. The thickness of the RuO _x film 7a can be, for example, 2 to 30 nm, preferably 5 to 30 nm. Regarding these points, the same can be said for IrO _x film 7b. When forming the IrO _x film 7b in which the coefficient x is in the range of 0 <x <2, it is preferable to use a target material formed of a metal material of iridium (Ir), and the coefficient x is 2 ≦. When forming the IrO _x film 7b in the range of x, preferably 2 <x, it is preferable to use a target material prepared by firing IrO ₂ powder or the like.

(2) Configuration of Piezoelectric Membrane Device FIG. 4 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 KNN 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 KNN 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 KNN 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, an oscillator 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, after forming a KNN film 3 on the lower electrode film 2 by using, for example, a sputtering method, the KNN film 3 (a laminate having the KNN film 3) is subject to a predetermined temperature (for example, 500 ° C.). Underneath, annealing (heat treatment) is performed for a predetermined time (for example, 2 hours). Then, a RuO _x film 7a or IrO _x film 7b is formed on the KNN film 3 by, for example, a sputtering method, and an upper electrode film 4 is formed on the RuO _x film 7a or IrO _x film 7b. The laminated substrate 10 is obtained.

After forming the RuO _x film 7a or IrO _x film 7b and the upper electrode film 4, the laminated substrate 10 may be annealed.

The annealing conditions for the above-mentioned laminated substrate 10 include
Annealing temperature (temperature of laminated substrate 10): 600 ° C. or higher, preferably 600 ° C. or higher and 800 ° C. or lower, more preferably 700 ° C.
Annealing time: 0.5-12 hours, preferably 1-6 hours, more preferably 2-3 hours Annealing atmosphere: Air or oxygen atmosphere is exemplified. However, this annealing does not have to be performed.

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) By providing the RuO _x film 7a or the IrO _x film 7b between the KNN film 3 and the upper electrode film 4, in the piezoelectric film device 30 produced by using the laminated substrate 10 according to the present embodiment, the KNN It is possible to prolong the time until the film 3 reaches dielectric breakdown, that is, to prolong the life of the KNN film 3. For example, with the laminated substrate 10 heated to a temperature of 200 ° C., a high acceleration life is applied by applying an electric field of −300 kV / cm (voltage of −60 V) between the lower electrode film 2 and the upper electrode film 4. When the test (Highly Accelerated Life Test, abbreviated as HALT) is performed, the time from the start of electric field application to the dielectric breakdown of the KNN film 3 can be set to 3300 seconds or more. In this embodiment, it is considered that the KNN film 3 has undergone dielectric breakdown when the leakage current density flowing through the KNN film 3 exceeds 30 mA / cm ² .

In particular, by forming the RuO _x film 7a, it is possible to further extend the life of the KNN film 3 as compared with the case of forming the IrO _x film 7b. For example, the lifetime of the KNN film 3 by HALT described above can be set to 7600 seconds or more.

Here, in contrast to the method of the present embodiment described above, between the KNN film and the upper electrode film, a film made of titanium (Ti) (Ti film) or a film made of an oxide represented by the composition formula TiO _x ( A method of providing a TiO _x film) is also conceivable. However, in the piezoelectric film device produced by processing the laminated substrate obtained by this method, the life of the KNN film by HALT described above is shorter than that of the piezoelectric film device 30 according to the present embodiment. It is considered that this is because Ti diffuses (moves) into the KNN film due to some factor, and this Ti adversely affects the life of the KNN film.

(B) The piezoelectric film device 30 produced by using the laminated substrate 10 according to the present embodiment has better ferroelectricity than the conventional piezoelectric film device. For example, the absolute value of the saturated polarization amount (P _max− ) when an electric field is applied to the KNN film 3 is 23 μC / cm ² or more (| P _max− | ≧ 23 μC / cm ² ), and the residual polarization amount (P _{r). -} the absolute value of) the 14μC / cm ² or more _(| a ^{_{≧ 14μC / cm 2) | P}} r-. The saturated polarization amount is the polarization amount when the polarization amount does not increase even if the electric field is continuously applied, and the residual polarization amount is when the applied electric field is returned to zero after reaching the saturation polarization amount. The amount of polarization of.

(C) By providing the RuO _x film 7a or the IrO _x film 7b between the KNN film 3 and the upper electrode film 4, the ferroelectricity of the KNN film 3 can be enhanced. On the other hand, the present application states that the above-mentioned conventional piezoelectric film device produced by processing a laminated substrate having a Ti film or a TiO _x film has a lower ferroelectricity than the piezoelectric film device 30 according to the present embodiment. The inventor has confirmed.

(D) By setting the thickness of the RuO _x film 7a to 2 to 30 nm, preferably 5 to 30 nm, the above-mentioned life improving effect and ferroelectricity improving effect can be obtained, and the performance of the piezoelectric film device 30 can be obtained. It is possible to suppress the decrease. The same can be said for IrO _x film 7b.

If the thickness of the RuO _x film 7a is less than 2 nm, the in-plane film thickness of the RuO _x film 7a may be non-uniform or the film may be discontinuous. Therefore, the above-mentioned effect of improving the life and the effect of improving the ferroelectricity may not be sufficiently obtained. By setting the thickness of the RuO _x film 7a to 2 nm or more, these problems can be solved, and the above-mentioned life improving effect and ferroelectricity improving effect can be obtained. By setting the thickness of the RuO _x film 7a to 5 nm or more, the above-mentioned problems can be surely solved, and the above-mentioned life improving effect and ferroelectricity improving effect can be surely obtained.

If the thickness of the RuO _x film 7a exceeds 30 nm, the life of the KNN film 3 by HALT described above may be less than 3300 seconds. If the thickness of the RuO _x film 7a is increased, the film stress of the RuO _x film 7a itself is increased, it becomes easily peeled off RuO _x film 7a. Further, since Ru and Ir are hard metal materials, the RuO _x film 7a and IrO _x film 7b containing Ru and Ir are hard films. When the thickness of such a hard RuO _x film 7a is increased, the vibrating portion including the KNN film 3 is less likely to vibrate (resonate), which causes a decrease in sensitivity when the laminated substrate 10 is applied to the sensor, or an actuator. When applied to, it may lead to an increase in power consumption. For these reasons, the thickness of the RuO _x film 7a is preferably 30 nm or less.

(E) As the RuO _x film 7a, it is preferable to provide a film represented by the composition formula RuO _x (0 <x <2) in that a decrease in the film formation rate of the RuO _x film 7a can be suppressed.

As described above, the higher the O ₂ gas ratio in the atmospheric gas (Ar / O ₂ mixed gas) during sputtering of the RuO _x film 7a, the larger the value of the coefficient x, and the smaller the O ₂ gas ratio. , The value of the coefficient x tends to be small. However, the ejection of Ru atoms from the sputtering target material is performed by Ar gas (ionized Ar atoms (Ar ⁺ )). Therefore, when the above-mentioned O ₂ gas ratio is high, that is, when the Ar gas ratio is low, the amount of Ru atoms ejected from the target (amount per unit time) is small, so that the RuO _x film 7a is formed. The rate drops. O ₂ gas ratio by, for example to 50% or less, it is possible to obtain a practical deposition rate, in this case, the value of the coefficient x is less than 2.

(F) As the RuO _x film 7a, it is preferable to provide a film represented by the composition formula RuO _x (2 <x) in that the life of the KNN film 3 can be reliably extended.

By providing the film represented by the composition formula RuO _x (2 <x), the amount of oxygen (O) diffused from the RuO _x film 7a into the KNN film 3 can be increased. As a result, oxygen defects in the KNN film 3, which is one of the causes of the KNN film 3 leading to dielectric breakdown, can be filled with oxygen diffused from the RuO _x film 7a. As a result, the life of the KNN film 3 can be reliably extended. The term "oxygen defect" as used herein means, for example, a portion where oxygen generated in the crystal constituting the KNN film 3 is released by annealing after forming the KNN film 3.

(G) After the formation of the RuO _x film 7a and the upper electrode film 4, the laminated substrate 10 is annealed under a temperature condition of 600 ° C. or higher, or the laminated substrate 10 is laminated after the formation of the RuO _x film 7a and the upper electrode film 4. By not performing annealing of the substrate 10, it is possible to surely extend the life of the KNN film 3. The inventor of the present application has confirmed that annealing does not affect the ferroelectricity of the KNN film 3.

On the other hand, a method of annealing the laminated substrate under a temperature condition of less than 600 ° C. (for example, 500 ° C.) after forming the RuO _x film and the upper electrode film is also conceivable. However, when annealing the laminated substrate at a temperature below 600 ° C., and when the non-implementation annealing of the laminated substrate after the film of RuO _x film and an upper electrode film, a layered substrate at a temperature of above 600 ° C. The life of the KNN film is shorter than that in the case of annealing.

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

(Modification example 1)
For example, a RuO _x film 7a or an IrO _x film 7b may be provided between the substrate 1 and the lower electrode film 2. That is, as the adhesion layer 6, a film made of an oxide represented by the composition formula RuO _x or IrO _x may be formed. Further, for example, a RuO _x film 7a or an IrO _x film 7b may be provided between the lower electrode film 2 and the KNN film 3. In these cases, the RuO _x film 7a or the IrO _x film 7b may or may not be provided between the KNN film 3 and the upper electrode film 4. With these, the same effect as that of the above-described embodiment can be obtained.

(Modification 2)
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 embodiments of the present invention have 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.

Hereinafter, the experimental results supporting the effects of the above-described embodiments will be described.

As a substrate, a Si substrate having a surface (100) plane orientation, a thickness of 610 μm, a diameter of 6 inches, and a thermal oxide film (thickness of 200 nm) formed on the surface was prepared. Then, on the thermal oxide film of this substrate, a Ti film (thickness 2 nm) as the first adhesion layer and a Pt film as the lower electrode film (priority orientation and thickness in the (111) plane orientation with respect to the surface of the substrate). 200 nm), KNN film as a piezoelectric film (priority orientation in the (001) plane orientation with respect to the surface of the substrate, thickness 2 μm), RuO _x film, IrO _x film, TiO _x film (thickness) as the second adhesion layer. A laminated substrate was produced by sequentially forming either a 2 nm) or Ti film (thickness 2 nm) and a Pt film (thickness 100 nm) as an upper electrode film. The thickness of the RuO _x film and the IrO _x film was changed in the range of 2.5 to 30 nm. Further, after the formation of the KNN film and before the formation of the second adhesion layer, the laminate having the KNN film was annealed under the condition of 500 ° C. for 2 hours. In addition, annealing of the laminated substrate after the formation of the upper electrode film is not performed, or it is performed under a temperature condition of 500 ° C. for 2 hours, a temperature condition of 600 ° C. for 2 hours, and a temperature condition of 700 ° C. for 2 hours. It was done under each condition of time.

The Ti film, Pt film, KNN film, RuO _x film, IrO _x film, and TiO _x film were all formed by the RF magnetron sputtering method.

The treatment conditions for forming the Ti film and the Pt film were as follows.
Substrate temperature: 300 ° C
Discharge power: 1200W
Introduced gas: Ar gas Ar atmosphere pressure: 0.3Pa
Film formation time: 5 minutes

The treatment conditions for forming the KNN film were as follows.
Substrate temperature: 600 ° C
Discharge power: 2200W
Introduced gas: Ar / O ₂ mixed gas Ar / O ₂ mixed gas Atmospheric pressure: 0.3 Pa
Partial pressure of Ar gas / O ₂ Partial pressure of gas: 25/1
Film formation speed: 1 μm / hr

The treatment conditions for forming the RuO _x film, IrO _x film, and TiO _x film were as follows.
Substrate temperature: Room temperature (25 ° C)
Discharge power: 300W
Introduced gas: Ar / O ₂ mixed gas Ar + O ₂ mixed atmosphere pressure: 0.3 Pa
Partial pressure of Ar gas / Partial pressure of O ₂ gas: 1/1
Film formation rate: 0.1 μm / hr

Then, the life and the ferroelectricity of the KNN film contained in the laminated substrate were evaluated. Tables 1 and 2 show the evaluation results regarding the lifetime of the KNN film, and FIGS. 5 (a) to 5 (f) and 6 (a) and (b) show the evaluation results regarding the ferroelectricity of the KNN film, respectively. The figure shows the hysteresis curve of the voltage-polarization amount and the piezoelectric displacement characteristic with respect to the applied voltage, respectively.

(Evaluation of life)
The evaluation of the life was performed by measuring the time (sec) until the dielectric breakdown of the KNN film by HALT under the conditions described in the above-described embodiment. The numerical values in Tables 1 and 2 are average values of life values measured at 7 points within 0.5 mmφ per sample. Further, in Tables 1 and 2, "no annealing" means that the annealing after the film formation of the upper electrode film was not performed, and "600 ° C. annealing" means that the laminated substrate was formed after the film formation of the upper electrode film. Is annealed for 2 hours under a temperature condition of 600 ° C. The notations of "500 ° C. annealing" and "700 ° C. annealing" in Table 2 have the same meaning as "600 ° C. annealing".

As shown in Table 1, it was confirmed that the life of the KNN film was 3300 seconds or more in the laminated substrate in which the RuO _x film or the IrO _x film was provided between the KNN film and the upper electrode film. On the other hand, it was confirmed that the life of the KNN film was less than 3300 seconds in the laminated substrate in which the TiO _x film was provided between the KNN film and the upper electrode film.

As shown in Tables 1 and 2, when the film thickness of the RuO _x film and the film thickness of the IrO _x film are the same, the laminated substrate provided with the RuO _x film is more suitable than the laminated substrate provided with the IrO _x film. , It was confirmed that the life of the KNN film was extended.

As shown in Table 2, it was confirmed that the life of the KNN film was 3300 seconds or more in the laminated substrate in which the annealing after the formation of the upper electrode film was not performed. Further, it was confirmed that the life of the KNN film was 3300 seconds or more in the laminated substrate obtained by annealing at 600 ° C. and annealing at 700 ° C. after forming the upper electrode film. On the other hand, it was confirmed that the life of the KNN film was less than 3300 seconds in the laminated substrate obtained by annealing at 500 ° C. after forming the upper electrode film.

That is, it was confirmed that by providing the RuO _x film or the IrO _x film between the KNN film and the upper electrode film, the life of the KNN film can be extended as compared with the case where the TiO _x film is provided. Further, it was confirmed that the life of the KNN film can be further extended by providing the RuO _x film as compared with the case where the IrO _x film is provided. Furthermore, it was confirmed that the life of the KNN film can be reliably extended by not performing annealing after forming the upper electrode film or by performing annealing under a temperature condition of 600 ° C. or higher.

(Evaluation of ferroelectricity)
For the evaluation of ferroelectricity, an electric field of ± 100 kV / cm was applied to the KNN film at a frequency of 1 kHz to obtain a hysteresis curve showing the relationship between the voltage and the amount of polarization.

As shown in FIGS. 5 (a) to 5 (e), in a laminated substrate in which a RuO _x film or an IrO _x film is provided between the KNN film and the upper electrode film, | P _max − | ≧ 23 μC / cm ² Yes, _| it was able to confirm that it is ^{_{≧ 14μC / cm 2 | P r-}} . On the other hand, as shown in FIG. 5 (f), in the laminated substrate in which the Ti film is provided between the KNN film and the upper electrode film, | P _max- | is 17.6 μC / cm ² , and | P. It was confirmed that _r- | was 10.4 μC / cm ² . The laminated substrates shown in FIGS. 5 (a) to 5 (e) were not annealed after the upper electrode film was formed, and the laminated substrate shown in FIG. 5 (f) was used under a temperature condition of 500 ° C. for 2 hours. Annealing is performed.

As shown in FIG. 5A, in a laminated substrate in which a RuO _x film having a thickness of 10 nm was provided as a second adhesion layer and annealing was not performed after the formation of the upper electrode film, | P _max- | was 23. is a _{^{.8μC / cm 2, | P r-}} | was 15.7μC / cm ^2. Further, as shown in FIG. 6 (a), the thickness of the second adhesive layer is provided RuO _x film 10 nm, the laminated substrate was annealed for two hours at a temperature of 700 ° C. after the film of the upper electrode film _{in, | P max- |} is _{^{23.8μC / cm 2, | P r-}} | was 17.9μC / cm ^2. Further, as shown in FIG. 5 (d), the thickness of the second adhesive layer is provided IrO _x film 20 nm, a laminated board was not an annealing after the film of the upper electrode _{film, | P max-} | there is a _{^{24.2μC / cm 2, | P r-}} | was 14.5μC / cm ^2. Further, as shown in FIG. 6 (b), the thickness of the second adhesive layer is provided IrO _x film 20 nm, the laminated substrate was annealed for two hours at a temperature of 500 ° C. after the film of the upper electrode film _{in, | P max- |} is _{^{24.0μC / cm 2, | P r-}} | was 14.8μC / cm ^2.

That is, from the comparison between FIGS. 5 (a) and 6 (a) and the comparison between FIGS. 5 (d) and 6 (b), either the RuO _x film or the IrO _x film was used as the second adhesion layer. even when provided, the laminated substrate was annealed after the film of the upper electrode film _{| P max- |, | P r-} | values and not an annealing after film of the upper electrode film was of the laminated substrate _{| P max- |, | P r-} | and of value, it was confirmed that almost no change. That is, in any case, it was confirmed that the annealing performed on the laminated substrate after the formation of the upper electrode film did not affect the ferroelectricity of the KNN film.

<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 laminated substrate having a piezoelectric film, comprising a substrate, a first electrode film formed on the substrate, and a piezoelectric film formed on the first electrode film.
An oxide film made of an oxide represented by the composition formula RuO _x or IrO _x is formed on the piezoelectric film.

(Appendix 2)
The substrate of Appendix 1, preferably
An oxide film made of an oxide represented by the composition formula RuO _x or IrO _x is formed between the substrate and the first electrode film, or at least between the first electrode film and the piezoelectric film. It is formed.

(Appendix 3)
The substrate of Appendix 1 or 2, preferably
The oxide film is a film made of an oxide represented by the composition formula RuO _x .

(Appendix 4)
It is any one of the substrates of Appendix 1 to 3, preferably
The oxide film is a film made of an oxide represented by the composition formula RuO _x (0 <x <2).

(Appendix 5)
It is any one of the substrates of Appendix 1 to 3, preferably
The oxide film is a film made of an oxide represented by the composition formula RuO _x (2 <x).

(Appendix 6)
The substrate according to any one of Appendix 1 to 5, preferably.
The thickness of the oxide film is 2 nm or more and 30 nm or less, preferably 5 nm or more and 30 nm or less.

(Appendix 7)
The substrate according to any one of Supplementary note 1 to 6, preferably.
The piezoelectric film is a film made of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-y N _y ) NbO ₃ (0 <y <1).

(Appendix 8)
The substrate according to any one of Supplementary note 1 to 7, preferably
The piezoelectric film is
The absolute value of the saturated polarization amount (P _max- ) is 23 μC / cm ² or more.
The absolute value of the residual polarization _{(P r-)} is 14μC / cm ² or more.

(Appendix 9)
The substrate according to any one of Appendix 1 to 8, preferably.
The oxide film has not been annealed (heat treated).

(Appendix 10)
The substrate according to any one of Appendix 1 to 8, preferably.
The oxide film is annealed under a temperature condition of 600 ° C. or higher and 800 ° C. or lower.

(Appendix 11)
According to another aspect of the invention
A laminated substrate having a piezoelectric film, comprising a substrate, a first electrode film formed on the substrate, and a piezoelectric film formed on the first electrode film.
The piezoelectric film is a film made of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-y N _y ) NbO ₃ (0 <y <1).
A second electrode film is formed on the piezoelectric film and heated so that the temperature of the laminated substrate becomes 200 ° C., and between the first electrode film and the second electrode film is −300 kV / cm. Provided is a laminated substrate having a piezoelectric film, wherein when an electric field (voltage of -60 V) is applied, the time from the start of applying the electric field to the leakage current density flowing through the piezoelectric film exceeds 30 mA / cm ² is 3300 seconds or more. Will be done.

(Appendix 12)
The substrate of Appendix 11, preferably
An oxide film made of an oxide represented by the composition formula RuO _x or IrO _x is formed on the piezoelectric film.

(Appendix 13)
According to yet another aspect of the invention.
A substrate, a first electrode film formed on the substrate, a piezoelectric film formed on the first electrode film, and a second electrode film formed on the piezoelectric film are provided.
An element having a piezoelectric film or a device having a piezoelectric film in which an oxide film made of an oxide represented by the composition formula RuO _x or IrO _x is provided between the piezoelectric film and the second electrode film. Is provided.

(Appendix 14)
According to yet another aspect of the invention.
The process of forming an electrode film on a substrate and
The process of forming a piezoelectric film on the electrode film and
Provided is a method for producing a laminated substrate having a piezoelectric film, comprising a step of forming an oxide film made of an oxide represented by the composition formula RuO _x or IrO _x on the piezoelectric film.

(Appendix 15)
The method of Appendix 14, preferably
It does not have a step of annealing the laminated substrate after performing the step of forming the oxide film.

(Appendix 16)
The method of Appendix 14, preferably
After performing the step of forming the oxide film, there is further a step of annealing the laminated substrate under a temperature condition of 600 ° C. or higher, preferably 600 ° C. or higher and 800 ° C. or lower.

1 Substrate 3 Piezoelectric film 7a RuO _x film 7b IrO _x film 10 Laminated substrate

Claims (9)

A laminated substrate having a piezoelectric film, comprising a substrate, a first electrode film formed on the substrate, and a piezoelectric film formed on the first electrode film.
The piezoelectric film is a film made of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-y N _y ) NbO ₃ (0 <y <1).
The piezoelectric film is an oxide film made of an oxide represented by the composition formula RuO _x or IrO _x , and when the second electrode film is provided on the oxide film, the piezoelectric film and the second electrode film are provided. An oxide film is provided to improve the adhesion between the electrode film and the electrode film .
Wherein when an electric field of ± 100 kV / cm was applied at 1kHz frequency for the piezoelectric film, the saturation polarization _{(P max-)} of absolute value be 23.6 [mu] C / cm ² or more 27.1μC / cm ² or less , the absolute value of the residual polarization _{(P r-)} is 14.2 [mu] C / cm ² or more 17.5μC / cm ² or less, a laminated substrate having a piezoelectric film. The laminated substrate having the piezoelectric film according to claim 1, wherein the thickness of the oxide film is 2.5 nm or more and 30 nm or less. The laminated substrate having the piezoelectric film according to claim 1 or 2, wherein the oxide film is a film that has not been annealed. The laminated substrate having the piezoelectric film according to claim 1 or 2, wherein the oxide film is a film that has been annealed under a temperature condition of 600 ° C. or higher and 700 ° C. or lower. A laminate having a substrate, a first electrode film formed on the substrate, a piezoelectric film formed on the first electrode film, and a second electrode film formed on the piezoelectric film. Equipped with a board
The piezoelectric film is a film made of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-y N _y ) NbO ₃ (0 <y <1).
Between the piezoelectric film and the second electrode film, an oxide film made of an oxide represented by the composition formula RuO _x or IrO _x is provided to enhance the adhesion between the piezoelectric film and the second electrode film. Is provided,
Wherein when an electric field of ± 100 kV / cm was applied at 1kHz frequency for the piezoelectric film, the saturation polarization _{(P max-)} of absolute value be 23.6 [mu] C / cm ² or more 27.1μC / cm ² or less , the absolute value of the residual polarization _{(P r-)} is 14.2 [mu] C / cm ² or more 17.5μC / cm ² or less, element having a piezoelectric film. The process of forming the first electrode film on the substrate and
A step of forming a piezoelectric film made of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-y N _y ) NbO ₃ (0 <y <1) on the first electrode film.
An oxide film made of an oxide represented by the composition formula RuO _x or IrO _x on the piezoelectric film, and when the second electrode film is provided on the oxide film, the piezoelectric film and the second electrode The process of forming an oxide film that enhances the adhesion between the film and
When an electric field of ± 100 kV / cm is applied to the piezoelectric film at a frequency of 1 kHz, the absolute value of the saturated polarization amount (P _max- ) is 23.6 μC / cm ² or more and 27.1 μC /. cm ² or less, the absolute value of the residual polarization _{(P r-)} to produce a 14.2 [mu] C / cm ² or more 17.5MyuC / cm ² or less is stack manufacturing method of a multilayer substrate having a piezoelectric film .. The method for manufacturing a laminated substrate having a piezoelectric film according to claim 6, which does not include a step of annealing the laminated substrate after performing the step of forming the oxide film. The method for producing a laminated substrate having a piezoelectric film according to claim 6, further comprising a step of annealing the laminated substrate under a temperature condition of 600 ° C. or higher and 700 ° C. or lower after performing the step of forming the oxide film. .. In the step of forming the oxide film, the laminated substrate having the piezoelectric film according to any one of claims 6 to 8 for forming a film having a thickness of 2.5 nm or more and 30 nm or less as the oxide film. Production method.