JP2001152361A - Thick film structure of piezoelectric ceramics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To particularly reduce the damage of a substrate in a piezoelectric ceramics thick film structure by a gas deposition method and to prevent deterioration in the mechanical properties of a multilayered structure composed of the piezoelectric ceramics thick film/substrate. SOLUTION: PZT piezoelectric ceramics fine particles 3 are floated in carrier gas and are made into an aerosol, and this aerosol is injected from a nozzle 5 at a high speed on a substrate to deposite a film. By the collision of the particles accerated at a high speed against the substrate, the kinetic energy of the particles causes a film deposition phenomenon. The damage of the substrate by the collision remarkably appears in ceramics, glass, Si wafers and various oxide crystal materials destroyed by brittle fracture. In particular, in the case the application to a mechanical element such as an actuator is considered, deterioration in its mechanical strength is made important from the viewpoint of the reliability on the element. Not so as to give the damage by the collision with powder to the substrate, an intermediate film is arranged on the substrate, and after that, gas deposition film formation is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic thick film structure, and more particularly, to a piezoelectric ceramic film formed by a gas deposition method in which ceramic particles are sprayed from a nozzle onto a substrate to obtain a deposited film. In the ceramic thick film structure, in particular, the substrate damage is reduced, and the mechanical strength of the laminated structure composed of the piezoelectric ceramic thick film / substrate is prevented from lowering.

[0002]

2. Description of the Related Art A piezoelectric ceramic film is arranged on a substrate,
Attempts have been made to use it for actuators and sensor elements. Elements that have been commercialized as a unimorph element and a bimorph element have been unsuitable for miniaturization of the elements because they are formed by joining respective materials. In recent years, the gas deposition method has made it possible to form piezoelectric ceramics on a substrate, which has been conventionally difficult to produce, and has been shown to be effective in miniaturizing elements.

The gas deposition method is disclosed, for example, in Japanese Patent No.
This is a film formation method using ultrafine particles described in Japanese Patent No. 660799. As in the case of the vacuum evaporation method, a metal heating source and a vacuum container are arranged, ultrafine particles are formed from metal vapor, and a film composed of the ultrafine particles is formed. The formation of a metal film by such a gas deposition method has been put to practical use with wiring materials such as Ni and Cu, and specifically, for repairing disconnection of various printed wiring boards and formation of surface mounting pad electrodes in semiconductor devices. Used.

[0004] On the other hand, a film formation using ultrafine particles of an oxide ceramic material different from a metal material has been proposed.
JP-A-3-93606 discloses Bi-Pb-Sr-C
A method for forming an oxide superconducting thick film made of a-Cu-O is shown. Japanese Patent Application Laid-Open No. Hei 4-188503 discloses BaTi
A method for forming a composite film of an O ₃ ceramic dielectric thick film and a polymer coating film for securing this withstand voltage is shown. Japanese Patent Application Laid-Open No. Hei 6-93418 discloses a method for forming a patterned thick film which is formed directly on a substrate by a gas deposition method using a wide range of fine particle materials. Japanese Patent Application Laid-Open No. 9-268378 discloses a manufacturing method in which a gas deposition film is formed directly on a substrate, a substrate mounting stage is operated, and a large-area film can be easily formed.

[0005] The present inventors have disclosed in Japanese Patent Application Laid-Open No. 10-202.
No. 171 proposes a manufacturing method and an apparatus for obtaining a finely-shaped object by keeping a nozzle / film surface distance relationship by film deposition when jetting ultrafine particles from a nozzle to a substrate constant.

[0006] Also, Jpn.J.Appl.Phys.VOl.36 (1997) 1159
Discloses an example in which PZT is formed by gas deposition at a substrate temperature of 700 ° C. on a Si substrate on which a Pt film is deposited, and then heat treatment is performed at a high temperature of about 900 ° C. The description in the middle shows damage to the substrate due to the collision of the fine particles and the deterioration of the PZT film characteristics due to the damage.

Further, the present inventors have proposed Proceeding of AMF-2.
Has shown the production of a PZT thick film on a SUS substrate. In Jpn.J.Appl.Phys.VOl.38 (1999),
An example of PZT fabrication on a Si substrate is shown. But,
In this report, the substrate damage phenomenon due to particle collision is shown by TEM (transmission electron microscope) observation.

[0008]

As described above, when a PZT piezoelectric film formed on a substrate is used for an electro-mechanical transducer, it is not preferable to reduce the mechanical strength of the structure. In particular, a Si single crystal substrate is advantageous for forming a three-dimensional microstructure by anisotropic etching.
An element in which a piezoelectric film such as PZT is arranged on a workpiece is effective for miniaturization and high performance of the element. On the other hand, the above-described induction of crystal defects due to substrate damage and reduction of mechanical strength are required for the reliability of the element. Unfavorable in terms of surface.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances. Therefore, the present invention relates to a piezoelectric ceramic thick film structure formed by gas deposition, in which ceramic particles are sprayed from a nozzle onto a substrate to obtain a deposited film. The purpose of the present invention is to reduce the damage to the substrate and to prevent the mechanical strength of the laminated structure composed of the piezoelectric ceramic thick film / substrate from decreasing.

According to a first aspect of the present invention, an intermediate film for reducing substrate damage caused by gas deposition film formation is provided to prevent a decrease in mechanical strength of a structure.
By gas deposition film formation, substrate damage when forming a film using Si on the substrate is mitigated by the intermediate film arrangement,
A third aspect of the present invention is to prevent a decrease in mechanical strength of a structure by using an oxide thin film as an intermediate film when a piezoelectric ceramic film such as PZT is formed on a substrate by a gas deposition method. The invention of claim 4 is to reduce the damage at the time of film formation by making the thickness of the intermediate film 0.05 μm or more, and the invention of claim 5 is to arrange the electrode at the intermediate film. Layered on a Si substrate, and
The purpose of the present invention is to deposit a piezoelectric film by a gas deposition method and reduce damage at the time of deposition.

According to a sixth aspect of the present invention, an intermediate film is provided with an electrode function, laminated on a Si substrate, and a piezoelectric film is deposited thereon by a gas deposition method to reduce damage at the time of deposition. The invention according to claim 7 corresponds to the composition of a piezoelectric ceramic film formed by a gas deposition method.
Arranging a suitable intermediate film composition, specifically, the piezoelectric ceramic composition is a lead-based piezoelectric ceramic composition,
The purpose of the present invention is to reduce damage during film formation by forming an intermediate film having at least one common ceramic composition except for oxygen in the intermediate film.

The invention according to claim 8 is to provide an intermediate film satisfying the above conditions by a sol-gel method having excellent composition controllability and excellent film thickness controllability, and supplying the intermediate film. According to a ninth aspect of the present invention, an intermediate film satisfying the above conditions is formed by a sputtering method having excellent composition controllability and excellent film thickness controllability, and the intermediate film is supplied. Is excellent in the composition controllability of the intermediate film satisfying the above conditions,
Further, it is intended to supply an intermediate film by forming a film by an MO-CVD method having excellent film thickness controllability.

[0013]

According to the first aspect of the present invention, piezoelectric ceramic fine particles are suspended in a gas to form an aerosol, and the aerosol is sprayed at high speed onto a substrate to deposit the piezoelectric ceramic. In the film structure, between the substrate and the gas deposition film, 1
It is characterized by having an intermediate film composed of at least layers.

According to a second aspect of the present invention, in the first aspect, the substrate is an Si single crystal substrate. According to a third aspect of the present invention, in the first or second aspect, the intermediate film is an oxide thin film. According to a fourth aspect of the present invention, in the third aspect, the thickness of the intermediate film made of the oxide thin film is 0.0.
It has a thickness of 5 μm or more.

According to a fifth aspect of the present invention, an intermediate film made of an oxide thin film having a thickness of 0.05 μm or more is formed by using an Si substrate on which an electrode film for applying an electric field is applied to the piezoelectric ceramic film. It is characterized by being arranged between an electrode film and a piezoelectric ceramics thick film formed by a gas deposition method.

According to a sixth aspect of the present invention, in the fifth aspect, the electrode film for applying an electric field to the piezoelectric ceramic film is a conductive oxide ceramic film. According to a seventh aspect of the present invention, in the third to fifth aspects, at least one or more of the elements constituting the piezoelectric ceramics formed by the gas deposition method are common except for oxygen. It is characterized by being composed of elements.

According to an eighth aspect of the present invention, in the seventh aspect, the intermediate film is formed by a sol-gel method. According to a ninth aspect of the present invention, in the seventh aspect, the intermediate film is formed by a sputtering method. According to a tenth aspect of the present invention, the intermediate film described in the seventh aspect is formed by MO-CVD.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Invention of Claim 1) FIG. 1 is a schematic diagram of a main portion for explaining a configuration diagram of a gas deposition apparatus, wherein 1 is a carrier gas cylinder, 2 is an aerosol chamber. 3, PZT piezoelectric ceramic fine particles, 4
Is a deposition chamber, 5 is a nozzle, 6 is a pattern mask, 7 is a substrate holder, 8 is an XYZ stage, 9
Is a vacuum system in which the PZT piezoelectric ceramic particles 3 are suspended in a carrier gas to form an aerosol, and the aerosol is sprayed onto a substrate at a high speed to form a film. For the substrate, metal, ceramics, glass, Si wafer or various oxide crystal materials are used. When particles accelerated at high speed collide with the substrate, the kinetic energy of the particles causes a film deposition phenomenon. The substrate damage due to the collision is particularly remarkable in a material broken by brittle fracture, and specifically, corresponds to the above-described various substrates except for a metal material. In particular, when application to a mechanical element such as an actuator is considered, a decrease in mechanical strength becomes important from the viewpoint of element reliability. Such brittleness of the substrate material is derived from the fact that the constituent atoms are connected by ionic bonds or covalent bonds and have a structure that is difficult to move. In such a structure, stress relaxation is unlikely to occur, and even a relatively small stress will cause breakage. In the brittle fracture at this time, the mode in which the tensile stress acts perpendicular to the crack plane becomes dominant.

As a method of not causing the powder collision damage to the substrate, there is a method of arranging an intermediate film on the substrate and then performing gas deposition film formation. The prevention of mechanical strength reduction of the substrate by the intermediate film is constituted by the following mechanism. The brittle fracture material is broken by the propagation of the crack. Therefore, it is advisable to prevent the propagation of cracks as described in (1) and (2) below. (1) Prevention of crack propagation due to material discontinuity at the interface between different materials (that is, the interface between the intermediate film and the substrate). (2) Stoppage of crack propagation due to crack bending phenomenon utilizing the structure in the interlayer film.

Here, the intermediate film structure corresponds to a grain boundary of a crystalline material or the like. The cracks driven from the surface are bent in the direction of propagation at each grain boundary, and each time the propagation energy is reduced, and as a result, the cracks travel only a short distance. It is important to deposit the intermediate film on the substrate because the above two effects can be obtained.

Specific measurement of mechanical strength will be described. Important parameters representing mechanical properties
There are hardness indicating elastic strength and fracture toughness indicating brittleness.
As a method of measuring the latter fracture toughness indicating brittleness, a method is generally used in which a Vickers indenter is press-fitted, a crack is artificially generated, and the critical stress intensity factor and the fracture toughness are obtained from the length of the crack. However, the configuration in the usage form of the present invention is a piezoelectric film / substrate laminate, and when the fracture toughness of the substrate is a problem, such a measurement method is not suitable. Therefore, in order to quantify the strength of the structure, the bending strength (flexural strength) is measured by a three-point bending test.

The three-point bending test method is a general material strength evaluation method (not shown here).
The width is b, the height is h, the breaking load is P, and the measured data is statistically processed using a Weibull distribution function. This is because the nondestructive probability P (σ) under a certain stress σ is expressed by the following equation (1).
It follows.

[0023]

(Equation 1)

Σ ₀ represents the average bending strength, and m is the Weibull coefficient. From the above-mentioned shape, the breaking stress σ _n is expressed by the equation (2).

[0025]

(Equation 2)

Here, assuming that the sample numbers are assigned in ascending order of the breaking stress and the total number of the samples is N, the non-destruction probability P (σ) is expressed by the following equation (3).

[0027]

(Equation 3)

Therefore, lnln (1 / P (σ)) vs. ln
A graph of σ was drawn, and the average bending strength was calculated from this linear relationship.

(Inventions of Claims 2 and 7) The Si single crystal substrate is advantageous for forming a three-dimensional microstructure by anisotropic etching, and a piezoelectric film such as PZT is disposed on the Si processed material. The element is effective for miniaturization and high performance of the element. A sample in which a gas deposition film is directly formed on a Si (100) single crystal substrate without an intermediate film is prepared, and a cross-sectional TEM observation is performed. Cross-sectional TEM observation is suitable for evaluation because macroscopic structural defects such as cracks and further microscopic defects in crystal engineering can be observed. Correspondence between the damage structure and mechanical strength change by TEM observation is shown, the validity of the strength measurement by the three-point bending test method is demonstrated, and the average bending strength of the sample formed with the intermediate film is compared. . In addition, S prepared by a sol-gel method as an intermediate film
An iO ₂ film with a thickness of 200 nm is used.

(Inventions of Claims 2, 3 and 8) The oxide material provides good adhesion over various kinds of substrates. In particular, Si
Strong adhesion to the substrate can be easily obtained. As various oxide materials, titanium oxide, zirconium oxide,
Tantalum oxide is formed by a sputtering method and examined as an intermediate film candidate. The method is a comparison of the transverse rupture strength between the sample formed by gas deposition without the intermediate film and the sample formed by gas deposition with the intermediate film.

(Invention of Claim 4) From FIG. 3, the damage area of the Si substrate is estimated to be about 0.15 μm. When an intermediate film is arranged and there is no contribution such as a crack stop or a random bending of a crack due to a heterogeneous interface, it is easily associated that an intermediate film thickness of at least 0.15 μm is required. Since an actual interlayer film has a crack stopping function, it is suggested that a value smaller than this value is sufficient. Accordingly, the thickness of the intermediate film is changed, and the change in the transverse rupture strength of the sample formed by gas deposition is examined.

(Invention of claim 5) As a method of applying an electric field to a piezoelectric thick film by a gas deposition method, a base on which an electrode is disposed on a Si substrate is used, and a gas deposition film forming damage relieving layer is formed thereon. An intermediate film is disposed. Electrodes are arranged above the piezoelectric ceramic film, and an electric field is applied to the upper electrode and the electrode below the intermediate film to form an electromechanical transducer. On the electrode on the Si substrate, a thermal oxide film is grown for electrical insulation from the Si substrate. As the electrode, a film of a material made of a platinum group element such as Ir, Pt, Pt-Rh or an alloy thereof is preferable.
In addition, since these electrode materials and the SiO ₂ film have weak adhesion,
It is preferable to appropriately use Ta, Ti, or a nitride film thereof as the adhesion layer. The electrode film and the adhesion film are formed to a desired thickness by a DC magnetron sputtering method. With such a configuration, a Si substrate with an electrode film is completed.

(Invention of claim 6) The function of alleviating gas deposition damage is imparted to the electrode film on the Si substrate to simplify the process.

(Invention of claim 7) A film having the same composition as the gas deposition piezoelectric film is deposited as an intermediate film by another film forming technique. When the gas deposition piezoelectric material is a lead zirconate titanate-based ceramic material, lead oxide, which is a constituent element of the piezoelectric material, is used as an intermediate film due to compatibility with the film and a voltage distribution effect of a driving voltage described later. , Titanium oxide, zirconium oxide, and other single element oxides,
A composite oxide material such as lead titanate and lead zirconate, or a solid solution composition of lead titanate and lead zirconate may be used. In particular, it is preferable that the composition of the gas deposition piezoelectric film is the same as that of the intermediate film.

(Invention of Claim 8) A case where an intermediate film is formed by a sol-gel method will be described. sol-g
The el method is a method for producing an inorganic oxide that is completed by hydrolyzing and polycondensing a metal organic compound such as a metal alkoxide in a solution system, growing a metal-oxygen-metal bond, and finally sintering. is there. The features of the sol-gel method are as follows:
The reason is that a film having a uniform large area can be obtained at a relatively low substrate temperature. Further, since the film is formed from the solution, the adhesion to the substrate is excellent. Specifically, a mixed solution of a metal-organic compound corresponding to the metal contained in the finally obtained composite oxide is applied onto a substrate, and a thick film made of these inorganic oxides is laminated, followed by firing. Perform a knot. Examples of the metal organic compound to be used include alkoxides such as methoxide, ethoxide, propoxide, butoxide and the like of metals constituting the inorganic oxide, and acetate compounds (S1). Inorganic salts such as nitrates, oxalates and perchlorates may be used. In order to produce an inorganic oxide from these compounds, it is necessary to promote hydrolysis and polycondensation reactions, so that water must be added to the coating solution.

The amount of water to be added differs depending on the system. If the amount of water added is too large, the reaction proceeds rapidly, so that the quality of the obtained film tends to be non-uniform, and it is difficult to control the reaction rate. If the amount of water added is too small, it is difficult to control the reaction, and there is an appropriate amount. Generally, it is preferable to use an equimolar to 5-fold equimolar to the number of bonds to be hydrolyzed. Further, by adding a hydrolysis solvent, the reaction rate and the reaction form can be controlled.
As the catalyst, general acids and bases are used. It is said that an acid catalyst easily forms a linear polymer, and a basic catalyst easily forms a three-dimensional polymer.
It cannot be said unconditionally because of this. In the case of the present invention, an intermediate structure between the two is desirable. As the solvent for addition, (S
3), those having excellent compatibility are desirable. Further, a chelating agent or the like may be added.

By applying the above-described solution (S7) and annealing (S8, S9), the inorganic oxide is crystallized from amorphous. Although the sintering temperature varies depending on the material, the sintering can be performed at a temperature lower than the temperature required for firing ordinary metal oxide powder. In order to produce a crack-free film by coating, drying, and baking, the film thickness that can be formed in one step must be about 100 nm or less, which is easily achieved by adjusting the concentration of the coating solution (S5). Can be executed. Further, in order to obtain a desired film thickness, this coating film (S7), drying (S7)
8), the firing step (S9) can be performed by repeating a plurality of times. This manufacturing example is shown in FIG.

(Invention of claim 9) Next, a method of forming an intermediate film by a sputtering method will be described. It is better to use a sputtering phenomenon by rf discharge for forming a film of an oxide or the like. Generally, in a vacuum of 0.1Pa～10Pa, applying an AC signal of 13.56MH _Z parallel plate capacitor consisting of the target surface to be substrate and the film deposition, to form a sputtering discharge. A material having a composition to be formed into a film is arranged on the target, and rf power is applied to the target electrode side. A negative self-bias is generated on the target electrode side due to a difference in mobility between holes and electrons. The sputter ions during the discharge generate a sputtering phenomenon with respect to this negative potential, and the target material can be formed into a film. In particular, film formation by magnetron sputtering in which a magnetic field is arranged is preferable in order to increase the film formation speed. Also, from the size of the ion cross section,
A discharge using Ar gas is used.

When a PZT film is to be obtained as an intermediate film, a PZT ceramic disk is used as a target. In order to improve film / substrate adhesion or to obtain a high-quality crystallized film, substrate heating during film formation is important. As the oxide film formed by heating the substrate, a film lacking oxygen atoms is easily formed. Therefore, it is preferable to use a mixed gas obtained by adding some oxygen to Ar of the sputtering gas. In addition to using a PZT ceramic sintered body as the target material,
A metal target of lead, titanium, or zirconium may be used. In this case, a desired intermediate film can be formed by sputtering using an oxygen-containing gas as a sputtering gas in combination with an oxidation reaction.

It should be noted that a film having a composition different from the target composition may be formed. This is due to the so-called difference in the sputter yield, which is how many atoms are sputtered per colliding Ar ion. It is also caused by the probability of sputtered atoms adhering to the substrate. Therefore, it is necessary to bias the target to a specific composition in advance so as to correct this difference. Further, when producing a composite oxide thin film containing lead, it is necessary to consider a composition deviation due to a high vapor pressure of lead and lead oxide. In this case, in particular, as an effective manufacturing method, sputter discharge is performed with a target composition on which a sufficient lead excess composition is deposited, and the substrate temperature during film formation is set at 5%.
The temperature is kept in the range of 00 ° C to 650 ° C. In the case of producing a lead titanate thin film, titanium oxide particles and lead oxide particles are simultaneously deposited on a substrate. The titanium oxide that has reached the substrate does not re-evaporate at the substrate temperature. On the other hand, while lead oxide reacts with titanium oxide to form lead titanate, excess lead oxide also reaches the substrate. At this time, if the substrate temperature is sufficient for re-evaporation of lead oxide, the excess amount of lead oxide will re-evaporate and will not be reflected in the film composition. By such self-aligned film formation, a stable intermediate layer composition thin film can be obtained.

(Invention of Claim 10) Finally, the intermediate film is
A method for manufacturing by an O-CVD method will be described. This method uses a metal organic compound or an organometallic compound as a raw material for vapor phase growth. In the case of a PZT thin film, Pb (C ₂ H ₅ ) ₄ , Pb (DPM) ₂ , (C ₂ H ₅ ) is used as a lead raw material. )
₃ PbOCH ₂ C (CH ₃ ) ₃ , Pb (C ₂ H ₅ ) ₃ (t-O
Zr (t-O) as a zirconium raw material such as C ₄ H ₉ ).
_{C 4 H 9), Zr (} DPM) 4, etc., as the titanium material _{Ti (i-OC 3 H 7} ) 4, Ti (DPM) 2 (i-OC 3 H
₇ ) ₂ , Ti (OC ₂ H ₅ ) _{4 and the} like can be used. When the raw material is liquid at room temperature, it is relatively easy to introduce the raw material gas into the reactor by a normal bubbling method.However, when a raw material that is solid at room temperature such as a metal complex is used, It is necessary to sublimate and send it to the reaction chamber. In particular, Pb (DPM) ₂ and (C ₂ H ₅ ) ₃ PbO
When comparing _{CH 2 C (CH 3) 3} , lead content in the film to the film forming times _{(C 2 H 5) 3 PbOCH} 2 C (CH 3) 3 towards less variation, and the film growth The speed is also stable and suitable. Alternatively, a solution vaporization method in which a solid raw material is transported in a liquid state using tetrahydrofuran or alcohol as a solvent, and introduced into a reaction chamber using a vaporizer may be used. When an oxide thin film is obtained, Ar and oxygen are used as carrier gases. These gas pipes have a heating mechanism for preventing deposition of sublimation gas substances during transportation.

The gaseous raw material transported as described above is introduced into the reactor under reduced pressure, and contributes to a desired film formation.
The pressure in the reaction chamber is reduced to about 1 Torr to 40 Torr, and the film is formed at a film growth temperature of 500 ° C. to 650 ° C. The film quality strongly depends on film forming parameters such as a growth temperature, a gas supply amount, and a reaction pressure, and optimal conditions for a CVD apparatus and a source gas are selected.

Example 1 (corresponding to claim 1) A PZT film was formed on various substrates by a gas deposition method for about 50 hours.
A film was formed with a thickness of μm. Table 1 shows the film forming conditions.

[0044]

[Table 1]

Table 2 shows how the bending strength changed depending on the type of substrate used and the presence or absence of the intermediate film. The intermediate film is PZT (52/48) formed by the sol-gel method described in Example 7 described later, and has a thickness of 0.15 μm.

[0046]

[Table 2]

The values in Table 2 indicate the value of (deflection strength after film formation) / (deflection strength before film formation). This is because the bending strength measurement has a statistical distribution, and it is easier to understand the comparison with relative values. In the numerical values in Table 2, if the value is 1 or more, the transverse rupture strength after film formation is increased, and if the value is 1 or less,
This means that the transverse rupture strength after film formation was reduced. Further, since SUS304 in Table 2 is not a brittle fracture material, the Young's modulus is obtained from the relationship between the load and the displacement at the load point, and the numerical value is shown.

As shown in Table 2, in the cubic single crystal substrate,
When the cleavage plane exists on two axes and the collision energy of gas deposition particles is irradiated from a direction perpendicular to one of the axes, the bending strength of the substrate material is 1 / maximum of the initial value. It turned out to be reduced to 20. On the other hand, an increase in the transverse rupture strength after film formation was confirmed in all the samples on which the intermediate film was disposed. This increase is due to the fact that the interlayer film has reduced gas deposition damage,
It can be seen that the PZT film of m contributed to the strength improvement. In the SUS304 sample, the strength is different between the case where the intermediate film is not arranged and the case where the intermediate film is arranged. In other words, although the damage due to gas deposition is small, it can also be applied to a rigid material, and it can be said that this damage can be removed by the arrangement of the intermediate film.

Example 2 (corresponding to claim 2) A PZT film having a thickness of about 50 μm was formed on various Si substrates by a gas deposition method. The film forming conditions are shown in Table 1 above. The intermediate film is a sol-gel PZT film having a thickness of 0.15 μm. The test piece was L = 10 m, b = 3 m
m, h = 0.65 mm (L, b, h correspond to equation (2))
And the bending strength of each sample, at least 6 samples, was calculated. From the measurement data, the Weibull coefficient m exists in the range of 4.8 to 5.3. Table 3 shows the results.

[0050]

[Table 3]

FIG. 3 shows a cross-sectional TEM image of a sample in which PZT is directly deposited on Si (100) by gas deposition. Microcracks were generated over a range of 1.5 μm at the film / substrate interface, and it was found that this was the cause of the strength reduction. Also, the Si substrate has cleavage planes at (100) and (111), and when grain collision energy is applied perpendicularly to the (100) plane, a large number of cleavage planes are formed at approximately 55 ° corresponding to the cleavage plane (111). It was also found that cracks had occurred. Furthermore, it is shown that the method of testing the material strength of the piezoelectric ceramic / substrate laminate by the three-point bending test, which is the evaluation method of this experiment, is appropriate, and the arrangement of the intermediate film prevents the reduction of the substrate strength. It shows what you can do.

Embodiment 3 (corresponding to claim 3) In the above-described embodiments, the sol-gel method PZT intermediate film was partially shown. In this example, a single-component oxide film was mainly formed by a sputtering method described later (Example 8), and its function as an intermediate film was confirmed. As a feature of sputtering, in the case of a single-component oxide film, it is relatively easy to form the film.
₂ , YSZ (yttria partially stabilized zirconia), Ta ₂ O
_Five films were evaluated. Table 4 shows the film forming conditions.

[0053]

[Table 4]

The intermediate film as described above was directly deposited on a Si (100) substrate. After that, the gas deposition PZT film is
0 μm was deposited, and the bending strength was measured. As a result, no decrease in the strength of the laminated structure was observed in all the samples.
The cross section of the film was observed with a scanning electron microscope (SEM).
The intermediate film structure has a stone wall-like structure composed of grains having a size of 50 nm or less, and the crack progressed randomly by this structure. This is because crack growth was suppressed.

Embodiment 4 (corresponding to claim 4) FIG. 4 shows the relationship of the change in the strength of the structure when the thickness of the intermediate film is changed. Sol-gel PZT as interlayer
A film and a sputtered YSZ film were arranged at respective film thicknesses. The substrate is Siz (100), and the gas deposition film forming conditions are the same as in the first embodiment. Due to gas deposition damage, the Si (100) substrate is reduced to 1/20 or less of the initial strength. The function of the intermediate film is determined to be effective at a film thickness at which the transverse rupture strength is higher than 1 GPa. It can be seen that the two types of intermediate films both have a thickness of 0.05 μm or more and have an effect as a damage relieving layer.

Example 5 (corresponding to claims 5 and 6) A Si (100) substrate on which an electrode film is disposed is manufactured by the following procedure. Wet thermal oxidation of Si wafer after RCA cleaning,
A thermal oxide film for electrical insulation is grown to 800 nm. next,
In order to secure the adhesion between the oxide film and the Pt electrode film, a Ta film is formed. The film is deposited to a thickness of 100 nm by DC magnetron sputtering. Next, an Ir film as an electrode film, P
The thickness of each of the t films was 3
Deposit 00 nm. After arranging the electrode film on the Si substrate in this way, an intermediate film is formed. The intermediate film is the sol-gel PZT film described in Example 1 and has a thickness of 0.15 μm. Further, a gas deposition PZT film was deposited to a thickness of 50 μm and used as a test piece. FIG. 1 shows a cross-sectional TEM image. From this image, it can be seen that there is no evidence of any crack at the Si interface. The flexural strength of this sample was 1.47 Gpa.
Which also showed reduced results of damage. Further, an SiO ₂ thermal oxide film is disposed on a Si substrate, and a conductive oxide material is formed thereon. The ceramic film has an intermediate film function, and since the ceramic material has a function as an electrode, the film structure can be simplified.

Example 6 (corresponding to claim 7) An electrode is formed on an upper part of a piezoelectric ceramics thick film produced by a gas deposition method, and an electric field can be applied. This method includes, for example, an intermediate film formed on an Nb-doped strontium titanate single crystal substrate (in this case, also serving as a substrate and a lower electrode), a piezoelectric ceramic thick film,
This is the configuration of the upper electrode, or the configuration of the Si substrate, the intermediate film, the piezoelectric ceramic thick film, and the upper electrode on which an electrode film such as Pt is disposed. The input electric field is distributed to the intermediate film of the dielectric material and the piezoelectric film existing between the electrodes.
It can be described by direct connection of two capacitive elements. In an actuator using a piezoelectric ceramic material, it is preferable that a voltage is efficiently applied to the piezoelectric ceramic layer. The distribution of the applied voltage depends on the thickness of the piezoelectric ceramic thick film, the relative dielectric constant,
_{T F} such voltages, respectively, epsilon _{F, V F,} the film thickness of the intermediate layer, the dielectric constant, the voltage applied respectively _{t i,} ε _{i, V i}
And then, when the same area of the piezoelectric ceramic capacitor and the intermediate layer capacitor, when a voltage is applied to V, V _F, V
_i is given by equation (4).

[0058]

(Equation 4)

Here, ε _F = 1000, t _F = 10 μ
Assuming that m and t _i = 0.1 μm, the relationship between the electric field (E _F = V _F / t _F ) applied to the piezoelectric ceramic thick film portion and the relative dielectric constant of the intermediate film is as shown in FIG. The dielectric constant of the intermediate film is 4
When (for example, SiO ₂ ) is low, the applied electric field is applied to the intermediate film much, and is hardly applied to the piezoelectric ceramic film. This leads to a higher drive voltage. If the relative dielectric constant of the intermediate film is 10 or more, 50% of the applied voltage is distributed (at each film thickness), so that the relative dielectric constant material of 10 or more is preferable as the intermediate film.

In general, the relative dielectric constant of a dielectric material is derived from the bonding state of the constituent elements, and is low for covalent bonding and large for ionic bonding. From such a viewpoint, an oxide material of a metal element is preferable. Needless to say, a ferroelectric material containing PbO is suitable. The relative permittivity of the TiO ₂ sputtered film was 17, and the relative permittivity of the PbTiO ₃ sputtered film was 120, which satisfied the above condition of the relative permittivity of 10 or more. In addition, sol-gel PZT (52/4
8) The dielectric constant of the film was 400.

Example 7 (corresponding to claim 8) A sol-gel PZT film was manufactured by the method shown in FIG.
Was. Starting materials are lead acetate trihydrate and zirconium propoxy.
Sid, titanium isopropoxide, methoxy as common solvent
Use ethanol. TiO_TwoIf you get a film, titanium
It is made according to the flow of FIG. 2 using only isopropoxide.
It is possible to Also, PbTiO _ThreeFor membranes,
Use lead acetate trihydrate and titanium isopropoxide
No. Vinegar in sufficiently dehydrated methoxyethanol
Dissolve lead acid trihydrate. Here, crystallization water is removed.
U. Ultimately 60pp by Karl Fischer moisture meter
Dewatering is performed until the water content reaches m or less. Zirconium
Mupropoxide and titanium isopropoxide are
Dissolve in toxic ethanol and reflux for alcohol
Allow exchange reaction. The end point of the reaction is liquid chromatography
Detection of propanol and isopropanol concentrations
Indicates the end point. In addition, here also 60 ppm or less
Desirably the amount of water. Mix these three solutions
The mixture is further refluxed to combine the complex alkoxide compound.
To achieve. Combine this solution with the stock solution (preservation solution).
And, if necessary, dried under reduced pressure.
Diluted with methoxyethanol to the desired concentration,
A water decomposition reaction is applied, dried and fired to obtain a film. here
Is dried under reduced pressure with excellent preservability, and 0.1 m
Adjust the concentration of O1 / 1, and make it equal to the total alkoxide concentration.
After spin-coating and film formation
Was. An Si wafer having a Pt electrode disposed on a substrate was used.
The film thickness formed in one process was 0.05 μm. This
As a method to increase the film thickness of the coating solution, the coating solution concentration is set to a maximum of 0.4 mO.
It can be increased to 1/1, increase of coating solution concentration and film thickness
The increase was directly proportional. Alternatively, polyet
Tylene glycol is added to the coating solution to increase the viscosity and form a film
It is also possible in this case to use a maximum of 0.7 in one process.
A film having a thickness of μm was possible. In this way, an interlayer film is formed.
It was found that it was possible to manufacture
This effect has already been described in the first embodiment).

Embodiment 8 (corresponding to claim 9) The above-described embodiment relates to the formation of a single component oxide film by sputtering.
3. Here, the lead-based piezoelectric material PMN-P
It shows about the film formation of Z-PT and the function of the intermediate film.
You. The detailed chemical formula of PMN-PZ-PT is 0.125PMN-0.875PZT (54/46): Pb (Mg_1/3 Nb_2/3) O_Three
-Pb (Zr_0.54 Ti_0.46) O _Three (Sr 0.18 mO1% substitution), the Pb site was substituted by 18% Sr. This chemical formula
Of stoichiometric ceramic target based on
did. Table 5 shows the film forming conditions. The substrate used was a Pt electrode film
FIG.

[0063]

[Table 5]

When forming a film by sputtering with a stoichiometric composition,
The formed film composition mainly forms a lead-deficient film. Therefore,
In order to correct this lead deficiency, several PbO pellets were arranged on a ceramic target, and lead correction was performed. Also,
Self-alignment of excess lead occurred at a substrate temperature of 550 ° C. or higher, and a good PMN-PZ-PT film could be formed mainly at a substrate temperature of 550 ° C. or higher. The dielectric constant of this film reached 2070, which was suitable for distribution of applied voltage. A gas deposition PZT thick film was placed on this intermediate film-placed Si substrate, and the bending strength of the laminated structure was measured. The value reaches 1.5 GPa and this PMN
It was confirmed that the -PZ-PT film also functions as an intermediate film.

Example 9 (corresponding to claim 10) Pb (C ₂ H ₅ ) ₄ , Ti (OiC)
_A PbTiO ₃ film was produced using ₃ H ₇ ) ₄ . The pressure in the reaction chamber was 5 Torr. Pt electrode film arrangement S on substrate
An i-wafer was used. In the CVD film formation process, the growth rate is determined by the transport and supply amount of the reaction gas molecules to the substrate surface. Therefore, the deposition rate of the single substance was determined in advance, and the raw material gas was supplied in an appropriate flow rate range. Since the deposition rate of PbO strongly depends on the oxygen gas concentration, while the deposition rate of TiO ₂ did not depend on the oxygen concentration, the oxygen partial pressure that gave a stable deposition rate of both was determined. In this experimental system, the oxygen partial pressure was 50%. Also, PbO with respect to the substrate temperature
The rate of precipitation changed and showed a very steep change with respect to temperature such that precipitation started at a substrate temperature of 400 ° C. and was saturated at 500 ° C. On the other hand, in the case of TiO ₂ ,
Further, the precipitation started, and it had a diffuse change of being saturated at 500 ° C. Therefore, film formation was performed at 550 ° C., which gives a stable deposition rate to both. As the carrier gas flow rate increases, the film growth rate increases. PbTiO ₃ growth rate at a carrier gas flow rate of 60 sccm, 0.6 μm / h
Was obtained. The relative dielectric constant of this film was 120. This is a value having no problem with the distribution of the applied voltage. A gas deposition PZT thick film was placed on this intermediate film-placed Si substrate, and the bending strength of the laminated structure was measured. The value reached 1.5 Gpa, and it was confirmed that this PMN-PZ-PT film also functions as an intermediate film.

[0066]

According to a first aspect of the present invention, there is provided a piezoelectric ceramic thick film structure by gas deposition in which piezoelectric ceramic fine particles are suspended in a gas to form an aerosol, and the aerosol is jetted and deposited on a substrate at a high speed. Since an intermediate film including at least one layer is provided between the substrate and the gas deposition film, damage to the substrate due to gas deposition film formation can be reduced, and a reduction in mechanical strength of the structure can be prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, since the substrate is a Si single crystal substrate, in the gas deposition film-formed structure using the Si substrate, damage to the substrate is reduced, and Can be prevented from being reduced in mechanical strength.

According to a third aspect of the present invention, in the first or second aspect, since the intermediate film is an oxide thin film, it is possible to provide a simple and effective damage relieving film.

According to a fourth aspect of the present invention, in the third aspect of the present invention, since the thickness of the intermediate film made of an oxide thin film is 0.05 μm or more, a function of alleviating damage can be exhibited.

According to a fifth aspect of the present invention, a silicon substrate having an electrode film for applying an electric field to a piezoelectric ceramic film is used, and the oxide intermediate film according to the fourth aspect is formed with this electrode by a gas deposition method. Since it is arranged between the piezoelectric ceramic thick films, the same damage to the substrate can be mitigated by arranging the intermediate film on the lower electrode arrangement substrate which can be used for applying an electric field.

According to a sixth aspect of the present invention, since the electrode film for applying an electric field to the piezoelectric ceramics film according to the fifth aspect is a conductive oxide ceramics film, the use of a conductive oxide ceramics material makes it possible to simplify the process. Can be achieved.

According to a seventh aspect of the present invention, at least one or more of the elements constituting the piezoelectric ceramics formed by the gas deposition method of which the intermediate film composition is common except for oxygen are included. By arranging an intermediate film of the same quality as the gas deposition film, the partial pressure of the electric field during driving can be improved, and the damage to the substrate can be reduced.

According to an eighth aspect of the present invention, the intermediate film according to the seventh aspect is formed by a sol-gel method.
By the l-gel method, an intermediate film having excellent composition controllability and film thickness controllability can be provided.

According to the ninth aspect of the present invention, since the intermediate film according to the seventh aspect is formed by a sputtering method, an intermediate film having excellent composition controllability and film thickness controllability can be provided by the sputtering method.

According to a tenth aspect of the present invention, the intermediate film according to the seventh aspect is formed by MO-CVD.
-An intermediate film having excellent composition controllability and film thickness controllability can be provided by the CVD method.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part for describing a configuration diagram of a gas deposition apparatus.

FIG. 2 is a diagram showing an example of forming a PZT film by a sol-gel method.

FIG. 3 is a view showing a cross-sectional TEM image of a sample in which PZT is directly deposited on Si (100) by gas deposition.

FIG. 4 is a diagram showing a relationship of a structural strength change when the thickness of an intermediate film is changed.

FIG. 5 is a view showing a cross-sectional TEM image when an oxide intermediate film having a thickness of 0.05 μm or more is formed on a Si substrate.

FIG. 6 shows an electric field (E _F) applied to the piezoelectric ceramic thick film portion.
= V _F / t _F ) and the non-dielectric constant of the intermediate film.

[Explanation of symbols]

1 ... Carrier gas cylinder, 2 ... Aerosol chamber, 3
... PZT piezoelectric ceramic fine particles, 4 ... deposition chamber, 5 ... nozzle, 6 ... pattern mask, 7 ... substrate holder, 8 ... XYZ stage, 9 ... vacuum system.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Jun Akito 1-2-2 Namiki, Tsukuba, Ibaraki Pref. LA11 4K044 AA02 AA11 AA12 AA13 BA12 BB03 BC14 CA13 CA14 CA15 CA23

Claims (10)

[Claims] In a piezoelectric ceramic thick film structure by gas deposition in which piezoelectric ceramic fine particles are suspended in a gas to form an aerosol, and the aerosol is jetted onto a substrate at a high speed and deposited, the substrate and the gas deposition deposited film are formed. A piezoelectric ceramic thick film structure comprising an intermediate film composed of one or more layers between them. 2. The piezoelectric ceramic thick film structure according to claim 1, wherein said substrate is a Si single crystal substrate. 3. The piezoelectric ceramic thick film structure according to claim 1, wherein the intermediate film is an oxide thin film. 4. The piezoelectric ceramic thick film structure according to claim 3, wherein the intermediate film made of the oxide thin film has a thickness of 0.05 μm or more. 5. An Si substrate having an electrode film for applying an electric field to the piezoelectric ceramic film, the thickness of which is 0.05 μm.
A piezoelectric ceramic thick film structure comprising an intermediate film made of an oxide thin film having the above-mentioned thickness between the electrode film and a piezoelectric ceramic thick film formed by a gas deposition method. 6. The piezoelectric ceramic thick film structure according to claim 5, wherein said electrode film for applying an electric field to said piezoelectric ceramic film is a conductive oxide ceramic film. 7. The composition of the intermediate film, wherein at least one or more of the elements constituting the piezoelectric ceramics formed by the gas deposition method, excluding oxygen, are composed of common elements. 6. The piezoelectric ceramic thick film structure according to any one of 5. 8. The piezoelectric ceramic thick film structure according to claim 7, wherein said intermediate film is formed by a sol-gel method. 9. The piezoelectric ceramic thick film structure according to claim 7, wherein said intermediate film is formed by a sputtering method. 10. The piezoelectric ceramic thick film structure according to claim 7, wherein said intermediate film is formed by MO-CVD.