JP4142726B2 - Film-forming method, piezoelectric film, and piezoelectric element - Google Patents

Description

 The present invention includes a film forming method for forming a film by a vapor phase growth method using plasma, a piezoelectric film formed using the film forming method, a piezoelectric element using the piezoelectric film, and the piezoelectric element. The present invention relates to a liquid ejection device.

  A piezoelectric element having a piezoelectric film having a piezoelectric property that expands and contracts as the electric field application intensity increases and decreases, and an electrode that applies an electric field to the piezoelectric film is used as an actuator mounted on an ink jet recording head. Yes. As a piezoelectric material, a perovskite oxide such as lead zirconate titanate (PZT) is known.

  The piezoelectric film can be formed by a vapor phase growth method such as a sputtering method. In a piezoelectric film made of a Pb-containing perovskite oxide such as PZT, Pb detachment tends to occur when the film is formed at a high temperature. For this reason, in a piezoelectric film made of a Pb-containing perovskite oxide, it is necessary to obtain film forming conditions in which a perovskite crystal with a small pyrochlore phase grows well and Pb detachment does not easily occur.

For example, in Non-Patent Document 1, a suitable film forming condition for a piezoelectric film is required by fixing conditions other than the film forming temperature and changing the film forming temperature. In FIG. 3 described in Non-Patent Document 1, the PbTiO ₃ film has a pyrochlore phase structure at a film formation temperature of about 500 ° C. or less, and a perovskite crystal grows at a film formation temperature of about 550 to 700 ° C. It is shown that an amorphous structure is obtained at a temperature of 0 ° C. or higher.

In Patent Document 1, in the PZT film, the relationship between the film forming pressure and the Pb amount in the film and the relationship between the film forming temperature and the Pb amount in the film are required (FIGS. 1 and 2 of Patent Document 1). See). Patent Document 1 describes that the film forming pressure is preferably 1 to 100 mTorr, and the film forming temperature is preferably 600 to 700 ° C. (see claims 2 and 5 of Patent Document 1).
JP-A-6-49638 Ceramics 21 (1986) 119

  As described in Non-Patent Document 1 and Patent Document 1, conventionally, a piezoelectric film made of a Pb-containing perovskite oxide such as PZT is preferably formed at a film forming temperature of 550 to 700 ° C. However, as a result of studies by the present inventors, it has been found that a perovskite crystal having a small pyrochlore phase grows even at about 420 to 480 ° C., and a piezoelectric film having good piezoelectric characteristics can be obtained. It is preferable that the film can be formed at a lower temperature because Pb loss can be suppressed.

  Regardless of whether Pb is contained or not, when the film forming temperature is increased, stress is applied to the piezoelectric film during or after film formation due to the difference in thermal expansion coefficient between the substrate and the piezoelectric film. It is preferable that the film can be formed at a lower temperature because cracks or the like may occur in the film. If the film can be formed at a lower temperature, a substrate having a relatively low heat resistance such as a glass substrate can be used.

  In the formation of piezoelectric films, factors other than temperature and pressure are effective, and perovskite crystals with little pyrochlore phase are expected to grow when factors that affect film properties are within the preferred range. It is done.

The present invention has been made in view of the above circumstances, and in the vapor phase growth method using plasma such as sputtering, the factors of the film formation conditions that affect the film characteristics are clarified, and thereby the sputtering method and the like are clarified. It is an object of the present invention to provide a film forming method capable of stably forming a high-quality film by a vapor phase growth method using plasma.
In particular, an object of the present invention is to provide a method for forming a piezoelectric film capable of stably growing a perovskite crystal having a small pyrochlore phase, and a piezoelectric film formed by the film forming method. is there.

  In particular, the present invention can stably grow a perovskite crystal having a small pyrochlore phase and stably suppress Pb loss in a method for forming a piezoelectric film made of a Pb-containing perovskite oxide such as PZT. It is an object of the present invention to provide a method for forming a piezoelectric film that can be used, and a piezoelectric film formed by the film forming method.

  The present inventor has intensively studied to solve the above problems, and in the vapor phase growth method using plasma such as sputtering, the characteristics of the film to be formed are the film formation temperature Ts (° C.) and the plasma in the plasma. The present invention was completed by finding that a high-quality film can be formed by greatly depending on two factors of the plasma potential Vs (V) and optimizing these factors.

  The film formation method of the present invention is a film formation method in which a film is formed by a vapor phase growth method using plasma. A film formation temperature Ts (° C.), a plasma potential Vs (V) in plasma during film formation, The film forming conditions are determined based on the relationship with the characteristics of the film to be formed.

In this specification, “film formation temperature Ts (° C.)” means the center temperature of the substrate on which film formation is performed.
In this specification, the “plasma potential Vs” is measured by a single probe method using a Langmuir probe.
The plasma potential Vs (V) can be converted directly into the electron temperature (eV). This corresponds to an electron temperature of 1 eV = 11600 K (K is an absolute temperature).

  Examples of the film to which the film forming method of the present invention can be applied include a piezoelectric film (which may contain unavoidable impurities) made of one or more perovskite oxides.

When the film forming method of the present invention is applied to a piezoelectric film (which may contain inevitable impurities) made of one or more perovskite oxides represented by the following general formula (P), the following formula ( It is preferable to determine the film forming conditions within a range satisfying 1) and (2) or within a range satisfying the following formulas (3) and (4).
Formula ABO ₃ (P),
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe, Ni, and lanthanide element At least one element selected from the group consisting of:
O: oxygen atom,
The ratio of the total number of moles of the A-site element and the total number of moles of the B-site element to the number of moles of oxygen atoms is typically 1: 3, but deviates from 1: 3 within a range where a perovskite structure can be obtained. Also good. ),
400 ≦ Ts (° C.) ≦ 475 (1),
20 ≦ Vs (V) ≦ 50 (2),
475 ≦ Ts (° C.) ≦ 600 (3),
Vs (V) ≤ 40 (4)

The piezoelectric film of the present invention is a piezoelectric film (which may contain inevitable impurities) made of one or more perovskite oxides represented by the following general formula (P).
It is formed by vapor phase growth using plasma,
The film is formed under the film forming conditions satisfying the following formulas (1) and (2) or satisfying (3) and (4).
Formula ABO ₃ (P),
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe, Ni, and lanthanide element At least one element selected from the group consisting of:
O: oxygen atom,
The ratio of the total number of moles of the A-site element and the total number of moles of the B-site element to the number of moles of oxygen atoms is typically 1: 3, but deviates from 1: 3 within a range where a perovskite structure can be obtained. Also good. ),
400 ≦ Ts (° C.) ≦ 475 (1),
20 ≦ Vs (V) ≦ 50 (2),
475 ≦ Ts (° C.) ≦ 600 (3),
Vs (V) ≤ 40 (4)

According to the present invention, when the number of moles of the A-site element in the formula (P) is a, a piezoelectric film having no Pb loss, where 1.0 ≦ a, preferably 1.0 ≦ a ≦ 1.3. Can be provided. Here, the number of moles of the A site element in the formula (P) means the number of moles of the A site element when the number of moles of oxygen atoms is ₃ in the general formula ABO ₃ .

A piezoelectric element according to the present invention includes the above-described piezoelectric film according to the present invention and an electrode for applying an electric field to the piezoelectric film.
The liquid ejection device of the present invention is
The above-described piezoelectric element of the present invention;
A liquid storage chamber in which liquid is stored, and a liquid storage and discharge member having a liquid discharge port through which the liquid is discharged from the liquid storage chamber are provided.

  In the present invention, in the vapor phase growth method using plasma such as sputtering, the factors of the film formation conditions that affect the film characteristics are the film formation temperature Ts (° C.) and the plasma in the plasma during the film formation. It is clarified that the potential is Vs (V).

  According to the film forming method of the present invention, the film forming conditions are determined based on the relationship between the above two factors affecting the film characteristics and the characteristics of the film to be formed. A high-quality film can be stably formed by a vapor phase growth method using plasma.

  The film forming method of the present invention can be preferably applied to film formation of a piezoelectric film. According to the present invention, it is possible to stably grow a perovskite crystal having a small pyrochlore phase in the formation of a piezoelectric film made of a perovskite oxide. According to the present invention, in the formation of a piezoelectric film made of a Pb-containing perovskite oxide such as PZT, it is possible to stably grow a perovskite crystal having a small pyrochlore phase and to stably suppress Pb loss. Is possible.

"Film formation method"
The film formation method of the present invention is a film formation method in which a film is formed by a vapor phase growth method using plasma. A film formation temperature Ts (° C.), a plasma potential Vs (V) in plasma during film formation, The film forming conditions are determined based on the relationship with the characteristics of the film to be formed.

  Examples of the vapor deposition method to which the film forming method of the present invention can be applied include a sputtering method, an ion beam sputtering method, an ion plating method, and a plasma CVD method. In the film forming method of the present invention, the characteristics of the film for which the relationship is required include the crystal structure and / or film composition of the film.

  Based on FIG. 1, a configuration example of a film forming apparatus using plasma will be described by taking a sputtering apparatus as an example. FIG. 1A is a schematic cross-sectional view of an RF sputtering apparatus, and FIG. 1B is a diagram schematically showing a state during film formation.

  The RF sputtering apparatus 1 includes a heater 11 capable of heating the mounted substrate B to a predetermined temperature and a plasma electrode (cathode electrode) 12 for generating plasma. The vacuum vessel 10 is generally configured. The heater 11 and the plasma electrode 12 are spaced apart so as to face each other, and a target T having a composition corresponding to the composition of the film formed on the plasma electrode 12 is mounted. The plasma electrode 12 is connected to a high frequency power supply 13.

A gas introduction pipe 14 for introducing a gas G required for film formation into the vacuum container 10 and a gas discharge pipe 15 for exhausting the gas V in the vacuum container 10 are attached to the vacuum container 10. As the gas G, Ar, Ar / O ₂ mixed gas, or the like is used. As schematically shown in FIG. 1B, the gas G introduced into the vacuum vessel 10 by the discharge of the plasma electrode 12 is turned into plasma, and positive ions Ip such as Ar ions are generated. The generated positive ions Ip sputter the target T. The constituent element Tp of the target T sputtered by the positive ions Ip is emitted from the target and deposited on the substrate B in a neutral or ionized state. In the figure, the symbol P indicates the plasma space.

  The potential of the plasma space P becomes the plasma potential Vs (V). Usually, the substrate B is an insulator and is electrically insulated from the ground. Therefore, the substrate B is in a floating state, and the potential thereof is the floating potential Vf (V). The constituent element Tp of the target between the target T and the substrate B has a kinetic energy corresponding to the acceleration voltage of the potential difference Vs−Vf between the potential of the plasma space P and the potential of the substrate B. It is thought that it will collide with. Therefore, as the plasma potential Vs changes, the kinetic energy of the constituent element Tp of the target T that collides with the substrate B also changes.

The plasma potential Vs can be measured using a Langmuir probe. When the tip of a Langmuir probe is inserted into the plasma P and the voltage applied to the probe is changed, for example, current-voltage characteristics as shown in FIG. 2 can be obtained (Mitsuharu Onuma, “Plasma and Film Formation Fundamentals” p. 90, published by Nikkan Kogyo Shimbun). In this figure, the probe potential at which the current becomes 0 is the floating potential Vf. This state is that the ion current and the electron current flow into the probe surface become equal. The surface of the metal in the insulating state and the surface of the substrate are at this potential. As the probe voltage is made higher than the floating potential Vf, the ionic current gradually decreases, and only the electron current reaches the probe. The voltage at this boundary is the plasma potential Vs.
Vs can be changed by installing a ground between the substrate and the target (see Examples 1 and 2 described later).

  In the vapor phase growth method using plasma, the factors that influence the characteristics of the film to be formed include the film forming temperature, the type of the substrate, the composition of the substrate if there is a film previously formed on the substrate, and the surface of the substrate. The energy, the deposition pressure, the amount of oxygen in the atmospheric gas, the input electrode, the distance between the substrate and the target, the electron temperature and electron density in the plasma, the active species density in the plasma and the lifetime of the active species can be considered.

  The present inventor has found that, among many film formation factors, the characteristics of the film to be formed largely depend on two factors of the film formation temperature Ts and Vs, and by optimizing these factors, It has been found that a good quality film can be formed. That is, when the film forming temperature Ts is plotted on the horizontal axis and Vs is plotted on the vertical axis, and the film characteristics are plotted, it has been found that a good film can be formed within a certain range (see FIG. 12).

It has been described that the kinetic energy of the constituent element Tp of the target T colliding with the substrate B changes as Vs changes. As shown in the following equation, kinetic energy E is generally expressed as a function of temperature T, so Vs is considered to have the same effect as temperature on substrate B.
E = 1 / 2mv ² = 3 / 2kT
(Where m is mass, v is velocity, k is a constant, and T is absolute temperature.)
Vs is considered to have effects such as the effect of promoting surface migration and the effect of etching weakly bonded portions in addition to the same effect as temperature.

  Japanese Patent Application Laid-Open No. 2004-119703 proposes that a bias is applied to the substrate in order to relieve the tensile stress applied to the piezoelectric film when the piezoelectric film is formed by sputtering. Applying a bias to the substrate changes the energy amount of the constituent element of the target that enters the substrate. However, JP 2004-119703 A does not describe the plasma potential Vs.

  Normally, Vs and Vf of a film forming apparatus are almost determined to be one value depending on the structure of the apparatus and cannot be changed greatly. Therefore, conventionally, there has been almost no idea of changing Vs. The only film forming method for forming an amorphous silicon film or the like by a high-frequency plasma CVD method is disclosed in Japanese Patent Application Laid-Open No. 10-60653, wherein Vs−Vf is controlled within a specific range. Has been. In the present invention, Vs−Vf is controlled within a specific range in order to eliminate the nonuniformity of Vs−Vf on the substrate surface. However, Japanese Patent Application Laid-Open No. 10-60653 does not describe that the film formation conditions are determined based on the relationship between the film formation temperatures Ts and Vs and the characteristics of the film to be formed.

  The film forming method of the present invention can be applied to any film as long as it can be formed by a vapor phase growth method using plasma. Examples of the film to which the film forming method of the present invention can be applied include a piezoelectric film made of one or more kinds of perovskite oxides. The piezoelectric film may contain inevitable impurities.

When applying the film forming method of the present invention to a piezoelectric film composed of one or more perovskite oxides represented by the following general formula (P), the following formulas (1) and (2) It has been found that it is preferable to determine the film-forming conditions within a range that satisfies the following equation (3) and (4) (see FIG. 12).
Formula ABO ₃ (P),
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe, Ni, and lanthanide element At least one element selected from the group consisting of:
O: oxygen atom,
The ratio of the total number of moles of the A-site element and the total number of moles of the B-site element to the number of moles of oxygen atoms is typically 1: 3, but deviates from 1: 3 within a range where a perovskite structure can be obtained. Also good. ),
400 ≦ Ts (° C.) ≦ 475 (1),
20 ≦ Vs (V) ≦ 50 (2),
475 ≦ Ts (° C.) ≦ 600 (3),
Vs (V) ≤ 40 (4)

  Examples of the perovskite oxide represented by the general formula (P) include lead titanate, lead zirconate titanate (PZT), lead zirconate, lead lanthanum titanate, lead lanthanum zirconate titanate, zirconium magnesium niobate Lead-containing compounds such as lead titanate, lead nickel niobate and zirconium titanate, and non-lead-containing compounds such as barium titanate, sodium bismuth titanate, potassium bismuth titanate, sodium niobate, potassium niobate, lithium niobate Is mentioned. The piezoelectric film may be a mixed crystal system of perovskite oxides represented by the above general formula (P).

The present invention is preferably applicable to PZT represented by the following general formula (P-1) or a B site substitution system thereof, and mixed crystal systems thereof.
Pb _a (Zr _b Ti _c X _d ) O ₃ (P-1)
(In Formula (P-1), X is at least one metal element selected from the group of elements of Group V and Group VI. A> 0, b> 0, c> 0, d ≧ 0, a = 1.0 and b + c + d = 1.0 is standard, but these values may deviate from 1.0 within a range where a perovskite structure can be taken.)

The perovskite oxide represented by the general formula (P-1) is lead zirconate titanate (PZT) when d = 0, and when d> 0, part of the B site of PZT is group V. And an oxide substituted with X which is at least one metal element selected from the group of elements of group VI.
X may be any metal element of Group VA, Group VB, Group VIA, and Group VIB, and is preferably at least one selected from the group consisting of V, Nb, Ta, Cr, Mo, and W. .

  When forming a piezoelectric film made of a perovskite oxide represented by the above general formula (P), the present inventor found that the film formation temperature was too low under the film formation condition of Ts (° C.) <400, and the perovskite crystal It has been found that the film does not grow well and a film with a pyrochlore phase as the main film is formed (see FIG. 12).

  Further, when the present inventors form a piezoelectric film made of a perovskite oxide represented by the general formula (P), the condition of 400 ≦ Ts (° C.) ≦ 475 satisfying the above formula (1) is satisfied. In the range where the film formation temperatures Ts and Vs satisfy the above formula (2) and under the condition of 475 ≦ Ts (° C.) ≦ 600 that satisfies the above formula (3), the film formation temperatures Ts and Vs are expressed by the above formula (4). It is found that the perovskite crystal having a small pyrochlore phase can be stably grown and the Pb loss can be stably suppressed by determining the film forming conditions within a range satisfying (1).

In addition, in order to stably form a piezoelectric film having a better crystal structure and film composition, the present inventor can determine film forming conditions within a range satisfying the following formulas (5) and (6). It has been found that it is particularly preferable to determine the film forming conditions within a range satisfying the following formulas (7) and (8) or (9) and (10) (see FIG. 12).
420 ≦ Ts (° C.) ≦ 575 (5),
−0.2Ts + 114 ≦ Vs (V) ≦ −0.15Ts + 111 (6)
420 ≦ Ts (° C.) ≦ 460 (7),
30 ≦ Vs (V) ≦ 48 (8),
475 ≦ Ts (° C.) ≦ 575 (9),
10 ≦ Vs (V) ≦ 38 (10)

  In sputter deposition of PZT, it is known that Pb loss tends to occur when the film is formed at a high temperature (see FIG. 2 of Patent Document 1 listed in “Background Art”). The inventor has found that Pb loss depends on Vs in addition to the film formation temperature. Of Pb, Zr, and Ti, which are constituent elements of PZT, Pb has the largest sputtering rate and is easily sputtered. For example, in Table 8.1.7 of “Vacuum Handbook” (published by ULVAC, Inc., published by Ohm), the sputtering rate under the conditions of Ar ion 300 ev is Pb = 0.75, Zr = 0.48, Ti = 0.65. Easily sputtered means that the sputtered atoms are likely to be re-sputtered after adhering to the substrate surface. It is considered that the higher the plasma potential Vs, the higher the resputtering rate and the more likely Pb loss occurs. The same applies to Pb-containing perovskite oxides other than PZT. The same applies to vapor phase growth methods using plasma other than sputtering.

As can be seen from FIG. 12, the perovskite crystals tend not to grow well under conditions where the film formation temperatures Ts and Vs are both too low. Further, when at least one of the film formation temperatures Ts and Vs is excessive, Pb loss tends to occur easily.
In the present embodiment, the substrate / target distance is not particularly limited and is preferably in the range of 30 to 80 mm. A closer substrate / target distance is preferable in terms of efficiency because the film formation rate is faster, but if it is too close, plasma discharge becomes unstable and it is difficult to form a good film.

The present inventor satisfies the following formulas (1) and (11) or (3) and (12) when forming a piezoelectric film made of the perovskite oxide represented by the general formula (P). It has been found that a piezoelectric film having a high piezoelectric constant can be obtained by determining the film forming conditions within a range.
400 ≦ Ts (° C.) ≦ 475 (1),
35 ≦ Vs (V) ≦ 45 (11),
475 ≦ Ts (° C.) ≦ 600 (3),
10 ≦ Vs (V) ≦ 35 (12)

When forming a piezoelectric film made of a perovskite oxide represented by the general formula (P), the present inventor has Vs (V) = about 48 under the condition of film formation temperature Ts (° C.) = About 420. By doing so, it is possible to grow a perovskite crystal without Pb loss, but it has been found that the piezoelectric constant d ₃₁ of the obtained film is as low as about 100 pm / V. Under this condition, Vs, that is, the energy of the constituent element Tp of the target T that collides with the substrate is too high, so that defects are likely to occur in the film, and the piezoelectric constant is considered to decrease. The inventor determines a film forming condition within a range satisfying the above formulas (1) and (5) or (3) and (6), thereby forming a piezoelectric film having a piezoelectric constant d ₃₁ ≧ 130 pm / V. It has been found that a film can be formed.

  In the present invention, in the vapor phase growth method using plasma such as sputtering, the factors affecting the film characteristics are the film formation temperature Ts (° C.) and the plasma potential Vs (V in the plasma during film formation). ).

According to the film forming method of the present invention, the film forming conditions are determined based on the relationship between the above two factors affecting the film characteristics and the characteristics of the film to be formed. A high-quality film can be stably formed by a vapor phase growth method using plasma.
By employing the film forming method of the present invention, it is possible to easily find a condition for forming a high-quality film even if the apparatus conditions are changed, and it is possible to stably form a high-quality film.

  The film forming method of the present invention can be preferably applied to film formation of a piezoelectric film. According to the present invention, it is possible to stably grow a perovskite crystal having a small pyrochlore phase in the formation of a piezoelectric film made of a perovskite oxide. According to the present invention, in the formation of a piezoelectric film made of a Pb-containing perovskite oxide such as PZT, it is possible to stably grow a perovskite crystal having a small pyrochlore phase and to stably suppress Pb loss. Is possible.

"Piezoelectric film"
By applying the film forming method of the present invention, the following piezoelectric film of the present invention can be provided.
That is, the piezoelectric film of the present invention is a piezoelectric film composed of one or more perovskite oxides represented by the following general formula (P):
It is formed by vapor phase growth using plasma,
The film is formed under film forming conditions satisfying the following formulas (1) and (2) or (3) and (4).
General formula ABO ₃ (P)
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe, Ni, and lanthanide element At least one element selected from the group consisting of:
O: oxygen atom,
The ratio of the total number of moles of the A-site element and the total number of moles of the B-site element to the number of moles of oxygen atoms is 1: 3, respectively. Also good. ),
400 ≦ Ts (° C.) ≦ 475 (1),
20 ≦ Vs (V) ≦ 50 (2),
475 ≦ Ts (° C.) ≦ 600 (3),
Vs (V) ≤ 40 (4)

The piezoelectric film of the present invention is preferably formed under the film formation conditions satisfying the following formulas (5) and (6), and the following formulas (7) and (8) or (9) and (9) It is particularly preferable that the film is formed under the film forming conditions satisfying 10) (see FIG. 12).
420 ≦ Ts (° C.) ≦ 575 (5),
−0.2Ts + 114 ≦ Vs (V) ≦ −0.15Ts + 111 (6)
420 ≦ Ts (° C.) ≦ 460 (7),
30 ≦ Vs (V) ≦ 48 (8),
475 ≦ Ts (° C.) ≦ 575 (9),
10 ≦ Vs (V) ≦ 38 (10)

  According to the present invention, it is possible to stably provide a high-quality piezoelectric film having a perovskite crystal structure with a small pyrochlore phase, suppressing Pb loss, and having a good crystal structure and film composition.

  According to the present invention, when the number of moles of the A-site element in the formula (P) is a, it is possible to provide a piezoelectric film having a composition with 1.0 ≦ a and no Pb loss, and 1.0 < It is also possible to provide a piezoelectric film having a Pb-rich composition which is a. The upper limit of a is not particularly limited, and the present inventor has found that a piezoelectric film having good piezoelectric performance can be obtained when 1.0 ≦ a ≦ 1.3.

The piezoelectric film of the present invention is preferably formed under film forming conditions that satisfy the following formulas (1) and (11) or (3) and (12). With such a configuration, a piezoelectric film having a high piezoelectric constant can be provided.
400 ≦ Ts (° C.) ≦ 475 (1),
35 ≦ Vs (V) ≦ 45 (11),
475 ≦ Ts (° C.) ≦ 600 (3),
10 ≦ Vs (V) ≦ 35 (12)

"Piezoelectric element and inkjet recording head"
With reference to FIG. 3, the structure of the piezoelectric element of embodiment which concerns on this invention, and a liquid discharge apparatus provided with the same is demonstrated. FIG. 3 is a sectional view (a sectional view in the thickness direction of the piezoelectric element) of the main part of the ink jet recording head (liquid ejecting apparatus). In order to facilitate visual recognition, the scale of the constituent elements is appropriately changed from the actual one.

  The piezoelectric element 2 according to the present embodiment is an element in which a lower electrode 30, a piezoelectric film 40, and an upper electrode 50 are sequentially stacked on a substrate 20, and the lower electrode 30, the upper electrode 50, and the piezoelectric film 40 are stacked. Thus, an electric field is applied in the thickness direction.

  The lower electrode 30 is formed on substantially the entire surface of the substrate 20, and a piezoelectric film 40 having a pattern in which line-shaped convex portions 41 extending from the front side to the rear side in the drawing are arranged in a stripe shape is formed thereon. An upper electrode 50 is formed on 41.

  The pattern of the piezoelectric film 40 is not limited to that shown in the figure, and is designed as appropriate. The piezoelectric film 40 may be a continuous film. However, the piezoelectric film 40 is not a continuous film, but formed by a pattern composed of a plurality of protrusions 41 separated from each other, so that the expansion and contraction of the individual protrusions 41 occurs smoothly, so that a larger displacement amount can be obtained. preferable.

The substrate 20 is not particularly limited, and examples thereof include silicon, glass, stainless steel (SUS), yttrium-stabilized zirconia (YSZ), alumina, sapphire, silicon carbide and the like. As the substrate 20, a laminated substrate such as an SOI substrate in which a SiO ₂ oxide film is formed on the surface of a silicon substrate may be used.

The main component of the lower electrode 30 is not particularly limited, and examples thereof include metals or metal oxides such as Au, Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ , and SrRuO ₃ , and combinations thereof.
The main component of the upper electrode 50 is not particularly limited, and examples thereof include materials exemplified for the lower electrode 30, electrode materials generally used in semiconductor processes such as Al, Ta, Cr, and Cu, and combinations thereof. .

  The piezoelectric film 40 is a film formed by the film forming method of the present invention. The piezoelectric film 40 is preferably a piezoelectric film made of a perovskite oxide represented by the general formula (P).

  The thickness of the lower electrode 30 and the upper electrode 50 is not particularly limited and is, for example, about 200 nm. The film thickness of the piezoelectric film 40 is not particularly limited and is usually 1 μm or more, for example, 1 to 5 μm.

 The ink jet recording head (liquid ejecting apparatus) 3 generally includes an ink chamber (liquid storing chamber) 71 in which ink (liquid) is stored via a vibration plate 60 on the lower surface of the substrate 20 of the piezoelectric element 2 having the above-described configuration. In addition, an ink nozzle (liquid storage and discharge member) 70 having an ink discharge port (liquid discharge port) 72 through which liquid is discharged from the ink chamber 71 to the outside is attached. A plurality of liquid storage chambers 71 are provided corresponding to the number and pattern of the convex portions 41 of the piezoelectric film 40.

  In the ink jet recording head 3, the electric field strength applied to the convex portion 41 of the piezoelectric element 2 is increased / decreased for each convex portion 41 to expand / contract, thereby controlling the ejection of ink from the ink chamber 71 and the ejection amount. Is called.

  The piezoelectric element 2 and the ink jet recording head 3 of the present embodiment are configured as described above.

"Inkjet recording device"
With reference to FIG. 4 and FIG. 5, a configuration example of an ink jet recording apparatus including the ink jet recording head 3 of the above embodiment will be described. 4 is an overall view of the apparatus, and FIG. 5 is a partial top view.

  The illustrated ink jet recording apparatus 100 includes a printing unit 102 having a plurality of ink jet recording heads (hereinafter simply referred to as “heads”) 3K, 3C, 3M, and 3Y provided for each ink color, and each head 3K, An ink storage / loading unit 114 that stores ink to be supplied to 3C, 3M, and 3Y, a paper feeding unit 118 that supplies recording paper 116, a decurling unit 120 that removes curling of the recording paper 116, and a printing unit An adsorption belt conveyance unit 122 that conveys the recording paper 116 while maintaining the flatness of the recording paper 116, and a print detection unit that reads a printing result by the printing unit 102. 124 and a paper discharge unit 126 that discharges printed recording paper (printed matter) to the outside.

  Each of the heads 3K, 3C, 3M, and 3Y forming the printing unit 102 is the ink jet recording head 3 of the above embodiment.

  In the decurling unit 120, heat is applied to the recording paper 116 by the heating drum 130 in the direction opposite to the curl direction, and the decurling process is performed.

  In the apparatus using roll paper, as shown in FIG. 4, a cutter 128 is provided at the subsequent stage of the decurling unit 120, and the roll paper is cut into a desired size by this cutter. The cutter 128 includes a fixed blade 128A having a length equal to or larger than the conveyance path width of the recording paper 116, and a round blade 128B that moves along the fixed blade 128A. The fixed blade 128A is provided on the back side of the print. The round blade 128B is arranged on the print surface side with the conveyance path interposed therebetween. In an apparatus using cut paper, the cutter 128 is unnecessary.

  The decurled and cut recording paper 116 is sent to the suction belt conveyance unit 122. The suction belt conveyance unit 122 has a structure in which an endless belt 133 is wound between rollers 131 and 132, and at least portions facing the nozzle surface of the printing unit 102 and the sensor surface of the printing detection unit 124 are horizontal ( Flat surface).

  The belt 133 has a width that is wider than the width of the recording paper 116, and a plurality of suction holes (not shown) are formed on the belt surface. An adsorption chamber 134 is provided at a position facing the nozzle surface of the printing unit 102 and the sensor surface of the print detection unit 124 inside the belt 133 that is stretched between the rollers 131 and 132. The recording paper 116 on the belt 133 is sucked and held by suctioning at 135 to make a negative pressure.

  When the power of a motor (not shown) is transmitted to at least one of the rollers 131 and 132 around which the belt 133 is wound, the belt 133 is driven in the clockwise direction in FIG. 4 and is held on the belt 133. The recording paper 116 is conveyed from left to right in FIG.

  Since ink adheres to the belt 133 when a borderless print or the like is printed, the belt cleaning unit 136 is provided at a predetermined position outside the belt 133 (an appropriate position other than the print region).

  A heating fan 140 is provided on the upstream side of the printing unit 102 on the paper conveyance path formed by the suction belt conveyance unit 122. The heating fan 140 heats the recording paper 116 by blowing heated air onto the recording paper 116 before printing. Heating the recording paper 116 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 102 is a so-called full line type head in which line type heads having a length corresponding to the maximum paper width are arranged in a direction (main scanning direction) perpendicular to the paper feed direction (see FIG. 5). Each of the print heads 3K, 3C, 3M, and 3Y is a line-type head in which a plurality of ink discharge ports (nozzles) are arranged over a length exceeding at least one side of the maximum-size recording paper 116 targeted by the ink jet recording apparatus 100. It is configured.

  Heads 3K, 3C, 3M, and 3Y corresponding to the respective color inks are arranged in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 116. ing. A color image is recorded on the recording paper 116 by ejecting the color ink from each of the heads 3K, 3C, 3M, 3Y while conveying the recording paper 116.

  The print detection unit 124 includes a line sensor that images the droplet ejection result of the print unit 102, and detects ejection defects such as nozzle clogging from the droplet ejection image read by the line sensor.

  A post-drying unit 142 including a heating fan or the like for drying the printed image surface is provided at the subsequent stage of the print detection unit 124. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  A heating / pressurizing unit 144 is provided downstream of the post-drying unit 142 in order to control the glossiness of the image surface. The heating / pressurizing unit 144 presses the image surface with a pressure roller 145 having a predetermined surface irregularity shape while heating the image surface, and transfers the irregular shape to the image surface.

The printed matter obtained in this manner is outputted from the paper output unit 126. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. In the ink jet recording apparatus 100, there is provided sorting means (not shown) for switching the paper discharge path in order to select the print product of the main image and the print product of the test print and send them to the discharge units 126A and 126B. It has been.
When the main image and the test print are simultaneously printed on a large sheet of paper, the cutter 148 may be provided to separate the test print portion.
The ink jet recording apparatus 100 is configured as described above.

(Design changes)
The present invention is not limited to the above-described embodiment, and the design can be changed as appropriate without departing from the spirit of the present invention.

Examples and comparative examples according to the present invention will be described.
(Example 1)
Pb _1.3 Zr _0.52 Ti _0.48 under the conditions of a vacuum of 0.5 Pa and an Ar / O ₂ mixed atmosphere (O ₂ volume fraction 2.5%) using the sputtering apparatus shown in FIG. A piezoelectric film made of PZT or Nb-doped PZT was formed by using a target of O ₃ or Pb _1.3 Zr _0.43 Ti _0.44 Nb _0.13 O ₃ . Hereinafter, Nb-doped PZT is abbreviated as “Nb-PZT film”.

  As a film formation substrate, a substrate with an electrode was prepared in which a 30 μm thick Ti adhesion layer and a 150 nm thick Ir lower electrode were sequentially laminated on a Si wafer. The distance between the substrate and the target was 60 mm. The substrate was placed in a floating state, and a ground was arranged at a position away from the substrate, not between the target and the substrate. The plasma state of the apparatus changes depending on the position of the ground, and thus the plasma potential Vs also changes.

  At the film formation temperature Ts = 525 ° C., the position of the earth was changed to adjust the plasma potential Vs within the range of Vs (V) = about 10-50, and film formation was performed. An Nb-PZT film was formed at plasma potential Vs = 23, and a PZT film was formed at other plasma potentials. X-ray diffraction (XRD) measurement of the obtained film was performed. As a result, a perovskite crystal having crystal orientation was obtained in the range of plasma potential Vs (V) = 10 to 38 under the condition of Ts = 525 ° C. The XRD patterns of the main films obtained are shown in FIGS.

  At plasma potential Vs = 10, a perovskite crystal having crystal orientation can be obtained. However, even if it was prepared under the same conditions, the orientation was disturbed and a pyrochlore phase was observed. FIG. 6 shows the XRD of a sample with disordered orientation and a pyrochlore phase.

  Since the orientation began to be disturbed from the plasma potential Vs (V) = 38, the plasma potential Vs (V) = 38 was determined as “▲” (FIG. 8), and Vs (V) = mainly the pyrochlore phase. 50 was determined to be “x” (FIG. 9). Since a perovskite crystal having good crystal orientation was stably obtained at a plasma potential Vs (V) = 23, it was determined as “●” (FIG. 7). Since the peak intensity varies depending on the film thickness, various values are shown in FIGS. 7 to 9 using samples having different film thicknesses. However, since the peak position indicating orientation and the relative intensity ratio do not depend on the film thickness, there is no problem in the evaluation of crystallinity. In FIG. 7, since it has a very good orientation, the peak of the electrode becomes relatively small and can hardly be observed.

(Example 2)
Next, the plasma potential Vs (V) = about 23, and under this plasma condition, the film formation temperature Ts was changed within the range of 450 to 600 ° C., and the evaluation was performed in the same manner as in Example 1. It was. An Nb-PZT film was formed at a film formation temperature Ts = 525 ° C., and a PZT film was formed at other film formation temperatures Ts. X-ray diffraction (XRD) measurement of the obtained film was performed. The XRD pattern of the main film obtained is shown in FIG.

  As shown in FIG. 10, under the condition of Vs (V) = about 23, a perovskite crystal having crystal orientation was obtained within a film forming temperature Ts = 475-575 ° C. The film forming temperature Ts = 475 ° C. was judged as “▲” because pyrochlore phase was observed in other samples prepared under the same conditions. Since the orientation started to break from the film formation temperature Ts = 575 ° C., the film formation temperature Ts = 575 ° C. was determined as “「 ”.

  The obtained piezoelectric film was subjected to composition analysis by XRF. The results are shown in FIG. “Pb / B site element” in FIG. 11 indicates the ratio between the molar amount of Pb and the total molar amount of the B site element (Zr + Ti or Zr + Ti + Nb).

  As shown in FIG. 11, under the condition of Vs (V) = about 23, PZT with 1.0 ≦ Pb / B site element ≦ 1.3 with no Pb loss in the film forming temperature Ts = 350 to 550 ° C. A film or an Nb-PZT film could be formed. However, when the film formation temperature Ts was less than 400 ° C., the perovskite crystal did not grow because the film formation temperature was insufficient. Further, when the film formation temperature Ts exceeded 600 ° C., the perovskite crystal did not grow due to Pb loss.

For example, the composition of the Nb-PZT film formed under the conditions of Vs (V) = about 23 and film forming temperature Ts = 525 ° C. is Pb _1.12 Zr _0.43 Ti _0.44 Nb _0.13 O ₃ . there were.

For the Pb _1.12 Zr _0.43 Ti _0.44 Nb _0.13 O ₃ sample, a Pt upper electrode was formed on the piezoelectric film with a thickness of 100 nm by sputtering, and the piezoelectric constant d ₃₁ of the piezoelectric film was separated. Measured by the cantilever method. The piezoelectric constant d ₃₁ was as high as 250 pm / V, which was good.

(Summary of results of Examples 1 and 2)
FIG. 12 shows that all samples of Examples 1 and 2 and samples formed at other arbitrary film formation temperatures Ts and Vs have the film formation temperature Ts as the horizontal axis and Vs as the vertical axis. The measurement results were plotted. In FIG. 12, the range in which perovskite growth is possible is surrounded by a straight line.

In FIG. 12, in the PZT film or the Nb-PZT film, by determining the film formation conditions within the range satisfying the following formulas (1) and (2) or (3) and (4), the pyrochlore phase It has been shown that a small number of perovskite crystals can be stably grown, Pb loss can be stably suppressed, and a high-quality piezoelectric film having a good crystal structure and film composition can be stably formed. .
400 ≦ Ts (° C.) ≦ 475 (1),
20 ≦ Vs (V) ≦ 50 (2),
475 ≦ Ts (° C.) ≦ 600 (3),
Vs (V) ≤ 35 (4)

  The film forming method of the present invention can be applied when a film is formed by a vapor phase growth method using plasma, and is used in an ink jet recording head, a ferroelectric memory (FRAM), a pressure sensor, and the like. It can be applied to film formation such as a film.

(A) is a schematic sectional view of an RF sputtering apparatus, (b) is a diagram schematically showing a state during film formation. Explanatory drawing which shows the measuring method of plasma potential Vs and floating potential Vf Sectional drawing which shows the structure of the piezoelectric element of the embodiment which concerns on this invention, and an inkjet recording head The figure which shows the structural example of the inkjet recording device provided with the inkjet recording head of FIG. Partial top view of the ink jet recording apparatus of FIG. XRD pattern of main piezoelectric film obtained in Example 1 XRD pattern of main piezoelectric film obtained in Example 1 XRD pattern of main piezoelectric film obtained in Example 1 XRD pattern of main piezoelectric film obtained in Example 1 XRD pattern of main piezoelectric film obtained in Example 2 The figure which shows the composition analysis result of the piezoelectric film obtained in Example 2 FIG. 5 is a graph in which XRD measurement results are plotted for all samples of Examples 1 and 2 and samples formed under arbitrary conditions, with the film formation temperature Ts on the horizontal axis and Vs on the vertical axis.

Explanation of symbols

1 RF sputtering equipment (film deposition equipment)
2 Piezoelectric element 3, 3K, 3C, 3M, 3Y Inkjet recording head (liquid ejection device)
20 Substrate 30, 50 Electrode 40 Piezoelectric film 70 Ink nozzle (liquid storage and discharge member)
71 Ink chamber (liquid storage chamber)
72 Ink ejection port (liquid ejection port)
100 Inkjet recording device

Claims (2)

A target having a composition corresponding to the composition of a film to be deposited and a substrate are arranged to face each other, and constituent elements of the target are released by a sputtering method, and one or more types represented by the following general formula (P) are formed on the substrate. In a film forming method for forming a piezoelectric film (which may contain inevitable impurities) made of a plurality of perovskite oxides,
The distance between the substrate and the target is 60 mm,
In an Ar / O ₂ mixed atmosphere with a vacuum degree of 0.5 Pa and an O ₂ volume fraction of 2.5%, the potential of the substrate is set to a floating potential,
A film forming method for determining film forming conditions within a range satisfying the following formulas (5) and (6).
Formula ABO ₃ (P),
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe, Ni, and lanthanide element At least one element selected from the group consisting of:
O: oxygen atom,
The ratio of the total number of moles of the A-site element and the total number of moles of the B-site element to the number of moles of oxygen atoms is 1: 3, respectively. Also good. ),
420 ≦ Ts (° C.) ≦ 575 (5),
−0.2Ts + 114 ≦ Vs (V) ≦ −0.15Ts + 111 (6)
(In the formula, Ts (° C.) is a film forming temperature, and Vs (V) is a plasma potential.) The piezoelectric film is made of one or more perovskite oxides represented by the following general formula (P-1) (may contain unavoidable impurities). The film forming method.
Pb _a (Zr _b1 Ti _b2 X _b3 ) O ₃ (P-1)
(In formula (P-1), X is at least one metal element selected from the group of elements of group V and group VI. A> 0, b1> 0, b2> 0, b3 ≧ 0, a = 1.0 and b1 + b2 + b3 = 1.0 is standard, but these values may deviate from 1.0 within a range where a perovskite structure can be taken.)

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