JP4226647B2 - Piezoelectric film, method for forming the same, and piezoelectric element - Google Patents

Description

  The present invention relates to a method for forming a piezoelectric film formed 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 apparatus including

  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.

  Japanese Patent Laid-Open No. 2005-350735 discloses a method for producing an oxide thin film in which an oxide thin film is formed by sputtering using metal atoms knocked out from a target facing a substrate. A method for controlling film formation conditions so that the process is longer than the distance between the substrate and the target is disclosed, and the oxide thin film can be preferentially oriented in a specific orientation by post-baking at a temperature higher than a certain temperature after film formation. (See paragraph 0010).

  However, the film formation is performed without heating the substrate, and the distance between the substrate and the target is as long as 160 mm, so the film formation speed is very slow and further heat treatment in the subsequent process is necessary. Not relevant (see paragraphs 0036-0041). Therefore, the invention described in Japanese Patent Application Laid-Open No. 2005-350735 provides a film forming method capable of stably and efficiently forming a high-quality film by a vapor phase growth method using plasma such as a sputtering method. The problem of the present invention is not solved. If the film formation rate is too slow, it becomes difficult to grow high-quality crystals.

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 method for forming a piezoelectric film capable of stably and efficiently forming a high-quality piezoelectric 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-described problems, and 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 the target is obtained by vapor phase growth using plasma such as sputtering. In the method of forming a piezoelectric film in which a piezoelectric film made of the target constituent element is formed on the substrate, the characteristics of the piezoelectric film to be formed are determined by the film forming temperature Ts (° C.). And a separation distance between the substrate and the target (hereinafter referred to as a substrate-target distance) D (mm) greatly depends on the factors, and by optimizing these factors, a high-quality piezoelectric film can be formed. The headline and the present invention were completed.

In the first piezoelectric film forming method of the present invention, a target having a composition corresponding to the composition of the film to be formed is placed opposite to the substrate, and the constituent elements of the target are released by a sputtering method using plasma, A piezoelectric film made of the target constituent element and made of one or more perovskite oxides represented by the following general formula (P) (may contain inevitable impurities) is formed on the substrate. In the way to
Among the compositions of the target as the target, the composition of elements other than Pb is substantially the same as the composition of the piezoelectric film to be deposited, and the composition of Pb includes Pb that is desorbed during the deposition. Using a target that is substantially the same as the composition of the piezoelectric film,
The film forming conditions are determined within a range satisfying the following formulas (1) and (2).
General formula A _a B _b O ₃ (P)
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, from the group consisting of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe and Ni At least one element selected,
O: oxygen atom,
Although it is standard that a is 1.0 and b is 1.0, a and b may deviate from 1.0 within a range where a perovskite structure can be taken. ),
400 ≦ Ts (° C.) ≦ 500 (1),
30 ≦ D (mm) ≦ 80 (2)
(In formulas (1) and (2), Ts (° C.) is the film forming temperature, and D (mm) is the distance between the substrate and the target.)

In this specification, “the composition of elements other than Pb in the composition of the target is substantially the same as the composition of the piezoelectric film to be deposited” refers to an element other than Pb of the target composition containing oxygen and the film to be deposited. Is a target that has the same composition, but is considered to be “substantially the same composition” in consideration of an error in the composition caused by an unavoidable change in composition during the manufacturing process of the piezoelectric film .
About Pb element, it is known on the sputtering characteristic that it will volatilize easily. Therefore, in the target, the composition of the Pb element is set to be substantially the same as the composition of the piezoelectric film containing the Pb element that is desorbed from the film by volatilization or the like during the sputtering film formation.
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 “substrate-target distance” is defined as a distance obtained by connecting the center of the substrate surface on the target side and the target so as to be perpendicular to the target. When film formation is performed simultaneously using a plurality of targets, the average value of the distance between each substrate and the target is used.

Further, in the second piezoelectric film forming method of the present invention, a target having a composition corresponding to the composition of the film to be formed and a substrate are arranged to face each other, and the constituent elements of the target are released by sputtering using plasma. A piezoelectric film made of a constituent element of the target on the substrate and made of one or more perovskite oxides represented by the following general formula (P) (may contain inevitable impurities). In the method of forming a film,
Among the compositions of the target as the target, the composition of elements other than Pb is substantially the same as the composition of the piezoelectric film to be deposited, and the composition of Pb includes Pb that is desorbed during the deposition. Using a target that is substantially the same as the composition of the piezoelectric film,
The film forming conditions are determined within a range satisfying the following formulas (3) and (4).
General formula A _a B _b O ₃ (P)
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, from the group consisting of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe and Ni At least one element selected,
O: oxygen atom,
Although it is standard that a is 1.0 and b is 1.0, a and b may deviate from 1.0 within a range where a perovskite structure can be taken. ),
500 ≦ Ts (° C.) ≦ 525 (3),
60 ≦ D (mm) ≦ 75 (4)
(In formulas (3) and (4), Ts (° C.) is the film forming temperature, and D (mm) is the distance between the substrate and the target.)

In the first method for forming a piezoelectric film, it is preferable to determine film forming conditions within a range that further satisfies the following formula (5).
40 ≦ D (mm) ≦ 75 (5)
(In Formula (5), Ts (° C.) is the film formation temperature, and D (mm) is the distance between the substrate and the target.)
In the present invention, it is preferable to perform film formation at a film formation rate of 0.5 μm / h or more.

The piezoelectric film forming method of the present invention is applied to a piezoelectric film made of one or more perovskite oxides (which may contain inevitable impurities) represented by the following general formula (P-1). can do.
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.)

  In the present invention, a target having a composition corresponding to the composition of a film to be formed is placed opposite to the substrate, and constituent elements of the target are released by a vapor phase growth method using plasma such as a sputtering method. In the piezoelectric film forming method for forming a piezoelectric film composed of constituent elements, two factors of the film forming temperature Ts (° C.) and the substrate-target distance D (mm) depend on the film characteristics and the film forming speed. It has been clarified that it has an influence.

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

  Further, 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"
In the method for forming a piezoelectric film of the present invention, a target having a composition corresponding to the composition of a film to be formed and a substrate are arranged to face each other, and constituent elements of the target are released by a vapor phase growth method using plasma, In the method of forming a piezoelectric film, which forms a piezoelectric film made of the constituent elements of the target on a substrate,
The film forming conditions are determined within a range satisfying the following formulas (1) and (2).
400 ≦ Ts (° C.) ≦ 500 (1),
30 ≦ D (mm) ≦ 80 (2)

In addition, in the method for forming a piezoelectric film according to the present invention, a target having a composition corresponding to the composition of a film to be formed and a substrate are arranged to face each other, and constituent elements of the target are released by a vapor phase growth method using plasma. In the method of forming a piezoelectric film for forming a piezoelectric film made of a constituent element of the target on the substrate,
The film forming conditions are determined within a range satisfying the following formulas (3) and (4).
500 ≦ Ts (° C.) ≦ 600 (3),
30 ≦ D (mm) ≦ 100 (4)

  As a vapor phase growth method to which the method for forming a piezoelectric film of the present invention can be applied, a sputtering method is exemplified.

  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. The separation distance (substrate-target distance) between the substrate B and the target T is D (mm).

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.

  When the target element Tp between the target T and the substrate B collides with the substrate B during film formation with kinetic energy corresponding to the acceleration voltage of the potential difference between the potential of the plasma space P and the potential of the substrate B. Conceivable.

  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 substrate-target distance, 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 greatly depend on two factors, the film formation temperature Ts and the substrate-target distance D (mm). It has been found that by optimizing the factor, a high-quality piezoelectric film can be efficiently formed. That is, when the characteristics of the piezoelectric film are plotted with the film formation temperature Ts as the horizontal axis and the substrate-target distance D as the vertical axis, it has been found that a good quality piezoelectric film can be formed within a certain range (see FIG. 11). reference).

The piezoelectric film to which the method for forming a piezoelectric film of the present invention is applicable is not particularly limited, and examples thereof include a piezoelectric film made of one or more perovskite oxides represented by the following general formula (P). . The piezoelectric film may contain inevitable impurities.
General formula A _a B _b O ₃ (P)
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, from the group consisting of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe and Ni At least one element selected,
O: oxygen atom,
Although it is standard that a is 1.0 and b is 1.0, a and b may deviate from 1.0 within a range where a perovskite structure can be taken. )

  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 _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.)

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 the present inventor forms a piezoelectric film made of the perovskite oxide represented by the general formula (P) or (P-1), Ts (° C.) <400, which does not satisfy the formula (1). It has been found that under the film formation conditions, the film formation temperature is too low and the perovskite crystal does not grow well, and a main film with a pyrochlore phase is formed.

  Furthermore, when the present inventors form a piezoelectric film made of a perovskite oxide represented by the general formula (P) or (P-1), 400 ≦ Ts (° C.) that satisfies the above formula (1). Under the condition of ≦ 500, the substrate-target distance D (mm) is within the range satisfying the above formula (2), and under the condition of 500 ≦ Ts (° C.) ≦ 600 where the above formula (3) is satisfied, the substrate − By determining the film forming conditions within a range where the distance D (mm) between the targets satisfies the above formula (4), it is possible to stably grow a perovskite crystal with a small pyrochlore phase, and to stably eliminate Pb. It has been found that a high-quality piezoelectric film that can be suppressed and has a good crystal structure and film composition can be stably formed (see FIG. 11).

  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 present inventor has found that the Pb loss depends not only on the film forming temperature but also on the substrate-target distance. 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 shorter the substrate-target distance is, the higher the resputtering rate is, and Pb loss is likely to occur. The same applies to Pb-containing perovskite oxides other than PZT. The same applies to vapor phase growth methods using plasma other than sputtering.

When the film formation temperature Ts is excessively low and the substrate-target distance D is excessively large, the perovskite crystal tends not to grow well. Further, when the film formation temperature Ts is excessive and the substrate-target distance D is excessively small, Pb loss tends to occur.
That is, under the condition of 400 ≦ Ts (° C.) ≦ 500 that satisfies the above formula (1), when the film formation temperature Ts is relatively low, in order to grow the perovskite crystal satisfactorily, the substrate-target distance D When the film formation temperature Ts is relatively high, the substrate-target distance D needs to be relatively long in order to suppress Pb loss. This is represented by the above formula (2). In the case of 500 ≦ Ts (° C.) ≦ 600 that satisfies the above expression (3), since the film forming temperature is a relatively high temperature region, the upper limit of the range of the substrate-target distance D increases, but the tendency is the same. It is.

The film formation rate is preferably higher in terms of production efficiency, preferably 0.5 μm / h or more, and more preferably 1.0 μm / h or more. As shown in FIG. 5, the shorter the substrate-target distance D, the faster the film formation rate. FIG. 5 is a diagram showing the relationship between the film formation speed and the substrate-target distance D when a PZT film is formed using the RF sputtering apparatus 1. In FIG. 5, the film formation temperature Ts = 525 ° C. and the target input power (rf power) = 2.5 W / cm ² . As shown in Example 1, according to the present invention, it is possible to form a high-quality film even under high-speed film forming conditions where the film forming speed is 1.0 μm / h or more.

  Depending on the substrate-target distance D, the deposition rate may be less than 0.5 μm / h. In such a case, it is preferable to adjust the target input power or the like so that the deposition rate is 0.5 μm / h or more.

  A shorter substrate-target distance D is preferable because the film formation rate is faster, and is preferably 80 mm or less in the range of 400 ≦ Ts (° C.) ≦ 500, and preferably 100 mm or less in the range of 500 ≦ Ts (° C.) ≦ 600, but 30 mm If it is less than 1, the plasma state becomes unstable, and there is a possibility that film formation with good film quality cannot be performed. In order to stably form a piezoelectric film having a higher film quality, the substrate-target distance D is set to be either 400 ≦ Ts (° C.) ≦ 500 or 500 ≦ Ts (° C.) ≦ 600. 50 ≦ D (mm) ≦ 70 is preferable.

  In “Problems to be Solved by the Invention”, the film forming method described in Japanese Patent Application Laid-Open No. 2005-350735 is formed because the film formation is performed without heating the substrate and the distance between the substrate and the target is as long as 160 mm. He stated that the film speed is very slow and further heat treatment (post-baking) in the post-process is necessary, so that it is not practical in terms of production efficiency. If the film formation rate is too slow, it is difficult to achieve good crystal growth. In this method, too, the film formation rate is low, so that the film formed by sputtering is not crystallized and is crystallized by post-baking. Yes.

  As described above, in the present invention, the substrate-target distance D is set to 100 mm or less in order to form a high-quality piezoelectric film with high production efficiency, that is, at a high film formation speed and stably. That is, the substrate-target distance D of the present invention is shorter than the substrate-target distance that is the subject of the film forming method described in Japanese Patent Application Laid-Open No. 2005-350735. A high-quality piezoelectric film can be formed without requiring treatment such as firing.

  In the present invention, a target having a composition corresponding to the composition of a film to be formed is placed opposite to the substrate, and constituent elements of the target are released by a vapor phase growth method using plasma such as a sputtering method. In the piezoelectric film forming method for forming a piezoelectric film composed of constituent elements, two factors of the film forming temperature Ts (° C.) and the substrate-target distance D (mm) depend on the film characteristics and the film forming speed. It has been clarified that it has an influence.

According to the piezoelectric film forming method of the present invention, the film forming conditions are determined based on the relationship between the above two factors that affect the film characteristics and the characteristics of the film to be formed. A good-quality piezoelectric film can be stably and efficiently formed by vapor phase growth using plasma such as sputtering.
By adopting the method for forming a piezoelectric film of the present invention, it is possible to easily find a condition for forming a high-quality piezoelectric film even if the apparatus conditions change, and to stably form a high-quality piezoelectric film. Can do.

  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"
The following piezoelectric film of the present invention can be provided by applying the above-described method for forming a piezoelectric film of the present invention.
That is, 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).
A vapor phase growth method in which a target having a composition corresponding to the composition of a film to be deposited is placed opposite to the substrate, a constituent element of the target is released using plasma, and a film made of the constituent element of the target is formed. The film was formed by
And it is what was formed on the film-forming conditions which satisfy | fill following formula (1) and (2) or (3) and (4), It is characterized by the above-mentioned.
General formula A _a B _b O ₃ (P),
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, from the group consisting of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe and Ni At least one element selected,
O: oxygen atom,
Although it is standard that a is 1.0 and b is 1.0, a and b may deviate from 1.0 within a range where a perovskite structure can be taken. ),
400 ≦ Ts (° C.) ≦ 500 (1),
30 ≦ D (mm) ≦ 80 (2)

Moreover, 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).
A film forming method for forming a piezoelectric film by a vapor phase growth method using plasma,
Using the plasma, the constituent element of the target is released from the target made of the material according to the composition of the piezoelectric film, and the piezoelectric film made of the constituent element of the target is placed on the substrate arranged opposite to the target. The film is formed by a film forming method for forming a film,
The film is formed under the conditions satisfying the following formulas (3) and (4).
General formula A _a B _b O ₃ (P),
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, from the group consisting of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe and Ni At least one element selected,
O: oxygen atom,
Although it is standard that a is 1.0 and b is 1.0, a and b may deviate from 1.0 within a range where a perovskite structure can be taken. ),
500 ≦ Ts (° C.) ≦ 600 (3),
30 ≦ D (mm) ≦ 100 (4)

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 _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.)

  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, it is possible to provide a piezoelectric film having a composition with no Pb loss and 1.0 ≦ a, and it is also possible to provide a piezoelectric film having a Pb-rich composition with 1.0 <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.

"Piezoelectric element and inkjet recording head"
With reference to FIG. 2, the structure of a piezoelectric element according to an embodiment of the present invention and an ink jet recording head (liquid ejecting apparatus) including the same will be described. FIG. 2 is a sectional view (a sectional view in the thickness direction of the piezoelectric element) of the ink jet recording head. 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 above-described piezoelectric 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 is stored via a vibration plate 60 and an ink chamber on the lower surface of the substrate 20 of the piezoelectric element 2 configured as described above. An ink nozzle (liquid storage and discharge member) 70 having an ink discharge port (liquid discharge port) 72 through which ink is discharged from 71 to the outside is attached. A plurality of ink 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. 3 and FIG. 4, a configuration example of an ink jet recording apparatus including the ink jet recording head 3 of the above embodiment will be described. 3 is an overall view of the apparatus, and FIG. 4 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.

  The heads 3K, 3C, 3M, and 3Y that form the printing unit 102 are the ink jet recording heads 3 of the above-described 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 orthogonal to the paper feed direction (main scanning direction) (see FIG. 4). 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 using an O ₃ target. 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.

Film formation temperature Ts is set to 525 ° C., rf power of 2.5 W / cm ² is applied to the target, and film formation is performed under conditions of substrate-target distance D (mm) = 40, 60, 80, 100, 120 mm. It was. An Nb-PZT film was formed at a substrate-target distance D = 60 mm, and a PZT film was formed at other distances D.

Even when the same power is applied to the target, the deposition rate increases as the substrate-target distance D decreases. FIG. 5 shows the relationship between the substrate-target distance D and the deposition rate when the deposition temperature Ts = 525 ° C. and the power applied to the target (rf power) is 2.5 W / cm ² . According to FIG. 5, for example, the film formation speed when the substrate-target distance D (mm) = 60 is 1.0 μm / h.

X-ray diffraction (XRD) measurement was performed on the obtained film. The XRD patterns of the main films obtained are shown in FIGS.
As shown in FIGS. 6 to 10, perovskite crystals having crystal orientation were obtained in the range of the substrate-target distance D = 40 mm to 100 mm under the condition of the film formation temperature Ts = 525 ° C. Corresponding to FIG. 5, the deposition rate is 0.5 μm / h to 1.2 μm / h, and the perovskite crystal is obtained with good production efficiency.

  When the substrate-target distance D = 120 mm (see FIG. 10), a film having a pyrochlore phase as a main film was obtained. In this case, it is considered that the substrate-target distance D was too long, the film formation rate was slow, and the perovskite growth could not be sufficiently performed. At the substrate-target distance D = 100 mm (see FIG. 9), the pyrochlore phase was observed in the other samples prepared under the same conditions, and therefore, “▲” was determined. In the case where the substrate-target distance D = 40 mm (see FIG. 6), a pyrochlore phase was similarly observed, and therefore, “▲” was determined. Since perovskite crystals having good crystal orientation were stably obtained at the substrate-target distances D = 60 mm and 75 mm, it was determined as “●” (see FIGS. 7 and 8).

  The composition analysis by XRF was performed on the piezoelectric film (D = 60 mm, Nb-PZT film) shown in FIG. As a result, the ratio of the molar amount of Pb and the total molar amount of the B site element (Zr + Ti + Nb) in the piezoelectric film shown in FIG. 7 is Pb / (Zr + Ti + Nb) = 1.02, and Nb− without Pb missing. It was confirmed to be a PZT film.

This Nb-PZT film, a Pt upper electrode was formed with 100nm thickness by sputtering on the piezoelectric film, and the piezoelectric constant _{d 31} of the piezoelectric film was measured by a cantilever technique. Films deposited with a substrate-target distance D = 60 mm ((100) orientation) were good, with a high piezoelectric constant d ₃₁ of 250 pm / V.

For the PZT film containing a slight pyrochlore phase shown in FIG. 9 (D = 100 mm), the piezoelectric constant d ₃₁ was measured in the same manner, and d ₃₁ = 110 pm / V.

(Example 2)
A PZT film was formed in the same manner as in Example 1 except that the film formation temperature Ts = 420 ° C. and the substrate-target distance D = 60 mm.
Under this condition, a perovskite crystal having a good crystal orientation with (100) orientation was obtained although it contained a slight pyrochlore phase.

(Summary of results of Examples 1 and 2)
FIG. 11 plots XRD measurement results for all samples of Examples 1 and 2 and samples formed under other conditions, with the deposition temperature Ts on the horizontal axis and the substrate-target distance D on the vertical axis. In FIG. 11, in the PZT film or the Nb-PZT film, the film formation conditions are determined within a range satisfying the following formulas (1) and (2), or (3) and (4). As a result, it is shown that a perovskite crystal with a small amount of Pb 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. Yes.
400 ≦ Ts (° C.) ≦ 500 (1),
30 ≦ D (mm) ≦ 80 (2),
500 ≦ Ts (° C.) ≦ 600 (3),
30 ≦ D (mm) ≦ 100 (4)

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

(A) is a schematic sectional view of an RF sputtering apparatus, (b) is a diagram schematically showing a state during film formation. Sectional drawing which shows the structure of the piezoelectric element of embodiment which concerns on this invention, and an inkjet recording head (liquid discharge apparatus) 2 is a diagram illustrating a configuration example of an ink jet recording apparatus including the ink jet recording head (liquid ejection apparatus) of FIG. Partial top view of the ink jet recording apparatus of FIG. The figure which shows the relationship between the substrate-target distance and the film-forming speed | velocity 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 1 XRD pattern of main piezoelectric film obtained in Example 1 FIG. 5 is a graph in which XRD measurement results are plotted for all the samples of Examples 1 and 2 and other samples, with the film-forming temperature Ts as the horizontal axis and the substrate-target distance D as 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 (5)

A target having a composition corresponding to the composition of the film to be deposited is placed opposite to the substrate, the constituent elements of the target are released by a sputtering method using plasma, and the constituent elements of the target are formed on the substrate. In a method of forming a piezoelectric film made of one or more perovskite oxides (which may contain inevitable impurities) represented by the formula (P):
Among the compositions of the target as the target, the composition of elements other than Pb is substantially the same as the composition of the piezoelectric film to be deposited, and the composition of Pb includes Pb that is desorbed during the deposition. Using a target that is substantially the same as the composition of the piezoelectric film,
A method for forming a piezoelectric film, wherein film forming conditions are determined within a range satisfying the following formulas (1) and (2).
General formula A _a B _b O ₃ (P)
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, from the group consisting of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe and Ni At least one element selected,
O: oxygen atom,
Although it is standard that a is 1.0 and b is 1.0, a and b may deviate from 1.0 within a range where a perovskite structure can be taken. ),
400 ≦ Ts (° C.) ≦ 500 (1),
30 ≦ D (mm) ≦ 80 (2)
(In formulas (1) and (2), Ts (° C.) is the film forming temperature, and D (mm) is the distance between the substrate and the target.) A target having a composition corresponding to the composition of the film to be deposited is placed opposite to the substrate, the constituent elements of the target are released by a sputtering method using plasma, and the constituent elements of the target are formed on the substrate. In a method of forming a piezoelectric film made of one or more perovskite oxides (which may contain inevitable impurities) represented by the formula (P):
Among the compositions of the target as the target, the composition of elements other than Pb is substantially the same as the composition of the piezoelectric film to be deposited, and the composition of Pb includes Pb that is desorbed during the deposition. Using a target that is substantially the same as the composition of the piezoelectric film,
A method for forming a piezoelectric film, wherein film forming conditions are determined within a range satisfying the following expressions (3) and (4):
General formula A _a B _b O ₃ (P)
(In the formula, A: an A site element and at least one element including Pb,
B: Element of B site, from the group consisting of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe and Ni At least one element selected,
O: oxygen atom,
Although it is standard that a is 1.0 and b is 1.0, a and b may deviate from 1.0 within a range where a perovskite structure can be taken. ),
500 ≦ Ts (° C.) ≦ 525 (3),
60 ≦ D (mm) ≦ 75 (4)
(In formulas (3) and (4), Ts (° C.) is the film forming temperature, and D (mm) is the distance between the substrate and the target.) 2. The method for forming a piezoelectric film according to claim 1, wherein film forming conditions are determined within a range satisfying the following formulas (1) and (5).
400 ≦ Ts (° C.) ≦ 500 (1),
40 ≦ D (mm) ≦ 75 (5)
(In formulas (1) and (5), Ts (° C.) is the film forming temperature, and D (mm) is the distance between the substrate and the target.)   The method for forming a piezoelectric film according to claim 1, wherein the film formation is performed at a film formation rate of 0.5 μm / h or more. The method for forming a piezoelectric film according to claim 1, wherein the one or more perovskite oxides are represented by the following formula (P-1).
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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