JP4808689B2 - Ferroelectric film and manufacturing method thereof, ferroelectric element, and liquid ejection apparatus - Google Patents

Description

  The present invention relates to a PZT-based ferroelectric film, a manufacturing method thereof, a ferroelectric element using the ferroelectric film, and a liquid discharge apparatus.

  A piezoelectric element including a piezoelectric body having piezoelectricity that expands and contracts as the electric field application intensity increases and decreases, and an electrode that applies an electric field to the piezoelectric body is used for applications such as a piezoelectric actuator mounted on an ink jet recording head. in use. As the piezoelectric material, perovskite oxides such as lead zirconate titanate (PZT) are widely used. Such a piezoelectric material is a ferroelectric having spontaneous polarization when no electric field is applied.

It has been known since the 1960s that PZT to which various donor ions having a valence higher than that of a substituted ion are added has improved properties such as ferroelectric performance compared to intrinsic PZT. As donor ^ions for substituting Pb ²⁺ at the A site, various lanthanoid cations such as Bi ³⁺ and La ³⁺ are known. V ⁵⁺ , Nb ⁵⁺ , Ta ⁵⁺ , Sb ⁵⁺ , Mo ⁶⁺ , W ^{6+ and the} like are known as donor ions for substituting Zr ⁴⁺ and / or Ti ⁴⁺ on the B site.

  In the past, ferroelectrics mixed multiple types of oxide powders containing constituent elements of the desired composition, and molded and fired the resulting mixed powder, or multiple types of oxide powders containing the constituent elements of the desired composition. A material dispersed in an organic binder is applied to a substrate and baked. In such a method, the ferroelectric has been manufactured through a baking step of 600 ° C. or higher, usually 1000 ° C. or higher. In such a method, since the production is carried out in a high temperature thermal equilibrium state, it was impossible to dope a high concentration of an additive whose valence is not suitable.

  Non-Patent Document 1 describes a study on the addition of various donor ions to PZT bulk ceramics. FIG. 9 shows FIG. 14 is shown. This figure is a diagram showing the relationship between the amount of added donor ions and the dielectric constant. This figure shows that the characteristics are the best at about 1.0 mol% (corresponding to about 0.5 wt% in the figure), and that the characteristics deteriorate when added more.

  Similarly, Patent Document 9 describes that when Nb, Sb, or W is added to PZT, the characteristics are improved up to 3 mol%, but the characteristics are lowered when it is further added. Patent Document 10 describes that when V is added to PZT, the sintering temperature can be lowered, but the amount of addition is limited to 0.4 wt%. Patent Document 11 describes that the addition of W and / or Mo to PZT can lower the sintering temperature in liquid phase sintering, but the total amount added is limited to 9.8 mol%. It is described. Patent Document 12 describes that when Sb is added to PZT, variation in characteristics is suppressed, but the addition amount is limited to 3.0 wt%.

  As described above, in the conventional method, the amount of D-ion added at the B site is limited to 9.8 mol%. In addition, when adding about 9.8 mol% of the doping limit for the purpose of lowering the sintering temperature, other characteristics are sacrificed.

As described in Non-Patent Document 2, etc., characteristics are improved by co-doping low-valence acceptor ions such as Ni ²⁺ and Co ²⁺ in accordance with expensive donor ions in order to match valences. It is known to do (= relaxor system). An example is a system in which Pb (Ni _1/3 Nb _2/3 ) O ₃ is added to PZT. In this system, Ni ²⁺ is co-doped with Nb ⁵⁺ so that the average valence of the B site is +4, and a thermal equilibrium state is obtained. In this system, high concentration doping of Nb is possible.

However, as described in Non-Patent Document 1, it is known that acceptor ions having a low valence such as Ni ²⁺ , Co ^{2+ and the} like lower the ferroelectric properties. In a relaxor system co-doped with acceptor ions, donor ions are used. The effect of addition cannot be fully obtained.

In recent years, Patent Documents 1 to 8 disclose ferroelectric films in which 10 to 50 mol% of donor ions such as V, Nb, and Ta are added to the B site without co-doping with acceptor ions.
JP 2005-72474 A JP 2005-97073 A Japanese Patent No. 3791614 JP 2005-101512 A JP 2006-182642 A JP 2006-188427 A JP 2005-150694 A JP 2005-333105 A JP 2003-55045 A JP 2005-35843 A JP 2002-255646 A Japanese Unexamined Patent Publication No. 7-330425 S. Takahashi, Ferroelectrics (1981) Vol.41 p.143 Tetsuro Tanaka, Kiyoshi Okazaki, Noboru Ichinose, “Piezoelectric Ceramic Materials”, Gakudensha, 1973, p.110-131

  The ferroelectric films described in Patent Documents 1 to 8 are all formed by a sol-gel method. The sol-gel method is a thermal equilibrium process, and in the methods described in Patent Documents 1 to 8, it is essential to add Si as a sintering aid in order to promote sintering and obtain a thermal equilibrium state. In addition to Si, Ge and Sn are also known as sintering aids. When such a sintering aid is added, the ferroelectric characteristics are lowered, so that the methods described in Patent Documents 1 to 8 cannot sufficiently bring out the effect of adding donor ions.

  In the methods described in Patent Documents 1 to 8, relatively low-temperature firing is possible by adding Si as a sintering aid, but in this case, if the film thickness is increased, cracks occur, so that the thickness is 1 μm or less. Only a thin film can be formed. In Patent Documents 1 to 8, only a thin film of about 0.2 μm is actually formed. Such a thin film may be used for applications such as a ferroelectric memory, but the piezoelectric film preferably has a thickness of 3 μm or more because sufficient displacement cannot be obtained with a piezoelectric element. Although it is not impossible to increase the film thickness by repeating the lamination of thin films, it is not practical.

  Moreover, as described in Patent Document 7, Pb deficiency is likely to occur in the sol-gel method described in Patent Documents 1-8. When Pb deficiency occurs, the ferroelectric performance tends to decrease, which is not preferable.

The present invention has been made in view of the above circumstances, and a PZT-based ferroelectric film capable of adding 10 mol% or more of donor ions to the B site without adding a sintering aid or acceptor ions. An object of the present invention is to provide a manufacturing method.
Another object of the present invention is to provide a PZT-based ferroelectric film excellent in ferroelectric performance by adding 10 mol% or more of donor ions to the B site by the above production method.
Another object of the present invention is to provide a PZT-based ferroelectric film having no A site deficiency and having 10 mol% or more of donor ions added to the B site.
Another object of the present invention is to provide a PZT-based ferroelectric film having a thickness of 3.0 μm or more in which 10 mol% or more of donor ions are added to the B site.

The ferroelectric film of the present invention has a columnar crystal film structure composed of a large number of columnar crystals, and is characterized by containing a perovskite oxide represented by the following formula (P) as a main component.
A _{1 + δ} [(Zr _x Ti _1-x ) _1-y M _y ] O _z (P)
(In the formula, A is an A-site element and is at least one element mainly composed of Pb.
Zr, Ti, and M are B site elements. M is at least one element selected from the group consisting of V, Nb, Ta, and Sb.
0 <x ≦ 0.7, 0.1 ≦ y ≦ 0.4.
Although δ = 0 and z = 3 are standard, these values may deviate from the reference value within a range where a perovskite structure can be taken. )
In the present specification, the “main component” is defined as a component having a content of 80% by mass or more.

In the present invention, a ferroelectric film substantially free of Si can be provided. “Substantially free of Si” means that Si is not included except for inevitable impurities.
In the present invention, it is possible to provide a ferroelectric film having a composition rich in the A-site element in which δ in the formula (P) is in the range of 0 <δ ≦ 0.2.

In the ferroelectric film of the present invention, y in the formula (P) is preferably in the range of 0.2 ≦ y ≦ 0.4.
In the ferroelectric film of the present invention, a suitable additive element at the A site in the perovskite oxide represented by the formula (P) is Bi.
In the present invention, a ferroelectric film having a perovskite oxide represented by the formula (P) as a main component and a film thickness of 3.0 μm or more can be provided.

  The ferroelectric film of the present invention can be formed by a non-thermal equilibrium process. As a suitable film formation method for the ferroelectric film of the present invention, a sputtering method may be mentioned.

In the sputtering method, a target having a composition corresponding to the film composition of the ferroelectric film to be deposited is separated from the substrate, and a shield layer surrounding the outer periphery of the target on the substrate side is spaced apart in the vertical direction. The shields are arranged in a non-contact state with the target, and the height of the shield is a difference Vs− between the plasma potential Vs (V) and the floating potential Vf (V) in the plasma during film formation by the sputtering method. It is preferable that the film is formed on the substrate under the condition that Vf (V) is 35 eV or less and the temperature of the substrate is 400 ° C. or higher .
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 and floating potential Vf” are measured by a single probe method using a Langmuir probe. The floating potential Vf is measured in as short a time as possible so that the tip of the probe is placed in the vicinity of the substrate (about 10 mm from the substrate) so as not to include errors due to the film being deposited on the probe. To do. ◎
The potential difference Vs−Vf (V) between the plasma potential Vs and the floating potential Vf can be directly converted to the electron temperature (eV). This corresponds to an electron temperature of 1 eV = 11600 K (K is an absolute temperature).

A ferroelectric element of the present invention includes the ferroelectric film of the present invention described above and an electrode for applying an electric field to the ferroelectric film.
The liquid ejection device of the present invention includes a piezoelectric element comprising the ferroelectric 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.

  The present invention realizes the addition of 10 to 40 mol% of donor ions to the B site without adding a sintering aid or acceptor ions in a PZT-based ferroelectric film. The ferroelectric film of the present invention is a film excellent in ferroelectric performance (piezoelectric performance) because a high concentration of 10-40 mol% of donor ions is added to the B site. In the ferroelectric film of the present invention, since a high concentration of donor ions applied to the B site can be added without adding a sintering aid or acceptor ion, a decrease in ferroelectric performance due to the sintering aid or acceptor ion is suppressed. Therefore, the improvement of the ferroelectric performance due to the addition of dona ions is maximized.

"Ferroelectric film"
The present inventor has found that by forming a film by a non-thermal equilibrium process such as sputtering, 10 mol% or more of donor ions can be added to the B site without adding a sintering aid or acceptor ions. Specifically, the present inventor has found that 10-40 mol% of donor ions can be added to the B site. The inventor has also found that a film formed by this method has a columnar crystal film structure composed of a large number of columnar crystals. In the sol-gel method described in Patent Documents 1 to 8, such a columnar crystal film structure cannot be obtained.

That is, the ferroelectric film of the present invention has a columnar crystal film structure composed of a large number of columnar crystals, and is mainly composed of a perovskite oxide represented by the following formula (P). is there.
A _{1 + δ} [(Zr _x Ti _1-x ) _1-y M _y ] O _z (P)
(In the formula, A is an A-site element and is at least one element mainly composed of Pb.
Zr, Ti, and M are B site elements. M is at least one element selected from the group consisting of V, Nb, Ta, and Sb.
0 <x ≦ 0.7, 0.1 ≦ y ≦ 0.4.
Although δ = 0 and z = 3 are standard, these values may deviate from the reference value within a range where a perovskite structure can be taken. )

In the section “Background Art”, Non-Patent Document 2 and the like stated that co-doping with acceptor ions such as Ni ²⁺ and Co ²⁺ was proposed in order to dope the donor ions at a high concentration. The present invention can provide a ferroelectric film substantially free of such acceptor ions.

  In the methods described in Patent Documents 1 to 8, it is essential to add Si as a sintering aid, but in the present invention, a ferroelectric film substantially free of Si can be provided. Ge and Sn are also known as sintering aids, but the present invention can also provide a ferroelectric film substantially free of Ge and Sn.

It is known that ferroelectric performance is lowered by sintering aids and acceptor ions. In the present invention, since the sintering aid and acceptor ions are not essential, the deterioration of the ferroelectric performance due to the sintering aid and acceptor ions is suppressed, and the improvement of the ferroelectric performance due to the addition of donor ions is maximized. In the present invention, sintering aids and acceptor ions are not essential, but they can be added as long as the characteristics are not hindered.

  Since the ferroelectric film of the present invention has a columnar crystal film structure composed of a number of columnar crystals extending non-parallel to the substrate surface, an alignment film having a uniform crystal orientation can be obtained. Such a film structure is preferable because high piezoelectric performance can be obtained.

For piezoelectric strain,
(1) A normal electric field induced piezoelectric strain that expands and contracts in the electric field application direction when the vector component of the spontaneous polarization axis coincides with the electric field application direction,
(2) Piezoelectric strain generated by reversibly rotating the polarization axis by non-180 ° by increasing or decreasing the electric field applied intensity,
(3) Piezoelectric strain that uses a volume change due to phase transition by changing the phase of the crystal by increasing or decreasing the electric field applied intensity,
(4) Larger strain can be obtained by using a material that has the property of phase transition upon application of an electric field and having a crystalline orientation structure that includes a ferroelectric phase having crystal orientation in a direction different from the direction of the spontaneous polarization axis. Piezoelectric strain using engineered domain effect (when engineered domain effect is used, it may be driven under conditions where phase transition occurs, or it may be driven within a range where phase transition does not occur) It is done.

  A desired piezoelectric strain can be obtained by using the piezoelectric strains (1) to (4) singly or in combination. In addition, any of the above piezoelectric strains (1) to (4) can have a larger piezoelectric strain by adopting a crystal orientation structure corresponding to the principle of strain generation. Therefore, in order to obtain high piezoelectric performance, the ferroelectric film preferably has crystal orientation. For example, in the case of a PZT ferroelectric film having an MPB composition, a columnar crystal film with a (100) orientation can be obtained.

The growth direction of the columnar crystals may be non-parallel to the substrate surface, and may be substantially vertical or oblique.
The average column diameter of the many columnar crystals forming the ferroelectric film is not particularly limited and is preferably 30 nm or more and 1 μm or less. If the average column diameter of the columnar crystals is too small, sufficient crystal growth as a ferroelectric material may not occur, and a desired ferroelectric performance (piezoelectric performance) may not be obtained. If the average column diameter of the columnar crystals is excessive, the shape accuracy after patterning may decrease.

In the sol-gel method described in Patent Documents 1 to 8, Pb deficiency tends to occur, and when Pb deficiency occurs, the ferroelectric performance tends to decrease. However, according to the present invention, δ in the above formula (P) is δ. It is possible to provide a ferroelectric film having a composition free from defects of the A site element satisfying ≧ 0, and providing a ferroelectric film having a composition rich in the A site element satisfying δ> 0. Specifically, the present inventors have found that a ferroelectric film having a composition rich in the A-site element in which δ in the above formula (P) is 0 <δ ≦ 0.2 can be provided. In the present invention, it is possible to provide a ferroelectric film having a composition free from deficiency of the A site element satisfying δ ≧ 0 as described above. However, as long as the characteristics are not hindered, the A film may be deficient. In the ferroelectric film of the present invention, y in the formula (P) is preferably in the range of 0.2 ≦ y ≦ 0.4. The present inventor shows that when y <0.2, the polarization-electric field characteristic (PE characteristic) exhibits an asymmetric hysteresis in which it is biased to the positive side, and when 0.2 ≦ y, the asymmetry is relaxed and becomes close to the symmetry hysteresis. Is heading. That the PE hysteresis is asymmetric is defined by the fact that the absolute value of the coercive electric field Ec1 on the negative electric field side is different from the coercive electric field Ec2 on the positive electric field side (| Ec1 | ≠ Ec2).

  Usually, a ferroelectric film is used in the form of a ferroelectric element in which a lower electrode, a ferroelectric film, and an upper electrode are sequentially stacked, and an applied voltage is applied to one of the lower electrode and the upper electrode. The ground electrode is fixed at 0V, and the other electrode is driven as an address electrode whose applied voltage is varied. Since it is easy to drive, the driving is usually performed using the lower electrode as a ground electrode and the upper electrode as an address electrode. The “state in which a negative electric field is applied to the ferroelectric film” means a state in which a negative voltage is applied to the address electrodes. Similarly, “a state where a positive electric field is applied to the ferroelectric film” means a state where a positive voltage is applied to the address electrodes.

  A ferroelectric film having PE asymmetric hysteresis biased to the positive side is not easily polarized when a positive electric field is applied, and is easily polarized when a negative electric field is applied. In this case, piezoelectric characteristics are difficult to be obtained when a positive electric field is applied, and piezoelectric characteristics are likely to be obtained when a negative electric field is applied. In order to apply a negative electric field, the drive driver IC for the upper electrode needs to be used for a negative voltage, but the negative voltage is not widely used, and the development cost of the IC is increased. If the lower electrode is patterned to be an address electrode and the upper electrode is a ground electrode, a general-purpose positive voltage driver IC can be used, but the manufacturing process becomes complicated, which is not preferable. 0.2 ≦ y ≦ 0.4 is preferable from the viewpoint of driving because the PE characteristics are close to symmetrical hysteresis.

  In the ferroelectric film of the present invention, a suitable additive element at the A site in the perovskite oxide represented by the formula (P) is not particularly limited, and Bi or the like is preferable. The present inventor has found that by adding Bi to the A site, the asymmetry of the PE hysteresis is relaxed and becomes close to the symmetric hysteresis even at y <0.2.

Further, in the perovskite oxide represented by the formula (P), the value of x indicating the composition of Ti and Zr may be 0 <x ≦ 0.7, but the tetragonal phase and the rhombohedral phase A value close to the morphotropic phase boundary (MPB) composition, which is the phase transition point, is preferable because higher ferroelectric performance can be obtained. That is, 0.45 <x ≦ 0.7 is preferable, and 0.47 <x <0.57 is more preferable.
In the present invention, a ferroelectric film having a perovskite oxide represented by the formula (P) as a main component and a film thickness of 3.0 μm or more can be provided.

"Manufacturing method of ferroelectric film"
The ferroelectric film of the present invention in which 10-40 mol% of donor ions M are added to the B site can be formed by a non-thermal equilibrium process. Examples of suitable film formation methods for the ferroelectric film of the present invention include sputtering, plasma CVD, firing quench quench, annealing quench, and spray quench. As the film forming method of the present invention, the sputtering method is particularly preferable.

  In thermal equilibrium processes such as the sol-gel method, it is difficult to dope high concentrations of additives that do not have the proper valence, and it is necessary to devise methods such as using sintering aids or acceptor ions. In addition, the donor ions can be doped at a high concentration.

When the ferroelectric film of the present invention is formed by sputtering, the sputtering apparatus is not particularly limited, but includes a shield that surrounds the outer periphery of the target holder that holds the target on the film formation substrate side. It is preferable to use one that can adjust the potential state of the space. (See Japanese Patent Application No. 2006-263981 filed earlier by the present inventor (not disclosed at the time of filing this application).)
Hereinafter, a configuration example of the sputtering apparatus and a state of film formation will be described with reference to FIGS. Here, an RF sputtering apparatus using an RF power source will be described as an example, but a DC sputtering apparatus using a DC power source can also be used. FIG. 1A is a schematic cross-sectional view of the film forming apparatus of the present embodiment, and FIG. 1B is a view schematically showing a state during film formation. FIG. 2 is an enlarged view of the shield in FIG. 1 and the vicinity thereof.

  As shown in FIG. 1A, a film forming apparatus 200 includes a substrate holder 11 such as an electrostatic chuck that can hold a substrate (film forming substrate) B and heat the substrate B to a predetermined temperature, and a plasma. And a vacuum vessel 210 provided with a plasma electrode (cathode electrode) 12 for generating the. The plasma electrode 12 corresponds to a target holder that holds the target T.

  The substrate holder 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 to be formed on the plasma electrode 12 is mounted. The plasma electrode 12 is connected to a high frequency power supply 13. The plasma electrode 12 and the high-frequency power source 13 are referred to as a plasma generation unit. In this embodiment, a shield 250 surrounding the outer periphery of the target T on the film formation substrate side is provided. In addition, this structure can also be said to include the shield 250 surrounding the outer periphery of the plasma electrode 12 holding the target T, that is, the target holder on the film formation substrate side.

  A gas introduction pipe 214 for introducing a gas (film formation gas) G required for film formation into the vacuum container 210 and a gas discharge pipe 15 for exhausting the gas V in the vacuum container 210 are attached to the vacuum container 210. It has been. The gas introduction port 214 for introducing the gas G is provided at the same height as the shield 250 on the side opposite to the gas exhaust pipe 15.

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 an acceleration voltage of a 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.

The plasma potential Vs and the floating potential Vf 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. 3 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. ◎
It has been described that Vs−Vf correlates with the kinetic energy of the constituent element Tp of the target T colliding with the substrate B. As shown in the following equation, kinetic energy E is generally expressed as a function of temperature T, and therefore Vs−Vf 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 Boltzmann's constant , and T is absolute temperature.)
Vs−Vf 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.

  The vacuum vessel 210 of FIG. 1A is characterized in that a shield 250 surrounding the outer periphery of the target T on the film formation substrate side is disposed in the vacuum vessel 210. The shield 250 is disposed on the bottom surface 210 a of the vacuum vessel 210 so as to surround the outer periphery of the target T on the film formation substrate side on the earth shield, ie, the ground member 202, which is provided so as to surround the plasma electrode 12. . The ground member 202 is for preventing discharge to the vacuum vessel 210 from the plasma electrode 12 to the side or downward.

  As an example, the shield 250 is composed of a plurality of annular metal plates or rings (fins, shield layers) 250a as shown in FIGS. 1A and 2. Four of these rings 250a are used in the illustrated example, and a conductive spacer 250b is disposed between each ring 250a. A plurality of spacers 250b are arranged at intervals in the circumferential direction of the ring 250a, and a gap 204 is formed so that the gas G can easily flow between the spacers 250b. From this point of view, the spacer 250b is preferably disposed between the grounding member 202 and the ring 250a placed immediately above the grounding member 202.

  In the above configuration, the shield 250 is electrically connected to the ground member 202 and grounded. The material of the ring 250a and the spacer 250b is not particularly limited, and SUS (stainless steel) or the like is preferable.

  A conductive member (not shown) that electrically connects the plurality of rings 250a may be attached to the outer peripheral side of the shield 250. The rings 250a of the shield 250 are electrically connected to each other by the conductive spacer 250b and can be grounded by itself. However, by separately attaching a conductive member to the outer peripheral side, it becomes easy to ground the plurality of rings 250a. .

  As described above, since the shield 250 is arranged so as to surround the outer periphery of the target T on the film formation substrate side, a ground potential is formed by the shield 250 on the outer periphery of the target T on the film formation substrate side.

  In the film forming apparatus 200, the plasma condition can be adjusted and optimized by the shield 250 having the above-described configuration, and Vs−Vf (V), which is the difference between the plasma potential Vs (V) and the floating potential Vf (V). Can be adjusted and optimized. The reason is considered as follows.

  When the voltage of the high-frequency power source 13 is applied to the plasma electrode 12 to form a film on the substrate B, plasma is generated above the target T and discharge is also generated between the shield 250 and the target T. By this discharge, plasma is confined in the shield 250, the plasma potential Vs is lowered, and Vs−Vf (V), which is the difference between the plasma potential Vs (V) and the floating potential Vf (V), is considered to be lowered. It is done. When Vs−Vf (V), which is the difference between the plasma potential Vs (V) and the floating potential Vf (V), decreases, the energy with which the constituent element Tp of the target T emitted from the target T collides with the substrate B decreases. . By optimizing Vs−Vf (V), which is the difference between the plasma potential Vs (V) and the floating potential Vf (V), the particle energy of the constituent element Tp of the target T can be optimized, and the quality is good. A film can be formed.

  As the number of rings 250a increases and the height of the entire shield 250 increases, Vs−Vf (V), which is the difference between the plasma potential Vs (V) and the floating potential Vf (V), tends to decrease ( (See FIG. 7 in Example 1 below). This is because the discharge between the shield 250 and the target T becomes stronger as the height of the entire shield 250 increases, and Vs−Vf (V), which is the difference between the plasma potential Vs (V) and the floating potential Vf (V). This is thought to be due to a decline.

  At a specific film formation temperature, Vs−Vf (V) with the best film formation conditions is determined. In order to obtain this most preferable potential difference, the number of rings 250a can be increased or decreased without changing the film forming temperature so that a desired potential difference is obtained. Since the rings 250a are stacked as a shield layer simply via the spacers 250b, the number of the rings 250a can be changed by removing the rings 250a.

  The lowermost ring 250a of the shield 250 is separated from the outer periphery of the target T. When the distance between the target T and the shield 250 is zero, discharge does not occur. Since the effect of the shield is reduced, it is desirable that the distance is about 1 mm to 30 mm in order to obtain the effect efficiently.

  The constituent element Tp of the target T emitted from the target T adheres to the substrate B and also to the ring 250a of the shield 250 around the target T. The most adhering amount is the inner peripheral edge 251 facing the target T of the ring 250a and its vicinity. This state is shown in FIG. As shown in FIG. 2, particles (evaporated particles) of the constituent element Tp adhere to the inner edge 251 of the ring 250a and the upper and lower surfaces of the ring 250a in the vicinity thereof to form a film 253. If this film 253 is formed on the entire surface of each ring 250a, the function of the shield 250 as a ground potential is impaired. Therefore, it is preferable to configure the shield 250 so that the film 253 is not attached as much as possible.

  In the film forming apparatus 200, the shield 250 is constituted by a plurality of rings 250a arranged in the vertical direction with the gap 204 therebetween, so that vapor deposition particles made up of constituent elements emitted from the target adhere to the entire shield 250. Thus, the potential state is prevented from changing. Therefore, the shield 250 functions stably even when repeated film formation is performed, and the difference Vs−Vf between the plasma potential Vs and the floating potential Vf is stably maintained.

In particular, the thickness L of the shield wall material orthogonal to the stacking direction of each ring 250a, which is the shield layer, and the distance between the rings 250a adjacent to each other in the stacking direction, that is, the distance S between the shield layers, have a relationship of L > S. It is desirable to be. This relationship has an effect of making it difficult for the film 253 to adhere to the entire ring 250a by expanding the thickness L within a predetermined range with respect to the distance S between the rings 250a. That is, by increasing the depth of the ring 250a as viewed from the vapor deposition particles, it becomes difficult for the constituent element Tp to enter the outer peripheral side of the gap 204, and the shield 250 can be prevented from functioning in a short period of time.

  Other effects can be expected in the gap 204. That is, since the gap 204 serves as a passage for the film forming gas G, the film forming gas G easily passes through the gap 204 of the shield 250 and reaches the plasma space near the target T. The gas ions thus made can easily reach the target, and the constituent element Tp of the target can be effectively released. As a result, it is considered that a high-quality film having desired characteristics can be stably formed.

  Since the shield 250 with a gap also forms an equipotential wall on the inner peripheral side in the same manner as a shield without a gap, the effect of adjusting Vs-Vf of a shield with a gap is equivalent to that of a shield without a gap. It is.

  In the film forming apparatus 200, Vs−Vf can be controlled by adjusting the height of the shield 250. Vs−Vf can also be adjusted by changing the target input power, the deposition pressure, and the like. However, when Vs−Vf is controlled by changing the target input power, the film forming pressure, etc., other parameters such as the film forming speed may change, and the desired film quality may not be obtained. When the present inventor conducted an experiment under certain conditions, Vs-Vf can be reduced from 38 eV to 25 eV when the target input power is changed from 700 W to 300 W, but the film formation speed is reduced from 4 μm / h to 2 μm / h. I have. In the apparatus 200 of the present embodiment, Vs−Vf can be adjusted without changing other parameters such as the film formation speed, so that the film formation conditions can be easily optimized, and a high-quality film can be stably formed. be able to.

  When forming a piezoelectric film such as a PZT ferroelectric film, the present inventor performs the film formation with the difference between the plasma potential Vs and the floating potential Vf being 35 eV or less and the temperature of the substrate B being 400 ° C. or more. It is found to be preferable. By adjusting the height of the shield in the film forming apparatus 200 and the temperature of the substrate B so as to form a film under such film forming conditions, a perovskite crystal having a small pyrochlore phase can be stably grown, and Pb is lost. Therefore, it is possible to stably form a high-quality ferroelectric film having a good crystal structure and film composition.

  In sputter deposition of a PZT-based ferroelectric film, it is known that Pb detachment easily occurs when the film is deposited at a high temperature. The present inventor has found that Pb loss depends not only on the film forming temperature but also on Vs−Vf. 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 greater the difference between the plasma potential and the substrate potential, that is, the greater the difference in Vs−Vf, the higher the resputtering rate and the more likely Pb loss occurs.

If the film-forming temperature Ts and Vs−Vf are both too low, the perovskite crystal tends not to grow well. Further, when at least one of the film forming temperature Ts and Vs−Vf is excessive, Pb loss tends to occur.
That is, under the condition of Ts (° C.) ≧ 400, when the film formation temperature Ts is relatively low, it is necessary to make Vs−Vf relatively high in order to grow the perovskite crystal satisfactorily. When Ts is relatively high, Vs−Vf needs to be relatively low in order to suppress Pb loss.

"Ferroelectric elements (piezoelectric elements), inkjet recording heads"
With reference to FIG. 4, the structure of a piezoelectric element (ferroelectric 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. 3 is a cross-sectional view of the main part 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 (ferroelectric element) 2 of the present embodiment is an element in which a lower electrode 30, a ferroelectric film (piezoelectric film) 40, and an upper electrode 50 are sequentially laminated on a substrate 20, and the ferroelectric element. An electric field is applied to the body film 40 in the thickness direction by the lower electrode 30 and the upper electrode 50. The ferroelectric film 40 is a ferroelectric film according to the present invention containing a perovskite oxide represented by the above formula (P) as a main component.

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

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

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 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 ferroelectric film 40 is not particularly limited and is usually 1 μm or more, for example, 1 to 5 μm. The film thickness of the ferroelectric film 40 is preferably 3 μm or more.

  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 ferroelectric 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.

Instead of attaching the vibration plate 60 and the ink nozzle 70 which are members independent of the substrate 20, a part of the substrate 20 may be processed into the vibration plate 60 and the ink nozzle 70. For example, when the substrate 20 is made of a laminated substrate such as an SOI substrate, the substrate 20 is etched from the back side to form the ink chamber 71, and the vibration plate 60 and the ink nozzle 70 are formed by processing the substrate itself. Can do.
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. 5 and FIG. 6, a configuration example of an ink jet recording apparatus including the ink jet recording head 3 of the above embodiment will be described. FIG. 5 is an overall view of the apparatus, and FIG. 6 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. 5, 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.

  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, so that the belt 133 is driven in the clockwise direction in FIG. 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.

Embodiments according to the present invention will be described.
Example 1
A commercially available sputtering apparatus was prepared, and five stainless steel (SUS) rings 250a having an inner diameter of 130 mmφ, an outer diameter of 180 mmφ, and a thickness of 1 mm were installed on the side of a 120 mmφ target T at a ground potential. The film forming apparatus shown in FIG. Each ring 250a was laminated via a columnar conductive spacer 250b having a diameter of 10 mmφ and a thickness of 5 mm. Since the spacer 250b is sufficiently smaller than the size of the ring 250a, the gas G introduced into the vacuum vessel 210 can easily pass through the gap 204 of the ring 250a and reach the target T without being affected by the spacer 250b. Can be reached.

The distance between the substrate B and the target T was 60 mm, and 700 W was applied to the high-frequency power source under the conditions of a vacuum degree of 0.5 Pa and an Ar / O ₂ mixed atmosphere (O ₂ volume fraction 2.5%). When the plasma potential Vs and the floating potential Vf generated under the above conditions were measured, Vs = 38 V and Vf = 16 V (Vs−Vf = 22 eV). Further, the number of rings 250a was changed between 0 and 4, and the measurement was performed in the same manner. FIG. 7 shows the relationship between the number of rings 250a and Vs−Vf.

  In the state without the ring 250a, Vs−Vf = 43 eV. The potential difference decreased as the number of sheets increased from 1 to 2, and Vs−Vf = 33 eV for 2 sheets and Vs−Vf = 22 eV for 5 sheets. As described above, according to the RF sputtering apparatus, Vs−Vf = decreases when the number of rings 250a is increased, and Vs−Vf can be controlled by changing the number of rings 250a.

As a film formation substrate, an electrode-attached substrate in which a 30-nm-thick Ti adhesion layer and a 300-nm-thick Ir lower electrode are sequentially stacked on a 25-mm square Si substrate is prepared, and the number of rings 250a is set to 5 for this substrate. A plurality of Nb- doped PZT ferroelectric films having different Nb addition amounts were formed under the same plasma conditions as described above using the above-mentioned RF sputtering apparatus. In any target, the Zr: Ti molar ratio was set to 52:48. When the plasma potential Vs and the floating potential Vf generated at this time were measured, Vs = 38 V and Vf = 16 V (Vs−Vf = 22 eV).

The film formation temperature Ts was 450 ° C. The film thickness of the ferroelectric film was 5 μm. Hereinafter, Nb- doped PZT is abbreviated as “ Nb- PZT”.
On the ferroelectric film, a Pt upper electrode was formed with a thickness of 100 nm by sputtering to obtain a ferroelectric element of the present invention.

  Except for changing the target composition, a plurality of types of Ta-doped PZT ferroelectric films having different Ta addition amounts were formed in the same manner as described above, and a ferroelectric element was obtained for each. Hereinafter, Ta-doped PZT is abbreviated as “Ta-PZT”.

<EDX measurement>
Composition analysis by EDX was performed for each of a plurality of types of Nb-PZT ferroelectric films having different Nb addition amounts and a plurality of types of Ta-PZT ferroelectric films having different Ta addition amounts.
All the films had a composition represented by Pb _{1 + δ} [(Zr _0.52 Ti _0.48 ) _1-y M _y ] O _z (M is Nb or Ta). With the Nb-PZT film, films with y = 0.12, 0.15, 0.18, and 0.25 were obtained. With the Ta-PZT film, a film with y = 0.02 to 0.20 was obtained. All the films had 1 + δ = 1.02 to 1.10 and had a Pb-rich composition. In any film, since the K-line intensity of oxygen was weak, it was found that 2 <z ≦ 3, but the oxygen amount z could not be specified.

<SEM cross section observation>
When SEM cross-section observation was performed on each of a plurality of types of Nb-PZT ferroelectric films having different Nb addition amounts and a plurality of types of Ta-PZT ferroelectric films having different Ta addition amounts, both were observed with respect to the substrate surface. It was a columnar crystal structure film composed of a large number of columnar crystals (average column diameter of about 150 nm) grown in a substantially vertical direction.

<XRD measurement>
XRD measurement was performed on each of a plurality of types of Nb-PZT ferroelectric films having different Nb addition amounts and a plurality of types of Ta-PZT ferroelectric films having different Ta addition amounts.
All of the Nb-PZT films having an Nb addition amount of 12 to 18 mol% were (100) -oriented perovskite structure films. In the Nb-PZT film having an Nb addition amount of 25 mol%, diffraction peaks were observed at three of (100), (110), and (111). All of the Ta-PZT films were (100) -oriented perovskite structure films.

<PE hysteresis measurement>
For each of a plurality of types of Nb-PZT ferroelectric films having different Nb addition amounts and a plurality of types of Ta-PZT ferroelectric films having different Ta addition amounts, polarization-electric field hysteresis measurement (PE hysteresis measurement) is performed to obtain maximum polarization. The value Pmax (μC / cm ² ) was determined. The polarization value at E = 100 kV / cm at which the polarization value is almost saturated was determined as Pmax.

  FIG. 8 shows the relationship between the amount of donaion M added (molar concentration in the B site) and the maximum polarization value Pmax. As shown in FIG. 8, it is shown that by forming a film using the sputtering apparatus, it is possible to add 10 mol% or more of donor ions to the B site of PZT without adding a sintering aid or acceptor ions. It was. In particular, Nb-PZT was found to exhibit high ferroelectric performance within a range of 10 to 25 mol%.

  As a result of measuring PE hysteresis of Nb addition amount of 12 mol% and 25 mol%, the Nb addition amount of 25 mol% is larger than the absolute value of the coercive electric field Ec1 on the negative electric field side and the positive electric field side as compared with the Nb addition amount of 12 mol%. It was confirmed that the difference from the coercive electric field Ec2 was reduced, and the PE hysteresis approached symmetry.

(Example 2)
An experiment was conducted on a system in which Bi was added to the A site of PZT and Nb was added to the B site in the same manner as in Example 1 except that the target composition was changed. Two types of ferroelectric films having different Nb addition amounts and Bi addition amounts were formed, and ferroelectric elements were obtained for each.

<EDX measurement>
When the EDX measurement was performed in the same manner as in Example 1, the obtained film had a ferroelectric film in which the Nb addition amount was 14 mol% and the Bi addition amount was 6%, and the Nb addition amount was 16 mol%. A ferroelectric film having a Bi addition amount of 9%.

<PE hysteresis measurement>
As a result of performing the PE hysteresis measurement in the same manner as in Example 1, by adding Bi according to Nb, the difference between the absolute value of the coercive electric field Ec1 on the negative electric field side and the coercive electric field Ec2 on the positive electric field side becomes small, It was confirmed that PE hysteresis approached symmetry.

  The ferroelectric film of the present invention includes a piezoelectric actuator mounted on an ink jet recording head, a magnetic recording / reproducing head, a MEMS (Micro Electro-Mechanical Systems) device, a micro pump, an ultrasonic probe, and a ferroelectric memory. It can be preferably used for ferroelectric elements such as.

Schematic cross section of sputtering equipment Diagram showing the state during film formation Enlarged view of the shield and its vicinity in FIG. 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 (ferroelectric element) and inkjet recording head (liquid discharge apparatus) of embodiment which concerns on this invention The figure which shows the structural example of the ink jet type recording apparatus provided with the ink jet type recording head of FIG. Partial top view of the ink jet recording apparatus of FIG. The figure which shows the measurement result (The relationship between the number of rings and the difference of a plasma potential and a floating potential) of Example 1. The figure which shows the relationship between the addition amount of the donor ion M of the B site of Example 1, and the maximum polarization value Pmax. FIG. 14

Explanation of symbols

2 Piezoelectric elements (ferroelectric elements)
3, 3K, 3C, 3M, 3Y Inkjet recording head (liquid ejection device)
11 Substrate holder 12 Plasma electrode (target holder) (plasma generator)
13 High frequency power supply (plasma generator)
20 Substrate 30, 50 Electrode 40 Ferroelectric film (piezoelectric film)
71 Ink chamber (liquid storage chamber)
72 Ink ejection port (liquid ejection port)
200, 300 Film forming apparatus 204 Gap 210, 310 Vacuum container 250 Shield 250a Ring (shield layer)
330 Control power source B Film formation substrate G Film formation gas L Thickness P Plasma space T Target Vf Floating potential Vs Plasma potential S Distance

Claims (10)

A method for forming a ferroelectric film containing a perovskite oxide represented by the following formula (P) on a substrate by sputtering,
In the sputtering method, a target having a composition corresponding to the composition of the ferroelectric film and a substrate are spaced apart, and a plurality of shield layers surrounding an outer periphery of the target on the substrate side are vertically overlapped with each other. Arranged in a non-contact state with the target, the height of the shield is a difference Vs−Vf (V) between the plasma potential Vs (V) in the plasma and the floating potential Vf (V) during film formation by the sputtering method. A method of forming a ferroelectric film, characterized in that the film is formed on the substrate under a condition of 35 eV or less and a temperature of the substrate of 400 ° C. or more .
A _{1 + δ} [(Zr _x Ti _1-x ) _1-y M _y ] O _z (P)
(In the formula, A is an A-site element and is at least one element mainly composed of Pb.
Zr, Ti, and M are B site elements. M is at least one element selected from the group consisting of V, Nb, Ta, and Sb.
0 <x ≦ 0.7, 0.1 ≦ y ≦ 0.4.
Although δ = 0 and z = 3 are standard, these values may deviate from the reference value within a range where a perovskite structure can be taken. ) 2. The method of forming a ferroelectric film according to claim 1, wherein the ferroelectric film does not substantially contain Si. The method for forming a ferroelectric film according to claim 1, wherein δ in the formula (P) is in a range of 0 <δ ≦ 0.2. The method of forming a ferroelectric film according to claim 1, wherein y in the formula (P) is in a range of 0.2 ≦ y ≦ 0.4. The method for forming a ferroelectric film according to claim 1, wherein A contains Bi.
A ferroelectric film formed by the method for forming a ferroelectric film according to claim 1. 7. The ferroelectric film according to claim 6 , wherein the ferroelectric film has a film structure composed of a number of columnar crystals. The ferroelectric film according to claim 6, wherein the ferroelectric film has a film thickness of 3.0 μm or more. A ferroelectric element comprising the ferroelectric film according to claim 6 and an electrode for applying an electric field to the ferroelectric film. A piezoelectric element comprising the ferroelectric element according to claim 9 ;
A liquid discharge apparatus comprising: a liquid storage chamber in which liquid is stored; and a liquid storage / discharge member having a liquid discharge port through which the liquid is discharged from the liquid storage chamber.

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