JP4735834B2 - Ferroelectric capacitor manufacturing method, ferroelectric memory manufacturing method, piezoelectric element manufacturing method, piezoelectric actuator manufacturing method, and liquid jet head manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a ferroelectric capacitor, a method for manufacturing a ferroelectric memory, a method for manufacturing a piezoelectric element, a method for manufacturing a piezoelectric actuator, and a method for manufacturing a liquid jet head.

  In recent years, research and development of ferroelectric films such as PZT and SBT, ferroelectric capacitors using the films, and ferroelectric memory devices have been actively conducted. The structure of the ferroelectric memory device can be roughly classified into 1T, 1T1C, 2T2C, and a simple matrix type. Among them, the 1T type has an internal electric field generated in the capacitor because of its structure, so that the retention (data retention) is as short as one month, and it is said that the 10-year guarantee required in general semiconductors is impossible. The 1T1C type and 2T2C type have almost the same configuration as the DRAM and have a transistor for selection, so that the manufacturing technology of the DRAM can be utilized and the writing speed equivalent to that of the SRAM can be realized. The following small-capacity products have been commercialized.

Up to now, Pb (Zr, Ti) O ₃ (PZT) has been mainly used as a ferroelectric material. In the case of the same material, a ridge face body having a Zr / Ti ratio of 52/48 or 40/60 is used. A mixed region of crystal and tetragonal crystals and a composition in the vicinity thereof are used, and elements such as La, Sr, and Ca are doped and used. This region is used in order to ensure the most necessary reliability of the memory element. Originally, the tetragonal region rich in Ti is good for the hysteresis shape, but Schottky defects due to the ionic crystal structure occur, which causes leakage current characteristics or imprint characteristics (so-called hysteresis characteristics). Degree of deformation) defects occur and it is difficult to ensure reliability.

  On the other hand, the simple matrix type has a smaller cell size than the 1T1C type and 2T2C type, and can be multi-layered with capacitors, so that high integration and cost reduction are expected.

  A conventional simple matrix ferroelectric memory device is disclosed in Japanese Patent Laid-Open No. 9-116107. This publication discloses a driving method in which a voltage that is 1/3 of a write voltage is applied to an unselected memory cell when data is written to a memory cell.

  However, in this technique, the hysteresis loop of the ferroelectric capacitor required for operation is not specifically described. In order to obtain a simple matrix ferroelectric memory device that can actually operate, a hysteresis loop with good squareness is indispensable. Ti-rich tetragonal PZT is considered as a candidate for the ferroelectric material that can cope with this, but as with the 1T1C and 2T2C ferroelectric memories described above, ensuring reliability is the most important issue.

  PZT tetragonal crystals exhibit a hysteresis characteristic having a squareness suitable for memory applications, but have low reliability and have not been put into practical use. The reason is as follows.

  First, the PZT tetragonal thin film after crystallization tends to have a higher leakage current density as the Ti content is higher. In addition, when a so-called static imprint test is performed in which data is written only once in either the + or-direction and the data is read after being heated and held at 100 ° C., the written data is almost all after 24 hours. Not left. These are essential elements possessed by PZT, which is an ionic crystal, and Pb, which is a constituent element of PZT, and Ti itself, and this is the maximum that a PZT tetragonal thin film, most of which comprises Pb and Ti. It has become an issue. This problem is essential for PZT because PZT perovskite is often an ionic crystal.

  FIG. 35 is a list of main energies related to the bonding of each constituent element of PZT. PZT is known to contain many oxygen vacancies after crystallization. That is, it is expected from FIG. 35 that Pb—O has the smallest binding energy among the PZT constituent elements, and can be easily cut off during firing and polarization inversion. That is, when Pb is lost, O is lost due to the principle of charge neutrality.

  Next, during heating and holding such as in an imprint test, each constituent element of PZT vibrates and repeats collision, but Ti is the lightest among the PZT constituent elements and is easily removed by vibration collision during holding at a high temperature. Therefore, when Ti is released, O is released due to the principle of charge neutrality. In addition, since it contributes to bonding with the maximum valences of Pb: +2 and Ti: +4, charge neutrality does not hold except for the elimination of O. That is, in PZT, two anions such as O are easily removed with respect to one cation such as Pb and Ti, and so-called Schottky defects are easily formed.

Here, a mechanism of generation of leakage current due to oxygen deficiency in the PZT crystal will be described. FIGS. 36A to 36C are diagrams for explaining generation of leakage current in an oxide crystal having a brown mirrorite type crystal structure represented by a general formula ABO _2.5 . As shown in FIG. 36A, the brown mirrorlite type crystal structure is a crystal structure having an oxygen deficiency with respect to a perovskite type crystal structure possessed by a PZT crystal represented by the general formula ABO ₃ or the like. Then, as shown in FIG. 36B, in the brown mirrorlite type crystal structure, oxygen ions come next to the cations, so that the cation defects are less likely to cause an increase in leakage current. However, as shown in FIG. 36 (C), oxygen ions are connected in series with the entire PZT crystal, and when the oxygen deficiency increases and the crystal structure becomes a brown mirrorite type crystal structure, the leakage current increases accordingly. It will end up.

  Further, in addition to the occurrence of the leakage current described above, Pb and Ti deficiency and accompanying O deficiency are so-called lattice defects, which cause space charge polarization as shown in FIG. Then, in the PZT crystal, a counter electric field due to lattice defects is generated by the electric field due to the polarization of the ferroelectric, and a so-called bias potential is applied, and as a result, the hysteresis is shifted or depolarized. Furthermore, this phenomenon occurs more rapidly as the temperature increases.

The above is an essential problem of PZT, and it is thought that pure PZT is difficult to solve the above problem. Up to the present, a memory device using tetragonal PZT has sufficient characteristics. Not done.
JP-A-9-116107 JP-A-4-37076 JP-A-6-150716 JP-A-8-335676 JP 2001-80995 A Ken Kijima, Hiroshi Ishihara, “New Development of Ferroelectric Materials for FeRAM”, Spring 2002, 49th Joint Physics Related Lecture Proceedings Vol. 0, March 27, 2002 Issue, p.105

  An object of the present invention is to provide a 1T1C, 2T2C, and a simple matrix ferroelectric memory including a ferroelectric capacitor having a hysteresis characteristic that can be used for both 1T1C, 2T2C, and a simple matrix ferroelectric memory. It is in. Another object of the present invention is to provide a method for manufacturing the ferroelectric memory and a method for manufacturing a ferroelectric capacitor suitable for manufacturing the ferroelectric memory. Another object of the present invention is to provide a method for manufacturing a piezoelectric element using a ferroelectric film. Another object of the present invention is to provide a method for manufacturing a piezoelectric actuator using the method for manufacturing a piezoelectric element. Furthermore, another object of the present invention is to provide a method for manufacturing a liquid jet head using the method for manufacturing a piezoelectric actuator.

(1) The ferroelectric film according to the present invention is represented by a general formula of AB _1-x Nb _x O ₃ , wherein the A element is composed of at least Pb, and the B element is Zr, Ti, V, W, and Hf Of Nb in the range of 0.05 ≦ x <1.

Further, the ferroelectric film in accordance with the present invention, A element _{consists Pb 1-y} Ln y, Ln is, La, Ce, Pr, Nd , Pm, Sm, Eu, Gd, Tb, Dy, Ho, It is composed of a combination of at least one of Er, Tm, Yb, and Lu, and can be in a range of 0 <y ≦ 0.2.

(2) The ferroelectric film according to the present invention is represented by a general formula of (Pb _1-y A _y ) (B _1-x Nb _x ) O ₃ , and the A element includes La, Ce, Pr, It consists of a combination of at least one of Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and the B element is Zr, Ti, V, W and Hf. , One or more combinations, and includes Nb in the range of 0.05 ≦ x <1.

  Further, the ferroelectric film according to the present invention may contain Nb in a range of 0.1 ≦ x ≦ 0.3.

  (3) The ferroelectric film according to the present invention is a PZT-based ferroelectric film having a Ti composition higher than the Zr composition, and 2.5 mol% or more and 40 mol% or less of the Ti composition. Is replaced by Nb.

  Further, in the ferroelectric film according to the present invention, Nb can be substituted for 10 mol% or more and 30 mol% or less of the Ti composition.

  In the ferroelectric film according to the present invention, the PZT ferroelectric film may have a crystal structure of at least one of a tetragonal system and a rhombohedral system.

  Further, the ferroelectric film according to the present invention may contain 0.5 mol% or more of Si or Si and Ge.

  Further, the ferroelectric film according to the present invention may contain 0.5 mol% or more and less than 5 mol% of Si or Si and Ge.

(4) Further, the ferroelectric film according to the present invention is represented by a general formula of ABO ₃ , and includes Pb as a constituent element of the A site, and PZT type ferroelectric including at least Zr and Ti as constituent elements of the B site. In the body membrane, the amount of Pb deficiency at the A site is at most 20 mol% with respect to the stoichiometric composition of the ABO ₃ .

  In the ferroelectric film of the present invention, the B site can contain Nb at a composition ratio corresponding to twice the amount of Pb deficiency at the A site.

  Further, in the ferroelectric film according to the present invention, the Ti composition at the B site is higher than the Zr composition, and it can have a rhombohedral crystal structure.

  The ferroelectric films (3) and (4) according to the present invention can be formed using a sol-gel solution.

(5) Moreover, the manufacturing method of the ferroelectric film according to the present invention is the manufacturing method of the ferroelectric film according to the above (3) and (4), and the sol-gel solution includes a sol-gel solution for PbZrO ₃ , PbTiO _{3. A} mixture of a sol-gel solution for ₃ and a sol-gel solution for PbNbO ₃ is used.

In the method for manufacturing a ferroelectric film according to the present invention, a sol-gel solution further mixed with a sol-gel solution for PbSiO ₃ can be used.

  (6) The method for manufacturing a ferroelectric film according to the present invention is the method for manufacturing a ferroelectric film according to (4) above, wherein the stoichiometric composition of Pb, which is a constituent element of the A site, is 1. In this case, a sol-gel solution containing Pb in the range of 0.9 to 1.2 is used.

  (7) Moreover, the manufacturing method of the ferroelectric film of this invention can include forming the said PZT type ferroelectric film on the metal film which consists of a platinum type metal.

  (8) In the method for manufacturing a ferroelectric film of the present invention, the platinum metal may be at least one of Pt and Ir.

  (9) Further, the present invention can be applied to a ferroelectric memory device, a piezoelectric element, and a semiconductor element using the above ferroelectric film. Further, the present invention can be applied to a piezoelectric actuator using the above piezoelectric element. Further, the present invention can be applied to a liquid ejecting head using the above piezoelectric actuator. Further, the present invention can be applied to a printer using the liquid ejecting head. In addition, the present invention can be applied to a ferroelectric capacitor manufacturing method and a piezoelectric element manufacturing method using the ferroelectric film manufacturing method. Further, the present invention can be applied to a manufacturing method of a ferroelectric memory using the manufacturing method of the ferroelectric capacitor and a manufacturing method of a piezoelectric actuator using the manufacturing method of the piezoelectric element. Furthermore, the present invention can be applied to a method for manufacturing a liquid jet head using the method for manufacturing a piezoelectric actuator.

  (10) A ferroelectric memory according to the present invention includes a first electrode electrically connected to either a source or drain electrode of a CMOS transistor previously formed on a Si wafer and a ferroelectric formed on the first electrode. A capacitor composed of the first electrode, the ferroelectric film and the second electrode is previously formed on the Si wafer. A ferroelectric memory that performs a selective operation using a CMOS transistor, wherein the ferroelectric film is composed of tetragonal PZT having a Ti ratio of 50% or more, and 5 mol% to 40 mol% of the Ti composition is Nb. And a ferroelectric film containing 1 mol% or more of Si and Ge at the same time.

  (11) Further, the ferroelectric memory according to the present invention includes a first electrode built in advance, a second electrode arranged in a direction crossing the first electrode, at least the first electrode, and the first electrode. A ferroelectric memory including a ferroelectric film disposed in a region intersecting with the two electrodes, and a capacitor constituted by the first electrode, the ferroelectric film, and the second electrode disposed in a matrix The ferroelectric film is made of tetragonal PZT having a Ti ratio of 50% or more, and 5 mol% or more and 40 mol% or less of Ti composition is substituted with Nb, and at the same time, 1 mol% or more of Si and It consists of a ferroelectric film containing Ge.

(12) A method for manufacturing a ferroelectric memory according to the present invention includes a sol-gel solution for forming PbZrO ₃ that is a first raw material solution, a sol-gel solution for forming PbTiO ₃ that is a second raw material solution, and a third raw material solution. comprising the step of crystallizing a certain PbNbO ₃ sol-gel solution for forming a PbSiO ₃ sol-gel solution for forming a fourth raw material solution after coating, the first, second, and third raw material solutions, the ferroelectric The fourth raw material solution is a paraelectric material having a catalytic effect that is indispensable for forming the first, second, and third raw material solutions as ferroelectric layers. It is the raw material liquid for producing | generating a layer.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

1. Ferroelectric Film, Ferroelectric Capacitor, and Manufacturing Method Thereof FIG. 1 is a cross-sectional view schematically showing a ferroelectric capacitor 100 using a ferroelectric film 101 according to an embodiment of the present invention.

  As shown in FIG. 1, the ferroelectric capacitor 100 includes a ferroelectric film 101, a first electrode 102, and a second electrode 103.

  The first electrode 102 and the second electrode 103 are made of a single noble metal such as Pt, Ir, or Ru or a composite material mainly composed of the noble metal. When a ferroelectric element diffuses into the first electrode 102 and the second electrode 103, a composition shift occurs at the interface between the electrode and the ferroelectric film 101, and the squareness of the hysteresis is lowered. The two electrodes 103 are required to be dense so that ferroelectric elements do not diffuse. In order to increase the density of the first electrode 102 and the second electrode 103, for example, a method of forming a sputter film with a gas having a heavy mass, a method of dispersing an oxide such as Y, La, or the like in a noble metal electrode is used. It is done.

The ferroelectric film 101 is formed using a PZT-based ferroelectric made of an oxide containing Pb, Zr, and Ti as constituent elements. In particular, the present embodiment is characterized in that this ferroelectric film 101 employs Pb (Zr, Ti, Nb) O ₃ (PZTN) in which Nb is doped at the Ti site.

Nb is substantially the same size as Ti (the ionic radius is the same and the atomic radius is the same), is twice as heavy, and does not easily escape from the lattice due to collisions between atoms due to lattice vibration. Also, the valence is +5 and stable, and even if Pb is lost, the valence of Pb loss can be compensated by Nb ⁵⁺ . Further, even if Pb loss occurs during crystallization, it is easier to enter small Nb than large O loss.

In addition, since Nb also has a +4 valence, Ti ⁴⁺ can be sufficiently replaced. Furthermore, in fact, Nb has a very strong covalent bond, and Pb is considered to be difficult to escape (H. Miyazawa, E. Natori, S. Miyashita; Jpn. J. Appl. Phys. 39 (2000). 5679).

  So far, Nb doping to PZT has been mainly performed in the Zr-rich rhombohedral region, but the amount is 0.2-0.025 mol% (J. Am. Ceram. Soc, 84 ( 2001) 902; Phys. Rev. Let, 83 (1999) 1347) and so on. It is considered that the reason why Nb could not be doped in a large amount as described above was that the crystallization temperature increased to 800 ° C. or more when Nb was added at, for example, 10 mol%.

Therefore, when forming the ferroelectric film 101, it is preferable to further add PbSiO ₃ silicate at a ratio of 1 to 5 mol%, for example. Thereby, the crystallization energy of PZTN can be reduced. That is, when PZTN is used as the material of the ferroelectric film 101, the crystallization temperature of PZTN can be reduced by adding PbSiO ₃ silicate together with Nb.

  In the present embodiment, the ferroelectric film 101 has the same effect even if Ta, W, V, or Mo is added as an additive to PZT instead of Nb. Moreover, even if Mn is used as an additive substance, it has an effect equivalent to Nb. Further, in the same way of thinking, in order to prevent the loss of Pb, substitution of Pb with an element having a valence of +3 or more may be considered, and these candidates include La, Ce, Pr, Nd, Pm, Sm, Eu, Gd. Lanthanoids such as Tb, Dy, Ho, Er, Tm, Yb and Lu. In addition, germanate (Ge) can be used instead of silicate (Si) as an additive for promoting crystallization. FIG. 42 (A) shows the hysteresis characteristics when 10 mol% Ta is used as the additive substance in place of Nb with respect to PZT. FIG. 42B shows hysteresis characteristics in the case where 10 mol% of W is used as an additive in place of Nb with respect to PZT. It can be seen that the same effect as that of Nb addition can be obtained even when Ta is used. It can also be seen that even when W is used, the same effect as that of Nb addition can be obtained in that a good hysteresis characteristic can be obtained.

  Next, an example of a method for forming the PZTN ferroelectric film 101 applied to the ferroelectric capacitor 100 of the present embodiment will be described.

  The PZTN ferroelectric film 101 is prepared by preparing a mixed solution composed of first to third raw material solutions containing at least one of Pb, Zr, Ti, and Nb, and heat-treating oxides contained in these mixed solutions. Can be obtained by crystallization.

As the first raw material solution, among the constituent metal elements of the PZTN ferroelectric phase, a solution obtained by dissolving a condensation polymer in a solvent such as n-butanol in an anhydrous state in order to form a PbZrO ₃ perovskite crystal by Pb and Zr. It can be illustrated.

As the second raw material solution, among the constituent metal elements of the PZTN ferroelectric phase, a solution obtained by dissolving a condensation polymer in a solvent such as n-butanol in an anhydrous state in order to form a PbTiO ₃ perovskite crystal with Pb and Ti. It can be illustrated.

As the third raw material solution, among the constituent metal elements of the PZTN ferroelectric phase, a solution obtained by dissolving a condensation polymer in an anhydrous state in a solvent such as n-butanol in order to form a PbNbO ₃ perovskite crystal by Pb and Nb. It can be illustrated.

When the ferroelectric film 101 made of, for example, PbZr _0.2 Ti _0.6 Nb _0.2 O ₃ (PZTN) is formed using the first, second, and third raw material solutions, the first The raw material solution: the second raw material solution: the third raw material solution = 2: 6: 2 is mixed, but the PZTN ferroelectric film 101 is produced even if this mixed solution is crystallized as it is. In order to achieve this, a high crystallization temperature is required. That is, when Nb is mixed, the crystallization temperature rises rapidly, and crystallization is impossible in the temperature range where the element can be formed at 700 ° C. or less. It has not been used as an additive until now. In addition, there was no example of PZT tetragonal crystals containing more Ti than Zr. This is described in reference J.A. Am. Ceram. Soc, 84 (20001) 902 and Phys. Rev. Let, 83 (1999) 1347 and the like.

Therefore, in the present embodiment, the above-described problem is solved by, for example, adding 1 mol% of a solution obtained by dissolving a condensation polymer in a solvent such as n-butanol to form PbSiO ₃ crystals as a fourth raw material solution. This can be solved by further adding less than 5 mol% in the mixed solution.

  That is, by using the mixed solution of the first, second, third, and fourth solutions, it becomes possible to crystallize PZTN at a crystallization temperature range of 700 ° C. or less in which the element can be formed.

  Specifically, the ferroelectric film 101 is formed according to the flowchart shown in FIG. A series of processes including a mixed solution coating process (step ST11), an alcohol removal process, a drying heat treatment process, a degreasing heat treatment process (step ST12, step ST13) are performed a desired number of times, and then baked by crystallization annealing (step ST14). A ferroelectric film 101 is formed.

  Examples of conditions in each step are shown below.

  First, a noble metal for an electrode such as Pt is coated on a Si substrate to form a lower electrode (step ST10). Next, the liquid mixture is applied by a coating method such as spin coating (step ST11). Specifically, the mixed solution is dropped on the Pt-coated substrate. For the purpose of spreading the dropped solution over the entire surface of the substrate, spinning is performed at about 500 rpm, and then the number of rotations is reduced to 50 rpm or less and the rotation is performed for about 10 seconds. The drying heat treatment step is performed at 150 ° C. to 180 ° C. (step ST13). The drying heat treatment is performed using a hot plate or the like in an air atmosphere. Similarly, the degreasing heat treatment step is performed in an air atmosphere on a hot plate maintained at 300 ° C. to 350 ° C. (step ST13). Firing for crystallization is performed using thermal rapid annealing (RTA) or the like in an oxygen atmosphere (step ST14).

  The film thickness after sintering can be about 100 to 200 nm. Next, after the upper electrode is formed by sputtering or the like (step ST15), post-annealing is performed for the purpose of forming the interface between the second electrode and the ferroelectric thin film and improving the crystallinity of the ferroelectric thin film. Similarly, the ferroelectric capacitor 100 is obtained by using RTA or the like in an oxygen atmosphere (step ST16).

  Below, the influence on the hysteresis characteristic to the ferroelectric capacitor 100 by using the PZTN ferroelectric film 101 is considered.

  FIG. 3 is a diagram schematically showing a P (polarization) -V (voltage) hysteresis curve of the ferroelectric capacitor 100. First, when a voltage of 10 Vs is applied, the polarization amount P (10 Vs) is obtained, and when the voltage is reduced to 0, the polarization amount Pr is obtained. Furthermore, when the voltage is set to -1/3 Vs, the polarization amount is P (-1/3 Vs). When the voltage is −Vs, the polarization amount is P (−Vs), and when the voltage is 0 again, the polarization amount is −Pr. Further, when the voltage is set to +1/3 Vs, the polarization amount becomes P (+1/3 Vs), and when the voltage is set again to + Vs, the polarization amount returns to P (+ Vs) again.

  The ferroelectric capacitor 100 also has the following characteristics in hysteresis characteristics. First, once the voltage Vs is applied to obtain a polarization amount P (+ Vs), a voltage of −1/3 Vs is applied, and when the applied voltage is set to 0, the hysteresis loop is a locus indicated by an arrow A in FIG. The amount of polarization has a stable value PO (0). Further, once the voltage −Vs is applied and the amount of polarization is set to P (−Vs), then a voltage of + 1/3 Vs is applied and the applied voltage is further set to 0, the hysteresis loop is indicated by an arrow B in FIG. Following the trajectory shown, the amount of polarization has a stable value PO (1). If the difference between the polarization amount PO (0) and the polarization amount PO (1) is sufficiently large, a simple matrix type ferroelectric memory device can be manufactured by the driving method disclosed in Japanese Patent Laid-Open No. 9-116107. It is possible to operate.

According to the ferroelectric capacitor 100 of the present embodiment, the crystallization temperature can be lowered, the squareness of hysteresis can be improved, and Pr can be improved. Further, the improvement in the squareness of hysteresis by the ferroelectric capacitor 100 has a significant effect on the stability of disturbance, which is important for driving a simple matrix ferroelectric memory device. In a simple matrix ferroelectric memory device, a voltage of ± 1/3 Vs is applied to a cell that is not written to or read from, so that the polarization does not change at this voltage, and so-called disturb characteristics must be stable. Actually, the inventor of the present application shows that when the 1/3 Vs pulse is applied 10 ⁸ times in the direction of reversing the polarization from a stable state of polarization in general PZT, the polarization amount is reduced by about 80%. According to the ferroelectric capacitor 100 of the form, it was confirmed that the amount of decrease was 10% or less. Therefore, if the ferroelectric capacitor 100 of the present embodiment is applied to a ferroelectric memory device, a simple matrix memory can be put into practical use.

  Hereinafter, a detailed example of the present embodiment will be described.

  In this embodiment, PZTN according to the present invention is compared with conventional PZT. The film formation flow shown in FIG.

Pb: Zr: Ti: Nb = 1: 0.2: 0.6: 0.2. It was added PbSiO ₃ 0 to 1 mol% here.

  The surface morphology of the film at this time is shown in FIGS. 4 (A) to 4 (C). Further, when the crystallinity of this film was measured by the X-ray diffraction method, it was as shown in FIG. 5 (A) to FIG. 5 (C). In the case of 0% (none) shown in FIG. 5A, only paraelectric pyrochlore was obtained even when the crystallization temperature was increased to 800 ° C. Further, in the case of 0.5% shown in FIG. 5B, PZT and pyrochlore were mixed. In the case of 1% shown in FIG. 5C, a PZT (111) single alignment film was obtained. Also, the crystallinity was so good that it had never been obtained.

Next, when the film thickness was set to 120 to 200 nm with respect to the 1% -added PZTN thin film of PbSiO ₃ , as shown in FIGS. 6 (A) to 6 (C) and FIGS. 7 (A) to 7 (C). The crystallinity was proportional to the film thickness. 6A to 6C are electron micrographs showing surface morphology at a film thickness of 120 nm to 200 nm, and FIGS. 7A to 7C are those at a film thickness of 120 nm to 200 nm. It is a measurement result by the X ray diffraction method which shows the crystallinity of a PZTN thin film. In addition, as shown in FIGS. 8A to 8C and FIGS. 9A to 9C, hysteresis characteristics with good squareness are obtained in the entire film thickness range of 120 nm to 200 nm. Obtained. 9A to 9C are enlarged views of the hysteresis curves of FIGS. 8A to 8C. In particular, as shown in FIGS. 9 (A) to 9 (C), it was confirmed that the PZTN thin film of the present example was firmly opened and saturated at a voltage as low as 2 V or less.

As for the leakage characteristics, as shown in FIGS. 10A and 10B, 5 × 10 ^{−8 to} 7 × 10 ⁻ when 2 V is applied (at saturation) regardless of the film composition and film thickness. ⁹ a / cm ² and then was very _good, was measured PbZr _0.2 Ti _{0.6 Nb 0.2 O 3} fatigue characteristics of the thin film, and the static imprint, FIG. 11 (a) and FIG. As shown in 11 (B), it was very good. In particular, the fatigue characteristics shown in FIG. 11A are very good despite using Pt for the upper and lower electrodes.

Further, as shown in FIG. 12, an SiO ₂ film 604 made of ozone TEOS is formed on a ferroelectric capacitor 600 on which a lower electrode 601, a PZTN ferroelectric film 603 of this embodiment, and an upper electrode 603 are formed on a substrate 601. Tried to form. It is known that conventional PZT forms a SiO ₂ film by ozone TEOS, so that hydrogen generated from TEOS reduces PZT through the upper Pt, and the PZT crystal breaks to such an extent that no hysteresis is shown.

  However, as shown in FIG. 13, the PZTN ferroelectric film 603 according to this example hardly deteriorates and maintains good hysteresis. That is, it was found that the PZTN ferroelectric film 603 according to the present example was also strong in reduction resistance. In addition, in the tetragonal PZTN ferroelectric film 603 according to the present invention, when Nb did not exceed 40 mol%, good hysteresis was obtained according to the amount of Nb added.

Next, a conventional PZT ferroelectric film was evaluated for comparison. As conventional PZT, Pb: Zr: Ti = 1: 0.2: 0.8, 1: 0.3: 0.7, and 1: 0.6: 0.4, respectively. As shown in FIG. 14, the leak characteristics deteriorate as the Ti content increases. When Ti is 80%, the leak characteristics are 10 ⁻⁵ A / cm ² when 2 V is applied. It turns out that it is not suitable. Similarly, as shown in FIG. 15, the fatigue properties deteriorated as the Ti content increased. Further, it was found that almost no data could be read after imprinting as shown in FIG.

  As can be seen from the above examples, the PZTN ferroelectric film according to this example has not only solved the problems of increase in leakage current and deterioration of imprint characteristics, which are considered to be caused by the essence of PZT. Tetragonal PZT, which has not been used for the reason, can be used for memory regardless of the type and structure of the memory. In addition, for the same reason, this material can be applied to piezoelectric element applications in which tetragonal PZT is not used.

In this example, in the PZTN ferroelectric film, the Nb addition amount was changed to 0, 5, 10, 20, 30, and 40 mol%, and the ferroelectric characteristics were compared. In all samples, 5 mol% of PbSiO ₃ silicate was added. Further, the pH of the sol-gel solution for forming a ferroelectric film, which is a raw material for film formation, was adjusted to 6 by adding methyl succinate. The film formation flow is the same as that shown in FIG.

  17 to 19 show hysteresis characteristics obtained by measuring the PZTN ferroelectric film of this example.

  As shown in FIG. 17A, a leaky hysteresis was obtained when the Nb addition amount was 0, but when the Nb addition amount was 5 mol% as shown in FIG. High and good hysteresis characteristics were obtained.

  Further, as shown in FIG. 18A, the ferroelectric characteristics hardly changed until the Nb addition amount was 10 mol%. Even when the amount of Nb added is 0, although it is leaky, no change is observed in the ferroelectric characteristics. Further, as shown in FIG. 18B, when the Nb addition amount is 20 mol%, a hysteresis characteristic having a very good squareness was obtained.

  However, as shown in FIG. 19A and FIG. 19B, it was confirmed that when the Nb addition amount exceeds 20 mol%, the hysteresis characteristics greatly change and deteriorate.

  Therefore, the X-ray diffraction patterns were compared as shown in FIG. When the amount of Nb added is 5 mol% (Zr / Ti / Nb = 20/75/5), the (111) peak position is the same as that of the conventional PZT film to which Nb is not added. As the amount increases to 20 mol% (Zr / Ti / Nb = 20/60/20) and 40 mol% (Zr / Ti / Nb = 20/40/40), the (111) peak shifts to the lower angle side. did. That is, although the composition of PZT is Ti-rich and a tetragonal region, it can be seen that the actual crystal is a rhombohedral crystal. It can also be seen that the ferroelectric properties change as the crystal system changes.

  In addition, when 45 mol% of Nb was added, the hysteresis did not open and the ferroelectric characteristics could not be confirmed (not shown).

  In addition, the PZTN film according to the present invention has already been described to have very high insulating properties, but when the conditions for PZTN being an insulator are obtained here, it is as shown in FIG.

That is, the PZTN film according to the present invention has a very high insulating property, which means that Nb is added to the Ti site at a composition ratio corresponding to twice the amount of Pb deficiency. In addition, as can be seen from the crystal structure of WO ₃ shown in FIG. 22, the perovskite crystal is established even if the A-site ion is 100% deficient, and WO ₃ is known to change its crystal system easily. .

  Therefore, in the case of PZTN, by adding Nb, the amount of Pb deficiency is positively controlled and the crystal system is controlled.

  This indicates that the PZTN film of the present embodiment is very effective for application to piezoelectric elements. In general, when PZT is applied to a piezoelectric element, a rhombohedral crystal region having a Zr rich composition is used. At this time, the Zr-rich PZT is called a soft PZT. This literally means that the crystal is soft. For example, a soft PZT is used for an ink discharge nozzle of an ink jet printer. However, since the soft PZT is too soft, an ink with a very high viscosity cannot be pushed out against the pressure of the ink.

  On the other hand, Ti-rich tetragonal PZT is called hard PZT, which means that it is hard and brittle. However, although the PZTN film of the present invention is a hard system, the crystal system can be artificially changed to a rhombohedral crystal. In addition, the crystal system can be arbitrarily changed by the amount of Nb added, and the Ti-rich PZT ferroelectric film has a small relative dielectric constant, so that the device can be driven at a low voltage. .

  This makes it possible to use a hard PZT that has not been used so far, for example, as an ink discharge nozzle of an ink jet printer. In addition, since Nb brings softness to PZT, it is possible to provide PZT that is moderately hard but not brittle.

  Finally, as described above, in this embodiment, not only Nb is added, but also silicate is added simultaneously with Nb addition, so that the crystallization temperature can be reduced.

  In this embodiment, for example, a ferroelectric capacitor constituting a memory cell portion of a ferroelectric memory or a platinum-based material such as Pt or Ir used as an electrode material of a piezoelectric actuator constituting an ink discharge nozzle portion of an ink jet printer, for example. The effectiveness of using a PZTN film was examined from the viewpoint of lattice matching when a PZTN film was formed on a metal film made of metal. The platinum-based metal is a material useful as an electrode material as well as a base film that determines the crystal orientation of the ferroelectric film when a PZT-based ferroelectric film is applied to the device. However, since the lattice matching between the two is not sufficient, the fatigue characteristics of the ferroelectric film become a problem for device application.

  Accordingly, the inventors of the present application have developed a technique for improving the lattice mismatch between the PZT-based ferroelectric film and the platinum-based metal thin film by including Nb in the constituent elements of the PZT-based ferroelectric film. developed. FIG. 23A to FIG. 23C show the film forming process of the PZT ferroelectric film in this case.

  First, as shown in FIG. 23A, a given substrate 10 is prepared. As the substrate 10, a substrate in which a TiOx layer was formed on an SOI substrate was used. In addition, as the board | substrate 10, a suitable thing can be selected and used from what consists of a well-known material.

Next, as shown in FIG. 23B, a metal film (first electrode) 102 made of Pt is formed on the substrate 100 by using, for example, a sputtering method, and thereafter, as shown in FIG. Then, a PZTN film is formed as the ferroelectric film 101 on the metal film 102. As a material for forming the PZTN film, for example, a sol-gel solution can be used. More specifically, a sol-gel solution for PbZrO _3, a sol-gel solution for PbTiO _3, and PbNbO ₃ that the sol-gel solution was mixed for uses which was further added PbNbO ₃ sol-gel solution. Note that since the PZTN film contains Nb as a constituent element, the crystallization temperature is high. For this reason, in order to reduce the crystallization temperature, it is preferable to use one further added with a sol-gel solution for PbSiO ₃ . In this embodiment, the above-described sol-gel mixed solution is applied onto the Pt metal film 102 by a spin coating method and crystallized by performing a predetermined heat treatment. The flow of the film forming process is the same as that shown in FIG.

In this example, when the lattice constant of a crystal was measured using an X-ray diffraction method for a PZTN film obtained with an addition amount of Nb in the range of 0 mol% to 30 mol%, FIG. 24 (A) and FIG. ). According to FIGS. 24A and 24B, it can be seen that as the amount of Nb added increases, the lattice constant on the a-axis (or b-axis) approaches the lattice constant on the c-axis. In addition, V (abc) in FIG. 24A is an index obtained by volume-converting the lattice constant (a, b, c). Further, V / V ₀ in FIG. 24A is a ratio of V (abc) for the PZTN crystal to an index V ₀ obtained by volume conversion of the lattice constant of the PZT crystal to which Nb is not added. Thus, it can be confirmed from the column of V (abc) or V / V _{0 that} the crystal lattice of the PZTN crystal becomes smaller as the amount of Nb added increases.

  Then, from the lattice constant of the PZTN film formed by adding Nb in this way, the lattice mismatch rate with the lattice constant (a, b, c = 3.96) of the Pt metal film is calculated to add Nb. A plot of the amount (mol%) on the horizontal axis is shown in FIG. According to FIG. 25, the effect of including Nb in the PZT-based ferroelectric film is not only the effect of improving the ferroelectric characteristics as in the above-described embodiments, but also the lattice constant of Pt or the like. It was confirmed that there is also an effect of bringing it close to the lattice constant of platinum-based metal crystals. In particular, it was confirmed that the effect appears remarkably in the region where the amount of Nb added is 5 mol% or more.

  Therefore, by using the method of the present invention, the lattice mismatch between the metal film as the electrode material and the ferroelectric film is reduced. For example, when the addition amount of Nb is 30 mol%, the lattice mismatch rate is 2%. It was confirmed that it was improved to the extent. This is because, in the crystal structure of PZTN, a strong bond having both an ionic bond and a covalent bond occurs between the Nb atom substituted for the Ti atom at the B site and the O atom, and the bond force compresses the crystal lattice. It is considered that the lattice constant changed in the direction of decreasing in the direction of the direction.

  Further, platinum-based metals such as Pt are chemically stable substances and are suitable as electrode materials for ferroelectric memories and piezoelectric actuators. According to the method of this embodiment, the platinum metal is formed on the Pt metal film. Even if the PZTN film is directly formed, the lattice mismatch can be relaxed as compared with the conventional case, and the interface characteristics can be improved. Therefore, it can be said that the method of this embodiment can reduce the fatigue deterioration of the PZT ferroelectric film, and is suitable for element application to a ferroelectric memory, a piezoelectric actuator, and the like.

(Reference example)
In this example, a PbZr _0.4 Ti _0.6 O ₃ ferroelectric film was produced.

  In the conventional method, a solution containing about 20% Pb in excess is used for the purpose of suppressing volatile Pb and reducing the crystallization temperature. However, it is unclear how excess Pb is formed in the thin film thus produced, and should be suppressed with a minimum Pb excess.

Therefore, a 10% by weight PbZr _0.4 Ti _0.6 O ₃ forming sol-gel solution (solvent: n-butanol) having an excess Pb of 0, 5, 10, 15, 20% is used, and further 10% by weight. A sol-gel solution for forming PbSiO _{3 having a} concentration (solvent: n-butanol) was added in an amount of 1 mol%, and steps ST20 to ST25 shown in FIG. 26 were performed to obtain 200 nm of PbZr _0.4 Ti _0.6. An O ₃ ferroelectric film was formed. The surface morphology at this time was as shown in FIGS. 27 (A) to 27 (C), and the XRD pattern was as shown in FIGS. 28 (A) to 28 (C).

Conventionally, an excess of Pb of about 20% was required, but it was shown that crystallization progressed sufficiently with an excess of Pb of 5%. This indicates that as little as 1 mol% of PbSiO ₃ catalyst has lowered the crystallization temperature of PZT, so little excess Pb is needed. Thereafter, as the PZT, PbTiO ₃ , and PbZrTiO ₃ forming solutions, all 5% Pb excess solutions are used.

Next, a 10% by weight PbZrO ₃ forming sol-gel solution (solvent: n-butanol) and 10% by weight PbTiO ₃ forming sol-gel solution (solvent: n-butanol) are mixed at a ratio of 4: 6. 10 wt% concentration of PbSiO ₃ sol-gel solution for forming the (solvent: n-butanol), was prepared in accordance with the flow of FIG. 2 with 1 mol% added with the mixed _{solution, 200nm-PbZr 0.4 Ti 0.6 O} 3 A ferroelectric film was prepared. The hysteresis characteristics at this time were excellent in squareness as shown in FIGS. 29 (A) and 29 (B). However, it turned out to be leaky at the same time.

For comparison, 10% is added to a sol-gel solution for forming PbZr _0.4 Ti _0.6 O ₃ (solvent: n-butanol) having a concentration of 10% by weight using the flow of FIG. A 200 nm-PbZr _0.4 Ti _0.6 O ₃ ferroelectric thin film was prepared using a mixed solution to which 1 mol% of a sol-gel solution for PbSiO ₃ formation (solvent: n-butanol) having a concentration by weight of 1% was added. At this time, the hysteresis characteristic was not very good as shown in FIG.

  Then, when degassing analysis was performed using each ferroelectric film, it was as shown in FIG. 31 (A) and FIG. 31 (B).

  As shown in FIG. 31 (A), in the conventional ferroelectric film produced with the PZT sol-gel solution, degassing that is always associated with H and C was confirmed as the temperature rose from room temperature to 1000 ° C.

On the other hand, as shown in FIG. 31 (B), a 10 wt% PbZrO ₃ forming sol-gel solution (solvent: n-butanol) and a 10 wt% PbTiO ₃ forming sol-gel solution (solvent: n-butanol) were used. In the case of the ferroelectric film according to the present invention using the solution mixed at a ratio of 4: 6, it was found that almost no degassing was observed until the film was decomposed.

This is because 10% by weight PbZrO ₃ forming sol-gel solution (solvent: n-butanol) and 10% by weight PbTiO ₃ forming sol-gel solution (solvent: n-butanol) were mixed at a ratio of 4: 6. By using the solution, PbTiO ₃ is first crystallized on Pt by a 10% by weight sol-gel solution for forming PbTiO ₃ (solvent: n-butanol) in the mixed solution, which becomes a crystal initial nucleus, and Pt and PZT It was thought that PZT crystallized easily. Moreover, it is considered that by using the mixed solution, PbTiO ₃ and PZT were continuously formed at a good interface, which led to good hysteresis squareness.

2. Ferroelectric Memory Device FIGS. 32A and 32B are diagrams showing a configuration of a simple matrix ferroelectric memory device 300 in the embodiment of the present invention. 32A is a plan view thereof, and FIG. 32B is a cross-sectional view taken along the line AA of FIG. 32A. As shown in FIGS. 32A and 32B, the ferroelectric memory device 300 has a predetermined number of word lines 301 to 303 formed on the substrate 308 and a predetermined number of the word lines. Bit lines 304 to 306. The ferroelectric film 307 made of PZTN described in the above embodiment is inserted between the word lines 301 to 303 and the bit lines 304 to 306, and the word lines 301 to 303 and the bit lines 304 to 306 intersect. A ferroelectric capacitor is formed in the region.

  In the ferroelectric memory device 300 in which memory cells configured by this simple matrix are arranged, writing to and reading from the ferroelectric capacitors formed in the intersecting regions of the word lines 301 to 303 and the bit lines 304 to 306 are as follows: This is performed by a peripheral drive circuit, a read amplifier circuit (not shown) or the like (referred to as “peripheral circuit”). This peripheral circuit may be formed by a MOS transistor on a substrate different from the memory cell array and connected to the word lines 301 to 303 and the bit lines 304 to 306, or a single crystal silicon substrate may be used as the substrate 308. By using the peripheral circuit, it is possible to integrate the peripheral circuit on the same substrate as the memory cell array.

  FIG. 33 is a cross-sectional view showing an example of a ferroelectric memory device 300 in which the memory cell array is integrated with peripheral circuits on the same substrate in the present embodiment.

  In FIG. 33, a MOS transistor 402 is formed on a single crystal silicon substrate 401, and this transistor formation region becomes a peripheral circuit portion. The MOS transistor 402 includes a single crystal silicon substrate 401, source / drain regions 405, a gate insulating film 403, and a gate electrode 404.

  The ferroelectric memory device 300 includes an element isolation oxide film 406, a first interlayer insulating film 407, a first wiring layer 408, and a second interlayer insulating film 409.

  The ferroelectric memory device 300 includes a memory cell array including ferroelectric capacitors 420. The ferroelectric memory 420 includes a lower electrode (first electrode or second electrode) 410 serving as a word line or a bit line, From a ferroelectric film 411 including a ferroelectric phase and a paraelectric phase, and an upper electrode (second electrode or first electrode) 412 formed on the ferroelectric film 411 and serving as a bit line or a word line Composed.

  Further, the ferroelectric memory device 300 includes a third interlayer insulating film 413 on the ferroelectric capacitor 420, and the memory cell array and the peripheral circuit portion are connected by the second wiring layer 414. In the ferroelectric memory device 300, a protective film 415 is formed on the third interlayer insulating film 413 and the second wiring layer 414.

  According to the ferroelectric memory device 300 having the above configuration, the memory cell array and the peripheral circuit portion can be integrated on the same substrate. Note that the ferroelectric memory device 300 shown in FIG. 4 has a configuration in which a memory cell array is formed on the peripheral circuit portion, but, of course, no memory cell array is arranged on the peripheral circuit portion, It is good also as a structure which is in contact with the circuit part planarly.

  Since the ferroelectric capacitor 420 used in this embodiment is composed of the PZTN according to the above-described embodiment, the squareness of hysteresis is very good and it has a stable disturb characteristic. Furthermore, the ferroelectric capacitor 420 has less damage to peripheral circuits and other elements due to lower process temperature, and less process damage (especially hydrogen reduction), thereby suppressing deterioration of hysteresis due to damage. Can do. Therefore, by using the ferroelectric capacitor 420, the simple matrix ferroelectric memory device 300 can be put into practical use.

  FIG. 34A shows a structural diagram of a 1T1C type ferroelectric memory device 500 as a modification. FIG. 34B is an equivalent circuit diagram of the ferroelectric memory device 500.

  As shown in FIG. 34, the ferroelectric memory device 500 includes a capacitor comprising a lower electrode 501, an upper electrode 502 connected to a plate line, and a ferroelectric film 503 to which the PZTN ferroelectric of the present embodiment is applied. 504 (1C) and a memory having a structure similar to that of a DRAM comprising a switching transistor element 507 (1T) having one of source / drain electrodes connected to a data line 505 and a gate electrode 506 connected to a word line It is an element. Since the 1T1C type memory can perform writing and reading at a high speed of 100 ns or less and the written data is nonvolatile, it is promising for the replacement of SRAM.

3. Piezoelectric Element and Inkjet Recording Head Hereinafter, an inkjet recording head in an embodiment of the present invention will be described in detail.

  A part of the pressure generation chamber communicating with the nozzle opening for discharging ink droplets is constituted by a vibration plate, and the vibration plate is deformed by a piezoelectric element to pressurize the ink in the pressure generation chamber to discharge ink droplets from the nozzle opening. Two types of ink jet recording heads have been put into practical use: those using a longitudinal vibration mode piezoelectric actuator that extends and contracts in the axial direction of the piezoelectric element, and those using a flexural vibration mode piezoelectric actuator.

  As an example of using an actuator in a flexural vibration mode, for example, a uniform piezoelectric layer is formed by a film forming technique over the entire surface of the diaphragm, and this piezoelectric layer is formed into a pressure generating chamber by a lithography method. A device in which a piezoelectric element is formed so as to be cut into a corresponding shape and independent for each pressure generating chamber is known.

  38 is an exploded perspective view showing an outline of an ink jet recording head according to an embodiment of the present invention, FIG. 39 is a plan view and a cross-sectional view along AA ′ of FIG. 38, and FIG. 3 is a schematic diagram showing a layer structure of an element 700. FIG. As shown in the figure, the flow path forming substrate 10 is made of a silicon single crystal substrate having a plane orientation (110) in the present embodiment, and one surface thereof is made of silicon dioxide previously formed by thermal oxidation. A 2 μm elastic film 50 is formed. A plurality of pressure generating chambers 12 are arranged in parallel in the width direction of the flow path forming substrate 10. In addition, a communication portion 13 is formed in a region outside the longitudinal direction of the pressure generation chamber 12 of the flow path forming substrate 10, and the communication portion 13 and each pressure generation chamber 12 are provided for each pressure generation chamber 12. Communication is made via a supply path 14. The communication part 13 constitutes a part of a reservoir 800 that communicates with a reservoir part 32 of the sealing substrate 30 described later and serves as a common ink chamber for the pressure generation chambers 12. The ink supply path 14 is formed with a narrower width than the pressure generation chamber 12, and maintains a constant flow path resistance of ink flowing into the pressure generation chamber 12 from the communication portion 13.

  Further, on the opening surface side of the flow path forming substrate 10, a nozzle plate 20 having a nozzle opening 21 communicating with the vicinity of the end portion of each pressure generating chamber 12 on the side opposite to the ink supply path 14 is provided with an adhesive or It is fixed via a heat welding film or the like.

  On the other hand, as described above, the elastic film 50 having a thickness of, for example, about 1.0 μm is formed on the side opposite to the opening surface of the flow path forming substrate 10. For example, an insulator film 55 having a thickness of about 0.4 μm is formed. Further, on the insulator film 55, a lower electrode film 60 having a thickness of, for example, about 0.2 μm, a piezoelectric layer 70 having a thickness of, for example, about 1.0 μm, and a thickness of, for example, about 0 The upper electrode film 80 having a thickness of 0.05 μm is laminated by a process described later to constitute the piezoelectric element 700. Here, the piezoelectric element 700 refers to a portion including the lower electrode film 60, the piezoelectric layer 70, and the upper electrode film 80. In general, one electrode of the piezoelectric element 300 is used as a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure generating chamber 12. In addition, here, a portion that is configured by any one of the patterned electrodes and the piezoelectric layer 70 and in which piezoelectric distortion is generated by applying a voltage to both electrodes is referred to as a piezoelectric active portion. In this embodiment, the lower electrode film 60 is a common electrode of the piezoelectric element 700, and the upper electrode film 80 is an individual electrode of the piezoelectric element 700. However, there is no problem even if this is reversed for the convenience of the drive circuit and wiring. In either case, a piezoelectric active part is formed for each pressure generating chamber. Further, here, the piezoelectric element 700 and a vibration plate that is displaced by driving the piezoelectric element 700 are collectively referred to as a piezoelectric actuator. The piezoelectric layer 70 is provided independently for each pressure generating chamber 12, and is composed of a plurality of layers of ferroelectric films 71 (71a to 71f) as shown in FIG.

  The ink jet recording head constitutes a part of a recording head unit having an ink flow path communicating with an ink cartridge or the like, and is mounted on the ink jet recording apparatus. FIG. 41 is a schematic view showing an example of the ink jet recording apparatus. As shown in FIG. 41, recording head units 1A and 1B having an ink jet recording head are provided with cartridges 2A and 2B constituting an ink supply means in a detachable manner, and a carriage 3 on which the recording head units 1A and 1B are mounted. Is provided on a carriage shaft 5 attached to the apparatus body 4 so as to be movable in the axial direction. The recording head units 1A and 1B, for example, are configured to eject a black ink composition and a color ink composition, respectively. The driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and timing belt 7 (not shown), so that the carriage 3 on which the recording head units 1A and 1B are mounted is moved along the carriage shaft 5. The On the other hand, the apparatus body 4 is provided with a platen 8 along the carriage shaft 5, and a recording sheet S which is a recording medium such as paper fed by a paper feed roller (not shown) is conveyed onto the platen 8. It is like that.

  Although an ink jet recording head that discharges ink has been described as an example of the liquid ejecting head, the present invention is intended for liquid ejecting heads and liquid ejecting apparatuses that use piezoelectric elements. Examples of the liquid ejecting head include a recording head used in an image recording apparatus such as a printer, a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an organic EL display, and an electrode formation such as an FED (surface emitting display). Electrode material ejecting heads used in manufacturing, bioorganic matter ejecting heads used in biochip production, and the like.

  Since the piezoelectric element according to the present embodiment uses the PZTN film according to the above-described embodiment as a piezoelectric layer, the following effects can be obtained.

  (1) Since the covalent bond in the piezoelectric layer is improved, the piezoelectric constant can be improved.

  (2) Since defects of PbO in the piezoelectric layer can be suppressed, generation of a different phase at the interface with the electrode of the piezoelectric layer is suppressed, and an electric field is easily applied, thereby improving the efficiency as a piezoelectric element. it can.

  (3) Since the leakage current of the piezoelectric layer can be suppressed, the piezoelectric layer can be thinned.

  In addition, since the liquid ejecting head and the liquid ejecting apparatus according to the present embodiment use the piezoelectric element including the piezoelectric layer described above, the following effects can be obtained.

  (4) Since the fatigue deterioration of the piezoelectric layer can be reduced, the change in the displacement amount of the piezoelectric layer with time can be suppressed and the reliability can be improved.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention.

FIG. 2 is a cross-sectional view schematically showing a ferroelectric capacitor in the present embodiment. The figure which shows the flowchart for forming the PZTN film | membrane in this embodiment by a spin coat method. The figure which shows the P (polarization) -V (voltage) hysteresis curve of the ferroelectric capacitor in this embodiment. The figure which shows the surface morphology of the PZTN film | membrane in Example 1 which concerns on this embodiment. The figure which shows the crystallinity of the PZTN film | membrane in Example 1 which concerns on this embodiment. The figure which shows the relationship between the film thickness of PZTN film | membrane in Example 1 which concerns on this embodiment, and surface morphology. The figure which shows the relationship between the film thickness and crystallinity of the PZTN film | membrane in Example 1 which concerns on this embodiment. The figure which shows the film thickness and hysteresis characteristic of the PZTN film | membrane in Example 1 which concerns on this embodiment. The figure which shows the film thickness and hysteresis characteristic of the PZTN film | membrane in Example 1 which concerns on this embodiment. The figure which shows the leakage current characteristic of the PZTN film | membrane in Example 1 which concerns on this embodiment. The figure which shows the fatigue characteristic and static imprint characteristic of the PZTN film | membrane in Example 1 which concerns on this embodiment. It shows a capacitor structure of the SiO ₂ protective film formed by ozone TEOS in Example 1 of the present embodiment. It shows the hysteresis characteristics of the capacitor after the SiO ₂ protective film formed by ozone TEOS in Example 1 of the present embodiment. The figure which shows the leakage current characteristic of the conventional PZT film | membrane in Example 1 which concerns on this embodiment. The figure which shows the fatigue characteristic of the conventional PZT capacitor in Example 1 which concerns on this embodiment. The figure which shows the static imprint characteristic of the conventional PZT capacitor in Example 1 which concerns on this embodiment. The figure which shows the hysteresis characteristic of the PZTN film | membrane in Example 2 which concerns on this embodiment. The figure which shows the hysteresis characteristic of the PZTN film | membrane in Example 2 which concerns on this embodiment. The figure which shows the hysteresis characteristic of the PZTN film | membrane in Example 2 which concerns on this embodiment. The figure which shows the X-ray-diffraction pattern of the PZTN film | membrane in Example 2 which concerns on this embodiment. The figure which shows the relationship between the Pb defect | deletion amount in the PZTN crystal | crystallization in Example 2 which concerns on this embodiment, and the composition ratio of Nb. Diagram for explaining the crystal structure of WO ₃ is perovskite crystal. The figure which shows typically the formation process of the PZTN film | membrane in Example 3 which concerns on this embodiment. The figure for demonstrating the change of the lattice constant of the PZTN film | membrane in Example 3 which concerns on this embodiment. The figure for demonstrating the change of the lattice mismatch rate of the PZTN film | membrane and Pt metal film in Example 3 which concerns on this embodiment. The figure which shows the flowchart for forming the conventional PZT film | membrane in the reference example of this embodiment by a spin coat method. The figure which shows the surface morphology of the PZT film | membrane in the reference example of this embodiment. The figure which shows the crystallinity of the PZT film | membrane in the reference example of this embodiment. The figure which shows the hysteresis of the tetragonal PZT film | membrane in the reference example of this embodiment. The figure which shows the hysteresis of the conventional tetragonal PZT film | membrane in the reference example of this embodiment. The figure which shows the degassing analysis result of the tetragonal PZT film | membrane in the reference example of this embodiment. 1A and 1B are a plan view and a cross-sectional view schematically showing a simple matrix ferroelectric memory device according to an embodiment. 1 is a cross-sectional view showing an example of a ferroelectric memory device in which a memory cell array is integrated with peripheral circuits on the same substrate in the present embodiment. Sectional drawing and its circuit diagram which show typically the 1T1C type ferroelectric memory in the modification of this embodiment. The figure which shows the various characteristics regarding the coupling | bonding of the constituent element of a PZT type ferroelectric. The figure for demonstrating the Schottky defect of a brown mirror light type crystal structure. The figure for demonstrating the space charge polarization of a ferroelectric. FIG. 3 is an exploded perspective view of the recording head according to the embodiment. 2A and 2B are a plan view and a cross-sectional view of a recording head according to the present embodiment. Schematic which shows the layer structure of the piezoelectric element which concerns on this embodiment. 1 is a schematic diagram illustrating an example of an ink jet recording apparatus according to an embodiment. The figure which shows the hysteresis characteristic of the ferroelectric film which added Ta or W to PZT which concerns on this embodiment.

Explanation of symbols

101 Ferroelectric film, 102 1st electrode, 103 2nd electrode

Claims (17)

Forming a lower electrode on the substrate;
Preparing a second mixed solution in which a sol-gel solution for PbSiO ₃ is added to a first mixed solution containing Pb, Zr, Ti, and Nb;
Applying the second mixed solution on the lower electrode;
Crystallizing the applied second mixed solution by dry heat treatment, degreasing heat treatment, and rapid thermal annealing to form a ferroelectric film represented by AB _1-x Nb _x O ₃ ;
Forming an upper electrode on the ferroelectric film,
The element represented by A is lead,
The elements represented by B are zirconium and titanium,
0.1 ≦ x ≦ 0.4, and
The method of manufacturing a ferroelectric capacitor, wherein the ferroelectric film includes Si of 0.5 mol% or more and less than 5 mol%. In claim 1,
The method of manufacturing a ferroelectric capacitor, wherein the first mixed solution is a sol-gel solution for PbZrO ₃ , a sol-gel solution for PbTiO ₃ , and a sol-gel solution for PbNbO ₃ . In claim 1 or 2,
A method for manufacturing a ferroelectric capacitor, wherein methyl succinate is added to the second mixed solution. In any one of Claims 1-3,
A method for manufacturing a ferroelectric capacitor, wherein 0.2 ≦ x ≦ 0.4. In any one of Claims 1-3,
A method for manufacturing a ferroelectric capacitor, wherein 0.1 ≦ x ≦ 0.3. In any one of Claims 1-3,
A method for manufacturing a ferroelectric capacitor, wherein 0.2 ≦ x ≦ 0.3. In any one of Claims 1-6,
The method for manufacturing a ferroelectric capacitor, wherein the ferroelectric film includes Nb at a composition ratio corresponding to twice the amount of Pb deficiency.   A method for manufacturing a ferroelectric memory using the method for manufacturing a ferroelectric capacitor according to claim 1. Forming a lower electrode on the substrate;
Preparing a second mixed solution in which a sol-gel solution for PbSiO ₃ is added to a first mixed solution containing Pb, Zr, Ti, and Nb;
Applying the second mixed solution on the lower electrode;
Crystallizing the applied second mixed solution by dry heat treatment, degreasing heat treatment, and rapid thermal annealing to form a ferroelectric film represented by AB _1-x Nb _x O ₃ ;
Forming an upper electrode on the ferroelectric film,
The element represented by A is lead,
The elements represented by B are zirconium and titanium,
0.1 ≦ x ≦ 0.4, and
The method for manufacturing a piezoelectric element, wherein the ferroelectric film contains 0.5 mol% or more and less than 5 mol% of Si. In claim 9,
The method for manufacturing a piezoelectric element, wherein the first mixed solution is a mixture of a sol-gel solution for PbZrO ₃ , a sol-gel solution for PbTiO ₃ , and a sol-gel solution for PbNbO ₃ . In claim 9 or 10,
A method for manufacturing a piezoelectric element, wherein methyl succinate is added to the second mixed solution. In any one of Claims 9-11,
A method for manufacturing a piezoelectric element, wherein 0.2 ≦ x ≦ 0.4. In any one of Claims 9-11,
A method for manufacturing a piezoelectric element, wherein 0.1 ≦ x ≦ 0.3. In any one of Claims 9-11,
A method for manufacturing a piezoelectric element, wherein 0.2 ≦ x ≦ 0.3. In any one of Claims 9-14,
The method of manufacturing a piezoelectric element, wherein the ferroelectric film includes Nb at a composition ratio corresponding to twice the amount of Pb deficiency.   A method for manufacturing a piezoelectric actuator using the method for manufacturing a piezoelectric element according to claim 9.   A method for manufacturing a liquid ejecting head using the method for manufacturing a piezoelectric actuator according to claim 16.