JP2009094526A - Solgel solution for forming ferroelectric film, method of manufacturing solgel solution for forming ferroelectric film, ferroelectric film, ferroelectric memory, piezoelectric element, and pyroelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve, in PZT in usage for ferroelectric memory, problems that a rhombohedral system PZT, which contains Zr more than in a rate, Zr/Ti=52/48, shows a hysteresis of a slim figure, and can drive in a low voltage, however, shows a defective hysteresis in a characteristic of polygon, and problems that a pyramidal quadratic system PZT, which contains rich in Ti, has a figure of hysteresis good in a characteristic of polygon, however, an anti-electric field is large, low voltage driving is difficult, and is impossible to keep reliability. <P>SOLUTION: An ester of organic acid is added to a solgel solution for forming a pyramidal quadratic system PZT in a range of 4≤pH<7 to form a three-dimentional huge network gel, and lattice information of a substrate covered with a Pt(111) film is more utilized to a (111) orientation PZT film than before an additive is added. Or a base alcohol is added to a solgel solution for forming a rhombohedral system PZT ferroelectric film in a range of 7≤pH<10 to form a two-dimentional fine network gel, and a rhombohedral system PZT ferroelectric crystal to be obtained itself can more stably exist in a (001) orientation film than before an additive is added. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ferroelectric memory device configured by using a ferroelectric capacitor, and in particular, has a so-called 1T1C, 2T2C type and a cell transistor having a ferroelectric capacitor and a selection cell transistor. In addition, a ferroelectric thin film that can be used in common for both simple matrix type in which a memory cell is composed only of a ferroelectric capacitor, a manufacturing technology for the thin film, and a ferroelectric memory device and the manufacturing thereof Regarding the method.

  In recent years, research and development of thin films such as PZT and SBT, and ferroelectric capacitors and ferroelectric memory devices using the thin films 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 the ferroelectric material. In the case of the same material, the 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 and doped in order to ensure the reliability most necessary for the memory element.

PZT, which is the most advanced in ferroelectric memory applications, is a solid solution of PbZrO ₃ and PbTiO ₃ , and when it contains a large amount of Zr at a Zr / Ti ratio of 52/48, it shows a slim hysteresis shape and a large amount of Ti When included, it is known to exhibit good squareness hysteresis.

  Originally, the hysteresis shape immediately after data writing is good in the tetragonal region containing Ti rich, and if it is only the shape of the hysteresis, the Ti-rich tetragonal region is suitable for memory applications. Since PZT cannot ensure reliability, it has not been commercialized as a ferroelectric memory device.

  Among many reliability tests, the reliability test called static imprint is the most severe. In this test, a ferroelectric memory in which data of 1 or 0 is written, that is, a ferroelectric thin film in which either + or − is polarized is subjected to a certain temperature (for example, 85 ° C. or 150 ° C.) for a certain time. This is a test of whether the written data can be read as written data after being held (for example, 100 hours or 1000 hours).

  As described above, the hysteresis shape immediately after data writing is good in the tetragonal region containing Ti richly. However, the tetragonal region containing Ti richly is mainly composed of Pb and Ti among the crystal constituent elements. Is meant to be. Pb has a high vapor pressure, and PbO vapor is generated even at a low temperature of about 100 ° C. as is known from the phase diagram of Ellingham. In addition, the bond energy with oxygen is the lowest at 38.8 kcal / mol, and Pb deficiency is likely to occur in the PZT crystal. In the case of Ti, the bond energy with oxygen is 73 kcal / mol and approximately twice the bond energy of Pb-O, but compared with 91.224 of Zr of the B site constituent element with the same atomic weight as 47.88. Is the lightest among the constituent elements of PZT, about half, and is most likely to be repelled at the time of vibration collision that occurs during heat treatment in the static imprint test, and easily causes Ti deficiency in the PZT crystal. These defects cause space charge polarization and further deteriorate the imprint characteristics.

  Furthermore, O deficiency occurs due to the principle of charge neutrality, and so-called Schottky defects due to the ionic crystal structure occur, which causes deterioration of leakage current characteristics. Cannot be secured.

  In addition, due to the increase in the degree of integration of the ferroelectric memory and the need for low voltage driving, the thinning of the ferroelectric thin film has progressed as the element size has decreased, and when PZT is used as the ferroelectric material, It is impossible to continue to use the Zr-rich composition used at the time, and as a result, the Ti-rich composition PZT must be used.

  That is, the relative permittivity increases due to the thin film, and the hysteresis shape changes more slimly. Although the reliability of conventional Zr-rich PZT, such as imprint characteristics, has not been a practical problem, the hysteresis has changed, and the hysteresis shape has become slimmer. It becomes surface. Therefore, in order to reduce the relative dielectric constant and bring the hysteresis shape closer to the hysteresis shape used in the small-capacity memory, it is necessary to use PZT having a Ti-rich composition. As a result, the above-described problems appear, and in any case, unless the problems of the Ti-rich PZT are solved, high integration of the ferroelectric memory becomes impossible.

  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 JP-A-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. As the inventors proceeded with development, it was found that a hysteresis loop with good squareness is indispensable for obtaining a simple matrix ferroelectric memory device that can actually operate. 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.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a 1T1C, 2T2C and simple matrix ferroelectric memory device including a ferroelectric capacitor having hysteresis characteristics that can be used for both 1T1C, 2T2C and simple matrix ferroelectric memory, and its manufacture. It is to provide a method.

  In the case of a ferroelectric thin film used for a ferroelectric memory, it is common to use the ferroelectric with its polarization axis aligned with the direction of application of electrolysis.

  For example, in the case of PZT, a Zr / Ti ratio of 52/48 is called a phase boundary, which is a mixed region of rhombohedral crystals and tetragonal crystals, and when Zr exceeds 52, it is tetragonal when the rhombohedral crystals and Ti composition exceed 48. It becomes a crystal.

  In the case of the rhombohedral PZT, the polarization axis exists on the <001> axis, and in the case of the tetragonal PZT, it exists on the <111> axis. Therefore, when a PZT thin film is used for a ferroelectric memory, it is used with the orientation aligned in the direction of the polarization axis as shown in Document 1 (Preliminary Proceedings of the 49th Applied Physics Related Conference Lecture 27a-ZA-6). It is common.

  However, a ferroelectric region has a polarization region (domain) that is a source of the development of ferroelectricity apart from crystal orientation. The domain includes a 180 ° domain and a 90 ° domain.

  When the polarization axis is the crystal orientation axis, the 180 ° domain parallel to the applied electric field contributes to the polarization, but the 90 ° domain does not contribute to the polarization at all.

If an ideal ferroelectric capacitor is formed, the 90 ° domain does not contribute to polarization, so even if it exists, it does not cause much problem. However, the contribution ratio to the polarization of the entire PZT thin film is reduced by the presence of the 90 ° domain.
In an actual ferroelectric capacitor, the outermost surface of the electrode is not completely flat and has irregularities, and the crystal itself grows in an inclined manner. In this case, the 90 ° domain has an applied electric field. It will not be completely vertical, but will have a slight angle. In this case, although the 90 ° domain contributes to polarization, since the polarization axis exists in a direction substantially perpendicular to the applied electric field, in order to contribute the 90 ° domain as a polarization component, compared to the 180 ° domain, A considerably large electric field is required. That is, it becomes difficult to use at a low voltage.

  However, the PZT crystal can be used for any type of ferroelectric memory as long as good squareness can be obtained regardless of the Zr / Ti composition and crystal system. .

  In the present invention, an organic acid ester is added in a range of 4 ≦ pH <7 in a conventionally used ferroelectric film forming sol-gel solution to form a three-dimensional giant network gel, or a conventional method. In the sol-gel solution for forming a ferroelectric film, a basic alcohol is added at 7 ≦ pH <10 to form a two-dimensional micro network gel.

  Of these, the three-dimensional giant network gel with the addition of an organic acid ester is for maximizing the use of information on the underlying layer on which the ferroelectric film is formed, while the two-dimensional micro-network gel with the addition of basic alcohol is a ferroelectric. This is for growing the crystal itself in a direction where it can exist stably, completely ignoring the information of the base on which the body film is formed.

  For example, in the case of a rhombohedral PZT whose hysteresis shape is poorly square and too slim, although reliability can be ensured, a two-dimensional micro-network gel by adding basic alcohol can be used to achieve an unprecedented good square It becomes possible to add sex.

  On the other hand, in the case of tetragonal PZT, which has a good coercive electric field but is difficult to use at low voltage, the hysteresis shape has a good squareness. The single orientation can be increased to the limit, and the low voltage driving can be performed while the squareness is good.

  In addition, in the case of tetragonal PZT, where it has been difficult to ensure reliability in the past, the improvement of crystallinity has been achieved by using a three-dimensional giant network gel with the addition of organic acid esters, resulting in a reduction in impurities and lattice defects. And improved reliability is achieved.

  The present invention can be applied to any sol-gel solution regardless of not only PZT but also Bi-based ferroelectric materials and tungsten bronze-based ferroelectric materials, and the present invention is not limited to ferroelectric memories. In addition, it is effective for all elements utilizing ferroelectricity, such as piezoelectric elements and pyroelectric elements.

1. Functions of acids and bases given to the sol-gel solution First, a synthesis method of the PZT sol-gel solution will be described.
System of metal alkoxide and carboxylic acid metal salt, namely lead acetate (CH ₃ CO ₂ ) ₂ Pb · 3H ₂ O as lead source, titanium tetrapropoxide (CH ₃ ) ₂ CHO ₄ Ti as titanium source, zirconium as zirconium source Description will be made using tetra-n-butoxide CH ₃ (CH ₂ ) ₃ O) ₄ Zr and 2-methoxyethanol CH ₃ O (CH ₂ ) ₂ OH as a solvent.

First, in order to remove the crystal water of lead acetate, methoxyethanol is added to lead acetate, and when heated to reflux, an esterification reaction product of acetic acid (acetyl group) and methoxyethanol in lead acetate is by-produced.
(CH ₃ CO ₂ ) ₂ Pb · 3H ₂ O + CH ₃ O (CH ₂ ) ₂ OH → CH ₃ CO ₂ PbO (CH ₂ ) ₂ OCH ₃ · XH ₂ O (X <0.5)
Next, when methoxyethanol is added to titanium tetrapropoxide, a part or all of the isopropoxy group ((CH ₃ ) 2 CHO—) is converted into a 2-methoxyethoxy group (CH ₃ O (CH ₂ ) ₂ O— by an alcohol exchange reaction. ).
(CH ₃ ) ₂ CHO ₄ Ti + nCH ₃ O (CH ₂ ) ₂ OH → ((CH ₃ ) ₂ CHO) _4-n Ti (O (CH ₂ ) ₂ OCH ₃ ) _n (n = 1 to 4)
Therefore, when methoxyethanol is added to zirconium tetra-n-butoxide, a similar alcohol exchange reaction occurs.
(CH ₃ ) ₂ CHO ₄ Ti + nCH ₃ O (CH ₂ ) ₂ OH → ((CH ₃ ) ₂ CHO) _4-n Zr (O (CH ₂ ) ₂ OCH ₃ ) _n (n = 1 to 4)
These are mixed, hydrolyzed, and polycondensed to produce the following polymer.

  As mentioned above, the acetic acid component in lead acetate produces methoxyethanol and lead acetate ester, and it mixes with the alcohol reaction product of Zr and Ti, repeats hydrolysis and polycondensation to produce the desired polycondensate. That is why. The table below summarizes this easily.

  When an ester of an organic acid is added, the pH becomes lower than 7 due to the acid component in the ester, and it becomes acidic. At this time, the reaction shifts to the esterification enhancement due to Le Chatelier's principle of the whole solution. As the esterification proceeds, water is generated and polycondensation proceeds with the alcohol exchange reaction product of Zr and Ti, and the PZT generating gel forms a huge network in the three-dimensional direction.

  At this time, if the pH is lower than 4, the corrosion of the base electrode metal or the like proceeds, so that it cannot be used.

  When basic alcohol is added, the whole solution becomes higher than pH 7 and becomes basic. At this time, the equilibrium of the lead acetate ester moves in the direction of returning to the original lead acetate. At that time, lead acetate takes the water of the system as crystal water, and the entire PZT generating gel moves in a direction in which it is difficult to form a huge network, thus forming a small two-dimensional network.

  At this time, if the pH is higher than 10, the network is completely disjointed, the elements are not connected to each other, the formation of PZT initial nuclei itself becomes difficult, and the crystallization temperature rises too much. Cannot be used.

  In the case of a huge three-dimensional network, if PZT initial nuclei are generated somewhere, the whole system is connected, so it is considered that the whole may be easily oriented in the same direction with low energy. At this time, if a (111) -oriented Pt electrode is used as the base, the PZT initial nuclei aligned in this direction determine the orientation of the entire network, and a (111) -oriented PZT film can be obtained.

  In the case of a short two-dimensional network, the network itself needs to be crystallized independently. When crystallization of PZT is performed under a certain energy environment, compared with the case of a huge three-dimensional network, It can be easily guessed that higher energy will be required.

Further, consider the stability of each face of the PZT perovskite crystal.
100), (010), (001) and crystal planes along the crystal axes a, b, and c, the same number of metal cations and oxygen anions no matter which atomic position is viewed in the plane. They are lined up next to each other, are neutral in the plane, and are energetically stable. On the other hand, the (111) orientation plane is unstable because it contains a large amount of oxygen depending on the atomic plane to be cut and cannot be electrically neutral.

  Therefore, in the case of a short two-dimensional network, since the network itself needs to be crystallized independently, it can be inferred that it will be essential that a stable surface grows parallel to the electrode surface. Therefore, in the case of a short two-dimensional network, it is considered that a PZT crystal oriented in the (001) plane is likely to be formed. However, when crystallizing at a sufficiently high temperature, that is, when large thermal energy is applied, the (111) plane of Pt is dragged to become (111) oriented PZT, but a PZT capacitor is formed as part of the semiconductor process. Since the crystallization temperature cannot be increased too much, the present invention is very effective particularly when a PZT capacitor is formed at a temperature of 700 ° C. or lower.

  This is proved by the fact that the SBT thin film on Pt (111) is randomly oriented and contains a c-axis orientation component (001). It is also known that (001) is more likely to be included as the crystallization temperature is lowered. SBT shows that the crystallization temperature is as high as about 800 ° C., and as the crystallization temperature is lowered, the crystal in the stable plane direction is easily grown by the reduced thermal energy.

  Carboxylic acid is used in the present invention among all acids to promote the formation of a huge three-dimensional network. However, if it is too strong, the network becomes too large and unsuitable for thin films. In order to corrode the lower electrode and the like, it is preferable that the pH is 5 or more and does not exceed 7. In addition, in view of the gas generated after crystallization, organic acids are preferable from the environmental aspect, and carboxylic acids of organic acids and esters of organic acids are particularly preferable.

  Examples of organic acids and organic acid esters used for forming a giant three-dimensional network include citric acid, malic acid, succinic acid, picric acid, methyl citrate, and esters thereof with alcohols such as methanol, ethanol, and propanol.

  Examples of the basic alcohol used for forming a minute two-dimensional network include 2-aminoethanol, 2-dimethylaminoethanol, 2-diethylaminoethanol, and 4-amino-1-butanol.

In addition, as a substrate on which the sol-gel solution for forming a ferroelectric thin film is applied, a semiconductor substrate such as an elemental semiconductor such as silicon or germanium, a compound semiconductor such as GaAs or ZnSe, a metal substrate such as Pt, a sapphire substrate, an MgO substrate, Examples include SrTiO ₃ , BaTiO ₃ , and insulating substrates such as glass substrates. Of these, a silicon substrate is preferable, and a silicon single crystal substrate is more preferable.

Of course, a substrate on which an electrode is formed is also included. The electrode is not particularly limited as long as it is a conductive material. Metal such as Pt, Ir, Au, Al and Ru, oxide conductor such as IrO ₂ and RuO ₂ , and nitride such as TiN and TaN It can be formed of a conductor or the like. As for the film thickness of an electrode, about 100-200 nm is mentioned, for example.

An intermediate layer such as an insulating layer and an adhesive layer may be formed between the electrode and the substrate. The insulating layer can be formed of, for example, SiO ₂ , Si ₃ N ₄ or the like. In addition, the material of the adhesive layer is not particularly limited as long as the adhesive strength between the substrate and the electrode or the insulating layer and the electrode can be secured. For example, a high melting point such as tantalum or titanium. A metal is mentioned. These intermediate layers can be formed by various methods such as thermal oxidation, CVD, sputtering, vacuum deposition, and MOCVD.

2. Method for Producing PZT Ferroelectric Thin Film An n-butanol solution containing 10% by weight of a polycondensate of an alcohol exchange reaction product of lead acetate, Ti tetrapropoxide and Zr tetra-n-butoxide with n-butanol. A sol-gel solution for forming standard PZT was used.

In the above-mentioned standard PZT forming sol-gel solution, a composition prepared by synthesizing 0.8 mol of Ti tetrapropoxide and 0.2 mol of Zr tetra-n-butoxide with respect to 1 mol of lead acetate is used for forming the first standard PZT. A sol-gel solution was prepared by synthesizing 0.2 mol of Ti tetrapropoxide and 0.8 mol of Zr tetra-n-butoxide with respect to 1 mol of lead acetate as a second standard PZT forming sol-gel solution.
That is, when the first standard PZT forming sol-gel solution is used, the purpose is to form tetragonal PbZr _0.2 Ti _0.8 O ₃ , and when the second standard PZT forming sol-gel solution is used, the rhombohedral PbZr _0.8 Ti It can be seen that the solution is intended to form _0.2 O ₃ .

  A solution obtained by mixing and stirring 1000 ml of the first standard PZT forming sol-gel solution and 100 ml of ethyl succinate was used as the first solution.

  Further, a solution obtained by mixing and stirring 1000 ml of the second standard PZT forming sol-gel solution and 100 ml of 2 diethylaminoethanol was used as the second solution.

  Next, spin coating was performed on the Pt (111) lower electrode-covered Si wafer using the first and second solutions under the same conditions described below.

  [Ferroelectric thin film formation conditions]

  As a result, a PZT thin film having a thickness of about 200 nm was obtained. The XRD pattern at this time is shown in FIG.

  As shown in FIG. 1, an almost complete (111) -oriented PZT thin film was obtained with the first solution, and an almost complete (001) -oriented PZT thin film was obtained with the second solution.

  The ferroelectric hysteresis characteristics at this time are as shown in FIG. 2, and both showed hysteresis characteristics having good squareness.

  This is because, in the case of the tetragonal structure PZT, since the polarization axis is at (001), only the (111) orientation plane is suitable for inversion at a low voltage or effective use of all polarization components. In the case of the plane structure PZT, the (001) orientation plane is reflected.

  However, the PZT crystal on Pt (111) is not a little on the conventional, but inherits the lattice information of Pt (111), and PZT also contains the (111) orientation component, and the good square shape shown in FIG. It was very difficult to bring out sex.

  In order to prove this, only the sol-gel solution for forming the second standard PZT that does not contain 2 diethylaminoethanol is spin-coated on the Pt (111) lower electrode-coated Si wafer using the above film formation conditions, and XRD is applied. As a result of diffraction evaluation, it was a random alignment film having XRD peaks in the (111) and (001) directions. At this time, a hysteresis characteristic as shown in FIG. 3 was obtained, and a hysteresis characteristic having a good squareness as shown in FIG. 2 was not obtained.

  As described above, by using the present invention, it is possible to easily form a (001) alignment film, which has been difficult until now, in the ridged surface structure PZT, and to create a PZT thin film having good squareness. .

3. Application Example to Ferroelectric Memory Manufacturing Method FIG. 4 is a cross-sectional view schematically showing an example of a manufacturing process of a ferroelectric memory according to this embodiment.

In this embodiment, first, as shown in FIG. 4A, the above-described ferroelectric thin film is formed on the substrate 50 in which the Pt metal thin film 60 to be the lower electrode of the ferroelectric capacitor 80 is formed. A Pt metal thin film 62 to be the upper electrode of the ferroelectric capacitor 80 is formed on the PbPt ₃ alloy film 61 and the PZT crystal layer 72 according to the present invention by using the forming method. For example, as shown in FIG. 4, a substrate 50 in which a cell selection transistor 56 is formed on a semiconductor substrate 51 can be used as the substrate 50. The transistor 56 can include a source / drain 53, a gate oxide film 54, and a gate electrode 55. Further, a plug electrode 57 made of, for example, tungsten is formed on one source / drain 53 of the transistor 56 so that it can be connected to the Pt metal thin film 60 that becomes the lower electrode of the ferroelectric capacitor 80. The stack structure can be adopted. Further, in the substrate 50, the transistor 56 is separated for each cell by an element isolation region 52 between cells, and a first interlayer insulating film 58 made of, for example, an oxide film is provided on the transistor 56. I can do it.

  Next, in this embodiment, as shown in FIG. 4B, the ferroelectric capacitor 80 is patterned into a desired size and shape. Finally, as shown in FIG. 4C, a hydrogen barrier film 91 is formed so as to cover the ferroelectric capacitor 80, and then a second interlayer insulating film 92 is formed. A ferroelectric memory is obtained by forming metal wiring layers 93 and 94 for connecting the ferroelectric capacitor 80 and the transistor 56 to the outside through through holes formed in the two interlayer insulating film 92. According to the manufacturing process of the present embodiment, a PZT ferroelectric thin film having a good crystal quality is formed, so that a ferroelectric memory having excellent characteristics can be realized.

  In the present embodiment, the manufacturing process of the so-called 1T1C type ferroelectric memory has been described. However, the ferroelectric thin film forming method of the present embodiment can also be applied to the so-called 2T2C type, 1T type and simple matrix. The present invention can also be applied to a manufacturing process of a ferroelectric memory using various types of cells such as a mold (cross point type).

The figure which showed the XRD pattern of the ferroelectric thin film in embodiment of this invention. The figure which showed the hysteresis characteristic of the ferroelectric thin film in embodiment of this invention. The figure which showed the hysteresis characteristic of the conventional random-oriented ridge-plane-crystal PZT capacitor in embodiment of this invention. Sectional drawing which shows the manufacturing process of the ferroelectric memory to which the formation process of the ferroelectric thin film which concerns on embodiment of this invention is applied.

Explanation of symbols

  50 ... Base, 60 ... Metal thin film, 61 ... Alloy film, 71 ... Ferroelectric thin film.

Claims (14)

  The sol-gel solution for forming a ferroelectric film is characterized by being used in a state in which an additive for changing the pH from the initial state is added.   In the sol-gel solution for forming a ferroelectric film, an organic acid or an ester of an organic acid is added to change the pH in the acidic direction from the initial state.   In the sol-gel solution for forming a ferroelectric film, basic alcohol is added, and the pH is changed in the basic direction from the initial state.   In the sol-gel solution for forming a ferroelectric film, an organic acid or an organic acid ester is added to form a three-dimensional giant network gel from the initial state.   In a sol-gel solution for forming a ferroelectric film, a basic alcohol is added to form a three-dimensional giant network gel from the initial state.   In the sol-gel solution for forming a ferroelectric film, an organic acid ester is added in the range of 4 ≦ pH <7 to form a three-dimensional giant network gel.   A sol-gel solution for forming a ferroelectric film is characterized in that a two-dimensional micro-network gel is formed by adding basic alcohol 7 ≦ pH <10.   In the sol-gel solution for forming a ferroelectric film, an organic acid ester is added in the range of 4 ≦ pH <7 to form a three-dimensional giant network gel, and the lattice information of the film-forming substrate is obtained more than before addition of the additive. It is characterized by obtaining an alignment film utilizing it.   In a sol-gel solution for forming a ferroelectric film, a basic alcohol is added to 7 ≦ pH <10 to form a two-dimensional micro-network gel, and the target ferroelectric crystal itself is more than before the additive is added. It is characterized in that an alignment film in a direction that can exist stably is obtained.   In the sol-gel solution for forming a tetragonal PZT, an organic acid ester is added in the range of 4 ≦ pH <7 to form a three-dimensional giant network gel, and the Pt (111) film coated substrate is formed more than before the addition of the additive. It is characterized in that a (111) -oriented PZT film utilizing the lattice information is obtained.   In a sol-gel solution for forming a rhombohedral PZT ferroelectric film, a basic alcohol is added at 7 ≦ pH <10 to form a two-dimensional micro-network gel. It is characterized in that a (001) oriented film in a direction in which the crystal PZT ferroelectric crystal itself can exist stably is obtained.   According to claims 1 to 11, the 90 ° domain does not exist in a direction parallel to the film coating surface.   A ferroelectric memory device using the ferroelectric thin film manufactured according to claim 1.   A ferroelectric piezoelectric element using the ferroelectric thin film produced according to claim 1.

Images