JP3991537B2 - Method for producing oxide thin film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for forming an oxide thin film, and more particularly to a technique for microcrystallizing a ferroelectric thin film crystal used for a memory element, a piezoelectric element and the like.
[0002]
[Prior art]
Compound oxide crystalline material exhibiting ferroelectricity, for example, lead zirconate titanate, barium titanate, lithium niobate Have many functions such as spontaneous polarization, high dielectric constant, electro-optic effect, piezoelectric effect, pyroelectric effect, etc., and thus are applied to a wide range of device development. For example, as a piezoelectric element using the piezoelectricity, as a capacitor such as FeRAM (Ferroelectric Random Access Memory) using spontaneous polarization or high dielectric property, as an infrared linear array sensor using pyroelectricity, It is used in various fields such as a waveguide type optical modulator utilizing the electro-optic effect. Such a ferroelectric thin film element having various functions is also referred to as a functional element.
[0003]
A thin film in such a ferroelectric thin film element or the like is manufactured by, for example, a sol-gel method, a MOD method, a sputtering method, a laser ablation method, a CVD method, or the like. Among these film forming methods, the sol-gel method and the MOD method are preferably used from the viewpoint of simplifying the manufacturing apparatus. When this sol-gel method or MOD method is used, it is manufactured through the following steps (1) to (4), for example. That is, (1) a solution coating step in which a solution made into a liquid (sol) form using a starting material such as lead zirconate titanate is applied to a wafer by spin coating; (2) then in the atmosphere at 80 to 180 ° C. (3) Thereafter, a preliminary firing step is performed in which a preliminary firing is performed at 200 to 400 ° C. in a dry air atmosphere for a predetermined time (however, the step (2) can be omitted). The film thickness obtained in this temporary baking step is determined by the concentration (viscosity) of the starting material and the coating conditions. And after repeating the process of said (1)-(3) until it becomes a desired film thickness, it passes through the main baking process which performs the heat processing of crystallization at 550-750 degreeC (4).
[0004]
By the way, when a ferroelectric thin film is used for FeRAM, in order to achieve high integration of the FeRAM, it is required that the crystal of the ferroelectric thin film be a fine crystal (Fine Grain: crystal grain size is less than 0.1 μm). Is done. However, the oxide thin film crystal formed through the steps (1) to (4) often has very coarse crystal grains (Corse Grain: crystal grain size exceeding 0.1 μm). Thus, when the crystal grains become coarse and become larger than the cell portion of the capacitor, the electrical characteristics differ from cell to cell, and in particular, the amount of polarization of the cell of each capacitor varies, causing malfunction.
[0005]
Conventionally, in order to obtain fine grains, titanium (Ti) or PbTiO is formed on the lower electrode (or substrate).₃Etc. had to be deposited very thinly as a seed layer.
[0006]
[Problems to be solved by the invention]
However, when the seed layer is deposited very thinly on the upper part of the lower electrode as in the above prior art, the film thickness suitable for the seed layer is as thin as several nanometers. There was a problem that it was difficult.
[0007]
Accordingly, an object of the present invention is to provide a method capable of easily obtaining microcrystals in a method of manufacturing an oxide thin film including a ferroelectric thin film as described above. It is another object of the present invention to provide a simple memory element manufacturing method and piezoelectric element manufacturing method using this manufacturing method. Furthermore, it is an object to provide an excellent oxide thin film, a memory element and a piezoelectric element manufactured by these manufacturing methods. It is another object of the present invention to provide an excellent information processing apparatus using the memory element and an ink jet recording head using the piezoelectric element.
[0008]
[Means for Solving the Problems]
In the method for producing an oxide thin film of the present invention, a solution of an organometallic compound containing a metal element capable of forming an oxide is used as a starting material, the solution is applied onto a substrate and dried, followed by calcination, When the oxide thin film is formed by performing the main baking, the temporary baking is performed in an atmosphere inert to the organometallic compound.
[0009]
Moreover, the oxide thin film of this invention is manufactured with the manufacturing method of the said oxide thin film. In the method for manufacturing a memory element of the present invention, the memory element is formed by using the method for manufacturing an oxide thin film. The memory element of the present invention is manufactured by the above-described method for manufacturing a memory element. The information processing apparatus according to the present invention uses the memory element. In the piezoelectric element manufacturing method of the present invention, the piezoelectric element is formed using the oxide thin film manufacturing method. The piezoelectric element of the present invention is manufactured by the above-described method for manufacturing a piezoelectric element. The ink jet recording head of the present invention uses the piezoelectric element.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
(Method for producing oxide thin film)
Hereinafter, the manufacturing method of the oxide thin film of this invention is demonstrated in detail.
[0011]
In the method for producing an oxide thin film of the present invention, a solution of an organometallic compound containing a metal element capable of forming an oxide is used as a starting material, the solution is applied onto a substrate and dried, followed by calcination, In forming an oxide thin film by performing main baking, the temporary baking is performed in an atmosphere inert to the organometallic compound.
[0012]
This production method is suitably applied to the sol-gel method or the MOD method as a method for forming the oxide thin film because it has regularity in crystallization and is suitable for microcrystallization.
[0013]
The sol-gel method is generally an inorganic oxidation that is completed by hydrolyzing and polycondensing organometallic compounds such as metal alkoxides in a solution system to grow metal-oxygen-metal bonds and finally sintering. This is a manufacturing method of an object. A feature of the sol-gel method is that a uniform film can be obtained at a low substrate temperature. Furthermore, since it forms into a film from a solution, it is excellent in adhesiveness with a board | substrate. On the other hand, the MOD method is a method for producing an inorganic oxide that is completed by a process similar to the sol-gel method except that hydrolysis is not performed. The MOD method is characterized in that the solution is chemically very stable compared to the solution used in the sol-gel method.
[0014]
The atmosphere inert to the organometallic compound is not particularly limited, and examples thereof include a nitrogen atmosphere and an argon atmosphere. Among these, a nitrogen atmosphere is particularly preferable. In general, in the sol-gel method or the MOD method, the pre-baking is performed in the atmosphere to an oxygen atmosphere. In the manufacturing method of the present invention, the pre-baking is performed in the inert atmosphere. By doing so, a microcrystallized oxide thin film can be easily manufactured.
[0015]
Moreover, as an organometallic compound used for this manufacturing method, alkoxide, acetate compounds, etc., such as metal methoxide, ethoxide, propoxide, and butoxide which can form an oxide are mentioned. Further, inorganic salts such as nitrates and perchlorates of the metals and organic salts such as oxalates of the metals may be used. Therefore, as a solution of the organometallic compound as a starting material, specifically, for example, Pb (CH₃COO)₂・ 3H₂O, Zr (t-OC₄H₉)₄, Ti (i-OC₃H₇)₄The mixed solution is a starting material for the PZT film and is particularly useful.
[0016]
Further, the organometallic compound and the solution of the organometallic compound are not limited to the above-described examples, and various types can be used. For example, starting materials that can obtain the composition of the oxide thin film described later can be appropriately selected.
[0017]
The organometallic compound solution is preferably liquid or sol.
[0018]
In addition, when forming a film by the sol-gel method, it is necessary to proceed with hydrolysis and polycondensation reactions to form oxides from solutions of these organometallic compounds, so it is necessary to add water to the coating solution. It becomes. Although the amount added varies depending on the system, if the amount is too large, the reaction proceeds fast, so that the resulting film quality tends to be non-uniform and the reaction rate is difficult to control. Even if the amount of water added is too small, it is difficult to control the reaction and there is an appropriate amount. Furthermore, it is possible to control the reaction rate and reaction mode by adding a hydrolysis accelerating catalyst or a chelating agent coordinated to a metal atom. Common acids and bases are used as the acceleration catalyst. The film quality is greatly affected by the type of catalyst. Examples of the chelating agent include acetylacetone, ethyl acetoacetate, diethyl malonate and the like. As the solvent, a solvent in which the above materials are not precipitated, that is, a solvent having excellent compatibility is desirable. The solution is applied on the substrate by a spin coating method, an LSMCD method (Liquid Source Misted Chemical Deposition method), or the like, particularly preferably by a spin coating method.
[0019]
The solution concentration depends on the coating method, but in the case of the spin coating method, the solution viscosity may be adjusted so as to be several cP to several tens cP.
[0020]
The substrate coated with the solution is dried at 80 to 180 ° C., more preferably 100 to 160 ° C. in the air, for example, with a hot plate or the like.
[0021]
The dried coated substrate is temporarily fired in an atmosphere that is inert to the organometallic compound as described above. Here, pre-baking is performed, for example, in an electric furnace, preferably at 200 to 400 ° C., more preferably at 250 to 350 ° C., preferably for 10 to 60 minutes, and more preferably for 20 to 40 minutes.
[0022]
And the process of the said application | coating, drying, and temporary baking is made into a desired film thickness. The film thickness at this time is preferably 0.1 to 0.3 μm, particularly preferably 0.15 to 0.25 μm.
[0023]
Thereafter, the temporarily fired substrate is subjected to main firing by heat treatment in an electric furnace, preferably at 550 to 750 ° C., more preferably at 600 to 700 ° C., and the film thickness is about 0.1 to 0.3 μm. A crystallized oxide thin film is obtained.
[0024]
The substrate for applying the solution is not particularly limited, and a silicon substrate, a quartz substrate, a glass substrate, an oxide single crystal substrate, or the like is used.
[0025]
As the composition of the oxide thin film produced by the production method of the present invention, for example, (BaSr) TiO₃, SrTiO₃Paraelectric material such as Pb (Zr, Ti) O₃, BaTiO₃, Bi₄Ti₃O₁₂, (Pb, La) (Zr, Ti) O₃And the like. When used as a ferroelectric thin film, the type is preferably a dielectric having at least titanium and lead as constituents, for example, lead titanate (PbTiO 2).₃), Lead zirconate titanate (Pb (Zr, Ti) O)₃), Lead lanthanum titanate ((Pb, La), TiO)₃), Lead lanthanum zirconate titanate ((Pb, La) (Zr, Ti) O)₃Or lead magnesium titanate zirconate (Pb (Zr, Ti) (Mg, Nb) O)₃And the like are preferred. In particular, lead zirconate titanate (PZT) is suitable.
[0026]
Moreover, as a composition of the oxide thin film manufactured by the manufacturing method of this invention, it is not limited to the composition of the example mentioned above. According to the production method of the present invention, oxide thin films having various compositions can be obtained by appropriately selecting starting materials for the organometallic compound.
[0027]
The oxide thin film produced by the production method of the present invention is particularly preferably used as a ferroelectric thin film. A ferroelectric thin film has an extremely large relative dielectric constant of several hundred to several thousand, and when used as an insulating film of a capacitor, a capacitor having a small area and a large capacity suitable for a large scale integrated circuit can be obtained. Since the ferroelectric thin film has spontaneous polarization and can reverse the polarization direction by the action of an external electric field, a nonvolatile memory can be manufactured using this characteristic. FeRAM using such a ferroelectric thin film as a capacitor insulating film has features that are not found in conventional nonvolatile memories, such as non-volatility, high-speed operation, low power consumption, and large number of rewrites.
[0028]
Since the oxide thin film obtained by the manufacturing method of the present invention is an excellent microcrystalline film, it can be used as a ferroelectric thin film element as described above for a capacitor of an FeRAM memory cell. Specifically, zirconium oxide is formed as an underlayer of the capacitor, and a lower electrode, a titanium thin film, a ferroelectric thin film, and an upper electrode are sequentially formed on this film.
[0029]
(Method for manufacturing memory element)
Next, a method for manufacturing the memory element of the present invention will be described in detail.
[0030]
The method for manufacturing a memory element of the present invention is a method for forming a memory element using the above-described method for manufacturing an oxide thin film.
[0031]
The oxide thin film is preferably formed as a dielectric thin film, particularly a ferroelectric thin film. In this case, the memory element is a dielectric memory element, particularly a ferroelectric memory element.
[0032]
As the best mode for carrying out the memory element manufacturing method of the present invention, a dielectric thin film as an oxide thin film is formed on a semiconductor thin film formed by a lithography method and a diffusion method using the above-described oxide thin film manufacturing method. A method of manufacturing an MFSFET (Metal Ferro-electric Semiconductor Field Effect Transistor) as a semiconductor element by forming is described, and this embodiment will be described with reference to the drawings.
[0033]
FIG. 1 shows a cross-sectional view of an MFSFET manufactured by the manufacturing method according to the present embodiment. In particular, in this embodiment, an n-type MFSFET is illustrated. As shown in FIG. 1, the present MFSFET includes a substrate 100, an electrode thin film 101, an insulating film 102, a dielectric thin film 103, and an electrode thin film 104. The substrate 100 forms a base on which a semiconductor element is formed, and is formed by processing a silicon wafer to an appropriate thickness. For example, if the FET is formed in a p-type, the substrate is formed by previously doping silicon with elements such as boron (B), aluminum (Al), and gallium (Ga) by ion implantation or thermal diffusion. The electrode thin film 101 is formed by doping impurities around the electrodes that serve as the source and drain of the FET. For example, if the FET is formed of n-type, it is formed by doping phosphorus (P), arsenic (As), antimony (Sb), etc. by ion implantation. The insulating film 102 is formed by, for example, oxidizing the surface of silicon to about 20 nm to 100 nm of SiO.₂It is formed in a film. SiO₂And Si₃N₄Nitride film such as Al₂O₃A metal oxide film such as can be applied. The insulating film 102 is configured to insulate and protect the surface of the semiconductor element. The dielectric thin film 103 is manufactured by the above-described oxide thin film manufacturing method. Examples of the composition of the dielectric thin film 103 include the paraelectric or ferroelectric as the composition of the oxide thin film described above. When a ferroelectric is used, this MFSFET becomes an element for a nonvolatile memory. The electrode 104 is formed by depositing an electrode material such as aluminum by sputtering and performing anisotropic etching. For the source electrode and the drain electrode, an electrode pattern is formed by a resist mask and anisotropic etching. The gate electrode and the substrate side electrode are also configured by depositing an electrode material by sputtering. Various known materials can be applied to the electrode material.
[0034]
In the MFSFET configuration, the dielectric thin film 103 has a hysteresis characteristic that the control voltage applied to the gate electrode for flowing the drain current differs depending on the polarization direction of the dielectric molecules. If this hysteresis characteristic is used, information can be stored by applying a control voltage sufficient to reverse the polarization direction of the dielectric molecules. Accordingly, the semiconductor element including the MFSFET can function as a memory element.
[0035]
In addition to the configuration in which the dielectric thin film 103 is formed directly on the insulating film 102 formed on the channel as described above, the channel layer-insulating film-metal thin film-dielectric thin film-metal thin film sandwiched between the electrode thin films. Even in a configuration in which layers are stacked in order from the lower layer, good characteristics are exhibited.
[0036]
The manufacturing method of this embodiment can be performed by using a manufacturing apparatus capable of forming the dielectric thin film 103 by the above-described oxide thin film manufacturing method. In this case, any film other than the dielectric thin film 103 may be formed by a conventional lithography method or sputtering method.
[0037]
A method for manufacturing the MFSFET of this embodiment will be described with reference to FIG. In the following description, an ultraviolet transfer method and an X-ray transfer method will be described as a pattern formation method, but an electron beam transfer method for directly drawing a pattern may be used.
[0038]
FIG. 2 (a): First, an element such as boron (B), aluminum (Al), gallium (Ga) or the like is applied to the silicon single crystal substrate 100 manufactured by a single crystal manufacturing apparatus or the like using an impurity introduction apparatus such as an ion implantation apparatus. And doping. The surface of the p-type silicon substrate 100 thus formed is oxidized using an oxidation furnace or the like, and SiO 2₂The oxide film 102 is formed. This oxide film can prevent silicon crystal defects from being induced. Next, Si as a selective oxidation mask₃N₄Etc. are applied by a coating apparatus or the like to form the mask film 201. As a method for applying the mask material, a known method such as spin coating, die coating, or roll coating is applied. Then, a mask 202 is provided in the element isolation region.
[0039]
FIG. 2B: Next, the mask layer 201 is exposed using an ultraviolet transfer device or an X-ray transfer device, and developed using a developing device or the like to remove the mask film 201 in the element isolation region. Next, an oxide film 102 in the element isolation region is grown to a thickness of 500 nm to 1000 nm at a temperature of about 1000 ° C. using a vapor phase growth apparatus or the like for element isolation. Thereafter, the mask film 201 is removed.
[0040]
FIG. 2C: Next, a resist 203 is provided on the gate electrode region, that is, the channel region using a resist coating apparatus or the like. Next, using an impurity introduction apparatus such as an ion implantation apparatus, P as a dopant is used.⁺Etc. By this treatment, the electrode region is made n-type (FIG. 2D). Thus, a surface to be a base for forming the dielectric thin film by the ink jet method of the present invention is formed. The processes so far may be produced in a factory, and the subsequent formation of the dielectric thin film may be formed in a small factory.
[0041]
Note that the metal element may move from the dielectric material to the silicon side through the oxide film, and if the metal element moves too much, the semiconductor deteriorates. In order to prevent this, a dielectric thin film may be formed after providing a buffer film on the oxide film in advance. The buffer layer is, for example, CaF₂, MgAl₂O₄, CeO₂Or SrTiO₃Etc.
[0042]
FIG. 2E: Next, the dielectric thin film 103 is formed using the above-described oxide thin film manufacturing method. That is, a solution of an organometallic compound containing a metal element capable of forming an oxide is used as a starting material, and the solution is formed on a SiO substrate 100 formed on a silicon substrate 100.₂When the dielectric thin film is formed by applying and baking on the oxide film 102 and drying, followed by temporary baking and then performing main baking, the temporary baking is inactive with respect to the organometallic compound. By performing in an atmosphere, the dielectric thin film 103 which is an excellent microcrystallized film is formed.
[0043]
FIG. 2F: Next, contact holes are provided in the oxide films in the source region and the drain region, and a metal such as aluminum is deposited using a sputtering apparatus or the like. A known technique is applied to the electrode formation. Finally, anisotropic etching is performed using an etching apparatus or the like so as to obtain an electrode shape, and a source electrode, a drain electrode, and a gate electrode 104 are provided. Further, a ground electrode is provided on the back surface of the substrate 100. Thereafter, bonding and assembly are performed to complete a memory element using the MFSFET.
[0044]
In addition, it is preferable to perform a surface treatment on the surface to be the base because adhesion between the dielectric thin film 103 and the surface to be the base is improved. For this surface treatment, various known methods such as a method of applying a silane coupling agent can be applied.
[0045]
The method for manufacturing a memory element of the present invention can be applied with various modifications regardless of the embodiment. For example, in the above-described embodiment, the MFSFET for explaining the formation of the dielectric thin film has been exemplified and the manufacturing method thereof has been shown. However, the present invention can be applied to any semiconductor element conventionally manufactured by a semiconductor process. For example, storage capacitor type semiconductor devices, PN junction diodes, thyristors, double base diodes, Gunn diodes, inpatient diodes, Schottky diodes, bipolar transistors, MOSFETs, nonvolatile MOSFET memories, junction type FETs, Schottky gate FETs, and statics The present invention is applicable to semiconductor elements such as electrically inductive transistors (SIT) and semiconductor circuits manufactured by integrating these semiconductor elements. Semiconductor barrier photovoltaic devices (photodiodes, APDs, phototransistors, etc.), photoelectric conversion devices such as photoconductive devices, imaging devices such as Si photodiode array and solid-state imaging devices (CCD), LEDs, LDs (Laser Diodes) It can also be applied to light emitting elements such as EL (Electro-luminescence), conversion elements such as magnetoelectric elements, thermoelectric / temperature sensitive elements, and stress conversion elements, and other conversion / functional elements.
[0046]
According to the method for manufacturing a memory element of the present invention, a dielectric thin film as an oxide thin film that is easily microcrystallized can be formed. Therefore, an excellent memory element, for example, an MFSFET using the dielectric thin film can be easily obtained. Can be manufactured. In addition, an excellent information processing apparatus can be provided by using such a memory element.
[0047]
(Method for manufacturing piezoelectric element)
Next, the manufacturing method of the piezoelectric element of the present invention will be described in detail.
[0048]
The method for manufacturing a piezoelectric element of the present invention is a method for forming a piezoelectric element by using the above-described method for manufacturing an oxide thin film. In the present invention, a piezoelectric element means a phenomenon in which a mechanical quantity such as pressure or vibration and an electrical quantity such as voltage are utilized by utilizing a phenomenon that a crystal is charged when it is distorted or is placed in an electric field. It refers to an element that performs mutual conversion, and is also called an actuator or an electromechanical conversion element.
[0049]
The piezoelectric element is preferably used as an ink discharge drive source for an ink jet recording head. This ink jet recording head can be applied to a commonly used ink jet printer. That is, the present invention can be applied to an ink jet printer mainly including an ink jet recording head 300, a main body 301, a tray 302, and a head driving mechanism 303 as shown in FIG. An exploded perspective view of the ink jet recording head is shown in FIG. Here, a type in which a common ink passage is provided in the pressure chamber substrate is shown. As shown in the figure, the ink jet recording head includes a pressurizing chamber substrate 1, a nozzle plate 2, and a base 3. The pressurizing chamber substrate 1 is separated into each after the silicon single crystal substrate is etched. The pressurizing chamber substrate 1 is provided with a plurality of strip-shaped pressurizing chambers 10 and includes a common passage 12 for supplying ink to all the pressurizing chambers (cavities) 10. The pressurizing chambers 10 are separated by side walls 11. A piezoelectric element is attached to the base 3 side of the pressurizing chamber substrate 1 as an ink discharge drive source. This piezoelectric element is a ferroelectric thin film element using an oxide thin film manufactured by the above-described oxide thin film manufacturing method. Further, the wiring from each piezoelectric element is converged on the wiring board 4 which is a flexible cable, and is controlled by the print engine unit. The nozzle plate 2 is bonded to the pressurizing chamber substrate 1. A discharge port for discharging ink droplets is provided at a corresponding position of the pressurizing chamber 10 in the nozzle plate 2.
[0050]
A cross-sectional view of the main part of the ink jet recording head is shown in FIG. A pressurizing chamber 10 is formed on the pressurizing chamber substrate 1 by etching. A piezoelectric element 13 is formed on the upper surface of the pressurizing chamber 10 via the diaphragm film 5 and the base layer 6. The mechanical displacement of the piezoelectric element 13 changes the internal volume in the pressurizing chamber 10 and ejects ink filled in the pressurizing chamber 10 from the nozzle 21. The underlayer 6 plays a role of a base when the piezoelectric element 13 is formed. The piezoelectric element 13 includes a lower electrode 71, a titanium layer 8, a ferroelectric thin film 9 as an oxide thin film, and an upper electrode 72.
[0051]
An embodiment of a method for manufacturing a piezoelectric element of the present invention will be described with reference to FIG. 5 together with a method for manufacturing a main part of an ink jet recording head. First, as shown in FIG. 2A, the diaphragm film 5 and the base layer 6 were formed on the pressure chamber substrate 1. As the pressurizing chamber substrate 1, for example, a silicon single crystal substrate having a diameter of 100 mm and a thickness of 220 μm was used. The diaphragm film 5 was thermally oxidized for about 22 hours by flowing dry oxygen in a furnace at 1100 ° C. to form a thermal oxide film having a thickness of about 1 μm. In addition, a film forming method such as a CVD method may be selected as appropriate. The diaphragm film 5 is not limited to a silicon dioxide film, and may be a zirconium oxide film, a tantalum oxide film, a silicon nitride film, or an aluminum oxide film. Next, zirconium oxide (ZrO) is used as the underlayer 6.₂) Was formed to a thickness of about 400 nm by a reactive sputtering method using oxygen gas as a target. As other film forming methods, a film may be formed by RF sputtering with a zirconium oxide target, or zirconium may be formed by DC sputtering and then thermally oxidized.
[0052]
Next, a lower electrode 71 was formed on the underlayer 6 ((B) in the same figure). The lower electrode 71 was formed to a thickness of about 100 nm so as to have a platinum / iridium laminated structure from the base layer 6 side. In addition, the film may be formed in a laminated structure of iridium / platinum and iridium / platinum / iridium from the base layer 6 side, or may be formed by sputtering using iridium alone as a target. In a heat treatment process for the ferroelectric thin film, which will be described later, iridium is oxidized, and an iridium oxide layer is formed between the columnar crystals of platinum. Such iridium oxide can prevent the escape of oxygen from the ferroelectric thin film and can prevent the deterioration of the characteristics of the ferroelectric thin film.
[0053]
Subsequently, a titanium layer 8 was laminated on the lower electrode 71 (FIG. 3C). The titanium layer 8 was formed in a range of 10 nm to 20 nm using a DC magnetron sputtering method. The reason for setting this range will be described later. The titanium layer 8 can be formed by a film forming method such as a CVD method or a vapor deposition method.
[0054]
Next, a ferroelectric thin film 9 and an upper electrode 72 were formed on the titanium layer 8 ((D) in the figure). The ferroelectric thin film 9 was formed by the above-described oxide thin film manufacturing method. That is, by using a solution of an organometallic compound containing a metal element capable of forming an oxide as a starting material, applying and drying the solution on the titanium layer 8, pre-baking, and then performing main baking When forming the ferroelectric thin film, the provisional firing is performed in an atmosphere inert to the organometallic compound, thereby forming the ferroelectric thin film 9 which is an excellent microcrystalline film.
[0055]
Next, platinum was deposited as a top electrode 72 on the ferroelectric thin film 9 to a thickness of 100 nm by DC sputtering.
[0056]
Next, a resist is spin-coated on the upper electrode 72, and patterning is performed by exposure and development in accordance with the position where the pressurizing chamber is to be formed. Using the remaining resist as a mask, the upper electrode 72, the ferroelectric thin film 9, the titanium layer 8 and the lower electrode 71 are etched to separate the piezoelectric element 13 in accordance with the position where the pressurizing chamber is to be formed (see FIG. (E)). Subsequently, an etching mask is applied in accordance with the position where the pressurizing chamber is to be formed, and the pressurizing chamber substrate 1 is moved to a predetermined depth by dry etching using an active gas such as parallel plate type reactive ion etching. Etching was performed to form the pressurizing chamber 10 ((E) in the figure). The portion that remains without being etched becomes the side wall 11. The pressurization chamber substrate 1 can be etched by wet etching with a high concentration alkaline aqueous solution such as a 5% to 40% by weight potassium hydroxide aqueous solution.
[0057]
Finally, as shown in FIG. 5F, the nozzle plate 2 was joined to the pressurizing chamber substrate 1 using a resin or the like. The nozzle 21 can be formed by opening at a predetermined position of the nozzle plate 2 using a lithography method, laser processing, FIB processing, electric discharge processing, or the like. When the nozzle plate 2 is bonded to the pressurizing chamber substrate 1, the nozzles 21 are aligned so as to be arranged corresponding to the respective spaces of the pressurizing chamber 10. When the pressurizing chamber substrate 1 to which the nozzle plate 2 is bonded is attached to the base 3, an ink jet recording head is completed.
[0058]
According to the method for manufacturing a piezoelectric element of the present invention, a dielectric thin film as an oxide thin film that is easily microcrystallized can be formed. Therefore, an excellent piezoelectric element, for example, as an ink discharge drive source for an ink jet recording head A piezoelectric element can be easily manufactured. Further, by using such a piezoelectric element, an excellent ink jet recording head can be provided.
[0059]
【Example】
Hereinafter, the production method of the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples.
[0060]
Commercially available Pb (Zr, Ti) O₃Using a MOD coating solution [PZT-20 (mixed solution of Pb / Zr / Ti = 110/35/65 (molar ratio)), manufactured by High Purity Chemical Laboratory Co., Ltd.], double-sided thermal oxidation treatment (150 ° C. 1 minute and then at room temperature for 1 minute.) On the Ir / Ti (150 nm / 50 nm) lower electrode formed by sputtering on a 6-inch Si (100) wafer subjected to MOD. Pb (Zr, Ti) O₃A thin film was formed.
[0061]
(1) Solution coating process: Pb (Zr, Ti) O₃-1.5 ml of MOD solution was applied by spin coating method (120 rpm ... 3 seconds, 1000 rpm ... 2 seconds,
3500 rpm ... 30 seconds, edge rinse; 1500 rpm ... 10 seconds).
[0062]
(2) Drying step: The wafer was dried on a hot plate at 120 ° C. for 5 minutes.
[0063]
{Circle around (3)} Pre-firing step: Pre-firing was carried out in an electric furnace in a nitrogen atmosphere at 350 ° C. for 30 minutes.
The steps (1) to (3) were repeated twice so as to obtain a desired film thickness (0.2 μm).
[0064]
(4) Main firing step: The main firing was performed in an electric furnace in an oxygen atmosphere at 700 ° C. for 30 minutes.
[0065]
Pb (Zr, Ti) O as an oxide thin film having a thickness of 0.2 μm through the above steps.₃A thin film was obtained.
[0066]
Pb (Zr, Ti) O as the obtained oxide thin film₃About the thin film, the crystal state was observed using the scanning electron microscope (SEM). The SEM image at that time is shown in FIG.
[0067]
As a comparative example, Pb (Zr, Ti) O 2 was used in the same manner as in the example except that the atmosphere in the preliminary firing step of (3) was changed to the atmosphere (under an oxygen atmosphere) instead of the nitrogen atmosphere.₃A thin film was formed, and its crystal state was observed by SEM as in the example. The SEM image at that time is shown in FIG.
[0068]
As is clear from these comparisons, it can be seen that according to the production method of the present invention, a microcrystalline oxide thin film can be easily obtained.
[0069]
Further, when a memory element and a piezoelectric element were produced using this manufacturing method, excellent memory elements and piezoelectric elements were easily obtained. Furthermore, an excellent information processing apparatus could be easily obtained using this memory element. Also, an excellent ink jet recording head could be easily obtained using the piezoelectric element.
[0070]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the oxide thin film which can obtain a microcrystal easily can be provided. In particular, an oxide thin film can be microcrystallized by a simple manufacturing method without requiring a special seed layer formation process, and an excellent oxide thin film can be obtained. Thereby, the difference in crystallinity in the substrate surface of the oxide thin film crystal which has been caused by the film thickness unevenness in the substrate surface of the conventional seed layer can be eliminated. Further, by using the method for producing the oxide thin film, it is possible to provide an excellent method for producing a memory element and a piezoelectric element by a simple production method. Furthermore, an excellent information processing apparatus can be provided by using the memory element, and an excellent ink jet recording head can be provided by using the piezoelectric element.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a memory element obtained by an embodiment of a method for manufacturing a memory element using the method for manufacturing an oxide thin film of the present invention.
FIG. 2 is a manufacturing process cross-sectional view of the memory element shown in FIG. 1;
FIG. 3 is a configuration diagram of an ink jet printer including an ink jet recording head having a piezoelectric element obtained by an embodiment of a piezoelectric element manufacturing method using the oxide thin film manufacturing method of the present invention.
4 is an exploded perspective view of an ink jet recording head included in the ink jet printer shown in FIG. 3;
5 is a manufacturing process cross-sectional view of the main part of the ink jet recording head shown in FIG. 4;
FIG. 6 is an SEM image showing a crystal state of an oxide thin film manufactured by the oxide thin film manufacturing method (Example) of the present invention.
FIG. 7 is an SEM image showing a crystal state of an oxide thin film manufactured by a conventional oxide thin film manufacturing method (comparative example).

Claims (5)

A solution of an organometallic compound containing a metal element capable of forming an oxide is used as a starting material. The solution is applied onto a substrate and dried, then pre-baked and then fired to form an oxide thin film. When filming,
The pre-baking is performed at 200 to 400 ° C. in an atmosphere inert to the organometallic compound ,
The main baking is performed by heat treatment at 550 to 750 ° C.
The solution of the organometallic compound, and characterized in that a mixed solution of _{Pb (CH 3 COO) 2 ·} 3H 2 O, Zr (t-OC 4 H 9) 4 and _{Ti (i-OC 3 H 7} ) 4 A method for manufacturing an oxide thin film.   The method for producing an oxide thin film according to claim 1, wherein the oxide thin film is formed by a sol-gel method or a MOD method (Metal Organic Decomposition Process).   The method for producing an oxide thin film according to claim 1 or 2, wherein the inert atmosphere is a nitrogen atmosphere or an argon atmosphere. The method for producing an oxide thin film according to any one of claims 1 to 3 , wherein the oxide thin film is a dielectric thin film. The method for producing an oxide thin film according to claim 4 , wherein the dielectric thin film is a ferroelectric thin film.

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