JP2007277082A - Method of forming ferroelectric film by sol-gel process and method of manufacturing capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferroelectric film having suppressed crystal orientation, exhibiting excellent electrical characteristics, free from crack and capable of easily forming the film thick in a sol-gel process. <P>SOLUTION: The ferroelectric film containing perovskite crystals and having ≤1,000Å film thickness is formed by applying a raw material solution containing an organic metallic compound of a structural metal element of the ferroelectric film, a stabilizer containing one or both of alkanol amine and β-diketone and a solvent on a silicon substrate, drying the applied raw material solution at a temperature higher than the boiling point of the solvent and lower than the boiling point of the stabilizer to form a dried gel film and sintering the dried gel film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming a ferroelectric film (particularly lead zirconate titanate (PZT) film) by a sol-gel method and a method for manufacturing a capacitor (particularly a capacitor of a semiconductor memory cell).

For example, as an insulating film (dielectric film) constituting a capacitor of a dynamic RAM memory cell, an ONO film having a structure in which SiO ₂ , Si ₃ N ₄ and SiO ₂ are sequentially laminated is used.

  However, since the effective relative dielectric constant of this ONO film is as small as about 5, when applied to a large capacity memory of 256 Mb or more, the capacitor dielectric film can be made thin or In order to expand the process, a complicated shape is required.

  On the other hand, perovskite crystal structure type ferroelectric materials are attracting attention as insulating film materials for capacitors for future dynamic RAMs because of their extremely high relative dielectric constants of several hundreds to several thousands.

In order to form a PZT film represented by Pb (Zr, Ti) O ₃ among such ferroelectric materials, it is known to use a sol-gel method which is one of thin film forming methods.

With reference to FIG. 18, a method of forming a Pb (Zr, Ti) O ₃ thin film by a sol-gel method will be described.

First, a sol-gel raw material solution as a precursor is prepared through hydrolysis and polycondensation of a metal alkoxide in Step 1, and this is applied on a substrate by, for example, spin coating or dip coating in Step 2, and then 100 in Step 3. It is dried at a temperature of ˜300 ° C., and the applied sol-gel thin film is brought into a dry gel state (polymer gel). Next, in step 4, an oxidation sintering process is performed in a high-temperature oxygen atmosphere at 600 ° C. or higher to obtain a thin film sintered body of Pb (Zr, Ti) O _{3 having} a perovskite crystal structure from the dried gel, thereby completing the process. In order to increase the thickness of the obtained PZT film, the above steps 2 and 3 are repeated.

Here, conventionally, as a sol-gel raw material solution for Pb (Zr, Ti) O ₃ , Pb (CH ₃ COO) ₂ .3H ₂ O (lead acetate), which is an organometallic compound of a constituent metal element, Ti (i− OC ₃ H ₇ ) ₄ (titanium isopropoxide) and Zr (i-OC ₃ H ₇ ) ₄ (zirconium isopropoxide) and a stabilizer NH (C ₂ H ₄ OH) ₂ (diethanolamine: hereinafter referred to as DEA) A solution in which CH ₃ OC ₂ H ₄ OH (methoxyethanol) as a solvent is diluted is used.

  By the way, since the electrical characteristics of the PZT film strongly depend on the crystal orientation, it is extremely important to control the electrical characteristics in order to obtain excellent electrical characteristics. However, conventionally, it has been difficult to obtain a crystal orientation film exhibiting excellent electrical characteristics.

For example, crystal orientation is not clearly observed in a PZT thin film formed by Suzuki et al. [“Journal of the Ceramic Society of Japan” 98 [8] 754-78 (1990)]. Yamamura et al. ["Ferroelectric Thin Film Integration Technology", Chapter 3 (Section 4-2)] reported that a thin film with good crystal orientation was formed from a solution containing acetic acid as a solvent. . However, this is a method suitable for increasing the film thickness of several m and a thin film with good crystallinity has not been obtained from a conventional solution using CH ₃ OC ₂ H ₄ OH as a solvent.

Thus, so far, Pb (CH ₃ COO) ₂ .3H ₂ O, Ti (i-OC ₃ H ₇ ) ₄ , Zr (i-OC ₃ H ₇ ) ₄ , DEA and CH ₃ OC ₂ H ₄ OH It has been considered difficult to form a PZT thin film with good crystal orientation from a solution composed of

  Also, among the series of steps shown in FIG. 18, the temperature setting for the drying process in step 3 is extremely important for the following reason.

  First, if the drying temperature is too high, many cracks will occur in the dried gel film. Moreover, this crack is not repaired by the oxidation sintering process in step 4. On the other hand, if the drying temperature is too low, the lower layer of the dried gel film formed in the previous step is not sufficiently dried and re-dissolved in the newly applied sol-gel thin film, making it difficult to increase the film thickness. .

  Thus, in thin film formation technology by the sol-gel method, the temperature setting when forming a dry gel state from a sol-gel raw material is extremely important, but since no clear guideline for drying conditions has been conventionally shown, Experiments have been repeated to find the optimum conditions.

  An object of the present invention is to form a ferroelectric film exhibiting excellent electrical characteristics by controlling the crystal orientation of the ferroelectric film in the sol-gel method described above.

  Another object of the present invention is to obtain a ferroelectric film which is free from cracks and can be easily made thick. Another object of the present invention is to provide a capacitor having the ferroelectric film according to the present invention as a dielectric film between electrodes.

  In order to achieve the above object, the method for forming a ferroelectric film by the sol-gel method in the present invention comprises one or both of an organometallic compound of a constituent metal element of the ferroelectric film, an alkanolamine, and a β-diketone. A step of applying a raw material solution containing a stabilizer and a solvent contained on a silicon substrate; and drying the applied raw material solution at a temperature higher than the boiling point of the solvent and lower than the boiling point of the stabilizer. A step of forming a film, and a step of sintering the dried gel film to form a ferroelectric film having a thickness of 1000 mm or less including a perovskite crystal.

  In this method, ferroelectric films having a film thickness of 1000 mm or less can be sequentially laminated by repeating a series of steps of applying a raw material solution, drying and sintering.

  As a result of intensive investigation of the film thickness dependence of the crystal orientation of the ferroelectric film, the inventor has determined that the film thickness (the thickness of each layer when laminating a plurality of films by coating and drying) is 1000 mm or less. For example, it has been found that a thin film exhibiting a (100) crystal orientation can be easily formed by oxidizing and sintering at a temperature at which a perovskite crystal is formed.

  In the present invention, the film thickness of the ferroelectric film formed by the series of steps of applying the raw material solution, drying and sintering as described above is set to 1000 mm or less, and among these, 500 mm to 1000 mm is particularly preferable.

  In this regard, the present inventor has found a method that enables the optimum setting of the drying treatment temperature in the sol-gel method, based on the result of thermogravimetry (TGA) for the sol-gel raw material.

  That is, TGA is measured for a conventional ferroelectric film, and from the results, the cause of cracks generated in the dry gel film is due to thermal contraction that occurs due to rapid evaporation of the stabilizer contained in the sol-gel raw material. I found out. FIG. 19 shows the TGA results obtained for the sol-gel raw material. Here, the peak seen around about 200 ° C. is the weight change accompanying the rapid evaporation (sudden boiling) of DEA.

  In addition, it was found that the factor that hindered thickening was the solvent remaining in the dry gel film, and if the drying temperature was set too low for the purpose of preventing cracks, the dry state became incomplete and formed in the previous process. It was clarified that the dried gel film was redissolved in the newly applied sol-gel film.

  Based on these results, the inventor specified a drying temperature in the range of 130 to 200 ° C., and in particular, lower than the boiling point of the stabilizer contained in the sol-gel raw material and more than the boiling point of the solvent contained in the sol-gel raw material. It was found that a completely crack-free film can be formed thick if the value is set too high.

In one embodiment of the present invention, fatty acid lead such as lead acetate represented by Pb (CH ₃ COO) ₂ .3H ₂ O and titanium alkoxide represented by Ti (i-OC ₃ H ₇ ) ₄ and Zr ( A raw material solution containing a zirconium alkoxide represented by i-OC ₃ H ₇ ) ₄ and an alkanolamine such as diethanolamine (DEA) and / or a diketone such as acetylacetone is applied and dried, and the resulting dried film is obtained. A ferroelectric film of lead zirconate titanate is formed by oxidation sintering.

  According to another aspect of the present invention, there is provided a method of manufacturing a capacitor, comprising: forming a first conductive film to be one electrode of a capacitor on a silicon substrate; and forming a ferroelectric film on the silicon substrate including the first conductive film. A step of applying a raw material solution containing a stabilizer and a solvent containing one or both of an organometallic compound of an elemental metal element, alkanolamine and β-diketone, and the applied raw material solution is more than the boiling point of the solvent. A step of forming a dried gel film by drying at a temperature lower than the boiling point of the stabilizer, and a step of sintering the dried gel film to form a ferroelectric film having a thickness of 1000 mm or less including perovskite crystals. And forming a dielectric film of the capacitor by patterning the ferroelectric material, and forming a second conductive film to be the other electrode of the capacitor on the dielectric film. .

According to the present invention, when forming the ferroelectric film by the sol-gel method, the raw material solution applied on the substrate is higher than the boiling point of the solvent contained in the raw material solution and the boiling point of the stabilizer contained in the raw material solution. In particular, a thin film having a (100) crystal orientation can be easily formed by drying at a lower temperature and performing a sintering process so as to obtain a ferroelectric film having a thickness of 1000 mm or less containing perovskite crystals. . Particularly preferably, by specifying the drying temperature of the raw material solution within the range of 130 to 200 ° C., a completely crack-free film can be formed in a desired film thickness.
In addition, according to the present invention, it is possible to obtain a capacitor having excellent electrical characteristics, no cracks, and a dielectric film that is easily thickened between electrodes.

  Examples of the present invention will be described below.

First, as shown in Table 1 below, the raw material solution used in the sol-gel method according to this example is Pb (CH ₃ COO) ₂ .3H ₂ O, Ti (i-OC ₃ H ₇ ) ₄ , Zr (i -OC ₃ H ₇₎ is ₄ and DEA to (diethanolamine) which was diluted with CH ₃ OC ₂ H ₄ OH.

  Then, as schematically shown in FIG. 3, this raw material solution was applied onto the Pt electrode 1 and dried according to Step 2 and Step 3 shown in FIG. 18. At this time, six types of dry gel films 7 were formed so that the film thickness T obtained by oxidation sintering after drying was 480 mm, 720 mm, 960 mm, 1200 mm, 1440 mm, and 2400 mm.

  In addition, since the coating thickness of the above raw material solution is limited to 480 mm in a single coating, in practice, by applying a film thickness of 480 mm or less, 480 mm (one or two times coating), 720 mm ( Film thickness of 2 to 3 times), 960 mm (2 to 4 times), 1200 mm (3 to 5 times), 1440 mm (3 to 6 times), 2400 mm (5 to 10 times) Respectively.

  Next, after oxidizing and sintering at 600 ° C. for 1 hour, the crystal orientation of each sample was examined by X-ray diffraction. FIG. 1 shows X-ray diffraction patterns for the respective film thicknesses.

  According to this X-ray diffraction pattern, the (100) and (200) diffraction peaks of the perovskite crystals are observed at the film thicknesses of 480 mm, 720 mm, and 960 mm, and the thin film having these film thicknesses is the (100) crystal orientation film. I understand.

  On the other hand, (100), (110), (200), and (211) diffraction peaks are recognized at film thicknesses of 1200 mm, 1440 mm, and 2400 mm, indicating that the film is non-oriented. Thus, in these thin films, the crystal orientation deteriorated as the film thickness increased beyond 1000 mm.

  As is clear from the above, the orientation of the thin film greatly depends on the film thickness, and (100) crystal orientation can be obtained by setting the film thickness within a specific range. That is, by reducing the film thickness to 1000 mm or less, a (100) crystal oriented thin film is formed, but when the film thickness exceeds 1000 mm, only a non-oriented thin film is formed. The film thickness is preferably 500 to 1000 mm. In addition, the lower limit of the film thickness is preferably 240 mm from the viewpoint of actual measurement possibility.

  As described above, for the formation of the PZT ferroelectric thin film by the sol-gel method, the present invention revealed for the first time that the film thickness to be subjected to the oxidation sintering process has a great influence on the crystal orientation characteristics of the thin film.

  Next, as shown in FIG. 4, the PZT ferroelectric thin film is not applied once, but sequentially laminated with the first layer 7a, the second layer 7b,... According to step 2, step 3 and step 4 shown in FIG. Thus, a thick film of the orientation film was formed. For example, the (100) orientation film 7 having a film thickness of 2400 mm was formed by laminating five layers each having a thickness of 480 mm.

At the time of this lamination, as shown in FIG. 4, the raw material solution 17a of the _first layer 7a is applied to a thickness of t ₁ , this is dried and gelled at 100 to 300 ° C., and further oxidized and sintered at 600 ° C. for 1 hour. Thus, a _first- layer sintered film 7a having a thickness of T1 was formed. On this, similarly, applying the raw material solution 17b of the second layer 7b to a thickness of t _2, dried, oxidized sintered to form a second layer of sintered film 7b of thickness T _2. Further coating a raw material solution 17c to a thickness of t _3, dried, and the as sintered ..., sintered film 7a of five layers, 7b, a PZT thin film 7 having a thickness of T consisting 7c ... formed did.

Here, each of the laminated sintered film thicknesses T ₁ , T ₂ ... Is 480 mm, and the total thickness T is 2400 mm. The X-ray diffraction pattern of the obtained PZT thin film 7 is shown in FIG.

  According to this, the PZT thin film 7 shows diffraction peaks of perovskite crystals at (100) and (200), and it can be seen that it is a (100) crystal orientation film. This is because even if the total thickness T of the PZT thin film is 2400 mm, each film 7a, 7b,... Constituting the film thickness is 480 mm and is within the scope of the present invention (1000 mm or less). This is because the (100) crystal orientation of each film is obtained.

  FIG. 5 shows the measurement of the PZT (100) crystal orientation film 7 having a total thickness T of 2400 mm and the non-orientation film (see FIG. 1) having a thickness of 2400 mm obtained based on the present invention. Current (leakage current) -applied voltage characteristics are shown.

From this result, in the thin film according to the present invention, as shown in FIG. 5A, the leakage current increases in the voltage range of 0V to 2V, but the leakage current shows a substantially constant value in the voltage range of 2V to 10V. The value at a voltage of 3 V (electric field strength of 125 kV / cm) is 1.2 × 10 ⁻⁷ A / cm ² . However, in the non-oriented film, the value at a voltage of 3 V is 2.2 × 10 ⁻⁵ A / cm ^{2 as shown} in FIG. Therefore, it can be seen that the leakage current of the oriented film according to the present invention is remarkably reduced as compared with the non-oriented film.

  On the other hand, FIG. 6 shows measured current (leakage current) -voltage application time characteristics for the PZT (100) crystal orientation film 7 having a total thickness T of 2400 mm obtained according to the present invention.

From this result, the leakage current decreases monotonously depending on the application time. A value of 3 nA / cm ² is obtained after applying a voltage of 3 V and about 5 minutes. By using an alignment film in this manner, leakage current can be reduced without adding La or Fe.

  Next, when forming a thin film by the sol-gel method, various drying temperatures were set based on the thermal decomposition characteristics of the raw material solution, and the state of the obtained thin film was examined.

  The sol-gel solution used here was the same as that in Table 1 described above. Then, according to the process shown in FIG. 18, a dry gel film having a thickness of 2400 mm was formed on the Pt electrode 1 in the same manner as described above, and the surface thereof was observed.

  FIG. 7A shows the result when the drying temperature is set to 170 ° C. lower than the boiling point of DEA (269 ° C.) and higher than the boiling point of the solvent (94 ° C.), and no cracks are observed. . However, when the drying temperature is set to 280 ° C., which is higher than the boiling point of DEA, it can be seen that many cracks are generated as shown in FIG. 7B.

  This indicates that by performing drying at a temperature lower than the boiling point of the stabilizer (DEA), DEA bumping is prevented and a crack-free dry gel film is obtained.

  Next, a description will be given of the result of thickening when the above-described overcoating is performed. FIG. 8 shows the relationship between the number of repeated coatings and the thickness of the dried gel film, obtained when the steps 2 and 3 shown in FIG. 18 are repeated, and this is used as the parameter for the drying temperature in step 3. Show. However, the coating was performed by spin coating at 3000 rpm × 20 seconds.

From this result, when the drying temperature is lower than the boiling point of the solvent CH ₃ OC ₂ H ₄ OH (94 ° C.), no increase in the film thickness is observed with respect to the number of repetitions, and the drying temperature is It can be seen that if the temperature is set to 170 ° C. higher than the boiling point, the film thickness increases in proportion to the number of repetitions.

  That is, if the drying temperature is lower than the boiling point of the solvent, the dry state becomes incomplete, the dried gel film formed in the previous step is redissolved in the newly applied sol-gel thin film, and cannot be thickened. If the drying temperature is set higher than the boiling point of the solvent based on the above, the lower gel film can be sufficiently dried, and the upper gel film can be satisfactorily laminated to form a thick film as a whole.

  Thus, the drying temperature is specified within the range of 130 to 200 ° C. (170 ° C. in this example), and in particular, set lower than the boiling point of the stabilizer contained in the sol-gel raw material and higher than the boiling point of the solvent contained in the sol-gel raw material. Then, a completely crack-free film can be formed thick. If the drying temperature is further set to 150 to 190 ° C., the above-described effect becomes more remarkable.

  And the optimum value of the drying temperature in the sol-gel method varies depending on the type of stabilizer and solvent used, and many experiments are required for this purpose, but according to the present invention, the results of thermogravimetry are used. Optimal drying conditions can be easily determined in a short time.

  As described above, the PZT crystal thin film according to the present invention is improved in electrical characteristics (for example, reduction in leakage current) due to (100) orientation, and can be formed in a desired film thickness without cracks. It is extremely advantageous when used for a capacitor (for example, a stack type) of a RAM memory cell. 9 and 10 show examples of dynamic RAM memory cells.

An element region partitioned by a field oxide film 2 is formed on one main surface of the P ⁻ -type silicon substrate 1, and a memory cell M-CEL including a transfer gate TR including a MOS transistor and a capacitor CAP is provided therein. It has been.

In the transfer gate TR, an N ⁺ type source region 3 and an N ⁺ type drain region 4 are formed by impurity diffusion, respectively, and a word line WL is provided between these regions via a gate oxide film 5. A bit line BL is connected to a contact hole 11 of insulating layers 9 and 10 such as SiO ₂ .

  The capacitor CAP is called a stack type, and the lower electrode 6 is connected to the source region 3 through the contact hole 12 of the insulating layer 10, and the PZT ferroelectric film 7 and the upper electrode 8 are formed on the lower electrode. Are sequentially stacked.

The ferroelectric film 7 constituting the capacitor CAP is made of a PZT, that is, a Pb (Zr, Ti) O ₃ film formed by the sol-gel method based on the present invention using the above-described raw material solution. The lower electrode 6 is made of, for example, Pt or the like deposited on a tungsten or titanium nitride layer (however, Pt and the like are not shown). The upper electrode 8 in contact with the ferroelectric film is made of aluminum or Pt.

  Next, a method for manufacturing the memory cell M-CEL will be described with reference to FIGS.

First, as shown in FIG. 11, a field oxide film 2 is formed on a P ^-- type silicon substrate (wafer) 1 by a selective oxidation method, a gate oxide film 5 by a thermal oxidation method and a polysilicon word by a chemical vapor deposition method. Each of the lines WL is formed, and an N ⁺ -type source region 3 and a drain region 4 are formed by thermal diffusion of an N-type impurity such as As.

Then, a contact hole 12 is formed on the source region 3 by photolithography with respect to the SiO ₂ insulating layer 10 deposited on the entire surface by chemical vapor deposition.

  Next, as shown in FIG. 12, a lower electrode 6 having a Pt layer is formed on the tungsten or titanium nitride layer so as to be joined to the source region 3 in the contact hole 12. This can be formed by patterning the tungsten or titanium nitride layer and the Pt surface layer deposited on the entire surface by photolithography.

  Next, as shown in FIG. 13, a sol-gel raw material solution 17 is applied to the entire surface including the lower electrode 6 by spin coating or dip coating. This raw material solution 17 has the same composition as the above-described solution (see Table 1).

  Next, the wafer coated with the raw material solution 17 is heated at a predetermined temperature (100 to 300 ° C., particularly 130 to 200 ° C.), and the coated solution is dried to form a dry gel film 27 as shown in FIG. .

  Next, the dried wafer is oxidized and sintered at a temperature at which the perovskite crystal is formed, and a ferroelectric thin film 7 is formed on the entire surface as shown in FIG.

  In order to form the ferroelectric thin film 7 with a predetermined film thickness (for example, 2400 mm), the coating process of FIG. 13 and the drying process of FIG. 14 are repeated as necessary to obtain a desired coating thickness at a time. Instead, the final film thickness can be obtained by laminating dry films and repeating the formation of a sintered film of 1000 mm or less.

  And it is desirable to dry each film | membrane at 130-200 degreeC based on this invention. At the same time, after each film is oxidized and sintered to form a sintered film, an upper layer is applied, dried, and oxidized and sintered to form a thin film 7 according to the present invention having a total thickness of 1000 mm or less. It is desirable to do. However, this need not necessarily be employed when the above-described drying conditions (130 to 200 ° C.) are employed (the reverse is also true).

  Next, as shown in FIG. 16, unnecessary portions of the ferroelectric thin film 7 formed on the entire surface are removed by a dry etching method or the like, and a PZT ferroelectric film 7 is formed in a predetermined pattern on the lower electrode 6.

  Next, as shown in FIG. 17, the upper electrode 8 made of aluminum, Pt, or the like is formed in a predetermined pattern at the junction with the ferroelectric thin film 7 by photolithography.

  A memory cell is manufactured as described above. In particular, if the film thickness of the PZT ferroelectric film 7 (the film thickness of each layer when laminating a plurality of films by coating and drying) is 1000 mm or less, the perovskite By performing oxidation sintering treatment at a temperature at which crystals are formed, a thin film exhibiting a (100) crystal orientation can be easily formed, and thus required electrical characteristics such as a reduction in leakage current are exhibited.

  Further, the drying temperature of the PZT film 7 is specified within the range of 130 to 200 ° C., and in particular, it is set lower than the boiling point of the stabilizer contained in the sol-gel raw material and higher than the boiling point of the solvent contained in the sol-gel raw material. Therefore, a completely crack-free film can be formed thick.

  Although the embodiments of the present invention have been described above, the above-described embodiments can be further modified based on the technical idea of the present invention.

  For example, as a component of the sol-gel raw material solution described above, alkanolamines such as dipropanolamine and triethanolamine or 竈 -diketones such as acetylacetone can be used alone or in combination in addition to DEA.

  In addition to lead acetate, fatty acid lead such as lead 2-ethylhexanoate and lead naphthenate, and lead alkoxide such as lead-di-n-butoxide and lead-di-n-pentoxide can be used.

  In addition to titanium isopropoxide, titanium alkoxides such as titanium-tetra-n-butoxide and titanium-tetra-n-pentoxide, and titanium salts of fatty acids such as titanium 2-ethylhexanoate and titanium naphthenate can be used.

  Besides zirconium isopropoxide, zirconium alkoxides such as zirconium-tetra-n-butoxide and zirconium-tetra-n-pentoxide, and zirconium salts of fatty acids such as zirconium 2-ethylhexanoate and zirconium naphthenate can be used.

  As the solvent for the raw material solution, isopropanol, n-butanol and the like can be used in addition to methoxyethanol.

The composition of the ferroelectric according to the present invention may be variously changed. Further, the application object is not limited to the above-described stacked capacitor, and the above-described stacked capacitor may be provided on the SiO ₂ film, and the lower electrode of this capacitor may be extended to connect to the source region of the transfer gate. Alternatively, the present invention can be applied to a capacitor having a structure in which a capacitor is incorporated in a so-called trench (groove) instead of the stack type.

It is an X-ray diffraction spectrum figure for every film thickness when a thin film is formed by the sol-gel method. It is an X-ray diffraction spectrum figure of the thin film obtained by laminating | stacking five films | membranes based on this invention. It is a schematic sectional drawing of the state which formed the PZT thin film on the board | substrate. It is a schematic sectional drawing when forming a PZT thin film on a substrate by lamination of a plurality of layers. (A) is a current-voltage characteristic diagram of a PZT oriented film, and (B) is a current-voltage characteristic diagram of a non-oriented film. It is a current-time characteristic view (at the time of voltage 3V application) of a PZT alignment film. (A) is a micrograph of a crack-free film, and (B) is a micrograph of a cracked film. It is a graph which shows the film thickness change by the frequency | count of application | coating for every drying temperature. FIG. 11 is an enlarged cross-sectional view of a dynamic RAM memory cell (cross-sectional view taken along line IX-IX in FIG. 10). 2 is an enlarged plan view of the memory cell. FIG. FIG. 6 is an enlarged cross-sectional view of one step of the method for manufacturing the memory cell. It is an expanded sectional view of the other one process step of the manufacturing method of the memory cell. It is an expanded sectional view of the other one process step of the manufacturing method of the memory cell. It is an expanded sectional view of the other one process step of the manufacturing method of the memory cell. It is an expanded sectional view of the other one process step of the manufacturing method of the memory cell. It is an expanded sectional view of the other one process step of the manufacturing method of the memory cell. FIG. 14 is an enlarged cross-sectional view of yet another process step in the method for manufacturing the memory cell. FIG. 5 is a process flow diagram for forming a Pb (Zr, Ti) O ₃ thin film by a sol-gel method. It is a graph showing the weight change (TGA) by the drying temperature for forming the Pb (Zr, Ti) O ₃ thin film sol-gel method.

Explanation of symbols

1 ... Substrate (Pt electrode)
3 ... N ⁺ type source region 4 ... N ⁺ type drain region 6 ... Lower electrode 7, 7a, 7b ... Ferroelectric film (PZT thin film)
8 ... Upper electrode
17a, 17b, 17c ... Coating liquid CAP ... Capacitor TR ... Transfer gate M-CEL ... Memory cell

Claims (13)

Applying a raw material solution containing a stabilizer and a solvent containing an organometallic compound of a constituent metal element of the ferroelectric film and one or both of alkanolamine and β-diketone on a silicon substrate;
Drying the coated raw material solution at a temperature higher than the boiling point of the solvent and lower than the boiling point of the stabilizer to form a dry gel film;
A method of forming a ferroelectric film by a sol-gel method, comprising: sintering the dried gel film to form a ferroelectric film having a thickness of 1000 mm or less including a perovskite crystal.   The method for forming a ferroelectric film by a sol-gel method according to claim 1, wherein the temperature in the step of forming the dry gel film is in the range of 130 to 200 ° C.   The method for forming a ferroelectric film by a sol-gel method according to claim 2, wherein the stabilizer contains diethanolamine and the solvent contains methoxyethanol.   4. The method for forming a ferroelectric film by a sol-gel method according to claim 1, wherein the organometallic compound contains lead acetate, titanium isopropoxide and zirconium isopropoxide.   4. The method for forming a ferroelectric film by a sol-gel method according to claim 1, wherein the organometallic compound contains fatty acid lead, titanium alkoxide, and zirconium alkoxide.   6. The method of forming a ferroelectric film by a sol-gel method according to claim 1, wherein the thickness of the dry gel film is in the range of 500 to 1000 mm.   7. The ferroelectric film by the sol-gel method according to claim 1, wherein a laminated structure of the ferroelectric film is formed by repeating the steps of coating, drying and sintering. Forming method. Forming a first conductive film to be one electrode of a capacitor on a silicon substrate;
Applying a raw material solution containing an organic metal compound of a constituent metal element of a ferroelectric film, a stabilizer containing one or both of alkanolamine and β-diketone, and a solvent on the silicon substrate including the first conductive film. And a process of
Drying the coated raw material solution at a temperature higher than the boiling point of the solvent and lower than the boiling point of the stabilizer to form a dry gel film;
Sintering the dried gel film to form a ferroelectric film having a thickness of 1000 mm or less containing a perovskite crystal;
Patterning the ferroelectric to form a capacitor dielectric film;
Forming a second conductive film to be the other electrode of the capacitor on the dielectric film.   The method for producing a capacitor according to claim 8, wherein a temperature in the step of forming the dry gel film is in a range of 130 to 200 ° C.   The method for manufacturing a capacitor according to claim 9, wherein the stabilizer includes diethanolamine, and the solvent includes methoxyethanol.   The method for producing a capacitor according to claim 8, 9 or 10, wherein the organometallic compound contains lead acetate, titanium isopropoxide and zirconium isopropoxide.   The method for producing a capacitor according to claim 8, 9, 10 or 11, wherein the thickness of the dry gel film is in the range of 500 to 1000 mm.   13. The method of manufacturing a capacitor according to claim 8, 9, 10, 11 or 12, wherein a laminated structure of a ferroelectric film is formed by repeating the steps of coating, drying and sintering.

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