JP2011228178A - Composition for forming conductive film and method for forming conductive film - Google Patents

Abstract

An object of the present invention is to provide a composition for forming a conductive film that can form a strontium-ruthenium oxide-based conductive film and is excellent in long-term stability and processability.
The conductive film forming composition is a composition containing a strontium carboxylate, a ruthenium carboxylate and a solvent, wherein the solvent is selected from the group consisting of a ketone and a carboxylic acid. It contains at least one kind. In the conductive film forming composition, the solvent preferably contains a carboxylic acid.
[Selection figure] None

Description

  The present invention relates to a composition for forming a conductive film and a method for forming a conductive film using the composition. More specifically, the present invention relates to a composition and method for forming a strontium-ruthenium oxide-based conductive film having excellent conductivity by a simple method.

A strontium-ruthenium oxide conductive film (SRO film) having a perovskite crystal structure is expected to be applied as various electrode materials because of its excellent conductivity. Further, in a substituted SRO film in which a part of ruthenium atoms contained in the SRO film is replaced with another metal atom, for example, titanium, the carrier concentration in the film is an appropriate value, for example, 1 × 10 ¹⁶ to 1 × 10 ^19. If the number is about ³ / cm ³ , for example, it can be used as a channel of a ferroelectric gate transistor.
Such an SRO film or a substituted SRO film (hereinafter collectively referred to as “SRO film”) can be formed by a vapor phase method such as sputtering, laser ablation, or reactive vapor deposition. However, the vapor phase method requires a heavy and expensive apparatus, and the productivity of the film is low, so it is difficult to say that it is practical.
On the other hand, a sol-gel method is known as a method of forming an SRO film that is not based on a vapor phase method. In this technique, a composition solution containing a metal oxide precursor, such as a metal alkoxide, is applied onto a substrate to form a coating film, which is then heated to hydrolyze and condense the precursor to oxidize. This is a technique for crystallizing a material film and then heating it at a higher temperature. Although this technique has advantages such as easy film composition control and high film thickness uniformity, it has the disadvantage that the composition solution is low in stability and the solution cannot be stored for a long time.

In order to solve this problem, Patent Document 1 proposes a composition for forming an SRO film using strontium and ruthenium carboxylates as precursors and dissolving them in a water-immiscible solvent. However, the technique of Patent Document 1 requires that the Sr concentration and the Ru concentration in the composition be lowered and the amount of water must be strictly controlled, and is easy to handle in the manufacturing process (hereinafter referred to as “processability”). Inferior. Furthermore, heating at a high temperature of about 750 ° C. is required for crystallization after forming the oxide film, and there is a concern that the device is deteriorated during the film forming operation.
Under such circumstances, a composition for forming a conductive film that has excellent long-term stability and high processability, and formation of a conductive film that is simple and does not require high-temperature heating, using the composition. The method is eager.

JP 2000-128697 A

An object of the present invention is to provide an unprecedented unique composition and method in order to overcome the above-described current situation in the formation of a strontium-ruthenium oxide-based conductive film.
That is, an object of the present invention is to provide a composition for forming a conductive film that can form a strontium-ruthenium oxide-based conductive film and has excellent long-term stability and processability, and a strontium-ruthenium oxide-based conductive film. An object of the present invention is to provide a method for forming a conductive film that can be formed and is simple and does not require high-temperature heating.

According to the present invention, the above objects and advantages of the present invention are, firstly,
A composition comprising a strontium carboxylate, a ruthenium carboxylate and a solvent,
This is achieved by the conductive film forming composition, wherein the solvent contains at least one selected from the group consisting of ketones and carboxylic acids.
The above objects and advantages of the present invention are, secondly,
This is achieved by a method for forming a conductive film, which comprises applying the composition for forming a conductive film on a substrate to form a coating film, and heating the coating film in an oxidizing atmosphere.

According to the present invention, a composition for forming a conductive film having excellent long-term stability and processability, and a method for forming a conductive film that is simple and does not require high-temperature heating using the composition for forming a conductive film are provided. Is done.
Since the composition for forming a conductive film of the present invention is easy to prepare, there is an advantage that it can be easily and quickly prepared on-site when it is necessary to use it. Even if the content ratio is not controlled, the composition is excellent in storage stability, so that even a composition after long-term storage can be used effectively. The conductive film formed by the method of the present invention becomes a perovskite SRO film having high crystallinity or a novel conductive film having no crystallinity depending on the heating temperature.
The composition for forming a conductive film of the present invention and the conductive film formed therefrom are suitable for various electrode materials, barrier layers between electrodes and ferroelectric capacitors, and channels of ferroelectric gate transistors. Can be applied.

The X-ray-diffraction chart of the electroconductive film obtained in Example 1 and 3-6, respectively. 10 is a graph showing the relationship between the heating temperature and conductivity checked in Example 7. The thermogravimetric analysis chart of the composition for conductive film formation of this invention measured in Example 8. FIG.

<Composition for forming conductive film>
The composition for forming a conductive film of the present invention comprises:
A composition comprising a strontium carboxylate, a ruthenium carboxylate and a solvent,
The solvent contains at least one selected from the group consisting of ketones and carboxylic acids. In addition to these, the composition for forming a conductive film of the present invention can optionally further contain a carboxylate of titanium or the like.
The strontium carboxylate and ruthenium carboxylate and optionally used titanium carboxylate are each preferably a salt of a carboxylic acid having an alkyl group having 1 to 10 carbon atoms. A salt of a carboxylic acid having an alkyl group of 1 to 8 is more preferable, and examples thereof include acetate, propionate, butyrate, valerate, and 2-ethylhexanoate. Among these, propionate or 2-ethylhexanoate is preferable from the viewpoint of availability of salts or synthesis, and 2-ethylhexanoate is particularly preferable from the viewpoint of solubility.
Any of the strontium carboxylate, ruthenium carboxylate and titanium carboxylate may be anhydrous or hydrated.

The ratio of the strontium and ruthenium carboxylates as described above and the optionally used titanium carboxylate should be set appropriately according to the desired metal atomic ratio in the conductive film to be formed. is there. For example, when it is desired to form a SrRuO ₃ film, the atomic ratio of Sr: Ru: Ti in the composition for forming a conductive film of the present invention may be 1: 1: 0, and 50% of the Ru atoms in SrRuO ₃ may be Ti. When it is desired to replace with atoms, Sr: Ru: Ti = 1: 0.5: 0.5 may be set. In addition, all the above numerical values are molar ratios.
A composition conventionally known for forming an SRO film by a sol-gel method (for example, the composition described in Patent Document 1) is electrically conductive by highly crystallizing an oxide film by high-temperature heating. Therefore, it was necessary to set the metal atomic ratio in the film, and hence the metal atomic ratio Sr: (Ru + Ti) in the precursor composition, to a constant stoichiometric ratio. On the other hand, since the film formed from the composition for forming a conductive film of the present invention exhibits conductivity without being crystallized, the metal atomic ratio Sr / (Ru + Ti) (molar ratio) in the composition Can be any value in the range of 0.1-20, and is preferably in the range of 0.5-2.
However, the titanium carboxylate should be used at a ratio below a certain value in order to obtain an appropriate value for the conductivity of the formed film. The value of the formula Ti / (Ru + Ti) is preferably 0.8 or less, more preferably 0.6 or less in terms of molar ratio.

The solvent used in the composition for forming a conductive film of the present invention contains at least one selected from the group consisting of ketones and carboxylic acids. When the solvent used in the composition for forming a conductive film of the present invention contains at least one selected from the group consisting of ketones and carboxylic acids, the stability of the composition is ensured and the composition The heating temperature when the coating film formed from the conductive film is used as a conductive film can be lowered. In particular, the heating temperature necessary to form a perovskite-type SRO film having high crystallinity is lower than that in the case where a conventionally known composition for forming an SRO film is used. Further, when the solvent in the composition for forming a conductive film contains a carboxylic acid, the dissolution of the carboxylate of each metal as a raw material in the solvent becomes easier, and the obtained composition Stability is dramatically improved. For example, even when the composition contains about 10% by weight of the weight of the composition, it can be stored for a long period of time.
As said ketone, it is preferable that it is a C3-C10 ketone, and it is more preferable that it is a C4-C7 ketone. This carbon number is the number including the carbon of the carbonyl group. Specific examples of such ketones include methyl ethyl ketone, methyl isobutyl ketone, and diethyl ketone.
The carboxylic acid is preferably a carboxylic acid having an alkyl group having 1 to 10 carbon atoms, and more preferably a carboxylic acid having an alkyl group having 2 to 8 carbon atoms. Specific examples of such carboxylic acids include propionic acid, n-butyric acid, isobutyric acid, n-hexanoic acid, n-octanoic acid and 2-ethylhexanoic acid.

The solvent in the composition for forming a conductive film of the present invention contains, in addition to at least one selected from the group consisting of ketones and carboxylic acids as described above, other solvents as long as the effects of the present invention are not inhibited. It may be. Examples of such other solvents include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, alcohols and ester ethers. Specific examples thereof include, for example, hexane, octane and the like as the aliphatic hydrocarbons;
Examples of the alicyclic hydrocarbon include cyclohexane,
Examples of the aromatic hydrocarbon include benzene, toluene, xylene and the like;
Examples of the alcohol include methanol, ethanol, propanol, isopropanol, ethylene glycol, glycerin and the like;
Examples of the ester include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl acetate, methyl 2-ethylhexanoate, ethyl 2-ethylhexanoate and the like;
Examples of the ether include diethyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol ethyl methyl ether, tetrahydrofuran, tetrahydropyran, and dioxane.

The solvent in the composition for forming a conductive film of the present invention preferably contains at least one selected from the group consisting of ketones and carboxylic acids in an amount of 50% by weight or more based on the total amount of the solvent, 75 It is more preferable that the content is not less than wt%.
When carboxylic acid is used in the solvent of the composition for forming a conductive film of the present invention, the use ratio is preferably 1 g or more with respect to 1 g of strontium carboxylate in the composition. More preferably.
The proportion of the ketone and the carboxylic acid used in the solvent of the composition for forming a conductive film of the present invention is preferably 10% by weight or more, more preferably 25% by weight or more, as the ratio of the carboxylic acid to the total of these. Is more preferably 50% by weight or more, and particularly preferably 75% by weight.
It is particularly preferable to use only carboxylic acid as the solvent.

The composition for forming a conductive film of the present invention preferably has its liquidity set in an acidic region, more preferably 6.5 or less, and particularly preferably 3 to 6. By setting it as such liquid property, it can be set as the composition for electroconductive film formation which is excellent in storage stability in which a carboxylate is not decomposed | disassembled even after long-term progress.
The solid content concentration of the composition for forming a conductive film of the present invention (the ratio of the total weight of components other than the solvent in the composition to the total weight of the composition) is preferably 0.1 to 10% by weight. More preferably, the content is 0.5 to 6% by weight.
The composition for forming a conductive film of the present invention can be prepared by mixing and dissolving components other than the solvent in the solvent as described above. At this time, the solvent and each component may be mixed and dissolved at a time, each component may be added sequentially in the solvent, or several components obtained by dissolving each component separately in the solvent. It may be by a method of mixing solutions, or by other appropriate methods. When preparing a solution by dissolving strontium or titanium carboxylate in a solvent, if the solution contains a carboxylic acid as described above, mixing at room temperature is sufficient, and if it does not contain a carboxylic acid, strontium Alternatively, depending on the type of titanium carboxylate, for example, the stirring method can be performed at 20 to 150 ° C. Since ruthenium carboxylate is easily dissolved in a solvent containing a ketone, mixing at room temperature is sufficient even if the solvent does not contain a carboxylic acid.
The prepared composition solution may be used after being filtered through a filter having an appropriate pore size.

  As described above, since the carboxylate of each metal that is a raw material of the composition for forming a conductive film of the present invention may be a hydrate salt, the composition for forming a conductive film of the present invention is water immediately after preparation. May be contained. Further, since the solvent contains at least one selected from the group consisting of hydrophilic ketones and carboxylic acids, moisture may be absorbed during use or during storage of the composition. However, the composition for forming a conductive film of the present invention can be stored for a long period of time without controlling the water ratio in the composition. For example, even if the water content in the composition is 1% by weight or more, or even 2% by weight or more, the shelf life is not affected, and even if it is about 10% by weight, it is stable for at least several months to several years. Can be stored and used. Therefore, the composition for forming a conductive film of the present invention can form a highly conductive strontium-ruthenium oxide based conductive film by a simple method as described later, but its preparation cost and storage cost are low. This is a significant reduction and contributes to a reduction in the manufacturing cost of electrical devices.

<Method for forming conductive film>
The method for forming a conductive film of the present invention is a method in which a conductive film forming composition as described above is applied on a substrate to form a coating film, and the coating film is heated in an oxidizing atmosphere.
Although it does not specifically limit as a board | substrate used for the formation method of the electroconductive film of this invention, For example, quartz; Glass, such as borosilicate glass and soda glass; Plastic; Silicone resin; Carbon; Gold, silver, copper, silicon, Metals such as nickel, titanium, aluminum, and tungsten; a substrate made of glass or plastic having such a metal or an oxide or mixed oxide thereof (for example, ITO) on the surface can be used. The method for forming a conductive film of the present invention can form a film showing conductivity without heating at a high temperature. In such a case, the conductive film can be applied to a plastic substrate having low heat resistance. There is.
In applying the composition for forming a conductive film on the substrate, for example, an appropriate application method such as a spin coating method, a roll coating method, a curtain coating method, a dip coating method, a spray method, or a droplet discharge method is adopted. Can do. Next, the coating film can be formed on the substrate by removing the solvent from the liquid coating film comprising the conductive film forming composition as required. At this time, even if some solvent remains in the coating film, the effect of the present invention is not diminished. In the case of removing the solvent after coating, for example, it can be performed by a method of standing at room temperature to 450 ° C. for about 1 to 30 minutes. The thickness of the coating film to be formed should be appropriately set depending on the purpose of application, but the thickness after removal of the solvent can be, for example, 30 to 500 nm. In order to obtain this film thickness, coating and arbitrary solvent removal may be performed only once (one cycle), or coating and arbitrary solvent removal may be performed by multiple coating (multiple cycles).

The coating film thus formed is then heated under an oxidizing atmosphere.
Heating in an oxidizing atmosphere can be realized preferably by performing a heating operation in a gas containing oxygen. As the substrate containing oxygen, air, oxygen and the like are preferable. The gas at the time of heating can be made into arbitrary pressure, for example, can heat at 5 * 10 < ⁴ > -1 * 10 < ⁶ > Pa.
In the method for forming a conductive film of the present invention, different types of conductive films can be obtained by selecting the temperature during heating. That is, a conductive film having a perovskite crystal structure can be obtained by setting the heating temperature to 450 ° C. or higher, while a conductive film having no crystallinity can be obtained by setting the heating temperature to less than 450 ° C. be able to.

When the heating temperature is less than 450 ° C, the preferred heating temperature is 100 ° C or more and less than 450 ° C, more preferably 200 ° C or more and less than 450 ° C, and further preferably 350 ° C or more and less than 450 ° C. The heating time in this case is preferably 1 to 60 minutes, and more preferably 5 to 30 minutes. The heating in this case may be performed as the same process as the heating for removing the solvent, or may be performed as a separate process.
When the heating temperature is 450 ° C. or higher, the preferable heating temperature is 450 to 700 ° C., more preferably 500 to 650 ° C., further preferably 500 ° C. or higher and lower than 600 ° C., and further 500 to 550 ° C. It is preferable. The heating time in this case is preferably 5 to 120 minutes, more preferably 10 to 60 minutes. In this case, the heating may be performed after passing through the heating step of less than 450 ° C. as described above, or only the heating at 450 ° C. or more may be performed without passing through the heating step. In the latter case, the heating at 450 ° C. or higher may be performed as the same process as the heating for removing the solvent, or may be performed as a separate process.
The conductive film may be formed by applying the conductive film forming composition as described above, removing an arbitrary solvent, and heating process only once (one cycle), or repeating this cycle a plurality of times. The conductive film may be formed by an overcoating method.

<Conductive film>
A conductive film can be formed as described above.
The thickness of the conductive film should be appropriately set according to the application, and is not particularly limited, but can be, for example, 30 to 500 nm.
The conductive film formed by the method of the present invention is excellent in conductivity. In the case of a conductive film formed from a composition for forming a conductive film that does not contain titanium carboxylate, the volume resistivity measured by the four-probe method should be 5 × 10 ⁻² Ω · cm or less. Furthermore, it can be set to 1 × 10 ⁻² Ω · cm or less, and particularly 5 × 10 ⁻³ Ω · cm or less. In the case of a conductive film formed from a composition for forming a conductive film containing titanium carboxylate, the content ratio of titanium atoms in the film (that is, the content of titanium carboxylate in the composition) By varying the ratio) and the heating temperature, the conductivity can be arbitrarily and continuously set from a good conductor exhibiting high conductivity as described above to a non-conductor level. Therefore, the content ratio of titanium atoms is adjusted, and the volume resistivity is about 3 × 10 ^{−1 to} 5 × 10 ² Ω · cm (carrier density is about 1 × 10 ¹⁹ to 1 × 10 ¹⁶ pieces / cm ³ ). Thus, for example, it can be used as a channel of a ferroelectric gate transistor.

The conductivity of the conductive film formed by the method of the present invention is determined by the content of titanium atoms and the heating temperature. A person skilled in the art can easily know by a few preliminary experiments what proportion of titanium atom should be contained and what heating temperature should be adopted in order to obtain a desired conductivity.
The conductive film formed by the method of the present invention is excellent in film surface smoothness. In the case of a conductive film formed from a composition for forming a conductive film that does not contain a titanium carboxylate, the root mean square roughness (RMS) can be 50 nm or less, and further 30 nm or less. This value rapidly decreases as the content ratio of titanium atoms in the film is improved, and even if the content ratio of titanium atoms is within a range not impairing the conductivity, RMS is 5 nm or less, further 3 nm or less, particularly 2 nm or less. It can be.
As described above, in the method for forming a conductive film of the present invention, different types of conductive films can be obtained by selecting the temperature at the time of heating. By setting the heating temperature to 450 ° C. or higher, a conductive film having a perovskite crystal structure can be obtained. On the other hand, by setting the heating temperature to less than 450 ° C., a conductive film having no crystallinity can be obtained. it can. The conductive film having no crystallinity is believed to contain a significant amount of organic matter in the film, as will be apparent from examples described later. Nevertheless, it is surprising that it exhibits such high conductivity.
Note that in the case of forming a conductive film having no crystallinity, it is preferable to maintain the temperature of the film below 450 ° C. at all points in the film formation process.

In the following synthesis examples, titanium 2-ethylhexanoate (anhydrous salt, Ti content = 10.54 wt%) and ruthenium 2-ethylhexanoate (anhydrous salt, Ru content = 17.73 wt%) were respectively ) A commercial product made by ADEKA was used.
<Preparation of metal carboxylate>
The Sr content in the strontium carboxylate obtained in the following synthesis examples was measured by high frequency inductively coupled plasma (ICP) emission analysis, and the purity was obtained by dividing the measured value of the Sr content by the theoretical value as an anhydrous salt. Value.

Synthesis Example 1 (Synthesis of strontium propionate)
In a 500 mL flask, 26.6 g of Sr (OH) ₂ .8H ₂ O and 200 mL of pure water were charged, and the temperature was raised to 80 ° C. while stirring, and then 16 g of propionic acid was added. By this operation, a transparent solution containing strontium propionate was obtained. The white powder obtained by removing water at 100 ° C. was further dried at 150 ° C. for 24 hours, so that strontium propionate (Sr content = 36.8 wt%, purity 98.2 wt%) Got.

Synthesis Example 2 (Synthesis of strontium 2-ethylhexanoate)
In a 500 mL flask, 26.6 g of Sr (OH) ₂ .8H ₂ O and 200 mL of pure water were charged and heated to 80 ° C. with stirring. The reaction was carried out with stirring at 80 ° C. for 1 hour. Subsequently, water was removed under reduced pressure at 60 to 80 ° C. using an evaporator. In order to remove water remaining even by this operation, the crude product after the evaporator treatment was dissolved in 100 mL of toluene, and water was again removed under reduced pressure at 80 ° C. using an evaporator. This evaporator treatment using toluene was further repeated twice. The obtained product was further heat-dried at 160 ° C. for 24 hours to obtain strontium 2-ethylhexanoate as a waxy solid.
With respect to the strontium 2-ethylhexanoate, the Sr content determined by ICP emission analysis was 21.3% by weight, and the purity was 90.9% by weight. The impurity is considered to be mainly 2-ethylhexanoic acid. The purity calculated assuming that the impurities contain excess of 2-ethylhexanoic acid used is 98.4% by weight.
This strontium 2-ethylhexanoate was used as it was in the following preparation examples without further purification (without removing 2-ethylhexanoic acid), and used for the examples.

<Preparation of composition for forming conductive film>
Preparation Example 1
In a 30 mL glass bottle, 3.99 g of ruthenium 2-ethylhexanoate was added, and 16.11 g of methyl isobutyl ketone was added thereto and dissolved at room temperature to obtain a solution.
In a separate 30 mL glass bottle, 10 g of the above solution was taken, 4 g of propionic acid and 0.818 g of strontium propionate obtained in Synthesis Example 1 were added thereto, and the mixture was stirred and dissolved at room temperature, whereby strontium carboxylate And a ruthenium carboxylate (C-1) was obtained.

Preparation Example 2
(1) Take 3.179 g of titanium 2-ethylhexanoate in a 30 mL glass bottle, add 16.8221 g of methyl isobutyl ketone, heat to 100 to 120 ° C. and dissolve to obtain a solution.
In a separate 30 mL glass bottle, 10 g of the above solution was taken, 4 g of propionic acid and 0.818 g of strontium propionate obtained in Synthesis Example 1 were added thereto, and the mixture was stirred and dissolved at room temperature, whereby strontium carboxylate And a composition (T-1) containing titanium carboxylate.
(2) By mixing 0.8 g of the composition (C-1) obtained in Preparation Example 1 above and 0.2 g of the composition (T-1) obtained in (1) above in a 6 mL glass bottle. , A composition for forming a conductive film (C−) containing a strontium carboxylate, a ruthenium carboxylate and a titanium carboxylate and having a Ti / (Ti + Ru) value (molar ratio) of 0.2. 2) was obtained.
Preparation Examples 3-5
(2) in Preparation Example 2 except that the mixing ratio of the composition (C-1) and the composition (T-1) was changed as shown in Table 1, respectively. Similarly, conductive film forming compositions (C-3) to (C-5) having Ti / (Ti + Ru) values (molar ratios) of 0.4, 0.6, and 0.8, respectively, were obtained. It was.

Preparation Example 6
(1) 3.99 g of ruthenium 2-ethylhexanoate was taken in a 30 mL glass bottle, and 16.11 g of propionic acid was added thereto and dissolved at room temperature to obtain a solution.
(2) Take 5 g of the solution of (1) above in a 13.5 mL glass bottle, add 2 g of propionic acid and 0.327 g of strontium 2-ethylhexanoate obtained in Synthesis Example 2, and stir at room temperature. A composition for forming a conductive film containing strontium carboxylate and ruthenium carboxylate by dissolving strontium 2-ethylhexanoate and having a Sr / Ru value (molar ratio) of 0.45 (C-6) was obtained.
Preparation Examples 7 and 8
Preparation Example 6 (2) except that the amount of strontium 2-ethylhexanoate added to the solution of (1) was 0.458 g (Preparation Example 7) and 0.655 g (Preparation Example 8), respectively. 6 (2), conductive film forming compositions (C-7) and (C-8) having Sr / Ru values (molar ratios) of 0.63 and 0.91, respectively, were obtained. .

<Formation of conductive film>
Example 1
After spin-coating the conductive film-forming composition (C-1) obtained in Preparation Example 1 on a silicon substrate having an oxide film on a surface of 20 mm × 20 mm under the conditions of 2,000 rpm for 25 seconds In the air, heating was performed on a hot plate at 370 ° C. for 5 minutes. This spin coating and heating operation was repeated for a total of 3 cycles, and the coating film was applied repeatedly on the substrate. Further, the obtained coated substrate was heated in air on a hot plate at 370 ° C. for 30 minutes to obtain a conductive film having a thickness of 330 nm on the substrate.
With respect to this conductive film, the volume resistivity measured by the four probe method was 0.009 Ω · cm.
An X-ray diffraction chart (2θ = 20 to 47 °) of this conductive film measured under the following conditions is shown in FIG.
(X-ray diffraction measurement conditions)
Measuring device: manufactured by MacScience, product name “M18XHF-SRA”
Radiation source: Cu Κα ray Sample size: 1cm x 2cm
Voltage and current: 40 kV, 60 mA
Measurement range: 2θ = 10-50 °
Scan speed: 5 ° / min

Example 2
In the same manner as in Example 1, a coating film was formed by recoating on a silicon substrate having an oxide film on the surface. Next, this coated substrate was placed in a commercially available RTA (Rapid Thermal Annealing) apparatus and heated in oxygen at 410 ° C. for 1 hour while supplying oxygen at a flow rate of 0.2 L / min. A conductive film having a thickness of 330 m was obtained.
With respect to this conductive film, the volume resistivity measured in the same manner as in Example 1 was 0.024 Ω · cm.
Examples 3-6
In Example 2 above, the heating temperature in oxygen using RTA was set to 450 ° C. (Example 3), 500 ° C. (Example 4), 550 ° C. (Example 5) and 600 ° C. (Example 6), respectively. Was heated in oxygen as in Example 2.
The volume resistivity measured for the conductive film after heating in oxygen in the same manner as in Example 1 was 0.047 Ω · cm in Example 3, 0.025 Ω · cm in Example 4, and 0.005 in Example 5. It was 01 Ω · cm and 0.004 Ω · cm in Example 6.
The X-ray diffraction charts measured in the same manner as in Example 1 for the conductive films after heating in oxygen are shown in FIG. As seen in FIG. 1, when the heating temperature in oxygen is 450 ° C. or higher, a peak attributed to the (110) plane of the substantially cubic perovskite crystal was confirmed at 2θ = 32 °. The intensity of this peak increases remarkably at a heating temperature in oxygen of 500 to 600 ° C., and it is understood that sufficient crystallization occurs even at such a low temperature.

Example 7
In this example, it was examined what conductivity can be obtained when the heating temperature is 370 ° C. or lower.
After spin-coating the conductive film-forming composition (C-1) obtained in Preparation Example 1 on a silicon substrate having an oxide film on a surface of 20 mm × 20 mm under the conditions of 2,000 rpm for 25 seconds In the air, heating was performed on a 210 ° C. hot plate for 5 minutes. This spin coating and heating operation was repeated for a total of 3 cycles, and a coating film was formed on the substrate by overcoating. With respect to this coating film, the sheet resistance measured by the four-point probe method was 1.7 × 10 ³ Ω / □.
The substrate with the coating film after this measurement was placed on the hot plate again and heated in air at 240 ° C. for 5 minutes, and then the sheet resistance was measured in the same manner as described above. Similarly, heating was performed in air at 280 ° C. and 370 ° C. for 5 minutes each, and the sheet resistance of the coating film after each heating was measured.
The sheet resistance value after heating at each temperature is shown in FIG.
From the result of FIG. 2, it is understood that the coating film formed from the composition for forming a conductive film of the present invention already has excellent conductivity at a heating temperature of 210 ° C.
In addition, the film thickness of the coating film after heating at 370 ° C. was 330 nm.

Example 8
In this example, the thermal decomposition behavior of the composition for forming a conductive film of the present invention was examined.
FIG. 3 shows a thermogravimetric analysis (TG) chart of the conductive film-forming composition (C-1) prepared in Preparation Example 1 measured under the following conditions.
(TG measurement conditions)
Measuring device: Product name “TG / DTA6200” manufactured by SII Nano Technology
Supply gas: Air, 300 mL / min Measurement temperature range: 25-600 ° C
Temperature rising rate: 5 ° C./min Sample: The conductive film-forming composition (C-1) prepared in Preparation Example 1 above was directly taken into an aluminum measurement pan without removing the solvent, and this was used as a sample. .
Sample weight: 16.616 mg
In FIG. 3, the rapid weight loss observed from the start of measurement to around 100 ° C. is due to the evaporation of the solvent. If the temperature is further increased, the weight of the sample will be reduced to a temperature of 450 ° C and then become a constant value. Therefore, the conductive film formed at a heating temperature of less than 450 ° C contains organic substances derived from the starting carboxylate. It is thought that. It is surprising that the conductive film formed at a heating temperature of less than 450 ° C. exhibits high conductivity as seen in Examples 1, 2 and 7 while containing an organic substance. On the other hand, the conductive film formed at a heating temperature of 450 ° C. or higher does not substantially contain an organic substance and has a crystal structure as understood from FIGS.

Example 9
In this example, the influence of the substitution rate of Ru atoms with Ti atoms and the heating temperature in oxygen on the resistivity of the obtained conductive film was examined.
Five silicon substrates (25 mm × 25 mm) having an oxide film on the surface were prepared. After spin-coating the conductive film-forming compositions (C-1) to (C-5) obtained in Preparation Examples 1 to 5 on the respective substrates under the conditions of 2,000 rpm and 25 seconds, Heating was performed in air on a hot plate at 370 ° C. for 5 minutes. This operation was repeated for a total of 2 cycles, and the coating film was applied repeatedly on the substrate. Next, each of these coated substrates was heated in air on a hot plate at 370 ° C. for 30 minutes to obtain a conductive film having a thickness of 220 nm on the substrate. For each conductive film obtained from each composition for forming a conductive film, four Pt upper electrodes were formed by sputtering, and volume resistivity, carrier mobility and carrier density were determined by Hall measurement (van der Pauw method). It was measured.
Next, each coated substrate was placed in an RTA apparatus and heated in oxygen at 430 ° C. for 1 hour while supplying oxygen at a flow rate of 0.2 L / min. Carrier mobility and carrier density were measured. Similarly, heating in oxygen for 1 hour each was performed at 550 ° C. and 600 ° C., and measurement after each heating was performed.
These measured values are shown in Table 2, respectively. In addition, the measured value considered to be poor in reliability was not listed in Table 2.

From Table 2, it is understood that the conductivity of the obtained conductive film can be arbitrarily set in the range of a good conductor to a nonconductor by changing the substitution rate of Ru atoms with Ti atoms and the heating temperature in oxygen.
Example 10
In this example, the influence of the substitution rate of Ru atoms with Ti atoms on the surface smoothness of the obtained conductive film was examined.
Five sheets of 20 mm × 20 mm amorphous silica substrate were prepared. The conductive film-forming compositions (C-1) to (C-5) obtained in Preparation Examples 1 to 5 were each spin-coated on a substrate at 2,000 rpm for 25 seconds, and then 370 Heated on a hot plate at 5 ° C. for 5 minutes. This operation was repeated to coat the coating film twice on the substrate. Furthermore, the obtained coated substrate was heated in air on a hot plate at 370 ° C. for 30 minutes to obtain a conductive film on the substrate. Next, a conductive film having a thickness of 330 nm was obtained on the substrate by heating in oxygen in the same manner as in Example 2 except that the heating temperature in oxygen was 550 ° C.
Table 3 shows the root mean square roughness (RMS) of these coating films measured by an atomic force microscope under the following conditions.
(RMS measurement method)
Measuring apparatus: Atomic force microscope measurement using SII SPM Nano Navi Station equipped with S-image unit and SN-AF01S-NT cantilever Scanning frequency: 1 Hz

Example 11
In this example, the relationship between the Sr / Ru ratio in the SRO film and the resistivity of the obtained conductive film was examined. The firing temperature in this example is as low as 370 ° C.
Three silicon substrates (20 mm × 20 mm) having an oxide film on the surface were prepared. After spin-coating the conductive film-forming compositions (C-6) to (C-8) obtained in Preparation Examples 6 to 8 on the respective substrates under the conditions of 2,000 rpm and 25 seconds, In the air, heating was performed on a hot plate at 250 ° C. for 5 minutes to form a coating film. Next, these coated substrates were each heated in air on a hot plate at 370 ° C. for 5 minutes to obtain a conductive film having a thickness of 60 nm on the substrate.
Separately from the above, the composition (C-8) was subjected to the same application and heating as described above twice (two cycles), whereby a conductive film having a thickness of 120 nm was formed on a silicon substrate having an oxide film on the surface. A characteristic film was formed.
The volume resistivity of each of these conductive films was measured by the four probe method measurement. The results are shown in Table 4.

<Verification of storage stability of composition for forming conductive film>
Example 12
In this example, it was verified that long-term storage was possible even when the composition for forming a conductive film of the present invention contained moisture.
0.1 g of water was added to 1 g of the conductive film-forming composition (C-8) prepared in Preparation Example 8, so that the water content of the composition was about 9% by weight.
The conductive film-forming compositions (C-7) and (C-8) prepared in Example 11 and the composition (C-8) containing 9% by weight of water prepared above were each at room temperature. Although stored for 4 weeks, there was no change in the appearance of the composition.
Using each composition after storage for 4 weeks, a conductive film was formed in the same manner as in Example 11, and the volume resistivity was measured. The results are shown in Table 5. For the conductive film forming compositions (C-7) and (C-8), the volume resistivity of the conductive film formed using the composition immediately after preparation (that is, the conductive film formed in Example 11). Also shown together.
In Table 5, the composition (C-8) containing 9% by weight of water was represented as “C-8 / H ₂ O”.

  As shown in Table 5, the volume resistivity of the conductive film formed from the composition after storing the composition for forming a conductive film of the present invention for a long period of time is the conductivity formed from the composition immediately after preparation. The volume resistivity of the conductive film was the same as the experimental error. Further, a conductive film exhibiting excellent conductivity is formed even after the composition (C-8) containing 9% by weight of water by intentionally adding water is stored for a long period of time. It was shown that it can.

Claims (8)

A composition comprising a strontium carboxylate, a ruthenium carboxylate and a solvent,
The composition for forming a conductive film, wherein the solvent contains at least one selected from the group consisting of ketones and carboxylic acids.   The composition for forming a conductive film according to claim 1, wherein the solvent contains a carboxylic acid.   Furthermore, the composition for electroconductive film formation of Claim 1 or 2 containing the carboxylate of titanium.   A conductive film forming composition according to any one of claims 1 to 3 is applied onto a substrate to form a coating film, and the coating film is heated in an oxidizing atmosphere. A method for forming a conductive film.   The method for forming a conductive film according to claim 4, wherein the heating temperature is less than 450 ° C.   A conductive film formed by the method according to claim 5.   The method for forming a conductive film according to claim 4, wherein the heating temperature is 450 ° C. or higher.   A conductive film formed by the method according to claim 7.

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