JP3944894B2 - Tantalum oxide film forming composition and tantalum oxide film forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to methods and compositions for forming a tantalum oxide film. More particularly, it relates to efficient methods and compositions for forming the preferred tantalum oxide film as the capacitor insulating film to be used for DRAM.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a capacitor area in a DRAM (Dynamic Random Access Memory) has become smaller due to higher integration and higher density of semiconductor devices. If the capacitance decreases as the capacitor area decreases, the device may malfunction due to a soft error or the like. Therefore, even if the capacitor area decreases, a sufficient capacitance must be ensured. One method for solving this problem is to use an insulating film (high dielectric film) having a high relative dielectric constant as a capacitor insulating film. Conventionally, SiO ₂ or Si ₃ N ₄ is generally used as a capacitor insulating film, and the capacity has been secured by making the memory cell structure three-dimensional. However, with the recent rapid integration and miniaturization of DRAMs, it has become difficult to ensure the memory cell capacity by the conventional method.
[0003]
Tantalum oxide (Ta ₂ O ₅ ) has a relative dielectric constant that is more than three times that of SiO ₂ and Si ₃ N ₄ that have been used as capacitor insulating films in the past, and can be easily step-covered by CVD. It is possible to deposit an excellent thin film. For this reason, Ta ₂ O ₅ has been studied as a next-generation DRAM capacitor insulating film.
However, the insulating film formed by depositing Ta ₂ O ₅ by the CVD method contains a large amount of impurities and oxygen vacancies resulting from the raw material and the film forming method, which cause a leak current and have a poor withstand voltage. There was a problem and it was desired to improve it. In addition, tantalum alkoxide used as a raw material in film formation by the CVD method has high hydrolyzability and has a problem that a large amount of impurities such as carbon remain in the film.
Furthermore, in the film formation by the CVD method, a large-scale apparatus is required, and the apparatus itself is not only expensive, but also consumes a lot of energy in the vacuum system and the plasma system, leading to high product costs. Yes.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a composition and method for easily and effectively forming a Ta ₂ O ₅ film.
Another object of the present invention, Ru near to provide methods and compositions for forming the Ta ₂ O ₅ film of high quality.
Still other objects and advantages of the present invention will become apparent from the following description.
[0005]
[Means for Solving the Problems]
In accordance with the present invention, the above objects and advantages of the present invention are primarily as follows:
Is achieved by the tantalum oxide film-forming composition characterized by comprising a reaction product and a solvent of an amino alcohol and a tantalum alkoxide is a compound capable of reacting with the tantalum alkoxide.
[0006]
According to the present invention, the above objects and advantages of the present invention, secondly, Ru is achieved by the formation method of the Ta ₂ O ₅ film, which comprises applying to then heat-treated above coating composition onto a substrate .
[0007]
The present invention is described in detail below.
As the tantalum alkoxide used in the present invention, for example, the following formula (1)
Ta (OR ¹ ) ₅ (1)
Here, R ¹ is an alkyl group having 1 to 6 carbon atoms, and five R ¹ may be the same or different.
Is preferably used.
Specific examples of the tantalum alkoxide include tantalum pentamethoxide, tantalum pentaethoxide, tantalum pentaisopropoxide, tantalum pentaboxide, and the like. These tantalum alkoxides can be used alone or in combination of two or more.
[0008]
As the compound capable of reacting with the tantalum alkoxide, generated power sale Rua amino alcohols new bond with tantalum or oxygen atom reacts with the tantalum alkoxide in the tantalum alkoxide is used. Here, the newly formed bond can be, for example, a covalent bond, an ionic bond, a coordinate bond, or an intermediate bond between these bonds.
Examples of the amino alcohol include compounds such as triethanolamine, diethanolamine, triisopropanolamine, diisopropanolamine, diisopropanolamine, methyldiethanolamine, and ethyldiethanolamine.
[0011]
A reaction product of an amino alcohol capable of reacting with tantalum alkoxide and tantalum alkoxide is described in, for example, J. Org. Am. Chem. Soc. As shown in 1994, 116, 6143-6148, it is obtained by mixing amino alcohol and tantalum alkoxide which can react with tantalum alkoxide and heating as necessary. The reaction is, for example, Ru is suitably carried out at a temperature of room temperature to 150 DEG ° C..
[0012]
In the present invention, the above reaction products can be used alone or in combination of two or more.
The composition for forming a tantalum oxide film of the present invention comprises at least one tantalum compound as described above and a solvent.
[0013]
The solvent to be used is not particularly limited as long as it dissolves the tantalum compound as described above and does not react with the tantalum compound. For example, n-pentane, cyclopentane, n-hexane, cyclohexane, n-heptane, cycloheptane, n-octane, cyclooctane, decane, cyclodecane, dicyclopentadiene hydride, benzene, toluene, xylene, durene, indene, tetrahydro Hydrocarbon solvents such as naphthalene, decahydronaphthalene, squalane;
Diethyl ether, dipropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, tetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane, bis Ether solvents such as (2-methoxyethyl) ether and p-dioxane;
Polar solvents such as propylene carbonate, γ-butyrolactone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, dimethyl sulfoxide, methylene chloride, chloroform;
Methanol, ethanol, propanol, butanol, hexanol, cyclohexanol, octanol, decanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol, propylene Alcohol solvents such as glycol monomethyl ether, propylene glycol monoethyl ether, glycerol, glycerol monomethyl ether, glycerol dimethyl ether, glycerol monoethyl ether, glycerol diethyl ether;
And water.
[0014]
When water is used as a solvent, the reaction product may be hydrolyzed.
These solvents can be used alone or as a mixture of two or more.
Of these, alcohol solvents and mixed solvents of alcohol solvents and water and / or polar solvents are preferred in view of the solubility of the reaction product and the stability of the solution.
The concentration of the reaction product in the composition solution can be appropriately adjusted according to the desired thickness of the Ta ₂ O ₅ film. Preferably it is 0.5 to 50 weight%. Further, in order to increase the tantalum concentration in the solution, other tantalum compounds other than the above reaction products can be added and used as necessary.
In addition, a small amount of a surface tension modifier such as a fluorine-based, silicone-based, or nonionic-based one can be added to the above composition solution as needed within a range that does not impair the intended function.
[0015]
The composition solution thus obtained can be used by appropriately mixing with fine particles of metal oxide such as aluminum oxide, zirconium oxide, titanium oxide and silicon oxide as required. Also, nonionic surfactants, etc. to improve the wettability of the solution to the application object, improve the leveling property of the applied film, and prevent the occurrence of crushing and distortion skin on the coating film Can be used.
[0016]
The above composition, i.e., solution or mixture (for example, when a metal oxide is used) is coated on a support to form a tantalum compound coating. At this time, the material, shape, and the like of the support are not particularly limited, but it is preferable that the material can withstand the heat treatment in the next step. The support for forming the coating film may be a flat surface or a non-planar surface having a step, and the form is not particularly limited. Specific examples of the material for these supports include glass, metal, plastic, and ceramics. As glass, for example, quartz glass, borosilicate glass, soda glass, lead glass, and the like can be used. As the metal, for example, gold, silver, copper, nickel, silicon, aluminum, iron, and stainless steel can be used. As the plastic, for example, polyimide, polyethersulfone, and the material shape thereof is a bulk shape, a plate shape, It is not particularly limited by the film shape or the like.
[0017]
In the application of the above solution, the application method is not particularly limited, and can be performed by an appropriate method such as spin coating, dip coating, flow coating, curtain coating, roll coating, spray coating, bar coating, ink jet, and printing. . The application may be performed once, or may be applied multiple times. A suitable thickness of the coating film varies appropriately depending on the coating method and the solid content concentration, but the film thickness is preferably 0.001 to 10 μm, more preferably 0.005 to 1 μm as a dry film thickness.
[0018]
Thereafter, the coating film of the tantalum compound is converted into a Ta ₂ O ₅ film by heat treatment. In order to obtain a high-purity and dense Ta ₂ O ₅ film, it is preferable to appropriately adjust the heat treatment temperature, the heating time, the heating atmosphere, and the like.
The temperature of the heat treatment is preferably 200 ° C. or higher, and more preferably 300 ° C. or higher. The heating time may be an appropriate time depending on the film thickness or the like, but in order to obtain a highly pure film, it is preferable to heat for 15 minutes or more, and more preferably for 30 minutes or more.
[0019]
Also, the film quality obtained depends on the heating atmosphere, and as the oxygen concentration is higher, a film with fewer oxygen vacancies can be obtained in a shorter time. This is because oxygen vacancies can be replenished with oxygen and the wetting current characteristics can be improved. As the heat treatment atmosphere, an oxygen-containing atmosphere is preferable.
Oxygen in the heat treatment atmosphere may be used as a mixed gas with other inert gases such as nitrogen, helium, argon and the like.
[0020]
Moreover, in order to modify the characteristics of the obtained Ta ₂ O ₅ film, heat treatment and / or light treatment may be performed afterwards. As a light source used for light processing, low-pressure or high-pressure mercury lamp, deuterium lamp or discharge light of rare gas such as argon, krypton, xenon, YAG laser, argon laser, carbon dioxide laser, XeF, XeCl, XeBr Excimer lasers such as KrF, KrCl, ArF, and ArCl can be used as the light source. As these light sources, those having an output of 10 to 5000 W are preferably used, and those having an output of 100 to 1000 W are more preferable. Although the wavelength of these light sources is not specifically limited, Preferably it is 170 nm-600 nm. The use of laser light is particularly preferred from the viewpoint of the film quality modification effect of Ta ₂ O ₅ . The temperature during these light treatments is usually about room temperature. In light irradiation, irradiation may be performed through a mask in order to irradiate only a specific part. The Ta ₂ O ₅ film formed according to the present invention is suitably used as a capacitor insulating film. Further, a Ta ₂ O ₅ film oxidized at a low temperature such as oxygen plasma or UV-ozone treatment can be applied to the DRAM.
[0021]
The present invention will be described in detail below with reference to the following examples, but the present invention is not limited to these examples. Note that Ta in the elemental analysis value is a value calculated as Ta from the ash content of the elemental analysis, and O is a value obtained by subtracting Ta, C and H% from 100%.
[0022]
【Example】
Synthesis example 1
To a solution of 8.1 g of tantalum pentaethoxide in 67 mL of tetrahydrofuran (THF), a mixed solution of 10 g of triethanolamine and 67 mL of THF was added in a nitrogen atmosphere over 15 minutes while stirring at room temperature. After completion of the addition, the mixture was further stirred at room temperature for 1 hour. The reaction solution changed from colorless and transparent to slightly cloudy. Thereafter, the mixture was concentrated under reduced pressure, and the residue was washed with hexane, redissolved in a small amount of tetrahydrofuran, and reprecipitated with hexane. The resulting white solid was filtered off and dried under reduced pressure. ^When analyzed by ¹ H-NMR, the peak derived from ethoxy of tantalum pentaethoxide disappeared and the peak derived from triethanolamine appeared. The yield was 80%. FIG. 1 shows an NMR chart.
[0023]
Synthesis example 2
The reaction was conducted under the same conditions as in Synthesis Example 1 except that 3.8 g of triisopropanolamine was used instead of triethanolamine. The obtained reaction liquid was slightly cloudy. Thereafter, the mixture was concentrated under reduced pressure to obtain a viscous residue. ^When analyzed by ¹ H-NMR, the peak ratio of tantalum pentaethoxide derived from ethoxy decreased to 2/5, and a peak derived from triethanolamine appeared. That is, prior to the NMR measurement, elemental analysis was performed, the amounts of tantalum were aligned in the NMR analysis of the reaction raw material and the product, and the TMS in the NMR solvent (deuterated chloroform) was compared as a standard. Had decreased. The elemental analysis values of the reaction product were as follows.
Ta 43.31; C 28.35; H 5.89; O 19.28; N 3.17.
The yield was 95%.
[0024]
Example 1
1 g of the tantalum compound obtained in Synthesis Example 1 was dissolved in 10 mL of a diethylene glycol monoethyl ether / water = 90/10 volume% mixed solution to prepare a solution. This solution was filtered through a Teflon filter having a pore size of 0.2 μm to remove foreign matters, and then applied on a silicon substrate by spin coating at 2000 rpm. After evaporating the solvent in the air, it was heated at 500 ° C. for 30 minutes in the presence of air, and a transparent film was obtained on the substrate. The film thickness was 800 angstroms. Measurement of the ESCA spectrum of this film, a peak attributed to Ta _{4f7 / 2} orbit was observed in 26EV, since the peak attributed to O _1S orbit was observed 531 eV, the film Ta ₂ O ₅ It turned out that. This ESCA spectrum is shown in FIG.
[0025]
Example 2
Example except that 20 mL of diethylene glycol monoethyl ether / water / 2-propoxyethanol = 80/5/15 vol% mixture was used as the solvent instead of the diethylene glycol monoethyl ether / water = 90/10 vol% mixture. Film formation was performed according to 1. The film thickness was 350 nm. When the ESCA spectrum of this film was measured, the peak attributed to the Ta _{4f7 / 2} orbital was observed at 26 eV and the peak attributed to the O _1S orbital was observed at 531 eV, as in Example 1. It was found to be Ta ₂ O ₅ .
[0026]
Example 3
Forming a film in accordance with Example 1 except that 10 mL of diethylene glycol monoethyl ether / 2-propoxyethanol = 50/50 vol% mixture was used as the solvent instead of the diethylene glycol monoethyl ether / water = 90/10 vol% mixture. Went. The film thickness was 800 nm. When the ESCA spectrum of this film was measured, the peak attributed to the Ta _{4f7 / 2} orbital was observed at 26 eV and the peak attributed to the O _1S orbital was observed at 531 eV, as in Example 1. It was found to be Ta ₂ O ₅ .
[0027]
Example 4
Film formation was performed according to Example 1 except that the tantalum compound obtained in Synthesis Example 2 was used. The film thickness was 700 angstroms. When the ESCA spectrum of this film was measured, the peak attributed to the Ta _{4f7 / 2} orbital was observed at 26 eV and the peak attributed to the O _1S orbital was observed at 531 eV, as in Example 1. It was found to be Ta ₂ O ₅ .
[0028]
【The invention's effect】
According to the present invention, an advantage that a tantalum oxide film can be easily formed on a substrate is obtained.
[Brief description of the drawings]
1 is an NMR spectrum diagram of the product obtained in Synthesis Example 1. FIG.
2 is an ESCA spectrum diagram of the Ta ₂ O ₅ film obtained in Example 1. FIG.

Claims (3)

A composition for forming a tantalum oxide film, comprising a reaction product of amino alcohol and tantalum alkoxide, which is a compound capable of reacting with tantalum alkoxide, and a solvent.   A method for forming a tantalum oxide film, wherein the composition according to claim 1 is applied onto a substrate and heat-treated. The method according to claim 2, wherein the tantalum oxide film is an insulating film for a capacitor.

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