JP5214191B2 - Thin film forming raw material and thin film manufacturing method - Google Patents

Description

  The present invention relates to a raw material for forming a thin film comprising a strontium compound having a specific structure, and a method for producing a thin film using the raw material.

  Thin films containing strontium include electronic components such as high-dielectric capacitors, ferroelectric capacitors, gate insulating films, and barrier films, optical members for optical communication devices such as optical waveguides, optical switches, and optical amplifiers, superconductivity It is used as a member.

  Examples of the method for producing the thin film include a sputtering method, an ion plating method, a MOD method such as a coating pyrolysis method and a sol-gel method, a chemical vapor deposition method, etc., but has excellent composition controllability and step coverage. Since it has many advantages such as being suitable for mass production and being capable of hybrid integration, it is a chemical vapor deposition (hereinafter sometimes simply referred to as CVD) method including an ALD (Atomic Layer Deposition) method. Is the optimal manufacturing process.

  In the CVD method, a metal compound using an organic ligand is used as a precursor for supplying metal atoms to a thin film. The properties required for a compound (precursor) suitable for a raw material used for the CVD method are that it can be transported in a liquid state during vaporization and transportation, has a large vapor pressure and is easily vaporized, and is stable against heat. That is. In addition, during thin film deposition, decomposition by heat and / or oxidation proceeds easily. As the strontium precursor, many bis (pentamethylcyclopentadienyl) strontium and bis (pentamethylcyclopentadienyl) strontium adducts obtained by adding an organic compound to this have been reported.

  For example, Patent Document 1 discloses bis (pentamethylcyclopentadienyl) strontium and bis (pentamethylcyclopentadienyl) strontium ether adducts. Patent Document 2 discloses bis (pentamethylcyclopentadienyl) strontium to which an aliphatic ether such as ethyl ether or amyl ether, a heterocyclic ether such as tetrahydrofuran or dioxane, or a heterocyclic nitrogen compound such as phenanthroline is added. Is disclosed.

These bis (pentamethylcyclopentadienyl) strontium compounds have a low vapor pressure or sublimation pressure and are difficult to volatilize compared to commonly used CVD precursors, so they are heated to a high temperature to supply sufficient raw materials for the CVD method. It is necessary to.
However, the above-mentioned bis (pentamethylcyclopentadienyl) strontium compound has a problem that the thermal stability is insufficient and the raw material cannot be supplied to the CVD method due to deterioration of the raw material due to heating. Yes.

  Further, since the bis (pentamethylcyclopentadienyl) strontium compound is a solid, a liquid supply method using a solution dissolved in an organic solvent is a preferable method. In the liquid supply method, if the solubility of the precursor in the organic solvent is small, solid precipitation will occur due to temperature change in the vaporizer, partial volatilization of the solvent, and concentration change, and the supply amount will change over time due to clogging of the piping etc. Therefore, the solubility of the precursor in the organic solvent is also an important factor that gives a stable process to the production of the thin film.

JP-A-5-287534 (particularly, Example 1 and Example 2) JP-A-6-157191 (in particular, [0017], Example 1 and Example 3)

  The problem to be solved by the present invention is to provide a raw material for forming a thin film containing a strontium precursor having properties such as volatility and thermal stability that are particularly suitable as a raw material for CVD.

  As a result of repeated studies, the present inventors have found that a strontium compound obtained by adding a bidentate coordination compound having a specific structure to bis (pentamethylcyclopentadienyl) strontium can solve the above problems. As a result, the present invention has been reached.

This invention is made | formed based on the said knowledge, and provides the raw material for thin film formation formed by containing the strontium compound represented by following General formula (2) .

（式中、Ｒ¹及びＲ⁶は、それぞれ独立に、炭素数１〜４のアルキル基を表し、Ｒ ² は、水素原子、メチル基又はイソプロピル基を表し、Ｒ³〜Ｒ⁵は、それぞれ独立に、水素原子又は炭素数１〜４のアルキル基を表し、Ｘ及びＹは、それぞれ独立に、酸素原子、−ＮＨ―又は−ＮＲ−を表し、Ｒは炭素数１〜４のアルキル基を表す。）

(In the formula, R ¹ and R ⁶ each independently represent an alkyl group having 1 to 4 carbon atoms, R ² represents a hydrogen atom, a methyl group or an isopropyl group, and R ^{3 to} R ⁵ represent each independently. Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X and Y each independently represent an oxygen atom, —NH— or —NR—, and R represents an alkyl group having 1 to 4 carbon atoms. .)

  The present invention also provides a method for producing a thin film, wherein a vapor containing the strontium compound obtained by vaporizing the raw material for forming the thin film is introduced into the substrate, and this is decomposed and / or chemically reacted to form a thin film on the substrate. Is to provide.

  According to the present invention, it is possible to provide a thin film forming raw material containing a strontium precursor having properties such as volatilization characteristics and thermal stability that are particularly suitable as a raw material for CVD.

（式中、Ｒ ¹ 及びＲ ⁶ は、それぞれ独立に、炭素数１〜４のアルキル基を表し、Ｒ ² は、水素原子、メチル基又はイソプロピル基を表し、Ｒ ³ 〜Ｒ ⁵ は、それぞれ独立に、水素原子又は炭素数１〜４のアルキル基を表し、Ｘ及びＹは、それぞれ独立に、酸素原子、−ＮＨ―又は−ＮＲ−を表し、Ｒは炭素数１〜４のアルキル基を表す。）
上記一般式（１）で表される二座配位化合物において、Ｒ¹、Ｒ⁶、Ｒ³〜Ｒ⁵及びＲで表される炭素数１〜４のアルキル基としては、メチル、エチル、プロピル、イソプロピル、ブチル、２−ブチル、イソブチル、ｔ−ブチルが挙げられる。 Hereinafter, the raw material for forming a thin film of the present invention and a method for producing a thin film using the raw material will be described in detail.
The raw material for forming a thin film of the present invention contains a strontium compound represented by the general formula (2) (hereinafter also referred to as a strontium compound according to the present invention). The strontium compound according to the present invention is obtained by adding a bidentate coordination compound represented by the following general formula (1) to bis (pentamethylcyclopentadienyl) strontium.

(In the formula, R ¹ and R ⁶ each independently represent an alkyl group having 1 to 4 carbon atoms, R ² represents a hydrogen atom, a methyl group or an isopropyl group, and R ^{3 to} R ⁵ each independently represents Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X and Y each independently represent an oxygen atom, —NH— or —NR—, and R represents an alkyl group having 1 to 4 carbon atoms. .)
In bidentate compound represented by the above following general formula (1), the ^{R 1, R 6, R 3} ~R 5 and alkyl groups having 1 to 4 carbon atoms represented by R, methyl, ethyl, Examples include propyl, isopropyl, butyl, 2-butyl, isobutyl, and t-butyl.

  Specific examples of the bidentate coordination compound include the compound No. 1 shown below. 1-No. 43.

  Among the above bidentate coordination compounds, those in which X and Y are oxygen atoms (Compound Nos. 1 to 12) are preferable because the solubility of the coordinated strontium compound in an organic solvent is good.

Further, bidentate compound described above, as the above following general formula (2), which coordinated at a rate of one molecule against bi scan (pentamethylcyclopentadiene) strontium 1 molecule, like this coordination form a is that the thermal stability, that in terms of volatility characteristics text as a precursor material for CVD.

  The strontium compound according to the present invention is not particularly limited by its production method, and can be produced by applying a known method of adding a bidentate coordination compound to bis (pentamethylcyclopentadienyl) strontium. it can. As such a production method, 1) a method in which pentamethylcyclopentadienyl sodium and strontium halide are reacted in an ether solvent and then a desired bidentate coordination compound is added. 2) metal strontium and pentane A method in which a toluene suspension with methylcyclopentadiene is heated and reacted to react, and then a desired bidentate coordination compound is added. 3) A toluene suspension of metal strontium and pentamethylcyclopentadiene is cooled. Examples include a method of adding a desired coordination compound after introducing ammonia gas and reacting, and among these methods, the method of introducing ammonia gas of the above 3) has a short reaction time and produces efficiently. Is preferable.

  The raw material for forming a thin film of the present invention is a thin film precursor made of the strontium compound according to the present invention, and the form varies depending on the process. The thin film forming raw material of the present invention is particularly useful as a CVD raw material having a step of vaporizing a strontium compound because of its physical properties.

  When the thin film forming raw material of the present invention is a chemical vapor deposition (CVD) raw material, the form thereof is appropriately selected depending on the method of transport and supply of the CVD method used.

  As the transport and supply method described above, the CVD raw material is vaporized by heating and / or depressurizing in the raw material container, and introduced into the deposition reaction section together with a carrier gas such as argon, nitrogen, and helium used as necessary. There is a gas transport method and a liquid transport method in which a CVD raw material is transported to a vaporization chamber in a liquid or solution state, vaporized by heating and / or decompressing in the vaporization chamber, and introduced into a deposition reaction section. In the case of the gas transport method, the strontium compound itself according to the present invention is a raw material for CVD, and in the case of the liquid transport method, a solution in which the strontium compound according to the present invention is dissolved in an organic solvent is the raw material for CVD.

  In the multi-component CVD method for producing a multi-component thin film, a CVD raw material is vaporized and supplied independently for each component (hereinafter sometimes referred to as a single source method), a multi-component raw material There is a method of vaporizing and supplying a mixed raw material prepared by mixing in advance with a desired composition (hereinafter sometimes referred to as a cocktail sauce method). In the case of the cocktail source method, a mixture of the strontium compound according to the present invention and another precursor or a mixed solution obtained by adding an organic solvent medium to these mixtures is a raw material for CVD.

  As the organic solvent used for the above-mentioned CVD raw material, an inert organic solvent can be used for the strontium compound according to the present invention. Examples of the organic solvent include: acetates such as ethyl acetate, butyl acetate, and methoxyethyl acetate; methyl butyl ketone, methyl isobutyl ketone, ethyl butyl ketone, dipropyl ketone, diisobutyl ketone, methyl amyl ketone, cyclohexanone, methylcyclohexanone Ketones such as hexane, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, heptane, octane, toluene, xylene, etc .; 1-cyanopropane, 1-cyanobutane, 1-cyanohexane, cyanocyclohexane, cyanobenzene Carbon having a cyano group such as 1,3-dicyanopropane, 1,4-dicyanobutane, 1,6-dicyanohexane, 1,4-dicyanocyclohexane, 1,4-dicyanobenzene Motorui and the like, which, solubility of the solute, operating temperature and the boiling point, the relationships of the flash point, used alone or two or more kinds of mixed solvents. When these organic solvents are used, the total amount of the precursor components in the organic solvent is preferably 0.01 to 2.0 mol / liter, particularly 0.05 to 1.0 mol / liter. .

  In addition, in the multi-component CVD method using a single source method or a cocktail source method, other precursors used together with the strontium compound according to the present invention are not particularly limited and are well known as CVD raw materials. A general precursor can be used.

  As said other precursor, one type or two or more types selected from organic coordination compounds such as alcohol compounds, glycol compounds, β-diketone compounds, cyclopentadiene compounds and organic amine compounds, and silicon, boron, phosphorus or A compound with a metal is mentioned. Examples of metal species include Group 1 elements such as lithium, sodium, potassium, rubidium, and cesium, Group 2 elements such as beryllium, magnesium, calcium, and barium, scandium, yttrium, and lanthanoid elements (lanthanum, cerium, praseodymium, neodymium, promethium, Samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium), group 3 elements such as actinoid elements, group 4 elements of titanium, zirconium, hafnium, group 5 elements of vanadium, niobium, tantalum, chromium , Molybdenum, tungsten group 6 elements, manganese, technetium, rhenium group 7 elements, iron, ruthenium, osmium group 8 elements, cobalt, rhodium, iridium group 9 elements, ni Kel, palladium, platinum group 10 elements, copper, silver, gold group 11 elements, zinc, cadmium, mercury group 12 elements, aluminum, gallium, indium, thallium group 13 elements, germanium, tin, lead group 14 Element, arsenic, antimony, group 15 element of bismuth, group 16 element of polonium.

  In the case of the single source method, the other precursor is preferably a compound having similar thermal and / or oxidative decomposition behavior to the strontium compound according to the present invention, and in the case of the cocktail source method, the heat and / or In addition to the similar behavior of oxidative decomposition, those that do not undergo alteration due to chemical reaction during mixing are preferred.

  The raw material for forming a thin film of the present invention contains as little impurities metal elements as possible, impurities halogen such as impurity chlorine, and impurities organic components as much as possible. The impurity metal element content is preferably 100 ppb or less and more preferably 10 ppb or less for each element. The total amount is preferably 1 ppm or less, and more preferably 100 ppb or less. The impurity halogen content is preferably 100 ppm or less, more preferably 10 ppm or less, and still more preferably 1 ppm or less. The total amount of impurity organic components is preferably 500 ppm or less, preferably 50 ppm or less, and more preferably 10 ppm or less. Moreover, since moisture causes generation of particles in the raw material for forming a thin film and generation of particles by the CVD method, the metal compound and the organic solvent are reduced in water as much as possible before use in order to reduce the respective moisture. Should be removed. The water content of each of the metal compound and the organic solvent is preferably 10 ppm or less, and more preferably 1 ppm or less.

  In addition, the raw material for forming a thin film of the present invention can be used to reduce or prevent particle contamination of a thin film to be produced. In the particle measurement by a light scattering submerged particle detector in a liquid phase, The number is preferably 100 or less in 1 ml of liquid phase, more preferably the number of particles larger than 0.2 μm is 1000 or less in 1 ml of liquid phase, and the number of particles larger than 0.2 μm is liquid. More preferably, no more than 1000 in 1 ml of phase.

  The method for producing a thin film of the present invention uses the raw material for forming a thin film of the present invention, and vaporized vapors of the strontium compound according to the present invention and other precursors used as necessary, and is used as necessary. A reactive gas is introduced onto the substrate, and then a precursor is decomposed and / or chemically reacted on the substrate to grow and deposit a thin film on the substrate. There are no particular restrictions on the method of transporting and supplying the raw material, the deposition method, the production conditions, the production apparatus, etc., and well-known general conditions and methods can be used.

  Examples of the reactive gas used as needed include, for example, oxygen, ozone, nitrogen dioxide, nitric oxide, water vapor, hydrogen peroxide, formic acid, acetic acid, acetic anhydride and the like as oxidizing gases. Examples of reducing agents include hydrogen, and examples of nitrides that can be used include organic amine compounds such as monoalkylamines, dialkylamines, trialkylamines, and alkylenediamines, hydrazine, ammonia, and nitrogen. It is done.

  Examples of the transport and supply method include the gas transport method, the liquid transport method, the single source method, and the cocktail sauce method.

  In addition, as the above deposition method, source gas, or thermal CVD in which source gas and reactive gas are reacted only by heat to deposit a thin film, plasma CVD using heat and plasma, photo CVD using heat and light, Examples include optical plasma CVD using heat, light and plasma, and ALD (Atomic Layer Deposition) in which the deposition reaction of CVD is divided into elementary processes and deposition is performed stepwise at the molecular level.

  Moreover, as said manufacturing conditions, reaction temperature (substrate temperature), reaction pressure, a deposition rate, etc. are mentioned. About reaction temperature, 160 degreeC or more which is the temperature which the strontium compound concerning this invention fully reacts is preferable, and 250 to 800 degreeC is more preferable. The reaction pressure is preferably atmospheric pressure to 10 Pa in the case of thermal CVD or photo CVD, and preferably 2000 Pa to 10 Pa in the case of using plasma. The deposition rate can be controlled by the raw material supply conditions (vaporization temperature, vaporization pressure), reaction temperature, and reaction pressure. When the deposition rate is large, the properties of the obtained thin film may be deteriorated. When the deposition rate is small, productivity may be problematic. Therefore, the deposition rate is preferably 0.5 to 5000 nm / min, and more preferably 1 to 1000 nm / min. In the case of ALD, the number of cycles is controlled so as to obtain a desired film thickness.

  In the method for producing a thin film of the present invention, after thin film deposition, annealing may be performed in an inert atmosphere, an oxidizing atmosphere, or a reducing atmosphere in order to obtain better electrical characteristics. When embedding is necessary, a reflow process may be provided. The temperature in this case is usually 400 to 1200 ° C, preferably 500 to 800 ° C.

  The thin film produced by the method for producing a thin film of the present invention using the raw material for forming a thin film of the present invention can be obtained by appropriately selecting a precursor of other components, a reactive gas, and production conditions, thereby providing oxide ceramics and nitride ceramics. Or a desired type of thin film such as glass. Examples of the type of thin film to be produced include strontium, strontium titanate, barium strontium titanate, bismuth strontium tantalate, bismuth barium strontium tantalum niobate, etc. Examples thereof include electronic component members such as capacitor films, gate insulating films, gate films, ferroelectric capacitor films, capacitor films, and barrier films, and optical glass members such as optical fibers, optical waveguides, optical amplifiers, and optical switches.

  Hereinafter, the present invention will be described in more detail with examples, evaluation examples, and comparative examples. However, the present invention is not limited by the following examples.

[Example 1] Compound No. 1 with respect to 1 mol of bis (pentamethylcyclopentadienyl) strontium. Production of Strontium Compound Coordinating 1 Mol of 1 (Sr Compound 1) In a dry argon stream, a mixture of pentamethylcyclopentadiene (0.20 mol) and dehydrated toluene (2.7 mol) was mixed with metal strontium ( 0.089 mol) was added, and after cooling to -40 ° C, ammonia gas was dissolved and reacted at -40 ° C for 3-4 hours. After confirming that the reaction solution became dark blue and all metal strontium disappeared, the temperature of the solution was returned to room temperature, and then toluene was distilled off by heating and decompression. To the ammonia adduct of bis (pentamethylcyclopentadienyl) strontium obtained as the residue, compound No. After 1 (7.5 mol) was added and dissolved, insoluble impurities were filtered off. The filtrate was concentrated, the precipitated white needle crystals were taken out, and the target Sr compound 1 was obtained in a yield of 56%. About the obtained Sr compound 1, Sr content measurement was performed by < ¹ > H-NMR measurement and ICP emission analysis in a heavy benzene solution. The results are shown below.
・¹ H-NMR (chemical shift ppm; multiplicity; H number)
(2.130; singlet; 30) (2.584; broad: 4) (2.678; broad; 6)
Elemental analysis Sr: 19.4% by mass (theoretical value: 19.5%)

Example 2 Compound No. 1 was added to 1 mol of bis (pentamethylcyclopentadienyl) strontium. Preparation of strontium compound (Sr compound 2) in which 1 mol of 2 was coordinated In the same manner as in Example 1 except that 1,2-diethoxyethane was used instead of 1,2-dimethoxyethane, With respect to 1 mol of (pentamethylcyclopentadienyl) strontium, the compound No. A strontium compound (Sr compound 2) in which 1 mol of 2 was coordinated was obtained in a yield of 52%. The obtained Sr compound 2 was analyzed in the same manner as in Example 1 above. The results are shown below.
・ 1H-NMR (chemical shift ppm; multiplicity; H number)
(2.170; singlet; 30) (0.831; broad: 6) (2.662; broad; 4) (3.009; broad; 4)
Elemental analysis Sr: 18.7% by mass (theoretical value: 18.4%)

Example 3 Compound No. 1 was added to 1 mol of bis (pentamethylcyclopentadienyl) strontium. Preparation of strontium compound (Sr compound 3) in which 1 mol of 4 is coordinated In the same manner as in Example 1 except that 1,2-dibutoxyethane was used instead of 1,2-dimethoxyethane, bis With respect to 1 mol of (pentamethylcyclopentadienyl) strontium, the compound No. A strontium compound (Sr compound 3) in which 1 mol of 4 was coordinated was obtained in a yield of 55%. The obtained Sr compound 3 was analyzed in the same manner as in Example 1 above. The results are shown below.
・ 1H-NMR (chemical shift ppm; multiplicity; H number)
(0.870; triplet; 6) (1.090; broad; 4) (1.421; broad: 4) (2.188; singlet; 30) (2.825; broad; 4) (3.116; Broad; 4)
Elemental analysis Sr: 17.6% by mass (theoretical value: 17.4%)

Example 4 Compound No. 1 was added to 1 mol of bis (pentamethylcyclopentadienyl) strontium. Production of Strontium Compound Coordinating 1 Mole of 9 (Sr Compound 4) The same method as in Example 1 except that 1-methyl-1,2-dimethoxyethane was used instead of 1,2-dimethoxyethane And 1 mol of bis (pentamethylcyclopentadienyl) strontium which is a white solid, A strontium compound (Sr compound 4) in which 1 mol of 9 was coordinated was obtained in a yield of 50%. The obtained Sr compound 4 was analyzed in the same manner as in Example 1 above. The results are shown below.
1H-NMR (chemical shift ppm; multiplicity; H number)
(0.385; Broad; 3) (2.139; Singlet; 30) (2.635; Broad; 2) (2.695: Broad; 6) (3.061; Broad; 1)
Elemental analysis Sr: 18.8% by mass (theoretical value: 19.0%)

[Evaluation Example 1]
TG-DTA was measured for the Sr compounds 1 to 4 obtained in Examples 1 to 4 and the compound in which 2 moles of tetrahydrofuran were coordinated to 1 mole of bis (pentamethylcyclopentadienyl) strontium (comparative Sr compound). did. The measurement conditions were Ar 100 ml / min, 1 ° C./min temperature rise, and the measurement sample amounts are shown in Table 2. The remaining amount at 295 ° C. and the state of mass reduction are shown in Table 1.

  From Table 1 above, it was confirmed that Sr compounds 1 to 4 had no divergence of the addition compound when compared with the comparative Sr compound. This indicates that the volatile characteristics are good as a CVD raw material. Among them, Sr compound 1 and Sr compound 2 have a small amount of remaining volatile and good thermal stability.

[Example 5] Production of strontium titanate thin film A 0.07 mol% 1,2-dimethoxyethane solution of Sr Compound 1 obtained in the above Example was used as a strontium source, and the titanium compound contained 0 of titanium tetratertiary butoxide. A strontium titanate thin film was produced on a silicon wafer using the 0.07 mol% 1,2-dimethoxyethane solution by the CVD apparatus shown in FIG. About the obtained thin film, when the film thickness measurement and the thin film composition were confirmed by fluorescent X-rays, the film thickness was 10 nm and the film composition was strontium titanate.
(conditions)
Reaction temperature (substrate temperature); 350 ° C., reactive gas; oxygen (process)
A series of steps consisting of the following (1) to (5) was set as one cycle, repeated 20 cycles, and finally annealed at 500 ° C. for 3 minutes.
(1) Vaporization chamber temperature: Introducing vapor of a strontium compound vaporized under the conditions of 170 ° C. and vaporization chamber pressure of 90 Pa, and depositing at a system pressure of 90 Pa for 2 seconds.
(2) Unreacted raw materials are removed by argon purging for 3 seconds.
(3) Vaporizing chamber temperature: 160 ° C., vapor of a titanium compound vaporized under the conditions of a vaporizing chamber pressure of 90 Pa is introduced and deposited for 2 seconds at a system pressure of 90 Pa.
(4) A reactive gas is introduced and reacted at a system pressure of 90 Pa for 2 seconds.
(5) Unreacted raw material is removed by argon purging for 2 seconds.

FIG. 1 is a schematic view showing a CVD apparatus used in Example 5 and used in the method for producing a thin film of the present invention.

Claims (4)

A raw material for forming a thin film comprising a strontium compound represented by the following general formula (2) .

(In the formula, R ¹ and R ⁶ each independently represent an alkyl group having 1 to 4 carbon atoms, R ² represents a hydrogen atom, a methyl group or an isopropyl group, and R ^{3 to} R ⁵ represent each independently. Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X and Y each independently represent an oxygen atom, —NH— or —NR—, and R represents an alkyl group having 1 to 4 carbon atoms. .) The raw material for forming a thin film according to claim 1 , wherein in the general formula (2), X and Y are oxygen atoms. Furthermore, the raw material for thin film formation of Claim 1 or 2 formed by containing the organic solvent. The vapor containing the claims 1 to strontium compound obtained by vaporizing the thin film-forming material according to any one of 3 are introduced into the substrate, a thin film degradation and / or chemical reacted with the substrate to which A method for producing a thin film to be formed.

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