JP3584097B2 - Calcium source material for CVD and film forming method using the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a calcium source material for CVD suitable for depositing calcium or a calcium-containing material by a chemical vapor deposition (CVD) method.
[0002]
[Prior art]
[0003]
Various proposals have been made for forming a thin film of calcium or a calcium-containing substance by a CVD method as a thin film useful for a superconducting material or an EL material. It is advantageous to use an organic calcium complex as a raw material compound when depositing calcium or a calcium-containing substance by a CVD method.
[0004]
BACKGROUND ART Conventionally, an organic complex of a metal or a compound thereof has been used as a raw material compound when a film is formed by a CVD method, and an organic portion (ligand) constituting such an organometallic complex is as follows. Β-diketones such as dipivaloylmethane and hexafluoroacetylacetone are generally known. JP-A-4-72066 and JP-A-4-74866 disclose organic compounds constituting a complex with metals belonging to Group IIA, IIIA, IVA and IB of the periodic table having 1 to 5 carbon atoms. 1,3 diketones having a lower alkyl group are described.
[0005]
As the CVD method, a thermal CVD method, an optical CVD method, a plasma CVD method, and the like are known. In each case, a thin film is formed by decomposing a vapor of a raw material compound. In this case, the vapor is generally sublimated from the raw material compound in a solid state.
[0006]
[Problems to be solved by the invention]
Organic calcium complexes using a conventionally proposed β-diketone organic compound as a ligand generally have a high melting point (about 200 ° C.). For this reason, when it is applied to a raw material compound of the CVD method, a raw material vapor is generated by sublimation from a solid state without heating it to a high temperature higher than its melting point.
[0007]
In the case of sublimation from the solid state, as the remaining amount of the raw material in the raw material container decreases, the surface area of the raw material compound decreases, and the vaporization rate slows down. There is a problem that the film speed cannot be secured for a long time. In addition, when the vaporization rate changes, a thin film (for example, Bi ₂ Sr ₂ Ca ₂ Cu ₃ O ₉ ) of a substance in which calcium and other elements are compounded is to be produced, and the composition is controlled. There is also a problem that it becomes difficult.
[0008]
The organometallic complexes described in the above-mentioned JP-A-4-72066 and JP-A-4-74866 are also characterized in that they have high sublimability, and as a raw material compound for CVD, they are evaporated in a solid state. Things. Therefore, there is the same problem as described above.
[0009]
An organometallic complex using a ligand containing fluorine in the molecule, such as hexafluoroacetylacetone, has a low melting point, but fluoride may be present as an impurity in the formed film. Results in significantly impairing the properties of the film.
[0010]
Accordingly, an object of the present invention is to provide a calcium source material for CVD having a low melting point capable of solving the above-mentioned problems.
[0011]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to solve such a problem. As a result, an organic calcium complex having β-diketone of 6-ethyl-2,2-dimethyl-3,5-octanedione as a ligand was obtained by CVD. It has a low melting point (approximately 155 to 160 ° C.) that can be used in the liquid state as a raw material compound, and has extremely advantageous properties for film formation by the CVD method, in which the evaporation temperature and the decomposition temperature are clearly separated. . Due to this characteristic, when this is used as a calcium source material in the CVD method, it can be evaporated from a liquid state, and supply of a raw material vapor of calcium to a base material and decomposition and precipitation of calcium on the base material Can be performed stably, so that the above-mentioned problem can be solved.
[0012]
That is, according to the present invention, 6-ethyl-2,2-dimethyl-3,5-octanedione is a calcium source material for CVD used for depositing calcium or a calcium-containing material by a CVD method. The present invention provides a source material for CVD comprising an organic calcium complex as a ligand of
[0013]
According to the present invention, when calcium or a calcium-containing substance is deposited on a substrate by a CVD method, 6-ethyl-2,2-dimethyl-3,5-octanedione is coordinated with calcium as a calcium source substance. A film of calcium or a calcium-containing substance formed by a CVD method, wherein the organic calcium complex is heated to a temperature equal to or higher than its melting point, and the complex is evaporated from a liquid phase of the complex. Provide the law.
[0014]
The organic calcium complex according to the present invention is represented by the general formula (I) and is considered to be a novel compound.
[0015]
Embedded image
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
The β-diketone organic calcium complex according to the present invention is obtained by heating and stirring metal calcium and the ligand 6-ethyl-2,2-dimethyl-3,5-octanedione in a toluene-ethanol solution. The solid precipitated by distillation can be obtained by a purification method such as recrystallization or distillation.
[0017]
In order to use the thus obtained organic calcium complex of the present invention as a raw material compound for the CVD method and form a film of the calcium or calcium-containing material by the CVD method, for example, as shown in FIG. The raw material container 2 containing the calcium complex 1 is kept at a predetermined temperature (a temperature higher than the melting point, for example, 160 to 170 ° C.) in the thermostat 3, and an inert carrier gas (for example, argon gas) 4 is flowed by a flow meter 5. Is introduced into the raw material container 2 while adjusting (for example, 5 to 500 ml / min), a gas flow accompanied by the organic calcium complex is generated from the container 2.
[0018]
The generated organic calcium complex vapor is led into the reaction tube 7 of the pyrolysis furnace 6. The reaction tube (eg, quartz tube) 7 is heated by a heater 8, and the substrate 9 placed in the tube is heated and maintained at a predetermined temperature (eg, 400 to 800 ° C.). Calcium is deposited on the film to form a film. The piping from the raw material container 2 to the thermal decomposition furnace 6 is preferably maintained at a temperature of 165 to 175 ° C. by the heat insulating layer 10 or a heat insulating means in order to prevent condensation. Exhaust gas from the reaction tube 7 is discharged through a cooling trap 11. In the figure, reference numeral 12 denotes a valve, and reference numeral 13 denotes a rotary pump. In forming the calcium oxide film, an appropriate amount of gaseous oxygen is supplied from the oxygen container 14 through the flow meter 15 and the valve 16 into the reaction atmosphere (for example, during the reaction 7). In addition, in order to form a film of a composite material with another element, a raw material compound of the other material is simultaneously introduced into the reaction chamber 7, although not shown.
[0019]
【Example】
[Example 1]
Using the CVD equipment shown in FIG. 1, bis (6-ethyl-2,2-dimethyl-3,5-octanedithione) shown in Chemical Formula 1 was placed in a stainless steel raw material container 2 as a raw material compound as a calcium source. Nato) Calcium was added, and a silicon substrate was used as the substrate 9 to form a film thereon.
[0020]
In addition, bis (6-ethyl-2,2-dimethyl-3,5-octandionato) calcium of Chemical Formula 1 was produced as follows. First, under nitrogen atmosphere, 200 ml of ethanol and 100 ml of toluene were added to 4 g of metal calcium, 40 g of 6-ethyl-2,2-dimethyl-3,5-octanedione was added thereto, and the mixture was stirred at 100 ° C. After the calcium was completely dissolved, the solvent was distilled off under reduced pressure, and the residue was further dried under reduced pressure, and then purified by sublimation to obtain 41 g of bis (6-ethyl-2,2-dimethyl-3,5-octanedionato) calcium. When the melting point of the obtained complex was measured, it was 155 to 160 ° C.
[0021]
1 g of this organic calcium complex was charged into the container 2, and the temperature of the thermostat 3 was kept at a constant temperature of 160 ° C. With the silicon substrate 9 heated and maintained at 600 ° C. by the heater 8, argon gas as a carrier gas was passed at 100 ml / min to guide the compound to the quartz reaction tube 7. The piping from the vessel 2 to the pyrolysis furnace 6 was kept warm so as to be kept at 170 ° C.
[0022]
When a film forming operation was performed under these conditions for 30 minutes, a uniform calcium thin film having a thickness of 1000 Å was obtained.
[0023]
The film forming operation was repeated under exactly the same conditions as described above, except that the amount of bis (6-ethyl-2,2-dimethyl-3,5-octanedionato) calcium charged in the container 2 was changed to 2 g. In this case, a uniform calcium thin film having a thickness of 1000 Å was obtained. That is, even when the amount of the raw material compound charged in the container 2 was changed, a film having the same thickness could be formed. This indicates that the amount of evaporation from the starting compound is constant during the treatment time and the amount of decomposition is also constant.
[0024]
[Example 2]
The same process as in Example 1 was performed for 30 minutes, except that gaseous oxygen was added from the oxygen source 14 via the flowmeter 15 and the valve 16 into the reaction tube 7 at a flow rate of 100 ml / min. As a result, a calcium oxide thin film having the same thickness of 1700 angstroms was obtained for both the raw material loading amounts of 1 g and 2 g.
[0025]
[Comparative Example 1]
Example 1 except that bis (dipivaloylmethanato) calcium having a melting point of 199 to 200 ° C was used in place of bis (6-ethyl-2,2-dimethyl-3,5-octandionato) calcium. A film was formed under the same conditions as described above. As a result, after 30 minutes, a thin film of calcium having a thickness of 1800 angstroms was obtained for a material having a loading of 1 g, and a thin film of calcium having a thickness of 2900 angstroms for a loading of 2 g. This indicates that the evaporation amount also changed over time with the change in the volume of the raw material in the container.
[0026]
[Comparative Example 2]
The same process as in Comparative Example 1 was performed for 30 minutes, except that gaseous oxygen was added from the oxygen source 14 to the reaction tube 7 via the flowmeter 15 and the valve 16 at a flow rate of 100 ml / min. As a result, a thin film of calcium oxide having a thickness of 2700 angstroms was obtained with a raw material loading of 1 g, and a thickness of 3700 angstroms was obtained with a raw material loading of 2 g.
[0027]
【The invention's effect】
As described above, since the β-diketone organic calcium complex according to the present invention has a low melting point, a high vaporization property, and an evaporating temperature and a decomposition temperature separated from each other, a thin film of calcium or a calcium-containing substance is formed by the CVD method. When used as a calcium source material for production, there is an excellent advantage that it can be used in a liquid state. Also, since the evaporation rate is constant, a stable film formation rate can be obtained, and a high speed and uniform It has the feature that it is possible to form a thin film.
[0028]
Therefore, according to the present invention, a great contribution can be made to a technique for forming calcium or a calcium-containing substance useful for a superconducting material or an EL material.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of equipment arrangement of equipment for performing a thermal CVD method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Organometallic complex 2 Raw material container 3 Thermostat 4 Inert carrier gas 5 Flow meter 6 Pyrolysis furnace 7 Quartz reaction tube 8 Heater 9 Substrate 10 Heat insulation layer 11 Cooling trap 12 Valve 13 Rotary pump 14 Oxygen source

Claims (4)

A calcium source material for CVD used for depositing calcium or a calcium-containing material by a CVD method, wherein the organic calcium has 6-ethyl-2,2-dimethyl-3,5-octanedione as a calcium ligand. A calcium source material for CVD comprising a complex. The calcium source material for CVD according to claim 1, wherein the organic calcium complex is represented by Chemical Formula 1.

The calcium source material for CVD according to claim 1 or 2, wherein the organic calcium complex has a melting point of 155 to 160 ° C. When calcium or a calcium-containing substance is deposited on a substrate by the CVD method, an organic calcium complex using 6-ethyl-2,2-dimethyl-3,5-octanedione as a calcium ligand as a calcium source substance is used. A method of forming a film of calcium or a calcium-containing substance by a CVD method, wherein the organic calcium complex is heated to a temperature equal to or higher than a melting point of the organic calcium complex, and the complex is evaporated from a liquid phase of the complex.

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