JP2005281734A - Raw material solution for metal organic chemical vapor deposition, method for purifying Pb (dpm) 2 complex, and method for forming dielectric thin film using the raw material solution - Google Patents

Abstract

Provided is a raw material solution for metal organic chemical vapor deposition which has excellent vaporization characteristics and vaporization stability even when the raw material solution is stored for a predetermined period. Provided is a method for purifying a Pb (dpm) ₂ complex that is not suspended over time even if the raw material solution is stored for a predetermined period.
The raw material solution for metal organic chemical vapor deposition of the present invention comprises a Pb (dpm) ₂ complex dissolved in an organic solvent, and has a visible light transmittance of 95% or more in the wavelength range of 500 to 600 nm. It is characterized by being. The method for purifying the Pb (dpm) ₂ complex of the present invention comprises a step of preparing a solution by dissolving the Pb (dpm) ₂ complex in a solvent having a water content of 50 ppm or less, and a predetermined ratio to the solution. Adding a moisture adsorbent and removing the residual moisture contained in the solution by the moisture adsorbent; and removing the solvent from the solution from which the moisture has been removed to remove the solvent to a Pb (dpm) ₂ complex having a moisture content of 200 ppm or less Obtaining the step.
[Selection figure] None

Description

In the present invention, a lead-based thin film such as lead oxide required for manufacturing a semiconductor ferroelectric memory device or the like is formed by metal organic chemical vapor deposition (hereinafter referred to as MOCVD method). In the case of forming by the above, a raw material solution for MOCVD containing a Pb (dpm) ₂ complex suitable as a raw material solution for film formation, a method for purifying a Pb (dpm) ₂ complex suitable as a raw material for the raw material solution, and the raw material solution The present invention relates to a method for forming a dielectric thin film.

Conventionally, bis (2,2,6,6-tetramethyl-3,5-heptanedionato) is used as a deposition material for forming a lead oxide thin film for manufacturing a ferroelectric memory device of a semiconductor device by MOCVD. Lead (II) (hereinafter referred to as Pb (dpm) ₂ ) complexes are known. This Pb (dpm) ₂ complex has poor vaporization characteristics, and a residue is generated during vaporization. Further, when this Pb (dpm) ₂ complex is used as a raw material for MOCVD as it is, there is a problem that the reproducibility of the film formation is poor because the vaporization characteristic is greatly deteriorated with time.

Therefore, the present applicant has proposed a raw material solution for MOCVD characterized by dissolving a Pb (dpm) ₂ complex in an organic solvent (see, for example, Patent Document 1). Examples of the organic solvent disclosed in Patent Document 1 include one or more selected from the group consisting of tetrahydrofuran, dimethyltetrahydrofuran, and dimethylfuran. According to the MOCVD raw material solution, a lead-based thin film can be stably and efficiently formed at a high film formation rate by the MOCVD method, which is useful as a superconducting material, a ferroelectric material, a semiconductor thin film material, and the like. It can be effectively used for the production of lead-based thin films.
In addition, the present applicants can use one or more organometallic compound raw materials as a cyclic or acyclic diether, an alkyl-substituted cyclic monoether, a mono- or di-branched alkyl monoether, an alkoxy alcohol, a diol, and an acetoate. The solution raw material for complex oxide type dielectric thin film formation by the MOCVD method which consists of the solution dissolved in the 1 type (s) or 2 or more types of solvent chosen from acetate was proposed (for example, refer patent document 2). When the dielectric thin film is formed by the MOCVD method using the solution raw material shown in Patent Document 2, each organometallic compound of the raw material is stably supplied to the film forming chamber without causing thermal decomposition or non-volatility. Therefore, even if the substrate temperature changes, a complex oxide type dielectric thin film having a composition ratio close to the composition ratio of the metal in the solution raw material can be reliably formed with a uniform thickness even if there is a step. In addition, a dielectric thin film having good dielectric properties can be stably formed on the capacitor electrode of FeRAM having a step.

  On the other hand, a metal compound solution obtained by dissolving a metal compound in a cyclohexane compound represented by the following formula (1) is disclosed (for example, see Patent Document 3).

In the formula, R ₅ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and p represents an integer of 1 to 2.
The metal compound solution disclosed in Patent Document 3 can provide a metal compound solution having stability and concentration suitable for the solution CVD method, and a CVD raw material comprising the solution.
JP-A-10-195086 (Claims 4 and 5, paragraph [0071]) JP 11-323556 A (Claim 1, paragraph [0139]) JP 2001-234343 A (Claim 1, paragraph [0007])

However, since the Pb (dpm) ₂ complex is particularly vulnerable to moisture compared to other organic lead complexes, there is a problem that a hydroxide is formed over time in the presence of moisture. Therefore, even when a raw material solution for MOCVD is prepared by dissolving the Pb (dpm) ₂ complex in the organic solvent disclosed in Patent Documents 1 to 3, the raw material solution is stored in the raw material solution when stored for a predetermined period. There was a problem that a colloidal precipitate was formed and the solution was suspended. This precipitate has a problem that the vaporization characteristics are poor, and the nozzle portion of the vaporizer is clogged, and a residue is generated during vaporization.

An object of the present invention is to provide a raw material solution for metal organic chemical vapor deposition which is excellent in solution stability, vaporization characteristics and vaporization stability even when the raw material solution is stored for a predetermined period.
Another object of the present invention is to provide a method for purifying a Pb (dpm) ₂ complex that does not suspend the raw material solution over time even when stored for a predetermined period.

The invention according to claim 1 is characterized in that the Pb (dpm) ₂ complex is dissolved in an organic solvent, and the visible light transmittance in the wavelength range of 500 to 600 nm is 95% or more. This is a raw material solution for a phase growth method.
In the invention according to claim 1, by defining the transmittance of visible light in the wavelength range of 500 to 600 nm to 95% or more, a raw material excellent in solution stability, vaporization characteristics and vaporization stability even when stored for a predetermined period A solution can be provided.

The invention according to claim 2 is the raw material solution according to claim 1, wherein the water content contained in the solution is 200 ppm or less.
In the invention according to claim 2, since the moisture content contained in the solution is regulated to 200 ppm or less, no precipitate is generated in the raw material solution even if the raw material solution is stored for a predetermined period. It is possible to provide a raw material solution having excellent vaporization characteristics and vaporization stability.
The invention according to claim 3 is the invention according to claim 1, which is a raw material solution in which a Pb (dpm) ₂ complex is dissolved in an organic solvent having a water content of 50 ppm or less.

The invention according to claim 4 includes a step of preparing a solution by dissolving a Pb (dpm) ₂ complex in a solvent having a water content of 50 ppm or less, adding a water adsorbent to the solution at a predetermined ratio, Pb including a step of removing residual water contained in the solution by the adsorbent and a step of removing the solvent from the solution from which water has been removed to obtain a Pb (dpm) ₂ complex having a water content of 200 ppm or less. dpm) _{2 is} a purification method of the complex.
In the invention according to claim 4, when a raw material solution is prepared by dissolving the Pb (dpm) ₂ complex purified through the above steps in an organic solvent, the raw material solution may be stored over time even if stored for a predetermined period. There is no suspension.

The invention according to claim 5 is a Pb (dpm) ₂ complex purified by the method according to claim 4.
The invention according to claim 6 is a raw material solution for metal organic chemical vapor deposition method in which the Pb (dpm) ₂ complex purified by the method according to claim 4 is dissolved in an organic solvent having a water content of 50 ppm or less. .
An invention according to a seventh aspect of the invention is characterized in that the raw material solution according to any one of the first, second, third, or sixth aspect further includes one or both of an organic zirconium complex and an organic titanium complex. This is a raw material solution for metal chemical vapor deposition.
In the invention according to claim 8, the Pb (dpm) ₂ complex purified by the method according to claim 4 is mixed with either one or both of an organic zirconium complex and an organic titanium complex at a predetermined ratio. A raw material solution for metal organic chemical vapor deposition characterized by being prepared and dissolved in an organic solvent having a water content of 50 ppm or less.
The invention according to claim 9 is a dielectric characterized in that a film is formed by metal organic chemical vapor deposition using the raw material solution according to any one of claims 1, 2, 3, 6, 7, or 8. This is a method for forming a thin body film.

The raw material solution for metal organic chemical vapor deposition of the present invention is a raw material solution in which a Pb (dpm) ₂ complex is dissolved in an organic solvent, and the visible light transmittance in the wavelength range of 500 to 600 nm is 95% or more. By prescribing, a raw material solution having excellent solution stability, vaporization characteristics, and vaporization stability can be obtained even when stored for a predetermined period. The raw material solution of the present invention preferably has a water content contained in the solution of 200 ppm or less. By defining the water content contained in the solution to 200 ppm or less, even if the raw material solution is stored for a predetermined period, no precipitate is generated in the raw material solution. Excellent in properties and can suppress vaporization residue.
Thereby, for example, when a lead-based thin film such as lead zirconate titanate (PZT) is formed by the MOCVD method, the raw material solution can be stably supplied, and the controllability of the film composition can be expected to be improved. In the case of a raw material solution containing a plurality of types of organometallic complexes, the film composition can be controlled by the concentration ratio of the plurality of types of organometallic complexes contained in the source solution.

Next, the best mode for carrying out the present invention will be described.
The raw material solution for MOCVD of the present invention is characterized in that a Pb (dpm) ₂ complex is dissolved in an organic solvent, and the visible light transmittance in the wavelength range of 500 to 600 nm is 95% or more. By defining the visible light transmittance in the wavelength range of 500 to 600 nm to 95% or more, a raw material solution having excellent solution stability, vaporization characteristics, and vaporization stability can be provided even when stored for a predetermined period.
The molar concentration in the raw material solution for MOCVD of the present invention is preferably in the range of 0.01 to 0.5 mol / l. A range of 0.1 to 0.3 mol / l is particularly preferable. Organic solvents include tetrahydrofuran, methyltetrahydrofuran, dimethyltetrahydrofuran, furan, dimethylfuran, hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, heptane, cycloheptane, n-octane, isooctane, cyclooctane, pyridine, lutidine, butyl acetate, acetic acid Examples include amyl, glyme, diglyme, triglyme, tetraglyme, diethylene glycol diethyl ether, diethoxyethane, ethylenediamine, diethylenetriamine, triethylenetetramine, etc. These solvents may be used alone or in combination of two or more. May be used.

Moreover, it is preferable that the moisture content contained in the raw material solution for MOCVD of this invention is 200 ppm or less. By defining the water content contained in the solution to 200 ppm or less, even if the raw material solution is stored for a predetermined period, no precipitate is generated in the raw material solution, so that the raw material solution has excellent vaporization characteristics and vaporization stability. Can be provided. The raw material solution for MOCVD of the present invention may be prepared by dissolving a Pb (dpm) ₂ complex in an organic solvent having a water content of 50 ppm or less. By using an organic solvent having a low water content, the MOCVD raw material solution of the present invention can be easily prepared.

Next, a method for purifying the Pb (dpm) ₂ complex of the present invention will be described.
First, a Pb (dpm) ₂ complex is dissolved in a solvent having a water content of 50 ppm or less to prepare a solution. Next, a moisture adsorbent is added to the solution at a predetermined ratio, and residual moisture contained in the solution is removed by the moisture adsorbent. Examples of the moisture adsorbent used in the purification method of the present invention include magnesium sulfate, calcium sulfate, sodium sulfate, and molecular sieve. Next, the solvent is removed from the solution from which moisture has been removed to obtain a Pb (dpm) ₂ complex having a moisture content of 200 ppm or less. When the Pb (dpm) ₂ complex purified through the above steps is prepared by dissolving the purified Pb (dpm) ₂ complex in an organic solvent, the prepared raw material solution is stored for a predetermined period. However, it does not suspend over time.

Moreover, the raw material solution for MOCVD of the present invention may be a raw material solution containing a plurality of types of organometallic complexes in which one or both of an organic zirconium complex and an organic titanium complex are further included in the raw material solution described above. In addition, the MOCVD raw material solution of the present invention is prepared by mixing the Pb (dpm) ₂ complex purified by the above method with either or both of an organic zirconium complex and an organic titanium complex at a predetermined ratio. Then, this mixture may be dissolved in an organic solvent having a water content of 50 ppm or less to prepare a raw material solution containing a plurality of types of organometallic complexes. The mixing ratio of one or both of the Pb (dpm) ₂ complex and the organic zirconium complex or the organic titanium complex is arbitrarily prepared according to the composition ratio of the composite film that can be prepared using this raw material solution. It is possible.
Examples of the organic zirconium complex include Zr (dmhd) _x (dpm) _4-x (0≤x≤4), Zr (O-iPr) _y (dpm) _4-y (0≤y≤4), Zr (O- tBu) _z (dpm) _4-z (0 ≦ z ≦ 4) and the like. Examples of the organic titanium complex include Ti (O—iPr) ₂ (dpm) ₂ , Ti (O—tBu) ₂ (dpm) ₂ , Ti (O—iPr) ₂ (dmhd) ₂ , Ti (O—tBu) ₂ ( dmhd) ₂ , [TiO (dpm) ₂ ] _{2 and the} like. Here, dmhd represents a 2,6-dimethyl-3,5-heptanedione residue, O-iPr represents isopropoxide, and O-tBu represents tertiary butoxide.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
First, 200 ml of anhydrous toluene was added to 20.7 g of metallic lead to prepare a suspension. After adding 36.9 g of dipivaloylmethane, which was dehydrated and purified while vigorously stirring the suspension, to a 2-fold equivalent to metal lead, the suspension was heated to reflux for 24 hours to be reacted. Next, the reaction solution was concentrated under reduced pressure to 80 ° C. and 10 Torr (about 1.33 kPa) to obtain a Pb (dpm) ₂ complex. Next, as a purification step, the obtained Pb (dpm) ₂ complex was dissolved in 200 ml of tetrahydrofuran having a water content of 50 ppm or less to prepare a solution. 20 g of magnesium sulfate as a water adsorbent was added to the solution to remove water remaining in the solution. Subsequently, the solution from which moisture was removed was filtered to remove the moisture adsorbent, and then the obtained filtrate was concentrated under reduced pressure at 80 ° C. and 10 Torr (about 1.33 kPa) to remove tetrahydrofuran and remove Pb ( A purified product of dpm) ₂ complex was obtained.
<Comparative Example 1>
A Pb (dpm) ₂ complex was obtained in the same manner as in Example 1 except that the purification step was not performed.

<Comparison evaluation 1>
The weight ratio of Pb, C and H contained in the Pb (dpm) ₂ complex obtained in Example 1 and Comparative Example 1 was determined by elemental analysis. Moreover, the water content contained in the Pb (dpm) ₂ complex obtained in Example 1 and Comparative Example 1 was measured with a Karl Fischer moisture meter. The obtained analysis results are shown in Table 1, respectively. In Table 1, the theoretical values of Pb, C and H contained in the Pb (dpm) ₂ complex are also shown.

As is clear from Table 1, the Pb (dpm) ₂ complex of Comparative Example 1 that was not subjected to the purification step contained a large amount of water, even though it was a stage before the raw material solution. On the other hand, in the Pb (dpm) ₂ complex of Example 1, the water content was significantly reduced.

<Example 2>
First, the Pb (dpm) ₂ complex obtained in Example 1 was dissolved in tetrahydrofuran so as to have a concentration of 0.3 mol / l to prepare a raw material solution. Next, divide the prepared raw material solution into 7 parts and adjust the water content so that the water content in the raw material solution is 50 ppm, 100 ppm, 200 ppm, 250 ppm, 300 ppm, 400 ppm and 500 ppm, respectively, while checking with a Karl Fischer moisture meter. did. Next, the raw material solution whose water content was adjusted was stored for about 2 weeks under an argon atmosphere. Each raw material solution after storage was subjected to transmittance measurement, residue measurement after thermogravimetric analysis, and residue measurement after vaporization experiment.
(1) Transmittance measurement Using an ultraviolet-visible light absorption spectrum apparatus, the raw material solution after storage is placed in a sample cell, and the control cell serving as a comparative control sample contains the raw material solution to be measured immediately after the raw material solution is prepared. The raw material solution adjusted to the same water content was added, and the transmittance at a wavelength near 540 nm was measured.
(2) Residue measurement after thermogravimetric analysis First, all the solvent was removed by maintaining each raw material solution under reduced pressure. Next, the solid obtained by removing the solvent is sealed in a measurement sample holder of a thermogravimetric analyzer, and the inside of the apparatus is maintained in an argon atmosphere, and the temperature is increased from room temperature to 500 ° C. at a rate of 10 ° C./min. Thermogravimetric analysis was performed. Next, the residue weight in the sample holder after completion of thermogravimetric analysis was measured.
(3) Residue measurement after vaporization experiment First, a vaporization experiment was performed under the vaporization conditions shown in Table 2 below using a commercially available vaporizer as the vaporizer of the MOCVD apparatus.

Next, after collecting the vaporization residue remaining in the vaporizer after the vaporization experiment was completed, the weight of the vaporization residue was measured, and the residue rate after the vaporization experiment was obtained based on the following equation.
Residue rate after vaporization (%) = (weight of vaporized residue / weight of Pb (dpm) ₂ complex before dissolution) × 100
Each measurement result is shown in Table 3 below.

As is clear from Table 3, the transmittance measurement showed that the transmittance was not changed even when compared with the control sample immediately after preparation of the raw material solution until the water content was 250 ppm, and the transparency was maintained. On the other hand, in the raw material solution having a water content of 300 ppm, the transmittance decreased, and the transmittance tended to decrease as the water content contained in the raw material solution increased. This is because when a raw material solution having a high water content is stored for a certain period of time, a part of the Pb (dpm) ₂ complex forms a hydroxide due to the water contained in the raw material solution, and colloidal precipitates are deposited. It is thought that the solution was suspended.
In residue measurement after thermogravimetric analysis, no residue was produced when a raw material solution having a water content of 250 ppm or less was used. On the other hand, in the raw material solution with a water content of 300 ppm, a residue was generated after thermogravimetric analysis, and the amount of residue after thermogravimetric analysis tended to increase as the water content contained in the raw material solution increased. . This is because when a raw material solution with a high water content is stored for a certain period of time, a part of the Pb (dpm) ₂ complex forms a hydroxide due to the water contained in the raw material solution, resulting in a colloidal precipitate. The product is considered to be a residue without thermal decomposition.
In residue measurement after the vaporization experiment, no residue was produced when a raw material solution having a water content of 250 ppm or less was used. On the other hand, in the raw material solution having a water content of 300 ppm, a residue was generated after the vaporization experiment, and the amount of the residue after the vaporization experiment tended to increase as the water content contained in the raw material solution increased. In this way, when a raw material solution that generates a lot of vaporization residue is used continuously, it is difficult to control the vaporization rate, etc., because it is clogged with piping in the MOCVD apparatus, etc. It causes a decrease. Moreover, in the raw material solution with a water content of 500 ppm, there were many precipitates, and the vaporization nozzle was blocked.

<Example 3>
First, the Pb (dpm) ₂ complex obtained in Example 1 was converted into a Zr (dmhd) ₄ complex, a Ti (O-iPr) ₂ (dpm) ₂ complex, and a Pb (dpm) ₂ complex at 0.30 mol / l. , Zr (dmhd) ₄ complex is mixed at 0.15 mol / l and Ti (O—iPr) ₂ (dpm) ₂ complex is mixed at 0.15 mol / l. A raw material solution in which the organometallic complex was dissolved was prepared. Next, divide the prepared raw material solution into 7 parts and adjust the water content so that the water content in the raw material solution is 50 ppm, 100 ppm, 200 ppm, 250 ppm, 300 ppm, 400 ppm and 500 ppm, respectively, while checking with a Karl Fischer moisture meter. did. Next, the raw material solution whose water content was adjusted was stored for about 2 weeks under an argon atmosphere. Each raw material solution after storage was subjected to transmittance measurement, residue measurement after thermogravimetric analysis, and residue measurement after a vaporization experiment in the same manner as in Example 2. Note that (3) the vaporization conditions in the residue measurement after the vaporization experiment were the conditions shown in Table 4 below.

  Each measurement result is shown in Table 5 below.

As apparent from Table 5, the transmittance measurement showed that the transmittance was not changed even when compared with the control sample immediately after preparation of the raw material solution until the water content was 250 ppm, and the transparency was maintained. On the other hand, in the raw material solution having a water content of 300 ppm, the transmittance decreased, and the transmittance tended to decrease as the water content contained in the raw material solution increased. This is because when a raw material solution having a high water content is stored for a certain period of time, a part of the Pb (dpm) ₂ complex forms a hydroxide due to the water contained in the raw material solution and colloidal precipitates are deposited. It is thought that the solution was suspended.
In residue measurement after thermogravimetric analysis, no residue was produced when a raw material solution having a water content of 250 ppm or less was used. On the other hand, in the 300 ppm, 400 ppm and 500 ppm raw material solutions whose water content exceeds 250 ppm, residues are generated after thermogravimetric analysis, and the residual amount after thermogravimetric analysis increases as the water content contained in the raw material solution increases. There was a tendency to increase. This is because when a raw material solution with a high water content is stored for a certain period of time, a part of the Pb (dpm) ₂ complex forms a hydroxide due to the water contained in the raw material solution, resulting in a colloidal precipitate. The product is considered to be a residue without thermal decomposition.
In residue measurement after the vaporization experiment, no residue was produced when a raw material solution having a water content of 250 ppm or less was used. On the other hand, in the 300 ppm and 400 ppm raw material solutions whose water content exceeds 250 ppm, residues are generated after the vaporization experiment, and the residual amount after the vaporization experiment tends to increase as the water content contained in the raw material solution increases. It was seen. As described above, when a raw material solution that generates a large amount of vaporization residue is used continuously, it is difficult to control the vaporization rate or the like because it is clogged with piping in the MOCVD apparatus or the like. It causes a decrease. Moreover, in the raw material solution with a water content of 500 ppm, there were many precipitates, and the vaporization nozzle was blocked.

<Example 4>
First, the Pb (dpm) ₂ complex obtained in Example 1 was converted into a Zr (dmhd) ₄ complex, a Ti (O-iPr) ₂ (dpm) ₂ complex, and a Pb (dpm) ₂ complex at 0.30 mol / l. , Zr (dmhd) ₄ complex is mixed at 0.15 mol / l and Ti (O—iPr) ₂ (dpm) ₂ complex is mixed at 0.15 mol / l. A raw material solution in which the organometallic complex was dissolved was prepared. Next, divide the prepared raw material solution into 7 parts and adjust the water content so that the water content in the raw material solution is 50 ppm, 100 ppm, 200 ppm, 250 ppm, 300 ppm, 400 ppm and 500 ppm, respectively, while checking with a Karl Fischer moisture meter. did. Next, the raw material solution whose water content was adjusted was stored for about 2 weeks under an argon atmosphere. For each raw material solution after storage, a PZT dielectric thin film was formed on a silicon substrate on which Pt was deposited as an electrode under the film forming conditions shown in Table 6 below using a substrate heating type MOCVD apparatus.

  The obtained PZT dielectric thin film was subjected to ICP analysis to determine the element ratio of Pb, Zr and Ti contained in the thin film. The measurement results are shown in Table 7 below.

As is clear from Table 7, since the raw material solution having a water content of 250 ppm or less does not produce precipitates in the raw material solution even after being stored for 2 weeks, the ratio of Pb, Zr and Ti in the formed thin film is It can be controlled by the concentration ratio in the raw material solution, and it can be seen that the raw material solution has excellent composition controllability. On the other hand, in the 300 ppm and 400 ppm raw material solutions in which the water content in the raw material solution exceeds 250 ppm, a precipitate is deposited in the raw material solution after being stored for 2 weeks, and this precipitate can be vaporized. As a result, the element ratio in the thin film could not be controlled by the concentration ratio in the raw material solution. Further, the raw material solution having a water content of 500 ppm could not form a PZT dielectric thin film because the nozzle part of the vaporizer was blocked during the film formation.

Claims (9)

Pb (dpm) ₂ complex is dissolved in an organic solvent,
A raw material solution for metal organic chemical vapor deposition characterized by having a visible light transmittance of 95% or more in a wavelength range of 500 to 600 nm.   The raw material solution according to claim 1, wherein a water content contained in the solution is 200 ppm or less. The raw material solution according to claim 1, wherein the Pb (dpm) ₂ complex is dissolved in an organic solvent having a water content of 50 ppm or less. Dissolving a Pb (dpm) ₂ complex in a solvent having a water content of 50 ppm or less to prepare a solution;
Adding a water adsorbent in a predetermined ratio to the solution, and removing residual water contained in the solution by the water adsorbent;
Pb (dpm) ₂ purification process of the complex and a step of water content by removing the solvent from the solution obtained by removing the water to obtain the following Pb (dpm) ₂ complex 200 ppm. A Pb (dpm) ₂ complex purified by the method according to claim 4. A raw material solution for metal organic chemical vapor deposition, wherein the Pb (dpm) ₂ complex purified by the method according to claim 4 is dissolved in an organic solvent having a water content of 50 ppm or less.   7. A raw material for metal organic chemical vapor deposition characterized by further comprising one or both of an organic zirconium complex and an organic titanium complex in the raw material solution according to claim 1, 2, 3 or 6. solution. A Pb (dpm) ₂ complex purified by the method according to claim 4 is mixed with one or both of an organic zirconium complex and an organic titanium complex at a predetermined ratio, and the mixture contains water. A raw material solution for metal organic chemical vapor deposition characterized by being dissolved in an organic solvent having an amount of 50 ppm or less. A method for forming a dielectric thin film, comprising forming a film by a metal organic chemical vapor deposition method using the raw material solution according to any one of claims 1, 2, 3, 6, 7, or 8.