JP2002212129A - Metal chelate complex and method for synthesizing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a metal chelate complex capable of reducing its vaporization temperature and having a vaporization stability. SOLUTION: This metal chelate complex is expressed by formula (1): [M(dmhd)x] [wherein M is a metal ion expressed by Pb2+, Zr4+, La3+, Ba2+, Sr2+ or Ca2+; (x) is a valence number of the metal ion; and dmhd is 2,6- dimethyl-3,5-heptanedione residue expressed by formula (2)].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a composite oxide dielectric thin film used for a dielectric memory such as a DRAM (Dynamic Random Access Memory) or a dielectric filter by a metal organic chemical vapor deposition method.
Vapor Deposition, hereinafter referred to as MOCVD method. The present invention relates to a metal chelate complex suitable as a raw material for forming the compound according to (1) and a synthesis method thereof.

[0002]

2. Description of the Related Art As the degree of integration of DRAMs increases at a rapid pace, dielectric thin films used as capacitors have become
Conventional SiO ₂ is becoming difficult to cope with, and a dielectric material having a higher dielectric constant is required. Examples of such a dielectric material include lead titanate (PT), lead zirconate titanate (PZT), lanthanum lead zirconate titanate (PLZT), strontium titanate (ST), barium titanate (BT), and titanium. Barium strontium acid (BST) and the like. Among them, PZT is the most excellent in terms of dielectric properties.

As a method of forming such a complex oxide-based dielectric thin film, a sol-gel method of forming a film on a substrate by spin coating using a metal alkoxide raw material has been actively studied. Since the sol-gel method does not vaporize metal components, it is easy to control the composition of the film. But DRAM
The capacitor electrode has a step, and the higher the degree of integration, the larger the step and the more complicated it becomes. Therefore, it is difficult to form a dielectric thin film uniformly on the electrode serving as a substrate by the spin coating method.

Therefore, in recent years, in view of the high degree of integration of devices, step coverage (= step coverage,
M with excellent step coverage on complex shaped surfaces with steps)
Research on the production of dielectric thin films by the OCVD method has been activated. Dipivaloylmethane (DP)
M) etc. as a ligand or [Zr (OtB)
u) ₄ ] and the like.
Both metal alkoxides and DPM complexes are used as raw materials for metals such as Ti, Zr, and Ta, and DPM complexes are mainly used as raw materials for Sr and Ba.

[0005] The MOCVD method is a method in which a metal material is heated under reduced pressure to be vaporized, and the vapor is transported to a film forming chamber and thermally decomposed on the substrate, whereby the generated metal oxide is deposited on the substrate. It is. In the formation of a dielectric thin film by the MOCVD method, initially, an organic metal compound as a raw material is directly heated and vaporized, and the generated vapor is sent to a film forming chamber to form a film.

[0006]

However, since the DPM complex generally used in the prior art has a high vaporization temperature, when a thin film is formed on a substrate, there is a problem that the formed substrate is damaged by heat. It also has a low vaporization temperature [Zr (O-
Although there are metal alkoxides such as [t-Bu) ₄ ], they have a problem that they are extremely reactive to air and very difficult to handle. An object of the present invention is to provide a metal chelate complex having reduced vaporization temperature and having vaporization stability, and a method for synthesizing the same.

[0007]

According to the first aspect of the present invention,
It is a metal chelate complex represented by the following formula (1).

[0008]

Embedded image Here, M is a metal ion represented by Pb ²⁺ , Zr ⁴⁺ , La ³⁺ , Ba ²⁺ , Sr ²⁺ or Ca ²⁺ , x is a valence of the metal ion M, and dmhd is 2,6-dimethyl-3,5-heptanedione residue represented by the formula (2).

[0009]

Embedded image In the invention according to claim 1, dmhd is a metal chelate complex formed by coordinating to a metal ion. Since dmhd has a smaller molecular weight than DPM which has been generally used in the past, it has a low vaporization temperature. Therefore, the metal chelate complex formed using dmhd also has a low vaporization temperature.

[0010] The invention according to claim 2 is to dissolve a lead compound, zirconium butoxide, a lanthanum compound, barium, strontium or calcium in an organic solvent,
This is a method for synthesizing a metal chelate complex, which comprises adding 6-dimethyl-3,5-heptanedione and heating to reflux.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The metal chelate complex of the present invention is a compound represented by the above formula (1). M in the formula (1) is a metal ion represented by Pb ²⁺ , La ³⁺ , Zr ⁴⁺ , Ba ²⁺ , Sr ²⁺ or Ca ²⁺ , and x is a valence of the metal ion M. And dmhd is a 2,6-dimethyl-3,5-heptanedione residue represented by the aforementioned formula (2). The metal chelate complex of the present invention is a complex formed by coordinating dmhd to one metal ion by the valence of the metal ion.

In order to synthesize the metal chelate complex of the present invention, first, the starting material of the metal chelate complex is dissolved in an organic solvent. The starting material is dissolved in the organic solvent to a concentration of 15 to 30% by weight. As a starting material, a lead compound is selected for a lead chelate complex, a zirconium butoxide for a zirconium chelate complex, a lanthanum compound for a lanthanum chelate complex, a metal barium for a barium chelate complex, a metal strontium for a strontium chelate complex, and a metal calcium for a calcium chelate complex. . The organic solvent is not limited to toluene, but includes tetrahydrofuran (THF), hexane, octane and the like. Next, Hdmhd is added to this solution. Hdmhd
Is added in a molar amount twice the valence of the metal ion. This solution is heated and refluxed at a temperature higher than the boiling point of the organic solvent for 5 hours. This heating and reflux removes residual moisture and OH groups by azeotropy, and is concentrated to obtain crystals of a synthesized product. Since the crystal of this synthesized product is a crude crystal, recrystallization using an organic solvent is performed, and then purification by sublimating the solvent under reduced pressure is repeated, whereby a crystal of the purified metal chelate complex is obtained.

[0013]

Next, embodiments of the present invention will be described. <Example 1> First, lead acetate trihydrate was used as a lead compound as a starting material.
し た 25% by weight. Next, Hdmhd in an amount twice as much as that of lead acetate trihydrate is added to this solution, and this solution is heated and refluxed at a temperature higher than the boiling point of the organic solvent for 5 hours to azeotropically remove residual moisture and OH groups. And concentrated to give white crystals. Next, the white crystals were recrystallized from toluene, and the purification was repeated by sublimating the solvent under reduced pressure to obtain purified crystals. Identification of the obtained crystals elemental analysis, mass spectroscopy and ¹
H-NMR (C ₆ D ₆ ) was used. As a result of elemental analysis, Pb 39.8% (theoretical value 40.0%), C41.9
% (Theoretical 41.7%), H 5.85% (theoretical 5.8)
0%). In mass spectrometry, m / Z = 517 [Pb
(dmhd) ₂ ] and 363 [Pb (dmhd)] ⁺ .
^{According to} the result of ¹ H-NMR analysis, δ = 5.2400 (1H, H
-C ((CO) CH (CH ₃ ) ₂ ) ₂ ), 2.4428 (2H, H
-C (CH ₃ ) _2- ), 1.1926, 1.1789 (12
H, CH ₃ ). The crystals obtained from the above analysis results were identified as a lead chelate complex of [Pb (dmhd) ₂ ].

<Example 2> First, [Zr (On-Bu) ₄ ] was used as a starting material as zirconium butoxide.
This was dissolved in toluene as an organic solvent to a concentration of 20 to 27% by weight. Next, [Zr (On-
Bu) ₄ ] with respect to the amount of Hdmhd, and refluxing the solution at a temperature higher than the boiling point of the organic solvent for 5 hours to remove residual water and OH groups by azeotropic distillation and to concentrate. And white crystals were obtained. Next, the white crystals were recrystallized from toluene, and the purification was repeated by sublimating the solvent under reduced pressure to obtain purified crystals. The obtained crystals were identified by elemental analysis, mass spectrometry and ¹ H-NMR.
(C ₆ D ₆ ). According to the result of elemental analysis, Zr1
It was 2.5% (theoretical 12.8%), C60.9% (theoretical 60.7%), and H8.7% (theoretical 8.4%). In mass spectrometry, m / Z = 556 [Zr (dmh
d) ₃ ] ⁺ , 402 [Zr (dmhd) ₂ ] ₂ ⁺ . ¹ H-
According to the result of NMR analysis, δ = 5.4922 (1H, H—C
((CO) CH (CH ₃ ) ₂ ) ₂ ), 2.3928 (2H, HC
(CH ₃ ) _2- ), 1.2241, 1.2076 (12H,
CH ₃ ). The crystal obtained from the above analysis results was identified as a zirconium chelate complex of [Zr (dmhd) ₄ ].

Example 3 First, lanthanum nitrate hexahydrate was used as a starting material as a lanthanum compound, and this was dissolved in toluene as an organic solvent to a concentration of 15 to 20% by weight. Next, Hdmhd in an amount 3 times the molar amount of lanthanum nitrate hexahydrate is added to this solution, and this solution is heated and refluxed at a temperature higher than the boiling point of the organic solvent for 5 hours to azeotropically remove residual moisture and OH groups. To remove
Concentration gave white crystals. Next, the white crystals were recrystallized from toluene, and the purification was repeated by sublimating the solvent under reduced pressure to obtain purified crystals. The obtained crystals were identified by elemental analysis, mass spectrometry and ¹ H-NMR (C ₆ D ₆ ).
Was performed. According to the result of elemental analysis, La 23.2%
(Theoretical value: 23.0%), C53.9% (theoretical value: 53.6%)
%) And H 7.53% (theoretical 7.44%). In mass spectrometry, m / Z = 605 [La (dmhd) ₃ ], 44
9 [La (dmhd) ₂ ] ⁺ . ^{According to} the result of ¹ H-NMR analysis, δ = 5.4035 (1H, HC ((CO) CH (C
_{H 3) 2) 2),} 2.3033 (2H, H-C (CH 3) 2 -),
1.1356,1.1195 (12H, CH ₃₎ was. The crystal obtained from the above analysis result is [La (dmhd)
₃ ] was identified as the lanthanum chelate complex.

Example 4 First, barium was dissolved in toluene as an organic solvent in an amount of 15 to 20% by weight.
Next, a twice molar amount of Hd with respect to barium was added to this solution.
mhd was added, and this solution was heated and refluxed at a temperature higher than the boiling point of the organic solvent for 5 hours to remove residual moisture and OH groups by azeotropic distillation and concentrated to obtain white crystals. Next, the white crystals were recrystallized from toluene, and the purification was repeated by sublimating the solvent under reduced pressure to obtain purified crystals. The obtained crystals were identified by elemental analysis, mass spectrometry and ¹ H-NMR (C ₆ D ₆ ). As a result of elemental analysis, Ba was 30.5% (theoretical value was 30.7%),
C was 48.4% (theoretical 48.2%) and H was 6.71% (theoretical 6.70%). M / Z = 44 in mass spectrometry
8 [Ba (dmhd) ₃ ], 293 [Ba (dmhd)] ⁺ . ^{According to} the result of ¹ H-NMR analysis, δ = 5.4333.
(1H, H-C (( CO) CH (CH 3) 2) 2), 2.4575
(2H, HC (CH ₃ ) _2- ), 1.2293, 1.211
9 (12H, CH ₃₎ was. The crystal obtained from the above analysis results was identified as a barium chelate complex of [Ba (dmhd) ₃ ].

Example 5 First, strontium was dissolved in an organic solvent.
Dissolved in toluene as a medium to become 15-20% by weight
did. Then add 2x the strontium to this solution
A molar amount of Hdmhd was added, and the solution was heated to the boiling point of the organic solvent.
By heating and refluxing at a higher temperature for 5 hours, residual water is removed.
And OH groups are removed by azeotropic distillation, and concentrated.
Color crystals were obtained. Next, the white crystals are re-used with toluene.
After crystallization, purification by sublimating the solvent under reduced pressure is repeatedly performed.
Thus, purified crystals were obtained. The identity of the crystals obtained is
Elemental analysis, mass spectrometry and¹H-NMR (C₆D₆Done by
Was. As a result of elemental analysis, Sr 22.2% (theoretical value 2
2.0%), C54.5% (theoretical 54.3%), H
7.42% (theoretical 7.54%). Mass spectrometry
Is m / Z = 243 [Sr (dmhd)]⁺, 639 [Sr_Two
(dmhd)_Three]⁺793 [Sr_Two(dmhd)_Four]
Was.¹According to the result of the H-NMR analysis, δ = 5.3545 (1
H, HC ((CO) CH (CH_Three)_Two)_Two), 2.3632 (2
H, HC (CH_Three) _Two-), 1.1780, 1.1615
(12H, CH_Three)Met. Obtained from the above analysis results
The crystal obtained is [Sr (dmhd)_Three] Strontium killer
The complex was identified.

Example 6 First, calcium was dissolved in toluene as an organic solvent in an amount of 15 to 20% by weight. Next, Hdmhd in a molar amount twice as much as that of calcium is added to the solution, and the solution is heated and refluxed at a temperature higher than the boiling point of the organic solvent for 5 hours, so that residual water and O 2 are removed.
The H group was removed by azeotropic distillation, and the mixture was concentrated to obtain white crystals. Next, the white crystals were recrystallized from toluene, and the purification was repeated by sublimating the solvent under reduced pressure to obtain purified crystals. The obtained crystals were identified by elemental analysis, mass spectrometry and ¹ H-NMR (C ₆ D ₆ ).
According to the result of elemental analysis, Ca was 11.2% (theoretical value was 11.4).
%), C61.8% (theoretical 61.6%), H8.55
% (Theoretical 8.56%). M / Z in mass spectrometry
= 351 [Ca (dmhd) ₂ ], 195 [Ca (dmhd)
d)] ⁺ . ^{According to} the result of ¹ H-NMR analysis, δ = 5.3.
545 (1H, H-C ( (CO) CH (CH 3) 2) 2), 2.3
632 (2H, HC (CH ₃ ) _2- ), 1.1780,1.
1615 (12H, CH ₃₎ was. The crystal obtained from the above analysis result was identified as a calcium chelate complex of [Ca (dmhd) ₃ ].

<Example 7> [Pb synthesized in Example 1
(dmhd) ₂ ] and [Pb (DPM) ₂ ] which is a DPM complex in an argon atmosphere at 10 ° C./min.
Thermogravimetric analysis was carried out at the elevated temperature. Example 8 [Zr (dmh) synthesized in Example 2
d) ₄ ] and [Zr (DPM) ₄ ], which is a DPM complex, were each subjected to thermogravimetric analysis at an elevated temperature of 10 ° C./min in an argon atmosphere. <Embodiment 9> [La (dmh) synthesized in Embodiment 3
d) ₃ ] and [La (DPM) ₃ ], which is a DPM complex, were each subjected to thermogravimetric analysis at an elevated temperature of 10 ° C./min in an argon atmosphere. <Example 10> [Ba (dmhd) synthesized in Example 4
₃ ] and [Ba (DPM) ₂ ] which is a DPM complex,
Thermogravimetric analysis was performed at a temperature rise rate of 10 ° C./min in an argon atmosphere. <Example 11> [Sr (dmhd) synthesized in Example 5
₃ ] and [Sr (DPM) ₂ ], which is a DPM complex,
Thermogravimetric analysis was performed at a temperature rise rate of 10 ° C./min in an argon atmosphere. <Example 12> [Ca (dmhd) synthesized in Example 6
₃ ] and [Ca (DPM) ₂ ] which is a DPM complex,
Thermogravimetric analysis was performed at a temperature rise rate of 10 ° C./min in an argon atmosphere. <Comparative Evaluation> TG curves of thermogravimetric analysis of Examples 7 to 12 are shown in FIGS. As is clear from FIGS. 1 to 6, it is found that the metal chelate complex of the present invention has a lower vaporization temperature than the conventional DPM complex. Thus, when a film is formed using the metal chelate complex of the present invention, the film-formed substrate is not damaged by heat.

[0020]

As described above, the general formula [M
(dmhd) _x ], a metal chelate complex formed by MOCVD using this complex as a raw material has a lower vaporization temperature than a DPM complex represented by a conventional organometallic complex. The problem that the substrate is damaged by heat can be prevented.

[Brief description of the drawings]

FIG. 1 is a view showing a result of a TG curve by thermogravimetric analysis of Example 7.

FIG. 2 is a view showing a result of a TG curve by thermogravimetric analysis in Example 8.

FIG. 3 is a graph showing a result of a TG curve by thermogravimetric analysis in Example 9.

FIG. 4 is a view showing a result of a TG curve by thermogravimetric analysis of Example 10.

FIG. 5 is a view showing a result of a TG curve by thermogravimetric analysis of Example 11.

FIG. 6 is a graph showing a result of a TG curve by thermogravimetric analysis in Example 12.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07F 3/04 C07F 3/04 5/00 5/00 D 7/00 7/00 A 7/24 7 / 24 (72) Inventor Atsushi Sai 1-297 Kitabukurocho, Omiya City, Saitama Prefecture Inside Mitsubishi Materials Research Laboratory (72) Inventor Katsumi Ogi 1-297 Kitabukurocho Omiya City, Saitama Prefecture Mitsubishi Materials Research Laboratory F Terms (reference) 4H006 AA01 AA02 AB80 AB90 AC90 BB10 BB11 BB25 BC10 4H048 AA01 AA02 AB80 AB90 AC90 BB10 BB11 BB25 BC10 VA20 VA60 VA70 VB10 VB40 4H049 VN04 VN06 VP01 VQ24 VQ92 VS24 VU01 V02 BA31 V02 V31 V02A03

Claims (2)

[Claims] 1. A metal chelate complex represented by the following formula (1). Embedded image However, M is ^{Pb 2+, Zr 4+, La 3+} , Ba 2+, a metal ion represented by Sr ²⁺ or Ca ^2+, x is the valence of the metal ion M, dmhd the following 2,6-dimethyl-3,5-heptanedione residue represented by the formula (2). Embedded image 2. After dissolving a lead compound, zirconium butoxide, a lanthanum compound, barium, strontium or calcium in an organic solvent, 2,6-dimethyl-3,5.
-A method for synthesizing a metal chelate complex, comprising adding heptanedione and heating to reflux.