JPH1036379A - Tantalum compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a tantalum compound being the specific one, having a high volatility, an excellent volatile stability and characteristics capable of stably and effectively forming a membrane and useful as a vapor deposition raw material for producing a ceramic thin film by a metal organic chemical vapor deposition method. SOLUTION: This tantalum compound is the new one of the formula [A is a group of the formula C(CH3 )3 or (CH2 )3 CH3 ; R is a group of the formula C(CH3 )3 or CH3 ]. The tantalum compound has a high volatility, an excellent volatile stability and is useful as a vapor deposition raw material, etc., for producing an oxide-based ceramic thin film containing the tantalum, a layered ceramic, etc., by a metal organic chemical vapor deposition (MOCVD method) capable of stably and effectively forming a film. The compound is obtained by, in an inert gas current, dissolving tantalum pentachloride in toluene, adding 4 equivalent amount of butanol based on the amount of the tantalum to the solution, further adding dipivaloylmethane, etc., to the solution with the added butanol and heating and refluxing the resultant solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel tantalum compound and, more particularly, to a metalorganic chemical vapor deposition method.
mical Vapor Deposition: Hereinafter referred to as “MOCVD method”. The present invention relates to a tantalum compound useful as a vapor deposition raw material for producing an oxide-based ceramic thin film or a layered ceramic containing tantalum.

[0002]

2. Description of the Related Art In recent years, the MOCVD method has been used as an effective means for producing oxide-based ceramic thin films or layered ceramics, and has been actively studied. For example, the production of a dielectric thin film is one example. In the production, a material having a high volatility and a stable supply amount is required as a deposition material for MOCVD.

[0003] Conventionally, tantalum compounds as a material for vapor deposition by the MOCVD method have been disclosed in JP-A-6-96.
No. 60, Ta (DPM) ₄ Cl (where DPM is a ligand from dipivaloylmethane) of a tantalum metal complex of β-diketonate and Ta represented by the following structural formula. (I-PrO) ₄ (DPM) is known.

[0004]

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In order to form a tantalum oxide thin film by MOCVD using such a deposition material, for example, as shown in a schematic explanatory view of FIG. 1, a substrate 6 is placed on a heater 7 provided in a reaction furnace 8. On the other hand, in a heating furnace 3 provided in connection with the reaction furnace 8, the vapor deposition raw material 1 made of the organic bismuth compound in the vaporization vessel 2 is vaporized. , N _{2 and the} like are fed into the reaction furnace 8 and diffused, and an oxidizing gas such as O ₂ , N ₂ O and ozone as a reaction gas is introduced into the reaction furnace 8 from the pipe 5 and heated. Tantalum oxide is deposited on the substrate 6. If the oxidizing gas is not introduced, tantalum will precipitate. In the drawing, reference numeral 9 denotes a vacuum pipe, and P denotes a pressure gauge. This method is called a thermal decomposition type MOCVD method.

[0006]

Generally, a β-diketonate tantalum metal complex reacts with moisture in the air to cause hydrolysis, and is also very easily deteriorated, for example, to be increased in quantity, and has poor storage stability. Chip. Such a phenomenon is particularly problematic at the time of film formation, and since a stable supply amount cannot be provided, a large variation occurs in the vaporization rate (that is, the film formation rate). Thus, variations in the vaporization rate cause problems such as impairing the uniformity of the formed film and making it difficult to control the composition.

[0007] Ta (DPM) ₄ Cl or Ta (i-PrO) ₄ conventionally provided as a vapor deposition material for MOCVD.
(DPM) also has the same drawbacks. In particular, since Ta (DPM) ₄ Cl described in Japanese Patent Application Laid-Open No. 6-9660 contains chlorine, there is a concern that it may cause problems such as corrosion of the apparatus and damage to the film quality.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a tantalum compound for forming a thin film by a MOCVD method which has high volatility, excellent vaporization stability, and enables stable and efficient film formation. I do.

[0009]

Means for Solving the Problems The tantalum compound of the present invention is represented by the following general formula [I].

[0010]

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(However, in the above formula [I], A is -C (CH
₃ ) ₃ or — (CH ₂ ) ₃ CH ₃ , wherein R is —C (C
H _{3) 3} or an -CH _3. The tantalum compound according to the present invention is capable of coordinating a t-butoxy group or an n-butoxy group which is bulkier than a ligand of a conventional β-diketonate tantalum metal complex, thereby forming molecules such as moisture in the air. It is possible to avoid a general attack, and the solid crystallinity is improved as compared with a conventional compound. For this reason, the tantalum compound of the present invention shows high volatility and vaporization stability in the monomer structure,
The method enables efficient film formation at a high film formation rate under good composition control.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The tantalum compound of the present invention has the following structural formula
[i] to [iv].

[0014]

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[0015]

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[0016]

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[0017]

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The tantalum compound of the present invention can be obtained by reacting tantalum pentachloride, t-butanol or n-butanol with dipivaloylmethane or acetylacetone, as will be described in Examples below. Can be synthesized by

The tantalum compound of the present invention can be prepared by the same operation as that of a conventional tantalum compound.
It can be used as a raw material for vapor deposition of a tantalum or tantalum oxide thin film by MOCVD such as CVD.

[0020]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 [Synthesis of Tantalum Compound] Under an inert gas stream, 355 g (1.0 mol) of tantalum pentachloride was dissolved in 500 ml of dehydrated and purified toluene. Next, 4 equivalents of n-butanol based on the amount of tantalum were added to this solution, and the mixture was vigorously stirred. Further, dipivaloyl methane (HD
After slowly adding 1.5 equivalents of PM) to the amount of tantalum, the mixture was refluxed for 48 hours. The reaction solution was distilled under reduced pressure (120 ° C., 2 Torr) to obtain a white residue. By recrystallizing this residue with toluene, the structural formula
The tantalum compound Ta (n-Bu) of the present invention represented by [i]
O) ₄ (DPM) was obtained in an amount of 320 g. The obtained tantalum compound was identified by elemental analysis by ICP-MS and IR, N
Performed by MR and MS.

Elemental analysis; actual values (%): C = 49.8, H = 8.40, O = 14.
8, Ta = 27.7 Calculated value (%): C = 49.4, H = 8.38, O = 14.
6, Ta = 27.6 IR (cm ^-1 ); 3400, 3000, 2980, 29
00, 2300, 1600, 1470, 1460, 13
80, 1360, 1300, 1250, 1240, 12
20, 1200, 1130, 1020, 920, 88
0,800,750 ¹ H-NMR; δ (ppm) 6.2 (CH), 1.3
(C (CH ₃ ) ₃ ), 1.1 (C (CH ₃ ) ₃ ) MS; m / e660 [Evaluation of vaporization characteristics] A thermogravimetric curve (temperature rise) was used to evaluate the vaporization characteristics of the obtained tantalum compound. Speed 10 ° C / min,
(Dry argon atmosphere) was obtained and the results are shown in FIG.

[Thin film formation test of tantalum oxide thin film] Using the obtained tantalum compound, a tantalum oxide thin film was formed by the apparatus shown in FIG. The thickness of each film was measured. The film thickness was measured from a cross-sectional SEM image of the film. The measurement results are shown in Table 1.

Substrate: 300 nm Pt sputtered film / 80
nm Ti sputtered film / 500 nm SiO ₂ thermal oxide film /
Si (100) Substrate temperature; 600 ° C. Vaporization temperature; 200 ° C. Pressure; 10 Torr Carrier gas Ar flow rate; 200 sccm Reactant gas O ₂ flow rate; 1000 sccm Ar: O ₂ ratio; volume ratio 1: 1 -The same procedure was repeated except that t-butanol was used in place of butanol to obtain the above-mentioned structural formula [ii].
The tantalum compound Ta (t-BuO) of the present invention represented by
₄ (DPM) was obtained. The identification results of this tantalum compound are as follows. 3 and Table 1 show the evaluation results of the vaporization characteristics and the film formation test results obtained in the same manner as in Example 1.

Elemental analysis; actual values (%): C = 48.9, H = 8.35, O = 14.
2, Ta = 27.2 Calculated value (%): C = 49.4, H = 8.38, O = 14.
6, Ta = 27.6 IR (cm ^-1 ); 3350, 2960, 2950, 28
80,2360,2300,1600,1460,13
80, 1360, 1300, 1250, 1220, 11
30, 1070, 1060, 950, 880, 850,
800, 750, 740 ¹ H-NMR; δ (ppm) 6.1 (CH), 1.1
5 (CH ₃ ), 1.5 (CH ₃ -CH ₂₎ , 2.3 (C
H2 ₎ , 3.8 (CH2 ₎ , 1.1 (C (CH3 _{) 3} ) MS; m / e 660 Example 3 In Example 1, acetylacetone (Hacac) was used in place of sibiparoylmethane. Except for the above, a tantalum compound Ta (n-BuO) ₄ (acac) of the present invention represented by the structural formula [iii] was obtained. The identification results of this tantalum compound are as follows. 4 and Table 1 show the evaluation results of the vaporization characteristics and the film formation test results obtained in the same manner as in Example 1.

Elemental analysis; actual values (%): C = 43.9, H = 7.55, O = 16.
5, Ta = 31.3 Calculated value (%): C = 44.1, H = 7.52, O = 16.
8, Ta = 31.6 IR (cm ^-1 ); 3350, 3050, 2950, 29
40, 2880, 2370, 2350, 1700, 16
30, 1465, 1460, 1420, 1380, 13
60, 1250, 1160, 1118, 1070, 10
40, 1025, 1000, 990, 950, 920,
850, 798, 780, 640 ¹ H-NMR; δ (ppm) 5.7 (CH), 1.1
8 (CH ₃ ), 1.3 (CH ₃ -CH ₂₎ , 2.1 (C
H / ₎ 3.5 (CH2 ₎ , 1.2 (-CH3 ₎ MS; m / e577 Example 4 In Example 3, except that t-butanol was used instead of n-butanol. Performed, the structural formula [iv]
The tantalum compound Ta (t-BuO) of the present invention represented by
₄ (acac) was obtained. The identification results of this tantalum compound are as follows. 5 and Table 1 show the evaluation results of the vaporization characteristics and the film formation test results obtained in the same manner as in Example 1.
Shown in

Elemental analysis; actual values (%): C = 44.0, H = 7.54, O = 16.8
2, Ta = 31.5 Calculated value (%): C = 44.1, H = 7.52, O = 16.
8, Ta = 31.6 IR (cm ^-1 ); 3360, 3050, 2970, 28
80, 1700, 1630, 1470, 1420, 13
80, 1365, 1250, 1240, 1200, 11
60,1023,1000,950,920,795
780, 750, 640 ¹ H-NMR; δ (ppm) 5.9 (CH), 1.4
(CH ₃ ), 1.1 (C (CH _{3) 3)} MS; m / e577 Comparative Example 1 In Example 1, diviparoylmethane was added in an amount of 4 equivalents to the amount of tantalum without using n-butanol. Except for this, the same procedure is performed to obtain the conventional tantalum Ta (DPM ₄ ) Cl.
I got With respect to this tantalum compound, the evaluation results of the vaporization characteristics and the film formation test results obtained in the same manner as in Example 1 are shown in FIG.

Comparative Example 2 A conventional tantalum Ta (i-PrO) ₄ (DPM) was obtained in the same manner as in Example 1 except that t-propyl alcohol was used instead of n-butanol. With respect to this tantalum compound, the evaluation results of the vaporization characteristics and the film formation test results obtained in the same manner as in Example 1 are shown in FIG.

[0029]

[Table 1]

The following is clear from the results shown in FIGS. That is, the tantalum compound of the present invention can be completely vaporized at a temperature from room temperature to about 430 ° C., whereas the conventional tantalum compound has a
About 5% of the residue is formed. From this, it is clear that the tantalum compound of the present invention has excellent vaporization stability.

The following is evident from Table 1. That is, in the tantalum compound of the present invention, the film thickness increases at a substantially constant rate with respect to the film formation time, and the film formation rate is higher than that of the conventional tantalum compound, whereas the case of the conventional tantalum compound is In the method, the rate of increase in the film thickness is not constant, and the film formation amount is small.

[0032]

As described in detail above, the tantalum compound of the present invention exhibits excellent volatility and a stable vaporization rate. Therefore, according to the tantalum compound of the present invention, the tantalum oxide-based ceramic thin film obtained by MOCVD is used. In film formation such as
Under good composition control, efficient film formation can be performed at a high film formation rate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an apparatus for explaining a thermal decomposition type MOCVD method.

FIG. 2 shows a tantalum compound of the present invention: Ta (n-BuO).
₄ is a graph showing a thermogravimetric curve of (DPM).

FIG. 3 shows a tantalum compound of the present invention: Ta (t-BuO).
₄ is a graph showing a thermogravimetric curve of (DPM).

FIG. 4 is a tantalum compound of the present invention: Ta (n-BuO).
₄ is a graph showing a thermogravimetric curve of (acac).

FIG. 5: Tantalum compound of the present invention: Ta (t-BuO)
₄ is a graph showing a thermogravimetric curve of (acac).

FIG. 6: Conventional tantalum compound: Ta (DPM) ₄ Cl
3 is a graph showing a thermogravimetric curve of the sample.

FIG. 7: Conventional tantalum compound: Ta (i-PrO) ₄
It is a graph which shows a thermogravimetric curve of (DPM).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Deposition raw material 2 Vaporization container 3 Heating furnace 4 Carrier gas introduction pipe 5 Reaction gas introduction pipe 6 Substrate 7 Heater 8 Reaction furnace 9 Vacuum piping

Claims (2)

[Claims] 1. A tantalum compound represented by the following general formula [I]. Embedded image (However, in the above formula [I], A is -C (CH ₃ ) ₃ or-
(CH ₂₎ shows a ₃ CH _3, R represents a -C (CH _{3) 3} or -CH _3. ) 2. The tantalum compound according to claim 1, which is a deposition material for forming a thin film by metal organic chemical vapor deposition.