JP2822946B2 - High purity Ti complex, method for producing the same, and liquid composition for forming BST film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a T film useful as a dielectric film, a semiconductor film, an optical thin film, a surface enhancement film, a thin film catalyst and the like.
A metal oxide thin film containing i is deposited by chemical vapor deposition (CVD).
The present invention relates to a high-purity Ti complex suitable as a raw material for forming by the method, a method for producing the same, and a liquid composition for forming a BST film.

[0002]

2. Description of the Related Art Conventionally, various metal alkoxide compounds and TiDPM (herein referred to as "strontium titanate, barium strontium titanate (BST), lead zirconate titanate, etc.) "DPM" is dipivaloylmethane: (CH
_{3) 3 -C-CO-CH} 2 -CO-C- (CH 3) shows a _3. ) Complexes are used together with alkoxide compounds such as Ba, Sr and Zr and DPM complexes.

[0003] Among these CVD raw materials, the TiDPM complex is described in Japanese Patent Application Laid-Open No. 5-271253 as "High purity titanium complex and method for producing the same".
₂ (R2) ₂ (R1 is a β-diketone such as acetylacetone, 3,5-heptanedione, dipivaloylmethane, R
2 is methoxy, ethoxy, isopropoxy (hereinafter "O-
i-Pr ". ), Normal propoxy, normal butoxy and the like) and a method for producing the same. Incidentally, the TiDPM disclosed as a specific example in Japanese Patent Application Laid-Open No. 5-271253 is disclosed.
The complex is only Ti (Oi-Pr) ₂ (DPM) ₂ .

[0004]

SUMMARY OF THE INVENTION BST by CVD
Ba (DPM) ₂ , Sr (DP
When Ti (Oi-Pr) ₂ (DPM) ₂ is used together with M) ₂ , the thermal decomposition temperature of Ba (DPM) ₂ and Sr (DPM) ₂ is 350 to 410 ° C. and Ti (O− i-P
r) ₂ (DPM) _{2 has} a thermal decomposition temperature of 270 ° C. (255 to
290 ° C.), so that Ti (O—
The decomposition reaction of i-Pr) ₂ (DPM) ₂ easily proceeds, and the probability of adsorption of the gas phase decomposition species to the substrate increases. For this reason, there is a disadvantage that the step coverage at the time of film formation on a substrate having irregularities on the surface is deteriorated.

[0005] A normal butoxy group (O-
Ti (On-Bu) ₂ (DP with n-Bu) introduced
M) _{2 is} also known, but the pyrolysis temperature of this material is 28
Only a slight improvement of 0 ° C. (260 ° C. to 310 ° C.) is observed, but no improvement in step coverage at the time of film formation on the uneven substrate by the thermal CVD method is observed.

Further, TiCl is used as a material having good thermal stability.
₂ (DPM) ₂ (pyrolysis temperature 330 ° C (320-340)
° C.)) are also known, but this one, in the molecules chloride ion (Cl - because it contains ^a), when used as a raw material for BST film, taken the chlorine in the film as impurities There is a problem that will be.

In forming a metal oxide film having a composite composition, as a method of supplying a CVD raw material, a solution in which a metal compound as a raw material is dissolved in an organic solvent is supplied in a liquid state to a vaporizer, and the solvent is supplied to the vaporizer. Together with heating and vaporization, and as a gas CV
A method of supplying the film to a D film formation chamber is known. In this method, a conventional Ti compound, Ti (Oi-Pr)
₂ (DPM) ₂ , Ti (On-Bu) ₂ (DPM) ₂
Easily reacts with Ba (DPM) ₂ and Sr (DPM) ₂ in a solution to form a complex having a large molecular weight,
There is a problem that the vaporization characteristics are deteriorated. Further, in this method, if an OH group is contained as an impurity in the Ti compound, Ba (DPM) ₂ and Sr (DPM) ₂ have extremely high reaction activity with respect to the OH group, so that the Ti compound reacts with the OH group. As a result, the vaporization characteristics deteriorate, causing an increase in the amount of residues inside the vaporizer, an increase in the amount of decomposition products deposited on gas pipes, showerheads, and the like, and a problem that it becomes difficult to control the composition of the film. .

The present invention solves the above-mentioned conventional problems and has no problem due to impurities due to remarkably high purity. Further, there is no problem of deterioration of vaporization characteristics due to the formation of the complex, and
A high-purity Ti complex having a high thermal decomposition temperature and no problem of lowering step coverage due to gas-phase decomposition, and a method for producing the same; and
An object of the present invention is to provide a liquid composition for forming a BST film using the high-purity Ti complex.

[0009]

Means for Solving the Problems The high purity Ti complex of the present invention is a high purity Ti complex represented by the following structural formula (I).

[0010]

Embedded image

The cis-Ti represented by the structural formula (I)
(Ot-Bu) ₂ (DPM) ₂ has a thermal decomposition temperature of 31.
5 ° C. (300-340 ° C.) and conventional Ti (OiP
r) ₂ (DPM) ₂ or Ti (On-Bu) ₂ (DP
M) ₂ higher than Ba (DPM) ₂ or Sr (DPM)
Thermal decomposition temperature almost equivalent to ₂ . Therefore, adsorption of the gas phase decomposition species to the substrate is reduced, and the step coverage is improved.

Moreover, cis-Ti (Ot-Bu) ₂
Since (DPM) ₂ can be purified to a high purity with an OH group content of 0.1% by weight or less and a chlorine content of 5 ppm or less, there is no problem of impurity contamination, and a high-purity Ti oxide thin film can be formed. it can.

Also, cis-Ti (Ot-Bu) ₂
(DPM) ₂ is Ti (Oi-Pr) ₂ (DPM) ₂
Reaction with Ba (DPM) ₂ and Sr (DPM) _{2 in} a solution because it has a bulky alkoxy group (Ot-Bu) as compared with Ti (On-Bu) ₂ (DPM) _2. Is suppressed, the problem that the reaction of the Ti compound with the Ba and Sr compounds forms a complex having a large molecular weight and the vaporization characteristics are deteriorated is solved.

The high-purity Ti complex of the present invention is obtained by dissolving tetra-tert-butoxytitanium in an organic solvent, adding dipivaloylmethane, and heating and refluxing at 100 ° C. or higher to remove residual moisture and OH groups. Can be easily produced by the method for producing a high-purity Ti complex of the present invention, in which crystallization is removed while azeotropic removal is performed to obtain crystals.

In this method, the content of impurities such as OH groups and residual chlorine in the high-purity Ti complex can be remarkably reduced by purifying the obtained crystals with an aprotic solvent.

The liquid composition for forming a BST film of the present invention comprises the high purity Ti complex of the present invention and a bis (dipivaloylmethanato) barium complex (Ba (DPM) ₂ ) and / or bis (dipi (Balloylmethanato) strontium complex (Sr (DPM) ₂ ) dissolved in an organic solvent.

In the liquid composition for forming a BST film of the present invention, the high purity Ti complex used as the Ti
Since it has a very low purity of the H group content and is extremely high in purity and does not have the above-mentioned problem of complex formation, Ba (DPM)
₂ , in combination with a raw material that is reactive to OH groups, such as Sr (DPM) ₂ , does not impair the vaporization characteristics, and therefore increases the residue inside the vaporizer, gas piping, showerhead Thus, a BST film having a desired composition can be efficiently formed without causing a problem such as an increase in the amount of decomposition products deposited on the BST film.

In the liquid composition for forming a BST film of the present invention, one or more organic solvents selected from the group consisting of pyridine, lutidine and tetrahydrofuran are preferred.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The high-purity Ti complex of the present invention has a single T complex as estimated from the analysis results of Example 1 described later.
For the i atom, two oxygens of the carbonyl group of dipivaloylmethane and two tertiary butoxy groups are ci.
cis- (bis (dipivaloylmethanite) di (tertiary butoxy) titanium complex cis-Ti (Ot-Bu) ₂ (DPM) ₂ having a structure bonded at the s position.

In order to produce the high-purity Ti complex of the present invention, first, as shown in Example 1 below, tetratertiary butoxytitanium Ti (Ot-Bu) ₄ is used as a starting material. This is added to an organic solvent such as an aromatic hydrocarbon such as toluene, xylene or mesitylene, or an aliphatic hydrocarbon such as pentane or normal hexane.
Dissolves to a concentration by weight of Ti (Ot-Bu)
₄ added 2.0 to 2.5 times the molar amount of dipivaloylmethane HDPM respect, 10-5 than the boiling point of the organic solvent used
By heating and refluxing at a temperature of 100 ° C. or higher at a temperature of an oil bath higher by 0 ° C., residual moisture and OH groups are removed by azeotropic distillation, and concentrated to obtain crystals.

The crystals are recrystallized using an aprotic anhydrous organic solvent such as toluene, xylene and mesitylene, and then repeatedly purified by sublimation of the solvent under reduced pressure to give an OH group content of 0.1% by weight. % Or less and the residual chlorine content is 5 ppm or less.
u) ₂ (DPM) ₂ can be obtained.

In the high purity Ti complex of the present invention, cis
If the OH group content of —Ti (Ot-Bu) ₂ (DPM) ₂ exceeds 0.1% by weight, Ba (DPM) ₂ or Sr
(DPM) When a liquid composition for forming a composite metal oxide film is used together with other raw materials having a high reaction activity against OH groups such as ₂ or the like, the vaporization characteristics are deteriorated, the residue inside the vaporizer increases, and This causes an increase in the amount of decomposition products deposited on pipes, showerheads, and the like, and a shift in film composition.

If the residual chlorine content exceeds 5 ppm, the purity of the obtained Ti oxide film is impaired.

Therefore, the high-purity Ti complex of the present invention is
Group content is less than 0.1% by weight, chlorine content is 5ppm
The following is preferred.

The liquid composition for forming a BST film of the present invention comprises the [TiO (DPM) ₂ ] _{2 of the} present invention and Ba (D
PM) ₂ and / or Sr (DPM) ₂ are dissolved in an organic solvent so as to have a desired film composition.

Here, as the organic solvent, it is preferable to use one or more selected from the group consisting of pyridine, lutidine and tetrahydrofuran (THF).
[TiO (DPM) ₂ ] ₂ and Ba (DPM) ₂ and / or Sr (DPM) ₂ are preferably dissolved in such an organic solvent so that the total concentration thereof is 1 to 20% by weight. .

The high-purity Ti complex of the present invention can be used as it is in a solid state as a raw material for CVD according to a conventional method, or, if necessary, dissolved in an organic solvent together with another metal compound as necessary. It can be used as a CVD raw material in the same manner as in the prior art.

[0028]

【Example】

Example 1 High Purity cis-Ti (Ot-Bu) ₂ (D
Synthesis of PM) _{2 To} a solution of Ti (Ot-Bu) ₄ in toluene (concentration of 30% by weight) was added twice as much HD as Ti (Ot-Bu) ₄ .
PM is added and the solution is brought to an oil bath temperature of 130-15.
The mixture was heated and refluxed at 0 ° C. to remove residual moisture and OH groups by azeotropic distillation, and then concentrated to obtain white crystals. After recrystallizing these crystals with toluene, sublimation purification was performed at 190 ° C. under reduced pressure.

The obtained crystals were identified by ¹ H-NMR (C
_{6 D 6 + d-THF)} , mass spectrometry, was carried out by elemental analysis. The results are as follows.

¹ H-NMR: δ: 1.1092 (9H, C (C
_{H 3) 3, DPM),} 1.2682 (9H, OC (CH 3) 3),
1.4056 (9H, C (CH ₃ ) ₃ , DPM) Elemental analysis: (calculated values) Ti = 8.54%, C = 64.27%, H = 10.07%, O = 1
7.12%, Cl = 0% (actual value) Ti = 8.59%, C = 64.21%, H = 10.05%, O = 17.15%, Cl <1
ppm mass spectrometry: As shown in FIG. 1, a molecular ion peak of M / Z560 is confirmed.

From the above analysis results, the obtained cis-T
As a structural formula of i (Ot-Bu) ₂ (DPM) ₂ ,
The following structure is presumed.

[0032]

Embedded image

The obtained cis-Ti (OtB)
According to elemental analysis of u) ₂ (DPM) ₂ crystal, the residual Cl content was <1 ppm, and the OH group was <
It was confirmed to be 0.1% by weight.

The cis-Ti (Ot-Bu) ₂ (D
PM) _Two crystals were heated under an Ar gas flow at a temperature rising rate of 10 ° C. /
When TG analysis was carried out at MIN, the cis-Ti (Ot-Bu) ₂ (DPM) ₂ was 1 as shown in FIG.
It was confirmed that vaporization was started at 75 ° C and 100% vaporized at 280 ° C.

The cis-Ti (Ot-Bu)
₂ (DPM) The ₂ crystal was sealed in an Al container, and DTA analysis was performed at a heating rate of 10 ° C./min under an Ar gas flow. The thermal decomposition temperature was found to be 315 ° C. (300 to 340 ° C.). confirmed.

Example 2: CVD film forming test In Example 1, by using Ti (Ot-Bu) ₄ containing 5 ppm to 300 ppm of chlorine as a raw material, the residual chlorine amounts were 4 ppm, 6 ppm, and 6 ppm, respectively.
50 ppm, 200 ppm of cis-Ti (Ot-B
u) ₂ (DPM) ₂ crystals, and these cis-Ti
(Ot-Bu) ₂ (DPM) ₂ crystals and the cis-Ti (O-
t-Bu) ₂ (DPM) ₂ crystal is used as a Ti raw material, respectively, and Ba (DPM) ₂ and Sr (DP
M) ₂ in combination with BST under the following film-forming conditions by the CVD method.
A (Ba _0.7 Sr _0.3 Ti _0.1 ) film was formed.

Film formation conditions CVD apparatus: substrate heating type CVD apparatus Reactive gas: O ₂ carrier gas: Ar vaporization temperature: cis-Ti (Ot-Bu) ₂ (DPM) ₂ = 160
Ba (DPM) ₂ = 200 ° C. Sr (DPM) ₂ = 190 ° C. Deposition pressure: 2.0 torr Substrate: Pt / Ti electrode Substrate temperature: 600 ° C. Thickness: 1000 ° Au on the obtained BST film Electrodes were deposited, and the electrical characteristics were evaluated. The results are shown in Table 1.

[0038]

[Table 1]

Example 3: Test for CVD step coverage Ti (OiP) described in JP-A-5-271253
r) ₂ (DPM) ₂ and Ti (On-Bu) ₂ (DP
M) ₂ and the high-purity cis-Ti (O
-T-Bu) ₂ (DPM) by using the _2, each performs deposition of the TiO ₂ film under the following conditions by a thermal CVD method on the trench substrate 1 cross-sectional shape shown in FIG. 5, CVD-TiO ₂ film The step coverage was evaluated by the ratio a / b of the film thickness a to the film thickness b of No. 2 (the closer the a / b was to 1, the better the step coverage). The results are shown in Table 2. Was.

Film formation conditions Vaporization temperature: cis-Ti (Ot-Bu) ₂ (DPM) ₂ = 160
° C Ti (Oi-Pr) ₂ (DPM) ₂ = 140 ° C Ti (On-Bu) ₂ (DPM) ₂ = 180 ° C Deposition pressure: 2.0 torr Substrate temperature: 600 ° C —I-Pr) ₂ (DPM) ₂ and Ti
TG analysis and DTA analysis were performed on (On-Bu) ₂ (DPM) _{2 in the} same manner as in Example 1, respectively.
The results are shown in FIGS.

[0041]

[Table 2]

Example 4: Evaluation of vaporization characteristics of BST solution In Example 1, benzene was used as a solvent, and the mixture was heated at a temperature of 100 ° C. or 80 ° C. and concentrated under reduced pressure, so that the OH group was 0.2% by weight and 0%. C present at 0.8% or 2% by weight
Each is-Ti (Ot-Bu) ₂ (DPM) ₂ crystal was produced. These cis-Ti (Ot-Bu) ₂
(DPM) ₂ crystals and the high-purity cis-Ti (Ot-Bu) ₂ obtained in Example 1 with an amount of <0.1% OH groups
(DPM) ₂ and Ba (DPM) ₂ and Sr, respectively.
(DPM) ₂ and the anhydrous solvent shown in Table 3 together with Ba: S
The solution dissolved at a composition ratio (molar ratio) of r: Ti = 0.5: 0.5: 1 was concentrated under reduced pressure, and the vaporization characteristics of the precipitated solid were evaluated by TG analysis under Ar. It was shown to.

[0043]

[Table 3]

Example 5: Evaluation of vaporization characteristics of BST solution In Example 5, the amount of OH groups was <0.1% of cis-
Ti (Ot-Bu) ₂ (DPM) ₂ and Ti (On
-Bu) ₂ (DPM) ₂ and Ba (DP
Bs: S in anhydrous solvent with M) ₂ and Sr (DPM) ₂
TG analysis was similarly performed on the solution dissolved at a composition ratio (molar ratio) of r: Ti = 0.7: 0.3: 1, and the results are shown in Table 4.

[0045]

[Table 4]

[0046]

As described in detail above, the high purity Ti of the present invention
The complex has a high thermal decomposition temperature, can significantly reduce the content of impurities such as OH groups and residual chlorine, and has Ba (D
Since there is no problem of complex formation with PM) ₂ , Sr (DPM) _2, etc., adsorption of the gas phase decomposed species to the substrate by decomposition of the Ti complex in the gas phase during CVD film formation is reduced. Good step coverage at the time of film formation. High-purity Ti with no impurity contamination and excellent electrical properties
An oxide film can be formed. There is no problem of complexation of Ba (DPM) ₂ , Sr (DPM) _2, etc., and in combination with raw materials having a high activity for reacting to OH groups, the vaporization characteristics of these raw materials are not impaired. It is possible to easily control the film composition without causing an increase in residues inside the vessel and an increase in the amount of decomposition products deposited on gas pipes, shower heads, etc., and to obtain a Ti-containing metal composite oxide film having a desired composition. Can be formed.

The above-described effects are obtained. Therefore, by using the high-purity Ti complex of the present invention as a raw material for forming a BST film by a CVD method or the like, it is possible to form a dielectric thin film of a memory device having a fine and complicated structure required after 1G. Becomes possible.

According to the high-purity Ti complex of the second aspect, the above effects can be reliably obtained.

Such a high-purity Ti complex of the present invention is easily produced by the method for producing a high-purity Ti complex of the present invention.

According to the method of the fourth aspect, a high-purity Ti complex having an extremely small impurity content can be produced.

According to the liquid composition for forming a BST film according to claim 5, Ti and B can be added to the same organic solvent without impairing the vaporization characteristics.
a, a solution in which the Sr raw material is dissolved can be prepared, and this solution is supplied to a vaporizer, heated and vaporized together with a solvent in the vaporizer, and is stably adapted to a CVD raw material supply method of supplying a gas to a CVD film forming chamber. it can.

[Brief description of the drawings]

FIG. 1 shows cis-Ti (OtB) produced in Example 1.
7 is a graph showing mass analysis results of u) ₂ (DPM) ₂ crystal.

FIG. 2 shows cis-Ti (OtB) produced in Example 1.
9 is a graph showing a TG analysis result of u) ₂ (DPM) ₂ crystal.

FIG. 3 is a graph showing a TG analysis result of Ti (Oi-Pr) ₂ (DPM) ₂ .

FIG. 4 is a graph showing a TG analysis result of Ti (On-Bu) ₂ (DPM) ₂ .

FIG. 5 is a cross-sectional view illustrating a step coverage evaluation method of Example 3.

[Explanation of symbols]

1 trench substrate 2 CVD-TiO ₂ film

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Katsumi Ogi 1-297 Kitabukuro-cho, Omiya-shi, Saitama Mitsui Materials Co., Ltd. (56) References JP-A-5-271253 (JP, A) JP-A-2-57387 (JP, A) JP-A-6-101049 (JP, A) JP-A-7-169648 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C07F 7 / 28 C23C 16/40 CA (STN) REGISTRY (STN) WPIDS (STN)

Claims (6)

(57) [Claims] 1. High purity Ti represented by the following structural formula (I)
Complex. Embedded image 2. The high purity Ti complex according to claim 1, wherein the OH group content is 0.1% by weight or less and the chlorine content is 5 ppm or less. 3. Titanium tert-butoxytitanium is dissolved in an organic solvent, and dipivaloylmethane is added to the solution.
2. The method for producing a high-purity Ti complex according to claim 1, wherein the mixture is heated and refluxed at a temperature of 00 ° C. or higher to remove residual moisture and OH groups by azeotropic distillation and concentrated to obtain crystals. 4. The high purity Ti complex according to claim 3, wherein the obtained crystals are purified with an aprotic solvent. 5. The high purity Ti complex according to claim 1 or 2 and a bis (dipivaloylmethanato) barium complex (Ba (DP
A liquid composition for forming a BST film obtained by dissolving M) ₂ ) and / or a bis (dipivaloylmethanato) strontium complex (Sr (DPM) ₂ ) in an organic solvent. 6. The BST according to claim 5, wherein the organic solvent is one or more selected from the group consisting of pyridine, lutidine and tetrahydrofuran.
Liquid composition for film formation.