JP3383330B2 - Method for producing metal composite oxide film - Google Patents

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 metal composite oxide film such as an oxide-based superconductor or a dielectric by a chemical vapor deposition method (hereinafter abbreviated as a CVD method), and more specifically. Relates to a method for producing a metal composite oxide film, in which only a high-purity β-diketonate metal complex of the metal is used as a raw material of all metal species forming the metal composite oxide film.

[0002]

2. Description of the Related Art In recent years, the CVD method has come to be used as a promising means for producing oxide-based ceramic thin films or layered ceramics, and its research has been actively conducted. For example, the CVD method is also used in the production of oxide-based superconductors such as YBa ₂ Cu ₃ O _x and ferroelectric thin films such as PbLaZrTiO _y (PLZT), or in the production process of integrated circuits such as LSI and optical ICs. ing. As the vapor phase source, an alkyl compound of a metal element (for example, Pb (C
₂ H ₅ ) ₄ ) and alkoxide compounds (for example, Zr (iO)
C ₃ H ₇ ) ₄ ) or β-diketone (R ₁ -CO
A metal complex such as —CH ₂ —CO—R ₂ ) is used.

The metal complex of β-diketone has good volatility, and its bond is weak due to a coordinate bond, so that it is also excellent in reactivity and is suitable as a vapor phase source for the CVD method. Such β
-For the usefulness of the diketonate metal complex as a raw material for the CVD method, see T.OZAWA (Thermokimika
Actor (Thermochimica Acta), Volume 174 (1991)
Year) has analyzed in detail.

However, metal complexes of β-diketones are generally deteriorated under the influence of moisture and carbon dioxide gas in the air, are easily deteriorated, and it is difficult to obtain a highly pure product. For example, dipivaloyl methane ((CH ₃ ) ₃
CCOCH ₂ COC (CH ₃ ) ₃ , hereinafter abbreviated as DPM) is a typical β-diketone, but its metal complex Ba (DPM) ₂ and Sr (DPM) ₂ have different purities depending on the production method. Furthermore, it is extremely sensitive to the manufacturing conditions or environment during synthesis. For example, as a typical production method thereof, a method is known in which a basic reaction promoter such as ammonia or sodium hydroxide is added dropwise to a β-diketone in an aqueous chloride solution of Ba or Sr. However, in this method, it is difficult to dehydrate in the process because it passes through an aqueous solution, and a complex of high purity cannot be obtained due to the influence of water. In addition, the water remaining in the complex may cause deterioration or deterioration of the complex during storage. This is also shown in thermogravimetric analysis as shown in FIG. As shown by the curve in FIG. 1, weight reduction (impurity vaporization amount) due to vaporization of impurities in the low temperature region is observed, or residual vaporization amount is recognized after chelate vaporization. Also,
The chelate evaporation curve also shows a step like a curve, and it may be recognized that it is not a single substance.

In order to obtain a highly pure β-diketonate metal complex, it is necessary to synthesize it in a water-free environment. Japanese Patent Application No. 4-55693 already proposed by the present inventors.
According to the publication, alkaline earth metals and β- in anhydrous organic solvents
By directly reacting with a diketone (anhydrous direct synthesis method), a highly pure β-diketonate complex of an alkaline earth metal can be obtained. According to this method, as shown by the curve in FIG. 1, neither the amount of vaporized impurities nor the residual amount of evaporation is recognized, and the chelate evaporation becomes a one-step curve, so that a complex having substantially 100% purity can be obtained. Conventionally, oxide-based superconductors (YBa ₂ C
It was difficult to prepare u ₃ O _x ) by the CVD method using the β-diketonate metal complex as a raw material, but it became possible by using the complex obtained by such an anhydrous direct synthesis method.

By the way, the CVD method has also been actively studied recently as a method for forming a ferroelectric thin film. Lead-containing perovskite-based PbTiO ₃ , Pb (Zr, Ti) O
₃ (hereinafter abbreviated as PZT), (Pb, La) (Z
A metal composite oxide film such as r, Ti) O ₃ (hereinafter abbreviated as PLZT) is expected to be applied to a capacitor material of a DRAM of an integrated circuit, a non-volatile memory, an infrared sensor and the like. Then, the CVD method is adopted as a method for producing these thin films. The recent research status is described in detail in Chapter 3 (p.115) of "Ferroelectric thin film integration technology" published by Science Forum Co., Ltd. (supervised by Tadashi Shiozaki). According to it, as a gas phase source, in addition to a β-diketonate metal complex such as Pb (DPM) ₂ , Pb (C ₂ H _2
5) alkyl compounds, such as ₄ or _{Ti (i-O-C 3} H
Alkoxide compounds such as ₇ ) are also used.

[0007]

However, regarding the evaluation of the film-forming property of these raw materials, in most cases, β-diketonate complexes such as DPM are highly evaluated.
No clear conclusion has been reached. The main reason for this is probably that high-purity metal β-diketonate complexes constituting these lead-containing perovskite thin films cannot be easily obtained at present. In the film formation of a metal composite oxide thin film by the CVD method, the purity of raw materials greatly contributes to the film forming property. Therefore, it is considered that the evaluation of the influence of the difference in the organic group of the organic metal on the film-forming property even for the same metal depends on the future research results of the high-purity raw material.

In addition to the good volatility and reactivity of the β-diketonate complex system, the toxicity of alkyl lead is taken into consideration.
With regard to lead, it is preferable to use Pb (DPM) ₂ as the gas phase source. Considering the uniformity of the film due to the increase in the area of the substrate, it is desirable to use raw materials having the same reaction rate and diffusion rate. From this, it has been desired to use the β-diketonate complex-based raw materials for other Ti, Zr, and La in addition to Pb (DPM) ₂ in the film formation of the lead-containing perovskite-based ferroelectric. . However, under the present circumstances, it is not always easy to obtain a high-purity complex thereof, so that CV of PZT or PZLT is not easily obtained.
In the film formation by the D method, there has been no example of using β-diketone-based raw materials for all the constituent elements so far.

[0009]

The present invention is characterized by using a β-diketonate metal complex having a purity of 99.0% or more as a vapor phase source in a method for forming a metal composite oxide film by a CVD method. Each with a purity of 9
9.0% or more of Pb (DPM) ₂ , Zr (DPM) ₄ ,
Gas and _Ti a _{(DPM) 2 (O-i} -C 3 H 7) 2
Used as _{Aiminamoto, Pb (Zr X Ti 1-} X) O 3 film form
A method for producing a metal complex oxide film,
And Pb (DPM) each having a purity of 99.0% or more
₂ , Zr (DPM) ₄ , Ti (DPM) ₂ (O-i-C)
₃ H ₇ ) ₂ and La (DPM) ₃ as a gas phase source
Using a Pb _1-X La _X (Zr _1-Y Ti _Y ) O ₃ film.
Method of producing metal composite oxide film characterized by forming
I will provide a.

[0010]

EXAMPLES Hereinafter, dipivaloylmethane will be mentioned as a typical example of β-diketone, and P will be mentioned as an example of a metal composite oxide film.
The present invention will be described in detail with reference to ZT films and PLZT films.

The β-diketonate metal complex raw material having a purity of 99.0% or more used as a gas phase source in the present invention can be synthesized by the following method already proposed by the present inventors. Regarding Pb, according to Japanese Patent Application No. 4-67440, a highly pure dipivaloylmethane (DPM) complex: Pb (DPM) ₂ can be obtained.
That is, in a dehydrated organic solvent, in the presence of a basic reaction accelerator, lead acetate is reacted with β-diketone, and the obtained product is purified by a recrystallization method in an organic solvent, A complex having a purity of 99.5% or more is obtained. β-
When dipivaloyl methane (DPM) is used as a diketone,
Pb (DPM) ₂ of substantially 100% purity is obtained.

Regarding Zr, according to Japanese Patent Application No. 4-1008, a high-purity Zr complex is prepared by reacting a chloride of Zr with a β-diketone in an organic solvent under an inert gas atmosphere. Is obtained. When dipivaloylmethane (DPM) is used for β-diketone, the purity is substantially 100%.
Zr (DPM) _{4 of} is obtained.

Regarding Ti, according to Japanese Patent Application No. 4-67441, a high-purity dipivaloylmethane (DPM) complex; Ti (DPM) ₂ (Oi-C ₃ H ₇ ) ₂ is obtained. To be That is, by directly reacting tetraalkoxy titanium and β-diketone in a dehydrated organic solvent, Ti (DPM) ₂ (O- having a purity of substantially 100% is obtained.
i-C ₃ H _{7) 2} is obtained.

Regarding La, Japanese Patent Application No. 4-227581
According to the publication, an anhydrous salt of La and a β-diketone are reacted in an anhydrous organic solvent with a basic reaction accelerator, washed with pure water, and vacuum dried to obtain a purity of 99.0%.
The above La complex is obtained. When dipivaloylmethane was used as the β-diketone, La with substantially 100% purity was obtained.
(DPM) ₃ is obtained.

Further, in the present invention, the film formation by the CVD method can be carried out by using an ordinary CVD apparatus. FIG. 3 shows an example of a CVD apparatus. In the figure, reference numeral 1 is a thermostat, 2 is a flow controller, 3 is a raw material container, 4 is a heater, and 5 is an R.I. F-coil, 6 is a chamber, 7 is a filter, 8 is a pump, 9 is an adsorption gas processing apparatus, and 10 is a substrate. In the apparatus of this example, the β-diketonate metal complex serving as the gas phase source is used as the raw material containers 3 and 3, respectively.
Enclosed in ... The raw material containers 3, 3, ... Are heated to a predetermined temperature, and the .beta.-diketonate metal complex inside is vaporized. The vaporized vapor of the β-diketonate metal complex is entrained in the Ar carrier gas introduced through the flow rate controllers 2, 2 ...
Is supplied to. On the other hand, oxygen gas is β-
The diketonate metal complex vapor is introduced into the pipe and is supplied into the chamber 6 together with these vapors. Further, in order to prevent the vapor of the β-diketonate metal complex from condensing,
The piping part is kept warm by the constant temperature bath 1, and the front part of the chamber 6 is kept warm by the heater 4. A substrate 10 is arranged in the chamber 6, and the substrate 10 is an R.V. It is adapted to be heated by the F coil 5. Further, the inside of the chamber 6 is exhausted by the pumps 8 and 8 through the filter 7 and is kept at a predetermined pressure.
Further, an adsorption type gas treatment device 9 is provided after the pumps 8, 8. Then, the substrate 10 is heated to a predetermined temperature, and the source gas and oxygen are introduced into the chamber 6, so that the metal complex oxide film is formed on the substrate 10.

As a raw material synthesis example, a synthesis example of a β-diketonate metal complex will be described below. (Raw material synthesis example 1) Synthesis of Pb (DPM) ₂ ; anhydrous methanol 680 ml
Into, was dissolved 136 g of DPM and 29.5 g of NaOH. On the other hand, 140 g of lead acetate trihydrate was dissolved in anhydrous methanol. These solutions were then mixed at room temperature to give a white precipitate. The precipitate was filtered off, recrystallized in anhydrous methanol, and vacuum dried at 60 ° C. for 1 hour. The result of thermogravimetric analysis of the obtained Pb (DPM) ₂ is shown in FIG.
Shown in. The amount of evaporated chelate was 100.0%, and it was substantially 100% pure Pb (DPM) ₂ .

(Synthesis Example 2 of raw material) Synthesis of Zr (DPM) ₄ ; 500 ml of anhydrous methanol was placed in a three-necked flask substituted with nitrogen gas, and DP was added thereto.
M136g was dissolved. On the other hand, zirconium chloride (Zr
Cl ₄ ) 60 g is dissolved in anhydrous methanol 500 ml,
It was injected into a dropping funnel which was replaced with nitrogen gas. In a nitrogen atmosphere, while stirring the methanol solution of DPM in the three-necked flask, the ZrCl ₄ solution was gradually added dropwise thereto from the funnel. After completion of dropping, stirring was continued for 1 hour. The generated precipitate was collected by filtration, washed with methanol, and dried in vacuum. The result of thermogravimetric analysis of the obtained Zr (DPM) ₄ is shown in FIG. 2 (b). Chelate evaporation is 100.0
%, And it was substantially 100% pure Zr (DPM) ₄ .

(Raw material synthesis example 3) Synthesis of Ti (DPM) ₂ (Oi-C ₃ H ₇ ) ₂ ; titanium tetraisopropoxide (Ti (Oi-C ₃ H ₇ ))
₄ ) 25 g was dissolved in 300 g of n-hexane. On the other hand, 32 g of DPM was dissolved in 300 g of n-hexane. This DPM solution was kept at 25 ° C. and stirred. T here
_{i (O-i-C 3} H 7) 4 solution was added dropwise, the temperature rise started after 1 hour, was 69 ° C.. This state was maintained for 5 hours, after which it was concentrated using a rotary evaporator to remove isopropyl alcohol by evaporation. Then, the obtained concentrate was placed in a freezer at −20 ° C. for crystallization,
The product was filtered and vacuum dried at 40 ° C. for 10 hours. The results of the obtained _{Ti (DPM) 2 (O-} i-C 3 H 7) 2 thermogravimetric analysis shown in Figure 2 (c). Chelate evaporation is 1
00.0% and substantially 100% pure Ti (DP
_{M) 2 (O-i-} C 3 H 7) was _2.

(Raw material synthesis example 4) Synthesis of La (DPM) ₃ ; 150 ml of anhydrous methanol
With 5.87 g of sodium hydroxide and 27.05 of DPM.
and g were added and completely dissolved. On the other hand, 12.0 g of lanthanum chloride (LaCl ₃ ) was dissolved in 50 ml of anhydrous methanol. Mix both solutions well and keep at about 25 ℃,
The mixture was stirred for about 3 hours to complete the precipitation reaction. Pure water 1000m
1 was added and stirring was continued for about 3 hours to wash the precipitate with pure water to dissolve the water-soluble salt. Then, the solid matter obtained by filtration was vacuum dried at 100 ° C. for 10 hours to obtain La (DPM) ₃ . The obtained La (DPM)
The result of thermogravimetric analysis of ₃ is shown in FIG. The amount of evaporated chelate was 100.0%, which was substantially 100% pure La (DPM) ₃ . As can be seen from the results of FIGS. 2A to 2D, the four kinds of complexes thus obtained have similar volatilization characteristics, and their evaporation temperatures are close to each other, and at the same time, they are easy to handle. Was confirmed.

As an embodiment of the present invention, an example of forming a metal composite oxide film will be shown below. (Example 1) Pb obtained in the above raw material synthesis examples 1 to 3
(DPM) ₂ , Zr (DPM) ₄ , and Ti (DP
M) ₂ (Oi-C ₃ H ₇ ) ₂ as a vapor phase source, and using the CVD apparatus shown in FIG. 3, PZT (Pb (Zr _x
A film of Ti _1-x ) O ₃ ) was formed. Three raw material containers 3,3
3 was filled with each of the above three kinds of raw materials, and Pb (Zr _x Ti _1-x ) O ₃ having a film thickness of 2000 Å was formed on the MgO single crystal (100 face) substrate 10 under the film forming conditions shown in Table 1 below. Filmed

[0021]

[Table 1]

The MgO substrate temperature is 500, 550,
The film was formed by changing the temperature to 600 ° C. The X-ray diffraction result of the obtained PZT film is shown in FIG. As a result, at a substrate temperature of 550 ° C,
A Pb (Zr _x Ti _1-x ) O ₃ perovskite single-phase film was obtained, and at 600 ° C., a crystal film having a strong C-axis orientation was obtained. Substrate temperature 600 ° C, film formation rate 150Å / mi
As a result of examining the electrical characteristics of the PZT film having a film thickness of 2000 Å obtained with n, the relative dielectric constant is 350, and the leak current value at the time of applying 1.5 V is on the order of 10 ⁻⁷ A / cm ² , which is high performance. It was expected to be applied to electronic devices.

Example 2 In Example 1, the temperature of the MgO single crystal substrate 10 was set to 600 ° C., the fourth raw material container 3 was filled with La (DPM) ₃ obtained in the above raw material synthesis example 4, PLZT (P) with a film thickness of 2000 Å under the same conditions as in Example 1 except that the temperature of the fourth raw material container was set to 180 ° C.
b _1-X La _X (Zr _1-Y Ti _Y ) O ₃ ) was deposited. The relative permittivity of the obtained PLZT film is about the same as that of the PZT thin film of Example 1, and the leakage current is one digit lower, and 10 ⁻⁸
It was on the order of A / cm ² . Therefore, the method of the present invention can be applied to high performance electronic devices.
A b _{1 -X} La _X (Zr _{1 -Y} Ti _Y ) O ₃ thin film could be formed.

[0024]

As described above, the present invention uses a β-diketonate metal complex having a purity of 99.0% or more as a vapor phase source in a method of forming a metal composite oxide film by a CVD method. is there. Therefore, a homogeneous and highly functional thin film can be formed. Further, the β-diketone-based metal complex is excellent in reactivity due to the coordination bond, has good volatility, and has the similar properties of all raw materials. Therefore, two or more kinds of raw materials are used for the metal complex oxide. Even when the film is formed, the reaction can be easily controlled and a homogeneous film can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing an example of a thermogravimetric curve of Ba (DPM) ₂ .

FIG. 2 is a graph showing thermogravimetric properties of DPM metal complexes used in Examples of the present invention.

FIG. 3 is a schematic configuration diagram of a CVD apparatus used in an example of the present invention.

FIG. 4 is an X-ray diffraction diagram of a PZT thin film obtained in an example of the present invention.

[Explanation of symbols]

3 raw material containers 10 substrates

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Asako Tsuyama, 10 Okubo, Tsukuba City, Ibaraki Japan Oxygen Co., Ltd. (56) Reference JP-A-3-141118 (JP, A) JP-A-2-57686 (JP , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 16/00-16/56 C30B 29/32 CA (STN)

Claims (2)

(57) [Claims] 1. A method for forming a metal composite oxide film by a chemical vapor deposition method, wherein the purity of each is 99.0%.
The above Pb (DPM) ₂ , Zr (DPM) ₄ , and T
i (DPM) ₂ (O-i-C ₃ H ₇ ) ₂ as a gas phase source
Te _{used, Pb (Zr X Ti 1-} X) O 3 film manufacturing method for a metal composite oxide film, wherein the this <br/> be formed. 2. A metal composite oxide by a chemical vapor deposition method.
In the method for forming the film, the purity is 99.0%.
The above Pb (DPM) ₂ , Zr (DPM) ₄ , Ti (D
PM) ₂ (Oi-C ₃ H ₇ ) ₂ and La (DP
M) ₃ as a gas phase source and Pb _1-X La _X (Zr
_1-Y Ti _Y ) O ₃ film forming metal
Method for manufacturing complex oxide film.