CHEMICAL VAPOR DEPOSITION RAW MATERIAL COMPRISING ORGANIC RUTHENIUM COMPOUND AND CHEMICAL VAPOR DEPOSITION METHOD USING CHEMICAL VAPOR DEPOSITION RAW MATERIAL

Abstract

The invention provides a raw material for chemical deposition having properties required for a CVD compound, that is, which has a high vapor pressure, can be formed into a film at low temperatures (about 250° C. or less), and also has moderate thermal stability. The invention relates to a raw material for chemical deposition, for producing a ruthenium thin film or a ruthenium compound thin film by a chemical deposition method, the raw material for chemical deposition including an organoruthenium compound represented by the following formula, in which a cyclohexadienyl group or a derivative thereof and a pentadienyl group or a derivative thereof are coordinated to ruthenium:

##STR00001## wherein the substituents R.sub.1 to R.sub.12 are each independently a hydrogen atom, a linear or cyclic hydrocarbon, an amine, an imine, an ether, a ketone, or an ester, and the substituents R.sub.1 to R.sub.12 each have 6 or less carbon atoms.

Claims

1. A raw material for chemical deposition, for producing a ruthenium thin film or a ruthenium compound thin film by a chemical deposition method, the raw material for chemical deposition comprising an organoruthenium compound represented by the following formula, in which a derivative of a cyclohexadienyl group and a derivative of a pentadienyl group are coordinated to ruthenium: ##STR00019## wherein the derivative of a cyclohexadienyl group is such that, out of the substituents R.sub.1 to R.sub.7, two to four substituents are each a hydrogen atom, and the remaining substituents are each a methyl group or an ethyl group, with the proviso that the substituents R.sub.6 and R.sub.7 are each a methyl group or an ethyl group, and the derivative of a pentadienyl group is dimethylpentadienyl wherein, out of the substituents R.sub.8 to R.sub.12, R.sub.8, R.sub.10, and R.sub.12 are each a hydrogen atom, and the substituents R.sub.9 and R.sub.11 are each a methyl group.

2. (canceled)

3. (canceled)

4. (canceled)

5. (canceled)

6. (canceled)

7. (canceled)

8. A chemical deposition method for a ruthenium thin film or a ruthenium compound thin film, comprising the steps of: vaporizing a raw material including an organoruthenium compound into a raw material gas; and heating and introducing the raw material gas onto a substrate surface, the chemical deposition method using the raw material for chemical deposition defined in claim 1 as the raw material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a diagram showing the results of the TG-DTA measurement of compounds in this embodiment.

[0033] FIG. 2 shows SEM observation photographs of ruthenium thin films in this embodiment.

DESCRIPTION OF EMBODIMENTS

[0034] Hereinafter, best modes for carrying out the present invention will be described.

[0035] In this embodiment, three kinds of organoruthenium compounds represented by the following formulae were produced. Additionally, the decomposition temperature and the performance of the formed thin film were evaluated.

##STR00013##

Synthesis of Compound A

[0036] As compound A,

(2,4-dimethylpentadienyl)(2,6,6-trimethylcyclohexadienyl)ruthenium(II) was synthesized by the following steps.

[0037] 2.38 ml of acetonitrile, 35.3 g (366.4 mmol) of 2,4-dimethyl 1,3-pentadiene, 13.5 g (183.2 mmol) of lithium carbonate, and 28.2 g (45.8 mmol) of

[0038] di-μ-chlorodichloro-bis[(1-3 η):(6-8 η)-2,7-dimethyloctadiendiyl]diruthenium(IV) were added to a flask containing 900 ml of ethanol in this order to form a suspension. The suspension was heated and stirred under reflux for 4 hours, and then cooled to room temperature. 5.6 g (45.8 mmol) of 2,6,6-trimethy-1,3-cyclohexadiene was added to the cooled liquid, and then heated and stirred under reflux for 6 hours. After the completion of the reaction, the mixture was cooled to room temperature and concentrated to give a muddy reaction mixture. Extraction from the muddy reaction mixture was performed with pentane, and the extract was subjected to column chromatography using a silica gel (or alumina) as the carrier and pentane as the eluent, and further to sublimation purification, thereby giving 2.0 g (6.3 mmol) of (2,4-dimethylpentadienyl)(2,6,6-trimethylcyclohexadienyl)ruthenium(II) as the object substance (yield: 7%, melting point: 104° C.).

##STR00014##

Synthesis of Compound B

[0039] As compound B,

(2,4-dimethylpentadienyl)(2,4,6,6-tetramethylcyclohexadienyl)ruthenium(II) was synthesized by the following steps.

[0040] 1.04 ml of acetonitrile, 15.4 g (160 mmol) of 2,4-dimethyl 1,3-pentadiene, 6.0 g (80 mmol) of lithium carbonate, and 12.4 g (20 mmol) of di-μ-chlorodichloro-bis[(1-3 η):(6-8 η)-2,7-dimethyloctadiendiyl]diruthenium(IV) were added to a flask containing 400 ml of ethanol in this order to form a suspension. The suspension was heated and stirred under reflux for 4 hours, and then cooled to room temperature. 2.8 g (20 mmol) of 1,3,5,5-tetramethyl-1,3-cyclohexadiene was added to the cooled liquid, and then heated and stirred under reflux for 6 hours. After the completion of the reaction, the mixture was cooled to room temperature and concentrated to give a muddy reaction mixture. Extraction from the muddy reaction mixture was performed with pentane, and the extract was subjected to column chromatography using a silica gel (or alumina) as the carrier and pentane as the eluent, and further to sublimation purification, thereby giving 1.3 g (3.92 mmol) of (2,4-dimethylpentadienyl)(2,4,6,6-tetramethylcyclohexadienyl)ruthenium(II) as the object substance (yield: 10%, melting point: 67° C.).

##STR00015##

Synthesis of Compound C (1)

[0041] As the compound C,

(2,4-dimethylpentadienyl)(3-ethyl-2,6,6-trimethylcyclohexadienyl)ruthenium(11) was synthesized by the following steps.

[0042] 0.52 ml of acetonitrile, 7.7 g (80 mmol) of 2,4-dimethyl 1,3-pentadiene, 3.0 g (40 mmol) of lithium carbonate, and 6.2 g (10 mmol) of di-μ-chlorodichloro-bis[(1-3 η):(6-8 η)-2,7-dimethyloctadiendiyl]diruthenium(IV) were added to a flask containing 200 ml of ethanol in this order to form a suspension. The suspension was heated and stirred under reflux for 4 hours, and then cooled to room temperature. 2.7 g (20 mmol) of 2-ethyl-1,5,5-trimethyl-1,3-cyclohexadiene was added to the cooled liquid, and then heated and stirred under reflux for 6 hours. After the completion of the reaction, the mixture was cooled to room temperature and concentrated to give a muddy reaction mixture. Extraction from the muddy reaction mixture was performed with pentane, and the extract was subjected to column chromatography using a silica gel (or alumina) as the carrier and pentane as the eluent, and further to distillation, thereby giving 0.8 g (3.92 mmol) of (2,4-dimethylpentadienyl)(3-ethyl-2,6,6-trimethylcyclohexadienyl)ruthenium(II) as the object substance (yield: 12%, melting point: −20° C. or less).

##STR00016##

Synthesis of Compound C (2)

[0043] The synthesis of compound C was also performed by the following method.

[0044] 114.4 g (1.19 mol) of 2,4-dimethyl 1,3-pentadiene and 31.1 g (0.21 mol) of 2-ethyl-1,5,5-trimethyl-1,3-cyclohexadiene were added to a flask containing 20.0 g (3.06 mol) of zinc in this order to form a suspension. A solution of 30.0 g (0.12 mol) of ruthenium chloride trihydrate dissolved in 500 ml of ethanol was slowly added dropwise to the suspension with stirring at room temperature. The mixture was stirred for about 30 minutes at room temperature, and then heated and stirred under reflux for 4 hours. After the completion of the reaction, the mixture was cooled to room temperature, and zinc was removed from the reaction solution by filtration, followed by concentration to give a reaction mixture. Extraction from the obtained reaction mixture was performed with hexane, and the extract was subjected to column chromatography using a silica gel as the carrier and hexane as the eluent, and further to distillation, thereby giving 13.1 g (0.038 mol) of

(2,4-dimethylpentadienyl)(3-ethyl-2,6,6-trimethylcyclohexadienyl)ruthenium(II) as the object substance (yield: 33%, melting point: −20° C. or less).

##STR00017##

[0045] Incidentally, it was also possible to synthesize (2,4-dimethylpentadienyl)(2,6,6-trimethylcyclohexadienyl)ruthenium(II) and (2,4-dimethylpentadienyl) (2,4,6,6-tetramethylcyclohexadienyl)ruthenium(II) in the same manner as in the above Synthesis of Compound C (2).

[0046] The thermal properties of the compounds A, B, and C synthesized above were evaluated by DSC.

[0047] calorimetry (DSC): By use of Q2000 manufactured by TA Instruments, each compound (sample weight: 3.8 mg) was placed in a pressure-resistant cell made of stainless steel, and, in a nitrogen atmosphere, changes in heat were observed at a temperature rise rate of 10° C./min and a measurement temperature ranging from room temperature to 300° C. The results are shown in the following table. As the decomposition temperatures of the organoruthenium compounds (X1 to X3) of the following conventional examples, the values described in Non Patent Document 2 are also shown in the table.

[0048] Non Patent Document 2: Electrochemical and Solid-State Letters, Vol. 12, No. 10, pD80-83 (2009)

##STR00018##

TABLE-US-00001 TABLE 1 Decomposition Basic skeleton temperature Compound A CHD—Ru—PD 250° C. Compound B CHD—Ru—PD 250° C. Compound C CHD—Ru—PD 240° C. Compound X1 Cp—Ru—Cp 350° C. Compound X2 Cp—Ru—PD 270° C. Compound X3 PD—Ru—PD 210° C.

[0049] As shown by the above results, the decomposition temperatures of the compounds A to C were all 250° C. or less, allowing for film formation at low temperatures. At the same time, the decomposition temperatures were not low enough to cause decomposition during handling, and the compounds had moderate thermal stability.

[0050] Thermodravimetry-Differential Thermal Analysis (TG-DTA): By use of TG-DTA2000SA manufactured by BRUKER, the compounds A, B, and C (sample weight: 5 mg) were each placed in a cell made of aluminum, and, in a nitrogen atmosphere, changes in heat and weight were observed at a temperature rise rate of 5° C./min and a measurement temperature ranging from room temperature to 500° C. The results are shown in FIG. 1.

[0051] From FIG. 1, in all the compounds A, B, and C, a weight loss was observed at 210° C. or less in TG, indicating that they are suitable for deposition at low temperatures (250° C. or less).

[0052] Deposition Test: By use of a cold-wall film deposition device, ruthenium thin films were formed by CVD from the compound C as a raw material. In Test No. 1, the deposition conditions were as follows: substrate for thin film formation: silicon, sample heating temperature: 90° C., substrate heating temperature: 210° C., reactant gas: hydrogen supplied at 20 sccm, pressure: 150 torr, deposition time: 180 minutes. Additionally, films of Test Nos. 2 to 6 were also formed under the conditions shown in the following table, in which silicon oxide was used as the substrate, the substrate heating temperature varied, etc.

TABLE-US-00002 TABLE 2 Sample Substrate heating heating Reactant Deposition Test No. Substrate temperature temperature gas Pressure time 1 Si 90° C. 210° C. Hydrogen 150 torr 180 min  2 SiO.sub.2 20 sccm 3 Si 250° C. 60 min 4 SiO.sub.2 5 350° C. Hydrogen 225 torr 30 min 6 70° C. 450° C. 30 sccm 150 torr 40 min

[0053] Film thickness measurement by SEM observation and specific resistance measurement were performed on the ruthenium films produced at the various substrate heating temperatures. FIG. 2 shows the SEM observation photographs of Test Nos. 3 to 5. Additionally, the specific resistance is shown in the following table.

TABLE-US-00003 TABLE 3 Film Specific Test No. Substrate thickness/nm resistance/μ Ω cm 1 SiO.sub.2 46.3 59.1 2 Si 22.4 34.1 3 SiO.sub.2 30.3 16.8 4 Si 42.2 16.0 5 SiO.sub.2 8.5 28.4 6 SiO.sub.2 9.5 59.4

[0054] As a result of SEM observation, in all the ruthenium films produced at the above substrate heating temperatures, the thickness was uniform and continuous, and no cracks, holes, island-like aggregation, or the like was observed.

[0055] Additionally, with respect to the specific resistance, all the ruthenium films produced under the above test example conditions showed low specific resistances of 60 μΩcm or less. In particular, the ruthenium films of the Test Nos.

[0056] 3 to 5, in which the substrate heating temperature at the time of deposition was 220° C. to 350° C., had particularly low specific resistances of 30 μΩcm or less.

INDUSTRIAL APPLICABILITY

[0057] The raw material according to the present invention has a high vapor pressure, moderate thermal stability, and also a low decomposition temperature (about 250° C. or less), offering excellent film formability at low temperatures, and its specific resistance is also low. Accordingly, the raw material is suitable also for use as a thin-film electrode material for a semiconductor device, such as DRAM or FERAM.