Chemical deposition raw material including iridium complex and chemical deposition method using the chemical deposition raw material

Abstract

The present invention relates to a chemical deposition raw material for manufacturing an iridium thin film or an iridium compound thin film by a chemical deposition method, including an iridium complex in which cyclopropenyl or a derivative thereof and a carbonyl ligand are coordinated to iridium. The iridium complex that is applied in the present invention enables an iridium thin film to be manufactured even when a reducing gas such as hydrogen is applied. ##STR00001##
in which R.sub.1 to R.sub.3, which are substituents of the cyclopropenyl ligand, are each independently hydrogen, or a linear or branched alkyl group with a carbon number of 1 or more and 4 or less.

Claims

1. A chemical deposition method of an iridium thin film or an iridium compound thin film, comprising: preparing a raw material gas by vaporizing a raw material including an iridium complex; introducing the raw material gas to a surface of a substrate; and simultaneously heating the raw material gas to decompose the iridium complex, wherein the raw material used is an iridium complex in which a cyclopropenyl ligand and a carbonyl ligand are coordinated to iridium, the iridium complex being represented by a following formula: ##STR00030## and, wherein R.sub.1 to R.sub.3, which are substituents of the cyclopropenyl ligand, are each independently hydrogen, or a linear or branched alkyl group with a carbon number of 1 or more and 4 or less.

2. The chemical deposition method according to claim 1, wherein a reducing gas is used as a reaction gas.

3. A chemical deposition method of an iridium thin film or an iridium compound thin film, comprising: preparing a raw material gas by vaporizing a raw material including an iridium complex; introducing the raw material gas to a surface of a substrate; and simultaneously heating the raw material gas to decompose the iridium complex, wherein the chemical deposition raw material defined in claim 1 in the raw material.

4. The chemical deposition method according to claim 1, wherein the raw material is heated at 40° C. or higher and 120° C. or lower to be vaporized to obtain a raw material gas.

5. The chemical deposition method according to claim 4, wherein the iridium complex is heated at a deposition temperature of 160° C. or higher and 400° C. or lower to be decomposed to obtain a raw material gas.

6. The chemical deposition method according to claim 1, wherein the iridium complex is heated at a deposition temperature of 160° C. or higher and 400° C. or lower to be decomposed to obtain a raw material gas.

7. The chemical deposition raw material according to claim 1, wherein each of R.sub.1 and R.sub.2 is a t-butyl group, and R.sub.3 is one of a methyl group, an ethyl group, an isopropyl group and a t-butyl group.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a result of TG-DTA measurement (in a nitrogen atmosphere) of an iridium complex of a first embodiment.

(2) FIG. 2 illustrates a result of TG-DTA measurement (in a hydrogen atmosphere) of the iridium complex of the first embodiment.

(3) FIG. 3 shows a SEM image of an iridium thin film manufactured using the iridium complex of the first embodiment as a raw material.

DESCRIPTION OF EMBODIMENTS

(4) Hereinafter, the best embodiments in the present invention will be described.

First Embodiment

(5) In this embodiment, tricarbonyl[η.sup.3-1,2,3-tri-t-butylcyclopropenyl]iridium of the following formula was synthesized as an iridium complex having a cyclopropenyl ligand and a carbonyl ligand as ligands, and physical property measurement and deposition tests of the resultant were conducted.

(6) ##STR00024##
[Synthesis of Complex]

(7) 5 ml of a solution of 1.00 g (1.19 mmol) of bis(triphenylphosphoranylidene)ammonium tetracarbonyliridate in dichloromethane was prepared. To this solution was added dropwise 10 ml of a solution of 0.35 g (1.19 mmol) of 1,2,3-tri-t-butylcyclopropenyl tetrafluoroborate in dichloromethane. The mixed solution was stirred for 2 hours, the solvent was then distilled off under a reduced pressure, hexane was added to the residues thus obtained, and the mixture was extracted.

(8) From the extract, hexane was distilled off under a reduced pressure, and the crude product thus obtained was subjected to sublimation purification. Through the above operation, 0.34 g (0.70 mmol) of tricarbonyl(η.sup.3-1,2,3-tri-t-butylcyclopropenyl)iridium as a specified substance was obtained (yield: 59%). The reaction formula in the above synthesis operation is shown below.

(9) ##STR00025##
[Differential Thermal Analysis-Thermogravimetry]

(10) The physical properties of the iridium complex manufactured in this embodiment were evaluated. In an evaluation test thereof, differential thermal analysis-thermogravimetry (TG-DTA) was performed in each of a nitrogen atmosphere and a hydrogen atmosphere to examine the decomposition property of the complex. In this evaluation test, TG-DTA2000SA manufactured by BRUKER Corporation was used as an analyzer. An iridium complex sample (sample weight: 5 mg) was packed in an aluminum cell, and a change in weight was observed over a measurement temperature range, i.e. of room temperature to 400° C., at a temperature elevation rate of 5° C./min.

(11) Further, in this physical property evaluation test, TG-DTA was also performed for (1-methylcyclopentadienyl)(1,5-cyclooctadiene)iridium (Comparative Example 1) and (1-ethylcyclopentadienyl)(1,3-cyclohexadiene)iridium (Comparative Example 2) as conventional arts, and a difference in decomposition property between these complexes and the complex of this embodiment was examined. These iridium complexes of Comparative Examples were synthesized in accordance with the methods in the patent documents, and used as samples.

(12) FIG. 1 illustrates a result of TG-DTA measured in a nitrogen atmosphere. From FIG. 1, it is revealed that as compared to the conventional iridium complexes of Comparative Examples 1 and 2, the iridium complex of this embodiment has a more favorable vaporization property because a weight loss occurs at a lower temperature. Further, it can be confirmed that the iridium complex of this embodiment has a lower decomposition temperature as compared to Comparative Examples 1 and 2, and thus can be deposited at a lower temperature.

(13) Next, FIG. 2 illustrates a result of TG-DTA measured in a hydrogen atmosphere. In the hydrogen atmosphere, the iridium complex of this embodiment underwent a mass loss and decomposition at a lower temperature as compared to the conventional iridium complexes of Comparative Examples, and thus showed the same tendency as in the nitrogen atmosphere. Further, the mass loss ended at a low temperature. From the above result, the iridium complex of this embodiment was confirmed to be effectively decomposed in a hydrogen atmosphere.

(14) [Deposition test]

(15) An iridium thin film was deposited by a CVD apparatus (hot wall-type CVD deposition apparatus) by use of the iridium complex according to this embodiment as a raw material. The deposition conditions are as described below. An iridium thin film was deposited while the deposition temperature and the deposition pressure were changed, and the thickness and the specific resistance of the thin film were measured. The results of the deposition test are shown in Table 2, and SEM images of the manufactured iridium thin films are shown in Table 3.

(16) Substrate: Si

(17) Deposition temperature: 250° C., 300° C. and 350° C.

(18) Sample temperature (vaporization temperature): 45° C.

(19) Pressure: 3 torr, 15 torr

(20) Reaction gas (carrier gas): hydrogen gas

(21) Gas flow rate: 50 sccm

(22) Deposition time: 30 min

(23) TABLE-US-00002 TABLE 2 Deposition Deposition Ir Specific Test No. temperature pressure thickness/nm resistance/μΩ .Math. cm 1 350° C.  3 torr 26 300 2 300° C. 18 270 3 250° C. 13 130 4 300° C. 15 torr 20 99

(24) From FIG. 3, it is appreciated that when the iridium complex according to this embodiment is used as a raw material, an iridium thin film can be manufactured with a hydrogen gas as a reaction gas under any deposition conditions. Comparison of the results under the deposition conditions of tests Nos. 1 to 4 revealed that the specific resistance of a thin film manufactured became lower as the deposition temperature decreased and the pressure during deposition increased. The results of the deposition tests showed that application of the iridium complex according to this embodiment enabled a more favorable iridium film to be manufactured through reaction with hydrogen at a low temperature.

Second Embodiment

(25) In this embodiment, tricarbonyl[η.sup.3-1,2-di-t-butyl-3-ethylcyclopropenyl)iridium of the following formula was synthesized as an iridium complex having a cyclopropenyl ligand and a carbonyl ligand as ligands.

(26) ##STR00026##

(27) 1 ml of a solution of 0.084 g (0.10 mmol) of bis(triphenylphosphoranylidene)ammonium tetracarbonyliridate in acetone was prepared. To this solution was added dropwise 2 ml of a solution of 0.028 g (0.10 mmol) of 1,2-di-t-butyl-3-ethylcyclopropenyl tetrafluoroborate in acetone. The mixed solution was stirred for 1 hour, the solvent was then distilled off under a reduced pressure, hexane was added to the residues thus obtained, and the mixture was extracted.

(28) From the extract, hexane was distilled off under a reduced pressure to obtain 0.015 g (0.033 mmol) of tricarbonyl (η.sup.3-1,2-di-t-butyl-3-ethylcyclopropenyl)iridium as a specified substance (yield: 33%). The reaction formula in the above synthesis operation is shown below.

(29) ##STR00027##

Third Embodiment

(30) In this embodiment, tricarbonyl[η.sup.3-1,2-di-t-butyl-3-methylcyclopropenyl)iridium of the following formula was synthesized as an iridium complex having a cyclopropenyl ligand and a carbonyl ligand as ligands.

(31) ##STR00028##

(32) 1 ml of a solution of 0.084 g (0.10 mmol) of bis(triphenylphosphoranylidene)ammonium tetracarbonyliridate in acetone was prepared. To this solution was added dropwise 2 ml of a solution of 0.027 g (0.10 mmol) of 1,2-di-t-butyl-3-methylcyclopropenyl tetrafluoroborate in acetone. The mixed solution was stirred for 1 hour, the solvent was then distilled off under a reduced pressure, hexane was added to the residues thus obtained, and the mixture was extracted.

(33) From the extract, hexane was distilled off under a reduced pressure to obtain 0.015 g (0.036 mmol) of tricarbonyl (η.sup.3-1,2-di-t-butyl-3-methylcyclopropenyl)iridium as a specified substance (yield: 36%). The reaction formula in the above synthesis operation is shown below.

(34) ##STR00029##

(35) For the iridium complexes manufactured in the second and third embodiments, TG-DTA was performed in the same manner as in the first embodiment, and the results showed that both the iridium complexes had a lower decomposition temperature as compared to conventional arts, and were easily decomposed even in a hydrogen atmosphere. Further, for the iridium complexes manufactured in the second and third embodiments, a deposition test was conducted under the same conditions as in the first embodiment (250° C., 3 torr) with a hydrogen gas used as a reaction gas, and the results showed that a favorable iridium thin film comparable to that of the first embodiment was manufactured.

INDUSTRIAL APPLICABILITY

(36) A chemical deposition raw material according to the present invention includes an iridium complex having thermal stability in an appropriate range, and enables an iridium-containing thin film with favorable quality to be manufactured even when a hydrogen gas is used as a reaction gas. The chemical vapor deposition raw material of the present invention is suitably used as a thin film electrode material of a semiconductor device such as DRAM or FERAM.