TW202444732A - Ruthenium complexes and process for producing ruthenium film - Google Patents

Abstract

The invention relates to ruthenium complexes of Formula (I) or (II), a process for producing a ruthenium film by a chemical deposition method using the complexes, and a method for preparing the complexes from a ([eta]<SP>5</SP>-2,4-dimethylpentadienyl)(CH3CN)3 ruthenium (II) salt.

Description

Ruthenium complex and method for preparing ruthenium film

The present invention relates to ruthenium complexes for preparing ruthenium films.

Hereinafter, (η ⁵ -2,4-dimethylpentadienyl) is abbreviated as DMPD, (η ⁵ -2,4-dimethyl-1-oxa-pentadienyl) is abbreviated as DMOPD and (η ⁵ -3,5-dimethyl-1-oxa-pentadienyl) is abbreviated as 3,5-DMOPD.

The article "Low-Temperature Preparation of Metallic Ruthenium Films by MOVCD Using Bis(2,4-dimethylpentadienyl) ruthenium" Electrochemical and Solid-State Letters, 10 (6) D60-D62 (2007) describes the deposition of crystalline ruthenium films onto thermally oxidized Si substrates by MOCVD using the ruthenium complex Ru(DMPD) _2. The complex is reported to have the following properties: melting point 89°C; vapor pressure 0.1 Torr at 82°C; decomposition temperature (DSC) 210°C.

A similar complex Ru(DMOPD) ₂ is also known. The article "Bis[η ⁵ -(2,4-dimethyl-1-oxapentadienyl)] ruthenium(II): the First Homoleptic Open Ruthenocenes with Non-hydrocarbon Ligands" J. Chem. Soc., Chem. Commun. , 1991, 1427-1429 describes the preparation of this complex from RuCl ₃ ·aq and 4-methylbut-3-en-2-one in pure ethanol, wherein the reduction is carried out using zinc powder as reducing agent. The reaction produces a mixture of isomers in a ratio of about 1:1. The complex Ru(DMOPD) ₂ does not seem to have been used previously as a precursor for the preparation of ruthenium films.

Mixed ruthenium complexes containing a single DMOPD ligand are also known.

The article "Half-Open Ruthenocenes Derived from [Ru(C ₅ Me ₅ )Cl] ₄ : Syntheses, Characterizations, and Solid-State Structures" Organometallics 1992, 11 , 1686-1692 describes the complex Ru(C ₅ Me ₅ )(DMOPD). This complex was prepared by the reaction between [Ru(C ₅ Me ₅ )Cl] ₄ and isopropylidene ketone in K ₂ CO ₃ /THF as part of an isomeric mixture. These complexes were not investigated for the preparation of ruthenium films.

US8884044B2 describes complexes of the formula Ru(DMPD)(P), where P is a chiral diphosphorus donor ligand. These complexes are described for catalytic hydrogenation, but their use for the preparation of ruthenium films has not been investigated.

US9349601B2 describes ruthenium complexes having a variety of general structures, including the family of formula (1a) containing substituted or unsubstituted _Cp ligands and DMOPD-type ligands. Examples include the preparation of the complexes Ru( _C5H5 ) ₍ DMOPD) [Example 7], Ru( _C5H4Me )(DMOPD) [Example 8], Ru( _C5H4Et )(DMOPD) [Examples 9, ₁₂ , ₁₃ ], Ru( _C5Me5 )(DMOPD) [Example 11].

Although both Ru(DMPD) ₂ and Ru(DMOPD) ₂ are known, only the former has been previously explored for use in preparing ruthenium films. The lack of any discussion on the use of Ru(DMOPD) ₂ to prepare membranes may indicate that this complex is not suitable, perhaps because of its insufficient thermal stability.

Ideally, a ruthenium complex used to make ruthenium films should meet some or all of the following criteria. First, the complex should have a high vapor pressure. Second, the complex should be stable enough to be vaporized and transported to a substrate, and reactive enough to react with reactant gases to make a ruthenium film on the substrate. Third, the complex should be simple to manufacture.

The present invention provides a complex that meets the above requirements.

In a first aspect, the present invention relates to complexes of formula (I): (Formula I) wherein R ² and R ⁴ are each independently selected from C ₁ to C ₆ alkyl groups; provided that the total number of carbon atoms in the combined groups R ² and R ⁴ is 2-7.

For the avoidance of doubt, as an example, if ^R2 = ^R4 = Et, then the total number of carbon atoms in the combined groups ^R2 and ^R4 is 4.

In a second aspect, the present invention relates to a complex of formula (II): (Formula II) wherein R ³ and R ⁵ are each independently selected from C ₁ to C ₆ alkyl groups; provided that the total number of carbon atoms in the combined groups R ³ and R ⁵ is 2-7.

Mixed complexes of formula (I) or (II) containing a DMPD ligand and a second, different ligand described herein are expected to have stabilities intermediate between Ru(DMPD) ₂ and Ru(DMOPD) ₂ and, therefore, are suitable for the preparation of membranes.

Those skilled in the art will appreciate that conformational isomers may be possible in the complexes of formula (I) or (II), especially given known conformational isomers in the related complex Ru(DMOPD) ₂ (see J. Chem. Soc., Chem. Commun., 1991, 1427-1429). For the avoidance of doubt, formulas (I) and (II) are not intended to indicate specific conformational isomers and should be understood in their broadest sense.

The substituents ^R2 and ^R4 (in the case of formula (I)) or the groups ^R3 and ^R5 (in the case of formula (II)) are each independently selected from _C1 to C6 _alkyl groups. "Alkyl" herein means a group containing only carbon atoms and hydrogen atoms. Each group may be saturated or unsaturated, preferably saturated. Preferred groups are Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, n-pentyl, cyclopentyl, n-hexyl.

It will be appreciated that the greater the number of carbon atoms in the groups ^R2 and ^R4 (formula (I)) or in the groups ^R3 and ^R5 (formula (II)), the less volatile the complex is and the higher the temperature required for the complex to volatilize. Preferably, the volatility temperature is low in order to minimize the risk of premature decomposition of the complex. Thus, preferably, the total number of carbon atoms in the combined groups ^R2 and ^R4 or in the combined groups ^R3 and ^R5 is 2 to 6, preferably 2 to 5, preferably 2 to 4, preferably 2 to 3, and most preferably 2.

A particularly preferred complex of formula (I) is (η ⁵ -2,4-dimethylpentadienyl)(η ⁵ -2,4-dimethyl-1-oxo-pentadienyl)ruthenium(II) "Ru(DMPD)(DMOPD)", ie wherein R ² = R ⁴ = Me.

A particularly preferred complex of formula (II) is (η ⁵ -2,4-dimethylpentadienyl)(η ⁵ -3,4-dimethyl-1-oxo-pentadienyl)ruthenium(II) "Ru(DMPD)(3,5-DMOPD)", ie wherein R ³ = R ⁵ = Me.

In a third aspect, the present invention relates to a method for preparing a ruthenium film by chemical deposition, wherein the ruthenium precursor has formula (I) or (II). Preferred methods include chemical vapor deposition (CVD) and atomic layer deposition (ALD).

In a fourth aspect, the present invention relates to a method for preparing a complex according to formula (I) or (II), comprising the step of reacting (η ⁵ -2,4-dimethylpentadienyl)(CH ₃ CN) ₃ ruthenium(II) salt with an α,β-unsaturated carbonyl compound of formula R ² C(=O)CH=CR ⁴ CH ₃ in the case of formula (I), or with an α,β-unsaturated carbonyl compound of formula CH(=O)CR ³ =CHCH ₂ R ⁵ in the case of formula (II).

In a preferred embodiment, the α,β-unsaturated carbonyl compound is isopropylidene ketone.

In a preferred embodiment, the α,β-unsaturated carbonyl compound is 2-methyl-2-pentenal.

Suitable (η ⁵ -2,4-dimethylpentadienyl)(CH ₃ CN) ₃ ruthenium(II) salts include perchlorate, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, bis(trifluoromethanesulfonyl)imide salt (bistriflimide), etc. A preferred salt is (η ⁵ -2,4-dimethylpentadienyl)(CH ₃ CN) ₃ ruthenium(II) tetrafluoroborate.

Any suitable solvent can be used for the reaction. A preferred solvent is THF, preferably THF at -78°C.

The reaction according to the fourth and fifth aspects of the present invention is preferably carried out in the presence of a base. The base preferably contains an amine functional group. A preferred base is triethylamine.

Examples Ru(DMPD)(DMOPD) was prepared by the reaction between [Ru(DMPD)(CH ₃ CN) ₃ ][BF ₄ ] and isopropylidene ketone. [Ru(DMPD)(CH ₃ CN) ₃ ][BF ₄ ] was also prepared following a procedure adapted from US884044B2.

Preparation of [Ru(DMPD)(CH ₃ CN) ₃ ][BF ₄ ] In an argon glove box, a 100 ml Schlenk flask was charged with 0.681 g Ru(DMPD) ₂ (2.34 mmol) followed by 31 mL anhydrous ether and stirred. Over 10 minutes, 0.32 mL HBF ₄ -Et ₂ O (2.33 mmol) was added dropwise, causing a light yellow solid to precipitate. The mixture was filtered using an airless filter funnel attached to a 200 mL receiving Schlenk flask. The solid was briefly pumped to remove the ether, scraped from the filter funnel and weighed: 0.813 g. The solid was placed back in the 100 mL Schlenk flask and dissolved in 23 mL anhydrous acetonitrile. The solution was stirred briefly, and the flask was removed from the glove box to remove volatiles by pumping the stirred solution through a cold trap. A warm water bath was used. When the pressure reached 0.27 mbar, the flask containing the orange solid was separated and returned to the glove box.

Preparation of [Ru(DMPD)(DMOPD)] The next day, anhydrous THF (13 mL) was added to the remaining orange solid. The flask was removed from the glove box and placed in a -78 °C bath. Under stirring, isopropylidene ketone (distilled from 3Å MS; 0.60 mL; 5.2 mmol) was added, followed by triethylamine (distilled from 3Å MS; 0.45 mL, 3.27 mmol). After 10 minutes, the flask was removed from the cold bath and placed in a heating block and heated to 40 °C over 1 hour. This block temperature was maintained for 3 hours. After cooling to ambient temperature, volatiles were removed by pumping the stirred solution through a cold trap. A warm water bath was used. When the pressure reaches 0.18 mbar, the flask is separated and brought into the glove box. The next day, the residue is extracted with 20 mL of anhydrous hexane and then filtered using an airless filter funnel attached to a 200 mL receiving Schlenk flask. The flask is removed from the glove box to remove volatiles by suctioning the stirred solution through a cold trap. A warm water bath is used. When the pressure reaches 0.14 mbar, the flask is separated and brought into the glove box. The crude product is purified by vacuum sublimation at 45°C/0.1 mbar. The cryofinger is water-cooled. At the end of sublimation, yellow crystals are observed on the cryofinger. The sublimation apparatus flask was separated and brought into the glove box where most of the yellow solid was scraped from the cryofinger into a pre-weighed vial. Mass: 0.0654 g. Yield: 10%.

The complex Ru(DMPD)(DMOPD) is a low melting solid with a melting point of about 70°C and is volatile below 220°C without decomposition.

Ruthenium Film Deposition Ru(DMPD)(DMOPD) and Ru(DMPD) ₂ were used as drivers before ruthenium film deposition in a Beneq TFS-200 ALD tool. After deposition, the film thickness and its resistivity were measured. Film thickness was measured using a FISCHERSCOPE ^™ X-RAY XDV ^™ -SDD from Fischer. Film resistivity was measured by a four-point probe method using a Loresta-GX from Nittoseiko Analytech. Deposition conditions are summarized below. Deposition results are shown in Table 1.

Deposition conditions: Substrate: Si with native oxide Deposition temperature: 220°C Precursor temperature: 75°C Oxygen pressure: 4 mbar Deposition cycle: Ru pulse (5s); Oxygen pulse (20s) Cycle number: 300 Film thickness (nm) Resistivity (µΩ ^. cm) Ru(DMPD)(DMOPD) 22.7 twenty one Ru(DMPD) ₂ 12.2 28 Table 1.

After the same number of cycles, Ru(DMPD)(DMOPD) produced thicker films with lower resistivity than films produced using Ru(DMPD) ₂ .

Ruthenium films were deposited using Ru(DMPD)(DMOPD) in the temperature range of 165 to 220°C. The films were analyzed as described above. The deposition results are shown in Table 2. Deposition temperature (℃) Cycle times Film thickness (nm) Resistivity (µΩ ^. cm) 220 300 22.7 twenty one 200 276 11.6 72 180 300 7.5 77 165 300 6.1 88 Table 2.

Conductive ruthenium films can be deposited in the temperature range of 165-220°C using Ru(DMPD)(DMOPD) and oxygen as co-reactants.

Claims (13)

A complex of formula (I), (Formula I) wherein R ² and R ⁴ are each independently selected from C ₁ to C ₆ alkyl groups; provided that the total number of carbon atoms in the combined groups R ² and R ⁴ is 2 to 7. The complex of claim 1, wherein the total number of carbon atoms in the combined groups R ² and R ⁴ is 2 or 3. The complex of claim 1, wherein R ² = R ⁴ = Me. A complex of formula (II), (Formula II) wherein R ³ and R ⁵ are each independently selected from C ₁ to C ₆ alkyl groups; provided that the total number of carbon atoms in the combined groups R ³ and R ⁵ is 2 to 7. The complex of claim 4, wherein the total number of carbon atoms in the combined groups ^R3 and ^R5 is 2 or 3. The complex of claim 4, wherein R ³ = R ⁵ = Me. A method for preparing a ruthenium film by chemical deposition using a ruthenium precursor, wherein the ruthenium precursor is a complex as described in any one of claims 1 to 6. The method of claim 7, wherein the chemical deposition method is chemical vapor deposition. The method of claim 7, wherein the chemical deposition method is atomic layer deposition. A method for preparing the complex of any one of claims 1 to 6, comprising the step of reacting (η ⁵ -2,4-dimethylpentadienyl)(CH ₃ CN) ₃ ruthenium(II) salt with an α,β-unsaturated carbonyl compound of the formula R ² C(═O)CH═CR ⁴ CH ₃ in the case of formula (I) or with an α,β-unsaturated carbonyl compound of the formula CH(═O)CR ³ ═CHCH ₂ R ⁵ in the case of formula (II). The method of claim 10, wherein the (η ⁵ -2,4-dimethylpentadienyl)(CH ₃ CN) ₃ ruthenium(II) salt is (η ⁵ -2,4-dimethylpentadienyl)(CH ₃ CN) ₃ ruthenium(II) tetrafluoroborate. The method of claim 10 or claim 11, wherein the α,β-unsaturated carbonyl compound is isopropyl ketone. The method of claim 10 or claim 11, wherein the α,β-unsaturated carbonyl compound is 2-methyl-2-pentenal.