WO2006015225A1

WO2006015225A1 - Copper (ii) complexes for deposition of copper films by atomic layer deposition

Info

Publication number: WO2006015225A1
Application number: PCT/US2005/027019
Authority: WO
Inventors: Alexander Z. Bradley; Jeff S. Thompson; Kyung-Ho Park
Original assignee: E.I. Dupont De Nemours And Company
Priority date: 2004-07-30
Filing date: 2005-07-29
Publication date: 2006-02-09
Also published as: IL180764A0; US7619107B2; JP2008508426A; KR20070043865A; KR20070048215A; JP2008508427A; TW200617198A; EP1771594A1; US20080044687A1; US20080299322A1; EP1771595A1; IL180768A0; WO2006015200A1; TW200622024A

Abstract

The present invention relates to novel 1,3-diimine copper complexes and the use of 1,3-diimine copper complexes for the deposition of copper on substrates or in or on porous solids in an Atomic Layer Deposition process.

Description

TITLE

COPPER(I) COMPLEXES FOR DEPOSITION OF COPPER FILMS BY ATOMIC LAYER DEPOSITION

FIELD OF THE INVENTION The present invention relates to novel 1 ,3-diimine copper complexes. The invention also relates to processes for forming copper deposits on substrates or in or on porous solids, using the 1 ,3-diimine copper complexes.

BACKGROUND Atomic layer deposition (ALD) processes are useful for the creation of thin films, as described by M. Ritala and M. Leskela in "Atomic Layer Deposition" in Handbook of Thin Film Materials. H. S. Nalwa, Editor, Academic Press, San Diego, 2001 , Volume 1 , Chapter 2. Such films, especially metal and metal oxide films, are critical components in the manufacture of electronic circuits and devices.

In an ALD process for depositing copper films, a copper precursor and a reducing agent are alternatively introduced into a reaction chamber. After the copper precursor is introduced into the reaction chamber and allowed to adsorb onto a substrate, the excess (unadsorbed) precursor vapor is pumped or purged from the chamber. This process is followed by introduction of a reducing agent that reacts with the copper precursor on the substrate surface to form copper metal and a free form of the ligand. This cycle can be repeated if needed to achieve the desired film thickness.

This process differs from chemical vapor deposition (CVD) in the decomposition chemistry of the metal complex. In a CVD process, the complex undergoes pyrolytic decomposition on contact with the surface to give the desired film. In an ALD process, the complex is not completely decomposed to metal on contact with the surface. Rather, formation of the metal film takes place on introduction of a second reagent, which reacts with the deposited metal complex. In the preparation of a copper film from a copper(l) complex, the second reagent is a reducing agent. Advantages of an ALD process include the ability to control the film thickness and improved conformality of coverage because of the self-limiting adsorption of the precursor to the substrate surface in the first step of the process. The ligands used in the ALD processes must also be stable with respect to decomposition and be able to desorb from the complex in a metal-free form. Following reduction of the copper, the ligand is liberated and must be removed from the surface to prevent its incorporation into the metal layer being formed.

S.G. McGeachin, Canadian Journal of Chemistry, 46, 1903 -1912 (1968), describes the synthesis of 1 ,3-diimines and metal complexes of these ligands, including bis-chelate or homoleptic complexes of the form ML₂.

US 6,464,779 discloses a Cu atomic layer CVD process that requires treatment of a copper precursor containing both oxygen and fluorine with an oxidizing agent to form copper oxide, followed by treatment of the surface with a reducing agent.

WO 2004/036624 describes a two-step ALD process for forming copper layers comprising forming a copper oxide layer from a non-fluorine containing copper precursor on a substrate and reducing the copper oxide layer to form a copper layer on the substrate. Copper alkoxides, copper β- diketonates and copper dialkylamides are preferred copper precursors. The reducing agent is a hydrogen (H₂) containing gas.

US 2003/0135061 discloses a dimeric copper(l) precursor which can be used to deposit metal or metal-containing films on a substrate under ALD or CVD conditions. WO 2004/046417 describes the use of dimeric copper (I) complexes comprising amidinate ligands for use in an ALD process.

SUMMARY OF THE INVENTION

One aspect of this invention is a process for forming copper deposits on a substrate comprising: a. contacting a substrate with a copper complex, (I), to form a deposit of a copper complex on the substrate; and

(I)

b. contacting the deposited copper complex with a reducing agent, wherein L is selected from C₂- C₁₅ olefins, C2- C₁₅ alkynes, nitriles, aromatic heterocycles, and phosphines;

R¹ and R⁴ are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, isobutyl, neopentyl and C₃-C₅ alkylene; R², R³ and R⁵ are independently selected from hydrogen, fluorine, trifluoromethyl, phenyl, C-₁-C10 alkyl and C-3-Cs alkylene; with the proviso that at least one of (R¹, R²) and (R³, R⁴) taken together is -(CR⁶R⁷) n-, where R⁶ and R⁷ are independently selected from hydrogen, fluorine, trifluoromethyl, Ci-C₅ alkyl, and CrC₅ alkyl ester, and n is 3, 4 or 5; and the reducing agent is selected from 9-BBN (9-borabicyclo[3.3.1]nonane); diborane; boranes of the form BR_xH_3-X, where x = 0, 1 or 2, and R is independently selected from phenyl and C₁-C₁₀ alkyl groups; dihydrobenzofuran; pyrazoline; disilane; silanes of the form SiR'_yH_4-y, where y = 0, 1 , 2 or 3, and R' is independently selected from phenyl and C₁-C₁₀ alkyl groups; and germanes of the form GeR"_zH_4-z, where z = 0, 1 , 2, or 3, and R" is independently selected from phenyl and C₁-C₁₀ alkyl groups.

Another aspect of the present invention is an article comprising a 1 ,3-diimine copper complex, (I), deposited on a substrate. DETAILED DESCRIPTION

Applicants have discovered an atomic layer deposition (ALD) process suitable for creation of copper films for use as seed layers in the formation of copper interconnects in integrated circuits, or for use in decorative or catalytic applications. This process uses copper(l) complexes that are volatile, thermally stable and derived from ligands that contain C, H, and N, but are not limited to these elements. The ligands are chosen to form copper(l) complexes that are volatile in an appropriate temperature range but do not decompose to copper metal in this temperature range. Rather, the complexes decompose to metal on addition of a suitable reducing agent. The ligands are further chosen so that they will desorb without decomposition upon exposure of the copper complex to a reducing agent. The reduction of these copper complexes to copper metal by readily available reducing agents has been demonstrated to proceed cleanly at moderate temperatures.

In a process of this invention, copper is deposited on a substrate by means of:

(a) contacting a substrate with a copper complex, (I), to form a deposit of a copper complex on the substrate; and

(I)

(b.) contacting the deposited copper complex with a reducing agent, wherein L is selected from C₂- Ci₅ olefins, C₂- C₁₅ alkynes, nitriles, aromatic heterocycles, and phosphines;

R¹ and R⁴ are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, isobutyl, neopentyl, and C₃-C₅ alkylene; R², R³ and R⁵ are independently selected from hydrogen, fluorine, trifluoromethyl, phenyl, C-i-C-to alkyl and C₃-C₅ alkylene, with the proviso that at least one of (R¹, R²) and (R³, R⁴) taken together is -(CR⁶R⁷) _n-, where R⁶ and R⁷ are independently selected from hydrogen, fluorine, trifluoromethyl, CrC₅ alkyl, and Ci-C₅ alkyl ester, and n is 3, 4 or 5; and the reducing agent is selected from 9-BBN (9-borabicyclo[3.3.1]nonane); diborane; boranes of the form BR_xH₃-_X, where x = 0, 1 or 2, and R is independently selected from phenyl and C₁-C₁₀ alkyl groups; dihydrobenzofuran; pyrazoline; disilane; silanes of the form SiR'yH_4-y, where y = 0, 1 , 2 or 3, and R' is independently selected from phenyl and C₁-C₁₀ alkyl groups; and germanes of the form GeRy-U_-2, where z = 0, 1 , 2, or 3, and R" is independently selected from phenyl and C₁-C₁₀ alkyl groups.

The present deposition process improves upon the processes described in the art by allowing the use of lower temperatures and producing higher quality, more uniform films. The process of this invention also provides a more direct route to a copper film, avoiding the formation of an intermediate oxide film.

In a copper deposition process of this invention, the copper can be deposited on the surface, or in or on porosity, of the substrate. Suitable substrates include conducting, semiconducting and insulating substrates, including copper, silicon wafers, wafers used in the manufacture of ultra large scale integrated circuits, wafers prepared with dielectric material having a lower dielectric constant than silicon dioxide, and silicon dioxide and low k substrates coated with a barrier layer. Barrier layers to prevent the migration of copper include tantalum, tantalum nitride, titanium, titanium nitride, tantalum silicon nitride, titanium silicon nitride, tantalum carbon nitride, and niobium nitride. The processes of the invention can be conducted in solution, i.e., by contacting a solution of the copper complex with the reducing agent. However, it is preferred to expose the substrate to a vapor of the copper complex, and then remove any excess copper complex (i.e., undeposited complex) by vacuum or purging before exposing the deposited complex to a vapor of the reducing agent. After reduction of the copper complex, the free form of the ligand can be removed via vacuum, purging, heating, rinsing with a suitable solvent, or a combination of such steps.

This process can be repeated to build up thicker layers of copper, or to eliminate pin-holes.

The deposition of the copper complex is typically conducted at 0 to 200 ⁰C. The reduction of the copper complex is typically carried out at similar temperatures, 0 to 200 ⁰C, more preferably 50 to 150 ⁰C.

In the process of this invention, it is initially a copper complex that is deposited on the substrate. The formation of a metallic copper film does not occur until the copper complex is exposed to the reducing agent.

Aggressive reducing agents are used to reduce the copper complex rapidly and completely. Suitable reducing agents are volatile and do not decompose on heating. They are also of sufficient reducing power to react rapidly on contact with the copper complex deposited on the substrate surface. Suitable reducing agents have been identified that have been used for copper(l) reduction in an ALD process. One feature of these reagents is the presence of a proton donor. The reducing agent is desirably able to transfer at least one electron to reduce the copper ion of the complex and at least one proton to protonate the ligand. It is also desirable that the oxidized reducing agent and the protonated ligand be able to be easily removed from the surface of the newly formed copper deposit. Preferably, the protonated ligand is removed by vacuum, by purging or by flushing the surface with a suitable solvent. Suitable reducing agents for the copper deposition processes of this invention include 9-BBN, borane, diborane, dihydrobenzofuran, pyrazoline, germanes, diethylsilane, dimethylsilane, ethylsilane, phenylsilane, silane and disilane. Diethylsilane and silane are preferred. In one embodiment of a copper deposition process, the copper complexes are admitted to a reactor chamber containing the substrate under conditions of temperature, time and pressure to attain a suitable fluence of complex to the surface of the substrate. The selection of these variables (time, T, P) will depend on individual chamber and system design, and the desired process rate. After at least a portion of the copper complex has been deposited on the substrate, the undeposited complex vapor is pumped or purged from the chamber and the reducing agent is introduced into the chamber at a pressure of approximately 50 to 760 mTorr to reduce the adsorbed copper complex. The substrate is held at a temperature between approximately 0 to 200 ⁰C during reduction. With suitable combinations of copper complex and reducing agent, this reduction is rapid and substantially complete. Desirably, the reaction is at least 95% complete within an exposure time of from less than a second to several minutes. It is desired that the products from this reaction are readily removed from the surface of the substrate under the reducing conditions.

In one embodiment of a process of this invention, the copper complex is a copper 1 ,3-diimine complex (I), wherein R¹ and R⁵ are hydrogen groups, R² is a methyl group, R³, R⁴ are taken together to form - (CHb)_n-, n = 3, L= vinyltrimethylsilane, and the reducing agent is diethylsilane.

This invention also provides novel 1 ,3-diimine copper complexes,

(I).

(I)

wherein

L is selected from C₂- Ci₅ olefins, C₂- Ci₅ alkynes, nitriles, aromatic heterocycles, and phosphines; R¹ and R⁴ are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, isobutyl, neopentyl and C₃-C₅ alkylene; R², R³ and R⁵ are independently selected from hydrogen, fluorine, trifluoromethyl, phenyl, C₁-C₁₀ alkyl and C₃-C₅ alkylene, with the proviso that at least one of (R¹, R²) and (R³, R⁴) taken together is -(CR⁶R⁷) „-, where R⁶ and R⁷ are independently selected from hydrogen, fluorine, trifluoromethyl, Ci-C₅ alkyl, and C₁-C₅ alkyl ester, and n is 3, 4 or 5.

In one embodiment, L is a linear, terminal olefin. For olefins of 4 - 15 carbons, L can also be an internal olefin of cis- or trans-configuration; cis-configuration is preferred. L can be a cyclic or bicyclic olefin. L can also be substituted, for example with fluorine or silyl groups. Suitable olefins include, but are not limited to, vinyltrimethylsilane, allyltrimethylsilane, 1-hexene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, and norbornene. L can also be alkyne, nitrile, or an aromatic nitrogen heterocycle such as pyridine, pyrazine, triazine, or Λ/-substituted imidazole, pyrazole, or triazole. L can also be a phosphine.

The synthesis of one ligand useful for making the copper complexes of this invention is given in Example 1 below. Thus, a cyclic ketimine can be deprotonated by strong base, then treated with an electrophile such as an ester or acid halide derivative to provide the corresponding keto cyclic enamine as an intermediate. Treatment of this intermediate with an alkylating agent such as dimethylsulfate, followed by the addition of a primary amine affords the desired cyclic diketimine. Alternatively, the cyclic ketimine, after deprotonation by strong base, can be directly coupled with an imidoyl derivative to provide the desired cyclic diketimine. Other ligands can be prepared similarly. In another embodiment, this invention provides an article comprising a 1 ,3-diimine copper complex of structure (I), deposited on a substrate. Suitable substrates include: copper, silicon wafers, wafers used in the manufacture of ultra-large scale integrated circuits, wafers prepared with dielectric material having a lower dielectric constant than silicon dioxide, and silicon dioxide and low k substrates coated with a barrier layer. Barrier layers can be used to prevent the migration of copper into the substrate. Suitable barrier layers include: tantalum, tantalum nitride, titanium, titanium nitride, tantalum silicon nitride, titanium silicon nitride, tantalum carbon nitride, and niobium nitride. EXAMPLES

Unless otherwise stated, all organic reagents are available from Sigma-Aldrich Corporation (Milwaukee, Wl, USA). [Cu(CH3CN)4]SO3CF3 can be prepared according to the method described in: T. Ogura, Transition Metal Chemistry, 1 , 179-182 (976). EXAMPLE 1

Preparation of [2-(4,5-Dihydro-3H-pyrrol-2-yl)-1-methyl-vinyl]- methyl-amine

To a solution of diisopropylamine (22.2 g, 219.3 mmol) in THF (200 mL) was dropwise added n-BuLi (2.89 M, 75.9 mL, 219.3 mmol) at -78 ⁰C under nitrogen. Once all the n-BuLi was added, the temperature was adjusted to -5 ⁰C, and the reaction mixture was stirred for 30 min. Then a solution of 2-methyl-1-pyrroline (11.3 g, 135.7 mmol) in THF (15 mL) was added dropwise to the reaction mixture at -5⁰C, and then stirred. After 30 min, ethylacetate (9.20 g, 104.4 mmol) was added dropwise over 30 min. The reaction mixture was stirred as the temperature was allowed to gradually rise to room temperature, and was continuously stirred at room temperature overnight. THF solvent was removed under reduced pressure, then 80 mL of methanol was added dropwise to the residue. After removing all of the volatile solvent, ether (100 ml_) was added to the residue, and the mixture was filtered. Concentration of the filtrate under reduced pressure, followed by column chromatography, delivered 11 g of product, β-ketoenamine (1-pyrrolidin-2-ylidene-propan-2-one, 84%). The isolated material, 1-pyrrolidin-2-ylidene-propan-2-one, (5 g,

39.94 mmol) was reacted with dimethlysulfate (5.04 g, 39.94 mmol) by stirring at room temperature overnight. THF (50 mL) was added to the resultant mixture, followed by the addition of methylamine solution (25.9 mL, 2.0 M in THF). After overnight reaction at room temperature, the solvent was removed under reduced pressure, followed by addition of sodium methoxide (39.94 mmol) solution (2.16 g of MeONa in 10 mL of MeOH). After stirring the mixture at room temperature for 30 min, the reaction mixture was concentrated under reduced pressure. Pentane (100 mL) was added to the residue, then the insoluble material was filtered. Concentration of the filtrate under reduced pressure, followed by vacuum distillation (31 ⁰C, 46 mTorr), afforded 4.2 g (76% yield) of product as a liquid.

EXAMPLE 2 Preparation and Reduction of Vinyltrimethylsilane- [[2-(4,5-Dihydro-3H-pyrrol-2-yl)-1-methyl-vinyl]-methylaminate]copper Preparation: In a dry box, Cu[(CH₃CN)₄] SO3CF3 (0.818 g, 2.17 mmol) and vinyltrimethylsilane (1.09 g) were mixed together in ether (15 mL), and the mixture was stirred at room temperature for 20 min. At the same time, the solution of diketimine, [2-(4,5-dihydro-3H-pyrrol-2-yl)-1- methyl-vinyl]-methylamine, (0.3 g, 2.17 mmol, prepared as in Example 1) in ether (15 mL) was treated with ⁴BuLi (1.28 mL, 1.7 M), and the resultant solution was stirred at room temperature for 20 min. The butyl lithium solution was added to the copper mixture, and the resultant mixture was stirred at room temperature for 1h. The reaction mixture was concentrated under vacuum, followed by the addition of pentane (2 x 20 mL) to the residue. Filtration, followed by concentration of the filtrate, afforded a desired product as viscous oil (0.63 g, 92% yield). Reduction: This material is volatile at 55 ⁰C under 500 mTorr, and was reduced to copper metal at 100 ⁰C by exposure to diethylsilane as a reducing agent.

Reduction on a substrate: The viscous oil (vinyltrimethylsilane- [[2-(4,5-dihydro-3H-pyrrol-2-yl)-1-methyl-vinyl]-methylaminate]copper, prepared as described above) was used as a copper precursor to create a copper film on a substrate. The substrate consisted of a silicon dioxide wafer with 250-Angstrom layer of tantalum on the silicon dioxide and a 100 Angstrom layer of copper on the tantalum. Approximately 0.030 g of copper precursor was loaded in a dry box into a porcelain boat. The boat and wafer (~1 cm²) were placed in a glass tube approximately 3.5 inches apart. The glass tube was removed from the dry box and attached to a vacuum line. Heating coils were attached to the glass tube surrounding both the area around the porcelain boat and the area around the wafer chip. This configuration allows the two areas to be maintained at different temperatures. Following evacuation of the system, an argon gas flow was created through the tube, passing first over the sample in the boat and then over the wafer. The pressure inside the tube was maintained at 120-200 mTorr. The region around the wafer was warmed to 120 ⁰C. After approximately an hour, the temperature of the region around the sample boat was raised to 50⁰C. These temperatures and gas flow were maintained for approximately 2 hours. The area around the sample boat was then cooled to room temperature. The tube was evacuated to a pressure of ~10 mTorr and was back-filled with diethylsilane. The area of the tube at 110 ⁰C quickly turned a copper color. The apparatus was cooled and returned to the dry box. The copper color was perceptively darker. The process was repeated to yield a wafer with a smooth copper film.

EXAMPLE 3 Preparation of Vinyltrimethylsilane[[2-(pyrrolidin-2-ylidenemethyl)-1 - pyrrolinate]copper

To a solution of diisopropylamine (11.1 g, 109.7 mmol) in THF (200 mL) was dropwise added n-BuLi (2.89 M, 37.97 mL, 109.7 mmol) at -78 ⁰C under nitrogen. Once all the n-BuLi was added, the temperature was adjusted to -5 ⁰C, and the reaction mixture was stirred for 30 min. Then a solution of 2-methyl-1-pyrroline (5.65 g, 67.9 mmol) in THF (15 ml_) was added dropwise to the reaction mixture at -5⁰C, and then stirred. After 30 min, 2-methylthio-1-pyrroline (6.02 g, 52.3 mmol) was added dropwise over 30 min at -78 ⁰C. The reaction mixture was stirred as the temperature was allowed to gradually rise to room temperature, and was continuously stirred at room temperature overnight. THF solvent was removed under reduced pressure, then 50 mL of methanol was added dropwise to the residue. After removing all of the volatile solvent, pentane (2 x 10OmL) was added to the residue, and the mixture was filtered. Concentration of the filtrate under reduced pressure, followed by vacuum distillation (65 ⁰C at 110 mTorr) delivered 6.2 g of 2-(pyrrolidin-2- ylidenemethyl)-1 -pyrroline (79%). In a dry box, 2-(pyrrolidin-2-ylidenemethyl)-1 -pyrroline (0.3 g, 2 mmoi) was treated with t-BuLi (1.7 M, 1.17 mL, 2 mmol) in ether (15 mL), and the mixture was stirred at room temperature for 20 min. At the same time Cu[(CH₃CN)₄] SO3CF3 (0.75 g, 2 mmol) and vinyltrimethylsilane (1 g,

10 mmol) were mixed together in ether (15 mL), and the resultant mixture was stirred at room temperature for 20 min. The pyrrolinate solution was added to the copper solution, and the resultant mixture was stirred at room temperature for 1 h. The reaction mixture was concentrated under reduced pressure, followed by addition of pentane (2 x 15 mL). Filtration, followed by concentration of filtrate, afforded the desired product, vinyltrimethylsilane[[2-(pyrrolidin-2-ylidenemethyl)-1 -pyrrolinate]copper, as a viscous liquid (0.59 g, 90% yield).

EXAMPLE 4

Preparation of Vinyltrimethylsilane[[2-(1 -pyrrolin-2-ylmethylene) piperidinate]copper To a solution of diisopropylamine (6.32 g, 62.52 mmol) in THF (100 mL) was dropwise added n-BuLi (2.89 M, 21.63 mL, 62.52 mmol) at -78 ⁰C under nitrogen. Once all the n-BuLi was added, the temperature was adjusted to -5 ⁰C, and the reaction mixture was stirred for 30 min. Then a solution of 2-methyl-3,4,5,6-tetrahydropyridine (3.76 g, 38.70 mmol) in THF (15 ml_) was added dropwise to the reaction mixture at -5 ⁰C, and then stirred. After 30 min, 2-methylthio-1-pyrroline (3.43 g, 29.77 mmol) was added dropwise over 30 min at -78 ⁰C. The reaction mixture was stirred as the temperature was allowed to gradually rise to room temperature, and was continuously stirred at room temperature overnight. THF solvent was removed under reduced pressure, then 30 ml_ of methanol was added dropwise to the residue. After removing all of the volatile solvent, pentane (2 x 50 ml_) was added to the residue, and the mixture was filtered. Concentration of the filtrate under reduced pressure, followed by vacuum distillation (75⁰C at 185 mTorr) delivered 4.1 g of 2- (1 -pyrrolin-2-ylmethylene)piperidine (84%).

In a dry box, 2-(1-pyrrolin-2-ylmethylene)piperidine (0.328 g, 2 mmol) was treated with t-BuLi (1.7 M, 1.17 ml_, 2 mmol) in ether (15 ml_), and the mixture was stirred at room temperature for 20 min. At the same time, Cu[(CH₃CN)₄] SO3CF3 (0.75 g, 2 mmol) and vinyltrimethylsilane (1 g, 10 mmol) were mixed together in ether (15 mL), and the resultant mixture was stirred at room temperature for 20 min. The piperidine solution was added to the copper solution, and the resultant mixture was stirred at room temperature for 1 h. The reaction mixture was concentrated under reduced pressure, followed by addition of pentane ( 2 x 15 mL). Filtration, followed by concentration of filtrate, afforded the desired product, vinyltrimethylsilane[[2-(1 -pyrrolin-2-ylmethylene) piperidinate]copper, as a viscous liquid (0.62 g, 91 % yield).

Claims

CLAIMS What is claimed is:

1. A process for forming copper deposits on a substrate comprising: a. contacting a substrate with a copper complex, (I), to form a deposit of a copper complex on the substrate; and

b. contacting the deposited copper complex with a reducing agent, wherein

L is selected from C-₂- Ci₅ olefins, C₂- Ci₅ alkynes, nitriles, aromatic heterocycles, and phosphines; R¹ and R⁴ are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, isobutyl, neopentyl, and C₃-C₅ alkylene; R², R³ and R⁵ are independently selected from hydrogen, fluorine, trifluoromethyl, phenyl, C₁-C₁₀ alkyl and C₃-C₅ alkylene, with the proviso that at least one of (R¹, R²) and (R³, R⁴) taken together is -(CR⁶R⁷) n-, where R⁶ and R⁷ are independently selected from hydrogen, fluorine, trifluoromethyl, Ci-C₅ alkyl, and Ci-C₅ alkyl ester, and n is 3, 4 or 5; the reducing agent is selected from 9-BBN (9- borabicyclo[3.3.1]nonane); diborane; boranes of the form BR_xH_3-X, where x = 0, 1 or 2, and R is independently selected from phenyl and C₁-C₁₀ alkyl groups; dihydrobenzofuran; pyrazoline; disilane; silanes of the form SiR'_yH₄-_y, where y = 0, 1 , 2 or 3, and R' is independently selected from phenyl and C₁-C₁₀ alkyl groups; and germanes of the form GeR"_zH_4-2, where z = 0, 1 , 2, or 3, and R" is independently selected from phenyl and C-1-C-10 alkyl groups.

2. The process of Claim 1 , wherein R⁵ is hydrogen.

3. The process of Claim 1 or Claim 2, wherein R¹ and R² taken together are

-(Ch^)_n-, where n is 3, 4, or 5.

4. The process of Claim 3, wherein R³ and R⁴ taken together are -(CH₂)_n-, where n is 3, 4, or 5.

5. The process of Claim 3, wherein R³ is methyl and R⁴ is H.

6. The process of Claim 1 , wherein L is vinyltrimethylsilane.

7. The process of Claim 1 , wherein the substrate is selected from copper, silicon wafers and silicon dioxide coated with a barrier layer.

8. The process of Claim 1 , wherein the substrate is exposed to a vapor of the copper complex.

9. The process of Claim 1 , wherein the deposition is carried out at a temperature of 0 to 200 ⁰C.

10. The process of Claim 1 , wherein the reducing agent is silane or diethylsilane.

11. A copper complex, (I),

(D

wherein L is selected from C2- C₁₅ olefins, C₂- C₁₅ alkynes, nitriles, aromatic heterocycles, and phosphines; R¹ and R⁴ are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, isobutyl, neopentyl, and C₃-C₅ alkylene; R², R³ and R⁵ are independently selected from hydrogen, fluorine, trifluoromethyl, phenyl, Ci-C₁₀ alkyl and C₃-C₅ alkylene; with the proviso that at least one of (R¹ , R²) and (R³, R⁴) taken together is

-(CR⁶R⁷) n-, where R⁶ and R⁷ are independently selected from hydrogen, fluorine, trifluoromethyl, C₁-C₅ alkyl, and CrC₅ alkyl ester, and n is 3, 4 or 5.

12. The copper complex (I) of Claim 11 , wherein L is vinyltrimethylsilane; R¹ and R⁵ are hydrogen' R² is methyl, (R³, R⁴) taken together is -(CH₂)_n- and n is 3.

13. An article produced by contacting a substrate with a copper complex of Claim 11.

14. The article of Claim 13, wherein the substrate is selected from copper, silicon wafers, and silicon dioxide coated with a barrier layer.

15. The article of Claim 14, wherein the barrier layer is selected from tantalum, tantalum nitride, titanium, titanium nitride, tantalum silicon nitride, titanium silicon nitride, tantalum carbon nitride, and niobium nitride.