SUBSTITUTED CYCLOALKENE NEW COPPER PRECURSORS FOR CHEMICAL VAPOR DEPOSITION OF COPPER METAL THIN FILMS

Abstract: A method of forming a volatile copper precursor for chemical vapor deposition of copper metal thin film includes formation of avo latile liquid having a chemical formula of (n-R-m-cyclohexene)Cu(I)(hfac) or (n-R-m-cyclopentene)Cu(I)(hfac), where n,m=1-6, and where R is a alkyl, such as methyl and ethyl.

Description: DESCRIPTION SUBSTITUTED CYCLOALKENE NEW COPPER PRECURSORS FOR CHEMICAL VAPOR DEPOSITION OF COPPER METAL THIN FILMS TECHNICAL FIELD This invention relates to the synthesis of volatile liquid copper precursors and their applications in chemical vapor deposition of copper metal thin films. BACKGROUND ART Recently, there has been a great interest in chemical vapor deposition of copper metal thin films. Because of its low resistivity, *- 1.7 μΩ-cm, and high electromigration resistance, copper metal thin film material is considered to be ideal for use as metal interconnections in integrated circuits. Chemical vapor deposition (CVD) of copper requires the use of a stable yet volatile precursor. For the purpose of commercialization, the cost of the copper precursor is an issue. In addition, the copper precursor must have good adhesion to metal nitride coated substrates, low resistivity, ~1,8 μΩ-cm, excellent conformity to surface structures, and good electromigration resistance. In CVD processes, generally performed at elevated temperatures, the copper precursor must have a vapor pressure high enough to achieve a reasonable deposition rate, and must also be stable at deposition temperatures, without any decomposition in the CVD liquid delivery line or during vaporizer. Copper metal thin films may be prepared via chemical vapor deposition using a variety of copper precursors. In 1990, D. B. Beach et αZ Low-Temperature Chemical Vapor Deposition of High Purity Copper from an Organometallic Source, Chem. Mater. (2) 216 (1990), obtained pure copper films via CVD by using At about the same time, Hampden-Smith, M. J. et al, Chem. Mater, (2) 636 (1990) declared the same results by using (Jer£-BuO)Cu(PMe 3 ). These copper films, however, contain carbon and phosphorus, which elements constitute contaminants when used as interconnections in integrated circuits, and so they cannot be used as interconnectors in microprocessors. The studies of copper precursors conducted in the early of 1990's were concentrated on the evaluation of a series of copper(L) fLuo inated β-di etonate complexes, which have been proven to be very promising sources for the use in the chemical vapor deposition of copper metal thin films. Copper® fluorinated p-di etonate complexes were synthesize* by Gerald Doyle, as described in U.S. Patent No. 4,385,005, granted May 24, 1983, for Process for separating unsaturated hydrocarbons using copper or silver complexes with fluorinated diketonates, and U.S. Patent No.4,425,281, granted Jan 10, 1984, for Copper or silver complexes with fluorinated diketones and unsaturated ligands, in which he presented the synthesis method and its application in the separation of unsaturated organic hydrocarbons. U.S. Patent No. 5,096,737, to Bau et al, granted March 17, 1992, for Ligand Stabilisation +1 Metal Beta-Diketonate Coordination Complexes and Their Use in Chemical Vapor Deposition of Metal Thin Films, described the application of copper(ϊ)fluorinated β-di&etonate complexes as copper precursors for CVD copper thin film preparation. Copper thin films have been prepared via ohemical vapor deposition using these precursors. Among several liquid copper precursors, 1,5-dimethyl l,5«cyclooctadiene copper(I)hexafluoroacetylacetonate mixed with 1,6-dimethyl 1,5-cyclooctadiene copper(I)hexafluoroacetylacetonate ((DMCOD)Cu(hfac)) and hexyne copper(I)hexafluoroacetylacetonate ((HYN)Cu(hfac)) were evaluated in detail. The copper thin films deposited using (DMCOD)Cu(hfac) have very good adhesion to metal or metal nitride substrates, but a high resistivity, ϊ.e., '-2,5 μΩ'c , and a low deposition rate, whereas by using (HyN)Cu(hfac), the copper film has poor adhesion to a TiN substrate, and high resistivity, i.e. } ~2.1 μΩ-cm. Another compound, 2-butyne copper(I)(hfac), ((BUΣ)Cu(hfac)), forms a copper film with low resistivity, ~ 1.98 μΩ « cm, but has poor adhesion and is relatively expensive, and, because the compound is a solid, it must be vaporized prior to CVD, The formation of copper(I)(hfac) stabilized with a series of trialkylvinylsilane (TMVS), as described in U.S. Patent No. 5,085,731, to Norman et σZ., granted February 4, 1992, fbr Volatile liquid precursors for the chemical vapor deposition of copper, results in improved copper thin films. Copper films, deposited using liquid copper precursor of (bfac)Cu(TMVS) are of low resistivities and are reasonably adhesive to substrates. This liquid copper precursor has been used for the preparation of copper metal thin films via CVD for some time, but still has some drawbacks: stability, the poor adhesion of the copper film, and the cost o£the trimethylvinylsilane stabilizer are significant impediments to the widespread use of this technique. Other references of note are: Gerald Doyle, . A. Eriksen and D. Van Engen, Organometallics 4, 830 (1985); Thomas H. Baum and Carl E. Larson, Chem. Mater. 4, 365 (1992); and Thomas H. Bau and Carl E. Larson, J. Electrochem. Soc. 140(1), 154 (1993). DISCLOSURE OF THE INVENTION A method of forming a volatile copper precursor for chemical vapor deposition of copper metal thin film includes formation of a volatile liquid having a chemical formula of (n*R-m-cyclohexene)Cu(I)(hfac) or (n-R-m-cyclopentene)Cu(I)(hfac), where n,m = 1 - 6, and where R is a alkyl, such as methyl and ethyl. An object of the invention is to provide a series of new high volatile liquid copper precursors for chemical vapor deposition of copper metal thin films. Another object of the invention is to provide such precursors in an economical and stable form. These and other objeots and advantages of the invention will become more fully apparent as the description which follows is read in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 depiots the structure of (n-R ' m-cyclohexene)Cu(I)(hfac). Fig. 2. depicts the structure of (n-R-m-cycloρentene)Cu(I)(hfac). Fig. 3 depicts the structure of (l»methyl-l-cyclohexene) Cu(I)(hfac). BEST MODE FOR CARRYING OUT THE INVENTION The invention involves the chemical vapor deposition (CVD) synthesis of a series of volatile copper precursors, to form copper metal thin films, and the synthesis of the precursors. The copper films deposited using these new liquid copper precursors exhibit excellent electrical properties, and good adhesion to metal and metal nitride substrates, such as W, Ti, TiN, Ta, TaN, Al, Pt, and the like. To achieve the objects of this invention, a precursor must: a. have a high volatile liquid phase and a high deposition rate of copper to form a copper thin film; b. be stable at room temperature to provide easy storage and handling; and c. have reasonable synthesis cost for commercialization. Copper films prepared via CVD using this new copper precursor must; a. have good adhesion to metal and metal nitride substrates, such as TiN, WN, TaN, etc.; b, have low resistivity, < 1.9 μΩ-cm; c. have high electromigration resistance; and d. have excellent conformity to extreme surface morphology. The invention described herein includes the preparation of a new, highly volatile liquid thin metal copper precursor, known as (l-methyl-l-cycloheχene)-copper(I) hexa luoroacetylacetonate, or (lMlCH)Cu(I)(hfac). The price for 1-methyM-cyclohexene is' approximately US$120,00 for lOOg, which is much lower than that of trimethylvinylsilane, used in the prior art, whic generally costs about US$180.00 for lOOg, Experimental use of this precursor in CVD tests have proven that this new, highly volatile liquid copper thin metal precursor has the desired properties and meets all of the requirements listed above. The copper films deposited using these new liquid copper precursors have exhibited excellent electrical properties, and good adhesion to metal and metal nitride substrates, such as , Ti, TiN, Ta, TaN, Al, Pt, and the like. These organometaHic copper complexes are represented by the structural formula (n-R-m-cyclohexene)Cu(0(hfac), shown in Fig, 1, or (n-R-m-cyelopentene) Cu(I)(hfac), shown in Fig. 2, where (n,m "= 1 - 6), and where R is alkyl, such as methyl and ethyl, Preferably, the R is CHs, whereby (l-methyl « l-cyclohexene)Ou(I)(hfac) compound is formed, as shown in Fig. 3. All steps in the synthesis process are conducted in an air-free dry glovebox, or by using standard Schlenk techniques, Solvents are purified before synthesis. Dichloromethane is refluxed and distilled over calcium hydride under an atmosphere of nitrogen prior to use. 1-Metbyl-l-cyclohexene and 1,1,1,5,5,5-hexafluoroacetylacetone, in the preferred embodiment, are supplied by Aldrich and Strem, respectively, and used as supplied, without further purification. The synthesis procedure of organometallic copper® complexes is described in U.S. Patent No. 4,885,005, supra, in which copper monoxide reacted with unsaturated organic hydrocarbon and 1,1,1,5,5,5-hexafLuoroacetylacetone in dichloromethane or THF. The reaction is described by the following equation: CHaCls orTHF CuaO + 2(CF.)C(0)CH?C(0)(CFa) + 2 5 2 Cu(h ac)( ) + H 2 0 where L is unsaturated organic hydrocarbon l gand. Following the synthesis procedure described above, the synthesis of (iMlCH)Cu(hfac) results in a desired product, which, unfortunately, is not stable at room temperature over a long time. To resolve the stability issue, about 5% 1-methyl-l-cyclohexene (by product weight) is introduced into the product for stabilization. Following this procedure, and after letting the compound sit for one month, no solid precipitation was observed. In the synthesis of (lMlCH)Cu(hfac), CugO in the amount of 41.26 g, (0.29 mol) is added to a 500 ml round bottom flask having 200 mL of CH2CI2 therein. The flask is equipped with a stirring bar. To this CuaO dichloromethane red solution, 57 mL of 1-methyl-l-cyclohexene, (0,48 mol) is added. The solution is stirred at room temperature jfor about five minutes, 100 g of 1,1,1,5,5,5-hexafiuoroacetylacetone (0.48 mol) is introduced, with stirring. After one minute, the solution color gradually changes to green. The green solution is continually stirred for about another 10 minutes, and then filtered through celite, having a filter pore size of between about lOμm and 25μm. The green filtrate is stripped under vacuum for two hours and then heated to 35°C, under vacuum, for another half-hour of stripping. This produces a green liquid organometallic copper compound containing a small number of little green crystals, which is then filtered through a fine filter (Iμm) to yield 145.7g of product, having a yield of 82.64%, based on hfac. The theoretical yield based on ,H(hfac) is 176.8g. For stabilization, 1-methyl-l-cyclohexene (6,437 g) was introduced into the product (138.621, total of 145.058 gram), in which the product contained 4.44% free 1-methyl-l-oyclohexene. The NMR structural analysis was carried out on a QE 800 MHz NMR instrument. The results are as follows: NMR (CeDs) ( 1.22 (multi., 2, C6H7H2CΗ3), 1.30 (multi, 2, CeHTU CHa)), 1.41(β, 3, CeHTϋrøHa)), 1.75 (multi., 2, C e H 7 #2(CH 3 )), 1.80 (multi, 2, 4.79 (multi, 1, C e H8#(CH 3 )), 6.15 (s, 1, CF3C(O)C2JC(O)OFs). The results of copper metal thin film deposition via CVD using (lMlCH)Cu(hfac) liquid precursor were very good. The copper thin films have shown good adhesion to metal and metal nitride substrates, low resistivity, - 1.8 μΩ « cm, and very good reproducibility. The precursor is very volatile, and an extremely high deposition rate, approximately 500 Λ per minute using 0.1 ml/ in liquid injection rate at 50°C of very low vaporizer temperature, has been achieved, INDUSTRIAL APPLICABILITY Thus, a new synthesis method has been employed for the synthesis of (1-methyl 1- cydohexene)copper(l)(hexafluoroacetylacetonate). (l-methyM»cyclohexene)σopper® hexafl.uoroacetylacθtonate) is a new liquid copper precursor, which is made stable at room temperature, by the inclusion of about 5% 1-methyl-l-cyclohexene as a stabilizer, and is highly volatile, Copper films prepared via chemical vapor deposition of (1-methyl-l- cyclohexene)copper® (hexafluoroacetylacetonate) have good adhesion to metal and metal nitride substrates and low resistivity. Copper films prepared via chemical vapor deposition using (1-methyl-l-cyclohexene) copper(I)(hexafluoroacetylacetonate) are useful and fully functional in ΪC devices. Although a preferred embodiment of the invention, and several variations thereof have been disclosed, it will be appreciated that further variations and modifications may be made thereto without departing from the scope of the invention as defined in the appended claims.

Claims: CLAIMS 1. A method of forming a volatile liquid copper precursor for chemical vapor deposition of copper metal thin films, comprising: placing 200 mL of CH2CI2 in a vessel; adding about 41.26 g (0.29 mol) of Cu 2 O, thereby forming CujjO dichloromethane red solution; adding 57 mL (0.48 mol) of 1-methyl-l-cyclohexene; stirring the solution at room temperature for about five minutes; adding about 0.48 mol of a β-diketone; stirring for about eleven minutes; filtering the solution through celite, having a filter pore size of between about lOμ and 25μm; stripping the solution, under vacuum, for about two hours; heating the solution to about 35°C, under vacuum, and stripping for about 30 minutes; filtering the solution through a fine filter having a pore size of about lμm; and adding about 5% to about 10%, by weight, of a stabilizing ligand. 2. The method of claim 1 wherein said adding about 0.48 mol of a β-diketone includes adding about lOOg of 1, 1, 1, 5,5, 5-hexafluoroacetylacetone. 3. The method of claim 1 wherein said adding a stabilizing ligand includes adding about 6.437 g of 1-methyl-l-cyclohexene to produce a copper precursor having a ohemical formula taken from the group of chemical formulas consisting of (n-R-m-cyclohexene)Cu(I)(hfac) and (n-R-m-cyclopentene)Cu(I)(hfac), where (n,m = 1 - 6), and where R is a alkyl, taken from the group of alkyls consisting of methyl and ethyl. 4. A method of forming, a volatile copper precursor for chemical vapor deposition of copper metal thin film, comprising: forming a volatile liquid having a chemical formula taken from the group of chemical formulas consisting of (n-R-m-cyclohexene)Cu(I)(hfac) and (n-R-m-cyclopentene)Cu(I)(hfac), where n,m = 1 - 6, and where R is a alkyl, taken from the group of alkyls consisting of methyl and ethyl. 5. The method of claim 4 which includes adding a stabilize g' ligand. 6. The method of claim 5 wherein said adding a stabilizing Hgand includes adding 1-methyl-l-cyclohexene. 7. The method of claim 6 wherein said adding 1-methyl-l-cyclohexene includes adding about 6% to 10% of l-methyl«l-cyclohexene by weight. 8. The method of claim 4 which further includes adding a β- diketone. 9. The method of claim 8 wherein said adding a β- diketone includes adding 1,1,1,5,5,5-hexafl.uoroacetylacetone.

Inventors: CHARNESKI LAWRENCE J, EVANS DAVID R, HSU SHENG TENG, NGUYEN TUE, ZHUANG WEI-WEI, CHARNESKI, LAWRENCE, J., EVANS, DAVID, R., HSU, SHENG, TENG, NGUYEN, TUE, ZHUANG, WEI-WEI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 2001
Main classification: C23C16
IPC codes: C07C45, C07C49, C07F1, C23C16, H01L21