Patent Application
20080171890
The present invention relates to a volatile nickel aminoalkoxide complex; a process of the preparation thereof; and a metal organic chemical vapor deposition (MOCVD) process for forming a nickel thin film on a substrate using said compound.
Thin films of nickel, nickel alloys such as AuGeNi and NiP2, nickel silicides, nickel gallides or nickel aluminides are widely used for the manufacture of semiconductor devices, nano-structures, hydrogen storage alloys and microelectromechanical actuators.
There have been reported studies of preparing such nickel-containing films by metal organic chemical vapor deposition (MOCVD) using nickel tetracarbonyl [Ni(CO)4]; nickelocene compounds such as bis(cyclopentadienyl) nickel [Ni(η5-C5H5)2] and bis(methylcyclopentadienyl) nickel [Ni(η5-CH3C5H4)2]; nickel β-diketonate compounds such as Ni(acac)2 (acac=2,4-pentanedionato) and Ni(hfac)2 (hfac=1,1,1,5,5,5-hexafluoro-2,4-pentanedionato). In addition, there have been disclosed reports regarding an organonickel precursor containing two β-ketoimine or aminoalkoxide ligands with nitrogen donor moieties which are capable of forming dative bonds with nickel [J. D. Martin, P. Hogan, K. A. Abboud, K.-H. Dahmen, Chem. Mater., 1998, 10, 2525; and L. G. Hubert-Pfalzgraf, H. Guillon, Appl. Organomet. Chem., 1998, 12, 221].
However, Ni(CO)4 is very toxic while the nickel β-ketoimine compound has relatively low volatility, and the above conventional precursors are known to give nickel thin films containing carbon and oxygen contaminants.
Accordingly, it is an object of the present invention to provide a novel organonickel compound which has high volatility and high thermal stability, and can be advantageously used in forming a nickel thin film of improved quality under a mild condition.
It is another object of the present invention to provide a process for preparing said compound.
It is a further object of the present invention to provide a process for depositing a nickel thin film on a substrate using said compound.
In accordance with one aspect of the present invention, there is provided a nickel aminoalkoxide complex of formula (I):
wherein, R1, R2, R3 and R4 are each independently linear or branched C1-4 alkyl; and m is an integer in the range of 1 to 3.
In accordance with another aspect of the present invention, there is provided a process for preparing said nickel aminoalkoxide complex of formula (I) comprising reacting a compound of formula (II) with a compound of formula (III) or reacting a compound of formula (IV) with a compound of formula (V), in an organic solvent:
Ni(OY)2 (II)
HOCR1R2(CH2)mNR3R4 (III)
Ni(NH3)6X2 (IV)
MOCR1R2(CH2)mNR3R4 (V)
wherein, X is halogen; Y is C1-4 alkyl; M is Li or Na; and R1, R2, R3, R4 and m are the same as previously defined.
In accordance with further another aspect of the present invention, there is provided a process for depositing a nickel thin film on a substrate which comprises bringing the vapor of the nickel aminoalkoxide complex of formula (I) into contact with a substrate heated to a temperature ranging from 200 to 500° C.
The above and other objects and features of the present invention will become apparent from the following description of the invention taken in conjunction with the following accompanying drawings, which respectively show:
The novel compound of formula (I) of the present invention is a complex formed between two aminoalkoxide ligands and one divalent nickel ion, wherein the coordination of the nickel ion is saturated, and the two C1-4 alkyl groups at the α-carbon and the two C1-4 alkyl groups bonded to the amino-nitrogen atom serve to shield the oxygen and nitrogen atoms of the aminoalkoxide ligand. This minimizes the compounds' intermolecular interactions and confers on the compound a high affinity toward an organic solvent such as diethyl ether, tetrahydrofuran, toluene, hexane and a mixture thereof.
The inventive nickel complex is either a liquid or solid at room temperature, can be vaporized or sublimed at a low temperature in the range of 30 to 100° C., and undergoes facile and clean thermal decomposition to provide a contaminant-free nickel thin film under a mild condition when applied to an MOCVD process, while generating volatile hydrocarbon species through intramolecular 8-hydrogen elimination.
Among the compounds of formula (I) of the present invention, the preferred are those wherein R1, R2, R3 and R4 are each independently CH3, C2H5, CH(CH3)2 or C(CH3)3, and m is 1 or 2.
The inventive complex of formula (I) may be prepared by reacting a compound of formula (II) with a compound of formula (III) in an organic solvent such as toluene under a refluxing condition, as shown in Reaction Scheme A:
wherein, R1, R2, R3, R4, m and Y have the same meanings as defined above.
Alternatively, the inventive complex of formula (I) may be prepared by reacting a compound of formula (IV) with a compound of formula (V) in an organic solvent such as toluene under a refluxing condition, as shown in Reaction Scheme B:
wherein, R1, R2, R3, R4, m, X and M have the same meanings as defined above.
As shown in Reaction Schemes A and B, the compound of formula (III) or (V) is reacted with the compound of formula (II) or (IV) in a stoichiometric ratio, e.g., in an amount of 2 equivalents based on 1 equivalent of the compound of formula (II) or (IV) to prepare the inventive nickel complex of formula (I).
In accordance with the present invention, a nickel thin film may be deposited on a substrate by bringing the vapor of the nickel aminoalkoxide complex of formula (I) into contact with a substrate heated to a temperature ranging from 200 to 500° C., preferably from 250 to 350° C.
The decomposition mechanism for the conversion of the inventive nickel complex into metallic nickel in such MOCVD is shown in Reaction Scheme C:
wherein, R1, R2, R3, R4 and m have the same meanings as defined above.
The inventive nickel complex converts to metallic nickel through intramolecular β-hydrogen elimination on decomposition, while generating volatile hydrocarbon species such as aminoalcohols, ketones and endiamines.
The substrate which may be used in practicing the present invention is any inorganic solid that is stable at or above the film deposition temperature and examples thereof include glass, quartz, silicon, gallium arsenide, sapphire, alkali metal niobate and alkaline earth metal titanate, among which a TiN- or TaN-coated single crystal of silicon is preferred when the coated substrate is intended for use in electronic applications.
The following Examples are given for the purpose of illustration only, and are not intended to limit the scope of the invention.
3.50 g (15.10 mmol) of Ni(NH3)6Cl2 was suspended in 50 mL of toluene in a 125 mL Schlenk flask and 4.62 g (33.20 mmol) of sodium dimethylamino-2-methyl-2-propoxide [Na(dmamp)] was slowly added thereto. The color of the mixed solution gradually changed to dark brown. The dark brown mixture was refluxed for 8 hours under a nitrogen atmosphere and filtered. The resulting filtrate was distilled in a vacuum to remove the solvent. The solid obtained was purified by sublimation at 60° C. under a reduced pressure of 10−2 Torr, to give 3.20 g of the title compound in the form of a dark brown solid having a melting point of 118-119° C. (yield: 72.9%).
1H NMR (ppm, C6D6): 1.379 (s, 6H, —C(CH3)2), 1.728 (s, 2H, —CH2), 2.317 (s, 6H, —N(CH3)2) (see
Elemental analysis: Calculated for C12H28N2O2Ni: C, 49.52; H, 9.70; N, 9.62. Found: C, 49.08; H, 9.45; N, 9.47.
FT-IR (cm−1, KBr pellet): ν(Ni—O) 551, 527, 453 (see
Mass spectrometry (EI, 70 eV), m/z (ion, relative intensity): 290 ([Ni(L)2]+, 38), 232 ([Ni(L)2-CH2NMe2]+, 11), 217 ([Ni(L)2-CH2NMe2-Me]+, 14), 174 ([Ni(L)]+, 100), 159 ([Ni(L)-Me]+, 20), 116 ([Ni(L)-CH2NMe2]+, 29), 58 ([CH2NMe2]+, 77).
2.00 g (8.63 mmol) of Ni(NH3)6Cl2 was suspended in 50 mL of toluene in a 125 mL Schlenk flask and 2.90 g (17.34 mmol) of sodium diethylamino-2-methyl-2-propoxide [Na(deamp)] was slowly added thereto. The color of the mixed solution gradually changed to dark brown. The dark brown mixture was refluxed for 8 hours under a nitrogen atmosphere and filtered. The resulting filtrate was distilled in a vacuum to remove the solvent. The solid obtained was purified by sublimation at 60° C. under a reduced pressure of 10−2 Torr, to give 1.85 g of the title compound in the form of a dark brown solid having a melting point of 54-55° C. (yield: 61.7%).
1H NMR (ppm, C6D6): 1.335 (s, 6H, —C(Cl3)2), 1.675 (s, br, 6H, —N(CH2CH3)), 1.873 (s, 2H, —CH2), 2.422, 3.009 (s, br 4H, —N(CH2CH3)) (see
Elemental analysis: Calculated for C16H36N2O2Ni: C, 55.35; H, 10.45; N, 8.07. Found: C, 50.95; H, 9.69; N, 8.60.
FT-IR (cm−1, KBr pellet): ν(Ni—O) 592, 531, 443 (see
Mass spectrometry (EI, 70 eV), m/z (ion, relative intensity): 346 ([Ni(L)2]+, 16), 230 ([Ni(L)2-CH2NEt2-Me2]+, 25), 202 ([Ni(L)]+, 39), 130 ([Ni(L)-NEt2]+, 44), 86 ([L-Et2]+, 100), 58 ([OCMe2]+, 45).
4.50 g (19.3 mmol) of Ni(NH3)6Cl2 was suspended in 50 mL of toluene in a 125 mL Schlenk flask and 6.00 g (38.6 mmol) of sodium dimethylamino-2-methyl-2-butoxide [Na(dmamb)] was slowly added thereto. The color of the mixed solution gradually changed to dark brown. The dark brown mixture was refluxed for 8 hours under a nitrogen atmosphere and filtered. The resulting filtrate was distilled in a vacuum to remove the solvent. The liquid residue was purified by sublimation at 80° C. under a reduced pressure of 10−2 Torr, to give 5.07 g of the title compound in the form of a green liquid (yield: 82.6%).
1H NMR (ppm, C6D6): 0.93 (t, J=7.6 Hz, 6H, —CH2CH3), 1.35 (d, J=3.6 Hz, 6H, —C(CH3)), 1.65 (m, 4H, —CH2CH3), 1.81 (m, 4H, —NCH2C—), 2.29 (d, J=7.5 Hz, 6H, —N(CH3)2), 2.38 (d, J=8.7 Hz, 6H, —N(CH3)2).
13C NMR ppm, C6D6): 9.7, 28.9, 37.5, 51.1, 75.2, 75.9.
Elemental analysis: Calculated for C14H32N2O2Ni: C, 52.69; H. 10.11; N, 8.78. Found: C, 52.33; H, 10.50; N, 9.84.
FT-IR (cm−1, KBr pellet): ν(Ni—O) 555, 492, 451.
Mass spectrometry (EI, 70 eV), m/z (ion, relative intensity): 318 ([Ni(L)2]+, 100), 289 ([Ni(L)2-CH2CH3]+, 78), 231 ([Ni(L)2-CH2CH3—C(O)(Me)(Et)]+, 61), 188 ([Ni(L)]+, 74), 159 ([Ni(L)-CH2CH3]+, 30), 58 ([CH2NMe2]+, 79).
Thermogravimetric/differential thermal analysis (TG/DTA) scans of the nickel aminoalkoxide complexes prepared in Examples 1 and 3 are shown in
These results suggest that the nickel complexes synthesized in Examples 1 to 3 have high volatility, are thermally stable and convert to relatively pure nickel on decomposition, and therefore, they are suitable MOCVD precursors for nickel deposition.
A Si(001) wafer having an oxide layer on its surface was heated to a temperature selected from 200, 250, 300 and 350° C. at an initial pressure of 10−5 Torr. Ni(dmamp)2 prepared in Example 1 was vaporized at 60° C. and the vapor was transported to the surface of the wafer using an argon carrier gas (flow rate 4 sccm) at a total pressure of 10 mTorr to deposit a film thereon.
X-ray photoelectron spectra of the deposited films showed that the films were pure metallic nickel. XRD patterns thereof showed that the films deposited at 250-350° C. were crystalline (
A Si(001) wafer having an oxide layer on its surface was heated to a temperature selected from 250, 300, 350, 400, 450 and 500° C. at an initial pressure of 10−3 Torr. Ni(dmamp)2 prepared in Example 1 was vaporized at 60° C. and the vapor was transported to the surface of the wafer using an argon carrier gas (flow rate 4 sccm) at a total pressure of 100 mTorr to deposit a film thereon.
X-ray photoelectron spectra of the deposited films showed that the films were pure metallic nickel (
A Si(001) wafer having an oxide layer on its surface was heated to 300° C. at an initial pressure of 40 mTorr. Ni(dmamb)2 prepared in Example 3 was vaporized at 40° C. and the vapor was transported to the surface of the wafer using an argon carrier gas (flow rate 10 sccm) together with a hydrogen gas flow (flow rate 10 sccm) at a total pressure of 70 mTorr to deposit a film thereon.
An X-ray photoelectron spectrum of the deposited film shown in
A Si(001) wafer having an oxide layer on its surface was heated to a temperature selected from 270, 280, 290, 300, 310, 330 and 350° C. at an initial pressure of 2 mTorr. Ni(dmamb)2 prepared in Example 3 was vaporized at 70° C. and the vapor was transported to the surface of the wafer without using a carrier gas at a total pressure of 80 mTorr to deposit a film thereon.
X-ray photoelectron spectra of the deposited films showed that the films were pure metallic nickel. XRD patterns thereof shown in
As shown above, the nickel complex of the present invention can be vaporized at a low temperature and is thermally stable, and therefore, it may be effectively employed in MOCVD of a nickel thin film having an improved quality.
While the embodiments of the subject invention have been described and illustrated, it is obvious that various changes and modifications can be made therein without departing from the spirit of the present invention which should be limited only by the scope of the appended claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR05/01002 | 4/7/2005 | WO | 00 | 10/4/2007 |
