Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
2001-01-25
2003-03-25
Chen, Bret (Department: 1762)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C556S113000, C556S114000, C427S250000, C427S123000, C427S124000
Reexamination Certificate
active
06538147
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to syntheses and utilization of new copper compounds as precursors for chemical vapor deposition to obtain high-quality copper films.
2. Description of the Prior Art
Chemical vapor deposition (CVD) processes have several advantages over physical vapor deposition (PVD) processes, such as the ability of conformal coverage and the possibility of selective deposition, to deposit copper and other metal films. To fabricate desirable materials by CVD processes, it is important to identify precursors which satisfy several requirements. The precursors should be vaporized easily and be thermally, stable at the temperatures at which vaporization occurs and yet can deposit desirable films at low, substrate temperatures.
The need for high performance interconnection materials increases as device feature sizes shrink and device density increases. Copper is expected to provide an alternative to CVD-aluminum or CVD-tungsten for metallization of ultra large scale integrated (ULSI) devices due to its low resistivity (1.67 &mgr;&OHgr;cm for Cu, 2.65 &mgr;&OHgr;cm for Al and 5.7 &mgr;&OHgr;cm for W), high electromigration resistance and high melting point (1083° C. for Cu, 660° C. for Al and 3410° C. for W). Low interconnect resistivity allows for faster devices.
Copper CVD precursors arc divided into two groups, i.e., Cu(I) and Cu(II) complexes. The precursors in the former group are quite volatile and show low deposition temperatures, but are highly, sensitive to heat and oxygen. The latter precursors are rather stable, but are isolated as solids with high melting points and thus require high deposition temperatures. It is not uncommon that impurities such as carbon or oxygen are incorporated during the thermal CVD process when using certain organometallic precursors. For instance, (&eegr;
5
-C
5
H
5
)Cu(PMe
3
) and (tert-BuO)Cu(PMe
3
) produce copper films via thermal decomposition reactions leading to incorporation of impurities. To avoid such a problem, it is necessary to tailor an organocopper precursor to deposit copper without decomposition of the ligands.
(hfac)CuL, where hfac=1,1,1,5,5,5-hexafluoro-2,4-pentanedionate and L=Lewis base, have been the most studied copper precursors to date because they can deposit copper via thermal disproportionation reaction. Especially (hfac)Cu(tmvs), where tmvs=trimethylvinylsilane, has attracted much attention since it is a liquid with reasonably high vapor pressure. Other copper compounds such as (hfac)CuL, where L=1,5-cyclooctadiene (COD), alkyne or trialkylphosphine, are either solids or liquids with a low vapor pressure. Although (hfac)Cu(tmvs) has been the most utilized copper precursor, its stability is not satisfactory for the selective growth of copper films with reproducibility (L. H. Dubois, et al., J. Electrochem. Soc., 1992, 139, 3295). In addition, a study (V. M. Donnelly, et al., Vac. Sci. Technol. A, 1993, 11, 66) demonstrated that the chemical vador deposition reaction of (hfac)Cu(tmvs) under ultra high vacuum conditions produced contamination by carbon and fluorine in the deposited films. This implies a possibility of fluorine contamination during the deposition process under certain conditions. Copper compounds of fluorinated (&bgr;-diketonates other than (hfac)CuL, such as (fod)CuL, where fod=2,2-dimethyl-6,6,7,7,8,8-heptafluoro-3,5-octanedionate (fod), or (tfac)CuL, where tfac=1,1,1-trifluoro-2,4-pentanedionate, were reported not to exhibit sufficient thermal stability to be used as CVD precursors (K. M. Chi, et al., J. Organomet. Chem., 1993, 449, 181). Therefore, a precursor with high volatility and stability, which contains no fluorinated ligands, is more desirable for the deposition of copper by CVD.
Copper compounds of acetoacetate derivatives which contain no fluorinated ligands were reported as CVD precursors. They were reported to be volatile and to deposit copper films at low substrate temperatures (H. Choi, et al., U.S. Pat. No. 5,441,766). Cu(II) acetoacetate derivatives in the report were found to be attractive since they were volatile without employing fluorinated ligands and deposited copper films at temperatures below 200° C. However, they were solids with high melting points and were incapable of selective deposition of copper. On the other hand, the Cu(I) acetoacetate derivatives deposited copper films at relatively low temperatures via disproportionation reaction. However, few are practical for use as CVD precursors since they are either solids or liquids with a low vapor pressure or they have an extremely low thermal stability (i.e. their decomposition temperature is within a few degrees of their vaporization temperature). A limited claim was made to the alkylphosphite family of Cu(I) acetoacetate precursors demonstrated to deposit copper at low temperatures (H. Choi, Korean Patent Application No. 1998-32069). This is an expansion of those claims to include other recent works presented by Choi et al. (H. Choi, et al. Chem. Mater. 1998, 2326).
SUMMARY OF THE INVENTION
The object of the present invention is to provide new Cu(I) CVD precursors which contain no fluorinated ligands and are capable of depositing high-quality copper at low deposition temperatures.
The precursors according to the invention include: (R
3
COOCR
2
COR
1
)Cu
+1
{L}
x
, where x is 1, 2 or 3, L is a neutral ligand which is a phosphine, phosphite or an unsaturated hydrocarbon, and R
1
and R
3
are each independently C
1
-C
9
alkyl or aryl groups and R
2
may be H, F or C
1
-C
9
alkyl or aryl groups, wherein R
3
may also be an alkylsilane group, {—Si(R
4
)(R
5
)(R
6
)}, wherein R
4
, R
5
and R
6
independently may be C
1-C
9
alkyl or aryl or alkoxy (—OR where R is C
1
-C
9
alkyl or aryl) groups attached to silicon. The precursors in the present invention, which are low melting solids or distillable liquids with high volatility and thermal stability, can be vaporized without decomposition and used to deposit high-quality copper films. The improved stability of the copper compounds in the present invention enables them to reproducibly produce selective copper films on metallic or electrically conductive surfaces.
Further objects and advantages of the invention will become apparent through reading the remainder of the specification.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, the general formula of the organocopper precursor is (R
3
COOCR
2
COR
1
)Cu
+1
{L}
x
where
x is 1, 2 or 3;
R
1
and R
3
are each independently C
1
-C
9
alkyl or aryl groups and R
2
may be H, F or C
1
-C
9
alkyl or aryl groups, wherein R
3
may also be an alkylsilane group, {—Si(R
4
)(R
5
)(R
6
)}, wherein R
4
, R
5
and R
6
independently may be C
1
-C
9
alkyl or aryl or alkoxy (—OR where R is C
1
-C
9
alkyl or aryl) groups attached to silicon; and
L is a neutral ligand which can be a phosphine or phosphite ligand, {P(R
7
)(R
8
)(R
9
)} wherein R
7
, R
8
and R
9
are each independently hydroxy or C
1
-C
9
alkyl or aryl or alkoxy (—OR where R is C
1
-C
9
alkyl or aryl) groups wherein if at least one of R
7
, R
8
or R
9
groups is an alkoxy group the electron donating ability of oxygen in the phosphite ligand strengthens the bond between the Cu and the phosphite ligand resulting in enhanced stability of the compound.
The neutral ligand, L, may also be an unsaturated hydrocarbon described as (R
10
)(R
11
)—C═C—(R
12
)(R
13
) containing at least one carbon-carbon double bond, wherein R
10
, R
11
, R
12
and R
13
are each independently H, F, C
1
-C
9
alkyl or aryl or an alkylsilane group, {—Si(R
14
)(R
15
)(R
16
)}, wherein R
14
, R
15
and R
16
independently may be C
1
-C
9
alkyl or aryl or alkoxy (—OR where R is C
1
-C
9
alkyl or aryl) groups attached to silicon, and any combination of R
10
, R
11
, R
12
or R
13
may be joined together to form at least one C
4
-C
16
cycloaliphatic ring containing at least one carbon-carbon double bond.
Chen Bret
Ohlandt Greeley Ruggiero & Perle L.L.P.
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