Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
1999-12-10
2001-10-16
Nazario-Gonzalez, Porfirio (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C427S252000
Reexamination Certificate
active
06303809
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to organometallic source reagents for chemical vapor deposition. More particularly, it relates to thermally decomposable ruthenium and osmium organometallic compounds and complexes which are useful in chemical vapor deposition processes, for formation of ruthenium, osmium, RuO
2
, OSO
2
, and other ruthenium- or osmium-containing films on substrates. The invention also relates to a method for forming a ruthenium- or osmium-containing film by chemical vapor deposition utilizing such compounds.
2. Description of the Related Arts
Chemical vapor deposition (hereafter indicated as “CVD”) is widely used for the formation of ruthenium, osmium, RuO
2
and OSO
2
thin films on a variety of substrates. CVD is a particularly attractive method for forming films because it is readily scaled up to production runs, and because the electronic industry has a wide experience and suitable equipment that can be applied to CVD processes.
CVD processes require suitable source reagents which are sufficiently volatile to permit a rapid transport of their vapors into the CVD reactor. The source reagents, which may be called the precursors, should be thermally stable and relatively inert against oxygen and moisture in air at room temperature to allow long-term storage. They also should decompose cleanly in the CVD reactor to deposit high purity metal component at the desired growth temperature on the substrate.
Various ruthenium organometallic complexes have been proposed as source reagents for CVD applications, which include ruthenocene and its alkyl substituted derivative complexes, such as Ru(C
5
H
4
Pr
i
)
2
, and carbonyl complexes, such as Ru(CO)
4
(hfb), hfb=hexafluoro-2-butyne, [(C
5
H
5
) Ru (CO)
2
]
2
and Ru
3
(CO)
12
; tris-&bgr;-diketonate complexes, such as Ru(acac)
3
, Ru(tfac)
3
and Ru(TMHD)
3
; and organometallic olefin complexes, such as bis(2,4-dimethylpentadienyl)ruthenium, bis(2,4-dimethyloxapentadienyl)ruthenium, (&eegr;
6
-C
6
H
6
)Ru(&eegr;
4
-C
6
H
8
), C
6
H
8
=1,3-cyclohexadiene, and Ru(C
3
H
5
)
2
(COD), COD=1,4-cyclooctadiene. Although some of these compounds are liquids or relatively volatile low-melting solids, which are amenable to sublimation for gas-phase transport into the CVD reactor, most of them are high-melting solids and associate with fairly high decomposition temperature, or thermally unstable and reactive towards moisture and oxygen upon exposure to air, which make them difficult to store and handle. Selected physical properties of these known organometallic reagents are listed in Table 1.
TABLE 1
Selected physical properties of known organometallic ruthenium source reagents
Sublimation Condition
Decomposition
or Vapor Pressure
Compound
Melting Point (° C.)
Temperature (° C.)
(mmHg)
Remarks
Ruthenocene
194-198
—
vap. 85° C./0.01 mm
—
Ru
3
(CO)
12
150
150
—
—
Ru(CO)
4
(hfb)
No m.p. data
—
Subl. at 25° C./0.05 mm
Unstable above 25° C.
Vap. 25° C./1.5 mm
Ru(acac)
3
~223
~220
—
—
Ru(tfac)
3
155-160 (2 isomers)
—
—
Sublimed at 85-100° C.
Ru(TMHD)
3
200-203
250
Subl. at 120° C./0.5 mm
—
Ru(TMHD)
2
(COD)
187-190
220
subl. at 100° C./0.05 mm
—
Ru(C
3
H
5
)
2
(COD)
—
—
volatile at ≧50° C.
Air sensitive solid
RuO
4
—
—
—
Highly toxic
Accordingly, there is an urgent need for low-melting, highly volatile and relatively air and thermal stable ruthenium and osmium organometallic compounds as source reagents for various CVD applications, such as the formation of bottom electrodes, diffusion barriers, conductors, superconductors, dielectrics, capacitors, protective coating and catalytic metal alloy films. More specifically, these ruthenium source material may find applications in fabricating the four-layer RuO
2
/Ru/TiN/TiSi
x
storage node for Gb-scale DRAM's and for manufacturing Ru pillar and Ta
2
O
5
/Ru capacitor in embedded DRAM technology compatible to the 0.15-&mgr;m high-speed logics, whereas the osmium source reagent may find application in replacing the relatively less stable source reagent Os(CO)
5
for making the osmium-coated thermionic cathodes and abrasive-resistant osmium hard-coating.
It is therefore an object of the present invention to provide improved organometallic source reagents which are amenable to use in the deposition of ruthenium- and osmium-containing films.
It is another object of the present invention to provide a CVD method for forming a ruthenium- or osmium-containing film on a substrate utilizing these source reagents.
Other objects, features, and advantages will be more fully apparent from the ensuing disclosure and appended claims.
SUMMARY OF THE INVENTION
The present invention provides an organometallic source reagent for the chemical vapor deposition of ruthenium- or osmium-containing films, of the formula:
M(CO)
2
L
2
wherein
M is Ru or Os; and
L is a &bgr;-diketonate ligand RC(O)CHC(O)R
1
where each of R and R
1
is independently selected from the group consisting of atoms of the element, C, H, O and F.
In a methodological aspect, the present invention provides a method for forming a ruthenium- or osmium-containing film on a substrate, comprising the steps of:
(a) providing a precursor composition comprising an organometallic source reagent of the formula:
M(CO)
2
L
2
wherein
M is Ru or Os; and
L is a &bgr;-diketonate ligand RC(O)CHC(O)R
1
where each of R and R
1
is independently selected from the group consisting of atoms of the element, C, H, O and F;
(b) volatilizing the organometallic source reagent to form a metal source vapor therefrom; and
(c) contacting the metal source vapor with the substrate in a chemical vapor deposition reactor, to deposit the ruthenium- or osmium-containing film thereon.
The method of the present invention may further comprise employing a carrier gas to transport the metal source vapor to the CVD reactor.
The precursor composition may further comprise a second metal source reagent for the deposition of binary mixed-metal oxide materials such as SrRuO
3
, BaRuO
3
, Sr
2
RuO
4
and Bi
2
Ru
2
O
7
, or bimetallic alloys such as Pt/Ru and Pd/Ru.
Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The present invention generally relates to a series of organometallic complexes of the formula: [M(CO)
2
L
2
] wherein M is ruthenium or osmium, CO is a carbonyl ligand coordinated to the metal atom, L is a bidentate &bgr;-diketonate RC(O)CHC(O)R
1
ligand coordinated to the metal, wherein each of two substituents R and R
1
, which may be the same or different, is independently selected from the group consisting of atoms of the element, C, H, O and F.
Preferably, R and R
1
are hydrocarbyl or fluorinated hydrocarbyl groups, e.g., CH
3
, CH
2
CH
3
, C(CH
3
)
3
, CF
3
, CF
2
CF3 and CF
2
CF
2
CF
3
, etc., or any other sterically acceptable and sufficiently volatile hydrocarbyl or fluorinated hydrocarbyl substituent.
Specific examples of L include:
(hfac)=1,1,1,5,5,5-hexafluoro-2,4-pentanedionate;
(tfac)=1,1,1-trifluoro-2,4-pentanedionate;
(ofac)=1,1,1,5,5,6,6,6-octafluoro-2,4-hexanedionate;
(fod)=6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate;
(TMHD)=2,2,6,6-tetramethyl-3,5-heptanedionate;
(DMHD)=2,2-dimethyl-3,5-heptanedionate; and
(acac)=2,4-pentanedionate.
The organometallic complexes of the present invention are readily synthesized by typical organometallic synthesis techniques involving conventional procedures for forming the desired complexes. The most useful synthetic method involves the direct treatment of Ru
3
(CO)
12
or OS
3
(CO)
12
with six equivalents of the neutral ligand LH in a sealed stainless steel autoclave at elevated temperature, and using low boiling hydrocarbon solvent as reaction media to minimize the loss of volatile product during separation. Any other reagents that can cleanly produce the ruthenium- or osmium-containing fragment [M(CO)
2
] durin
Chi Yun
Lee Feng Jen
Liu Chao-Shiuan
Chi Yun
Darby & Darby
Nazario-Gonzalez Porfirio
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