Coating processes – Coating by vapor – gas – or smoke – Mixture of vapors or gases utilized
Reexamination Certificate
2000-04-28
2001-08-14
Nazario-Gonzalez, Porfirio (Department: 1621)
Coating processes
Coating by vapor, gas, or smoke
Mixture of vapors or gases utilized
C556S056000, C427S248100
Reexamination Certificate
active
06274195
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an organometallic complex useful as a precursor for a thin metal compound layer fabricated in semiconductor devices, a process for the preparation thereof and metal organic chemical vapor deposition using same.
BACKGROUND OF THE INVENTION
Semi-conductor devices have recently become more highly integrated and smaller in size than ever before, which generated needs to develop sophisticated materials and processes for forming thin films in the fabrication of semi-conductor devices. In response to such needs, there have been developed, for example, barium strontium titanate(BST) used in a capacitor for dynamic random access memory(DRAM), and ferroelectric materials such as lead zirconate titanate(PZT), strontium bismuth titanate(SBT), bismuth lanthanum titanate(BLT) used in ferroelectric random access memory(FRAM) and yttrium stabilized zirconia(YSZ) and metal oxides such as TiO
2
and ZrO
2
. Thin films of such materials are prepared by using such techniques as radio frequency magnetron sputtering, ion beam sputtering, reactive co-evaporation, metal organic decomposition(MOD), liquid source misted chemical decomposition(LSMCD), laser ablation and metal organic chemical vapor deposition(MOCVD).
Among these methods, MOCVD is carried out by vaporizing one or more organometallic precursor compounds, transporting, using a carrier gas, the vaporized precursor(s) to the surface of a heated solid substrate and forming a thin film on the surface of the substrate through a chemical reaction. The MOCVD method is advantageous in that: it can be carried out at a relatively low temperature; the constitution and deposition rate of the thin film can be readily controlled by changing the amounts of the source materials and the carrier gas; and the final thin film has good uniformity and excellent conformal step coverage without causing any damage on the surface of the substrate. Therefore, MOCVD is widely used in manufacturing semi-conductor devices such as DRAM and FRAM.
Generally, a precursor for CVD is required to have such properties as a high vapor pressure, high purity, high deposition rate, easy handling, nontoxicity, low cost and a suitable deposition temperature. However, conventional organometallic compounds for CVD such as metal alkyls, metal alkoxides and &bgr;-diketonates have many drawbacks. For example, metal alkyls having relatively high vapor pressures such as Pb(C
2
H
5
)
4
are very toxic (see Reference of Organometallic Dictionary). Metal alkoxides are sensitive to moisture, which relatively expensive metal &bgr;-diketonates have low vapor pressures and are solids at room temperature, posing handling difficulties in CVD process(see Anthony C. Jones et al.,
Journal of the European Ceramic Society
, 19(1999), 1431-1434).
Besides the above problems, Ti(O
i
Pr)
4
(titanium tetraisopropoxide) is unstable at room temperature and a thin layer obtained from Ti(O
i
Pr)
2
(tmhd)
2
(tmhd=tetramethylheptanedionate) has a fluctuating amount of Ti depending on the substrate temperature(see Jung-Hyun Lee et al.,
Electrochemical and Solid
-
State Letters
, 2(10) (1999), 507-509).
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a nontoxic organometallic complex which has a good thermal stability; is not sensitive to moisture; stays in the liquid form at room temperature; and can be conveniently used in a low temperature MOCVD for the production of a contaminant-free metal oxide film having a good conformal step-coverage
In accordance with on aspect of the present invention, there is provided an organometallic complex of formula(I):
where, M is Ti or Zr;
R
1
, R
2
, R
3
and R
4
are each independently H or a C
1-4
alkyl group; and
m is an integer ranging from 2 to 5.
In accordance with another aspect of the present invention, there is provided a process for preparing an organometallic complex of formula(I) which comprises the steps of: mixing a metal compound of formula(II) or (III) with an amine compound of formula(IV) in an organic solvent in a molar ratio ranging from 1:4 to 1:5 and refluxing the mixture:
M(NR
2
)
4
(II)
M(OR′)
4
(III)
HO—(CR
3
R
4
)
m
—NR
1
R
2
(IV)
wherein, R and R′ are each independently, a C
1-4
alkyl;
R
1
, R
2
, R
3
and R
4
are each independently H or a C
1-4
alkyl; and
m is an integer ranging from 2 to 5.
In accordance with still another aspect of the present invention, there is provided a process for depositing a metal oxide compound film on a substrate which comprises the steps of vaporizing the organometallic complex of formula(I) of claim
1
, optionally together with one or more organometallic precursors, at a temperature ranging from 20 to 300° C. and bringing the resulting vapor into contact with the substrate heated to a temperature ranging from 300 to 600° C.
REFERENCES:
patent: 4568703 (1986-02-01), Ashida
Bharara et al., Chemical Abstracts, vol. 83, No. 2, p. 769, abstract No. 21225f, Jul. 1975.*
Bharara et al., Synth. React. Inorg. Met.-Org. Chem., vol. 7, No. 6, pp. 537-546, 1977.
Kim Dae-Hwan
Lee Jung-Hyun
Rhee Shi-Woo
Shim Jae-Young
Anderson Kill & Olick PC
Nazario-Gonzalez Porfirio
Postech Foundation
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