Complex of an element of transition group IV or V for...

Details Complex of an element of transition group IV or V for... Complex of an element of transition group IV or V for...

2001-05-29

2003-03-04

Brunsman, David (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Heavy metal compound containing

C427S255320

Reexamination Certificate

active

06527848

ABSTRACT:

BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a new complex of an element of transition group IV or V for forming an improved precursor and/or precursor combination for use in chemical vapor deposition (CVD). The term “precursor combination” refers to a mixture (e.g. a metal complex or precursor and a solvent) which is vaporized at commencement of a CVD reaction.
Precursor combinations are known from U.S. Pat. No. 5,820,664. In order to effect chemical vapor deposition of, for example, SrBi
2
Ta
2
O
3
(SBT), use is made of a precursor combination including [Ta(OiPr)
4
thd] (see column 6, line 42), in which a Ta complex with an alkoxide ligand having an &agr; proton and thus a potential reducing agent (to form the corresponding ketone) is present.
The precursor Bi(Ph)
3
has been replaced by Bi(thd)
3
in order to obtain stable Bi
2
O
3
deposition rates (see a presentation by F. Hintermaier et al., given at the International Symposium on Integrated Ferroelectrics, Monterey, Calif., USA, 1998). However, Bi(thd)
3
is easily reduced to the metal in the presence of a reducing agent. Thus, for example, hydrolysis of the precursor [Ta(OiPr)
4
thd] liberates HOiPr which acts as a reducing agent or in a ligand exchange reaction according to the equation:
Ta(OiPr)
4
thd+Bi(tdh)
3
−>Ta(thd)
2
(OiPr)
3
+Bi(thd)
2
(OiPr)
forms (Bi(thd)
2
(OiPr) which undergoes an internal redox reaction with reduction of the Bi
3+
metal ion to liberate elemental bismuth.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a new complex, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known complexes of this general type, which is suitable as a precursor and which remains stable in chemical vapor deposition using a Bi
3+
precursor and/or, in the case of a ligand exchange reaction, promotes formation of a by-product which is thermally stable under reaction conditions of a CVD technique and in which bismuth continues to be present in oxidized form.
This object is achieved according to the invention by a complex which has only alkoxides without an &agr; proton and very bulky ligands as complex formers.
The invention provides a complex of the formula:
M (L)
x
(R
3
C—O—)
y-x
where:
M is a stable central atom from transition group IV or V of the Periodic Table;
L is a &bgr;-diketonate, a &bgr;-ketiminate and/or a &bgr;-diiminate;
(R
3
C—O—) is an alkoxide ligand in which R may be identical or different and are each an alkyl radical which has from 1 to 24 carbon atoms and may be branched or linear and substituted or unsubstituted and/or complexed;
x is not equal to zero and is from 1 to 4; and
y is not equal to zero and is 2, 3, 4 or 5, depending on the oxidation state of the central atom.
The invention also provides for the use of this complex for the deposition of ferroelectric, paraelectric and high-&egr; layers.
Finally, the invention provides a precursor combination including the new complex as a precursor.
Preference is given to using tantalum or niobium as a central atom of the complex.
Preference is given to using the tert-butyl radical and/or the tert-pentyl radical as a tertiary radical on the alkoxide ligand.
In an advantageous embodiment, thd, namely 2,2,6,6-tetramethyl-3,5-heptanedionate, is used as a bulky ligand.
In a further advantageous embodiment, 4 alkoxide ligands and one (thd) ligand are bound to the central atom of the complex.
The term “stable central atom of the complex” refers to an element of the Periodic Table having a most abundant isotope which does not undergo radioactive decay. Preference is given to a metal selected from the group consisting of Ti, Zr, Hf, V, Nb and Ta. Particular preference is given to using Ta.
The term “alkoxide ligand” refers to the alcoholate ligand which is bound by the oxygen atom of the alcohol group and has the formula:
—O—CR
3
where R may be identical or different and are each an alkyl radical which has from 1 to 24 carbon atoms and may be branched or linear and substituted or unsubstituted and/or complexed. It is advantageous, for example for the alcoholate ligand to contain ether, amine and/or sulfide groups which can additionally act as donors toward the central atom.
Particular preference is given to using an alkoxide ligand of the formula:
—O—C (CH
3
)
3-n
[(CH
2
)
m
—CH
3
]
n
where:
n is in a range from 0-3; and
m is in a range from 0-3.
Preference is given to using derivatives of a &bgr;-diketonate, a &bgr;-ketiminate and a &bgr;-diiminate.
2,2,6,6-tetramethyl3,5-heptanedionate is preferably used. Other preferred ligands are, for example, acetylacetonate (acac); hexafluoropentanedionate (hfac); 1,1,1-trifluoro-2,4-pentanedionate (tfac); 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate; 2,2,7-trimethyl-3,5-octanedionate; 1,1,1,5,5,6,6,7,7,7-decafluoro-2,4-heptanedionate; and finally 1,1,1-trifluoro-6-methyl-2,4-dionate.


REFERENCES:
patent: 5820664 (1998-10-01), Gardiner et al.
patent: 5916359 (1999-06-01), Baum et al.
patent: 6133051 (2000-10-01), Hintermaier et al.
patent: 6214105 (2001-04-01), Hintermaier et al.
patent: 6303391 (2001-10-01), Hintermaier et al.
patent: WO 95/26355 (1995-10-01), None
Kapoor, R. N. et al.: “Organic Compounds of Niobium and Tantalum. Reactions of Niobium and Tantalum Pentaethoxides with Dibenzoylmethane”, Bulletin of the Chemical Society of Japan, vol. 40,(1967), No month provided pp. 1384-1386, Chemical Abstracts XP-002131326.
Narula, A.K. et al.: “Preparation and characterization of tantalum(V) &bgr;-diketonates”, Chemical Abstracts XP-002131328 No date provided.
Itsuki, Atsushi et al.: “Tantalum compound for vapor deposition”, Chemical Abstracts XP-002131327 No date provided.

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