Synthesis of metal oxide and oxynitride

Details Synthesis of metal oxide and oxynitride Synthesis of metal oxide and oxynitride

1999-02-24

2003-09-09

Meeks, Timothy (Department: 1762)

Coating processes

Coating by vapor, gas, or smoke

Mixture of vapors or gases utilized

C427S255394, C438S785000

Reexamination Certificate

active

06616972

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
Electronic grade metal oxides and oxynitrides have found increasing interest as dielectric films in microelectronic devices. For instance, tantalum oxide (Ta
2
O
5
) has a high dielectric constant (k=22) and is considered a promising material for applications in microelectronics devices as a gate oxide and as a DRAM storage capacitor. For example, Treichel et al.
Adv. Mat. Opt. Elec
. 1992, 1, p.299-308. As the size of integrated circuit devices become increasingly smaller, chemical vapor deposition (CVD) shows a unique advantage over physical vapor deposition (PVD) for device fabrication in terms of excellent step coverage for trench and stack cell structures. For the CVD processing of Ta
2
O
5
thin films, various precursors have been studied thus far. A liquid precursor is desirable for the ease and reproducibility of precursor delivery. Tantalum halides (TaX
5
, X═F, Cl), Devine, R. A. B. et al.
Appl. Phys. Lett
. 1996, 68, p.1775-1777, Devine, R. A. B. et al. Microelec. Eng. 1997, 36, p.61-64, Jeon, S. R. et al.
J. Appl. Phys
. 1995, 77, p.5978-5981, suffer from low volatility and difficulty in delivery due to their solid nature. A solid amide complex Ta(NMe
2
)
5
(pentakis(dimethylamino)tantalum) has been reported to provide Ta
2
O
5
films by CVD. Tabuchi, T. et al.
Jap. J. Appl. Phys
. 1991, 30, p.L1974-1977. These films, however, contain significant impurities such as carbon and nitrogen. The most commonly studied alkoxide complex Ta(OEt)
5
(tantalum pentaethoxide), Laviale, D.
Appl. Phys. Lett
. 1994, 65, p.2021-2023, Nagahori et al.
J. Am. Ceram. Soc
. 1995, 78, p.1585-92, Kim, I. et al.
J. Mat. Res. Soc
. 1995, 10, p.2864-2869, Aoyama, T. et al.
J. Electrochem. Soc
. 1996, 143, p.977-983, is a liquid and has a marginal vapor pressure for CVD applications, and the resulting films contain carbon impurities. Therefore, an alternative liquid precursor which has sufficient volatility and capability to afford pure Ta
2
O
5
is of keen interest.
U.S. Pat. No. 5,677,015 discloses the preparation of tantalum oxynitride materials from a precursor of Cp
m
Ta(N
3
)
n
where Cp is cyclopentadienyl. The reaction can be thermal or plasma CVD. Ammonia, oxygen, ozone, nitrous oxide, hydrazine are used in the reaction. No physical characteristics of the precursors are described in the patent.
U.S. Pat. No. 5,248,629 discloses the preparation of TaO
x
N
y
films from the reaction of Ta[N(R)
2
]
5
such as Ta[N(CH
3
)
2
]
5
and Ta(OCH
3
)
5
. Ta[N(CH
3
)
2
]
5
and Ta(OCH
3
)
5
are both solid at room temperature.
Reactions of various tantalum sources containing alkylamide ligands to produce tantalum nitride or carbonitride are disclosed in Fix, et. al., Chemical Vapor Deposition of Vanadium, Niobium and Tantalum Nitride Thin Films, Chem. Mater., Vol. 5, (1993) pp. 614-619; Tsai, et. al., Metalorganic Chemical Vapor Deposition Of Tantalum Nitride By Tertbutylimidotris(Diethylamido)Tantalum For Advanced Metallization, Appl. Phys. Lett. 67, (8) August 1995, pp. 1128-1130; Chiu, et. al., Syntheses and Characterization of Organoimido Complexes of Tantalum; Potential Single-Source Precursors to Tantalum Nitride, Polyhedran, Vol. 17, Nos. 13-14, (1998) pp. 2187-2190; and Chiu, et. al., Deposition of Tantalum Nitride Thin Films From Ethylimidotantalum Complex, J. Mat. Sci. Lett, Vol. 11, (1992) pp. 96-98. The latter article indicates that some authors have misidentified Ta(NCH
2
CH
3
)
5
, when in fact they were using a combination of [(CH
3
CH
2
)
2
N]
3
Ta═NCH
2
CH
3
and [(CH
3
CH
2
)
2
N]
3
Ta[&eegr;
2
—CH
3
CH
2
N═CH(CH
3
)]. Jun et. al., Low Temperature Deposition of TaCN Films Using Pentakis(diethylamido)tantalum, Jpn. J. Appl. Phys. , Vol. 37, (1998), pp.L30-L32, discloses the deposition of the name compounds.
EP 0 869 544 A2 describes the reaction of [(CH
3
CH
2
)
2
N]
3
Ta═NCH
2
CH
3
with ammonia to form tantalum nitride.
Chiu, et. al., Deposition of Molybdenum Carbonitride Thin Films From Mo(NBu
t
)
2
(NHBu
t
)
2
, J. Mater. Res., Vol. 9, No. 7, (July 1994), pp.1622-1624, describes the CVD deposition of molybdenum carbonitride compounds from the title precursor.
Chiu, et. al., Tungsten Nitride Thin Films Prepared by MOCVD, J. Mater. Res., Vol. 8, No. 6, (June 1993), pp.1353-1360, describes the MOCVD deposition of tungsten nitride compounds from W(NBu
t
)
2
(NHBu
t
)
2
.
Chiu, et. al., Syntheses and Characterization of Organoimido Complexes of Niobium(V); Potential CVD Precursors, J. Chin. Chem. Soc., Vol. 45, No. 3, (1998), pp. 355-360, describes the multi-step synthesis of (RN)Nb(NEt
2
)
3
without formation of the cyclic precursor structure typified in the tantalum analog. The niobium compounds are reported to be useful for metal nitrides and carbonitrides.
The problems of the prior art have been overcome by the present invention, by providing an appropriate liquid precursor with an attractive vapor pressure for chemical vapor deposition of tantalum, niobium, molybdenum and tungsten oxide and oxynitride in a thermal process as will be set forth in greater detail below.
BRIEF SUMMARY OF THE INVENTION
The present invention is a method for producing a material selected from the group consisting of a metal oxide, metal oxynitride and mixtures thereof, wherein the metal is tantalum, niobium, molybdenum or tungsten, on a substrate, comprising; reacting a first reactant selected from the group consisting of (R
1
R
2
N)
x
M(═NR
3
)
y
, (R
4
R
5
N)
x
M[&eegr;
2
—R
6
N═C(R
7
)(R
8
)]
y
and mixtures thereof with an oxidant and up to 95 volume percent of a source of nitrogen selected from the group consisting of ammonia, N
2 O
, NO, NO
2
, alkyl amines, N
2
H
2
, alkyl hydrazine, N
2
and mixtures thereof, to produce the material on the substrate, where R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
and R
8
are individually C
1-6
alkyl, aryl or hydrogen, M Ta, Nb, W, Mo or mixtures thereof, and when M═Ta or Nb, x=3 and y=1 and when M═W or Mo, y=x=2.
Preferably, the oxidant is selected from the group consisting of oxygen, ozone, water, hydrogen peroxide, nitrous oxide and mixtures thereof.
Preferably, the material is tantalum oxide.
Alternatively, the material is tantalum oxynitride.
Preferably, the first reactant is selected from the group consisting of [(CH
3
CH
2
)
2
N]
3
Ta═NCH
2
CH
3
, [(CH
3
CH
2
)
2
N]
3
Ta[&eegr;
2
—CH
3
CH
2
N═CH(CH
3
)] and mixtures thereof.
Preferably, the pressure is in the range of 1 mTorr to 760 Torr, more preferably 0.5 to 1.5 Torr.
Preferably, the temperature is in the range of 200° C. to 600° C., more preferably 280° C. to 400° C.
Preferably, the substrate is silicon.
Preferably, the precursor vaporization temperature is in the range of 50° C. to 150° C., more preferably 85° C. to 100° C.
More specifically, the present invention is a chemical vapor deposition method for producing a material selected from the group consisting of tantalum oxide, tantalum oxynitride and mixtures thereof on a silicon substrate comprising reacting a first reactant selected from the group consisting of [(CH
3
CH
2
)
2
N]
3
Ta═NCH
2
CH
3
, [(CH
3
CH
2
)
2
N]
3
Ta[&eegr;
2
—CH
3
CH
2
N═CH(CH
3
)] and mixtures thereof with an oxidant selected from the group consisting of oxygen, ozone, hydrogen peroxide, water, nitrous oxide and mixtures thereof and up to 95 volume percent of a source of nitrogen selected from the group consisting of ammonia, N
2
O, NO, NO
2
, alkyl amines, N
2
H
2
, alkyl hydrazine, N
2
, and mixtures thereof, to produce the material on the silicon substrate.
Alternatively, more specifically, the present invention is a chemical vapor deposition method for producing tantalum oxide on a silicon substrate comprising reacting a first reactant selected from the group co

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