Semiconductor capacitors having tantalum oxide layers

Details Semiconductor capacitors having tantalum oxide layers Semiconductor capacitors having tantalum oxide layers

2002-01-15

2004-05-11

Nguyen, Tuan H. (Department: 2813)

Active solid-state devices (e.g., transistors, solid-state diode

Field effect device

Having insulated electrode

C257S301000, C257S306000, C257S532000

Reexamination Certificate

active

06734480

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority to Korean Patent Application No. 01-3165 filed Jan. 19, 2001, the disclosure of which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
The present invention generally relates to semiconductor capacitors, methods of making semiconductor capacitors, as well as microelectronic devices comprising semiconductor capacitors.
BACKGROUND OF THE INVENTION
As the integration density of semiconductor devices increases, the employment of dielectric layers having relatively high dielectric constants is desirable for potentially securing high capacitance in relatively small areas. One representative example of a dielectric layer having a relatively high dielectric constant is a tantalum oxide (Ta
2
O
5
) layer.
Notwithstanding its relatively high dielectric constant, the use of the tantalum oxide layer is potentially problematic in that it typically is potentially highly reactive with polysilicon present as a lower electrode in a conventional capacitor. In particular, polysilicon is usually oxidized in the formation of a tantalum oxide layer or a thermal treatment process after the formation of a tantalum oxide layer.
In an attempt to address this problem, lower electrodes have been formed from materials which are believed to be relatively difficult to oxidize. Examples of such materials include noble metals such as platinum (Pt), ruthenium (Ru), or iridium (Ir), or a conductive metal nitride layer such as titanium nitride (TiN). However, the use of a noble metal or metal nitride also presents potential problems. A conventional tantalum oxide layer is typically formed by chemical vapor deposition in an oxygen atmosphere using pentaethoxide tantalum (PET), Ta(OCH
3
)
5
, or TaCl
5
as a tantalum source. Oxygen (O
2
), water (H
2
O), hydrogen peroxide (H
2
O
2
), or nitrous oxide (N
2
O) is employed as an oxygen source in such a method. Notwithstanding any advantages associated therewith, a composition of these source gases often negatively impacts the coverage of the tantalum oxide layer, presumably due to the oxidation of the lower electrode. For example, when a ruthenium (Ru) layer is used as a lower electrode, the surface of the Ru layer is oxidized by an oxygen source which results in the formation of RuO
2
.
The formation of RuO
2
is carried out so as to minimize or prevent the formation of a tantalum oxide layer. The formation of a tantalum oxide layer often occurs when such a layer is used as a dielectric layer in a cylindrical or concave-shaped capacitor having a large aspect ratio. In such an instance, the tantalum oxide layer is not deposited on the lower portion of the cylindrical opening in the Ru electrode. Instead, the tantalum oxide layer is typically deposited on the upper portion to deteriorate step coverage of this layer.
There is a need in the art to address the above-mentioned problems in the art. More specifically, there is a need in the art to provide a semiconductor capacitor having a tantalum oxide layer present thereon with a more uniform thickness. It would be desirable to obtain a capacitor having a relatively high aspect ratio.
SUMMARY OF THE INVENTION
In one aspect, the invention provides semiconductor capacitors comprising first electrodes, second electrodes, and tantalum oxide layers positioned between the first electrodes and the second electrodes. The tantalum oxide layers are formed by depositing at least one precursor and ozone gas, with the precursor represented by the formula:
wherein X is selected from the group consisting of nitrogen, sulfur, oxygen, and a carbonyl group, and R
1
and R
2
are independently alkyl (e.g., C
1
to C
4
alkyl).
In another aspect, the invention provides methods of making semiconductor capacitors. The methods comprise forming first electrodes on semiconductor substrates, and then forming tantalum oxide layers on the first electrodes by depositing at least one precursor and ozone gas. The at least one precursor is represented by the formula:
wherein X is selected from the group consisting of nitrogen, sulfur, oxygen, and a carbonyl group; and R
1
and R
2
may be independently alkyl; and
forming second electrodes on the tantalum oxide layers.
These and other aspects and advantages of the present invention are described herein.


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Kawahara, T. et al. Conformal Step Coverage of (Ba,Sr) TiO3Films Prepared by Liquid Source CVD Using Ti(t-BuO)2(DPM)2Jpn. J. Appl. Phys.38, 2205-2209 (1999).
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