Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Utility Patent
1999-05-28
2001-01-02
Chaudhuri, Olik (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S683000, C427S099300, C427S253000, C427S901000
Utility Patent
active
06169031
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for forming titanium thin films on the substrates and, more specifically to a method for forming titanium thin films on the substrates with in-situ prepared TiCl
2
and TiCl
3
precusors by chemical vapor deposition.
BACKGROUND OF THE INVENTION
Titanium (Ti) thin film is conventionally an ohmic-contact material and a metal contact material for integrated-circuit (IC) devices. Techniques of depositing titanium thin films is always important for the fabrication of IC devices. Due to the damage to common IC devices under high temperature conditions, process temperature for IC devices should be as low as possible. In average cases, 800° C. is a minimum requirement. For some temperature-sensitive devices, requirement on process temperature can be even down to 650° C.
Conventionally, titanium thin films are prepare mainly by sputtering, a branch of physical vapor deposition (PVD). Though PVD method can prepared films with higher purity at lower temperatures, it also has drawbacks such as high equipment costs, inadequacy for large-area growth, and poor step converage. On the other hand, chemical vapor deposition (CVD) is known for growing films in large area with better step converage. Therefore, it is potentially important to form titanium thin films on the substrate by chemical vapor deposition.
DESCRIPTION OF THE PRIOR ART
In 1959, Homer prepared titanium thin films by CVD with
Ti(&eegr;
5
-C
5
H
5
)
2
as the precursor. Other metalic complexes such as
Ti(&eegr;
7
-C
7
H
7
)(&eegr;
5
-C
5
H
5
)
,
(&eegr;
5
-C
5
H
5
)
with
R
2
=CH
3
,C
6
H
5
were also introduced for the growth of titanium thin films. However, carbon-contamination is unavoidable by using metalorganic titanium compounds as precursors.
Some applications also use titanium halides (TiCl
4
, TiBr
4
) as precursors for growing titanium thin films either by thermal or lasered chemical methods. However, process temperature as high as 1200° C. in thermal chemical reactions is too high to be applied in IC processes. Though, lasered chemical reactions proceed at lower temperature, they also rely on expensive equipments.
SUMMARY OF THE INVENTION
In accordance with the present invention, titanium halides are introduced as precursors to form titanium thin films on the substrates.
In accordance with one embodiment of the present invention, TiCl
2
and TiCl
3
are used as precursors to form titanium thin films. Due to the low decomposition temperature of TiCl
2
and TiCl
3
, titanium thin films can be prepared at low process temperature.
In accordance with another embodiment of the present invention, TiCl
2
and TiCl
3
are in-situ prepared by reacting TiCl
4
and a titanium stripe at the front portion of the reaction chamber. Difficulty to introduce TiCl
2
and TiCl
3
is hence overcome.
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patent: 4696834 (1987-09-01), Varaprath
patent: 4820775 (1989-04-01), Shiga et al.
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patent: 5716870 (1998-02-01), Foster et al.
patent: 5789321 (1998-08-01), Ohshita
patent: 5914276 (1999-06-01), Shin et al.
patent: 5946594 (1999-08-01), Iyer et al.
patent: 76028599 (1976-08-01), None
Chaudhuri Olik
Jacobson Price Holman & Stern PLLC
National Science Council
Rao Steven H.
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