Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1994-07-29
2001-10-23
Talbot, Brian K. (Department: 1762)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S637000, C438S685000, C427S097100, C427S255280, C427S255391, C427S255392, C427S255150, C427S571000, C427S575000, C427S576000
Reexamination Certificate
active
06306765
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for forming thin films which are used in semiconductor devices.
2. Description of the Prior Art
A titanium nitride (TiN) or titanium oxide nitride (TiON) film has been used as a layer, for example, for intimately contacting a substrate of a semiconductor device and an electrode therewith.
For contacting the substrate and the electrode, there are known techniques wherein a plug is formed in a contact hole. One such technique is a burying technique using so-called blanket tungsten (hereinafter abbreviated as BLK-W).
This burying technique is described with reference to the FIGS.
5
(A) to
5
(C) which illustrate the formation process.
As is particularly shown in FIG.
5
(A), a diffusion layer
62
is formed in a semiconductor substrate
61
(made, for example, of monocrystal silicon). Thereafter, an insulating film
63
is formed on the semiconductor substrate
61
. The insulating film
63
at its portion which has been formed on the diffusion layer
62
is provided with a contact hole
64
as shown.
As shown in FIG.
5
(B), a contact layer
65
made, for example, of TiN is formed according to a chemical vapor deposition (CVD) process in such a way that inner walls of the contact hole
64
and the upper surface of the insulating film
63
are covered with the contact layer
65
.
Finally, as shown in FIG.
5
(C), a BLK-W film
66
is formed on the inside of the contact hole
64
and on the contact layer
65
, for example, according to the CVD process.
If a tungsten (W) plug (not shown) is formed, the BLK-W film
66
is etched back, thereby leaving the BLK-W film
66
in the inside of the contact hole
64
to form a tungsten plug.
However, a disadvantage with the burying technique using the BLK-W is that if the contact hole
64
is not fully covered with the contact layer
65
, there will be produced a void
67
(see
FIG. 6
) in the BLK-W film
66
which has been formed according to the CVD process.
Moreover, where titanium chloride (TiCl
4
) is employed as a source for the formation of a TiN film as the contact layer
65
according to the CVD process, chlorine (Cl) may be included in the thus formed contact layer
65
. This will degrade the contact layer and lower its barrier property. In addition, the TiN film causes the contact resistance between the bottom of the contact hole
64
and the diffusion layer
62
to be undesirably increased.
Alternatively, if a titanium oxide nitride (TiON) film is formed as the contact layer
65
according to the CVD process, the problem of the chlorine inclusion in the contact layer
65
is solved but another problem of increasing the contact resistance is left unresolved. Thus, the contact resistance is undesirably increased in either case.
To avoid the above problem, it is usual to first form a titanium (Ti) film by sputtering and then a TiON film according to the CVD process. By this, the contact resistance is reduced with an improved barrier property. Since, however, the Ti film is formed by sputtering and the TiON film is formed by the CVD process, the throughput is considerably lowered.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for forming thin films which has a low contact resistance and good film properties with a good throughput.
The above object can be achieved, according to one embodiment of the invention, by a thin film formation method which comprises:
the first step of forming a high melting metal film on a substrate to cover an insulating pattern formed on the substrate therewith; and
the second step of forming on the surface of the high melting metal film a high melting metal oxide nitride film which consists of a compound of the high melting metal used to form the high melting metal film, oxygen and nitrogen,
the high melting metal film in the first step being formed by a chemical vapor deposition process, after which the high melting metal oxide nitride film is continuously formed by the chemical vapor deposition process.
According to another embodiment of the invention, there is also provided a film formation method which comprises:
the first step of forming a high melting metal film on a substrate to cover an insulating pattern formed on the substrate therewith; and
the second step of forming on the surface of the high melting metal film a high melting metal nitride film which consists of a compound of the high melting metal used to form the high melting metal film and nitrogen,
the high melting metal film in the first step being formed by a chemical vapor deposition process, after which the high melting metal nitride film is continuously formed by the chemical vapor deposition process.
Preferably, the chemical vapor deposition process in the first and second steps of both embodiments is effected while applying an RF bias to the substrate.
In the thin film formation methods of both embodiments, the high melting metal film is first formed according to the CVD process and then a high melting metal oxide nitride film or high melting metal nitride film is formed on the metal film according to the CVD process. By this, the throughput is significantly improved. In addition, the formation of the high melting-metal film results in the reduction of contact resistance with the substrate. The formation of the high melting metal oxide nitride film or the high melting metal nitride film improves the barrier property against the substrate.
When the CVD process in the first and second steps is effected under application of an RF bias, the step coverage of the high melting metal film is increased along with an increase in the step coverage of the high melting metal oxide nitride film or high melting metal nitride film.
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Kumar et al. “Growth & Properties of TiN and TiOxNy, Diffusion Barrier in Silicon on Sapphire Integrated Circuits”, Thin Solid Films, 153(1987), pp. 287-301.*
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Sonnenschein Nath & Rosenthal
Sony Corporation
Talbot Brian K.
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