Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-08-02
2002-10-29
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S618000, C438S637000, C438S675000, C438S700000
Reexamination Certificate
active
06472318
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device having a trench interconnection to prevent diffusion of ions and the like between layers and a method of forming a barrier film for a semiconductor device. More particularly, the present invention relates to a barrier film capable of preventing increase in an interconnect resistance caused by heat treatment in the course of fabrication of the device.
2. Description of the Related Art
Recently, a trend of higher integration of elements in a semiconductor device has been advanced in accordance with miniaturization of its size. Accordingly, in a conventional semiconductor device, a size of a contact hole and a line width in interconnection have been smaller, but an aspect ratio (a quotient of a height or depth divided by a width) has been larger, since a dimension in a direction of the thickness of a substrate has not been smaller. In the case of 256 Mb DRAM, an aspect ratio of a contact hole is 4 or more. As for a method of forming interconnection, a damascene method has been used in many cases. The damascene method is to form a trench in an insulating film, and thereafter to fabricate an interconnect by filling the trench with a metal, and the method draws keen attention as a method of fabricating a copper interconnect, which has difficulty in fine etching.
Conventionally, as fabricating method of barrier films for a contact hole and a trench, it has been common to deposit a TiN film by means of a sputtering method. When an aspect ratio is larger, however, a film cannot be deposited on the side and bottom surfaces of the contact hole or the trench even with employment of a sputtering method. Therefore, a chemical vapor deposition method (CVD method) has recently come to be employed.
A method of fabricating a metal compound thin film, such as a WN
x
film and a WSi
x
film is disclosed in, for example, Publication of Unexamined Japanese Patent Application No. Sho 63-317676. In the publication, it is described that the WN
x
film has a non-granular structure. A method of fabricating a semiconductor device has the step of forming a WN
x
film by giving a nitrogen plasma treatment on a substrate in the course of deposition of a tungsten film. These are methods of fabricating WN
x
film better as a barrier than a W film.
As described above, a conventional WN
x
film has an advantage that the WN
x
film exhibits better performance as a barrier than the W film. However, it is well known that the WN
x
film is crystallized from its original amorphous structure at about 700° C. and nitrogen is dissociated from W in a bond of W—N at 850° C. Therefore, if the WN
x
film is employed as a barrier film, a property as a barrier may be deteriorated through a structural change of the film, depending on fabrication conditions of a semiconductor device.
A method of fabricating a W film on a substrate with ease is disclosed in Publication of Unexamined Japanese Patent Application No. Hei 6-291067.
FIG. 1
is a typical view showing a conventional apparatus of fabricating a W film. In
FIG. 1
, a substrate holder
2
is disposed in a CVD chamber
1
and an electrode
26
is arranged above the substrate holder
2
. The substrate holder
2
and electrode
26
are connected with a high frequency electric source
27
placed outside the CVD chamber
1
. A gas in the CVD chamber
1
is discharged by a pump
4
through a discharge port
1
a
. Gas supply ports
1
b
,
1
c
are provided to the CVD chamber
1
and the gas supply port
1
b
is connected with a WF
6
gas bomb
5
through a mass flow controller
8
and the gas supply port
1
c
is connected with a nitrogen gas bomb
21
through a mass flow controller
8
.
In the case where a W film is formed on a substrate with use of the CVD apparatus as constructed in such a manner, after a substrate
3
is placed on the substrate holder
2
, the CVD chamber
1
is evacuated by means of the pump
4
. Then, a nitrogen gas and a WF
6
gas are supplied into the CVD chamber
1
, while flow rates are controlled by the mass flow controller
8
and simultaneously, a voltage is applied between the electrode
26
and substrate holder
2
by means of the high frequency electric source
27
. In this condition, a plasma
28
is produced between the substrate
3
and the electrode
26
, and the surface of the substrate
3
is charged by free electrons in the plasma. The free electrons work as a catalyst to form a W film on the substrate
3
.
With use of a method shown in
FIG. 1
, since a plasma CVD method is adopted, a reaction in a gas phase becomes active and a W film can be formed on the substrate with no use of SiH
4
gas.
However, in the case where the above mentioned plasma CVD method is used to form a W film, products produced in a gas phase are deposited on the periphery of a substrate and thus in general a coverability of a W film on the substrate is reduced and it becomes hard to deposit a barrier film on the inner surfaces of a contact hole and a trench with high aspect ratios in a uniform manner, as in the case of employment of a sputtering method.
When a barrier film is formed, the barrier having a higher resistivity, compared with a W film, a Cu film or the like as interconnection, there arises a problem that a interconnect resistance is increased, since cross-sectional areas of a contact hole and an interconnect are decreased if a thickness of the barrier film is thick. For example, a device having a size of 0.25 &mgr;m or less requires that a thickness of a film is about 20 nm or less. Therefore, there is a demand for proposal for a semiconductor device having a trench interconnection and a method of forming a barrier film for a semiconductor device and fabricating method thereof, not only thinner compared with a conventional practice, but also better in coverability.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor device having a trench interconnection and method of forming a barrier film with a thin thickness inside a fine contact hole, a fine interconnect trench or the like, thereby increase in a resistance of interconnects formed inside the contact hole or the interconnect trench can prevented and the barrier film has a high-temperature stability.
A semiconductor device having a trench interconnection according to the present invention comprises a semiconductor substrate, an insulating film having a trench formed on the substrate, a barrier film formed on an inner surface of the trench and a conductive material filled into the trench to form an interconnect line. The barrier film is made of material of one kind selected from the group consisting of WSi
x
N
y
and WC
x
N
y
.
A depth of the trench may be smaller than a thickness of the insulating film or so large as to reach the substrate. The conductive material can be Cu, and a Ti film may be formed between the insulating film and the barrier film.
A method of fabricating a semiconductor device according to the present invention comprises the step of forming a barrier film made of material of one kind selected from the group consisting of WSi
x
N
y
and WC
x
N
y
on a semiconductor substrate by causing a reaction among a raw material gas containing W, one kind of gas selected from the group consisting of silane, dichlorosilane and a hydrocarbon gas, and a nitrogen supply source.
The nitrogen supply source can be at least one kind selected from the group consisting of a nitriding plasma, a NH
3
plasma, nitrogen gas, NH
3
gas, hydrazine and dimethyl hydrazine. The hydrocarbon gas can be a gas of one kind selected from the group consisting of methane gas, ethane gas and propane gas. The gas containing W can be a gas of one kind selected from the group consisting of WF
6
gas, W(N(CH
3
)
2
)
6
and W(N(C
2
H
5
)
2
)
6
.
A method of fabricating a semiconductor device according to the present invention may further comprise the steps of forming an insulating film on the semiconductor substrate and subsequently forming a trench in the insulating film. Th
Hayes & Soloway PC
Le Dung Auh
NEC Corporation
Nelms David
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