Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-02-03
2001-10-30
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S627000, C438S637000, C438S656000, C438S671000, C438S702000, C438S970000
Reexamination Certificate
active
06309963
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More particularly, it relates to a method of manufacturing a semiconductor device wherein a titanium film and a titanium nitride film overlying the titanium film are formed.
2. Description of the Related Art
As also seen in very large scale integration (VLSI), ultra LSI (ULSI), or the like, a proportion occupied by wiring portions tends to increase on a semiconductor device or chip as the device is heightened in the density of integration and is enhanced in functionality. A wiring pitch has been shortened in order to prevent the area of the chip from enlarging due to the increase of the occupied proportion.
In applying a borderless VIA hole to the shortened wiring pitch, there has been adopted a structure wherein a titanium nitride film formed over a lower-layer wiring line and to constitute a cap metal is left in the bottom of the VIA hole at the step of etching the VIA hole. In this case, a wiring line structure wherein a titanium film
112
is sandwiched in between an aluminum-copper alloy film
111
being the material of the lower-layer wiring line and the above titanium nitride film
113
as shown in
FIG. 3
of the accompanying drawings, has been usually adopted in order to lower a VIA resistance.
A related art method of forming the titanium film and the titanium nitride film will be explained below. As illustrated in
FIG. 4
, titanium film and the titanium nitride film to constitute the cap metal are formed by employing a sputtering apparatus in which a chamber
201
for the titanium film and a chamber
202
for the titanium nitride film are disposed separately from each other, and in such a way that, after the titanium film has been formed in the chamber
201
, the titanium nitride film is formed in the chamber
202
. Alternatively, using a single chamber, not shown, which is furnished with a shutter for cleaning a target surface, only the target surface is cleaned by closing the shutter before the formation of the titanium film, and the titanium film and the titanium nitride film are thereafter formed by sputtering.
The titanium film obtained by the film forming method stated above has a thickness of 5 [nm]~10 [nm] or so ordinarily, and it is a film of good quality containing nitrogen and the like impurities little.
The wiring line structure obtained by the related art film forming method, however, has a problem as stated below. An aluminum-titanium alloy layer
114
which is produced by the reaction of aluminum and titanium is formed on the aluminum-copper alloy film
111
as shown in
FIG. 5
, due to a heat treatment at 400° C. or above. The aluminum-titanium alloy layer
114
has been reported to act as the diffusing path of atoms. It forms a cause for the drift of aluminum atoms, and deteriorates an electromigration lifetime.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve the problem explained above, and it consists in a method of manufacturing a semiconductor device wherein the step of forming a titanium film and a titanium nitride film on an aluminum-based alloy film overlying a substrate is carried out for a plurality of such substrates in succession, characterized by comprising the step of forming the titanium film and the titanium nitride film within an identical chamber by changing a processing gas, and under a condition that, in forming said titanium film by sputtering, a titanium target having been employed for the formation of said titanium nitride film is used.
According to the above method of manufacturing a semiconductor device, the titanium film and the titanium nitride film are formed within the identical chamber by changing the processing gas, and under the condition that, in the case of forming the titanium film by sputtering, the titanium target having been employed for the formation of the titanium nitride film is used. Therefore, the surface of the target for forming the titanium film bears titanium nitride produced. At the initial stage of the formation of the titanium film, accordingly, the titanium nitride borne on the target surface is deposited together with titanium, and the titanium film is formed in a state where nitrogen is contained. That is, a so-called “titanium film of charged quality” is formed. It is consequently possible to suppress the reaction between the titanium film and aluminum contained in the aluminum-based alloy film underlying this titanium film. That is, the production of an aluminum-titanium alloy can be suppressed to greatly enhance an electromigration immunity.
REFERENCES:
patent: 5231053 (1993-07-01), Bost et al.
patent: 5646449 (1997-07-01), Nakamura et al.
patent: 5961791 (1999-10-01), Frisa et al.
patent: 407263444A (1995-10-01), None
Anya Igwe U.
Kananen Ronald P.
Rader Fishman & Grauer
Smith Matthew
Sony Corporation
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