Process for forming fine wiring

Details Process for forming fine wiring Process for forming fine wiring

1999-03-17

2001-09-25

Smith, Matthew (Department: 2825)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S683000, C438S685000, C438S627000, C438S761000

Reexamination Certificate

active

06294467

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for forming a fine wiring for LSI, and in particular to a process for forming a fine wiring using a chemical vapor deposition process.
BACKGROUND
Ever reducing design rule has become more strict to meet the requirements to increase the scale of integration and speed of the LSI. Reduction in wiring pitch has led to reduction in the width of wiring and distance between the wirings. However, reduction in thickness of wiring has not been largely achieved in comparison with the reduction in wiring pitch in order to prevent an increase in resistance of wiring.
Accordingly, the aspect ratio of the wiring height to the wiring width or distance between wirings tends to increase. Embedding of metal has become more difficult in particular when trench wiring is used. Similarly, the aspect ratio of via for connecting with an active area or underlying wiring has also increased, so that embedding of metal has become more difficult.
Efforts to use materials having a low resistance have been actively made to increase the speed of devices. Researches have been carried out to use copper-based wiring materials in lieu of conventional aluminum-based wiring materials.
SUMMARY OF THE DISCLOSURE
However, in the course of the investigations toward the present invention the following problems have been encountered. Namely, since it is difficult to etch copper by a dry process which is used for aluminum, LSIs are often formed into a dual damascene structure by a process comprising preliminarily forming a wiring pattern of trench and the like on an insulating film of silicon oxide and the like, embedding copper in the formed insulating film by a sputtering process and making the device planar by a chemical and mechanical polishing process. When the dual damascene structure in which wirings and contacts are simultaneously formed is adopted to meet the requirements for high aspect ratio of trench wiring and multilayered wiring, embedding of a metal becomes more difficult.
Since copper will diffuse into a silicon oxide film when it is in direct contact with the silicon oxide film (refer to, for example,Appl. Phys. Lett. 57 (17), Oct. 22, 1990), a barrier metal such as tantalum and TiN is necessary between the silicon oxide film and copper. Coverage of a barrier metal which is deposited by a sputtering process has raised concerns. If the coverage of the barrier metal or power supply layer is poor also when a copper wiring is formed by a plating process which is excellent in embedding ability, the copper wiring having a high reliability and excellent embedding ability could not be formed.
Problems of the prior art using the dual damascene structure will be described with reference to FIG.
7
. As shown in FIG.
7
(
a
), a first and second openings
5
and
6
of a via which will provide a wiring pattern are formed in a first and second interlayer insulating films
3
and
4
, respectively. Subsequently, a barrier metal
17
such as tantalum or TiN is sputtered by a sputtering process as shown in FIG.
7
(
b
).
However, it is hard to form the barrier metal film
17
in such a manner that an excellent convergence is provided when the pattern is complicated and has a high aspect ratio. When the coverage of the barrier metal film
17
is poor, the underlying layer may be exposed at an area
16
. The copper which is deposited on the exposed area is liable to diffuse into the silicon oxide film. This may cause malfunctions of the resultant device.
Therefore, the present invention has been achieved in view of the above-mentioned problems. It is a main object of the present invention to provide a fine wiring and a process for manufacturing the same, which enables a uniform and good quality barrier metal film to be formed on a pattern side wall and its bottom in such a manner that the step overage is excellent without exposing the underlying layer or a pattern having a high aspect ratio of the wiring height to the wiring width or the distance between wirings.
It is another object of the present invention to provide a process which enables a fine wiring having a low resistance to be formed by uniformly loading a dominant wiring metal into a pattern on which a barrier metal is formed.
Further objects of the present invention will become apparent in the entire disclosure.
Briefly, in order to accomplish the above-mentioned objects, the present invention contemplates providing a metal film which will become a barrier metal film by reducing a metal oxide film after the metal oxide film has been deposited when the barrier metal film adapted to become a wiring layer is to be formed. Specifically, the present invention has features as follows:
According to one aspect of the present invention, there is provided a process for forming a fine or micro-wiring, wherein in order to form a wiring layer, a metal film which becomes the wiring layer is formed by reducing a metal oxide film or metal salt film after the wiring layer has been deposited as the metal oxide film or metal salt film.
According to a second aspect, there is provided a process for forming a fine wiring, wherein in order to form a barrier metal film on which a wiring layer is formed, a metal film which becomes the barrier metal film is formed by reducing a metal oxide film or metal salt film after the barrier metal film has been deposited as the metal oxide film or metal salt film.
According to a third aspect, there is provided a process for forming a fine wiring, wherein in order to form a barrier metal film on a pattern which is formed on an interlayer insulating film on a substrate, the barrier metal film is formed by coating an insulating layer with a metal oxide film or metal salt film and by reducing the metal oxide film or metal salt film and in that the wiring layer is formed into the pattern by an electrolytic plating or electroless plating process.
According to a fourth aspect of the present invention there is provided a process for forming fine wiring. The process comprises the steps of: (a) forming a film of a metal oxide or metal salt, containing a first metal element; or containing a first metal element and one or more additional metal elements which are different from the first metal element, which becomes a barrier metal film or wiring layer as any one of layers which are provided on a substrate; and (b) converting said metal oxide film or metal salt film into a metal film by reducing it in a solution which contains hydrogen ions.
According to a fifth aspect of the present invention, the process comprises the steps of: (a) forming a film of a metal oxide or metal salt, containing a first metal element; or containing a first metal element and one or more additional metal elements which are different from the first metal element, which becomes a barrier metal film or wiring layer as any one of layers which are provided on a substrate; (b) converting said metal oxide film or metal salt film into a metal film by reducing it in a solution which contains hydrogen ions; and (c) heat treating said metal film under a reduced pressure or in an inert atmosphere.
According to a sixth aspect of the present invention, the process comprises the steps of: (a) forming a film of a metal oxide or metal salt, containing a first metal element; or containing a first metal element and one or more additional metal elements which are different from the first metal element, which becomes a barrier metal film as any one of layers which are provided on a substrate; (b) converting said metal oxide film or metal salt film into a metal film by reducing it in a solution which contains hydrogen ions; and (c) forming a wiring layer on the metal film which becomes the barrier metal film by electrochemically precipitating ions of the metal in an electrolytic solution which contains ions of the metal which becomes a main material of the wiring layer.
According to a further aspect of the present invention, the process comprises the steps of: (a) forming a film of a metal oxide or metal salt, containing a first metal elem

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