Method of plasma-assisted film deposition

Details Method of plasma-assisted film deposition Method of plasma-assisted film deposition

2000-09-07

2003-06-10

Dang, Trung (Department: 2823)

Semiconductor device manufacturing: process

Coating of substrate containing semiconductor region or of...

Insulative material deposited upon semiconductive substrate

C438S783000, C438S789000, C438S790000

Reexamination Certificate

active

06576569

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a method for forming for example an interlayer dielectric film of a semiconductor device, for example a film of carbon added fluorine (fluorine-added carbon).
BACKGROUND OF THE INVENTION
In order to integrate semiconductor devices in higher density, various ideas have been proposed, for example, making patterns minute or multilayering circuits. As one of the ideas, there is known an art for multilayering wires. In order to achieve a multilayered wiring structure, an (n)-th wiring layer and an (n+1)-th wiring layer are connected with each other via an electric conducting layer. In addition, a thin film, which is called an interlayer dielectric film, is formed at an area or areas except the electric conducting layer.
An SiO
2
film is a typical interlayer dielectric film. However, recently, it is required to lower a dielectric constant of the interlayer dielectric film in order to raise a speed of operation of the device further more. Then, characteristics of materials for the interlayer dielectric films are examined and studied. The SiO
2
has a dielectric constant of about 4. Thus, various efforts have been made to find or form a material having a smaller dielectric constant. As one of the efforts, an SiOF film having a dielectric constant of 3.5 has been developed. However, inventors of this invention have paid attention to a film of flurorine-added carbon (hereafter, which is abbreviated as a CF film) having a further smaller dielectric constant.
Such a CF film is formed for example by using Argon (Ar) gas as a plasma gas, using a mixed gas including a compound gas of carbon (C) and fluorine (F) and a hydrocarbon gas as a film-forming gas, and making the film-forming gas into plasma in a plasma unit which can generate plasma for example by using electron cyclotron resonance. Then, the inventors have examined to use C
6
F
6
(hexafluorobenzene) gas as the film-forming gas in order to raise thermal stability of the CF film.
SUMMARY OF THE INVENTION
If the CF film is used as an interlayer dielectric film, for example as shown in
FIG. 10
, a CF film
13
is accumulated on a SiO
2
film
11
on which aluminum wires
12
are formed, so that gaps between the wires
12
,
12
are filled up with the CF film
13
. However, if C
6
F
6
gas is used as the film-forming gas, since the C
6
F
6
gas has a benzene ring i.e. a molecule of the C
6
F
6
is large, as shown in FIG.
10
(
a
), shoulder-like portions of the accumulated film above both side edges of a concave portion
14
between the wires
12
,
12
bulge out while the CF film
13
is accumulated. Then, the shoulder-like portions may contact with each other to block access to the concave portion
14
. Thus, even if the concave portion
14
has an aspect ratio that is not so large, the concave portion
14
can not be filled with the CF film
13
. That is, a or more large voids (spaces)
15
may be formed in the portion (see FIG.
10
(
b
)).
This invention is intended to solve the above problem. The object of this invention is to provide a plasma film-forming method which can satisfactory fill up a concave portion with a CF film.
In order to achieve the object, a plasma film-forming method (a method of plasma-assisted film deposition) has a feature of comprising: a plasma-making step of making into plasma a film-forming gas including a compound of carbon and fluorine and an etching gas which can etch a film of fluorine-added carbon; and a film-forming step of forming a film of fluorine-added carbon onto an object to be processed by means of the plasma made in the plasma-making step.
According to the feature, if the CF film is used as an interlayer dielectric film, since the etching gas for etching the CF film is supplied in addition to the film-forming gas, a concave portion can be satisfactory filled up with the CF film.
The film-forming gas including a compound of carbon and fluorine includes for example a gas of a compound having a benzene ring, in particular hexafluorobenzene.
Preferably, the etching gas which can etch a film of fluorine-added carbon is a gas including fluorine, a gas including oxygen or a gas including hydrogen.
Preferably, hydrocarbon gas or a gas including silicon is supplied in addition to the film-forming gas and the etching gas, in the plasma-making step.


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Grill et al., “Wear Resistant Flourinated Diamondlike Carbon Films”,Diamond Films and Technology, vol. 6, No. 1, pp. 13-21, 1996.
Sah et al. “Amorphous Carbon Coatings Prepared by High Rate RF Plasma Deposition From Flourinated Benzenes”,Applied Physics Letters, vol. 46, No. 8, pp. 739-741, Apr. 15, 1985.

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