Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of...
Reexamination Certificate
2000-02-10
2002-07-02
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
C438S759000, C438S760000
Reexamination Certificate
active
06413879
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming an interlayer insulating film and, more particularly, to a method for forming an interlayer insulating film having a low dielectric constant, which is necessary for a highly-integrated semiconductor device. A progress in high integration regarding the semiconductor device in recent years has resulted in a narrower interval between wiring lines. As the narrowed interval between the wiring lines causes an increase in capacitance between the wiring lines, a request has been made for formation of an interlayer insulating film, which has a low dielectric constant.
With recent progresses in high integration of an LSI device, the wiring line has been micronized and multilayered. There has also been an increase in capacitance between the wiring lines. Such an increase in capacitance has caused a great reduction in an operating speed. Thus, improvement in this regard has been strongly demanded. As one of improvement measures, a method for reducing capacitance between the wiring lines has been studied. This method uses an interlayer insulating film, which has a dielectric constant lower than that of SiO
2
currently used for an interlayer insulating film.
Typical interlayer insulating films of low dielectric constants currently under study are {circle around (1)} an SiOF film, and {circle around (2)} an organic insulating film of a low dielectric constant. Description will now be made of these films.
{circle around (1)} SiOF Film
An SiOF film is formed by using source gas containing F and substituting Si—F bond for a portion of Si—O bond in SiO
2
. This SiOF film has a relative dielectric constant, which is monotonically reduced as concentration of F in the film increases.
For forming such SiOF films, several methods have been reported (see p.82 of monthly periodical “Semiconductor World”, February issue of 1996). Most promising among these methods is one for forming an SiOF film by using SiH
4
, O
2
, Ar and SiF
4
as source gases, and by a high-density plasma enhanced CVD method (HDPCVD method). A relative dielectric constant of an SiOF film formed by this method is in a range of 3.1 to 4.0 (varies depending on F concentration in the film). This value is lower than a relative dielectric constant 4.0 of SiO
2
, which has conventionally been used for the interlayer insulating film.
{circle around (2)} Organic Insulating Film of Low Dielectric Constant
As an insulating film which has a lower dielectric constant (3.0 or lower) compared with the SiOF film, an organic insulating film of a low dielectric constant is now a focus of attention. Table 1 shows a few organic insulating films of low dielectric constants, which have been reported, and respective relative dielectric constants and thermal decomposition temperatures thereof.
TABLE 1
Thermal
Organic
Relative
Decomposition
Insulating
Dielectric
Temperature
Film
Constant
(° C.)
Note
Fluorine-
2.4
420
p. 82 of monthly periodical
containing
“Semiconductor World”,
resin
February issue of 1997
Cytop
2.1
400
p. 90 of monthly periodical
“Semiconductor World”,
February issue of 1996
Amorphous
1.9
400
p. 91 of monthly periodical
telon
“Semiconductor World”,
February issue of 1996
However, the SiOF film is disadvantageous in that an increase in concentration of F in the film leads to a reduction in moisture absorption resistance. The reduced moisture absorption resistance poses a serious problem, because a transistor characteristic and adhesion of an upper barrier metal layer are affected.
Peeling-off easily occurs in the organic insulating film of a low dielectric constant, because of bad adhesion with a silicon wafer or the SiO
2
film. Furthermore, the organic insulating film is disadvantageous in that heat resistivity is low since a thermal decomposition temperature is around 400° C. The disadvantage of low heat resistivity poses a problem for annealing a wafer at a high temperature.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for forming an interlayer insulating film of a low dielectric constant, which has good moisture absorption resistance and heat resistivity. It is another object of the invention to provide a semiconductor device, which employs the above method.
Description will now be made of an interlayer insulating film of the present invention by referring to Table 2.
TABLE 2
Porous Film
Source Gas
Film by Plasma Polymerization
SiO
2
film
TEOS
Si—C film
Si—C—H film
TEOS + O
2
Si—C—O film
Si—C—O—H film
TEOS + H
2
O
Si—C—O—H film
B-containing
TEOS + B
2
H
6
Si—C—B film
SiO
2
film
Si—C—B—H film
TEOS + B
2
H
6
+ O
2
Si—C—B—O film
Si—C—B—O—H film
TEOS + B
2
H
6
+ H
2
O
Si—C—B—O—H film
F-containing
TEOS + C
2
F
6
Si—C—F film
SiO
2
film
Si—C—F—H film
TEOS + C
2
F
6
+ O
2
Si—C—F—O film
Si—C—F—O—H film
TEOS + C
2
F
6
+ H
2
O
Si—C—F—O—H film
For formation of a porous SiO
2
film of the present invention, TEOS, TEOS+O
2
or TEOS+H
2
O is used as source gas. By performing plasma polymerization for such source gas, an Si—C film, an Si—C—H film, an Si—C—O film or an Si—C—O—H film is formed on a formed body. Then, by performing O (oxygen) plasma treatment for these films, C or H is oxidized in the film. C or H is oxidized in the film, and voids are formed in portions from which C or H has been discharged. Accordingly, a porous SiO
2
film is formed. A porous SiO
2
film can also be formed by using methylsilane (Si(CH
3
)H
3
), instead of TEOS.
For formation of a porous B(boron)-containing SiO
2
film of the present invention, TEOS+B
2
H
6
, TEOS+B
2
H
6
+O
2
or TEOS+B
2
H
6
+H
2
O is used as source gas. By performing plasma polymerization for such source gas, an Si—C—B film, an Si—C—B—H film, an Si—C—B—O film or an Si—C—B—O—H film is formed on a formed body. Then, by performing O (oxygen) plasma treatment for these films, C or H is oxidized in the film. C or H is oxidized in the film, and voids are formed in portions from which C or H has been discharged. Accordingly, a porous B-containing SiO
2
film is formed. A porous B-containing SiO
2
film can also be formed by using methylsilane (Si(CH
3
)H
3
) or trimethyl-siliruborate ({(CH
3
)
3
SiO}
3
B), instead of TEOS in source gas. Instead of B
2
H
6
in source gas, TMB(B(OCH
3
)) or TEB(B(OC
2
H
5
)
3
) can be used to form a porous B-containing SiO
2
film.
For formation of a porous F-containing SiO
2
film of the present invention, TEOS+C
2
F
6
, TEOS+C
2
F
6
+O
2
or TEOS+C
2
F
6
+H
2
O is used as source gas. By performing plasma polymerization for such source gas, an Si—C—F film, an Si—C—F—H film, an Si—C—F—O film or an Si—C—F—O—H film is formed on an object to be formed. Then, by performing O (oxygen) plasma treatment for there films, C or H is oxidized in the film. C or H is oxidized in the film, voids are formed in portions from which C or H has been discharged. Accordingly, a porous F-containing SiO
2
film is formed. A porous F-containing SiO
2
film can also be formed by using methylsilane (Si(CH
3
)H
3
), instead of TEOS.
REFERENCES:
patent: 5494859 (1996-02-01), Kapoor
patent: 5614270 (1997-03-01), Yeh et al.
patent: 5644156 (1997-07-01), Suzuki
patent: 5661344 (1997-08-01), Havemann et al.
patent: 5744399 (1998-04-01), Rostoker et al.
patent: 6030706 (2000-02-01), Eissa
patent: 849796 (1998-06-01), None
patent: 2313954 (1997-12-01), None
patent: 9-275103 (1997-10-01), None
patent: WO99/12196 (1999-03-01), None
Berry Renee′ R.
Canon Sales Co., Inc.
Lorusso & Loud
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