Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2000-01-04
2002-04-16
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S788000, C438S627000, C438S629000
Reexamination Certificate
active
06372670
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) cared 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
Relative
Thermal
Organic
Dielectric
Decomposition
Insulating Film
Constant
Temperature (° C.)
Note
Fluorine-
2.4
420
p. 82 of monthly
containing resin
periodical
“Semiconductor
World”, February
issue of 1997
Cytop
2.1
400
p. 90 of monthly
periodical
“Semiconductor
World”, February
issue of 1996
Amorphous telon
1.9
400
p. 91 of
monthly
periodical
“Semiconductor
World”,
February issue
of 1996
However, the SiLOF 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 having good moisture absorption resistance and heat resistivity and a low dielectric constant, a semiconductor device using the interlayer insulating film, and a semiconductor manufacturing apparatus for forming the interlayer insulating film.
According to the method for forming the interlayer insulating film according to the present invention, an underlying insulating film is formed on an object to be formed (a substrate), and then a porous SiO
2
film is formed on the underlying insulating film. This porous SiO
2
film is formed by three following methods.
(1) Chemical vapor deposition method using Si
2
H
6
and O
2
or Si
3
H
8
and O
2
as a reaction gas as illustrated in FIG.
1
C.
The present inventor found that this method is used whereby Si
2
H
6
and O
2
or Si
3
H
8
and O
2
react with each other in a vapor phase and particulate SiO
2
is formed in the vapor phase. Particulate SiO
2
is deposited on an underlying insulating film
105
. The surface of underlying insulating film
105
can not be densely filled with particulate SiO
2
due to a shape of particulate SiO
2
. Thus, an SiO
2
film
106
having many voids is formed on the underlying insulating film
105
.
(2) Method in which plasma is intermittently or periodically generated in an atmosphere of SiH
4
and O
2
under a low pressure as illustrated in
FIGS. 3C and 4
The present inventor found that the plasma is generated in the atmosphere of SiH
4
and O
2
under the low pressure whereby particulate SiO
2
is formed in the vapor phase. The surface of the substrate can not be densely filled with particulate SiO
2
due to the shape of particulate SiO
2
. Thus, the particulate SiO
2
is deposited on the substrate, so that the porous SiO
2
film is formed on the substrate.
The present inventor further found that the porous SiO
2
film and a SiO
2
film formed by typical low pressure chemical vapor deposition are laminated whereby the porous SiO
2
film having a stable film quality is formed. The inventor invented the method in which the plasma is intermittently or periodically generated in the atmosphere of SiH
4
and O
2
under the low pressure, as the method for laminating these films.
FIG. 4
shows an example of the plasma which is periodically generated. In this drawing, plasma enhanced chemical vapor deposition method is performed under the low pressure during a time period from T
1
to T
2
. The low pressure chemical vapor deposition method is performed during the time period from T
2
to T
3
.
(3) Method in which an organic film and the SiO
2
film are alternately laminated and then the film is subjected to O (oxygen) plasma treatment as illustrated in
FIGS. 6C and 6D
According to this method, a film
506
having the organic film and the SiO
2
film, these films being alternately laminated, is first formed. Then, the film
506
is subjected to the O (oxygen) plasma treatment. The O (oxygen) plasma treatment is thus performed, whereby the organic film previously formed is selectively removed and thus the voids are created in an area in the film in which the organic film is formed. Thus, SiO
2
alone remains in the film and many voids are created. That is, a porous SiO
2
film
507
is formed.
(4) H (hydrogen) plasma treatment for the porous SiO
2
film
The porous SiO
2
film formed as described above has many voids in the film. Thus, a surface area of the porous SiO
2
film is larger than the surface area of the SiO
2
film having no void. Thus, the porous SiO
2
film is prone to adsorb moisture in the air. As illustrated in
FIGS. 1D
,
3
D and
6
E, the porous SiO
2
film is subjected to the H (hydrogen) plasma treatment. Thus, a dangling bond in an Si—O bond on the inner surface of the voids is replaced by an Si—H bond. Consequently, it is possible to prevent the moisture from being adsorbed on the inner surface of the voids.
(5) Formation of a cover insulating film
As illustrated in
FIG. 1E
, the porous SiO
2
film is subjected to the H (hydrogen) plasma treatment, and then the por
Canon Sales Co., Inc.
Lorusso & Loud
Niebling John F.
Zarneke David A.
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