Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
2001-10-26
2004-08-24
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S315500, C428S315700, C428S901000, C524S588000, C525S474000, C525S477000, C528S031000, C528S035000, C556S431000, C438S781000
Reexamination Certificate
active
06780498
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority from Japanese Patent Application No. 2001-84475, filed in Mar. 23, 2001, the content being incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device using a low dielectric constant film and a silicon-based composition used for the same, a low dielectric constant film, and a method for producing the low dielectric constant film.
2. Description of the Related Arts
It is important for integration and miniaturization of a semiconductor to reduce the parasitic capacitance that is generated between wirings in multilayer wiring processes of a semiconductor integrated circuit and to reduce the delay of the signal propagation speed (i.e., the wiring delay).
Although the reduction of the signal propagation speed by the parasitic capacitance of an insulating film has been recognized so far, the influence of the wiring delay on the entire device has not been so remarkable in the semiconductor devices of generations in which the wiring gap is larger than 1 &mgr;m.
In the case the wiring gap is 1 &mgr;m or less, however, the influence on the device speed becomes large. In particular, when a circuit is formed with the wiring gap being 0.5 &mgr;m or less as will be expected in near future, the parasitic capacitance between wirings will be affecting the device speed more. Accordingly this will be a big obstacle for the integration and miniaturization of a semiconductor.
In other words, while the reduction of the signal propagation speed depends largely on the wiring resistance and parasitic capacitance between wirings in the multilayer wiring of a semiconductor integrated circuit, higher integration of a device makes the width of a wiring and wiring gap narrower, resulting in increase in the wiring resistance and parasitic capacitance between wirings.
The capacitance of an insulating film can be reduced by making the wiring thickness thinner to reduce the cross-sectional area. However, making the wiring thinner results in larger wiring resistance, and therefore, a higher signal propagation speed cannot be achieved.
Accordingly, it is indispensable for achieving a higher signal propagation speed to make the resistance of a wiring and the dielectric constant of an insulating film lower, and it is expected that they will play very important roles in deciding properties of a device in future.
Wiring delay (T) is affected by wiring resistance (R) and capacitance (C) between wirings as shown in Eq. 1.
T∝CR (1)
In eq. 1, the relation between e (dielectric constant) and C is expressed by Eq. 1′.
C=∈
0
∈
r
·S/d
(1′)
wherein S is an electrode area; co is a dielectric constant of the vacuum; ∈
r
is a relative dielectric constant of an insulating film; and d is a wiring gap.
Therefore, the wiring delay is effectively diminished by making the dielectric constant of the insulating film lower.
Inorganic films such as silicon dioxide (SiO
2
), silicon nitride (SiN), and phosphate silicate glass (PSG) and organic polymers such as polyimide have been used as insulating materials so far.
However, the dielectric constant of CVD-SiO
2
films, which are most frequently used for semiconductor devices, is about 4 or so. Although the dielectric constant of an SiOF film, which is now being calling attentions as a low dielectric constant CVD film, is about 3.3-3.5, it is hygroscopic, so that it has a problem in that the dielectric constant is increased by absorbing water.
In addition, as a low dielectric constant film, a porous film made of a siloxane resin having SiH bonds is known. However, when a semiconductor device is subjected to washing with an alkaline solution, there is a problem in that highly hygroscopic SiOH groups are formed as a result of hydrolysis, resulting in an increased dielectric constant, together with the problem of mechanical damages on the semiconductor part such as cracks caused by the washing. To solve these problems, a protecting film such as a SiO
2
film has been formed conventionally. However, this will make relatively smaller the rate of the low dielectric constant film in a semiconductor device, and accordingly, the effective dielectric constant will be increased when multilayer wirings are formed.
To compare, organic polymer films can be used to have a lower dielectric constant. However, the glass transition temperatures are as low as 200-350° C. and the coefficients of thermal expansion are large, so that the damages to the wiring are problematic.
SUMMARY OF THE INVENTION
It is, therefore, the object of the present invention to solve the above-mentioned several problems in order to form an excellent film, as well as to provide an insulating film having a lower dielectric constant than those of conventional insulating films, and to provide fast and reliable semiconductor devices.
In addition, the present invention improves, in many cases, chemical resistance, especially against alkali solutions of a silica-based film, and it can solve the problem of highly hygroscopic characteristic presented in conventional porous films made of a siloxane resin.
According to one aspect of the present invention there is provided a composition comprising a siloxane resin, a silicon compound substantially consisting of silicon, carbon and hydrogen, wherein the number ratio of carbon to silicon atoms forming an —X— bond (wherein X is (C)
m
(where m is an integer in the range of from 1 to 3), or a substituted or unsubstituted aromatic group with carbon atoms of not more than 9) in the main chain of one molecule is from 2:1 to 12:1, as well as a solvent. Hereupon, it is to be noted that ‘C’ of (C)
m
means a carbon atom.
As other aspects of the present invention, there are provided a low dielectric constant film obtained by subjecting the composition to a heat treatment, a semiconductor device having the low dielectric constant film as an interlayer insulating film, and a method for producing the low dielectric constant film.
It was found that a film obtained by adding a silicon compound having a silicon-carbon bond(s) in the skeletal chain (main chain) to a siloxane resin is given a nature of repelling chemicals such as an alkali.
It was also found that, when the compound was added to a siloxane resin, the compound was homogeneously dispersed into the siloxane resin because of its high compatibility, and that the resistance against acidic and alkaline solutions was improved and was lasting even if the compound was added to the siloxane resin at a weight ratio of 0.1 part by weight based on 100 parts by weight of the siloxane resin.
It was also found that a silicon compound having a silicon-carbon bond(s) in its skeleton had a high moisture resistance, and therefore, the composition according to the present invention was effective even in forming porous films that would have a problem of low moisture resistance, unless it were used.
It was also found that the combination of a siloxane resin and such a silicon compound can prevent damages (mechanical damages such as cracks) caused on a siloxane-based low dielectric constant film in an alkaline solution, which has been a problem for low dielectric constant films having a SiH bond(s), and that the increase in the dielectric constant caused by the hygroscopic behavior can be solved in many cases, which has been another problem for low dielectric constant porous films.
Such a silicon compound can be identified as a silicon compound having an —X— bond (wherein X is (C)
m
(where m=1 to 3) or a substituted or unsubstituted aromatic group with 9 or less carbon atoms) in its main chain.
By using s silicon compound having the above-mentioned —X— bond (wherein X is (C)
m
(where m=1 to 3) or a substituted or unsubstituted aromatic group with 9 or less carbons) in its main chain, together with a siloxane resin, forming a coating film containing both, and heating the resultant film, it is possible to produce a low die
Nakata Yoshihiro
Sugiura Iwao
Suzuki Katsumi
Yano Ei
Armstrong Kratz Quintos Hanson & Brooks, LLP
Fujitsu Limited
Morris Terrel
Vo Hai
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