Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-11-12
2002-09-10
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S858000, C528S026000, C528S029000, C528S039000, C528S010000, C423S339000, C423S335000, C428S412000, C428S447000, C428S448000, C428S700000, C525S903000, C525S419000, C525S474000, C525S464000, C427S226000, C427S387000, C501S082000, C501S053000
Reexamination Certificate
active
06448331
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alkoxysilane/organic polymer composition for use in producing an insulating thin film.
More particularly, the present invention is concerned with an alkoxysilane/organic polymer composition for use in producing an insulating thin film, comprising (A) a specific alkoxysilane; (B) a specific organic polymer; and (C) a solvent for alkoxysilane (A) and organic polymer (B), wherein the solvent (C) comprises at least one organic solvent selected from the group consisting of amide linkage-containing organic solvents and ester linkage-containing organic solvents. In a current process for producing a semiconductor device, a silicon oxide insulating layer is produced by a method comprising dissolving a silicon oxide precursor in an appropriate solvent to thereby obtain a solution of the silicon oxide precursor, forming a coating of the obtained solution on a substrate by spin coating technique or the like, and calcining the coating at an appropriate temperature. When the composition of the present invention is used as a material for an insulating layer in the production of a multilevel interconnect for a semiconductor device, an insulating layer having a low dielectric constant can be produced by a method which can be easily performed in the current process for producing a semiconductor device. The present invention is also concerned with a multilevel interconnect for a semiconductor device, which comprises a plurality of insulating layers and circuits formed on the insulating layers, wherein at least one layer of the insulating layers is obtained using the above-mentioned composition. Further, the present invention is concerned with a semiconductor device comprising the above-mentioned multilevel interconnect.
2. Background Art
Conventionally, as a material for an insulating layer for a multilevel interconnect for a semiconductor device, such as an LSI, silica (having a dielectric constant of from 4.0 to 4.5) or the like has generally been used. In recent years, the density of the circuit of a semiconductor device (such as an LSI) has become higher and higher, and, hence, the distance between mutually adjacent conducting lines in the circuit has become extremely small. As a consequence of this, the mutually adjacent conducting lines having insulators therebetween have inadvertently come to function as a condenser. This has posed a problem that, when the dielectric constant of the insulator is high, the electrostatic capacity of the condenser inadvertently formed by the mutually adjacent conducting lines and the insulators present therebetween becomes high, so that the transmission of the electric signals through each of the mutually adjacent conducting lines is markedly delayed. In order to solve this problem, with respect to a material for an insulating layer for a multilevel interconnect, studies have been made to develop a material having a much lower dielectric constant.
It is known that, among conventional materials, polytetrafluoroethylene has a lowest dielectric constant, which is approximately 1.9. However, in general, fluororesins have a problem in that fluororesins have not only poor adhesion to a substrate and a circuit but also poor heat resistances. Further, in recent years, the dielectric constant of an insulating layer is required to be less than 1.9.
On the other hand, attempts have been made in which the dielectric constant of a conventional material is decreased by rendering the material porous, thereby providing a porous material which is a composite comprised of the conventional material and air (having a dielectric constant of 1.0).
A silica aerogel (which is a type of porous silica) is a representative example of such porous materials. However, production of a silica aerogel requires supercritical drying. Therefore, production of a silica aerogel requires not only a long time, but also extremely complicated steps of operations using a specially designed apparatus, so that it is practically impossible to introduce a step for producing a silica aerogel insulating layer into the current process for producing a semiconductor device.
U.S. Pat. No. 5,472,913 discloses a method for producing a porous silica by a special technique requiring no supercritical drying. However, this method still requires extremely complicated steps of operations, so that it is difficult to introduce a step in which a porous silica insulating layer is produced by this method into the current process for producing a semiconductor device.
Journal of Macromolecular Science-Chemistry
, A27, 13-14 p.1603 (1990) discloses a method for producing a porous silica, which comprises subjecting an alkoxysilane to a hydrolysis and dehydration-condensation reaction in the presence of a specific organic polymer so as to cause a gelation of the alkoxysilane, thereby obtaining a homogeneous organic-inorganic composite comprised of the organic polymer and silica, and heating the obtained composite for calcination so that the organic polymer in the composite can be thermally decomposed and removed, thereby obtaining a porous silica. However, in this method, the calcination for completely decomposing and removing the organic polymer is required to be conducted in an atmosphere of air at a temperature as high as 600° C. or more, so that it is impossible to introduce a step in which a porous silica insulating layer is produced by this method into the current process for producing a semiconductor device.
Further, as described below, methods for producing a porous thin film or the like, which are similar to the above-mentioned method disclosed in
Journal of Macromolecular Science
-
Chemistry,
are disclosed in Unexamined Japanese Patent Application Laid-Open Specification Nos. 8-245278 and 7-100389 and WO97/06896.
Unexamined Japanese Patent Application Laid-Open Specification No. 8-245278 discloses a method for producing a porous ceramic thin film, which comprises coating a substrate with an alcohol solution of a metal alkoxide, which solution contains polyethylene glycol added thereto, and calcining the resultant coating.
Unexamined Japanese Patent Application Laid-Open Specification No. 7-100389 discloses a method for producing a carrier for a catalyst for use in petroleum refining, which comprises subjecting a metal alkoxide to a hydrolysis and dehydration-condensation reaction in the presence of an organic polymer, and calcining the resultant product.
WO97/06896 discloses a method for producing a porous metal oxide film, which comprises dissolving a metal alkoxide, an acid and an organic polymer in a mixed solvent of a first solvent and water to thereby obtain a coating solution, coating the obtained solution onto a glass substrate to form a gel film on the substrate, drying the gel film, immersing the dried gel film in a second solvent to extract and remove the organic polymer from the gel film, and calcining the gel film to thereby obtain a porous metal oxide film.
It is noted that, in each of the methods disclosed in Unexamined Japanese Patent Application Laid-Open Specification Nos. 8-245278 and 7-100389 and WO97/06896, an alcohol is used as a solvent for each of the metal alkoxide and the organic polymer. For the reason as described below, the use of an alcohol as a solvent disadvantageously causes a lowering of the void ratio of an obtained porous material, thereby making it impossible to obtain such a porous insulating thin film having a low dielectric constant as can be suitably used in a multilevel interconnect for a semiconductor device.
As is apparent from the above, such an insulating thin film having a low dielectric constant as can be suitably used in a multilevel interconnect for a semiconductor device has conventionally been unable to be produced by a method which can be easily performed in the current process for producing a semiconductor device.
SUMMARY OF THE INVENTION
In this situation, the present inventors have made extensive and intensive studies with a view toward developing an insulating thin film f
Ioka Takaaki
Tanabe Tsuneaki
Asahi Kasei Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Moore Margaret G.
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