Coating processes – Heat decomposition of applied coating or base material
Reexamination Certificate
2003-02-24
2004-06-08
Stein, Stephen (Department: 1775)
Coating processes
Heat decomposition of applied coating or base material
C427S126200, C427S373000, C427S397700
Reexamination Certificate
active
06746714
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a porous silica coating with a low dielectric constant, a semiconductor device comprising the porous silica coating, and a coating composition which becomes the porous silica coating.
BACKGROUND ART
Polysilazane coatings are converted into silica coatings by firing in atmospheric air. These silica coatings are used as interlayer dielectrics for semiconductors because of excellent electrical insulating properties. Among these silica coatings, a completely inorganic silica coating has already been employed as an excellent interlayer dielectric for a semiconductor because it has high heat resistance and can be used in a non-etch back process. In this case, the physical properties of the silica coating are similar to those of silicon dioxide (SiO
2
) and its dielectric constant is within a range from 3.0 to 4.7.
With the increase of the speed and integration density of integrated circuits, a further reduction in dielectric constant is required of electronic materials such as interlayer dielectrics. However, the dielectric constant of a conventional silica coating is too high for such a requirement. It is known to make the silica coating porous so as to reduce the dielectric constant, however, the silica coating generally has moisture absorption properties and the dielectric constant increases with the elapse of time, under an ambient atmosphere. It has been proposed that a porous coating is subjected to a water repellent treatment thereby to add an organic group such as a trimethylsilyl group to the surface in order to prevent an increase in dielectric constant with the elapse of time due to moisture absorption. However, such an additional water repellent treatment causes the problem that the manufacturing cost increases and introduction of the organic group impairs an inorganic material's ability to make it possible to be used in a non-etch back process.
Thus, an object of the present invention to provide a silica coating which makes it possible to drastically reduce the dielectric constant (especially to less than 2.5) and to substantially maintain the reduced dielectric constant under an ambient atmosphere without being subjected to a water repellent treatment. Another object of the present invention is to provide a semiconductor device comprising the silica coating with such a low dielectric constant as an interlayer dielectric, and a coating composition which becomes the silica coating.
DISCLOSURE OF THE INVENTION
In order to achieve the objects described above, the present inventors have intensively studied and thus completed the present invention.
According to the present invention, there is provided a porous silica coating having a dielectric constant of less than 2.5, which is obtained by firing a coating of a composition comprising an aluminum-containing polysilazane and a polyacrylate or polymethacrylate ester.
According to the present invention, there is also provided a semiconductor device comprising the porous silica coating as an interlayer dielectric.
According to the present invention, there is also provided a coating composition comprising an aluminum-containing polysilazane and a polyacrylate or polymethacrylate ester in an organic solvent.
MODE FOR CARRYING OUT THE INVENTION
The porous silica coating of the present invention is obtained by firing a coating of a composition comprising an aluminum-containing polysilazane and a polyacrylate or polymethacrylate ester. The aluminum-containing polysilazane is obtained by mixing a polysilazane with an aluminum compound.
The polysilazane as a material for forming the silica coating has in its molecular chain a silazane structure represented by the following general formula (1):
In the above formula, R
1
, R
2
and R
3
each independently represents a hydrogen atom, a hydrocarbon group, a hydrocarbon group-containing silyl group, a hydrocarbon group-containing amino group, or a hydrocarbonoxy group. At least one of R
1
and R
2
represents a hydrogen atom. The hydrocarbon group may be combined with a substituent, and examples of the substituent include halogen such as chlorine, bromine and fluorine, an alkoxy group, an alkoxycarbonyl group, and an amino group.
The hydrocarbon group includes an aliphatic hydrocarbon group and an aromatic hydrocarbon group, and the aliphatic hydrocarbon group includes a chain hydrocarbon group and a cyclic hydrocarbon group. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, and an arylalkyl group. The number of carbon atoms in these hydrocarbon atoms is not limited, but is usually 20 or less, and preferably 10 or less. In the present invention, preferred is an alkyl group having 1 to 8 carbon atoms, and particularly 1 to 4 carbon atoms. In the hydrocarbon group-containing silyl group, a preferable hydrocarbon group is an alkyl group having 1 to 20 carbon atoms, and particularly 1 to 6 carbon atoms. The number of hydrocarbon atoms to be combined with Si is within a range from 1 to 3. In the hydrocarbon-containing amino group and hydrocarbonoxy group, the number of carbon atoms in the hydrocarbon group is within a range from 1 to 3.
The polysilazane having a silazane structure represented by the general formula (1) in a molecular chain may be a polysilazane having a chain, cyclic or crosslinked structure, or a mixture thereof. The number-average molecular weight is within a range from 100 to 100,000, and preferably from 300 to 10,000. Such a polysilazane includes conventional perhydropolysilazane, organopolysilazane, and a modified compound thereof.
Examples of the modified polysilazane include a platinum- or palladium-containing polysilazane, an alcohol residue-containing polysilazane, an HMDS (hexamethyldisilazane) residue-containing polysilazane, an amine-containing polysilazane, and an organic acid-containing polysilazane.
For example, these modified polysilazanes are described in Japanese Unexamined Patent Publication Nos. 9-31333, 8-176512, 8-176511, and 5-345826.
The aluminum to be incorporated into the polysilazane may be an aluminum compound in the form capable of being dissolved in an organic solvent. Such a soluble aluminum compound includes an alkoxide, a chelete compound, an organoaluminum, and a halide.
Examples of the alkoxide of aluminum include those represented by the following general formula (2):
In the above formula, R
4
, R
9
and R
6
represent a hydrocarbon group. The hydrocarbon group includes an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The aliphatic hydrocarbon group includes a chain hydrocarbon group and a cyclic hydrocarbon group. Examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, and a cycloalkenyl group. The number of carbon atoms is not specifically limited, but is usually 20 or less, and preferably 8 or less. Specific examples of the aliphatic hydrocarbon group include methyl, ethyl, propyl, butyl, pentyl, octyl, dodecyl, octadecyl, dodecenyl, cyclohexyl, and cyclohexenyl. The aromatic hydrocarbon group includes an aryl group and an arylalkyl group. Specific examples of the aromatic hydrocarbon group include phenyl, tolyl, xylyl, naphthyl, benzyl, phenethyl, and naphthylmethyl.
Examples of the chelete compound of aluminum include aluminum acetylacetonate and aluminum ethylacetonate.
Examples of the organoaluminum include those represented by the following general formula (3):
In the above formula, R
4
, R
5
and R
6
represent a hydrocarbon group. The hydrocarbon group includes those described in connection with the general formula (2).
Examples of the halide of aluminum include those represented by the following general formula (4):
AlX
3
(4)
wherein X represents a halogen. The halogen includes chlorine, bromine, iodine, and fluorine.
The organic solvent-soluble aluminum compounds can be used alone or in combination.
The amount of the aluminum compound to be added to the polysilazane varies depending on the kind, but is within a ran
Aoki Tomoko
Shimizu Yasuo
Clariant Finance (BVI) Limited
Kass Alan P.
Stein Stephen
LandOfFree
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