Stock material or miscellaneous articles – Composite – Of polycarbonate
Reexamination Certificate
1999-12-23
2003-05-13
Dunn, Tom (Department: 1725)
Stock material or miscellaneous articles
Composite
Of polycarbonate
C428S312600, C428S319100, C428S391000, C428S446000, C428S447000, C106S286100
Reexamination Certificate
active
06562465
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a coating liquid for forming a silica-containing film with a low dielectric constant which enables easily forming an insulating film having a dielectric constant (relative permittivity) as low as 3 or less and being excellent in microphotolithography workability, and relates to a substrate having a silica-containing film which exhibits the above properties.
In semiconductor devices with a multilayer wiring integrated at design rules of 0.3 micron or less, metal wiring impedance attributed to electrostatic induction is increased because of a narrow spacing between metal wiring layers required for the advanced integration of such semiconductor devices. Thus, a decrease of response speed and an increase of power consumption become problems to be resolved. For coping with this, it is necesary to minimize the dielectric constant of an interconnect insulating film disposed between a semiconductor substrate and a metal wiring layer such as an aluminum wiring layer or between metal wiring layers.
The interconnect insulating film disposed for the above purpose is generally formed on a substrate by a vapor phase growth method such as CVD method or by a coating method for forming an insulating coating film by use of a coating liquid.
However, it is believed that the dielectric constant of silica-containing film obtained by the vapor phase growth method such as the CVD method is 3.5 (in case of a fluorine-doped silica coating film) or higher, and forming a silica-containing film having a dielectric constant of lower than 3 is difficult.
On the other hand, the coating film containing a polyaryl resin, a fluorinated polyimide resin or a fluororesin, which is formed on a substrate by the CVD method or the coating method, exhibits a dielectric constant of about 2. However, these films have drawbacks in that not only the adherence to a substrate surface or to a resist material employed in its processing is poor, but also the resistance to chemicals and oxygen plasma is inferior.
The conventional coating liquid for forming a silica-containing film, which comprises a partial hydrolyzate of alkoxysilane, enables obtaining a coating film whose dielectric constant is about 2.5. However, the coating film has a drawback in that the adherence to a substrate surface is poor.
Some of the inventors of the present invention found that the coating film obtained from a coating liquid comprising a product of reaction between fine particles of silica and a halogenated silane or a hydrolyzate thereof exhibits a dielectric constant as low as 3 or less and is excellent in not only adherence to a substrate surface, mechanical strength and chemical resistance such as alkali resistance but also crack resistance. Based on such finding, a patent application was filed and published as Japanese Patent Laid-open Publication No. 9(1997)-315812.
The inventors of the present invention have made further studies. As a result, it has been found that, with respect to the above prior coating film, the deterioration in the properties of the coating film due to the plasma etching at a microphotolithography working stage or oxygen plasma irradiation at a resist peeling stage may cause adsorption (or re-adsorption) of moisture to the coating film, which results in an increase of the dielectric constant of the coating film and decreases of adherence, chemical resistance and crack resistance.
That is, it has been found that, when a silica-containing film is formed from the conventional coating liquid which contains, as a film forming component, a hydrolyzate of an alkoxysilane or a halogenated silane and fine particles of silica reacted therewith, the crosslinking density of Si—O—Si bond in the coating film is decreased by interstices or pores formed between the fine particles of silica and also by the organic group, fluorine atom and hydrogen atom bonded to the Si atom constituting the fine particles of silica. As a result, a coating film having a low dielectric constant can be obtained, however the above functional groups have poor plasma resistance by which the properties of the coating film are deteriorated at the time of microphotolithography working and hence a stable silica-containing film with a low dielectric constant would not be obtained.
SUMMARY OF THE INVENTION
The present invention has been made with a view to solving the above problems of the prior art. Accordingly, it is an object of the present invention to provide a coating liquid for forming a silica-containing film which enables forming an insulating film having a dielectric constant as low as 3 or less and being excellent in microphotolithography workability. It is another object of the present invention to provide a substrate furnished with a silica-containing film having the above properties.
The coating liquid for forming a silica-containing film with a low-dielectric constant according to the present invention comprises:
(i) fine particles of silica having a phenyl group thereon, and
(ii) a polysiloxazane obtained by reacting a hydrolyzate or hydrolyzates of an alkoxysilane represented by the general formula (I) and/or a halogenated silane represented by the general formula (II) with a polysilazane represented by the general formula (III), each of the formulae is shown below:
X
n
Si(OR
1
)
4−n
(I),
X
n
SiX′
4−n
(II), and
wherein X represents a hydrogen atom, a fluorine atom, an unfluorinated or fluorinated alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group; each of R
1
, R
2
, R
3
and R
4
represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group; X′ represents a halogen atom; and m is an integer while n is an integer of 0 to 3.
Alternatively, the coating liquid for forming a silica-containing film with a low dielectric constant according to the present invention comprises:
(i) fine particles of silica having a phenyl group thereon, and
(ii′) an oxidatively decomposable resin,
the weight ratio of the fine particles of silica having a phenyl group to the oxidatively decomposable resin (i.e., the fine particles/the resin) being in the range of 0.5 to 5.
This oxidatively decomposable resin is preferably a resin which is soluble in an organic solvent and which is decomposed by heating in a gas containing oxygen at room temperature to 500° C. or by irradiation with ultraviolet light, infrared rays, electron beams, X-rays or oxygen plasma.
It is preferred that the fine particles of silica having a phenyl group as mentioned above be obtained by the following steps:
i) hydrolyzing at least one alkoxysilane represented by the general formula (I) as shown below, and thereafter aging the hydrolyzed alkoxysilane, to thereby obtain fine particles of silica, and
ii) bonding a hydrolyzate or hydrolyzates of an alkoxysilane having a phenyl group and/or a chlorosilane having a phenyl group with a surface of at least part of the obtained fine particles of silica:
X
n
Si(OR
1
)
4−n
(I),
wherein X represents a hydrogen atom, a fluorine atom, an unfluorinated or fluorinated alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group; R
1
represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group; and n is an integer of 0 to 3.
The above alkoxysilane having a phenyl group is preferably represented by the general formula (IV), and the above chlorosilane having a phenyl group is preferably represented by the general formula (V), each of the formulae is shown below:
X
p
R
2
q
Si(OR
1
)
4−(p+q)
(IV),
and
X
p
R
2
q
SiX′
4−(p+q)
(V),
wherein X represents a hydrogen atom, a fluorine atom, an unfluorinated or fluorinated alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group; R
1
represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group; R
2
represents a phenyl group; X′ represents a chlorine atom; and p is an integ
Komatsu Michio
Nakashima Akira
Tonai Atsushi
Catalysts & Chemicals Industries Co. Ltd.
Dunn Tom
Edmondson L.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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