Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-05-24
2002-09-17
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S413000, C428S474400, C428S480000, C428S500000, C106S287100, C106S287120, C106S287130, C106S287140, C106S287160, C427S487000, C427S489000, C427S515000, C427S385500, C427S387000, C427S226000, C524S858000, C524S859000, C438S781000, C438S782000, C438S787000
Reexamination Certificate
active
06451436
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a coating liquid for forming a silica-containing film with a low dielectric constant which enables the formation of a low-density film having a dielectric constant as low as 3 or less and being excellent in resistance to oxygen plasma and in process adaptation such as etching performance, and relates to a substrate coated with a silica-containing film which exhibits the above properties.
BACKGROUND OF THE INVENTION
In semiconductor devices with a multi-level integrated circuit designed at the rules of 0.25 micron or less, metal wiring impedance attributed to electrostatic induction is increased because of the narrow spacing between metal wiring layers required for the advanced integration of such semiconductor devices. Thus, a delay in response speed and an increase in power consumption become problems to be resolved. For coping with this, it is necessary to minimize the dielectric constant of the interconnect insulating film disposed between the semiconductor substrate and the 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 (chemical vapor deposition) method or by a coating method using a conventional coating liquid.
However, it is believed that the dielectric constant of silica-containing film obtained by vapor phase growth methods such as the CVD method is 3.5 (in the case of a fluorine-doped silica film) or higher, and that 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 fluoro-resin, 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 their adhesion to a substrate surface or to a resist material employed in its processing is poor, but also their 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 the obtaining of a coating film with a dielectric constant of about 2.5. However, the coating film has a drawback in that its adhesion to a substrate surface is poor.
The inventors of the present invention have found that the silica-containing film obtained from a coating liquid comprising a reaction product 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 the adhesion to a substrate surface, mechanical strength and chemical resistance such as alkali resistance but also in crack resistance. Based on such findings, a patent application was filed and published as Japanese Patent Laid-open Publication No. 9(1997)-315812.
In order to obtain an insulating film with a low-dielectric constant, it was proposed to form a porous low-density film so as to decrease the dielectric constant. For example, Japanese Patent Laid-Open Publication No. 8(1996)-330300 discloses a process for forming an insulating film with a dielectric constant of not more than 3. According to the invention disclosed in this publication, the insulating film having a low-dielectric constant is formed by applying a coating liquid having dissolved therein a gas-generating substance of organic components such as 5-naphthoquinonediazidosulfonic esters, 4-naphthoquinonediazidosulfonic esters, quinonediazides, diazonium salts, azide compounds, maleic acid derivatives, acetoacetic acid derivatives, diazomeldrum derivatives, t-butoxycarbonic ester derivatives and polybutenesulfone derivatives onto a substrate by SOG (spinning on glass) method, and then heating the thus coated film or irradiating it with radiation to render the film porous.
However, it is known that although an insulating film having a dielectric constant of not more than 3 can be obtained from the coating liquid containing such a gas-generating substance, the adhesion of the resulting film to a substrate and film strength are not always satisfactory.
As a result of various studies made by the inventors of the present invention, it was found that rendering the coating film too porous to attain a low-dielectric constant will cause deterioration of the film quality attributed to the irradiation of oxygen plasma in the process of plasma etching or peeling of a resist material, and such a deterioration tendency is conspicuous particularly in a porous film (including a porous silica-containing film) having pores or voids with a relatively large size.
Under such circumstances as described above, there has been a strong requirement for development of a coating liquid for forming a silica-containing film with a low-dielectric constant, which enables the formation of a low-density insulating film having a dielectric constant as low as 3 or less and being excellent not only in resistance to oxygen plasma and in process adaptation such as etching performance, but also in adhesion to a substrate and in film strength.
SUMMARY OF THE INVENTION
The present invention has been accomplished with a view to solving the above problems of the prior art. Accordingly, the present invention provides a coating liquid for forming a silica-containing film, which enables the formation of a low-density insulating film having a dielectric constant as low as 3 or less and being excellent not only in resistance to oxygen plasma and in process adaptation such as etching performance but also in adhesion to a substrate and in film strength. In addition, the present invention provides 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 a polymer composition mainly constituted by (i) a hydrolyzate of at least one alkoxysilane represented by the following formula (I) and/or at least one halogenated silane represented by the following formula (II), and (ii) a readily decomposable resin,
X
n
Si (OR)
4−n
(I)
X
n
SiX′
4−n
(II)
wherein X represents a hydrogen atom, a fluorine atom, an unfluorinated or fluorinated alkyl group of 1 to 8 carbon atoms, an aryl group or a vinyl group; R represents a hydrogen atom, an alkyl group of 1 to 8 carbon atoms, an aryl group or a vinyl group; X′ represents a halogen atom; and n is an integer of 0 to 3.
The polymer composition is preferably an interpenetrated polymer composition in which the hydrolyzate and the readily decomposable resin are entangled in each other on the molecular chain level.
The readily decomposable resin is preferably a resin which is decomposed or vaporized by heating at a temperature of not higher than 500° C. or by irradiating with ultraviolet radiation, infrared radiation, electron beam, X-ray or oxygen plasma. Moreover, the readily decomposable resin preferably has a number-average molecular weight of 500 to 50,000 based on polystyrene.
The polymer composition is preferably obtained by performing a catalytic hydrolysis reaction of alkoxysilane and/or halogenated silane in a solution comprising:
(a) at least one alkoxysilane represented by the above formula (I) and/or at least one halogenated silane represented by the above formula (II), and
(b) the readily decomposable resin dissolved in an organic solvent being insoluble in water,
with addition thereto of water and an acid catalyst, or an aqueous solution containing the acid catalyst.
In the polymer composition, the weight ratio (A/B) of the hydrolyzate of alkoxysilane and/or halogenated silane (A), in terms of SiO
2
, to the readily decomposable resin (B) is preferably in the range of 1/0.1 to 1/20.
The substrate coated with a silica-containing film with a low-dielectric constant according to the present invention is a low-density film formed by:
applying
Egami Miki
Komatsu Michio
Nakashima Akira
Catalysts & Chemicals Industries Co. Ltd.
Dawson Robert
Robertson Jeffrey B.
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