Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2001-08-28
2003-07-29
Cao, Phat A. (Department: 2814)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S778000, C438S780000, C438S782000, C438S623000
Reexamination Certificate
active
06599846
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of steadily forming, on a semiconductor substrate, a silica-containing film having characteristics of a low-dielectric constant as low as 3 or less, a low moisture adsorptivity and high film strength without causing any damage to the metal wiring arranged on the substrate, and also relates to a semiconductor substrate coated with a silica-containing film having the above characteristics.
BACKGROUND OF THE INVENTION
In semiconductor devices with a multi-level integrated circuit designed at a rule of 0.25 micron or less, the 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 solved. To cope with this, it is necessary to minimize the dielectric constant of an interconnect insulating film disposed between a semiconductor substrate and metal wiring layer such as an aluminum wiring layer or between metal wiring layers.
The interconnect insulating film disposed for the above purposes is generally formed on a substrate by a vapor phase growth method such as CVD method or by an ordinary coating method which uses a conventional coating liquid.
However, it is considered that the dielectric constant of the silica-containing film produced by the vapor phase growth method such as CVD method is limited to 3.5 (which is obtainable only in the case of the fluorine-doped silica-containing film), and that decreasing it to 3 or less is difficult. On the other hand, the coating film containing polyaryl resin, fluorinated polyimide resin or fluoro-resin, formed on a substrate by the CVD method or the ordinary coating method, exhibits the low-dielectric constant of around 2. However, the coating film containing such a resin has other types of drawbacks such as insufficient adhesion to the substrate or resist used for its fine processing, and poor resistance to chemicals and oxygen plasma.
The conventional coating liquid for forming a silica-containing film, which comprises hydrolyzate of alkoxysilane or halogenated silane and/or a partial hydrolyzate thereof, gives a coating film with the low-dielectric constant of around 2.5. However, there is a problem of the coating film insufficiently adhering to the substrate.
The inventors of the present invention have found, after extensive studies to solve the above problems, that each of the coating liquids described below gives a silica-containing film with the low-dielectric constant of 3 or less, and being excellent not only in adhesion to the substrate, mechanical strength, resistance to chemicals (e.g., alkali) and anti-cracking, but also in process suitability (e.g., resistance to oxygen plasma and etching processability). Based on such findings, they have filed several patent applications as follows:
(1) Invention 1 (Japanese Patent Laid-Open Publication No. 315812/1997)
A coating liquid comprising a reaction product between fine particles of silica, and alkoxysilane and/or halogenated silane or hydrolyzate thereof.
(2) Invention 2 (International Publication No. WO 00/18847)
A coating liquid comprising alkoxysilane and/or halogenated silane or hydrolyzate thereof, and a readily decomposable resin which decomposes or vaporizes at a temperature of 500° C. or lower.
(3) Invention 3 (International Publication No. WO 00/12640)
A coating liquid comprising polysiloxane as a reaction product between fine particles of silica, and alkoxysilane and/or halogenated silane or hydrolyzate thereof, and a readily decomposable resin which decomposes or vaporizes at a temperature of 500° C. or lower.
Thereafter, the inventors of the present invention have repeatedly conducted tests for forming a low-dielectric silica coating film from the above coating liquids on various semiconductor substrates by the ordinary film forming method, and then they have found that, although a coating film having the above characteristics can be obtained, metal wiring arranged on some types of the substrates may be damaged, and that it is difficult to stably form the coating film having excellent characteristics, that is, a low-dielectric constant of 3 or less, a low moisture adsorptivity and high film strength. Therefore, they have further continued the investigations to solve the above problems, and have found that such problems can be easily solved by forming a low-dielectric, silica-containing film on a semiconductor substrate under specific conditions as described below.
DETAILED DESCRIPTION OF THE INVENTION
The present invention has been accomplished with a view to solving the above problems of the prior art.
Accordingly, it is an objective of the present invention to provide a method of steadily forming, on a semiconductor substrate, a low-dielectric, silica-containing film having characteristics of a low-dielectric constant of 3 or less, a low moisture adsorptivity and high film strength without causing any damage to the metal wiring arranged on the substrate. It is another objective of the present invention to provide a semiconductor substrate coated with a silica-containing film having the above characteristics.
The method of the present invention for forming a silica-containing film with a low-dielectric constant of 3 or less steadily on a semiconductor substrate comprises steps of:
(a) applying a coating liquid for forming a silica-containing film with a low-dielectric constant onto a semiconductor substrate,
(b) heating the thus coated film at 50 to 350° C., and then
(c) curing the thus treated film at 350 to 450° C. in an inert-gas atmosphere containing 500 to 15,000 ppm by volume of oxygen.
The coating liquid for forming a silica-containing film with a low-dielectric constant preferably contains hydrolyzate of at least one silicon compound selected from the group consisting of alkoxysilanes and halogenated silanes represented by the following general formula (I) and (II), respectively:
X
n
Si(OR)
4-n
(I),
X
n
SiX′
4-n
(II),
wherein, X represents a hydrogen atom, fluorine atom, unfluorinated or fluorinated alkyl group of 1 to 8 carbon atoms, aryl group or vinyl group; R represents a hydrogen atom, alkyl group of 1 to 8 carbon atoms, aryl group or vinyl group; X′ represents a halogen atom; and n is an integer of 0 to 3.
The coating liquid for forming a silica-containing film with a low-dielectric constant also preferably contains a compound of polysiloxane as a reaction product between fine particles of silica and hydrolyzate of at least one silicon compound selected from the group consisting of alkoxysilanes and halogenated silanes represented by the following general formula (I) and (II), respectively:
X
n
Si(OR)
4-n
(I),
X
n
SiX′
4-n
(II),
wherein, X represents a hydrogen atom, fluorine atom, an unfluorinated or fluorinated alkyl group of 1 to 8 carbon atoms, aryl group or vinyl group; R represents a hydrogen atom, alkyl group of 1 to 8 carbon atoms, aryl group or vinyl group; X′ represents a halogen atom; and n is an integer of 0 to 3.
The coating liquid for forming a silica-containing film with a low-dielectric constant also preferably contains a readily decomposable resin having a number-average molecular weight of 500 to 50,000 in terms of polystyrene, and decomposing or vaporizing easily when thermally treated at a temperature of 450° C. or lower.
The readily decomposable resin is preferably constituted with a composition of an interpenetrated polymer in which the hydrolyzate of the silicon compound or polysiloxane and the readily decomposable resin are homogeneously entangled in each other on the molecular chain level.
The coating liquid for forming a silica-containing film with a low-dielectric constant preferably has the Si—H group at the terminal of any one of the hydrolyzate of the silicon compound, the polysiloxane and/or the interpenetrated polymer.
The thermal treatment step (b) as describ
Egami Miki
Komatsu Michio
Muraguchi Ryo
Nakashima Akira
Cao Phat A.
Catalysts & Chemicals Industries Co. Ltd.
Le Thao X.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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