JP2009081291A - Method for forming insulating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming an insulating film which is suitably used as a low dielectric constant interlayer insulating film of a semiconductor element device etc. <P>SOLUTION: After a coating film containing a high molecular compound formed by polymerizing a cage type silsesquioxane compound having two or more unsaturated groups as substituents is formed on a substrate, baking is carried out at 250 to 350°C in an oxygen atmosphere, and a treatment is performed using a medium containing a crosslinking compound which can be bonded to a hydroxyl group. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for forming an insulating film, and more particularly, a method for forming a coating film having an appropriate uniform thickness as an interlayer insulating film material in a semiconductor element and the like, and forming an insulating film at a low temperature. About.

Conventionally, a silica (SiO ₂ ) film formed by a vacuum process such as a vapor deposition (CVD) method is frequently used as an interlayer insulating film in a semiconductor element or the like. In recent years, for the purpose of forming a more uniform interlayer insulating film, a coating type insulating film called a SOG (Spin on Glass) film containing a hydrolysis product of tetraalkoxylane as a main component has been used. It has become. In addition, with high integration of semiconductor elements and the like, an interlayer insulating film having a low dielectric constant, which is mainly composed of polyorganosiloxane called organic SOG, has been developed.

However, these films are often formed in an atmosphere of 300 ° C. or higher, and an insulating film forming method at a lower temperature is required from the viewpoint of reducing damage caused by heat and saving energy.
In addition, since the organic component contained in the insulating film affects the dry etching rate and the like, pure SiO ₂ containing no organic component is often required.

As a known technique for solving these problems, an example using a polymer of alkoxysilane is widely known (see, for example, Patent Document 1). However, since a dehydration condensation system is used, water is always generated, which is not necessarily suitable in the semiconductor manufacturing field. In addition, a multi-step baking process is required to prevent cracks, leading to a decrease in productivity. In addition, it is widely known that the SiO ₂ film generally contains more hydroxyl groups as it is formed at a lower temperature. This hydroxyl group has a problem that it is widely known that it adsorbs many water molecules and significantly increases the dielectric constant.

JP 2006-303129 A

  Accordingly, an object of the present invention relates to an insulating film forming method for solving the above-described problems, and more particularly, to provide an insulating film forming method suitable for use as a low dielectric constant interlayer insulating film in a semiconductor element device or the like. That is.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means.
(1) A coating film containing a polymer compound obtained by polymerizing a cage silsesquioxane compound having two or more unsaturated groups as a substituent is formed on a substrate, and then 250 to 350 ° C. in an oxygen atmosphere. And a treatment with a medium containing a crosslinkable compound that can be bonded to a hydroxyl group.
(2) The method for forming an insulating film according to (1), wherein the oxygen content in the oxygen atmosphere is 500 ppm or more.
(3) The method for forming an insulating film according to (1), wherein the crosslinkable compound capable of binding to a hydroxyl group is hexachlorodisiloxane.

  According to the present invention, a film suitable for use as an interlayer insulating film in a semiconductor device or the like or a low refractive index film in an optical device has a high mechanical strength and a very low dielectric constant only by a low temperature process of 350 ° C. or lower. Can be formed.

  Hereinafter, the method for forming an insulating film of the present invention is a method in which a coating film containing a polymer compound obtained by polymerizing a cage-type silsesquioxane compound having two or more unsaturated groups as a substituent is formed on a substrate. This is a method for forming an insulating film which is baked in an oxygen atmosphere and further treated with a medium containing a crosslinkable compound capable of bonding to a hydroxyl group.

The insulating film of the present invention uses a polymer compound obtained by polymerizing a cage silsesquioxane compound having two or more unsaturated groups as substituents. Such a cage-type silsesquioxane polymer has a property that a hydroxyl group is formed when placed in an oxygen atmosphere at a temperature of about 250 to 350 ° C.
A feature of the present invention is that the coating film having a hydroxyl group generated in an oxygen atmosphere is treated with a medium containing a crosslinkable compound capable of binding to a hydroxyl group, thereby achieving both mechanical strength and low dielectric constant of the coating film. There is. Further, the present invention is characterized in that the heating temperature is lower than 350 to 450 ° C., which is a normal firing temperature of an insulating film, so that the semiconductor device can be fired with little damage due to the temperature.

The cage-type silsesquioxane compound (hereinafter also referred to as compound (I)) having two or more unsaturated groups as substituents in the present invention is, for example, m RSi (O _0.5 ) ₃ units (m is Each represents an integer of 8 to 16, each R independently represents a non-hydrolyzable group, and at least two of R are groups containing a vinyl group or an ethynyl group), Examples thereof include a compound (hereinafter also referred to as compound (I ′)) in which the oxygen atom in the unit is shared and linked to another unit to form a cage structure.
For example, m in the compound (I ′) is preferably 8, 10, 12, 14, or 16 from the viewpoint of the effect of decreasing the dielectric constant, and 8, 10, or 12 is more preferable from the viewpoint of availability.

Here, the cage structure refers to a molecule whose volume is determined by a plurality of rings formed of covalently bonded atoms, and a point located within the volume cannot leave the volume without passing through the ring.
Each R independently represents a non-hydrolyzable group. The non-hydrolyzable group is a group that remains at least 95% when brought into contact with 1 equivalent of neutral water at room temperature for 1 hour. It is preferable that 99% or more remain.
At least two of R are groups containing a vinyl group or an ethynyl group. Examples of non-hydrolyzable groups for R include alkyl groups (methyl, t-butyl, cyclopentyl, cyclohexyl, etc.), aryl groups (phenyl, 1-naphthyl, 2-naphthyl, etc.), vinyl groups, ethynyl groups, allyl groups. And silyloxy groups (trimethylsilyloxy, triethylsilyloxy, t-butyldimethylsilyloxy) and the like.

Of the groups represented by R, at least two are groups containing a vinyl group or an ethynyl group, but at least two are preferably vinyl groups. When the group represented by R includes a vinyl group or an ethynyl group, the vinyl group or ethynyl group is preferably bonded to the silicon atom to which R is bonded, directly or through a divalent linking group. Examples of the divalent linking group include-[C (R ¹¹ ) (R ¹² )] _k- , -CO-, -O-, -N (R ¹³ )-, -S-, -O-Si (R ¹⁴ ) (R ¹⁵ ) —, and divalent linking groups formed by arbitrarily combining these. (R ^{11 to} R ¹⁵ each independently represents a hydrogen atom, a methyl group, an ethyl group, or a phenyl group, and k represents an integer of 1 to 6), among them — [C (R ¹¹ ) (R ¹² )] _k- , -O-, -O-Si (R ¹⁴ ) (R ¹⁵ )-or a divalent linking group formed by arbitrarily combining these is preferable.
In compound (I), the vinyl group or ethynyl group is preferably directly bonded to the silicon atom to which R is bonded.
More preferably, at least two vinyl groups out of R in compound (I) are directly bonded to the silicon atom to which R is bonded, and more preferably at least half of R in compound (I) is a vinyl group. , R are all preferably vinyl groups.

  Specific examples of compound (I) include, but are not limited to, the following.

  Compound (I) may be a commercially available product or may be synthesized by a known method.

  It is also preferred that R in the compound (I) of the present invention is a group represented by the following general formula (II). In this case, the compound represented by the following general formula (III) and the following general formula (IV) It can synthesize | combine by making the compound made to react.

(R ¹ ) ₃ —Si—O— (II)
[MO-Si (O _0.5 ) ₃ ] _m (III)
(R ¹ ) ₃ —Si—Cl (IV)

The compound represented by the general formula (III) can be synthesized according to the method described in, for example, Angew. Chem. Int. Ed. Engl. 1997, 36, No. 7, 743-745.
In these formulas, each R ¹ independently represents a non-hydrolyzable group. Specific examples of the non-hydrolyzable group represented by R ¹ include an alkyl group, an aryl group, a vinyl group, and an ethynyl group. can give. m and R ¹ are the same as in compound (I ′) and general formula (II).
M represents a metal atom (for example, Na, K, Cu, Ni, Mn) or an onium cation (for example, tetramethylammonium). When M is a polyvalent metal atom, it means a form in which a plurality of —O—Si (O _0.5 ) ₃ is bonded to the polyvalent metal atom M.

The reaction between the compound represented by the general formula (III) and the compound represented by the general formula (IV) is carried out, for example, in a solvent by combining the compound represented by the general formula (III) and the general formula (III) 1 to 100 times mol of the compound represented by the general formula (IV) of the number of Si-OM groups contained in the compound represented by formula (IV) is added, and the stirring is usually performed at 0 to 180 ° C. for 10 minutes to 20 hours. .
As the solvent, organic solvents such as toluene, hexane, and tetrahydrofuran (THF) are preferable.
When the compound represented by the general formula (III) and the compound represented by the general formula (IV) are reacted, a base such as triethylamine or pyridine may be added.

The composition for forming the insulating film of the present invention (hereinafter, also simply referred to as “insulating film forming composition”) may contain a polymer of a plurality of different compounds (I). In that case, the copolymer which consists of several different compound (I) may be sufficient, and the mixture of a homopolymer may be sufficient. In the case where the composition for forming an insulating film includes a copolymer composed of a plurality of different compounds (I), the copolymer weight of a mixture of two or more compounds (I ′) selected from m = 8, 10, and 12 It is preferably a coalescence.
The polymer compound obtained by polymerizing the compound (I) contained in the insulating film forming composition may be a copolymer with a compound other than the compound (I). The compound used in that case is preferably a compound having a plurality of polymerizable carbon-carbon unsaturated bonds or SiH groups. Examples of preferred compounds include vinyl silanes, vinyl siloxanes, phenylacetylenes, [(HSiO _0.5 ) ₃ ] _{8 and the} like.
The composition for forming an insulating film is a solution in which a polymer compound obtained by polymerizing the compound (I) and a polymerization initiator are dissolved in an organic solvent.
Of the solid content contained in the composition for forming an insulating film, the total amount of the polymer obtained by reacting the compounds (I) is preferably 70% by mass or more, preferably 80% by mass or more, and 90% by mass. % Or more is more preferable, and 95% by mass or more is most preferable.
The higher these contents in the solid content, the lower the density, refractive index and dielectric constant film can be formed.
The solid content mentioned here is a component obtained by removing volatile components from all components contained in the composition. Volatile components also include components that volatilize after being decomposed into low molecular weight compounds. Examples of the volatile component include water, an organic solvent, a hole-decomposing heat-decomposable polymer, and a heat-releasing substituent.
Components other than the polymer obtained by reacting the compounds (I) included in the solid content of the composition for forming an insulating film are included in the copolymer (I) and a copolymer containing a reaction product of the compound (I). Components other than the reaction product of compound (I), non-volatile additives and the like can be mentioned.

In order to form a film having a good coated surface and a small film loss during firing, it is preferable that the unreacted compound (I) in the solid content contained in the composition for forming an insulating film is small.
The compound (I) in the solid content is 15% by mass or less, preferably 10% by mass or less, and most preferably 5% by mass or less.
The Mw of the portion excluding the compound (I) monomer from the solid GPC chart contained in the composition for forming an insulating film is preferably 30,000 to 210,000, but is preferably 40,000 to 180,000. More preferred is 50,000 to 160,000.
From the viewpoints of solubility in organic solvents, filter filterability, and coating film surface conditions, the polymer of the present invention preferably contains substantially no component having a molecular weight of 3 million or more, and substantially does not contain 2 million or more components. It is more preferable that it contains no more than 1 million components.

In the solid content contained in the composition for forming an insulating film, it is preferable that 10 to 90 mol% of the vinyl group or ethynyl group of the compound (I) remain unreacted, and 20 to 80 mol% is preferable. Preferably, it remains unreacted, and most preferably 30 to 70 mol% remains unreacted.
In addition, a polymerization initiator, an additive, or a polymerization solvent may be bonded to the reaction product of the compound (I) in the insulating film forming composition in an amount of 0.1 to 40% by mass. 20 mass% is preferable, 0.1-10 mass% is more preferable, 0.1-5 mass% is the most preferable.
About these, it can quantify from the NMR spectrum etc. of a composition.

As a method for producing the composition for forming an insulating film, the reaction product of the compound (I) is preferably produced by using a polymerization reaction between carbon-carbon unsaturated bonds.
In particular, it is particularly preferred that compound (I) is dissolved in a solvent and a polymerization initiator is added to react the vinyl group or ethynyl group.
The polymerization reaction may be any polymerization reaction, and examples thereof include radical polymerization, cationic polymerization, anionic polymerization, ring-opening polymerization, polycondensation, polyaddition, addition condensation, and transition metal catalyst polymerization.
The compound (I) remaining at the end of the polymerization reaction is preferably 25% by mass or less, more preferably 20% by mass or less, and most preferably 15% by mass or less of the addition amount. If this condition is satisfied at the time of polymerization, a film-forming composition having a good coated surface shape and a small film loss at the time of firing can be produced with a high yield.
The weight average molecular weight (Mw) of the polymer at the end of the polymerization reaction is more preferably 30,000 to 160,000, further preferably 40,000 to 140,000, and most preferably 50,000 to 120,000.
The Z + 1 average molecular weight (M _{Z + 1} ) of the polymer at the end of the polymerization reaction is preferably 90,000 to 700,000, more preferably 120,000 to 550,000, and most preferably 150,000 to 400,000 preferable.
The polymer at the end of the polymerization reaction is preferably substantially free of components having a molecular weight of 3 million or more, more preferably substantially free of components of 2 million or more, and no components of 1 million or more. Is most preferred.
When these molecular weight conditions are satisfied during polymerization, a film-forming composition that is soluble in an organic solvent, has good filter filterability, and can form a low-density, low-dielectric constant film can be produced.

In order to satisfy the above molecular weight condition, the concentration of the compound (I) during the polymerization reaction is 12% by mass.
The following is preferable. The concentration of compound (I) is more preferably 10% by mass or less, further preferably 8% by mass or less, and most preferably 6% by mass or less.
From the viewpoint of productivity during the reaction, the higher the concentration of compound (I) during polymerization, the more advantageous. In that sense, the concentration of compound (I) during polymerization is 0.1% by mass or more, more preferably 1% by mass or more.

Moreover, after polymerizing compound (I), it can also be processed by a method such as removing high molecular weight components by filtration or centrifugation, and purifying using column chromatography. This method is preferable.
In particular, it is possible to increase the Mn and reduce the amount of the remaining compound (I) by performing reprecipitation treatment on the solid matter generated by the polymerization reaction and removing the low molecular weight component and the remaining compound (I). This is preferred as a method for producing a film-forming composition.

The polymerization reaction of compound (I) is preferably performed in the presence of a nonmetallic polymerization initiator. For example, polymerization can be carried out in the presence of a polymerization initiator that exhibits activity by generating free radicals such as carbon radicals and oxygen radicals by heating.
As the polymerization initiator, an organic peroxide or an organic azo compound is particularly preferably used.

  Examples of the organic peroxide include ketone peroxides such as perhexa H, peroxyketals such as perhexa TMH, hydroperoxides such as perbutyl H-69, park mill D, perbutyl C, etc. From dialkyl peroxides such as perbutyl D, diacyl peroxides such as Nyper BW, peroxyesters such as perbutyl Z and perbutyl L, peroxydicarbonates such as perroyl TCP, xineodecanoate, and Arkema Yoshitosha Commercially available Lupelox 11 or the like is preferably used.

  As organic azo compounds, azonitrile compounds such as V-30, V-40, V-59, V-60, V-65, and V-70, which are commercially available from Wako Pure Chemical Industries, Ltd., VA-080, Azoamide compounds such as VA-085, VA-086, VF-096, VAm-110 and VAm-111, cyclic azoamidine compounds such as VA-044 and VA-061, and azoamidine compounds such as V-50 and VA-057 Azo ester compounds such as V-601 and V-401, 2,2-azobis (4-methoxy-2,4-dimethylvaleronitrile), and the like are preferably used.

The polymerization initiator is preferably an organic azo compound in view of the safety of the reagent itself and the molecular weight reproducibility of the polymerization reaction, and most preferably an azo ester compound such as V-601 which does not incorporate harmful cyano into the polymer.
The 10-hour half-life temperature of the polymerization initiator is preferably 100 ° C. or lower. If the 10-hour half-life temperature is 100 ° C. or less, it is easy to prevent the polymerization initiator from remaining at the end of the reaction.
The polymerization initiator of the present invention may be used alone or in combination of two or more.
The amount of the polymerization initiator used in the present invention is preferably 0.0001 to 2 mol, more preferably 0.003 to 1 mol, and particularly preferably 0.001 to 0.5 mol with respect to 1 mol of the monomer.

Any solvent can be used for the polymerization reaction as long as it can dissolve the compound (I) at a necessary concentration and does not adversely affect the properties of the film formed from the polymer obtained. Also good.
For example, water, alcohol solvents, ketone solvents, ester solvents, ether solvents, aromatic hydrocarbon solvents, amide solvents, halogen solvents, aliphatic hydrocarbon solvents and the like can be used. Among these solvents, more preferred are ester solvents, among which methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, pentyl acetate, hexyl acetate, methyl propionate, ethyl propionate, propylene glycol monomethyl ether acetate , Γ-butyrolactone and methyl benzoate, particularly preferably ethyl acetate and butyl acetate.
These may be used alone or in admixture of two or more.
The boiling point of the organic solvent is preferably 75 ° C. or higher and 140 ° C. or lower so that the reaction solution can be heated to a temperature necessary for decomposing the polymerization initiator during the reaction and the organic solvent can be distilled off after completion of the reaction. The addition method of polymerization initiator includes batch addition, divided addition, continuous addition, etc., but it can be increased in molecular weight with a small amount of polymerization initiator added and is advantageous from the viewpoint of film strength. Is preferred.

Optimum conditions for the polymerization reaction in the present invention vary depending on the polymerization initiator, monomer, solvent type, concentration, etc., but preferably the internal temperature is 0 ° C. to 200 ° C., more preferably 40 ° C. to 170 ° C., particularly preferably 70. C. to 140.degree. C., preferably 1 to 50 hours, more preferably 2 to 20 hours, and particularly preferably 3 to 10 hours.
Moreover, in order to suppress the inactivation of the polymerization initiator by oxygen, it is preferable to make it react under inert gas atmosphere (for example, nitrogen, argon, etc.). The oxygen concentration during the reaction is preferably 100 ppm or less, more preferably 50 ppm or less, and particularly preferably 20 ppm or less.

When producing an insulating film forming composition, the reaction solution obtained by subjecting the compound (I) to the polymerization reaction may be used as it is as the insulating film forming composition, but the reaction solvent is distilled off and concentrated. It is preferable to use it. Moreover, it is preferable to use after performing a reprecipitation process.
The concentration is preferably carried out by heating and / or reducing the pressure of the reaction solution using a rotary evaporator, a distillation apparatus or a reaction apparatus in which a polymerization reaction is performed. The temperature of the reaction solution at the time of concentration is generally 0 ° C to 180 ° C, preferably 10 ° C to 140 ° C, more preferably 20 ° C to 100 ° C, and most preferably 30 ° C to 60 ° C. The pressure at the time of concentration is generally 0.133 Pa to 100 kPa, preferably 1.33 Pa to 13.3 kPa, and more preferably 1.33 Pa to 1.33 kPa.
When concentrating the reaction solution, it is preferably concentrated until the solid content in the reaction solution becomes 10% by mass or more, more preferably concentrated until it becomes 30% by mass or more, and 50% by mass or more. Most preferably, it is concentrated to

In the present invention, the composition for forming an insulating film may further contain a polymerization initiator.
As an example of the polymerization initiator in that case, an organic peroxide or an organic azo compound as described in the polymerization reaction of the compound (I) is preferably used.

  Furthermore, the composition for forming an insulating film includes a radical generator, colloidal silica, and surface activity as long as the properties of the obtained insulating film (heat resistance, dielectric constant, mechanical strength, coatability, adhesion, etc.) are not impaired. You may add additives, such as an agent, a silane coupling agent, and an adhesive agent.

  Any surfactant may be used in the present invention, and examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, silicone surfactants, and fluorine-containing interfaces. Activators, polyalkylene oxide surfactants, and acrylic surfactants can be mentioned. The surfactant used in the present invention may be one type or two or more types. As the surfactant, silicone surfactants, nonionic surfactants, fluorine-containing surfactants, and acrylic surfactants are preferable, and silicone surfactants are particularly preferable.

The addition amount of the surfactant used in the present invention is 0.01% by mass with respect to the total amount of the film-forming coating solution.
The content is preferably 1% by mass or less and more preferably 0.1% by mass or more and 0.5% by mass or less.

  In the present invention, the silicone-based surfactant is a surfactant containing at least one Si atom. The silicon-based surfactant used in the present invention may be any silicon-based surfactant, and preferably has a structure containing alkylene oxide and dimethylsiloxane.

  In the present invention, each of the above components is dissolved in a suitable solvent and used by coating on a support. Solvents that can be used include propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, 2-heptanone, cyclohexanone, γ-butyrolactone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, Propylene glycol monoethyl ether, ethylene carbonate, butyl acetate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, N-methylpyrrolidone, N, N-dimethylformamide, tetrahydrofuran, methyl isobutyl ketone, xylene, mesitylene, Mention may be made of diisopropylbenzene.

  A solution obtained by dissolving the insulating film forming composition in a suitable solvent is also included in the range of the insulating film forming composition. The total solid concentration in the solution of the present invention is preferably 1 to 30% by mass, and is appropriately adjusted according to the purpose of use. When the total solid content concentration of the composition is 1 to 30% by mass, the film thickness of the coating film is in an appropriate range, and the storage stability of the coating solution is also more excellent.

In the composition for forming an insulating film, a pore forming factor can be used within the range allowed by the mechanical strength of the film to make the film porous and reduce the dielectric constant.
There are no particular limitations on the pore-forming factor of the additive that serves as the pore-forming agent, but non-metallic compounds are preferably used, solubility in the solvent used in the film-forming coating solution, and the polymer of the present invention. It is necessary to satisfy the compatibility of

  A polymer can also be used as the pore-forming agent. Examples of the polymer that can be used as the pore forming agent include polyvinyl aromatic compounds (polystyrene, polyvinyl pyridine, halogenated polyvinyl aromatic compounds, etc.), polyacrylonitrile, polyalkylene oxide (polyethylene oxide, polypropylene oxide, etc.), polyethylene, poly Lactic acid, polysiloxane, polycaprolactone, polycaprolactam, polyurethane, polymethacrylate (such as polymethyl methacrylate) or polymethacrylic acid, polyacrylate (such as polymethyl acrylate) and polyacrylic acid, polydiene (such as polybutadiene and polyisoprene), polyvinyl chloride , Polyacetal, and amine-capped alkylene oxide, other polyphenylene oxide, poly (dimethyl) Siloxane), polytetrahydrofuran, poly cyclohexyl ethylene, polyethyl oxazoline, polyvinyl pyridine, may be a polycaprolactone.

  In particular, polystyrene can be suitably used as a pore forming agent.

Moreover, the boiling point or decomposition temperature of the pore-forming agent is preferably 100 to 500 ° C, more preferably 200 to 450 ° C, and particularly preferably 250 to 400 ° C. As molecular weight, it is preferable that it is 200-50000, More preferably, it is 300-10000, Most preferably, it is 400-5000.
The amount of the pore-forming agent added is preferably 0.5 to 75%, more preferably 0.5 to 30%, and particularly preferably 1% to 20% by mass% with respect to the polymer forming the film. .
The polymer may contain a decomposable group as a pore-forming factor, and the decomposition temperature is preferably 100 to 500 ° C, more preferably 200 to 450 ° C, and particularly preferably 250 to 400 ° C. Good to have. The content of the decomposable group is 0.5 to 75%, more preferably 0.5 to 30%, and particularly preferably 1 to 20% in terms of mol% with respect to the polymer forming the film.

  The film-forming composition of the present invention is preferably used for film formation after removing insolubles, gel components and the like by filter filtration. The pore size of the filter used at that time is preferably 0.001 to 0.2 μm, more preferably 0.005 to 0.05 μm, and most preferably 0.005 to 0.03 μm. The material of the filter is preferably PTFE, polyethylene, or nylon, and more preferably polyethylene or nylon.

The film obtained by using the film forming composition of the present invention can be obtained by any method such as spin coating method, roller coating method, dip coating method, scanning method, spray method, bar coating method. After applying to a substrate such as a silicon wafer, a SiO ₂ wafer, a SiN wafer, glass, or a plastic film, the solvent can be removed by heat treatment as necessary. As a method of applying to the substrate, a spin coating method or a scanning method is preferable. Particularly preferred is the spin coating method. As for spin coating, commercially available clean track series (manufactured by Tokyo Electron), D-spin series (manufactured by Dainippon Screen), SS series or CS series (manufactured by Tokyo Ohka Kogyo Co., Ltd.) can be preferably used. Further, from the viewpoint of transporting the substrate, it is also preferable to perform processing (edge rinse, back rinse) so as not to leave the film at the edge portion of the substrate. The method of heat treatment is not particularly limited, but it is possible to apply commonly used hot plate heating, heating method using a furnace, light irradiation heating using a xenon lamp by RTP (Rapid Thermal Processor), etc. Can do. A heating method using hot plate heating or furnace is preferable.
The film thickness when forming the insulating film is a dry film thickness of about 0.05 to 1.5 μm in thickness when applied once, and about 0.1 to 3 μm in thickness when applied twice. Can do.

In the present invention, the film is further heat-treated at a temperature of 250 to 350 ° C. in an oxygen atmosphere. The oxygen atmosphere in the present invention may be an atmosphere containing oxygen having a concentration of 500 ppm or more, and may be in an atmosphere consisting of only oxygen gas or in the presence of other gases such as nitrogen gas and carbon dioxide gas. It does not matter even in the atmosphere.
This heat treatment time is about 1 minute to 2 hours, preferably 10 minutes to 1.5 hours, more preferably 30 minutes to 1 hour. The heat treatment may be performed in several times. It is a feature of the present invention that the heating temperature can be lower than 350 to 450 ° C. which is a normal firing temperature.
By this heat treatment, hydroxyl groups are formed in the cage-type silsesquioxane polymer.
Next, in the present invention, the coating film having a hydroxyl group generated in an oxygen atmosphere is treated with a medium containing a crosslinkable compound capable of binding to the hydroxyl group to eliminate the hydroxyl group.

  The crosslinkable compound capable of binding to the hydroxyl group is preferably a compound having a plurality of silyl groups. Examples of such compounds include Hexachlorodisiloxane (HCDS), tetramethylcyclotetrasiloxane (TMCTS) hexamethyldisilazane (HMDS), tetramethyldisilazane (TMDS), trimethylsilyidimethylamine (TMSDMA), trimethylsilyldiethylamine (TMSDEA), N-trimethylsilyl-imidazole (TMSI), methyltrimethoxysilane (MTMOS) , vinyltrimethoxysilane (VTMOS), trimethylchlorosilane (TMCS), dimethylsilyidimethylamine (DMSDMA), dimethylsilyldiethylamine (DMSDEA), bis (dimethylamino) methyl silane (B [DMA] MS), bis (dimethylamino) dimethyl silane (B [DMA] DS), dimethylaminopentamethyldisilane (DMAPMDS), dimethylaminodimethyldisilane (DMADMDS), disila-aza-cyclopentane (TDACP), disila-oza-cyclopentane (TDOCP), triethylchlorosilane (TECS), tetramethoxysilane (TMOS), dimethyldimethoxysilane (DMDMOS), tetraethoxysilane (TEOS), methyltriethoxysilane (MTEOS) ), dimethyldiethoxysilane (DMDEOS), vinyltriethoxysilane (VTEOS), trimethylmethoxysilane (TMMS), trimethylethoxysilane (TMES), trimethylsilanol (TMS-OH), bis (tr imethoxysilyl) hexane, bis (trimethoxysilyl) octane, bis (trimethylsilylmethyl) dimethoxysilane, bistrimethoxysilylethane, cyclohexylmethyldimethoxysilane, cyclohexyltrimethoxysilane, dicyclopentyldimethoxysilane, diisobutyldimethoxysilane, diisopropyldimethoxysilane, dimethyldimethoxysilane, hexadecyltrimethoxysilane, octyldimethylmethoxysilane, trimethoxysilane, trimethylmethoxysil HCDS is particularly preferable.

  Next, examples of the medium containing a crosslinkable compound capable of bonding with a hydroxyl group include the gasified compound itself, a vapor obtained by diluting the compound with an arbitrary solvent, and a fluid in which the compound is added to a supercritical fluid. The processing is performed by exposing the substrate to these medium atmospheres. Furthermore, the method etc. which make the said compound melt | dissolve and contact in a solvent can also be selected arbitrarily. As disclosed in Japanese Patent Application Laid-Open No. 2002-289604, it is preferable to dilute the compound with an arbitrary solvent and expose the substrate to the vapor atmosphere of the compound.

When the film obtained by using the present invention is used as an interlayer insulating film for a semiconductor, the wiring structure may have a barrier layer for preventing metal migration on the side surface of the wiring. In addition to the cap layer and interlayer adhesion layer that prevent separation by CMP (Chemical Mechanical Polishing), there may be an etching stopper layer, etc. on the bottom surface of the top surface, and other layers of interlayer insulating film may be used as necessary. The seed material may be divided into a plurality of layers.

  The insulating film of the present invention may be used by forming a laminated structure with other Si-containing insulating films or organic films. It is preferable to use it laminated with a hydrocarbon film.

  The film obtained using the film forming composition of the present invention can be etched for copper wiring or other purposes. Etching may be either wet etching or dry etching, but dry etching is preferred. For dry etching, either ammonia-based plasma or fluorocarbon-based plasma can be used as appropriate. These plasmas can use not only Ar but also oxygen, or gases such as nitrogen, hydrogen, and helium. In addition, after the etching process, ashing can be performed for the purpose of removing the photoresist or the like used for the processing, and further, cleaning can be performed to remove a residue at the time of ashing.

  The film obtained by using the film forming composition of the present invention can be subjected to CMP (Chemical Mechanical Polishing) in order to planarize the copper plating portion after the copper wiring processing. As the CMP slurry (chemical solution), commercially available slurries (for example, manufactured by Fujimi, manufactured by Rodel Nitta, manufactured by JSR, manufactured by Hitachi Chemical, etc.) can be used as appropriate. Moreover, as a CMP apparatus, a commercially available apparatus (Applied Materials Co., Ltd., Ebara Seisakusho etc.) can be used suitably. Furthermore, it can be washed to remove the slurry residue after CMP.

  The film obtained using the film forming composition of the present invention can be used for various purposes. For example, it is suitable as an insulating film for semiconductor devices such as LSI, system LSI, DRAM, SDRAM, RDRAM, and D-RDRAM, and electronic parts such as multichip module multilayer wiring boards, interlayer insulating film for semiconductor, etching stopper film, surface protection In addition to films, buffer coat films, LSI passivation films, alpha ray blocking films, flexographic printing plate cover lay films, overcoat films, flexible copper clad cover coats, solder resist films, liquid crystal alignment films, etc. I can do it. It can also be used as a surface protective film, an antireflection film, or a retardation film for optical devices.

  The present invention will be described more specifically with reference to the following examples. However, the scope of the present invention is of course not limited by these examples.

[Synthesis Example 1]
1 g of exemplified compound (Id) (manufactured by Aldrich) was added to 80 g of butyl acetate. While heating and refluxing (internal temperature 127 ° C.) in a nitrogen stream, a solution obtained by diluting 5 mg of V-601 (10 hours half temperature 66 ° C.) manufactured by Wako Pure Chemical Industries, Ltd. with 4 ml of butyl acetate as a polymerization initiator for 2 hours The solution was added dropwise, and after completion of the addition, the mixture was refluxed for 1 hour. After adding 20 mg of 4-methoxyphenol as a polymerization inhibitor, the mixture was cooled to room temperature, concentrated under reduced pressure to a liquid weight of 2 g, added with 20 ml of methanol and stirred for 1 hour, and then the solid was collected by filtration and dried. This was dissolved in 10 ml of tetrahydrofuran, and 1.8 ml of water was added dropwise with stirring. After stirring for 1 hour, the supernatant was discarded by decantation, and 10 ml of methanol was added. The solid content was collected by filtration and dried to obtain 0.49 g of solid content. When the solid content was analyzed by GPC, components having a molecular weight larger than that of the exemplary compound (Id) were Mw = 1580 thousand, M _{z + 1} = 310,000, and Mn = 89,000. The unreacted exemplary compound (Id) was 3% by mass or less in the solid. No component with a molecular weight of 3 million or more was contained. When ¹ H-NMR spectrum of solid content was measured using deuterated chloroform as a measurement solvent, the proton peak derived from the alkyl group formed by polymerization of the vinyl group and the remaining proton peak derived from the vinyl group were integrated at 48:52. The ratio was observed and it was found that vinyl groups were polymerized.
When 0.3 ml of this composition was added with 5 ml of propylene glycol methyl ether acetate and stirred at 40 ° C. for 3 hours, it was uniformly dissolved. This was filtered through a Teflon (registered trademark) filter having a pore diameter of 0.2 μm to obtain a composition A of the present invention.
From the weight of the remaining monomer and the weight of the additive, it is apparent that the polymer obtained by the reaction of the vinyl groups of the monomers in the solid content in the composition is 70% by mass or more.

[Example 1]
After applying composition A prepared in the above synthesis example onto a 4-inch silicon wafer by spin coating, the substrate is dried on a hot plate at 200 ° C. for 1 minute, and further heated on an air hot plate at 300 ° C. for 30 minutes. Thus, a coating film was produced (film thickness 600 nm). Next, the sample was placed in a glove box substituted with a nitrogen atmosphere at normal temperature and normal pressure, and kept in an HCDS vapor atmosphere having a concentration (wt%) of 0.05% to 0.1% diluted with chloroform for 1 hour. The dielectric constant of the coating film was 1.97 as measured using the mercury probe method. Further, when the Young's modulus was measured using the nanoindentation method, it was 5.7 GPa at a position of about 60 nm from the film surface.

[Comparative Example 1]
The dielectric constant was 2.25 when evaluated in the same manner as in Example 1 except that heating was performed at 300 ° C. for 30 minutes on a hot plate in a nitrogen atmosphere with an oxygen concentration of 500 ppm or less. The Young's modulus was 4.3 GPa.

  From the above results, it can be seen that when the present invention is used, a film having a very low dielectric constant of high mechanical strength and a dielectric constant of less than 2.0 can be formed only by a low temperature process of 350 ° C. or lower.

Claims (3)

  A coating film containing a polymer compound obtained by polymerizing a cage-type silsesquioxane compound having two or more unsaturated groups as substituents is formed on a substrate, and then baked at 250 to 350 ° C. in an oxygen atmosphere. And a method of forming an insulating film, wherein the insulating film is further treated with a medium containing a crosslinkable compound capable of bonding to a hydroxyl group.   The method for forming an insulating film according to claim 1, wherein the oxygen content in the oxygen atmosphere is 500 ppm or more.   2. The method for forming an insulating film according to claim 1, wherein the crosslinkable compound capable of binding to a hydroxyl group is hexachlorodisiloxane.