JP4241880B2 - Coating liquid for forming low dielectric constant silica coating - Google Patents

Description

  The present invention forms an insulating film having a low relative dielectric constant of 3 or less, excellent oxygen plasma resistance during micro-photolithography processing, and excellent chemical resistance such as mechanical strength and alkali resistance, and crack resistance. The present invention relates to a coating liquid for forming a low dielectric constant silica-based film, and a substrate on which the low dielectric constant silica-based film is formed.

With the high integration of semiconductor devices, semiconductor devices with a multilayer wiring of 0.3μ rule or less have narrow metal wiring spacing, which increases the impedance of metal wiring due to electrostatic induction, delays in response speed, and power consumption. There is concern about the increase. For this reason, it is necessary to make the relative dielectric constant of an interlayer insulating film provided between a semiconductor substrate and a metal wiring layer such as an aluminum wiring layer or between metal wiring layers as small as possible.

  The interlayer insulating film used for the above purpose is generally formed on a substrate by a vapor deposition method such as a CVD method or a coating method for forming an insulating film using a coating forming coating solution.

However, in the case of a vapor phase growth method such as a CVD method, in the case of a silica-based film, a relative dielectric constant of 3.5
The fluorine-doped silica film is said to be a limit, and there is a problem that it is difficult to form a silica-based film of 3 or less.

  In addition, a CVD film such as polyaryl resin, fluorine-added polyimide resin or fluorine-based resin or a film formed using a coating solution containing these has a relative dielectric constant of about 2, but the adhesion between the base material and the film. In addition, there are also disadvantages such as poor adhesion to a resist material used for microfabrication and poor chemical resistance and oxygen plasma resistance.

Furthermore, a coating film for forming a silica-based film containing a partially hydrolyzed product of alkoxysilane that has been used in the past can provide a film having a relative dielectric constant of 2.5, but has a drawback of poor adhesion to the surface to be coated. is there.

The present inventors have a coating film formed by using a coating liquid for forming a low dielectric constant silica-based film containing a reaction product of silica fine particles and a halogenated silane or a hydrolyzate thereof, and has a relative dielectric constant of 3 or less, Moreover, it has been found that it has excellent chemical resistance such as adhesion to the coated surface, mechanical strength, and alkali resistance, and at the same time excellent crack resistance (Japanese Patent Application No. 8-299684). .

  Furthermore, as a result of repeated studies by the inventors, in the conventional film as described above, deterioration of the film quality causes re-adsorption of water to the film due to plasma etching during micro-photolithography processing and oxygen plasma during resist removal, It has been found that there is a possibility that the dielectric constant of the coating is increased, the adhesiveness, chemical resistance and crack resistance are deteriorated, and the conductive yield is lowered.

The present invention is intended to solve the above-mentioned problems in the prior art, and has a relative dielectric constant as small as 3 or less, excellent oxygen plasma resistance during micro-photolithography processing, mechanical strength, Provided is a coating liquid for forming a low dielectric constant silica-based film capable of forming an insulating film excellent in chemical resistance such as alkali resistance and crack resistance, and a substrate on which such a low dielectric constant silica-based film is formed. The purpose is that.

The coating liquid for forming a low dielectric constant silica-based film according to the present invention comprises (i) silica-based fine particles having a phenyl group, (ii) an alkoxysilane represented by the following general formula (I) and / or the following general formula (II ) And a polysiloxazan which is a reaction product of polysilazane represented by the following general formula (III).

X _n Si (OR ¹ ) _4-n (I)
_{X n SiX '4-n (} II)

（Ｘは、水素原子、フッ素原子、または炭素数１〜８のアルキル基、フッ素置換アルキル基、アリール基またはビニル基を表し、Ｒ¹、Ｒ²、Ｒ³およびＲ⁴は、水素原子または炭素数１〜８のアルキル基、アリール基またはビニル基を表し、Ｘ'はハロゲン原子を表す
。また、mは整数、nは０〜３の整数である。）

(X represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 8 carbon atoms, a fluorine-substituted alkyl group, an aryl group or a vinyl group, and R ¹ , R ² , R ³ and R ⁴ are a hydrogen atom or a carbon atom. (Expression 1 represents an alkyl group, aryl group, or vinyl group, X ′ represents a halogen atom, m is an integer, and n is an integer of 0 to 3).

  The silica-based fine particles (i) having a phenyl group are obtained by hydrolyzing one or more of alkoxysilanes represented by the general formula (I), or by hydrolyzing and then aging the silica fine particles. It is preferably obtained by bonding a hydrolyzate of phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane to at least a part of the surface.

The hydrolysis temperature or aging temperature when preparing silica fine particles from one or more of the alkoxysilanes represented by the general formula (I) is preferably 180 ° C. or higher.
The substrate with a low dielectric constant film according to the present invention is characterized by having a low dielectric constant silica-based film formed using the coating liquid for forming a low dielectric constant silica-based film.

  According to the coating liquid for forming a low dielectric constant silica-based film according to the present invention, the relative dielectric constant is as small as 3 or less, and it is excellent in oxygen plasma resistance at the time of microphotolithographic processing, as well as resistance to mechanical strength, alkali resistance and the like. An insulating film excellent in chemical properties and crack resistance can be formed.

Such a coating liquid for forming a low dielectric constant silica-based film according to the present invention contains a reaction product of (i) silica-based fine particles having a phenyl group and (ii) polysiloxazan. The silica-based fine particles in the coating solution make the coating porous by pores between the particles. In addition, the phenyl group on the surface of the silica-based fine particles has the effect of preventing re-adsorption of water into the pores in the coating and has high oxygen plasma resistance. Therefore, when a low dielectric constant silica-based coating is formed using the low dielectric constant silica-based coating liquid according to the present invention, film quality deterioration due to plasma etching during micro-photolithography processing or oxygen plasma during resist stripping is reduced. In addition, it prevents water re-adsorption to the film, so it has a low dielectric constant, excellent adhesion, chemical resistance, crack resistance, etc., improved conductive yield, and flattening characteristics. A good and stable low dielectric constant silica-based film can be formed. In addition, the anchor effect of the silica-based fine particles is excellent in adhesion to the coated surface.

In addition, according to the present invention, silica having a relative dielectric constant as small as 3 or less, excellent oxygen plasma resistance at the time of microphotolithographic processing, and at the same time excellent chemical resistance such as mechanical strength and alkali resistance, and crack resistance. Various base materials having a system coating can be obtained.

The coating liquid for forming a low dielectric constant silica-based film according to the present invention will be specifically described below.
[Low-dielectric-constant silica-based coating solution]
The coating liquid for forming a low dielectric constant silica-based film according to the present invention comprises (i) silica-based fine particles having a phenyl group, (ii) an alkoxysilane represented by the following general formula (I) and / or the following general formula (II ) And a polysiloxazan which is a reaction product of polysilazane represented by the following general formula (III).

X _n Si (OR ¹ ) _4-n (I)
_{X n SiX '4-n (} II)

（Ｘは、水素原子、フッ素原子、または炭素数１〜８のアルキル基、フッ素置換アルキル基、アリール基またはビニル基を表し、Ｒ¹、Ｒ²、Ｒ³およびＲ⁴は、水素原子または炭素数１〜８のアルキル基、アリール基またはビニル基を表し、Ｘ'はハロゲン原子を表す
。また、mは整数、nは０〜３の整数である。）

(X represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 8 carbon atoms, a fluorine-substituted alkyl group, an aryl group or a vinyl group, and R ¹ , R ² , R ³ and R ⁴ are a hydrogen atom or a carbon atom. (Expression 1 represents an alkyl group, aryl group, or vinyl group, X ′ represents a halogen atom, m is an integer, and n is an integer of 0 to 3).

(i) Silica-based fine particles having a phenyl group First, (i) silica-based fine particles having a phenyl group will be described.
Silica-based fine particles having a phenyl group are prepared by hydrolyzing and polycondensing one or more alkoxysilanes represented by the above formula (I) in the presence of water, an organic solvent and ammonia. The obtained silica fine particles are reacted with phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane.

Specific examples of the alkoxysilane represented by the above formula (I) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, tetraoctylsilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisoiso Propoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, octyltrimethoxysilane, octyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, tri Methoxysilane, triethoxysilane, triisopropoxysilane, fluorotrimethoxysilane, fluorotriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxy Orchids, diethyl dimethoxysilane, diethyl diethoxysilane, dimethoxysilane, diethoxy silane, difluoromethyl dimethoxysilane, difluoro diethoxy silane, trifluoromethyl trimethoxy silane, trifluoromethyl triethoxy silane.

Examples of the organic solvent include alcohols, ketones, ethers, esters and the like, more specifically, alcohols such as methanol, ethanol, propanol and butanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, Glycol ethers such as methyl cellosolve, ethyl cellosolve and propylene glycol monopropyl ether, glycols such as ethylene glycol, propylene glycol and hexylene glycol, and esters such as methyl acetate, ethyl acetate, methyl lactate and ethyl lactate are used.

As the catalyst, in addition to ammonia, basic compounds such as amines, alkali metal hydrides, quaternary ammonium compounds, and amine coupling agents can be used.
The method for preparing such silica fine particles will be described in more detail. For example, while stirring a water-alcohol mixed solvent, alkoxysilane and aqueous ammonia are added to the mixed solvent to carry out hydrolysis / polycondensation reaction of the alkoxysilane. Do.

At this time, it is desirable that water is used in an amount of 0.5 to 50 moles, preferably 1 to 25 moles, per mole of Si-OR groups constituting the alkoxysilane. Ammonia is desirably blended in an amount of 0.01 to 1 mole, preferably 0.05 to 0.8 mole, per mole of alkoxysilane.

The hydrolysis / polycondensation reaction of alkoxysilane is usually performed at 180 ° C. or higher, preferably 200 ° C. or higher, and using a heat and pressure resistant container such as an autoclave.
Furthermore, after this, you may age | cure | ripen at the same temperature as hydrolysis or higher temperature. A higher hydrolysis reaction temperature and aging temperature are desirable because the polycondensation of alkoxysilane is further promoted and the inside of the silica fine particles is densified. Further, when the silica fine particles are densified in this way, the hygroscopicity of the particles themselves is lowered and the residual functional groups on the particle surface can be reduced.

Alternatively, silica fine particles may be generated and grown by adding a high-boiling solvent such as ethylene glycol to a water-alcohol mixed solvent under stirring to hydrolyze the alkoxysilane. If such a high boiling point solvent is added during the hydrolysis of the alkoxysilane, an ester exchange reaction of the alkoxy group occurs, and the high boiling point solvent is taken into the silica fine particles to obtain porous silica fine particles having a low density. It is done.

  In addition to the above, in the present invention, silica sol obtained by ion-exchange or hydrolysis of alkali metal silicate can be used as the silica fine particles. Furthermore, fine particles made of porous zeolite obtained by removing aluminum from zeolite made of aluminosilicate can also be used.

The silica fine particles as described above desirably have an average particle size in the range of 30 to 100 mm, preferably 50 to 500 mm. The silica fine particles having an average particle diameter in such a range may be a uniform particle diameter or a mixture of two or more kinds of fine particles having different particle diameters, that is, even if the particle size distribution is sharp. It may be a thing or a bimodal thing.

  When the average particle size is less than 30 mm, the formed film may not have a low dielectric constant. On the other hand, when the average particle size exceeds 1000 mm, the formed film causes defects during microfabrication in the photolithography process. Cheap.

(I) Silica-based fine particles having a phenyl group used in the present invention can be obtained by bonding the above-described silica fine particles and phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane by a condensation reaction.

Examples of the phenyl group-containing alkoxysilane include those represented by the following general formula (IV).
X _p Ph _q Si (OR ¹ ) _{4- (p + q)} (IV)
X and R ¹ are the same as X and R ¹ in the general formula (I). Ph represents a phenyl group. The phenyl group may be substituted with an alkyl group.

  P is an integer of 0 to 3, q is an integer of 1 to 4, and p + q is an integer of 4 or less. Specific examples of such a phenyl group-containing alkoxysilane include phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriacetoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, phenyldimethylethoxysilane, and phenyldimethylacetoxysilane. Is mentioned.

Examples of the chlorosilane having a phenyl group include those represented by the following general formula (V).
X _p Ph _q SiCl _{4- (p + q)} (V)
X represents the same as X in the general formula (I).

  P is an integer of 0 to 3, q is an integer of 1 to 4, and p + q is an integer of 4 or less. Specific examples of such a phenyl group-containing chlorosilane include phenyltrichlorosilane, phenylmethyldichlorosilane, phenylethyldichlorosilane, phenyldimethylchlorosilane, phenylmethylchlorosilane, and phenyldichlorosilane.

  In the present invention, hydrolyzates of these phenyl group-containing alkoxysilanes or phenyl group-containing chlorosilanes can also be used. Moreover, a phenyl group-containing alkoxysilane and a phenyl group-containing chlorosilane can be mixed and used.

  The reaction between the silica fine particles and the phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane does not cause the growth of silica fine particles or the generation of new silica fine particles. A condensation reaction with the phenyl group-containing alkoxysilane or the phenyl group-containing chlorosilane occurs, whereby a phenyl group is introduced onto the surface of the silica fine particles.

When the silica fine particles are reacted with phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane, the mixing ratio of both is converted to SiO ₂ and the phenyl group-containing alkoxysilane or phenyl group-containing per 1 part by weight of silica fine particles. It is desirable that the amount of chlorosilane is in the range of 0.01 to 0.3 parts by weight, preferably 0.05 to 0.2 parts by weight.

When the amount of phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane is less than 0.01 parts by weight, the amount of phenyl groups on the surface of the silica-based fine particles to be prepared decreases, and the resulting silica coating has poor oxygen plasma resistance and chemical resistance. Tend. If the amount of phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane is more than 0.3 parts by weight, surplus phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane that does not participate in the reaction with the silica-based fine particles remains. A silica-based film obtained by applying a coating solution to be produced may have poor adhesion to the surface to be coated, mechanical strength, coatability, and the like.

The reaction between such silica fine particles and phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane is usually carried out in the presence of water, an organic solvent and a catalyst. The water to be used may be an amount of 0.1 mol or more per 1 mol of Si-OR group constituting the phenyl group-containing alkoxysilane or Si-Cl group constituting the phenyl group-containing chlorosilane.

Examples of the organic solvent are the same as those used when preparing the silica fine particles. Moreover, as a catalyst, in addition to the thing used at the time of the said silica fine particle preparation, an acid catalyst can also be used. Specific examples of the acid catalyst include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, organic acids such as acetic acid, oxalic acid, and toluenesulfonic acid, and compounds that show acidity in an aqueous solution such as metal soap. However, a basic catalyst is preferable as the catalyst.

The reaction between the silica fine particles and the phenyl group-containing alkoxysilane or the phenyl group-containing chlorosilane is usually at a temperature of about 100 ° C. or less, preferably 80 ° C. or less, and varies depending on temperature conditions. It is desirable to heat for ~ 50 hours, preferably 0.5-15 hours.

  By such heat treatment, a hydrolyzate of phenyl group-containing alkoxysilane or phenyl group-containing chlorosilane is bonded to the surface of at least a part of the silica-based fine particles, and silica-based fine particles having a phenyl group are obtained.

The silica-based fine particles having an unpurified phenyl group obtained by the above method may be used as they are, but prior to the reaction with polysiloxazan described later, by means such as ultrafiltration or distillation in advance. It is desirable to replace the water-organic solvent system of the dispersion medium with an organic solvent system.

(ii) Polysiloxazan Next, (ii) polysiloxazan will be described. (Ii) Polysiloxazan used in the present invention is a reaction product of a hydrolyzate of alkoxysilane and / or halogenated silane and polysilazane. [Alkoxysilane and / or Halogenated Silane Hydrolyzate] In the present invention, the component that forms polysiloxazan is represented by the following general formula (I) or the following general formula (II): Hydrolysates of halogenated silanes are used.

X _n Si (OR ¹ ) _4-n (I)
_{X n SiX '4-n ...} (II)
In the formula, X represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 8 carbon atoms, a fluorine-substituted alkyl group, an aryl group or a vinyl group, and R ¹ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Represents an aryl group or a vinyl group, and X ′ represents a halogen atom. N is an integer of 0-3.

Examples of the alkoxysilane represented by the general formula (I) include the same ones as exemplified for the silica fine particles. Examples of the halogenated silane represented by the general formula (II) include trichlorosilane, tribromosilane, dichlorosilane, fluorotrichlorosilane, and fluorotribromosilane.

The hydrolyzate used in the present invention is an alkoxysilane represented by the above general formula (I) and / or
Alternatively, it can be obtained by hydrolyzing and polycondensing the halogenated silane represented by the general formula (II) in the presence of water, an organic solvent and a catalyst. Examples of such hydrolysis / polycondensation methods include conventionally known methods.

  Examples of the organic solvent include alcohols, ketones, ethers, esters and the like. Specifically, alcohols such as methanol, ethanol, propanol and butanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and methyl cellosolve. Glycol ethers such as ethyl cellosolve and propylene glycol monopropyl ether, glycols such as ethylene glycol, propylene glycol and hexylene glycol, and esters such as methyl acetate, ethyl acetate, methyl lactate and ethyl lactate are used.

  Examples of the catalyst include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid, organic acids such as acetic acid, oxalic acid and toluenesulfonic acid, or compounds showing acidity in an aqueous solution such as metal soap, ammonia, amine, alkali metal hydride, fourth Examples include basic compounds such as quaternary ammonium compounds and amine coupling agents.

The water required for the hydrolysis reaction is usually 0.1 to 5 moles, preferably 0.1 to 1 mole per mole of Si—OR group constituting alkoxysilane or Si—X ′ group constituting halogenated silane.
It is desirable to be used in an amount of 2 moles. The catalyst is preferably added in an amount of 0.001 to 1 mole per mole of alkoxysilane or halogenated silane.

The reaction conditions for hydrolysis are not particularly limited. However, when alkoxysilane is hydrolyzed, the reaction temperature is 0 to 80 ° C., preferably 5 to 60 ° C., and the reaction time is 0.1 to 1.
Desirably, it is 0 hour, preferably 1 to 5 hours. When hydrolyzing a halogenated silane, the reaction temperature is 0 to 50 ° C., preferably 5 to 20 ° C., and the reaction time is 0.1.
It is desirable that it is ˜20 hours, preferably 1 to 10 hours.

The hydrolyzate thus obtained has a number average molecular weight of 100 to 50,000, preferably 500 to 10,000 (polystyrene equivalent molecular weight).
In addition, when using alkoxysilane, the alkoxysilane may be the same as that used for the preparation of the silica-based fine particles, or may be different.

[Polysilazane]
In the present invention, polysilazane represented by the following general formula (III) is used.

Ｒ²、Ｒ³およびＲ⁴は、水素原子または炭素数１〜８のアルキル基、アリール基または
ビニル基を示し、mは整数である。上記式(III)でＲ²、Ｒ³およびＲ⁴がすべて水素原子で
あり、１分子中にケイ素原子が５５〜６５重量％、窒素原子が２０〜３０重量％、水素原子が１０〜１５重量％であるような量で存在している無機ポリシラザンが特に好ましい。

R ² , R ³ and R ⁴ represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group, and m is an integer. In the above formula (III), R ² , R ³ and R ⁴ are all hydrogen atoms, silicon atoms are 55 to 65% by weight, nitrogen atoms are 20 to 30% by weight and hydrogen atoms are 10 to 15% by weight in one molecule. Inorganic polysilazane present in an amount such as% is particularly preferred.

  Moreover, it is preferable that ratio (Si / N ratio) of Si atom and N atom in polysilazane is 1.0-1.3. Such an inorganic polysilazane is, for example, a method of reacting dihalosilane with a base to form an adduct of dihalosilane and then reacting with ammonia (Japanese Examined Patent Publication No. 63-16325), methylphenyldichlorosilane, dimethyldichlorosilane, etc. It can be produced according to a known method such as a method of reacting ammonia with ammonia (Japanese Patent Laid-Open No. Sho 62-88327).

The polysilazane having a repeating unit represented by the above formula (III) may be linear or cyclic, or a mixture of linear polysilazane and cyclic polysilazane.
The number average molecular weight (polystyrene conversion) of these polysilazanes is desirably in the range of 100 to 10,000, preferably 500 to 2,000.

[(Ii) Preparation of polysiloxazan]
(Ii) Polysiloxazan used in the present invention is obtained by mixing and reacting the hydrolyzate of alkoxysilane and / or halogenated silane obtained as described above and polysilazane in an organic solvent. .

  The organic solvent only needs to dissolve the hydrolyzate of alkoxysilane or halogenated silane and polysilazane. For example, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatic hydrocarbons such as toluene, xylene, and mesitylene can be used. Can be used.

  The mixing amount of the hydrolyzate of alkoxysilane or halogenated silane and polysilazane is preferably in the range of 91 to 99% by weight of hydrolyzate of alkoxysilane or halogenated silane and 9 to 1% by weight of polysilazane. When the polysilazane is more than 9% by weight, Si—N bonds are likely to remain in the silica-based film obtained by applying the coating solution produced therefrom, and the dielectric constant may be increased. If the polysilazane is less than 1% by weight, chemical resistance such as adhesion to the coated surface, mechanical strength, and alkali resistance may be inferior.

The reaction conditions of the above-mentioned alkoxysilane and / or halogenated silane hydrolyzate and polysilazane are not particularly limited, but usually a mixture of an alkoxysilane or halogenated silane hydrolyzate and polysilazane is about It is desirable to heat at a reaction temperature of 100 ° C. or lower, preferably 80 ° C. or lower, usually for 0.5 to 5 hours, preferably 0.5 to 3 hours.

  By the above reaction, (ii) polysiloxazan in which polysilazane is bonded to the terminal of a part of the hydrolyzate of alkoxysilane or halogenated silane is obtained. The number average molecular weight (polystyrene conversion) of the obtained (ii) polysiloxazan is preferably in the range of 100 to 50,000, preferably 500 to 10,000.

Preparation of coating liquid for forming low dielectric constant silica-based film The coating liquid for forming a low dielectric constant silica-based film according to the present invention comprises (i) a dispersion containing silica-based fine particles having a phenyl group, and (ii) polysiloxazan. Are mixed by adding a solvent as necessary, and (i) silica-based fine particles having a phenyl group and (ii) polysiloxazan are reacted by heat treatment.

  (i) The mixing ratio of silica-based fine particles having a phenyl group and (ii) polysiloxazan is sufficient for (i) at least a part of the surface of the silica-based fine particles having a phenyl group to bind to the polysiloxazan. The amount of polysiloxazan may be any amount, but preferably the weight ratio of silica-based fine particles having phenyl groups to polysiloxazan (weight of silica-based fine particles having phenyl groups / weight of polysiloxazan) is 0.1. It is desirable to mix and react at a weight ratio of ˜20, preferably 0.5˜10.

When the weight ratio is more than 20, the resulting silica-based coating becomes porous including many interparticle voids of silica-based fine particles having phenyl groups, and although it can be expected to lower the dielectric constant, it adheres to the coated surface. There is a tendency that properties, mechanical strength, planarization performance of the surface to be coated and the like are deteriorated. On the other hand, when the weight ratio is smaller than 0.1, the silica-based film obtained in the same manner may be filled with polysiloxazan between silica-based fine particles having phenyl groups, and the dielectric constant may not be lowered.

  The heat treatment is usually performed at a reaction temperature of about 100 ° C. or lower, preferably 80 ° C. or lower for 0.5 to 5 hours, preferably about 0.5 to 3 hours. By this heat treatment, (i) the surface of the silica-based fine particles having a phenyl group reacts with (ii) polysiloxazan. In this reaction as well, no growth of silica-based fine particles or generation of new silica-based fine particles occurs, and the surface of the silica-based fine particles and polysiloxazan are bonded.

  The thus prepared coating liquid for forming a low dielectric constant silica-based film according to the present invention has a solid content (total of silica-based fine particles and polysiloxazan) of 5 to 40% by weight, preferably 10 to 10%. It is desirable to include 30% by weight.

  Since the coating liquid for forming a low dielectric constant silica-based film according to the present invention contains silica-based fine particles as a film-forming component, the film can be made porous by pores between the silica-based particles. In addition, the phenyl group on the surface of the silica-based fine particles has an effect of preventing re-adsorption of water into the pores in the coating and also has a high oxygen plasma resistance. For this reason, when a low dielectric constant silica-based film is formed using a coating liquid for forming a film containing a reaction product of such silica-based fine particles having a phenyl group and polysiloxazan, plasma etching or Deterioration of film quality due to oxygen plasma at the time of resist stripping can be prevented, and water re-adsorption to the film is also prevented, so the dielectric constant is low, and adhesion, chemical resistance, crack resistance, etc. are excellent. It is possible to form a stable low dielectric constant silica-based film with improved conductive yield and good planarization characteristics.

  In addition, the coating liquid for forming a low dielectric constant silica-based film obtained by the above method is replaced with a solvent such as methyl isobutyl ketone by using a rotary evaporator or the like to completely remove alcohol and moisture generated by the above reaction. After that, the concentration may be adjusted so as to obtain the above-described solid content concentration.

  Furthermore, the coating liquid for forming a low dielectric constant silica-based film according to the present invention may contain a filler. Examples of the filler include alumina, titanium dioxide, zinc oxide, tungsten oxide, ruthenium oxide, titanium. Examples include potassium acid, barium titanate, barium sulfate, calcium carbonate, mica, kaolin, and talc.

[Substrate with low dielectric constant silica coating]
The coated substrate according to the present invention can be obtained by applying the coating liquid for forming a low dielectric constant silica-based coating obtained as described above to the surface of various substrates and then heating.

  As a coating method of such a coating solution, a normal method such as a spray method, a spin coating method, a dip coating method, a roll coating method, or a transfer printing method can be employed. The heating temperature after application is usually in the range of 300 to 450 ° C, preferably 350 to 400 ° C. This heating is preferably performed in an inert gas atmosphere such as nitrogen, and as a result, a film having a lower relative dielectric constant can be obtained.

When the coating liquid is applied onto the substrate as described above, dried and then heated, polymerization of the film-forming component in the coating liquid proceeds and cures, but when the melt viscosity of the polymer decreases during the heating process, The reflow property is increased, and the flatness of the resulting film is improved. When forming a coating film using the coating solution for forming a silica-based film according to the present invention, a decrease in the melt viscosity of the polymer occurs due to heating, and 350 ° C.
Reflowability due to low viscosity is maintained to the extent. As a result, a film with further improved flatness can be obtained.

  The film thickness of the low dielectric constant silica-based film thus formed varies depending on the base material on which the film is formed and its purpose. For example, it is usually about 1000 to 2500 mm on a silicon substrate in a semiconductor device. In the case of between the wiring layers, it is usually 3000 to 5000 mm.

  Specific examples of the substrate with a low dielectric constant silica-based film according to the present invention include a semiconductor device, a liquid crystal display device, a photomask with a phase shifter, and the like. Particularly in a semiconductor device, a multilayer wiring structure on a silicon substrate. The above-mentioned low dielectric constant silica-based coating is formed on the wiring layers, on the element surface, or on the PN junction.

[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

[Production example]
1. Preparation of silica-based fine particles with phenyl groups
(1) A mixed solution of 139.1 g of pure water and 169.9 g of methanol is kept at 60 ° C., and this is added to a water-methanol solution of tetraethoxysilane (ethyl silicate-28, manufactured by Tama Chemical Industries) (water with a weight ratio of 2/8). A mixture of 2450 g of a methanol / methanol mixture and 532.5 g of tetraethoxysilane) 2982.5 g and 596.4 g of 0.25% aqueous ammonia were simultaneously added over 52 hours. After completion of the addition, the mixture was further aged at this temperature for 3 hours. Thereafter, unreacted tetraethoxysilane, methanol and ammonia were removed by ultrafiltration, and at the same time purified water was added for purification. After adjusting the silica concentration to 5% by weight, condensation reaction is performed in an autoclave at 300 ° C for 10 hours, and then purified with an amphoteric ion exchange resin (AG-501, manufactured by Bio-Rad) to obtain silica having an average particle size of 300 mm A fine particle dispersion (A) was obtained.

  (2) A porous silica fine particle dispersion having an average particle size of 250 mm, prepared under the same conditions as the silica fine particle dispersion (A) except that a mixed solution of 139.1 g of pure water, 140 g of methanol and 29.9 g of ethylene glycol was used. (B) was obtained.

  (3) Adjust the silica fine particle dispersion (A) to a concentration of 5% by weight, add 5 to 10 times the amount of ethanol, and then replace the solvent with a rotary evaporator to obtain a concentration of 5% by weight and moisture of 5% by weight. After adjusting to ethanol dispersion of 1%, phenyltrimethoxysilane was converted to SiO2 and 10% by weight of silica-based fine particles were added, and pH was adjusted to 10 with 1% by weight of ammonia water. After reacting at 50 ° C for 15 hours, add 10 times the amount of MIBK (methyl isobutyl ketone) and replace the solvent with a rotary evaporator to obtain a MIBK dispersion (C) with a concentration of 5% by weight and a water content of 0.5% by weight. It was.

  (4) Adjust the silica fine particle dispersion (B) to a concentration of 5% by weight, add 5 to 10 times the amount of ethanol, and then perform solvent replacement with a rotary evaporator to obtain a concentration of 5% by weight and a moisture of 5% by weight. After adjusting to ethanol dispersion of 1%, phenyltrimethoxysilane was converted to SiO2 and 10% by weight of silica-based fine particles were added, and pH was adjusted to 10 with 1% by weight of ammonia water. After reacting at 50 ° C for 15 hours, add 10 times the amount of MIBK (methyl isobutyl ketone) and replace the solvent with a rotary evaporator to obtain a MIBK dispersion (D) with a concentration of 5% by weight and a water content of 0.5% by weight. It was.

2. Preparation of polysiloxazan
(1) Preparation of hydrolyzate of alkoxysilane and halogenated silane According to the method disclosed in Japanese Patent Publication No. 6-41518, trichlorosilane was hydrolyzed in toluene using toluenesulfonic acid hydrate as a catalyst. A hydrogensilsesquioxane polymer having a number average molecular weight of 3500 was obtained.

(2) Preparation of polysilazane The polysilazane was produced by the following production method according to the production method described in Japanese Patent Publication No. 63-16325.
600 ml of pyridine was placed in a reactor installed in a thermostat kept at 0 ° C., and 28.3 g of dichlorosilane was added with stirring to form a complex (pyridine adduct). To this, ammonia gas was blown in for 2 hours until the amount of NH ₃ was 15 mol times that of dichlorosilane to obtain a solution containing the reaction product. The resulting precipitate was removed by filtration, and then the filtrate was decompressed and the solvent was replaced with xylene to obtain polysilazane having a number average molecular weight of 800 and 5% by weight.

(3) Preparation of polysiloxazan The hydrogensilsesquioxane polymer obtained as described above was dissolved in MIBK to prepare a 5 wt% solution, and the polysilazane solution was added over 3 hours. After reacting at 50 ° C. for 5 hours, the solvent was replaced with MIBK by a rotary evaporator to obtain polysiloxazan having a number average molecular weight of 4000 and 5% by weight.

3. Preparation of coating solution for coating film formation Silica-based fine particles (C), (D) having a phenyl group obtained as described above and polysiloxazan were mixed at a predetermined ratio shown in Table 1, and 50 ° C. For 1 hour. Thereafter, the solvent is replaced with methyl isobutyl ketone again by a rotary evaporator, and alcohol and water generated by heat treatment are completely removed, and the coating liquid for film formation (1) to (4) having a silica concentration of 20% by weight. Was prepared.

For comparison, coating liquids (5) and (6) for film formation were prepared by reacting silica fine particles (A) and (B) having no phenyl group with polysiloxazan in the same manner. Table 1 shows the composition of the prepared coating liquid for film formation.

（B）および(D)は、微粒子調製時にエチレングリコールを含んでいる。

(B) and (D) contain ethylene glycol when the fine particles are prepared.

[Examples 1 to 4, Comparative Examples 1 and 2]
Fabrication of a semiconductor device with a silica-based coating Coating solution for forming a coating (1) to (2) is applied by spin coating onto a semiconductor substrate on which metal wiring of a minimum of 0.25 μ rule has been applied, respectively, at 250 ° C. for 3 minutes Dried. Then, in nitrogen, 400 ° C, 30
A silica-based film was formed by baking for a minute. All of these silica-based coatings were 5000 mm. The SiO ₂ film is 4000Å is formed by plasma CVD on these films, and planarizing the wiring step by CMP (Chemical Mechanical Polishing). A via hole was formed in an ordinary micro-photolithography process, and the remaining resist was removed by irradiation with oxygen plasma, and then the via hole was washed with an organic amine and water. TiN is formed by a sputtering method as a barrier metal,
Further, a via plug was formed by forming a W plug by a CVD method and a CMP method. Thereafter, an upper layer metal wiring was formed to produce a semiconductor device.

The relative dielectric constant of the silica-based film of each semiconductor device thus obtained and the conduction yield of 100 continuous vias were measured. The relative dielectric constant is calculated from the CV measurement between adjacent wires, and is 100
The conduction yield of consecutive vias was evaluated by measuring the wiring resistance.

  The results are shown in Table 2.

表２に示すように、実施例１〜４のフェニル基を有するシリカ系微粒子を用いたシリカ系被膜では、比誘電率は低く、viaの導通歩留まりは大きくなった。これに対し、比較例
１，２のフェニル基を有していないシリカ微粒子を用いたシリカ系被膜では、比誘電率は高くなり、viaの導通歩留まりが小さくなった。

As shown in Table 2, in the silica-based film using the silica-based fine particles having phenyl groups of Examples 1 to 4, the relative dielectric constant was low, and the via yield was increased. On the other hand, in the silica-based film using silica fine particles having no phenyl group in Comparative Examples 1 and 2, the relative dielectric constant was high and the via conduction yield was low.

  From the results in Table 2, the silica-based coating using the silica-based fine particles having phenyl groups in the examples has a small relative dielectric constant and excellent oxygen plasma resistance at the time of micro-photolithography processing, as compared with the comparative example. It is recognized that it is excellent in chemical resistance such as mechanical strength and alkali resistance, and crack resistance. For this reason, if the coating liquid for forming a low dielectric constant silica-based film according to the present invention is used, an excellent semiconductor device can be provided.

Claims (4)

(i) Hydrolysis of one or more of alkoxysilanes represented by the following general formula (I), or at least a part of the surface of silica fine particles obtained by aging after hydrolysis, a phenyl group-containing alkoxy Silica-based fine particles having a phenyl group obtained by binding a hydrolyzate of silane or phenyl group-containing chlorosilane,
(ii) a reaction product of an alkoxysilane represented by the following general formula (I) and / or a hydrolyzate of a halogenated silane represented by the following general formula (II) and a polysilazane represented by the following general formula (III): A coating liquid for forming a low dielectric constant silica-based film, comprising a reaction product with a certain polysiloxazan.
X _n Si (OR ¹ ) _4-n (I)
_{X n SiX '4-n (} II)

(X represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 8 carbon atoms, a fluorine-substituted alkyl group, an aryl group or a vinyl group, and R ¹ , R ² , R ³ and R ⁴ are a hydrogen atom or a carbon atom. An alkyl group, an aryl group or a vinyl group represented by formulas 1 to 8 is represented, and X ′ represents a halogen atom.
M is an integer, and n is an integer of 0 to 3. ) The hydrolysis temperature or aging temperature when preparing silica fine particles from one or more of alkoxysilanes represented by the general formula (I) is 180 ° C or higher.
A coating solution for forming a low dielectric constant silica-based coating according to 1.   The mixed amount of the hydrolyzate of alkoxysilane or halogenated silane and polysilazane is in the range of 91 to 99% by weight of hydrolyzate of alkoxysilane or halogenated silane and 9 to 1% by weight of polysilazane. Item 3. The coating liquid for forming a low dielectric constant silica-based film according to Item 1 or 2. The weight ratio of silica-based fine particles having a phenyl group to polysiloxazan (weight of silica-based fine particles having a phenyl group / weight of polysiloxazan) is in a weight ratio of 0.1 to 20. The coating liquid for low dielectric constant silica type film formation in any one of 1-3.