JP2006188547A - Coating composition and low dielectric porous siliceous material produced by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating composition capable of producing a porous siliceous film equipped with an excellent mechanical strength and also a very low dielectric constant stably and equipped with chemical resistance against various chemicals jointly, and a method for producing a siliceous material by using the same. <P>SOLUTION: This coating composition contains a polyalkylsilazane compound, a siloxy group-containing polymer and an organic solvent, and a siliceous material obtained by calcining the coating composition and a method for producing the same are also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coating composition. Furthermore, the present invention relates to a method for producing a low dielectric siliceous material using the same, and a low dielectric siliceous film produced using the same. Furthermore, the present invention also relates to a semiconductor device comprising the low dielectric siliceous material thus manufactured.

  Electronic materials such as semiconductor interlayer insulating films (IMD) are required to have a lower dielectric constant as the integrated circuit speeds up and becomes higher. To reduce the relative dielectric constant of siliceous films. It is known to make membranes porous. Since the siliceous film generally has hygroscopicity, the relative permittivity tends to increase with time depending on the surrounding environment.

  As a method for preventing such a relative dielectric constant from increasing with time, a method of making an organic siliceous film obtained by baking polyorganosilazane porous is conceivable. Since the organic siliceous film thus obtained has a structure in which an organic group is bonded to a silicon atom of silica, the film itself has high water repellency, and the relative permittivity increases with time due to moisture absorption. It is possible to obtain a porous film that is suppressed and has the heat resistance and environmental resistance required for an interlayer insulating film for semiconductors.

  Further, higher integration of integrated circuits has prompted the development of multilayer wiring process technology for more efficiently realizing miniaturization and multilayering of internal wiring in semiconductor devices. In such a technique, for example, a wiring material such as Cu is embedded in the groove by sputtering reflow method or CVD method, and the wiring material deposited outside the groove is removed by CMP (Chemical Mechanical Polishing) method. What is formed. With the progress of such trench wiring technology, the semiconductor device can be miniaturized in internal wiring and can be further multilayered in combination with surface planarization by CMP.

The high integration of such an integrated circuit requires a mechanical strength that can withstand the process of removing the wiring material by the CMP method in addition to lowering the dielectric constant of the interlayer insulating film existing between the wirings. Furthermore, in addition to chemicals used in the CMP method, when removing photoresist by wet stripping, the chemicals, and when removing photoresist by ashing, various chemicals such as chemicals for removing residues after ashing. It also requires chemical resistance.
JP 2002-75982 A

  In order to meet the demand for the siliceous material as described above, several methods have been studied. For example, the present inventors have found that a high-strength porous siliceous film can be obtained by firing a film of a composition comprising polyalkylsilazane and polyacrylic acid ester or polymethacrylic acid ester. (Patent Document 1). The porous siliceous film described in Patent Document 1 has an effect that an increase in the relative permittivity with time due to moisture absorption can be suppressed. However, as a result of further studies by the present inventors, the porous siliceous film generally has an elastic modulus of 3 GPa or less when the relative dielectric constant is about 2.2. It turns out that there is room for improvement.

  On the other hand, when forming a multilayer wiring structure using a porous film as an interlayer insulating film, it is important that the hole diameters of the holes formed in the porous film are smaller and the hole diameters are uniform. When the porous insulating film is exposed to an etching gas or a stripping solution used when forming a multilayer wiring structure, the gas or the stripping solution may enter and erode into large holes. In addition, the stress and heat applied when metal wiring and other thin films are formed on the porous film triggers the pores to expand, and that part becomes leak-parsed, and the porous film functions as an insulating film. May not. From this point of view, it is known that the pore diameter of the porous membrane is desirably 2 nm or less. However, in the conventional method, usually, only a porous film having fine pores having a pore diameter of 5 to 8 nm can be obtained, and it was difficult to form a porous film having pores having a uniform pore diameter of 5 nm or less. .

  The present invention relates to a coating composition comprising a polyalkylsilazane compound, a siloxy group-containing polymer, and an organic solvent.

  In addition, the siliceous material of the present invention is characterized in that it is formed by applying the coating composition on a substrate or filling a groove, and further firing it.

  A semiconductor device according to the present invention includes the siliceous material as an interlayer insulating film.

  Furthermore, the method for producing a siliceous material according to the present invention is characterized in that the coating composition is pre-fired at a temperature of 50 to 300 ° C. in a steam-containing atmosphere and further fired at a temperature of 300 to 500 ° C. in a dry atmosphere. To do.

  Furthermore, the siliceous material according to the present invention is characterized by having fine pores of 0.5 to 3 μm inside.

  The present invention solves the problems in the conventional production of porous materials as described above, has an excellent mechanical strength that can withstand the latest high integration processes such as the damascene method, and is extremely Coating that can stably produce a porous siliceous material having a small pore size and a stable low dielectric constant, especially less than 2.5, and having chemical resistance against various drugs. A composition is provided.

上記式（１）〜（３）において、Ｒ^１〜Ｒ^１１は、それぞれ水素原子または炭素数１〜３のアルキル基を表すが、化合物中のＲ^１、Ｒ^５およびＲ^６、ならびにＲ^９〜Ｒ^１１のすべてが水素ではない。より好ましい態様においては、各式中のＲ^１〜Ｒ^１１は以下の通りである。 Polyalkylsilazane compound The polyalkylsilazane compound in the present invention has an alkyl-substituted silazane bond. Although the structure is not limited, the preferred polyalkylsilazane compound is preferably a repeating unit represented by the following general formula (1) and at least a unit represented by the general formula (2) or (3) Including one kind.

In the above formulas (1) to (3), R ^{1 to} R ¹¹ each represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ¹ , R ⁵ and R ⁶ in the compound, and R ⁹ to All of R ¹¹ are not hydrogen. In a more preferred embodiment, R ^{1 to} R ^{11 in} each formula are as follows.

In the above formula (1), R ¹ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, but not all R ^{1 in the} entire compound is simultaneously hydrogen,
R ^{2 to} R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, but all of R ^{2 to} R ⁴ are not simultaneously hydrogen,
p, q, and r are each 0 or 1, and 0 ≦ p + q + r ≦ 3.

Here, in the general formula (1), when R ¹ is a methyl group and R ^{2 to} R ⁴ are present, it is preferable that all of them are hydrogen.

In the above formula (2), R ^{5 to} R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, but not all R ⁵ and R ^{6 in the} entire compound are simultaneously hydrogen. .

Here, in the general formula (2), it is preferable that either R ⁵ or R ⁶ is a hydrogen atom, the rest is a methyl group, and R ⁷ is a hydrogen atom.

In the above formula (3), R ^{8 to} R ¹¹ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, but all R ^{9 to} R ^{11 in the} entire compound are not simultaneously hydrogen. .

In the general formula (3), a ^{R 8} is a hydrogen ^atom, it is preferable that all of R 9 ^{to R 11} is a methyl group.

  In the present invention, a polyalkylsilazane compound containing a repeating unit represented by the general formula (1) and at least one repeating unit represented by the general formula (2) or (3) is stored in the coating composition. It is particularly useful in that gelation at the time can be prevented. In that case, the number of repeating units represented by the general formula (1) is preferably 50 mol% or more of the total number of units represented by the general formulas (1) to (3), and is 80 mol% or more. It is more preferable that it is 90 mol% or more. When the repeating unit of the general formula (1) is 50 mol% or more with respect to the total number of the repeating units of the general formulas (1) to (3), problems such as repelling and coating unevenness are less likely to occur during film formation. It is.

  The polysilazane compound according to the present invention preferably has a number average molecular weight of 100 or more in order to improve the coating property of the coating composition, particularly the coating property when applied by spin coating. In addition, the polysilazane compound according to the present invention preferably has a number average molecular weight of 50,000 or less in order to suppress the gelation of the composition by adjusting the number of crosslinking groups. In the present invention, a particularly preferred polyalkylsilazane compound comprises a repeating unit of the above general formula (1) and at least one unit of the above general formula (2) or (3). In the present invention, the number average molecular weight of the polyalkylsilazane compound is preferably 100 to 50,000, and more preferably 1,000 to 20,000.

These polyalkylsilazane compounds are alkyltrichlorosilanes (R ¹ SiCl ₃ ) in the case of polyalkylsilazanes containing repeating units of the general formula (1) in the ammonolysis when synthesizing ordinary polysilazanes obvious to those skilled in the art. Dialkyldichlorosilane (R ⁵ R ⁶ SiCl ₂ ) in the case of a polyalkylsilazane containing a repeating unit of the general formula (2), and a trialkyl in the case of a polyalkylsilazane containing a unit of the general formula (3) It can be obtained by starting with chlorosilane (R ⁹ R ¹⁰ R ¹¹ SiCl), and in the case of polyalkylsilazanes containing both of these repeating units, a mixture thereof. The mixing ratio of these chlorosilanes determines the abundance of each unit.

Siloxy group-containing polymer The coating composition according to the present invention comprises a siloxy group-containing polymer. This polymer contains a siloxy group (—Si—O —)-containing monomer as a polymer unit, and contains a siloxy group in the main chain, side chain, or terminal unit.

  Specific examples of the group containing a siloxy group include trimethylsiloxy group, dimethylbutylsiloxy group, methylhydrosiloxy group, dimethylsiloxy group, phenylmethylsiloxy group, diphenylsiloxy group, methylvinylsiloxy group, phenylvinylsiloxy group, 2- (trimethoxysilyl) ethyl (meth) acryl group, γ- (trimethoxysilyl) propyl (meth) acryl group, 2- (trimethylsiloxy) ethyl (meth) acryl group, γ- (trimethylsiloxy) propyl (meth) ) Acrylic group, trimethylsiloxymethacrylic group, trimethylsilyloxysiloxanyl group and the like. Here, the (meth) acryl group means either an acryl group or a methacryl group.

  The siloxy group-containing polymer according to the present invention may contain a polymer unit containing no siloxy group as long as it contains the above-mentioned siloxy group. Such siloxy group-free polymer units include, for example, methyl (meth) acrylic acid, isobutyl (meth) acrylic acid, n-butyl (meth) acrylic acid, tert-butyl (meth) acrylic acid, polyethylene oxide, Examples thereof include, but are not limited to, polypropylene oxide and polypropylene glycol (meth) acrylic acid. Among these, the siloxy group-containing polymer in the present invention is preferably a polymer containing a polymer unit selected from the group consisting of acrylic acid, methacrylic acid, and a polyethylene oxide compound.

  An example of this polyethylene oxide compound is shown as the following general formula.

_{HO- (CH 2 CH 2 O)} m -L- (SiR '2 -O) n -SiR' 3 (A)
Here, R ′ is an arbitrary substituent such as hydrogen, an alkyl group, or an alkoxy group, and a plurality of R ′ in one molecule may be mixed. R ′ is a polymerizable group and can be polymerized with other monomer units.

  L is a linking group, such as a single bond or an alkylene group.

  m and n are numbers representing the degree of polymerization.

  The molecular weight of the siloxy group-containing polymer can be arbitrarily selected as long as the effects of the present invention are not impaired. However, the polymer is sublimated, decomposed or evaporated at an appropriate temperature to form a porous film. Thus, the molecular weight of the polymer is preferably not less than a certain value, and on the other hand, it is preferably not more than a certain value from the viewpoint of preventing the generation of voids and the resulting decrease in film strength. These lower limit value and upper limit value are appropriately selected depending on the type of the siloxy group-containing polymer to be used. When the siloxy group-containing polymer used in the present invention contains a polyethylene oxide compound as a polymerization unit, the molecular weight is preferably 100 to 5,000, and more preferably 500 to 2,000. Furthermore, when the siloxy group-containing polymer contains acrylic acid or methacrylic acid as a polymerization unit, the molecular weight is preferably 1,000 to 80,000, and preferably 10,000 to 20,000. More preferred.

  More preferred siloxy group-containing polymers are a polymer containing 2- (trimethylsiloxy) ethyl methacrylic acid as a polymer unit and a polymer containing hydroxy (polyethyleneoxy) propyl / polydimethylsilicone as a polymer unit. Of these, preferred specific examples of the siloxy group-containing polyethylene oxide compound include α- [3- [1,1,3,3-tetramethyl-1-[(trimethylsilyl) oxy] disiloxanyl] propyl] -ω-hydroxy-poly. (Oxy-2,3-ethanel), hydroxy (polyethyleneoxy) propylpolydimethylsilicone, Gelest MCR-13, and the like.

  In such a siloxy group-containing polyethylene oxide compound, the structure of polyethylene oxide is not particularly limited, but the weight of the ethyleneoxy portion relative to the weight of the molecule is preferably 30 to 90% from the viewpoint of maintaining the viscosity appropriately. Moreover, it is preferable that the weight of the siloxy group part in a polysiloxy structure is 10 to 40%.

  This siloxy group-containing polyethylene oxide compound, or a copolymer containing it as a monomer unit, increases the strength of the siliceous material because the polyethylene oxide structure terminated with a hydroxyl group crosslinks with the polyalkylsilazane compound. Further, it is considered to be made porous. Furthermore, when the siloxy group-containing polyethylene oxide is sublimated by heating, the siloxy group as a part thereof remains in the fired film of the polyalkylsilazane as a matrix, thereby producing a stronger siliceous material. Play.

  The siloxy group-containing polymer in the present invention must contain a siloxy group. The ratio of the polymerization units containing a siloxy group is preferably 1% or more, more preferably 10% or more, more preferably 30% or more with respect to the total number of polymerization units constituting the siloxy group-containing polymer. It is particularly preferred.

Organic Solvent The coating composition according to the present invention is obtained by dissolving or dispersing the above-described polyalkylsilazane compound and acetoxysilane compound and, if necessary, other additives described later in an organic solvent. At this time, it is preferable to use an inert organic solvent having no active hydrogen as the organic solvent. Examples of such organic solvents include aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, and triethylbenzene; cyclohexane, cyclohexene, decahydronaphthalene, ethylcyclohexane, methylcyclohexane, p-menthin, and dipentene. (Limonene) and other alicyclic hydrocarbon solvents; ether solvents such as dipropyl ether and dibutyl ether; ketone solvents such as methyl isobutyl ketone; ester solvents such as propylene glycol monomethyl ether acetate and the like. .

Other Additives The coating composition according to the present invention may contain other additive components as required. Examples of such a component include a siloxy group-free polymer.

  As the siloxy group-free polymer that can be used in the coating composition according to the present invention, any polymer can be used, but it is selected from the group consisting of homopolymers and copolymers of (meth) acrylic acid esters. Among these side groups, those containing a carboxyl group or a hydroxyl group are preferred. Such a polymer has the effect of making the fine pores of the siliceous material formed small and uniform. Such polymers include homopolymers of acrylate esters such as polymethyl acrylate and polyethyl acrylate; homopolymers of methacrylate esters such as polymethyl methacrylate and polyethyl methacrylate; acrylic acid Copolymers of esters, such as poly (methyl acrylate-co-ethyl acrylate); Copolymers of methacrylate esters, such as poly (methyl methacrylate-co-ethyl methacrylate); Acrylic esters and methacrylic acid A copolymer with an ester, for example, poly (methyl acrylate-co-ethyl methacrylate), and the like can be mentioned. When this polymer is a copolymer, there is no restriction | limiting in the monomer arrangement | sequence, A random copolymer, a block copolymer, and other arbitrary arrangement | sequences can be used.

  Monomers constituting (meth) acrylic acid ester homopolymers and copolymers include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, methyl acrylate. , Ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, and the like, but are not limited thereto. In particular, methyl methacrylate and n-butyl methacrylate, and n-butyl acrylate and i-butyl acrylate are more preferable from the viewpoint of compatibility with polyalkylsilazane.

  The carboxyl group and hydroxyl group contained in such a (meth) acrylic acid ester polymer form a crosslink with the polyalkylsilazane compound. Since this crosslinking reaction affects the strength and structure of the final siliceous material, the amounts of carboxyl groups and hydroxyl groups are important. The amount of the carboxyl group and the hydroxyl group is preferably 0.01 mol% or more and preferably 0.1 mol% or more with respect to the total number of monomers constituting the polymer component in order to obtain a sufficient crosslinked structure. More preferred. Moreover, in order to prevent the gelatinization by excessive bridge | crosslinking, it is preferable that it is 50 mol% or less, and it is more preferable that it is 30 mol% or less.

  In addition, when a non-siloxy group-containing polymer is used, the molecular weight of the polymer may be 1,000 or more so that the polymer is sublimated, decomposed, or evaporated at an appropriate temperature to form a porous film. Preferably, it is 10,000 or more. On the other hand, from the viewpoint of preventing the generation of voids and the resulting decrease in film strength, the molecular weight of the polymer is preferably 800,000 or less, and more preferably 200,000 or less.

  The coating composition according to the present invention may contain other additive components as required. Examples of such components include viscosity modifiers and crosslinking accelerators. In addition, a phosphorus compound such as tris (trimethylsilyl) phosphate may be contained for the purpose of obtaining a sodium gettering effect when used in a semiconductor device. Furthermore, in order to accelerate the reaction of the polymer component in the coating composition, a reaction accelerator, such as an acetoxysilane compound, can be blended. The acetoxysilane compound may exhibit an effect of making the micropores formed in the siliceous material after firing small and uniform.

Coating composition The polymerizable composition according to the present invention comprises a polyalkylsilazane compound, a siloxy group-containing polymer, and, if necessary, the above-mentioned other additives dissolved or dispersed in the organic solvent. The reaction is made into a coating composition. Here, the order in which each component is dissolved in the organic solvent is not particularly limited, and two or more kinds of solutions, for example, a solution of a polyalkylsilazane compound and a solution of a siloxy group-containing polymer may be mixed.

  After mixing each component, it is possible to obtain a homogeneous coating composition in which crosslinks are formed by physical stirring while heating as necessary. In the case of heating, heating is generally performed at 30 to 80 ° C., but this temperature varies depending on the type of component used. In particular, care should be taken because the composition may gel if the temperature is excessively high. The stirring time is generally about 1 to 24 hours, although it depends on the type and temperature of the reacting components. Furthermore, performing ultrasonic dispersion treatment for about 5 to 90 minutes on a 30 to 80 ° C. hot water bath is more preferable because the reaction is accelerated.

  In addition, the solvent can be replaced after the components are reacted.

  When used, the amount of the siloxy group-containing polymer according to the present invention is preferably 5% by weight or more based on the weight of the polyalkylsilazane compound in order to effectively realize a porous siliceous material. More preferably, it is used at an addition amount of 10% by weight or more, particularly preferably 20% by weight or more. On the other hand, in order to prevent a decrease in film strength due to the occurrence of voids or cracks, it is preferably used at 50% by weight or less based on the weight of the polyalkylsilazane compound.

  Further, the content of each component described above varies depending on the intended use of the coating composition, but the solid content weight is preferably 5% by weight or more in order to form a siliceous material having a sufficient film thickness. In order to ensure the storage stability of the coating composition and to keep the viscosity appropriately, it is preferably 50% by weight or less. That is, generally, the solid content weight is preferably 5 to 50% by weight, and more preferably 10 to 30% by weight with respect to the entire coating composition. Usually, when the solid content is 10 to 30% by weight, a generally preferable film thickness, for example, 2000 to 8000 kg can be obtained.

Production method of siliceous material The coating composition according to the present invention is applied on a substrate or filled into a mold or a groove, and then dried as necessary to remove excess organic solvent, followed by firing. A siliceous material can be obtained. When the siliceous material according to the present invention is applied to an electronic component such as a semiconductor device, the siliceous material is usually directly formed on the semiconductor device by baking the coating composition applied on the substrate to obtain a siliceous material. Is generally formed.

  Examples of the method for applying the coating composition to the substrate surface include conventionally known methods such as spin coating, dipping, spraying, and transfer.

  The coating film formed on the substrate surface is pre-baked in a water vapor atmosphere after removing (drying) an excess organic solvent as necessary. Here, the water vapor atmosphere refers to an atmosphere having a relative humidity of 40% or higher at 23 ° C. At this time, the gas other than water vapor forming the atmosphere is air, nitrogen, helium, argon or the like. Pre-baking is performed at a temperature of 50 to 350 ° C., preferably 100 to 300 ° C. This pre-baking can also be performed while raising the temperature stepwise or continuously.

  After this preliminary baking, if necessary, it is left for a short time (for example, 3 to 30 minutes) in a humidified atmosphere or for a long time (for example, 24 hours) in an air atmosphere, and then heated and fired in a dry atmosphere. This firing step is performed in a dry atmosphere. Here, the dry atmosphere is an atmosphere containing almost no water vapor such as dry air, dry nitrogen, and dry helium, and means an atmosphere having a relative humidity at 25 ° C. of 10% or less.

  The calcination temperature is 300 to 500 ° C., preferably 350 to 450 ° C., and the calcination time varies depending on the calcination temperature and blending components, but is generally 1 minute to 1 hour. From the viewpoint of productivity, the firing temperature is preferably 300 ° C. or higher in order to finish the firing process in as short a time as possible, but is 500 ° C. or lower in order to maintain the quality of the siliceous material to be formed. Is preferred.

  Silica having unoxidized SiH and SiR bonds by the oxidation of only the SiN bonds among the SiH, SiR (R: hydrocarbon group) and SiN bonds in the polyalkylsilazane by the above-mentioned firing step. A quality material is formed. Thus, in the siliceous material to be formed, SiO bonds formed by selective oxidation of SiN bonds and unoxidized SiH and SiR bonds can be present. A quality material can be obtained. In general, the dielectric constant of a siliceous material decreases as the density of the siliceous material decreases. On the other hand, when the density of the siliceous material decreases, adsorption of water, which is a high dielectric material, occurs. Therefore, if the siliceous material is left in the atmosphere, there may be a problem that the dielectric constant of the film increases. On the other hand, in the case of the siliceous material according to the present invention containing SiH or SiR bonds, since these bonds have water repellency, it is possible to prevent water adsorption while having a low density. Therefore, the siliceous material according to the present invention has a great advantage that the dielectric constant of the siliceous material hardly increases even when left in the atmosphere containing water vapor. Furthermore, since the siliceous material according to the present invention has a low density, there is an advantage that the internal stress of the film is small and cracks are hardly generated.

  In the firing of the coating composition according to the present invention, fine pores mainly having a pore diameter of 0.5 to 3 nm are formed inside the siliceous material. And this siliceous material does not have substantially the micropore whose pore diameter exceeds 5 nm. The pore diameter of this micropore can be measured by the X-ray diffuse scattering method. As an apparatus that can be used for this measurement, an ATX-G type multi-function X-ray diffractometer for surface structure evaluation (manufactured by Rigaku Corporation) can be mentioned. These micropores are considered to be formed by decomposition of the acetoxysilane compound and evaporation or sublimation of the decomposition product. Due to the presence of the fine pores, the density of the siliceous material is further lowered, and as a result, the relative dielectric constant of the siliceous material is further lowered.

  Since the porous siliceous material according to the present invention can form extremely fine pores, it has excellent mechanical strength. Specifically, the porous siliceous material according to the present invention exhibits a remarkably high mechanical strength as a porous material having a modulus of elasticity of 3 GPa or more, and in some cases 5 GPa or more as a nanoindentation method described later. .

  Therefore, it has mechanical strength and various chemical resistances that can withstand the removal process of wiring material by CMP method, so it can be used as an interlayer insulation film suitable for the latest high integration process such as damascene method. is there.

  Furthermore, the siliceous material according to the present invention has sufficient water-repellent groups derived from the polyalkylsilazane compound, which is a matrix component thereof, remaining sufficiently after firing, so that the relative permittivity is almost increased even when left in an atmosphere containing water vapor. do not do. Thus, according to the present invention, the low density and water repellency due to the binding component (SiH, SiR) of the siliceous material and the low density of the entire film due to the fine pores are combined and less than 2.5, preferably 2 It is possible to obtain a porous siliceous material that can stably maintain an extremely low relative dielectric constant of 0.0 or less, and in some cases, about 1.6.

When the other properties of the porous siliceous material according to the present invention are shown, its density is 0.5 to 1.6 g / cm ³ , preferably 0.8 to 1.4 g / cm ³ , and its crack limit film thickness is 1. 0.0 μm or more, preferably 5 μm or more, and its internal stress is 80 MPa or less, preferably 50 MPa or less. Further, the Si-containing group present as a SiH or SiR (R: hydrocarbon group) bond contained in the siliceous material is 10 to 100 atom%, preferably 25 to 25% of the number of Si atoms contained in the material. 75 atomic percent. Moreover, Si content which exists as a SiN bond is 5 atomic% or less. The thickness of the porous siliceous material obtained after firing varies depending on the use of the substrate surface, but is usually 0.01 to 5 μm, preferably 0.1 to 2 μm. In particular, when used as an interlayer insulating film of a semiconductor device, the thickness is preferably 0.1 to 2 μm.

  As described above, the porous siliceous material according to the present invention has a low density, and the crack limit film thickness, that is, the maximum film thickness that can be formed without causing film cracking is as high as 5 μm or more. It also has the advantage of showing. In the case of a conventional siliceous material, the crack limit film thickness is about 0.5 to 1.5 μm.

  Thus, the siliceous material according to the present invention has a lower dielectric constant, lower density, higher water repellency, better chemical resistance and higher mechanical strength than conventional siliceous materials, The low dielectric constant can be kept stable, and is particularly preferable for application to an interlayer insulating film in a semiconductor device.

  The present invention will be described below with reference to examples. In addition, the evaluation of various physical properties regarding the siliceous material is described collectively at the end.

Reference example 1

(Synthesis of polymethylsilazane (1))
A stainless steel tank for supplying raw materials was attached to a stainless steel tank reactor having an internal volume of 5 liters. After the inside of the reactor was replaced with dry nitrogen, 780 g of methyltrichlorosilane was placed in the stainless steel for raw material supply, and this was introduced into the reaction tank by nitrogen pressure. Next, a raw material supply tank containing pyridine was connected to the reactor, and 4 kg of pyridine was similarly pumped and introduced with nitrogen. The pressure of the reactor was adjusted to 1.0 kg / cm ² and the temperature was adjusted so that the temperature of the mixed solution in the reactor became −4 ° C. Ammonia was blown in there while stirring, and the ammonia supply was stopped when the pressure in the reactor reached 2.0 kg / cm ² . The exhaust line was opened to lower the reactor pressure, and then dry nitrogen was blown into the liquid phase for 1 hour to remove excess ammonia. The obtained product was subjected to pressure filtration under a dry nitrogen atmosphere using a pressure filter to obtain 3200 ml of a filtrate. When pyridine was distilled off using an evaporator, about 340 g of polymethylsilazane was obtained.

When the number average molecular weight of the obtained polymethylsilazane was measured by gas chromatography using chloroform as a developing solution, it was 1800 in terms of polystyrene. Infrared absorption spectrum (hereinafter, referred to as IR spectrum) was measured, absorption based on N-H bond around 3350 cm ^-1 and 1200 cm ^-1, absorption based on Si-C bonds of 2900 cm ^-1 and 1250 cm ^-1, and Absorption based on 1020-820 cm ⁻¹ Si—N—Si bonds was observed.

Reference example 2

(Synthesis of polymethylsilazane (2))
Synthesis was carried out in the same manner as in Reference Example 1, except that a mixture of 720 g of methyltrichlorosilane and dimethyldichlorosilane 656 was used instead of 780 g of methyltrichlorosilane as a raw material, and 370 g of polymethylsilazane was obtained.

When the number average molecular weight of the obtained polymethylsilazane was measured by gas chromatography using chloroform as a developing solution, it was 1400 in terms of polystyrene. It was measured infrared absorption spectrum, absorption based on N-H bond around 3350 cm ^-1 and 1200 cm ^-1, absorption based on Si-C bonds of 2900 cm ^-1 and 1250 cm ^-1, and Si of 1020～820Cm ^-1 Absorption based on -N-Si bonds was observed.

  Copolymerization of isobutyl methacrylate 70 mol% and 2- (trimethylsiloxy) ethyl methacrylate 30 mol% into 80 g of 15% propylene glycol monomethyl ether acetate (hereinafter referred to as PGMEA) solution of polymethylsilazane synthesized in Reference Example 1 A solution prepared by dissolving 3 g of a combination (molecular weight: about 100,000) in 17 g of PGMEA was mixed and sufficiently stirred. Subsequently, the solution was filtered with a PTFE syringe filter (manufactured by Advantech) having a filtration accuracy of 0.2 microns. The filtrate was applied on a silicon wafer having a diameter of 10.2 cm (4 inches) and a thickness of 0.5 mm using a spin coater under the condition of 3000 rpm / 20 seconds, and further dried at room temperature for 5 minutes. The silicon wafer was heated in an air atmosphere (relative humidity 40% at 23 ° C.) at 150 ° C. for 3 minutes, and then on a 250 ° C. hot plate for 3 minutes. This film was allowed to stand for 24 hours in an air atmosphere (23 ° C. relative humidity 40%), and then baked in a dry nitrogen atmosphere at 400 ° C. for 30 minutes to obtain a siliceous film.

IR spectrum for the siliceous film, of 1020 cm ^-1, and Si-O bonds to based absorption 450 cm ^-1, absorption based on Si-C bonds of 1270 cm ^-1 and 780 cm ^-1, of 2970cm ^-1 C- Absorption based on H bonds was observed, absorption based on N—H bonds at 3350 cm ⁻¹ and 1200 cm ⁻¹ , and absorption based on a copolymer of isobutyl methacrylate and 2- (trimethylsiloxy) ethyl methacrylic acid 30 was burned out Was.

When the obtained siliceous film was evaluated, the relative dielectric constant was 2.20, the density was 1.1 g / cm ³ , the internal stress was 36 MPa, and the crack limit film thickness was 5 μm or more. Further, after the obtained film was left in the atmosphere at a temperature of 23 ° C. and a relative humidity of 50% for one week, the relative dielectric constant was measured again, and there was no change at all.

  The elastic modulus of this film by the nanoindentation method was 4.5 GPa.

  Using ACT-970 (manufactured by Ashland Chemical), ST-210 and ST250 (manufactured by ATMI), EKC265 and EKC640 (manufactured by EKC), which are widely used as etching residue stripping solutions, When the (Rity) test was performed, the etching rate was 0.5% / min or less, respectively, and the increase in dielectric constant by the test was also 1.0% or less.

  Furthermore, when the pore diameter of the siliceous film was measured by the X-ray diffuse scattering method, the average pore diameter was 2 nm.

  A solution obtained by dissolving 8 g of a copolymer (molecular weight: about 1,000) of 50 mol% of ethylene oxide and 50 mol% of dimethylsiloxane in 32 g of PGMEA in 160 g of a 20% PGMEA solution of polymethylsilazane synthesized in Reference Example 2. Were mixed and stirred well. Subsequently, the solution was filtered with a PTFE syringe filter (manufactured by Advantech) having a filtration accuracy of 0.2 microns. The filtrate was applied on a silicon wafer having a diameter of 20.3 cm (8 inches) and a thickness of 1 mm using a spin coater under conditions of 3500 rpm / 20 seconds and further dried at room temperature for 5 minutes. The silicon wafer was heated in an air atmosphere (relative humidity 40% at 23 ° C.) at 150 ° C. for 3 minutes, and then on a 250 ° C. hot plate for 3 minutes. This film was left in a humidifier at 70 ° C. and a relative humidity of 85% for 3 minutes and baked in a dry nitrogen atmosphere at 400 ° C. for 10 minutes to obtain a siliceous film.

IR spectrum for the siliceous film, of 1020 cm ^-1, and Si-O bonds to based absorption 440 cm ^-1, absorption based on Si-C bonds of 1290cm ^-1 and 770 cm ^-1, of 2980cm ^-1 C- absorption based on H bond was observed, absorption based on N-H bonds of 3350 cm ^-1 and 1200 cm ^-1, and absorption based on a copolymer of ethylene key side and dimethylsiloxane disappeared.

When the obtained siliceous film was evaluated, the relative dielectric constant was 2.24, the density was 1.2 g / cm ³ , the internal stress was 35 MPa, and the crack limit film thickness was 5 μm or more. Further, after the obtained film was left in the atmosphere at a temperature of 23 ° C. and a relative humidity of 50% for one week, the relative dielectric constant was measured again, and there was no change at all.

  The elastic modulus of this film by the nanoindentation method was 5.0 GPa.

  When the resistance test of the siliceous film was performed using the etching residue removing solution ACT-970 (manufactured by Ashland Chemical), ST-210 and ST250 (manufactured by ATMI), EKC265 and EKC640 (manufactured by EKC), the etching rate was Each was 0.8 kg / min or less, and the increase in dielectric constant by the test was 1.1% or less.

  Furthermore, when the pore diameter of the siliceous film was measured by the X-ray diffuse scattering method, the average pore diameter was 1.7 nm.

Comparative Example 1

  A solution prepared by dissolving 3 g of poly n-butyl methacrylate (molecular weight: about 160,000) in 17 g of dibutyl ether was mixed with 80 g of a 15% dibutyl ether solution of polymethylsilazane synthesized in Reference Example 1 and sufficiently stirred. Subsequently, the solution was filtered with a PTFE syringe filter (manufactured by Advantech) having a filtration accuracy of 0.2 microns. The filtrate was applied onto a silicon wafer having a diameter of 10.2 cm (4 inches) and a thickness of 0.5 mm using a spin coater under the condition of 2000 rpm / 20 seconds, and further dried at room temperature for 5 minutes. The silicon wafer was heated in an air atmosphere (relative humidity 40% at 23 ° C.) at 150 ° C. for 3 minutes, and then on a 250 ° C. hot plate for 3 minutes. This film was allowed to stand for 24 hours in an air atmosphere (23 ° C. relative humidity 40%), and then baked in a dry nitrogen atmosphere at 400 ° C. for 30 minutes to obtain a siliceous film.

IR spectrum for the siliceous film, 1030 cm ^-1, and Si-O bonds to based absorption 450 cm ^-1, absorption based on Si-C bonds of 1270 cm ^-1 and 780 cm ^-1, of 2970cm ^-1 C- Absorption based on H bonds was observed, and absorption based on N—H bonds at 3350 cm ⁻¹ and 1200 cm ⁻¹ and absorption based on poly n-butyl methacrylate were burned out.

When the obtained siliceous film was evaluated, the relative dielectric constant was 2.31, the density was 1.1 g / cm ³ , and the internal stress was 35 MPa.

  The elasticity modulus of this film by the nanoindentation method was 2.6 GPa, which was lower than that of the siliceous film according to the present invention.

  Furthermore, when the pore diameter of the siliceous film was measured by the X-ray diffuse scattering method, the average pore diameter was 7 nm, which was larger than that of the siliceous film according to the present invention.

[Method of evaluating physical properties of siliceous film]
Dielectric constant Pyrex (registered trademark: manufactured by Dow Corning) glass plate (thickness 1 mm, size 50 mm x 50 mm) was washed thoroughly in the order of neutral detergent, dilute NaOH aqueous solution, dilute H ₂ HO ₄ aqueous solution, and dried. Let An aluminum film is formed on the entire surface of the glass plate by vacuum deposition (thickness: 0.2 μm). After the sample composition solution is applied onto this glass plate by spin coating to form a film, the four corners of the glass plate are rubbed with a cotton swab to remove signals from the electrode (3 mm × 3 mm). Subsequently, it is converted into a siliceous film according to the method of each example. The obtained siliceous film is covered with a stainless steel mask, and an aluminum film is formed by vacuum deposition. There are 18 patterns with a square of 2 mm × 2 mm and a thickness of 2 μm. The capacitance is measured at 100 kHz using a 4192 ALF impedance analyzer (manufactured by Yokogawa, Curette, Packard). Further, an M-44 spectroscopic ellipsometer (manufactured by JA Woollam) is used for measuring the film thickness. As the relative dielectric constant, a value obtained by averaging the values calculated by the following formula is adopted for all 18 patterns.

(Relative permittivity) = (capacitance [pF]) × (film thickness [μm]) / 35.4
The weight of a silicon wafer having a film density of 10.16 cm (4 inches) and a thickness of 0.5 mm is measured with an electronic balance. A sample composition solution is applied thereto by spin coating to form a film, converted into a siliceous film according to the method of each example, and the weight of the silicon wafer with the film is measured again with an electronic balance. The film weight is the difference in weight of the wafer before and after film formation. The film thickness is measured with an M-44 spectroscopic ellipsometer (manufactured by JA Woollam). The film density is calculated according to the following formula.

(Film density [g / cm ³ ]) = (film weight [g]) / (film thickness [μm]) / 0.008
A warp of a silicon wafer having an internal stress diameter of 20.32 cm (8 inches) and a thickness of 1 mm is input to an FLX-2320 laser internal stress measuring instrument (manufactured by Tencor). Further, a sample composition solution was applied onto this silicon wafer by spin coating, and the film was converted into a siliceous film according to the method of each example. After returning to room temperature (23 ° C.), the laser internal stress measurement was performed again. Measure the internal stress with the instrument. The film thickness is measured with an M-44 spectroscopic ellipsometer (manufactured by JA Woollam).

A sample composition solution is applied by spin coating to a silicon wafer having a crack limit film thickness of 10.16 cm (4 inches) and a thickness of 0.5 mm, and converted into a siliceous film according to the method of each example. A sample having a film thickness varied from about 0.5 μm to about 5 μm is prepared by adjusting the solid content concentration of the sample composition solution or the rotation speed of the spin coater during coating. The surface of the film after firing is observed with a microscope (120 times), the presence or absence of cracks in each sample is examined, and the maximum film thickness at which no cracks occur is defined as the crack limit film thickness.

Elastic modulus (nanoindentation method)
A sample composition solution is applied to a silicon wafer having a diameter of 20.32 cm (8 inches) and a thickness of 1 mm by spin coating to form a film, which is converted into a siliceous film according to the method of each example. About the obtained siliceous film | membrane, an elastic modulus is measured with the mechanical characteristic evaluation system for thin films (Nano Indenter DCM by the US MTS systems company).

Etching rate It calculates by processing a siliceous film | membrane using the etching residue peeling liquid described in each example, and remove | dividing the film thickness change amount before and behind the process by processing time. The film thickness is measured with an M-44 spectroscopic ellipsometer (manufactured by JA Woollam).

A sample composition solution is applied to a silicon wafer having a pore diameter measurement diameter of 20.32 cm (8 inches) and a thickness of 1 mm by spin coating to form a film, which is converted into a siliceous film according to the method of each example. About the obtained siliceous film | membrane, a hole diameter is measured by a X-ray diffuse scattering method using the multifunctional X-ray-diffraction apparatus (Rigaku Denki Co., Ltd. product) for ATX-G type surface structure evaluation.

  The present invention provides a porous siliceous film having a stable low dielectric constant, mechanical strength that can withstand the latest fine wiring processes, and various chemical resistances in a balanced manner. By using the porous siliceous film according to the present invention as an interlayer insulating film of a semiconductor device, the integrated circuit can be further highly integrated and multilayered.

  As described above, the present invention is most preferably applied to form an interlayer insulating film in an electronic material such as a semiconductor, but can also be applied to other electronic material elements such as an insulating film under a metal film. Is.

  Moreover, a siliceous film | membrane can also be formed with respect to the solid surface of various materials, such as a metal, ceramics, and wood, using the coating composition of this invention other than an electronic material. According to the present invention, a metal substrate (silicon, SUS, tungsten, iron, copper, zinc, brass, aluminum, etc.) having a siliceous film formed thereon, or a ceramic substrate (silica, alumina) having a siliceous film formed thereon. In addition to metal oxides such as magnesium oxide, titanium oxide, zinc oxide, and tantalum oxide, metal nitrides such as silicon nitride, boron nitride, and titanium nitride, silicon carbide, and the like are provided.

Claims (6)

  A coating composition comprising a polyalkylsilazane compound, a siloxy group-containing polymer, and an organic solvent.   The coating composition according to claim 1, wherein the siloxy group-containing polymer includes a polymer unit selected from the group consisting of acrylic acid, methacrylic acid, and a polyethylene oxide compound. The polyalkylsilazane compound comprises a repeating unit represented by the following general formula (1) and at least one unit represented by the general formula (2) or (3). The coating composition according to any one of the above.

(In the above formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, but not all R ^{1 in the} entire compound are simultaneously hydrogen,
R ^{2 to} R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, but all of R ^{2 to} R ⁴ are not simultaneously hydrogen,
p, q, and r are each 0 or 1, 0 ≦ p + q + r ≦ 3,
R ^{5 to} R ⁷ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, but all R ⁵ and R ^{6 in the} entire compound are not simultaneously hydrogen,
R ^{8 to} R ¹¹ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, but all R ^{9 to} R ^{11 in the} entire compound are not simultaneously hydrogen. )   A siliceous material formed by applying the coating composition according to any one of claims 1 to 3 on a substrate, filling a mold or groove, and further firing. .   A semiconductor device comprising the siliceous material according to claim 4 as an interlayer insulating film.   The coating composition according to any one of claims 1 to 3, wherein the coating composition is pre-fired at a temperature of 50 to 300 ° C in a steam-containing atmosphere, and further fired at a temperature of 300 to 500 ° C in a dry atmosphere. , Production method of siliceous material.