JP2007053300A - Silica-based film, method for manufacturing the same, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica-based film which is excellent in a dielectric constant and a Young's modulus representing a film strength, and in particular, a method for forming the silica-based film which has a relative dielectric constant having a small value of 2.7 or less, and also, a strength characteristic in which the Young's modulus representing the film strength can endure a production process of a semiconductor wiring layer. <P>SOLUTION: (i) A coating agent for forming the silica-based film is coated on a substrate, (ii) the substrate after coating is heated, and (iii) active energy lines are irradiated on the substrate after heating in the atmosphere containing a substance which can stabilize unpaired electrons of silicon to obtain the silica-based film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a silica-based coating. More specifically, the present invention relates to a silica-based film that can be used as an insulating film of a semiconductor device.

  Conventionally, a decrease in signal propagation speed (that is, wiring delay) due to the parasitic capacitance of the insulating film has been known. However, in the generation in which the wiring interval of the semiconductor device is 1 μm or more, the influence of the wiring delay on the entire device is small. However, when the wiring interval is 1 μm or less, the influence on the device speed is increasing. Especially when a circuit is formed with a wiring interval of 100 nm or less in the future, the parasitic capacitance between the wirings greatly affects the signal propagation speed of the device. It becomes.

  The wiring delay (T) is affected by the wiring resistance (R) and the capacitance (C) between the wirings, and is expressed by the following equation (1).

T∝CR (1)
On the other hand, the relationship between ε (dielectric constant) and C is expressed by equation (2).

C = ε ₀ ε _r S / d (2)
(S is the electrode area, ε ₀ is the dielectric constant of the vacuum, ε _r is the dielectric constant of the insulating film, and d is the wiring interval)
Therefore, reducing the dielectric constant of the insulating film is an effective means for reducing the wiring delay.
JP-A-9-315812 (Claims) International Application Publication WO 00/18847 (Claims) International Application Publication WO 00/12640 (Claims) Japanese Patent Laid-Open No. 14-30249 (Claims)

  However, in order to reduce the dielectric constant of an insulating film, since holes are incorporated in the insulating film or organic materials are used, there is a problem that the strength of the film generally tends to be insufficient. For example, in the semiconductor device formation process, there are several processes that are mechanically stressed, such as a CMP (Chemical Mechanical Polishing) process for forming a copper wiring and a wire bonding process for taking an electrode from a pad. The breakdown inside the insulating film is likely to occur during the manufacture of semiconductor devices, which is a major cause of yield and reliability degradation.

When we conducted intensive research to solve these problems,
(A) A coating liquid for forming a low dielectric constant silica-based film containing polysiloxane which is a reaction product of alkoxysilane and / or halogenated silane or a hydrolyzate thereof and silica fine particles (see, for example, Patent Document 1),
(B) A coating liquid for forming a low dielectric constant silica-based film comprising an alkoxysilane and / or a halogenated silane or a hydrolyzate thereof and a readily decomposable resin that decomposes or volatilizes at a temperature of 500 ° C. or less (for example, patent documents) 2).
(C) Low dielectric constant containing alkoxysilane and / or halogenated silane or polysiloxane which is a reaction product of these hydrolyzate and silica fine particles, and an easily decomposable resin which decomposes or volatilizes at a temperature of 500 ° C. or lower. A coating solution for forming a silica-based film (see, for example, Patent Document 3),
(D) A coating liquid for forming a low dielectric constant silica-based film containing an alkoxysilane and / or a halogenated silane or a hydrolyzate thereof and an organic template agent (see, for example, Patent Document 4).
Etc., the dielectric constant is as small as 3 or less, and it is excellent in chemical resistance such as adhesion to the coated surface, coating strength, base resistance, crack resistance, and smoothness of the coating surface. It was found that a film having excellent process compatibility such as oxygen plasma property and etching processability can be formed.

  However, when these coating solutions were repeatedly tested to form a low dielectric constant silica-based coating on various semiconductor substrates using a conventionally known coating formation method (spin coating method or other coating method), Although a film having the following characteristics can be obtained, if a film having a relative dielectric constant of 2.7 or less is formed, the film strength is lowered, and the value more than 6.0 GPa (gigapascal), which has been requested from the recent semiconductor manufacturing industry. It has been found that it is difficult to stably obtain a material having a Young's modulus.

  The present invention solves the above-described problems, and provides a novel method for forming a silica-based film excellent in dielectric constant and Young's modulus representing film strength, and a dielectric constant as small as 2.7 or less, and further represents film strength. It is an object of the present invention to provide a method for forming a silica-based coating film having a strength characteristic that allows Young's modulus to withstand a semiconductor wiring layer manufacturing process. Still other objects and advantages of the present invention will become apparent from the following description.

According to one aspect of the invention,
(I) Applying a silica-based film-forming coating solution on a substrate;
(Ii) heat-treating the substrate after application;
(Iii) There is provided a method for producing a silica-based coating, which comprises irradiating the substrate after heating with active energy rays in an atmosphere containing a substance capable of stabilizing unpaired electrons of silicon. According to the embodiment of the present invention, a novel method for forming a silica-based film excellent in dielectric constant and Young's modulus representing film strength is provided. If the conditions are selected, there can be obtained a method for forming a silica-based film having a relative dielectric constant as small as 2.7 or less and a Young's modulus representing the film strength with strength characteristics that can withstand the semiconductor wiring layer manufacturing process.

The coating liquid for forming a silica-based film is an alkoxysilane or a hydrolyzate of a substituted alkoxysilane in which a halogen atom is bonded directly to silicon or a hydrogen atom of a hydrocarbon group bonded directly to silicon may be substituted with a halogen atom. The coating solution for forming a silica-based film contains a hydrolyzate of at least one compound selected from the group consisting of the compound represented by the following general formula (I) and the compound represented by (II): ,
_{Xa n Si (OR) 4-} n ··· (I)
Xb {Si (OR) ₃ } ₂ (II)
(In the formulas (I) and (II), Xa represents an iodine atom, a bromine atom, a hydrocarbon group having 3 or more carbon atoms, an aryl group, a vinyl group, or one or more hydrogen atoms represented by a bromine atom or an iodine atom. Xb represents a hydrocarbon group having 3 or more carbon atoms, or a hydrocarbon group in which one or more hydrogen atoms have been substituted with iodine or bromine, and R represents each formula and each formula. Each independently represents a hydrogen atom, an aliphatic group having 1 to 8 carbon atoms, an alicyclic group having 1 to 8 carbon atoms, an aryl group, or a vinyl group, and n is independently 0 to 3 for each formula. Is an integer.)
The coating liquid for forming a silica-based film is at least selected from the group consisting of a compound represented by the following general formula (I), a compound represented by the following general formula (II), and a compound represented by the following general formula (III). Including a silicon compound obtained by hydrolyzing one compound and tetraalkylorthosilicate (TAOS) in the presence of tetraalkylammonium hydroxide (TAAOH);
_{Xa n Si (OR) 4-} n ··· (I)
Xb {Si (OR) ₃ } ₂ (II)
Xc _n Si (OR) _4-n (III)
(In the formulas (I), (II), and (III), Xa represents an iodine atom, a bromine atom, a hydrocarbon group having 3 or more carbon atoms, an aryl group, a vinyl group, or one or more hydrogen atoms as a bromine atom. Alternatively, a hydrocarbon group substituted with an iodine atom, Xb represents a hydrocarbon group having 3 or more carbon atoms, or a hydrocarbon group in which one or more hydrogen atoms are substituted with iodine or bromine, Xc represents a hydrogen atom, Represents a fluorine atom, an alkyl group having 1 to 8 carbon atoms or a fluorine-substituted alkyl group, wherein R represents a hydrogen atom, an aliphatic group having 1 to 8 carbon atoms, or 1 carbon atom independently for each formula or in each formula; Represents an alicyclic group, an aryl group, or a vinyl group of ˜8, and n is an integer of 0 to 3 independently for each formula.
In particular, Xa of the general formula (I) is
(A) having 4 or more carbon atoms (b) containing tertiary or quaternary carbon (c) having at least one of iodine and bromine atoms (d) cyclic structure A hydrocarbon group satisfying any of the above, in particular, the substance capable of stabilizing the unpaired electrons of silicon is a hydrocarbon having 1 to 8 carbon atoms, and the hydrocarbon has 1 to 3 carbon atoms. Preferably, the hydrocarbon has an unsaturated bond, and the hydrocarbon is methane, ethane, ethylene or a mixture containing these. Moreover, the wavelength of the active energy ray used for the active energy ray irradiation is in a range of 150 to 500 nm, in particular, the wavelength of the active energy ray used for the active energy ray irradiation is in a range of 350 to 500 nm, Or it is preferable that it exists in the range of 200-300 nm.

  According to the other one aspect | mode of this invention, the silica-type film manufactured using said manufacturing method of a silica-type film is provided. According to the embodiment of the present invention, a silica-based film having excellent dielectric constant and Young's modulus can be realized. This silica-based film can be used as an insulating film of a semiconductor device.

  The average diameter of vacancies in the obtained silica-based coating is 1 nm or less, and the ratio of the volume of vacancies to 1 nm or less in the total pore volume is 70% or more. The relative dielectric constant is preferably 2.7 or less.

  According to yet another aspect of the present invention, a semiconductor device comprising the above silica-based coating is provided. According to the aspect of the present invention, a semiconductor device having a high response speed can be obtained.

  According to the present invention, a novel method for forming a silica-based film excellent in dielectric constant and Young's modulus representing film strength is provided. This silica-based film can be used as an insulating film of a semiconductor device. If the conditions are selected, there can be obtained a method for forming a silica-based film having a relative dielectric constant as small as 2.7 or less and a Young's modulus representing the film strength with strength characteristics that can withstand the semiconductor wiring layer manufacturing process. By these methods, a silica-based film excellent in dielectric constant and Young's modulus can be realized, and a semiconductor device having a high response speed can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, tables, formulas, examples and the like. In addition, these figures, tables, formulas, examples, etc., and explanations exemplify the present invention, and do not limit the scope of the present invention. It goes without saying that other embodiments may belong to the category of the present invention as long as they match the gist of the present invention. In order to avoid complication, in FIG. 1 to FIG.

In the method for producing a silica-based film according to the present invention,
(I) Applying a silica-based film-forming coating solution on a substrate;
(Ii) heat-treating the substrate after application;
(Iii) Irradiating the substrate after heating with active energy rays in an atmosphere containing a substance capable of stabilizing unpaired electrons of silicon is included.

  According to the present invention, a silica-based coating excellent in dielectric constant and Young's modulus representing coating strength can be obtained. If conditions are selected, the relative dielectric constant is as small as 2.7 or less, and the Young's modulus representing coating strength is further reduced to semiconductor wiring. A method for forming a silica-based film having strength characteristics that can withstand the layer production process is obtained. This is probably because pores of a molecular level are generated by combining the heat treatment and the active energy ray treatment after applying the silica-based film-forming coating solution on the substrate. . In addition, by using a coating liquid for forming a silica-based film, excellent hydrophobicity can be realized as a film, and a smooth film is often obtained by this treatment method.

  The substrate material that can be used in the present invention is not particularly limited, and examples thereof include a general silicon substrate, a gallium arsenide substrate, and an indium phosphorus substrate. Before applying the coating liquid for coating formation on the semiconductor substrate, the surface of the semiconductor substrate is treated with a silane coupling agent, ozone water, UV, X-rays, electron beam, etc. for the purpose of improving adhesion strength. Also good. A known treatment method is used.

  As a coating liquid for forming a silica-based film according to the present invention, any liquid may be used as long as it contains a material (silica-based film forming material) that can form a silica-based film as a result. “Silica-based coating” means a coating made of a crosslinked structure having a skeleton of silicon and oxygen. The molar ratio of oxygen to silicon (O / Si) is preferably 1.5 or more. As other components, carbon, hydrogen, fluorine and the like may coexist. Carbon is preferably 15% by weight or less, hydrogen is 4% by weight or less, and fluorine is 27% by weight or less. The silica-based film is generally amorphous.

  The silica-based film-forming material according to the present invention can be selected from siloxane compounds and derivatives thereof, and alkoxysilane or a hydrocarbon group hydrogen directly bonded to silicon or bonded to silicon is a halogen atom. The hydrolyzate of the substituted alkoxysilane which may be substituted by can be mentioned. More specifically, illustrating a hydrolyzate of at least one compound selected from the group consisting of the compound represented by the general formula (I), the compound represented by (II) and the compound represented by (III) Can do.

_{Xa n Si (OR) 4-} n ··· (I)
Xb {Si (OR) ₃ } ₂ (II)
Xc _n Si (OR) _4-n (III)
In the formulas (I), (II) and (III), Xa represents an iodine atom, a bromine atom, a hydrocarbon group having 3 or more carbon atoms, an aryl group, a vinyl group, or one or more hydrogen atoms as a bromine atom or This represents a hydrocarbon group substituted with an iodine atom. Xb represents a hydrocarbon group having 3 or more carbon atoms or a hydrocarbon group in which one or more hydrogen atoms are substituted with iodine or bromine. Xc represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 8 carbon atoms or a fluorine-substituted alkyl group. R represents a hydrogen atom, an aliphatic group having 1 to 8 carbon atoms, an alicyclic group having 1 to 8 carbon atoms, an aryl group, or a vinyl group independently for each formula and in each formula. n is an integer of 0 to 3 independently for each formula. With such a material, it is possible to obtain a silica-based film having pores large enough to lower the dielectric constant and having a high strength.

  When Xc is a fluorine atom, the Xc-Si bond is not decomposed by active energy rays, and fluorine is contained in the generated silica-based film. However, the presence of fluorine reduces the dielectric constant. Since it contributes, it may be preferable. Accordingly, in at least one compound selected from the group consisting of the compound represented by the general formula (I), the compound represented by (II) and the compound represented by (III), the compound represented by (III) is It may be preferable that it is contained.

  The compounds represented by the general formula (I) include iodotriethoxysilane, bromotriethoxysilane, propyltriethoxysilane, isobutyltriethoxysilane, n-octadecyltrimethoxysilane, cyclohexyltrimethoxysilane, phenyltriethoxysilane, 3- Bromopropyltrimethoxysilane and 3-iodopropyltrimethoxysilane are represented by (II), and bis (triethoxysilyl) propane and bis (triethoxysilyl) 2-iodopropane are represented by (III). Examples of the compound include triethoxysilane, fluorotriethoxysilane, methyltriethoxysilane, and (3,3,3-trifluoropropyltrimethoxysilane).

  In addition to the above alkoxysilane or substituted alkoxysilane, the compound represented by the general formula (I), the compound represented by (II) and the compound represented by (III), other compounds may be allowed to coexist. For example, coexistence of alkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, etc. may increase the degree of crosslinking and improve the mechanical strength.

  The hydrolyzate according to the present invention can be obtained by dissolving an appropriate compound in a solvent and adding water and preferably an acidic substance or a basic substance thereto. The system may be heated to promote hydrolysis, but is generally possible at room temperature.

  The acidic substance or basic substance to be used is not particularly limited, but those that do not remain in the film in the subsequent treatment or do not have a chemical effect even if they remain are preferable. Specifically, nitric acid and tetraalkylammonium hydroxide (TAAOH) can be exemplified.

  Regarding the type and amount of the silica-based film forming material, other compounds, acidic substances, and basic substances used, the properties of the resulting film, such as mechanical strength and relative dielectric constant, should be in the desired ranges. It can be selected appropriately. It is not necessary to actually check how much the hydrolysis has progressed, and it is sufficient to appropriately determine the reaction time in view of the influence on the mechanical strength and relative dielectric constant. The mechanical strength is preferably 4 GPa or more and the relative dielectric constant is 2.7 or less. Furthermore, the mechanical strength is desirably 6 GPa or more in order to reduce yield reduction due to breakage during the process.

  The coating liquid for forming a silica-based film according to the present invention contains a solvent in addition to the above-described material for forming a silica-based film. The solvent may be selected from any solvents that can dissolve the silica-based film-forming material according to the present invention and have a boiling point to the extent that a film is formed by the treatment of the present invention.

  Examples of the solvent include alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, and tert-butyl alcohol, phenol, cresol, diethylphenol, triethylphenol, propylphenol, nonylphenol, vinyl Phenols such as phenol, allylphenol and nonylphenol, ketones such as cyclohexanone, methyl isobutyl ketone and methyl ethyl ketone, cellosolvs such as methyl cellosolve and ethyl cellosolve, hydrocarbons such as hexane, octane and decane, propylene glycol, propylene glycol monomethyl Ether, propylene glycol monoethyl ether, propylene glycol monop Pills ether, propylene glycol monobutyl ether, etc. glycol and water, such as propylene glycol monomethyl ether acetate. One of the above may be used as the solvent, or some of the above solvents may be mixed.

  More preferable examples of the coating solution for forming a silica-based film according to the present invention include, more specifically, a compound represented by the general formula (I), a compound represented by the general formula (II), and the general formula (III). A silicon compound obtained by hydrolyzing at least one compound selected from the group consisting of the following compounds and tetraalkylorthosilicate (TAOS) in the presence of tetraalkylammonium hydroxide (TAAOH). It is done. In this case, at least one compound selected from the group consisting of the compound represented by the general formula (I), the compound represented by the general formula (II) and the compound represented by the general formula (III) is propyltriethoxysilane. , Isobutyltriethoxysilane, n-octadecyltrimethoxysilane, cyclohexyltrimethoxysilane, (2,2-dimethylpropyl) triethoxysilane, and examples of the solvent include water, methyl alcohol, ethyl alcohol, propyl alcohol, Mention may be made of isopropyl alcohol, dimethyl ketone, methyl isobutyl ketone, propylene glycol, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monomethyl ether acetate. .

  There are no particular restrictions on the method of application on the substrate. For example, the method of apply | coating the said coating liquid on a board | substrate by a spin coat method can be illustrated.

  There is no restriction | limiting in particular also about the conditions of heat processing, A hot plate, a heating furnace, and a hot stove can be illustrated. Since the solvent is removed by the heat treatment and a film having a cross-linked structure is generated by curing, conditions for obtaining a cross-linked structure to the extent of giving desired mechanical strength can be selected. In addition, although the void | hole which is useful for a low dielectric constant also arises by heat processing, since the particle size is large in many cases and a mechanical property becomes easy to deteriorate correspondingly, it is often disadvantageous. Therefore, it is more preferable to select a heat treatment condition that does not easily generate vacancies and gives desired mechanical strength. Examples thereof include a method in which the solvent is dried at 100 ° C. to 250 ° C. and then cured by heat treatment at 250 ° C. to 400 ° C.

  Thereafter, by irradiating with active energy rays, the silica-based film-forming material is decomposed and pores having a molecular level are generated. For example, in the case of general formulas (I), (II), and (III), Xa-Si, Xb-Si, Xc-Si bonds, etc. are decomposed to generate vacancies of molecular level. it is conceivable that. As a result, it is possible to reduce the dielectric constant. Examples of active energy rays include visible light, ultraviolet rays, X-rays, and electron beams. When using visible light and ultraviolet rays as active energy rays for irradiation, the wavelength is preferably in the range of 150 to 500 nm. This is because the decomposition is efficiently performed by using such active energy rays. Furthermore, in order to suppress the possibility of dissociation of bonds such as silicon-oxygen, the wavelength of the active energy ray is more preferably 200 nm or more. When the silicon-oxygen bond is dissociated, silanol groups are generated to increase the hygroscopicity, resulting in a problem that the dielectric breakdown voltage is lowered and further the divergence proceeds to cause the breakdown of the insulating film.

  The active energy ray irradiation according to the present invention is performed in an atmosphere containing a substance capable of stabilizing unpaired electrons of silicon. For this purpose, it is preferable to perform active energy ray irradiation in a suitable container such as a vacuum chamber. The atmosphere in that case may be a so-called reduced pressure state.

  The role of the substance that can stabilize the unpaired electrons of silicon is the problem of rapidly capturing silicon radicals that occur during irradiation with active energy rays and reacting with moisture in the atmosphere to generate SiOH to increase the dielectric constant. It is believed to be an avoidance.

For example, when methane is used as a substance that can stabilize unpaired electrons in silicon,
During active energy ray irradiation,
Si-R → Si ・ + R ・
Silicon radicals (unpaired electrons) generated by the decomposition reaction of
Si · + CH ₄ → SiCH ₃ + H ·
Stabilized by
Si · + H ₂ O → SiOH + H ·
This reaction is prevented.

  The substance that can stabilize the unpaired electrons of silicon can be appropriately selected from substances that can capture silicon radicals. It is not necessary to confirm whether or not silicon unpaired electrons are actually stabilized when used in the method of the present invention. If a decrease in dielectric constant is observed as a result of employing a certain substance, the silicon according to the present invention It can be considered as a substance that can stabilize unpaired electrons. For example, a hydrocarbon can be mentioned.

  For example, when hydrocarbons are introduced, for example, the Xa-Si, Xb-Si, and Xc-Si bonds of the general formulas (I), (II), and (III) are decomposed by active energy rays to generate unpaired electrons of Si. Substituting the hydrogen of the hydrocarbon to form an alkyl group or the like, which can prevent an increase in dielectric constant due to the generation of a silanol group or the like. The hydrocarbon has preferably 1 to 8 carbon atoms, more preferably 1 to 3 carbon atoms.

  When the introduced gas has an unsaturated bond, it is more preferable because the decomposition reaction occurs and the dissociation of the silicon-oxygen bond can be prevented even if the wavelength of the irradiation active energy ray is 350 to 500 nm. It becomes a condition.

  It may be preferable to irradiate an active energy ray of 200 to 300 nm. Even when there is no unsaturated bond, the above decomposition reaction is efficiently performed. For example, the Xa-Si, Xb-Si, and Xc-Si bonds of the general formulas (I), (II), and (III) are active energy rays. It is possible to eliminate unpaired electrons such as Si without reducing the size of the vacancies generated by decomposition by the above, to reduce the dielectric constant more effectively, and to dissociate the silicon-oxygen bond. This is because there are cases where it can be suppressed. This is a particularly preferable condition when the gas to be introduced is methane, ethane or ethylene. In the case of ethylene, although it is a preferable condition when the wavelength of the irradiation active energy ray is in the range of 350 to 500 nm, it is generally more preferable to irradiate the active energy ray of 200 to 300 nm.

  In addition, about Xa of the said general formula (I), (a) it has 4 or more carbon atoms, (b) it contains tertiary or quaternary carbon, (c) an iodine atom and a bromine atom It is preferable to have at least one of at least one of them, and (d) to have a cyclic structure. If the number of carbon atoms is 4 or more, the size of the vacancies to be generated increases, so that the dielectric constant can be reduced. If a tertiary or quaternary carbon is included, the Si-C bond energy decreases. Decomposition reaction due to irradiation with active energy rays is likely to occur, and if there are iodine atoms or bromine atoms, decomposition reaction due to irradiation with active energy rays is likely to occur. An example having 4 or more carbon atoms is n-octadecyltriethoxysilane, an example containing tertiary or quaternary carbon is (2,2-dimethylpropyl) triethoxysilane, an iodine atom and a bromine atom. Examples of having at least one of these are 3-bromopropyltrimethoxysilane and 3-iodopropyltrimethoxysilane, and examples having a cyclic structure are cyclohexyltrimethoxysilane and phenyltriethoxysilane. Can do. The cyclic structure can include both alicyclic rings and aromatic rings.

  The silica-based film produced by the method described above can be used as a silica-based film that is excellent in dielectric constant and Young's modulus and can be applied to circuit boards and the like that require high response speed. It can be suitably used as an insulating film. Moreover, a semiconductor device including such a silica-based film as an insulating film, for example, has a high response speed and is excellent in reliability. Accordingly, by adopting the present invention, a low dielectric constant insulating film material having a strength sufficient to maintain sufficient reliability without being destroyed during a process in a highly integrated semiconductor device such as an IC or LSI can be obtained. This makes it possible to produce high performance and highly reliable semiconductor device products.

  The vacancies generated in the silica-based coating produced by the method according to the present invention can be made finer (for example, at the molecular level) compared to the vacancies generated in the conventional silica-based coating. The average diameter thereof is in the range of 1 nm or less, and the ratio of the pore volume of 1 nm or less to the total pore volume is preferably 70% or more in terms of lowering the dielectric constant and maintaining an appropriate Young's modulus. The silica-based film thus produced is preferable because it can easily have a relative dielectric constant of 2.7 or less. The size of the vacancies generated in the silica-based film can be measured by a small angle scattering X-ray diffraction method.

  Next, examples and comparative examples of the present invention will be described in detail.

[Example 1]
20.8 g (0.1 mol) of tetraethoxysilane, 22.0 g (0.1 mol) of isobutyltriethoxysilane, and 42.8 g of dimethyl ketone were charged into a 200 mL reaction vessel, and then 400 ppm by weight of nitric acid was added to the reaction vessel. An aqueous solution (15.1 g) was added dropwise over 10 minutes, and after completion of the addition, an aging reaction was performed for 2 hours to obtain a hydrolyzate. 50 mL of dimethyl ketone was added to the obtained reaction solution to prepare a coating solution for forming a silica-based film.

The prepared coating solution for forming a silica-based film is spin-coated on a low resistance silicon substrate, prebaked at 250 ° C. for 3 minutes, and then 950 cm ⁻¹ using FT-IR (Fourier transform infrared spectroscopy). When calculated from the absorption strength of nearby SiOH, the crosslinking rate was 75%.

Next, it was heated in an electric furnace in an N ₂ gas atmosphere at 400 ° C. for 30 minutes and further cured. This pre-baking and heating correspond to the heat treatment according to the present invention.

  Subsequently, UV irradiation was performed in a vacuum chamber except for No. 1. After the vacuum chamber was once evacuated, a gas (ethylene, methane, or air) was introduced so that the chamber pressure became a predetermined pressure during the ultraviolet irradiation, and the atmosphere was introduced after exhausting the gas after irradiation.

  Table 1 shows the characteristics of the obtained film. The relative dielectric constant was calculated from the capacity measured with a mercury probe (CVmap92A, Four Dimensions Inc.), and the Young's modulus was measured by an indentation method (Nano Indenter XP, Nano Instruments, Inc.) in which a needle with a triangular pyramid was pushed. Table 1 shows the vacuum chamber pressure, the wavelength of ultraviolet light, and the ultraviolet irradiation time during ultraviolet irradiation.

  Numbers 2-8 and 10-13 are examples. No. 1 is a comparative example in which ultraviolet irradiation was not performed, and No. 9 is a comparative example in which ultraviolet irradiation was performed in an atmosphere not containing a substance capable of stabilizing silicon unpaired electrons. Each of the examples is excellent in the dielectric constant and the Young's modulus representing the film strength. In particular, Nos. 2 to 8, 10, 12, and 13 have a sufficiently low Young's modulus and a sufficient Young's modulus as compared with the comparative examples.

  The obtained film was amorphous and was formed of silicon, oxygen, carbon, and hydrogen. Moreover, when the hole of number 6 was measured by the small angle scattering X-ray diffraction method, the average diameter was 0.7 nm.

［例２］
本例は、誘電率を低減させる目的で、例１とは異なる組成・作成方法で作成したシリカ系被膜形成用塗布液を使用した実施例である。

[Example 2]
In this example, for the purpose of reducing the dielectric constant, a silica-based coating-forming coating solution prepared by a composition / preparation method different from Example 1 is used.

  20.8 g (0.1 mol) of tetraethoxysilane, 17.8 g (0.1 mol) of methyltriethoxysilane, 22.0 g (0.1 mol) of isobutyltriethoxysilane, and 39.6 g of methyl isobutyl ketone were placed in a 200 mL reaction vessel. Then, 16.2 g (0.9 mol) of a 1% by weight tetramethylammonium hydroxide aqueous solution was dropped into this reaction vessel over 10 minutes, and after completion of the dropwise addition, an aging reaction was performed for 2 hours to obtain a hydrolyzate. Obtained.

  Next, 5 g of magnesium sulfate was added to remove excess water, and then the ethanol produced by the aging reaction was removed with a rotary evaporator until the reaction solution reached 50 mL. 20 mL of methyl isobutyl ketone was added to the obtained reaction solution to prepare a coating solution for forming a silica-based film.

The silica-based film-forming coating solution was spin-coated on a low-resistance silicon substrate, pre-baked at 250 ° C. for 3 minutes, and then calculated from the absorption intensity of SiOH near 950 cm ⁻¹ using FT-IR. The crosslinking rate was 75%.

Next, curing was performed at 400 ° C. for 30 minutes in an N ₂ gas atmosphere electric furnace. Subsequently, ultraviolet irradiation was performed in a vacuum chamber. The ultraviolet irradiation conditions are the same as those in Example 1.

  After irradiation, the chamber was evacuated and the atmosphere was introduced. When the relative dielectric constant of the obtained film was calculated from the capacity measured with a mercury probe, it was 2.0, and the Young's modulus was 7 GPa as measured by the indentation method.

[Example 3]
This example is an example in which the present invention is used to fabricate a semiconductor wiring layer. 1 to 17 show the manufacturing method. First, a transistor layer was formed on the Si wafer 1 by forming the gate electrode 4 having the source diffusion layer 5a, the drain diffusion layer 5b, and the sidewall insulating film 3 separated by the element isolation film 2 (FIG. 1). . Then, an interlayer insulating film 6 (phosphorous glass) and a stopper film 7 were formed thereon (FIG. 2), and contact holes 19 for electrode extraction were formed (FIG. 3).

After forming 50 nm of TiN8 on this contact hole by sputtering (FIG. 4), WF ₆ and hydrogen were mixed and reduced to embed a conductor plug 9 (FIG. 5), and parts other than vias were removed by CMP. (FIG. 6). Subsequently, a film was formed under the condition of 250 nm on the Si flat plate by the method of No. 6 in Example 1 to form a silica-based film (wiring isolation insulating film) 10 and then manufactured from TEOS (tetraethylorthosilicate). The protective film 11 made of SiO ₂ was laminated to 50 nm (FIG. 7).

This film was processed by F plasma using CF ₄ / CHF ₃ gas as a raw material, using a resist layer for obtaining a wiring pattern as a mask, to form a first layer wiring groove 20 (FIG. 8). In this wiring groove 20, TiN 8 ′ serving as a diffusion barrier to the Cu insulating layer was formed by sputtering and a seed layer 21 (Cu, 50 nm thickness) serving as an electrode during electrolytic plating was formed by sputtering (FIG. 9). Further, after Cu600 was deposited to 600 nm by electrolytic plating (FIG. 10), metal other than the wiring pattern portion was removed by CMP to form a wiring layer 22 (FIG. 11).

Next, a dual damascene method for simultaneously forming a via layer and a wiring layer will be described. As a stopper film for preventing Cu diffusion, a SiN film 12 of 50 nm was deposited by plasma CVD using silane and ammonia gas, and a 250 nm of SiOC film 13 formed by plasma CVD was laminated on the first wiring layer. . Further, the SiN film 14 is formed as a stopper film by plasma CVD using silane and ammonia gas to a thickness of 50 nm, and then the film is formed on the Si flat plate by the method of Example 6 under the condition of 400 nm, After the silica-based coating 15 was formed, a protective film 16 made of SiO ₂ made of TEOS was laminated to 50 nm (FIG. 12).

With respect to this film, a protective layer 16 / silica-based coating 15 / SiN film 14 / by changing the gas composition by F plasma using CF ₄ / CHF ₃ gas as a raw material with a resist layer for obtaining a via pattern as a mask. The SiOC film 13 / SiN film 12 were processed in this order (FIG. 13). Subsequently, the resist layer for obtaining the second layer wiring pattern was used as a mask, and further processed by F plasma using CF ₄ / CHF ₃ gas as a raw material (FIG. 14).

  In this via 23 and the wiring groove 24, TiN8 ″ that works as a diffusion barrier to the insulating layer of Cu and 50 nm of seed layer Cu25 that works as an electrode during electrolytic plating are formed by sputtering (FIG. 15). After Cu 1400 nm was deposited by plating (FIG. 16), the metal other than the wiring pattern portion was removed by CMP to form wiring and vias (FIG. 17) The following steps were repeated to form a three-layer wiring.

  The yield of 1 million continuous vias using the prototype multilayer wiring was 95% or more. Moreover, when wire bonding was performed, no destruction was observed due to bonding pressure. It was 3.0 when the effective dielectric constant was calculated by measuring the comb-tooth pattern.

[Example 4]
This example is an example not including the compound represented by the general formula (I), the compound represented by (II) and the compound represented by (III). 20.8 g (0.1 mol) of tetraethoxysilane, 17.8 g (0.1 mol) of methyltriethoxysilane, and 38.6 g of dimethyl ketone were charged into a 200 mL reaction vessel, and 15.1 g of 400 wt ppm nitric acid aqueous solution was added for 10 minutes. And a ripening reaction was performed for 2 hours after completion of the dropping to obtain a hydrolyzate. 50 mL of dimethyl ketone was added to the resulting reaction solution to prepare a coating solution for forming a wiring separation layer coating.

The prepared coating solution was spin-coated on a low-resistance silicon substrate, pre-baked at 250 ° C. for 3 minutes, and calculated from the absorption intensity of SiOH near 950 cm ⁻¹ using FT-IR. 75%.

Next, curing was performed at 400 ° C. for 30 minutes in an N ₂ gas atmosphere electric furnace. Subsequently, ultraviolet irradiation was performed in a vacuum chamber. The ultraviolet irradiation conditions are the same as those in Example 1.

  After irradiation, the chamber was evacuated and the atmosphere was introduced. The relative dielectric constant of the obtained film was 3.31 as calculated from the capacity measured with a mercury probe, and the Young's modulus was 20 GPa as measured by the indentation method.

[Example 5]
This example is a comparative example in which active energy ray irradiation is not performed. In Example 3, when the silica-based coatings 10 and 15 were formed, the number 1 condition of Example 1 was adopted to form a multilayer wiring. The yield of 1 million continuous vias using a prototype multilayer wiring was 95% or more. Moreover, when wire bonding was performed, no destruction was observed due to bonding pressure. The effective relative permittivity was calculated by measuring the comb tooth pattern and found to be 3.3.

[Example 6]
This example is a comparative example in which the active energy ray irradiation conditions do not satisfy the conditions of the present invention. In Example 3, the multilayer wiring was formed by adopting the condition of No. 9 in Example 1 when forming the silica-based films 10 and 15. The yield of 1 million continuous vias using a prototype multilayer wiring was 95% or more. Moreover, when wire bonding was performed, no destruction was observed due to bonding pressure. It was 5.7 when the effective dielectric constant was calculated by measuring the comb-tooth pattern.

[Example 7]
A coating solution was prepared using 18.4 g (0.05 mol) of bis (triethoxysilyl) propane instead of 22.0 g (0.1 mol) of isobutyltriethoxysilane of Example 1, and the conditions of No. 6 in Example 1 Was used to produce a film. The obtained film had a relative dielectric constant of 2.42 and a Young's modulus of 9 GPa.

[Example 8]
A coating solution was prepared using 33.2 g (0.1 mol) of 3-iodopropyltrimethoxysilane instead of 22.0 g (0.1 mol) of isobutyltriethoxysilane of Example 1, and the conditions of No. 6 in Example 1 Was used to produce a film. The obtained film had a relative dielectric constant of 2.20 and a Young's modulus of 8 GPa.

  In addition, the invention shown to the following additional remarks can be derived from the content disclosed above.

(Appendix 1)
(I) Applying a silica-based film-forming coating solution on a substrate;
(Ii) heat-treating the substrate after application;
(Iii) A method for producing a silica-based coating, comprising irradiating the heated substrate with active energy rays in an atmosphere containing a substance capable of stabilizing unpaired electrons of silicon.

(Appendix 2)
The coating liquid for forming a silica-based film is an alkoxysilane or a hydrolyzate of a substituted alkoxysilane in which a halogen atom is bonded directly to silicon or a hydrogen atom of a hydrocarbon group bonded directly to silicon may be substituted with a halogen atom. The manufacturing method of the silica-type coating film of Claim 1 containing this.

(Appendix 3)
Additional remark 1 or 2 wherein the coating liquid for forming a silica-based film contains a hydrolyzate of at least one compound selected from the group consisting of the compound represented by the following general formula (I) and the compound represented by (II) The manufacturing method of the silica-type coating film as described in any one of.

_{Xa n Si (OR) 4-} n ··· (I)
Xb {Si (OR) ₃ } ₂ (II)
(In the formulas (I) and (II), Xa represents an iodine atom, a bromine atom, a hydrocarbon group having 3 or more carbon atoms, an aryl group, a vinyl group, or one or more hydrogen atoms represented by a bromine atom or an iodine atom. Xb represents a hydrocarbon group having 3 or more carbon atoms, or a hydrocarbon group in which one or more hydrogen atoms have been substituted with iodine or bromine, and R represents each formula and each formula. Each independently represents a hydrogen atom, an aliphatic group having 1 to 8 carbon atoms, an alicyclic group having 1 to 8 carbon atoms, an aryl group, or a vinyl group, and n is independently 0 to 3 for each formula. Is an integer.

(Appendix 4)
The coating liquid for forming a silica-based film is at least selected from the group consisting of a compound represented by the following general formula (I), a compound represented by the following general formula (II), and a compound represented by the following general formula (III). The production of a silica-based coating according to appendix 1 or 2, comprising a silicon compound obtained by hydrolyzing one compound and tetraalkylorthosilicate (TAOS) in the presence of tetraalkylammonium hydroxide (TAAOH) Method.

_{Xa n Si (OR) 4-} n ··· (I)
Xb {Si (OR) ₃ } ₂ (II)
Xc _n Si (OR) _4-n (III)
(In the formulas (I), (II), and (III), Xa represents an iodine atom, a bromine atom, a hydrocarbon group having 3 or more carbon atoms, an aryl group, a vinyl group, or one or more hydrogen atoms as a bromine atom. Alternatively, a hydrocarbon group substituted with an iodine atom, Xb represents a hydrocarbon group having 3 or more carbon atoms, or a hydrocarbon group in which one or more hydrogen atoms are substituted with iodine or bromine, Xc represents a hydrogen atom, Represents a fluorine atom, an alkyl group having 1 to 8 carbon atoms or a fluorine-substituted alkyl group, wherein R represents a hydrogen atom, an aliphatic group having 1 to 8 carbon atoms, or 1 carbon atom independently for each formula or in each formula; Represents an alicyclic group, an aryl group, or a vinyl group of ˜8, and n is an integer of 0 to 3 independently for each formula.
(Appendix 5)
Xa in the general formula (I) is
(A) having 4 or more carbon atoms (b) containing tertiary or quaternary carbon (c) having at least one of iodine and bromine atoms (d) cyclic structure The method for producing a silica-based coating according to appendix 3 or 4, which is a hydrocarbon group satisfying any one of the following.

(Appendix 6)
The method for producing a silica-based film according to any one of appendices 1 to 5, wherein the substance capable of stabilizing the unpaired electrons of silicon is a hydrocarbon having 1 to 8 carbon atoms.

(Appendix 7)
The method for producing a silica-based coating according to appendix 6, wherein the hydrocarbon has 1 to 3 carbon atoms.

(Appendix 8)
The method for producing a silica-based coating according to appendix 6 or 7, wherein the hydrocarbon has an unsaturated bond.

(Appendix 9)
The method for producing a silica-based coating according to appendix 6, wherein the hydrocarbon is methane, ethane, ethylene or a mixture containing these.

(Appendix 10)
The method for producing a silica-based coating according to any one of appendices 1 to 9, wherein the wavelength of the active energy ray used for the active energy ray irradiation is in the range of 150 to 500 nm.

(Appendix 11)
The method for producing a silica-based coating according to appendix 10, wherein the wavelength of the active energy ray used for the active energy ray irradiation is in the range of 350 to 500 nm.

(Appendix 12)
The method for producing a silica-based coating according to appendix 10, wherein the wavelength of the active energy ray used for the active energy ray irradiation is in the range of 200 to 300 nm.

(Appendix 13)
A silica-based coating produced using the method for producing a silica-based coating according to any one of appendices 1 to 12.

(Appendix 14)
The silica-based coating according to appendix 13, wherein the average diameter of pores in the obtained silica-based coating is 1 nm or less, and the ratio of the volume of pores of 1 nm or less to the total pore volume is 70% or more.

(Appendix 15)
The silica-based coating according to appendix 13 or 14, wherein the obtained silica-based coating has a relative dielectric constant of 2.7 or less.

(Appendix 16)
A semiconductor device comprising the silica-based film according to any one of appendices 13 to 15.

It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention. It is a typical cross-sectional view which shows the mode of preparation of the wiring layer of the semiconductor which uses the silica-type film concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Si wafer 2 Interelement isolation film 3 Side wall insulating film 4 Gate electrode 5a Source diffusion layer 5b Drain diffusion layer 6 Interlayer insulating film 7 Stopper film 8 TiN
8 'TiN
8 ”TiN
9 Conductor plug 10 Silica-based coating (wiring isolation insulating film)
11 Protective film 12 SiN film 13 SiOC film 14 SiN film 15 Silica film 16 Protective film 17 Cu
18 Cu
19 Contact hole 20 Wiring groove 21 Seed layer 22 Wiring layer 23 Via 24 Wiring groove 25 Seed layer

Claims (5)

(I) Applying a silica-based film-forming coating solution on a substrate;
(Ii) heat-treating the substrate after application;
(Iii) A method for producing a silica-based coating, comprising irradiating the heated substrate with active energy rays in an atmosphere containing a substance capable of stabilizing unpaired electrons of silicon. The said coating liquid for silica-type film formation contains the hydrolyzate of at least 1 compound chosen from the group which consists of the compound shown by the compound shown by the compound shown by the following general formula (I), and (II). The manufacturing method of the silica-type film of description.
_{Xa n Si (OR) 4-} n ··· (I)
Xb {Si (OR) ₃ } ₂ (II)
(In the formulas (I) and (II), Xa represents an iodine atom, a bromine atom, a hydrocarbon group having 3 or more carbon atoms, an aryl group, a vinyl group, or one or more hydrogen atoms represented by a bromine atom or an iodine atom. Xb represents a hydrocarbon group having 3 or more carbon atoms, or a hydrocarbon group in which one or more hydrogen atoms have been substituted with iodine or bromine, and R represents each formula and each formula. Each independently represents a hydrogen atom, an aliphatic group having 1 to 8 carbon atoms, an alicyclic group having 1 to 8 carbon atoms, an aryl group, or a vinyl group, and n is independently 0 to 3 for each formula. Is an integer.) The coating liquid for forming a silica-based film is at least selected from the group consisting of a compound represented by the following general formula (I), a compound represented by the following general formula (II), and a compound represented by the following general formula (III). The method for producing a silica-based coating according to claim 1, comprising a silicon compound obtained by hydrolyzing one compound and tetraalkylorthosilicate (TAOS) in the presence of tetraalkylammonium hydroxide (TAAOH). .
_{Xa n Si (OR) 4-} n ··· (I)
Xb {Si (OR) ₃ } ₂ (II)
Xc _n Si (OR) _4-n (III)
(In the formulas (I), (II), and (III), Xa represents an iodine atom, a bromine atom, a hydrocarbon group having 3 or more carbon atoms, an aryl group, a vinyl group, or one or more hydrogen atoms as a bromine atom. Alternatively, a hydrocarbon group substituted with an iodine atom, Xb represents a hydrocarbon group having 3 or more carbon atoms, or a hydrocarbon group in which one or more hydrogen atoms are substituted with iodine or bromine, Xc represents a hydrogen atom, Represents a fluorine atom, an alkyl group having 1 to 8 carbon atoms, or a fluorine-substituted alkyl group, and R represents a hydrogen atom, an aliphatic group having 1 to 8 carbon atoms, or a carbon number independently for each formula and in each formula. Represents an alicyclic group, aryl group or vinyl group of 1 to 8. n is an integer of 0 to 3 independently for each formula.   The silica-type film manufactured using the manufacturing method of the silica-type film in any one of Claims 1-3.   A semiconductor device comprising the silica-based film according to claim 4.

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