JP2013121892A - Method for preparing porous silica precursor coating liquid - Google Patents
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本発明は、多孔質シリカ膜の形成に用いられる多孔質シリカ前駆体塗布液の作製方法に関する。 The present invention relates to a method for producing a porous silica precursor coating solution used for forming a porous silica film.
近年、例えば半導体デバイスの層間絶縁膜として、例えば比誘電率が２．４以下の多孔質シリカ膜が用いられている。多孔質シリカ膜の形成にはＣＶＤ法や塗布法が用いられているが、簡単な設備で実施することができる塗布法が有望視されている。例えば、特許文献１には、塗布法を用いた多孔質シリカ膜の形成方法が開示されている。このものでは、界面活性剤を添加したアルコキシシラン溶液を触媒存在下で加水分解及び脱水縮合することで前駆体塗布液を作製し、この作製した前駆体塗布液を基材表面に塗布し、この塗布したものを焼成する。これにより、前駆体塗布液に含まれる界面活性剤が除去され、この除去部分が空孔となり、多孔質シリカ膜が形成される。 In recent years, for example, a porous silica film having a relative dielectric constant of 2.4 or less is used as an interlayer insulating film of a semiconductor device, for example. A CVD method or a coating method is used to form the porous silica film, but a coating method that can be carried out with simple equipment is promising. For example, Patent Document 1 discloses a method for forming a porous silica film using a coating method. In this, a precursor coating solution is prepared by hydrolyzing and dehydrating and condensing an alkoxysilane solution to which a surfactant is added in the presence of a catalyst, and the prepared precursor coating solution is applied to the surface of a substrate. The applied one is baked. As a result, the surfactant contained in the precursor coating solution is removed, and the removed portion becomes pores, thereby forming a porous silica film.
このように形成された多孔質シリカ膜には、配線形成工程において、ドライエッチングによりトレンチやホール等の凹部が形成される。そして、エッチング残渣を酸（例えばフッ酸）で除去した後、凹部内に配線材料として例えばＣｕを埋め込み、スラリーを用いたＣＭＰにより平坦化することで配線構造が得られる。ここで、配線構造の形成に用いられる酸やアルカリ（例えばＣＭＰ用スラリー）等の薬液に対し多孔質シリカ膜の耐性が低いと、薬液と接触した空孔のサイズが大きくなり、多孔質シリカ膜の強度が低下すると共に比誘電率が高くなるという不具合が生じる。 In the porous silica film thus formed, recesses such as trenches and holes are formed by dry etching in the wiring formation step. Then, after the etching residue is removed with an acid (for example, hydrofluoric acid), Cu, for example, is embedded as a wiring material in the recess, and the wiring structure is obtained by planarization by CMP using slurry. Here, if the resistance of the porous silica film is low with respect to chemicals such as acids and alkalis (for example, CMP slurry) used for forming the wiring structure, the size of the pores in contact with the chemicals increases, and the porous silica film This causes a problem that the relative dielectric constant increases as the strength decreases.
多孔質シリカ膜に対して疎水性ひいては耐薬液性を高めるために、上記特許文献１では、テトラアルコキシシランと疎水基たるメチル基を有するメチルトリアルコキシシランとをＳｉＯ２換算で１：０．０１〜０．３のモル比で混合することが提案されている。また、特許文献２では、メチルトリアルコキシシランの添加割合を上記特許文献１よりも高くして、テトラアルコキシシランとメチルトリアルコキシシランとのモル比を１：０．２５〜１．５にすることが提案されている。 In order to improve the hydrophobicity and thus the chemical resistance to the porous silica membrane, in Patent Document 1, tetraalkoxysilane and methyltrialkoxysilane having a methyl group as a hydrophobic group are converted to SiO 2 in terms of 1: 0.01. It has been proposed to mix at a molar ratio of ~ 0.3. Moreover, in patent document 2, the addition ratio of methyltrialkoxysilane is made higher than the said patent document 1, and the molar ratio of tetraalkoxysilane and methyltrialkoxysilane shall be 1: 0.25-1.5. Has been proposed.
然しながら、本発明者らが鋭意検討した結果、比誘電率が２．４以下の多孔質シリカ膜を形成する場合に上記従来例に記載された割合でメチルアルコキシシランを混合すると、焼成時に過度な膜収縮が生じ、その分の比誘電率が上昇し、所望の比誘電率が得られないことが判明した。これは、基材表面に形成された塗布膜が焼成により重合していく過程において、界面活性剤などの空孔の鋳型となるポロジェンが除去された時点での重合度が低く強度が不十分であるため、膜収縮に耐えられないからであると考えられる。焼成時の膜収縮を低減するには、テトラアルコキシシランの割合を高くすることが有効であるが、これでは耐薬液性が低くなる。即ち、上記従来例では、焼成時に起きる膜収縮を低減しつつ、比誘電率が２．４以下の優れた耐薬液性を有する多孔質シリカ膜を形成することが困難であった。 However, as a result of intensive studies by the present inventors, when forming a porous silica film having a relative dielectric constant of 2.4 or less, when methylalkoxysilane is mixed at a ratio described in the above-mentioned conventional example, an excessive amount is generated during firing. It was found that film contraction occurred, the relative dielectric constant increased, and the desired relative dielectric constant could not be obtained. This is because the degree of polymerization is low and the strength is insufficient when the porogen that is a pore template such as a surfactant is removed in the process of polymerizing the coating film formed on the substrate surface by baking. This is considered to be because the film cannot withstand film shrinkage. In order to reduce film shrinkage during firing, it is effective to increase the proportion of tetraalkoxysilane, but this reduces the chemical resistance. That is, in the above conventional example, it is difficult to form a porous silica film having excellent chemical resistance with a relative dielectric constant of 2.4 or less while reducing film shrinkage that occurs during firing.
本発明は、以上の点に鑑み、焼成時に起きる膜収縮を低減でき、かつ、比誘電率が２．４以下の耐薬液性に優れた多孔質シリカ膜を得ることが可能な多孔質シリカ前駆体塗布液を提供することをその課題とする。 In view of the above points, the present invention provides a porous silica precursor that can reduce film shrinkage that occurs during firing and that can provide a porous silica film having a relative dielectric constant of 2.4 or less and excellent chemical resistance. It is an object of the present invention to provide a body coating liquid.
上記課題を解決するために、本発明は、多孔質シリカ膜の形成に用いられる多孔質シリカ前駆体塗布液の作製方法であって、アルキル基を有する第１のトリアルコキシシランもしくはその重合体と、テトラアルコキシシランもしくはその重合体と、アリール基を有する第２のトリアルコキシシランもしくはその重合体とを界面活性剤と共に溶媒に溶解させ、この溶解させたものを触媒存在下で加水分解及び脱水縮合する工程を含み、Ｓｉ原子換算基準で、前記溶媒に溶解させたアルコキシシランもしくはその重合体の総量に対する前記第１のトリアルコキシシランもしくはその重合体の比率を５０〜９５モル％、前記テトラアルコキシシランもしくはその重合体の比率を５〜４０モル％、前記第２のトリアルコキシシランもしくはその重合体の比率を１〜２０モル％に夫々設定したことを特徴とする。尚、本発明において、「重合体」とは、アルコキシシランを部分的に加水分解させ、この加水分解させたものを脱水縮合させることで得られたものをいう。 In order to solve the above-mentioned problems, the present invention provides a method for preparing a porous silica precursor coating solution used for forming a porous silica film, which comprises a first trialkoxysilane having an alkyl group or a polymer thereof. , Tetraalkoxysilane or a polymer thereof and a second trialkoxysilane having an aryl group or a polymer thereof are dissolved in a solvent together with a surfactant, and the dissolved product is hydrolyzed and dehydrated in the presence of a catalyst. The ratio of the first trialkoxysilane or polymer thereof to the total amount of alkoxysilane or polymer thereof dissolved in the solvent on the basis of Si atom conversion, and the tetraalkoxysilane Or the ratio of the polymer is 5 to 40 mol%, the second trialkoxysilane or the polymer thereof And characterized in that each set a ratio 1 to 20 mol%. In the present invention, the “polymer” refers to a product obtained by partially hydrolyzing an alkoxysilane and subjecting the hydrolyzed product to dehydration condensation.
本発明によれば、３種類のアルコキシシランもしくはその重合体を界面活性剤と共に溶媒に溶解させ、この溶解させたものを加水分解及び脱水縮合することで、脱水縮合体を含む多孔質シリカ前駆体塗布液（ゾル）が得られる。このようにして得られた多孔質シリカ前駆体塗布液を基材表面に塗布し、この塗布したものを焼成することで、溶媒が除去すると共に、脱水縮合体に含まれる界面活性剤が脱離して空孔が生じる。その結果、基材表面に多孔質シリカ膜が形成される。 According to the present invention, a porous silica precursor containing a dehydrated condensate is prepared by dissolving three types of alkoxysilane or a polymer thereof in a solvent together with a surfactant, and hydrolyzing and dehydrating the dissolved product. A coating solution (sol) is obtained. The porous silica precursor coating solution thus obtained is applied to the substrate surface, and the applied material is baked to remove the solvent and to desorb the surfactant contained in the dehydrated condensate. As a result, holes are formed. As a result, a porous silica film is formed on the substrate surface.
アルキル基を有する第１のトリアルコキシシランもしくはその重合体を主成分として用いることで、得られる多孔質シリカ膜は、その表面にアルキル基が存在するものとなるので、耐薬液性を向上させることができる。ここで、第１のトリアルコキシシランは、シリカ骨格を形成する手が３つしかないため、この第１のトリアルコキシシランのみを加水分解及び脱水縮合させると、焼成時の膜強度が低く膜収縮が大きくなる。焼成時の膜収縮を低減するために、テトラアルコキシシランもしくはその重合体を添加すると、多孔質シリカ膜の耐薬液性が低下するという不具合が生じる。 By using the first trialkoxysilane having an alkyl group or a polymer thereof as a main component, the resulting porous silica film has an alkyl group on its surface, so that the chemical resistance is improved. Can do. Here, since the first trialkoxysilane has only three hands for forming the silica skeleton, if only the first trialkoxysilane is hydrolyzed and dehydrated and condensed, the film strength at the time of firing becomes low and the film shrinks. Becomes larger. If tetraalkoxysilane or a polymer thereof is added to reduce film shrinkage during firing, there is a problem that the chemical resistance of the porous silica film is lowered.
そこで、本発明では、テトラアルコキシシランもしくはその重合体を添加することによる耐薬液性の低下を防ぐため、アリール基を有する第２のトリアルコキシシランもしくはその重合体を１〜２０モル％添加することとした。さらに、この第２のトリアルコキシシランもしくはその重合体を添加することによる焼成時の膜収縮の増加を防ぐため、テトラアルコキシシランもしくはその重合体の添加割合を５〜４０モル％とした。このように、３種類のアルコキシシランもしくはその重合体を上記モル比で溶媒に溶解させるようにしたので、焼成時に起きる膜収縮を低減でき、比誘電率が２．４以下の耐薬液性に優れた多孔質シリカ膜が得られる。 Therefore, in the present invention, in order to prevent a decrease in chemical resistance due to the addition of tetraalkoxysilane or a polymer thereof, 1 to 20 mol% of a second trialkoxysilane having an aryl group or a polymer thereof is added. It was. Furthermore, in order to prevent an increase in film shrinkage during firing due to the addition of the second trialkoxysilane or polymer thereof, the addition ratio of tetraalkoxysilane or polymer thereof was set to 5 to 40 mol%. As described above, since three types of alkoxysilanes or polymers thereof are dissolved in the solvent at the above molar ratio, film shrinkage that occurs during firing can be reduced, and the chemical resistance is excellent with a relative dielectric constant of 2.4 or less. A porous silica membrane is obtained.
本発明は、第１のトリアルコキシシランがメチルアルコキシシランであり、かつ、第２のトリアルコキシシランがフェニルトリアルコキシシランである場合に好適である。 The present invention is suitable when the first trialkoxysilane is methylalkoxysilane and the second trialkoxysilane is phenyltrialkoxysilane.
以下、本発明の実施形態の多孔質シリカ前駆体塗布液の作製方法について説明する。本実施形態の多孔質シリカ前駆体塗布液の作製方法は、先ず、槽内にて、アルキル基を有する第１のアルコキシシランもしくはその重合体、テトラアルコキシシランとランもしくはその重合体、及びアリール基を有する第２のアルコキシシランもしくはその重合体を界面活性剤と共に溶媒に溶解させ、この溶解させて得た溶液に触媒と加水分解用の水とを添加して攪拌する。これにより、３種類のアルコキシシランもしくは重合体が加水分解及び脱水縮合し、この脱水縮合により得られた脱水縮合物を含む多孔質シリカ前駆体塗布液（ゾル）が得られる。脱水縮合物には、焼成時に空孔となる界面活性剤が取り込まれている。 Hereinafter, a method for producing a porous silica precursor coating solution according to an embodiment of the present invention will be described. In the method for producing the porous silica precursor coating liquid of the present embodiment, first, in the tank, a first alkoxysilane having an alkyl group or a polymer thereof, a tetraalkoxysilane and a run or a polymer thereof, and an aryl group The second alkoxysilane having the above or a polymer thereof is dissolved in a solvent together with a surfactant, and a catalyst and hydrolysis water are added to the solution obtained by the dissolution, followed by stirring. Thereby, three types of alkoxysilanes or polymers undergo hydrolysis and dehydration condensation, and a porous silica precursor coating solution (sol) containing a dehydration condensate obtained by this dehydration condensation is obtained. The dehydrated condensate incorporates a surfactant that becomes pores during firing.
ここで、Ｓｉ原子換算基準で、前記溶媒に溶解させたアルコキシシランもしくはその重合体の総量に対する第１のアルコキシランもしくはその重合体の比率を５０〜９５モル％、テトラアルコキシシランもしくはその重合体の比率を５〜４０モル％、第２のアルコキシシランもしくはその重合体の比率を１〜２０モル％に夫々設定した。第１のアルコキシシランもしくはその重合体の比率が５０モル％未満であると、多孔質シリカ膜の耐薬液性が不十分となる一方で、９５モル％を超えると、焼成時の膜収縮が大きくなって所望の比誘電率を有する多孔質シリカ膜が得られない。テトラアルコキシシランもしくはその重合体の比率が５モル％未満であると、焼成時の膜収縮が大きくなって所望の比誘電率を有する多孔質シリカ膜が得られない一方で、４０モル％を超えると、多孔質シリカ膜の耐薬液性が不十分となる。また、第２のアルコキシシランもしくはその重合体の比率が１モル％未満であると、多孔質シリカ膜の耐薬液性が不十分となる一方で、２０モル％を超えると、焼成時の膜収縮が大きくなって所望の比誘電率を有する多孔質シリカ膜が得られない。 Here, the ratio of the first alkoxysilane or polymer thereof to the total amount of alkoxysilane or polymer thereof dissolved in the solvent on the basis of Si atom conversion is 50 to 95 mol%, tetraalkoxysilane or polymer thereof. The ratio was set to 5 to 40 mol%, and the ratio of the second alkoxysilane or polymer thereof was set to 1 to 20 mol%. When the ratio of the first alkoxysilane or the polymer thereof is less than 50 mol%, the chemical resistance of the porous silica film becomes insufficient. On the other hand, when the ratio exceeds 95 mol%, the film shrinkage during firing is large. Thus, a porous silica film having a desired dielectric constant cannot be obtained. When the ratio of tetraalkoxysilane or a polymer thereof is less than 5 mol%, the film shrinkage during firing becomes large and a porous silica film having a desired dielectric constant cannot be obtained, but exceeds 40 mol%. As a result, the chemical resistance of the porous silica film becomes insufficient. Further, when the ratio of the second alkoxysilane or the polymer thereof is less than 1 mol%, the chemical resistance of the porous silica film becomes insufficient, while when it exceeds 20 mol%, the film shrinks during firing. As a result, the porous silica film having a desired dielectric constant cannot be obtained.
第１のトリアルコキシシランとしては、例えば、メチルトリメトキシシラン、メチルトリエトキシシラン、エチルトリメトキシシラン、エチルトリエトキシシラン等から選択された少なくとも１種を好適に用いることができる。テトラアルコキシシランとしては、テトラメトキシシラン（ＴＭＯＳ）、テトラエトキシシラン（ＴＥＯＳ）等から選択された少なくとも１種を好適に用いることができる。テトラアルコキシシランの重合体としては、メチルシリケート（ＭＳ）、エチルシリケート（ＥＳ）等から選択された少なくとも１種を用いることができる。第２のトリアルコキシシランとしては、例えば、フェニルトリメトキシシラン、フェニルトリエトキシシラン、トリルトリメトキシシラン、トリルトリエトキシシラン、キシリルトリメトキシシラン、キシリルトリエトキシシラン等から選択された少なくとも１種を好適に用いることができる。 As the first trialkoxysilane, for example, at least one selected from methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, and the like can be suitably used. As the tetraalkoxysilane, at least one selected from tetramethoxysilane (TMOS), tetraethoxysilane (TEOS) and the like can be suitably used. As the polymer of tetraalkoxysilane, at least one selected from methyl silicate (MS), ethyl silicate (ES) and the like can be used. As the second trialkoxysilane, for example, at least one selected from phenyltrimethoxysilane, phenyltriethoxysilane, tolyltrimethoxysilane, tolyltriethoxysilane, xylyltrimethoxysilane, xylyltriethoxysilane and the like is preferable. Can be used.
界面活性剤としては、ポリオキシエチレン−ポリオキシプロピレン縮合物等の非イオン性界面活性剤を好適に用いることができる。溶媒としては、メタノール、エタノール、２−プロパノール等のアルコール類；アセトン等のケトン類；エチルエーテル等のエーテル類；アセトニトリル等のニトリル類から選択された少なくとも１種を単独で又は混合して好適に用いることができる。 As the surfactant, a nonionic surfactant such as a polyoxyethylene-polyoxypropylene condensate can be suitably used. As the solvent, at least one selected from alcohols such as methanol, ethanol and 2-propanol; ketones such as acetone; ethers such as ethyl ether; and nitriles such as acetonitrile is used alone or in combination. Can be used.
触媒としては、酸触媒及びアルカリ触媒から選択される少なくとも一種を用いることができる。酸触媒としては、例えば硝酸、塩酸、硫酸等の無機酸や例えばギ酸、酢酸等の有機酸が挙げられる。アルカリ触媒としては、例えば水酸化テトラメチルアンモニウム等のアンモニウム塩が挙げられる。 As the catalyst, at least one selected from an acid catalyst and an alkali catalyst can be used. Examples of the acid catalyst include inorganic acids such as nitric acid, hydrochloric acid and sulfuric acid, and organic acids such as formic acid and acetic acid. Examples of the alkali catalyst include ammonium salts such as tetramethylammonium hydroxide.
加水分解及び脱水縮合時間は少なくとも１０分以上に設定することができる。１０分より短いと、脱水縮合が不十分となり、分子量の小さい脱水縮合体しか得られないという不具合が生じる。加水分解及び脱水縮合の温度は、溶媒の気化温度より低い温度に設定すればよく、例えば室温に設定することが好ましい。 The hydrolysis and dehydration condensation time can be set to at least 10 minutes or more. If it is shorter than 10 minutes, the dehydration condensation becomes insufficient, resulting in a problem that only a dehydration condensate having a low molecular weight can be obtained. The temperature of hydrolysis and dehydration condensation may be set to a temperature lower than the vaporization temperature of the solvent, and is preferably set to room temperature, for example.
以上説明したように、本実施形態によれば、第１のトリアルコキシシランもしくはその重合体を主成分として（５０〜９５モル％）溶媒に溶解させることによる焼成時の膜収縮の増加を防ぐため、テトラアルコキシシランもしくはその重合体を添加した。そして、このテトラアルコキシシランもしくはその重合体を添加することによる多孔質シリカ膜の耐薬液性の低下を防ぐため、第２のトリアルコキシシランもしくはその重合体を１〜２０モル％添加した。さらに、この第２のトリアルコキシシランもしくは重合体を添加することによる焼成時の膜収縮の増加を防ぐため、テトラアルコキシシランもしくは重合体の添加割合を５〜４０モル％とした。このように、３種類のアルコキシシランもしくはその重合体を上記モル比で溶媒に溶解させることで、焼成時に起きる膜収縮を低減でき、比誘電率が２．４以下の耐薬液性に優れた多孔質シリカ膜を形成することが可能となる。尚、脱水縮合により得られた脱水縮合体を含むゾルに上記溶媒を更に加えて粘度調整し、この粘度調整したゾルを多孔質シリカ前駆体塗布液としてもよい。また、多孔質シリカ前駆体塗布液の塗布方法や焼成方法については公知のものを用いることができるため、ここでは詳細な説明を省略する。 As described above, according to the present embodiment, in order to prevent an increase in film shrinkage at the time of firing by dissolving the first trialkoxysilane or a polymer thereof as a main component (50 to 95 mol%) in a solvent. Then, tetraalkoxysilane or a polymer thereof was added. And in order to prevent the chemical-resistant fall of the porous silica film | membrane by adding this tetraalkoxysilane or its polymer, 1-20 mol% of 2nd trialkoxysilane or its polymer was added. Furthermore, in order to prevent an increase in film shrinkage during firing due to the addition of the second trialkoxysilane or polymer, the addition ratio of tetraalkoxysilane or polymer was set to 5 to 40 mol%. Thus, by dissolving three types of alkoxysilanes or polymers thereof in a solvent at the above molar ratio, film shrinkage that occurs during firing can be reduced, and a porous with excellent chemical resistance with a relative dielectric constant of 2.4 or less. A porous silica film can be formed. The sol containing the dehydrated condensate obtained by dehydration condensation may be further added with the above solvent to adjust the viscosity, and the viscosity-adjusted sol may be used as the porous silica precursor coating solution. Moreover, since a well-known thing can be used about the coating method and baking method of a porous silica precursor coating liquid, detailed description is abbreviate | omitted here.
以下、本発明の実施例について説明する。
（実施例１）
本実施例１では、槽内にて、メチルトリメトキシシラン（ＭＴＭＳ）０．１モル、フェニルトリメトキシシラン（ＰｈＴＭＳ）０．０１モル、テトラエトキシシラン（ＴＥＯＳ）０．０１モル及び非イオン性界面活性剤（第一工業製薬株式会社製の商品名「Ｐ４５０」、ＨＯ（ＣＨ２ＣＨ２Ｏ）１３（ＣＨ（ＣＨ３）ＣＨ２Ｏ）２０（ＣＨ２ＣＨ２Ｏ）１３Ｈで表される。）０．０１モルをエタノール中に溶解させる。このとき、ＭＴＭＳ、ＰｈＴＭＳ、ＴＥＯＳのモル比は、それぞれ８０モル％、１０モル％、１０モル％となる。これら３種類のアルコキシシランを溶解させて得た溶液に硝酸０．０１モルと水１モルとを更に添加し、これら硝酸及び水を添加したものを２５℃で３時間攪拌してゾルを得た。次いで、このゾルにエタノールを加えて塗布に好適な粘度に調整することにより、透明で均一な多孔質シリカ前駆体塗布液を作製した。
Examples of the present invention will be described below.
Example 1
In Example 1, 0.1 mol of methyltrimethoxysilane (MTMS), 0.01 mol of phenyltrimethoxysilane (PhTMS), 0.01 mol of tetraethoxysilane (TEOS) and a nonionic interface in the tank Active agent (trade name “P450” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., HO (CH 2 CH 2 O) 13 (CH (CH 3 ) CH 2 O) 20 (CH 2 CH 2 O) 13 H .) 0.01 mol is dissolved in ethanol. At this time, the molar ratio of MTMS, PhTMS, and TEOS is 80 mol%, 10 mol%, and 10 mol%, respectively. To the solution obtained by dissolving these three types of alkoxysilanes, 0.01 mol of nitric acid and 1 mol of water were further added, and the sol was obtained by stirring these added nitric acid and water at 25 ° C. for 3 hours. . Subsequently, ethanol was added to the sol to adjust the viscosity to be suitable for coating, thereby preparing a transparent and uniform porous silica precursor coating solution.
本実施例１で得られた多孔質シリカ前駆体塗布液をシリコン基板表面にスピンコート法により回転数１２００ｒｐｍで塗布し、この塗布したものに対して真空雰囲気下にて３５０℃で１分間ＵＶ照射することで焼成した。焼成により得られた多孔質シリカ膜の比誘電率ｋは２．１であり、屈折率は１．２５であり、弾性率は３．８ＧＰａであり、残膜率（＝焼成後の膜厚／焼成前の膜厚）は７０．２％であった。この多孔質シリカ膜が形成されたシリコン基板を３０ｍｍ角に切断し、この切断したものを５０℃加熱の１ｗｔ％ＫＯＨ水溶液に１０分間浸漬させた結果、膜厚減少量（ウェットエッチング量）は１５ｎｍであり、また、上記切断したものを２３℃加熱の０．５ｗｔ％ＨＦ水溶液に１０分間浸漬させた結果、膜厚減少量は１０ｎｍであることが確認された。 The porous silica precursor coating solution obtained in Example 1 was applied to the silicon substrate surface by a spin coating method at a rotation speed of 1200 rpm, and this applied material was irradiated with UV at 350 ° C. for 1 minute in a vacuum atmosphere. And fired. The relative dielectric constant k of the porous silica film obtained by firing is 2.1, the refractive index is 1.25, the elastic modulus is 3.8 GPa, and the residual film ratio (= film thickness after firing / The film thickness before firing) was 70.2%. The silicon substrate on which this porous silica film was formed was cut into 30 mm square, and this cut piece was immersed in a 1 wt% KOH aqueous solution heated at 50 ° C. for 10 minutes. As a result, the film thickness reduction amount (wet etching amount) was 15 nm. Moreover, as a result of immersing the cut piece in a 0.5 wt% HF aqueous solution heated at 23 ° C. for 10 minutes, it was confirmed that the film thickness reduction amount was 10 nm.
（実施例２）
本実施例２では、ＴＥＯＳに代えてメチルシリケート（ＭＳ）０．００２５モルを添加した以外は、上記実施例１と同様の方法で前駆体塗布液を作製した。このとき、ＭＴＭＳ、ＰｈＴＭＳ、ＭＳのモル比は、それぞれ８０モル％、１０モル％、１０モル％となる。上記実施例１と同様に、本実施例２で得られた前駆体塗布液をシリコン基板表面に塗布し焼成することで得られた多孔質シリカ膜の比誘電率ｋは２．０であり、屈折率は１．２３であり、弾性率は３．６ＧＰａであり、残膜率は７２．８％であった。この多孔質シリカ膜が形成されたシリコン基板を３０ｍｍ角に切断し、この切断したものを５０℃加熱の１ｗｔ％ＫＯＨ水溶液に１０分間浸漬させた結果、膜厚減少量は２０ｎｍであり、また、上記切断したものを２３℃加熱の０．５ｗｔ％ＨＦ水溶液に１０分間浸漬させた結果、膜厚減少量は１１ｎｍであることが確認された。
(Example 2)
In Example 2, a precursor coating solution was prepared in the same manner as in Example 1 except that 0.0025 mol of methyl silicate (MS) was added instead of TEOS. At this time, the molar ratio of MTMS, PhTMS, and MS is 80 mol%, 10 mol%, and 10 mol%, respectively. Similar to Example 1 above, the relative dielectric constant k of the porous silica film obtained by applying the precursor coating solution obtained in Example 2 to the surface of the silicon substrate and baking it is 2.0. The refractive index was 1.23, the elastic modulus was 3.6 GPa, and the remaining film rate was 72.8%. The silicon substrate on which the porous silica film was formed was cut into 30 mm squares, and the cut piece was immersed in a 1 wt% KOH aqueous solution heated at 50 ° C. for 10 minutes. As a result, the film thickness reduction amount was 20 nm. As a result of immersing the cut piece in a 0.5 wt% HF aqueous solution heated at 23 ° C. for 10 minutes, it was confirmed that the film thickness reduction amount was 11 nm.
以上説明したように、本実施例１及び２の多孔質シリカ前駆体塗布液を基材表面に塗布して焼成することで、焼成時の膜収縮を低減でき、焼成後に得られる多孔質シリカ膜の比誘電率を２．０〜２．１と低くでき、しかも、耐薬液性に優れた多孔質シリカ膜が得られることが判った。 As described above, the porous silica film obtained after firing can be reduced by applying the porous silica precursor coating liquid of Examples 1 and 2 to the surface of the base material and firing it, thereby reducing film shrinkage during firing. It was found that a porous silica film having a low relative dielectric constant of 2.0 to 2.1 and excellent chemical resistance can be obtained.
以下、上記実施例に対する比較例について説明する。
（比較例１）
本比較例１では、槽内にて、ＭＴＭＳ０．１モル（すなわち、ＭＴＭＳ１００％）と非イオン性界面活性剤０．０１モルとをエタノール中に溶解させ、この溶解させて得た溶液に硝酸０．０１モルと水１モルとを更に添加し、これら硝酸及び水を添加したものを２５℃で３時間攪拌してゾルを得た。このゾルにエタノールを加えて塗布に好適な粘度に調整することにより、透明で均一な多孔質シリカ前駆体塗布液を得た。上記実施例１と同様に、本比較例１で得られた前駆体塗布液をシリコン基板表面に塗布し焼成することで得られた多孔質シリカ膜の比誘電率ｋは２．３であり、屈折率は１．２８であり、弾性率は５．０ＧＰａであったが、残膜率は５０．７％と低かった。この多孔質シリカ膜が形成されたシリコン基板を３０ｍｍ角に切断し、この切断したものを５０℃加熱の１ｗｔ％ＫＯＨ水溶液に１０分間浸漬させた結果、膜厚減少量は４２ｎｍであり、また、上記切断したものを２３℃加熱の０．５ｗｔ％ＨＦ水溶液に１０分間浸漬させた結果、膜厚減少量は１７ｎｍであることが確認された。
Hereinafter, a comparative example with respect to the above embodiment will be described.
(Comparative Example 1)
In this comparative example 1, 0.1 mol of MTMS (that is, MTMS 100%) and 0.01 mol of nonionic surfactant were dissolved in ethanol in a tank, and the solution obtained by this dissolution was mixed with 0 nitric acid. .01 mol and 1 mol of water were further added, and these nitric acid and water added were stirred at 25 ° C. for 3 hours to obtain a sol. Ethanol was added to this sol to adjust the viscosity to be suitable for coating to obtain a transparent and uniform porous silica precursor coating solution. As in Example 1 above, the relative dielectric constant k of the porous silica film obtained by applying the precursor coating solution obtained in Comparative Example 1 to the surface of the silicon substrate and baking it is 2.3. The refractive index was 1.28 and the elastic modulus was 5.0 GPa, but the remaining film rate was as low as 50.7%. The silicon substrate on which the porous silica film was formed was cut into 30 mm square, and the cut piece was immersed in a 1 wt% KOH aqueous solution heated at 50 ° C. for 10 minutes. As a result, the film thickness reduction amount was 42 nm. As a result of immersing the cut piece in a 0.5 wt% HF aqueous solution heated at 23 ° C. for 10 minutes, it was confirmed that the film thickness reduction amount was 17 nm.
（比較例２）
本比較例２では、ＭＴＭＳ０．１モルに加えてＴＥＯＳ０．０１モルを用いる以外は、上記比較例１と同様の方法で前駆体塗布液を作製した。このとき、ＭＴＭＳ、ＴＥＯＳのモル比は、それぞれ９０モル％、１０モル％となる。上記実施例１と同様に、本比較例２で得られた前駆体塗布液をシリコン基板表面に塗布し焼成することで得られた多孔質シリカ膜の比誘電率ｋは２．０であり、屈折率は１．２２であり、弾性率は３．２ＧＰａであり、膜厚率は７２．４％と高かった。然し、この多孔質シリカ膜が形成されたシリコン基板を３０ｍｍ角に切断し、この切断したものを５０℃加熱の１ｗｔ％ＫＯＨ水溶液に１０分間浸漬させた結果、膜厚減少量は１０２ｎｍであり、また、上記切断したものを２３℃加熱の０．５ｗｔ％ＨＦ水溶液に１０分間浸漬させた結果、膜厚減少量は８８ｎｍであり、耐薬液性が低いことが確認された。
(Comparative Example 2)
In Comparative Example 2, a precursor coating solution was prepared in the same manner as Comparative Example 1 except that 0.01 mol of TEOS was used in addition to 0.1 mol of MTMS. At this time, the molar ratio of MTMS and TEOS is 90 mol% and 10 mol%, respectively. As in Example 1 above, the relative dielectric constant k of the porous silica film obtained by applying the precursor coating solution obtained in Comparative Example 2 to the surface of the silicon substrate and baking it is 2.0. The refractive index was 1.22, the elastic modulus was 3.2 GPa, and the film thickness rate was as high as 72.4%. However, the silicon substrate on which this porous silica film was formed was cut into 30 mm squares, and the cut piece was immersed in a 1 wt% KOH aqueous solution heated at 50 ° C. for 10 minutes. Moreover, as a result of immersing the cut piece in a 0.5 wt% HF aqueous solution heated at 23 ° C. for 10 minutes, the film thickness reduction amount was 88 nm, and it was confirmed that the chemical resistance was low.
（比較例３）
本比較例３では、ＭＴＭＳ０．１モルに加えてＭＳ０．００２５モルを用いる点以外は、上記比較例１と同様の方法で多孔質シリカ前駆体塗布液を作製した。このとき、ＭＴＭＳ、ＭＳのモル比は、それぞれ９０モル％、１０モル％となる。上記実施例１と同様に、本比較例３で得られた前駆体塗布液をシリコン基板表面に塗布し焼成することで得られた多孔質シリカ膜の比誘電率ｋは１．９であり、屈折率は１．２１であり、弾性率は３．０ＧＰａであり、膜厚率は７２．４％と高かった。然し、この多孔質シリカ膜が形成されたシリコン基板を３０ｍｍ角に切断し、この切断したものを５０℃加熱の１ｗｔ％ＫＯＨ水溶液に１０分間浸漬させた結果、膜厚減少量は１２５ｎｍであり、また、上記切断したものを２３℃加熱の０．５ｗｔ％ＨＦ水溶液に１０分間浸漬させた結果、膜厚減少量は８９ｎｍであり、耐薬液性が低いことが確認された。
(Comparative Example 3)
In Comparative Example 3, a porous silica precursor coating solution was prepared in the same manner as Comparative Example 1 except that 0.0025 mol of MSMS was used in addition to 0.1 mol of MTMS. At this time, the molar ratio of MTMS and MS is 90 mol% and 10 mol%, respectively. As in Example 1 above, the relative dielectric constant k of the porous silica film obtained by applying the precursor coating solution obtained in Comparative Example 3 to the surface of the silicon substrate and baking it is 1.9, The refractive index was 1.21, the elastic modulus was 3.0 GPa, and the film thickness ratio was as high as 72.4%. However, the silicon substrate on which this porous silica film was formed was cut into 30 mm squares, and as a result of immersing the cut piece in a 1 wt% KOH aqueous solution heated at 50 ° C. for 10 minutes, the film thickness reduction amount was 125 nm. Moreover, as a result of immersing the cut piece in a 0.5 wt% HF aqueous solution heated at 23 ° C. for 10 minutes, the film thickness reduction amount was 89 nm, and it was confirmed that the chemical resistance was low.
（比較例４）
本比較例４では、ＭＴＭＳ０．１モルに加えてＰｈＴＭＳ０．０１モルを用いる点以外は、上記比較例１と同様の方法で多孔質シリカ前駆体塗布液を作製した。このとき、ＭＴＭＳ、ＰｈＴＭＳのモル比は、それぞれ９０モル％、１０モル％となる。上記実施例１と同様に、本比較例４で得られた前駆体塗布液をシリコン基板表面に塗布し焼成することで得られた多孔質シリカ膜の比誘電率ｋは２．５であり、屈折率は１．３１であり、弾性率は６．７ＧＰａであったが、膜厚率は５３．３％と低く焼成時の膜収縮が大きいことが確認された。この多孔質シリカ膜が形成されたシリコン基板を３０ｍｍ角に切断し、この切断したものを５０℃加熱の１ｗｔ％ＫＯＨ水溶液に１０分間浸漬させた結果、膜厚減少量は１２ｎｍであり、また、上記切断したものを２３℃加熱の０．５ｗｔ％ＨＦ水溶液に１０分間浸漬させた結果、膜厚減少量は１５ｎｍであった。
(Comparative Example 4)
In Comparative Example 4, a porous silica precursor coating solution was prepared in the same manner as in Comparative Example 1 except that 0.01 mol of PhTMS was used in addition to 0.1 mol of MTMS. At this time, the molar ratio of MTMS and PhTMS is 90 mol% and 10 mol%, respectively. Similar to Example 1 above, the relative dielectric constant k of the porous silica film obtained by applying the precursor coating solution obtained in Comparative Example 4 to the surface of the silicon substrate and baking it is 2.5, Although the refractive index was 1.31 and the elastic modulus was 6.7 GPa, the film thickness ratio was as low as 53.3%, and it was confirmed that the film shrinkage during firing was large. The silicon substrate on which the porous silica film was formed was cut into 30 mm square, and the cut piece was immersed in a 1 wt% KOH aqueous solution heated at 50 ° C. for 10 minutes. As a result, the film thickness reduction amount was 12 nm. As a result of immersing the cut piece in a 0.5 wt% HF aqueous solution heated at 23 ° C. for 10 minutes, the film thickness reduction amount was 15 nm.
以上説明したように、本比較例１〜４の前駆体塗布液を基材表面に塗布して焼成することで得られる多孔質シリカ膜の耐薬液性が不十分であるか、または焼成時の膜収縮が大きいことが判った。 As described above, the chemical resistance of the porous silica film obtained by applying the precursor coating liquids of Comparative Examples 1 to 4 to the surface of the base material and firing is insufficient, or at the time of firing. It was found that the film shrinkage was large.
なお、本発明は上記実施形態及び実施例に限定されるものではない。例えば、ＭＴＭＳの代わりにこのＭＴＭＳの重合体を用い、ＰｈＴＭＳの代わりにこのＰｈＴＭＳの重合体を用いても、上記実施例１及び２と同様の効果を得ることができる。
In addition, this invention is not limited to the said embodiment and Example. For example, even if this MTMS polymer is used in place of MTMS, and this PhTMS polymer is used in place of PhTMS, the same effects as in Examples 1 and 2 can be obtained.
Claims (2)
アルキル基を有する第１のトリアルコキシシランもしくはその重合体と、テトラアルコキシシランもしくはその重合体と、アリール基を有する第２のトリアルコキシシランもしくはその重合体とを界面活性剤と共に溶媒に溶解させ、この溶解させたものを触媒存在下で加水分解及び脱水縮合する工程を含み、
Ｓｉ原子換算基準で、前記溶媒に溶解させたアルコキシシランもしくはその重合体の総量に対する前記第１のトリアルコキシシランもしくはその重合体の比率を５０〜９５モル％、前記テトラアルコキシシランもしくはその重合体の比率を５〜４０モル％、前記第２のトリアルコキシシランもしくはその重合体の比率を１〜２０モル％に夫々設定したことを特徴とする多孔質シリカ前駆体塗布液の作製方法。 A method for producing a porous silica precursor coating solution used for forming a porous silica film,
Dissolving a first trialkoxysilane having an alkyl group or a polymer thereof, a tetraalkoxysilane or a polymer thereof, and a second trialkoxysilane having an aryl group or a polymer thereof together with a surfactant in a solvent; A step of hydrolysis and dehydration condensation of the dissolved product in the presence of a catalyst,
Based on Si atom conversion standard, the ratio of the first trialkoxysilane or the polymer thereof to the total amount of the alkoxysilane or the polymer dissolved in the solvent is 50 to 95 mol%, the tetraalkoxysilane or the polymer thereof A method for producing a porous silica precursor coating liquid, wherein the ratio is set to 5 to 40 mol%, and the ratio of the second trialkoxysilane or polymer thereof is set to 1 to 20 mol%.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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| IT202100003311A1 (en) * | 2021-02-15 | 2022-08-15 | Qwarzo Italia S R L | PAPER WATERPROOFING TREATMENT AND WATERPROOF PAPER OBTAINED THUS |
| WO2022171893A1 (en) * | 2021-02-15 | 2022-08-18 | Qwarzo S.p.A. | Impermeabilization treatment of paper or cardboard and impermeable paper or cardboard thus obtained |
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