JP2010153649A - Cyclosiloxane composition and thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition with which stable film formation can be performed by adding a suitable polymerization inhibitor or polymerization retarder to a precursor which is used for a pore-in-molecule precursor process and to which a polymerization group is bonded, especially, a vinyl group bonded type cyclotrisiloxane. <P>SOLUTION: A thin film is formed by a PECVD method etc., using, as a raw material, a cyclosiloxane composition comprising a cyclosiloxane compound expressed by general formula (1) (where R represents an alkyl group of a straight chain or branch chain with C1-3, and (n) represents 3 or 4) and a nitrone derivative or nitroxide radical derivative. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to cyclic siloxane compositions and thin films made therefrom.

With the recent high integration of semiconductor elements, Cu, which has low resistance and excellent migration resistance, has been used as an LSI wiring from conventional Al, while a conventional silicon oxide film (SiO ₂ film) is used as an interlayer insulating film. Therefore, a layered dielectric film (Low-k film) having a lower dielectric constant has been studied.

  Currently, the plasma chemical vapor deposition method (PECVD method) is mainly used as a method for forming an interlayer insulating film. However, since the composition control is easy and a low k value can be realized, a coating method is also actively studied. . However, the coating method basically requires multiple steps in the film forming step, and the PECVD method is still mainstream because the PECVD method is basically one step and the process is long and inferior in productivity.

  As an effort to achieve a low k value, film formation is performed using a material in which a low-molecular-weight organic compound called porogen is mixed with a film-forming precursor (precursor), and pores are removed in the film by removing the porogen in post-processing. A method of forming (pores) (a porogen process) and a method of forming a PECVD film using a precursor having an intramolecular pore (intramolecular pore precursor process) are mainly studied. The porogen process requires multiple steps and is not only disadvantageous in terms of productivity, but also has a problem of hygroscopicity due to the pores formed. On the other hand, it is considered that the intramolecular pore precursor process is advantageous not only in that the process is short, but also because the intramolecular pore is smaller than the water molecule and is excellent in hygroscopicity. Precursors having pores in the molecule require a relatively large molecular weight because they require a large number of atoms that form a framework to form the pores. As a result, the vapor pressure is lower than that of tetraethoxysilane (TEOS). There was a drawback that the film speed decreased. So far, low-k film formation has been studied using cyclic siloxane as an intramolecular pore precursor, but the film formation speed can be increased by bonding a vinyl group which is a polymer group to a cyclic siloxane compound having a low vapor pressure. It has succeeded in speeding up (for example, refer patent document 1).

JP 2005-51192 A

  In the intramolecular pore precursor process, it is necessary to increase the film formation rate using a polymerized group or the like. While polymerized groups such as vinyl groups have the advantage of increasing the film formation rate, they gradually polymerize under storage conditions to produce high molecular weight polymers, and stable film formation is possible as the precursor changes over time. In addition, there is a possibility that the film forming apparatus line is blocked, and a device for suppressing polymerization has been desired. The present invention provides a composition that enables stable film formation by adding an appropriate polymerization inhibitor or polymerization inhibitor to a precursor having a polymerized group, which is used in an intramolecular pore precursor process. With the goal.

  As a result of intensive studies to solve the above problems, the present inventors have added a nitrone derivative or a nitroxide radical derivative to a cyclic siloxane compound having a vinyl group bonded thereto, without affecting the film forming characteristics. The present inventors have found that the above problems can be solved and have completed the present invention.

  That is, the present invention relates to the general formula (1)

（式中、Ｒは炭素数１〜３の直鎖または分岐鎖のアルキル基を示し、ｎは３または４を示す）で表される環状シロキサン化合物、およびニトロン誘導体またはニトロキシドラジカル誘導体から成ることを特徴とする、環状シロキサン組成物である。また本発明は、この組成物を原料として製造されることを特徴とする薄膜である。以下、本発明をさらに詳細に説明する。

(Wherein R represents a linear or branched alkyl group having 1 to 3 carbon atoms, and n represents 3 or 4), and a nitrone derivative or a nitroxide radical derivative. A cyclic siloxane composition is characterized. Moreover, this invention is a thin film characterized by being manufactured using this composition as a raw material. Hereinafter, the present invention will be described in more detail.

  In the present invention, in the cyclic siloxane compound represented by the general formula (1), R represents a linear or branched alkyl group having 1 to 3 carbon atoms, specifically a methyl group, an ethyl group, or a normal propyl group. Represents an isopropyl group. In the general formula (1), n represents 3 or 4. A compound in which n is 2 is outside the scope of the present invention because it has a synthesis example in which the substituent R is increased, but is unsuitable as a material due to extremely poor thermal stability. On the other hand, when n is 5 or more, the vapor pressure decreases as the molecular weight increases, and as a result, the film formation rate decreases, which is outside the scope of the present invention. In the present invention, the cyclic siloxane compound represented by the general formula (1) is preferably a compound represented by R = methyl group and n = 3 or 4, or R = isopropyl group and n = 3. A compound.

  As polymerization inhibitors, phenol derivatives, nitrone derivatives, nitroxide radical derivatives, and various other metal salts can be considered, but metal salts cause an increase in dielectric constant and leakage current in forming a low dielectric constant interlayer insulating film. Therefore, it is not preferable for the present invention. In the present invention, since the precursor and the polymerization inhibitor are used in an inert atmosphere, a phenolic system whose efficacy is enhanced in the presence of oxygen is also not preferable. Therefore, a nitrone derivative or a nitroxide radical derivative is used as a polymerization inhibitor in the present invention.

  Specific examples of nitrone derivatives include nitromethane, 2-methyl-2-nitrosopropane, α-phenyl (tertiarybutyl) nitrone, 5,5-dimethyl-1-pyrroline-1-oxide, and N-nitroso-N. -Phenylhydroxylamine ammonium salt etc. can be mentioned, However It does not specifically limit. Nitroxide radical derivatives used as polymerization inhibitors in the present invention include 2,2,6,6-tetramethyl-1-piperidinyloxy radical, 1,1,3,3-tetramethylisoindoline-N-oxyl, etc. There is no particular limitation. Among these, 2,2,6,6-tetramethyl-1-piperidinyloxy radical or 1,1,3,3-tetramethylisoindoline-N-oxyl is particularly preferable. The concentration of the polymerization inhibitor is not particularly defined, but even 1 ppm is effective, and as the concentration increases, the polymerization suppression effect increases. If the concentration is too high, there is a concern that the film characteristics after film formation will be affected, but no adverse effect was observed on the film characteristics such as the relative dielectric constant even at 100 ppm. For this reason, the concentration of the polymerization inhibitor is preferably from 0.01 to 10000 ppm, and more preferably from 0.1 to 1000 ppm in consideration of the effect of the polymerization inhibitor and the influence during film formation.

  A thin film can be produced by using the composition of the present invention as a raw material. The film forming method at this time is not particularly limited, and examples thereof include a coating method and a PECVD method, but the PECVD method is particularly preferable. The obtained thin film can be used as a dielectric thin film exhibiting a low dielectric constant.

  In the present invention, the stability of the cyclic siloxane compound is improved by allowing the cyclic siloxane compound represented by the general formula (1) to coexist with a nitrone derivative or a nitroxide radical derivative as described above. Therefore, when film formation is performed using the composition of the present invention, the stability of the precursor having a polymerization group can be improved. In addition, by using the composition of the present invention at the time of film formation in industrial production, it becomes possible to stably supply a precursor, and there is an effect that productivity is remarkably improved. In addition, the thin film produced using the composition of the present invention as a raw material has no adverse effect on the film properties, and can be used as a dielectric thin film exhibiting a low dielectric constant.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Example 1) Accelerated polymerization of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane added with 100 ppm of 2,2,6,6-tetramethyl-1-piperidinyloxy radical Weigh 2.0 g of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane added with 100 ppm of 2,2,6,6-tetramethyl-1-piperidinyloxy radical into an eggplant flask. The sample was heated and stirred in an argon atmosphere at 190 ° C. for 6 hours, 160 ° C. for 12 hours, and 140 ° C. for 24 hours to obtain an accelerated polymerization sample. Weight loss was measured by thermogravimetric analysis. 2,4,6-Triisopropyl-2,4,6-trivinylcyclotrisiloxane is vaporized by heating, but does not vaporize when polymerized and remains in the container. Therefore, the vaporized content of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane was defined as unpolymerized content (%), and the unvaporized content was defined as polymerized content (%). The results are shown in Table 1.

（実施例２） ２，２，６，６−テトラメチル−１−ピペリジニルオキシラジカルを１０ｐｐｍ添加した２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサンの加速重合
２，２，６，６−テトラメチル−１−ピペリジニルオキシラジカルを１０ｐｐｍ添加した２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサン２．０ｇをナスフラスコに量り取り、アルゴン雰囲気下、１９０℃２時間、１７０℃５時間、１４０℃１８時間でそれぞれ加熱攪拌し、加速重合サンプルとした。熱重量分析にて重量減少を測定し、２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサンの気化分を未重合分（％）とし、未気化分を重合分（％）とした。結果を表２に示す。

Example 2 Accelerated polymerization of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane to which 10 ppm of 2,2,6,6-tetramethyl-1-piperidinyloxy radical was added Weigh 2.0 g of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane added with 10 ppm of 2,2,6,6-tetramethyl-1-piperidinyloxy radical into an eggplant flask. The sample was heated and stirred in an argon atmosphere at 190 ° C. for 2 hours, 170 ° C. for 5 hours, and 140 ° C. for 18 hours to obtain an accelerated polymerization sample. The weight loss was measured by thermogravimetric analysis, and the vaporized content of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane was defined as the unpolymerized content (%), and the unvaporized content was determined as the polymerized content ( %). The results are shown in Table 2.

（実施例３） ２，２，６，６−テトラメチル−１−ピペリジニルオキシラジカルを１ｐｐｍ添加した２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサンの加速重合
２，２，６，６−テトラメチル−１−ピペリジニルオキシラジカルを１ｐｐｍ添加した２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサン２．０ｇをナスフラスコに量り取り、アルゴン雰囲気下、１９０℃２時間、１５０℃４時間、１３０℃１８時間、１１０℃２４時間でそれぞれ加熱攪拌し、加速重合サンプルとした。熱重量分析にて重量減少を測定し、２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサンの気化分を未重合分（％）とし、未気化分を重合分（％）とした。結果を表３に示す。

(Example 3) Accelerated polymerization of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane added with 1 ppm of 2,2,6,6-tetramethyl-1-piperidinyloxy radical Weigh 2.0 g of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane added with 1 ppm of 2,2,6,6-tetramethyl-1-piperidinyloxy radical into an eggplant flask. The sample was heated and stirred at 190 ° C. for 2 hours, 150 ° C. for 4 hours, 130 ° C. for 18 hours, and 110 ° C. for 24 hours to obtain an accelerated polymerization sample. The weight loss was measured by thermogravimetric analysis, and the vaporized content of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane was defined as the unpolymerized content (%), and the unvaporized content was determined as the polymerized content ( %). The results are shown in Table 3.

（比較例１） 重合禁止剤を添加しない場合の２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサンの加速重合
重合禁止剤を添加していない２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサン２．０ｇをナスフラスコに量り取り、アルゴン雰囲気下、１８０℃２時間、１６０℃２時間、１４０℃４時間、１２０℃６時間、１００℃２４時間でそれぞれ加熱攪拌し、加速重合サンプルとした。熱重量分析にて重量減少を測定し、２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサンの気化分を未重合分（％）とし、未気化分を重合分（％）とした。結果を表４に示す。

(Comparative Example 1) Accelerated polymerization of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane without addition of polymerization inhibitor 2,4,6-without addition of polymerization inhibitor 2.0 g of triisopropyl-2,4,6-trivinylcyclotrisiloxane was weighed into an eggplant flask, 180 ° C. 2 hours, 160 ° C. 2 hours, 140 ° C. 4 hours, 120 ° C. 6 hours, 100 ° C. in an argon atmosphere. Each sample was heated and stirred for 24 hours to obtain an accelerated polymerization sample. The weight loss was measured by thermogravimetric analysis, and the vaporized content of 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane was defined as the unpolymerized content (%), and the unvaporized content was determined as the polymerized content ( %). The results are shown in Table 4.

（実施例４） ２，２，６，６−テトラメチル−１−ピペリジニルオキシラジカルを１００ｐｐｍ添加した２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサンを原料として用いたＰＥＣＶＤ成膜
図１に示す、平行平板容量結合型ＰＥＣＶＤ装置を用い、チャンバー内に原料を設置して真空ポンプで減圧し、原料の蒸気圧のみで原料を供給する簡易な方法で成膜を検討した。２，２，６，６−テトラメチル−１−ピペリジニルオキシラジカルを１００ｐｐｍ添加した、２，４，６−トリイソプロピル−２，４，６−トリビニルシクロトリシロキサンを原料として室温で成膜を行った。原料圧力１２．５Ｐａ、ＲＦ電源周波数１３．５６ＭＨｚ、ＲＦ電源出力３０Ｗ、成膜時間３４分、成膜を行った結果、膜厚１９６５ｎｍ、成膜速度５７．８ｎｍ／ｍｉｎで得られた膜の比誘電率（ｋ値）は３．３１であった。

Example 4 Using 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane added with 100 ppm of 2,2,6,6-tetramethyl-1-piperidinyloxy radical as a raw material Using PECVD film formation as shown in Fig. 1, using a parallel plate capacitively coupled PECVD apparatus, a raw material is placed in a chamber, depressurized by a vacuum pump, and formed by a simple method of supplying the raw material only by the vapor pressure of the raw material. It was investigated. Film formation at room temperature using 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane with 100 ppm 2,2,6,6-tetramethyl-1-piperidinyloxy radical added Went. Ratio of films obtained at a film thickness of 1965 nm and a film formation speed of 57.8 nm / min as a result of film formation at a source pressure of 12.5 Pa, an RF power frequency of 13.56 MHz, an RF power output of 30 W, and a film formation time of 34 minutes. The dielectric constant (k value) was 3.31.

(Comparative Example 2) PECVD film formation using 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane as a raw material when no polymerization inhibitor is added Parallel plate capacitive coupling shown in FIG. Using a PECVD apparatus, the raw material was placed in a chamber, depressurized with a vacuum pump, and film formation was studied by a simple method of supplying the raw material only by the vapor pressure of the raw material. Film formation was performed at room temperature using 2,4,6-triisopropyl-2,4,6-trivinylcyclotrisiloxane without addition of a polymerization inhibitor as a raw material. The relative dielectric constant of the film obtained at a film thickness of 2212 nm and a film formation speed of 51.4 nm / min as a result of film formation with a raw material pressure of 14 Pa, an RF power supply frequency of 13.56 MHz, an RF power output of 30 W, and a film formation time of 43 minutes. The (k value) was 3.37.

It is the schematic of the PECVD film-forming apparatus used in Example 4 and Comparative Example 2.

Explanation of symbols

1. PECVD chamber Substrate 3. Upper electrode 4. Lower electrode 5. Raw material glass container 6. Raw material 7. Vacuum pump 8. 8. Matching circuit RF power supply 10. Earth

Claims (2)

General formula (1)

(Wherein R represents a linear or branched alkyl group having 1 to 3 carbon atoms, and n represents 3 or 4), and a nitrone derivative or a nitroxide radical derivative. A cyclic siloxane composition, characterized. A thin film produced using the composition according to claim 1 as a raw material.

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