KR100555941B1 - Organosilicate inorganic-organic hybrid block copolymers with pore generators for ultra-low dielectric thin film insulator applications and methods for preparing the same - Google Patents

Abstract

The present invention relates to an organic silicate-based inorganic-organic hybrid block copolymer, a method for preparing the same, and an ultra low dielectric coating film using the same.

The organosilicate-based inorganic-organic hybrid block copolymer of the present invention employs an atomic transfer radical polymerization (ATRP) method of poly (methylmethacrylate) (PMMA), which acts as a pore-forming agent. And a block copolymer made by covalently bonding to poly (methylsilsesquioxane) (PMSSQ). When the block copolymer is heat treated by spin coating with a low dielectric matrix polymer, the resulting coating film is a low dielectric matrix. Since it contains nanometer-sized uniform micropores in the resin and has an ultra-low dielectric constant of 2.3 or less, it is used as an insulating material necessary for manufacturing copper wiring chips, which are next-generation semiconductors, thereby improving product performance.

Organosilicate, copolymer, polymethyl methacrylate, ATRP, ultra low dielectric, nanopore, thin film

Description

Organic silicate-based organic-inorganic hybrid block copolymers with pore-forming agents for ultra-low dielectric thin film products, manufacturing methods and uses thereof for preparing the same}

1 is a graph showing the results of nuclear magnetic resonance (NMR) of the organosilicate block copolymer of the present invention.

Figure 2 is a graph showing the results of measuring the molecular weight of the organosilicate block copolymer and polymethylsilsesquioxane homopolymer of the present invention using gel permeation chromatography (GPC).

FIG. 3 shows experimental results of differential scanning calorimetry (DSC) for measuring glass transition temperature of the organosilicate block copolymer, polymethylmethacrylate homopolymer, and polymethylsilsesquioxane homopolymer of the present invention. Shows the graph.

4 is a thermogravimetric blend of the organosilicate block copolymers, polymethylmethacrylate homopolymers, polymethylsilsesquioxane homopolymers, and polymethylmethacrylate homopolymers and polymethylsilsesquioxane homopolymer blends of the present invention. Graph showing analysis (TGA) results.

5 is an optical micrograph of a thin film surface after firing of a polymethylsilsesquioxane homopolymer.

6 is an optical micrograph of a thin film surface after firing of a blend of polymethylmethacrylate homopolymer and polymethylsilsesquioxane homopolymer.

7 is an optical micrograph of the surface of a thin film after firing of a polymethylmethacrylate-polymethylsilsesquioxane block copolymer and a polymethylsilsesquioxane blend.

In the recent semiconductor industry, as the size of semiconductor devices decreases and the degree of integration increases, the delay of signal transmission due to the mixing effect of resistance x charge capacity (R x C) and mutual interference between metal leads is very serious. Has emerged. According to the US semiconductor industry's prediction, if the distance between the metal conductors of integrated circuits is reduced to less than 100nm, the signal delay in multi-layer interconnects will determine the actual operating time of the entire device.

In this situation, to reduce the resistance of metal conductors, efforts have been made to develop copper having higher electrical conductivity than conventional aluminum, and have a very low dielectric constant (k <2.3) for the electrically insulating film filled between the metal conductors. In progress.

In relation to these low-k dielectrics, a silicon oxide film (SiO ₂ ) having a dielectric constant of about 4.2 was conventionally used as an insulating film between metal wires. However, in view of the trend that the distance between conductors continues to decrease as mentioned above. The dielectric constant of the dielectric film has already reached its functional limit, and it is urgent to develop an insulating film having a lower dielectric constant.

Under these circumstances, various development attempts have been made as low dielectric constant materials for semiconductors, such as polysilsesquioxane, polyimide, amorphous PTFE (amorphous poly (tetrafluoroethylene)), and the like.

Polysilsesquioxanes having an empirical formula of (RSiO _3/2 ) n (R = hydrogen or organic functional groups) have been studied as electrical insulators at high temperatures since the initial commercialization of silicon polymers. In particular, polyphenylsilsesquioxane (PPSSQ), in which the organic functional group is phenyl, is the most studied, and many patents have already been registered for the synthesis of this material. In recent years, polysilsesquioxane polymers have received a lot of attention once it is revealed that it can be used as a low dielectric material in the next-generation semiconductor industry.

On the other hand, along with the development of these materials, ultra-low dielectric constants of 2.3 or lower ultimately result in the lowest dielectric constant of air (k = 1) uniformly generated in the insulating film thin film in nanometer (nm) size. There is an active research in the field of developing a biomolecule (eg, Morgen, M .; Ryan, ET; Zhao, J.-H .; Hu, C .; Cho, T .; Ho, PS Annu. Rev. Mater. Sci. 2000 , 30, 645. Maier, G. Prog. Polymer Sci 2001 , 26, 3. Wang, Z .; Mitra, A .; Wang, H .; Huang, L .; Yan, Y. Adv. Mater. 2001 , 13, 1463. etc.).

Among the many research results related to low dielectric materials, the method using inorganic / organic polymer hybrid system shows the most expected result in the development of ultra low dielectric material for semiconductor, and polymethylsilsesqiuoxane (PMSSQ) It is well known as an electrical insulator thin film material because it has not only a low dielectric constant of k = 2.7 to 2.9 but also a low water absorption and high thermal stability and relatively good mechanical properties to withstand high temperatures of 450 ° C or higher.

On the other hand, in order to lower the dielectric constant to 2.3 or less, polymethylsilsesquioxane insulator polymer based on the bond between silicon and oxygen and organic polymer that can be decomposed at high temperature to form pores (pore forming agent: porogen or sacrificial polymer) Should be adjusted to form nanometer-sized microphase separation by moderate interpulsion. However, since the width of the interlayer insulator is 100 nm or less, the pore size should be maintained at least one order or less (<4 nm). The compatibility between the polymethylsilsesquioxane insulator polymer and the organic polymer for forming the pore is miscibility. Due to this limitation, the maximum possible porosity that can be achieved while maintaining the pore size of 4 nm or less using this method is not so great.

In order to overcome the limitations of the compatibility between the polymethylsilsesquioxane insulator and the pore-forming agent, a method of making an inorganic-organic block copolymer in which the pore-forming agent and the polymethylsilsesquioxane are covalently linked have. By doing so, it is possible to form uniform and fine pores of 3 nanometers or less in the insulator resin after heat treatment, while solving the compatibility problem between the polymethylsilsesquioxane insulator and the pore-forming agent, thereby achieving an ultra-low dielectric constant of 2.3 or less. To create an insulator material. However, since the synthesis of the inorganic-organic block copolymer is not easy, there is no detailed study on the synthesis of the inorganic-organic block copolymer for the purpose of low dielectric material.

Accordingly, the present invention is to provide an inorganic-organic hybrid block copolymer based on polymethylsilsesquioxane having a use as a low dielectric insulator and a method of manufacturing the same. That is, the present invention relates to an inorganic-organic hybrid block copolymer based on polymethylsilsesquioxane, a synthesis method for obtaining the same, and a use as a low dielectric insulator.

Poly (methylmethacrylate) (PMMA) was used as an organic material serving as a pore former. Since polymethylmethacrylate has optical transparency, good weather resistance, and high strength, nanocomposites containing polymethylmethacrylate may also have improved physical properties while maintaining optical transparency.

Detailed studies have been made on inorganic-organic polymers based on cubic silsesquioxane (POSS). In this work, the introduction of organic polymers into inorganic silsesquioxanes has shown new possibilities for improving the properties of materials. However, since POSS does not react and there is no Si-OH remaining, there is a problem in blending with polymethylsilsesquioxane for forming a low dielectric thin film, and thus it cannot be used as a pore-forming agent.

The present invention covalently bonds a polymethylmethacrylate block to a low molecular weight polymethylsilsesquioxane, thereby making it possible to serve as a pore-forming agent of polymethylmethacrylate during heat treatment. Atom transfer radical polymerization (ATRP) initiator is introduced into polymethylsilsesquioxane, and from this, the polymerization of methyl methacrylate (MMA) proceeds to give a block copolymer (PMSSQ-PMMA) structure. will be.

Methyltrialkoxysilane [CH ₃ Si (OR) ₃ ] used in the present invention is represented by the formula (1).

[Formula 1]

R is an alkyl group having 1-5 carbon atoms.

Polymethylsilsesquioxane using the formula (1) is represented by the following formula (2).

[Formula 2]

In Formula 2, n is an integer of 10 or more as the degree of polymerization, the number average molecular weight (Mn) normalized to the molecular weight of the standard polystyrene polymer measured by gel permeation chromatography is 1,000 or more, and silanol (Si-OH) in the terminal group The amount of is more than 5 mol%.

Alkenyl ester of 2-halo-isobutyric acid (2-halo-isobutyric acid alkenylate) used in the present invention is represented by the following formula (3).

[Formula 3]

Wherein p is an integer from 1 to 10 and X is Br or Cl.

2- (halo-isobutyric acid 5- (chlorodimethysilanyl) alkyl ester) of 2-halo-isobutyric acid using the ester of Chemical Formula 3 is represented by the following Chemical Formula 4.

[Formula 4]

The polymethylsilsesquioxane introduced with the ATRP initiator using Formulas 2 and 4 is represented by the following Formula 5.

Polymethylsilsesquioxane which introduce | transduced the initiator

Methyl methacrylate (methylmethacrylate, MMA) which acts as a pore-forming agent in polymethylsilsesquioxane having the initiator of Formula 5 is covalently bonded to polymethylsilsesquioxane (PMSSQ) using the ATRP method. The polymethylsilsesquioxane-polymethyl methacrylate block copolymer is represented by the following Chemical Formula 6.

Polymethylsilsesquioxane-polymethyl methacrylate block copolymer

In Formula 6, n and m are polymerization degrees, n is 10 or more, m is 10 or more, p is an integer of 1 to 10, and X is Br or Cl. The number average molecular weight (Mn) is at least 5,000, and the amount of silanol (Si-OH) in the terminal group is at least 5 mol% (but not observed on NMR).

Hereinafter, the present invention will be described in detail.

The polymethylsilsesquioxane represented by the formula (2) is a silanol having a molecular weight and a terminal group by controlling the number of moles of HCl and H ₂ O used as a catalyst, the amount of THF used as a solvent, and the reaction time. The amount of (Si-OH) can be adjusted.

The polymethylsilsesquioxane production process represented by Chemical Formula 2 is shown in Scheme 1 below.

Scheme 1

[Formula 2]

The alkenyl ester of 2-halo-isobutyric acid represented by the formula (3) is synthesized by adding 2-halo-isobutyryl bromide little by little in chloroform, alkenyl alcohol and triethylamine solution. After washing with distilled water, water is removed with MgSO ₄ and the solvent is removed with a vacuum pump. Pure product is obtained by vacuum distillation.

The preparation process of the alkenyl ester of 2-halo-isobutyric acid represented by Chemical Formula 3 is shown in Scheme 2 below.

Scheme 2

[Formula 3]

5- (chlorodimethylsilanyl) alkyl ester of 2-halo-isobutyric acid represented by Chemical Formula 4 includes toluene having water removed from platinum / carbon (Pt / C) used as a catalyst and 2 represented by Chemical Formula 3 above. Alkenyl ester of halo-isobutyric acid and dimethylchlorosilane are added using a syringe, reacted, filtered through celite, and obtained by vacuum distillation.

The preparation process of 5- (chlorodimethylsilanyl) alkyl ester of 2-halo-isobutyric acid represented by Chemical Formula 4 is shown in Scheme 3 below.

Scheme 3

[Formula 3] [Formula 4]

The polymethylsilsesquioxane having introduced the initiator represented by the formula (5) is represented by the polymethylsilsesquioxane represented by the formula (2) in the tetrahydrofuran (THF) and triethylamine from which water is removed and represented by the formula (4) It can be obtained by reacting the 5- (chlorodimethylsilanyl) alkyl ester of 2-halo-isobutyric acid.

A method of preparing polymethylsilsesquioxane having introduced the initiator represented by Chemical Formula 5 is shown in Scheme 4 below.

Scheme 4

[Formula 5]

The polymethylsilsesquioxane-polymethyl methacrylate block copolymer represented by Chemical Formula 6 is prepared by dissolving methyl methacrylate, CuBr or CuCl, and 2,2'-bipyridine in THF. ATRP method by purging with nitrogen, and then separately dissolving polymethylsilsesquioxane introduced with the initiator of Formula 5 in THF, and then refluxing with nitrogen and then adding to the methylmethacrylate solution using a syringe. Can be obtained by The resulting polymethylsilsesquioxane-polymethylmethacrylate block copolymer can be obtained by precipitating in hexane followed by reprecipitation and vacuum drying to obtain pure product.

The method for preparing the polymethylsilsesquioxane-polymethyl methacrylate block copolymer represented by Chemical Formula 6 is shown in Scheme 5 below.

Scheme 5

[Formula 6]

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention. These examples are given to illustrate the invention, and it will be apparent to those skilled in the art that the scope of the invention is not limited by these examples.

EXAMPLE

reagent

All reagents were commercially available and most reagents were used without further purification. Methyl methacrylate was used by distillation under reduced pressure. Tetrahydrofuran was used after distillation after adding sodium / benzophenone in a nitrogen environment. Copper bromide (CuBr) was stirred in acetic acid for 24 hours, filtered, washed with methanol and dried in vacuo.

How to measure

All new compounds were checked for structure using ¹ H and ¹³ C-NMR. ¹ H-NMR and ¹³ C-NMR were recorded using Bruker DPX-300 MHz NMR spectroscopy. Molecular weights were normalized to the molecular weight of standard polystyrene polymers measured by gel permeation chromatography (GPC) with mixed bead Jordi column and Waters 2410 differential refractometer using THF as eluent. Glass transition temperature and thermogravimetric analysis were measured using DSC 2910 and TGA from TA Instruments, respectively.

Polymethylsilsesquioxane Synthesis

6.81 g (0.05 mole) of methyltrimethoxysilane (MTMS) was placed in a flask and placed on an ice-bath. 1 mL of hydrochloric acid (2M HCl) with R1 (molar ratio of acid catalyst and total monomer) = 0.03 , 0.002 mole) and 9 g (0.5 mole) of distilled water having a ratio of R 2 (molar ratio of water and total monomers) = 10.0, drop by drop while stirring, and keep stirring at 0 ° C. for 4 hours. Dilute this solution with 75 mL of methyl-isobutylketone (MIBK), wash at least 3 times with distilled water until neutral, and separate the organic layer to remove the remaining water with magnesium sulfate (MgSO ₄ ) and filter through a filter. It is then dried while removing the solvent in vacuo. The product was about 3.05 g as a colorless solid. The number average molecular weight (Mn, GPC) was 3000 and the polydispersity (Mw / Mn) was 3.4.

¹ H NMR (d ₆ -acetone): 6.2-5.4 (Si-OH), 3.5 (Si-OCH ₃ ), 0.13 (Si-CH ₃ )

Pent-4-enyl Ester Synthesis of 2-Bromo-isobutyric Acid

6.89 g (0.08 mol) of 4-pentenol is dissolved in chloroform, and an appropriate amount of triethylamine is added thereto. In this solution, a solution of 18.4 g (0.08 mol) of 2-bromoisobutyryl bromide dissolved in 50 mL chloroform was added dropwise at 0 ° C. and then stirred at room temperature for 4 hours. The organic layer was separated, washed three times with distilled water, the remaining water was removed with magnesium sulfate (MgSO ₄ ), filtered, and dried with a solvent removed in vacuo. The product was about 13.6 g (72% yield).

¹ H NMR (CDCl ₃ ): 5.81 (m, 1H, CH = CH ₂ ), 5.05 (m, 2H, CH = CH ₂ ), 4.15 (t, 2H, O-CH _2- ), 2.15 (q, 2H , CH ₂ -CH =), 1.90 (s, 6H, -CH ₃ ), 1.78 (p, 2H, CH ₂ -CH ₂ -CH ₂ ).

¹³ C NMR: 171.8 (C = O), 137.6 (CH = CH ₂ ), 115.8 (CH = CH ₂ ), 65.6 (O-CH ₂ ), 56.2 (C-Br), 30.2 (CH ₂ ), 27.8 ( CH ₃ ).

5- (chlorodimethylsilanyl) pentyl ester synthesis of 2-bromo-isobutyric acid

In a glove box, a mass of 100 mg of platinum / carbon (Pt / C-10 wt%) used as a catalyst is put in a flask, and 20 mL of toluene, from which water is removed, is represented by Chemical Formula 3 above. 2 mL of pent-4-enyl ester of bromo-isobutyric acid and 6 mL of dimethylchlorosilane were added using a syringe and reacted at 65 ° C for 24 hours, followed by celite to remove the catalyst. The solvent was then removed by vacuum distillation to give a pure product. The product was 1.9 g (0.0058 mol) and the yield was 53%.

¹ H NMR (CDCl ₃ ): 4.14 (t, 2H, O-CH ₂ ), 1.89 (s, 6H, -CH ₃ ), 1.67 (m, 2H, O-CH ₂ -CH ₂ ), 1.41 (m, 4H, CH ₂ ), 0.80 (t, 2H, CH ₂ -Si), 0.37 (s, 6H, Si-CH ₃ ).

¹³ C NMR: 171.7 (C = O), 66.0 (O-CH ₂ ), 56.0 (C-Br), 30.8 (CH ₂ ), 29.2 (CH ₂ ), 28.1 (CH ₃ ), 22.7 (CH ₂ ), 18.9 (Si-CH ₂ ), 1.7 (Si-CH ₃ ).

Synthesis of Polymethylsilsesquioxane with Initiator

Synthesis of polymethylsilsesquioxane having introduced the initiator represented by the formula (5) dissolves 500 mg of the polymethylsilsesquioxane represented by the formula (2) in 10 mL of THF from which water is removed, and then triethylamine (using a syringe) triethylamine). After cooling in an ice bath at 0 ° C., 5- (chlorodimethylsilanyl) pentyl ester of 2-bromo-isobutyric acid represented by Chemical Formula 4 is added dropwise. The solution was stirred at room temperature for 3 hours and then diluted with 40 mL of MIBK. The organic layer was separated, washed three times with distilled water, the remaining water was removed with magnesium sulfate (MgSO ₄ ), filtered and dried under vacuum to remove the solvent. A liquid product having a very high viscosity represented by Chemical Formula 5 was obtained. The change in the amount of -OH in the polymer according to the amount of 2-bromoisobutylate serving as an initiator is shown in Table 1 below. Each amount was calculated using the amount of Si-OH, Si-CH ₃ , Br-C- (CH ₃ ) groups of NMR. As expected, the amount of silanol groups (Si-OH) decreased as the amount of initiator increased. However, the larger decrease in silanol groups than the increase in amount of initiator seems to be due to the intermolecular condensation between the silanol groups during the reaction. Nevertheless, it indicates that there is a sufficient amount of silanol groups for subsequent reaction with polysilsesquioxane.

¹ H NMR (CDCl ₃ ): 6.2-5.4 (Si-OH), 3.5 (Si-OCH ₃ ), 4.14 (O-CH ₂ ), 1.89 (-CH ₃ ), 1.67 (O-CH ₂ -CH ₂ ) , 1.41 (CH ₂ ), 0.80 (CH ₂ -Si), 0.37 (Si-CH ₃ ) 0.13 (Si-CH ₃ ).

 [Table 1] Change of -OH content according to the amount of initiator in the polymer

Polymer Si-OH (mol%) Initiator (mol%) Polymethylsilsesquioxane 23.4 0 Polymer 1 15.2 1.8 Polymer 2 19.4 2.6 Polymer 3 18.8 3.2 Polymer 4 17.2 4.8

Polymethylsilsesquioxane-polymethylmethacrylate block copolymer synthesis

Synthesis of the polymethylsilsesquioxane-polymethyl methacrylate block copolymer represented by the formula (6) used a general atomic transfer radical polymerization reaction. Methyl methacrylate, CuBr, and 2,2'-bipyridine are dissolved in tetrahydrofuran (THF) dewatered and then air is removed by refluxing for 5 minutes. In another flask, polymethylsilsesquioxane having the initiator represented by Chemical Formula 5 was dissolved in tetrahydrofuran (THF), and then refluxed with nitrogen for 5 minutes to remove air, and then the methyl methacryl using a syringe. Add to the raid solution and stir at 60 ° C. for 30 minutes. The resulting polymethylsilsesquioxane-polymethyl methacrylate block copolymer was obtained by precipitating in hexane and then dissolved in THF and then reprecipitating in hexane, followed by vacuum drying to obtain a pure white product. The NMR results of the product are shown in FIG. 1. At 0 ppm the peaks of the methyl groups of silsesquioxanes can be seen, and the peaks of polymethyl methacrylate can be seen at 3.5 ppm, 1.8 ppm and 1 ppm.

Characterization of Block Copolymers

The molecular weight was measured using gel permeation chromatography (GPC) to determine if the product was a block copolymer or only a blend of two polymers. The results are shown in FIG. Figure 2 shows the peak of the block copolymer after the reaction with polymethylsilsesquioxane (PMSSQ) as a starting material before the reaction. Polymethylsilsesquioxane (PMSSQ) showed the highest peak at molecular weight 3,740, whereas the synthesized block copolymer showed the highest peak at 24,500 with increased molecular weight. And one peak showing peak indicates that the methyl methacrylate (MMA) monomer started the initiation reaction only from the polymethylsilsesquioxane (PMSSQ) in which the block copolymer introduced the initiator.

3 shows the results of measuring the glass transition temperature of the block copolymer using DSC. As expected, the glass transition temperature could be measured in the polymethyl methacrylate (PMMA) block. The glass transition temperature of the polymethyl methacrylate (PMMA) homopolymer used as a standard under the same conditions was 109 ° C, and the block copolymer showed a glass transition temperature at 115 ° C which was slightly higher than this.

The results of thermogravimetric analysis (TGA), the most important analysis, are shown in FIG. 4. The analysis section ranged from 30 ° C to 500 ° C. The polymethyl methacrylate (PMMA) homopolymer synthesized under the same conditions did not lose mass up to 280 ° C., but began to decompose at higher temperatures and quantitatively decomposed by the amount contained near 410 ° C.

The polymethylsilsesquioxane-polymethylmethacrylate block copolymer synthesized by the method proposed in this study also exhibited a thermal decomposition curve similar to that of the polymethylmethacrylate (PMMA) homopolymer used as a standard. The polymethylsilsesquioxane homopolymer, also used as a standard, showed a simple pyrolysis curve. There is a slight loss of mass from 150 ° C because of the secondary condensation reaction between silanol groups remaining unreacted. From this point, crosslinking due to intermolecular condensation began and was completed near 300 ° C. From then on, no mass loss was observed from 500 ° C.

 Polymethylsilsesquioxane-polymethylmethacrylate block copolymers exhibited the properties of both materials described above. From 175 ° C to 275 ° C, condensation reaction due to intermolecular crosslinking between silanol groups showed a slight loss of mass, similar to that of polymethylsilsesquioxane homopolymer, and polymethylmethacrylate block from 280 ° C. The decomposition started and ended at 410 ° C., showing a pattern similar to that of the polymethylmethacrylate (PMMA) homopolymer. From then on, no further mass loss was observed from 500 ° C. The remaining material, on the order of 10% by mass, agrees within the expected range with the polymethylsilsesquioxane remaining after crosslinking in the block copolymer.

On the other hand, the thermogravimetric test results for the blend of pure polymethylsilsesquioxane and polymethylsilsesquioxane-polymethyl methacrylate block copolymer (16 wt%) showed pure polymethylsilicone in FIG. 4. Secondary condensation of the silanol groups of sesquioxanes with the silane groups in the block copolymers occurred between 150 ° C and 275 ° C, as expected, and pyrolysis of the polymethylmethacrylate blocks in the block copolymers then occurred at temperatures Leave 80% by weight of the residue of the blend amount.

Finally, a polymethylsilsesquioxane homopolymer, a blend of polymethylsilsesquioxane and polymethyl methacrylate, and polymethylsilsesquioxane and polymethylsilsesquioxane-polymethylmethacrylate 5 to 7 show optical micrographs of the block copolymer prepared by calcination up to 450 ° C. after the thin film was prepared. Polymethylsilsesquioxane homopolymer (FIG. 5; 500 times, thickness: 5,030 nm refractive index: 1.361) shows a clean and uniform surface even after firing, while polymethylsilicone using polymethylmethacrylate as pore-forming agent When the blend of sesquioxane and polymethyl methacrylate (FIG. 6; PMSSQ + PMMA 10wt% porogen. 100 times) is fired after coating, polymethylsilsesquioxane is cross-linked with polymethylmethacrylate and phase-separated. And cracked. However, blends of polymethylsilsesquioxane and polymethylsilsesquioxane-polymethylmethacrylate block copolymers (FIG. 7; PMSSQ + hybrid polymer 8 wt% porogen, 500 times, film thickness: 4830 nm, refractive index: 1.343) ) Was able to produce a thin film with a clear surface that polymethyl methacrylate was sufficient as a pore-forming agent and did not cause phase separation or cracking after firing.

Pore size analysis of low dielectric thin films of block copolymers used as pore formers

The basic matrix resin to form the pores is a polymethylsilsesquioxane series terpolymer, methyltrimethoxysilane, 1,2-bis (trimethoxysilyl) ethane (1,2-bis (trimethoxysilylethane) and dimethoxy-dimethylsilane have a molar ratio of 7: 2: 1.

As shown in Table 2 below, the amount of the block copolymer to be used as the pore-forming agent was tested in six different ways. After dissolving the block copolymer and terpolymer used as a pore-forming agent in a solvent, spin coating, and firing to 450 ° C. near a vacuum, the size of the pores formed in the thin film is measured by a positronium annihilation lifetime spectroscopy. , PALS). At porosity of about 25%, the pore size was measured to be less than 3 nanometers, and the expected dielectric constant was about 2.2, making it an excellent candidate as a pore-forming agent for making ultra-low dielectric insulation materials.

[Table 2] Pore size formed in the thin film after firing at 450 ℃

Sample Addition volume [% by volume] Expected porosity [%] Measured porosity [%] Postronicium [Ps] Lifespan [ns]  Calculated pore diameter [nm] One 0 0 0 - - 2 10 8.7 9.4 22.5 1.7 3 15 13.1 14.0 24.7 1.7 4 20 17.4 17.1 31.1 2.0 5 25 21.8 22.6 37.1 2.2 6 30 26.1 25.4 41 2.4

As described above, the present invention provides a polymethylsilsesqui by making a block copolymer in which a polymethyl methacrylate serving as a pore-forming agent is covalently linked to a polymethylsilsesquioxane-based material by using an ATRP reaction. By overcoming the limitations of compatibility between the oxane insulator and the pore-forming agent, it is possible to form uniform and fine pores of 3 nanometers or less in the insulator resin after heat treatment, thereby making an insulator material having an ultra-low dielectric constant of 2.3 or less. There is an advantage.

Claims (7)

An initiator of formula (5) characterized by reacting a poly (methylsilsesquioxane) represented by formula (2) with a 5- (chlorodimethylsilanyl) alkyl ester of 2-halo-isobutyric acid represented by formula (4) under a base: Method for producing polymethylsilsesquioxane introduced. [Formula 2]

In Chemical Formula 2, n is 10 or more as the degree of polymerization, the number average molecular weight (Mn) is 1,000 or more, and the amount of silanol (Si-OH) in the terminal group is 5 mol% or more. [Formula 4]

In Formula 4, p is an integer of 1 to 10, X is Br or Cl. [Formula 5]

In Chemical Formula 5, n is 10 or more as the degree of polymerization, and the amount of silanol (Si-OH) in the terminal group is 5 mol% or more. p is an integer from 1 to 10 and X is Br or Cl. Polymethyl represented by the following formula (6) characterized in that it is obtained by reacting a methyl methacrylate (MMA) and a polymethylsilsesquioxane having an initiator represented by the following formula (5) using an atomic transfer radical polymerization (ATRP) method. Method for producing silsesquioxane-polymethyl methacrylate block copolymer. [Formula 5]

In Chemical Formula 5, n is 10 or more as the degree of polymerization, and the amount of silanol (Si-OH) in the terminal group is 5 mol% or more. p is an integer from 1 to 10 and X is Br or Cl.  [Formula 6]

In Formula 6, n and m are polymerization degrees, n is 10 or more, m is 10 or more, the number average molecular weight (Mn) is 5,000 or more, and the amount of silanol (Si-OH) in the terminal group is 5 mol% or more. p is an integer from 1 to 10 and X is Br or Cl. The method for producing polymethylsilsesquioxane having an initiator according to claim 1, wherein the reaction solvent is tetrahydrofuran (THF) and the base is triethylamine. 3. The polymethylsilsesquioxane-polymethylmethacrylate block aerial according to claim 2, wherein the polymerization is carried out in the presence of CuBr or CuCl and 2,2'-bipyridine. Process for the preparation of coalescing. Polymethylsilsesquioxane having introduced the initiator of formula (5) [Formula 5]

In Chemical Formula 5, n is a polymerization degree n is 10 or more, and the amount of silanol (Si-OH) in the terminal group is 5 mol% or more. p is an integer from 1 to 10 and X is Br or Cl. Polymethylsilsesquioxane-polymethyl methacrylate block copolymer of the formula  [Formula 6]

In Formula 6, n and m are polymerization degrees, n is 10 or more, m is 10 or more, the number average molecular weight (Mn) is 5,000 or more, and the amount of silanol (Si-OH) in the terminal group is 5 mol% or more. p is an integer from 1 to 10 and X is Br or Cl. Low dielectric insulator using polymethylsilsesquioxane-polymethylmethacrylate block copolymer of formula (6)

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