KR20160138760A - Method of Fabricating Perpendicularly Oriented Block Copolymer Thin Film By Introducing Star Polymer - Google Patents

Abstract

In the nanolithography process according to the present invention, a block copolymer and a neutral star polymer are introduced into the block copolymer thin film to obtain a block copolymer in which the microstructure of the block copolymer is oriented in a direction perpendicular to the substrate The orientation of the microdomains can be controlled without modifying the surface of the additional substrate by preparing a thin film, and the block copolymer pattern can be variously performed regardless of the kind of the substrate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for producing a vertically oriented block copolymer thin film by introducing a molding polymer,

More particularly, the present invention relates to a method of preparing a block copolymer thin film by introducing a block copolymer and a neutral star polymer into a block copolymer thin film in a nanolithography process. And a method for producing a block copolymer thin film in which the microstructure is oriented in a direction perpendicular to the substrate.

Self-assembly is one of the useful ways of fabricating functional nanostructures that have a specific structure and exhibit electro-optic properties. It forms a spontaneous stable structure by finding the thermodynamic stability of the basic units constituting the structure. And has been attracting attention in the field of nanotechnology for several decades. Such self-assembling phenomenon has also been found in block copolymers, one of the chemically synthesized polymers.

Block copolymers are a type of polymeric material, in which two or more polymers link the ends of each other through covalent bonds. The simplest diblock copolymer of block copolymers is that two polymers with different propensities are linked together to form a polymer. The two polymers connected to each other are easily phase-separated due to their different material properties, and finally the block copolymer can self-assemble to form a nanostructure.

Self-assembling block copolymers perform phase-separation of the copolymer blocks with various chemical properties by performing order-disorder transitions at specific temperature intervals, resulting in chemically-defined sizes of tens or even less than 10 nm And can form separated ordered domains, which is a useful compound for nanostructure fabrication.

The size and shape of the domains can be controlled by manipulating the molecular weight of the copolymer and the composition of the various block types of the copolymer. Interfaces between domains can have widths of the order of 1 to 5 nm and can be manipulated by modifying the chemical composition of the copolymer block.

The block copolymer is composed of different blocks, each block comprising one or more identical monomers, these different blocks being arranged side by side along the polymer chain. Each block may contain a plurality of monomers of that type. That is, for example, the AB block copolymer may have a plurality of A type monomers in (each) A block and a plurality of B type monomers in (each) B block. An example of a suitable block copolymer is a polymer in which a polystyrene monomer (hydrophobic block) and a polymethyl methacrylate (PMMA) monomer (hydrophilic block) are covalently bonded. Other block copolymers with different hydrophobic / hydrophilic blocks may also be used. For example, alternating or periodic block copolymers such as [-ABABAB-] _n or [-ABCABC] _m , where n and m are integers. The blocks are interconnected by covalent bonds in a linear or branched fashion.

On the other hand, instead of the conventional top-down method for making a nano-scale structure, the self-assembly of a block copolymer as an alternative to overcome the limitations of the top-down method, A bottom-up method using a high-temperature plasma is often used. In the case of the block copolymer thin film, it is necessary to have a vertical orientation with respect to the substrate to exhibit a function as a nanotemplate. However, since one domain block of the block copolymer has a higher affinity with the substrate, Mostly. Therefore, various methods such as solvent annealing, neutral layer treatment, rough surface and electric field have been used to realize the vertical orientation of the block copolymer thin film, An efficient technique of orienting the structure in a direction perpendicular to the substrate is required.

As a result of intensive efforts to solve the above problems, the present inventors have found that the block copolymer thin film has a vertical orientation only by the simple introduction of a star polymer without pretreatment of a substrate such as a neutral layer treatment and introduces inorganic nanoparticles It is confirmed that the nanoparticles do not remain in the thin film after etching, thereby completing the present invention.

It is an object of the present invention to provide a method for preparing a vertically oriented block copolymer thin film in which the microstructure of the block copolymer is oriented in a direction perpendicular to the substrate and can function as a nanotemplate.

In order to achieve the above object, the present invention provides a process for preparing a vertically oriented block copolymer thin film, characterized in that a block copolymer and a neutral star polymer are mixed and coated on a substrate, followed by heat treatment .

The process can be simplified because the block copolymer thin film has a vertical orientation only by the simple introduction of the molding polymer without substrate pretreatment such as the neutral layer treatment of the vertically oriented block copolymer thin film according to the present invention.

In addition, since the molding polymer is made of only pure organic material containing no inorganic substance, unlike the case of introducing inorganic nanoparticles, there is an effect that the nanoparticles do not remain in the thin film after etching.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram schematically illustrating the synthesis process of a P (S- r- MMA) molding polymer.
2 is a SEM image of a PS- b- PMMA thin film containing 20 wt% of a neutral P (S- r- MMA) forming polymer.
FIG. 3 is a graph showing the results of PS- b (a) including star 6-4, (b) star 5-5, (c) star 4-6, (d) star 3-7, -PMMA thin film.
4 is a SEM image of 101,000 g / mol PS- b- PMMA thin film containing 10 wt% of star 3-7 (a), 20 wt% of (b) and 40 wt% of (c).
Figure 5 is a star 3-7 20wt% neutron reflectivity (a) and scattering length density of 101,000g / mol PS- b -PMMA thin film of (c) a graph comprising a linear PS- d r - d PMMA chain 40wt (B) and scattering length density (d) of a PS- b -PMMA thin film containing 10 wt.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

In the case of the PS- b- PMMA thin film, due to the preferential interaction between the PMMA domain and the silicon wafer, the microstructure of the block copolymer is usually in a direction parallel to the substrate . In the present invention, a neutral star polymer is introduced into the block copolymer thin film so that the microstructure of the block copolymer can be oriented in a direction perpendicular to the substrate.

Accordingly, in one aspect, the present invention relates to a process for preparing a vertically oriented block copolymer thin film, characterized in that a block copolymer and a neutral star polymer are mixed and coated on a substrate, followed by heat treatment.

The present invention also relates to a vertically oriented block copolymer thin film produced by the above method from another viewpoint, characterized in that the microstructure of the block copolymer and the substrate are oriented in directions perpendicular to each other.

In the present invention, the block copolymer is poly (styrene - b - methyl methacrylate) (PS- b -PMMA), poly (styrene - b -2- vinyl pyridone) (PS- b -PVP), poly (styrene - b - butadiene) (PS- b -PB), poly (styrene - b - peroxide enyl dimethylsilane) (PS- b -PFS), poly (styrene - b - polydimethylsiloxane) (PS- b -PDMS ), poly (styrene - b - ethylene oxide) (PS- b -PEO), poly (styrene - b - isoprene) (PS- b -PI), poly (ethylene oxide - b - isoprene) (PEO- b -PI ), But the present invention is not limited thereto.

One example of forming the neutral polymer is poly (styrene-r-methyl methacrylate) (poly (styrene- r -methyl methacrylate , PS- r -PMMA) and include a random copolymer, which "etch-affinity ( etching-friendly "additive to control the orientation of the microdomains of the lamellar to form the PS- b- PMMA thin film.

The present invention is based on the assumption that when a star polymer, which is neutral to two domains of PS / PMMA, is cast into a thin film together with a PS- b- PMMA block copolymer and then subjected to heat treatment, the molding polymer is mainly located above and below the thin film In addition to the effect of neutralizing the substrate, the interfacial tension is lowered so that the microstructure of the block copolymer becomes perpendicular to the substrate.

The molding polymer can be synthesized by an arm-first method using atom transfer radical polymerization (ATRP), and the process is schematically shown in FIG.

In the present invention, the molding polymer comprises the steps of: (a) synthesizing a linear random polymer for an arm chain of a molding polymer using a spinning radical polymerization method; And (b) adding a cross-linking agent to the cross-linked polymer core to form a linear random polymer arm chain to produce a star-shaped shaped polymer.

Preferably, the PS- r- PMMA molding polymer synthesized in the examples of the present invention is prepared as follows.

The composition of styrene and MMA in the PS- r- PMMA arm chains confirms the optimal neutral composition to induce the vertical orientation of the PS- b- PMMA thin film. A linear random polymer PS- r -PMMA-Br, which is an arm chain for linear copolymers, is synthesized. The composition of styrene and MMA in PS- r -PMMA-Br is modified by controlling the molar ratio of styrene and MMA fed in the synthesis to have the desired interaction of the PS and PMMA domains of the block copolymer template of the linear copolymer . PS- r -PMMA-Br random copolymers with PS / PMMA composition of 60:40, 50:50, 40:60, 30:70 and 20:80 were respectively arm 6-4, arm 5-5, arm 4- 6, arm 3-7, and arm 2-8, respectively.

The molecular weights ( M n's) of these copolymers can be adjusted to ~3000 g / mol. To remove the unreacted linear polymer, fractional precipitation was performed using dichloromethane as a solvent and diethyl ether as a nonsolvent.

As a result, a molded copolymer composed of a highly crosslinked polyDVB core and PS- r- PMMA brush arms was synthesized.

In addition, the absolute molecular weight and arm numbers of the molded copolymer were measured by performing a multiangle light scattering (MALS) method in addition to the relative M n measured by gel permeation chromatography.

Comparing the molecular weight obtained from GPC with the absolute molecular weight obtained from MALS, the molecular weight obtained from GPC is 3-4 times larger than the molecular weight obtained from GPC (Matojaszewski et al., Gao, H., Matyjaszewski, KJ Am. Chem. 11828-11834).

Absolute M n's and arm numbers ( N _arms ) of the shaped copolymer are M n = ~ 170000-340000 g / mol and N _arm = ~ 40-100, respectively.

Also, the hydrodynamic radius ( R _h ) of the shaped copolymer was measured using dynamic light scattering (DLS), and R _h = ~ 8.8-17.2 nm.

In the present invention, the influence of the shaped copolymer on the PS- b- PMMA thin film morphology was confirmed.

Since the preceding PS- r -PMMA chains are dispersed within the PS- b- PMMA film, they exhibit a parallel arrangement and do not effectively neutralize the top / bottom boundaries. FIG. 3 is a scanning electron microscope (SEM) photograph of a PS- b- PMMA thin film containing star-6-4, star 5-5, star 4-6, star 3-7 and 20 wt% Respectively. In the above, the film containing star 3? 7 exhibited a vertical orientation in good order as a whole while the other film exhibited a low degree of vertical orientation in a less ordered structure. As a result, the PS- b- PMMA thin film containing the molded copolymer containing 30 mol% of styrene and 70 mol% of MMA in the PS- r- PMMA arm was found to exhibit well-defined vertical orientation after the thermal annealing treatment .

Therefore, in the present invention, the molar ratio of styrene to methyl methacrylate may be 20:80 to 40:60 (mol%), and the molar ratio of styrene to methyl methacrylate may be 30:70 (mol%). .

In addition, the content of the shaped copolymer in the present invention may also be an important factor in optimizing the vertical orientation of the PS- b- PMMA thin film.

4 is a graph showing the results of the measurement of 101,000 g / mol of PS- b- PMMA containing 10 wt% (9.1 vol%) of star 3_7, 20 wt% (16.7 vol%), and 40 wt% (28.6 vol% SEM image of thin film. star 3-7 PS- b- PMMA thin films containing 10wt% exhibit partially vertical orientation. This may be due to the fact that the top surface and the bottom interface contain insufficient amounts of the shaped copolymer. PS- b- PMMA thin film containing 20 wt% star 3-7 exhibits a well-oriented vertical orientation over the entire area.

Therefore, in the present invention, 10 to 30 wt% of molding polymer may be included in the block copolymer thin film.

Au nanoparticles of about 5 wt% (2.3 vol%) were required to induce the vertical orientation of the PS- b- PMMA thin film in the prior art on neutral Au nanoparticles. This difference can be attributed to the contrast hardness of the particle cores. In general, neutral particles are located in intermaterial dividing surfaces (IMDS) due to balanced enthalpy interactions between the two microdomains, and the particles modify the chain arrangement of the BCPs near the IMDS causing entropic penalty.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are for illustrative purposes only and that the scope of the present invention is not limited by these embodiments.

[Example]

Example 1

First, P (S- r- MMA) -Br, which is to become an arm portion through atom transfer radical polymerization (ATRP), was synthesized. A star polymer composed of a crosslinked polyDVB core and a P (S- r- MMA) arm was synthesized using divinylbenzene as a crosslinking agent as shown in FIG. The PS- r -PMMA-Br random copolymer having a PS / PMMA composition of 60:40, 50:50, 40:60, 30:70 and 20:80 in the molar ratio is designated arm 6-4, arm 5-5, arm 4-6, arm 3-7, and arm 2-8. The molecular weights (Mns) of these copolymers were adjusted to ~3000 g / mol. Properties of the PS- r -PMMA random copolymer are shown in Table 1.

The synthesized P (S- r- MMA) star polymer was mixed with 20 wt% of PS- b- PMMA (Mn = 89 kg / mol) block copolymer in the lamellar form and spin- coating, and then annealed at 190 ℃ for 4 days under vacuum condition. The microstructure of the block copolymer thin film observed through a scanning electron microscope (SEM) after the annealed thin film was etched by reactive ion etching (RIE) is shown in Fig. 2 finger print pattern, and it was confirmed that the vertical orientation was achieved.

Chemical compositions of the cancer and molded copolymer are shown in Table 2 below.

Neutron reflectivity was measured using a deuterated shaped copolymer to determine the position of the neutral shaped copolymer in the PS- b- PMMA thin film.

FIG. 5 shows the neutron reflectivity profile and the scattering length density (SLD) profile of the film according to the present invention.

In Figs. 5 (a) and 5 (b), the solid line is the most suitable line for the data based on the model profile according to the depth of the film. The SLD calculated values of PS- b- PMMA and d-star 3-7 composed of dPS- r -dPMMA and hydrogenated DVB were ~1.25 × 10 ^-6 Å ^-2 and ~ 4.2 × 10 ^-6 Å ^-2 , respectively , High contrast SLD between them. Thus, as shown in Figure 5 (c), the high SLD portion refers to the separation of the d-star 3-7 molded copolymer from the SLD profile, where d-star 3-7 is mainly the top (polymer / And at the bottom (polymer / substrate interface) surface. Upper / lower separation is also observed in systems of other nonlinear structures such as bottlebrush or branched polymers in linear polymer films. On the other hand, the neutron reflectance profile and the SLD calculation profile in Figs. 5 (b) and 5 (d) show that the linear chains are dispersed in the PS- b- PMMA film with slight separation at the top and bottom of the film. The above results support the fact that the neutral molded copolymer reduces entropy disadvantages due to its bulk size and highly grafted cancer, resulting in separation at the top and bottom surfaces to effectively induce vertical orientation of the PS- b- PMMA lamella Do it.

As a result, according to the present invention, it is possible to control the orientation of the microdomains without further surface modification process by using a neutral-shaped copolymer as an etching-friendly additive in the BCP thin film, and various applications of the block copolymer pattern . ≪ / RTI >

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (10)

Wherein the block copolymer is mixed with a neutral star polymer and then coated on a substrate and then heat-treated to form a vertically oriented block copolymer thin film.
The method of claim 1 wherein the block copolymer is poly (styrene - b - methyl methacrylate) (PS- b -PMMA), poly (styrene - b -2- vinyl pyridone) (PS- b -PVP), poly (styrene - b - butadiene) (PS- b -PB), poly (styrene - b - peroxide enyl dimethylsilane) (PS- b -PFS), poly (styrene - b - polydimethylsiloxane) (PS- b - PDMS), poly (styrene - b - ethylene oxide) (PS- b -PEO), poly (styrene - b - isoprene) (PS- b -PI), poly (ethylene oxide - b - isoprene) (PEO- b - PI). ≪ RTI ID = 0.0 > 11. < / RTI >
The method of claim 1, wherein the forming polymer is poly (styrene- r -methyl methacrylate) (PS- r- PMMA).
[4] The method of claim 3, wherein the molar ratio of styrene to methyl methacrylate is 20:80 to 40:60 (mol%).
5. The method of claim 4, wherein the molar ratio of styrene to methyl methacrylate is 30:70 (mole%).
The method for producing a vertically oriented block copolymer thin film according to claim 1, comprising 10 to 30 wt% of a molding polymer based on the block copolymer thin film.
The method of claim 1, wherein the forming polymer is prepared by a method comprising the steps of:
(a) synthesizing a linear random polymer for an arm chain of a forming polymer using a spinning radical polymerization process; And
(b) adding a cross-linking agent to the cross-linked polymer core to form a linear random polymer arm chain to produce a star-shaped molded polymer.

8. The method of claim 7, wherein the molecular weight of the linear random polymer is 3000 g / mol or less.
8. The process of claim 7, wherein the unreacted linear polymer is removed by performing fractional precipitation using a dichloromethane solvent and a diethyl ether nonsolvent, ≪ / RTI >
9. A vertically oriented block copolymer thin film produced by the method of any one of claims 1 to 9, wherein the microstructure of the block copolymer and the substrate are oriented in directions perpendicular to each other.

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