KR100570285B1 - Copolymer for oxide pattern and method for oxide pattern formation thereof - Google Patents

Abstract

The present invention relates to an oxidation pattern copolymer, an oxidation pattern using the same, and a method for forming the same, and more particularly, a novel copolymer in which a photoacid generator substituted with a fluoroalkylsulfonium salt is substituted with a side chain group, and the new air. By applying coalescence to AFM lithography, a fine oxide pattern of several nm level is formed on a semiconductor or a metal substrate, and the present invention relates to an oxide pattern and a method of forming the same that can be used in semiconductor devices and ultra-thin pattern applications.

Photoacid generator, sulfonium salt substituent, AFM, lithography

Description

Copolymer for oxide pattern and method for forming oxide pattern using same             

1 shows a schematic diagram of AFM lithography described in the present invention.

(a) is a tip of an AFM, (b) is an organic thin film resist layer, and (c) is a solid substrate.

Figure 2 shows the results of ¹ H-NMR (nuclear magnetic resonance) analysis of the copolymer synthesized in the embodiment according to the present invention.

Figure 3 shows an AFM image of an oxide pattern formed by AFM lithography on a silicon substrate coated with the copolymer of the embodiment according to the present invention.

The present invention relates to an oxidation pattern copolymer, an oxidation pattern using the same, and a method for forming the same, and more particularly, a novel copolymer in which a photoacid generator substituted with a fluoroalkylsulfonium salt is substituted with a side chain group, and the new air. By applying the coalescence to AFM lithography, the present invention relates to an oxide pattern and a method of forming the same, which can be used in semiconductor devices and ultra-thin pattern applications by forming a fine monolayer pattern on the semiconductor or metal substrate.

In the field of electronics, the miniaturization trend has been rapidly progressing, and this phenomenon can be easily confirmed in information processing, communication, and various home appliances. Based on the information processing industry, it can be said that the era of micro-technology has already passed to the era of sub-micro technology. Thanks to this miniaturization trend, Microelectronics' optical micromachining technology has evolved since the emergence of 4K DRAM in the mid 70s, enabling high integration of line widths of 0.1 µm in 1996.

The microfabrication technology that enables the resolution of 1 μm or less is expected to be i-ray, excimer laser, X-ray, electron beam, focused ion beam technology, and the developed countries are strategically developing the next-generation micromachining technology. The transition from the era of small technology to the era of microtechnology has been successful without technical difficulties. It is clear that this natural transfer was possible because early scientific knowledge, methods, and techniques were supported.

Electron beam micromachining technology has emerged as a very promising technology for small device processes of 0.1 μm or less, requiring a new type of ideal molecular film resist that can overcome the limitations of the conventional spin-coated photoresist. Electron beam resists are currently widely used in the fabrication of microfabrication masks, but are not directly used in semiconductor device processing. However, with the development of ultra-fine processing equipment and the improvement of the performance of resists, the possibility of device processing using electron beam resists is increasing. So, we recently conducted basic research for the formation of ultra fine patterns using AFM, which has been spotlighted as a new micromachining technology.

In general, AFM (Atomic Force Microscope) is used to shape the surface of a sample without damaging the sample. Nanolithography is a technique that applies the force to the probe to damage the surface of the sample and manipulates the atomic or molecular arrangement of the sample surface with the probe. By using these techniques to create artificial nanostructures, materials can be controlled at the nanoscale. In the area of 10 nm or less, the field is not yet easily accessible by conventional techniques such as e-beam lithography, and AFM is almost exclusive in this area.

In the field of nanolithography using AFM, a method of forming an ultrafine pattern using a resist material, a method of obtaining an oxide film formation pattern by an electric field of an AFM tip on a surface such as hydrogen surface stabilized Si-wafer or poly-Si, etc. Methods are going on. In addition, it can be combined with electrostatic force microscopy (EMF) and scanning capacitance microscopy (SCM) to enable applications for next-generation information storage.

In the conventional AFM lithography, a pattern was formed by fabricating a self-assembled monomolecular film using an organic resist [ Jpn. J. Appl. Phys ., 37, 7148, 1998, Kim JC, J. Kor. Phys. Soc. , 35, 1013, 1999, Kim, JC, Adv. Mater. , 12, 6, 424, 2000, Rivka M.].

The technique of forming an oxide pattern using AFM is described by applying an organic thin film of a certain thickness on a silicon substrate and applying a voltage of several volts locally through the tip of the AFM to form an oxide pattern. At this time, the resist layer in the portion where the voltage was applied is destroyed, and the reaction mechanism of the reaction formula [Journal of Vacuum Science and Technology, Vol. A14, No. 3 (1996), pp 1223], Si reacts with moisture in the air and SiOx is formed and pops out onto the resist thin film. 1 is a schematic diagram of AFM lithography described in the present invention.

AFM Cathode Reaction:

2nH ₂ O + 2ne--> nH ₂ + 2nOH-

Silicon substrate (Anode reaction):

Si + nH ₂ O-> SiOn + 2nH + + 2ne-

At this time, the structure of the silicon oxide formed is very poor in structure and the etching rate is much faster than other parts during etching. In addition, the remaining organic thin film in the portion where no voltage is applied may act as a resist to produce a desired positive pattern during etching. However, in actual process, the chemical bond between the substrate and the thin film was so strong that there was a significant difficulty in removing the thin film completely after the pattern.

In addition, important factors in AFM lithography are applied voltage and current flowing, scanning speed, humidity and high performance resist [ Vac. Sci. Technol ., 1223, 1996, Sugimura, A., J. Vac. Sci. Technol ., 2912, 1997, Birkelund K., J. Appl. Phys. Lett. , 285, 1997, Avouris P.].

Therefore, it can be seen that when the lithography is performed under an optimal condition, the line width is not constant and a pattern in which the line is broken is formed. In order to form better patterns, it is necessary to first develop high-performance resists, and to control the applied voltage, scanning speed, and humidity to optimum conditions.

On the other hand, sulfonium salts are generally used as photoinitiators or radical photoinitiators in polymer polymerization or as acid catalyst generators for deprotection of organic compounds. Sulfonium salts, which generate cationic photoinitiators in response to ultraviolet light in a specific region, have been developed for various kinds of applications that cannot be obtained from conventional radical curing, and with the recent development of electronics, microelectronics engineering It is used for the formation of fine patterns. The sulfonium salt, which is a cationic photoinitiator, has a strong acid generated when it is irradiated with light, thereby increasing the efficiency of the photopolymerization reaction, but having a poor solubility in organic solvents.

In order to compensate for this drawback, it has been reported that the solubility in organic solvents is improved along with a method of generating an acid when irradiated with a nonionic photoinitiator [Journal of Photopolymer Science and Technology, Vol. 13, No. 2 (2000), pp 223-230. However, the acid generated from the nonionic photoinitiator has a problem of relatively low acid strength because methylsulfonic acid, propylsulfonic acid and camphorsulfonic acid are generated instead of the strong acid trifluoromethanesulfonic acid.

Accordingly, the present inventors have made efforts to solve the problems such as the uniformity and continuity of the line width when forming the conventional oxidation pattern, as a result, a photoacid generator substituted with a fluoroalkylsulfonium salt is introduced into the side chain to the organic solvent. Since the solubility is improved and the copolymer into which the side chain group is introduced is formed on the semiconductor or the metal substrate by a spin coating method rather than a chemical bond, it has been found that a thin and uniform thin film is formed to complete the present invention.

In addition, it has been found that the novel resist material according to the present invention can be applied to AFM lithography to adjust to optimal conditions to form fine oxide patterns of several micrometers.

Accordingly, an object of the present invention is to provide a fine resist pattern and a method of forming the same by applying a novel resist material to AFM lithography under optimal conditions.

The present invention is characterized by a copolymer represented by the following formula (1) in which a photoacid generator substituted with a fluoroalkylsulfonium salt is introduced into a side chain group.

In Formula 1, R ₁ and R ₂ are hydrogen atoms, C ₁ to C ₂₀ linear, branched or cyclic alkyl group, halogen atom, alkoxy group, phenoxy group, phenyl group, thioalkoxy group or thiophenoxy group , R ₃ to R ₅ are C ₁ to C ₆ alkylcarbonyl group, aldehyde group, cyano group, nitro group, phenyl group or phenyl group substituted with electron donating group and electron withdrawing group, n represents an integer of 0 to 20.

Hereinafter, the present invention will be described in more detail.

The present invention relates to a copolymer for an oxidation pattern, as shown in the copolymer represented by the above formula, by generating a cationic initiator in response to ultraviolet light in a specific region of the photoinitiator, radical initiator and deprotection of organic compounds In the course of progress, a photo generator substituted with a fluoroalkylsulfonium salt, which is used as an acid catalyst generator, is introduced into the side chain to improve solubility in an organic solvent, and form a fine oxidation pattern by excellent photopolymerization of the sulfonium salt to form a stable resist. It is possible to perform a role. In the coating of the oxide pattern copolymer on a semiconductor or metal substrate, a thin and uniform ultra thin film may be formed on the substrate by a spin coating method instead of a chemical bond, and a fine oxide pattern of several μm may be formed.

The copolymer in which the side chain group of the photoacid generator substituted with the fluoroalkylsulfonium salt according to the present invention is a novel compound, in which a polybenzyl methacrylate and a sulfoxide compound are introduced into the side chain in order to introduce the photoacid generator into the side chain. It is synthesized together with the hydride at a low temperature of −78 ° C. to form a copolymer having a photoacid generator substituted with a fluoroalkylsulfonium salt introduced into the side chain.

The method of applying the copolymer in which the side chain group is introduced into the photoacid generator in which the fluoroalkylsulfonium salt is substituted is specifically described as follows.

The photoacid generator substituted with the above-mentioned fluoroalkylsulfonium salt dissolves the copolymer in which the side chain group is introduced into a solvent, and then contains a resist component which is usually used in preparing a resist composition to prepare a resist composition. However, the present invention prepares a resist composition by dissolving the copolymer prepared by the above synthesis in an organic solvent without adding any component. As the solvent, single or two or more kinds of mixed solvents selected from ketones, halogenated hydrocarbons, aromatics, hydrocarbons, aliphatic alcohols, halogenated aliphatic alcohols, aliphatic esters, glycol ethers and the like can be used.

On the other hand, using the resist composition to form a thin film on a semiconductor or metal substrate, the metal substrate to form the thin film is immersed in a solution made of sulfuric acid and hydrogen peroxide in the ratio of 3: 1 for 30 minutes, and then deionized water Washed in turn. As the substrate, conventional substrate materials such as Si, Ga, Aa, Ti, Cr, and Mn can be used. Preferably, a Si substrate is used.

The resist composition is coated on the prepared substrate, and any coating method known in the art may be applied. Examples of known coating methods include spin coating, spray coating, dip coating, row coating, and the like, and preferably, spin coating is performed. When forming a film by the spin coating method, the resist composition prepared using the spin coater is spun for 20 to 40 seconds at a speed of 2,000 to 4,000 rpm to form a thin film on the substrate. When the thin film is formed, heat treatment is performed at a temperature of 70 to 80 ° C. for 1 to 2 minutes to remove the solvent present in the thin film and to improve adhesion of the resist to the substrate. The thickness of the prepared thin film was 0.004-0.006 μm.

The substrate to which the photoacid generator substituted with the fluoroalkylsulfonium salt is substituted by the method is coated with a copolymer in which a side chain group is introduced to perform AFM lithography. At this time, the adjustment of the voltage, main pressure, humidity, etc. applied to the AFM tip serves as an important factor to form a finer line width. In the present invention, the voltage applied to the AFM tip was 10 to 15 V, the humidity was 40 to 60%, the speed was 1 to 5 μm, and lines were drawn at intervals of 1 μm / s on the surface of 10 μm × 10 μm. A fine pattern having a line width of 400 to 600 nm and a height of 20 to 40 Hz can be formed.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are not intended to limit the present invention.

Synthesis Example 1 Synthesis of Polybenzylmethacrylate

3.00 g of benzyl methacrylate was dissolved in 20 ml of tetrahydrofuran, 0.45 g of azobisisobutyronitrile was added thereto, and the mixture was stirred at 66 ° C for 22 hours. After completion of the reaction, the viscous polymer solution was poured into tetrahydrofuran and diluted, and hexane was poured slowly to precipitate. The precipitate was filtered and dried under vacuum to yield 2.85 g, a compound having a yield of 95.0%.

In the ¹ H-NMR (Acetone- d ₆ solvent) 4.94 ppm of the compound prepared in the step in which two hydrogen peak (proton peak), 7.33 ppm to 5 hydrogen peaks of the benzene ring was identified as poly benzyl methacrylate. At this time, the molecular weight was 42500 g / mol.

Example 1 Synthesis of Polybenzylmethacrylate with Substituents (22%) of Triphenylsulfonium Triflate

2.00 g (11.34 mmol) of polybenzyl methacrylate and 0.92 g (4.54 mmol) of phenylsulfoxide were dissolved in 40 ml of dichloromethane, and the temperature inside the reactor was adjusted to -78 ° C using acetone-dry ice bath. , 1.28 g (4.54 mmol) of triple anhydride was slowly added dropwise. After the addition was completed, the reaction was carried out at the same temperature for 1 hour, and then slowly heated up to room temperature and stirred for 3 hours. Then, 0.57 g (5.68 mmol) of triethylamine was injected at -0 ° C to stop the reaction. The mixture was washed with distilled water again, and the washed organic layer was slowly poured into a hexane: isopropyl alcohol (8: 2 volume ratio) solvent to precipitate. The precipitate was washed again with a solvent of hexane, filtered and dried in vacuo to give 1.60 g of a white solid compound with a yield of 67.0%.

In Figure ¹ H-NMR (Acetone- d ₆ solvent) 4.94 and 5.13 ppm The results of the compound is shown in Fig. 1 two hydrogen peak (proton peak), at 5 and 7.87 ppm peak hydrogen of the benzene ring at 7.33 ppm triphenyl Fifteen hydrogen peaks in the aromatics of the sulfonium triflate were identified to identify polybenzyl methacrylate with a substituent of the triphenylsulfonium triflate. At this time, the substitution degree represents 22%.

Example 2 Synthesis of Polybenzylmethacrylate with Substituent (66%) of Triphenylsulfonium Triflate

1.60 g (7.94 mmol) and the amount of phenylsulfoxide and tricyclic anhydride added to the reaction are 0.7 equivalents to the molecular weight of the polybenzyl methacrylate monomer. 2.24 g (7.94 mmol) was added.

Thus, a yield of 60.0% of polybenzyl methacrylate having a substituent of triphenylsulfonium triflate was obtained, and the degree of substitution was 66%.

Experimental Example 1: Fine Oxidation Pattern Formation Method

0.05 g of a copolymer composed of a polymer sulfonium salt in which the polymer photoacid generator synthesized in Example 1 was introduced into the polymer side chain was dissolved in 100 g of a solution of propylene glycol methyl ether: dichloromethane (vol. 95: 5) by a stirrer. Dissolved. This resist composition was filtered using a 0.2 μm membrane filter. The prepared silicon substrate was immersed in a solution made of sulfuric acid and hydrogen peroxide in a ratio of 3: 1 for 30 minutes, washed sufficiently with deionized water, and then treated with hexamethylsilazane.

The resist composition filtered on the silicon substrate treated by the above method was spin-coated for 40 seconds at a speed of about 3,000 rpm, and softbaked to prepare a resist thin film. The thickness of the prepared resist thin film was 50 mm when measured by an ellipsometer.

An AFM probe was placed on the prepared thin film, and an oxide pattern was formed according to the accompanying drawings. At this time, the voltage applied to the AFM tip was 12 V, the humidity was 50%, the scan speed was 3 mm / sec. As a result of the lithography, the line width of the protruding SiOx was 508 nm and the height was 30 mW. 3 shows an AFM image of a pattern formed over a 10 μm × 10 μm area.

Experimental Example 2

Experimental Example 1 was carried out in the same manner as in Example 2 to form a fine oxide pattern. As a result of the lithography, the line width of the protruding SiOx was 508 nm and the height was 30 mW.

As described above, by using a copolymer including a sulfonium salt substituent in which the photoacid generator polymer according to the present invention is introduced into the side chain, it is excellent in solubility in organic solvents, and has sufficient sensitivity in forming an oxidation pattern using AFM. It has excellent coating performance on the substrate. In addition, since it can be used to form a pattern having a line width of 0.5 ㎛ or less can be very useful for high-capacity semiconductor devices and ultra-thin pattern applications.

Claims (5)

A copolymer represented by the following Chemical Formula 1, wherein a photoacid generator substituted with a fluoroalkylsulfonium salt is introduced into the side chain group: [Formula 1]

In the above formula, R ₁ and R ₂ are each a hydrogen atom, a C ₁ to C ₂₀ linear, branched or cyclic alkyl group, halogen atom, alkoxy group, phenoxy group, phenyl group, thioalkoxy group or thiophenoxy group , R ₃ , R ₄ and R ₅ are each a C ₁ to C ₆ alkylcarbonyl group, an aldehyde group, a cyano group, a nitro group, a phenyl group or an phenyl group substituted with an electron donating group and an electron withdrawing group, and n is an integer of 0 to 20, respectively. Indicates. In the method of forming a fine oxide pattern using AFM lithography, Next, the copolymer represented by Chemical Formula 1 is spin-coated on a semiconductor or metal substrate to form an ultra-thin film, and then subjected to AFM lithography at a voltage of 10 to 15 V, a humidity of 40 to 60%, and a speed of 1 to 5 μm. Method of forming a fine oxide pattern. [Formula 1]

In Formula 1, R ₁ and R ₂ are each a hydrogen atom, a C ₁ to C ₂₀ linear, branched or cyclic alkyl group, a halogen atom, an alkoxy group, a phenoxy group, a phenyl group, a thioalkoxy group or a thiophenoxy group R ₃ , R ₄ and R ₅ are each a C ₁ to C ₆ alkylcarbonyl group, an aldehyde group, a cyano group, a nitro group, a phenyl group or an electron donor group and an electron withdrawing group, and n is 0-20. Represents an integer. The method of claim 2, wherein the metal substrate is a substrate of a metal selected from Si, Ga, Aa, Ti, Cr, and Mn. Next, the fine oxide pattern, characterized in that formed by AFM lithography using a copolymer represented by the formula (1). [Formula 1]

In Formula 1, R ₁ and R ₂ are each a hydrogen atom, a C ₁ to C ₂₀ linear, branched or cyclic alkyl group, a halogen atom, an alkoxy group, a phenoxy group, a phenyl group, a thioalkoxy group or a thiophenoxy group R ₃ , R ₄ and R ₅ are each a C ₁ to C ₆ alkylcarbonyl group, an aldehyde group, a cyano group, a nitro group, a phenyl group or an electron donor group and an electron withdrawing group, and n is 0-20. Represents an integer. The micro-oxidation pattern according to claim 4, wherein the pattern has a line width of 400 to 600 nm and a height of 20 to 40 Hz.

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