Block copolymer as well as synthesis method, etching method, product and application thereof

Abstract

The invention provides a PS-PMMA (polystyrene-polymethyl methacrylate) block copolymer as well as a preparation method, an etching method, a product and application thereof, the PS-PMMA block copolymer comprises a PS chain segment, a PMMA chain segment and a linking group for connecting the PS chain segment and the PMMA chain segment, and the linking group comprises a Schiff base bond. The PS chain segment and the PMMA chain segment in the PS-PMMA block copolymer provided by the invention are connected through the linking group containing the Schiff base bond, ultraviolet exposure and etching equipment are not needed, complete separation of a PS phase and a PMMA phase can be realized only through short-time simple organic acid soaking treatment, and the integrity of a mask pattern is reserved to the maximum extent.

Description

Technical Field

[0001] The invention belongs to the field of polymer self-assembly and relates to a block copolymer and a synthesis method, an etching method, a product and use thereof. Background Art

[0002] Directed Self-Assembly (DSA) is a new type of lithography technology based on the microphase separation of block copolymers (BCPs) to form high-resolution patterns. The pattern resolution of DSA is mainly determined by the properties of the block copolymers themselves. By regulating the chemical structure of the block copolymers, the pattern resolution can cover the range of 5-100nm. In addition, by regulating the volume fraction of a certain block in the block copolymer, the preparation of different graphics (such as columnar and layered structures) can be achieved. After selective etching, the preparation of nanopores or nanowire patterns can be achieved. It has a very huge application potential in integrated circuit storage and logic chips, and is expected to become the next generation of sub-ten-nanometer advanced lithography technology.

[0003] Polystyrene-polymethyl methacrylate diblock copolymer (PS-b-PMMA) has similar surface energies of polystyrene (PS) and polymethyl methacrylate (PMMA) at the air interface, so large-area highly ordered self-assembled patterns can be achieved through simple chemical modification of the substrate and short-term thermal annealing, making it the material with the most practical application potential at present.

[0004] The dry etching of block copolymer PS-b-PMMA was carried out by using O 2 PMMA is etched away by plasma dry etching, and the substrate pattern is transferred using PS as a mask. Although this etching method can etch PMMA efficiently, the etching selectivity is relatively low, and PMMA can only be etched at an etching selectivity ratio of PMMA / PS=2. PS will also be etched to a certain extent, resulting in a low retention rate of the PS mask. In addition, the cross-section of the pattern formed by dry etching in the thickness direction is a cone that is wide at the top and narrow at the bottom, which limits the diameter of the circular pattern on the substrate or the width of the linear pattern.

[0005] PS-b-PMMA can also be removed by wet etching. This method first degrades PMMA by UV exposure at an appropriate dose, and then washes away the PMMA fragments with acetic acid, which can achieve better etching results than dry etching. However, this method is limited by the depth of UV exposure and can only etch and transfer thinner PS-b-PMMA films to the substrate. In addition, this method cannot completely remove PMMA at the interface, resulting in PMMA residue at the interface, which leads to defects such as rough pattern edges.

[0006] Therefore, there is a need in the art for a novel PS-PMMA block copolymer and an etching method suitable for the material that can overcome the defects of existing dry etching and wet etching. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a novel block copolymer and its synthesis method, etching method, product and use. In the PS-PMMA block copolymer provided by the present invention, the PS segment and the PMMA segment are connected by a connecting group containing a Schiff base bond, and no ultraviolet exposure and etching equipment are required. Only a short-term simple organic acid immersion treatment can achieve complete separation of the PS phase and the PMMA phase, thereby maximally retaining the integrity of the mask pattern.

[0008] Specifically, the first aspect of the present invention provides a PS-PMMA block copolymer, wherein the PS-PMMA block copolymer comprises a PS segment, a PMMA segment and a connecting group connecting the PS segment and the PMMA segment, wherein the connecting group comprises a Schiff base bond.

[0009] In one or more embodiments, the linking group has a structure shown in Formula I or Formula II:

[0010]

[0011] In Formula I and Formula II, * represents the position where the linking group is connected to the PS segment or the PMMA segment;

[0012] L 1 connected to the PMMA segment, and L 2 Connected to the PS segment, or L 1 Connected to the PS segment, and L 2 connected to the PMMA segment;

[0013] L 3 and L 4 connected to the PMMA segment, and L 5 Connected to the PS segment, or L 3 and L 4 Connected to the PS segment, and L 5 connected to the PMMA segment;

[0014] R 1 Selected from H and C1-C10 hydrocarbon groups;

[0015] L 1 , L 3 and L 4 Each is independently a covalent bond or a group containing 1 to 20 carbon atoms and 0 to 10 oxygen atoms;

[0016] L 2 and L 5 Each is independently a covalent bond or a group containing 1 to 20 carbon atoms and 0 to 2 nitrogen atoms.

[0017] In one or more embodiments, L 1 Contains an aromatic ring directly connected to a Schiff base bond, L 3 and L 4 One or both of the two contain an aromatic ring directly connected to a Schiff base bond.

[0018] In one or more embodiments, L 1 , L 3 or L 4 The aromatic ring directly connected to the Schiff base bond is a benzene ring.

[0019] In one or more embodiments, in Formula I and Formula II, L 1 , L 3 and L 4 Connected to the PMMA segment, L 2 and L 5 Connected to the PS segment.

[0020] In one or more embodiments, the linking group has a structure as shown in Formula I, and in Formula I, R 1 For H, L 1 is a group containing 10 to 20 carbon atoms and 1 to 5 oxygen atoms, and L 1 Contains an aromatic ring directly connected to a Schiff base bond, L 2 It is a group containing 1 to 10 carbon atoms and 0 to 2 nitrogen atoms.

[0021] In one or more embodiments, L 1 Connected to the PMMA segment, L 2 Connected to the PS segment.

[0022] In one or more embodiments, the linking group has a structure shown in Formula III, Formula IV or Formula V:

[0023]

[0024]

[0025] In Formula III, Formula IV and Formula V, a represents the position where the linking group is connected to the PS segment, and b represents the position where the linking group is connected to the PMMA segment, or a represents the position where the linking group is connected to the PMMA segment, and b represents the position where the linking group is connected to the PS segment.

[0026] In one or more embodiments, the PS-PMMA block copolymer contains only one PS segment and one PMMA segment.

[0027] In one or more embodiments, in the PS-PMMA block copolymer, the number average molecular weight of the PS segment is 5,000 to 100,000, preferably 10,000 to 100,000.

[0028] In one or more embodiments, in the PS-PMMA block copolymer, the number average molecular weight of the PMMA segment is 5,000 to 100,000, preferably 10,000 to 100,000.

[0029] In one or more embodiments, in the PS-PMMS block copolymer, the ratio of the number average molecular weight of the PS segment to the number average molecular weight of the PMMA segment is (0.1-10):1, preferably (0.2-3):1.

[0030] Another aspect of the present invention provides a method for synthesizing the PS-PMMA block copolymer described in any embodiment of the present invention, the method comprising the following steps:

[0031] (1) Preparation of hydroxyl-modified PMMA or PS by atom transfer radical polymerization;

[0032] (2) chemically modifying the hydroxyl-modified PMMA or PS to obtain aldehyde- or ketocarbonyl-modified PMMA or PS;

[0033] (3) reacting the aldehyde- or ketocarbonyl-modified PMMA or PS with an amino-modified PS or PMMA, so that the aldehyde or ketocarbonyl reacts with the amino to form a Schiff base bond, thereby obtaining the PS-PMMA block copolymer.

[0034] In one or more embodiments, in step (3), dichloromethane is used as the reaction solvent.

[0035] In one or more embodiments, the synthesis method comprises the following steps:

[0036] (1) using an atom transfer radical polymerization method, with 2-bromo-2-methylpropionic acid 2-hydroxyethyl ester as an initiator, in the presence of pentamethyldipropylenetriamine and ketone bromide, methyl methacrylate is polymerized to obtain a hydroxyl-modified PMMA as shown in formula A, wherein n is the number of repeating units of PMMA;

[0037]

[0038] (2) reacting the hydroxy-modified PMMA of formula A with p-formylbenzoic acid in the presence of 4-dimethylaminopyridine and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to obtain the aldehyde-modified PMMA of formula B;

[0039]

[0040] (3) reacting the aldehyde-modified PMMA of formula B with the amino-modified PS of formula C, so that the aldehyde group reacts with the amino group to form a Schiff base bond, thereby obtaining a PS-PMMA block copolymer of formula D, wherein m is the number of repeating units of PS;

[0041]

[0042] Another aspect of the present invention provides a self-assembled PS-PMMA block copolymer film, which is obtained by spreading the PS-PMMA block copolymer described in any embodiment of the text on a substrate, then heating and annealing, and cooling.

[0043] In one or more embodiments, the self-assembled PS-PMMA block copolymer film has a nanowire or nanohole pattern.

[0044] Another aspect of the present invention provides a method for etching the self-assembled PS-PMMA block copolymer film described in any embodiment of the present invention, the method comprising contacting the self-assembled PS-PMMA block copolymer film with an organic acid.

[0045] In one or more embodiments, the contacting is carried out by immersing the self-assembled PS-PMMA block copolymer film in an organic acid;

[0046] In one or more embodiments, the organic acid is acetic acid.

[0047] Another aspect of the present invention provides a mask, comprising a substrate and a nanowire or nanohole pattern formed on the substrate by etching the self-assembled PS-PMMA block copolymer film described in any embodiment of the present invention.

[0048] In one or more embodiments, etching is performed using the method described in any of the embodiments herein.

[0049] Another aspect of the present invention provides an aluminum oxide mask, which is prepared by a method comprising the following steps:

[0050] (1) depositing aluminum oxide on the PMMA portion of the self-assembled PS-PMMA block copolymer film described in any embodiment of the present invention;

[0051] (2) The PS-PMMA block copolymer film after the aluminum oxide is deposited is etched using the method described in any of the embodiments to obtain the aluminum oxide mask.

[0052] Another aspect of the present invention provides the use of the PS-PMMA block copolymer described in any embodiment herein, the self-assembled PS-PMMA block copolymer film described in any embodiment herein, or the mask described in any embodiment herein in photolithography, or in the preparation of microelectronic devices, optoelectronic devices or porous membranes.

[0053] In one or more embodiments, the microelectronic device is a chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Schematic diagram of the etching principle of PS-PMMA block copolymer film in some embodiments of the present invention.

[0055] Figure 2 1 is the infrared spectra of PMMA-OH, PMMA-CHO, PS-NH2 and PS-N=CN-PMMA in Example 1 of the present invention.

[0056] Figure 3 This is the NMR spectrum of PMMA-OH in Example 1 of the present invention.

[0057] Figure 4 This is the NMR spectrum of PMMA-CHO in Example 1 of the present invention.

[0058] Figure 5 This is the NMR spectrum of PS-NH2 in Example 1 of the present invention.

[0059] Figure 6 This is the NMR spectrum of PS-N=CN-PMMA in Example 1 of the present invention.

[0060] Figure 7 This is an electron microscope photograph of the surface of the PS-PMMA block copolymer film after being etched with acetic acid in Example 2 of the present invention.

[0061] Figure 8 This is an electron microscope photograph of a cross section in the thickness direction of the PS-PMMA block copolymer film in Example 2 of the present invention after being etched with acetic acid. Specific implementation plan

[0062] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0063] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0064] Herein, “comprising”, “including”, “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of”. For example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to be disclosed herein.

[0065] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0066] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0067] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0068] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0069] The Schiff base bond (-N=CN-) is a pH-responsive chemical bond that can break under acidic conditions and can withstand higher temperatures. The present invention creatively replaces the covalent bond between the PS and PMMA phases in PS-b-PMMA with a Schiff base bond, and the obtained new PS-PMMA block copolymer can remove PMMA by a simple wet etching method. The etching method provided by the present invention does not use ultraviolet exposure and etching equipment. It can achieve complete separation at the interface of the PS phase and the PMMA phase by simply soaking in an organic weak acid (such as acetic acid) for a short time, thereby maximizing the retention of the integrity of the mask (PS or PMMA) pattern.

[0070] The PS-PMMA block copolymer of the present invention comprises a PS segment, a PMMA segment and a connecting group connecting the PS segment and the PMMA segment. The PS-PMMA block copolymer of the present invention is that the connecting group between the PS segment and the PMMA segment comprises a Schiff base bond.

[0071] In some embodiments, the linking group between the PS segment and the PMMA segment has a structure shown in Formula I or Formula II:

[0072]

[0073] In Formula I and Formula II, * indicates the position where the linking group is connected to the PS segment or PMMA segment;

[0074] L 1 Connected to PMMA segments, and L 2 Connected to PS segment, or L 1 Connected to PS segment, and L 2 Connected to PMMA segment; L 3 and L 4 Connected to PMMA segments, and L 5 Connected to PS segment, or L 3 and L 4 Connected to PS segment, and L 5 Connected to PMMA segments;

[0075] R 1 Selected from H and C1-C10 hydrocarbon groups;

[0076] L 1 , L 3 and L 4 Each is independently a covalent bond or a group containing 1 to 20 carbon atoms and 0 to 10 oxygen atoms;

[0077] L 2 and L 5 Each is independently a covalent bond or a group containing 1 to 20 carbon atoms and 0 to 2 nitrogen atoms.

[0078] Preferably, L 1 , L 3 and L 4 Connected to PMMA chain segment, L 2 and L 5 Connected to the PS segment.

[0079] Preferably, L 1 Contains an aromatic ring directly connected to a Schiff base bond. Preferably, L 3 and L 4 One or both of them contain an aromatic ring directly connected to the Schiff base bond. In the present invention, the aromatic ring directly connected to the Schiff base bond in the linking group includes but is not limited to a benzene ring, a naphthalene ring, an anthracene ring, In some embodiments, the aromatic ring directly connected to the Schiff base bond in the linking group is a benzene ring.

[0080] In some embodiments, L 1 Contains 10 to 20 (e.g., 12, 14, 16, 18) carbon atoms. In some embodiments, L 1 Contains 1 to 5 (e.g., 2, 3, 4) oxygen atoms. In some preferred embodiments, L 1 Contains aromatic rings directly connected to Schiff base bonds, such as benzene rings.

[0081] In some embodiments, L 2 Contains 1 to 10 (e.g., 2, 4, 6, 8) carbon atoms. In some embodiments, L 2 Contains 0 to 2 (e.g., 1) nitrogen atoms. In some embodiments, L 2 It is a covalent bond or a C1-C5 alkylene group (eg, 1,3-propylene).

[0082] In some embodiments, L 2 Contains 1 to 5 (e.g., 2, 3, 4) carbon atoms. In some embodiments, L 2 Contains 0 to 2 (e.g., 1) nitrogen atoms. In some embodiments, L 2 It is a covalent bond or a C1-C5 alkylene group (eg, 1,3-propylene).

[0083] In some embodiments, R 1 is selected from H and C1-C5 hydrocarbon groups. 1 is selected from H and C1-C5 alkyl. In some embodiments, in some embodiments, R 1is H or methyl. In some embodiments, R 1 For H.

[0084] In some embodiments, L 3 and L 4 Each independently contains 10 to 20 (e.g., 12, 14, 16, 18) carbon atoms. 3 and L 4 Each independently contains 1 to 5 (e.g., 2, 3, 4) oxygen atoms. In some preferred embodiments, L 3 and L 4 Each independently contains an aromatic ring, such as a benzene ring, directly connected to a Schiff base bond.

[0085] In some embodiments, L 5 Contains 1 to 5 (e.g., 2, 3, 4) carbon atoms. In some embodiments, L 5 Contains 0 to 2 (e.g., 1) nitrogen atoms. In some embodiments, L 5 is a covalent bond or a C1-C5 alkylene group (eg, a methylene group).

[0086] In some preferred embodiments, the linking group has a structure shown in Formula III, Formula IV or Formula V:

[0087]

[0088] In Formula III, Formula IV and Formula V, a represents the position where the linking group is connected to the PS segment, and b represents the position where the linking group is connected to the PMMA segment, or a represents the position where the linking group is connected to the PMMA segment, and b represents the position where the linking group is connected to the PS segment.

[0089] In some preferred embodiments, in Formula III, Formula IV and Formula V, a represents the position where the linking group is connected to the PS segment, and b represents the position where the linking group is connected to the PMMA segment.

[0090] It is understandable that those skilled in the art can design various structures of the connecting groups between PS segments and PMMA segments based on the content disclosed in the present invention, so that the connecting groups contain Schiff base bonds.

[0091] Preferably, the PS-PMMA block copolymer of the present invention is a diblock copolymer, that is, the PS-PMMA block copolymer contains only one PS segment and one PMMA segment.

[0092] In the present invention, by adjusting the number average molecular weight and the ratio of the number average molecular weight of the PS segment and the PMMA segment in the PS-PMMA block copolymer, the shape and resolution of the self-assembled pattern formed by the PS-PMMA block copolymer after heating and annealing can be controlled. In the PS-PMMA block copolymer of the present invention, the number average molecular weight of the PS segment can be 5000 to 100000, preferably 10000 to 100000, for example, 20000, 30000, 40000, 46000, 50000, 60000, 70000, 80000, 90000. In the PS-PMMA block copolymer of the present invention, the number average molecular weight of the PMMA segment can be 5000-100000, preferably 10000-100000, for example, 15000, 20000, 25000, 30000, 40000, 46000, 50000, 60000, 70000, 80000, 90000. The ratio of the number average molecular weight of the PS segment to the PMMA segment can be (0.1-10):1, preferably (0.2-3):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 7:3, 2.5:1. For example, when the ratio of the number average molecular weight of the PS segment to the PMMA segment is close to 1:1, the copolymer tends to self-assemble into a nanowire pattern after heating and annealing; when the ratio of the number average molecular weight of the PS segment to the PMMA segment is close to 7:3, the copolymer tends to self-assemble into a nanohole pattern after heating and annealing. In the present invention, nanometer means that the resolution of the pattern (such as a line or hole) is 1 to 100 nm, such as 3 to 50 nm, 10 to 20 nm.

[0093] The PS-PMMA block copolymer of the present invention can be prepared by a method comprising the following steps:

[0094] (1) Preparation of hydroxyl-modified PMMA or PS by atom transfer radical polymerization;

[0095] (2) chemically modifying hydroxyl-modified PMMA or PS to obtain aldehyde- or ketocarbonyl-modified PMMA or PS;

[0096] (3) PMMA or PS modified with aldehyde or ketocarbonyl groups is reacted with PS or PMMA modified with amino groups, so that the aldehyde or ketocarbonyl groups react with the amino groups to form Schiff base bonds, thereby obtaining PS-PMMA block copolymers.

[0097] In step (1), the method of preparing hydroxy-modified PMMA or PS by atom transfer radical polymerization (ATRP) may be known, for example, a hydroxy-containing atom transfer radical polymerization initiator may be used to initiate polymerization of methyl methacrylate or styrene to obtain hydroxy-modified PMMA or PS. Examples of hydroxy-containing atom transfer radical polymerization initiators include, but are not limited to, 2-bromo-2-methylpropionic acid 2-hydroxyethyl ester. ATRP is preferably carried out in the presence of a catalyst. Available catalysts include, but are not limited to, a combination of pentamethyldipropylenetriamine (PMDETA) and oxadiazine bromide (CuBr).

[0098] In step (2), hydroxy-modified PMMA or PS can be subjected to an esterification reaction with a compound containing carboxyl and aldehyde groups (e.g., p-formylbenzoic acid) or a compound containing carboxyl and ketocarbonyl groups to obtain PMMA or PS modified with aldehyde groups or ketocarbonyl groups. The conditions for the esterification reaction can be conventional, for example, a combination of 4-dimethylaminopyridine (DMAP) and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) can be used as a catalyst, and dichloromethane (DCM) can be used as a solvent.

[0099] In step (3), amino-modified PS or PMMA is commercially available. For example, commercially available amino-modified PS may have the following structure:

[0100] Where n is the degree of polymerization of PS.

[0101] In step (3), the reaction of the aldehyde group or ketone carbonyl group with the amino group to form a Schiff base bond can be carried out at 20 to 50° C. (e.g., 30° C., 35° C., 40° C.). The reaction time can be 12 to 48 hours, e.g., 24 hours. The reaction can be carried out in a DCM solvent.

[0102] In step (3), dichloromethane is preferably used as the reaction solvent. The present invention has found that using dichloromethane as the reaction solvent can promote the reaction to proceed in the direction of generating Schiff base bonds.

[0103] In some embodiments, the synthesis method of the PS-PMMA block copolymer of the present invention comprises the following steps:

[0104] (1) using an atom transfer radical polymerization method, with 2-bromo-2-methylpropionic acid 2-hydroxyethyl ester as an initiator, in the presence of pentamethyldipropylenetriamine and ketone bromide, methyl methacrylate is polymerized to obtain a hydroxyl-modified PMMA as shown in formula A, wherein n is the number of repeating units of PMMA;

[0105]

[0106] (2) reacting the hydroxy-modified PMMA of formula A with p-formylbenzoic acid in the presence of 4-dimethylaminopyridine and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to obtain the aldehyde-modified PMMA of formula B, wherein the reaction solvent may be DCM;

[0107]

[0108] (3) reacting the aldehyde-modified PMMA of formula B with the amino-modified PS of formula C, so that the aldehyde group reacts with the amino group to form a Schiff base bond, thereby obtaining a PS-PMMA block copolymer of formula D, wherein m is the number of repeating units of PS, the reaction solvent may be DCM, the reaction temperature may be 20 to 50° C., and the reaction time may be 12 to 48 hours;

[0109]

[0110] In some embodiments, hydroxyl-modified PMMA (hereinafter referred to as PMMA-OH) is synthesized by ATRP, and then the hydroxyl group is chemically modified to obtain aldehyde-modified PMMA (hereinafter referred to as PMMA-CHO), and amino-modified PS (hereinafter referred to as PS-NH2) is obtained by anionic polymerization. PMMA-CHO and PS-NH2 are dissolved in dichloromethane and stirred at 20 to 50° C., for example, 35° C., for 12 to 48 hours, for example, for 24 hours, to obtain the PS-PMMA block copolymer of the present invention.

[0111] The PS-PMMA block copolymer of the present invention has pH responsiveness. Figure 1 As shown, in an acidic environment (e.g., pH < 5.6), the Schiff base bond will break, so the PS phase and the PMMA phase can be separated by contacting the PS-PMMA block copolymer of the present invention with an acid (e.g., an organic acid). Available organic acids include acetic acid. Acetic acid can not only break the Schiff base bond, but also dissolve the PMMA phase, thereby conveniently removing PMMA. In some embodiments, the PS-PMMA block copolymer of the present invention can be soaked in acetic acid for 5 to 30 minutes, for example, 10 minutes, to achieve rapid removal of PMMA.

[0112] The PS-PMMA block copolymer of the present invention can achieve self-assembly by heating and annealing. For example, the PS-PMMA block copolymer of the present invention can be spread on a substrate, then heated and annealed, and cooled to obtain a self-assembled PS-PMMA block copolymer film with a nano pattern. Available substrates include, but are not limited to, silicon substrates, glass substrates, silicon nitride substrates, polyimide substrates, polyvinyl fluoride polymer substrates, and the like. Examples of silicon substrates include silicon wafers with a neutral layer on the surface. According to self-assembly (SA) and guided self-assembly (DSA) experimental verification, the PS-PMMA block copolymer of the present invention can be perfectly compatible with the existing heating annealing process of PS-PMMA block copolymers. Heating and annealing can be carried out in an air atmosphere or a protective atmosphere (e.g., nitrogen). The temperature of heating and annealing can be 170 to 250°C, such as 200°C, 210°C, 220°C, 230°C, and 240°C. The time of heating and annealing can be 5 minutes to 48 hours, such as 30 minutes, 1 hour, 2 hours, 4 hours, 8 hours, 12 hours, and 24 hours.

[0113] The self-assembled PS-PMMA block copolymer film of the present invention can be used as a nano pattern template to form a nano material with a patterned structure. For example, the PMMA phase can be etched away by contacting the self-assembled PS-PMMA block copolymer film with an acid (e.g., an organic acid, particularly acetic acid), thereby obtaining a mask pattern. The PMMA in the self-assembled PS-PMMA block copolymer film can be quickly removed by soaking in acetic acid, and the defects and roundness of the obtained pattern are greatly improved.

[0114] The present invention achieves the following beneficial technical effects:

[0115] The present invention uses a PS-PMMA block copolymer containing a Schiff base bond to replace conventional PS-b-PMMA for SA and DSA, which is not only perfectly compatible with the existing thermal annealing process, but also can quickly and effectively remove the PMMA phase of the thicker film through a simple organic acid (such as acetic acid) soaking method, and retain the integrity of the PS phase mask to the maximum extent, which is of great significance for the transfer of the PS phase pattern to the substrate. Secondly, the etching method of the present invention does not require the use of an ultraviolet exposure machine required for conventional wet etching, nor does it require the use of expensive instruments such as a reactive ion etcher (RIE) and an inductively coupled plasma emission spectrometer (ICP) used for dry etching. Only organic acids (such as acetic acid) are needed to achieve a good etching effect, which is economical and environmentally friendly. The present invention helps to accelerate the industrialization process of applying PS-PMMA block copolymers to DSA and efficiently prepare large-area nanowires or nanopore patterns.

[0116] The present invention will be described below in the form of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents and materials used in the examples are, unless otherwise stated, conventional methods, reagents and materials in the art. The raw material compounds in the examples can all be purchased through commercial routes.

[0117] In the embodiment, PS-NH2 with a number average molecular weight of 46,000 was purchased from Polymer source with a brand name of P10457-SNH2. The structural formula of P10457-SNH2 is Where n is the degree of polymerization of PS.

[0118] Example 1

[0119] (1) Synthesis of PMMA-OH: 2-hydroxyethyl 2-bromo-2-methylpropionate (0.21 g), PMDETA (0.173 g), methyl methacrylate (100 mL) and anisole (200 mL) were added to a 500 mL Slack bottle, and nitrogen was bubbled for deoxygenation for 1 h. Then cuprous bromide (0.143 g) was added, and nitrogen was continued for 30 min. The mixture was placed in an oil bath at 60°C for 2 h. The reaction was quenched with liquid nitrogen, diluted with tetrahydrofuran, and the copper salt was removed with a neutral alumina column. Finally, the solution obtained by passing through the column was dropped into 20 times anhydrous methanol to obtain a white solid precipitate. The white precipitate was dried in a vacuum oven for 48 hours to obtain the final product PMMA-OH.

[0120] (2) Synthesis of PMMA-CHO: PMMA-OH (0.42 g), DMAP (0.25 g), EDC·HCl (1.9 g), 4-formylbenzoic acid (12.2 g) and dichloromethane (100 mL) prepared in step (1) were added to a 250 mL round-bottom flask in sequence and magnetically stirred at 35° C. for 72 h. Subsequently, the reaction solution was precipitated with anhydrous ether to obtain a white solid, which was repeatedly washed with tetrahydrofuran and anhydrous methanol as solvents. Finally, the precipitate was dried in a vacuum oven at 40° C. for 24 h to obtain the final product PMMA-CHO.

[0121] (3) Synthesis of PS-N=CN-PMMA: PMMA-CHO prepared in step (2), PS-NH2 with a number average molecular weight of 46,000 and dichloromethane were mixed in a sealed round-bottom glass bottle at a molar ratio of 1:1:10,000, and magnetically stirred at 35°C for 24 hours. The reaction was quenched with liquid nitrogen, and dichloromethane was removed by rotary evaporation to obtain a white solid powder. The white solid was repeatedly washed with cyclohexane until the volume did not change. Finally, tetrahydrofuran and anhydrous methanol were used as solvents at a volume ratio of THF / CH 3The white solid was graded and precipitated with OH=3:5, which was repeated three times. The precipitate was then washed with anhydrous methanol, and the excess methanol was finally removed by suction filtration. The white solid was dried in a vacuum oven for 48 hours to obtain the final product PS-N=CN-PMMA.

[0122] The number average molecular weights of PMMA-OH, PMMA-CHO, PS-NH2 and PS-N=CH-PMMA in Example 1 were measured by GPC and were 20915, 21356, 46191 and 67174, respectively, proving that the materials were successfully synthesized.

[0123] The infrared spectra of PMMA-OH, PMMA-CHO, PS-NH2 and PS-N=CN-PMMA in Example 1 are shown in FIG. Figure 2 As shown. Figure 2 As shown in Figure 2, infrared testing qualitatively confirmed the successful preparation of PMMA-CHO and PS-N=CN-PMMA, with a wave number of 1784 cm -1 and 1634cm -1 The locations are the characteristic absorption peaks of aromatic aldehyde and Schiff base respectively.

[0124] The NMR spectra of PMMA-OH, PMMA-CHO, PS-NH2 and PS-N=CN-PMMA are shown in Figure 3 , Figure 4 , Figure 5 , Figure 6 shown.

[0125] Example 2

[0126] The PS-N=CN-PMMA prepared in Example 1 was subjected to SA experiment and acetic acid etching experiment, and the specific operations were as follows:

[0127] (1) A silicon wafer (2 cm × 2 cm) was taken and ultrasonically cleaned using ethanol, acetone, and isopropanol, respectively, to obtain a clean silicon wafer;

[0128] (2) treating the clean silicon wafer with oxygen plasma for 10 min to obtain an activated silicon wafer;

[0129] (3) Spin coating styrene-methyl methacrylate-glycidyl methacrylate copolymer (P(St-r-MMA-GMA)) (0.5 wt%, 100 μL, solvent: toluene) on an activated silicon wafer at 2000 rpm and heating at 250°C for 10 min to obtain a NML silicon wafer;

[0130] (4) After ultrasonic cleaning of the NML silicon wafer, PS-N=CN-PMMA (1.5 wt %, 100 μL, solvent: propylene glycol methyl ether acetate (PGMEA)) was spin-coated on the NML silicon wafer at 3000 rpm and heated at 230°C, N2 The SA silicon wafer was obtained by heating for 1 h in an atmosphere for annealing;

[0131] (5) Soak the SA silicon wafer in acetic acid for 10 minutes to obtain the etched pattern.

[0132] The surface morphology and cross-sectional morphology of the PS-N=CN-PMMA self-assembled film after acetic acid etching were observed by scanning electron microscopy and transmission electron microscopy, respectively. Figure 7 and Figure 8 shown. Figure 8 This is a focused ion beam-transmission electron microscopy (FIB-TEM) photograph of the PS-N=CN-PMMA self-assembled film after acetic acid etching. The small particles in the picture are nano-gold sprayed during the shooting. Figure 7 and Figure 8 It is proved that PS-N=CN-PMMA can form a large area of ​​vertical columnar phase, and the holes after immersion in acetic acid can directly reach the substrate. The holes have high roundness and smooth edges and have a very high etching selectivity.

Claims

1. A PS-PMMA block copolymer, It is characterized in that The PS-PMMA block copolymer comprises a PS segment, a PMMA segment and a connecting group connecting the PS segment and the PMMA segment, wherein the connecting group comprises a Schiff base bond.

2. The PS-PMMA block copolymer according to claim 1, It is characterized in that The linking group has a structure shown in Formula I or Formula II: In Formula I and Formula II, * represents the position where the linking group is connected to the PS segment or the PMMA segment; L 1 connected to the PMMA segment, and L 2 Connected to the PS segment, or L 1 Connected to the PS segment, and L 2 connected to the PMMA segment; L 3 and L 4 connected to the PMMA segment, and L 5 Connected to the PS segment, or L 3 and L 4 Connected to the PS segment, and L 5 connected to the PMMA segment; R 1 Selected from H and C1-C10 hydrocarbon groups; L 1 , L 3 and L 4 Each is independently a covalent bond or a group containing 1 to 20 carbon atoms and 0 to 10 oxygen atoms; preferably, L 1 Contains an aromatic ring directly connected to a Schiff base bond, L 3 and L 4 One or both of them contain an aromatic ring directly connected to the Schiff base bond, and the aromatic ring is, for example, a benzene ring; L 2 and L 5 Each is independently a covalent bond or a group containing 1 to 20 carbon atoms and 0 to 2 nitrogen atoms; Preferably, L 1 , L 3 and L 4 Connected to the PMMA segment, L 2 and L 5 Connected to the PS segment.

3. The PS-PMMA block copolymer according to claim 2, It is characterized in that The linking group has a structure as shown in Formula I, and in Formula I, R 1 For H, L 1 is a group containing 10 to 20 carbon atoms and 1 to 5 oxygen atoms, and L 1 Contains an aromatic ring directly connected to a Schiff base bond, L 2 is a group containing 1 to 10 carbon atoms and 0 to 2 nitrogen atoms; Preferably, L 1 Connected to the PMMA segment, L 2 connected to the PS segment; Preferably, the linking group has a structure shown in Formula III, Formula IV or Formula V: In Formula III, Formula IV and Formula V, a represents the position where the linking group is connected to the PS segment, and b represents the position where the linking group is connected to the PMMA segment, or a represents the position where the linking group is connected to the PMMA segment, and b represents the position where the linking group is connected to the PS segment.

4. The PS-PMMA block copolymer according to claim 1, It is characterized in that The PS-PMMA block copolymer has one or more of the following characteristics: The PS-PMMA block copolymer contains only one PS segment and one PMMA segment; In the PS-PMMA block copolymer, the number average molecular weight of the PS segment is 5000 to 100000, preferably 10000 to 100000; In the PS-PMMA block copolymer, the number average molecular weight of the PMMA segment is 5000 to 100000, preferably 10000 to 100000; In the PS-PMMS block copolymer, the ratio of the number average molecular weight of the PS segment to the number average molecular weight of the PMMA segment is (0.1-10):1, preferably (0.2-3):

1.

5. The method for synthesizing the PS-PMMA block copolymer according to claim 1, It is characterized in that The synthesis method comprises the following steps: (1) Preparation of hydroxyl-modified PMMA or PS by atom transfer radical polymerization; (2) chemically modifying the hydroxyl-modified PMMA or PS to obtain aldehyde- or ketocarbonyl-modified PMMA or PS; (3) reacting the aldehyde- or ketocarbonyl-modified PMMA or PS with an amino-modified PS or PMMA, so that the aldehyde or ketocarbonyl reacts with the amino to form a Schiff base bond, thereby obtaining the PS-PMMA block copolymer; Preferably, in step (3), dichloromethane is used as the reaction solvent; Preferably, the synthesis method comprises the following steps: (1) using an atom transfer radical polymerization method, with 2-bromo-2-methylpropionic acid 2-hydroxyethyl ester as an initiator, in the presence of pentamethyldipropylenetriamine and ketone bromide, methyl methacrylate is polymerized to obtain a hydroxyl-modified PMMA as shown in formula A, wherein n is the number of repeating units of PMMA; (2) reacting the hydroxy-modified PMMA of formula A with p-formylbenzoic acid in the presence of 4-dimethylaminopyridine and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to obtain the aldehyde-modified PMMA of formula B; (3) reacting the aldehyde-modified PMMA of formula B with the amino-modified PS of formula C, so that the aldehyde group reacts with the amino group to form a Schiff base bond, thereby obtaining a PS-PMMA block copolymer of formula D, wherein m is the number of repeating units of PS; 6. A self-assembled PS-PMMA block copolymer film, It is characterized in that The self-assembled PS-PMMA block copolymer film is obtained by spreading the PS-PMMA block copolymer according to any one of claims 1 to 4 on a substrate, heating and annealing, and cooling; Preferably, the self-assembled PS-PMMA block copolymer film has a nanowire or nanopore pattern.

7. A method for etching the self-assembled PS-PMMA block copolymer film according to claim 6, It is characterized in that The method comprises contacting the self-assembled PS-PMMA block copolymer film with an organic acid; Preferably, the contacting is carried out by immersing the self-assembled PS-PMMA block copolymer film in an organic acid; Preferably, the organic acid is acetic acid.

8. A mask, It is characterized in that The mask comprises a substrate and a nanowire or nanopore pattern formed by etching the self-assembled PS-PMMA block copolymer film according to claim 6 on the substrate; Preferably, etching is performed using the method described in claim 7.

9. An aluminum oxide mask, It is characterized in that The mask is prepared by a method comprising the following steps: (1) depositing aluminum oxide on the PMMA portion of the self-assembled PS-PMMA block copolymer film of claim 6; (2) The PS-PMMA block copolymer film after aluminum oxide deposition is etched using the method described in claim 7 to obtain the aluminum oxide mask.

10. Use of the PS-PMMA block copolymer according to any one of claims 1 to 4, the self-assembled PS-PMMA block copolymer film according to claim 6, the mask according to claim 8 or the aluminum oxide mask according to claim 9 in photolithography, or in the preparation of microelectronic devices, optoelectronic devices or porous membranes; Preferably, the microelectronic device is a chip.

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