Method for plasma modification of 3d nanometer patterns and guiding self-assembly of block copolymers

Abstract

The application belongs to the technical field of nanostructure manufacturing, and discloses a method for modifying 3D nano patterns by plasma and guiding self-assembly of block copolymers. The preparation steps of the application include: grafting polymer brushes / felts to a substrate surface, cleaning, spin coating photoresist, exposure, development, plasma modification and cleaning. In the method, the interface free energy between the block copolymer and the brush / felt is adjusted by modifying the polymer brush / felt by plasma, so that a non-selective substrate is obtained. The method is easy to implement, simple to synthesize, and is a way to obtain neutral molecular brushes worthy of promotion. At the same time, the block copolymer is guided to carry out density multiplication assembly, and a defect-free long-range ordered morphology is obtained. Compared with the traditional chemical pattern method, the method reduces the step of trimming etching, has lower requirements for equipment in the preparation process, and has a simple preparation process and is easy to control. By changing the exposure dose and oxygen plasma modification conditions, different block copolymers can be guided to carry out assembly, and a higher density multiplication effect can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanostructure manufacturing, and particularly relates to a method for plasmonic modification of 3D nano-pattern and guiding block copolymer self-assembly. BACKGROUND

[0002] From the 10 pm process technology in the 1970s to the mass production of 22 nm Ivy bridge processor by Intel in 2012, the semiconductor industry has brought about earth-shaking changes to human life in the past half century. However, with the development of the semiconductor industry, the light source of the 193 nm photolithography method has reached the physical resolution limit, and the electron beam exposure is difficult to apply due to low production capacity, and the extreme ultraviolet photolithography method (EUV) can solve the current process problem, but its price and maintenance cost are extremely expensive. Therefore, three alternative technologies for preparing ≤12 nm node chips are proposed in the 2020 version of International Roadmap for Devices and Systems: extreme ultraviolet (EUV), 193 immersion self-aligned quadruple pattern process (193SAQP) and block copolymer directed assembly (DSA).

[0003] Block copolymer is a polymer in which two or more different polymers are connected by covalent bonds, and can self-assemble to generate periodic nanostructures of 5-100 nm through microphase separation. In 2003, the Paul Nealey group of the University of Wisconsin, USA, invented a method for preparing long-range ordered structures by chemical pattern guided block copolymer thin film assembly (Nature, 2003, 424, 411). However, the 1:1 chemical pattern guided assembly is limited in application prospect in the chip industry. In 2008, the chemical pattern density multiplication guided assembly was proposed, and Ruiz et al. used a hexagonal lattice chemical pattern with a period (L s ) of 54 nm / 78 nm to guide the intrinsic phase separation period (L o) for 27 nm / 39 nm cylindrical phase PMMA-b-PS was performed 4-fold (2-fold laterally x 2-fold vertically) density multiplication assembly, and the assembly results were consistent with the results on a 1:1 chemical pattern (Science, 2008, 321, 936-939.). This means that a tight (small period) pattern can be prepared by a sparse (large period) chemical pattern, realizing the miniaturization of the pattern. In 2018, ChiChun Liu et al. of IBM prepared the fin of the fin field effect transistor of the 7nm node process in the chip production test workshop by the chemical pattern density multiplication method, and compared it with the current mainstream self-aligned quadruple pattern process (193SAQP). They found that compared with SAQP, the chemical pattern density multiplication method reduced the process complexity by 30-40%, and the cost was reduced by 9.5% (Nature electronics, 2018, 1, 562-569). Therefore, the chemical pattern density multiplication method has great application potential in the field of semiconductor lithography. Compared with the photolithography method, the guided assembly also has the following advantages: 1) the nanostructure obtained by guided assembly has smaller line edge roughness (LER) and line width roughness (LWR); 2) the block copolymer has a self-repairing function, which can correct some defects generated by the photolithography method.

[0004] In the chemical pattern density multiplication guided assembly technology, the surface between the chemical pattern guide lines (reference lines) needs to be modified by random copolymer or homopolymer (Macromolecules, 2011, 44(7): 1876-1885, CN 106674395B) to make the interaction between the block copolymer film and the surface "neutral" so as to obtain vertical linear nanostructure. Therefore, the typical density multiplication chemical pattern needs to go through the following steps: grafting polymer brush / felt to the surface of the substrate-washing-spinning photoresist-exposure-development-plasma etching-trimming etching-washing-backfilling molecular brush-heating grafting-washing. According to the existing reports, the highest density multiplication guided assembly of this kind of chemical pattern is only 5 times. Although it has been proved that the preparation of 7nm finFET transistor by the chemical pattern density multiplication method is superior to the current mainstream self-aligned quadruple pattern technology, the operation steps are still cumbersome, and at the same time, the random copolymer or homopolymer matching the different block copolymer needs to be screened and synthesized. SUMMARY

[0005] Therefore, the present application provides a method for plasma modification of 3D nano pattern and guided block copolymer self-assembly, to solve the problem that the existing operation steps for obtaining vertical linear nanostructure are cumbersome, and at the same time, the random copolymer or homopolymer matching the different block copolymer needs to be screened and synthesized.

[0006] In order to achieve the above object, the present application adopts the following technical scheme:

[0007] The present application provides a method for modifying 3D nano-pattern by plasma and guiding self-assembly of block copolymer, comprising the following steps:

[0008] forming polymer brush / felt on the substrate;

[0009] coating photoresist on the polymer brush / felt;

[0010] exposing the photoresist layer by photolithography method, selectively removing the unexposed photoresist layer, and then treating by plasma modification to obtain a substrate with 3D nano-pattern with period L s modified on the surface;

[0011] coating block copolymer with phase separation period L o on the substrate with 3D nano-pattern with period L s modified on the surface, and annealing to induce phase separation of the block copolymer to form nanostructure;

[0012] selectively removing one phase of the nanostructure formed by phase separation of the block copolymer, and transferring the nanostructure to the substrate using the unremoved phase as a mask.

[0013] As a preferred embodiment, the polymer forming the polymer brush / felt contains functional groups that can react with the substrate or can crosslink by itself; the polymer forming the polymer brush / felt contains one or more of hydroxyl, azide, epoxy, double bond and isocyanate groups.

[0014] As a preferred embodiment, the molar content of the functional groups contained in the polymer forming the polymer brush / felt is 0.3-20%; the molecular weight of the polymer forming the polymer brush / felt is 5 kg-80 kg / mol.

[0015] As a preferred embodiment, the thickness T of the polymer brush / felt is in the range of 50 nm≥T≥5 nm.

[0016] As a preferred embodiment, the photoresist is a negative photoresist, and the negative photoresist is an electron beam type photoresist, a laser type photoresist, an ultraviolet light type photoresist or an X-ray type photoresist.

[0017] As a preferred embodiment, L s =nL o , wherein 20≥n≥2.

[0018] As a preferred embodiment, the substrate with 3D nano-pattern with period L sThe preparation of the substrate of the 3D nano-pattern includes the following steps: placing the obtained nano-pattern after exposure in a plasma environment for modification, so that the photoresist on the nano-pattern and the polymer substrate surface not protected by the photoresist are chemically changed, and a plasma-modified 3D nano-pattern is obtained.

[0019] As preferred, the plasma environment is one or more of oxygen, nitrogen, argon, air, carbon dioxide, chlorine, and halogenated alkanes.

[0020] As preferred, the surface is modified with a 3D nano-pattern with a period of L s The thickness H of the photoresist on the 3D nano-pattern on the substrate with a 3D nano-pattern with a period of L o ≥H≥0.1L o , the surface is modified with a 3D nano-pattern with a period of L s The thickness D of the substrate on the substrate with a 3D nano-pattern with a period of L

[0021] As preferred, the block copolymer is a two-block, three-block, multi-block or star-shaped block copolymer; the block copolymer forms columnar phase, lamellar phase, bicontinuous phase or spherical phase different phase separation morphologies through phase separation.

[0022] As can be seen from the above technical solutions, compared with the prior art, the present application has the following advantages:

[0023] 1. The present application uses a polymer brush / felt as a pre-substrate, adjusts the interfacial energy between the homopolymer brush / felt and the block copolymer by changing the plasma conditions, thereby guiding different block copolymers to form nanostructures and realizing "one bottom, multiple uses";

[0024] 2. The present application combines plasma modification technology to prepare 3D chemical patterns to guide block copolymers to realize density multiplication assembly, and the process is simpler and easier to control than existing chemical pattern methods. No additional random copolymer or homopolymer needs to be prepared, and higher density multiplication assembly (L s ≥10L o ) is achieved, in addition, only changing the plasma conditions can guide different block copolymers to perform density multiplication assembly. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0026] Figure 1SEM images of nanostructures obtained in Examples 6-12 and Comparative Examples 1-2 of the present application, wherein a is the SEM image of nanostructures obtained in Comparative Example 1, b is the SEM image of nanostructures obtained in Example 6, c is the SEM image of nanostructures obtained in Example 7, d is the SEM image of nanostructures obtained in Example 8, e is the SEM image of nanostructures obtained in Example 9, f is the SEM image of nanostructures obtained in Example 10, g is the SEM image of nanostructures obtained in Example 11, h is the SEM image of nanostructures obtained in Example 12, and i is the SEM image of nanostructures obtained in Comparative Example 2;

[0027] Figure 2 SEM images of the substrate after self-assembly of the PS-b-PMMA block copolymer obtained in Example 6 of the present application followed by removal of the PMMA phase by oxygen plasma, wherein the left image is the SEM plan view after removal of the PMMA, and the right image is the SEM image at an angle of 45° after removal of the PMMA;

[0028] Figure 3 SEM images of nanostructures obtained in Examples 13-16 of the present application;

[0029] Figure 4 SEM images of nanostructures obtained in Examples 17-20 of the present application, wherein a is the SEM image of nanostructures obtained in Example 17, b is the SEM image of nanostructures obtained in Example 18, c is the SEM image of nanostructures obtained in Example 19, and d is the SEM image of nanostructures obtained in Example 20;

[0030] Figure 5 SEM images of the density multiplication directed assembly (L s = 3L0) of PS-b-PMMA block copolymer on 3D chemical patterns with different oxygen plasma oxidation times obtained in Examples 22-26 and Comparative Examples 3-5 of the present application;

[0031] Figure 6 SEM images of the modified substrate with 3D chemical patterns, the obtained nanostructures, and the nanostructures obtained in Example 27 of the present application after oxygen plasma etching (20w, oxygen flow rate 30 cc / min, 10-15s) to remove the PMMA phase;

[0032] Figure 7 SEM images of nanostructures obtained in Example 28 of the present application;

[0033] Figure 8 SEM images of nanostructures obtained in Example 29 of the present application;

[0034] Figure 9Test results of water contact angle of modified neutral substrate and treated modified central neutral substrate obtained in Examples 6-12 and Comparative Examples 1-2 and 6-7 of the present application, wherein a is the test result of water contact angle of the modified neutral substrate, and b is the test result of water contact angle of the treated modified central neutral substrate;

[0035] Figure 10 Test results of film thickness of modified neutral substrate and treated modified central neutral substrate obtained in Examples 6-12 and Comparative Examples 1-2 and 6-7 of the present application;

[0036] Figure 11 Test results of water contact angle of pure silicon substrate and cross-linked PS film obtained in Example 30 of the present application, wherein the left graph is the test result of water contact angle of the obtained pure silicon substrate, oxidized substrate and cleaned substrate, and the right graph is the test result of thickness of cross-linked PS film of the obtained modified neutral substrate and cross-linked PS film of the cleaned substrate;

[0037] Figure 12 SEM images of modified substrate with different morphologies of three-dimensional chemical patterns obtained in Example 31 of the present application;

[0038] Figure 13 Test results of line width of reference line of modified substrate with different morphologies of three-dimensional chemical patterns obtained in Example 31 of the present application;

[0039] Figure 14 Characterization images of modified substrate with different morphologies of three-dimensional chemical patterns obtained in Example 32 of the present application, wherein a is a graph showing the relationship between the thickness of cross-linked PS layer of the modified substrate with different morphologies of three-dimensional chemical patterns and the height of reference line of the three-dimensional chemical patterns and the oxidation time, b is an SEM image of the cross section of the obtained modified substrate with different morphologies of three-dimensional chemical patterns, and c is a schematic diagram showing the change of the modified substrate with different morphologies of three-dimensional chemical patterns with the oxidation time. DETAILED DESCRIPTION

[0040] The present application provides a method for plasma modification of 3D nano-pattern and guiding self-assembly of block copolymer, which comprises the following steps:

[0041] forming polymer brush / felt on the substrate;

[0042] coating photoresist on the polymer brush / felt;

[0043] exposing the photoresist layer by photolithography method, selectively removing the unexposed photoresist layer, and then treating by plasma modification to obtain a substrate with 3D nano-pattern with a period of L s

[0044] separating the phase with a period of L​o a block copolymer of Formula (I) is coated on the surface of the substrate modified with a 3D nano-pattern with a period of L s annealing induces phase separation of the block copolymer to form nanostructures;

[0045] selectively removing one phase of the nanostructures formed by phase separation of the block copolymer, and transferring the nanostructures to a substrate using the unremoved phase as a mask.

[0046] In the present application, the preparation of the polymer brush / felt on the substrate comprises the following steps:

[0047] reacting the pretreated surface of the substrate with a solution of the polymer containing cross-linking groups, and post-treating to obtain the polymer brush / felt.

[0048] In the present application, the cross-linking groups in the polymer containing cross-linking groups are preferably functional groups that can react with the substrate or can be cross-linked by themselves; the polymer containing cross-linking groups is preferably a polymer containing one or more of the following functional groups: hydroxyl, azide, epoxy, double bond and isocyanate group, further preferably a polystyrene containing hydroxyl group and its derivatives, a polystyrene containing epoxy group and its derivatives, or a polymer containing benzene ring, and more preferably a polystyrene containing epoxy group.

[0049] In the present application, the molar content of the cross-linking groups in the polymer containing cross-linking groups is preferably 0.3-20%, and further preferably 3-10%; the molecular weight of the polymer containing cross-linking groups is preferably 5 kg-80 kg / mol, and further preferably 10 kg-50 kg / mol.

[0050] In the present application, L s = nL o , and n is in the range of 20≥n≥2.

[0051] In the present application, the substrate can comprise a semiconductor material, an insulating material, a conductive material or a combination thereof. Further, the substrate is preferably a silicon wafer, silicon with oxide layer, hydrogenated silicon, halogenated silicon, silicon nitride, silicon carbide, germanium, hydrogenated germanium, halogenated germanium, germanium nitride, germanium carbide, platinum and platinum oxide, tungsten and tungsten oxide, gold, titanium nitride or graphene, etc.; more preferably a silicon material, and most preferably a silicon wafer or silicon with thermal oxide layer, silicon germanium alloy, and silicon nitride, silicon carbide or a combination or modification thereof.

[0052] In the present application, the pretreatment of the surface of the substrate comprises the following steps: sequentially ultrasonic cleaning the substrate with chloroform, acetone and ethanol for 5-10 min, drying with nitrogen, and then cleaning with oxygen plasma for 3-5 min at a power of 100-200 w.

[0053] The time of the ultrasonic cleaning is preferably 5-10 minutes, further preferably 5-8 minutes; the time of the oxygen plasma cleaning is preferably 3-5 minutes, further preferably 3-4 minutes; the power of the oxygen plasma is preferably 100-200 W, further preferably 100-150 W.

[0054] In the present application, the mass concentration of the solution of the polymer containing crosslinking groups is preferably 0.2-5 wt%, further preferably 0.2-3 wt%;

[0055] The preparation of the solution of the polymer containing crosslinking groups comprises the following steps: dissolving the polymer containing crosslinking groups in a corresponding good solvent, and then filtering with a 0.22 μm PTFE filter membrane to obtain the solution of the polymer containing crosslinking groups.

[0056] In the present application, the temperature of the reaction is preferably 80-300 °C, further preferably 245-255 °C; the time of the reaction is preferably 0.01-240 h, further preferably 0.5-24 h; the reaction is carried out under a protective atmosphere, preferably nitrogen.

[0057] In the present application, the post-treatment comprises the following steps: cooling the substrate after the reaction, then washing with a solvent for 3-5 times, each time for 4-6 minutes, and finally blowing dry with nitrogen for standby. The un-crosslinked polymer can be removed by the post-treatment.

[0058] In the present application, the thickness T of the polymer brush / felt is preferably in the range of 50 nm≥T≥5 nm, further preferably 30 nm≥T≥10 nm.

[0059] In the present application, the photoresist is preferably a negative photoresist, further preferably an electron beam type photoresist, a laser type photoresist, an ultraviolet light type photoresist or an X-ray type photoresist, more preferably PMMA950.

[0060] In the present application, the photoetching method of the photoresist is preferably an exposure photoetching method by electron beam, very far ultraviolet light, 193 nm dry / immersed, 248 nm or 365 nm, further preferably an exposure photoetching method by electron beam;

[0061] The exposure photoetching method by electron beam comprises the following steps:

[0062] The photoresist coated substrate is heated on a hot stage at 170-190°C for 2-5 minutes to remove residual solvent and then subjected to electron beam exposure, with a line dose of 670-1150 pC / cm and a design pattern line dose of 10-17 pC / cm. After exposure, the substrate is developed in tetrahydrofuran or a methyl isobutyl ketone / isopropyl alcohol mixture (methyl isobutyl ketone / isopropyl alcohol volume ratio of 1:2-3) for 50-70 seconds.

[0063] In the present application, the surface of the substrate modified with the 3D nano-pattern with a period of L s is prepared by the following steps:

[0064] The nano-pattern obtained after exposure is placed in a plasma environment for modification, so that the photoresist on the nano-pattern and the polymer substrate surface not protected by the photoresist undergo chemical changes, obtaining a plasma-modified 3D nano-pattern.

[0065] In the present application, when the formation of the polymer brush / felt on the substrate includes a photoresist coating process, the polymer brush / felt needs to be post-treated after oxygen plasma oxidation, including the following steps: the modified polymer brush / felt is cleaned with N-methyl pyrrolidone or toluene for 3-5 times, each time for 4-6 minutes, and finally dried with nitrogen to obtain a modified polymer brush / felt with a pattern.

[0066] The pattern in the modified polymer brush / felt with a pattern is a three-dimensional chemical pattern.

[0067] In the present application, the plasma environment is one or more of oxygen, nitrogen, argon, air, carbon dioxide, chlorine, and halogenated alkanes.

[0068] In the present application, the power in the plasma environment is preferably 0.1-200 w, further preferably 8-18 w; the vacuum degree is preferably 195-205 torr; the gas rate is preferably 0-200 cc / min, further preferably 10-50 cc / min; the time is preferably 0.2 s-10 h, further preferably 5-60 s;

[0069] Further, when the formation of the polymer brush / felt on the substrate includes a photoresist coating process, the power of the oxygen plasma is 15-17 W, the vacuum degree is 200 torr, the oxygen rate is 30 cc / min, and the oxidation time is 5-60 s; when the formation of the polymer brush / felt on the substrate does not include a photoresist coating process, the power of the oxygen plasma is 15-18 w, the vacuum degree is 200 torr, the oxygen rate is 10-50 cc / min, and the oxidation time is 5-40 s.

[0070] In the present application, the solution mass concentration of the block copolymer is preferably 0.8-5wt%, further preferably 1-4wt%.

[0071] In the present application, the block copolymer is preferably one of PS-b-PMMA, PS-b-PMA, PS-b-PPC, PS-b-PLGA, further preferably PS-b-PMMA or PS-b-PMA.

[0072] In the present application, the annealing temperature is preferably 100-300℃, further preferably 140-270℃, and the annealing time is preferably 0.01-240h, further preferably 0.5-24h.

[0073] In the present application, the surface of the substrate is decorated with a 3D nanometer pattern with a period of L s The thickness H of the photoresist on the 3D nanometer pattern on the substrate decorated with a 3D nanometer pattern with a period of L o ≥H≥0.1L o , further preferably 0.5L o ≥H≥0.2L o； The thickness D of the substrate on the substrate decorated with a 3D nanometer pattern with a period of L s is preferably 15nm≥T≥5nm, further preferably 10nm≥T≥6nm.

[0074] In the present application, the block copolymer is preferably a two-block, three-block, multi-block or star-shaped block copolymer, further preferably a multi-block copolymer; the block copolymer is phase-separated under certain conditions to form different phase separation morphologies such as columnar phase, lamellar phase, bicontinuous phase, spherical phase, etc. Preferably, a two-block copolymer.

[0075] The technical solutions provided by the present application will be described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0076] Example 1

[0077] Synthesis of PMMA macroinitiator:

[0078] Methyl methacrylate (MMA) (TsCl, 55 g, 0.55 mol) and anisole (60 g, 0.54 mol) were added to a two-necked reaction flask fitted with a stopcock, stirred, purged with high purity nitrogen for 15 min, CuCl (0.99 g, 1.0 mmol) was added and purging with high purity nitrogen was continued for 30 min, then the flask was capped with a rubber septum. 2,2'-Bipyridine (0.312 g, 2.0 mmol) and p-toluenesulfonyl chloride (0.19 g, 1.0 mmol) were dissolved in MMA (5 g, 0.05 mmol) and purged with high purity nitrogen for 30 min, then transferred to the above flask. The flask was placed in an oil bath at 60 °C and samples were removed at timed intervals to monitor the extent of reaction. When the desired extent of reaction was achieved, the flask was immediately quenched by immersion in liquid nitrogen. Dilution with tetrahydrofuran was followed by precipitation in methanol, filtration to give a pale blue solid, dissolution in tetrahydrofuran, passage over a column of neutral alumina to remove CuCl2, and precipitation in methanol. After three dissolution-precipitation cycles, the solid was dried under vacuum at 40 °C for 48 h to give PMMA-Cl.

[0079] Example 2

[0080] Synthesis of PS macroinitiator:

[0081] 2-Bromoethylbenzene (0.185 g, 1 mmol) and styrene (St) (55 g, 0.55 mol) were added to a two-necked reaction flask fitted with a stopcock, stirred, purged with high purity nitrogen for 15 min, CuBr (0.143 g, 1.0 mmol) was added and purging with high purity nitrogen was continued for 30 min, then the flask was capped with a rubber septum. N,N,N',N,'N"-pentamethyldiethylenetriamine (PMDETA) (0.346 g, 2.0 mmol) was dissolved in St (5 g, 0.05 mmol) and purged with high purity nitrogen for 30 min, then transferred to the above flask. The flask was placed in an oil bath at 100 °C and samples were removed at timed intervals to monitor the extent of reaction. When the desired extent of reaction was achieved, the flask was immediately quenched by immersion in liquid nitrogen. Dilution with tetrahydrofuran was followed by precipitation in methanol, filtration to give a pale blue solid, dissolution in tetrahydrofuran, passage over a column of neutral alumina to remove CuBr2, and precipitation in methanol. After three dissolution-precipitation cycles, the solid was dried under vacuum at 40 °C for 48 h to give PS-Br.

[0082] Example 3

[0083] Synthesis of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer:

[0084] Into a two-necked flask with a stopcock, 0.1 mmol of PMMA-Cl and 0.2 mmol of CuCl were added. After the flask was sealed with a rubber stopper, it was evacuated for 15 min and then filled with high purity nitrogen. This vacuum-nitrogen cycle was repeated three times. N,N,N',N',N"-pentamethyldiethylenetriamine (PMDETA) (0.086 g, 0.5 mmol) was dissolved in styrene (St) (20 g, 0.2 mol) and bubbled with nitrogen for 30 min, and then transferred into the flask. The flask was placed in an oil bath at 100 °C, and samples were taken at timed intervals to monitor the extent of the reaction. When the desired extent of reaction was reached, the flask was immediately immersed in liquid nitrogen to quench the reaction. Tetrahydrofuran was added to dilute the reaction mixture, which was then precipitated in methanol and filtered to obtain a light blue solid. The solid was dissolved in tetrahydrofuran and passed through a column of neutral alumina to remove CuCl2, and then precipitated in methanol. The dissolution-precipitation cycle was repeated three times, and the solid was dried under vacuum at 40 °C for 48 h to obtain the PMMA-b-PS block copolymer.

[0085] Example 4

[0086] Synthesis of polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer:

[0087] Into a two-necked flask with a stopcock, 0.1 mmol of PS-Br and 0.2 mmol of CuBr were added. After the flask was sealed with a rubber stopper, it was evacuated for 15 min and then filled with high purity nitrogen. This vacuum-nitrogen cycle was repeated three times. N,N,N',N',N"-pentamethyldiethylenetriamine (PMDETA) (0.086 g, 0.5 mmol) was dissolved in methyl acrylate (MA) (20 g, 0.2 mol) and bubbled with nitrogen for 30 min, and then transferred into the flask. The flask was placed in an oil bath at 80 °C, and samples were taken at timed intervals to monitor the extent of the reaction. When the desired extent of reaction was reached, the flask was immediately immersed in liquid nitrogen to quench the reaction. Tetrahydrofuran was added to dilute the reaction mixture, which was then precipitated in methanol and filtered to obtain a light blue solid. The solid was dissolved in tetrahydrofuran and passed through a column of neutral alumina to remove CuBr2, and then precipitated in methanol. The dissolution-precipitation cycle was repeated three times, and the solid was dried under vacuum at 40 °C for 48 h to obtain the PS-b-PMA block copolymer.

[0088] Example 5

[0089] Synthesis of cross-linked PS (XPS):

[0090] Cross-linked PS: Styrene (St) (5 g, 50 mmol), glycidyl methacrylate (GMA) (0.15 g, 1 mmol), toluene (5 g) and azobisisobutyronitrile (AIBN) (0.041 g, 0.25 mmol) were added into a two-necked flask with a rubber stopper, and high purity nitrogen was bubbled for 30 min. The rubber stopper was sealed. The flask was placed in an oil bath at 70 °C, and samples were taken at regular intervals to monitor the reaction degree. When the desired reaction degree was reached, the flask was immediately immersed in liquid nitrogen to quench the reaction. Tetrahydrofuran was added for dilution, and the mixture was precipitated in methanol, filtered, and the solid was dissolved in tetrahydrofuran. After three cycles of dissolution-precipitation, the solid was dried under vacuum at room temperature for 48 h to obtain cross-linked PS.

[0091] Example 6

[0092] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on neutral substrates:

[0093] Preparation of modified neutral substrates: Single-side polished monocrystalline silicon wafers with a native oxide layer were ultrasonically cleaned with chloroform, acetone and ethanol for 5 min, respectively, and then dried with nitrogen. The wafers were then subjected to oxygen plasma cleaning at a power of 100 W for 3 min. The XPS synthesized in Example 5 was dissolved in toluene to form a 1 wt% solution, which was filtered with a 0.22 μm PTFE filter membrane and spin-coated on the above-mentioned treated silicon wafers. The wafers were heated at 250 °C for 1 h in a nitrogen atmosphere to cross-link the polymer to the surface of the silicon wafers. After cooling, the wafers were ultrasonically cleaned with toluene for 3 times, each for 5 min, to remove the uncross-linked polymer, and then dried with nitrogen for later use.

[0094] The above-mentioned substrates were evenly divided into small pieces of 0.5*0.5 cm, and subjected to oxygen plasma oxidation in an oxygen plasma cleaning machine. The oxygen plasma power was set at 15 W, the vacuum degree was set at 200 torr, and the oxygen flow rate was set at 30 cc / min. The oxidation time was set at 5 s to obtain modified neutral substrates.

[0095] Self-assembly of block copolymer: Poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer was dissolved in toluene to form a 1 wt% solution, which was filtered with a 0.22 μm PTFE filter membrane and spin-coated on the above-mentioned substrates. After annealing at 270 °C for 1 min in a nitrogen atmosphere, the substrates were removed and quenched to room temperature on a copper plate to obtain nanostructures.

[0096] The substrates subjected to self-assembly of block copolymer were subjected to oxygen plasma cleaning (20 W, 30 cc / min) for 20 s, at which time the PMMA was completely removed, and the planar and cross-sectional morphologies were characterized, as shown in FIG. 2. Figure 2

[0097] Example 7

[0098] ​Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymers on neutral substrates:

[0099] The difference with Example 6 is that the oxidation time during the preparation of the modified neutral substrate is 10 s, otherwise the same as Example 6.

[0100] Example 8

[0101] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymers on neutral substrates:

[0102] The difference with Example 6 is that the oxidation time during the preparation of the modified neutral substrate is 20 s, otherwise the same as Example 6.

[0103] Example 9

[0104] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymers on neutral substrates:

[0105] The difference with Example 6 is that the oxidation time during the preparation of the modified neutral substrate is 30 s, otherwise the same as Example 6.

[0106] Example 10

[0107] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymers on neutral substrates:

[0108] The difference with Example 6 is that the oxidation time during the preparation of the modified neutral substrate is 40 s, otherwise the same as Example 6.

[0109] Example 11

[0110] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymers on neutral substrates:

[0111] The difference with Example 6 is that the oxidation time during the preparation of the modified neutral substrate is 50 s, otherwise the same as Example 6.

[0112] Example 12

[0113] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymers on neutral substrates:

[0114] The difference with Example 6 is that the oxidation time during the preparation of the modified neutral substrate is 60 s, otherwise the same as Example 6.

[0115] Example 13

[0116] Self-assembly of polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer on neutral substrate:

[0117] Preparation of modified neutral substrate: The single side polished single crystal silicon wafer with native oxide layer was cleaned with chloroform, acetone and ethanol respectively for 5 min by ultrasonic, and dried with nitrogen. Then the wafer was treated with oxygen plasma for 3 min at a power of 100 w. The XPS synthesized in Example 5 was dissolved in toluene to form a 1 wt% solution, which was filtered with a 0.22 μm PTFE filter membrane and spin-coated on the treated silicon wafer. The wafer was heated at 250 °C for 1 h in a nitrogen atmosphere to crosslink the polymer with the surface of the silicon wafer. After cooling, the wafer was cleaned with toluene by ultrasonic for 3 times, 5 min each time, to remove the uncrosslinked polymer, and dried with nitrogen for use.

[0118] The wafer was divided into small pieces of 0.5*0.5 cm, and treated with oxygen plasma. The oxygen plasma power was set at 15 w, the vacuum degree was 200 tor, and the oxygen flow rate was 30 cc / min. The wafer was treated with oxygen plasma for 5 s to obtain the modified neutral substrate.

[0119] Self-assembly of block copolymer: The polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer was dissolved in toluene to form a 1 wt% solution, which was filtered with a 0.22 μm PTFE filter membrane and spin-coated on the above-mentioned substrate. The wafer was annealed at 160 °C for 30 min in a nitrogen atmosphere, and then removed from the copper plate to quench to room temperature to obtain the nanostructure.

[0120] Example 14

[0121] Self-assembly of polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer on neutral substrate:

[0122] The difference from Example 13 is that the oxidation time for the preparation of the modified neutral substrate is 10 s, and the other conditions are the same as those in Example 13.

[0123] Example 15

[0124] Self-assembly of polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer on neutral substrate:

[0125] The difference from Example 13 is that the oxidation time for the preparation of the modified neutral substrate is 20 s, and the other conditions are the same as those in Example 13.

[0126] Example 16

[0127] Self-assembly of polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer on neutral substrate:

[0128] The difference from Example 13 is that the oxidation time for the preparation of the modified neutral substrate is 30 s, and the other conditions are the same as those in Example 13.

[0129] Example 22

[0130] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on chemical patterned substrate:

[0131] Preparation of chemical patterned substrate: The single-side polished single crystal silicon wafer with native oxide layer was cleaned with chloroform, acetone and ethanol respectively for 5 min under ultrasonication, and then dried with nitrogen. The wafer was treated with oxygen plasma for 3 min at a power of 100 W. The XPS was dissolved in toluene to form a 1 wt% solution, which was filtered with a 0.22 μm PTFE filter and spin-coated on the treated silicon wafer. The wafer was heated at 250 °C for 1 h in nitrogen atmosphere to crosslink the polymer on the wafer surface. After cooling, the wafer was cleaned with toluene for 3 times, each for 5 min, to remove the uncrosslinked polymer, and then dried with nitrogen for use.

[0132] The wafer was divided into small pieces of 0.5*0.5 cm. The photoresist PMMA950 was dissolved in anisole to form a 2 wt% solution, which was filtered with a 0.22 μm PTFE filter and spin-coated on the XPS film. After heating at 180 °C for 2 min to remove the residual solvent, the wafer was exposed to electron beam. The line doses of the electron beam exposure were 670, 870 and 1140 pC / cm, respectively, and the designed line dose was 10-17 pC / cm. After exposure, the wafer was developed with THF or methyl isobutyl ketone / isopropyl alcohol (volume ratio 1:3) for 60 s. After drying with nitrogen, the wafer was placed in a plasma generator. The oxygen plasma power was set at 15 W, the vacuum degree was 200 torr, the oxygen flow rate was 30 cc / min, and the oxidation time was 5 s. After oxidation, the wafer was cleaned with N-methyl pyrrolidone (NMP) or toluene for 3 times, each for 5 min. The modified wafer with three-dimensional chemical pattern was obtained after drying with nitrogen (the L s = 94 nm).

[0133] Self-assembly of block copolymer: The block copolymer was dissolved in toluene to form a 1 wt% solution, which was filtered with a 0.22 μm PTFE filter and spin-coated on the wafer. After annealing at 270 °C for 1 h in nitrogen atmosphere, the wafer was quenched to room temperature to obtain the nanostructure.

[0134] Example 23

[0135] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on chemical patterned substrate:

[0136] The difference from Example 22 is that the oxidation time in the preparation of the chemical patterned substrate was 10 s, and the other conditions were the same as in Example 22.

[0137] Example 24

[0138] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a chemical patterned substrate:

[0139] The difference from Example 22 is that the oxidation time during the preparation of the chemical patterned substrate is 20 s, and the others are the same as Example 22.

[0140] Example 25

[0141] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a chemical patterned substrate:

[0142] The difference from Example 22 is that the oxidation time during the preparation of the chemical patterned substrate is 30 s, and the others are the same as Example 22.

[0143] Example 26

[0144] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a chemical patterned substrate:

[0145] The difference from Example 22 is that the oxidation time during the preparation of the chemical patterned substrate is 40 s, and the others are the same as Example 22.

[0146] Example 27

[0147] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a chemical patterned substrate:

[0148] The nanostructure is obtained by using the same preparation process as Example 23, except that the line dose of electron beam exposure during the preparation of the chemical patterned substrate is 780 pC / cm, the oxygen plasma power is 10 w, and the modification time is 5 s, and the L s The modified substrates with three-dimensional chemical patterns having a thickness of 90 nm, 92 nm, and 96 nm, respectively. The obtained modified substrates with three-dimensional chemical patterns, the obtained nanostructures, and the nanostructures with the PMMA phase removed by oxygen plasma etching (20 w, oxygen flow rate 30 cc / min, 10-15 s) are characterized by SEM, and the characterization results are shown in Figure 6

[0149] Example 28

[0150] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a chemical patterned substrate:

[0151] ​The same preparation process as Example 23 was used to obtain the nanostructure, except that in the preparation of the chemical patterned substrate, the line dose of the electron beam exposure was 900 pC / cm, the oxygen plasma power was 10 w, and the modification time was 10 s, obtaining a substrate with L s The modified substrates with three-dimensional chemical patterns having 184 nm, 248 nm, and 310 nm, respectively. The obtained nanostructures were characterized by SEM, and the characterization results are shown in Figure 7

[0152] Example 29

[0153] Self-assembly of polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer on a chemical patterned substrate:

[0154] The chemical patterned substrate was prepared as in Example 22

[0155] The above substrate was divided into small pieces of 0.5*0.5 cm, and a 2 wt% solution of the photoresist PMMA950 was prepared by dissolving the photoresist in anisole and filtering with a 0.22 μm PTFE filter membrane. The solution was spin-coated on the XPS film. After heating at 180 °C for 2 min to remove residual solvent, electron beam exposure was performed at a line dose of 900 pC / cm, and the line dose of the designed pattern was 10-17 pC / cm. After exposure, development was performed with THF or methyl isobutyl ketone / isopropyl alcohol (volume ratio 1:3) for 60 s. After blowing dry with nitrogen, the substrate was placed in a plasma generator, and the oxygen plasma power was set to 15 w, the vacuum degree was 200 tor, the oxygen flow rate was 30 cc / min, and the oxidation time was 15 s. After oxidation, the substrate was ultrasonically cleaned with N-methyl pyrrolidone (NMP) or toluene for 3 times, each for 5 min. After blowing dry with nitrogen, a modified substrate with a three-dimensional chemical pattern was obtained.

[0156] Self-assembly of the block copolymer: The block copolymer was dissolved in toluene to form a 1 wt% solution, which was filtered with a 0.22 μm PTFE filter membrane and spin-coated on the above substrate. After annealing at 180 °C for 30 min in a nitrogen atmosphere and quenching to room temperature, a nanostructure was obtained.

[0157] The obtained nanostructure was characterized by SEM, and the characterization results are shown in Figure 8

[0158] Example 30

[0159] Measurement of water contact angle and thickness of the pure silicon substrate and the crosslinked PS film:

[0160] Measurement of water contact angle of the pure silicon substrate:

[0161] ​​The pure silicon substrate was divided into 0.5*0.5 cm small pieces and placed in an oxygen plasma cleaning machine for oxygen plasma oxidation. The oxygen plasma power was set to 15 w, the vacuum degree was 200 tor, the oxygen rate was 30 cc / min, and the oxidation time was 10 s, respectively, to obtain the oxidized substrate;

[0162] The oxidized substrate was placed in toluene and ultrasonically cleaned for 3 times, 5 min each time. Nitrogen was blown to dry, and a hot table was heated at 160-170 °C for 2 min to remove residual solvent, to obtain the cleaned substrate.

[0163] The water contact angle of the pure silicon substrate, the oxidized substrate, and the cleaned substrate was tested, and the test results are shown in the left graph of Figure 11 .

[0164] Determination of changes in cross-linked PS film produced by oxidation:

[0165] The modified neutral substrate obtained in Example 7 was placed in toluene and ultrasonically cleaned for 3 times, 5 min each time. Nitrogen was blown to dry, and a hot table was heated at 160-170 °C for 2 min to remove residual solvent, to obtain the cleaned substrate.

[0166] The thickness of the cross-linked PS film of the modified neutral substrate obtained in Example 7 and the cleaned substrate was tested, and the test results are shown in the right graph of Figure 11 .

[0167] Example 31

[0168] Determination of the reference line of the three-dimensional chemical pattern in the modified substrate of the three-dimensional chemical pattern:

[0169] By adjusting the line dose of the electron beam exposure in Example 22 to be 670, 870, 1140, 1400 pC / cm, respectively, and the oxidation time to be 0, 5, 10, 20, 30, 40, 50, 60 s, respectively, 32 modified substrates with different three-dimensional chemical patterns were obtained, as shown in Figure 12 .

[0170] The reference line width of the modified substrate with different three-dimensional chemical patterns was tested, and the test results are shown in Figure 13 .

[0171] Example 32

[0172] The crosslinked PS layer thickness of the modified substrates with different topographies of three-dimensional chemical patterns obtained from Example 31 at a line dose of 1140 pC / cm for e-beam exposure and oxidation times of 0, 20, 40, 60 s, and the reference line height of the three-dimensional chemical patterns versus the oxidation time were measured, and the cross-section SEM images of the modified substrates with different topographies of three-dimensional chemical patterns were characterized, and the results are shown in Figure 14

[0173] Comparative Example 1

[0174] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a neutral substrate:

[0175] The difference from Example 6 is that the neutral substrate is not oxidized by oxygen plasma during the preparation of the modified neutral substrate, and the rest is the same as Example 6.

[0176] Comparative Example 2

[0177] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a neutral substrate:

[0178] The difference from Example 6 is that the oxidation time during the preparation of the modified neutral substrate is 70 s, and the rest is the same as Example 6.

[0179] Comparative Example 3

[0180] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a chemical pattern substrate:

[0181] The difference from Example 22 is that the chemical pattern substrate is not oxidized by oxygen plasma during the preparation of the chemical pattern substrate, and the rest is the same as Example 22.

[0182] Comparative Example 4

[0183] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a chemical pattern substrate:

[0184] The difference from Example 22 is that the oxidation time during the preparation of the chemical pattern substrate is 50 s, and the rest is the same as Example 22.

[0185] Comparative Example 5

[0186] Self-assembly of poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PS) block copolymer on a chemical pattern substrate:

[0187] ​The difference from Example 22 is that the line dose of the electron beam exposure during the preparation of the chemical pattern substrate is 1400 pC / cm, and the others are the same as Example 22. And by changing the oxidation time during the preparation of the chemical pattern substrate, the nanostructures obtained for oxidation times of 0 s, 5 s, 10 s, 20 s, 30 s, 40 s, 50 s are characterized by SEM.

[0188] Comparative Example 6

[0189] Preparation of the modified neutral substrate:

[0190] The difference from the preparation of the modified neutral substrate in Examples 6-12 and Comparative Examples 1-2 is that the power of the oxygen plasma during the preparation of the modified neutral substrate is 20 W. The others are the same as Examples 6-12 and Comparative Examples 1-2. Finally, the modified neutral substrates corresponding to oxidation times of 0 s, 5 s, 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s are obtained.

[0191] Comparative Example 7

[0192] Preparation of the modified neutral substrate:

[0193] The difference from the preparation of the modified neutral substrate in Examples 6-12 and Comparative Examples 1-2 is that the power of the oxygen plasma during the preparation of the modified neutral substrate is 30 W. The others are the same as Examples 6-12 and Comparative Examples 1-2. Finally, the modified neutral substrates corresponding to oxidation times of 0 s, 5 s, 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s are obtained.

[0194] The modified neutral substrates obtained in Examples 6-12 and Comparative Examples 1-2 and 6-7 are treated, and the specific steps are as follows: the modified neutral substrate is placed in toluene and ultrasonically cleaned for 3 times, each for 5 min. Nitrogen is blown to dry, and a hot stage is heated at 160-170°C for 2 min to remove residual solvent, obtaining the treated modified neutral substrate. The water contact angle and film thickness of the modified neutral substrates obtained in Examples 6-12 and Comparative Examples 1-2 and 6-7 and the treated modified neutral substrates are tested, and the test results are shown in Tables 1 and 2. Figure 9 and 10

[0195] Figure 1 and 3 ​​It is known that both PS-b-PMA and PS-b-PMMA block copolymers self-assemble to form vertically penetrating fingerprint-like structures. When the PS-b-PMMA film self-assembles on an unoxidized XPS film, a morphology is obtained in which PS blocks are mostly at the bottom and PMMA blocks are arranged in parallel. This is because the unoxidized XPS film selectively wets the PS blocks in PS-b-PMMA, thus forming a layered phase parallel to the substrate. When the XPS film is oxidized by oxygen plasma for 5–60 s, the PS-b-PMMA block copolymer self-assembles to form a fingerprint-like structure on its surface. When the oxidation time is 70 s, the fingerprint-like structure disappears, forming a pattern that is basically the same as that when the oxidation time is 0 s, i.e., a parallel layered phase structure. This is because at the oxidation time of 70 s, the silicon substrate is already exposed, and the PMMA blocks are selectively wetted, thus forming a parallel layered phase structure.

[0196] Depend on Figure 2 It can be seen that the obtained fingerprint-like structure is a vertically penetrating structure. That is, the interaction between the interface and the PS-b-PMMA block copolymer can be adjusted by plasma oxidation of the XPS surface.

[0197] Depend on Figure 4 It can be seen that, under the same conditions, cross-linked PS with different molecular weights does not affect the self-assembly morphology of PS-b-PMMA.

[0198] Depend on Figure 5 It is known that only when the trenches of the three-dimensional substrate, i.e. the unprotected XPS film, are oxidized by oxygen plasma for 5–40 s can PS-b-PMMA be guided to assemble into a defect-free, long-range ordered morphology. When the line dose of electron beam exposure is ≥1400 pC / cm, a defect-free structure cannot be obtained.

[0199] Depend on Figure 6 It can be seen that, in different matrix L s Under the conditions described above, defect-free phase separation morphologies were formed, indicating that the method described in this invention can not only obtain superior nanostructures, but also that the modified substrate has a certain tolerance range.

[0200] Depend on Figure 7 It can be seen that the present invention has prepared L s Substrates with wavelengths of 184, 248, and 310 nm, corresponding to PS-b-PMMA block copolymers 6L0, 8L0, and 10L0 respectively, all achieved long-range ordered morphologies after guided assembly. This is higher than the highest reported fold of chemical pattern-guided assembly (N≤5) and close to the fold of layered phase block copolymer assembly guided by patterned epitaxy (6~16X).

[0201] Depend on Figure 8It can be seen that the modified substrate-guided layered phase PS-b-PMA (Vps% = 49% L0 = 22nm) prepared in this invention, when assembled with 6 to 10X density multiplication, also yields a defect-free long-range ordered structure.

[0202] Depend on Figure 9 and 10 It is known that heating causes CL-PS to crosslink on a silicon substrate to form a molecular brush, and the epoxy groups in GMA undergo a condensation reaction with the silanol groups on the silicon substrate surface, grafting them onto the silicon surface. The crosslinked PS film prepared by this invention has a thickness of about 20 nm, which is greater than the thickness of a normal chemical pattern imaging layer (≤8 nm). With the extension of oxygen plasma oxidation time, the XPS film becomes thinner and thinner; when the oxidation time is 70 s, the XPS film is only 5 nm thick. This invention prepares a substrate with a relatively thick polymer film, which avoids the risk of exposed silicon substrates in modified substrates.

[0203] Depend on Figure 11 It can be seen that, without any treatment, the water contact angle on the silicon substrate surface is 27°. After oxygen plasma treatment, the surface SiO2 is oxidized to form Si(OH). x The crosslinked PS film exhibits hydrophilicity. After ultrasonic cleaning with a solvent, the unstable silanol groups easily form silyl ether bonds, causing the water contact angle to rise to 18°. Following oxygen plasma oxidation, the thickness of the crosslinked PS film changes, but only by less than 2 nm during subsequent cleaning. Therefore, the crosslinked PS film is oxidized in an oxygen plasma environment, forming small molecules that are then extracted from the surface under vacuum. During this process, the oxidized polystyrene on the film surface, which has a larger molecular weight, is not removed, leading to a drastic change in the surface water contact angle. After cleaning, the severely oxidized polystyrene is removed, leaving only slightly oxidized crosslinked polystyrene, causing the surface water contact angle to change. Alternatively, after ultrasonic cleaning of the crosslinked PS film in a solvent, the oxidized polystyrene on the surface dissolves, exposing most of the unoxidized polystyrene. In other words, during solvent cleaning, the unoxidized crosslinked PS in the inner layer migrates, resulting in a surface water contact angle closer to that of the unoxidized crosslinked polystyrene.

[0204] Depend on Figure 12 and 13 It can be seen that the baseline linewidth gradually decreases with the extension of plasma oxidation time. This is because during oxygen plasma oxidation, the outer PMMA layer has a lower degree of cross-linking than the PMMA at the exposure center. In the oxygen plasma environment, chemical bonds break first, forming small molecules that are removed by vacuum. Larger molecules are removed during subsequent cleaning, resulting in a narrower baseline linewidth. Furthermore, the higher the line dose of electron beam exposure, the deeper the cross-linking, and the wider the linewidth retained under different oxidation conditions.

[0205] Depend onFigure 14 It can be seen that the etching rate of the cross-linked PS layer is less than the cross-linked PMMA reference line under the condition of oxygen plasma oxidation, wherein the height variation of the cross-linked PMMA reference line is caused by statistical number and local non-uniformity of oxygen plasma (the line width is only 20 nm), and the variation rule is not absolutely linear, but the overall trend is obviously less than that of the XPS layer. From 40 s to 60 s, the height of the reference line is almost unchanged, and the cross-linked PS layer is reduced. This is because when the oxidation time is 40 s, the cross-linked PMMA is almost completely oxidized, and the cross-linked PS layer is not completely removed due to better etching resistance. The composition of the reference line is changed to cross-linked PS. Continue to extend the oxidation time, the cross-linked PS reference line and the cross-linked PS layer are reduced at the same time, so the height of the reference line is almost unchanged, but at this time the surface of the three-dimensional chemical pattern is composed of oxidized cross-linked PS.

[0206] The present application adjusts the free energy of the block copolymer and the interface by oxidizing the XPS film with oxygen plasma, so as to obtain a non-selective substrate. The method is simple and easy to realize, and the synthesis is simple, so it is a way to obtain neutral molecular brush which is worth promoting. In the present application, XPS is used as an imaging layer, PMMA photoresist is spin-coated, and high exposure dose is used to make the PMMA photoresist in the exposed area cross-linked, and after development, it is retained as a reference line of the chemical pattern. By changing the chemical properties of the XPS surface not protected by the photoresist through oxygen plasma oxidation, a 3D chemical pattern is prepared, and the PS-b-PMMA block copolymer is guided to N times (N=3, 6, 8, 10) density multiplication assembly, and a long-range ordered morphology without defect is obtained. Compared with the traditional chemical pattern method, not only the step of trimming etching is reduced, but also a higher density multiplication effect is obtained, and different block copolymers can be guided to assemble only by changing the exposure dose and the oxygen plasma oxidation conditions. And the preparation of 3D chemical pattern has low equipment requirement and simple preparation process which is easy to control.

[0207] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A method for plasma-modified 3D nanopatterns and guided self-assembly of block copolymers, characterized in that, Includes the following steps: Forming polymer brushes / felts on a substrate; Coat photoresist onto a polymer brush / felt; The photoresist layer is exposed using photolithography, and the unexposed photoresist layer is selectively removed. Then, plasma modification treatment is performed to obtain a surface-modified layer with a period of L. s The 3D nanopatterned substrate, with patterned modified polymer brushes / felts having three-dimensional chemical patterns; The phase separation period is L o The block copolymer is coated on the surface and modified with a period of L s On a substrate with 3D nanopatterns, annealing induces phase separation of the block copolymer to form a nanostructure; Selectively remove one phase from the nanostructure formed by phase separation of block copolymers, and use the unremoved phase as a mask to transfer the nanostructure onto a substrate; The plasma environment is one or more of oxygen, nitrogen, argon, air, carbon dioxide, chlorine, and haloalkanes. By using polymer brushes / felts as a pre-substrate, the interfacial energy between the polymer brushes / felts and block copolymers is adjusted by changing the plasma conditions, thereby guiding different block copolymers to form nanostructures.

2. The method for plasma-modified 3D nanopatterns and guided self-assembly of block copolymers according to claim 1, characterized in that, The polymer forming the polymer brush / felt contains functional groups that react with the substrate or undergo cross-linking reactions; the polymer forming the polymer brush / felt contains one or more functional groups selected from hydroxyl, azide, epoxy, double bond and isocyanate groups.

3. The method for plasma-modified 3D nanopatterns and guided self-assembly of block copolymers according to claim 2, characterized in that, The polymer forming the polymer brush / felt has a functional group content of 0.3-20%; the polymer forming the polymer brush / felt has a molecular weight of 5 kg-80 kg / mol.

4. The method for plasma-modified 3D nanopatterns and guided block copolymer self-assembly according to claim 2 or 3, characterized in that, The thickness T of the polymer brush / felt is in the range of 50nm ≥ T ≥ 5nm.

5. The method for plasma-modified 3D nanopatterns and guided self-assembly of block copolymers according to claim 1, characterized in that, The photoresist is a negative photoresist, which can be an electron beam photoresist, a laser photoresist, an ultraviolet light photoresist, or an X-ray photoresist.

6. The method for plasma-modified 3D nanopatterns and guided self-assembly of block copolymers according to claim 1, characterized in that, The L s =nL o , where 20≥n≥2.

7. The method for plasma-modified 3D nanopatterns and guided self-assembly of block copolymers according to claim 6, characterized in that, The preparation of a substrate with a period of Ls modified by plasma modification includes the following steps: the exposed nanopattern is placed in a plasma environment for modification, so that the photoresist on the nanopattern and the surface of the polymer substrate not protected by the photoresist undergo chemical changes, resulting in a plasma-modified 3D nanopattern.

8. The method for plasma-modified 3D nanopatterns and guided self-assembly of block copolymers according to claim 7, characterized in that, The photoresist thickness H on the 3D nanopatterns on the substrate with a surface modified with a period of Ls ranges from 0.9L. o ≥H≥0.1L o The surface modification has a period of L. s The thickness D of the substrate on the 3D nanopatterned substrate ranges from 15nm to T≥5nm.

9. The method for plasma-modified 3D nanopatterns and guided self-assembly of block copolymers according to claim 7 or 8, characterized in that, The block copolymer is a diblock, triblock, multiblock, or star-shaped block copolymer; the block copolymer forms different phase separation morphologies such as columnar phase, layered phase, bicontinuous phase, or spherical phase through phase separation.

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