Imprint mold and manufacturing method thereof

Abstract

To provide an imprint mold in which synthetic quartz glass is selected as an essential material and which has a fine pattern requiring high precision, which can prevent breakage due to the fineness of the pattern, and in which, when a coating layer is formed on the pattern, even when a foreign object is caught in the pattern, the coating layer can be easily removed and a new coating layer can be formed to regenerate the mold.SOLUTION: An imprint mold includes a synthetic quartz glass substrate on the surface of which a micropattern for transfer is formed, and a coating layer formed on at least a portion of the micropattern from at least one material different from the substrate, and the material different from the substrate is Al2O3 or the like, the coating layer has a thickness of 3 nm or less, and the breaking strength of the portion of the micropattern for transfer on which the coating layer is formed is higher than the breaking strength of the micropattern for transfer before the coating layer is formed.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an imprint mold and a method for manufacturing the same. [Background technology]

[0002] Imprinting technology, an alternative to photolithography that has become popular in recent years, is considered advantageous in terms of its ability to transfer patterns faithfully to the shape of the mold used as the model, as well as in terms of equipment costs. Imprinting can be broadly divided into two methods. The first is thermal imprinting, and the second is photoimprinting. The former is a method in which a mold pattern is pressed against a material to be imprinted and a pattern is transferred to the material by applying heat and pressure. The latter is a method in which a mold pattern is pressed against a photocurable material and the pattern is transferred by irradiating it with light.

[0003] In general, thermal imprinting is relatively simple and can be performed using inexpensive materials and equipment, but the applied pressure is high and there are limitations to the pattern dimensions and accuracy due to thermal expansion and contraction.In contrast, photoimprinting requires a low applied pressure and is said to enable highly accurate dimensional control during pattern transfer, and is used depending on the application.

[0004] In addition to the differences in the methods mentioned above, various materials such as resin, metal, glass, and ceramics are used for imprint molds depending on the transfer accuracy and durability required for the target device. Chemical treatments are also carried out as necessary to improve releasability.

[0005] Patent Document 1 proposes an imprint mold having a concave-convex pattern formed from a resin. Resin has the advantage that it can be easily manufactured, even for imprint molds having a concave-convex pattern with a complex shape. Imprint molds having a concave-convex pattern formed from a resin have a problem in that the concave-convex pattern collapses due to low chemical (solvent) resistance and strength, but it has been reported that this problem can be solved by adjusting the gel fraction of the resin or by forming a coating layer on the concave-convex pattern.

[0006] Furthermore, Patent Document 2 proposes an imprint mold formed from a resin that is free of transfer defects and has excellent mold release properties. This imprint mold has an oxide layer on the surface of a resin substrate and a release agent layer formed thereon, but there is a problem in that the oxide layer and the release agent layer become integrated and migrate to the transferred resin film. To solve this problem, Patent Document 2 reports controlling the reactivity of the resin contained in the imprint mold. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-170863 [Patent Document 2] International Publication No. 2012 / 018048 Summary of the Invention [Problem to be solved by the invention]

[0008] Generally, for fine patterns requiring high precision, optical imprinting using UV light as a light source is selected, and synthetic quartz glass is selected as the mold material, because molds formed from synthetic quartz glass have superior strength, hardness, dimensional stability, etc. of the concave-convex pattern compared to the resin molds described in Patent Documents 1 and 2. However, even with molds made of synthetic quartz glass, as the concave-convex pattern becomes finer, problems may occur due to breakage of the pattern.

[0009] The present invention has been made in view of the above circumstances, and aims to provide an imprint mold in which synthetic quartz glass is selected as an essential material and which has a fine pattern requiring high precision, in which damage due to the fineness of the pattern can be prevented, and in which, when a coating layer is formed on the pattern, even if a foreign matter or the like becomes trapped in the pattern or the pattern becomes soiled, the coating layer can be easily removed and the mold can be regenerated by forming a new coating layer. [Means for solving the problem]

[0010] As a result of intensive research to achieve the above-mentioned object, the inventors have found that by coating at least a portion of the portion of an imprint mold formed from a synthetic quartz glass substrate where a fine pattern for transfer is formed, with a film made of a material different from that of the substrate, the strength of the mold pattern portion can be improved, and that the coated film can be easily removed without damaging the mold pattern and can be re-coated, thereby completing the present invention.

[0011] That is, the present invention provides the following imprint mold and method for manufacturing the same. 1. A synthetic quartz glass substrate having a fine pattern for transfer formed on its surface; a coating layer formed on at least a portion of the fine pattern and made of at least one material different from the substrate; An imprint mold having: the material different from the substrate is Al2O3, ZrO2, HfO2, TiN, TaN, or WN; The thickness of the coating layer is 3 nm or less, and An imprint mold in which the breaking strength of a portion of a transfer fine pattern on which a coating layer is formed is higher than the breaking strength of the transfer fine pattern before the coating layer is formed. 2. The imprint mold according to 1, wherein the material different from the substrate is Al2O3. 3. The imprint mold according to 1 or 2, wherein the variation in thickness of the coating layer is within 10% of the average thickness of the coating layer. 4. An imprint mold according to any one of 1 to 3, wherein the breaking strength of the portion of the transfer micropattern on which the coating layer is formed is at least 1.05 times the breaking strength of the transfer micropattern before the coating layer is formed. 5. A method for producing an imprint mold according to any one of 1 to 4, in which at least a portion of a transfer micropattern formed on the surface of a synthetic quartz glass substrate is alternately exposed to at least two reactive precursors, which are raw materials for a material different from the substrate, by sequential chemical vapor deposition, and these precursors are reacted to form a coating layer made of a material different from the substrate. 6. The method for producing an imprint mold according to 5, wherein a heating step is carried out after forming the coating layer. 7. The method for producing an imprint mold according to 6, wherein the heating temperature is 100 to 900°C. [Effects of the Invention]

[0012] The imprint mold of the present invention can avoid or reduce damage to a pattern during an imprinting process, particularly damage to a fine pattern caused by the inclusion of foreign matter. Furthermore, the coating layer formed on the pattern can be easily removed and a new coating layer can be regenerated. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an atomic force microscope image of the line pattern obtained in Experimental Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in more detail below. The imprint mold of the present invention comprises a synthetic quartz glass substrate having a fine transfer pattern formed on its surface, and a coating layer formed on at least a portion of the fine pattern from at least one material different from that of the synthetic quartz glass substrate.

[0015] [Imprint mold] The synthetic quartz glass substrate used in the present invention can be obtained by forming a synthetic quartz glass ingot into the desired shape, which is produced by reacting a silica raw material compound such as a silane compound or a siloxane compound with an oxyhydrogen flame, annealing the ingot, slicing it to the desired thickness, lapping it, polishing the outer periphery as needed, and then rough polishing and precision polishing the resulting ingot.

[0016] The shape of the synthetic quartz glass substrate is not particularly limited, but for ease of manufacture, it can be a quadrilateral shape such as a rectangle, a circle, etc. For example, a quadrilateral substrate having a side length of 10 to 300 mm is preferably used, and a circular glass substrate having a diameter of 10 to 300 mm is preferably used. The thickness of the synthetic quartz glass substrate is selected appropriately and is not particularly limited, but from the viewpoint of transmittance, a thinner thickness is preferable, while from the viewpoints of strength, deformation due to its own weight, and ease of handling, a certain thickness is necessary, and is preferably 10 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more, and is preferably 300 mm or less, more preferably 100 mm or less, and even more preferably 30 mm or less.

[0017] In the present invention, examples of fine patterns include line patterns, nanopillar patterns, and 3D patterns. The size and shape of the fine patterns are not particularly limited, but examples of line patterns include simple straight lines, angled bent shapes, curved R-shapes, branched shapes, and cross shapes. Examples of nanopillar patterns include rectangular pillar shapes, cylindrical shapes, elliptical pillar shapes, truncated pyramid shapes, truncated conical shapes, truncated elliptical pyramid shapes, inverted truncated pyramid shapes, inverted truncated conical shapes, and inverted truncated elliptical pyramid shapes. Examples of 3D patterns include stepped shapes such as staircase shapes, sloped shapes, and shapes with partial spherical surfaces. The fine patterns may be one type of shape or a combination of multiple types of shapes.

[0018] The breaking strength of the substrate at the portion where the transfer micropattern is formed is preferably 70 GPa or more, more preferably 75 GPa or more, from the viewpoint of the formation, removal, and regeneration of the coating layer described below. In the present invention, the breaking strength can be determined by a nanoindentation test method. The nanoindentation test method is a method for measuring the hardness and Young's modulus of a substrate based on the pressing force and indentation depth when a hard indenter is pressed against the substrate. It can be said that the higher the Young's modulus, the higher the breaking strength.

[0019] The imprint mold of the present invention has a coating layer formed on at least a portion of the transfer micropattern, the coating layer being made of at least one material different from the synthetic quartz glass substrate. By providing this coating layer on the transfer micropattern, the transfer micropattern formed of synthetic quartz glass can be protected from contamination and deterioration, and the material is appropriately selected for this purpose. Among these, metals, inorganic oxides, and inorganic nitrides are particularly preferred from the viewpoints of coating thickness accuracy, strength, etc. Examples of metals include elemental metals such as Cr, Cu, Mo, and Ni, and alloys containing these. Examples of inorganic oxides include Al2O3, ZrO2, and HfO2. Examples of inorganic nitrides include TiN, TaN, and WN. Among these, alumina (Al2O3) is preferred for reasons of coating film performance, coating stability, and versatility.

[0020] The thickness of the coating layer is not particularly limited, but is preferably 50 nm or less, more preferably 10 nm or less. The lower limit is not particularly limited, but is preferably 0.1 nm or more, more preferably 1 nm or more. A thickness within the above range is preferable not only from the viewpoint of the strength variation of the pattern including the coating film layer but also from the viewpoint of the dimensional reliability of the fine pattern. Furthermore, the thickness variation (maximum thickness minus minimum thickness) is preferably within 10% of the average thickness of the coating layer. By keeping the thickness variation within the above range, good results can be obtained in terms of strength stability and reproducibility.

[0021] The hardness of the coating layer is preferably high from the viewpoint of protecting and strengthening the fine pattern of the synthetic quartz glass, and specifically, for example, a Mohs hardness of 6 or more is preferred.

[0022] Furthermore, by providing the coating layer, the fracture strength of the portion where the transfer micropattern is formed can be favorably improved. If the fracture strength of the transfer micropattern portion before providing the coating layer is, for example, 73 GPa, the fracture strength of the transfer micropattern portion with the coating layer provided is preferably 77 GPa or more, more preferably 80 GPa or more. By providing the coating layer, the fracture strength of the transfer micropattern portion can be increased by preferably 1.05 times or more, more preferably 1.1 times or more, compared to before providing the coating layer, which is effective not only from the viewpoint of preventing pattern destruction due to hard foreign matter but also from the viewpoint of suppressing pattern deformation during imprinting.

[0023] In the present invention, the coating layer is formed so as to cover at least a portion of the transfer micropattern, but from the viewpoint of improving strength, it is preferable that it is formed so as to cover the entire micropattern, and it is more preferable that it is formed so as to cover the entire surface on which the micropattern is formed.

[0024] The imprint mold of the present invention, which has a transfer fine pattern provided with such a coating layer, can avoid or reduce damage to the fine pattern, particularly breakage of the fine pattern when foreign matter is mixed in, and therefore can achieve significantly higher precision and longer life than conventional imprint molds. In the imprint mold of the present invention, even if the fine pattern provided with the above-mentioned coating layer becomes soiled for some reason, the coating layer can be easily regenerated by the method described below, and therefore, in this respect as well, a longer life can be expected.

[0025] [Imprint mold manufacturing method] [1] Method for forming fine patterns In the imprint mold of the present invention, the fine pattern formed on the surface of the synthetic quartz glass substrate can be produced by lithography methods such as electron beam lithography, photolithography, and nanoimprint lithography.

[0026] Specifically, it can be produced by a method including the following steps. (1) A step of forming an inorganic film on the surface of a synthetic quartz glass substrate on which a fine pattern is to be formed (first step) (2) Step of forming an organic film on the inorganic film (second step) (3) A step of patterning the organic film to form an organic film pattern on the inorganic film (third step). (4) A step of etching the inorganic film using the organic film pattern as an etching mask to form an inorganic film pattern (fourth step). (5) A step of etching the surface of the synthetic quartz glass substrate using the organic film pattern and / or inorganic film pattern as an etching mask to form a fine pattern (fifth step). (6) Step of removing the organic film pattern and / or the inorganic film pattern (sixth step)

[0027] (1) First step In the first step, an inorganic film is typically formed on the entire surface of the synthetic quartz glass substrate on which the fine pattern is to be formed. Examples of inorganic films include metal films and films of metal compounds such as metal nitrides, metal oxides, metal carbides, metal nitride oxides, metal nitride carbides, metal oxide carbides, and metal nitride oxycarbides. The metal film may be a simple film or an alloy film. Furthermore, the metal compound film may consist of a single metal or a combination of two or more metals. Specific examples of metals constituting metal films and metal compound films include Ag, Al, Au, Cr, Cu, Mo, Ni, Ru, Si, Ta, Ti, and W. Among these, from the viewpoint of ease of etching in etching the inorganic film in the fourth step, Cr film, Si film, Cr compound film, and Si compound film are preferred, and specific examples of Cr compounds include CrN, CrO, CrNO, and CrNOC (these formulas represent the constituent elements of the compound, and the ratio of each element is arbitrary), and specific examples of Si compounds include SiN (this formula represents the constituent elements of the compound, and the ratio of each element is arbitrary). The thickness of the inorganic film is preferably 200 nm or less, more preferably 50 nm or less, and preferably 2 nm or more, from the viewpoint of preventing an increase in pattern width, which is counter to miniaturization, and obtaining a sufficient strength improvement effect.

[0028] The inorganic film can be formed by sputtering. Specifically, a metal target, a metal compound target, or the like is used as the target, and a rare gas such as argon gas, and optionally a reactive gas such as an oxygen-containing gas, a nitrogen-containing gas, or a carbon-containing gas, is used as the sputtering gas, and the inorganic film is formed on a synthetic quartz glass substrate in a sputtering apparatus. The power source may be either DC or AC, but when using a DC power source, it is preferable to apply measures to suppress arc generation.

[0029] (2)Second process In the second step, an organic film is formed on the inorganic film, and the organic film is formed on a part or the entire surface of the inorganic film. Suitable materials for the organic film are resist materials (photoresist materials) that are sensitive to desired activation energy rays such as electron beams, X-rays, ultraviolet rays, excimer lasers (ArF, KrF, etc.), high-pressure mercury lamps (i-rays, g-rays, etc.), etc. Both positive-type and negative-type resist materials can be used as the resist material, but positive-type resist materials are preferred from the standpoints of accuracy and environmental considerations. The thickness of the organic film can be selected in the range of 10 nm to several tens of μm, but a thin film is preferable from the viewpoint of resolution, and a thick film is preferable from the viewpoint of etching resistance. Taking both factors into consideration, if wet etching is used for etching the surface portion of the synthetic quartz glass substrate in the fifth step, a thickness of about 0.5 to 5 μm is preferable, and if dry etching is used, a thickness of about 10 to 500 nm is preferable.

[0030] The organic film can be formed by coating using methods such as spin coating, spray coating, slit coating, and stencil printing, but spin coating is preferred for more uniform application. In spin coating, the coating is performed at a maximum rotation speed of 2,000 to 4,000 rpm, and baking (pre-baking) is performed after coating. The pre-baking temperature is preferably about 80 to 120°C, although this depends on the type of organic film material.

[0031] (3) Third step In the third step, the organic film is patterned to form an organic film pattern on the inorganic film. Methods for forming the organic film pattern include electron beam lithography, photolithography, and nanoimprint lithography.

[0032] In the electron beam lithography method, an organic film pattern can be formed by drawing an organic film formed on an inorganic film using an electron beam drawing device and developing the pattern drawn on the organic film.

[0033] In addition, in a photolithography method, an organic film pattern can be formed by exposing an organic film formed on an inorganic film using a photomask having predetermined light-shielding and non-light-shielding portions, and developing the pattern transferred to the organic film. The liquid used for development may be selected appropriately depending on the type of resist material, and suitable developing liquids include, for example, aqueous alkaline solutions such as tetramethylammonium hydroxide (TMAH) and xylene-based organic solvents. After development, a rinse treatment using pure water or the like is performed to wash away any remaining developer and components derived from the resist material dissolved in the developer, followed by drying, thereby forming an organic film pattern on the inorganic film. After drying, post-baking may be performed to strengthen the organic film. Post-baking is performed at a temperature and / or for a time period that makes the organic film insensitive to light, and is preferably performed at a temperature higher than the pre-baking temperature before exposure (e.g., 130°C or higher).

[0034] In the nanoimprint lithography method, the concave-convex structure of an imprint mold having a predetermined concave-convex pattern is pressed against an organic film, the recesses of the mold are filled with a resist material, and the upper surface of the resist material is molded to have the shape of the concave-convex pattern.The organic film is hardened in this state, and then the imprint mold is separated from the hardened organic film, thereby forming an organic film pattern.

[0035] The concave-convex structure of the imprint mold is preferably pressed against the organic film in a helium gas atmosphere or a readily condensable gas atmosphere. A readily condensable gas atmosphere is a gas atmosphere that is easily liquefied by pressure when gas is trapped in the mold voids. In such an atmosphere, bubble defects are less likely to occur. Specific examples of such gases include 1,1,1,3,3-pentafluoropropane (PFP, HFC-245fa) and trans-1,3,3,3-tetrafluoropropene (TFP). If bubbles form between the surface of the concave-convex structure of the imprint mold and the resist material, pattern defects may occur in the organic film pattern. However, if the pressing is performed in a helium or readily condensable gas atmosphere, the helium gas or readily condensable gas that constitutes the bubbles dissolves into the resist material, preventing pattern defects. The method of curing the organic film may be selected according to the curing type of the material that constitutes the organic film. For example, if the organic film material is an ultraviolet curing type, a method of irradiating ultraviolet light onto the organic film through an imprint mold may be used.

[0036] After the imprint mold is separated from the cured organic film, a considerable thickness of the organic film (for example, 1 nm or more, particularly 5 nm or more, and 20 nm or less, particularly 10 nm or less) usually remains at the positions where the organic film was in contact with the convex portions of the imprint mold, and this remaining portion is preferably removed before etching the synthetic quartz glass substrate. The method for removing the remaining portion is not particularly limited, but examples include ashing treatment using oxygen plasma, UV ozone treatment using ultraviolet light, and VUV treatment using vacuum ultraviolet light.

[0037] (4) 4th step In the fourth step, the inorganic film pattern (hard mask pattern) is formed by selectively removing the inorganic film exposed by removing the organic film. Etching is suitable for selectively removing the inorganic film. The etching may be either a wet process or a dry process. In the case of a wet process, etching is performed using an etching solution appropriate for the type of inorganic film. Specific examples of wet processes include wet etching using a Cr etching solution (aqueous solution of cerium diammonium nitrate) when the inorganic film is Cr or a Cr compound. The concentration of the Cr etching solution is not particularly limited, but is preferably 5 to 20 mass %. On the other hand, anisotropic etching is suitable for dry processes, such as argon ion milling and dry etching using reactive gases such as CF, C3F6, C3F8, C4F8, C5F8, and CHF3. After the selective removal of the inorganic film, an organic film pattern usually remains on the inorganic film pattern. The fifth step may be carried out with this remaining organic film pattern left on the inorganic film pattern, or may be carried out after removing the organic film pattern from the inorganic film pattern.

[0038] (5) Fifth step In the fifth step, if the organic film pattern remains after the inorganic film has been selectively removed in the fourth step, the surface of the synthetic quartz glass substrate is etched using the organic and inorganic film patterns (hard mask patterns) as an etching mask, or if the organic film pattern has been removed, using the inorganic film pattern (hard mask pattern) as an etching mask, to form a fine pattern. In this etching, the exposed portions of the surface of the synthetic quartz glass substrate that are not covered by the organic and inorganic film patterns or the inorganic film pattern are etched (digged in), and the portions covered by the patterns remain unetched, thereby forming a fine pattern.

[0039] Methods for etching synthetic quartz glass substrates are not particularly limited, but examples include wet etching in which the substrate is immersed in an etching solution containing hydrofluoric acid or sodium fluoride, and dry etching using reactive gases such as CF, C3F6, C3F8, C4F8, C5F8, and CHF3.

[0040] (6) 6th step In the sixth step, if the organic film pattern remains after the inorganic film is selectively removed in the fourth step, the organic film pattern and the inorganic film pattern are removed, and if the organic film pattern is removed, the inorganic film pattern is removed. The organic film pattern can be removed simultaneously with the inorganic film pattern, and the inorganic film pattern can be removed by etching. The etching may be either a wet process or a dry process. In the case of a wet process, etching is performed using an etching solution appropriate for the type of inorganic film. Specific examples of wet processes include wet etching using a Cr etching solution (aqueous solution of cerium diammonium nitrate) when the inorganic film is Cr or a Cr compound. The concentration of the Cr etching solution is not particularly limited, but is preferably 5 to 20 mass %. On the other hand, anisotropic etching is suitable for dry processes, such as argon ion milling and dry etching using reactive gases such as CF, C3F6, C3F8, C4F8, C5F8, and CHF3.

[0041] Up to this point, the method for producing a fine pattern has been described using as an example a method in which an inorganic film is first formed on a synthetic quartz glass substrate and then an organic film is formed thereon, but the method is not limited to these embodiments. The fine pattern can also be produced by a so-called lift-off method, in which an organic film is first formed on a synthetic quartz glass substrate, the organic film is patterned to form an organic film pattern, and then an inorganic film is formed.

[0042] Specifically, it can be produced by a method including the following steps. (11) A step of forming an organic film on the surface of the synthetic quartz glass substrate on which the fine pattern is to be formed (11th step) (12) A step of patterning the organic film to form an organic film pattern on the surface of the synthetic quartz glass substrate on which the fine pattern is to be formed (12th step). (13) A step of forming an inorganic film on the organic film pattern and the exposed surface of the synthetic quartz glass substrate (13th step) (14) A step of removing the organic film pattern together with the inorganic film formed on the organic film pattern (14th step) (15) a step of etching the surface of the synthetic quartz glass substrate using the inorganic film pattern formed by the inorganic film on the surface of the synthetic quartz glass substrate as an etching mask to form a fine pattern (step 15); (16) Step of removing the inorganic film pattern (step 16)

[0043] (11) 11th step In the eleventh step, an organic film is formed on part or all of the surface of the synthetic quartz glass substrate on which the fine pattern is to be formed. Suitable materials for the organic film are resist materials (photoresist materials) that are sensitive to desired activation energy rays such as electron beams, X-rays, ultraviolet rays, excimer lasers (ArF, KrF, etc.), high-pressure mercury lamps (i-rays, g-rays, etc.), etc. Both positive-type and negative-type resist materials can be used as the resist material, but positive-type resist materials are preferred from the standpoints of accuracy and environmental considerations. The thickness of the organic film can be selected in the range of 10 nm to several tens of μm, but a thin film is preferable from the viewpoint of resolution, and from the viewpoint of removing the organic film pattern together with the inorganic film in the 14th step, it is preferable that the thickness is sufficiently thicker than the inorganic film described below (for example, at least twice as thick as the inorganic film).

[0044] The organic film can be formed by spin coating, spray coating, slit coating, stencil printing, or other coating methods, but spin coating is preferred for achieving a more uniform coating. Spin coating is performed at a maximum rotation speed of 2,000 to 4,000 rpm, and baking (pre-baking) is performed after coating. The pre-baking temperature varies depending on the type of organic film material, but is preferably about 80 to 120°C.

[0045] (12) 12th step In step 12, the organic film is patterned to form an organic film pattern on the surface of the synthetic quartz glass substrate on which the fine pattern is to be formed. Methods for forming the organic film pattern include electron beam lithography, photolithography, and nanoimprint lithography.

[0046] In the electron beam lithography method, an organic film pattern can be formed by drawing an organic film formed on an inorganic film using an electron beam drawing device and developing the pattern drawn on the organic film.

[0047] In addition, in a photolithography method, an organic film pattern can be formed by exposing an organic film formed on an inorganic film using a photomask having predetermined light-shielding and non-light-shielding portions, and developing the pattern transferred to the organic film. The liquid used for development may be selected appropriately depending on the type of resist material, and suitable developing liquids include, for example, aqueous alkaline solutions such as tetramethylammonium hydroxide (TMAH) and xylene-based organic solvents. After development, a rinse treatment using pure water or the like is performed to wash away any remaining developer and components derived from the resist material dissolved in the developer, followed by drying, thereby forming an organic film pattern on the inorganic film. After drying, post-baking may be performed to strengthen the organic film. Post-baking is performed at a temperature and / or for a time period that makes the organic film insensitive to light, and is therefore preferably performed at a temperature higher than the pre-baking temperature before exposure (e.g., 130°C or higher).

[0048] In the nanoimprint lithography method, the concave-convex structure of an imprint mold having a predetermined concave-convex pattern is pressed against an organic film, the recesses of the mold are filled with a resist material, and the upper surface of the resist material is molded to have the shape of the concave-convex pattern.The organic film is hardened in this state, and then the imprint mold is separated from the hardened organic film, thereby forming an organic film pattern.

[0049] The concave-convex structure of the imprint mold is preferably pressed against the organic film in a helium gas atmosphere or a readily condensable gas atmosphere. A readily condensable gas atmosphere is a gas atmosphere that is easily liquefied by pressure when gas is trapped in the mold voids. In such an atmosphere, bubble defects are less likely to occur. Specific examples of such gases include 1,1,1,3,3-pentafluoropropane (PFP, HFC-245fa) and trans-1,3,3,3-tetrafluoropropene (TFP). If bubbles form between the surface of the concave-convex structure of the imprint mold and the resist material, pattern defects may occur in the organic film pattern. However, if the pressing is performed in a helium or readily condensable gas atmosphere, the helium gas or readily condensable gas that constitutes the bubbles dissolves into the resist material, preventing pattern defects. The method of curing the organic film may be selected according to the curing type of the material that constitutes the organic film. For example, if the organic film material is an ultraviolet curing type, a method of irradiating ultraviolet light onto the organic film through an imprint mold may be used.

[0050] After the imprint mold is separated from the cured organic film, a considerable thickness of the organic film (for example, 1 nm or more, particularly 5 nm or more, and 20 nm or less, particularly 10 nm or less) usually remains at the positions where the organic film was in contact with the convex portions of the imprint mold, and this remaining portion is preferably removed before etching the synthetic quartz glass substrate. The method for removing the remaining portion is not particularly limited, but examples include ashing treatment using oxygen plasma, UV ozone treatment using ultraviolet light, and VUV treatment using vacuum ultraviolet light.

[0051] (13) 13th process In the thirteenth step, an inorganic film is typically formed over the organic film pattern and the entire surface of the exposed synthetic quartz glass substrate. Examples of inorganic films include metal films and films of metal compounds such as metal nitrides, metal oxides, metal carbides, metal nitride oxides, metal nitride carbides, metal oxide carbides, and metal nitride oxycarbides. The metal film may be a simple film or an alloy film. Furthermore, the metal compound film may consist of a single metal or a combination of two or more metals. Specific examples of metals constituting the metal film and metal compound film include Ag, Al, Au, Cr, Cu, Mo, Ni, Ru, Si, Ta, Ti, and W. Among these, from the viewpoint of ease of etching in etching the inorganic film in the 14th step, Cr film, Si film, Cr compound film, and Si compound film are preferred, and specific examples of Cr compounds include CrN, CrO, CrNO, and CrNOC (these formulas represent the constituent elements of the compound, and the ratio of each element is arbitrary), and specific examples of Si compounds include SiN (this formula represents the constituent elements of the compound, and the ratio of each element is arbitrary). The thickness of the inorganic film is preferably 200 nm or less, more preferably 50 nm or less, and is preferably 10 nm or more.

[0052] The inorganic film can be formed by sputtering. Specifically, a metal target, a metal compound target, or the like is used as the target, and a rare gas such as argon gas, and optionally a reactive gas such as an oxygen-containing gas, a nitrogen-containing gas, or a carbon-containing gas, is used as the sputtering gas, and the inorganic film is formed on a synthetic quartz glass substrate in a sputtering apparatus. The power source may be either DC or AC, but when using a DC power source, it is preferable to apply measures to suppress arc generation.

[0053] (14) 14th step In the fourteenth step, the organic film pattern is removed together with the inorganic film formed on the organic film pattern. If the organic film is formed to be sufficiently thicker than the inorganic film, the organic film pattern is removed from the side of the organic film pattern where the inorganic film is not formed, thereby removing only the inorganic film formed on the organic film pattern. In this case, the organic film pattern can be removed using an alkaline aqueous solution such as tetramethylammonium hydroxide (TMAH), a xylene-based organic solvent, or the like.

[0054] (15) 15th process In the fifteenth step, the surface of the synthetic quartz glass substrate is etched using the inorganic film pattern (hard mask pattern) drawn by the inorganic film formed on the surface of the synthetic quartz glass substrate as an etching mask to form a fine pattern. In this etching, the exposed surface portions of the synthetic quartz glass substrate that are not covered with the inorganic film pattern are etched (digged in), while the portions covered with the pattern remain unetched, thereby forming the fine pattern.

[0055] Methods for etching synthetic quartz glass substrates are not particularly limited, but examples include wet etching in which the substrate is immersed in an etching solution containing hydrofluoric acid or sodium fluoride, and dry etching using reactive gases such as CF, C3F6, C3F8, C4F8, C5F8, and CHF3.

[0056] (16) 16th step In the sixteenth step, the inorganic film pattern is removed by etching. The etching may be either a wet process or a dry process. In the case of a wet process, etching is performed using an etching solution appropriate for the type of inorganic film. Specific examples of wet processes include wet etching using a Cr etching solution (aqueous solution of cerium diammonium nitrate) when the inorganic film is Cr or a Cr compound. The concentration of the Cr etching solution is not particularly limited, but is preferably 5 to 20 mass %. On the other hand, anisotropic etching is suitable for dry processes, such as argon ion milling and dry etching using reactive gases such as CF, C3F6, C3F8, C4F8, C5F8, and CHF3.

[0057] [2] Coating layer formation method Next, a method for forming a coating layer on the fine pattern obtained as described above will be described. In the present invention, a coating layer is formed on at least a portion of the fine pattern using at least one material different from the synthetic quartz glass substrate. Methods for forming a coating layer on a fine pattern include sequential chemical vapor deposition, CVD, sputtering, and vapor deposition. However, to form a uniform coating layer even around the periphery of a fine pattern, sequential chemical vapor deposition is preferred, and atomic deposition, which is a type of sequential chemical vapor deposition, can be preferably used.

[0058] Sequential chemical vapor deposition (SCCVD) is a method for depositing inorganic layers by exposing a substrate to at least one, preferably at least two, reactive precursors that are the raw materials for the inorganic layer, and then reacting the precursors with the substrate surface or reacting the precursors on the substrate to form an inorganic layer. Examples of inorganic layers formed by this method include inorganic oxide layers such as Al2O3, ZrO2, and HfO2, and inorganic nitride layers such as TiN, TaN, and WN. Alumina (Al2O3) films are widely used, and various methods have been proposed for depositing these coating layers. The most common method is to react trimethylaluminum (TMA) with water.

[0059] This method allows for the growth of coating layers at substrate temperatures ranging from room temperature to over 300°C, and the coating layer is grown using the following mechanism. Specifically, TMA and water are alternately supplied. During the TMA supply, TMA dissociates and AlCH3 is adsorbed onto the substrate surface. The excess TMA is discharged without adsorption, and a single layer of AlCH3 is formed on the substrate surface. When water is then supplied, it reacts with the CH3 groups on the surface, generating the by-product CH4, leaving hydroxylated Al2O3 on the surface. By repeating this cycle, an Al2O3 layer of the desired thickness is formed on the substrate surface. For example, in the case of Al2O3, 20 cycles are required to form a coating layer of approximately 3 nm.

[0060] After the coating layer is formed, a heating step may be carried out to remove unreacted materials and moisture and to stabilize the coating layer. The heating temperature is not particularly limited, but is preferably 100 to 900°C, as this is a temperature that does not affect the fine pattern and does not cause structural changes in alumina.

[0061] The thickness of the coating layer is preferably thicker from the viewpoint of improving strength, but thinner from the viewpoint of miniaturization. Considering that the dimensions of fine patterns for semiconductor applications are on the order of several tens of nanometers, the thickness of the coating layer is preferably 50 nm or less, more preferably 10 nm or less. There is no particular lower limit, but a thickness of 0.1 nm or more is preferred, and a thickness of 1 nm or more is more preferred.

[0062] [Manufacturing method for recycled imprint molds] The coating layer of the imprint mold of the present invention can be easily removed. For example, an Al2O3 film can be easily removed using a commercially available mixed acid alumina etching solution. Therefore, even if the transfer micropattern becomes contaminated for some reason or the coating layer formed on the transfer micropattern deteriorates, the coating layer can be removed as described above. The imprint mold can be regenerated by forming a new coating layer on the transfer micropattern from which the coating layer has been removed using the above-mentioned method. This makes it possible to obtain a regenerated mold without damaging the transfer micropattern formed on the synthetic quartz glass substrate.

[0063] Specifically, as a method for producing the above-mentioned recycled imprint mold, for example, a method including the following steps can be adopted. (21) Step of peeling off the coating layer formed on the transfer fine pattern of the synthetic quartz glass substrate (step 21) (22) Step of cleaning the transfer fine pattern from which the coating layer has been peeled off (step 22) (23) A step of confirming that the cleaned transfer micropattern maintains its shape and breaking strength compared to the pattern before the coating layer was peeled off (step 23). (24) A step of forming a new coating layer on at least a part of the confirmed fine pattern for transfer using the same material as the peeled coating layer or a different material (step 24).

[0064] (21) 21st process In step 21, the coating layer formed on the transfer micropattern of the synthetic quartz glass substrate is peeled off. In this step, it is preferable to use a chemical that can remove the existing coating layer without damaging the transfer micropattern. The chemical can be selected appropriately depending on the material of the coating layer. For example, if the coating layer is made of alumina, a commercially available mixed acid alumina etching solution can be used.

[0065] (22) 22nd process In step 22, the transfer micropattern from which the coating layer has been peeled is cleaned. In this step, the transfer micropattern is cleaned taking into consideration the possibility of foreign matter being trapped inside. Specifically, this can be done by combining wet cleaning methods, such as aqueous solutions generally referred to as SC1 and SC2, which combine acids, alkalis, surfactants, etc. for semiconductors, and dry cleaning methods such as plasma, ozone, and DUV.

[0066] (23) 23rd process In step 23, the coating layer is peeled off and the cleaned transfer micropattern is confirmed to maintain its shape and fracture strength compared to the pattern before the coating layer was formed. In this step, it is confirmed whether the transfer micropattern is not damaged before and after the coating layer is peeled off (before and after the formation of the peeled coating layer) and can be reused without any problems. Specifically, the shape and fracture strength before and after the coating layer is peeled off (before and after the formation of the peeled coating layer) can be confirmed using techniques such as time-of-flight secondary ion mass spectrometry and nanoindentation testing.

[0067] Time-of-flight secondary ion mass spectrometry is a method for identifying elements by irradiating the surface of a substrate with ions to generate secondary ions of the substrate, and measuring the mass of the substance present on the substrate surface from the flight time corresponding to the mass. The surface condition of the substrate can be analyzed from the detection results of the secondary ions. Furthermore, the breaking strength (Young's modulus) can be determined by nanoindentation testing. In the present invention, one of these techniques can be used alone or two or more can be used in combination, but in the present invention, it is preferable to use the nanoindentation test method.

[0068] In the present invention, the shape and strength of the transfer micropattern before the formation of the coating layer are maintained means that the breaking strength (Young's modulus) of the micropattern portion after peeling and cleaning, as measured by the nanoindentation test method, is preferably 65 GPa or more, more preferably 70 GPa or more, and the absolute value of the difference from the breaking strength (Young's modulus) of the micropattern portion before the formation of the peeled coating layer is preferably 6 GPa or less, more preferably 5 GPa or less. If the above conditions are met, it is believed that there will be no damage to the pattern, and by forming a new coating layer in the next step, a recycled imprint mold having the desired breaking strength (Young's modulus) can be obtained.

[0069] (24) 24th process In step 24, a new coating layer is formed on at least a portion of the transfer micropattern whose shape and breaking strength have been confirmed, using the same material as the peeled coating layer or a different material. In this step, a new coating layer is formed using a method similar to the method for forming the coating layer described above. The same material as described above can also be used for the coating layer.

[0070] The preferred ranges for the thickness, thickness variation, Mohs hardness, breaking strength (Young's modulus), and percentage improvement in breaking strength (Young's modulus) compared to before coating for the new coating layer are all the same as those described for the coating layer before regeneration. The number of times of regeneration is not particularly limited, and as long as the shape and breaking strength of the pattern after peeling off the coating layer are within the above-mentioned ranges, it can be regenerated any number of times, but preferably two or more times, more preferably three or more times.

[0071] The imprint mold thus recycled can be used in the same way as the imprint mold before recycling. [Example]

[0072] The present invention will be explained in more detail below with reference to examples and experimental examples, but the present invention is not limited to the following examples.

[0073] [Example 1] Preparation of imprint mold [Fabrication of synthetic quartz glass molds for organic film deposition using electron beam lithography] First, an imprint mold for use in nanoimprint lithography of organic films was prepared. A 10-nm-thick CrN layer was formed by sputtering on a 20 mm × 20 mm, 0.525 mm-thick square synthetic quartz glass substrate. A positive electron beam resist (ZEP520A, manufactured by Zeon Corporation) was then spin-coated onto the CrN layer and prebaked at 180°C for 10 minutes to form an 80-nm-thick positive electron beam resist layer. A conductive polymer charge-up inhibitor (Espacer 300Z, manufactured by Showa Denko K.K.) was then spin-coated to form a 10-nm-thick antistatic layer.

[0074] Next, a linear pattern with a line width of 100 nm and a space width of 100 nm was electron-beam lithography using an electron beam lithography system (ELS-G125S, manufactured by Elionix Co., Ltd.) to form a latent image. The antistatic layer was removed by rinsing with ultrapure water, and the CrN layer was developed by immersion in a developer (ZED-N50, manufactured by Zeon Corporation) and then a rinse solution (ZMD-B, manufactured by Zeon Corporation) and drying. A linear pattern with 100-nm space-width resist openings exposed to the electron beam and 100-nm line-width resist remaining areas not exposed to the electron beam was formed on the CrN layer.

[0075] Next, an argon ion beam milling system (20IBE-C, Hakuto Co., Ltd.) was used to selectively remove the exposed surface of the CrN layer in the resist openings corresponding to the space width, forming a CrN hard mask pattern corresponding to the line width. The surface of the synthetic quartz glass substrate not covered by the CrN mask pattern was then etched using octafluoropropane (CF) gas using a dry etching system (EIS-200ER, Elionix Co., Ltd.). The substrate was then immersed in a chrome etching solution (Hayashi Pure Chemical Industries, Ltd.) to remove the CrN hard mask pattern, resulting in a synthetic quartz glass imprint mold with a linear pattern of 100 nm line width and 100 nm space width. A release agent, FAS13 ((tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane), was vapor-deposited onto the resulting imprint mold.

[0076] [Fabrication of nanoline structures (micropatterns for transfer) in synthetic quartz glass using nanoimprint lithography] Next, a 10-nm-thick CrN film (inorganic film) was formed on a circular synthetic quartz glass substrate with a diameter of 100 mm and a thickness of 0.525 mm by sputtering. After that, a photo-curable resist was applied to the CrN film to form an 80-nm-thick resist film (organic film). Next, a nanoimprinting device (ImpFlex Essential, manufactured by Sanmei Co., Ltd.) was used to press a release-treated imprint mold against the CrN film to form a resist film, which was then cured to form a resist film pattern (organic film pattern) with a line width of 100 nm and a space width of 100 nm on the CrN film. An oxygen reactive etching device (IM-TU01, manufactured by Tohoku University) was then used to remove the resist film remaining in the space width areas other than the 100 nm line width resist film pattern areas, exposing the surface of the CrN film in areas where the linear resist film pattern was not formed.

[0077] Next, an argon ion beam milling system (20IBE-C, Hakuto Co., Ltd.) was used to selectively remove the CrN film from the exposed surface where the linear resist film pattern was not formed, forming a CrN hard mask pattern (inorganic film pattern). The surface of the synthetic quartz glass substrate not covered by the CrN mask pattern was then etched using a dry etching system (EIS-200ER, Elionix Co., Ltd.) with octafluoropropane (CF) gas. The synthetic quartz glass substrate was then immersed in a chrome etching solution (Hayashi Pure Chemical Industries, Ltd.) to remove the CrN mask pattern along with the resist film pattern, yielding a synthetic quartz glass substrate with a nanoline structure (transfer micropattern) formed on its surface, which had a linear pattern with a line width of 100 nm and a space width of 100 nm. The shape and breaking strength of the patterned portion were measured by the following methods.

[0078] [Alumina coating by atomic layer deposition (ALD)] The surface of the resulting synthetic quartz glass nanoline structure (micropattern for transfer) was coated with alumina using ALD. The synthetic quartz glass substrate was placed on a heated platform in a vacuum chamber so that the surface temperature was 140°C. A total of 20 ALD cycles were performed, each consisting of 0.1 s of exposure to the inorganic precursor trimethylaluminum, 600 s of nitrogen purging and evacuation, 0.1 s of exposure to the oxidizing agent water, and 600 s of nitrogen purging and evacuation. The breaking strength of the patterned portion after coating was measured by the following method.

[0079] [Alumina removal by wet etching] The alumina coating layer formed by ALD was removed by wet etching. The substrate was immersed in a mixed acid aluminum etching solution (Kanto Chemical Co., Inc.) at a liquid temperature of 30°C for 3 minutes, washed with ultrapure water, and dried. The shape and breaking strength of the patterned portion after drying were measured by the following methods.

[0080] [Example 2] Preparation of recycled imprint mold 1 [Alumina coating by ALD] The surface of the nanoline structure (fine pattern for transfer) made of synthetic quartz glass from which the coating layer was removed in Example 1 was coated with alumina by ALD in the same manner as in Example 1. The breaking strength of the patterned portion after coating was measured in the same manner as in Example 1.

[0081] [Alumina removal by wet etching] The coating layer was removed in the same manner as in Example 1, and the substrate was dried. After drying, the shape and breaking strength of the patterned portion were measured in the same manner as in Example 1.

[0082] [Example 3] Preparation of recycled imprint mold 2 [Alumina coating by ALD] The surface of the nanoline structure (fine pattern for transfer) made of synthetic quartz glass from which the coating layer was removed in Example 2 was coated with alumina by ALD in the same manner as in Example 1. The breaking strength of the patterned portion after coating was measured in the same manner as in Example 1.

[0083] [Alumina removal by wet etching] The coating layer was removed in the same manner as in Example 1, and the substrate was dried. After drying, the shape and breaking strength of the patterned portion were measured in the same manner as in Example 1.

[0084] (Strength evaluation by nanoindentation test) Using a nanoindentation tester (ENT-2100, Elionix Co., Ltd.) equipped with a diamond spherical indenter (200 μm radius of curvature, Elionix Co., Ltd.), a diamond spherical indenter (rigid body) was brought into contact with and pressed into the area of ​​the synthetic quartz glass where the nanoline structures (micropatterns for transfer) were formed, thereby pressing a portion of the nanoline structures (micropatterns for transfer) in the height direction to plastically deform them. Specifically, pressing was performed 100 times consecutively at the same position with a pressing speed of 5 mN / s and a load of 10 mN.

[0085] (Strength test results by nanoindentation test before and after coating in Example 1) The Young's modulus of the line pattern portion of the synthetic quartz glass before coating was 77.0 GPa. The Young's modulus of the line pattern portion of the alumina-coated synthetic quartz glass that had been subjected to atomic layer deposition was 83.5 GPa, demonstrating the improvement in mechanical strength due to the deposition of alumina. The Young's modulus of the line pattern portion after alumina removal was 75.8 GPa, and a change in Young's modulus before and after alumina coating was confirmed. These results are shown in Table 1.

[0086] (Results of strength test and pattern shape confirmation for repeated reproduction by nanoindentation test in Examples 1 to 3) The Young's modulus of the line pattern was determined by repeating the deposition and removal of alumina. The results are shown in Table 1. It was confirmed that the mechanical strength was improved by the deposition of alumina by ALD. In Example 1, a decrease in Young's modulus was observed after alumina removal (first alumina removal) compared to the Young's modulus before alumina deposition (ALD-untreated substrate). However, in Example 2, the Young's modulus was confirmed to be restored after repeated alumina coating (second ALD). In Example 2, a decrease in Young's modulus was observed after alumina removal (second alumina removal) compared to the Young's modulus after the first alumina stripping (first alumina removal). However, in Example 3, the Young's modulus was confirmed to be reproduced after repeated alumina coating (third ALD). From these results, it was confirmed that the pattern shape before the peeled coating layer was formed was maintained in all cases.

[0087] [Table 1]

[0088] [Experimental Example 1] (Fabrication of Micropatterns and Results) In the same manner as in Example 1, a synthetic quartz glass substrate was obtained on the surface of which a nanoline structure (fine pattern for transfer) having a linear pattern with a line width of 100 nm and a space width of 100 nm was formed. An atomic force microscope image of the resulting line pattern is shown in Figure 1. It was confirmed that a fine pattern with a line width of 100 nm and a height of 115 nm had been formed.

[0089] [Experimental Example 2] (Measurement and results of thickness of alumina coating layer) Alumina was coated on a synthetic quartz glass substrate without a pattern using the same procedure and conditions as in Example 1 [Coating of alumina by atomic layer deposition (ALD)], and the film thickness was measured using a stylus-type microprofile measuring instrument (ET4000, manufactured by Kosaka Laboratory Co., Ltd.). Measurements were performed with a measuring force of 5 μN and a speed of 20 μm / s. The alumina film thickness was approximately 3 nm.

Claims

1. a synthetic quartz glass substrate having a fine transfer pattern formed on its surface; a coating layer formed on at least a portion of the fine pattern from at least one material different from the substrate; An imprint mold having: The material different from the substrate is Al 2 O 3 , ZrO 2 , HfO 2 , TiN, TaN and WN; The thickness of the coating layer is 3 nm or less, and An imprint mold in which the breaking strength of a portion of a transfer fine pattern on which a coating layer is formed is higher than the breaking strength of the transfer fine pattern before the coating layer is formed.

2. The material different from the substrate is Al 2 O 3 2. The imprint mold according to claim 1, wherein

3. 3. The imprint mold according to claim 1, wherein the variation in thickness of the coating layer is within 10% of the average thickness of the coating layer.

4. The imprint mold according to any one of claims 1 to 3, wherein the breaking strength of the portion of the transfer micropattern on which the coating layer is formed is 1.05 times or more the breaking strength of the transfer micropattern before the coating layer is formed.

5. 5. A method for producing an imprint mold according to any one of claims 1 to 4, wherein at least a portion of a fine pattern for transfer formed on the surface of a synthetic quartz glass substrate is alternately exposed to at least two reactive precursors, which are raw materials for a material different from the substrate, by sequential chemical vapor deposition, and these precursors are reacted to form a coating layer made of a material different from the substrate.

6. The method for producing an imprint mold according to claim 5, wherein a heating step is carried out after the coating layer is formed.

7. The method for producing an imprint mold according to claim 6, wherein the heating temperature is 100 to 900°C.

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