Imprinting molds and their manufacturing methods, as well as methods for manufacturing recycled imprinting molds.

Abstract

[Problem] To provide an embossing mold that, in which synthetic quartz glass must be selected as the material and a fine pattern with high precision is required, can prevent damage caused by the fine pattern and form a coating layer on the pattern. Even if there are foreign objects or dirt in the pattern, the coating layer can be easily removed to form a new coating layer, thereby enabling regeneration. [Solution] An embossing mold comprising: a synthetic quartz glass substrate on which a transfer micro-pattern is formed for forming on the surface; and a coating layer formed of at least one of a material different from the substrate on at least a portion of the aforementioned micro-pattern.

Description

Technical Field

[0001] This invention relates to embossing molds and their manufacturing methods, as well as methods for manufacturing recycled embossing molds. Prior Technology

[0002] Imprinting, a technique that has emerged in recent years as an alternative to photolithography, is considered advantageous from the perspectives of faithfully transferring patterns into the shape of the mold and reducing equipment costs. Imprinting can be broadly categorized into two methods: thermal embossing and photolithography. Thermal embossing involves pressing a mold pattern onto the material to be imprinted, applying heat and pressure to transfer the pattern. Photolithography involves pressing a mold pattern onto a photocurable material and transferring the pattern using light irradiation.

[0003] While conventional hot embossing can be performed with relatively simple and inexpensive materials and equipment, it has limitations in pattern size and accuracy due to the high pressure applied and thermal expansion / contraction. In contrast, photolithography applies low pressure and allows for high-precision dimensional control during pattern transfer, and can be differentiated according to the application.

[0004] Besides the differences mentioned above, various materials such as resin, metal, glass, and ceramics are used in embossing molds from the perspective of the transfer accuracy and durability required by the target device. Furthermore, chemical treatments are performed as necessary to improve release properties.

[0005] Patent document 1 proposes an embossing mold with an embossed pattern formed from resin. The advantage of resin is that even embossing molds with complex embossed patterns can be easily manufactured. While embossing molds with resin-formed embossed patterns have issues with pattern breakage due to low chemical (solvent) resistance and strength, it has been reported that this problem can be solved by adjusting the resin's gel content or forming a coating layer on the embossed pattern.

[0006] Furthermore, Patent Document 2 proposes an imprinting mold made of a resin with excellent release properties, free from transfer defects. While this imprinting mold has an oxide layer and a release agent layer formed thereon on the surface of a resin-formed substrate, there is a problem that the oxide layer and the release agent layer can become integrated and migrate to the resin film being transferred. To solve this problem, Patent Document 2 reports on controlling the reactivity of the resin contained in the aforementioned imprinting mold. [Previous Technical Documents] [Patent Literature]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2020-170863 [Patent Document 2] International Publication No. 2012 / 018048 Summary of the Invention

[0008] [The problem the invention aims to solve]

[0009] Furthermore, in applications requiring high-precision micro-patterns, UV light is typically used as the light source for photoimaging, and synthetic quartz glass is chosen as the mold material. This is because molds made of synthetic quartz glass offer superior strength, hardness, and dimensional stability of the raised and recessed patterns compared to the resin molds described in Patent Documents 1 and 2. However, even molds made of synthetic quartz glass can suffer from defects due to pattern breakage as the embossed pattern becomes finer.

[0010] In view of the above circumstances, the inventors of this invention aim to provide an embossing mold that, in which synthetic quartz glass must be selected as the material and a fine pattern requiring high precision is required, can prevent damage caused by the fine pattern and form a coating layer on the pattern. Even if there are foreign objects or dirt in the pattern, the coating layer can be easily removed to form a new coating layer, thereby enabling regeneration. [Problem-solving methods]

[0011] In order to achieve the above-mentioned objective, the inventors have conducted a thorough investigation and discovered that by coating at least a portion of the portion of the transfer micro-pattern formed by the imprinting mold made of a synthetic quartz glass substrate with a film of a different material from the substrate, the strength of the mold pattern portion can be improved. Furthermore, it has been found that the coating film does not damage the mold pattern and can be easily removed, allowing for recoating, thus completing the present invention.

[0012] That is, the present invention provides the following embossing mold and its manufacturing method, as well as a method for manufacturing a recycled embossing mold. 1. An embossing mold comprising: a synthetic quartz glass substrate on which a transfer micro-pattern is formed for printing; At least a portion of the aforementioned micro-pattern is coated with at least one of a material different from the aforementioned substrate. 2. The embossing mold as described in 1, wherein the material different from the aforementioned substrate is a metal, an inorganic oxide, or an inorganic nitride. 3. The embossing mold as described in 1 or 2, wherein the thickness of the aforementioned coating layer is 50 nm or less, and the deviation of the aforementioned thickness is within 10% of the average thickness of the coating layer. 4. The embossing mold described in any one of 1 to 3, wherein the destructive strength of the portion of the micro-pattern for transfer forming the coating layer is higher than the destructive strength of the micro-pattern for transfer before the aforementioned coating layer is formed. 5. The embossing mold as described in 4, wherein the destructive strength of the portion of the micro-pattern for transfer forming the coating layer is at least 1.05 times the destructive strength of the micro-pattern for transfer before the formation of the aforementioned coating layer. 6. A method for manufacturing an embossing mold as described in any one of 1 to 5, wherein at least a portion of a transfer micro-pattern formed on the surface of a synthetic quartz glass substrate is subjected to reaction by sequential chemical vapor deposition of at least two reactive precursors of raw materials that are different from the substrate, thereby forming a coating layer from the material different from the substrate. 7. A method for manufacturing a recycled embossing mold, comprising: a process of peeling off a coating layer from an embossing mold having a synthetic quartz glass substrate having a transfer micro-pattern formed on its surface, and a coating layer formed on at least a portion of the micro-pattern using at least one of a material different from the substrate; The process of cleaning the transfer print with fine patterns after the coating has been peeled off; The process of maintaining the shape and destructive strength of the micro-pattern for transfer after cleaning, before the formation of the aforementioned coating layer; The process of forming a new coating layer on at least a portion of the confirmed transfer micro-pattern using atomic stacking, with the same or different material as the peeled coating layer. 8. The method for manufacturing a regenerated embossing mold as described in 7, wherein the aforementioned confirmation process is achieved by time-of-flight secondary ion mass analysis or nano-indentation testing. [The effects of the invention]

[0013] The embossing mold of the present invention can avoid or reduce damage to the pattern during the embossing process, especially damage to fine patterns caused by the incorporation of foreign matter. Furthermore, the coating layer formed on the pattern can be easily removed, and a new coating layer can be regenerated. Simple Explanation of the Diagram

[0014] [Figure 1] An atomic force microscope image of the line pattern obtained in Experiment Example 1. Implementation

[0015] The present invention will now be described in more detail. The embossing mold of the present invention has a synthetic quartz glass substrate on which a transfer micro-pattern is formed, and a coating layer formed on at least a portion of the aforementioned micro-pattern with at least one of a material different from the synthetic quartz glass substrate.

[0016] [Embossing Die] As the synthetic quartz glass substrate used in this invention, it is possible to use a synthetic quartz glass ingot made by reacting silica raw material compounds such as silane compounds and siloxane compounds with an oxyhydrogen flame to form a desired shape, anneal it, slice it to a desired thickness, and then obtain it by encapsulation, and as necessary, perform peripheral grinding, coarse grinding, and fine grinding.

[0017] While there are no particular restrictions on the shape of the synthetic quartz glass substrate, from the perspective of ease of manufacturing, it can be made into rectangular or other square shapes, round shapes, etc. For example, square-shaped substrates are suitable for substrates with a side length of 10 to 300 mm, and round glass substrates are suitable for substrates with a diameter of 10 to 300 mm. The thickness of the synthetic quartz glass substrate can be appropriately selected without particular limitations; from the viewpoint of transmittance, a thinner substrate is preferable. However, from the viewpoints of strength, self-weight deformation, and handling, a certain thickness is necessary, preferably 10 μm or more, further preferably 50 μm or more, and even more preferably 100 μm or more. Moreover, preferably 300 mm or less, further preferably 100 mm or less, and even more preferably 30 mm or less.

[0018] In this invention, the micro-patterns include not only line patterns and nano-pillar patterns, but also 3D patterns. While there are no particular limitations on size and shape, line patterns can include simple straight lines, angled bends, R-shaped curves, bifurcated shapes, cross shapes, etc. Nano-pillar patterns can include angular prism shapes, cylindrical shapes, elliptical prism shapes, angled hammer trapezoid shapes, conical trapezoid shapes, elliptical hammer trapezoid shapes, inverted angled hammer trapezoid shapes, inverted conical trapezoid shapes, and inverted elliptical hammer trapezoid shapes. Furthermore, 3D patterns can include stepped shapes, sloped shapes, and shapes with a portion of a sphere. A micro-pattern can be a single type of shape or a combination of multiple types of shapes.

[0019] The destructive strength of the substrate forming the micro-pattern for transfer is preferably 70 GPa or higher, and more preferably 75 GPa or higher, considering the formation, removal, and regeneration of the coating layer (described later). Furthermore, in this invention, the destructive strength can be obtained using a nano-indentation test. The nano-indentation test measures the hardness and Young's coefficient of the substrate based on the indentation force and depth when a hard indenter is pressed onto the substrate. Generally speaking, the higher the Young's coefficient, the higher the destructive strength.

[0020] In the embossing mold of the present invention, at least a portion of the aforementioned micro-pattern for transfer is provided with a coating layer formed of at least one material different from the synthetic quartz glass substrate. By providing this coating layer on the micro-pattern for transfer, the micro-pattern for transfer formed of synthetic quartz glass can be protected from contamination and deterioration, and the aforementioned materials are suitable for this purpose. In particular, from the viewpoint of coating thickness accuracy, strength, etc., metals, inorganic oxides, or inorganic nitrides are preferred. As metals, there are metallic monomers such as Cr, Cu, Mo, and Ni, as well as alloys containing these. As inorganic oxides, there are Al₂O₃, ZrO₂, and HfO₂. As inorganic nitrides, there are TiN, TaN, and WN. Among these, alumina (Al₂O₃) is suitable from the perspectives of coating performance, coating stability, and versatility.

[0021] The thickness of the coating layer is not particularly limited, but it is preferably below 50 nm, more preferably below 10 nm. The lower limit is not particularly limited, but it is preferably above 0.1 nm, more preferably above 1 nm. A thickness within the above range is preferable not only in terms of the strength deviation of the coating layer pattern, but also from the viewpoint of the reliability of the micro-pattern dimensions. Furthermore, the thickness deviation (maximum thickness - minimum thickness) is preferably within 10% of the average thickness of the coating. Because the thickness deviation is within this range, good results can be obtained in terms of strength stability and reproducibility.

[0022] From the perspective of protecting and strengthening the micro-patterns of synthetic quartz glass, a higher hardness of the aforementioned coating is preferable. Specifically, for example, a Mohs hardness of 6 or higher is preferred.

[0023] Furthermore, by providing the aforementioned coating layer, the destructive strength of the portion forming the micro-pattern for transfer can be significantly improved. For example, if the destructive strength of the micro-pattern for transfer before the coating layer is provided is 73 GPa, the destructive strength of the micro-pattern for transfer with the coating layer is preferably 77 GPa or higher, and more preferably 80 GPa or higher. By providing the coating layer, compared to before the coating layer is provided, the destructive strength of the micro-pattern for transfer is preferably increased by 1.05 times or more, and more preferably by 1.1 times or more. This is effective not only in preventing pattern damage caused by hard foreign objects, but also in suppressing pattern deformation during imprinting.

[0024] In this invention, the coating layer is formed in such a way that it covers at least a portion of the micro-pattern for transfer, but from the point of strength enhancement, it is preferable to form it in such a way that it covers the entire micro-pattern, or in such a way that it covers the entire surface on which the micro-pattern is formed.

[0025] The embossing mold of the present invention, which has a transfer micro-pattern with such a coating layer, can avoid or reduce damage to the micro-pattern, especially damage to the micro-pattern caused by foreign matter contamination. Compared with previous embossing molds, it can achieve high precision and long service life in each section. Even if the fine pattern of the coating layer described above is soiled for any reason, the embossing mold of the present invention can be easily regenerated by the method described later, and in this respect, a long service life can be expected.

[0026] [Manufacturing method of embossing mold] [1] Methods for forming fine patterns In the imprinting mold of the present invention, the fine patterns formed on the surface of the synthetic quartz glass substrate can be manufactured, for example, by photolithography, photolithography, nanoimprint photolithography, or other photolithography methods.

[0027] Specifically, for example, it can be manufactured by a method that includes the following process. (1) Process of forming an inorganic film on the surface of a synthetic quartz glass substrate with fine patterns (First Process) (2) Engineering for forming organic membranes on inorganic membranes (Project 2) (3) The process of patterning organic films to form organic film patterns on inorganic films (Project 3) (4) The process of using the pattern of the organic film as an etching mask to etch the inorganic film to form an inorganic film pattern (Project 4) (5) A process of etching the surface of a synthetic quartz glass substrate to form a fine pattern by using organic film patterns and inorganic film patterns, or inorganic film patterns, as an etching mask (process 5). (6) The process of removing organic film patterns and inorganic film patterns, or inorganic film patterns (Process 6)

[0028] (1) Project 1 In the first process, an inorganic film is typically formed over the entire surface of the surface where the fine pattern of the synthetic quartz glass substrate is formed. Inorganic films include metal films, or films of metal compounds such as metal nitrides, metal oxides, metal carbides, metal oxide nitrides, metal carbides, metal oxide carbides, and metal oxide carbides. Metal films can be monomeric films or alloy films. Furthermore, metal compound films can contain only one type of metal or a combination of two or more types. Specific 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 easy etching in the etching of inorganic films in Project 4, Cr films, Si films, Cr compound films, and Si compound films are preferred. Cr compounds specifically include CrN, CrO, CrNO, and CrNOC (these equations represent the constituent elements of the compound, and the proportions of each element are arbitrary). Si compounds specifically include SiN (these equations represent the constituent elements of the compound, and the proportions of each element are arbitrary). From the perspective of preventing the reverse of micro-refinement caused by the increase in pattern width and obtaining sufficient strength enhancement, the thickness of inorganic films is preferably below 200 nm, more preferably below 50 nm, and even more preferably above 2 nm.

[0029] Inorganic films can be formed by sputtering. Specifically, metal targets or metal compound targets are used as the target material, and rare gases such as argon are used as the sputtering gas, along with reactive gases such as oxygen-containing gases, nitrogen-containing gases, and carbon-containing gases as needed. The inorganic film is formed on a synthetic quartz glass substrate using a sputtering apparatus. While the power supply can be either direct current or alternating current, using a direct current power supply is preferable due to the availability of effective methods to suppress arc generation.

[0030] (2) Project 2 In the second process, an organic membrane is formed on top of the inorganic membrane. In the second process, the organic membrane is formed on part or all of the surface of the inorganic membrane. As a material for organic films, photoresist is suitable for sensing desired activation energy lines from electron beams, X-rays, ultraviolet light, excimer lasers (ArF, KrF, etc.), and high-pressure mercury lamps (i-line, g-line, etc.). Both positive and negative photoresist materials can be used, but from the perspective of precision and environmental considerations, positive photoresist is preferable. The thickness of the organic film can be selected in the range of 10 nm to tens of μm, but from the point of view of resolution, a thin film is better, while from the point of view of etching resistance, a thick film is better. When considering both factors, in the case of wet etching of the surface of the synthetic quartz glass substrate in Project 5, the thickness is preferably about 0.5 to 5 μm, and in the case of dry etching, the thickness is preferably about 10 to 500 nm.

[0031] Organic films can be formed using methods such as spin coating, spray coating, slot coating, and stencil printing. However, spin coating is more suitable for achieving a more uniform coating. In spin coating, the maximum rotation speed is 2000~4000 rpm, followed by baking (pre-baking). The pre-baking temperature varies depending on the type of organic film material, but is generally best performed at approximately 80~120℃.

[0032] (3) Project 3 In the third process, the organic film is patterned to form an organic film pattern on the inorganic film. Methods for forming organic film patterns include electron beam etching or photolithography, and nanoimprint etching.

[0033] In the electron beam etching method, an organic film formed on an inorganic film is drawn using an electron beam drawing device, and the pattern drawn on the organic film is visualized to form an organic film pattern.

[0034] Furthermore, in the photolithography method, an organic film formed on an inorganic film is exposed using a photomask with predetermined light-shielding and non-light-shielding portions, and the pattern transferred on the organic film is developed, thus forming an organic film pattern. The developing liquid can be selected according to the type of photoresist material. For example, alkaline aqueous solutions such as tetramethylammonium hydroxide (TMAH) and xylene-based organic solvents can be used as developing liquids. After development, a rinsing process with pure water or similar methods is performed to remove residual developer and components derived from photoresist dissolved in the developer. The film is then dried, allowing an organic film pattern to form on the inorganic film. After drying, post-baking can be performed to strengthen the organic film. Post-baking is preferably performed at a temperature and / or time when the organic film is not photosensitive, preferably at a higher temperature than the pre-baking temperature before exposure (e.g., above 130°C).

[0035] In the method of nanoimprint photolithography, an organic film is pressed against the concave and convex structure of an imprinting mold having a predetermined concave and convex pattern. The concave part of the mold is filled with photoresist material, and the top surface of the photoresist material is shaped in such a way that it becomes a concave and convex pattern. The organic film is then hardened in this state, and the imprinting mold is then separated from the hardened organic film to form an organic film pattern.

[0036] When pressing an organic film against the uneven surface of an imprinting mold, it is preferable to do so in a helium atmosphere or an atmosphere of a readily condensable gas. An atmosphere of readily condensable gas is one in which a gas that easily liquefies when pressed is used to seal the mold gaps; in such an atmosphere, it is difficult for bubble defects to form. Specific examples of such gases include 1,1,1,3,3-pentafluoropropane (PFP, HFC-245fa) or trans-1,3,3,3-tetrafluoropropylene (TFP). When bubbles are generated between the surface of the uneven surface of the imprinting mold and the photoresist material, pattern defects may occur in the organic film pattern. However, in a helium atmosphere or an atmosphere of readily condensable gas, the helium or readily condensable gas that forms the bubbles dissolves into the photoresist material, preventing the formation of pattern defects. As a method for curing organic films, a method can be adopted that corresponds to the curing state of the material constituting the organic film. For example, if the organic film material is in an ultraviolet curing state, a method of irradiating the organic film with ultraviolet light through an imprinting mold can be used.

[0037] After separating the imprinting die from the hardened organic film, at the contact point between the organic film and the protrusion of the imprinting die, the organic film typically leaves a residue of a corresponding thickness (e.g., 1 nm or more, especially 5 nm or more and 20 nm or less, especially 10 nm or less). It is preferable to remove this residue before etching the synthetic quartz glass substrate. While there are no particular limitations on the method for removing the residue, methods such as ashing treatment caused by oxygen plasma, UV ozone treatment caused by ultraviolet light, and VUV treatment caused by vacuum ultraviolet light are also possible.

[0038] (4) Project 4 In the fourth process, the portion of the inorganic film exposed by removing the organic film is selectively removed to form an inorganic film pattern (hard mask pattern). Selective removal of the inorganic film is suitable for etching. Etching can be either a wet or dry process, but in the case of a wet process, an etching solution appropriate to the type of inorganic film is used. Specifically, as a wet process, for example, when the inorganic film is Cr or a Cr compound, wet etching using a Cr etching solution (aqueous solution of cerium diammonium nitrate) is employed. While the concentration of the Cr etching solution is not particularly limited, it is preferably 5-20% by mass. On the other hand, dry processes are suitable for anisotropic etching. Specific examples of dry processes include, for instance, dry etching caused by reactive gases such as argon ion polishing, CF4, C3F6, C3F8, C4F8, C5F8, and CHF3. After the inorganic membrane is selectively removed, an organic membrane pattern usually remains on top of the inorganic membrane pattern. However, the fifth process can be carried out while the organic membrane pattern remains on top of the inorganic membrane pattern, or the fifth process can be carried out after the organic membrane pattern has been removed from the inorganic membrane pattern.

[0039] (5) Project 5 In the fifth process, if the inorganic film is selectively removed in the fourth process, leaving an organic film pattern, the organic film pattern and the inorganic film pattern (hard mask pattern) are used as an etching mask. If the organic film pattern is removed, the inorganic film pattern (hard mask pattern) is used as an etching mask to etch the surface of the synthetic quartz glass substrate, forming a fine pattern. In this etching process, the exposed portion of the surface of the synthetic quartz glass substrate that is not covered by the organic and inorganic film patterns, or the inorganic film pattern, is etched (digging in), while the portion covered by the pattern is not etched and remains, forming a fine pattern.

[0040] There are no particular limitations on the method for etching synthetic quartz glass substrates, but there are, for example, wet etching by immersing in an etching aqueous solution containing hydrofluoric acid and sodium fluoride, and dry etching by reactive gases such as CF4, C3F6, C3F8, C4F8, C5F8, and CHF3.

[0041] (6) Project 6 In the sixth process, after the inorganic film is selectively removed in the fourth process, if there is a residual organic film pattern, both the organic and inorganic film patterns are removed. If the organic film pattern is removed, the inorganic film pattern is also removed. The organic film pattern can be removed simultaneously with the inorganic film pattern, and the inorganic film pattern can be removed by etching. Etching can be either a wet or dry process, but in the case of a wet process, an etching solution appropriate to the type of inorganic film is used. Specifically, as a wet process, for example, when the inorganic film is Cr or a Cr compound, wet etching using a Cr etching solution (aqueous solution of cerium diammonium nitrate) is employed. While the concentration of the Cr etching solution is not particularly limited, it is preferably 5-20% by mass. On the other hand, dry processes are suitable for anisotropic etching. Specific examples of dry processes include, for instance, argon ion polishing, and dry etching caused by reactive gases such as CF4, C3F6, C3F8, C4F8, C5F8, and CHF3.

[0042] Up to this point, although the method for fabricating fine patterns has been described using the method of first forming an inorganic film and then forming an organic film on a synthetic quartz glass substrate as an example, it is not limited to this isomorphic sample. Micro-patterns, for example, can also be manufactured by first forming an organic film on a synthetic quartz glass substrate, then patterning the organic film to form an organic film pattern, and finally forming an inorganic film using a so-called extraction method.

[0043] Specifically, for example, it can be manufactured by a method that includes the following process. (11) A process for forming an organic film on the surface of a synthetic quartz glass substrate with fine patterns (Project 11) (12) The process of patterning an organic film on the surface of a synthetic quartz glass substrate to form a micro-pattern (Project 12) (13) A process for forming an inorganic film on an organic film pattern and the exposed surface of a synthetic quartz glass substrate (Project 13) (14) A process for removing the organic film pattern along with the inorganic film formed on the organic film pattern (Project 14) (15) A process of etching the surface of a synthetic quartz glass substrate to form a fine pattern by using an inorganic film pattern drawn on an inorganic film formed on the surface of the substrate as an etching mask (process 15). (16) In the process of removing inorganic film patterns (Project 16)

[0044] (11) Project 11 In Project 11, an organic film is formed on part or all of the surface on which the fine pattern of the synthetic quartz glass substrate is formed. As a material for organic films, photoresist is suitable for sensing desired activation energy lines from electron beams, X-rays, ultraviolet light, excimer lasers (ArF, KrF, etc.), and high-pressure mercury lamps (i-line, g-line, etc.). Both positive and negative photoresist materials can be used, but from the perspective of precision and environmental considerations, positive photoresist is preferable. The thickness of the organic membrane can be selected in the range of 10 nm to several tens of μm, but from the point of view of resolution, a thinner membrane is better. From the point of view of removing the organic membrane pattern together with the inorganic membrane in Project 14, a membrane that is sufficiently thick (e.g., more than twice as thick as the inorganic membrane) is better than the inorganic membrane described later.

[0045] Organic films can be formed using methods such as spin coating, spray coating, slot coating, and stencil printing. However, spin coating is more suitable for achieving a more uniform coating. Spin coating is performed at a maximum speed of 2000-4000 rpm, followed by baking (pre-baking). The pre-baking temperature varies depending on the type of organic film material, but is generally best performed at approximately 80-120°C.

[0046] (12) Project 12 In Project 12, an organic film is patterned, forming an organic film pattern on the surface on which a fine pattern is formed on a synthetic quartz glass substrate. Methods for forming organic film patterns include electron beam etching or photolithography, and nanoimprint etching.

[0047] In the electron beam etching method, an organic film formed on an inorganic film is drawn using an electron beam drawing device, and the pattern drawn on the organic film is visualized, thereby forming an organic film pattern.

[0048] Furthermore, in the photolithography method, an organic film formed on a synthetic quartz glass substrate is exposed using a photomask with predetermined light-shielding and non-light-shielding portions, and the pattern transferred from the organic film is developed, thus forming an organic film pattern. The developing liquid can be selected according to the type of photoresist material. For example, alkaline aqueous solutions such as tetramethylammonium hydroxide (TMAH) and xylene-based organic solvents can be used as developing liquids. After development, a rinsing process with pure water or similar methods is performed to remove residual developer and components derived from photoresist dissolved in the developer. The substrate is then dried, allowing an organic film pattern to form on the synthetic quartz glass substrate. After drying, post-baking can be performed to strengthen the organic film. Post-baking, since it is performed at a temperature and / or time when the organic film is not photosensitive, is preferably performed at a higher temperature than the pre-baking temperature before exposure (e.g., above 130°C).

[0049] In the method of nanoimprint photolithography, an organic film is pressed against the concave and convex structure of an imprinting mold having a predetermined concave and convex pattern. The concave part of the mold is filled with photoresist material, and the top surface of the photoresist material is shaped in such a way that it becomes a concave and convex pattern. The organic film is then hardened in this state, and the imprinting mold is then separated from the hardened organic film to form an organic film pattern.

[0050] When pressing an organic film against the uneven surface of an imprinting mold, it is preferable to do so in a helium atmosphere or an atmosphere of a readily condensable gas. An atmosphere of readily condensable gas is one in which the gas is easily liquefied by pressing when it is sealed into the mold cavity; in this atmosphere, it is difficult for bubble defects to form. Specific examples of such gases include 1,1,1,3,3-pentafluoropropane (PFP, HFC-245fa) or trans-1,3,3,3-tetrafluoropropylene (TFP). When bubbles form between the surface of the uneven surface of the imprinting mold and the photoresist material, pattern defects may occur in the organic film pattern. However, in a helium atmosphere or an atmosphere of readily condensable gas, the helium or readily condensable gas that forms the bubbles dissolves into the photoresist material, preventing the formation of pattern defects. As a method for curing organic films, a method can be adopted that corresponds to the curing state of the material constituting the organic film. For example, if the organic film material is in an ultraviolet curing state, a method of irradiating the organic film with ultraviolet light through an imprinting mold can be used.

[0051] After separating the imprinting die from the hardened organic film, at the contact point between the organic film and the protrusion of the imprinting die, the organic film typically leaves a residue of a corresponding thickness (e.g., 1 nm or more, especially 5 nm or more and 20 nm or less, especially 10 nm or less). It is preferable to remove this residue before etching the synthetic quartz glass substrate. While there are no particular limitations on the method for removing the residue, methods such as ashing treatment caused by oxygen plasma, UV ozone treatment caused by ultraviolet light, and VUV treatment caused by vacuum ultraviolet light are also possible.

[0052] (13) Project 13 In Project 13, an inorganic film is typically formed over the entire organic film pattern and the exposed surface of the synthetic quartz glass substrate. Inorganic films include metal films, or films of metal compounds such as metal nitrides, metal oxides, metal carbides, metal oxide nitrides, metal carbides, metal oxide carbides, and metal oxide carbides. Metal films can be monomeric films or alloy films. Furthermore, metal compound films can contain only one type of metal or a combination of two or more types. Specific 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 easy etching in the etching of the inorganic film of Project 14, Cr film, Si film, Cr compound film, and Si compound film are preferred. Cr compounds specifically include CrN, CrO, CrNO, and CrNOC (these equations represent the constituent elements of the compound, and the proportions of each element are arbitrary). Si compounds specifically include SiN (these equations represent the constituent elements of the compound, and the proportions of each element are arbitrary). The thickness of the inorganic membrane is preferably below 200 nm, more preferably below 50 nm, and even more preferably above 10 nm.

[0053] Inorganic films can be formed by sputtering. Specifically, metal targets or metal compound targets are used as the target material, and rare gases such as argon are used as the sputtering gas, along with reactive gases such as oxygen-containing gases, nitrogen-containing gases, and carbon-containing gases as needed. The inorganic film is formed on a synthetic quartz glass substrate using a sputtering apparatus. While the power supply can be either direct current or alternating current, using a direct current power supply is preferable due to the availability of effective methods to suppress arc generation.

[0054] (14) Project 14 In the 14th process, the organic film pattern is removed along with the inorganic film formed on top of the organic film pattern. However, 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 has not formed. In the inorganic film, only the inorganic film formed on top of the organic film pattern is removed. In this case, the organic film pattern can be removed by alkaline aqueous solutions such as tetramethylammonium hydroxide (TMAH) or xylene-based organic solvents.

[0055] (15) Project 15 In Project 15, an inorganic film pattern (hard mask pattern) drawn on an inorganic film formed on the surface of a synthetic quartz glass substrate is used as an etching mask to etch the surface portion of the synthetic quartz glass substrate, forming a fine pattern. In this etching process, the exposed portion of the surface of the synthetic quartz glass substrate not covered by the inorganic film pattern is etched (digging in), while the portion covered by the pattern is not etched and remains, forming a fine pattern.

[0056] There are no particular limitations on the method for etching synthetic quartz glass substrates, but there are, for example, wet etching by immersing in an etching aqueous solution containing hydrofluoric acid and sodium fluoride, and dry etching by reactive gases such as CF4, C3F6, C3F8, C4F8, C5F8, and CHF3.

[0057] (16) Project 16 In step 16, the inorganic film pattern is removed. The inorganic film pattern can be removed by etching. Etching can be either a wet or dry process, but in the case of a wet process, an etching solution appropriate to the type of inorganic film is used. Specifically, as a wet process, for example, when the inorganic film is Cr or a Cr compound, wet etching using a Cr etching solution (aqueous solution of cerium diammonium nitrate) is employed. While the concentration of the Cr etching solution is not particularly limited, it is preferably 5-20% by mass. On the other hand, dry processes are suitable for anisotropic etching. Specific examples of dry processes include, for instance, dry etching caused by reactive gases such as argon ion polishing, CF4, C3F6, C3F8, C4F8, C5F8, and CHF3.

[0058] [2] Methods for forming the coating layer Next, a method for forming a coating layer on a micro-pattern as described above will be explained. In this invention, a coating layer is formed on at least a portion of the aforementioned micro-pattern using at least one material different from the synthetic quartz glass substrate. Methods for forming coatings on fine patterns include sequential chemical vapor deposition, CVD, sputtering, and evaporation. However, in order to set a uniform coating on the outer periphery of the fine pattern, sequential chemical vapor deposition is preferred. One method that can be applied to sequential chemical vapor deposition is atomic deposition.

[0059] Successive chemical vapor deposition (CVD) is generally a deposition method for inorganic layers. It involves exposing a substrate to at least one, preferably at least two, reactive precursors that form the inorganic layer, allowing the precursors to react with the substrate surface or on the substrate to form the inorganic layer. Examples of inorganic layers formed include inorganic oxide films such as Al₂O₃, ZrO₂, and HfO₂, and inorganic nitride layers such as TiN, TaN, and WN. Among these, alumina (Al₂O₃) films are widely used. Of the various methods proposed for depositing this coating, the most common is the reaction of trimethylaluminum (TMA) with water.

[0060] In this method, a coating layer can be grown on a substrate at temperatures ranging from room temperature to above 300°C, through the following mechanism: Specifically, TMA and water are supplied alternately. During the supply of TMA, the TMA dissociates and adsorbs AlCH3 on the substrate surface. The remaining TMA is discharged without adsorption, forming a 1-atom layer of AlCH3 on the substrate surface. Here, water is supplied, and the water reacts with the CH3 groups on the surface to produce CH4 byproducts, leaving hydroxylated Al2O3 on the surface. This cycle is repeated to form an Al2O3 layer of the desired thickness on the substrate surface. For example, in the case of Al2O3, repeating 20 cycles forms a coating layer of approximately 3 nm.

[0061] After the coating is formed, unreacted substances and moisture are removed. A heating process can also be performed to stabilize the coating. Although there is no particular limitation on the heating temperature, 100~900℃ is preferred from the point of view that it will not affect the micro-pattern and the structure of alumina will not change.

[0062] Regarding the thickness of the coating layer, a thicker layer is preferable from the perspective of improving strength, but a thinner layer is preferable from the perspective of miniaturization. Given that the size of the fine patterns used in semiconductor alignment applications is around tens of nm, the thickness of the coating layer is preferably 50 nm or less, and more preferably 10 nm or less. There is no particular limitation on the lower limit, but it is preferably 0.1 nm or more, and more preferably 1 nm or more.

[0063] [Manufacturing Method of Recycled Embossing Die] The embossing mold of the present invention allows for easy removal of the coating layer. For example, the Al₂O₃ film can be easily removed with a commercially available mixed acid alumina etching solution. Therefore, even if the transfer micro-pattern is contaminated for any reason, or if the coating layer formed on the transfer micro-pattern deteriorates, as described above, the coating layer can be removed, and the coating layer can be re-formed on the transfer micro-pattern with the coating layer removed using the above method, thus regenerating the embossing mold. In this way, a regenerated mold can be obtained without damaging the transfer micro-pattern provided on the synthetic quartz glass substrate.

[0064] Specifically, as a method for manufacturing the aforementioned recycled embossing mold, for example, a method including the following steps can be adopted. (21) A process for peeling off a coating layer formed on a micro-pattern for transfer on a synthetic quartz glass substrate (Project 21) (22) Process of cleaning the transfer of the peeled coating layer with a fine pattern (Project 22) (23) Confirm the process of maintaining shape and destructive strength of the micro-pattern for transfer after cleaning compared with the pattern before peeling off the coating (Project 23). (24) A process of forming a new coating layer on at least a portion of the confirmed transfer micro-pattern using a material that is the same as or different from the peeled coating layer (process 24).

[0065] (21) Project 21 In step 21, a coating layer formed on a transfer micro-pattern on a synthetic quartz glass substrate is peeled off. In this step, a reagent that does not erode the transfer micro-pattern but can remove the existing coating layer is suitable. The reagent can be selected appropriately depending on the material of the coating layer; for example, if the coating layer is alumina, a commercially available mixed acid alumina etching solution can be used.

[0066] (22) Project 22 In the 22nd process, the transfer micro-pattern used to peel off the coating layer is cleaned. In this process, the transfer micro-pattern is cleaned to account for the contamination of foreign matter. Specifically, it can generally be performed by combining wet cleaning with semiconductor-oriented acids, alkalis, surfactants, etc., such as aqueous solutions called SC1 and SC2, or by combining dry cleaning with plasma, ozone, DUV, etc.

[0067] (23) Project 23 In Project 23, the shape and destructive strength of the micro-pattern for transfer after peeling and cleaning of the coating layer are confirmed to be maintained compared with the pattern before the coating layer was formed. This project confirms that the micro-pattern for transfer is undamaged before and after the coating layer is peeled off (before and after the formation of the peeled coating layer), and whether it can be reused without problems. Specifically, for example, the shape and destructive strength of the coating layer before and after peeling (before and after the formation of the peeled coating layer) can be confirmed using methods such as time-of-flight secondary ion mass analysis and nano-indentation testing.

[0068] Time-of-flight secondary ion mass analysis (TOF-MIA) involves irradiating the surface of a substrate with ions to generate secondary ions. The mass of the substances present on the substrate surface is then measured by the time of flight of these secondary ions, thereby identifying the elements. The surface condition of the substrate can be analyzed from the detection results of secondary ions. Furthermore, the destructive strength (Young's coefficient) can be determined using the nano-indentation test method. In this invention, one or more of these methods can be used alone or in combination. In this invention, the nano-indentation test method is preferred.

[0069] In this invention, maintaining the shape and strength of the transfer micro-pattern before the formation of the coating layer means that the destructive strength (Young's coefficient) of the micro-pattern portion after peeling and washing caused by the nano-indentation test is preferably 65 GPa or more, more preferably 70 GPa or more, and the absolute value of the difference between the destructive strength (Young's coefficient) of the micro-pattern portion before the formation of the coating layer after peeling is preferably 6 GPa or less, more preferably 5 GPa or less. If the above conditions are met, the pattern should be undamaged, and a new coating layer should be formed in the next process to obtain a recycled embossing mold with the desired destructive strength (Young's coefficient).

[0070] (24) Project 24 In step 24, at least a portion of the transfer micro-pattern, after confirming its shape and destructive strength, is covered with a new coating layer made of the same or a different material as the peeled-off coating layer. In this step, the coating layer is applied again using the same method as described above. The material used for the coating layer can also be the same as described above.

[0071] The optimal ranges for the thickness, thickness deviation, Mohs hardness, breaking strength (Young's coefficient), and the percentage increase in breaking strength (Young's coefficient) of the new coating are the same as those described for the coating before recycling. There is no particular limit to the number of regenerations. If the shape and damage strength of the pattern after the coating is peeled off are within the above range, then regeneration can be performed as many times as desired, preferably more than 2 times, and more preferably more than 3 times.

[0072] The embossing mold regenerated in this way can be used in the same way as the embossing mold before regeneration. [Example]

[0073] The present invention will be described in more detail below with examples and experimental examples, but the present invention is not limited to the following examples.

[0074] [Example 1] Fabrication of Imprinting Die Fabrication of synthetic quartz glass molds for forming organic films by electron beam etching. First, an imprinting mold for nanoimprint photolithography of the organic film was fabricated. A 10 nm thick CrN layer was formed on a 20 mm × 20 mm square synthetic quartz glass substrate with a thickness of 0.525 mm by sputtering. Next, a positive electron beam photoresist (ZEP520A, manufactured by ZEON Corporation, Japan) was spin-coated onto the CrN layer and pre-baked at 180°C for 10 minutes to form an 80 nm thick positive electron beam photoresist layer. Then, a conductive polymer antistatic agent (ESPACER 300Z, manufactured by Shoden Kogyo Corporation) was spin-coated to form a 10 nm thick antistatic layer.

[0075] Next, an electron beam mapping apparatus (ELS-G125S, manufactured by ELIONIX) was used to map a linear pattern with a linewidth of 100 nm and a spatial width of 100 nm to form a latent image. The antistatic layer was removed by washing with ultrapure water, and the image was then immersed in a developer (ZED-N50, manufactured by ZEON, Japan) and a rinsing solution (ZMD-B, manufactured by ZEON, Japan) in sequence. After drying, the image was developed to form a linear pattern on the CrN layer, which has a photoresist opening with a spatial width of 100 nm after electron beam exposure and a photoresist residue with a linewidth of 100 nm where the electron beam is not irradiated.

[0076] Next, using an argon ion beam polishing apparatus (20IBE-C, manufactured by H.O.T.), the exposed portion of the CrN layer corresponding to the space width of the photoresist opening was selectively removed to form a hard mask pattern of CrN corresponding to the linewidth. Then, using acetylene octafluoride (C3F8) gas and a dry etching apparatus (EIS-200ER, manufactured by ELIONIX), the surface portion of the synthetic quartz glass substrate not covered by the CrN mask pattern was etched. The substrate was then immersed in a chromium etching solution (manufactured by Hayashi Chun-Yaku Kogyo Co., Ltd.) to remove the CrN hard mask pattern, resulting in an imprinting mold made of synthetic quartz glass with a linear pattern having a linewidth of 100 nm and a space width of 100 nm. In the obtained imprinting mold, a release agent FAS13 ((tetrazolium-1,1,2,2-tetrahydrooctyl)trimethoxysilane) was vapor-deposited.

[0077] Fabrication of nanowire structures (fine patterns for transfer) in synthetic quartz glass by nanoimprint photolithography. Next, a 10 nm thick CrN film (inorganic film) was formed on a circular synthetic quartz glass substrate with a diameter of 100 mmφ and a thickness of 0.525 mm by sputtering. Then, a photocurable photoresist was coated on the CrN film to form an 80 nm thick photoresist film (organic film). Next, using a nanoimprint lithography apparatus (ImpFlex Essential, manufactured by Sanming Corporation), the photoresist film is shaped by pressing an imprinting mold treated with a release agent. The photoresist film is then hardened in this state, forming a linear pattern (organic film pattern) with a linewidth of 100 nm and a spatial width of 100 nm on the CrN film. Afterwards, using an oxygen reactive etching apparatus (IM-TU01, manufactured by Tohoku University), the remaining photoresist film in the spatial width portion outside the 100 nm linewidth photoresist pattern is removed, exposing the surface of the CrN film in the areas where a linear photoresist pattern has not formed.

[0078] Next, using an argon ion beam polishing apparatus (20IBE-C, manufactured by Hapton Corporation), the exposed portion of the CrN film on the surface where a linear photoresist pattern was not formed was selectively removed to form a hard mask pattern (inorganic film pattern) of CrN. Then, using acetylene octafluoride (C3F8) gas and a dry etching apparatus (EIS-200ER, manufactured by ELIONIX Corporation), the surface portion of the synthetic quartz glass substrate not covered by the CrN mask pattern was etched. Immersed in a chromium etching solution (manufactured by Hayashi Chun-Yaku Industrial Co., Ltd.), the hard mask pattern of CrN and the photoresist pattern were removed together, resulting in a synthetic quartz glass substrate with a nanowire structure (fine pattern for transfer) forming a linear pattern with a linewidth of 100 nm and a spatial width of 100 nm on the surface portion of the substrate. The shape and destructive strength of the patterned portion were determined by the following method.

[0079] Alumina coating resulting from atomic layer deposition (ALD) Alumina was coated onto the surface of the obtained synthetic quartz glass nanowire structure (fine pattern for transfer) using ALD. The synthetic quartz glass substrate was placed on a heated stage in a vacuum chamber with the surface temperature set to 140°C. ALD was performed for a total of 20 cycles, consisting of one cycle of exposure to trimethylaluminum (inorganic precursor) for 0.1 s, nitrogen purification and exhaust for 600 s, and exposure to water (oxidant) for 0.1 s, followed by nitrogen purification and exhaust for 600 s. The destructive strength of the covered pattern portion was determined by the following method.

[0080] [Removal of alumina caused by wet etching] The alumina coating formed by ALD was removed by wet etching. The sample was immersed in a mixed acid aluminum etching solution (manufactured by Kanto Chemical Co., Ltd.) at a liquid temperature of 30°C for 3 minutes, then rinsed with ultrapure water and dried. The shape and destructive strength of the dried patterned area were determined by the following method.

[0081] [Example 2] Fabrication of a recycled embossing mold 1 [Alumina coating caused by ALD] On the surface of the nanowire structure (fine pattern for transfer) of the synthetic quartz glass after the coating layer was removed in Example 1, aluminum oxide was coated by ALD in the same manner as in Example 1. The destructive strength of the covered patterned portion was measured in the same manner as in Example 1.

[0082] [Removal of alumina caused by wet etching] As in Example 1, the coating was removed and the material was allowed to dry. The shape and destructive strength of the dried patterned portion were measured in the same manner as in Example 1.

[0083] [Example 3] Fabrication of a recycled embossing mold 2 [Alumina coating caused by ALD] On the surface of the nanowire structure (fine pattern for transfer) of the synthetic quartz glass after the coating layer was removed in Example 2, aluminum oxide was coated by ALD in the same manner as in Example 1. The destructive strength of the covered patterned portion was measured in the same manner as in Example 1.

[0084] [Removal of alumina caused by wet etching] As in Example 1, the coating was removed and the material was allowed to dry. The shape and destructive strength of the dried patterned portion were measured in the same manner as in Example 1.

[0085] (Strength evaluation due to nano-indentation test) Using an ENT-2100 nanoindentation testing machine (manufactured by ELIONIX) equipped with diamond spherical indenters (radius of curvature 200 μm), diamond spherical indenters (rigid bodies) are brought into contact with and pressed into the area of ​​the nanowire structure (micro-pattern for transfer) forming the synthetic quartz glass. A portion of the nanowire structure (micro-pattern for transfer) is pressed in the height direction to plastically deform it. Specifically, 100 consecutive presses are performed at the same location with a pressing speed of 5 mN / s and a load of 10 mN.

[0086] (Strength test results from nano-indentation tests before and after coating in Example 1) The Young's coefficient of the line pattern portion of the uncoated synthetic quartz glass is 77.0 GPa. The Young's coefficient of the alumina coated with atomic layer deposition to form a quartz glass line pattern was 83.5 GPa, confirming the improvement in mechanical strength due to alumina deposition. The Young's coefficient of the line pattern after alumina removal was 75.8 GPa, confirming the change in Young's coefficient before and after alumina coating. These results are shown in Table 1.

[0087] (Results of repeated regeneration strength tests and pattern shape confirmation based on nanoindentation tests in Examples 1-3) The deposition and removal of alumina were repeated, and the Young's coefficient of the line pattern region was calculated. The results are shown in Table 1. The increase in mechanical strength was confirmed by the alumina deposition caused by ALD. In Example 1, a decrease in the Young's coefficient was confirmed after alumina removal (first alumina removal) compared to the Young's coefficient before alumina deposition (ALD untreated substrate). However, in Example 2, the Young's coefficient was confirmed to be reproduced after repeated alumina coating (second ALD). Similarly, in Example 2, although a decrease in the Young's coefficient was confirmed after alumina removal (second alumina removal) compared to the Young's coefficient after the first alumina stripping (first alumina removal), in Example 3, the Young's coefficient was confirmed to be reproduced after repeated alumina coating (third ALD). Based on these findings, it was confirmed that the pattern shape was maintained before the formation of the coating layer after peeling.

[0088]

[0089] [Experimental Example 1] (The creation and result of fine patterns) Similar to Example 1, a synthetic quartz glass substrate was obtained in which a nanowire structure (fine pattern for transfer) with a linear pattern having a linewidth of 100 nm and a spatial width of 100 nm was formed on the surface of the synthetic quartz glass substrate. Figure 1 shows an atomic force microscope image of the resulting linear pattern. A fine pattern with a linewidth of 100 nm and a height of 115 nm was confirmed.

[0090] [Experimental Example 2] (Measurement and results of the thickness of the alumina coating) On a patternless synthetic quartz glass substrate, alumina was deposited under the same conditions as in Example 1 [Atomic Layer Deposition (ALD-induced alumina coating)]. The film thickness was measured using a stylus-type micro-shape measuring machine (ET4000, manufactured by Kosaka Research Institute). The measuring force was 5 μN and the speed was 20 μm / s. The alumina film thickness was approximately 3 nm.

Claims

1. An imprinting mold comprising: a synthetic quartz glass substrate on which a transfer micro-pattern is formed for forming on the surface; and a coating layer formed of at least one of a material different from the substrate on at least a portion of the micro-pattern, wherein the thickness of the coating layer is 3 nm or less, and the deviation of the thickness is within 10% relative to the average thickness of the coating layer.

2. The embossing mold as described in claim 1, wherein, The materials that differ from the aforementioned substrates are Al2O3, ZrO2, HfO2, TiN, TaN, or WN.

3. The embossing die as described in claim 1 or 2, wherein, The material that differs from the aforementioned substrate is Al2O3.

4. The embossing die as described in claim 1 or 2, wherein, The destructive strength of the portion of the micro-pattern used for transfer that forms the coating layer is higher than the destructive strength of the micro-pattern used for transfer before the aforementioned coating layer is formed.

5. The embossing die as described in claim 4, wherein, The destructive strength of the portion of the micro-pattern for transfer forming the coating layer is more than 1.05 times that of the micro-pattern for transfer before the aforementioned coating layer is formed.

6. A method for manufacturing an embossing die as described in claim 1 or 2, wherein, At least a portion of the transfer micropattern formed on the surface of a synthetic quartz glass substrate is subjected to a reaction by sequential chemical vapor deposition, in which at least two reactive precursors of a material different from the substrate are alternately exposed to react, thereby forming a coating layer from the material different from the substrate.

7. A method for manufacturing a regenerated embossing mold, comprising: a process of peeling off a coating layer from an embossing mold having a synthetic quartz glass substrate having a transfer micro-pattern formed on its surface, and a coating layer formed on at least a portion of the micro-pattern with a material different from the substrate; a process of cleaning the transfer micro-pattern after peeling off the coating layer; a process of confirming, based on the cleaned transfer micro-pattern, that it retains the shape and destructive strength of the transfer micro-pattern before the formation of the coating layer; and a process of forming a new coating layer on at least a portion of the confirmed transfer micro-pattern with a material that is the same as or different from the peeled coating layer by atomic deposition.

8. The method for manufacturing a recycled embossing die as described in claim 7, wherein, The aforementioned confirmed engineering was caused by time-of-flight secondary ion mass analysis or nano-indentation testing.

Images