JP2011148227A - Substrate for mask blank, method for manufacturing the same, mask blank for imprint mold, and method for manufacturing imprint mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a mask blank for use in manufacturing an imprint mold, allowing accurate formation of a recess for facilitating the release (separation) of the imprint mold, requiring a small process load for such a processing, and minimizing the degradation of strength and rigidity of the mold caused by forming the recess. <P>SOLUTION: The substrate is used for the mask blank having the substrate and a thin film formed on the front side main surface of the substrate, for manufacturing the imprint mold by etching the thin film and the substrate. The substrate 1 is formed with the recess 3 formed of a hole 2 of predetermined shape bored in a base material 1a, in a region excluding at least an outer peripheral part of a rear side main surface of the substrate by joining at least two base materials including the base material 1a with the hole 2 bored. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for producing an imprint mold used for production of a semiconductor device or an optical component to which an optical function is added by a fine pattern, an imprint mold mask blank used for the production, the mask blank substrate and the production thereof. Regarding the method.

In recent years, in order to transfer a large amount of the same fine pattern in the fine circuit pattern of a semiconductor device, the production of an optical component with an optical function added by the fine pattern, and the fine pattern formation of a magnetic layer in a magnetic recording medium used for a hard disk drive, etc. The imprint method has been used.
An imprint mold (stamper) used for the imprint method is a master for transferring a large amount of the same fine pattern. The imprint method is a method in which the imprint mold is directly pressed against the resist film applied on the transfer object to transfer the pattern, so the cross-sectional shape of the imprint mold pattern is also greatly increased to the shape of the fine pattern to be produced. Affect. As the degree of integration of semiconductor circuits is improved, the dimensions of patterns are becoming smaller, and higher imprint mold accuracy is required. In particular, the imprint method is a transfer method in which an imprint mold is directly pressed as described above, and pattern transfer is performed at the same magnification, so that the required precision is the same as a fine pattern to be manufactured, for example, a semiconductor circuit pattern. The imprint mold is required to have a higher precision than, for example, a photomask.

  In the production of a conventional imprint mold, a mask blank in which a thin film such as chromium is formed on a translucent substrate such as quartz glass is used, and after applying a resist on this mask blank, electron beam exposure or the like is used. Then, a resist pattern is formed, and the thin film is etched by using the resist pattern as a mask to form a thin film pattern (mask pattern).

  Furthermore, in an imprint mold used for a transfer object coated with a photocurable resin, light is emitted during transfer. Therefore, the translucent substrate is etched using the thin film pattern as a mask to form a step pattern (uneven pattern). In this case as well, the pattern size and accuracy of the translucent substrate are directly affected by the size and accuracy of the thin film pattern. Therefore, in order to produce an imprint mold in which a fine pattern with high accuracy is finally formed, it is necessary to form the thin film pattern in the mask blank with high pattern accuracy.

  However, in the imprint method, no matter how much a pattern is transferred using an imprint mold on which a highly accurate fine pattern is formed, the imprint mold and the cured resin are in close contact with each other. Since a strong force is required when peeling (releasing) from the transfer object, the resulting pattern on the transfer object may be destroyed or the imprint mold may be damaged. It was.

  Therefore, in Patent Document 1, for the purpose of preventing breakage of the transferred pattern and facilitating the imprint mold peeling process, the substrate on the surface opposite to the surface on which the concavo-convex pattern is formed, There has been proposed an imprint mold in which a recess formed so that a recess becomes deeper from an outer edge toward a center of a substrate.

JP 2009-170773 A

  According to the disclosure of Patent Document 1, by forming a recess in the substrate on the surface opposite to the surface on which the uneven pattern of the imprint mold is formed, stress is applied to the recess due to the adhesive force between the resin and the imprint mold at the time of peeling. Since the imprint mold itself is curved and the peeling force concentrates around the adhesion surface, peeling can be started with less force than before, and the peeling force is centered from the surroundings as peeling progresses. However, in order to provide such an effect, it is necessary to form the recesses with high accuracy, and the processing load for processing the recesses is large. If the dimensions and shape accuracy of the recesses are not very good, the balance of stress applied to the recesses during peeling may be lost, which may cause damage to the mold. Further, it is necessary to dig up to a depth of more than half of the thickness of the substrate at the deep part of the concave part, and if such concave part processing is performed using a single base material, the strength and rigidity of the mold itself are reduced. , It is easy to cause mold destruction at the time of peeling.

  Further, when the recess processing is performed by machining or the like, there is a possibility that residual stress remains on the bottom surface of the recess or the like, and the front main surface of the substrate may be deformed to deteriorate the flatness. The surface roughness of the bottom surface of the recess after processing the recess of the substrate is greatly deteriorated. In particular, in the case of an imprint mold for transferring a pattern to a photocurable resin, light is incident from the bottom surface of the recess, so that if the surface roughness is deteriorated, it reaches the photocurable resin due to light scattering or the like. This is a problem because the amount of light decreases. Further, if the surface roughness inside the recess (bottom surface, side wall, etc.) is deteriorated, there is a possibility that particles such as shavings adhere to the surface roughness. A polishing process is required to make the surface roughness of the bottom surface of the concave portion and the side wall equal to or greater than a predetermined value, but it is difficult to polish the concave portion such as the bottom surface of the concave portion and the side wall with high accuracy.

  Therefore, the present invention has been made in view of such a conventional situation, and the object of the present invention is to first provide a concave portion for facilitating mold release (peeling) of the imprint mold. It can be formed, and the processing load of such processing can be reduced. Further, the depression of the strength and rigidity of the mold due to the formation of the recess can be suppressed, the surface roughness inside the recess can be improved, and the photocurable resin can be reached. The present invention provides a mask blank substrate used for manufacturing an imprint mold that can prevent the decrease in the amount of light to be generated and particle generation, and a method for manufacturing the same. Second, such a mask blank substrate is provided. Third, the mask blank for imprint mold used is provided. Third, the mold can be easily peeled off by using such a mask blank. Etc. is also to provide a method for manufacturing an imprint mold can be prevented.

That is, in order to solve the above problems, the present invention has the following configuration.
(Configuration 1)
A substrate used as a mask blank for manufacturing an imprint mold by etching the thin film and the substrate, the substrate comprising a substrate and a thin film formed on a front main surface of the substrate, Forming a recess made of the hole in a region excluding at least the outer peripheral portion of the backside main surface of the substrate by bonding at least two substrates including a substrate formed by drilling holes of a predetermined shape This is a mask blank substrate.

(Configuration 2)
2. The mask blank substrate according to Configuration 1, wherein at least two of the base materials constituting the substrate include at least a base material made of glass.
(Configuration 3)
The mask blank substrate according to Configuration 1 or 2, wherein the concave portion formed in the substrate is formed in a region larger than a mold pattern forming region on the front main surface.

(Configuration 4)
4. The mask blank substrate according to claim 1, wherein the surface roughness of the bottom surface of the recess is an arithmetic average roughness Ra of 0.3 nm or less. 5.
(Configuration 5)
Any one of Structures 1 to 4, wherein the base material formed with holes of a predetermined shape constituting the substrate and the other base materials are combined with materials having different thermal expansion coefficients. It is a mask blank board | substrate as described in an item.

(Configuration 6)
A substrate manufacturing method comprising a substrate and a thin film formed on a front main surface of the substrate, the substrate being used as a mask blank for producing an imprint mold by etching the thin film and the substrate. A step of producing a flat plate-like first base material formed by drilling at least one hole having a predetermined shape; the first base material; and at least one flat plate-like second base material. And a step of forming a recess made of the hole in a region excluding at least the outer peripheral portion thereof on the back main surface of the substrate.

(Configuration 7)
7. The mask blank substrate according to Configuration 6, comprising a step of finishing the joining surfaces of the first base material and the second base material so as to have a predetermined flatness when joining the first base material and the second base material. It is a manufacturing method.
(Configuration 8)
8. The method for manufacturing a mask blank substrate according to Configuration 6 or 7, wherein both the first base material and the second base material are made of glass.

(Configuration 9)
A mask blank for imprint molding, comprising a thin film for pattern formation on the front main surface of the mask blank substrate according to any one of Structures 1 to 5.

(Configuration 10)
It is a manufacturing method of the imprint mold characterized by having the process of etching the said thin film and the said board | substrate in the mask blank for imprint molds of the structure 9.

(Configuration 11)
The process of producing the 1st base material formed by drilling the hole of a predetermined shape, and the surface of the 2nd base material using the mask blank provided with the thin film for pattern formation on the surface of the 2nd base material A step of forming a concavo-convex pattern on the substrate, and a step of bonding the first substrate and a surface of the second substrate opposite to the surface on which the concavo-convex pattern is formed. It is a manufacturing method of a print mold.

According to the present invention, a substrate used for a mask blank for producing an imprint mold is obtained by joining at least two substrates including a substrate formed by drilling holes of a predetermined shape. By forming a recess made of the hole in a region excluding at least the outer peripheral portion on the back side main surface, a recess for facilitating mold release (peeling) of the imprint mold can be accurately formed, and such processing is performed. It is possible to reduce the process load of the mold, and further suppress the decrease in the strength and rigidity of the mold due to the formation of the recesses, improve the surface roughness inside the recesses, prevent the decrease in the amount of light reaching the photo-curing resin, and particles It is possible to provide a mask blank substrate used for producing an imprint mold capable of suppressing generation and a method for producing the same.
Moreover, according to this invention, the mask blank for imprint molds using such a mask blank board | substrate can be provided.
In addition, according to the present invention, it is possible to provide a method for manufacturing an imprint mold that can facilitate the peeling of the mold using such a mask blank and can prevent damage to the mold.

It is a schematic sectional drawing for demonstrating the structure of the board | substrate for mask blanks of this invention. It is a top view of the 1st base material which constitutes the substrate for mask blanks of the present invention. It is a schematic sectional drawing of the mask blank for imprint molds of this invention. It is a schematic sectional drawing for demonstrating the use condition of the imprint mold of this invention. It is a schematic sectional drawing for demonstrating the manufacturing process of the imprint mold of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The mask blank substrate of the present invention comprises a substrate and a thin film formed on the front main surface of the substrate, and a mask blank for producing an imprint mold by etching the thin film and the substrate. The substrate has at least an outer peripheral portion removed from the main surface on the back side of the substrate by bonding at least two substrates including a substrate formed with a hole having a predetermined shape. It is characterized by forming a recess made of the hole in the region.

FIG. 1 is a schematic cross-sectional view for explaining the configuration of a mask blank substrate of the present invention.
FIG. 1 shows an embodiment of a mask blank substrate according to the present invention, and the mask blank substrate (hereinafter sometimes simply referred to as “substrate”) 1 is formed on a flat base material. The main surface of the first base material 1a formed by perforating the hole 2 and the flat second base material 1b are joined to each other, so that one side of the substrate 1, that is, the imprint mold pattern On the back side main surface (recessed surface) 12, which is the surface opposite to the front side main surface (pattern forming surface) 11 on the side of forming the concave portion 3, the concave portion 3 including the hole 2 is formed at least in the region excluding the outer peripheral portion. Is. FIG. 2 is a plan view of the first base material 1a constituting the substrate 1, but in the present embodiment, the first base material 1a has a rectangular shape as a whole, and the holes 2 has a circular shape. Further, the second base 1b as a whole has the same rectangular shape as the first base 1a. Of course, the outer shape of the substrate 1 need not be limited to such a rectangular shape, and the shape of the hole 2 need not be limited to such a circular shape, and may be rectangular or polygonal. It is determined as appropriate according to the use and size of the imprint mold.

  When the imprint mold produced from this mask blank substrate is used to transfer the pattern, the transfer device (stamper device) is a substrate in which the imprint mold is sandwiched between the opposite end faces and fixed. The outer shape of 1 is desirably a rectangular shape having a high degree of parallelism in which a variation in width between opposing end faces is 50 μm or less, more preferably 40 μm or less. In this case, it is desirable that the flatness of the end face is 20 μm or less, more preferably 10 μm or less.

  The center of the hole 2 of the substrate 1 is most preferably coincident with the center of the substrate 1, and at least the deviation is preferably 100 μm or less, more preferably 50 μm or less. It is common to make the center of the mold pattern (uneven pattern) formed on the front main surface coincide with the center of the substrate, and when imprint mold is pressed against the resist film of the transfer object or when peeling This is because the deformation gradually spreads from the center of the uneven pattern. The shape (cross-sectional shape) of the hole 2 is preferably a perfect circle. When the imprint mold is fixed to the transfer device and transferred, the influence of the internal pressure in the space formed by the recess 3 of the hole 2 and the fixing device of the transfer device on the deformation of the front main surface becomes a concentric distribution and is adjusted. It is because it is easy to do. In addition, although it is the magnitude | size of the hole 2, it is preferable that it is 50 mm or more in the diameter in the case of a circular shape, and the length of a short side direction in the case of a rectangle, and it is suitable that it is 60 mm or more. In consideration of securing the rigidity of the base material 1b in which the hole 2 is formed, when the size of the substrate 1 is about 152 mm square, the diameter of the hole 2 or the length in the short side direction is 100 mm or less. It is desirable that it is 90 mm or less.

Since the mask blank substrate 1 of the present invention is used as an imprint mold by forming an uneven pattern which is a mask pattern on the pattern forming surface 11, the first base material constituting the substrate 1 is used. As a material of 1a and the 2nd base material 1b, if it is a material which has the moderate intensity | strength and rigidity required for using as an imprint mold, there will be no restriction | limiting in particular and it can use arbitrarily. For example, glass materials such as quartz glass, SiO ₂ —TiO ₂ low expansion glass, soda lime glass, aluminosilicate glass, CaF ₂ glass, metal materials such as silicon, stainless steel (SUS), aluminum, copper, nickel, and resin materials Etc. Of these, glass materials are particularly suitable. The glass material can be processed with very high accuracy and is excellent in flatness and smoothness. Therefore, when pattern transfer is performed using the imprint mold obtained by the present invention, distortion of the transfer pattern does not occur. Can perform highly accurate pattern transfer. Therefore, it is preferable that the first base material 1a and the second base material 1b constituting the substrate 1 include at least a base material made of glass. In the case of a mask blank substrate for producing an imprint mold for pattern transfer to a photo-curing resin, it is desirable that at least the substrate 1b is made of a glass material, such as quartz glass or SiO ₂ —TiO ₂ -based low expansion. Glass is particularly preferred.

  The first base material 1a and the second base material 1b may be made of the same material or different materials. When different materials are used, it is particularly preferable to combine materials having different thermal expansion coefficients. Since the first base material 1a and the second base material 1b are made of materials having different thermal expansion coefficients, in addition to forming the recesses 3 in the substrate 1, heating or cooling is performed when the imprint mold is released. Thus, a relative tensile stress or compressive stress acts between the first base material 1a and the second base material 1b, so that the mold can be released more easily (that is, the mold can be released with a smaller force). ). For example, quartz glass and silicon have a thermal expansion coefficient that differs by an order of magnitude. Therefore, when silicon is used for the first substrate 1a and quartz glass is used for the second substrate 1b, the mold is cooled during mold release. A difference in thermal expansion occurs between the first base material 1a and the second base material 1b, and compressive stress acts on the first base material 1a, while relative to the second base material 1b. Since tensile stress acts on the mold, the mold can be easily released.

  Moreover, although the said recessed part 3 formed in the board | substrate 1 for mask blanks of this invention is formed in the area | region except an outer peripheral part at least, it forms in the front side main surface 11 on the opposite side to the back side main surface 12 in which this recessed part 3 was formed. It is preferably formed in a region larger than the mold pattern (uneven pattern) forming region. If the area where the recesses 3 are formed is smaller than the mold pattern formation area, a portion that hardly deforms may occur in the outer mold pattern, and the resist film sandwiched between the mold pattern that deforms outward may be crushed. It is. In particular, in the case of a mask blank substrate for producing an imprint mold for performing pattern transfer on a photo-curing resin, the boundary portion between the concave portion 3 and the back side main surface 12 forms a mold pattern on the front side main surface 11. If it falls on the region, the light for curing the photo-curing resin cannot be normally incident, and there is a possibility that the resin may be poorly cured.

  According to such a mask blank substrate of the present invention, at least the outer periphery of the substrate is formed on the back main surface of the substrate by bonding at least two substrates including a substrate formed by drilling holes of a predetermined shape. Since the concave portion made of the hole is formed in the region excluding the portion, the concave portion for facilitating the release (peeling) of the imprint mold has a predetermined shape on at least one base material constituting the substrate. Therefore, it is possible to reduce the process load of such processing, and it is possible to accurately form the concave portion on the back main surface of the substrate after bonding. Furthermore, since the substrate of the present invention joins at least two base materials, ie, the base material having the holes and the flat base material, the concave portion is formed on one conventional substrate. It is possible to suppress a decrease in strength and rigidity of the mold. In addition, it is possible to obtain a mask blank substrate using at least two substrates having different materials.

  Therefore, the imprint mold obtained by using the mask blank using the mask blank substrate of the present invention can be easily peeled off with a smaller force at the time of mold release, and the transfer object (transfer object) It is possible to effectively prevent damage to the pattern transferred to the mold and damage to the mold itself.

  In addition, if the recess processing is performed by machining or the like, residual stress may remain on the bottom surface of the recess, etc., and the front main surface of the substrate may be deformed and flatness may deteriorate. According to the mask blank substrate of the invention, it is possible to suppress the residual stress due to the formation of the recess. Moreover, when the process which forms a recessed part from the back surface main surface of the conventional one board | substrate is performed, the surface roughness of the recessed part bottom face after processing a recessed part has deteriorated significantly. In particular, in the case of an imprint mold for pattern transfer to a photocurable resin, light is incident from the bottom surface of the recess, and therefore the amount of light that reaches the photocurable resin due to light scattering when the surface roughness is deteriorated. This is a problem because it decreases. Further, if the surface roughness inside the recess (bottom surface, side wall, etc.) is deteriorated, there is a possibility that particles such as shavings adhere to the surface roughness. A polishing process is required to make the surface roughness of the bottom surface of the concave portion and the side wall to be a predetermined value or more. However, it is very difficult to accurately polish the inside of the concave portion such as the bottom surface of the concave portion and the side wall after forming the concave portion. According to the mask blank substrate of the present invention, since the base material having the holes penetrating the front and back is first prepared, it is relatively easy to polish the side wall of the recess to a desired surface roughness. Moreover, the back surface of the flat base material used as the bottom face of a recessed part can be easily processed into desired surface roughness and flatness by a conventional polishing technique. And if the two base materials grind | polished to the desired surface roughness are joined, the inside of a recessed part (a bottom face or a side wall) can be made into the desired surface roughness.

In the present embodiment, both the first base material 1a and the second base material 1b use one base material, but one of the first base material and the second base material is Alternatively, both may have a configuration in which two or more base materials are joined.
Further, the thickness of each of the first base material 1a and the second base material 1b constituting the substrate of the present invention is not particularly limited, but the thickness of the first base material is the mask blank after joining. The total thickness of the substrate 1 is preferably in the range of 0.1 to 0.25 times. If the thickness of the first substrate is more than 0.25 times, the force applied to deform the first substrate becomes too large, and there is a risk that it will not return to its original shape after deformation or cracks may occur. is there. Further, if the thickness of the first base material is less than 0.1 times, the proof stress of the base material is low and there is a risk of cracking during deformation.

Next, a method for manufacturing the mask blank substrate of the present invention as described above will be described.
The present invention also provides a method for producing a mask blank substrate of the present invention, and a step of producing a flat plate-like first base material formed by drilling at least one hole having a predetermined shape; By bonding the first base material and at least one flat plate-like second base material, a recess made of the hole is formed in a region excluding at least the outer peripheral portion of the back side main surface of the substrate. And a process for producing a mask blank substrate.

Each of the first base material 1a and the second base material 1b uses a flat base material finished in a predetermined shape, external dimensions, and plate thickness.
The processing means for forming the hole 2 having a predetermined shape in the step of manufacturing the first base material 1a is not particularly limited, and a fine processing method such as a known machining method or etching method. Can be used arbitrarily. Specifically, for example, laser processing, cutting processing, ion beam milling processing represented by gas cluster ion beam (GCIB), magneto-rheological finishing (MRF) processing, water jet processing, etching (wet etching) , Dry etching), polishing using a polishing slurry, and the like, and the like may be appropriately selected in consideration of the material of the substrate, the shape and size of the hole to be processed, and the like.

  Next, as a means for joining the first base material 1a having the hole 2 having the predetermined shape and the flat second base material 1b, the first base material and the second base material are used. There is no need to be particularly limited as long as the method can obtain a sufficient adhesive strength. Here, the sufficient adhesive force is an adhesive force that does not cause peeling between the first base material and the second base material when the imprint mold is used.

  In the present invention, specifically, methods such as a welding (welding) method, an adhesion method, an anodic bonding method, a hydrofluoric acid bonding method, and an optical welding method (optical contact) can be preferably used.

  The welding (welding) method is a method in which the joining surfaces of two members to be joined (in the present invention, the first base material 1a and the second base material 1b) are melted and integrated (fused) by heating or the like. It is. This method is applicable regardless of the materials of the first base material 1a and the second base material 1b in the present invention and when the materials of the first base material 1a and the second base material 1b are the same or different. can do.

  In addition, the bonding method is an adhesive (for example, an ultraviolet (UV) curable adhesive is preferable) between two members to be bonded (in the present invention, the first base material 1a and the second base material 1b). It is the method of pasting using. Although this method depends on the type of adhesive used, it is preferable because particularly high adhesion can be obtained when the materials of the first substrate 1a and the second substrate 1b are the same.

  The anodic bonding method is a method in which the bonding surfaces of two members to be bonded (in the present invention, the first base material 1a and the second base material 1b) are overlapped and heated (for example, about 300 to 500 ° C.). In this method, a voltage (for example, about 400 to 600 V) is applied, and by this, covalent bonding can be performed at the bonding interface. However, this method can be preferably applied when one of the first substrate 1a and the second substrate 1b is a glass material and the other is silicon or metal. When glass materials are bonded to each other, a thin film such as SiN, SiC, or amorphous silicon is preferably formed on at least one bonding surface.

  The hydrofluoric acid bonding method is a method in which hydrofluoric acid is dropped on the bonding surfaces of two members to be bonded (the first base material 1a and the second base material 1b in the present invention), and then the bonding surfaces are overlapped. It is a method of joining by pressurizing with a predetermined pressure, and is suitable when joining glass materials.

The optical welding method (also referred to as optical contact) refers to the joining of two members (in the present invention, the first base material 1a and the second base material 1b) finished with high flatness and high smoothness. In this method, the surfaces are brought into close contact with each other (in some cases, pressure is applied simultaneously), and bonding is performed by intermolecular force (intermolecular bond) generated at the bonding interface. This method is particularly suitable when bonding precisely polished glass planes.
Therefore, a suitable joining method may be appropriately selected and used depending on the materials of the first base material 1a and the second base material 1b to be joined.

  In addition, when joining the said 1st base material 1a and the 2nd base material 1b, even if it uses which joining method as mentioned above, in order to obtain strong joining force, both flat surfaces of both joining surfaces are used. In particular, the optical welding method requires high flatness and high smoothness of the joint surface. Therefore, prior to the step of joining the first base material 1a and the second base material 1b, the joining surfaces of both the first base material 1a and the second base material 1b are each set to a predetermined flatness, for example, It is preferable to include a step of finishing to have a flatness of about 5 μm or less. Here, the flatness is a value representing a warp (deformation amount) of the surface indicated by TIR (Total Indicated Reading). For example, in a 142 mm square area, a plane defined by the least square method with reference to the substrate surface is a focal plane. And the absolute value of the difference in height between the highest position of the substrate surface above the focal plane and the lowest position of the substrate surface below the focal plane. However, in the case of bonding by the optical welding method, high bonding strength is required in the present invention. Therefore, the surface accuracy of both bonding surfaces is, for example, λ / 10 (at λ = 633 nm) and the flatness is set to high accuracy of 60 nm or less. It is desirable to keep it.

  The processing means for finishing the joint surfaces of the first base material 1a and the second base material 1b so as to have a predetermined flatness is not particularly limited, and is a known machining method. A surface processing method such as an etching method can be arbitrarily used. Specifically, for example, processing by local plasma etching, ion beam processing represented by gas cluster ion beam (GCIB), magnetic-fluid polishing (MRF) processing, etching (wet etching, dry etching), A surface treatment method such as mirror polishing using a polishing slurry or chemical mechanical polishing (CMP) may be appropriately selected in consideration of the material of the substrate. The glass material can be subjected to surface processing with extremely high accuracy, and high flatness and high smoothness can be obtained.

For the first base material 1a, either the process of drilling the hole 2 having a predetermined shape or the process of finishing the bonding surface to have a predetermined flatness may be performed first. From the viewpoint of reducing the process load, it is preferable to perform the processing in which the joint surface is first finished to have a predetermined flatness and then the processing in which the hole 2 having a predetermined shape is formed.
Moreover, about the surface on the opposite side to the bonding surface in the second substrate 1b, that is, the pattern forming surface 11, a thin film for forming a mask blank for forming a fine mold pattern (uneven pattern) of the imprint mold is used. It is desirable to finish in a suitable surface state so that a film can be formed.

  As described above, according to the method for manufacturing a mask blank substrate of the present invention, the recess for facilitating the release (peeling) of the imprint mold has at least one base constituting the substrate. Since it can be formed by drilling holes of a predetermined shape in the material in advance, the processing load of such processing can be reduced, and the concave portion can be accurately formed on one side of the substrate after bonding. In addition, the mask blank substrate of the present invention is obtained by joining at least two base materials, ie, a base material in which the hole is formed in a flat base material and another flat base material, It is possible to suppress a decrease in the strength and rigidity of the mold due to the formation of the recesses on one conventional substrate. Furthermore, it is possible to obtain a mask blank substrate using at least two substrates having different materials.

Next, an imprint mold mask blank using the mask blank substrate of the present invention as described above will be described.
The present invention also provides a mask blank for imprint mold, and includes a thin film for pattern formation on the front main surface opposite to the back main surface on which the concave portion of the mask blank substrate of the present invention is formed. An imprint mold mask blank characterized by the above.

FIG. 3 is a schematic cross-sectional view of the mask blank for imprint molds of the present invention, and shows one embodiment of the mask blank for imprint molds of the present invention.
That is, the imprint mold mask blank 10 shown in FIG. 3 forms the front main surface opposite to the back main surface on which the concave portion 3 of the mask blank substrate 1 of the present invention is formed, that is, the imprint mold pattern. The thin film 4 for pattern formation is provided on the surface (pattern formation surface) 11 on the side to be processed.

The thin film 4 for pattern formation in such an imprint mold mask blank 10 may be a single layer or a plurality of layers. For example, a mask blank or the like in which the thin film 4 is formed of a single layer film of a chromium material can be given as an example. Further, for example, a mask blank in which the thin film 4 is composed of at least an upper layer and a lower layer laminated film, the upper layer is formed of a chromium (Cr) -based material, and the lower layer is formed of a material containing tantalum (Ta) as a main component. Can be mentioned. Examples of the chromium-based material include Cr alone or Cr compounds such as Cr nitride, carbide and carbonitride, and CrOCN is particularly preferable in the case of a single layer film. Further, as a material mainly composed of tantalum, for example, Ta compounds such as TaHf, TaZr, TaHfZr, or such Ta compounds as base materials, for example, secondary materials such as B, Ge, Nb, Si, C, and N are used. There are added materials.
Needless to say, the configuration and material of such a thin film are merely examples, and the present invention is not necessarily limited to these.

The method for forming the thin film 4 is not particularly limited, but a sputtering film forming method is particularly preferable. The sputtering film forming method is preferable because a uniform film having a constant film thickness can be formed.
When a TaHf film, for example, is formed as a lower layer of a thin film made of the above-described laminated film by a sputtering film forming method, an alloy target of Ta and Hf is used as a sputtering target, and the sputtering gas introduced into the chamber is argon gas or helium. An inert gas such as a gas is used. Further, when a CrN film, for example, is formed as an upper layer of the laminated film, a Cr target is used as a sputtering target, and a sputtering gas introduced into the chamber is a mixture of an inert gas such as argon gas or helium gas with nitrogen gas. Use things.

In the mask blank 10, the pattern forming thin film 4 is first formed on one surface of the second substrate 1b, and then the second substrate 1b and the first hole having the holes 2 formed therein are formed. It can also be produced by bonding the substrate 1a.
The imprint mold mask blank of the present invention may have a form in which a resist film is formed on the thin film 4.

Next, a method for producing an imprint mold using the mask blank for imprint mold of the present invention as described above will be described.
The present invention also provides a method for producing an imprint mold, and is a method for producing an imprint mold characterized by etching the thin film and the substrate in the mask blank for imprint mold of the present invention.

FIG. 5 is a schematic cross-sectional view for explaining the manufacturing process of the imprint mold of the present invention. With reference to this FIG. 5, the manufacturing method of the imprint mold using the mask blank 10 for imprint molds of this invention (refer FIG. 3) is demonstrated. In FIGS. 5A to 5E, the recess 3 of the substrate 1 is not shown.
First, for example, a resist for electron beam drawing is applied to the upper surface of the thin film 4 of the mask blank 10 of the present invention, and a predetermined baking process is performed to form a resist film 5 on the mask blank 10 (FIG. 5A )reference).

  Next, after drawing a predetermined pattern (for example, a line and space pattern) on the resist film 5 of the mask blank 10 using an electron beam drawing machine or the like, the resist film 5 is developed to form a resist pattern 5a ( (See (b) in the figure).

Next, the mask blank 10 on which the resist pattern 5a is formed is introduced into a dry etching apparatus, and the thin film 4 is etched using the resist pattern 5a as a mask to form the thin film pattern 4a as shown in FIG. To do.
Here, the mask blank may be once taken out from the dry etching apparatus, and the remaining resist pattern 5a may be removed (see FIG. 4D).
Depending on the layer configuration and material of the thin film 4, the etching process may be performed in two or more stages instead of one stage.
Next, the substrate 1 is etched using the thin film pattern 4a as a mask to form a concavo-convex pattern (step pattern) 6 of the substrate 1 (see FIG. 4E).

Next, a resist pattern 7 for a pedestal structure shown in FIG. 5F is formed on the mask blank on which the uneven pattern 6 of the substrate 1 is formed.
Next, with respect to the mask blank on which the resist pattern 7 is formed, the thin film 4 other than the portion protected by the resist pattern 7 is removed by, for example, wet etching, and further, for example, wet etching is performed on the substrate 1 to further form the resist pattern 7. By removing the base structure 8 as shown in FIG. Further, by removing the thin film pattern 4a on the concavo-convex pattern 6, an imprint mold 20 having a structure shown in FIG.

  The method for manufacturing the imprint mold using the mask blank shown in FIG. 3 has been described above, but the method for manufacturing the imprint mold of the present invention is not limited to this. The present invention uses a step of producing a first base material formed by drilling holes of a predetermined shape, and a mask blank provided with a thin film for pattern formation on the surface of the second base material. Forming a concavo-convex pattern on the surface of the base material, and joining the first base material and a surface opposite to the surface of the second base material on which the concavo-convex pattern is formed. A feature of the imprint mold manufacturing method is also provided.

That is, by etching the thin film 4 and the base material 1b using a mask blank in which the thin film 4 for pattern formation is formed on one surface of the second base material 1b, the second base material 1b An uneven pattern is formed on the surface. Then, an imprint mold may be produced by joining the surface of the second base material 1b opposite to the surface on which the concave / convex pattern is formed and the first base material 1a having the holes 2 formed therein. Is possible.
In the case of this imprint mold manufacturing method, when joining the first base material and the second base material, protection for at least protecting the concave-convex pattern formed on the front main surface of the second base material. It is desirable to form a film. As the protective film, a material that damages the substrate as much as possible when peeling after bonding is desirable. For example, a high etching selection for a resin material that can be removed with a solvent such as a resist film or a material that forms the substrate Examples thereof include metallic materials (Cr-based materials and Ta-based materials) having properties. In the case where a resin material is applied to the protective film, the bonding method between the first base material and the second base material is an adhesive method that does not require heating or a hydrofluoric acid bonding method among the above-mentioned bonding methods. The optical welding method is desirable.

FIG. 4 is a schematic cross-sectional view for explaining the usage state of the imprint mold of the present invention.
The imprint mold 20 obtained by the present invention includes a resist film (for example, a UV curable resin or a thermosetting resin) applied on a transfer target constituent layer (for example, a silicon wafer) 31 in a transfer target (transfer target) 30. ) Direct pressing on 32 to transfer the concavo-convex pattern 6.
By using the imprint mold obtained by the present invention, the mold can be easily peeled off with a smaller force at the time of mold release, so that the pattern transferred onto the transfer target or the mold is effectively damaged. Can be prevented.

Hereinafter, the embodiment for carrying out the present invention will be described more specifically with reference to examples.
Example 1
A first substrate 1a (size 152 mm × 152 mm × thickness 5.00 mm) and a second substrate 1b (size 152 mm × 152 mm × thickness) made of synthetic quartz processed into a predetermined shape, size, and plate thickness 1.30 mm) was prepared.
Both of these two base materials 1a and 1b were mirror-polished using a polishing slurry so that both main surfaces had predetermined smoothness and flatness. In particular, the polishing process was performed so that the flatness of the surface to be the bonding surface of each of the substrates 1a and 1b was 5 μm or less. In addition, polishing was performed so that the surface roughness of both main surfaces of the second substrate 1b was 0.3 nm or less in terms of arithmetic average roughness Ra.

The first base material 1a that had been subjected to the polishing process was formed by punching (that is, forming a hole) a hole 2 having a circular cross section with a diameter of 70 mm centered on the main surface of the base material.
Next, the first base material 1a and the second base material 1b were joined in a high-temperature furnace at 1700 ° C. in a state where the joining surfaces finished to have a flatness of 5 μm or less were overlapped.
As described above, the mask blank substrate of the present invention was produced.

(Example 2)
A first substrate 1a made of synthetic quartz subjected to surface polishing and punching in the same manner as in Example 1, and a second substrate made of synthetic quartz subjected to surface polishing in the same manner as in Example 1. The substrate for mask blank of the present invention was produced by bonding the material 1b using a UV curable adhesive.

(Example 3)
A first substrate 1a made of synthetic quartz subjected to surface polishing and punching in the same manner as in Example 1, and a second substrate made of synthetic quartz subjected to surface polishing in the same manner as in Example 1. The material 1b was joined by a hydrofluoric acid bonding method. A hydrofluoric acid solution (hydrofluoric acid concentration: 5 wt%) is dropped on the joint surface of the second base material 1b, and the joint surfaces of the first base material 1a and the second base material 1b are overlapped to join the base materials. The main surface opposite to the surface was pressed and joined.
As described above, the mask blank substrate of the present invention was produced.

Example 4
A first substrate 1a made of synthetic quartz subjected to surface polishing and punching in the same manner as in Example 1, and a second substrate made of synthetic quartz subjected to surface polishing in the same manner as in Example 1. The material 1b was joined by an optical welding method. However, unlike Example 1, the surface to be the bonding surface of each of the substrates 1a and 1b was polished so that the surface accuracy was λ / 10 and the flatness was 60 nm or less. Then, the bonding surfaces of the first base material 1a and the second base material 1b finished with high surface accuracy (high flatness) are overlapped, and pressure is applied from the main surface opposite to the bonding surfaces of both base materials. And joined.
As described above, the mask blank substrate of the present invention was produced.

(Example 5)
A first base material 1a made of silicon subjected to surface polishing and punching in the same manner as in Example 1, and a second base material made of synthetic quartz subjected to surface polishing in the same manner as in Example 1. 1b was joined by anodic bonding. The anodic bonding method was performed by applying a voltage of 500 V while heating to 1000 ° C.
As described above, the mask blank substrate of the present invention was produced.

(Example 6)
On the front main surface of the mask blank substrate of the present invention obtained in Example 1, using a single-wafer sputtering apparatus, an alloy target (atomic% ratio) of tantalum (Ta) and hafnium (Hf) as a sputtering target. Ta: Hf = 80: 20), an argon gas atmosphere (gas pressure 0.3 Pa), the power of the DC power source is 2.0 kW, and reactive sputtering (DC sputtering) is performed to form a TaHf film (conductive film). A film having a film thickness of 7 nm was formed, and subsequently a CrN film (Cr: N = 80: 20 atomic% ratio) was formed in a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) using a chromium target with a film thickness of 2 A laminated thin film of a TaHf film and a CrN film was formed by forming a film with a thickness of 0.5 nm, and a mask blank used for manufacturing an imprint mold was manufactured.

(Example 7)
An imprint mold was produced as follows using the mask blank obtained in Example 6 above.
An electron beam drawing resist (Fuji Film Electronics Materials PRL009) is applied to a thickness of 50 nm on the upper surface of a mask blank in which a laminated thin film of a TaHf film and a CrN film is formed on the mask blank substrate of the present invention. A baking process was performed to form a resist film on the mask blank.

Next, after drawing a line and space pattern with a half pitch of 20 nm on the resist film of the mask blank using an electron beam drawing machine, the resist film was developed to form a resist pattern.
Next, the mask blank on which the resist pattern is formed is introduced into a dry etching apparatus, and dry etching is performed using a chlorine gas not containing oxygen, whereby the TaHf film and the CrN film are stacked using the resist pattern as a mask. The pattern which consists of this laminated thin film was formed by etching. The etching end point at this time was determined by using a reflection optical end point detector.
Here, the mask blank was once taken out from the dry etching apparatus, and the remaining resist pattern was removed with an aqueous sulfuric acid solution.

Next, the mask blank is again introduced into the same dry etching apparatus, and by performing dry etching using a fluorine-based (CHF ₃ ) gas, the substrate made of synthetic quartz glass is etched using the laminated thin film pattern as a mask, A glass pattern (glass step pattern) was formed.
Here, in order to confirm the cross-sectional shape of the glass pattern, the evaluation blank produced in the same manner as described above was broken, and the pattern cross-section was observed with a scanning electron microscope. It was confirmed that the width was almost the same as the width of the thin film pattern and that the depth of the glass pattern was uniform.

Next, a photoresist (iP3500, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied to a thickness of 460 nm on the mask blank on which the glass pattern was formed, and exposure and development with ultraviolet light were performed to form a resist pattern for a pedestal structure.
Next, with respect to the mask blank on which the resist pattern for the pedestal structure is formed, the laminated thin film other than the portion protected by the resist pattern is removed by wet etching with a ceric ammonium nitrate solution, and hydrofluoric acid and By performing wet etching on a substrate made of synthetic quartz glass with a mixed solution of ammonium fluoride (HF concentration 4.6 wt%, NH ₄ F concentration 36.4 wt%), and further removing the resist pattern with sulfuric acid / hydrogen peroxide, A pedestal structure having a depth of, for example, about 15 μm was produced. Further, the laminated thin film pattern on the glass pattern was removed with a ceric ammonium nitrate solution to obtain an imprint mold (see FIG. 5 (h) described above).

Since the obtained imprint mold had good pattern accuracy of the laminated thin film pattern of the TaHf film and CrN film, a pattern with good dimensions and accuracy was also obtained for the glass pattern.
Next, as shown in FIG. 4 described above, the obtained imprint mold is directly pressed against a resist film (for example, UV curable resin) applied on, for example, a silicon wafer in a transfer target (transfer target). The process of transferring the pattern was repeated, but by using the imprint mold obtained by the present invention, the mold can be easily peeled off with a smaller force at the time of releasing, and the pattern transferred onto the transfer target ( The resist pattern) and the mold were not damaged.

1 Substrate (mask blank substrate)
DESCRIPTION OF SYMBOLS 1a 1st base material 1b 2nd base material 2 Hole 3 Recess 4 Thin film 4a Thin film pattern 5 Resist layer 5a Resist pattern 6 Uneven pattern 7 Resist pattern 8 Base structure 10 Mask blank 11 for imprint mold 11 Pattern formation surface 12 Recess formation Surface 20 Imprint mold 30 Transfer object 31 Transfer object constituting layer 32 Resist film

Claims (11)

A substrate used for a mask blank for forming an imprint mold by etching the thin film and the substrate, comprising a substrate and a thin film formed on the front main surface of the substrate,
The substrate has a recess made of the hole in a region excluding at least the outer peripheral portion thereof on the back main surface of the substrate by bonding at least two substrates including a substrate formed by drilling holes of a predetermined shape. A mask blank substrate, characterized in that is formed.   The mask blank substrate according to claim 1, wherein at least two of the base materials constituting the substrate include at least a base material made of glass.   3. The mask blank substrate according to claim 1, wherein the recess formed in the substrate is formed in a region larger than a mold pattern formation region on the front main surface. 4.   4. The mask blank substrate according to claim 1, wherein the surface roughness of the bottom surface of the recess is an arithmetic average roughness Ra of 0.3 nm or less. 5.   5. The substrate according to any one of claims 1 to 4, wherein the base material formed with holes having a predetermined shape constituting the substrate and the other base material are combined with materials having different thermal expansion coefficients. The mask blank substrate according to one item. A substrate manufacturing method comprising a substrate and a thin film formed on a front main surface of the substrate, the substrate being used as a mask blank for producing an imprint mold by etching the thin film and the substrate. ,
A step of producing a flat plate-like first base material formed by drilling at least one hole having a predetermined shape; the first base material; and at least one flat plate-like second base material; Forming a recess made of the hole in a region excluding at least the outer peripheral portion thereof on the back main surface of the substrate by bonding the substrate.   The mask blank according to claim 6, further comprising a step of finishing the joining surfaces of the first base material and the second base material so as to have a predetermined flatness when joining the first base material and the second base material. A method for manufacturing a substrate.   The method for manufacturing a mask blank substrate according to claim 6 or 7, wherein both the first base material and the second base material are made of glass.   A mask blank for imprint mold, comprising a thin film for pattern formation on the front main surface of the substrate for mask blank according to any one of claims 1 to 5.   An imprint mold manufacturing method comprising: etching the thin film and the substrate in the mask blank for imprint mold according to claim 9. The process of producing the 1st base material formed by drilling the hole of a predetermined shape, and the surface of the 2nd base material using the mask blank provided with the thin film for pattern formation on the surface of the 2nd base material A step of forming a concavo-convex pattern on the substrate, and a step of bonding the first substrate and a surface of the second substrate opposite to the surface on which the concavo-convex pattern is formed. A method for producing a print mold.

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