JP5428513B2 - Method for treating substrate for nanoimprint mold and method for producing nanoimprint mold using the same - Google Patents

Description

  The present invention relates to a method for producing a nanoimprint mold capable of forming a fine pattern and a method for treating a substrate for nanoimprint mold.

In recent years, nanoimprint technology has attracted attention as a next-generation microfabrication technology. The nanoimprint technology is a pattern formation technology that uses a mold member having a fine concavo-convex structure formed on the surface of a substrate, and transfers the concavo-convex structure to a workpiece to transfer the fine structure at an equal magnification. A mold member on which such a fine concavo-convex structure is formed is called a nanoimprint mold (see, for example, Patent Document 1 and Patent Document 2).
The following processes can be mentioned as an example of the manufacturing method of the conventional nanoimprint mold. (1) First, a base material is prepared, (2) a resist film is formed on the base material, and (3) ultraviolet rays having short wavelengths called g-line, h-line and i-line are used for this resist film. A pattern latent image is created by the mask exposure, and (4) the substrate is etched using a resist pattern formed by developing the pattern latent image as a mask to obtain a fine concavo-convex structure. As the pattern size becomes finer, it has become difficult to form a pattern latent image by mask exposure using ultraviolet rays. For this reason, it is required to form a pattern latent image by direct drawing with an electron beam instead of mask exposure.

  In direct drawing with an electron beam, for example, an electron beam drawing apparatus conventionally used for manufacturing a photomask having a highly accurate pattern dimension can be used. In forming a fine pattern in such an electron beam drawing apparatus, it is important to appropriately set the focus position of the electron beam on the substrate surface. For this reason, it is necessary to detect the surface position of the substrate and control the focus position of the electron beam so as to be suitable for the surface position. By repeating the surface position detection and the focus position control while scanning the drawing position, A desired pattern latent image is formed on a predetermined area.

  Here, an example of a drawing procedure in the electron beam drawing apparatus will be described with reference to the drawings. FIG. 10 is a view for explaining the principle of detecting the position of the substrate surface in the electron beam drawing apparatus. As shown in FIG. 10A, a base material 108 is placed on a movable stage 107, and a light source 101 and a light beam detector 102 are disposed obliquely above the base material 108. A light beam (height detection light) emitted from the light source 101 is applied to the base material 108 (incident light A), and the position (for example, peak position) of the light beam (reflected light B) reflected by the surface of the base material 108 is detected. The control unit 109 calculates the position of the base material surface based on the detection, and draws the electron beam focused on the position. Then, as shown in FIGS. 10B and 10C, when the surface position (base material height) of the base material 108 fluctuates, the light beam reflected on the surface of the base material 108 is reflected as reflected light B ′. The peak position of the reflected light detected by the position detector 102 also varies. Since there is a proportional relationship between the height fluctuation amount Δ of the base material 108 and the fluctuation amount δ of the light beam position, the height fluctuation amount Δ of the base material can be detected by measuring the fluctuation amount δ of the light beam position.

US Pat. No. 5,772,905 Special Table 2002-539604

  In the electron beam drawing apparatus as described above, for example, when the height of a base material used in a conventional photomask or the like (so-called 6025 base material: thickness 6.35 mm) is detected, the thickness of the base material is large. The peak positions of the reflected light from the surface of the substrate and the reflected light from the back surface are sufficiently separated, and they were not detected simultaneously by the light beam position detector. This will be described with reference to FIG. When the base material 108 has a sufficient thickness, the incident light A incident obliquely with respect to the base material 108 is reflected by the surface of the base material 108 (surface reflected light B1), and the base position The peak position of the light (reflected return light B <b> 2) incident on 108 and reflected by the back surface of the base material 108 is separated, and these are not simultaneously detected by the light beam position detector 102.

However, in the nanoimprint mold, a transparent substrate (for example, 1 mm or less in thickness) thinner than the 6025 substrate may be used. When such a thin transparent substrate is used as a substrate for a nanoimprint mold and height detection is performed in an electron beam drawing apparatus, reflected light (surface reflected light B1) from the surface of the substrate and the back surface The reflected light (reflected return light B2) approaches and enters the light beam position detector 102 at the same time. This will be described with reference to FIG. As shown in FIG. 12A, when the base material 108 is thin, the peak positions of the surface reflected light B1 and the reflected return light B2 are close to each other, and the light beam position detector 102 detects them simultaneously. As described above, when the position peak of the surface reflected light B1 and the position peak of the reflected return light B2 are simultaneously incident on the light beam detection surface of the light beam position detector 102, the light beam position detector 102 side uses both signals. In order to calculate the height of the material, a value different from the actual height is calculated. That is, as shown in FIG. 12B, the position of the base material is calculated based on the peak position of the apparent reflected light B ″, and is lower than the actual position as shown by a two-dot chain line in the drawing. Accordingly, there is a problem in that the focus of the electron beam does not coincide with the surface of the base material 108 and drawing cannot be performed with a desired accuracy.
The present invention has been made in view of the above-described circumstances, and when a pattern is drawn on a resist with an electron beam, processing of the substrate for nanoimprint mold for accurately detecting the surface position of the substrate It is an object of the present invention to provide a method and a manufacturing method for manufacturing a nanoimprint mold having a highly accurate uneven pattern.

In order to achieve such an object, the nanoimprint mold substrate processing method of the present invention is a transparent nanoimprint mold substrate processing method having a thickness of 4 mm or less, and at least a part of the back surface side of the substrate. Or an antireflection part for preventing detection light incident on the base material from the front surface side of the base material from being reflected on the back surface of the base material and emitted to the front surface side in at least a part of the inside of The antireflection portion is an optical base material in which the spread of the detection light (Gaussian beam or Gaussian beam approximating the intensity distribution of the detection light with Gaussian) is a, and the incident angle to the surface of the base material is θ. In the surface position detection mechanism, the thickness from the substrate surface to the antireflection portion is D, the refractive index of the substrate is ns, the reflected light from the substrate surface and the interface between the antireflection portion and the substrate or Opposite from the back of the substrate Is the intensity ratio between the return light alpha, cross-sectional intensity distribution of the Gaussian beam to be synthesized
f = exp (-x ² / a ² ) + αexp (-(x-d) ² / a ² )
Here, d is the amount of positional deviation between the reflected light and the reflected return light,
d = 2D cos θ tan (sin ⁻¹ (sin θ / ns))
In the system represented by
A range of the intensity ratio α is obtained such that a value obtained by multiplying the value of X at which the differential value of the cross-sectional intensity distribution profile is 0 by 1 / (2 tan θcos θ) is 10 μm or less, and the intensity of the reflected return light is the intensity ratio α and an antireflection structure and to so that configuration to satisfy the range of.

As another aspect of the present invention, the back surface of the base material is roughened to form the antireflection portion.
As another aspect of the present invention, an antireflection layer is provided on the back surface of the base material to form the antireflection portion, the refractive index n of the antireflection layer is 1.35 or less, and the wavelength of the detection light is When λ, the thickness L of the antireflection layer is determined from the phase condition:
nL = (2m−1) λ / 4 (m is an integer)
To satisfy the requirements.
Further, as another aspect of the present invention, an antireflection layer is laminated on the back surface of the base material to form an antireflection portion having a two-layer structure, and the reflection of each layer so as to satisfy the amplitude condition and the phase condition in the two-layer structure. It was set as the structure which sets the refractive index and thickness of a prevention layer.
As another aspect of the present invention, a light absorption layer is provided on the back surface of the base material to form the antireflection portion, and the difference from the refractive index of the base material is ± 25%. A material having the following refractive index was used, and the light absorption layer was formed so that the absorbance with respect to the detection light satisfies the intensity ratio α.
As another aspect of the present invention, the antireflection portion is formed by forming a low light transmittance layer inside the base material.
The nanoimprint mold substrate treatment method of the present invention is a transparent nanoimprint mold substrate treatment method having a thickness of 4 mm or less, wherein at least a part of the back side of the substrate, or at least a part of the interior of the substrate. An antireflection portion is provided in the region to prevent detection light incident on the base material from the front surface side of the base material from being reflected from the back surface of the base material and emitted to the front surface side, and the antireflection portion is provided on the base material. The back surface was provided with a rough surface.
The nanoimprint mold substrate treatment method of the present invention is a transparent nanoimprint mold substrate treatment method having a thickness of 4 mm or less, wherein at least a part of the back side of the substrate, or at least a part of the interior of the substrate. An antireflection portion is provided in the region to prevent detection light incident on the base material from the front surface side of the base material from being reflected from the back surface of the base material and emitted to the front surface side, and the antireflection portion is provided on the base material. It was set as the structure provided by arrange | positioning the light absorption layer in the back surface.
The nanoimprint mold substrate treatment method of the present invention is a transparent nanoimprint mold substrate treatment method having a thickness of 4 mm or less, wherein at least a part of the back side of the substrate, or at least a part of the interior of the substrate. An antireflection portion is provided in the region to prevent detection light incident on the base material from the front surface side of the base material from being reflected from the back surface of the base material and emitted to the front surface side, and the antireflection portion is provided on the base material. It was set as the structure provided by forming a low light transmittance layer in the inside.

  The method for producing a nanoimprint mold of the present invention comprises a step of forming an antireflection part by a treatment method for a substrate for nanoimprint mold on a transparent substrate having a thickness of 4 mm or less, and a surface of the substrate. Forming a resist film on the stage in the electron beam lithography apparatus, placing the base material so that the back surface of the base material faces the stage, and irradiating the base material with height detection light The height detection light detects the reflected light reflected on the surface of the base material to detect the height of the base material, and the electron beam focus position is adjusted so as to be suitable for the detected surface position of the base material. Irradiating an electron beam to the resist film while controlling to form a desired pattern latent image, and forming a concavo-convex pattern on the substrate using the resist pattern obtained by developing the resist film as a mask Process and It was configured such that.

According to the method for treating a substrate for nanoimprint mold of the present invention, by providing an antireflection part on the substrate, the detection light irradiated on the surface of the substrate is reflected on the back surface of the substrate and emitted to the surface. Therefore, the detection can be equivalent to the detection of the surface position by only the reflected light reflected from the substrate surface (peak position of the surface reflected light) among the detection light irradiated on the surface of the substrate. In addition, it is possible to accurately detect the surface position of the nanoimprint mold substrate using detection light.
According to the method for producing a nanoimprint mold of the present invention, the height detection light applied to the surface of the base material is reflected on the back surface of the base material and emitted to the front surface when the pattern is drawn on the resist film by the electron beam. The anti-reflection part suppresses the peak position of the reflected light on the surface, so that the surface position of the base material can be detected with high accuracy by the detection light. It is prevented, pattern drawing can be performed with high accuracy, and a nanoimprint mold having a highly accurate uneven pattern can be manufactured.

It is sectional drawing which shows an example of the nanoimprint mold manufactured by this invention. It is sectional drawing which shows the other example of the nanoimprint mold manufactured by this invention. It is a figure for demonstrating arrangement | positioning of the reflection preventing part in the nanoimprint mold manufactured by this invention. It is sectional drawing for demonstrating an example of the reflection preventing part which comprises the nanoimprint mold manufactured by this invention. It is sectional drawing for demonstrating the other example of the reflection preventing part which comprises the nanoimprint mold manufactured by this invention. It is sectional drawing for demonstrating the other example of the reflection preventing part which comprises the nanoimprint mold manufactured by this invention. It is sectional drawing for demonstrating the other example of the reflection preventing part which comprises the nanoimprint mold manufactured by this invention. It is sectional drawing for demonstrating the other example of the reflection preventing part which comprises the nanoimprint mold manufactured by this invention. It is process drawing for demonstrating one Embodiment of the manufacturing method of the nanoimprint mold of this invention. It is drawing explaining the principle which detects the position of the base-material surface in an electron beam drawing apparatus. It is drawing explaining the height detection of the 6025 base material in an electron beam drawing apparatus. It is drawing explaining the height detection of the base material for nanoimprint molds in an electron beam drawing apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the nanoimprint mold manufactured by the present invention will be described.
FIG. 1 is a cross-sectional view showing an example of a nanoimprint mold produced by the present invention. In FIG. 1, a nanoimprint mold 1 has a transparent base material 2, an uneven pattern 3 formed on the surface 2a side of the base material 2, and an antireflection part 4 formed on the back surface 2b side of the base material. doing. Moreover, the nanoimprint mold manufactured by this invention may be equipped with the reflection preventing part 4 inside the base material 2, as shown in FIG.

  The antireflection part 4 prevents light incident on the base material 2 from the front surface 2a side of the base material 2 from being reflected by the back surface 2b of the base material 2 and emitted to the front surface 2a side. Such an antireflection part 4 is arranged in at least a part of the back surface 2 b side of the base material 2 or in at least a part of the inside of the base material 2. FIG. 3 is a view for explaining the arrangement of the antireflection part 4, and the arrangement part of the antireflection part 4 is indicated by hatching. As shown in FIG. 3A, the antireflection portion 4 may be arranged so as to include a region where the concave / convex pattern 3 is formed (a region surrounded by a chain line). Further, as shown in FIG. 3B, even if the concave / convex pattern 3 is formed so as to surround the concave / convex pattern 3 in a portion excluding the region where the concave / convex pattern 3 is formed (region surrounded by a chain line). Good. Further, as shown in FIG. 3 (C), it may be partially arranged so as to surround the uneven pattern 3 in a portion excluding the region where the uneven pattern 3 is formed (region surrounded by a chain line). . Of course, the antireflection part 4 may be arranged in the whole area of the back surface 2b of the base material 2 or in the whole area inside the base material 2.

Such an antireflection portion 4 can be a rough surface portion 11 provided on the back surface 2b of the substrate 2 as shown in FIG.
Moreover, the antireflection part 4 can be an antireflection layer 12 provided on the back surface 2b of the substrate 2 as shown in FIG.
Further, as shown in FIG. 6, the antireflection portion 4 may have a two-layer structure including antireflection layers 13 a and 13 b laminated on the back surface 2 b of the substrate 2.
Moreover, the antireflection part 4 can be a light absorption layer 14 provided on the back surface 2b of the substrate 2 as shown in FIG.
Furthermore, the antireflection part 4 can be a low light transmittance layer 15 located inside the substrate 2 as shown in FIG.
Such a nanoimprint mold can solve the problem of focus shift occurring at the time of electron beam drawing in the manufacturing stage, and can form a fine pattern with high accuracy. In addition, at the inspection stage, it is possible to eliminate the problem of focus shift on the inspection surface and to inspect even a fine pattern with high accuracy. Furthermore, at the time of imprinting, the height position between the mold and the substrate can be grasped with high accuracy, and imprinting can be performed efficiently.

[Method of processing substrate for nanoimprint mold]
Next, the processing method of the base material for nanoimprint molds of this invention is demonstrated.
In the present invention, the transparent nanoimprint mold base material having a thickness of 4 mm or less is incident on the base material from the front surface side of at least a part of the back surface side or at least a part of the inside of the base material. An antireflection part for preventing light from being reflected from the back surface of the base material and emitted to the front surface side is provided.
Examples of the substrate to which the treatment method of the present invention is applied include quartz glass, silicate glass, calcium fluoride, Pyrex (registered trademark) glass, soda glass, soda glass, BK-7, and the like. The thickness of the substrate is 4 mm or less, and can be set as appropriate depending on the use of the nanoimprint mold. The lower limit of the thickness is not particularly limited, and the shape and dimensions of the uneven pattern formed on the nanoimprint mold and the strength of the substrate. It can be set in consideration of handling aptitude and the like. In addition, even if it is a case where the thickness of a base material exceeds 4 mm, it is possible to apply the processing method of this invention. However, when the thickness of the substrate exceeds 4 mm, the thickness of the substrate becomes sufficient, and as described with reference to FIG. 11, the peak position of the surface reflected light and the peak position of the reflected return light are separated. Thus, these are not simultaneously detected by the light beam position detector. Therefore, there is no need to apply the processing method of the present invention.

The anti-reflective part formed on the back side of the base material is reflected by the back surface when the height detection light irradiated on the base material surface is detected to detect the surface position of the base material in the nanoimprint mold manufacturing process. Thus, it is prevented from emitting to the surface side. This antireflection portion is a surface of an optical base material in which the spread of the detection light (Gaussian beam or a Gaussian beam obtained by approximating the intensity distribution of the detection light with Gaussian) is a, and the incident angle to the surface of the base material is θ. In the position detection mechanism, the thickness from the substrate surface to the antireflection portion is D, the refractive index of the substrate is ns, the reflected light from the substrate surface and the interface between the antireflection portion and the substrate, or the substrate The intensity ratio with the reflected return light from the back surface is α, and the cross-sectional intensity distribution of the synthesized Gaussian beam is f = exp (−x ² / a ² ) + αexp (− (x−d) ² / a ² )
Here, d is the amount of positional deviation between the reflected light and the reflected return light,
In a system represented by d = 2D cos θ tan (sin ⁻¹ (sin θ / ns)),
A range of the intensity ratio α is obtained such that a value obtained by multiplying the value of X at which the differential value of the cross-sectional intensity distribution profile is 0 by 1 / (2 tan θcos θ) is 10 μm or less, and the intensity of the reflected return light is the intensity ratio α An antireflection structure that satisfies this range is adopted.

  The antireflection part having such an antireflection structure is disposed in at least a partial region on the back surface side of the substrate or in at least a partial region inside the substrate. For example, the antireflection part can be disposed on the entire back surface of the substrate or the entire interior of the substrate. Further, as shown in FIG. 3 in the description of the nanoimprint mold described above, the antireflection portion 4 may be formed so as to include a region for forming the concave / convex pattern 3 in a later process (see FIG. 3A). ), The antireflection portion 4 may be formed in a corridor shape so as to surround this region at a position excluding the region for forming the concavo-convex pattern 3 in a later step (see FIG. 3B). The antireflection portion 4 may be partially formed so as to surround this region at a position excluding the region for forming the uneven pattern 3 in the process (see FIG. 3C). Thus, the formation position of the antireflection part is not particularly limited. However, if there is a variation due to the shape such as warpage or distortion in the base material used, the surface position of the base material can be detected in the region itself for forming the concave / convex pattern 3 in the subsequent process or in the vicinity of this region. It is preferable to form the antireflection part 4 on the surface.

  Here, a method of forming the antireflection portion will be described with reference to FIGS. 4 to 8 described above. In addition, about the same member as the above-mentioned nanoimprint mold, it demonstrates using the same member number. In the processing method of the present invention, as shown in FIG. 4, the back surface 2 b of the base material 2 is roughened to form the rough surface portion 11, thereby forming the antireflection portion 4. Roughening for forming the rough surface portion 11 can be performed using, for example, mechanical polishing, sandblast polishing, chemical etching, or the like. The degree of roughening can be set, for example, so that the average roughness Ra is 0.1 to 100 μm, preferably 0.5 to 10 μm, more preferably about 1 to 2 μm. When the average roughness Ra of the rough surface portion 11 is less than 0.1 μm, the antireflection structure as described above is not obtained and a sufficient antireflection effect cannot be obtained. On the other hand, if the average roughness Ra exceeds 100 μm, the function of the antireflection part 4 can be obtained, but the rigidity of the mold itself is insufficient, and problems such as distortion at the time of imprinting may occur. In addition, average roughness Ra shall be measured with the level | step difference measuring device DEKTAK8000 by ULVAC. Such a rough surface portion 11 can scatter light incident on the substrate 2 from the surface 2a side of the substrate 2 and has a low reflectance. Therefore, it is effective for a plurality of manufacturing apparatuses and inspection apparatuses having different detection light wavelengths.

Further, in the treatment method of the present invention, as shown in FIG. 5, an antireflection layer 12 having a refractive index smaller than the refractive index of the base material 2 is formed on the back surface 2 b of the base material 2 and the antireflection portion 4 and can do. This antireflection layer 12 can be provided with the antireflection structure as described above by setting the refractive index and thickness within a specific range as follows. That is, the refractive index of the antireflection layer 12 is 1.35 or less, preferably about ns ^1/2 from the amplitude condition, for example, ns ^1/2 when the refractive index of the substrate 2 is ns. It is about ± 10%. The refractive index can be measured by a commercially available ellipsometer. Such an antireflection layer 12 is, for example, a method of applying and drying (curing) a material such as fluorine resin, Teflon (registered trademark) AF, Cytop (registered trademark) by a coating method such as spin coating. Further, it can be formed by a vacuum film forming method such as an ionized vapor deposition method. Further, the thickness L of the antireflection layer 12 is determined from the phase condition when the wavelength of the detection light is λ.
nL = (2m−1) λ / 4 (m is an integer)
Can be set to satisfy. Therefore, the thickness at which the reflectivity is minimal exists periodically, and the thickness L of the antireflection layer 12 is appropriately set within a range of ± 0.03 μm, preferably ± 0.02 μm, relative to the minimum thickness. be able to. Also, under this phase condition, there is a wavelength at which the reflectance is minimal on the short wavelength side for a certain thickness. That is, the antireflection layer 12 can exhibit a low reflection function due to thin film interference for multiple wavelengths by adjusting the refractive index and thickness. Therefore, it is effective for a plurality of manufacturing apparatuses and inspection apparatuses having different detection light wavelengths.

Further, in the treatment method of the present invention, as shown in FIG. 6, the antireflection layer 4 having a two-layer structure may be formed by laminating antireflection layers 13a and 13b on the back surface 2b of the substrate 2. The antireflection part 4 having such a two-layer structure can appropriately set the refractive index and the thickness so as to satisfy the amplitude condition and the phase condition in the two-layer structure. For example, when the surrounding is air (refractive index n ₁ = 1), the refractive index and thickness of the antireflection layer 13a constituting the antireflection part 4 having the two-layer structure are set to n ₁ and L ₁ , and the antireflection layer 13b. When the refractive index and thickness of the substrate 2 are n ₂ and L _2, and the refractive index of the substrate 2 is n _s , the substrate 2 is formed with a thickness of n ₁ L ₁ = n ₂ L ₂ = λ / 4. The reflectance R of
_{R = [1-n s (} n 2 / n 1) 2] 2 / [1 + n s (n 2 / n 1) 2] 2
Given in. In order to set the reflectance R to 0, a material may be selected so that n _s (n ₂ / n ₁ ) ² becomes 1. Here, a case is described in which a transparent material with negligible absorption is used and a laminated structure is formed with a thickness of n ₁ L ₁ = n ₂ L ₂ = λ / 4. The material and thickness can be set as appropriate by calculation of a characteristic matrix defined by constants. The antireflection part 4 having such a two-layer structure can be formed by a method of applying and drying (curing) by a coating method such as spin coating, using a selected material, and a vacuum film forming method such as sputtering. .

  Moreover, in the processing method of this invention, as FIG. 7 shows, the light absorption layer 14 can be provided in the back surface 2b of the base material 2, and it can be set as the reflection preventing part 4. FIG. This light absorbing layer 14 is coated by a coating method such as spin coating and dried using a light absorbing material whose difference from the refractive index of the substrate 2 is ± 25% or less, preferably ± 20% or less. It can be formed by a (curing) method or a vacuum film forming method such as sputtering. When the light incident on the light absorption layer 14 is attenuated, the increase / decrease in the reflectance due to the thin film interference depending on the film thickness is eliminated, so that the difference between the refractive index of the light absorption layer 14 and the refractive index of the substrate 2 increases. The reflection at the interface between the substrate 2 and the light absorption layer 14 is increased. When the difference between the refractive index of the light absorption layer 14 and the refractive index of the substrate 2 exceeds ± 25%, even if the light absorption layer 14 absorbs almost 100% light, the antireflection structure as described above is not obtained. A sufficient antireflection effect cannot be obtained.

The effect of the light absorption layer 14 is determined by appropriately setting the absorption coefficient and thickness. That is, since the light absorption layer 14 changes the degree of light absorption depending on the absorption coefficient and thickness of the material, the light absorption layer 14 is preferably defined by the absorbance determined by the thickness and the absorption coefficient. For this reason, the light absorption layer 14 is formed so as to satisfy the above-described intensity ratio α (having an antireflection structure). Such a light absorption layer 14 can be formed using materials, such as a pigment resist containing red absorption organic pigment pigment | dyes, such as a phthalocyanine compound, anthraquinone compound, and a naphthoquinone compound, for example.
As described above, the refractive index of the light absorption layer 14 is close to the refractive index of the substrate 2 (matching the refractive index), and the absorbance of the light absorption layer 14 is in a predetermined range, so that the reflection prevention as described above is performed. Since it has a structure, a low reflection effect is expressed. Therefore, it is effective for a plurality of manufacturing apparatuses and inspection apparatuses having different detection light wavelengths.

  Furthermore, in the processing method of the present invention, as shown in FIG. 8, the low light transmittance layer 15 can be formed inside the base material 2 to form the antireflection portion 4. The light transmittance of the low light transmittance layer 15 can be about 5 to 68% of the light transmittance of the substrate 2. When the light transmittance of the low light transmittance layer 15 exceeds 68% of the light transmittance of the base material 2, the antireflection structure as described above is not obtained and a sufficient antireflection effect cannot be obtained. If the ratio is less than 5%, the surface position can be detected with extremely high accuracy, but the transfer resin curing time in the imprint process becomes long and the throughput is low, so that it is not suitable as an imprint mold. Become. Such a low light transmittance layer 15 can be a layer in which the optical properties of the substrate 2 are changed by converging laser light inside the substrate 2. Specifically, the layer 2 can be made opaque by causing dielectric breakdown to the base material 2 by laser light. In this case, a YAG laser, a YLF laser, or the like can be used as the laser light, and the laser light is irradiated under conditions that cause dielectric breakdown of the base material at the converged site. The thickness causing dielectric breakdown can be set, for example, in the range of 100 μm or more and not more than the thickness of the substrate 2.

Moreover, the low light transmittance layer 15 can be a layer in which bubbles having an average diameter of about 10 to 100 μm are densely or scattered on the base material 2. In this case, it is necessary to form bubbles when the substrate 2 is produced. As a method for forming bubbles, there is, for example, a method in which silicon nitride is added to silica powder and molded and heated in a nitrogen atmosphere. The number of closed cells can be set, for example, in the range of 3 × 10 ^{5 to} 5 × 10 ⁶ / cm ³ , and the bubble density in the thickness direction may have a gradient. The number of closed cells can be measured using a polarizing microscope having a scaled lens. Such a low light transmittance layer 15 has an antireflection structure as described above, and exhibits low light transmittance with respect to multiple wavelengths. Therefore, for a plurality of manufacturing apparatuses and inspection apparatuses having different wavelengths of detection light, It is effective.

According to such a processing method of the present invention, by providing an antireflection part on the base material, it is possible to suppress detection light irradiated on the surface of the base material from being reflected on the back surface of the base material and emitted to the surface. Can do. When the antireflection part is not formed on the base material, as shown in FIG. 12 (B), the detection light A irradiated onto the base material 2 is a surface reflected light B1 reflected by the surface 2a of the base material 2, and It is detected as reflected return light B2 reflected by the back surface 2b of the substrate 2. That is, the position of the substrate 2 is calculated from the peak position of the combined light (apparent reflected light) B ″ of the surface reflected light B1 and the reflected return light B2. Therefore, the deviation between the combined light B ″ and the surface reflected light B1 is calculated. The smaller the amount d ′, the higher the detection accuracy of the surface position of the substrate 2. Then, the combined light B ″ approaches the surface reflected light B1 as the intensity of the reflected return light B2 decreases, and the shift amount d ′ decreases. In the present invention, the reflected return light B2 is provided by the antireflection portion provided on the base material. Accordingly, the above-described deviation d ′ is extremely small, and therefore, of the detection light irradiated on the surface of the base material, the reflected light reflected on the base material surface (the peak of the surface reflected light) It becomes possible to detect the surface position of the nanoimprint mold substrate using the detection light with high accuracy by detecting the surface position only by the position).

When the thickness of the base material 2 is sufficiently large like the 6025 base material (thickness 6.35 mm), the surface reflected light B1 and the reflected return light B2 are sufficiently separated, and only the peak position of the surface reflected light B1 is present. Is detected, and the positional deviation amount d between the surface reflected light B1 and the reflected return light B2 can be ignored (see FIG. 11).
The above-described embodiment is an exemplification, and the present invention is not limited to this.

[Production method of nanoimprint mold]
Next, the manufacturing method of the nanoimprint mold of this invention is demonstrated.
FIG. 9 is a process diagram for explaining an embodiment of a method for producing a nanoimprint mold of the present invention.
In the present invention, first, the antireflection portion 4 is formed on the back surface 2b side of the transparent substrate 2 (FIG. 9A). Examples of the substrate 2 to be used include quartz glass, silicate glass, calcium fluoride, Pyrex (registered trademark) glass, blue plate glass, soda glass, and BK-7. The thickness of the base material 2 is 4 mm or less, and can be appropriately set depending on the use. The lower limit of the thickness is not particularly limited, and the shape, dimensions, strength of the base material, suitability for handling, etc. are considered. Can be set.
Formation of the antireflection part 4 can be performed by the above-described processing method of the present invention, and the description thereof is omitted here.
Even when the thickness of the substrate 2 exceeds 4 mm, the nanoimprint mold can be manufactured by the manufacturing method of the present invention. However, when the thickness of the base material 2 exceeds 4 mm, the thickness of the base material becomes sufficient, and as described with reference to FIG. 11, the peak position of the surface reflected light and the peak position of the reflected return light are separated. Thus, these are not simultaneously detected by the light beam position detector. Therefore, it is not necessary to apply the manufacturing method of the present invention.

As the next step, a resist film 7 is formed on the surface of the base material 2 via the chromium thin film 6, and the back surface 2b of the base material 2 faces the stage on a stage (not shown) in the electron beam drawing apparatus. The base material 2 is arrange | positioned so that it may do (FIG. 9 (B)). Note that the resist film 7 may be formed without using the chromium thin film 6.
Next, the base material 2 is irradiated with height detection light, and the height detection light detects reflected light (the peak position of the surface reflection light) reflected by the surface 2 a of the base material 2 to detect the height of the base material 2. Then, the resist film 7 is irradiated with an electron beam while controlling the focus position of the electron beam so as to be suitable for the detected surface position of the substrate 2 to form a desired pattern latent image.
Next, the resist film 7 is developed to form a resist pattern 8 (FIG. 9C), and the concave / convex pattern 3 is formed on the substrate 2 using the resist pattern 8 as a mask. Then, the nanoimprint mold 1 is obtained by removing the resist pattern 8 and the chromium thin film 6 which became unnecessary (FIG.9 (D)). Formation of the concavo-convex pattern 3 using the resist pattern 8 as a mask can be performed using, for example, chemical etching, reactive ion etching, or the like. The dimensions and the like of the concavo-convex pattern can be set as appropriate depending on the application.

According to the method for producing a nanoimprint mold of the present invention, the height detection light irradiated on the surface of the base material is reflected on the back surface of the base material when the pattern is drawn on the resist film with an electron beam, and is reflected on the surface. The antireflection part suppresses emission. For this reason, since the peak position of surface reflected light is detected reliably, the surface position of the base material by detection light can be detected accurately. Thereby, pattern drawing with high precision is possible, and a nanoimprint mold provided with a high-precision uneven pattern can be manufactured.
The above-described embodiment is an exemplification, and the present invention is not limited to this.

Next, the present invention will be described in more detail by showing more specific examples.
[Example 1]
Quartz glass having a thickness of 675 μm (manufactured by Atock Co., Ltd., synthetic quartz wafer, refractive index 1.45) was prepared as a base material for a nanoimprint mold. The back surface of this base material was roughened by mechanical polishing to form a rough surface portion (antireflection portion). Here, by changing the level of the roughening treatment, rough surface portions having various average roughness Ra as shown in Table 1 below are formed, and five types of base materials (Sample 1-2 to Sample 1) are formed. -6) was produced. The average roughness Ra was measured using a step measuring device DEKTAK8000 manufactured by ULVAC.
In addition, as a base material for comparison, a 6025 base material (thickness 6.35 mm) was prepared.
Next, a chromium thin film (thickness 5 nm) was formed on the surface of each substrate by sputtering, and then a resist (ZEP520A manufactured by Nippon Zeon Co., Ltd.) was spin-coated on the chromium thin film.

Next, the base material is arranged on the stage in the electron beam drawing apparatus (JBX9000 manufactured by JEOL Ltd.) so that the back surface of the base material faces the stage, and the detection light is incident on the base material at an incident angle of 70 °. (Wavelength 600-800 nm) was irradiated, and the reflected light was detected with a photodetector. Then, using the beam shape and the reflectance and transmittance of the substrate as parameters, the composition of the Gaussian beam (Gaussian beam) (f = exp (-x ² / a ² ) + αexp (-(x-d) ² / a ² ), the shift amount d ′ between the peak position of the synthesized light B ″ calculated by the beam shape a = 0.5) and the peak position of the surface reflected light B1 (see FIG. 12B), and the height of the base material The amount of deviation ΔD was calculated and shown in the following Table 1. In addition, in order to detect the surface position of the substrate with high accuracy, it is necessary that the amount of deviation ΔD of the substrate is 10 μm or less. The same applies to the following embodiments.

As shown in Table 1, in Sample 1-3 to Sample 1-7 having a rough surface portion with an average roughness Ra in the range of 0.1 to 100 μm, the height deviation amount ΔD of the base material is 10 μm or less. It was confirmed that the surface position of the base material can be detected with extremely high accuracy.
On the other hand, in the sample 1-1 that has not been subjected to the roughening treatment and the sample 1-2 in which the average roughness Ra is less than 0.1 μm, the height deviation amount ΔD of the base material exceeds 10 μm. It was.

[Example 2]
The same quartz glass as in Example 1 was prepared as a base material for a nanoimprint mold. Teflon (registered trademark) AF was applied to the back surface of the base material by spin coating and formed into a film to form an antireflection layer (antireflection portion). The refractive index of this antireflection layer was 1.3. Here, the thickness of the antireflection layer was changed, and five types of base materials (Sample 2-2 to Sample 2-6) shown in Table 2 below were produced. That is, when the thickness L of the antireflection layer is n = 1.3 and the wavelength of the detection light is λ (680 nm), from the phase condition,
nL = (2m−1) λ / 4 (m is an integer)
Therefore, the thicknesses of the antireflection layers of Sample 2-3 to Sample 2-5 are the thickness L of the antireflection layer satisfying the above formula (L = 0.0 when m = 1). 13 μm) within a range of ± 0.04 μm. In Samples 2-2 and 2-6, the thickness of the antireflection layer was set so as to be out of the range of ± 0.04 μm of the thickness L of the antireflection layer that satisfied the above formula.

Further, assuming that the materials used for forming the antireflection layer are those shown in Table 2 below, the refractive index of the antireflection layer is changed, and two kinds of base materials shown in Table 2 below (Sample 2-7 to Sample 2) -8) was produced. The thickness of the antireflection layer is n = 1.35, n = 1.4, and when the wavelength of the detection light is λ (680 nm), respectively, from the phase condition,
nL = (2m−1) λ / 4 (m is an integer)
The thickness L of the antireflection layer satisfying the above was set.
Next, for each base material, in the same manner as in Example 1, the shift amount d ′ between the peak position of the synthesized light B ″ and the peak position of the surface reflected light B1 and the height shift amount ΔD of the base material are calculated. The results are shown in Table 2 below.

As shown in Table 2, Sample 2-3 to Sample 2-5, and Sample 2-7, in which the thickness of the antireflection layer is in the range of ± 0.04 μm of the thickness L of the antireflection layer satisfying the above formula, The height deviation amount ΔD of the base material is 10 μm or less, and it was confirmed that the surface position of the base material can be detected with extremely high accuracy.
On the other hand, Sample 2-2 and Sample 2-6 in which the thickness of the antireflection layer deviates from the range of ± 0.04 μm of the thickness L of the antireflection layer satisfying the above formula does not form the antireflection layer. Although the height deviation amount ΔD of the substrate was smaller than that of the sample 2-1, the value exceeded 10 μm.
Further, Sample 2-8 in which the refractive index of the antireflection layer exceeds 1.35 is the thickness L of the antireflection layer satisfying the above formula, but the height deviation amount ΔD of the base material is less. Since it exceeds 10 μm, it is difficult to detect the surface position of the substrate with high accuracy.

Here, from the refractive index ns = 1.45 of the used base material, assuming an antireflection layer made of a material having a refractive index of 1.2 corresponding to ns ^1/2 from the amplitude condition, the thickness L of the antireflection layer is , N = 1.2, detection light wavelength λ = 680 nm), from the phase condition,
nL = (2m−1) λ / 4 (m is an integer)
When m = 1, the thickness L of the antireflection layer is 0.142 μm, and at this time, the height deviation amount ΔD of the base material is 0 μm. Therefore, it is important to select a material closer to the refractive index satisfying the amplitude condition for the antireflection film, which means that the above-described base materials of Sample 2-3 to Sample 2-5 and Sample 2-7 are high. It is clear from the comparison of the height deviation amount ΔD of the base material of Sample 2-8 with respect to the deviation amount ΔD.

[Example 3]
The same quartz glass as in Example 1 was prepared as a base material for a nanoimprint mold. A magnesium oxide (refractive index: 1.70) or chromium (refractive index: 2.51) film was formed on the back surface of the base material by sputtering to form a first antireflection layer. Next, Teflon (registered trademark) AF is applied onto the antireflection layer by spin coating to form a second antireflection layer (refractive index: 1.3). As a result, two types of base materials (Sample 3-1 to Sample 3-2) were prepared.
In the formation of the antireflection portion having the two-layer structure, the thickness is determined by using the characteristic matrix defined by the optical constants of the thin film so as to satisfy the amplitude condition and the phase condition in the two-layer structure. It set as shown in.
Next, for each base material, in the same manner as in Example 1, the shift amount d ′ between the peak position of the synthesized light B ″ and the peak position of the surface reflected light B1 and the height shift amount ΔD of the base material are calculated. The results are shown in Table 3 below.

  As shown in Table 3, by making the antireflection part into a two-layer structure, the reflectance can be made almost zero, and the height deviation amount ΔD of the base material is 0 μm, and the base material is extremely highly accurate. It was confirmed that the surface position could be detected.

[Example 4]
The same quartz glass as in Example 1 was prepared as a base material for a nanoimprint mold. The back surface of this base material is coated with a pigment resist containing a red-absorbing organic pigment dye by spin coating to form a light-absorbing layer (antireflection part), and six types of base materials shown in Table 4 below are formed. (Sample 4-2 to Sample 4-7) were produced. Here, three types of pigment resists having different absorption coefficients were used as the pigment resists, and the thickness of the light absorption layer was changed for each pigment resist. The refractive index of the light absorbing layer was 1.45 regardless of which pigment resist was used. Thus, since the refractive index of the light absorption layer was set to 1.45, which is the same as that of the base material, the reflectance at the interface between the light absorption layer and the base material could be almost zero. The absorbance of each light absorbing layer is shown in Table 4 below.
Moreover, the light absorption layer was formed using the material which has a refractive index different from the refractive index (1.45) of a base material, and 2 types of base materials (sample 4-8, sample 4-9) were produced. In addition, the thickness of the light absorption layer was set to 5 μm so that the light absorption ability was almost saturated in both the samples 4-8 and 4-9.
Next, for each base material, in the same manner as in Example 1, the shift amount d ′ between the peak position of the synthesized light B ″ and the peak position of the surface reflected light B1 and the height shift amount ΔD of the base material are calculated. The results are shown in Table 4 below.

As shown in Table 4, Sample 4-3, Sample 4-5, and Sample 4-7, in which the absorbance of the light absorption layer is 0.39 or more, have a height deviation amount ΔD of the substrate of 10 μm or less, It was confirmed that the surface position of the substrate can be detected with extremely high accuracy.
On the other hand, Sample 4-2, Sample 4-4, and Sample 4-6, in which the absorbance of the light absorption layer is less than 0.39, are the base materials compared to Sample 4-1 that does not form the light absorption layer. Although the height deviation amount ΔD was small, the value exceeded 10 μm.
Sample 4-8 in which the refractive index of the light absorption layer is in the range of 1.09 to 1.82 (the difference from the refractive index of the base material 1.45 is ± 25% or less) is the height of the base material. The deviation amount ΔD was 10 μm or less, and it was confirmed that the surface position of the substrate could be detected with extremely high accuracy.
On the other hand, in the sample 4-9 in which the refractive index of the antireflection layer is out of the above range (the difference from the refractive index of the base material is ± 25% or less), the height deviation amount ΔD of the base material exceeds 10 μm. It was a thing.

[Example 5]
The same quartz glass as in Example 1 was prepared as a base material for a nanoimprint mold. From the surface of the base material, laser light was converged inside the base material with an energy of 400 μJ to cause dielectric breakdown, and a low light transmittance layer (antireflection portion) was formed at a depth of 100 to 500 μm. Here, four types of base materials (samples 5-2 to 5-5) having different light transmittances were produced by changing the laser irradiation conditions to control the thickness of the low light transmittance layer. The light transmittance of the substrate was measured using a light transmittance measuring device (MCPD manufactured by Otsuka Electronics Co., Ltd.).
Next, for each base material, in the same manner as in Example 1, the shift amount d ′ between the peak position of the synthesized light B ″ and the peak position of the surface reflected light B1 and the height shift amount ΔD of the base material are calculated. The results are shown in Table 5 below.

As shown in Table 5, Sample 5-3 to Sample 5-5 having a light transmittance in the range of 5 to 68% have a substrate height deviation amount ΔD of 10 μm or less, and extremely high accuracy. It was confirmed that the surface position of the substrate could be detected.
On the other hand, the sample 5-2 whose light transmittance is out of the above range has a smaller height deviation amount ΔD of the base material than the sample 5-1 in which the dielectric breakdown layer is not formed, but the value thereof is It exceeded 10 μm. In addition, the substrate with a light transmittance of less than 5% can detect the surface position with extremely high accuracy. However, since the time for curing the transfer resin in the imprint process is prolonged and the throughput is lowered, the imprint mold is used. It was not suitable.

  It can be used for microfabrication using nanoimprint technology.

DESCRIPTION OF SYMBOLS 1 ... Nanoimprint mold 2 ... Base material 3 ... Uneven pattern 4 ... Antireflection part 7 ... Resist film 8 ... Resist pattern 11 ... Rough surface part 12 ... Antireflection layer 13a, 13b ... Antireflection layer 14 ... Light absorption layer 15 ... Low light Transmittance layer

Claims (11)

In the method for processing a transparent nanoimprint mold substrate having a thickness of 4 mm or less,
Detection light incident on the base material from the front surface side of the base material is reflected on the back surface of the base material and emitted to the front surface side in at least a partial region on the back surface side of the base material or at least a partial region inside the base material An antireflection part is provided to prevent
The antireflection portion is a surface of an optical base material in which a spread of detection light (Gaussian beam or a Gaussian beam obtained by approximating the intensity distribution of detection light with Gaussian) is a, and an incident angle to the surface of the base material is θ. In the position detection mechanism, the thickness from the substrate surface to the antireflection portion is D, the refractive index of the substrate is ns, the reflected light from the substrate surface and the interface between the antireflection portion and the substrate, or the substrate The intensity ratio with the reflected return light from the back surface is α, and the cross-sectional intensity distribution of the synthesized Gaussian beam is
f = exp (-x ² / a ² ) + αexp (-(x-d) ² / a ² )
Here, d is the amount of positional deviation between the reflected light and the reflected return light,
d = 2D cos θ tan (sin ⁻¹ (sin θ / ns))
In the system represented by
A range of the intensity ratio α is obtained such that a value obtained by multiplying the value of X at which the differential value of the cross-sectional intensity distribution profile is 0 by 1 / (2 tan θcos θ) is 10 μm or less, and the intensity of the reflected return light is the intensity ratio α A method for treating a substrate for a nanoimprint mold, characterized in that the antireflection structure satisfies the above range.   The method for treating a nanoimprint mold substrate according to claim 1, wherein the back surface of the substrate is roughened to form the antireflection portion. An antireflection layer is provided on the back surface of the base material to form the antireflection portion, and when the refractive index n of the antireflection layer is 1.35 or less and the wavelength of detection light is λ, the antireflection layer The thickness L of the
nL = (2m−1) λ / 4 (m is an integer)
The method for treating a substrate for nanoimprint mold according to claim 1, wherein:   An antireflection layer is laminated on the back surface of the base material to form a two-layer antireflection portion, and the refractive index and thickness of each antireflection layer are set so as to satisfy the amplitude condition and phase condition in the two-layer structure. The processing method of the base material for nanoimprint molds of Claim 1 characterized by the above-mentioned.   The method for treating a nanoimprint mold substrate according to claim 1, wherein a light absorption layer is disposed on the back surface of the substrate to form the antireflection portion.   A material having a refractive index whose difference from the refractive index of the substrate is ± 25% or less is used, and the light absorption layer is formed so that the absorbance with respect to detection light satisfies the intensity ratio α. Item 6. A method for treating a nanoimprint mold substrate according to Item 5.   The method for treating a nanoimprint mold substrate according to claim 1, wherein the antireflection portion is formed by forming a low light transmittance layer inside the substrate. In the method for processing a transparent nanoimprint mold substrate having a thickness of 4 mm or less,
Detection light incident on the base material from the front surface side of the base material is reflected on the back surface of the base material and emitted to the front surface side in at least a partial region on the back surface side of the base material or at least a partial region inside the base material A method for treating a base material for a nanoimprint mold, wherein an antireflection portion for preventing the formation of the nanoimprint mold is provided, and the antireflection portion is provided by roughening the back surface of the base material. In the method for processing a transparent nanoimprint mold substrate having a thickness of 4 mm or less,
Detection light incident on the base material from the front surface side of the base material is reflected on the back surface of the base material and emitted to the front surface side in at least a partial region on the back surface side of the base material or at least a partial region inside the base material A method for treating a substrate for a nanoimprint mold, comprising: providing an antireflection part for preventing the antireflection part, and providing the antireflection part by disposing a light absorption layer on the back surface of the base material. In the method for processing a transparent nanoimprint mold substrate having a thickness of 4 mm or less,
Detection light incident on the base material from the front surface side of the base material is reflected on the back surface of the base material and emitted to the front surface side in at least a partial region on the back surface side of the base material or at least a partial region inside the base material A method for treating a substrate for nanoimprint mold, comprising: providing an antireflection portion for preventing the formation of the antireflection portion, and providing the antireflection portion by forming a low light transmittance layer inside the base material. A step of forming an antireflection part by a method for treating a substrate for nanoimprint mold according to any one of claims 1 to 10 , with respect to a transparent substrate having a thickness of 4 mm or less,
Forming a resist film on the surface of the base material, and placing the base material on a stage in an electron beam drawing apparatus so that the back surface of the base material faces the stage;
The base material is irradiated with height detection light, and the height detection light detects reflected light reflected from the surface of the base material to detect the height of the base material. Irradiating the resist film with an electron beam while controlling the focus position of the electron beam so as to be suitable for the surface position, and forming a desired pattern latent image;
Forming a concavo-convex pattern on the substrate using a resist pattern obtained by developing the resist film as a mask, and a method for producing a nanoimprint mold.

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