JP5476796B2 - Nanoimprint mold and pattern forming method - Google Patents

Description

  The present invention relates to a nanoimprint mold capable of forming a fine pattern and a pattern forming method using the nanoimprint mold.

In recent years, attention has been focused on nanoimprint technology as a 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 the same magnification (Patent Document 1).
As one method of the nanoimprint technique, an optical imprint method is known. In this optical imprinting method, for example, a photocurable resin layer is formed on the surface of a substrate, and a mold (mold member) having a desired concavo-convex structure is pressure-bonded to the resin layer. In this state, the resin layer is irradiated with ultraviolet rays from the mold side to cure the resin layer, and then the mold is released from the resin layer. Thereby, the uneven structure in which the unevenness of the mold is inverted can be formed on the resin layer as the workpiece (Patent Document 2). Such an optical imprint method is capable of forming a fine pattern on the order of nanometers, which is difficult to form with conventional photolithography technology, and is promising as a next-generation lithography technology.

  However, in the case of the optical imprint method, when the parallelism between the mold and the workpiece is not ensured, the thickness of the resin layer on which the concavo-convex structure is transferred is formed, which makes it difficult to form a high-definition pattern. was there. For this reason, laser light is incident from the back side of the mold, and interference between the diffracted light and the reference light generated by the alignment mark provided on the surface of the mold (surface on which the concavo-convex structure is formed) is detected by a photodetector. Measuring the surface position at a plurality of locations on the mold and controlling the parallelism is performed (Patent Document 3). In addition, laser light is obliquely applied to the surface of the mold (surface on which the concavo-convex structure is formed), the position of reflected light from the surface is monitored, and the parallelism is controlled by measuring the position. (Patent Document 4).

US Pat. No. 5,772,905 Special Table 2002-539604 JP 2007-200553 A JP 2003-264136 A

However, the control of the parallelism as in Patent Document 3 described above performs position measurement using interference between the reflected light from the mold and the reference light, so that the measurement target mold is thin like a wafer mold (for example, , The thickness is 4mm or less), and there is a possibility that the measured value may be blurred due to multiple reflection of the back and front surfaces of the mold, and the difference between the reflectance on the front surface and the reflectance on the back surface becomes small, which interference There is a problem that it is unclear whether the peak corresponds to the surface of the mold.
On the other hand, the parallelism control as described in Patent Document 4 irradiates the surface of the mold with laser light, so there is no such problem as described above, and there is a reflection plane on the surface side of the mold. If the thickness has a sufficient thickness exceeding 4 mm, for example, the position of the mold surface can be detected. This will be described with reference to FIG. When the mold 61 has a sufficient thickness, the peak position of the light (surface reflected light B <b> 1) reflected by the surface of the mold 61 from the incident light A obliquely incident on the mold 61 from the light source 71, and the mold 61. Is separated from the peak position of the light (reflected return light B 2) incident on the back surface and reflected by the back surface, and these are not detected simultaneously by the light beam position detector 72.

However, when the mold is 4 mm or less like the wafer mold, the reflected light from the surface of the mold 61 (surface reflected light B1) and the reflected light from the back surface (reflected return light B2) approach each other. Then, as shown in FIG. 17A, the light beam position detector 72 detects these 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 72, the light beam position detector 72 side uses both signals to mold. Therefore, a value different from the actual surface position is calculated. That is, as shown in FIG. 17B, the surface position of the mold is calculated based on the peak position of the apparent reflected light B ″, which is higher than the actual position as shown by a two-dot chain line in the drawing. As described above, when the surface positions measured at a plurality of locations of the mold are not accurate, there is a problem that the parallelism between the mold and the workpiece cannot be controlled with high accuracy. .

In order to achieve such an object, the nanoimprint mold of the present invention has a transparent substrate having a thickness of 4 mm or less, a concavo-convex pattern formed on the surface side of the substrate, and an antireflection part. The antireflection portion is located in at least a part of the back side of the base material or at least a part of the base material, and the surface of the base material is a pattern in which the uneven pattern is formed. An area and a non-pattern area located around the pattern area, the pattern area is convex with respect to the non-pattern area, and the antireflection part is incident on the substrate from the pattern area The detection light is configured to be prevented from being reflected and emitted from the pattern region.

As another aspect of the present invention, the antireflection portion is an optical substrate surface position detection mechanism in which the spread of the detection light (Gaussian beam) is a and the incident angle to the substrate surface is θ. The thickness from the substrate surface to the antireflection portion is D, the refractive index of the substrate is ns, and the reflected light from the substrate surface is reflected from the interface between the antireflection portion and the substrate or from the back surface of the substrate. The intensity ratio with the return light 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 = 2Dcosθtan (sin ⁻¹ (sinθ / ns)), a value obtained by multiplying the value of X at which the differential value of the cross-sectional intensity distribution profile becomes 0 by 1 / (2tanθcosθ) is 10 μm or less. The range of the intensity ratio α is determined so that an antireflection structure is provided so that the intensity of the reflected return light satisfies the range of the intensity ratio α.

As another aspect of the present invention, the antireflection portion is configured to be a rough surface portion provided on the back surface of the base material.
Further, as another aspect of the present invention, the antireflection portion is composed of an antireflection layer disposed on the back surface of the base material, and the refractive index n of the antireflection layer is 1.30 or less, When the wavelength of the detection light is λ, the thickness L of the antireflection layer is based on the phase condition,
nL = (2m−1) λ / 4 (m is an integer)
To satisfy the requirements.
As another aspect of the present invention, the antireflection portion has a two-layer structure in which an antireflection layer is laminated on the back surface of the base material, and the antireflection layer located on the back surface side of the base material is refracted. The rate was set to be larger than the refractive index of the substrate.
Moreover, as another aspect of the present invention, the antireflection portion is constituted by a light absorption layer disposed on the back surface of the base material.
As another aspect of the present invention, the antireflection portion is configured to be a low light transmittance layer located inside the base material.

The nanoimprint mold of the present invention has a transparent base material having a thickness of 4 mm or less, a concavo-convex pattern formed on the surface side of the base material, and an antireflection part, and the antireflection part is formed of the base material. Located in at least a part of the back surface side or at least a part of the inside of the base material, the antireflection portion a spreads the detection light (Gaussian beam), and is incident on the surface of the base material. In the optical substrate surface position detection mechanism where θ is θ, the thickness from the substrate surface to the antireflection portion is D, the refractive index of the substrate is ns, and the reflected light and reflection from the substrate surface The intensity ratio of the reflected light from the interface between the prevention part and the substrate or the back surface of the substrate 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 this system, the range of the intensity ratio α is obtained such that the value obtained by multiplying the value of X at which the differential value of the cross-sectional intensity distribution profile becomes 0 by 1 / (2 tan θcos θ) is 10 μm or less, and the reflected return light Is provided with an antireflection structure that satisfies the range of the intensity ratio α.
As another aspect of the present invention, the antireflection portion is configured to be a rough surface portion provided on the back surface of the base material.
Further, as another aspect of the present invention, the antireflection portion is composed of an antireflection layer disposed on the back surface of the base material, and the refractive index n of the antireflection layer is 1.30 or less, When the wavelength of the detection light is λ, the thickness L of the antireflection layer is based on the phase condition,
nL = (2m−1) λ / 4 (m is an integer)
To satisfy the requirements.
As another aspect of the present invention, the antireflection portion has a two-layer structure in which an antireflection layer is laminated on the back surface of the base material, and the antireflection layer located on the back surface side of the base material is refracted. The rate was set to be larger than the refractive index of the substrate.
Moreover, as another aspect of the present invention, the antireflection portion is constituted by a light absorption layer disposed on the back surface of the base material.
As another aspect of the present invention, the light absorption layer is made of a material having a refractive index that is ± 12% or less from the refractive index of the base material, and the absorbance with respect to the detection light is the intensity ratio. The configuration satisfies α.
As another aspect of the present invention, the antireflection portion is configured to be a low light transmittance layer located inside the base material.

The pattern forming method of the present invention ensures parallelism between a workpiece having a photocurable resin layer on the substrate surface and any one of the above-described nanoimprint molds, and the uneven pattern forming surface of the nanoimprint molds. In this state, the workpiece is irradiated with ultraviolet rays through the nanoimprint mold to cure the resin layer, and then the nanoimprint mold is released from the resin layer. It was.

In the nanoimprint mold of the present invention, since the base material includes an antireflection portion, the detection light irradiated on the surface of the base material is prevented from being reflected on the back surface of the base material and emitted to the surface, and the surface of the nanoimprint mold It is possible to detect the mold surface position only by the reflected light reflected from the substrate surface (peak position of the surface reflected light) from the detection light irradiated on the mold. Parallelism between objects can be ensured with high accuracy.
In addition, the pattern forming method of the present invention can ensure the parallelism between the mold and the workpiece with high accuracy, so that a fine pattern can be formed with high accuracy.

It is sectional drawing which shows one Embodiment of the nanoimprint mold of this invention. It is sectional drawing which shows other embodiment of the nanoimprint mold of this invention. It is a figure for demonstrating arrangement | positioning of the reflection preventing part in the nanoimprint mold of this invention. It is sectional drawing which shows other embodiment of the nanoimprint mold of this invention. It is sectional drawing which shows other embodiment of the nanoimprint mold of this invention. It is a figure for demonstrating arrangement | positioning of the reflection preventing part in the nanoimprint mold of this invention. It is sectional drawing for demonstrating an example of the reflection preventing part which comprises the nanoimprint mold of this invention. It is sectional drawing for demonstrating the other example of the reflection preventing part which comprises the nanoimprint mold of this invention. It is sectional drawing for demonstrating the other example of the reflection preventing part which comprises the nanoimprint mold of this invention. It is sectional drawing for demonstrating the other example of the reflection preventing part which comprises the nanoimprint mold of this invention. It is sectional drawing for demonstrating the other example of the reflection preventing part which comprises the nanoimprint mold of this invention. It is process drawing for demonstrating the manufacture example of the nanoimprint mold of this invention. It is a figure for demonstrating an example of the pattern formation method of this invention. It is a figure for demonstrating an example of the pattern formation method of this invention. It is a figure for demonstrating an example of the pattern formation method of this invention. It is drawing explaining the detection of the surface position of a thick mold. It is drawing explaining the detection of the surface position of a mold with small thickness.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Nanoimprint mold]
FIG. 1 is a cross-sectional view showing an embodiment of a nanoimprint mold of 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 of the present invention may be provided with an antireflection part 4 inside the substrate 2 as shown in FIG.

  The antireflection part 4 prevents the light for detecting the surface position incident on the mold 1 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. It is. 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.

  FIG. 4 is a cross-sectional view showing another embodiment of the nanoimprint mold of the present invention. In FIG. 4, the nanoimprint mold 11 includes a transparent base material 12, an uneven pattern 13 formed on the front surface side of the base material 12, and an antireflection portion 14 formed on the back surface 12 b side of the base material. ing. The surface of the substrate 12 is demarcated into a pattern area 10A where the uneven pattern 3 is formed and a non-pattern area 10B located around the pattern area 10A. The surface 12a of the pattern area 10A is a non-pattern area 10B. The surface 12a 'is convex and has a so-called mesa structure. Moreover, the nanoimprint mold 11 of the present invention may be provided with an antireflection part 14 inside the substrate 12 as shown in FIG.

  Similarly to the antireflection unit 4, the antireflection unit 14 also reflects the surface position detection light incident on the mold 11 from the front surface 12 a side of the pattern region 10 </ b> A of the base material 12 on the back surface 12 b of the base material 12. This prevents the light from being emitted toward the surface 12a. Such an antireflection portion 14 is disposed in at least a part of the base 12 on the back surface 12 b side, or in at least a part of the base 12. FIG. 6 is a diagram for explaining the arrangement of the antireflection part 14, and the arrangement part of the antireflection part 14 is shown by hatching. As shown in FIG. 6A, the antireflection portion 14 may be arranged so as to include the pattern region 10A. Further, as shown in FIG. 6B, the uneven pattern 13 is surrounded by a part of the pattern area 10A excluding the area where the uneven pattern 13 is formed (area surrounded by a chain line). It may be arranged in a corridor shape. Further, as shown in FIG. 6C, the concave / convex pattern 13 is surrounded by a portion of the pattern region 10A excluding the region where the concave / convex pattern 13 is formed (region surrounded by a chain line). It may be partially arranged. Of course, the antireflection part 14 may be disposed in the entire area of the back surface 12 b of the base material 12 or in the entire area of the base material 12.

Here, the antireflection portions 4 and 14 are optical surfaces of the optical base materials 2 and 12 where a is the spread of the detection light (Gaussian beam) and θ is the incident angle to the surfaces 2a and 12a of the base materials 2 and 12. In the position detection mechanism, the thickness from the surfaces 2a and 12a to the antireflection portions 4 and 14 is D, the refractive index of the base materials 2 and 12 is ns, the reflected light from the surfaces 2a and 12a, and the antireflection portion 4 and 14 and the intensity ratio of the reflected light from the back surfaces 2b and 12b of the substrates 2 and 12 to the interface between the substrates 2 and 12 and 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 the value obtained by multiplying the X value at which the differential value of the cross-sectional intensity distribution profile becomes 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 the range is provided.

The base materials 2 and 12 constituting the nanoimprint molds 1 and 11 are transparent base materials, and examples of the material include quartz glass, silicate glass, calcium fluoride, Pyrex (registered trademark) glass, blue plate glass, soda glass, BK-7 or the like can be used. The thickness of the base materials 2 and 12 is 4 mm or less, and can be set as appropriate depending on the application. The lower limit of the thickness is not particularly limited, and the shape and dimensions of the uneven patterns 3 and 13, the strength of the base material, and the handling It can be set in consideration of suitability and the like.
The uneven patterns 3 and 13 constituting the nanoimprint mold 1 are micro uneven structures of micro to nano order formed on the surfaces 2a and 12a of the substrates 2 and 12. The dimensions of the concavo-convex patterns 3 and 13 can be set as appropriate according to the application and the like, and are not particularly limited.

In the present invention, the antireflection portion 4 as described above can be a rough surface portion 21 provided on the back surface 2b of the substrate 2 as shown in FIG. Such a rough surface portion 21 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 0.4 to 100 μm, preferably 1 to 40 μm, more preferably about 10 to 40 μm. When the average roughness Ra of the rough surface portion 21 is less than 0.4 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 becomes insufficient, and problems such as distortion at the time of imprinting may occur. Here, average roughness Ra shall be measured with the level | step difference measuring device DEKTAK8000 by ULVAC. Such a rough surface portion 21 can scatter light that has entered the substrate 2 from the surface 2a side of the substrate 2 and has a low reflectance. Therefore, the mold 1 of the present invention having the rough surface portion 21 as the antireflection portion 4 can be used for a plurality of imprint apparatuses having different wavelengths of detection light. Further, at the time of imprinting, irradiation light irradiated from the back surface of the mold 1 is diffused by the rough surface portion 21, and the workpiece is uniformly exposed.
In FIG. 7, the antireflection part 4 is described, but the antireflection part 14 may be the same. The same applies to the description of the antireflection portion 4 with reference to FIGS.

Moreover, the antireflection part 4 can be an antireflection layer 22 provided on the back surface 2b of the substrate 2 as shown in FIG. This antireflection layer 22 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 antireflection layer 22 has a refractive index smaller than the refractive index of the substrate 2 and has a refractive index of 1.30 or less, preferably when the refractive index of the substrate 2 is ns. more ns ^1/2 about, for example, may be formed of a material having a refractive index of about ± 10% of the ns ^1/2. The refractive index can be measured using a commercially available ellipsometry apparatus. Examples of such a material include a fluororesin, Teflon (registered trademark) AF, Cytop (registered trademark), and a porous silica nanoparticle dispersion. The thickness L of the antireflection layer 22 is such that 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 minimized periodically exists, and the thickness L of the antireflection layer 22 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 22 can exhibit a low reflection function due to thin film interference for multiple wavelengths by adjusting the refractive index and thickness. Therefore, it can be used for a plurality of imprint apparatuses having different wavelengths of detection light.

Further, as shown in FIG. 9, the antireflection part 4 may be formed as a two-layer antireflection part 4 by laminating antireflection layers 23 a and 23 b on the back surface 2 b 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 23a constituting the antireflection part 4 having a two-layer structure are set to n ₁ and L ₁ , and the antireflection layer 23b. 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, the antireflection part 4 can be a light absorption layer 24 provided on the back surface 2b of the substrate 2 as shown in FIG. This light absorbing layer 24 is coated by a coating method such as spin coating and dried using a light absorbing material having a difference from the refractive index of the substrate 2 of ± 12% or less, preferably ± 10% 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 24 is attenuated, the increase / decrease in reflectance due to thin film interference depending on the film thickness is eliminated, so that the difference between the refractive index of the light absorption layer 24 and the refractive index of the substrate 2 increases. The reflection at the interface between the substrate 2 and the light absorption layer 24 is increased. If the difference between the refractive index of the light absorption layer 24 and the refractive index of the substrate 2 exceeds ± 12%, the above-described antireflection structure is not sufficient even when the light absorption layer 24 absorbs almost 100% of light. The antireflection effect cannot be obtained.

The effect of the light absorption layer 24 is determined by appropriately setting the absorption coefficient and thickness. That is, since the light absorption layer 24 varies in the degree of light absorption depending on the absorption coefficient and thickness of the material, it is preferable to define the light absorption layer 24 with an absorbance determined by the thickness and the absorption coefficient. Then, the light absorption layer 24 is formed so as to satisfy the above-described intensity ratio α (having an antireflection structure). Such a light absorption layer 24 can be formed using materials, such as a pigment resist containing red absorption organic pigment pigment | dyes, such as a phthalocyanine compound, an anthraquinone compound, a naphthoquinone compound, for example.
Thus, the refractive index of the light absorption layer 24 is close to the refractive index of the substrate 2 (matching the refractive index), and the absorbance of the light absorption layer 24 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 can be used for a plurality of imprint apparatuses having different wavelengths of detection light.

  Furthermore, the antireflection part 4 can be a low light transmittance layer 25 located inside the substrate 2 as shown in FIG. The low light transmittance layer 25 is a layer having optical properties different from those of the substrate 2, and the light transmittance of the low light transmittance layer 25 is 5 to 18 of the light transmittance of the substrate 2. %. When the light transmittance of the low light transmittance layer 25 exceeds 18% 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. The low light transmittance layer 25 can be, for example, 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 25 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 calibrated lens. Such a low light transmittance layer 25 has an antireflection structure as described above, and exhibits low light transmittance with respect to multiple wavelengths. Therefore, it is used for a plurality of imprint apparatuses having different detection light wavelengths. can do.

Next, the manufacture example of the nanoimprint mold of this invention is demonstrated taking the mold 1 shown by FIG. 1 as an example.
FIG. 12 is a process diagram for explaining a production example of the nanoimprint mold of the present invention. First, the antireflection part 4 is formed on the back surface 2b side of the transparent base material 2 (FIG. 12A). 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.
The antireflection portion 4 can be formed as described in the explanation of the rough surface portion 21, the antireflection layer 22, the inner antireflection layer 23, the light absorption layer 24, and the low light transmittance layer 25, where Description of is omitted.

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.12 (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. 12C), 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.12 (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.
In the nanoimprint mold of the present invention, the uneven pattern 3 may be formed not by etching but by arranging a structure on the substrate 2.

In the nanoimprint mold of the present invention as described above, since the base material is provided with the antireflection part, the detection light irradiated on the surface of the mold is incident on the base material, reflected on the back surface and emitted to the surface. Can be suppressed. For example, when the mold 1 is not provided with the antireflection part 4 on the base material 2, the detection light A irradiated on the mold 1 is emitted from the surface 2 a of the base material 2 as shown in FIG. It is detected as the reflected surface reflected light B1 and the reflected return light B2 reflected by the back surface 2b of the substrate 2. That is, the position of the mold 1 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 amount of deviation between the combined light B ″ and the surface reflected light B1. The smaller d ′ (see FIG. 17B), the higher the detection accuracy of the surface position of the mold 1. 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. Therefore, the above-described deviation d ′ is extremely small, and therefore, among the detection lights irradiated on the mold surface, the reflected light reflected on the substrate surface (the peak position of the surface reflected light). ), It is possible to detect the surface position equivalent to the detection of the surface position only by imprinting. It can be formed with accuracy.

[Pattern formation method]
Next, an example of the pattern forming method of the present invention will be described with reference to FIGS.
As shown in FIG. 13, the back surface 2 b side of the nanoimprint mold 1 of the present invention is sucked and held by a vacuum chuck 31 and attached to the imprint apparatus. In the illustrated example, the nanoimprint mold 1 is illustrated in FIG. 1, and includes an antireflection portion 4 on the back surface 2 b side of the substrate 2. Further, a workpiece 41 having a photocurable resin layer 43 on the surface of the substrate 42 is placed on a substrate stage (not shown). In the illustrated imprint apparatus, a blind 37 is interposed between the illumination optical system 36 and the nanoimprint mold 1 in order to irradiate an appropriate part with ultraviolet rays from the illumination optical system 36. The imprint apparatus includes a plurality of pairs of mold position detection means including a pair of light sources 33 and a light beam position detector 34. Then, a plurality of points of the mold 1 mounted on the imprint apparatus are irradiated with detection light from the light source 33, and the reflected light reflected by the surface 2a of the mold 1 is detected by the light beam position detector 34. Surface position information (height and inclination) at the measurement point can be obtained. As shown in FIG. 3 and FIG. 6, the reflection points are formed at the plurality of points where the surface position is measured by irradiating the detection light in this way, and the light incident on the mold substrate is reflected on the back surface. It can be arbitrarily set from a region where it can be prevented or suppressed. The number of measurement points is 2 or more, preferably 4 or more, but is not particularly limited, and it is preferable to distribute the measurement points evenly to the mold in order to increase the measurement accuracy of the surface position.

Next, based on this surface position information, the vacuum chuck 31 is adjusted by a control means (not shown) to correct the tilt of the mold 1. Thereafter, the distance between the mold 1 and the resin layer 43 is reduced, and the mold 1 is brought into contact with the resin layer 43 as shown in FIG. In this state, the illumination optical system 36 irradiates the nanoimprint mold 1 with ultraviolet rays, and the resin layer 43 is cured by the ultraviolet rays transmitted through the mold 1.
Thereafter, as shown in FIG. 15, the nanoimprint mold 1 is released from the resin layer 43. Thereby, the concavo-convex structure 44 in which the concavo-convex pattern 3 of the nanoimprint mold 1 is inverted is transferred and formed on the resin layer 43.
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, five kinds of base materials were produced by changing the degree of the roughening treatment and forming rough surface portions having various average roughness Ra as shown in Table 1 below. The average roughness Ra was measured using a step measuring device DEKTAK8000 manufactured by ULVAC.
For example, a concavo-convex pattern can be formed on the surface of such a substrate as described above with reference to FIG. 12 to produce the nanoimprint mold of the present invention. However, in this example, the purpose is to evaluate the detection accuracy of the surface position of the mold. For this reason, the base material on which the antireflection part is formed without forming the uneven pattern is regarded as a nanoimprint mold, and the following: Thus, the surface position of the mold was detected. The same applies to the following embodiments.

That is, a base material having a rough surface portion which is an antireflection portion was processed into a size of 65 mm square, thereby obtaining nanoimprint molds (Sample 1-1 to Sample 1-7). Sample 1-1 was a mold having no rough surface portion. The mold was mounted on the imprint apparatus so that the back surface (rough surface portion side) of the nanoimprint mold was directed to the illumination optical system. The imprint apparatus used was a measuring point in the vicinity of the four corners of a 65 mm square mold. Next, the surface of the mold was irradiated with detection light (wavelength 680 nm) at an incident angle of 70 °, 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 Gaussian beam synthesis (f = exp (-x ² / a ² ) + αexp (-(x-d) ² / a ² ) The amount of deviation d ′ (see FIG. 17B) between the peak position of the composite light B ″ calculated by the beam shape a = 0.5) and the peak position of the surface reflected light B1 (see FIG. 17B), and the surface position of the mold The amount of deviation ΔD was calculated and shown in the following Table 1. It should be noted that the amount of deviation ΔD is required to be 10 μm or less in order to detect the mold surface position with high accuracy. The same applies to the examples.

  In addition, as a comparative sample, a 6025 base material (thickness 6.35 mm) was processed into a 65 mm square outer shape and regarded as a nanoimprint mold (no concavo-convex pattern was formed). Detection was performed.

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 0.4 to 100 μm, the amount of deviation ΔD of the surface position is 10 μm or less, It was confirmed that the surface position of the mold can be detected with extremely high accuracy.
On the other hand, in the sample 1-1 that has not been subjected to the surface roughening treatment and the sample 1-2 in which the average roughness Ra is less than 0.4 μm, the deviation amount ΔD of the surface position exceeds 10 μm.
Since the comparative sample had a sufficient thickness exceeding 4 mm, it was possible to detect the surface position of the mold with high accuracy.

[Example 2]
The same quartz glass as in Example 1 was prepared as a base material for a nanoimprint mold. A porous silica nanoparticle dispersion was applied to the back surface of the base material by spin coating and formed into a film to form an antireflection layer (antireflection part). The refractive index of this antireflection layer was 1.27. Here, the thickness of the antireflection layer was changed, and five types (samples 2-2 to 2-6) of nanoimprint molds (no concavo-convex pattern formed) shown in Table 2 below were produced. That is, when the thickness L of the antireflection layer is n = 1.27 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). 135 .mu.m) was set within a range of. ± .0.005 .mu.m. In Sample 2-2 and Sample 2-6, the thickness of the antireflection layer was set so as to be out of the range of ± 0.005 μm of the thickness L of the antireflection layer satisfying 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 types of molds 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 = 1.38, and 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 nanoimprint mold, in the same manner as in Example 1, the deviation amount d ′ between the peak position of the synthesized light B ″ and the peak position of the surface reflected light B1 and the deviation amount ΔD of the surface position are calculated. The results are shown in Table 2 below.

As shown in Table 2, Sample 2-3 to Sample 2-5, in which the thickness of the antireflection layer satisfies the above formula, is within a range of ± 0.005 μm, the amount of deviation of the surface position ΔD is 10 μm or less, and it was confirmed that the surface position of the mold 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 ± 0.005 μm of the thickness L of the antireflection layer that satisfies the above formula does not form the antireflection layer. Although the amount of deviation ΔD of the surface position was smaller than that of Sample 2-1, the value exceeded 10 μm.
In Samples 2-7 and 2-8, in which the refractive index of the antireflection layer exceeded 1.30, the deviation ΔD of the surface position exceeded 10 μm.

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 deviation amount ΔD of the surface position is 0 μm. Therefore, it is important to select a material for the antireflection film that is closer to the refractive index satisfying the amplitude condition. This is due to the deviation of the surface positions of Sample 2-3 to Sample 2-5 and Sample 2-7. It is clear from the comparison of the amount of deviation ΔD of the surface position of the sample 2-8 with respect to the 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 (sample 3-1 to sample 3-2) of nanoimprint molds (without forming an uneven pattern) 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 nanoimprint mold, in the same manner as in Example 1, the deviation amount d ′ between the peak position of the synthesized light B ″ and the peak position of the surface reflected light B1 and the deviation amount ΔD of the surface position 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 surface position deviation ΔD is 0 μm, and the mold surface position can be adjusted with extremely high accuracy. It was confirmed that it could be detected.

[Example 4]
The same quartz glass as in Example 1 was prepared as a base material for a nanoimprint mold. A pigment resist containing a red-absorbing organic pigment dye is applied to the back surface of this base material by spin coating, and a film is formed to form a light-absorbing layer (antireflection part). Six types (sample 4) shown in Table 4 below are formed. A nanoimprint mold (no concavo-convex pattern was formed) of -2 to Sample 4-7) was 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.
In addition, a light-absorbing layer is formed using a material having a refractive index different from the refractive index (1.45) of the base material, and two types (sample 4-8, sample 4-9) of nanoimprint molds (a concavo-convex pattern is formed) Not). 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 nanoimprint mold, in the same manner as in Example 1, the deviation amount d ′ between the peak position of the synthesized light B ″ and the peak position of the surface reflected light B1 and the deviation amount ΔD of the surface position 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 1.04 or more have a surface position deviation amount ΔD of 10 μm or less, which is extremely high. It was confirmed that the surface position of the mold can be detected with 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 1.04 are compared with the surface position of sample 4-1 in which the light absorption layer is not formed. The amount of deviation ΔD was small, but the value exceeded 10 μm.
Sample 4-8 in which the refractive index of the light absorption layer is in the range of 1.28 to 1.62 (difference from the refractive index of 1.45 of the base material is ± 12% or less) is the amount of deviation of the surface position. ΔD is 10 μm or less, and it was confirmed that the surface position of the mold can be detected with extremely high accuracy.
On the other hand, 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 ± 12% or less) is such that the amount of deviation ΔD of the surface position exceeds 10 μm. there were.

[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, by changing the laser irradiation conditions and controlling the thickness of the low light transmittance layer, four types of nanoimprint molds (Sample 5-2 to Sample 5-5) having different light transmittances (form an uneven pattern). Was prepared. The light transmittance of the substrate was measured using a light transmittance measuring device (MCPD manufactured by Otsuka Electronics Co., Ltd.).
Next, for each nanoimprint mold, in the same manner as in Example 1, the deviation amount d ′ between the peak position of the synthesized light B ″ and the peak position of the surface reflected light B1 and the deviation amount ΔD of the surface position 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 18% have a surface position deviation amount ΔD of 10 μm or less, and the mold has a very high accuracy. It was confirmed that the surface position could be detected.
On the other hand, sample 5-2 whose light transmittance is out of the above range has a smaller amount of deviation ΔD of the surface position than sample 5-1 where the dielectric breakdown layer is not formed, but its value is 10 μm. It was over. Note that a mold with a light transmittance of less than 5% can detect the surface position with extremely high accuracy, but it is suitable as an imprint mold because the transfer resin curing time in the imprint process becomes long and the throughput decreases. It was not.

  It can be used for microfabrication using nanoimprint technology.

DESCRIPTION OF SYMBOLS 1,11 ... Nanoimprint mold 2,12 ... Base material 3,13 ... Uneven pattern 4,14 ... Antireflection part 10A ... Pattern area 10B ... Non-pattern area 21 ... Rough surface part 22 ... Antireflection layer 23a, 23b ... Antireflection layer 24 ... Light absorption layer 25 ... Low light transmittance layer

Claims (15)

A transparent base material having a thickness of 4 mm or less, a concavo-convex pattern formed on the surface side of the base material, and an antireflection part, wherein the antireflection part is at least part of the back side of the base material Located in at least a part of the region or inside the substrate, the surface of the substrate is defined as a pattern region in which the uneven pattern is formed and a non-pattern region located around the pattern region. The pattern area is convex with respect to the non-pattern area, and the antireflection portion prevents the detection light incident on the substrate from the pattern area from being reflected and emitted from the pattern area. Nanoimprint mold characterized by The antireflection part is an optical base material surface position detection mechanism in which the detection light (Gaussian beam) spreads a and the angle of incidence on the base material surface is θ, from the base material surface to the antireflection part. The thickness of the substrate is D, the refractive index of the substrate is ns, and the intensity ratio between the reflected light from the substrate surface and the reflected return light from the interface between the antireflection part and the substrate or the substrate back surface is α. 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 The nanoimprint mold according to claim 1 , further comprising an antireflection structure that satisfies the above-described range. The nanoimprint mold according to claim 1 , wherein the antireflection portion is a rough surface portion provided on a back surface of the base material. The antireflection portion is composed of an antireflection layer disposed on the back surface of the substrate, and the refractive index n of the antireflection layer is 1.30 or less, and the wavelength of the detection light is λ The thickness L of the antireflection layer is determined from the phase condition,
nL = (2m−1) λ / 4 (m is an integer)
The nanoimprint mold according to claim 1 or 2 , wherein the nanoimprint mold is satisfied. The antireflection part has a two-layer structure in which an antireflection layer is laminated on the back surface of the base material, and the refractive index of the antireflection layer located on the back side of the base material is higher than the refractive index of the base material. The nanoimprint mold according to claim 4 , wherein the mold is also large. 3. The nanoimprint mold according to claim 1 , wherein the antireflection portion includes a light absorption layer disposed on a back surface of the base material. The nanoimprint mold according to claim 1 , wherein the antireflection portion is a low light transmittance layer located inside the base material. A transparent base material having a thickness of 4 mm or less, a concavo-convex pattern formed on the surface side of the base material, and an antireflection part, wherein the antireflection part is at least part of the back side of the base material Located in a region, or at least a portion of the interior of the substrate ,
Before SL antireflective portion, the detection light spreads a, by the surface position detecting mechanism of the optical substrate to the incident angle to the surface of the substrate theta, antireflective portion from the substrate surface (Gaussian beam) The thickness ratio is D, the refractive index of the substrate is ns, and the intensity ratio between the reflected light from the substrate surface and the reflected return light from the interface between the antireflection part and the substrate or the back surface of the substrate is α. Yes, 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 nanoimprint molds characterized by Rukoto provided with anti-reflection structure that satisfies the range. The nanoimprint mold according to claim 8 , wherein the antireflection portion is a rough surface portion provided on a back surface of the base material. The antireflection portion is composed of an antireflection layer disposed on the back surface of the substrate, and the refractive index n of the antireflection layer is 1.30 or less, and the wavelength of the detection light is λ The thickness L of the antireflection layer is determined from the phase condition,
nL = (2m−1) λ / 4 (m is an integer)
The nanoimprint mold according to claim 8 , wherein: The antireflection part has a two-layer structure in which an antireflection layer is laminated on the back surface of the base material, and the refractive index of the antireflection layer located on the back side of the base material is higher than the refractive index of the base material. The nanoimprint mold according to claim 10 , wherein the mold is also large. The nanoimprint mold according to claim 8 , wherein the antireflection portion includes a light absorption layer disposed on a back surface of the base material. The light absorption layer is made of a material having a refractive index whose difference from the refractive index of the base material is ± 12% or less, and the absorbance to the detection light satisfies the intensity ratio α. The nanoimprint mold according to claim 12 . The nanoimprint mold according to claim 8 , wherein the antireflection part is a low light transmittance layer located inside the base material. The parallel surface between the workpiece provided with the photocurable resin layer on the base material surface and the nanoimprint mold according to any one of claims 1 to 14 , and ensuring a concavo-convex pattern forming surface of the nanoimprint mold In this state, the workpiece is irradiated with ultraviolet rays through the nanoimprint mold to cure the resin layer, and then the nanoimprint mold is released from the resin layer. Pattern forming method.

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