JP2017047618A - Glass sheet for imprint mold and manufacturing method of glass sheet for imprint mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass sheet for imprint mold suitable for correction of uneven pattern.SOLUTION: There is provided a glass sheet for imprint mold having a non-through hole in a center part of one main surface and an average value of an angle with a processing phase axis of birefringence measured by irradiating light to the main surface vertically and a linear connecting a measurement point of the processing phase axis and a center point of the main surface of more than 45° and 90° or less in a measurement range of 5 mm or more inside from an outer peripheral edge of the main surface and 5 mm or more outside from an opening edge of the non-through hole.SELECTED DRAWING: Figure 13

Description

  The present invention relates to a glass plate for imprint mold and a method for producing the glass plate for imprint mold.

  As an alternative technique to the photolithography method, an imprint method has attracted attention (see, for example, Patent Documents 1 and 2). The imprint method is a technique in which a transfer material is sandwiched between a mold and a substrate, and an uneven pattern of the mold is transferred to the transfer material. In the photolithography method, the resolution is limited by the wavelength of light used for exposure, but in the imprint method, a pattern can be formed according to the pattern carved in the mold, and a very fine pattern can be formed. In addition, an expensive optical system apparatus is unnecessary as compared with the photolithography method, and it can be expected to perform ultrahigh resolution lithography with a low-cost apparatus. The imprint method can be applied to the manufacture of various products such as antireflection sheets, biochips, magnetic recording media as well as semiconductor elements.

  The imprint method is expected to be developed especially for semiconductor integrated circuits. 2. Description of the Related Art In recent years, semiconductor integrated circuits have been miniaturized and integrated, and photolithography apparatuses have been improved in accuracy as a pattern transfer technique for realizing the fine processing. However, there has been a problem that the price of the apparatus becomes very high because the apparatus must be increased in size as the pattern becomes finer, and it is necessary to control the apparatus with high precision.

  On the other hand, there is an imprint method for performing a fine pattern at a low cost, and it is said that a pattern of about 10 nanometers can be transferred. The imprint method has been studied for its application to mass recording medium recording bit formation, semiconductor integrated circuit pattern formation, and the like, and is being studied for mass production.

  Here, high throughput is one of the problems in applying imprint technology to mass production. Even if the price of the imprint apparatus is low, if the throughput is low, the product cost becomes high, and a cost merit cannot be obtained as compared with a product manufactured by a conventional photolithography method.

  In the pattern transfer process, air bubbles are easily caught between the mold and the substrate. The entrained bubbles are gradually absorbed by the transfer material, and the bubbles disappear. In the transfer process, it is necessary to wait until the transfer material completely fills the space surrounded by the uneven pattern and the substrate. This is because when the transfer material is solidified with bubbles that cannot be absorbed, pattern defects are caused.

  Furthermore, as a technique for reducing the amount of entrained bubbles, a technique has been developed in which a mold having a non-through hole is transferred while being curved on the surface opposite to the pattern. In this state, the mold center and the transfer material are first contacted, and in this state, the contact area with the transfer material is gradually expanded from the mold center to the outer periphery of the mold. Can be made.

Special table 2009-536591 JP 2010-080714 A

  A glass plate is generally used for the production of an imprint mold. The glass plate has a first main surface and a second main surface. A concavo-convex pattern is formed in the central portion of the first main surface, and a non-through hole is formed in the central portion of the second main surface.

  For example, the glass plate is held by the upper chuck in a state where the first main surface faces downward and the second main surface faces upward. At this time, the second main surface is deformed following the holding surface of the chuck, and as a result, the uneven pattern on the first main surface is distorted.

  The distortion of the concavo-convex pattern can be corrected by clamping the outer peripheral surface of the glass plate. By pressing the outer peripheral surface of the glass plate, the concavo-convex pattern is reduced. Although the concavo-convex pattern can be reduced, it is difficult to enlarge the concavo-convex pattern.

  There has been a demand for a glass plate in which the concave / convex pattern of the first main surface is enlarged by deforming the second main surface following the holding surface of the chuck. The enlarged uneven | corrugated pattern can be reduced by pinching the outer peripheral surface of a glass plate.

  If the second main surface is a completely flat surface, it is not necessary to correct the uneven pattern, but it is difficult to produce a completely flat surface.

  This invention is made | formed in view of the said subject, Comprising: The main objective is to provide the glass plate for imprint molds suitable for correction of an uneven | corrugated pattern.

In order to solve the above problems, according to one aspect of the present invention,
It has a non-through hole in the center of one main surface,
A fast axis of birefringence measured by irradiating light perpendicularly to the main surface in a measurement region 5 mm or more inside from the outer peripheral edge of the main surface and 5 mm or more outside from the opening edge of the non-through hole. And an average value of the angle formed by the straight line connecting the measurement point of the fast axis and the center point of the main surface is greater than 45 ° and 90 ° or less.

  According to one aspect of the present invention, an imprint mold glass plate suitable for correction of an uneven pattern is provided.

It is a top view of the mold produced using the glass plate by one Embodiment. It is sectional drawing of the mold along the II-II line of FIG. It is sectional drawing of the deformation | transformation state of the mold shown in FIG. It is sectional drawing of the deformation | transformation cancellation | release state of the mold shown in FIG. It is a flowchart of the manufacturing method of the glass plate by one Embodiment. It is a flowchart of the non-through-hole formation process of FIG. It is sectional drawing of the glass plate after completion of the non-through-hole formation process of FIG. It is sectional drawing of the glass plate after completion of the protrusion surface formation process of FIG. It is sectional drawing which shows the state before non-through-hole formation of the glass plate by one Embodiment. It is sectional drawing which shows the natural state after non-through-hole formation of the glass plate by one Embodiment. It is sectional drawing which shows the restraint state by the chuck | zipper after non-through-hole formation of the glass plate by one Embodiment. It is a figure which shows an example of the relationship between the stress which acts on the measurement site | part of the birefringence of the glass plate by one Embodiment, and a fast axis. It is a figure which shows an example of the relationship between the measurement point of the birefringence of the glass plate by one Embodiment, and a fast axis. It is a figure which shows the thermal expansion coefficient distribution of the glass plate by one Embodiment. It is a diagram illustrating a TiO ₂ concentration distribution of the glass plate according to an exemplary embodiment. It is a figure which shows OH group concentration distribution of the glass plate by one Embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted. In this specification, the imprint mold is also simply referred to as a mold. Further, in the present specification, the plan view means that it is viewed from a direction perpendicular to the main surface.

  FIG. 1 is a plan view of a mold manufactured using a glass plate according to an embodiment. FIG. 2 is a cross-sectional view of the mold along the line II-II in FIG. FIG. 3 is a cross-sectional view of the mold shown in FIG. 2 in a deformed state. 4 is a cross-sectional view of the mold shown in FIG.

  As shown in FIG. 4, the mold 10 sandwiches the transfer material 17 between the substrate 15 and transfers the uneven pattern of the mold 10 to the transfer material 17. The concavo-convex pattern of the transfer material 17 is a inverting pattern of the mold 10.

The mold 10 is made of, for example, glass. The glass is preferably quartz glass containing 90% by mass or more of SiO ₂ . The upper limit of the SiO ₂ content in the quartz glass is 100% by mass.

  Quartz glass has higher ultraviolet transmittance than general soda lime glass. Quartz glass has a smaller coefficient of thermal expansion than ordinary soda lime glass, and its dimensional change due to temperature changes is small.

Quartz glass may contain TiO ₂ in addition to SiO ₂ . The greater the TiO ₂ content, the greater the density of OH groups on the glass surface, and the higher the affinity between the glass surface and the transfer material 17. Therefore, the disappearance time of bubbles entrained between the mold 10 and the substrate 15 can be shortened.

Quartz glass may contain 90 to 95% by mass of SiO ₂ and 5 to 10% by mass of TiO ₂ . When the TiO ₂ content is 5 to 10% by mass, the coefficient of thermal expansion near room temperature is substantially zero, and the dimensional change near room temperature hardly occurs.

Quartz glass may contain trace components other than SiO ₂ and TiO ₂ , but preferably does not contain trace components.

  As shown in FIG. 2, the mold 10 has a first main surface 11 and a second main surface 12. In a natural state where no external force is applied, the first main surface 11 and the second main surface 12 are substantially parallel.

  At the central portion of the first main surface 11, a projecting surface 13 called a mesa is formed that is surrounded by a step and projects beyond the periphery. In plan view, the shape of the projecting surface 13 is, for example, a rectangle as shown in FIG. An uneven pattern to be transferred to the transfer material 17 is formed on the protruding surface 13. In the plan view, the shape of the projecting surface 13 may be a circle, an ellipse, or a pentagon or more polygon.

  On the other hand, a non-through hole 14 is formed at the center of the second main surface 12. The shape of the non-through hole 14 is, for example, a cylinder as shown in FIGS. The shape of the non-through hole 14 may be a truncated cone, a prism, a truncated pyramid, or the like.

  As shown in FIG. 1, the protruding surface 13 is disposed inside the opening edge 14 a of the non-through hole 14 in plan view. Further, in the plan view, the center of the protruding surface 13 and the center of the non-through hole 14 coincide with the center of the mold 10.

  As shown in FIG. 2, the portion of the mold 10 where the non-through hole 14 is formed is thinner than the peripheral portion thereof, and thus is easily bent and deformed by an external force. Therefore, as shown in FIG. 3, the projecting surface 13 can be bent and deformed convexly toward the substrate 15 around the center line of the non-through hole 14. This bending deformation is performed by, for example, pressing the outer peripheral surface of the mold 10 or the inner bottom surface of the non-through hole 14. The inner bottom surface of the non-through hole 14 may be pressed by the pressure of the gas chamber formed in the non-through hole 14.

  Next, with reference to FIGS. 3 to 4 again, an imprint method using the mold 10 having the above-described configuration will be described.

  As shown in FIG. 3, in a state where the protruding surface 13 of the mold 10 is bent and deformed convexly toward the substrate 15, the mold 10 and the substrate 15 are brought close to each other, and the liquid transfer material 17 previously applied to the substrate 15 is applied. The protruding surface 13 of the mold 10 is brought into contact with the mold 10.

  Thereafter, before the transfer material 17 is solidified, the projecting surface 13 is returned from the deformed state shown in FIG. 3 to the deformed release state shown in FIG. Thereby, the protruding surface 13 gradually comes into contact with the transfer material 17 from the central portion toward the outer peripheral portion. The gas between the mold 10 and the substrate 15 can easily escape and gas confinement can be suppressed.

  After the transfer material 17 is solidified, the transfer material 17 and the mold 10 are separated. A product constituted by the uneven layer formed by solidifying the transfer material 17 and the substrate 15 is obtained. The concavo-convex pattern of the product is obtained by substantially inverting the concavo-convex pattern of the mold 10.

  FIG. 5 is a flowchart of a method of manufacturing an imprint mold glass plate according to an embodiment. FIG. 6 is a flowchart of the non-through hole forming step of FIG. FIG. 7 is a cross-sectional view of the glass plate after the non-through hole forming step of FIG. 5 is completed. FIG. 8 is a cross-sectional view of the glass plate after completion of the protruding surface forming step of FIG. In FIG. 8, an alternate long and two short dashes line shows the state of the glass plate before the start of the protruding surface forming step.

  The manufacturing method of the glass plate for imprint molds has non-through-hole formation process S11 and protrusion surface formation process S12, as shown in FIG. In FIG. 5, the protruding surface forming step S12 is performed after the non-through hole forming step S11. However, the order may be reversed, and the non-through hole forming step S11 may be performed after the protruding surface forming step S12. . Further, the protruding surface forming step S12 may be performed in the middle of the non-through hole forming step S11.

  In the non-through hole forming step S <b> 11, the non-through hole 24 is formed in the center portion of the second main surface 22 of the glass plate 20 as shown in FIG. 7. As shown in FIG. 6, the non-through hole forming step S11 includes a grinding step S13, an inner side surface polishing step S14, and an inner bottom surface polishing step S15. In FIG. 6, the inner bottom surface polishing step S15 is performed after the inner side surface polishing step S14. However, the order may be reversed, and the inner side surface polishing step S14 may be performed after the inner bottom surface polishing step S15. Further, the inner surface polishing step S14 and the inner bottom surface polishing step S15 may be performed simultaneously.

  In the grinding step S13, the second main surface 22 is ground. In the inner surface polishing step S14, the inner surface of the non-through hole 24 obtained by the grinding step S13 is polished. The inner bottom surface polishing step S15 polishes the inner bottom surface of the non-through hole 24 obtained by the grinding step S13.

  In the protruding surface forming step S12, the outer periphery of the first main surface 21 of the glass plate 20 is dug down as shown in FIG. 8, and the periphery of the first main surface 21 is surrounded by a step and protrudes from the periphery. A protruding surface 23 called a mesa is formed. Etching or the like is used as a method for digging up the outer peripheral portion of the first main surface 21. Etching may be either dry etching or wet etching.

  After the projecting surface forming step S <b> 12, the first main surface 21 includes a projecting surface 23 and a peripheral surface having a step between the projecting surface 23. The peripheral surface is parallel to the protruding surface 23.

  The glass plate 20 obtained by the above manufacturing method is used as the mold 10 by forming an uneven pattern on the protruding surface 23. As a method of forming the concave / convex pattern on the protruding surface 23, for example, an etching method or the like is used. The mask pattern for etching may be produced by either an imprint method or a photolithography method.

  In the present embodiment, a step is formed on the first main surface 21 and the protruding surface 23 is formed. However, a step may not be formed on the first main surface 21. An uneven pattern may be formed at the center of the first main surface 21 without a step.

  FIG. 9 is a cross-sectional view showing a state of the glass plate before forming a non-through hole according to one embodiment. In FIG. 9, the arrow indicates the direction of the stress remaining on the glass plate. In FIG. 9, hatching is omitted for convenience. FIG. 10 is a cross-sectional view showing a natural state after forming a non-through hole of a glass plate according to an embodiment. FIG. 11 is a cross-sectional view showing a restrained state by a chuck after forming a non-through hole in a glass plate according to an embodiment. 10 and 11, the bending of the glass plate is exaggerated.

  In the present embodiment, as shown in FIG. 9, a glass plate 20 in which a tensile stress remains in a direction orthogonal to the center line CL of the glass plate 20 is used. The center line CL is parallel to the thickness direction of the glass plate 20. A glass plate 20 shown in FIG. 9 has a flat first main surface 21 and a flat second main surface 22.

  As shown in FIG. 10, when the non-through hole 24 is formed in the central portion of the second main surface 22, the second main surface 22 protrudes on the opposite side to the first main surface 21 in a natural state without external force (see FIG. 10). 10 is convex upward). This is because the central portion of the second main surface 22 that restricts the outward displacement of the outer peripheral portion of the second main surface 22 disappears due to the formation of the non-through hole 24.

  As shown in FIG. 11, when the upper chuck 30 holds the glass plate 20 with the first main surface 21 facing downward and the second main surface 22 facing upward, the second main surface 22 is chucked. It deforms following the holding surface 31 of 30. As a result, the first main surface 21 is deformed into a convex shape (convex downward in FIG. 11) opposite to the second main surface 22 and is stretched in a direction perpendicular to the center line CL. Therefore, the uneven pattern formed on the first main surface 21 can be enlarged.

  The enlarged concavo-convex pattern can be reduced by clamping the outer peripheral surface of the glass plate 20. Therefore, the uneven pattern can be corrected, and the glass plate 20 suitable for correcting the uneven pattern can be obtained.

  If the second main surface 22 is a completely flat surface, it is not necessary to correct the uneven pattern, but it is difficult to produce a completely flat surface.

  For the production of the 20 glass plates, the stress distribution of the glass plate 20 and the formation of the non-through holes 24 are used. Therefore, compared with the case where curved surface processing is used for production of the glass plate 20, processing accuracy can be reduced.

  By the way, the stress distribution of the glass plate 20 shows the same tendency before and after the formation of the non-through holes 24. Therefore, by examining the stress distribution of the glass plate 20 after the formation of the non-through holes 24, the tendency of the stress distribution of the glass plate 20 before the formation of the non-through holes 24 can be understood.

  The stress distribution of the glass plate 20 can be confirmed with a commercially available birefringence measuring apparatus. This is because birefringence occurs due to the stress remaining on the glass plate 20. Birefringence is caused by stress anisotropy.

  The birefringence measuring device irradiates light perpendicularly to the main surface of the glass plate 20 and detects the phase difference between two orthogonal linearly polarized waves, thereby measuring the fast axis and the retardation. The wavelength of light used for measurement is, for example, 633 nm. For example, a He—Ne laser is used as the light source, and an optical heterodyne interferometry is used as the measurement method.

  The fast axis is the axis at which light travels the fastest and has the smallest refractive index. On the other hand, the slow axis is the axis with the slowest light traveling speed and the axis with the highest refractive index. Usually, the fast axis and the slow axis are orthogonal. Retardation is the optical path difference (nm) between the fast axis and the slow axis. By dividing the retardation (nm) by the thickness (cm) of the glass plate 20, the retardation per 1 cm can be calculated.

  FIG. 12 is a diagram illustrating an example of the relationship between the stress acting on the birefringence measurement site of the glass plate and the fast axis according to one embodiment. As shown in FIG. 12, tensile stress may act on the measurement direction 20S of the birefringence of the glass plate 20, and the compressive stress may act on the horizontal direction. In this case, the fast axis FA is parallel to the compressive stress and is perpendicular to the tensile stress. The anisotropy of stress is expressed by retardation. The greater the anisotropy of stress, the greater the retardation.

  FIG. 13 is a diagram illustrating an example of a relationship between a measurement point of birefringence of a glass plate and a fast axis according to an embodiment. When the angle θ formed by the fast axis FA at the birefringence measurement point SP and the straight line SL connecting the measurement point SP and the center point CP of the second main surface 22 is greater than 45 °, the measurement point SP 9, it can be estimated that tensile stress remains in a direction perpendicular to the center line CL of the glass plate 20.

  Here, the angle θ formed is 0 ° when the fast axis FA is parallel to the straight line SL, and 90 ° when the fast axis FA is perpendicular to the straight line SL. The angle θ formed represents the amount of rotation of the fast axis FA with respect to the straight line SL centered on the measurement point SP, and does not represent the direction of rotation. Therefore, the minimum value of the formed angle θ is 0 °, and the maximum value of the formed angle θ is 90 °. Regardless of the direction of rotation, if the angle θ formed is greater than 45 °, it can be estimated that tensile stress remains in the direction perpendicular to the center line CL of the glass plate 20 as shown in FIG. Note that the measured value of the angle θ formed above does not substantially depend on the wavelength of light used for measurement.

After the non-through hole 24 is formed, the average value θ _{ave of the} angle θ formed in the measurement area SA of the glass plate 20 is greater than 45 ° and 90 ° or less. The measurement area SA is an area 5 mm or more inside from the outer peripheral edge 22 a of the second main surface 22 that forms the non-through hole 24 and 5 mm or more outside from the opening edge 24 a of the non-through hole 24. The non-through hole 24 and the vicinity thereof are easily affected by processing distortion, and are thus excluded from the measurement area SA. Further, the vicinity of the outer peripheral edge 22a of the second main surface 22 is similarly affected by the processing strain, and thus is excluded from the measurement area SA. The average value θ _ave is used because the effect described later is provided if there are a small number of measurement points where the formed angle θ is less than 45 °, but there are a large number of measurement points where the formed angle θ is greater than 45 °. This is because

After the formation of the non-through hole 24, if the average value θ _{ave of the} angle θ formed in the measurement area SA is greater than 45 ° and not more than 90 °, the second main as shown in FIG. The surface 22 can be convex on the side opposite to the first main surface 21. Therefore, the glass plate 20 suitable for correction of the uneven pattern can be obtained. After the formation of the non-through hole 24, the average value θ _ave of the angle θ formed in the measurement region SA is preferably 50 ° or more, more preferably 60 ° or more.

Similarly, before the non-through hole 24 is formed, the average value θ _ave of the angle θ formed in the measurement region SA is, for example, greater than 45 ° and 90 ° or less. Before forming the non-through hole 24, the average value θ _ave of the angle θ formed in the measurement region SA is preferably 50 ° or more, more preferably 60 ° or more.

After the formation of the non-through hole 24, the maximum value Re _max of retardation Re per cm in the measurement region SA is, for example, 2 nm or more. In this case, the stress remaining on the glass plate 20 is sufficiently large. After the formation of the non-through hole 24, the maximum value Re _max of retardation Re per cm in the measurement region SA is preferably 3 nm or more, more preferably 5 nm or more. Further, after the formation of the non-through hole 24, the maximum value Re _max of retardation Re per cm in the measurement region SA is preferably 15 nm or less.

Similarly, before the formation of the non-through hole 24, the maximum value Re _max of the retardation Re per cm in the measurement region SA is, for example, 2 nm or more, preferably 3 nm or more, more preferably 5 nm or more. In addition, before the non-through hole 24 is formed, the maximum value Re _max of the retardation Re per cm in the measurement region SA is preferably 15 nm or less.

  The stress distribution shown in FIG. 9 can be realized by, for example, the thermal expansion coefficient distribution shown in FIG. FIG. 14 is a diagram illustrating a thermal expansion coefficient distribution of a glass plate according to an embodiment. In FIG. 14, the vertical axis represents the coefficient of thermal expansion, and the horizontal axis represents the distance from the center line CL (see FIG. 9 and the like). In FIG. 14, the coefficient of thermal expansion is larger as the distance from the center line CL of the glass plate 20 is closer.

  Since the glass plate 20 is molded at a temperature higher than the strain point of the glass, no stress is generated during the molding. After molding, the stress distribution shown in FIG. 9 occurs in the cooling process to room temperature. This is because the closer the distance from the center line CL of the glass plate 20 is, the greater the coefficient of thermal expansion and the greater the cooling shrinkage.

  Therefore, the average value of the coefficient of thermal expansion in the portion inside the opening edge 24a of the non-through hole 24 in plan view (hereinafter also simply referred to as “inner portion”) is larger than the opening edge 24a of the non-through hole 24 in plan view. May be larger than the average value of the coefficient of thermal expansion in the outer portion (hereinafter also simply referred to as “outer portion”). The coefficient of thermal expansion is represented by the coefficient of thermal expansion at 23 ° C. Here, the average value is adopted because, even if the magnitude relationship of the thermal expansion coefficient is locally reversed, if the average relationship is not reversed, the effect described later can be obtained. Since the coefficient of thermal expansion can be converted from the glass composition, the glass composition may be measured instead of the coefficient of thermal expansion. Naturally, the coefficient of thermal expansion does not change before and after the formation of the non-through hole 24.

  If the average value of the coefficient of thermal expansion in the inner portion is larger than the average value of the coefficient of thermal expansion in the outer portion, the second main surface 22 is replaced with the first main surface 21 as shown in FIG. Can be convex on the opposite side. Therefore, the glass plate 20 suitable for correction of the uneven pattern can be obtained. The average value of the coefficient of thermal expansion in the inner part is preferably 0.01 ppb / ° C. or more, more preferably 0.05 ppb / ° C. or more than the average value of the coefficient of thermal expansion in the outer part. Moreover, it is preferable that the magnitude | size of the difference of the average value of the thermal expansion coefficient in an inner part and the average value of the thermal expansion coefficient in an outer part is 10 ppb / degrees C or less.

The thermal expansion coefficient distribution shown in FIG. 14 can be realized by, for example, the TiO ₂ concentration distribution shown in FIG. FIG. 15 is a diagram showing a TiO ₂ concentration distribution of a glass plate according to an embodiment. In FIG. 15, the vertical axis represents the TiO ₂ concentration, and the horizontal axis represents the distance from the center line CL (see FIG. 9 and the like).

Quartz glass containing TiO ₂ is produced, for example, by the VAD (Vapor-phase Axial Depositon) method. In the VAD method, silicon chloride or titanium chloride is blown together with oxygen gas or hydrogen gas from below the rotating quartz rod, and a hydrolytic reaction is caused by the flame of the gas burner. This is a method of forming a reform. The porous preform is pulled up together with the quartz rod, and is formed into a transparent mold in a baking furnace, and then molded with a mold. In the VAD method, the TiO ₂ concentration distribution can be controlled by controlling the concentration of silicon chloride and the concentration of titanium chloride. Incidentally, preparation of silica glass containing TiO ₂ is not limited to the VAD method, for example direct method may be a plasma process.

In FIG. 15, the closer the distance from the center line CL of the glass plate 20 is, the smaller the TiO ₂ concentration is, and the higher the SiO ₂ concentration is. In the case of the TiO ₂ concentration distribution shown in FIG. 15, the thermal expansion coefficient distribution shown in FIG. 14 is obtained, and as a result, the stress distribution shown in FIG. 9 is obtained.

Therefore, the average value of the TiO ₂ concentration in the inner portion may be smaller than the average value of the TiO ₂ concentration in the outer portion. Here, the reason why the average value is adopted is that, even if the magnitude relation of the TiO ₂ concentration is locally reversed, if the average relationship is not reversed, the effect described later can be obtained. The TiO ₂ concentration does not naturally change before and after the formation of the non-through hole 24.

If the average value of the TiO ₂ concentration in the inner part is smaller than the average value of the TiO ₂ concentration in the outer part, the second main surface 22 is replaced with the first main surface 21 as shown in FIG. Can be convex on the opposite side. Therefore, the glass plate 20 suitable for correction of the uneven pattern can be obtained. The average value of the TiO ₂ concentration in the inner part is preferably 0.005% by mass or less, more preferably 0.01% by mass or less, than the average value of the TiO ₂ concentration in the outer part. Further, the average value of the TiO ₂ concentration in the inner part, the magnitude of the difference between the average value of the TiO ₂ concentration in the outer portion is preferably 0.5 mass% or less.

Note that the thermal expansion coefficient distribution of the glass plate shown in FIG. 14 can also be realized by the concentration distribution of components other than TiO ₂ . In this case, as the distance from the center line CL of the glass plate 20 is closer, the desired component concentration may be higher or the desired component concentration may be lower.

  Further, the stress distribution shown in FIG. 9 can also be realized by, for example, the OH group concentration distribution shown in FIG. FIG. 16 is a diagram illustrating an OH group concentration distribution of a glass plate according to an embodiment. In FIG. 16, the vertical axis represents the OH group concentration, and the horizontal axis represents the distance from the center line CL (see FIG. 9 and the like).

  Quartz glass containing OH groups is produced, for example, by the VAD method. In the VAD method, when the porous preform is made into a transparent glass, the OH group concentration distribution can be controlled by controlling the atmosphere, temperature, time, and the like. OH groups are reduced by dehydration from quartz glass.

  In FIG. 16, the closer the distance from the center line CL of the glass plate 20, the greater the OH group concentration. According to the knowledge of the present inventors, in the case of the OH group concentration distribution shown in FIG. 16, the stress distribution shown in FIG. 9 is obtained.

  Therefore, the average value of the OH group concentration in the inner portion may be larger than the average value of the OH group concentration in the outer portion. Here, the average value is adopted because even if the magnitude relationship of the OH group concentration is locally reversed, if the average relationship is not reversed, the effect described later can be obtained. The OH group concentration does not substantially change before and after the formation of the non-through hole 24.

  If the average value of the OH group concentration in the inner part is larger than the average value of the OH group concentration in the outer part, the second main surface 22 is replaced with the first main surface 21 as shown in FIG. Can be convex on the opposite side. Therefore, the glass plate 20 suitable for correction of the uneven pattern can be obtained. The average value of the OH group concentration in the inner portion is preferably 5 mass ppm or more, more preferably 10 mass ppm or more, higher than the average value of the OH group concentration in the outer portion. Moreover, it is preferable that the magnitude | size of the difference of the average value of OH group concentration in an inner part and the average value of OH group concentration in an outer part is 500 mass ppm or less.

  In Test Examples 1 to 5, a quartz glass plate prepared by the VAD method was prepared, and after both the first main surface and the second main surface were polished flat, a cylindrical shape was formed at the center of the second main surface. A non-through hole was formed, and then the shape of the second main surface in a natural state with no external force was confirmed. The quartz glass plate had a length of 152 mm, a width of 152 mm, and a thickness of 6.35 mm, and the non-through hole had a diameter of 64 mm and a depth of 5.25 mm. For the sake of convenience, no protruding surface or uneven pattern was formed at the center of the first main surface of the glass plate. The tendency of the result does not change depending on the presence or absence of the protruding surface or the uneven pattern.

In Test Examples 1 and 3 to 5, the stress field of the quartz glass plate was controlled by controlling the TiO ₂ concentration of the quartz glass plate. In Test Examples 1 and 3 to 5, the OH group concentration in the quartz glass plate was uniform. On the other hand, in Test Example 2, the stress field of the quartz glass plate was controlled by controlling the OH group concentration of the quartz glass plate. In Test Example 2, the TiO ₂ concentration in the quartz glass plate was substantially zero and uniform. Test examples 1 to 3 are examples, and test examples 4 to 5 are comparative examples.

The angle θ formed by the straight line SL and the fast axis FA in the measurement area SA and the retardation Re per cm in the measurement area SA were measured by a birefringence measuring apparatus (trade name ABR10A) manufactured by Uniopt. These measurements were performed at 10 mm pitches in the vertical and horizontal directions, respectively. Based on these measurement results, the average value θ _{ave of the} angle θ and the maximum retardation Re per cm in the region 5 mm or more inside from the outer periphery of the main surface and 5 mm or more outside the opening edge of the non-through hole. The value Re _max was calculated. These calculations were performed not only after the formation of the non-through holes but also before the formation of the non-through holes.

The TiO ₂ concentration C (mass%) was measured with a fluorescent X-ray elemental analyzer. The measurement of the TiO ₂ concentration C was carried out for each section by equally dividing the glass plate into 14 × 14 sections in plan view. Then, the average value C1 _ave of the TiO ₂ concentration C in the inner part and the average value C2 _ave of the TiO ₂ concentration C in the outer part were calculated, and the difference ΔC (ΔC = C1 _ave −C2 _ave ) was calculated. .

  Of the 196 sections, the section that overlaps the boundary between the inner part and the outer part is treated as the inner part section when the center of the section exists in the inner part, and the outer part when the center of the section exists in the outer part. Treat as a parcel of When the center of a partition exists on the boundary line, the numerical value of the partition is not used for calculating ΔC.

The thermal expansion coefficient CTE (ppb / ° C.) at 23 ° C. was converted from the TiO ₂ concentration C using the following formula (1) described in Japanese Patent No. 5742833.

上記式（１）を用いた熱膨張率ＣＴＥの算出は、ＴｉＯ_２濃度Ｃの測定と同様に、平面視でガラス板を１４×１４の区画に均等に区切り、区画毎に行った。そうして、内側部分における熱膨張率の平均値ＣＴＥ１_ａｖｅと、外側部分における熱膨張率の平均値ＣＴＥ２_ａｖｅとを算出し、その差ΔＣＴＥ（ΔＣＴＥ＝ＣＴＥ１_ａｖｅ−ＣＴＥ２_ａｖｅ）を算出した。

The calculation of the coefficient of thermal expansion CTE using the above formula (1) was performed for each section by equally dividing the glass plate into 14 × 14 sections in a plan view, similarly to the measurement of the TiO ₂ concentration C. Then, the average value _{CTE1 ave} in thermal expansion coefficient in the inner portion, and calculates the average value _{CTE2 ave} coefficient of thermal expansion in the outer portion, and the difference was calculated _{ΔCTE (ΔCTE = CTE1 ave -CTE2 ave} ).

  After the formation of the non-through hole, the shape of the second main surface in a natural state without external force was measured using FM200 manufactured by Corning Tropel. Hereinafter, the case where the second main surface is curved convexly on the side opposite to the first main surface is simply “convex”, and the second main surface is curved concavely on the side opposite to the first main surface Is simply expressed as “concave”.

  The test results are shown in Table 1.

表１から明らかなように、試験例１〜３では、非貫通穴の形成後の測定領域ＳＡにおいて上記なす角θの平均値θ_ａｖｅが４５°よりも大きく９０°以下であるため、自然状態で第２主表面が凸になっており、第１主表面に形成される凹凸パターンの矯正に適したガラス板が得られた。一方、試験例４〜５では、非貫通穴の形成後の測定領域ＳＡにおいて上記なす角θの平均値θ_ａｖｅが４５°よりも小さいため、自然状態で第２主表面が凹になってしまった。

As is apparent from Table 1, in Test Examples 1 to 3, the average value θ _{ave of the} angle θ formed in the measurement region SA after the formation of the non-through hole is greater than 45 ° and 90 ° or less, so that the natural state Thus, the second main surface was convex, and a glass plate suitable for correcting the uneven pattern formed on the first main surface was obtained. On the other hand, in Test Examples 4 to 5, since the average value θ _{ave of the} angle θ formed in the measurement area SA after the formation of the non-through hole is smaller than 45 °, the second main surface becomes concave in the natural state. It was.

  As mentioned above, although embodiment of the glass plate for imprint molds, etc. was described, the present invention is not limited to the above-mentioned embodiment etc., and within the scope of the gist of the present invention described in the claims, various modifications, Improvements are possible.

The OH group concentration can be measured by, for example, a Fourier transform infrared spectrometer. The average value of the OH group concentration is calculated in the same manner as the average value of the TiO ₂ concentration and the average value of the coefficient of thermal expansion.

DESCRIPTION OF SYMBOLS 10 Mold 11 1st main surface 12 2nd main surface 13 Projection surface 14 Non-through-hole 15 Substrate 17 Transfer material 20 Glass plate 21 First main surface 22 Second main surface 23 Projection surface 24 Non-through-hole 24a Opening edge SA Measurement area SP Measuring point FA Phase angle θ

Claims (12)

It has a non-through hole in the center of one main surface,
A fast axis of birefringence measured by irradiating light perpendicularly to the main surface in a measurement region 5 mm or more inside from the outer peripheral edge of the main surface and 5 mm or more outside from the opening edge of the non-through hole. And an average value of angles formed by the straight line connecting the measurement point of the fast axis and the center point of the main surface is greater than 45 ° and 90 ° or less.   The glass plate for imprint molds according to claim 1, wherein a maximum value of retardation per cm measured by irradiating light having a wavelength of 633 nm perpendicular to the main surface in the measurement region is 2 nm / cm or more. .   The average value of the thermal expansion coefficient at 23 ° C. of the portion inside the opening edge of the non-through hole in plan view is the average value of the thermal expansion coefficient at 23 ° C. of the portion outside the opening edge of the non-through hole in plan view. The glass plate for imprint molds according to claim 1 or 2, which is larger than an average value. Formed of quartz glass containing TiO ₂ ;
The average value of the TiO ₂ concentration in the portion inside the opening edge of the non-through hole in plan view is smaller than the average value of the TiO ₂ concentration in the portion outside the opening edge of the non-through hole in plan view. The glass plate for imprint molds of any one of Claims 1-3. Formed of quartz glass containing OH groups,
The average value of the OH group concentration in the portion inside the opening edge of the non-through hole in plan view is larger than the average value of the OH group concentration in the portion outside the opening edge of the non-through hole in plan view. The glass plate for imprint molds of any one of Claims 1-4.   The glass plate for imprint molds of any one of Claims 1-5 which has an uneven | corrugated pattern in the center part of the main surface on the opposite side to the said main surface. It has a non-through hole forming step of forming a non-through hole in the center of one main surface of the glass plate,
After the non-through hole forming step, light is irradiated perpendicularly to the main surface in a measurement region that is 5 mm or more inside from the outer peripheral edge of the main surface and 5 mm or more outside from the opening edge of the non-through hole. The average value of the angle formed by the fast axis of birefringence measured in step (1) and the straight line connecting the measurement point of the fast axis and the center point of the main surface is greater than 45 ° and 90 ° or less. Manufacturing method of glass plate for molds.   The glass plate for imprint molds according to claim 7, wherein a maximum value of retardation per cm measured by irradiating light having a wavelength of 633 nm perpendicular to the main surface in the measurement region is 2 nm / cm or more. Manufacturing method.   The average value of the thermal expansion coefficient at 23 ° C. of the portion inside the opening edge of the non-through hole in plan view is the average value of the thermal expansion coefficient at 23 ° C. of the portion outside the opening edge of the non-through hole in plan view. The manufacturing method of the glass plate for imprint molds of Claim 7 or 8 larger than an average value. The glass plate is made of quartz glass containing TiO ₂ ,
The average value of the TiO ₂ concentration in the portion inside the opening edge of the non-through hole in plan view is smaller than the average value of the TiO ₂ concentration in the portion outside the opening edge of the non-through hole in plan view. The manufacturing method of the glass plate for imprint molds of any one of Claims 7-9. The glass plate is made of quartz glass containing OH groups,
The average value of the OH concentration in the portion inside the opening edge of the non-through hole in a plan view is larger than the average value of the OH concentration in a portion outside the opening edge of the non-through hole in a plan view. The manufacturing method of the glass plate for imprint molds any one of 7-10.   The manufacturing method of the glass plate for imprint molds of any one of Claims 7-11 which has the process of forming an uneven | corrugated pattern in the center part of the main surface on the opposite side to the said main surface.

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