JP2011245816A - Method of manufacturing substrate for mask blank, method of manufacturing mask blank for imprinting mold, and method of manufacturing imprinting mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce residual stress inside a substrate for mask blank when a recessed part is formed on the rear side by grinding and to maintain a high degree of flatness on the front side of the substrate for mask blank.SOLUTION: The method is to manufacture a substrate used for mask blank for producing an imprinting mold. The method includes: a step of preparing the substrate 11 including a first main surface SF1 and a second main surface SF2 which face each other; a grinding step of grinding a predetermined region on the first main surface SF1 in a direction of the second main surface SF2 and forming a recessed part SCV; and an etching step of further etching the bottom surface bf1 of the recessed part SCV in a direction of the second main surface SF2 by a predetermined amount and forming a recessed part CV with a predetermined depth.

Description

  The present invention relates to a method for manufacturing a mask blank substrate in which a recess is formed in a main surface on the back side opposite to the main surface on the front side on which a mold pattern is formed, and a mask for imprint mold using the method for manufacturing the mask blank substrate. The present invention relates to a blank manufacturing method and an imprint mold manufacturing method using the imprint mold mask blank manufacturing method.

  2. Description of the Related Art Conventionally, there is known an imprint mold in which a concave portion is formed on a back main surface opposite to a front main surface on which a mold pattern is formed (see, for example, Patent Documents 1 and 2). By forming the recess on the back surface of the substrate, the thickness of the substrate in the region where the mold pattern is formed can be reduced. Thereby, after transferring the mold pattern to the photo-curing resin on the wafer, there is an effect that the mold pattern is deformed in the spreading direction so that the mold can be easily peeled off. In order to form such an imprint mold, it is desired that a recess is formed on the back surface of the imprint mold mask blank or mask blank substrate before forming the mold pattern. Yes.

  A mask blank substrate used for a mask blank for producing an imprint mold is required to have high flatness on the front main surface on which a mold pattern is formed. Also, on the main surface on the back side, the fixing jig used to place the produced imprint mold on the transfer device (stamper device) often comes into contact with the main surface on the back side. High flatness is required, though not so much. For this reason, first, grinding and precision polishing are performed on the front and back main surfaces of the substrate before forming the recesses, and the flatness of the front and back main surfaces is set to a predetermined value or more. Thereafter, a recess is formed in the main surface on the back side of the substrate. And as a method of forming a recess in the main surface on the back side of the mask blank substrate, for example, there is a method of grinding by pressing a grinding head of a grinding device against the main surface on the back side of the substrate.

Special table 2009-536591 JP 2009-170773 A

  However, when a concave portion is formed by the above method and a mask blank substrate is manufactured, the main surface on the front side is raised due to factors such as high pressure applied to the bottom surface of the concave portion when grinding the concave portion. There was a problem that the flatness of the main surface deteriorated.

  The present invention has been made in view of the above problems, and its purpose is to manufacture a mask blank substrate that maintains high flatness on the front side of the mask blank substrate, and to manufacture an imprint mold mask blank. It is to provide a method and a method for manufacturing an imprint mold.

  A first feature of the present invention is a method for manufacturing a mask blank substrate used in a mask blank for producing an imprint mold, which includes a first main surface and a second main surface that face each other. Preparing a substrate including a substrate having a surface, grinding a predetermined region on the first main surface of the substrate toward the second main surface to form a recess, and a bottom surface of the recess On the other hand, an etching process for further performing a predetermined amount of etching in the direction of the second main surface to form a recess having a predetermined depth is provided.

  Even if the inventor of the present invention increases the flatness of the front main surface (second main surface) of the substrate by precision polishing or the like, the concave portion is formed on the back main surface (first main surface) thereafter. We have conducted intensive research on the factors that deteriorate the flatness of the main surface on the front side. As a result, when the recess is formed by grinding, residual stress remains at a predetermined thickness from the bottom of the recess toward the inside of the substrate (in the direction of the main surface on the front side) due to the processing pressure applied to the bottom of the recess. I found out. And since the board | substrate thickness between a recessed part bottom face and a 2nd main surface is significantly thinner than the board | substrate which does not form the conventional recessed part, this residual stress will deform | transform a board | substrate. As a result, it has been found that the flatness of the second main surface is deteriorated. Furthermore, the portion where the residual stress that affects the flatness on the front side remains is not the entire area between the bottom surface of the recess and the second main surface, but is predetermined from the bottom surface of the recess toward the second main surface. It was elucidated that it was within the thickness range.

  On the other hand, as a method of forming a recess without leaving a residual stress on the first main surface of the substrate, it is not unthinkable to perform it by an etching process. However, the digging speed when forming the recesses is limited to an etching rate on the order of nm / sec, and there is a problem of processing time. The inventor of the present invention, as a result of considering the problem of forming a recess by a grinding process and the problem of forming a recess by an etching process, first forms a certain depth by grinding as a process of forming a recess on the first main surface. Then, by etching a predetermined amount and then forming a concave portion with a predetermined depth, the flatness of the second main surface deteriorates due to the concave portion formation while realizing an acceptable processing time at the production level. It was derived that the problem could be solved.

  Specifically, for example, the concave surface processing by grinding leaves a residual stress sufficient to affect the deterioration of flatness of the second main surface from the concave bottom surface on the first main surface side to the second main surface. The area inside the substrate in the meantime is obtained in advance by a predetermined amount of thickness (depth) in the direction from the bottom surface of the recess toward the inside of the substrate. Next, the recess formation in the first main surface performed in the grinding step is performed at a depth obtained by subtracting at least a predetermined amount obtained in advance from the predetermined depth. Thereafter, in the etching step, a predetermined amount of depth obtained in advance from the bottom surface of the recess is removed by etching, and a region inside the substrate where residual stress remains is removed. Thereby, the residual stress inside the substrate can be surely eliminated, the flatness of the second main surface can be maintained, and a recess having a predetermined depth can be formed.

  The predetermined amount in the etching process is desirably 1 μm or more and 1 mm or less. Thereby, a recessed part can be efficiently formed, maintaining the state with the high flatness of the 2nd main surface. In other words, a recess having a predetermined depth can be formed by taking full advantage of both processes. If the predetermined amount is less than 1 μm, it may not be possible to completely remove the region inside the substrate where the residual stress that affects the deterioration of the flatness of the second main surface remains. In order to remove more reliably, the predetermined amount in the etching step is desirably 10 μm or more, and more surely 50 μm or more. On the other hand, as the digging amount for etching the bottom surface of the recess in the etching process increases, the processing time takes longer. The predetermined amount in the etching step is preferably at least 1 mm or less. Preferably, it is 500 μm or less, more preferably 100 μm or less.

  The predetermined depth is preferably a depth at which a distance between the bottom surface of the recess and the second main surface is 0.5 mm or more and 2.0 mm or less. If it is less than 2.0 mm, the thickness of the substrate between the bottom surface of the recess and the second main surface becomes too thick, and the mold pattern is deformed when the mold is peeled for the purpose of forming the recess on the first main surface. It takes a lot of power to do. As a result, the thin part of the substrate (the substrate part between the bottom surface of the recess and the second main surface) may not return to its original shape after deformation, or cracks may occur. On the other hand, if it is larger than 0.5 mm, the thickness of the substrate between the bottom surface of the recess and the second main surface becomes too thin, and the proof strength of the thin portion of the substrate is low, and there is a risk of cracking during deformation.

  Moreover, the manufacturing method of the mask blank substrate may further include a flattening step of flattening the surface roughness of the bottom surface of the concave portion to 0.3 nm or less in terms of arithmetic average roughness Ra after the etching step. When pattern transfer is performed on a photo-curing resin using an imprint mold formed using a mask blank substrate, light scattering on the bottom surface of the recess can be suppressed.

  The recess is preferably formed in a region having a size including a region where the mold pattern on the second main surface is formed. Thereby, all the parts of the mold pattern can be deformed. In addition, when pattern transfer is performed on the photo-curing resin, since the boundary portion between the concave portion and the first main surface does not reach the mold pattern formation region, the entire main mold pattern formation region on the second main surface is exposed to light. Incident light can cure the entire photo-curing resin.

  According to a second aspect of the present invention, there is provided a film forming step of forming a thin film for pattern formation on the second main surface of the mask blank substrate manufactured by the method for manufacturing a mask blank substrate according to the first feature. The gist of the present invention is a method of manufacturing a mask blank for imprint mold.

  According to a third aspect of the present invention, there is provided an imprinting step comprising etching a thin film and a mask blank substrate in the imprint mold mask blank produced by the method for producing an imprint mold mask blank according to the second feature. The gist is that it is a method for producing a print mold.

  As described above, according to the present invention, manufacturing of a mask blank substrate that reduces the stress remaining in the mask blank substrate and maintains the flatness of the main surface on the front side of the mask blank substrate at a high level is achieved. The method, the manufacturing method of the mask blank for imprint molds, and the manufacturing method of an imprint mold can be provided.

FIG. 1A is a cross-sectional view showing the configuration of a mask blank substrate manufactured by the method for manufacturing a mask blank substrate according to the first embodiment of the present invention, and FIG. It is the top view seen from the 1st main surface SF1 side of the board | substrate for blanks. It is process sectional drawing which shows the manufacturing method of the mask blank substrate 5 concerning the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the mask blank 3 for imprint molds manufactured with the manufacturing method of the mask blank for imprint molds concerning 2nd Embodiment. FIG. 4A is a cross-sectional view showing a configuration of the imprint mold 2 manufactured by the method of manufacturing the imprint mold 2 according to the third embodiment. FIG. 4B is a cross-sectional view of FIG. It is a schematic sectional drawing for demonstrating the use condition of the imprint mold 2 of). FIG. 5A to FIG. 5G are process cross-sectional views illustrating a method for manufacturing the imprint mold 2 according to the third embodiment. It is a bird's-eye view which shows the flatness of the 2nd main surface of the board | substrate concerning a comparative example.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same portions are denoted by the same reference numerals, and description thereof is omitted.

(First embodiment)
With reference to FIGS. 1A and 1B, the configuration of the mask blank substrate 5 manufactured by the method for manufacturing a mask blank substrate according to the first embodiment of the present invention will be described. 1A is a cross-sectional view, and FIG. 1B is a top view as viewed from the first main surface SF1 side.

  The mask blank substrate 5 is a mask blank substrate used for a mask blank for producing an imprint mold. The mask blank substrate 5 has a concave portion CV having a predetermined size formed on the first main surface SF1 of the flat substrate 11 having the first main surface SF1 and the second main surface SF2 facing each other. It is. The recess CV is a recess defined by a bottom surface BF parallel to the first main surface SF1 and a side wall SD that connects the first main surface SF1 and the bottom surface BF substantially vertically. The distance TH between the bottom surface BF of the recess CV and the second main surface SF2 is, for example, 1.5 mm. Note that the side wall SD does not necessarily have to be vertical, and may have an inclined shape in which the concave portion CD has a mortar shape.

  A mask blank is obtained by forming a thin film for pattern formation made of chromium or the like on the second main surface SF2 of the mask blank substrate 5. An imprint mold is obtained by forming a mold pattern (uneven pattern) on the main surface of the substrate 11 on the side where the thin film of the mask blank is formed.

  That is, the mask blank substrate 5 is a substrate in which the concave portion CV is formed on the main surface (first main surface) on the side facing the main surface (second main surface SF2) on which the mold pattern is to be formed. 11 consists of.

  As shown in FIG. 1B, the substrate 11 has a square shape, and the recess CV has a circular shape. The recess CV has, for example, a circular shape with a diameter of 70 mmφ. Of course, the shape of the substrate 11 is not limited to such a rectangular shape, and the shape of the recess CV is not limited to such a circular shape, and may be a rectangular shape or other polygonal shapes. The shapes of the substrate 11 and the recess CV are appropriately determined according to the use and size of the imprint mold. The size of the recess CV is preferably 50 mm or more in terms of a diameter in the case of a circular shape and a length in the short side direction in the case of a rectangular shape, and is preferably 60 mm or more. In consideration of securing the rigidity of the mask blank substrate 5, when the size of the mask blank substrate 5 is about 152 mm square, the diameter of the recess CV or the length in the short side direction is 100 mm or less. Is preferable, and it is preferable that it is 90 mm or less.

  It is most desirable that the center of the substrate 11 and the center of the recess CV coincide with each other, and at least the deviation is desirably 100 μm or less, more preferably 50 μm or less. In general, the center of the region MR where the mold pattern is formed on the second main surface SF2 side is made to coincide with the center of the substrate 11. This is because the deformation when the imprint mold is pressed against the resist film of the transfer object or when the imprint mold is peeled off gradually spreads from the center of the mold pattern (uneven pattern). The recess CV desirably has a perfect circular shape. The influence of the internal pressure in the space formed by the concave portion CV and the transfer device fixing device when the imprint mold is fixed to the transfer device and the transfer device on the deformation of the second main surface SF2 has a concentric distribution. This is because it is easy to adjust.

Examples of the material of the substrate 11 include glass materials such as quartz glass, SiO ₂ —TiO ₂ low expansion glass, soda lime glass, aluminosilicate glass, and CaF ₂ glass, silicon, stainless steel (SUS), aluminum, copper, and nickel. Examples thereof include metal materials, resin materials, and the like. Among these, the glass material can be processed with high accuracy and is excellent in flatness and smoothness. Therefore, when performing pattern transfer using an imprint mold, the distortion of the transfer pattern is not likely to occur. Pattern transfer can be performed. Moreover, since the glass material is a brittle material in which residual stress is likely to remain, the effect of the present invention is more exhibited. When pattern transfer is performed on the photocurable resin, at least the substrate 11 is preferably made of a light-transmitting material such as glass, and quartz glass, quartz glass, or SiO ₂ —TiO ₂ based low expansion glass is preferable. .

  The recess CV is formed in a region excluding at least the outer periphery of the substrate 11. The recess CV is a region (hereinafter referred to as “mold pattern formation region”) MR in which a mold pattern (uneven pattern) is formed on the second main surface SF2 opposite to the first main surface SF1 in which the recess CV is formed. It is formed in a region having a size including it. If the region where the recess 3 is formed is smaller than the mold pattern formation region MR, a portion that hardly deforms is generated on the outer mold pattern, and the resist film sandwiched between the mold pattern deforming outward may be crushed. Because. In particular, when pattern transfer is performed on the photocurable resin, if the boundary portion between the concave portion CV and the first main surface SF1 is applied to the mold pattern formation region MR of the second main surface SF2, the photocurable resin is used. Incidence of light for curing the resin cannot be performed normally, and there is a possibility that resin curing failure will occur.

  With reference to FIG. 2, the manufacturing method of the mask blank substrate 5 according to the first embodiment of the present invention will be described.

  (A) First, the first main surface SF1 and the second main surface SF2 facing each other of the flat substrate 11 are subjected to predetermined grinding and precision polishing to obtain a main surface SF1 having high flatness and high surface roughness. A substrate 11 having SF2 is prepared. For the grinding and precision polishing of the main surfaces SF1 and SF2, the manufacturing methods used in the manufacture of conventional mask blanks are applied. The first main surface SF1 and the second main surface SF2 have a flatness of 0.3 μm in a region within 132 mm square with respect to the center of the substrate 11 when the size of the substrate 11 is 152 mm square, for example. It is preferable that it is less than or equal to 0.2 μm within a 132 mm square. The surface roughness of first main surface SF1 and second main surface SF2 is preferably 0.25 nm or less (smoothness in a 10 μm square area) in terms of root mean square roughness Rq.

  (B) Next, a predetermined region on the first main surface SF1 of the flat substrate 11 is ground in the direction of the second main surface SF2 to form the recess SCV (grinding step). Recess SCV is formed in the same region as recess CV when viewed from the normal direction of first main surface SF1. For example, a circular recess SCV having a diameter of 70 mmφ which is the same as that of the recess CV is formed.

In addition, as shown in FIG. 2, recess SCV is defined by bottom surface bf1, and side wall sd1 connecting bottom surface bf1 and first main surface SF1.
The depth dp1 of the recess SCV formed in the grinding step is shallower than the depth DP (predetermined depth) of the recess CV in FIG. The depth dp2, which is the difference between the bottom surface BF and the bottom surface bf1, is removed by an etching process that is a subsequent process of the grinding process. When the recess SCV is formed in the grinding process, a large processing pressure is applied to the bottom surface bf1, and the second inside of the substrate within a predetermined thickness in the direction from the surface of the bottom surface bf1 toward the second main surface SF2 Residual stress having a magnitude that deteriorates the flatness of the main surface SF2 remains. The depth dp2 (predetermined amount) of the substrate removed in the etching step needs to be at least the same as the predetermined thickness in which the residual stress remains, and is preferably larger than that. Therefore, the depth dp1 of the recess SCV formed in the grinding process is at most the distance between the bottom surface BF of the recess CV of the mask blank substrate 5 and the second main surface SF2 from the thickness of the substrate before the recess formation. (Thickness) TH and a depth obtained by subtracting the depth dp2 of the substrate to be removed in the etching process.

  Specifically, for example, a rotatable grinding head fixed to the tip of the rotating shaft is prepared. While rotating the grinding head, the grinding head is pressed against the region of the first main surface SF1 of the substrate 11 where the recess SCV is to be formed, and the substrate 11 is ground. Then, the grinding head may be inserted into the substrate 11 until the distance dp1 between the bottom surface bf1 of the recess SCV and the second main surface SF2 reaches the depth calculated by the above method.

  (C) After the grinding step, the bottom surface bf1 of the recess SCV is etched in the direction of the second main surface SF2, and the recess SCV is dug by a predetermined amount dp2 (etching step). A predetermined etching process is performed on the bottom surface bf1, and the concave portion SCV is dug to substantially the same depth as the concave portion CV shown in FIG. As the predetermined etching process, dry etching or wet etching using a resist film or a metal film having a concave pattern as a mask is preferable, and gas cluster ion beam (GCIB), plasma etching, etc. can be applied. In addition, an etching process in which residual stress does not remain on the substrate 11 can be given. In addition, non-contact polishing (MRF) or chemical mechanical polishing (CMP) using a magnetic fluid having a low processing pressure is also applicable.

In GCIB, an ion beam composed of clusters (aggregates) of atoms and molecules is generated, and this ion beam is irradiated onto the bottom surface bf1 of the recess SCV to etch the substrate in a direction perpendicular to the first main surface SF1. For example, the bottom surface bf1 of the recess SCV may be irradiated with an ion beam made of SF ₆ cluster or Ar cluster accelerated to 5 to 50 keV. Note that, according to GCIB, the flatness of the bottom surface BF of the recessed portion CV after the etching process is higher than that of RIE or ion beam etching (IBE).

  (C) After the etching process, the bottom surface BF and the side wall SD of the recess CV are mirror-polished by polishing with a low processing pressure by a method such as magnetic fluid polishing (MRF), polishing using a polishing slurry, or chemical mechanical polishing (CMP). Finish (planarization process). In the planarization step, it is desirable that at least the surface roughness of the bottom surface BF of the recess CV is planarized to an arithmetic average roughness Ra of 0.3 nm or less. Through the above steps, the mask blank substrate 5 shown in FIGS. 1A and 1B can be manufactured.

  As described above, according to the first embodiment of the present invention, the following operational effects can be obtained.

  When all of the concave portions CV having a predetermined depth shown in FIG. 1A are formed by the “grinding process”, the residual stress is applied to the inside of the substrate in the range of the predetermined thickness in the direction from the surface of the bottom surface BF toward the second main surface SF2. As a result, the flatness of the second main surface SF2 of the substrate 11 deteriorates. Further, when all of the concave portions CV having a predetermined depth shown in FIG. 1A are formed by the “etching process”, a very long processing time is required, which is difficult to apply at the production level. Therefore, in the grinding process where the processing pressure is relatively high, the concave portion SCV is formed by grinding only the depth dp1 shallower than the final predetermined depth DP, and the concave portion SCV is formed in the etching step where the processing pressure is hardly applied. Etching is carried out to a predetermined depth DP shown in FIG. Then, the etching process is performed so that a region where residual stress that affects the flatness of the second main surface SF2 does not reach the inside of the substrate closer to the second main surface SF2 than the position of the bottom surface BF. The predetermined amount dp2 is determined so as to include a region in which the residual stress resulting from the grinding process remains in the substrate within the range of the depth dp2 (predetermined amount). The depth dp1 to be dug in the grinding process includes the thickness of the substrate before forming the recess, the predetermined amount dp2 to be removed in the etching process, the bottom surface BF of the recess CV of the mask blank substrate 5, and the second main surface SF2. Is determined from the relationship with the distance (thickness) TH.

  By adopting such a manufacturing method, the flatness of the second main surface of the mask blank substrate 5 that is finally completed is high in processing speed up to the digging depth that can maintain the state before the recess processing, but there is a problem of residual stress. The recess SCV can be formed by a certain grinding process, and the remaining recess digging can be carried out in an etching process with no significant problem of residual stress, but the processing speed is significantly slow to form the recess CV having a predetermined depth. That is, the recess CV having a predetermined depth can be formed by making the most of the advantages of both processes.

  The “predetermined amount” in the etching step is preferably 1 μm or more and 1 mm or less. The predetermined amount is preferably 10 μm or more, and more preferably 50 μm or more. Furthermore, the predetermined amount is preferably 500 μm or less, and more preferably 100 μm or less. Thereby, the concave portion CV can be efficiently formed while maintaining the flatness of the second main surface SF2 high. That is, the recess CV having a predetermined depth can be formed by making the best use of the advantages of both processes.

  The predetermined depth is preferably a depth at which a distance between the bottom surface of the recess and the second main surface is 0.5 mm or more and 2.0 mm or less. Within this range, it is possible to avoid the possibility that the substrate between the bottom surface of the recess and the second main surface will not return to its original shape after deformation or the possibility of cracking. The lower limit of the distance between the bottom surface of the recess and the second main surface is more preferably 0.6 mm or more, and the upper limit is a depth of 1.6 mm or less. More preferred.

  In the planarization step, the surface roughness of the bottom surface BF of the recess CV is planarized to an arithmetic average roughness Ra of 0.3 nm or less. When pattern transfer is performed on the photo-curing resin using the imprint mold formed using the mask blank substrate 5, light scattering at the bottom surface BF of the recess CV can be suppressed.

  Recess CV is formed in a region having a size including mold pattern formation region MR of second main surface SF2. Thereby, all the parts of the mold pattern can be deformed. Further, when pattern transfer is performed on the photo-curing resin, the boundary portion between the concave portion CV and the first main surface SF1 does not reach the mold pattern formation region MR, so the mold pattern formation region MR of the second main surface SF2 As a result, light can be incident on the entire surface of the resin and the entire photo-curing resin can be cured.

(Second Embodiment)
In the second embodiment, a method for manufacturing an imprint mold mask blank using the above-described mask blank substrate 5 will be described.

  FIG. 3 is a cross-sectional view showing a configuration of an imprint mold mask blank 3 manufactured by the method of manufacturing an imprint mold mask blank according to the second embodiment. The mask blank 3 for imprint mold has a thin film 4 for pattern formation (for example, a chromium film) on the second main surface SF2 facing the first main surface SF1 in which the concave portion CV of the mask blank substrate 5 is formed. Is formed. That is, the pattern-forming thin film 4 is uniformly formed on the main surface SF2 on the side where the mold pattern is formed.

  The pattern forming thin film 4 may be a single layer or a plurality of layers. For example, a mask blank made of a single layer film of a chromium-based material is an example. As another example, the thin film 4 has a laminated structure of an upper layer and a lower layer, the upper layer is formed of a chromium (Cr) -based material, and the lower layer is formed of a material mainly containing tantalum (Ta). Etc. Examples of the chromium (Cr) -based material include Cr alone, or Cr compounds such as Cr nitride, carbide, and carbonitride. In the case of a single layer film of a chromium-based material, CrOCN is particularly preferable. Further, as a material mainly composed of tantalum, for example, Ta compounds such as TaHf, TaZr, TaHfZr, or such Ta compounds as base materials, for example, secondary materials such as B, Ge, Nb, Si, C, and N are used. There are added materials.

  A film forming process for forming a thin film for pattern formation will be described. In the film forming process of the thin film 4, for example, a sputtering film forming method may be used. According to the sputtering film forming method, the thin film 4 having a uniform film thickness can be formed. When a TaHf film is formed as the lower layer by sputtering film formation, an alloy target of Ta and Hf is used as a sputtering target, and an inert gas such as argon gas or helium gas is used as the sputtering gas introduced into the chamber. Use. When a CrN film, for example, is formed as the above upper layer, a Cr target is used as a sputtering target, and a sputtering gas introduced into the chamber is a mixture of nitrogen and an inert gas such as argon gas or helium gas. .

  The imprint mold mask blank 3 may be one in which a resist film is further formed on the thin film 4.

(Third embodiment)
In the third embodiment, an imprint mold manufacturing method using the above-described imprint mold mask blank 3 will be described.

  FIG. 4A is a cross-sectional view showing the configuration of the imprint mold 2 manufactured by the method of manufacturing the imprint mold 2 according to the third embodiment. The imprint mold 2 is obtained by forming a mold pattern 9 (concave / convex pattern) on the second main surface SF2 facing the first main surface SF1 in which the recess CV is formed. As described above, the recess CV is formed in a region having a size including the mold pattern formation region MR.

  FIG.4 (b) is a schematic sectional drawing for demonstrating the use condition of the imprint mold 2 of Fig.4 (a). The imprint mold 2 is applied to a resist film 32 such as a UV curable resin or a thermosetting resin, which is applied on the transfer member constituting layer 31 such as a silicon wafer in the transfer target (transfer object) 30. The mold pattern 9 is pressed directly. Thereby, the mold pattern 9 is transferred to the resist film 32. After the transfer, the mold pattern 9 can be easily deformed with a small force when the imprint mold 2 shown in FIG. Therefore, it is possible to suppress damage to the pattern transferred onto the transfer target 30, damage to the mold pattern 9, and the like.

  With reference to Fig.5 (a)-FIG.5 (g), the manufacturing method of the imprint mold 2 concerning 3rd Embodiment is demonstrated. FIG. 5A to FIG. 5G are cross-sectional views showing main steps for forming the mold pattern 9 on the second main surface SF2 of the imprint mold mask blank 3 of FIG. 5 (a) to 5 (e) are enlarged views showing a region G surrounded by a dotted line in FIGS. 3 and 4 (a) in order to show detailed processing steps of the mold pattern 9. FIG. Show.

  (I) First, as shown in FIG. 5A, for example, a resist for electron beam drawing is applied on the thin film 4 of the mask blank 3 for imprint mold, and a predetermined baking process is performed. Thus, a resist film 35 is formed on the second main surface SF2 of the imprint mold mask blank 3.

  (B) Next, a predetermined pattern (for example, a line and space pattern) is drawn on the resist film 35 using an electron beam drawing apparatus or the like. Thereafter, as shown in FIG. 5B, the resist film 35 is developed to form a resist pattern 35a. The portion where the resist pattern 35a is left corresponds to the convex portion of the mold pattern 9 formed later, and the portion where the resist film 35 is removed and the thin film 4 is exposed is the mold pattern 9 formed later. It corresponds to a concave portion.

  (Ii) The imprint mold mask blank 3 on which the resist pattern 35a is formed is introduced into a dry etching apparatus. Then, the thin film 4 is etched using the resist pattern 35a as a mask to form the thin film pattern 4a as shown in FIG. 5C (etching step). The shape of the thin film pattern 4a corresponds to the shape of the resist pattern 35a. Here, the imprint mold mask blank 3 may be temporarily removed from the dry etching apparatus, and the remaining resist pattern 35a may be removed as shown in FIG. Depending on the layer configuration and material of the thin film 4, the thin film pattern 4a may be formed by a plurality of stages of etching.

  (Ii) Using the thin film pattern 4a as a mask, the second main surface SF2 of the mask blank substrate 5 is etched to form the second main surface SF2 of the mask blank substrate 5 as shown in FIG. Then, the mold pattern 9 is formed (etching step). The shape of the mold pattern 9 corresponds to the shape of the thin film pattern 4a.

  (E) Next, as shown in FIG. 5 (f), a resist pattern 7 for a base structure is formed on the second main surface SF2 of the mask blank substrate 5 on which the mold pattern 9 is formed. The thin film 4 other than the portion protected by the resist pattern 7 is removed from the second main surface SF2 of the mask blank substrate 5 by a method such as wet etching. For example, wet etching is performed. As a result, as shown in FIG. 5G, a pedestal structure is obtained in which the periphery of the mold pattern 9 is lower than the surface on which the mold pattern 9 is formed.

  (F) Thereafter, the imprint mold 2 shown in FIG. 4A can be manufactured by removing the resist pattern 7 and the thin film pattern 4a.

  A 152 mm square substrate 11 is prepared, and a circular concave portion having a diameter of 70 mmφ and a depth (predetermined depth) DP of 5 mm is formed on the first main surface SF1 of the substrate 11, and FIGS. The mask blank substrate 5 shown in FIG. The formation of the recess was performed according to the procedure described with reference to FIG.

  A thin film 4 in which a TaHf film and a CrN film are laminated is formed on the second main surface SF2 of the above-described mask blank substrate 5, and an imprint mold mask blank 3 is manufactured. Furthermore, a resist for electron beam drawing (Fuji Film Electronics Materials PRL009) was applied on the thin film 4 to a thickness of 50 nm. And the predetermined baking process was performed and the resist film 35 was formed on the mask blank 3 for imprint molds.

  Next, a line and space pattern with a half pitch of 20 nm was drawn on the resist film 35 using an electron beam drawing machine, and then the resist film 35 was developed to form a resist pattern 35a.

  Next, the imprint mold mask blank 3 on which the resist pattern 35a was formed was introduced into a dry etching apparatus, and dry etching was performed using chlorine gas not containing oxygen. As a result, the thin film 4 in which the TaHf film and the CrN film were laminated was etched using the resist pattern 35a as a mask to form the thin film pattern 4a. The etching end point at this time was determined by using a reflection optical end point detector.

  Here, the mask blank 3 for imprint mold was once taken out from the dry etching apparatus, and the remaining resist pattern 35a was removed with a sulfuric acid / hydrogen peroxide solution.

Then, the imprint mold mask blank 3 was again introduced into the same dry etching apparatus, and dry etching using a fluorine-based (CHF ₃ ) gas was performed. Thereby, the substrate 11 made of synthetic quartz glass was etched using the thin film pattern 4a as a mask to form a glass pattern (glass step pattern) as the mold pattern 9.

  In addition, in order to confirm the cross-sectional shape of a glass pattern here, the blank for evaluation produced similarly to the above was fractured | ruptured, and the pattern cross section was observed with the scanning electron microscope. As a result, it was confirmed that the glass pattern had the same width as the thin film pattern 4a and the glass pattern had a uniform depth.

  Next, a photoresist (iP3500, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to a thickness of 460 nm on the mask blank 3 for imprint mold on which the above glass pattern has been created, and exposure and development with ultraviolet rays are performed to form a resist for a base structure. Pattern 7 was formed.

Next, the imprint mold mask blank 3 on which the resist pattern 7 for the pedestal structure is formed is subjected to wet etching with a ceric ammonium nitrate solution, and the portion other than the portion protected by the resist pattern 7 The thin film 4 was removed. Further, dry etching using a fluorine-based (CHF ₃ ) gas was performed to remove a part of the substrate 11 other than the part protected by the resist pattern 7. Further, by removing the resist pattern 7 with sulfuric acid / hydrogen peroxide, a pedestal structure having a depth of about 15 μm was created. Further, the thin film pattern 4a on the glass pattern was removed with a ceric ammonium nitrate solution. Thereby, the imprint mold 2 shown to Fig.4 (a) was able to be produced.

(Comparative example)
A 152 mm square substrate corresponding to the substrate 11 of FIGS. 1A and 1B was prepared, and a circular recess having a diameter of 70 mmφ and a depth of 5 mm was formed on the first main surface SF1 of the substrate. All the concave portions were formed by using countersink processing (grinding).

  After forming the concave portion, the flatness of the second main surface SF2 of the substrate facing the first main surface SF1 was measured. Here, the flatness is a value representing the warp (displacement amount) of the surface indicated by TIR (Total Indicated Reading), and is determined, for example, in the area of 142 mm square by the least square method with reference to the substrate surface. The plane is the focal plane, and the absolute value of the height difference between the highest position of the substrate surface above the focal plane and the lowest position of the substrate surface below the focal plane.

  As shown in FIG. 6, it can be seen that a region of the second main surface SF2 of the substrate facing the concave portion formed by countersinking is greatly raised. When the flatness of a 142 mm square was measured, the TIR was 0.448 μm. In FIG. 6, the center of the recess substantially overlaps the center of the 142 mm square area where the flatness was measured. Note that a polishing process using a circular polishing buff is performed in advance on the second main surface SF2 of the substrate facing the recess before forming the recess. For this reason, the four corners of the 142 mm square region are more difficult to be polished than the center portion and rise.

  Compared to the substrate of the comparative example described above, according to the first embodiment of the present invention, the flatness of the second main surface SF2 of the mask blank substrate 5 can be increased.

  As described above, the present invention has been described in terms of three embodiments. However, it should not be understood that the description and drawings that form part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

2 Imprint mold 3 Mask blank for imprint mold 4 Thin film 5 Substrate for mask blank 9 Mold pattern 11 Substrate BF, bf1 Bottom CV, SCV Recess MR Mold pattern formation area SD, sd1 Side wall SF1 First main surface SF2 Second Main surface

Claims (7)

A method for manufacturing a mask blank substrate used in a mask blank for producing an imprint mold,
Providing a substrate comprising opposing first and second major surfaces; and
Grinding a predetermined region on the first main surface of the substrate in the direction of the second main surface to form a recess;
An etching step of further performing a predetermined amount of etching in the direction of the second main surface on the bottom surface of the concave portion to form a concave portion having a predetermined depth;
A method for manufacturing a mask blank substrate, comprising:   The method for manufacturing a mask blank substrate according to claim 1, wherein the predetermined amount is 10 μm or more and 1 mm or less.   The said predetermined depth is a depth from which the distance between the bottom face of the said recessed part and the said 2nd main surface becomes 0.5 mm or more and 2.0 mm or less, The Claim 1 or 2 characterized by the above-mentioned. A method for manufacturing a mask blank substrate.   4. The method according to claim 1, further comprising a flattening step of flattening the surface roughness of the bottom surface of the concave portion to 0.3 nm or less with an arithmetic average roughness Ra after the etching step. 5. The manufacturing method of the board | substrate for mask blanks as described in a term.   5. The mask blank according to claim 1, wherein the concave portion is formed in a region having a size including a region in which a mold pattern on the second main surface is formed. 6. A method for manufacturing a substrate.   A film forming step for forming a thin film for pattern formation on the second main surface of the mask blank substrate manufactured by the method for manufacturing a mask blank substrate according to claim 1. The manufacturing method of the mask blank for imprint mold characterized by these.   An imprint mold comprising an etching process for etching the thin film and the mask blank substrate in the mask blank for imprint mold manufactured by the method for manufacturing a mask blank for imprint mold according to claim 6. Production method.

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