JP2008221516A - Machining method of substrate, imprint mold and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machining method capable of reducing the size of a crack due to chipping and suppressing foreign matter from adhering to the surface of the substrate. <P>SOLUTION: The machining method comprises a step which selectively forms a protective film 50 on the substrate 10, and exposes a part of the surface of the substrate 10 as a machining area 18, a step which removes the upper part of the substrate 10 of the machining area 18 with the depth of 400 nm or more, and 1000 nm or less, and a step for roughening so that an arithmetic average surface roughness Ra is within the range of 30 nm or more and 500 nm or less, and a step for cutting a part of the surface which is roughened by using a cutting tool 52 in the machining area 18. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a substrate processing method using a cutting tool, an imprint mold, and a manufacturing method thereof.

  In imprint lithography, an imprint mold is pressed to transfer a fine concavo-convex pattern in a pattern area on the surface of the imprint mold to a transfer object. In such imprint lithography, it is desired that the minute uneven pattern, which is the transfer pattern of the pattern area, is brought into contact with the transferred object side, but other non-pattern areas are not desired to be brought into contact. Stress is locally generated due to foreign matter or the like adhering to the non-pattern area due to contact with the transfer object, causing cracks. A proposal has been made to provide a step between a pattern region and a non-pattern region on the surface of the imprint mold (see, for example, Patent Document 1).

As the step processing method, a method of removing the surface of the non-pattern region, such as etching, abrasive processing, cutting processing, or the like can be used. Alternatively, a method of bonding a substrate on which a pattern region is formed to a substrate including a non-pattern region can be used. As a processing method, it is desirable to use cutting in consideration of ease of processing, processing speed, and the like.
In general, in the cutting process, a crack occurs due to chipping on the non-processed area side at the boundary between the cutting process area and the non-processed area on the substrate surface. The generation of a crack is synonymous with the generation of a minute piece, that is, the generation of a foreign material, and causes the foreign material to adhere to the substrate surface. In addition, the crack is a factor that should be avoided because it becomes a starting point of damage when an external force is applied to the substrate.

  Since the pattern transferred by the imprint mold is composed of minute irregularities on the surface, it is necessary to avoid adhesion of foreign matter to the surface. Therefore, it is necessary to take measures against chipping in imprint mold manufacturing. However, since the substrate surface on which the imprint mold pattern area or the like is formed is usually a mirror surface, stress during cutting tends to propagate to the substrate surface. Therefore, there is a limit to reducing chipping.

  There is a proposal for a method of suppressing chipping in the groove processing or cutting processing of a substrate. For example, there is a proposal of a method of roughing and cutting the substrate surface in a dicing region (see, for example, Patent Document 2). In addition, there is a proposal to process and form grooves on the substrate surface exposed between the chipping prevention films (see, for example, Patent Document 3).

  As shown in Patent Document 2, by roughening the surface of the dicing region, the chipping size and the number of occurrences of chipping can be reduced, and the size of cracks caused by chipping can be reduced. Therefore, it is effective to roughen the substrate surface even in the cutting process. However, it is impossible to prevent the adhesion of foreign matters due to chipping.

  Further, in cutting, as shown in Patent Document 3, by forming a protective film in the non-processed region of the substrate surface, it is possible to prevent foreign matter from adhering to the non-processed region. However, this method cannot prevent cracking due to chipping during cutting.

As a method of dealing with chipping, there is a method of reducing a chipping portion generated on a substrate by dry etching (see, for example, Patent Document 4). As other general methods, there are a method of chamfering (beveling) after processing, a method of polishing a surface on which chipping has occurred after processing, and the like. As in these methods, chipping generated during cutting can be reduced by cutting the chipping by etching or grinding after processing. As a result, at the same time, chipping starting from the chipping portion is less likely to occur. These methods are very effective as processing after cutting. However, such a processing method after processing cannot suppress the occurrence of chipping during processing.
JP 2005-508075 gazette JP 2005-329692 A JP 2005-243947 A JP 2005-322738 A

  An object of the present invention is to provide a substrate processing method, an imprint mold, and a manufacturing method thereof, which can reduce the size of cracks caused by chipping and suppress adhesion of foreign matter to the substrate surface.

  According to the first aspect of the present invention, (b) a step of forming a protective film on the substrate, and (b) a step of selectively removing the protective film and exposing a part of the surface of the substrate as a processing region; (C) removing the upper portion of the substrate in the processing region at a depth of 500 nm or more and 1000 nm or less, and roughening the arithmetic average roughness Ra to be in the range of 50 nm or more and 1000 nm or less; (D) cutting a part of the roughened surface of the substrate using a cutting tool in a processing region.

  According to the second aspect of the present invention, (b) a step of forming a pattern in the pattern region on the substrate surface, (b) a step of forming a protective film on the substrate, and (c) a protective film on the pattern region. The step of selectively removing the protective film so as to remain, exposing a part of the surface of the substrate as a processing region, and (d) removing the upper portion of the substrate in the processing region at a depth of 500 nm or more and 1000 nm or less. A step of roughening so that the arithmetic average roughness Ra is in the range of 50 nm or more and 1000 nm or less, and (e) a roughened substrate surface using the cutting tool in the processing region And a step of cutting a part of the surface of the processing region so as to remain along the outer periphery of the imprint mold.

According to the third aspect of the present invention, (b) a pattern region provided on the surface of the substrate and (b) provided along the outer periphery of the pattern region, and 500 nm or more and 1000 nm or less from the uppermost surface of the pattern region. A roughened region having a surface with an arithmetic average roughness Ra of 50 nm or more and 1000 nm or less, and (c) 500 nm or more from the surface of the roughened region. And an imprint mold comprising a cutting region having a surface at a depth of 1 mm or less.

  According to the present invention, it is possible to provide a substrate processing method, an imprint mold, and a manufacturing method thereof that can reduce the size of cracks caused by chipping and suppress adhesion of foreign matters to the substrate surface.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  As shown in FIGS. 1 and 2, the imprint mold according to the embodiment of the present invention has a pattern region 12 and a processing region 18 on the surface of the substrate 10. The processing region 18 includes a roughening region 14 provided along the outer periphery of the pattern region 12 and a cutting region 16 provided along the outer periphery of the roughening region 14. Patterns such as line and space (L / S), dots, pillars, and holes are arranged in the pattern area 12. The pattern shape may be concave or convex with respect to the surface of the substrate 10. Further, the pattern pitch and aspect ratio (the value of the ratio of the groove depth to the opening width) are not limited and are arbitrary.

In the case of optical imprint lithography, as the substrate 10, for example, transparent materials such as quartz glass having a thickness of about 6 mm to 7 mm, heat-resistant glass, calcium fluoride (CaF ₂ ), and magnesium fluoride (MgF ₂ ), and these transparent materials A laminated structure of materials is used. In the case of thermal imprint lithography, silicon carbide (SiC), Si, SiC / Si, silicon oxide (SiO ₂ ) / Si, silicon nitride (Si ₃ N ₄ ) / Si, or the like is used as the substrate 10. Further, a metal substrate such as tantalum (Ta), aluminum (Al), titanium (Ti), and tungsten (W) may be used.

  In the manufacture of an imprint mold, for example, after forming a plurality of pattern regions on a substrate such as quartz, a cutting process is performed in which a step is formed between the pattern regions using a cutting tool such as an end mill or a cutting tool. As shown in FIG. 3, when the cutting region 16 in which the surface 20 is cut using a cutting tool is formed on the substrate 10, a crack 24 is generated by chipping on the surface 20 side of the substrate 10 along the end of the cutting region 16. . In this specification, the dimension L of the crack 24 is from the end of the cutting region 16 where the crack 24 is generated in FIG. 3 to the ridgeline of the crack 24 in the direction perpendicular to the end of the cutting region 16 on the surface 20 of the substrate 10. The longest distance is defined as the following discussion.

  In imprint lithography, an imprint mold is pressed against a film to be transferred to transfer the pattern of the pattern region 12. Therefore, the crack generated in the substrate 10 becomes a base point for damage when a force is applied to the substrate 10. Further, if foreign matter generated by chipping adheres to the pattern region 12, it is impossible to transfer a faithful pattern. For this reason, it is desirable to reduce the size of cracks generated by cutting and to suppress the generation of foreign matter.

  When the surface of the substrate 10 is cut with a cutting tool, stress is generated on the surface of the substrate 10. In this case, for example, as shown in FIG. 4, when the surface 20 of the substrate 10 is a mirror surface, there is nothing to interrupt the stress propagating on the surface 20, so that the dimension La of the crack 24 due to chipping tends to increase. On the other hand, in the embodiment of the present invention, as shown in FIG. 5, before forming the cutting region 16, the substrate 10 is removed from the first horizontal level of the surface 20 to the depth D by etching, abrasive processing or the like. Then, the surface of the roughened region 14 is roughened. In this case, the stress propagating on the surface of the roughened region 14 is absorbed by the minute unevenness and stops. As a result, the size Lb of the crack due to chipping is smaller than La.

  For example, the processing region of the quartz glass substrate can be removed by dry etching so that the depth D is about 500 nm, the substrate surface can be roughened, and cutting can be performed by an end mill. The end mill has a diameter of about 0.5 mm and is held perpendicular to the cutting surface. The surface of the processing region is cut while moving the end mill from one corner to the other end in a direction parallel to the boundary between the roughening region 14 and the cutting region 16 shown in FIG. The end mill is sequentially moved in a direction perpendicular to the boundary, and parallel feed cutting is repeated to cut from the corner of the substrate to the boundary. The cutting depth is about 3 mm, for example.

  In that case, the relationship between the surface roughness, the crack size, and the number of foreign matters is examined as follows. The surface roughness may be measured by, for example, an atomic force microscope (AFM). In this specification, the surface roughness will be described using the arithmetic average roughness Ra defined in JIS B0601-1994. Further, the number of foreign matters adhered to the substrate surface is inspected by a foreign matter inspection machine at a level of 0.5 μm to 1 μm (hereinafter referred to as 1 μm) and 1 μm to 5 μm (hereinafter referred to as 5 μm).

  FIG. 6 shows the relationship between the surface roughness Ra and the crack size. It can be seen from FIG. 6 that both the maximum and average crack dimensions decrease as the surface roughness Ra increases to about 50 nm. When the surface roughness Ra is about 50 nm or more, the maximum value and the average value of the crack dimensions are reduced to about 12 μm and about 5 μm, respectively.

  FIG. 7 shows the relationship between the surface roughness Ra and the number of foreign matters. As shown in FIG. 7, it can be seen that both the 1 μm and 5 μm level foreign matter detected on the substrate surface decrease in number to about 30 or less when the surface roughness Ra exceeds about 50 nm.

  Thus, it can be seen that the surface roughness Ra of the substrate is desirably 50 nm or more in order to reduce the size of the cracks and to reduce foreign substances adhering to the substrate surface. When the roughening process is performed by dry etching, wet etching, or the like, the processing time becomes long to increase the surface roughness Ra. Therefore, practically, the surface roughness Ra is desirably about 1000 nm or less.

  FIG. 8 shows the relationship between the roughening depth of the substrate surface and the crack size. As shown in FIG. 8, it can be seen that the maximum value and the average value of the crack size are reduced by increasing the depth of the roughening process. It can be seen that both the 1 μm and 5 μm level foreign matter detected on the substrate surface decrease in number to about 30 or less when the roughening depth exceeds about 500 nm. Thus, it can be seen that the roughening depth is desirably 500 nm or more. In order to perform the roughening process by dry etching, wet etching, or the like, the etching conditions are such that etching for normal processing purposes is difficult. Therefore, if the roughening process is deepened, the processing time becomes longer. Therefore, practically, the roughening depth is desirably about 1000 nm or less.

  Next, a processing method according to an embodiment of the present invention will be described with reference to FIGS. 9 to 12 by taking the imprint mold manufacturing method shown in FIGS. 1 and 2 as an example.

  (A) A pattern is formed in the pattern region 12 on the surface of the substrate 10 by photolithography, dry etching, or the like. The substrate 10 is a transparent substrate, for example, a quartz substrate having a thickness of about 6.35 mm. A protective film 50 such as a resist is applied to the surface of the substrate 10. As shown in FIG. 9, the protective film 50 is selectively removed by photolithography or the like so that the protective film 50 remains in the pattern region 12, and the surface of the substrate 10 is exposed as the processing region 18.

(B) As shown in FIG. 10, the surface of the processing region 18 is roughened by dry etching or the like using the protective film 50 as a mask. By roughening, the surface roughness Ra of the processing region 18 is set to, for example, about 50 nm. The etching depth D is, for example, about 500 nm. As an etching gas, for example, carbon tetrafluoride (CF ₄ ), dicarbon hexafluoride (C ₂ F ₆ ), trifluoromethane (CHF ₃ ), or the like is used.

  (D) As shown in FIG. 11, a part of the processing region 18 is cut with a cutting tool 52 such as an end mill so that the roughening region 14 remains between the pattern region 12 covered with the protective film 50. Region 16 is formed. The width Wd of the roughened region 14 is determined so as to be larger than the maximum value of the crack size obtained in advance by a preliminary experiment. For example, as shown in FIG. 6, since the maximum value of the crack dimension is about 16 μm, the width Wd of the roughened region 14 is determined to be about 20 μm or more as a processing margin. In consideration of the dimensional accuracy and alignment accuracy of a stage of a processing machine that performs cutting, it is desirable that the width of the roughened region 14 is set to about 500 nm or less as a processing margin.

  (E) As shown in FIG. 12, the protective film 50 is removed, and the imprint mold shown in FIGS. 1 and 2 is manufactured.

  In the imprint mold manufacturing method according to the embodiment of the present invention, the pattern region 12 is covered with the protective film 50 when the cutting region 16 is cut by the cutting tool 52. Therefore, it is possible to prevent foreign matter from adhering to the surface of the pattern region 12 during cutting. Further, the surface roughness of the processing region 18 of the substrate 10 is in the range of about 50 nm to about 1000 nm, and the depth of the roughening processing is in the range of about 500 nm to about 1000 nm. Therefore, the size of cracks generated by chipping can be reduced and the generation of foreign matters can be suppressed. As a result, adhesion of foreign matters to the surface of the pattern region 12 can be reduced, and breakage of the substrate 10 due to cracks can be suppressed.

  In the processing region 18, the protective film 50 is selectively removed. The protective film 50 such as a resist is softer than the substrate 10 such as quartz. For example, if a cutting tool is used without removing the protective film, stress is applied from the cutting tool to the protective film. The soft protective film also applies stress to the cutting tool, affecting the cutting tool axis. For this reason, the occurrence of chipping during processing is promoted. Moreover, a protective film is caught in a cutting tool, and processing capability deteriorates. Furthermore, the substrate is easily cracked by the stress applied to the protective film. As described above, it is desirable to form the processing region 18 by removing the protective film 50.

  As the protective film 50, for example, a photosensitive resist can be used. However, the protective film is not limited to a resist, and may be, for example, a photosensitive resin such as photosensitive polyimide, or a resin such as polyvinyl alcohol (PVA) or polyimide that can be applied by spin coating or spray coating. Moreover, you may use the dry film which can be laminated, the film with adhesive materials, such as a thermoplastic polyimide film. Further, as the protective film 50, a metal thin film or the like deposited by sputtering or vapor deposition may be used. The metal thin film can increase resistance during roughening.

In the above description, the case where dry etching is used for the roughening process is shown. However, the roughening process may be wet etching using a tetramethylammonium hydroxide (TMAH) aqueous solution, potassium hydroxide (KOH) aqueous solution, hydrofluoric acid (HF) nitric acid (HNO ₃ ) mixed solution, sandblasting, etc. It may be an abrasive processing.

(Other embodiments)
Although the embodiments of the present invention have been described as described above, it should not be understood that the descriptions and drawings constituting a 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.

  In the embodiment of the present invention, an example in which an end mill is used as the cutting tool 52 has been shown. However, a cutting tool 52 such as a cutting tool or a blade may be used. In the case of an end mill, it has a rotation axis perpendicular to the cutting surface. On the other hand, when using a cutting tool, the tool is simply moved in the machining direction. The tool may be moved while vibrating. In the case of a blade, it has a rotation axis that is parallel to the cutting surface and orthogonal to the machining direction.

  As described above, the present invention naturally includes various embodiments that are not described herein. Accordingly, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is a plane schematic diagram showing an example of an imprint mold concerning an embodiment of the invention. It is the schematic which shows the AA cross section of the imprint mold shown in FIG. It is a plane schematic diagram which shows an example of the chipping which generate | occur | produces by cutting. It is a cross-sectional schematic diagram which shows an example of the chipping generate | occur | produced by cutting. It is a cross-sectional schematic diagram which shows the other example of the chipping generate | occur | produced by cutting. It is a figure which shows an example of the relationship between surface roughness and a crack dimension. It is a figure which shows an example of the relationship between surface roughness and the number of foreign materials. It is a figure which shows an example of the relationship between the depth of a roughening process, and a crack dimension. It is sectional drawing (the 1) which shows an example of the manufacturing method of the imprint mold which concerns on embodiment of this invention. It is sectional drawing (the 2) which shows an example of the manufacturing method of the imprint mold which concerns on embodiment of this invention. It is sectional drawing (the 3) which shows an example of the manufacturing method of the imprint mold which concerns on embodiment of this invention. It is sectional drawing (the 4) which shows an example of the manufacturing method of the imprint mold which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate 12 ... Pattern area | region 14 ... Roughening area | region 16 ... Cutting area | region 18 ... Processing area | region 50 ... Protective film 52 ... Cutting tool

Claims (7)

Selectively forming a protective film on the substrate, exposing a part of the surface of the substrate as a processing region;
Removing the upper part of the substrate in the processing region at a depth of 500 nm or more and 1000 nm or less, and roughening the arithmetic average roughness Ra to be in a range of 50 nm or more and 1000 nm or less;
And a step of cutting a part of the roughened surface in the processing region. Forming a pattern in a pattern area on the substrate surface;
Selectively forming a protective film on the pattern region, exposing a part of the surface of the substrate as a processing region;
Removing the upper part of the substrate in the processing region at a depth of 500 nm or more and 1000 nm or less, and roughening the arithmetic average roughness Ra to be in a range of 50 nm or more and 1000 nm or less;
Cutting the part of the upper part of the processed region so as to leave the roughened substrate surface along the outer periphery of the pattern region in the processed region. Method. The method for manufacturing an imprint mold according to claim 2, wherein the substrate is made of quartz glass.   The imprint mold manufacturing method according to claim 2, wherein the protective film is a resin film.   The imprint mold according to any one of claims 2 to 4, wherein the processing region is roughened using at least one of dry etching, wet etching, and abrasive processing. Manufacturing method.   The imprint mold according to any one of claims 2 to 5, wherein the roughened region left along the outer periphery of the pattern region has a width of 20 µm or more and 500 µm or less. Manufacturing method. A pattern area provided on the surface of the substrate;
A roughened region that is provided along the outer periphery of the pattern region, and has a surface having a depth of 500 nm or more and 1000 nm or less from the uppermost surface of the pattern region and an arithmetic average roughness Ra of 50 nm or more and 1000 nm or less When,
An imprint mold comprising: a cutting region provided along an outer periphery of the roughening region and having a surface at a depth of 500 nm or more and 1 mm or less from the surface of the roughening region.

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