JP2019072885A - Production method of molding tool by dry etching method - Google Patents

Abstract

To provide a new production method of a molding tool which can form a fine irregular structure on a surface by a reactive ion etching method, without a patterning or the like, on a surface of the molding tool, for example.SOLUTION: A production method of a molding tool having an irregular structure on a surface comprises an etching step for performing a reactive ion etching on a surface of a substrate by generating plasma in presence of a mixed gas, before the etching step, no patterning step for performing patterning to the surface of the substrate is included. The mixed gas includes two kinds of fluorine-based gases, out of the two kinds of fluorine-based gases, one is sulfur hexafluoride (SF), and the other is a fluorine-based gas other than the sulfur hexafluoride.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing a mold by a dry etching method.

  An optical element having an optical function is manufactured, for example, by molding a molding material such as resin or glass using a molding die. In the case where the optical element is provided with an antireflection function as the optical function, for example, a mold having a fine uneven structure on the surface is used. By using the molding die, the optical element to be obtained is formed on the surface thereof with an inverted concavo-convex structure to which the concavo-convex structure of the mold has been transferred, and the antireflection convexity is exhibited by the inverted concavo-convex structure.

  As a method of forming a fine uneven structure, for example, a method of performing resist patterning using electron beam drawing, UV exposure and the like can be mentioned (Patent Document 1, Patent Document 2). However, when using electron beam lithography, there are restrictions on the area and shape of patterning, the thickness of the workpiece, the material of the workpiece, etc., and it is difficult to form a fine uneven structure on the surface such as a flat surface or a curved surface of the mold.

JP, 2010-52398, A JP, 2009-87431, A

  Therefore, the present invention provides a new method of manufacturing a mold which can form a fine uneven structure on the surface of the mold by reactive ion etching without requiring patterning or the like, for example. The purpose is to

In order to achieve the above object, the method of manufacturing a mold having a concavo-convex structure on the surface of the present invention includes an etching step of generating plasma in the presence of mixed gas and performing reactive ion etching on the surface of a substrate
It does not include the patterning step of patterning on the surface of the substrate before the etching step.
The mixed gas contains two fluorine-based gases,
One of the two types of fluorine-based gas is sulfur hexafluoride gas (SF ₆ ),
The other is a fluorine-based gas other than sulfur hexafluoride gas.

  The mold of the present invention is characterized by being produced by the above-mentioned production method of the present invention.

  The method for producing a molded body according to the present invention is characterized by including the step of molding the forming raw material using the molding die according to the present invention.

The method for producing a concavo-convex structure having a concavo-convex structure on the surface of the present invention is
Generating an plasma in the presence of a mixed gas to perform reactive ion etching on the surface of the substrate;
It does not include the patterning step of patterning on the surface of the substrate before the etching step.
The mixed gas contains two fluorine-based gases,
One of the two types of fluorine-based gas is sulfur hexafluoride gas (SF ₆ ),
The other is a fluorine-based gas other than sulfur hexafluoride gas.

  According to the manufacturing method of the present invention, by using a mixed gas containing at least two kinds of fluorine-based gas, for example, a mold having a fine uneven structure formed on the surface is obtained without performing patterning or the like. be able to.

FIGS. 1A to 1C are schematic views showing an embodiment of a method for manufacturing a mold. In FIG. 2, (A) is a SEM image of a wafer etched under the conditions of Example 1, and (B) is a SEM image of a wafer etched under the conditions of Comparative Example 1. FIG. 3 is a graph showing the relationship between the wavelength and the reflectance for the wafer of Example 1 and the wafer of Comparative Example 1. (A) shows the reflectance (%) of the X axis at 0 to 50%. It is a graph shown and (B) is a graph which showed the reflectance of the X-axis by 0 to 3%. In FIG. 4, (A) is a SEM image of a wafer etched under the conditions of Example 2, and (B) is a SEM image of a wafer etched under the conditions of Comparative Example 2. FIG. 5 is a graph showing the relationship between the wavelength and the reflectance for the wafer of Example 2 and the wafer of Comparative Example 2, where (A) shows the reflectance (%) of the X axis at 0 to 50%. It is a graph shown and (B) is a graph which showed the reflectance of the X-axis by 0 to 3%. In FIG. 6, (A) is a SEM image of a wafer etched under the conditions of Example 3, and (B) is a SEM image of a wafer etched under the conditions of Comparative Example 3. FIG. 7 is a graph showing the relationship between the wavelength and the reflectance for the wafer of Example 3 and the wafer of Comparative Example 3. (A) shows the reflectance (%) of the X axis at 0 to 50%. It is a graph shown and (B) is a graph which showed the reflectance of the X-axis by 0 to 3%.

In the production method of the present invention, for example, the fluorine-based gas other than sulfur hexafluoride gas is selected from tetrafluoromethane (CF ₄ ), trifluoromethane (CHF ₃ ), and cyclofluoride octabutane (C ₄ F ₈ ). And at least one selected from the group consisting of

  In the production method of the present invention, for example, the mixed gas is a mixed gas containing no oxygen.

The manufacturing method of the present invention is, for example, a gas other than the sulfur hexafluoride gas with respect to a total amount of the sulfur hexafluoride gas (SF ₆ ) and a fluorine-based gas other than the sulfur hexafluoride gas in the mixed gas. The proportion of fluorine-based gas is 20% or more.

In the production method of the present invention, for example, in the mixed gas, the total proportion of the sulfur hexafluoride gas (SF ₆ ) and the fluorine-based gas other than the sulfur hexafluoride gas is 80% or more.

In the production method of the present invention, for example, the mixed gas is composed of sulfur hexafluoride gas (SF ₆ ) and the fluorine-based gas other than sulfur hexafluoride gas.

  In the manufacturing method of the present invention, for example, the substrate includes a main body and a surface layer, and the surface layer is a metal layer.

  In the manufacturing method of the present invention, for example, the surface layer is a metal layer that reacts with the mixed gas.

  In the manufacturing method of the present invention, for example, the surface layer is at least one metal layer selected from the group consisting of tantalum (Ta), silicon (Si), titanium (Ti), and tungsten (W).

  In the manufacturing method of the present invention, for example, the substrate includes an intervening layer between the main body and the surface layer, and the intervening layer is a chromium (Cr) layer.

  The present invention will be specifically described below with reference to the drawings. The present invention is not limited or restricted at all by the following embodiments.

(Method of manufacturing mold)
FIGS. 1A to 1C are schematic views showing an embodiment of a method for manufacturing a mold of the present embodiment. In FIG. 1, (A) is a cross-sectional view of a main body constituting the substrate used in the etching step, (B) is a cross-sectional view of the substrate used in the etching step, (C) is It is sectional drawing of the shaping | molding die obtained by the said etching process to the said board | substrate. In the present invention, "molding die" means a die used for molding. The mold is not particularly limited. For example, a concavo-convex structure is formed on the surface of a Si wafer, a glass substrate, etc., and a mold used as a mold for imprint molding, etc. The copy mold of the concavo-convex structure is manufactured with resin etc, and the mold used as a mold etc. are mention | raise | lifted.

  In the method of manufacturing a mold of the present embodiment, first, a substrate is prepared (preparation step). The form of the substrate used in the etching step is not particularly limited, and examples thereof include a substrate having a main body and a surface layer. In the substrate having the main body and the surface layer, the surface layer is formed on the surface of the main body. For example, as shown in FIG. 1 (A), first, the main body 1 is prepared, and then, as shown in FIG. 1 (B), the surface of the main body 1 is sputtered, ion plated, vapor deposited or the like. The substrate 10 is obtained by forming the surface layer 2.

  When the substrate has the main body 1 and the surface layer 2 like the substrate 10, the material of the main body 1 is, for example, metal. The metal is not particularly limited, and examples thereof include stainless steel, prehardened steel, maraging steel, die steel, nonmagnetic steel (superhard steel), azrolled steel, copper, aluminum and the like.

  The material of the surface layer 2 is preferably, for example, a metal that reacts with the mixed gas. Examples of the metal that reacts with the mixed gas include tantalum (Ta), silicon (Si), titanium (Ti), tungsten (W), alloys thereof, and the like. The thickness of the surface layer 2 is not particularly limited, and is, for example, 0.5 to 1 μm.

  When the substrate includes the main body 1 and the surface layer 2 as the substrate 10, for example, an intervening layer may be further included between the main body 1 and the surface layer 2. The material of the intervening layer is, for example, metal, and specific examples thereof include chromium (Cr) and the like. The thickness of the intervening layer is not particularly limited, and is, for example, 0.05 to 0.1 μm.

  Next, after the step of preparing the substrate, as described above, in the method of manufacturing a mold according to this embodiment, plasma is generated in the presence of mixed gas to perform reactive ion etching on the surface of the substrate (etching Process). The etching process can be performed, for example, by generating plasma in the presence of the mixed gas using a general reactive ion etching apparatus. The apparatus is not particularly limited, and examples thereof include a capacitively coupled ion etching apparatus and an inductively coupled ion etching apparatus.

  The apparatus generally comprises a chamber (chamber) in which the substrate is placed during etching. The chamber has, for example, a pair of electrodes, and plasma can be generated by applying a high frequency voltage between the pair of electrodes. Specifically, the surface of the substrate is etched by plasmatizing the mixed gas, and as shown in FIG. 1C, a mold 20 having a plurality of uneven structures 3 can be manufactured.

  The introduction of the mixed gas into the chamber is preferably performed, for example, after evacuating the chamber. For the introduction of the mixed gas into the chamber, for example, a mixed gas mixed in advance may be introduced, or the various gases constituting the mixed gas may be mixed in the chamber by introducing them into the chamber. It may be gas. The conditions for introducing the mixed gas into the chamber are not particularly limited. The composition of the mixed gas is, for example, as described above, and specific examples will be described later. The flow rate of the mixed gas is not particularly limited, and, for example, various gases contained in the mixed gas may be introduced at a ratio described later.

  The gas pressure in the chamber is not particularly limited, and is, for example, 0.1 to 20 Pa.

  The conditions for generating the plasma in the etching are not particularly limited. The high frequency of the high frequency voltage is, for example, 1 MHz to 1 GHz. The power of the high frequency voltage is, for example, 50 to 500 W, and the bias power is, for example, 0 to 500 W. The time for the etching process is not particularly limited, and is, for example, 0.5 to 60 minutes, and the process temperature is not particularly limited, and is, for example, -20 to 30 ° C.

As described above, the mixed gas used in the present embodiment contains two types of fluorine-based gas, and one of the two types of fluorine-based gas is sulfur hexafluoride gas (SF ₆ ), and the other is And fluorine-based gas other than sulfur hexafluoride gas (hereinafter, also referred to as non-SF ₆ fluorine-based gas). The present invention is characterized by using the above-mentioned mixed gas, and the other steps and conditions are not limited at all.

Examples of the non-SF ₆ fluorine-based gas include methane tetrafluoride (CF ₄ ), trifluoromethane (CHF ₃ ), cyclobutane octafluoride (C ₄ F ₈ ) and the like. The non-SF ₆ fluorine-based gas may be, for example, one type or two or more types in combination.

Among the gases constituting the mixed gas, the flow rate of the SF ₆ gas is, for example, 40 to 400 sccm (6.75 × 10 ^{−2 to} 6.75 × 10 ⁻¹ Pa / m ³ / sec). The non-SF ₆ fluorine gas flow rate, for example, the flow rate of the SF ₆ gas, and a ratio of the non-SF ₆ fluorine gas for the SF ₆ gas to be described later, can be set.

In the mixed gas, the total amount of the non-SF ₆ fluorine-based gas and the SF ₆ gas, the proportion of non-SF ₆ fluorine-based gas, the lower limit is, for example, 20% or more, 25% or higher, 30% or more Or 35% or more, and the upper limit is, for example, 70% or less, 60% or less, 55% or less, or 50% or less, and the range is, for example, 20 to 70%, 20 to 60%, 20 to 55%, 20 to 50%, 25 to 70%, 25 to 60%, 25 to 55%, 25 to 50%, 30 to 70%, 30 to 60%, 30 to 55%, 30 to 50%, 35 to 5 70%, 35 to 60%, 35 to 55%, or 35 to 50%.

The mixed gas is, for example, the SF ₆ may be a gas comprising said a non-SF ₆ fluorine-based gas and a gas, may comprise the said SF ₆ gas and a non-SF ₆ fluorine gas and other gases. The other gases are not particularly limited, and examples thereof include argon gas and the like. In the mixed gas, the total proportion of the SF ₆ gas and the non-SF ₆ fluorine-based gas is, for example, 80% or more, 85% or more, 90% or more, or 100%.

  The mixed gas preferably contains substantially no oxygen, for example. Substantially oxygen-free, the mixing ratio of oxygen in the mixed gas is, for example, less than 1%, 0%, and not more than the detection limit.

  The mold 20 manufactured by the manufacturing method of the present embodiment has the uneven structure 3 on the surface thereof. In the concavo-convex structure 3, the convex portion is, for example, conical. The height of the convex portion is, for example, 70 to 250 nm, 75 to 240 nm, 80 to 150 nm, or 200 to 500 nm. The width (diameter) of the bottom surface of the convex portion corresponding to the pitch of the convex portion is, for example, 50 to 300 nm, 50 to 200 nm, 55 to 150 nm, or 60 to 130 nm.

  In the manufacturing method of the present embodiment, for example, a substrate having only the main body may be used instead of the substrate having the main body and the surface layer. When the substrate has only a main body, for example, it is formed by generating plasma in the presence of the mixed gas and performing reactive ion etching on the surface of the substrate consisting of the main body without providing the above-mentioned surface layer. The type is obtained.

  When the substrate has only a main body, the material of the main body is preferably, for example, a metal that reacts with the mixed gas. Examples of the metal that reacts with the mixed gas include tantalum (Ta), silicon (Si), titanium (Ti), tungsten (W), alloys thereof, and the like.

  According to the manufacturing method of the present invention, a mold having a fine uneven structure on the surface can be easily manufactured by the etching process. Further, according to the present invention, since the patterning step of patterning on the surface of the substrate is unnecessary before the etching step, and it is sufficient to perform the reactive ion etching using the mixed gas, for example, Irrespective of the surface structure (for example, a flat surface or a curved surface) of the substrate, the uneven structure can be easily formed.

  Moreover, the manufacturing method of the shaping | molding die in this embodiment can be used not only a shaping | molding die but the manufacturing method of an uneven structure body. In this case, in the method of manufacturing a mold of the present invention described above, the description can be incorporated by replacing “mold” with “concave and convex structure”.

  In addition, since the mold obtained by the present invention has the fine uneven structure, for example, in a molded product produced using the mold, a surface of a reverse uneven structure in which the uneven structure is reversed is formed. it can. For this reason, according to the said shaping | molding die, the molded object which shows the reflection preventing ability which has the said inversion uneven structure on the surface can be obtained. As said molded object, an optical element is preferable, for example.

  According to the mold, since the uneven structure is provided on the surface, for example, after a molded body is manufactured using the mold, the releasability of the molded body from the mold is also excellent. In addition, according to the molding die, since the surface of the inverted uneven structure can be formed on the molded body, the adhesive property of, for example, an adhesive or the like is improved by the inverted uneven structure, for example. As a result, adhesion can be improved.

(Mold)
As described above, the mold of the present invention is characterized by being manufactured by the method of manufacturing a mold of the present invention. The mold of the present invention has a fine uneven structure on the surface as described above. The description of the method for manufacturing the mold of the present invention can be incorporated into the mold of the present invention.

  The molding die of the present invention is, for example, a molding die for an optical element, and specifically, for example, a molding die for an optical element exhibiting an antireflective ability. In the case where the molding die of the present invention is for an optical element exhibiting the above-mentioned antireflective ability, the wavelength range of light for preventing reflection is not particularly limited.

(Method of manufacturing molded body)
As described above, the method for producing a molded body of the present invention is characterized by including a molding step of molding a molding material using the mold of the present invention. The production method of the present invention is characterized by using the mold of the present invention, and the other steps and conditions are not particularly limited.

  The forming raw material is not particularly limited, and can be appropriately determined, for example, according to the intended use of the formed body. When the molded body is the optical element, for example, transparent resin, glass and the like can be used, and the transparent resin is, for example, polymethyl methacrylate resin (PMMA), cycloolefin polymer (COP), cyclic olefin copolymer (COC) ), Polyether imide (PEI), etc. can be used.

  The molding method in the molding step is not particularly limited, and examples thereof include injection molding.

Example 1
In Example 1, a mixed gas of SF ₆ gas and CHF ₃ gas was used to perform reactive ion etching on the wafer. And about the wafer after processing, confirmation of the concavo-convex structure of the surface and measurement of reflectance were performed.

Specifically, the etching was performed as follows using an etching apparatus (etching time: 30 minutes). The wafer used was a disk-shaped plate with a diameter of 50 mm in which a tantalum (Ta) thin film was laminated on the surface of a silicon (Si) layer. The thickness of the Si layer was 0.5 mm, and the thickness of the Ta thin film was 0.6 μm. Further, as Comparative Example 1, the same conditions as in Example 1 (etching process time except that a mixed gas of SF ₆ gas and O ₂ gas was used instead of the mixed gas of SF ₆ gas and CHF ₃ gas Reactive ion etching was carried out at 28 to 30 minutes, and in the same manner, confirmation of the concavo-convex structure on the surface and measurement of reflectance were performed on the treated wafer.

  The surface of the wafer after etching was photographed with a scanning electron microscope (SEM). Further, as a reference example, SEM imaging was similarly performed on a Ta thin film of the wafer before the etching process. These results are shown in FIG. In FIG. 1, (A) shows the result of a wafer etched under the conditions of Example 1 (magnification 100,000 times, bar 100 nm), and (B) shows the wafer etched under the conditions of Comparative Example 1. It is a result (15,000 times of magnification, bar 1 micrometer). As shown in FIG. 1 (B), the wafer of Comparative Example 1 is only formed with a large number of holes formed in the laminated structure of the Si layer and the Ta thin film, and a conical convex portion is formed. The uneven structure which it had was not able to be confirmed. Specifically, a hole having a diameter of 500 nm which penetrates the inside of the Si layer from the Ta thin film was formed. On the other hand, in the wafer of Example 1, only by changing the kind of mixed gas, as shown in FIG. 1 (A), a fine, concavo-convex pattern is confirmed on the Si layer, and the convex portion is The tip has a sharp conical shape, and the height of the projections is high, and the pitch of the projections is also dense. Specifically, the height of the protrusions was 200 to 500 nm, and the width (diameter) of the bottom of the protrusions corresponding to the pitch was about 70 to 130 nm.

  When the mold has a concavo-convex structure, the molded body formed by using the mold has a reverse concavo-convex structure corresponding to the concavo-convex structure. That is, the concavo-convex structure of the mold and the reverse concavo-convex structure of the molded body are in a corresponding relationship. For this reason, it can be said that the reflectance of the wafer after etching indirectly indicates the reflectance of the compact formed by the wafer after etching. Therefore, the reflectance (%) for the light of 250 nm to 850 nm was measured for the wafer of Example 1 and the wafer of Comparative Example 1. Further, as a reference example, the reflectance (%) was similarly measured for the Ta thin film on the wafer before the etching process.

  These results are shown in FIG. FIG. 2 is a graph showing the relationship between the wavelength and the reflectance, where (A) is a graph showing the reflectance (%) of the X axis at 0 to 50%, and (B) is the graph of the X axis It is the graph which showed the reflectance by 0 to 3%. As shown in FIG. 2 (A), the wafer of Example 1 was able to lower the reflectance significantly more than the wafer (reference example) before the etching process. In addition, as shown in FIG. 2B, the wafer after the etching process of Comparative Example 1 has a reflectance of 0.2% in a narrow wavelength range (287 to 288 nm), while Example 1 The wafer after the etching process showed a lower reflectance of 0.12% in a wider wavelength range (417 to 425 nm). That is, since the fine concavo-convex structure has a conical shape in the wafer of Example 1 compared to the wafer of Comparative Example 1, more light in a wide wavelength range is absorbed into the fine concavo-convex structure and reflected light is suppressed. It can be said that

Example 2
The gas flow ratio was changed, etching was performed in the same manner as in Example 1 and Comparative Example 1, and confirmation of the surface of the wafer after the etching process and measurement of the reflectance were performed. The etching conditions of Example 2 and Comparative Example 2 are shown in Table 2 below.

  The surface of the wafer after etching was photographed with a scanning electron microscope (SEM). Further, as a reference example, SEM imaging was similarly performed on a Ta thin film of the wafer before the etching process. These results are shown in FIG. In FIG. 3, (A) shows the result of the wafer etched under the conditions of Example 2 (magnification 100,000 times, bar 100 nm), and (B) shows the wafer etched under the conditions of Comparative Example 2. It is a result (100, 000 times magnification, bar 100 nm). As shown in FIG. 3B, in the wafer of Comparative Example 2, although the pattern of the concavo-convex structure was confirmed on the Si layer, the tips of the convex portions are blunt and the height of the convex portions is also low. The pitch of the convex portions was also broad. Specifically, the height of the protrusions was 70 nm, and the width (diameter) of the bottom of the protrusions corresponding to the pitch was about 140 nm. On the other hand, in the wafer of Example 2, only by changing the kind of mixed gas, as shown in FIG. 2 (A), a fine, concavo-convex pattern is confirmed on the Si layer, and the convex portion is The tip has a sharp conical shape, and the height of the projections is high, and the pitch of the projections is also dense. Specifically, the height of the protrusions was 80 to 150 nm, and the width (diameter) of the bottom of the protrusions corresponding to the pitch was about 50 to 70 nm.

  Next, the reflectance (%) for the light of 250 nm to 850 nm was measured for the wafer of Example 2 and the wafer of Comparative Example 2. Further, as a reference example, the reflectance (%) was similarly measured for the Ta thin film on the wafer before the etching process.

  These results are shown in FIG. FIG. 4 is a graph showing the relationship between the wavelength and the reflectance, where (A) is a graph showing the reflectance (%) of the X axis at 0 to 50%, and (B) is the graph of the X axis It is the graph which showed the reflectance by 0 to 3%. As shown in FIG. 4A, the wafer of Example 2 was able to significantly reduce the reflectance compared to the wafer (reference example) before the etching process. Further, as shown in FIG. 4B, the wafer of Comparative Example 1 has a reflectance of 0.2% in a narrow wavelength range (335 to 336 nm), whereas the wafer of Example 2 has a reflectance of 0.2%. It showed lower reflectivity of 0.08% over a wider wavelength range (380-395 nm). That is, the wafer of Example 2 has a conical shape whose tip is sharper than that of the wafer of Comparative Example 2, and light in a wide wavelength range is absorbed more into the fine uneven structure. It can be said that reflected light is suppressed.

[Example 3]
The gas flow ratio was changed, etching was performed in the same manner as in Example 1 and Comparative Example 1, and confirmation of the surface of the wafer after the etching process and measurement of the reflectance were performed. The etching conditions of Example 3 and Comparative Example 3 are shown in Table 3 below.

  The surface of the wafer after etching was photographed with a scanning electron microscope (SEM). Further, as a reference example, SEM imaging was similarly performed on a Ta thin film of the wafer before the etching process. These results are shown in FIG. In FIG. 5, (A) shows the result of the wafer etched under the conditions of Example 3 (magnification 100,000 times, bar 100 nm), and (B) shows the wafer etched under the conditions of Comparative Example 3. It is a result (100, 000 times magnification, bar 100 nm). As shown in FIG. 5B, in the wafer of Comparative Example 3, although the pattern of the concavo-convex structure was confirmed on the Si layer, the tip of the convex portion is blunt and the height of the convex portion is also low. The pitch of the convex portions was also broad. Specifically, the height of the protrusions was 70 nm, and the width (diameter) of the bottom of the protrusions corresponding to the pitch was about 70 nm. On the other hand, in the wafer of the third embodiment, only by changing the kind of mixed gas, as shown in FIG. 5A, a pattern of fine and uneven structure is confirmed on the Si layer, and the convex portion is The tip has a sharp conical shape, and the height of the projections is high, and the pitch of the projections is also dense. Specifically, the height of the protrusions was 80 to 130 nm, and the width (diameter) of the bottom of the protrusions corresponding to the pitch was about 50 to 100 nm.

  Next, the reflectance (%) for the light of 250 nm to 850 nm was measured for the wafer of Example 3 and the wafer of Comparative Example 3. Further, as a reference example, the reflectance (%) was similarly measured for the Ta thin film on the wafer before the etching process.

  These results are shown in FIG. FIG. 6 is a graph showing the relationship between the wavelength and the reflectance, (A) is a graph showing the reflectance (%) of the X axis at 0 to 50%, and (B) is a graph showing the X axis It is the graph which showed the reflectance by 0 to 3%. As shown in FIG. 6A, the wafer of Example 3 was able to reduce the reflectance significantly more than the wafer (reference example) before the etching process. Also, as shown in FIG. 6B, the wafer of Comparative Example 3 had a reflectance of 0.12% at 432 to 43 nm, while the wafer of Example 3 had a reflectance of 412 to 42 nm. It showed a low reflectance of 0.03%. That is, the wafer of Example 3 has a conical shape whose tip is sharper than that of the wafer of Comparative Example 3, and light in a wide wavelength range is absorbed more into the fine uneven structure body to suppress reflected light. It can be said that

  As shown in Examples 1 to 3 described above, it is possible to form a finer and sharper uneven structure for each comparative example in which the mixed gas ratio is the same condition only by changing the type of mixed gas in reactive ion etching. all right.

Further, as shown in Example 1-3, by changing the ratio of the SF ₆ gas and CHF ₃ gas in the mixed gas, it is also possible to adjust the pitch and height of the convex portion of the concavo-convex structure.

  Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. The configurations and details of the present invention can be modified in various ways that can be understood by those skilled in the art within the scope of the present invention.

As described above, according to the manufacturing method of the present invention, by using a mixed gas containing at least two types of fluorine-based gas, for example, a fine uneven structure is formed on the surface without performing patterning or the like. Can be obtained.

Claims (15)

Generating an plasma in the presence of a mixed gas to perform reactive ion etching on the surface of the substrate;
It does not include the patterning step of patterning on the surface of the substrate before the etching step.
The mixed gas contains two fluorine-based gases,
Of the two types of fluorine-based gas,
One is sulfur hexafluoride gas (SF ₆ ),
The other is fluorine gas other than sulfur hexafluoride gas, The manufacturing method of the shaping | molding die which has an uneven | corrugated structure on the surface characterized by the above-mentioned. The fluorine-based gas other than sulfur hexafluoride gas is at least one selected from the group consisting of methane tetrafluoride (CF ₄ ), trifluoromethane (CHF ₃ ), and octafluoride cyclobutane (C ₄ F ₈ ) The manufacturing method according to claim 1. The method according to claim 1, wherein the mixed gas is a mixed gas containing no oxygen. In the mixed gas, the ratio of the fluorine-based gas other than the sulfur hexafluoride gas to the total amount of the sulfur hexafluoride gas (SF ₆ ) and the fluorine-based gas other than the sulfur hexafluoride gas is 20% The manufacturing method according to any one of claims 1 to 3, which is the above. 5. The mixed gas according to claim 1, wherein a total proportion of the sulfur hexafluoride gas (SF ₆ ) and the fluorine-based gas other than the sulfur hexafluoride gas is 80% or more. The manufacturing method described in. The mixed gas is a sulfur hexafluoride gas (SF _6), consisting of the fluorine gas other than sulfur hexafluoride gas, the production method according to any one of claims 1 to 5. The substrate comprises a body and a surface layer,
The surface layer is a metal layer,
The manufacturing method according to any one of claims 1 to 6. The method according to claim 7, wherein the surface layer is a metal layer that reacts with the mixed gas. The method according to claim 8, wherein the surface layer is at least one metal layer selected from the group consisting of tantalum (Ta), silicon (Si), titanium (Ti), and tungsten (W). The substrate includes an intervening layer between the body and the surface layer,
The manufacturing method according to any one of claims 7 to 9, wherein the intervening layer is a chromium (Cr) layer. The manufacturing method according to any one of claims 1 to 10, which is a mold for an optical element. A mold produced by the method according to any one of claims 1 to 11. A method for producing a formed body, comprising the step of forming a forming raw material using the forming die according to claim 12. The manufacturing method according to claim 13, wherein the molded body is an optical element. Generating an plasma in the presence of a mixed gas to perform reactive ion etching on the surface of the substrate;
It does not include the patterning step of patterning on the surface of the substrate before the etching step.
The mixed gas contains two fluorine-based gases,
One of the two types of fluorine-based gas is sulfur hexafluoride gas (SF ₆ ),
The other method is fluorine gas other than sulfur hexafluoride gas, The manufacturing method of the uneven structure body which has uneven structure on the surface characterized by the above-mentioned.