JP2018183956A - Method of manufacturing a mold for manufacturing a microlens array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a mold for manufacturing a micro lens array capable of manufacturing a mold capable of manufacturing a microlens array with high precision with high spherical shape accuracy.SOLUTION: A resist mask having a pattern of a microlens array to be manufactured is formed on one surface of a substrate, selective etching of the substrate via the resist mask and slimming of the resist mask are repeated a plurality of times to form temporary recesses corresponding to the microlenses on the substrate, by removing the resist mask from the substrate and etching the substrate, the temporary concave portion is used as a manufacturing concave portion, thereby solving the problem.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a mold manufacturing method for manufacturing a microlens array in which lenses are two-dimensionally arranged.

  In a backlight of a liquid crystal display, an organic EL (Electro Luminescence) device, and various other optical devices, a substrate or film having a microlens array structure in which fine lenses (microlenses) are two-dimensionally arranged It's being used. In the following description, the “substrate or film having a microlens array structure” is also simply referred to as “microlens array”.

As an example of a method for manufacturing a microlens array, a method using a mold in which an inverted shape of a microlens to be formed is formed is known.
In the manufacture of a microlens array using this mold, first, a resin layer made of a thermosetting resin or an ultraviolet curable resin is formed on the surface of a film (sheet-like material) serving as a substrate. Next, the mold is pressed against the resin layer to transfer the shape of the mold, and the resin layer is cured in this state. Finally, the microlens array is manufactured by peeling the mold from the cured resin layer.

  In recent years, the microlens array has been required to be further miniaturized and diversified. In particular, in response to the demand for miniaturization, a method capable of producing a mold capable of producing a fine microlens array with high precision with high precision is important. Therefore, various methods for producing a mold for producing a microlens array have been proposed.

For example, in Patent Document 1, a mask layer is formed on a substrate, a mask opening is formed in the mask layer corresponding to the first region on the substrate, and the second region included in the first region. In this document, a concave portion having an opening region is formed, and a substrate in which the concave portion is formed is etched through a mask opening portion to form a lens shape.
Also. In Patent Document 2, a concave portion having an opening on the upper surface and a cross section of at least two steps is formed in the substrate body, and the substrate main body formed with the concave portion is etched isotropically with the inner peripheral surface of the concave portion as a base point. Thus, it is described that a lens shape is formed.

  Further, in Patent Document 3, a first step of forming a mask on a substrate: a second step of forming a resist on the mask: a third step of patterning and forming a plurality of first openings in the resist: Etching the mask through one opening to form a plurality of second openings: Fourth step: etching the substrate through the first and second openings to form a plurality of initial holes Fifth step: Isotropic etching is performed on the mask through the plurality of first openings to widen the diameter of the second opening. Sixth step: Seventh step of removing the resist: Through the second opening An initial hole is dug by performing anisotropic etching on the substrate, and a dug comprising a first hole opened to the second opening and a second hole opened at the bottom of the first hole Eighth step of opening the hole: Isotropic to the substrate through the second opening Etching, digging a fold hole, and forming a recess corresponding to the lens shape consisting of a straight line and a plurality of curves: a tenth step of removing the mask: and a transparent resin in the recess An eleventh step of filling to form a microlens: A method of manufacturing a microlens is described.

Japanese Patent Laid-Open No. 2007-101834 JP 2007-279088 A JP 2007-171858 A

In the methods described in Patent Documents 1 and 2, a sphere corresponding to a lens shape is formed on a substrate by performing photolithography a plurality of times using a plurality of types of photomasks on a mask formed on the substrate. A stepped mask approximating the above is formed. Next, the stepped structure of the mask is transferred to the substrate by etching the substrate through the mask. Finally, the mask is removed, and the substrate on which the stepped structure is formed is further etched to make the stepped structure spherical, thereby forming a microlens structure corresponding to the microlens array.
However, since this method requires a plurality of photolithography steps, the process is complicated and it is difficult to obtain high productivity. In addition, since photolithography is performed a plurality of times, the accuracy of the lens such as deterioration of lens shape accuracy and increase in variation in shape between lenses is likely to occur due to the positional deviation (alignment deviation) of the photomask during exposure. In particular, when the microlens is fine, the influence of the positional deviation of the photomask during exposure cannot be ignored.

On the other hand, in the method described in Patent Document 3, a mask layer and a resist layer are formed on a substrate, an opening pattern formed in the resist layer is sequentially transferred to the mask layer and the substrate, and then the mask layer is selected. Isotropically etched to widen the opening width of the mask layer, and the substrate is etched through the mask layer with the expanded opening width to form a stepped structure approximating the spherical surface corresponding to the microlens doing.
In this method, since the exposure process is performed once, there is no problem of misalignment of the photomask caused by performing multiple exposures.
Here, in order to increase the shape accuracy of the microlens, it is necessary to increase the number of steps of the staircase structure formed on the substrate. However, in the method described in Patent Document 3, it is difficult to form a stepped structure exceeding two steps. Therefore, in the method described in Patent Document 3, it is difficult to form a mold with high accuracy corresponding to a microlens having a fine structure. In particular, when a microlens having a low ratio of lens diameter to lens thickness (thickness / diameter) is manufactured, an etching process that spheroidizes a substrate starting from a two-step staircase structure has a desired shape and It is difficult to obtain a mold having spherical accuracy.

  An object of the present invention is to solve such problems of the prior art, and it is possible to manufacture a mold capable of manufacturing a microlens array formed by arranging fine microlenses with high accuracy with high spherical shape accuracy. An object of the present invention is to provide a method for producing a mold for manufacturing a microlens array.

In order to achieve such an object, a method for producing a mold for producing a microlens array of the present invention includes a mask forming step of forming a resist mask having a pattern of a microlens array to be produced on one surface of a substrate,
A recess forming step of forming a temporary recess corresponding to the microlens on the substrate by repeatedly performing selective etching of the substrate through the resist mask and slimming of the resist mask a plurality of times;
A removal step of removing the resist mask from the substrate; and
There is provided a method for manufacturing a mold for manufacturing a microlens array, which includes performing a finishing step of making a temporary recess into a manufacturing recess by etching a substrate.

In such a method for producing a mold for manufacturing a microlens array of the present invention, it is preferable that the depth of the temporary recess formed in the recess forming step is deeper than the manufacturing recess formed in the finishing step.
Moreover, it is preferable that the selective etching of the substrate through the resist mask in the recess forming step is isotropic etching.
In addition, it is preferable to gradually reduce the size of the resist mask slimming in the concave portion forming step in the surface direction of the substrate.
Further, when the thickness of the microlens in the microlens array to be manufactured is t [μm] and the diameter is d [μm], the aspect ratio represented by “t / d” is preferably 0.5 or less. .
In the recess forming step, the selective etching of the substrate through the resist mask is preferably performed 3 to 10 times.
In the mask formation step, it is preferable that an opening pattern having a diameter equal to or less than half the diameter of the microlens to be formed is formed in the resist mask as the pattern of the microlens array to be manufactured.
Furthermore, it is preferable that the thickness of the resist mask formed in the mask forming step is equal to or larger than the radius of the microlens to be formed.

  According to the present invention as described above, a mold for manufacturing a microlens array capable of manufacturing a microlens array in which fine microlenses are arranged with high accuracy can be manufactured with high spherical shape accuracy.

It is a conceptual diagram for demonstrating an example of the manufacturing method of the metal mold | die for microlens array manufacture of this invention. It is a conceptual diagram for demonstrating the manufacturing method of the metal mold | die for microlens array manufacture shown in FIG. It is a conceptual diagram for demonstrating another example of the manufacturing method of the metal mold | die for microlens array manufacture of this invention. It is a conceptual diagram for demonstrating the magnitude | size of the recessed part in FIG. It is a conceptual diagram for demonstrating another example of the manufacturing method of the metal mold | die for microlens array manufacture of this invention. It is a conceptual diagram for demonstrating another example of the manufacturing method of the metal mold | die for microlens array manufacture of this invention. It is a conceptual diagram for demonstrating another example of the manufacturing method of the metal mold | die for microlens array manufacture of this invention. It is a conceptual diagram for demonstrating the measuring method of an etching rate. It is a graph for demonstrating the metal mold | die for microlens array manufacture produced in the Example of this invention. It is a microscope picture of the metal mold | die for microlens array manufacture produced in the Example of this invention. It is a graph for demonstrating the metal mold | die for microlens array manufacture produced in the Example of this invention. It is a microscope picture of the metal mold | die for microlens array manufacture produced in the Example of this invention. It is a graph for demonstrating the metal mold | die for microlens array manufacture produced in the Example of this invention. It is a microscope picture of the metal mold | die for microlens array manufacture produced in the Example of this invention.

Hereinafter, a method for producing a mold for producing a microlens array of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.
In the following description, the “microlens array manufacturing mold” is also simply referred to as “mold”.

1 and 2 conceptually show an example of a method for producing a mold according to the present invention.
In the mold manufacturing method of the present invention, a resist mask 12 is formed on one surface of a substrate 10, and an opening pattern (resist hole) 12a having a pattern of a microlens array to be manufactured is formed on the resist mask 12 ( Mask formation step), and then selective etching of the substrate 10 through the resist mask 12 and slimming of the resist mask 12 are alternately repeated a plurality of times to form temporary recesses 14 (recess formation step), After removing the resist mask 12 (removing step), the substrate 10 is etched to make a temporary concave portion 16 as a manufacturing concave portion 16 (finishing step) to produce a mold for manufacturing a microlens array.
In the present invention, both etching and slimming are performed a plurality of times. However, as shown in FIGS. 1 and 5, the etching is performed once more frequently.

FIG. 1 is a cross-sectional view of a stacked body of a substrate 10 and a resist mask 12 cut in a direction perpendicular to the surface of the substrate 10. FIG. 2 is a plan view of the stacked body of the substrate 10 and the resist mask 12 as viewed from the resist mask 12 side in a direction perpendicular to the surface of the substrate 10. The cross section of FIG. 1 is a cross section taken along line II shown in the upper left portion of FIG.
In order to clearly show the configuration and clearly distinguish the substrate 10 and the resist mask 12, hatching is omitted in FIG. 1, and the resist mask 12 is hatched in FIGS.

1 and 2 exemplify a mold corresponding to a microlens array having four microlenses to simplify the drawings, but the present invention is not limited to this, and liquid crystal A mold corresponding to a microlens array having a large number of microlenses, such as a microlens array used in a display and an organic EL device, may be used.
There is no particular limitation on the arrangement of the microlenses in the microlens array to be manufactured. Accordingly, the arrangement of the microlenses may be, for example, a square lattice arrangement other than the staggered arrangement (honeycomb arrangement) corresponding to the close-packed hexagonal packing shown in FIG. 2, or has regularity. There may be no sequence.

In the method for producing a mold of the present invention, the substrate 10 is not particularly limited, and a known substrate (a plate or sheet) used for a mold for manufacturing a microlens array is used. Various types are available. Therefore, various substrates such as a silicon wafer, a glass substrate, and a metal substrate can be used as the substrate 10.
Among these, it is preferable to use a semiconductor silicon wafer as the substrate 10 in terms of surface flatness, few defects, cleanliness, purity, etching processability, and the like.

In the mold manufacturing method of the present invention, first, a mask formation step is performed.
In the mask formation step, first, as shown in the upper left part of FIG. 1, a resist mask 12 is formed on one main surface of the substrate 10.
The resist mask 12 is not particularly limited, and any resist mask made of a known resist material used in lithography or the like can be used. Therefore, the resist mask 12 may be made of a known material corresponding to the material for forming the substrate 10 and the shape and size of the target microlens. Examples of the resist mask 12 include commercially available i-line exposure resists, g-line exposure resists, KrF exposure resists, ArF exposure resists, immersion ArF resists, and electron beam resists. .

The method for forming the resist mask 12 is not particularly limited, and may be formed by a known method corresponding to the resist material to be the resist mask 12.
For example, when a semiconductor silicon wafer is used as the substrate 10, it is preferable to use spin coating as the coating method from the viewpoint of film thickness uniformity and defect reduction. In addition, after apply | coating a resist material, in order to remove a residual solvent, it is preferable to perform the baking process (heat processing (baking)) according to the kind of resist material, an application | coating film thickness, etc. FIG.

In the mold manufacturing method of the present invention, in order to improve the adhesion between the substrate 10 and the resist mask 12, the HMDS (hexamethyldisilazane) treatment is performed on the formation surface of the resist mask 12 of the substrate 10 prior to the formation of the resist mask 12. Is preferably performed.
The HMDS treatment method is not particularly limited, and known methods such as a vapor treatment method and a method by spin coating and baking treatment of an HMDS solution can be used.

The thickness of the resist mask 12 is not limited, and an optimal thickness may be appropriately selected according to the arrangement and shape of the microlenses to be manufactured.
Here, the resist mask 12 needs to remain until the last etching in the recess forming process described later, in which etching and slimming are repeatedly performed, is completed. Therefore, it is preferable that the necessary film thickness of the resist mask 12 is determined in advance by checking the etching rate of the resist mask 12 under various etching conditions in advance and appropriately setting the optimum thickness according to the result. . Any known method can be used as a method for measuring the etching rate. As an example of the method for measuring the etching rate, the method used in the examples described later is exemplified.
In particular, when the resist mask 12 is slimmed (horizontal dimension reduction) by oxygen plasma (O ₂ plasma), the reduction of the film thickness of the resist mask 12, that is, the vertical dimension is large. Considering this point, the thickness of the resist mask 12 is preferably not less than the radius of the microlens formed by the mold, more preferably not less than 1.5 times the radius, and still more preferably not less than twice the radius.
On the other hand, if the resist mask 12 is too thick, there is a possibility that the coating property of the resist material and the exposure property when forming the through hole are reduced. Considering this point, the thickness of the resist mask 12 is preferably 1 to 50 μm.

After the resist mask 12 is formed on one surface of the substrate 10, an opening pattern 12a is then formed as shown in the second left side of FIG. 1 and the upper stage of FIG. The opening pattern 12a is formed so that the center of the microlens formed by the microlens array mold coincides with the center.
Thereby, a mask formation process is complete | finished.

The shape of the opening pattern 12a is not limited as long as the center coincides with the microlens to be formed. Therefore, the opening pattern 12a may be a cylindrical shape or a square tube shape such as a hexagonal tube, but a regular polygonal tube shape and a cylindrical shape are preferable, and a cylindrical shape is more preferable.
The opening pattern 12 a is preferably formed so that the wall surface is perpendicular to the surface of the substrate 10.

There is no restriction | limiting in particular in the magnitude | size of the opening pattern 12a. The size of the opening pattern 12 a is the size in the surface direction of the substrate 10. In the following description, the surface direction refers to the surface direction of the main surface of the substrate 10 unless otherwise specified. The main surface is the maximum surface of the plate-like object.
Here, if the opening pattern 12a is too large, it becomes difficult to sufficiently spheroidize by etching in a finishing process described later, and in some cases, the bottom surface of the manufacturing recess 16, that is, the center of the microlens to be formed is planar. Become. Considering this point, the size of the opening pattern 12a is preferably not more than half of the diameter of the microlens to be formed, more preferably not more than 1/4, and still more preferably not more than 1/5.
In addition, when the opening surface of the manufacturing concave portion to be formed, such as a regular hexagon described later, that is, the shape (planar shape) of the microlens to be formed is not a circle but a polygon or an indeterminate shape, the opening surface of the manufacturing concave portion The diameter of the largest circle inscribed in can be regarded as the diameter of the macro lens. In this respect, the radius of the above-described microlens is the same.

The method for forming the opening pattern 12a on the resist mask 12 is not particularly limited, and all known methods can be used.
Therefore, in the exposure of the resist mask 12, an exposure light source and an exposure apparatus are appropriately selected according to the formation material of the resist mask 12, the pattern and size of the microlens array to be formed, the formation area of the opening pattern 12a, and the like. That's fine. As an example, exposure by a mask exposure apparatus such as a mask analyzer and a stepper, and exposure by a drawing apparatus such as an electron beam drawing apparatus and a laser drawing apparatus can be used.

  The development after exposure may be performed with a known developer corresponding to the material for forming the resist mask 12. In general, an alkaline developer such as TMAH (tetramethyl ammonium hydroxide), an organic solvent developer, or the like is used.

After the opening pattern 12a is formed in the resist mask 12, as shown in the second left side of FIG. 1 and the upper stage of FIG. 2, a recess forming step is then performed.
In the recess forming step, first, the substrate 10 is selectively etched through the resist mask 12 to form a first-step recess in the substrate 10 as shown in the third row on the left side of FIG. The area of the first recess corresponds to the center or top of the microlens at the bottom of the temporary recess 14, that is, the bottom of the manufacturing recess 16.
In the example shown in FIGS. 1 and 2, the etching of the substrate 10 is anisotropic etching in which etching is performed only in the thickness direction of the substrate 10. In the recess forming step, the method of selectively etching the substrate 10 by anisotropic etching produces a microlens array having a large aspect ratio “t / d” between the thickness t and the diameter d of the microlens to be formed. It is suitable for producing a mold. This aspect ratio will be described in detail later.
In this etching, the substrate 10 is selectively etched, but as shown in FIG. 1, the resist mask 12 is also etched and the thickness is slightly reduced.

There is no restriction | limiting in particular in the etching of the board | substrate 10, What is necessary is just to perform by the well-known method according to the formation material of the board | substrate 10. FIG.
Among these, plasma etching is preferable from the viewpoints of high-precision control of the etching amount and etching reproducibility. The plasma etching method is not particularly limited, but a method that can independently control the plasma density and the bias applied to the substrate 10 is preferable. Examples of plasma systems that can realize this method include an ICP (Inductively Coupled Plasm) system, a 2-frequency CCP (Capacitively Coupled Plasma) system, and an ECR (Electron Cyclotron Resonance) system.

The gas used for etching is not particularly limited, and a known material corresponding to the forming material of the substrate 10 may be used.
For example, when the substrate 10 is a silicon wafer for semiconductors, it is caused by fluorine radicals, chlorine radicals, bromine radicals, etc. generated by decomposing a gas containing elemental fluorine, chlorine and bromine in plasma. Etching is exemplified. Examples of the gas that efficiently generates fluorine radicals include SF ₆ , CF ₄ , and CHF ₃ . Examples of the gas that efficiently generates chlorine radicals include Cl _{2 and the} like. Examples of the gas that efficiently generates bromine radicals include Br ₂ and HBr.
In addition, an argon gas or the like may be mixed as an additive gas to the plasma generating gas in order to improve the plasma density.

There is no particular limitation on the plasma excitation power (plasma excitation power) for generating plasma. The plasma excitation power can increase the etching rate of the substrate 10 by applying high power within a range in which the discharge stability is ensured.
There is no particular limitation on the bias power applied to the substrate 10 (bias power). However, if the bias power is increased too much, the acceleration energy of ions drawn to the substrate 10 side increases, and the anisotropic etching of the substrate 10 proceeds, but the etching selectivity between the substrate 10 and the resist mask 12 decreases. . Therefore, it is preferable to determine the bias power applied to the substrate 10 in consideration of this point.

After the first etching of the substrate 10, the resist mask 12 is then slimmed to reduce the resist mask 12 in the surface direction (horizontal direction) as shown in the lower left part of FIG. The diameter of the opening pattern 12a is enlarged.
Therefore, by performing slimming, the periphery of the first formed recess is also exposed from the resist mask 12 on the surface of the substrate 10.

The slimming method of the resist mask 12 is not particularly limited, but the same plasma etching is preferably used for the same reason as the etching of the substrate 10.
Various gases can be used as the gas used for slimming (slimming gas) as long as it can generate radicals that etch only the resist mask 12 without etching the substrate 10. In the present invention, the slimming is preferably exemplified by etching with oxygen radicals. Therefore, a gas containing oxygen element is preferably used as a gas used for generating radicals in slimming. The gas containing oxygen elements is not particularly limited, usually oxygen gas (O ₂ gas) is used.
Further, when the resist mask 12 is slimmed, if the bias power is applied to the substrate 10, the etching rate in the thickness direction (vertical direction) of the resist mask 12 is increased. Therefore, it is preferable not to apply bias power to the substrate 10 when the resist mask 12 is slimmed.

When the slimming of the resist mask 12 is completed, the second selective etching of the substrate 10 is performed in the same manner as described above.
As described above, the substrate 10 has a recess formed through the resist mask 12 before the opening pattern 12a is expanded. Therefore, when the second selective etching of the substrate 10 is performed, two stepped concave portions are formed on the substrate 10 as shown in the upper right part of FIG. 1 and the second stage of FIG. .

When the second substrate 10 is selectively etched, the resist mask 12 is slimmed for the second time in the same manner as described above, and the opening pattern of the resist mask 12 is formed as shown in the second row on the right side of FIG. 12a is further expanded.
After slimming the resist mask 12 for the second time, the substrate 10 is selectively etched for the third time in the same manner as described above. As described above, the substrate 10 is formed with two stepped recesses. Therefore, when the substrate 10 is etched with the opening pattern 12a further expanded, the substrate 10 has three stepped concave portions as shown in the third step on the right side in FIG. 1 and the third step in FIG. Is formed.

In the example shown in FIG. 1 and FIG. 2, the etching of the substrate 10 and the slimming of the resist mask 12 are repeated alternately, and the etching of the substrate 10 is performed three times to approximate the spherical surface corresponding to the microlens to be formed. A temporary recess 14 is formed.
Thereby, a recessed part formation process is complete | finished.

In the recess forming step, the selective etching of the substrate 10 and the slimming of the resist mask 12 may be performed in the same etching apparatus, that is, in the same chamber, or in different etching apparatuses.
In consideration of the manufacturing cost and productivity of the mold, if possible, the selective etching of the substrate 10 and the slimming of the resist mask 12 are performed in the same etching apparatus according to the gas used for etching and slimming. It is preferable to carry out.

As will be described later, in the mold manufacturing method of the present invention, the temporary recesses 14 are formed, the resist mask 12 is removed, and then the substrate 10 is etched in the finishing step, so that the lower right side of FIG. 1 and the lower side of FIG. As shown in FIG. 4, the step of the temporary recess 14 is formed into a spherical shape, thereby forming a manufacturing recess 16 corresponding to the microlens.
Therefore, in the concave portion forming step, the spherical surface approximated by the temporary concave portion 14 shown by a broken line in the fourth step on the right side of FIG. 1 is shaped to correspond to the target concave portion 16 for manufacturing, that is, the microlens to be formed. The etching amount and frequency of the substrate 10 and the slimming amount of the resist mask 12 are set as appropriate.

Here, as shown in FIG. 1 and FIG. 2, when producing a mold for producing a microlens array in which adjacent microlenses are separated from each other, the surface of the substrate 10 and temporary recesses in etching in the finishing process The etching rate with the bottom of 14 is almost the same. Therefore, the relative height difference between the etched surface of the substrate 10 and the etched temporary recess 14, that is, the depth of the temporary recess 14 is substantially constant, and the entire temporary recess 14 is made spherical. .
Further, the opening diameter of the temporary recess 14, that is, the diameter of the microlens is increased by etching in the finishing process.

Accordingly, when a mold for manufacturing a microlens array in which adjacent microlenses are separated from each other, an etching amount (etching time) required for making the temporary concave portion 14 spherical and an opening diameter of the temporary concave portion 14 are obtained. In consideration of the increase amount (increase rate) of the spherical surface, the spherical opening approximated by the temporary concave portion 14 is smaller than the opening of the manufacturing concave portion 16, and the spherical depth approximated by the temporary concave portion 14 is manufactured. The etching amount and the number of times of the substrate 10 and the slimming amount of the resist mask 12 in the recess forming step and the slimming amount of the resist mask 12 are set as appropriate so that the depth of the recess 16 for use is equal.
In the recess forming step, the opening of the temporary recess 14 is substantially smaller than the opening of the manufacturing recess 16 and the depth of the temporary recess 14 is equal to the depth of the manufacturing recess 16. The etching amount and the number of times of the substrate 10 and the slimming amount of the resist mask 12 may be set as appropriate.
In addition, the etching amount and the number of times of the substrate 10 and the slimming amount of the resist mask 12 are set as appropriate, the spherical error of the temporary recess 14 is further reduced, and the etching time of the substrate 10 in the finishing process is reduced. When the increase in the opening diameter of the temporary recess 14 can be almost ignored, the spherical surface approximated by the temporary recess 14 and the spherical surface of the manufacturing recess 16 may be made equal.

In the mold manufacturing method of the present invention, the number of selective etching of the substrate 10 through the resist mask 12 in the recess forming step is not particularly limited, but is preferably 3 times or more, more preferably 5 times or more. . By setting the number of times of selective etching of the substrate 10 to 3 or more, the spherical approximate accuracy of the temporary recess 14 can be improved, and a highly accurate mold can be manufactured.
As the number of times of selective etching of the substrate 10 increases, the spherical approximate accuracy of the temporary recess 14 can be improved, so that a highly accurate mold can be manufactured. On the other hand, if the number of times of selective etching of the substrate 10 is large, the number of times of switching between the gas used for etching the substrate 10 and the gas used for slimming the resist mask 12 and the plasma re-lighting when using plasma etching are used. The number of times increases. As a result, the processing time becomes longer and the risk of generating particles in the etching apparatus increases. Considering this point, it is preferable that the number of times of selective etching of the substrate 10 is 10 or less.

When the recess formation process is completed, a removal process for removing the resist mask 12 from the substrate 10 is then performed as shown in the fourth stage on the right side in FIG. 1 and the fourth stage in FIG.
The method for removing the resist mask 12 in the removing step is not particularly limited, and may be performed by a known method according to the material for forming the resist mask 12. Therefore, the removal of the resist mask 12 may be performed using a plasma ashing apparatus even by peeling with an organic solvent.
Further, the removal of the resist mask 12 may be performed by the same etching apparatus as the slimming of the resist mask 12. When the removal of the resist mask 12 is performed by the same etching apparatus as that for slimming the resist mask 12, the bias power is applied to the substrate 10 within a range in which etching of the substrate 10 by physical sputtering does not occur in order to increase processing efficiency. May be applied.

When the removal step is completed, finally, the substrate 10 is etched to form a spherical surface by removing the steps of the temporary recesses 14, and the temporary recesses 14 are used as manufacturing recesses 16. A finishing process is performed.
In the finishing step, according to the spherical surface approximated by the step-like temporary concave portion 14 indicated by a broken line in the fourth step on the right side of FIG. 1, the manufacturing concave portion 16 becomes a target spherical surface corresponding to the microlens. Etching is performed to make the temporary recess 14 spherical. For example, after the temporary concave portion 14 becomes spherical to some extent, the radius of curvature of the manufacturing concave portion 16, that is, the microlens to be formed can be controlled by controlling the subsequent etching.

In the mold manufacturing method of the present invention, step-like temporary recesses 14 approximating a spherical surface are formed by repeatedly etching the substrate 10 and slimming the resist mask 12 in this way. The center of the opening pattern 12a does not go wrong. That is, in the present invention, since the temporary recess 14 can be formed by one exposure (photolithography), the productivity is high. Furthermore, since only one exposure is required, there is no deterioration in the shape accuracy of the temporary recesses 14 due to the displacement of the photomask and no variation in the shape between the temporary recesses 14. An accurate temporary recess 14 can be formed.
In addition, in the present invention, the step-like temporary recesses 14 are formed by repeatedly etching the substrate 10 and slimming the resist mask 12, so that the number of steps of the temporary recesses 14, that is, the number of etchings of the substrate 10 can be arbitrarily set. A step-like temporary concave portion 14 with high spherical approximation accuracy can be formed with an optimum number of etchings.
Therefore, according to the mold manufacturing method of the present invention, a microlens array manufacturing mold capable of manufacturing a microlens array formed by arranging fine microlenses with high accuracy can be manufactured with high spherical shape accuracy.

The etching of the substrate 10 in the finishing process is not particularly limited as long as it is a method capable of isotropically etching the substrate 10 (isotropic etching). Therefore, the etching of the substrate 10 in the finishing process may be performed by the same etching apparatus as the etching and slimming in the recess forming process. As an example, examples of the etching method of the substrate 10 in the finishing process include ion etching and plasma etching.
Moreover, you may use the etching apparatus and etching conditions in the case of forming a temporary recessed part by isotropic etching so that it may mention later.

As described above, the example shown in FIGS. 1 and 2 is for producing a mold for producing a microlens array in which adjacent microlenses are separated. In this case, the depth of the spherical surface approximated by the temporary recess 14 and the depth of the manufacturing recess 16 are the same depth, and the spherical opening approximated by the temporary recess 14 is made smaller than the opening of the manufacturing recess 16. .
On the other hand, when a mold for manufacturing a microlens array in which adjacent microlenses are in contact with each other in the entire surface direction as shown in the lower part of FIG. The spherical surface is made deeper than the manufacturing recess, and the spherical opening approximated by the temporary recess is made equal to or less than the opening of the manufacturing recess. Substantially, the depth of the temporary recess is made deeper than the depth of the manufacturing recess, and the opening of the temporary recess is made equal to or smaller than the opening of the manufacturing recess.
In FIG. 3, the left side is a plan view similar to FIG. 2, and the right side is a diagram conceptually showing a cross section similar to FIG.
In the following description, a microlens array in which adjacent microlenses are in contact with each other in the entire surface direction is also referred to as a “gapless microlens array” for convenience.

As shown in the upper part of FIG. 3, when producing a mold for producing a gapless microlens array, the mask forming step and the recessed portion forming step are performed to form the temporary recessed portion 24 in the same manner as described above. Further, the resist mask is removed from the substrate 10 by performing a removal process.
Next, similarly, in the finishing step, isotropic etching is performed on the substrate 10.
As in the previous example, when the etching is performed in the finishing process, the opening diameter of the temporary recess 24 is enlarged. Here, in the case of producing a mold for manufacturing a gapless microlens array, it is necessary to unite the opening ends in the entire area in the plane direction, including the opening portions that are farthest apart from each other between the adjacent temporary recesses 24. There is.

As shown in the second stage of FIG. 3, when the opening diameter of the temporary recess 24 increases, the opening ends between the adjacent temporary recesses 24 merge.
In addition, after the opening ends of the temporary recesses 24 are merged, the opening ends that are merged between the adjacent temporary recesses 24 expand at the same speed, so that the opening ends are linear. Therefore, for example, when the temporary recesses 24 are formed as in the hexagonal close packing (honeycomb arrangement) shown in FIG. 3, in the mold for manufacturing the gapless microlens array, the manufacturing recesses 26 on the surface of the substrate 10 are: It looks like a honeycomb structure.

As shown in the third row of FIG. 3, when the opening ends between adjacent temporary recesses 24 merge, the flat portion of the upper surface of the substrate 10 disappears, and the boundary portion of the temporary recess 24 becomes a sharp protrusion. . Therefore, the etching rate rapidly increases at the boundary portion of the temporary recess 24.
Furthermore, as described above, in order to manufacture a mold corresponding to a gapless type microlens array, it is necessary to perform etching until the farthest openings between adjacent temporary recesses 24 come into contact with each other.
As a result, as shown in FIG. 3 from the third stage to the lower stage, as shown in FIG. 1, the depth of the temporary concave portion 24 that is substantially constant while the adjacent temporary concave portions 24 are separated from each other is rapidly increased. It decreases, and the radius of curvature of the temporary recess 24 (that is, the microlens) that becomes the lens surface increases rapidly.
Therefore, in order to manufacture the mold 28 for manufacturing the gapless type microlens array, it is desirable that at least the depth of the temporary recess 24 is not deeper than the depth of the manufacturing recess 26 to be finally formed. It is impossible to manufacture a mold that can manufacture a microlens array having a shape and a radius of curvature.

Further, when the temporary recess 24 deeper than the depth of the manufacturing recess 26 to be formed is formed, a gapless type having a radius of curvature smaller than the target radius of curvature is obtained by performing spheroidization in the finishing process. A structure corresponding to the microlens array is formed.
Therefore, after realizing this structure, additional etching can be performed to reduce only the height of the boundary and increase the radius of curvature while maintaining the sphericalness corresponding to the gapless microlens array. Thus, the mold 28 capable of manufacturing a gapless microlens array having a desired radius of curvature can be manufactured.

In the mold manufacturing method shown in FIGS. 1 and 2, selective etching of the substrate 10 in the recess forming step is performed by anisotropic etching.
This method is preferably used when the thickness of the microlens array to be manufactured is t [μm] and the diameter is d [μm], and the aspect ratio indicated by “t / d” is large. Is done. As conceptually shown in FIG. 4, the thickness t of the microlens corresponds to the depth of the manufacturing recess 16, and the diameter d of the microlens corresponds to the opening diameter of the manufacturing recess 16.
In the case where the shape of the microlens is not circular, the diameter d of the microlens may correspond to the size of the opening pattern 12a.

As described above, the substrate 10 is preferably a semiconductor silicon wafer.
Usually, the etching action of silicon by fluorine radicals, chlorine radicals and bromine radicals is isotropic. Therefore, in order to realize anisotropic etching, it is necessary to generate a silicon side wall protective substance in plasma and supply it to the substrate.
For example, when a fluorine-containing gas is used for etching, it is preferable to generate a CF-based dissociation product having a deposition property, and a ratio of a gas containing a carbon element within a range in which an etching stop in the vertical direction of silicon does not occur. Can be increased. When a chlorine-containing gas or bromine-containing gas is used, by adding an appropriate amount of O ₂ gas, the volatile product of etched silicon and oxygen are combined, and a SiO ₂ film is formed on the side walls of the resist and the silicon non-etched surface. Thus, anisotropic etching can be realized.
If a sufficient resist film thickness can be secured, the anisotropy may be further increased by increasing the bias power.

On the other hand, in the present invention, the selective etching of the substrate 10 in the recess forming step may be performed by isotropic etching as conceptually shown in FIG.
In particular, when a microlens having a small aspect ratio is formed, it is preferable that the selective etching of the substrate 10 in the recess forming step is performed by isotropic etching. In particular, when a microlens having an aspect ratio (“t / d”) of 0.5 or less is formed, it is preferable to perform selective etching of the substrate 10 in the recess forming step by isotropic etching.

  When the temporary recesses 14 are formed by anisotropic etching, stepwise temporary recesses 14 are formed as conceptually shown in the upper part of FIG. The broken line is a spherical surface approximated by the temporary recess 14.

On the other hand, when the temporary recess 30 is formed by isotropic etching, the corners of the temporary recess 30 are reduced as shown in the lower part of FIG. 6, and the shape of the temporary recess 30 is indicated by a broken line in the figure. It is possible to make the shape closer to the spherical surface approximated by the temporary recess 30 shown. That is, the spherical approximate accuracy of the temporary recess 30 can be increased.
In addition, since the spherical approximate accuracy of the temporary recess 30 can be increased, the etching time of the substrate 10 in the finishing process for turning the temporary recess 30 into a spherical recess 16 from the middle stage on the right side to the lower stage in FIG. Can be shortened. Further, it is possible to prevent the adjacent temporary recesses 30 from being unnecessarily united before the temporary recesses 30 are made spherical by etching in the finishing process.
Therefore, by forming the temporary recess 30 by isotropic etching, a mold capable of manufacturing a target microlens array with high production efficiency, high accuracy, and few defects caused by particles can be manufactured with high accuracy. Can be made.

In the case where the temporary recess 30 is formed by isotropic etching, as an example, if a semiconductor silicon wafer is used as the substrate 10, the fluorine radical is reduced while reducing the carbon element ratio in the gas used for etching. What is necessary is just to increase the generation amount of radicals.
It is also preferable to reduce the bias power applied to the substrate 10 or not apply a bias to the substrate 10.

In the example shown in FIGS. 1 and 2, the width of the resist mask 12 to be removed by slimming in the recess forming step is made uniform. The width of the resist mask 12 is the size of the resist mask 12 in the surface direction.
The present invention is not limited to this. For example, as conceptually shown in FIG. 7, the width of the resist mask 12 to be removed by slimming in the recess forming step may be gradually reduced. This method is also suitable for forming a microlens having a small aspect ratio, and is particularly suitable for forming a microlens having an aspect ratio (“t / d”) of 0.5 or less.

As an example, in the example shown in FIGS. 1 and 2, the bottom (center) area where etching is performed first in the temporary recess 14 is performed three times until the temporary recess 14 is completed. Is called. In addition, the region surrounding the bottom etched first in the second etching after the first slimming is etched twice until the provisional recess 14 is completed.
After the first etching, if the subsequent etching is performed, the corners are cut and a spheroidized state is obtained. Therefore, as the number of times of etching performed in one region increases, the corners are cut, and the shape of the temporary concave portion 14 becomes closer to a spherical surface that approximates. That is, the region where the etching is frequently performed can be made to have a shape close to a spherical surface approximated by the temporary recess 14 even if the slimming amount, that is, the etching region in the surface direction is increased to some extent and the subsequent etching is performed.
On the other hand, the number of times the temporary recesses 14 are etched decreases toward the periphery. Moreover, in general, the gradient of the microlens, that is, the manufacturing recess 16 increases toward the periphery. Therefore, in order to form the temporary concave portion 14 having a high spherical approximation accuracy, the stepped shape of the temporary concave portion 14 is changed to a spherical surface approximated by the temporary concave portion 14 by making a finer approximation as it goes to the peripheral portion. It is preferable to approach.

  Accordingly, the size (X0) of the opening pattern 12a, the width of the resist mask 12 to be removed by slimming, and finally the width are left so that the width of the resist mask 12 to be removed by slimming in the recess forming step is gradually reduced. By setting the width of the resist mask 12, it is possible to produce a mold that can efficiently produce a target microlens array with high accuracy.

When the width of the resist mask 12 to be removed by slimming in the recess forming step is gradually narrowed, for example, the etching time of the substrate 10 and the slimming time of the resist mask 12 are defined as follows.
The number of etchings of the substrate 10 is n. Therefore, the number of slimming operations is n−1.
The etching rate in the thickness direction of the substrate 10 is Ry, the slimming rate in the surface direction of the resist mask 12 is Rx, the etching amount in the thickness direction of the substrate 10 in the nth etching is Yn, and the etching amount in the surface direction in the nth slimming is performed. The slimming amount of the resist mask 12 is Xn. X0 is the size of the opening pattern 12a.
In this case, the n-th etching time Tyn of the substrate 10 may be calculated by Yn / Ry. The nth resist pattern slimming time Txn may be calculated by Xn / Rx.

  As mentioned above, although the manufacturing method of the metal mold | die for microlens array manufacture of this invention was demonstrated in detail, this invention is not limited to the said Example, In the range which does not deviate from the summary of this invention, various improvement and change Of course, you may do.

  Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

[Formation of resist mask]
A silicon wafer for semiconductor was prepared as a substrate.
On this substrate, OAP manufactured by Tokyo Ohka Kogyo Co., Ltd. was spin-coated under the condition of 3000 rpm (Revolutions Per Minute) and 30 seconds. Next, the substrate was baked at 120 ° C. for 15 minutes to perform HMDS adhesion treatment of the substrate.
Next, a positive resist (manufactured by Tokyo Ohka Kogyo Co., Ltd., PMER-P-LA900) is spin-coated on the substrate 10 under the conditions of 2000 rpm and 30 seconds, and a baking process is performed at 110 ° C. for 30 minutes, and the thickness is 15 μm. A resist coating film was formed as a resist mask.
The resist mask thus formed was exposed using a contact aligner (MA 6 manufactured by Zose Microtech Co., Ltd.), developed with a 2.38% -TMAH solution for 180 seconds, and then rinsed with pure water for 60 seconds. Went.
Thus, a cylindrical opening pattern was formed on the resist mask provided on the surface of the substrate 10 and arranged in a honeycomb shape (honeycomb arrangement) at intervals of 20 μm. In addition, the space | interval of an opening pattern is a space | interval between the centers of a cylinder.

[Etching condition setting]
The etching of the substrate and the slimming of the resist mask were performed using an ICP plasma etching apparatus (manufactured by Panasonic Corporation, IPC etcher E620).
-Anisotropic etching conditions for substrate (silicon) Plasma excitation power was 800 W, bias power applied to the substrate was 30 W, and substrate temperature was 50 ° C.
As the etching gas, SF ₆ and CHF ₄ were used. The flow rates were 10 sccm for SF ₆ and 40 sccm for CHF ₄ , and the pressure was 0.6 Pa.
Resist mask slimming conditions Plasma excitation power was 800 W, bias power applied to the substrate was 0 W, and substrate temperature was 50 ° C.
Slimming gas with 0 _2, the flow rate is 300 sccm, the pressure was 10 Pa.
Resist mask ashing conditions Plasma excitation power was 800 W, bias power applied to the substrate was 100 W, and substrate temperature was 50 ° C.
The ashing gas used was 0 ₂ , the flow rate was 300 sccm, and the pressure was 10 Pa.
-Conditions for Isotropic Etching of Substrate (Silicon) and Etching in Finishing Process (Temporary Recess Spheroidization) Plasma excitation power was 800 W, bias power applied to the substrate was 10 W, and substrate temperature was 50 ° C.
The etching gas used was SF ₆ , the flow rate was 50 sccm, and the pressure was 1 Pa.

[Measurement of etching rate]
In exactly the same manner as the formation of the resist mask on the substrate surface, a resist mask (shaded line) having a thickness of 15 μm is formed on the surface of the substrate as conceptually shown in FIG. A sample in which an opening was formed was produced.
This sample was subjected to anisotropic etching of the substrate (arrow a), slimming of the resist mask (arrow b), and isotropic etching of the substrate (arrow c) for 120 seconds under the above conditions.
The cross-sectional shape of the sample after etching is observed with a field emission scanning electron microscope. From the amount of dimensional change in the resist mask thickness direction and surface direction, and the etching amount in the substrate thickness direction, etching is performed. The rate was calculated.
As a result, in the anisotropic etching of the substrate, the etching rate in the thickness direction of the substrate is 6 nm / second, the etching rate in the thickness direction of the resist mask is 2 nm / second,
In the resist mask slimming, the resist mask surface direction etching rate is 32 nm / second, the resist mask thickness direction etching rate is 44 nm / second (the substrate is not etched),
In resist mask ashing, the etching rate in the thickness direction of the resist mask is 75 nm / second (the substrate is not etched),
In the isotropic etching of the substrate, the etching rate in the thickness direction of the substrate was 8 nm / second, and the etching rate in the thickness direction of the resist mask was 1.5 nm / second.

[Example 1]
As described above, a resist mask having an opening pattern formed on the surface of the substrate was produced. The diameter of the opening pattern was 3 μm.
The substrate and the resist mask were subjected to anisotropic etching and slimming of the resist mask repeatedly to form temporary recesses in the substrate. In this example, the slimming amount of the resist mask was made uniform.
Details of etching and slimming are shown in Table 1 below. Note that PR is a photoresist, that is, a resist mask.

After forming the temporary recess, the resist mask is removed by ashing the resist mask, and in order to make the temporary recess spherical, isotropic etching of the substrate is performed for 1500 seconds, and the temporary recess is used as a manufacturing recess. A mold for producing a microlens array by the production method of the present invention was produced.
9 shows the spherical shape of the target manufacturing recess (target spherical shape, broken line), the spherical shape approximated by the temporary recess (approximate spherical shape, one-dot chain line), and the design of the temporary recess (design) Step shape, solid line). FIG. 10 shows a micrograph (plan view) of the produced mold.
FIG. 9 shows a half of the recess, where the vertical axis indicates the height from the bottom surface, and the horizontal axis indicates the distance in the surface direction from the center. The same applies to FIGS. 11 and 13 described later.

[Example 2]
As described above, a resist mask having an opening pattern formed on the surface of the substrate was produced. The diameter of the opening pattern was 5 μm.
The substrate and the resist mask were repeatedly subjected to isotropic etching and resist mask slimming to form temporary recesses in the substrate. In this example, the slimming amount of the resist mask was gradually reduced.
Details of etching and slimming are shown in Table 2 below.

After forming the temporary recess, the resist mask is removed in the same manner as in Example 1, and the substrate is subjected to isotropic etching for 900 seconds to make the temporary recess spherical, and the temporary recess is used as a manufacturing recess. A mold for producing a microlens array by the production method of the present invention was produced.
FIG. 11 shows a spherical shape of a target manufacturing recess (target spherical shape, broken line), a spherical shape approximated by a temporary recess (approximate spherical shape, one-dot chain line), and a design temporary recess shape (design) Step shape, solid line). FIG. 12 shows a micrograph (plan view) of the produced mold.

[Example 3]
As described above, a resist mask having an opening pattern formed on the surface of the substrate was produced. The diameter of the opening pattern was 5.5 μm.
The substrate and the resist mask were repeatedly subjected to isotropic etching and resist mask slimming to form temporary recesses in the substrate. In this example, the slimming amount of the resist mask was gradually reduced.
Details of etching and slimming are shown in Table 3 below.

After forming the temporary recess, the resist mask is removed in the same manner as in Example 1, and in order to make the temporary recess spherical, the substrate is isotropically etched for 1800 seconds, and the temporary recess is used as a manufacturing recess. A mold for producing a microlens array by the production method of the present invention was produced. This mold is a mold for producing a gapless type microlens array, and isotropic etching of the substrate for making a temporary recess into a spherical surface faces the opening end of the adjacent temporary recess. Combined across the direction.
FIG. 11 shows a spherical shape of a target manufacturing recess (target spherical shape, broken line), a spherical shape approximated by a temporary recess (approximate spherical shape, one-dot chain line), and a design temporary recess shape (design) Step shape, solid line). FIG. 14 shows a micrograph (plan view) of the produced mold.

With respect to the molds of Examples 1 to 3 thus produced, 10 concave portions for manufacturing were arbitrarily selected, and the shape was measured using a laser microscope (manufactured by Keyence Corporation, VK-9700). did.
The shape profile data at the center of the manufacturing recess was subjected to spherical fitting by the least square method to calculate the radius of curvature of the manufacturing recess. When the average radius of curvature of the 10 recesses was within ± 10% of the target radius of curvature of the manufacturing recess, the test was accepted.
Also, the formed manufacturing recess is measured, and the maximum depth (peak-to-valley) of the formed manufacturing recess is compared with the target maximum depth of the manufacturing recess, and the difference is determined as a spherical error. did. The test was accepted when the average spherical error of 10 concave portions was 0.1 μm or less.
As a result, the dies of Examples 1 to 3 both passed the radius of curvature and the spherical error. The results are shown in Table 4 below.

From the above results, the effects of the present invention are clear.

  It is suitably used for the manufacture of microlens arrays used in backlights for liquid crystal displays, light extraction films for organic EL devices, head-up display devices, and other various optical devices.

DESCRIPTION OF SYMBOLS 10 Board | substrate 12 Resist mask 12a Opening pattern 14, 24, 30 Temporary recessed part 16, 26 Recessed part 18 for manufacture
20, 28 (for micro lens manufacturing) Mold

Claims (8)

A mask forming step of forming a resist mask having a pattern of a microlens array to be manufactured on one surface of the substrate;
A recess forming step of forming a temporary recess corresponding to a microlens in the substrate by repeatedly performing selective etching of the substrate through the resist mask and slimming of the resist mask a plurality of times;
Removing the resist mask from the substrate; and
A method of manufacturing a mold for manufacturing a microlens array, comprising: performing a finishing step in which the temporary recess is made into a manufacturing recess by etching the substrate.   The manufacturing method of the metal mold | die for microlens array manufacture of Claim 1 which makes the depth of the said temporary recessed part formed at the said recessed part formation process deeper than the said recessed part for manufacture formed at the said finishing process.   The method for producing a mold for manufacturing a microlens array according to claim 1 or 2, wherein the selective etching of the substrate through the resist mask in the recess forming step is isotropic etching.   The method for producing a mold for manufacturing a microlens array according to any one of claims 1 to 3, wherein the size of the slimming of the resist mask in the recess forming step is gradually reduced in the surface direction of the substrate.   4. The aspect ratio represented by “t / d” is 0.5 or less when the thickness of the microlens in the microlens array to be manufactured is t [μm] and the diameter is d [μm]. Or 4. A method for producing a mold for producing a microlens array according to 4.   The method for producing a mold for manufacturing a microlens array according to any one of claims 1 to 5, wherein, in the recess forming step, selective etching of the substrate through the resist mask is performed 3 to 10 times. .   The micro of any one of claims 1 to 6, wherein, in the mask forming step, an opening pattern having a half or less diameter of a microlens to be formed is formed in the resist mask as a pattern of the microlens array to be manufactured. A method for producing a mold for manufacturing a lens array.   The method for producing a mold for manufacturing a microlens array according to any one of claims 1 to 7, wherein a thickness of the resist mask formed in the mask forming step is equal to or larger than a radius of a microlens to be formed.