JP2021184021A - Manufacturing method of optical element - Google Patents

Abstract

To provide a method of manufacturing an optical element with high accuracy and high productivity.SOLUTION: A manufacturing method of an optical element includes: preparing an original plate 10 having a first rugged shape 12 formed on a first surface 11; forming a first sacrificial layer 22 containing resin on a second surface 21 of an intermediate product 20; bringing the first surface of the original plate into contact with the first sacrificial layer and transferring the first rugged shape onto the first sacrificial layer; performing first etching of using the first sacrificial layer as etching mask to etch the second surface, and transferring a second rugged shape based on the first rugged shape formed on the first sacrificial layer onto the second surface; forming a second sacrificial layer containing resin on a third surface of an optical element substrate; bringing the second surface of the intermediate product into contact with the second sacrificial layer and transferring the second rugged shape onto the second sacrificial layer; and performing second etching of using the second sacrificial layer as etching mask to etch the third surface, and transferring a third rugged shape based on the second rugged shape formed on the second sacrificial layer to the third surface.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing an optical element.

As a method of manufacturing an optical element in which a plurality of microlenses are arranged in a plane, a master is made by etching the surface of a substrate into a predetermined uneven shape, and a mold is formed by electrocasting based on the uneven shape. A method of manufacturing an optical element from a mold is known (Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-132010

According to the first aspect, the method for manufacturing an optical element is to prepare an original plate having a first uneven shape formed on a first surface, and to form a first sacrificial layer containing a resin on the second surface of an intermediate. That is, the first surface of the original plate is brought into contact with the first sacrificial layer on the second surface of the intermediate, and the first uneven shape is transferred to the first sacrificial layer. Is used as an etching mask to etch the second surface, and a first etching process is performed in which the second uneven shape based on the first uneven shape formed on the first sacrificial layer is transferred to the second surface. That is, a second sacrificial layer containing a resin is formed on the third surface of the optical element base material, and the second surface of the intermediate is used as the second sacrificial layer on the third surface of the optical element base material. The second uneven shape is transferred to the second sacrificial layer by contacting the second sacrificial layer, and the third surface is etched using the second sacrificial layer as an etching mask to form the second sacrificial layer. The present invention comprises performing a second etching process of transferring the third uneven shape based on the uneven shape to the third surface.

The figure which shows the manufacturing method of the optical element of 1st Embodiment. The figure which shows the manufacturing method of the optical element of 1st Embodiment following FIG. The figure which shows the manufacturing method of the optical element of 1st Embodiment following FIG. The figure which shows the manufacturing method of the optical element of 1st Embodiment following FIG.

(Manufacturing method of optical element of the first embodiment)
Hereinafter, a method for manufacturing an optical element according to the first embodiment will be described with reference to FIGS. 1 to 4.
In the X, Y, and Z directions indicated by the arrows in each of FIGS. 1 to 4, the direction indicated by the arrow is the + direction. The X, Y, and Z directions are orthogonal to each other.

(Step 1)
As shown in FIG. 1 (a), the original plate 10 in which the first uneven shape 12 is formed on the first surface 11 is prepared. The first surface 11 may be a flat surface on either side of the flat plate-shaped original plate 10, but in FIG. 1A, the first surface 11 is a lower surface (−Z side) of the original plate 10. It is supposed to be.

As the original plate 10, a substrate made of quartz glass is used as an example.
The first uneven shape 12 may be formed on the first surface 11 of the original plate 10 by any method such as a conventionally used method by lithography or a method by mechanical processing.

As an example, the first uneven shape 12 has a convex curved surface or a concave curved surface shape on the surface, and a rectangular unit region viewed from the −Z direction is two-dimensionally arranged in the XY plane. Alternatively, the first concave-convex shape 12 each has a convex or concave cylindrical lens shape extending in the X direction (or Y direction), and the rectangular unit region seen from the −Z direction is in the Y direction (or Y direction). ) May be a shape that is arranged one-dimensionally.

The difference between the maximum value and the minimum value of the position (height) in the Z direction in the first uneven shape 12 is hereinafter referred to as the first height difference D1. The first height difference D1 is, for example, about 1 to 100 μm.
Further, the period of the X-direction or Y-direction arrangement of the unit regions arranged in the above-mentioned one-dimensional or two-dimensional manner is, for example, about 0.02 to 2 mm.

(Step 2)
As shown in FIG. 1 (b), a flat plate-shaped intermediate 20 is prepared as an example, and a second surface 21 which is one surface (the surface in the + Z direction) of the intermediate 20 is made of a material containing resin. 1 Form the sacrificial layer 22. As the intermediate 20, a substrate made of quartz glass is used as an example.

As the first sacrificial layer 22, a thermoplastic resin may be used, or an ultraviolet curable resin may be used. The thickness of the first sacrificial layer 22 is set to a thickness of about the first height difference D1 of the first uneven shape 12 formed on the original plate 10.

(Step 3)
As shown in FIG. 1 (c), the first surface 11 of the original plate 10 on which the first uneven shape 12 is formed and the first sacrificial layer 22 formed on the second surface 21 of the intermediate 20. Are placed facing each other.
Then, as shown in FIG. 2A, the first surface 11 of the original plate 10 is brought into contact with the first sacrificial layer 22 on the second surface 21 of the intermediate 20, and the first uneven shape is formed on the first sacrificial layer 22. Twelve is transcribed.

When a thermoplastic resin is used as the first sacrificial layer 22, it is heated and molded at a temperature equal to or higher than the glass transition temperature. After that, it is cooled to room temperature and released from the mold.
When an ultraviolet curable resin is used as the first sacrificial layer 22, the first sacrificial layer 22 is irradiated with ultraviolet rays through the original plate 10 or the intermediate 20 in a state where the original plate 10 and the intermediate 20 are in contact with each other. The first sacrificial layer 22 may be cured.

(Step 4)
As shown in FIG. 2B, the original plate 10 is peeled off from the intermediate 20 having the first sacrificial layer 22 to which the first uneven shape 12 is transferred. FIG. 2B shows only the intermediate 20 having the first sacrificial layer 22. On the second surface 21 of the intermediate 20, a first sacrificial layer 22 to which the first uneven shape 12 is transferred is formed on the surface thereof.

(Step 5)
The first etching process is performed on the second surface 21 of the intermediate 20 on which the above-mentioned first sacrificial layer 22 shown in FIG. 2B is formed, using the first sacrificial layer 22 as an etching mask. As a result, the second uneven shape 23 is formed on the second surface 21 of the intermediate body 20. The difference between the maximum value and the minimum value of the position (height) in the Z direction in the second uneven shape 23 is hereinafter referred to as the second height difference D2.

The first etching process is performed, for example, by reactive ion etching using a fluorocarbon-based etching gas such as CF4 or CHF3. Further, by using inductively coupled plasma as a source of reactive ions, the concentration or energy density of the reactive ions may be increased to improve the etching rate.

The first sacrificial layer 22 is a layer containing a resin and containing carbon and hydrogen as main components, whereas the intermediate 20 is quartz glass as an example and is made of a material containing silicon and oxygen as main components. Therefore, by changing the composition ratio of the reactive ions and radicals, the ratio (selection ratio) of the etching rates of the first sacrificial layer 22 and the intermediate 20 can be changed. For example, the selection ratio between the first sacrificial layer 22 and the intermediate 20 can be changed by changing the concentration of oxygen or hydrogen mixed in the fluorocarbon-based etching gas.

In the first embodiment, in the first etching process, as an example, the etching rate to the intermediate 20 is increased with respect to the etching rate to the first sacrificial layer 22. As a result, the second height difference D2 of the second uneven shape 23 of the second surface 21 is larger than the first height difference D1 of the first uneven shape 12 formed on the first surface 11 of the original plate 10. It can be expanded in the Z direction, which is the normal direction of 21. The enlargement ratio of the second height difference D2 with respect to the first height difference D1 is, for example, about 1 to 2 times.

After the completion of the first etching treatment, the first sacrificial layer 22 remaining on the second surface 21 is removed by an ashing treatment or a wet cleaning, if necessary.

(Step 6)
As shown in FIG. 3A, a flat plate-shaped optical element base material 30 is prepared as an example, and a resin is applied to a third surface 31 which is one surface (the surface in the −Z direction) of the optical element base material 30. A second sacrificial layer 32 made of the containing material is formed. As the optical element base material 30, a substrate made of quartz glass is used as an example. As the second sacrificial layer 32, the same material as the first sacrificial layer 22 described above is used.

(Step 7)
As shown in FIG. 3A, in step 5, the intermediate body 20 having the second uneven shape 23 formed on the second surface 21 is placed on the third surface 31 of the optical element base material 30 on the second surface 21. It is arranged so as to face the second sacrificial layer 32 of the above.
Then, as shown in FIG. 3B, the second surface 21 of the intermediate 20 is brought into contact with the second sacrificial layer 32 on the third surface 31 of the optical element base material 30, and the second sacrificial layer 32 is brought into contact with the second sacrificial layer 32. 2 Transfer the uneven shape 23. The transfer of the second uneven shape 23 to the second sacrificial layer 32 may be performed in the same manner as the transfer of the first uneven shape 12 to the first sacrificial layer 22 described above.

In FIGS. 3 (a) and 3 (b), the intermediate 20 is rotated by 180 ° with the Y direction as the rotation axis with respect to the directions shown in FIGS. 1 (b) to 2 (c). It is shown in the correct direction. In line with this, in FIGS. 3 (a), 3 (b) and the following drawings, the directions of the X direction, the Y direction, and the Z direction in the drawings are changed from FIGS. 1 (a) to 2 (c). ) Is different.

(Step 8)
As shown in FIG. 4A, the intermediate 20 is peeled off from the optical element base material 30 having the second sacrificial layer 32 to which the second uneven shape 23 is transferred. FIG. 4A shows only the optical element base material 30 having the second sacrificial layer 32. On the third surface 31 of the optical element base material 30, a second sacrificial layer 32 to which the second uneven shape 23 is transferred is formed on the surface thereof.

(Step 9)
A second etching process is performed on the third surface 31 of the optical element base material 30 on which the above-mentioned second sacrificial layer 32 shown in FIG. 4A is formed, using the second sacrificial layer 32 as an etching mask. As a result, the third uneven shape 33 is formed on the third surface 31 of the optical element base material 30. The difference between the maximum value and the minimum value of the position (height) in the Z direction in the third uneven shape 33 is hereinafter referred to as the third height difference D3.

As the second etching process, the same process as the above-mentioned first etching process may be performed. In the first embodiment, as an example, the etching rate to the optical element base material 30 is increased with respect to the etching rate to the second sacrificial layer 32. As a result, the third height difference D3 of the third uneven shape of the third surface 31 is more than the second height difference D2 of the second uneven shape 23 formed on the second surface 21 of the intermediate body 20. It is enlarged in the Z direction, which is the normal direction of 31.

The enlargement ratio of the third height difference D3 with respect to the second height difference D2 is, for example, about 1 to 2 times. Therefore, the third height difference D3 of the third uneven shape 33 formed on the third surface 31 of the optical element base material 30 is the first height difference D3 of the first uneven shape 12 formed on the first surface 11 of the original plate 10. The difference is about 1 to 4 times the difference D1.

After the completion of the second etching treatment, the second sacrificial layer 32 remaining on the third surface 31 is removed by an ashing treatment or a wet washing, if necessary.
By the above steps, the uneven shape formed on the first surface 11 of the original plate 10 is transferred to the third surface 31 of the optical element base material 30, and the optical element 40 is completed.

As an example, the uneven shape formed on the third surface 31 of the optical element 40 has a convex or concave shape on the surface like the shape of the first uneven shape 12 described above, and is a rectangular unit when viewed from the −Z direction. The region may have a shape that is two-dimensionally arranged in the XY plane. That is, the optical element 40 may be a microlens as an example.

(Various variants)
In the first embodiment described above, a material made of quartz glass is used for all of the original plate 10, the intermediate 20, and the optical element base material 30, but these materials are not limited to quartz glass. No. For example, for the original plate 10, a metal such as low expansion glass or nickel may be used, and for the intermediate 20, glass such as low expansion glass or ordinary alkaline glass may be used. As for the optical element base material 30, suitable glass may be used depending on the intended use.

However, when a thermoplastic resin is used as the first sacrificial layer 22 and the first uneven shape 12 of the original plate 10 is transferred to the intermediate body 20, the difference in linear expansion coefficient between the original plate 10 and the intermediate body 20 is 1 ×. It should be ^{10-6 or less.} As a result, in the first uneven shape 12 transferred to the first sacrificial layer 22 of the intermediate body 20, the difference in thermal expansion and contraction between the original plate 10 and the intermediate body 20 during heating and cooling during the formation of the first sacrificial layer 22. It is possible to reduce the positional error caused by the above.

Similarly, when a thermoplastic resin is used as the second sacrificial layer 32 and the second uneven shape 23 of the intermediate body 20 is transferred to the optical element base material 30, the line between the intermediate body 20 and the optical element base material 30 is used. The difference in expansion coefficient should be 1 × ^10-6 or less. As a result, in the second uneven shape 23 transferred to the second sacrificial layer 32 of the optical element base material 30, the intermediate 20 during heating and cooling during the formation of the third sacrificial layer 32 and the optical element base material 30 It is possible to reduce the positional error caused by the difference in thermal expansion and contraction.

As in the first embodiment described above, the difference in the coefficient of linear expansion can be eliminated by using a material made of quartz glass for any of the original plate 10, the intermediate 20, and the optical element base material 30. can. As a result, it is possible to reduce the positional error of the second uneven shape 23 transferred to the intermediate 20 and the third uneven shape 33 transferred to the optical element base material 30.

As at least one of the first sacrificial layer 22 or the second sacrificial layer 32 as the thermoplastic resin, a general novolak resist may be used as a photoresist material for photolithography. Novolac resist is a resist that has been used for many years in optical lithography technology, although it is not common as a thermoplastic resin. Therefore, by using the novolak resist, many knowledge about dry etching accumulated so far can be effectively utilized.

Since the base resin of the novolak resist contains a benzene ring, it has high etching resistance to dry etching such as reactive ion etching, and can increase the selectivity with the intermediate 20 made of quartz glass or the like or the optical element base material 30. It is also effective in terms of points.

As at least one of the first sacrificial layer 22 and the second sacrificial layer 32, not only the above-mentioned novolak resist but also a resin material containing a benzene ring may be used. This makes it possible to increase the selectivity with the intermediate 20 made of quartz glass or the like or the optical element base material 30.

(Effect of Manufacturing Method of Optical Element of First Embodiment and Each Modification Example)
(1) In the method for manufacturing the optical element of the first embodiment and each modification described above, the original plate 10 having the first uneven shape 12 formed on the first surface 11 is prepared, and the second surface of the intermediate 20 is prepared. Forming the first sacrificial layer 22 containing the resin in 21, contacting the first surface 11 of the original plate 10 with the first sacrificial layer 22 on the second surface 21 of the intermediate 20, and making the first sacrificial layer 22 first. The uneven shape 12 is transferred, the second surface 21 is etched using the first sacrificial layer 22 as an etching mask, and the second uneven shape 23 based on the first uneven shape 12 formed on the first sacrificial layer 22 is obtained. The first etching process for transferring to the two surfaces 21 is performed. Further, the second sacrificial layer 32 containing the resin is formed on the third surface 31 of the optical element base material 30, and the second surface 21 of the intermediate 20 is formed on the third surface 31 of the optical element base material 30. The second uneven shape 23 is transferred to the second sacrificial layer 32 by contacting with the sacrificial layer 32, and the third surface 31 is etched using the second sacrificial layer 32 as an etching mask to form the second sacrificial layer 32. It is provided with a second etching process of transferring the third uneven shape 33 based on the second uneven shape 23 to the third surface 31.
With this configuration, the optical element 40 can be manufactured with high accuracy and high productivity.

(2) In the first etching process, the intermediate 20 is selectively etched from the first sacrificial layer 22 so that the second uneven shape 23 is oriented in the normal direction of the second surface 21 from the first uneven shape 12. It may be an enlarged uneven shape. With this configuration, the first height difference D1 of the first uneven shape 12 to be formed on the original plate 10 can be made smaller than the third height difference D3 of the third uneven shape 33 to be finally formed on the optical element 40. can. As a result, the original plate 10 can be easily manufactured, the manufacturing cost of the original plate 10 can be reduced, and the manufacturing cost of the optical element 40 can be further reduced.

(3) In the second etching process, the optical element base material 30 is selectively etched from the second sacrificial layer 32, so that the third uneven shape 33 is the normal of the third surface 31 rather than the second uneven shape 23. It may be an uneven shape enlarged in the direction. With this configuration, the first height difference D1 of the first uneven shape 12 to be formed on the original plate 10 can be made smaller than the third height difference D3 of the third uneven shape 33 to be finally formed on the optical element 40. can. As a result, the original plate 10 can be easily manufactured, the manufacturing cost of the original plate 10 can be reduced, and the manufacturing cost of the optical element 40 can be further reduced.

Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Moreover, each embodiment and modification may be applied individually or may be used in combination. Other aspects considered within the scope of the technical idea of the present invention are also included within the scope of the present invention.

10: Original plate, 11: 1st surface, 12: 1st uneven shape, 20: Intermediate, 21: 2nd surface, 22: 1st sacrificial layer, 23: 2nd uneven shape, 30: Optical element base material, 31 : 3rd surface, 32: 2nd sacrificial layer, 33: 3rd uneven shape, 40: optical element

Claims (10)

Prepare an original plate with the first uneven shape formed on the first surface,
Forming a first sacrificial layer containing resin on the second surface of the intermediate,
The first surface of the original plate is brought into contact with the first sacrificial layer on the second surface of the intermediate, and the first uneven shape is transferred to the first sacrificial layer.
The second surface is etched using the first sacrificial layer as an etching mask, and the second uneven shape based on the first uneven shape formed on the first sacrificial layer is transferred to the second surface. 1 Etching process,
Forming a second sacrificial layer containing a resin on the third surface of the optical element base material,
The second surface of the intermediate is brought into contact with the second sacrificial layer on the third surface of the optical element base material, and the second uneven shape is transferred to the second sacrificial layer.
The third surface is etched using the second sacrificial layer as an etching mask, and the third uneven shape based on the second uneven shape formed on the second sacrificial layer is transferred to the third surface. Doing the processing,
A method for manufacturing an optical element. In the method for manufacturing an optical element according to claim 1,
In the first etching process, the intermediate is selectively etched from the first sacrificial layer, so that the second uneven shape is enlarged in the normal direction of the second surface from the first uneven shape. A method for manufacturing an optical element having an uneven shape. In the method for manufacturing an optical element according to claim 1 or 2.
In the second etching process, the optical element base material is selectively etched from the second sacrificial layer, so that the third uneven shape is oriented in the normal direction of the third surface from the second uneven shape. A method for manufacturing an optical element having an enlarged uneven shape. The method for manufacturing an optical element according to any one of claims 1 to 3.
When transferring the first uneven shape to the first sacrificial layer, the first sacrificial layer is molded by applying heat equal to or higher than the glass transition temperature, or when transferring the second uneven shape to the second sacrificial layer, the said A method for manufacturing an optical element, which is formed by applying heat equal to or higher than the glass transition temperature to the second sacrificial layer. In the method for manufacturing an optical element according to claim 4,
A method for manufacturing an optical element, which uses a novolak resist as at least one of the first sacrificial layer or the second sacrificial layer. In the method for manufacturing an optical element according to claim 4,
A method for manufacturing an optical element, which uses a resin material containing a benzene ring as at least one of the first sacrificial layer or the second sacrificial layer. The method for manufacturing an optical element according to any one of claims 4 to 6.
A method for manufacturing an optical element, wherein the difference between the original plate and the intermediate has a coefficient of linear expansion of 1 × ^{10-6 or less.} The method for manufacturing an optical element according to any one of claims 4 to 7.
A method for manufacturing an optical element, wherein the difference in linear expansion coefficient between the intermediate and the optical element base material is 1 × ^{10-6 or less.} The method for manufacturing an optical element according to any one of claims 1 to 8.
A method for manufacturing an optical element, which uses quartz glass for all of the original plate, the intermediate, and the optical element base material. The method for manufacturing an optical element according to any one of claims 1 to 9.
A method for manufacturing an optical element, wherein at least one of the first etching process and the second etching process is performed by reactive ion etching using inductively coupled plasma.

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