JP4307040B2 - Method for manufacturing an article having a fine surface structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the manufacture and processing of a product that exhibits an optical function, a mechanical function, or a physical function by performing fine processing on a surface. Such microfabrication is used for manufacturing optical elements such as MLA (micro lens array), diffractive optical elements, deflecting optical elements, refractive optical system elements, birefringent optical elements, optical fiber optical elements, beam splitters and the like. In particular, it is used in the manufacture of optical elements having a schematic dimension of 10 mm or less. In addition, this method can be applied and used in a wide range of industrial fields such as micromachining and surface treatment methods for machine sliding parts (automobile engines, air conditioner compressors, etc.).
[0002]
[Prior art]
A) As a manufacturing method of a multi-level device using a lithography technique, N = 2 in (M−1) times using M masks. ^M A method for manufacturing an element having a level stepwise phase distribution has been proposed (see Non-Patent Document 1).
[0003]
B) A method of combining a direct drawing method using an electron beam, a laser beam, an ion boom or the like, photolithography, and dry etching technology has also been proposed (see Non-Patent Document 2).
[0004]
C) It has been proposed to produce a desired three-dimensional structure on a photosensitive material layer by a density distribution mask method and to transfer this shape to a final product material by dry etching (see Patent Document 1). The density distribution mask is a mask having a transmittance distribution not only in the in-plane pattern but also in the film thickness direction.
[0005]
D) It has been proposed to manufacture a mold in advance and transfer the shape to the surface of the product material by resin transfer, and to transfer the transferred resin shape to the final product material by dry etching (see Patent Document 2). ).
[0006]
[Non-Patent Document 1]
"Optical Technology Contact", Vol.38, No.5 (2000) P.42-51, especially P.45
[Non-Patent Document 2]
“Applied Physics”, Vol. 68, No. 6 (1999), pp. 633-638
[Patent Document 1]
JP 2001-356470 A
[Patent Document 2]
JP 2002-192500 A
[0007]
[Problems to be solved by the invention]
The method A requires a large number of masks, a large number of alignments, this error cannot be ignored, an etching error in the depth direction cannot be ignored, and the minimum line width is limited to about 1 μm. It is a problem.
[0008]
In the method B, a device having a highly accurate control technique is required, the device is expensive, it takes a long time to draw (about 10 to 15 hours in a square of 500 μm × 500 μm), and there is no mass productivity. There are problems such as poor reproducibility, and there is no practical example.
[0009]
With respect to the problem of manufacturing a highly accurate surface three-dimensional structure with good reproducibility, the above methods C and D can achieve the problem well. Further, the method D for transferring using a mold also has an advantage of reducing the manufacturing cost.
[0010]
The present invention relates to the improvement of the above method D and aims to make it easy to increase the height of a three-dimensional structure. Increasing the height of the three-dimensional structure means that in the case of an optical lens, the numerical aperture (NA) is increased to brighten the lens.
The present invention also aims at extending the life of the mold.
[0011]
[Means for Solving the Problems]
The present invention is a manufacturing method for manufacturing an article having a fine surface structure by including the following steps (A) to (K).
(A) A step of producing a mold having a fine shape on the surface having a structure in which a target shape is similarly reduced in the height direction to 1 / n (n> 1),
(B) A step of performing a mold release treatment on the surface of the mold,
(C) a step of pressing an intermediate material through a curable resin to the mold surface subjected to the mold release treatment, and transferring a reverse shape of the surface shape of the mold to the resin;
(D) curing the resin after shape transfer;
(E) A step of peeling the resin from the mold in a state where the cured resin is bonded to the intermediate material;
(F) A step of transferring the shape transferred to the resin to the intermediate material by a dry etching method to form an intermediate mold, and the condition is set to be M1 (M1> 1) times higher in the height direction. Transfer process to be set,
(G) A step of releasing the surface of the intermediate mold after transferring the shape;
(H) a step of pressing the final product material through a curable resin to the surface of the intermediate mold subjected to the mold release treatment, and transferring the inverted shape of the surface shape of the intermediate mold to the resin;
(I) a step of curing the resin after transfer in step (H);
(J) a step of peeling the resin from the intermediate mold in a state where the resin cured in the step (I) is bonded to the final product material; and
(K) A step of transferring the shape transferred to the resin existing on the final product material after the step (J) to the final product material by a dry etching method, and M2 (M2> 1 in the height direction) ) Transfer process to obtain final target structure by transferring while making it high.
[0012]
There are various methods for manufacturing the mold, but the higher the height of the target shape, the more difficult it is to manufacture. Therefore, in the present invention, a mold having a fine shape having a structure in which a target shape is reduced to 1 / n in a similar manner in the height direction is manufactured. Then, by setting the conditions so as to increase the height in the subsequent two transfer processes by dry etching, the height of the shape of the final target structure becomes higher than the shape of the mold.
[0013]
It is preferable that the height magnifications M1 and M2 in the two dry etching steps have a relationship of M1 × M2 = n. In that case, a shape having a desired height can be obtained.
[0014]
The number of intermediate materials to be interposed from the first mold to the final product is 2 or more, and after shape transfer by dry etching to each intermediate material via resin, the shape is transferred to the final product material by dry etching. It can also be. By increasing the number of times of shape transfer by dry etching, it becomes easier to increase the height of the shape of the final product. In that case, when the magnification in the height direction in the shape transfer by dry etching from the resin to each intermediate material or final product material is sequentially M1, M2,... Mj (all are larger than 1),
M1 × M2 × …… Mj = n
It is preferable to have the following relationship. In that case, a shape having a desired height can be obtained.
[0015]
In the present invention, since the surface of the mold or the intermediate mold is released, the resin is easily peeled off from the mold or the intermediate mold. This also extends the life of the mold and intermediate mold and improves transferability.
[0016]
Furthermore, since the final product can be manufactured by using a mold whose shape is transferred to the intermediate material as a mold, a fine shape having a structure in which the target shape is reduced to 1 / n similarly in the height direction on the surface. The frequency of use of the first mold having can be reduced, and the life of the first mold can be greatly extended.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The intermediate material for forming the intermediate mold is preferably synthetic quartz or heat-resistant glass, which is heat-resistant and has a light-transmitting property with respect to a wavelength for curing the ultraviolet curable resin. Pyrex (registered trademark), Neoceram (registered trademark), or the like can be used as the heat resistant glass.
[0018]
As the resin for transferring the inverted shape of the surface shape of the mold and the intermediate mold, an ultraviolet curable resin or a thermosetting resin can be used.
[0019]
The use of an ultraviolet curable resin as the transfer resin has the following advantages.
(1) Curing at room temperature is possible.
{Circle around (2)} Since it can be applied in a liquid state, it has good fluidity and can prevent generation of bubbles and the like.
(3) Since it can be cured by uniformly irradiating with ultraviolet light, it can be cured uniformly.
(4) It can be cured in a short time.
[0020]
As a result, when an ultraviolet curable resin is used, the surface shape of a mold or an intermediate mold can be transferred more accurately and easily.
Further, even when a thermosetting resin is used as the transfer resin, the surface shape of the mold or intermediate mold can be accurately transferred in the same manner as the ultraviolet curable resin by being cured uniformly. As the thermosetting resin, a plastic spectacle lens or a resin used for manufacturing a contact lens can be used. Such a molding method using a thermosetting resin is called a casting method, in which a liquid thermosetting resin is poured into a mold and gradually heated to be cured for about 24 hours. .
[0021]
Regarding the mold production, if the fine shape of the mold surface is larger than 1 mm, it can be processed by a commercially available high-precision machining (NC lathe, NC ultra-precision machine, etc.).
[0022]
In addition, if the fine shape of the mold surface is 1 mm or less, it can be manufactured by the method proposed by the inventors (Japanese Patent Laid-Open No. 2001-356470), or glass or metal material can be formed by lithography and wet. It is also possible to manufacture by etching.
[0023]
If the mold surface has a very fine dimension of 10 μm or less, a resist (photosensitive layer) formed on the mold base material by a method already proposed by the inventors (Japanese Patent Laid-Open No. 2002-192500). It can be manufactured by drawing a desired shape with an electron beam (EB) or laser beam and developing it to form a fine structure, and transferring the fine structure to a mold base material by dry etching. is there. Thus, if the resist shape is transferred to the mold base material by a dry etching method, the resist shape, which is a soft material, can be transferred to the hard mold material.
[0024]
When a mold is manufactured by a dry etching method, the mold base material must be a material that can be dry etched, such as a metal material, a glass material, a ceramic material, a plastic material, a hard rubber material, etc. Can be used.
[0025]
In manufacturing a mold, the selectivity is changed stepwise or continuously in order to transfer the desired shape in the dry etching process in which the shape of the photosensitive material is transferred to the mold base material by the dry etching method. It is preferable to make it. Thus, by changing the selection ratio stepwise or continuously, a desired shape can be obtained during transfer.
[0026]
An example of the mold release treatment on the surface of the mold or intermediate mold is to form a metal thin film on the surface of the mold or intermediate mold, and the metal thin film is formed of Ni, Cr, Fe, Al, Co, Cu. , Mo, Pt, Au, Nb, Ti, or other single metal or composite material. By this releasing treatment, the shape transferability of the mold is remarkably increased and accurate transfer can be performed. At the same time, the releasability is facilitated and the life of the mold and the intermediate mold is dramatically improved.
[0027]
As the mold release treatment, it is preferable to perform a surface treatment with a layer containing a fluororesin having a fine structure on the metal thin film. This surface treatment can be performed by forming a layer containing a fluororesin by a plating method or a vapor deposition method.
As another mold release treatment method on the surface of the mold or intermediate mold, a method of forming an organic compound layer having a fluorine functional group on the surface of the mold or intermediate mold is also preferable.
[0028]
When an ultraviolet curable resin is used as a resin for transferring the inverted shape of the surface shape of a mold or an intermediate mold, as a method of curing the ultraviolet curable resin, among the three materials of the mold, the intermediate material, and the final product In addition, as at least one of the two materials applied to the transfer process using the ultraviolet curable resin, a material that is light transmissive with respect to light in a wavelength range that can cure the ultraviolet curable resin, In the curing process of the ultraviolet curable resin, if only one material is a light transmissive material, the light transmissive material is passed through. If both materials are light transmissive materials, one or both light transmissive materials are transmitted. It is preferable that the ultraviolet curable resin is irradiated with light through a property material to uniformly cure the ultraviolet curable resin. By uniformly curing the ultraviolet curable resin, the shape transferability of the mold and intermediate mold is dramatically increased, and accurate transfer can be performed.
[0029]
When a thermosetting resin is used as a resin to transfer the reverse shape of the surface shape of a mold or an intermediate mold, a method of curing the thermosetting resin includes a combination of a mold and an intermediate material, and an intermediate mold and a final mold. A set of product materials is fixed in a positioned state, a resin injection port is separately provided, and a thermosetting resin is injected between the mold and the material from the resin injection port. In the curing process of the thermosetting resin, it is desirable to heat and cure so that heat is uniformly distributed over the mold and the material sandwiching the thermosetting resin while gradually heating.
[0030]
In general, the resin shrinks upon curing. Therefore, the amount of shrinkage of the resin is obtained in advance, and in the manufacturing process of the mold or intermediate mold for transferring the shape to the resin, the shape of the mold or intermediate mold is deepened in anticipation of the amount of shrinkage. It is preferable to correct and process. This makes it possible to correct the amount of cure shrinkage.
[0031]
When pressing the intermediate material or final product material through the resin to the surface of the mold or intermediate mold that has been subjected to the mold release treatment, the adhesion between the resin and the intermediate material surface or the final product material surface should be improved. It is preferable to perform primer surface treatment such as silane coupling agent treatment for improvement. As a result, separation is selectively performed from the mold side or the intermediate mold side in the peeling process, and resin squealing (a part of the resin remains in the mold or intermediate mold during peeling) is drastically reduced. To do. As a result, the shape transferability in the next process is improved. In addition, when pressing the intermediate material or final product material through the resin to the surface of the mold or intermediate mold, a gap (space) is created between the surface of the mold or intermediate mold and the intermediate material or final product material. It is important to provide it. This gap can be used as a flow path for supplying shrinkage from around when the resin is cured. As a method therefor, a mold and an intermediate material mold are provided with a plurality of projections that form a flow path for supplying a volume reduction due to resin shrinkage from the surrounding resin between the oppositely bonded material surfaces. The part is preferably formed around the target structure.
[0032]
When the shape transferred to the resin is transferred to the intermediate material or the final product material by the dry etching method, the resin and the intermediate material or the final product material in the dry etching are formed in order to form a desired shape in the intermediate material or the final product material. It is preferable to change the etching selectivity of the stepwise or continuously. By adjusting the selection ratio, the shape can be corrected and transferred to a desired shape.
[0033]
【Example】
Example 1
A diffractive optical element 2 shown in FIG. 1 was produced. The final diffractive optical element 2 has a diameter of about 10 mm formed on a synthetic quartz material, and has a sawtooth shape arranged concentrically. The number of zones is about 965, the pitch is about 150 μm for the first zone, the final zone is 2 μm, and the height is about 1.5 μm.
[0034]
First, the product was manufactured in the following manner.
(1) Since the maximum value of resist height after drawing and development is considered to be the limit from the relationship between the electron beam drawing apparatus and the photosensitive material, the target height: 0.6 / 1 of 1.5 μm. A mold having a height of 0.5 (0.4 times reduction structure, ie, n = 2.5) was manufactured on a silicon substrate. When the shape is transferred to the silicon substrate, the selection ratio is 1.1.
[0035]
(2) Next, after the shape is transferred to the silicon substrate, it is transferred to a separately prepared quartz intermediate mold. At this time, transfer was performed at a selection ratio of 1.6 (the height after transfer was 0.6 μm × 1.6 = 0.96 μm). The shape at this time is reversed.
[0036]
(3) Finally, the intermediate mold shape is transferred to the quartz material which is the final product material. At this time, transfer was performed at a selection ratio of 1.6 (the height after transfer was 0.96 μm × 1.6 = 1.53 μm). The shape at this time is rotating forward (inverted with respect to the intermediate mold).
[0037]
Hereinafter, a manufacturing procedure of the diffractive optical element will be described with reference to FIGS.
(A) A silicon substrate having a diameter of 4 inches and a thickness of 1.0 mm was prepared as the mold base material 4. A photosensitive material for electron beam drawing (resist) 6 (manufactured by Tokyo Ohka Kogyo Co., Ltd .: OEBR-1000) 6 was applied on the surface of the mold base material 4 with a spinner at 500 rpm for 5 seconds and then at 2000 rpm for 30 seconds. Then, after prebaking for 20 minutes at 170 ° C. in an oven, it was rapidly cooled. The resist film thickness at this time was 1.0 μm.
[0038]
(B) On the other hand, in order to obtain the shape shown in FIG. 1, the division of the region traced by the EB irradiation beam, the path and beam diameter, the dose amount, the drawing time, etc. are input separately using CAD software. In the case of the present embodiment, the drawing program was created by approximating the round shape to a 1080 square and dividing the entire drawing area into square areas of 500 μm × 500 μm. There are two methods for drawing a round shape: (1) a method of drawing in a divided manner and (2) a method of drawing continuously. In the case of a large-diameter lens, it is more appropriate to write separately. On the other hand, in the case of a small-diameter lens, it is more suitable to write one stroke continuously. In this embodiment, since the diameter corresponds to a large-diameter lens having a diameter of 10 mm, the division writing method (1) was performed.
[0039]
The mold base material 4 coated with the resist 6 is set in an electron beam drawing apparatus and evacuated to a predetermined degree of vacuum.
Next, the CAD data is transferred to the controller of the drawing apparatus, and drawing is started. In this case, drawing was performed while moving the XY stage, and it took 30 hours to draw.
[0040]
After drawing, development was performed at 25 ° C. for 1 minute using a developer (OEBR-1000 developer). Subsequently, rinsing was performed. Immediate drying with a nitrogen blower and spinner rotation. Thereby, the resist pattern 6a was formed.
Thereafter, a UV hardening process for irradiating the resist pattern 6a with ultraviolet rays and curing it was performed. The height of the resist pattern 6a after curing was 0.6 μm.
[0041]
(C) Next, the resist pattern 6a after drawing was transferred to the mold base material 4 by a dry etching method. The dry etching at this time uses a TCP (inductively coupled plasma) etching apparatus and CHF. _Three : 15.0 sccm, CF _Four : Base bias voltage: 500 W, upper electrode power: 1250 W, vacuum degree: 1.5 × 10 while introducing 2 sccm of gas ^-3 Etching was performed at Torr (ie, 1.5 mTorr) for 2 minutes. The etching rate at this time was 0.4 μm / min. Slightly (about 0.2 μm) was over-etched. The etching selectivity (the etching rate of silicon of the mold base material 4 / the etching rate of the resist 6) was 1.1, and the shape height of the mold 4a after the etching was 0.66 μm. The surface roughness was good at Ra = 0.001 μm or less. This shape height was set in consideration of shrinkage of the shape transfer resin in the next step as 10%. In order to secure a flow path for supplying uncured resin from the surroundings when the shape transfer resin in the next process is cured, a pattern that forms a convex shape on the silicon substrate is drawn during electron beam drawing. did.
[0042]
The shape of the mold at this time was the same as the shape at the time of drawing, and only the height was 1.1 times.
In order to release the surface of the mold, a metal Ni thin film is formed on the mold surface by a sputtering method to 7 × 10. ^-3 A film of 500 mm was formed at a vacuum degree of Torr. Since the film was formed at a relatively high pressure, the wraparound was sufficiently performed and the film was uniformly formed on the mold surface.
[0043]
Next, the Ni surface was surface-treated with a triazine thiol organic compound having a fluorine functional group. This was done by a method called the organic plating method. Specifically, electrolytic polymerization treatment (organic plating) was performed in a solution in which fluorinated SFTT (super fine triazine thiol) was dissolved in a solvent to form a fluorine-based organic thin film on the mold surface. Fluorinated SFTT is a fluorinated side chain of triazine thiol, which is one of organic sulfur compounds. As for the number n of fluorine molecules, n = 7 had the highest water repellent effect (peeling effect). However, the same water-repellent effect can be obtained by using triazine thiol having a silanol group without performing Ni sputtering.
[0044]
(D) Next, the mold subjected to the release treatment was set down, and 3 cc of an acrylic resin (manufactured by Dainippon Ink Co., Ltd .: GRANDIC RC-8720) was applied thereon as the ultraviolet curable resin 8.
[0045]
(E) This mold 4a is set in a dedicated bonding machine, and a flat substrate of intermediate material 10 (manufactured by Shin-Etsu Quartz Co., Ltd .: synthetic quartz) that has been subjected to silane coupling treatment (adhesion improvement treatment) in a separate process in advance Push it slowly. At this time, bonding was performed by an automatic bonding machine in which the descending speed was controlled so that bubbles were not generated in the ultraviolet curable resin 8.
[0046]
Next, it was slowly pushed up from the mold 4a side to the intermediate material 10 side, and the ultraviolet curable resin 8 that was excessive during shape transfer was removed from the outer periphery of the substrate.
Further, the ultraviolet curable resin layer 8 was cured by irradiating 3000 mJ of uniform ultraviolet light from the back side of the intermediate material 10. At this time, the thickness of the ultraviolet curable resin layer 8 (the distance between the top of the three-dimensional structure of the ultraviolet curable resin layer 8 and the intermediate material 10) was 0.1 μm or less. Naturally, the maximum thickness of the ultraviolet curable resin layer 8 is “pattern depth 0.66” + “top layer interval 0.1” = 0.76 μm.
[0047]
(F) Next, in order to peel the ultraviolet curable resin layer 8 from the surface of the mold 4a while being bonded to the intermediate material 10, the silicon substrate of the low-rigid mold 4a is made slightly convex using a jig. It peeled, making it deform | transform.
Next, when the transfer shape of the resin layer 8 on the surface of the intermediate material 10 was measured, the depth (concave shape) of the optical element portion was as small as 0.60 μm. This is because the resin layer was cured and shrunk, and the curing shrinkage rate was about 11% on average. The depth at this time is accurately measured with an optical (non-contact) shape measuring machine, and the selection ratio in the subsequent (G) to (K) steps and the etching conditions (change of the selection ratio over time) are appropriately determined. It is important to set
[0048]
(G) Next, the transfer shape of the resin layer 8 on the intermediate material 10 was transferred to the intermediate material 10 by the dry etching method in the same manner as described above to obtain an intermediate mold 10a. The dry etching conditions are TCP etching equipment, CHF _Three : 12.0sccm, CF _Four : Base gas bias voltage: 500 W, upper electrode power: 1250 W, vacuum degree: 1.5 × 10 while introducing 4 sccm of gas ^-3 Etching was performed at Torr (ie 1.5 mTorr) for 5.0 minutes. The etching rate at this time was 0.25 μm / min.
[0049]
In the second half of etching, CHF _Three Etching was carried out by increasing the gas amount by 2.0 sccm to slightly increase the selectivity. By changing the selection ratio stepwise, it was possible to obtain a desired shape during transfer. The etching selection ratio (etching rate of the quartz intermediate material 10 / etching rate of the resin layer 8) is 1.75 on average, and the height of the surface shape of the intermediate mold 10a after the etching is 1.05 μm. It was. The surface roughness (Ra) was good at Ra = 0.001 μm or less. The optical surface had a linear shape. Further, in order to secure the flow path of the resin used for the next transfer at the time of shape transfer, a convex spacer was manufactured in the intermediate material 10.
[0050]
At this time, the shape of the intermediate mold 10a was constant in pitch and 1.75 times (1.05 μm / 0.6 μm) in height as compared with the silicon mold 4.
[0051]
(H) In order to release the surface of the intermediate mold 10a, the surface of the intermediate mold 10a was surface-treated with a triazine thiol organic compound having a fluorine functional group. This was done by a method called the organic plating method. Specifically, a compound having an OH group was synthesized at the terminal of fluorinated SFTT and subjected to electrolytic polymerization treatment in a solution in which the solution was dissolved in a solvent to form a fluorine-based organic thin film on the mold surface. A film having a thickness of 1000 mm was formed under these conditions.
Next, the intermediate mold 10a subjected to the release treatment was set down, and 3 cc of an acrylic resin (manufactured by Dainippon Ink Co., Ltd .: GRANDIC RC-8720) was applied as an ultraviolet curable resin 12 thereon.
[0052]
(I) This intermediate mold 10a is set in a dedicated bonding machine, and a flat substrate of the final product material 14 of quartz (Shin-Etsu quartz company: Slowly press the synthetic quartz. At this time, it joined with the automatic joining machine which controlled the descent | fall speed so that a bubble might not generate | occur | produce in the ultraviolet curable resin 12. FIG.
Next, it was slowly pushed up from the intermediate mold 10a side to the final product material 14 side, and the ultraviolet curable resin 12 that was excessive during shape transfer was removed from the outer periphery of the substrate.
[0053]
Further, the ultraviolet curable resin layer 12 was cured by irradiating 3000 mJ of uniform ultraviolet light from the back side of the final product material 14. At this time, the thickness of the ultraviolet curable resin layer 12 (the distance between the top of the three-dimensional structure of the ultraviolet curable resin layer 12 and the final product material 14) was 0.1 μm or less. Naturally, the maximum thickness of the ultraviolet curable resin layer is “pattern depth 1.0” + “top layer spacing 0.1” = 1.1 μm.
[0054]
(J) Next, in order to peel off the ultraviolet curable resin layer 12 from the surface of the intermediate mold 10a while being bonded to the final product material 14, it was peeled off using a jig.
Next, when the transfer shape of the resin layer 12 on the surface of the final product material 14 was measured, the height (convex shape) of the optical element portion was as small as 0.96 μm. This is because the resin layer 12 was cured and shrunk, and the curing shrinkage rate was about 5% on average.
[0055]
The difference between the shrinkage rate of about 11% in the step (F) and the shrinkage rate of about 5% in this step is that in this step, ultraviolet irradiation was performed slowly over a long period of time. It became possible to supply from the surroundings, and the shrinkage rate during curing was reduced.
[0056]
(K) Next, the shape of the resin layer 12 on the final product material 14 was transferred to the final product material 14 in the same manner as described above. The dry etching conditions are TCP etching equipment and CHF. _Three : 12.0sccm, CF _Four : Base gas bias voltage: 500 W, upper electrode power: 1250 W, vacuum degree: 1.5 × 10 while introducing 4 sccm of gas ^-3 Etching was performed at Torr (ie, 1.5 mTorr) for 7.0 minutes. The etching rate at this time was 0.25 μm / min.
[0057]
In the second half of etching, CHF _Three Etching was carried out by increasing the gas amount by 2.0 sccm to slightly increase the selectivity. By changing the selection ratio stepwise, it was possible to obtain a desired shape during transfer. The etching selectivity (etching rate of the final product material 14 of quartz / etching rate of the resin layer 12) was 1.6 on average, and the height of the shape after etching was 1.53 μm. The surface roughness was good at Ra = 0.001 μm or less.
The final product 14a thus obtained is the diffractive optical element 2 shown in FIG.
[0058]
(Example 2)
The optical element (lens) for optical communication shown in FIG. 1 was manufactured. The final target structure of the optical element for optical communication is a single lens having a diameter of 50 μm formed on a synthetic quartz material. Its radius of curvature is 6.16 μm and its height is 28.0 μm.
[0059]
First, the product was manufactured in the following manner.
(1) Target height: 28.0 μm of 15.5 / 28.0 height (0.55 times reduction structure, ie, n = 1.82) mold is manufactured on a silicon substrate did. When the shape is transferred to the silicon substrate, the selection ratio is 1.0.
[0060]
(2) Next, after transferring the shape to the silicon substrate, the mold is transferred to a separately prepared quartz intermediate material to obtain an intermediate mold. At this time, transfer was performed at a selection ratio of 1.4 (the height after transfer was 15.5 μm × 1.4 = 21.7 μm). The shape at this time is reversed.
[0061]
(3) Finally, the intermediate mold shape is transferred to the quartz material which is the final product material. At this time, the transfer was performed at a selection ratio of 1.29 (the height after transfer was 21.7 μm × 1.29 = 28.0 μm). The shape at this time is rotating forward (inverted with respect to the intermediate mold).
[0062]
The manufacturing procedure of this optical element will be described in more detail with reference to FIGS. 4A to 5H.
(A) A silicon substrate having a diameter of 6 inches and a thickness of 0.625 mm was prepared as the mold base material 411. A Cr film 414 is formed on the mold base material 411 by a sputtering method to a thickness of 800 mm, and a Cr film around a region where a target optical lens is formed is partially formed along a circle by a photolithography method and etching. For example, six points 415 are formed along a circular outer periphery.
This portion 415 serves as a spacer for the resin flow path in the process of transferring the shape from the intermediate mold to the final product material. That is, this portion 415 is in a convex state higher than the surroundings corresponding to the spacer convex portion 455 in the step (E) described later.
[0063]
A photosensitive material (resist) (manufactured by Tokyo Ohka Kogyo Co., Ltd .: TGMR-950) was applied on the surface of the mold base material 411 having the Cr film 414 with a spinner. The resist film thickness at this time was 20.0 μm. Next, prebaking was performed at 100 ° C. with a baking time of 180 seconds.
Next, 1800 mJ was irradiated with a stepper using a concentration distribution mask (designed in advance so as to have a target structure and a height of 15.5 μm).
[0064]
Then, after developing and rinsing, a UV hardening process was performed to form resist patterns 412 and 413. This state is shown in FIG. Reference numeral 413 denotes a resist pattern for a spacer for securing the resin flow path in the process of transferring the shape from the silicon mold to the intermediate mold. The height of the target optical element resist pattern 412 (reduced to 1 / n) is about 0.2 μm lower than the resist pattern 413 for the flow path securing spacer.
[0065]
(B) Next, the resist patterns 412 and 413 and the Cr film pattern 414 were transferred to the mold base material 411 by dry etching. The dry etching at this time uses a TCP (inductively coupled plasma) etching apparatus and CHF. _Three : 5.0 sccm, CF _Four While introducing 10.0 sccm of gas, base bias voltage: 500 W, upper electrode power: 1250 W, degree of vacuum 1.5 × 10 ^-3 Etching was performed for 21 minutes at Torr (ie, 1.5 mTorr). The etching rate at this time was 0.8 μm / min. The process was slightly over-etched. The etching selectivity (etching rate of silicon as the mold base material / resist etching rate) was 1.0, and the height of the optical lens portion 422 after the etching was 15.5 μm. The surface roughness was good at Ra = 0.001 μm or less. This shape height does not allow for shrinkage of the resin in the next step. Here, in order to ensure a resin flow path in the next step, a convex spacer 423 is formed on the silicon mold 411a on the outer peripheral side of the optical lens portion 422 during mask exposure, and a sufficient resin flow path is formed. This is because it was secured.
[0066]
Reference numeral 425 denotes a recess formed in the silicon mold 411a, which corresponds to the portion 415 from which the Cr film has been removed in the step (A). The concave portion 425 is the lowest point portion, and since the selection ratio of (silicon / Cr film) is larger than the selection ratio of (silicon / resist), the concave portion 425 has a Cr film thickness of about 3 × 800 mm. It is deeply etched to about 0.2 μm.
[0067]
At this time, the shape of the optical lens portion 422 of the silicon mold 411a was similar to the shape of the resist pattern 412 after exposure.
In order to release the surface of this silicon mold 411a, a surface treatment was carried out by forming a film of 1000 mg of a triazinethiol organic compound having a fluorine functional group in the same manner as in Example 1.
[0068]
(C) Next, the release-molded silicon mold 411a is set so that the surface on which the optical lens portion 422 is formed faces upward, and an acrylic resin 434 (Dainippon Ink as an ultraviolet curable resin) is set thereon. 3 cc of GRANDIC RC-8720) was applied.
[0069]
This silicon mold 411a is set in a dedicated bonding machine, and is subjected to a silane coupling process (adhesion improvement process) in a separate process in advance. A flat intermediate material 431 (manufactured by Nippon Sheet Glass: Neoceram (registered trademark)) Press the plane slowly. At this time, it joined with the automatic joining machine which controlled the descent | fall speed | rate so that a bubble might not generate | occur | produce in the ultraviolet curable resin 434. FIG.
[0070]
Next, it was slowly pushed up from the silicon mold 411a side to the intermediate material 431 side, and the ultraviolet curable resin 434 that was excessive during shape transfer was removed from the outer periphery of the substrate.
[0071]
Further, the ultraviolet curable resin layer 434 was cured by irradiating 4000 mJ of uniform ultraviolet light from the back side of the intermediate material 431. Ultraviolet irradiation was performed from the center of the optical element. At this time, the volume of the resin 434 shrinks, but the intermediate material 431 is pressed by the spacer 423 (prevents lowering), so that the surrounding resin moves to compensate for the volume reduction due to the resin shrinkage. . Therefore, there is no difference in volume shrinkage and height. The thickness of the ultraviolet curable resin layer 434 after curing was 0.1 μm or less. The maximum thickness of the ultraviolet curable resin layer 434 is “pattern depth 15.5” + “top layer interval 0.1” = 15.6 μm.
[0072]
(D) Next, in order to peel the ultraviolet curable resin layer 434 from the surface of the silicon mold 411a while being bonded to the intermediate material 431, a slightly rigid silicon substrate (silicon mold 411a) is slightly detached using a jig. It peeled, transforming into a convex shape. When the silicon mold 411a is peeled off from the resin 434, the surface shape of the silicon mold 411a is reversed and transferred to the resin 434 remaining on the intermediate material 431. The optical lens portion 422 of the silicon mold is a concave portion 442, and the concave portion 425 of the silicon mold is a convex portion 445 for spacer.
When the transfer shape of the resin layer 434 on the surface of the intermediate material 431 was measured, the depth (concave shape) of the optical element portion 442 was reduced to 15.5 μm. This was because the resin layer 434 was cured and shrunk.
[0073]
(E) Next, the shape of the resin layer 434 on the intermediate material 431 was transferred to the intermediate material 431 by the dry etching method as described above. The dry etching conditions are TCP etching equipment and CHF. _Three : 15.0 sccm, CF _Four While introducing gas of 15.0 sccm and Ar: 10.0 sccm, base bias voltage: 500 W, upper electrode power: 1250 W, degree of vacuum 1.5 × 10 ^-3 Etching was performed at Torr (ie, 1.5 mTorr) for 49.0 minutes. The etching rate at this time was 0.45 μm / min.
[0074]
In the second half of etching, CHF _Three Etching was performed by increasing the gas amount by 4.0 sccm and slightly increasing the selectivity. By changing the selection ratio stepwise, it was possible to obtain a desired shape during transfer. The etching selectivity was 1.4 on average, and the height of the shape after etching was 21.7 μm. The surface roughness was good at Ra = 0.001 μm or less.
[0075]
As a result, an intermediate mold 431a having a lens concave portion 452 and a spacer convex portion 455 that secures a resin flow path in the next shape transfer step was obtained. The shape of the intermediate mold 431a at this time was a constant pitch and only 1.4 times the height (21.7 μm / 15.5 μm) compared to the silicon mold 411a.
[0076]
In order to release the surface of the intermediate mold 431a, the surface of the intermediate mold 431a was surface-treated with a triazine thiol organic compound having a fluorine functional group. This was done by a method called the organic plating method. Specifically, an electropolymerization treatment was performed in a solution in which a compound having an —OH group at a terminal of the fluorinated SFTT was dissolved in a solvent to form a fluorine-based organic thin film on the surface of the intermediate mold 431a. A film having a thickness of 1000 mm was formed under these conditions. The neoceram and quartz of the intermediate mold 431a are both composed of SiO2 ₂ Therefore, the same mold release process can be used.
[0077]
(F) Next, the mold 431a subjected to the release treatment is placed so that the surface having the shape faces upward, and an acrylic resin (manufactured by Dainippon Ink Co., Ltd .: GRANDIC RC) is used as an ultraviolet curable resin 464 thereon. -8720) was applied in 3 cc. The UV curable resin 464 is applied to the lens part in a large amount.
[0078]
This intermediate mold 431a is set in a dedicated bonding machine, and a flat substrate made of quartz material (Shin-Etsu quartz) for the final product that has been subjected to silane coupling treatment (adhesion improvement treatment) in advance in a separate process from the resin. (Manufactured by Synthetic Quartz) 461 is slowly pressed. At this time, it joined with the automatic joining machine which controlled the descent | fall speed | rate so that a bubble might not generate | occur | produce in the ultraviolet curable resin 464. FIG. As a result, the ultraviolet curable resin 464 is sandwiched between the intermediate mold 431a and the flat substrate 461.
[0079]
Next, it was slowly pushed up from the intermediate mold 431a side to the final product material (quartz) 461 side, and the UV curable resin 464 that was excessive during shape transfer was removed from the outer periphery of the substrate.
[0080]
Next, 3000 mJ of uniform ultraviolet light was irradiated from the back side of the final product material 461 to cure the ultraviolet curable resin layer 464. In this case as well, ultraviolet irradiation is performed from the center of the optical element. At this time, the volume of the resin 464 shrinks, but the final product material 461 is pressed by the spacer 455 (prevents lowering), so that the surrounding resin compensates for the volume reduction due to the resin shrinkage. (In the figure, the spacer 455 seems to seal the resin, but the spacer 455 is only partially formed and the resin can move. The difference does not occur.
The thickness of the ultraviolet curable resin layer 464 after curing (portion other than the optical element portion) was 0.1 μm or less. The maximum thickness of the ultraviolet curable resin layer 464 is “pattern depth 21.7” + “top layer interval 0.1” = 21.8 μm.
[0081]
(G) Next, in order to peel off the ultraviolet curable resin layer 464 from the surface of the intermediate mold 431a while being bonded to the final product material 461, it was peeled off using a jig.
When the shape of the resin layer 464 on the surface of the final product material 461 was measured, the height (convex shape) of the optical element portion was reduced to 21.7 μm.
[0082]
(H) Next, the shape of the resin layer 464 on the final product material 461 was transferred to the final product material 461 by dry etching as described above. The dry etching conditions are TCP etching equipment and CHF. _Three : 10.0 sccm, CF _Four : Base gas bias voltage: 500W, upper electrode power: 1250W, degree of vacuum 1.5 × 10 while introducing gas of 24 sccm, Ar: 5.0 sccm ^-3 Etching was performed at Torr (ie, 1.5 mTorr) for 37.0 minutes. The etching rate at this time was 0.78 μm / min.
[0083]
In the second half of etching, CHF _Three The etching was performed by increasing the gas amount by 3.0 sccm and slightly increasing the selection ratio. By changing the selection ratio stepwise, it was possible to obtain a desired shape during transfer. The etching selectivity was 1.3 on average, and the height of the shape after etching was 28.0 μm. The surface roughness was good at Ra = 0.001 μm or less.
[0084]
【The invention's effect】
In the present invention, the mold surface having a fine shape on the surface is subjected to a mold release treatment, and an intermediate material is pressed against the mold surface via a curable resin so that the inverted shape of the mold surface shape is obtained. Transfer to resin, cure the resin, peel the mold in a state where the resin is bonded to the intermediate material, then transfer the shape transferred to the resin to the intermediate material by dry etching method Get. By transferring the shape from the intermediate mold to the final target material or further to the final target material via the intermediate mold by the dry etching method, an article having a fine surface structure is manufactured. Thus, it becomes easy to increase the height of the fine structure, and a fine structure (high-precision surface three-dimensional structure) having a desired height can be produced in large quantities with high accuracy.
In addition, the life of the first mold can be further extended by interposing the intermediate mold.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a final target structure of a diffractive optical element manufactured in an example.
FIG. 2 is a process flow sectional view showing the first half of the first embodiment.
FIG. 3 is a process flow sectional view showing the latter half of the same example;
FIG. 4 is a process flow sectional view showing the first half of a second embodiment.
FIG. 5 is a process flow sectional view showing the latter half of the same example;
[Explanation of symbols]
2 Diffractive optical elements
4,411 Mold base material (silicon substrate)
4a Mold
6 resists
6a resist pattern
8, 12, 434, 464 UV curable resin
10,431 Intermediate material
10a, 13a, 431a Intermediate mold
14,461 Final product materials
14a Final product
411a Silicon mold
412,413 resist pattern
414 Cr film
415 Cr film partially removed along a circle
422 Optical lens unit
423 Spacer
425 Concave part formed in silicon mold
442,452 Lens recess
445, 455 Spacer convex part

Claims (13)

A manufacturing method for manufacturing an article having a fine surface structure whose height is difficult to manufacture by a mold manufactured by lithography and dry etching once, comprising the following steps (A) to (K).
(A) A step of manufacturing a mold having a fine shape on the surface having a structure in which a target shape is similarly reduced to 1 / n (n> 1) in the height direction by lithography and dry etching,
(B) A step of performing a mold release treatment on the surface of the mold,
(C) a step of pressing an intermediate material through a curable resin to the mold surface subjected to the mold release treatment, and transferring a reverse shape of the surface shape of the mold to the resin;
(D) curing the resin after shape transfer;
(E) A step of peeling the resin from the mold in a state where the cured resin is bonded to the intermediate material;
(F) A step of transferring the shape transferred to the resin to the intermediate material by a dry etching method to form an intermediate mold, and the condition is set to be M1 (M1> 1) times higher in the height direction. Transfer process to be set,
(G) A step of releasing the surface of the intermediate mold after transferring the shape;
(H) a step of pressing the final product material through a curable resin to the surface of the intermediate mold subjected to the mold release treatment, and transferring the inverted shape of the surface shape of the intermediate mold to the resin;
(I) a step of curing the resin after transfer in step (H);
(J) a step of peeling the resin from the intermediate mold in a state where the resin cured in the step (I) is bonded to the final product material, and (K) on the final product material after the step (J). Is transferred to the final product material by a dry etching method, and is transferred while being increased by M2 (M2> 1) times in the height direction. A transfer step of obtaining a final target structure in which the height of the fine shape is difficult to manufacture in the mold manufacturing step (A) by the height being multiplied by M1 × M2 by the transfer twice.   The manufacturing method of Claim 1 which has a relationship of M1xM2 = n. The number of intermediate materials to be interposed from the first mold to the final product is 2 or more, and after shape transfer to each intermediate material via resin, shape transfer to the final product,
When the magnification in the height direction in the shape transfer from the resin to each intermediate material or final product material is sequentially M1, M2,... Mj (all are greater than 1),
M1 × M2 × …… Mj = n
The manufacturing method of Claim 1 which has the relationship of these.   The manufacturing method according to claim 1, wherein the step of transferring by dry etching includes a step of changing the selectivity.   The manufacturing method according to claim 4, wherein the change in the selection ratio includes a change with time.   The manufacturing method according to claim 1, wherein a silicon material is used as at least one of the mold and the intermediate material. At least one of the curable resins used for transfer is a photocurable resin,
Wavelength at which the photocurable resin can be cured as at least one of the two materials applied to the transfer process using the photocurable resin among the three materials of the mold, the intermediate material, and the final product Using a material that is transparent to the light in the region,
In the resin curing step, when only one material is a light-transmitting material, the light-transmitting material is used. When both materials are light-transmitting materials, the one or both light-transmitting materials are used. The manufacturing method according to claim 1, wherein the photocurable resin is irradiated with light to uniformly cure the photocurable resin.   The manufacturing method according to claim 7, wherein the photocurable resin is an ultraviolet curable resin, the light transmissive material is an ultraviolet transmissive material, and light to be irradiated is ultraviolet light.   The manufacturing method according to any one of claims 1 to 8, wherein the mold is formed by forming the fine shape on a flat surface of a flat substrate serving as a mold base material. The amount of shrinkage when each resin is cured is determined in advance,
10. The manufacturing method according to claim 1, wherein when the fine shape is formed on the intermediate material by dry etching, the fine amount is corrected so as to allow for a shrinkage amount portion.   Primer surface treatment for improving the adhesion between the resin and the other material surface when other materials are pressed through the resin to the mold surface or intermediate material surface subjected to the mold release treatment The manufacturing method in any one of Claim 1 to 10 which gave. The manufacturing method according to claim 1, wherein the fine shape of the mold surface is formed by the following steps (a) to (c).
(A) a step of applying a photosensitive material on the surface of a mold base material where the fine shape is to be formed;
(B) exposing the photosensitive material using a density distribution mask and then developing to form a desired shape on the photosensitive material; and (c) forming the shape of the photosensitive material by dry etching. The process of transferring to the mold base material.   The mold and the intermediate material mold have a plurality of convex portions that form a flow path for supplying a volume reduction due to resin shrinkage from the surrounding resin between the material surfaces that are bonded to each other. The manufacturing method in any one of Claim 1 to 12 formed in the circumference | surroundings.

Images