JP2001239532A - Method for manufacturing microlens substrate and mold for microlens substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for a microlens substrate, hard to damage, high in durability and having a molding surface shape higher in accuracy than before and to manufacture the microlens substrate of high accuracy in a high yield using this mold high in durability and shape accuracy. SOLUTION: A mask layer 11 is formed on the surface of a silicon substrate 10 and openings 11a are bored in the mask layer 11. Thereafter, the silicon substrate 10 is etched from the openings 11a in an almost isotropic manner by a wet etching method to form semispherical recessed parts 10a and the mask layer 11 is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microlens substrate forming die and a method of manufacturing a microlens substrate, and more particularly to a manufacturing method suitable for manufacturing a fine microlens array with high precision and a configuration of the forming die. About.

[0002]

2. Description of the Related Art Conventionally, there is a method called a photopolymer method as a method for forming a microlens array. In this method, as shown in FIG. 8A, for example, a glass substrate 21 is placed on a microlens substrate molding die 20 having a curved surface portion 20a formed on the surface thereof via an ultraviolet-curable uncured transparent resin 22. Glue and irradiate with ultraviolet light to make transparent resin 2
The optical surface 22a corresponding to the curved surface portion 20a is formed by curing the glass substrate 21 and the transparent resin 2
2 is released from the microlens substrate molding die 20,
As shown in FIG. 8B, a glass substrate 24 is bonded onto the optical surface 22a via a transparent resin 23 having a different refractive index.

In the case where a panel substrate which is a component of a liquid crystal panel is formed by using the above method, FIG.
As shown in FIG. 8, the glass substrate 24 is thinned by grinding, polishing, etching, or the like.
As shown in (d), the light shielding film 2 is formed on the surface of the glass substrate 24.
6 and the transparent electrode 27 are formed.

In the above-mentioned method, a microlens substrate can be manufactured efficiently and with high productivity because a microlens substrate mold is used. The above-described microlens substrate molding die is formed, for example, by etching the surface of a glass substrate into a concave curved surface shape corresponding to the optical surface of the microlens.

[0005]

However, in the above method, since the glass substrate is used as the microlens substrate forming die, it cannot withstand repeated use of the microlens substrate forming die, and particularly, the large-sized microlens substrate is not used. There is a problem that durability is lacking when forming a mold. When the glass substrate having the curved surface portion 20a is used as the microlens substrate molding die 20, the shape of the curved surface portion 20a corresponding to the optical surface shape of the microlens is formed with high precision due to the restriction of the processing method for glass. There is a problem that it is difficult. In particular, when etching glass with many impurities, pure glass (Si
O ₂ ) has a problem that it is difficult to obtain a smooth optical surface even if an etching solution having isotropic etching characteristics is used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a microlens substrate molding die which is hardly damaged, has high durability, and has a molding surface shape which is more precise than conventional ones. It is in. Another object of the present invention is to realize a method of manufacturing a microlens substrate with high accuracy and high yield by using a microlens substrate mold having high durability and high shape accuracy as described above.

[0007]

According to the present invention, there is provided a method of manufacturing a microlens, comprising: forming a mask layer having etching resistance on a surface of a silicon substrate;
An opening is formed in the mask layer, the silicon substrate is substantially isotropically etched through the opening to form a concave curved surface portion corresponding to the optical surface of the microlens, and the silicon layer is removed by removing the mask layer. By forming a microlens substrate molding die composed of a substrate, applying an uncured transparent resin to the microlens substrate molding die or a copy thereof, and curing the resin, a convex curved optical surface corresponding to the concave curved surface portion is formed. It is characterized by being molded.

According to the present invention, a highly accurate concave curved surface portion can be easily formed by etching a silicon substrate through a mask layer having an opening, and the optical surface of a microlens can be formed with high accuracy. Can be molded.

Further, a mask layer having etching resistance is formed on the surface of the silicon substrate, an opening is formed in the mask layer, and the silicon substrate is substantially isotropically etched through the opening to form a micro lens. Forming a concave curved surface portion corresponding to the optical surface, forming a microlens substrate molding die made of a silicon substrate by removing the mask layer,
Using the microlens substrate molding die or a copy thereof, an inversion mold having a convex curved surface portion corresponding to the concave curved surface portion is formed, and an uncured transparent resin is applied to the inversion mold and cured to form the convex shape. A concave curved optical surface corresponding to the curved surface portion is formed.

In the present invention, it is preferable that the mask layer is a thermal oxide film of a silicon substrate, and the opening is formed by a dry etching method. According to the invention,
By using a thermal oxide film as a mask layer, a dense film can be efficiently formed, and a fine opening can be formed with high accuracy by using a dry etching method. Etching can be performed with high precision.

In the present invention, it is preferable to use an etching solution containing hydrofluoric acid and nitric acid as main components to form the concave curved surface portion. By performing wet etching with an etching solution containing hydrofluoric acid and nitric acid as main components, isotropic etching can be performed and a smooth etching surface can be formed.

In the present invention, it is preferable to use the etching solution to which acetic acid is further added. By mixing acetic acid into the etching solution, the composition range in which a smooth etched surface can be obtained with isotropic etching characteristics is expanded, so that highly accurate etching can be performed more stably.

In the present invention, it is preferable that a fluorine-based carbide film is formed on the molding surface of the microlens substrate molding die before use. In this case, it is preferable to use a fluorine-based resin, and it is particularly preferable to use polytetrafluoroethylene.

In the present invention, it is preferable that a support substrate is fixed to the surface opposite to the molding surface of the microlens substrate molding die.

In the present invention, it is preferable that the support substrate is directly fixed to the opposite molding surface by anodic bonding. In this case, it is preferable that the anti-molding surface of the silicon substrate and the bonding surface of the supporting substrate are mirror-finished.

In the present invention, it is preferable that a coating is formed on the bonding surface of the support substrate, and the anti-molding surface of the support substrate and the coating are fixed by eutectic bonding. In this case, for example, it is preferable that an Au thin film is formed on the surface of the support substrate, and the Au thin film is brought into contact with the non-molded surface of the silicon substrate and heated to form an Au-Si eutectic. When a glass substrate is used as the support substrate, it is desirable to form a Cr layer or a Ti layer as an underlayer of the Au thin film to enhance the adhesion.

Next, the microlens substrate molding die according to the present invention is characterized in that a curved surface portion corresponding to the optical surface of the microlens is provided on the surface of the silicon substrate.

According to the present invention, by using a silicon substrate, it is easy to control the impurity and improve the quality and to easily form a fine and highly accurate curved surface portion by the characteristics to which the semiconductor manufacturing technology can be applied. Therefore, productivity can be improved, and a microlens having a highly accurate optical surface shape can be manufactured. In this case, it is particularly preferable to use a silicon single crystal substrate as the silicon substrate.

In the present invention, it is preferable that a fluorine-based carbide film covering the surface of the silicon substrate is provided. According to the present invention, since the mold surface is covered with the fluorine-based carbide film, the releasability is improved and the breakage of the mold can be reduced, so that the durability of the mold can be increased. Here, as the fluorine-based carbide film, for example, there is a fluorine-containing resin, and polytetrafluoroethylene is particularly preferable.

In the present invention, it is preferable that a support substrate fixed on the back surface of the silicon substrate is provided.
According to the present invention, since the rigidity of the mold is improved by fixing the support substrate on the back surface of the silicon substrate, the molding accuracy is increased, and it is possible to manufacture a highly accurate microlens.

In the present invention, it is preferable that the support substrate is directly fixed to the back surface of the silicon substrate by anodic bonding. According to the present invention, since the silicon substrate and the support substrate are directly fixed to each other by anodic bonding, there is no need to use an adhesive or the like. Sex can be maintained.

In the present invention, it is preferable that the supporting substrate has a coating on a bonding surface, and the back surface of the silicon substrate and the coating are fixed by eutectic bonding. According to the present invention, since the silicon substrate and the coating film are fixed by eutectic bonding, bending and mismatching of the bonding surface are less likely to occur than in the case where an adhesive is used, and the flatness of the silicon substrate is maintained. In addition, a high adhesion can be obtained by the eutectic bonding surface. Further, since a film is formed on the support substrate and the film and the silicon substrate are eutectic, the material selection range of the support substrate can be widened.

In any case, the above-mentioned support substrate is preferably more rigid than, for example, a silicon substrate, and is preferably, for example, a glass substrate.

In the present invention, the curved surface portion is preferably a concave curved surface portion formed by substantially isotropic wet etching. By using substantially isotropic wet etching, it is possible to easily form a concave curved surface with high precision.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a microlens substrate forming die and a method of manufacturing a microlens substrate according to the present invention will be described in detail with reference to the accompanying drawings. FIG.
FIG. 4 is a process explanatory view showing a manufacturing process of the microlens substrate molding die in the present embodiment. In this embodiment, first, as shown in FIG. 1A, a mask layer 11 is formed on the surface of a silicon substrate 10 made of silicon single crystal or the like. As the silicon substrate 10, a large substrate of 8 inches or more can be easily obtained by manufacturing a semiconductor. As the mask layer 11, a material obtained by depositing various materials whose etching rate is sufficiently lower than that of silicon in the silicon etching process can be used. In the present embodiment, a silicon substrate formed by thermally oxidizing the silicon substrate 10 is used. A silicon oxide layer which is a thermal oxide film is formed. Since a silicon oxide layer can be easily formed on a silicon substrate by using a semiconductor manufacturing technique, it can be formed with good mass productivity and at low cost, and can have a dense film quality, so that a stable etching mask can be formed. It can be used as a layer. In addition,
The mask layer can also be formed by a CVD method, a sputtering method, or the like.

Next, as shown in FIG. 1B, an opening 11a is formed in a portion of the mask layer 11 on the surface (the upper surface in the figure) of the silicon substrate 10. The openings 11a are formed by, for example, coating a resist layer made of a photoresist on the mask layer 11 by photolithography, exposing and developing the resist layer to partially form pores, It can be formed by performing etching. The opening 11a is arranged in accordance with the arrangement of the optical center of each microlens in the microlens array to be manufactured. The diameter of the opening 11a is desirably sufficiently smaller than the diameter of a concave portion 10a to be actually formed, which will be described later, and is, for example, about 5 μm.

Next, as shown in FIG. 1 (c), the silicon substrate 10 is subjected to wet etching to form a concave portion 10 having a substantially hemispherical concave curved surface on the surface of the silicon substrate 10.
a is formed. For this wet etching, an etchant capable of isotropically etching the silicon substrate 10, for example, a hydrofluoric acid-based etchant such as a mixed aqueous solution of hydrogen fluoride and nitric acid is used. The mixing ratio of hydrofluoric acid and nitric acid is adjusted so that the isotropic etching of the silicon substrate 10 is obtained and the etching surface is smooth. Also,
It is preferable that the etching selectivity of the silicon substrate 10 / mask layer 11 is adjusted to be within a practical range (for example, 10 or more). Usually, when the selectivity is 10 or more, the concave portion 10a can be sufficiently formed if the thickness of the silicon oxide layer is about 1.5 μm.

Since the surface of the concave portion 10a of the silicon substrate becomes the optical surface of the microlens, it is particularly important that the isotropy of the etching to determine the shape of the optical surface and the smoothness of the etching surface to determine the surface roughness of the optical surface. become. Since the composition range of the etching solution that can provide the isotropic etching and the smoothness of the etched surface is widened by adding acetic acid, the etching process can be performed more stably. As an example of the composition ratio, HF: HNO ₃ : CH ₃ CO
OH = 1: 3: 8 or 9:75:30.

This step is not limited to the wet etching as described above, but may be performed by various dry etchings using carbon tetrafluoride, oxygen, chlorine or the like as an active species.

In this embodiment, the substantially hemispherical concave portion 10a having a circular outline in plan view is formed on the surface of the silicon substrate 10. However, the outline shape is not limited to a circular shape due to the shape of the opening 11a. It may be formed in various shapes such as a rectangle and a square. The diameter of the concave portion 10a for forming the optical surface of the microlens varies depending on the purpose of use and the field of use of the microlens array.
It is about 100 μm, preferably about 10 to 50 μm. Electro-optical devices, particularly those used for liquid crystal devices, are formed to have substantially the same size as each pixel region.

Next, as shown in FIG.
mask layer 1 on the front side of silicon substrate 10 on which a is formed
Remove one. The removal of the mask layer 11 is performed by, for example, wet etching using a mixed aqueous solution of hydrofluoric acid and ammonium fluoride. At this time, a coating layer having etching resistance may be formed on the side surface and the back surface (the lower surface in the figure) of the silicon substrate 10, and the mask layer 11 formed on the side surface and the back surface may be left without being removed. In this case, the remaining mask layer 11 protects the back surface of the silicon substrate 10 until it is necessary to expose the back surface (the lower surface in the figure) of the silicon substrate 10 as in the case of bonding the silicon substrate 10 to a support substrate, which will be described later. Play a role.

The microlens substrate molding die thus formed can perform fine processing of the concave portion 10a with high precision by using a semiconductor manufacturing technique by using the silicon substrate 10 as a base material. Because large silicon substrates can be easily obtained and easily processed,
The yield and mass productivity at the time of manufacturing the mold are improved.

The microlens substrate molding die formed as described above may not have sufficient releasability since the Si surface is exposed. Therefore, as shown in FIG. 2, it is preferable to form a surface coating layer 12 made of a fluorine-based carbide film on at least the surface (upper surface in the drawing) which is a molding surface.
The surface coating layer 12 is, for example, a fluorine resin layer made of polytetrafluoroethylene. The surface coating layer 12 is deposited,
It is formed by a method such as sputtering, spin coating, and dipping (immersion). By forming this surface coating layer 12, the mold releasability at the time of molding is improved, the probability of breakage of the microlens substrate mold at the time of mold release is reduced, and the average life of the mold is greatly extended. .

Next, as shown in FIG. 3, when the back surface of the silicon substrate 10 of the microlens substrate molding die is not a mirror surface, the silicon substrate 10 is mirror-finished by lapping or polishing, and the back surface is cleaned. Substrate 10
Is placed on a conductive hot plate 14 with its surface facing down. Then, the back surface of the silicon substrate 10 is brought into close contact with the mirror-finished clean surface of the support substrate 13 made of glass (for example, borosilicate glass), and
While heating to about 50 ° C., a cathode was placed on the support substrate 13 and an anode was placed on the hot plate 14.
By applying a voltage of V, preferably about 300 V, the silicon substrate 10 and the supporting substrate 13 are anodically bonded. In this case, the silicon substrate 1 is used as the support substrate 13.
It is preferable that the rigidity is higher than 0. Therefore, for example, the support substrate 1 thicker than the silicon substrate 10
It is preferable to use 3. Further, it is desirable that the bonding surface of the support substrate 13 be formed as a highly accurate flat surface (mirror surface).

By joining the silicon substrate 10 to the support substrate 13, the rigidity of the microlens substrate forming die is increased and the flatness is also improved. Thickness unevenness is less likely to occur in the molded resin layer due to bending or distortion. Further, in this embodiment, since the silicon substrate 10 is directly bonded to the supporting substrate 13 without using an adhesive or the like, the flatness of the silicon substrate 10 can be improved, and the silicon substrate 10 can be bent. It is also possible to avoid being forcibly fixed to the support substrate 13.

Next, a method which can be used in place of the method of bonding the silicon substrate 10 and the support substrate 13 by the above-described anodic bonding will be described with reference to FIGS. First,
As shown in FIG. 4, the surface of a support substrate 15 made of glass (for example, trade name of Pyrex glass) is Au /
A coating 16 having a laminated structure of Cr (Ti) is formed. The coating 16 is formed by first depositing Cr on the surface of the support substrate 15.
Alternatively, a base thin film made of Ti or the like is formed by vapor deposition or sputtering, and an Au thin film is further formed on the base thin film by a vapor deposition method or the like. Here, the underlying thin film is A
This is for improving the adhesion of the u thin film. Then, the surface of the support substrate 15 on which the coating 16 is formed is brought into contact with the back surface of the cleaned silicon substrate 10 and is heated to bond as shown in FIG. Au and Si
Is about 380 ° C., and the Au thin film on the surface side of the coating 16 and the surface of the silicon substrate 10 become eutectic by heating the bonding surface near this temperature, and the Au—Si eutectic layer is formed. The silicon substrate 10 and the support substrate 15 are fixed through the intermediary. However, the temperature below the eutectic point (for example, 300
C), it is also possible to make it eutectic by heating for a long time. According to this method, the silicon substrate and the supporting substrate are joined by eutectic, so that the warpage and bending of the silicon substrate 10 are reduced as compared with the method using an adhesive or the like, and the eutectic solidification is achieved. Since the adhesion can be increased by the proper bonding, it is possible to reduce an accident such as separation of the support substrate.

As shown in FIGS. 6A and 6B, the microlens substrate molding die of this embodiment is
Alternatively, in a state where the surface coating layer 12 is formed, a transparent resin for forming a microlens substrate is poured,
The resin molded body 31 having an optical surface may be used to form the resin molded body 31. Alternatively, a transparent substrate 32 such as glass may be bonded via the transparent resin 31 and the resin molded body fixed on the transparent substrate 32 may be used. It may be used to form. In this case, since the resin molded body has a convex curved surface shape, a microlens can be configured as it is. Further, the resin molded body may be adhered to the transparent substrate 34 via another transparent resin 33 having a different refractive index to form a microlens substrate as shown in FIG. 6B.

On the other hand, as shown in FIGS. 7A and 7B, an inversion mold 35 is formed on the surface of the above-mentioned microlens substrate molding mold by a plating layer made of Ni or the like by, for example, electroless plating. You may. in this case,
The microlens substrate molding die is used as a prototype for forming the reversing die 35 for molding. In this case, by bonding a transparent substrate 37 to the inversion mold 35 made of Ni or the like formed as described above via a transparent resin 36,
As shown in FIG. 7B, a resin molded body having substantially the same shape as the silicon substrate 10 can be formed. And FIG.
Similarly to (b), a microlens substrate can be formed by joining a transparent resin having a different refractive index to the resin molded body.

After forming the microlens substrate as described above, for example, when forming a panel substrate incorporating one microlens of a liquid crystal panel, FIG.
And (d), after adhering a transparent substrate such as a glass substrate to the optical surface via a transparent resin, the thickness of the transparent substrate is reduced as necessary, and the inner surface structure of the panel substrate, that is, A light-shielding film, a transparent electrode, and the like are formed.

It should be noted that the microlens substrate molding die and the method of manufacturing the microlens substrate of the present invention are not limited to the illustrated examples described above, and various changes can be made without departing from the gist of the present invention. Of course.

[0041]

As described above, according to the present invention,
By using a silicon substrate, high quality can be easily achieved, and a fine and highly accurate curved surface portion can be easily formed due to characteristics to which semiconductor manufacturing technology can be applied, so that productivity can be improved. Thus, a microlens substrate having a highly accurate optical surface shape can be manufactured.

[Brief description of the drawings]

FIGS. 1A to 1D are process explanatory views showing a method for manufacturing a microlens substrate molding die according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a case where a surface coating layer is coated on a surface of a silicon substrate of the microlens substrate molding die.

FIG. 3 is a schematic configuration diagram showing a state where a support substrate is fixed to the back surface of the silicon substrate of the microlens substrate molding die by anodic bonding.

FIG. 4 is a schematic cross-sectional view showing a state in which a support substrate having a coating layer formed thereon is bonded to the back surface of the silicon substrate of the microlens substrate molding die.

FIG. 5 is a schematic cross-sectional view showing a state in which the silicon substrate and the support substrate of the microlens substrate molding die are fixed by eutectic bonding.

FIGS. 6A and 6B are schematic process diagrams (a) and (b) showing a case where a microlens substrate is directly molded from a microlens substrate molding die.

7A and 7B are schematic configuration diagrams showing a case where an inversion mold is once formed from a microlens substrate molding mold and the microlens substrate is molded by the inversion mold.

8A to 8D are process explanatory views showing a method for manufacturing a microlens array or a counter substrate for a liquid crystal panel by a conventional photopolymer method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Silicon substrate 10a ... Concave part 11 ... Mask layer 11a ... Opening 12 ... Surface coating layer 13 ... Support substrate 14 ... Hot plate 15 ... Support substrate 16 ... Coating 20 ... Micro lens substrate forming type 21 ... Glass substrate 22 ... Transparent resin 20a ... curved surface portion 22a ... optical surface 23 ... transparent electrode 24 ... glass substrate 26 ... light shielding film 27 ... transparent electrode 31 ... transparent resin 32 ... transparent electrode 33 ... transparent resin 34 ... transparent electrode 35 ... inversion type 36 ... transparent resin 37 ... Transparent substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29L 11:00 B29L 11:00 F term (Reference) 4F202 AH75 AJ06 CA03 CB01 CC10 CD08 CD24 CK13 CM32 CM47 CM83 4F204 AH75 AJ06 EA03 EB01 EK17 EK24 EW15

Claims (15)

[Claims] A mask layer having etching resistance is formed on a surface of the silicon substrate, an opening is formed in the mask layer, and the silicon substrate is substantially isotropically etched through the opening to form a micro lens. A concave curved surface portion corresponding to the optical surface is formed, a microlens substrate molding die made of a silicon substrate is formed by removing the mask layer, and an uncured transparent resin is applied to the microlens substrate molding die or a copy thereof. Forming a convex-shaped optical surface corresponding to the concave-curved surface portion by curing the microlens substrate. A mask layer having etching resistance is formed on the surface of the silicon substrate, an opening is formed in the mask layer, and the silicon substrate is substantially isotropically etched through the opening to form a micro lens. Forming a concave curved surface portion corresponding to the optical surface, forming a microlens substrate molding die made of a silicon substrate by removing the mask layer, and forming the microlens substrate molding die or a copy thereof on the concave curved surface portion. Forming an inverted mold having a corresponding convex curved surface portion, applying an uncured transparent resin to the inverted mold and curing the resin, thereby forming a concave curved optical surface corresponding to the convex curved surface portion. A method for manufacturing a microlens substrate. 3. The method of manufacturing a microlens substrate according to claim 1, wherein the mask layer is a thermal oxide film of a silicon substrate, and the opening is formed by a dry etching method. 4. One of claims 1 to 3
3. The method of manufacturing a microlens substrate according to claim 1, wherein an etching solution containing hydrofluoric acid and nitric acid as main components is used to form the concave curved surface portion. 5. The method for manufacturing a microlens substrate according to claim 4, wherein said etching solution further containing acetic acid is used. 6. Any one of claims 1 to 5
9. The method of manufacturing a microlens substrate according to claim 1, wherein a fluorine-based carbide film is formed on a molding surface of the microlens substrate molding die. 7. Any one of claims 1 to 5
9. The method for manufacturing a microlens substrate according to the above item, wherein a support substrate is fixedly used on an opposite molding surface of the microlens substrate molding die. 8. The method of manufacturing a microlens substrate according to claim 7, wherein the support substrate is directly fixed to the opposite molding surface by anodic bonding. 9. The micro-device according to claim 7, wherein a coating is formed on the bonding surface of the support substrate, and the anti-molding surface of the support substrate and the coating are fixed by eutectic bonding. A method for manufacturing a lens substrate. 10. A microlens substrate molding die, comprising a curved portion corresponding to an optical surface of a microlens on a surface of a silicon substrate. 11. The microlens substrate forming die according to claim 10, further comprising a fluorine-based carbide film covering a surface of said silicon substrate. 12. The method according to claim 10, wherein
A microlens substrate molding die, comprising a support substrate fixed on the back surface of the silicon substrate. 13. The microlens substrate molding die according to claim 12, wherein the support substrate is directly fixed to the back surface of the silicon substrate by anodic bonding. 14. The microlens substrate molding according to claim 12, wherein the support substrate has a coating on a bonding surface, and the back surface of the silicon substrate and the coating are fixed by eutectic bonding. Type. 15. The microlens substrate molding according to claim 10, wherein the curved surface portion is a concave curved surface portion formed by substantially isotropic wet etching. Type.