JP2001255660A - Generation method for special, surface shape and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a novel generation method which is capable of easily generating a special surface shape of a three-dimensional structure which changes smoothly and continuously in a height direction on a photosensitive material layer or a substrate. SOLUTION: The generation method for the special surface shape changes the thickness of the photosensitive material layer 11 according to the desired special surface shape by applying a photosensitive material to a prescribed thickness on the surface of a substrate material 10 to be formed with the special surface shape of the desired three-dimensional structure to form the photosensitive material layer and exposing a mask pattern LF of a prescribed light transmittance distribution on the photosensitive material layer 11 by using a mask for exposure stepwise changing in the light transmittance in correspondence to the special surface shape. When the pattern LF of the mask for exposure is exposed to the photosensitive material layer 11, the exposure pattern is slightly deviated in focus by defocusing, by which the level difference of the light transmittance distribution of the mask pattern is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for creating a special surface shape having a three-dimensional structure and an optical element.

[0002]

2. Description of the Related Art A special surface shape represented by a spherical surface or an aspherical surface has been used for a refracting surface or a reflecting surface of an optical element, and recently, a liquid crystal display element, a liquid crystal projector, or In connection with optical communication and the like, special surface shapes are also required for microlenses and microlens arrays. Therefore, as a method of creating a special surface shape such as a spherical surface or aspherical surface without molding or polishing, glass, metal,
There has been proposed a method of creating a special surface shape having a three-dimensional structure such as a curved surface on the surface of a substrate such as a resin. As an example, a material layer is formed by applying a photosensitive material (photoresist or the like) to a predetermined thickness on a surface of a substrate material on which a special surface shape having a desired three-dimensional structure is to be formed. A mask pattern having a predetermined light transmittance distribution (light intensity distribution) is exposed on the photosensitive material layer using an exposure mask in which the light transmittance changes stepwise according to the shape, and a target special surface shape is obtained. A method is known in which the thickness of the photosensitive material layer is changed in accordance with the conditions to form a three-dimensional structure surface shape (for example, Japanese Patent Application Laid-Open No. 7-23 which was previously proposed by the present inventors.
No. 0159 and Japanese Patent Application Laid-Open No. 9-146259), a gradation mask, a method for producing the same, and a method for creating a special surface shape using the gradation mask. This method is very excellent as a method for forming a curved surface such as a microlens, and is extremely effective in exposing a desired curved surface shape as a surface shape of a photosensitive material layer and exposing a mask pattern using a gradation mask (density distribution mask) as an exposure mask. Since the curved surface shape can be accurately transferred as the surface shape of the substrate by anisotropic etching, a desired curved surface shape can be formed accurately.

However, a method of creating a special surface shape using a gradation mask has many advantages as a method of forming a curved surface of an optical element such as a microlens. A gradation mask whose light transmittance changes stepwise (see, for example,
When a photosensitive material layer is exposed to a mask pattern using a gradation mask described in JP-A-6259, and the thickness of the photosensitive material layer is changed according to a target special surface shape, the light transmittance in the mask is changed. When the photosensitive material layer is exposed to a discontinuous portion of the distribution curve, the photosensitive material layer is also exposed as a discontinuous shape. Therefore, there is a problem that the discontinuous shape (step) is transferred to the surface of the photosensitive material layer. Therefore, as a method of solving the above problems, use a photosensitive material of low sensitivity,
A method such as adding a large amount of a light absorbing material was required. In addition, the technique of patterning using an exposure mask is often used in the semiconductor field, but in the semiconductor field, since the purpose is to arrange the presence or absence of a line pattern two-dimensionally, the pattern changes in the height direction. The three-dimensional shape to be controlled has not been controlled with high accuracy.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel method for forming a special surface shape and an optical element formed by the method. In the present invention, in order to solve the conventional problem of creating a special surface shape using an exposure mask such as a gradation mask (density distribution mask), a discontinuous portion of a light transmittance distribution curve in the mask is exposed. When the photosensitive material layer is exposed, the photosensitive material layer is prevented from being transferred to the photosensitive material layer as a discontinuous shape (step), a light transmission amount in a unit cell forming a light transmittance distribution curve,
That is, the two-dimensional light transmittance distribution is smoothed on the exposure mask, and the light transmittance of the exposure mask such as the density distribution mask is a black and white arrangement when observed microscopically for each unit cell. If the exposure is continued as it is, the height of the photosensitive material layer will also be (high, low) black and white density information. To prevent this, reduce the sensitivity of the photosensitive material, or change the material to a photosensitive material with low sensitivity. Proposal of a method for transferring shapes with high precision without any need to control the three-dimensional shape that changes smoothly and continuously in the height direction with high accuracy.Smooth and continuous changes in the height direction It is an object to provide an optical element having a special surface shape.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a photosensitive material is applied to a predetermined thickness on a surface of a substrate material on which a special surface shape having a desired three-dimensional structure is to be formed to form a photosensitive material layer. Then, the photosensitive material layer is exposed to a mask pattern having a predetermined light transmittance distribution (light intensity distribution) using an exposure mask whose light transmittance changes stepwise according to the special surface shape. The present invention relates to a method for creating a special surface shape in which the thickness of the photosensitive material layer is changed according to the special surface shape to be used, and an optical element manufactured by the method for creating a special surface shape.

In the method for creating a special surface shape according to the present invention, as described above, a photosensitive material is applied to a predetermined thickness on the surface of a substrate material on which a special surface shape having a desired three-dimensional structure is to be formed. Forming a photosensitive material layer and exposing a mask pattern to the photosensitive material layer using an exposure mask that has a transmittance that changes in a stepwise manner that is previously designed according to a special surface shape of interest. . The pattern exposed here is a three-dimensional pattern formed by the exposure mask. The exposure mask is given by a function experimentally determined from the relationship between the “sensitivity curve” of the photosensitive material applied to the substrate material surface and the “light energy amount” of each unit cell constituting the exposure mask. It is something that can be done. Here, "experimentally determined" means that the "sensitivity characteristics" and "light transmission amount" of the photosensitive material differ depending on the process conditions. In other words, it means that the function given differs when the process condition parameter is changed. The "sensitivity curve" of a photosensitive material is basically determined by the relationship between the light irradiation energy to the photosensitive material and the photosensitive component of the material. However, it is a curve (that is, a function) that is also changed by photolithography conditions, exposure conditions, development conditions, baking conditions, and the like during patterning. In addition, since the light transmission coefficient varies depending on the molecular structure contained in the photosensitive material, the light energy (light amount) decreases according to the depth when the light travels through the photosensitive material. I do. That is, the thickness (depth) of the photosensitive material and the amount of irradiation light energy are in inverse proportion. Therefore, the "light transmittance" of the exposure mask and the "sensitivity" (light absorption) of the photosensitive material
Can be combined from experimental data to form a light energy distribution having a distribution in the thickness direction of the photosensitive material.

By the above method, the present invention is not intended to form a photosensitive material of a certain height (thickness) as a two-dimensional line pattern as in a semiconductor process.
It is an object of the present invention to form a special surface shape having a three-dimensional structure, that is, a structure having a controlled pattern also in the height direction. Then, in the method of creating a special surface shape having a three-dimensional structure in which the thickness of the photosensitive material layer is changed by the above method, when exposing the mask pattern to the photosensitive material layer, the mask pattern is directly subjected to stepper exposure, alignment exposure, or the like. Upon exposure, the black and white density information of the unit cell of the exposure mask is directly transferred to the photosensitive material layer. The higher the performance of a stepper exposure device or the like, the more two-dimensional line-and-space, such as when patterning a semiconductor, It becomes an array.

Therefore, in the present invention, the pattern 3 at the time of exposure is
As a method of producing the light energy distribution in the dimensional direction, a method of intentionally defocusing is adopted. That is, when exposing the pattern of the exposure mask to the photosensitive material layer on the substrate, defocusing (defocusing) is performed to slightly defocus the exposure pattern, thereby eliminating a step in the light transmittance distribution of the mask pattern. (Claims 1 and 3).

As another method, according to the present invention, when exposing a pattern to a photosensitive material layer on a substrate using an exposure mask whose light transmittance changes stepwise, a mask pattern is formed with diffused light. Exposure eliminates a step in the light transmittance distribution (claim 2). As an example of a method of exposing a mask pattern with diffused light, an exposure mask is formed by diffusing exposure light to a light source side surface, that is, a light incident side of exposure, on a side opposite to a pattern forming surface of the exposure mask used at the time of exposure. There is a method of arranging an optical element for adding an oblique incident component to a light component incident on a unit cell. More specifically, when exposing the pattern of the exposure mask to the photosensitive material layer, a light diffusion optical element is arranged on the light source side on the side opposite to the pattern formation surface of the exposure mask, and diffused light is used. The step of the light transmittance distribution of the mask pattern is eliminated by exposing the mask pattern (claim 4). Here, the oblique incident component of the light component incident on the exposure mask can be changed by the optical design of the light diffusing optical element (diffuser). By changing the characteristic (pitch, height, pattern width, refractive index of material, etc.) of the microstructure, it is possible to manage with extremely high reproducibility. In addition, the light having the diffusion component that has passed through the diffuser passes through the mask for exposure and reaches the pattern surface, and the light of the obliquely incident component is diffracted at the pattern boundary of the unit cell and reaches the photosensitive material. . Therefore, it is possible to eliminate a step in the digital pattern of the exposure mask.

As still another method, in the present invention, when a pattern of an exposure mask is exposed on a photosensitive material layer on a substrate, a diffused light generating method is used as a method of generating diffused light on the side opposite to the pattern forming surface of the exposure mask. A light diffusion function film having a light transmission function is disposed on the surface, and the mask pattern is exposed to diffused light to eliminate a step in the light transmittance distribution of the mask pattern (claim 5). More specifically, the pattern formation surface of an exposure mask is formed by the applicant's “Method of manufacturing birefringent film by plasma deposition method (Japanese Patent Application No. 3-294346, Japanese Patent Application No. 3-297400)” or the like. Forms a light diffusion functional film on the opposite surface. This functional film for light diffusion,
It has a thin film structure of at least three layers so as to have a light transmitting function and a light diffusing function, efficiently transmit light incident on the mask substrate, and change the film thickness and the film forming material. Thus, the light diffusion performance (birefringence) can be changed. Therefore, when the light having the diffusion component that has passed through the light diffusion functional film passes through the exposure mask and reaches the pattern surface, the light of the diffusion component is diffracted at the pattern boundary of the unit cell, and the photosensitive material To reach. Therefore, it is possible to eliminate a step in the digital pattern of the exposure mask.

As yet another method, the present invention provides:
When exposing the pattern of the exposure mask to the photosensitive material layer, a thin light diffusion functional film having a light transmitting function is arranged on the pattern formation surface of the exposure mask as a diffused light generation method, and the diffused light mask is used. The step of the light transmittance distribution of the mask pattern is eliminated by exposing the pattern (claim 6). More specifically, the present applicant describes a method for producing a birefringent film by a plasma deposition method (Japanese Patent Application No. Hei 3-2943).
No. 46, Japanese Patent Application No. 3-297400), etc., a light diffusion functional film is formed on the pattern formation surface of the exposure mask. The light diffusion functional film has a thin film configuration of at least three layers so as to have a light transmission function at the same time as having a light transmission function, efficiently transmits light transmitted through the pattern surface of the mask substrate, and The light diffusion performance (birefringence amount) can be changed by changing the film thickness and the film forming material. Therefore, light that has passed through the pattern surface of the exposure mask passes through the light diffusion functional film and reaches the photosensitive material as light having a diffusion component, so that a step in the pattern of the exposure mask can be eliminated. . Further, in this case, since the light diffusion functional film is formed on the pattern forming surface of the exposure mask, the same function is realized by a thin film as compared with the fifth aspect. In the method of claim 5 or claim 6, the light diffusion function film is disposed on one surface of the exposure mask as a method of generating diffused light. A functional film for light diffusion having the following may be arranged (claim 7).

In the method for creating a special surface shape according to the present invention, a density distribution mask (gradation mask) having a mask pattern whose light transmittance changes stepwise according to the special surface shape is used as the exposure mask. A reticle mask obtained by enlarging the density distribution mask at a predetermined enlargement ratio can be used. Here, as the concentration distribution mask (gradation mask), “a metal and / or metal oxide film is formed on a transparent substrate, and this film is divided into a plurality of unit cells, and an opening (light) in each unit cell is formed. The transmission area is controlled so that the area of the light transmission area of each unit cell has a predetermined light transmittance distribution corresponding to the target special surface shape. A film whose film thickness changes stepwise on the substrate is formed of metal and / or metal oxide, and the film thickness of this film is controlled for each unit cell to change the film thickness of the whole and individual unit cells. However, as a method of controlling the amount of light transmission of each unit cell, a method of controlling the amount of light transmission of each unit cell, as a method of controlling the amount of light transmission corresponding to the desired special surface shape. In order to provide a light transmission light amount distribution, for example, The light exposure method disclosed in Japanese Patent Application Laid-Open No. Hei 7-230159 describes that a gradation mask is appropriately formed by a comprehensive combination of “light transmission area” and “light transmittance (Cr film thickness)” of light passing through each unit cell. Which can be manufactured, and the like, for example, as a type, a gradation mask or the like described in JP-A-9-146259 by the present inventors can be appropriately changed and used. . Also, this density distribution mask
For example, a mask pattern of the same size is formed on the photosensitive material layer by an alignment exposure method or a stepper exposure method of the same size. In the case of using an enlarged density distribution mask (reticle mask) which is designed at a predetermined enlargement ratio and manufactured by any of the above methods, the mask pattern of the reticle mask is exposed by a stepper exposure apparatus of a reduced exposure type. A stepper exposure method for reducing exposure to a conductive material layer can be employed.

Further, in the method for creating a special surface shape according to the present invention, a photoresist or a photocurable resin can be used as the photosensitive material.
Here, when a photoresist is used as the photosensitive material, the photoresist layer applied on the surface of the substrate material has
After exposing a mask pattern having a predetermined three-dimensional light intensity distribution using the above-mentioned concentration distribution mask or reticle mask, the photoresist layer is subjected to processes such as development, rinsing, post-exposure bake, and resist curing treatment. Is patterned into a desired three-dimensional structure (claim 10). When a photocurable resin (a resin that is cured by irradiation with visible light, ultraviolet light, or infrared light) is used as the photosensitive material, a liquid photocurable resin is applied to the surface of the substrate material, Exposing a mask pattern having a predetermined three-dimensional light intensity distribution with the above-mentioned concentration distribution mask or reticle mask in a state where the curable resin layer has fluidity, and controlling the irradiation time, exposure amount, and heating by exposure. The photocurable resin layer is gradually cured from the surface side by, for example, and the surface of the resin layer is deformed by volume reduction and flow of the photocurable resin accompanying the curing, and is patterned into a desired three-dimensional structure. 11).

Further, in the present invention, the thickness of the photosensitive material layer is adjusted in accordance with the desired special surface shape by the method for creating a special surface shape according to any one of claims 1 to 8. After the change, the photosensitive material layer and the substrate can be subjected to anisotropic etching to engrave and transfer the surface shape of the photosensitive material layer to the substrate surface (claim 12). Also, when performing the anisotropic etching,
By setting the selectivity ratio (substrate engraving speed / photosensitive material layer engraving speed) to a value other than 1, the height difference of the irregular shape of the starting shape can be enlarged or reduced and transferred to the substrate. Alternatively, by changing the selection ratio over time and controlling the change over time of the selection ratio, the starting shape can be transformed into a desired shape and transferred. By using such a method, for example, an aspherical surface or the like can be easily formed. Further, unlike a method by molding or polishing, since a very small curved surface can be formed, it is suitable as a method for forming a refraction surface shape or a reflection surface shape of a micro optical element such as a micro lens.

The optical element of the present invention can be obtained by forming an optically curved surface on the surface of the photosensitive material layer or the substrate material by using the above-described method for creating a special surface shape (claim 13). In this case, the optical curved surface can be formed as a continuous surface such as a spherical surface, an aspherical surface, or a conical shape. Further, the optical curved surface may be composed of a continuous surface and a discontinuous surface like a Fresnel shape. further,
By making the optical curved surface a light transmissive refraction surface,
It can function as an optical element such as a lens or a prism, and can be used as a microlens or microlens array (ML).
A), various transmission optical elements such as a prism, a prism array, and a Fresnel lens can be obtained. In addition, a reflective optical element can be obtained by forming a reflective film on the optically curved surface by a method such as vapor deposition to form a reflective surface.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a process explanatory view showing one embodiment of a method for creating a special surface shape according to the present invention.
In FIG. 1A, reference numeral 10 denotes a substrate made of glass, metal, resin, or the like, and a photosensitive material is applied to a surface of the substrate to form a photosensitive material layer 11. Here, a case where a photoresist is used as an example of a photosensitive material will be described. The photoresist 11 is applied to the substrate 10 and baked to form a resist layer. The photoresist used in the example of FIG. 1 is a positive type.

Next, as shown in FIG. 1B, a three-dimensional light intensity distribution as shown in the figure is applied to the photoresist layer 11 formed on the substrate 10 by a predetermined method using an exposure mask. The light beam LF of the mask pattern having the pattern is exposed. As the exposure mask, for example, a density distribution mask (gradation mask) having a mask pattern in which light transmittance changes stepwise according to a desired surface shape, or the density distribution mask is enlarged at a predetermined magnification. A reticle mask is used. As the exposure method, there is a method of performing stepper exposure on a photoresist layer using a concentration distribution mask manufactured at an equal magnification to a desired surface shape, or a method of applying this mask in close contact or close proximity to the photoresist layer. There is an alignment exposure method in which exposure is performed by exposure, or a stepper exposure method in which a mask pattern is reduced and exposed on a photoresist layer by a stepper exposure apparatus using a reticle mask manufactured at a predetermined magnification with respect to a desired surface shape. . The details of the density distribution mask and the exposure method will be described later.

After the exposure of the mask pattern, the photoresist layer 11 is developed, rinsed, and post-exposure bake (PEB) treated to three-dimensionally pattern the photoresist layer 11 according to a desired surface shape. I do. When this patterning step is completed, as shown in FIG. 1 (c), the resist layer 11 changes the surface shape corresponding to the light intensity distribution at the time of exposure (the shape of the resist layer becomes thicker as the exposure amount is smaller). It is formed. Next, an etching step is performed, and anisotropic dry etching is performed on the resist layer 11 having the desired resist surface shape formed thereon and the substrate 10 at a predetermined selectivity to change the surface shape of the resist layer 11 By engraving and transferring the surface shape, a surface shape of a three-dimensional structure as shown in FIG. 1D is formed on the substrate surface. In this etching step, when the selectivity of the anisotropic etching is set to be larger than 1 (that is, the etching rate of the substrate 10 is set to be larger than the etching rate of the resist layer 11),
The height difference: H of the surface shape of the substrate 10 to which the above-mentioned surface shape has been transferred becomes larger (H> h) with respect to the height difference of the surface shape: h, and if the selection ratio is 1, then H = h, If the selection ratio is set smaller than 1, H <h.

Here, the example shown in FIG. 1 is an example in which a convex curved surface 12 made of a spherical or aspherical surface is formed on the substrate surface.
By using an optical substrate made of a transparent glass substrate or a resin substrate as the substrate 10 and making the above-mentioned curved surface a refracting surface, it can be used as an optical element 13 such as a microlens. A microlens array can be formed by forming a two-dimensional array. If a reflective film is formed on the curved surface by vapor deposition or sputtering, a reflective optical element can be obtained.

FIG. 2 is a process explanatory view showing another embodiment of the method for creating a special surface shape according to the present invention. FIG.
1A, reference numeral 14 denotes a substrate made of glass, metal, resin, or the like. A photosensitive material is applied to the surface of the substrate to form a photosensitive material layer 15. Here, as an example of a photosensitive material, a case where a photocurable resin (a resin that is cured by irradiation with visible light, ultraviolet light, or infrared light) whose volume decreases with curing is used will be described. The application of the photocurable resin to the substrate 14 can be performed by a roll coating method, a spin coating method, or a dipping method, but the light is applied so that the surface of the formed resin layer becomes a flat surface without undulation or the like. After the resin layer 15 is formed by application of the curable resin, it is desirable to increase the fluidity of the resin in the resin layer 15 to smooth the surface of the resin layer 15.

Next, as shown in FIG. 2A, a three-dimensional light intensity distribution as shown in the figure is applied to the resin layer 15 formed on the substrate 14 by a predetermined method using an exposure mask. The luminous flux LF of the held mask pattern is exposed. As the exposure mask, for example, a density distribution mask (gradation mask) having a mask pattern in which light transmittance changes stepwise according to a desired surface shape, or the density distribution mask is enlarged at a predetermined magnification. A reticle mask is used, and as an exposure method, a method of performing stepper exposure on the resin layer using a concentration distribution mask manufactured at an equal magnification with respect to a desired surface shape, or a method in which the mask is brought into close contact with or close to the resin layer There are an alignment exposure method for exposing, a stepper exposure method for reducing and exposing a mask pattern to a resin layer with a stepper exposure apparatus using a reticle mask manufactured at a predetermined magnification with respect to a desired surface shape.
The details of the density distribution mask and the exposure method will be described later. The light source for exposure is appropriately selected depending on the type of the photocurable resin and the exposure method, and various lamps such as an ultraviolet lamp, a halogen lamp, and an infrared lamp, and various laser light sources in an ultraviolet region to an infrared region. For example, if the photo-curable resin is an ultraviolet-curable resin, an ultraviolet lamp such as a mercury lamp or a metal halide lamp, or an ultraviolet light source such as an ultraviolet laser light source is used as a light source.

FIG. 2B shows a state at a relatively early stage after the start of the exposure step. When the resin layer 15 is irradiated with the light beam LF having a predetermined light intensity distribution, curing starts from the surface side. In FIG. 2B, reference numeral 15a denotes a cured resin portion. In the light intensity distribution of the irradiation light beam LF, the higher the intensity, the more the curing progresses. Therefore, the shape of the cured resin portion 15a is as shown in the drawing. Becomes The volume of the photocurable resin constituting the resin layer 15 decreases with curing. That is, the resin constituting the resin layer 15 contracts with curing. In FIG. 2B, a portion indicated by reference numeral 15b (a hatched portion) indicates a volume portion reduced from the state of FIG. 2A due to the curing of the resin portion 15a on the resin layer surface side. .

When the exposure step is performed, the resin constituting the resin layer 15 is in a fluid state. Therefore, when the volume is reduced due to the shrinkage as described above, the uncured resin portion 15c in the fluid state has the above volume. A flow occurs so as to compensate for the decrease (the arrow in the figure shows the state of the flow as an explanatory diagram). When the time further elapses, the cured resin portion 15a in the resin layer grows by curing, and as shown in FIG.
The shape is as shown in FIG. Reference numeral 15b indicates a volume portion reduced with curing in the same manner as described above, and an arrow in the drawing indicates a flow state of the uncured resin portion 15c which is to compensate for the reduced volume portion 15b. Here, the irradiation light beam LF
In the portion where the light intensity is high, the curing progresses rapidly, and the volume decreases with the curing, so that the inflow of resin from the surroundings is large. For this reason, in a portion irradiated with a light beam with a large light intensity, the resin is constantly flowing from the surroundings,
In the area where the ambient light intensity is relatively low, the resin layer relatively lowers because the resin flows into the high light intensity area.

In this manner, exposure is continuously performed,
When the resin constituting the resin layer 15 is completely cured, FIG.
As shown in (d), the cured resin layer 15A has a convex curved surface shape according to the light intensity distribution of the exposure light beam LF of the mask pattern used in the exposure step. Therefore, if a transparent photocurable resin is used in a cured state, such a convex curved surface can be used as, for example, a convex lens surface (a convex refractive surface). If the light intensity distribution of the exposure mask in the exposure step is, for example, as shown in FIG. 4 (a-1), the cured resin layer 15 is formed according to the light intensity distribution.
The shape of B can be made as shown in FIG. 4 (a-2), and if the distribution of the light intensity is as shown in FIG. Thus, the shape of the cured resin layer 15C can be made as shown in FIG. 4B-2. That is, as the surface shape of the cured resin layer, various shapes such as a convex surface and a concave surface are possible depending on the pattern design of the exposure mask. When viewed three-dimensionally, it is possible to form an axially symmetrical shape, a convex or concave cylindrical shape, surfaces having different curvatures in directions orthogonal to each other, and the like.

In FIG. 2D, the photocurable resin layer whose surface is curved by curing on the substrate 14 can be used as it is as a convex lens surface, but the surface shape of the resin layer 15A is anisotropic. It can be transferred to the substrate 14 by etching. FIG. 3A shows a photocurable resin layer 15A having a curved surface on the substrate 14 by the process shown in FIG.
Is formed. From the state of FIG. 3A, anisotropic etching is performed on the cured resin layer 15A and the substrate 14 at a predetermined selection ratio, and as shown in FIG. 3B, the surface shape of the resin layer 15A is changed. It can be transferred to the substrate 14. Further, by adjusting the selectivity at the time of etching, the height difference H of the curved shape 16 transferred to the substrate 14 is changed to the height difference H of the curved shape of the surface of the resin layer 15A.
h can be enlarged or reduced.

Next, an example of a concentration distribution mask (gradation mask) used in the exposure step in the manufacturing steps shown in FIGS. 1 and 2, a method of manufacturing the same, and an example of an exposure method using the gradation mask will be described. FIG. 5 is a diagram for explaining an example of a gradation mask.
FIG. 2 is an enlarged plan view showing a part of a gradation mask 17. The gradation mask 17 is formed by forming a light-shielding film made of a metal such as chromium (Cr) or a metal compound on a transparent substrate such as a parallel plate glass by vapor deposition or the like, and patterning the light-shielding film to arrange minute light transmitting portions. The area of each light transmitting portion is set so as to form a predetermined light transmittance distribution. In FIG. 5, in order to simplify the explanation and make it easier to understand, the parts separated by broken lines are:
For example, a case where one side is a square area having a size of about several μm is shown. Needless to say, it need not be square. With the square area as a unit cell, a minute light transmitting portion AP having a rectangular shape is formed in each unit cell as an example. Needless to say, the light transmitting portion does not need to have a rectangular shape, and can be formed in a polygonal shape including a circular shape. Since the amount of light transmitted through the light transmitting portion AP is proportional to the area of the light transmitting portion AP, for example, as shown in the figure, the unit cells are arranged by changing the area of the rectangular light transmitting portion AP two-dimensionally. Thereby, a two-dimensional transmittance distribution in which the amount of transmitted light changes stepwise can be formed.

Here, when a special surface shape of a desired three-dimensional structure such as a liquid crystal microlens array is formed in the manufacturing process as shown in FIG. 1 as an example, a substrate material on which the special surface shape is to be formed. As the photosensitive material applied on the surface, for example, a commercially available photoresist material (TGMPR-950 (trade name) manufactured by Tokyo Ohka Co., Ltd.) or the like is used. First, the relationship between the light irradiation amount of the resist material and the resist removal amount is grasped, and a sensitivity curve is obtained. Next, a gradation mask serving as a model is designed and manufactured in accordance with the surface shape of the desired three-dimensional structure. This gradation mask is composed of unit cells divided into squares as in the example shown in FIG. And the amount of light transmission in each unit cell is controlled.

Here, as a method of controlling the light transmittance of the unit cells constituting the gradation mask, when a Cr film is formed as a light-shielding film on a transparent substrate such as quartz glass, C is applied.
As a method of controlling the opening area of the r film, a method of controlling the thickness of the Cr film, or a method of controlling the light transmission amount of each unit cell, an overall light transmission light amount distribution corresponding to a desired shape is obtained. In order to provide light transmission, the “light transmission area” and “light transmittance (C
There is a method of appropriately manufacturing a gradation mask by a comprehensive combination of “(r film thickness)”, but here, the method is performed by an example method. That is, as a method of manufacturing a gradation mask having a unit cell configuration as described above, first, a transparent mask having a thickness of, for example, 2 mm
A 00 nm Cr film is formed by vapor deposition or the like, and a photosensitive positive resist material is applied thereon to form a mask blank. The resist material layer of the mask blank is irradiated with a light beam by a light beam irradiation device, and the total of the “light transmission area” and “light transmittance (Cr film thickness)” of light transmitted through each unit cell. Is two-dimensionally patterned so as to obtain a transmittance distribution of a desired shape by a specific combination. Here, a laser beam irradiation apparatus (laser drawing apparatus) developed in-house as shown in FIG. 7 is used as a light beam irradiation apparatus, and the resist material layer is irradiated with laser light to draw a mask pattern.

The laser beam irradiation device shown in FIG. 7 includes a laser beam transmitter 1, a beam splitter 2 for dividing the laser beam from the laser beam transmitter 1 into a plurality of laser beams, a mirror 3 for bending the optical path of the laser beam, and a laser. An optical modulator for modulating light and a control device for controlling the optical modulator (OLEDs of individual laser beams by a signal from the data path 5)
N, OFF) 4, an optical deflector for deflecting the laser light, a controller 6 for controlling the optical deflector, an objective lens 7 for condensing the laser light on the resist material layer, a mask blank mounted thereon Is moved in the X direction and the Y direction.
It is composed of main components such as an optical interferometer 9 for controlling the operation of the Y stage 8 and the XY stage 8, and operates the XY stage 8 according to the design data and turns on the individual laser beams. , OFF, a desired mask pattern is drawn on the resist material layer of the mask blank. That is, the resist material layer is irradiated with a laser beam by a laser beam irradiator so that a light transmitting region or a light shielding region is formed in each unit cell so as to have a desired transmittance distribution.
Pattern in a dimension. At this time, the irradiation of laser light is controlled in accordance with the transmittance distribution of each unit cell calculated according to the desired special surface shape, and the area of the light transmitting region in each unit cell is controlled.

Then, the resist material portion irradiated with the laser beam by the laser beam irradiator is subjected to the next development,
The mask pattern is formed in the resist material layer by being removed by the rinsing step. Next, by using the patterned resist material layer as an etching mask, the Cr film is dry- or wet-etched to obtain a desired 2
A gradation mask having a dimensional transmittance distribution is obtained.

In the unit cell of the gradation mask patterned by the above method, the portion where the Cr film (light shielding film) is removed, the portion where the Cr film is thinned, and the portion where the Cr film remains (light shielding) Thus, one unit cell can be characterized and configured as the total light transmission amount. Therefore,
The mask pattern is composed of a plurality of unit cells, and the light transmission area in each unit cell is two-dimensionally designed so as to have a transmittance distribution according to a desired special surface shape. , A gradation mask having a configuration in which the light transmitted through the mask pattern has a three-dimensional light intensity distribution corresponding to the special surface shape can be obtained. In addition, when the mask pattern is designed and manufactured by enlarging the mask pattern at a predetermined enlargement ratio at the time of the above design, a reticle mask (enlarged mask) used in a stepper exposure apparatus described later can be obtained.

When the photosensitive material layer is patterned by using the above-described gradation mask, the amount of the photosensitive material removed varies depending on the exposure amount, defocus amount, and light transmittance of the unit cell. A sensitivity curve is created for each of the above process conditions. That is, the relationship characterizing the light transmittance and the removal amount of the photosensitive material is expressed as one function (removal amount and light transmittance (pattern No.), and the area of the light transmission region in each unit cell of the gradation mask is represented. ,
The Cr film thickness and the like are determined. The “sensitivity curve (removal amount and light transmittance (pattern No.)”) can be converted into a mathematical expression by graphing the above relationship and converting it into a function. The relationship between the height of the surface shape (for example, microlenses) and the remaining amount of the photosensitive material (“the thickness of the photosensitive material layer” − “the removal amount”) is expressed by a mathematical formula. Clarify the relationship between the “lens arrangement position” and “lens height (resist remaining amount).” Further develop this to replace the “lens arrangement position” with the “unit cell number” of the mask. Next, the CAD data is converted into data, set in the computer of the control unit of the laser light irradiation device, and sequentially irradiates the mask blanks with laser light to draw a mask pattern. After,
By etching, a desired gradation mask in which unit cells of “unit cell number” corresponding to a desired lens shape are regularly arranged at “lens arrangement position” can be manufactured. Therefore, in this way, a gradation mask (or reticle mask) corresponding to the surface shape of the target three-dimensional structure is designed and manufactured.

Next, an exposure method using the gradation mask manufactured by the above method will be described. A gradation mask in which unit cells having the above characteristics are regularly arranged is manufactured, and a mask pattern is formed by a predetermined method on a photosensitive material layer formed on a substrate on which a desired special surface shape is to be formed. Is exposed. At this time, as the exposure method, as shown in FIG. 8, the mask pattern of the gradation mask 25 is
A method using an exposure device for projecting and exposing at approximately the same magnification to
As shown in FIG. 9, a gradation mask 28 is disposed in close contact with or close to a photosensitive material layer 27 on a substrate 26, and a light beam BF having a uniform light intensity distribution is provided from the back of the mask.
Further, there is an alignment exposure method for irradiating a mask, and further, as an exposure mask, a gradation mask formed by enlarging at a predetermined magnification to a target surface shape, that is, a reticle mask is used, as shown in FIG. There is a stepper exposure method in which a mask pattern is reduced and exposed using a stepper exposure apparatus having the above configuration.

Here, when the alignment and contact exposure apparatuses shown in FIGS. 8 and 9 are used, the light beam emitted from the light source 21 is converted into a parallel light beam by the collimating lens 22.
The optical path is bent vertically downward by the mirror 23, enters the beam expander 24, expands the luminous flux diameter to a desired size, and then passes through the gradation mask 25. Since the gradation mask 25 has the transmittance distribution for making the light intensity distribution of the transmitted light beam a desired distribution as described above, the light beam having the desired light intensity distribution can be applied to the photosensitive material layer on the substrate 26. 27 is irradiated to expose the mask pattern. In this exposure method, the exposure state of the mask pattern differs depending on the distance d between the gradation mask 25 and the photosensitive material layer 27. When the distance d between the gradation mask 25 and the photosensitive material layer 27 is short, the gradation mask is exposed. 25, the light intensity distribution of the light beam exposed on the photosensitive material layer 27 also becomes stepwise, but the distance d between the gradation mask 25 and the photosensitive material layer 27 is set to a predetermined distance ( By separating the mask pattern by the amount of alignment, the mask pattern is exposed in a defocused state due to the diffraction effect of light, and the step in the light intensity distribution can be eliminated.

In the exposure apparatus shown in FIG. 8, the light source 21 is appropriately selected according to the type of the photosensitive material layer 27. When the photosensitive material layer 27 is a photoresist,
A laser light source or a lamp light source in a wavelength range according to the sensitivity of the photoresist is used. When the photosensitive material layer 27 is a photocurable resin, an ultraviolet lamp, a halogen lamp, or the like is used depending on the type of the photocurable resin. And various lamps such as infrared lamps, and various laser light sources in the ultraviolet to infrared regions.

In the exposure method shown in FIG. 9, the gradation mask 28 is formed on the photosensitive material layer 2 on the substrate 26.
7 is arranged at a very small interval and exposed through a gradation mask 28 with a light beam BF for exposure having a uniform light intensity distribution, but using a gradation mask having a unit cell configuration as shown in FIG. In this case, the light intensity distribution immediately after passing through the gradation mask 28 changes stepwise according to the arrangement of the minute light transmitting portions. Is defocused by providing a gap (for example, about 50 μm), and the light intensity distribution is continuously leveled by the light diffusing action in the gap, and the continuous light intensity distribution is Exposure can be realized.

Next, in a stepper exposure method in which a mask pattern is reduced and exposed on a photosensitive material layer on a substrate 29 by a stepper exposure apparatus as shown in FIG. Since the reticle mask is used to reduce and expose the mask pattern, a desired special surface shape can be created with high accuracy. For example, 5
Using a reticle mask manufactured at twice the magnification, a mask pattern was formed on the photosensitive material layer by ５ by a stepper exposure method.
When the exposure is performed after reducing the size to 5
A special surface shape can be created with double precision.

In the stepper exposure apparatus shown in FIG. 10, light from a light source lamp 30 is condensed by a condensing lens 31 and irradiated on a reticle mask 32 as irradiation light having a uniform light intensity. Is incident on an image forming lens 33 having a reduced magnification, and a reticle mask 3 is formed on a surface of a photosensitive material on a substrate 37 mounted on an XY stage 34.
The XY stage 34 is sequentially moved by the stepping motors 35 and 36 to expose the mask pattern. In the case of this exposure method, when the exposure is performed by focusing the focus position of the mask pattern on the photosensitive material layer, the light of the light flux exposed on the photosensitive material layer is obtained by the stepwise transmittance distribution of the gradation mask 32. The intensity distribution is also stepwise, but by slightly shifting the focus position of the mask pattern from the photosensitive material layer,
The mask pattern is exposed in a defocused state, so that a step in the light intensity distribution can be eliminated.

Next, FIG. 6 is a diagram for explaining another example of the gradation mask. As shown in FIG. 6A, the gradation mask 18 is formed by forming a film 20 whose film thickness changes stepwise from a metal and / or a metal oxide on one surface of a transparent parallel flat plate 19 as a transparent substrate. Become
The change in the thickness of the film 20 is set so as to form a predetermined light transmittance distribution. As such a gradation mask 18 whose film thickness changes stepwise, for example, there is a mask described in Japanese Patent Application Laid-Open No. Hei 9-146259 previously proposed by the present inventors. The described method can be used as appropriate.

In the case of the gradation mask having the structure shown in FIG. 6A, the respective exposure methods described with reference to FIGS. 8, 9 and 10 can be used as the exposure method. Here, as an example, an exposure method using the alignment method in FIG. 9 will be described. The gradation mask 18 shown in FIG. 6A is brought into close contact with the surface of the photosensitive material layer (photoresist layer or photocurable resin layer), and the surface on which the film 20 is not formed (the opposite side of the parallel plate 19). When a light beam having a uniform light intensity distribution is irradiated from the (surface), the surface of the photosensitive material layer has a stepwise change in transmittance corresponding to a stepwise change in the film thickness of the film 20, for example, as shown in FIG. However, in this case, if the gradation mask 18 is separated from the photosensitive material layer by a minute distance and is irradiated with uniform light from the opposite surface, the above-described minute light intensity distribution can be obtained. Due to the diffusion of the light at the intervals, the pattern of the light intensity distribution that changes smoothly and continuously as shown in FIG. 6C is exposed to the photosensitive material layer. When the stepper exposure apparatus shown in FIG. 10 is used, the mask pattern is exposed in a defocused state by slightly shifting the focus position of the mask pattern from the photosensitive material layer. Steps in the distribution can be eliminated.

The example of the gradation mask and the exposure method has been described above. As a method for eliminating the step in the light transmittance distribution of the gradation mask as shown in FIG. 5 or FIG. Although the method of defocusing and exposing is described, as another step eliminating method, a light diffusing optical element is arranged on the light source side on the side opposite to the pattern forming surface of the exposure mask,
There is a method of exposing the mask pattern with diffused light to eliminate a step in the light transmittance distribution of the mask pattern. FIG. 11 shows an example of such a case, in which Cr is placed on a quartz substrate 38a.
This is an example in which a light diffusing optical element 39 is arranged on the surface on the light source side opposite to the pattern forming surface of the gradation mask 37 on which the mask pattern 38b of the film is formed. The light diffusing optical element 39 can be formed directly on the substrate 38a before the formation of the mask pattern.
On the light incident side of the substrate 38a, pitch: 5 μm, height: 1.
A 2 μm microlens array (MLA) is formed by a resist thermal deformation method or the like. Next, by forming a mask pattern 38b of a Cr film on the surface of the substrate 38a opposite to the surface on which the light diffusion optical element 39 is formed, a gradation mask 37 having the light diffusion optical element 39 is obtained.
Since the gradation mask 37 having the configuration shown in FIG. 11 includes the light diffusing optical element 39 composed of a minute microlens array on the light incident surface side, the mask pattern can be exposed with a light beam having a diffusion component, and the light of the mask pattern can be exposed. Steps in the transmittance distribution can be eliminated.

Next, the light transmittance of the gradation mask
Yet another method of eliminating the steps on the cloth is to use an exposure mask.
The surface opposite to the disk pattern formation surface (the light incident side
Surface) or the pattern formation surface of the exposure mask (light emission
Side) or both sides of the exposure mask
Arrange a functional film for light diffusion with a function and mask with diffused light
By exposing the pattern, the light of the mask pattern
There is a method for eliminating a step in the transmittance distribution. FIG.
An example is shown, and a mask formed of a Cr film on a quartz substrate 40 is shown.
A gradation mask on which a mask pattern 45 is formed.
After making, the pattern forming surface of the gradation mask
, Undercoat (SiO etc.) 41 and light diffusion function
Membrane (Ta_TwoO_Five, W_TwoO_FiveEtc.) 42 and anti-reflection functional film
(ZrO_Two/ MgF_Two/ ZrO _TwoEtc.) sequentially, quartz
The surface opposite to the pattern forming surface of the substrate 40 (the light incident side
This is an example in which an antireflection function film 44 is formed on the (surface). FIG.
In the gradation mask of the configuration shown in
Light diffusion function with light diffusion function and anti-reflection function film on the surface
Since it has a film, the mask
Turns can be exposed, and the step in the light transmittance distribution of the mask pattern
The difference can be eliminated. In the example of FIG.
The light diffusion functional film is formed on the
The surface opposite to the pattern forming surface of the substrate 40 (the light incident side
Surface), or even if a functional film for light diffusion is formed on both surfaces
Similar effects can be obtained.

The examples of the exposure mask (gradation mask or reticle mask) according to the present invention, the exposure method using the mask, and the method of eliminating the step in the light transmittance distribution have been described above. 1 and 2, the smooth light intensity distribution shown in the exposure step in FIGS. 1 and 2 can be realized, and the surface shape of the desired three-dimensional structure in which the steps are eliminated in the photosensitive material layer It can be created. Further, the surface shape created in the photosensitive material layer can be transferred to a substrate.

Next, anisotropic etching is performed on the photosensitive material layer and the substrate, and when the surface shape of the photosensitive material layer is engraved and transferred to the substrate surface, the selectivity of the anisotropic etching is changed. By changing over time, it is possible to deform the surface shape transferred onto the substrate. FIG.
2A shows a state in which a resist layer 11 having a curved surface is formed on a substrate 10. In an etching step using such a curved surface shape as a starting shape, if the selectivity is changed with time, the substrate 10 may have, for example, FIG.
As shown in (b), the image can be transferred as a curved surface shape completely different from the starting shape. In this example, the inclination of the portion I is increased on the substrate 10 by setting the selection ratio when transferring the foot portion of the starting shape (the portion indicated by “I” in the figure) to be greater than 1. Transfer to the next intermediate area
At the time of the transfer of II, the selection ratio is set to approximately 1 and a shape close to the starting shape is transferred. The image is transferred with the height difference enlarged. As described above, by performing the etching step while changing the selectivity, the starting shape can be subjected to desired deformation and transferred as the surface shape 12 of the substrate 10.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, as a specific embodiment of the method for forming a special surface shape and the optical element according to the present invention, a micro lens array (MLA) having a small size used for a liquid crystal device will be described.
Examples of manufacturing a micro lens (ML) having a large diameter and a high sag amount as an optical element for optical communication will be described.

Embodiment 1 FIG. 15 is a view showing an example of a liquid crystal device for a liquid crystal projector.
01 is a TFT substrate, 202 is a microlens array substrate, 203 is a flat substrate, and 205 is a liquid crystal layer.
On the surface of the TFT substrate 201 on the side in contact with the liquid crystal layer 205,
A TFT 201A for driving each pixel and a bus line (not shown) are formed, and a portion not covered by the TFT 201A and the bus line is an opening 20 as a pixel.
1B. Reference numeral 201C indicates a transparent conductive film. The flat substrate 203 sandwiching the liquid crystal layer 205 together with the TFT substrate 201 is a transparent parallel flat plate.
A black matrix 204 is formed on the surface in contact with 5, and a transparent electrode 204A is formed of an ITO film on the black matrix 204. On the microlens array substrate 202, an array arrangement of microlenses 302 that are convex as refraction surfaces on the surface in contact with the flat substrate 203, that is, a microlens array is formed. FIG. 16 is a view showing the microlens array substrate 202, and reference numeral 303 denotes a spacer portion. The symbol h in the figure indicates the height of the spacer portion 303 (from the surface on which the microlens 302 is formed), and h ′ indicates the height of the microlens 3.
02 shows the height. These h and h ′ are related: h ≧
h ′ must be satisfied.
It is formed at a height equal to or higher than the height of each microlens 302.

The first embodiment is an example of manufacturing a microlens array arranged at a fine pitch as shown in FIGS. 15 and 16, and is an example of manufacturing the microlens 302 with the adjacent distance between the microlenses 302 as close to zero as possible. . Here, as shown in FIG. 17, pixel 3 of the liquid crystal device for the liquid crystal projector is used.
02A is assumed to be a square, and its pixel size (area) is X
In the case of A × XA, since the pixel size of the liquid crystal element for 0.9 ″ -XGA is about □ 18 × 18 (μm), a micro lens having the same size as this pixel size is ideally arranged. However, when forming a microlens array,
When there is a lens non-forming portion of 1 μm each on both sides of the lens (when there is a gap between the lenses), the lens forming region becomes a region 302B shown by a broken line in the drawing, and its area X
B × XB is □ 17 × 17 (μm), and the ratio of the microlens array area to the total area is (17 × 1
7) / (18 × 18) × 100 = 289/324 × 100
= 89.2, and even though all light can be effectively collected by the microlens array, the light collection efficiency is only 89.2%. Therefore, it is important to reduce the area of the non-formed portion of the micro lens in order to improve the light use efficiency. As shown in the examples shown in FIGS. It is desirable.

Next, in manufacturing a microlens array as shown in FIGS. 15 and 16, first, a density distribution mask manufactured by the above-described method is prepared in advance. More specifically, in this embodiment, since a 1 / 5-fold reduction exposure is performed by using a stepper exposure apparatus as shown in FIG. 10, the actually manufactured density distribution mask enlarges the microlens shape by 5 times. Reticle mask (enlarged mask) of the mask pattern shown in FIG.
0 (μm). FIG. 14 shows an example of a mask pattern for one microlens. This mask pattern 46 is configured to be divided into a number of unit cells in which the opening area and the thickness of the Cr light-shielding film are controlled. In this embodiment, this one microlens portion is divided into a unit cell of length × width = 30 × 30 (pieces) = 900 (pieces) with the unit cell size being 3.0 × 3.0 (μm). Designed mask pattern. In the design of this mask pattern, the unit cell number 1 (Cr light-shielded) is placed in the center unit cell (3 × 3 (μm) on the reticle mask → 0.6 × 0.6 (μm) in the actual pattern). A unit cell in a state in which all the films remain) is arranged. In addition, at the four corners of the microlens formation region, the unit cell number 80 (there is no remaining Cr light-shielding film)
Place. And the unit cell number 1 during this time
In the 80 unit cells, the distribution of the “opening area” and the “Cr film thickness” corresponding to each “gradation (light transmission amount)” are made to correspond to each other, and the two-dimensional transmission according to the target lens surface shape is performed. CAD data is created by designing to have a rate distribution. The relationship between the lens surface shape and the unit cell number is a relationship obtained from the exposure process and the sensitivity curve of the photosensitive material as described above. Of course, when the photosensitive material and the exposure process are different, it is necessary to grasp the sensitivity curve each time.

On the basis of the above basic concept, a lens formula and a unit cell number of a mask pattern are added as functions to a unit on a CAD design screen on a personal computer from a calculation formula and a program supported by detailed data. A cell number is arranged and CAD data is created. Next, a mask blank in which a photosensitive material was applied to quartz glass was prepared.
After being set on the stage 8, the CAD data created as described above is input to the control unit of the laser light irradiation device, and the XY stage 8 is moved and the laser light source 1 is turned on and off.
While controlling the FF, the mask blank is irradiated with laser light by a predetermined method to draw a mask pattern. Then, by performing development and rinsing by a predetermined method, a mask pattern was obtained on the photosensitive material layer. Next, using the patterned photosensitive material layer as an etching mask, C
The Cr film was etched with a wet etchant for r. According to this method, each unit cell has a target opening area and film thickness in a pattern as shown in FIG.
A reticle mask having a two-dimensional transmittance distribution corresponding to the lens shape as a whole was manufactured.

Next, an example of a method for manufacturing a microlens array using the reticle mask will be described. The manufacturing method was the same as that of FIG. First, as shown in FIG. 1A, a neoceram substrate is prepared as a substrate 10 on which a desired surface shape is to be formed, and a commercially available photoresist (TGMR manufactured by Tokyo Ohka Co., Ltd.) is provided on the substrate 10 as a photosensitive material. -950 (trade name)) 8.55
It is applied to a thickness of μm. Next, the substrate 10 coated with the photoresist 11 is placed on a hot plate, and
Prebaking was performed at a heating temperature of 00 ° C. for a baking time of 180 seconds. Next, the substrate 10 on which the resist layer 11 was formed was placed on an X-ray of a stepper exposure apparatus having a configuration as shown in FIG.
The reticle mask was set on a Y stage and exposed to a stepper at a reduction ratio of 1/5 using the reticle mask as an exposure mask. The exposure conditions are such that the image formation position of the mask pattern is slightly defocused from the surface of the resist layer 11, the defocus amount is +25 μm, and the irradiation amount of the exposure light beam LF is 390 mW.
× 1.92 seconds (illuminance: 720 mJ). In the exposure of the mask pattern, as shown in FIG.
Since the pattern of the light intensity distribution corresponding to the lens surface shape of the microlens array is exposed, the resist layer 11
It is three-dimensionally exposed according to the microlens shape.
After the above-described exposure step, PEB (post-exposure bake) is performed at a temperature of 105 ° C. for 270 seconds, thereby forming a resist layer 11 as shown in FIG.
A micro lens shape was obtained. Next, the substrate 22 was set in a vacuum chamber of an ultraviolet curing device,
The resist layer was hardened by irradiating it with ultraviolet rays for a second while evacuating. By this operation, the plasma resistance of the resist is improved, and the resist can be processed in the next step. Note that the resist height at this time is 6.
It was 7 μm.

Next, the substrate 10 was set in a vacuum chamber of a TCP dry etching apparatus, and the degree of vacuum: 1.5 × 10
After evacuating to ^-3 Toor, CHF ₃ : 5.0 scc
m, CF ₄ : 50 sccm, O ₂ : 20 sccm, a mixed gas was introduced into the vacuum chamber, and the substrate bias power was 600 W.
Anisotropic dry etching was performed under the conditions where the power of the upper electrode (antenna electrode) disposed above the substrate was 1.25 kW and the substrate cooling temperature was -20 ° C. At this time, the etching was performed while changing the substrate bias power and the upper electrode power with time, and changing the selectivity of anisotropic dry etching (to decrease) with time. The average etching rate of the substrate 10 is 0.63 μm /
Minutes, but the actual etching time required 11.5 minutes. Through the above dry etching process, the shape of the resist layer was engraved on the substrate (FIG. 1 (d)), and a microlens array having a sectional shape as shown in FIG. 16 was manufactured. The lens height H after etching is H = 5.3.
It was 3 μm.

(Embodiment 2) Next, another embodiment for manufacturing a microlens array for a liquid crystal device similar to that of Embodiment 1 will be described. Also in this embodiment, 0.9 ″ -XGA
Assuming that the pixel size of the liquid crystal element for use is □ 18 × 18 (μm), a microlens array in which the distance between adjacent pixels is as close as possible to zero as shown in FIG. 16 is manufactured. In the present embodiment, as the exposure mask used in the exposure step, a reticle mask manufactured in the same manner as in Embodiment 1 and provided with a micro optical element having a light diffusion function on the light incident side is used. FIG. 11 shows an example, in which a light diffusing optical element 39 is arranged on the light source side opposite to the pattern forming surface of a reticle mask 37 in which a mask pattern 38b of a Cr film is formed on a quartz substrate 38a. It is an example. The light diffusing optical element 39 can be formed directly on the substrate 38a before the mask pattern is formed. For example, the light diffusing optical element 39 has a pitch of 5 μm and a height of 1.2 μm on the light incident side of the quartz substrate 38a. A microlens array (MLA) is formed by a resist thermal deformation method or the like. Next, a mask pattern 38b of a Cr film is formed on the surface of the substrate 38a opposite to the surface on which the light diffusing optical element 39 is formed by the same method as in the first embodiment. Thus, a reticle mask 37 including the light diffusing optical element 39 is obtained. In the reticle mask 37 having the configuration shown in FIG. 11, since the light diffusing optical element 39 composed of the microscopic microlens array is provided on the light incident surface side, the mask pattern can be exposed with a light beam having a diffusion component. Can be eliminated in the light transmittance distribution of the mask pattern composed of the unit cells.

The reticle mask is set in the stepper exposure apparatus shown in FIG. 10 and the same exposure process as that in the first embodiment is performed. There is no need to defocus. Further, the same procedure as in Example 1 was performed except that the exposure step was performed using a reticle mask provided with a light diffusion optical element. That is, conditions such as PEB and etching after exposure are the same as those in the first embodiment.

(Embodiment 3) Next, another embodiment for manufacturing the same microlens array for a liquid crystal device as in Embodiment 1 will be described. Also in this embodiment, 0.9 ″ -XGA
Assuming that the pixel size of the liquid crystal element for use is □ 18 × 18 (μm), a microlens array in which the distance between adjacent pixels is as close as possible to zero as shown in FIG. 16 is manufactured. In this embodiment, as the exposure mask used in the exposure step, the surface opposite to the pattern formation surface of the reticle mask (the light incident side) manufactured in the same manner as in Embodiment 1, or the pattern formation surface of the reticle mask A light diffusing functional film having a light transmitting function is disposed on the (light emitting side surface). FIG. 12 shows an example of this, and the quartz substrate 40 is formed in the same manner as in the first embodiment.
After manufacturing a reticle mask on which a mask pattern 45 made of a Cr film is formed, a pattern forming surface of the reticle mask is formed on, for example, Japanese Patent Application No. 11-28 by the present applicant.
No. 8430, the center wavelength is adjusted to i-line, the SiO film is λ / 4 as the undercoat 41 from the substrate side, and Ta ₂ O _{5 is used} as the light diffusion functional film 42 from the substrate side.
Is λ / 4, and ZrO ₂ :
An equivalent film of 0.4 + MgF ₂ : 0.2 + ZrO ₂ : 0.4 is sequentially formed, and an anti-reflection function film 44 is formed on the surface of the quartz substrate 40 opposite to the pattern formation surface (light incident side). did. In the reticle mask having the configuration shown in FIG. 12, since the pattern forming surface is provided with a light diffusion functional film having an anti-reflection function, the mask pattern can be exposed with a light beam having a diffusion component, and the light transmittance distribution of the mask pattern can be improved. Can be eliminated. In the example of FIG. 12, the light diffusion functional film is formed on the pattern forming surface side.
The same effect can be obtained by forming a light diffusing functional film on the surface opposite to the 0 pattern formation surface (the surface on the light incident side) or on both surfaces.

The reticle mask is set in the stepper exposure apparatus shown in FIG. 10 and the same exposure process as in the first embodiment is performed. At this time, the reticle mask has a light-reflecting function on the pattern formation surface. There is no need to defocus because of having a diffusion functional film. Further, the same procedure as in Example 1 was performed except that the exposure step was performed using a reticle mask having a light diffusion functional film. That is, conditions such as PEB and etching after exposure are the same as those in the first embodiment.

(Embodiment 4) The purpose of this embodiment is to form a large-diameter and high-sag microlens as an optical element for optical communication. This embodiment is an example of a short focal length microlens having a high lens height, which is difficult to manufacture by the conventional method, and furthermore, has a lens configuration of microlenses on both sides. Hereinafter, an embodiment in which the shape of the double-sided microlens is manufactured as a special surface shape will be described. In the conventional method, when the lens height is high, it is necessary to apply a thick photosensitive material and pattern it. However, in this case, there are problems such as thick coating of the photosensitive material, patterning property, heat deformability, and the like, and it has been difficult to manufacture a short focal length microlens having a high lens height as described above. Further, there is a method of changing the selectivity at the time of etching, specifically, a method of setting the selectivity to 1 or more, but there is a limit to increasing the selectivity.

In this embodiment, a photo-curable resin is used as a photosensitive material, and a double-sided microlens is manufactured in the same manufacturing process as in FIGS. At this time, the amount of shrinkage of the photocurable resin used is 6.8%, and the amount of movement is about several tenths of the target lens diameter. Further, the sensitivity, the amount of movement, and the amount of shrinkage of the photocurable resin are physical quantities determined for each material, and are physical values inherent to the material. In this embodiment, the height after deformation is about 20 to 30 μm with respect to the diameter of about 800 μm, and the ratio is about 1/30. There is no restriction on the amount of shrinkage.

The objective lens surface shape in this embodiment is the first lens shape.
Both the surface and the second surface are aspherical, and the aspherical shape is
Using the radius of curvature: R, the distance from the optical axis: Y, the conic constant: k, the higher-order constants: a, b,..., And the height in the optical axis direction: X, the following polynomial is used. The design results of the spherical microlens are as shown in Table 1 below. ^{X = (Y 2 / R)} / [1 + √ {1- (k + 1) (Y / R) 2}] + a
Y ⁴ + bY ⁶ ··

In the case of the present embodiment, since the microlenses have a single lens configuration, it is not necessary to consider the lens interval. Further, the film thickness was set to twice (about 20 μm) the amount of shrinkage deformation of the photocurable resin (about 10 μm in this embodiment). Further, a gradation mask having a controlled film thickness as shown in FIG. 6 was used as an exposure mask, and the exposure was carried out by an exposure method as shown in FIG. The alignment amount at this time was set to 20 μm based on the conventional performance data, and the mask pattern was exposed in a defocused state. Then, these conditions and the target shape are input to a personal computer, and a mask pattern having a two-dimensional transmittance distribution is designed and manufactured from a predetermined calculation formula. The gradation mask having a controlled film thickness corresponds to the shape of the first surface and the second surface of the microlens using the method described in Japanese Patent Application Laid-Open No. Hei 9-146259 previously proposed by the present inventors. Each gradation mask was designed and manufactured.

[0060]

[Table 1]

First, the first surface is processed. First, the diameter:
Acrylic adhesive (Dai Nippon Ink Co., Ltd. GRANDIC RC-8720) as a photo-curable resin on a φ4 ”neoceram substrate
(Trade name)) at a substrate temperature of 20 ° C. and a film thickness of 20 μm.
Is applied by using a spin coater to form a resin layer. The viscosity of the acrylic adhesive at 25 ° C. is 11
00CPS, and a thick film can be applied by a spin coater. Thereafter, the substrate temperature is increased to 30 ° C. on a hot plate, the viscosity of the adhesive is reduced to 795 CPS, and the surface of the uncured resin is made uniform. Then
The temperature of the substrate is lowered to 20 ° C. or less to lower the viscosity. This lowers the mobility of the resin layer and facilitates handling of the substrate.

Next, this substrate is set on a semiconductor aligner. On the other hand, a gradation mask manufactured based on the above design data is set on the aligner. Thereafter, by a predetermined operation, an exposure light beam (for example, ultraviolet light) is irradiated from the back side of the gradation mask at an illuminance of 7 mW / cm ² for 200 seconds under the condition of an alignment amount: 20 μm, and an integrated irradiation light amount: 1400 mJ / cm ² Is irradiated. At this time, since the change amount of the resin layer is large, the resin layer is cured while irradiating the exposure light beam with low illuminance for a long time. During this period, the substrate is heated at the beginning of the irradiation to raise the temperature to 30 ° C. The substrate was heated by the light even during the light irradiation time: 200 seconds, and the substrate temperature rose to 40 ° C. at the end of the irradiation. During this time, the viscosity of the resin layer decreases, and the resin layer contracts with curing, and its height increases.

Next, after the above processing, the substrate temperature is further raised to 50 ° C. Then, the viscosity of the resin layer becomes 217
Ascend to CPS. When the substrate is left for 5 minutes in this state, the resin in the portion that has not been photocured (the concave portion of the surface layer) gradually flows, and the surface is flattened by the surface tension. Of course, by omitting this processing, a concave shape around the lens can be left. After this step, the entire surface of the substrate is irradiated with uniform parallel light to completely cure the resin. When the surface shape of the resin layer cured by the above method was evaluated, the following results were obtained. Micro lens diameter: D = 69
9 μm, height of resin: h = 20.9 μm, height from substrate to resin top: H = 30.8 μm.

Next, the substrate having the resin layer having the above-mentioned shape is set in a vacuum chamber of a TCP dry etching apparatus for semiconductors, evacuated to a degree of vacuum of 3.0 × 10 ^-4 Toor, and then Ar: 5 sccm. , CF ₄ : 20 sccm, CH
F ₃ : a mixed gas of 5 sccm was introduced into the vacuum chamber, the substrate bias power was 1100 W, the power of the upper electrode (antenna electrode) disposed above the substrate was 1200 W, and the substrate cooling temperature was −20 ° C. Anisotropic dry etching was performed below. The etching rate at this time was 0.85 μm / min for both the substrate and the resin layer. The ratio (selectivity) of the etching rate between the substrate material and the resin layer was 1. Under these conditions, etching was performed for 39 minutes. As a result of measuring the surface shape of the substrate after the etching, the shape of the substrate after the first surface processing is as follows. Micro lens diameter: D = 699 μm Lens height: H = 20.9 μm Curvature radius: R = 2.657 mm

Next, the second surface is manufactured in the same process as described above. First, an acrylic adhesive (GRANDIC RC-8720 (trade name) manufactured by Dainippon Ink Co., Ltd.) was used as a photocurable resin on the back surface (second surface) side of the processed substrate.
At 20 ° C., a resin layer is formed by application using a spin coater so as to have a thickness of 20 μm. Next, this substrate is set on a semiconductor aligner. On the other hand, a gradation mask manufactured based on the above design data is set on the aligner. Thereafter, by a predetermined operation, under the condition of the alignment amount: 30 μm, the exposure light flux (for example, ultraviolet rays) is applied from the back side of the gradation mask by 7 mW /
Irradiation is performed for 220 seconds at an illuminance of cm ² to irradiate the mask pattern with an irradiation light amount of 1540 mJ / cm ² to cure the resin layer. During this period, the substrate is heated at the beginning of the irradiation to raise the temperature to 30 ° C. Also, the substrate was heated by the light during the light irradiation time: 220 seconds, and the substrate temperature rose to 40 ° C. at the end of the irradiation. During this time, the viscosity of the resin layer decreases, and the resin layer contracts with curing, and its height increases.

Next, after the above processing, the substrate temperature was further raised to 50 ° C., and the substrate was left for 5 minutes in this state. The surface is flattened by the surface tension. Of course, by omitting this processing, a concave shape around the lens can be left. After this step, the entire surface of the substrate is irradiated with uniform parallel light to completely cure the resin. When the surface shape of the resin layer cured by the above method was evaluated, the following results were obtained. Micro lens diameter: D = 79
8 μm, height of resin: h = 29.9 μm, height from substrate to resin top: H = 40.5 μm.

Next, the substrate having the resin layer having the above-mentioned shape is set in a vacuum chamber of a TCP dry etching apparatus for semiconductors, evacuated to a vacuum of 3.0 × 10 ⁻⁴ Toor, and then Ar: 5 sccm. , CF ₄ : 20 sccm, CH
F ₃ : a mixed gas of 5 sccm was introduced into the vacuum chamber, the substrate bias power was 1100 W, the power of the upper electrode (antenna electrode) disposed above the substrate was 1200 W, and the substrate cooling temperature was −20 ° C. Anisotropic dry etching was performed below. The etching rate at this time was 0.85 μm / min for both the substrate and the resin layer. The ratio (selectivity) of the etching rate between the substrate material and the resin layer was 1. Under these conditions, etching was performed for 51 minutes. As a result of measuring the surface shape of the substrate after the etching, the shape after the second surface processing of the substrate is as follows. Micro lens diameter: D = 790 μm Lens height: H = 30.0 μm Curvature radius: R = 2.641 mm

Incidentally, the optical axis alignment accuracy of the first surface and the second surface is φ
It was 0.2 μm or less. When the microlens was incorporated in an optical communication module and the optical performance was evaluated, the following performance was obtained. Outgoing / incident side optical fiber diameter (core diameter): 8 μm Divergence angle (half angle) from fiber: 8 ° (full width: 16)
°) Dummy pinhole: 500 μm diameter at a position 50 mm from the lens end face Lens performance (light loss) target value: 4 dB or less Lens performance (light loss) result: 3.81 dB

[0069]

As described above, according to the present invention,
It is possible to provide a method for creating a new special surface shape and an optical element formed by the method. In the present invention, when a special surface shape is formed on the photosensitive material layer using an exposure mask such as a gradation mask (density distribution mask) or a reticle mask, the exposure mask is used.
Since the two-dimensional light transmittance distribution can be smoothed so that the discontinuous portion of the light transmittance distribution curve in the mask is not exposed to the photosensitive material layer, the photosensitive material layer has a discontinuous shape (step). Can be prevented from being transferred. Therefore, according to the present invention, shape transfer can be performed with high precision without lowering the sensitivity of the photosensitive material or changing the material to a photosensitive material having a lower sensitivity, and the shape can be smoothly continuously transferred in the height direction. It is possible to create a three-dimensional shape that changes dynamically with high accuracy. In addition, 3 formed on the photosensitive material layer
By transferring the three-dimensional shape to the substrate by anisotropic etching, a special surface shape having a three-dimensional structure can be created on the substrate. Therefore, according to the present invention, a special surface shape of a three-dimensional structure that changes smoothly and continuously in the height direction can be easily created on the photosensitive material layer or the substrate, and this surface shape can be formed optically. By using the curved surface, an optical element such as a large-diameter microlens for optical communication or a fine-pitch microlens array for a liquid crystal device can be easily provided.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing one embodiment of a method for creating a special surface shape according to the present invention.

FIG. 2 is a process explanatory view showing another embodiment of the method for creating a special surface shape according to the present invention.

FIG. 3 is an explanatory view of a process when transferring the surface shape of the resin layer manufactured in the process shown in FIG. 2 to a substrate.

FIG. 4 is a diagram for explaining a correspondence between a light intensity distribution of irradiation light and a surface shape to be formed in an exposure step.

FIG. 5 is a diagram for explaining an example of an exposure mask according to the present invention.

FIG. 6 is a view for explaining another example of the exposure mask according to the present invention.

FIG. 7 is a diagram showing an example of a configuration of a laser beam irradiation device used when manufacturing a gradation mask according to the present invention.

FIG. 8 is a diagram showing an example of the configuration of an exposure apparatus used for patterning a special surface shape.

FIG. 9 is a diagram showing an example of an exposure method used when patterning a special surface shape.

FIG. 10 is a diagram showing another configuration example of an exposure apparatus used at the time of patterning a special surface shape.

FIG. 11 is a view showing one embodiment of the present invention, and is a cross-sectional view of a main part of an exposure mask provided with a light diffusing optical element.

FIG. 12 is a view showing another embodiment of the present invention and is a cross-sectional view of a main part of an exposure mask provided with a light diffusion functional film.

FIG. 13 is a view for explaining that a surface shape different from a starting shape is formed on a substrate by changing a selection ratio with time in an etching step.

FIG. 14 is a diagram showing an example of a mask pattern of a reticle mask used in the first embodiment.

FIG. 15 is a sectional view of a main part showing an example of a liquid crystal device for a liquid crystal projector.

16 is a cross-sectional view of a principal part showing an example of a microlens array substrate used in the liquid crystal device shown in FIG.

FIG. 17 is a diagram illustrating a relationship between a pixel of a liquid crystal device and a microlens formation region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light transmission apparatus 2 Beam splitter 3 Mirror 4 Optical modulator and its control apparatus 5 Data path 6 Optical deflector and its control apparatus 7 Objective lens 8 XY stage 9 Optical interferometer 10 Substrate 11 Photosensitive material layer ( Photoresist layer) 13 Optical element 14 Substrate 15 Photosensitive material layer (photocurable resin layer) 17 Gradation mask (density distribution mask) 18 Gradation mask (density distribution mask) 21 Light source 22 Collimating lens 23 Mirror 24 Beam expander 25 Gradation mask 26 Substrate 27 Photosensitive Material Layer 28 Gradation Mask 29 Substrate 30 Light Source Lamp 31 Condensing Lens 32 Reticle Mask 33 Imaging Lens 34 XY Stage 37 Gradation Mask 38a Quartz Substrate 38b Mask Pattern (Cr Film) 3 Light diffusion optical element 40 Quartz substrate 41 Undercoat 42 Light diffusion function film 43 Antireflection function film 44 Antireflection function film 45 Mask pattern (Cr film) 46 Mask pattern 201 TFT substrate 202 Microlens array substrate 203 Flat substrate 205 Liquid crystal 302 Micro lens

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA22 LA01 PA01 PA17 PB01 QA02 QA07 QA14 QA34 RA05 RA12 RA13 UA01 2H096 AA28 AA30 BA05 CA20 EA11 EA30 HA23 2H097 BA01 FA02 LA12 LA16 LA17 9A001 BB06 JJ48JJ50J

Claims (13)

[Claims] An exposure pattern for exposing a pattern on a photosensitive material layer on a substrate using an exposure mask whose light transmittance changes stepwise according to a special surface shape of a desired three-dimensional structure. The method of creating a special surface shape, characterized in that the focus is shifted and the step of the light transmittance distribution is eliminated. 2. The method according to claim 1, further comprising the step of: exposing a pattern to the photosensitive material layer on the substrate using an exposure mask whose light transmittance changes stepwise in accordance with a desired special surface shape of the three-dimensional structure. A step of exposing a mask pattern to eliminate a step in a light transmittance distribution. 3. A photosensitive material layer is formed by applying a photosensitive material to a predetermined thickness on a surface of a substrate material on which a special surface shape having a desired three-dimensional structure is to be formed. Then, the photosensitive material layer is exposed to a mask pattern having a predetermined light transmittance distribution using an exposure mask whose light transmittance changes stepwise, and the photosensitive material layer is exposed according to a target special surface shape. In the method of creating a special surface shape for changing the thickness of the mask pattern, when exposing the pattern of the exposure mask to the photosensitive material layer, defocusing and slightly defocusing the exposure pattern, the light of the mask pattern A method for creating a special surface shape characterized by eliminating a step in transmittance distribution. 4. A photosensitive material layer is formed by applying a photosensitive material to a predetermined thickness on a surface of a substrate material on which a special surface shape having a desired three-dimensional structure is to be formed, and the photosensitive material layer is formed. Then, the photosensitive material layer is exposed to a mask pattern having a predetermined light transmittance distribution using an exposure mask whose light transmittance changes stepwise, and the photosensitive material layer is exposed according to a target special surface shape. In the method of creating a special surface shape to change the thickness of the, when exposing the pattern of the exposure mask to the photosensitive material layer, on the light source side opposite to the pattern formation surface of the exposure mask A method for creating a special surface shape, comprising disposing a light diffusing optical element and exposing a mask pattern with diffused light to eliminate a step in the light transmittance distribution of the mask pattern. 5. A method for forming a special surface shape according to claim 2, wherein a light diffusion function film having a light transmission function is arranged on a surface opposite to a pattern formation surface of the exposure mask as a method for generating diffused light.
A method for creating a special surface shape characterized by eliminating a step in a light transmittance distribution. 6. A method for generating a special surface shape according to claim 2, wherein a light diffusion function film having a light transmission function is disposed on a pattern forming surface of the exposure mask as a method for generating a diffused light, and a light transmittance distribution is obtained. A method for creating a special surface shape characterized by eliminating steps. 7. The method for creating a special surface shape according to claim 2, wherein a light diffusion function film having a light transmission function is disposed on both surfaces of the exposure mask as a method of generating diffused light, and a step in the light transmittance distribution is reduced. A method for creating a special surface shape characterized by eliminating. 8. The method for creating a special surface shape according to claim 1, wherein the mask for the exposure has a light transmittance that changes stepwise according to the special surface shape. And a reticle mask obtained by enlarging the density distribution mask at a predetermined magnification ratio. 9. The method for creating a special surface shape according to claim 1, wherein a photoresist or a photocurable resin is used as the photosensitive material. Creation method. 10. A method according to claim 9, wherein when a photoresist is used as the photosensitive material, the photoresist layer applied to the surface of the substrate material is provided with a concentration distribution mask or a reticle mask. After exposing a mask pattern having a three-dimensional light intensity distribution, the photoresist layer is patterned into a desired three-dimensional structure through processes such as development, rinsing, post-exposure bake, and resist curing. A method for creating a special surface shape, characterized in that: 11. A method according to claim 9, wherein when a photocurable resin is used as the photosensitive material, a liquid photocurable resin is applied to the surface of the substrate material, and then the photocurable resin is cured. Exposure of a mask pattern having a predetermined three-dimensional light intensity distribution with the above-mentioned concentration distribution mask or reticle mask in a state where the conductive resin layer has fluidity, and control of the irradiation time, exposure amount, and fluidity by heating The photo-curable resin layer is gradually cured from the surface side by, and the surface of the resin layer is deformed by the volume reduction and flow of the photo-curable resin due to the curing, and is patterned into a desired three-dimensional structure. To create special surface shapes. 12. The method for creating a special surface shape according to any one of claims 1 to 11, wherein the thickness of the photosensitive material layer is changed according to a target special surface shape. A method for creating a special surface shape, wherein anisotropic etching is performed on a photosensitive material layer and a substrate, and the surface shape of the photosensitive material layer is engraved and transferred to a substrate surface. 13. An optical element characterized in that an optical curved surface is formed on the surface of a photosensitive material layer or a substrate material by using the method for forming a special surface shape according to any one of claims 1 to 12. .