JP3611613B2 - Three-dimensional shape forming method, three-dimensional structure formed by the method, and press mold - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for forming a three-dimensional shape, and in particular, a microstructure whose structure is precisely controlled in three dimensions, such as a microlens, a micromachine, and a microsensor, and press molding for mass production of these microstructures. The present invention relates to a method for forming a mold and the like.
[0002]
[Prior art]
In recent years, attempts have been made to fabricate a microstructure such as a micromachine using a lithography technique used in semiconductor manufacturing or the like. Specifically, a photoresist is applied to the microstructure forming substrate, exposed and developed through a photomask to obtain a resist pattern, and this resist pattern is transferred to the microstructure forming substrate by etching to form a minute pattern. A method of manufacturing a structure is known, but with this method, the shape of the obtained microstructure in the depth direction is limited to a rectangle, and the shape in the depth direction cannot be controlled.
[0003]
Therefore, various methods for producing a microstructure whose structure is precisely controlled in three dimensions such as a three-dimensional curved surface have been studied and proposed.
[0004]
For example, a method has been proposed in which a resin pattern array formed in a rectangular shape is heated and melted to be deformed into a spherical shape to produce a resin-made convex microlens array (Japanese Patent Laid-Open No. 5-40216) (with known example 1). To do).
[0005]
As another method, a method of producing a stepped shape by repeating exposure and development has been proposed (Journal Vacuum Science Technology, B9 (6), 1991, pages 3117-3120) (known example 2 and To do).
[0006]
Furthermore, as another method, there has been proposed a method of producing a shape corresponding to the exposure amount of the electron beam by changing the exposure amount of the electron beam depending on the exposure position, exposing the electron beam resist, and developing the resist. JP-B-2-44060) (referred to as publicly known example 3).
[0007]
Further, exposing the photoresist through a photomask that gives a transmitted light amount in which the interval between the light shielding portions of the photomask is less than the diffraction limit of the exposure wavelength and the light transmitted through the light shielding portion continuously changes in a plane, Next, a method of forming an afterimage resin pattern (three-dimensional resist image) corresponding to the exposure amount in the exposed area by developing is proposed (IEE Proceedings on MM SMS, (1994, pp. 205-210) (known example 4).
[0008]
On the other hand, regarding the manufacturing method of press molds for mass production of microstructures, the shape of a transparent matrix that has been subjected to microfabrication is transferred to a photosensitive resin, and the transferred photosensitive resin is etched by a base press. A method of transferring to a mold for molding has been proposed (Japanese Patent Publication No. 6-15184) (referred to as known example 5).
[0009]
[Problems to be solved by the invention]
However, the above-described conventional microstructure manufacturing method has the following problems.
[0010]
That is, the method described in the known example 1 has a problem that the shape obtained is limited to a spherical shape because the surface is made spherical by utilizing the surface tension of the molten resin.
[0011]
Further, in the method described in the known example 2, since it is necessary to repeat the steps of resist film formation, exposure, and development a plurality of times, the manufacturing is complicated, and the alignment between the photomask and the object to be exposed is performed. There is a problem that it is technically difficult to manufacture.
[0012]
Furthermore, in the method described in the known example 3, since all patterns are drawn with an electron beam, there is a problem that exposure takes time and productivity is extremely low.
[0013]
Further, in the method described in the known example 4, a three-dimensional resist image can be produced with high productivity. However, the three-dimensional resist image actually produced by the method of the known example 4 is microscopic. Since the surface shape is stepped (jagged), there is a problem that it is difficult to actually apply to the manufacture of products such as microlenses that require a smooth surface shape.
[0014]
Furthermore, the method described in the known example 5 has a problem that it is difficult to produce a three-dimensional shape of 100 μm or less because the mother die is produced by machining. In the production of a press die using a super hard material, since grinding and polishing are usually performed with a grindstone, there is a problem that the size of a work die is limited to millimeters or more.
[0015]
The present invention has been made in view of the above-described problems, and an object thereof is to provide a method for forming a microscopically smooth three-dimensional surface shape.
Another object of the present invention is to provide a microstructure having a three-dimensional surface shape that is microscopically smooth and whose structure is precisely controlled in three dimensions, a press mold for mass-producing these microstructures, and the like.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the three-dimensional shape forming method of the present invention comprises a resist mask formed on a substrate, and a lithography mask having a light-shielding pattern that continuously changes the exposure intensity reaching the resist layer. A step of exposing the resist layer, a step of developing the resist layer after the exposure to form a three-dimensional resist image, and simultaneously etching the resist image and the substrate to form a resist image. In a method for forming a three-dimensional shape including a step of transferring a three-dimensional shape to a substrate, resist and / or resist image forming conditions are used such that the residual film curve of the resist becomes a residual film curve having a gentle slope. As a configuration.
[0017]
The three-dimensional shape forming method of the present invention is the same as the three-dimensional shape forming method of the present invention, wherein the resist that forms the remaining film curve having a gentle slope is a resist with low contrast and low resolution. ,
A resist image forming condition that results in a gradual residual film curve is a resist baking condition and / or a developing condition;
The resist and / or the resist image forming conditions that form the residual film curve with the gentle slope are the conditions that the resist contrast is 2.0 or less in terms of gamma value,
In the step of exposing the resist layer, a configuration in which reduced projection exposure is performed, or after the step of forming a three-dimensional resist image by the development process, the three-dimensional resist image is higher than the melting point of the resist. It is as composition which heats at temperature.
[0018]
Further, the micro three-dimensional structure of the present invention is configured to produce a three-dimensional structure having a three-dimensional surface shape that is smooth microscopically by the above three-dimensional shape forming method.
[0019]
Furthermore, the press mold of the present invention is configured to produce a press mold having a smooth three-dimensional surface shape microscopically by the above three-dimensional shape forming method.
[0020]
Hereinafter, the present invention will be described in detail.
In the method for forming a three-dimensional shape of the present invention, first, a resist layer is formed on a substrate, and a lithography mask having a light-shielding pattern that continuously changes the exposure intensity reaching the resist layer is used. The resist layer is exposed.
[0021]
Here, as the base material, any material can be used as long as it has high light resistance and high mechanical strength, and is not particularly limited. For example, SiC, WC, TiC, Cr₃C₂TiN, Al₂O₃Examples thereof include superhard materials such as quartz, glass materials such as quartz, infrared transmitting materials such as Si and Ge, engineering plastics represented by polyamides, and the like. The shape of the substrate is not particularly limited, but a substrate is usually used.
[0022]
In addition, the resist layer is formed by existing methods such as spin coating, dip coating, and spray coating for solution type resists, and existing methods such as vacuum deposition, sputtering, and CVD for solid type resists such as inorganic resists. It is formed by the method.
[0023]
In the present invention, a lithography mask having a light-shielding pattern that continuously changes the exposure intensity reaching the resist layer is used.
This is because, in general, the residual film thickness after development of the resist changes in accordance with the exposure light intensity (exposure amount) exposed on the resist, so that the exposure intensity reaching the resist layer is continuously changed to change the resist thickness. This is for continuously changing the remaining film thickness after development.
[0024]
Here, there are several types of lithography masks having a light-shielding pattern that continuously changes the exposure intensity reaching the resist layer.
For example, a mask in which at least a part of the optical density of the light shielding portion is continuously changed can be used. Such a mask can be obtained by continuously changing the thickness of the light shielding film or continuously changing the composition of the light shielding film.
[0025]
As another mask, a mask in which at least a part of the interval between the light shielding portions of the mask is an interval below the diffraction limit of the exposure wavelength, or at least a part of the interval of the opening portion of the mask is an interval below the diffraction limit of the exposure wavelength. Masks.
In this case, in order to set the interval between the light shielding portions of the mask or the interval between the opening portions to be equal to or less than the diffraction limit of the exposure wavelength, these intervals may be set to be equal to or less than the limit pitch shown below.
Pc = λ / NA (1 + σ)
Here, Pc is the limit pitch, λ is the exposure wavelength, NA is the numerical aperture of the exposure device, and σ is the filling factor of the light shielding portion in the pixel. Here, regarding the filling ratio of the light shielding portion, the shape of the light shielding portion is not particularly limited as long as the light shielding area in one pixel can be varied, but shapes such as a linear shape, a dot shape, and a rectangular shape are mainly used.
[0026]
In the case of reducing exposure using a stepper, the actual mask (reticle) is not projected with the interval between the light shielding portions or the opening portion being less than the diffraction limit of the exposure wavelength. The interval between the light shielding portions on the resist or the interval between the opening portions is set to be equal to or smaller than the diffraction limit of the exposure wavelength.
[0027]
The above-described mask has a pattern width (pitch) or pattern area that can be accurately transferred without being affected by diffraction, and the exposure intensity in this case is 1, and the pattern width or area is 1 or less. The intermediate exposure intensity of 1 or less is to be obtained using the influence of the above.
[0028]
Still another mask is a mask in which at least a part of the interval between the light shielding portions of the mask is an interval below the resolution limit of the resist, or at least a part of the interval between the openings of the mask is an interval below the resolution limit of the resist. And the mask.
For example, if the resolution limit of the resist is 1 μm, the interval between the light shielding portions of the mask or the interval between the opening portions is set to an interval of 1 μm or less. This is to be considered because the above-mentioned limit pitch is different if the resolution limit (resolution) of the resist is different. Therefore, if the resolution limit of the resist is 2 μm, the interval between the light shielding portions of the mask or the interval between the opening portions is set to an interval of 2 μm or less.
[0029]
In addition, regarding the formation material of the lithography mask having a light-shielding pattern that continuously changes the exposure intensity described above, any material that is transparent to the exposure wavelength can be used as the mask substrate. Any material that can transfer a pattern having a contrast of optical density required for a transfer target through a mask can be used as the light-shielding film constituting the film. Specifically, examples of the mask substrate include a quartz glass plate and an aluminoborosilicate glass plate. Examples of the light shielding film material include chromium, chromium oxide, tungsten silicide, tantalum silicide, molybdenum silicide, and silver colloid.
[0030]
The lithography mask includes an electron beam mask and an ion beam mask in addition to a photomask and an X-ray mask. In addition, the exposure method includes contact exposure (contact exposure), proximity exposure (proximity exposure), 1 × exposure such as 1 × projection exposure (mirror projection exposure), reduced projection exposure, and the like. When the reduction projection exposure is used, a finer microstructure can be easily formed as compared with the same magnification exposure. Further, the exposure light source includes ultraviolet / visible light, excimer laser, X-ray (including synchrotron radiation), electron beam, ion beam, and the like.
[0031]
In the present invention, when the resist layer after the exposure is developed to form a three-dimensional resist image, a condition that a resist image having a smooth surface as viewed microscopically is used is used. It is characterized by.
This is because, when a resist with high contrast and high resolution is used, the exposure intensity reaching the resist layer is continuously changed by the lithography mask having the specific light-shielding pattern. This is because the continuous change is stepped when viewed microscopically, and the surface of the obtained three-dimensional resist image is stepped (notched) when viewed microscopically.
[0032]
Accordingly, the present inventors have come up with an active use of conditions that do not allow a sharp resist image to be formed.
Specifically, in the present invention, a resist and / or resist image forming conditions that provide a remaining film curve with a gentle slope are used.
[0033]
Here, the residual film curve (characteristic curve) of the resist generally takes a value (residual film ratio) in which the horizontal axis represents the common logarithm of the dose and the vertical axis represents the film thickness after development with the coating film thickness. The residual film curve shape (slope, etc.) is the characteristics of the resist itself (type of resin constituting the resist, etc.), the heat treatment conditions of the resist (pre-bake conditions, etc.), development processing conditions, exposure It varies depending on the light source.
The slope of the remaining film curve is called a gamma value (γ value), and this γ value serves as an index representing the contrast of the resist. The higher this value, the higher the contrast and the higher the resolution. In general, the γ value of the negative resist is defined by the slope of the remaining film curve (tangent value of the tilt angle) when the residual film ratio is 0.5, and the γ value of the positive resist has a residual film ratio of 0. Defined by the slope of the remaining film curve.
[0034]
Therefore, using resist and resist image forming conditions that form a residual film curve with a gentle slope as a whole, a resist image having a smooth shape (edge, etc.) with low contrast and low resolution can be formed. This is because if the slope of the residual film curve is gentle, the residual film thickness of the resist can be controlled over a wide range of exposure intensity, and the residual resist film thickness can be obtained in accordance with subtle changes in the exposure intensity. .
[0035]
Here, examples of the resist that has a gently-sloping residual film curve include resists with low contrast and low resolution. Such resists include the types of resins constituting the resist, sensitizers, and solvents. It is prepared by selectively adjusting the content and the like.
[0036]
Also, resist image forming conditions that form a residual film curve with a gentle slope include resist baking conditions and / or development conditions. This is because, as described above, the shape of the remaining film curve changes depending on the heat treatment conditions and development processing conditions of the resist.
[0037]
Examples of development conditions include development time, development method, type of developer, concentration and temperature, resist dissolution characteristics, and the like, and these conditions are set so that a residual film curve with a gentle slope is obtained. In particular, the development time and the dissolution property of the resist affect the resist shape (resist profile) after development, and therefore the conditions are set in consideration thereof. Specifically, these conditions can be changed variously to actually create a residual film curve, and various conditions can be set based on this.
Further, since the developing temperature, the developing method (spray pressure in the spray method or the convection speed of the developer in the dipping method, etc.) affect the resolving power, conditions are set in consideration thereof.
[0038]
Pre-baking is usually performed for the purpose of removing the solvent from the resist film, but in the present invention, the pre-baking temperature and the pre-baking time are set so that the remaining film curve has a gentle slope.
[0039]
In view of the fact that a high-contrast, high-resolution resist having a gamma value of 2.0 or more is used in a normal semiconductor process, resist and / or resist image formation that forms a residual film curve with a gentle slope It can be said that the conditions are such that the resist contrast is 2.0 or less in terms of gamma value.
Here, the value of the γ value changes depending on the characteristics of the resist itself, the heat treatment condition of the resist, the development process condition, etc., as in the case of the residual film curve described above. Can be obtained.
The value of γ value is preferably 2.0 or less for the above reason, but in order to make the effect of the present invention more reliable, the γ value is preferably 1.5 or less, More preferably, it is 1.0 or less.
With regard to the lower limit of the γ value, care should be taken not to make it extremely low in order to obtain a residual resist film thickness corresponding to a subtle change in exposure intensity.
[0040]
The types of resins constituting the resist include, for example, photocrosslinkable resins such as cinnamate-based photodimerization-type photosensitive resins, metal ion dichromate-type photosensitive resins, and azide-type photodecomposition-crosslinking-type photosensitive resins. , Photodegradable resins such as diazo-based photodegradable insoluble photosensitive resins, quinonediazide-based photodegradable soluble photosensitive resins, unsaturated polyester-based photosensitive resins, acrylate-based photosensitive resins, nylon-based photosensitive resins, Examples thereof include photopolymerizable resins such as cationic polymerization photosensitive resins, chalcogenide inorganic resists, and the like. These resins may be used alone or in combination of two or more.
[0041]
In the present invention, the three-dimensional resist image may be heated at a temperature higher than the melting point of the resist after the step of forming the three-dimensional resist image by the development process. As a result, the resist is deformed and becomes smooth. Thus, when heat-melting is performed after the above steps, a smoother three-dimensional resist image can be obtained in a short time with less undulation and fewer local defects than when heat-melting alone.
[0042]
In the present invention, after the developing step, the resist image and the base material are simultaneously etched to transfer the three-dimensional shape of the resist image to the base material.
In this case, in order to transfer the same shape as the resist image, the etching rates of the resist and the base substrate are made equal. Also, to obtain a shape compressed in the vertical direction, the resist etching rate should be higher than the etching rate of the base material. Make it slower.
[0043]
Since the etching rate varies depending on the resist used and the etching conditions in the etching apparatus, it is necessary to comprehensively judge these and select the etching conditions. In particular, when using a dry etching system, the etching rate varies depending on conditions such as the structure (type) of the system, etching pressure (gas pressure), etching output, gas flow rate, and substrate temperature. It is necessary to judge and select the etching conditions.
[0044]
The etching method includes wet etching and dry etching, but it is preferable to employ dry etching in order to transfer the shape of the resist pattern onto the substrate as accurately as possible.
The dry etching apparatus is not particularly limited. For example, a known dry etching apparatus such as a parallel plate type reactive ion etching apparatus or a magnetron ion etching apparatus is used.
[0045]
The gas used for dry etching is CF₄, CHF₃, C₂F₆, Cl₂Fluorine-based and chlorine-based single gases represented by the above, or mixed gases containing these gases are preferred. Further, these gases may be mixed with a gas such as oxygen or hydrogen, or an inert gas such as He or Ar, if necessary.
[0046]
According to the method of the present invention, a smooth three-dimensional surface shape can be formed when viewed microscopically. Further, according to the method of the present invention, it is possible to efficiently manufacture a microstructure with a smooth surface whose structure is accurately controlled in three dimensions. This is particularly effective as a production method. Furthermore, according to the method of the present invention, it is possible to efficiently produce a fine press mold having a smooth surface whose structure is accurately controlled in three dimensions, which could not be obtained conventionally.
Note that the three-dimensional shape forming method of the present invention is not limited to a microstructure, and can be applied to a structure having a normal size.
[0047]
Another invention of the present invention is a three-dimensional structure manufactured by the above-described method for forming a three-dimensional shape.
The three-dimensional structure of the present invention is a microstructure that has a microscopically smooth three-dimensional surface shape and is precisely controlled in three dimensions, and requires a practically microscopically smooth surface shape. It is particularly effective as a micro optical component. That is, the present invention is intended for practical use of micro optical components that could not be obtained as a practical product in the past, and has an extremely high industrial utility value.
[0048]
Note that the use and type of the microstructure are not particularly limited. Examples of the use of the microstructure include use as a micro optical component, a micro machine component, and a micro sensor component. Also, the types of micro optical components include spherical lenses such as convex lenses, concave lenses, anamorphic lenses, lenticular lenses, and aspherical lenses, triangular waveform gratings, sine waveform gratings, trapezoidal waveform gratings, prisms, zone plates, etc. , Fresnel lenses, holographic lenses, and the like. Examples of the types of micromachine parts and microsensor parts include convex spherical bodies, concave spherical bodies, aspherical bodies, and conical projections.
[0049]
Note that in the present invention, a plurality of microstructures can be arranged in an arbitrary arrangement, and the microstructures can be continuously manufactured, or a continuous monolithic microstructure continuum can be manufactured. Can do.
[0050]
Another invention of the present invention is a press mold characterized by being manufactured by the above-described method for forming a three-dimensional shape.
According to the press mold of the present invention, a microstructure can be easily mass-produced.
[0051]
Here, as a base material processed into a micro press mold, any material can be used as long as it is a material having high light resistance, heat resistance, and mechanical strength, and is not particularly limited. For example, SiC, WC, TiC, Cr₃C₂TiN, Al₂O₃Examples thereof include superhard materials such as quartz, glass materials such as quartz, infrared transmitting materials such as Si and Ge, engineering plastics represented by polyamides, and the like.
[0052]
In addition, glass, plastics, etc. are used as a material to press. In this case, optical glass such as BK-7 is used as the glass.
When plastic is used as the material to be pressed, a transparent material such as quartz is used for the press die, an ultraviolet curable resin is filled between the press die and the transfer substrate, and the resin is cured by irradiating ultraviolet rays. Resin micro optical elements can be press-molded.
Here, as the ultraviolet curable resin, a known resin such as polystyrene resin, epoxy resin, urethane resin, polyolefin resin, polyimide resin, polyamide resin, polyester resin, or a mixture of these resins can be used.
[0053]
Furthermore, a heat-resistant material can be used for the press mold, a thermosetting resin can be filled between the press mold and the transfer substrate, and the thermosetting resin can be cured by heating to mold a resin-made micro optical element or the like. .
Here, as the thermosetting resin, a known resin such as polystyrene resin, acrylic resin, epoxy resin, urethane resin, polyolefin resin, polyimide resin, polyamide resin, polyester resin, or a mixture of these resins can be used.
[0054]
【Example】
Hereinafter, the present invention will be described more specifically based on examples.
[0055]
Example 1
A g-line-compatible positive styrene-based photoresist 4 with a γ value adjusted to 1.0 is applied onto a quartz substrate 3 and a photomask 1 having a circular light-shielding pattern 2 as shown in FIG. The resist 4 was exposed with a line contact exposure machine (FIG. 2A).
Here, the photomask 1 shown in FIG. 1 has a light-shielding pattern 2 in which the area occupied by the light-shielding portion gradually decreases toward the outer periphery of the circle, and the interval between the light-shielding portions is less than the limit pitch (Pc = 0.11 μm). What was used was used.
[0056]
Next, the photoresist 4 is developed with a developer (AZ developer manufactured by Hoechst) (development time 120 seconds, pre-baking temperature 90 ° C., time 60 minutes), and a convex spherical resist image 5 having a diagonal of 20 μm and a height of 1 μm is obtained. It formed (FIG.2 (b)).
[0057]
Subsequently, using a parallel plate type reactive ion etching apparatus, high frequency power of 250 W was supplied, and C₂F₆The quartz substrate having the convex spherical resist image is dry-etched under the conditions that the flow rate is 50 sccm and the etching rate of the resist 4 is the same as the etching rate of the substrate 3, and the convex spherical resist image 5 is transferred to the quartz substrate 3. A quartz convex spherical body having a diagonal of 20 μm and a height of 1 μm was formed (FIG. 2C).
[0058]
Example 2
The quartz convex spherical body having a diagonal of 20 μm and a height of 1 μm obtained in Example 1 is used as a matrix, and a photopolymerizable monomer (Nippon Chemical Co., Ltd. 2P monomer INC312) is interposed between the matrix and the substrate. Filled, 20mW / cm²The monomer was polymerized and cured by irradiation with a mercury lamp for 240 seconds at an irradiation intensity of 2 to form a resin concave spherical body having a diagonal of 20 μm and a depth of 1 μm.
[0059]
Example 3
A g-line compatible positive styrene-based photoresist 4 having a γ value of 2.0 is applied on the SiC substrate 3, and a light shielding pattern 2 in which the interval between the light shielding portions, a part of which is shown in FIG. The resist 4 was exposed using a photomask 1 having Pc (Pc = 0.11 μm or less) with an equal-magnification g-line contact exposure machine (FIG. 4A).
[0060]
Next, the photoresist 4 is developed with a developer (AZ developer manufactured by Hoechst), and further subjected to heat treatment at 200 ° C. for 30 minutes, and a sine wave diffraction grating resist having a grating pitch of 105.6 μm and a grating depth of 0.698 μm. An image 5 was formed (FIG. 4B).
[0061]
Subsequently, using a parallel plate type reactive ion etching apparatus, high frequency power of 250 W was supplied, and CF₄The SiC substrate having the sine wave diffraction grating resist image is dry-etched under the condition that the flow rate is 40 sccm and the etching speed of the resist 4 is higher than the etching speed of the substrate 3, and the sine wave diffraction grating resist image 5 is longitudinally applied to the quartz substrate 3. Sine wave diffraction grating having a grating pitch of 105.6 μm and a grating depth of 0.279 μm was formed (FIG. 4C).
[0062]
Example 4
A glass composed of a sine wave diffraction grating having a grating pitch of 105.6 μm and a grating depth of 0.279 μm obtained in Example 3 and comprising 70% by weight of silicon dioxide, 25% by weight of lead oxide, and several other trace element components. Was heated and pressed to form a glass sine wave diffraction grating having a grating pitch of 105.6 μm and a grating depth of 0.279 μm.
[0063]
Example 5
A g-line compatible positive styrene-based photoresist 4 with a γ value adjusted to 0.7 is applied on the SiC substrate 3, and the area occupied by the light-shielding portion gradually increases toward the outer periphery shown in part in FIG. 5. Using the photomask 1 (Pc = 0.50 μm or less) having a ring-shaped light shielding pattern 2 that decreases to a minimum, the resist 4 was exposed using a g-line 5-fold reduction projection exposure machine (FIG. 6A).
[0064]
Next, the photoresist 4 was developed with a developer (AZ developer manufactured by Hoechst) to form a Fresnel lens resist image 5 in which the shape having a diameter of 48 μm and a depth of 3.88 μm was inverted (FIG. 6B).
[0065]
Subsequently, using a parallel plate type reactive ion etching apparatus, high frequency power of 250 W was supplied, and CF₄Under the condition that the flow rate is 40 sccm and the etching rate of the resist 4 is higher than the etching rate of the substrate 3, the SiC substrate having the Fresnel lens resist image having the inverted shape is dry-etched, and the Fresnel lens resist image 5 having the inverted shape is obtained. A SiC Fresnel lens body having a diameter of 48 μm and a depth of 1.55 μm inverted was formed by being compressed and transferred in the vertical direction on the quartz substrate 3 (FIG. 6C).
[0066]
Example 6
The SiC Fresnel lens body obtained by inverting the shape obtained in Example 5 was used as a matrix, and an epoxy resin obtained by mixing Epicoat 152 manufactured by Yuka Shell Epoxy and EpiCure 114 manufactured by Yuka Shell Epoxy Co., Ltd. was used as a matrix. After filling between the mold and the quartz substrate and heat-curing at 30 ° C. for 4 days, the mother mold was peeled off to form an epoxy resin Fresnel lens having a diameter of 48 μm and a height of 1.55 μm.
[0067]
Example 7
A g-line compatible positive styrene-based photoresist 4 having a γ value adjusted to 0.7 is applied on the PMMA substrate 3, and a part thereof (corresponding to the part A in the figure) is shown in FIG. The resist 4 was exposed with a g-line 5-fold reduction projection exposure machine using a photomask 1 (Pc = 0.50 μm or less) having a light-shielding pattern 2 with a gradually changing width (FIG. 8A). .
[0068]
Next, the photoresist 4 was developed with a developer (AZ Developer manufactured by Hoechst) to form a V-groove resist image 5 having a groove angle of 120 ° and a groove depth of 40 μm (FIG. 8B).
[0069]
Subsequently, using a parallel plate type reactive ion etching apparatus, high frequency power of 250 W was supplied, and CF₄Under the conditions that the flow rate is 40 sccm and the etching rate of the resist 4 is slower than the etching rate of the substrate 3, the PMMA substrate having the V-groove resist image is dry-etched, and the V-groove resist image 5 is stretched vertically on the PMMA substrate 3. Thus, a PMMA V-groove mold having a groove angle of 60 ° and a groove depth of 120 μm was formed (FIG. 8C).
[0070]
In addition, when the surface of the microstructure formed in Examples 1 to 7 and the minute press mold was observed with a SEM (scanning electron microscope), it was confirmed that the surface shape was smooth when viewed microscopically. .
[0071]
Although the present invention has been described with reference to the preferred embodiments, the present invention is not necessarily limited to the above embodiments.
[0072]
【The invention's effect】
As described above, according to the three-dimensional surface shape forming method of the present invention, a smooth three-dimensional surface shape can be formed microscopically.
Further, according to the method of the present invention, it is possible to efficiently manufacture a microstructure with a smooth surface whose structure is accurately controlled in three dimensions. This is particularly effective as a production method.
Furthermore, according to the method of the present invention, it is possible to efficiently produce a fine press mold having a smooth surface whose structure is accurately controlled in three dimensions, which could not be obtained conventionally.
[0073]
Further, the micro three-dimensional structure having a three-dimensional surface shape that is smooth from the microscopic viewpoint according to the present invention is an industrial application of a micro optical component that could not be obtained as a practical product. The utility value of is extremely high.
[0074]
Furthermore, according to the press mold of the present invention, the microstructure can be easily mass-produced.
[Brief description of the drawings]
FIG. 1 is a plan view showing a photomask used in an embodiment of the present invention.
FIG. 2 is a process explanatory view showing a manufacturing process in an embodiment of the present invention.
FIG. 3 is a plan view showing a part of a light shielding pattern of a photomask used in another embodiment of the present invention.
FIG. 4 is a process explanatory view showing a manufacturing process in another embodiment of the present invention.
FIG. 5 is a plan view showing a part of a light shielding pattern of a photomask used in another embodiment of the present invention.
FIG. 6 is a process explanatory view showing a manufacturing process in another embodiment of the present invention.
FIG. 7 is a plan view showing a part of a light shielding pattern of a photomask used in another embodiment of the present invention.
FIG. 8 is a process explanatory view showing a manufacturing process in another embodiment of the present invention.
[Explanation of symbols]
1 Photomask
2 Shading pattern
3 Substrate
4 photoresist
5 resist image

Claims (4)

Applying a resist on a substrate to form a resist layer, and exposing the resist layer using a lithography mask having a light-shielding pattern that continuously changes the exposure intensity reaching the resist layer;
A step of developing the resist layer after the exposure to form a three-dimensional resist image;
In the method for forming a three-dimensional shape, including simultaneously etching the resist image and the base material to transfer the three-dimensional shape of the resist image to the base material,
The residual film curve of the resist in the resist layer is a curve obtained by taking the common logarithm of the irradiation amount and the residual film ratio obtained by standardizing the resist film thickness after development with the resist coating film thickness, A method for forming a three-dimensional shape, comprising using a resist and / or resist image forming conditions in which a gamma value, which is a slope of a residual film curve, is 2.0 or less .
However, the gamma value is the slope of the residual film curve when the residual film ratio is 0.5 when the resist is a negative resist, and the residual value when the residual film ratio is 0 when the resist is a positive resist. The slope of the membrane curve . The lithographic mask is a mask in which at least a part of the interval between the light-shielding portions of the mask is an interval below the diffraction limit of the exposure wavelength, or at least a portion of the interval between the opening portions of the mask is an interval below the diffraction limit of the exposure wavelength. The three-dimensional shape forming method according to claim 1, wherein the mask is any one of the masks . The manufacturing method of the microstructure press-molding die which uses the three-dimensional shape formation method of Claim 1 or 2 and manufactures the press-molding die for microstructures . A method for manufacturing a microstructure, wherein the microstructure is manufactured by press molding using the microstructure pressing mold obtained by the method for manufacturing a microstructure pressing mold according to claim 3 .

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