Exposure apparatus

Abstract

To provide an exposure apparatus which is capable of collectively exposing the surface of an object to be exposed having a step, and which makes it possible to realize both fine patterning and enlarged exposure area.SOLUTION: An exposure apparatus 100 according to the present invention exposes an outer surface of an object to be exposed M with speckle light, the apparatus comprising a light source 10 that emits coherent light, a light diffusion member 20 arranged on an optical axis AX of the light source 10, a collimator lens 30 that makes speckle light scattered by the light diffusion member 20 into parallel light, a collimator lens holder 50 by which the collimator lens 30 is movable in an optical axis AX direction, and an object holder 40 that retains the object to be exposed, where the collimator lens 30 is a Fresnel lens.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an exposure apparatus. [Background technology]

[0002] In recent years, it has become known that by processing irregular structures on the surface of materials on the order of micrometers to submicrometers, it is possible to impart functions that the material itself does not have. The size and density of the structures created on the surface can greatly change the functions, leading to a wide range of applications.

[0003] Functions that can be imparted include imparting water repellency or hydrophilicity (for example, improving dispensing residue by processing the tip of a pipette tip, or use in dispensing equipment, medical equipment, and analytical equipment), imparting high lubricity (for example, reducing wear and friction in sliding parts. By micro-processing (dimples) on the metal surface and storing oil in them, wear and friction in sliding parts can be reduced), and imparting a friction reduction effect (for example, improving sliding properties by controlling frictional force through a reduced contact area, improving engine combustion energy in the automotive industry, and extending the lifespan of parts by suppressing deterioration).

[0004] Methods for producing fine structures on metal surfaces include machining for micrometer-order structures, and direct processing methods using energy beams (ion beams, high-power lasers such as femtosecond lasers (ultra-short pulse lasers) and thermal lithography) for structures on the sub-micrometer order, as well as methods using electron beams and synchrotron light, which result in highly precise structures. Another method of microfabrication is optical lithography. Optical lithography uses a mask, which is the original image of the pattern, and projects the mask pattern at a reduced size by irradiating the mask from above through a projection lens. This makes it an excellent processing method for reducing patterns, and is suitable for producing multiple items identical to the mask pattern with high precision. The resolution R in exposure using a reduction projection lens is expressed by equation (1) and depends on the wavelength λ of the light source and the numerical aperture NA (sinθ: in air) of the projection lens. Here, k1 is the process factor. From equation (1), it can be seen that the shorter the wavelength and the larger the numerical aperture, the higher the resolution and the finer the patterns that can be transferred. The depth of focus DOF ​​is expressed by equation (2), where k2 is the process factor. From equations (1) and (2), it can be seen that if the NA (sinθ) is increased to increase the resolution and create a finer pattern, the depth of focus decreases exponentially. In other words, the finer the pattern that is obtained, the shallower and smaller the depth of focus becomes.

[0005]

number

[0006] Optical lithography using speckle light is known as a microfabrication technique for irregular patterns (see, for example, Patent Document 1). This technique involves irradiating a light diffusing material with light to generate speckle light, which is then projected onto an object coated with photosensitive resin, thereby transferring randomly shaped fine patterns without the need for a mask. For this reason, it has attracted attention as a technique capable of transferring fine patterns on the micrometer to submicrometer order without using a master with a predetermined pattern or a reduction projection lens. By irradiating speckle light onto a surface coated with photosensitive resin, it is possible to create fine photosensitive resin patterns on the micrometer to submicrometer order. By using this as a masking material for metal etching, fine structures can be created on metal surfaces. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-140967 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in methods using energy beams, not only are the lasers themselves expensive, but they cannot be used to expose objects with a wide variety of shapes, such as three-dimensional surfaces with steps other than flat surfaces. For this reason, they cannot be easily used when prototyping products, and their applications are limited. Currently, there is no microfabrication method that can be used easily and inexpensively on three-dimensional surfaces. Furthermore, even with optical lithography, there are problems with the exposure area becoming narrower when the reduction projection magnification is increased as the pattern becomes finer, and because a projection lens is used, the depth of focus becomes shallower depending on the size of the pattern to be transferred according to the above formula (2), so fine patterns cannot be produced in a single exposure on an exposed object with steps.For this reason, optical lithography is only used on highly flat surfaces such as silicon wafers, and it is generally not possible to expose fine patterns on surfaces with large steps in a single process.

[0009] Optical lithography technology using speckle light is designed for flat plates. Therefore, it is not possible to transfer a pattern in one go onto a three-dimensional surface, for example, where the surface of the object to be exposed has steps of several millimeters to several tens of centimeters. This is because the light intensity distribution of the speckle light depends on the distance from the master light diffusion member to the object to be exposed. In other words, as shown in Figure 9, the light intensity distribution of the speckle light weakens in proportion to the square of the distance between the light diffusion member and the object to be exposed, so it is not possible to expose an object with large steps under the same exposure conditions. Furthermore, the light intensity distribution of the speckle light causes the pattern arrangement to become wider in proportion to the distance, which changes the density of the transferred fine pattern.

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide an exposure apparatus that is capable of performing exposure in one go on the surface of an exposure object having steps, and that is capable of achieving both finer patterns and larger exposure areas. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides the following means.

[0012] A first aspect of the present invention is an exposure apparatus that exposes an object to light using speckle light, comprising: a light source that emits coherent light; a light diffusion member that is arranged on the optical axis of the light source; a collimating lens that converts the speckle light scattered by the light diffusion member into parallel light; a collimating lens holder that can move the collimating lens in the optical axis direction; and an object holder that holds the object to be exposed, wherein the collimating lens is a Fresnel lens or a microlens array.

[0013] A second aspect of the present invention is an exposure apparatus according to the first aspect, further comprising a grayscale mask disposed on the optical axis between the light diffusing member and the collimating lens.

[0014] A third aspect of the present invention is an exposure apparatus according to the first or second aspect, wherein the collimator lens is a microlens array, and each element lens constituting the microlens array is a Fresnel lens.

[0015] A fourth aspect of the present invention is an exposure apparatus according to the second or third aspect, wherein the collimator lens is a microlens array, and each element lens constituting the microlens array is an aspherical lens.

[0016] A fifth aspect of the present invention is the exposure apparatus of any one of the first to fourth aspects, wherein the collimator lens is detachable from the collimator lens holder and replaceable.

[0017] A sixth aspect of the present invention is an exposure apparatus according to any one of the first to fifth aspects, wherein the light diffusing member is detachable and replaceable. [Effects of the Invention]

[0018] The exposure apparatus of the present invention can provide an exposure apparatus that can expose the surface of an exposure object having steps all at once, and can simultaneously achieve finer patterns and larger exposure areas. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a conceptual diagram of an embodiment of an exposure apparatus according to the present invention. [Figure 2] 1A and 1B are schematic diagrams showing an example of a Fresnel lens used as a collimating lens in an exposure apparatus according to the present invention, where FIG. 1A is a diagram illustrating the principle of the Fresnel lens, and FIG. 1B is a schematic diagram showing the propagation direction of light. [Figure 3] FIG. 10 is a conceptual diagram of another embodiment of the exposure apparatus according to the present invention. [Figure 4] 4A and 4B are schematic diagrams showing an example of a microlens array used as a collimating lens in an exposure apparatus according to the present invention, in which (a) is a perspective schematic diagram showing an example of a microlens array, and (b) is a schematic diagram showing the propagation direction of light before and after the microlens array. [Figure 5] 1 is a cross-sectional view showing a schematic configuration of an exposure apparatus according to the present invention. [Figure 6] FIG. 10 is a schematic diagram illustrating an example of a grayscale mask. [Figure 7] FIG. 10 is a flowchart showing a procedure for step exposure. [Figure 8] The distance between the Fresnel lens and the silicon wafer was changed assuming a step of 50 mm in the depth direction of the optical axis relative to the reference plane (0 mm), and the image was exposed for the same exposure time, developed, and then observed with an optical microscope. [Figure 9] This is a conceptual diagram to explain that the light intensity distribution of speckle light weakens with the square of the distance, and that the density changes because the pattern arrangement becomes wider in proportion to the distance. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional proportions of each component may differ from the actual dimensions. The dimensions and other details exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the effects of the present invention. Hereinafter, even if not specifically explained, the configuration described in one embodiment may be applied to other embodiments.

[0021] FIG. 1 shows a conceptual diagram of an embodiment of an exposure apparatus according to the present invention. The exposure apparatus 100 shown in FIG. 1 is an exposure apparatus capable of exposing the surface Ma of an exposure object M having a step D using speckle light S, and is equipped with a light source 10 that emits coherent light, a light diffusing member 20 that is arranged on the optical axis AX of the light source 10, and a collimating lens 30 that converts the speckle light scattered by the light diffusing member 20 into approximately parallel light, in which the collimating lens 30 is a Fresnel lens. The exposure apparatus 100 shown in FIG. 1 uses a Fresnel lens with a structure divided into areas on the lens surface as a collimating lens, which allows a pattern to be transferred in a single process to an object having a large step, and furthermore, it is possible to achieve both finer patterns and larger exposure areas.

[0022] A cross-sectional schematic diagram showing an example of a Fresnel lens is shown in Figure 2. Figure 2(a) is used to explain the principle of the Fresnel lens, and Figure 2(b) is a schematic diagram showing the propagation direction of light. A Fresnel lens is a lens in which the curved portions of a lens are arranged in concentric regions on a plane, based on the principle that the propagation direction of light does not change within a certain medium and is refracted only at the surface of the medium. This allows for a lens with a short focal length while reducing the space and weight in the optical axis direction. Furthermore, compared to optical systems that combine multiple lenses in the optical axis direction, such as single lenses, aspherical lenses, or lenses, the area perpendicular to the optical axis can be increased, thereby increasing the light capture area. As shown in Figure 2(a), the Fresnel lens can be said to be a replacement for a conventional optical lens, where the curved surface is divided into concentric rings in order to reduce the thickness of the lens.

[0023] The Fresnel lens may be spherically aberrated, with smaller spherical aberration resulting in better collimation.

[0024] FIG. 3 shows a conceptual diagram of another embodiment of the exposure apparatus according to the present invention. The exposure apparatus 200 shown in FIG. 3 is an exposure apparatus capable of exposing the surface Ma of an exposure object M having a step D using speckle light S, and is equipped with a light source 10 that emits coherent light, a light diffusion member 20 that is arranged on the optical axis AX of the light source 10, and a collimating lens 31 that converts the speckle light scattered by the light diffusion member 20 into approximately parallel light, in which the collimating lens 31 is a microlens array. The exposure apparatus 200 shown in Figure 3 uses a microlens array with a structure divided into areas on the lens surface as a collimating lens, which allows patterns to be transferred in a single process to an object to be exposed that has large steps, and further enables both finer patterns and larger exposure areas to be achieved.

[0025] Fig. 4(a) is a perspective schematic diagram showing an example of a microlens array, and Fig. 4(b) is a schematic diagram showing the propagation direction of light before and after the microlens array. A microlens array is a collection of lenses, each of which has a size ranging from mm to μm, arranged side by side, and is sometimes called a fly's eye lens because it resembles the compound eyes of a fly.

[0026] Each element lens of the microlens array may be a Fresnel lens. Each element lens of the microlens array may be an aspherical lens. A microlens array made up of spherical lenses may not be able to collimate properly due to the influence of spherical aberration.

[0027] The exposure apparatus of the present invention is an optical lithography technology that applies speckle light to the surface of a photosensitive material to transfer patterns with irregular arrangements and shapes, and is an exposure apparatus that can transfer fine patterns of several μm in size in one go (with a single exposure) onto a three-dimensional exposure object that has a large step in the depth direction exceeding 20 cm. There is a strong need in optical lithography technology for microfabrication of not only flat surfaces but also three-dimensional surfaces with steps. However, methods using energy beams and optical lithography technology cannot handle the wide variety of shapes with steps other than flat surfaces. Furthermore, even if optical lithography technology is simply used that utilizes speckle light, the speckle light spread by the light diffusing element weakens with the square of the distance, making it impossible to expose large steps under the same exposure conditions. Furthermore, the pattern arrangement becomes wider in proportion to the distance, resulting in changes in pattern density. For this reason, it is not possible to simultaneously expose fine patterns of several microns to objects other than flat surfaces. The exposure apparatus of the present invention solves these problems.

[0028] FIG. 5 is a cross-sectional view showing the general configuration of the exposure apparatus according to the first embodiment. The exposure apparatus 300 shown in FIG. 5 is an exposure apparatus capable of exposing the surface Ma of an exposure object M having a step D using speckle light S, and includes a light source 10 that emits coherent light, a light diffusion member 20 that is arranged on the optical axis AX of the light source 10, a collimating lens 30 that converts the speckle light scattered by the light diffusion member 20 into parallel light, a collimating lens holder 50 that can move the collimating lens 30 in the direction of the optical axis AX, and an exposure object holder 40 that holds the exposure object. The exposure apparatus 300 can perform exposure all at once on the surface Ma of the exposure object M, which has a step D. The step D is, for example, 1 mm to several hundreds of mm.

[0029] The exposure apparatus 300 shown in Figure 5 further includes an illumination optical system 11 that controls the illumination area located between the light source 10 and the light diffusion member 20, a light diffusion member holding base 60 that supports the light diffusion member 20, a light source support section 70 that supports the light source 10 via a fixed base 2 on which the light source 10 is placed, and a mounting base 1 on which the entire exposure apparatus is placed.

[0030] <Exposed object> The exposure object M exposed by the exposure apparatus according to this embodiment is, for example, a three-dimensional object having a step D, but it is also possible to expose a three-dimensional object that does not have a step D. In addition, the three-dimensional object may have a cross section with a curved periphery such as a circle or ellipse, or a polygonal shape such as a rectangle.

[0031] Examples of the object to be exposed M include not only highly flat silicon wafers, but also three-dimensional structures made of metals such as aluminum, stainless steel, brass, etc. When the object to be exposed M is exposed, the object to be exposed is exposed in a state where a photosensitive material (resist) is attached to its surface Ma to a predetermined thickness (for example, 1 μm to several hundred μm). The object to be exposed M is held in a detachable state by a holding mechanism such as a suction jig (not shown).

[0032] <Light source, illumination optical system> Examples of light sources that emit coherent light include lasers and LDs (laser diodes). Light from the light source can be guided to the exposure device via fiber and connected with an FC connector. Using an FC connector allows for reproducible attachment and detachment, so changing the wavelength of the light source can be achieved by simply replacing the light source with another one, eliminating the need for a large-scale optical system.

[0033] The exposure apparatus 300 shown in Figure 5 has an illumination optical system 11 that controls the illumination area between the light source 10 and the light diffusion member 20, but it may also be configured to directly irradiate the coherent light emitted from the light source 10 onto the light diffusion member 20. The light beam emitted from the light source 10 is expanded or contracted by the illumination optical system 11 (11a, 11b, 11c in the example shown in FIG. 5) and illuminates the light diffusing member 20 at a predetermined size.

[0034] <Light diffusing material> By irradiating a coherent light onto a light diffusing member, it is possible to generate speckle light, which is scattered light with a random arrangement and a random shape of light intensity. By installing a collimating lens system so that the light diffusing member is located approximately at the focal position of the spread speckle light, the light rays become parallel, and it is possible to transfer the light intensity distribution pattern of the speckle light all at once onto the surface of an exposed object with large steps.

[0035] The light diffusing member 20 shown in FIG. 5 is of a transmissive type, but may also be of a reflective type. In the case of a transmission type light diffusing member, it may be a diffusion plate made of flat glass with one or both sides roughened, or it may be opal glass or phase-separated glass that diffuses light inside the material. In the case of a reflective light diffusing member, it may be a diffusion plate whose surface is processed to be rough, or it may be a reflective light diffusing member whose surface is coated with a perfect diffusion material such as Spectralon.

[0036] The light diffusion member 20 may be detachable from the light diffusion member holder 60 .

[0037] <Collimating lens> Generally, a collimating lens is an optical system that is used to convert divergent light into parallel light and is composed of a single spherical or aspherical lens or multiple lenses arranged in the optical axis direction. However, the collimating lens 30 shown in FIG. 5 is a Fresnel lens, and can also be a microlens array.

[0038] When a Fresnel lens is used as a collimating lens, a commercially available one (for example, manufactured by Sigma Koki) is thin, only 2 mm thick, has a short focal length of 3 mm, and can collimate light over a wide area with a diameter of 15 mm. As will be described in detail later in the section on the principles of speckle pattern formation, lenses with short focal lengths are advantageous for finer patterns. However, shortening the focal length generally reduces the lens diameter, reducing the range over which light can be collimated. Even with a short focal length, Fresnel lenses can be manufactured with a large area perpendicular to the optical axis, making it possible to collimate light over a large area. Utilizing speckle light collimated over this large area makes it possible to achieve both finer patterns and larger exposure areas. If a Fresnel lens is used as a collimating lens in speckle lithography, it is possible to obtain a large depth of field, while achieving both finer patterns and larger exposure areas.

[0039] Furthermore, when a microlens array is used as a collimating lens, the use of multiple lenses with shorter focal lengths ensures a large depth of field, while simultaneously achieving both finer patterning and a larger exposure area compared to optical systems consisting of a single spherical or aspherical lens or multiple lenses arranged in the optical axis direction. As will be described in detail in the speckle pattern formation principle below, lenses with short focal lengths are advantageous for finer patterning. However, shortening the focal length generally reduces the lens diameter and the range over which light can be collimated. By using microlenses with short focal lengths and a large number of arrays, which are components of a microlens array, and by arranging multiple microlens arrays perpendicular to the optical axis to increase the lateral area, it is possible to further expand the range of incident light compared to a Fresnel lens and collimate a larger range of light. By increasing the illumination area on the light diffuser to increase the scattering area and then collimating the light scattered over a larger range by the microlens array, it is possible to easily expand the exposure area while achieving finer patterning.

[0040] The collimating lens 30 is held by a collimating lens holder 50 that is movable in the optical axis direction.

[0041] By configuring at least one of the light diffusing member 20 and the collimating lens 30 to be movable in the direction of the optical axis AX, it is possible to adjust the distance between the light diffusing member 20 and the collimating lens 30. This makes it possible to use collimating lenses with different focal lengths, and to control the shape of the pattern transferred to the exposed object.

[0042] <Exposed object holder> The exposure object M is held by an exposure object holder. The exposure object holder preferably includes a movement mechanism (exposure object movement mechanism) for moving the position and orientation of the exposure object, either separately or integrally.

[0043] 5 is placed on the mounting table 1. The exposure object holding table 40 is equipped with a gripping portion 40a that grips the exposure object M, a z-axis rotation stage 40b on which the gripping portion 40a is placed and which is rotatable about the z-axis, a z-axis translation stage 40c on which the z-axis rotation stage 40b is placed and which is translatable in the z direction (direction perpendicular to the xy plane), a y-axis rotation stage 40d on which the z-axis translation stage 40c is placed and which is rotatable about the y-axis, and an x-axis translation stage 40e on which the y-axis rotation stage 40d is placed and which is translatable in the x-axis (optical axis) direction. The exposure object holder 40 may further include a y-axis translation stage capable of translation in the y direction (a direction perpendicular to the x direction in a horizontal plane) and an x-axis rotation stage capable of rotation about the x axis.

[0044] <Collimating lens holder> The collimating lens holder supports the collimating lens from below. The collimator lens holder includes a movement mechanism (collimator lens movement mechanism) that moves the position and orientation of the collimator lens. The collimator lens moving mechanism has a moving mechanism that can move translationally in the optical axis (light ray) direction, so that when a collimator lens with a different focal length is attached, the collimator lens moving mechanism can be moved relatively to a predetermined position to adjust the relative distance between the light diffusion member 20 and the collimator lens 30 to a predetermined distance.

[0045] 5 is placed on a mounting table 1. The collimating lens 30 is supported by the collimating lens holding table 50 placed on the mounting table 1. The collimating lens holding table 50 includes a support portion 50a that directly supports the collimating lens 30, a z-axis translation stage 50b on which the support portion 50a is placed and which is capable of translational movement in the z-axis direction, a y-axis rotation stage 50c on which the z-axis translation stage 50b is placed and which is rotatable about the y-axis, and an x-axis translation stage 50d on which the y-axis rotation stage 50c is placed and which is capable of translational movement in the x-axis (optical axis) direction. The collimator lens holder 50 may further include a y-axis translation stage that can translate in the y direction (a direction perpendicular to the x direction in a horizontal plane), an x-axis rotation stage that can rotate about the x axis, and a z-axis rotation stage that can rotate about the z axis.

[0046] In the exposure apparatus 300 shown in Figure 5, the collimator lens holder 50 has an x-axis translation stage 50d, so when collimator lenses with different focal lengths are used, the relative distance between the light diffusion member 20 and the collimator lens 30 can be maintained at a predetermined distance by translating the collimator lens 30 in the optical axis direction. Furthermore, in the exposure apparatus 300 shown in Figure 5, the light diffusion member holding base 60 has an x-axis translational movement stage 60d, so that the light diffusion member 20 can be moved relative to a predetermined position with respect to the collimator lens 30 by translating the light diffusion member 20 in the optical axis direction without moving the collimator lens 30. Furthermore, in the exposure apparatus 300 shown in FIG. 5, the light diffusion member 20 can be moved relative to a predetermined position of the collimator lens 30 by using both the x-axis translational movement stage 60d of the light diffusion member holding base 60 and the x-axis translational movement stage 50d of the collimator lens holding base 50 to translate both the light diffusion member 20 and the collimator lens 30 relatively in the optical axis direction.

[0047] <Positioning of the object to be exposed> The object M to be exposed is attached to a suction jig (not shown) or the like and positioned so that it is within the range of the exposure light. Also, it is positioned so that the surfaces Ma1, Ma2, and Ma3 to be exposed are perpendicular to the optical axis AX. If positioning is difficult, this can be resolved by changing the exposure light source to a wavelength to which the resist is insensitive and illuminating the diffusing material. The speckle light emitted from the diffusing material is illuminated within a circular range by a collimating optical system. The stage (object holder) attached to the object is adjusted so that the object coincides with this light.

[0048] As another method, there is also a method in which positioning is carried out in advance using an exposure object for positioning that is different from the exposure object, and then the exposure object is changed to exposure object M and exposed.

[0049] Once the positioning of the object to be exposed M is complete, it is exposed for a predetermined time using an exposure light source with the photosensitive wavelength of the resist. After exposure, the object to be exposed M is developed to form a resist pattern. When a positive resist is used, the resist is removed where the light hits, and when a negative resist is used, the areas where the light hits remain as a structure.

[0050] <Light diffusion material holder> The light diffusion member holder supports the light diffusion member from below. The light diffusion member holder preferably includes a moving mechanism (light diffusion member moving mechanism) for moving the position and orientation of the light diffusion member, either separately or integrally.

[0051] 5 is placed on the mounting table 1. The light diffusing member 20 is supported by the light diffusing member holding table 60 placed on the mounting table 1. The light diffusing member holding table 60 includes a support portion 60a that directly supports the light diffusing member 20, a z-axis translation stage 60b on which the support portion 50a is placed and which is capable of translational movement in the z-axis direction, a y-axis rotation stage 60c on which the z-axis translation stage 60b is placed and which is rotatable about the y-axis, and an x-axis translation stage 60d on which the y-axis rotation stage 60c is placed and which is capable of translational movement in the x-axis (optical axis) direction.

[0052] <Light source support part> The light source support portion supports the light source from below. The light source support portion preferably includes a moving mechanism (light source moving mechanism) that moves the position and orientation of the light source, either separately or integrally.

[0053] 5 is placed on a mounting table 1. The light source 10 is supported by the light source support 70 placed on the mounting table 1 via a fixed base 2. The light source support 70 is equipped with a z-axis rotation stage 70a that is rotatable about the z-axis, a z-axis translation stage 70b on which the z-axis rotation stage 70a is placed and which is capable of translational movement in the z direction (a direction perpendicular to the xy plane), a y-axis rotation stage 70c on which the z-axis translation stage 70b is placed and which is rotatable about the y-axis, and an x-axis translation stage 70d on which the y-axis rotation stage 70c is placed and which is capable of translational movement in the x-axis (optical axis) direction. The light source support 70 may further include a y-axis translation stage capable of translation in the y direction (a direction perpendicular to the x direction within a horizontal plane), and an x-axis rotation stage capable of rotation about the x axis.

[0054] <Principles of pattern formation> In the following, in order to briefly explain the pattern formation principle of the present invention, the case where a normal collimating lens is used will be explained. The same logic applies even if the collimating lens is replaced with a Fresnel lens or a microlens array. The following explanation will also show that in the exposure principle of the present invention, the collimating lens is not used in the illumination optical system, but in the imaging optical system required to form the pattern. In other words, the collimating lens is not installed between the light source and the light diffusing member, but is installed between the light diffusing member that serves as the master and the object to be exposed, and parameters such as the focal length of the collimating lens play an important role that is directly related to pattern formation. The size, shape, and density of the resist pattern produced using the exposure apparatus of this embodiment vary depending on the exposure wavelength, laser illumination area, focal length of the collimating lens, surface roughness of the light diffusing member, and exposure time. Relational formula (3) is shown below. To produce a small resist pattern, the exposure wavelength should be short, the illumination area should be large, the focal length of the collimating lens should be short, the surface roughness of the diffusing material should be high (high scattering), and the exposure time should be short. When a positive resist is used, a small hole pattern is produced in the resist. When a negative resist is used, a needle-shaped pattern is produced. In the following formula, R is the size of the pattern transferred to the resist, λ is the wavelength of the laser light, D is the irradiation diameter of the laser light, S is the roughness of the light diffusing member, f is the focal length of the collimating lens, and t is the exposure time.

[0055]

number

[0056] Next, regarding resist pattern density, if you want to increase the density of the resist pattern, you need to shorten the exposure wavelength, increase the illumination area, shorten the focal length of the collimator lens, increase the surface roughness of the diffusing material (increase scattering), and increase the exposure time. In the following equation (4), W is the resist pattern density, λ is the wavelength of the laser light, D is the irradiation diameter of the laser light, S is the roughness of the light diffusing material, f is the focal length of the collimator lens, and t is the exposure time.

[0057]

number

[0058] <Grayscale mask> A grayscale mask with a stepwise change in transmittance as shown in FIG. 6 may be provided between the light diffusing member and the collimating lens on the optical axis. Within the exposure area, pattern non-uniformity occurs due to the strong light in the center and weak light on the periphery. As a result, a pattern cannot be formed across the entire exposure area, and only partially near the center or periphery. Therefore, to eliminate the non-uniformity of the light intensity distribution, the intensity distribution is measured in advance using a light intensity meter or similar device, and a grayscale mask is prepared that reflects this measurement. By placing the mask between the Fresnel lens and the diffuser, the uniformity of the light that passes through the Fresnel lens is improved, allowing a pattern to be formed across the entire exposure area.

[0059] Resist can be applied uniformly to the surface of the object to be exposed by known methods such as spin coating, which creates a uniform film by dropping and rotating a photosensitive substance, spraying, or dipping the object in the photosensitive substance and then pulling it out (dip coating).By changing the application conditions, the thickness of the resist film applied to the surface of the object to be exposed can be adjusted as desired, from 1 μm to several hundred μm.

[0060] (Exposure method) The exposure apparatus according to the present invention is used to carry out the following steps: - A step of directing light from a light source onto a light diffusing member; A step of collimating the light scattered by the light diffusing member using a collimating lens; A step of placing an object to be exposed coated with a photosensitive material at a predetermined position on the optical axis; - exposing the object to scattered light for a predetermined time; can be carried out to expose the object to be exposed.

[0061] (Exposure procedure) The procedure of step exposure will be described as an example of an exposure method using the flow chart of FIG. First, in step S1, a photosensitive material is applied to the object to be exposed. This photosensitive material is called resist, and is a resin that reacts when exposed to light of a specific wavelength band. For example, if a negative resist such as SU-8 is used, only the areas exposed to light are exposed, and a resist pattern of the exposed areas remains after development. If a positive resist such as THMR-iP3300 is used, only the areas exposed to light are exposed, and the resist pattern of the exposed areas is removed after development, leaving a hole pattern. The photosensitive material can be applied uniformly to the surface of the object to be exposed by spin coating, which creates a uniform film by dripping and rotating the photosensitive material, spraying, or dip coating, which involves immersing the object in the photosensitive material and then removing it. The film thickness can be adjusted freely from 1 μm to several hundred μm.

[0062] In step S2, an object having the same shape as the object to be exposed is placed in advance in the exposure apparatus, and the positional relationship between the object to be exposed, the collimator lens, etc. is adjusted.

[0063] In step S3, the exposure object, which is the object to be actually exposed, is attached to a chuck (not shown) for fixing the exposure object. In step S4, a desired light diffusing member is installed. In step S5, the power source of the light source is turned on to irradiate the light diffusing member with light for a predetermined period of time, thereby starting exposure of the object to be exposed.

[0064] In step S6, exposure is continued until a predetermined exposure amount is reached. In step S7, when a predetermined exposure amount is reached, the power source of the light source is turned off. In step S8, it is determined whether or not to expose other portions of the object. In step S9, if exposure of another location is to be performed, the exposure object is attached and moved in the axial direction and / or in the direction of rotation about the axis using a movement mechanism provided on the exposure object holder on which the exposure object is placed, and exposure of the other location is started. When there are no more locations to be exposed, exposure is finished.

[0065] In step S10, the exposed object is removed and a development process is carried out, which forms a predetermined pattern of the photosensitive material. In step S11, etching or plating is performed as necessary. The photosensitive material pattern can be used as a masking material for etching, allowing the desired pattern to be removed from the exposed object. Furthermore, plating prevents plating from directly adhering to areas covered with the photosensitive material pattern, allowing for the creation of a clean, desired male pattern.

[0066] The above steps omit details of bake and post-exposure bake, which are typically performed with exposure.

[0067] If it is desired to continuously transfer a photosensitive resin pattern, in step S6, scanning exposure is performed by continuously moving the object to be exposed while irradiating it with light from the light source. By moving the object to be exposed horizontally along the optical axis, a linear pattern can be exposed.

[0068] By the above steps, an irregular pattern can be transferred all at once onto the outer surface of the object to be exposed. [Example]

[0069] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0070] Exposure was carried out using the exposure apparatus shown in FIG. 5 to form a resist pattern.

[0071] Figure 8 shows the results of applying a 1 μm thick layer of positive resist THMR-iP3300 to a silicon wafer, using a Fresnel lens with a focal length of 30 mm and dimensions of 150 mm x 150 mm as the collimating lens, and varying the distance between the collimating lens and the silicon wafer, assuming a 50 mm step in the depth direction of the optical axis, exposing the sample for the same exposure time, developing it, and then observing it with an optical microscope.

[0072] It can be seen that hole patterns of about several μm in size are created in the resist for both the reference surface and the stepped surface under the same exposure conditions. This shows that even when an exposure target with a step of 50 mm is used, holes of several μm in size are formed on the surface with irregular shapes and arrangements, and that the fine resist pattern can be exposed all at once on the stepped surface. [Explanation of symbols]

[0073] 10 light source 20 Light diffusion material 30 Collimating lens (Fresnel lens) 31 Collimating lens (microlens array) 40 Exposed object holder 50 Collimating lens holder 60 Light diffusion member holder 100, 200, 300 exposure equipment

Claims

1. An exposure apparatus that exposes an object using speckle light, a light source that emits coherent light; a light diffusing member disposed on the optical axis of the light source; a collimator lens that converts the speckle light scattered by the light diffusing member into parallel light; a collimator lens holder that can move the collimator lens in the optical axis direction; an exposure object holder that holds the exposure object, The exposure apparatus, wherein the collimating lens is a Fresnel lens or a microlens array.

2. The exposure apparatus according to claim 1 , further comprising a grayscale mask on the optical axis between the light diffusing member and the collimating lens.

3. 3. The exposure apparatus according to claim 1, wherein the collimating lens is a microlens array, and each element lens constituting the microlens array is a Fresnel lens.

4. 3. The exposure apparatus according to claim 1, wherein the collimating lens is a microlens array, and each element lens constituting the microlens array is an aspherical lens.

5. 3. The exposure apparatus according to claim 1, wherein the collimator lens is detachable from the collimator lens holder and replaceable.

6. 3. The exposure apparatus according to claim 1, wherein the light diffusing member is detachable and replaceable.

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