Internal exposure apparatus

Abstract

To provide an inner-surface exposure device capable of applying lithography onto an inner surface of a hollow of a solid structure having the hollow, with one shot.SOLUTION: An inner-surface exposure device 100 exposes an inner surface Mb of a hollow Ma of an exposure target M having the hollow Ma. The inner-surface exposure device includes: a light source 10; an exposure mask 20 to be arranged between the light source 10 and an exposure target M; a reflection mirror 30 to be arranged inside a hollow Ma of the exposure target M and having a reflection surface 30a capable of reflecting light emitted from the light source 10 and transmitted through the exposure mask 20 onto an inner surface Mb of the hollow Ma; a reflection mirror holding part 40 configured to hold the reflection mirror 30; and an exposure target stage 50 configured to support the exposure target M.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inner surface exposure device.

Background Art

[0002] Conventionally, for the precision machining of cylindrical materials, cutting machining has been used, and machining using a tool called a tool bit has been performed. However, with the miniaturization, high-precision, and energy-saving of products, the parts to be machined have become smaller and more precise, and there have been cases where machining on the extension line of conventional machining cannot cope. Therefore, in recent years, a method of machining by thermal reaction using a high-energy laser has been developed and put into practical use. It is a method of machining a desired shape by melting and evaporating with heat by laser light.

[0003] On the other hand, lithography technology can be cited as a microfabrication technology in the micro- to nano-order dimension range. Lithography is a microfabrication technology used in the manufacture of semiconductor integrated circuits, optoelectronic devices, liquid crystal panels, and the machining of various sensors and actuators. It is a technology that passes light from a light source through a master plate (reticle, mask) that patterns the light, and irradiates a substrate having a photosensitive substance on its surface to transfer the pattern. Visible light, ultraviolet light, far ultraviolet light, vacuum ultraviolet light, extreme ultraviolet light, X-rays, electron beams, and ion beams are used as light sources, and the emitted light rays or particle beams are irradiated onto the resist of the photosensitive substance in a desired shape to cause photosensitivity, and then, by a subsequent development process, the photosensitive part is retained or removed to obtain a fine pattern of the photosensitive substance having a desired shape.

[0004] To cause the photosensitive substance to be photosensitive to a desired pattern, a master plate (reticle, mask) having a pattern is used to control the transmission and blocking of light. In particular, in the case of a light source with strong directivity such as X-rays or lasers, the transmitted light is directly irradiated onto the object to be exposed for exposure. For other light sources, the light passing through the mask or reticle is projected onto the object to be exposed by a projection optical system using a lens or a mirror, or a projection optical system combining a lens and a mirror, and an image of the pattern on the mask or reticle is formed for exposure.

[0005] Traditionally, this lithography technology has utilized flat substrates with good flatness, such as semiconductor wafers and glass substrates, as the objects to be exposed. Recently, however, processing techniques for applying lithography to curved objects such as cylindrical or cylindrical shapes have been proposed (see Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-171896 [Patent Document 2] Patent No. 5067757 [Overview of the project] [Problems that the invention aims to solve]

[0007] Patent Document 1 discloses a projection exposure method and apparatus in which a pattern on a reticle is projected onto the outer surface of a cylindrical object to be exposed via a projection lens, using visible light as the exposure light source, thereby forming a light image of the pattern, and exposing a resist coated on the outer surface of the object to be exposed to light to form the pattern. However, this method cannot be used to perform lithography on structures such as cylinders or rectangular tubes, which are surrounded and have an inner surface that is not directly exposed to light from the surface.

[0008] To address this problem, Patent Document 2 discloses an exposure apparatus and exposure method that includes a guide rod on which optical fibers and reflective elements are arranged to guide exposure light rays, and by moving and changing the angle of the guide rod relative to the object to be exposed, the light irradiated by the optical fibers and reflective elements is directed onto a photosensitive material coated on the inside of the object to be exposed, thereby exposing the photosensitive material to a predetermined pattern.

[0009] None of the above methods can be used to apply lithography to the entire inner surface of a hollow three-dimensional structure.

[0010] This invention has been made in view of the above circumstances, and aims to provide an internal exposure apparatus capable of performing lithography on the inner surface of a hollow three-dimensional structure all at once. [Means for solving the problem]

[0011] To solve the above problems, the present invention provides the following means.

[0012] An internal exposure apparatus according to one aspect of the present invention is an internal exposure apparatus for exposing the inner surface of a hollow object to be exposed, comprising: a light source; an exposure mask disposed between the light source and the object to be exposed; a reflective mirror disposed in the hollow and having a reflective surface capable of reflecting light from the light source that has passed through the exposure mask to the inner surface of the hollow; a reflective mirror holding part for holding the reflective mirror; and an object to be exposed stage for supporting the object to be exposed.

[0013] The internal exposure apparatus according to the above embodiment may include a projection optical system that causes light transmitted through the exposure mask to form a predetermined pattern on the hollow inner surface.

[0014] In the internal exposure apparatus according to the above embodiment, the reflective mirror may have a vertex on its surface that is closest to the light source, and a sloped surface formed such that it approaches the internal surface as it moves away from the light source.

[0015] In the internal exposure apparatus according to the above embodiment, the reflective surface may be conical, polygonal pyramidal, or convex spherical in shape.

[0016] In the above embodiment, the internal exposure apparatus may be positioned such that the vertex is offset from the optical axis when viewed from the optical axis direction.

[0017] The internal exposure apparatus according to the above embodiment may include at least one of the following: an object to be exposed stage that moves in the direction in which the light from the light source travels, and a reflective mirror moving mechanism that moves the reflective mirror holding part in the direction in which the light from the light source travels.

[0018] In the internal exposure device according to the above aspect, the object to be exposed moving mechanism may have a six-axis adjustment mechanism that can be adjusted in six axes including the translation directions of the xyz axes orthogonal to each other and the rotation directions around the axes parallel to the x, y, and z axes.

[0019] In the internal exposure device according to the above aspect, the reflecting mirror moving mechanism may have a six-axis adjustment mechanism that can be adjusted in six axes including the translation directions of the xyz axes orthogonal to each other and the rotation directions around the axes parallel to the x, y, and z axes.

[0020] The internal exposure device according to the above aspect may include an object to be exposed rotating mechanism that rotates the object to be exposed around the optical axis.

[0021] In the internal exposure device according to the above aspect, as a projection optical unit installed on a fixed base such that the light source, the illumination optical system, the exposure mask, and the projection optical system have the same optical axis, it may be integrally movable and rotatable.

[0022] In the internal exposure device according to the above aspect, as an exposure unit installed in a transparent container such that the light source, the illumination optical system, the exposure mask, the projection optical system, and the reflecting mirror have the same optical axis, it may be integrally movable and rotatable.

Advantages of the Invention

[0023] According to the present invention, it is possible to provide an internal exposure device capable of collectively performing lithography on the inner surface of the hollow of a three-dimensional structure having a hollow.

Brief Description of the Drawings

[0024] [Figure 1] It is a cross-sectional schematic view showing a schematic configuration of an internal exposure device according to the first embodiment. [Figure 2] It is a diagram for explaining that the exposure amount of the mask pattern changes due to the patterns in the central portion and the outer peripheral portion of the exposure mask. [Figure 3]These are photographs taken using a cylindrical sample made of transparent, non-corrosive quartz glass, which allows observation of the pattern from the outside of the cylinder, as the object to be exposed. (a) is a photograph taken from an oblique angle near the cylindrical sample, and (b) is a photograph taken from the side near the cylindrical sample. [Figure 4] (a) is a diagram of the exposure mask used to expose the inner surface of a cylindrical sample made of the same quartz glass as in Figure 3 with a finer pattern than that in Figure 3, and (b) is a photograph of the vicinity of the cylindrical sample viewed from the side during the actual exposure process. [Figure 5] (a) is a diagram similar to the exposure mask shown in Figure 4(a), and (b) is a photograph of the pattern formed on the inner surface of the cylindrical sample after development. [Figure 6] This is a schematic cross-sectional view showing the general configuration of an internal exposure apparatus equipped with a reflective mirror that is a modified version of the reflective mirror shown in Figure 1. [Figure 7] (a) is a reflective mirror in which the vertex of the reflective surface is positioned offset from the optical axis when viewed from the optical axis direction; (b) is a reflective mirror in which the height of the conical portion of the conical mirror is even lower than that of (a); and (c) is a reflective mirror in which the height of the conical portion of the conical mirror is even higher than that of (a). [Figure 8] (a) is a schematic diagram showing the exposure pattern when using the reflective mirror 30 in Figure 1, and (b) is a schematic diagram showing the exposure pattern when using the reflective mirror 31 in Figure 2. [Figure 9] This is a schematic cross-sectional view showing the general configuration of an internal exposure apparatus according to the second embodiment. [Figure 10] This is a schematic cross-sectional view showing the general configuration of an internal exposure apparatus according to the third embodiment. [Figure 11] This is a schematic cross-sectional view showing the general configuration of an internal exposure apparatus according to the fourth embodiment. [Figure 12] This is a schematic cross-sectional view showing the general configuration of an internal exposure apparatus according to the fifth embodiment. [Figure 13] This is a schematic cross-sectional view showing the general configuration of an internal exposure apparatus according to another embodiment. [Figure 14]This is a schematic cross-sectional view showing the general configuration of an internal exposure apparatus according to another embodiment. [Figure 15] This is a flowchart showing an example of the exposure procedure. [Figure 16] These figures illustrate the effect of alignment (optical axis adjustment) errors between the object to be exposed and the conical mirror on the pattern. (a) shows an exposure mask for adjustment when there are two concentric intermittent patterns. (b) shows the case where the apex of the conical mirror is shifted downwards (-z direction) relative to the optical axis. (c) shows partial light intensity patterns IPu and IPd, corresponding to the partial patterns MPu and MPd positioned above and below the mask pattern of the adjustment exposure mask, among the light intensity patterns projected onto the inner surface of the object to be exposed as viewed from the direction of light propagation. (d) shows the case where the conical mirror has an installation error that causes it to be tilted relative to the optical axis. [Figure 17] This is a flowchart showing another example of the exposure procedure. [Figure 18] (a) is a diagram showing the exposure mask used in Example 2, and (b) is a photograph of the transferred pattern. [Figure 19] This is a photograph of the inner surface of a cylindrical SUS304 sample after exposure and development, viewed from an oblique angle. [Modes for carrying out the invention]

[0025] The present invention will be described in detail below, with reference to the drawings as appropriate. The drawings used in the following description may be enlarged for convenience to clearly illustrate the features, and the dimensional ratios of each component may differ from those of the actual components. The dimensions and other specifications exemplified in the following description are examples only, and the present invention is not limited to them. It is possible to modify and implement the invention as appropriate within the scope of achieving its effects. Unless otherwise specified, the configuration described in one embodiment may be applied to other embodiments.

[0026] (First Embodiment) Figure 1 shows a schematic cross-sectional view illustrating the general configuration of the internal exposure apparatus according to the first embodiment. The internal exposure apparatus 100 shown in Figure 1 is an internal exposure apparatus for exposing the inner surface Mb of the hollow Ma of an object to be exposed M having a hollow Ma, and comprises a light source 10, an exposure mask 20 placed between the light source 10 and the object to be exposed M, a reflective mirror 30 placed inside the hollow Ma of the object to be exposed M and having a reflective surface 30a capable of reflecting light that has come out of the light source 10 and passed through the exposure mask 20 to the inner surface Mb of the hollow Ma, a reflective mirror holder 40 that holds the reflective mirror 30, and an object to be exposed stage 50 that supports the object to be exposed M.

[0027] <Exposed object> The portion exposed by the internal exposure apparatus according to this embodiment is the inner surface of the hollow of an object to be exposed, which has a hollow interior. Here, "hollow" includes not only objects that penetrate the object to be exposed M, as shown in Figure 1, but also "holes" that are open on one side and have a bottom on the other, and sealed containers that transmit light on at least one side or surface. The object to be exposed can be any three-dimensional structure with a hollow interior. For example, a three-dimensional structure made of metal such as stainless steel or brass can be used. During exposure, the object to be exposed has a photosensitive material (resist) applied to its hollow interior surface to a predetermined thickness. For example, it is held in a detachable state by a holding mechanism such as a vise, which is not shown in the diagram.

[0028] <Light source> As a light source, you can use a light source with a wavelength that causes photosensitive materials attached to the object to be exposed to light, such as halogen lamps, xenon lamps, metal halide lamps, light-emitting diodes, lasers, X-ray sources, electron beams, or ion beams. The internal exposure apparatus 100 shown in Figure 1 is an example of a case where a highly directional light source is used. Examples of highly directional light sources include lasers and X-ray sources.

[0029] <Exposure mask> The exposure mask 20 is a mask on which an arbitrary pattern is drawn and controls the transmission or opacity of light. In the figure, reference numerals 20a (reference numerals 20a1 to 20a4) indicate the transmission area, and reference numeral 20b indicates the opacity area. For example, a plate-shaped glass or film in which chromium is used in the light-shielding area can be used as an example.

[0030] Figure 2 shows a diagram illustrating how the exposure amount of the mask pattern changes between the central and outer edges. In this configuration using a reflective mirror, the area of ​​the transparent portion differs circumferentially between the mask pattern near the center of the optical axis and the mask pattern near the outer edge, provided the patterns have the same width. This results in a difference in the amount of light projected onto the pattern. Therefore, if we let R1 be the distance to the mask pattern near the center of the optical axis and R2 be the distance to the mask pattern near the outer edge, it is necessary to apply a contrast ratio (transmittance ratio) to the mask when exposing them simultaneously. This contrast ratio is simply calculated as an area ratio determined by the distance from the optical axis, such as R1 / R2. This can be resolved by adjusting the transmittance by making the transparent portion of the mask pattern gray by the area ratio (transmittance = incident light × R1 / R2) as it moves away from the optical axis.

[0031] <Reflective mirror> The reflective mirror 30 has a reflective surface 30a that can reflect light that has come out of the light source 10 and passed through the exposure mask 20 onto the inner surface Mb of the hollow Ma. The reflective surface of a reflective mirror is made of materials that have high reflectivity at the wavelength of the exposure light source, such as aluminum, gold, silver, platinum, or multi-layer coatings. The reflective mirror 30 shown in Figure 1 has a conical reflective surface 30a, but the reflective surface 30a may also be polygonal pyramidal or convex spherical (these are sometimes called "polygonal pyramidal mirrors" and "convex spherical mirrors," respectively). If the hollow inner surface of the object to be exposed is cylindrical, a conical shape can be used; if it is a square tube, a square pyramidal shape can be used; and if it is a polygonal tube, a polygonal pyramidal shape can be used. By using these shapes, the light reflected by the reflective mirror is projected onto the photosensitive resin without distortion, allowing for the projection of a highly accurate pattern. Furthermore, conical reflective mirrors are particularly difficult to machine accurately, especially the inclined surfaces, often resulting in wavy surfaces or machining marks, and high processing costs. Therefore, a convex spherical shape can be used instead of a cone. Spherical surfaces can be machined with high precision and at low cost through polishing, similar to the machining of optical lenses.

[0032] A reflective mirror may have a reflective surface that is closest to the light source on that surface (in the case of reflective mirror 30, reference numeral 30aa), and a sloped surface (in the case of reflective mirror 30, reference numeral 30ab) formed so that it approaches the inner surface as it moves away from the light source.

[0033] The vertex 30aa of the reflective surface 30a of the reflective mirror 30 is positioned to coincide with the optical axis AX when viewed from the direction of the optical axis AX. In this specification, "optical axis" refers to a hypothetical ray of light connecting the center O of the light source's emission surface to the geometric center of the reflecting mirror, as viewed from the center O of the light source's emission surface. Here, "geometric center of the reflecting mirror" refers to the geometric center of the shape obtained by projecting the reflecting mirror onto a plane perpendicular to the "optical axis". If the reflective surface of a reflective mirror is rotationally symmetric or n times symmetric (where n is an integer) with respect to the optical axis, the vertices of the reflective surface are positioned on the "optical axis". If the internal exposure apparatus according to the present invention includes a projection optical system, the optical axis of the projection optical system is adjusted to coincide with the "optical axis".

[0034] Figure 3 shows photographs of exposure performed on a cylindrical sample made of transparent, non-corrosive quartz glass, which allows observation of the pattern from the outside of the cylinder. Figure 3(a) is a photograph of the vicinity of the cylindrical sample viewed from an oblique angle, and Figure 3(b) is a photograph of the vicinity of the cylindrical sample viewed from the side. A conical mirror (corne mirror, apex angle 90 degrees) was used as the reflective mirror, and the exposure mask was a pattern in which two circular lines with different diameters and a line width of 1 mm were arranged concentrically (i.e., a pattern in which two circular lines are arranged with one space in between). The internal exposure apparatus used was substantially the same as the configuration shown in Figure 9, which will be described later.

[0035] From the photographs in Figures 3(a) and 3(b), it can be seen that two circular lines (lines 1 and 2 in (b)) and one space are clearly exposed on the inner surface of the cylindrical sample. Subsequently, development was performed, and the transfer of the pattern to the inner surface of the cylindrical sample was confirmed.

[0036] Figure 4(a) shows the pattern of the exposure mask used in Example 1, which will be described later. Figure 4(b) shows a photograph of the exposure of the inner surface of a cylindrical sample made of the same quartz glass as in Figure 3, using the exposure mask shown in Figure 4(a), with a finer pattern than in Figure 3. The exposure was performed under the same conditions as in Figure 3, except for the pattern of the exposure mask used. The exposure mask pattern shown in Figure 4(a) consists of seven circular lines with a line width of 0.3 mm and the spaces between each line. The outermost circular line has a diameter of 10 mm, and the radial distance between the innermost circular line and the outermost circular line is 3.9 mm.

[0037] The photograph in Figure 4(b) clearly shows that a pattern of seven circular lines spaced apart on the inner surface of the cylindrical sample is exposed.

[0038] Subsequently, development was performed, and a photograph of the pattern formed on the inner surface of the cylindrical sample is shown in Figure 5(b). Figure 5(b) shows a photograph of a portion of the pattern formed in the circumferential direction on the inner surface of the cylindrical sample. Figure 5(a) is the exposure mask shown in Figure 4(a). It can be seen that a line and space pattern is formed on the inner surface of the cylindrical sample, corresponding to the line and space pattern of the exposure mask.

[0039] Figure 6 shows a schematic cross-sectional view illustrating the general configuration of an internal exposure apparatus according to the first embodiment, which includes a reflective mirror whose vertex is positioned offset from the optical axis when viewed from the optical axis direction. In this case, the reflective mirror whose vertex is positioned offset from the optical axis when viewed from the optical axis direction does not include cases where the vertex of the reflective surface was offset from the optical axis before position adjustment, but is aligned with the optical axis during actual exposure. Rather, it refers specifically to a reflective mirror whose vertex is positioned offset from the optical axis during actual exposure. Such reflective mirrors include cases such as those shown in Figure 7(a), where the vertex of the reflective surface is simply positioned offset from the optical axis when viewed from the optical axis direction, and cases such as those shown in Figures 7(b) and (c), where not only is the vertex of the reflective surface offset from the optical axis when viewed from the optical axis direction, but the height of the conical portion of the conical mirror is also different. In Figures 7(a) to (c), the configurations shown in Figure 1 are illustrated together for clarity. The symbols Lx0, Lx1, and Lx2 in the figures indicate the height of the conical portion, respectively.

[0040] The internal exposure apparatus 101 shown in Figure 6 includes a reflective mirror 31 in which the vertex 31aa of the reflective surface 31a is offset from the optical axis AX. The reflective mirror 31 has a vertex (reference numeral 31aa) and a slope (reference numeral 31ab) formed from that vertex so as it moves away from the light source it approaches the inner surface of the cylinder. The height of the conical portion is the same as that of the reflective mirror 30, but the vertex of the reflective surface is offset from the optical axis AX, which is different from the reflective mirror 30. Note that reference numerals 31aba and 31abb in Figure 6 indicate different parts of the slope 31ab.

[0041] This section explains the differences in the exposed pattern when using a conical mirror whose reflective surface vertex is offset from the optical axis AX, compared to using a conical mirror whose reflective surface vertex coincides with the optical axis AX. Let's assume the exposure mask pattern is one in which two circular lines are arranged with a space in between, as shown in Figure 2. When the exposure mask pattern is a pattern consisting of multiple circular lines and the space between them (line and space pattern), as shown in Figure 5(b), the resist on the inner surface of the cylindrical sample is exposed with the line and space pattern, and after development, the line and space pattern is formed on the inner surface of the cylindrical sample.

[0042] Figures 8(a) and 8(b) schematically show how, in (a) when using the reflective mirror 30 in Figure 1 and (b) when using the reflective mirror 31 in Figure 2, the resist on the inner surface of the cylindrical sample is exposed in a line and space pattern corresponding to the line and space pattern of the exposure mask, and how the line and space pattern is formed on the inner surface of the cylindrical sample after development. The terms "upper side" and "lower side" in Figure 8 refer to the patterns of the upper side (around the area indicated by the symbol Mba in Figure 6) and lower side (around the area indicated by the symbol Mbb in Figure 6) of the figure.

[0043] When using the reflective mirror 30 shown in Figure 8(a), the spacing between the transparent portion 20a1 and the transparent portion 20a2 in the exposure mask 20 is equal to the spacing between the transparent portion 20a3 and the transparent portion 20a4. Therefore, the spacing (space) of the exposed linear pattern is the same d0 on both the upper and lower sides. In contrast, when using the reflective mirror 31 shown in Figure 8(b), even though the spacing between the transparent portions 20a1 and 20a2 and the spacing between the transparent portions 20a3 and 20a4 in the exposure mask 20 are the same, the spacing and width of the exposed linear patterns change between the upper and lower sides by the difference in the angle of the reflective mirror. When using a deformed conical mirror, the changes in the exposure pattern include not only changes in the spacing between linear patterns, but also changes in the size of the light intensity pattern due to changes in the distance of the light rays. When using highly symmetrical shapes such as polygonal pyramidal mirrors or convex spherical mirrors (described later) as the base shape before deformation, in addition to conical mirrors, and then using a deformed reflective mirror, the exposure pattern and processing pattern after deformation are easier to visualize. When the degree of deformation is small, the exposure pattern and processing pattern after deformation are even easier to visualize. In this way, by using a reflective mirror whose vertex does not coincide with the optical axis, the exposure pattern can be changed compared to when using a reflective mirror whose vertex coincides with the optical axis.

[0044] The modified example shown in Figure 6 is a deformation in which the vertex of the reflective surface 30a is shifted from the optical axis, based on a reflective mirror having a conical shape (hereinafter sometimes referred to as a "conical mirror"). When the reference shape of the reflective surface is rotationally symmetric or n times symmetric (where n is an integer) with respect to the optical axis, for example, when it is a polygonal pyramidal shape or a convex spherical shape other than a cone (sometimes referred to as a "polygonal pyramidal mirror" or a "convex spherical mirror," respectively), the change in the exposure pattern is easier to predict when the reflective mirror is deformed by shifting the vertex of the reflective surface from the optical axis based on these shapes. Therefore, in the following, a reflective mirror that has been modified by shifting the vertex of the reflective surface from the optical axis, based on such an optically symmetric reflective surface, is sometimes referred to as an "optically axially shifted reflective mirror." In particular, a reflective mirror in which the deviation of the vertex of the reflective surface from the optical axis is 5% or less relative to the longest diameter of the shape obtained by projecting the reflective mirror onto a plane perpendicular to the optical axis is called a "minor optical axis shift reflective mirror," a reflective mirror with a deviation greater than 5% but less than or equal to 10% is called a "small optical axis shift reflective mirror," a reflective mirror with a deviation greater than 10% but less than or equal to 20% is called a "medium optical axis shift reflective mirror," and a reflective mirror with a deviation greater than 20% is called a "large optical axis shift reflective mirror."

[0045] <Stage for objects to be exposed to light> The exposure stage supports the exposure object. The exposure stage preferably includes a separate or integrated moving mechanism (exposure object moving mechanism) for moving the position and orientation of the exposure object. The object to be exposed movement mechanism has at least a movement mechanism that is movable in the direction of the light ray.

[0046] The exposure stage 50 shown in Figure 1 is mounted on a mounting table 1 and includes a z-stage 50b that can move in the z direction (a direction perpendicular to the xy plane), an alpha rotation stage 50a that can rotate around the y axis, and a theta rotation stage 50c that can rotate around the z axis. The exposure stage 50 may further include an x-stage that can move in the x-direction (direction of light propagation, optical axis direction), a y-stage (not shown) that can move in the y-direction (in a horizontal plane, in a direction perpendicular to the x-direction), and a beta rotation stage that can rotate around the x-axis.

[0047] <Reflective mirror holder> The reflective mirror holder part holds the reflective mirror. The reflective mirror holder preferably includes a separate or integrated moving mechanism (reflective mirror moving mechanism) for moving the position and orientation of the reflective mirror. The reflective mirror moving mechanism includes at least a moving mechanism that moves in the direction in which light propagates.

[0048] The reflective mirror holder 40 is placed on the mounting base 1 and holds the reflective mirror 30 via the reflective mirror holder member 35. The reflective mirror holder 40 includes an x-stage 40d that is movable in the x-direction (direction of light propagation, optical axis direction), a z-stage 40b that is movable in the z-direction (direction perpendicular to the xy plane), an alpha rotation stage 40a that is rotatable around the y-axis, and a theta rotation stage 40c that is rotatable around the z-axis. Here, the x-stage 40d is used to determine the exposure range of the object to be exposed. The reflective mirror holder 40 may further include a y-stage (not shown) that is movable in the y-direction (in the horizontal plane, in a direction perpendicular to the x-direction) and a beta-rotating stage that is rotatable with respect to the x-axis.

[0049] (Second Embodiment) Figure 9 shows a schematic cross-sectional view illustrating the general configuration of the internal exposure apparatus according to the second embodiment. The main difference between the internal exposure apparatus according to the second embodiment and the internal exposure apparatus according to the first embodiment is that the second embodiment is composed of multiple optical components and includes an illumination optical system that appropriately enlarges and reduces the light emitted from a light source and shapes it into a parallel light beam to illuminate the exposure mask, and a projection optical system that projects the light transmitted through the exposure mask onto the surface of the object to be exposed at the same size or enlarged and reduced. Hereinafter, components common to the internal exposure apparatus according to the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted.

[0050] The internal exposure apparatus 200 shown in Figure 9 comprises a light source 10A which is not as directional as the light source 10, an illumination optical system 60 placed between the light source 10A and the exposure mask 20, the exposure mask 20, a projection optical system 70 placed between the exposure mask 20 and the reflection mirror 30, the reflection mirror 30, a reflection mirror holder 42, and an exposure object stage 52.

[0051] <Light source> Examples of light sources 10A that do not have high directionality include halogen lamps, xenon lamps, metal halide lamps, and light-emitting diodes.

[0052] <Illumination optical system> The illumination optical system 60 shown in Figure 9 is composed of multiple optical components (60a, 60b, and 60c in the example shown in Figure 9) that magnify and reduce the light rays emitted from the light source to illuminate the exposure mask at a predetermined size. In this case, it is preferable to use a fly-eye lens, Kohler illumination, rod lens, etc., to make the light intensity as uniform as possible when illuminating the exposure mask.

[0053] <Projection optical system> A projection lens is used to project any pattern of an exposure mask onto the surface of the object to be exposed, either at actual size or enlarged / reduced. It allows for changes in magnification and ensures a sufficient distance between the exposure mask and the surface of the object to be exposed. Furthermore, it allows for a greater depth of field. The projection optical system 70 shown in Figure 9 is illustrated with a single projection lens, but it may be composed of multiple lenses.

[0054] <Projection Optical Unit> The internal exposure apparatus 200 shown in Figure 9 includes a projection optical unit 200a mounted on a fixed base 2 such that the light source 10A, illumination optical system 60, exposure mask 20, and projection optical system are aligned on the optical axis. For the mounting base 2, for example, it can be made of metal such as aluminum alloy, stainless steel, or iron, or in some cases, plastic. The projection optical unit 200a is supported by the unit support portion 80. The unit support section 80 shown in Figure 9 is equipped with an integrated moving mechanism (projection optical unit moving mechanism) that moves the position and orientation of the projection optical unit 200a. The unit support section 80 is mounted on a fixed base 1 and includes a z-stage 80b that is movable in the z-direction (direction perpendicular to the xy-plane), an alpha rotation stage 80a that is rotatable around the y-axis, a theta rotation stage 80c that is rotatable around the z-axis, and a fixing section 80d that is fixed to the fixed base 1. The unit support section 80 may further include an x-stage that can move in the x-direction (direction of light propagation, optical axis direction), a y-stage (not shown) that can move in the y-direction (in a horizontal plane, in a direction perpendicular to the x-direction), and a beta rotation stage that can rotate around the x-axis.

[0055] The exposure stage 52 shown in Figure 9 is mounted on a fixed base 1 and includes an x-stage 52d that can move in the x-direction (direction of light propagation, optical axis direction), a z-stage 52b that can move in the z-direction (direction perpendicular to the xy plane), an alpha rotation stage 52a that can rotate around the y-axis, and a theta rotation stage 52c that can rotate around the z-axis. The exposure stage 52 may further include a y-stage (not shown) that is movable in the y-direction (in the horizontal plane, in a direction perpendicular to the x-direction) and a beta-rotating stage that is rotatable with respect to the x-axis.

[0056] The reflective mirror holder 42 shown in Figure 9 is mounted on a fixed base 1 and holds the reflective mirror 30 via a reflective mirror holding member 35. It comprises a z-stage 42b that is movable in the z-direction (direction perpendicular to the xy-plane), an alpha rotation stage 42a that is rotatable around the y-axis, a theta rotation stage 42c that is rotatable around the z-axis, and a fixing part 42d that is fixed to the fixed base 1. The reflective mirror holder 42 may further include an x-stage that can move in the x-direction (direction of light propagation, optical axis direction), a y-stage (not shown) that can move in the y-direction (in a horizontal plane, in a direction perpendicular to the x-direction), and a beta rotation stage that can rotate around the x-axis.

[0057] In the internal exposure apparatus 100 shown in Figure 1, the relative movement between the object to be exposed M and the reflective mirror 30 was handled by a reflective mirror holding unit 40 equipped with an x-stage 40d that can move in the x-direction (the direction of light propagation, the optical axis direction). In contrast, in the internal exposure apparatus 200 shown in Figure 9, the relative movement between the object to be exposed M and the reflective mirror 30 is handled by the object to be exposed stage 52, which is equipped with an x-stage 52d that can move in the x-direction (the direction of light propagation, the optical axis direction). In the internal exposure apparatus 200, the x-stage 52 is used to determine the exposure range of the object to be exposed. The relative movement between the object to be exposed M and the reflective mirror 30 may be handled by the reflective mirror holder, the object to be exposed stage, or both the reflective mirror holder and the object to be exposed stage may move relative to each other.

[0058] (Third embodiment) Figure 10 shows a schematic cross-sectional view illustrating the general configuration of the internal exposure apparatus according to the third embodiment. The main difference between the internal exposure apparatus according to the third embodiment and the internal exposure apparatus according to the second embodiment is that the internal exposure apparatus according to the third embodiment comprises an exposure unit in which a light source, an illumination optical system, an exposure mask, a projection optical system, and a reflective mirror are installed in a transparent container so that their optical axes are aligned. Hereinafter, components common to the internal exposure apparatus according to the first and second embodiments will be denoted by the same reference numerals, and their descriptions will be omitted.

[0059] The internal exposure apparatus 300 shown in Figure 10 comprises an exposure unit 300a in which a light source 10C, an illumination optical system 60, an exposure mask 20, a projection optical system 70, and a reflective mirror 30 are installed in a transparent container 3 so that their optical axes are aligned.

[0060] The transparent container 3 can be made of, for example, glass, acrylic or other plastics, or transparent resin. The inner surface of the hollow container may be transparent only in the areas through which light rays pass, while the rest is opaque, or it may be treated with different materials or coatings to prevent unwanted light leakage.

[0061] The exposure unit 300a is supported by the exposure unit support 81. The exposure unit support section 81 is equipped with an integrated moving mechanism (projection optical unit moving mechanism) for moving the position and orientation of the exposure unit 300a. The exposure unit support section 81 is mounted on a fixed base 1 and includes a z-stage 81b that is movable in the z-direction (direction perpendicular to the xy-plane), an alpha rotation stage 81a that is rotatable around the y-axis, a theta rotation stage 10c that is rotatable around the z-axis, and a fixing section 81d that is fixed to the fixed base 1. The exposure unit support section 81 may further include an x-stage that can move in the x-direction (direction of light propagation, optical axis direction), a y-stage (not shown) that can move in the y-direction (in a horizontal plane, in a direction perpendicular to the x-direction), and a beta rotation stage that can rotate with respect to the x-axis.

[0062] The exposure-target stage 53 supports the exposure-target object M.

[0063] (Fourth Embodiment) Figure 11 shows a schematic cross-sectional view illustrating the general configuration of the internal exposure apparatus according to the fourth embodiment. The internal exposure apparatus according to the fourth embodiment is an internal exposure apparatus with an observation optical system, and comprises an observation light source in the non-photosensitive wavelength region, a synthesis optical system that combines light of the non-photosensitive wavelength and exposure light, and an image acquisition device for observation.

[0064] The internal exposure apparatus 400 shown in Figure 11 is an example of a modification of the internal exposure apparatus 200 shown in Figure 9 into an internal exposure apparatus with an observation optical system. The differences from the internal exposure apparatus 200 are that it has a light source 10D having an observation light source and an exposure light source in the non-photosensitive wavelength region, an optical filter 61 as a combining optical system that combines the non-photosensitive wavelength light and the exposure light, and an image acquisition device for observation consisting of a beam splitter or half mirror 71, a lens 72 and a CCD 73. Light emitted from the observation light source passes through the mask and projects the mask image onto the hollow inner surface of the object being exposed via the projection lens and reflective mirror. The reflected light from the image projected onto the hollow inner surface is then imaged onto a CCD via a reflective mirror and projection lens, and further via a beam splitter or half-mirror and lens. By observing the formed image, it is possible to see how the mask pattern is projected onto the hollow inner surface of the object being exposed. In other words, it is possible to check the image before exposure and adjust the optical axis of the conical mirror or mounting stand. After adjustment, by using light from the exposure light source to expose the hollow inner surface of the object to be exposed, it becomes possible to project a highly accurate mask pattern.

[0065] (Fifth embodiment) Figure 12 shows a schematic cross-sectional view illustrating the general configuration of the internal exposure apparatus according to the fifth embodiment. The internal exposure apparatus according to the fifth embodiment is equipped with a rotation mechanism that rotates the object to be exposed M with respect to the optical axis AX.

[0066] The internal exposure apparatus 500 shown in Figure 12 is an example of a modified version of the internal exposure apparatus 200 shown in Figure 4, which is equipped with a rotation mechanism (not shown) that rotates the object to be exposed M with respect to the optical axis AX. A known rotation mechanism for rotating the object to be exposed M with respect to the optical axis AX can be employed.

[0067] (Other embodiments) In the above embodiment, instead of an exposure mask, a liquid crystal display element (LCD) (see Figure 13) or a DMD (Digital Mirror Device) display element (see Figure 14) may be provided. In this configuration using a reflective mirror, the area of ​​the transparent portion differs circumferentially between the mask pattern near the center of the optical axis and the mask pattern near the periphery. This results in a difference in the amount of light projected. Therefore, when simultaneously exposing the mask pattern at the center of the optical axis and the mask pattern at the periphery, it is necessary to introduce a contrast difference (transmittance difference) into the masks. This contrast difference is simply calculated using the area ratio determined by the distance from the optical axis, and a uniform projection pattern can be obtained by adjusting the transmittance by setting the transparent portion of the mask pattern to an arbitrary contrast using a liquid crystal display element or DMD display element.

[0068] (Other configurations) In the above embodiment, the ON / OFF state of the light source and the movement of each stage can be controlled by a PC (not shown). Although the movement of each stage can be done manually, when performing scan exposure as described later, the x-stage attached to the object to be exposed needs to be an electric stage, and therefore needs to be controlled by a PC or controller.

[0069] (Effects and Benefits) The internal exposure apparatus according to the present invention can form a pattern of photosensitive material on the inner surface of a hollow object to be exposed, such as a cylindrical or rectangular tube, by applying lithography. By using these photosensitive materials as a masking material to etch the inner surface of the object to be exposed, or by using the pattern of the photosensitive material as a mold to perform plating, micro-components such as nut-shaped parts and splined cylindrical parts can be manufactured.

[0070] Furthermore, the internal exposure apparatus according to the present invention has the following advantages over the conventional technology. The pattern can be exposed simultaneously in the circumferential direction on the inner surface of a hollow object to be exposed. This allows for faster processing. Step-and-repeat exposure can be performed by intermittently moving the object to be exposed and / or the projection optical system relative to each other, and scanning exposure can be performed by scanning movement. Therefore, continuous exposure can be performed on the inner surface in the longitudinal direction of a hollow object to be exposed. In scan exposure, the exposure mask needs to move in sync. Therefore, instead of using a glass or film mask, a liquid crystal display element or DMD (Digital Mirror Device) is used as a mask, and the display on the mask changes according to the exposure area. This allows for continuous exposure to the inner surface along the longitudinal direction of a hollow object to be exposed. By installing an observation optical system within the projection optical system, it becomes possible to position the object to be exposed and the projection optical system, as well as to confirm the pattern to be transferred, enabling the transfer of a highly accurate pattern.

[0071] (Exposure procedure) Using the flowchart in Figure 15, we will explain the procedure for step exposure as an example. First, as a preparation step, in step S1, a photosensitive material is attached to the object to be exposed. The photosensitive material is called a resist, and it is a resin that reacts when exposed to light in a specific wavelength range. For example, if a negative-type resist such as SU-8 is used, only the areas exposed to light will be exposed, and the resist pattern in the areas exposed to light will remain after development. If a positive-type resist such as THMR-iP3300 is used, only the areas exposed to light will be exposed, and the resist pattern in the areas exposed to light will be removed after processing. The attachment method allows for uniform attachment to the inner surface of the object to be exposed by spraying the photosensitive material or by dipping the object in the photosensitive material and then removing it (dip coating method). The thickness of the film can be arbitrarily adjusted from 1 μm to several tens of μm.

[0072] In step S2, an object with a shape equivalent to the object to be exposed is placed in the exposure apparatus beforehand, and the positional relationship between the projection optical system unit, the object to be exposed, and the reflective mirror is adjusted. The adjustment method is performed by setting up the exposure mask and observing the light intensity pattern projected onto an object with a shape equivalent to the object to be exposed. If the inner surface of the object to be exposed is difficult to observe, a transparent object with a shape equivalent to the object to be exposed is used as a substitute, and the adjustment is made by checking the light intensity pattern from the outside. Examples of transparent materials include glass tubes and plastic tubes such as acrylic.

[0073] Using Figure 16 as an example, we will explain the influence of alignment (optical axis adjustment) errors between the object being exposed and the conical mirror on the pattern. Optical axis adjustment is performed by setting up an adjustment exposure mask with multiple concentric intermittent patterns drawn on it, and observing the light intensity pattern projected onto an object of the same shape as the object to be exposed. Figure 16(a) shows an adjustment exposure mask with two concentric intermittent patterns.

[0074] The pattern in the center of the adjustment exposure mask is highly sensitive to the alignment of the optical axis between the conical mirror and the object being exposed. Therefore, if the optical axis is misaligned vertically or horizontally, the light intensity pattern projected onto the inner surface of the object being exposed will stretch in the circumferential direction, and the change in the distance of the light rays will also alter the size (thickness) of the light intensity pattern. Figure 16(b) illustrates the case where the apex of the conical mirror is misaligned downwards (-z direction). Figure 16(c) shows the partial patterns MP positioned above and below the mask pattern of the adjustment exposure mask, within the light intensity pattern projected onto the inner surface of the object being exposed as viewed from the direction of light propagation. u MP d Each corresponding partial light intensity pattern IP u IP d This demonstrates the partial pattern MP. u Corresponding partial light intensity pattern IP u The size shrinks in the circumferential direction, and the partial pattern MP d Corresponding partial light intensity pattern IP dIts size is elongated in the circumferential direction. Furthermore, its position on the inner surface of the exposed object is also shifted.

[0075] Figure 16(d) illustrates the case where the conical mirror has an installation error that causes it to be tilted relative to the optical axis. In this case, the position of the light intensity pattern projected onto the inner surface of the object being exposed will change in all directions (up, down, left, and right). By observing this change, the optical axis is adjusted to minimize the error.

[0076] In step S3, the object to be exposed is attached to a chuck (not shown) for securing it. In step S4, a predetermined exposure mask is set up. In step S5, the light source is turned on and the exposure mask is irradiated with light for a predetermined time.

[0077] In step S6, a decision is made as to whether to project light onto other parts of the object being exposed. As shown in step S7, when projecting light to other areas, with the object to be exposed still attached, the stage installed on the object to be exposed is used to move the object in the axial direction and / or rotational direction relative to the axis, and exposure is repeatedly performed on other areas. The exposure mask pattern is changed as needed.

[0078] In step S8, the object to be exposed is attached and removed and then developed. The development process forms a predetermined pattern of photosensitive material. In step S9, etching or plating is performed as needed. The photosensitive material pattern can be used as a masking material for etching, allowing the desired pattern to be removed from the object to be exposed. In addition, by applying plating, the plating does not directly adhere to the areas covered by the photosensitive material pattern, allowing for the creation of a clean, desired pattern.

[0079] The steps above omit details commonly performed during exposure, such as baking and post-exposure baking.

[0080] To continuously transfer a photosensitive resin pattern, in step 6 (S), scan exposure is performed by continuously moving the object to be exposed while irradiating it with light from a light source. By moving the object to be exposed horizontally in the direction of the optical axis using an intermittent mask, a linear pattern can be exposed. In addition, by rotating it relative to the optical axis, a spiral pattern can be exposed, and by changing the horizontal movement to a reciprocating motion, a complex mesh-like pattern can be exposed circumferentially.

[0081] By following the steps described above, a pattern can be projected circumferentially onto the inner surface of the object to be exposed.

[0082] Figure 16 shows a flowchart for another example. In the flow shown in Figure 16, the exposure is performed while moving and rotating the stage so that the relative position between the reflective mirror and the object to be exposed changes. [Examples]

[0083] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0084] [Example 1] A cylindrical internal exposure apparatus, schematicly shown in Figure 9, was used. The apparatus is approximately 500 mm long, 100 mm deep, and 200 mm high. A metal halide lamp (dominant wavelength 440 nm) is used as the light source, and light is guided to the exposure apparatus using a fiber optic light guide. Furthermore, the mask is illuminated via a rod lens to ensure a uniform light intensity distribution. A conical mirror with a total length of 10 mm, an outer diameter of 10 mm, and an apex angle of 90° was used as the reflective mirror. For projection, an objective lens with a long working distance and high resolution was used. The magnification of the objective lens is 1, and the numerical aperture is 0.03. The resolution R during planar exposure is given by the following formula when the resist film thickness is approximately 1 μm.

number

number

[0085] A Laser Beam Expander (LBE) is used in the sample holding section to allow for tilt adjustment, and an X-axis stage and a Z-axis stage are attached to the reflection mirror holding section. In addition, height-adjustable rod stands are used in each holding section.

[0086] The exposure mask used is shown in Figure 5(a). This exposure mask is a plate-shaped glass with chromium used in the light-shielding portion, on which a pattern (0.3 mm line and space pattern) is drawn, consisting of six concentric circles of different diameters with a width of 0.3 mm.

[0087] A cylindrical sample made of quartz glass with an inner diameter of 14 mm and an outer diameter of 16.5 mm was used as the sample (object to be exposed). After ultrasonic cleaning to remove contaminants from the sample surface, a negative-type resist PMER N-CA3000 was applied to a thickness of 10 μm.

[0088] The prepared sample was exposed to light on its inner surface using a cylindrical internal exposure apparatus. Subsequently, development was performed to form a pattern. Developer P-7g (Tokyo Ohka Kogyo) was used for development.

[0089] The results of observing the developed sample under a stereomicroscope are shown in Figure 5(b). It can be seen that the line pattern has been successfully transferred.

[0090] Regarding the exposure mask for a line and space pattern, as shown in Figure 5(a), which has concentric transparent areas of different diameters, we also conducted exposure experiments on the same quartz glass cylindrical sample with even finer widths of 0.1 mm (100 μm) and 0.05 mm (50 μm), confirming that it is possible to transfer the line and space pattern.

[0091] [Example 2] Next, as the exposure mask, a pattern was used in which rectangles, which become wider as they move away from the center, are intermittently spaced apart in a radial pattern, as shown in Figure 17(a). Exposure and development were performed under the same conditions as in Example 1. The line width was 0.3 mm, the same as in Example 1. Figure 17(b) shows the resulting transcription pattern. It can be seen that an intermittent rectangular pattern has been transferred in the circumferential direction.

[0092] [Example 3] Next, as the exposure mask, a pattern consisting of two circular lines with different diameters and a line width of 0.1 mm arranged concentrically (i.e., a line and space pattern in which two circular lines are arranged with a space in between) was used, and as the sample (object to be exposed), a cylindrical sample made of SUS304 with an inner diameter of 14 mm and an outer diameter of 15 mm was used. Exposure and development were carried out under the same conditions as in Example 1. Figure 18 is a photograph of the inner surface of a cylindrical SUS304 sample after exposure and development, viewed from an oblique angle. The vicinity of the apex of the cone mirror is also visible inside. You can see that the line and space pattern has been transferred.

[0093] As shown in Examples 1 to 3, it has been found that a transfer pattern corresponding to the pattern of the exposure mask can be formed on the hollow inner surface of a hollow object to be exposed using the internal exposure apparatus of the present invention. [Explanation of Symbols]

[0094] 10, 10A, 10C, 10D light source 20 Exposure Mask 30, 31 Reflective mirror 30a, 31a reflective surface 30aa, 31aa vertices 30ab, 31ab slope 40 Reflective mirror holding part 50 Exposed object stage 60 Illumination optical system 70 Projection optical system 100, 101, 200, 300, 400, 500 Internal Exposure Devices 200a Projection Optics Unit 300a Exposure Unit

Claims

1. An internal exposure apparatus for exposing the inner surface of the hollow of an object to be exposed, which has a hollow structure, Light source and An exposure mask is placed between the light source and the object to be exposed, A reflective mirror is disposed within the hollow space and has a reflective surface capable of simultaneously reflecting light from the light source that has passed through the exposure mask onto the inner surface of the hollow space in a circumferential direction. A reflective mirror holding part that holds the reflective mirror, A stage for supporting the object to be exposed, An internal exposure apparatus equipped with the following features.

2. The internal exposure apparatus according to claim 1, comprising a projection optical system in which light transmitted through the exposure mask forms a predetermined pattern on the inner surface of the hollow surface.

3. The internal surface exposure apparatus according to claim 2, wherein the reflective mirror has a vertex on its surface that is closest to the light source, and a sloped surface formed so that it approaches the internal surface as it moves away from the light source.

4. The internal exposure apparatus according to claim 3, wherein the reflective surface is conical in shape.

5. The internal surface exposure apparatus according to claim 3, wherein the reflective surface is either a polygonal pyramidal shape or a convex spherical shape.

6. The internal exposure apparatus according to claim 3, wherein the vertex is positioned at a location offset from the optical axis when viewed from the optical axis direction.

7. An internal exposure apparatus according to any one of claims 1 to 6, comprising at least one of the following: an object to be exposed stage that moves in the direction in which the light from the light source travels, and a reflective mirror moving mechanism that moves the reflective mirror holding portion in the direction in which the light from the light source travels.

8. The internal exposure apparatus according to claim 7, wherein the object to be exposed moving mechanism has a six-axis adjustment mechanism that is adjustable in six axes: translational directions of mutually orthogonal x, y, and z axes and rotational directions around axes parallel to the x, y, and z axes.

9. The internal exposure apparatus according to claim 7 or 8, wherein the reflective mirror moving mechanism has a six-axis adjustment mechanism that is adjustable in six axes: translational directions of mutually orthogonal x, y, and z axes and rotational directions around axes parallel to the x, y, and z axes.

10. The internal exposure apparatus according to any one of claims 7 to 9, further comprising an object rotation mechanism for rotating the object to be exposed around the optical axis.

11. The internal exposure apparatus according to any one of claims 2 to 6, wherein the light source, illumination optical system, exposure mask, and projection optical system are mounted on a fixed base so as to align their optical axes, and are integrally movable and rotatable as a projection optical unit.

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