Exposure apparatus

Abstract

This invention widens an exposable area in a situation in which a relative position between an imaging optical system and an exposure object is not changed. This exposure apparatus is provided with: a single imaging lens; a plurality of objective lenses; an optical path selector that selects one of the plurality of objective lenses on which an exposure beam that has passed through the imaging lens is to be incident; and an optical path length adjustment unit that aligns the air-equivalent optical path lengths of the optical paths from the imaging lens to the objective lenses.

Description

exposure equipment

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

[0002] A stereolithography method is known in which a desired pattern is formed in a swollen gel by exposing the gel to light. An example of such a stereolithography method is the Implosion Fabrication (hereinafter abbreviated as ImpFab) method (see Patent Document 1 and Non-Patent Document 1). The ImpFab method exposes the gel using a high-magnification, high-NA objective lens, allowing for stereolithography of micrometer-scale or nanometer-scale patterns. An example of an objective lens used in the ImpFab method is an objective lens with a magnification of 20x and an NA of 1.0. The ImpFab method performs stereolithography by applying the principle of multiphoton absorption. Therefore, in addition to stereolithography in the in-plane direction parallel to the main surface of the gel, stereolithography can also be performed in the thickness direction perpendicular to the main surface of the gel.

[0003] US Patent Application Publication No. 2017 / 0081489

[0004] Daniel Oran et. al., Science 362, 1281-1285 (2018) 14 December 2018

[0005] However, the actual field of view (FOV) of a high-magnification, high-NA objective lens tends to be narrow. The FOV of the above-mentioned objective lens (magnification: 20x, NA: 1.0) is, for example, about 600 μm × 600 μm.

[0006] A narrow FOV of the objective lens means that the area that can be exposed is narrow when the relative position between the imaging optical system and the exposure object is not changed. Therefore, when photolithography is performed to form a pattern that spans an area wider than the FOV of the objective lens, exposure is repeated while changing the relative position between the imaging optical system and the exposure object many times.

[0007] Note that the "relative position between the imaging optical system and the exposure object" referred to here means the relative position in the in-plane direction of the plane perpendicular to the direction parallel to the optical axis of the imaging optical system. Changes in the relative position in the direction parallel to the optical axis of the imaging optical system have almost no effect on the area of ​​the exposable region, and are therefore not taken into consideration here. The imaging optical system is an optical system that focuses the exposure beam at a desired position on the exposure object, and is an optical system that includes an imaging lens and an objective lens.

[0008] One aspect of the present invention has been developed in consideration of the above-mentioned problems, and its purpose is to provide an exposure apparatus that can expand the area that can be exposed without changing the relative position between the imaging optical system and the object to be exposed.

[0009] In order to solve the above problems, the exposure apparatus according to aspect 1 of the present invention comprises a single imaging lens arranged on the optical path of an exposure beam, a plurality of objective lenses that focus the exposure beam on an exposure object, an optical path selector that switches which of the plurality of objective lenses the exposure beam that has passed through the imaging lens is incident on, and an optical path length adjustment unit that aligns the air-equivalent optical path lengths of the optical paths from the imaging lens to each of the plurality of objective lenses.

[0010] An exposure apparatus according to one aspect of the present invention can widen the area that can be exposed when the relative position between the imaging optical system and the exposure object is not changed.

[0011] It is a schematic diagram of an exposure apparatus according to embodiment 1 of the present invention. It is a front view and a plan view of an optical path selector provided in the exposure apparatus shown in Fig. 1. It is a schematic diagram of an exposure apparatus according to embodiment 2 of the present invention. It is a front view and a plan view of an optical path selector provided in the exposure apparatus shown in Fig. 3.

[0012] [Embodiment 1] An exposure apparatus 10 according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram of the exposure apparatus 10. FIG. 2 is a front view (bottom view) and a plan view (top view) of an optical path selector 12 included in the exposure apparatus 10. Note that in the Cartesian coordinate system shown in FIG. 1, the direction parallel to the optical axes of the objective lenses 131 to 133 (described later) is defined as the Z-axis direction (the up-down direction in FIG. 1), one direction perpendicular to the Z-axis direction is defined as the X-axis direction (the depth direction in FIG. 1), and the direction perpendicular to both the Z-axis direction and the X-axis direction is defined as the Y-axis direction (the left-right direction in FIG. 1). Furthermore, the direction in which the exposure beam propagates in the Z-axis direction is defined as the positive Z-axis direction (the up direction in FIG. 1), and the positive X-axis direction (the forward direction in FIG. 1) and the positive Y-axis direction (the rightward direction in FIG. 1) are defined so that, together with the Z-axis direction, they form a right-handed Cartesian coordinate system. In FIG. 1, the Z-axis direction is parallel to the vertical direction. The orthogonal coordinates shown in FIG. 2 are the same as those shown in FIG.

[0013] <Object to be Exposed> The exposure apparatus 10 is an exposure apparatus used for stereolithography using the Implosion Fabrication (ImpFab) method described in Patent Document 1, Non-Patent Document 1, etc. In this embodiment, as shown in FIG. 1 , a gel 41 is used as the object to be exposed. The gel 41 can be appropriately selected from gels used in the ImpFab method. In this embodiment, a hydrogel is used as the gel 41.

[0014] The volume of a hydrogel increases when it absorbs an aqueous solvent and decreases when it dries. In the ImpFab method, a swollen hydrogel is exposed to light, and the exposed hydrogel is dried to shrink it. By shrinking the hydrogel after exposure in this way, a stereolithography object with a finer structure than at the time of exposure can be obtained.

[0015] 1, a gel 41 is contained in the internal space of a petri dish 42. The internal space of the petri dish 42 is filled with an aqueous solvent 43, and a glass plate 44 is placed on the solvent 43. By placing the glass plate 44 on the solvent 43, it is possible to use immersion lenses as the objective lenses 131 to 133 that make up the objective lens group 13, which will be described later. The solvent 43 may also contain a dye that reacts with the hydrogel when exposed to light.

[0016] A petri dish 42 containing gel 41 is placed on a stage provided in the exposure apparatus 10. Note that the stage is not shown in Fig. 1. In the exposure apparatus 10, the stage and the imaging optical system are configured so that their relative positions can be changed. Note that the imaging optical system will be described later.

[0017] 1, the exposure apparatus 10 includes an imaging lens 11, an optical path selector 12, an objective lens group 13, a laser 14, a Pockels cell 15, a galvano scanner 16, and a field lens 17. The exposure apparatus 10 also includes a stage as described above.

[0018] In this embodiment, we will explain the imaging optical system located at the rear stage of the optical system of the exposure apparatus 10, and then we will explain the laser 14, Pockels cell 15, galvanometer scanner 16, and field lens 17 located at the front stage of the exposure apparatus 10.

[0019] In the exposure apparatus 10, the exposure beam output by the laser 14 passes through the Pockels cell 15, the galvanometer scanner 16, the field lens 17, the imaging lens 11, the optical path selector 12, and the objective lens group 13 and reaches the gel 41 (see FIG. 1). In the optical system of the exposure apparatus 10, the side closer to the laser 14 along the propagation direction of the exposure beam is called the front side, and the side closer to the gel 41 is called the rear side.

[0020] (Imaging Optical System) As shown in FIG. 1, the imaging optical system of the exposure apparatus 10 includes an imaging lens 11, an optical path selector 12, and an objective lens group 13.

[0021] The imaging lens 11 is an example of a single imaging lens arranged on the optical path of the exposure beam. In the exposure apparatus 10, the imaging lens 11 is composed of a single lens, as shown in FIG. 1 . However, in one aspect of the exposure apparatus 10, the imaging lens 11 may be composed of a lens assembly combining multiple lenses. The expression "single imaging lens" indicates that the correspondence between the imaging lens and the objective lenses constituting the objective lens group 13, which will be described later, is one to multiple (one to three in this embodiment), and does not indicate that the imaging lens 11 is composed of a single lens.

[0022] The objective lens group 13 is composed of multiple objective lenses. Each objective lens focuses the exposure beam onto the gel 41. Each of the multiple objective lenses has the same specifications. In this embodiment, the objective lens group 13 is composed of three objective lenses 131, 132, and 133. However, the number of objective lenses constituting the objective lens group 13 is not limited to three. It may be two, four, or more. In the exposure apparatus 10, each of the objective lenses 131, 132, and 133 is composed of a lens assembly combining multiple lenses. In FIG. 1, a rectangle is used to schematically represent the lens barrel housing the lens assembly in order to illustrate each of the objective lenses 131, 132, and 133. However, in one aspect of the exposure apparatus 10, each of the objective lenses 131, 132, and 133 may be composed of a single lens.

[0023] The objective lens 131 is an example of a first objective lens. Furthermore, one of the objective lens 132 and the objective lens 133 is an example of a second objective lens. In the exposure apparatus 10, the objective lens 131 can be considered as the first objective lens and the objective lens 132 can be considered as the second objective lens, or the objective lens 133 can be considered as the second objective lens. In this embodiment, the objective lens 131 and the objective lens 132 will be described as the first objective lens and the second objective lens, respectively. Furthermore, the objective lens 133 will be described as the third objective lens.

[0024] In this embodiment, immersion lenses are used as the objective lenses 131, 132, and 133. In Fig. 1, the exit surface of each of the objective lenses 131, 132, and 133 and the surface of the glass plate 44 (the main surface exposed to the atmosphere) are shown as being spaced apart in the Z-axis direction, but in reality, they are close to each other. In addition, a matching liquid (not shown in Fig. 1) is interposed between the exit surface of each of the objective lenses 131, 132, and 133 and the surface of the glass plate 44 to match the refractive indexes of the two.

[0025] The optical path selector 12 is configured to switch the exposure beam transmitted through the imaging lens 11 to be incident on any one of the objective lenses 131, 132, and 133. The optical path selector 12 also functions as an optical path length adjustment unit that aligns the air-equivalent optical path lengths of the optical paths from the imaging lens 11 to the objective lenses 131, 132, and 133.

[0026] The optical path selector 12 is disposed after the imaging lens 11 and before the objective lens group 13. In the following, on the optical path of the exposure beam, the distance from the center of the imaging lens 11 to the incident point of the exposure beam on the mirror 124 is defined as length a1, and the distance from this incident point to the entrance pupil P131 is defined as length a2. Furthermore, the optical path from the center of the imaging lens 11 to the incident point of the exposure beam on the mirror 124 is divided into an optical path along which the exposure beam propagates in air and an optical path along which the exposure beam propagates through the optical path selector 12. In the following, of length a1, the length of the optical path along which the exposure beam propagates in air is defined as length a11, and the length of the optical path along which the exposure beam propagates through the optical path selector 12 is defined as length a12. Also, on the optical path of the exposure beam, the distance from the incident point of the exposure beam on mirror 125 to entrance pupil P132 and the distance from the incident point of the exposure beam on mirror 126 to entrance pupil P133 are both the same length a2.

[0027] The optical path selector 12 is a block made of glass (quartz glass in this embodiment). Front views of the optical path selector 12 are shown in the lower drawings of Figures 1 and 2, and a plan view of the optical path selector 12 is shown in the upper drawing of Figure 2.

[0028] The optical path selector 12 includes a first block 121, a second block 122, a third block 123, a mirror 124, a mirror 125, and a mirror 126. In this embodiment, the first block 121, the second block 122, and the third block 123 are integrally molded, and there are no clear boundaries between them. However, in one aspect of the optical path selector 12, the first block 121, the second block 122, and the third block 123 may be molded as separate bodies and joined to each other (for example, by adhesion or fusion).

[0029] The shape of the front surface of the first block 121 is a parallelogram. In this embodiment, of the two pairs of diagonal angles of the first block 121, one pair of diagonal angles is 45° and the other pair of diagonal angles is 135°. The angle of each of the two pairs of diagonal angles is not limited to 45°.

[0030] In this embodiment, one pair of opposite sides of the first block 121 is arranged parallel to the Y-axis direction. That is, the other pair of opposite sides of the first block 121 is arranged so as to form an angle of 45° with the negative Z-axis direction. Hereinafter, the length of the pair of opposite sides of the first block 121 that is arranged parallel to the Y-axis direction is referred to as length a3 (see the plan view in FIG. 2 ).

[0031] Hereinafter, of the surfaces perpendicular to the front surface of the first block 121, the surfaces parallel to the XY plane will be referred to as the lower and upper surfaces. The lower surface is located on the negative side of the Z axis, and the upper surface is located on the positive side of the Z axis. Furthermore, of the surfaces perpendicular to the front surface of the first block 121, the surfaces other than the upper and lower surfaces will be referred to as the left and right surfaces. The left surface is located on the negative side of the Y axis, and the right surface is located on the positive side of the Y axis.

[0032] The upper and lower base surfaces of the first block 121 are congruent rectangles.

[0033] The shape of the front surface of the second block 122 is a parallelogram. In this embodiment, of the two pairs of diagonal angles of the second block 122, one pair of diagonal angles is 45° and the other pair of diagonal angles is 135°. The angles of the two pairs of diagonal angles are not limited to this.

[0034] In this embodiment, one pair of opposite sides of the second block 122 is arranged parallel to the Y-axis direction. That is, the other pair of opposite sides of the second block 122 is arranged so that the angle between the pair of opposite sides and the negative Z-axis direction is 45°. Hereinafter, the length of the pair of opposite sides of the second block 122 that is arranged parallel to the Y-axis direction is longer by a length a4 than the length a3 of the pair of opposite sides of the first block 121 that is arranged parallel to the Y-axis direction (see the plan view in FIG. 2 ). Note that in this embodiment, the lengths a3 and a4 are equal. Therefore, the sum of the lengths a3 and a4 of the pair of opposite sides of the second block 122 that are arranged parallel to the Y-axis direction is twice the length a3.

[0035] The method of defining the upper, lower, right, and left sides of the second block 122 in a plane perpendicular to the front surface is the same as the method of defining the upper, lower, right, and left sides of the first block 121 in a plane perpendicular to the front surface.

[0036] The upper and lower base surfaces of the second block 122 are congruent rectangles.

[0037] The front surface of the third block 123 has a rectangular shape. That is, the third block 123 is a rectangular parallelepiped. In this embodiment, one pair of opposite sides of the two pairs of opposite sides that form the front surface of the third block 123 is arranged parallel to the Y-axis direction.

[0038] The method of defining the upper, lower, right, and left sides of the third block 123 in a plane perpendicular to the front surface is the same as the method of defining the upper, lower, right, and left sides of the first block 121 in a plane perpendicular to the front surface.

[0039] In this embodiment, the first block 121 and the second block 122 are arranged so that their left side surfaces are located on the same plane (i.e., flush) (see FIG. 2). Hereinafter, when the left side surface of the first block 121 and the left side surface of the second block 122 are not distinguished from each other, they are collectively referred to simply as the left side surface of the optical path selector 12. Furthermore, because the first block 121 and the second block 122 are integrally molded, the rear surface of the first block 121 and the front surface of the second block 122 are in close contact with each other (see FIG. 2). Furthermore, because the second block 122 and the third block 123 are integrally molded, the lower bottom surface of the second block 122 and the upper bottom surface of the third block 123 are in close contact with each other (see FIG. 4).

[0040] A metal film is formed on each of the left side surface of the optical path selector 12, the right side surface of the first block 121, and the right side surface of the second block 122. The interface between each metal film and the first block 121, and each metal film and the second block 122 function as a reflective surface that reflects the exposure beam incident on the optical path selector 12. The material constituting the metal film may be any material that has a specularly reflective surface, and may be appropriately selected from such materials. In this embodiment, aluminum is used as the material constituting the metal film. However, other examples of such materials include gold and silver. Alternatively, a dielectric multilayer film may be used instead of each metal film constituting the reflective surface together with the first block 121 or the second block 122.

[0041] In the following, the metal film formed on the left side of the optical path selector 12 will be referred to as mirror 124, and the metal films formed on the right side of the first block 121 and the right side of the second block 122 will be referred to as mirror 125 and mirror 126, respectively.

[0042] The mirror 124 is an example of a first reflecting surface that reflects the exposure beam that has passed through the imaging lens 11. One of the mirrors 125 and 126 is an example of a second reflecting surface that further reflects the exposure beam reflected by the mirror 124 (an example of a first reflecting surface). In the exposure apparatus 10, the mirror 124 can be considered as the first reflecting surface and the mirror 125 can be considered as the second reflecting surface, or the mirror 126 can be considered as the second reflecting surface. In this embodiment, the mirrors 124 and 125 will be described as the first reflecting surface and the second reflecting surface, respectively. The mirror 126 will also be described as a third reflecting surface.

[0043] As shown in Fig. 1, the optical path selector 12 is disposed on the optical path of the exposure beam transmitted through the imaging lens 11. That is, the optical path selector 12 is disposed after the imaging lens 11. The optical path selector 12 is configured so that it can mechanically translate in a direction perpendicular to the direction in which the exposure beam propagates (in this embodiment, the X-axis direction in the coordinate system shown in Fig. 1). As a mechanical mechanism for translating the optical path selector 12, a stage that can translate in at least one axial direction can be used.

[0044] In this way, the mirrors 124, 125, and 126 can be translated, so that the optical path selector 12 can be mechanically inserted into or removed from the optical path of the exposure beam.

[0045] When the position of the optical path selector 12 in the X-axis direction is determined so that the exposure beam does not enter the optical path selector 12, i.e. so that the exposure beam does not enter the mirror 124, the exposure beam enters the objective lens 131 as is. In this way, a state in which the exposure beam does not enter the mirror 124, in other words, a state in which the mirror 124 does not reflect the exposure beam, is hereinafter referred to as a state in which the mirror 124 is disabled.

[0046] On the other hand, when the position of the optical path selector 12 in the X-axis direction is determined so that the exposure beam is incident on an area of ​​the mirror 124 that corresponds to the left side of the first block 121, the exposure beam reflected by the mirror 124 propagates inside the first block 121 in the positive direction of the Y-axis, is further reflected by the mirror 125, and is incident on the objective lens 132. In this way, the state in which the exposure beam is incident on the mirror 124, in other words, the state in which the mirror 124 is reflecting the exposure beam, will be referred to below as the state in which the mirror 124 is enabled. Similarly, the state in which the exposure beam is incident on the mirror 125, in other words, the state in which the mirror 125 is reflecting the exposure beam, will be referred to as the state in which the mirror 125 is enabled.

[0047] Furthermore, when the position of the optical path selector 12 in the X-axis direction is determined so that the exposure beam is incident on an area of ​​the mirror 124 that corresponds to the left side surface of the second block 122, the exposure beam reflected by the mirror 124 propagates inside the second block 122 in the positive direction of the Y-axis, is further reflected by the mirror 126, and is incident on the objective lens 133. This state is the state in which the mirror 124 is enabled. Furthermore, as in the case of the mirror 125, the state in which the exposure beam is incident on the mirror 126, in other words, the state in which the mirror 126 is reflecting the exposure beam, is defined as the state in which the mirror 126 is enabled.

[0048] In the optical path selector 12 configured as described above, (1) when mirror 124 is disabled, mirrors 125 and 126 are also disabled, and the exposure beam is incident on objective lens 131, (2) when mirrors 124 and 125 are enabled, the exposure beam is incident on objective lens 132, and (3) when mirrors 124 and 126 are enabled, the exposure beam is incident on objective lens 133. In this way, the optical path selector 12 mechanically inserts and removes mirrors 124, 125, and 126 into and from the optical path of the exposure beam, thereby switching between objective lens 131, objective lens 132, and objective lens 133 onto which the exposure beam is incident.

[0049] Furthermore, when expressing the function of the optical path selector 12 from the perspective of the objective lens group 13, (1) the exposure beam obtained when mirror 124 of the optical path selector 12 is disabled is incident on objective lens 131, (2) when mirror 124 is enabled, the exposure beam reflected by mirror 124 is further reflected by mirror 125 and incident on objective lens 132, and (3) when mirror 124 is enabled, the exposure beam reflected by mirror 124 is further reflected by mirror 126 and incident on objective lens 133.

[0050] Next, the function of the optical path selector 12 as an optical path length adjuster will be described. As shown in FIG. 1 , the optical path L1 of the exposure beam from the imaging lens 11 to the objective lens 131 is linear. On the other hand, the optical path L2 of the exposure beam from the imaging lens 11 to the objective lens 132 via the mirrors 124 and 125 is crank-shaped because the exposure beam is reflected by the mirrors 124 and 125 at a substantially right angle (a right angle in this embodiment). Similarly, the optical path L3 of the exposure beam from the imaging lens 11 to the objective lens 133 via the mirrors 124 and 126 is crank-shaped because the exposure beam is reflected by the mirrors 124 and 126 at a substantially right angle (a right angle in this embodiment). On the optical path L2, the distance from the incident point of the exposure beam on the mirror 125 to the lower bottom surface of the first block 121 is defined as a length a5. On the optical path L3, the distance from the incident point of the exposure beam on the mirror 126 to the lower bottom surface of the second block 122 is also defined as a length a5. The sum of lengths a11 and a5 is equal to the thickness of the optical path selector 12 (the distance between the upper and lower bottom surfaces of the first block 121 and the second block 122). Also, on optical path L3, the length of the optical path propagating through the third block 123 is defined as length a6. Length a6 is equal to the thickness of the third block 123 (the distance between the lower and upper bottom surfaces of the third block 123). Also, on optical path L3, the distance from the emission point of the exposure beam in the third block 123 to the entrance pupil P133 is defined as length a7. As can be seen from FIG. 1 , the sum of lengths a5, a6, and a7 is equal to length a2.

[0051] 1, when comparing the optical path lengths of the optical paths L1 to L3, the optical path length of the optical path L1 is the shortest, the optical path length of the optical path L2 is longer than the optical path L1 by a length a3, and the optical path length of the optical path L3 is longer than the optical path L1 by the sum of the lengths a3 and a4. The optical path adjustment unit is configured to make the air-equivalent optical path lengths of the optical paths L1 to L3, which are different from one another, uniform.

[0052] In the optical path selector 12, a mirror 124 and a mirror 125 are formed on the left and right sides, respectively, of the first block 121. Therefore, in the optical path L2, quartz glass is interposed between the mirror 124 and the mirror 125 and between the mirror 125 and the objective lens 132. In other words, a high refractive index medium is disposed on the optical path L2 from the imaging lens 11 to the objective lens 132.

[0053] Similarly, in the optical path selector 12, a mirror 124 and a mirror 126 are formed on the left and right sides, respectively, of the second block 122. Therefore, in the optical path L3, quartz glass is interposed between the mirror 124 and the mirror 126 and between the mirror 126 and the objective lens 133. In other words, a high refractive index medium is disposed on the optical path L3 from the imaging lens 11 to the objective lens 133.

[0054] Silica glass is an example of a high-refractive index medium having a refractive index higher than that of air. The relative refractive index of silica glass to air is approximately 1.5. If the relative refractive index of the high-refractive index medium is N, the optical path length of the optical path in the high-refractive index medium is L, and the air-equivalent optical path length of the optical path is L', then the air-equivalent optical path length L' is given by L' = L / N. Because the relative refractive index N of the high-refractive index medium is greater than 1, the air-equivalent optical path length L' can be made shorter than the optical path length L.

[0055] Here, the optical path lengths L(L1), L(L2), and L(L3) of the optical paths L1, L2, and L3 are respectively as follows: L(L1) = a1 + a5 + a6 + a7 L(L2) = a1 + a3 + a5 + a6 + a7 L(L3) = a1 + a3 + a4 + a5 + a6 + a7 Furthermore, the air-equivalent optical path lengths L'(L1), L'(L2), and L'(L3) of the optical paths L1, L2, and L3 are respectively as follows: L'(L1) = a11 + a12 / N + a5 + a6 + a7 L'(L2) = a11 + a12 / N + (a3 + a5) / N + a6 + a7 L'(L3) = a11 + a12 / N + (a3 + a4 + a5 + a6) / N + a7 Here, in order to align (in other words match) the air-equivalent optical path lengths L'(L1), L'(L2), and L'(L3), the shape of the optical path selector 12 may be designed so that a5 + a6 + a7, (a3 + a5) / N + a6 + a7, and (a3 + a4 + a5 + a6) / N + a7 are equal. In this embodiment, the shape of the optical path selector 12 is designed so that the air-equivalent optical path length L' (L1), the air-equivalent optical path length L' (L2), and the air-equivalent optical path length L' (L3) are equal.

[0056] (Optical System Preceding the Imaging Optical System) We will now explain the optical system preceding the imaging optical system among the optical systems of the exposure apparatus 10. This optical system is located preceding the imaging lens 11, and as shown in FIG. 1 , includes a laser 14, a Pockels cell 15, a galvanometer scanner 16, and a field lens 17.

[0057] The laser 14 is a laser light source that outputs the above-mentioned exposure beam. The exposure device 10 is an exposure device used for stereolithography using the ImpFab method. Therefore, the laser 14 can be appropriately selected from laser light sources used in the ImpFab method. The laser 14 may be a fixed-wavelength laser that cannot change the wavelength of the exposure beam it outputs, or a tunable laser that can change the wavelength of the exposure beam it outputs. In this embodiment, a Ti:sapphire laser, an example of a tunable laser, is used as the laser 14.

[0058] Preferred wavelengths of the laser 14 include 780 nm, 915 nm, and 1060 nm. However, the wavelength of the laser 14 is not limited to these and can be appropriately selected depending on the material constituting the gel 41 and the dye contained in the solvent 43.

[0059] In addition, the ImpFab method performs optical shaping by applying the principle of multiphoton absorption, and therefore the laser 14 is preferably a pulsed laser.

[0060] The Pockels cell 15 is disposed after the laser 14 and is an example of an intensity modulator that modulates the intensity of the exposure beam output from the laser 14, and is classified as an electro-optic modulator (EOM). Other examples of intensity modulators include an acousto-optic modulator (AOM) and a semiconductor optical modulator (SOM).

[0061] The galvano scanner 16 is disposed after the Pockels cell 15 and before the imaging lens 11, and is an example of a scanning optical system that switches the direction of the chief ray of the exposure beam intensity-modulated by the Pockels cell 15. A fixed point P16 of the galvano scanner 16 is disposed at a conjugate point of the objective lens 131 (more specifically, pupil P131) on the optical path of the exposure beam intensity-modulated by the Pockels cell 15.

[0062] As described above, the shape of the optical path selector 12 is designed so that the air-equivalent optical path lengths L' (L1), L' (L2), and L' (L3) are equal. Therefore, the fixed point P16 of the galvano scanner 16 is located at a conjugate point of the objective lens 132 (more specifically, pupil P132) and at a conjugate point of the objective lens 133 (more specifically, pupil P133) on the optical path of the exposure beam intensity-modulated by the Pockels cell 15. That is, the galvano scanner 16 is located at a common conjugate point with respect to the multiple objective lenses 131 to 133 on the optical path of the exposure beam intensity-modulated by the Pockels cell 15. In other words, the multiple objective lenses 131 to 133 have a common conjugate position with respect to the imaging lens 11, and the galvano scanner 16 is located at this common conjugate position.

[0063] In the exposure apparatus 10 configured as described above, a point located downstream of the galvano scanner 16 where the exposure beam is focused is referred to as focus PC, and a point where the exposure beam emitted from the objective lens 131 is focused at a desired depth in the gel 41 is referred to as focus P411. Similarly, the foci corresponding to the objective lens 132 and the objective lens 133 are referred to as focus P412 and focus P413, respectively. On the optical path of the exposure beam intensity-modulated by the Pockels cell 15, the focus PC is located at a common conjugate point with respect to the multiple foci P411 to P413. In other words, the multiple foci P411 to P413 have a common conjugate position with respect to the imaging optical system (the imaging lens 11 and the objective lenses 131 to 133), and the focus PC is located at this common conjugate position.

[0064] The field lens 17 is a lens located near the fixed point P16 of the galvano scanner 16, and adjusts the direction of travel of the light not only in the center of the exposure beam but also in the peripheral area. As a result, the area that can be exposed can be expanded compared to when the field lens 17 is omitted.

[0065] In exposure apparatus 10, field lens 17 is composed of a single lens as shown in Fig. 1. However, in one aspect of exposure apparatus 10, field lens 17 may be composed of a compound lens that combines multiple lenses.

[0066] [Embodiment 2] An exposure apparatus 20 according to embodiment 2 of the present invention will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram of the exposure apparatus 20. Figure 4 is a front view (lower diagram) and a plan view (upper diagram) of an optical path selector 22 provided in the exposure apparatus 20. The Cartesian coordinates shown in Figures 3 and 4 can be obtained by replacing the objective lenses 131 to 133 in the explanation of the Cartesian coordinates shown in Figure 1 with the objective lenses 231 to 233.

[0067] <Object to be Exposed> The object to be exposed used in exposure apparatus 20 is gel 41, the same as the object to be exposed used in exposure apparatus 10. In addition, a petri dish 42 that contains gel 41, a solvent 43 filled in petri dish 42, and a glass plate 44 that serves as a lid are also the same as those used in exposure apparatus 10. Therefore, in embodiment 2, description of these will be omitted.

[0068] <Configuration of exposure device> As shown in Figure 3, the exposure device 20 includes an imaging lens 21, an optical path selector 22, an objective lens group 23, a laser 24, a DMD 25, a galvanometer scanner 26, a field lens 27, a field lens 28, a field lens 29, a projection lens 31, and a mirror 32.

[0069] In this embodiment, we will explain the imaging optical system located at the rear stage of the optical system of the exposure device 20, and then we will explain the laser 24, DMD 25, galvanometer scanner 26, field lenses 27 to 29, projection lens 31, and mirror 32 located at the front stage of the exposure device 20.

[0070] (Imaging Optical System) As shown in FIG. 3, the imaging optical system of the exposure apparatus 20 includes an imaging lens 21, an optical path selector 22, and an objective lens group 23.

[0071] The imaging lens 21 is the same lens as the imaging lens 11 of the exposure apparatus 10 .

[0072] The objective lens group 23 is the same lens group as the objective lens group 13 of the exposure apparatus 10. That is, the objective lens group 23 is made up of three objective lenses 231, 232, and 233. Furthermore, the pupil P231 of the objective lens 231, the pupil P232 of the objective lens 232, and the pupil P233 of the objective lens 233 correspond to the pupil P131 of the objective lens 131, the pupil P132 of the objective lens 132, and the pupil P133 of the objective lens 133, respectively, in the exposure apparatus 10. Description of these will be omitted here.

[0073] The optical path selector 22 is a modified example of the optical path selector 12 of the exposure apparatus 10. The optical path selector 22 is a block made of glass (quartz glass in this embodiment) like the optical path selector 12. Front views of the optical path selector 22 are shown in the lower drawings of Figures 3 and 4, and a plan view of the optical path selector 22 is shown in the upper drawing of Figure 4.

[0074] The optical path selector 22 includes a first block 221, a second block 222, a third block 223, a mirror 224, a mirror 225, and a mirror 226. In this embodiment, the first block 221 and the second block 222 are molded as separate bodies. The second block 222 and the third block 223 are molded as a single body. However, in one aspect of the optical path selector 22, the second block 222 and the third block 223 may be molded as separate bodies and joined to each other (for example, by adhesion or fusion).

[0075] The first block 221 has the same shape as the first block 121 of the optical path selector 12. That is, the shape of the front of the first block 221 is a parallelogram, with one pair of diagonals at 45° and the other pair of diagonals at 135°. Of the two pairs of opposite sides of the first block 221, the length of the pair of opposite sides that are arranged parallel to the Y-axis direction is a3 (see the plan view in FIG. 4). Here, a description of the first block 221 will be omitted.

[0076] The second block 222 has the same shape as the first block 221. That is, the front shape of the second block 222 is a parallelogram, with one pair of diagonal angles at 45° and the other pair of diagonal angles at 135°. Of the two pairs of opposite sides of the second block 222, the pair of opposite sides that are arranged parallel to the Y-axis direction has a length a4 (see the plan view in FIG. 4 ) that is equal to the length a3. Here, a description of the second block 222 will be omitted.

[0077] The third block 223 has the same shape as the third block 123 of the optical path selector 12. That is, the third block 223 is a rectangular parallelepiped. Here, a description of the third block 223 will be omitted.

[0078] In this embodiment, a mirror 224 (described later) is provided on the left side surface of the first block 221. A mirror 225 (described later) is provided between the right side surface of the first block 221 and the left side surface of the second block 222. A mirror 226 (described later) is provided on the right side surface of the second block 222.

[0079] The mirror 224 is an example of a first reflecting surface that reflects the exposure beam that has passed through the imaging lens 21. One of the mirrors 225 and 226 is an example of a second reflecting surface that further reflects the exposure beam reflected by the mirror 224 (an example of a first reflecting surface). In the exposure device 20, the mirror 224 can be considered as the first reflecting surface and the mirror 225 can be considered as the second reflecting surface, or the mirror 226 can be considered as the second reflecting surface. In this embodiment, the mirrors 224 and 225 will be described as the first reflecting surface and the second reflecting surface, respectively. The mirror 226 will also be described as a third reflecting surface.

[0080] In the optical path selector 12, metal films are used as the mirrors 124 to 126. On the other hand, in the optical path selector 22, mirrors called switchable mirrors or switchable mirror devices are used as the mirrors 224 to 226. Mirrors called switchable mirrors or switchable mirror devices can be electrically switched between a light reflecting state and a light transmitting state. In the following, for each of the mirrors 224 to 226, the light reflecting state is referred to as the enabled state of the mirror, and the light transmitting state is referred to as the disabled state of the mirror.

[0081] In the optical path selector 22 configured as described above, (1) when mirror 224 is disabled, the exposure beam incident on mirror 224 is incident on objective lens 231, (2) when mirrors 224 and 225 are enabled, the exposure beam is incident on objective lens 232, and (3) when mirrors 224 and 226 are enabled, the exposure beam is incident on objective lens 233. In this way, the optical path selector 22 switches whether the exposure beam is incident on objective lens 231, objective lens 232, or objective lens 233 by electrically controlling whether mirrors 224, 225, and 226 transmit or reflect the exposure beam.

[0082] Furthermore, when expressing the function of the optical path selector 22 from the perspective of the objective lens group 23, (1) the exposure beam obtained when mirror 224 of the optical path selector 22 is disabled is incident on objective lens 231, (2) when mirror 224 and mirror 225 are enabled, the exposure beam reflected by mirror 224 is further reflected by mirror 225 and incident on objective lens 232, and (3) when mirror 224 and mirror 226 are enabled, the exposure beam reflected by mirror 224 is further reflected by mirror 226 and incident on objective lens 233.

[0083] The function of the optical path selector 22 as an optical path length adjustment unit is the same as the function of the optical path selector 12 as an optical path length adjustment unit. Therefore, here, a description of the function of the optical path selector 22 as an optical path length adjustment unit will be omitted.

[0084] (Optical System Preceding the Imaging Optical System) We will now explain the optical system preceding the imaging optical system among the optical systems of the exposure apparatus 20. This optical system is arranged preceding the imaging lens 21, and as shown in Figure 3, includes a laser 24, a DMD 25, a galvanometer scanner 26, a field lens 27, a field lens 28, a field lens 29, a projection lens 31, and a mirror 32.

[0085] The laser 24 is the same laser light source as the laser 14, and therefore its description will be omitted.

[0086] The galvanometer scanner 26 is disposed downstream of the laser 24 and is an example of a scanning optical system that switches the chief ray direction of the exposure beam output from the laser 24. The galvanometer scanner 26 is the same galvanometer scanner as the galvanometer scanner 16. A fixed point P26 of the galvanometer scanner 26 is disposed at a conjugate point of the projection lens 31 (more specifically, pupil P31) on the optical path of the exposure beam output from the laser 24. In other words, the fixed point P26 of the galvanometer scanner 26 is located at a conjugate position of the projection lens 31 (more specifically, pupil P31) with respect to the DMD 25.

[0087] The DMD 25 is an abbreviation for Digital Mirror Device. The DMD 25 is disposed after the galvanometer scanner 26 and is an example of a spatial intensity modulator that performs two-dimensional spatial intensity modulation on the exposure beam emitted from the galvanometer scanner 26. An example of a spatial intensity modulator other than the DMD is LCOS (Liquid Crystal On Silicon).

[0088] The projection lens 31 is disposed after the DMD 25 and before the imaging lens 21. The projection lens 31 is disposed on the optical path of the exposure beam spatially intensity modulated by the DMD 25, with its pupil P31 being at a conjugate point with the objective lens 231 (more specifically, pupil P231).

[0089] Similarly to the optical path selector 12, the optical path selector 22 is designed such that the air-equivalent optical path lengths L' (L1), L' (L2), and L' (L3) are equal. Therefore, the pupil P31 of the projection lens 31 is located at a conjugate point of the objective lens 232 (more specifically, pupil P232) and at a conjugate point of the objective lens 233 (more specifically, pupil P233) on the optical path of the exposure beam whose intensity has been modulated by the DMD 25. That is, the pupil P31 of the projection lens 31 is located at a common conjugate point with respect to the objective lenses 231 to 233 on the optical path of the exposure beam whose intensity has been modulated by the DMD 25. In other words, the pupils P231 to P233 of the objective lenses 231 to 233 are located at a common conjugate point with respect to the imaging lens 21.

[0090] In the exposure apparatus 20 configured as described above, the point located after the projection lens 31 where the exposure beam focuses is referred to as focus PC. As in the case of the exposure apparatus 10, the point where the exposure beam emitted from the objective lens 231 focuses at a position of the desired depth in the gel 41 is referred to as focus P411. Similarly, the focal points corresponding to the objective lens 232 and the objective lens 233 are referred to as focus P412 and focus P413, respectively. On the optical path of the exposure beam two-dimensionally spatially intensity modulated by the DMD 25, the focus PC is located at a common conjugate point with respect to the multiple foci P411 to P413. In other words, the multiple foci P411 to P413 have a common conjugate position with respect to the imaging lens 21, and the focus PC is located at this common conjugate position.

[0091] Furthermore, the pupil P25 of the DMD 25 is disposed at a conjugate point of the focal point PC on the optical path of the exposure beam emitted from the galvano scanner 26. In other words, the pupil P25 of the DMD 25 is located at a conjugate position of the focal point PC with respect to the projection lens 31.

[0092] The field lens 27 is a lens disposed near the pupil P31 of the projection lens 31, and adjusts the direction of travel of the light not only in the center but also in the peripheral portion of the exposure beam. As a result, the area that can be exposed can be expanded compared to when the field lens 27 is omitted.

[0093] Field lens 28 is a field lens arranged in the vicinity of the rear stage of galvano scanner 26. Field lens 29 is a field lens arranged in the vicinity of the front stage of DMD 25. Like field lens 27, field lenses 28 and 29 adjust the traveling direction of light not only in the center of the exposure beam but also in the peripheral portion.

[0094] The mirror 32 is disposed after the projection lens 31 and before the imaging lens 21. The mirror 32 reflects the exposure beam, thereby folding back the chief ray of the exposure beam at a right angle.

[0095] <Summary of exposure device> As described above, the exposure device 20 comprises a single imaging lens 21 arranged on the optical path of the exposure beam, a plurality of objective lenses 231 to 233 that focus the exposure beam on the gel 41, an optical path selector 22 that switches which of the plurality of objective lenses 231 to 233 the exposure beam that has passed through the imaging lens 21 is to be incident on, and an optical path length adjustment unit that aligns the air-equivalent optical path lengths L1' to L3' of the optical paths L1 to L3 from the imaging lens 21 to each of the plurality of objective lenses 231 to 233.

[0096] Furthermore, the optical path selector 22 includes a mirror 224 (an example of a first reflecting surface) that reflects the exposure beam that has passed through the imaging lens 21, and a mirror 225 or a mirror 226 (an example of a second reflecting surface) that further reflects the exposure beam reflected by the mirror 224, and the multiple objective lenses 231 to 223 include an objective lens 231 onto which the exposure beam obtained when the mirror 224 is disabled is incident, and an objective lens 232 or an objective lens 233 other than the objective lens 231. For example, if the second reflecting surface is the mirror 225, the mirror 225 causes the exposure beam reflected by the mirror 224 to be incident on the objective lens 232 when the mirror 224 is enabled, and the optical path length adjustment unit of the optical path selector 22 includes a high refractive index medium arranged on the optical path from the mirror 224 to the objective lens 232.

[0097] In addition, the optical path selector 22 electrically controls whether the mirror 224 transmits or reflects the exposure beam, thereby switching between making the exposure beam incident on the objective lens 231 and making the exposure beam incident on the objective lens 232.

[0098] The exposure device 20 also includes, in front of the imaging lens 21, a galvanometer scanner 26 which is an example of a scanning optical system that switches the direction of the chief ray of the exposure beam output from the laser 24, a DMD 25 which is an example of a spatial intensity modulator that performs two-dimensional spatial intensity modulation on the exposure beam output from the galvanometer scanner 26, and a projection lens 31 which is arranged at a common conjugate point with respect to the plurality of objective lenses 231 to 233 on the optical path of the exposure beam spatially intensity modulated by the DMD 25.

[0099] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0100] [Summary] In order to solve the above problems, the exposure apparatus according to aspect 1 of the present invention comprises a single imaging lens arranged on the optical path of an exposure beam, a plurality of objective lenses that focus the exposure beam on an exposure object, an optical path selector that switches which of the plurality of objective lenses the exposure beam that has passed through the imaging lens is incident on, and an optical path length adjustment unit that aligns the air-equivalent optical path lengths of the optical paths from the imaging lens to each of the plurality of objective lenses.

[0101] According to the above configuration, by using an optical path selector to select the objective lens to be used for exposure, it is possible to expose the exposure area corresponding to each objective lens without changing the relative position between the imaging optical system and the exposure object. For example, if the number of objective lenses provided in this exposure apparatus is n, this exposure apparatus can expose an exposure area with an area n times larger than that of a conventional exposure apparatus that uses a single objective lens. Therefore, this exposure apparatus can expand the area that can be exposed without changing the relative position between the imaging optical system and the exposure object.

[0102] In addition, in an exposure apparatus according to a second aspect of the present invention, in addition to the configuration of the exposure apparatus according to the first aspect described above, the optical path selector includes a first reflecting surface that reflects the exposure beam that has passed through the imaging lens, and a second reflecting surface that further reflects the exposure beam reflected by the first reflecting surface, the plurality of objective lenses include a first objective lens onto which the exposure beam obtained when the first reflecting surface is disabled is incident, and a second objective lens other than the first objective lens, the second reflecting surface causes the exposure beam reflected by the first reflecting surface to be incident on the second objective lens when the first reflecting surface is enabled, and the optical path length adjustment unit includes a high refractive index medium arranged on the optical path from the first reflecting surface to the second objective lens.

[0103] Here, the optical path from the first reflecting surface to the first objective lens when the optical path selector selects the first objective lens is called the "first optical path," and the optical path length from the first reflecting surface to the second objective lens when the optical path selector selects the second objective lens is called the "second optical path." Since the second optical path is reflected by each of the first reflecting surface and the second reflecting surface, the optical path length of the second optical path is longer than the optical path length of the first optical path. In this exposure apparatus, a high-refractive-index medium is disposed on the optical path from the first reflecting surface to the second objective lens, so that the difference between the air-equivalent optical path length of the first optical path and the air-equivalent optical path length of the second optical path can be reduced.

[0104] Furthermore, in the exposure apparatus according to the third aspect of the present invention, in addition to the configuration of the exposure apparatus according to the second aspect described above, the optical path selector is configured to switch between causing the exposure beam to be incident on the first objective lens or causing the exposure beam to be incident on the second objective lens by mechanically inserting and removing the first reflecting surface and the second reflecting surface from the optical path of the exposure beam.

[0105] Furthermore, in the exposure apparatus according to the fourth aspect of the present invention, in addition to the configuration of the exposure apparatus according to the second aspect described above, a configuration is adopted in which the optical path selector electrically controls whether the first reflecting surface transmits or reflects the exposure beam, thereby switching between making the exposure beam incident on the first objective lens or making the exposure beam incident on the second objective lens.

[0106] As in the exposure apparatus according to the third aspect, the selection of whether to enable or disable the first and second reflecting surfaces can be performed by mechanically inserting or removing the first and second reflecting surfaces, or as in the exposure apparatus according to the fourth aspect, the selection can be performed by electrical control.

[0107] Furthermore, in an exposure apparatus according to a fifth aspect of the present invention, in addition to the configuration of the exposure apparatus according to any one of the first to fourth aspects described above, an intensity modulator that intensity-modulates the exposure beam output from a light source, and a scanning optical system that switches the direction of the chief ray of the exposure beam intensity-modulated by the intensity modulator, the scanning optical system being positioned at a common conjugate point with respect to the plurality of objective lenses on the optical path of the exposure beam intensity-modulated by the intensity modulator, are provided upstream of the imaging lens.

[0108] According to the exposure apparatus of the fifth aspect, an object can be patterned by scanning an intensity-modulated exposure beam within the range of the field-of-view size of the objective lens. In this exposure apparatus, the scanning optical system and each of the plurality of objective lenses are located at a common conjugate point, so the field-of-view size of each objective lens can be effectively utilized to expose the object. Therefore, the exposable area can be reliably expanded without changing the relative position between the imaging optical system and the exposure object.

[0109] Furthermore, in an exposure apparatus according to a sixth aspect of the present invention, in addition to the configuration of the exposure apparatus according to any one of the first to fourth aspects described above, the exposure apparatus further comprises, in front of the imaging lens, a scanning optical system that switches the direction of the chief ray of the exposure beam output from a light source, a spatial intensity modulator that performs two-dimensional spatial intensity modulation on the exposure beam output from the scanning optical system, and a projection lens that is positioned at a common conjugate point with respect to the plurality of objective lenses on the optical path of the exposure beam that has been spatial intensity modulated by the spatial intensity modulator.

[0110] According to the exposure apparatus of the sixth aspect, an object can be patterned by irradiating it with a spatially modulated exposure beam within the range of the field of view size of the objective lens. In this exposure apparatus, the projection lens and each of the objective lenses are positioned at a common conjugate point, so the field of view size of each objective lens can be effectively utilized to expose the object. Therefore, the exposable area can be reliably expanded without changing the relative position between the imaging optical system and the exposure object.

[0111] 10, 20 Exposure device 11, 21 Imaging lens 12, 22 Optical path selector 121, 221 First block 122, 222 Second block 123, 223 Third block 124 to 126, 224 to 226 Mirror 13, 23 Objective lens group 131 to 133, 231 to 233 Objective lens 14, 24 Light source (laser) 15, 25 Intensity modulator (Pockels cell, DMD) 16, 26 Galvano scanner 17, 27, 28, 29 Field lens 31 Projection lens 32 Mirror 41 Gel 42 Petri dish 43 Solvent 44 Glass plate

Claims

1. An exposure apparatus comprising: a single imaging lens arranged on the optical path of an exposure beam; a plurality of objective lenses that focus the exposure beam on an object to be exposed; an optical path selector that switches which of the plurality of objective lenses the exposure beam that has passed through the imaging lens is incident on; and an optical path length adjustment unit that aligns the air-equivalent optical path lengths of the optical paths from the imaging lens to each of the plurality of objective lenses.

2. The exposure apparatus according to claim 1, wherein the optical path selector includes a first reflecting surface that reflects the exposure beam that has passed through the imaging lens, and a second reflecting surface that further reflects the exposure beam reflected by the first reflecting surface; the plurality of objective lenses include a first objective lens onto which the exposure beam obtained when the first reflecting surface is disabled is incident, and a second objective lens other than the first objective lens; the second reflecting surface causes the exposure beam reflected by the first reflecting surface to be incident on the second objective lens when the first reflecting surface is enabled; and the optical path length adjustment unit includes a high refractive index medium arranged on the optical path from the first reflecting surface to the second objective lens.

3. The exposure apparatus according to claim 2, wherein the optical path selector switches between directing the exposure beam to the first objective lens and directing the exposure beam to the second objective lens by mechanically inserting and removing the first reflecting surface and the second reflecting surface into and from the optical path of the exposure beam.

4. The exposure apparatus according to claim 2, wherein the optical path selector switches between directing the exposure beam to the first objective lens or directing the exposure beam to the second objective lens by electrically controlling whether the first reflecting surface transmits or reflects the exposure beam.

5. An exposure apparatus according to any one of claims 1 to 4, comprising, in front of the imaging lens, an intensity modulator that intensity-modulates the exposure beam output from a light source, and a scanning optical system that switches the direction of the chief ray of the exposure beam intensity-modulated by the intensity modulator, the scanning optical system being positioned at a common conjugate point with respect to the plurality of objective lenses on the optical path of the exposure beam intensity-modulated by the intensity modulator.

6. An exposure apparatus according to any one of claims 1 to 4, comprising: a scanning optical system that switches the direction of the chief ray of the exposure beam output from a light source; a spatial intensity modulator that performs two-dimensional spatial intensity modulation on the exposure beam output from said scanning optical system; and a projection lens that is positioned at a common conjugate point with respect to said plurality of objective lenses on the optical path of the exposure beam that has been spatially intensity modulated by said spatial intensity modulator, located before said imaging lens.

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