Light source device and exposure device

Abstract

To provide a light source device which lowers such a light quantity that return light reaches an emission end of an optical fiber while suppressing increase in a divergence angle.SOLUTION: A light source device includes: a light source; an optical fiber for guiding light emitted from the light source; a refractive optical system for condensing the light emitted from the optical fiber; and a rod integrator including an incident surface on which the light emitted from the refractive optical system has been incident. The rod integrator has such a shape that the incident surface is inclined on a reference plane orthogonal to an optical axis of the refractive optical system in a clockwise or counter clockwise rotation direction by an angle θi(0<θi<90 degrees), and a central axis is inclined to the optical axis in the rotation direction by an angle θr(0<θr<90 degrees). The angle θi and the angle θr satisfy a relation of expression (1). Expression (1): θr<2×(θi-asin(sin(θi) / n)). (where n is a refractive index of the rod integrator.).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a light source device and an exposure apparatus. [Background technology]

[0002] Direct imaging (DI) exposure is one of the photolithography techniques that forms a desired pattern on a photosensitive material applied to a workpiece. In DI exposure, light of the desired circuit pattern formed by a spatial light modulator is irradiated onto the photosensitive material applied to the workpiece for exposure.

[0003] A light source device used in DI exposure has a light source and an incident optical system that causes the light emitted from the light source to enter the spatial light modulator. The incident optical system may use an optical unit that includes an optical fiber that guides the light emitted from the light source and a rod integrator (sometimes called a "rod lens" or "integrator rod") that homogenizes the light emitted from the optical fiber.

[0004] In an optical unit including an optical fiber and a rod integrator, when light emitted from the optical fiber is incident on the rod integrator, a part of the emitted light is reflected on the incident surface of the rod integrator, which may cause backlight. The backlight reaches the output end of the optical fiber, penetrates into the optical fiber, and returns to the light source, which may cause fluctuations in the magnitude of the optical output of the light source.

[0005] Patent Document 1 is a conventionally known technique for dealing with such a problem. Patent Document 1 discloses a method of arranging a bundle fiber 91 and a rod integrator 92 so that the optical axis of light L9 (more specifically, the main ray) emitted from a bundle fiber 91 made of bundled optical fibers is inclined (at an angle θ9) with respect to the normal direction of an incident surface 93 of the rod integrator 92, as shown in an optical unit 90 in Fig. 9. According to this method, even if light L9 emitted from the bundle fiber 91 is reflected by the incident surface 93 of the rod integrator 92, the optical axis of the main ray B9 of the reflected light faces a different direction from the exit end of the bundle fiber 91, so that the amount of return light reaching the exit end of the bundle fiber 91 decreases. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-300823 A Summary of the Invention [Problem to be solved by the invention]

[0007] 9, the light L9 incident on the rod integrator 92 is largely deviated from the central axis 92c of the rod integrator 92, and the light L9 traveling inside the rod integrator 92 is repeatedly reflected inside the rod integrator 92. As a result, the divergence angle of the light L9 increases when it is emitted from the rod integrator 92. If the divergence angle of the light emitted from the rod integrator 92 increases, the optical system disposed downstream must be increased in size. In addition, there is a concern that the light utilization efficiency may decrease due to the presence of light that is not incident on the downstream optical system.

[0008] Therefore, an object of the present invention is to provide a light source device that reduces the amount of returned light that reaches the output end of the optical fiber while suppressing an increase in the divergence angle, and an exposure apparatus equipped with such a light source device. [Means for solving the problem]

[0009] The light source device of the present invention comprises a light source and an optical fiber that guides the light emitted from the light source; a refractive optical system that collects the light emitted from the optical fiber; a rod integrator including an incident surface onto which the light emitted from the refractive optical system is incident, the rod integrator has a shape in which the entrance surface is inclined by an angle θi (0<θi<90 degrees) in a clockwise or counterclockwise rotational direction with respect to a reference plane orthogonal to an optical axis of the refractive optical system, and a central axis is inclined by an angle θr (0<θr<90 degrees) in the rotational direction with respect to the optical axis, The angle θi and the angle θr satisfy the relationship of the following formula (1). θr<2×(θi-asin(sin(θi) / n)) …(1) (In formula (1), n ​​is the refractive index of the rod integrator.)

[0010] Although the details will be described later, the rod integrator has a shape in which the incident surface is inclined at an angle θi and the central axis is inclined at an angle θr, so that the light incident on the rod integrator proceeds without being significantly deviated from the central axis of the rod integrator. As a result, the number of times that the light proceeding inside the rod integrator is reflected inside the rod integrator is reduced, and an increase in the divergence angle of the light emitted from the rod integrator is suppressed. Furthermore, since the optical fiber and the rod integrator are separated to the extent that a refractive optical system is interposed between them, even if returning light occurs, the amount of the returning light that reaches the light exit end of the optical fiber can be reduced.

[0011] Furthermore, the angle θi and the angle θr may satisfy the relationship of the following formula (2). 0.8×(θi-asin(sin(θi) / n)) < θr < 1.2×(θi-asin(sin(θi) / n)) …(2) This can further reduce the amount of deviation of the light traveling inside the rod integrator from the central axis of the rod integrator, thereby further reducing the number of times the light traveling inside the rod integrator is reflected inside the rod integrator, and further suppressing an increase in the divergence angle of the light emitted from the rod integrator.

[0012] Furthermore, θr may be substantially equal to θi-asin(sin(θi / n). When θr is substantially equal to θi-a sin(sin(θi / n)), the number of times the light traveling inside the rod integrator is reflected within the rod integrator is further reduced, further suppressing the increase in the divergence angle of the light exiting the rod integrator.

[0013] In the actual design of an optical device, various manufacturing errors and the like usually occur. In addition, when measuring an optical device, measurement errors and calculation errors of the angles of optical members also occur. Therefore, in this specification, in a certain optical device, when the angle difference between the measured value of θr and the value obtained by calculating θi-asin(sin(θi / n)) from the measured θi is less than 1 degree, it is considered that "θr is substantially equal to θi-asin(sin(θi / n))."

[0014] the rod integrator includes an exit surface from which light incident from the entrance surface is emitted, The normal to the exit surface may be inclined with respect to the central axis, which will be described in detail later, thereby reducing the amount of return light reflected by the exit surface of the rod integrator and reaching the exit end of the optical fiber.

[0015] A light shielding portion that blocks return light from the incident surface of the rod integrator may be provided.

[0016] the light blocking portion has an opening larger than a diameter of light passing through the refractive optical system, The light emitted from the refractive optical system may pass through the opening and be incident on the incident surface of the rod integrator.

[0017] The light blocking portion may have a first light blocking region and a second light blocking region disposed opposite to each other with the optical system therebetween.

[0018] The entrance surface of the rod integrator may be rectangular and may have a shape rotated by the angle θi with respect to the reference plane around a short side of the rectangle as a rotation axis.

[0019] A plurality of said light sources; a plurality of optical fibers each guiding light emitted from the plurality of light sources, The plurality of optical fibers may form a bundle fiber in which at least the respective emission ends are bundled together.

[0020] The total amount of light emitted from the multiple light sources may exceed 1 W. Even if the light source has a high output of more than 1 W, it is possible to reduce the amount of returned light reaching the output end of the optical fiber while suppressing an increase in the divergence angle.

[0021] The main wavelength of the light emitted from the light source may be 350 to 450 nm. In this case, the wavelength of the return light is also 350 to 450 nm. An adhesive is sometimes used at the output end of the optical fiber, and return light having a wavelength of 350 to 450 nm is easily absorbed by the adhesive and burned. However, since the amount of return light that reaches the output end of the optical fiber is reduced, it is possible to prevent the adhesive from burning.

[0022] The exposure apparatus of the present invention includes the above light source device. Effect of the Invention

[0023] It is possible to provide a light source device in which the amount of returned light reaching the output end of the optical fiber is reduced while suppressing an increase in the divergence angle, and an exposure apparatus including the light source device. [Brief description of the drawings]

[0024] [Figure 1]FIG. 2 is a schematic cross-sectional view showing a main part of a light source device. [Diagram 2] FIG. 2 is an enlarged view of the vicinity of an incident surface of the rod integrator. [Figure 3A] This is a reference diagram in which the central axis of the rod integrator is on the extension of the optical axis of the condenser lens. [Figure 3B] FIG. 13 is a diagram showing an example of the present embodiment in which the central axis of the rod integrator is inclined with respect to the optical axis of the collecting lens. [Figure 4A] 2 is a diagram showing the position and shape of a light-shielding portion shown in FIG. 1. [Figure 4B] 13A and 13B are diagrams illustrating modified examples of the light blocking portion. [Figure 4C] 13A and 13B are diagrams illustrating modified examples of the light blocking portion. [Diagram 5] FIG. 13 is a diagram showing a modified example of an optical fiber. [Figure 6] FIG. 1 is a schematic diagram showing an exposure apparatus. [Figure 7] 1A to 1C are schematic diagrams showing features of rod integrators in nine types of light source devices. [Figure 8] 13 shows the results of a simulation regarding the divergence angle of light emitted from a rod integrator in nine types of light source devices. [Figure 9] FIG. 1 is a schematic diagram of a conventional optical unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Each embodiment will be described with reference to the drawings. Note that each drawing disclosed in this specification is merely a schematic illustration. In other words, the dimensional ratios on the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match.

[0026] In the following, each drawing will be described with reference to the XYZ coordinate system as appropriate. In this specification, when a direction is expressed and a positive or negative direction is to be distinguished, it is described with a positive or negative sign, such as "+X direction" and "-X direction". When a direction is expressed without distinguishing between positive and negative directions, it is simply described as "X direction". In other words, in this specification, when it is simply described as "X direction", both "+X direction" and "-X direction" are included. The same applies to the Y direction and the Z direction.

[0027] [Light source overview] 1 is a schematic cross-sectional view showing a main part of a light source device 10. The light source device 10 includes a light source 1, a fiber bundle 5 which is a bundle of optical fibers that guides the light emitted from the light source 1, a rod integrator 7 which homogenizes the light emitted from the fiber bundle 5, and a focusing lens 6 (corresponding to a "refractive optical system") which focuses the light emitted from the fiber bundle 5 onto the rod integrator 7.

[0028] 1, the light source 1 includes a plurality of solid-state light sources 3 arranged on a substrate 2. In this embodiment, laser diodes are used as the solid-state light sources 3, but other solid-state light sources such as LED light sources may also be used. By using a plurality of solid-state light sources, the output of the light source 1 can be increased. For example, the light source 1 can be configured to have an output of 20 W by using 20 laser diodes, each with an output of 1 W.

[0029] The light emitted from each solid-state light source 3 is incident on each optical fiber constituting the bundle fiber 5. The bundle fiber 5 is formed by bundling the emission ends of the individual optical fibers and bonding them with adhesive 15. In this way, by bundling the optical fibers, the light emitted from the multiple solid-state light sources is collected, thereby achieving high brightness of the light source 1. Such a structure of the light source device can also be applied to a light source device for an exposure device that requires high output.

[0030] The light emitted from the bundle fiber 5 passes through a condenser lens 6 that condenses the light onto a rod integrator 7, and enters an entrance surface 7a of the rod integrator 7. The condenser lens 6 is disposed so as to form an image of the exit surface of the bundle fiber 5 approximately on the entrance surface 7a of the rod integrator 7.

[0031] The "position where the image is almost formed" in the previous paragraph will be explained. As a result of the light being collected by the condenser lens 6, the light density at the incident surface 7a becomes excessively high. If there is a foreign object or a scratch on the incident surface 7a, there is a risk that the light will be concentrated on the foreign object or the scratch, causing the incident surface 7a to heat up and burn out. In order to reduce such a risk, the incident surface 7a is arranged at a position slightly shifted from the ideal imaging position of the condenser lens 6. This allows most of the light collected by the condenser lens 6 to be incident on the rod integrator 7, and prevents the incident surface 7a from burning out. Of course, if there is a small risk of the incident surface 7a burning out, the incident surface 7a may be arranged at the imaging position of the condenser lens 6.

[0032] In FIG. 1, the optical axis of focusing lens 6 (corresponding to optical axis 6c described later in FIG. 3A) is shown as being along the Z axis. However, if a reflecting mirror is placed after focusing lens 6 and the optical axis is bent, the direction in which the light ray along the original Z axis is reflected and travels is also called the Z axis, and no new coordinate axis is taken.

[0033] [Outline of the Rod Integrator] FIG. 2 is an enlarged perspective view of the vicinity of the incident surface of the rod integrator 7. In this embodiment, the rod integrator 7 is composed of a quadrangular prism lens (see FIG. 2). The quadrangular prism lens has four long side surfaces along the extension direction of the prism lens and two bottom surfaces arranged opposite to each other in the extension direction of the prism lens. Of the two bottom surfaces, one bottom surface is used as the incident surface 7a, and the other bottom surface is used as the exit surface 7b (see FIG. 1). The axis connecting the centers of the two bottom surfaces is called the central axis of the rod integrator 7. Light enters the prism lens from the incident surface 7a, and is homogenized by repeating total reflection within the prism lens, and the light exits the prism lens from the exit surface 7b. In this embodiment, a quadrangular prism lens is used for the rod integrator 7, but a triangular prism lens, a prism lens with five or more sides, or a cylindrical lens may also be used.

[0034] [Inclination of the entrance surface of the rod integrator] The shape of the rod integrator 7 will be described with reference to FIG. 1 and FIG. 2. First, the inclination of the incident surface 7a will be described. The incident surface 7a is inclined by an angle θi (0<θi<90 degrees) in a clockwise or counterclockwise rotational direction with respect to the reference plane 7s. The reference plane 7s is a surface perpendicular to the optical axis 6c of the condenser lens 6. Although FIG. 1 and FIG. 2 show a case in which the incident surface 7a is inclined by an angle θi counterclockwise, the following description is similar to the case in which the incident surface 7a is inclined by an angle θi clockwise. The same is true for the angles θr and θo. When distinguishing between positive and negative angles, the direction of the incident surface 7a with respect to the reference plane 7s is taken as the positive direction. That is, θi is always a positive value, and θr and θo are positive values ​​if they are in the same direction as θi, and negative values ​​if they are in the opposite direction.

[0035] Referring to FIG. 2, the incident surface 7a is a flat rectangle. The incident surface 7a has a shape rotated by an angle θi with respect to the reference plane 7s around the short side 7e of the rectangle as the rotation axis. This shape allows light to be incident on the rod integrator more easily than the incident surface 7a rotated by an angle θi with respect to the reference plane 7s around the long side 7q of the rectangle as the rotation axis. As a modified example, the incident surface 7a may be rotated by an angle θi with respect to the reference plane 7s around the long side 7q of the rectangle as the rotation axis. The incident surface 7a may also be a triangle, a trapezoid, a parallelogram, a polygon, or a circle. The incident surface 7a does not have to be flat. When the incident surface 7a is not flat, the inclination angle of the incident surface 7a is represented by the rotation angle of the tangent plane at the center of the incident surface 7a with respect to the reference plane 7s.

[0036] The effect obtained by inclining the incident surface 7a with respect to the reference plane 7s will be described. As shown in FIG. 1, a part of the light heading toward the rod integrator 7 is reflected by the incident surface 7a. Because the incident surface 7a is inclined with respect to the reference plane 7s, most of the light reflected by the incident surface 7a does not head toward the condenser lens 6. In the example of FIG. 1, most of the light reflected by the incident surface 7a heads toward the light blocking portion 18. Because the light reflected by the incident surface 7a does not head toward the condenser lens 6, it is possible to reduce the return light that reaches the output end of the bundle fiber 5.

[0037] If the returning light passes through the condenser lens 6, reaches the output end of the bundle fiber 5, and returns to the light source, the output of the output light may fluctuate. In addition, the coating material such as an anti-reflection material or foreign matter at the output end of the optical fiber may be heated, causing the coating material to peel off or the foreign matter to burn out.

[0038] Furthermore, as described above, in this embodiment, the adhesive 15 is used to bundle and fix the individual optical fibers at the output end (see FIG. 1). The adhesive 15 may be burned by the return light irradiated to the output end. In particular, light having a main wavelength of 350 to 450 nm is easily absorbed by the adhesive 15 and is easily burned. Therefore, when the main wavelength of the light emitted from the light source 1 is 350 to 450 nm, it is particularly important to suppress the return light irradiated to the output end of the bundle fiber 5. In this embodiment and in this specification, the "main wavelength" refers to the wavelength with the highest relative intensity on the emission spectrum.

[0039] [Tilt arrangement of rod integrator] 1 and 2, the central axis 7c of the rod integrator 7 (hereinafter sometimes simply referred to as "central axis 7c") is inclined at an angle θr (0<θr<90 degrees) in the counterclockwise rotational direction with respect to the optical axis 6c of the focusing lens 6. The effect of this will be described with reference to FIGS. 3A and 3B. Note that, in FIGS. 3A and 3B, for simplicity of explanation, it is assumed that the exit surface 7b of the rod integrator 7 is perpendicular to the central axis 7c.

[0040] FIG. 3A is a reference diagram showing a case where the central axis 7c is on the extension of the optical axis 6c of the condenser lens 6, that is, where θr is 0 degrees. The light emitted from the rod integrator 7 will be considered by taking as an example light L1 traveling on the optical axis 6c of the condenser lens 6 and light L2 traveling parallel to a position slightly shifted from L1. The light L1 and the light L2 are refracted at the incident surface 7a of the rod integrator 7 and travel inside the rod integrator 7 while being reflected at the side surface of the rod integrator 7 at an angle with respect to the central axis 7c. In FIG. 3A, the light L1 is reflected only once and the light L2 is reflected only twice, but since the actual rod integrator 7 is long in the direction of the central axis 7c, the light L1 and the light L2 are repeatedly reflected inside the rod integrator 7. It is assumed that the light L1 is reflected an odd number of times and the light L2 is reflected an even number of times.

[0041] Light L1 and light L2 are refracted at exit surface 7b and emitted. Both light L1 and light L2 emitted from exit surface 7b form an angle θd with respect to central axis 7c, but because light L1 is reflected an odd number of times within rod integrator 7 and light L2 is reflected an even number of times, they are emitted in opposite directions with respect to central axis 7c. Therefore, when the angle θd of light L1 is large, the divergence angle of the light beam emitted from rod integrator 7 also becomes large. In this specification, the divergence angle is defined as 1 / e 2 This refers to half the spread angle of a light beam that exhibits an intensity equal to or greater than this value.

[0042] 3B shows an example of this embodiment in which the central axis 7c is inclined with respect to the optical axis 6c of the collecting lens. Light L1 traveling on the optical axis 6c of the collecting lens 6 is refracted at the entrance surface 7a of the rod integrator 7 and travels inside the rod integrator 7. At this time, since the central axis 7c of the rod integrator 7 is also inclined, the number of times that the light L1 is reflected inside the rod integrator 7 decreases, and as a result, the divergence angle of the light beam emitted from the rod integrator 7 becomes a small value.

[0043] In Fig. 3B, rod integrator 7 is tilted in the counterclockwise rotation direction with respect to optical axis 6c, and the angle θr is set so that light L1 traveling inside rod integrator 7 travels along central axis 7c. As a result, in Fig. 3B, light L1 is not reflected inside rod integrator 7. When light L1 travels along central axis 7c, the divergence angle of the light beam emitted from rod integrator 7 has a particularly small value.

[0044] To design rod integrator 7 so that light L1 traveling within it travels along central axis 7c, in accordance with Snell's law, angles θi and θr should satisfy the following formula (3), where n is the refractive index of rod integrator 7. sin(θi)=nsin(θi-θr) …(3) Equation (3) can be transformed to obtain equation (4). θr=(θi-asin(sin(θi) / n)) …(4) In formula (4), asin represents arcsin.

[0045] In a theoretical design, formula (4) is satisfied, but in a practical design, there are manufacturing errors when manufacturing the rod integrator and assembly errors when assembling it to the optical device. In addition, there are measurement errors when measuring the manufactured optical device, and calculation errors when calculating the value of the above formula from the measurement values ​​of the optical device. Therefore, if the angle difference between θr and θi-asin(sin((θi) / n) is less than 1 degree, θr and θi-asin(sin((θi) / n) are considered to be substantially equal. In other words, when θr and θi-asin(sin((θi) / n) are substantially equal, the light L1 traveling inside the rod integrator 7 travels along the central axis 7c, reducing the number of reflections inside the rod integrator, and further suppressing an increase in the divergence angle of the light emitted from the rod integrator.

[0046] If θr is a value equal to or greater than 2×(θi-asin(sin(θi) / n)), rod integrator 7 will be excessively tilted, increasing the number of times that light L1 traveling inside rod integrator 7 is reflected within rod integrator 7. As a result, the divergence angle increases. Therefore, it is preferable that θr satisfy the following formula (1). θr<2×(θi-asin(sin(θi) / n)) …(1)

[0047] If θr is in a range that satisfies the following formula (2), it is possible to reduce the number of times that light L1 traveling inside rod integrator 7 is reflected inside rod integrator 7. As a result, it is possible to reduce the divergence angle. 0.8×(θi-asin(sin(θi) / n)) < θr < 1.2×(θi-asin(sin(θi) / n)) …(2)

[0048] [Inclination of the exit surface of the rod integrator] Referring to FIG. 1, the exit surface 7b of the rod integrator 7 is inclined at an angle θo counterclockwise with respect to a reference plane 7t. The reference plane 7t is a plane perpendicular to the optical axis 6c of the condenser lens 6. The angle θo that the exit surface 7b makes with respect to the reference plane 7t is not the same value as the angle θr. That is, in the embodiment of FIG. 1, the exit surface 7b is not perpendicular to the central axis 7c. Note that, in the embodiment of FIG. 1, the exit surface 7b is inclined by an angle θo around the Y-axis direction, but the rotation axis of the exit surface 7b is not limited to this direction. For example, the exit surface 7b may rotate around the X-axis direction, or may be inclined around any axis in the XY plane.

[0049] The effect of the exit surface 7b not being perpendicular to the central axis 7c will be described. The light traveling inside the rod integrator 7 may also be reflected by the exit surface 7b of the rod integrator 7, generating return light. For example, as shown in FIG. 3B, if the exit surface 7b is perpendicular to the central axis 7c, the light L1 traveling inside the rod integrator 7 is reflected by the exit surface 7b, generating return light B1. The return light B1 returns to follow the optical path of the light L1 that has traveled inside the rod integrator 7, passes through the condenser lens 6, and reaches the exit end of the bundle fiber 5. Therefore, the amount of return light that reaches the exit end of the bundle fiber 5 increases.

[0050] 1, when the exit surface 7b is not perpendicular to the central axis 7c, the returning light generated by reflection at the exit surface 7b returns along an optical path different from the optical path of the light that has traveled through the rod integrator 7. Therefore, compared to FIG. 3B, the returning light that reaches the exit end of the bundle fiber 5 is reduced.

[0051] [Shading part] 1, light source device 10 of the present embodiment has a light-shielding portion 18. Light-shielding portion 18 is a member for blocking return light from rod integrator 7. Light-shielding portion 18 is a dedicated member provided for blocking return light from rod integrator 7. Light-shielding portion 18 of the present embodiment is disposed on the +Z side with respect to condenser lens 6.

[0052] The light shielding portion 18 does not have to be a dedicated member for shielding the return light. For example, the return light may be shielded by a member provided for another purpose, such as a lens holder that supports the condenser lens 6. The housing of the light source device 10 also has a function of shielding the return light. In other words, the light source device 10 does not have to include the light shielding portion 18 as a dedicated member, and a member provided for a purpose other than light shielding may also serve as the light shielding portion 18.

[0053] 1 is viewed in the -Z direction from the position of the rod integrator 7. Because the incident surface 7a is inclined with respect to the reference plane 7s, the light-shielding portion 18 is disposed so that the center of the light-shielding portion 18 is located on the +X side of the center of the condenser lens 6. Because the light-shielding portion 18 is disposed in a space through which a large amount of return light passes, the return light can be effectively blocked.

[0054] In this embodiment, the light shielding portion 18 has a rectangular shape. In order to suppress reflection of light at the light shielding portion 18, it is preferable that the surface of the light shielding portion 18 has a high light absorbing effect, for example, a surface provided with minute irregularities that can diffusely reflect returning light.

[0055] Other examples of the light-shielding part are shown in Figs. 4B and 4C. As in Fig. 4A, Figs. 4B and 4C are views of the light-shielding part 18 and the condenser lens 6 viewed in the -Z direction from the position of the rod integrator 7. In the example of Fig. 4B, the light-shielding part 18 is composed of two light-shielding regions (18a, 18b). The center of the first light-shielding region 18a is located in the +X direction from the center of the condenser lens 6. The center of the second light-shielding region 18b is located in the -X direction from the center of the condenser lens 6. The first light-shielding region 18a and the second light-shielding region 18b are arranged opposite each other on the X axis with the center of the condenser lens 6 in between. The space in which the second light-shielding region 18b is arranged has the second largest amount of return light after the space in which the first light-shielding region 18a is arranged.

[0056] In the example of FIG. 4C, it is configured with an annular light-shielding portion 18c. The light-shielding portion 18c has an opening larger than the diameter of the light passing through the condenser lens 6. The light emitted from the condenser lens 6 passes through this opening and heads toward the incident surface 7a of the rod integrator 7. In this specification, the diameter of the light is expressed as 1 / e 2 It represents the diameter of a light beam that exhibits an intensity of 1000 nm or more.

[0057] The embodiment and modified examples of the light source device of the present invention have been described above. However, the light source device of the present invention is not limited to the above-mentioned embodiment and modified examples, and various changes and improvements can be made to the above-mentioned embodiment without departing from the spirit of the present invention.

[0058] In the above embodiment, the optical fiber is not necessarily a bundle fiber. FIG. 5 shows a modified example of the optical fiber. In this modified example, instead of the bundle fiber 5, a single optical fiber 31 is used. A ferrule 32 for holding the optical fiber 31 is arranged around the output end of the optical fiber 31. An adhesive 15 may be used between the optical fiber 31 and the ferrule 32. Even if the adhesive 15 is not used to fix the output end of the optical fiber 31 to the ferrule 32, as described above, foreign matter attached to the output end of the optical fiber may be burned by the return light, and a coating material such as an anti-reflection material formed on the output end surface of the optical fiber may be peeled off by the return light. Therefore, even if the optical fiber is not a bundle fiber 5, it is necessary to suppress the return light.

[0059] In the above embodiment, the refractive optical system that collects the light emitted from the optical fiber is composed of only one collecting lens 6. However, the refractive optical system is not limited to this configuration. For example, the refractive optical system may be composed of multiple lenses.

[0060] [Outline of the exposure equipment] The light source device 10 described above can be used as a light source for an exposure device. An outline of the exposure device will be described with reference to FIG. 6. FIG. 6 is a schematic diagram of the exposure device. The exposure device 100 includes the light source device 10, a spatial light modulator 51, a projection optical system 55, and a stage 61 on which a workpiece 60 is placed. The exposure device 100 is a DI (direct imaging) exposure device that projects an exposure pattern formed by the spatial light modulator 51 onto the workpiece 60 via the projection optical system 55. In the example of FIG. 6, the light source device 10 is equipped with a collimator lens 21 that converts the light emitted from the rod integrator 7 into parallel light, and a mirror 22 that reflects the light emitted from the collimator lens 21 toward the spatial light modulator 51.

[0061] By providing the above-described light source device 10, it is possible to suppress the spread of the divergence angle from the rod integrator 7 while suppressing the return light to the optical fiber (such as the bundle fiber 5). This reduces the device scale of the downstream optical system (such as the collimator lens 21).

[0062] Although the example of using the light source device 10 in a DI exposure device has been shown, the light source device 10 may be used in an exposure device other than a DI exposure device. Furthermore, the application of the light source device 10 is not limited to an exposure device. For example, the light source device 10 may be used as a light source device for a projector. EXAMPLES

[0063] FIG. 7 shows the characteristics of rod integrators 7 used in nine types of light source devices (device numbers (1-9)). Device numbers (1-9) differ in the inclination (angle θi) of incident surface 7a of rod integrator 7, the inclination (angle θo) of exit surface 7b, or the inclination (angle θr) of central axis 7c of the rod integrator. Simulations were performed for device numbers (1-9) to clarify the optical characteristics of the light source devices with device numbers (1-9).

[0064] Table 1 shows the characteristics of the rod integrators with device numbers (1 to 9) in numerical form. Angle θi represents the inclination angle of the entrance surface 7a with respect to a reference plane 7s perpendicular to the optical axis 6c of the focusing lens 6. Angle θr represents the inclination angle of the central axis 7c with respect to the optical axis 6c of the focusing lens 6. Angle θo represents the inclination angle of the exit surface 7b with respect to a reference plane 7t perpendicular to the optical axis 6c of the focusing lens 6 (see FIG. 1).

[0065] [Table 1]

[0066] In the rod integrators 7 with device numbers (1, 5, 6), θi is 6 degrees and θr is 1.9 degrees. In other words, θr is substantially equal to θi-asin(sin(θi / n). The rod integrator 7 including the device number 2 in addition to the device numbers (1, 5, 6) satisfies the relationship of the above formula (2), that is, 0.8×(θi-asin(sin(θi) / n)) < θr < 1.2×(θi-asin(sin(θi) / n)). The rod integrators 7 having device numbers (1 to 6) satisfy the above formula (1), that is, θr<2×(θi−asin(sin(θi) / n)). The rod integrator 7 of device number 7 satisfies the relationship θr=2×(θi−a sin(sin(θi) / n)). In the rod integrator 7 of device number 8, θr and θo are both 0 degrees. In the rod integrator 7 of device number 9, θr, θi, and θo are all 0 degrees.

[0067] Regarding the characteristics of the light source device other than the shape and arrangement of the rod integrator described above, the nine types of light source devices have the same characteristics as the light source device 10 shown in Fig. 1. In addition, the numerical values ​​shown below are common to the device numbers (1 to 9). Optical fiber configuration: 2 vertical x 2 horizontal, total of 4 bundled fibers Core diameter of each optical fiber: φ205μm Optical fiber bundle pitch: 260μm Divergence angle of optical fiber output: 4.5 degrees (1 / e 2 half width) Refractive optics: A condenser lens that focuses the end face of the fiber bundle onto the input surface of the rod integrator at a magnification of 1.5x. Shape of rod integrator: Prismatic lens with base dimensions of 1.2 mm x 1.7 mm Rod integrator length: 200mm Rod integrator incident light divergence angle: 3 degrees (1 / e 2 half width) Refractive index of rod integrator: n=1.47 Shading part: Circular aperture with opening of φ10mm

[0068] Fig. 7 shows how light L1 traveling on optical axis 6c of condenser lens 6 travels inside rod integrator 7. Referring to Fig. 7, it can be seen that in device numbers (1, 5, 6, 9), light L1 and central axis 7c coincide. In device numbers (2 to 4, 7, 8), it can be seen that light L1 and central axis 7c do not coincide.

[0069] 8 shows the results of simulating the angular spectrum of the light emitted from the emission surface 7b of each light source device. Table 2 shows the evaluation results of the divergence angle and the simulation results regarding the return light of each device.

[0070] [Table 2]

[0071] [Evaluation of the divergence angle of emitted light] The divergence angle was evaluated based on the angular spectrum in FIG. 8. The evaluation was made in four stages, A, B, C, and D, from best to worst. Referring to FIG. 8, the device numbers (1, 5, 6, 9) in which the center of the light L1 coincides with the central axis 7c of the rod, show an angular spectrum with a Gaussian distribution with small irregularities, with the center of the light L1 being the maximum intensity. It can be seen that the angular width is 8 to 10 degrees, and the divergence angle is small. Therefore, as shown in Table 2, the evaluation of the divergence angle of the device numbers (1, 5, 6, 9) is A. Note that when the center of the angular spectrum is not at the 0 degree position, this indicates that the light emitted from the rod integrator is generally tilted, but the overall tilt of the emitted light can be adjusted by the optical system in the subsequent stage.

[0072] Referring to Figure 8, it can be seen that with device number 2, the angular width of the light is 8 to 10 degrees, which is a small divergence angle. However, there is some unevenness in the angular spectrum, and the angular spectrum is uneven. Therefore, as shown in Table 2, the divergence angle of device number 2 is evaluated as B. The unevenness in the angular spectrum is caused by the light being reflected inside the rod integrator.

[0073] 8, it can be seen that the angle width of the device number (3, 4) is 10 to 12 degrees, which is a slightly large divergence angle. In addition, the unevenness of the angular spectrum is larger than that of the device number 2, and the unevenness of the angular spectrum is slightly larger. Therefore, the divergence angle of the device number (3, 4) is evaluated as C.

[0074] Referring to Figure 8, it can be seen that the angle width of the device number (7,8) is about 14 degrees, which is a fairly large divergence angle. In addition, the unevenness of the angular spectrum is larger than that of the device number (3,4), and the unevenness is considerably larger. Therefore, the divergence angle of the device number (7,8) is evaluated as D.

[0075] [Evaluation of return light and overall evaluation] In Table 2, "amount of returned light" refers to the amount of light that the returned light reaches the entire output end of the optical fiber. In Table 2, "maximum irradiance of returned light" refers to the irradiance at the point at which the strongest light is irradiated at the output end of the optical fiber. "Overall evaluation" refers to an evaluation that combines the evaluation of the divergence angle with the evaluation of the amount of returned light and the maximum irradiance. The overall evaluation was rated on a four-level scale, A, B, C, and D, from best to worst. A rating of C or higher indicates that the desired effect of suppressing the return light from irradiating the output end of the optical fiber while suppressing an increase in the divergence angle is achieved. A rating of D indicates that either the divergence angle or the amount of returned light is too large, and the desired effect cannot be achieved.

[0076] Regarding the device numbers (1,5,6,9) with the evaluation of the divergence angle of A, the light quantity and maximum irradiance of the return light of the device number (1,5) are both small, so the overall evaluation of the device number (1,5) is A. Although the evaluation of the divergence angle of the device number 6 is excellent, the light quantity and maximum irradiance of the return light are relatively large, so the overall evaluation of the device number 6 is C. The reason why the return light of the device number 6 is large is because θo is the same value as θr, that is, the exit surface 7b is perpendicular to the central axis 7c of the rod integrator 7. This is because the light reflected by the exit surface 7b passes through the condenser lens 6 and reaches the exit end of the bundle fiber 5 in a large amount. The light quantity and maximum irradiance of the return light of the device number 9 are too large, so there is a risk of burning the exit end of the optical fiber. Therefore, the overall evaluation of the device number 9 is D.

[0077] Equipment number 2, which was rated a B for the divergence angle, had relatively small values ​​for the amount of returned light and maximum irradiance. Therefore, the overall rating for equipment number 2 is a B. Equipment number (3,4), which was rated a C for the divergence angle, had relatively small values ​​for the amount of returned light and maximum irradiance. Therefore, the overall rating for equipment number (3,4) is a C. Equipment number (7,8) was rated a D for the divergence angle, so the overall rating for equipment number (7,8) is a D, regardless of the rating of the returned light. [Explanation of symbols]

[0078] 1:Light source 2: Board (where the solid-state light source is placed) 3: Solid state light source 5: Fiber bundle 6: Condenser lens 6c: Optical axis 7: Rod Integrator 7a:Incidence surface 7b: Output surface 7c: Central axis 7e: Left end 7f: Rear end 7s, 7t: Reference plane 10:Light source device 15: Adhesive 18: Light shielding section 18a: First shade area 18b:Second light shielding area 18c: Light shielding part 21: Collimator lens 22: Mirror 31: Optical fiber 32: Ferrule 51: Spatial light modulator 55: Projection optical system 60: Work 61: Stage 90: Optical unit 91: Fiber bundle 92: Rod Integrator 92c: (Rod integrator) central axis 93:Incidence plane 100: Exposure device

Claims

1. A light source; an optical fiber that guides the light emitted from the light source; a refractive optical system that collects the light emitted from the optical fiber; a rod integrator including an incident surface onto which the light emitted from the refractive optical system is incident; a light shielding portion that shields return light from the incident surface of the rod integrator; Equipped with the rod integrator has a shape in which the entrance surface is inclined by an angle θi (0<θi<90 degrees) in a clockwise or counterclockwise rotational direction with respect to a reference plane orthogonal to an optical axis of the refractive optical system, and a central axis is inclined by an angle θr (0<θr<90 degrees) in the rotational direction with respect to the optical axis, The light source device, wherein the angle θi and the angle θr satisfy the relationship of the following formula (1). θr<2×(θi−asin(sin(θi) / n))…(1) (In formula (1), n ​​is the refractive index of the rod integrator.)

2. 2. The light source device according to claim 1, wherein the angle θi and the angle θr satisfy the relationship of the following formula (2). 0.8×(θi-asin(sin(θi) / n)) < θr<1.2×(θi-asin(sin(θi) / n))…(2)

3. 3. The light source device of claim 2, wherein θr is substantially equal to θi-asin(sin(θi / n)).

4. the rod integrator includes an exit surface from which light incident from the entrance surface is emitted, 4. The light source device according to claim 1, wherein a normal to said light exit surface is inclined with respect to said central axis.

5. the light blocking portion has an opening larger than a diameter of light passing through the refractive optical system, 5. The light source device according to claim 1, wherein the light emitted from the refractive optical system passes through the opening and is incident on the entrance surface of the rod integrator.

6. 5. The light source device according to claim 1, wherein the light blocking portion has a first light blocking region and a second light blocking region that are arranged opposite to each other with the refractive optical system therebetween.

7. 7. The light source device according to claim 1, wherein the entrance surface of the rod integrator is rectangular, and has a shape rotated by the angle θi with respect to the reference plane around a short side of the rectangle as a rotation axis.

8. A plurality of said light sources; a plurality of optical fibers each guiding light emitted from the plurality of light sources, 8. The light source device according to claim 1, wherein the plurality of optical fibers form a bundle fiber with at least their respective emission ends bundled together.

9. 9. The light source device according to claim 8, wherein a total amount of light emitted from said plurality of light sources exceeds 1 W.

10. 10. The light source device according to claim 1, wherein the peak wavelength of the light emitted from the light source is in the range of 350 to 450 nm.

11. An exposure apparatus comprising the light source device according to any one of claims 1 to 10.

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