Interference exposure device and interference exposure method

Abstract

The present invention provides an interference exposure device and an interference exposure method capable of easily achieving exposure at various slant angles and pitch widths.　An interference exposure device according to one embodiment of the present invention performs interference exposure on an irradiation target arranged along an exposure surface by superimposing, in an irradiation area on the exposure surface, a first beam and a second beam obtained by splitting coherent emitted light, the interference exposure device including an optical system. The optical system is configured such that an incident angle of at least one of the first beam and the second beam with respect to the exposure surface is variable, and is capable of performing the interference exposure in an asymmetric mode in which the first beam and the second beam are incident on the irradiation target so as to be asymmetric with respect to a normal to the exposure surface in the irradiation area.

Description

Interference Exposure Device and Interference Exposure Method

[0007] ,

[0006] , ,

[0001] The present invention relates to an interference exposure device and an interference exposure method that perform exposure using interference fringes of two light beams.

[0002] Conventionally, two-beam interference exposure (hereinafter also simply referred to as interference exposure) in which a workpiece is exposed using interference fringes of two light beams obtained by splitting laser light or the like is known.

[0003] For example, Patent Document 1 describes an exposure device that changes the incident angle θ of each light beam with respect to a wafer by changing the angles of interference mirrors arranged symmetrically with respect to the wafer with both incident angles of the two light beams being θ. Further, Patent Document 2 describes an interference exposure device that adjusts the rotation control amount of two exposure mirrors arranged symmetrically toward a stage and the distance of the stage with respect to each exposure mirror to make the incident angles θ of the two light beams the same. Also, Patent Document 3 describes an interference exposure device that makes the ideal incident angles of the left beam and the right beam with respect to a workpiece both θ and eliminates the deviation between the actual incident angle and the ideal incident angle θ of each beam by a rotatable and translatable first mirror and second mirror.

[0004] Japanese Unexamined Patent Application Publication No. 2004 - 14867, Japanese Unexamined Patent Application Publication No. 2002 - 311218, Japanese Unexamined Patent Application Publication No. 2023 - 163737

[0005] As in Patent Documents 1 to 3, by making the incident angles of two light beams with respect to a workpiece equal, interference fringes orthogonal to the workpiece are generated, and a pattern with a slant angle of 0° can be exposed. Also, by changing the crossing angle of each light beam, the pitch width of the interference fringes can be changed.

[0006] On the other hand, when it is desired to incline the slant angle, it is necessary to make the incident angles of the two light beams different according to the desired slant angle and pitch width. In an optical system designed to make the incident angles of the two light beams equal as described above, it is conceivable that it is necessary to replace optical components or change the entire optical system. For this reason, a technique for easily realizing exposure at various slant angles and pitch widths is required. <000001In view of the above circumstances, the object of the present invention is to provide an interference exposure apparatus and an interference exposure method that can easily achieve exposure at various slant angles and pitch widths.

[0008] To achieve the above objective, an interference exposure apparatus according to one embodiment of the present invention is an interference exposure apparatus that performs interference exposure on an object to be irradiated arranged along the exposure surface by superimposing a first beam and a second beam obtained by splitting coherent emitted light in an irradiation area on the exposure surface, and comprises an optical system. The optical system has a variable incidence angle of at least one of the first beam or the second beam with respect to the exposure surface, and interference exposure is possible in an asymmetric mode in which the first beam and the second beam are incident on the object to be irradiated such that they are asymmetric with respect to the normal to the exposure surface in the irradiation area.

[0009] This interference exposure apparatus enables interference exposure in an asymmetric mode, where the first and second beams are incident on the object to be irradiated in a manner asymmetric with respect to the normals of the beams to the object in the irradiation area. This asymmetric mode allows for exposure at various slant angles. Furthermore, the pitch width of the interference fringes can be adjusted by adjusting the intersection angle of the first and second beams in each mode. This makes it easy to achieve exposure at various slant angles and pitch widths.

[0010] The optical system may be switchable between interference exposure in the asymmetric mode and interference exposure in the symmetric mode, in which the first beam and the second beam are incident on the object to be irradiated symmetrically with respect to the normal.

[0011] The interference exposure apparatus may further include a control unit that controls at least one of the incident angles of the first beam or the second beam to the exposure surface in accordance with input values ​​relating to the slant angle and pitch width of the interference fringes formed on the irradiated object, and sets the mode of the optical system to either the symmetric mode or the asymmetric mode.

[0012] The interference exposure apparatus may further include a sensor unit for detecting the incident angle of the first beam to the exposure surface and the incident angle of the second beam to the exposure surface. In this case, the control unit may control the optical system based on the detection results of the sensor unit.

[0013] The sensor unit may include a multiplexing element that combines the first beam and the second beam, an attitude adjustment element that adjusts the attitude of the multiplexing element according to the slant angle, and an image sensor or the like that measures the intensity distribution of the combined beam combined by the multiplexing element.

[0014] The optical system may include a demultiplexing element that splits the emitted light into a first beam and a second beam, a first mirror that moves along a first drive axis and rotates with respect to the first drive axis to reflect the first beam toward the irradiation area, and a second mirror that moves along a second drive axis and rotates with respect to the second drive axis to reflect the second beam toward the irradiation area.

[0015] The first drive shaft and the second drive shaft may be provided along a common reference plane set perpendicular to the exposure surface.

[0016] The first drive shaft and the second drive shaft may be provided such that both the first mirror and the second mirror can be positioned on one side of the normal plane in the reference plane.

[0017] The first drive shaft and the second drive shaft may each be an arc-shaped axis that surrounds the irradiation area.

[0018] The first drive shaft and the second drive shaft may be a common arc shaft.

[0019] The optical system may include a first arm that moves along a first drive axis so that the first adjustment optical system faces the illumination area, and a first adjustment optical system that adjusts the first mirror and the first beam reflected by the first mirror, and a second arm that moves along a second drive axis so that the second adjustment optical system faces the illumination area, and a second adjustment optical system that moves along a second drive axis so that the second adjustment optical system faces the illumination area.

[0020] The demultiplexing element may move along a linear axis different from the first drive axis and the second drive axis. In this case, the optical system may have a third mirror that moves along the linear axis and rotates with respect to the linear axis to reflect the first beam toward the first mirror, and a fourth mirror that moves along the linear axis and rotates with respect to the linear axis to reflect the second beam toward the second mirror.

[0021] The first drive shaft and the second drive shaft may be a common linear shaft.

[0022] The demultiplexing element may move along the common linear axis so as not to obstruct the movement of the first mirror and the second mirror.

[0023] The optical system may include a third arm, one end of which is provided on the first drive shaft and which moves along the first drive shaft and is rotatable relative to the first drive shaft; a fifth mirror, rotatably mounted on the one end of the third arm and which reflects the first beam toward the first mirror; a fourth arm, one end of which is provided on the second drive shaft and which moves along the second drive shaft and is rotatable relative to the second drive shaft; and a sixth mirror, rotatably mounted on the one end of the fourth arm and which reflects the second beam toward the second mirror. In this case, the first mirror may be provided on the other end of the third arm. The second mirror may also be provided on the other end of the fourth arm.

[0024] The incident angle θ1 of the first beam with respect to the exposure surface may be -75° ≤ θ1 ≤ 65°. Also, the incident angle θ2 of the second beam with respect to the exposure surface may be -65° ≤ θ2 ≤ 75°.

[0025] The aforementioned asymmetric mode may include a mode in which the slant angle α of the interference fringes formed on the irradiated object is α ≥ 5°.

[0026] An interference exposure method according to one embodiment of the present invention is an interference exposure method in which a first beam and a second beam obtained by splitting coherent emitted light are superimposed in an irradiation area on an exposure surface and interference exposure is performed on an object to be irradiated arranged along the exposure surface, and input values ​​relating to the slant angle and pitch width of interference fringes formed on the object to be irradiated are obtained. In an optical system capable of performing interference exposure in an asymmetric mode in which the incident angle of at least one of the first beam or the second beam to the exposure surface is variable and the first beam and the second beam are incident on the object to be irradiated such that they are asymmetric with respect to the normal to the exposure surface in the irradiation area, the incident angles of the first beam and the second beam to the exposure surface are adjusted according to the input values.

[0027] As described above, the present invention makes it possible to easily achieve exposure at various slant angles and pitch widths. The effects described herein are not necessarily limited, and any of the effects described in this disclosure may be used.

[0028] This is a schematic diagram illustrating the outline of an interference exposure apparatus according to the first embodiment of the present invention. This is a schematic diagram illustrating interference exposure. This is a schematic diagram illustrating the outline of the optical system of the interference exposure apparatus. This is a schematic front view showing an example of the configuration of the interference exposure apparatus. This is a schematic side view showing an example of the configuration of the interference exposure apparatus. This is a schematic diagram showing an example of the configuration of the sensor section. This is a schematic diagram illustrating the difference in the incident angles of the first beam and the second beam. This is a flowchart illustrating an example of the operation of the interference exposure apparatus. This is a diagram illustrating an example of the adjustment of the drive mirror. This is a graph showing the range of the incident angle of the beam in the interference exposure apparatus. This is a graph showing the range of slant angle and pitch width that the interference exposure apparatus can expose. This is a schematic diagram showing an example of the configuration of an interference exposure apparatus according to the second embodiment. This is a schematic diagram showing an example of the configuration of an interference exposure apparatus according to the third embodiment.

[0029] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0030] [Overview of Interferometric Exposure Apparatus] Figure 1 is a schematic diagram illustrating the overview of an interferometric exposure apparatus according to the first embodiment of the present invention. The interferometric exposure apparatus 100 is an apparatus that performs interferometric exposure on a workpiece W arranged along the exposure surface 4 by superimposing a first beam B1 and a second beam B2, which are obtained by splitting coherent emitted light, in the irradiation area 5 on the exposure surface 4.

[0031] The workpiece W of the interference exposure apparatus 100 is, for example, a substrate on which a photosensitive material is provided on the surface. Any substrate can be used as the substrate, such as a glass substrate, a resin substrate, or a semiconductor substrate. The photosensitive material can be a material coated on the substrate or a sheet-like material bonded to the substrate. In addition, the types of substrates and photosensitive materials are not limited.

[0032] The coherent emitted light that forms the basis of the first beam B1 and the second beam B2 is coherent light, typically laser light emitted from a laser light source. The first beam B1 and the second beam B2 are light beams generated by splitting the laser light into two using a demultiplexing element such as a beam splitter or diffraction grating. The exposure surface 4 is a virtual plane in the interference exposure apparatus 100 where interference exposure is performed. For example, each part of the interference exposure apparatus 100 is arranged with respect to the exposure surface 4. The workpiece W is also arranged, for example, so that its surface coincides with the exposure surface 4. The irradiation area 5 is an area set on the exposure surface 4 as the target region for interference exposure. The first beam B1 and the second beam B2 are irradiated such that their respective irradiation spots overlap in the irradiation area 5. In this disclosure, the term "beam" can be read as "light wave" or "light beam."

[0033] Interference exposure using two light beams (first beam B1 and second beam B2) is generally also called two-beam interference exposure, and is a method of exposing a workpiece W by utilizing interference fringes (see Figure 2) that are generated by superimposing the light beams. In the interference exposure apparatus 100, the photosensitive material of the workpiece W placed in the irradiation area 5 is exposed to the interference fringes of the first beam B1 and the second beam B2.

[0034] As shown in Figure 1, the interference exposure apparatus 100 includes an optical system 10 for irradiating the first beam B1 and the second beam B2 toward the irradiation area 5, and a stage mechanism 11 for supporting the workpiece W. In Figure 1, the optical system 10 provided in the interference exposure apparatus 100 is schematically shown by the dotted line area. The specific configurations of the optical system 10 and the stage mechanism 11 will be described in detail later.

[0035] In the following, directions that are orthogonal to each other on the surface on which the workpiece W is placed (the upper surface of the stage mechanism 11 in Figure 1) will be referred to as the X direction and the Y direction, and the direction that is orthogonal to the XY plane will be referred to as the Z direction. The X direction, Y direction, and Z direction correspond to the left-right direction, front-back direction, and up-down direction, respectively, in the interference exposure apparatus 100. Furthermore, the exposure surface 4 described above is a plane parallel to the XY plane.

[0036] The optical system 10 of the interference exposure apparatus 100 has a variable incident angle of at least one of the first beam B1 or the second beam B2 with respect to the exposure surface 4, and interference exposure is possible in asymmetric mode when the first beam B1 and the second beam B2 are incident on the workpiece W asymmetric with respect to the normal L to the exposure surface 4 in the irradiation area 5. The optical system 10 is also capable of interference exposure in symmetric mode when the first beam B1 and the second beam B2 are incident on the workpiece W as symmetric with respect to the normal L. The optical system 10 is configured to be switchable between interference exposure in these asymmetric modes and interference exposure in symmetric modes.

[0037] The left side of Figure 1 illustrates interference exposure in symmetric mode, while the right side of Figure 1 illustrates interference exposure in asymmetric mode. The optical system 10 can change the incident angles of the first beam B1 and the second beam B2 with respect to the exposure surface 4 by adjusting the position and orientation of optical components such as mirrors that control the optical paths of the first beam B1 and the second beam B2. This realizes both symmetric and asymmetric modes. The incident angles of each beam will be described later with reference to Figure 2, etc.

[0038] The symmetric mode refers to a mode in which the optical axes (sometimes referred to as incident axes hereafter) of the first beam B1 and the second beam B2 directed toward the irradiation area 5 are set substantially symmetrically with respect to the normal L to the exposure surface 4 in the irradiation area 5. This is, for example, a state in which the incident axes of the first beam B1 and the second beam B2 are set rotationally symmetrically with respect to the normal L. Therefore, in the symmetric mode, the incident axes of the first beam B1 and the second beam B2 are set so that when one incident axis is rotated 180° around the normal L, it coincides with the other incident axis. From another perspective, a mode in which there exists a normal L that is rotationally symmetrical to the two incident axes can also be called a symmetric mode.

[0039] The normal L between the irradiation area 5 and the exposure surface 4 is a hypothetical straight line that is perpendicular to the exposure surface 4 within the irradiation area 5 and extends in the Z direction. In the optical system 10, each incident axis is set to achieve the symmetric mode described above, with reference to the normal L passing through a predetermined position within the irradiation area 5 (for example, the center position of the irradiation area 5). Depending on how each incident axis is set, a symmetric mode may also be achieved with reference to the normal L passing through a position shifted from the predetermined position. In other words, if the incident axes of the first beam B1 and the second beam B2 are arranged in a rotationally symmetrical configuration with respect to a certain axis of symmetry, and that axis of symmetry is the normal L of the exposure surface 4, then the arrangement will be in a symmetric mode regardless of the position of the normal L. The workpiece W is basically arranged parallel to the exposure surface 4. Therefore, the normal L to the exposure surface 4 can also be rephrased as the normal L to the workpiece W.

[0040] Asymmetric mode refers to a mode in which the incident axes of the first beam B1 and the second beam B2 are set substantially asymmetrically with respect to the normal L to the exposure surface 4 in the irradiation area 5. For example, a state in which each incident axis is set in a configuration different from the symmetric mode described above is an asymmetric mode. Therefore, in asymmetric mode, even if one incident axis is rotated 180° with respect to the normal L, it will not overlap with the other incident axis. From another perspective, a mode in which there is no normal L that is rotationally symmetric to each incident axis can also be called an asymmetric mode.

[0041] In this embodiment, the optical system 10 is configured such that the first beam B1 and the second beam B2 can irradiate the irradiation area 5 along a substantially identical plane (hereinafter referred to as the incident plane). This means that the optical system 10 can be adjusted such that each incident axis of the first beam B1 and the second beam B2 is included in a common incident plane and has an intersection point within the incident plane. In FIG. 1, the incident plane is set as a plane parallel to the XZ plane. Note that each incident axis may be set to intersect at the surface of the workpiece W (exposure surface 4), or may be set to intersect at a position shifted in the vertical direction (Z direction) from the surface of the workpiece W (exposure surface 4).

[0042] As shown on the left side of FIG. 1, in the symmetric mode, with the normal line L of the exposure surface 4 passing through the intersection point of each incident axis of the first beam B1 and the second beam B2 as the target axis, each incident axis is set to be line-symmetric with respect to the normal line L in the incident plane. On the other hand, as shown on the right side of FIG. 1, in the asymmetric mode, each incident axis is included in the incident plane, but is asymmetric rather than line-symmetric with respect to the normal line L of the exposure surface 4 passing through the intersection point of each incident axis.

[0043] Note that if the irradiation spots of the first beam B1 and the second beam B2 overlap in the irradiation area 5, it is not necessarily required that each incident axis of the first beam B1 and the second beam B2 be set to be included in the same incident plane. For example, a state in which one or both incident axes are shifted from the above-described line-symmetric state so that they are not included in the same incident plane is also included in the symmetric mode. Thus, even when the incident axes have a twisted positional relationship where they do not intersect each other, if the arrangement is rotationally symmetric about the normal line L, it is the symmetric mode.

[0044] FIG. 2 is a schematic diagram for explaining interference exposure. In FIG. 2, the first beam B1 and the second beam B2 incident toward the irradiation area 5 and the interference fringes generated by the two beams (hereinafter referred to as exposure interference fringes 6) are schematically illustrated. Here, the principle of interference exposure (two-beam interference exposure) using the exposure interference fringes 6 and the slant angle α and pitch width p controlled by the incident angles of the two beams will be explained.

[0045] As described above, the first beam B1 and the second beam B2 are generated by splitting the interferable emitted light. In the region where such two beams overlap, interference fringes 6 for exposure are generated in which regions where the beams reinforce each other (black regions) and regions where they weaken each other (white regions) are alternately formed. In interference exposure, the photosensitive material provided on the surface of the workpiece W is exposed by the interference fringes 6 for exposure. As a result, for example, a periodic pattern similar to the interference fringes 6 for exposure is formed on the workpiece W.

[0046] As shown in FIG. 2, the pattern of the interference fringes 6 for exposure can be represented by the slant angle α and the pitch width p. Here, the slant angle α is the inclination angle of the interference fringes 6 for exposure with respect to the normal line L (Z direction) of the exposure surface 4. For example, in the incident plane (here, the XZ plane) of the two beams, the angle formed by the direction in which the stripes of the interference fringes 6 for exposure extend and the normal line L of the exposure surface 4 is the slant angle α. Also, the period of the stripes of the interference fringes 6 for exposure (the period of the regions where the beams reinforce each other (or weaken each other)) is the pitch width p. Note that the pitch width p is the period in the direction orthogonal to each stripe.

[0047] Here, for the first beam B1 (left beam) incident from the upper left in the figure and the second beam B2 (right beam) incident from the upper right, the incident angles with respect to the exposure surface 4 (XY plane) are denoted as θ1 and θ2, respectively. The incident angle θ1 is the angle between the incident axis of the first beam B1 and the normal line L (Z direction), and the incident angle θ2 is the angle between the incident axis of the second beam B2 and the normal line L (Z direction). Hereinafter, for the incident angle θ1 and the incident angle θ2, when the incident axis of the beam (B1 or B2) and the normal line L coincide, it is set to 0°, and the direction counterclockwise with respect to the normal line L is the positive direction. For example, in FIG. 2, θ1 is a negative value and θ2 is a positive value. Using the incident angles θ1 and θ2, the slant angle α is represented by the following equation (1).

[0048]

[0049] Furthermore, if the wavelengths of the first beam B1 and the second beam B2 are λ, and the refractive index of the medium in which the exposure interference fringes 6 are formed (for example, the photosensitive material on the workpiece W in which the exposure interference fringes 6 are exposed) is n, then the pitch width p of the exposure interference fringes 6 can be expressed using the following equation (2).

[0050]

[0051] From equation (1), the slant angle α is the angle obtained by bisecting the sum of the incident angles (θ1 + θ2), and is the angle that the bisectors of each incident axis on the incident plane make with the normal L. Also, from equation (2), the pitch width p changes according to the angle between each incident axis (|θ1 - θ2|). In this way, the slant angle α and the pitch width p can be adjusted by appropriately setting the incident angles θ1 and θ2 of the first beam B1 and the second beam B2.

[0052] For example, when the absolute values ​​of the incident angles θ1 and θ2 are equal (in Figure 2, -θ1 = θ2 = θ), the first beam B1 and the second beam B2 are incident symmetrically with respect to the normal L, resulting in a symmetric mode. In this case, the slant angle α = 0°, and exposure interference fringes 6 are formed perpendicular to the workpiece W (exposure surface 4). Thus, a symmetric mode can be described as a mode in which the slant angle α is 0°. Note that the pitch width p of the interference fringes with a slant angle α = 0° can be changed by changing the angle between the first beam B1 and the second beam B2 (|θ1 - θ2| = 2θ).

[0053] In symmetric mode, for example, an exposure interference fringe 6 with α = 0° is exposed to the photoresist on the surface of the workpiece W. When this workpiece W is developed, a periodic pattern perpendicular to the surface is formed, and this periodic pattern can be used as a mask to perform etching on the substrate, etc. This makes it possible to form a diffraction grating with a slant angle α = 0°.

[0054] Furthermore, as shown in Figure 2, when the absolute values ​​of the incident angles θ1 and θ2 are different (in Figure 2, -θ1 ≠ θ2), the first beam B1 and the second beam B2 are incident asymmetrically with respect to the normal L, resulting in an asymmetric mode. In this case, the slant angle α ≠ 0°, and exposure interference fringes 6 are formed that are inclined with respect to the workpiece W (exposure surface 4) at a slant angle α. Thus, an asymmetric mode can be described as a mode in which the slant angle α is a value other than 0°. Note that even in an asymmetric mode, by changing the angle between the first beam B1 and the second beam B2 (|θ1 - θ2| = 2θ), the pitch width p of the interference fringes can be changed, for example, while maintaining the slant angle α.

[0055] In this embodiment, the asymmetric mode includes a mode in which the slant angle α of the interference fringes formed on the workpiece W is α ≥ 5°. That is, the optical system 10 of the interference exposure apparatus 100 is configured to be able to adjust the incident angles θ1 and θ2 of the first beam B1 and the second beam B2 so that the slant angle α is at least 5°. This makes it possible to expose, for example, a pattern with a significant inclination. The slant angle α that can be exposed in the interference exposure apparatus 100 is not limited, and for example, from the viewpoint of increasing the slant angle α, a configuration in which the slant angle α is at least 10° is preferred, and a configuration in which it is 15° or more is more preferred.

[0056] In this asymmetric mode, exposure interference fringes 6 tilted at a slant angle α are exposed to a photosensitive material such as a photoresist or sheet material on the surface of a workpiece W. This makes it possible to form a diffraction grating that bends light incident from the front (Z direction) by a slant angle α through diffraction. Such diffraction gratings can be used, for example, in augmented reality (AR) display devices (such as transmissive AR glasses) or combiners for in-vehicle displays.

[0057] Furthermore, increasing the slant angle α reduces the proportion of zero-order light that is incident on the diffraction grating from the front and passes through the grating without being diffracted, thereby increasing the efficiency of utilizing the deflected light. In the asymmetric mode of the interference exposure apparatus 100, interference exposure with a relatively large slant angle α can be easily achieved, and it is suitably used for manufacturing diffraction gratings that have the light deflection function described above.

[0058] Figure 3 is a schematic diagram illustrating the outline of the optical system 10 of the interference exposure apparatus 100. As shown in Figure 3, the optical system 10 includes a laser light source 20, a relay mirror 21, a demultiplexer 22, two relay drive mirrors 23a and 23b, and two irradiation drive mirrors 24a and 24b.

[0059] The laser light source 20 emits laser light (beam B0) with wavelength λ. The laser light source 20 can be a light source device that emits a CW laser or a light source device that emits a pulsed laser. Furthermore, the type of laser light source 20 and the wavelength λ of beam B0 are not limited. In this embodiment, beam B0 is an example of coherent emitted light. The beam B0 emitted from the laser light source 20 is appropriately reflected by the relay mirror 21 and incident on the demultiplexer 22.

[0060] The demultiplexing element 22 splits beam B0 into a first beam B1 and a second beam B2. A beam splitter or diffraction grating can be used as the demultiplexing element 22. Figure 3 illustrates that beam B0, incident on the demultiplexing element 22 from above, is split into a first beam B1 directed to the left and a second beam B2 directed to the right. In reality, the first beam B1 and the second beam B2 are not necessarily split in opposite directions, so the exit direction of each beam is adjusted as appropriate using mirrors or the like (see Figure 4, etc.).

[0061] The relay drive mirrors 23a and 23b are mirrors that are driven to control the reflection direction of the incident beam. The relay drive mirror 23a reflects the first beam B1 emitted from the demultiplexer 22 toward the irradiation drive mirror 24a. The relay drive mirror 23b reflects the second beam B2 emitted from the demultiplexer 22 toward the irradiation drive mirror 24b.

[0062] The illumination drive mirror 24a moves along the first drive shaft 25a and rotates relative to the first drive shaft 25a, reflecting the first beam B1 toward the illumination area 5. The illumination drive mirror 24b moves along the second drive shaft 25b and rotates relative to the second drive shaft 25b, reflecting the second beam B2 toward the illumination area 5. In this embodiment, the illumination drive mirrors 24a and 24b correspond to the first mirror and the second mirror, respectively.

[0063] Here, the drive shafts (first drive shaft 25a and second drive shaft 25b) refer to axes that define the movement path of, for example, the mirrors (illumination drive mirror 24a and illumination drive mirror 24b). For example, suppose a mirror is mounted on a base that moves along a guide member. In this case, since the mirror moves along the guide member, the guide member can be considered as the drive shaft of the mirror. The mechanism for moving the mirror is not limited.

[0064] Furthermore, the rotation of the mirror relative to the drive shaft includes rotation around the Y-axis (rotational drive). It may also include rotation that tilts relative to the XZ plane (tilt drive). The rotational drive controls the reflection direction of the beam along the XZ plane, and the tilt drive controls the tilt of the reflection direction of the beam relative to the XZ plane. The mechanism for rotating the mirror is not limited.

[0065] The first drive shaft 25a and the second drive shaft 25b are positioned along a common reference plane 26 set perpendicular to the exposure surface 4. For example, the surface of the optical table on which the optical system 10 is installed (the so-called optical surface) is the reference plane 26. As a result, for example, the first drive shaft 25a and the second drive shaft 25b become axes aligned with the incident planes (XZ planes) of the first beam B1 and the second beam B2. As a result, it is possible to sufficiently avoid situations in which the incident axes of each beam shift significantly in the Y direction (big deviation from the XZ plane) even when, for example, the irradiation drive mirror 24a or the irradiation drive mirror 24b moves, thereby improving the stability of interference exposure.

[0066] Furthermore, the first drive shaft 25a and the second drive shaft 25b can be configured such that both the illumination drive mirror 24a and the illumination drive mirror 24b can be positioned on one side of the reference plane 26 with respect to the normal L. As shown in Figure 3, the reference plane 26 is divided into a left region and a right region by the normal L. The first drive shaft 25a and the second drive shaft 25b may be configured such that the illumination drive mirror 24a and the illumination drive mirror 24b can be positioned in either of these two regions.

[0067] For example, one or both of the first drive shaft 25a and the second drive shaft 25b are positioned to intersect the normal L on the reference plane 26. In Figure 3, the second drive shaft 25b intersects the normal L. Therefore, by moving the irradiation drive mirror 24b to the region to the left when viewed from the normal L, the irradiation drive mirrors 24a and 24b can be positioned in the left region. This makes it possible to inject the first beam B1 and the second beam B2 from one side (in this case, the left side) of the normal L, and makes it possible to easily achieve a relatively large slant angle α.

[0068] In Figure 3, the first drive shaft 25a and the second drive shaft 25b are shown as straight shafts, but other shafts, such as arc-shaped shafts, may also be used. Furthermore, the first drive shaft 25a and the second drive shaft 25b do not need to be individually configured shafts, but can be configured as a common shaft.

[0069] Furthermore, as shown in Figure 3, the interference exposure apparatus 100 includes a sensor unit 12 and a control unit 13. The sensor unit 12 is a sensor for detecting the incidence angles θ1 and θ2 of the first beam B1 and the second beam B2 with respect to the exposure surface 4. The sensor unit 12 is composed of a measuring instrument that measures the slant angle α, pitch width p, and interference fringe direction of the interference fringes caused by the first beam B1 and the second beam B2, and is used by moving it appropriately within the irradiation area 5. The incidence angles θ1 and θ2 are detected from these measurement results. The sensor unit 12 will be described later with reference to Figure 6, etc.

[0070] The control unit 13 is a control device that controls the operation of the entire interference exposure apparatus 100, and has the necessary hardware configuration for a computer, such as a CPU and memory. The control unit 13 controls the incident angle (θ1 or θ2) of at least one of the first beam B1 or the second beam B2 with respect to the exposure surface 4 according to input values ​​relating to the slant angle α and pitch width p of the exposure interference fringes 6 formed on the workpiece W, and sets the mode of the optical system 10 to either a symmetric mode or an asymmetric mode. In the example shown in Figure 3, both the incident angle θ1 of the first beam B1 and the incident angle θ2 of the second beam B2 are controlled.

[0071] In this way, the interference exposure apparatus 100 automatically controls the optical arrangement of the optical system 10 (for example, the position and rotation angle of the illumination drive mirrors 24a and 24b) to achieve a desired slant angle α and pitch width p. This makes it possible to achieve a wide range of slant angles α and any pitch width p.

[0072] Furthermore, the control unit 13 controls the optical system 10 based on the detection results of the sensor unit 12. This enables feedback control, such as adjusting the position and rotation angle of the irradiation drive mirrors 24a and 24b according to the actual state of the exposure interference fringes 6, thereby accurately realizing the desired exposure interference fringes 6. The operation of the control unit 13 will be described later with reference to Figure 8, etc.

[0073] [Configuration of Interference Exposure Apparatus] Figure 4 is a schematic front view showing an example of the configuration of an interference exposure apparatus. Figure 5 is a schematic side view showing an example of the configuration of an interference exposure apparatus. Below, a specific example of the configuration of the interference exposure apparatus 100 will be described. Below, parts that are common with the configuration of the optical system 10 described with reference to Figure 2 will be described using the same reference numerals.

[0074] As shown in Figure 4, in this embodiment, the first drive shaft 25a and the second drive shaft 25b are each arc axes surrounding the illumination area 5. The arc axes are arranged, for example, so as to be centered on the illumination area 5. By using arc axes, the positions of the illumination drive mirrors 24a and 24b in the X and Z directions can be easily changed. This makes it possible to sufficiently widen the control range of the incident angle θ1 and the incident angle θ2. It also makes it possible to configure the optical system 10 in a compact manner.

[0075] Here, a common arc-shaped shaft (an arc-shaped drive shaft 35, described later) is used as the first drive shaft 25a and the second drive shaft 25b. This simplifies the device configuration and reduces manufacturing and maintenance costs. Alternatively, the first drive shaft 25a and the second drive shaft 25b may be provided individually as concentric arc-shaped shafts. In this case, for example, the second drive shaft 25b may be positioned outside or inside the first drive shaft 25a.

[0076] The interference exposure apparatus 100 includes a frame section 14, an optical system 10, a stage mechanism 11, a sensor section 12, and a control unit 13 (not shown).

[0077] The frame section 14 is the frame of the interference exposure apparatus 100 and supports the optical system 10 and the stage mechanism 11. The frame section 14 includes a stage support base 15, an optical table support frame 16, a light source support base 17, and a connecting frame 18.

[0078] The stage support base 15 is a plate-shaped member that supports the stage mechanism 11. The stage support base 15 may have, for example, legs with a suspension function. The optical table support frame 16 is provided on the upper surface of the stage support base 15 and supports the optical table 30 of the optical system 10, which will be described later. The light source support base 17 is a plate-shaped member that supports the laser light source 20 of the optical system 10, which will be described later, and is positioned above the optical table 30. The connecting frame 18 connects the optical table support frame 16 and the light source support base 17 and is a frame that supports the light source support base 17. As shown in Figure 5, the connecting frame 18 is provided on the front and rear surfaces of the interference exposure apparatus 100. Note that in Figure 4, the connecting frame 18 provided on the front surface is not shown.

[0079] The optical system 10 includes a laser light source 20, an exposure shutter S, four relay mirrors 21a to 21d, a demultiplexer 22, relay drive mirrors 23a and 23b, and irradiation drive mirrors 24a and 24b. The optical system 10 also includes an optical table 30, a linear drive shaft 31, linear motion sections 32a and 32b, a demultiplexer 27, an arc drive shaft 35, and arm sections 36a and 36b. These components constitute the optical system 10, which comprises an output optical system 37, a linear bench optical system 38, and an arc arm optical system 39.

[0080] The emission optical system 37 is an optical system that emits beam B0, which is the source of the first beam B1 and the second beam B2, toward the linear bench optical system 38. The emission optical system 37 is configured on the light source support base 17 and includes a laser light source 20, an exposure shutter S, a relay mirror 21a, and a relay mirror 21b.

[0081] The laser light source 20 is provided on the upper surface of the light source support base 17 and emits laser light (beam B0) of wavelength λ toward the relay mirror 21a. The exposure shutter S is a shutter for blocking the beam B0 and is provided between the laser light source 20 and the relay mirror 21a. A rotary shutter is used here, but other types of shutters may be used. The relay mirror 21a is provided on the upper surface of the light source support base 17 and reflects the beam B0 toward the relay mirror 21b. The relay mirror 21b is provided on the lower surface of the light source support base 17 and reflects the beam B0 toward the relay mirror 21c.

[0082] In the example shown in Figure 4, the beam B0 emitted from the laser light source 20 is reflected on the upper surface of the light source support base 17 by the relay mirrors 21a and 21b located to the right of the light source support base 17 so that it travels to the left on the lower surface of the light source support base 17.

[0083] Next, the portion of the optical system 10 provided on the optical table 30 (linear bench optical system 38, arc arm optical system 39) will be described. The optical table 30 is a rectangular plate member as a whole. The rear surface of the optical table 30 is connected to the optical table support frame 16 and is supported along the XZ plane such that one pair of edges (in this case, the long side) is parallel to the X direction. The front surface of the optical table 30 is the reference plane 26, as explained with reference to Figure 2. The optical paths of the first beam B1 and the second beam B2 are basically set to be parallel to the reference plane 26.

[0084] The linear bench optical system 38 generates a first beam B1 and a second beam B2 and supplies each beam toward the arc arm optical system 39. The linear bench optical system 38 includes relay mirrors 21c and 21d, a demultiplexer 22, relay drive mirrors 23a and 23b, linear motion units 32a and 32b, a demultiplexer 27, and a linear drive shaft 31, and is configured along the upper edge of the optical table 30.

[0085] The linear drive shaft 31 is a linear drive shaft provided along the X direction on the upper edge of the optical table 30. The linear motion sections 32a and 32b are bases that can move along the linear drive shaft 31. Optical components are arranged on the surfaces of each linear motion section 32a and 32b that face forward. In this embodiment, the linear drive shaft 31 corresponds to a linear shaft different from the first drive shaft and the second drive shaft.

[0086] The linear motion units 32a and 32b each move independently along the linear drive shaft 31. The configuration of the linear motion mechanism is not limited, and any mechanism that allows the base to move along a predetermined guide (arc drive shaft 35), such as a rail or groove, can be used.

[0087] As shown in Figure 4, a relay mirror 21c, a demultiplexing element 22, and a relay mirror 21d are arranged in order from top to bottom on the front of the demultiplexing unit 27. The relay mirror 21c reflects the beam B0 incident from the relay mirror 21b toward the demultiplexing element 22 located below it.

[0088] The demultiplexing element 22 splits beam B0 (coherent emitted light) into a first beam B1 and a second beam B2. Here, a beam splitter is used as the demultiplexing element 22, but a diffraction grating or the like can be used instead. The beam splitter may be an intensity-type beam splitter or a deflection-type beam splitter. Also, a planar plate type beam splitter is used here, but a prism type may also be used.

[0089] In the example shown in Figure 4, the demultiplexer 22 (beam splitter) is positioned at a 45° tilt with respect to the ZY plane, with its upper end tilted to the right. As a result, of the beam B0 incident on the demultiplexer 22, a portion is reflected by the demultiplexer 22 and becomes a first beam B1 that propagates to the left, while another portion passes through the demultiplexer 22 and becomes a second beam B2 that propagates downward. The second beam B2 is reflected by the relay mirror 21d positioned directly below the demultiplexer 22 so that it propagates to the right.

[0090] The relay drive mirror 23a moves along the linear drive axis 31 and rotates relative to the linear drive axis 31, reflecting the first beam B1 toward the illumination drive mirror 24a. The relay drive mirror 23a is rotatably mounted on the front of the left linear motion section 32a of the demultiplexing element 22. The relay drive mirror 23b also moves along the linear drive axis 31 and rotates relative to the linear drive axis 31, reflecting the second beam B2 toward the illumination drive mirror 24b. The relay drive mirror 23b is rotatably mounted on the front of the right linear motion section 32b of the demultiplexing element 22. In this embodiment, the relay drive mirrors 23a and 23b correspond to the third and fourth mirrors.

[0091] Thus, in the linear bench optical system 38, the relay drive mirrors 23a and 23b can move independently of each other along a single linear drive axis 31. This makes it possible to improve the degree of freedom of the optical path of each beam relative to the arc arm optical system 39.

[0092] The arc-arm optical system 39 is an optical system that irradiates the first beam B1 and the second beam B2 toward the irradiation area 5. The arc-arm optical system 39 has irradiation drive mirrors 24a and 24b, arm sections 36a and 36b, and an arc drive shaft 35, and is configured along the front surface (reference plane 26) of the optical table 30.

[0093] The arc drive shaft 35 is an arc-shaped drive shaft provided along the reference plane 26 (XZ plane) of the optical table 30. The arm portions 36a and 36b are bases that can move along the arc drive shaft 35. In this embodiment, the arc drive shaft 35 corresponds to a common arc shaft that becomes the first drive shaft 25a and the second drive shaft 25b.

[0094] Each arm portion 36a and 36b moves independently along the arc drive shaft 35. The configuration of the arc drive mechanism is not limited, and any mechanism that allows the base to move along a predetermined guide (arc drive shaft 35), such as a rail or groove, can be used.

[0095] The arc drive axis 35 is typically positioned around the irradiation area 5. For example, when viewed in the XZ plane, the arc drive axis 35 is positioned on the optical table 30 such that its center coincides with the center point of the irradiation area 5 (such as the intersection point of the first beam B1 and the second beam B2). This makes it easy to associate the respective incident angles θ1 and θ2 of the first beam B1 and the second beam B2 with the positions on the arc drive axis 35 of the irradiation drive mirrors 24a and 24b.

[0096] The illumination drive mirrors 24a and 24b reflect the first beam B1 and the second beam B2 toward the illumination area 5. Irradiation drive mirror 24a is rotatably mounted on the front of the left arm portion 36a, and illumination drive mirror 24b is rotatably mounted on the front of the right arm portion 36b. As a result, illumination drive mirrors 24a and 24b each move independently along the arc drive axis 35 and rotate relative to the arc drive axis 35.

[0097] Arm sections 36a and 36b are longitudinal bases on which optical components are mounted. In addition to the illumination drive mirrors 24a and 24b, adjustment optical systems 40a and 40b are provided on arm sections 36a and 36b, respectively. Adjustment optical system 40a is an optical system that adjusts the first beam B1 reflected by the illumination drive mirror 24a, and adjustment optical system 40b is an optical system that adjusts the second beam B2 reflected by the illumination drive mirror 24b. For example, the adjustment optical systems 40a and 40b are arranged along the longitudinal direction of arm sections 36a and 36b. Therefore, the longitudinal direction of each arm section 36a and 36b is the direction of the incident axis of the first beam B1 and the second beam B2. In this embodiment, adjustment optical systems 40a and 40b correspond to the first adjustment optical system and the second adjustment optical system.

[0098] As shown in Figure 4, the arm portion 36a moves along the arc drive shaft 35 so that the adjustment optical system 40a faces the irradiation area 5. Similarly, the arm portion 36b moves along the arc drive shaft 35 so that the adjustment optical system 40b faces the irradiation area 5. For example, the arm portions 36a and 36b are moved so that their longitudinal direction coincides with the radial direction (direction toward the center) of the arc drive shaft 35. This is achieved, for example, by using a mechanism to maintain the attitude of the arm portions 36a and 36b relative to the arc drive shaft 35, or by using guides formed concentrically with the arc drive shaft 35. As a result, regardless of the position of the arm portions 36a and 36b (irradiation drive mirrors 24a and 24b) on the arc drive shaft 35, the incident axes of the first beam B1 and the second beam B2 are directed toward the irradiation area 5. In this embodiment, the arm portions 36a and 36b correspond to the first arm and the second arm.

[0099] The adjustment optical systems 40a and 40b are equipped with, for example, an expander (objective lens, etc.) to widen the beam spot, a spatial filter (pinhole element, etc.) to form the beam wavefront, and a collimating lens to parallelize the beam. This allows the first beam B1 and the second beam B2 to be irradiated onto the irradiation area 5 as parallel light with a predetermined spot. Sensors for monitoring the beam intensity and spot may also be provided.

[0100] Furthermore, the specific configuration of the adjustment optical systems 40a and 40b is not limited, and optical systems necessary for beam adjustment may be added as appropriate. Also, it is not necessarily required to provide the adjustment optical systems 40a and 40b on the arm sections 36a and 36b. For example, it is possible to adjust the beam BI as appropriate before the irradiation drive mirror 24.

[0101] The stage mechanism 11 has a stage 50 on which the workpiece W is placed. The stage 50 holds the workpiece W by a vacuum suction mechanism or a clamping mechanism. The stage mechanism 11 is configured so that the stage 50 can move in the X and Y directions. The stage mechanism 11 may also be configured so that the position of the stage 50 in the Z direction (height position of the workpiece W) can be adjusted, or the stage 50 may be configured so that it can rotate around a rotation axis along the Z direction.

[0102] Furthermore, the stage mechanism 11 is provided with a sensor unit 12. For example, the sensor unit 12 can be appropriately positioned on the outer edge of the stage 50. This makes it possible to easily move the sensor unit 12 to the irradiation area 5 using the stage mechanism 11. The specific configuration of the stage mechanism 11 is not limited, and any mechanism capable of positioning with the precision required for interference exposure can be used.

[0103] The sensor unit 12 detects the incidence angle θ1 of the first beam B1 to the exposure surface 4 and the incidence angle θ2 of the second beam B2 to the exposure surface 4. When operating the sensor unit 12, for example, the sensor unit 12 is moved using the stage mechanism 11 so that it overlaps with the irradiation area 5.

[0104] In the interference exposure apparatus 100, as described above, the first beam B1 and the second beam B2 are incident not only in a symmetric mode where the magnitudes of θ1 and θ2 are the same, but also in an asymmetric mode where θ1 and θ2 do not coincide with each other. Therefore, the incidence conditions of each beam change depending on the input values ​​of the slant angle α and the pitch width p. The sensor unit 12 is configured to take into account these changes in the incidence conditions of each beam.

[0105] For example, the incidence angles of the first beam B1 and the second beam B2 to the sensor unit 12 change depending on the incidence conditions of each beam. Therefore, the sensor unit 12 detects the incidence angles θ1 and θ2 of the first beam B1 and the second beam B2 by adjusting the orientation of the part of the sensor unit 12 that receives each beam (the multiplexing element 66, described later) according to input values ​​such as the slant angle α and pitch width p. This makes it possible to set the incidence surface of the sensor unit 12 based on the expected incidence angle, and thus various incidence angles can be detected appropriately. The configuration of the sensor unit 12 will be described in detail below.

[0106] Figure 6 is a schematic diagram showing an example of the configuration of the sensor unit. The upper and lower diagrams of Figure 6 show examples of the arrangement of the sensor unit 12 in symmetric mode and asymmetric mode. In each mode shown in Figure 6, the incidence angle θ1 of the first beam B1 is the same, while the incidence angle θ2 of the second beam B2 is different.

[0107] As shown in Figure 6, the sensor unit 12 includes a multiplexing element 66, an attitude adjustment element 67, and an image sensor 68. The multiplexing element 66 receives the first beam B1 and the second beam B2 directed toward the irradiation area 5 and combines the first beam B1 and the second beam B2. The multiplexing element 66 emits a combined beam BA, which is the combined beam of the first beam B1 and the second beam B2. For example, a beam splitter (also called a beam combiner) can be used as the multiplexing element 66. However, other elements such as diffraction gratings may be used as long as they are capable of combining the first beam B1 and the second beam B2. In the sensor unit 12 shown in Figure 6, the multiplexing element 66 corresponds to the light receiving unit 65 described above.

[0108] The multiplexing element 66 is positioned where the first beam B1 and the second beam B2 intersect. It transmits the beam incident from one incident surface (in this case, the first beam B1 incident on the left incident surface) and reflects the beam incident from the other incident surface (in this case, the second beam B2 incident on the right incident surface). The optical paths of the transmitted beam (first beam B1) and the reflected beam (second beam B2) coincide, forming a multiplexed beam BA.

[0109] The attitude adjustment element 67 adjusts the attitude of the multiplexing element 66 according to the slant angle α. For example, a drive mechanism that rotates a holder to which the multiplexing element 66 is fixed is used as the attitude adjustment element 67. In this case, the attitude adjustment element 67 rotates the multiplexing element 66 around a rotation axis along the Y direction. The rotation angle (amount of rotation) of the multiplexing element 66 is controlled by the control unit 13, which acquires the input value of the slant angle α.

[0110] The image sensor 68 measures the intensity distribution of the combined beam BA, which is combined by the multiplexing element 66. For example, the image sensor 68 is positioned in the optical path of the combined beam BA (here, on the incident axis of the first beam B1). Alternatively, the combined beam BA may be guided to the image sensor 68 via a reflective mirror or the like. As the image sensor 68, a beam-detecting sensor such as a CMOS camera or CCD camera can be used. The intensity distribution measured by the image sensor 68 will be interference fringes with a longer pitch width (period) than the exposure interference fringes 6 explained with reference to Figure 2. Hereafter, the interference fringes composed of the combined beam BA will be referred to as measurement interference fringes. Thus, the sensor unit 12 can also be said to be a rotationally driven interference measurement camera.

[0111] The angle of the multiplexing element 66 is important for properly generating the multiplexed beam BA. For example, as shown in the upper part of Figure 6, in the symmetric mode, the multiplexing element 66 is positioned so that the incident plane is aligned with the normal L. This makes it possible to make the transmission direction of the first beam B1 and the reflection direction of the second beam B2 coincide, and to properly overlap each beam.

[0112] On the other hand, suppose that in the upper part of Figure 6, for example, the incident angle θ2 of the second beam B2 is changed, resulting in an asymmetric mode. In this case, if the multiplexing element 66 remains positioned along the normal L, the reflection direction of the second beam B2 changes due to the change in the incident angle θ2. As a result, the transmission direction of the first beam B1 and the reflection direction of the second beam B2 no longer coincide, making it impossible to generate the multiplexed beam BA.

[0113] Therefore, in this embodiment, as shown in the lower part of Figure 6, when the incident angle θ2 of the second beam B2 is changed, the attitude adjustment element 67 changes the inclination angle of the multiplexing element 66 so that a multiplexed beam BA can be generated. In a multiplexing element 66 such as a beam splitter, the condition for generating a multiplexed beam BA is to position the multiplexing element 66 along the angle bisector of the angle formed by the incident axes of the first beam B1 and the second beam B2. That is, the attitude adjustment element 67 should be used to tilt the multiplexing element 66 so that its inclination angle with respect to the normal L matches the slant angle α.

[0114] In the combined element 66 with its orientation adjusted in this way, the transmission direction of the first beam B1 and the reflection direction of the second beam B2 coincide, and the combined beam BA is properly generated. Regardless of the values ​​set for the incident angles of the first beam B1 and the second beam B2, the combined beam BA can be generated, and the actual incident angle can be detected.

[0115] In Figure 6, the angle of incidence θ1 of the first beam B1 also changes the bisector between the beams, but in this case as well, the tilt angle of the demultiplexer 22 can be set using the method described above. In this case, since the emission direction of the combined beam BA changes, operations such as changing the light receiving position of the image sensor 68 or changing the angle of the mirror that relays the combined beam BA to the image sensor 68 are performed.

[0116] Here, we will explain how the sensor unit 12 detects the incidence angles of the first beam B1 and the second beam B2. The following explanation is applicable to both symmetric and asymmetric modes.

[0117] Figure 7 is a schematic diagram illustrating the difference in the incident angles of the first beam B1 and the second beam B2. In the above explanation, it was assumed that the incident axes of the first beam B1 and the second beam B2 are contained within the XZ plane, and that each beam is incident along the XZ plane at incident angles θ1 and θ2. However, for example, in a state where calibration is not yet complete, the incident angles θ1 and θ2 may be misaligned, or the incident axes of each beam may be tilted with respect to the XZ plane.

[0118] In the following, the deviations of the incident angles θ1 and θ2 of the first beam B1 and the second beam B2 with respect to the normal L will be denoted as Δθ1 and Δθ2, respectively. Furthermore, the inclination angles (amount of deviation in azimuth angle) of the first beam B1 and the second beam B2 with respect to the XZ plane will be denoted as ΔΦ1 and ΔΦ2, respectively.

[0119] The actual incidence angle of the first beam B1 is expressed as θ1 + Δθ1, and the actual incidence angle of the second beam B1 is expressed as θ2 + Δθ2. Furthermore, the actual inclination angles of the first beam B1 and the second beam B2 with respect to the XZ plane are ΔΦ1 and ΔΦ2, respectively. In an ideal state, Δθ1, Δθ2, ΔΦ1, and ΔΦ2 are all 0.

[0120] Here, the characteristics of the interference fringes measured by the image sensor 68 will be described. If the measurement surface of the image sensor 68, which is positioned behind the multiplexing element 66, is the xy plane, then, for example, interference fringes with a period in the x direction (i.e., stripes extending in the y direction) are formed.

[0121] The spatial frequency νy in the y-direction of the interference fringes for measurement on the measurement surface is expressed by equation (3). Furthermore, the relationship between spatial frequency ν and pitch width p is ν = 2π / p.

[0122] Furthermore, the angular displacement γ of the interference fringes used for measurement with respect to the y-direction is expressed by equation (4) using the spatial frequency νy in the y-direction.

[0123] Furthermore, the spatial frequency νx in the x-direction of the interference fringes for measurement on the measurement surface is expressed by equation (5).

[0124] From equation (5) and the relationship between the spatial frequency ν and pitch width p described above, the pitch width px in the x-direction of the interference fringes for measurement on the measurement surface is expressed by equation (6).

[0125] For example, the pitch width pX in the X direction of the exposure interference fringes 6 shown in Figure 2 is the length projected onto the exposure surface with the pitch width p shown in equation (2), but its scale is determined by the laser wavelength λ and is on the order of submicrometers. For this reason, it is difficult to photograph the exposure interference fringes 6 with sufficient resolution.

[0126] In contrast, the pitch width px in the x-direction of the interference fringes for measurement is relatively large, exceeding the laser wavelength λ, because the denominator contains the difference between the sine values ​​of the incident angles, as shown in equation (6). Therefore, the interference fringes for measurement can be sufficiently captured even with the resolution of the image sensor 68. Furthermore, the parameters shown in equations (3) to (6) are all parameters obtained by analyzing the image data (intensity distribution) of the interference fringes for measurement.

[0127] For example, the control unit 13 performs calculation processing to detect the current state of the first beam B1 and the second beam B2 based on the measured image data. Here, detecting the current state of each beam means calculating at least one of Δθ1, Δθ2, ΔΦ1, and ΔΦ2.

[0128] For example, by calculating the spatial frequency νy in the y-direction of the interference fringes for measurement from the image data, ΔΦ1 + ΔΦ2 can be calculated according to equation (3). Also, by calculating the angular displacement γ of the interference fringes for measurement and the spatial frequency νx in the x-direction (or the pitch width px in the x-direction) from the image data, the actual incident angle of the first beam B1 (θ1 + Δθ1) and the actual incident angle of the second beam B2 (θ2 + Δθ2) can be calculated according to equations (4) to (6). Furthermore, by controlling each drive mirror of the optical system 10 so that the values ​​of Δθ1, Δθ2, ΔΦ1, and ΔΦ2 become 0, interference exposure at the desired incident angles θ1 and θ2 becomes possible.

[0129] The method of using the image data measured by the image sensor 68 is not limited. For example, it is possible to calculate the pitch width pX in the X direction of the exposure interference fringe, the angular displacement of the exposure interference fringe 6 with respect to the Y direction, etc., from the above calculation results and feed this back into the control of the stage mechanism 11. In addition, it is possible to apply, for example, the calibration processing example described in Patent Document 3.

[0130] [Operation of Interference Exposure Apparatus] Figure 8 is a flowchart showing an example of the operation of an interference exposure apparatus. Figure 8 shows the process by which the optical system 10 is automatically adjusted in accordance with the input values ​​when the slant angle α and pitch width p of the exposure interference fringes 6 to be exposed on the workpiece W are input to the interference exposure apparatus 100. This process is a preparation process (calibration process) performed before the exposure process in which interference exposure is performed.

[0131] First, the control unit 13 acquires the input values ​​for the slant angle α and pitch width p of the exposure interference fringes 6 (step 101). For example, the user inputs the desired slant angle α and pitch width p via a predetermined input UI, and these input values ​​are read. Here, the wavelength λ of the laser light is assumed to be set in advance.

[0132] Next, the control unit 13 calculates the incident angle of the beam (step 102). Here, based on the input values ​​of the slant angle α and the pitch width p, the incident angle θ1 of the first beam B1 and the incident angle θ2 of the second beam B2 are calculated according to equations (1) and (2), respectively.

[0133] Next, the optical system 10 is controlled by the control unit 13, and the position and angle of each mirror are adjusted (step 103). Initially, the control unit 13 calculates the position and angle of the illumination drive mirrors 24a and 24b that realize the respective incident angles θ1 and θ2 calculated in step 102, and the optical system 10 moves and rotates the illumination drive mirrors 24a and 24b according to the calculation results of the control unit 13. In addition, the position and angle of the relay drive mirrors 23a and 23b are calculated, and the relay drive mirrors 23a and 23b are moved and rotated according to the calculation results. Note that the process of calculating the position and angle of each drive mirror may be performed in step 102.

[0134] For example, when the slant angle α = 0°, the symmetric mode is realized. If the slant angle α is not 0°, the asymmetric mode is realized. In this way, the interference exposure apparatus 100 automatically sets the symmetric mode and the asymmetric mode according to input values ​​such as the slant angle α. Note that when the slant angle α is 5° or less, the difference between the incident angles of the first beam B1 and the second beam B2 (for example, |θ1| - |θ2|) is sufficiently small, so it can also be considered as the symmetric mode.

[0135] Next, the incident angle of the beam is measured by the sensor unit 12 (step 104). For example, the sensor unit 12 is moved to the irradiation area 5 in advance by the stage mechanism 11. The inclination angle of the multiplexing element 66 is also set in advance by the sensor unit 12 according to the slant angle α acquired in step 101. In this state, the beam B0 from the laser light source is supplied to the optical system 10, and the image sensor 68 measures the exposure fringes for measurement by the combined beam BA of the first beam B1 and the second beam B2 as image data, which is output to the control unit 13.

[0136] The control unit 13 analyzes the image data and calculates the actual incident angles (θ1 + Δθ1, θ2 + Δθ2) of the first beam B1 and the second beam B2. It also calculates the inclination angles (ΔΦ1, ΔΦ2) of the first beam B1 and the second beam B2 with respect to the XZ plane. In other words, it calculates the difference between the current beam angle and the ideal value. In addition, any other parameters necessary for the calibration process may be calculated. In this way, the interference exposure apparatus 100 automatically calculates the current beam incident angle and other parameters.

[0137] Next, the control unit 13 determines whether the calculation result in step 104 is within the standard range (step 105). For example, it is determined whether each parameter (Δθ1, Δθ2, ΔΦ1, ΔΦ2, etc.) calculated in step 104 is below a predetermined threshold. The thresholds for each parameter are set appropriately according to the required exposure accuracy, etc.

[0138] For example, if any of these parameters exceed a threshold, step 103 is executed, assuming that the incidence angles of the first beam B1 and the second beam B2 do not reach the standard (NO in step 105). In step 103, the positions and angles of the relay drive mirrors 23a and 23b, etc., are adjusted so that the parameters that exceed the threshold fall within the threshold. For example, if the deviation amount Δθ1 of the incidence angle θ1 exceeds the threshold, the angle and position of the irradiation drive mirror 24a around the Y axis that makes Δθ1 zero is calculated, and the angle and position of the irradiation drive mirror 24a are adjusted according to the calculation result. The angles and positions of the corresponding mirrors are also adjusted as appropriate for other parameters.

[0139] After adjusting the angle and position of each drive mirror, steps 104 and 105 are performed again. By repeating this process, the incidence angles of the first beam B1 and the second beam B2 are adjusted to the beam angles calculated in step 102. When all parameters such as Δθ1, Δθ2, ΔΦ1, and ΔΦ2 are below the threshold, the incidence angles of the first beam B1 and the second beam B2 are considered to have reached the standard (YES in step 105), the preparation process is completed, and interference exposure on the workpiece W is started.

[0140] Figure 9 illustrates an example of drive mirror adjustment. The upper part of Figure 9 shows image data of the measurement interference fringes 7 captured by the image sensor 68 during beam angle adjustment. In this data, the left-right direction in the figure is the x-direction of the measurement surface, and the up-down direction is the y-direction. The lower part of Figure 9 shows a graph representing the adjustment result of the drive mirror. This graph shows the result of adjusting the rotation angle around the Y-axis of the irradiation drive mirror 24a, which is located to the left of the arc drive shaft 35 in Figure 4.

[0141] The interference fringes 7 for measurement shown in Figure 9 have stripes that are inclined with respect to the x-direction. Let's consider the case where these interference fringes 7 are adjusted so that they are stripes parallel to the x-direction. Here, the number of interference fringes along the x-direction, Nx, is used as a parameter indicating the degree of inclination of the interference fringes 7 with respect to the x-direction. Nx is, for example, the number of stripes counted on a straight line 69 extending in the x-direction, and a state where Nx is 0 represents a state where stripes parallel to the x-direction are realized.

[0142] The graph in Figure 9 plots Nx on the vertical axis, with the rotation angle of the illumination drive mirror 24a on the horizontal axis. For example, when the rotation angle of the illumination drive mirror 24a was 31.5°, Nx was 83 lines. From this state, when the rotation angle of the illumination drive mirror 24a was decreased, Nx also decreased, and at a rotation angle of around 30.6°, Nx became 0. In this way, by using the sensor unit 12, it becomes possible to monitor the measurement interference fringes 7, and to adjust the position and angle of the drive mirror with high precision.

[0143] Figure 10 is a graph showing the range of beam incidence angles in an interference exposure apparatus. Figure 10 illustrates the settable range 70 (shaded area) of incidence angles θ1 and θ2 of the first beam B1 and second beam B2 in an optical system 10 having a single arc drive axis 35, as explained with reference to Figure 4, etc. Figure 10 also illustrates examples of beam angles that can be achieved at each point in the settable range 70.

[0144] In the optical system 10 having an arc drive axis 35, the illumination drive mirrors 24a and 24b can move beyond the normal L of the exposure surface 4. As a result, the settable range 70 is not interrupted in the region near the normal L where θ1 and θ2 are 0 (the region along the θ1 axis and θ2 axis in the graph), and a continuous settable range 70 spanning the θ1 axis and θ2 axis can be realized.

[0145] This makes it possible to configure the system in a way that, for example, two beams are incident from the left side of the normal vector L (the upper left region of the graph), or in a way that two beams are incident from the right side of the normal vector L (the lower right region of the graph). Furthermore, in configurations where beams are incident from both the left and right sides of the normal vector L, it becomes possible to cover a wide range of incident angles, from those parallel to the normal vector L to those significantly inclined relative to the normal vector L. In this way, the optical system 10 with the circular arc drive axis 35 is able to achieve a wider range of beam angles despite having only one drive axis.

[0146] For example, by using the arc drive shaft 35 shown in Figure 4, the incident angle θ1 of the first beam B1 to the exposure surface 4 can be set to -75° ≤ θ1 ≤ 65°. Similarly, the incident angle θ2 of the second beam B2 to the exposure surface 4 can be set to -65° ≤ θ2 ≤ 75°. This significantly expands the range of exposureable slant angle α and pitch angle p. Note that the setting ranges for θ1 and θ2 are not limited, and an optical system 10 capable of setting them to a wider range than the above range may be configured.

[0147] Figure 11 is a graph showing the range of slant angles and pitch widths that can be exposed by the interference exposure apparatus. Here, the settable range 71 (shaded area) of slant angle and pitch width that can be exposed by the interference exposure apparatus 100 having the arc drive shaft 35 shown in Figure 4 is illustrated. The horizontal axis of the graph is the slant angle α (degrees) and the vertical axis is the pitch width p (nm).

[0148] In this embodiment, the slant angle α and pitch p are not limited by constraints such as the irradiation drive mirrors 24a and 24b only being able to move on one side of the normal L, and a wide and continuous settable range 71 is realized. From the graph shown in Figure 11, it can be seen that in the interference exposure apparatus 100, the slant angle α can be set in the range of 0° ≤ α ≤ 30°, and the pitch width p can be set in the range of 150 nm ≤ p ≤ 600 nm. In this way, by using the interference exposure apparatus 100, it is possible to sufficiently widen the range of exposureable slant angle α and pitch width p.

[0149] As described above, in the interference exposure apparatus according to this embodiment, interference exposure is possible in an asymmetric mode in which the first beam B1 and the second beam B2 are incident on the workpiece W asymmetric with respect to the normal L to the exposure surface 4 in the irradiation area 5. By using the asymmetric mode, exposure at various slant angles α becomes possible. Furthermore, by adjusting the intersection angle of the first beam B1 and the second beam B2 in each mode, the pitch width p of the exposure interference fringes 6 can be adjusted. This makes it possible to easily achieve exposure at various slant angles α and pitch widths p.

[0150] As an optical system for interference exposure, a system is generally known that generates interference fringes with a slant angle of 0° by setting the incident angles of two beams to the workpiece to be equal. Such an optical system is equipped with a function to adjust the pitch width, for example, by changing the common incident angle θ of the two beams. However, in an optical system configured on the premise that the incident angles of the two beams are equal, it can be difficult to set the incident angle of each beam individually. In addition, depending on the set value of the incident angle, it may be necessary to change the optical components, but changing shafts driven by, for example, an automatically adjustable motor or pneumatically is extremely difficult.

[0151] In this embodiment, the optical system 10 is configured to enable interference exposure in both symmetric and asymmetric modes. This makes it possible to individually adjust the incidence angles θ1 and θ2 of the first beam B1 and the second beam B2 with respect to the exposure surface 4 without changing optical components or axes.

[0152] Furthermore, in this embodiment, the position and angle of each mirror in the optical system 10 are automatically adjusted using the control unit 13. This makes it possible to automatically perform exposure at a desired slant angle α and pitch width p. In addition, feedback control of the mirror adjustment is performed using a sensor unit 12 that can detect the incident angles of the two beams in both symmetric and asymmetric modes. This makes it possible to accurately achieve various slant angles α and pitch widths p.

[0153] <Second Embodiment> An interference exposure apparatus according to a second embodiment of the present invention will now be described. In the following description, parts that are the same as the configuration and operation of the interference exposure apparatus 100 described in the above embodiment will be omitted or simplified.

[0154] Figure 12 is a schematic diagram showing an example configuration of an interference exposure apparatus according to a second embodiment. The optical system 210 of the interference exposure apparatus 200 includes a relay mirror 221, a demultiplexer 222, two irradiation drive mirrors 224a and 224b, and a linear drive shaft 231. The configuration of the optical system 210 can be realized, for example, using the configuration of the linear bench optical system 38 shown in Figure 4. The upper part of Figure 12 shows an example of arrangement when the irradiation drive mirror 224a is moved, and the lower part shows an example of arrangement when the irradiation drive mirror 224b is moved.

[0155] In the optical system 210, two illumination drive mirrors 224a and 224b, which reflect the first beam B1 and the second beam B2 toward the workpiece W (irradiation area 5), ​​are moved along the same linear drive axis 231. That is, the first drive axis 25a, which is the drive axis for illumination drive mirror 224a, and the second drive axis 25b, which is the drive axis for illumination drive mirror 224b, are the same linear drive axis 231. In this embodiment, the linear drive axis 231 corresponds to a common linear axis.

[0156] Furthermore, a demultiplexing element 222 is provided between the two illumination drive mirrors 224a and 224b, which emit the first beam B1 and the second beam B2 toward each mirror. In this embodiment, the demultiplexing element 222 moves along a common linear drive axis 231 so as not to obstruct the movement of the illumination drive mirrors 224a and 224b. This makes it possible to expand the range of movement of the illumination drive mirrors 224a and 224b compared to, for example, the case where the demultiplexing element 222 is fixed.

[0157] As shown in the upper part of Figure 12, when moving the illumination drive mirror 224a, the demultiplexer 222 is positioned to the right of the linear drive shaft 231 so as not to interfere with the illumination drive mirror 224a. This widens the driving range of the illumination drive mirror 224a, making it possible to move it, for example, beyond the normal vector L to the right. Also, as shown in the lower part of Figure 12, when moving the illumination drive mirror 224b, the demultiplexer 222 is positioned to the left of the linear drive shaft 231. This makes it possible to move the illumination drive mirror 224b beyond the normal vector L to the left.

[0158] This makes it possible to irradiate with two beams from one side of the normal vector L, thereby widening the angular range of the slant angle α. In this way, by using the linear drive shaft 231 as the drive shaft for the irradiation drive mirrors 224a and 224b, it is possible to construct a simple optical system 210 with a small number of parts. Note that it is not necessary for both the irradiation drive mirrors 224a and 224b to be movable; for example, one of the drive mirrors may be configured as a rotating mirror with a fixed position.

[0159] <Third Embodiment> Figure 13 is a schematic diagram showing an example of the configuration of an interference exposure apparatus according to the third embodiment. As shown in Figure 13, the optical system 310 includes a relay mirror 321, a demultiplexer 322, two relay drive mirrors 323a and 323b, two irradiation drive mirrors 324a and 324b, two arm portions 325a and 325b, and a linear drive shaft 331. The optical system 310 of the interference exposure apparatus 300 is configured such that arm portions 325a and 325b are provided on the linear drive shaft 331, which was described with reference to Figure 12, and irradiation drive mirrors 324a and 324b are placed at the tips of each arm portion 325a and 325b.

[0160] Each of the arm portions 325a and 325b is provided with one end on the linear drive shaft 331 and is configured to move along the linear drive shaft 331 and to rotate relative to the linear drive shaft 331. In this embodiment, the arm portions 325a and 325b correspond to the third arm and the fourth arm.

[0161] The relay drive mirror 323a is rotatably mounted at one end of the arm portion 325a on the linear drive shaft 331 and reflects the first beam B1 toward the illumination drive mirror 324a. The relay drive mirror 323b is rotatably mounted at one end of the arm portion 325b on the linear drive shaft 331 and reflects the second beam B2 toward the illumination drive mirror 324b. In this embodiment, the relay drive mirrors 323a and 323b correspond to the fifth and sixth mirrors.

[0162] The illumination drive mirrors 324a and 324b are mirrors that reflect the first beam B1 and the second beam B2 incident from the relay drive mirrors 323a and 323b toward the workpiece W (irradiation area 5). In this embodiment, the illumination drive mirror 324a is provided at the other end of the arm portion 325a opposite to the relay drive mirror 323a. The illumination drive mirror 324b is provided at the other end of the arm portion 325b opposite to the relay drive mirror 323b.

[0163] For example, as shown in the upper part of Figure 13, when moving the arm portion 325a, the demultiplexing element 322 is positioned to the right of the linear drive shaft 331 so as not to interfere with the arm portion 325a. Similarly, as shown in the lower part of Figure 13, when moving the arm portion 325b, the demultiplexing element 322 is positioned to the left of the linear drive shaft 331.

[0164] Furthermore, the tips of the arm portions 325a and 325b, each equipped with the illumination drive mirrors 324a and 324b, are positioned closer to the illumination area 5 when viewed from the linear drive shaft 331. This makes it possible to shorten the distance between the illumination drive mirrors 324a and 324b and the illumination area 5, for example, in the Z direction. This makes it possible to easily achieve a larger incidence angle without, for example, expanding the linear drive shaft 331 in the left-right direction. This makes it possible to widen the range of the slant angle α with a compact device configuration.

[0165] <Other Embodiments> The present invention is not limited to the embodiments described above, and various other embodiments can be realized.

[0166] The above embodiment describes an interference exposure apparatus capable of interference exposure in both symmetric and asymmetric modes. However, it is not limited to this, and for example, an interference exposure apparatus may be configured to be capable of interference exposure only in asymmetric mode. For example, an optical system in which the movable range of the mirror on one side of the normal is widened in order to increase the slant angle may be used.

[0167] The above embodiment mainly described a configuration in which the optical system is automatically adjusted. For example, each drive mirror of the optical system may be manually adjustable. In this case, for example, the user moves each drive mirror along the drive shaft to adjust the rotation angle and tilt angle of the drive mirror. Even when manual adjustment is performed, it is possible to adjust each drive mirror with high precision by, for example, monitoring using a sensor unit.

[0168] It is also possible to combine at least two of the feature features of the present technology described above. In other words, the various feature features described in each embodiment may be combined arbitrarily, regardless of the specific embodiment. Furthermore, the various effects described above are merely examples and not limiting, and other effects may also be exhibited.

[0169] B1...First beam B2...Second beam L...Normal 4...Exposure surface 5...Irradiation area 6...Interference fringes for exposure 10, 210, 310...Optical system 12...Sensor unit 13...Control unit 22, 222, 322...Demultiplexer 24, 24a, 24b, 224a, 224b, 324a, 324b...Irradiation drive mirror 25a...First drive shaft 25b...Second drive shaft 31, 231, 331...Linear drive shaft 35...Circular arc drive shaft 65...Light receiving unit 100, 200, 300...Interference exposure apparatus

Claims

1. An interference exposure apparatus that performs interference exposure on an object to be irradiated arranged along an exposure surface by superimposing a first beam and a second beam, obtained by splitting coherent emitted light, in an irradiation area on an exposure surface, wherein the optical system is capable of performing interference exposure in an asymmetric mode in which the incident angle of at least one of the first beam or the second beam with respect to the exposure surface is variable, and the first beam and the second beam are incident on the object to be irradiated in an asymmetric mode with respect to the normal of the irradiation area to the exposure surface.

2. An interference exposure apparatus according to claim 1, wherein the optical system is switchable between interference exposure in the asymmetric mode and interference exposure in the symmetric mode in which the first beam and the second beam are incident on the object to be irradiated symmetrically with respect to the normal.

3. An interference exposure apparatus according to claim 2, further comprising a control unit that controls the incident angle of at least one of the first beam or the second beam with respect to the exposure surface according to input values ​​relating to the slant angle and pitch width of interference fringes formed on the irradiated object, and sets the mode of the optical system to either the symmetric mode or the asymmetric mode.

4. An interference exposure apparatus according to claim 3, further comprising a sensor unit for detecting the incident angle of the first beam to the exposure surface and the incident angle of the second beam to the exposure surface, wherein the control unit controls the optical system based on the detection result of the sensor unit.

5. An interference exposure apparatus according to claim 4, wherein the sensor unit comprises a multiplexing element that combines the first beam and the second beam, an attitude adjustment element that adjusts the attitude of the multiplexing element according to the slant angle, and an image sensor that measures the intensity distribution of the multiplexed beam combined by the multiplexing element.

6. An interference exposure apparatus according to claim 1, wherein the optical system comprises: a demultiplexing element for splitting the emitted light into a first beam and a second beam; a first mirror that moves along a first drive axis and rotates with respect to the first drive axis to reflect the first beam toward the irradiation area; and a second mirror that moves along a second drive axis and rotates with respect to the second drive axis to reflect the second beam toward the irradiation area.

7. An interference exposure apparatus according to claim 6, wherein the first drive shaft and the second drive shaft are provided along a common reference plane set perpendicular to the exposure surface.

8. An interference exposure apparatus according to claim 7, wherein the first drive shaft and the second drive shaft are provided such that both the first mirror and the second mirror can be positioned on one side with respect to the normal in the reference plane.

9. An interference exposure apparatus according to claim 6, wherein the first drive shaft and the second drive shaft are each arc axes surrounding the irradiation area.

10. An interference exposure apparatus according to claim 9, wherein the first drive shaft and the second drive shaft are common arc axes.

11. An interference exposure apparatus according to claim 9, wherein the optical system comprises a first arm that moves along a first drive axis so that the first adjustment optical system faces the irradiation area, and the optical system comprises a second arm that moves along a second drive axis so that the second adjustment optical system faces the irradiation area, and the optical system comprises a second arm that moves along a second drive axis so that the second adjustment optical system faces the irradiation area, and the optical system comprises a first adjustment optical system that moves along a second drive axis so that the second adjustment optical system faces the irradiation area.

12. An interference exposure apparatus according to claim 6, wherein the optical system comprises a third mirror that moves along a linear axis different from the first drive axis and the second drive axis and rotates with respect to the linear axis and reflects the first beam toward the first mirror, and a fourth mirror that moves along the linear axis and rotates with respect to the linear axis and reflects the second beam toward the second mirror.

13. An interference exposure apparatus according to claim 6, wherein the first drive shaft and the second drive shaft are common linear axes.

14. An interference exposure apparatus according to claim 13, wherein the demultiplexing element moves along the common linear axis so as not to obstruct the movement of the first mirror and the second mirror.

15. An interference exposure apparatus according to claim 6, wherein the optical system comprises: a third arm having one end on the first drive shaft and moving along the first drive shaft and rotatable with respect to the first drive shaft; a fifth mirror rotatably mounted on the one end of the third arm and reflecting the first beam toward the first mirror; a fourth arm having one end on the second drive shaft and moving along the second drive shaft and rotatable with respect to the second drive shaft; and a sixth mirror rotatably mounted on the one end of the fourth arm and reflecting the second beam toward the second mirror, wherein the first mirror is provided at the other end of the third arm and the second mirror is provided at the other end of the fourth arm.

16. An interference exposure apparatus according to claim 1, wherein the incident angle θ1 of the first beam with respect to the exposure surface is -75° ≤ θ1 ≤ 65°, and the incident angle θ2 of the second beam with respect to the exposure surface is -65° ≤ θ2 ≤ 75°.

17. An interference exposure apparatus according to claim 1, wherein the asymmetric mode includes a mode in which the slant angle α of the interference fringes formed on the irradiated object is α ≥ 5°.

18. An interference exposure method for performing interference exposure on an object to be irradiated arranged along an exposure surface by superimposing a first beam and a second beam obtained by splitting coherent emitted light in an irradiation area on the exposure surface, wherein input values ​​relating to the slant angle and pitch width of interference fringes formed on the object to be irradiated are obtained, and the incident angle of at least one of the first beam or the second beam with respect to the exposure surface is variable, and the interference exposure is possible in an optical system that is incident on the object to be irradiated in an asymmetric mode such that the first beam and the second beam are asymmetric with respect to the normal to the exposure surface in the irradiation area, wherein the incident angles of the first beam and the second beam with respect to the exposure surface are adjusted according to the input values.

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