Illumination device, measurement device, substrate processing device, and method for manufacturing an article

Abstract

To provide an illumination apparatus that suppresses degradation in performance and durability of a light source.SOLUTION: An illumination apparatus configured to provide illumination while changing a spectrum of light from a light source includes an optical system configured to guide the light from the light source, and a wavelength variable unit configured to move in a linear direction along a first axis perpendicular to an optical axis of the optical system, thereby changing the spectrum of the light from the optical system. The wavelength variable unit is disposed so that its incident surface on which the light emitted from the optical system is incident is tilted in a rotary direction about the first axis.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an illumination device, a measurement device, a substrate processing device, and a method for manufacturing an article. [Background technology]

[0002] BACKGROUND ART In the manufacture of products such as semiconductor devices, MEMS, color filters, and flat panel displays, patterns formed on substrates are becoming increasingly finer, and there is an increasing demand for improved dimensional accuracy of the patterns.

[0003] Therefore, substrate processing apparatuses that process substrates require high accuracy in measuring the position of the substrate on which a pattern is to be formed. An example of a substrate processing apparatus is an exposure apparatus that exposes a substrate to light to form a pattern on the substrate. In an exposure apparatus, exposure light is focused at a predetermined position on the substrate via a projection optical system, and a stage carrying the substrate is moved to form a pattern on the substrate. Furthermore, the accuracy of measuring the pattern on the substrate in order to align the relative position of the exposure light with the predetermined position on the substrate where the pattern is to be formed, and the accuracy of measuring the relative positions of patterns formed on different layers on the substrate, are important.

[0004] One method for measuring the position of a pattern formed on a substrate (hereinafter simply referred to as a pattern) is to illuminate the pattern and detect the light reflected by the pattern. Another method for measuring the pattern with higher accuracy is to select the wavelength of light that illuminates the pattern depending on the physical and optical properties of the pattern and its surrounding area. The physical properties of the material that makes up the pattern and the shape of the pattern change depending on the process in which the substrate is processed. Therefore, by illuminating the pattern with light of a wavelength selected depending on the process in which the substrate is processed, the intensity of the detection signal of the light reflected from the pattern is improved, the error in the detection signal is reduced, and the accuracy of pattern position measurement is improved.

[0005] Patent Document 1 describes an imaging system for imaging a sample, in which the wavelength of light irradiated onto the sample is changed and the sample is imaged in synchronization with the change in wavelength. It also describes that a light source device included in the imaging system drives a filter to change the wavelength of light that passes through the filter and irradiates the sample. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6568041 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 1, when light emitted from a light source is reflected on the surface of a filter, the reflected light may return and irradiate the light source, which may cause the temperature of the light source to rise, deteriorating the performance and durability of the light source.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an illumination device, a measurement device, a substrate processing apparatus, and a method for manufacturing an article that suppress deterioration in the performance and durability of a light source. [Means for solving the problem]

[0009] An illumination device according to one aspect of the present invention for solving the above-described problems is an illumination device that illuminates by changing the spectrum of light from a light source, the illumination device including: an optical system that guides light from the light source; and a wavelength tunable unit that changes the spectrum of the light from the optical system by moving in a linear direction along a first axis perpendicular to an optical axis of the optical system; a second optical system that guides light from the wavelength variable unit; and a second wavelength variable unit that changes the spectrum of the light from the second optical system by moving in a second linear direction along a second axis that is perpendicular to a second optical axis of the second optical system; the wavelength tunable unit is disposed so that an incident surface of the wavelength tunable unit onto which the light irradiated by the optical system is incident is inclined in the rotation direction around the first axis. The second wavelength tunable unit is disposed so that a second incident surface of the second wavelength tunable unit, onto which the light irradiated by the second optical system is incident, is inclined in the rotation direction around the second axis. do. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an illumination device, a measurement device, a substrate processing apparatus, and a method for manufacturing an article that suppress deterioration in the performance and durability of a light source. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a measurement device according to a first embodiment. [Figure 2] FIG. 4 is a diagram showing an illumination unit according to a comparative example of the first embodiment. [Figure 3] FIG. 10 is a diagram showing wavelength characteristics of an illumination device according to a comparative example of the first embodiment. [Figure 4] 3A and 3B are diagrams illustrating optical paths of an illumination unit according to the first embodiment and an illumination unit according to a modified example. [Figure 5] FIG. 10 is a diagram showing an illumination unit according to a second embodiment. [Figure 6] FIG. 10 is a diagram showing an illumination unit according to a first modified example of the second embodiment. [Figure 7] FIG. 10 is a diagram showing an illumination unit according to a second modified example of the second embodiment. [Figure 8] FIG. 10 is a diagram showing wavelength characteristics of an illumination unit according to the second embodiment. [Figure 9] FIG. 10 is a diagram showing wavelength characteristics of an illumination unit according to a first modified example of the second embodiment. [Figure 10] FIG. 10 is a diagram showing wavelength characteristics of an illumination unit according to the second embodiment. [Figure 11] FIG. 10 is a diagram showing wavelength characteristics of an illumination unit according to a second modified example of the second embodiment. [Figure 12] FIG. 10 is a diagram showing an illumination unit according to a third embodiment. [Figure 13] FIG. 10 is a diagram showing an exposure apparatus according to a fourth embodiment. [Figure 14] FIG. 10 is a diagram illustrating an exposure process according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. In each drawing, the same components are designated by the same reference numerals, and duplicate explanations will be omitted. Note that the present invention is not limited to the following embodiments, which merely illustrate specific examples advantageous for carrying out the present invention. Furthermore, not all of the combinations of features described in the following embodiments are necessarily essential for solving the problems of the present invention.

[0013] First Embodiment First, a measurement device having an illumination unit (illumination device) according to the first embodiment will be described. FIG. 1 is a diagram showing the measurement device according to the first embodiment. In the following, the direction parallel to the optical axis of an illumination optical system 362 (described later) will be referred to as the Z-axis direction, and two mutually perpendicular directions along a plane perpendicular to the Z-axis direction will be referred to as the X-axis direction and the Y-axis direction. The rotation directions around the X-axis, Y-axis, and Z-axis will be referred to as the ωX-axis direction, ωY direction, and ωZ direction, respectively.

[0014] 1(a) is a diagram showing the configuration of a measurement apparatus 100. The measurement apparatus 100 is, for example, a measurement apparatus that measures the positions in the X-axis direction and the Y-axis direction of a pattern provided on a substrate 73. The measurement apparatus 100 may also be, for example, a measurement apparatus that measures the positions in the X-axis direction and the Y-axis direction of patterns provided on different layers on the substrate 73, and measures the distance between the patterns. The measurement apparatus 100 also has a substrate stage WS that holds the substrate 73, a measurement unit 50, and a control unit 1100.

[0015] Here, the substrate 73 is an object for which alignment errors and overlay errors are measured by the measuring device 100. The substrate 73 is, for example, a substrate used to manufacture devices such as semiconductor elements and liquid crystal display elements, and specifically includes wafers, liquid crystal substrates, other substrates to be processed, and the like.

[0016] The substrate stage WS holds the substrate 73 via a substrate chuck (not shown) and is configured to be drivable by a stage driver (not shown). The stage driver includes a linear motor and the like, and is capable of moving the substrate 73 held by the substrate stage WS by driving the substrate stage WS in the X-axis direction, Y-axis direction, Z-axis direction, ωX-axis direction, ωY direction, and ωZ direction. A mirror 82 is provided on the substrate stage WS. A laser interferometer 81 is provided opposite the mirror 82. The laser interferometer 81 measures the distance to the mirror 82 in the X-axis direction to measure the position of the substrate stage WS in the X-axis direction. Similarly, laser interferometers (not shown) are provided for measuring the positions of the substrate stage WS in the Y-axis direction and the Z-axis direction. The position of the substrate stage WS is measured in real time by these laser interferometers, and the measurement results are output to the controller 1100, whereby the substrate stage WS is driven to a predetermined position under the control of the controller 1100. Furthermore, the measuring apparatus 100 may have a scale arranged on the substrate stage WS, and an encoder that measures the position of the substrate stage WS by detecting the position of the scale.

[0017] The control unit 1100 comprehensively controls each unit of the measuring device 100 to operate the measuring device 100. The control unit 1100 also performs measurement processing in the measuring device 100 and arithmetic processing of measurement values ​​obtained by the measuring device 100. The control unit 1100 is configured as a computer (information processing device). The control unit 1100 includes, for example, a processing unit having a processor such as a CPU that performs calculations for control according to a program, a storage unit such as a ROM that stores control programs and fixed data, and a storage unit such as a RAM that stores a work area for the processing unit and temporary data. The control unit 1100 may also include, as a storage unit, a magnetic storage device (HDD) that can store larger amounts of data than ROM and RAM. The control unit 1100 may also include, as a storage unit, a drive device that loads external media such as CDs, DVDs, and memory cards and reads and writes data. In this embodiment, at least one of the ROM, RAM, magnetic storage device, and drive device is used as the storage unit, and the storage unit stores the control program, fixed data, the work area for the processing unit, and temporary data.

[0018] The measurement unit 50 illuminates a pattern provided on the substrate 73, detects light from the pattern, and captures an image of the pattern provided on the substrate 73. FIG. 1(b) illustrates the configuration of the measurement unit 50. The measurement unit 50 includes an illumination system that illuminates the substrate 73 with light from an illumination unit (illumination device) 301, and an imaging system (detection system) that focuses light from the pattern 72 on the detection unit 75 (forming an image of the pattern 72). The detection unit 75 includes a light-receiving unit (not shown) that receives light from the pattern 72 and acquires a detection signal of the light received by the light-receiving unit. The detection unit 75 can also function as an imaging unit that forms an imaging area for capturing an image of the pattern 72 using the light-receiving unit. Here, the pattern 72 is a pattern for measuring alignment errors and overlay errors on the substrate 73, and the position of the pattern 72 is measured based on the detection signal acquired by the detection unit 75.

[0019] 1(c) is a diagram showing the configuration of the illumination unit 301. The illumination unit 301 has a light source 361, an illumination optical system (optical system) 362, a wavelength tuner 340, and a driver 341.

[0020] Light emitted from the light source 361 is guided to the wavelength variable section 340 via an illumination optical system 362. The light source 361 may be, for example, a laser light source, an LED, a halogen lamp, or the like.

[0021] The illumination optical system 362 irradiates the wavelength variable unit 340 with light emitted from the light source 361. The illumination optical system 362 may be, for example, an axially symmetric transmission optical system including a lens through which light passes. The illumination optical system 362 may also be, for example, a reflection optical system including a mirror such as a concave mirror or a convex mirror, or a cylindrical optical system including a cylindrical lens.

[0022] The wavelength tuning unit 340 includes a wavelength tuning element that changes the relationship between the wavelength and intensity of the irradiated light (hereinafter referred to as the spectrum) depending on the position and angle at which the light is incident. The spectrum may include, for example, information indicating the relationship between the wavelength of the light and the intensity of the light. The spectrum may include, for example, information on the wavelength of the light at which the intensity of the light is maximum, minimum, or a predetermined value. The spectrum may include, for example, information on the wavelength band of the light at which the intensity of the light falls within a predetermined range. The spectrum may also include, for example, information on the waveform of the spectrum. The wavelength tuning unit 340 will be described as including a transmissive wavelength tuning element, but it may also include a reflective wavelength tuning element.

[0023] The wavelength tuning unit 340 is disposed at a light-condensing position of the illumination optical system 362 on the optical axis of the illumination optical system 362, and is driven (moved) by a driving unit 341 (moving unit) in a direction perpendicular to the direction along the optical axis of the illumination optical system 362 (the X-axis direction in the example of FIG. 1( c)). Here, in the description of this embodiment, the wavelength tuning unit 340 is described as being driven by the driving unit 341 in the X-axis direction, but the direction of the driving axis (driving direction) of the driving unit 341 is not limited to the X-axis direction. Note that if the beam diameter of light incident on the wavelength tuning unit 340 varies depending on the direction, it is desirable to drive the wavelength tuning unit 340 in a direction that minimizes the beam diameter of the light from the viewpoint of wavelength characteristics. Furthermore, for example, if a cylindrical optical system is used in the illumination optical system 362, it is desirable to drive the wavelength tuning unit 340 in the power direction of the cylindrical optical system.

[0024] The driving unit 341 has a driving means such as a linear motor, and can drive the wavelength tuning unit 340 in a predetermined direction perpendicular to the optical axis. The position of the wavelength tuning unit 340 is measured by, for example, an encoder or an interferometer, and the control unit 1100 controls the wavelength tuning unit 340 so that it is driven to a predetermined position.

[0025] Here, the wavelength tuner 340 is arranged so that the surface through which light enters the wavelength tuner 340 (hereinafter referred to as the incident surface of the wavelength tuner) is inclined at a predetermined inclination angle with respect to a plane perpendicular to the optical axis of the illumination optical system 362. Furthermore, in the example of FIG. 1(c), the wavelength tuner 340 is arranged so that the incident surface of the wavelength tuner 340 is inclined at a predetermined inclination angle in the rotation direction around the X axis (ωX axis direction) perpendicular to the optical axis. In other words, the wavelength tuner 340 is arranged so that it is inclined at a predetermined inclination angle around the drive axis of the drive unit 341. The arrangement of the wavelength tuner 340 will be described later.

[0026] The illumination unit 301 can illuminate the substrate 73 with light of a desired wavelength by aligning the wavelength tunable unit 340 with the drive unit 341 based on the relationship between the position of the wavelength tunable unit 340 in a predetermined direction perpendicular to the optical axis and the wavelength of light transmitted through the wavelength tunable unit 340. Here, the predetermined direction perpendicular to the optical axis is a direction perpendicular to the optical axis of the illumination optical system 362, such as the X-axis direction or the Y-axis direction. The relationship between the position and the wavelength will be described later.

[0027] In this way, by changing the position of the wavelength tuner 340 using the driver 341, the wavelength of light passing through the wavelength tuner 340 can be changed. The wavelength tuner 340 can be, for example, a wavelength-tunable filter. Here, the wavelength tuner is, for example, a bandpass filter having a multilayer laminated film formed on the surface on which light is incident, and the film thickness of the multilayer laminated film is formed to increase along the wavelength change direction. This allows the wavelength of the transmitted light to change continuously due to optical interference. Alternatively, the wavelength tuner 340 can be, for example, a transmission type diffraction grating that separates light into different wavelengths using a diffraction grating formed on a light-transmitting member. Here, the wavelength tuner 340 can be, for example, a short-wavelength pass filter (low-pass filter, short-pass filter) that transmits light with wavelengths shorter than a predetermined wavelength. Alternatively, the wavelength tuner 340 can be, for example, a long-wavelength pass filter (high-pass filter, long-pass filter) that transmits light with wavelengths longer than a predetermined wavelength.

[0028] 1(b) . Light emitted from the illumination unit 301 passes through an illumination optical system (first optical system) 63 and enters an illumination aperture stop 64. The diameter of the light beam at the illumination aperture stop 64 is smaller than the diameter of the light beam at the illumination unit 301. The light that passes through the illumination aperture stop 64 passes through a relay lens 67 and enters a beam splitter 68. The beam splitter 68 is, for example, a polarizing beam splitter, and transmits P-polarized light parallel to the Y-axis direction and reflects S-polarized light parallel to the X-axis direction. The light that passes through the beam splitter 68 passes through an aperture stop 69 and a λ / 4 plate 70 where it is converted into circularly polarized light, and then passes through an objective optical system 71 to Koehler illuminate a pattern 72 provided on a substrate 73.

[0029] Here, the illumination optical system 63 may have a light intensity adjustment unit (not shown) that can switch between a plurality of ND filters having different transmittances for the light from the illumination unit 301. The control unit 1100 can adjust with high precision the intensity of the light that illuminates the substrate 73 by controlling the light intensity adjustment unit. Furthermore, the illumination optical system may be provided with a fiber or optical rod for routing the illumination light, or with a microlens array for uniformizing the illumination light.

[0030] The light from pattern 72 passes through objective optical system 71, passes through λ / 4 plate 70, is converted from circularly polarized light to S-polarized light, and enters aperture stop 69. Here, the light from pattern 72 includes light that is reflected, diffracted, or scattered by pattern 72. The polarization state of the light from pattern 72 is circularly polarized in the opposite direction to the circularly polarized light that illuminates pattern 72. Therefore, if the polarization state of the light that illuminates pattern 72 is right-handed circularly polarized, the polarization state of the light from pattern 72 will be left-handed circularly polarized. The light that has passed through aperture stop 69 is reflected by beam splitter 68, passes through imaging optical system 74, and enters detection unit 75.

[0031] In this way, in the measurement unit 50, the beam splitter 68 separates the optical path of the light illuminating the substrate 73 from the optical path of the light from the substrate 73, and an image of the pattern 72 is formed on the detection unit 75. Then, the control unit 1100 acquires the positions of the pattern elements that make up the pattern 72 and the position of the pattern 72, based on the position information of the substrate stage WS obtained by the laser interferometer 81 and the waveform of the detection signal obtained by detecting the image of the pattern 72.

[0032] Here, in the measurement unit 50, the detection aperture stop may be configured by arranging multiple lenses between the beam splitter 68 and the detection unit 75. Alternatively, the illumination aperture stop 64 and the detection aperture stop may each be provided with multiple aperture stops that can set different numerical apertures for the illumination system and the detection system, respectively, and these multiple aperture stops may be switchable. This makes it possible to adjust the σ value, which is a coefficient that represents the ratio between the numerical aperture of the illumination system and the numerical aperture of the detection system.

[0033] FIG. 1(d) is a diagram showing the relationship between the wavelength and intensity of light transmitted through the wavelength tunable unit 340. This diagram illustrates the relationship between the wavelength and intensity of light transmitted through the wavelength tunable unit 340 when the wavelength tunable unit 340 is disposed at multiple discrete positions in the X-axis direction. The position at which light is incident changes depending on the position of the wavelength tunable unit 340, and the wavelength of the light transmitted through the wavelength tunable unit 340 changes. Here, since the absolute position of the light incident on the wavelength tunable unit 340 does not change in the measurement unit 50, the relative position of the incident light with respect to the wavelength tunable unit 340 changes when the drive unit 341 drives the wavelength tunable unit 340. Therefore, in the illumination unit 301 shown in FIG. 1(c), the drive unit 341 drives the wavelength tunable unit 340 in the X-axis direction, changing the position of the wavelength tunable unit 340 relative to the incident light, thereby adjusting the wavelength of the light illuminating the substrate 73.

[0034] 2 and 3, an illumination unit 901 according to the comparative example will be described. FIG. 2 is a diagram showing the illumination unit 901 according to the comparative example. The illumination unit 901 has a light source 961, an illumination optical system 962, a wavelength tuner 940, and a drive unit 941. The light source 961, the illumination optical system 962, the wavelength tuner 940, and the drive unit 941 correspond to the light source 361, the illumination optical system 362, the wavelength tuner 340, and the drive unit 341 in FIG. 1(c), respectively, and therefore detailed description thereof will be omitted. Also, unlike the wavelength tuner 340 in FIG. 1(c), the wavelength tuner 940 is arranged so that the incident surface of the wavelength tuner 940 is parallel to a plane perpendicular to the optical axis of the illumination optical system 962.

[0035] FIG. 3 is a diagram showing wavelength characteristics of an illumination unit according to a comparative example of this embodiment. The wavelength of light transmitted through the wavelength tunable unit 940 continuously changes depending on the position in the X-axis direction where the light is incident. Therefore, the wavelength characteristics of the transmitted light change depending on the beam diameter of the light incident on the wavelength tunable unit 940 by the illumination optical system 962. FIG. 3(a) shows that the region including the light 910 incident on the wavelength tunable unit 940 is divided into regions 910a to 910e. FIGS. 3(b) and 3(c) show the wavelength characteristics of light transmitted through the wavelength tunable unit 940. In FIG. 3(b), wavelength characteristics 980a to 980e are shown for the light when the light incident on the regions 910a to 910e is transmitted through the wavelength tunable unit 940. Because the center wavelength changes depending on the position in the X-axis direction where the light is incident on the wavelength tunable unit 940, the wavelength characteristics of the light transmitted through the regions 910a to 910e change as shown by 980a to 980e. The wavelength characteristics of the entire light passing through the wavelength tunable unit 940 are the sum of wavelength characteristics 980a to 980e, resulting in wavelength characteristic 980 as shown in FIG. 3(c). In other words, the larger the beam diameter of light 910 entering the wavelength tunable unit 940 in the direction in which the wavelength characteristics change in the wavelength tunable unit 940 (the X-axis direction), the wider the wavelength range of light passing through the wavelength tunable unit 940. This is undesirable because it means that the light passing through the wavelength tunable unit 940 contains more light of wavelengths other than the desired center wavelength. For this reason, it is desirable to position the wavelength tunable unit 940 at a position where the beam diameter of the light entering the wavelength tunable unit 940 is small. In other words, it is desirable to position the wavelength tunable unit 940 near the position where the light 910 entering the wavelength tunable unit 940 is focused, and it is even more desirable to position the wavelength tunable unit 940 at the position where the light 910 entering the wavelength tunable unit 940 is focused. Here, in the following explanation, when the wavelength variable section is positioned at a position where the incident light is focused, this includes cases where the wavelength variable section is positioned at a position where the incident light is focused, and cases where the wavelength variable section is positioned near the position where the incident light is focused.

[0036] However, if the wavelength tunable unit 940 is disposed at a position where the light 910 is condensed, the light reflected by the wavelength tunable unit 940 may be condensed at the light source 961 by the illumination optical system 962. This may cause, for example, an increase in the temperature of the light source 961, which may deteriorate the performance and durability of the light source 961. This may have a particularly significant effect when the light source 961 includes a point light source.

[0037] Here, the optical path of the light reflected by the wavelength tuner 940 will be described with reference to FIG. 2(b). Incident light 921a emitted from the light source 961 enters the wavelength tuner 940 via the illumination optical system 962. Because the wavelength tuner 940 is arranged parallel to a plane perpendicular to the optical axis of the illumination optical system 962, reflected light 921b from the wavelength tuner 940 travels along an optical path symmetrical with respect to the optical axis of the illumination optical system 962 and enters the light source 961. In the example of FIG. 2(b), incident light 921a and reflected light 921b are illustrated, but reflected light of incident light traveling along other optical paths also enters the light source 961. Therefore, the light reflected by the wavelength tuner 940 is collected by the light source 961 via the illumination optical system 962. This can deteriorate the performance and durability of the light source 961.

[0038] Therefore, in the illumination unit 301 according to this embodiment, the wavelength tuner 340 is arranged so as to be tilted at a predetermined tilt angle in the rotation direction about an axis (the X axis in the example of FIG. 1(c)) perpendicular to the optical axis direction of the illumination optical system 362. In other words, the wavelength tuner 340 is arranged so that the incidence surface of the wavelength tuner 340 is not parallel to a plane perpendicular to the optical axis of the illumination optical system 362. This makes it possible to reduce the amount of reflected light from the wavelength tuner 340 entering the light source 361, and to suppress deterioration in the performance and durability of the light source 361.

[0039] FIG. 4 is a diagram showing the optical path of the illumination unit according to this embodiment and an illumination unit according to a modified example. The optical path of light reflected by the wavelength tuner 340 according to this embodiment will be described using FIG. 4(a). Incident light 321a emitted from the light source 361 enters the wavelength tuner 340 via the illumination optical system 362. The incident surface of the wavelength tuner 340 is tilted at a predetermined angle with respect to a plane perpendicular to the optical axis of the illumination optical system 362, thereby reducing the incidence of reflected light from the wavelength tuner 340 entering the light source 361 via the illumination optical system 362. The example of FIG. 4(a) shows that reflected light 321b travels outside the effective range of the illumination optical system 362 and does not return to the light source 361.

[0040] Here, the inclination angle θ is defined as the angle at which the incident surface of the wavelength tuner 340 is tilted with respect to a plane perpendicular to the optical axis of the illumination optical system 362. The inclination angle θ can be the angle between the optical axis of the illumination optical system 362 and the perpendicular to the incident surface of the wavelength tuner 340. Increasing the inclination angle θ has the effect of reducing the amount of reflected light entering the light source 361, but may affect the wavelength characteristics of the wavelength tuner 340. Therefore, the inclination angle θ should be determined based on the effective radius r of the illumination optical system 362 and the distance d between the illumination optical system 362 and the wavelength tuner 340 in the direction along the optical axis of the illumination optical system 362. If the inclination angle α is the angle at which the incident surface of the wavelength tuner 340 is tilted so that a ray emitted from the light source 361 and traveling along the optical axis of the illumination optical system 362 is reflected by the incident surface of the wavelength tuner 340 and becomes a ray (marginal ray) that passes through the boundary of the effective range of the illumination optical system 362, the inclination angle α is expressed by the following equation (1): tan(2α)=r / d (1)

[0041] For example, if θ>6α, the effect of reducing the light incident on the light source 361 can be sufficiently obtained, but there is a possibility that this will affect the wavelength characteristics of the wavelength tuner 340. Also, if θ<α, the effect of reducing the effect on the wavelength characteristics of the wavelength tuner 340 can be sufficiently obtained, but there is a possibility that the reduction of the light incident on the light source 361 will be suppressed. Therefore, in order to achieve both the reduction of the light incident on the light source 361 and the reduction of the effect on the wavelength characteristics of the wavelength tuner 340, it is desirable to satisfy α≦θ≦6α, and it is even more desirable to satisfy 2α≦θ≦4α.

[0042] Furthermore, the influence on the wavelength characteristics of the wavelength tuner 340 may differ depending on the tilt direction of the incident surface of the wavelength tuner 340. FIG. 4(b) is a diagram showing the luminous flux of light 310 incident on the wavelength tuner 340. As shown in FIG. 1(c), when the incident surface of the wavelength tuner 340 is tilted around the drive axis (X axis) of the wavelength tuner 340 (in the ωX-axis direction), the luminous flux diameter of the light 310 incident on the wavelength tuner 340 increases in the Y-axis direction but remains unchanged in the X-axis direction. Furthermore, the wavelength of the light passing through the wavelength tuner 340 changes in the X-axis direction, which is the drive direction of the wavelength tuner 340. Therefore, when the incident surface of the wavelength tuner 340 is tilted around the drive axis of the wavelength tuner 340, the influence on the wavelength characteristics of the wavelength tuner 340 is suppressed.

[0043] Here, as a modified example, an embodiment in which the incident surface of the wavelength tuner is tilted around an axis perpendicular to the drive axis of the wavelength tuner (in the ωY-axis direction) will be described. FIG. 4(c) is a diagram showing an illumination unit 801 according to the modified example. The illumination unit 801 has a light source 861, an illumination optical system 862, a wavelength tuner 840, and a drive unit 841. The incident surface of the wavelength tuner 840 is perpendicular to the optical axis of the illumination optical system 862, and is tilted by a predetermined tilt angle in the direction of rotation (in the ωY-axis direction) around an axis (in the Y-axis) perpendicular to the drive axis of the wavelength tuner 840. The other configurations are the same as those of the illumination unit 301 in FIG. 1(c).

[0044] FIG. 4(d) is a diagram showing the luminous flux of light 810 incident on the wavelength tuner 840. As shown in FIG. 3(c), when the incident surface of the wavelength tuner 840 is tilted around an axis (Y-axis) perpendicular to the drive axis of the wavelength tuner 840 (ωY-axis direction), the diameter of the luminous flux of light 810 incident on the wavelength tuner 840 remains unchanged in the Y-axis direction but becomes longer in the X-axis direction. Furthermore, the wavelength of light passing through the wavelength tuner 840 changes in the X-axis direction, which is the drive direction of the wavelength tuner 840. Therefore, when the incident surface of the wavelength tuner 840 is tilted around an axis perpendicular to the drive axis of the wavelength tuner 840, the wavelength characteristics of the wavelength tuner 840 change more significantly than in the case of FIG. 4(b). In other words, from the viewpoint of the influence on the wavelength characteristics of the wavelength tuner, it is desirable to tilt the incident surface of the wavelength tuner around the drive axis of the wavelength tuner.

[0045] Furthermore, the wavelength tuner has a shape that is long in the driving direction in order to widen the range of wavelengths of light that is transmitted. If the incident surface of the wavelength tuner 840 is tilted around the Y axis, as in the illumination unit 801, more space is required in the Z axis direction, and depending on the angle of tilt, there is a possibility of interference with the illumination optical system 862. In other words, from the perspective of space saving as well, it is desirable to tilt the incident surface of the wavelength tuner around the driving axis of the wavelength tuner.

[0046] In the present embodiment, the wavelength tuning unit 340 is described as being arranged at a position where the incident light is focused, but the wavelength tuning unit 340 may be arranged at a position away from the position where the incident light is focused. Also, the light incident on the wavelength tuning unit 340 may be parallel light that is incident parallel to the incident surface of the wavelength tuning unit 340.

[0047] In this embodiment, the wavelength tunable element of the wavelength tunable unit 340 has wavelength characteristics that change in a linear direction, but this is not limited to this. For example, the wavelength tunable unit 340 may use a method of rotating a disk-shaped wavelength tunable element whose wavelength characteristics change in the circumferential direction. In this case, the circumferential direction can be considered as the driving direction. Furthermore, the wavelength tunable unit 340 may have wavelength characteristics that change linearly depending on the position at which light is incident, or may have wavelength characteristics that change nonlinearly. Furthermore, the wavelength tunable unit 340 may be composed of multiple wavelength tunable units (wavelength tunable elements).

[0048] As described above, according to the illumination device of this embodiment, the wavelength-tunable section is arranged at an angle with respect to a plane perpendicular to the optical axis of the illumination optical system, thereby preventing the reflected light reflected by the wavelength-tunable section from entering the light source, thereby preventing deterioration in the performance and durability of the light source.

[0049] Second Embodiment Next, an illumination device according to this embodiment will be described. Matters not mentioned here may follow those of the first embodiment. Fig. 5 is a diagram showing an illumination unit 401 according to this embodiment. The illumination unit 401 corresponds to the illumination unit 301 according to the first embodiment, and differs from the illumination unit 301 in that it is configured with two wavelength tunable units, 440a and 440b.

[0050] FIG. 5(a) shows the configuration of the illumination unit 401 according to this embodiment. Light emitted from a light source 461 is guided to a wavelength tuning unit 440a via an illumination optical system 462a (optical system). Light transmitted through the wavelength tuning unit 440a is guided to a wavelength tuning unit 440b (second wavelength tuning unit) via an illumination optical system 462b (second optical system). The wavelength tuning units 440a and 440b are driven (moved) by drivers 441a and 441b, respectively, in a direction perpendicular to the optical axis direction of the illumination optical systems 462a and 462b (the X-axis direction in the example of FIG. 5(a)). Here, the driving directions of the drivers 441a and 441b are the same (the X-axis direction), but this is not limiting. For example, the driving direction of the driver 441a may be the X-axis direction, and the driving direction of the driver 441b may be the Y-axis direction. That is, the driving directions of the driving units 441a and 441b may be different directions perpendicular to the optical axis directions of the illumination optical systems 462a and 462b.

[0051] By using a long wavelength pass filter as the wavelength tuner 440a and a short wavelength pass filter as the wavelength tuner 440b, the illumination unit 401 can emit light having an arbitrary center wavelength and an arbitrary wavelength width. Furthermore, by using a long wavelength pass filter as the wavelength tuner 440a that transmits light with wavelengths longer than a predetermined wavelength, it is possible to reduce short wavelength light incident on the illumination optical system 462b and the wavelength tuner 440b. In particular, by using a long wavelength pass filter as the wavelength tuner 440a that transmits light with wavelengths longer than light with wavelengths in the 10 to 380 nm range, it is possible to reduce ultraviolet light. This makes it possible to suppress deterioration in the performance and durability of the illumination optical system 462b and the wavelength tuner 440b.

[0052] The wavelength tuning units 440a and 440b are disposed at the light-condensing positions of the illumination optical systems 462a and 462b, respectively. The wavelength tuning units 440a and 440b are disposed so that the incident surfaces of the wavelength tuning units 440a and 440b are inclined in the same direction with respect to a plane perpendicular to the optical axis of the illumination optical systems 462a and 462b. In the example of Fig. 5, the wavelength tuning units 440a and 440b are disposed so that the incident surfaces of the wavelength tuning units 440a and 440b are inclined by a predetermined angle in the rotation direction (ωX-axis direction) about the X-axis perpendicular to the optical axis. That is, the wavelength tuning units 540a and 540b are disposed so that they are inclined by a predetermined angle about the drive axes of the drive units 441a and 441b.

[0053] Here, θ1 is defined as the inclination angle at which the incident surface of the wavelength tuner 440a is inclined with respect to a plane perpendicular to the optical axis of the illumination optical system 462a. θ2 is defined as the inclination angle at which the incident surface (second incident surface) of the wavelength tuner 440b is inclined with respect to a plane (second plane) perpendicular to the optical axis (second optical axis) of the illumination optical system 462b. The inclination angle θ1 can be defined as the angle between the optical axis of the illumination optical system 462a and a line perpendicular to the incident surface of the wavelength tuner 440a. The inclination angle θ2 can be defined as the angle between the optical axis of the illumination optical system 462b and a line perpendicular to the incident surface of the wavelength tuner 440b.

[0054] Increasing the tilt angles θ1 and θ2 has the effect of reducing the amount of reflected light entering the light source 461, but may affect the wavelength characteristics of the wavelength tunable units 440a and 440b. Therefore, the tilt angle θ1 should be determined based on the effective radius r1 of the illumination optical system 462a and the distance d1 between the illumination optical system 462a and the wavelength tunable unit 440a in the direction along the optical axis of the illumination optical system 462a. Furthermore, the tilt angle θ2 should be determined based on the effective radius r2 of the illumination optical system 462b and the distance d2 (second distance) between the illumination optical system 462b and the wavelength tunable unit 440b in the direction along the optical axis (second optical axis) of the illumination optical system 462b.

[0055] If the inclination angle when the incident surface of the wavelength tunable unit 440a is tilted so that the light irradiated from the light source 461 and traveling along the optical axis of the illumination optical system 462a is reflected by the incident surface of the wavelength tunable unit 440a and becomes a light ray that passes through the boundary of the effective range of the illumination optical system 462a is α1, the inclination angle α1 is expressed by the following equation (2). tan(2α1)=r1 / d1 (2)

[0056] For example, if θ1>6α1, the effect of reducing the light incident on the light source 461 can be sufficiently obtained, but there is a possibility that the wavelength characteristics of the wavelength tuner 440a will be affected. Also, if θ1<α1, the effect of reducing the effect on the wavelength characteristics of the wavelength tuner 440a can be sufficiently obtained, but there is a possibility that the reduction of the light incident on the light source 461 will be suppressed. Therefore, in order to achieve both the reduction of the light incident on the light source 461 and the reduction of the effect on the wavelength characteristics of the wavelength tuner 440a, it is desirable to satisfy α1≦θ1≦6α1, and it is even more desirable to satisfy 2α1≦θ1≦4α1.

[0057] Similarly, if the incident surface of the wavelength variable section 440b is tilted so that a ray of light irradiated from the light source 461 via the wavelength variable section 440a and traveling along the optical axis of the illumination optical system 462b is reflected by the incident surface of the wavelength variable section 440b and passes through the boundary of the effective range of the illumination optical system 462b, the tilt angle α2 is expressed by the following equation (3). tan(2α2)=r2 / d2 (3)

[0058] For example, if θ2>6α2, the effect of reducing the light incident on the light source 461 and the wavelength tuner 440a can be sufficiently obtained, but there is a possibility that the wavelength characteristics of the wavelength tuner 440b will be affected. Also, if θ2<α2, the effect of reducing the effect on the wavelength characteristics of the wavelength tuner 440b can be sufficiently obtained, but there is a possibility that the reduction of the light incident on the light source 461 and the wavelength tuner 440a will be suppressed. Therefore, in order to achieve both the reduction of the light incident on the light source 461 and the wavelength tuner 440a and the reduction of the effect on the wavelength characteristics of the wavelength tuner 440b, it is desirable to satisfy α2≦θ2≦6α2, and it is even more desirable to satisfy 2α2≦θ2≦4α2.

[0059] Furthermore, the wavelength tuning units 440a and 440b are arranged so that their wavelength characteristics are the same in the X-axis direction. That is, in Fig. 5(a), the wavelength tuning units 440a and 440b are arranged so that the wavelength characteristics of the wavelength tuning units 440a and 440b are such that the +X-axis direction is the long wavelength side and the -X-axis direction is the short wavelength side.

[0060] 5(b), of the light emitted from the light source 461, the light beams emitted at different angles and guided to the wavelength tuning unit 440a by the illumination optical system 462a are designated as light 421a, 422a, and 423a, respectively, and the light beams 421a, 422a, and 423a that pass through the wavelength tuning unit 440a and are guided to the wavelength tuning unit 440b via the illumination optical system 462b are designated as light 421b, 422b, and 423b, respectively. Furthermore, as shown in FIG. 5(c), of the light beam 410a guided to the wavelength tuning unit 440a, the light beam guided to a position on the short wavelength side of the wavelength tuning unit 440a is designated as light 411a, the light beam guided to a position on the long wavelength side is designated as light 413a, and the light beam guided to a position having wavelength characteristics intermediate between them is designated as light 412a. Furthermore, of the light 410b guided to the wavelength variable section 440b, the light guided to a position on the long wavelength side of the wavelength variable section 440b is light 411b, the light guided to a position on the short wavelength side is light 413b, and the light guided to a position having wavelength characteristics intermediate between them is light 412b.

[0061] Here, a modification of this embodiment will be described. Fig. 6 is a diagram showing an illumination unit 701 according to a first modification of this embodiment. As shown in Fig. 6, wavelength tunable units 740a and 740b are arranged to be tilted in opposite directions in the ωX-axis direction. Furthermore, compared to the illumination unit 401 shown in Fig. 5, the wavelength tunable unit 740a and the wavelength tunable unit 440a are arranged to be tilted in the same direction in the ωX-axis direction. Furthermore, compared to the illumination unit 401, the wavelength tunable unit 740b is arranged to be tilted in the opposite direction in the ωX-axis direction to the wavelength tunable unit 440b.

[0062] FIG. 7 is a diagram illustrating an illumination unit 601 according to a second modified example of this embodiment. As shown in FIG. 7, the wavelength tuner 740a and the wavelength tuner 740b are arranged so that the wavelength characteristics of the wavelength tuner 740a and the wavelength tuner 740b are reversed in the X-axis direction. That is, the wavelength tuner 740a is arranged so that the wavelength characteristics are longer in the +X-axis direction and shorter in the −X-axis direction. On the other hand, the wavelength tuner 740b is arranged so that the wavelength characteristics are shorter in the +X-axis direction and longer in the −X-axis direction. Compared to the illumination unit 401 shown in FIG. 5, the wavelength tuner 640a and the wavelength tuner 440a are arranged so that their wavelength characteristics are the same in the X-axis direction. Compared to the illumination unit 401, the wavelength tuner 640b and the wavelength tuner 440b are arranged so that their wavelength characteristics are reversed in the X-axis direction.

[0063] Next, the difference between using the illumination unit 401 and using the illumination unit 701 will be described with reference to FIGS. 8 and 9. FIG. 8 is a diagram showing wavelength characteristics related to the illumination unit 401. FIG. 8(a) shows the wavelength characteristics of light transmitted through the wavelength tunable unit 440a, and FIG. 8(b) shows the wavelength characteristics of light transmitted through the wavelength tunable unit 440b. FIG. 8(c) shows the wavelength characteristics of light transmitted through the wavelength tunable units 440a and 440b. In FIG. 8(a), wavelength characteristics 481a, 482a, and 483a are the wavelength characteristics of the light 421a, 422a, and 423a in FIG. 5(b), respectively, when transmitted through the wavelength tunable unit 440a. In FIG. 8(b), wavelength characteristics 481b, 482b, and 483b are the wavelength characteristics of the light 421b, 422b, and 423b in FIG. 5(b), respectively, when transmitted through the wavelength tunable unit 440b.

[0064] Generally, the larger the angle of incidence of light on the wavelength tunable element, the shorter the wavelength characteristic graph shifts. In FIG. 5(b), light 423a enters wavelength tunable unit 440a at a larger angle than light 421a, so in FIG. 8(a), the graph of wavelength characteristic 483a shifts to the shorter wavelength side than the graph of wavelength characteristic 481a. For the same reason, in FIG. 8(b), the graph of wavelength characteristic 481b shifts to the shorter wavelength side than the graph of wavelength characteristic 483b. In FIG. 8(c), wavelength characteristics 481, 482, and 483 are the product of wavelength characteristics 481a and 481b, the product of wavelength characteristics 482a and 482b, and the product of wavelength characteristics 483a and 483b, respectively. The wavelength characteristic of the light illuminated by illumination unit 401 is the sum of wavelength characteristics 481, 482, and 483, resulting in wavelength characteristic 480 shown in FIG. 8(d).

[0065] FIG. 9 is a diagram showing wavelength characteristics related to the illumination unit 701. FIG. 9(a) shows the wavelength characteristics of light transmitted through the wavelength tunable unit 740a, and FIG. 9(b) shows the wavelength characteristics of light transmitted through the wavelength tunable unit 740b. FIG. 9(c) shows the wavelength characteristics of light transmitted through the wavelength tunable units 740a and 740b. In FIG. 9(a), wavelength characteristics 781a, 782a, and 783a are the wavelength characteristics of the light 721a, 722a, and 723a in FIG. 6(b), respectively, when transmitted through the wavelength tunable unit 740a. In FIG. 9(b), wavelength characteristics 781b, 782b, and 783b are the wavelength characteristics of the light 721b, 722b, and 723b in FIG. 6(b), respectively, when transmitted through the wavelength tunable unit 740b.

[0066] Because the wavelength tuner 740b is tilted in the opposite direction to the wavelength tuner 440b, the graph of wavelength characteristic 783b in the illumination unit 701 is shifted to the shorter wavelength side in FIG. 9(b). Therefore, wavelength characteristics 781, 782, and 783 in FIG. 9(c) are different from wavelength characteristics 481, 482, and 483 in FIG. 8(c). The wavelength characteristics 781, 782, and 783 have a constant wavelength width and a changing center wavelength, whereas the wavelength characteristics 481, 482, and 483 have a constant center wavelength and a changing wavelength width. Therefore, the wavelength characteristics 781, 782, and 783 have less light intensity near the center compared to the wavelength characteristics 481, 482, and 483. As a result, the wavelength characteristics of the light illuminated by the illumination unit 701 are as shown in wavelength characteristic 780 in FIG. 9(d). From this, it can be seen that the wavelength characteristic 480 shown in Fig. 8(d) is steeper than the wavelength characteristic 780 shown in Fig. 9(d). Therefore, the light emitted by the illumination unit 401 is more advantageous than the light emitted by the illumination unit 701 in terms of the wavelength characteristics of the light.

[0067] Furthermore, by arranging the wavelength tunable units 440a and 440b at an angle, the optical path length of light passing through the wavelength tunable units 440a and 440b varies depending on the thickness and tilt angle of the wavelength tunable units 440a and 440b. In the illumination unit 401, the wavelength tunable units 440a and 440b are arranged at an angle such that the optical path length difference between the light 421b and the light 423b, which is caused by the wavelength tunable units 440a and 440b being arranged at an angle, becomes smaller. On the other hand, in the illumination unit 701, the wavelength tunable units 740a and 740b are arranged at an angle such that the optical path length difference between the light 721b and the light 723b, which is caused by the wavelength tunable units 740a and 740b being arranged at an angle, becomes larger. This shows that the illumination unit 401 can reduce the optical path length difference between the light 421b and the light 423b compared to the optical path length difference between the light 721b and the light 723b. Therefore, the light illuminated by the illumination unit 401 is more advantageous in terms of light quality than the light illuminated by the illumination unit 701. However, it is desirable that the wavelength tunable units 440a and 440b be arranged so that the optical path length difference between the light 421b and the light 423b is the same, but this is not limited to this. The wavelength tunable units 440a and 440b may be arranged to be tilted at different tilt angles, or the wavelength tunable units 440a and 440b may be arranged to be tilted in different directions in the ωX-axis direction.

[0068] Next, the difference between using the illumination unit 401 and using the illumination unit 601 will be described with reference to FIGS. 10 and 11. FIG. 10 is a diagram showing wavelength characteristics related to the illumination unit 401. FIG. 10(a) shows the wavelength characteristics of light transmitted through the wavelength tunable unit 440a, and FIG. 10(b) shows the wavelength characteristics of light transmitted through the wavelength tunable unit 440b. FIG. 10(c) shows the wavelength characteristics of light transmitted through the wavelength tunable units 440a and 440b. In FIG. 10(a), wavelength characteristics 491a, 492a, and 493a are the wavelength characteristics when the light 411a, 412a, and 413a in FIG. 5(c) are transmitted through the wavelength tunable unit 440a, respectively. 10(b), wavelength characteristics 491b, 492b, and 493b are the wavelength characteristics when light 411b, 412b, and 413b in FIG. 5(c) are transmitted through wavelength tunable unit 440b, respectively. In FIG. 10(c), wavelength characteristics 491, 492, and 493 are the product of wavelength characteristics 491a and 491b, the product of wavelength characteristics 492a and 492b, and the product of wavelength characteristics 493a and 493b, respectively. The wavelength characteristics of the light illuminated by illumination unit 401 are the sum of wavelength characteristics 491, 492, and 493, and therefore become wavelength characteristic 490 shown in FIG. 10(d).

[0069] FIG. 11 is a diagram showing wavelength characteristics related to the illumination unit 610. FIG. 11(a) shows the wavelength characteristics of light transmitted through the wavelength tunable unit 640a, and FIG. 11(b) shows the wavelength characteristics of light transmitted through the wavelength tunable unit 640b. FIG. 11(c) shows the wavelength characteristics of light transmitted through the wavelength tunable units 640a and 640b. In FIG. 11(a), wavelength characteristics 681a, 682a, and 683a are the wavelength characteristics of the light 621a, 622a, and 623a in FIG. 7(b), respectively, when transmitted through the wavelength tunable unit 640a. In FIG. 11(b), wavelength characteristics 681b, 682b, and 683b are the wavelength characteristics of the light 621b, 622b, and 623b in FIG. 7(b), respectively, when transmitted through the wavelength tunable unit 640b.

[0070] The wavelength tuning unit 640b is arranged so that its wavelength characteristics are reversed in the X-axis direction compared to the wavelength tuning unit 440b. Therefore, in FIG. 11(b), wavelength characteristics 693b have long-wavelength characteristics, and wavelength characteristics 691b have short-wavelength characteristics. Therefore, wavelength characteristics 691, 692, and 693 in FIG. 11(c) are different from wavelength characteristics 491, 492, and 493 in FIG. 10(c). Wavelength characteristics 691, 692, and 693 have a constant wavelength width and varying center wavelengths, whereas wavelength characteristics 491, 492, and 493 have a constant center wavelength and varying wavelength widths. Therefore, wavelength characteristics 691, 692, and 693 have less light intensity near the center compared to wavelength characteristics 491, 492, and 493. As a result, the wavelength characteristics of the light emitted by the illumination unit 601 are as shown in wavelength characteristic 690 in FIG. 11(d). From this, it can be seen that the wavelength characteristic 490 shown in Fig. 10(d) is steeper than the wavelength characteristic 690 shown in Fig. 11(d). Therefore, the light emitted by the illumination unit 401 is more advantageous in terms of wavelength characteristics than the light emitted by the illumination unit 601.

[0071] 5(c) illustrates an embodiment in which the wavelength tuning unit 440b is arranged so that the light 411b is guided to a position on the long wavelength side of the wavelength tuning unit 440b and the light 413b is guided to a position on the short wavelength side of the wavelength tuning unit 440b, but this is not limiting. For example, the wavelength tuning unit 440b may be arranged so that the light 411b is guided to a position on the short wavelength side of the wavelength tuning unit 440b and the light 413b is guided to a position on the long wavelength side. Furthermore, the illumination optical system 462b may include an optical rod or a fiber, and the lights 411b, 412b, and 413b may be guided to the wavelength tuning unit 440b in a mixed state.

[0072] In addition, although a configuration in which a long wavelength pass filter is used as the wavelength tuner 440a and a short wavelength pass filter is used as the wavelength tuner 440b has been described, the present invention is not limited to this. A short wavelength pass filter may be used as the wavelength tuner 440a and a long wavelength pass filter may be used as the wavelength tuner 440b. A band pass filter may be used for at least one of the wavelength tuner 440a and 440b. Each of the wavelength tuner 440a and 440b may be composed of multiple wavelength tuner sections (wavelength tunable elements).

[0073] As described above, according to the illumination device of this embodiment, the wavelength tunable unit is disposed at an angle with respect to a plane perpendicular to the optical axis of the illumination optical system, and therefore, the reflected light reflected by the wavelength tunable unit is prevented from entering the light source, thereby suppressing deterioration in the performance and durability of the light source. Furthermore, by configuring multiple wavelength tunable units, it is possible to suppress deterioration in the performance and durability of not only the light source but also the illumination optical system and the wavelength tunable unit.

[0074] <Third embodiment> Next, an illumination device according to this embodiment will be described. Matters not mentioned here may follow those of the first and second embodiments. The illumination unit 501 according to this embodiment corresponds to the illumination unit 301 according to the first embodiment and the illumination unit 401 according to the second embodiment. The illumination unit 501 differs from the illumination unit 301 in that it includes two wavelength tuning units, 540a and 540b. The illumination unit 501 also differs from the illumination unit 401 in that an illumination optical system 562, located between the light source 561 and the wavelength tuning unit 540a, has the property of focusing illuminating light at two different positions. The illumination unit 501 also differs from the illumination unit 401 in that no illumination optical system is located between the wavelength tuning unit 540a and the wavelength tuning unit 540b.

[0075] 12 is a diagram showing an illumination unit 501 according to this embodiment. The illumination unit 501 includes a light source 561, an illumination optical system 562, wavelength tuners 540a and 540b, and drivers 541a and 541b.

[0076] Light emitted from the light source 561 is guided to a wavelength tuning unit 540a (first wavelength tuning unit) via an illumination optical system 562 (optical system). Light emitted from the wavelength tuning unit 540a is guided to a wavelength tuning unit 540b (second wavelength tuning unit). The illumination optical system 562 is configured, for example, with a cylindrical optical system including a cylindrical lens, and has the property of focusing the emitted light at two different positions. As shown in FIG. 12 , the light emitted by the illumination optical system 562 is focused on the XZ plane at the first focusing position, and focused on the YZ plane at the second focusing position. That is, the light emitted by the illumination optical system 562 is focused along the Y-axis direction at the first focusing position, and focused along the X-axis direction at the second focusing position.

[0077] The wavelength tuning section 540a is disposed at the first light collecting position, and the wavelength tuning section 540b is disposed at the second light collecting position.

[0078] The driver 541a (first moving unit) and the driver 541b (second moving unit) respectively drive the wavelength tuning unit 540a and the wavelength tuning unit 540b in two mutually different directions perpendicular to the optical axis direction of the illumination optical system 562. The driver 541a drives the wavelength tuning unit 540a in the X-axis direction (direction of the first axis), and the driver 541b drives the wavelength tuning unit 540b in the Y-axis direction (direction of the second axis). In other words, the wavelength tuning unit 540a and the wavelength tuning unit 540b are driven in directions in which light is focused at the first focusing position and the second focusing position, respectively. In other words, the driver 541a drives the wavelength tuning unit 540a in a direction in which the beam diameter of light from the illumination optical system 562 is shortest on the incident surface of the wavelength tuning unit 540a. Furthermore, the driver 541b drives the wavelength tuner 540b in a direction in which the diameter of the beam of light from the wavelength tuner 540a becomes the shortest on the incident surface of the wavelength tuner 540b. This makes it possible to reduce the width of the beam irradiating the wavelength tuner 540a and the wavelength tuner 540b in the direction in which the wavelengths of the wavelength tuner 540a and the wavelength tuner 540b change, which is advantageous from the viewpoint of wavelength characteristics.

[0079] The wavelength tuning units 540a and 540b are arranged so that the incident surfaces of the wavelength tuning units 540a and 540b, respectively, are inclined with respect to a plane perpendicular to the optical axis of the illumination optical system 562. In addition, in the example of Fig. 12, the wavelength tuning unit 540a is arranged so that the incident surface (first incident surface) of the wavelength tuning unit 540a is inclined by a predetermined inclination angle in the rotation direction about the X axis (ωX axis direction) perpendicular to the optical axis, and the wavelength tuning unit 540b is arranged so that the incident surface (second incident surface) of the wavelength tuning unit 540b is inclined by a predetermined inclination angle in the rotation direction about the Y axis (ωY axis direction) perpendicular to the optical axis. In other words, the wavelength tuning units 540a and 540b are arranged so that they are inclined by a predetermined inclination angle about the drive axes of the drive units 541a and 541b, respectively.

[0080] Here, the inclination angles of the incident surfaces of the wavelength tunable units 540a and 540b are defined as θ3 and θ4, respectively. The inclination angles θ3 and θ4 can be defined as the angles between the optical axis of the illumination optical system 562 and the perpendicular to the incident surfaces of the wavelength tunable units 540a and 540b. Increasing the inclination angles θ3 and θ4 has the effect of reducing the incidence of reflected light on the light source 561, but may affect the wavelength characteristics of the wavelength tunable units 540a and 540b. Therefore, the inclination angle θ3 should be determined based on the effective radius r3 of the illumination optical system 562 and the distance d3 between the illumination optical system 562 and the wavelength tunable unit 540a in the direction along the optical axis of the illumination optical system 562. The inclination angle θ4 should be determined based on the effective radius r3 of the illumination optical system 562 and the distance d4 between the illumination optical system 562 and the wavelength tunable unit 540b in the direction along the optical axis of the illumination optical system 562.

[0081] When the incident surface of the wavelength variable section 540a is tilted so that the light irradiated from the light source 561 and traveling along the optical axis of the illumination optical system 562 is reflected by the incident surface of the wavelength variable section 540a and becomes a light ray that passes through the boundary of the effective range of the illumination optical system 562, the tilt angle α3 is expressed by the following equation (4). tan(2α3)=r3 / d3 (4)

[0082] For example, if θ3>6α3, the effect of reducing the light incident on the light source 561 can be sufficiently obtained, but there is a possibility that the wavelength characteristics of the wavelength tuner 540a will be affected. Also, if θ3<α3, the effect of reducing the effect on the wavelength characteristics of the wavelength tuner 540a can be sufficiently obtained, but there is a possibility that the reduction of the light incident on the light source 561 will be suppressed. Therefore, in order to achieve both the reduction of the light incident on the light source 561 and the reduction of the effect on the wavelength characteristics of the wavelength tuner 540a, it is desirable to satisfy α3≦θ3≦6α3, and it is more desirable to satisfy 2α3≦θ3≦4α3.

[0083] Similarly, if the incident surface of the wavelength variable section 540b is tilted so that a ray of light irradiated from the light source 561 through the wavelength variable section 540a and traveling along the optical axis of the illumination optical system 562 is reflected by the incident surface of the wavelength variable section 540b and becomes a ray of light passing through the boundary of the effective range of the illumination optical system 562, the inclination angle α4 is expressed by the following equation (5). tan(2α4)=r3 / d4 (5)

[0084] For example, if θ4>6α4, the effect of reducing the light incident on the light source 561 and the wavelength tuner 540a can be sufficiently obtained, but there is a possibility that the wavelength characteristics of the wavelength tuner 540b will be affected. Also, if θ4<α4, the effect of reducing the effect on the wavelength characteristics of the wavelength tuner 540b can be sufficiently obtained, but there is a possibility that the reduction of the light incident on the light source 561 and the wavelength tuner 540a will be suppressed. Therefore, in order to achieve both the reduction of the light incident on the light source 561 and the wavelength tuner 540a and the reduction of the effect on the wavelength characteristics of the wavelength tuner 540b, it is desirable to satisfy α4≦θ4≦6α4, and it is even more desirable to satisfy 2α4≦θ4≦3α4.

[0085] In the present embodiment, the illumination optical system 562 is described as being configured as a cylindrical optical system including a cylindrical lens, but is not limited to this. The illumination optical system 562 may be configured as another optical system as long as it has the property of focusing the irradiated light at two different positions.

[0086] In addition, in this embodiment, the wavelength tuning unit 540a is arranged at the first focusing position where light is focused on the XZ plane of the illumination optical system 562, and the wavelength tuning unit 540b is arranged at the second focusing position where light is focused on the YZ plane of the illumination optical system 562, but this is not limiting. The wavelength tuning units 540a and 540b may be arranged at positions away from the first focusing position and the second focusing position, respectively.

[0087] As described above, according to the illumination device of this embodiment, the wavelength tunable unit is disposed at an angle with respect to a plane perpendicular to the optical axis of the illumination optical system, thereby preventing light reflected by the wavelength tunable unit from entering the light source, thereby preventing deterioration in the performance and durability of the light source. Furthermore, by configuring multiple wavelength tunable units, deterioration in the performance and durability of not only the light source but also the illumination optical system and wavelength tunable unit can be prevented. Furthermore, since there is no need to dispose an illumination optical system between the multiple wavelength tunable units, this is advantageous from the perspective of saving space.

[0088] <Fourth embodiment> In this embodiment, a form will be described in which an exposure apparatus serving as a substrate processing apparatus has a measurement apparatus (measurement unit). Matters not mentioned here may follow the first to third embodiments. The exposure apparatus according to this embodiment will be described with reference to FIG. 13. The exposure apparatus EXA is a lithography apparatus used in a lithography process, which is a manufacturing process for devices such as semiconductor elements and liquid crystal display elements, and forms a pattern on a substrate 73. The exposure apparatus EXA exposes the substrate 73 (wafer) via a reticle (original, mask) 31, and performs an exposure process (processing on the substrate) in which the pattern of the reticle 31 is transferred onto the substrate 73.

[0089] Here, the reticle 31 is a reticle, original, or mask on which a predetermined pattern such as a circuit pattern is formed, and is made of, for example, quartz. The reticle 31 transmits light illuminated by an illumination optical system 91 (described below). The substrate 73 is a workpiece onto which the pattern of the reticle 31 is transferred, and is, for example, a silicon wafer, a glass plate, a film-like substrate, or other workpiece substrate. The pattern is transferred to the substrate 73 by exposing it to light while it is coated with photoresist.

[0090] Also, here, the explanation will be given taking as an example a case where the exposure apparatus EXA is a scanning exposure apparatus (scanner) that exposes a pattern formed on the reticle 31 onto the substrate 73 while moving the reticle 31 and the substrate 73 synchronously in the scanning direction. Note that this embodiment can also be applied to an exposure apparatus (stepper) of the type that exposes the reticle pattern onto the substrate 73 while fixing the reticle 31.

[0091] The exposure apparatus EXA has a light source unit 90 , an illumination optical system 91 , a reticle stage RS, a projection optical system 32 , a substrate stage WS, a measurement unit 50 , and a control unit 1100 .

[0092] The light source unit 90 includes at least one light source selected from the group consisting of a mercury lamp, a KrF excimer laser, and an ArF excimer laser, and may also include a light source of extreme ultraviolet light (EUV light) with a wavelength of several nm to several hundred nm.

[0093] The illumination optical system 91 shapes the light emitted from the light source unit 90 into a slit beam having a predetermined shape optimal for exposure, and irradiates the reticle 31 held by the reticle stage RS with this beam, illuminating a predetermined illumination area on the reticle 31. The illumination optical system 91 illuminates the predetermined illumination area on the reticle 31 with light having a uniform illuminance distribution. The illumination optical system 91 includes, for example, lenses, mirrors, an optical integrator, an aperture stop, etc., and is configured by arranging a condenser lens, a fly's-eye lens, an aperture stop, a condenser lens, a slit, and an imaging optical system in this order.

[0094] The reticle stage RS moves while holding the reticle 31. The reticle stage RS is movable, for example, within a plane perpendicular to the optical axis of the projection optical system 32, i.e., within the XY plane, and is rotatable in the θZ direction. The reticle stage RS is driven by a driving device (not shown) such as a linear motor, which is capable of driving in three axial directions, X, Y, and θZ, and is controlled by a control unit 1100, which will be described later. Note that although the driving device is capable of driving in three axial directions, it may also be capable of driving in any one of one to six axial directions.

[0095] The projection optical system 32 irradiates the substrate 73 held by the substrate stage WS with light that has passed through the reticle 31, and projects an image of the pattern formed on the reticle 31 onto the substrate 73 at a predetermined projection magnification β. In this way, the substrate 73 is exposed to the light irradiated from the projection optical system 32, and a pattern is formed on the substrate 73. The projection optical system 32 is composed of multiple optical elements, and the predetermined projection magnification β is, for example, 1 / 4 or 1 / 5.

[0096] Regarding the substrate stage WS, a description of the components common to the first embodiment will be omitted. A reference plate 39 equipped with a reference mark is installed on the substrate stage WS. The height of the surface of the reference plate 39 is determined to be the same height as the surface of the substrate 73 held by the substrate stage WS, and the measurement unit 50 also measures the position of the reference mark on the reference plate 39.

[0097] A control unit 1100 comprehensively controls each unit of the exposure apparatus EXA, including the measurement apparatus 100. The configuration of the control unit 1100 is the same as that of the first embodiment, and therefore a description thereof will be omitted.

[0098] The measurement unit 50 is the same as in the first embodiment, and therefore description thereof will be omitted. Furthermore, in this embodiment, a form in which a measurement device having the illumination unit of the first embodiment is used will be described, but a measurement device having the illumination unit described in either the second or third embodiment may also be used.

[0099] Next, the exposure process according to this embodiment will be described with reference to Fig. 14. The exposure process shown in Fig. 14 is performed by a control unit 1100 that comprehensively controls each unit of the exposure apparatus EXA.

[0100] In S101, the control unit 1100 causes the exposure apparatus EXA to load the substrate 73. In S102, the control unit 1100 causes a shape measurement device (not shown) to detect the surface (height) of the substrate 73 and measure the surface shape of the entire area of ​​the substrate 73.

[0101] In S103, the control unit 1100 performs calibration. Specifically, based on the position of a reference mark provided on the reference plate 39, the control unit 1100 drives the substrate stage WS so that the reference mark is positioned on the optical axis of the measurement unit 50. Next, the control unit 1100 measures the positional deviation of the reference mark relative to the optical axis of the measurement unit 50, and based on this positional deviation, resets the coordinate system of the substrate stage WS so that the origin of the coordinate system of the substrate stage WS coincides with the optical axis of the measurement unit 50. Next, based on the positional relationship between the optical axis of the measurement unit 50 and the optical axis of the projection optical system 32, the control unit 1100 drives the substrate stage WS so that the reference mark is positioned on the optical axis of the exposure light. Then, the control unit 1100 controls a TTL (through-the-lens) measurement system (not shown) to measure the positional deviation of the reference mark relative to the optical axis of the exposure light via the projection optical system 32. In S104, the control unit 1100 determines the baseline between the optical axis of the measurement unit 50 and the optical axis of the projection optical system 32 based on the result of the calibration in S103.

[0102] Here, in S103, a pattern measurement process is performed to measure the positional deviation of the reference mark. The control unit 1100 measures the pattern included in the reference mark using the measurement unit 50. The pattern measurement process may be performed, for example, every predetermined number of measurements or every predetermined number of substrates 73 to be subjected to the exposure process.

[0103] In S105, the control unit 1100 causes the measurement unit 50 to measure the position of the pattern 72 provided on the substrate 73. In S106, the control unit 1100 performs global alignment. Specifically, based on the measurement results in S105, the control unit 1100 calculates the shift, magnification, and rotation for the arrangement of the shot areas on the substrate 73, and determines the regularity of the arrangement of the shot areas. Then, correction coefficients are calculated from the regularity of the arrangement of the shot areas and the baseline, and the substrate 73 is aligned with the reticle 31 (exposure light) based on these correction coefficients.

[0104] Here, in S105, a pattern measurement process is performed to measure the position of the pattern 72. The control unit 1100 measures the pattern 72 using the measurement unit 50. The pattern measurement process may be performed, for example, every predetermined number of measurements or every predetermined number of substrates 73 to be subjected to the exposure process.

[0105] In S107, the control unit 1100 exposes the substrate 73 while controlling the reticle stage RS and the substrate stage WS to scan the reticle 31 and the substrate 73 in the scanning direction (Y direction). At this time, based on the surface shape of the substrate 73 measured by the shape measurement device, the control unit 1100 drives the substrate stage WS in the Z direction and tilt direction to sequentially align the surface of the substrate 73 with the imaging plane of the projection optical system 32.

[0106] In S108, the control unit 1100 determines whether exposure of all of the shot areas to be exposed on the substrate 73 has been completed (i.e., whether there are any unexposed shot areas among the shot areas to be exposed). If it is determined that exposure of all of the shot areas to be exposed has not been completed, the control unit 1100 shifts the process to S107. That is, S107 and S108 are repeated until exposure of all of the shot areas to be exposed is completed. On the other hand, if it is determined that exposure of all of the shot areas to be exposed has been completed, the control unit 1100 shifts the process to S109. In S109, the control unit 1100 unloads the substrate 73 from the exposure apparatus EXA.

[0107] <Production method of the article> A method for manufacturing an article, such as a device (semiconductor device, magnetic storage medium, liquid crystal display element, etc.), a color filter, or a hard disk, will be described. This manufacturing method includes a step of forming a pattern on a substrate (wafer, glass plate, film-like substrate, etc.) using a lithography apparatus (e.g., exposure apparatus, imprint apparatus, drawing apparatus, etc.). This manufacturing method further includes a step of processing the substrate on which the pattern has been formed. This processing step may include a step of removing a residual film of the pattern. It may also include other well-known steps, such as a step of etching the substrate using the pattern as a mask. The method for manufacturing an article in this embodiment is advantageous over conventional methods in at least one of the performance, quality, productivity, and production cost of the article.

[0108] Although the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention.

[0109] Furthermore, although an exposure apparatus has been described as an example of a substrate processing apparatus, the present invention is not limited to this. Another example of a substrate processing apparatus may be an imprint apparatus that forms a pattern of an imprint material on a substrate using a mold (template) having a concave-convex pattern. Another example of a substrate processing apparatus may be a planarization apparatus that uses a mold (flat template) having a flat portion without a concave-convex pattern to form a composition on a substrate so as to flatten it. Another example of a substrate processing apparatus may be an apparatus such as a drawing apparatus that draws on a substrate with a charged particle beam (such as an electron beam or an ion beam) via a charged particle optical system to form a pattern on the substrate.

[0110] Furthermore, the first to fourth embodiments can be implemented not only independently but also in any combination of the first to fourth embodiments.

Claims

1. An illumination device that illuminates by changing the spectrum of light from a light source, an optical system for guiding light from the light source; a wavelength tunable unit that changes the spectrum of light from the optical system by moving in a linear direction along a first axis perpendicular to an optical axis of the optical system; a second optical system that guides light from the wavelength variable unit; a second wavelength variable unit that changes the spectrum of light from the second optical system by moving in a second linear direction along a second axis perpendicular to a second optical axis of the second optical system, the wavelength tunable unit is disposed such that an incident surface of the wavelength tunable unit onto which the light irradiated by the optical system is incident is inclined in a rotation direction around the first axis, the second wavelength-tunable unit is disposed such that a second incident surface of the second wavelength-tunable unit onto which the light irradiated by the second optical system is incident is inclined in a rotation direction around the second axis. A lighting device characterized by:

2. the wavelength tunable unit is disposed so that the incident surface is inclined at an inclination angle θ with respect to a plane perpendicular to the optical axis, When the incident surface is tilted so that a ray of light traveling along the optical axis is reflected by the incident surface and passes through the boundary of the effective range of the optical system, the tilt angle with respect to the plane is defined as α, the effective radius of the optical system is defined as r, and the distance between the optical system and the wavelength tunable unit in the direction along the optical axis is defined as d, tan(2α)=r / d, and α≦θ≦6α fulfill, 2. The lighting device according to claim 1.

3. a moving unit that moves the wavelength tunable unit in the linear direction along the first axis, 3. The lighting device according to claim 1 or 2.

4. The moving unit moves the wavelength variable unit in a direction in which the diameter of the beam of light from the optical system becomes shortest on the incident surface.

4. The lighting device according to claim 3.

5. the wavelength tunable unit is disposed at a position where the light from the optical system is condensed.

5. The lighting device according to claim 1, wherein the light source is a light source.

6. The second incident surface is inclined at an angle θ with respect to a second plane perpendicular to the second optical axis. ２ the second wavelength tunable unit is disposed so as to be inclined only by When the second incident surface is tilted so that the light ray traveling along the second optical axis is reflected by the second incident surface and passes through the boundary of the effective range of the second optical system, the inclination angle with respect to the second plane is defined as α ２ , the effective radius of the second optical system is r ２ , the distance between the second optical system and the second wavelength tunable unit in the direction along the second optical axis is d ２ Then, tan (2α ２ ) = r ２ / d ２ , and a ２ ≦θ ２ ≦6a ２ fulfill, 6. The lighting device according to claim 1, wherein the light source is a light source.

7. a second moving unit that moves the second wavelength tunable unit in the second linear direction; 7. The lighting device according to claim 1, wherein the light source is a light source.

8. The second moving unit moves the second wavelength-tunable unit in a direction in which a beam diameter of the light from the second optical system becomes shortest on the second incident surface.

8. The lighting device according to claim 7.

9. the second wavelength tunable unit is disposed at a light-condensing position where the light from the second optical system is condensed.

9. The lighting device according to claim 1, wherein the light source is a light source.

10. A lighting device that illuminates by changing the spectrum of light from a light source, an optical system for directing the light from the light source; a first wavelength variable unit that changes the spectrum of light from the optical system by moving in a first linear direction along a first axis that is perpendicular to an optical axis of the optical system; a second wavelength-tunable unit that changes the spectrum of light from the first wavelength-tunable unit by moving in a second linear direction along a second axis that is perpendicular to the optical axis of the optical system and different from the direction of the first axis, the first wavelength-tunable unit is disposed such that a first incident surface of the first wavelength-tunable unit onto which the light irradiated by the optical system is incident is inclined in a rotation direction around the first axis, the second wavelength tuning unit is disposed so that a second incident surface of the second wavelength tuning unit, onto which the light irradiated by the optical system via the first wavelength tuning unit, is incident, is inclined in the rotation direction around the second axis. A lighting device characterized by:

11. The first incident surface has an inclination angle θ with respect to a plane perpendicular to the optical axis. ３ the first wavelength tunable unit is disposed so as to be inclined only by When the first incident surface is tilted so that the light ray traveling along the optical axis is reflected by the first incident surface and passes through the boundary of the effective range of the optical system, the inclination angle with respect to the plane is defined as α ３ , the effective radius of the optical system is r ３ , the distance between the optical system and the first wavelength tunable unit in the direction along the optical axis is d ３ Then, tan (2α ３ ) = r ３ / d ３ , and a ３ ≦θ ３ ≦6a ３ Fulfilling The second incident surface is inclined at an angle θ with respect to the plane. ４ the second wavelength tunable unit is disposed so as to be inclined only by When the second incident surface is tilted so that a ray traveling along the optical axis of the optical system is reflected by the second incident surface and passes through the boundary of the effective range of the optical system, the inclination angle with respect to the plane is defined as α ４ , the distance between the optical system and the second wavelength tunable unit in the direction along the optical axis is d ４ Then, tan (2α ４ ) = r ３ / d ４ , and a ４ ≦θ ４ ≦6a ４ fulfill, 11. The lighting device according to claim 10.

12. a first moving unit that moves the first wavelength tunable unit in the first linear direction; a second moving unit that moves the second wavelength tunable unit in the second linear direction; 12. The lighting device according to claim 10 or 11.

13. the first moving unit moves the first wavelength-tunable unit in a direction in which a beam diameter of the light from the optical system becomes shortest on the first incident surface; the second moving unit moves the second wavelength-tunable unit in a direction in which a beam diameter of the light from the first wavelength-tunable unit becomes shortest on the second incident surface, 13. The lighting device according to claim 12.

14. the first wavelength tunable unit is disposed at a first light collection position where the light from the optical system is collected, the second wavelength-tunable unit is disposed at a second light-collecting position where the light from the first wavelength-tunable unit is collected; 14. The lighting device according to claim 10, wherein the light source is a light source.

15. A measurement apparatus for measuring a position of a pattern, comprising: A lighting device according to any one of claims 1 to 14; a detection unit that detects light from the pattern illuminated by the light from the illumination device, A measuring device characterized by:

16. A substrate processing apparatus for processing a substrate on which a pattern is formed, The measuring device according to claim 15, Processing the substrate aligned based on the position of the pattern measured by the metrology device A substrate processing apparatus comprising:

17. processing a substrate using the substrate processing apparatus according to claim 16; and manufacturing an article from the processed substrate. A method for manufacturing an article.

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