Substrate processing device

Abstract

Provided is a technology that makes it possible to easily correct a stage position that is based on a refractive index distribution. This substrate processing device comprises: a stage (10) that holds a substrate (W); a position measurement unit (60) that irradiates the stage (10) with laser light (611) and that, on the basis of the results of detecting the laser light (611) reflected from the stage (10), measures the position of the stage (10); an imaging unit (70) that captures, by means of the laser light (611), a background image (33) having a prescribed pattern; and a position calculation unit (94) that calculates the position of the stage (10) on the basis of the measurement results from the position measurement unit (60). The position calculation unit (94): calculates a refractive index distribution from the image obtained by the imaging unit (70); and corrects the measurement results from the position measurement unit (60) on the basis of the calculated refractive index distribution.

Description

Substrate processing equipment

[0001] The subject matter disclosed herein relates to substrate processing equipment.

[0002] In position measurement using laser interferometers, measurement errors due to changes in refractive index along the optical path of the laser beam are a major problem. For example, Patent Document 1 proposes addressing this problem by arranging numerous environmental sensors (temperature sensors, pressure sensors) along the optical path, detecting changes in refractive index at each point, and correcting the measurement results.

[0003] Japanese Patent Publication No. 2005-345298

[0004] Junichi Akatsuka, et al., "Improvement of a Visualization Method for Density Gradient Based on the Background-Oriented Schlieren Method," Transactions of the Japan Society of Mechanical Engineers, December 2011, Vol. 77, No. 784, pp. 2391-2400.

[0005] However, using a large number of sensors, as in conventional technology, not only leads to increased system complexity and cost, but also makes the calibration and maintenance of the sensors themselves cumbersome. For this reason, correcting the stage position based on the refractive index distribution is not easy, and there was room for improvement.

[0006] The object of the present invention is to provide a technology that can easily realize stage position correction based on refractive index distribution.

[0007] To solve the above problems, the first embodiment is a substrate processing apparatus for processing a substrate, comprising: a stage for holding a substrate; a position measuring unit that irradiates the stage with laser light and measures the position of the stage based on the detection result of the laser light reflected from the stage; an imaging unit that captures a background image having a predetermined pattern via the laser light; and a position calculation unit that calculates the position of the stage based on the measurement result of the position measuring unit, wherein the position calculation unit calculates a refractive index distribution from the image obtained by the imaging unit and corrects the measurement result of the position measuring unit based on the calculated refractive index distribution.

[0008] The second embodiment is a substrate processing apparatus according to the first embodiment, wherein the imaging unit captures the laser light from multiple different directions to acquire multiple images, and the position calculation unit calculates a refractive index distribution from the multiple images acquired by the imaging unit and corrects the measurement results based on the obtained refractive index distribution.

[0009] The third embodiment is a substrate processing apparatus according to the first or second embodiment, wherein the predetermined pattern is a random dot pattern.

[0010] The fourth embodiment is a substrate processing apparatus according to the third embodiment, wherein the position calculation unit calculates the refractive index distribution using the cross-correlation method.

[0011] The fifth embodiment is a substrate processing apparatus according to any of the first to fourth embodiments, wherein the position measuring unit measures the position of the stage in a first direction and a second direction, and the position calculation unit corrects the measurement results for the first direction and the second direction obtained by the position measuring unit, respectively.

[0012] The sixth embodiment is a substrate processing apparatus according to any of the first to fifth embodiments, wherein the position measuring unit includes a laser interferometer.

[0013] The seventh embodiment is a substrate processing apparatus according to any of the first to sixth embodiments, further comprising a moving mechanism for moving the stage, wherein the position measuring unit measures the position of the stage moved by the moving mechanism.

[0014] The eighth embodiment is a substrate processing apparatus according to any of the first to seventh embodiments, further comprising an exposure head for exposing a substrate held on the stage.

[0015] According to the substrate processing apparatus of the first to seventh embodiments, the refractive index distribution is calculated from an image obtained by capturing a background image. Therefore, correction of the stage position based on the refractive index distribution can be easily achieved compared to when using a large number of sensors.

[0016] According to the substrate processing apparatus of the second embodiment, a three-dimensional refractive index distribution can be calculated by imaging laser light from multiple directions, thereby enabling accurate correction of the stage position measurement results.

[0017] According to the substrate processing apparatus of the third embodiment, the amount of image displacement on the image can be easily calculated using a random dot pattern.

[0018] According to the substrate processing apparatus of the fourth embodiment, the refractive index distribution can be easily calculated by the cross-correlation method.

[0019] According to the substrate processing apparatus of the fifth embodiment, the position of the stage in multiple directions can be calculated with high accuracy.

[0020] According to the substrate processing apparatus of the seventh embodiment, the position of the stage that moves by the moving mechanism can be calculated with high accuracy.

[0021] This is a side view showing an exposure apparatus, which is a substrate processing apparatus of the first embodiment. This is a schematic diagram showing a position measuring instrument for measuring the position of the stage. This is a schematic diagram showing an imaging unit that images the laser light of the laser interferometer shown in Figure 2. This is a schematic diagram showing a plurality of cameras that image the laser light of the laser interferometer. This is a schematic side view showing a first arrangement example of the laser interferometer and cameras. This is a schematic top view showing a first arrangement example of the laser interferometer and cameras. This is a schematic side view showing a second arrangement example of the laser interferometer and cameras. This is a schematic top view showing a second arrangement example of the laser interferometer and cameras. This is a schematic side view showing a third arrangement example of the laser interferometer and cameras. This is a schematic top view showing a third arrangement example of the laser interferometer and cameras. This is a block diagram showing the control unit shown in Figure 1. This is a schematic perspective view showing the imaging unit of the second embodiment. This is a schematic perspective view showing a modified example of the imaging unit according to the second embodiment.

[0022] Embodiments of the present invention will be described below with reference to the attached drawings. Note that in the drawings, the dimensions and number of parts may be exaggerated or simplified for ease of understanding. Figure 1 and subsequent figures show arrows indicating the X, Y, and Z directions. The X and Y directions are orthogonal to each other in the horizontal plane. The Z direction is a vertical direction orthogonal to both the X and Y directions. Furthermore, the +Z direction is defined as vertically upward, and the -Z direction as vertically downward.

[0023] <1. First Embodiment> Figure 1 is a side view showing an exposure apparatus 100, which is a substrate processing apparatus of the first embodiment. The exposure apparatus 100 draws a pattern on a photosensitive material by irradiating the upper surface of a substrate W, on which a layer of photosensitive material such as a resist is formed, with laser light of a predetermined pattern. Various substrates can be used as the substrate W, such as semiconductor substrates, printed circuit boards, color filter substrates, glass substrates for flat panel displays provided in liquid crystal display devices and plasma display devices, and optical disc substrates.

[0024] The exposure apparatus 100 includes a main frame 101. Inside the main frame 101, the exposure apparatus 100 has a processing area 102 and a transfer area 103. The processing area 102 contains a base 1, a stage 10, a stage moving mechanism 20, and an exposure unit 40. The transfer area 103 contains a transport device Tf1 for loading and unloading substrates W. The exposure apparatus 100 also includes a control unit 90.

[0025] A cassette mounting section 104 for placing cassette Ca1 is located adjacent to the transfer area 103. The transport device Tf1 takes out the unprocessed substrate W contained in cassette Ca1 and transports it to the processing area 102, and also transports the processed substrate W from the processing area 102 and places it in cassette Ca1. The transfer of cassette Ca1 to and from cassette mounting section 104 is performed by an external transport device (not shown). The loading and unloading of substrate W by the transport device Tf1 is performed under the control of the control unit 90.

[0026] The stage 10 has a rectangular shape when viewed from above. The stage 10 has an upper surface for holding the substrate W. The substrate W is placed on the upper surface of the stage 10 in a horizontal position. Multiple suction holes are formed on the upper surface of the stage 10 in a predetermined pattern as a mechanism for holding the substrate W, and a negative pressure (suction pressure) lower than atmospheric pressure is applied to each suction hole via a vacuum pump. As a result, the substrate W is fixed to the upper surface of the stage 10 by suction force. Alternatively, multiple chucks that mechanically grip the peripheral edge of the substrate W may be provided on the upper surface of the stage 10 as a holding mechanism. In this case, the substrate W is fixed to the stage 10 by the gripping force of the multiple chucks.

[0027] The stage moving mechanism 20 is located on the upper surface of the base 1. It is a mechanism that moves the stage 10 in the θ direction around the rotation axis A which extends in the Y direction (main scanning direction), the X direction (sub-scanning direction), and the Z direction. The stage moving mechanism 20 includes a support plate 22, a sub-scanning mechanism 23, a base plate 24, a main scanning mechanism 25, and a rotation mechanism 27.

[0028] The support plate 22 rotatably supports the stage 10. The base plate 24 supports the support plate 22 and the sub-scanning mechanism 23. The sub-scanning mechanism 23 moves the support plate 22 and the stage 10 in the X direction relative to the base plate 24. The main scanning mechanism 25 moves the support plate 22 and the stage 10 in the Y direction together with the base plate 24. The rotation mechanism 27 rotates the stage 10 around the rotation axis A relative to the support plate 22. The sub-scanning mechanism 23, the main scanning mechanism 25, and the rotation mechanism 27 are composed of a ball screw mechanism equipped with a rotary motor and a ball screw, or a linear motor mechanism, etc. The operation of the sub-scanning mechanism 23, the main scanning mechanism 25, and the rotation mechanism 27 is controlled by the control unit 90.

[0029] The exposure unit 40 has a plurality (for example, five) of exposure heads 41 positioned above the substrate W on the stage 10, and a light irradiation unit 43 that irradiates the plurality of exposure heads 41 with laser light. The light irradiation unit 43 has a laser drive unit 431, a laser oscillator 432, and an illumination optical system 433. Laser light emitted from the laser oscillator 432 by the operation of the laser drive unit 431 is irradiated onto the exposure heads 41 via the illumination optical system 433. The exposure heads 41 modulate the laser light irradiated from the light irradiation unit 43 with a spatial light modulator 411 and project it onto the substrate W moving directly below them. By exposing the substrate W with laser light, a pattern is drawn on the substrate W (exposure operation).

[0030] The spatial light modulator 411 is, for example, a diffraction grating type light modulator called a GLV (Grating Light Valve, a registered trademark of Silicon Light Machines, Inc.). However, the spatial light modulator 411 is not limited to a GLV and may also be a MEMS such as a DMD (Digital Mirror Device).

[0031] The exposure unit 40 is attached to a pair of bridging bodies 31 fixed to the base 1. The pair of bridging bodies 31 are spaced apart in the Y direction and are provided so as to traverse the X direction above the stage 10 and the stage moving mechanism 20. The stage 10 passes inside the pair of bridging bodies 31 by the drive of the main scanning mechanism 25. The light irradiation section 43 of the exposure unit 40 is positioned across the top of the pair of bridging bodies 31. The exposure head 41 of the exposure unit 40 is positioned on the +Y side of the +Y side bridging body 31.

[0032] Figure 2 is a schematic diagram of a position measuring unit 60 that measures the position of the stage 10. The position measuring unit 60 shown in Figure 2 measures the position of the stage 10 in the Y direction. The position measuring unit 60 has a laser interferometer 61 and a mirror 63 attached to the side of the stage 10 in the Y direction. The laser interferometer 61 has a laser light source that emits laser light 611 parallel to the Y direction toward the mirror 63 of the stage 10, and a detector that detects the laser light 611 reflected from the mirror 63 of the stage 10. The mirror 63 is a planar mirror that reflects incident light. Note that if the surface of the stage 10 itself is capable of reflecting laser light 611, the mirror 63 may not be necessary.

[0033] The laser interferometer 61 has an internal interference optical system. The interference optical system is an optical system that superimposes the original laser beam 611 and the reflected laser beam 611 and guides them to the detector. The detector detects the brightness and darkness of the light (interference signal) generated when the reflected laser beam 611 overlaps with the original laser beam 611. The brightness and darkness of the interference signal are repeated each time the mirror 63 moves by half the wavelength of the laser beam 611. Therefore, the movement of the mirror 63, i.e., the movement of the stage 10, can be measured with high accuracy using the wavelength of the laser beam 611 as the unit. The laser interferometer 61 is electrically connected to the control unit 90 and inputs the detection result of the laser beam 611 (for example, the interference signal) to the control unit 90.

[0034] As shown in Figure 2, in the Y direction, the stage 10 moves by a distance d1 (movable distance) from the approach position p1, where it is closest to the laser interferometer 61, to the distance position p2, where it is furthest from the laser interferometer 61. Furthermore, let d2 be the distance in the Y direction from the laser interferometer 61 to the mirror 63 of the stage 10 at the approach position p1. Then, the distance d is the distance the laser beam 611 travels from the laser interferometer 61 to the mirror 63. ｌ It fluctuates within the range from distance d2 to distance d1+d2.

[0035] Figure 3 is a schematic diagram showing the imaging unit 70 that images the laser beam 611 of the laser interferometer 61 shown in Figure 2. As shown in Figure 3, the imaging unit 70 has a camera 71. The camera 71 images a background image 33 with a predetermined pattern formed on it via the laser beam 611 of the laser interferometer 61. The camera 71 has an image sensor such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor). As shown in Figure 3, the lens of the camera 71 is directed towards the -X side, and its optical axis is preferably set parallel to the X direction perpendicular to the optical path of the laser beam 611.

[0036] The pattern of the background image 33 may be a geometric repeating pattern such as dots or stripes, or it may be a random pattern or design. The background image 33 is placed on the surface of a structure inside the exposure apparatus 100. The background image 33 is placed on a plane (YZ plane) that intersects with the optical axis (X axis) of the lens of the camera 71. The camera 71 is focused on the background image 33. The camera 71 inputs the image obtained by imaging to the control unit 90. As will be described later, the position calculation unit 94 of the control unit 90 calculates the refractive index distribution using the image (measured image) obtained by imaging by the camera 71, and corrects the measurement result of the position measurement unit 60 based on the refractive index distribution.

[0037] The background image 33 is positioned between the laser interferometer 61 and the stage 10 in the Y direction. The length L in the Y direction of the background image 33. １ This is the distance d shown in Figure 2. １ +d ２ It is larger than that.

[0038] The camera 71 preferably can image the entire optical path of the laser beam 611 from the exit of the laser beam 611 in the laser interferometer 61 to the mirror 63 of the stage 10. It is preferable to image the entire optical path of the laser beam 611 together with the background image 33. By imaging the entire optical path of the laser beam 611, the refractive index distribution of the entire optical path can be obtained, so that the actual distance can be calculated with high accuracy. The length L in the Y direction of the background image 33 required for such imaging １ is the distance d in the X direction from the camera 71 to the laser beam 611 ｘ１ and the distance d in the X direction from the camera to the background image 33 ｘ２ When this is set, (d １ + d ２ )·d ｘ１ / d ｘ２ is obtained. In order to allow some margin in the imaging conditions, the length L of the background image 33 １ is preferably about 10 - 30% larger than the value obtained by the above formula.

[0039] Note that it is not essential for the camera 71 to image the entire optical path of the laser beam 611, and it may be configured to image only a part of the optical path of the laser beam 611. Then, the position calculation unit 94 may correct the measurement result of the position measurement unit 60 based on the refractive index distribution of a part of the optical path.

[0040] FIG. 4 is a diagram schematically showing a plurality of cameras 71 that image the laser beam 611 of the laser interferometer 61. As shown in FIG. 4, the laser beam 611 from one laser interferometer 61 may be imaged by a plurality of cameras 71. In the example shown in FIG. 4, the path from the laser interferometer 61 to the mirror 63 of the stage 10 is divided into two regions in the Y direction, and each region is imaged by one camera 71. In this way, by photographing the laser beam 6十一 with a plurality of cameras 71, an image with a necessary and sufficient resolution can be obtained even when the moving distance (movable distance) of the stage is long or the resolution of each camera 71 is low.

[0041] The position measurement unit 60 further includes a laser interferometer 61a for measuring the position of the stage 10 in the X direction. The laser interferometer 61a has the same configuration as the laser interferometer 61. The imaging unit 70 further includes a camera 71a that irradiates laser light emitted from the laser interferometer 61a for measuring the position of the stage 10 in the X direction. Next, an arrangement example of the laser interferometer 61a and the camera 71a will be described.

[0042] <First Arrangement Example>FIG. 5A is a side view schematically showing a first arrangement example of the laser interferometer 61a and the camera 71a. FIG. 5B is a top view schematically showing a first arrangement example of the laser interferometer 61a and the camera 71a. In this first arrangement example, the laser interferometer 61a is arranged at a position away from the stage 10 on the +X side. Then, the laser light 611 is irradiated onto a mirror 63a attached to the side surface of the stage 10 on the +X side, and the position of the stage 10 in the X direction is measured by detecting the reflected laser light 611. In this first arrangement example, the camera 71a images the laser light 611 emitted from the laser interferometer 61a in the Z direction.

[0043] More specifically, the laser interferometer 61a and the camera 71a are fixed to the -Y side of the cross member 31 on the +Y side. The camera 71a is arranged on the +Z side of the laser interferometer 61a. The lens of the camera 71a is directed in the -Z direction, and its optical axis is set parallel to the Z direction. The background image 33 is arranged on the upper surface (+Z side surface) of the base 1. The laser interferometer 61a is arranged between the camera 71a and the background image 33 in the Z direction.

[0044] In the present embodiment, the base plate 24 is longer than the stage 10 in the +X direction. Therefore, in the case of the first arrangement example, when the base plate 24 moves directly below the camera 71a, a partial region of the background image 33 is hidden, and the refractive index distribution of that region cannot be calculated. To avoid this, for example, a mirror 63a may be provided on the base plate 24.

[0045] <Second Arrangement Example> Figure 6A is a schematic side view showing a second arrangement example of the laser interferometer 61a and the camera 71a. Figure 6B is a schematic top view showing a second arrangement example of the laser interferometer 61a and the camera 71a. In this second arrangement example, the camera 71a images the laser light 611 emitted from the laser interferometer 61a in the Y direction.

[0046] More specifically, the laser interferometer 61a is attached to the +Y side bridging body 31, as in the first arrangement example, and emits laser light 611 in the -X direction. The camera 71a is positioned on the +Y side of the +Y side bridging body 31 via a support member. The lens of the camera 71a is pointed in the -Y direction, and its optical axis is set parallel to the Y direction. The background image 33 is positioned on the -Y side of the -Y side bridging body 31. The laser interferometer 61a is positioned between the camera 71a and the background image 33 in the Y direction.

[0047] <Third Arrangement Example> Figure 7A is a schematic side view showing a third arrangement example of the laser interferometer 61a and camera 71a. Figure 7B is a schematic top view showing a third arrangement example of the laser interferometer 61a and camera 71a. In this third arrangement example, the camera 71a images the laser beam 611 emitted from the laser interferometer 61a in the Y direction.

[0048] More specifically, the laser interferometer 61a is attached to the +Y side bridging member 31, as in the first arrangement example, and emits laser light 611 in the -X direction. The camera 71a and background image 33 are fixed to the upper surface of the base 1 via a support member. The camera 71a is positioned on the -Y side of the +Y side bridging member 31 and is located between the pair of bridging members 31. The background image 33 is positioned on the +Y side of the +Y side bridging member 31. In the Y direction, the laser interferometer 61a is positioned between the camera 71a and the background image 33.

[0049] The above is a description of an example arrangement of the laser interferometer 61a and camera 71a, but these are merely examples and can be changed as needed.

[0050] Figure 8 is a block diagram of the control unit 90 shown in Figure 1. The control unit 90 is a computer comprising a processor such as a CPU (Central Processing Unit), memory such as RAM (Random-Access Memory) electrically connected to the processor, and a storage unit such as ROM (Read-Only Memory) or a hard disk drive. The storage unit stores programs that the computer can execute. The processor functions as a lighting control unit 91, a stage control unit 92, a drawing control unit 93, and a position calculation unit 94 by loading and executing programs in memory.

[0051] The illumination control unit 91 controls the light irradiation unit 43 of the exposure unit 40 and emits laser light for drawing from the light irradiation unit 43 to each exposure head 41. The stage control unit 92 controls the stage moving mechanism 20 to move the stage 10 relative to the exposure head 41. The drawing control unit 93 controls the spatial light modulator 411 based on the drawing data stored in the memory unit and modulates the laser light to correspond to the drawing pattern indicated by the drawing data.

[0052] When drawing a pattern on a substrate W, the substrate W coated with photosensitive material is held on the stage 10, and the substrate W is aligned (position adjusted). Specifically, alignment marks on the substrate W are captured by a camera, and alignment is performed based on the position of the alignment marks identified from the obtained image. After alignment, the stage control unit 92 controls the stage movement mechanism 20 to move the stage 10 in the Y direction (main scanning direction) relative to each exposure head 41. Then, according to the position of the stage 10, the drawing control unit 93 controls the spatial light modulator 411 to modulate the laser light for drawing so that it corresponds to the drawing pattern, and irradiates the substrate W. As a result, a band-shaped region extending in the Y direction on the upper surface of the substrate W is exposed (main scanning exposure). After the movement in the Y direction is completed, the stage 10 is moved in the X direction (sub-scanning direction) by the width of the band-shaped region. By repeatedly performing this stage movement in the Y direction and the stage movement in the X direction, the pattern is drawn over the entire upper surface of the substrate W.

[0053] The position of the substrate W during alignment and exposure is calculated by the position calculation unit 94. Specifically, the position calculation unit 94 calculates the position of the stage 10 based on the measurement results sent from the position measurement unit 60. The position calculation unit 94 also calculates the refractive index distribution based on the image sent from the imaging unit 70, and corrects the measurement results based on the refractive index distribution to calculate the position of the stage 10. More specifically, the position calculation unit 94 calculates the refractive index distribution in and around the optical path of the laser beam 611 using the Background Oriented Schlieren (BOS) method with the measurement image input from the camera 71 of the imaging unit 70. Then, it corrects the position of the stage 10 based on the calculated refractive index distribution.

[0054] As a method for calculating the refractive index distribution, for example, the cross-correlation method described in Non-Patent Document 1 can be used. In this cross-correlation method, a random dot pattern is used as the background image 33. Then, using the reference image of the random dot pattern and the measurement image, the refraction angle ε of the laser beam is calculated by the following equation.

[0055]

[0056] In equation (1) above, Δh is the amount of image displacement on the image, G is the physical size of one pixel in the image, m is the magnification, and Z ｂ０ is the distance between the background image 33 and the object being measured. The total refraction angle is determined using equation (1), and the refractive index distribution is calculated by performing image reconstruction. In this way, the amount of image displacement on the image can be easily calculated by using a random dot pattern. If the background image 33 is a periodic pattern such as a stripe pattern, the amount of image displacement on the image can be calculated using known phase difference detection methods.

[0057] The refractive index is calculated from the difference between the reference image and the measured image, but the pattern of the background image 33 and the method for calculating the refractive index can be arbitrarily selected.

[0058] Furthermore, the position calculation unit 94 calculates the wavelength correction coefficient C from the calculated refractive index using the following equation (EDLEN's equation).

[0059]

[0060] In equation (2) above, T is the temperature [°C], P is the atmospheric pressure [mmHg], and H is the relative humidity [%]. Furthermore, the position calculation unit 94 calculates the actual distance using the wavelength correction coefficient C according to the following equation.

[0061] (Actual distance) = (Number of wavelength counts) × C × (Vacuum wavelength) (3)

[0062] As described above, in the exposure apparatus 100 of this embodiment, the position calculation unit 94 calculates the refractive index distribution from the image acquired by the imaging unit 70 and corrects the measurement result of the position measurement unit 60 based on the refractive index distribution. In this way, by calculating the refractive index distribution without using a large number of sensors, the system can be simplified and costs can be reduced, and complex tasks such as sensor calibration and maintenance can be eliminated. Therefore, correction of the stage position can be easily achieved.

[0063] <2. Second Embodiment> Next, a second embodiment will be described. In the following description, elements having the same function as those already described will be given the same reference numeral or a reference numeral with an additional alphabetic character, and detailed descriptions may be omitted.

[0064] In the first embodiment, the refractive index distribution is calculated from an image obtained by imaging the area around the laser beam 611 in one direction. However, the laser beam 611 of the laser interferometer 61 is imaged from multiple directions. However, the area around the laser beam 611 may be imaged from multiple directions.

[0065] Figure 9 is a schematic perspective view of the imaging unit 70 according to the second embodiment. In this embodiment, the imaging unit 70 further includes a camera 71b in addition to the camera 71. The camera 71b is positioned above the laser interferometer 61. The lens of the camera 71b is directed downward, and its optical axis is set parallel to the Z direction. The camera 71b captures a background image 33a, which is positioned away from the laser interferometer 61 on the -Z side, via the laser light 611 from the laser interferometer 61. The background image 33a is located on a plane (XY plane) that intersects the optical axis (Z axis) of the camera 71b.

[0066] When the background image 33 is captured by camera 71, the refractive index distribution in the Y and Z directions can be calculated from the obtained image, but it is difficult to calculate the refractive index distribution in the X direction (along the optical axis direction of camera 71). On the other hand, when the background image 33a is captured by camera 71b, the refractive index distribution in the X direction can be calculated from the obtained image. In other words, by applying the BOS method to the images obtained by cameras 71 and 71b, the three-dimensional refractive index distribution in each of the X, Y, and Z directions can be calculated. As a result, the refractive index distribution along the optical path of the laser beam 611 can be obtained with greater accuracy, and the position of the stage 10 can be corrected with greater accuracy.

[0067] Figure 10 is a schematic perspective view showing a modified image of the imaging unit 70 according to the second embodiment. In this modified image of the imaging unit 70, in addition to the cameras 71 and 71b, there is an additional camera 71c. Camera 71c is positioned below the laser interferometer 61. The lens of camera 71c is oriented in the +Y direction, and its optical axis is set parallel to the Y direction. A background image 33b is provided on the -Y side of the stage 10 (excluding the mirror 63). The background image 33b is perpendicular to the optical axis of camera 71c. Camera 71c captures the background image 33b via laser light 611 from the laser interferometer 61.

[0068] By applying the BOS method to the image obtained by camera 71c, the refractive index distribution in the X and Z directions can be calculated. By combining this calculation result with the refractive index distribution calculated from the images obtained by cameras 71 and 71b, the three-dimensional refractive index distribution can be calculated with greater accuracy. Therefore, the position of stage 10 can be corrected with greater accuracy.

[0069] <3. Modifications> Although embodiments have been described above, the present invention is not limited to those described above, and various modifications are possible.

[0070] For example, in the above embodiment, the position measurement unit 60 may have a laser interferometer that measures the position of the stage 10 in the Z direction. Alternatively, the imaging unit 70 may have a camera that captures a background image 33 via the laser light of the laser interferometer, and the position calculation unit 94 may correct the measurement result of the stage position in the Z direction based on the refractive index distribution calculated from the image of the camera.

[0071] The position measurement unit 60 may have a laser interferometer for measuring the rotation angle of the stage 10 in the θ direction. For example, two laser interferometers (and mirrors) separated in the X direction may be used to measure the positions in the Y direction at two different locations in the X direction of the stage 10, and the rotation angle of the stage 10 may be calculated from the difference between the obtained measured values. Alternatively, the imaging unit 70 may have a camera that captures a background image 33 via the laser light from the two laser interferometers, and the position calculation unit 94 may correct the measurement result of the stage position in the θ direction based on the refractive index distribution calculated from the image from the camera.

[0072] The camera of the imaging unit 70 may also be used to image the alignment marks on the substrate W. Specifically, the alignment marks on the substrate W may be imaged using a camera 71a shown in Figure 5A, or a camera positioned above the stage 10, such as the camera 71b shown in Figures 9 and 10.

[0073] The substrate processing apparatus according to the above embodiment is an exposure apparatus 100 equipped with an exposure head 41 for exposing a substrate W. However, the substrate processing apparatus is not limited to the exposure apparatus 100. For example, the substrate processing apparatus may be configured as an appearance inspection apparatus that inspects the appearance of a substrate on a stage using a camera or the like for image processing.

[0074] Although this invention has been described in detail, the above description is illustrative in all respects, and the invention is not limited thereto. It is understood that countless variations not illustrated can be conceived without falling outside the scope of this invention. The components described in each of the above embodiments and variations can be combined or omitted as appropriate, as long as they do not contradict each other.

[0075] 10: Stage 20: Stage moving mechanism 33, 33a, 33b: Background image 41: Exposure head 60: Position measurement unit 61, 61a: Laser interferometer 70: Imaging unit 94: Position calculation unit 100: Exposure apparatus (substrate processing device) 611: Laser light W: Substrate

Claims

1. A substrate processing apparatus for processing a substrate, comprising: a stage for holding the substrate; a position measuring unit for irradiating the stage with laser light and measuring the position of the stage based on the detection result of the laser light reflected from the stage; an imaging unit for capturing a background image having a predetermined pattern via the laser light; and a position calculation unit for calculating the position of the stage based on the measurement result of the position measuring unit, wherein the position calculation unit calculates a refractive index distribution from the image obtained by the imaging unit and corrects the measurement result of the position measuring unit based on the calculated refractive index distribution.

2. A substrate processing apparatus according to claim 1, wherein the imaging unit captures the laser light from a plurality of different directions to acquire a plurality of images, and the position calculation unit calculates a refractive index distribution from the plurality of images acquired by the imaging unit and corrects the measurement result based on the obtained refractive index distribution.

3. A substrate processing apparatus according to claim 1 or claim 2, wherein the predetermined pattern is a random dot pattern.

4. A substrate processing apparatus according to claim 3, wherein the position calculation unit calculates the refractive index distribution using the cross-correlation method.

5. A substrate processing apparatus according to any one of claims 1 to 4, wherein the position measuring unit measures the position of the stage in a first direction and a second direction, and the position calculating unit corrects the measurement results for the first direction and the second direction obtained by the position measuring unit, respectively.

6. A substrate processing apparatus according to any one of claims 1 to 5, wherein the position measuring unit includes a laser interferometer.

7. A substrate processing apparatus according to any one of claims 1 to 6, further comprising a moving mechanism for moving the stage, wherein the position measuring unit measures the position of the stage moved by the moving mechanism.

8. A substrate processing apparatus according to any one of claims 1 to 7, further comprising: an exposure head for exposing a substrate held on the stage.

Images