Exposure apparatus and exposure method

Abstract

This technology provides high-precision detection of alignment mark misalignment, even with low-resolution cameras. [Solution] The exposure apparatus 1 includes an exposure head 41, a second stage 25 that holds a substrate W on which a plurality of alignment marks M are formed, an alignment camera 50 that acquires an alignment image by imaging the plurality of alignment marks M on the substrate W, a storage unit 73 that stores design data 83 including information on the shape and position of the plurality of alignment marks M, and a processor 71 that calculates the displacement of the alignment marks M by a sampling moiré method using an alignment image FA1 and a design image FB1 based on the design data 83. The alignment marks M include a pattern having periodicity in at least one direction.

Description

TECHNICAL FIELD

[0001] The subject matter disclosed in the present specification relates to an exposure apparatus and an exposure method.

BACKGROUND ART

[0002] Conventionally, for manufacturing substrates such as semiconductor substrates and printed circuit boards, an exposure apparatus that exposes a pattern directly onto the upper surface of the substrate is known. In this type of exposure apparatus, high-precision alignment may be performed on an already exposed pattern to expose a new pattern. This alignment is performed by alignment using a camera (for example, Patent Document 1).

[0003] Specifically, a plurality of alignment marks exposed simultaneously with the previous layer are imaged, and the position thereof is detected to calculate the distortion amount in the substrate. Then, the exposure data is corrected according to the distortion amount in the substrate.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] In order to improve exposure accuracy, it is conceivable to detect the positional deviation of each alignment mark with higher accuracy. For example, increasing the resolution of the camera can improve the detection accuracy of the positional deviation of the alignment marks. However, the introduction of a high-resolution camera incurs costs. In addition, making the camera high-resolution increases the data size of the obtained image, leading to an increase in the data transfer amount. Therefore, there is a demand for a technique that detects the positional deviation of alignment marks with high accuracy using a low-resolution camera.

[0006] The objective of the present invention is to provide a technology that can detect misalignment of alignment marks with high accuracy, even with a low-resolution camera. [Means for solving the problem]

[0007] To solve the above problems, the first embodiment is an exposure apparatus comprising: an exposure head; a substrate holding unit for holding a substrate on which a plurality of alignment marks are formed; an alignment camera for acquiring an alignment image by imaging the plurality of alignment marks on the substrate; a storage unit for storing design data including information on the shape and position of the plurality of alignment marks; and a calculation processing unit for calculating the displacement of the alignment marks by a sampling moiré method using the alignment image and a design image based on the design data, wherein the alignment marks include a pattern having periodicity in at least one direction.

[0008] The second embodiment is an exposure apparatus according to the first embodiment, wherein the storage unit stores exposure data representing the pattern exposed by the exposure head, and the calculation processing unit corrects the exposure data based on the calculated displacement of the plurality of alignment marks.

[0009] A third embodiment is an exposure apparatus according to the first or second embodiment, further comprising a marking mask disposed in the substrate holding section and having periodicity in at least one direction, wherein the calculation processing unit calculates the position of the alignment camera relative to the substrate holding section by a sampling moiré method based on a marking image obtained by imaging the marking mask with the alignment camera.

[0010] A fourth embodiment is an exposure apparatus according to the third embodiment, further comprising a calibration camera that acquires a beam image by imaging the beam emitted from the exposure head through the marking mask, wherein the processing unit calculates the position of the beam relative to the marking mask based on the beam image.

[0011] The fifth embodiment is an exposure apparatus according to the first to fourth embodiments, wherein the alignment camera includes a line sensor having an imaging area larger than the width of the substrate.

[0012] The sixth embodiment is an exposure apparatus according to the first to fourth embodiments, wherein the alignment camera includes an area sensor capable of capturing images of the entire substrate at once.

[0013] The seventh aspect is an exposure method comprising: a) holding a substrate on which a plurality of alignment marks are formed in a substrate holding unit; b) capturing images of the plurality of alignment marks on the substrate with an alignment camera and acquiring an alignment image; c) acquiring a design image based on design data including the shape and position of the plurality of alignment marks; and d) calculating the displacement of the plurality of alignments by a sampling moiré method using the alignment image and the design image, wherein the alignment marks include a pattern having periodicity in at least one direction. [Effects of the Invention]

[0014] According to the first to seventh embodiments, the displacement of each alignment mark can be calculated using subpixels smaller than the pixel size of the alignment camera using the sampling moiré method. As a result, even if the alignment camera has low resolution, the displacement of the alignment marks can be calculated, enabling high-precision measurement of distortion within the substrate.

[0015] According to the exposure apparatus of the second embodiment, the effect is achieved by correcting the exposure data.

[0016] According to the exposure apparatus of the third embodiment, the positional relationship between the stage and the alignment camera can be determined.

[0017] According to the exposure apparatus of the fourth embodiment, the positional relationship between the exposure head and the alignment camera can be determined from the positional relationship between the stage and the alignment camera, and the positional relationship between the stage and the exposure head. This makes it possible to obtain the positional displacement of the substrate relative to the exposure head.

[0018] According to the exposure apparatus of the fifth aspect, the imaging time for a plurality of alignment marks can be shortened.

[0019] According to the exposure apparatus of the sixth aspect, the imaging time for a plurality of alignment marks can be shortened. [Brief Description of the Drawings]

[0020] [Figure 1] It is a perspective view showing the overall configuration of the exposure apparatus. [Figure 2A] It is a diagram showing an example of an alignment mark. [Figure 2B] It is a diagram showing another example of the alignment mark. [Figure 3] It is a top view showing the second stage 25 in the exposure apparatus. [Figure 4] It is a side view showing the second stage 25 in the exposure apparatus. [Figure 5] It is a control block diagram of the exposure apparatus. [Figure 6] It is a diagram showing a flowchart of the exposure method according to the embodiment. [Figure 7] It is a flowchart showing a specific processing procedure of the distortion measurement step. [Figure 8] It is a flowchart showing a specific processing procedure of the offset amount measurement step shown in Fig. 6. [Figure 9A] It is a diagram schematically showing a part of the reticle mark mask K. [Figure 9B] It is a diagram showing a vertical stripe pattern. [Figure 9C] It is a diagram showing an enlarged part of the vertical stripe pattern. [Figure 10] It is a diagram conceptually showing position measurement of an alignment camera by a sampling moiré method. [Mode for Carrying Out the Invention]

[0021] Embodiments of the present invention will be described below with reference to the attached drawings. Note that the components described in these embodiments are merely illustrative and are not intended to limit the scope of the present invention to them alone. In the drawings, for ease of understanding, the dimensions and number of parts may be exaggerated or simplified as needed.

[0022] Figure 1 and subsequent figures define an XYZ Cartesian coordinate system to explain the positional relationships of the elements. Here, the X and Y axes are defined as horizontal directions, and the Z axis is defined as vertical. In the following explanation, the +Z direction is defined as vertically upward, and the -Z direction is defined as vertically downward.

[0023] <1. Embodiment> Figure 1 is a perspective view showing the overall configuration of the exposure apparatus 1. The exposure apparatus 1 is a substrate processing device that exposes a pattern on the upper surface of a substrate W coated with a photosensitive material by irradiating it with light. The substrate W is, for example, a printed circuit board or a semiconductor substrate. For example, in the manufacturing process of a printed circuit board, the process of forming a layer on the upper surface of the substrate W in another device and the process of exposing a pattern on the upper surface of the substrate W in this exposure apparatus 1 are repeatedly performed. This produces a multilayer printed circuit board.

[0024] The exposure apparatus 1 comprises a base 10, a gantry 15, a first stage 21, a first moving mechanism 23, a second stage 25, a second moving mechanism 27, an exposure unit 40, an alignment camera 50, and a control unit 70.

[0025] The base 10 is a support base that supports each element of the exposure apparatus 1, such as the gantry 15 and the first stage 21. The base 10 has a flat, plate-like shape that extends along the horizontal plane. The base 10 is made of a stone material such as granite. The base 10 is fixed to the factory floor. The base 10 is rectangular in shape when viewed from above. The long side of the base 10 is parallel to the Y-axis direction. The short side of the base 10 is parallel to the X-axis direction.

[0026] The gantry 15 is fixed to the upper surface of the base 10. The gantry 15 has a pair of legs 151 and a bridging portion 152. The pair of legs 151 are spaced apart in the X-axis direction. Each leg 151 extends upward (+Z direction) from the upper surface of the base 10. The bridging portion 152 connects the upper ends of the legs 151 in the X-axis direction. A through-hole 18 is formed between the upper surface of the base 10 and the gantry 15, through which the substrate W can pass in the Y-axis direction.

[0027] The first stage 21 is movable along the Y-axis. The first stage 21 has a flat, plate-like shape. In a top view, the shape of the first stage 21 is rectangular, smaller than the base 10. The first stage 21 is positioned above the base 10 in a substantially horizontal position.

[0028] The first moving mechanism 23 is a mechanism for moving the first stage 21 in the Y-axis direction relative to the base 10 and the gantry 15. The first moving mechanism 23 is a linear motor mechanism having a pair of guide rails and a linear motor. The pair of guide rails are rails for guiding the first stage 21 in the Y-axis direction. The pair of guide rails are provided on the upper surface of the base 10 at intervals in the X-axis direction and extend linearly along the Y-axis direction. The linear motor has a stator provided on the upper surface of the base 10 and a mover fixed to the lower surface of the first stage 21. When a drive signal is supplied to the linear motor from the control unit 70, the mover moves along the stator in the Y-axis direction due to the magnetic attractive and repulsive forces generated between the stator and the mover. As a result, the first stage 21 moves in the Y-axis direction relative to the base 10. Note that the drive source of the first moving mechanism 23 is not limited to a linear motor. The first moving mechanism 23 may be, for example, a mechanism that converts the rotational motion of a servo motor into linear motion using a ball screw.

[0029] The second stage 25 is movable along the X-axis. The second stage 25 has a flat, plate-like shape. In a top view, the shape of the second stage 25 is a smaller rectangle than that of the first stage 21. The second stage 25 is positioned above the first stage 21 in a substantially horizontal position.

[0030] The second moving mechanism 27 is a mechanism for moving the second stage 25 in the X-axis direction relative to the first stage 21. The second moving mechanism 27 is a linear motor mechanism having a pair of guide rails and a linear motor. The pair of guide rails are arranged on the upper surface of the first stage 21 at intervals in the Y-axis direction. Each guide rail extends linearly along the X-axis direction. The pair of guide rails are rails for guiding the second stage 25 in the X-axis direction. The linear motor also includes, for example, a stator provided on the upper surface of the first stage 21 and a mover fixed to the lower surface of the second stage 25. However, the second moving mechanism 27 is not limited to a linear motor mechanism, but may be, for example, a ball screw mechanism.

[0031] The substrate W is supported on the upper surface of the second stage 25 in a substantially horizontal position. The second stage 25 has chuck pins that grip the peripheral edge of the substrate W. The upper surface of the second stage 25 may also be provided with a plurality of suction holes for adsorbing the substrate W, and may have a negative pressure device (negative pressure pump) that generates a negative pressure lower than atmospheric pressure in the suction holes. The exposure apparatus 1 moves the substrate W in the Y-axis direction (main scanning direction) and the X-axis direction (sub-scanning direction), respectively, by operating the first moving mechanism 23 and the second moving mechanism 27.

[0032] The exposure unit 40 is a unit that exposes the substrate W supported by the second stage 25. The exposure unit 40 has four exposure heads 41. The multiple exposure heads 41 are fixed to the bridging portion 152 of the gantry 15. The multiple exposure heads 41 are arranged at equal intervals along the X-axis. Each exposure head 41 has a spatial light modulation element to form a desired pattern on the substrate W. As the spatial light modulation element, for example, a GLV (Grating Light Valve) (registered trademark) or a DMD (Digital Micromirror Device) can be used. A GLV is a diffraction grating type spatial light modulator that uses a minute diffraction grating structure to control the diffraction of laser light, thereby adjusting the transmittance and reflectance of the light and forming a patterned light. A DMD uses a minute mirror array to change the direction of light reflection by tilting individual mirrors and forming a patterned light.

[0033] The exposure unit 40 spatially modulates the laser light supplied from the light source 43 to form patterned light, which is then irradiated onto the substrate W. The light source 43 can be, for example, a laser oscillator, an LED (Light Emitting Diode), or a mercury lamp. The laser light from the light source 43 is converted into linear laser light by the illumination optical system 45 and guided to the spatial light modulator of the exposure head 41. The illumination optical system 45 includes, for example, a collimator lens that converts the light from the light source 43 into parallel light, and a cylindrical lens that converts it into a linear beam.

[0034] When exposing a substrate W, the exposure apparatus 1 alternately performs a main scanning process and a sub-scanning process. In the main scanning process, the exposure apparatus 1 moves the substrate W in the Y-axis direction while multiple exposure heads 41 emit pattern light. In the main scanning process, the exposure apparatus 1 moves the substrate W relative to the multiple exposure heads 41 in the Y-axis direction. This draws a pattern in a striped area. In the sub-scanning process, the substrate W is moved a predetermined distance in the X-axis direction to position the substrate W at the starting position of the next exposure. The exposure apparatus 1 exposes the entire surface of the substrate W by repeating these main scanning and sub-scanning processes.

[0035] The alignment camera 50 captures the alignment marks M formed on the substrate W supported by the second stage 25 and acquires an image (alignment image FA1) including the alignment marks M. The alignment camera 50 is attached to the bridging portion 152 of the gantry 15. The alignment camera 50 performs imaging based on a drive signal from the control unit 70.

[0036] The imaging area of ​​the alignment camera 50 is larger than the width of the substrate W in the X-axis direction. Therefore, by moving the substrate W in the Y-axis direction only once, the entire top surface of the substrate W can be imaged. Consequently, all alignment marks M can be imaged in a single movement, which reduces the imaging time compared to imaging in multiple steps.

[0037] The alignment camera 50 has an image sensor. The image sensor is a semiconductor device having multiple photodetectors that convert light into electrical signals, and specifically includes an image sensor such as a CCD (Charge-Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor). The alignment camera 50 is a line sensor in which multiple photodetectors are arranged in the X-axis direction. However, the alignment camera 50 may be a two-dimensional image sensor. The pixel size of the alignment camera 50 is selected, for example, to be 5 to 10 times the value required for the reproducibility of the alignment.

[0038] Alignment marks M are reference marks provided to ensure the precise positioning of patterns (circuits, wiring, etc.) formed on each layer of a multilayer substrate. In a multilayer structure, alignment marks M function as reference points for accurately stacking the patterns of each layer. The formation of alignment marks M is usually carried out in the same process as the circuit patterns of each layer. Specifically, alignment marks M are formed together with the patterns during the exposure and development process after resist coating in the photolithography process.

[0039] Figure 2A shows an example of alignment mark M. Figure 2B shows another example of alignment mark M. Alignment mark M has a pattern having a periodic brightness distribution in at least one direction. For example, the alignment mark M shown in Figure 2A includes a vertical striped pattern Pm1 consisting of three equally spaced parallel lines, and a horizontal striped pattern Pm2 consisting of three equally spaced parallel lines. The alignment mark M shown in Figure 2B has a grid pattern Pm3 in which rectangular (here, square) figures are arranged in a 3x3 grid. The shape of the figures forming pattern Pm3, as well as the number of rows and columns, can be arbitrarily changed. Patterns Pm1, Pm2, and Pm3 are patterns showing a rectangular waveform brightness distribution, but they may also be patterns showing a sinusoidal waveform brightness distribution (gradation).

[0040] Figure 3 is a top view showing the second stage 25 in the exposure apparatus 1. As shown in Figure 3, the exposure apparatus 1 has a marking mask K. The marking mask K has a linear pattern that serves as a reference for alignment in the exposure apparatus 1. The marking mask K is formed on the upper surface of a transparent substrate such as quartz glass fixed to the -Y side of the second stage 25. The marking mask K has a light-shielding pattern formed by etching or metal deposition. The marking mask K is positioned at approximately the same height as the upper surface of the second stage 25 in the Z-axis direction.

[0041] The marking mask K has a periodic pattern in at least one direction. In this embodiment, the marking mask K has vertical and horizontal striped light-shielding patterns (see Figure 2A) that show a brightness distribution of a rectangular waveform. The marking mask K may also have a grid-like light-shielding pattern (see Figure 2B). Furthermore, the marking mask K may have a pattern that shows a brightness distribution of a sinusoidal waveform in at least one direction.

[0042] Figure 4 is a side view showing the second stage 25 in the exposure apparatus 1. As shown in Figure 4, the exposure apparatus 1 includes a calibration camera 60. The calibration camera 60 is fixed to the -Y side of the second stage 25.

[0043] The calibration camera 60 has a two-dimensional image sensor such as a CCD or CMOS. The resolution of the calibration camera 60 is higher than the resolution of the alignment camera 50. The pixel size of the calibration camera 60 is selected to be, for example, 5 to 10 times the value required for the repeatability of the calibration.

[0044] The calibration camera 60 is positioned away from the guide mask K on the -Z side. The calibration camera 60 images the laser light that has been emitted from the exposure head 41 and passed through the guide mask K. A portion of the linear beam 411 emitted from the exposure head 41 is blocked by the pattern of the guide mask K. The portion of the beam 411 that is not blocked is then incident on the calibration camera 60. The calibration camera 60 transmits the image acquired by imaging to the control unit 70.

[0045] Figure 5 is a control block diagram of the exposure apparatus 1. The control unit 70 is a unit for controlling the operation of each part of the exposure apparatus 1. The control unit 70 includes a processor 71 and a storage unit 73.

[0046] The processor 71 includes a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The processor 71 may also include a general-purpose arithmetic unit, a dedicated arithmetic unit, or a GPU (Graphics Processing Unit). A dedicated arithmetic unit includes, for example, an ASIC (Application Specific Integrated Circuit). A processor is an example of an "arithmetic processing unit."

[0047] The storage unit 73 includes a main memory. The main memory is, for example, a semiconductor memory such as RAM (Random-Access Memory). The storage unit 73 may also include non-volatile memory such as ROM (Read-Only Memory) for storing programs and data. Furthermore, the storage unit 73 may also include auxiliary storage devices and removable media. The auxiliary storage devices include, for example, a solid-state drive (SSD) and a hard disk drive (HDD).

[0048] The memory unit 73 stores the computer program P1. The computer program P1 includes a program for controlling the operation of the exposure apparatus 1. The computer program P1 also includes a program for performing the alignment process described later.

[0049] The control unit 70 is electrically connected to and can communicate with the first moving mechanism 23, the second moving mechanism 27, the exposure unit 40, the alignment camera 50, and the calibration camera 60. The control unit 70 is electrically connected to the input unit 75 and the output unit 77. The input unit 75 inputs instructions or data to the control unit 70 in accordance with the operator's operation. The input unit 75 includes, for example, a keyboard and a mouse. The input unit 75 may also include a reader that reads data from removable media. The output unit 77 may include a display that displays various information, as well as a speaker, printer, or lamp. The display is a liquid crystal display or an organic EL (electroluminescent) display, etc. A GUI (Graphical User Interface) may be configured by superimposing a touch sensor on the display surface of the display.

[0050] Figure 6 is a flowchart of the exposure method according to the embodiment. Unless otherwise specified, each step in this flowchart is performed under the control of the control unit 70. The order of each step can be changed as appropriate depending on the purpose. Furthermore, some steps can be omitted or other steps can be added in the flowchart.

[0051] The exposure method includes a holding step S1. In the holding step S1, the substrate W is placed on the second stage 25 by a transport robot (not shown) or the like. The transport of the substrate W may be performed by a person. The second stage 25 (substrate holding section) then holds the substrate W.

[0052] After the holding process S1, the control unit 70 performs an alignment process. The alignment process is a process to accurately align the existing pattern on the substrate W with the newly drawn pattern. The alignment process includes a strain measurement process S2 and an offset amount measurement process S3.

[0053] The strain measurement step S2 is a step in which strain is measured within the substrate W based on a plurality of alignment marks M placed within the substrate W. The offset amount measurement step S3 is a step in which the relative position (offset amount) of the substrate W with respect to the exposure head 41 is measured. The order in which the strain measurement step S2 and the offset amount measurement step S3 are performed is arbitrary. Each step will be described below.

[0054] Figure 7 is a flowchart showing the specific processing procedure for the strain measurement process S2. The strain measurement process S2 is executed, for example, based on a start instruction input from an operator. When the control unit 70 starts the strain measurement process S2, it executes the mark imaging process S11.

[0055] In the mark imaging process S11, the control unit 70 images a plurality of alignment marks M provided on the substrate W with the alignment camera 50. Specifically, the first moving mechanism 23 moves the second stage 25 in the Y-axis direction while the alignment camera 50 images the substrate W. As a result, the control unit 70 acquires an alignment image FA1. The control unit 70 may perform appropriate preprocessing on the acquired alignment image FA1, such as noise reduction or contrast adjustment.

[0056] After the mark imaging process S11, the control unit 70 executes the rasterization process S12. The control unit 70 can also execute the mark imaging process S11 and the rasterization process S12 in reverse order or in parallel. In the rasterization process S12, the control unit 70 acquires exposure data 81 from the storage unit 73 or an external storage device (such as a database), and converts the acquired exposure data 81 into raster data such as a bitmap. The exposure data 81 is information that defines the fine structures, such as circuit patterns, to be formed on the substrate W. The exposure data 81 is vector-format CAD data and includes geometric elements such as points, lines, or polygons and their coordinate information. The exposure data 81 also includes alignment marks M. That is, the exposure data 81 includes design data 83 that shows the shape and position of the alignment marks M. For this reason, the design image FB1 obtained by rasterization also includes the alignment marks M. In the design image FB1, the alignment marks M are placed in their ideal positions (i.e., positions when there is no distortion in the substrate W). Note that the design data 83 may be different from the exposure data 81. In this case, the rasterization process S12 generates a design image that includes only the alignment marks M and does not include circuit patterns, etc.

[0057] After the rasterization process S12, the control unit 70 executes the displacement calculation process S13. In the displacement calculation process S13, the control unit 70 calculates the displacement (positional deviation) of each alignment mark M using the sampling moiré method with the alignment image FA1 and the design image FB1.

[0058] As a sampling moiré method, for example, the method described in Japanese Patent Publication No. 2009-264852 can be employed. Specifically, multiple downsampled images are generated by performing sampling of equally spaced pixels on both the alignment image FA1 and the design image FB1, changing the starting pixel multiple times (three or more times). Then, multiple moiré fringe images are generated by interpolating the obtained downsampled images. Furthermore, the phase distribution of the moiré fringe is calculated from the multiple moiré fringe images that have been generated. The control unit 70 performs the calculation of the phase distribution for both the X-axis and Y-axis directions.

[0059] The difference (phase difference distribution) between the phase distribution based on the alignment image FA1 and the phase distribution based on the design image FB1 corresponds to the positional deviation (direction and amount of deviation) of each alignment mark M from the reference position indicated by the design data 83. The control unit 70 appropriately stores the calculated positional deviation information in the storage unit 73.

[0060] The control unit 70 calculates the displacement in the X-axis direction (for example, dx1, dx2 shown in Figure 7) and the displacement in the Y-axis direction from the reference position for each of the multiple alignment marks M. By measuring the displacement of multiple alignment marks M in this way, the strain within the substrate W can be quantified.

[0061] <Offset Amount Measurement Process> Figure 8 is a flowchart showing the specific processing procedure for the offset amount measurement process S3 shown in Figure 6. When the control unit 70 starts the offset amount measurement process S3, it executes the beam imaging process S21. In the beam imaging process S21, the control unit 70 images the linear beam 411 emitted from the exposure head 41 via the marking mask K. Specifically, the first moving mechanism 23 and the second moving mechanism 27 move the second stage 25 to position the marking mask K directly below the exposure head 41. Then, the beam 411 is emitted from the exposure head 41, and the beam 411 is imaged by the calibration camera 60.

[0062] After the beam imaging process S21, the control unit 70 performs a beam position measurement process S22. In the beam position measurement process S22, the control unit 70 acquires the relative position of the beam 411 with respect to the guide mask K based on the image (beam image) obtained by the calibration camera 60. This allows for the quantification of the positional relationship between the second stage 25 and the exposure head 41.

[0063] Figure 9A is a schematic diagram showing a part of the marking mask K. As shown in Figure 9A, the marking mask K has multiple vertical stripe patterns Pv1 arranged at predetermined intervals in the X-axis direction. Although the horizontal stripe patterns are not shown in Figure 9A, they are provided, for example, near each vertical stripe pattern Pv1.

[0064] Figure 9B shows the vertical stripe pattern Pv1. As shown in Figure 9B, the vertical stripe pattern Pv1 is composed of multiple vertical lines Lv1 (10 in this case) extending in the Y-axis direction. The width of the vertical lines Lv1 themselves and the spacing between the vertical lines Lv1 are the same, but this is not mandatory.

[0065] Figure 9C is a magnified view of a portion of the vertical stripe pattern Pv1. As shown in Figure 9C, the imaging field of view Fv1 of the calibration camera 60 is sufficiently smaller than the stripe width W1 (width or pitch of one period) of the vertical stripe pattern of the guide mark mask K. The calibration camera 60 simultaneously images the vertical lines Lv1 of the guide mark mask K and the beam 411. Specifically, a portion of the entire imaging field of view Fv1 (here, a region with a width of 1 / 4 to 2 / 3 from one end in the X-axis direction) overlaps with the vertical lines Lv1 of the guide mark mask K. That is, a portion of the imaging field of view Fv1 is obscured by the vertical lines Lv1 of the guide mark mask K.

[0066] Furthermore, as shown in Figure 9C, it is preferable that the X-axis end of the imaged beam 411 overlaps with the vertical line Lv1 of the gauge mask K. However, it is not essential to overlap the beam 411 with the vertical line Lv1 of the gauge mask K. Also, it is preferable that the imaged beam 411 is a dashed beam having a discontinuous region in the middle where the light intensity is off, as shown in Figure 9C. By using a beam 411 with a discontinuous region in the middle, a clear edge can be formed in the middle of the beam 411. Therefore, by observing the intermediate edge, the position of the beam 411 relative to the gauge mask K can be measured with high accuracy. However, the imaged beam 411 may also be a linear beam with a uniform light intensity distribution in the X-axis direction.

[0067] Returning to Figure 8, after the beam position measurement process S22, the control unit 70 executes the guide mark mask imaging process S23. In the guide mark mask imaging process S23, the control unit 70 images the guide mark mask K with the alignment camera 50. Specifically, the first moving mechanism 23 moves the second stage 25 in the Y-axis direction, thereby moving the guide mark mask K in the Y-axis direction. The alignment camera 50 then images the guide mark mask K moving directly below it. As a result, the control unit 70 acquires the guide mark mask image F2.

[0068] After the guideline mask imaging process S23, the control unit 70 performs the camera position measurement process S24. In the camera position measurement process S24, the control unit 70 measures the relative position of the alignment camera 50 with respect to the guideline mask K based on the guideline mask image F2.

[0069] Figure 10 is a conceptual diagram illustrating the position measurement of the alignment camera 50 using the sampling moiré method. In the camera position measurement step S24, the control unit 70 executes the moiré sampling method described above using the guide mask image F2 acquired in the guide mask imaging step S23. Specifically, the control unit 70 performs sampling of equally spaced pixels in the guide mask image F2 multiple times (three or more times) while changing the starting pixel, thereby generating multiple downsampled images. Then, by interpolating each of the obtained downsampled images, multiple phase-shifted moiré fringe images are generated. Furthermore, the control unit 70 obtains the phase distribution by generating a phase distribution image from the multiple phase-shifted moiré fringe images.

[0070] In the example shown in Figure 10, the control unit 70 performs sampling every four pixels, shifting the starting point four times, and then performs interpolation. As a result, four moiré fringe images F21, F22, F23, and F24 are generated from one guideline mask image F2. As described in Japanese Patent Application Publication No. 2009-264852, in the case of sampling every four pixels, the phase θ of the moiré fringe is determined by the following equation.

[0071] θ = tan -1 (I3 - I1) / (I0 - I2) ... (1) (I0 to I3 are the brightness values ​​in the four moiré fringe images F21 to F24)

[0072] In the phase distribution φ calculated by the sampling moiré method, the phase -π (rad) corresponds to the position where the color changes significantly in the original image (in this case, from white to black). Therefore, by analyzing the obtained phase distribution φ, the position of, for example, the leftmost vertical line Lv1 out of the 10 vertical lines Lv1 can be identified. In other words, the relative position of the alignment camera 50 with respect to the guideline mask K can be measured.

[0073] As described above, by performing the beam position measurement step S22 and the camera position measurement step S24, the relative position of the alignment camera 50 with respect to the exposure head 41 can be measured according to the offset amount measurement step S3.

[0074] In the distortion measurement step S2, the alignment camera 50 captures an image of the alignment mark M on the substrate W and measures its position. Since the drive coordinate systems of the alignment camera 50 and the exposure head 41 are different, it is difficult to expose to the correct position even if the exposure data is corrected using the position information obtained from the alignment camera 50. In other words, in order to reflect the position of the substrate W measured by the alignment camera 50 in the correction of the exposure data 81, it is also necessary to reflect the relative position (offset amount) of the alignment camera 50 and the exposure head 41. For this reason, the offset amount is acquired in the offset amount measurement step S3.

[0075] <Correction of exposure data> Returning to Figure 6, after the offset amount measurement step S3, the control unit 70 corrects the exposure data 81 in the correction step S4. Specifically, the control unit 70 corrects the exposure data 81 so that exposure is performed at the appropriate position, based on the strain distribution in the substrate W measured in the strain measurement step S2 and the offset amount obtained in the offset amount measurement step S3. Subsequently, in the exposure step S5, the control unit 70 exposes the substrate W based on the corrected exposure data 81.

[0076] As described above, according to this embodiment, by applying the sampling moiré method when measuring the displacement of multiple alignment marks M, the displacement of the alignment marks M can be identified with an accuracy of approximately 1 / 100 to 1 / 1000 of the pixel pitch. Therefore, even when using a low-resolution alignment camera 50, the displacement of multiple alignment marks M can be calculated with high accuracy, and the distortion of the substrate W can be measured appropriately.

[0077] Furthermore, by using a low-resolution alignment camera 50, the size of the obtained image data can be reduced. This allows for a reduction in the transfer time from the alignment camera 50 to the control unit 70.

[0078] By using a lower resolution for the alignment camera 50, the installation cost can be kept down even if the imaging area of ​​the alignment camera 50 is increased.

[0079] In the offset amount measurement process S3, when calculating the offset amount, the positional displacement of the alignment camera 50 can be measured with high accuracy by applying the sampling moiré method to the image obtained by capturing the guide line mask K with the alignment camera 50. Therefore, the offset amount can be appropriately obtained.

[0080] It should be noted that applying the sampling moiré method in the offset amount measurement step S3 (more specifically, the camera position measurement step S24) is not mandatory. For example, the position of the alignment camera 50 relative to the guideline mask K may be measured by identifying the position of each vertical line Lv1 in the guideline mask image F2 using a known method such as pattern matching.

[0081] <2. Variant Example> Although embodiments have been described above, the present invention is not limited to those described above, and various modifications are possible.

[0082] For example, in the above embodiment, the alignment camera 50 is a line sensor. However, the alignment camera 50 may have an area sensor with a two-dimensional image sensor. In this case, the imaging time can be shortened by using an area sensor that can capture the entire substrate surface at once.

[0083] 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. [Explanation of symbols]

[0084] 1: Exposure device 25: Second stage (circuit board holding section) 41: Exposure head 50: Alignment Camera 60: Calibration Camera 73: Storage section 81: Exposure data 83: Design data 100: Exposure equipment 411: Beam FA1: Alignment image FB1: Design image K: Marking mask M: Alignment mark W: Circuit board

Claims

1. An exposure apparatus, Exposure head and A substrate holding section that holds a substrate on which multiple alignment marks are formed, An alignment camera that images the plurality of alignment marks on the substrate and acquires an alignment image, A storage unit that stores design data including information on the shape and position of the plurality of alignment marks, A calculation processing unit that calculates the displacement of the alignment marks by a sampling moiré method using the alignment image and the design image based on the design data, Equipped with, An exposure apparatus in which the alignment marks include a pattern having periodicity in at least one direction.

2. An exposure apparatus according to claim 1, The storage unit stores exposure data representing the exposure pattern of the exposure head. The arithmetic processing unit corrects the exposure data based on the calculated displacement of the plurality of alignment marks in the exposure apparatus.

3. An exposure apparatus according to claim 1 or claim 2, A marking mask is provided in the substrate holding portion and has periodicity in at least one direction. Furthermore, The arithmetic processing unit calculates the position of the alignment camera relative to the substrate holding portion by a sampling moiré method based on a marking image obtained by imaging the marking mask with the alignment camera, in an exposure apparatus.

4. An exposure apparatus according to claim 3, A calibration camera captures the beam emitted from the exposure head via the marking mask and acquires a beam image. Furthermore, The arithmetic processing unit calculates the position of the beam relative to the marking mask based on the beam image, in an exposure apparatus.

5. An exposure apparatus according to claim 1 or claim 2, The alignment camera is an exposure apparatus that includes a line sensor having an imaging area larger than the width of the substrate.

6. An exposure apparatus according to claim 1 or claim 2, The alignment camera is an exposure apparatus that includes an area sensor capable of capturing images of the entire substrate in a single image.

7. An exposure method, a) A step of holding a substrate on which multiple alignment marks have been formed in a substrate holding section, b) A step of capturing the plurality of alignment marks on the substrate with an alignment camera and acquiring an alignment image, c) A step of acquiring a design image based on design data including the shapes and positions of the plurality of alignment marks, d) A step of calculating the displacement of the multiple alignments by a sampling moiré method using the alignment image and the design image, Includes, An exposure method wherein the alignment marks include a pattern having periodicity in at least one direction.

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