JP6706164B2 - Alignment apparatus, exposure apparatus, and alignment method - Google Patents

Description

  The present invention relates to an alignment (positioning) device incorporated in an exposure device or the like, and more particularly to calibration of the position of an alignment camera.

  In an exposure apparatus or the like, in order to accurately align a work object such as a substrate (hereinafter referred to as a work), an alignment camera is used to image the alignment mark provided on the work and By comparing the position with the design (theoretical), the amount of displacement of the work position due to the conveyance accuracy or the like is detected. Then, the work position adjustment or the like is performed based on the detected displacement amount.

  Normally, the work size and the position of the alignment mark differ depending on the product type and the like, and the alignment camera is attached so as to be movable in the sub-scanning direction. Therefore, the visual field center position of the camera lens deviates from its original center position due to pitching, yawing, feed error, and the like of the camera drive mechanism. In order to calibrate this, a scale provided with a calibration mark indicating a reference position is attached to the stage, and an image of the calibration mark is picked up by an alignment camera to detect the positional deviation of the camera (for example, refer to Patent Document 1).

  On the other hand, in an exposure apparatus or the like, the exposure position may be displaced due to heat generation due to driving of the light source, driving of the transport stage, temperature change, or the like. In order to solve this, the temperature of the apparatus is detected by the temperature detector, and the exposure position is corrected based on the correlation between the apparatus temperature and the exposure position fluctuation amount obtained by the preliminary measurement (see Patent Document 2). In this case, the exposure position is corrected in consideration of the temperature-dependent positional deviation of the calibration scale.

JP, 2005-316461, A JP, 2014-197136, A

  The temperature change of the apparatus varies depending on its usage condition, accumulated usage time, etc., and it is difficult to derive the actual exposure position deviation from the correlation uniquely by pre-measurement. Even if the exposure position is corrected in consideration of the temperature information previously measured, it does not match the actual displacement amount, and the exposure position cannot be corrected accurately. Particularly, in an exposure apparatus or the like that requires micron order or sub-micron order, the difference between the estimated work position fluctuation and the actual work position fluctuation causes a position shift that cannot be overlooked.

  Therefore, it is required to calibrate the camera position accurately so that the position shift does not occur due to the influence of heat or the like, regardless of the usage status of the device.

  INDUSTRIAL APPLICABILITY The alignment apparatus of the present invention is applicable to an exposure apparatus and the like, and is attached to at least one alignment camera that images an alignment mark provided on a work and a stage unit that moves in a predetermined direction with respect to the apparatus main body portion. , A calibration scale in which a plurality of calibration marks imaged by the alignment camera are arranged.

  The work is mounted on the stage unit and is a processing target. For example, a substrate is mounted on the stage unit. Further, the apparatus main body portion represents a fixed base portion of an apparatus in which an alignment apparatus is incorporated, such as a mount/base on which the stage portion is mounted, or a support body that supports the exposure head and the optical system, and the stage portion is the apparatus. It moves relative to the body.

  The alignment apparatus of the present invention includes a position shift measuring unit capable of detecting the positional fluctuation of the calibration scale or the predetermined calibration mark with respect to the apparatus main body portion when the stage unit is positioned at the predetermined position. The alignment device can correct the amount of positional deviation of the calibration scale based on the amount of positional fluctuation detected by the positional deviation measuring unit.

  Unlike the alignment camera, which cannot detect the position change of the calibration mark due to its own moving mechanism, the position deviation measuring unit that does not cause the position change at least in the stage moving direction is the stage unit When a member such as a table expands or contracts due to the influence of heat of the table, it is possible to detect the positional fluctuation of the calibration scale or the calibration mark.

  That is, the position shift measuring unit is configured so as not to change its position with respect to the coordinate system defined for the apparatus main body part, and the position of the calibration scale or the calibration may be changed depending on the coordinate system used when correcting the position of the alignment camera by the calibration scale. It is possible to detect the position variation of the mark. For example, the positional fluctuation of the calibration scale or the calibration mark when the stage part is positioned at the position where the calibration mark is measured by the alignment camera may be detected.

  As the configuration of the position shift measuring unit, for example, an image capturing unit (camera or the like) different from the alignment camera can be used. Considering that the position shift of the alignment camera is caused by the moving mechanism of the alignment camera, the position shift measuring unit is fixed to the main body of the apparatus at least in the moving direction of the alignment camera (for example, the sub-scanning direction) and provided on the stage unit. That is, it can be configured by an image pickup unit capable of picking up an image of the reference mark whose position is changed with respect to the apparatus main body portion due to the influence of heat of the stage portion.

  Considering that the expansion and contraction of the members such as the stage unit differs depending on the location, it is desirable to be able to detect the position variation in the state in which the alignment mark is imaged by the alignment camera. Therefore, it is preferable to provide the reference mark along the arrangement line of the plurality of calibration marks.

  Various configurations can be adopted as the arrangement configuration of the reference marks. For example, a reference member provided with a reference mark can be attached to the stage unit. In this case, by disposing the reference member near the calibration scale, the positional variation amount of the reference mark can be reliably matched with the calibration scale or the positional variation amount of the calibration mark.

  On the other hand, instead of providing a dedicated member for the reference mark, the reference mark may be included in the calibration scale. For example, in consideration of providing the imaging unit outside the movement range of the alignment camera, it is possible to provide the reference marks next to both ends of the plurality of constituent marks.

  As the fixing portion of the image pickup unit with respect to the apparatus main body portion, it is possible to fix the image pickup unit to the camera base portion that supports the alignment camera. For example, when the alignment camera and the camera forming the imaging unit have the same product and the same optical characteristics, they may be installed at the same height as the alignment camera and the reference mark may be set at the same height as the calibration mark.

  When the expansion and contraction of the member due to the heat of the stage portion differs depending on the location, it is preferable to align the installation location of the calibration scale and the installation location of the reference mark. For example, the calibration scale and the reference mark can be provided on the stage on the table on which the work is mounted, or on a unique calibration scale support table provided near the table.

  In the alignment method according to another aspect of the present invention, an alignment mark provided on the work is imaged by an alignment camera, and a plurality of calibration scales provided on a stage unit that moves in a predetermined direction with respect to the apparatus main body unit are provided. A method of capturing an image of a calibration mark by an alignment camera and an image of a reference mark different from the calibration mark provided on the stage part by a camera different from the alignment camera fixed to the main body of the apparatus. It is possible to correct the positional deviation amount of the calibration mark from the deviation amount.

  According to the present invention, appropriate alignment adjustment can be performed without being affected by heat or the like.

It is a schematic side view of the exposure apparatus which is the present embodiment. It is a schematic plan view seen from above the exposure apparatus. It is the figure which showed the calibration scale and reference plate attached to a table. It is a block diagram of an exposure apparatus. 7 is a flowchart showing a camera position calibration process executed by a control unit. It is a figure showing the modification of the stage part of an exposure device.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic side view of an exposure apparatus according to this embodiment. FIG. 2 is a schematic plan view seen from above the exposure apparatus.

  The exposure apparatus 10 includes a gantry 15 and a support 40 installed on the upper surface 15S of the gantry 15. The support 40 is composed of a rectangular support base 42 and leg portions 43A, 43B, 44A, 44B provided at the four corners thereof, and the leg portions 43A, 43B, 44A, 44B are fixed to the mount 15. . The exposure head 20 and the light source unit 30 are provided on the upper surface 42S of the support table 42.

  Guide rails 60A and 60B are arranged on the upper surface 15S of the pedestal 15 so as to be parallel to each other at predetermined intervals along the longitudinal direction of the pedestal 15, and the leg portions 43A and 43B and the legs from one end of the support table 42. It extends between the portions 44A and 44B to the other end. A stage unit 50 that is movable along the guide rails 60A and 60B is installed on the guide rails 60A and 60B.

  The stage unit 50 includes a table 52 on which a substrate (work) W is mounted, and a stage moving mechanism 55 that supports the table 52 from below and moves the table 52 in the X, Y, and Z directions. The stage moving mechanism 55 includes an X stage mechanism 56 that moves the stage unit 50 along the guide rails 60A and 60B, and a fine movement stage mechanism 54 that moves the stage unit 50 in the Y direction and rotates about the Z axis.

  An XY coordinate system based on the device is defined on the upper surface 15S of the gantry 15, and the Z direction is defined as the vertical (vertical) direction of the XY coordinate system. The guide rails 60A and 60B are arranged along the X direction, and the linear scale 58 for detecting the X direction position of the stage unit 50 is installed on the pedestal 15. The rectangular table 52 is provided on the stage unit 50 such that its longitudinal end face 52L and its end face 52T perpendicular to it are parallel to the X and Y directions, respectively.

  A plate (hereinafter, referred to as a camera base) 45 extending in the Y direction is fixed to the side surfaces of the support body 40 and the leg portions 44A and 44B on the leg portions 44A and 44B side of the support body 40, that is, on the center side. A guide mechanism 46 for moving the alignment camera 80 in the Y direction is attached to the surface of the guide plate 45 opposite to the support 40. The guide mechanism 46 is composed of, for example, a ball screw mechanism or the like, and moves the alignment camera 80 by a camera driving unit equipped with a motor or the like not shown here. Here, the alignment camera 80 is composed of two alignment cameras 80A and 80B that are separated by a predetermined distance.

  As shown in FIG. 2, a plurality of alignment marks (here, nine) AM are regularly arranged at predetermined intervals on the substrate W placed at a predetermined position on the table 52. The alignment camera 80 can image each alignment mark AM by moving the stage unit 50 in the X direction and moving the alignment camera 80 in the Y direction.

  A scale (hereinafter, referred to as a calibration scale) 62 for camera position calibration is installed on the table 52 along one end surface 52T parallel to the camera base 45. The calibration scale 62 is provided with a plurality of (here, 10) calibration marks CM arranged along the table end surface 52T, that is, along the Y direction. The alignment camera 80 can take an image of each calibration mark CM by moving the stage unit 50 and the alignment camera 80.

  In addition to the calibration scale 62, a rectangular plate (hereinafter referred to as a reference plate) 72 having one mark (hereinafter referred to as a reference mark) SM formed thereon is attached to the table 52. The reference mark SM is on the same line as the calibration marks CM of the calibration scale 62 are lined up. A camera (hereinafter referred to as a reference camera) 70 different from the alignment camera 80 is fixed to the camera base 45 at the same height as the alignment camera 80.

  The reference camera 70 is held by a holding unit 71 attached to the camera base 46 in a movement range of the alignment camera 80 along the Y direction, that is, a position retracted from the imaging range. It is possible to image the mark SM. Further, the position of the reference camera 70 in the X direction with respect to the camera base 46 is fixed at the same position as the alignment camera 80. That is, the reference camera 70 is attached to the camera base 46 via the holding portion 71 so that the center of the visual field of the alignment camera 80 and the center of the visual field of the reference camera 70 both have the same position coordinate in the X direction. .

  FIG. 3 is a view showing a calibration scale and a reference plate attached to the table.

  The calibration scale 62 is made of glass, and has a chromium film having a calibration mark CM drawn on the surface thereof. The pitch at which the calibration marks CM are arranged is determined according to the field of view size of the alignment camera 80 and the like. The calibration mark CM is sized and shaped so that the mark position coordinates can be accurately obtained when the image is taken by the alignment camera 80. Here, it is formed in a cross shape so that the angle error can be detected.

  The calibration scale 62 is installed in a recess provided on the table end surface 52T side, and its height is determined so that the surface of the calibration scale 62 is flush with the surface of the substrate W (see FIG. 2). . Like the calibration scale 62, the reference plate 72 is made of glass, and a cross-shaped reference mark SM having the same shape and size as the calibration mark CM is formed on the surface thereof. The reference plate 72 is attached to the table 52 so that the reference mark SM is located on the same line as the calibration mark CM. The surface of the reference plate 72 is also flush with the surface of the substrate W.

  Here, the reference camera 70 is made of the same type of product as the alignment camera 80, and the imaging characteristics such as optical magnification and field size and the appearance characteristics such as size are the same as those of the alignment camera 80. As described above, since the mounting position of the alignment camera 80 and the mounting position of the reference camera 70 are the same, the image images of the calibration mark CM and the reference mark SM obtained by imaging are images of the same size.

  FIG. 4 is a block diagram of the exposure apparatus.

  The control unit 25 controls the overall operation of the exposure apparatus, such as the exposure operation of the exposure apparatus 10, alignment adjustment, and illumination. When the light source 32 is turned on by the light source controller 31, the illumination light enters the DMD (Digital Micro-mirror Device) 24 via the optical system 23.

  The exposure control unit 34 converts the pattern data (vector data) transmitted from the workstation into raster data, and transmits the raster data (exposure data) to the DMD drive unit 22. The DMD drive unit 22 controls ON/OFF of each micromirror of the DMD 24 based on the raster data so as to project the pattern light according to the exposure position. The light reflected by the DMD 24 is imaged as pattern light on the surface of the substrate W by the projection optical system 25.

  A stage drive unit (moving mechanism) 55 including a motor drives the fine movement stage mechanism 54 and the X stage mechanism 56 shown in FIG. 1 to move the stage unit 50, that is, the table 52 in the X and Y directions. The position detector 59 including the linear scale 58 (see FIG. 1) detects the position coordinates of the table 52 with respect to the pedestal 15 (that is, the exposure apparatus main body which is one structure including the support 40).

  The camera drive unit 82 drives and controls the alignment camera 80 and moves the alignment camera 80 according to the alignment line of the alignment marks AM of the substrate W when performing alignment adjustment. As shown in FIG. 3, on the substrate W, three alignment marks AM are formed along both ends and central lines a1 to a3.

  When performing the alignment adjustment, the alignment cameras 80A and 80B move along the Y direction so as to be located on the lines a1 to a3. The alignment mark AM is imaged by moving the table 52 in the X direction so that the alignment mark AM is located below the alignment camera 80.

  The image processing unit 83 detects the position of the alignment mark AM based on the image pickup signals output from the alignment cameras 80A and 80B. Specifically, the deviation of the alignment mark center position from the center of the visual field of the alignment cameras 80A80B is detected. The alignment control unit 35 controls the exposure control unit 34 based on the positional information sent, and corrects the raster data so as to compensate the substrate deformation and the like.

  Further, when the alignment camera 80 images the calibration mark CM, the image processing unit 83 detects the amount of displacement of the calibration mark CM from the center of the visual field. The camera calibration unit 37 calculates a correction amount based on the camera position shift amount.

  Further, the image processing unit 83 can detect the amount of positional deviation of the reference mark SM from the center of the visual field based on the image pickup signal from the reference camera 70. The camera calibration unit 37 calculates a correction amount (hereinafter referred to as a scale correction amount) calculated based on the positional deviation of the calibration mark CM. The alignment control unit 35 corrects the raster data based on the correction amount including the scale correction amount.

  Here, the position variation of the calibration scale 62, that is, the calibration mark CM with respect to the apparatus main body portion, that is, the gantry 15 and the support 40 will be described.

  The alignment cameras 80A and 80B are attached to the guide mechanism 46 so as to be movable along the Y direction, and errors in attachment and assembly have occurred, and the guide mechanism 46 causes the alignment cameras 80A and 80B to reciprocate. The position of the visual field center deviates from the designed position due to the position error of the guide mechanism 46, the change of the camera axis angle, and the like.

  In order to correct the shift of the center position of the visual field, that is, the shift of the alignment cameras 80A and 80B, the position of the calibration mark CM is measured. A deviation amount (that is, an error in the positional relationship between the alignment camera 80 and the support base 42 that fixes the exposure head 20) is obtained. The measurement of the amount of displacement of the alignment camera 80 is based on the position of the calibration scale 62. That is, it is premised that the position coordinates of the calibration scale 62 with respect to the pedestal 15 and the support 42 that is a part of the support 40 do not change.

  However, the positional deviation of the calibration scale 62 (calibration mark CM) itself occurs depending on the usage status of the exposure apparatus 10. When the stage unit 50 is moved back and forth for a long time during use of the exposure apparatus 10, heat is generated in the fine movement stage mechanism 54 of the stage unit 50, the table 52, etc. due to the influence of heat generation by the motor of the X stage mechanism 56. Expansion and deformation occur. The heat of the light source unit 30 and the exposure head 20 generated during the exposure operation may also affect the stage unit 50.

  When the table 52 thermally expands along the X direction due to the influence of such heat, the position of the calibration scale 62 changes. In particular, since the expansion change appears more greatly on the end surface 52T of the table 52 than on the central portion thereof, the position of the calibration scale 62 is likely to change.

  Therefore, even if the position with respect to the gantry 15 is detected by the linear scale 58, in the vicinity of the end surface 52T of the table 52 which is distant from the X stage mechanism 56 in the height direction and the X direction, there is a position variation that cannot be ignored in alignment adjustment, that is, pattern accuracy. May have occurred.

  Even if the above-mentioned correction of the camera position shift by the calibration scale 62 is performed in this state, the correction amount is calculated in the state in which the position error of the calibration scale 62 is included, so that the alignment adjustment cannot be performed correctly. On the other hand, since the alignment camera 80 has a camera displacement, the alignment camera 80 having an error cannot detect the displacement of the calibration scale 62.

  Therefore, in the present embodiment, the reference mark 70 of the reference plate 72 installed near the calibration scale 62 is imaged by the reference camera 70 independently provided for measuring the position variation of the calibration scale 62 (calibration mark CM). .. Since the reference mark SM is formed on the same line as the calibration mark CM of the calibration scale 62 along the Y direction, it can be considered that the same positional variation as that of the calibration scale 62 (calibration mark CM) occurs. ..

  Therefore, the position coordinate of the reference mark SM to be measured is compared with the position coordinate of the design (ideal) reference mark SM to obtain the position shift amount, and this is added to the camera position shift correction amount (subtraction). Therefore, it becomes possible to perform accurate alignment adjustment.

  FIG. 5 is a flowchart showing a camera position calibration process executed by the control unit. The camera position calibration process can be executed for each lot or for each substrate. For example, when the number of alignment mark rows is larger than the number of alignment cameras, it is necessary to move the alignment cameras in the Y-axis direction, so it is preferable to perform the process for each substrate.

  First, the alignment camera 80 is moved to the Y coordinate of the alignment mark AM. Here, the positions are aligned with the lines a1 to a3 shown in FIG. Then, the table 52 is moved and controlled so that the calibration scale 62 is located at the designed visual field center position of the alignment camera 80 (S101, S102). The position of the table 52 (stage unit 50) corresponds to the position where the center position of the visual field of the reference camera 70 coincides with the theoretical center position of the reference mark SM.

  Next, in the pre-stage of the camera calibration process, the reference mark SM is imaged by the reference camera 70 (S103), and the amount of displacement of the reference mark SM from the visual field center position is calculated (S104). Here, the positional deviation in the X and Y directions and the rotation angle (θ) are calculated as the positional deviation amount. The center position of the reference camera 70 has the same X coordinate as the center position of the field of view of the alignment camera 80, that is, the center position of the field of view is on the same line along the Y direction. It can be regarded as the amount of positional deviation of the calibration mark CM).

  Then, the alignment camera 80 measures the coordinates of the calibration mark CM in the field of view (S105), and a value obtained by subtracting the displacement amount of the reference mark SM from the measured camera displacement amount is calculated as a correction amount for camera calibration ( S106). When the camera calibration process is completed, the position of the alignment mark AM on the substrate W is measured and the alignment adjustment is performed.

  As described above, according to the present embodiment, in the exposure apparatus 10 in which the alignment can be adjusted by the alignment camera 80, the calibration scale 62 in which the plurality of calibration marks CM are arranged is attached to the end of the table 52, and the reference plate provided with the reference marks SM is provided. The 72 is attached to the table 52 so that the calibration mark CM and the reference mark SM are on the same line. Then, the reference camera 70 having the center of the visual field of the same X-direction position coordinate with respect to the alignment camera 80 is fixed to the camera base 45. During the camera calibration process, the camera position shift calculated by the image pickup of the calibration mark CM by the alignment camera 80 based on the position shift amount of the calibration scale 62 (reference mark SM) calculated by the reference camera 70 taking the reference mark SM. Correct the amount.

  By arranging the installation locations of the reference camera 70 and the reference plate 72 in the X direction in accordance with the installation locations of the alignment camera 80 and the calibration scale 62, the calibration scale 62 due to the influence of heat or the like can be formed by a simple configuration and simple processing steps. The position shift of the calibration mark CM can be detected. In particular, by disposing the reference plate 72 near the calibration scale 62, it is possible to detect an accurate position change.

  Note that the alignment camera position may be finely adjusted instead of calculating the camera position shift amount. Further, the amount of positional deviation of the reference mark SM may be subtracted from the amount of alignment correction during alignment adjustment, or the raster data may be corrected in consideration of the amount of positional deviation of the reference mark SM.

  Instead of separately providing a reference plate, the calibration scale may include a reference mark. For example, the calibration scale may be extended in the longitudinal direction and the reference mark may be provided at the end.

  Regarding the misregistration detection, the correction amount with respect to the camera misregistration amount may be calculated only in the X direction in which the position variation amount of the calibration scale is the largest. Further, if the position reproducibility in the X direction is secured, a supporting member for the reference camera may be separately installed and moved to retract the reference camera in the X or Y direction. Further, the positional deviation amount of the calibration scale may be detected by imaging the four corner positions of the calibration scale without providing the reference mark.

  With respect to the calibration scale and the reference plate, the calibration scale and the reference plate may not be attached to the table but may be fixed to another portion of the stage unit 50 to be independent of the table. FIG. 6 is a diagram showing a modified example of the stage unit of the exposure apparatus. A calibration scale 62 and a reference plate 72 are attached to the upper surface of a support base 92 attached to the X stage mechanism 56. By mounting the stage unit 50 closer to the end side, it becomes easier to detect the position variation.

  The installation location of the reference camera and the installation location of the reference plate are not limited to those in the above-described embodiment. Moreover, you may image with a camera etc. which are not the same kind as an alignment camera. Furthermore, the reference plate and the imaging unit may not be provided. For example, a light emitting unit such as a laser is radiated along the X direction, reflected vertically by a mirror, and light is received by a photosensor provided in the reflecting direction. The position shift amount may be calculated.

  In the present embodiment, the alignment apparatus is configured in the exposure apparatus, but it is also applicable to an alignment apparatus incorporated in an apparatus for performing work on a workpiece, such as a board inspection apparatus, a board drilling apparatus, and a component mounting apparatus. ..

10 exposure apparatus 50 stage section 52 table 62 calibration scale 70 reference camera (imaging section, scale position measuring section)
72 Reference plate (reference member)

Claims (8)

At least one alignment camera for capturing an image of an alignment mark provided on the work;
A calibration scale that is attached to a stage unit that moves in a predetermined direction with respect to the apparatus main body and that has a plurality of calibration marks arranged by the alignment camera,
A position shift measuring unit capable of detecting a position change of the calibration scale or a predetermined calibration mark with respect to the apparatus main body portion when the stage unit is positioned at a predetermined position ,
An alignment apparatus, wherein the position shift measuring section includes an image capturing section that is fixed to at least the apparatus main body portion in the alignment camera moving direction and is capable of capturing an image of a reference mark provided on the stage section . The alignment apparatus according to claim 1 , wherein the reference mark is provided along an array line of the plurality of calibration marks. The displacement measuring section has a reference member provided with the reference mark,
The reference member, the alignment device according to claim 1 or 2, characterized in that it is arranged beside the calibration scale. Said reference mark, the alignment device according to claim 1 or 2, characterized in that included in the calibration scale. The imaging unit, an alignment apparatus according to any one of claims 1 to 4, characterized in that it is fixed to the camera base section for supporting the alignment camera. Any the calibration scale and the reference mark, at the stage portion, of claims 1 to 5, characterized in that provided on the calibration scale support table provided near the table mounting the workpiece or the table, The alignment device according to claim 1. Based on the position variation amount detected by the position shift measuring section, the alignment device according to any one of claims 1 to 6, characterized in that to correct the positional deviation amount of the calibration scale. An exposure apparatus comprising the alignment apparatus according to any one of claims 1 to 7 .

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