JP6210525B1 - Alignment method and alignment apparatus - Google Patents

Abstract

An alignment method and an alignment apparatus are provided that can determine the position of a wafer when the wafer is supported on a rotating table with high accuracy and at low cost. In an alignment method according to the present invention, illumination light that illuminates an inner surface 49a of a notch 49 formed on a side surface 48 of a wafer 40 at an end 45 of the wafer 40 is used as reflected light reflected by the inner surface 49a. Then, the wafer 40 is positioned. Further, the wafer 40 is positioned by rotating the wafer 40 based on the position of the end 45 where the image of the condensed image obtained by collecting the reflected light by the inner surface 49a is captured. [Selection] Figure 1

Description

  The present invention relates to an alignment method and an alignment apparatus, for example, an alignment method and an alignment apparatus for positioning a wafer when the wafer is supported on a rotating table.

  When inspecting a defect in a wafer, it is indispensable to accurately align the wafer on a table in order to specify the position of the defect. Therefore, the wafer is positioned on the table based on the notch formed on the wafer (notch alignment).

  For example, Patent Documents 1 to 4 disclose performing notch alignment on a wafer supported on a rotating table.

JP 2010-014676 A Japanese Patent Laying-Open No. 2015-040698 JP 2002-134575 A International Publication No. 2008/1223459

  Patent Document 1 describes that a notch of a wafer is detected and a notch alignment of the wafer is performed by a transmission sensor provided so as to sandwich an end portion of the wafer. In the method described in Patent Document 1, it is necessary to prepare an additional device such as a sensor or a camera for the notch alignment.

  Patent Document 2 describes that a plurality of points on a wafer are imaged from above the wafer to obtain an alignment image, and the notch alignment of the wafer after pattern formation is performed using the alignment image. In the method described in Patent Document 2, in order to capture an alignment image, it is necessary to prepare a camera facing the wafer and an image processing apparatus for comparison with the alignment image.

  Patent Documents 3 and 4 describe a wafer edge inspection apparatus. In the apparatuses described in Patent Documents 3 and 4, the inspection is performed on the assumption that the center of the wafer positioned by the notch alignment is coincident with the rotation center of the stage. The amount of eccentricity between the center of rotation is not taken into account, and the wafer may not be positioned accurately.

  As described above, the conventional notch alignment of a wafer is generally performed using a camera or the like directly facing the wafer, and it is necessary to prepare a sensor, a camera, and a peripheral processing system for that purpose. In addition, the amount of eccentricity between the center of the wafer and the center of rotation of the stage is not considered, and there is a possibility that the wafer is not accurately positioned.

  The present invention has been made to solve such a problem, and provides an alignment method and an alignment apparatus that can accurately and inexpensively position a wafer when the wafer is supported on a rotating table. The purpose is to provide.

  In the alignment method according to the present invention, the illumination light that illuminates the inner surface of the notch formed at the edge of the wafer and sandwiched between the side surfaces of the wafer in a direction along the periphery of the wafer is The wafer is positioned using the reflected light reflected by the inner surface. With such a configuration, the wafer can be positioned accurately and at low cost.

  Further, the alignment method includes positioning the wafer by rotating the wafer based on the position of the end where the image of the linear image in which the reflected light is linearly collected by the inner surface is captured. Do. With such a configuration, the rotational deviation of the wafer can be accurately corrected.

  Further, in the alignment method, the wafer is supported on a table having a rotation axis, the table is rotated around the rotation axis, the end portion is illuminated with the illumination light, and the illumination light is transmitted by the end portion. The reflected light is collected by an objective lens, and the reflected light collected by the objective lens is detected to capture an image of the end, and the image is focused by an autofocus optical system. The position of the objective lens in the optical axis direction is derived, the objective lens is moved to the position guided by the autofocus optical system, and predetermined additional data is added to the image data. Then, based on the position of the objective lens in the optical axis direction when the wafer is rotated once, the amount of eccentricity between the rotation axis and the wafer is calculated, By moving the table based on the core weight, for positioning of the wafer. With such a configuration, the amount of eccentricity of the wafer can be corrected accurately and at low cost.

  The additional data includes the position of the notch when the image is captured, the position of the end when the image is captured, and the position of the objective lens in the optical axis direction. With such a configuration, it is possible to associate the rotational deviation and the eccentricity amount with the position of the end portion of the wafer.

  Further, the end portion is imaged along the rotation axis direction by a plurality of pixels arranged in one direction. With such a configuration, the amount of eccentricity of the wafer can be accurately measured.

  In the alignment apparatus according to the present invention, the illumination light that illuminates the inner surface of the notch formed at the edge of the wafer and sandwiched between the side surfaces of the wafer in the direction along the periphery of the wafer is The wafer is positioned using the reflected light reflected by the inner surface. With such a configuration, the wafer can be positioned accurately and at low cost.

  In addition, the alignment apparatus positions the wafer by rotating the wafer based on the position of the end where the image of the linear image in which the reflected light is linearly collected by the inner surface is captured. Do. With such a configuration, the rotational deviation of the wafer can be accurately corrected.

  Furthermore, the alignment apparatus has a rotation axis, generates a table that supports the wafer, a first drive unit that rotates the table around the rotation axis, and the illumination light that illuminates the edge of the wafer. A light source, an objective lens that collects the reflected light reflected by the end portion of the illumination light, a second drive unit that moves the objective lens in the optical axis direction of the objective lens, and the objective lens. An imaging unit that captures an image of the end portion by detecting the reflected light that is emitted; an autofocus optical system that guides a position of the objective lens in the optical axis direction where the image is focused in the imaging unit; A moving unit that moves the table; and a control unit that controls the first driving unit and the second driving unit. The control unit is guided by the autofocus optical system. Based on the position of the objective lens in the optical axis direction when the objective lens is moved to the position, predetermined additional data is added to the image data, and the wafer is rotated once, the rotation axis The wafer is positioned by calculating the amount of eccentricity between the wafer and the wafer and moving the table based on the amount of eccentricity. With such a configuration, the amount of eccentricity of the wafer can be corrected accurately and at low cost.

  The additional data includes the position of the notch when the image is captured, the position of the end when the image is captured, and the position of the objective lens in the optical axis direction. With such a configuration, it is possible to associate the rotational deviation and the eccentricity amount with the position of the end portion of the wafer.

  The imaging unit includes a plurality of pixels arranged in one direction, and the plurality of pixels images the end portion along the rotation axis direction. With such a configuration, the amount of eccentricity of the wafer can be accurately measured.

  According to the present invention, there is provided an alignment method and an alignment apparatus capable of positioning a wafer with high accuracy and low cost when the wafer is supported on a rotating table.

It is the figure which illustrated the outline | summary of the alignment apparatus which concerns on Embodiment 1. FIG. It is the top view which illustrated the shape of the notch of a wafer. FIG. 3 is a flowchart illustrating the alignment method according to the first embodiment. It is the figure which illustrated the notch of the wafer imaged in the alignment apparatus which concerns on Embodiment 1. FIG. 4 is a graph illustrating the luminance change of a notch imaged in the alignment apparatus according to the first embodiment, where the horizontal axis indicates the position of the end portion in the circumferential direction of the wafer, and the vertical axis indicates the luminance. In the alignment apparatus which concerns on Embodiment 1, it is the figure which illustrated the illumination light from an objective lens to a notch. In the alignment apparatus which concerns on Embodiment 1, it is the figure which illustrated the illumination light and reflected light in case the optical axis of an objective lens passes the center part of a notch. In the alignment apparatus which concerns on Embodiment 1, it is the figure which illustrated the illumination light and reflected light when the optical axis of an objective lens has shifted | deviated from the center part of a notch. FIG. 6 is a diagram illustrating a configuration of an alignment apparatus according to a second embodiment. FIG. 6 is a configuration diagram illustrating an alignment apparatus according to a second embodiment. FIG. 5 is a configuration diagram illustrating an optical system according to a second embodiment. FIG. 6 is a flowchart illustrating an alignment method according to a second embodiment. 6 is a graph illustrating the amount of eccentricity measured by the alignment method according to the second embodiment, in which the horizontal axis is the position of the end indicated by the rotation angle (the position corresponding to the angle θ), and the vertical axis is on the optical axis. This is the amount of eccentricity indicated by the position of the objective lens. 4 is a graph illustrating the amount of eccentricity corrected by the alignment method according to the second embodiment, where the horizontal axis is the position of the end indicated by the rotation angle, and the vertical axis is the amount of eccentricity indicated by the position of the objective lens on the optical axis. It is.

  Hereinafter, a specific configuration of the present embodiment will be described with reference to the drawings. The following description shows preferred embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments. In the following description, the same reference numerals indicate substantially the same contents.

(Embodiment 1)
An alignment apparatus and an alignment method according to Embodiment 1 will be described. FIG. 1 is a diagram illustrating an outline of the alignment apparatus according to the first embodiment. As shown in FIG. 1, the alignment apparatus 1 according to this embodiment includes a table 10 and an optical system 20. The alignment apparatus 1 is an apparatus that positions the wafer 40 supported on the table 10.

  The table 10 has an upper surface and supports the wafer 40 on the upper surface. For example, the wafer 40 is supported by adsorbing the wafer 40 on the upper surface. The table 10 has a rotation shaft 14 in a direction perpendicular to the upper surface. The table 10 rotates around the rotation shaft 14. As a result, the wafer 40 supported on the upper surface also rotates about the rotation shaft 14. A direction passing through the rotation shaft 14 and orthogonal to the rotation shaft 14 is referred to as a radial direction. A direction along the periphery of the wafer 40 is referred to as a circumferential direction.

  The wafer 40 is a disk-shaped thin member, for example, a silicon wafer. The wafer 40 has a front surface 41 and a back surface 42. The back surface 42 is in contact with the top surface of the table 10. The wafer 40 has a central axis 44 that passes through the center 43 of the wafer 40 and is orthogonal to the front surface 41 and the back surface 42. In addition, the case where the deviation (eccentricity) between the rotating shaft 14 and the central shaft 44 is taken into account will be described in a second embodiment to be described later. The wafer 40 may be a bare wafer. In addition, an electronic circuit pattern such as LSI (Large-Scale Integration) may be formed on the surface of the wafer 40.

  The side surface 48 of the wafer 40 is formed between the periphery of the front surface 41 and the periphery of the back surface 42. The side surface 48 of the wafer 40 includes a surface parallel to the central axis 44. A bevel surface may be formed at the corner formed by the surface 41 and the side surface 48 of the wafer 40. Further, a bevel surface may be formed at a corner formed by the back surface 42 and the side surface 48 of the wafer 40.

  A notch 49 is formed in a part of the end portion 45 of the wafer 40. The notch 49 is formed on the side surface 48 of the wafer 40. The notch 49 is formed from the front surface 41 to the back surface 42 of the wafer 40. The inner surface 49 a of the notch 49 is connected to the surface 41 of the wafer 40 above the central axis 44. The inner surface 49 a of the notch 49 is connected to the rear surface 42 of the wafer 40 below the central axis 44. The inner surface 49 a of the notch 49 is connected to the side surface 48 of the wafer 40 in the circumferential direction of the wafer 40. Therefore, the inner surface 49a of the notch 49 is sandwiched between the side surfaces 48 of the wafer 40 in the circumferential direction of the wafer. A bevel surface may be formed between the inner surface 49 a of the notch 49 and the front surface 41, the back surface 42, and the side surface 48 of the wafer 40.

  FIG. 2 is a top view illustrating the shape of the notch 49 of the wafer 40. FIG. 2 illustrates only a portion of the surface 41 of the wafer 40 where the notch 49 is formed. As shown in FIG. 2, the notch 49 formed in the end portion 45 of the wafer 40 has a curved shape. The central portion in the circumferential direction of the notch 49 is the deepest portion in the radial direction of the notch 49. The length D between the deepest part of the notch 49 and the end part 45 of the wafer 40 is, for example, about 1.2 mm, and 1 + 0.25 mm in terms of specifications. The angle U between the inner surfaces 49a on both sides across the center of the notch 49, that is, the deepest part of the notch 49 is, for example, 90 °. The notch 49 is symmetric with respect to the center. In order to align the wafers 40, a notch 49 is formed in such a shape that a pin P having a diameter of 3 mm can be inserted. For example, the inner surface 49a of the notch 49 has a shape similar to the inner surface of the cylindrical side wall.

  As shown in FIG. 1, the optical system 20 includes a light source 50, an objective lens 60, and an imaging unit 70. The optical system 20 includes optical members such as a plurality of lenses and a half mirror.

  The light source 50 generates illumination light that illuminates the end portion 45 of the wafer 40. The light source 50 is, for example, a xenon lamp. The light source 50 is not limited to a xenon lamp. The illumination light generated by the light source 50 illuminates the end 45 of the wafer 40 including the inner surface 49 a of the notch 49. The objective lens 60 collects the reflected light that is reflected by the end portion 45 of the wafer 40 and the inner surface 49 a of the notch 49. The optical axis 64 of the objective lens 60 is a radial direction orthogonal to the rotation axis 14 of the table 10.

  The imaging unit 70 captures an image of the end 45 of the wafer 40 by detecting the reflected light collected by the objective lens 60. The imaging unit 70 is an image sensor in an imaging camera, for example.

  The alignment apparatus 1 positions the wafer 40 by using the reflected light reflected by the inner surface 49 a of the notch 49, which is the illumination light that illuminates the inner surface 49 a of the notch 49 formed at the end 45 of the wafer 40.

  For example, the illumination light illuminates the inner surface 49 a of the notch 49 from the side of the wafer 40 orthogonal to the central axis 44 of the wafer 40. The inner surface 49a of the notch 49 has a shape similar to the inner surface of the cylindrical side wall. Therefore, the inner surface 49a of the notch 49 has a function of condensing illumination light as a cylindrical mirror. The inner surface 49a of the notch 49 is a mirror surface. Even when a pattern is formed on the surface of the wafer 40, the inner surface 49a of the wafer 40 is often a mirror surface.

Next, an alignment method for the wafer 40 will be described.
FIG. 3 is a flowchart illustrating the alignment method according to the first embodiment. As shown in step S <b> 11 of FIG. 3, first, the wafer 40 is supported on the table 10 having the rotation shaft 14. For example, the wafer 40 is sucked onto the upper surface of the table 10 and supported.

  Next, as shown in step S <b> 12 of FIG. 3, the table 10 that supports the wafer 40 is rotated about the rotation shaft 14. And the edge part 45 of the wafer 40 is illuminated with illumination light. At this time, as shown in step S13, the inner surface 49a of the notch 49 is also illuminated with illumination light.

  Next, the reflected light reflected by the end portion 45 of the wafer 40 is condensed by the objective lens 60. At this time, as shown in step S <b> 14 of FIG. 3, the objective lens 60 condenses the reflected light that is reflected by the inner surface 49 a of the notch 49. The inner surface 49a of the notch 49 has a function of condensing illumination light as a cylindrical mirror. Therefore, the reflected light is collected linearly by the inner surface 49 a of the notch 49. The objective lens 60 collects the reflected light collected in a linear shape.

  Next, as shown in step S15 of FIG. 3, an image of a linear image in which reflected light is linearly collected by the inner surface 49a of the notch 49 is captured.

  FIG. 4 is a diagram illustrating a notch 49 of the wafer 40 imaged by the alignment apparatus 1 according to the first embodiment. As shown in FIG. 4, when imaging is performed using the reflected light reflected by the end portion 45 of the wafer 40, a high-luminance image extending along the end portion 45 in the circumferential direction of the wafer 40 and the center portion of the notch 49. An image including a linear image condensed in a thin line shape in the vertical direction is captured.

  FIG. 5 is a graph illustrating the change in luminance of the notch 49 imaged in the alignment apparatus 1 according to the first embodiment. The horizontal axis indicates the position of the end portion in the circumferential direction of the wafer 40, and the vertical axis indicates the luminance. Indicates. As shown in FIG. 5, the luminance of the end portion 45 other than the notch 49 of the wafer 40 has a substantially constant value. On the other hand, in the portion of the inner surface 49a of the notch 49, the luminance decreases and becomes a low value. However, a peak appears in luminance at the center of the inner surface 49a of the notch 49. It should be noted that even if the reflectance is locally lowered at the end portion 45 other than the notch 49 and an image like the notch 49 is approximately obtained, the notch 49 can be specified by designating a region in the vicinity of the notch 49. Can be avoided.

  FIG. 6 is a diagram illustrating illumination light from the objective lens 60 to the notch 49 in the alignment apparatus 1 according to the first embodiment. As shown in FIG. 6, the illumination light that illuminates the end portion 45 of the wafer 40 by rotating the wafer 40 illuminates the inner surface 49 a of the notch 49 when illuminating the notch 49. For example, the illumination light illuminates the end portion 45 of the wafer 40 from the objective lens 60 as Koehler illumination. When the illumination light illuminates the inner surface 49a of the notch 49, the illumination light is directed in the radial direction. Then, since the inner surface 49a of the notch 49 has a cylindrical mirror shape, a linear line image is formed.

  FIG. 7 illustrates illumination light (dotted line in the figure) and reflected light (solid line in the figure) when the optical axis 64 of the objective lens 60 passes through the center of the notch 49 in the alignment apparatus 1 according to the first embodiment. FIG. As shown in FIG. 7, when the optical axis 64 of the objective lens 60 passes through the center of the notch 49, the reflected light reflected by the inner surface 49a of the notch 49 forms a linear line image on the focal plane. To do.

  FIG. 8 shows illumination light (dotted line in the figure) and reflected light (solid line in the figure) when the optical axis 64 of the objective lens 60 is shifted from the center of the notch 49 in the alignment apparatus 1 according to the first embodiment. FIG. As shown in FIG. 8, when the optical axis 64 of the objective lens 60 deviates from the center of the notch 49, the reflected light reflected by the inner surface 49 a of the notch 49 is not condensed on the objective lens 60. Therefore, as shown in FIGS. 4 and 5, the luminance decreases.

  As described above, the position of the end portion 45 of the wafer 40 when a linear image is captured indicates that the optical axis 64 of the objective lens 60 passes through the center portion of the notch 49. Therefore, the wafer 40 can be positioned by rotating the wafer 40 based on the position of the end portion 45 of the wafer 40 from which the linear image is captured.

  Therefore, as shown in step S16 of FIG. 3, a rotational deviation between the position of the end 45 of the wafer 40 where the linear image is captured and the position where the notch 49 should be originally positioned is calculated. For example, the position where the notch 49 should be originally positioned is set in advance by an encoder provided in the table 10. Then, the position of the end 45 of the wafer 40 where the linear image is captured is read by an encoder provided on the table 10. The rotational deviation is calculated from the difference between the two encoder values.

  Next, as shown in step S <b> 17 of FIG. 3, the wafer 40 is rotated by the calculated rotational deviation. Thereby, positioning of the wafer 40 can be performed. Note that the wafer 40 does not necessarily have to be rotated by the calculated rotational deviation, and may be eliminated in consideration of the rotational deviation in the subsequent steps.

Next, effects of the alignment apparatus 1 and the alignment method according to the first embodiment will be described.
The alignment apparatus 1 positions the wafer 40 by using the reflected light reflected by the inner surface 49 a of the notch 49 as the illumination light that illuminates the inner surface 49 a of the notch 49 formed at the end 45 of the wafer 40. Therefore, the position of the wafer 40 can be determined with high accuracy. In particular, since the shape of the inner surface 49a of the notch 49 is formed with high accuracy in a symmetrical shape with the center portion as the center, the position of the wafer 40 can be determined with high accuracy.

  Further, since a camera or the like directly facing the surface 41 of the wafer 40 is not required, the wafer 40 can be positioned at a low cost.

(Embodiment 2)
Next, an alignment apparatus 2 and an alignment method according to the second embodiment will be described. Compared with the first embodiment, the present embodiment has a function of measuring the amount of eccentricity of the wafer 40 and correcting the position of the wafer 40 based on the measured amount of eccentricity. First, the structure of the alignment apparatus 2 of this embodiment is demonstrated. FIG. 9 is a diagram illustrating the configuration of the alignment apparatus 2 according to the second embodiment. As shown in FIG. 9, the alignment apparatus 2 according to this embodiment includes a table 10, a θ-axis motor 15, an optical system 20, a Z-axis motor 25, and a control unit 30.

  The table 10 has an upper surface 11 and supports the wafer 40 on the upper surface 11. For example, the wafer 40 is attracted to the upper surface 11 to support the wafer 40. The table 10 has a rotation shaft 14 in a direction perpendicular to the upper surface 11. The table 10 rotates around the rotation shaft 14. As a result, the wafer 40 supported on the upper surface 11 also rotates about the rotation shaft 14. The direction passing through the rotating shaft 14 and perpendicular to the rotating shaft 14 is called the radial direction, and the direction along the periphery of the wafer 40 is called the circumferential direction, as in the first embodiment.

  The wafer 40 is a disk-shaped thin member, for example, a silicon wafer. The wafer 40 has a central axis 44 that passes through the center 43 of the wafer 40 and is orthogonal to the front surface 41 and the back surface 42. When the wafer 40 is held on the table 10, there may be a positional shift between the center 43 of the wafer 40 and the rotating shaft 14 of the table 10. Thus, it is said that the center 43 is decentered with respect to the rotating shaft 14. For example, the amount of eccentricity between the rotating shaft 14 and the center 43 is 100 μm. A notch 49 is formed in a part of the end portion 45 of the wafer 40.

  The θ-axis motor 15 (first drive unit) rotates the table 10 around the rotation shaft 14. The θ-axis motor 15 is provided below the table 10, for example. The driving of the θ-axis motor 15 is controlled by a control signal from the control unit 30. Further, the θ-axis motor 15 outputs information related to rotation to the control unit 30 by, for example, an encoder.

  The optical system 20 includes an autofocus optical system 80 in addition to the light source 50, the objective lens 60, and the imaging unit 70. The optical system 20 includes optical members such as a plurality of lenses and a half mirror as in the first embodiment.

  The light source 50 generates illumination light that illuminates the end portion 45 of the wafer 40. The optical axis 64 of the objective lens 60 is a radial direction orthogonal to the rotation axis 14 of the table 10. Of the radial direction, a direction substantially coincident with the optical axis 64 of the objective lens 60 is referred to as a Z-axis direction. The Z-axis direction is also called the focus direction. Among the Z-axis directions, the direction from the rotation axis 14 toward the objective lens 60 is defined as + Z-axis direction, and the opposite direction is defined as -Z-axis direction.

  A Z-axis motor 25 (second drive unit) is attached to the objective lens 60. The Z-axis motor 25 moves the objective lens 60 in the optical axis 64 direction, that is, in the Z-axis direction. The driving of the Z-axis motor 25 is controlled by a control signal from the control unit 30. Further, the Z-axis motor 25 outputs information related to the position of the objective lens 60 in the direction of the optical axis 64 to the control unit 30 by using, for example, an encoder.

  The imaging unit 70 captures an image of the end 45 of the wafer 40 by detecting the reflected light collected by the objective lens 60. The end 45 also includes a notch 49. The imaging unit 70 outputs the captured image of the end portion 45 to the control unit 30.

  The autofocus optical system 80 derives the position of the objective lens 60 in the optical axis 64 direction at a position where the image of the end portion 45 of the wafer 40 is in focus in the imaging unit 70. Then, the autofocus optical system 80 outputs the derived position information of the objective lens 60 to the control unit 30.

  An optical member such as a plurality of lenses and a half mirror guides the illumination light generated by the light source 50 to the end portion 45 of the wafer 40, reflects the reflected light at the end portion 45, and collects the reflected light collected by the objective lens 60. It leads to part 70.

  The control unit 30 controls driving of the θ-axis motor 15 and the Z-axis motor 25. The controller 30 drives the θ-axis motor 15 to rotate the table 10 at a predetermined rotational speed. Thereby, the control part 30 can guide | lead-out the position of the edge part 45 of the wafer 40 when an image is imaged. Further, the control unit 30 receives information on the position of the objective lens 60 from the autofocus optical system 80. Then, the control unit 30 drives the Z-axis motor 25 to move the objective lens 60 to the position guided by the autofocus optical system 80.

  As the table 10 rotates, the wafer 40 also rotates. When the rotation shaft 14 of the table 10 and the center 43 of the wafer 40 are eccentric, the position of the end portion 45 on the Z-axis changes as the wafer 40 rotates. The autofocus optical system 80 detects a change in the position of the end portion 45 on the Z-axis from a shift of the focus (focus) of the image of the end portion 45. Then, the autofocus optical system 80 derives the position of the objective lens 60 in which the image of the end 45 is in focus, and outputs information on the position to the control unit 30. The control unit 30 moves the position of the objective lens 60 based on the position information received from the autofocus optical system 80. As the wafer 40 continues to rotate, the position of the end 45 on the Z-axis changes. The autofocus optical system 80 outputs the position of the objective lens 60 to the control unit 30 so as to follow the change. The control unit 30 causes the objective lens 60 to follow the position received from the autofocus optical system 80. In this way, the control unit 30 performs feedback control of the position of the objective lens 60.

  The control unit 30 also adds predetermined additional data to the image data received from the imaging unit 70. The additional data includes, for example, the position indicated by the rotation angle of the end portion 45 of the wafer 40 when the image is captured and the position of the objective lens 60 in the optical axis 64 direction. Further, the additional data includes the position of the notch 49 when an image including a linear image is captured. The position of the notch 49 is also indicated by the rotation angle. The additional data is not limited to these. The control unit 30 is, for example, a PC (Personal Computer).

  Next, details of the configuration of the alignment apparatus according to the second embodiment will be described. FIG. 10 is a configuration diagram illustrating the alignment apparatus 2 according to the second embodiment. As shown in FIG. 10, the table 10 includes an R axis table 13, guides 16 a and 16 b, a θ axis table 17, and a vacuum chuck 18. The control unit 30 includes an axis control processing unit 31, a camera control unit 32, an autofocus control unit 33, and a data processing unit 34.

  The R-axis table 13 is provided on the guides 16a and 16b. For example, the guides 16a and 16b are fixed on the stage and extend in the same direction as the optical axis 64 direction of the objective lens 60, that is, in the Z-axis direction. The R axis table 13 can move along the Z axis direction by moving the wafer 40 supported on the table 10 by moving along the guides 16a and 16b. Thus, the R-axis table 13 serves as a moving unit that moves the table 10. Note that the direction in which the guides 16a and 16b extend and the movement of the R-axis table 13 are not limited to the Z-axis direction as long as the movement can be performed so that the eccentricity can be corrected.

  The R axis table 13 is moved by driving the R axis motor 12. The drive of the R-axis motor 12 is controlled by the axis control processing unit 31 in the control unit 30 via the motor driver 19. For example, movement start, movement stop, and movement speed change of the R-axis table 13 are performed by the control unit 30 controlling the R-axis motor 12 via the motor driver 19. Further, the R-axis motor 12 outputs information related to the position of the table 10 to the control unit 30 by, for example, an encoder.

  The θ-axis table 17 is provided on the R-axis table 13. The θ-axis table 17 is a rotating member in the table 10 and rotates around the rotation shaft 14. The θ-axis table 17 is rotated by driving the θ-axis motor 15.

  The vacuum chuck 18 is provided on the θ-axis table 17. The vacuum chuck 18 sucks the wafer 40 placed on the upper surface 11 of the table 10 and supports the wafer 40 on the table.

  The θ-axis motor 15 rotates the θ-axis table 17. The driving of the θ-axis motor 15 is controlled by an axis control processing unit 31 in the control unit 30 via a motor driver 19a. For example, rotation start, rotation stop, and rotation speed change of the θ-axis table 17 are performed by the control unit 30 controlling the θ-axis motor 15 via the motor driver 19a.

  The wafer 40 is supported on the upper surface 11 of the table 10 by the vacuum chuck 18. The back surface 42 of the wafer 40 is attracted to the vacuum chuck 18. On the surface 41 of the wafer 40, the intersection with the rotation axis 14 is set as the rotation center 46. In the case of eccentricity, there is a deviation between the center 43 and the rotation center 46.

  A straight line extending from the rotation center 46 to an arbitrary phrase on the surface of the wafer 40 is defined as a reference line 47. For example, a straight line extending from the rotation center 46 to the notch 49 may be used as the reference line 47. The position of an arbitrary end 45 of the wafer 40 is defined by a rotation angle θ between a straight line connecting the end 45 to the rotation center 46 and the reference line 47. Therefore, the end portion 45 of the wafer 40 can be associated with a rotation angle θ from 0 ° to 360 ° over the entire circumference.

  The position indicated by the rotation angle of the end 45 corresponding to the reference line 47 is 0 °. The position indicated by the rotation angle of the end 45 corresponding to a straight line rotated 30 ° from the reference line 47 is 30 °. It is assumed that the end portion 45 at the position indicated by the rotation angle of 0 ° corresponding to the reference line 47 is imaged at the start of measurement. Then, as the table 10 rotates, the rotation angle θ of the position indicated by the rotation angle of the end 45 to be imaged increases from 0 °. Then, when the position indicated by the rotation angle of the end 45 to be imaged is 360 °, the wafer 40 is rotated once.

  The axis control processing unit 31 acquires position information indicated by the rotation angle of the end 45 when the image is captured from the rotation information by the encoder of the θ-axis table 17 and transfers the position information to the data processing unit 34. The data processing unit 34 stores the received position information as additional data.

  A bevel surface may be formed on the end portion 45 of the wafer 40. The imaging unit 70 may image the end 45 including the bevel surface, or may image the end surface between the bevel surfaces.

  A focus moving shaft 21 is attached to the optical system 20. The focus moving shaft 21 moves the objective lens 60 in the direction of the optical axis 64 of the objective lens 60, that is, in the Z-axis direction. The focus moving shaft 21 is operated by driving a Z-axis motor 25. The driving of the Z-axis motor 25 is controlled by an axis control processing unit 31 in the control unit 30 via a motor driver 29. For example, the movement of the focus moving shaft 21 is started, stopped, and the moving speed is changed by the control unit 30 controlling the Z-axis motor 25 via the motor driver 29.

  FIG. 11 is a configuration diagram illustrating an optical system according to the second embodiment. As shown in FIGS. 10 and 11, the optical system 20 includes a light source 50, an objective lens 60, an imaging unit 70, an autofocus optical system 80, and optical members such as a lens and a half mirror.

  The illumination light generated by the light source 50 is reflected by the half mirror 22a and passes through the lens 23a. For example, the lens 23a is an f80 lens. The illumination light transmitted through the lens 23a is reflected by the half mirror 22b and passes through the lens 23b. For example, the lens 23b is an f50 lens. The illumination light transmitted through the lens 23 b is collected by the objective lens 60 and illuminates the end portion 45 of the wafer 40. For example, the objective lens 60 is f20.

  On the other hand, the reflected light reflected by the end portion 45 of the wafer 40 is collected by the objective lens 60. The reflected light collected by the objective lens 60 passes through the lens 23b and enters the half mirror 22b. A part of the reflected light incident on the half mirror 22 b enters the autofocus optical system 80.

  The autofocus optical system 80 includes, for example, a lens 23c, a half mirror 22c, and photodiodes (PD: Photodiode) 24a and 24b, and focuses using a phase difference autofocus method.

  In the phase difference autofocus method, for example, the reflected light entering from the lens 23c is separated into two by the half mirror 22c and guided to the photodiodes 24a and 24b. The direction and amount of focus are determined from the two images formed by the photodiodes 24a and 24b. Thereby, the amount by which the objective lens 60 is moved in the + Z axis direction or the −Z axis direction is derived. The autofocus optical system 80 is not limited to the phase difference autofocus method. A contrast method, an auxiliary light method, or a confocal method may be used.

  In this manner, the autofocus optical system 80 guides the position of the objective lens 60 where the image of the end portion 45 is in focus in the imaging unit 70. Then, the autofocus optical system 80 outputs the guided position of the objective lens 60 to the autofocus control unit 33 of the control unit 30. The autofocus control unit 33 transfers information on the position of the objective lens 60 received from the autofocus optical system 80 to the axis control processing unit 31. The axis control processing unit 31 moves the position of the objective lens 60 based on the received position information. As the wafer 40 rotates, the position of the end 45 on the Z axis changes. The control unit 30 moves the position of the objective lens 60 so as to follow the change. In this way, the control unit 30 performs feedback control.

  When the rotation speed of the wafer 40 is fast, the objective lens 60 may not be able to follow the position where the focus is guided by the autofocus optical system 80 in the notch 49 portion. However, at the notch 49, as described above, for example, a linear image collected by the inner surface 49a of the notch 49 is captured. Further, the autofocus by the autofocus optical system 80 may be stopped. Even when the autofocus is stopped, a linear image condensed by the inner surface 49a of the notch 49 can be captured at the notch 49 portion.

  The autofocus control unit 33 transfers information on the position of the objective lens 60 received from the autofocus optical system 80 to the data processing unit 34. The data processing unit 34 stores the received position information of the objective lens 60 as additional data.

  A part of the reflected light incident on the half mirror 22b is reflected by the half mirror 22b. The reflected light passes through the lens 23a and enters the half mirror 22a. Part of the reflected light incident on the half mirror 22 a passes through the half mirror 22 a and enters the imaging unit 70. The imaging unit 70 detects incident reflected light and acquires an image of the end portion 45.

The imaging unit 70 is an image sensor in an imaging camera, for example. For example, the imaging unit 70 includes a plurality of pixels 71 arranged linearly in one direction. For example, the pixels 71 of 1024 pixels are arranged linearly. For example, the pixels 71 from the 0th to the 1023th are arranged. The plurality of pixels 71 arranged in one direction image the end 45 of the wafer 40 along the direction of the rotation axis 14. For example, the 0th pixel 71 images the portion of the end 45 extending in the direction of the rotation axis 14 on the most back surface 42 side, and the 1023th pixel 71 images the most surface 41 side portion. That is, the lower-numbered pixels 71 image the portion on the back surface 42 side, and the larger-numbered pixels 71 image the portion on the front surface 41 side. In addition, you may make it image the part by the side of the surface 41, so that the pixel 71 of a smaller number. As described above, the imaging unit 70 acquires an image of an area extending along the direction of the rotation axis 14 of the end portion 45 of the wafer 40. The imaging unit 70 outputs the acquired image information to the camera control unit 32 of the control unit 30. Note that the imaging unit 70 may be a two-dimensional CMOS camera including a plurality of pixels arranged two-dimensionally. The plurality of pixels arranged in two dimensions image the end portion 45 for each region having the direction of the rotation axis 14 and the circumferential direction as sides.

  The camera control unit 32 receives image data captured by the imaging unit 70. The camera control unit 32 transfers the received image data to the data processing unit 34. The camera control unit 32 controls the start and end of imaging of the imaging unit 70 and other operations related to imaging.

  The data processing unit 34 adds additional data to the image data. The image data is data corresponding to the pixel 71 of 1024 pixels. The data of one pixel 71 is 16-bit data, for example. The data processing unit 34 adds additional data for several pixels to the image data. For example, as the additional data, the data processing unit 34 includes a position indicated by the rotation angle of the end 45 when the image is captured (data associated with the θ angle) and the position of the objective lens 60 (position on the focus axis). Data). Further, the additional data includes a position indicated by the rotation angle of the notch 49. The data processing unit 34 adds additional data in synchronization with image capturing. The additional data is not limited to the position indicated by the rotation angle of the end 45 when the image is captured, the position of the objective lens 60, and the position indicated by the rotation angle of the notch 49.

  Next, an alignment method will be described as an operation of the alignment apparatus 2 according to the second embodiment. FIG. 12 is a flowchart illustrating the alignment method according to the second embodiment.

  First, as shown in step S <b> 21 of FIG. 12 and FIGS. 9 to 10, a wafer 40 such as a silicon wafer is supported on the table 10. Then, the wafer 40 is sucked onto the table 10 by the vacuum chuck 18. As a result, the wafer 40 is supported on the table 10 having the rotating shaft 14. The wafer 40 is not limited to a silicon wafer.

  Next, the axis control processing unit 31 in the control unit 30 is activated to cause the motor driver 19a to output a control signal for driving the θ-axis motor 15. As a result, the motor driver 19a drives the θ-axis motor 15 to rotate the table 10 supporting the wafer 40 at a predetermined rotation speed around the rotation shaft 14 as shown in step S22 of FIG.

  Further, position information indicated by the rotation angle of the end 45 when the image is captured is acquired from the rotation information of the table 10. For example, the axis control processing unit 31 acquires position information indicated by the rotation angle of the end 45 when an image is captured. The acquired position information is transferred to the data processing unit 34 and stored as additional data.

  As the θ-axis table 17 rotates, the wafer 40 supported by the θ-axis table 17 also rotates. At this time, a deviation may occur between the rotation shaft 14 of the θ-axis table 17 and the center 43 of the wafer 40, and this deviation is the eccentricity as described above.

  Next, the optical member which comprises the optical system 20 is arrange | positioned in a predetermined position. In other words, the illumination light generated by the light source 50 illuminates the end portion 45 of the wafer 40, and the reflected light reflected by the end portion 45 is condensed by the objective lens 60. Further, the optical axis 64 of the objective lens 60 is aligned with the radial direction of the rotating shaft 14 of the table 10. The direction is set as the Z-axis direction, and the objective lens 60 is opposed to the end portion 45 of the wafer 40.

  Next, the light source 50 is activated to generate illumination light, and the end portion 45 of the wafer 40 is illuminated with illumination light as shown in step S23 of FIG. At that time, the inner surface 49a of the notch 49 is also illuminated with illumination light. Then, as shown in step S <b> 24 of FIG. 12, the reflected light reflected by the end portion 45 of the illumination light is collected by the objective lens 60. At that time, the reflected light reflected by the inner surface 49 a of the notch 49 is also collected.

  Next, part of the reflected light collected by the objective lens 60 reaches the autofocus optical system 80. Then, the position of the objective lens 60 in which the image of the end 45 is in focus in the imaging unit 70 is guided by the autofocus optical system 80 that focuses the image of the end 45. Then, the objective lens 60 is moved in the direction of the optical axis 64, that is, in the Z-axis direction, up to the position of the guided objective lens 60.

  Further, information on the position of the objective lens 60 is acquired. For example, the autofocus control unit 33 acquires information on the position of the objective lens 60 in which the image of the end portion 45 is focused in the imaging unit 70. The acquired position information is transferred to the data processing unit 34 and stored as additional data.

  On the other hand, a part of the reflected light collected by the objective lens 60 reaches the imaging unit 70. Then, the reflected light collected by the objective lens 60 is detected by the imaging unit 70, thereby capturing an image of the end 45 as shown in step S25 of FIG. At that time, in the portion of the notch 49, an image including a linear image condensed linearly by the inner surface 49a of the notch 49 is captured.

  Next, image data captured by the image capturing unit 70 is output to the control unit 30. Then, the control unit 30 adds predetermined additional data to the image data received from the imaging unit 70. For example, the additional data includes the position of the end 45 when an image is captured and the position of the objective lens 60 in the direction of the optical axis 64. The position of the end 45 when the image is captured includes the position of the end 45 when the linear image is captured. The position of the end 45 is indicated by the rotation angle.

  FIG. 13 is a graph illustrating the amount of eccentricity measured by the alignment method according to the second embodiment, where the horizontal axis is the position of the end indicated by the rotation angle (position corresponding to the angle θ), and the vertical axis is This is the amount of eccentricity indicated by the position of the objective lens on the optical axis. The dotted line indicates an ideal case where there is no eccentricity.

  As shown in FIG. 13, the roundness of the wafer 40 such as a silicon wafer is ensured with high accuracy by the processing method, and the eccentric amount of the wafer 40 is a sine wave with respect to the rotation angle. That is, the position of the objective lens 60 on the optical axis 64 varies as a function of a sine wave depending on the position of the end 45 indicated by the rotation angle. For example, as shown in FIG. 13, the position of the objective lens 60 when the end 45 corresponding to the rotation angles of 0 ° and 180 ° is imaged is an ideal position with small eccentricity. On the other hand, the position of the objective lens 60 when the end portion 45 corresponding to the 90 ° rotation angle is imaged changes greatly in the + Z-axis direction, and the end portion 45 corresponding to the 270 ° rotation angle is imaged. Conversely, the position of the objective lens 60 greatly changes in the −Z-axis direction. In this way, by fitting the rotation angle and the eccentric amount at the rotation angle to a sine wave, the relationship between the rotation angle and the eccentric amount is derived, and the correction amount is calculated. In addition, you may correct | amend using the eccentricity data itself in each measured rotation angle, without fitting to a sine wave.

  As shown in step S26 of FIG. 12, the control unit 30 determines the amount of eccentricity between the rotation shaft 14 and the wafer 40 based on the position of the objective lens 60 in the direction of the optical axis 64 when the wafer 40 is rotated once. calculate. For example, the control unit 30 calculates a value of (maximum value + minimum value) / 2 at the position of the objective lens 60 as the amount of eccentricity between the rotation shaft 14 and the center 43. In this way, the alignment apparatus 2 calculates the amount of eccentricity.

  In addition, the control unit 30 calculates a rotational deviation between the position of the end portion 45 of the wafer 40 where the linear image is captured and the position where the notch 49 should be originally positioned.

Next, the alignment device 2 corrects the eccentricity and the rotational deviation.
As shown in step S <b> 27 of FIG. 12, the control unit 30 corrects the eccentricity amount by moving the table 10 based on the eccentricity amount calculated by the alignment apparatus 2. Specifically, the axis control processing unit 31 of the control unit 30 cancels the eccentricity at the position of the end 45 corresponding to the rotation angle θ stored in the data processing unit 34, that is, the rotation angle θ. The R-axis table 13 is moved in the direction of the optical axis 64 so that the amount of movement in the direction opposite to the amount of eccentricity at the position of the end portion 45 corresponding to. For example, when the end portion 45 corresponding to the rotation angle of 90 ° comes to the position for imaging, the R-axis table 13 is moved in the −Z-axis direction. Further, when the end portion 45 corresponding to the rotation angle of 270 ° comes to the position for imaging, the R-axis table 13 is moved in the + Z-axis direction. The driving of the R-axis table 13 is controlled by the control unit 30 via the motor driver 19. In the feedback control, when there is a response delay in driving the R-axis table and driving the objective lens 60 in the Z-axis direction, additional data considering the delay can be used.

  FIG. 14 is a graph illustrating the amount of eccentricity corrected by the alignment method according to the second embodiment, where the horizontal axis is the position of the end indicated by the rotation angle, and the vertical axis is the position of the objective lens on the optical axis. The amount of eccentricity shown. As shown in FIG. 14, the eccentric amount can be suppressed by moving the table 10 in the Z-axis direction so as to cancel the eccentric amount.

  In addition, the control unit 30 rotates the table 10 based on a rotational deviation between the position of the end 45 of the wafer 40 where the linear image is captured and the position where the notch 49 should be originally positioned.

Next, effects of the alignment apparatus 2 and the alignment method according to the present embodiment will be described.
The alignment apparatus 2 calculates the amount of eccentricity of the wafer 40 from the position of the objective lens 60 guided by autofocus. Thereby, the amount of eccentricity of the wafer 40 can be measured accurately and at low cost.

  In addition, the position indicated by the rotation angle of the end 45 when the image is captured, the position indicated by the rotation angle of the notch 49, and the position of the objective lens 60 in the direction of the optical axis 64 are added to the image data. Yes. Thereby, these positions can be associated with images. In addition, since the addition of data is performed simultaneously with imaging, the time required for data acquisition can be shortened.

  Furthermore, the imaging unit 70 includes a plurality of pixels 71 arranged in one direction, and images the end 45 along the direction of the rotation axis 14. Therefore, the end portion 45 can be finely imaged, and the accuracy of the eccentricity amount can be further improved.

  Data other than the position of the end 45 and the position of the objective lens 60 can be added to the additional data, whereby various data can be added to the image data.

  In the alignment apparatus 2, for example, the end 45 is captured as an 8 × image by the lens of the optical system 20. In the imaging unit 70, for example, 1024 pixels having a width of 14 μm are arranged in a line. Therefore, the field of view is 1.792 mm from 14 μm × 1024 pixels ÷ 8. The peripheral length of the 300 mm wafer is 942.47 mm. Therefore, when imaging the periphery of the wafer, 525 images are captured. On the other hand, since the imaging unit 70 is operated at 60 kHz, an image of the end 45 for one rotation can be acquired by making one rotation in 8.96 seconds from 525 sheets × 1024 pixels ÷ 60. That is, the rotation speed can be 0.11 rps. Thus, by rotating the wafer 40 once in 8.96 seconds, the image of the end portion 45 of the wafer 40, the position of the end portion 45 when the image is captured, and the position of the objective lens 60 in the optical axis 64 direction are captured. Can be obtained. Therefore, the time required for measuring the eccentricity can be shortened.

  In addition, since the amount of eccentricity can be measured without acquiring an image of the portion of the surface 41 of the wafer 40, the time required for imaging can be shortened and the memory for storing the image can be reduced.

  Furthermore, since the alignment apparatus 2 can be used for correcting the eccentricity as it is, the time required for correcting the eccentricity of the wafer 40 can be shortened. Further, the wafer 40 can be scanned with the amount of eccentricity suppressed by using the alignment apparatus 2.

  As mentioned above, although embodiment of this invention was described, this invention contains the appropriate deformation | transformation which does not impair the objective and advantage, Furthermore, it does not receive the limitation by said embodiment.

DESCRIPTION OF SYMBOLS 1 Alignment apparatus 10 Table 11 Upper surface 12 R-axis motor 13 R-axis table 14 Rotating shaft 15 (theta) axis motor (1st drive part)
16a, 16b Guide 17 θ axis table 18 Vacuum chuck 19 Motor driver 20 Optical system 21 Focus moving shafts 22a, 22b, 22c Half mirrors 23a, 23b, 23c Lenses 24a, 24b Photo diode 25 Z-axis motor (second drive unit)
29 Motor driver 30 Control unit 31 Axis control processing unit 32 Camera control unit 33 Autofocus control unit 34 Data processing unit 40 Wafer 41 Front surface 42 Back surface 43 Center 44 Center axis
45 End 46 Rotation Center 47 Reference Line 48 Side 49 Notch 49a Inner Surface 50 Light Source 60 Objective Lens 64 Optical Axis 70 Imaging Unit 71 Pixel 80 Autofocus Optical System

Claims (9)

Illumination light that illuminates the inner surface of the notch formed at the edge of the wafer and that is sandwiched between the side surfaces of the wafer in a direction along the periphery of the wafer is reflected light reflected by the inner surface. An alignment method for positioning the wafer using :
The wafer is positioned by rotating the wafer based on the position of the end where the image of the linear image in which the reflected light is linearly collected by the inner surface is captured.
Alignment method. Supporting the wafer on a table having a rotation axis;
Rotate the table around the rotation axis,
Illuminating the end with the illumination light;
The reflected light reflected by the end portion of the illumination light is collected by an objective lens,
Taking an image of the end by detecting the reflected light collected by the objective lens,
By the autofocus optical system, the position of the objective lens at which the image is focused, and the position of the objective lens in the optical axis direction is derived,
Moving the objective lens to the position guided by the autofocus optical system;
Add predetermined additional data to the image data,
Based on the position of the objective lens in the optical axis direction when the wafer is rotated once, the amount of eccentricity between the rotation axis and the wafer is calculated,
The wafer is positioned by moving the table based on the amount of eccentricity.
The alignment method according to claim 1 . The additional data is
The position of the notch when the image is captured, the position of the end when the image is captured, and the position of the objective lens in the optical axis direction are included.
The alignment method according to claim 2 . The end portion is imaged along the direction of the rotation axis by a plurality of pixels arranged in one direction.
The alignment method according to claim 2 or 3 . Illumination light that illuminates the inner surface of the notch formed at the edge of the wafer and that is sandwiched between the side surfaces of the wafer in a direction along the periphery of the wafer is reflected light reflected by the inner surface. An alignment apparatus for positioning the wafer using :
The wafer is positioned by rotating the wafer based on the position of the end where the image of the linear image in which the reflected light is linearly collected by the inner surface is captured.
Alignment device. A table having a rotation axis and supporting the wafer;
A first drive unit that rotates the table about the rotation axis;
A light source that generates the illumination light that illuminates an edge of the wafer;
An objective lens that collects the reflected light reflected by the end portion of the illumination light;
A second drive unit that moves the objective lens in the optical axis direction of the objective lens;
An imaging unit that captures an image of the end portion by detecting the reflected light collected by the objective lens;
An autofocus optical system for guiding the position of the objective lens in the optical axis direction where the image is focused in the imaging unit;
Moving means for moving the table;
A control unit for controlling the first drive unit and the second drive unit;
With
The controller is
Moving the objective lens to the position guided by the autofocus optical system;
Add predetermined additional data to the image data,
Based on the position of the objective lens in the optical axis direction when the wafer is rotated once, the amount of eccentricity between the rotation axis and the wafer is calculated,
The wafer is positioned by moving the table based on the amount of eccentricity.
The alignment apparatus according to claim 5 . The additional data is
Including the position of the notch when the image is captured, the position of the end when the image is captured, and the position of the objective lens in the optical axis direction,
The alignment apparatus according to claim 6 . The imaging unit includes a plurality of pixels arranged in one direction,
The plurality of pixels image the end along the direction of the rotation axis,
The alignment apparatus according to claim 6 or 7 . The imaging unit is a two-dimensional CMOS camera including a plurality of pixels arranged two-dimensionally,
The plurality of pixels image the end portion for each region with the direction of the rotation axis and the circumferential direction as sides.
The alignment apparatus according to claim 6 or 7 .