Substrate edge detection method

Abstract

This substrate edge detection method comprises: a step for acquiring, before detection of an edge position, correction data of the edge position with respect to the exposure time in a saturation section in which the luminance of a background image reaches saturation with respect to the change in the exposure time in imaging processing; and a step for using, as the edge position, a position obtained by correcting, in an adjacent direction in accordance with the correction data corresponding to the exposure time in the imaging processing, an actually measured edge position detected on the basis of an image obtained by the imaging processing in the saturation section. Thus, when an image is obtained by the imaging processing in the saturation section, the actually measured edge position detected on the basis of said image is corrected by the correction data, and the edge position is detected with higher accuracy.

Description

Board edge detection method

[0001] The present invention relates to a technique for detecting the edge position of a substrate such as a semiconductor wafer from an image obtained by capturing an image of the peripheral portion of the substrate.

[0002] The disclosures in the specifications, drawings and claims of the following Japanese applications are incorporated herein by reference in their entirety: Japanese Patent Application No. 2023-135245 (filed August 23, 2023).

[0003]

[0003] Processing systems are known that perform various processes on the peripheral edge of an object to be imaged, such as a semiconductor wafer. In such substrate processing systems, for example, to monitor the processing status, the substrate being processed is illuminated and imaged using an imaging device such as a CCD camera. The peripheral edge of the substrate can have a variety of shapes, including a beveled surface formed by polishing.

[0004] For the purpose of observing the finish state of the bevel portion of such a substrate, it is possible to apply a combination of the above-mentioned imaging means and image processing technology for the image obtained by imaging. For example, Patent Document 1 discloses a substrate processing apparatus that evaluates the peripheral portion, including the bevel portion, of a wafer (substrate) having multiple films stacked on its surface by imaging and image processing. In this technology, the edge position of each film is detected from the image, and it is evaluated whether the film has been removed from the edge of the wafer by a desired WEE (Wafer Edge Exclusion) width in the bevel portion.

[0005] JP 2020-144102 A (for example, paragraph 0157)

[0006] In the substrate processing system, the wafer's peripheral edge is also inspected for defects based on the image. If the signal-to-noise ratio of the image needs to be improved for this defect inspection, the exposure time of the imaging device is increased, for example. This can result in the brightness of the area outside the wafer edge (background image) becoming saturated, resulting in so-called "overexposed" areas. In this case, the brightness of the background image in the image does not necessarily represent the actual brightness. In practice, as will be described in detail later, the edge position actually measured based on the image (hereinafter referred to as the "measured edge position") is calculated to be located further inward than the actual edge position of the substrate (hereinafter referred to as the "true edge position"). As a result, the calculated WEE width is shorter than it actually is.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to determine the edge position of a substrate with high accuracy from an image captured including the peripheral edge of the substrate and the background of the peripheral edge, even if the background is captured brightly.

[0008] This invention is a substrate edge detection method for detecting the edge position of a substrate from an image including a peripheral image corresponding to the peripheral portion and a background image corresponding to the background, obtained by an imaging process that images the peripheral portion of the substrate and an adjacent portion adjacent in a predetermined adjacent direction where the background is brighter than the peripheral portion, and is characterized by comprising: (a) a step of acquiring correction data for the edge position with respect to the exposure time in a saturated section in which the brightness of the background image is saturated with respect to changes in the exposure time in the imaging process, prior to detecting the edge position; and (b) a step of correcting the actual edge position detected based on the image obtained by the imaging process within the saturated section in the adjacent direction in accordance with the correction data corresponding to the exposure time in the imaging process, and setting the position as the edge position.

[0009] If the exposure time is increased to the extent that the brightness of the background image becomes saturated, the brightness of the peripheral image in the saturated section will be higher than the value reflecting the actual brightness, as shown in Figure 11 (described later). Therefore, the measured edge position will shift toward the inside of the substrate. Therefore, in the present invention, correction data is acquired in advance for the exposure time in the saturated section to correct the edge position shift that occurs when imaging processing is performed using that exposure time. Then, when an image is obtained by imaging processing within the saturated section, the measured edge position detected based on that image is corrected with the correction data, thereby improving the accuracy of edge position detection.

[0010] According to this invention, even when the brightness of the background image is saturated, the edge position of the substrate can be determined with high accuracy from the image obtained by the imaging process.

[0011] Not all of the multiple components of each of the above-described aspects of the present invention are essential, and in order to solve some or all of the above-described problems or achieve some or all of the effects described in this specification, it is possible to modify, delete, or replace some of the multiple components with new components, or to delete some of the limitations, as appropriate. Furthermore, in order to solve some or all of the above-described problems or achieve some or all of the effects described in this specification, it is possible to combine some or all of the technical features included in one aspect of the present invention described above with some or all of the technical features included in another aspect of the present invention described above to form an independent aspect of the present invention.

[0012] 4 is a diagram showing a substrate processing system equipped with an example of a substrate processing apparatus to which a substrate edge detection method according to the present invention can be applied. FIG. 4 is a diagram showing a schematic configuration of the substrate processing apparatus. FIG. 5 is a plan view of a part of the substrate processing apparatus seen from above. FIG. 6 is a diagram illustrating an example of the shape of a peripheral portion of a substrate to be imaged. FIG. 7 is a block diagram showing the electrical configuration of the substrate processing apparatus shown in FIGS. 2 and 3. FIG. 8 is a perspective view showing a head unit of an imaging mechanism. FIG. 9 is a perspective view showing a head unit of an imaging mechanism. FIG. 10 is a diagram showing a schematic view of the progression of light that contributes to top surface imaging. FIG. 11 is a diagram showing a schematic view of the progression of light that contributes to side surface imaging. FIG. 12 is a diagram showing a schematic view of the progression of light that contributes to side surface imaging. FIG. 13 is a diagram showing a schematic view of an image of the peripheral portion of a substrate imaged by an imaging unit. FIG. 14 is a diagram showing an edge inspection image and the luminance distribution of the image. FIG. 15 is a graph showing the relationship between exposure time in imaging processing, and luminance and edge position of a background image. FIG. 16 is a flowchart showing substrate processing executed in the substrate processing apparatus shown in FIG. 2. FIG. 17 is a flowchart showing a correction table acquisition process. FIG. 18 is a flowchart showing an edge detection process which is an embodiment of the substrate edge detection method according to the present invention.

[0013] 1 is a diagram showing a substrate processing system equipped with an example of a substrate processing apparatus to which the substrate edge detection method according to the present invention can be applied. The substrate processing system 200 includes a substrate processing unit 210 that processes substrates S and an indexer unit 220 coupled to the substrate processing unit 210. The indexer unit 220 includes a container holder 221 that can hold multiple containers C for accommodating substrates S (e.g., FOUPs (Front Opening Unified Pods), SMIF (Standard Mechanical Interface) pods, and OCs (Open Cassettes) that hermetically accommodate multiple substrates S), and an indexer robot 222 that accesses the containers C held by the container holder 221 to remove unprocessed substrates S from the container C and store processed substrates S into the container C. Each container C accommodates multiple substrates S in a substantially horizontal position.

[0014] In this specification, the pattern-forming surface (one main surface) of both main surfaces of the substrate S on which a pattern is formed is referred to as the "front surface," and the other main surface on the opposite side on which no pattern is formed is referred to as the "rear surface." The surface facing downward is referred to as the "lower surface," and the surface facing upward is referred to as the "upper surface." In this specification, the "pattern-forming surface" refers to the surface of the substrate on which a concave-convex pattern is formed in any region.

[0015] The indexer robot 222 comprises a base 222a fixed to the apparatus housing, an articulated arm 222b rotatable about a vertical axis relative to the base 222a, and a hand 222c attached to the tip of the articulated arm 222b. The hand 222c is structured so that a substrate S can be placed on its upper surface and held thereon. Indexer robots having such articulated arms and hands for holding substrates are well known, and therefore a detailed description thereof will be omitted.

[0016] The substrate processing section 210 includes a substrate transfer robot 211 disposed approximately in the center in a plan view, and a plurality of processing units 1 disposed to surround the substrate transfer robot 211. Specifically, the plurality of processing units 1 are disposed facing the space in which the substrate transfer robot 211 is disposed. The main components of the processing units 1 are installed inside the processing chamber 100. The substrate transfer robot 211 accesses these processing units 1 as needed to hand over substrates S. Meanwhile, each processing unit 1 performs a predetermined process on the substrate S. In this embodiment, one of these processing units 1 corresponds to the substrate processing apparatus according to the present invention.

[0017] FIG. 2 is a diagram showing a schematic configuration of a substrate processing apparatus. FIG. 3 is a plan view of a portion of the substrate processing apparatus seen from above. FIG. 4 is a diagram showing an example of the shape of the peripheral portion of a substrate to be imaged. FIG. 5 is a block diagram showing the electrical configuration of the substrate processing apparatus shown in FIGS. 2 and 3. In FIGS. 2, 3, and the other figures referred to below, the dimensions and number of parts may be exaggerated or simplified for ease of understanding. In addition, to clarify the directional relationships, each figure is appropriately provided with a coordinate system in which the Z axis is the vertical direction and the XY plane is the horizontal plane.

[0018] The substrate processing apparatus (processing unit) 1 includes a rotation mechanism 2, a scattering prevention mechanism 3, a processing mechanism 4, a peripheral heating mechanism 5, and an imaging mechanism 6. These components 2 to 6 are housed in an internal space 101 of a processing chamber 100. Each component 2 to 6 is electrically connected to a control unit 9 that controls the entire apparatus, and operates in response to instructions from the control unit 9.

[0019] The control unit 9 may be, for example, a device similar to a general computer. That is, in the control unit 9, a CPU serving as an arithmetic processing unit 91 performs arithmetic processing to control each part of the substrate processing apparatus 1. As a result, the substrate processing apparatus 1 supplies a processing liquid to the peripheral portion of the upper surface of the substrate S in the processing chamber to perform a bevel etching process. The detailed configuration and operation of the control unit 9 will be described in detail later. In addition, in this embodiment, a control unit 9 is provided for each substrate processing apparatus 1, but a configuration may be adopted in which a single control unit controls multiple substrate processing apparatuses 1. In addition, a configuration may be adopted in which the substrate processing apparatus 1 is controlled by a control unit (not shown) that controls the entire substrate processing system 200.

[0020] The rotation mechanism 2 rotates the substrate S in a rotation direction AR1 ( FIG. 3 ) while holding it in a substantially horizontal position with its surface facing upward. The rotation mechanism 2 rotates the substrate S around a vertical rotation axis AX passing through the center of the main surface of the substrate S. The rotation mechanism 2 includes a spin chuck 21, which is a disk-shaped member smaller than the substrate S. The spin chuck 21 is disposed so that its upper surface is substantially horizontal and its central axis coincides with the rotation axis AX. A rotation shaft 22 is connected to the lower surface of the spin chuck 21. The rotation shaft 22 extends vertically with its axis coincident with the rotation axis AX. A rotation drive unit (e.g., a motor) 23 is also connected to the rotation shaft 22. The rotation drive unit 23 drives the rotation shaft 22 to rotate around its axis in response to a rotation command from the control unit 9. Therefore, the spin chuck 21 can rotate together with the rotation shaft 22 around the rotation axis AX. The rotation drive unit 23 and the rotation shaft unit 22 function to rotate the spin chuck 21 around the rotation axis AX.

[0021] A through-hole (not shown) is provided in the center of the spin chuck 21, and communicates with the internal space of the rotating shaft 22. A pump 24 ( FIG. 5 ) is connected to the internal space via a pipe having a valve (not shown). The pump 24 and the valve are electrically connected to the control unit 9 and operate in response to commands from the control unit 9. This allows negative pressure and positive pressure to be selectively applied to the spin chuck 21. For example, when the pump 24 applies negative pressure to the spin chuck 21 with the substrate S placed on the upper surface of the spin chuck 21 in a substantially horizontal position, the spin chuck 21 suction-holds the substrate S from below. On the other hand, when the pump 24 applies positive pressure to the spin chuck 21, the substrate S can be removed from the upper surface of the spin chuck 21. When the suction of the pump 24 is stopped, the substrate S can be moved horizontally on the upper surface of the spin chuck 21.

[0022] 2 and 3, the anti-scattering mechanism 3 has a generally cylindrical cup 31 provided to surround the outer periphery of the substrate S held by the spin chuck 21, and a liquid receiving portion 32 provided below the outer periphery of the cup 31. A guard driving portion 33 (FIG. 5) is operated in response to a control command from the control unit 9, thereby raising and lowering the cup 31. When the cup 31 is positioned at the lower position, the upper end of the cup 31 is located below the peripheral portion Ss of the substrate S held by the spin chuck 21, as shown in FIG. 2. Conversely, when the cup 31 is positioned at the upper position, the upper end of the cup 31 is located above the peripheral portion Ss of the substrate S.

[0023] 2, when the cup 31 is in the lower position, the substrate S held by the spin chuck 21 is exposed to the outside of the cup 31. This prevents the cup 31 from becoming an obstacle when, for example, the substrate S is loaded onto or unloaded from the spin chuck 21.

[0024] On the other hand, when the cup 31 is in the upper position, the inner peripheral surface of the cup 31 surrounds the outer periphery of the substrate S held by the spin chuck 21. This prevents droplets of the processing liquid shaken off from the peripheral portion Ss of the substrate S from scattering inside the processing chamber 100 during the bevel etching process described below. It also enables the processing liquid to be reliably recovered. That is, as the substrate S rotates, droplets of the processing liquid shaken off from the peripheral portion Ss of the substrate S adhere to the inner peripheral surface of the cup 31, flow downward, and are collected and recovered by the liquid receiving portion 32 disposed below the cup 31.

[0025] The processing mechanism 4 has a base 41, a pivotal support shaft 42, an arm 43, and a processing liquid nozzle 44. The base 41 is fixed to the processing chamber 100. The pivotal support shaft 42 is rotatably mounted on the base 41. An arm 43 extends horizontally from the pivotal support shaft 42, and a processing liquid nozzle 44 is attached to its tip. The pivotal support shaft 42 rotates in response to a control command from the control unit 9, causing the arm 43 to swing. As a result, the processing liquid nozzle 44 at the tip of the arm 43 moves between a retracted position retracted from above the substrate S to the side, and a processing position above the peripheral edge of the substrate S. In FIG. 3 , the nozzle 44 indicated by the two-dot chain line is in the retracted position, and the nozzle 44 indicated by the solid line is in the processing position.

[0026] The processing liquid nozzle 44 is connected to a processing liquid supply unit 45 ( FIG. 5 ). When the processing liquid supply unit 45 supplies the processing liquid toward the processing liquid nozzle 44 in response to a supply command from the control unit 9, the processing liquid is ejected from the processing liquid nozzle 44 toward a processing start position Ps. This processing start position Ps is a point on the path along which the peripheral edge Ss of the substrate S moves. Therefore, as the spin chuck 21 rotates while the processing liquid nozzle 44 ejects the processing liquid, each portion of the peripheral edge Ss of the substrate S receives a supply of the processing liquid while passing through the processing start position Ps. As a result, a bevel etching process using the processing liquid is performed on the entire peripheral edge Ss of the substrate S.

[0027] The peripheral edge heating mechanism 5 includes an annular heater 51. The heater 51 incorporates a heating element that extends in the circumferential direction of the substrate S along the peripheral edge of the lower surface of the substrate S. When a heating command is given to this heater 51 from the control unit 9, the peripheral edge Ss of the substrate S is heated from below by heat emitted from the heating element. This raises the temperature of the peripheral edge Ss to a value suitable for the bevel etching process.

[0028] The imaging mechanism 6 includes a base 6A, a pivotal support shaft 6B, an arm 6C, a head driver 6D, a light source 6E, an imaging unit 6F, and a head unit 6G. The base 6A is fixed to the processing chamber 100. The pivotal support shaft 6B is rotatably mounted on the base 6A. An arm 6C extends horizontally from the pivotal support shaft 6B, and a head unit 6G is attached to its tip. When a control command is given from the control unit 9 to the head driver 6D ( FIG. 5 ) that drives the arm 6C, the head driver 6D swings the arm 6C in response to the command. As a result, as shown by the dashed-dotted line in FIG. 3 , the head unit 6G attached to the tip of the arm 6C reciprocates between a retracted position P1, where it is retracted from above the substrate S to the side, and an imaging position P2, where the peripheral edge Ss of the substrate S is imaged. 3, the head unit 6G indicated by the dashed line is in the retracted position, and the head unit 6G indicated by the solid line is in the imaging position. At the imaging position P2, the head unit 6G is positioned close to the (-Y) side end of the substrate S.

[0029] As shown in FIG. 3 , the illumination optical system 6E and the observation optical system 6F are located at a distance P3, which is spaced from the imaging position P2 in the X direction. This distance P3 is spaced from the components (rotation mechanism 2, anti-scattering mechanism 3, processing mechanism 4, and peripheral heating mechanism 5) that perform the bevel etching process on the substrate S and the cup 31. The illumination optical system 6E irradiates illumination light L1 from outside the cup 31 toward the imaging position P2. At this time, the cup 31 is positioned in a downward position, and the head unit 6G is positioned at the imaging position P2, so that the illumination light L1 is incident on the head unit 6G. The illumination light L1 is diffusely reflected by the head unit 6G. The diffused light thus generated illuminates the peripheral edge Ss of the substrate S. The reflected light L2 reflected by the peripheral edge Ss of the substrate S is then further reflected by the head unit 6G. The reflected light L2 is guided from the head unit 6G toward the distance P3 and incident on the observation optical system 6F. As a result, the observation optical system 6 F acquires an image of the peripheral edge portion Ss of the substrate S, and sends the image data to the control unit 9 .

[0030] Here, the peripheral edge Ss of the substrate S, which is the image target in this embodiment, will be described with reference to Fig. 4. As shown in Fig. 4, some substrates S, such as semiconductor wafers, have a bevel portion with an inclined surface formed on their peripheral edge. The "bevel portion" here refers to the entire area of ​​the peripheral edge Ss of the substrate S, where the surface is inclined with respect to the horizontal plane when the substrate S is in a horizontal position.

[0031] The cross-sectional shape and dimensions of the beveled portion are defined as standard specifications, with a maximum dimension Dmax shown by the dotted line and a minimum dimension Dmin shown by the dashed line, and generally a relatively high degree of freedom is given as long as they fall within these dimensions. In many cases, the cross section of the beveled portion is made up of multiple surfaces with different inclinations, as shown in Figure 4, but it can also be made up of a continuous curved surface.

[0032] In the following, where necessary, the portion of the peripheral portion Ss of the substrate S that is flush with the upper surface of the substrate S will be referred to as the "A surface" and given the symbol Sa, and the edge surface of the substrate S will be referred to as the "C surface" and given the symbol Sc. The inclined surface connecting the A surface Sa and the C surface Sc will be referred to as the "B surface" and given the symbol Sb. Furthermore, the portion that is flush with the lower surface of the substrate S will be referred to as the "E surface" and given the symbol Se, and the inclined surface connecting the C surface Sc and the E surface Se will be referred to as the "D surface" and given the symbol Sd. In this specification, the term "periphery portion Ss" is a concept that comprehensively includes each of these surfaces.

[0033] As described above, the head unit 6G has both a diffuse illumination function of receiving illumination light L1 from the illumination optical system 6E, generating diffuse light, and illuminating the peripheral edge Ss of the substrate S with the diffused light, and a guide function of guiding reflected light L2 reflected by the peripheral edge Ss to the observation optical system 6F. The configuration and operation of the head unit 6G will be described below with reference to Figures 6A, 6B, 7A, 7B, 8A, 8B, and 9. After that, the configuration and operation of the illumination optical system 6E will be described in detail.

[0034] 6A and 6B are perspective views showing the head unit of the imaging mechanism. More specifically, FIG. 6A shows the state in which head unit 6G is positioned at imaging position P2, and FIG. 6B shows the state in which substrate S has been removed from head unit 6G. Head unit 6G has a diffuse illumination unit 61 having a diffusion surface 610, a guide unit 62 composed of three mirror members 62a to 62c each surrounded by diffusion surface 610, and a holder 63 that holds diffuse illumination unit 61. In FIGS. 6A and 6B, a dot is added to the area corresponding to holder 63 to distinguish it from diffuse illumination unit 61.

[0035] The diffuse lighting unit 61 is made of a white fluorine-based resin, such as PTFE (polytetrafluoroethylene). The diffuse lighting unit 61 has a plate shape that is approximately parallel to the YZ plane, and has a notch 611 formed at the end on the (+Y) direction side. This notch 611 has a U-shape rotated 90 degrees clockwise when viewed from the (+X) direction side.

[0036] In the diffuse illumination unit 61, an inclined surface 610 is provided along the cutout portion 611. The inclined surface 610 is provided so as to surround the cutout portion 611 in the vertical direction and the (-Y) direction, and is a tapered surface that is finished so as to incline in the (-X) direction as it approaches the cutout portion 611. The surface is finished so as to diffusely reflect incident light, and as will be described later, functions as the diffusion surface 610 that diffusely reflects the illumination light and causes it to be incident on the peripheral portion Ss of the substrate S.

[0037] Mirror members 62a to 62c are attached so as to be surrounded by diffusion surface 610. More specifically, on diffusion surface 610, first mirror member 62a is attached at a position vertically above notch 611, second mirror member 62b is attached on the (-Y) side of notch 611, and third mirror member 62c is attached at a position vertically below notch 611. In this embodiment, mirror members 62a to 62c are made of Si (silicon) in consideration of chemical resistance, heat resistance, and the like.

[0038] On the other hand, the holding unit 63 is made of a resin that is highly resistant to chemicals and heat, such as PEEK (polyetheretherketone), and is a plate-like member formed with an outline roughly equivalent to that of the diffuse illumination unit 61. The holding unit 63 is connected to the back surface of the diffuse illumination unit 61, i.e., the (-X) side principal surface, and functions as a backup member. The holding unit 63 is also connected to the arm 6C. Therefore, by swinging the arm 6C, the diffuse illumination unit 61 and the holding unit 63 move together between the retracted position P1 and the imaging position P2.

[0039] As shown in FIG. 6A , when the head unit 6G is at the imaging position P2 and the substrate S is held by the spin chuck 21, the peripheral edge Ss of the substrate S is positioned within the notch 611. When the notch 611 is viewed from the (+X) side toward the (-X) direction, the first mirror member 62a reflects the image of the portion of the substrate peripheral edge Ss that is visible when viewed from above, i.e., the A-side Sa and the B-side Sb. Similarly, the second mirror member 62b reflects the image of the portion of the substrate peripheral edge Ss that is visible when viewed from the side, i.e., the B-side Sb, the C-side Sc, and the D-side Sd. Furthermore, the third mirror member 62c reflects the image of the portion of the substrate peripheral edge Ss that is visible when viewed from below, i.e., the D-side Sd and the E-side Se.

[0040] As will be described in detail later, the observation optical system 6F captures images in an imaging field of view that is set so as to view all three mirror members 62a to 62c from the (+X) side. As a result, the images of the substrate S reflected on each of the mirror members 62a to 62c are captured in a single image. In other words, the observation optical system 6F can capture all of the A-side Sa, B-side Sb, C-side Sc, D-side Sd, and E-side Se of the substrate Ss in a single image. By capturing images multiple times as the substrate S rotates, it is possible to obtain images of multiple regions of the peripheral edge portion Ss that are positioned differently from one another along the circumferential direction.

[0041] In the following description, capturing images of the A-side Sa and B-side Sb of the substrate S reflected in the first mirror member 62a is referred to as "top surface capturing." Capturing images of the B-side Sb, C-side Sc, and D-side Sd of the substrate S reflected in the second mirror member 62b is referred to as "side surface capturing." Capturing images of the D-side Sd and E-side Se of the substrate S reflected in the third mirror member 62c is referred to as "bottom surface capturing."

[0042] 7A and 7B are diagrams schematically illustrating the progression of light that contributes to top-surface imaging. More specifically, FIG. 7A is a perspective view showing the path of light that is incident on and reflected by the head unit 6G, and FIG. 7B is a cross-sectional view taken along a vertical cut plane thereof. As indicated by solid arrows in FIGS. 7A and 7B, illumination light L1a of illumination light L1 traveling in the (-X) direction along the top surface of the substrate S is incident on the diffusing surface 610 of the head unit 6G. The light that is incident on the diffusing surface 610, particularly on the upper diffusing surface 61a located above the cutout portion 611, and diffused and reflected is incident on the top surface of the substrate S from various directions, thereby illuminating the substrate peripheral portion Ss.

[0043] As indicated by the dotted arrows, the light reflected by the substrate S can travel in various directions, but light L2a that is incident on the mirror member 62a and is reflected by the mirror member 62a and travels in the (+X) direction is incident on the observation optical system 6F arranged on the optical path. By receiving this light, "top surface imaging" is achieved, in which the peripheral edge portion Ss of the substrate S is imaged as viewed from the top surface side.

[0044] 7B , the same phenomenon as on the upper surface side occurs on the lower surface side of the substrate S. That is, the head unit 6G has a vertically symmetrical structure, and part of the illumination light L1, illumination light L1c traveling in the (−X) direction along the lower surface side of the substrate S, is incident on the diffusion surface 610, particularly on the lower diffusion surface 61c located below the notch 611, and is diffusely reflected, thereby illuminating the lower surface of the substrate S. At this time, reflected light L2c reflected by the substrate S and the mirror member 62c traveling in the (+X) direction is received, thereby achieving "lower surface imaging" that images the peripheral edge portion Ss as viewed from the lower surface side of the substrate S.

[0045] 8A and 8B are diagrams schematically illustrating the progression of light that contributes to side-side imaging. More specifically, FIG. 8A is a perspective view showing the path of light incident on and reflected from the head unit 6G, and FIG. 8B is a cross-sectional view of the same at a horizontal cut plane. As indicated by the solid arrows in FIGS. 8A and 8B, illumination light L1b of illumination light L1 traveling in the (-X) direction along the side of the substrate S is incident on the diffusion surface 610 of the head unit 6G and is diffusely reflected, particularly by the lateral diffusion surface 61b located to the side of the cutout portion 611. This light is incident on the side of the substrate S from various directions, thereby illuminating the substrate peripheral portion Ss.

[0046] Of the light reflected from the substrate S indicated by the dotted arrow, light L2b that is reflected by the mirror member 62b and travels in the (+X) direction is incident on the observation optical system 6F arranged on the optical path. This realizes "side surface imaging" that images the peripheral edge portion Ss of the substrate S as viewed from the side.

[0047] The observation optical system 6F includes an observation lens system composed of an object-side telecentric lens and, for example, a CMOS camera. Therefore, of the reflected light, only the reflected light L2 (L2a, L2b, L2c) parallel to the optical axis of the observation lens system is incident on the sensor surface of the CMOS camera, and an image of the peripheral edge Ss of the substrate S and the adjacent area is formed on the sensor surface. In this way, the observation optical system 6F captures an image of the peripheral edge Ss of the substrate S and the adjacent area, and acquires an image Im including, for example, a top surface image area Ma, a side surface image area Mb, and a bottom surface image area Mc, as shown in FIG. 9 . The observation optical system 6F then transmits image data representing the image to the control unit 9.

[0048] 9A and 9B are diagrams showing an image of the peripheral edge of a substrate captured by the imaging unit. Fig. 9A is a schematic diagram of the head unit 6G and the substrate S viewed from the (+X) side to the (-X) direction, and the area FV enclosed by the dashed line represents the imaging field of the observation optical system 6F. In this way, the imaging field of view FV of the observation optical system 6F is set to include the mirror members 62a to 62c of the head unit 6G.

[0049] 9(b) schematically shows images of the substrate S reflected on the mirror members 62a to 62c within the imaging field of view FV. As shown in FIG. 9(b), images of the A-side Sa and B-side Sb of the peripheral edge portion Ss of the substrate S are reflected on the first mirror member 62a. Images of the B-side Sb, C-side Sc, and D-side Sd of the peripheral edge portion Ss of the substrate S are reflected on the second mirror member 62b. Images of the D-side Sd and E-side Se of the peripheral edge portion Ss of the substrate S are reflected on the third mirror member 62c. The observation optical system 6F captures these images collectively to obtain a single image.

[0050] 9(c) is a schematic diagram of an image actually obtained by imaging. In the imaging mechanism 6 configured as described above, illumination light from the illumination optical system 6E is diffused by the diffusion surface 610 to illuminate the substrate S, and an image is captured by receiving a portion of the light reflected from the substrate S. As a result, neither the amount of illumination light nor the amount of received light can be said to be sufficient. In order to capture an image satisfactorily under such circumstances, the sensitivity of the camera must be increased, and as a result, the detailed structure of the head unit 6G is hardly reflected in the image due to so-called overexposure.

[0051] Therefore, as shown in Figure 9 (c), the image Im actually obtained includes a dark area Md corresponding to the cutout portion 611 and including an image of the side of the substrate S reflected out of focus within it, an upper surface image area Ma corresponding to the image of the peripheral portion Ss of the substrate S viewed from above, a side surface image area Mb corresponding to the image of the peripheral portion Ss of the substrate S viewed from the side, and a lower surface image area Mc corresponding to the image of the peripheral portion Ss of the substrate S viewed from below.

[0052] By analyzing the image Im including these regions, it is possible to obtain information indicating the shape of the peripheral edge of the substrate S in the circumferential direction, the etching status, etc. From this information, it is possible to inspect the amount of eccentricity of the substrate S placed on the spin chuck 21 with respect to the rotation axis AX, the amount of warpage of the substrate S, the bevel etching result (etching width), etc.

[0053] In the substrate processing apparatus 1 equipped with the imaging mechanism 6 configured as described above, the control unit 9 controls each section of the apparatus to perform (A) substrate inspection before bevel etching, (B) alignment, (C) bevel etching after alignment, and (D) substrate inspection after bevel etching. As shown in Fig. 5, the control unit 9 has an arithmetic processing section 91 that performs various types of arithmetic processing, a storage section 92 that stores basic programs and image data, and an input display section 93 that displays various types of information and receives input from the operator.

[0054] In the control unit 9, a calculation processor (CPU) 91 serving as a main control unit performs calculations in accordance with procedures written in a program, thereby controlling each part of the substrate processing apparatus 1 as follows. That is, as shown in Fig. 5, the calculation processor 91 functions as a positioning control unit 911 that positions the head unit 6G, an entire peripheral image acquisition unit 912 that acquires an entire peripheral image, an eccentricity amount derivation unit 913 that derives the amount of eccentricity of the substrate S from the entire peripheral image before the bevel etching process, a warpage amount derivation unit 914 that derives the amount of warpage of the substrate S from the entire peripheral image before the bevel etching process, an etching width derivation unit 915 that derives the etching width from the entire peripheral image after the bevel etching process, and a residue analysis unit 916 that analyzes residues from a residue-enhanced image obtained by image processing the entire peripheral image.

[0055] 5 denotes an eccentricity correction mechanism that corrects the eccentricity of the substrate S with respect to the rotation axis AX by moving the substrate S by the above-mentioned amount of eccentricity. Since a conventionally known eccentricity correction mechanism can be used, a detailed description of the configuration of the eccentricity correction mechanism 7 will be omitted here.

[0056] The illumination optical system 6E of the imaging mechanism 6 irradiates the illumination light L1 as primary illumination light onto an area FV (see FIG. 9A) including the diffusion surface 610, thereby generating diffused light that is diffusely reflected by the diffusion surface 610 as secondary illumination light. The substrate S is then illuminated by this diffused light (illumination process). The observation optical system 6F of the imaging mechanism 6 receives a portion of the light reflected from the substrate S, thereby capturing an image of the peripheral portion Ss of the substrate S. In this way, the peripheral portion Ss is observed by the observation optical system 6F (observation process).

[0057] Here, in order to inspect the WEE width in particular, an image including the outer side of the peripheral edge Ss and the C surface Sc of the substrate S (FIG. 4), that is, an image including the background of the substrate S (for example, the area surrounded by the thick dotted line in FIG. 9(c)), is acquired by imaging processing using the imaging mechanism 6. Hereinafter, for convenience of explanation, this image will be referred to as an "edge inspection image Me."

[0058] FIG. 10 shows an edge inspection image and the brightness distribution of the image. Here, the substrate processing apparatus 1 performs bevel etching on a substrate S having a film to be etched (not shown) formed on its surface. The upper part of FIG. 10 schematically illustrates an edge inspection image Me obtained by imaging the substrate S using the imaging mechanism 6. This edge inspection image Me includes a peripheral image IM1 corresponding to the peripheral edge Ss of the upper surface of the substrate S and a background image IM2 corresponding to the background of the substrate S. Looking more closely at the peripheral image IM1, it is seen to be composed of an image IMf of the film to be etched remaining after the bevel etching, an image IMa of the surface A Sa, and an image IMb of the surface B Sb. The boundary between the peripheral image IM1 and the background image IM2 corresponds to the measured edge position Pse, and the boundary between the image IMf and the image IMa corresponds to the etching boundary Pb. Furthermore, the distance between the measured edge position Pse and the etching boundary Pb in the radial direction RD (corresponding to the adjacent direction in the present invention) of the substrate S corresponds to the WEE width. In the same figure, the symbol Pie indicates the image edge on the background side in the edge inspection image Me.

[0059] The lower part of the figure shows a graph showing the luminance distribution of the edge inspection image Me along the radial direction RD. In this graph, the horizontal axis indicates the distance from the image edge Pie toward the center of the substrate S, and the vertical axis indicates the luminance of the edge inspection image Me at each position in 256 gradations. In this graph, the luminance drops sharply at the boundary between the background image IM2 and the peripheral image IM1. In other words, the peripheral edge Ss of the substrate S and the background, which is brighter than the peripheral edge Ss, are adjacent in the radial direction RD, which corresponds to an example of the "adjacent portion" of the present invention. In this embodiment, if the upper and lower limits of the luminance range occurring in this adjacent portion are "Iemax" and "Iemin," respectively, the edge luminance Ie is calculated based on the following formula: Ie = (Iemax - Iemin) / 2. The position corresponding to this edge luminance Ie is determined to be the measured edge position Pse of the substrate S. Of course, the method for determining the measured edge position Pse is not limited to this, and for example, the position where the brightness starts to drop suddenly may be determined as the measured edge position Pse. Note that the etching boundary Pb is also determined using the same method as the measured edge position Pse.

[0060] When the actual measured edge position Pse of the substrate S is determined in this manner, the above-mentioned problem occurs. This problem will be explained with reference to FIG.

[0061] FIG. 11 is a graph showing the relationship between exposure time in the imaging process and the brightness and edge position of the background image. The solid line in the graph shows the change in brightness I of the background image IM2 with respect to exposure time, and the dashed line shows the change in the measured edge position Pse of the substrate S calculated by the above-mentioned determination. The following technical features can be read from the graph. As the exposure time increases, the brightness of the background image IM2 increases proportionally, reaching a maximum brightness of 255 at a predetermined exposure time and saturating at exposure times longer than that. In other words, the graph shows a non-saturated section in which the brightness of the background image IM2 increases linearly, and a saturated section in which the brightness of the background image IM2 saturates at the maximum brightness of 255. Furthermore, the measured edge position Pse is approximately constant in the non-saturated section, but increases linearly in the saturated section. Therefore, if the exposure time is increased to the point where the brightness enters the saturated section in order to improve the signal-to-noise ratio of the edge inspection image Me, the measured edge position Pse shifts toward the inside of the substrate S depending on the exposure time. In other words, it becomes difficult to accurately detect the edge position of the substrate S.

[0062] Therefore, in this embodiment, as shown in FIG. 11 , the average value Pse(av) of the measured edge positions Pse(1), ..., in the non-saturation section is calculated, and the shift amounts CLm, ..., CLn of the measured edge positions Pse(m), ..., Pse(n) in the saturation section are calculated. Here, the measured edge positions Pse(1), ..., Pse(m), ..., Pse(n) indicate the measured edge positions corresponding to the exposure times ET1, ..., ET(m), ..., ET(n), respectively. Furthermore, the shift amounts CLm, ..., CLn indicate the amount of change from the average value Pse(av) of the measured edge positions Pse(m), ..., Pse(n). Therefore, the true edge position can be detected by subtracting the shift amount CL from the measured edge position Pse in the saturation section. In this embodiment, the shift amounts CLm, ..., CLn corresponding to the exposure times ETm, ..., ETn, respectively, are used as correction data. These correction data are stored in advance in table format in the storage unit 92. Then, as will be described next, edge detection is performed using the correction data.

[0063] Fig. 12 is a flowchart showing substrate processing executed by the substrate processing apparatus shown in Fig. 2. Fig. 13 is a flowchart showing a correction table acquisition process. When bevel etching is performed on a substrate S by the substrate processing apparatus 1, the arithmetic processing unit 91 determines whether or not a correction table TBL (Fig. 13) corresponding to the bevel etching process has been obtained (step S1). The correction table is a correction table in which correction data is stored in a table format, as shown in the lower right portion of Fig. 13.

[0064] If the determination in step S1 is "YES," the arithmetic processing unit 91 executes a process of acquiring a correction table (step S2) prior to the bevel etching process on the substrate S. On the other hand, if the determination in step S1 is "NO," the arithmetic processing unit 91 proceeds to step S3 without executing the process of acquiring a correction table.

[0065] The process of acquiring the correction table is performed using, as a correction substrate, a substrate S that has been bevel-etched, i.e., a substrate having a peripheral edge Ss with the same configuration as the substrate S whose edge position is to be detected (steps S21 to S27). The arithmetic processing unit 91 positions the cup 31 at a lower position using the guard drive unit 33 to prevent the illumination light L1 and the reflected light L2 from being blocked by the cup 31, a phenomenon known as vignetting. The arithmetic processing unit 91 also positions the head unit 6G at a retracted position P1 (the position indicated by the dashed-dotted line in FIG. 3 ) using the head drive unit 6D. This creates a transfer space above the spin chuck 21 large enough for the hand of the substrate transfer robot 211 to enter. After confirming that the transfer space has been created, the arithmetic processing unit 91 issues a loading request for the correction substrate S to the substrate transfer robot 211 and waits for the correction substrate S to be loaded into the substrate processing apparatus 1 and placed on the upper surface of the spin chuck 21, as shown in FIG. 2 . Then, the substrate S is placed on the spin chuck 21 (step S21). Subsequently, the pump 24 is operated to suction-hold the substrate S on the spin chuck 21. In this embodiment, the correction substrate S is stored in a container C and automatically carried in by the substrate transport robot 211, but the correction substrate S may also be placed on the upper surface of the spin chuck 21 by an operator.

[0066] Once the loading of the substrate S is complete, the substrate transport robot 211 retreats from the substrate processing apparatus 1. Subsequently, the arithmetic processing unit 91 starts an edge calculation loop. Here, measured edge positions Pse(1), ..., Pse(m), ..., Pse(n) corresponding to each exposure time ET1, ..., ETm, ..., ETn are acquired. More specifically, each time the variable k is switched from 1 to m, ..., n, the arithmetic processing unit 91 controls each component of the apparatus to capture a correction image (step S22). The correction image is essentially the same as the inspection image Me shown in the upper part of FIG. 10. The arithmetic processing unit 91 then acquires measured edge positions based on the correction image (step S23) and temporarily stores them in the storage unit 92. The arithmetic processing unit 91 then terminates the edge calculation loop.

[0067] Next, the calculation processing unit 91 extracts the measured edge positions included in the non-saturation section from the plurality of measured edge positions acquired in the edge calculation loop, and calculates the average value Pse(av) of those (step S24).

[0068] Subsequently, the arithmetic processing unit 91 starts a correction data calculation loop. Here, in the saturated section, shift amounts CLm, . . . CLn corresponding to exposure times ETm, . . . ETn are acquired as correction data. More specifically, each time the variable k is switched from m to n, the arithmetic processing unit 91 calculates the correction data CLk by calculating the difference between the measured edge position Pse(k) and the average value Pse(av) using the following equation: CLk = measured edge position Pse(k) - average value Pse(av) (step S25). Then, the arithmetic processing unit 91 writes and stores the correction data CLk in the correction table TBL in the storage unit 92 in association with the exposure time ETk (step S26). Then, the arithmetic processing unit 91 ends the correction data calculation loop.

[0069] Now that the desired correction table TBL has been obtained, the arithmetic processing unit 91 issues a request to the substrate transport robot 211 to unload the correction substrate S. In response to this, the correction substrate S is unloaded from the substrate processing apparatus 1 (step S27).

[0070] 12, the operation will be further described. With the correction table TBL corresponding to the bevel etching process already acquired, the arithmetic processing unit 91 issues a loading request for the substrate S to be subjected to the bevel etching process. As a result, the substrate S is loaded onto the spin chuck 21 (step S3) in the same manner as in the loading operation of the correction substrate (step S21).

[0071] Next, the arithmetic processing unit 91 executes edge detection processing (step S4).

[0072] 14 is a flowchart showing edge detection processing, which is one embodiment of a substrate edge detection method according to the present invention. The arithmetic processing unit 91 acquires imaging conditions for acquiring an image of the entire peripheral edge of the substrate S (step S41). The imaging conditions include information regarding exposure time. In this embodiment, the edge detection processing (step S4) is performed twice in total: once before correcting eccentricity of the substrate S on the spin chuck 21 and once before inspecting the substrate S that has undergone bevel etching. Therefore, the imaging conditions may be different before eccentricity correction and before inspection.

[0073] Next, based on the imaging conditions, the arithmetic processing unit 91 controls each unit of the apparatus to acquire an entire peripheral image of the substrate S (step S42). That is, the arithmetic processing unit 91 turns on the light source of the illumination optical system 6E and starts diffuse illumination of the peripheral portion Ss of the substrate S and the adjacent area by the head unit 6G. Subsequently, the arithmetic processing unit 91 issues a rotation command to the rotation drive unit 23, causing the rotation of the substrate S held by the spin chuck 21. Thereafter, each time the substrate S rotates by a predetermined angle, the arithmetic processing unit 91 extracts a top surface image Ma, a side surface image Mb, and a bottom surface image Mc from the images captured by the observation optical system 6F and stitches them together. This process is performed until the substrate S makes one rotation around the rotation axis AX. This results in an entire peripheral image of the substrate S, including the inspection image Me.

[0074] The arithmetic processing unit 91 issues a rotation stop command to the rotation drive unit 23 to stop the rotation of the substrate S held by the spin chuck 21, and also turns off the light source to stop the illumination. Subsequently, the arithmetic processing unit 91 causes the head drive unit 6D to move and position the head unit 6G from the imaging position P2 to the retracted position P1. In parallel with these operations, the arithmetic processing unit 91 determines the measured edge position based on the inspection image Me included in the entire peripheral image (step S43).

[0075] Thereafter, the calculation processing unit 91 determines whether the imaging process in step S42 was performed in a saturated section or a non-saturated section based on information about the exposure time included in the imaging conditions. If the imaging process was performed in a saturated section, the calculation processing unit 91 reads out correction data corresponding to the exposure time from the correction table TBL in the storage unit 92 and corrects the measured edge position using the correction data. The corrected position is determined as the true edge position (step S45). On the other hand, if the imaging process was performed in a non-saturated section, the measured edge position is determined as the true edge position (step S46). In step S46, the average value Pse(av) may be determined as the true edge position.

[0076] Returning to Fig. 12, the explanation of the operational flowchart will be continued. The edge position information relating to the edge position obtained by the edge detection process executed immediately after loading of the substrate S includes information reflecting the eccentricity of the substrate S with respect to the rotation axis AX. Therefore, in this embodiment, as shown in Fig. 12, the arithmetic processing unit 91 calculates the amount of eccentricity of the substrate S from the edge position information for one circumference of the substrate S (step S5), and corrects the eccentricity of the substrate S (step S6).

[0077] Next, the processor 91 controls the guard driver 33 to raise the cup 31 to an upper position. As a result, the inner peripheral surface of the cup 31 surrounds the outer periphery of the substrate S held by the spin chuck 21. When preparations for supplying the processing liquid to the substrate S are thus completed, the processor 91 issues a rotation command to the rotation driver 23 to start rotating the spin chuck 21 holding the substrate S. The processor 91 also activates the heater 51 of the peripheral heating mechanism 5. Subsequently, the processor 91 positions the processing liquid nozzle 44 at the processing start position Ps, and then controls the processing liquid supply unit 45 to supply the processing liquid. As a result, each portion of the peripheral portion Ss of the substrate S receives the processing liquid while passing through the processing start position Ps. As a result, the entire peripheral portion Ss of the substrate S is bevel-etched using the processing liquid (step S7). When the arithmetic processing unit 91 detects that the processing time required for the bevel etching process of the substrate S has elapsed, the arithmetic processing unit 91 issues a supply stop command to the processing liquid supply unit 45 to stop the discharge of the processing liquid. Subsequently, the arithmetic processing unit 91 issues a rotation stop command to the rotation drive unit 23 to stop the rotation of the spin chuck 21 and also stop the heating by the heater 51.

[0078] Upon completion of the bevel etching process, the processor 91 again executes the edge detection process (step S4) shown in FIG. 14 . This acquires an entire peripheral image after the bevel etching process, and acquires edge position information for one circumference of the substrate S (step S4). Based on the entire peripheral image and the edge position information, the processor 91 inspects the substrate S (step S8). For example, based on the edge position information, the processor 91 inspects whether the peripheral portion Ss of the substrate S has been bevel-etched with the desired WEE width, displays the inspection results on the input display unit 93, and stores them in the memory unit 92. The processor 91 also applies image processing to the entire peripheral image to enhance residues, thereby acquiring a residue-enhanced image. Based on the residue-enhanced image, the processor 91 detects residues remaining in the peripheral portion Ss of the substrate S and adjacent regions, counts the number of residues by size, and reports the results as one of the bevel etching results (residue analysis).

[0079] After the inspection, the arithmetic processing unit 91 requests the substrate transport robot 211 to unload the substrate S, and the processed substrate S is unloaded from the substrate processing apparatus 1 (step S9). Note that this series of steps is repeatedly executed.

[0080] As described above, in this embodiment, taking into consideration that the measured edge position measured in the saturated section shifts from the true edge position, correction data corresponding to this shift is stored in advance in the correction table TBL. Then, when the measured edge position is calculated by imaging processing in the saturated section, the measured edge position is corrected with the correction data to detect the true edge position. On the other hand, when the measured edge position is calculated by imaging processing in the non-saturated section, the shift does not occur, and the measured edge position is detected as the true edge position. Therefore, the edge position of the substrate S can be determined with high accuracy regardless of whether the image is captured against a bright background or not.

[0081] As described above, in the above embodiment, steps S2 and S45 correspond to examples of "step (a)" and "step (b)" of the present invention. The average value Pse(av) corresponds to an example of a "reference position" of the present invention. The entire peripheral image acquired by the imaging process of step S42 corresponds to an example of a "correction image" of the present invention.

[0082] The present invention is not limited to the above-described embodiment, and various modifications other than those described above are possible without departing from the spirit of the present invention. For example, in the embodiment, images of the peripheral edge Ss of the substrate S as viewed from above, from the side, and from below are captured in a single imaging field of view. However, the edge position calculation process according to the present invention can be performed as long as there is an image that includes at least one of the top and bottom surfaces of the substrate together with its background; for example, only the top surface may be captured.

[0083] In the above embodiment, the average value Pse(av) of the measured edge positions Pse(1), ... in the non-saturation section is determined as the "reference position" of the present invention (step S24), but the method for setting the reference position is not limited to this. For example, one of the measured edge positions in the non-saturation section may be set as the "reference position" of the present invention.

[0084] Furthermore, in the above embodiment, the present invention is applied to the substrate processing apparatus 1 that bevel-etches the peripheral edge portion Ss of the substrate S, but the application of the present invention is not limited to this and can be applied to general techniques for capturing images to observe the peripheral edge portion of a substrate. For example, the present invention can also be applied to inspection techniques that inspect a substrate based on captured images. Furthermore, the imaging mechanism 6 and inspection device corresponding to the imaging device of the present invention can also be applied to a substrate processing apparatus that, for example, supplies a coating film remover to the peripheral edge portion of the substrate S on which a coating film has been formed, thereby removing the coating film from the peripheral edge portion of the substrate S.

[0085] Furthermore, the substrate processing apparatus 1 of the above embodiment is equipped with a processing section for processing the substrate and an imaging section for imaging the peripheral portion of the substrate. However, even if the device that performs processing on the substrate and the device that images the substrate for observation are configured as separate entities, the present invention can be applied as image processing in the latter.

[0086] While the invention has been described with reference to specific embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as other embodiments of the invention, will become apparent to those skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover such modifications or embodiments within the true scope of the invention.

[0087] The present invention can be applied to any substrate edge detection technology that detects the edge position of a substrate from an image obtained by capturing an image of the peripheral edge of a substrate such as a semiconductor wafer.

[0088] 1...Substrate processing apparatus 6...Image capture mechanism CL, CLm, CLn...Shift amount CLk...Shift amount (correction data) ET1, ETk, ETm, ETn...Exposure time IM1...Periphery image IM2...Background image Me...(Edge) inspection image Pb...Etching boundary Pse...Measured edge position RD...Radial direction S...Substrate Ss...Periphery (of substrate) TBL...Correction table

Claims

1. A substrate edge detection method for detecting an edge position of a substrate from an image including a peripheral image corresponding to the peripheral portion and a background image corresponding to the background obtained by an imaging process that images the peripheral portion of the substrate and an adjacent portion adjacent in a predetermined adjacent direction where the background has a higher brightness than the peripheral portion, the method comprising: (a) a step of obtaining correction data for the edge position with respect to the exposure time in a saturation section in which the brightness of the background image is saturated with respect to changes in the exposure time in the imaging process, prior to detecting the edge position; and (b) a step of correcting an actual edge position detected based on the image obtained by the imaging process within the saturation section in the adjacent direction in accordance with the correction data corresponding to the exposure time in the imaging process, as the edge position.

2. A substrate edge detection method as claimed in claim 1, wherein the step (a) comprises: (a-1) preparing a correction substrate having a peripheral portion of the same configuration as the substrate as the object of edge position detection; (a-2) acquiring the edge position of the correction substrate as a reference position based on a correction image acquired by the imaging process for the correction substrate in a non-saturation section in which the brightness of the background image is not saturated with respect to changes in the exposure time; and (a-3) determining the edge positions of the correction substrate based on the correction images acquired by the imaging process for the correction substrate within the saturation section and for a plurality of exposure times different from each other, and acquiring each difference from the reference position as the correction data.

3. A substrate edge detection method as set forth in claim 2, wherein step (a-2) includes a step of determining edge positions of the correction substrate within the non-saturation section and for a plurality of exposure times different from one another, and setting the average value of the plurality of edge positions as the reference position.

4. A substrate edge detection method as described in claim 2 or 3, comprising the step of: (c) determining, as the edge position, an actual measured edge position detected based on the image obtained by the imaging process within the non-saturation section.

Images