Imaging apparatus, substrate processing apparatus, and imaging method

Abstract

The present invention relates to an imaging apparatus, an imaging method, and a substrate processing apparatus which involve imaging a peripheral edge portion of a substrate. A substrate support unit supports the substrate and rotates the substrate around a rotation axis perpendicular to the main surface of the substrate, and a rotation detection unit outputs a signal every time the rotation amount of the substrate reaches a predetermined value obtained by equally dividing one circumference into a plurality of parts. An imaging unit is disposed so as to include a part of a peripheral edge portion of the substrate in an imaging field of view, and executes imaging in response to a trigger signal from the outside. The imaging unit executes imaging a plurality of times using a signal output a plurality of times by the rotation detection unit as a trigger signal, thereby acquiring a plurality of images of the peripheral edge portion. Thus, each image can be correctly acquired at a predetermined angle interval.

Description

Imaging device, substrate processing apparatus, and imaging method

[0001] The present invention relates to a technique for imaging the peripheral portion of a substrate such as a semiconductor wafer for the purpose of inspection, for example.

[0002]

[0003] Processing systems that perform various processes on processing objects such as semiconductor wafers are known. In such substrate processing systems, images of the substrate are taken to inspect the state of the substrate before and after processing, for example. In particular, when observing the peripheral edge of the substrate, an imaging device is positioned so that a portion of the peripheral edge is included in the imaging field of view, and images of the entire peripheral edge are obtained by periodically capturing images of the substrate while rotating it.

[0003] For example, Patent Document 1 describes a technique in which a semiconductor wafer (substrate) is rotated and periodically imaged, and multiple images are combined to create an image of the entire peripheral portion of the wafer, and the center of the wafer is identified based on the position of the wafer's outer edge detected from this image. In this technique, the wafer is rotated at a constant speed, and the shutter of an imaging device is opened for a predetermined time at predetermined time intervals, thereby acquiring multiple images each associated with the rotation angle (phase) of the wafer.

[0004] Japanese Patent Application Laid-Open No. 2021-125646

[0005] The above embodiment does not provide a detailed description of the specific method for associating the captured image with the rotation angle, but the disclosure appears to assume that a linear relationship exists between the passage of time and the rotation angle. However, this assumption is not necessarily correct. This is because, due to precision constraints, mainly in terms of mechanism and control, the peripheral speed of the substrate during one rotation (the speed of movement of the outer periphery in the case of a circular substrate) is not necessarily constant and small fluctuations are unavoidable.

[0006] The above-mentioned conventional technology does not recognize this problem and captures images at fixed time intervals. As a result, there is a problem that the images cannot be captured while correctly associating them with the rotation angle. This causes the relative positions of each image to fluctuate in the circumferential direction when combining images, resulting in distortion in the resulting combined image and other degradation in image quality.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a technology for capturing images of the peripheral portion of a rotating substrate multiple times, in which each image can be accurately acquired at a predetermined angular interval.

[0008] One aspect of the present invention is an imaging device that images the peripheral portion of a substrate, and includes a substrate support portion that supports the substrate and rotates around a rotation axis perpendicular to the main surface of the substrate, an imaging portion that is positioned to include a portion of the peripheral portion in its imaging field of view and performs imaging in response to an external trigger signal, and a rotation detection portion that outputs a signal corresponding to the amount of rotation of the substrate support portion.

[0009] Another aspect of the present invention is a substrate processing apparatus that rotates a substrate to perform a predetermined process, and includes a substrate support unit that supports the substrate and rotates around a rotation axis perpendicular to a main surface of the substrate, an imaging unit that is positioned to include a portion of the peripheral edge of the substrate in its imaging field of view and performs imaging in response to an external trigger signal, and a rotation detection unit that outputs a signal corresponding to the amount of rotation of the substrate support unit.

[0010] In these inventions, the rotation detection unit outputs the signal each time the amount of rotation of the substrate support unit reaches a predetermined value that is equal to multiple divisions of one revolution, and the imaging unit performs the imaging multiple times using the signal output multiple times by the rotation detection unit as a trigger signal, thereby obtaining multiple images of the peripheral portion.

[0011] Another aspect of the present invention is an imaging method for imaging a peripheral portion of a substrate, in which a substrate support section supports the substrate and rotates it around a rotation axis perpendicular to a main surface of the substrate, a rotation detection section outputs a signal each time the amount of rotation of the substrate reaches a predetermined value obtained by dividing one revolution into multiple equal parts, and an imaging section positioned to include a portion of the peripheral portion of the substrate in its imaging field of view performs imaging multiple times in response to an external trigger signal, thereby obtaining multiple images of the peripheral portion.

[0012] In the invention configured as described above, an imaging unit capable of performing imaging using an externally applied signal as a trigger is combined with a rotation detection unit capable of outputting a signal corresponding to the actual measurement result of the amount of rotation of the substrate. Specifically, the imaging operation by the imaging unit is performed using a signal output by the rotation detection unit as a trigger signal each time the substrate rotates a certain amount. When images are taken at regular time intervals, any fluctuation in the speed during one rotation of the substrate will result in a fluctuation in the angular interval between images.

[0013] In contrast, in the present invention, the effects of speed fluctuations can be eliminated by capturing images in synchronization with a signal output in accordance with the actual amount of rotation of the substrate. Specifically, for example, if the rotation speed of the substrate decreases and it takes longer than usual to reach a predetermined amount of rotation, the image capturing interval is adjusted to be longer accordingly. The same is true in the reverse case. Therefore, although the time interval between images is not necessarily constant, it is possible to acquire multiple images accurately at predetermined angular intervals.

[0014] According to this invention, an imaging unit that captures images using an external signal as a trigger is combined with a rotation detection unit that outputs a signal each time the substrate rotates a predetermined amount, and imaging is performed using the signal output by the rotation detection unit as a trigger signal. Therefore, multiple images can be accurately captured at predetermined angular intervals without being affected by fluctuations in the rotation speed of the substrate.

[0015] The above and other objects and novel features of the present invention will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings, which are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0016] 1 is a diagram showing a schematic configuration of an embodiment of an imaging device according to the present invention. FIG. 1 is a diagram showing a schematic configuration of an embodiment of an imaging device according to the present invention. FIG. 2 is a diagram showing an example of the configuration of a rotation detection unit. FIG. 3 is a diagram showing an example of the configuration of the rotation detection unit. FIG. 4 is a diagram showing another example of the configuration of the imaging unit. FIG. 5 is a diagram showing another example of the configuration of the imaging unit. FIG. 6 is a flowchart showing the operation of the entire imaging device. FIG. 7 is a flowchart showing the operation of the imaging unit. FIG. 8 is a diagram explaining a problem when the imaging interval is fixed. FIG. 9 is a diagram explaining a problem when the imaging interval is fixed. FIG. 10 is a diagram explaining a problem when the imaging interval is fixed. FIG. 11 is a diagram showing a schematic representation of imaging timing in this embodiment. FIG. 12 is a diagram explaining a problem in image synthesis. FIG. 13 is a diagram explaining a problem in image synthesis.

[0017] 1A and 1B are diagrams showing the schematic configuration of an embodiment of an imaging device according to the present invention. More specifically, Fig. 1A is a diagram showing a schematic structure of the main parts of the imaging device 1 of this embodiment, and Fig. 1B is a block diagram showing a control system of the imaging device 1. This imaging device 1 is a device that receives a substrate S to be imaged and intermittently images a peripheral portion Ss of the substrate S while rotating the substrate S.

[0018] The imaging device 1 can be used to capture an image of the peripheral edge of a substrate S for the purpose of observing the appearance of the peripheral edge. Specific applications include, for example, a substrate surface defect inspection device such as that described in Japanese Patent Application Laid-Open No. 2018-036235 previously disclosed by the applicant of the present application, and a substrate processing device that performs processing such as etching on a bevel portion provided on the peripheral edge of a substrate.

[0019] Various substrates S can be used as the substrate to be processed, but substrates having a generally circular disk-like outer shape are particularly suitable. Examples include semiconductor wafers and glass substrates for various disks. The term "generally circular disk-like" here refers not only to substrates having a circular shape whose outer periphery is significantly longer than its thickness, but also to substrates having a generally circular outer periphery but with partial irregularities, such as substrates having an orientation flat or a notch formed on part of their periphery.

[0020] Furthermore, the peripheral portion of the substrate S is a concept that broadly includes annular regions within a predetermined distance from the outer periphery of both main surfaces of the substrate S, as well as the side surfaces of the substrate S. If a bevel portion is provided on the substrate S, this is also included. However, in a narrower sense, it can refer to only a part of them, i.e., only one of the annular region on one main surface, the bevel portion, and the side surface of the substrate. In the following explanation, the "peripheral portion Ss" will primarily refer to the annular region close to the outer periphery of the substrate that can be seen when the substrate S is held in a horizontal position and viewed from above.

[0021] The imaging device 1 includes a substrate support section 2 that holds and rotates the substrate S, a rotation detection section 3 that detects the rotation, an imaging section 4 that images the peripheral portion Ss of the substrate S, and a control section 9 that controls these sections to perform predetermined operations.

[0022] The substrate support portion 2 includes a disk-shaped chuck portion 21, a rotating shaft 22 extending downward from the center of the underside of the chuck portion, a rotation mechanism 23 that rotates the rotating shaft 22 around a vertical rotation axis AX, and a vacuum suction mechanism 24.

[0023] The chuck 21 has a diameter smaller than the diameter of the substrate S to be processed, and is supported by a rotating shaft 22 so that its upper surface is horizontal. Although not shown, a plurality of air intake holes are provided on the upper surface of the chuck 21, and each air intake hole is connected to a vacuum suction mechanism 24 that supplies negative pressure. With the substrate S placed on the chuck 21, the vacuum suction mechanism 24 supplies negative pressure to the air intake holes in response to a suction control command given by the suction control unit 98 of the control unit 9, thereby allowing the chuck 21 to hold the substrate S by vacuum suction.

[0024] The rotation mechanism 23 rotates the rotary shaft 22 around a rotation axis AX that passes through the center of the chuck portion 21. For this purpose, the rotation mechanism 23 is provided with a rotary motor 231. A direct drive system in which the rotary shaft 22 is directly connected to the output shaft of the rotary motor 231 may be employed, or a structure in which the rotary motor 231 and the rotary shaft 22 are connected via an appropriate power transmission mechanism such as a gear or a timing belt may be employed.

[0025] The motor control unit 97 of the control unit 9 provides a motor control signal to the rotary motor 231, which rotates in response to the motor control signal, thereby rotating the rotary shaft 22. This causes the chuck unit 21 and the substrate S supported thereby to rotate at a predetermined rotation speed. The amount of rotation of the chuck unit 21 is detected by the rotation detection unit 3.

[0026] 2A and 2B are diagrams showing an example of the configuration of the rotation detection unit. More specifically, Fig. 2A is a diagram showing the configuration of a rotary encoder for detecting the rotation of the chuck unit 21, and Fig. 2B is a block diagram showing the electrical configuration of the rotation detection unit 3. The rotation detection unit 3 mainly comprises a scale unit 31 attached to the underside of the chuck unit 21, and a reading unit 32 that optically reads the scale formed on the scale unit 31.

[0027] 2A, the scale unit 31 has a flat, annular shape made of, for example, glass, and has a number of graduations 311 radially arranged at regular angular intervals on its surface. The scale unit 31 is attached to the underside of the chuck unit 21 coaxially with the rotating shaft 22. Therefore, the scale unit 31 rotates as the chuck unit 21 rotates.

[0028] The reading unit 32 has a structure in which various electronic components are mounted on a circuit board 321 that is fixed to the housing of the rotation mechanism 23 by a support member 35. The circuit board 321 is disposed directly below the scale unit 31 that is attached to the underside of the chuck unit 21. An optical sensor 33 and a waveform shaping unit 34 are provided on the circuit board 321. The optical sensor 33 has a light-emitting unit 331 that irradiates light Li toward the scale unit 31, and a light-receiving unit 332 that receives reflected light Lr from the scale unit 31.

[0029] As the graduations 311 of the scale unit 31, which moves with the rotation of the chuck unit 21, pass through the optical path from the light-emitting unit 331 through the underside of the scale unit 31 to the light-receiving unit 332, the amount of light received by the light-receiving unit 332 changes. By detecting this change in the amount of light, the reading unit 32 can detect the rotation of the chuck unit 21. That is, each time the graduations 311 of the scale unit 31 pass through the optical path with the rotation of the chuck unit 31, the amount of light received by the light-receiving unit 332 fluctuates. The waveform shaping unit 34 shapes the analog signal output by the light-receiving unit 332 in accordance with the amount of received light, thereby obtaining a pulse signal in which one pulse is generated each time the graduations 311 pass through the optical path. Note that the waveform shaping unit 34 may be configured to output a multiplied pulse signal, i.e., to output multiple pulses each time one graduation 311 passes through.

[0030] Since the graduations 311 are provided at equal angular intervals, one pulse is output each time the chuck 21 rotates a certain amount. Therefore, the number of pulses generated in a certain period represents the amount of rotation of the chuck 21 in that period, and the pulse interval represents the time required to achieve a certain amount of rotation. In other words, the number of pulses is information related to the rotation angle of the chuck 21, and the pulse interval is information related to the rotation speed of the chuck 21. Therefore, in FIG. 1A, the pulse signal output by the reading unit 32 is referred to as "rotation information."

[0031] Since the substrate S is held by the chuck section 21 and rotates integrally with the chuck section 21, it can also be said that the reading section 32 outputs information relating to the rotation of the substrate S. In this way, the scale section 31 and the reading section 32 function together as a rotary encoder that outputs a signal including information relating to the amount of rotation (rotation angle, rotation speed) of the chuck section 21 (substrate S).

[0032] The pulse signal output by the reading unit 32 is input to a trigger signal generating unit 96 of the control unit 9. The trigger signal generating unit 96 generates a trigger signal to be given to the imaging unit 4, which will be described next, to determine the imaging timing. Specifically, the trigger signal generating unit 96 appropriately divides and multiplies the pulse signal output from the reading unit 32 to generate a pulse signal to be output at a time interval corresponding to the imaging interval, and gives this to the imaging unit 4 as a trigger signal.

[0033] Here, let us assume that the scale unit 31 is one in which one revolution is divided into 3600 equal parts (i.e., 0.1 degree pitch), and that 480 images are captured while the substrate S makes one revolution. In this case, based on the ratio of the two, the reading unit 32 should generate one trigger signal every time it outputs 7.5 pulses. More specifically, for example, the trigger signal can be generated by doubling the pulse signal output by the reading unit 32 and then dividing it by 15.

[0034] 1 , the imaging device 1 includes an imaging unit 4. The imaging unit 4 includes an imaging optical system 41 arranged so as to include a portion of the peripheral portion Ss of the substrate S in an imaging field of view FV, an imaging element 42 that receives light incident through the imaging optical system 41 and outputs image data corresponding to an image of the peripheral portion Ss within the imaging field of view FV, a shutter 43 provided on the optical path between the imaging optical system 41 and the imaging element 42, and a shutter control unit 44 that opens and closes the shutter 43. The imaging element 42 can be, for example, a two-dimensional image sensor such as a CCD element or a CMOS element.

[0035] The shutter control unit 44 operates in response to a trigger signal provided by the control unit 9. Specifically, when a pulse of the trigger signal is input, the shutter control unit 44 opens the shutter 43, and closes the shutter 43 after a predetermined period of time has elapsed. Light incident on the image sensor 42 while the shutter 43 is open forms an image of the peripheral portion Ss. Image capture is performed in this manner. When a pulse signal serving as a trigger signal is input multiple times, the shutter 43 is opened each time and image capture is performed.

[0036] The image data acquired by imaging is input to the image processing unit 92 of the control unit 9. The image processing unit 92 performs appropriate image processing on the received image data to create the required image. For example, it can perform image processing to create an entire peripheral image of the peripheral portion Ss, which will be described later.

[0037] In addition to the components described above, the control unit 9 also includes an operation control unit 91 that controls the overall operation of the imaging device 1, an inspection processing unit 93 that performs visual inspection processing of the substrate S based on images processed by the image processing unit 92, a memory 94 and a storage 95 that store various data, etc. The content of the inspection processing performed by the inspection processing unit 93 is arbitrary. Furthermore, the imaging device 1 may not include an inspection processing unit, and the inspection processing based on the images acquired by the imaging device 1 may be performed by an external inspection device.

[0038] Of the components of the control unit 9, the operation control unit 91, image processing unit 92, inspection processing unit 93, motor control unit 97, and suction control unit 98 can be realized in software, for example, by a CPU (Central Processing Unit) executing a prepared control program. However, some functions may be realized by dedicated hardware. The control program executed by the CPU can be stored in advance in the storage 95.

[0039] On the other hand, it is preferable that the trigger signal generator 96 be realized as independent hardware, because it basically operates relatively simply by dividing the frequency of an input pulse signal to obtain an output signal, and also because it is possible to avoid delays that would occur due to processing by the CPU.

[0040] 3A and 3B are diagrams showing other configuration examples of the imaging unit. In FIG. 1A, the imaging unit 4 is arranged above the substrate peripheral portion Ss, which is the object to be imaged, but the following arrangement is also possible. In the configuration example shown in FIG. 3A, a reflecting mirror 401 is arranged above the peripheral portion Ss of the substrate S. The imaging unit 4 is then arranged on the optical path (broken line) of light that is emitted from the upper surface of the substrate S and reflected by the reflecting mirror 401. With this configuration, the imaging unit 4 can capture an image of the substrate peripheral portion Ss reflected on the reflecting surface of the reflecting mirror 401 by imaging the reflecting mirror 401.

[0041] 3B, in addition to the reflecting mirror 401 that reflects light from the top surface of the substrate S, reflecting mirrors 402 and 403 that reflect light from the side and bottom surfaces of the substrate S, respectively, are further provided. These reflecting mirrors 401 to 403 are arranged so that the light reflected from the top, side, and bottom surfaces of the substrate S is incident on the imaging unit 4. With this configuration, it becomes possible to include images of the top, side, and bottom surfaces of the substrate S in a single image captured by the imaging unit 4.

[0042] As a more specific structure for realizing the configuration example shown in FIG. 3B, for example, an optical head equivalent to that described in Japanese Patent Application Laid-Open No. 2023-153470 (Patent Application No. 2022-062763) filed by the applicant of the present application can be applied.

[0043] When these configurations are used, it becomes possible to freely set the position of the imaging unit 4 to a certain extent. For example, when the imaging unit 4 is disposed to the side of the substrate support unit 2, the height of the entire imaging device 1 can be reduced compared to the configuration of FIG. 1A. In addition, the imaging unit 4 can be disposed at a position away from the substrate S. Therefore, for example, it becomes possible to combine a similar imaging function with a substrate processing apparatus that processes the substrate S by supplying gas, liquid, etc. to the substrate S without being affected by these.

[0044] Next, the operation of the imaging device 1 configured as described above will be described. As described above, this imaging device 1 is a device for acquiring images of the peripheral portion Ss of the substrate S, for example, for the purpose of visual inspection. Below, the operation of the imaging device 1 in a series of processes will be described, in which multiple images of the peripheral portion Ss for one circumference are acquired by intermittently capturing images multiple times while rotating the substrate S, these images are stitched together to create a composite image representing the entire peripheral portion Ss (hereinafter referred to as a "full peripheral image"), and visual inspection is performed based on these images.

[0045] Fig. 4 is a flowchart showing the operation of the entire imaging device, and Fig. 5 is a flowchart showing the operation of the imaging unit. These operations are realized by the operation control unit 91 controlling each unit of the device to perform a predetermined operation in accordance with a control program pre-stored in the storage 95. Note that the imaging operation by the imaging unit 4 may be performed autonomously without being controlled by the operation control unit 91.

[0046] First, the substrate S is carried into the imaging device 1 by an external transport device and placed on the chuck unit 21 so that its center coincides with the rotation center AX of the chuck unit 21. The vacuum suction mechanism 24 is activated, and the chuck unit 21 suctions and holds the substrate S (step S101). Then, the rotation detection unit 3 having a rotary encoder starts a detection operation (step S102), and the rotation motor 231 rotates, causing the substrate S to rotate integrally with the chuck unit 21 at a predetermined rotational speed (step S103).

[0047] In this state, the imaging unit 4 intermittently performs imaging a plurality of times, thereby acquiring a plurality of images of the peripheral edge portion Ss corresponding to one circumference of the substrate S (step S104). The imaging can be performed as follows.

[0048] 5, the image capturing unit 4 is prepared for image capturing in advance (step S201). That is, various image capturing conditions, such as frame rate, shutter speed, exposure, and other parameters, are set, and the image capturing unit 4 is ready to capture an image immediately. These parameters may be provided by the control unit 9, or the image capturing unit 4 itself may store the settings in advance.

[0049] When an external trigger signal is given in a state where preparations for image capture are complete (step S202), the shutter control unit 44 operates to open the shutter 43 for a predetermined time (step S203). Digital image data is created by analog-to-digital conversion (AD conversion) of the image signal generated by the image sensor 42 according to the amount of received light (step S204), and the image data is output to the control unit 9 (step S205). In this manner, the image capture operation is performed. The processes of steps S202 to S205 are repeated until the acquisition of the predetermined number of images has been completed (step S206).

[0050] 4, the image data for one rotation of the substrate output from the imaging unit 4 is stored in the storage 95 (step S105). When the imaging is completed, the rotation of the substrate S is stopped (step S106). The operation of the rotation detection unit 3 may also be stopped.

[0051] The image processing unit 92 creates an entire peripheral image by cutting out an effective area from each of the images of the peripheral portion Ss obtained as described above and stitching them together (steps S107 and S108). Since known image processing techniques can be applied to this type of image synthesis processing, a description thereof will be omitted here.

[0052] Based on the entire peripheral image thus created, the inspection processing unit 93 performs a visual inspection of the peripheral portion Ss of the substrate S (step S109). For example, for the substrate S after bevel etching, calculation of the etching width and evaluation of the processing results can be performed as part of the visual inspection. Note that the content of the visual inspection is not limited to this and is arbitrary. After the inspection is completed, the substrate S is unloaded, and the series of processes is completed (step S110).

[0053] As described above, in this embodiment, when the peripheral edge Ss of the rotating substrate S is intermittently imaged, the timing of imaging by the imaging unit 4 is determined by an external trigger signal. The trigger signal is generated based on a pulse signal output from the rotation detection unit 3 in response to the rotation of the substrate S (chuck unit 21). In other words, the imaging interval in this embodiment is not a predetermined constant value, but is determined in response to the amount of rotation of the substrate S. The reason for this is explained below.

[0054] 6A to 6C are diagrams illustrating problems that arise when the imaging interval is constant. As shown in FIG. 6A, in this embodiment, a portion of the peripheral edge Ss of the substrate S is included in the imaging field of view FV of the imaging unit 4. In one imaging, an image of the area of ​​the peripheral edge Ss included in the imaging field of view FV is acquired as image data. By intermittently capturing images multiple times while the imaging field of view FV is fixed and the substrate S is rotated, each portion of the peripheral edge Ss can be imaged. Here, the rotational angular velocity of the substrate S is represented by the symbol ω.

[0055] FIG. 6B schematically illustrates the relationship between the rotational angular velocity ω of the substrate S and the imaging timing. As shown by the dotted line in the upper diagram of FIG. 6B, it is desirable that the rotational angular velocity ω be constant relative to time T while the substrate S is rotating. However, as shown by the solid line, the rotational velocity of the substrate S fluctuates. For the sake of explanation, the diagram only shows macroscopic fluctuations with relatively long periods, but in reality, microscopic fluctuations with shorter periods also occur. Such speed fluctuations can be caused by a variety of factors, including eccentricity of the substrate S, dimensional accuracy or expansion / contraction of mechanical components, and time lags in rotation control. The inventors of the present application have observed microscopic speed fluctuations of approximately 1.5% in a configuration in which the rotation of a motor is transmitted to a rotating shaft via a timing belt, for example.

[0056] As shown in the lower diagram of Fig. 6B, the cumulative rotation angle R over a certain period can be expressed by integrating the rotation angular velocity ω with respect to time T. If the rotation angular velocity ω is constant, the cumulative rotation angle R increases linearly as shown by the dotted line, but if there is a velocity fluctuation, the cumulative rotation angle R also becomes a curve as shown by the solid line. When the trigger signal that determines the timing of imaging by the imaging unit 4 is a pulse signal with equal time intervals, such fluctuations in the cumulative rotation angle R cause the angle interval when imaging is performed to not be constant.

[0057] 6C , the intervals between the imaging fields of view FV defined for each image taken along the peripheral portion Ss are not constant, and in severe cases, gaps may occur between the imaging fields of view FV, resulting in loss of image information, as indicated by arrow A. Even if such loss does not occur, there is a risk of misalignment occurring when stitching together the images acquired in each imaging field of view FV.

[0058] For example, such problems can occur when a trigger signal is generated by dividing an internal clock with a fixed period generated for operational control, or when a trigger signal is generated based on a drive pulse for driving a pulse motor. These trigger signals do not necessarily accurately represent the actual microscopic rotation angle of the substrate S at each time. Furthermore, in digital control, selectable settings for the rotation speed of the chuck unit 21 and the timing of imaging are discrete, and in principle, the rotation of the substrate S and imaging may not be synchronized. There is often no correlation between speed fluctuations and the rotation angle of the substrate S, and it is also impossible to estimate the amount of deviation by measuring the magnitude of the speed fluctuations in advance.

[0059] 7A and 7B are diagrams showing schematic diagrams of imaging timing in this embodiment. In this embodiment, a pulse signal created by dividing the frequency of the pulse signal output from the rotation detection unit 3 each time the substrate S rotates by a fixed angle is used as the trigger signal. For this reason, as shown in FIG. 7A, the pulse interval varies depending on the speed fluctuation of the substrate S. However, when viewed in terms of the cumulative rotation angle R, trigger signals are generated at regular rotation angles, i.e., at equal angular intervals.

[0060] 7B, the intervals between the imaging fields of view FV defined for each image are constant, preventing loss of image information and eliminating the problem of misalignment when stitching and combining images.

[0061] 8A and 8B are diagrams illustrating problems with image synthesis. FIG. 8A shows an example in which trigger signals at equal angular intervals according to this embodiment are used. For ease of understanding, it is assumed that a line pattern LP extending obliquely relative to the radial direction is formed on the top surface of the substrate S near its outer periphery. Note that the image acquired in one imaging session captures only a small portion of the peripheral edge Ss of the substrate S, so the outer periphery of the substrate S can be considered to be a straight line.

[0062] Consider a case in which an image I(N) captured in the Nth (N is a natural number) imaging session and an image I(N+1) captured in the (N+1)th imaging session are combined. To avoid loss of image information, these images I(N) and I(N+1) are captured so that they partially overlap. The distance ΔL1 between regions on the substrate S corresponding to these images I(N) and I(N+1) can be expressed by the amount of movement of the outer periphery of the substrate S between the two imaging sessions. That is, using the diameter D of the substrate S, this can be expressed by the following equation: ΔL1=(D / 2)·Δθ1 (Equation 1). Here, Δθ1 is the rotation angle of the substrate S between the two imaging sessions.

[0063] Then, effective regions R(N) and R(N+1), excluding the peripheral portions, are extracted from each image and spliced ​​together to create a composite image Is. In this embodiment, images are captured at a constant angular interval (=Δθ1) regardless of fluctuations in the rotation speed of the substrate S. Therefore, by regularly arranging the effective regions extracted from each image at a constant pitch, a composite image with good image quality can be obtained. As shown in the composite image Is in Figure 8A, the smooth connection of the line pattern LP can be an indicator of good image quality.

[0064] On the other hand, Figure 8B shows an example in which trigger signals with equal time intervals are used. The interval ΔL2 between images in this case can also be expressed by the following equation: ΔL2 = (D / 2) Δθ2 ... (Equation 2). However, in the equation, the rotation angle Δθ2 of the substrate S between the two captures is not necessarily a constant value because it is affected by speed fluctuations during this period. For example, if ΔL2 > ΔL1, as shown in Figure 8B, a gap will occur between the effective regions R(N) and R(N+1) cut out from each image I(N) and I(N+1). In the composite image Is obtained by stitching these images together, the line pattern LP will be discontinuous. A similar discontinuity will occur if ΔL2 < ΔL1.

[0065] This degradation in image quality occurs due to a circumferential shift in the positional relationship of the effective areas cut out from each image. Therefore, if the amount of positional shift can be determined, correction is possible by adjusting the cut-out position of the effective area within the image. However, it is necessary to first determine the amount of positional shift in some way, and it is not possible to deal with gaps such as those indicated by arrow A in Figure 6C. Therefore, it is more effective to perform imaging at equal angular intervals, as in this embodiment.

[0066] As described above, in the imaging device 1 of this embodiment, the rotation detection unit 3 constituting a rotary encoder detects the amount of rotation of the chuck unit 21, which rotates integrally with the substrate S. The timing of imaging by the imaging unit 4 is determined by a trigger signal created from a pulse signal output each time the chuck unit 21 rotates a predetermined amount. Therefore, even if there is a fluctuation in the rotation speed of the substrate S, imaging can be performed at equal angular intervals relative to the rotation of the substrate S.

[0067] This means that the imaging fields of view FV defined for each image are arranged at regular intervals along the circumferential direction of the substrate S. Therefore, in this embodiment, it is possible to obtain multiple images of the peripheral portion Ss of the substrate S at regular intervals. By stitching these images together, it is possible to create an entire peripheral image with good image quality and no missing parts.

[0068] As described above, the imaging device 1 of this embodiment corresponds to the "imaging device" and "substrate processing device" of the present invention. Also, the trigger signal generating unit 96 in the above embodiment functions as the "signal converting unit" of the present invention.

[0069] 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, the imaging device 1 of the above embodiment has an imaging function of imaging the peripheral portion Ss of the substrate S while rotating it, an image processing function of performing image processing on the captured image, and an inspection function of performing an appearance inspection based on the processed image, and functions as the "substrate processing device" of the present invention. However, it is sufficient for the "imaging device" referred to in the present invention to have at least the imaging function, and at least one of the image processing function and the inspection function may be realized by an external device.

[0070] Furthermore, for example, in the above embodiment, the substrate support part 2 is provided to rotate the substrate S in order to capture an image of the peripheral edge Ss of the substrate S. However, many substrate processing apparatuses that perform various processes on substrates, such as physical processes and chemical processes, are also provided with a mechanism for rotating the substrate for the process. When the present invention is applied to such apparatuses, the mechanism for rotating the substrate for substrate processing can also be used for imaging purposes.

[0071] Furthermore, for example, in the above embodiment, the rotation of the substrate S is detected by a rotary encoder that is a combination of an annular scale unit 31 attached to the underside of the chuck unit 21 and a reading unit 32 that optically reads it. However, if the rotary shaft and the output shaft of the rotary motor are directly connected and the rotary motor has a built-in rotary encoder for control, the trigger signal may be generated based on the output of this rotary encoder.

[0072] As described above with reference to specific embodiments, the imaging device and imaging method according to the present invention may be configured to, for example, arrange multiple images along the circumferential direction of the substrate and combine them. For example, they may be configured to create an image of the peripheral edge corresponding to one circumference of the substrate. Speed ​​fluctuations in the rotation of the substrate cause relative positional deviations between images in the circumferential direction, resulting in a decrease in image quality when images are combined in this manner. By applying the present invention, this problem can be resolved, and good image quality can be obtained in the combined image.

[0073] In these cases, it is preferable that each of the multiple images be captured so that it overlaps at least partially with other images captured immediately before or after the image in question, thereby preventing loss of image information between adjacent captured images.

[0074] For example, the rotation detection unit may include a scale unit having a scale with markings at regular angular intervals that rotates integrally with the substrate support unit, and a reading unit that outputs a pulse signal as a signal each time the scale is read. With this configuration, the output interval of the pulse signal varies depending on the fluctuations in the rotation speed, but the rotation angle between pulses is always constant. Therefore, it is possible to operate the imaging unit according to the actual amount of rotation of the substrate and acquire images at regular angular intervals.

[0075] In this case, the rotation detection unit may have a signal conversion unit that generates a trigger signal by dividing the frequency of the pulse signal repeatedly output by the reading unit. That is, the rotation detection unit outputs a pulse signal with a cycle shorter than the imaging cycle, and divides the cycle to generate a trigger signal, thereby making it possible to respond to short-term fluctuations in the rotation speed of the substrate.

[0076] Furthermore, for example, the substrate support unit may be configured to rotate the substrate around the center of the disk-shaped substrate. With this configuration, it is possible to obtain images of the entire peripheral portion of the substrate by fixing the imaging field of view of the imaging unit and capturing images multiple times while rotating the substrate.

[0077] In this case, the predetermined process may be configured to execute an inspection process for inspecting the appearance of the peripheral portion based on a plurality of images. According to the present invention, it is possible to acquire images of the entire peripheral portion of the substrate without interruption, and therefore it is possible to effectively perform an appearance inspection of the peripheral portion of the substrate without omission based on those images.

[0078] 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.

[0079] The present invention can be applied to applications involving imaging the peripheral edge of a substrate, particularly a circular substrate such as a semiconductor wafer, and is particularly suitable for applications where it is necessary to image the entire peripheral edge of the substrate without any omissions.

[0080] REFERENCE SIGNS LIST 1 Imaging device (imaging device, substrate processing apparatus) 2 Substrate support section 3 Rotation detection section 4 Imaging section 31 Scale section 32 Reading section 92 Image processing section 96 Trigger signal generating section (signal converting section) FV Imaging field of view S Substrate Ss Periphery

Claims

1. An imaging device for imaging a peripheral portion of a substrate, comprising: a substrate support part which supports the substrate and rotates about a rotation axis perpendicular to a main surface of the substrate; an imaging part which is arranged to include a portion of the peripheral portion in its imaging field of view and which performs imaging in response to an external trigger signal; and a rotation detection part which outputs a signal corresponding to an amount of rotation of the substrate support part, wherein the rotation detection part outputs the signal each time the amount of rotation of the substrate support part reaches a predetermined value which is equal to a number of divisions of one revolution, and the imaging part performs the imaging multiple times using the signal output multiple times by the rotation detection part as the trigger signal, thereby obtaining multiple images of the peripheral portion.

2. The imaging device according to claim 1, further comprising an image processing section that arranges the multiple images along the circumferential direction of the substrate and combines them.

3. The imaging device according to claim 2, wherein the image processing section creates an image of the peripheral portion corresponding to one circumference of the substrate.

4. An imaging device as described in claim 2 or 3, wherein each of the plurality of images is captured so as to overlap at least partially with another image captured immediately before or after the image in question.

5. The imaging device of claim 1, wherein the rotation detection unit has a scale unit having markings at regular angular intervals and rotating integrally with the substrate support unit, and a reading unit that outputs a pulse signal as the signal each time the scale is read.

6. The imaging device according to claim 5, wherein the rotation detection section has a signal conversion section that generates the trigger signal by dividing the frequency of the pulse signal repeatedly output by the reading section.

7. The imaging device according to claim 1, wherein the substrate support section rotates the substrate around a center of the disk-shaped substrate.

8. A substrate processing apparatus which rotates a substrate to perform a predetermined process, comprising: a substrate support section which supports the substrate and rotates about a rotation axis perpendicular to a main surface of the substrate; an imaging section which is arranged to include a portion of a peripheral portion of the substrate within an imaging field of view and which performs imaging in response to an external trigger signal; and a rotation detection section which outputs a signal corresponding to an amount of rotation of the substrate support section, wherein the rotation detection section outputs the signal each time the amount of rotation of the substrate support section reaches a predetermined value which is equal to a number of divisions of one revolution, and the imaging section performs the imaging using the signal output multiple times by the rotation detection section as the trigger signal, thereby obtaining multiple images of the peripheral portion.

9. The substrate processing apparatus according to claim 8, wherein the predetermined process includes an inspection process for inspecting the appearance of the peripheral portion based on the plurality of images.

10. An imaging method for imaging a peripheral portion of a substrate, comprising: a substrate support section supports the substrate and rotates it about a rotation axis perpendicular to a main surface of the substrate; a rotation detection section outputs a signal each time the amount of rotation of the substrate reaches a predetermined value obtained by equally dividing one revolution into multiple parts; and an imaging section is positioned to include a part of the peripheral portion of the substrate within its imaging field of view, and performs imaging in response to an external trigger signal, and performs the imaging multiple times using the signal output multiple times by the rotation detection section as the trigger signal, thereby obtaining multiple images of the peripheral portion.

11. The imaging method according to claim 10, further comprising arranging the multiple images along the circumferential direction of the substrate and combining the images to create an image of the peripheral portion corresponding to one circumference of the substrate.

Images