Imaging device, substrate processing device, and imaging method

Abstract

To provide a technique capable of correctly acquiring each image at a predetermined angle interval, in a technique for imaging the peripheral edge part of a rotating substrate in a plurality of batches.SOLUTION: In an imaging device for imaging the peripheral edge part of a rotating substrate, an imaging method, and a substrate processing device, a substrate support part supports the substrate and rotates it around a rotation axis perpendicular to the main surface of the substrate, a rotation detection part outputs a signal whenever the rotation amount of the substrate reaches a predetermined value obtained by dividing one circumference into a plurality of equal parts, and an imaging part which is arranged so as to include a part of the peripheral edge part of the substrate in an imaging visual field and executes imaging according to a trigger signal from the outside executes imaging by using the signal outputted by the rotation detection part as the trigger signal, to acquire a plurality of images of the peripheral edge part.SELECTED DRAWING: Figure 5

Description

[Technical field]

[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, for example, inspection. [Background technology]

[0002] There are known processing systems that perform various processes on processing objects such as semiconductor wafers. In such substrate processing systems, for example, images of the substrate are captured to inspect the state of the substrate before and after processing. In particular, when observing the peripheral portion of the substrate, an imaging device is disposed so that a part of the peripheral portion is included in an imaging field, and the substrate is rotated while periodically capturing images to obtain an image of the entire peripheral portion.

[0003] For example, Patent Document 1 describes a technique in which a semiconductor wafer (substrate) is rotated and periodically imaged, multiple images are acquired, and then an image of the entire peripheral portion of the wafer is created by synthesizing the multiple images, and the center of the wafer is identified from 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 the imaging device is opened for a predetermined time at predetermined time intervals, thereby acquiring multiple images each associated with the rotation angle of the wafer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-125646 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above embodiment, there is no detailed description of the specific method of relating the image captured to the rotation angle, but from the disclosure, it is assumed that a linear relationship is established 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 moving speed 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 takes images at fixed time intervals, which means that it is sometimes impossible to correctly associate the images with the rotation angle when taking images. This causes the relative positions of the images to fluctuate in the circumferential direction when combining images, resulting in distortion of the combined image and other degradation of image quality.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a technology for imaging the peripheral portion of a rotating substrate multiple times, whereby each image can be obtained correctly at a specified angular interval. [Means for solving the problem]

[0008] One aspect of the present invention is an imaging device that images a peripheral portion of a rotating substrate, and includes a substrate support portion that supports the substrate and rotates around a rotation axis perpendicular to a 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] Moreover, one aspect of the present invention is a substrate processing apparatus that rotates a substrate to perform a predetermined process, and includes a substrate support section that supports the substrate and rotates about a rotation axis perpendicular to a main surface of the substrate, an imaging section that is positioned to include a portion of the peripheral portion of the substrate within an imaging field of view and that performs imaging in response to an external trigger signal, and a rotation detection section that outputs a signal in accordance with the amount of rotation of the substrate support section.

[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 which is equal to one revolution divided into multiple parts, and the imaging unit performs the imaging using the signal output 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 rotating substrate, wherein a substrate support portion supports the substrate and rotates it about an axis of rotation perpendicular to a main surface of the substrate, a rotation detection portion outputs a signal each time the amount of rotation of the substrate reaches a predetermined value which is equal to a number of divisions of one revolution, and an imaging portion positioned to include a portion of the peripheral portion of the substrate within its imaging field of view performs imaging in response to an external trigger signal, thereby obtaining multiple images of the peripheral portion.

[0012] In the invention configured in this way, an imaging section capable of performing imaging using an externally applied signal as a trigger is combined with a rotation detection section capable of outputting a signal according to the actual measurement result of the amount of rotation of the substrate. Specifically, imaging operation by the imaging section is performed using a signal output by the rotation detection section as a trigger signal each time the substrate rotates a certain amount. When imaging is performed at a certain time interval, if there is a speed fluctuation during one rotation of the substrate, the angular interval between images will vary.

[0013] In contrast, in the present invention, the effects of speed fluctuations can be eliminated by capturing images in synchronization with a signal output according to the actual amount of rotation of the substrate. Specifically, for example, if the rotation speed of the substrate slows down 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 correctly capture multiple images at a predetermined angular interval. Effect of the Invention

[0014] According to this invention, an imaging section that captures images using an external signal as a trigger is combined with a rotation detection section that outputs a signal each time the substrate rotates a predetermined amount, and imaging is performed using the signal output by the rotation detection section as a trigger signal, so that multiple images can be correctly acquired at a predetermined angle interval without being affected by fluctuations in the substrate rotation speed. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing a schematic configuration of an embodiment of an imaging device according to the present invention; [Diagram 2] FIG. 4 is a diagram illustrating an example of the configuration of a rotation detection unit. [Diagram 3] FIG. 13 is a diagram illustrating another example of the configuration of the imaging unit. [Figure 4] 4 is a flowchart showing the overall operation of the imaging apparatus. [Diagram 5] 4 is a flowchart showing the operation of an imaging unit. [Figure 6] 11A and 11B are diagrams for explaining problems that arise when the imaging interval is constant. [Figure 7] FIG. 4 is a diagram illustrating an image capturing timing according to the present embodiment. [Figure 8] FIG. 1 is a diagram illustrating a problem in image synthesis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Fig. 1 is a diagram showing a schematic configuration of an embodiment of an imaging device according to the present invention. More specifically, Fig. 1(a) is a diagram showing a schematic structure of a main part of an imaging device 1 of this embodiment, and Fig. 1(b) is a block diagram showing a control system of the imaging device 1. This imaging device 1 is a device for receiving a substrate S to be imaged and intermittently imaging a peripheral portion Ss of the substrate S while rotating the substrate S.

[0017] This imaging device 1 can be used to capture an image of the peripheral portion of a substrate S for the purpose of observing the appearance of the peripheral portion. Specific applications include, for example, a defect inspection device for a substrate surface as described in JP 2018-036235 A 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 portion of a substrate.

[0018] Various types of substrates S can be used as the substrate S to be processed, but those having an approximately disk-shaped outer shape are particularly suitable. Examples of such substrates include semiconductor wafers and glass substrates for various disks. The term "approximately disk-shaped" substrate as used here includes not only substrates whose outer circumference is a circular shape significantly larger than their thickness, but also substrates whose outer circumference is roughly circular but has partial irregularities, such as substrates with an orientation flat or notch provided on part of the outer circumference.

[0019] Furthermore, the peripheral portion of the substrate S is a concept that includes, in a broad sense, annular regions within a predetermined distance from the outer periphery of both main surfaces of the substrate S, and the side surfaces of the substrate S. If a bevel portion is provided on the substrate S, this is also included. However, in a narrow sense, it can refer to only a part of them, i.e., only a circular region on one main surface, a bevel portion, or a substrate side surface. In the following explanation, the "peripheral portion Ss" is primarily used to refer to the circular region close to the outer periphery of the substrate that can be seen when the substrate S held in a horizontal position is viewed from above.

[0020] 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.

[0021] The substrate support portion 2 includes a disk-shaped chuck portion 21, a rotating shaft 22 extending downward from the center of the lower surface 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.

[0022] The chuck section 21 has a diameter smaller than the diameter of the substrate S to be processed, and is supported by the rotating shaft 22 so that the upper surface is horizontal. Although not shown, a plurality of intake holes are provided on the upper surface of the chuck section 21, and each intake hole is connected to a vacuum suction mechanism 24 that supplies negative pressure. With the substrate S placed on the chuck section 21, the vacuum suction mechanism 24 supplies negative pressure to the intake holes in response to an adsorption control command given from the adsorption control section 98 of the control section 9, so that the chuck section 21 can hold the substrate S by vacuum suction.

[0023] The rotation mechanism 23 rotates the rotating 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 rotating motor 231. A direct drive system in which the rotating shaft 22 is directly connected to the output shaft of the rotating motor 231 may be adopted, or a structure in which the rotating motor 231 and the rotating shaft 22 are connected via an appropriate power transmission mechanism such as a gear or a timing belt may be adopted.

[0024] The motor control unit 97 of the control unit 9 provides a motor control signal to the rotary motor 231, and the rotary motor 231 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.

[0025] Fig. 2 is a diagram showing an example of the configuration of the rotation detection unit. More specifically, Fig. 2(a) is a diagram showing the configuration of a rotary encoder for detecting the rotation of the chuck unit 21, and Fig. 2(b) 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 lower surface of the chuck unit 21, and a reading unit 32 that optically reads the scale formed on the scale unit 31.

[0026] 2(a), the scale unit 31 has a flat ring 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.

[0027] The reading unit 32 has a structure in which various electronic components are mounted on a circuit board 321 fixed to the housing of the rotation mechanism 23 by a support member 35, and the circuit board 321 is disposed directly below the scale unit 31 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 projecting 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.

[0028] When the graduations 311 of the scale section 31, which moves with the rotation of the chuck section 21, pass through the optical path from the light projecting section 331 through the lower surface of the scale section 31 to the light receiving section 332, the amount of light received by the light receiving section 332 changes. By detecting this change in the amount of light, the reading section 32 can detect the rotation of the chuck section 21. That is, every time the graduations 311 of the scale section 31 pass through the optical path with the rotation of the chuck section 31, the amount of light received by the light receiving section 332 varies. The waveform shaping section 34 shapes the analog signal output by the light receiving section 332 according to the amount of received light, and a pulse signal can be obtained in which one pulse is generated each time the graduations 311 pass through the optical path. The waveform shaping section 34 may be configured to output a multiplied pulse signal, that is, to output multiple pulses each time one graduation 311 passes through.

[0029] Since the graduations 311 are spaced at equal angular intervals, one pulse is output each time the chuck portion 21 rotates a certain amount. Therefore, the number of pulses generated during a certain period represents the amount of rotation of the chuck portion 21 during 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 portion 21, and the pulse interval is information related to the rotation speed of the chuck portion 21. Therefore, in Fig. 1, the pulse signal output by the reading portion 32 is referred to as "rotation information."

[0030] Since the substrate S is held by the chuck portion 21 and rotates integrally therewith, it can also be said that the reading portion 32 outputs information relating to the rotation of the substrate S. In this manner, the scale portion 31 and the reading portion 32 function integrally as a rotary encoder that outputs a signal including information relating to the amount of rotation (rotation angle, rotation speed) of the chuck portion 21 (substrate S).

[0031] 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 provided to the imaging unit 4, which will be described next, in order to define 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 provides this to the imaging unit 4 as a trigger signal.

[0032] Here, if the scale unit 31 is one in which one revolution is divided into 3600 equal parts (i.e., 0.1 degree pitch), and 480 images are captured while the substrate S makes one revolution, then, based on the ratio of the two, a trigger signal may be generated once every 7.5 pulses output by the reading unit 32. 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.

[0033] Returning to Fig. 1, the imaging device 1 includes an imaging section 4. The imaging section 4 includes an imaging optical system 41 arranged so as to include a part of the peripheral portion Ss of the substrate S in an imaging field of view FV, an imaging element 42 that receives light incident via 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 an optical path between the imaging optical system 41 and the imaging element 42, and a shutter control section 44 that opens and closes the shutter 43. As the imaging element 42, for example, a two-dimensional image sensor such as a CCD element or a CMOS element can be used.

[0034] The shutter control unit 44 operates in response to a trigger signal provided from 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 imaging element 42 while the shutter 43 is open forms an image of the peripheral portion Ss. In this manner, imaging is performed. When a pulse signal is input multiple times as a trigger signal, the shutter 43 is opened each time and imaging is performed.

[0035] The image data acquired by imaging is input to an 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 a required image. For example, image processing for creating an entire peripheral image of the peripheral portion Ss, which will be described later, can be performed.

[0036] In addition to the components described above, the control unit 9 includes an operation control unit 91 that controls the operation of the entire 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, and a memory 94 and storage 95 that store various data. 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 images acquired by the imaging device 1 may be performed by an external inspection device.

[0037] 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 control program prepared in advance. However, some functions may be realized by dedicated hardware. The control program executed by the CPU can be stored in the storage 95 in advance.

[0038] On the other hand, the trigger signal generating unit 96 basically operates in a relatively simple manner of dividing the input pulse signal to obtain an output signal, and it is preferable that it be realized as independent hardware in order to avoid delays that arise from processing by the CPU.

[0039] Fig. 3 is a diagram showing another example of the configuration of the imaging unit. In Fig. 1(a), the imaging unit 4 is disposed above the peripheral portion Ss of the substrate, which is the object to be imaged, but the following arrangement is also possible. In the example of the configuration shown in Fig. 3(a), a reflecting mirror 401 is disposed above the peripheral portion Ss of the substrate S. Then, the imaging unit 4 is disposed on the optical path (broken line) of light 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 reflecting mirror 401, thereby acquiring an image of the peripheral portion Ss of the substrate reflected on the reflecting surface.

[0040] 3(b), 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 reflected light from the top, side, and bottom surfaces of the substrate S enter 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 one image captured by the imaging unit 4.

[0041] As a more specific structure for realizing the configuration example shown in FIG. 3(b), for example, an optical head equivalent to that described in Japanese Patent Application No. 2022-062763 filed by the applicant of the present application can be applied.

[0042] When these configurations are used, it becomes possible to freely set the position of the imaging unit 4 to a certain degree. For example, when the imaging unit 4 is disposed to the side of the substrate support unit 2, the height of the imaging device 1 as a whole can be reduced compared to the configuration of Fig. 1(a). In addition, since the imaging unit 4 can be disposed at a position away from the substrate S, it becomes possible to combine a similar imaging function with, for example, a substrate processing device that supplies gas, liquid, or the like to the substrate S for processing, without being affected by these.

[0043] Next, the operation of the imaging device 1 configured as above will be described. As described above, the 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. In the following, 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 revolution are acquired by intermittently capturing images multiple times while rotating the substrate S, and these images are joined together to create a composite image (hereinafter, referred to as a "full peripheral image") representing the entire peripheral portion Ss, and visual inspection is performed based on the images.

[0044] 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 section. These operations are realized by the operation control section 91 controlling each section of the device to execute a predetermined operation in accordance with a control program previously stored in the storage 95. Note that the imaging operation by the imaging section 4 may be executed autonomously without being controlled by the operation control section 91.

[0045] First, the substrate S is carried into the imaging device 1 by an external transport device, and is placed on the chuck portion 21 so that its center coincides with the rotation center AX of the chuck portion 21. The vacuum suction chuck portion 21 suctions and holds the substrate S (step S101). Then, a detection operation by the rotation detection portion 3 having a rotary encoder is started (step S102), and the rotation motor 231 rotates, so that the substrate S is rotated integrally with the chuck portion 21 at a predetermined rotation speed (step S103).

[0046] In this state, the imaging unit 4 intermittently performs imaging a plurality of times, thereby acquiring a plurality of images of the peripheral portion Ss corresponding to one circumference of the substrate S (step S105). The imaging can be performed as follows.

[0047] 5, the imaging unit 4 is prepared for imaging in advance (step S201). That is, various imaging conditions, such as parameters such as frame rate, shutter speed, and exposure, are set, and the imaging unit 4 is ready to start imaging immediately. These parameters may be provided by the control unit 9, or the imaging unit 4 itself may store the settings in advance.

[0048] When an external trigger signal is given in a state where image capture preparation is 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 acquisition of the predetermined number of images is completed (step S206).

[0049] 4, image data for one revolution 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.

[0050] The image processor 92 creates an entire peripheral image by cutting out the effective area from each of the images of the peripheral portion Ss for one circumference obtained as described above and stitching them together (steps S107 and S108). Since a known image processing technique can be applied to such image synthesis processing, a description thereof will be omitted here.

[0051] Based on the entire peripheral image thus created, the inspection processing unit 93 performs an appearance inspection of the peripheral portion Ss of the substrate S (step S109). For example, for the substrate S after bevel etching processing, calculation of the etching width and evaluation of the processing results can be performed as part of the appearance inspection. Note that the contents of the appearance inspection are not limited to this and are arbitrary. After the inspection is completed, the substrate S is unloaded and the series of processes is completed (step S110).

[0052] As described above, in this embodiment, when the peripheral portion Ss of the rotating substrate S is intermittently imaged, the imaging timing 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 portion 21). That is, 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.

[0053] Fig. 6 is a diagram for explaining problems that arise when the imaging interval is constant. As shown in Fig. 6(a), in this embodiment, a part of the peripheral portion Ss of the substrate S is included in the imaging field of view FV of the imaging unit 4, and an image of an area of ​​the peripheral portion Ss included in the imaging field of view FV is acquired as image data in one imaging. Each part of the peripheral portion Ss can be imaged by intermittently imaging multiple times while the imaging field of view FV is fixed and the substrate S is rotated. Here, the rotational angular velocity of the substrate S is represented by the symbol ω.

[0054] FIG. 6(b) shows a schematic diagram of 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. 6(b), it is desirable that the rotational angular velocity ω is constant with respect to time T while the substrate S rotates. However, as shown by the solid line, the rotational velocity of the substrate S fluctuates. For the sake of explanation, the diagram shows macroscopic fluctuations with a relatively long period, but in reality there are microscopic fluctuations with a finer period. Such speed fluctuations can be caused by various factors such as eccentricity of the substrate S, dimensional accuracy and expansion / contraction of mechanical parts, and time lag in rotation control. The inventor of the present application has observed microscopic speed fluctuations of about 1.5% in a configuration in which the rotation of a motor is transmitted to a rotating shaft by a timing belt, for example.

[0055] As shown in the lower diagram of Fig. 6(b), the accumulated rotation angle θ over a certain period of time can be expressed by integrating the rotation angular velocity ω with respect to time T. If the rotation angular velocity ω is constant, the accumulated rotation angle θ increases linearly as shown by the dotted line, but if there is a velocity fluctuation, the accumulated rotation angle R also becomes a curve as shown by the solid line. When the trigger signal that determines the imaging timing by the imaging unit 4 is a pulse signal with equal time intervals, such fluctuations in the accumulated rotation angle θ cause the angle interval when imaging is performed to not be constant.

[0056] 6(c), 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, causing loss of image information, as indicated by the arrow A. Even if there is no such loss, there is a risk of misalignment occurring when the images captured in the imaging fields of view FV are stitched together.

[0057] For example, such a problem may occur when a trigger signal is generated by dividing an internal clock with a constant period generated for operation 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 microscopic rotation angle of the actual substrate S at each time. In addition, in digital control, the selectable setting values ​​for the rotation speed of the chuck part 21 and the imaging timing are discrete, and in principle, the rotation of the substrate S and the imaging may not be synchronized. There is often no correlation between the speed fluctuation 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 fluctuation in advance.

[0058] Fig. 7 is a diagram showing a schematic diagram of the imaging timing in this embodiment. In this embodiment, a pulse signal generated by dividing the pulse signal output from the rotation detection unit 4 each time the substrate S rotates by a certain angle is used as a trigger signal. Therefore, as shown in Fig. 7(a), the pulse interval varies according to the speed fluctuation of the substrate S, but when viewed on the scale of the cumulative rotation angle R, a trigger signal is generated every certain rotation angle, that is, at equal angular intervals.

[0059] Therefore, as shown in Fig. 7(b), the interval of the imaging field of view FV defined for each image is constant, and the loss of image information is avoided. In addition, there is no problem of misalignment when stitching together the images.

[0060] Fig. 8 is a diagram for explaining problems in image synthesis. Fig. 8(a) 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 to the radial direction is formed on the upper surface close to the outer periphery of the substrate S. Note that an image acquired in one imaging session is an image of only a small portion of the peripheral portion Ss of the substrate S, so here it is assumed that the outer periphery of the substrate S can be regarded as a straight line.

[0061] Consider the case where image I(N) captured the Nth time (N is a natural number) of multiple intermittently performed image captures is combined with image I(N+1) captured the (N+1)th time. In order to avoid loss of image information, these images I(N) and I(N+1) are captured so that they partially overlap each other. The distance ΔL1 between the regions on the substrate S corresponding to these images I(N) and I(N+1) can be expressed by the amount that the outer periphery of the substrate S moves between the two image captures. That is, using the diameter D of the substrate S, the following equation is used: ΔL1=(D / 2)·Δθ1 … (Equation 1) Here, Δθ1 is the rotation angle of the substrate S between two imaging operations.

[0062] Then, effective areas R(N), R(N+1) excluding the peripheral areas are cut out from each image and joined 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, so that a composite image with good image quality can be obtained by regularly arranging the effective areas cut out from each image at a constant pitch. As shown in the composite image Is in FIG. 8(a), the smooth connection of the line pattern LP can be an indicator of good image quality.

[0063] On the other hand, Fig. 8(b) shows an example in which a trigger signal with equal time intervals is used. In this case, the interval between images, ΔL2, is also expressed by the following equation: ΔL2=(D / 2)·Δθ2 … (Equation 2) In the formula, however, the rotation angle Δθ2 of the substrate S between two captures is not necessarily a constant value because it is affected by the speed fluctuation during this period. For example, if ΔL2>ΔL1, as shown in FIG. 8(b), a gap will be generated between the effective areas R(N) and R(N+1) cut out from the images I(N) and I(N+1), and the line pattern LP will be discontinuous in the composite image Is obtained by joining these images together. A similar discontinuity will occur if ΔL2<ΔL1.

[0064] Such degradation of 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 is obtained, it is possible to correct it by adjusting the cut-out position of the effective area in the image. However, it is necessary to first obtain the amount of positional shift by some method, and it is not possible to deal with gaps such as those shown by arrow A in FIG. 6(c). Therefore, it is more effective to perform imaging itself at equal angular intervals, as in this embodiment.

[0065] 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, and 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 with respect to the rotation of the substrate S.

[0066] This means that the imaging fields of view FV defined for each imaging are arranged at regular intervals along the circumferential direction of the substrate S. Therefore, in this embodiment, it is possible to obtain a plurality of images of the peripheral portion Ss of the substrate S captured at regular intervals, and by stitching these images together, it is possible to create an entire peripheral image with good image quality and no missing images.

[0067] As described above, the imaging device 1 of this embodiment corresponds to the "imaging device" and the "substrate processing device" of the present invention. Also, the trigger signal generating unit 96 in the above embodiment functions as the "signal conversion unit" of the present invention.

[0068] The present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the imaging device 1 of the above-mentioned 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" of 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.

[0069] Also, for example, in the above embodiment, a substrate support part 2 is provided that rotates the substrate S in order to image the peripheral portion Ss of the substrate S. However, many substrate processing apparatuses that perform various processes, such as physical processes and chemical processes, on substrates are provided with a mechanism for rotating the substrate for the processes. When the present invention is applied to such an apparatus, the mechanism for rotating the substrate for substrate processing can also be used for imaging purposes.

[0070] Also, for example, in the above embodiment, the rotation of the substrate S is detected by a rotary encoder formed by a combination of an annular scale portion 31 attached to the underside of the chuck portion 21 and a reading portion 32 that optically reads it. However, if the rotating shaft and the output shaft of the rotating motor are directly connected and the rotating motor has a built-in rotary encoder for control, the trigger signal may be created based on the output of this rotary encoder.

[0071] As described above by way of example of specific embodiments, the imaging device and imaging method according to the present invention may be configured to, for example, arrange a plurality of images along the circumferential direction of the substrate and combine them together. For example, it may be configured to create an image of the peripheral portion corresponding to one revolution of the substrate. Since speed fluctuations in the rotation of the substrate cause relative positional deviations between images in the circumferential direction, combining images in this manner leads to a decrease in image quality. By applying the present invention, this problem is eliminated, and good image quality can be obtained in the combined image.

[0072] In these cases, it is preferable that each of the multiple images is captured so that it at least partially overlaps with other images captured before and after the current image in time, thereby making it possible to avoid a loss of image information between adjacent captured images.

[0073] For example, the rotation detection unit may have a scale unit having graduations at regular angular intervals and rotating 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 according to 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 obtain images at equal angular intervals.

[0074] 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 period shorter than the imaging period, and divides the frequency of this signal to generate a trigger signal, which makes it possible to respond to short-term fluctuations in the rotation speed of the substrate.

[0075] For example, the substrate support unit may be configured to rotate the substrate around the center of the disk-shaped substrate as the center of rotation. With this configuration, it is possible to obtain an image of the entire peripheral portion of the substrate by fixing the imaging field of view of the imaging unit and imaging multiple times while rotating the substrate.

[0076] In this case, the predetermined process may be configured to execute an inspection process for inspecting the appearance of the peripheral portion based on the multiple 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 the images. [Industrial Applicability]

[0077] The present invention can be applied to applications in which the peripheral portion of a substrate, in particular a circular substrate such as a semiconductor wafer, is imaged, and is particularly suitable for applications in which the entire peripheral portion of the substrate must be imaged without omission. [Explanation of symbols]

[0078] 1 Imaging device (imaging device, substrate processing device) 2 Board support 3 Rotation detector 4. Imaging unit 31 Scale section 32 Reading unit 92 Image Processing Section 96 Trigger signal generator (signal converter) FV Imaging field of view S-substrate Ss periphery

Claims

1. An imaging device for imaging a peripheral portion of a rotating substrate, comprising: a substrate support section that supports the substrate and rotates about a rotation axis perpendicular to a main surface of the substrate; an imaging unit that is disposed so as to include a part of the peripheral portion in an imaging field of view and performs imaging in response to an external trigger signal; a rotation detection unit that outputs a signal corresponding to an amount of rotation of the substrate support unit; Equipped with the rotation detection unit outputs the signal each time an amount of rotation of the substrate support unit reaches a predetermined value obtained by equally dividing one revolution into a plurality of revolutions, The imaging unit performs the imaging using the signal output by the rotation detection unit as the trigger signal, thereby obtaining a plurality of images of the peripheral portion.

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

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. 4. The imaging device according to claim 2, wherein each of the plurality of images is captured such that at least a portion of the image overlaps with another image captured before or after the image in time.

5. 2. The imaging device according to 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 includes 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 portion rotates the substrate about a center of the disk-shaped substrate.

8. A substrate processing apparatus that rotates a substrate to perform a predetermined process, a substrate support section that supports the substrate and rotates about a rotation axis perpendicular to a main surface of the substrate; an imaging unit that is disposed so as to include a part of the peripheral portion of the substrate in an imaging field of view and performs imaging in response to an external trigger signal; a rotation detection unit that outputs a signal corresponding to an amount of rotation of the substrate support unit; Equipped with the rotation detection unit outputs the signal each time an amount of rotation of the substrate support unit reaches a predetermined value obtained by equally dividing one revolution into a plurality of revolutions, The imaging unit performs the imaging using the signal output by the rotation detection unit as the trigger signal, thereby obtaining a plurality of images of the peripheral portion.

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

10. 1. A method for imaging a peripheral portion of a rotating substrate, comprising: a substrate support portion supports the substrate and rotates the substrate about a rotation axis perpendicular to a main surface of the substrate; a rotation detection unit outputs a signal each time the amount of rotation of the substrate reaches a predetermined value obtained by equally dividing one revolution; An imaging method in which an imaging unit is positioned to include a portion of the peripheral portion of the substrate within an imaging field of view, and performs imaging in response to an external trigger signal, and acquires multiple images of the peripheral portion by performing the imaging using the signal output by the rotation detection unit as the trigger signal.

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

Images