JP2005217139A - Image acquiring device and image acquisition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for acquiring the image of a prescribed position on a rotating substrate. <P>SOLUTION: A substrate polishing system 1 is provided with a substrate rotation section 11 for rotating a substrate 9 where a notch is formed in the outer edge around a revolving shaft J1 vertical to the principal surface as a center, a head 2 for acquiring the principal surface of the substrate 9 while the substrate 9 rotates, a notch sensor 4 for detecting the rotating passage of the notch of the substrate 9, and a stroboscope controller 5 into which the signal indicating the passage of the notch from the notch sensor 4 is inputted. When the passage of the notch of the rotating substrate 9 is detected by the notch sensor 4, the stroboscope controller 5 performs the image pick-up of the substrate 9 by the head 2 after a predetermined delay time from the passage time of the notch. Thus, it is realized to acquire the picture of a prescribed position on the rotating substrate 9 with sufficient accuracy. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for acquiring an image of a rotating substrate.

  Conventionally, in a circuit formation process of a semiconductor substrate (hereinafter referred to as “substrate”), an image is picked up by aligning an image pickup position by an image pickup unit with a predetermined position on the substrate (that is, positioning), and an acquired image is obtained. Based on this, various measurement values used for the inspection of the circuit pattern are obtained (see Patent Document 1 as an example of a method for aligning the imaging position of the imaging unit with a predetermined position on the substrate).

On the other hand, in the damascene process of the circuit formation process, chemical mechanical polishing (hereinafter abbreviated as “CMP”) is used, and in the CMP apparatus, the main surface of the substrate is in contact with the polishing plate. By rotating the substrate in step 1, the film formed on the main surface of the substrate is polished.
Japanese Patent Laid-Open No. 11-345867

  By the way, in the conventional technique for aligning the imaging position of the imaging unit with a predetermined position on the substrate, it is assumed that the substrate is stationary, so that it can be used for processing performed while rotating the substrate like CMP. It is necessary to interrupt the processing and take an image by separating the substrate from the polishing plate. However, such interruption of processing causes a decrease in throughput.

  The present invention has been made in view of the above-described problems, and has as its main purpose to acquire an image at a predetermined position on a rotating substrate with high accuracy.

  The invention according to claim 1 is an image acquisition apparatus for acquiring an image of a substrate, wherein the substrate rotating unit rotates the substrate at a constant angular velocity about an axis perpendicular to the main surface, and the substrate rotating unit is a substrate. On the basis of the output from the edge passing detector, the edge passing detector for detecting the passage of the edge of the substrate rotated by the substrate rotating part, and the edge passing detector And an imaging control unit that executes imaging by the imaging unit after a predetermined time has elapsed from the time when the substrate is in a specific direction.

  A second aspect of the present invention is the image acquisition device according to the first aspect, wherein the edge passage detection unit detects passage of a notch formed in an outer edge portion of the substrate.

  Invention of Claim 3 is an image acquisition apparatus of Claim 2, Comprising: The said edge passage detection part emits light toward a board | substrate, The reflection from the board | substrate of the light from the said light source A light-receiving unit that receives light, and the imaging control unit obtains the detection time of passage of the notch by calculation based on characteristics of at least one output pulse from the light-receiving unit.

  A fourth aspect of the present invention is the image acquisition device according to any one of the first to third aspects, wherein template image data indicating a reference pattern and a position of a specific point on the substrate with respect to the reference pattern are provided. A position of a point corresponding to the specific point in the acquired image is obtained by performing pattern matching between the storage unit that stores information and the image acquired by the imaging unit and the template image. And an arithmetic unit.

  According to a fifth aspect of the present invention, in the image acquisition device according to any one of the first to third aspects, the polishing unit that polishes the main surface of the substrate rotated by the substrate rotating unit, and the imaging unit A polishing end point detecting unit for detecting a polishing end point based on the acquired image;

  The invention according to claim 6 is the image acquisition device according to claim 5, wherein the polishing end point detection unit polishes based on a value of a pixel at a specific position in the image acquired by the imaging unit. The end point of is detected.

  A seventh aspect of the present invention is the image acquisition device according to the fifth aspect of the present invention, which is a memory for storing template image data indicating a reference pattern and position information of the specific point on the substrate with respect to the reference pattern. And a calculation unit for obtaining a position of a point corresponding to the specific point in the acquired image by performing pattern matching between the image acquired by the imaging unit and the template image. The polishing end point detection unit detects a polishing end point based on a pixel value at a point position corresponding to the specific point in the acquired image.

  The invention according to claim 8 is an image acquisition method for acquiring an image of a substrate, wherein a) a step of rotating the substrate at a constant angular velocity about an axis perpendicular to the main surface, and b) the rotating substrate. C) detecting the passage of the edge by an edge passage detection unit; and c) based on the output from the edge passage detection unit, the main surface of the substrate after a predetermined time has elapsed from the time when the substrate is in a specific direction. And an image capturing unit.

  The invention according to claim 9 is the image acquisition method according to claim 8, wherein the edge passage detection unit detects passage of a notch formed in an outer edge portion of the substrate.

  The invention according to claim 10 is the image acquisition method according to claim 9, wherein the edge passage detection unit emits light toward the substrate and receives reflected light from the substrate. One output pulse is generated, and in step c), the detection time of passage of the notch is obtained by calculation based on the characteristics of the at least one output pulse.

  The invention according to claim 11 is the image acquisition method according to any one of claims 8 to 10, wherein the template image data indicating the reference pattern and on the substrate are provided before the step b). Preparing the position information of the specific point with respect to the reference pattern, and after the step c), the pattern acquisition is performed by performing pattern matching between the image acquired by the imaging unit and the template image. Obtaining a position of a point corresponding to the specific point in the image.

  The invention according to claim 12 is the image acquiring method according to any one of claims 8 to 10, wherein the main surface of the substrate is polished in parallel with the step a), and c) And a step of detecting an end point of polishing based on an image acquired by the imaging unit after the step.

  According to the present invention, an image of a predetermined position on a rotating substrate can be acquired with high accuracy.

  In the inventions of claims 3 and 10, the detection time of passage of the notch can be appropriately obtained.

  In the inventions of claims 4 and 11, the position of a specific point on the substrate in the acquired image can be obtained with high accuracy.

  According to the fifth and twelfth aspects of the present invention, it is possible to appropriately detect the polishing end point based on an image at a predetermined position on the substrate to be polished.

  In the invention of claim 6, the polishing end point can be easily detected.

  In the invention of claim 7, the end point of polishing of the substrate having a pattern can be detected with high accuracy.

  FIG. 1 is a diagram showing a configuration of the substrate polishing system 1. The substrate polishing system 1 of FIG. 1 is used, for example, in a damascene process in a circuit forming process, and a film (film forming a circuit pattern) formed on a main surface of a substrate is polished (for example, CMP). An image of the substrate being polished is acquired, and the polishing end point is detected based on the acquired image.

  A substrate polishing system 1 includes a substrate rotating unit 11 that holds a disk-shaped substrate 9 having a V-shaped notch formed on an outer edge and rotates the substrate 9 about a rotation axis J1 perpendicular to the main surface. The head unit 2 that images the main surface of the substrate 9 while the substrate 9 rotates, the illumination unit 3 that emits illumination light irradiated on the main surface of the substrate 9 via the head unit 2, and the rotating substrate 9 A notch sensor 4 that detects the passage of the notch, a strobe controller 5 that receives a signal indicating the passage of the notch from the notch sensor 4, a computer 6 that includes a CPU that performs various arithmetic processes, a memory that stores various information, and the like; , Another computer (hereinafter referred to as “overall control unit”) 7 responsible for overall control of the substrate polishing system 1 is provided.

  FIG. 2 is a view showing the vicinity of the substrate rotating portion 11 when the substrate 9 is polished. As shown in FIG. 2, the substrate 9 is attracted and held by the top ring 110 so that the center of the main surface is positioned on the rotation axis J1 in the substrate rotating portion 11, and a part of the main surface is polished by the polishing plate 71 (FIG. 1). Is not shown in the figure). The substrate rotating unit 11 has a motor 111 connected to the overall control unit 7 (see FIG. 1), and the substrate 9 rotates at a constant angular velocity when the motor 111 is driven. The substrate rotating unit 11 is supported by an advancing / retracting mechanism (not shown). When the substrate 9 is attached or removed, the advancing / retreating mechanism is controlled to retract the substrate 9 from the polishing plate 71. The substrate rotating unit 11 may be directly controlled by the computer 6.

  The polishing plate 71 is rotated by a motor 711, and an abrasive (also called slurry) is supplied on the surface thereof. Thus, the main surface of the substrate 9 rotated by the substrate rotating unit 11 is polished by the rotating polishing plate 71. The head unit 2 is supported on the stage 21 so as to be able to advance and retreat toward the polishing plate 71. When the substrate 9 is polished, the head unit 2 moves to the lower side of the substrate 9 outside the polishing plate 71. The main surface is imaged. The notch sensor 4 is provided to face the outer edge portion of the main surface of the substrate 9 at a position shifted from the head portion 2.

  The illumination unit 3 in FIG. 1 has a lamp power supply 31 connected to the strobe controller 5, and the flash lamp 32 emits flash light when a trigger signal is input from the strobe controller 5. Light from the flash lamp 32 is guided to the filter unit 34 through the lens 33. The filter unit 34 is provided with a plurality of filters 341, and one filter 341 a out of the plurality of filters 341 is arranged on the light path from the flash lamp 32 by a motor (not shown). The light transmitted through the filter 341a is guided to the optical fiber 36 by the lens 35 and introduced into the head unit 2, and is used for imaging the substrate 9 by the head unit 2.

  3 is a diagram of the vicinity of the head unit 2 shown in FIG. 2 as viewed from the side, and FIG. 4 is a diagram showing the internal configuration of the head unit 2 when viewed from the substrate 9 side. As shown in FIG. 3, the head portion 2 is supported in a state of being close to the lower main surface 91 of the substrate 9. The head portion 2 has a light transmission window 239 and an annular nozzle portion 22 surrounding the light transmission window 239 on the substrate 9 side, and a plurality of discharge ports are formed on the inner peripheral surface of the nozzle portion 22. The nozzle unit 22 is connected to a pure water supply unit 221, and pure water is discharged from a plurality of discharge ports of the nozzle unit 22 when the substrate 9 is polished, and faces the light transmission window 239 on the main surface 91 of the substrate 9. Slurry etc. adhering to the position are removed.

  As shown in FIG. 4, the light from the illumination unit 3 is introduced into the head unit 2 through the optical fiber 36, guided to the mirror 233 through the lens 231 and the aperture plate 232, and reflected toward the lens 234. Is done. The light incident on the lens 234 is guided to the half mirror 236 via the aperture plate 235 and reflected toward the lens 237. The light from the lens 237 is guided to the substrate 9 side by the prism 238 as shown in FIG. 3, and is irradiated onto the main surface 91 of the substrate 9 through the light transmission window 239.

  The reflected light from the substrate 9 is taken in by the translucent window 239 and guided to the half mirror 236 by the prism 238 and the lens 237. Part of the reflected light passes through the half mirror 236 and is guided to the imaging device 25 by the aperture plate 240 and the lens 241 to form an image of the substrate 9. In the imaging device 25, the received light is converted into an electrical signal and output to the computer 6 in FIG. The lens 237 can be moved by the lens moving mechanism 26 in the direction of the arrow denoted by reference numeral 291 in FIG. 4, and the lens 237 and the lens moving mechanism 26 constitute an autofocus mechanism of the head unit 2.

  FIG. 5 shows the internal configuration of the notch sensor 4 when the vicinity of the notch sensor 4 shown in FIG. 2 is viewed from the side. As shown in FIG. 5, the notch sensor 4 has two light sources 41 (for example, light sources having light emitting diodes (LEDs)) that emit light toward the substrate 9, and light from the light sources 41 is a transparent window 42. Is applied to the outer edge of the rotating substrate 9. Normally, the light from the light source 41 is reflected by the lower main surface 91 of the substrate 9 toward the outer peripheral side or the outer side of the light transmission window 42, but the light source is generated when the notch of the substrate 9 passes over the notch sensor 4. When the light from 41 is irregularly reflected, the reflected light from the substrate 9 is taken in by the light transmitting window 42 and received by the photodiode 44 through the lens 43. Also in the notch sensor 4, like the head part 2, an annular nozzle part 451 for cleaning the position facing the notch sensor 4 on the main surface 91 of the substrate 9, and pure water supply for supplying pure water to the nozzle part 451 A portion 452 is provided.

  FIG. 6 is a block diagram showing circuit configurations of the notch sensor 4 and the strobe controller 5. The photodiode 44 outputs an electrical signal according to the amount of light received, and the preamplifier 46 (for example, an IV amplifier) amplifies the output signal. The comparator 47 (for example, an analog comparator) compares the voltage of the amplified output signal with a predetermined threshold voltage, and outputs the minimum voltage (Low level) of the comparator output when the voltage of the output signal is smaller than the threshold voltage. When it is larger than the threshold voltage, the maximum voltage (High level) of the comparator output is output. In the notch sensor 4, a variable resistor or the like may be provided as necessary, and the threshold voltage of the comparator 47 may be adjustable.

  The strobe controller 5 includes a trigger generation circuit 51 and an I / O interface 52. The trigger generation circuit 51 outputs trigger signals 591 and 592 to the illumination unit 3 and the computer 6 based on signals from the notch sensor 4, respectively. . The trigger signal 591 is for causing the illumination unit 3 to emit flash light, and the trigger signal 592 is for acquiring image data of the substrate 9 via the head unit 2 by the computer 6. In the following description, they are called a strobe trigger signal 591 and a camera trigger signal 592, respectively. The I / O interface 52 is connected to the computer 6, and various parameters are input from the computer 6 to the trigger generation circuit 51.

  FIG. 7 is a diagram showing the configuration of the trigger generation circuit 51. The trigger generation circuit 51 shown in FIG. 7 includes a clock generation unit 511. The clock generation unit 511 receives a clock signal CLK having a predetermined frequency output from the crystal oscillator as a notch signal interface 512, an address counter 513, and a notch timing determination circuit. 514, notch signal condition register 515, and delay time setting register 516. Note that CLK may be obtained by further dividing the signal output from the crystal oscillator. A signal (noted NT_IN in FIG. 7) from the notch sensor 4 is input to the notch signal interface 512, and NT_IN asynchronous with CLK is latched according to CLK to generate a signal NT0.

  The notch signal condition register 515 is provided with two registers (hereinafter referred to as REG0 and REG1, respectively), and the delay time setting register 516 is also provided with two registers (hereinafter referred to as REG2 and REG3, respectively). In addition, 32-bit (DT_OUT) data indicating various parameters input from the computer 6 is input to the notch signal condition register 515, the delay time setting register 516, and the address counter 513 via the I / O interface 52. The (DT_OUT) data is written in 16 bits WDT for write data, bits WT0 for a write command to REG0, bits WT1 for a write command to REG1, and bits WT2 and REG3 for a write command to REG2. It consists of a bit WT3 for instruction, a bit ENABLE for ON / OFF instruction of processing in the address counter 513, and the like. For example, when WT0 is set to 0 and then WT0 is set to 1, data indicated by 16-bit WDT is written to REG0.

  Similarly, 32-bit (DT_IN) data is output from the notch signal condition register 515 and the delay time setting register 516 to the computer 6 as necessary, and two sets of 16 read data included in the (DT_IN) data are used. The bit RDT is data stored in any one of REG0 to REG3.

  The address counter 513 counts CLK in a state where the ENABLE is “1” (ON state). The notch timing determination circuit 514 generates a value NT1 indicating the notch detection time according to the rising and falling timings of the signal NT0 from the notch signal interface 512 and the number of these. The delay addition circuit 517 outputs a value (NT1 + DLY) obtained by adding the value DLY input from the delay time setting register 516 to NT1, and the coincidence detection circuit 518 outputs (NT1 + DLY) and the counter value COUNT from the address counter 513. If they match, a signal CNT_EQ and a signal CNT_END are generated. The timing fine adjustment circuit 519 outputs a strobe trigger signal 591 and a camera trigger signal 592 to the illumination unit 3 and the computer 6, respectively. The specific operation of the trigger generation circuit 51 will be described later.

  FIG. 8 is a diagram showing the configuration of the computer 6. The computer 6 has a general computer system configuration in which a CPU 611 that performs various arithmetic processes, a ROM 612 that stores basic programs, and a RAM 613 that stores various information are connected to a bus line. The bus line further includes a fixed disk 614 for storing information, a display 615 for displaying various information, a keyboard 616a and a mouse 616b for receiving input from an operator, an optical disk, a magnetic disk, a magneto-optical disk and the like. A reading device 617 that reads information from a recording medium, a communication unit 618 connected to the overall control unit 7 and the like, an electrical signal input from the head unit 2 is converted into image data of a predetermined format and stored in the image memory 621a. The I / O board 622 that inputs / outputs various parameters of the trigger generation circuit 51 and the image processing board 623 that performs pattern matching with the capture board 621, the strobe controller 5, and the interface (I / F) ) Or the like.

  FIG. 9 is a block diagram illustrating a functional configuration realized by the computer 6. In FIG. 9, each configuration of the processing unit 63 indicates functions realized by the CPU 611 and the like according to a predetermined program. The function of the processing unit 63 may be realized by a dedicated electric circuit, or a dedicated electric circuit may be partially used. Further, the function of the image processing board 623 in FIG. 9 may be realized by software.

  FIG. 10 is a diagram showing a flow of processing in which the substrate polishing system 1 acquires an image while polishing the substrate 9. Hereinafter, the polishing / image acquisition process of the substrate 9 will be described with reference to FIG.

  In the substrate polishing system 1, first, various information necessary for processing the substrate 9 is obtained and prepared using a predetermined reference substrate (step S11). Here, the reference substrate is formed with the same circuit pattern as the substrate 9 to be polished, and an image of a desired imaging position on the substrate 9 is acquired during polishing of the substrate 9 by advance preparation using the reference substrate. The image acquisition condition data 691 used for the acquisition, and the template image data 692 and the measurement point position information 693 used for specifying the position of a predetermined measurement point on the substrate 9 in the acquired image are acquired. And stored in the fixed disk 614. The processing for preparing these pieces of information will be described in detail after explanation of the polishing / image acquisition processing.

  Subsequently, the substrate 9 is fixed to the substrate rotating unit 11 and disposed on the polishing plate 71, and the state shown in FIG. Further, various parameters based on the image acquisition condition data 691 are input from the computer 6 to the trigger generation circuit 51, and the structure of the film formed on the substrate 9 from the plurality of filters 341 of the filter unit 34 in FIG. One filter 341a corresponding to the thickness of the light is selected and disposed on the light path from the flash lamp 32. Then, the supply of slurry onto the polishing plate 71 and the rotation of the polishing plate 71 are started by the overall control unit 7, and at the same time, the substrate 9 starts to rotate continuously, and polishing of the substrate 9 is started (step S12). . That is, the main surface of the substrate 9 is polished in parallel with the rotation of the substrate 9. Further, a signal indicating the start of polishing of the substrate 9 is output from the overall control unit 7 to the computer 6.

  FIG. 11 is a diagram showing the main surface 91 of the rotating substrate 9 as viewed from the polishing plate 71 side. As shown by an arrow 991 in FIG. 11, the substrate 9 is rotated at a constant angular velocity (for example, 2π rad / s (60 rpm)) in the clockwise direction, and the notch 92 of the substrate 9 is notched sensor 4 (in FIG. 5, the light emitted from the light source 41 of FIG. 5 to the substrate 9 is irregularly reflected by the notch 92, and the reflected light is received by the photodiode 44. Is done.

  At this time, as shown in FIG. 11, the notch 92 of the substrate 9 is notched and formed in a chevron shape, so that signals indicating two pulses respectively corresponding to the two edges of the notch 92 are transmitted from the photodiode 44. Is output. The output signal is amplified by the preamplifier 46 of FIG. 6 and then compared with the threshold voltage by the comparator 47 to generate a signal indicating the two pulses shown in FIG. 12 (hereinafter referred to as “notch detection signal”). The passage of the notch 92 formed at the outer edge of the is detected (step S13). The notch detection signal is output to the strobe controller 5.

  The strobe controller 5 specifies the time (hereinafter referred to as “notch passage time”) when the notch 92 of the substrate 9 passes the position facing the notch sensor 4 based on the two output pulses indicated by the notch detection signal. After a predetermined delay time based on the image acquisition condition data 691 has elapsed from the passage time, a strobe trigger signal 591 and a camera trigger signal 592 are output to the illumination unit 3 and the computer 6, respectively. Here, the delay time is, for example, when an imaging region existing at a position indicated by a two-dot chain line rectangle denoted by reference numeral 29b in FIG. 11 is present at a position denoted by reference numeral 29a at the notch passage time. The angle between the line segment 93a connecting the center of the imaging region 29a and the rotation axis J1 and the line segment 93b connecting the imaging region 29b and the rotation axis J1 is θ, and the angle θ is divided by the angular velocity of the substrate 9. Approximately the same time as

  The camera trigger signal 592 is input to the capture board 621 in FIG. 9, and the substrate 9 is imaged by outputting a trigger signal from the capture board 621 to the head unit 2. At this time, after the strobe trigger signal 591 is output from the strobe controller 5, the camera trigger signal 592 is output after a lapse of a predetermined time, so that the reflected light of the illumination light from the illumination unit 3 from the substrate 9 is sent to the imaging device 25. Then, imaging is performed at the time of being guided. Thus, based on the output from the notch sensor 4 by the strobe controller 5, imaging by the head unit 2 is executed after a predetermined delay time has elapsed from the notch passage time (step S14).

  The image signal from the head unit 2 is output to the capture board 621, and data of an image on the main surface 91 of the substrate 9 (hereinafter referred to as “acquired image”) is stored in the image memory 621a. The acquired image data is output to the image processing board 623, and pattern matching with the template image indicated by the template image data 692 is performed. The acquired image is displayed on the display 615 as necessary.

  FIG. 13 is a diagram illustrating an example of an acquired image, and FIG. 14 is a diagram illustrating a template image. The template image is an image showing a predetermined reference pattern, and in this embodiment, an image showing the reference pattern 81 shown in FIG. 14 is prepared by the processing in step S11. The image processing board 623 specifies the position and inclination of the reference pattern 81 in the acquired image by performing pattern matching between the acquired image in FIG. 13 and the template image in FIG. 14, and outputs the result to the processing unit 63. .

  Here, the measurement point position information 693 indicates the relative position of the measurement point with respect to the reference pattern 81 in the circuit pattern on the substrate 9 (or the reference substrate). Based on the inclination information and the measurement point position information 693, the position of the measurement point 82 in the acquired image (that is, the position of the point corresponding to the measurement point with respect to the reference pattern) is calculated. As described above, the image processing board 623 and the position calculation unit 631 perform pattern matching between the acquired image and the template image to determine the position of the measurement point 82 in the acquired image (step S15).

  Subsequently, the polishing end point detection unit 632 acquires the pixel value at the position of the measurement point 82 in the acquired image and compares it with a determination value prepared in advance. The determination value depends on the filter 341 selected in the illuminating unit 3 or the structure of the film on the substrate 9 and the film thickness after polishing (the information is inputted in advance from the overall control unit 7, for example). It is determined whether or not the end point of polishing of the substrate 9 has been reached by comparing the pixel value of the measurement point 82 with the determination value (step S16). When it is determined that the polishing end point has not been reached (step S17), after the passage of the next notch 92 (ie, after one rotation) is detected by the notch sensor 4 (step S13), step S14 is performed. Step S16 is repeated. If it is determined that the polishing end point has been reached (that is, the polishing end point is detected) (step S17), a signal indicating end point detection is output to the overall control unit 7.

  Note that the polishing end point may be detected based on a change in the pixel value of the measurement point. For example, the expected end point arrival time is obtained from the characteristics of the change in the pixel value, and the polishing has reached the end point at the scheduled time. May be considered. As described above, the polishing end point detection unit 632 appropriately sets the polishing end point based on the image acquired by the head unit 2 every rotation of the substrate 9 (more specifically, based on the pixel value of the measurement point). Detected.

  The overall control unit 7 retracts the top ring 110 from the polishing plate 71 based on the end point detection signal, stops supplying slurry to the polishing plate 71 and rotating the polishing plate 71 to finish polishing, and rotates the substrate. The rotation of the unit 11 is also stopped (step S18), and the polishing / image acquisition processing of the substrate 9 in the substrate polishing system 1 is completed.

  Next, the processing in the trigger generation circuit 51 of FIG. 7 in step S14 will be described. As described above, when various parameters based on the image acquisition condition data 691 are input, in the trigger generation circuit 51, REG0 and REG1 of the notch signal condition register 515 and REG2 and REG3 of the delay time setting register 516 are input. Data is written in advance.

  In the trigger generation circuit 51 shown in FIG. 7, the input notch detection signal NT_IN is latched to the clock signal CLK by the notch signal interface 512, and the latched signal NT0 is the address counter 513 while NT_IN in FIG. And output to the notch timing determination circuit 514. The address counter 513 starts counting CLK by inputting the first rising edge of NT0.

  Here, each of REG0 and REG1 provided in the notch signal condition register 515 is a condition for ignoring an abnormal notch detection signal NT_IN (actually input as NT0) in the notch timing determination circuit 514. A certain pulse minimum interval and pulse minimum width are stored, and a value NI indicating the pulse minimum interval and a value NW indicating the pulse minimum width are input to the notch timing determination circuit 514. The pulse minimum interval and the pulse minimum width can be set, for example, in units of 10 microseconds. When the interval between two pulses specified by NT0 is shorter than the pulse minimum interval set in REG0, these Two pulses are ignored as abnormal. In addition, even when the width of one pulse specified by NT0 is shorter than the minimum pulse width set in REG1, this pulse is ignored as being abnormal. Thereby, in the trigger generation circuit 51, erroneous detection of notches due to noise or the like is suppressed.

  In the notch timing determination circuit 514, a value indicating the detection time of passage of the notch 92 is obtained. Specifically, the rising time and falling time of the pulse are specified for each pulse included in NT0. The values indicating the rise time and fall time of the first pulse are A1 and A2, respectively, and the values indicating the rise time and fall time of the next pulse are A3 and A4, respectively. Then, the value NT 1 obtained by calculating ((A 1 + A 2 + A 3 + A 4) / 4) is set to a value indicating the detection time of passage of the notch 92 and is output to the delay addition circuit 517.

  Further, when a signal indicating only one pulse is output from the notch sensor 4 due to an error in the holding position of the substrate 9, the notch timing determination circuit 514 causes the rise time and fall time of one pulse. The values obtained by calculating ((B1 + B2) / 2), where B1 and B2 are the values indicating, are set to a value NT1 indicating the detection time of passage of the notch 92.

  When three or more pulses are detected, the notch timing determination circuit 514 considers that the notch 92 has not been detected and does not output the value NT1. Further, as described above, two pulses generated at intervals shorter than the minimum pulse interval set in REG0 and pulses shorter than the minimum pulse width set in REG1 are appropriately ignored.

  As described above, the trigger generation circuit 51 determines the detection time of passage of the notch 92 by calculation based on the characteristics (number of pulses, pulse generation timing, pulse width, pulse interval, etc.) of at least one output pulse from the photodiode 44. Appropriately required.

  The delay addition circuit 517 outputs (NT1 + DLY) by adding a value DLY indicating a fixed delay time to NT1. Specifically, the lower 16 bits of the delay time and the upper 4 bits of the delay time are stored in REG2 and REG3 of the delay time setting register 516, respectively, and the delay stored in REG2 and REG3. NT1 from the notch timing determination circuit 514 is added to DLY indicating time (for example, set in units of 50 microseconds and represented by 20 bits), and is output to the coincidence detection circuit 518.

  When the coincidence detection circuit 518 matches (NT1 + DLY) with the counter value COUNT input from the address counter 513, the signal CNT_EQ is output to the timing fine adjustment circuit 519 and the signal CNT_END is output to the address counter 513. Then, the timing fine adjustment circuit 519 having a shift register inputs the CNT_EQ, outputs the strobe trigger signal 591 to the illumination unit 3, and outputs the camera trigger signal 592 after a certain time from the output of the strobe trigger signal 591. Thereby, imaging by the head unit 2 is executed after the delay time based on the image acquisition condition data 691 has elapsed from the detection time of passage of the notch 92. The address counter 513 is reset to an initial value when CNT_END is input.

  Next, the process of step S11 performed using the reference substrate will be described. First, the reference substrate is fixed to the substrate rotating unit 11 and moved onto the polishing plate 71, and rotation is started at the same angular velocity as that when the substrate 9 is polished. Subsequently, predetermined various parameters for initial setting are input from the computer 6, and after the notch sensor 4 detects passage of the notch, an image is acquired with a delay of a set delay time. The acquired image is displayed on the display 615 of the computer 6 and is confirmed by the operator.

  When an image acquisition at a different position is instructed by the operator's operation, the delay time is slightly changed in the computer 6, and a position deviated from the position imaged immediately before on the main surface of the reference board is imaged. The next image is displayed on the display 615. The operator confirms the displayed image, and the delay time change and the image acquisition are repeated until a desired image is acquired.

  When a desired image (hereinafter referred to as “reference image”) is acquired, the operator selects a reference pattern in the reference image and designates a point corresponding to the measurement point, thereby indicating a template image indicating the reference pattern. Data 692 and measurement point position information 693 that is position information with respect to the reference pattern of the measurement points on the substrate 9 are stored in the fixed disk 614, and information on various parameters input when the reference image is acquired is also stored. Various information necessary for polishing and image acquisition processing of the substrate 9 is prepared as image acquisition condition data 691.

  Note that information indicating the imaging position of the reference image on the reference board may be stored as the image acquisition condition data 691 instead of the information on various parameters input to the trigger generation circuit 51. In this case, various parameters input to the trigger generation circuit 51 at the time of processing the substrate 9 include the relationship between the imaging position of the reference image on the reference substrate and the position of the notch by the computer 6, the angular velocity of rotation of the substrate 9, and the like. As required.

  In the trigger generation circuit 51, ENABLE is set to “0” (that is, the address counter 513 is OFF), and the image acquisition signal is directly input from the computer 6 to the trigger generation circuit 51, so that the strobe trigger signal 591 and the camera trigger are obtained. A signal 592 may be output to obtain an image of the reference board. Further, the delay time may be obtained by calculation based on circuit pattern design data.

  As described above, in the substrate polishing system 1 of FIG. 1, the passage of the rotating substrate 9 through the notch 92 is detected by the notch sensor 4, and after the predetermined delay time has elapsed from the passage time of the notch 92, The surface 91 is imaged. In other words, the image acquisition apparatus that is a part of the substrate polishing system 1 can accurately acquire an image at a predetermined position on the rotating substrate 9. In the image acquisition device, pattern matching is performed between the acquired image and a template image indicating the reference pattern, and calculation based on position information with respect to the reference pattern of the measurement points on the substrate 9 is performed. The position of the measurement point on the substrate 9 can be obtained with high accuracy. Further, the polishing end point detection unit 632 can accurately detect the polishing end point of the substrate 9 having a pattern based on the pixel value of the position of the obtained measurement point in the acquired image.

  In the substrate polishing system 1 of FIG. 1, the image processing board 623 and the position calculation unit 631 may be omitted, and the polishing end point may be detected based on a pixel value at a predetermined position in the acquired image. For example, when the substrate 9 on which the circuit pattern is not formed is polished, only the image acquisition condition data 691 is prepared in step S11 of FIG. When the rotation of the substrate 9 is started by the substrate rotating unit 11 and polishing of the substrate 9 is started (step S12), the passage of the notch 92 of the substrate 9 is detected by the notch sensor 4 (step S13), and the notch 92 is detected. After the predetermined time has elapsed from the passage time of the image, the head unit 2 performs imaging (step S14).

  Subsequently, step S15 is omitted, and a pixel value at a specific position in the acquired image (for example, an average value of a central pixel value or a pixel group value in the vicinity of the center, etc.) is input to the polishing end point detection unit 632. Based on the value (compared with a value prepared in advance or based on a change in pixel value), it is determined whether or not the polishing end point has been reached (step S16). If it is determined that the polishing end point has not been reached, steps S13, S14, and S16 are repeated (step S17). If it is determined that the polishing end point has been reached (polishing end point is detected), steps S13, S14, and S16 are repeated. Then, the polishing is finished and the rotation of the substrate 9 is also stopped (step S18), and the polishing / image acquisition processing of the substrate 9 is finished. Accordingly, it is possible to easily detect the polishing end point on the basis of the image acquired by the head unit 2 in accordance with the case where there is not much pattern on the substrate 9.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  In the above embodiment, the substrate 9 has a disk shape, but a rectangular substrate may be rotated around an axis perpendicular to the main surface, and an image at a predetermined position on the rotating rectangular substrate may be acquired. In this case, for example, the passage of the edge in the vicinity of the corner portion of the rectangular substrate is detected by the notch sensor 4, and the predetermined time from the time when the rectangular substrate is in a specific direction (that is, the time when the vicinity of one corner portion faces the notch sensor 4) After the delay time elapses, imaging by the head unit 2 is executed. Furthermore, a cutout having a shape other than the chevron may be formed in the outer edge portion of the substrate 9. In addition, the board | substrate 9 is not limited to a semiconductor substrate, Other board | substrates, such as a glass substrate and a printed wiring board, may be sufficient.

  The light receiving portion in the notch sensor 4 may be a photodiode array. In this case, outputs from the plurality of photodiodes are respectively amplified by the plurality of preamplifiers, and outputs from the plurality of preamplifiers are added by the adder circuit to output a notch detection signal.

  The image acquisition condition data 691 may include information on the imaging position of the head unit 2 in the radial direction of the substrate 9. In this case, the head unit 2 responds based on the information at the start of the polishing / image acquisition process. Move to the position you want.

  The processing flow shown in FIG. 10 may be appropriately changed within a possible range. For example, after rotation of the substrate 9 is started, template image data and measurement point position information may be input from the outside and prepared. That is, these pieces of information may be prepared before the process of detecting the passage of the notch.

  The function as an image acquisition device in the above embodiment is particularly suitable for an application for acquiring an image of a substrate being polished, but is applied to other types of processing for rotating a substrate to acquire an image of a rotating substrate. May be.

It is a figure which shows the structure of a board | substrate grinding | polishing system. It is a figure which shows the vicinity of a board | substrate rotation part. It is the figure which looked at the vicinity of a head part from the side. It is a figure which shows the internal structure of a head part. It is a figure which shows the internal structure of a notch sensor. It is a circuit block diagram of a notch sensor and a strobe controller. It is a figure which shows the structure of a trigger generation circuit. It is a figure which shows the structure of a computer. It is a block diagram which shows the function structure which a computer implement | achieves. It is a figure which shows the flow of the process which acquires an image, grind | polishing a board | substrate. It is a figure which shows on the main surface of the board | substrate to rotate. It is a figure which shows a notch detection signal. It is a figure which shows an example of an acquired image. It is a figure which shows a template image.

Explanation of symbols

2 Head unit 4 Notch sensor 5 Strobe controller 9 Substrate 11 Substrate rotating unit 41 Light source 44 Photodiode 71 Polishing plate 81 Reference pattern 82 Measurement point 91 Main surface 92 Notch 614 Fixed disk 623 Image processing board 631 Position calculation unit 632 Polishing end point detection unit 692 Template image data 693 Measurement point position information J1 Rotation axis S11 to S18 Steps

Claims (12)

An image acquisition device for acquiring an image of a substrate,
A substrate rotating unit that rotates the substrate at a constant angular velocity about an axis perpendicular to the main surface;
An imaging unit that images the main surface of the substrate while the substrate rotating unit rotates the substrate;
An edge passage detection unit that detects passage of an edge of the substrate rotated by the substrate rotation unit;
Based on the output from the edge passage detection unit, an imaging control unit that executes imaging by the imaging unit after a predetermined time has elapsed from the time when the substrate is in a specific orientation;
An image acquisition apparatus comprising: The image acquisition device according to claim 1,
The image acquisition apparatus, wherein the edge passage detection unit detects passage of a notch formed in an outer edge portion of a substrate. The image acquisition device according to claim 2,
The edge passage detection unit is
A light source that emits light toward the substrate;
A light receiving unit for receiving reflected light from the substrate of light from the light source;
Have
The image acquisition device, wherein the imaging control unit obtains a detection time of passage of a notch by calculation based on a characteristic of at least one output pulse from the light receiving unit. The image acquisition device according to any one of claims 1 to 3,
A storage unit that stores data of a template image indicating a reference pattern, and position information of a specific point on the substrate with respect to the reference pattern;
A calculation unit for obtaining a position of a point corresponding to the specific point in the acquired image by performing pattern matching between the image acquired by the imaging unit and the template image;
An image acquisition apparatus further comprising: The image acquisition device according to any one of claims 1 to 3,
A polishing unit for polishing a main surface of the substrate rotated by the substrate rotating unit;
A polishing end point detection unit for detecting a polishing end point based on the image acquired by the imaging unit;
An image acquisition apparatus further comprising: The image acquisition device according to claim 5,
The image acquisition apparatus, wherein the polishing end point detection unit detects a polishing end point based on a value of a pixel at a specific position in the image acquired by the imaging unit. The image acquisition device according to claim 5,
A storage unit that stores data of a template image indicating a reference pattern, and position information of a specific point on the substrate with respect to the reference pattern;
A calculation unit for obtaining a position of a point corresponding to the specific point in the acquired image by performing pattern matching between the image acquired by the imaging unit and the template image;
Further comprising
The image acquisition device, wherein the polishing end point detection unit detects a polishing end point based on a value of a pixel at a position of a point corresponding to the specific point in the acquired image. An image acquisition method for acquiring an image of a substrate,
a) rotating the substrate at a constant angular velocity about an axis perpendicular to the principal surface;
b) detecting the passage of the edge of the rotating substrate by an edge passage detector;
c) Based on the output from the edge passage detection unit, imaging the main surface of the substrate with an imaging unit after a predetermined time has elapsed from the time when the substrate is in a specific orientation;
An image acquisition method comprising: The image acquisition method according to claim 8,
The image acquisition method, wherein the edge passage detection unit detects passage of a notch formed in an outer edge portion of the substrate. The image acquisition method according to claim 9,
The edge passage detection unit emits light toward the substrate and receives reflected light from the substrate to generate at least one output pulse;
In the step c), the image acquisition method is characterized in that a notch passage detection time is obtained by calculation based on the characteristics of the at least one output pulse. The image acquisition method according to any one of claims 8 to 10,
Before the step b), preparing a template image data indicating a reference pattern and position information of the specific point on the substrate with respect to the reference pattern;
Step of obtaining a position of a point corresponding to the specific point in the acquired image by performing pattern matching between the image acquired by the imaging unit and the template image after the step c) When,
An image acquisition method further comprising: The image acquisition method according to any one of claims 8 to 10,
Polishing the main surface of the substrate in parallel with the step a);
A step of detecting an end point of polishing based on an image acquired by the imaging unit after the step c);
An image acquisition method further comprising:

Images