Method and apparatus for detecting key patterns

Abstract

A key pattern detection method and apparatus are provided for detecting the position of a key pattern in a short time. The method detects the position of a key pattern on an object to be detected and comprises the following steps: a coarse key pattern detection step, wherein a holding unit and a photographing unit holding the object to be detected are moved relative to each other while the photographing unit photographs the object to be detected to form a plurality of coarse photographed images, and pattern matching is performed between each of the formed coarse photographed images and a reference image showing the key pattern to detect the coarse photographed image showing the key pattern; a fine key pattern detection step, wherein the object to be detected is photographed according to the relative position of the photographing unit and the holding unit when the detected coarse photographed images were formed to form a fine photographed image, and pattern matching is performed between the fine photographed image and the reference image to detect the key pattern contained in the fine photographed image; and a key pattern position detection step, wherein the position of the detected key pattern is detected.

Description

Technical Field

[0001] The present invention relates to a method for detecting a key pattern from an object containing the key pattern and a device capable of detecting the key pattern from the object. Background Art

[0002] In the manufacturing process of device chips used in electronic devices, multiple intersecting dividing lines called streets are first set on the front surface of a semiconductor wafer. Devices are then formed within the areas demarcated by these streets. The wafer is then divided along these streets to form individual device chips.

[0003] Wafer division is performed, for example, using a cutting device having a cutting unit. The cutting unit includes a main shaft as a rotating axis and a cutting tool attached to one end of the main shaft. The main shaft rotates, causing the cutting tool to rotate, and the rotating cutting tool cuts into the wafer along the streets, thereby dividing the wafer.

[0004] Alternatively, wafer segmentation can be performed using a laser processing device with a laser processing unit. For example, a laser beam of a wavelength that is transparent to the wafer is directed along the strips and converged into the interior of the wafer, forming a modified layer. The wafer is then segmented when cracks extend from the modified layer to the front and back sides of the wafer. Alternatively, a laser beam of a wavelength that is absorptive to the wafer is directed along the strips onto the front side of the wafer, forming grooves along the strips, thereby segmenting the wafer.

[0005] In processing equipment such as cutting devices and laser processing devices, it is necessary to perform alignment to detect the position and direction of the streets on a wafer so that the cutting unit, laser processing unit, or other processing unit can be aligned with the streets (see Patent Documents 1 and 2). Here, an image of a characteristic pattern (key pattern) included on the wafer is pre-registered in the processing equipment as a reference image, and the distance from the key pattern to the streets is pre-stored.

[0006] When processing a wafer, the front side of the wafer to be processed is photographed to obtain an image. This image is then matched against a reference image registered in the processing equipment to detect the key pattern of the wafer to be processed. The position of the streets on the wafer is then detected based on the position of the detected key pattern, allowing the processing units to be aligned with the street positions.

[0007] If the key pattern is not detected from the image acquired by imaging the front surface of the wafer, the wafer is moved relative to the imaging camera, another area of the wafer is imaged, and pattern matching with the reference image is performed.

[0008] Furthermore, a method known as automatic measurement is known that uses pattern matching to measure the index dimensions of a wafer having multiple devices formed thereon (see Patent Document 3). In this method, the wafer and an imaging camera are repeatedly imaged while being moved relative to each other, and pattern matching is performed using the images obtained.

[0009] Here, the indexing dimension is, for example, the length corresponding to the amount by which the processing unit is indexed relative to the wafer when processing the wafer along an adjacent lane after processing the wafer along a particular lane. Alternatively, the indexing dimension can be described as the distance between the centerlines of a pair of adjacent lanes.

[0010] During automated measurement, a characteristic structure of a device formed on a wafer is designated as a key pattern. Pattern matching is then used to automatically detect adjacent key patterns. The distance between the two key patterns is then calculated as the index dimension. Pattern matching is sometimes used to detect additional adjacent key patterns to verify the calculated index dimension.

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 60-244803

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2005-166991

[0013] Patent Document 3: Japanese Patent Application Laid-Open No. 7-321073

[0014] To accurately detect the position of a key pattern using pattern matching, it is crucial to eliminate blur in the captured image. However, to obtain a blur-free captured image, the capture must be held until the wafer and camera are completely stationary relative to each other after moving. Therefore, when generating multiple captured images to search for a key pattern and detect its position, each image generation must be paused, significantly increasing the time required to detect the key pattern's position. Summary of the Invention

[0015] The present invention has been made in view of the above problem, and an object of the present invention is to provide a key pattern detection method capable of detecting the position of a key pattern in a short time, and an apparatus capable of detecting the position of a key pattern in a short time.

[0016] According to one embodiment of the present invention, a method for detecting a key pattern is provided, in which the position of a key pattern possessed by an object to be detected held by a holding unit is detected in the following device, the device comprising: a holding unit for holding the object to be detected having the key pattern; a photographing unit for photographing the object to be detected held by the holding unit; a moving unit for moving the holding unit and the photographing unit relative to each other; and a control unit for controlling the photographing unit and the moving unit, characterized in that the method for detecting a key pattern comprises the following steps: a holding step for holding the object to be detected by using the holding unit; a key pattern coarse detection step for photographing the object to be detected by using the photographing unit while moving the holding unit and the photographing unit relative to each other to form a plurality of images. a captured coarse image, performing pattern matching on each of the formed captured coarse images and a reference image pre-registered in the control unit reflecting the key pattern, thereby detecting the captured coarse image reflecting the key pattern from the multiple captured coarse images; a key pattern precision detection step, positioning the capturing unit and the holding unit at the relative positions of the capturing unit and the holding unit when the captured coarse image detected in the key pattern coarse detection step is formed, and in a state where the relative movement of the holding unit and the capturing unit is stopped, capturing the object to be detected by using the capturing unit to form a precision captured image, and performing pattern matching on the precision captured image and the reference image to detect the key pattern contained in the precision captured image; and a key pattern position detection step, detecting the position of the key pattern detected by the key pattern precision detection step.

[0017] In addition, according to another embodiment of the present invention, there is provided a key pattern detection device, which comprises: a holding unit for holding an object to be detected having a key pattern; a photographing unit for photographing the object to be detected held by the holding unit; a moving unit for moving the holding unit and the photographing unit relative to each other; and a control unit for controlling the photographing unit and the moving unit, wherein the control unit comprises: a reference image storage unit for storing a reference image showing the key pattern; a photographing unit control unit for controlling the photographing timing of the photographing unit; a moving unit control unit for controlling the relative movement of the holding unit and the photographing unit achieved by the moving unit; and a coarse pattern matching unit for respectively controlling the relative movement of the holding unit and the photographing unit which utilize the moving unit to move the holding unit and the photographing unit relative to each other. The element moves while using the imaging unit to photograph the object to be inspected, thereby performing pattern matching on a plurality of captured coarse images and the reference image to detect the captured coarse image reflecting the key pattern; a precision pattern matching unit, which performs pattern matching on the precision captured image and the reference image to detect the key pattern contained in the precision captured image, wherein the precision captured image is formed by positioning the imaging unit and the holding unit at the relative positions of the imaging unit and the holding unit when the captured coarse image detected by the coarse pattern matching unit is formed, and while the relative movement of the holding unit and the imaging unit is stopped, the imaging unit is used to photograph the object to be inspected to form a precision captured image; and a key pattern position detection unit, which detects the position of the key pattern detected by the precision pattern matching unit.

[0018] In a key pattern detection method and apparatus according to one embodiment of the present invention, a holding unit and an imaging unit, which hold an object to be inspected, such as a wafer, are moved relative to each other while the imaging unit captures the object, forming multiple captured coarse images. These multiple captured coarse images are acquired in a short period of time without stopping the holding unit and the imaging unit. However, the vibration associated with the relative movement results in blurred images. Furthermore, pattern matching using these blurred coarse images makes it difficult to accurately detect the position of the key pattern.

[0019] However, when using a reference image that reflects the key pattern, the coarse captured image that reflects the key pattern can be identified from multiple coarse captured images through pattern matching. Therefore, after identifying the coarse captured image that reflects the key pattern, the holding unit and the imaging unit are repositioned relative to the positions at which the coarse captured image was formed, and while they are stopped relative to each other, the object to be inspected is imaged to form a precise captured image.

[0020] The key pattern of the object being inspected is clearly reflected in the precisely captured image, so the position of the key pattern can be detected by pattern matching the precisely captured image with the reference image. In one embodiment of the present invention, the key pattern detection method and apparatus can precisely detect the position of the key pattern after the approximate position of the key pattern of the object being inspected is detected in a short period of time.

[0021] Therefore, according to the present invention, a key pattern detection method capable of detecting the position of a key pattern in a short time and an apparatus capable of detecting the position of a key pattern in a short time are provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a perspective view schematically showing a wafer as an example of an object to be inspected.

[0023] Figure 2 It is a perspective view schematically showing a cutting device as an example of the device.

[0024] Figure 3 (A) is a cross-sectional view schematically showing a holding step, Figure 3 (B) is a cross-sectional view schematically showing a state in which the front surface of the inspection object is photographed by the photographing unit.

[0025] Figure 4 It is a plan view illustrating the imaging field of a plurality of captured rough images formed in the key pattern rough detection step.

[0026] Figure 5 (A) is a top view schematically showing an example of a captured rough image showing a key pattern. Figure 5 (B) is a top view schematically showing another example of capturing a rough image. Figure 5 (C) is a plan view schematically showing another example of capturing a coarse image.

[0027] Figure 6 FIG. 1 is a plan view schematically showing an example of a precision captured image and a capturing field of view of the precision captured image.

[0028] Figure 7 (A) is a top view schematically showing an example of a reference image. Figure 7 (B) is a plan view schematically showing another example of a reference image.

[0029] Figure 8 : is a flowchart showing the flow of a key pattern detection method.

[0030] Description of labels

[0031] 1: Wafer; 1a: Front side; 1b: Back side; 3: Spacer; 5: Device; 7: Adhesive tape; 9: Frame; 11: Frame unit; 13: Terminal (electrode); 15: Wiring; 17a, 17b, 17c: Imaging field of view; 19a, 19b, 19c: Coarse image; 21: Key pattern; 23: Precision image; 25, 27: Reference image; 2: Cutting device; 4: Base; 6, 12, 42: Opening; 8: Cassette; 10: Transport guide; 12a: Bellows; 14: Chuck tool Workbench; 14a: Holding surface; 14b: Clamp; 16: Support part; 18, 28: Moving mechanism; 20, 30: Guide rails; 22, 32: Moving plate; 24, 34: Ball screw; 26, 36: Pulse motor; 38: Cutting unit; 40: Shooting unit; 44: Cleaning unit; 46: Control unit; 48: Moving unit control part; 50: Shooting unit control part; 52: Reference image storage part; 54: Coarse pattern matching part; 56: Precision pattern matching part; 58: Key pattern position detection part. DETAILED DESCRIPTION

[0032] An embodiment of one aspect of the present invention will be described with reference to the accompanying drawings. According to the key pattern detection method and apparatus of this embodiment, it is possible to image an object to be detected and detect the position of a key pattern on the object in a short period of time. First, an object to be detected having a key pattern will be described.

[0033] The object to be inspected may be, for example, a roughly circular wafer made of materials such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductors. Alternatively, the object to be inspected may be a substrate made of materials such as sapphire, glass, or quartz. Furthermore, the object to be inspected may be a package substrate containing multiple device chips sealed with a molded resin or the like.

[0034] Figure 1 1 is a perspective view schematically showing a wafer 1 as an example of an object to be inspected. Hereinafter, this embodiment will be described by taking as an example a case where the object to be inspected is a wafer 1 on which a plurality of devices 5 are formed, but the object to be inspected is not limited thereto.

[0035] The front side 1a of the wafer 1 is divided, for example, by a plurality of intersecting dividing lines called streets 3. Devices 5, such as ICs (Integrated Circuits) and LSIs (Large-Scale Integrated Circuits), are formed in the respective regions of the front side 1a of the wafer 1 divided by the streets 3. When the wafer 1 is divided along the streets 3, individual device chips are formed.

[0036] The wafer 1 is divided using, for example, a laser processing device that irradiates the wafer 1 with a laser beam along the streets 3 to perform laser processing on the wafer 1. Alternatively, a cutting device that can cut the wafer 1 along the streets 3 using an annular cutting blade is used.

[0037] In these processing devices, in order to process the wafer 1 along the streets 3, it is necessary to detect the position and direction of the streets 3 in advance and perform alignment to position the wafer 1 and the processing unit at a predetermined relative position. In addition, in these processing devices, after processing the wafer 1 along a certain street 3, in order to precisely process the wafer along another street 3, it is necessary to move the wafer 1 and the processing unit relative to each other according to the indexing dimension.

[0038] The key pattern detection method of this embodiment is implemented, for example, when performing index dimension detection or alignment using the processing device. Furthermore, the device of this embodiment is, for example, the processing device. Furthermore, by detecting the position of the key pattern on the object being detected, the position of the spacer 3 can be detected.

[0039] Here, a key pattern on an object to be inspected, such as a wafer 1, refers to a structure having a characteristic shape formed on the object to be inspected. The key pattern is appropriately set on a portion of a structure formed on the object to be inspected. The key pattern can be set as all or part of a structure formed on the object to be inspected to perform a function. For example, the key pattern can be selected from a functional layer where device 5 is formed. Alternatively, a dedicated structure that functions solely as a key pattern can be placed on the object to be inspected.

[0040] In a wafer 1 having a plurality of devices 5 formed thereon, a key pattern is set, for example, to include a portion of a metal layer used in a wiring layer, an electrode, or a terminal constituting the device 5. Furthermore, if the object to be inspected is transparent, the key pattern can be formed by a structure formed inside the object to be inspected.

[0041] Furthermore, to prevent false detection, the structure selected as the key pattern is preferably one that does not have a shape identical or similar to that of the object being detected. Alternatively, if it is desired to detect the key pattern and to detect the positions of multiple lanes 3 set on the object being detected based on the positional relationship between the key pattern and the lanes 3, it is preferable to set a structure having one each on multiple devices 5 as the key pattern.

[0042] like Figure 1As shown, before wafer 1 is loaded into a processing device such as a cutting device or laser processing device, wafer 1 is integrated with an annular frame 9 and adhesive tape 7 affixed to seal the opening of annular frame 9 to form a frame unit 11. Wafer 1 is loaded into the processing device in the form of frame unit 11 and processed. Furthermore, the individual device chips formed by dividing wafer 1 are supported by adhesive tape 7.

[0043] The following description will continue with the case where the apparatus of this embodiment is a cutting apparatus that cuts the wafer 1. However, the apparatus of this embodiment may be a processing apparatus other than the cutting apparatus, or an inspection apparatus that does not process the wafer 1. Figure 2 It is a perspective view schematically showing the cutting device 2 .

[0044] The cutting device 2 has a base 4 that supports each component. A rectangular opening 6 is formed at the front corner of the base 4, and a box support that can be raised and lowered is provided in the opening 6. A box 8 that stores a plurality of frame units 11 is placed on the upper surface of the box support. Figure 1 In the figure, for the sake of convenience, only the outline of the box 8 is shown.

[0045] A rectangular opening 12, elongated in the X-axis direction (the machining feed direction), is formed on the upper surface of the base 4, adjacent to the opening 6. Disposed within the opening 12 are a holding unit 14, an X-axis movement mechanism (not shown) for moving the holding unit 14 in the X-axis direction, and a dust and drip proof cover 12a covering the X-axis movement mechanism.

[0046] The cutting device 2 is provided with a conveying mechanism (not shown) for carrying in and out the frame units 11 stored in the cassette 8 placed on the cassette support table. The conveying mechanism pulls the frame units 11 stored in the cassette 8 onto a pair of conveying rails 10 provided so as to span the opening 12.

[0047] The pair of conveying rails 10 are movable in a direction away from each other. After the frame unit 11 is pulled onto the conveying rails 10 by the conveying mechanism, the frame unit 11 is held by the conveying mechanism, and the gap between the pair of conveying rails 10 is widened. When the conveying mechanism is lowered, the frame unit 11 can be conveyed onto the holding unit 14.

[0048] The holding unit 14 is, for example, a chuck table for holding the wafer 1 (the object to be inspected). A porous member is provided on the upper surface of the holding unit 14 (chuck table), and the upper surface of the porous member serves as a holding surface 14a for holding the frame unit 11. The holding unit 14 has a clamp 14b (see FIG. 1 ) on the outer periphery for clamping the frame unit 11 placed on the holding surface 14a. Figure 3 (A), etc.).

[0049] The porous member is connected to a suction source (not shown) via a suction passage (not shown) formed inside the holding unit 14. When the frame unit 11 is placed on the holding surface 144a and the suction source is activated to apply negative pressure to the frame unit 11 through the suction passage and the porous member, the frame unit 11 is sucked and held by the holding unit 14.

[0050] The holding unit 14 is connected to a rotation drive source (not shown) such as a motor and is rotatable about a rotation axis perpendicular to the holding surface 14a. The holding unit 14 is fed in the X-axis direction by the X-axis direction moving mechanism.

[0051] A gate-shaped support structure 16 for supporting the cutting unit 38 and the imaging unit 40 is arranged on the upper surface of the base 4 so as to span the opening 12. A Y-axis movement mechanism 18 for moving the cutting unit 38 and the imaging unit 40 in the Y-axis direction (indexing feed direction) and a Z-axis movement mechanism 28 for moving the cutting unit 38 and the imaging unit 40 in the Z-axis direction (height direction) are provided on the upper front surface of the support structure 16.

[0052] A pair of Y-axis guide rails 20 parallel to the Y-axis direction are provided on the front surface of the support structure 16. A Y-axis moving plate 22 is slidably mounted on the Y-axis guide rails 20. A nut portion (not shown) is provided on the back side (rear surface side) of the Y-axis moving plate 22, and a Y-axis ball screw 24 parallel to the Y-axis guide rails 20 is screwed onto the nut portion.

[0053] A Y-axis pulse motor 26 is connected to one end of the Y-axis ball screw 24. When the Y-axis pulse motor 26 rotates the Y-axis ball screw 24, the Y-axis moving plate 22 moves in the Y-axis direction along the Y-axis guide rail 20. In other words, the Y-axis guide rail 20, the Y-axis moving plate 22, the Y-axis ball screw 24, and the Y-axis pulse motor 26 constitute the Y-axis direction moving mechanism 18.

[0054] A pair of Z-axis guide rails 30 are provided on the front surface (front face) of the Y-axis moving plate 22, parallel to the Z-axis direction. The Z-axis moving plate 32 is slidably mounted on the Z-axis guide rails 30. A nut portion (not shown) is provided on the back side (rear face) of the Z-axis moving plate 32, and a Z-axis ball screw 34 is screwed onto the nut portion, parallel to the Z-axis guide rails 30.

[0055] A Z-axis pulse motor 36 is connected to one end of the Z-axis ball screw 34. When the Z-axis pulse motor 36 rotates the Z-axis ball screw 34, the Z-axis moving plate 32 moves in the Z-axis direction along the Z-axis guide rail 30. Specifically, the Z-axis guide rail 30, the Z-axis moving plate 32, the Z-axis ball screw 34, and the Z-axis pulse motor 36 constitute the Z-axis direction moving mechanism 28.

[0056] A cutting unit 38 is fixed to the lower portion of the Z-axis moving plate 32. The cutting unit 38 includes a main shaft as a rotation axis and an annular cutting tool attached to one end of the main shaft. The cutting tool has a grinding wheel at least on its outer periphery. When the main shaft is rotated, the cutting tool rotates and the grinding wheel contacts the wafer 1 held by the holding unit 14, thereby cutting the wafer 1.

[0057] Furthermore, an imaging unit (camera unit) 40 is provided adjacent to the cutting unit 38 to capture images of the wafer 1 (inspection target) held by the holding unit 14. The imaging unit 40 is, for example, a CCD camera. When the imaging unit 40 captures images of the wafer 1 held by the holding unit 14, an image of the structure formed on the front surface 1a of the wafer 1 is formed. Alternatively, the imaging unit 40 may be an infrared camera or the like that receives light other than visible light.

[0058] When the Y-axis moving plate 22 is moved in the Y-axis direction by the Y-axis moving mechanism 18, the cutting unit 38 and the imaging unit 40 are indexed and fed in the Y-axis direction. Furthermore, when the Z-axis moving plate 32 is moved in the Z-axis direction by the Z-axis moving mechanism 28, the cutting unit 38 and the imaging unit 40 are raised and lowered. Furthermore, when the X-axis moving mechanism (not shown) is operated while the wafer 1 is held by the holding unit 14, the wafer 1 is processed and fed along the X-axis direction.

[0059] That is, the X-axis moving mechanism, the Y-axis moving mechanism 18 , and the Z-axis moving mechanism 28 function as moving means for relatively moving the cutting unit 38 and the imaging unit 40 , the holding unit 14 , and the wafer 1 .

[0060] The cutting tool of the cutting unit 38 is rotated while the cutting unit 38 and the holding unit 14 are relatively moved by the moving unit so that the cutting tool cuts into the wafer 1, thereby cutting the wafer 1. Furthermore, when the imaging unit 40 and the holding unit 14 are relatively moved by the moving unit and the imaging unit 40 is operated at a predetermined position, the wafer 1 held by the holding unit 14 is photographed to form a captured image.

[0061] The formed captured images are sent from the imaging unit 40 to the control unit 46 described later. The control unit 46 records the relative positions of the imaging unit 40 and the holding unit 14 when each captured image was captured, along with each captured image.

[0062] A circular opening 42 is formed on the upper surface of the base 4, on the side opposite the opening 6 and relative to the opening 12. A cleaning unit 44 is provided within the opening 42 for cleaning the frame unit 11 after the wafer 1 has been cut. The cleaning unit 44, located within the opening 42, includes a cleaning table 44a that holds the frame unit 11 and a cleaning nozzle (not shown) that sprays a cleaning liquid from above the frame unit 11 held by the cleaning table 44a. The cleaning liquid is, for example, pure water.

[0063] The cutting device 2 includes a control unit 46 for controlling various components of the cutting device 2. The control unit 46 controls the aforementioned cassette mounting table, transport mechanism, transport rails 10, moving unit, cutting unit 38, imaging unit 40, cleaning unit 44, and other components. The control unit 46 is, for example, a computer having a central processing unit (CPU), a storage medium, and the like. The functions of the control unit 46 are implemented, for example, by software.

[0064] In order to cut (process) the wafer 1 held by the holding unit 14 along the streets 3, it is necessary to detect the position and direction of the streets 3 of the wafer 1 and perform alignment. First, the holding unit 14 is rotated so that the streets 3 of the wafer 1 are aligned along the X-axis direction (the processing feed direction). Next, the holding unit 14 and the cutting unit 38 are moved relative to each other so that the grinding tool of the cutting tool of the cutting unit 38 is positioned on the extension line of the streets 3. Then, the wafer 1 is cut by the cutting tool.

[0065] If the position of streets 3 on wafer 1 cannot be accurately detected during alignment, wafer 1 cannot be accurately cut along streets 3, resulting in reduced processing accuracy. Therefore, to accurately detect the position of streets 3, a key pattern is set on wafer 1 as described above, and the position of the key pattern is accurately detected using pattern matching.

[0066] When pattern matching is performed, the holding unit 14 and the imaging unit 40 are repeatedly moved, and the imaging unit 40 continuously captures images of the front surface 1a of the wafer 1. The plurality of captured images obtained are then compared with reference images showing the key pattern that are pre-registered in the control unit 46, and captured images showing the key pattern are detected.

[0067] The position of the key pattern on wafer 1 is detected based on the relative positional relationship between holding unit 14 and imaging unit 40 when the captured image is formed. The positional relationship between the key pattern and streets 3 is pre-stored in control unit 46, and the position of streets 3 is detected based on the positional relationship derived from the position of the key pattern.

[0068] When using pattern matching to compare two images and detect the position of a key pattern, it is crucial that the captured image used for comparison is free of blur. Therefore, to obtain a blur-free captured image, it is necessary to wait for a long period of time between the relative movement of the holding unit 14 and the imaging unit 40 and their complete stop. Furthermore, when repeatedly capturing images while searching for the key pattern, a wait period is required each time the captured image is generated, which has traditionally taken considerable time to detect the position of the key pattern.

[0069] Therefore, in the key pattern detection method and apparatus of the present embodiment, after the holding unit 14 and the imaging unit 40 are relatively moved, the imaging unit 40 is operated to form a captured image without waiting for the holding unit 14 and the imaging unit 40 to completely stop.

[0070] like Figure 2 As shown, the control unit 46 includes a moving unit control unit 48, an imaging unit control unit 50, a reference image storage unit 52, a coarse pattern matching unit 54, a fine pattern matching unit 56, and a key pattern position detection unit 58. The moving unit control unit 48 controls the relative movement of the holding unit 14 and the imaging unit 40 by the moving unit. The imaging unit control unit 50 controls the imaging timing of the imaging unit 40.

[0071] The reference image storage unit 52 stores a reference image showing a key pattern. This reference image is used when detecting the position of the key pattern on the wafer 1 using a pattern matching method. The reference image is pre-registered in the reference image storage unit 52 by the operator of the cutting device 2.

[0072] For example, after the frame unit 11 is loaded onto the holding unit 14 and the wafer 1 is held thereon via the adhesive tape 7, the front surface 1a of the wafer 1 is imaged by the imaging unit 40. The operator then selects a portion to be set as a key pattern based on a characteristic pattern formed on the wafer 1, creates a reference image, and registers it in the reference image storage unit 52. When the reference image is created, the positional relationship between the key pattern and the streets 3 on the wafer 1 is also registered.

[0073] Alternatively, when the cutting device 2 continuously cuts (processes) multiple wafers 1 of the same type, pattern matching may be performed using a reference image formed before cutting the initial wafer 1 and comparing it with a subsequent captured image showing the wafer 1 .

[0074] The coarse pattern matching unit 54 instructs the moving unit control unit 48 to move the holding unit 14 holding the wafer 1 relative to the imaging unit 40. Furthermore, the coarse pattern matching unit 54 instructs the imaging unit control unit 50 to continuously capture images of the front surface 1a of the wafer 1. At this time, the relative movement of the holding unit 14 and the imaging unit 40 continues. Therefore, the multiple captured images are blurry and rough. These rough images are referred to as captured coarse images.

[0075] Here, since the holding unit 14 and the imaging unit 40 are not stopped during the formation of the multiple captured coarse images, the time required to form the multiple captured coarse images is significantly shorter than if the holding unit 14 and the imaging unit 40 were stopped each time. However, the captured coarse images are coarse images, so even if pattern matching is performed by comparing the captured coarse images with the reference image, the position of the key pattern cannot be accurately detected. However, the captured coarse images that reflect the key pattern can be detected from the multiple captured coarse images.

[0076] Therefore, the coarse pattern matching unit 54 performs pattern matching on a plurality of captured coarse images formed by imaging the wafer 1 using the imaging unit 40 and the reference images registered in the reference image storage unit 52, thereby detecting the captured coarse image in which the key pattern is reflected. Furthermore, upon detecting the captured coarse image, the coarse pattern matching unit 54 transmits information regarding the relative position of the holding unit 14 and the imaging unit 40 when the captured coarse image was formed to the fine pattern matching unit 56.

[0077] After receiving this information from the coarse pattern matching unit 54, the fine pattern matching unit 56 issues a command to the movement unit control unit 48 to position the holding unit 14 and the imaging unit 40 relative to each other based on this information. Furthermore, while the relative movement of the holding unit 14 and the imaging unit 40 is stopped, a command is issued to the imaging unit control unit 50 to cause the imaging unit 40 to capture an image of the wafer 1 held by the holding unit 14.

[0078] This allows for the formation of a clear, unblurred captured image. Here, a clear, unblurred captured image is referred to as a precision captured image. The precision pattern matching unit 56 then performs pattern matching on the precision captured image and the reference image registered in the reference image storage unit 52 to detect the key pattern contained in the precision captured image.

[0079] The key pattern position detector 58 detects the position of the key pattern on the wafer 1. The key pattern position detector 58 precisely detects the position of the key pattern based on the relative positions of the holding unit 14 and the imaging unit 40 when the precise image is formed and the position of the key pattern in the precise image.

[0080] This precise captured image is formed with the holding unit 14 and the imaging unit 40 stopped, resulting in a clear, unblurred image. Therefore, when pattern matching is performed to compare this precise captured image with the reference image stored in the reference image storage unit 52, the position of the key pattern can be precisely detected.

[0081] When the reference image is registered in the reference image storage unit 52, the positional relationship between the key pattern and the streets 3 is also registered. Therefore, if the position of the key pattern can be accurately detected, the position of the streets 3 can also be accurately detected. In the cutting device 2, the position of the streets 3 can be accurately detected, so that the wafer 1 can be accurately cut (processed) along the streets 3.

[0082] Next, the key pattern detection method according to this embodiment will be described in detail. Figure 8 This is a flow chart showing the steps of the key pattern detection method of this embodiment. Figure 2 The detection method will be described using the example of detecting the position of a key pattern formed on a wafer 1 using the cutting device 2 shown. However, the detection method of this embodiment is not limited thereto, and devices other than the cutting device 2 may be used to detect the position of a key pattern on an object to be detected other than the wafer 1.

[0083] In this inspection method, first, a holding step S1 is performed, in which the wafer 1 as the inspection target object is held by the holding unit 14 . Figure 3 (A) is a cross-sectional view schematically showing the holding step S1. In the holding step S1, the frame unit 11 is loaded onto the holding unit 14, the frame 9 is gripped by the clamp 14b of the holding unit 14, and the suction source of the holding unit 14 is activated to hold the wafer 1 on the holding unit 14 via the adhesive tape 7.

[0084] Next, before executing the key pattern coarse detection step S2, a reference image registration step is executed. For example, when processing multiple wafers 1 (inspection objects) having the same pattern in succession, the reference image showing the key pattern may not be registered in the reference image storage unit 52 of the control unit 46 after the initial wafer 1 (inspection object) has been subjected to the holding step. In this case, the reference image registration step is executed after executing the holding step S1 and before executing the key pattern coarse detection step S2.

[0085] Then, after the reference image registration step is performed on the first wafer 1 and the reference image showing the key pattern is registered in the reference image storage unit 52, the key pattern rough detection step S2 is performed. In this case, the reference image registered in the reference image storage unit 52 is used when pattern matching is performed on the second and subsequent wafers 1.

[0086] In the reference image registration step, the front surface 1a of the wafer 1 held by the holding unit 14 is photographed by the imaging unit 40 to form a photographed image showing the structures on the wafer 1. Furthermore, an area that fits the key pattern is selected from the photographed image showing the various structures, and the selected area in the photographed image is registered in the reference image storage unit 52 as a reference image.

[0087] When registering the reference image in the reference image storage unit 52, information related to the relative position of the holding unit 14 and the imaging unit 40 at the time the reference image was formed is also registered with the reference image. Furthermore, if the reference image is previously registered in the reference image storage unit 52 of the control unit 46, the reference image forming step may be performed in order to update the reference image.

[0088] In the key pattern coarse detection step S2, the imaging unit 40 captures the wafer 1 while the holding unit 14 holding the wafer 1 (the object to be inspected) and the imaging unit 40 are relatively moved by the moving unit. A plurality of captured coarse images are then captured. Pattern matching is then performed between each of the captured coarse images and a reference image reflecting the key pattern, which is pre-registered in the reference image storage unit 52 of the control unit 46. The captured coarse image reflecting the key pattern is detected from the plurality of captured coarse images.

[0089] Figure 3 (B) is a cross-sectional view schematically showing a situation in which the front surface 1a side of the wafer 1 as the inspection object is photographed by the photographing unit 40. Figure 4 1 is a top view illustrating the photographing field of view of a plurality of photographed coarse images formed in the key pattern coarse detection step S2. Figure 4 1 schematically illustrates the front surface 1a of the wafer 1. For example, the device 5 formed on the wafer 1 includes elements (not shown) such as transistors, and structures such as terminals (electrodes) 13 and wirings 15 that serve as paths for supplying electrical signals to the elements.

[0090] When the holding unit 14 and the imaging unit 40 are moved relative to each other at a predetermined speed and the imaging unit 40 is operated for a predetermined period of time, for example, Figure 4 As shown, captured images showing the ranges of the capturing field of view 17 a , the capturing field of view 17 b , and the capturing field of view 17 c are continuously formed.

[0091] Here, the captured image is a blurred captured rough image. Figure 5 (C) schematically shows a captured rough image 19a captured in the capturing field of view 17a. Figure 5 (B) schematically shows a captured rough image 19b captured in the captured visual field 17b. Figure 5 (A) schematically shows a captured rough image 19c captured in the capturing field of view 17c.

[0092] In the key pattern rough detection step S2, the captured rough images 19a, 19b, and 19c are compared with the reference image to perform pattern matching, and the captured rough image showing the key pattern is detected. Figure 7 In (A), the reference image 25 registered in the reference image storage unit 52 of the control unit 46 is schematically shown as an example. Figure 7 In the example shown in (A) of FIG. 1 , a region including a portion of the wiring 15 and the terminal (electrode) 13 is set as the key pattern 21 .

[0093] First, since the key pattern 21 is not included in the captured coarse image 19a, when pattern matching is performed between the captured coarse image 19a and the reference image 25, it is determined that the key pattern 21 is not reflected in the captured coarse image 19a. Next, since all the key patterns 21 are not reflected in the captured coarse image 19b, when pattern matching is performed between the captured coarse image 19b and the reference image 25, it is determined that the key pattern 21 is not reflected in the captured coarse image 19b.

[0094] When pattern matching is performed between captured coarse image 19c and reference image 25, all key patterns 21 are reflected in captured coarse image 19c, and therefore, it is determined that key pattern 19b is reflected in captured coarse image 19c. In this case, captured coarse image 19c is detected as a captured coarse image reflecting the key pattern. The relative movement of holding unit 14 and imaging unit 40 is then stopped, terminating the coarse key pattern detection step.

[0095] In the key pattern rough detection step S2 , a series of imaging fields overlap by a size equal to or larger than the reference image 25 so that all key patterns 21 appear in any of a plurality of captured rough images formed by imaging in each imaging field.

[0096] In the key pattern detection method of this embodiment, the key pattern fine detection step S3 is then performed. In the key pattern fine detection step S3, the holding unit 14 and the imaging unit 40 are positioned at the relative positions at which the rough image 19 c detected in the key pattern coarse detection step S2 was formed.

[0097] Then, in a state where the relative movement between the holding unit 14 and the imaging unit 40 is stopped, the wafer 1 as the inspection object is imaged by the imaging unit 40 to form a precise image. Figure 6 1 shows a top view of the front surface 1a of the wafer 1 showing the imaging field 17c when forming the precise imaging image 23 and an example of the precise imaging image 23. Figure 6 As shown, when the precise captured image 23 is formed, the holding unit 14 and the imaging unit 40 are stopped, so the precise captured image 23 becomes a clear captured image without blurring.

[0098] In the key pattern precise detection step S3 , pattern matching is further performed between the precise captured image 23 and the reference image 25 registered in the reference image storage unit 52 to detect the key pattern 21 included in the precise captured image 23 .

[0099] Next, the key pattern position detection step S4 is performed. In the key pattern position detection step S4, the position of the key pattern 21 detected in the key pattern precision detection step S3 is detected. In the key pattern position detection step S4, the position of the key pattern 21 is precisely detected based on the relative positions of the holding unit 14 and the imaging unit 40 when the precision captured image 23 is formed, and the position of the key pattern 21 reflected in the precision captured image 23.

[0100] Furthermore, in the key pattern detection method of this embodiment, when the object to be detected is a wafer 1 having streets 3 defined on the front surface 1a, a street position detection step may be performed after the key pattern position detection step S4. In this street position detection step, the position of the streets 3 is detected with reference to the position of the key pattern 21 detected in the key pattern position detection step. In this case, the relative positional relationship between the key pattern 21 and the streets 3, which is pre-registered in the control unit 46 of the cutting device 2, is referenced.

[0101] In addition, in the key pattern detection method of this embodiment, when the object to be detected is an object to be processed (workpiece) that is predetermined to be processed along the spacing lane 3, a processing step of processing the object to be detected along the spacing lane 3 can be implemented after the spacing lane position detection step.

[0102] The key pattern detection method and apparatus of this embodiment can quickly detect the position of a key pattern on an object having a key pattern. This is because the approximate position of the key pattern is detected using a plurality of coarse captured images that can be formed in a short period of time, and then a precise captured image is formed to precisely detect the position of the key pattern.

[0103] The present invention is not limited to the above-described embodiment and can be implemented with various modifications. For example, in the above-described embodiment, the holding unit is described as a chuck table that suction-holds the wafer 1 (the object to be inspected). However, one embodiment of the present invention is not limited to this.

[0104] That is, the holding unit may be a transport unit (not shown) that carries the wafer 1 (the object to be inspected) in and out of the cassette 8, or a transport rail 10 that temporarily places the wafer 1. In this case, the imaging unit 40 is disposed at a position where it can capture an image of the wafer 1 held by the holding unit.

[0105] In addition, in the above embodiment, the position of the key pattern 21 is mainly detected during alignment, and the position of the spacer 3 is detected based on the positional relationship between the key pattern 21 and the spacer 3. However, one embodiment of the present invention is not limited to this. One embodiment of the present invention can be implemented for the purpose of automatically measuring the index dimension of an object to be inspected in which a plurality of spacers 3 are set at equal intervals.

[0106] During automatic measurement, the front side 1a of the wafer 1 is first imaged while the imaging unit 40 and the holding unit 14 are relatively moved in a first direction (e.g., the Y-axis direction) to form a rough image. The rough key pattern detection step and the fine key pattern detection step are then performed in the same manner as described above to precisely detect the position of the first key pattern 21. Similarly, the position of the adjacent second key pattern 21 is precisely detected. The distance between the two key patterns 21 is then measured as the index dimension in the first direction.

[0107] Next, the imaging unit 40 and the holding unit 14 are relatively moved along the second direction (eg, the X-axis direction), and the key pattern coarse detection step and the key pattern fine detection step are similarly performed to detect the index dimension in the second direction.

[0108] Alternatively, the detection of the indexed dimension in the second direction (X-axis direction) can be performed using another method. In this case, after the indexed dimension in the first direction (Y-axis direction) is detected, the holding unit 14 is rotated 90 degrees about an axis perpendicular to the holding surface 14a. Then, the imaging unit 40 and the holding unit 14 are relatively moved in the same manner as when the indexed dimension in the first direction is detected, and the indexed dimension in the second direction is detected using the same steps.

[0109] In addition, the reference image storage unit 52 may be used to register the image data. Figure 7 The reference image 25 schematically shown in (A) is different in Figure 7 (B) schematically shows a reference image 27 showing a wider field of view. In this case, for example, the reference image 27 is used when the object to be inspected is oriented in a direction suitable for processing, that is, when the direction of the lane 3 is aligned with the processing feed direction.

[0110] For example, the corner of the device 5 is shown in the reference image 27. The imaging unit 40 captures an image of the wafer 1 (object to be measured) held by the holding unit 14, and the holding unit 14 is moved so that the same field of view as the reference image 27 is displayed. Next, the holding unit 14 and the imaging unit 40 are moved relative to each other in a predetermined direction, such as the X-axis direction, and the imaging unit 40 captures the corner of another device 5.

[0111] If the direction of the lanes 3 is aligned with the predetermined direction, a captured image can be formed that reflects the same field of view as the reference image 27. On the other hand, if the direction of the lanes 3 is not aligned with the predetermined direction, a captured image is formed that is offset in a direction perpendicular to the predetermined direction (the Y-axis direction) by comparison with the reference image 27. In this case, the holding unit 14 is rotated about an axis perpendicular to the holding surface 14a to prevent such offset, thereby aligning the direction of the lanes 3 with the predetermined direction.

[0112] Alternatively, when obtaining a captured image to be compared with the reference image 27, the holding unit 14 and the imaging unit 40 may be maintained without stopping to form a captured coarse image, and pattern matching may be performed by comparing the blurred captured coarse image with the reference image 27. In this case, a captured fine image is formed and compared with the reference image 27 to further perform pattern matching.

[0113] Alternatively, the apparatus according to one embodiment of the present invention may be a tape attaching machine used to integrate wafer 1, adhesive tape 7, and frame 9, or an expander for expanding adhesive tape 7 of wafer unit 11 after processing wafer 1. When the apparatus according to one embodiment of the present invention is one of these apparatuses, a rough image is captured when the direction of streets 3 of wafer 1 is aligned with a predetermined direction and used for pattern matching.

[0114] In addition, the structure, method, etc. of the above-mentioned embodiment can be appropriately modified and implemented without departing from the scope of the purpose of the present invention.

Claims

1. A method for detecting a key pattern, comprising detecting the position of a key pattern on an object held by a holding unit in an apparatus comprising: The holding unit holds the detected object having the key pattern; a photographing unit configured to photograph the object held by the holding unit; a moving unit that moves the holding unit and the photographing unit relative to each other; and a control unit, which controls the shooting unit and the moving unit, It is characterized in that The key pattern detection method has the following steps: a holding step of holding the detected object by using the holding unit; a key pattern coarse detection step, wherein the holding unit holding the object to be detected and the imaging unit are relatively moved by the moving unit without stopping the relative movement of the holding unit and the imaging unit, and the imaging unit is used to image the object to be detected to form a plurality of captured coarse images, and pattern matching is performed between each of the formed captured coarse images and a reference image pre-registered in the control unit that reflects the key pattern, thereby detecting the captured coarse image that reflects the key pattern from the plurality of captured coarse images; a key pattern fine detection step, positioning the imaging unit and the holding unit at their relative positions when the coarse captured image detected in the key pattern coarse detection step is formed, stopping relative movement of the holding unit and the imaging unit, photographing the object to be inspected using the imaging unit to form a fine captured image, and performing pattern matching between the fine captured image and the reference image to detect the key pattern contained in the fine captured image; and The key pattern position detecting step detects the position of the key pattern detected by the key pattern precise detecting step.

2. A key pattern detection device, comprising: a holding unit for holding the object to be detected having the key pattern; a photographing unit configured to photograph the object held by the holding unit; a moving unit that moves the holding unit and the photographing unit relative to each other; and a control unit, which controls the shooting unit and the moving unit, It is characterized in that The control unit has: a reference image storage unit storing a reference image showing the key pattern; a shooting unit control unit for controlling the shooting timing of the shooting unit; a moving unit control unit for controlling the relative movement of the holding unit and the photographing unit achieved by the moving unit; a coarse pattern matching unit for performing pattern matching on a plurality of captured coarse images formed by capturing the object to be detected by the capturing unit while the holding unit and the capturing unit holding the object to be detected are moved by the moving unit without stopping the relative movement of the holding unit and the capturing unit, and the reference image, to detect the captured coarse image reflecting the key pattern; a precise pattern matching unit for performing pattern matching between a precise captured image and the reference image to detect a key pattern included in the precise captured image, wherein the precise captured image is formed by positioning the capturing unit and the holding unit at relative positions corresponding to those when the captured coarse image detected by the coarse pattern matching unit is formed, and capturing the object to be detected by the capturing unit while the relative movement of the holding unit and the capturing unit is stopped, thereby capturing the precise captured image; and A key pattern position detection unit detects the position of the key pattern detected by the precise pattern matching unit.

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