JP2020123622A - Detection method and device for key pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a position of a key pattern of an object to be detected in a short time. SOLUTION: This is a method of detecting a key pattern for detecting the position of a key pattern possessed by an object to be detected, and the image pickup unit is while relatively moving a holding unit holding the object to be detected and an image pickup unit. A plurality of captured rough images are formed by imaging the object to be detected, and the formed rough images and the reference image in which the key pattern is captured are pattern-matched and the key pattern is captured. The object to be detected is imaged at a relative position between the key pattern coarse detection step for detecting the captured rough image, the imaging unit when the detected rough image is formed, and the holding unit. A key pattern precision detection step of forming a precision captured image, pattern matching the precision captured image and the reference image to detect the key pattern included in the precision captured image, and the detected key. It includes a key pattern position detection step for detecting the position of the pattern. [Selection diagram] Fig. 5

Description

The present invention relates to a method for detecting a key pattern from an object to be detected including a key pattern, and an apparatus capable of detecting the key pattern from the object to be detected.

In the process of manufacturing a device chip used in electronic equipment, first, a plurality of dividing lines called streets that intersect with each other are set on the surface of a semiconductor wafer, and devices are formed in each region partitioned by the streets. Then, the wafer is divided along the streets to form individual device chips.

The division of the wafer is performed, for example, by a cutting device having a cutting unit. The cutting unit includes a spindle that serves as an axis of rotation, and a cutting blade attached to one end of the spindle. When the cutting blade is rotated by rotating the spindle and the rotating cutting blade is cut along the street of the wafer to cut the wafer, the wafer is divided.

Further, the wafer division may be performed by a laser processing apparatus having a laser processing unit. For example, a laser beam having a wavelength that is transparent to the wafer is irradiated onto the wafer along the streets to be condensed inside the wafer to form a modified layer. Then, when a crack is extended from the modified layer to the front and back of the wafer, the wafer is divided. Alternatively, the wafer may be divided by irradiating the surface of the wafer with a laser beam having a wavelength having an absorptivity with respect to the wafer to form a groove along the street.

In a processing device such as a cutting device or a laser processing device, it is necessary to detect the position and direction of a street of a wafer and perform alignment for aligning a processing unit such as a cutting unit or a laser processing unit with the street (Patent Document 1 and See Patent Document 2). Here, in the processing apparatus, a captured image obtained by capturing a characteristic pattern (key pattern) included in the wafer is registered in advance as a reference image, and the distance from the key pattern to the street is stored.

Then, when processing the wafer, the surface of the wafer to be processed is imaged to obtain a captured image, and the captured image and the reference image registered in the processing device are subjected to pattern matching to perform processing. The key pattern of the wafer is detected. Then, the position of the street of the wafer is detected based on the position of the detected key pattern, and the processing unit is aligned with the position of the street.

If the key pattern is not detected from the image obtained by imaging the surface of the wafer, the wafer is moved relative to the imaging camera, and another region of the wafer is imaged to form a pattern with the reference image. Perform matching.

By the way, there is known a method called auto measure for measuring an index size of a wafer on which a plurality of devices are formed by using a pattern matching method (see Patent Document 3). In this method, imaging is repeated while relatively moving the wafer and the imaging camera, and pattern matching is performed using each of the obtained captured images.

Here, the index size is, for example, the amount of indexing and feeding the processing unit relative to the wafer when processing the wafer along a certain street and then processing the wafer along the adjacent street. It is a corresponding length. Alternatively, the index size can be said to be the distance between the center lines of a pair of adjacent streets.

When carrying out the auto measure, a characteristic structure included in the device formed on the wafer is set as a key pattern, and another key pattern adjacent to the key pattern is automatically detected by pattern matching. Then, the distance between both key patterns is calculated as an index size. Further, in order to verify the calculated index size, further adjacent key patterns may be detected by pattern matching.

JP-A-60-244803 JP 2005-166991 A JP, 7-321073, A

In order to accurately detect the position of the key pattern using the pattern matching method, it is important that the captured image is not blurred. However, in order to obtain a captured image without blurring, it is necessary to wait for the image capturing after the wafer and the image capturing camera are moved until the wafer and the image capturing camera are relatively completely stopped. Therefore, when detecting the position of the key pattern while forming a plurality of picked-up images and searching for the key pattern, it is necessary to wait each time the picked-up image is formed, so that it takes a particularly long time to detect the position of the key pattern. Was there.

The present invention has been made in view of the above problems, and an object thereof 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 the key pattern in a short time. It is to be.

According to one aspect of the present invention, a holding unit that holds an object to be detected having a key pattern, an imaging unit that images the object to be detected held by the holding unit, the holding unit and the imaging unit are provided. A key for detecting the position of the key pattern of the detection target held by the holding unit in an apparatus including a moving unit that relatively moves and a control unit that controls the imaging unit and the moving unit A method for detecting a pattern, comprising: holding a step of holding the object to be detected by the holding unit; moving the holding unit holding the object to be detected; While the imaging unit captures the detected object to form a plurality of captured rough images, each of the formed captured rough images, and a reference image in which the key pattern registered in the control unit in advance appears. , A key pattern rough detection step of detecting the picked-up rough image in which the key pattern appears in the plurality of picked-up rough images, and the picked-up rough image detected in the key pattern rough detection step are formed. The image pickup unit and the holding unit are positioned relative to the image pickup unit and the holding unit at the time of stopping, and the relative movement of the holding unit and the image pickup unit is stopped. In this state, the object to be detected is imaged by the imaging unit to form a precision captured image, and the precision captured image and the reference image are pattern-matched to generate the key pattern included in the precision captured image. There is provided a key pattern detection method comprising: a key pattern precision detection step of detecting; and a key pattern position detection step of detecting the position of the key pattern detected in the key pattern precision detection step. ..

According to another aspect of the present invention, a holding unit that holds an object to be detected having a key pattern, an imaging unit that images the object to be detected held by the holding unit, the holding unit, and An apparatus comprising: a moving unit that relatively moves the imaging unit; and a control unit that controls the imaging unit and the moving unit, the control unit storing a reference image in which the key pattern appears. A reference image storage unit, an imaging unit control unit that controls the imaging timing of the imaging unit, a moving unit control unit that controls the relative movement of the holding unit by the moving unit, and the imaging unit. , A plurality of imaging rough images formed by imaging the detected object with the imaging unit while moving the holding unit holding the detected object and the imaging unit with the moving unit, and the reference Pattern for each of the target image and the rough pattern matching section for detecting the captured rough image in which the key pattern is captured, and the imaging unit when the captured rough image detected by the rough pattern matching section is formed. And the holding unit, the imaging unit and the holding unit are positioned relative to each other, and in the imaging unit with the relative movement of the holding unit and the imaging unit stopped. A precision pattern matching unit that detects the key pattern included in the precision captured image by pattern matching the precision captured image formed by capturing the detected object and the reference image; and the precision pattern matching unit. And a key pattern position detection unit that detects the position of the key pattern detected in step 1.

In a key pattern detection method and apparatus according to an aspect of the present invention, a holding unit that holds an object to be detected such as a wafer and an imaging unit are moved relatively while the imaging unit images the object. Then, a plurality of captured rough images are formed. Although the plurality of captured rough images captured without stopping the holding unit and the imaging unit are acquired in a short time, the images are blurred due to vibrations caused by relative movement. Then, the pattern matching using the captured rough image in which the blur has occurred cannot accurately detect the position of the key pattern.

However, by using the reference image in which the key pattern is captured, the captured coarse image in which the key pattern is captured can be specified from a plurality of captured coarse images by pattern matching. Therefore, after the picked-up rough image showing the key pattern is specified, the holding unit and the pick-up unit are relatively positioned again at the position where the picked-up rough image is formed, and the holding unit and the pick-up unit are stopped with each other. The detection object is imaged to form a precision captured image.

Since the key pattern of the object to be detected is clearly reflected in the precision captured image, the position of the key pattern can be detected by performing pattern matching between the precision captured image and the reference image. With the key pattern detection method and device according to one aspect of the present invention, the position of the key pattern can be accurately detected after the approximate position of the key pattern of the object to be detected is detected in a short time.

Therefore, the present invention provides a key pattern detecting method capable of detecting the position of the key pattern in a short time and an apparatus capable of detecting the position of the key pattern in a short time.

It is a perspective view which shows typically the wafer which is an example of a to-be-detected object. It is a perspective view which shows typically the cutting device which is an example of a device. FIG. 3A is a cross-sectional view schematically showing the holding step, and FIG. 3B is a cross-sectional view schematically showing how the surface of the object to be detected is imaged by the imaging unit. It is a top view explaining the field of view of a plurality of imaged rough images formed in a key pattern rough detection step. FIG. 5(A) is a plan view schematically showing an example of a captured rough image showing a key pattern, and FIG. 5(B) is a plan view schematically showing another example of a captured rough image. FIG. 5C is a plan view schematically showing still another example of the captured rough image. It is a top view which shows the example of a precision picked-up image and the imaging visual field of this precision picked-up image typically. FIG. 7A is a plan view schematically showing an example of the reference image, and FIG. 7B is a plan view schematically showing another example of the reference image. It is a flowchart which shows the flow of the detection method of a key pattern.

An embodiment according to an aspect of the present invention will be described with reference to the accompanying drawings. According to the method and apparatus for detecting a key pattern according to the present embodiment, it is possible to image the object to be detected and detect the position of the key pattern of the object in a short time. First, an object to be detected having a key pattern will be described.

The object to be detected is, for example, a substantially disk-shaped wafer made of a material such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or another semiconductor. .. Alternatively, the object to be detected is a substrate made of a material such as sapphire, glass, or quartz. Further, the object to be detected may be a package substrate including a plurality of device chips sealed with a mold resin or the like.

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

The front surface 1a of the wafer 1 is partitioned by, for example, a plurality of planned dividing lines called streets 3 that intersect each other. Devices 5 such as ICs (Integrated Circuits) and LSIs (Large-Scale Integrated circuits) are formed in the areas defined by the streets 3 on the front surface 1a of the wafer 1. When the wafer 1 is divided along the streets 3, individual device chips can be formed.

For dividing the wafer 1, for example, a laser processing apparatus that irradiates the laser beam onto the wafer 1 along the streets 3 to perform laser processing on the wafer 1 is used. Alternatively, a cutting device capable of cutting the wafer 1 along the streets 3 with an annular cutting blade is used.

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. .. Further, in these processing devices, after processing the wafer 1 along a certain street 3, the wafer 1 and the processing unit are relatively moved according to the index size in order to accurately process the wafer along another street 3. Need to move to.

The key pattern detection method according to the present embodiment is performed, for example, when the processing apparatus performs index size detection or alignment. The device according to this embodiment is, for example, the processing device. Then, the position of the street 3 is detected by detecting the position of the key pattern of the detected object.

Here, the key pattern of the object to be detected such as the wafer 1 means, for example, a structure having a characteristic shape formed on the object to be detected. The key pattern is appropriately set on a part of the structure formed on the detected object. All or a part of the structure formed to exhibit some function in the detected object may be set as a key pattern, for example, may be selected and set from the functional layers forming the device 5. Alternatively, a dedicated structure that functions only as a key pattern may be provided on the detected object.

In the wafer 1 on which a plurality of devices 5 are formed, for example, a part of a metal layer used for wiring layers, electrodes, terminals or the like that configure the device 5 is set as a key pattern. When the object to be detected is transparent, the key pattern may be composed of a structure formed inside the object to be detected.

In addition, the structure selected as the key pattern is preferably a structure in which another structure having the same or similar shape is not formed on the detected object in order to suppress erroneous detection. Alternatively, in the case of detecting the key pattern and detecting the positions of the plurality of streets 3 set on the object from the positional relationship between the key pattern and the streets 3, the plurality of devices 5 each have one structure. The object is preferably set as a key pattern.

As shown in FIG. 1, before the wafer 1 is carried into a processing device such as a cutting device or a laser processing device, the wafer 1 has an annular frame 9 and an adhesive stuck so as to close the opening of the annular frame 9. A frame unit 11 is formed by being integrated with the tape 7. The wafer 1 is carried into the processing apparatus and processed in the state of the frame unit 11. The individual device chips formed by dividing the wafer 1 are supported by the adhesive tape 7.

Hereinafter, the case where the apparatus according to the present embodiment is a cutting apparatus for cutting the wafer 1 will be described as an example. However, the apparatus according to this embodiment may be a processing apparatus other than the cutting apparatus, and may be an inspection apparatus that does not process the wafer 1. FIG. 2 is a perspective view schematically showing the cutting device 2.

The cutting device 2 includes a base 4 that supports each component. A rectangular opening 6 is formed at the front corner of the base 4, and a cassette support that can be moved up and down is provided in the opening 6. A cassette 8 that houses a plurality of frame units 11 is placed on the upper surface of the cassette support base. Note that, in FIG. 1, only the outline of the cassette 8 is shown for convenience of description.

A rectangular opening 12 that is long in the X-axis direction (processing feed direction) is formed at a position adjacent to the opening 6 on the upper surface of the base 4. The opening 12 is provided with a holding unit 14, an X-axis direction moving mechanism (not shown) that moves the holding unit 14 in the X-axis direction, and a dustproof and drip-proof cover 12a that covers the X-axis direction moving mechanism. ing.

The cutting device 2 is provided with a transport mechanism (not shown) for loading and unloading the frame unit 11 housed in the cassette 8 placed on the cassette support table. The transport mechanism pulls out the frame unit 11 housed in the cassette 8 on a pair of transport rails 10 provided so as to straddle the opening 12.

The pair of transport rails 10 are movable in directions away from each other. After the frame mechanism 11 is pulled out by the transport mechanism onto the transport rail 10, the frame mechanism 11 is held by the transport mechanism, the interval between the pair of transport rails 10 is widened, and the transport mechanism is lowered to hold the holding unit 14. The frame unit 11 can be transported on top.

The holding unit 14 is, for example, a chuck table that holds the wafer 1 (object to be detected). 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 14 a that holds the frame unit 11. The holding unit 14 is provided with a clamp 14b (see FIG. 3A and the like) that clamps the frame unit 11 placed on the holding surface 14a on the outer peripheral portion.

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 14a and a suction source is operated to apply a 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. It

The holding unit 14 is connected to a rotary drive source (not shown) such as a motor and can rotate around a rotation axis perpendicular to the holding surface 14a. Further, the holding unit 14 is processed and fed in the X-axis direction by the above-mentioned X-axis direction moving mechanism.

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 straddle the opening 12. A Y-axis direction moving 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 direction for moving the Z-axis direction (height direction) are provided on the upper front surface of the support structure 16. And a moving mechanism 28 are provided.

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 attached to the Y-axis guide rail 20. A nut portion (not shown) is provided on the rear surface side (rear surface side) of the Y-axis moving plate 22, and a Y-axis ball screw 24 parallel to the Y-axis guide rail 20 is screwed into the nut portion.

A Y-axis pulse motor 26 is connected to one end of the Y-axis ball screw 24. When the Y-axis ball screw 24 is rotated by the Y-axis pulse motor 26, the Y-axis moving plate 22 moves in the Y-axis direction along the Y-axis guide rail 20. That is, 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.

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

A Z-axis pulse motor 36 is connected to one end of the Z-axis ball screw 34. When the Z-axis ball screw 34 is rotated by the Z-axis pulse motor 36, the Z-axis moving plate 32 moves in the Z-axis direction along the Z-axis guide rail 30. That is, 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.

A cutting unit 38 is fixed to the lower portion of the Z-axis moving plate 32. The cutting unit 38 includes a spindle that serves as a rotating shaft, and an annular cutting blade that is mounted on one end side of the spindle. The cutting blade is provided with a grindstone at least on the outer peripheral portion, and when the spindle is rotated to rotate the cutting blade to bring the grindstone into contact with the wafer 1 held by the holding unit 14, the wafer 1 is cut.

An image pickup unit (camera unit) 40 for picking up an image of the wafer 1 (object to be detected) held by the holding unit 14 is provided at a position adjacent to the cutting unit 38. The image pickup unit 40 is, for example, a CCD camera. When the image of the wafer 1 held by the holding unit 14 is picked up using the image pickup unit 40, a picked-up image showing the structure formed on the front surface 1 a of the wafer 1 can be formed. The image pickup unit 40 may be an infrared camera or the like that receives light other than visible light.

When the Y-axis moving plate 22 is moved in the Y-axis direction by the Y-axis direction moving mechanism 18, the cutting unit 38 and the imaging unit 40 are indexed and fed in the Y-axis direction. Further, if the Z-axis moving plate 32 is moved in the Z-axis direction by the Z-axis direction moving mechanism 28, the cutting unit 38 and the imaging unit 40 move up and down. Further, when the X-axis direction moving mechanism (not shown) is operated with the holding unit 14 holding the wafer 1, the wafer 1 is processed and fed along the X-axis direction.

That is, the X-axis direction moving mechanism, the Y-axis direction moving mechanism 18, and the Z-axis direction moving mechanism 28 relatively move the cutting unit 38 and the imaging unit 40, the holding unit 14 and the wafer 1. It functions as a mobile unit.

When the cutting unit 38 and the holding unit 14 are relatively moved by the moving unit while rotating the cutting blade of the cutting unit 38 and the cutting blade is cut into the wafer 1, the wafer 1 is cut. .. Further, 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 imaged and a picked-up image is formed. To be done.

The formed captured image is sent from the image capturing unit 40 to the control unit 46 described later. Then, in the control unit 46, the relative positions of the imaging unit 40 and the holding unit 14 at the time when each captured image is captured are recorded together with each captured image.

A circular opening 42 is formed at a position opposite to the opening 6 with respect to the opening 12 on the upper surface of the base 4. A cleaning unit 44 for cleaning the frame unit 11 after cutting the wafer 1 is provided in the opening 42. The cleaning unit 44 provided inside the opening 42 includes a cleaning table 44a for holding the frame unit 11, and a cleaning nozzle (a cleaning nozzle for discharging the cleaning liquid to the frame unit 11 from above the frame unit 11 held by the cleaning table 44a). (Not shown), and. The cleaning liquid is pure water, for example.

The cutting device 2 includes a control unit 46 that controls each component of the cutting device 2. The control unit 46 controls the cassette mounting table, the transfer mechanism, the transfer rail 10, the moving unit, the cutting unit 38, the imaging unit 40, the cleaning unit 44, and other mechanisms described above. The control unit 46 is, for example, a computer including a central processing unit (CPU), a storage medium, and the like. The function of the control unit 46 is realized by software, for example.

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 or the like. First, the holding unit 14 is rotated so that the streets 3 of the wafer 1 are along the X-axis direction (processing feed direction). Next, the holding unit 14 and the cutting unit 38 are relatively moved so that the grindstone of the cutting blade of the cutting unit 38 is positioned on the extension line of the street 3. Then, the wafer 1 is cut with a cutting blade.

If the position of the streets 3 of the wafer 1 cannot be accurately detected when performing the alignment or the like, then the wafer 1 cannot be precisely cut along the streets 3 and the processing accuracy is lowered. Therefore, in order to accurately detect the position of the street 3, the key pattern is set on the wafer 1 as described above, and the position of the key pattern is accurately detected by using the pattern matching method.

When performing the pattern matching, the holding unit 14 and the image pickup unit 40 are repeatedly moved, and the surface 1a of the wafer 1 is picked up by the image pickup unit 40 one after another. Then, the obtained plurality of captured images are respectively compared with the reference image in which the key pattern registered in the control unit 46 is captured, and the captured image in which the key pattern is captured is detected.

Then, the position of the key pattern on the wafer 1 is detected from the relative positional relationship between the holding unit 14 and the imaging unit 40 when the captured image is formed. The positional relationship between the key pattern and the street 3 is stored in the control unit 46 in advance, and the position of the street 3 is detected from the position of the derived key pattern based on the positional relationship.

When the position of a key pattern is detected by comparing two images using a pattern matching method, it is important that a captured image to be compared does not have a blur. Therefore, in order to acquire a captured image without blurring, it is necessary to wait for a long period of time until the holding unit 14 and the imaging unit 40 are relatively moved and then completely stopped. In addition, since it is necessary to wait each time a captured image is formed when repeatedly capturing images while searching for a key pattern, conventionally, it takes a long time to detect the position of the key pattern.

Therefore, in the key pattern detection method and apparatus according to the present embodiment, after the holding unit 14 and the image pickup unit 40 are relatively moved, the image pickup unit 40 is operated without waiting for complete stop. Then, a captured image is formed.

As shown in FIG. 2, the control unit 46 includes a moving unit control unit 48, an imaging unit control unit 50, a reference image storage unit 52, a rough pattern matching unit 54, a precise pattern matching unit 56, and a key pattern position. And a detection unit 58. The moving unit controller 48 controls the relative movement of the holding unit 14 and the imaging unit 40 by the moving unit. The imaging unit controller 50 controls the imaging timing of the imaging unit 40.

The reference image storage unit 52 stores the reference image in which the key pattern appears. The reference image is used when detecting the position of the key pattern of the wafer 1 by the pattern matching method. The reference image is registered in the reference image storage unit 52 in advance by the operator of the cutting device 2.

For example, after the frame unit 11 is loaded onto the holding unit 14 and the wafer 1 is held by the holding unit 14 via the adhesive tape 7, the front surface 1a of the wafer 1 is imaged by the imaging unit 40. Then, the operator selects a portion to be set as a key pattern from the characteristic pattern formed on the wafer 1, forms a reference image, and registers it in the reference image storage unit 52. Here, when forming the reference image, the positional relationship between the key pattern on the wafer 1 and the street 3 is registered together.

When a plurality of wafers 1 of the same type are sequentially cut (processed) by the cutting device 2, the reference image formed before the first wafer 1 is cut is used to show the subsequent wafers 1. You may implement the pattern matching which compares with a captured image.

The rough pattern matching unit 54 issues a command to the moving unit control unit 48 to relatively move the holding unit 14 holding the wafer 1 and the imaging unit 40 with the moving unit. Then, a command is issued to the imaging unit controller 50 to sequentially image the front surface 1a of the wafer 1. At this time, the relative movement of the holding unit 14 and the imaging unit 40 is not stopped. Therefore, the plurality of captured images formed are rough images with blurring. This rough image will be referred to as a captured rough image.

Here, since the holding unit 14 and the imaging unit 40 are not stopped while forming the plurality of captured rough images, the time required to form the plurality of captured rough images is the holding unit 14, the imaging unit 40, and It is extremely short compared to stopping every time. However, since the captured coarse image is a coarse image, even if the captured coarse image and the reference image are compared to perform pattern matching, the position of the key pattern cannot be accurately detected. However, it is possible to detect a picked-up rough image in which a key pattern appears from a plurality of picked-up rough images.

Therefore, the rough pattern matching unit 54 pattern-matches the plurality of picked-up rough images formed by picking up the image of the wafer 1 by the image pickup unit 40 and the reference image registered in the reference image storage unit 52, respectively. The captured rough image in which the key pattern is captured is detected. Then, the rough pattern matching unit 54, when the picked-up rough image is detected, outputs the information about the relative positions of the holding unit 14 and the pick-up unit 40 when the picked-up rough image is formed, to the fine pattern. It is sent to the matching unit 56.

After receiving the information from the rough pattern matching unit 54, the fine pattern matching unit 56 issues a command to the moving unit control unit 48 to relate the holding unit 14 and the imaging unit 40 to the information based on the information. Position relative position. Then, in a state where the relative movement between the holding unit 14 and the image pickup unit 40 is stopped, a command is issued to the image pickup unit controller 50, and the image pickup unit 40 picks up the image of the wafer 1 held by the holding unit 14.

Then, a clear captured image without blurring can be formed. Here, a clear captured image without blurring is called a precision captured image. After that, the precision pattern matching unit 56 performs pattern matching between the precision captured image and the reference image registered in the reference image storage unit 52 to detect a key pattern included in the precision captured image.

The key pattern position detector 58 detects the position of the key pattern on the wafer 1. The key pattern position detection unit 58 accurately determines the position of the key pattern from the relative positions of the holding unit 14 and the imaging unit 40 when the precision captured image is formed and the position of the key pattern in the precision captured image. To detect.

Since the precision captured image is formed with the holding unit 14 and the image capturing unit 40 stopped, it becomes a clear image without blurring. Therefore, if pattern matching is performed to compare the precision captured image and the reference image registered in the reference image storage unit 52, the position of the key pattern can be accurately detected.

When registering the reference image in the reference image storage unit 52, the positional relationship between the key pattern and the street 3 is also registered. Therefore, if the position of the key pattern can be accurately detected, the position of the street 3 can be accurately detected. The position of the street 3 is precisely detected by the cutting device 2, and the wafer 1 is precisely cut (worked) along the street 3.

Next, the key pattern detecting method according to the present embodiment will be described in detail. FIG. 8 is a flowchart showing a flow of each step of the key pattern detecting method according to the present embodiment. Hereinafter, the detection method will be described by taking as an example a case where the above-described wafer 1 is used as an object to be detected and the position of the key pattern formed on the wafer 1 is detected by using the cutting device 2 shown in FIG. However, the detection method according to the present embodiment is not limited to this, and the position of the key pattern of the detected object other than the wafer 1 may be detected using a device other than the cutting device 2.

In the detection method, first, a holding step S1 of holding the wafer 1 as an object to be detected by the holding unit 14 is performed. FIG. 3A is a 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 held by the clamp 14b included in the holding unit 14, and the suction source of the holding unit 14 is operated to move the wafer 1 through the adhesive tape 7. The holding unit 14 holds it.

Next, the reference image registration step is performed before the key pattern rough detection step S2. For example, when a plurality of wafers 1 (objects to be detected) having the same pattern are continuously processed, the control unit 46 is performed at a stage after the holding step is performed on the first wafer 1 (objects to be detected). The reference image in which the key pattern appears may not be registered in the reference image storage unit 52. In this case, the reference image registration step is performed after the holding step S1 and before the key pattern rough detection step S2.

Then, the reference image registration step is performed on the first wafer 1 to register the reference image in which the key pattern appears in the reference image storage unit 52, and then the key pattern rough detection step S2 is performed. In this case, when performing pattern matching on the second and subsequent wafers 1, the reference image registered in the reference image storage unit 52 is used.

In the reference image registration step, the surface 1a of the wafer 1 held by the holding unit 14 is imaged by the imaging unit 40, and a captured image showing the structure of the wafer 1 is formed. Then, an area suitable for the key pattern is selected from the captured image showing various structures, and the area of the captured image is registered in the reference image storage unit 52 as the reference image.

When registering the reference image in the reference image storage unit 52, information regarding the relative positions of the holding unit 14 and the imaging unit 40 when the reference image is formed is used for the reference image. Register along with the image. In addition, the reference image forming step may be performed to update the reference image even when the reference image is registered in advance in the reference image storage unit 52 of the control unit 46.

In the key pattern rough detection step S2, while the holding unit 14 holding the wafer 1 (object to be detected) and the imaging unit 40 are relatively moved by the moving unit, the wafer 1 is imaged by the imaging unit 40. A plurality of captured rough images are formed. After that, each of the formed captured rough images and the reference image in which the key pattern registered in the reference image storage unit 52 of the control unit 46 is captured are subjected to pattern matching to obtain one of the plurality of captured rough images. The captured rough image in which the key pattern appears is detected.

FIG. 3B is a cross-sectional view schematically showing how the imaging unit 40 images the front surface 1 a side of the wafer 1 that is the object to be detected. In addition, FIG. 4 is a plan view illustrating the imaging fields of view of the plurality of captured rough images formed in the key pattern rough detection step S2. In FIG. 4, the surface 1 a of the wafer 1 is enlarged and schematically shown. For example, the device 5 formed on the wafer 1 has structures such as terminals (electrodes) 13 and wirings 15 that serve as paths for supplying electric signals to the respective elements, as well as elements (not shown) such as transistors.

When the holding unit 14 and the image pickup unit 40 are relatively moved at a predetermined speed and the image pickup unit 40 is operated at regular time intervals, for example, as shown in FIG. Captured images showing the range of the visual field 17c are formed one after another.

Here, the captured image formed is a captured rough image with blurring. FIG. 5C schematically shows a captured rough image 19a captured in the imaging field of view 17a. FIG. 5B schematically shows a captured rough image 19b captured in the imaging field of view 17b. FIG. 5A schematically shows a captured rough image 19c captured in the imaging field of view 17c.

In the key pattern rough detection step S2, these picked-up rough images 19a, 19b, 19c are respectively compared with the reference images and pattern matching is performed, and picked-up rough images in which the key patterns are photographed are detected. As an example, FIG. 7A schematically shows the reference image 25 registered in the reference image storage unit 52 of the control unit 46. In the example shown in FIG. 7A, a region including a part of the wiring 15 and the terminal (electrode) 13 is set as the key pattern 21.

First, since the captured rough image 19a does not include the key pattern 21, it is determined that the key pattern 21 does not appear in the captured rough image 19a when pattern matching is performed between the captured rough image 19a and the reference image 25. Is done. Next, since all of the key patterns 21 are not shown in the captured coarse image 19b, when pattern matching is performed between the captured coarse image 19b and the reference image 25, the key pattern 21 is shown in the captured coarse image 19b. It is determined that there is no.

Then, when pattern matching is performed on the captured rough image 19c and the reference image 25, the key pattern 19b is captured in the captured coarse image 19c because all of the key patterns 21 are captured in the captured coarse image 19c. Is determined. In this case, the captured coarse image 19c is detected as the captured coarse image showing the key pattern. Then, the relative movement between the holding unit 14 and the imaging unit 40 is stopped, and the key pattern rough detection step is ended.

In the key pattern rough detection step S2, a series of imaging visual fields are mutually referred to as reference images so that all of the key patterns 21 are reflected in any one of a plurality of imaging coarse images formed by performing imaging in each imaging visual field. Overlap the size of 25 or more.

In the key pattern detection method according to this embodiment, next, a key pattern precision detection step S3 is performed. In the key pattern precision detection step S3, the holding unit 14 is provided at a relative position between the holding unit 14 and the imaging unit 40 when the imaged rough image 19c detected in the key pattern rough detection step S2 is formed. , The imaging unit 40 is positioned.

Then, in the state where the relative movement of the holding unit 14 and the image pickup unit 40 is stopped, the image pickup unit 40 picks up an image of the wafer 1 which is the object to be detected to form a precision picked up image. FIG. 6 shows a plan view of the front surface 1a of the wafer 1 showing an imaging visual field 17c when the precision captured image 23 is formed, and an example of the precision captured image 23. As shown in FIG. 6, when the precision captured image 23 is formed, the holding unit 14 and the image capturing unit 40 are stopped, so the precision captured image 23 becomes a clear captured image without blurring. ..

In the key pattern precision detection step S3, the precision captured image 23 and the reference image 25 registered in the reference image storage unit 52 are pattern-matched to detect the key pattern 21 included in the precision captured image 23. To do.

Next, the key pattern position detecting step S4 is performed. In the key pattern position detecting step S4, the position of the key pattern 21 detected in the key pattern precision detecting step S3 is detected. In the key pattern position detecting step S4, the key pattern 21 is calculated from 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 shown in the precision captured image 23. The position of is accurately detected.

Further, when the object to be detected according to the key pattern detecting method according to the present embodiment is the wafer 1 having the streets 3 set on the surface 1a, the street position detecting step is further performed after the key pattern position detecting step S4. May be done. In the street position detecting step, the position of the street 3 is detected based on the position of the key pattern 21 detected in the key pattern position detecting step. In this case, the relative positional relationship between the key pattern 21 registered in advance in the control unit 46 of the cutting device 2 and the street 3 is referred to.

Furthermore, when the detected object according to the key pattern detection method according to the present embodiment is a processed object (workpiece) scheduled to be processed along the street 3, after the street position detecting step, the detected object is processed along the street 3. A processing step of processing the object to be detected may be performed.

According to the key pattern detection method and apparatus according to the present embodiment, the position of the key pattern can be detected in a short time from the detection object included in the key pattern. This is because the approximate position of the key pattern is detected using a plurality of captured coarse images that can be formed in a short time, and then the precise captured image is formed to accurately detect the position of the key pattern.

It should be noted that the present invention is not limited to the description of the above embodiment and can be implemented with various modifications. For example, in the above embodiment, the case where the holding unit is the chuck table that sucks and holds the wafer 1 (object to be detected) has been described as an example, but one embodiment of the present invention is not limited thereto.

That is, the holding unit may be a transfer unit (not shown) for loading/unloading the wafer 1 (object to be detected) from the cassette 8 or a transfer rail 10 on which the wafer 1 is temporarily placed. In this case, the imaging unit 40 is arranged at a position where the wafer 1 held by the holding unit can be imaged.

Further, in the above-described embodiment, the case where the position of the key pattern 21 is detected and the position of the street 3 is detected based on the positional relationship between the key pattern 21 and the street 3 when performing the alignment has been mainly described. One embodiment of the invention is not limited to this. One aspect of the present invention may be carried out for the purpose of carrying out an automatic measure for measuring the index size in an object to be detected in which a plurality of streets 3 are set at equal intervals.

When carrying out the auto-measure, first, while the imaging unit 40 and the holding unit 14 are relatively moved along the first direction (for example, the Y-axis direction), the front surface 1a side of the wafer 1 is imaged, and the imaging is performed. Form a coarse image. Then, similarly to the above, the key pattern coarse detection step and the key pattern precision detection step are performed to accurately detect the position of the first key pattern 21. Similarly, the 21 positions of the adjacent second key patterns are precisely detected. Then, the distance between both key patterns 21 is detected as the index size in the first direction.

Then, the imaging unit 40 and the holding unit 14 are relatively moved along the second direction (for example, the X-axis direction), and similarly, the key pattern rough detection step and the key pattern precision detection step are performed, Then, the index size in the second direction is detected.

In addition, the detection of the index size in the second direction (X-axis direction) may be performed by another method. In this case, after detecting the index size in the first direction (Y-axis direction), the holding unit 14 is rotated 90 degrees about the 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 index size in the first direction is detected, and the same steps are performed to detect the index size in the second direction.

In addition to the reference image 25 schematically shown in FIG. 7A, a reference image 27 having a wider field of view schematically shown in FIG. 7B is registered in the reference image storage unit 52. It may have been done. In this case, for example, the reference image 27 is used when the detected object is oriented in a direction suitable for machining or the like, that is, when the direction of the street 3 is aligned with the machining feed direction or the like.

For example, the reference image 27 shows the corner of the device 5. The wafer 1 (object to be measured) held by the holding unit 14 is imaged by the imaging unit 40, and the holding unit 14 is moved so that the same field of view as the reference image 27 can be seen. Next, the holding unit 14 and the imaging unit 40 are relatively moved in a predetermined direction such as the X-axis direction, and the corners of the other device 5 are captured by the imaging unit 40.

If the direction of the street 3 is aligned with the predetermined direction, at this time, it is possible to form a captured image in which the same imaging field of view as the reference image 27 is captured. On the other hand, when the direction of the street 3 is not aligned with the predetermined direction, a captured image that is shifted from the reference image 27 in the direction perpendicular to the predetermined direction (Y-axis direction) is formed. .. In this case, the holding unit 14 is rotated around an axis perpendicular to the holding surface 14a so that such a deviation does not occur, and the direction of the street 3 is aligned with the predetermined direction.

Note that when obtaining a captured image to be compared with the reference image 27, the holding unit 14 and the imaging unit 40 are not stopped to form a captured coarse image, and the captured coarse image with blurring and the reference The pattern matching may be performed by comparing the target image 27 with the target image 27. In this case, a captured precision image is formed and compared with the reference image 27 to further perform pattern matching.

The apparatus according to an aspect of the present invention is a mounter used when the wafer 1, the adhesive tape 7, and the frame 9 are integrated, and the adhesive tape 7 of the wafer unit 11 after processing the wafer 1. It may be an expander that expands. When the device according to one aspect of the present invention is these devices, when the direction of the streets 3 of the wafer 1 is aligned with a predetermined direction, a captured rough image is formed and used for pattern matching.

In addition, the structures, methods, and the like according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the invention.

1 wafer 1a front surface 1b back surface 3 street 5 device 7 adhesive tape 9 frame 11 frame unit 13 terminal (electrode)
15 wirings 17a, 17b, 17c imaging field of view 19a, 19b, 19c imaging rough image 21 key pattern 23 precision imaging image 25, 27 reference image 2 cutting device 4 base 6, 12, 42 opening 8 cassette 10 transport rail 12a bellows 14 Chuck table 14a Holding surface 14b Clamp 16 Supporting part 18,28 Moving mechanism 20,30 Guide rail 22,32 Moving plate 24,34 Ball screw 26,36 Pulse motor 38 Cutting unit 40 Imaging unit 44 Cleaning unit 46 Control unit 48 Moving unit control Part 50 Imaging unit control part 52 Reference image storage part 54 Coarse pattern matching part 56 Precision pattern matching part 58 Key pattern position detection part

Claims (2)

A holding unit for holding an object to be detected having a key pattern, an imaging unit for imaging the object to be detected held by the holding unit, a moving unit for relatively moving the holding unit and the imaging unit, A method of detecting a key pattern for detecting a position of the key pattern included in the object to be detected held by the holding unit in an apparatus including a control unit that controls the imaging unit and the moving unit,
A holding step of holding the object to be detected by the holding unit;
The holding unit that holds the detection target and the imaging unit are relatively moved by the moving unit, and the detection unit images the detection target to form a plurality of captured rough images. The captured rough image in which the key pattern is captured from among the plurality of captured rough images by performing pattern matching between the captured rough images and the reference image in which the key pattern registered in the control unit is captured in advance. A key pattern coarse detection step for detecting
Positioning the imaging unit and the holding unit at a relative position of the imaging unit and the holding unit when the imaging rough image detected in the key pattern rough detection step is formed, In the state where the relative movement of the holding unit and the imaging unit is stopped, the object to be detected is imaged by the imaging unit to form a precision imaging image, and the precision imaging image and the reference image are , A key pattern precision detection step of detecting the key pattern included in the precision captured image by pattern matching,
A key pattern position detecting step of detecting a position of the key pattern detected in the key pattern precision detecting step. A holding unit for holding an object to be detected having a key pattern, an imaging unit for imaging the object to be detected held by the holding unit, a moving unit for relatively moving the holding unit and the imaging unit, A device comprising a control unit for controlling the imaging unit and the moving unit,
The control unit is
A reference image storage unit that stores a reference image in which the key pattern appears,
An imaging unit control unit for controlling the imaging timing of the imaging unit;
A moving unit controller that controls relative movement of the holding unit by the moving unit and the imaging unit;
A plurality of imaged rough images formed by imaging the object to be detected by the imaging unit while moving the holding unit holding the object to be detected and the imaging unit with the moving unit, and the reference image. A rough pattern matching unit that detects the captured rough image in which the key pattern is captured by pattern matching each of the images and
The imaging unit and the holding unit are positioned relative to the imaging unit and the holding unit when the imaging rough image detected by the rough pattern matching unit is formed, and the holding unit A precision imaged image formed by imaging the object to be detected by the imaging unit in a state where the relative movement of the unit and the imaging unit is stopped, and the reference image are pattern-matched to perform the pattern matching. A precision pattern matching unit that detects a key pattern included in a precision captured image,
A key pattern position detection unit that detects the position of the key pattern detected by the precision pattern matching unit.

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