JP7088771B2 - Alignment method - Google Patents

Description

The present invention relates to an alignment method for specifying a planned division line of a wafer.

A wafer in which a device is formed in an area partitioned by a planned division line is cut along a planned division line by cutting a cutting blade to form a cutting groove, or a laser beam is irradiated along the planned division line to form a processing groove. When performing laser machining to form a device, the device needs to be aware of the planned split line.

The same circuit pattern is formed on the device surface of the wafer. Then, one pattern having a characteristic shape among the circuit patterns is set as a macro alignment mark. Further, a micro-alignment mark smaller than the macro-alignment mark is set at a position separated from the macro-alignment mark by a predetermined distance in a predetermined direction. The planned division line is set at a position separated from the microalignment mark by a predetermined distance in a predetermined direction.

In macro alignment, the processing device finds the macro alignment mark of the wafer held on the chuck table, and then uses the macro alignment mark to align the planned division line with the X-axis direction, which is one axis in the horizontal plane. Coarse θ adjustment is performed (see, for example, Patent Document 1). Next, the micro-alignment mark located at a predetermined distance away from the macro-alignment mark in a predetermined direction is confirmed, and the micro-alignment mark is used to perform high-precision θ alignment in which the planned division line is aligned in parallel with the X-axis direction with high accuracy. .. After that, the scheduled division line separated from the microalignment mark by a predetermined distance in a predetermined direction is recognized.

Japanese Unexamined Patent Publication No. 2007-080282

In preparation for macro alignment, the macro alignment mark is imaged by an imaging means having an imaging region smaller than the region partitioned by the planned division line (that is, an imaging region smaller than the size of the device), and the macro is further smaller than the imaging region. The target image centered on the alignment mark is registered in the processing device.

In macro alignment, pattern matching is performed to determine whether or not the target image is present in the image captured by the image pickup means for the wafer to be processed, which is newly sucked and held by the chuck table. That is, for example, the target image is moved one pixel at a time in the captured image to perform pattern matching. Then, if there is no target image in the captured image, the target image is overlapped by the pixels of the target image to image the position next to the previous imaging position to form a new captured image, and the target image is captured in the new captured image. Perform pattern matching to find the macro alignment mark.

In this way, the movement of the imaging position (specifically, the spiral movement of the imaging position on the wafer) and the target image in the new captured image captured by the movement of the imaging position until the macro alignment mark is found. The pattern matching using the above is repeated until the cumulative area of each captured image captured by overlapping the pixels is at least the same area as the area partitioned by the planned division line. Such a conventional procedure for finding a macro alignment mark is called a spiral search.

In the spiral search, the imaging area by the imaging means is expanded while overlapping the pixels of the target image, so if the target image is large (that is, if the macro alignment mark is large), the imaging means is placed at the position next to the previous imaging position. The amount of movement when moving to is reduced. The reason for overlapping the pixels of the target image is to prevent the entire target image from being overlooked when only a part of the target image is shown in the captured image. Therefore, since the imaging means is moved to the position next to the previous imaging position by the distance obtained by subtracting the size of the target image from the size of the entire image, the amount of movement of the imaging area is small when the target image is large. Therefore, it becomes necessary to move the imaging position in a spiral shape many times to perform imaging many times, which causes a problem that it takes time to find the macro alignment mark.

Specifically, for example, when the image pickup area of the image pickup means is 512 × 480 pixels, the size of the macro alignment mark is small, and if the target image is 16 × 18 pixels, the image pickup area of the image pickup means. The number of imagings associated with the spiral movement can be, for example, up to 6 times. On the other hand, if the size of the macro alignment mark is large and the target image is 250 × 250 pixels, the number of imaging times due to the spiral movement of the imaging area of the imaging means increases, for example, up to 25 times. ..

Therefore, in the alignment method for specifying the planned division line of the wafer, there is a problem that the alignment mark (macro alignment mark) can be quickly found and the alignment time can be shortened.

In the present invention for solving the above problems, a device is formed in a region partitioned by a first scheduled division line set on the surface and a second scheduled division line intersecting the first scheduled division line. The wafer is held on a chuck table, the wafer held by the chuck table is imaged by an image pickup means, an alignment mark arranged in the region is detected, and the first division schedule line and the second division schedule are scheduled. An alignment method for specifying a line, in which the imaging region of the imaging means is smaller than the region and a registration step of registering a target image including an alignment mark in an region smaller than the imaging region and a new holding in the chuck table. At least two side-by-side captured images captured by the imaging means are combined to form a combined image, and each time the combined image is formed, it is patterned whether or not the target image is present in the combined image. A confirmation step for matching and confirmation, and an alignment method for identifying the first scheduled division line and the second scheduled division line from the alignment mark in the target image after the target image is detected in the confirmation step. be.

In the alignment method according to the present invention, at least two side-by-side captured images of a wafer newly held on a chuck table captured by an imaging means are combined to form a combined image, and each time the combined image is formed, the combined image is included. By performing a confirmation process of pattern matching and confirming whether or not there is a target image in the image, it is not necessary to perform the conventional spiral search when finding the alignment mark of the new wafer to be processed. That is, unlike the conventional case, it is not necessary to overlap the imaging region of the imaging means by the pixels of the target image and move it in a spiral shape to perform imaging many times, and the target is captured for each image captured by overlapping the pixels. There is no need to perform image pattern matching. Therefore, the alignment mark (macro alignment mark) can be quickly found and the alignment time can be shortened.

It is a perspective view which shows an example of the cutting apparatus which cuts a wafer. It is explanatory drawing explaining the case of registering the target image including the alignment mark of the region smaller than the imaging region. It is explanatory drawing explaining the image capture image which image | photographed the wafer newly held in the chuck table by the image pickup means. It is explanatory drawing explaining the case where two side-by-side captured images are combined to form a combined image, and pattern matching is performed to confirm whether or not there is a target image in the combined image. It is explanatory drawing explaining the case where three side-by-side captured images are combined to form a combined image, and pattern matching is performed to confirm whether or not there is a target image in the combined image. It is explanatory drawing explaining the case where four side-by-side captured images are combined to form a combined image, and pattern matching is performed to confirm whether or not there is a target image in the combined image.

The cutting device 1 shown in FIG. 1 is an apparatus for cutting a wafer W, which is a plate-shaped workpiece held on a chuck table 30, by rotating a cutting blade 63 included in a cutting means 6 to cut the wafer W. Is.

A cutting feed means 11 for reciprocating the chuck table 30 in the cutting feed direction (X-axis direction) is disposed on the base 10 of the cutting device 1. The cutting feed means 11 includes a ball screw 110 having an axial center in the X-axis direction, a pair of guide rails 111 arranged in parallel with the ball screw 110, a motor 112 for rotating the ball screw 110, and a ball screw 110 having an internal nut. It is composed of a movable plate 113 which is screwed into a screw and whose bottom is slidably in contact with the guide rail 111. Then, when the motor 112 rotates the ball screw 110, the movable plate 113 is guided by the guide rail 111 and moves in the X-axis direction, and the chuck table 30 arranged on the movable plate 113 moves in the X-axis direction. Move to.

The chuck table 30 that holds the wafer W has, for example, a circular outer shape, and sucks and holds the wafer W on a horizontal holding surface 30a made of a porous member or the like. The chuck table 30 is fixed on the movable plate 113 via a rotating means 31 arranged on the bottom surface side thereof. The rotating means 31 can support the chuck table 30 and rotate the chuck table 30 around the axis in the Z-axis direction.
A plurality of clamps 32 for sandwiching and fixing the annular frame F are arranged around the chuck table 30 at equal intervals in the circumferential direction.

On the rear side (-X direction side) on the base 10, a portal column 14 is erected so as to straddle the cutting feed means 11. An index feeding means 12 for reciprocating the cutting means 6 in the Y-axis direction is arranged on the front surface of the portal column 14. The index feeding means 12 includes a ball screw 120 having an axial center in the Y-axis direction, a pair of guide rails 121 arranged in parallel with the ball screw 120, a motor 122 for rotating the ball screw 120, and a ball screw 120 having an internal nut. It is composed of a movable plate 123 whose side portion is screwed into the guide rail 121 and is in sliding contact with the guide rail 121. Then, when the motor 122 rotates the ball screw 120, the movable plate 123 is guided by the guide rail 121 and moves in the Y-axis direction, and is arranged on the movable plate 123 via the cutting feeding means 16. The cutting means 6 is index-fed in the Y-axis direction.

On the movable plate 123, a cutting feeding means 16 for reciprocating the cutting means 6 in the Z-axis direction (vertical direction) orthogonal to the holding surface 30a of the chuck table 30 is arranged. The notch feeding means 16 includes a ball screw 160 having an axial center in the Z-axis direction, a pair of guide rails 161 arranged in parallel with the ball screw 160, a motor 162 for rotating the ball screw 160, and a ball screw 160 having an internal nut. It is composed of a support member 163 screwed to and whose side portion is in sliding contact with the guide rail 161. Then, when the motor 162 rotates the ball screw 160, the support member 163 is guided by the guide rail 161 and moves in the Z-axis direction, and the cutting means 6 supported by the support member 163 is cut and fed in the Z-axis direction. Will be done.

The cutting means 6 includes a rotary shaft 60 whose axial direction is the Y-axis direction, a housing 61 fixed to the lower end of the support member 163 and rotatably supporting the rotary shaft 60, and a motor (not shown) for rotating the rotary shaft 60. An annular cutting blade 63 mounted on the rotating shaft 60 is provided, and the cutting blade 63 also rotates at high speed as a motor (not shown) rotationally drives the rotating shaft 60.

For example, on the side surface of the housing 61 of the cutting means 6, a macro imaging means 51 for imaging the wafer W at a low magnification and a micro imaging means 52 for imaging the wafer W at a high magnification are arranged. The macro image pickup means 51 includes, for example, an image pickup element (not shown), a low-magnification objective lens, and illumination that irradiates the wafer W sucked and held on the chuck table 30 with light. The micro image pickup unit 52 includes, for example, an image pickup element (not shown), a high-magnification objective lens, and illumination that irradiates the wafer W sucked and held on the chuck table 30 with light. The macro imaging means 51, the micro imaging means 52, and the cutting means 6 move in the Y-axis direction and the Z-axis direction in conjunction with each other.
For example, the magnification of the high-magnification objective lens is 10 times the magnification of the low-magnification objective lens, and one pixel in the image captured by the macro imaging means 51 is 10 μm.

The cutting device 1 includes, for example, a control means 9 that controls the entire device. The control means 9 is connected to the cutting feed means 11, the index feed means 12, the cut feed means 16, the rotation means 31, and the like by a wiring (not shown), and is controlled by the cutting feed means 11 under the control of the control means 9. The cutting feed operation of the chuck table 30 in the X-axis direction, the index feed amount of the cutting means 6 by the index feed means 12 in the Y-axis direction, the cut feed amount of the cutting means 6 by the cut feed means 16 in the Z-axis direction, and the rotation means 31. The rotation operation of the chuck table 30 and the like are controlled.

Hereinafter, each of the alignment methods according to the present invention in the case of specifying the first scheduled division line S1 and the second scheduled division line S2 of the wafer W to be cut using the cutting apparatus 1 shown in FIG. The process will be described.

(1) Registration Process The wafer W shown in FIG. 1 is, for example, a circular silicon semiconductor wafer, and the device D is located on the surface Wa of the wafer W in a grid-like region partitioned by orthogonally different scheduled division lines. It is formed. A dicing tape T having a diameter larger than that of the wafer W is attached to the back surface Wb of the wafer W. An annular frame F having a circular opening is attached to the outer peripheral region of the adhesive surface of the dicing tape T, and the wafer W is supported by the annular frame F via the dicing tape T and handled via the annular frame F. Is in a possible state.
Each scheduled division line extending in the same direction (for example, the X-axis direction in FIG. 1) set on the surface Wa of the wafer W is designated as the first scheduled division line S1, while the first division line is on the surface Wa of the wafer W. Each scheduled division line extending in a direction orthogonal to the scheduled division line S1 (Y-axis direction orthogonal to the X-axis direction in the horizontal plane) is referred to as a second scheduled division line S2.

In the registration step, first, the wafer W is sucked and held by the chuck table 30 shown in FIG. 1 with the surface Wa facing upward. Then, the chuck table 30 that sucks and holds the wafer W is moved in the X-axis direction by the cutting feed means 11. Further, the macro imaging means 51 is moved in the Y-axis direction by the index feeding means 12, and the substantially center of the wafer W is located directly below the objective lens of the macro imaging means 51.
Then, the surface Wa of the wafer W is imaged by the macro imaging means 51, and an image captured image is formed.

The size of the imaging region 510 of the macro imaging means 51 is smaller than the region partitioned by the first scheduled division line S1 and the second scheduled division line S2, that is, the size of the device D.

Then, one pattern having a characteristic shape among the circuit patterns on the surface of the device D of the wafer W shown in the captured image is selected by the operator as the macro alignment mark MA. The macro alignment mark MA is formed at a similar position for each of the plurality of devices D, for example, at a corner portion (lower left corner in FIG. 2) of the device D. The macro alignment mark MA may have a simple shape such as a cross shape shown in FIG. 2 or a pattern having a simple shape such as a circle or a square. Further, the macro alignment mark does not have to be a part of the circuit pattern.

Next, some of the characteristics of the elements and wiring formed on the surface of the device D and located at a predetermined distance in a predetermined direction from the macro alignment mark MA are given to the operator as a micro alignment mark MB considerably smaller than the macro alignment mark MA. Be selected. The microalignment mark MB is formed at the same position for each of the plurality of devices D, for example, at a corner portion (lower right corner in FIG. 2) of the device D.
As the micro-alignment mark MB is selected, the distance and direction from the macro-alignment mark MA to the micro-alignment mark MB are stored in the storage unit 91. That is, it is stored that the micro-alignment mark MB exists at a position separated by a distance Lx1 in the X-axis direction and a distance Ly1 in the Y-axis direction from the macro alignment mark MA by counting the number of pixels or the like. Further, the distance from the microalignment mark MB to the center line passing through the center of the width of the second scheduled division line S2 and the distance from the microalignment mark MB to the center line passing through the center of the width of the first scheduled division line S1. Ly2 is stored in the storage unit 91.

Further, the operator registers the macro alignment mark MA in the storage unit 91 of the control means 9 in a rectangular area indicated by a two-dot chain line smaller than the image pickup area 510 of the macro image pickup means 51. That is, the target image GT including the entire macro alignment mark MA is stored in the storage unit 91.

This registration process is sometimes called a teaching process for the cutting device 1 shown in FIG. 1, and when cutting a plurality of wafers W of the same type, before cutting the first wafer W. If it is performed once, it is not necessary to perform it after newly sucking and holding the second and subsequent wafers W on the chuck table 30.

The registration process is not limited to this embodiment. For example, the storage unit 91 may store device data in which a plurality of processing conditions corresponding to each type of wafer to be processed are listed in advance. The processing conditions are data in which various settings for performing appropriate cutting processing on the wafer for each type of wafer to be a workpiece are collectively stored, and the various settings are the cutting feed means shown in FIG. In addition to the cutting feed rate of the chuck table 30 holding the wafer by 11 and the index feed amount of the cutting means 6 by the index feed means 12, information on macro-alignment marks and micro-alignment marks for each type of wafer is also included. .. Therefore, by selecting the appropriate processing conditions for the wafer W shown in FIG. 1 from the device data, the entire macro alignment mark MA is included in the region indicated by the alternate long and short dash line smaller than the imaging region 510 of the macro imaging means 51. The target image GT may be registered. In this case, the image pickup of the wafer W by the macro image pickup means 51 may not be performed in the main registration step.

(2) Confirmation Step The chuck table 30 shown in FIG. 1 sucks and holds a new wafer W for cutting with the surface Wa facing upward. The chuck table 30 that sucks and holds the new wafer W shown in FIG. 1 is moved in the X-axis direction by the cutting feed means 11. Further, the macro imaging means 51 is moved in the Y-axis direction by the index feeding means 12. Then, the surface Wa of the wafer W is located directly under the objective lens of the macro imaging means 51. The imaging position of the surface Wa of the wafer W by the macro imaging means 51 is not limited to a specific position as long as it is a region where the device D is formed.

In this state, the surface Wa of the wafer W is imaged by the macro image pickup means 51, and the image pickup image G1 shown in FIG. 3 is formed. Since the size of the captured image G1 is the same as the size of the imaging region 510 of the macro imaging means 51 shown in FIG. 2, it is smaller than the size of the device D. The captured image G1 is stored in the storage unit 91 of the control means 9.

After the captured image G1 is formed, for example, the chuck table 30 for holding the wafer W is moved by the cutting feed means 11 shown in FIG. That is, the chuck table 30 that sucks and holds the wafer W is, for example, relatively moved by a predetermined distance in the + X direction with respect to the macro imaging means 51 in a state where the movement is stopped. The moving distance of the chuck table 30 is, for example, the same value as the length of the imaging region 510 of the macro imaging means 51 shown in FIG. 2 in the X-axis direction.

By moving the chuck table 30 as described above, the imaging region 510 of the macro imaging means 51 is positioned next to the imaging position in the X-axis direction when the imaging image G1 is captured. Then, the surface Wa of the wafer W is imaged by the macro imaging means 51, and the captured image G2 shown in FIG. 4 is formed side by side in the X-axis direction on the captured image G1. The captured image G2 is stored in the storage unit 91 of the control means 9.

For example, the control means 9 shown in FIG. 1 includes a combined image forming unit 92 that combines the captured images formed by the macro imaging means 51 to form a combined image. The combined image forming unit 92 is, for example, the combined image shown in FIG. 4 in which the captured image G1 stored in the storage unit 91 and the newly captured captured image G2 are combined on a virtual screen having a predetermined resolution. Display GA.

Next, the pattern matching unit 93 included in the control means 9 shown in FIG. 1 performs pattern matching as to whether or not the target image GT is present in the combined image GA. That is, the pattern matching unit 93 superimposes the target image GT on the combined image GA displayed on a virtual screen having a predetermined resolution, for example, and sets the target image GT on the combined image GA in units of one pixel, for example, on the X-axis. It is moved in the direction or the Y-axis direction, and the region having the highest correlation with the target image GT in the combined image GA is detected as a region matching with the target image GT.

As shown in FIG. 4, since the pattern matching unit 93 cannot detect the region matching with the target image GT in the combined image GA, the surface Wa of the W is further imaged by the macro imaging means 51. That is, the index feeding means 12 shown in FIG. 1 moves the macro imaging means 51 by a predetermined distance, for example, relatively in the + Y direction with respect to the chuck table 30 in a state where the movement is stopped. The moving distance of the macro imaging means 51 is, for example, the same value as the length of the imaging region 510 of the macro imaging means 51 in the Y-axis direction.

By moving the macro imaging means 51 as described above, the imaging region 510 of the macro imaging means 51 is positioned next to the imaging position when the captured image G2 is captured in the Y-axis direction. Then, the surface Wa of the wafer W is imaged by the macro imaging means 51, and the captured image G3 shown in FIG. 5 is formed side by side in the Y-axis direction on the captured image G2. The captured image G3 is stored in the storage unit 91 of the control means 9.

The combined image forming unit 92 combines the captured image G1 and the captured image G2 stored in the storage unit 91 on a virtual screen having a predetermined resolution with the combined image GA and the newly captured captured image G3. The combined combined image GB is displayed. Next, the pattern matching unit 93 superimposes the target image GT on the combined image GB and moves the target image GT on the combined image GB in pixel-by-pixel units in the X-axis direction or the Y-axis direction. The area that matches the target image GT of is detected.

As shown in FIG. 5, since the pattern matching unit 93 cannot detect the region matching with the target image GT in the combined image GB, the macro imaging means 51 further images the surface Wa of the W on the way. That is, the chuck table 30 that sucks and holds the wafer W with respect to the macro imaging means 51 in the state where the movement is stopped is, for example, in the X-axis direction of the imaging region 510 of the macro imaging means 51 in the relative −X direction. It is moved by the same distance as the length, and the image pickup region 510 is located next to the image pickup position in the X-axis direction when the image pickup image G3 is imaged. Then, the surface Wa of the wafer W is imaged by the macro imaging means 51, and the captured images G4 shown in FIG. 6 arranged side by side in the X-axis direction are formed in the captured image G3 and stored in the storage unit 91.
As shown in FIGS. 4 to 6, the imaging of the wafer W by the macro imaging means 51 is performed so that, for example, the imaging region 510 draws a spiral trajectory in the clockwise direction on the wafer W when viewed from above. ..

As shown in FIG. 6, the combined image forming unit 92 combines the combined image GB stored in the storage unit 91 and the newly captured imaged image G4 on a virtual screen having a predetermined resolution. Display image GC. Next, the pattern matching unit 93 superimposes the target image GT on the combined image GC, moves the target image GT on the combined image GC in pixel-by-pixel units in the X-axis direction or the Y-axis direction, and is in the combined image GC. The area matching with the target image GT of the above is detected to find the macro alignment mark MA.

As described above, in the alignment method according to the present invention, at least two side-by-side captured images of the wafer W newly held on the chuck table 30 captured by the macro imaging means 51 are combined to form combined images GA to GC. By performing a confirmation step of pattern matching and confirming whether or not there is a target image GT in the combined images GA to GC each time each combined image GA to GC is formed, a new wafer W to be machined is processed. When finding the macro alignment mark MA, it is not necessary to perform the conventional spiral search. That is, unlike the conventional case, it is not necessary to overlap the imaging region 510 of the macro imaging means 51 by the pixels of the target image GT and move it in a spiral shape for imaging, and for each captured image captured by overlapping the pixels. There is no need to perform pattern matching on the target image GT. Therefore, since the macro alignment mark MA can be found more than before, the alignment time can be shortened.

In the conventional spiral search, a captured image is formed by the macro imaging means 51, pattern matching is performed using the captured image and the target image GT, and the target image GT cannot be detected in the captured image. In that case, after that, the formed captured image was erased from the storage unit 91 and the next imaging was performed. On the other hand, in the alignment method according to the present invention, since the combined images GA to GC are formed, the capacity of the image data stored in the storage unit 91 increases. However, since the number of times the wafer W is imaged by the macro image pickup means 51 is significantly reduced as compared with the conventional case, the operation load of the control means 9 of the cutting apparatus 1 is relatively reduced.

(3) Identification of Scheduled Division Line As described above, the macro alignment mark MA is found for, for example, two devices D located at positions separated from each other in the X-axis direction. Next, the first scheduled division line S1 and the second scheduled division line S2 are specified from the found macro alignment mark MA and micro alignment mark MB.

First, for example, coarse θ alignment is performed in which the first scheduled division line S1 of the wafer W is aligned substantially parallel to the X-axis direction. In the coarse θ alignment, the wafer W is sucked and held so that the Y-axis coordinate positions of the macro alignment marks MA of the two coarse θ alignment image images (for example, the combined image G4 formed in the confirmation step) are approximately the same. The chuck table 30 shown in FIG. 1 is angle-adjusted by the rotating means 31.

Further, after the chuck table 30 is moved in the X-axis direction by several devices D, an image is taken by the macro imaging means 51, and an image for coarse θ alignment in which the macro alignment mark MA of a certain device D is captured is obtained. It is formed. So that the Y-axis coordinate position of the macro alignment mark MA of the captured image for coarse θ alignment used earlier and the Y-axis coordinate position of the macro alignment mark MA of the captured image for coarse θ alignment further formed are approximately the same. The angle of the chuck table 30 is adjusted by the rotating means 31, and the straight line connecting the macro alignment marks MA located at positions distant from the X-axis direction is substantially parallel to the X-axis direction, and the first scheduled division line S1 is set to the X-axis direction. Coarse θ alignment that is almost parallel is completed.

Next, the cutting device 1 shown in FIG. 1 is in a state where the wafer W can be imaged by the micro image pickup means 52. Further, one of the macro alignment marks MA (see FIG. 6) that could be found earlier is positioned in the center of the imaging region of the micro imaging means 52.

Under the control of the control means 9, the chuck table 30 sucking and holding the wafer W by the cutting feed means 11 has a distance Lx1 (storage unit 91) between the macro alignment mark MA and the micro alignment mark MB shown in FIG. 2 in the X-axis direction. It is moved by the distance Lx1) stored in the index feeding means 12, and the micro-imaging means 52 is stored in the distance Ly1 (storage unit 91) between the macro-alignment mark MA and the micro-alignment mark MB in the Y-axis direction. It is moved by the distance Ly1). After that, the surface Wa of the wafer W is imaged by the micro-imaging means 52, and an image for high-precision θ alignment in which the micro-alignment mark MB is captured is formed.

High-precision θ alignment is, for example, for high-precision θ alignment in which each micro-alignment mark MB of two devices D adjacent to one first scheduled division line S1 and separated from each other in the X-axis direction is shown. This is done using the captured image of. Then, the chuck table 30 is angle-adjusted by the rotating means 31 until the deviation of the Y-axis coordinate position of each micro-alignment mark MB of the two high-precision θ-alignment captured images is within the permissible value, and the high-precision θ alignment is performed. Is completed.

Further, the chuck table 30 shown in FIG. 1 moves in the X-axis direction, the center of the surface Wa of the wafer W is positioned in the image pickup region of the micro image pickup means 52, and the image pickup image is formed by the micro image pickup means 52. The micro alignment mark MB in the captured image is recognized. Then, it is determined whether or not the deviation of the Y-axis coordinate position of the micro-alignment mark MB is within the allowable value, and if it is outside the allowable value, the deviation of the Y-axis coordinate position of the micro-alignment mark MB is within the allowable value. The micro-imaging means 52 is appropriately moved in the Y-axis direction by the index feeding means 12.

After the deviation of the Y-axis coordinate position of the micro-alignment mark MB reaches the allowable value, the index feeding means 12 extends from the micro-alignment mark MB shown in FIG. 2 to the center line in the width direction of the first scheduled division line S1. By moving the micro-imaging means 52 in the Y-axis direction by the distance Ly2, the hairline alignment is performed so that the reference line (hairline) of the micro-imaging means 52 overlaps with the first scheduled division line S1. Then, the coordinate position of the hairline in the Y-axis direction when the hairline is overlapped with the first scheduled division line S1 is a control means as a position where the cutting means 6 is positioned when the cutting blade 63 actually cuts the wafer W. It is stored in the storage unit 91 of 9.

As described above, after the coordinate position in the Y-axis direction when actually cutting the first scheduled division line S1 is stored in the storage unit 91, the chuck table 30 is accurately rotated by 90 degrees by the rotating means 31. , Highly accurate θ alignment is performed to align the second scheduled division line S2 of the wafer W in parallel with the X-axis direction, and then the cutting means 6 is positioned when actually cutting the second scheduled division line S2. The Y-axis coordinate position is detected and stored in the storage unit 91 (hairline alignment is performed).
As a result, in the cutting apparatus 1, the first scheduled division line S1 and the second scheduled division line S2 of the new wafer W are specified.

(4) Cutting the Wafer Next, the cutting device 1 shown in FIG. 1 cuts a new wafer W sucked and held by the chuck table 30. For example, first, the cutting means 6 is positioned by the index feeding means 12 at the Y-axis coordinate position when the first scheduled division line S1 stored in the storage unit 91 of the control means 9 is actually cut. Further, under the control of the control means 9, the cutting means 16 lowers the cutting means 6 in the −Z direction, and the cutting means 6 is positioned at a predetermined cutting feed position. Further, the cutting feed means 11 cuts and feeds the chuck table 30 holding the wafer W toward the cutting means 6 at a predetermined cutting feed rate.

A motor (not shown) rotates the rotating shaft 60 of the cutting means 6 at high speed, so that the cutting blade 63 fixed to the rotating shaft 60 cuts into the wafer W while rotating along with the rotation of the rotating shaft 60. The scheduled division line S1 is cut.

When the chuck table 30 advances to a predetermined position in the X-axis direction where the cutting blade 63 finishes cutting the first scheduled division line S1, the cutting feed means 16 raises the cutting means 6 to separate the cutting blade 63 from the wafer W. Then, the cutting feed means 11 returns the chuck table 30 to the cutting feed start position. Then, the index feed means 12 moves the cutting means 6 in the Y-axis direction by a predetermined index feed amount to the first scheduled split line S1 located next to the first scheduled split line S1 that has been cut. On the other hand, the cutting blade 63 is positioned. Then, the cutting process is carried out in the same manner as before. Hereinafter, by sequentially performing the same cutting, all the first scheduled division lines S1 are cut.
Further, by rotating the chuck table 30 by 90 degrees and then cutting the second scheduled division line S2, all the scheduled division lines of the wafer W are cut vertically and horizontally.

It goes without saying that each step of the alignment method according to the present invention is not limited to the above-described embodiment, and may be carried out in various different forms within the scope of the technical idea. Further, the constituent elements of the cutting apparatus 1 shown in the attached drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention can be exhibited.
The alignment method according to the present invention may be carried out in a laser processing apparatus that performs desired processing on the wafer W by laser irradiation.

W: Wafer Wa: Wafer surface S1: First scheduled division line S2: Second scheduled division line D: Device Wb: Wafer back surface F: Circular frame T: Dicing tape 1: Cutting device 10: Base 14: Gate column 11: Cutting feed means 12: Index feed means 16: Cut feed means
30: Chuck table 30a: Holding surface 31: Rotating means
6: Cutting means 60: Rotating shaft 61: Housing 63: Cutting blade 51: Macro imaging means 52: Micro imaging means 9: Control means 91: Storage unit 92: Combined image forming unit 93: Pattern matching unit

Claims (1)

A wafer having a device formed in a region partitioned by a first scheduled division line set on the surface and a second scheduled division line intersecting the first scheduled division line is held on a chuck table, and the chuck is held. An alignment method in which a wafer held by a table is imaged by an imaging means, an alignment mark arranged in the region is detected, and the first scheduled division line and the second scheduled division line are specified.
The imaging region of the imaging means is smaller than the region, and a registration step of registering a target image including an alignment mark in an region smaller than the imaging region.
A wafer newly held on the chuck table is combined with at least two side-by-side captured images captured by the imaging means to form a combined image, and each time the combined image is formed, the target image is included in the combined image. A confirmation process to confirm whether or not there is a pattern by pattern matching,
An alignment method for identifying the first scheduled division line and the second scheduled division line from the alignment mark in the target image when the target image is detected in the confirmation step.

Images