CN110783246A - Alignment method - Google Patents

Alignment method Download PDF

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CN110783246A
CN110783246A CN201910674919.1A CN201910674919A CN110783246A CN 110783246 A CN110783246 A CN 110783246A CN 201910674919 A CN201910674919 A CN 201910674919A CN 110783246 A CN110783246 A CN 110783246A
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imaging
unit
wafer
macro
image
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CN110783246B (en
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宫田谕
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Disco Corp
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Disco Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/68—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for positioning, orientation or alignment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/68—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for positioning, orientation or alignment
    • H01L21/681—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for positioning, orientation or alignment using optical controlling means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/304—Mechanical treatment, e.g. grinding, polishing, cutting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67242—Apparatus for monitoring, sorting or marking
    • H01L21/67259—Position monitoring, e.g. misposition detection or presence detection
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67242—Apparatus for monitoring, sorting or marking
    • H01L21/67282—Marking devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/76—Making of isolation regions between components
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/77—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate
    • H01L21/78—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices

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  • Microelectronics & Electronic Packaging (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
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  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • Container, Conveyance, Adherence, Positioning, Of Wafer (AREA)
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Abstract

An alignment method is provided for quickly finding an alignment mark when determining a division scheduled line. The alignment method comprises the steps of imaging a wafer (W) having devices (D) formed in regions defined by a 1 st planned dividing line (S1) and a 2 nd planned dividing line (S2) by an imaging unit (51), detecting an alignment Mark (MA), and determining the 1 st planned dividing line and the 2 nd planned dividing line, wherein the alignment method comprises the following steps: a step of registering a target image (GT) including an alignment Mark (MA) in an area smaller than an imaging area (510) of an imaging means, the area being smaller than the imaging area (510); and a step of combining at least two parallel images obtained by imaging the wafer (W) held by the table (30) by an imaging means to form a combined image, and checking the presence or absence of the target image (GT) by performing pattern matching in the combined image every time the combined image is formed, and after the target image (GT) is detected, determining the 1 st line and the 2 nd line based on the alignment Mark (MA) in the target image (GT).

Description

Alignment method
Technical Field
The present invention relates to an alignment method for determining a dividing line of a wafer.
Background
When a wafer having devices formed in regions defined by planned dividing lines is subjected to cutting processing in which a cutting tool cuts along the planned dividing lines to form cutting grooves, or laser processing in which laser beams are irradiated along the planned dividing lines to form processed grooves, the apparatus needs to recognize the planned dividing lines.
The same circuit pattern is formed on the device front side of the wafer. And, one of the circuit patterns having a characteristic shape is set as a macro alignment mark. In addition, a micro alignment mark smaller than the macro alignment mark is set at a position apart from the macro alignment mark by a predetermined distance in a predetermined direction. The planned dividing line is set at a position separated from the micro-alignment mark by a predetermined distance in a predetermined direction.
In the macro alignment, the processing apparatus finds a macro alignment mark of the wafer held by the chuck table, and then performs rough θ alignment in which the line to divide is aligned substantially parallel to the X-axis direction, which is one axis on a horizontal plane, using the macro alignment mark (see, for example, patent document 1). Next, the micro alignment marks at positions separated from the macro alignment marks by a predetermined distance in a predetermined direction are checked, and high-precision θ alignment for aligning the lines to be divided in parallel with the X-axis direction with high precision is performed using the micro alignment marks. Then, a line to divide is identified which is a predetermined distance from the micro-alignment mark in a predetermined direction.
Patent document 1: japanese laid-open patent publication No. 2007-088028
As preparation for the macro alignment, the macro alignment mark is photographed by a photographing unit having a photographing area smaller than an area divided by the division predetermined line (i.e., a photographing area smaller than the size of the device), and a target image smaller than the photographing area and centered on the macro alignment mark is registered in the processing apparatus.
In the macro alignment, pattern matching is performed on whether or not the target image is present in a captured image obtained by capturing an image of a wafer to be processed after the chuck table is newly held by suction by the imaging unit. That is, for example, the target image is moved pixel by pixel within the captured image to perform pattern matching. Then, if there is no target image in the captured image, the next position to the previous captured position is captured while repeating the number of pixels of the target image, a new captured image is formed, and pattern matching of the target image is performed in the new captured image, thereby finding the macro alignment mark.
In this way, until the macro alignment mark is found, the movement of the imaging position (specifically, the spiral movement of the imaging position on the wafer) and the pattern matching using the target image in the new captured image captured by the movement of the imaging position are repeated until the cumulative area of the captured images captured by repeating the number of pixels becomes at least the same area as the area divided by the division lines. Such a step of finding a macro alignment mark, which has been performed in the past, is called a spiral search.
In the spiral search, since the imaging area of the imaging unit is enlarged while repeating the number of pixels of the target image, if the target image is large (that is, the macro alignment mark is large), the amount of movement when the imaging unit is moved to a position adjacent to the previous imaging position is reduced. The reason why the number of pixels of the target image is repeated is that the entire target image is not overlooked when only a part of the target image is reflected in the captured image. Therefore, since the imaging means is moved to a position adjacent to the previous imaging position by a 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 reduced when the target image is large, and therefore, it is necessary to perform imaging a plurality of times by moving the imaging position a plurality of times in a spiral shape, which causes a problem that it takes time to find the macro alignment mark.
Specifically, for example, when the imaging area of the imaging means is 512 × 480 pixels, if the size of the macro alignment mark is small and the target image is 16 × 18 pixels, the number of times of imaging associated with the spiral movement of the imaging area of the imaging means ends up being 6 times, for example, at the maximum. On the other hand, if the macro alignment mark has a large size and the target image is 250 × 250 pixels, the number of times of imaging is performed according to the spiral movement of the imaging area of the imaging means is, for example, 25 times at the maximum.
Disclosure of Invention
Thus, in an alignment method for specifying lines to divide a wafer, there is a problem that an alignment mark (macro alignment mark) is quickly searched for and an alignment time is shortened.
The present invention for solving the above problems is an alignment method for determining a 1 st planned dividing line and a 2 nd planned dividing line by holding a wafer having devices in an area defined by the 1 st planned dividing line set on a front surface and the 2 nd planned dividing line intersecting the 1 st planned dividing line by a chuck table, imaging the wafer held by the chuck table by an imaging means, and detecting an alignment mark arranged in the area, wherein the alignment method includes the steps of: a registration step of registering a target image including an alignment mark in an area smaller than an imaging area of the imaging unit, the area being smaller than the imaging area; and a confirmation step of combining at least two parallel images obtained by imaging the wafer newly held on the chuck table by the imaging unit to form a combined image, performing pattern matching in the combined image to confirm whether the target image is present or absent each time the combined image is formed, and if the target image is detected in the confirmation step, determining the 1 st line and the 2 nd line according to the alignment mark in the target image.
The alignment method of the present invention performs the following confirmation process: at least two parallel images obtained by imaging a wafer newly held on a chuck table by an imaging unit are combined to form a combined image, and each time the combined image is formed, pattern matching is performed in the combined image to check whether a target image exists, so that when an alignment mark of a new wafer to be processed is searched, a conventional spiral search is not required. That is, it is not necessary to perform a plurality of times of photographing by spirally moving the photographing region of the photographing means while repeating the number of pixels of the target image as in the conventional art, and it is not necessary to perform pattern matching of the target image for each photographed image photographed while repeating the number of pixels. It is possible to quickly find an alignment mark (macro alignment mark) to shorten the alignment time.
Drawings
Fig. 1 is a perspective view showing an example of a cutting apparatus for cutting a wafer.
Fig. 2 is an explanatory diagram for explaining a case where a target image including an alignment mark in an area smaller than the imaging area is registered.
Fig. 3 is an explanatory view for explaining a captured image obtained by capturing an image of a wafer newly held on the chuck table by the imaging unit.
Fig. 4 is an explanatory diagram for explaining a case where two parallel captured images are combined to form a combined image, pattern matching is performed in the combined image, and the presence or absence of a target image is checked.
Fig. 5 is an explanatory diagram for explaining a case where three captured images arranged in parallel are combined to form a combined image, and pattern matching is performed in the combined image to check whether or not an object image is present.
Fig. 6 is an explanatory diagram for explaining a case where four parallel captured images are combined to form a combined image, pattern matching is performed in the combined image, and the presence or absence of a target image is checked.
Description of the reference symbols
W: a wafer; wa: a front side of the wafer; s1: a 1 st division predetermined line; s2: a 2 nd division predetermined line; d: a device; wb: the back side of the wafer; f: an annular frame; t: scribing a tape; 1: a cutting device; 10: a base station; 14: a gate post; 11: a cutting feed unit; 12: a indexing and feeding unit; 16: a cutting-in feeding unit; 30: a chuck table; 30 a: a holding surface; 31: a rotation unit; 6: a cutting unit; 60: a rotating shaft; 61: a housing; 63: a cutting tool; 51: a macro photography unit; 52: a microscopic photographing unit; 9: a control unit; 91: a storage unit; 92: a combined image forming part; 93: a pattern matching section.
Detailed Description
The cutting apparatus 1 shown in fig. 1 is an apparatus that performs cutting by rotating a cutting tool 63 included in a cutting unit 6 and cutting into a wafer W that is a plate-like workpiece held by a chuck table 30.
A cutting feed unit 11 is disposed on the base 10 of the cutting apparatus 1, and the cutting feed unit 11 reciprocates the chuck table 30 in a cutting feed direction (X-axis direction). The cutting feed unit 11 includes: a ball screw 110 having an axis in the X-axis direction; a pair of guide rails 111 arranged in parallel with the ball screw 110; a motor 112 that rotates the ball screw 110; and a movable plate 113 in which a nut is screwed to the ball screw 110, and a bottom portion of the movable plate 113 is in sliding contact with the guide rail 111. When the ball screw 110 is rotated by the motor 112, the movable plate 113 is guided by the guide rail 111 and moves in the X-axis direction, and the chuck table 30 disposed on the movable plate 113 moves in the X-axis direction.
The chuck table 30 for holding the wafer W has, for example, a circular outer shape, and sucks and holds the wafer W on a horizontal holding surface 30a formed of a porous member or the like. The chuck table 30 is fixed to the movable plate 113 by a rotating unit 31 disposed on the bottom surface side thereof. The rotation unit 31 can support the chuck table 30 and can rotate the chuck table 30 about the axis in the Z-axis direction.
A plurality of clamps 32 for clamping and fixing the annular frame F are disposed around the chuck table 30 at equal intervals in the circumferential direction.
A gate post 14 is provided upright on the base 10 on the rear side (the (-X direction side) so as to straddle the cutting feed unit 11. An index feed unit 12 is disposed on the front surface of the gate post 14, and the index feed unit 12 reciprocates the cutting unit 6 in the Y-axis direction. The index feeding unit 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 that rotates the ball screw 120; and a movable plate 123 having a nut screwed to the ball screw 120 and a side portion of the movable plate 123 slidably contacting the guide rail 121. 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 the cutting unit 6 disposed on the movable plate 123 is indexed in the Y-axis direction by the cutting and feeding unit 16.
A cutting feed unit 16 is disposed on the movable plate 123, and the cutting feed unit 16 reciprocates the cutting unit 6 in a Z-axis direction (vertical direction) perpendicular to the holding surface 30a of the chuck table 30. The incision feeding unit 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 that rotates the ball screw 160; and a support member 163 having a nut screwed to the ball screw 160 and having a side portion in sliding contact with the guide rail 161. When the ball screw 160 is rotated by the motor 162, the support member 163 is guided by the guide rail 161 and moves in the Z-axis direction, and the cutting unit 6 supported by the support member 163 performs plunge feed in the Z-axis direction.
The cutting unit 6 has: a rotary shaft 60 whose axial direction is the Y-axis direction; a housing 61 fixed to a lower end of the support member 163 and rotatably supporting the rotary shaft 60; a motor, not shown, that rotates the rotary shaft 60; and an annular cutting tool 63 attached to the rotary shaft 60, wherein the cutting tool 63 is also rotated at a high speed as the rotary shaft 60 is rotated by a motor not shown.
For example, a macro imaging unit 51 for imaging the wafer W at a low magnification and a micro imaging unit 52 for imaging the wafer W at a high magnification are disposed on a side surface of the housing 61 of the cutting unit 6. The macro photography unit 51 includes, for example: an imaging element not shown; a low magnification objective lens; and illumination for irradiating the wafer W sucked and held on the chuck table 30 with light. The microscopic imaging unit 52 includes, for example: an imaging element not shown; a high magnification objective lens; and illumination for irradiating the wafer W sucked and held on the chuck table 30 with light. The macro photographing unit 51 and the micro photographing unit 52 move in the Y-axis direction and the Z-axis direction in association with the cutting unit 6.
For example, the high-magnification objective lens has a magnification 10 times that of the low-magnification objective lens, and one pixel in the image captured by the macro imaging unit 51 is 10 μm.
The cutting apparatus 1 includes, for example, a control unit 9 for controlling the entire apparatus. The control unit 9 is connected to the cutting feed unit 11, the index feed unit 12, the incision feed unit 16, the rotation unit 31, and the like through unillustrated wiring, and controls, under the control of the control unit 9, the cutting feed operation of the chuck table 30 in the X-axis direction by the cutting feed unit 11, the index feed amount of the cutting unit 6 in the Y-axis direction by the index feed unit 12, the incision feed amount of the cutting unit 6 in the Z-axis direction by the incision feed unit 16, the rotation operation of the chuck table 30 by the rotation unit 31, and the like.
Hereinafter, the respective steps of the alignment method according to the present invention in the case of determining the 1 st line to divide S1 and the 2 nd line to divide S2 of the wafer W cut by the cutting apparatus 1 shown in fig. 1 will be described.
(1) Registration process
The wafer W shown in fig. 1 is, for example, a circular silicon semiconductor wafer, and devices D are formed on the front side Wa of the wafer W in lattice-like regions defined by lines to be divided which intersect perpendicularly. A dicing tape T having a larger diameter than the wafer W is attached to the back surface Wb of the wafer W. A ring frame F having a circular opening is attached to an outer peripheral region of the bonding surface of the dicing tape T, and the wafer W is supported by the ring frame F via the dicing tape T and can be handled by the ring frame F.
The lines to be divided set on the front surface Wa of the wafer W extending in the same direction (for example, in the X-axis direction in fig. 1) are defined as lines to be divided S1 1, and the lines to be divided on the front surface Wa of the wafer W extending in a direction perpendicular to the lines to be divided S1 (in the Y-axis direction perpendicular to the X-axis direction on a horizontal plane) are defined as lines to be divided S2 2.
In the registration step, the wafer W is first sucked and held with the front side Wa directed upward by the chuck table 30 shown in fig. 1. Then, the chuck table 30 that suctions and holds the wafer W is moved in the X-axis direction by the cutting and feeding unit 11. Further, the macro imaging unit 51 is moved in the Y axis direction by the index feeding unit 12, and the approximate center of the wafer W is positioned directly below the objective lens of the macro imaging unit 51.
Then, the macro imaging unit 51 images the front side Wa of the wafer W to form an image.
The size of the imaging area 510 of the macro imaging unit 51 is smaller than the size of the device D, which is an area divided by the 1 st predetermined dividing line S1 and the 2 nd predetermined dividing line S2.
Then, the operator selects one of the circuit patterns on the front surfaces of the devices D of the wafer W reflected in the captured image, which has a characteristic shape, as the macro alignment mark MA. The macroscopic alignment marks MA are formed at the same position on each of the plurality of devices D, for example, 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 quadrangle. In addition, the macro alignment marks may not be part of the circuit pattern.
Next, the operator selects a part of the features of the elements or wirings formed on the front surface of the device D as the micro alignment marks MB which are much smaller than the macro alignment marks MA, and the part of the features of the elements or wirings are located at a predetermined distance from the macro alignment marks MA in a predetermined direction. The micro alignment marks MB are formed at the same position on each of the plurality of devices D, for example, a corner portion (lower right corner in fig. 2) of the device D.
Along with the selected micro alignment mark MB, 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, by counting the number of pixels or the like, it is stored that the micro alignment mark MB exists at a position distant from the macro alignment mark MA by a distance Lx1 in the X-axis direction and distant from the macro alignment mark MA by a distance Ly1 in the Y-axis direction. In addition, a distance Lx2 from the micro alignment mark MB to a center line passing through the width center of the 2 nd line to divide S2 and a distance Ly2 from the micro alignment mark MB to a center line passing through the width center of the 1 st line to divide S1 are stored in the storage unit 91.
In addition, the operator registers the macro alignment mark MA in the storage section 91 of the control unit 9 with a rectangular area indicated by a two-dot chain line smaller than the imaging area 510 of the macro imaging unit 51. That is, the target image GT including the entire macro alignment mark MA is stored in the storage unit 91.
The registration step may be referred to as a Teaching process (a Teaching process) for the cutting apparatus 1 shown in fig. 1, and if the registration step is performed once before the first wafer W is cut, the registration step is not necessary after the second and subsequent wafers W are newly sucked and held by the chuck table 30 when a plurality of wafers W of the same kind are cut.
The registration step is not limited to the present embodiment. For example, the storage unit 91 may store device data in advance, the device data being obtained by tabulating processing conditions for each of a plurality of wafers to be processed. The machining conditions are data obtained by storing various settings for performing appropriate cutting on wafers for each type of wafer to be machined, including information on macro alignment marks and micro alignment marks for each type of wafer, in addition to the cutting feed speed of the chuck table 30 holding the wafer by the cutting feed unit 11, the index feed amount of the cutting unit 6 by the index feed unit 12, and the like shown in fig. 1. Thus, the operator can select an appropriate processing condition of the wafer W shown in fig. 1 from the device data, and register the target image GT including the entire macro alignment mark MA with an area indicated by a two-dot chain line smaller than the imaging area 510 of the macro imaging unit 51. In this case, the macro imaging unit 51 may not take an image of the wafer W in the present registration step.
(2) Confirmation step
The new wafer W to be cut is sucked and held with the front side Wa directed upward by the chuck table 30 shown in fig. 1. The chuck table 30 shown in fig. 1, which suctions and holds a new wafer W, is moved in the X-axis direction by the cutting and feeding unit 11. In addition, the macro imaging unit 51 is moved in the Y axis direction by the index feeding unit 12. The front side Wa of the wafer W is positioned directly below the objective lens of the macro imaging unit 51. The imaging position of the macro imaging unit 51 with respect to the front side Wa of the wafer W is not limited to a specific position as long as the device D is formed in the region.
In this state, the macro imaging unit 51 images the front side Wa of the wafer W to form an imaged image G1 shown in fig. 3. The size of the captured image G1 is the same as the size of the capturing area 510 of the macro capturing unit 51 shown in fig. 2, and is therefore smaller than the size of the device D.
The captured image G1 is stored in the storage section 91 of the control unit 9.
After the photographed image G1 is formed, the chuck table 30 holding the wafer W is moved by, for example, the cutting feed unit 11 shown in fig. 1. That is, the macro imaging unit 51, which is in a state where the chuck table 30 holding the wafer W by suction is stopped, is moved by a predetermined distance in the + X direction, for example. This moving distance of the chuck table 30 is, for example, the same value as the length in the X-axis direction of the imaging area 510 of the macro imaging unit 51 shown in fig. 2.
By moving the chuck table 30 as described above, the imaging area 510 of the macro imaging unit 51 is positioned beside the imaging position in the X-axis direction when the captured image G1 is captured. Then, the front side Wa of the wafer W is photographed by the macro photographing unit 51, and a photographed image G2 shown in fig. 4 is formed in parallel with the photographed image G1 in the X-axis direction. The captured image G2 is stored in the storage section 91 of the control unit 9.
For example, the control unit 9 shown in fig. 1 has a combined image forming section 92, and the combined image forming section 92 combines the captured images formed by the macro imaging unit 51 to form a combined image. The combined image forming unit 92 displays, for example, a combined image GA shown in fig. 4, which is a combination of the photographed image G1 stored in the storage unit 91 and the newly photographed image G2, on a virtual screen having a predetermined resolution.
Next, the pattern matching unit 93 included in the control unit 9 shown in fig. 1 performs pattern matching on the presence or absence of the target image GT in the combined image GA. That is, the pattern matching unit 93 overlaps the target image GT with the combined image GA displayed on the virtual screen of a predetermined resolution, for example, moves the target image GT in the X-axis direction or the Y-axis direction on the combined image GA by, for example, one pixel, and detects a region having the highest correlation with the target image GT in the combined image GA as a region matching the target image GT.
As shown in fig. 4, the pattern matching unit 93 cannot detect a region matching the target image GT in the combined image GA, and therefore the macro imaging unit 51 further images the front side Wa of the wafer W. That is, the macro imaging unit 51 is moved by the index feeding unit 12 shown in fig. 1, for example, by a predetermined distance in the + Y direction with respect to the chuck table 30 in a stopped state. The moving distance of the macro photography unit 51 is, for example, the same value as the length in the Y-axis direction of the photography area 510 of the macro photography unit 51.
By moving the macro imaging unit 51 as described above, the imaging area 510 of the macro imaging unit 51 is positioned beside the imaging position in the Y-axis direction when the captured image G2 is captured. Then, the front side Wa of the wafer W is photographed by the macro photographing unit 51, and a photographed image G3 shown in fig. 5 is formed in parallel with the photographed image G2 in the Y-axis direction. The captured image G3 is stored in the storage section 91 of the control unit 9.
The combined image forming unit 92 displays a combined image GB obtained by combining the combined image GA stored in the storage unit 91, which is obtained by combining the photographed image G1 and the photographed image G2, with the newly photographed image G3, on a virtual screen having a predetermined resolution. Next, the pattern matching unit 93 superimposes the target image GT on the combined image GB, moves the target image GT in the X-axis direction or the Y-axis direction on the combined image GB on a pixel-by-pixel basis, and detects a region in the combined image GB that matches the target image GT.
As shown in fig. 5, the pattern matching unit 93 cannot detect a region matching the target image GT in the combined image GB, and therefore the macro imaging unit 51 further images the front side Wa of the wafer W. That is, the macro imaging unit 51 in the state where the chuck table 30 holding the wafer W by suction is moved relatively to the stop, for example, in the-X direction by the same length as the length of the imaging area 510 of the macro imaging unit 51 in the X axis direction, and the imaging area 510 is located beside the imaging position in the X axis direction when the captured image G3 is captured. Then, the macro imaging unit 51 images the front side Wa of the wafer W, and a captured image G4 shown in fig. 6 is formed and stored in the storage unit 91, aligned with the captured image G3 in the X-axis direction.
As shown in fig. 4 to 6, the macro imaging unit 51 images the wafer W such that the imaging area 510 draws a clockwise spiral track on the wafer W when viewed from above.
As shown in fig. 6, the combined image forming unit 92 displays a combined image GC obtained by combining the combined image GB stored in the storage unit 91 and the newly captured image G4 on a virtual screen having a predetermined resolution. Next, the pattern matching unit 93 superimposes the target image GT on the combined image GC, moves the target image GT in the X-axis direction or the Y-axis direction on the combined image GC in units of one pixel, and detects a region in the combined image GC that matches the target image GT to find the macro alignment mark MA.
As described above, the alignment method of the present invention performs the following confirmation process: at least two parallel images obtained by imaging the wafer W newly held on the chuck table 30 by the macro imaging unit 51 are combined to form the combined images GA to GC, and each time the combined images GA to GC are formed, pattern matching is performed in the combined images GA to GC to check whether the target image GT exists, so that when searching for the macro alignment mark MA of the new wafer W to be processed, it is not necessary to perform a conventional spiral search. That is, it is not necessary to perform photographing by repeating the number of pixels of the target image GT in the photographing region 510 of the macro photographing unit 51 and spirally moving the photographing region, and it is not necessary to perform pattern matching of the target image GT for each photographed image which is photographed by repeating the number of pixels. Therefore, the macro alignment mark MA can be found faster than before, and thus the alignment time can be shortened.
In the conventional spiral search, a captured image is formed by the macro imaging unit 51, pattern matching is performed using the captured image and the target image GT, and when the target image GT is not detected in the captured image, the formed captured image is deleted from the storage unit 91 and the next imaging is performed. In contrast, in the alignment method of the present invention, since the combined images GA to GC are formed, the capacity of the image data stored in the storage unit 91 is increased. However, since the number of times of imaging of the wafer W by the macro imaging unit 51 is significantly reduced compared to the conventional art, the operation load of the control unit 9 of the cutting apparatus 1 is relatively reduced.
(3) Determination of a segmentation-intended line
The finding of the macro alignment mark MA as described above is performed for two devices D located at positions separated from each other in the X-axis direction, for example. Next, the 1 st line S1 and the 2 nd line S2 are determined based on the found macro alignment mark MA and micro alignment mark MB.
First, for example, rough alignment θ is performed to align the 1 st line to divide S1 of the wafer W substantially parallel to the X-axis direction. In the rough θ alignment, the chuck table 30 shown in fig. 1 holding the wafer W by suction is angularly adjusted by the rotating unit 31 so that the Y-axis coordinate positions of the macro alignment marks MA of the two captured images for rough θ alignment (for example, the bonding image G4 formed in the confirmation step) substantially match.
After the chuck table 30 is moved in the X-axis direction by the number of devices D, the macro imaging unit 51 performs imaging to form an image for rough θ alignment in which the macro alignment mark MA of a certain device D is reflected. The rotation unit 31 angularly adjusts the chuck table 30 so that the Y-axis coordinate position of the macro alignment mark MA of the previously used captured image for rough θ alignment substantially coincides with the Y-axis coordinate position of the macro alignment mark MA of the subsequently formed captured image for rough θ alignment, and the straight line connecting the macro alignment marks MA at the positions spaced apart in the X-axis direction is substantially parallel to the X-axis direction, thereby completing rough θ alignment in which the 1 st line to divide S1 is substantially parallel to the X-axis direction.
Next, the cutting apparatus 1 shown in fig. 1 is in a state in which the wafer W can be imaged by the microscopic imaging means 52. In addition, one of the macro alignment marks MA (refer to fig. 6) found before is positioned at the center of the imaging area of the micro imaging unit 52.
Under the control of the control unit 9, the chuck table 30 that holds the wafer W by suction is moved by the cutting feed unit 11 in accordance with the distance Lx1 in the X-axis direction between the macro alignment mark MA and the micro alignment mark MB (the distance Lx1 stored in the storage unit 91) shown in fig. 2, and the micro imaging unit 52 is moved by the index feed unit 12 in accordance with the distance Ly1 in the Y-axis direction between the macro alignment mark MA and the micro alignment mark MB (the distance Ly1 stored in the storage unit 91). Then, the microscopic imaging unit 52 images the front side Wa of the wafer W to form a high-precision captured image for θ alignment in which the microscopic alignment marks MB are reflected.
The high-precision θ alignment is performed, for example, using a captured image for high-precision θ alignment in which the respective microscopic alignment marks MB of two devices D adjacent to one line to divide 1S 1 and spaced apart from each other in the X-axis direction are reflected. Then, the rotation unit 31 angularly adjusts the chuck table 30 until the deviation of the Y-axis coordinate position of each of the microscopic alignment marks MB in the two captured images for high-precision θ alignment falls within the allowable value, thereby completing the θ alignment with high precision.
Next, the chuck table 30 shown in fig. 1 is moved in the X-axis direction, for example, to position the center of the front side Wa of the wafer W in the imaging area of the microscopic imaging unit 52, a captured image is formed by the microscopic imaging unit 52, and the microscopic alignment mark MB in the captured image is recognized. Then, it is determined whether or not the shift of the Y-axis coordinate position of the micro alignment mark MB is within the allowable value, and if not, the index feeding unit 12 appropriately moves the micro imaging unit 52 in the Y-axis direction so that the shift of the Y-axis coordinate position of the micro alignment mark MB is within the allowable value.
After the shift of the Y-axis coordinate position of the micro alignment mark MB is within the allowable value, the index feeding unit 12 moves the micro imaging unit 52 in the Y-axis direction by the distance Ly2 from the micro alignment mark MB shown in fig. 2 to the center line of the 1 st line to divide S1 in the width direction, thereby performing alignment of the reference line (reticle) of the micro imaging unit 52 with the reticle overlapping the 1 st line to divide S1. Then, the coordinate position of the reticle in the Y axis direction when the reticle overlaps the 1 st line to divide S1 is stored in the storage unit 91 of the control unit 9 as a position at which the cutting unit 6 is positioned when the cutting tool 63 actually cuts the wafer W.
As described above, the coordinate position in the Y axis direction when the 1 st line to divide S1 is actually cut is stored in the storage unit 91, then the chuck table 30 is accurately rotated by 90 degrees by the rotating means 31, and the highly accurate θ alignment for aligning the 2 nd line to divide S2 of the wafer W in parallel with the X axis direction is performed, and then the Y axis coordinate position at which the cutting means 6 is positioned when the 2 nd line to divide S2 is actually cut is detected and stored in the storage unit 91 (alignment of the reticle is performed).
Thus, the cutting apparatus 1 is in a state in which the 1 st line to divide S1 and the 2 nd line to divide S2 of the new wafer W are determined.
(4) Cutting of wafers
Next, the cutting apparatus 1 shown in fig. 1 cuts a new wafer W sucked and held by the chuck table 30. For example, first, the index feeding unit 12 positions the cutting unit 6 at the Y-axis coordinate position stored in the storage unit 91 of the control unit 9 when the 1 st line to divide S1 is actually cut. Under the control of the control unit 9, the cutting feed unit 16 lowers the cutting unit 6 in the-Z direction to position the cutting unit 6 at a predetermined cutting feed position. The cutting feed unit 11 performs cutting feed at a predetermined cutting feed speed toward the cutting unit 6 from the chuck table 30 holding the wafer W.
The motor, not shown, rotates the rotary shaft 60 of the cutting unit 6 at a high speed, and cuts the cutting tool 63 fixed to the rotary shaft 60 into the wafer W while rotating with the rotation of the rotary shaft 60, thereby cutting the line to divide 1S 1.
When the chuck table 30 moves to a predetermined position in the X axis direction where the cutting tool 63 finishes cutting the 1 st line to divide S1, the cut-in feed unit 16 raises the cutting unit 6 to separate the cutting tool 63 from the wafer W, and the cut feed unit 11 returns the chuck table 30 to the cut feed start position. The index feeding unit 12 moves the cutting unit 6 in the Y axis direction by a predetermined index feed amount, and positions the cutting tool 63 in the 1 st line to divide S1 located beside the 1 st line to divide S1. Then, the cutting process is performed in the same manner as before. Thereafter, the same cutting is performed in sequence, and all the lines to divide 1S 1 are cut.
After the chuck table 30 is rotated by 90 degrees, the 2 nd planned dividing line S2 is cut, and all the planned dividing lines of the wafer W are cut vertically and horizontally.
The steps of the alignment method of the present invention are not limited to the above-described embodiments, and may be implemented in various different ways within the scope of the technical idea thereof. The constituent elements of the cutting apparatus 1 shown in the drawings are not limited thereto, and may be appropriately modified within a range in which the effects of the present invention can be exhibited.
The alignment method of the present invention can be implemented in a laser processing apparatus that performs desired processing on a wafer W by laser irradiation.

Claims (1)

1. An alignment method for determining a 1 st planned dividing line and a 2 nd planned dividing line by holding a wafer having devices in an area defined by the 1 st planned dividing line set on a front surface and the 2 nd planned dividing line intersecting the 1 st planned dividing line by a chuck table, imaging the wafer held by the chuck table by an imaging unit, and detecting an alignment mark arranged in the area,
the alignment method comprises the following steps:
a registration step of registering a target image including an alignment mark in an area smaller than an imaging area of the imaging unit, the area being smaller than the imaging area; and
a confirmation step of combining at least two parallel images obtained by imaging the wafer newly held on the chuck table by the imaging means to form a combined image, and confirming whether the target image is present or not by performing pattern matching in the combined image every time the combined image is formed,
if the target image is detected in the verification process, the 1 st line and the 2 nd line are determined based on the alignment mark in the target image.
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