JP7208036B2 - Wafer alignment method - Google Patents

Description

The present invention relates to a wafer alignment method.

A cutting apparatus is used to divide a wafer on which semiconductor devices, SAW filters, etc. are formed into individual device chips. The cutting device cuts the wafer along the streets, but before cutting, alignment is performed to align the processing feed direction (X-axis direction) of the cutting device with the direction of the streets, that is, align the positions of the cutting blade and the streets. In alignment, normally, the circuit of the device or the like is used as a key pattern, and the alignment is performed with the key pattern as a reference. For example, when matching the angle between the street and the processing feed direction, the angle is adjusted by arranging two key patterns corresponding to the same street parallel to the processing feed direction (see, for example, Patent Document 1).

JP-A-07-106405

In particular, at first, roughly align the direction with a nearby key pattern, and then finely adjust the angle using a key pattern that is gradually separated to accurately make the street parallel to the processing feed direction (align θ). can be done. However, this method requires a large number of key patterns corresponding to the same street, and in the case of a wafer in which the key patterns are exposed only on the outer periphery, the key patterns are separated from each other with the center region sandwiched in the processing feed direction. If θ adjustment is performed from , there is a risk of detecting key patterns that do not correspond to the same street. Therefore, there is a possibility that the .theta. adjustment is performed by a so-called misaligned key pattern, and accurate .theta. adjustment cannot be performed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wafer alignment method capable of accurate .theta.

In order to solve the above problems and achieve the object, the present invention provides a rotatable chuck table that holds a wafer, a cutting unit that cuts the wafer held on the chuck table with a cutting blade, and the chuck table. and a machining feed unit that relatively feeds the cutting unit in the X-axis direction, an indexing feed unit that relatively indexes and feeds the chuck table and the cutting unit in the Y-axis direction, and Using a cutting device having an alignment unit having a camera for photographing a wafer and a control means for controlling each component, devices are formed in each region partitioned into grid-like streets on the surface, and the outer periphery of the surface is formed. A wafer alignment method using, as a key pattern, part of devices exposed on the outer periphery of a circular wafer whose area is covered with a covering member, the wafer holding step of holding the wafer on the chuck table; The alignment unit detects the key pattern of each of the two devices exposed in the edge region of the outer periphery of the wafer held on the chuck table, corresponding to the same street and adjacent in the X-axis direction, and the chuck a rough alignment step of rotating the table to align the two key patterns in parallel with the X-axis direction and adjusting the streets parallel to the X-axis direction; The pair of key patterns exposed on both sides of the covering member are detected in the X-axis direction by the alignment unit which is indexed and fed, and the chuck table is rotated to align the pair of key patterns in parallel with the X-axis direction. and a fine adjustment step of finely adjusting the street and the X-axis direction in parallel.

In this configuration, in the rough alignment step, a key pattern near the outermost circumference of the wafer in the Y-axis direction diameter is used, and in the fine adjustment step, the key pattern used in the rough alignment step is separated from the key pattern by n, which is the distance between the streets. Key patterns located on both sides of the covering member at the center of the wafer in the Y-axis direction by a distance of twice (n is a natural number) may be used.

According to the present invention, the key patterns exposed on the outer circumference of the wafer and adjacent in the X-axis direction are roughly aligned so as to be parallel to the X-axis direction, and then exposed at positions separated from each other on the outermost circumference of the wafer near the center of the wafer. By completing the .theta. adjustment by finely adjusting the pair of key patterns to be parallel to the X-axis direction, there is an effect that the .theta.

FIG. 1 is a perspective view showing a configuration example of a cutting apparatus in which the wafer alignment method according to the first embodiment is implemented. FIG. 2 is a perspective view showing a configuration example of a wafer. FIG. 3 is a flow chart showing the procedure of the wafer alignment method. FIG. 4 is a plan view showing the rough matching step. FIG. 5 is a plan view showing fine adjustment steps. FIG. 6 is a perspective view showing a configuration example of a wafer used in the wafer alignment method according to the second embodiment. FIG. 7 is a plan view showing the rough matching step. FIG. 8 is a plan view showing fine adjustment steps.

A form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions, or changes in configuration can be made without departing from the gist of the present invention.

[Embodiment 1]
A wafer alignment method according to the first embodiment will be described. FIG. 1 is a perspective view showing a configuration example of a cutting apparatus in which the wafer alignment method according to the first embodiment is implemented. FIG. 2 is a perspective view showing a configuration example of a wafer. As shown in FIG. 1, the cutting device 1 has a base 2 that supports each structure. An opening 2a is formed at the corner of the base 2, and a cassette elevator 3 capable of ascending and descending is installed in this opening 2a. A cassette 4 that can accommodate a plurality of wafers 100 is placed on the upper surface of the cassette elevator 3 . 1, only the outline of the cassette 4 is shown for convenience of explanation.

As shown in FIG. 2, the wafer 100 is, for example, a disk-shaped semiconductor wafer whose base material is silicon, or an optical device wafer whose base material is sapphire, SiC (silicon carbide), or the like. A surface 101 of a wafer 100 is partitioned into a plurality of regions by division lines (street) 102 orthogonal to each other (lattice-like), and devices 103 such as ICs and LEDs are formed in each region. . Each device 103 also includes a key pattern 104 having a characteristic shape. That is, a plurality of key patterns 104 are arranged on the surface 101 of the wafer 100 .

A plurality of planned division lines 102 are formed along two orthogonal directions, and the distance (interval) a between two adjacent planned division lines 102 is approximately constant. The distance (interval) between two adjacent key patterns 104 is also equal to the distance a between the two adjacent dividing lines 102 . Further, if the distances between the plurality of planned division lines 102 extending along the same direction are equal, the distance between the plurality of planned division lines 102 extending along one direction and the distance between the plurality of planned division lines 102 extending along the one direction and the other direction orthogonal to this are equal. The distances between the plurality of planned division lines 102 extending along the direction may differ from each other.

The surface 101 side of the region (central portion) excluding the region (peripheral portion) near the outer periphery of the wafer 100 is sealed with a resin (coating member) 105. In this region (central portion), a division line is provided. 102, device 103 and key pattern 104 are not exposed. On the other hand, the surface 101 side of the area near the outer periphery (peripheral portion) is not covered with the resin 105, and the planned division line 102, the device 103, and the key pattern 104 are partly exposed. A notch (notch) 106 for indicating the crystal orientation or the like is provided on the outer peripheral edge of the wafer 100 . Further, the wafer 100 may have a configuration in which a plurality of electrodes (not shown) made of a material such as solder are arranged at positions corresponding to the respective devices 103 on the upper surface of the resin 105 .

A dicing tape (adhesive tape) 108 having a larger diameter than the wafer 100 is attached to the back surface 107 of the wafer 100 . An annular frame 109 is fixed to the outer peripheral portion of the dicing tape 108 . Thereby, the wafer 100 is supported by the annular frame 109 via the dicing tape 108 .

Returning to FIG. 1 again, the cutting device 1 will be described. At a position adjacent to the cassette elevator 3, a rectangular opening 2b elongated in the X-axis direction (processing feed direction) is formed. A moving table 5, a table moving mechanism (processing feed unit) 6 for moving the moving table 5 in the X-axis direction, and a dust and drip proof cover 7 covering the table moving mechanism 6 are provided in the opening 2b.

A chuck table 8 for sucking and holding the wafer 100 is installed on the moving table 5 . Four clamps 9 are provided around the chuck table 8 to fix an annular frame 109 supporting the wafer 100 from four sides.

The chuck table 8 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the Z-axis direction (height direction). When the moving table 5 is moved in the X-axis direction by the table moving mechanism 6, the chuck table 8 is processed and fed in the X-axis direction. The upper surface of the chuck table 8 serves as a holding surface 8a for holding the wafer 100. As shown in FIG. The holding surface 8a is formed substantially parallel to the X-axis direction and the Y-axis direction (index feed direction), and a suction source (not shown) or the like formed inside the chuck table 8 passes through a flow path (not shown) or the like. shown).

A temporary placement mechanism 10 for temporarily placing the wafer 100 is provided above the opening 2b. The temporary placement mechanism 10 includes, for example, a pair of guide rails 10a and 10b that are arranged to approach and separate from each other in the X-axis direction while maintaining parallelism in the Y-axis direction. The guide rails 10a and 10b, with the wafer 100 (frame 109) drawn out from the cassette 4 placed thereon, are brought closer together in the X-axis direction (processing feed direction) to align them at a predetermined position.

A gate-shaped first support structure 11 is arranged above the base 2 so as to straddle the opening 2b. A first rail 12 extending in the Y-axis direction is fixed to the surface of the first support structure 11 (the surface facing the temporary placement mechanism 10). The first transport mechanism 14 is connected to the . The first transport mechanism 14 is lifted and lowered by the first moving mechanism 13 and moves in the Y-axis direction along the first rails 12 .

The first transport mechanism 14 is provided with a gripping mechanism 14a for gripping the frame 109 on the cassette 4 side. For example, if the frame 109 is gripped by the gripping mechanism 14a and the first transfer mechanism 14 is moved in the Y-axis direction, the wafers 100 stored in the cassette 4 are pulled out onto the guide rails 10a and 10b of the temporary placement mechanism 10, Alternatively, the wafer 100 placed on the guide rails 10a and 10b can be inserted into the cassette 4. FIG.

A second rail 15 extending in the Y-axis direction is fixed above the first rail 12 on the surface of the first support structure 11 (the surface on the temporary placement mechanism 10 side). A second transport mechanism 17 is connected to the second rail 15 via a second moving mechanism 16 . The second transport mechanism 17 is lifted and lowered by the second moving mechanism 16 and moves in the Y-axis direction along the second rails 15 .

A gate-shaped second support structure 18 is arranged on the back side of the first support structure 11 . Two sets of cutting units 20 are provided on the surface of the second support structure 18 (the surface on the side of the first support structure 11) via a moving mechanism (index feed unit) 19, respectively. The cutting unit 20 includes a cutting blade 21 mounted on a rotating spindle (not shown) that is driven to rotate. While the cutting blade 21 rotates, the chuck table 8 (wafer 100) is processed and fed in the X-axis direction. , cuts the wafer 100 along the division line 102 . Also, a cutting blade 21 having a thickness thicker than that for cutting is attached to a rotating spindle, and the chuck table 8 (wafer 100) is rotated around a rotation axis parallel to the Z-axis direction while the cutting blade 21 is rotating. Thus, for example, edge trimming of the outer periphery of the wafer 100 can be performed.

A camera 22 for photographing the surface 101 (FIG. 2) side of the wafer 100 is installed at a position adjacent to the cutting unit 20 . The cutting unit 20 and camera 22 are moved in the Y-axis direction and Z-axis direction by the moving mechanism 19 . In this embodiment, the chuck table 8 and the camera 22 constitute an alignment unit 23 . Moreover, as the camera 22, it is good also as a structure which has an infrared camera.

A cleaning unit 24 is arranged at a position opposite to the opening 2a with respect to the opening 2b. The cleaning unit 24 has a spinner table 25 that sucks and holds the wafer 100 in a cylindrical cleaning space. A rotation drive source (not shown) is connected to the lower portion of the spinner table 25 to rotate the spinner table 25 at a predetermined speed. Above the spinner table 25, an injection nozzle 26 for injecting a cleaning fluid (typically, two fluids of water and air mixed together) toward the wafer 100 is arranged. The wafer 100 can be cleaned by rotating the spinner table 25 holding the wafer 100 and ejecting the cleaning fluid from the ejection nozzle 26 .

The wafer 100 processed by the cutting unit 20 is carried into the cleaning unit 24 by the second transport mechanism 17, for example. The wafer 100 cleaned by the cleaning unit 24 is placed on the temporary placement mechanism 10 by, for example, the first transport mechanism 14 and accommodated in the cassette 4 .

Components such as the table moving mechanism 6, the chuck table 8, the first transport mechanism 14, the second transport mechanism 17, the moving mechanism 19, the cutting unit 20, the camera 22, the cleaning unit 24, etc. are each connected to the control unit 30. there is This control unit 30 controls each component described above in accordance with a series of steps required for processing the wafer 100 . In addition, the control unit 30 has information about the wafer 100, such as the distance a (FIG. 2) between the two adjacent dividing lines 102, the diameter of the wafer 100, or the diameter of the resin 105 provided on the surface of the wafer 100. Information is registered.

Next, the procedure of the alignment method for the wafer 100 will be described. FIG. 3 is a flow chart showing the procedure of the wafer alignment method. FIG. 4 is a plan view showing the rough matching step. FIG. 5 is a plan view showing fine adjustment steps. The alignment method for the wafer 100 according to this embodiment includes a wafer holding step ST11, a rough alignment step ST12, and a fine adjustment step ST13, as shown in FIG. In this embodiment, a case will be described in which the direction of one of the planned division lines 102 and the X-axis direction are adjusted to be parallel (alignment with θ).

[Wafer holding step]
The wafer holding step ST11 is a step of holding the wafer 100 on the chuck table 8. FIG. Specifically, the wafer 100 supported by the annular frame 109 via the dicing tape 108 is sucked and held on the holding surface 8a of the chuck table 8 with the surface 101 side of the wafer facing upward and exposed. Also, the annular frame 109 is fixed by the clamp 9 .

[Rough adjustment step]
The rough alignment step ST12 is a step for adjusting the orientation of the planned division line 102 and the X-axis direction to be roughly parallel. As in the present embodiment, in the wafer 100 whose central portion of the surface is coated with the resin 105, the number of exposed key patterns 104 is small. and the X-axis direction are roughly parallel to each other. In the rough matching step ST12, the key pattern 104 near the outermost circumference of the wafer 100 in the Y-axis direction is used. Specifically, as shown in FIG. 4, two devices 103 exposed in a region outside the resin 105 of the wafer 100 (peripheral edge region) and adjacent to each other in the X-axis direction along the same dividing line 102 are removed. A first area 111 and a second area 112 including the area are photographed by the camera 22 (FIG. 1). The control unit 30 determines whether the key pattern 104 is detected in the photographed first area 111 by, for example, pattern matching. The coordinates of P1 are stored as (X1, Y1), for example.

Next, the control unit 30 determines whether the key pattern 104 is detected in the photographed second area 112, and if the key pattern 104 is detected, coordinates of the reference point P2 of the key pattern 104 is stored as (X2, Y2), for example. If the Y coordinates of the reference points P1 and P2 are the same (Y1=Y2), the control unit 30 aligns the straight line 120 connecting the reference points P1 and P2 in parallel with the X axis (processing feed direction, cutting direction by the cutting blade). Therefore, the rough matching step ends without angle correction.

On the other hand, when the Y coordinates of the reference points P1 and P2 are not the same (Y1≠Y2), the control unit 30 needs angle correction because the straight line 120 connecting the reference points P1 and P2 is not parallel to the X axis. . The control unit 30 calculates the angle of deviation from the coordinates of the reference points P1 and P2, and rotates the chuck table 8 in the circumferential direction (the direction R in the drawing), so that the straight line 120 connecting the reference points P1 and P2 and the X axis are aligned. are parallel to each other. When the adjustment is completed, the process proceeds to fine adjustment step ST13.

[Fine adjustment step]
The fine adjustment step ST13 is a step of finely adjusting the direction of the dividing lines 102 on the roughly aligned wafer 100 so as to be parallel to the X-axis direction. In the fine adjustment step ST13, the camera 22 is indexed and fed by a predetermined distance toward the center of the wafer 100 in the Y-axis direction, and a third region 113 including a pair of devices 103 exposed on both sides of the resin 105 in the X-axis direction. 4 regions 114 are photographed by the camera 22 (FIG. 1). The predetermined distance for index feeding is, for example, n times (n is a natural number; for example, 3 times) the distance (interval) a between the key pattern 104 photographed in the rough matching step ST12 and the division line 102 .

In this embodiment, as shown in FIG. 5, the key pattern 104 (FIG. 4) used in the rough alignment step ST12 is separated from the center of the wafer 100 in the Y-axis direction by a distance 3a (three times the distance a of the dividing line 102). A third area 113 and a fourth area 114 on the planned dividing line 102 separated by . The control unit 30 determines whether the key pattern 104 is detected in the photographed third area 113 by pattern matching, and if the key pattern 104 is detected, the reference point P3 of the key pattern 104 is determined. The coordinates are stored as (X3, Y3), for example. The control unit 30 determines whether the key pattern 104 is detected in the photographed fourth area 114. If the key pattern 104 is detected, the coordinates of the reference point P4 of the key pattern 104 are set to ( X4, Y4). If the Y coordinates of the reference points P3 and P4 are the same (Y3=Y4), the control unit 30 aligns the straight line 121 connecting the reference points P3 and P4 in parallel with the X axis (processing feed direction, cutting direction by the cutting blade). judge to be.

On the other hand, when the Y coordinates of the reference points P3 and P4 are not the same (Y3≠Y4), the control unit 30 needs angle correction because the straight line 121 connecting the reference points P3 and P4 is not parallel to the X axis. . The control unit 30 calculates the angle of deviation from the coordinates of the reference points P3 and P4, and rotates the chuck table 8 in the circumferential direction (direction R in the drawing), so that the straight line 121 connecting the reference points P3 and P4 and the X-axis are parallel to each other.

When the adjustment is completed, the control unit 30 again indexes and feeds the camera 22 toward the center of the wafer 100 in the Y-axis direction by a predetermined distance, and moves the key pattern 104 used in the previous fine adjustment toward the center of the wafer 100 in the Y-axis direction. A fifth area 115 and a sixth area 116 on the line to be divided 102 separated by a distance 3a (three times the distance a of the line to be divided 102) are photographed. The control unit 30 determines whether the key pattern 104 is detected in the photographed fifth region 115 by pattern matching. The coordinates are stored as (X5, Y5), for example. The control unit 30 determines whether the key pattern 104 is detected in the photographed sixth region 116. If the key pattern 104 is detected, the coordinates of the reference point P6 of the key pattern 104 are set to, for example, ( X6, Y6). If the Y coordinates of the reference points P5 and P6 are the same (Y5=Y6), the control unit 30 controls the straight line 122 connecting the reference points P5 and P6 to be parallel to the X axis (processing feed direction, cutting direction by the cutting blade). judge to be.

On the other hand, when the Y coordinates of the reference points P5 and P6 are not the same (Y5≠Y6), the control unit 30 needs angle correction because the straight line 122 connecting the reference points P5 and P6 is not parallel to the X axis. . The control unit 30 calculates the angle of deviation from the coordinates of the reference points P5 and P6, and rotates the chuck table 8 in the circumferential direction (the direction R in the figure), so that the straight line 122 connecting the reference points P5 and P6 and the X-axis are parallel to each other.

In this embodiment, the key pattern 104 used in the previous fine adjustment is moved to the center of the wafer 100 in the Y-axis direction by a predetermined distance, and the fine adjustment is repeated until reaching the center of the wafer 100 in the Y-axis direction. As a result, the distance between the key patterns 104 located on both sides of the wafer 100 in the X-axis direction with the resin 105 interposed therebetween can be gradually increased. can be adjusted to be exactly parallel. Here, when the dividing line 102 used for the fine adjustment reaches near the center of the wafer 100 in the Y-axis direction, the fine adjustment step ST13 is finished because the adjustment cannot be made accurately any more. It should be noted that the moving distance from the coarse adjustment or the previous fine adjustment may be appropriately changed as long as it is n times (n is a natural number) the distance (interval) a of the dividing line 102 .

[Embodiment 2]
Next, a wafer alignment method according to the second embodiment will be described. The same reference numerals are assigned to the same configurations as in the first embodiment, and the description thereof is omitted. FIG. 6 is a perspective view showing a configuration example of a wafer used in the wafer alignment method according to the second embodiment. FIG. 7 is a plan view showing the rough matching step. FIG. 8 is a plan view showing fine adjustment steps. In Embodiment 2, the configuration of the wafer 200 is different from that in Embodiment 1 described above. As shown in FIG. 6, the wafer 200 according to the second embodiment is a disk-shaped SAW device wafer whose base material is lithium tantalate (LiTaO3), lithium niobate (LiNbO3), or the like.

A surface 201 of the wafer 200 is partitioned into a plurality of regions by mutually orthogonal (lattice-like) dividing lines (street) 202, and a device 203 such as a SAW filter is formed in each region. Each device 203 also includes a key pattern 204 having a characteristic shape. That is, a plurality of key patterns 204 are arranged on the front surface 201 of the wafer 200 .

A plurality of planned division lines 202 are formed along two orthogonal directions, and the distance (interval) a between two adjacent planned division lines 202 is approximately constant. The distance (interval) between two adjacent key patterns 204 is also equal to the distance a between the two adjacent dividing lines 202 . Further, if the distances between the plurality of planned division lines 102 extending along the same direction are equal, the distance between the plurality of planned division lines 102 extending along one direction and the distance between the plurality of planned division lines 102 extending along the one direction and the other direction orthogonal to this are equal. The distances between the plurality of planned division lines 102 extending along the direction may differ from each other.

A notch (notch) 206 for indicating the crystal orientation or the like is provided on the outer peripheral edge of the wafer 200, and a metal film (coating member) 205 such as copper is provided on the back surface 207 side of the wafer 200. It is A dicing tape (adhesive tape) 108 having a diameter larger than that of the wafer 200 is attached to the surface 201 of the wafer 200 . An annular frame 109 is fixed to the outer peripheral portion of the dicing tape 108 . As a result, the wafer 200 is supported by the annular frame 109 via the dicing tape 108 with the back surface 207 (metal film 205) facing up.

When this type of wafer 200 is cut and divided by the cutting device 1, chipping can be effectively suppressed. Since this metal film 205 does not transmit infrared rays, even if an infrared camera is used as the camera 22 , it is not possible to photograph the dividing lines 202 and the devices 203 on the front surface 201 side from the rear surface 207 side of the wafer 200 . In this embodiment, the outer peripheral portion of the metal film 205 provided on the back surface 207 of the wafer 200 is removed by annular cutting (for example, edge trimming). As a result, the rear surface 207 side of the outer peripheral portion of the wafer 200 excluding the central portion is not covered with the metal film 205 , and by using an infrared camera as the camera 22 , the line 202 to divide the wafer 200 from the rear surface 207 side. A part of the device 203 and the key pattern 204 can be photographed.

Next, the procedure of the alignment method for the wafer 200 will be described. In the present embodiment as well, a case will be described in which the direction of one of the planned division lines 202 and the X-axis direction are adjusted to be parallel (alignment with θ).

[Wafer holding step]
In the wafer holding step ST11, the wafer 200 supported by the annular frame 109 via the dicing tape 108 is placed on the holding surface 8a of the chuck table 8 with the rear surface 207 (metal film 205) side of the wafer facing upward and exposed. aspirate and hold. Also, the annular frame 109 is fixed by the clamp 9 .

[Rough adjustment step]
In the rough alignment step ST12, the key pattern 204 near the outermost periphery of the wafer 200 with the diameter in the Y-axis direction is used to adjust the direction of the dividing line 202 to be roughly parallel to the X-axis direction. In the case of the wafer 200 in which the central portion of the back surface 207 is coated with the metal film 205 as in this embodiment, even if an infrared camera is used as the camera 22, only a small number of key patterns 204 exposed at the outer peripheral portion can be photographed. As a step, the direction of the planned dividing line 202 and the X-axis direction are adjusted to be roughly parallel based on the adjacent key patterns 204 . Specifically, as shown in FIG. 7, a second device including two devices 203 adjacent to each other in the X-axis direction of the same dividing line 202 in the outer region (peripheral edge region) of the metal film 205 in the wafer 200 . A first area 211 and a second area 212 are photographed by the camera 22 (FIG. 1). This camera 22 is an infrared camera. The control unit 30 determines whether the key pattern 204 is detected in the photographed first area 211 by, for example, pattern matching, and if the key pattern 204 is detected, the reference point of the key pattern 104 is determined. The coordinates of Q1 are stored as (X'1, Y'1), for example.

Next, the control unit 30 determines whether the key pattern 204 is detected in the photographed second area 212. If the key pattern 204 is detected, the coordinates of the reference point Q2 of the key pattern 204 are determined. is stored as (X'2, Y'2), for example. If the Y coordinates of the reference points Q1 and Q2 are the same (Y'1=Y'2), the control unit 30 determines that the straight line 220 connecting the reference points Q1 and Q2 is the X axis (processing feed direction, cutting direction by the cutting blade). ), the rough alignment step is completed without angle correction.

On the other hand, when the Y coordinates of the reference points Q1 and Q2 are not the same (Y'1 ≠ Y'2), the control unit 30 corrects the angle because the straight line 220 connecting the reference points Q1 and Q2 is not parallel to the X axis. Is required. The control unit 30 calculates the angle of deviation from the coordinates of the reference points Q1 and Q2, and rotates the chuck table 8 in the circumferential direction (the direction R in the drawing), so that the straight line 220 connecting the reference points Q1 and Q2 and the X-axis are parallel to each other. When the adjustment is completed, the process proceeds to fine adjustment step ST13.

[Fine adjustment step]
The fine adjustment step ST13 is a step of finely adjusting the direction of the dividing line 202 in the rough-aligned wafer 200 so as to be parallel to the X-axis direction. In the fine adjustment step ST13, the camera 22 is indexed and fed by a predetermined distance to the central side of the wafer 200 in the Y-axis direction, and a third region including a pair of devices 203 at positions corresponding to both sides of the metal film 205 in the X-axis direction. 213 and the fourth area 214 are respectively photographed by the camera 22 (FIG. 1). The predetermined distance for indexing and feeding is, for example, a distance n times (n is a natural number; for example, 3 times) the distance (interval) a between the key pattern 204 photographed in the rough matching step ST12 and the division line 202 .

In this embodiment, as shown in FIG. 8, the key pattern 204 (FIG. 7) used in the rough alignment step ST12 is positioned at the center of the wafer 200 in the Y-axis direction by a distance 3a (three times the distance a of the line to be divided 202). A third area 213 and a fourth area 214 on the planned dividing line 202 separated by . The control unit 30 determines whether the key pattern 204 is detected in the photographed third region 213 by pattern matching. The coordinates are stored as (X'3, Y'3), for example. The control unit 30 determines whether the key pattern 204 is detected in the photographed fourth region 214. If the key pattern 204 is detected, the coordinates of the reference point Q4 of the key pattern 204 are set to, for example, ( X'4, Y'4) is stored. If the Y coordinates of the reference points Q3 and Q4 are the same (Y'3=Y'4), the control unit 30 determines that the straight line 221 connecting the reference points Q3 and Q4 is the X axis (processing feed direction, cutting direction by the cutting blade). ) will be parallel.

On the other hand, when the Y coordinates of the reference points Q3 and Q4 are not the same (Y'3≠Y'4), the control unit 30 corrects the angle because the straight line 221 connecting the reference points Q3 and Q4 is not parallel to the X axis. Is required. The control unit 30 calculates the angle of deviation from the coordinates of the reference points Q3 and Q4, and rotates the chuck table 8 in the circumferential direction (the direction R in the figure), so that the straight line 221 connecting the reference points Q3 and Q4 and the X-axis are parallel to each other.

When the adjustment is completed, the control unit 30 again indexes and feeds the camera 22 by a predetermined distance toward the center of the wafer 200 in the Y-axis direction, and moves the key pattern 204 used in the previous fine adjustment to the center of the wafer 200 in the Y-axis direction. A fifth area 215 and a sixth area 216 on the line to be divided 202 separated by a distance 3a (three times the distance a of the line to be divided 202) are photographed. The control unit 30 determines whether the key pattern 204 is detected in the photographed fifth region 215 by pattern matching, and if the key pattern 204 is detected, the reference point Q5 of the key pattern 204 is determined. For example, the coordinates are stored as (X'5, Y'5). The control unit 30 determines whether the key pattern 204 is detected in the photographed sixth region 216. If the key pattern 204 is detected, the coordinates of the reference point Q6 of the key pattern 204 are set to, for example, ( X'6, Y'6) is stored. If the Y coordinates of the reference points Q5 and Q6 are the same (Y'5=Y'6), the control unit 30 determines that the straight line 222 connecting the reference points Q5 and Q6 is the X axis (processing feed direction, cutting direction by the cutting blade). ) will be parallel.

On the other hand, when the Y coordinates of the reference points Q5 and Q6 are not the same (Y'5≠Y'6), the control unit 30 corrects the angle because the straight line 222 connecting the reference points Q5 and Q6 is not parallel to the X axis. Is required. The control unit 30 calculates the angle of deviation from the coordinates of the reference points Q5 and Q6, and rotates the chuck table 8 in the circumferential direction (direction R in the drawing), so that the straight line 222 connecting the reference points Q5 and Q6 and the X-axis are parallel to each other.

In this embodiment, the key pattern 204 used in the previous fine adjustment is moved to the center of the wafer 200 in the Y-axis direction by a predetermined distance, and the fine adjustment is repeated until reaching the center of the wafer 200 in the Y-axis direction. As a result, the distance of the key patterns 204 located on the front surface 201 side corresponding to both sides of the wafer 200 in the X-axis direction with the metal film 205 interposed therebetween can be gradually increased. The line 202 can be adjusted to be exactly parallel to the X-axis direction. Here, when the dividing line 202 used for the fine adjustment reaches near the center of the wafer 200 in the Y-axis direction, the fine adjustment step ST13 is finished because the fine adjustment cannot be made more accurately. It should be noted that the moving distance from the rough adjustment or the previous fine adjustment may be appropriately changed as long as it is n times (n is a natural number) the distance (interval) a of the dividing line 202 .

As described above, according to the present embodiment, two devices 103 located on the outer peripheral portion of the wafer 100 (200) held on the chuck table 8, corresponding to the same dividing line 102 (202) and adjacent to each other in the X-axis direction. (203) are detected by the camera 22 (infrared camera) of the alignment unit 23, and the chuck table 8 is rotated to align the two key patterns 104 (204) in parallel with the X-axis direction. A rough alignment step ST12 for adjusting the division line 102 (202) to be parallel to the X-axis direction, and after performing the rough alignment step ST12, the camera 22 of the alignment unit 23 indexed and fed to the center side of the wafer 100 (200). Then, the pair of key patterns 104 (204) on both sides of the resin 105 (metal film 205) are detected in the X-axis direction, and the chuck table 8 is rotated to move the pair of key patterns 104 (204) parallel to the X-axis direction. Since the fine adjustment step ST13 is provided for finely adjusting the planned division line 102 (202) and the X-axis direction to be parallel to each other, the θ adjustment can be performed accurately even if the exposed key pattern 104 (204) is small. play.

Further, according to this embodiment, in the rough alignment step ST12, adjacent key patterns 104 (204) near the outermost circumference of the wafer 100 (200) in the Y-axis direction are used, and in the fine adjustment step ST13, rough alignment is performed. Keys located on both sides of the resin 105 (metal film 205) near the center of the wafer in the Y-axis direction by a distance n times the distance a (n is a natural number) from the key pattern 104 (204) used in step ST12 to the line to be divided. Since the pattern 104 (204) is used, the distance between the key patterns 104 (204) located on both sides of the wafer 100 (200) in the X-axis direction with the resin 105 (metal film 205) interposed therebetween can be gradually increased. Based on these key patterns 104 (204), it is possible to accurately adjust the θ alignment between the planned dividing line 102 (202) and the X-axis direction.

It should be noted that the present invention is not limited to the above embodiments. That is, various modifications can be made without departing from the gist of the present invention. In this embodiment, the direction of one of the planned division lines 102, 202 extending in the X-axis direction (processing feed direction) and the direction of the X-axis are adjusted (aligned with θ) in parallel, but the present invention is not limited to this. Instead, for example, the direction of the other planned dividing line 102, 202 extending in the Y-axis direction (index feed direction) and the Y-axis direction may be adjusted (aligned with θ) in parallel.

Reference Signs List 1 cutting device 8 chuck table 20 cutting unit 21 cutting blade 22 camera 23 alignment unit 30 control unit 100, 200 wafer 101, 201 surface 102, 202 division line 103, 203 device 104, 204 key pattern 105 resin (coating member)
205 metal film (coating member)
107, 207 back side 108 dicing tape 109 frame a distance (interval)

Claims (2)

A rotatable chuck table that holds a wafer, a cutting unit that cuts the wafer held on the chuck table with a cutting blade, and a processing feed unit that relatively feeds the chuck table and the cutting unit in the X-axis direction. , an indexing unit that relatively indexes and feeds the chuck table and the cutting unit in the Y-axis direction, an alignment unit that has a camera that photographs the wafer held on the chuck table, and a control that controls each component. A device is formed in each area partitioned into grid-like streets on the surface by using a cutting device comprising means, and the outer circumference of a circular wafer covered with a covering member except for the outer circumference of the surface is exposed. A method of aligning a wafer using a part of a device obtained by performing the following steps as a key pattern,
a wafer holding step of holding the wafer on the chuck table;
The alignment unit detects the key pattern of each of the two devices exposed in the edge region of the outer periphery of the wafer held on the chuck table, corresponding to the same street and adjacent in the X-axis direction, and the chuck a rough alignment step of rotating the table to align the two key patterns parallel to the X-axis direction and adjusting the streets parallel to the X-axis direction;
After performing the rough alignment step, the alignment unit indexed and sent to the center of the wafer detects the pair of key patterns exposed on both sides of the covering member in the X-axis direction, rotates the chuck table, and rotates the pair of key patterns. and a fine adjustment step of aligning the key patterns in parallel with the X-axis direction and finely adjusting the streets and the X-axis direction in parallel. In the rough alignment step, a key pattern near the outermost periphery of the wafer in the Y-axis direction is used. 2. The method of aligning a wafer according to claim 1, wherein the key patterns on both sides of the covering member are used near the center of the wafer in the Y-axis direction by a distance of (natural number).

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