JP7218055B2 - chuck table - Google Patents

Description

The present invention relates to a chuck table for holding wafers.

In the process of manufacturing a device chip, a device region in which devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are formed in a plurality of regions partitioned by lines to be divided (streets), and a device region. A wafer with a surrounding peripheral redundant area is used. A plurality of device chips each having a device are manufactured by dividing the wafer along the planned division lines.

For dividing the wafer, for example, a cutting device is used that includes a chuck table that holds the wafer and a cutting unit to which an annular cutting blade that cuts the wafer is mounted. By rotating the cutting blade to cut into the wafer held by the chuck table, the wafer can be cut into a plurality of device chips.

On the other hand, a method of processing wafers with a laser processing apparatus is also widely used. A laser processing apparatus includes a chuck table that holds a wafer and a laser irradiation unit that irradiates the wafer with a laser beam (see Patent Document 1).

By placing a wafer on the holding surface of the chuck table and applying the negative pressure of the suction source to the holding surface, the wafer is sucked and held by the chuck table. Then, a predetermined processing is performed on the wafer by irradiating a laser beam from the laser irradiation unit toward the wafer held by the chuck table. By this laser processing apparatus, for example, a process of forming grooves on the surface of a wafer, a process of forming a modified layer inside the wafer as a starting point for dividing the wafer, and the like are performed.

In recent years, along with the miniaturization and thinning of electronic equipment, there is a demand for thinning of device chips. Therefore, a technology has been proposed for thinning the wafer by grinding it before splitting. For grinding the wafer, for example, a grinding apparatus is used that includes a chuck table that holds the wafer and a grinding unit that is equipped with a grinding wheel to which a grinding wheel is fixed. The wafer is ground and thinned by holding the wafer on a chuck table and bringing the grinding wheel into contact with the back side of the wafer while rotating the chuck table and the grinding wheel.

When the wafer is thinned by grinding, the rigidity of the wafer decreases, and the wafer tends to warp. When the wafer is warped, it may become difficult to perform predetermined processes (transfer of the wafer, process of coating the back surface of the wafer with a metal film, etc.) after grinding the wafer. Therefore, when thinning the wafer, a method of grinding only the central region corresponding to the device region on the back side of the wafer has been proposed (see Patent Document 2). When this method is used, since the outer peripheral portion of the wafer is not thinned, the decrease in rigidity of the wafer is suppressed, and the occurrence of warping of the wafer is suppressed.

JP 2006-281434 A Japanese Unexamined Patent Application Publication No. 2007-19461

As described above, if only the region corresponding to the device region of the wafer is ground, recesses are formed on the back side of the wafer. When processing the front side of the wafer with a laser processing apparatus, it is necessary to suck the back side of the wafer with the holding surface of the chuck table. However, since the holding surface of the chuck table is generally formed flat, it is difficult to bring the back surface of the wafer having the concave portion into close contact with the holding surface of the chuck table. As a result, it may be difficult for the chuck table to properly hold the wafer.

Further, when processing a wafer using a laser processing apparatus, the chuck table may be irradiated with the laser beam when the laser beam passes through the wafer or protrudes outside the wafer. As a result, the chuck table may be processed by the laser beam and damaged. If the chuck table is damaged, it becomes necessary to replace the chuck table, resulting in reduced work efficiency and increased costs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a chuck table that can properly hold a wafer having recesses and that is less likely to be damaged by laser beam irradiation.

According to one aspect of the present invention, a wafer is provided with a device region in which a device is formed and an outer peripheral surplus region surrounding the device region on the front side, and a concave portion in a region corresponding to the device region on the back side. A chuck table that is provided in a laser processing apparatus capable of processing the wafer by irradiating it with a beam and holds the wafer, the upper surface side of which is inserted into the recess of the wafer and that is transparent to the laser beam. a table base comprising: a porous plate having a lower surface side; an accommodation recess for accommodating the lower surface side of the porous plate; and a suction path connecting the accommodation recess to a suction source ; a pressing fixing part that detachably fixes the porous plate to the table base by pressing the porous plate against the inner wall of the table base, the porous plate comprising: The chuck is arranged such that its upper surface side protrudes upward from the upper surface of the table base, and the height difference between the upper surface of the porous plate and the upper surface of the table base corresponds to the depth of the recess of the wafer. A table is provided. Further, according to another aspect of the present invention, a device region in which a device is formed and an outer peripheral surplus region surrounding the device region are provided on the front side, and a concave portion is formed in a region corresponding to the device region on the back side. A chuck table that is provided in a laser processing apparatus capable of processing a wafer by irradiating the wafer with a laser beam, and that holds the wafer, the upper surface side of which is inserted into the concave portion of the wafer, and is adapted to the laser beam a table base comprising a porous plate permeable to the bottom surface of the porous plate, an accommodation recess in which the lower surface side of the porous plate is accommodated, and a suction path connecting the accommodation recess to a suction source; side projecting upward from the top surface of the table base, the height difference between the top surface of the porous plate and the top surface of the table base corresponds to the depth of the recess of the wafer, and the A table base is provided with a chuck table having an atmosphere release groove connecting the accommodation recess and the side surface of the table base.

In addition , preferably , the table base includes a light-emitting portion arranged at a position overlapping the outer peripheral portion of the wafer. Moreover, preferably, a sealing member is provided on a side surface of the porous plate.

A chuck table according to an aspect of the present invention includes a porous plate fixed to a table base, and the upper surface side of the porous plate protrudes upward from the upper surface of the table base. Then, the wafer is arranged so that the upper surface side of the porous plate is inserted into the concave portion formed on the back surface side of the wafer. Thereby, the concave portion of the wafer is supported by the porous plate, and the wafer having the concave portion is properly held by the chuck table.

Also, the porous plate is made of a material that is transparent to the laser beam. Therefore, for example, even if a laser beam passes through the wafer and irradiates the porous plate, it is difficult for the porous plate to be processed by the laser beam. This suppresses damage to the porous plate.

FIG. 1(A) is a perspective view showing a wafer, and FIG. 1(B) is a perspective view showing a wafer to which a protective member is attached. It is a perspective view which shows a grinding apparatus. It is a perspective view showing a wafer after grinding. FIG. 4A is a perspective view showing the wafer supported by the frame, and FIG. 4B is a sectional view showing the wafer supported by the frame. It is a perspective view which shows a laser processing apparatus. FIG. 6A is a plan view showing the chuck table, and FIG. 6B is a sectional view showing the chuck table. It is sectional drawing which expands and shows a part of pressing fixing|fixed part. FIG. 4 is a cross-sectional view showing the chuck table from which the table base and the porous plate are separated; FIG. 4 is a cross-sectional view showing a chuck table holding a wafer; FIG. 5 is a cross-sectional view showing a chuck table according to a first modified example; FIG. 11 is a cross-sectional view showing a chuck table according to a second modified example;

An embodiment according to one aspect of the present invention will be described below with reference to the accompanying drawings. First, a configuration example of a wafer that can be held by the chuck table according to this embodiment will be described. FIG. 1A is a perspective view showing the wafer 11. FIG.

The wafer 11 is made of a material such as silicon and has a disc shape, and has a front surface 11a and a back surface 11b. The wafer 11 is partitioned into a plurality of regions by a plurality of dividing lines (streets) 13 arranged in a grid pattern so as to intersect each other. A device 15 such as an LSI (Large Scale Integration) is formed.

The wafer 11 has a substantially circular device region 17 in which a plurality of devices 15 are formed, and an annular outer peripheral surplus region 19 surrounding the device region 17 on the surface 11a side. The outer peripheral surplus region 19 is located at the outer peripheral portion of the wafer 11 and corresponds to a region where the devices 15 are not formed. In FIG. 1A, a boundary 21 between the device region 17 and the peripheral surplus region 19 is indicated by a chain double-dashed line.

The material, shape, structure, size, etc. of the wafer 11 are not limited. For example, the wafer 11 may be made of a material such as a semiconductor other than silicon (GaAs, InP, GaN, SiC, etc.), glass, ceramics, resin, metal, or the like. Moreover, there are no restrictions on the type, number, shape, structure, size, arrangement, etc. of the device 15 .

A plurality of device chips each including a device 15 are obtained by dividing the wafer 11 along the dividing line 13 . For the purpose of thinning the device chips, the wafer 11 before splitting is subjected to a grinding process. Specifically, the wafer 11 is thinned by grinding the back surface 11b side of the wafer 11 with a grinding wheel.

When grinding the back surface 11 b side of the wafer 11 , first, a circular protective member 23 is attached to the front surface 11 a side of the wafer 11 . As the protective member 23, for example, a film tape made of resin or the like is used. FIG. 1B is a perspective view showing the wafer 11 to which the protective member 23 is attached. The protective member 23 covers the front surface 11a side of the wafer 11 and protects the plurality of devices 15 .

Next, a configuration example of a grinding apparatus used for grinding the wafer 11 will be described. FIG. 2 is a perspective view showing the grinding device 2. FIG. The grinding device 2 includes a chuck table (holding table) 4 that holds the wafer 11 and a grinding unit 6 that grinds the wafer 11 .

The upper surface of the chuck table 4 is circular in plan view corresponding to the shape of the wafer 11 and constitutes a holding surface for holding the wafer 11 . This holding surface is connected to a suction source via a suction path (not shown) formed inside the chuck table 4 .

The chuck table 4 is connected to a rotary drive source (not shown) such as a motor, and this rotary drive source rotates the chuck table 4 around a rotary shaft substantially parallel to the vertical direction. A moving mechanism (not shown) is provided below the chuck table 4, and this moving mechanism moves the chuck table 4 in the horizontal direction.

A grinding unit 6 is arranged above the chuck table 4 . Grinding unit 6 comprises a cylindrical housing 8 supported by a lifting mechanism (not shown). A cylindrical spindle 10 is accommodated in the housing 8 , and the lower end of the spindle 10 is exposed to the outside of the housing 8 . A disk-shaped grinding wheel 12 is attached to the lower end of the spindle 10 .

The grinding wheel 12 has an annular base 14 made of a metal material such as stainless steel or aluminum. Note that the diameter of the base 14 is smaller than the diameter of the device region 17 (see FIG. 1A) of the wafer 11 held by the chuck table 4 . A plurality of rectangular parallelepiped grinding wheels 16 are fixed to the lower surface of the base 14 along the outer periphery of the base 14 .

A rotary drive source (not shown) such as a motor is connected to the upper end side (base end side) of the spindle 10, and the grinding wheel 12 is driven by a force generated by this rotary drive source to rotate a rotating shaft substantially parallel to the vertical direction. rotate around. A nozzle (not shown) for supplying a grinding liquid such as pure water to the wafer 11 and grinding wheel 16 held by the chuck table 4 is provided inside or near the grinding unit 6 .

When grinding the back surface 11b side of the wafer 11, first, the wafer 11 is placed on the chuck table 4 so that the front surface 11a side (protective member 23 side) of the wafer 11 faces the holding surface of the chuck table 4. . Then, the negative pressure of the suction source is applied to the holding surface of the chuck table 4 . As a result, the wafer 11 is suction-held by the chuck table 4 through the protection member 23 .

Next, the chuck table 4 holding the wafer 11 is moved below the grinding unit 6 . At this time, the position of the chuck table 4 is such that the plurality of grinding wheels 16 overlap the device region 17 of the wafer 11 (see FIG. 1A), and the surplus peripheral region 19 of the wafer 11 (see FIG. 1A). are adjusted so that they do not overlap.

Then, the chuck table 4 and the grinding wheel 12 are rotated, and the housing 8 is lowered while supplying the grinding liquid toward the back surface 11b of the wafer 11. As shown in FIG. For example, the chuck table 4 rotates in the direction indicated by arrow A at a predetermined number of revolutions (eg, 300 rpm), and the grinding wheel 12 rotates in the direction indicated by arrow B at a predetermined number of revolutions (eg, 6000 rpm). The lowering speed of the housing 8 is adjusted so that the grinding wheel 16 is pressed against the back surface 11b side of the wafer 11 with an appropriate force.

When the housing 8 descends and the plurality of grinding wheels 16 come into contact with the wafer 11, the rear surface 11b side of the wafer 11 is ground. At this time, the plurality of grinding wheels 16 are in contact with the first region 11c corresponding to the device region 17 (overlapping with the device region 17) of the back surface 11b of the wafer 11, and corresponding to the outer peripheral surplus region 19 (outer peripheral surplus region 19) is not in contact with the second region 11d. Therefore, only the first region 11c of the wafer 11 is ground by the grinding wheel 16 and thinned.

When the wafer 11 is thinned to the desired thickness, the grinding process of the wafer 11 is completed. FIG. 3 is a perspective view showing the wafer 11 after grinding. A circular concave portion 11e is formed on the rear surface 11b side of the wafer 11 after grinding. The recess 11 e is formed in a region corresponding to the device region 17 (see FIG. 1A) and surrounded by the outer peripheral portion 11 f of the wafer 11 . The outer peripheral portion 11f is not ground, and the thickness of the outer peripheral portion 11f is the same as the thickness of the wafer 11 before grinding.

If the entire rear surface 11b side of the wafer 11 were ground, the rigidity of the wafer 11 would be reduced, and the wafer 11 would be more likely to warp. If the wafer 11 is warped, it may become difficult to carry out predetermined processes (transfer of the wafer 11, coating of the back surface 11b side of the wafer 11 with a metal film, etc.) after grinding the wafer.

On the other hand, if only the region (first region 11c) corresponding to the device region 17 of the back surface 11b of the wafer 11 is ground as described above, the outer peripheral portion 11f of the wafer 11 is not thinned as shown in FIG. maintained in condition. As a result, the deterioration of the rigidity of the wafer 11 is suppressed, and the warp of the wafer 11 is suppressed.

Next, the wafer 11 is processed by irradiating the ground wafer 11 with a laser beam. When processing the wafer 11 with a laser beam, the wafer 11 is first supported by an annular frame. 4A is a perspective view showing the wafer 11 supported by the frame 27, and FIG. 4B is a sectional view showing the wafer 11 supported by the frame 27. FIG.

A circular tape 25 having a diameter larger than that of the wafer 11 is attached to the rear surface 11 b side of the wafer 11 . For example, the tape 25 is a flexible film obtained by forming a rubber- or acrylic-based adhesive layer (glue layer) on a resin base material such as polyolefin, polyvinyl chloride, or polyethylene terephthalate. As shown in FIG. 4B, the tape 25 is attached not only to the outer peripheral portion 11f of the wafer 11 but also to the inside of the recess 11e along the contour of the recess 11e.

The outer peripheral portion of the tape 25 is attached to an annular frame 27 having a circular opening 27a with a diameter larger than that of the wafer 11 in the center. Thereby, the wafer 11 is supported by the frame 27 via the tape 25 while being placed inside the opening 27a. Then, the wafer 11 supported by the frame 27 is transported to a laser processing apparatus and processed.

FIG. 5 is a perspective view showing the laser processing device 22. As shown in FIG. The laser processing device 22 includes a base 24 that supports each component included in the laser processing device 22 . A rectangular parallelepiped support structure 26 is arranged behind the base 24 along the Z-axis direction (vertical direction, vertical direction).

A protrusion 24a is provided at a front corner of the base 24 and protrudes upward. An opening is formed inside the projecting portion 24a, and a cassette elevator 28 connected to a lifting mechanism (not shown) is installed inside this opening. A cassette 30 capable of accommodating a plurality of wafers 11 (see FIGS. 4A and 4B) supported by the frame 27 is mounted on the upper surface of the cassette elevator 28 .

A temporary placement mechanism 32 for temporarily placing the wafer 11 is provided behind the projecting portion 24a. The temporary placement mechanism 32 includes a pair of guide rails 32a and 32b arranged substantially parallel to the Y-axis direction (index feed direction, front-rear direction). The guide rails 32a and 32b move along the X-axis direction (processing feed direction, left-right direction) so as to approach and separate while maintaining a parallel state. Each of the guide rails 32a and 32b has a support surface for supporting the frame 27 (see FIGS. 4A and 4B) and a side surface substantially perpendicular to the support surface.

A transfer mechanism 34 for transferring the wafer 11 is provided above the temporary placement mechanism 32 . A gripping portion 34a for gripping the frame 27 that supports the wafer 11 is provided on the protruding portion 24a side of the transfer mechanism 34 . A plurality of suction pads (not shown) for sucking and holding the wafer 11 or the frame 27 are provided on the lower surface side of the transfer mechanism 34 .

The wafers 11 accommodated in the cassette 30 are pulled out from the cassette 30 by the transfer mechanism 34 that grips the frame 27 with the gripping portion 34a, and are placed on the guide rails 32a and 32b. Also, the guide rails 32a and 32b move closer to each other to sandwich the wafer 11 and align the wafer 11 in the X-axis direction.

A moving mechanism 36 is provided in the central portion of the base 24 . The moving mechanism 36 includes a pair of Y-axis guide rails 38 arranged substantially parallel to the Y-axis direction. A Y-axis moving table 40 is slidably attached to the Y-axis guide rail 38 .

A nut portion (not shown) is provided on the back side (lower side) of the Y-axis moving table 40, and a Y-axis ball screw 42 arranged substantially parallel to the Y-axis guide rail 38 is screwed into this nut portion. are combined. A Y-axis pulse motor 44 is connected to one end of the Y-axis ball screw 42 . When the Y-axis ball screw 42 is rotated by the Y-axis pulse motor 44, the Y-axis moving table 40 moves along the Y-axis guide rail 38 in the Y-axis direction.

A pair of X-axis guide rails 46 arranged substantially parallel to the X-axis direction is provided on the surface (upper surface) of the Y-axis movement table 40 . An X-axis moving table 48 is slidably attached to the X-axis guide rail 46 .

A nut portion (not shown) is provided on the back side (lower side) of the X-axis moving table 48, and an X-axis ball screw 50 arranged substantially parallel to the X-axis guide rail 46 is screwed into this nut portion. are combined. An X-axis pulse motor (not shown) is connected to one end of the X-axis ball screw 50 . When the X-axis ball screw 50 is rotated by the X-axis pulse motor, the X-axis moving table 48 moves along the X-axis guide rail 46 in the X-axis direction.

A columnar table base 52 is provided on the surface side (upper surface side) of the X-axis moving table 48 . A chuck table (holding table) 54 for holding the wafer 11 is arranged above the table base 52 . Four clamps 56 are provided around the chuck table 54 to fix the frame 27 (see FIGS. 4A and 4B) that supports the wafer 11 .

The table base 52 is connected to a rotary drive source (not shown) such as a motor. When the table base 52 is rotated by the rotation drive source, the chuck table 54 rotates around a rotation axis substantially parallel to the Z-axis direction. Further, when the moving mechanism 36 moves the X-axis moving table 48 in the X-axis direction, the table base 52 and the chuck table 54 move in the X-axis direction (processing feed). Further, when the Y-axis moving table 40 is moved in the Y-axis direction by the moving mechanism 36, the table base 52 and the chuck table 54 are moved in the Y-axis direction (index feed).

The upper surface of the chuck table 54 constitutes a holding surface 54a that holds the wafer 11 . The holding surface 54 a is connected to a suction source (not shown) through a suction path (not shown) formed inside the chuck table 54 . The details of the structure of the chuck table 54 will be described later (see FIGS. 6A and 6B, etc.).

The support structure 26 also includes a support arm 26a projecting forward. A laser irradiation unit 58 that emits a laser beam downward is arranged at the tip of the support arm 26a. An imaging unit (camera) 60 for imaging the wafer 11 is installed at a position adjacent to the laser irradiation unit 58 .

The laser irradiation unit 58 includes, for example, a laser oscillator (not shown) that pulse-oscillates a laser beam having a wavelength that is absorbed by the wafer 11 (a laser beam having a wavelength that is absorptive to the wafer 11). For example, when the wafer 11 is made of a semiconductor material such as silicon and the wafer 11 is subjected to ablation processing, a laser oscillator having a laser medium such as Nd:YAG that pulse-oscillates a laser beam with a wavelength of 355 nm is used. be able to.

The laser irradiation unit 58 also includes a condenser (not shown) that collects the laser beam pulse-oscillated from the laser oscillator. This concentrator converges the laser beam at a predetermined position on the wafer 11 held by the chuck table 54 . The wafer 11 is processed by moving the chuck table 54 while irradiating the laser beam with the laser irradiation unit 58 .

It should be noted that the operation of the chuck table 54 is appropriately set according to the details of machining. For example, the wafer 11 is processed along the X-axis direction or the Y-axis direction by moving the wafer 11 along the X-axis direction or the Y-axis direction. Further, by rotating the chuck table 54 , the wafer 11 is processed into an annular shape along the rotation direction of the chuck table 54 .

The wafer 11 temporarily placed on the temporary placement mechanism 32 is processed by the laser irradiation unit 58 after being transferred to the chuck table 54 by the transfer mechanism 34 . After processing, the wafer 11 is held by, for example, the transfer mechanism 34 and placed in the temporary placement mechanism 32 .

Incidentally, while the wafer 11 is being transported from the chuck table 54 to the temporary placement mechanism 32, the wafer 11 may be transported to a cleaning unit (not shown) to be cleaned. The wafers 11 placed on the temporary placement mechanism 32 are sandwiched between the guide rails 32 a and 32 b and aligned, and then stored in the cassette 30 by the transfer mechanism 34 .

Each component such as the temporary placement mechanism 32, the transport mechanism 34, the moving mechanism 36, the chuck table 54, the laser irradiation unit 58, the imaging unit 60, etc. is connected to a control unit (not shown). This control unit controls the operation of each component of the laser processing apparatus 22 in accordance with a series of steps required for processing the wafer 11 .

When processing the front surface 11a side of the wafer 11 shown in FIGS. 4A and 4B with the laser processing apparatus 22, first, the wafer 11 is supported by the chuck table . Specifically, the wafer 11 is placed on the chuck table 54 so that the back surface 11 b side (tape 25 side) of the wafer 11 and the holding surface 54 a face each other, and the frame 27 is fixed by the clamps 56 . In this state, when a negative pressure of a suction source is applied to the holding surface 54a, the wafer 11 is sucked and held by the chuck table 54 via the tape 25. As shown in FIG.

However, a recess 11e (see FIG. 4B) is formed on the back surface 11b side of the wafer 11, and the tape 25 is also attached along the recess 11e. Therefore, if the holding surface 54a of the chuck table 54 were formed horizontally, a gap would be formed between the tape 25 and the holding surface 54a when the wafer 11 was placed on the chuck table 54, and the wafer 11 would not be chucked. It may not be properly held by the table 54.

Therefore, in this embodiment, a chuck table 54 including a table base and a porous plate fixed to the table base is used. The porous plate is arranged so that its upper surface side protrudes upward from the upper surface of the table base, and the wafer 11 is inserted so that the upper surface side of the porous plate is inserted into a recess formed on the back surface 11b side of the wafer 11. placed.

Thereby, the concave portion 11 e of the wafer 11 is supported by the porous plate, and the wafer 11 having the concave portion 11 e is appropriately held by the chuck table 54 . A specific configuration example of the chuck table 54 will be described below.

FIG. 6A is a plan view showing the chuck table 54, and FIG. 6B is a cross-sectional view of the chuck table 54 taken along line AA'. The chuck table 54 includes a disk-shaped table base 70 . The table base 70 is made of, for example, metal such as SUS, ceramics, resin, or the like. Further, the table base 70 may be made of a transparent material (such as glass) that is transparent to the laser beam emitted from the laser irradiation unit 58 (see FIG. 5).

A circular convex portion 70b that protrudes upward is provided on the surface 70a side of the table base 70 . The upper surface 70c of the projection 70b corresponds to the upper surface of the table base 70 and constitutes a holding surface for holding the outer peripheral portion 11f of the wafer 11 (see FIG. 9).

In addition, the table base 70 has an accommodation recess 70d on its upper surface side (on the upper surface 70c side of the projection 70b). The housing recess 70d is circular in plan view from the upper surface 70c of the projection 70b toward the lower surface of the table base 70. As shown in FIG. The inner wall of the table base 70 is formed by the side surface of the housing recess 70d. The diameter of the accommodation recess 70d is smaller than the diameter of the protrusion 70b, and the protrusion 70b and the accommodation recess 70d are arranged concentrically.

A suction path 70e is formed at the bottom of the housing recess 70d. The suction path 70 e is formed from the bottom of the housing recess 70 d toward the rear surface (lower surface) of the table base 70 and is connected to the suction source 100 via the valve 98 . The accommodation recess 70d is connected to the suction source 100 by the suction path 70e.

In addition, on the side of the upper surface 70c of the convex portion 70b, there are a plurality of air release grooves connecting the side surface of the accommodation concave portion 70d (the inner wall of the table base 70) and the outer peripheral surface of the convex portion 70b (the side surface of the table base 70). 70f is formed. As will be described later, the atmosphere opening groove 70f is provided to communicate the housing recess 70d with the outside of the chuck table 54 and to open the atmosphere when the wafer 11 is held by the chuck table 54. FIG. Although FIG. 6A shows an example in which four atmospheric release grooves 70f are formed at approximately equal intervals along the circumferential direction of the convex portion 70b, there is no limit to the number and arrangement of the atmospheric release grooves 70f. .

A disk-shaped suction part 72 for sucking and holding the wafer 11 is accommodated in the accommodation recess 70d. The suction part 72 includes a porous plate 74 made of a porous material and having a large number of through holes communicating from the upper surface to the lower surface. The porous plate 74 is made of a material that is transparent to the laser beam emitted from the laser irradiation unit 58 (see FIG. 5). That is, the light emitted from the laser irradiation unit 58 passes through the porous plate 74 . The upper surface 74a of the porous plate 74 constitutes a holding surface for holding the concave portion 11e of the wafer 11 (see FIG. 9).

For example, the porous plate 74 is made of porous glass. As a material for the porous glass, soda glass (soda lime glass), borosilicate glass, quartz glass, or the like can be used. In particular, quartz glass is preferable as a material for the porous plate 74 because of its high heat resistance.

The thickness of the porous plate 74 is greater than the depth of the accommodation recess 70d. Therefore, when the suction portion 72 is arranged inside the accommodation recess 70d, the lower surface side of the porous plate 74 is inserted into the accommodation recess 70d, and the upper surface 74a side of the porous plate 74 becomes the upper surface of the table base 70 (the upper surface 70c of the convex portion 70b). ).

A sealing member 76 is provided on the side surface of the porous plate 74 . The sealing member 76 is made of resin or the like and is formed so as to surround the porous plate 74 . When the diameter of the suction portion 72 is smaller than the diameter of the accommodation recess 70d, when the suction portion 72 is arranged in the accommodation recess 70d, a gap is formed between the protrusion 70b and the seal member 76 as shown in FIG. 6B. 78 is formed.

The chuck table 54 also includes a pressing fixing portion 80 that fixes the porous plate 74 to the table base 70 . The pressing fixing portion 80 includes a fixing portion 82 fixed to the surface 70 a of the table base 70 and a pressing portion 84 pressing the porous plate 74 . The fixed portion 82 and the pressing portion 84 are connected to each other via a biasing member 86 .

The biasing member 86 is made of a member capable of biasing the pressing portion 84, and is configured, for example, by an elastic member (such as a spring) capable of pressing the pressing portion 84 with an elastic force. In this embodiment, a spring is used as the biasing member 86 . One end of the biasing member 86 is fixed to the fixing portion 82 and the other end is fixed to the pressing portion 84 .

As shown in FIG. 6B, a portion of the lower side of the convex portion 70b has a gap extending from the side surface of the accommodation concave portion 70d (the inner wall of the table base 70) to the outer peripheral surface of the convex portion 70b (the side surface of the table base 70). 70 g of through-holes are formed. Further, the pressing portion 84 is formed in a shape and size that can be inserted into the through hole 70g. The side surface of the pressing portion 84 opposite to the fixing portion 82 is formed in a curved shape corresponding to the shape of the side surface of the porous plate 74, and constitutes a pressing surface 84a that presses the porous plate 74. .

In addition, as shown in FIG. 6A, the fixed portion 82 is formed with a plurality of elongated holes 82a penetrating through the fixed portion 82 in the vertical direction. The elongated hole 82 a is formed so that its longitudinal direction is along a straight line connecting the fixed portion 82 and the center of the table base 70 . A screw 88 for fixing the fixing portion 82 to the table base 70 is inserted into the long hole 82a.

FIG. 7 is a cross-sectional view showing an enlarged portion of the pressing fixing portion 80. As shown in FIG. On the surface 70a side of the table base 70, a screw groove 70h into which the tip of the screw 88 is inserted is formed. When the fixing portion 82 is arranged so that the long hole 82a and the screw groove 70h overlap each other, the screw 88 is inserted into the long hole 82a and screwed into the screw groove 70h. It is pressed against the base 70 and fixed to the table base 70 .

When fixing the porous plate 74 to the table base 70, first, the pressing portion 84 is inserted into the through hole 70g in a state where the porous plate 74 is arranged inside the accommodation recess 70d, and the fixing portion 82 is fixed to the table base. 70 on surface 70a. By pressing the fixing portion 82 toward the accommodation recess 70d, the pressing surface 84a of the pressing portion 84 is brought into contact with the side surface (sealing member 76) of the porous plate 74, and the biasing member 86 composed of a spring is activated. Shrink to less than natural length.

As a result, the porous plate 74 is pressed from the side surface side by the pressing portion 84 , and the porous plate 74 is pressed against a region of the inner wall of the table base 70 located on the opposite side of the pressing fixing portion 80 . In this state, the screw 88 is inserted into the elongated hole 82a of the fixing portion 82 and screwed into the screw groove 70h to fix the fixing portion 82 to the surface 70a of the table base 70. As shown in FIG. As a result, the porous plate 74 is fixed to the table base 70 while being sandwiched between the inner wall of the table base 70 and the pressing portion 84 .

On the other hand, when removing the porous plate 74 from the table base 70, the screw 88 is loosened and the pressing fixing portion 80 is removed. As a result, the pressing of the porous plate 74 by the pressing fixing portion 80 is released, and the porous plate 74 can be taken out from the accommodating recess 70d. FIG. 8 is a sectional view showing the chuck table 54 with the table base 70 and the porous plate 74 separated. In this manner, the porous plate 74 is detachably fixed to the table base 70 by the pressing fixing portion 80 .

A plurality of light-emitting portions 90 are formed in regions of the convex portion 70b where the air release grooves 70f are not formed. The light emitting unit 90 includes a light source 92 arranged inside a recess 70i formed on the upper surface 70c side of the protrusion 70b. The light source 92 is made up of an LED (Light Emitting Diode) or the like, and is connected to a power source (not shown) that supplies voltage to the light source 92 via wiring 94 . Further, the upper portion of the recess 70i that accommodates the light source 92 is covered with a cover 96 made of a transparent member.

When a predetermined voltage is supplied to the light source 92 through the wiring 94, the light source 92 emits light. The light emitted by the light source 92 is directed upwards toward the chuck table 54 through the cover 96 . For example, the light emitting unit 90 is used as a light that illuminates the outer peripheral portion 11f of the wafer 11 when the wafer 11 is photographed by the imaging unit 60 (see FIG. 5).

The chuck table 54 holds the wafer 11 (see FIG. 4(B)) in which the concave portion 11e is formed on the back surface 11b side. FIG. 9 is a sectional view showing the chuck table 54 holding the wafer 11. As shown in FIG.

When the wafer 11 is held by the chuck table 54, first, the wafer 11 is placed on the chuck table 54 so that the back surface 11b side (tape 25 side) of the wafer 11 and the upper surface 74a of the porous plate 74 face each other. At this time, the wafer 11 is positioned so that the concave portion 11 e overlaps the porous plate 74 . Also, the frame 27 supporting the wafer 11 is fixed by a clamp 56 (see FIG. 5).

Here, the thickness of the porous plate 74 is defined by the difference in height between the upper surface of the table base 70 (the upper surface 70c of the convex portion 70b) and the upper surface 74a of the porous plate 74 (protrusion amount of the porous plate 74). is set so as to correspond to the depth of the recess 11e. Specifically, the amount of protrusion of the porous plate 74 and the depth of the recess 11e are substantially the same. Also, the diameter of the porous plate 74 is set to be smaller than the diameter of the recess 11e.

Therefore, when the wafer 11 is placed on the chuck table 54 , the upper surface 74 a side of the porous plate 74 is inserted into the recess 11 e of the wafer 11 . The concave portion 11e of the wafer 11 is supported by the upper surface 74a of the porous plate 74 through the tape 25, and the outer peripheral portion 11f of the wafer 11 is supported through the tape 25 by the upper surface 70c of the convex portion 70b.

The amount of protrusion of the porous plate 74 and the depth of the recess 11e may be different as long as the holding of the wafer 11 is not hindered. In this case, the difference between the amount of protrusion of the porous plate 74 and the depth of the recess 11e is preferably 100 μm or less.

Further, as described above, the diameter and thickness of the porous plate 74 are set according to the diameter of the wafer 11, the depth of the recess 11e, and the like. Therefore, it is preferable to prepare a plurality of porous plates 74 having different dimensions in advance. Thereby, the porous plate 74 can be replaced according to the size of the wafer 11 held by the chuck table 54 . It should be noted that the replacement of the porous plate 74 can be easily carried out by attaching and detaching the pressing fixing portion 80 .

Next, the valve 98 is opened to apply the negative pressure of the suction source 100 to the suction passage 70e. At this time, the upper surface 74a of the porous plate 74 is covered with the concave portion 11e of the wafer 11, and the side surface of the porous plate 74 is covered with the sealing member 76. As shown in FIG. Therefore, when the valve 98 is opened, the suction passage 70 e is easily decompressed by the suction source 100 , and negative pressure acts on the upper surface 74 a of the porous plate 74 . As a result, the wafer 11 is suction-held by the chuck table 54 via the tape 25 .

When the wafer 11 is placed on the chuck table 54, a gap 102 may be formed between the seal member 76 and the tape 25 as shown in FIG. If the valve 98 is opened with the gap 102 sealed, the negative pressure of the suction source 100 acts on the gap 102 through the gap between the upper surface of the sealing member 76 and the tape 25, etc., and the gap 102 is reduced. may be As a result, the outer peripheral portion 11f of the wafer 11 is drawn toward the seal member 76, and the wafer 11 may be deformed and damaged.

On the other hand, the chuck table 54 has an air release groove 70f formed in the convex portion 70b, and the gap 102 is opened to the atmosphere through the air release groove 70f. Therefore, even if the valve 98 is opened, the gap 102 is less likely to be decompressed and the wafer 11 is less likely to be deformed. This prevents the wafer 11 from being damaged.

After holding the wafer 11 by the chuck table 54, the chuck table 54 is moved under the laser irradiation unit 58 (see FIG. 5). A laser beam is emitted from the laser irradiation unit 58 toward the front surface 11 a of the wafer 11 . As a result, the front surface 11a side of the wafer 11 is processed in a predetermined manner.

In addition, there is no restriction on the content of the processing of the wafer 11 . For example, a process of forming grooves on the surface of the wafer 11 by ablation, a process of forming a modified layer inside the wafer 11 as a starting point for dividing the wafer, and the like are performed.

A protective film may be formed on the front surface 11a side of the wafer 11 before irradiating the wafer 11 with the laser beam. The protective film is formed, for example, by curing a water-soluble liquid resin applied to the front surface 11a of the wafer 11 . PVA (polyvinyl alcohol), PEG (polyethylene glycol), or the like can be used as the water-soluble resin.

This protective film can prevent debris generated when the wafer 11 is processed with a laser beam from adhering to the front surface 11a of the wafer 11 . The protective film made of water-soluble resin is removed by supplying pure water to the front surface 11a side of the wafer 11 after the laser beam processing is completed.

In addition, before irradiating the wafer 11 with the laser beam, the outer peripheral portion 11f of the wafer 11 held by the chuck table 54 is photographed by the imaging unit 60 (see FIG. 5) to confirm the position of the wafer 11. is preferred. For example, the imaging unit 60 captures images of three or more outer peripheral edges of the wafer, and acquires the coordinates of the outer peripheral edge of the wafer 11 and the center coordinates based on the captured images. By controlling the irradiation position of the laser beam based on the positional information of the wafer 11 obtained in this way, for example, problems such as unintentional irradiation of the laser beam to the outside of the wafer 11 can be avoided.

When the imaging unit 60 scans the wafer 11, it is preferable to emit light from a plurality of light-emitting portions 90 (see FIG. 6A, etc.) provided on the convex portion 70b of the table base 70. FIG. As a result, the light emitting unit 90 functions as a backlight, and a clear image can be obtained, so that the position of the wafer 11 can be accurately grasped.

As described above, the chuck table 54 according to the present embodiment includes the porous plate 74 fixed to the table base 70, and the upper surface 74a side of the porous plate 74 is the upper surface of the table base 70 (the upper surface 70c of the convex portion 70b). protrudes upward from the The wafer 11 is arranged such that the upper surface 74a side of the porous plate 74 is inserted into the recess 11e formed on the back surface 11b side of the wafer 11 . Thereby, the concave portion 11 e of the wafer 11 is supported by the porous plate 74 , and the wafer 11 having the concave portion 11 e is appropriately held by the chuck table 54 .

Also, the porous plate 74 is made of a material that is transparent to the laser beam emitted from the laser irradiation unit 58 . Therefore, for example, even if a laser beam passes through the wafer 11 and irradiates the porous plate 74, the porous plate 74 is unlikely to be processed by the laser beam. This suppresses damage to the porous plate 74 .

Furthermore, the porous plate 74 is detachably fixed to the table base 70 by a pressing fixing portion 80 . Therefore, even if the porous plate 74 is processed by laser beam irradiation and the porous plate 74 needs to be replaced, the replacement work can be performed quickly. Moreover, since it is not necessary to replace the chuck table 54 together with the table base 70 when the porous plate 74 is damaged, the cost can be reduced. Similarly, when exchanging the porous plate 74 according to the dimensions of the wafer 11 (the diameter of the wafer 11, the depth of the concave portion 11e, etc.), the exchanging work can be performed smoothly by attaching and detaching the pressing fixing portion 80.

In this embodiment, the porous plate 74 is fixed to the table base 70 by the pressing fixing portion 80, but the fixing method of the porous plate 74 is not limited. For example, if the porous plate 74 is not frequently replaced, the porous plate 74 may be fixed to the table base 70 using an adhesive. Thereby, the porous plate 74 is firmly fixed to the table base 70 .

Further, the detailed structure of the chuck table 54 described in this embodiment can be changed as appropriate within the range in which the wafer 11 having the recess 11e can be held. FIG. 10 is a cross-sectional view showing a chuck table (holding table) 110 according to a first modified example. The chuck table 110 differs from the chuck table 54 in that it includes a light emitting unit 112 instead of the light emitting unit 90 shown in FIG. 6B. Other chuck table 110 structures and functions are similar to chuck table 54 .

The light-emitting portion 112 includes a plurality of light-projecting through holes 70j that are formed in the convex portion 70b and penetrate the table base 70 from the upper surface to the lower surface. The lower end side of the light-projecting through-hole 70 j opens toward the inclined surface 52 a formed on the surface (upper surface) side of the outer peripheral portion of the table base 52 .

A light source 114 such as an LED is provided outside the chuck table 110 . The light emitted by the light source 114 is reflected by the inclined surface 52a of the table base 52, and is irradiated upward on the chuck table 110 through the light projection through-hole 70j. In this way, the light source 114 forming the light emitting unit 112 may be provided outside the chuck table 110 .

The light emitting unit 112 is arranged at the same position as the light emitting unit 90 shown in FIG. 6A, for example. However, the number and arrangement of the light emitting units 90 are not limited.

FIG. 11 is a cross-sectional view showing a chuck table (holding table) 120 according to a second modification. The chuck table 120 has a table base 122 . The structure, material, etc. of the table base 122 are the same as those of the table base 70 (see FIGS. 6(B) and 10) except for the matters described below.

The table base 122 includes a lower base 124 and an upper base 126 fixed to the upper surface 124 a side of the lower base 124 . The upper base 126 corresponds to the convex portion 70b of the chuck table 54 (see FIG. 6B). That is, the chuck table 120 corresponds to a modified example in which the convex portion 70b of the chuck table 54 (see FIG. 6B) is made of a material different from that of the table base 70. As shown in FIG.

The upper base 126 has a circular opening 126c penetrating from the upper surface 126a to the lower surface 126b. This opening 126c corresponds to the accommodation recess 70d of the chuck table 54 (see FIG. 6B). A suction path 124 b connected to the suction source 100 via a valve 98 is formed in a region overlapping the opening 126 c of the lower base 124 . Further, the upper base 126 has an eave-like holding portion (eaves portion) 126d protruding radially inward (central side) of the opening 126c on the upper surface 126a side thereof.

A suction part 128 having a porous plate 130 and a sealing member 132 is accommodated in the opening 126c. The porous plate 130 is configured such that the diameter on the side of the upper surface 130a is smaller than the diameter on the side of the lower surface. Therefore, a step portion 130b is formed on the side surface of the porous plate 130. As shown in FIG. Other structures and materials of the suction portion 128 are the same as those of the suction portion 72 of the chuck table 54 (see FIG. 6B).

In addition, the upper base 126 has an atmosphere release groove 126e and a notch 126f. The structures of the atmosphere release groove 126e and the notch 126f are the same as those of the atmosphere release groove 70f and the through hole 70g of the chuck table 54 (see FIG. 6B).

The upper base 126 is detachably fixed to the lower base 124 . Specifically, the upper base 126 has a through hole 126g extending vertically through its outer peripheral portion. Further, a screw groove 124c is formed on the upper surface 124 side a of the lower base 124 at a position overlapping with the through hole 126g. With the upper base 126 placed on the lower base 124, the upper base 126 is fixed to the lower base 124 by inserting the screw 134 into the through hole 126g and screwing it into the screw groove 124c.

When fixing the porous plate 130 to the table base 122, first, with the lower base 124 and the upper base 126 separated, the porous plate 130 is inserted into the opening 126c from the lower surface 126b side of the upper base 126. , placing the upper base 126 and the porous plate 130 on the lower base 124 . At this time, the stepped portion 130 b formed on the side surface of the porous plate 130 is pressed toward the lower base 124 by the pressing portion 126 d of the upper base 126 .

Next, the lower base 124 and the upper base 126 are fixed with screws 134 . Then, the porous plate 130 is fixed to the upper base 126 by the pressing fixing portion 80 . The fixing method of the porous plate 130 by the pressing fixing portion 80 is the same as the case of using the chuck table 54 (see FIG. 6B).

As described above, when the upper base 126 is used to fix the porous plate 130 , the stepped portion 130 b of the porous plate 130 is pressed toward the lower base 124 by the pressing portion 126 d of the upper base 126 . This can prevent the porous plate 130 from coming off the upper surface 126 a side of the upper base 126 when the wafer 11 is processed, transported, or the like.

When the wafer 11 (see FIG. 4B) is placed on the chuck table 120, the gap 136 formed between the upper base 126 and the sealing member 132 is covered by the tape 25 attached to the wafer 11. will be However, an air release groove 126e is formed in the upper base 126, and the opening 126c is open to the atmosphere through the air release groove 126e. Therefore, even if the valve 98 is opened, the gap 136 is less likely to be depressurized, and the wafer 11 is less likely to be deformed.

A chuck table 110 or a chuck table 120 may be mounted on the laser processing apparatus 22 shown in FIG. 5 instead of the chuck table 54 .

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

REFERENCE SIGNS LIST 11 Wafer 11a Front surface 11b Back surface 11c First region 11d Second region 11e Recess 11f Periphery 13 Planned division line (street)
REFERENCE SIGNS LIST 15 device 17 device region 19 peripheral surplus region 21 boundary 23 protective member 25 tape 27 frame 27a opening 2 grinding device 4 chuck table (holding table)
6 Grinding Unit 8 Housing 10 Spindle 12 Grinding Wheel 14 Base 16 Grinding Wheel 22 Laser Processing Device 24 Base 24a Projection 26 Support Structure 26a Support Arm 28 Cassette Elevator 30 Cassette 32 Temporary Placement Mechanism 32a, 32b Guide Rail 34 Transfer Mechanism 34a Gripper 36 Moving mechanism 38 Y-axis guide rail 40 Y-axis moving table 42 Y-axis ball screw 44 Y-axis pulse motor 46 X-axis guide rail 48 X-axis moving table 50 X-axis ball screw 52 Table base 54 Chuck table (holding table)
54a holding surface 56 clamp 58 laser irradiation unit 60 imaging unit (camera)
70 Table base 70a Surface 70b Protrusion 70c Upper surface 70d Accommodating recess 70e Suction path 70f Atmospheric release groove 70g Through hole 70h Screw groove 70i Recess 70j Light projecting through hole 72 Suction part 74 Porous plate 74a Upper surface 76 Sealing member 78 Gap 80 Pressing Fixing part 82 Fixing part 82a Long hole 84 Pressing part 84a Pressing surface 86 Biasing member 88 Screw 88a Head 90 Light emitting part 92 Light source 94 Wiring 96 Cover 98 Bulb 100 Suction source 102 Gap 110 Chuck table (holding table)
112 light emitting unit 114 light source 120 chuck table (holding table)
122 table base 124 lower base 124a upper surface 124b suction path 124c screw groove 126 upper base 126a upper surface 126b lower surface 126c opening 126d holding portion (eaves portion)
126e Atmospheric opening groove 126f Notch 126g Through hole 128 Suction part 130 Porous plate 130a Upper surface 130b Stepped part 132 Sealing member 134 Screw 136 Gap

Claims (4)

A wafer having a device region in which a device is formed and an outer peripheral surplus region surrounding the device region on the front side, and a concave portion in a region corresponding to the device region on the back side is irradiated with a laser beam to remove the wafer. A chuck table provided in a laser processing apparatus capable of processing and holding the wafer,
a porous plate having an upper surface side inserted into the recess of the wafer and having transparency to the laser beam;
a table base comprising a housing recess in which the lower surface side of the porous plate is housed, and a suction path connecting the housing recess to a suction source;
The porous plate is detachably fixed to the table base by pressing the side surface of the porous plate and pressing the porous plate against the inner wall of the table base formed by the side surface of the accommodating recess. a contact fixing part ;
The porous plate is arranged so that the upper surface side protrudes upward from the upper surface of the table base,
A chuck table , wherein a difference in height between the upper surface of the porous plate and the upper surface of the table base corresponds to the depth of the recess of the wafer . A wafer having a device region in which a device is formed and an outer peripheral surplus region surrounding the device region on the front side, and a concave portion in a region corresponding to the device region on the back side is irradiated with a laser beam to remove the wafer. A chuck table provided in a laser processing apparatus capable of processing and holding the wafer,
a porous plate having an upper surface side inserted into the recess of the wafer and having transparency to the laser beam;
a table base comprising an accommodation recess in which the lower surface side of the porous plate is accommodated, and a suction path connecting the accommodation recess to a suction source;
The porous plate is arranged so that the upper surface side protrudes upward from the upper surface of the table base,
the height difference between the top surface of the porous plate and the top surface of the table base corresponds to the depth of the recess of the wafer;
A chuck table, wherein the table base includes an atmosphere release groove connecting the accommodation recess and a side surface of the table base. 3. The chuck table according to claim 1 , wherein the table base has a light emitting portion arranged at a position overlapping the outer peripheral portion of the wafer. 4. The chuck table according to any one of claims 1 to 3, wherein a sealing member is provided on a side surface of said porous plate.

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