JP6366393B2 - Wafer processing method - Google Patents

Description

  The present invention relates to a wafer processing method in which a modified layer serving as a starting point of division is formed and a wafer is divided into a plurality of chips.

  In a small and lightweight electronic device typified by a mobile phone, a device chip including a device such as an IC is indispensable. Device chips (hereinafter referred to as chips), for example, divide the surface of a wafer made of a material such as silicon into multiple division lines called streets, form devices in each area, and then divide the wafers along these streets It is manufactured by doing.

  In recent years, a dividing method in which a modified layer serving as a starting point for dividing is formed along a street of a wafer and an external force is applied to divide the wafer into a plurality of chips has been put into practical use. In this dividing method, for example, the central portion of the expanded tape is attached to the wafer on which the modified layer is formed, and the expanded tape is expanded so as to push up the central portion, thereby applying an external force to the wafer.

  By the way, in order to maintain the space between the expanded tapes by expanding the expanded tape, the area between the inner periphery of the annular frame that fixes the outer peripheral portion of the expanded tape and the outer periphery of the wafer is heated to expand the expanded expanded tape. A method of partially shrinking a slack portion of a tape has been proposed (see, for example, Patent Document 1). If the distance between the chips is maintained in this way, the subsequent handling can be facilitated. Further, according to this method, it is possible to prevent the chips from rubbing due to the slack of the tape and to avoid breakage.

JP 2007-27562 A

  In the above method, before the area between the inner periphery of the frame and the outer periphery of the wafer is heated, the expanded tape is sucked with the chuck table to maintain the chip interval, and the expansion tape is released. Thus, the wafer and the frame are positioned at the same height.

  However, when the expansion tape is released from pushing up, the expansion tape may bend and rise between the inner periphery of the frame and the outer periphery of the wafer, and the expand tape may be rolled from the chuck table. In this case, in particular, the gap between the chips cannot be maintained appropriately in the expanded portion of the expanded tape.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a wafer processing method that suppresses wobbling from the chuck table due to the protrusion of the expanded tape.

According to the present invention, a device region that is partitioned into a plurality of regions by lattice-shaped division planned lines and in which devices are formed in each region, and surrounds the device region, and a plurality of regions by the lattice-shaped division planned lines A wafer processing method for dividing a wafer having a surplus outer peripheral region partitioned on the surface along the planned division line, and a modified layer along the planned division line by a laser beam having a wavelength transmitted through the wafer A modified layer forming step for forming the wafer inside the wafer, a wafer unit preparing step for preparing a wafer unit in which the wafer is supported in the opening of the annular frame via the expanded tape, the modified layer forming step, and the wafer After performing the unit preparation step, the wafer of the wafer unit is passed through the expanded tape. An expansion preparation step for placing the frame on the holding surface of the chuck table and holding the frame by the frame holding means; and after performing the expansion preparation step, the chuck table is pushed up against the frame holding means. Expansion that expands the expanded tape by relatively moving the table and the frame holding means, and dividing the wafer into a plurality of chips along the division line starting from the modified layer. And after the expansion step, the chuck table is pushed up with respect to the frame holding means while the wafer is sucked and held by the holding surface of the chuck table via the expanded tape and the distance between the chips is maintained. After performing the push-up release step for releasing the push-up and the push-up release step, A slack removing step for stimulating the expanded tape between the outer periphery of the chuck table that has been expanded and slackened in the expansion step and the inner periphery of the frame to remove slack, and in the modified layer forming step, A wafer processing method characterized in that the area of the end material chip formed in the outer peripheral surplus area is increased by forming the modified layer excluding the outer peripheral surplus area at the predetermined division line. Provided.

  In the present invention, in the modified layer forming step, the modified layer is preferably formed in the outer peripheral surplus region to such an extent that the device region is divided into a plurality of chips in the expanding step.

  In the wafer processing method according to the present invention, in the modified layer forming step, the modified layer is formed by excluding the outer peripheral surplus region in a predetermined division line, and the end material chip is enlarged, so that the expanded tape is Even if it bends and rises, it becomes difficult to droop from the chuck table. As described above, according to the present invention, it is possible to provide a wafer processing method in which wobbling from the chuck table due to the bulging of the expanded tape is suppressed.

It is a perspective view which shows typically the wafer unit of this embodiment. It is a partial cross section side view showing typically a modification layer formation step. It is a perspective view which shows typically the relationship between the direction of an expanded tape, and a modified layer. FIG. 4A is a diagram schematically illustrating the expansion preparation step, and FIG. 4B is a diagram schematically illustrating the expansion step. FIG. 5A is a diagram schematically illustrating the push-up release step, and FIG. 5B is a diagram schematically illustrating the slack removal step.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The wafer processing method according to the present embodiment includes a wafer unit preparation step (see FIG. 1), a modified layer formation step (see FIG. 2), an expansion preparation step (see FIG. 4A), and an expansion step (see FIG. 4). B)), a push-up releasing step (see FIG. 5A), and a slack removing step (see FIG. 5B).

  In the wafer unit preparation step, a wafer unit in which a wafer is supported on an annular frame via an expand tape is prepared. In the modified layer forming step, the laser beam is condensed inside the wafer to form a modified layer along the street (division planned line).

  In the expansion preparation step, the wafer is placed on a chuck table provided in the chip interval maintaining device, and the frame is held by a frame holding table (frame holding means). In the expansion step, the expand tape is expanded by moving the chuck table so as to push up the frame holding table. Thereby, the wafer is divided into a plurality of chips along the street where the modified layer is formed, and the interval between the chips is increased.

  In the push-up release step, the chuck table is released from the push-up state while the wafer is sucked and held by the chuck table to maintain the chip interval. In the slack removal step, the expanded tape is stimulated between the outer periphery of the chuck table and the inner periphery of the frame to remove the slack of the expanded tape. Hereinafter, the wafer processing method according to the present embodiment will be described in detail.

  First, a wafer unit preparation step for preparing a wafer unit is performed. FIG. 1 is a perspective view schematically showing the wafer unit of the present embodiment. As shown in FIG. 1, the wafer unit 1 includes a disk-shaped wafer 11 formed of a material such as silicon, for example.

  The surface 11 a of the wafer 11 is divided into a central device region 13 and an outer peripheral surplus region 15 surrounding the device region 13. The device area 13 and the outer peripheral surplus area 15 are further divided into a plurality of small areas by streets (division planned lines) 17 arranged in a lattice pattern. Each small area in the device area 13 includes an IC or the like. A device 19 is formed.

  In the wafer unit preparation step, for example, an expanded tape 21 having a diameter larger than that of the wafer 11 is attached to the back surface 11 b side of the wafer 11. The expanded tape 21 is formed of a material such as resin and is expanded by applying an external force. An annular frame 23 having a substantially circular opening is attached to the outer peripheral portion of the expand tape 21.

  Thereby, the wafer 11 is supported by the annular frame 23 via the expanded tape 21. In FIG. 1, the expand tape 21 is attached to the back surface 11 b side of the wafer 11, but the expand tape 21 may be attached to the front surface 11 a side of the wafer 11.

  After the wafer unit preparation step, a modified layer forming step for forming a modified layer along the street 17 of the wafer 11 is performed. FIG. 2 is a partial cross-sectional side view schematically showing the modified layer forming step. This modified layer forming step is performed by, for example, the laser processing apparatus 2 shown in FIG.

  The laser processing apparatus 2 includes a holding table 4 that holds the wafer 11 by suction. The holding table 4 is connected to a rotation drive source (not shown) such as a motor, and rotates around a vertical axis. Further, a moving mechanism (not shown) is provided below the holding table 4, and the holding table 4 moves in the horizontal direction by this moving mechanism.

  The upper surface of the holding table 4 is a holding surface 4 a that sucks and holds the back surface 11 b side (expanded tape 21 side) of the wafer 11. A negative pressure of a suction source (not shown) acts on the holding surface 4a through a flow path (not shown) formed inside the holding table 4, and a suction force for sucking the wafer 11 is generated. Around the holding table 4, a plurality of clamps 6 for holding and fixing the annular frame 23 are arranged.

  A laser processing head 8 is disposed above the holding table 4. The laser processing head 8 focuses the laser beam L oscillated by a laser oscillator (not shown) inside the wafer 11 sucked and held by the holding table 4. The laser oscillator is configured to be able to oscillate a laser beam L having a wavelength that is difficult to be absorbed by the wafer 11 (wavelength that passes through the wafer 11).

  In the modified layer forming step, first, the back surface 11b side (expanded tape 21 side) of the wafer 11 is brought into contact with the holding surface 4a of the holding table 4 to apply the negative pressure of the suction source. Thereby, the wafer 11 is sucked and held by the holding table 4 with the surface 11a side exposed upward.

  Next, the holding table 4 is moved and rotated to position the laser processing head 8 above the street 17 to be processed. Thereafter, the holding table 4 is moved in a direction parallel to the processing target street 17 while irradiating the laser beam L from the laser processing head 8 toward the wafer 11. Thereby, multiphoton absorption is generated in the vicinity of the condensing point of the laser beam L, and the modified layer 25 along the street 17 can be formed.

  In this modified layer formation step, as shown in FIG. 1, the modified layer 25 is not formed in the outer peripheral surplus region 15 in some streets 17. That is, on the predetermined street 17, the modified layer 25 is formed only in the device region 13.

  Thus, if the modified layer 25 is formed on the predetermined street 17 except for the outer peripheral surplus region 15, the end material chips divided by the outer peripheral surplus region 15 can be increased in area. As a result, as will be described later, even if the expanded tape 21 bends and rises between the outer periphery of the wafer 11 and the inner periphery of the frame 23, the expanded tape 21 is difficult to bend.

  If the number of such predetermined streets 17 (streets 17 in which the modified layer 25 is formed only in the device region 13) increases, the device region 13 of the wafer 11 cannot be appropriately divided. Therefore, the number of the predetermined streets 17 is adjusted to such an extent that the device region 13 can be appropriately divided.

  For example, when the expanded tape 21 wound in a roll shape is used, it is preferable to set the predetermined street 17 described above according to the orientation of the expanded tape 21 and the like. FIG. 3 is a perspective view schematically showing the relationship between the orientation of the expanded tape 21 and the modified layer 25.

  As shown in FIG. 3, the expanded tape 21 wound in a roll shape is difficult to expand in the width direction D <b> 2 perpendicular to the feed direction D <b> 1 than the feed direction D <b> 1. Therefore, the expand tape 21 rises between the outer periphery of the wafer 11 and the inner periphery of the frame 23 in the width direction D <b> 2, and is easy to bend from the holding table 4.

  Therefore, in such a case, the predetermined street 17 is set so that the end material chip is enlarged in the outer peripheral surplus region 15 corresponding to the end A in the width direction D2. Thereby, the expansion tape 21 can be more appropriately prevented from being twisted.

  When the modified layer 25 is formed along all the streets 17, the modified layer forming step ends. In this embodiment, the modified layer forming step is performed after the wafer unit preparing step is performed. However, the wafer unit preparing step may be performed after the modified layer forming step is performed.

  After the wafer unit preparation step and the modified layer formation step, an expansion preparation step for preparing to expand the expanded tape 21 is performed. FIG. 4A is a diagram schematically showing the expansion preparation step.

  The expansion preparation step and the subsequent steps are performed by the chip interval maintaining device 12 shown in FIG. The chip interval maintaining device 12 includes a chuck table 14 that holds the wafer 11. The chuck table 14 includes a disk-shaped frame 16 made of a metal material such as stainless steel, and a porous member 18 disposed at the center of the upper surface of the frame 16.

  The porous member 18 is formed in a disk shape having a diameter larger than that of the wafer 11, and is connected to a suction source 24 through a suction path 20, a valve 22, and the like provided below the chuck table 14. The upper surface of the porous member 18 serves as a holding surface 18a for holding the wafer 11, and the negative pressure of the suction source 24 can be applied to suck and hold the wafer 11.

  A chuck table elevating mechanism 26 is provided below the frame body 16. The chuck table elevating mechanism 26 includes a cylinder case 28 and a piston rod 30 inserted through the cylinder case 28, and the frame body 16 is fixed to the upper end portion of the piston rod 30. The height position of the chuck table 14 is adjusted by the chuck table lifting mechanism 26.

  A frame holding table (frame holding means) 32 on which the frame 23 is placed is provided outside the frame body 16. A circular opening corresponding to the chuck table 14 is formed in the center of the frame holding table 32, and the chuck table 14 is positioned in this opening. Below the frame holding table 32, support legs 34 that support the frame holding table 32 are provided.

  A plate 36 for fixing the frame 23 placed on the frame holding table 32 from above is provided above the frame holding table 32. An opening corresponding to the opening of the frame holding table 32 is formed at the center of the plate 36. The wafer 11 and a part of the expanded tape 21 are exposed upward from the opening of the plate 36.

  In the expansion preparation step, the frame 23 is placed on the upper surface of the frame holding table 32 and fixed by the plate 36 so that the surface 11 a side of the wafer 11 is exposed upward. As a result, the frame 23 is held by the frame holding table 32, and the wafer 11 is placed on the holding surface 18 a of the chuck table 14 via the expanded tape 21. In this expansion preparation step, the valve 22 of the suction path 20 is closed.

  The expansion step is performed after the expansion preparation step. FIG. 4B is a diagram schematically showing the expansion step. In the expansion step, the chuck table 14 is moved relative to the frame holding table 32 so as to push up. Specifically, as shown in FIG. 4B, the chuck table 14 is raised by the chuck table lifting mechanism 26.

  In this expansion step, the valve 22 of the suction path 20 is closed so that the wafer 11 is not sucked by the chuck table 14. Since the annular frame 23 is sandwiched and fixed by the frame holding table 32 and the plate 36, the expanded tape 21 expands when the chuck table 14 is raised with respect to the frame holding table 32.

  As a result, an external force in the direction of expanding the expanded tape 21 is applied to the wafer 11. As a result, the device region 13 of the wafer 11 is divided into a plurality of chips 27a along the street 17 where the modified layer 21 is formed, and the modified layer 21 is formed in the device region 13 of the wafer 11. Divided into a plurality of end material chips 27 b along the street 17.

  In the present embodiment, since the modified layer 25 is formed so as to remove the outer peripheral surplus area 15 on the predetermined street 17, the outer peripheral surplus area 15 of the wafer 11 is divided into end material chips 27b having a relatively large area. The In addition, the space | interval of the divided | segmented chip | tip 27a and the end material chip | tip 27b is fully expanded by expansion of this expand tape 21. FIG.

  After the expansion step, a push-up release step for releasing the push-up state of the chuck table 14 is performed. FIG. 5A is a diagram schematically showing the push-up release step. In the push-up release step, as shown in FIG. 5A, the valve 22 of the suction path 20 is opened, and the negative pressure of the suction source 24 is applied to the holding surface 18a.

  Thereby, the chip | tip 27a and the end material chip | tip 27b of the state in which the space | interval was expanded can be attracted-held by the chuck table 14 via the expanded tape 21. FIG. After sucking and holding the chip 27 a and the end material chip 27 b, the chuck table 14 is lowered to substantially the same height as the frame holding table 32.

  Since the expanded tape 21 has been expanded in the previous expansion step, when the chuck table 14 is lowered to substantially the same height as the frame holding table 32, the expanded tape 21 is between the outer periphery of the wafer 11 and the inner periphery of the frame 23. Sag and produce a ridge 21a.

  In the present embodiment, since the end material chip 27b has a large area as described above, the suction force of the chuck table 14 is sufficiently applied to each end material chip 27b, and the expanded tape 21 is bent due to the ridge 21a. Can be suppressed.

  After the push-up release step, a slack removal step for removing slack of the expanded tape 21 between the outer periphery of the wafer 11 and the inner periphery of the frame 23 is performed. FIG. 5B is a diagram schematically showing the slack removal step. In the slack removal step, as shown in FIG. 5B, for example, a far infrared heater (stimulus imparting means) 38 is positioned between the outer periphery of the wafer 11 and the inner periphery of the frame 23, and the far infrared ray is applied to the expanded tape 21. Irradiate.

  Specifically, for example, a far infrared ray that heats the expanded tape 21 to about 180 ° C. is irradiated from the far infrared heater 38. Note that the valve 22 of the suction path 20 is kept open even in this loosening removal step. Accordingly, the expansion tape 21 can be heated and contracted in a region between the outer periphery of the wafer 11 and the inner periphery of the frame 23 while the chips 27a and the end material chips 27b are sucked and held by the chuck table 14, thereby removing slack. .

  As described above, in the wafer processing method according to the present embodiment, in the modified layer forming step, the modified layer 25 is formed on the predetermined street (division planned line) 17 excluding the outer peripheral surplus region 15, and the end material is formed. Since the chip 27b has a large area, the end material chip 27b can be sufficiently sucked and held by the chuck table 14. For this reason, even if the expanded tape 21 is bent to form a bulge 21 a, the expanded tape 21 is difficult to roll from the chuck table 14.

  Therefore, the distance between the tip 27a and the end material tip 27b can be appropriately maintained by the chuck table 14. From the above principle, the wafer processing method according to the present embodiment is particularly effective when the area of the chip 27a is small.

  In addition, this invention is not limited to description of the said embodiment, A various change can be implemented. For example, in the above-described embodiment, far infrared rays are irradiated to the expanded tape 21 in the slack removal step, but slack may be removed by giving another stimulus to the expanded tape 21.

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

DESCRIPTION OF SYMBOLS 1 Wafer unit 11 Wafer 11a Front surface 11b Back surface 13 Device area | region 15 Peripheral surplus area | region 17 Street (division plan line)
DESCRIPTION OF SYMBOLS 19 Device 21 Expanding tape 21a Raising 23 Frame 25 Modified layer 27a Chip 27b End material chip 2 Laser processing device 4 Holding table 4a Holding surface 6 Clamp 8 Laser processing head 12 Chip interval maintenance device 14 Chuck table 16 Frame body 18 Porous member 18a Support surface 20 Suction path 22 Valve 24 Suction source 26 Chuck table lifting mechanism 28 Cylinder case 30 Piston rod 32 Frame holding table (frame holding means)
34 Support leg 36 Plate 38 Far-infrared heater (stimulation means)

Claims (2)

A device region in which devices are formed in each region by a grid-like division line and a device is formed in each region, and an outer peripheral surplus that surrounds the device region and is divided into a plurality of regions by the grid-like division line And a wafer processing method for dividing a wafer having a region on a surface thereof along the division line.
A modified layer forming step of forming a modified layer along the planned dividing line inside the wafer by a laser beam having a wavelength that transmits the wafer;
A wafer unit preparation step of preparing a wafer unit in which a wafer is supported by an opening of an annular frame via an expanding tape;
After performing the modified layer formation step and the wafer unit preparation step, the wafer of the wafer unit is placed on the holding surface of the chuck table via the expand tape, and the frame is held by the frame holding means. Expansion preparation steps,
After performing the expansion preparation step, the expanded tape is expanded by relatively moving the chuck table and the frame holding means so that the chuck table is pushed up with respect to the frame holding means, and the modified layer is started. An expansion step of expanding the interval between the chips while dividing the wafer into a plurality of chips along the division line.
After performing the expansion step, the wafer is sucked and held by the holding surface of the chuck table via the expanded tape, and the chuck table is lifted from the frame holding means while maintaining the distance between the chips. A push-up release step;
A slack removing step of applying a stimulus to the expanded tape between the outer periphery of the chuck table and the inner periphery of the frame which has been expanded and slackened in the expansion step to remove slack after performing the push-up releasing step; Prepared,
In said modified layer forming step, by forming a reforming layer except outer peripheral surplus region at given the dividing lines, to increase the area of the end material chip formed in the outer peripheral marginal area A wafer processing method that is characterized.   2. The wafer according to claim 1, wherein in the modified layer forming step, the modified layer is formed in the outer peripheral surplus region to the extent that the device region is divided into a plurality of the chips in the expanding step. Processing method.