JP5389433B2 - Grinding wheel - Google Patents

Description

  The present invention relates to a grinding wheel of a grinding apparatus in which a plurality of grinding wheels are mounted on a free end.

  A semiconductor wafer in which a number of devices such as IC and LSI are formed on the surface, and each device is partitioned by a line to be divided (street), the back surface is ground by a grinding machine and processed to a predetermined thickness. A division line is cut by a dicing apparatus to be divided into individual devices, and the divided devices are used for electric devices such as mobile phones and personal computers.

  A grinding apparatus for grinding a back surface of a wafer includes a chuck table for holding a wafer, a grinding means for rotatably supporting a grinding wheel provided with a grinding wheel for grinding the wafer held by the chuck table, and a grinding region And a grinding water supply means for supplying the grinding water to the wafer, so that the wafer can be ground to a desired thickness (see, for example, Japanese Utility Model Publication No. 7-31268).

  In recent years, in order to achieve a reduction in weight and size of electrical equipment, it has been required to make the wafer thinner, for example, about 50 μm. Such thinly ground wafers are difficult to handle and may be damaged during transportation.

  Accordingly, Japanese Patent Laid-Open No. 2007-243112 proposes a grinding method in which only the back surface corresponding to the device region of the wafer is ground and a ring-shaped reinforcing portion is formed on the back surface of the wafer corresponding to the outer peripheral surplus region surrounding the device region. Has been.

As described above, a wafer having a ring-shaped reinforcing portion formed on the outer periphery of the back surface is divided along a planned dividing line called street from the front surface side of the wafer after the ring-shaped reinforcing portion is removed (for example, a special feature). (See JP 2007-193895).
Japanese Utility Model Publication No. 7-31268 JP 2007-243112 A JP 2007-19395 A

  Semiconductor wafers are ground while supplying grinding water to the grinding region. Therefore, in the grinding region, the wafer grinding waste becomes turbid in the grinding water. Grinding water or waste liquid in which grinding debris is turbid flows out between a plurality of grinding wheels arranged in a ring shape by centrifugal force, but a part of the grinding water stays inside the grinding wheel.

  Conventionally, in general, a recess for adjusting the rotational balance is often formed on the outer peripheral side surface or the inner peripheral side surface of the grinding wheel. In a grinding wheel having a recess for adjusting the rotational balance in this way, the accumulated grinding scrap adheres to the recess of the grinding wheel and grows into a snowball, and the grown lump falls and mixes with the lump. There is a problem that abrasive grains such as diamond are sandwiched between the wafer and the grinding wheel, causing scratches on the ground surface of the wafer and reducing the bending strength.

  In particular, in a wafer in which only the back surface corresponding to the device region of the wafer is ground and a ring-shaped reinforcing portion is formed on the outer periphery, the abrasive grains sandwiched between the wafer and the grinding wheel crack the root portion of the ring-shaped reinforcing portion. Causing bending strength to decrease.

  In addition, a part of the grinding water or waste liquid in which grinding debris becomes turbid stays in the grinding wheel, which causes the grinding wheel to become clogged and the grinding wheel must be dressed frequently, resulting in poor productivity. There is.

  The present invention has been made in view of these points, and an object of the present invention is to provide a grinding wheel that can reduce the number of dressings of a grinding wheel and that does not cause scratches on the wafer. It is.

According to the present invention, there is provided a grinding wheel that is detachably mounted on the wheel mount of a grinding apparatus having a spindle that is rotationally driven and a wheel mount that is coupled to the tip of the spindle, the inner peripheral side face and the outer peripheral side face. And an annular base having a mounting portion to be attached to the wheel mount, and a plurality of grinding wheels arranged in a ring shape at a free end of the annular base, the mount of the annular base A recess for adjusting the rotational balance is formed only in the mounting portion, and when the grinding wheel is mounted on the wheel mount, the recess is sealed by the mount mounting portion of the wheel mount and the annular base and externally mounted. A grinding wheel is provided that is not exposed to the surface.

  According to the present invention, a depression is formed only in the mount mounting portion of the annular base constituting the grinding wheel to adjust the rotational balance, and no depression is formed on the outer peripheral side surface and the inner peripheral side surface of the annular base. As a result, grinding debris does not adhere to the recesses formed on the inner and outer peripheral surfaces of the grinding wheel as in the prior art and grows in a snowball type, creating scratches on the ground surface of the wafer and increasing the bending strength. The problem of lowering can be avoided.

  In addition, the phenomenon that clogging of grinding scraps or abrasive grains in the grinding wheel can be reduced, and the number of dressings of the grinding wheel can be reduced, so that productivity is improved.

  Hereinafter, a grinding wheel according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a semiconductor wafer before being processed to a predetermined thickness. A semiconductor wafer 11 shown in FIG. 1 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets 13 are formed in a lattice shape on the surface 11a, and a plurality of streets partitioned by the plurality of streets 13 are formed. A device 15 such as an IC or LSI is formed in the region.

  The thus configured silicon wafer 11 includes a device region 17 in which the device 15 is formed and an outer peripheral surplus region 19 that surrounds the device region 17. A notch 21 as a mark indicating the crystal orientation of the silicon wafer is formed on the outer periphery of the silicon wafer 11.

  A protective tape 23 is attached to the surface 11a of the silicon wafer 11 by a protective tape attaching process. Therefore, the front surface 11a of the silicon wafer 11 is protected by the protective tape 23, and the back surface 11b is exposed as shown in FIG.

  Hereinafter, the grinding apparatus 2 for grinding the back surface 11b of the silicon wafer 11 thus configured to a predetermined thickness will be described with reference to FIG. The housing 4 of the grinding device 2 is composed of a horizontal housing part 6 and a vertical housing part 8.

  A pair of guide rails 12 and 14 extending in the vertical direction are fixed to the vertical housing portion 8. A grinding means (grinding unit) 16 is mounted along the pair of guide rails 12 and 14 so as to be movable in the vertical direction. The grinding unit 16 is attached to a moving base 18 that moves up and down along a pair of guide rails 12 and 14 via a support portion 20.

  The grinding unit 16 includes a spindle housing 22 attached to the support portion 20, a spindle 24 rotatably accommodated in the spindle housing 22, and a servo voter 26 that rotationally drives the spindle 24.

  As best shown in FIG. 6, a wheel mount 28 is fixed to the tip of the spindle 24, and a grinding wheel 30 is attached to the wheel mount 28 with a screw 31. For example, as shown in FIG. 4, the grinding wheel 30 has a plurality of grinding stones 34 in which diamond abrasive grains having a grain size of 0.3 to 1.0 μm are hardened by vitrified bonds or the like are fixed to the free end portion of the annular base 32. It is configured.

  Grinding water is supplied to the grinding means (grinding unit) 16 via a hose 36. Preferably, pure water is used as the grinding water. As shown in FIG. 6, the grinding water supplied from the hose 36 is formed in the grinding water supply hole 38 formed in the spindle 24, the space 40 formed in the wheel mount 28, and the annular base 32 of the grinding wheel 30. Then, it is supplied to the wafer 11 held by the grinding wheel 34 and the chuck table 50 through the plurality of grinding water supply holes 42.

  Referring to FIG. 3 again, the grinding apparatus 2 includes a grinding unit feed mechanism 44 that moves the grinding unit 16 in the vertical direction along the pair of guide rails 12 and 14. The grinding unit feed mechanism 44 includes a ball screw 46 and a pulse motor 48 fixed to one end of the ball screw 46. When the pulse motor 48 is pulse-driven, the ball screw 46 rotates, and the moving base 18 is moved in the vertical direction via the nut of the ball screw 46 fixed inside the moving base 18.

  A chuck table 50 sucks and holds the wafer 11 to be ground, and is configured to be movable in the Y-axis direction by a chuck table moving mechanism (not shown). That is, the chuck table 50 is moved in the Y-axis direction between the illustrated wafer loading / unloading position and the grinding position facing the grinding wheel 30. 52 and 54 are bellows.

  Referring to FIG. 5, a perspective view of the grinding wheel 30 of the first embodiment of the present invention is shown. 6 is a cross-sectional view taken along a line 6-6 in FIG. 5 taken along with the wheel mount, and FIG. 7 is a partially enlarged cross-sectional view of FIG.

  As shown in FIGS. 6 and 7, the annular base 32 of the grinding wheel 30 has an outer peripheral side surface 32a, a tapered inner peripheral side surface 32b, a bottom surface (free end) 32c, and a mount mounting portion 32d. Yes.

  As shown in FIG. 5, four screw holes 33 for mounting the grinding wheel 30 to the wheel mount 28 are formed in the mount mounting portion 32d of the annular base 32. Further, one or more recesses 35 for adjusting the rotation balance are formed in the mount mounting portion 32d. The depression for adjusting the rotation balance is not formed on the outer peripheral side surface 32 a and the inner peripheral side surface 32 b of the annular base 32.

  The grinding operation of the grinding device 2 configured as described above will be described below. When the wafer 11 sucked and held by the chuck table 50 with the protective tape 23 down is positioned at the grinding position shown in FIG. 4, the grinding wheel 32 is moved to the chuck table while rotating the chuck table 50 in the direction of arrow a at, for example, 300 rpm. The grinding wheel 34 is rotated in the same direction as 50, that is, in the direction of the arrow b at 6000 rpm, for example, and the grinding unit feed mechanism 44 is operated to bring the grinding wheel 34 into contact with the back surface 11b of the wafer 11.

  Then, the grinding wheel 30 is ground and fed by a predetermined amount at a predetermined grinding feed speed (for example, 3 to 5 μm / second), and the wafer 11 is ground. The wafer is finished to a desired thickness, for example, 100 μm while measuring the thickness of the wafer using a contact-type thickness measurement gauge (not shown).

  During grinding of the wafer 11, grinding is performed while the grinding water is supplied to the grinding region via the hose 36 and the grinding water supply hole 42, but the waste liquid in which the grinding waste of the wafer 11 is mixed in the grinding water is removed from the grinding wheel 30. However, some waste liquid flows back to the inside of the grinding wheel and the inner peripheral side surface 32b of the annular base 32 and the grinding wheel disposed in an annular shape. It stays in the space defined by 34 and the wafer 11.

  In the grinding wheel 30 of the present embodiment, the recess 35 for adjusting the rotational balance is formed only on the mount mounting portion 32d of the annular base 32, and no recess is formed on the outer peripheral side surface 32a and the inner peripheral side surface 32b. Grinding debris mixed in is not deposited in the recess of the annular base 32 and grows like a snowman.

  As a result, a lump of grinding scrap that has grown in the conventional manner falls and abrasive grains such as diamond mixed in the lump are sandwiched between the wafer and the grinding wheel 34, causing a scratch on the ground surface of the wafer. Thus, the problem of reducing the bending strength can be avoided.

  Furthermore, the phenomenon that the lump of grinding waste mixed in the waste liquid clogs the grinding wheel 34 can be avoided, the number of dressings of the grinding wheel 34 can be reduced, and the productivity can be improved.

  Next, a grinding wheel 30A according to a second embodiment of the present invention will be described with reference to FIG. In the grinding wheel 30A of the second embodiment, only the back surface corresponding to the device region 17 of the wafer 11 is ground, and a ring-shaped reinforcing portion is formed on the back surface of the wafer corresponding to the outer peripheral surplus region 19 surrounding the device region 17. Grinding wheel suitable for

  Compared with the grinding wheel 30 of the first embodiment shown in FIG. 4, the grinding wheel 30 </ b> A of the present embodiment is formed with a small diameter. The grinding wheel 30A is attached to a wheel mount 28A fixed to the tip of the spindle 24A by screwing.

  The configuration of the annular base 32A of the grinding wheel 30A is the same as that of the annular base 32 except that the annular base 32A has a smaller diameter than the annular base 32 of the first embodiment shown in FIG. Therefore, the detailed description is abbreviate | omitted.

  In this embodiment, the rotation center of the chuck table 50 and the rotation center of the grinding wheel 30 </ b> A are eccentric, and the outer diameter of the grinding wheel 34 is smaller than the diameter of the boundary line between the device region 17 and the outer peripheral surplus region 19 of the wafer 11. The size is set to be larger than the radius of the boundary line, and the annular grinding wheel 34 is set so as to pass through the center of rotation of the chuck table 50.

  Similarly to the first embodiment, the grinding wheel 30A is rotated at 6000 rpm in the direction indicated by the arrow b while the chuck table 50 is rotated at 300 rpm in the direction indicated by the arrow a, and the grinding feed mechanism 44 is operated to operate the grinding wheel. A 30 A grinding wheel 34 is brought into contact with the back surface of the wafer 11. Then, the grinding wheel 30A is ground and fed downward by a predetermined amount at a predetermined grinding feed speed.

  As a result, as shown in FIG. 8, the region corresponding to the device region 17 is ground to form a circular recess 25 and the region corresponding to the outer peripheral surplus region 19 remains on the back surface of the semiconductor wafer 11. A ring-shaped reinforcing portion 27 is formed.

  Also in the grinding wheel 30A of the present embodiment, as in the grinding wheel 30 of the first embodiment, the depression for adjusting the rotational balance is formed only in the mount mounting portion of the annular base, so that the grinding waste mixed in the waste liquid is removed. It does not grow like a snowman by adhering to the depressions formed on the outer peripheral side surface and inner peripheral side surface of the grinding wheel 30A.

  As a result, a lump of grinding scrap that has grown in the conventional manner falls and diamond or other abrasive grains mixed in the lump are sandwiched between the wafer and the grinding wheel 34 and cracked at the base of the ring-shaped reinforcing portion 27. Can be prevented, and the bending strength of the wafer can be prevented from being lowered.

  Moreover, the phenomenon that the lump of grinding waste mixed in the waste liquid clogs the grinding wheel 34 can be reduced, and the number of times of dressing the grinding wheel 34 can be reduced.

It is a surface side perspective view of a semiconductor wafer. It is a back surface side perspective view of the semiconductor wafer where the protective tape was stuck. It is an external appearance perspective view of a grinding device. It is a perspective view which shows the positional relationship of the chuck table at the time of grinding, and the grinding wheel of 1st Embodiment. It is a perspective view of the grinding wheel of a 1st embodiment. FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. It is a partially expanded sectional view of FIG. It is a perspective view which shows the relationship between the wafer hold | maintained at the chuck table at the time of grinding, and the grinding wheel of 2nd Embodiment.

Explanation of symbols

2 Grinding device 11 Semiconductor wafer 16 Grinding unit 30, 30A Grinding wheel 32, 32A Annular base 34 Grinding wheel 35 Recess 42 Grinding water supply hole 50 Chuck table

Claims (1)

A grinding wheel detachably mounted on the wheel mount of a grinding apparatus having a spindle that is rotationally driven and a wheel mount coupled to the tip of the spindle,
An annular base having an inner peripheral side surface, an outer peripheral side surface and a mount mounting portion mounted on the wheel mount;
A plurality of grinding wheels arranged in a ring shape at the free end of the annular base,
A recess for adjusting the rotation balance is formed only in the mount mounting portion of the annular base. When a grinding wheel is mounted on the wheel mount, the recess is mounted on the wheel mount and the annular base. A grinding wheel that is sealed by a portion and is not exposed to the outside .

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