JP6283486B2 - Grinding wheel - Google Patents

Description

The present invention relates to wafer, leaving a ring-shaped reinforcing portion on the outer peripheral marginal area of the back surface of the wafer on the grinding WHEEL for grinding recesses.

  A wafer on which a plurality of devices are formed is divided into individual devices by a dividing device such as a dicing device, and used for various electronic devices such as a mobile phone and a personal computer. In order to reduce the weight and size of electronic equipment, the thickness of the wafer is thinly ground to about 100 μm to 50 μm to reduce the weight and size of the device.

  Here, if the wafer is thinly ground, it becomes difficult to handle. Therefore, only the back surface corresponding to the device area of the wafer is ground and thinned to leave a ring-shaped reinforcing portion in the outer peripheral area surrounding the device area, thereby leaving the wafer. Has been proposed (see, for example, Patent Document 1).

JP 2007-019461 A

  When the region corresponding to the device region on the back surface of the wafer is ground to form the thickness of the device region to a predetermined thickness, and when the annular reinforcing portion is formed by leaving the outer peripheral surplus region on the back surface of the wafer, Due to the R shape formed at the outer peripheral corner of the grinding surface, an R shape is formed at the boundary between the device region and the outer peripheral surplus region, and the thickness of the device adjacent to the outer peripheral surplus region is directed toward the outer peripheral surplus region. There is a problem of becoming thicker.

The present invention was made in view of the above, in the thickness of the device area of the wafer to provide a grinding WHEEL be suppressed to become thicker toward the outer peripheral marginal area.

In order to solve the above-described problems and achieve the object, the grinding wheel of the present invention includes a device region in which a plurality of devices are formed on a surface and an outer peripheral surplus region surrounding the device region. A grinding wheel for use in a wafer processing method for grinding a back surface of a region into a concave shape and forming a ring-shaped reinforcing portion on a back surface of the outer peripheral surplus region, comprising: a disc-shaped grindstone base; and the grindstone base A plurality of grinding wheels mounted in an annular shape on one end surface thereof, and the grinding wheels are formed of abrasive grains and a bonding agent, and are formed in at least two layers, an inner peripheral side and an outer peripheral side of the annular shape. And the bending strength of the inner peripheral layer grindstone is smaller than the bending strength of the outer peripheral layer grindstone, and both the inner peripheral layer grindstone and the outer peripheral layer grindstone are: At the center of the spindle where the grinding wheel is mounted Cormorant is formed in a rectangular shape in cross section, the grindstone of the inner circumferential side of the layer of the grinding wheels, 10 to 20 MPa in flexural strength defined by JIS R 1601, grinding of the outer circumferential side of the layer, in flexural strength 30 It is formed by vitrified bond of ˜40 MPa .

  In the present invention, since the grindstone of the outer peripheral layer of the grinding wheel is formed of a layer harder than the grindstone of the inner peripheral layer, wear of the outer peripheral layer of the grinding grindstone can be suppressed. For this reason, the present invention makes it difficult to form an R shape at the boundary between the device region and the outer peripheral surplus region on the back surface of the wafer, and the R shape is formed on the inner peripheral surface of the ring-shaped reinforcing portion. Can be suppressed. Therefore, this invention can suppress that the thickness of the device area | region of a wafer becomes thick toward an outer peripheral surplus area | region.

FIG. 1 is a perspective view of a grinding apparatus that performs a wafer processing method according to an embodiment. FIG. 2 is a plan view of the wafer processed by the wafer processing method according to the embodiment. FIG. 3 is an exploded perspective view of the grinding wheel according to the embodiment. FIG. 4 is a cross-sectional view during grinding of the wafer processing method according to the embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the structures described below can be combined as appropriate. Various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

Embodiment
A grinding wheel and wafer processing method according to the present embodiment will be described with reference to the drawings. FIG. 1 is a perspective view of a grinding apparatus that performs a wafer processing method using the grinding wheel according to the embodiment. FIG. 2 is a plan view of the wafer that is processed by the wafer processing method using the grinding wheel according to the embodiment. 3 is an exploded perspective view of the grinding wheel according to the embodiment, and FIG. 4 is a cross-sectional view of the wafer processing method using the grinding wheel according to the embodiment during grinding.

  The wafer processing method according to the present embodiment is a wafer W processing method (hereinafter simply referred to as a processing method) for processing the wafer W shown in FIG. 2 using the grinding wheel 22 shown in FIG.

  Note that the wafer W processed by the processing method according to the present embodiment is a disk-shaped semiconductor wafer or optical device wafer having a base material of silicon, sapphire, gallium, or the like in the present embodiment. As shown in FIG. 2, the wafer W includes a device region W1 in which a plurality of devices D are formed on the surface Wa, and an outer peripheral surplus region W2 surrounding the device region W1. The wafer W has a protective tape T attached to the surface Wa, and the surface Wa side is held by the suction table 10 of the grinding apparatus 1 provided with the grinding wheel 22 via the protective tape T. The wafer W is ground into a concave shape from the back surface Wb (shown in FIG. 1) by the grinding device 1 to form a concave WR (shown in FIG. 1).

  The grinding apparatus 1 grinds the back surface of the device region W1 of the wafer W into a concave shape to form a concave portion WR. That is, the grinding apparatus 1 performs so-called TAIKO processing on the wafer W. As shown in FIG. 1, the grinding apparatus 1 includes a suction table 10 that holds a wafer W, and a grinding unit 20 that grinds the wafer W held on the suction table 10.

  The suction table 10 is a so-called TAIKO processing suction table. The suction table 10 has a disk shape in which a portion constituting the surface is made of porous ceramic or the like. The suction table 10 is connected to a vacuum suction source (not shown) through a vacuum suction path (not shown) to suck the wafer W placed on the surface. Hold by. The suction table 10 is rotatably provided around a vertical axis by a rotation drive source (not shown).

  The grinding unit 20 includes a spindle 21 that is rotated around a vertical axis, and a grinding wheel 22 that is attached to the lower end of the spindle 21.

  The grinding wheel 22 is used in a processing method, and includes a disc-shaped grinding wheel base 23 and a plurality of grinding wheels 24 as shown in FIG. The grindstone base 23 is attached to a flange portion 25 provided at the tip of the spindle 21 with bolts 26. The grinding wheel 24 is mounted in an annular shape on one end surface 23 a of the grinding wheel base 23. The grinding wheel 24 is arranged in an annular shape on the outer edge portion of the one end surface 23 a of the grinding wheel base 23. The diameter of the circle surrounded by the outer peripheral edges of the plurality of grinding wheels 24 is smaller than the radius of the wafer W.

  The grinding wheel 24 is formed of abrasive grains and a bonding agent that hardens the abrasive grains. As shown in FIG. 4, the grinding wheel 24 includes at least an annular inner peripheral first grindstone 24a and an outer peripheral second grindstone 24b. It is formed in two layers. The bending strength of the first grindstone 24a that is the grindstone of the inner peripheral layer is formed to be smaller than the bending strength of the second grindstone 24b that is the grindstone of the outer peripheral layer. The bending strength of the first grindstone 24a and the second grindstone 24b is appropriately changed by appropriately changing the amount of the binder mixed in the bond agent.

  In the present embodiment, the first grindstone 24 a that is a layer on the inner peripheral side of the grinding grindstone 24 is formed to have a bending strength defined by JIS (Japanese Industrial Standard) R 1601 at 10 MPa to 20 MPa. The first grindstone 24a is formed of a vitrified bond of 10 MPa to 20 MPa with a bending strength defined by JIS R 1601, for example, when the bonding agent is composed of a porous vitrified bond.

  Moreover, in this embodiment, the 2nd grindstone 24b which is a layer by the side of the outer periphery of the grinding grindstone 24 is formed in 30-40 MPa by the bending strength prescribed | regulated by JISR1601. The second grindstone 24b is formed of a vitrified bond of 30 MPa to 40 MPa with a bending strength defined by JIS R 1601, for example, when the bonding agent is composed of a high strength vitrified bond. Thus, the bending strength as used in the field of this invention has shown the bending strength prescribed | regulated by JISR1601.

  Further, in the present embodiment, the grinding wheel 24 is obtained by sintering one of the first grinding wheel 24a and the second grinding wheel 24b after performing the other press molding. Moreover, in this embodiment, the 1st grindstone 24a and the 2nd grindstone 24b are comprised by the same composition except the quantity of binder being changed suitably and bending strength differing. That is, the first grindstone 24a and the second grindstone 24b are made of the same abrasive grains and bond material, and are also formed with the same grain size and abrasive concentration.

  Next, a processing method using the grinding apparatus 1 will be described. In the processing method using the grinding apparatus 1, the back surface of the device region W1 of the wafer W is ground into a concave shape using the grinding wheel 22, and the ring-shaped reinforcing portion WS (shown in FIG. 1 and the like) is formed on the back surface of the outer peripheral surplus region W2. ). In the processing method using the grinding apparatus 1, first, the protective tape T attached to the surface Wa of the wafer W is placed on the surface of the suction table 10, and the surface Wa side of the wafer W is passed through the protective tape T. The suction table 10 is suction-held. The processing method is such that the outer peripheral edge of the grinding wheel 24 of the grinding wheel 22 is positioned at a position corresponding to the inner peripheral edge of the back surface of the outer peripheral surplus area W2 of the wafer W and the center of the wafer W, and the grinding wheel 24 is moved to the wafer W. Is pressed against the back surface Wb. The processing method is to rotate the suction table 10 holding the wafer W around the axis while supplying the grinding water to the wafer W from a grinding water supply unit (not shown), and to rotate the grinding unit 20 in the same direction as the suction table 10. Rotate around the axis.

  In the processing method, the grinding apparatus 1 grinds the back surface of the device region W1 of the wafer W, and processes the back surface of the device region W1 into a concave shape. In the processing method, the concave portion WR is formed on the back surface Wb of the wafer W, and the ring-shaped reinforcing portion WS corresponding to the outer peripheral surplus region W2 is formed on the outer periphery of the concave portion WR.

At this time, the first grinding wheel 24 a is mainly subjected to rough grinding the back surface of the device region W1 of the wafer W, with a second grinding wheel 24 b processes the back surface of the device region W1 of the wafer W in a concave shape The inner peripheral surface IC of the recess WR and the outer edge portion of the bottom surface BR of the recess WR are finish-ground. As described above, the processing method forms the reinforcing portion WS while leaving the outer peripheral surplus region W2 without grinding the back surface of the outer peripheral surplus region W2 of the wafer W with the grinding wheel 22.

Then, the wafer W is on the bottom BR inner Specification raised grinding the inner peripheral side of the peripheral surface IC is not subjected portion of the reinforcing section WS of the recess WR, is subjected to finish grinding using the finishing grindstone . After that, the wafer W is subjected to stress release that removes a fractured layer during grinding by spin etching or the like.

  According to the grinding wheel 22 and the processing method according to the embodiment, the second grindstone 24b on the outer peripheral side of the grinding grindstone 24 is formed of a layer in which the bond agent is harder than the first grindstone 24a on the inner peripheral side. For this reason, according to the grinding wheel 22 and the processing method, the wear of the second grindstone 24b on the outer peripheral side of the grinding grindstone 24 can be suppressed more than the wear of the first grindstone 24a, and the device region W1 on the back surface Wb of the wafer W. It is possible to make it difficult to form an R shape at the boundary between the outer peripheral surplus region W2. Therefore, according to the grinding wheel 22 and the processing method, it is possible to prevent the R shape from being formed between the inner peripheral surface IC of the ring-shaped reinforcing portion WS and the bottom surface BR of the concave portion WR. Therefore, according to the grinding wheel 22 and the processing method, it is possible to suppress the thickness of the device region W1 of the wafer W from becoming thicker toward the outer peripheral surplus region W2. Furthermore, according to the grinding wheel 22 and the processing method, since the bonding agent for the first grindstone 24a and the second grindstone 24b is composed of vitrified bonds, the first grindstone 24a and the second grindstone 24b are in close contact with each other. However, the back surface of the device region W1 can be reliably processed into a concave shape without being mixed.

  In the embodiment described above, the bending strength of the first grindstone 24a is formed smaller than the bending strength of the second grindstone 24b. However, in the present invention, the concentration degree of the second grindstone 24b may be formed higher than the concentration degree of the first grindstone 24a. In this case, the concentration of the first grindstone 24a is preferably 10 to 20 (volume%), and the concentration of the second grindstone 24b is desirably 20 to 30 (volume%). It is desirable that the bonding agent of the second grindstone 24b be vitrified bond. Further, it is desirable that the first grindstone 24a and the second grindstone 24b are made of the same material for the abrasive grains and the bonding agent, and the abrasive grains have the same grain size and bending strength. The degree of concentration represents the amount of abrasive grains contained in the grindstones 24a and 24b. The concentration of the second grindstone 24b is set to 30 (volume%) or less because when the concentration exceeds 30 (volume%), the second grindstone 24b becomes too brittle and wear increases. This is because the R shape is easily formed.

  By setting the concentration degree of the first grindstone 24a to 10 to 20 (volume%) and the concentration degree of the second grindstone 24b to 20 to 30 (volume%), the second grindstone on the outer peripheral side of the grinding wheel 24 is obtained. 24b has improved grinding performance than the first grindstone 24a, and can suppress the wear of the second grindstone 24b more than the wear of the first grindstone 24a. It is possible to make it difficult to form an R shape at the boundary. Therefore, the inner circumference of the ring-shaped reinforcing portion WS is set such that the concentration of the first grindstone 24a is 10 to 20 (volume%) and the concentration of the second grindstone 24b is 20 to 30 (volume%). An R shape is prevented from being formed between the surface IC and the bottom surface BR of the recess WR. Therefore, the thickness of the device region W1 of the wafer W is set such that the concentration of the first grindstone 24a is 10 to 20 (volume%) and the concentration of the second grindstone 24b is 20 to 30 (volume%). Can be prevented from becoming thicker toward the outer peripheral surplus region W2.

  Next, the inventor of the present invention made a trial production of the grinding wheel 24 and attached the trial grinding wheel 24 to the grinding wheel 22 to grind the wafer W, thereby confirming the effect of the present invention. The results are shown in Table 1 below.

  The product 1 of the present invention in Table 1 uses abrasive grains made of diamond having a particle size of 50 μm and a bonding agent made of vitrified bond, and the bending strength of the first grindstone 24a is 15 MPa. The bending strength of the grindstone 24b was set to 35 MPa. The concentration of the first grindstone 24a and the second grindstone 24b was 20% by volume.

  The product 2 of the present invention in Table 1 uses abrasive grains composed of diamond having a particle diameter of 50 μm and a bonding agent composed of vitrified bonds, and the concentration of the first grindstone 24a is 15% by volume. The concentration of the second grindstone 24b was set to 25% by volume. The bending strength of the first grindstone 24a and the second grindstone 24b was 15 MPa.

  Comparative Example 1 in Table 1 uses abrasive grains composed of diamond having a particle size of 50 μm and a bonding agent composed of vitrified bonds, and has a grinding wheel 24 as a one-layer structure with a bending strength of 15 MPa. The concentration of the grindstone 24 was set to 15% by volume.

  Comparative Example 2 in Table 1 uses abrasive grains made of diamond having a particle size of 50 μm and a bonding agent made of resin, and the first grinding wheel 24a has a bending strength of 15 MPa. The bending strength of 24b was set to 35 MPa. The concentration of the first grindstone 24a and the second grindstone 24b was 15% by volume.

  The circles in Table 1 indicate that there is almost no R-shape and that the grindstones are not mixed. The crosses in Table 1 indicate that an R shape is generated and that the grindstones are mixed.

  According to Table 1, in Comparative Example 1, an R shape is formed between the inner peripheral surface IC of the ring-shaped reinforcing portion WS and the bottom surface BR of the recess WR, whereas in the products 1 and 2 of the present invention. The R shape was hardly formed between the inner peripheral surface IC of the ring-shaped reinforcing portion WS and the bottom surface BR of the concave portion WR. Accordingly, the bending strength of the first grindstone 24a is set to 10 to 20 MPa, the bending strength of the second grindstone 24b is set to 30 to 40 MPa, and the concentration degree of the first grindstone 24a is set to 10 to 20 (volume%). In addition, by setting the concentration degree of the second grindstone 24b to 20 to 30 (volume%), it is possible to suppress the thickness of the device region W1 of the wafer W from becoming thicker toward the outer peripheral surplus region W2. It became clear.

  According to Table 1, in Comparative Example 2, since the bonding agent is made of a resin, the first layer corresponding to one of the first grindstone 24a and the second grindstone 24b and the other correspond to the other at the time of manufacture. When the second layer is filled and then sintered by hot iron pressing, the first layer and the second layer are mixed, and there is a possibility that the difference between the first grindstone 24a and the second grindstone 24b is eliminated. . In contrast, in the products 1 and 2 of the present invention, one of the first grindstone 24a and the second grindstone 24b is sintered after press molding and after the other press molding is performed. And the 2nd grindstone 24b closely_contact | adheres and does not mix. Thereby, it became clear that the back surface of the device region W1 can be reliably processed into a concave shape by configuring both the first grindstone 24a and the second grindstone 24b with vitrified bonds.

  In the embodiment described above, the grinding wheel 24 having a two-layer structure is used. However, the grinding wheel 24 may have a three or more layer structure without departing from the gist of the present invention. At this time, it is desirable to decrease the bending strength of each layer toward the inner peripheral side, or to lower the concentration degree of each layer toward the inner peripheral side.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Adsorption table 22 Grinding wheel 23 Grinding wheel base 23a One end surface 24 Grinding wheel 24a First whetstone 24b Second whetstone D Device W Wafer W1 Device area W2 Outer peripheral area Wa Surface WS Reinforcement part

Claims (1)

A wafer having a device region having a plurality of devices formed on the surface and an outer peripheral surplus region surrounding the device region, the back surface of the device region is ground into a concave shape, and a ring-shaped reinforcement is formed on the rear surface of the outer peripheral surplus region. A grinding wheel used in a method of processing a wafer forming a part,
A disk-shaped grinding wheel base, and a plurality of grinding wheels mounted in an annular shape on one end surface of the grinding wheel base,
The grinding wheel is formed of abrasive grains and a bonding agent, and is formed in at least two layers of the annular inner peripheral side and outer peripheral side, and the bending strength of the inner peripheral layer of the grindstone is the outer peripheral layer. The grinding wheel of the inner circumferential layer and the grinding wheel of the outer circumferential layer are both formed in a rectangular shape in a cross section along the axis of the spindle on which the grinding wheel is mounted. It is,
The grinding wheel of the inner circumferential side layer of the grinding wheel is formed of a vitrified bond having a bending strength of 10 to 20 MPa as defined in JIS R 1601, and the grinding wheel of the outer circumferential side layer of 30 to 40 MPa of a bending strength. A grinding wheel characterized by

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