JP2015053344A - Grinding wheel, and method for processing wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding wheel and a method for processing a wafer, capable of making a processing state of a ring-shaped reinforcement part excellent, in particular, in rough grinding processing when processing the wafer into a concave shape.SOLUTION: A grinding wheel 22 is used in a method for processing a wafer, in which: a rear face of a device region W1 of the wafer W is ground into a concaved shape, the device region having the device region W1 on which a plurality of devices are formed and an outer circumference excessive region W2 surrounding the device region W1; and a ring-shaped reinforcement part WS is formed on a rear face of the outer circumference excessive region W2. The grinding wheel 22 includes a grindstone base 23 and a plurality of grindstones 24 annularly fitted to one edge surface 23a of the grindstone base 23. The grindstones 24 are formed as two layers of first grindstones 24a on the annular outer peripheral side and second grindstones 24b on the inner peripheral side. Grain sizes of abrasive grains contained in the first grindstones 24a on the outer peripheral side are smaller than grain sizes of abrasive grains contained in the second grindstones 24a on the inner peripheral side.

Description

  The present invention relates to a grinding wheel and a wafer processing method for grinding a wafer into a concave portion while leaving a ring-shaped reinforcing portion in an outer peripheral surplus region on the back surface of the wafer.

  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).

  Here, in order not to cause troubles such as breakage after singulation into the device area or chip of the concave wafer, when grinding the back surface corresponding to the device area so as not to leave processing damage on the wafer, as much as possible It is necessary to finish with a grindstone with a small abrasive grain size. However, if grinding is performed from the original thickness of the wafer with a grindstone made of fine abrasive grains, not only will the time required for the process become longer and the productivity will be lowered, but also the wear of the grindstone will be faster and the consumption tool cost will be higher. There's a problem. Then, after grinding to some extent by rough grinding, finish grinding is performed with a grindstone of fine abrasive grains (see, for example, Patent Document 2).

JP 2007-019461 A JP 2009-176896 A

  At the time of finish grinding, the grinding wheel for finishing is positioned slightly on the inner peripheral side from the inner wall of the recess at the time of rough grinding, and the grinding is slowly performed to form a finish concave shape inside the recess at the time of rough grinding. Therefore, the concave inner wall of the ring-shaped reinforcing part is ground with a rough grindstone for rough grinding, and grinding marks may remain even after etching with subsequent stress release, or during transportation There is a problem of chipping from the ring-shaped reinforcing portion.

  The present invention has been made in view of the above, and when processing a wafer into a concave shape, a grinding wheel and a wafer capable of improving the processing state of a ring-shaped reinforcing portion particularly in rough grinding processing. It is to provide a processing method.

  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 face thereof, and the grinding wheels are formed in at least two layers, a first grinding wheel on the outer circumferential side of the annular shape and a second grinding wheel on the inner circumferential side. The particle diameter of the abrasive grains contained in the first grindstone on the outer peripheral side is smaller than the grain diameter of the abrasive grains contained in the second grindstone on the inner peripheral side.

  The method for processing a wafer according to the present invention includes the grinding wheel according to claim 1, wherein the back surface of the device region of the wafer is provided with a device region having a plurality of devices formed on the surface and an outer peripheral surplus region surrounding the device region. A method of processing a wafer, wherein the wafer is ground into a concave shape and a ring-shaped reinforcing portion is formed on the back surface of the outer peripheral surplus region, the front side of the wafer being held on a suction table, and the rear surface of the outer peripheral surplus region of the wafer The outer peripheral edge of the first grindstone of the grinding wheel is positioned at a position corresponding to the inner peripheral edge of the wafer, and the back surface of the device region of the wafer is processed into a concave shape.

  Since the present invention uses a grinding wheel having a two-layer structure in which abrasive grains for finish grinding are contained on the outer peripheral side of the grinding wheel and normal abrasive grains are contained on the inner peripheral side, a ring shape is used. The inner peripheral side of the reinforcing portion is ground with abrasive grains for finish grinding on the outer peripheral side. For this reason, this invention can make the processing state of the internal peripheral surface of a ring-shaped reinforcement part favorable, and can make it a favorable surface state in the case of stress release in a later process. Further, since the inner peripheral layer contains abrasive grains for normal rough grinding, an excessive decrease in processing speed can be suppressed.

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. FIG. 5 is a cross-sectional view of the wafer processing method according to the embodiment during finish grinding.

  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. FIG. 3 is an exploded perspective view of the grinding wheel according to the embodiment, FIG. 4 is a cross-sectional view of the wafer processing method using the grinding wheel according to the embodiment during grinding, and FIG. It is sectional drawing in the finish grinding process of the processing method of the wafer using the grinding wheel which concerns on a form.

  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 composed of a bonding agent such as abrasive grains and vitrified bonds, and is configured by mixing abrasive grains, vitrified bonds, and a binder. As shown in FIG. 4, the grinding wheel 24 is formed in at least two layers of an annular outer peripheral first grindstone 24 a and an inner peripheral second grindstone 24 b. The particle size of the abrasive grains contained in the first grindstone 24a on the outer peripheral side is smaller than the grain size of the abrasive grains contained in the second grindstone 24b on the inner peripheral side. For example, the abrasive grains contained in the second grindstone 24b on the inner peripheral side are abrasive grains mainly used in rough grinding processing for thinning the wafer W, and for example, resin or vitrified bond abrasive grains are used. The thing with a particle size of about 40 micrometers-60 micrometers is used. The abrasive grains contained in the first grindstone 24a on the outer peripheral side are abrasive grains mainly used in finish grinding for removing grinding marks on the wafer W, and for example, grains having a grain size of about 2 μm to 20 μm are used. It is done.

  Moreover, in this embodiment, the 1st grindstone 24a and the 2nd grindstone 24b are comprised by the same composition except the particle size of an abrasive grain differing. That is, the first grindstone 24a and the second grindstone 24b have the same abrasive grain and bond material, the same amount of binder is mixed and the bending strength is equal, and the degree of concentration of the abrasive grains. Are equally formed.

  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. ). Note that the back surface Wb of the wafer W is constituted by the back surface of the device region W1 and 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. And the processing method positions the outer periphery of the 1st grindstone 24a of the grinding wheel 22 in the location corresponding to the inner periphery of the back surface of the outer peripheral surplus area | region W2 of the wafer W, and the center of the wafer W, Press against the back surface Wb of the wafer W. 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 second grindstone 24b mainly performs a rough grinding process on the back surface of the device area W1 of the wafer W, and the first grindstone 24a processes the back surface of the device area W1 of the wafer W into a concave shape and a recess WR. The outer peripheral portion of the inner peripheral surface IC and 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.

  And, as shown in FIG. 5, the wafer W has a portion that has not been subjected to finish grinding by the first grindstone 24 a on the inner peripheral side of the inner peripheral surface IC of the reinforcing portion WS of the bottom surface BR of the recess WR. Finish grinding using the finishing grindstone 30 is performed. 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, at least a two-layer structure in which abrasive grains for finish grinding are contained on the outer peripheral side and normal abrasive grains are contained on the inner peripheral side. A grinding wheel 24 is used. For this reason, according to the grinding wheel 22 and the processing method, the outer peripheral portion of the inner peripheral surface IC of the ring-shaped reinforcing portion WS and the bottom surface BR of the concave portion WR is ground with the abrasive grains for outer finish grinding. Sudden chipping can be suppressed from occurring on the inner peripheral surface IC of the portion WS and the bottom surface BR of the concave portion WR, and the processing state of the inner peripheral surface IC of the reinforcing portion WS and the bottom surface BR of the concave portion WR can be improved. Therefore, according to the grinding wheel 22 and the processing method, the inner peripheral surface IC and the bottom surface BR of the concave portion WR can be brought into a good surface state at the time of stress release in a later process, and the concave portion can be formed at the time of spin etching or the like. It is possible to suppress the occurrence of unevenness on the inner peripheral surface IC of the WR.

  Moreover, according to the grinding wheel 22 and the processing method, since the abrasive grains for normal rough grinding are contained on the inner peripheral side of the grinding wheel 24, an excessive decrease in the processing speed can be suppressed. 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 reduce the particle size of the abrasive grains contained in each layer toward the outer 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 (2)

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 in at least two layers, an annular outer peripheral first grindstone and an inner peripheral second grindstone, and the grain size of the abrasive grains contained in the outer peripheral first grindstone Is smaller than the grain size of the abrasive grains contained in the second grindstone on the inner peripheral side. The back surface of the device region of a wafer provided with a device region having a plurality of devices formed on the surface and an outer peripheral surplus region surrounding the device region is ground into a concave shape using the grinding wheel according to claim 1, A wafer processing method for forming a ring-shaped reinforcing portion on the back surface of the outer peripheral surplus region,
The front surface side of the wafer is held on the suction table, and the outer peripheral edge of the first grindstone of the grinding wheel is positioned at a position corresponding to the inner peripheral edge of the rear surface of the outer peripheral surplus area of the wafer. Processing the wafer into a concave shape.

Images