JP2023028797A - Wafer processing method - Google Patents

Abstract

To suppress dropping of relatively large offcuts when grinding a wafer.SOLUTION: A wafer processing method for thinning a wafer having a chamfered portion on the outer periphery thereof to achieve a finished thickness includes a trimming step of cutting the wafer along the outer peripheral edge thereof by cutting a first cutting blade from the surface side of the wafer into the chamfered portion up to a first depth position whose depth from the surface is equal to or more than the finished thickness, thereby forming an annular terrace portion, and a grinding step of polishing the wafer from the backside thereof to thin the wafer until the thickness thereof reaches the finished thickness. The wafer processing method further includes a first ultrasonic vibration cutting step in which before performing the grinding step, while applying ultrasonic vibration to a second cutting blade having a smaller blade thickness than the first cutting blade, the second blade is cut from the surface side of the wafer along the outer peripheral edge thereof up to a second depth position whose depth from the surface exceeds the first depth position, thereby forming a first annular cut groove.SELECTED DRAWING: Figure 4

Description

TECHNICAL FIELD The present invention relates to a wafer processing method for thinning a disk-shaped wafer having a chamfered portion on its outer periphery to a predetermined thickness.

In the manufacturing process of a device chip, a disk-shaped device such as an IC (Integrated Circuit) or LSI (Large Scale Integration) is formed in each of a plurality of regions partitioned by a plurality of intersecting dividing lines (streets). of wafers are used. A plurality of device chips each having a device is obtained by dividing the wafer along the planned division lines. Device chips are mounted on various electronic devices such as mobile phones and personal computers.

In recent years, there has been a marked trend toward miniaturization of electronic devices, and there is an increasing demand for thinner device chips. Therefore, before the wafer is divided, the wafer is thinned to a predetermined finish thickness by grinding from the back surface side with a grinding device, and the thinned wafer is divided. In this case, a thin device chip is finally obtained.

A chamfered portion is formed on the outer peripheral portion of the disk-shaped wafer by removing the corner portion. For this reason, when the wafer is thinned, a sharp knife-edge shape appears on the outer peripheral portion, and the wafer is easily damaged. Therefore, before grinding the wafer from the back side, an edge trimming process is performed to partially remove the chamfered portion by cutting the outer peripheral portion of the wafer from the front side to a depth equal to or greater than the finishing thickness (see Patent Document 1). ).

JP-A-2000-173961

However, when the wafer is thinned by grinding from the back side after performing the edge trimming process, the edge forming the terrace part is just before the grinding wheel reaches the annular terrace part protruding outside formed by the edge trimming process. The material breaks and relatively large remnants fall. Since the fallen mill ends accumulate in the drain for draining the grinding water used for grinding, the grinder has to be stopped and the drain must be cleaned frequently.

SUMMARY OF THE INVENTION 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 capable of suppressing the dropping of relatively large offcuts when grinding an edge-trimmed wafer.

According to one aspect of the present invention, there is provided a wafer processing method in which a disk-shaped wafer having a chamfered portion on the outer periphery is ground from the back surface side to thin the wafer to a finished thickness, wherein the wafer is thinned from the front surface side. A first cutting blade is cut into the chamfered portion to a first depth position whose depth from the surface is equal to or greater than the finished thickness, and the wafer is cut along the outer peripheral edge to form an annular terrace portion. a trimming step, after the trimming step, a protective member adhering step of adhering a protective member to the front surface of the wafer; and after the protective member adhering step, the wafer is ground from the back surface to A grinding step of thinning to a finished thickness, and before performing the grinding step, while applying ultrasonic vibration to a second cutting blade having a thinner blade thickness than the first cutting blade, the wafer. A first annular cutting groove is formed by cutting the second cutting blade from the surface side along the outer peripheral edge to a second depth position where the depth from the surface exceeds the first depth position A method of processing a wafer is provided further comprising a first ultrasonic vibration cutting step of forming a .

Preferably, before performing the grinding step, while applying ultrasonic vibration to the second cutting blade, the depth from the surface along the outer peripheral edge from the surface side of the wafer is the first depth further comprising a second ultrasonic vibration cutting step of cutting the second cutting blade to a third depth position exceeding the depth position to form a second annular cutting groove, wherein the first annular cutting groove and the second annular cut groove are formed concentrically.

More preferably, the first annular cut groove is formed inside the second annular cut groove, and the second depth position is closer to the surface than the third depth position.

Also preferably, the first ultrasonic vibration cutting step is performed after the trimming step.

In the wafer processing method according to one aspect of the present invention, before grinding the wafer from the back surface side, the wafer is cut along the outer peripheral edge with a first cutting blade to form an annular terrace portion. , with a second cutting blade to form a first annular cut groove. Since ultrasonic vibration is applied to the second cutting blade when forming the first annular cutting groove, the wafer is finely fractured near the formed first annular cutting groove to form a crushed layer. be done.

When the wafer is ground from the back side in a state where the terrace portion with the first annular cut groove is formed on the outer peripheral edge, the terrace portion is subdivided with the first annular cut groove and the crushed layer as the starting point of division, Fine scraps are produced. Since fine offcuts are easily washed away when dropped into the drain and are less likely to accumulate in the drain, there is no need to frequently clean the drain.

Therefore, according to one aspect of the present invention, there is provided a wafer processing method capable of suppressing relatively large offcuts from falling when grinding an edge-trimmed wafer.

It is a perspective view showing a wafer. It is a perspective view which shows a cutting device typically. FIG. 4 is a cross-sectional view schematically showing a wafer cut with a first cutting blade; FIG. 4 is a cross-sectional view schematically showing a wafer to be cut with a second cutting blade; FIG. 4 is an exploded perspective view schematically showing a second cutting unit; FIG. 4 is a cross-sectional view schematically showing a second cutting unit; FIG. 4 is a cross-sectional view schematically showing an enlarged part of a wafer in which a plurality of annular cut grooves are formed in a terrace portion; It is a perspective view which shows a grinding apparatus typically. FIG. 4 is a cross-sectional view schematically showing a wafer to which a protective member is adhered; FIG. 4 is a cross-sectional view schematically showing a wafer being ground; Further, it is a cross-sectional view schematically showing a wafer being ground. 4 is a flow chart showing the flow of each step of the wafer processing method according to the embodiment. 10 is a photograph showing, side by side, offcuts collected by implementing the wafer processing method according to the example and collected offcuts by implementing the wafer processing method according to the comparative example.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, a wafer to be processed by the wafer processing method according to the present embodiment will be described. FIG. 1 is a perspective view schematically showing a wafer 1. FIG.

The wafer 1 is a disk-shaped member made of a material such as silicon, and has a front surface 1a and a back surface 1b that are substantially parallel to each other. A plurality of planned division lines 3 arranged in a grid pattern are set on the front surface 1a of the wafer 1 so as to intersect each other. Devices 5, such as ICs and LSIs, are formed in respective regions partitioned by dividing lines 3 on the front surface 1a of the wafer 1. As shown in FIG. A region of the surface 1a of the wafer 1 where the devices 5 are formed is called a device region 7. FIG. An outer area surrounding the device area 7 is called a peripheral surplus area 9 .

The material, structure, size, etc. of the wafer 1 are not limited. For example, the wafer 1 may be a substrate made of a semiconductor other than silicon (GaAs, InP, GaN, SiC, etc.), sapphire, glass (quartz glass, borosilicate glass, etc.), or the like. Moreover, there are no restrictions on the type, number, shape, structure, size, arrangement, etc. of the devices 5 , and the devices 5 may not be formed on the wafer 1 .

If there is a corner on the outer periphery of the wafer 1, chipping or cracking is likely to occur when the wafer 1 receives an impact on the corner. If this chipping or crack progresses from the outer peripheral surplus region 9 to the device region 7, the device 5 is damaged. Therefore, the outer periphery 1c of the wafer 1 is chamfered in advance to remove the corners and form a rounded chamfered portion. FIG. 3 includes a cross-sectional view showing the chamfer of wafer 1. FIG.

When the wafer 1 is thinned by grinding from the back surface 1b side and divided along the dividing lines 3, a plurality of thin chips (device chips) each having a device 5 are manufactured. For dividing the wafer 1, for example, a cutting device having an annular cutting blade or a laser processing device having a laser processing unit for irradiating the wafer 1 with a laser beam is used. Device chips manufactured by these processing apparatuses are mounted on various electronic devices such as mobile phones and personal computers.

Next, in the wafer processing method according to the present embodiment, a cutting device for performing edge trimming and formation of an annular cut groove with a crushed layer will be described. FIG. 2 is a perspective view schematically showing the cutting device 2. As shown in FIG. However, the edge trimming process and the formation of the annular cut groove with the fracture layer need not be performed in the same cutting device.

The wafer 1 to be cut by the cutting device 2 is attached to, for example, an annular frame (not shown) having an opening with a diameter larger than the diameter of the wafer 1 and the annular frame so as to block the opening of the annular frame. It is carried into the cutting device 2 in a state integrated with the tape. When a frame unit is formed by integrating the wafer 1, the tape, and the annular frame by sticking the tape to the surface side of the wafer 1, the wafer 1 can be handled through the annular frame. easier.

The cutting device 2 includes a base 4 that supports each component. An opening 4a is formed in the front corner of the base 4, and a cassette support base 8 which is moved up and down by a lifting mechanism (not shown) is provided in the opening 4a. On the upper surface of the cassette support table 8, a cassette 10 is mounted which accommodates a plurality of wafers 1 each forming a part of the frame unit. Note that FIG. 1 shows only the outline of the cassette 10 for convenience of explanation.

A rectangular opening 4b is formed on the side of the cassette support 8 so that its longitudinal direction is along the X-axis direction (front-rear direction, processing feed direction). A ball-screw type X-axis moving mechanism (not shown), and a table cover 14 and a dust/splash proof cover 16 covering the upper part of the X-axis moving mechanism are arranged in the opening 4b. The X-axis movement mechanism includes an X-axis movement table (not shown) covered with a table cover 14, and moves this X-axis movement table in the X-axis direction.

A holding table 18 is arranged on the upper surface of the X-axis moving table so as to be exposed from the table cover 14 . The holding table 18 has a function of sucking and holding the wafer 1 placed on the holding surface 18a exposed upward. The holding table 18 is connected to a rotational drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the Z-axis direction (vertical direction).

The holding table 18 includes a porous member 18c having the same diameter as the wafer 1 and a frame covering the porous member 18c. A suction path (not shown) having one end connected to a suction source (not shown) such as an ejector provided outside the holding table 18 is formed inside the holding table 18 . The other end of the suction path reaches the porous member 18c.

The holding surface 18a of the holding table 18 exposes the upper surface of the porous member 18c. The upper surface of the porous member 18c has the same diameter as the wafer 1 and is formed substantially parallel to the X-axis direction and the Y-axis direction. Further, around the holding table 18, a plurality of clamps 18b are provided for fixing the annular frame supporting the wafer 1. As shown in FIG.

When holding the wafer 1 on the holding table 18 , first, the frame unit including the wafer 1 is placed on the holding surface 18 a of the holding table 18 . Then, the suction source and the porous member 18c are connected via the suction path, and a negative pressure is applied to the wafer 1 via the tape adhered to the back surface 1b of the wafer 1. FIG.

The cutting device 2 includes a transfer unit (not shown) that transfers the wafer 1 to the holding table 18 or the like in a region adjacent to the opening 4b. A temporary placement mechanism for temporarily placing the wafer 1 is provided at a position adjacent to the side of the cassette support table 8 . The temporary placement mechanism includes, for example, a pair of guide rails 12 that approach and separate while maintaining a state parallel to the Y-axis direction (indexing direction). The pair of guide rails 12 sandwich the wafer 1 drawn out from the cassette 10 by the transfer unit along the X-axis direction and align it at a predetermined position.

The wafer 1 aligned with the predetermined position is lifted up by the transport unit and transported to the holding table 18 . At this time, the pair of guide rails 12 are separated from each other and the wafer 1 is passed between the pair of guide rails 12 .

Above the holding table 18, a first cutting unit 24a and a second cutting unit 24b for cutting the wafer 1 with annular cutting blades are provided. A gate-shaped support structure 20 for supporting the first cutting unit 24a and the second cutting unit 24b is arranged on the upper surface of the base 4 so as to straddle the opening 4b.

A first moving unit 22a for moving the first cutting unit 24a in the Y-axis direction and Z-axis direction and a second cutting unit 24b for moving the second cutting unit 24b in the Y-axis direction and the Z-axis direction are provided on the upper front surface of the support structure 20. A second moving unit 22b is provided to allow the The first moving unit 22a has a Y-axis moving plate 28a, and the second moving unit 22b has a Y-axis moving plate 28b. The two Y-axis movement plates 28a, 28b are slidably mounted on a pair of Y-axis guide rails 26 arranged on the front surface of the support structure 20 along the Y-axis direction.

A nut portion (not shown) is provided on the back side (rear side) of the Y-axis moving plate 28a, and a Y-axis ball screw 30a substantially parallel to the Y-axis guide rail 26 is screwed into this nut portion. ing. A nut portion (not shown) is provided on the back side (rear side) of the Y-axis moving plate 28b, and a Y-axis ball screw 30b that is substantially parallel to the Y-axis guide rail 26 is screwed into this nut portion. are combined.

A Y-axis pulse motor 32a is connected to one end of the Y-axis ball screw 30a. By rotating the Y-axis ball screw 30a by the Y-axis pulse motor 32a, the Y-axis moving plate 28a moves along the Y-axis guide rail 26 in the Y-axis direction. A Y-axis pulse motor (not shown) is connected to one end of the Y-axis ball screw 30b. By rotating the Y-axis ball screw 30b with the Y-axis pulse motor, the Y-axis moving plate 28b moves along the Y-axis guide rail 26 in the Y-axis direction.

A pair of Z-axis guide rails 34a are provided along the Z-axis direction on the surface (front) side of the Y-axis moving plate 28a, and a pair of Z-axis guide rails 34a are provided on the surface (front) side of the Y-axis moving plate 28b in the Z-axis direction. A pair of Z-axis guide rails 34b are provided along. A Z-axis moving plate 36a is slidably attached to the pair of Z-axis guide rails 34a, and a Z-axis moving plate 36b is slidably attached to the pair of Z-axis guide rails 34b.

A nut portion (not shown) is provided on the back side (rear side) of the Z-axis moving plate 36a, and the nut portion is provided along a direction substantially parallel to the Z-axis guide rail 34a. A Z-axis ball screw 38a is screwed thereon. A Z-axis pulse motor 40a is connected to one end of the Z-axis ball screw 38a. By rotating the Z-axis ball screw 38a with this Z-axis pulse motor 40a, the Z-axis moving plate 36a moves along the Z-axis guide rail 34a. Move along the Z axis.

A nut portion (not shown) is provided on the back side (rear side) of the Z-axis moving plate 36b, and the nut portion is provided along a direction substantially parallel to the Z-axis guide rail 34b. A Z-axis ball screw 38b is screwed thereon. A Z-axis pulse motor 40b is connected to one end of the Z-axis ball screw 38b. By rotating the Z-axis ball screw 38b with this Z-axis pulse motor 40b, the Z-axis moving plate 36b moves along the Z-axis guide rail 34b. Move along the Z axis.

A first cutting unit 24a is provided below the Z-axis moving plate 36a. A camera unit 46a is provided at a position adjacent to the first cutting unit 24a for photographing the wafer 1 sucked and held by the holding table 18. As shown in FIG. A second cutting unit 24b is provided below the Z-axis moving plate 36b. A camera unit 46b is provided at a position adjacent to the second cutting unit 24b for photographing the wafer 1 sucked and held by the holding table 18. As shown in FIG.

The first moving unit 22a controls the positions of the first cutting unit 24a and the camera unit 46a in the Y-axis direction and the Z-axis direction, and the second moving unit 22b controls the Y-axis direction of the second cutting unit 24b and the camera unit 46b. Axial and Z-axis positions are controlled. The position of the first cutting unit 24a and the position of the second cutting unit 24b are independently controlled.

An opening 4c is formed at a position opposite to the opening 4a with respect to the opening 4b. A cleaning unit 48 for cleaning the wafer 1 is arranged in the opening 4 c , and the wafer 1 cut on the holding table 18 is cleaned by the cleaning unit 48 . The wafers 1 cleaned by the cleaning unit 48 are stored in the cassette 10 again. Each cutting unit 24a, 24b will be described in more detail below.

FIG. 3 is a cross-sectional view schematically showing the wafer 1 cut by the first cutting unit 24a. The first cutting unit 24a is used for trimming to cut the wafer 1 along the outer circumference 1c to remove a part of the chamfered portion. 3, the clamp 18b of the holding table 18, the camera unit 46a, the annular frame, the tape, etc. are omitted.

The first cutting unit 24a includes a spindle 50a along the Y-axis direction and a rotational drive source (not shown) such as a motor connected to the base end of the spindle 50a. An annular first cutting blade 56a is fixed to the tip of the spindle 50a via a flange mechanism 52a.

The first cutting blade 56a has an annular base 58a made of a material such as aluminum and having an insertion hole formed in the center, and a grindstone portion 60a fixed to the outer circumference of the base 58a. Type called cutting blade. However, the first cutting blade 56a is not limited to the hub type.

A grindstone portion 60a containing countless abrasive grains and a bonding material (bond) for dispersing and fixing the abrasive grains is fixed to the outer periphery of the base 58a. For example, the abrasive grains are made of a material such as diamond or cubic boron nitride (cBN), and the binding material is a nickel plating layer, resin bond, vitrified bond, metal bond, or the like. The blade thickness of the first cutting blade 56a used for edge trimming is determined according to the width of the terrace formed on the wafer 1, for example. However, the method for determining the blade thickness is not limited to this. The blade thickness of the first cutting blade 56a is preferably 2 mm or more, for example. However, the blade thickness is not limited to this.

A boss portion (not shown) protruding in the Y-axis direction of the flange mechanism 52a is inserted into the insertion hole of the base 58a, the first cutting blade 56a is brought into contact with the flange surface of the flange mechanism 52a, and fixed to the tip of the boss portion. Tighten the nut 54a. The first cutting blade 56a can then be fixed to the tip of the spindle 50a. The first cutting unit 24a also includes a pair of cutting fluid supply nozzles 62a arranged to sandwich the lower portion of the first cutting blade 56a fixed to the tip of the spindle 50a.

When the rotary drive source is operated to rotate the spindle 50a, the first cutting blade 56a can be rotated. can be cut. At this time, a cutting fluid such as pure water is sprayed from the cutting fluid supply nozzle 62a onto the wafer 1 and the first cutting blade 56a, and the cutting fluid removes chips and frictional heat generated by cutting.

FIG. 4 is a cross-sectional view schematically showing the wafer 1 cut by the second cutting unit 24b. 4, the clamp 18b of the holding table 18, the camera unit 46b, the annular frame, the tape, etc. are omitted. 5 is an exploded perspective view schematically showing the second cutting unit 24b, and FIG. 6 is a sectional view schematically showing the second cutting unit 24b. The second cutting unit 24b is used to cut the wafer 1 along the outer periphery to form an annular cut groove in the outer peripheral surplus region 9 .

The second cutting unit 24b includes a spindle 50b along the Y-axis direction and a housing 51b that rotatably accommodates the base end side of the spindle 50b. A rotary drive source (not shown) such as a motor connected to the proximal end of the spindle 50b is housed inside the housing 51b. An annular second cutting blade 56b is fixed to the tip of the spindle 50b via a flange mechanism 52b. The second cutting unit 24b includes a pair of cutting fluid supply nozzles 62b arranged to sandwich the lower part of the second cutting blade 56b fixed to the tip of the spindle 50b.

The second cutting blade 56b is a so-called washer-type cutting blade which consists of a grindstone portion and does not have an annular base. However, the second cutting blade 56b is not limited to the washer type. The grindstone portion includes a large number of abrasive grains such as diamond, and a binding material for dispersing and fixing the abrasive grains. For example, the abrasive grains are diamond, cubic boron nitride, etc., and the binding material is metal, ceramics, resin, or the like.

The blade thickness of the second cutting blade 56b used for forming the annular cutting groove in the outer peripheral surplus region 9 is preferably determined according to the width of the annular cutting groove to be formed, and is, for example, 300 μm. is preferred. However, the blade thickness of the second cutting blade 56b is not limited to this.

The second cutting unit 24b includes an ultrasonic vibration imparting unit that imparts ultrasonic vibrations radially outward along the second cutting blade 56b. The configuration of the second cutting unit 24b that applies ultrasonic vibration while rotating the second cutting blade 56b will be further described.

FIG. 5 is an exploded perspective view showing the second cutting unit 24b. A second cutting blade 56b attached to the second cutting unit 24b has a first surface 57a and a second surface 57b that are substantially parallel to each other, and a second cutting blade 56b has a second cutting blade 56b at its center. A circular opening 57c is provided through the blade 56b in the thickness direction.

A tip portion (one end side) of the spindle 50b is exposed from the housing 51b, and a screw portion (male screw) 53 is formed on the outer peripheral surface of the tip portion of the spindle 50b. A rotational drive source (not shown) such as a motor is connected to the base end (the other end) of the spindle 50b. This rotational drive source causes the spindle 50b to rotate around a rotation axis substantially parallel to the Y-axis direction.

A flange mechanism 52b to which a second cutting blade 56b is attached is fixed to the tip of the spindle 50b. The flange mechanism 52b has a rear flange 64 that supports the second cutting blade 56b from behind and a front flange 66 that supports the second cutting blade 56b from the front.

The rear flange 64 includes a disk-shaped flange portion 68 and a cylindrical support shaft (boss portion) 70 protruding from the central portion of the surface 68 a of the flange portion 68 . The flange portion 68 is provided with an opening 64 a penetrating through the central portion of the flange portion 68 and the central portion of the support shaft 70 . A threaded portion (male screw) 70 a is formed on the outer peripheral surface of the tip portion of the support shaft 70 .

A rear flange 64 of the flange mechanism 52b is attached to the spindle 50b such that the tip of the spindle 50b is inserted into the opening 64a. In this state, the annular fixing nut 72 is screwed onto the threaded portion 53 formed at the tip of the spindle 50b and tightened. Thereby, the rear flange 64 of the flange mechanism 52b is fixed to the tip of the spindle 50b.

An annular front flange (holding flange) 66 made of metal or the like is attached to the rear flange 64 . The front flange 66 has a first side (front side) 66a and a second side (back side) 66b (see FIG. 6) that are generally parallel to each other. A circular opening 66c is provided in the central portion of the front flange 66 so as to pass through the front flange 66 in the thickness direction.

The second cutting blade 56b and the front flange 66 are attached to the rear flange 64 by sequentially inserting the support shaft 70 of the rear flange 64 into the opening 57c of the second cutting blade 56b and the opening 66c of the front flange 66. . In this state, when the fixing nut 74 is tightened on the threaded portion 70a formed on the support shaft 70, the second cutting blade 56b and the front flange 66 are fixed to the flange mechanism 52b. Thereby, the second cutting blade 56b is sandwiched between the rear flange 64 and the front flange 66 and fixed to the tip of the spindle 50b.

With the second cutting blade 56b attached to the tip of the spindle 50b, when the spindle 50b is rotated by a rotational drive source connected to the spindle 50b, the second cutting blade 56b is moved substantially parallel to the Y-axis direction. Rotate around the axis of rotation at a predetermined number of revolutions.

FIG. 6 is a cross-sectional view showing the second cutting unit 24b with the second cutting blade 56b attached. An annular convex portion 68 b protruding from a surface 68 a is provided along the outer peripheral edge of the rear flange 64 on the outer peripheral portion of the flange portion 68 of the rear flange 64 . In addition, a plurality of through holes (slits) 68c that penetrate the flange portion 68 in the thickness direction are provided in a region inside the convex portion 68b of the flange portion 68. As shown in FIG. For example, four arc-shaped through holes 68c are formed in the flange portion 68 at approximately equal intervals along the circumferential direction of the flange portion 68 (see FIG. 5).

On the other hand, the front flange 66 has an outer peripheral portion along which an annular protrusion 66 d protruding from the second surface 66 b is provided along the outer peripheral edge of the front flange 66 . A plurality of through-holes (slits) 66e are formed through the front flange 66 in the thickness direction in a region inside the convex portion 66d of the front flange 66. As shown in FIG. For example, the front flange 66 is formed with four arc-shaped through holes 66e along the circumferential direction of the front flange 66 at approximately equal intervals (see FIG. 5).

An annular support member 76a that supports the first surface 57a side of the second cutting blade 56b is provided on the tip surface of the convex portion 68b of the flange portion 68. As shown in FIG. A ring-shaped support member 76b is provided on the tip surface of the convex portion 66d of the front flange 66 to support the second surface 57b side of the second cutting blade 56b. The support members 76a and 76b are made of synthetic resin or the like, and are in contact with the second cutting blade 56b to sandwich the second cutting blade 56b. The supporting members 76a and 76b are preferably members having a hardness of 40 or more as measured by a durometer type D.

A vibrator 78a is provided inside the convex portion 68b of the flange portion 68 . Further, inside the convex portion 66d of the front flange 66, a vibrator 78b is provided. For example, transducers 78a and 78b are fixed to rear flange 64 and front flange 66, respectively, by adhesive. The vibrators 78a and 78b constitute a vibration imparting unit 78 that vibrates the second cutting blade 56b at a frequency belonging to the ultrasonic band.

When the second cutting blade 56b and the front flange 66 are attached to the rear flange 64, the second cutting blade 56b is sandwiched and fixed by the support members 76a and 76b. The second cutting blade 56b is positioned such that the first surface 57a faces the oscillator 78a and the second surface 57b faces the oscillator 78b.

The vibrator 78a includes an annular piezoelectric body 80a provided along the circumferential direction of the flange portion 68 of the rear flange 64, a pair of electrodes 82a provided to sandwich the piezoelectric body 80a, the piezoelectric body 80a and a pair of electrodes 82a. and an insulator 84a covering the electrode 82a. Similarly, the vibrator 78b includes an annular piezoelectric body 80b provided along the circumferential direction of the front flange 66, a pair of electrodes 82b provided so as to sandwich the piezoelectric body 80b, and a piezoelectric body 80b and the pair of electrodes. and an insulator 84b covering 82b. For example, the piezoelectric bodies 80a and 80b are made of piezoelectric ceramics such as barium titanate, lead zirconate titanate, and lithium tantalate.

Wires 86a and 86b are provided inside the flange mechanism 52b. One ends of the wirings 86 a and 86 b are each branched into two and exposed on the side surface of the support shaft 70 . One electrode 82a of the vibrator 78a is connected to a wiring 86a via a lead wire 88a. The other electrode 82a of the vibrator 78a is connected to the wiring 86b through the lead wire 88b.

The front flange 66 is provided with connection electrodes 90a and 90b exposed at an opening 66c. One electrode 82b of the vibrator 78b is connected to the wiring 86a via the lead wire 88c and the connection electrode 90a. The other electrode 82b of the vibrator 78b is connected to the wiring 86b via the lead wire 88d and the connection electrode 90b.

Further, the second cutting unit 24b includes a voltage supply unit 92 that supplies AC voltage to the vibrators 78a and 78b that constitute the vibration imparting unit 78. As shown in FIG. The voltage supply unit 92 has a power receiving portion (power receiving unit) 94 provided on the rear surface side (housing 51b side) of the rear flange 64, and the power receiving portion 94 arranged on the front side (flange mechanism 52b side) of the housing 51b to face the power receiving portion 94. and a power feeding section (power feeding unit) 100 .

The power receiving portion 94 includes an annular core 96 provided on the back side of the rear flange 64 . An annular recess 96a is formed on the surface side of the core 96 (on the power supply unit 100 side), and an annular coil (receiving coil) 98 is provided inside the recess 96a. One end side of the coil 98 is connected to the wiring 86a, and the other end side of the coil 98 is connected to the wiring 86b.

The feeding section 100 has an annular core 102 . For example, the core 102 is fixed to the surface side of the housing 51b by bolts (not shown). An annular recess 102a is formed on the surface side (power receiving unit 94 side) of the core 102, and an annular coil (feeding coil) 104 is provided inside the recess 102a. The coil 104 is connected to an AC power supply 108 via wires 106a and 106b. Also, the AC power supply 108 is connected to a frequency converter 110 that controls the frequency of the AC voltage supplied from the AC power supply 108 .

Power receiving section 94 and power feeding section 100 constitute a rotary transformer that transmits an AC voltage supplied from AC power supply 108 to vibration imparting unit 78 . Then, when the wafer 1 is processed by the second cutting blade 56b, an AC voltage is applied to the coil 104 of the power supply unit 100 by the AC power supply . At this time, the frequency of the AC voltage is controlled by the frequency converter 110 .

The AC voltage applied to the coil 104 is applied to the pair of electrodes 82a of the vibrator 78a and the pair of supplied to electrode 82b. As a result, the piezoelectric body 80a of the vibrator 78a vibrates along the radial direction together with the rear flange 64. As shown in FIG. Also, the piezoelectric body 80b of the vibrator 78b vibrates along the radial direction together with the front flange 66. As shown in FIG.

As a result, the second cutting blade 56b sandwiched between the rear flange 64 and the front flange 66 vibrates along the radial direction of the second cutting blade 56b. The frequency of the AC voltage supplied from the AC power supply 108 is controlled by the frequency converter 110 so that the second cutting blade 56b vibrates at a frequency belonging to the ultrasonic band.

Here, the flange portion 68 of the rear flange 64 is provided with a plurality of through holes 68c, and the front flange 66 is provided with a plurality of through holes 66e (see FIG. 5). As a result, the rigidity in the radial direction of the flange portion 68 and the front flange 66 is reduced, making it easier for the flange portion 68 and the front flange 66 to vibrate along the radial direction. As a result, the second cutting blade 56b also tends to vibrate along the radial direction.

Next, a grinding device used for thinning the wafer 1 in the wafer processing method according to the present embodiment will be described. FIG. 8 is a perspective view schematically showing the grinding device 112. As shown in FIG. An opening 114 a is provided on the upper surface of the base 114 of the grinding device 112 . An X-axis moving table 118 on which a holding table 116 for holding the wafer 1 by suction is mounted is provided in the opening 114a.

The X-axis moving table 118 can move in the X-axis direction by an X-axis direction moving mechanism (not shown). The X-axis moving table 118 has a loading/unloading area 120 where the wafer 1 is loaded and unloaded on the holding table 116 by the X-axis direction moving mechanism, and a processing area where the wafer 1 sucked and held on the holding table 116 is ground. 122 and .

A porous member having an upper surface with a diameter equivalent to that of the wafer 1 is provided on the upper surface of the holding table 116 , and the upper surface of the porous member serves as a holding surface 116 a for holding the wafer 1 . The holding table 116 is internally provided with a suction path (not shown) having one end communicating with the porous member and the other end connected to a suction source (not shown). When the suction source is activated, a negative pressure is applied to the wafer 1 placed on the holding surface 116 a so that the wafer 1 is held on the holding table 116 by suction. Also, the holding table 116 can rotate around an axis perpendicular to the holding surface 116a.

A grinding unit 124 for grinding the wafer 1 is arranged above the processing area 122 . A support portion 126 is erected on the rear side of the base 114 , and the grinding unit 124 is supported by the support portion 126 . A pair of Z-axis guide rails 128 extending in the Z-axis direction is provided on the front surface of the support portion 126, and a Z-axis moving plate 130 is slidably attached to each of the Z-axis guide rails 128. As shown in FIG.

A nut portion (not shown) is provided on the back side (rear side) of the Z-axis moving plate 130, and a Z-axis ball screw 132 parallel to the Z-axis guide rail 128 is screwed into this nut portion. ing. A Z-axis pulse motor 134 is connected to one end of the Z-axis ball screw 132 . When the Z-ball screw 132 is rotated by the Z-axis pulse motor 134, the Z-axis moving plate 130 moves along the Z-axis guide rail 128 in the Z-axis direction.

A grinding unit 124 for grinding the wafer 1 is fixed to the lower front side of the Z-axis moving plate 130 . When the Z-axis moving plate 130 is moved in the Z-axis direction, the grinding unit 124 is moved in the Z-axis direction.

The grinding unit 124 has a spindle 138 along the Z-axis direction, a housing 136 that rotatably accommodates the upper end of the spindle 138 , and a disk-shaped wheel mount 140 fixed to the lower end of the spindle 138 . The housing 136 accommodates a rotary drive source such as a motor connected to the upper end of the spindle 138 to rotate the spindle 138 around the Z-axis direction.

An annular grinding wheel 142 is fixed to the lower surface of the wheel mount 140 . A grinding wheel 144 in which abrasive grains made of diamond or the like are dispersed and fixed in a bonding material is annularly arranged on the lower surface of the grinding wheel 142 .

As the spindle 138 is rotated to rotate the grinding wheel 142, the grinding wheel 144 is rotated on an annular orbit. When the grinding unit 124 is lowered to bring the rotating grinding wheel 144 into contact with the surface of the wafer 1 to be ground, the wafer 1 is ground. The grinding device 112 has a thickness measuring device (not shown), monitors the thickness of the wafer 1, and proceeds with grinding. exit.

When the wafer 1 is ground by the grinding wheel 144, the wafer 1 and the grinding wheel 144 generate processing dust and frictional heat. The grinding device 112 includes a grinding water supply nozzle 146 (see FIG. 10, etc.), and supplies grinding water 148 such as pure water to the wafer 1 and the like from the grinding water supply nozzle 146 while the wafer 1 is ground by the grinding wheel 144. . Processing debris and frictional heat are removed by grinding water 148 .

The grinding device 112 has a drainage groove 114b in the opening 114a through which used grinding water flows. A drain port 114c is formed in the bottom surface of the drain groove 114b, and the used grinding water that has flowed into the drain groove 114b is discharged from the drain port 114c.

Since a chamfered portion is formed on the outer circumference 1c of the wafer 1, if the wafer 1 is thinned to the finished thickness as it is, the chamfered portion partially remains and a knife-edge shape appears, and the wafer 1 is easily damaged. Become. Therefore, before grinding the wafer 1 from the back surface 1b side, edge trimming is performed to partially remove the chamfered portion by cutting the outer peripheral portion of the wafer 1 from the front surface 1a side to a depth equal to or greater than the finishing thickness.

However, when the wafer 1 is subsequently thinned by grinding from the back surface 1b side with the grinding device 112, the wafer 1 is cut just before the grinding wheel 144 reaches the terrace portion 13 (see FIG. 7 etc.) formed by the edge trimming process. The offcuts remaining on the outer circumference are broken, and relatively large offcuts fall. Large scraps that have fallen accumulate in the drain 114b for draining the grinding water or clog the drain 114c. rice field.

Therefore, in the wafer processing method according to the present embodiment, before grinding the wafer 1 from the back surface 1b side, an annular cut groove with a crushed layer is formed in the vicinity of the terrace portion 13 formed by edge trimming. When the wafer 1 is ground from the back surface 1b side in this state, the annular cut groove and the crushed layer serve as splitting starting points, and the terrace portion is subdivided to produce fine offcuts. Fine remnants tend to be washed away when dropped into the drain 114b, are less likely to accumulate, and are less likely to clog the drain 114c. Therefore, it is not necessary to frequently clean the drainage groove 114b.

A method for processing a wafer according to this embodiment will be described below. FIG. 12 is a flow chart showing the flow of each step of the wafer processing method according to the present embodiment, in which the disk-shaped wafer 1 having the chamfered portion on the outer periphery 1c is ground from the back surface 1b side to be thinned to the finished thickness. is.

In the wafer processing method according to the present embodiment, first, a trimming step S10 is performed in which the wafer 1 is cut along the outer peripheral edge to form an annular terrace portion in the chamfered portion. The trimming step S10 is performed by the cutting device 2 shown in FIG.

First, the cassette 10 containing the frame unit in which the wafer 1, the tape and the annular frame are integrated is carried to the cassette support base 8. As shown in FIG. Then, the wafer 1 (frame unit) is pulled out from the cassette 10 and placed on the holding surface 18a of the holding table 18, and the holding table 18 holds the wafer 1 by suction via the tape. At this time, the front surface 1a side of the wafer 1 is exposed upward.

Edge trimming of the wafer 1 is performed by the first cutting unit 24a. FIG. 3 is a cross-sectional view schematically showing the wafer 1 to be edge-trimmed. First, the wafer 1 is photographed by the camera unit 46a to detect the position of the outer circumference 1c of the wafer 1. As shown in FIG. Then, the positions of the first cutting unit 24a and the holding table 18 are adjusted so that the grindstone portion 60a of the first cutting blade 56a is positioned above the outer circumference 1c of the wafer 1. FIG.

Next, the spindle 50a is rotated to rotate the first cutting blade 56a so that the lowest end of the grindstone portion 60a is positioned at the first depth position 13a (FIG. 7) where the depth from the surface 1a of the wafer 1 is greater than or equal to the finished thickness. ), the first cutting unit 24a is lowered. For example, when the thickness of the wafer 1 is 700 μm, the first depth position 13a is preferably located below the surface 1a of the wafer 1 by about 300 μm.

With the first cutting blade 56a cutting into the chamfered portion from the front surface 1a side of the wafer 1, the holding table 18 is rotated by 360° or more around the table rotation axis perpendicular to the holding surface 18a. Then, the wafer 1 is cut along the outer peripheral edge and the chamfered portion is partially excised to form an annular terrace portion 13 (see FIG. 4, etc.) on the wafer 1 .

Next, in the cutting device 2, a first ultrasonic vibration cutting step S21 is performed in which the wafer 1 is cut by the second cutting unit 24b to form a first annular cutting groove. FIG. 4 is a cross-sectional view schematically showing the first ultrasonic vibration cutting step S21. In the first ultrasonic vibration cutting step S21, a second cutting blade 56b having a thinner blade thickness than the first cutting blade 56a is caused to cut into the wafer 1 at a position where the terrace portion 13 is formed from the surface 1a side.

In the first ultrasonic vibration cutting step S21, first, the positions of the second cutting unit 24b and the holding table 18 are adjusted to position the second cutting blade 56b above a predetermined position on the terrace portion 13. FIG. Then, while rotating the second cutting blade 56b, the vibration applying unit 78 (see FIG. 6) vibrates the second cutting blade 56b along the radial direction of the second cutting blade 56b.

At this time, the vibration imparting unit 78 vibrates the second cutting blade 56b at a frequency belonging to the ultrasonic band. For example, the frequency of the second cutting blade 56b is set to 20 kHz or higher. When vibration is applied to the second cutting blade 56b from the vibration applying unit 78, the second cutting blade 56b vibrates so that the diameter increases or decreases. The amount of variation in the diameter of the second cutting blade 56b (difference between maximum and minimum diameters) is, for example, about 5 μm.

In this state, until the lower end of the second cutting blade 56b reaches a second depth position 17a (see FIG. 7) that exceeds the first depth position 13a from the surface 1a of the wafer 1, the second lowers the cutting unit 24b. For example, the second depth position 17a is preferably located below the surface 1a of the wafer 1 by about 500 μm.

With the second cutting blade 56b cutting into the terrace portion 13 from the front surface 1a side of the wafer 1, the holding table 18 is rotated by 360° or more around the table rotation axis perpendicular to the holding surface 18a. Then, the wafer 1 is cut along the outer peripheral edge to form a first ring-shaped cut groove 15 a in the ring-shaped terrace portion 13 .

At this time, the vibration of the second cutting blade 56b at a frequency belonging to the ultrasonic band (ultrasonic vibration) causes the abrasive grains exposed from the lower end of the second cutting blade 56b to vibrate with a period corresponding to the ultrasonic vibration. Collide with wafer 1. As a result, the wafer 1 is fractured and a fractured layer (not shown) is formed around the first annular cut groove 15a.

In the wafer processing method according to the present embodiment, in addition to the first annular cutting groove 15a in the terrace portion 13 formed on the outer periphery 1c of the wafer 1, a second cutting blade 56b forms a further annular cutting groove. is preferred. Next, the second ultrasonic vibration cutting step S22 for forming the second annular cut groove 15b (see FIG. 7) will be described.

In the second ultrasonic vibration cutting step S22, first, the position of the second cutting unit 24b in the Y direction is adjusted to move the second cutting blade 56b from the first annular cutting groove 15a formed in the terrace portion 13. are also positioned above a predetermined position on the radially outer side of the wafer 1 . Then, as in the first ultrasonic vibration cutting step S21, while rotating the second cutting blade 56b, the vibration applying unit 78 (see FIG. 6) moves the second cutting blade 56b to the position of the second cutting blade 56b. Vibrate along the radial direction.

In this state, until the lower end of the second cutting blade 56b reaches a third depth position 17b (see FIG. 7), the depth from the surface 1a of the wafer 1 exceeds the second depth position 17a. lowers the cutting unit 24b. That is, the second depth position 17a is closer to the surface 1a than the third depth position 17b. For example, the third depth position 17b is preferably located below the surface 1a of the wafer 1 by about 550 μm.

With the second cutting blade 56b cutting into the terrace portion 13 from the front surface 1a side of the wafer 1, the holding table 18 is rotated by 360° or more around the table rotation axis perpendicular to the holding surface 18a. Then, the wafer 1 is cut along the outer peripheral edge to form a second ring-shaped cut groove 15b in the ring-shaped terrace portion 13. As shown in FIG. At this time, the wafer 1 is also fractured around the second annular cut groove 15b, forming a fracture layer (not shown) around the first annular cut groove 15a.

An annular cut groove may be further formed in the terrace portion 13 of the wafer 1 . FIG. 7 schematically shows an enlarged view of the vicinity of the outer circumference 1c of the wafer 1 in which the first annular cut groove 15a, the second annular cut groove 15b, and the third annular cut groove 15c are formed in the terrace portion 13. It is a sectional view.

Here, the third annular cut groove 15c is, for example, a fourth depth from the surface 1a of the wafer 1 greater than the third depth position 17b where the lower end of the second annular cut groove 15b is located. It is formed such that the lower end reaches the depth position 17c. For example, the fourth depth position 17c is preferably located below the surface 1a of the wafer 1 by about 600 μm. However, the depth position of the lower end of the third annular cut groove 15c is not limited to this.

Since each annular cutting groove is formed by rotating the holding table 18 at the same position, the first annular cutting groove 15a, the second annular cutting groove 15b, and the third annular cutting groove 15c are formed by the holding table. 18 are formed concentrically around the rotation axis. When a plurality of annular cut grooves 15a, 15b, and 15c are formed in the terrace portion 13 formed on the outer circumference 1c of the wafer 1, the outer annular cut grooves reach a deeper position at the lower end. is preferred.

Also, so far, the first cutting blade 56a used for edge trimming is a hub-type cutting blade, and the second cutting blade 56b used for cutting with ultrasonic vibration is a washer-type cutting blade. A case where is explained as an example. However, the first cutting blade 56a and the second cutting blade 56b are not limited to this.

That is, in the trimming step S10, a washer-type first cutting blade 56a may be used. Further, in the first ultrasonic vibration cutting step S21 and the second ultrasonic vibration cutting step S22, a hub-type second cutting blade 56b may be used. When the second cutting blade 56b is of a hub type, for example, a vibration imparting unit is incorporated in the base that supports the grindstone portion.

After the trimming step S10, the first ultrasonic vibration cutting step S21, and the second ultrasonic vibration cutting step S22, a protective member is applied to the front surface 1a side of the wafer 1 in preparation for grinding the wafer 1. Arrival step S30 is executed. FIG. 9 is a cross-sectional view schematically showing the wafer 1 placed on the holding table 116 of the grinding device 112 with the protective member 17 adhered to the front surface 1a side and the back surface 1b side facing upward.

The protective member 17 is a disk-shaped member having the same diameter as the wafer 1 and is made of a material such as resin. When the protective member 17 is attached to the front surface 1a of the wafer 1, the front surface 1a does not come into direct contact with the holding table 116 when the wafer 1 is ground from the rear surface 1b side. Therefore, the front surface 1a of the wafer 1 is not damaged. The wafer 1 with the protective member 17 adhered to the front surface 1a side is placed on the holding table 116 and held by the holding table 116 by suction.

After the protective member adhering step S30, a grinding step S40 is performed in which the wafer 1 is ground from the rear surface 1b and thinned to the finished thickness. FIG. 10 is a cross-sectional view schematically showing the initial stage of the grinding step S40, and FIG. 11 is a cross-sectional view schematically showing the final stage of the grinding step S40.

When grinding the wafer 1, the holding table 116 for sucking and holding the wafer 1 is moved to the processing area 122 (see FIG. 8), and the rotation of the spindle 138 and the holding table 116 are started. Then, while supplying grinding water 148 to the wafer 1 from the grinding water supply nozzle 146, the grinding unit 124 is lowered, and the grinding wheel 144 moving on the annular orbit is brought into contact with the back surface 1b of the wafer 1 to grind the wafer 1. Start.

When the wafer 1 is ground from the back surface 1b side, the thickness of the wafer 1 gradually decreases, and the deepest third annular cut groove 15c is first exposed on the back surface 1b side. At this time, the wafer 1 is divided by the third annular cut groove 15c to generate offcuts, and the offcuts are pulverized starting from the crushed layer formed around the third annular cut groove 15c.

As the grinding progresses further, the next deeper second annular cut groove 15b is exposed on the rear surface 1b side. At this time, the wafer 1 is divided by the second annular cut groove 15b to generate offcuts, and the offcuts are pulverized starting from the crushed layer formed around the second annular cut groove 15b. If the grinding is continued as it is, the next deep first annular cut groove 15a is exposed on the back surface 1b side. At this time, the wafer 1 is divided by the first annular cut groove 15a to generate offcuts, and the offcuts are pulverized starting from the crushed layer formed around the first annular cut groove 15a.

After that, as shown in FIG. 11, the grinding unit 124 is lowered until the wafer 1 reaches the finished thickness, and the grinding of the wafer 1 is finished. Then, the grinding unit 124 is lifted to return the holding table 116 to the loading/unloading area 120 , and the suction holding of the wafer 1 by the holding table 116 is released to unload the wafer 1 from the grinding device 112 .

As described above, in the wafer processing method according to the present embodiment, when the wafer 1 is thinned and the grinding wheel 144 reaches the terrace portion 13, the annular cutting groove and the crushed layer serve as splitting starting points on the outer periphery of the wafer 1. The 1c neighborhood is subdivided. Fragmented offcuts are easily washed away when dropped into the drain 114b and are less likely to accumulate in the drain 114b, so frequent cleaning of the drain 114b is not required.

If the magnitude relationship of the depths of the annular cut grooves 15a, 15b, and 15c is reversed, the annular cut groove exposed on the back surface 1b side first excises the portion outside the annular cut groove. However, since the cut portion is before being subdivided, the offcuts produced are relatively large. Therefore, it is preferable that the magnitude relationship is not reversed. However, even if the size relationship is reversed, the resulting offcuts are smaller than when no annular cut groove is formed at all, so that they are less likely to accumulate in the drainage groove 114b to some extent.

Next, the disk-shaped wafer 1 having a chamfered portion on the outer circumference 1c is subjected to edge trimming, two annular cut grooves 15a and 15b are formed in the formed terrace portion 13, and the wafer 1 is cut into the back surface 1b. An example in which offcuts generated by grinding from the side are collected and observed will be described. In the wafer processing method according to this embodiment, the two annular cut grooves 15a and 15b are formed by the second cutting blade 56b to which ultrasonic vibration is applied.

First, a plurality of silicon wafers having a thickness of 700 μm and a diameter of 8 inches were prepared as wafers 1 . Devices 5 are not formed on the front surface 1a of these wafers 1. FIG. This wafer 1 was carried into the cutting device 2 and processed one by one according to the following procedure. The cutting device 2 used for the edge trimming of the wafer 1 is "DFD6361" manufactured by DISCO Corporation. First, the wafer 1 was loaded onto the holding table 18 and held by the holding table 18 by suction.

Then, a washer-type first cutting blade 56a having a thickness of 2 mm or more manufactured by Disco Co., Ltd. was used to cut along the outer circumference 1c of the wafer 1 . At this time, a region having a width of 2 mm from the outer periphery 1c of the wafer 1 and a depth of 300 μm from the surface 1a was removed to form a terrace portion 13 on the wafer 1 along the outer periphery 1c. At this time, the rotation speed of the first cutting blade 56a was 30,000 rpm, the rotation speed of the holding table 18 was 1 degree per second, and the holding table 18 was rotated 370 degrees.

Next, the wafer 1 was loaded into "DAD3350" manufactured by DISCO Corporation, which has ultrasonic vibration cutting specifications. Then, using "U09RA-SDC600-BB200-50" manufactured by Disco Co., Ltd. and having a blade thickness of 300 μm as the hub-type second cutting blade 56b, the terrace portion 13 is cut along the outer circumference 1c to form the first cutting blade 56b. An annular cut groove 15 a was formed in the wafer 1 . At this time, the first annular cutting groove 15a is formed so that the distance from the outer circumference 1c of the wafer 1 is 500 μm, and the second cutting blade 56b is cut to a height position 550 μm lower than the surface 1a of the wafer 1. let me in

At this time, the rotation speed of the second cutting blade 56b was 30,000 rpm, the rotation speed of the holding table 18 was 1 degree per second, and the holding table 18 was rotated 370 degrees. At this time, an ultrasonic vibration having a radial amplitude of 5 μm and a frequency of 41 kHz was applied to the second cutting blade 56b.

Further, the second cutting blade 56b was used to cut the terrace portion 13 along the outer circumference 1c to form the second annular cut groove 15b in the wafer 1. As shown in FIG. At this time, the second annular cut groove 15b was formed radially inward of the wafer 1 from the first annular cut groove 15a so that the distance from the first annular cut groove 15a was 500 μm. At this time, the second cutting blade 56b was cut to a height position lower than the surface 1a of the wafer 1 by 500 μm.

At this time, the rotation speed of the second cutting blade 56b was 30,000 rpm, the rotation speed of the holding table 18 was 1 degree per second, and the holding table 18 was rotated 370 degrees. Also at this time, ultrasonic vibration with a radial amplitude of 5 μm and a frequency of 41 kHz was applied to the second cutting blade 56b.

Next, the wafer 1 in which the terrace portion 13, the first annular cut groove 15a, and the second annular cut groove 15b are formed is carried into a grinding apparatus 112 as shown in FIG. Grinded according to procedure. In addition, in the wafer processing method according to the present embodiment, the attachment of the protective member to the front surface 1a of the wafer 1 is omitted. The grinding device 112 used for grinding the wafer 1 is "DAG810" manufactured by DISCO Corporation. First, the wafer 1 was carried into the holding table 116 with the back surface 1b facing upward, and held by the holding table 116 by suction.

Then, the wafer 1 was ground from the back surface 1b side using a grinding wheel manufactured by DISCO Corporation as the grinding wheel 142 having the grinding wheel 144 . At this time, the rotating speed of the holding table 116 was set at 300 rpm, the rotating speed of the spindle 138 was set at 3500 rpm, and the lowering speed of the grinding unit 124 was set at 0.7 μm/sec. Then, the finished thickness of the wafer 1 was set to 300 μm, and the grinding unit 124 was lowered until the thickness of the wafer 1 reached the finished thickness.

When the wafer 1 is ground by the grinding device 112, offcuts are generated from the wafer 1 and dropped into the drainage groove 114b. In this example, after the grinding of the wafer 1 was finished, the offcuts dropped into the drainage groove 114b were collected, observed, and measured for size.

For comparison, two annular cutting grooves 15a and 15b were formed by a second cutting blade 56b without applying ultrasonic vibration to a terrace portion 13 similarly formed on another wafer 1 by edge trimming. Then, scraps generated by grinding the wafer 1 from the back surface 1b side were observed. The difference between the wafer processing method according to the example and the wafer processing method according to the comparative example is that when the two annular cutting grooves 15a and 15b are formed, ultrasonic vibration is applied to the second cutting blade 56b. It is only whether or not it has been granted.

FIG. 13 is a photograph of the collected mill ends placed on a mesh fabric. On the left side of the photograph, three of the offcuts 19a collected when the wafer processing method according to the example was carried out are shown. Also, on the right side of the photograph, one of the offcuts 19b collected when the wafer processing method according to the comparative example was carried out is shown. As is clear from the photograph shown in FIG. 13, the offcuts 19a are much smaller than the offcuts 19b.

More specifically, when the sizes of the collected offcuts 19a and 19b were measured, it was confirmed that the average widthwise size of the offcuts 19a was about 75% smaller than that of the offcuts 19b. rice field. This is probably because when the annular cutting grooves 15a and 15b are formed by applying ultrasonic vibration to the second cutting blade 56b, a crushed layer is formed on the bottom of the annular cutting grooves 15a and 15b. Then, when the wafer 1 was ground from the back surface 1b side, it is considered that the wafer 1 was subdivided near the terrace portion 13 with this crushed layer serving as a starting point for division.

Moreover, as is clear from the photograph shown in FIG. 13, the scrap 19a is smaller than the scrap 19b not only in the width direction but also in the length direction. This suggests that the fracture layer formed on the wafer 1 promoted fragmentation of the wafer 1 also in the longitudinal direction. According to the embodiment and the comparative example described above, the ring-shaped cutting grooves 15a and 15b are formed by the second cutting blade 56b to which ultrasonic vibration is applied, so that when the wafer 1 is finally ground, it is subdivided. It was confirmed that small scraps were generated.

It should be noted that the present invention is not limited to the description of the above embodiments, and can be implemented with various modifications. For example, in the above embodiment, the case where the three annular cut grooves 15a, 15b, and 15c are formed in the terrace portion 13 of the wafer 1 has been described, but the wafer processing method according to one aspect of the present invention is not limited to this. Only the first annular cutting groove 15a may be formed in the terrace portion 13, and the second ultrasonic vibration cutting step S22 may not be performed. Also in this case, the amount of offcuts produced during grinding of the wafer 1 is smaller than in the conventional case.

Further, in the above embodiment, the case where the first ultrasonic vibration cutting step S21 is performed after the trimming step S10 has been described, but one aspect of the present invention is not limited to this. That is, the first ultrasonic vibration cutting step S21 or the like is first performed to form one or more annular cutting grooves 15a, 15b, 15c near the outer periphery 1c of the wafer 1, and then the trimming step S10 is performed. Alternatively, the terrace portion 13 may be formed.

Also in this case, since the annular cut grooves 15a, 15b, and 15c are formed in the terrace portion 13 before the grinding step S40 is performed, the offcuts generated in the grinding step S40 can be reduced. Before the terrace portion 13 is formed, the outer circumference 1c of the wafer 1 can be easily detected by the camera unit 46b arranged near the second cutting unit 24b.

However, when the annular cutting grooves 15a, 15b, and 15c are formed without forming the terrace portion 13, the second cutting blade 56b must be cut deeply into the wafer 1 from the surface 1a, and the blade is long. A second cutting blade 56b is required.

It should be noted that the structure, method, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention.

REFERENCE SIGNS LIST 1 wafer 1a front surface 1b back surface 1c outer periphery 3 dividing line 5 device 7 device region 9 outer peripheral surplus region 13 terrace portion 13a, 17a, 17b, 17c depth position 15a, 15b, 15c annular cutting groove 17 protective member 19a, 19b edge material 2 Cutting device 4 Base 4a, 4b, 4c Opening 8 Cassette support 10 Cassette 12 Guide rail 14 Table cover 16 Dust and drip proof cover 18 Holding table 18a Holding surface 18b Clamp 18c Porous member 20 Supporting structure 22a, 22b Moving unit 24a, 24b Cutting unit 26, 34a, 34b Guide rail 28a, 28b, 36a, 36b Moving plate 30a, 30b, 38a, 38b Ball screw 32a, 40a, 40b Pulse motor 46a, 46b Camera unit 48 Cleaning unit 50a, 50b Spindle 51b Housing 52a, 52b flange mechanism 53 threaded portion 54a fixing nut 56a, 56b cutting blade 57a first surface 57b second surface 57c opening 58a base 60a grindstone portion 62a, 62b cutting fluid supply nozzle 64 rear flange 64a opening 66 front flange 66a first surface 66b Second surface 66c Opening 66d Protruding portion 66e Through hole 68 Flange portion 68a Surface 68b Protruding portion 68c Through hole 70 Support shaft 70a Threaded portion 72, 74 Fixing nuts 76a, 76b Supporting member 78 Vibration imparting unit 78a, 78b Vibrator 80a, 80b Piezoelectric bodies 82a, 82b Electrodes 84a, 84b Insulators 86a, 86b Wirings 88a, 88b, 88c, 88d Lead wires 90a, 90b Connection electrodes 92 Voltage supply unit 94 Power receivers 96, 102 Cores 96a, 102a Concave parts 98, 104 Coils 100 Power supply Parts 106a, 106b Wiring 108 AC power supply 110 Frequency converter 112 Grinding device 114 Base 114a Opening 114b Drain 114c Drain 116 Holding table 116a Holding surface 118 X-axis movement table 120 Loading/unloading area 122 Machining area 124 Grinding unit 126 Supporting part 128 Z-axis guide rail 130 Z-axis moving plate 132 Z-axis ball screw 134 Z-axis pulse Smotor 136 Housing 138 Spindle 140 Wheel mount 142 Grinding wheel 144 Grinding wheel 146 Grinding water supply nozzle 148 Grinding water

Claims (4)

A wafer processing method in which a disk-shaped wafer having a chamfered portion on the outer periphery is ground from the back surface side to be thinned to a finished thickness,
A first cutting blade is cut into the chamfered portion from the surface side of the wafer to a first depth position whose depth from the surface is equal to or greater than the finished thickness, thereby cutting the wafer along the outer peripheral edge. , a trimming step to form an annular terrace;
After the trimming step, a protective member adhering step of adhering a protective member to the front surface side of the wafer;
After the protective member attaching step, a grinding step of grinding the wafer from the back surface to thin it to the finished thickness,
Before performing the grinding step, while applying ultrasonic vibration to a second cutting blade having a thinner blade thickness than the first cutting blade, from the surface side of the wafer along the outer peripheral edge Further comprising a first ultrasonic vibration cutting step of cutting with the second cutting blade to a second depth position, the depth of which exceeds the first depth position, to form a first annular cutting groove. A wafer processing method characterized by: Before performing the grinding step, while applying ultrasonic vibration to the second cutting blade, the depth from the surface along the outer peripheral edge from the surface side of the wafer is the first depth position. further comprising a second ultrasonic vibration cutting step of cutting the second cutting blade to a greater than third depth position to form a second annular cutting groove;
2. The method of processing a wafer according to claim 1, wherein the first annular cut groove and the second annular cut groove are formed concentrically. The first annular cut groove is formed inside the second annular cut groove,
3. The method of processing a wafer according to claim 2, wherein said second depth position is closer to said surface than said third depth position. 4. The wafer processing method according to claim 1, wherein said first ultrasonic vibration cutting step is performed after said trimming step.

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