JP2019029398A - Processing method of wafer - Google Patents

Abstract

To provide a processing method of wafer capable of restraining the sticking of a dicing tape and a surface protection tape during transfer.SOLUTION: A processing method of a wafer includes a bevelling removal step ST1 of forming a step part by removing the bevelling part of the wafer from the surface to the depth of finish thickness of the wafer, a sidewall formation step ST3 of forming a sidewall by removing the inner peripheral wall of the step part to the depth reaching the back side on the outer peripheral side, a surface protection tape sticking step ST4 of sticking the surface protection tape to the wafer surface, a surface protection tape cutting step ST5 of cutting the surface protection tape by means of a cutter moved along the sidewall, a holding step ST6 of holding the surface side of the wafer by means of a chuck table via the surface protection tape, and a thinning step ST7 of thinning the reverse face of the wafer held by the chuck table to the finishing thickness.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a wafer processing method including a device region having a plurality of devices formed on the surface and an outer peripheral surplus region surrounding the device region, and a chamfered portion formed on the outer periphery.

  In order to solve the problem that when the wafer is thinly ground, the chamfered portion of the outer periphery is formed in a knife edge shape (eave shape), and the wafer is damaged due to chipping. A wafer processing method is used in which the edge trimming process for removing the chamfered portion (arc) from the side is performed, and then the back surface of the wafer is ground (see, for example, Patent Document 1).

JP 2000-173961 A

  The wafer is subjected to edge trimming by the processing method disclosed in Patent Document 1, and then a surface protection tape is attached to the surface, and the wafer is ground from the back side to the finished thickness. After grinding, the wafer is divided into individual devices by a cutting machine etc. after dicing tape (DAF: Die Attach Film may be attached) is attached to the back surface and the surface protection tape is peeled off. .

  Generally, the surface protective tape is attached to the surface of the wafer and then cut with a cutter along the outer peripheral edge of the wafer. That is, the surface protection tape attached to the wafer after edge trimming is cut to a size larger than the surface of the wafer. In this state, when the back surface of the wafer is ground, the surface protection tape generates an area that protrudes from the outer periphery of the ground wafer. If the wafer is transferred from the surface protective tape to the dicing tape after grinding, there arises a problem that the surface protective tape protruding from the outer peripheral side of the wafer sticks to the dicing tape, DAF or the like. Adhering a surface protective tape to a dicing tape, DAF or the like is difficult to remove because the adhesive surfaces are adhered to each other, and the wafer is damaged if it is forcibly removed.

  On the other hand, in recent years, a device formed by circuit layers exceeding 100 layers only in the device region has been designed. A wafer on which a device composed of more than 100 circuit layers is formed on the surface is trimmed and removed not only the chamfered portion but also the outer peripheral surplus region so as to eliminate the step with the outer peripheral surplus region. In this case, the surface protection tape greatly protrudes from the wafer, and the above problem is remarkably generated.

  If the surface protection tape is cut along the outer peripheral edge of the edge-trimmed wafer surface side and the surface protection tape is cut, the size of the ground wafer and the surface protection tape becomes the same, so the above problem is solved. However, it is not desirable to place the cutter along the outer peripheral edge on the front surface side of the wafer because fine cracks and scratches are formed on the front surface side of the wafer by the cutter and are easily damaged.

  It is also conceivable to eliminate the above problem by sticking a surface protective tape to the wafer surface in advance and removing the chamfered portion together with the surface protective tape. In this case, the surface protection tape is cut to generate thread-like waste, and thread-like waste becomes a problem.

  This invention is made | formed in view of this problem, The objective is to provide the processing method of the wafer which can suppress that a dicing tape and a surface protection tape stick at the time of transcription | transfer. .

  In order to solve the above-mentioned problems and achieve the object, the wafer processing method of the present invention is a wafer processing method comprising a plurality of devices on the surface and a chamfered portion formed on the outer periphery from the surface to the back surface. And removing the chamfered portion along the outer peripheral edge of the wafer to a depth from the surface to the finished thickness of the wafer, and performing the chamfering removing step to form a stepped portion on the outer peripheral edge, and the chamfering removing step. After that, it is removed from the inner peripheral wall of the step portion to the depth slightly on the outer peripheral side from the bottom surface of the step portion to the back surface of the wafer, and on the outer peripheral side of the step portion, the side wall extending from the bottom surface of the step portion to the back surface of the wafer A side wall forming step for forming a surface, a surface protective tape adhering step for adhering a surface protective tape covering the wafer to the surface of the wafer after performing the side wall forming step, and the surface protective tape adhering step After performing the surface protective tape cutting step of cutting the surface protective tape with the cutter while moving the cutter along the side wall, and after performing the surface protective tape cutting step, the wafer is passed through the surface protective tape. A holding step for holding the front side of the wafer by a chuck table, and a thinning step for removing the side wall by thinning the back surface of the wafer held by the chuck table to the finished thickness. It is characterized by.

  In the wafer processing method, the wafer has a notch indicating a crystal orientation in a region included in the stepped portion, and a mark is formed on the inside of the stepped portion based on the notch. A step may be further provided.

  The present invention has an effect that the dicing tape and the surface protection tape can be prevented from sticking during transfer.

FIG. 1 is a perspective view of a wafer to be processed in the wafer processing method according to the first embodiment. FIG. 2 is a side view of the wafer shown in FIG. FIG. 3 is a plan view illustrating a configuration example of a cutting apparatus used in the wafer processing method according to the first embodiment. FIG. 4 is a flowchart illustrating the wafer processing method according to the first embodiment. FIG. 5 is a sectional view showing a chamfer removing step of the wafer processing method shown in FIG. FIG. 6 is a plan view showing a mark forming step of the wafer processing method shown in FIG. FIG. 7 is a plan view of the wafer after the mark formation step of the wafer processing method shown in FIG. FIG. 8 is a cross-sectional view showing a side wall forming step of the wafer processing method shown in FIG. 9 is a cross-sectional view of the wafer after the side wall forming step of the wafer processing method shown in FIG. 10 is a plan view of the wafer after the side wall forming step of the wafer processing method shown in FIG. FIG. 11 is a cross-sectional view showing a surface protection tape attaching step of the wafer processing method shown in FIG. FIG. 12 is a cross-sectional view showing a surface protection tape cutting step of the wafer processing method shown in FIG. FIG. 13 is a cross-sectional view showing a holding step of the wafer processing method shown in FIG. FIG. 14 is a cross-sectional view showing a thinning step of the wafer processing method shown in FIG. FIG. 15 is a cross-sectional view of a wafer transferred to a dicing tape after the wafer processing method shown in FIG. 4 is performed.

  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 1
A wafer processing method according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a wafer to be processed in the wafer processing method according to the first embodiment. FIG. 2 is a side view of the wafer shown in FIG.

  The wafer processing method according to the first embodiment is a method for processing the wafer 200 shown in FIG. A wafer 200 to be processed by the wafer processing method according to the first embodiment is a disk-shaped semiconductor wafer having silicon as a substrate, an optical device wafer having sapphire, SiC (silicon carbide), or the like as a substrate. As shown in FIG. 1, the wafer 200 includes a device region 204 in which devices 202 are formed in a plurality of regions partitioned by a grid-like division line 203 on the surface 201, and an outer peripheral surplus region 205 in which devices 202 are not formed. And. That is, the wafer 200 includes a plurality of devices 202 on the surface 201. In addition, the wafer 200 has a notch 206 indicating a crystal orientation on the outer peripheral edge. Further, as shown in FIG. 2, the wafer 200 has a chamfered portion 208 having an arcuate cross section extending from the front surface 201 to the back surface 207 at the outer peripheral edge.

  The wafer processing method according to the first embodiment uses a cutting apparatus 1 shown in FIG. Next, an example of the cutting device 1 used in the wafer processing method according to the first embodiment will be described. FIG. 3 is a plan view illustrating a configuration example of a cutting apparatus used in the wafer processing method according to the first embodiment.

  The cutting device 1 cuts the cutting blade 21 into the wafer 200 and rotates the wafer 200 to perform a circular cutting process on the wafer 200, so that the surface 201 side of the chamfered portion 208 of the wafer 200 extends over the entire circumference. This is an apparatus for performing a so-called edge trimming process on the wafer 200 to remove and form a stepped portion 300 (indicated by a dotted line in FIG. 2). In the first embodiment, the stepped portion 300 formed by the cutting apparatus 1 by removing the surface 201 side of the chamfered portion 208 of the wafer 200 over the entire circumference has a depth from the surface 201 to the bottom surface 302 of the finished thickness of the wafer 200. The depth is 400. Further, in the first embodiment, the stepped portion 300 formed on the wafer 200 is positioned on the outer peripheral side of the wafer 200 with respect to the device 202, and the radial width of the wafer 200 is formed with a constant width over the entire periphery. ing.

  The cutting apparatus 1 is also an apparatus that forms the side wall 500 from the inner peripheral wall 301 of the stepped portion 300 to the outer peripheral side slightly from the bottom surface 302 to the back surface 207 over the entire circumference of the wafer 200 after the stepped portion 300 is formed. is there. The side wall 500 is formed in parallel with the inner peripheral wall 301. A distance 600 between the inner peripheral wall 301 and the side wall 500 is a finishing thickness of 400 or less, and is 100 μm in the first embodiment.

  As shown in FIG. 3, the cutting apparatus 1 includes a chuck table 10 that sucks and holds the back surface 207 of the wafer 200, a cutting unit 20 that performs edge trimming on the wafer 200 held on the chuck table 10, Relative movement of the cutting unit 20 in the X-axis direction parallel to the horizontal direction, and relative movement of the chuck table 10 and the cutting unit 20 in the Y-axis direction parallel to the horizontal direction and perpendicular to the X-axis direction A Y-axis moving unit 40 that moves, a Z-axis moving unit 50 that relatively moves the chuck table 10 and the cutting unit 20 in the Z-axis direction perpendicular to both the X-axis direction and the Y-axis direction, a control unit 100, Is provided.

  The chuck table 10 is formed in a disk shape, and is provided with a ring-shaped holding convex portion 12 that is convex from the facing surface 11 facing the back surface 207 of the wafer 200. The holding convex portion 12 has a holding surface 13 as an upper surface formed flat along the horizontal direction. The outer edge of the holding convex portion 12 is disposed at a position overlapping the side wall 500 formed on the wafer 200 held by the chuck table 10 or on the inner peripheral side of the side wall 500. In the chuck table 10, a suction port 14 connected to a suction source 17 is opened on a holding surface 13 via a vacuum suction path 15 and an on-off valve 16 shown in FIG. 5, and the wafer 200 placed on the holding surface 13. Hold by sucking. Further, the chuck table 10 is rotated around an axis parallel to the Z-axis direction by a rotation drive source (not shown).

  The X-axis moving unit 30 is a processing feed means for processing and feeding the chuck table 10 in the X-axis direction by moving the chuck table 10 in the X-axis direction together with the rotation drive source. The Y-axis moving unit 40 is an indexing feeding means for indexing and feeding the chuck table 10 by moving the cutting unit 20 in the Y-axis direction. The Z-axis moving unit 50 is a cutting feed unit that cuts and feeds the cutting unit 20 by moving the cutting unit 20 in the Z-axis direction. The X-axis moving unit 30, the Y-axis moving unit 40, and the Z-axis moving unit 50 are a known ball screw 41 provided so as to be rotatable around an axis, and a known pulse motor 42 that rotates the ball screw 41 around the axis. And a well-known guide rail that supports the chuck table 10 or the cutting unit 20 movably in the X-axis direction, the Y-axis direction, or the Z-axis direction.

  The cutting unit 20 accommodates the spindle 22 that rotates around an axis parallel to the Y-axis direction, and is moved in the Y-axis direction and the Z-axis direction by the Y-axis moving unit 40 and the Z-axis moving unit 50. A spindle housing 23 and a cutting blade 21 attached to the spindle 22. The cutting blade 21 is a cutting grindstone formed in an extremely thin ring shape, and is held by the chuck table 10 by being rotated by a spindle 22 around an axis parallel to the Y-axis direction while supplying cutting water. The wafer 200 is cut.

  Further, the cutting apparatus 1 carries the wafer 200 out of the cassette table 4 on which the cassettes 8 and 9 are installed, the alignment unit 5, and the cassette 8 placed on the cassette table 4 and carries it into the chuck table 10. A unit 63, a back surface cleaning unit 60 for cleaning the back surface 207 of the wafer 200 after cutting, a surface cleaning unit 61 for cleaning the surface 201 of the wafer 200 after cutting, and an imaging unit (not shown) are provided.

  The cassettes 8 and 9 are containers for storing a plurality of wafers 200. One cassette 8 accommodates the wafer 200 before cutting, and the other cassette 9 accommodates the wafer 200 after cutting. The alignment unit 5 is a table on which the wafer 200 taken out from the cassette 8 is temporarily placed and its center is aligned.

  The transport unit 63 includes a carry-in / out unit 64, a carry-in unit 65, a first carry-out unit 66, and a second carry-out unit 67. The carry-in / out unit 64 includes a multi-node link portion 511 including a plurality of arms, and a hand portion 512 provided at the tip of the multi-node link portion 511 and holding the wafer 200. The carry-in / out unit 64 carries the wafer 200 before cutting from the cassette 8 to the alignment unit 5 and carries the wafer 200 after cutting from the surface cleaning unit 61 to the cassette 9.

  The carry-in unit 65 carries the wafer 200 that has been aligned by the alignment unit 5 and before cutting into the chuck table 10. The first carry-out unit 66 carries the wafer 200 after cutting on the chuck table 10 to the back surface cleaning unit 60. The second carry-out unit 67 carries the wafer 200 after the cutting process from the back surface cleaning unit 60 to the front surface cleaning unit 61.

  The imaging unit images the wafer 200 held on the chuck table 10, and the imaging unit includes a CCD camera that images the wafer 200 held on the chuck table 10.

  The control unit 100 controls each component described above of the cutting apparatus 1 to cause the cutting apparatus 1 to perform a processing operation on the wafer 200. The control unit 100 includes an arithmetic processing device having a microprocessor such as a CPU (central processing unit), a storage device having a memory such as a read only memory (ROM) or a random access memory (RAM), and an input / output interface device. And a computer capable of executing a computer program. The arithmetic processing unit of the control unit 100 generates a control signal for controlling the cutting device 1 by executing a computer program stored in the ROM on the RAM. The arithmetic processing unit of the control unit 100 outputs the generated control signal to each component of the cutting device 1 via the input / output interface device. In addition, the control unit 100 is connected to a display unit (not shown) configured by a liquid crystal display device or the like that displays a processing operation state or an image, or an input unit used when an operator registers processing content information. . The input unit includes at least one of a touch panel provided on the display unit, a keyboard, and the like.

  Next, a wafer processing method according to the first embodiment will be described. FIG. 4 is a flowchart illustrating the wafer processing method according to the first embodiment.

  A wafer processing method (hereinafter, simply referred to as a processing method) is performed by cutting a cutting blade 21 into a wafer 200 and rotating the wafer 200 around an axis parallel to the Z-axis direction so that the wafer 200 has a circular shape. This is a processing method for forming a stepped portion 300 by performing a cutting process. The processing method is a processing method for forming the side wall 500 on the outer periphery of the stepped portion 300. As shown in FIG. 4, the processing method includes a chamfer removing step ST1, a mark forming step ST2, a side wall forming step ST3, a surface protective tape attaching step ST4, a surface protective tape cutting step ST5, and a holding step ST6. And a thinning step ST7. In the first embodiment, the processing method uses the cutting device 1 in the chamfer removing step ST1, the mark forming step ST2, and the side wall forming step ST3.

(Chamfer removal step)
FIG. 5 is a sectional view showing a chamfer removing step of the wafer processing method shown in FIG. The chamfer removing step ST1 is a step in which the chamfered portion 208 is removed along the outer peripheral edge of the wafer 200 to a depth from the surface 201 to the finished thickness 400 of the wafer 200 to form a stepped portion 300 on the outer peripheral edge.

  In the chamfer removal step ST1, the operator operates the input unit to register the processing content information in the control unit 100, and the operator stores the cassette 8 that contains the wafer 200 before cutting and the cassette 9 that does not contain the wafer 200. Install on the cassette base 4. In the chamfer removal step ST <b> 1, the control unit 100 causes the carry-in / out unit 64 to take out the wafer 200 from the cassette 8 and carry it out to the alignment unit 5 when the operator gives an instruction to start a machining operation. The control unit 100 causes the alignment unit 5 to perform the center alignment of the wafer 200, and loads the wafer 200 aligned with the loading unit 65 onto the chuck table 10.

  The control unit 100 drives the suction source 17 to suck and hold the wafer 200 on the chuck table 10, and moves the chuck table 10 toward the lower side of the cutting unit 20 on the X-axis moving unit 30. In the chamfer removing step ST1, as shown in FIG. 5, the control unit 100 causes the cutting blade 21 of one cutting unit 20 to move from the surface 201 side to the chamfered portion 208 while rotating the chuck table 10 around the axis as a rotational drive source. Then, the stepped portion 300 is formed by cutting the depth to the finished thickness 400. The processing method proceeds to the mark formation step ST2 after the chamfer removal step ST1.

(Mark formation step)
FIG. 6 is a plan view showing a mark forming step of the wafer processing method shown in FIG. FIG. 7 is a plan view of the wafer after the mark formation step of the wafer processing method shown in FIG.

  The mark formation step ST2 is a step of forming the orientation flat 210 shown in FIG. 7 which is a mark indicating the crystal orientation of the wafer 200 on the inner peripheral side of the stepped portion 300 based on the notch 206. As shown in FIG. 6, the wafer 200 in the chamfer removing step ST <b> 1 is included in the stepped portion 300 with the notch 206 positioned outside the inner peripheral wall 301 of the stepped portion 300 and provided on the outer edge of the bottom surface 302. It has a notch 206 in the region.

  In the mark formation step ST2, the control unit 100 causes the image pickup unit to pick up an image of the wafer and detects the position of the notch 206. In the first embodiment, the notch 206 is used as the rotational drive source or the like. The cutting blade 21 of one cutting unit 20 is moved to the wafer while the chuck table 10 is moved in the X-axis direction by positioning the planned dividing line 203 in parallel with the X-axis direction and the Y-axis direction. A depth reaching the finishing thickness 400 is cut in the outer peripheral surplus area 205 of 200 and inside the inner peripheral wall 301 of the stepped portion 300. In the processing method, in the mark formation step ST2, the orientation flat 210 is formed on the same surface as the inner peripheral wall 301. The processing method proceeds to the sidewall formation step ST3 after the mark formation step ST2.

(Side wall forming step)
FIG. 8 is a cross-sectional view showing a side wall forming step of the wafer processing method shown in FIG. 9 is a cross-sectional view of the wafer after the side wall forming step of the wafer processing method shown in FIG. 10 is a plan view of the wafer after the side wall forming step of the wafer processing method shown in FIG.

  In the side wall forming step ST3, after performing the chamfer removing step ST1 to form the stepped portion 300, the inner peripheral wall 301 of the stepped portion 300 slightly reaches the outer peripheral side and reaches the back surface 207 of the wafer 200 from the bottom surface 302 of the stepped portion 300. This is a step of removing the depth and forming a side wall 500 from the bottom surface 302 of the stepped portion 300 to the back surface 207 of the wafer 200 on the outer peripheral side of the stepped portion 300. In the side wall forming step ST3, as shown in FIG. 8, the control unit 100 moves the cutting blade 21 of one cutting unit 20 from the inner peripheral wall 301 of the bottom surface 302 while rotating the chuck table 10 around the axis as a rotational drive source. Slightly cut to the depth reaching the back surface 207 of the wafer 200 on the outer peripheral side. In the side wall forming step ST3, the control unit 100 cuts and removes the outer peripheral side slightly from the inner peripheral wall 301 of the stepped portion 300 over the entire circumference of the wafer 200, as shown in FIGS. A sidewall 500 is formed over the circumference. In the first embodiment, in the side wall forming step ST3, the side wall 500 is formed at a position where the distance 600 is equal to or less than the finishing thickness 400 from the inner peripheral wall 301 of the bottom surface 302.

  After forming the side wall 500 over the entire circumference, the control unit 100 retracts the cutting unit 20 from the wafer 200 and then moves the chuck table 10 toward the first carry-out unit 66. The control unit 100 stops the suction and holding of the chuck table 10, transfers the wafer 200 from the chuck table 10 to the back surface cleaning unit 60 to the first carry-out unit 66, and then transfers the back surface 207 of the wafer 200 to the back surface cleaning unit 60. To wash. The control unit 100 causes the second transport unit 54 to transport the wafer 200 from the back surface cleaning unit 60 to the front surface cleaning unit 61, cleans the front surface 201 of the wafer 200 using the front surface cleaning unit 61, and then transfers the cassette 9 to the carry-in / out unit 64. The wafer 200 is accommodated therein. In the first embodiment, in the processing method, the cutting apparatus 1 sequentially performs the chamfer removing step ST1, the mark forming step ST2, and the side wall forming step ST3 on each of the wafers 200 in the cassette 8. In the processing method, after the cutting device 1 performs the side wall forming step ST3 on all the wafers 200 in the cassette 8, the process proceeds to the surface protective tape attaching step ST4.

(Surface protection tape application step)
In Embodiment 1, a processing method uses the tape sticking apparatus which is not illustrated in surface protection tape sticking step ST4 and surface protection tape cutting step ST5. FIG. 11 is a cross-sectional view showing a surface protection tape attaching step of the wafer processing method shown in FIG.

  Surface protection tape sticking step ST4 is a step of sticking surface protection tape 220 covering wafer 200 to surface 201 of wafer 200 after performing sidewall formation step ST3. The surface protection tape 220 includes a base material layer 221 made of a synthetic resin, and a glue layer 222 disposed on the base material layer 221 and attached to the surface 201 of the wafer 200, and the entire surface 201 of the wafer 200 is covered. It is formed in a size that can be covered.

  In the first embodiment, after the surface protective tape attaching step ST4 makes the adhesive layer 222 and the surface 201 of the wafer 200 face each other, the adhesive layer 222 of the surface protective tape 220 is applied to the surface of the wafer 200 as shown in FIG. Stick to 201. The processing method proceeds to the surface protective tape cutting step ST5 after the surface protective tape attaching step ST4.

(Surface protection tape cutting step)
FIG. 12 is a cross-sectional view showing a surface protection tape cutting step of the wafer processing method shown in FIG. The surface protection tape cutting step ST5 is a step of cutting the surface protection tape 220 with the cutter 70 while moving the cutter 70 of the tape attaching device along the side wall 500 after performing the surface protection tape attaching step ST4.

  In the surface protection tape cutting step ST5, as shown in FIG. 12, the cutting edge of the cutter 70 is cut from the base material layer 221 of the surface protection tape 220, and the cutting edge of the cutter 70 is in contact with the side wall 500. Move along 500. In the surface protection tape cutting step ST5, the portion of the surface protection tape 220 that protrudes outside the side wall 500 is cut and removed. The processing method proceeds to the holding step ST6 after the surface protection tape cutting step ST5.

(Holding step)
In the first embodiment, the processing method uses the grinding apparatus 80 shown in FIG. 13 in the holding step ST6 and the thinning step ST7. FIG. 13 is a cross-sectional view showing a holding step of the wafer processing method shown in FIG. The holding step ST6 is a step of holding the surface 201 side of the wafer 200 with the chuck table 81 via the surface protective tape 220 after performing the surface protective tape cutting step ST5.

  In the holding step ST6, as shown in FIG. 13, the surface 201 side of the wafer 200 is placed on the holding surface 82 formed of porous ceramics or the like of the chuck table 81 of the grinding apparatus 80 via the surface protective tape 220. Then, the suction source 83 is driven to suck and hold the surface 201 of the wafer 200 on the holding surface 82 via the surface protection tape 220. The processing method proceeds to the thinning step ST7 after the holding step ST6.

(Thinning step)
FIG. 14 is a cross-sectional view showing a thinning step of the wafer processing method shown in FIG. FIG. 15 is a cross-sectional view of a wafer transferred to a dicing tape after the wafer processing method shown in FIG. 4 is performed. The thinning step ST7 is a step of removing the side wall 500 by thinning the back surface 207 of the wafer 200 held by the chuck table 10 to a finished thickness 400.

  In the thinning step ST7, the grinding wheel 84 is brought into contact with the back surface 207 of the wafer 200 held on the chuck table 81, and the chuck table 81 and the grinding wheel 84 are rotated around the axis until the finished thickness 400 is reached. The back surface 207 of the wafer 200 is ground. In the thinning step ST7, when the wafer 200 is thinned to the finished thickness 400, the stepped portion 300 is formed to a depth from the surface 201 to the finished thickness 400, so that the side wall 500 is removed over the entire circumference. It will be. The processing method ends when the wafer 200 is thinned to a finish thickness of 400.

  When the wafer 200 is thinned to the finished thickness 400, the side wall 500 is removed from the wafer 200, and an orientation flat 210 indicating the crystal orientation is provided on the outer edge. The wafer 200 thinned to the finished thickness 400 is transferred to a known transfer device and then aligned based on the orientation flat 210 by the transfer device. As shown in FIG. 15, the dicing tape 240 with the annular frame 230 attached to the outer peripheral edge is attached to the back surface 207 so that the wafer 200 is attached to the annular frame 230 in a predetermined orientation by the transfer device. After being attached, the surface protection tape 220 is peeled off from the surface 201 and supported by the annular frame 230. The dicing tape 240 includes a base material layer 241 made of a synthetic resin, and a glue layer 242 that is disposed on the base material layer 241 and is attached to the back surface 207 of the wafer 200.

  The wafer 200 supported by the annular frame 230 is divided into individual devices 202 by laser ablation processing or cutting processing. Further, the wafer 200 is irradiated with a laser beam having transparency from the back surface 207 side along the planned division line 203 to form a modified layer along the planned division line 203, and a thinning step, a transfer step, and an expansion step are performed. It may be carried out in order to form a crack from the modified layer to the surface 201 and be divided into individual devices 202.

  In the processing method according to the first embodiment, the side wall forming step ST3 is performed after the chamfer removal step ST1 is performed. In the surface protection tape cutting step ST5, the cutter 70 is moved along the side wall 500 to cut the surface protection tape 220, so that the surface protection tape 220 protrudes from the outer periphery of the wafer 200 after grinding without substantially protruding. It is possible to prevent the protective tape 220 from sticking to the dicing tape 240 during transfer.

  Further, the processing method according to the first embodiment includes the chamfer removing step ST1 even when the device 202 includes more than 100 circuit layers and not only the chamfered portion 208 of the wafer 200 but also the outer peripheral surplus region 205 is removed. In the surface protection tape cutting step ST5 after the side wall forming step ST3, the surface protection tape protrudes from the outer periphery of the wafer 200 after grinding in order to cut the surface protection tape 220 by moving the cutter 70 along the side wall 500. 220 can be suppressed. As a result, the processing method has an effect that the dicing tape 240 and the surface protective tape 220 can be prevented from sticking at the time of transferring the wafer 200 from the surface protective tape 220 to the dicing tape 240.

  Further, since the processing method cuts the surface protection tape 220 along the side wall 500 in the surface protection tape cutting step ST5, the side wall 500 is thinned even if scratches or cracks are formed on the side wall 500. Since it is removed in ST7, the wafer 200 can be prevented from being damaged.

  In the processing method according to the first embodiment, the surface protective tape attaching step ST4 is performed after the chamfer removing step ST1 and the side wall forming step ST3. Therefore, the surface protective tape 220 is cut when forming the stepped portion 300 or the like. Without generating thread-like waste.

  Further, in the mark forming step ST2, the processing method forms the orientation flat 210 indicating the crystal orientation of the wafer 200 on the same surface as the inner peripheral wall 301 of the stepped portion 300, so that the side wall 500 is removed after the thinning step ST7. In addition, the crystal orientation of the wafer 200 can be recognized.

  In the processing method, the side wall 500 is formed at a position where the distance 600 to the inner peripheral wall 301 is equal to or less than the finishing thickness 400. Therefore, even if the side wall 500 is removed after the thinning step ST7, it protrudes from the outer edge of the wafer 200. The surface protection tape 220 can be suppressed, and the surface protection tape 220 and the dicing tape 240 can be prevented from sticking.

In addition, according to the processing method of the wafer which concerns on Embodiment 1 mentioned above, the following cutting devices are obtained.
(Appendix 1)
A cutting device for cutting a wafer,
A chuck table for holding the back surface of the wafer;
A cutting unit that removes the chamfered portion from the surface to the finished thickness of the wafer along the outer peripheral edge of the wafer with a cutting blade, and forms a stepped portion on the outer peripheral edge;
A control unit for controlling each component,
After forming the stepped portion, the control unit removes the stepping unit from the inner peripheral wall of the stepped portion to the depth slightly from the outer peripheral side to the depth from the bottom surface of the stepped portion to the back surface of the wafer. The side wall which extends from the bottom face of this level | step-difference part to the back surface of a wafer is formed in the outer peripheral side of this.

  The said cutting device forms a side wall, after forming a level | step-difference part similarly to the processing method which concerns on Embodiment 1 grade | etc.,. For this purpose, the cutting device can cut the surface protection tape by moving the cutter along the side wall on the day when the surface protection tape is adhered to the surface of the wafer, and grinding without damaging the wafer. It is possible to suppress the surface protective tape that protrudes from the outer periphery of the subsequent wafer, and to prevent the protruding surface protective tape from sticking to the dicing tape during transfer.

  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. For example, in Embodiment 1 described above, the same cutting blade 21 is used in the chamfer removing step ST1 and the side wall forming step ST3. However, in the present invention, the cutting blade 21 of one cutting unit 20 is used in the chamfer removing step ST1. It is also possible to use different cutting blades 21 in the chamfer removing step ST1 and the side wall forming step ST3, such as using the cutting blade 21 of the other cutting unit 20 in the side wall forming step ST3. In the present invention, the stepped portion 300 and the side wall 500 may be formed by grinding with a grinding wheel (not shown) in the chamfer removing step ST1 and the side wall forming step ST3.

70 Cutter 81 Chuck table 200 Wafer 201 Front surface 202 Device 206 Notch 207 Back surface 208 Chamfered portion 210 Orientation flat (mark)
220 Surface protective tape 300 Stepped portion 301 Inner peripheral wall 302 Bottom surface 400 Finished thickness 500 Side wall ST1 Chamfer removing step ST2 Mark forming step ST3 Side wall forming step ST4 Surface protective tape attaching step ST5 Surface protective tape cutting step ST6 Holding step ST7 Thinning step

Claims (2)

A wafer processing method comprising a plurality of devices on the front surface and a chamfered portion formed on the outer periphery from the front surface to the back surface.
Removing the chamfered portion along the outer peripheral edge of the wafer to a depth from the surface to the finished thickness of the wafer, and forming a stepped portion on the outer peripheral edge; and
After performing the chamfer removing step, the step is removed from the inner peripheral wall of the stepped portion to the depth slightly from the bottom surface of the stepped portion to the back surface of the wafer on the outer peripheral side, and on the outer peripheral side of the stepped portion A side wall forming step for forming a side wall from the wafer to the back surface of the wafer;
After performing the side wall forming step, a surface protective tape attaching step for attaching a surface protective tape covering the wafer to the surface of the wafer;
A surface protective tape cutting step of cutting the surface protective tape with the cutter while moving the cutter along the side wall after performing the surface protective tape attaching step;
After performing the surface protection tape cutting step, a holding step of holding the surface side of the wafer with the chuck table via the surface protection tape;
And a thinning step of removing the side wall by thinning the back surface of the wafer held by the chuck table to the finished thickness. The wafer has a notch indicating a crystal orientation in a region included in the step portion,
The wafer processing method according to claim 1, further comprising a mark forming step of forming a mark indicating a crystal orientation inside the stepped portion based on the notch.

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