JP5864112B2 - Wafer division method - Google Patents

Description

  According to the present invention, a wafer in which a plurality of streets are formed in a lattice shape on the surface and a device is formed in a plurality of regions partitioned by the plurality of streets is divided into individual devices along the street. It relates to the division method.

  In the semiconductor device manufacturing process, a plurality of regions are defined by dividing lines called streets arranged in a lattice pattern on the surface of a semiconductor wafer having a substantially disk shape, and ICs, LSIs, and microelectronics are defined in the partitioned regions. Form devices such as mechanical systems (MEMS). Then, the semiconductor wafer is cut along the streets to divide the region in which the device is formed to manufacture individual devices.

  The above-described cutting along the wafer street is usually performed by a cutting device called a dicer. This cutting apparatus includes a chuck table for holding a workpiece such as a wafer, a cutting means having a cutting blade for cutting the workpiece held on the chuck table, and a chuck table and the cutting means relative to each other. And a cutting feed means for cutting and feeding the wafer. The wafer is cut along the street by rotating the cutting blade and cutting and feeding the chuck table while supplying cutting water to the cutting portion of the cutting blade.

  However, since the cutting blade has a thickness of about 20 to 30 μm, the street that partitions the device needs to have a width of about 50 μm. For this reason, the area ratio which a street occupies becomes high, and there exists a problem that productivity is bad.

  On the other hand, as a method of dividing the wafer along the street, a pulsed laser beam having a wavelength that is transmissive to the wafer is irradiated along the street with a focusing point inside, and the wafer is broken along the street. A method of dividing the wafer along the street by applying an external force along the street where the altered layer as the starting point is formed continuously and the altered layer as the starting point of breakage is formed and the strength is reduced has been proposed. ing. (For example, refer to Patent Document 1.)

Japanese Patent No. 3408805

As a method of dividing the wafer described in Patent Document 1, an altered layer is formed by irradiating a laser beam by locating a condensing point of a laser beam in a region corresponding to the street from the back side of the wafer where the street is not formed. After that, a method of dividing the wafer by applying an external force to the wafer having a deteriorated layer formed along the street is adhered to the dicing tape. However, there is a problem that the wafer breaks along the street when the wafer having the altered layer formed along the street is stuck on the dicing tape.
On the other hand, in a state where the back surface of the wafer is attached to a dicing tape attached to an annular frame, a method of forming a deteriorated layer by condensing a laser beam from the front surface side of the wafer to the inside of the street, Although the above-mentioned problems are avoided, the width of the wafer is required to be 20 to 30% as the irradiation area of the laser beam. For example, in a wafer in which a micro electro mechanical system (MEMS) having a thickness of 400 μm is formed. However, there is a problem that a street width of about 100 μm is necessary, and there are large restrictions on the design of the wafer, resulting in poor productivity.
If the method of forming a deteriorated layer by condensing a laser beam from the back side of the wafer to the inside of the street with the surface of the wafer attached to a dicing tape attached to an annular frame, the above problem will occur. However, in a wafer on which a device consisting of a micro electromechanical system (MEMS) such as a micro horn, acceleration sensor, pressure sensor, etc. is formed, the adhesive is fine when the surface of the device is attached to a dicing tape. There is a problem that the device is damaged by adhering to the electromechanical system (MEMS).

  The present invention has been made in view of the above-mentioned facts, and the main technical problem thereof is that an altered layer can be formed along the street inside the wafer without increasing the street width, thereby damaging the device. It is an object of the present invention to provide a method of dividing a wafer that can be divided into individual devices along the street without any problem.

In order to solve the above main technical problem, according to the present invention, a device region in which a plurality of streets are formed in a lattice shape on the surface and a device is formed in a plurality of regions partitioned by the plurality of streets, and the device region A wafer dividing method for dividing a wafer having an outer peripheral surplus area surrounding the wafer along the street,
The device region is positioned in the recess in a chuck table having a recess formed on the upper surface of the central portion and an annular holding portion formed outside the recess, and the outer peripheral surplus region on the wafer surface is located in the annular holding portion. Is placed directly on the wafer, and a laser beam with a wavelength that is transparent to the wafer is positioned along the street from the back side of the wafer and irradiated along the street. A first deteriorated layer forming step of forming a first deteriorated layer along the street leaving a raw region;
A wafer support step of attaching the back surface of the wafer on which the first deteriorated layer forming step has been performed to a dicing tape attached to an annular frame;
After carrying out the wafer support step, a laser beam having a wavelength that is transparent to the wafer is positioned along the street from the front surface side of the wafer whose back surface is attached to the dicing tape to the unprocessed region inside. A second deteriorated layer forming step of forming a second deteriorated layer along the street in the raw region of the wafer,
A rupture step of applying an external force to the wafer on which the second deteriorated layer forming step has been performed, and rupturing along the street where the first deteriorated layer and the second deteriorated layer are formed,
A method of dividing a wafer is provided.

  The device formed on the wafer is a device composed of a micro electro mechanical system (MEMS), and the first deteriorated layer forming step is performed in a state where only the outer peripheral surplus region is supported.

In the wafer dividing method according to the present invention, the device region is positioned in the concave portion of the chuck table including the concave portion formed on the upper surface of the central portion and the annular holding portion formed outside the concave portion, and the annular holding is performed. The outer peripheral surplus area on the wafer surface is directly placed on the wafer to hold the wafer, and a laser beam having a wavelength that is transparent to the wafer is positioned from the back side of the wafer to the inside along the street. Irradiation is performed, and a first deteriorated layer forming step is performed in which a first deteriorated layer is formed along the street leaving an unprocessed region on the surface side inside the wafer, so that the surface side is held on the chuck table. Further, since the outer peripheral surplus region is supported on the annular holding portion, the device is not damaged.
Further, in the wafer dividing method according to the present invention, since the first deteriorated layer forming step is performed, the wafer supporting step of sticking the back surface of the wafer to the dicing tape mounted on the annular frame is performed. Since the processing area maintains strength, the problem that the wafer breaks along the street when the wafer is unloaded from the chuck table of the laser processing apparatus or before and after being attached to the dicing tape can be solved. Since it is not necessary to apply a dicing tape to the surface of the device, which is the surface, even if the device is a micro electro mechanical system (MEMS), it is not damaged.
Further, in the wafer dividing method according to the present invention , the second deteriorated layer forming step of forming the second deteriorated layer along the street in the unprocessed region of the wafer has a wavelength that is transparent to the wafer. The laser beam is irradiated along the street from the front side of the wafer attached to the dicing tape to the unprocessed area inside the wafer, so that the laser beam is left in a shallow position on the front side from the front side of the wafer. Since the condensing point of the laser beam is positioned and irradiated in the processing area, the laser beam is not irradiated to the device even if the street width is narrow. Therefore, the width of the street is not restricted in the design of the wafer.

The perspective view of the wafer divided | segmented into each device by the division | segmentation method of the wafer by this invention. The principal part perspective view of the laser processing apparatus for implementing the 1st deteriorated layer formation process in the division | segmentation method of the wafer by this invention. Explanatory drawing of the 1st deteriorated layer formation process in the division | segmentation method of the wafer by this invention. Explanatory drawing of the wafer support process in the division | segmentation method of the wafer by this invention. The principal part perspective view of the laser processing apparatus for implementing the 2nd deteriorated layer formation process in the division | segmentation method of the wafer by this invention. Explanatory drawing of the 2nd deteriorated layer formation process in the division | segmentation method of the wafer by this invention. The perspective view of the tape expansion device for implementing the wafer fracture | rupture process in the division | segmentation method of the wafer by this invention. Explanatory drawing of the wafer fracture | rupture process in the division | segmentation method of the wafer by this invention. Explanatory drawing of the pick-up process in the division | segmentation method of the wafer by this invention.

  Preferred embodiments of a wafer dividing method according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a wafer divided into individual devices by the wafer dividing method according to the present invention. The wafer 2 shown in FIG. 1 is made of a silicon wafer having a thickness of, for example, 400 μm, and a plurality of areas are defined by a plurality of streets 21 formed in a lattice shape on the surface 2a. As a result, a micro electro mechanical system (MEMS) is formed. The semiconductor wafer 2 configured as described above includes a device region 220 in which the device 22 is formed, and an outer peripheral surplus region 230 surrounding the device region 220.

Hereinafter, a method for dividing the wafer 2 described above into individual devices 22 along a plurality of streets 21 will be described.
First, a laser beam having a wavelength that is transmissive to the wafer 2 is irradiated from the back surface side of the wafer 2 toward the inside along the street 21 to leave an unprocessed area on the front surface side of the wafer 2. Then, a first deteriorated layer forming step of forming a first deteriorated layer along the street 21 is performed. This first deteriorated layer forming step is performed using the laser processing apparatus 3 shown in FIG. The laser processing apparatus 3 shown in FIG. 2 has a chuck table 31 that holds a workpiece, laser beam irradiation means 32 that irradiates the workpiece held on the chuck table 31 with a laser beam, and a chuck table 31 that holds the workpiece. An image pickup means 33 for picking up an image of the processed workpiece is provided. The chuck table 31 includes a circular concave portion 311 formed on the upper surface of the central portion and an annular suction holding portion 312 formed outside the circular concave portion 311. A plurality of suction holes 313 are formed in the annular suction holding portion 312 and open to a suction holding surface that is an upper surface, and the plurality of suction holes 313 communicate with suction means (not shown). Accordingly, by operating a suction means (not shown), the workpiece placed on the suction holding surface which is the upper surface of the annular suction holding portion 312 is sucked and held. The chuck table 31 configured in this manner is processed and fed in a direction indicated by an arrow X in FIG. 2 by a processing feed means (not shown), and is indexed and fed in a direction indicated by an arrow Y in FIG. 2 by an index feed means (not shown). It has become so.

  The laser beam irradiation means 32 irradiates a pulsed laser beam from a condenser 322 mounted on the tip of a cylindrical casing 321 arranged substantially horizontally. In addition, the image pickup means 33 attached to the tip of the casing 321 constituting the laser beam irradiation means 32 is not a normal image pickup device (CCD) for picking up an image by visible light in the illustrated embodiment, but is applied to a workpiece. Infrared illuminating means for irradiating infrared light, an optical system for capturing the infrared light irradiated by the infrared illuminating means, an image pickup device (infrared CCD) for outputting an electrical signal corresponding to the infrared light captured by the optical system, and the like The captured image signal is sent to a control means (not shown).

The first deteriorated layer forming step performed using the laser processing apparatus 3 described above will be described with reference to FIGS.
In order to perform the first deteriorated layer forming step, first, the surface 2a side of the wafer 2 is placed on the chuck table 31 of the laser processing apparatus 3 shown in FIG. At this time, as shown in FIG. 3 (a), the outer peripheral surplus area 230 of the wafer 2 is placed on the suction holding surface which is the upper surface of the annular suction holding portion 312 of the chuck table 31, and the suction means (not shown) is operated. Then, the outer peripheral surplus area 230 of the wafer 2 is sucked and held on the annular suction holding portion 312 of the chuck table 31 (wafer holding step). Accordingly, the back surface 2b of the wafer 2 held on the chuck table 31 is on the upper side. In the wafer 2 having the surface side held on the chuck table 31 in this way, only the outer peripheral surplus region 230 is supported on the annular suction holding unit 312, so that the device 22 is not damaged. The chuck table 31 that sucks and holds the wafer in this way is positioned directly below the image pickup means 33 by a processing feed means (not shown).

  When the chuck table 31 is positioned immediately below the image pickup means 33, an alignment step for detecting a processing region to be laser processed along the street 21 of the wafer 2 is executed by the image pickup means 33 and a control means (not shown). That is, the imaging means 33 and the control means (not shown) align the street 21 formed in a predetermined direction of the wafer 2 with the condenser 322 of the laser beam irradiation means 32 that irradiates the laser beam along the street 21. Image processing such as pattern matching is performed to perform alignment of the laser beam irradiation position. In addition, the alignment of the laser beam irradiation position is similarly performed on the plurality of streets 21 formed in the direction orthogonal to the plurality of streets 21 formed on the wafer 2. At this time, the surface 2a on which the plurality of streets 21 of the wafer 2 are formed is positioned on the lower side. However, as described above, the imaging unit 33 is an infrared illumination unit, an optical system that captures infrared rays, and an electrical system corresponding to infrared rays. Since the image pickup unit (an infrared CCD) or the like that outputs a signal is provided, the street 21 can be imaged through the back surface 2b.

  When the street 21 formed on the wafer 2 held on the chuck table 31 is detected as described above and the alignment of the laser beam irradiation position is performed, the chuck table as shown in FIG. 31 is moved to the laser beam irradiation region where the condenser 322 of the laser beam irradiation means 32 is located, and one end of the predetermined street 21 (the left end in FIG. 3A) is directly below the condenser 322 of the laser beam irradiation means 32. Position. Then, the condensing point P of the pulse laser beam is adjusted to a position 100 μm above the surface 2 a (lower surface) of the wafer 2, for example. Next, the chuck table 31 is moved at a predetermined processing feed rate in the direction indicated by the arrow X1 in FIG. 3A while irradiating a pulse laser beam having a wavelength that is transmissive to the silicon wafer from the condenser 322. . Then, as shown in FIG. 3B, when the other end of the street 21 (the right end in FIG. 3B) reaches the irradiation position of the condenser 322 of the laser beam irradiation means 32, the irradiation of the pulsed laser beam is stopped. At the same time, the movement of the chuck table 31 is stopped. As a result, a first deteriorated layer 251 is formed inside the wafer 2 while leaving an unprocessed region 240 of about 70 μm on the surface 2 a (lower surface) side of the wafer 2 along the street 21. The first altered layer 251 is formed as a melt-resolidified layer.

The processing conditions in the first deteriorated layer forming step are set as follows, for example.
Light source: LD excitation Q switch Nd: YVO4 laser Wavelength: 1064 nm pulse laser Average output: 1.2 W
Repetition frequency: 80 kHz
Pulse width: 120 ns
Condensing spot diameter: φ2μm
Processing feed rate: 100 mm / sec

  Note that, under the above-described processing conditions, the thickness of the first deteriorated layer 251 formed by one laser beam irradiation is 50 to 60 μm. Therefore, in order to easily divide the wafer 2 having a thickness of 400 μm, it is desirable to form about 5 altered layers having a thickness of 50 to 60 μm. Therefore, in the illustrated embodiment, as shown in FIG. 3C, the unprocessed region 240 is left on the front surface 2a (lower surface) side of the wafer 2, and the first four layers are formed on the rear surface 2b side (upper surface). The altered layer 251 is laminated. In the first deteriorated layer forming step, since the pulse laser beam is irradiated from the back surface 2b (upper surface) side of the wafer 2, the device 22 is not irradiated with the pulse laser beam.

  When the first deteriorated layer forming step is executed along all the streets 21 extending in the predetermined direction of the wafer 2 in this way, the chuck table 31 is rotated by 90 degrees to move in the predetermined direction. The first deteriorated layer forming step is executed along each street 21 extending in a direction orthogonal to the above.

  If the above-mentioned first deteriorated layer forming step is performed, a dicing tape in which the back surface of the wafer 2 on which the first deteriorated layer 251 is formed leaving the unprocessed region 240 on the surface 2a side is mounted on an annular frame. A wafer support process for attaching to the wafer is carried out. That is, as shown in FIG. 4, the back surface 2b of the wafer 2 is adhered to the surface of the dicing tape 5 with the outer peripheral portion mounted so as to cover the inner opening of the annular frame 4. The dicing tape 5 is formed of a sheet base material made of polyvinyl chloride (PVC) or polyolefin (PO), and an adhesive is applied on the surface thereof to a thickness of about 5 μm. In this way, in the wafer support process, the back surface 2b of the wafer 2 on which the first deteriorated layer 251 is formed leaving the unprocessed region 240 on the front surface 2a side of the wafer 2 is attached to the dicing tape 5 attached to the annular frame 4. Since the unprocessed region 240 maintains strength, the wafer 2 is moved along the street 21 when the wafer 2 is carried out of the chuck table 31 of the laser processing apparatus 3 or before and after being attached to the dicing tape 5. In addition, since the dicing tape 5 does not need to be adhered to the surface of the device 22 which is the surface 2a of the wafer 2, the device 22 is made to be a micro electro mechanical system (MEMS) as in the illustrated embodiment. But it will not be damaged.

  Next, a condensing point is positioned along the street 21 from the surface 2a side of the wafer 2 on which a laser beam having a transmittance with respect to the wafer 2 is attached to the dicing tape 5 to the unprocessed region 240 inside. Irradiation is performed, and a second deteriorated layer forming step for forming a second deteriorated layer along the street 21 in the unprocessed region 240 of the wafer 2 is performed. This second deteriorated layer forming step is performed using a laser processing apparatus 30 shown in FIG. Since the laser processing apparatus 30 shown in FIG. 5 has substantially the same configuration as the laser processing apparatus 3 shown in FIG. 2 except for the chuck table 301 that holds the workpiece, the same reference numerals are assigned to the same members. The description is omitted. The chuck table 301 is configured to suck and hold a workpiece on a holding surface, which is the upper surface, and is moved in a processing feed direction indicated by an arrow X in FIG. The feed means can be moved in the index feed direction indicated by the arrow Y in FIG.

  In order to perform the second deteriorated layer forming step using the laser processing apparatus 30 described above, first, a dicing tape in which the back surface 2b of the wafer 2 is adhered on the chuck table 301 of the laser processing apparatus 30 shown in FIG. 5 is placed. Then, by operating a suction means (not shown), the wafer 2 is sucked and held on the chuck table 301 via the dicing tape 5 (wafer holding step). Accordingly, the wafer 2 held on the chuck table 301 has the surface 2a on the upper side. In FIG. 5, the annular frame 4 on which the dicing tape 5 is mounted is omitted, but the annular frame 4 is held by an appropriate frame holding unit disposed on the chuck table 301. In this way, the chuck table 301 that sucks and holds the wafer 2 is positioned directly below the image pickup means 33 by a processing feed means (not shown).

  When the chuck table 301 is positioned immediately below the image pickup means 33, an alignment operation for detecting a processing region to be laser processed on the wafer 2 is executed by the image pickup means 33 and a control means (not shown). That is, the imaging means 33 and the control means (not shown) align the street 21 formed in a predetermined direction of the wafer 2 with the condenser 322 of the laser beam irradiation means 32 that irradiates the laser beam along the street 21. Image processing such as pattern matching is performed to perform alignment of the laser beam irradiation position (alignment process). Similarly, alignment of the laser beam irradiation position is performed on the street 21 formed on the wafer 2 in a direction orthogonal to the predetermined direction.

  If the street 21 formed on the surface of the wafer 2 held on the chuck table 301 as described above is detected and the laser beam irradiation position is aligned, as shown in FIG. The chuck table 301 is moved to the laser beam irradiation region where the condenser 322 of the laser beam irradiation means 32 is located, and one end of the predetermined street 21 (the left end in FIG. 6A) is connected to the condenser 322 of the laser beam irradiation means 32. Position directly below. Then, the condensing point P of the pulse laser beam is matched with the intermediate position in the thickness direction of the unprocessed region 240 left on the surface 2a side of the wafer 2. Next, the chuck table 301 is moved at a predetermined processing feed rate in the direction indicated by the arrow X1 in FIG. 6A while irradiating a pulse laser beam having a wavelength that is transmissive to the silicon wafer from the condenser 322. . Then, as shown in FIG. 6B, when the other end of the street 21 (the right end in FIG. 6B) reaches the irradiation position of the condenser 322 of the laser beam irradiation means 32, the irradiation of the pulsed laser beam is stopped. And the movement of the chuck table 301 is stopped. As a result, the second deteriorated layer 252 is formed along the street 21 in the unprocessed region 240 of the wafer 2 as shown in FIGS. 6B and 6C. The second altered layer 252 is formed as a melt-resolidified layer. The processing conditions in the second deteriorated layer forming step may be the same as the processing conditions in the first deteriorated layer forming step. Therefore, the unprocessed region 240 of the wafer 2 has a thickness of 50 to 60 μm. Two altered layers 252 are formed. In this second deteriorated layer forming step, the unprocessed region 240 left in the shallow position on the surface side from the surface 2a side of the wafer 2 is irradiated with the focal point of the laser beam positioned, so that the width of the street 21 is narrow. The laser beam is not irradiated on the device 22.

  If the second deteriorated layer forming step described above is performed, an external force is applied to the wafer 2, and a breaking step of breaking along the street 21 where the first deteriorated layer 251 and the second deteriorated layer 252 are formed is performed. carry out. This breaking process is performed using the tape expansion device 6 shown in FIG. 7 includes a frame holding means 61 for holding the annular frame 4 and a tape extending means for expanding the dicing tape 5 attached to the annular frame 4 held by the frame holding means 61. 62 and a pickup collet 63. The frame holding means 61 includes an annular frame holding member 611 and a plurality of clamps 612 as fixing means provided on the outer periphery of the frame holding member 611. An upper surface of the frame holding member 611 forms a mounting surface 611a on which the annular frame 4 is mounted, and the annular frame 4 is mounted on the mounting surface 611a. Then, the annular frame 4 placed on the placement surface 611 a is fixed to the frame holding member 611 by the clamp 612. The frame holding means 61 configured in this manner is supported by the tape expanding means 62 so as to be able to advance and retract in the vertical direction.

  The tape expansion means 62 includes an expansion drum 621 disposed inside the annular frame holding member 611. The expansion drum 621 has an inner diameter and an outer diameter that are smaller than the inner diameter of the annular frame 4 and larger than the outer diameter of the wafer 2 attached to the dicing tape 5 attached to the annular frame 4. Further, the expansion drum 621 includes a support flange 622 at the lower end. The tape expansion means 62 in the illustrated embodiment includes support means 623 that can advance and retract the annular frame holding member 611 in the vertical direction. The support means 623 includes a plurality of air cylinders 623 a disposed on the support flange 622, and the piston rod 623 b is connected to the lower surface of the annular frame holding member 611. As described above, the support means 623 including the plurality of air cylinders 623 a is configured such that the annular frame holding member 611 has a reference position where the mounting surface 611 a is substantially the same height as the upper end of the expansion drum 621 as shown in FIG. Then, as shown in FIG. 8 (b), it is moved in the vertical direction between the extended positions below the upper end of the expansion drum 621 by a predetermined amount.

  The wafer implemented using the tape expansion apparatus 6 configured as described above will be described with reference to FIG. That is, the annular frame 4 to which the dicing tape 5 to which the wafer 2 is attached is mounted on the mounting surface 611a of the frame holding member 611 constituting the frame holding means 61 as shown in FIG. And fixed to the frame holding member 611 by the clamp 612 (frame holding step). At this time, the frame holding member 611 is positioned at the reference position shown in FIG.

  When the above-described frame holding step is performed, the plurality of air cylinders 623a as the supporting means 623 constituting the tape expanding means 62 are operated as shown in FIG. Lower to the extended position. Accordingly, since the annular frame 4 fixed on the mounting surface 611a of the frame holding member 611 is also lowered, the dicing tape 5 attached to the annular frame 4 is an expansion drum as shown in FIG. Expansion is performed in contact with the upper edge of 621 (tape expansion process). As a result, the tensile force acts radially on the wafer 2 adhered to the dicing tape 5. When a tensile force is applied to the wafer 2 in a radial manner in this way, the strength of the first altered layer 251 and the second altered layer 252 formed along the street 21 is reduced. The first deteriorated layer 251 and the second deteriorated layer 252 that have been lowered are broken along the streets 21 as breakage starting points and divided into individual devices 22.

  If the wafer breaking process described above is performed, the wafer 2 is broken along the streets 21 on which the first altered layer 251 and the second altered layer 252 are formed and divided into individual devices 22. As shown in FIG. 4, the pickup collet 63 is operated to attract the device 22, and peels off the dicing tape 5 to pick up. In the pickup process, since the gap S between the individual devices 22 is widened, the pickup can be easily performed without contact with the adjacent devices 22.

  Although the present invention has been described based on the illustrated embodiment, the present invention is not limited to the embodiment, and various modifications are possible within the scope of the gist of the present invention. For example, in the above-described embodiment, an example in which a wafer on which a device composed of a microelectromechanical system (MEMS) is formed is divided into individual devices, but the present invention is a semiconductor on which a device such as an IC or LSI is formed. You may apply to the optical device wafer in which optical devices, such as a wafer, a light emitting diode, and CCD, were formed.

2: Wafer 21: Street 22: Device 220: Device area 230: Peripheral surplus area 3: Laser processing apparatus 31: Chuck table of laser processing apparatus 32: Laser beam irradiation means 322: Condenser 33: Imaging means 30: Laser processing apparatus 301: chuck table of laser processing apparatus 4: annular frame 5: dicing tape 6: tape expansion device 61: frame holding means 62: tape expansion means 63: pickup collet

Claims (2)

A wafer having a device region in which a plurality of streets are formed in a lattice shape on the surface and a device is formed in a plurality of regions partitioned by the plurality of streets and an outer peripheral surplus region surrounding the device region is divided along the streets. A method of dividing a wafer,
The device region is positioned in the recess in a chuck table having a recess formed on the upper surface of the central portion and an annular holding portion formed outside the recess, and the outer peripheral surplus region on the wafer surface is located in the annular holding portion. Is placed directly on the wafer, and a laser beam with a wavelength that is transparent to the wafer is positioned along the street from the back side of the wafer and irradiated along the street. A first deteriorated layer forming step of forming a first deteriorated layer along the street leaving a raw region;
A wafer support step of attaching the back surface of the wafer on which the first deteriorated layer forming step has been performed to a dicing tape attached to an annular frame;
After carrying out the wafer support step, a laser beam having a wavelength that is transparent to the wafer is positioned along the street from the front surface side of the wafer whose back surface is attached to the dicing tape to the unprocessed region inside. A second deteriorated layer forming step of forming a second deteriorated layer along the street in the raw region of the wafer,
A rupture step of applying an external force to the wafer on which the second deteriorated layer forming step has been performed, and rupturing along the street where the first deteriorated layer and the second deteriorated layer are formed,
A wafer dividing method characterized by the above.   2. The wafer according to claim 1, wherein the device formed on the wafer is a device composed of a microelectromechanical system (MEMS), and the first deteriorated layer forming step is performed in a state where only the outer peripheral surplus region is supported. Split method.

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