JP2013219271A - Method for processing optical device wafer - Google Patents

Abstract

A modified layer can be formed along a street inside a substrate without damaging the optical device layer, and the thickness of the optical device is formed to a predetermined thickness.
A method of dividing an optical device wafer (2) into individual optical devices (23) along streets (221, 222), wherein a region where the streets (221, 222) are formed in an optical device layer (21) is removed to remove a substrate (20). A substrate exposure step for exposing the surface of the substrate, and a laser beam is irradiated along the streets 221 and 222 through the region where the optical device layer 21 is removed by positioning the condensing point from the optical device layer 21 side, The modified layer forming step to be formed, the protective member attaching step for attaching the protective member T to the surface of the wafer 2, the protective member T side of the wafer 2 is held by the holding means, and the grinding wheel is attached to the back surface of the substrate 20. A back grinding step of pressing and grinding to form a predetermined thickness and dividing along the street where the modified layer is formed.
[Selection] Figure 8

Description

  In the present invention, an optical device layer (epi layer) composed of an n-type nitride semiconductor layer and a p-type nitride semiconductor layer is laminated on the surface of a sapphire substrate or silicon carbide substrate, and is partitioned by a plurality of streets formed in a lattice shape. The present invention relates to a wafer processing method in which an optical device wafer in which optical devices are formed in a plurality of regions is divided into individual optical devices along a street.

  In the optical device manufacturing process, a plurality of optical device layers formed of an n-type nitride semiconductor layer and a p-type nitride semiconductor layer are formed in a lattice shape on the surface of a substantially disc-shaped sapphire substrate or silicon carbide substrate. An optical device wafer is formed by forming optical devices such as light-emitting diodes and laser diodes in a plurality of regions partitioned by streets. Then, the optical device wafer is cut along the streets to divide the region where the optical device is formed to manufacture individual optical devices.

  The above-mentioned cutting along the street of the optical device wafer is usually performed by a cutting device called a dicer. The cutting apparatus includes a chuck table for holding a workpiece, a cutting means for cutting the workpiece held on the chuck table, and a cutting feed means for relatively moving the chuck table and the cutting means. It has. The cutting means includes a rotary spindle, a cutting blade mounted on the spindle, and a drive mechanism that rotationally drives the rotary spindle. The cutting blade is composed of a disk-shaped base and an annular cutting edge mounted on the outer periphery of the side surface of the base. The cutting edge is fixed to the base by electroforming, for example, diamond abrasive grains having a particle size of about 3 μm. It is formed to a thickness of about 30 μm.

  However, since the sapphire substrate, the silicon carbide substrate and the like constituting the optical device wafer have high Mohs hardness, cutting with the cutting blade is not always easy.

  In order to solve the above-mentioned problem, as a method of dividing the optical device wafer along the street, a laser processing groove that becomes a starting point of breakage by irradiating the wafer with a pulsed laser beam having absorbency to the wafer is provided. There has been proposed a method of forming and cleaving by applying an external force along a street in which a laser processed groove serving as a starting point of the fracture is formed. (For example, refer to Patent Document 1.)

  However, when a laser processing groove is formed by irradiating a laser beam along the street formed on the surface of the sapphire substrate that constitutes the optical device wafer, the outer periphery of the optical device such as a light emitting diode is ablated, resulting in a decrease in luminance. There is a problem that the quality of the device is degraded.

  In order to solve such a problem, a laser beam having a wavelength having transparency to the sapphire substrate is focused from the back side of the sapphire substrate on which the optical device layer (epi layer) as the optical device layer is not formed. A method of processing a sapphire substrate that divides the sapphire substrate along the street where the modified layer is formed by irradiating along the street while being positioned inside and forming the modified layer along the street inside the sapphire substrate Is disclosed in Patent Document 2 below.

  In the optical device wafer, the sapphire substrate or silicon carbide substrate is damaged in the process of laminating the optical device layer made of gallium nitride compound semiconductor on the surface of the sapphire substrate or silicon carbide substrate and in the process of transporting the sapphire substrate or silicon carbide substrate. In order to avoid this, the thickness of the sapphire substrate or silicon carbide substrate is about 1 mm. And in order to improve the brightness | luminance of an optical device, the back surface of a sapphire substrate or a silicon carbide substrate is ground and formed in thickness of 100-200 micrometers.

  However, when the diameter of the sapphire substrate or silicon carbide substrate is as large as 100 to 150 mm, if the back surface of the sapphire substrate or silicon carbide substrate is ground and thinned, the sapphire substrate or silicon carbide substrate is warped and damaged. is there.

  In order to solve such problems, a wafer processing method is proposed in which a modified layer is formed along the street inside the substrate before the back surface of the substrate constituting the wafer is ground to a predetermined thickness. Has been. (For example, refer to Patent Document 3).

JP-A-10-305420 JP 2008-6492 A JP 2006-12902 A

  Thus, in the wafer processing method disclosed in Patent Document 3, a laser beam having a high output must be irradiated because the thickness of the sapphire substrate or the silicon carbide substrate increases as the diameter increases. Don't be. For this reason, the optical device layer laminated on the street formed on the surface of the laser beam irradiated from the back side of the sapphire substrate or silicon carbide substrate is destroyed and a crack is generated. There is a problem that the quality of the device is degraded.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is that it is possible to form a modified layer along the street inside the substrate without damaging the optical device layer, and to provide an optical device. An object of the present invention is to provide a method of processing an optical device wafer that can be formed to a predetermined thickness.

In order to solve the above main technical problem, according to the present invention, an optical device in which an optical device is formed in a plurality of regions partitioned by a plurality of streets formed by laminating an optical device layer on a surface of a substrate and forming a lattice shape. An optical device wafer processing method for dividing a wafer into individual optical devices along a street,
A substrate exposure step of exposing the surface of the substrate by removing a region where streets are formed in the optical device layer laminated on the surface of the substrate;
A laser beam having a wavelength that is transparent to the substrate is irradiated from the optical device layer side to the inside of the substrate along the street through the area where the optical device layer in the street is removed, and the street inside the substrate. A modified layer forming step of forming a modified layer along
A protective member attaching step of attaching a protective member to the surface of the optical device wafer on which the modified layer forming step has been carried out;
The protective member side of the optical device wafer on which the protective member attaching step has been performed is held by a holding means, and is ground by pressing the back surface of the substrate while rotating the grinding wheel to form the substrate with a predetermined thickness. A back grinding step of dividing along the street where the quality layer is formed,
An optical device wafer processing method is provided.

In the substrate exposing step, the surface of the substrate is exposed by irradiating the optical device layer with a laser beam having a wavelength having an absorptivity with respect to the optical device layer, and removing the optical device layer along the street.
In the substrate exposure step, the surface of the substrate is exposed by removing the optical device layer by cutting along the streets with a cutting blade.

  In the present invention, after performing the substrate exposure step of removing the region where the streets are formed in the optical device layer laminated on the surface of the substrate to expose the surface of the substrate, the wavelength of the substrate having the transparency is obtained. A laser beam is irradiated from the optical device layer side to the inside of the substrate and irradiated along the street through the area where the optical device layer is removed on the street to form a modified layer along the street inside the substrate. Since the substrate layer forming process is performed, the laser beam irradiated in the modified layer forming process is irradiated through the area where the substrate exposing process is performed and the optical device layer in the street is removed, so that the optical device layer is not destroyed. No cracks propagate to the optical device.

The perspective view and principal part expanded sectional view which show the optical device wafer processed by the processing method of the optical device wafer by this invention. The principal part perspective view of the laser processing apparatus for enforcing 1st Embodiment of the board | substrate exposure process in the processing method of the optical device wafer by this invention. Explanatory drawing which shows 1st Embodiment of the board | substrate exposure process in the processing method of the optical device wafer by this invention. The principal part perspective view of the cutting device for enforcing 2nd Embodiment of the board | substrate exposure process in the processing method of the optical device wafer by this invention. Explanatory drawing which shows 2nd Embodiment of the board | substrate exposure process in the processing method of the optical device wafer by this invention. The principal part perspective view of the laser processing apparatus for implementing the modified layer formation process in the processing method of the optical device wafer by this invention. Explanatory drawing of the modified layer formation process in the processing method of the optical device wafer by this invention. Explanatory drawing which shows the protection member sticking process in the processing method of the optical device wafer by this invention. The principal part perspective view of the grinding device for implementing the back surface grinding process in the processing method of the optical device wafer by this invention. Explanatory drawing of the back surface grinding process in the processing method of the optical device wafer by this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a method for processing an optical device wafer according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a perspective view of an optical device wafer processed by the optical device wafer processing method according to the present invention and a sectional view showing an enlarged main part.
In the optical device wafer 2 shown in FIG. 1, an optical device layer 21 composed of an n-type gallium nitride semiconductor layer 211 and a p-type gallium nitride semiconductor layer 212 is formed on the surface 20a of a substantially disc-shaped sapphire substrate 20 by an epitaxial growth method. ing. The optical device layer 21 is not limited to gallium nitride (GaN) but is formed of GaP, GaInP, GaInAs, GaInAsP, InP, InN, InAs, AIN, AIGaAs, or the like. In the optical device wafer 2 configured as described above, in the illustrated embodiment, the diameter of the sapphire substrate 20 is 100 mm, the thickness is 1.3 mm, and the thickness of the optical device layer 21 is 10 μm. In the optical device layer 21, as shown in FIG. 1A, optical devices 23 are formed in a plurality of regions partitioned by a plurality of streets 22 formed in a lattice shape. Note that the width of the street 22 is set to 40 μm in the illustrated embodiment. Hereinafter, a processing method for dividing the optical device wafer 2 into the individual optical devices 23 along the streets 22 will be described.

  In order to divide the optical device wafer 2 into the individual optical devices 23 along the streets 22, the region where the streets 22 are formed in the optical device layer 21 laminated on the surface 20 a of the sapphire substrate 20 is removed to remove the optical device wafer 2. A substrate exposure step for exposing the surface 20a of the substrate is performed. A first embodiment of this substrate exposure step will be described with reference to FIGS. The first embodiment of the substrate exposure step is performed using a 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 is configured to suck and hold the workpiece. The chuck table 31 is moved in a processing feed direction indicated by an arrow X in FIG. 2 by a processing feed means (not shown) and is also shown in FIG. 2 by an index feed means (not shown). It can be moved in the index feed direction indicated by the arrow Y.

  The laser beam irradiation means 32 includes a cylindrical casing 321 arranged substantially horizontally. In the casing 321, pulse laser beam oscillation means including a pulse laser beam oscillator and repetition frequency setting means (not shown) are arranged. A condenser 322 for condensing the pulse laser beam oscillated from the pulse laser beam oscillating means is attached to the tip of the casing 321. The laser beam irradiating means 32 includes a condensing point position adjusting means (not shown) for adjusting the condensing point position of the pulse laser beam condensed by the condenser 322.

  In the illustrated embodiment, the imaging means 33 attached to the tip of the casing 321 constituting the laser beam irradiation means 32 is constituted by an imaging element (CCD) that captures an image with visible light, and captures the captured image signal. It sends to the control means which is not illustrated.

Using the laser processing apparatus 3 described above, the optical device layer 21 constituting the optical device wafer 2 is irradiated with a laser beam having an absorptive wavelength along the street 22 to form the street 22 in the optical device layer 21. A substrate exposure process for removing the formed region and exposing the surface 20a of the sapphire substrate 20 will be described with reference to FIGS.
First, the back surface 20b side of the sapphire substrate 20 constituting the optical device wafer 2 is placed on the chuck table 31 of the laser processing apparatus 3 shown in FIG. Then, the optical device wafer 2 is sucked and held on the chuck table 31 by operating a suction means (not shown) (wafer holding step). Accordingly, in the optical device wafer 2 held on the chuck table 31, the surface 21a of the optical device layer 21 laminated on the surface 20a of the sapphire substrate 20 is on the upper side. In this way, the chuck table 31 that sucks and holds the optical device wafer 2 is positioned directly below the image pickup means 33 by a processing feed means (not shown).

  When the chuck table 31 that sucks and holds the optical device wafer 2 is positioned immediately below the image pickup means 33, the processing region to be laser-processed of the optical device layer 21 that constitutes the optical device wafer 2 by the image pickup means 33 and the control means (not shown). Execute the alignment work to be detected. That is, the image pickup means 33 and the control means (not shown) are a condensing of the street 22 formed in a predetermined direction on the optical device layer 21 of the optical device wafer 2 and the laser beam irradiation means 32 that irradiates the laser beam along the street 22. Image processing such as pattern matching for alignment with the device 322 is performed, and alignment of the laser beam irradiation position is performed (alignment process). Similarly, alignment of the laser beam irradiation position is performed on the street 22 formed on the optical device wafer 2 in a direction orthogonal to the predetermined direction.

  If the street 22 formed on the surface of the optical device layer 21 constituting the optical device wafer 2 held on the chuck table 31 as described above is detected and the laser beam irradiation position is aligned, FIG. 3 (a), the chuck table 31 is moved to the laser beam irradiation area where the condenser 322 of the laser beam irradiation means 32 is located, and one end (the left end in FIG. 3 (a)) of the predetermined street 22 is moved to the laser beam. It is positioned directly below the light collector 322 of the irradiation means 32. Then, the condensing point P of the pulsed laser beam irradiated from the condenser 322 is aligned with the surface (upper surface) position of the optical device layer 21 constituting the optical device wafer 2. Next, while irradiating the optical device layer 21 with a pulsed laser beam having an absorptive wavelength from the condenser 322, the chuck table 31 is moved in the direction indicated by the arrow X1 in FIG. Move it. 3B, when the irradiation position of the condenser 322 of the laser beam irradiation means 32 reaches the position of the other end of the street 22 (the right end in FIG. 3B), irradiation with a pulsed laser beam is performed. And the movement of the chuck table 31 is stopped. As a result, in the optical device layer 21 constituting the optical device wafer 2, laser processed grooves 221 are formed along the streets 22 as shown in FIG. 3B and FIG. The surface 20a is exposed (substrate exposure step). The above-described substrate exposure process is performed along all the streets 22 formed in the optical device wafer 2.

The processing conditions in the substrate exposure process are set as follows, for example.
Wavelength: 355 nm pulse laser Repeat frequency: 15 kHz
Average output: 0.5W
Pulse width: 100 ns
Condensing spot diameter: φ30μm
Processing feed rate: 90 mm / sec

  Next, a second embodiment of the substrate exposure process will be described with reference to FIGS. The second embodiment of the substrate exposure step is performed using a cutting device 4 shown in FIG. The cutting apparatus 4 shown in FIG. 4 includes a chuck table 41 that holds a workpiece, a cutting means 42 that cuts the workpiece held on the chuck table 41, and a workpiece held on the chuck table 41. An image pickup means 43 for picking up images is provided. The chuck table 41 is configured to suck and hold a workpiece. The chuck table 41 is moved in a machining feed direction indicated by an arrow X in FIG. 4 by a cutting feed means (not shown) and is indicated by an arrow Y by an index feed means (not shown). It can be moved in the index feed direction shown.

  The cutting means 42 includes a spindle housing 421 arranged substantially horizontally, a rotating spindle 422 rotatably supported by the spindle housing 421, and a cutting blade 423 attached to the tip of the rotating spindle 422. The rotating spindle 422 is rotated in a direction indicated by an arrow 422a by a servo motor (not shown) disposed in the spindle housing 421. In the illustrated embodiment, the cutting blade 423 is an electroforming blade having a cutting edge fixed to a base by electroforming diamond abrasive grains having a particle diameter of about 3 μm, and has a thickness of 30 μm. Therefore, the width of the cutting groove cut by the cutting blade 423 is 30 μm.

  In order to perform the substrate exposure process by the cutting device 4 shown in FIG. 4, the back surface 20 b side of the sapphire substrate 20 constituting the optical device wafer 2 is placed on the chuck table 41. Then, by operating a suction means (not shown), the optical device wafer 2 is sucked and held on the chuck table 41 (wafer holding step). Therefore, in the optical device wafer 2 held on the chuck table 41, the surface 21a of the optical device layer 21 laminated on the surface 20a of the sapphire substrate 20 is on the upper side. In this way, the chuck table 41 that sucks and holds the optical device wafer 2 is positioned directly below the imaging unit 43 by a processing feed unit (not shown).

  When the chuck table 41 that sucks and holds the optical device wafer 2 is positioned directly below the image pickup means 43, a cutting region to be cut of the optical device layer 21 constituting the optical device wafer 2 is detected by the image pickup means 43 and a control means (not shown). Execute alignment work. That is, the image pickup unit 43 and a control unit (not shown) perform image processing such as pattern matching for aligning the street 22 formed in the optical device layer 21 of the optical device wafer 2 in a predetermined direction and the cutting blade 423. To perform alignment of the cutting area (alignment process). Further, the alignment of the cutting area is similarly performed on the street 22 formed in the optical device wafer 2 and extending in a direction orthogonal to the predetermined direction.

  The street 22 formed on the surface 21a of the optical device layer 21 constituting the optical device wafer 2 held on the chuck table 41 as described above is detected, and the alignment of the cutting area to be cut by the cutting blade 423 is detected. If performed, the chuck table 41 holding the optical device wafer 2 is moved to the cutting start position in the cutting area. Then, as shown in FIG. 5 (a), one end of the street 22 to be cut (left end in FIG. 5 (a)) of the optical device wafer 2 is positioned so as to be located a predetermined amount on the right side from directly below the cutting blade 423. (Processing feed start position positioning step). When the optical device wafer 2 is positioned at the machining start position in the machining area in this way, the cutting blade 423 is rotated in the direction indicated by the arrow 422a and is moved from the standby position indicated by the two-dot chain line in FIG. The feed is cut downward and positioned at a predetermined cut feed position as shown by the solid line in FIG. As shown in FIG. 5A, the cutting feed position is set such that the lower end of the outer peripheral edge of the cutting blade 423 is on the surface 20a of the sapphire substrate 20 constituting the optical device wafer 2.

  Next, as shown in FIG. 5A, the cutting table 423 is rotated in the direction indicated by the arrow X1 in FIG. 5A while rotating the cutting blade 423 in the direction indicated by the arrow 422a at a predetermined rotational speed. Is fed at a machining feed rate (for example, 50 mm / second). As a result, as shown in FIGS. 5B and 5C, in the optical device layer 21 constituting the optical device wafer 2, a cutting groove 222 reaching the surface 20a of the sapphire substrate 20 along the street 22 is formed. The surface 20a of the sapphire substrate 20 is exposed (substrate exposure step). The above-described substrate exposure process is performed along all the streets 22 formed in the optical device wafer 2.

  If the substrate exposure process is performed as described above, a laser beam having a wavelength that is transmissive to the sapphire substrate 20 is positioned from the optical device layer 21 side to the inside of the sapphire substrate 20 to locate the optical device in the street 22. Irradiation is performed along the street 22 through the region from which the layer 21 has been removed, and a modified layer forming step is performed in which a modified layer is formed along the street 22 inside the sapphire substrate 20. This modified layer forming step is performed using a laser processing apparatus 30 shown in FIG. 6 having the same configuration as the laser processing apparatus 3 shown in FIG. In addition, since the laser processing apparatus 30 is comprised by the substantially same member as the laser processing apparatus 3, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

Using the laser processing apparatus 30 described above, a laser beam having a wavelength transmissive to the sapphire substrate 20 constituting the optical device wafer 2 is positioned from the optical device layer 21 side to the inside of the sapphire substrate 20. FIG. 6 and FIG. 7 show a modified layer forming step of irradiating along the street 22 through the area of the street 22 where the optical device layer 21 is removed and forming a modified layer along the street 22 inside the sapphire substrate 20. Will be described with reference to FIG.
To implement the modified layer forming step, first, the back surface 20 of the sapphire substrate 20 constituting the optical device wafer 2 is placed on the chuck table 31 of the laser processing apparatus 30 shown in FIG. Then, the optical device wafer 2 is sucked and held on the chuck table 31 by operating a suction means (not shown) (wafer holding step). Therefore, in the optical device wafer 2 sucked and held by the chuck table 31, the surface 20a of the sapphire substrate 20 is on the upper side. In this way, the chuck table 31 that sucks and holds the optical device wafer 2 is positioned directly below the image pickup means 33 by a processing feed means (not shown).

  When the chuck table 31 that sucks and holds the optical device wafer 2 is positioned immediately below the image pickup means 33, the processing region to be laser-processed of the optical device layer 21 that constitutes the optical device wafer 2 by the image pickup means 33 and the control means (not shown). Execute the alignment work to be detected. That is, the image pickup means 33 and the control means (not shown) are a condensing of the street 22 formed in a predetermined direction on the optical device layer 21 of the optical device wafer 2 and the laser beam irradiation means 32 that irradiates the laser beam along the street 22. Image processing such as pattern matching for alignment with the device 322 is performed, and alignment of the laser beam irradiation position is performed (alignment process). Similarly, alignment of the laser beam irradiation position is performed on the street 22 formed on the optical device wafer 2 in a direction orthogonal to the predetermined direction.

  If the street 22 formed on the surface 21a of the optical device layer 21 constituting the optical device wafer 2 held on the chuck table 31 as described above is detected and the alignment of the laser beam irradiation position is performed, As shown in FIG. 7A, the chuck table 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 22 (the left end in FIG. 8A) is moved. It is positioned directly below the light collector 322 of the laser beam irradiation means 32. Then, the condensing point P of the pulse laser beam irradiated from the condenser 322 is adjusted to a position, for example, 50 μm below the surface 20 a (lower surface) of the sapphire substrate 20 constituting the optical device wafer 2. In order to position the condensing point P of the pulse laser beam irradiated from the condenser 322 at a predetermined position of the sapphire substrate 20 constituting the optical device wafer 2, for example, a chuck described in JP 2009-63446 A The height position of the upper surface of the optical device wafer 2 held on the chuck table 31 is detected using a height position detection device for the workpiece held on the table, and the detected height of the upper surface of the optical device wafer 2 is detected. By operating a condensing point position adjusting means (not shown) with the position as a reference, the condensing point P of the pulse laser beam is positioned at a predetermined position. Next, in FIG. 7A, the chuck table 31 is irradiated with a pulsed laser beam having a wavelength that is transmissive to the sapphire substrate 20 from the condenser 322 through the area of the street 22 where the optical device layer 21 is removed. It is moved at a predetermined machining feed rate in the direction indicated by the arrow X1. 7B, when the irradiation position of the condenser 322 of the laser beam irradiation means 32 reaches the position of the other end of the street 22 (the right end in FIG. 7B), the pulse laser beam irradiation is performed. And the movement of the chuck table 31 is stopped. As a result, on the sapphire substrate 20 constituting the optical device wafer 2, a modified layer 210 continuous along the street 22 is formed inside as shown in FIG. 7B and FIG. 7C. (Modified layer forming step). The modified layer 210 is formed on the surface 20 a (lower surface) of the sapphire substrate 20, that is, on the back surface 20 b (upper surface) side from the optical device layer 21. When the modified layer forming step is performed as described above, the optical device layer 21 is destroyed because the substrate exposure step described above is performed and the pulsed laser beam is irradiated through the area of the street 22 where the optical device layer 21 is removed. That is, no crack propagates to the optical device 23. The above-described modified layer forming step is performed along all the streets 22 formed on the optical device wafer 2.

The processing conditions in the modified layer forming step are set as follows, for example.
Wavelength: 532 nm pulse laser Repeat frequency: 15 kHz
Average output: 0.15W
Pulse width: 500 ps
Condensing spot diameter: φ1μm
Processing feed rate: 90 mm / sec

  By performing the modified layer forming step under the above processing conditions, the modified layer 210 having a thickness of 50 to 60 μm is formed on the sapphire substrate 20 along the streets 22.

  If the modified layer formation process mentioned above is implemented, the protection member sticking process which sticks a protection member on the surface of the optical device wafer 2 will be implemented. That is, as shown in FIGS. 8A and 8B, the protective tape T is attached to the surface 21a of the optical device layer 21 in order to protect the optical device 23 formed on the optical device wafer 2. In addition, you may implement a protective member sticking process, after implementing the modified layer formation process mentioned later.

  Next, the protective member T side of the optical device wafer 2 on which the protective member attaching step has been carried out is held by a holding means, pressed against the back surface of the sapphire substrate 20 while rotating the grinding wheel, and ground. A back surface grinding step is performed in which the surface is divided along the streets 22 having a predetermined thickness and a modified layer formed thereon. This back grinding process is carried out using a grinding apparatus 5 shown in FIG. A grinding apparatus 5 shown in FIG. 9 includes a chuck table 51 as a holding unit for holding a workpiece, and a grinding unit 52 for grinding the workpiece held on the chuck table 51. The chuck table 51 is configured to suck and hold the workpiece on the upper surface, and is rotated in a direction indicated by an arrow 51a in FIG. 9 by a rotation driving mechanism (not shown). The grinding means 52 includes a spindle housing 521, a rotating spindle 522 that is rotatably supported by the spindle housing 521 and rotated by a rotation driving mechanism (not shown), a mounter 523 attached to the lower end of the rotating spindle 522, and the mounter And a grinding wheel 524 attached to the lower surface of 523. The grinding wheel 524 includes an annular base 525 and a grinding wheel 526 that is annularly attached to the lower surface of the base 525, and the base 525 is attached to the lower surface of the mounter 523 with fastening bolts 527. ing.

  In order to perform the grinding process using the grinding apparatus 5 described above, the protective tape T side of the optical device wafer 2 is placed on the upper surface (holding surface) of the chuck table 51 as shown in FIG. Then, by operating a suction means (not shown), the optical device wafer 2 is sucked and held on the chuck table 51 via the protective tape T (wafer holding step). Accordingly, in the optical device wafer 2 sucked and held on the chuck table 51 via the protective tape T, the back surface 20b of the sapphire substrate 20 is on the upper side. If the optical device wafer 2 is sucked and held on the chuck table 51 via the protective tape T in this way, the grinding means 52 is ground while rotating the chuck table 51 in the direction indicated by the arrow 51a in FIG. The wheel 524 is rotated in the direction indicated by the arrow 524a in FIG. 9 at, for example, 700 rpm, and the grinding wheel 526 is brought into contact with the back surface 20b of the sapphire substrate 20 constituting the optical device wafer 2 as the processing surface as shown in FIG. The grinding wheel 524 is ground and fed downward (in a direction perpendicular to the holding surface of the chuck table 51) at a grinding feed rate of, for example, 1 μm / second as shown by an arrow 524b in FIGS. 9 and 10 (back grinding process). As a result, the back surface 20b of the sapphire substrate 20 constituting the optical device wafer 2 is ground, the optical device wafer 2 is formed to a predetermined thickness (for example, 100 μm), and the thinned optical device wafer 2 is the modified layer 210. Are divided into individual optical devices 23 along the streets 22 formed.

2: Optical device wafer 20: Sapphire substrate 21: Optical device layer 3: Laser processing device 30: Laser processing device 31: Chuck table of laser processing device 32: Laser beam irradiation means 322: Condenser 33: Imaging means 4: Cutting device 41: chuck table of cutting device 42: cutting means 423: cutting blade 43: imaging means 5: grinding device 51: chuck table of grinding device 52: grinding means 524: grinding wheel 526: grinding wheel T: protective tape

Claims (3)

Light that divides an optical device wafer in which optical devices are formed in multiple areas partitioned by multiple streets that are formed in a lattice pattern by laminating optical device layers on the surface of the substrate, into individual optical devices along the streets A device wafer processing method,
A substrate exposure step of exposing the surface of the substrate by removing a region where streets are formed in the optical device layer laminated on the surface of the substrate;
A laser beam having a wavelength that is transparent to the substrate is irradiated from the optical device layer side to the inside of the substrate along the street through the area where the optical device layer in the street is removed, and the street inside the substrate. A modified layer forming step of forming a modified layer along
A protective member attaching step of attaching a protective member to the surface of the optical device wafer on which the modified layer forming step has been carried out;
The protective member side of the optical device wafer on which the protective member attaching step has been performed is held by a holding means, and is ground by pressing the back surface of the substrate while rotating the grinding wheel to form the substrate with a predetermined thickness. A back grinding step of dividing along the street where the quality layer is formed,
An optical device wafer processing method characterized by the above.   2. The substrate exposure step of exposing the surface of the substrate by irradiating the optical device layer with a laser beam having a wavelength that absorbs the optical device layer along the street and removing the optical device layer along the street. Method of optical device wafers.   2. The method of processing an optical device wafer according to claim 1, wherein in the substrate exposure step, the surface of the substrate is exposed by cutting and removing the optical device layer along the streets with a cutting blade.

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