JP6917792B2 - Processing method of work piece - Google Patents

Description

The present invention relates to a method for processing a workpiece having a planned division line.

A wafer in which a plurality of devices such as ICs and LSIs are partitioned by a scheduled division line and formed on the surface is divided into individual devices by a dicing apparatus and a laser processing apparatus. Each of the divided devices is used for electric devices such as mobile phones and personal computers.

The laser processing apparatus includes the following types (1) and (2), and is appropriately selected in consideration of the type of the workpiece, the processing quality, and the like.
(1) A groove is formed on the upper surface of the work piece by irradiating the work piece with a laser beam at a condensing point of a laser beam having a wavelength that absorbs the work piece and irradiating the work piece with ablation. Type to form (see, for example, Patent Document 1)
(2) A type in which a condensing point of a laser beam having a wavelength that is transparent to the workpiece is positioned inside the workpiece and the laser beam is irradiated to the workpiece to form a modified layer inside the workpiece. (See, for example, Patent Document 2.)

Japanese Unexamined Patent Publication No. 10-305420 Japanese Patent No. 3408805

However, when dividing a glass plate having a polycrystalline structure, ablation is performed along the planned division line to form a groove that is the starting point of the division, and then an external force is applied to divide the glass plate, resulting in fine irregularities on the divided surface. There is a problem that it occurs and the processing quality is poor.

Further, when dividing a glass plate having a polycrystalline structure, a modified layer that serves as a starting point of division is formed inside along a planned division line, and then an external force is applied to divide the glass plate, although the quality of the divided surface is improved. There is a problem that the corner portion of the upper surface is not formed neatly (for example, the upper end side portion of the divided surface is inclined with respect to the upper surface).

The above problems can also occur when processing _{sapphire (Al 2} O ₃ ), silicon carbide (SiC), lithium tantalate (LiTaO ₃ ), and lithium niobate (LiNbO ₃ ), which have a strong habit of crystal orientation.

An object of the present invention made in view of the above facts is to provide a processing method for a workpiece having improved processing quality.

In order to solve the above problems, the first aspect of the present invention provides the following processing method for the workpiece. That is, the oscillator that oscillates the laser beam, the concentrator that collects the laser beam oscillated by the oscillator and positions the condensing point inside the work piece and the condenser that positions it on the upper surface of the work piece, and the concentrator are protected. A processing method for processing a work piece having a planned division line using a laser processing device provided with a cover glass, in which the cover glass is removed from the end of the condenser to form a work piece. On the other hand, the condensing point of the laser beam having a transmissive wavelength is positioned inside the workpiece, and the laser beam having a transmissive wavelength is irradiated to the workpiece along the planned division line to form a modified layer. In the modified layer forming step, and with the cover glass positioned at the end of the condenser, the focusing point of the laser beam having a wavelength that is absorbent to the workpiece is positioned on the upper surface of the workpiece. Then, a groove forming step of irradiating a work piece with a laser beam having a wavelength having absorbency along a planned division line to form a groove by ablation processing and connecting the groove and the modified layer, and a groove forming step to be processed. It is a processing method of a work piece composed of at least a division step of applying an external force to the work piece and dividing the work piece along a planned division line.

In the method for processing a work piece according to the first aspect of the present invention, the wavelength of the laser beam having a wavelength that is transparent to the work piece and the wavelength of the laser beam having a wavelength that is absorbent to the work piece. The work piece is either glass, sapphire (Al ₂ O ₃ ), silicon carbide (SiC), lithium tantalate (LiTaO ₃ ), or lithium niobate (LiNbO ₃ ). preferable.

The second aspect of the present invention provides the following processing method for the workpiece. That is, the oscillator that oscillates the laser beam, the concentrator that collects the laser beam oscillated by the oscillator and positions the condensing point inside the work piece and the condenser that positions it on the upper surface of the work piece, and the concentrator are protected. A processing method for processing a work piece having a planned division line using a laser processing device provided with a cover glass, in which the cover glass is positioned at the end of the concentrator , and the work piece is formed. On the other hand, the focusing point of the laser beam of the wavelength having absorbency is positioned on the upper surface of the work piece, and the laser beam of the wavelength having absorbency is irradiated to the work piece along the planned division line to form a groove by ablation processing. The groove forming step of forming and the condensing point of the laser beam having a wavelength that is transparent to the workpiece with the cover glass removed from the end of the concentrator are on the opposite side of the groove formation. Is positioned inside the work piece and is irradiated with a laser beam having a wavelength that is transparent to the work piece along the planned division line to form a modified layer, and the modified layer and the groove are connected to each other. It is a processing method of a work piece composed of at least a modified layer forming step and a division step of applying an external force to the work piece to divide the work piece along a planned division line.

Also in the method for processing a work piece according to the second aspect of the present invention, the wavelength of the laser beam having a wavelength that is transparent to the work piece and the wavelength of the laser beam having a wavelength that is absorbent to the work piece. The work piece is either glass, sapphire (Al ₂ O ₃ ), silicon carbide (SiC), lithium tantalate (LiTaO ₃ ), or lithium niobate (LiNbO ₃ ). Suitable.

The method for processing a work piece provided by the first aspect of the present invention is an oscillator that oscillates a laser beam and a work piece that collects the laser beam oscillated by the oscillator and positions a condensing point inside the work piece. a collector positioned on the upper surface of, by using the laser processing apparatus and a cover glass for protecting the light-concentrating device, a machining method for machining a workpiece having a dividing line, said the cover glass With the light collector removed from the end, the focusing point of the laser beam with a wavelength that is transparent to the work piece is positioned inside the work piece, and the wavelength that is transparent to the work piece. The modified layer forming step of irradiating the laser beam of No. 1 along the planned division line to form the modified layer, and the absorption of the work piece with the cover glass positioned at the end of the condenser. The condensing point of the laser beam having a wavelength is positioned on the upper surface of the work piece, and the laser beam having a wavelength that absorbs the work piece is irradiated along the planned division line to form a groove by ablation processing. Since it is composed of at least a groove forming step of connecting the modified layer and the work piece and a division step of applying an external force to the work piece to divide the work piece along the planned division line, the work piece is to be worked. The modified layer formed inside the work piece and the groove formed on the upper surface of the work piece are connected so that fine irregularities do not occur on the divided surface, and the upper surface of the work piece that has been ablated. The corners are processed cleanly, thus improving the processing quality.

The method for processing a work piece provided by the second aspect of the present invention is an oscillator that oscillates a laser beam and a work piece that collects the laser beam oscillated by the oscillator and positions a condensing point inside the work piece. This is a processing method for processing an workpiece having a planned division line by using a laser processing apparatus including a concentrator positioned on the upper surface of the concentrator and a cover glass for protecting the condenser. Positioned at the end of the condenser, the focusing point of the laser beam with a wavelength that is absorbent to the work piece is positioned on the upper surface of the work piece, and the wavelength that is absorbable to the work piece. The groove forming step of irradiating the laser beam of No. 1 along the planned division line to form a groove by ablation processing and the state in which the cover glass is removed from the end of the concentrator, the work piece has transparency. The focusing point of the wavelength laser beam is positioned inside the work piece from the opposite side where the groove is formed, and the work piece is modified by irradiating the work piece with a wavelength laser light beam that is transparent along the planned division line. At least from the modified layer forming step of forming a layer and connecting the modified layer and the groove, and the dividing step of applying an external force to the workpiece to divide the workpiece along the planned division line. Since it is configured, the modified layer formed inside the work piece and the groove formed on the upper surface of the work piece are not connected to cause fine irregularities on the divided surface, and ablation processing can be performed. The corners on the upper surface of the applied workpiece are processed cleanly, and therefore the processing quality is improved.

Perspective view of the laser processing device. The block diagram which shows the structure of the laser beam irradiation means shown in FIG. Perspective view of the wafer. The schematic diagram which shows the state which the modified layer formation process is carried out. The schematic diagram which shows the state which the groove formation process is performed after the modified layer formation process is carried out. A perspective view of a wafer in which a modified layer and a groove are formed along a planned division line. A cross-sectional view of a dividing device and a wafer showing a state in which the dividing step is carried out. The schematic diagram which shows the state which the groove formation process is carried out when the modified layer formation step is carried out after the groove formation step is carried out. The schematic diagram which shows the state which the modified layer formation step is carried out after the groove formation step is carried out.

Hereinafter, embodiments of the method for processing the workpiece of the present invention will be described with reference to the drawings.

The laser machining apparatus 2 shown in FIG. 1 includes a holding means 4 for holding a work piece, a laser beam irradiating means 6 for irradiating a work piece held by the holding means 4 with a laser beam, and a holding means 4 and a laser beam irradiating means 6. At least includes a processing feed means 8 for relatively processing and feeding.

As shown in FIG. 1, the holding means 4 is attached to a rectangular X-axis direction movable plate 12 mounted on the base 10 so as to be movable in the X-axis direction and to the X-axis direction movable plate 12 which is movable in the Y-axis direction. A mounted rectangular Y-axis direction movable plate 14, a cylindrical support plate 16 fixed to the upper surface of the Y-axis direction movable plate 14, and a rectangular cover plate 18 fixed to the upper end of the support column 16 are included. .. An elongated hole 18a extending in the Y-axis direction is formed in the cover plate 18, and a circular chuck table 20 extending upward through the elongated hole 18a is rotatably mounted on the upper end of the column 16. On the upper surface of the chuck table 20, a circular suction chuck 22 formed of a porous material and extending substantially horizontally is arranged, and the suction chuck 22 is connected to a suction means (not shown) by a flow path. ing. Then, in the chuck table 20, by generating a suction force on the upper surface of the suction chuck 22 by the suction means, the workpiece placed on the upper surface of the suction chuck 22 can be sucked and held. Further, a plurality of clamps 24 are arranged on the peripheral edge of the chuck table 20 at intervals in the circumferential direction. The X-axis direction is the direction indicated by the arrow X in FIG. 1, and the Y-axis direction is the direction indicated by the arrow Y in FIG. 1 and is orthogonal to the X-axis direction. The plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

The laser beam irradiation means 6 will be described with reference to FIGS. 1 and 2. The laser beam irradiating means 6 includes a frame body 26 (see FIG. 1) extending upward from the upper surface of the base 10 and then extending substantially horizontally, an oscillator 28 (see FIG. 2) built in the frame body 26, and a frame. It includes a concentrator 30 (see FIG. 1) arranged on the lower surface of the tip of the body 26. The oscillator 28 is configured to oscillate a pulsed laser beam LB having a wavelength that is both transparent and absorbent with respect to the workpiece. For example, the pulse that the oscillator 28 oscillates when the workpiece is glass, sapphire (Al ₂ O ₃ ), silicon carbide (SiC), lithium tantalate (LiTaO ₃ ), or lithium niobate (LiNbO _3). The wavelength of the laser beam LB is set to 532 nm, which is a wavelength that is transparent and absorbable to any of glass, sapphire, silicon carbide, lithium tantalate, and lithium niobate.

Continuing the description of the laser beam irradiating means 6 with reference to FIG. 1, the concentrator 30 of the laser beam irradiating means 6 has a cylindrical casing 32 mounted on the lower surface of the tip of the frame 26 so as to be able to move up and down, and the casing 32. A condensing lens 34 that condenses the pulsed laser beam LB oscillated by the oscillator 28 built in the condensing lens 34, and a condensing point position adjusting means (FIG. Not shown.) Includes. The condensing point position adjusting means includes, for example, a ball screw whose nut portion is fixed to the casing 32 of the concentrator 30 and extends in the vertical direction (not shown), and a motor connected to one end of the ball screw (not shown). It may have a configuration having (not shown). In the condensing point position adjusting means having such a configuration, the rotary motion of the motor is converted into a linear motion by a ball screw and transmitted to the casing 32, and is transmitted along a guide rail (not shown) extending in the vertical direction. The casing 32 is moved up and down, whereby the focusing point of the pulsed laser beam LB focused by the focusing lens 34 is moved in the vertical direction. Then, in the condensing device 30, the condensing point of the pulsed laser beam LB is moved in the vertical direction by the condensing point position adjusting means, so that the condensing point of the pulsed laser beam LB is condensed inside the workpiece held by the holding means 4. The point can be positioned, and the condensing point of the pulsed laser beam LB can be positioned on the upper surface of the workpiece held by the holding means 4.

In the laser beam irradiating means 6, the cover glass that protects the condenser 30 is selectively positioned, and when the internal processing is performed in which the modified layer is formed inside the workpiece through the laser beam. When the cover glass is removed from the end of the condenser 30 and absorbs the laser beam to ablate the upper surface of the workpiece, the cover glass is preferably positioned at the end of the condenser 30. .. In the illustrated embodiment, as shown in FIG. 1, the laser beam irradiating means 6 is rotatable about a support rod 36 that is adjacent to the condenser 30 and extends downward from the lower surface of the tip of the frame body 26 and an axis of the support rod 36. Includes a cover glass 38 supported at the lower end of the support rod 36. The cover glass 38 rotates around the axis of the support rod 36 extending in the vertical direction to move away from the lower end of the casing 32 of the condenser 30 (position shown by a solid line in FIG. 1) and condensing. It is configured to be movable between the action position (the position shown by the alternate long and short dash line in FIG. 1) located at the lower end of the casing 32 of the vessel 30. The cover glass 38 is positioned at a non-acting position because debris does not scatter from the processed region when the internal processing is performed so that the modified layer is formed inside the workpiece. On the other hand, when the upper surface of the workpiece is ablated, debris scatters from the processed area. Therefore, the cover glass 38 is positioned at the working position, so that the cover glass 38 protects the condenser 30. That is, the cover glass 38 prevents debris from adhering to the condenser 30. Further, in the illustrated embodiment, as shown in FIG. 2, the laser beam irradiating means 6 further includes an attenuator 40 for adjusting the output of the pulsed laser beam LB oscillated by the oscillator 28 and a pulsed laser beam LB whose output is adjusted by the attenuator 40. Includes a mirror 42 that reflects and guides to the condenser lens 34 of the condenser 30.

As shown in FIG. 1, on the lower surface of the tip of the frame body 26 of the laser beam irradiating means 6, an imaging means 44 for imaging a work piece held by the holding means 4 and detecting a region to be laser-processed is focused. It is mounted at a distance from the vessel 30 in the X-axis direction. The imaging means 44 includes a normal imaging element (CCD) that images the work piece with visible light, an infrared irradiation means that irradiates the work piece with infrared rays, and an optical system that captures the infrared rays that are irradiated by the infrared rays irradiation means. It includes an image pickup element (infrared CCD) that outputs an electric signal corresponding to the infrared rays captured by the optical system (neither is shown).

The machining feed means 8 will be described with reference to FIG. The processing feed means 8 in the illustrated embodiment includes an X-axis direction moving means 46 that moves the chuck table 20 of the holding means 4 with respect to the laser beam irradiating means 6 in the X-axis direction, and a holding means 4 with respect to the laser beam irradiating means 6. Includes a Y-axis direction moving means 48 for moving the chuck table 20 in the Y-axis direction, and a rotating means (not shown) for rotating the chuck table 20 with respect to the support column 16 of the holding means 4. The X-axis direction moving means 46 has a ball screw 50 extending in the X-axis direction on the base 10 and a motor 52 connected to one end of the ball screw 50. The nut portion (not shown) of the ball screw 50 is fixed to the lower surface of the movable plate 12 in the X-axis direction. Then, the X-axis direction moving means 46 converts the rotational motion of the motor 52 into a linear motion by the ball screw 50 and transmits it to the X-axis direction movable plate 12, and moves in the X-axis direction along the guide rail 10a on the base 10. The plate 12 is moved back and forth in the X-axis direction, whereby the chuck table 20 is moved in the X-axis direction with respect to the laser beam irradiating means 6. The Y-axis direction moving means 48 has a ball screw 54 extending in the Y-axis direction on the X-axis direction movable plate 12 and a motor 56 connected to one end of the ball screw 54. The nut portion (not shown) of the ball screw 54 is fixed to the lower surface of the Y-axis direction movable plate 14. Then, the Y-axis direction moving means 48 converts the rotational motion of the motor 56 into a linear motion by the ball screw 54 and transmits it to the Y-axis direction movable plate 14, and Y along the guide rail 12a on the X-axis direction movable plate 12. The axially movable plate 14 is moved back and forth in the Y-axis direction, whereby the chuck table 20 is moved in the Y-axis direction with respect to the laser beam irradiating means 6. The rotating means has a motor (not shown) built in the support column 16 and rotates the chuck table 20 with respect to the support column 16 about an axis extending in the vertical direction.

FIG. 3 shows a wafer 60 as an example of the workpiece. The disc-shaped wafer 60 is formed of glass, sapphire, silicon carbide, lithium tantalate or lithium niobate. The surface 60a of the wafer 60 is divided into a plurality of rectangular regions by a grid-like division schedule line 62, and a device 64 is formed in each of the plurality of rectangular regions. In the illustrated embodiment, the back surface 60b of the wafer 60 is attached to the adhesive tape 68 whose peripheral edge is fixed to the annular frame 66. The surface 60a of the wafer 60 may be attached to the adhesive tape 68.

Using the work piece as a wafer 60, laser machining is performed along the planned division line 62 of the wafer 60 using the above-mentioned laser processing device 2, and an external force is applied to the wafer 60 to apply an external force to the wafer 60 along the planned division line 62. A method of processing a work piece for which is divided into individual devices 64 will be described. In the illustrated embodiment, first, the focusing point of the laser beam having a wavelength transparent to the wafer 60 is positioned inside the wafer 60, and the laser beam having a wavelength transparent to the wafer 60 is divided into the planned division line 62. The modified layer forming step of forming the modified layer by irradiating along the above is carried out. In the modified layer forming step in which the modified layer is formed inside the wafer 60 along the planned division line 62, debris does not scatter from the processed region. Therefore, first, the casing of the condenser 30 is used. The casing glass 38 is positioned at a non-acting position away from the lower end of the 32. Next, the wafer 60 is attracted to the upper surface of the chuck table 20 of the holding means 4 with the surface 60a of the wafer 60 facing upward. Further, the outer peripheral edge portion of the annular frame 66 is fixed by a plurality of clamps 24. Next, the wafer 60 is imaged from above by the imaging means 44. Next, based on the image of the wafer 60 captured by the imaging means 44, the chuck table 20 is moved and rotated by the X-axis direction moving means 46, the Y-axis direction moving means 48, and the rotating means of the processing feed means 8, thereby performing the lattice. The shape of the scheduled division line 62 is aligned in the X-axis direction and the Y-axis direction, and the concentrator 30 is positioned above one end of the scheduled division line 62 aligned in the X-axis direction. Next, by moving the focusing point FP of the pulse laser beam LB in the vertical direction by the focusing point position adjusting means, the focusing point FP of the pulse laser beam LB is positioned inside the wafer 60 as shown in FIG. Next, while moving the wafer 60 and the condensing point FP relatively in the X-axis direction, wavelengths that are transparent to the wafer 60 (in the illustrated embodiment, glass, sapphire, silicon carbide, lithium tantalate, and A modified layer forming process is performed in which a pulsed laser beam LB having a wavelength of 532 nm, which is a wavelength having both transparency and absorbency for any of the lithium sapphires, is irradiated along the planned division line 62. In the illustrated embodiment, in the modified layer forming process, the chuck table 20 is processed in the X-axis direction by the X-axis direction moving means 46 at a predetermined processing feed rate with respect to the focusing point FP without moving the focusing point FP. Send. When the modified layer forming process is performed, as shown in FIG. 4, the modified layer 70 is formed inside the wafer 60 along the scheduled division line 62, and cracks extending upward and downward from the modified layer 70. 72 is formed. In the illustrated embodiment, the wavelength of the pulsed laser beam LB irradiated in the modified layer forming process is a wavelength having both transparency and absorbability with respect to the wafer 60, but the focusing point FP is positioned inside the wafer 60. Therefore, the diameter of the spot formed on the surface 60a of the wafer 60 is larger than the diameter of the condensing point FP positioned inside the wafer 60, and the energy density of the spot on the surface 60a of the wafer 60 is that of the condensing point FP. Since it is smaller than the energy density, the modified layer 70 and the crack 72, which are the starting points of division, are formed inside the wafer 60, while the upper surface of the wafer 60 is not ablated. Next, the wafer 60 and the condensing point FP are relatively indexed in the Y-axis direction by the interval of the scheduled division line 62. In the illustrated embodiment, in the index feed, the chuck table 20 is moved in the Y-axis direction by the Y-axis direction moving means 48 with respect to the condensing point FP without moving the condensing point FP by the interval of the scheduled division line 62. Index feed. Then, by alternately repeating the modified layer forming process and the index feed, the modified layer forming process is performed on all of the planned division lines 62 aligned in the X-axis direction. Further, after rotating the chuck table 20 by 90 degrees by the rotating means of the processing feed means 8, the modified layer forming process and the index feed are alternately repeated, so that the division is scheduled to be divided by first performing the modified layer forming process. All of the planned division lines 62 orthogonal to the line 62 are also subjected to the modified layer forming process to form the modified layer 70 and the crack 72 along the grid-like planned division line 62. Such a modified layer forming step can be carried out under the following processing conditions, for example.
Numerical aperture of condenser lens (NA): 0.8
Repeat frequency: 15kHz
Average output: 0.8W
Processing feed rate: 150 mm / s

After carrying out the modified layer forming step, the focusing point of the laser beam having a wavelength that is absorbent to the wafer 60 will be positioned on the upper surface of the wafer 60, and the laser beam having a wavelength that is absorbent to the wafer 60 will be divided. A groove forming step of irradiating along the line 62 to form a groove by ablation processing and connecting the groove and the modified layer 70 is carried out. In the groove forming step of ablating the upper surface of the wafer 60 along the scheduled division line 62, first, in order to protect the condenser 30 by the cover glass 38, the action is located at the lower end of the casing 32 of the condenser 30. Position the covering glass 38 at the position. Next, the chuck table 20 adsorbing the wafer 60 on which the modified layer 70 is formed is appropriately moved by the processing feed means 8 based on the image of the wafer 60 imaged by the imaging means 44 in the modified layer forming step. Therefore, the condenser 30 is positioned above one end of the scheduled division line 62 that is aligned in the X-axis direction. Next, by moving the focusing point FP of the pulse laser beam LB in the vertical direction by the focusing point position adjusting means, the focusing point FP of the pulse laser beam LB is positioned on the surface 60a of the wafer 60 as shown in FIG. Next, while moving the wafer 60 and the condensing point FP relatively in the X-axis direction, wavelengths that are absorbent to the wafer 60 (in the illustrated embodiment, glass, sapphire, silicon carbide, lithium tantalate, and An ablation process is performed in which a pulsed laser beam LB having a wavelength of 532 nm, which is a wavelength having both transparency and absorbency for any of the lithium sapphires, is irradiated along the scheduled division line 62. In the illustrated embodiment, in the ablation processing, the chuck table 20 is processed and fed in the X-axis direction by the X-axis direction moving means 46 at a predetermined processing feed rate with respect to the focusing point FP without moving the focusing point FP. When the ablation process is performed, as shown in FIG. 5, a groove 74 is formed on the surface 60a of the wafer 60 along the scheduled division line 62, and the groove 74 is formed through the crack 72 extending upward from the modified layer 70. And the modified layer 70 are connected. In the illustrated embodiment, the wavelength of the pulsed laser beam LB irradiated in the ablation process is a wavelength that is transparent to the wafer 60 and has absorbency, but the wafer has a focusing point FP having a small spot diameter and a high energy density. By positioning it on the surface 60a of 60, the pulse laser beam LB is absorbed on the surface 60a of the wafer 60 where the condensing point FP is positioned, and ablation processing is performed to form a groove 74 which is a starting point of division, while the wafer 60 is formed. The modified layer 70 and the crack 72 are not formed inside the wafer. Further, during the ablation process, debris is scattered from the processed area, but since the cover glass 38 is positioned at the working position, debris is prevented from adhering to the condenser 30. Next, the wafer 60 and the condensing point FP are relatively indexed in the Y-axis direction by the interval of the scheduled division line 62. In the illustrated embodiment, in the index feed, the chuck table 20 is moved in the Y-axis direction by the Y-axis direction moving means 48 with respect to the condensing point FP without moving the condensing point FP by the interval of the scheduled division line 62. Index feed. Then, by alternately repeating the ablation processing and the index feed, the ablation processing is performed on all of the planned division lines 62 aligned in the X-axis direction. Further, by rotating the chuck table 20 by 90 degrees by the rotating means of the processing feed means 8 and then alternately repeating the ablation processing and the index feed, the division orthogonal to the scheduled division line 62 which has been subjected to the ablation processing earlier. All of the planned lines 62 are also subjected to ablation processing, and as shown in FIG. 6, grooves 74 are formed along the grid-shaped planned division lines 62. In FIG. 6, the reference numerals of the planned division line 62, the modified layer 70, and the crack 72 are omitted. Such a groove forming step can be carried out under the following processing conditions, for example.
Numerical aperture of condenser lens (NA): 0.8
Repeat frequency: 15kHz
Average output: 0.8W
Processing feed rate: 90 mm / s

After laser processing is performed along the scheduled division line 62 of the wafer 60 using the above-mentioned laser processing apparatus 2, an external force is applied to the wafer 60 to divide the wafer 60 into individual devices 64 along the scheduled division line 62. Carry out the division process. The dividing step can be carried out using, for example, the dividing device 80 shown in FIG. 7. The dividing device 80 includes a cylindrical expansion drum 82 extending in the vertical direction, an annular holding member 84 arranged so as to be able to move up and down in the radial direction of the expansion drum 82, and a holding member relative to the expansion drum 82. It includes a plurality of air cylinders 86 for raising and lowering the 84, and a plurality of clamps 88 attached to the outer peripheral edge of the holding member 84 at intervals in the circumferential direction. The inner diameter of the expansion drum 82 is larger than the outer diameter of the wafer 60, and the outer diameter of the expansion drum 82 is smaller than the inner diameter of the annular frame 66. The outer diameter and inner diameter of the holding member 84 correspond to the outer diameter and inner diameter of the annular frame 66, and the annular frame 66 is placed on the upper surface of the holding member 84. Further, there is a gap between the outer peripheral surface of the expansion drum 82 and the inner peripheral surface of the holding member 84. As shown in FIG. 7, the piston rods 86a of the plurality of air cylinders 86 extending in the vertical direction are connected to the lower surface of the holding member 84 at intervals in the circumferential direction of the holding member 84. In the plurality of air cylinders 86, the upper surface of the holding member 84 is at a reference position (position shown by a solid line in FIG. 7) at substantially the same height as the upper end of the expansion drum 82, and the upper surface of the holding member 84 is located above the upper end of the expansion drum 82. The holding member 84 is moved up and down relative to the expansion drum 82 with respect to the expansion position (position indicated by the alternate long and short dash line in FIG. 7) located below.

Continuing the description with reference to FIG. 7, in the dividing step, first, each air cylinder 86 is operated to position the holding member 84 at the reference position. Next, the wafer 60 on which the modified layer 70 and the groove 74 are formed is turned upward, and the annular frame 66 holding the wafer 60 is placed on the upper surface of the holding member 84 via the adhesive tape 68. Next, the outer peripheral edge portion of the annular frame 66 is fixed by a plurality of clamps 88. Next, each air cylinder 86 is operated to lower the holding member 84 from the reference position to the extended position. Then, since the annular frame 66 also descends together with the holding member 84, the adhesive tape 68 whose peripheral edge is fixed to the annular frame 66 is expanded by the relatively ascending expansion drum 82 as shown by the alternate long and short dash line in FIG. .. As a result, radial tension acts on the wafer 60 attached to the adhesive tape 68, so that the wafer 60 is divided into individual devices 64 along the planned division line 62 in which the modified layer 70 and the groove 74 are formed. can do.

As described above, in the processing method of the workpiece according to the illustrated embodiment, the modified layer 70 formed inside the wafer 60 as the workpiece 60 along the planned division line 62 and the groove formation in the modified layer forming step. Since the groove 74 formed along the planned division line 62 on the surface 60a of the wafer 60 in the process is connected via the crack 72 extending from the modified layer 70 toward the surface 60a of the wafer 60, it is planned to be divided in the division process. When the wafer 60 is divided into individual devices 64 along the line 62, fine irregularities do not occur on the divided surface of the device 64, and the corner portion of the surface 60a of the wafer 60 that has been ablated is clean. It is machined (ie, without the upper end portion of the split surface being tilted with respect to the top surface), thus improving machining quality. Further, the above-mentioned laser processing apparatus 2 has a wavelength (transmissive and absorbable) with respect to a wafer 60 (workpiece) formed of glass, sapphire, silicon carbide, lithium tantalate or lithium niobate. Since the oscillator 28 is configured to oscillate a pulsed laser beam LB of 532 nm), an ablation process for forming a groove 74 on the upper surface of the wafer 60 can be performed, and a modified layer 70 is formed inside the wafer 60. Therefore, there is a problem that it is uneconomical to prepare two types of laser processing devices, that is, a laser processing device that performs ablation processing and a laser processing device that forms a modified layer. do not have.

In the above-mentioned processing method of the workpiece, an example in which the groove forming step is carried out after the modified layer forming step is carried out has been described, but the modified layer forming step may be carried out after the groove forming step is carried out. good. For example, as shown in FIG. 8, first, the groove forming step is performed with the front surface 60a of the wafer 60 facing upward, and then, as shown in FIG. 9, the modified layer forming step with the back surface 60b of the wafer 60 facing upward. In this case as well, the groove 74 formed on the surface 60a of the wafer 60 along the planned division line 62 and the modification formed inside the wafer 60 along the planned division line 62. Since the quality layer 70 is connected via a crack 72 extending from the modified layer 70 toward the surface 60a of the wafer 60, when the wafer 60 is divided into individual devices 64 along the planned division line 62 in the division step. The corner portion of the surface 60a of the wafer 60 which has been subjected to the ablation process is neatly processed without causing fine irregularities on the divided surface of the device 64, and therefore the processing quality is improved. When the modified layer forming step is performed after the groove forming step is performed, the groove 74 is formed at the condensing point FP of the pulsed laser beam LB having a wavelength that is transparent to the wafer 60 in the modified layer forming step. Positioning the groove 74 from the opposite side (when the groove 74 is formed on the front surface 60a of the wafer 60 as shown in FIGS. 8 and 9 on the back surface 60b side of the wafer 60) to the inside of the wafer 60, with respect to the wafer 60. By irradiating a pulsed laser beam LB having a wavelength having a transmissive wavelength along the scheduled division line 62, a modified layer 70 is formed inside the wafer 60 to connect the modified layer 70 and the groove 74. As a result, the pulsed laser beam LB that irradiates the wafer 60 in the modified layer forming step is not diffusely reflected in the groove 74 formed in the groove forming step, and the modified layer 70 and the crack 72 as intended are formed inside the wafer 60. , The modified layer 70 and the groove 74 can be connected via the crack 72. Further, when the modified layer forming step is carried out with the back surface 60b of the wafer 60 facing upward, when the wafer 60 held on the chuck table 20 is imaged by the imaging means 44 to detect the region to be laser-processed. The surface 60a of the wafer 60 on which the scheduled division line 62 is formed faces downward. As described above, the imaging means 44 includes an infrared irradiation means, an optical system that captures infrared rays, and an electric signal corresponding to infrared rays. Since it includes an image pickup element (infrared CCD) that outputs an image of the wafer 60, the scheduled division line 62 of the front surface 60a can be imaged through the back surface 60b of the wafer 60.

In the illustrated embodiment, the modified layer forming step is performed by using one laser processing device 2 including an oscillator 28 that oscillates a pulsed laser beam LB having a wavelength that is transparent and absorbable with respect to the wafer 60. An example of carrying out the groove forming step by ablation processing has been described, but the modified layer forming step is carried out using a laser processing apparatus equipped with an oscillator that oscillates a laser beam having a wavelength that is transparent to the workpiece. The groove forming step may be carried out by using another laser processing apparatus including an oscillator that oscillates a laser beam having a wavelength that is absorbent to the workpiece.

60: Wafer (workpiece)
62: Scheduled division line 70: Modified layer 72: Crack 74: Groove LB: Pulse laser beam FP: Condensing point

Claims (3)

An oscillator that oscillates a laser beam, a concentrator that condenses the laser beam oscillated by the oscillator and positions the condensing point inside the work piece and on the upper surface of the work piece, and a cover glass that protects the condenser. It is a processing method for processing an workpiece having a planned division line by using a laser processing apparatus equipped with the above.
With the cover glass removed from the end of the concentrator, a condensing point of a laser beam having a wavelength that is transparent to the work piece is positioned inside the work piece to refer to the work piece. A modified layer forming step of irradiating a laser beam having a transmissive wavelength along a planned division line to form a modified layer,
With the cover glass positioned at the end of the concentrator, the condensing point of the laser beam having a wavelength that is absorbent to the workpiece is positioned on the upper surface of the workpiece so that the object is A groove forming step of irradiating a laser beam having an absorptive wavelength along a planned division line to form a groove by ablation processing and connecting the groove and the modified layer.
A division process in which an external force is applied to the work piece to divide the work piece along the planned division line, and
A method of processing a work piece that is composed of at least. An oscillator that oscillates a laser beam, a concentrator that condenses the laser beam oscillated by the oscillator and positions the condensing point inside the work piece and on the upper surface of the work piece, and a cover glass that protects the condenser. It is a processing method for processing an workpiece having a planned division line by using a laser processing apparatus equipped with the above.
With the cover glass positioned at the end of the concentrator, the condensing point of the laser beam having a wavelength that is absorbent to the workpiece is positioned on the upper surface of the workpiece so that the object is A groove forming process in which a laser beam having an absorptive wavelength is irradiated along a planned division line to form a groove by ablation processing,
With the cover glass removed from the end of the condenser, the focusing point of the laser beam having a wavelength that is transparent to the workpiece is placed inside the workpiece from the opposite side where the groove is formed. A modified layer forming step of irradiating a work piece with a laser beam having a wavelength that is transparent to the workpiece along a planned division line to form a modified layer and connecting the modified layer and the groove.
A division process in which an external force is applied to the work piece to divide the work piece along the planned division line, and
A method of processing a work piece that is composed of at least. The wavelength of the laser beam having a wavelength that is transparent to the work piece and the wavelength of the laser beam having a wavelength that is absorbent to the work piece are both 532 nm, and the work piece is glass or sapphire (Al _2). The method for processing a workpiece according to claim 1 or 2, which is any one of _{O 3} ), silicon carbide (SiC), lithium tantalate (LiTaO ₃ ), and lithium niobate (LiNbO _3).

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