JP2019220586A - Chip manufacturing method - Google Patents

Abstract

To provide a chip manufacturing method capable of manufacturing a plurality of chips by dividing a plate-like workpiece without using an expanded sheet.SOLUTION: A chip manufacturing method includes a first laser processing step, a second laser processing step, and a dividing step. The first laser processing step forms a first modified layer along division schedule lines of a chip region by irradiating only the chip region with a laser beam of a wavelength having permeability to a gallium nitride substrate along the division schedule lines. The second laser processing step forms a second modified layer along a boundary between the chip region and an outer peripheral excess region by radiating a laser beam of a wavelength having permeability to the gallium nitride substrate along the boundary. The dividing step divides the gallium nitride substrate into individual chips by applying force and ultrasonic vibration to the gallium nitride substrate.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a chip manufacturing method for manufacturing a plurality of chips by dividing a plate-shaped workpiece.

  In order to divide a plate-shaped workpiece (work) typified by a wafer into multiple chips, a transparent laser beam is focused inside the workpiece and modified by multiphoton absorption. A method of forming a modified layer (modified region) is known (for example, see Patent Document 1). Since the modified layer is more fragile than other regions, the modified layer is formed along the planned dividing line (street) and then a force is applied to the workpiece to process the modified layer as a starting point. Objects can be split into multiple chips.

  When a force is applied to the workpiece on which the modified layer has been formed, for example, a method is employed in which an expandable expandable sheet (expanded tape) is attached to the workpiece and expanded. reference). In this method, usually, before forming a modified layer on a workpiece by irradiating a laser beam, an expanded sheet is attached to the workpiece, and then, after forming the modified layer, the expanded sheet is expanded. The work piece is divided into a plurality of chips.

JP-A-2002-192370 JP 2010-206136 A

  However, in the method of expanding the expanded sheet as described above, since the used expanded sheet cannot be used again, the cost required for manufacturing the chip is likely to increase. In particular, a high-performance expanded sheet in which the adhesive material is unlikely to remain on the chip is expensive, and the use of such an expanded sheet increases the cost required for manufacturing the chip.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a chip manufacturing method capable of manufacturing a plurality of chips by dividing a plate-shaped workpiece without using an expanded sheet. It is to be.

  According to one embodiment of the present invention, a plurality of gallium nitride substrates having a chip region partitioned into a plurality of regions to be chips by a plurality of intersecting dividing lines and an outer peripheral surplus region surrounding the chip region are provided. A chip manufacturing method for manufacturing a chip, comprising: a holding step of directly holding a gallium nitride substrate on a holding table; and after performing the holding step, a laser beam having a wavelength that is transparent to the gallium nitride substrate. The laser beam is applied only to the chip area of the gallium nitride substrate along the dividing line so that the focal point is located inside the gallium nitride substrate held by the holding table, and the chip area of the gallium nitride substrate is divided. First laser processing in which a first modified layer is formed along a line, and the outer peripheral surplus region is used as a reinforcing portion where the first modified layer is not formed. Step and after performing the holding step, the chip area and the chip region so that the focal point of the laser beam having a wavelength that is transparent to the gallium nitride substrate is positioned inside the gallium nitride substrate held by the holding table. A second laser processing step of irradiating the laser beam along a boundary with the outer peripheral surplus area and forming a second modified layer along the boundary; a first laser processing step and a second laser processing step After carrying out, a carrying out step of carrying out the gallium nitride substrate from the holding table, and a dividing step of applying a force to the gallium nitride substrate to divide the gallium nitride substrate into the individual chips after performing the carrying out step. Wherein, in the dividing step, a method of manufacturing a chip is provided in which the gallium nitride substrate is divided into individual chips by applying ultrasonic vibration. That.

  In one embodiment of the present invention, after the first laser processing step and the second laser processing step are performed, before the division step is performed, the method may further include a reinforcing part removing step of removing the reinforcing part. . In one embodiment of the present invention, the upper surface of the holding table is formed of a flexible material, and in the holding step, the front side of the gallium nitride substrate may be held by the flexible material.

  In the method for manufacturing a chip according to one embodiment of the present invention, in a state where the gallium nitride substrate is directly held by the holding table, a laser beam is irradiated only to the chip region of the gallium nitride substrate, and the first modification along the scheduled dividing line is performed. After forming a second modified layer along the boundary by irradiating a laser beam on the boundary between the chip region and the outer peripheral surplus region, and applying ultrasonic vibration to the gallium nitride substrate, Therefore, there is no need to use an expanded sheet to apply a force to the gallium nitride substrate and divide the chips into individual chips. As described above, according to the method for manufacturing a chip according to one embodiment of the present invention, a plurality of chips can be manufactured by dividing a gallium nitride substrate which is a plate-like workpiece without using an expanded sheet.

  Further, in the method for manufacturing a chip according to one embodiment of the present invention, the first modified layer along the dividing line is formed by irradiating a laser beam only to the chip region of the gallium nitride substrate, and the outer peripheral surplus region is formed in the first region. Since the reinforcing portion is not formed with the modified layer, the chip region is reinforced by the reinforcing portion. Therefore, the gallium nitride substrate is not divided into individual chips due to the force applied during transportation or the like, and the gallium nitride substrate cannot be properly transported.

It is a perspective view which shows the example of a structure of a to-be-processed object typically. It is a perspective view showing typically the example of composition of a laser processing device. FIG. 3A is a cross-sectional view for explaining a holding step, and FIG. 3B is a cross-sectional view for explaining a first laser processing step. FIG. 9 is a cross-sectional view for describing a second laser processing step. FIG. 5A is a plan view schematically illustrating a state of a workpiece after a modified layer is formed, and FIG. 5B is a cross-sectional view schematically illustrating a state of the modified layer. It is. It is sectional drawing for demonstrating a reinforcement part removal step. FIG. 7A and FIG. 7B are cross-sectional views for describing the dividing step. It is sectional drawing for demonstrating the holding step concerning a modification. FIG. 9A is a cross-sectional view for describing a dividing step according to the modification, and FIG. 9B is a diagram illustrating a state of a workpiece before dividing a chip region in the dividing step according to the modification. It is a top view which shows typically.

  An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. The chip manufacturing method according to the present embodiment includes a holding step (see FIG. 3A), a first laser processing step (see FIG. 3B), a second laser processing step (see FIG. 4 and the like), unloading. This step includes a step, a reinforcing part removing step (see FIG. 6), and a dividing step (see FIGS. 7A and 7B).

  In the holding step, a workpiece (work) having a chip region divided into a plurality of regions by the planned dividing line and an outer peripheral surplus region surrounding the chip region is directly held by a chuck table (holding table). In the first laser processing step, a workpiece is irradiated with a laser beam having a wavelength having transparency so as to form a modified layer (first modified layer) along a line to be divided in the chip region, and The surplus region is defined as a reinforcing portion where no modified layer is formed.

  In the second laser processing step, a workpiece is irradiated with a laser beam having a wavelength having transparency so as to form a modified layer (second modified layer) along a boundary between the chip region and the outer peripheral surplus region. . In the unloading step, the workpiece is unloaded from the chuck table. In the reinforcing portion removing step, the reinforcing portion is removed from the workpiece. In the dividing step, the workpiece is divided into a plurality of chips by applying ultrasonic vibration. Hereinafter, the method for manufacturing a chip according to the present embodiment will be described in detail.

FIG. 1 is a perspective view schematically illustrating a configuration example of a workpiece (work) 11 used in the present embodiment. As shown in FIG. 1, the workpiece 11 is made of, for example, a semiconductor such as silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), gallium nitride (GaN), silicon carbide (SiC), or sapphire. (Al ₂ O ₃ ), dielectric (insulator) such as soda glass, borosilicate glass, quartz glass, or ferroelectric (ferroelectric) such as lithium tantalate (LiTa ₃ ) or lithium niobate (LiNb ₃ ) (A body crystal).

  The surface 11a side of the workpiece 11 is partitioned into a plurality of regions 15 to be chips by a plurality of intersection lines (streets) 13 that intersect. In the following, a substantially circular area including all of the plurality of areas 15 to be chips is referred to as a chip area 11c, and an annular area surrounding the chip area 11c is referred to as an outer peripheral surplus area 11d.

  In each area 15 in the chip area 11c, an IC (Integrated Circuit), a MEMS (Micro Electro Mechanical Systems), an LED (Light Emitting Diode), an LD (Laser Diode), a photodiode (Photodiode), a SAW Devices such as a (Surface Acoustic Wave) filter and a BAW (Bulk Acoustic Wave) filter are formed.

  By dividing the workpiece 11 along the dividing line 13, a plurality of chips can be obtained. Specifically, when the workpiece 11 is a silicon wafer, for example, a chip that functions as a memory, a sensor, or the like is obtained. When the workpiece 11 is a gallium arsenide substrate, an indium phosphide substrate, or a gallium nitride substrate, for example, a chip that functions as a light emitting element, a light receiving element, or the like is obtained.

  When the workpiece 11 is a silicon carbide substrate, for example, a chip that functions as a power device or the like is obtained. When the workpiece 11 is a sapphire substrate, for example, a chip that functions as a light emitting element or the like is obtained. When the workpiece 11 is a glass substrate made of soda glass, borosilicate glass, quartz glass, or the like, for example, a chip that functions as an optical component or a cover member (cover glass) is obtained.

  When the workpiece 11 is a ferroelectric substrate (ferroelectric crystal substrate) made of a ferroelectric substance such as lithium tantalate or lithium niobate, for example, a chip that functions as a filter, an actuator, or the like is obtained. The material, shape, structure, size, thickness, and the like of the workpiece 11 are not limited. Similarly, there is no limitation on the type, number, shape, structure, size, arrangement, and the like of devices formed in the region 15 to be a chip. A device may not be formed in the region 15 to be a chip.

  In the chip manufacturing method according to the present embodiment, a plurality of chips are manufactured using a disk-shaped gallium nitride substrate as the workpiece 11. Specifically, first, a holding step of holding the workpiece 11 directly on the chuck table is performed. FIG. 2 is a perspective view schematically illustrating a configuration example of a laser processing apparatus used in the present embodiment.

  As shown in FIG. 2, the laser processing apparatus 2 includes a base 4 on which each component is mounted. On the upper surface of the base 4, a horizontal moving mechanism for moving a chuck table (holding table) 6 for sucking and holding the workpiece 11 in the X-axis direction (machining feed direction) and the Y-axis direction (index feed direction). 8 are provided. The horizontal moving mechanism 8 includes a pair of X-axis guide rails 10 fixed to the upper surface of the base 4 and substantially parallel to the X-axis direction.

  An X-axis moving table 12 is slidably attached to the X-axis guide rail 10. A nut portion (not shown) is provided on the back surface (lower surface side) of the X-axis moving table 12, and an X-axis ball screw 14 that is substantially parallel to the X-axis guide rail 10 is screwed into the nut portion. ing.

  An X-axis pulse motor 16 is connected to one end of the X-axis ball screw 14. When the X-axis ball screw 14 is rotated by the X-axis pulse motor 16, the X-axis moving table 12 moves in the X-axis direction along the X-axis guide rail 10. At a position adjacent to the X-axis guide rail 10, an X-axis scale 18 for detecting the position of the X-axis moving table 12 in the X-axis direction is installed.

  A pair of Y-axis guide rails 20 that are substantially parallel to the Y-axis direction are fixed to the surface (upper surface) of the X-axis moving table 12. A Y-axis moving table 22 is slidably attached to the Y-axis guide rail 20. A nut (not shown) is provided on the back side (lower side) of the Y-axis moving table 22, and a Y-axis ball screw 24 that is substantially parallel to the Y-axis guide rail 20 is screwed into the nut. ing.

  A Y-axis pulse motor 26 is connected to one end of the Y-axis ball screw 24. When the Y-axis ball screw 24 is rotated by the Y-axis pulse motor 26, the Y-axis moving table 22 moves in the Y-axis direction along the Y-axis guide rail 20. At a position adjacent to the Y-axis guide rail 20, a Y-axis scale 28 for detecting the position of the Y-axis moving table 22 in the Y-axis direction is installed.

  A support table 30 is provided on the front side (upper surface side) of the Y-axis moving table 22, and the chuck table 6 is disposed above the support table 30. The front surface (upper surface) of the chuck table 6 is a holding surface 6a that sucks and holds the back surface 11b side (or the front surface 11a side) of the workpiece 11 described above. The holding surface 6a is made of, for example, a porous material having high hardness such as aluminum oxide. However, the holding surface 6a may be made of a flexible material typified by a resin such as polyethylene or epoxy.

  The holding surface 6a is connected to a suction source 34 (see FIG. 3 (A)) through a suction path 6b (see FIG. 3A) and a valve 32 (see FIG. 3A) formed inside the chuck table 6. A) etc.). A rotary drive source (not shown) is provided below the chuck table 6, and the rotary table rotates the chuck table 6 about a rotation axis substantially parallel to the Z-axis direction.

  Behind the horizontal moving mechanism 8, a columnar support structure 36 is provided. A support arm 38 extending in the Y-axis direction is fixed to an upper portion of the support structure 36. A wavelength having a transmittance to the workpiece 11 (a wavelength that is hardly absorbed) is provided at a tip of the support arm 38. A laser irradiation unit 40 for oscillating the laser beam 17 (see FIG. 3B) of the laser beam 17 and irradiating the workpiece 11 on the chuck table 6 with a pulse is provided.

  At a position adjacent to the laser irradiation unit 40, a camera 42 for imaging the front surface 11a side or the rear surface 11b side of the workpiece 11 is provided. The image formed by imaging the workpiece 11 or the like with the camera 42 is used, for example, when adjusting the position or the like between the workpiece 11 and the laser irradiation unit 40.

  Components such as the chuck table 6, the horizontal moving mechanism 8, the laser irradiation unit 40, and the camera 42 are connected to a control unit (not shown). The control unit controls each component so that the workpiece 11 is appropriately processed.

  FIG. 3A is a cross-sectional view for explaining the holding step. Note that in FIG. 3A, some components are shown as functional blocks. In the holding step, for example, the back surface 11b of the workpiece 11 is brought into contact with the holding surface 6a of the chuck table 6, as shown in FIG. Then, the valve 32 is opened to apply the negative pressure of the suction source 34 to the holding surface 6a.

  As a result, the workpiece 11 is sucked and held on the chuck table 6 in a state where the surface 11a side is exposed upward. In this embodiment, as shown in FIG. 3A, the back surface 11b side of the workpiece 11 is directly held by the chuck table 6. That is, in the present embodiment, there is no need to attach the expanded sheet to the workpiece 11.

  After the holding step, a first laser processing step of irradiating the laser beam 17 along the planned dividing line 13 to form a modified layer (first modified layer), and applying the laser beam 17 to the chip region 11c and the outer peripheral surplus. Irradiation is performed along the boundary with the region 11d to perform a second laser processing step of forming a modified layer (second modified layer). In this embodiment, a case will be described in which the second laser processing step is performed after the first laser processing step.

  FIG. 3B is a cross-sectional view for explaining a first laser processing step, FIG. 4 is a cross-sectional view for explaining a second laser processing step, and FIG. FIG. 5B is a plan view schematically illustrating a state of the workpiece 11 after the layer 19 is formed, and FIG. 5B is a cross-sectional view schematically illustrating the modified layer 19. Note that in FIG. 3B and FIG. 4, some components are shown as functional blocks.

  In the first laser processing step, first, the chuck table 6 is rotated so that, for example, the direction in which the target dividing line 13 extends is parallel to the X-axis direction. Next, the chuck table 6 is moved to adjust the position of the laser irradiation unit 40 on an extension of the target division line 13. Then, as shown in FIG. 3B, the chuck table 6 is moved in the X-axis direction (that is, the direction in which the target division planned line 13 extends).

  Thereafter, at the timing when the laser irradiation unit 40 reaches just above one of the boundaries between the chip region 11c and the outer peripheral surplus region 11d existing at two locations on the target dividing line 13, the laser irradiation unit 40 Irradiation of the object 11 with the laser beam 17 having a wavelength having transparency is started. In this embodiment, as shown in FIG. 3B, a laser beam 17 is emitted from a laser irradiation unit 40 disposed above the workpiece 11 toward the surface 11 a of the workpiece 11.

  The irradiation of the laser beam 17 is continued until the laser irradiation unit 40 reaches the position just above the other of the boundaries between the chip region 11c and the outer peripheral surplus region 11d existing at two locations on the target dividing line 13. That is, here, the laser beam 17 is applied only to the chip region 11c along the target scheduled division line 13.

  The laser beam 17 is irradiated so as to position the focal point at a position at a predetermined depth from the front surface 11a (or the back surface 11b) inside the workpiece 11. In this way, by condensing the laser beam 17 having a wavelength that is transmissive to the workpiece 11 inside the workpiece 11, a part of the workpiece 11 is focused at and near the focal point. The modified layer 19 (modified layer 19a or the like) serving as a starting point of division can be formed by modification by multiphoton absorption.

  In the first laser processing step of the present embodiment, since the laser beam 17 is applied only to the chip region 11c along the target division line 13, the laser beam 17 is irradiated only in the chip region 11c along the target division line 13. The quality layer 19 is formed. That is, as shown in FIG. 5B, in the first laser processing step, the modified layer 19 is not formed in the outer peripheral surplus region 11d.

  After the reformed layer 19 is formed at a position at a predetermined depth along the target division line 13, the modified layer 19 is formed at another depth along the target division line 13 in the same procedure. 19 is formed. In the present embodiment, as shown in FIG. 5B, for example, the modified layer 19 (modified layer 19a, modified layer 19a) is located at three different positions from the front surface 11a (or back surface 11b) of the workpiece 11. The quality layer 19b and the modified layer 19c) are formed.

  However, there is no particular limitation on the number and positions of the modified layers 19 formed along one dividing line 13. For example, the number of the modified layers 19 formed along one dividing line 13 may be one. Further, it is desirable that the modified layer 19 is formed under the condition that the crack reaches the front surface 11a (or the back surface 11b). Of course, the modified layer 19 may be formed under the condition that the crack reaches both the front surface 11a and the back surface 11b. Thereby, the workpiece 11 can be more appropriately divided.

  After forming the required number of modified layers 19 along the target scheduled division line 13, the above procedure is repeated to form the modified layers 19 along all other scheduled division lines 13. As shown in FIG. 5A, when the required number of modified layers 19 are formed along all the division lines 13, the first laser processing step ends.

  In this first laser processing step, after forming a required number of modified layers 19 along one planned dividing line 13, a similar modified layer 19 is formed along another planned dividing line 13. However, the order of forming the modified layer 19 is not particularly limited. For example, the modified layer 19 may be formed at a position of the same depth in all the planned dividing lines 13 and then the modified layer 19 may be formed at a position of another depth.

When the workpiece 11 is a silicon wafer, for example, the modified layer 19 is formed under the following conditions.
Workpiece: Silicon wafer Laser beam wavelength: 1340 nm
Laser beam repetition frequency: 90 kHz
Laser beam output: 0.1W ~ 2W
Moving speed of the chuck table (processing feed speed): 180 mm / s to 1000 mm / s, typically 500 mm / s

When the workpiece 11 is a gallium arsenide substrate or an indium phosphide substrate, for example, the modified layer 19 is formed under the following conditions.
Workpiece: gallium arsenide substrate, indium phosphide substrate Laser beam wavelength: 1064 nm
Laser beam repetition frequency: 20 kHz
Laser beam output: 0.1W ~ 2W
Moving speed of chuck table (processing speed): 100 mm / s to 400 mm / s, typically 200 mm / s

When the workpiece 11 is a sapphire substrate, for example, the modified layer 19 is formed under the following conditions.
Workpiece: Sapphire substrate Wavelength of laser beam: 1045 nm
Laser beam repetition frequency: 100 kHz
Laser beam output: 0.1W ~ 2W
Moving speed of chuck table (working feed speed): 400 mm / s to 800 mm / s, typically 500 mm / s

When the workpiece 11 is a ferroelectric substrate made of a ferroelectric substance such as lithium tantalate or lithium niobate, the modified layer 19 is formed under the following conditions, for example.
Workpiece: lithium tantalate substrate, lithium niobate substrate Laser beam wavelength: 532 nm
Laser beam repetition frequency: 15 kHz
Laser beam output: 0.02W ~ 0.2W
Moving speed of chuck table (working feed speed): 270 mm / s to 420 mm / s, typically 300 mm / s

When the workpiece 11 is a glass substrate made of soda glass, borosilicate glass, quartz glass, or the like, the modified layer 19 is formed under the following conditions, for example.
Workpiece: soda glass substrate, borosilicate glass substrate, quartz glass substrate Laser beam wavelength: 532 nm
Laser beam repetition frequency: 50 kHz
Laser beam output: 0.1W ~ 2W
Moving speed of chuck table (processing feed speed): 300 mm / s to 600 mm / s, typically 400 mm / s

When the workpiece 11 is a gallium nitride substrate, for example, the modified layer 19 is formed under the following conditions.
Workpiece: Gallium nitride substrate Laser beam wavelength: 532 nm
Laser beam repetition frequency: 25 kHz
Laser beam output: 0.02W ~ 0.2W
Moving speed (working feed speed) of chuck table: 90 mm / s to 600 mm / s, typically 150 mm / s

When the workpiece 11 is a silicon carbide substrate, for example, the modified layer 19 is formed under the following conditions.
Workpiece: Silicon carbide substrate Laser beam wavelength: 532 nm
Laser beam repetition frequency: 25 kHz
Laser beam power: 0.02 W to 0.2 W, typically 0.1 W
Moving speed of chuck table (working feed speed): 90 mm / s to 600 mm / s, typically 90 mm / s in the cleavage direction of silicon carbide substrate and 400 mm / s in the non-cleavage direction

  In the first laser processing step of this embodiment, the modified layer 19 (modified layers 19a, 19b, 19c) is formed only in the chip region 11c along the dividing line 13, and the modified outer layer 11d is formed in the outer peripheral surplus region 11d. Since the layer 19 is not formed, the strength of the workpiece 11 is maintained by the outer peripheral surplus region 11d. As a result, the workpiece 11 is not divided into individual chips due to the force applied during transportation or the like. As described above, the outer peripheral surplus region 11d after the first laser processing step functions as a reinforcing portion for reinforcing the chip region 11c.

  Further, in the first laser processing step of the present embodiment, since the modified layer 19 is not formed in the outer peripheral surplus region 11d, for example, cracks extending from the modified layer 19 reach both the front surface 11a and the rear surface 11b, and Even when the workpiece 11 is completely divided, each chip does not fall off or separate. Generally, when the modified layer 19 is formed on the workpiece 11, the workpiece 11 expands in the vicinity of the modified layer 19. In the present embodiment, the force of expansion generated by the formation of the modified layer 19 is applied inwardly to the ring-shaped outer peripheral surplus region 11d functioning as a reinforcing portion, thereby pressing down each chip and reducing the drop-off and discreteness. It is preventing.

  After the above-described first laser processing step, a second laser processing step is performed. In the second laser processing step, first, the chuck table 6 is moved to adjust the position of the laser irradiation unit 40 on the boundary between the chip area 11c and the outer peripheral surplus area 11d. Then, as shown in FIG. 4, the chuck table 6 is rotated while irradiating the workpiece 11 with the laser beam 17 having a transmissive wavelength from the laser irradiation unit 40. That is, in this embodiment, the laser beam 17 is irradiated from the laser irradiation unit 40 disposed above the workpiece 11 toward the surface 11 a of the workpiece 11.

  The laser beam 17 is emitted so as to position the focal point at a position at a predetermined depth from the front surface 11a (or the back surface 11b) inside the workpiece 11. In this way, by condensing the laser beam 17 having a wavelength that is transmissive to the workpiece 11 inside the workpiece 11, a part of the workpiece 11 is focused at and near the focal point. The modified layer 19 (modified layer 19d) serving as a starting point of division can be formed by modification by multiphoton absorption.

  In the second laser processing step of the present embodiment, since the laser beam 17 is applied along the boundary between the chip region 11c and the outer peripheral surplus region 11d, the modified layer 19 is formed along this boundary. There is no particular limitation on the number or position of the modified layers 19 formed along the boundary between the chip region 11c and the outer peripheral surplus region 11d. For example, the number of modified layers 19 formed along the boundary may be two or more.

  Further, it is desirable that the modified layer 19 along this boundary is formed under the condition that the crack reaches the front surface 11a (or the back surface 11b). Of course, the modified layer 19 along the boundary may be formed under the condition that the crack reaches both the front surface 11a and the back surface 11b. As a result, the workpiece 11 can be more appropriately divided, and the outer peripheral surplus area 11d can be separated from the chip area 11c.

  There are no particular restrictions on the specific conditions and the like for forming the modified layer 19 in the second laser processing step. For example, the modified layer 19 along the boundary can be formed under the same conditions as those for forming the modified layer 19 in the first laser processing step. Of course, the modified layer 19 along the boundary may be formed under conditions different from the conditions for forming the modified layer 19 in the first laser processing step.

  As shown in FIGS. 5A and 5B, when an annular modified layer 19 (modified layer 19d) is formed along the boundary between the chip region 11c and the outer peripheral surplus region 11d, the second laser is formed. The processing step ends. In the present embodiment, the modified layer 19 (modified layer 19d) is formed at a position at the same depth as the modified layer 19 (modified layer 19b) formed in the first laser processing step. The cracks reach the front surface 11a and the back surface 11b from the modified layer 19 (modified layer 19d).

  After the first laser processing step and the second laser processing step, an unloading step of unloading the workpiece 11 from the chuck table 6 is performed. Specifically, for example, the entire surface 11a of the workpiece 11 is sucked by a transport unit (not shown) that can suck and hold the entire front surface 11a (or the back surface 11b) of the workpiece 11, and then the valve 32 is closed to shut off the negative pressure of the suction source 34, and the workpiece 11 is carried out. In the present embodiment, as described above, since the outer peripheral surplus region 11d functions as a reinforcing portion, the workpiece 11 is divided into individual chips by the force applied during transport or the like, and the workpiece 11 is divided. 11 cannot be transported properly.

  After the unloading step, a reinforcing part removing step of removing the reinforcing part from the workpiece 11 is performed. FIG. 6 is a cross-sectional view for explaining the reinforcing portion removing step. In FIG. 6, some components are shown by functional blocks. The reinforcing portion removing step is performed using, for example, the workpiece holding device 52 shown in FIG.

  The workpiece holding device 52 includes a chuck table (holding table) 54 for sucking and holding the workpiece 11. A part of the upper surface of the chuck table 54 is a holding surface 54a for sucking and holding the chip area 11c of the workpiece 11. The holding surface 54a is connected to a suction source 58 via a suction path 54b and a valve 56 formed inside the chuck table 54.

  The chuck table 54 is connected to a rotation drive source (not shown) such as a motor, for example, and rotates around a rotation axis substantially parallel to the vertical direction. The chuck table 54 is supported by, for example, a moving mechanism (not shown), and moves in a direction substantially parallel to the above-described holding surface 54a.

  In the reinforcing portion removing step, first, the back surface 11 b of the workpiece 11 is brought into contact with the holding surface 54 a of the chuck table 54. Then, the valve 56 is opened to apply the negative pressure of the suction source 58 to the holding surface 54a. As a result, the workpiece 11 is sucked and held on the chuck table 54 in a state where the surface 11a side is exposed upward. In the present embodiment, as shown in FIG. 6, the back surface 11b of the workpiece 11 is directly held by the chuck table 54. That is, also here, there is no need to attach an expanded sheet to the workpiece 11.

  Next, an upward force (a force away from the holding surface 54a) is applied to the outer peripheral surplus region 11d. As described above, the modified layer 19 (modified layer 19d) serving as a starting point of division is formed at the boundary between the chip region 11c and the outer peripheral surplus region 11d. Therefore, by applying an upward force to the outer peripheral surplus region 11d, the outer peripheral surplus region 11d can be lifted and removed from the chuck table 54 as shown in FIG. As a result, only the chip area 11c of the workpiece 11 remains on the chuck table 54.

  After the reinforcing portion removing step, a dividing step of dividing the workpiece 11 into individual chips is performed. Specifically, the workpiece 11 is divided by applying ultrasonic vibration. FIG. 7A and FIG. 7B are cross-sectional views for describing the dividing step. Note that in FIG. 7A and FIG. 7B, some components are illustrated by functional blocks.

  The dividing step is performed using, for example, the dividing device 72 shown in FIGS. 7A and 7B. The dividing device 72 includes a tank 74 in which the liquid 21 such as pure water is stored. The tank 74 is formed in a size that can accommodate the entire workpiece 11 (chip region 11c), and an ultrasonic vibrator 76 for generating ultrasonic vibration is attached to the bottom thereof. ing.

  The ultrasonic transducer 76 includes, for example, a piezoelectric material layer made of a piezoelectric material such as barium titanate, lead zirconate titanate, lithium tantalate, lithium niobate, and a pair of electrode layers sandwiching the piezoelectric material layer. . An AC power supply 78 for supplying AC power of a predetermined frequency is connected to the electrode layer, and the ultrasonic vibrator 76 vibrates at a frequency corresponding to the frequency of the AC power supplied from the AC power supply 78. I do.

  Above the tank 74, a holding unit 80 for holding the workpiece 11 is arranged. A part of the lower surface side of the holding unit 80 is a contact surface 80a that is in contact with the front surface 11a side (or the back surface 11b side) of the workpiece 11. The contact surface 80a is preferably made of a flexible material typified by a resin such as polyethylene or epoxy.

  This makes it easier to prevent devices and the like formed on the surface 11a of the workpiece 11 from being damaged. However, there is no particular limitation on the material and the like of the contact surface 80a. At a position surrounding the contact surface 80a, an annular projection 80b protruding downward is provided. The projections 80b can prevent the workpiece 11 after being divided into individual chips from scattering as described later.

  Inside the holding unit 80, a suction path 80c for transmitting a negative pressure to the workpiece 11 in contact with the contact surface 80a is provided. One end of the suction path 80c is connected to a suction source 84 via a valve 82 or the like. The other end of the suction passage 80c is opened to the contact surface 80a so that each region 15 of the workpiece 11 in contact with the contact surface 80a can be sucked. That is, a plurality of openings corresponding to each region 15 are provided in the contact surface 80a.

  Therefore, after the workpiece 11 is brought into contact with the contact surface 80a, the negative pressure of the suction source 84 is applied to the plurality of openings through the valve 82, the suction path 80c, and the like, so that the workpiece 11 is appropriately sucked. , Can hold. As described above, in the present embodiment, since a plurality of openings are provided at positions corresponding to the regions 15, even the workpiece 11 divided into individual chips can be appropriately suctioned and held.

  In the dividing step according to the present embodiment, first, the contact surface 80a of the holding unit 80 is brought into contact with the surface 11a of the workpiece 11. Next, the valve 82 is opened to apply the negative pressure of the suction source 84 to the plurality of openings. Thereby, the workpiece 11 is sucked and held by the holding unit 80. Thereafter, as shown in FIG. 7A, the holding unit 80 is positioned above the tank 74.

  Then, as shown in FIG. 7B, the holding unit 80 is lowered to immerse the workpiece 11 in the liquid 21 stored in the tank 74. After sufficiently lowering the holding unit 80, the valve 82 is closed to shut off the negative pressure of the suction source 84. As a result, as shown in FIG. 7B, the workpiece 11 is removed from the holding unit 80.

  It is desirable that the amount of lowering of the holding unit 80 be adjusted in a range where the gap between the bottom of the tank 74 and the lower end of the projection 80b is smaller than the thickness of the workpiece 11. As a result, the position of the workpiece 11 is regulated by the protrusions 80b, so that the workpiece 11 after being divided into individual chips can be prevented from scattering.

  Next, AC power is supplied from the AC power supply 78 to the ultrasonic vibrator 76 to vibrate the ultrasonic vibrator 76. As a result, the workpiece 11 is provided with the ultrasonic vibration generated from the ultrasonic vibrator 76 via the tank 74 and the liquid 21. Then, the cracks 23 extend from the modified layer 19 of the workpiece 11 by the force of the ultrasonic vibration, and the workpiece 11 is divided into a plurality of chips 25 along the dividing line 13.

The conditions of the ultrasonic vibration applied to the workpiece 11 are, for example, as follows.
Output: 200W
Frequency: 20kHz, 28kHz
Application time: 30 seconds to 90 seconds

  However, the condition of the ultrasonic vibration can be arbitrarily set as long as the workpiece 11 can be appropriately divided. After the workpiece 11 is divided into the plurality of chips 25, the surface 11a of the workpiece 11 and the contact surface 80a are brought into contact again, the valve 82 is opened, and the negative pressure of the suction source 84 is applied. . Thereby, the workpiece 11 after being divided into the plurality of chips 25 can be sucked and held by the holding unit 80 and carried out of the tank 74.

  As described above, in the chip manufacturing method according to the present embodiment, the laser beam is applied only to the chip region 11c of the workpiece 11 while the workpiece (work) 11 is directly held by the chuck table (holding table) 6. A modified layer 19 (modified layers 19a, 19b, 19c) is formed along the dividing line 13 by irradiating the laser beam 17, and the laser beam 17 is irradiated on the boundary between the chip region 11c and the outer peripheral surplus region 11d. After forming the modified layer 19 (modified layer 19d) along the boundary, the workpiece 11 is divided into individual chips 25 by applying ultrasonic vibration, so that a force is applied to the workpiece 11 There is no need to use an expanded sheet to divide into individual chips 25. As described above, according to the chip manufacturing method according to the present embodiment, the plurality of chips 25 can be manufactured by dividing the gallium nitride substrate, which is the plate-shaped workpiece 11, without using an expanded sheet.

  Further, in the chip manufacturing method according to the present embodiment, the modified layer 19 (modified layers 19a, 19b, 19c) along the planned division line 13 by irradiating only the chip region 11c of the workpiece 11 with the laser beam 17 is provided. Is formed, and the outer peripheral surplus region 11d is a reinforcing portion where the modified layer 19 (the modified layers 19a, 19b, 19c) is not formed. Therefore, the chip region 11c is reinforced by the reinforcing portion. Therefore, the workpiece 11 is not divided into the individual chips 25 by the force applied at the time of transportation or the like, and the workpiece 11 cannot be properly transported.

  The present invention is not limited to the description of the above-described embodiment and the like, and can be implemented with various changes. For example, in the above embodiment, the second laser processing step is performed after the first laser processing step, but the first laser processing step may be performed after the second laser processing step. Further, the second laser processing step can be performed in the middle of the first laser processing step.

  In the above embodiment, the back surface 11b side of the workpiece 11 is directly held by the chuck table 6 and the laser beam 17 is irradiated from the front side 11a. The laser beam 17 may be directly held on the table 6 and irradiated from the back surface 11b side.

  FIG. 8 is a cross-sectional view illustrating a holding step according to a modification. In the holding step according to this modification, as shown in FIG. 8, for example, a chuck having an upper surface constituted by a porous sheet (porous sheet) 44 made of a flexible material represented by a resin such as polyethylene or epoxy. A table (holding table) 6 is preferably used.

  In the chuck table 6, the upper surface 44a of the sheet 44 suctions and holds the surface 11a of the workpiece 11 side. This can prevent damage to devices and the like formed on the front surface 11a side. The sheet 44 is a part of the chuck table 6 and is used repeatedly together with the main body of the chuck table 6 and the like.

  However, the upper surface of the chuck table 6 does not need to be constituted by the porous sheet 44 described above, and is at least flexible enough not to damage devices and the like formed on the surface 11 a side of the workpiece 11. What is necessary is just to be comprised with a material. Further, it is desirable that the sheet 44 is configured to be detachable from the main body of the chuck table 6 and can be replaced when it is damaged.

  Further, in the above embodiment, the reinforcing portion removing step is performed after the unloading step and before the dividing step. For example, after the first laser processing step and the second laser processing step, before the unloading step, A reinforcing portion removing step may be performed.

  Similarly, the reinforcing portion removing step can be performed simultaneously with or after the dividing step. In this case, the tip region 11c and the outer peripheral surplus region 11d are more reliably divided by the ultrasonic vibration applied in the dividing step, so that the reinforcing portion can be more easily removed in the reinforcing portion removing step.

  Further, the step of removing the reinforcing portion can be omitted. In this case, for example, the range in which the modified layer 19 is formed in the first laser processing step and the second laser processing step is set such that the width of the reinforcing portion is about 2 mm to 3 mm from the outer peripheral edge of the workpiece 11. Adjust it. Further, for example, before dividing the chip region 11c in the dividing step, a groove serving as a starting point of division may be formed in the reinforcing portion.

  FIG. 9A is a cross-sectional view for explaining a dividing step according to the modification, and FIG. 9B is a state of the workpiece before dividing the chip region 11c in the dividing step according to the modification. It is a top view which shows typically. In the dividing step according to the modified example, before applying ultrasonic vibration to the workpiece 11 by the dividing device 72, for example, the dividing unit 72 divides the workpiece 11 by using the cutting unit 62 provided in the workpiece holding device 52. A groove serving as a starting point is formed.

  The cutting unit 62 includes a spindle (not shown) that is a rotation axis substantially parallel to the holding surface 54a. At one end of the spindle, an annular cutting blade 64 in which abrasive grains are dispersed in a binder is mounted. A rotary drive source (not shown) such as a motor is connected to the other end of the spindle, and the cutting blade 64 mounted on one end of the spindle is rotated by a force transmitted from the rotary drive source. The cutting unit 62 is supported by, for example, an elevating mechanism (not shown), and the cutting blade 64 is moved vertically by the elevating mechanism.

  As shown in FIGS. 9A and 9B, when forming a groove serving as a starting point of division, for example, the above-described cutting blade 64 is rotated to rotate the outer peripheral surplus region 11 d (that is, the reinforcing portion). Cut into pieces. Thereby, the groove 11e serving as a starting point of division can be formed in the reinforcing portion. It is desirable that the groove 11e is formed, for example, along the dividing line 13. By forming such a groove 11e, it becomes possible to divide the chip region 11c of the workpiece 11 together with the outer peripheral surplus region 11d.

  In addition, the structures, methods, and the like according to the above-described embodiments and modified examples can be appropriately changed and implemented without departing from the scope of the present invention.

11 Workpiece (work)
11a Front surface 11b Back surface 11c Chip area 11d Surplus outer area 13 Planned division line (street)
15 area 17 laser beam 19, 19a, 19b, 19c, 19d modified layer 21 liquid 23 crack 25 chip 2 laser processing device 4 base 6 chuck table (holding table)
6a Holding surface 6b Suction path 8 Horizontal movement mechanism 10 X-axis guide rail 12 X-axis movement table 14 X-axis ball screw 16 X-axis pulse motor 18 X-axis scale 20 Y-axis guide rail 22 Y-axis movement table 24 Y-axis ball screw 26 Y-axis Pulse motor 28 Y-axis scale 30 Support base 32 Valve 34 Suction source 36 Support structure 38 Support arm 40 Laser irradiation unit 42 Camera 44 Sheet (porous sheet)
44a Upper surface 52 Work holding device 54 Chuck table (holding table)
54a holding surface 54b suction path 56 valve 58 suction source 62 cutting unit 64 cutting blade 72 dividing device 74 tank 76 ultrasonic vibrator 78 AC power supply 80 holding unit 80a holding surface 80b protrusion 80c suction path 82 valve 84 suction source

Claims (3)

A chip manufacturing method for manufacturing a plurality of chips from a gallium nitride substrate having a chip region divided into a plurality of regions to be chips by a plurality of intersecting planned dividing lines and an outer peripheral surplus region surrounding the chip region. So,
A holding step of holding the gallium nitride substrate directly on a holding table,
After performing the holding step, along the dividing line, the focal point of the laser beam having a wavelength that is transparent to the gallium nitride substrate is positioned inside the gallium nitride substrate held by the holding table. The laser beam is applied only to the chip region of the gallium nitride substrate to form a first modified layer along the planned dividing line in the chip region, and the first modified layer forms the extra peripheral region. A first laser processing step as an unreinforced reinforcement;
After performing the holding step, the chip area and the outer peripheral surplus are located so that the focal point of the laser beam having a wavelength that is transparent to the gallium nitride substrate is positioned inside the gallium nitride substrate held by the holding table. A second laser processing step of irradiating the laser beam along a boundary with the region and forming a second modified layer along the boundary;
An unloading step of unloading the gallium nitride substrate from the holding table after performing the first laser processing step and the second laser processing step;
Dividing the gallium nitride substrate into individual chips by applying force to the gallium nitride substrate after performing the unloading step.
In the dividing step, a gallium nitride substrate is divided into individual chips by applying ultrasonic vibration.   2. The method according to claim 1, further comprising: a step of removing the reinforcing portion after performing the first laser processing step and the second laser processing step and before performing the dividing step. 3. Chip manufacturing method. The upper surface of the holding table is made of a flexible material,
3. The method according to claim 1, wherein in the holding step, the front side of the gallium nitride substrate is held by the flexible material.