JP2018206946A - 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 laser processing step and a dividing step. The laser processing step forms a 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, and using an outer peripheral excess region as a reinforcing part in which the modified layer is not formed. The dividing step divides the gallium nitride substrate into individual chips by applying force to the gallium nitride substrate by single cooling or heating.SELECTED DRAWING: Figure 6

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-like workpiece (workpiece) represented by a wafer into multiple chips, a laser beam with transparency is focused inside the workpiece and modified by multiphoton absorption. A method of forming a modified layer (modified region) is known (see, for example, 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. Objects can be divided into multiple chips.

  When applying a force to the workpiece on which the modified layer is formed, for example, a method of applying an expandable expand sheet (expanding tape) to the workpiece and expanding it is employed (for example, Patent Document 2). reference). In this method, an expanded sheet is usually attached to a workpiece before the modified layer is formed on the workpiece by irradiation with a laser beam, and then the expanded sheet is expanded after the modified layer is formed. Divide the workpiece into multiple chips.

JP 2002-192370 A JP 2010-206136 A

  However, in the method of expanding the expanded sheet as described above, since the expanded sheet after use cannot be used again, the cost required for manufacturing the chip tends to be high. In particular, a high-performance expanded sheet in which the adhesive material hardly remains 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 problems, 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-like workpiece without using an expanded sheet. It is to be.

  According to one aspect of the present invention, a plurality of the gallium nitride substrates having a chip region partitioned into a plurality of regions to be chips by a plurality of intersecting division 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 for directly holding a gallium nitride substrate by a holding table; and a laser beam having a wavelength that is transparent to the gallium nitride substrate after the holding step is performed. The laser beam is irradiated only to the chip region of the gallium nitride substrate along the planned division line so that the focal point is positioned inside the gallium nitride substrate held by the holding table, and the division of the chip region is planned. A laser processing step of forming a modified layer along a line and using the outer peripheral surplus region as a reinforcing portion where the modified layer is not formed; -After carrying out the laser processing step, carrying out the gallium nitride substrate from the holding table; and after carrying out the carrying out step, a force is applied to the gallium nitride substrate to separate the gallium nitride substrate into the individual chips. A splitting step for splitting, and in the splitting step, a chip manufacturing method for splitting the gallium nitride substrate into the individual chips by applying the force by one cooling or heating is provided.

  In one aspect of the present invention, a reinforcing part removing step for removing the reinforcing part may be further provided after the laser processing step and before the dividing step. In one embodiment of the present invention, the upper surface of the holding table is made of a flexible material, and in the holding step, the surface side of the gallium nitride substrate may be held with the flexible material.

  In the method for manufacturing a chip according to one aspect of the present invention, the modified layer along the division line is formed by irradiating only the chip region of the gallium nitride substrate with the laser beam in a state where the gallium nitride substrate is directly held by the holding table. After forming, the gallium nitride substrate is divided into individual chips by applying a force by cooling or heating once, so the expanded sheet is used to divide the gallium nitride substrate into individual chips by applying a force to the gallium nitride substrate. There is no need. Thus, according to the chip manufacturing method of 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 chip manufacturing method according to one aspect of the present invention, only the chip region of the gallium nitride substrate is irradiated with a laser beam to form a modified layer along the planned division line, and the modified outer layer has an outer peripheral surplus region. Since the reinforcing portion is not formed, the tip region is reinforced by the reinforcing portion. Therefore, the gallium nitride substrate is not divided into individual chips due to the force applied at the time of transport or the like, and the gallium nitride substrate cannot be transported properly.

It is a perspective view which shows typically the structural example of a to-be-processed object. It is a perspective view which shows typically the structural example of a laser processing apparatus. FIG. 3A is a cross-sectional view for explaining the holding step, and FIG. 3B is a cross-sectional view for explaining the laser processing step. FIG. 4A is a plan view schematically showing the state of the workpiece after the laser processing step, and FIG. 4B schematically shows the state of the workpiece after the laser processing step. It is sectional drawing shown. FIG. 5A and FIG. 5B are cross-sectional views for explaining the reinforcing portion removing step. It is sectional drawing for demonstrating a division | segmentation step. It is sectional drawing for demonstrating the holding | maintenance step which concerns on a modification. FIG. 8A is a cross-sectional view for explaining the dividing step according to the modified example, and FIG. 8B shows the state of the workpiece before dividing the chip region in the dividing step according to the modified example. It is a top view shown typically.

  Embodiments 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 laser processing step (see FIGS. 3B, 4A, and 4B), an unloading step, and a reinforcement. A part removing step (see FIGS. 5A and 5B) and a dividing step (see FIG. 6).

  In the holding step, a workpiece (workpiece) having a chip area divided into a plurality of areas by a planned division line and an outer peripheral surplus area surrounding the chip area is directly held by a chuck table (holding table). In the laser processing step, the workpiece is irradiated with a laser beam having a wavelength having transparency, and a modified layer (modified region) along the planned dividing line is formed in the chip region, and the excess outer region is modified. The reinforcing part is not formed with a layer.

  In the unloading step, the workpiece is unloaded from the holding table. In the reinforcing portion removing step, the reinforcing portion is removed from the workpiece. In the dividing step, a workpiece is divided into a plurality of chips by applying a force by one cooling or heating. Hereinafter, the manufacturing method of the chip according to the present embodiment will be described in detail.

FIG. 1 is a perspective view schematically showing a configuration example of a workpiece (workpiece) 11 used in the present embodiment. As shown in FIG. 1, the workpiece 11 is, 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 ), soda glass, borosilicate glass, quartz glass and other dielectrics (insulators), or ferroelectrics such as lithium tantalate (LiTa ₃ ) and lithium niobate (LiNb ₃ ) (ferroelectric) It is a disc-shaped wafer (substrate) made of a body crystal.

  The surface 11a side of the workpiece 11 is partitioned into a plurality of regions 15 that become chips by a plurality of division lines (streets) 13 that intersect. In the following description, a generally circular area including all of the plurality of areas 15 serving as 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), and a SAW are provided as necessary. Devices such as (Surface Acoustic Wave) filters and BAW (Bulk Acoustic Wave) filters are formed.

  A plurality of chips can be obtained by dividing the workpiece 11 along the division line 13. 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 such as lithium tantalate or lithium niobate, 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, quantity, shape, structure, size, arrangement, etc. of the device formed in the region 15 to be the chip. A device may not be formed in the region 15 to be a chip.

  In the chip manufacturing method according to this embodiment, a disk-shaped gallium nitride substrate is used as the workpiece 11 to manufacture a plurality of chips. Specifically, first, a holding step for holding the workpiece 11 directly on the chuck table is performed. FIG. 2 is a perspective view schematically showing 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 movement mechanism that moves 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 is provided. The horizontal movement mechanism 8 includes a pair of X-axis guide rails 10 that are fixed to the upper surface of the base 4 and are 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 side (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. By rotating the X-axis ball screw 14 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. An X-axis scale 18 for detecting the position of the X-axis moving table 12 in the X-axis direction is installed at a position adjacent to the X-axis guide rail 10.

  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 portion (not shown) is provided on the rear surface side (lower surface side) of the Y-axis moving table 22, and a Y-axis ball screw 24 substantially parallel to the Y-axis guide rail 20 is screwed into the nut portion. ing.

  A Y-axis pulse motor 26 is connected to one end of the Y-axis ball screw 24. By rotating the Y-axis ball screw 24 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. A Y-axis scale 28 for detecting the position of the Y-axis moving table 22 in the Y-axis direction is installed at a position adjacent to the Y-axis guide rail 20.

  A support table 30 is provided on the surface side (upper surface side) of the Y-axis moving table 22, and the chuck table 6 is disposed on the support table 30. The 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 a porous material having high hardness such as aluminum oxide, for example. 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. 3 (A), etc.) formed in the chuck table 6 and a valve 32 (see FIG. 3 (A), etc.). A) etc.). A rotation drive source (not shown) is provided below the chuck table 6, and the chuck table 6 is rotated around a rotation axis substantially parallel to the Z-axis direction by the rotation drive source.

  A columnar support structure 36 is provided behind the horizontal movement mechanism 8. A support arm 38 extending in the Y-axis direction is fixed to the upper portion of the support structure 36, and a wavelength that is transmissive to the workpiece 11 (a wavelength that is difficult to be absorbed) is attached to the tip of the support arm 38. A laser irradiation unit 40 for irradiating the workpiece 11 on the chuck table 6 by pulsing the laser beam 17 (see FIG. 3B) is provided.

  At a position adjacent to the laser irradiation unit 40, a camera 42 that images the front surface 11a side or the back surface 11b side of the workpiece 11 is provided. An 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 of the workpiece 11 and the laser irradiation unit 40.

  Components such as the chuck table 6, the horizontal movement 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 processed appropriately.

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

  Thus, the workpiece 11 is sucked and held by the holding table 6 with the surface 11a side exposed upward. In the present embodiment, as shown in FIG. 3A, the back surface 11 b side of the workpiece 11 is held directly by the chuck table 6. That is, in this embodiment, there is no need to stick an expanded sheet to the workpiece 11.

  After the holding step, a laser processing step of irradiating the workpiece 11 with a laser beam 17 having a wavelength having transparency and forming a modified layer along the planned dividing line 13 is performed. FIG. 3B is a cross-sectional view for explaining the laser processing step, and FIG. 4A is a plan view schematically showing the state of the workpiece 11 after the laser processing step. 4 (B) is a cross-sectional view schematically showing the state of the workpiece 11 after the laser processing step. Note that in FIG. 3B, some components are illustrated as functional blocks.

  In the laser processing step, first, the chuck table 6 is rotated so that, for example, the direction in which the target division line 13 extends is parallel to the X-axis direction. Next, the chuck table 6 is moved, and the position of the laser irradiation unit 40 is aligned with the extension line of the target division planned 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 line 13 extends).

  Thereafter, at the timing when the laser irradiation unit 40 reaches just above one of the boundaries between the chip area 11c and the outer peripheral surplus area 11d existing at two places on the target division line 13, the laser beam is emitted from the laser irradiation unit 40. 17 irradiation is started. In the present embodiment, as shown in FIG. 3B, 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 irradiation with the laser beam 17 is continued until the laser irradiation unit 40 reaches directly above the other boundary between the tip region 11c and the outer peripheral surplus region 11d existing at two locations on the target division line 13. That is, here, the laser beam 17 is irradiated only within the chip region 11 c along the target division line 13.

  Further, the laser beam 17 is irradiated from the front surface 11a (or the back surface 11b) inside the workpiece 11 so as to position the focal point at a predetermined depth. 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. A modified layer (modified region) 19 that is modified by multiphoton absorption and serves as a starting point of division can be formed. In the present embodiment, since the laser beam 17 is irradiated only in the chip region 11c along the target division line 13, the modified layer 19 is formed only in the chip region 11c along the target division line 13. The

  After the modified layer 19 is formed at a predetermined depth along the target division line 13, the modified layer is formed at another depth along the target division line 13 in the same procedure. 19 is formed. Specifically, for example, as shown in FIG. 4B, the modified layer 19 (first modified layer 19a) is formed at three positions having different depths from the front surface 11a (or the back surface 11b) of the workpiece 11. , A second modified layer 19b and a third modified layer 19c) are formed.

  However, there is no particular limitation on the number and position of the modified layers 19 formed along one division line 13. For example, the number of modified layers 19 formed along one division line 13 may be one. In addition, the modified layer 19 is desirably 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.

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: 1340nm
Laser beam repetition frequency: 90 kHz
Laser beam output: 0.1 W to 2 W
Chuck table moving speed (working 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: 0.1 W to 2 W
Chuck table moving speed (machining feed 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 Laser beam wavelength: 1045 nm
Laser beam repetition frequency: 100 kHz
Laser beam output: 0.1 W to 2 W
Chuck table moving speed (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 material 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: 0.02 W to 0.2 W
Chuck table moving speed (processing 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: 0.1 W to 2 W
Chuck table moving speed (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: 0.02 W to 0.2 W
Chuck table moving speed (processing feed speed): 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 output: 0.02 W to 0.2 W, typically 0.1 W
Chuck table moving speed (processing feed speed): 90 mm / s to 600 mm / s, typically 90 mm / s in the cleavage direction of the silicon carbide substrate, 400 mm / s in the non-cleavage direction

  After the necessary number of modified layers 19 are formed along the target division line 13, the above-described operation is repeated to form the modified layers 19 along all the other division lines 13. As shown in FIG. 4A, when the modified layer 19 is formed along all the division planned lines 13, the laser processing step ends.

  In the present embodiment, the modified layer 19 is formed only in the chip region 11c along the planned dividing line 13, and the modified layer 19 is not formed in the outer peripheral surplus region 11d. 11 strength is maintained. Thereby, the workpiece 11 is not divided into individual chips by a force applied during conveyance or the like. Thus, the outer peripheral surplus area 11d after the laser processing step functions as a reinforcing portion for reinforcing the chip area 11 in which the modified layer 19 is formed.

  In this embodiment, since the modified layer 19 is not formed in the outer peripheral surplus region 11d, for example, a crack extending from the modified layer 19 reaches both the front surface 11a and the back surface 11b, and the workpiece 11 is completely formed. Even in a divided situation, each chip does not drop out or become discrete. In general, 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 expansion force generated by the formation of the modified layer 19 is applied inwardly in the ring-shaped outer peripheral surplus region 11d that functions as a reinforcing portion, thereby pressing each chip and preventing dropping and discreteness. doing.

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

  After the unloading step, a reinforcing portion removing step for removing the reinforcing portion from the workpiece 11 is performed. FIG. 5A and FIG. 5B are cross-sectional views for explaining the reinforcing portion removing step. Note that in FIG. 5A and FIG. 5B, some components are shown as functional blocks. The reinforcing portion removing step is performed using, for example, a dividing device 52 shown in FIGS. 5 (A) and 5 (B).

  The dividing device 52 includes a chuck table 54 for sucking and holding the workpiece 11. A part of the upper surface of the chuck table 54 serves as a holding surface 54 a that sucks and holds the chip region 11 c of the workpiece 11. The holding surface 54 a is connected to a suction source 58 through a suction path 54 b formed in the chuck table 54, a valve 56, and the like.

  Further, another part of the upper surface of the chuck table 54 is open at one end of a suction path 54c for sucking and holding the outer peripheral surplus region 11d (that is, the reinforcing portion) of the workpiece 11. The other end side of the suction path 54c is connected to a suction source 58 via a valve 60 or the like. The chuck table 54 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the vertical direction.

  A cutting unit 62 is disposed above the chuck table 54. The cutting unit 62 includes a spindle 64 serving as a rotation axis that is substantially parallel to the holding surface 54a. An annular cutting blade 66 in which abrasive grains are dispersed in a binder is attached to one end side of the spindle 64.

  A rotation drive source (not shown) such as a motor is connected to the other end side of the spindle 64, and the cutting blade 66 attached to one end side of the spindle 64 rotates by a force transmitted from the rotation drive source. The cutting unit 62 is supported by, for example, an elevating mechanism (not shown), and the cutting blade 66 is moved in the vertical direction by the elevating mechanism.

  Note that a cutting blade relief groove (not shown) for preventing contact with the cutting blade 66 at a position corresponding to the boundary between the tip region 11c and the outer peripheral surplus region 11d of the workpiece 11 is formed on the upper surface of the chuck table 54. ) Is formed.

  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 valves 56 and 60 are opened, and the negative pressure of the suction source 58 is applied to the holding surface 54a and the like. Thereby, the workpiece 11 is sucked and held by the chuck table 54 with the surface 11a side exposed upward. In this embodiment, as shown in FIG. 5A, the back surface 11 b side of the workpiece 11 is held directly by the chuck table 54. That is, here again, there is no need to apply an expanded sheet to the workpiece 11.

  Next, the cutting blade 66 is rotated and cut into the boundary between the tip region 11 c and the outer peripheral surplus region 11 d of the workpiece 11. At the same time, as shown in FIG. 5A, the chuck table 54 is rotated around a rotation axis substantially parallel to the vertical direction. Thereby, the workpiece 11 can be cut along the boundary between the tip region 11c and the outer peripheral surplus region 11d.

  Thereafter, the valve 60 is closed, and the negative pressure of the suction source 58 on the outer peripheral surplus region 11d of the workpiece 11 is shut off. Then, as shown in FIG. 5B, the outer peripheral surplus region 11d is removed from the chuck table 54. As a result, only the chip region 11 c of the workpiece 11 remains on the chuck table 54.

  After the reinforcing portion removing step, a dividing step for dividing the workpiece 11 into individual chips is performed. Specifically, for example, a large temperature difference is formed inside the workpiece 11 (between the front surface 11a and the back surface 11b), and the workpiece 11 is divided by applying a force by thermal shock (thermal shock). . FIG. 6 is a cross-sectional view for explaining the dividing step. In FIG. 6, some components are shown as functional blocks.

  The dividing step is continued using the dividing device 52. As shown in FIG. 6, the dividing device 52 further includes an injection nozzle (temperature difference forming unit) 68 disposed above the chuck table 54. In the dividing step of the present embodiment, a cooling fluid 21 is sprayed from the jet nozzle 68 onto the surface 11a of the workpiece 11, thereby forming a temperature difference necessary for generating a thermal shock. However, a temperature difference necessary for generating a thermal shock may be formed by spraying the heating fluid 21.

  As the cooling fluid 21, for example, a low-temperature liquid such as liquid nitrogen that can further remove heat by vaporization may be used. Thereby, the surface 11a side of the workpiece 11 can be quickly cooled to easily form a necessary temperature difference. Here, the necessary temperature difference means a temperature difference at which a thermal shock exceeding the stress necessary for breaking the workpiece 11 along the modified layer 19 is obtained. This temperature difference is determined according to, for example, the material and thickness of the workpiece 11 and the state of the modified layer 19.

  However, there are no particular restrictions on the type or flow rate of the fluid 21. For example, a sufficiently cooled gas such as air or a liquid such as water can be used. In addition, when using a liquid as the fluid 21, it is good to cool this liquid to low temperature (for example, about 0.1 degreeC-10 degreeC higher than a freezing point) so that it may not freeze.

  When the workpiece 11 is cooled so that a sufficient temperature difference is formed, a crack 23 extends from the modified layer 19 due to thermal shock, and the workpiece 11 is divided into a plurality of chips 25 along the division line 13. Divided. Thus, in this embodiment, a necessary force can be applied by a single cooling, and the workpiece 11 can be divided into individual chips 25. In this embodiment, the thermal shock is generated by rapidly cooling the workpiece 11. However, the thermal shock may be generated by rapidly heating the workpiece 11.

  As described above, in the chip manufacturing method according to the present embodiment, the laser beam is applied only to the chip region 11 c of the workpiece 11 while the workpiece (workpiece) 11 is directly held by the chuck table (holding table) 6. The modified layer 19 is formed along the line to be divided 13 by irradiating the beam 17, and then the workpiece 11 is divided into individual chips 25 by applying a force by cooling once. It is not necessary to use an expanded sheet to apply a force to the chip 25 and divide it into individual chips 25. Thus, according to the chip manufacturing method of the present embodiment, a plurality of chips 25 can be manufactured by dividing the gallium nitride substrate, which is the plate-like workpiece 11, without using an expanded sheet.

  Further, in the chip manufacturing method according to the present embodiment, only the chip region 11 c of the workpiece 11 is irradiated with the laser beam 17 to form the modified layer 19 along the scheduled division line 13, and the outer peripheral surplus region 11 d is formed. Since the reinforcing portion is not formed with the modified layer 19, the chip region 11c is reinforced by the reinforcing portion. Therefore, the workpiece 11 is not divided into the individual chips 25 due to the force applied during conveyance, and the workpiece 11 cannot be conveyed properly.

  In addition, this invention is not restrict | limited to description of the said embodiment etc., A various change can be implemented. For example, in the holding step of 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 surface 11a side. The side may be held directly by the chuck table 6 and the laser beam 17 may be irradiated from the back surface 11b side.

  FIG. 7 is a cross-sectional view for explaining a holding step according to a modification. In the holding step according to this modified example, as shown in FIG. 7, for example, a chuck whose upper surface is constituted by a porous sheet (porous sheet) 44 made of a flexible material typified by a resin such as polyethylene or epoxy. A table (holding table) 6 may be used.

  In the chuck table 6, the upper surface 44 a of the sheet 44 sucks and holds the surface 11 a side of the workpiece 11. Thereby, damage of the device etc. currently formed in the surface 11a side can be prevented. The sheet 44 is a part of the chuck table 6 and is repeatedly used 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 configured by the porous sheet 44 described above, and is flexible enough to at least not damage a device or the like formed on the surface 11a side of the workpiece 11. What is necessary is just to be comprised with the 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.

  In the above embodiment, the reinforcing portion removing step is performed after the unloading step and before the dividing step. For example, the reinforcing portion removing step may be performed after the laser processing step and before the unloading step. good. In addition, when performing a reinforcement part removal step after a carrying-out step and before a division | segmentation step, since it is not necessary to convey the workpiece 11 after a reinforcement part removal step, the workpiece 11 can be conveyed appropriately. It is easy to avoid problems such as disappearance.

  Further, the reinforcing portion removing step can be omitted. In this case, for example, the range in which the modified layer 19 is formed in the laser processing step may be adjusted so that the width of the reinforcing portion is about 2 mm to 3 mm from the outer peripheral edge of the workpiece 11. Further, for example, before dividing the chip region 11c in the dividing step, a groove serving as a starting point of the division may be formed in the reinforcing portion. FIG. 8A is a cross-sectional view for explaining the dividing step according to the modified example, and FIG. 8B is a cross-sectional view of the workpiece 11 before dividing the chip region 11c in the dividing step according to the modified example. It is a top view which shows a state typically.

  In the dividing step according to the modified example, as shown in FIGS. 8A and 8B, the cutting blade 66 is cut into the outer peripheral surplus region 11d (that is, the reinforcing portion), and the groove serving as the starting point of the division is obtained. 11e is formed. The groove 11e is desirably formed along the planned division line 13, for example. By forming such a groove 11e, the workpiece 11 can be divided along with the outer peripheral surplus region 11d by thermal shock. In the dividing step according to the modification, the suction path 54c, the valve 60, and the like of the chuck table 54 can be omitted.

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

11 Workpiece (work)
11a Front surface 11b Back surface 11c Chip region 11d Peripheral surplus region 13 Scheduled line (street)
15 region 17 laser beam 19 modified layer (modified region)
19a First modified layer 19b Second modified layer 19c Third modified layer 21 Fluid 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 Dividing device 54 Chuck table (holding table)
54a Holding surface 54b Suction path 54c Suction path 56 Valve 58 Suction source 60 Valve 62 Cutting unit 64 Spindle 66 Cutting blade 68 Injection nozzle (temperature difference forming unit)

Claims (3)

A chip manufacturing method for manufacturing a plurality of chips from a gallium nitride substrate having a chip region partitioned into a plurality of regions to be chips by a plurality of intersecting division lines and an outer peripheral surplus region surrounding the chip region. There,
A holding step for holding the gallium nitride substrate directly on the holding table;
After carrying out the holding step, the laser beam having a wavelength that is transmissive to the gallium nitride substrate is positioned along the planned dividing line so that the condensing point of the laser beam is positioned inside the gallium nitride substrate held by the holding table. Reinforcing part in which the laser beam is irradiated only to the chip region of the gallium nitride substrate, a modified layer is formed along the planned dividing line of the chip region, and the outer peripheral surplus region is not formed with the modified layer A laser processing step, and
An unloading step of unloading the gallium nitride substrate from the holding table after performing the laser processing step;
Dividing the gallium nitride substrate into individual chips by applying a force to the gallium nitride substrate after performing the unloading step; and
In the dividing step, the force is applied by one cooling or heating to divide the gallium nitride substrate into the individual chips.   The chip manufacturing method according to claim 1, further comprising a reinforcing portion removing step for removing the reinforcing portion after the laser processing step and before the dividing step. The upper surface of the holding table is made of a flexible material,
3. The chip manufacturing method according to claim 1, wherein in the holding step, the surface side of the gallium nitride substrate is held by the flexible material.