JP2013236001A - Method for dividing plate-like object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for dividing a plate-like object capable of reducing occurrence of undivided regions and dividing even a plate-like object having high Mohs hardness in a shorter time than before.SOLUTION: A method for dividing a plate-like object for forming a plurality of chips by dividing a plate-like object having a first surface on which a plurality of intersecting division schedule lines are set and a second surface which is a rear surface of the first surface along the division schedule lines comprises the steps of: positioning condensing points of a laser beam of a wavelength having permeability to the plate-like object at the inside of the plate-like object and forming a modified layer along the division schedule lines inside the plate-like object by irradiating the plate-like object with the laser beam along the division schedule lines; and dividing the plate-like object using the modified layer as a division start point by heating the first surface of the plate-like object and cooling the second surface or cooling the first surface of the plate-like object and heating the second surface after performing the modified layer formation step.

Description

  The present invention relates to a plate-like object dividing method for dividing a plate-like object, such as a wafer, on which a plurality of intersecting scheduled division lines are set along the scheduled division line to form a plurality of chips.

  A plate-like object in which division starting points such as a cutting groove, a laser processing groove, and a modified layer are formed along a division line is divided into individual chips by a dividing apparatus as disclosed in JP-A-2002-334852. Is done. In this dividing apparatus, a plate-like object on which a division starting point is formed is attached to an expanded tape, and the expanded tape is expanded to apply an external force to the plate-like object to divide the plate-like object.

  On the other hand, in recent years, the chip size tends to be reduced due to the demand for downsizing of electronic devices. However, for example, in the case of a small chip of several mm square, a sufficient external force cannot be applied to the plate-like object only by expanding the expanded tape, and an area that cannot be divided may occur. Moreover, it is difficult to divide a plate-like material having a high Mohs hardness such as sapphire or SiC only by expanding the expanded tape.

  Therefore, as disclosed in Japanese Patent Application Laid-Open No. 2010-45117, an external force applying member having a triangular cross-section is positioned on each division planned line of a plate-like object on which a division starting point is formed along the division planned line. There has also been proposed a method of dividing a plate-like object by pressing the plate against the plate-like object.

JP 2002-334852 A JP 2010-45117 A

  However, there is a problem that it takes a lot of time and effort to divide a plate-like object by pressing an external force imparting member as disclosed in Patent Document 2 against all the planned division lines. In particular, a plate-like object having a small chip size is a significant problem because the number of lines to be divided is large.

  The present invention has been made in view of these points, and the object of the present invention is to reduce the occurrence of undivided regions and to divide a plate having a high Mohs hardness in a shorter time than before. It is to provide a method for dividing a plate-like product.

  According to the present invention, a plurality of chips are obtained by dividing a plate-like object having a first surface on which a plurality of intersecting scheduled lines are set and a second surface behind the first surface along the scheduled lines. A method for dividing a plate-like object to be formed, wherein a condensing point of a laser beam having a wavelength that is transparent to the plate-like object is positioned inside the plate-like object, and the laser beam is aligned along the planned division line A modified layer forming step for forming a modified layer along the line to be divided within the plate by irradiation, and after performing the modified layer forming step, heating the first surface of the plate And the step of cooling the second surface, or cooling the first surface of the plate-like material and heating the second surface, to divide the plate-like material from the modified layer as a division starting point; and A method for dividing a plate-like object is provided.

  Preferably, the method for dividing the plate-like material includes an adhesive tape attaching step for attaching an adhesive tape to the first surface of the plate-like material before the modified layer forming step, and the adhesive tape attachment. And a holding step of exposing the second surface by holding the plate-like object on the chuck table via the adhesive tape after the step is performed, and holding the modified layer in the chuck table in the modified layer forming step In the dividing step, the chuck table is heated and the second surface of the plate is cooled, or the chuck table is cooled and the plate is irradiated with a laser beam. By heating the second surface of the sheet-like material, the plate-like material is divided using the modified layer as a division starting point.

  In the dividing method of the present invention, the first surface of the plate-like object having the modified layer formed therein is heated and the second surface is cooled. Alternatively, the second surface of the plate-like object is heated and the first surface is cooled. The difference in thermal expansion between the first surface and the second surface becomes stress, and when this stress is applied to the modified layer, the modified layer becomes the starting point of the division and the plate-like object is divided, so that an undivided region is generated. In addition, a plate-like material having a high Mohs hardness can be divided in a shorter time than conventional.

It is a perspective view of the laser processing apparatus suitable for implementing the division | segmentation method of the plate-shaped object of this invention. It is a block diagram of a laser beam irradiation unit. It is a surface side perspective view of an optical device wafer. It is a disassembled perspective view which shows a mode that the outer peripheral part sticks the surface side of an optical device wafer to the expanded tape with which the annular frame was mounted | worn. It is a longitudinal cross-sectional view which shows a holding step. It is a longitudinal cross-sectional view which shows a modified layer formation step. It is a longitudinal cross-sectional view which shows a division | segmentation step.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a schematic configuration diagram of a laser processing apparatus 2 suitable for forming a modified layer serving as a starting point of division in the plate-like object dividing method of the present invention.

  The laser processing apparatus 2 includes a first slide block 6 mounted on a stationary base 4 so as to be movable in the X-axis direction. The first slide block 6 is moved along the pair of guide rails 14 in the machining feed direction, that is, the X-axis direction, by the machining feed means 12 including the ball screw 8 and the pulse motor 10.

  A second slide block 16 is mounted on the first slide block 6 so as to be movable in the Y-axis direction. That is, the second slide block 16 is moved in the indexing direction, that is, the Y-axis direction along the pair of guide rails 24 by the indexing feeding means 22 constituted by the ball screw 18 and the pulse motor 20.

  A chuck table 28 is mounted on the second slide block 16 via a cylindrical support member 26, and the chuck table 28 can be moved in the X-axis direction and the Y-axis direction by the processing feed means 12 and the index feed means 22. . The chuck table 28 is provided with a clamp 30 that clamps an annular frame that supports the wafer sucked and held by the chuck table 28.

  A column 32 is erected on the stationary base 4, and a casing 35 for accommodating the laser beam irradiation unit 34 is attached to the column 32. As shown in FIG. 2, the laser beam irradiation unit 34 includes a laser oscillator 62 that oscillates a YAG laser or a YVO4 laser, a repetition frequency setting unit 64, a pulse width adjustment unit 66, and a power adjustment unit 68. .

  The pulse laser beam adjusted to a predetermined power by the power adjusting means 68 of the laser beam irradiation unit 34 is reflected by the mirror 70 of the condenser 36 attached to the tip of the casing 35 and further collected by the condenser objective lens 72. The light is applied to the optical device wafer 11 held on the chuck table 28.

  At the tip of the casing 35, an image pickup unit 38 that detects the processing region to be laser processed in alignment with the condenser 36 in the X-axis direction is disposed. The imaging unit 38 includes an imaging element such as a normal CCD that images the processing region of the optical device wafer 11 with visible light.

  The imaging unit 38 further outputs an infrared irradiation unit that irradiates the optical device wafer 11 with infrared rays, an optical system that captures infrared rays irradiated by the infrared irradiation unit, and an electrical signal corresponding to the infrared rays captured by the optical system. Infrared imaging means including an infrared imaging device such as an infrared CCD is included, and the captured image signal is transmitted to a controller (control means) 40.

  The controller 40 includes a central processing unit (CPU) 42 that performs arithmetic processing according to a control program, a read-only memory (ROM) 44 that stores a control program, and a random read / write that stores arithmetic results. An access memory (RAM) 46, a counter 48, an input interface 50, and an output interface 52 are provided.

  Reference numeral 56 denotes a processing feed amount detection means comprising a linear scale 54 disposed along the guide rail 14 and a read head (not shown) disposed on the first slide block 6. Is input to the input interface 50 of the controller 40.

  Reference numeral 60 denotes index feed amount detection means comprising a linear scale 58 disposed along the guide rail 24 and a read head (not shown) disposed on the second slide block 16. The detection signal is input to the input interface 50 of the controller 40.

  An image signal captured by the imaging unit 38 is also input to the input interface 50 of the controller 40. On the other hand, a control signal is output from the output interface 52 of the controller 40 to the pulse motor 10, the pulse motor 20, the laser beam irradiation unit 34, and the like.

  A cooling fluid ejection nozzle 39 is disposed adjacent to the imaging unit 38. From the cooling fluid injection nozzle 39, a fluid such as pure water cooled to a low temperature when the plate-like object is divided is jetted onto the surface of the plate-like object.

  Referring to FIG. 3, there is shown a front side perspective view of an optical device wafer 11 which is a processing target of the dividing method of the present invention. The optical device wafer 11 is configured by laminating an epitaxial layer (light emitting layer) 15 such as gallium nitride (GaN) on a sapphire substrate 13. The optical device wafer 11 has a front surface 11a on which an epitaxial layer 15 is laminated and a back surface 11b on which a reflective film 21 is formed.

  The sapphire substrate 13 has a thickness of 100 μm, for example, and the epitaxial layer 15 has a thickness of 5 μm, for example. A plurality of optical devices 19 such as LEDs are formed in the epitaxial layer 15 by being partitioned by division lines (streets) 17 formed in a lattice pattern.

  Here, the plate-like object to be processed in the present invention is not limited to the optical device wafer 11, but is a wafer such as a semiconductor wafer having a plurality of semiconductor devices formed on the surface, and a wafer on which no device is formed. It can be similarly applied to plate-like objects such as ceramic substrates and glass substrates.

  Next, with reference to FIG. 5 thru | or FIG. 7, the division | segmentation method of the plate-shaped object which concerns on embodiment of this invention is demonstrated in detail. In carrying out this dividing method, as shown in FIG. 5, the surface 11a side of the optical device wafer 11 is attached to an expanded tape T which is an adhesive tape having an outer peripheral portion attached to the annular frame F, The wafer 11 is supported by the annular frame F via the expanded tape T.

  Then, as shown in FIG. 5, the optical device wafer 11 is sucked and held by the chuck table 28 of the laser processing apparatus 2 via the expanded tape T, and the back surface 11 b of the optical device wafer 11 is exposed.

  The chuck table 28 of the present embodiment is a chuck table with a heater. The chuck table 28 has a first frame 74 formed of SUS or the like, and the first frame 74 has a circular recess 75 on the upper surface thereof. In this circular recess 75, a heat insulating material 76, a film heater 78, and an aluminum plate 80 are laminated and fitted in order from the bottom.

  Here, various products are available on the film heater 78. For example, the film heater 78 is composed of a thin-film planar heater in which a nickel alloy serving as a heating resistor is sandwiched between polyimide sheets of insulating material. The maximum use temperature is about 300 ° C.

  A second frame 82 made of SUS or the like is mounted on the first frame 74, and the circular recess 83 formed on the upper surface of the second frame 82 has good thermal conductivity. A suction holding portion 84 formed of a porous member is fitted. The suction holding unit 84 is selectively connected to a negative pressure suction source 88 via a switching valve (not shown) via a suction path 86 formed through the first frame 74 and the second frame 82. The

  Here, the reason why the film heater 78 is laminated via the heat insulating material 76 is to suppress heat conduction of the film heater 78 to the first frame 74. Further, an aluminum plate 80 is interposed between the film heater 78 and the second frame 82 in order to facilitate heat conduction of the film heater 78 to the second frame 82. Alternatively, another metal plate having good thermal conductivity may be interposed. Further, when the surface contact between the film heater 78 and the second frame 82 is sufficiently ensured, the aluminum plate 80 can be omitted.

  After the optical device wafer 11 is sucked and held by the chuck table 28 via the expanded tape T, the optical device wafer 11 is imaged from the back surface 11b side by the infrared imaging element of the imaging unit 38, and an area corresponding to the planned division line 17 is obtained. Alignment with the light collector 36 is performed in the X-axis direction. For this alignment, well-known image processing such as pattern matching is used.

  After performing the alignment of the planned dividing line 17 extending in the first direction, the chuck table 28 is rotated 90 degrees, and then the planned dividing line 17 extending in the second direction orthogonal to the first direction is aligned. .

  After performing the alignment, as shown in FIG. 6, the condensing point of the laser beam is positioned inside the optical device wafer 11, and the laser beam is irradiated from the back surface 11 b side of the optical device wafer 11 along the planned dividing line 17. A modified layer forming step for forming a modified layer 21 serving as a starting point for division inside the optical device wafer 11 is performed.

  Specifically, in this modified layer forming step, the condensing point of the laser beam is positioned inside the optical device wafer 11, and the laser beam is divided in a first direction from the back surface 11b side of the optical device wafer 11. Irradiation is performed along the planned line 17, and the chuck table 28 is processed and fed in the direction of arrow X 1 in FIG. 6, thereby forming the modified layer 21 extending in the first direction inside the optical device wafer 11.

  The reformed layer 21 is formed in the wafer 11 corresponding to all the division lines 17 that extend in the first direction while indexing and feeding the chuck table 28 in the Y-axis direction. Next, after the chuck table 28 is rotated 90 degrees, similar modified layers 21 are formed in the wafer 11 corresponding to all the division lines 17 extending in the second direction orthogonal to the first direction. .

  The modified layer 21 is a region where the density, refractive index, mechanical strength, and other physical characteristics are different from the surroundings. For example, it includes a melt-rehardened region, a crack region, a dielectric breakdown region, and a refractive index change region, and also includes a region in which these regions are mixed.

  The processing conditions in this modified layer forming step are set as follows, for example.

Light source: LD excitation Q switch Nd: YVO 4 pulse laser Wavelength: 1064 nm
Repetition frequency: 100 kHz
Pulse output: 10μJ
Processing feed rate: 100 mm / sec

  Referring to FIG. 7A, the optical device wafer 11 in which the modified layer 21 is formed inside the optical device wafer 11 along all the planned dividing lines 17 extending in the first direction and the second direction. A longitudinal sectional view showing a state in which the chuck table 28 is sucked and held is shown.

  Thus, after forming the modified layer 21 which becomes a division | segmentation starting point in the inside of the optical device wafer 11, a division | segmentation step is implemented. In this dividing step, as shown in FIG. 7B, the film heater 78 is heated to a high temperature, and the surface (first surface) 11a of the optical device wafer 11 is sucked into the aluminum plate 80, the second frame 82, and the suction. Heat to high temperature by heat conduction through the holding part 84 and the expanded tape T.

  At the same time, a cooling fluid 41 such as pure water cooled to a low temperature of, for example, about 5 ° C. is ejected from the cooling fluid ejection nozzle 39, and the back surface (second surface) 11b of the optical device wafer 11 is cooled. As described above, when the surface 11a of the optical device wafer 11 is heated to a high temperature and the back surface 11b is cooled to a low temperature, a stress is generated inside the optical device wafer 11 due to a difference in thermal expansion between the front surface 11a and the back surface 11b. The optical device wafer 11 is cleaved along the division line 17 with the modified layer 21 as a division starting point, and a plurality of optical device chips 25 are formed. In FIG. 7B, reference numeral 23 denotes a dividing groove.

  In the embodiment described above, the front surface (first surface) 11a of the optical device wafer 11 is heated and the back surface (second surface) 11b is cooled. However, the front surface 11a is cooled and the back surface 11b is heated. Also good.

  In this case, a chuck table that can be cooled to a low temperature is adopted as the chuck table 28, the back surface 11 b of the optical device wafer 11 is heated by a heater or warm air, and the like. Stress is generated inside the device wafer 11, and the optical device wafer 11 is cleaved into individual optical device chips 25 by using the modified layer 21 as a division starting point.

DESCRIPTION OF SYMBOLS 11 Optical device wafer 17 Scheduled division line 19 Optical device 21 Modified layer 25 Optical device chip 28 Chuck table 34 Laser beam irradiation unit 36 Condenser 38 Imaging unit 39 Cooling fluid injection nozzle 74 First frame body 76 Heat insulating material 78 Film Heater 82 second frame

Claims (2)

A plate-like object that forms a plurality of chips by dividing a plate-like object having a first surface on which a plurality of intersecting scheduled lines are set and a second surface on the back of the first surface along the scheduled lines. Dividing method,
A condensing point of a laser beam having a wavelength that is transmissive to the plate-like object is positioned inside the plate-like object, and the laser beam is irradiated along the planned dividing line to be divided into the plate-like object. A modified layer forming step for forming a modified layer along the line;
After performing the modified layer forming step, the first surface of the plate-like material is heated and the second surface is cooled, or the first surface of the plate-like material is cooled and the second surface is heated. A dividing step of dividing the plate-like material from the modified layer as a starting point;
A method for dividing a plate-like object comprising: Before performing the modified layer forming step,
An adhesive tape attaching step of attaching an adhesive tape to the first surface of the plate-like material;
A holding step of holding the plate-like object on the chuck table via the adhesive tape and exposing the second surface after performing the adhesive tape attaching step;
In the modified layer forming step, the second surface of the plate-like object held on the chuck table is irradiated with a laser beam,
In the dividing step, the modified layer is formed by heating the chuck table and cooling the second surface of the plate-like object, or cooling the chuck table and heating the second surface of the plate-like object. The plate-like material dividing method according to claim 1, wherein the plate-like material is divided at a division starting point.

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