JP2012106251A - Machining method of optical device unit and laser beam machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machining method of an optical device unit, which does not damage an optical device.SOLUTION: The machining method of the optical device unit which divides the optical device unit into each optical device by irradiating a laser beam along a dividing schedule line to form a dividing groove, includes a data acquisition step to acquire correlation data to specify the relation of the temperature and the degree of elongation of the optical device unit, a temperature measuring step to measure the temperature of the optical device unit, a dividing groove formation step to form the dividing groove by irradiating the laser beam along the dividing schedule line, an elongation amount calculation step to calculate the elongation amount of the interval of the dividing schedule line, based on the temperature of the optical device unit measured in the temperature measuring step and the degree of elongation corresponding to the temperature acquired in the data acquisition step, and a dividing schedule line correction step to correct the indexing amount of the dividing schedule line on which the laser beam should be irradiated, based on the elongation amount calculated by the elongation amount calculation step.

Description

  The present invention relates to an optical device unit processing method and a laser processing apparatus for dividing an optical device unit in which a semiconductor layer is peeled off by lift-off from a substrate such as a sapphire substrate and bonded to a metal support plate into individual optical devices.

  A street in which a semiconductor layer (epitaxial layer) such as gallium nitride (GaN) is formed on the surface of an epitaxial substrate such as a sapphire substrate or SiC substrate, and a plurality of optical devices such as LEDs are formed in a lattice shape on the semiconductor layer (divided) Optical device wafers that are defined by a predetermined line are relatively high in Mohs hardness and difficult to cut with a cutting blade. Therefore, they are generally divided into individual optical devices by laser beam irradiation. The optical device is used in electrical equipment such as a lighting fixture, a cellular phone, and a personal computer (see, for example, JP-A-10-305420).

  Recently, a semiconductor layer laminated on an epitaxial substrate such as a sapphire substrate or SiC substrate is peeled off from the substrate by laser lift-off and bonded to a metal support plate serving as a heat sink such as molybdenum (Mo) or copper (Cu). A technique in which a semiconductor layer in which a plurality of optical devices are formed is transferred to a metal support plate, and then is divided into individual optical devices together with the metal support plate by irradiating a laser beam onto the planned division line is disclosed in, for example, Japanese Translation of PCT International Publication No. 2005-516415. It is disclosed in the publication.

  According to this technology called laser lift-off, an expensive sapphire substrate, SiC substrate, etc. can be used repeatedly, and the optical device is bonded to a metal support plate serving as a heat sink, so that it has the advantage of excellent heat dissipation characteristics and the like. is there.

JP-A-10-305420 JP 2005-516415 gazette

  However, since the linear expansion coefficient of the metal support plate is relatively large, the metal support plate expands and contracts due to heat generated by laser beam irradiation or due to the release of internal stress due to the groove shape, and is scheduled to be divided at regular intervals. If the laser beam is irradiated by indexing and feeding at a constant interval, that is, at a predetermined pitch, the line spacing changes, there is a problem that the laser beam is detached from the line to be divided and the optical device is damaged.

  The present invention has been made in view of these points, and an object of the present invention is to provide an optical device unit in which a semiconductor layer is lifted off from a substrate and bonded to a metal support plate, and a laser beam along a division line. And a laser processing apparatus capable of performing the processing method. The processing method of the optical device unit is divided into individual optical devices without damaging the optical device.

  According to the first aspect of the present invention, an optical device unit having a semiconductor layer bonded to the surface of the metal support plate and formed by dividing a plurality of optical devices by the planned dividing line by the semiconductor layer is scheduled. A processing method of an optical device unit that divides a laser beam along a line to form a division groove and divides it into individual optical devices, and obtains correlation data that defines the relationship between the temperature and elongation rate of the optical device unit A data acquisition step, a temperature measurement step for measuring the temperature of the optical device unit, a split groove forming step for forming a split groove by irradiating a laser beam along a planned split line, and light measured in the temperature measurement step Based on the temperature of the device unit and the elongation corresponding to the temperature acquired in the data acquisition process, the amount of elongation is calculated to calculate the amount of expansion at the intervals between the division lines. And a division planned line correcting step for correcting the indexing amount of the division planned line to be irradiated with the laser beam based on the elongation calculated by the elongation calculating step. A method of processing the unit is provided.

  According to a second aspect of the present invention, there is provided a laser processing apparatus comprising a chuck table for holding a workpiece, a laser beam irradiation means for irradiating a workpiece held on the chuck table with a laser beam, and the chuck A machining feed means for relatively machining and feeding the table and the laser beam irradiation means; an index feed means for relatively indexing and feeding the chuck table and the laser beam irradiation means; and a workpiece held by the chuck table. Temperature detecting means for detecting the temperature of the workpiece, elongation amount calculating means for calculating the elongation amount of the workpiece based on the temperature detected by the temperature detecting means and the elongation percentage of the workpiece, and the elongation amount Correction means for correcting the index feed amount by the index feed means on the basis of the amount of elongation calculated by the calculation means. Over The processing device is provided.

  According to the first aspect of the present invention, the index feed amount is corrected while measuring the temperature of the optical device unit and calculating the extension amount of the optical device unit, thereby correcting the position in the index feed direction to be irradiated with the laser beam. Thus, the optical device unit is not irradiated with the laser beam outside the planned division line, and the optical device unit can be divided into individual optical devices without damaging the optical device.

  According to the second aspect of the present invention, it is possible to provide a laser processing apparatus capable of irradiating a laser beam at an accurate position in the indexing and feeding direction regardless of a temperature change.

1 is an external perspective view of a laser processing apparatus according to an embodiment of the present invention. It is a block diagram of a laser beam irradiation unit. It is a perspective view of the optical device unit supported by the annular frame via the dicing tape. It is the map which prescribed | regulated the relationship between temperature and the elongation rate of an optical device unit. It is a perspective view explaining the first division | segmentation groove | channel formation process. It is a perspective view explaining the division | segmentation groove | channel formation process after the 2nd time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a laser processing apparatus 2 suitable for carrying out the optical device unit 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 has a holding surface for holding a wafer supported by the frame via a dicing tape, and the chuck table 28 is provided with a clamper 30 for clamping the frame.

  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 unit 11 held on the chuck table 28.

  At the tip of the casing 35, an image pickup means 38 for detecting a processing region to be laser processed aligned with the condenser 36 in the X-axis direction is disposed. The image pickup means 38 includes an image pickup element such as a normal CCD that picks up an image of a processing region of a semiconductor wafer with visible light.

  The imaging unit 38 further outputs an infrared irradiation unit that irradiates the optical device unit 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.

  A temperature sensor 39 that detects the temperature of the workpiece held on the chuck table 28 is disposed adjacent to the imaging means 38. As the temperature sensor 39, for example, a digital radiation temperature sensor called “FT-H40K” provided by Keyence Corporation can be adopted. The temperature information detected by the temperature sensor 39 is input to the controller 40 via the input interface 50.

  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 picked up by the image pickup means 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.

  Next, the configuration of the wafer-shaped optical device unit 11 to be processed by the laser processing apparatus 2 will be described with reference to FIG. The optical device unit 11 peels the semiconductor layer 15 such as gallium nitride (GaN) from the sapphire substrate by laser lift-off from the optical device wafer, and solders it to the metal support plate 13 serving as a heat sink such as molybdenum (Mo) or copper (Cu). It is configured to be joined by attaching or the like.

  The manufacture of the optical device unit 11 having the semiconductor layer 15 bonded to the metal support plate 13 by laser lift-off is excellent in that an epitaxy substrate such as an expensive sapphire substrate or SiC substrate can be reused. Furthermore, since the semiconductor layer 15 is bonded to the metal support plate 13, the optical device 19 divided from the optical device unit 11 is excellent in terms of heat dissipation characteristics.

  For laser lift-off of the semiconductor layer 15, for example, a laser beam having a wavelength of 355 nm, which is the third harmonic of a YAG laser, is used. The sapphire substrate is transparent to the laser beam of this wavelength.

  The laser beam is irradiated from the substrate side, and the radiant energy is absorbed in the boundary layer between the sapphire substrate and the GaN semiconductor layer, and this boundary layer is heated to a high temperature of, for example, 850 ° C. or higher. The GaN boundary layer is decomposed under generation of nitrogen at this temperature, and the bond between the semiconductor layer and the substrate is separated.

  The separated semiconductor layer is joined to the metal support plate 13 by soldering or adhesive, and the wafer-shaped optical device unit 11 is manufactured. On the surface of the optical device unit 11, an optical device 19 such as an LED (light emitting diode) or an LD (laser diode) is formed in each region partitioned by a plurality of division lines (streets) 17 formed in a lattice pattern. ing.

  In the optical device unit 11, since the semiconductor layer 15 is peeled from the sapphire substrate and bonded to the metal support plate 13, a plurality of layers in which a p-type semiconductor layer and an n-type semiconductor layer are stacked in this order on the metal support plate 13. An optical device 19 is formed.

  Since the optical device unit 11 has the metal support plate 13 for dividing the optical device unit 11 into the individual optical devices 19, cutting with a cutting blade is difficult, and it is preferable to use a laser processing apparatus. .

  Prior to the division of the optical device unit 11 into the individual optical devices 19, the optical device unit 11 is attached to a dicing tape T that is an adhesive tape, and the outer periphery of the dicing tape T is attached to an annular frame F. Accordingly, the optical device unit 11 is supported by the annular frame F via the dicing tape T.

  Next, the method for dividing the optical device unit of the present invention using the laser processing apparatus 2 will be described in detail. First, the optical device unit 11 supported by the annular frame F is sucked and held by the chuck table 28 of the laser processing apparatus 2 via the dicing tape T, and the annular frame F is clamped by the clamper 30.

  Next, the chuck table 28 is moved in the X-axis direction so that the optical device unit 11 is positioned directly below the imaging means 38. Image processing such as pattern matching for aligning the condenser 36 of the laser beam irradiation unit 34 that irradiates the laser beam and the scheduled division line 17 by imaging the processing region of the optical device unit 11 with the imaging unit 38. Is performed, and alignment of the laser beam irradiation position is performed.

  When the alignment of the division line 17 extending in the first direction is completed, the chuck table 28 is rotated 90 degrees to extend in the second direction orthogonal to the division line 17 extending in the first direction. The alignment is performed in the same manner for the division line 17.

  In the processing method of the optical device unit of this embodiment, the relationship between the temperature and the elongation rate of the optical device unit 11 is measured in advance, and a map as shown in FIG. 4 defining the correlation between the temperature and the elongation rate is created. The map is stored in the ROM 44 of the controller 40. The map shown in FIG. 4 shows the elongation rate of the optical device unit 11 with the optical device unit 11 at 20 ° C. as a reference.

  Next, as shown in FIG. 5, an initial divided groove forming step of forming the first divided groove 23 by irradiating the laser beam from the condenser 36 of the laser beam irradiation unit 34 is performed. This first division groove forming step is performed along all the division lines 17 that extend in the first direction, and then the chuck table 28 is rotated 90 degrees and all the division lines 17 that extend in the second direction. It carries out similarly along.

  The laser processing conditions for the first divided groove forming step are set as follows, for example.

Light source: LD excitation Q switch Nd: YAG pulse laser Wavelength: 355 nm (third harmonic of YAG laser)
Output: 7.0W
Repetition frequency: 10 kHz
Spot shape: Ellipse with short axis 10 μm and long axis 10-200 μm Feed rate: 100 mm / s

  When the first divided groove forming step is performed, a relatively shallow first divided groove 23 is formed on the surface of the metal support plate 13. When the dividing grooves 23 are continuously formed, the metal support plate 13 has a relatively large linear expansion coefficient. Therefore, the metal support plate 13 is extended by the heat generated by the laser beam irradiation, and the scheduled dividing lines 17 are set at regular intervals. However, since the heat accumulation is not so large in the first divided groove forming step, the elongation of the metal support plate 13 is also limited.

  Therefore, in the initial divided groove forming step, it is not always necessary to perform the division planned line correction step described later. In the case where the elongation of the metal support plate 13 is large, it is preferable to carry out a division planned line correction step which will be described later in the first division groove forming step.

  In this first dividing groove forming step, the shallow dividing groove 23 is only formed, and the optical device unit 11 cannot be divided into individual optical devices 19. Therefore, in the processing method of the present invention, the division groove forming step is performed a plurality of times (in this embodiment, five times) to divide the optical device unit 11 into individual optical devices 19.

  That is, in the processing method of the optical device unit 11 according to the present invention, after the first divided groove forming step is performed, the divided groove 23 formed in the first divided groove forming step is overlaid on the light collecting unit 36 as shown in FIG. A second and subsequent divided groove forming step of forming the second and subsequent divided grooves 25 by irradiating a laser beam along the divided grooves 23 is performed. In the present embodiment, the second and subsequent divided groove forming steps are repeated four times.

  Since the second and subsequent divided groove forming steps are continuously performed, the metal support plate 13 is expanded by heat due to laser beam irradiation or release of stress caused by the groove shape, and is set at regular intervals. The interval of the scheduled division lines 17 changes.

  Therefore, if the divided grooves are formed by indexing and feeding in the Y-axis direction at regular intervals and performing the second and subsequent divided groove forming steps, the laser beam may be detached from the planned division line 17 and damage the optical device 19. .

  Therefore, in the processing method of the present invention, particularly in the second and subsequent divided groove forming steps, the position of the planned division line 17 to be irradiated with the laser beam is corrected according to the temperature of the optical device unit 11 detected by the temperature sensor 39. The division planned line correction process is performed.

  Specifically, this division planned line correction step is performed based on the temperature detected by the temperature sensor 39 after the second and subsequent division groove forming steps are performed on a predetermined number, for example, three division planned lines 17. The elongation rate is calculated with reference to the map shown in FIG. 5 and the amount of elongation at the interval between the division lines 17 is calculated based on the rate of elongation (elongation amount calculation step).

  Then, based on the elongation amount calculated in the elongation amount calculation step, the indexing amount of the scheduled division line to be irradiated with the laser beam next time is corrected, and the index feeding means 20 is driven based on this corrected indexing amount. Thus, the position of the division line 17 to be irradiated with the laser beam next time is corrected.

  After the scheduled division line correction process is performed, the second and subsequent divided groove forming processes are continuously performed on the next scheduled line 17. The processing conditions for the second and subsequent divided groove forming steps are the same as the processing conditions for the first divided groove forming step described above.

  The elongation rate of the optical device unit 11 using the temperature sensor 39 and the map shown in FIG. 4 is continuously calculated, and each time the elongation rate reaches a predetermined elongation rate, the division scheduled line correction step May be implemented.

  In the embodiment of the present invention described above, when the divided grooves 25 are formed at least for the second and subsequent times, the elongation amount of the optical device unit 11 is calculated based on the temperature detected by the temperature sensor 39, and the laser beam should be irradiated. Since the position of the scheduled division line 17 is corrected, even if the metal support plate 13 extends due to heat generated by the laser beam irradiation, the planned division line 17 can be reliably irradiated with the laser beam.

  In the laser processing apparatus of the present invention, the workpiece is not limited to the optical device unit 11, but can be applied to a workpiece that expands and contracts by heat due to laser beam irradiation.

  The laser processing apparatus of the present invention calculates the elongation amount of the workpiece by calculating the elongation amount of the workpiece based on the temperature sensor 39 that detects the temperature of the workpiece and the temperature detected by the temperature sensor 39 and the elongation percentage of the workpiece. And a correcting means for correcting the index amount by the index feeding means 20 based on the elongation amount calculated by the elongation amount calculating means. The elongation calculation means and the correction means are constituted by the CPU 42 of the controller 40.

2 Laser processing apparatus 11 Optical device unit 13 Metal support plate 15 Semiconductor layer 17 Scheduled division line 19 Optical device 23 First division groove 25 Second division groove 28 Chuck table 34 Laser beam irradiation unit 36 Condenser 38 Imaging means

Claims (2)

An optical device unit having a semiconductor layer bonded to the surface of the metal support plate and formed by dividing a plurality of optical devices by the planned dividing line by the semiconductor layer is irradiated with a laser beam along the planned dividing line. An optical device unit processing method for forming a division groove and dividing into individual optical devices,
A data acquisition step of acquiring correlation data defining the relationship between the temperature and elongation rate of the optical device unit;
A temperature measurement process for measuring the temperature of the optical device unit;
A split groove forming step of forming a split groove by irradiating a laser beam along a planned split line;
Based on the temperature of the optical device unit measured in the temperature measurement step and the elongation corresponding to the temperature acquired in the data acquisition step, an elongation amount calculation step of calculating the amount of extension of the interval between the planned division lines;
A planned division line correction step for correcting an index amount of a planned division line to be irradiated with the laser beam based on the elongation amount calculated by the elongation amount calculation step;
The processing method of the optical device unit characterized by comprising. A laser processing apparatus,
A chuck table for holding the workpiece;
A laser beam irradiation means for irradiating a workpiece held on the chuck table with a laser beam;
Processing feed means for relatively processing and feeding the chuck table and the laser beam irradiation means;
Indexing and feeding means for relatively indexing and feeding the chuck table and the laser beam irradiation means;
Temperature detecting means for detecting the temperature of the workpiece held on the chuck table;
An elongation amount calculating means for calculating an elongation amount of the workpiece based on the temperature detected by the temperature detecting means and the elongation percentage of the workpiece;
Correction means for correcting the index feed amount by the index feed means based on the stretch amount calculated by the stretch amount calculation means;
A laser processing apparatus comprising:

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