JP2012084682A - Method for dividing optical device unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for dividing an optical device unit which does not damage optical devices.SOLUTION: The method for dividing an optical device unit 11 which comprises radiating a laser beam along planned dividing lines 17 to divide individual optical devices 19 includes: a mark forming step of forming marks 21 as references of distance to the planned dividing lines 17 on surfaces of optical devices 19 selected from the plurality of optical devices 19; a first dividing groove forming step of radiating a laser beam along all the planned dividing lines 17 to form initial dividing grooves 23; and a second dividing groove forming step of radiating a laser beam along all the planned dividing lines 17 into the formed dividing grooves 23 to form second and later dividing grooves 25. And at least the second dividing groove forming step includes a planned dividing line correction step of periodically detecting the marks 21 formed in the mark forming step and correcting the position of the planned dividing line 17 to which the laser beam should be radiated.

Description

  The present invention relates to an optical device unit dividing method 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 Is to divide the optical device unit into individual optical devices without damaging the optical device.

  According to the present invention, an optical device unit having a semiconductor layer bonded to the surface of a metal support plate and formed by dividing a plurality of optical devices by the planned dividing line by the semiconductor layer is formed along the planned dividing line. A method of dividing an optical device unit that divides into individual optical devices by irradiating a laser beam and divides the optical device unit into a plurality of optical devices. A mark forming process for forming a mark to be formed, a first divided groove forming process for forming an initial divided groove by irradiating a laser beam along all the planned dividing lines, and a first divided groove forming process. And a second divided groove forming step of forming a divided groove for the second and subsequent times by irradiating a laser beam along all the planned division lines over the divided grooves. An optical device unit characterized by including a scheduled division line correcting step for periodically detecting a mark formed in the mark forming step and correcting a position of the planned division line to be irradiated with a laser beam in the groove forming step. Are provided.

  According to the present invention, since the mark formed on the optical device is detected and the position of the planned division line to be irradiated with the laser beam is corrected, even if the metal support plate is extended by the heat of the laser beam irradiation, the division is surely performed. The planned line can be irradiated with a laser beam, and the optical device unit can be divided into individual optical devices without damaging the optical device.

  In the present invention, since the mark is formed on the surface of the selected optical device, the optical device on which the mark is formed cannot be used at the sacrifice, but the other optical devices are not damaged, so that the yield is improved as a whole.

It is an external appearance perspective view of a laser beam processing apparatus. 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 a perspective view explaining a mark formation process. It is a perspective view explaining a 1st division process. It is a perspective view explaining a 2nd division process.

  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.

  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 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, as shown in FIG. 3, 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.

  When the alignment process is completed, the optical devices 19 are preferably selected from the plurality of optical devices 19 at predetermined intervals, and the selected optical devices 19 are collected from the condenser 36 as shown in FIG. A mark forming process is performed in which a mark 21 serving as a reference for the distance to the division-scheduled line 17 is formed by irradiating the laser beam.

  Preferably, this mark forming step is performed at a predetermined interval with respect to the optical device 19 in a row along the division line 17 extending in the first direction, and then the chuck table 28 is rotated by 90 degrees, It implements at a predetermined interval with respect to the optical device 19 of 1 row along the division | segmentation scheduled line 17 extended in a 2nd direction.

  In the example shown in FIG. 4, the mark 21 is formed on every other optical device 19, but in the actual optical device unit 11, many devices 19 are formed on the metal support plate 13. The marks 21 are implemented at predetermined intervals such as every third or fifth optical device 19 arranged on a straight line. The laser processing conditions are 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
Feeding speed: 100mm / s

  When the mark 21 is formed on the surface of the optical device 19 thus selected, the division line 17 and the optical device 19 are formed at a predetermined pitch from the design data. Therefore, the mark 21 is a reference for the distance to the division line 17. It becomes. That is, the distance from the mark 21 to the scheduled division line 17 is known.

  After the mark forming process, a first divided groove forming process (first divided groove forming process) is performed in which the first divided groove 23 is formed by irradiating the laser beam from the condenser 36. As shown in FIG. 5, the first divided groove forming step is performed along all the planned division lines 17 extending in the first direction, and then the chuck table 28 is rotated by 90 degrees in the second direction. The same operation is performed along all the planned division lines 17 to be extended.

  When the first divided groove forming step is performed, the first shallow 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 dividing step, the elongation of the metal support plate 13 is also limited.

  Therefore, in the first division 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 dividing method of the present invention, the dividing 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.

  Therefore, in the method for dividing the optical device unit 11 according to the present invention, after the first divided groove forming step (first divided groove forming step) is performed, the optical device unit 11 is overlapped with the divided grooves 23 formed in the first divided groove forming step, as shown in FIG. As described above, the second divided groove forming step of forming the divided grooves 25 for the second and subsequent times is performed by irradiating the laser beam from the condenser 36 along the scheduled division lines 17. In the present embodiment, this second divided groove forming step is repeated four times.

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

  Therefore, if the second divided groove forming step is performed by indexing and feeding in the Y-axis direction at regular intervals and performing the second divided groove forming step, there is a possibility that the optical device 19 may be damaged due to the laser beam coming off the planned division line 17.

  Therefore, in the division method of the present invention, the scheduled division line correction step is performed in which the marks 21 formed in the mark formation step are periodically detected and the position of the division line 17 to be irradiated with the laser beam is corrected.

  Specifically, in the scheduled division line correction step, after the second divided groove forming step is performed on a predetermined number, for example, three division planned lines 17, the chuck table 28 is moved in the index feed direction by the index feed means 22. Then, the imaging means 38 images the surface of the optical device unit 11 to detect the mark 21. A deviation from the design value is calculated when the mark 21 is detected.

  Then, the index feeding means 20 is driven with the amount of deviation taken into consideration with the mark 21 as a reference, and 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, the second divided groove forming process is continuously performed on the next scheduled line 17. The processing conditions for the first divided groove forming step and the second divided groove forming step are the same as the processing conditions for the mark forming step described above.

  In the present invention, the mark 21 is formed on the surface of the selected optical device 19 and is used as a reference for the distance to the planned dividing line 17. This is the dividing groove 23 along the planned dividing line 17 in the initial dividing groove forming process. This is because the dividing groove 23 becomes very rough and cannot be used as a reference in the Y-axis direction by imaging the dividing groove 23 by the imaging means 38.

  In the above-described embodiment of the present invention, when the division grooves 25 are formed at least for the second and subsequent times, the marks 21 formed on the optical device 19 are periodically detected, and the division lines 17 to be irradiated with the laser beam are detected. Since the position is corrected, even if the metal support plate 13 is extended by the heat generated by the laser beam irradiation, the laser beam can be reliably irradiated to the scheduled division line 17.

  In the present invention, since the mark 21 is formed on the surface of the selected optical device 19, the optical device 19 on which the mark 21 is formed is sacrificed and cannot be used. However, the other optical devices 19 are not damaged during the division. The yield as a whole can be improved.

2 Laser processing apparatus 11 Optical device unit 13 Metal support plate 15 Semiconductor layer 17 Planned division line 19 Optical device 21 Mark 23 First division groove 25 Second division groove 28 Chuck table 34 Laser beam irradiation unit 36 Condenser 38 Imaging means

Claims (1)

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 dividing method for forming divided grooves and dividing into individual optical devices,
A mark forming step of forming a mark serving as a reference for the distance to the division line on the surface of the optical device selected from the plurality of optical devices;
A first split groove forming step of forming a first split groove by irradiating a laser beam along all the planned split lines;
A second divided groove forming step of forming a divided groove for the second and subsequent times by irradiating a laser beam along all the planned dividing lines over the divided grooves formed in the first divided groove forming step;
At least in the second divided groove forming step, a scheduled division line correcting step for periodically detecting the mark formed in the mark forming step and correcting the position of the planned division line to be irradiated with the laser beam is included. An optical device unit dividing method.

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