JP2007111754A - Laser beam machining method and laser beam machining system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining method and a laser beam machining system by which laser beam machining grooves can be accurately formed in a plurality of machining areas along a predetermined street formed in a workpiece. <P>SOLUTION: A laser beam machining method which enables the accurate formation of laser beam machining grooves in a plurality of machining areas demarcated along a predetermined street formed in a workpiece includes a machining hole forming process for forming a laser beam machining hole through irradiation with a pulsed laser beam to each start point and end point in a plurality of machining areas demarcated along the street of the workpiece and a machining groove forming process for forming a laser beam machining groove through irradiation with a pulsed laser beam between laser beam machining holes formed in the start point and end point in the machining hole forming process. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus that forms laser processing grooves in a plurality of processing regions set on a workpiece.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in the partitioned regions. Form. Then, the semiconductor wafer is cut along the streets to divide the region in which the device is formed to manufacture individual semiconductor chips. In addition, optical device wafers in which light-receiving elements such as photodiodes and light-emitting elements such as laser diodes are stacked on the surface of the sapphire substrate are also divided into optical devices such as individual photodiodes and laser diodes by cutting along the streets. And widely used in electrical equipment.

  The above-described cutting along the wafer street is usually performed by a cutting device called a dicer. This cutting apparatus includes a chuck table for holding a workpiece such as a wafer, a cutting means for cutting the workpiece held on the chuck table, and a cutting for relatively moving the chuck table and the cutting means. And feeding means. The cutting means includes a cutting tool including a rotating spindle and a grindstone blade mounted on the spindle, and a spindle unit including a drive mechanism for driving the rotating spindle to rotate. In such a cutting apparatus, the cutting tool and the work piece held on the chuck table are relatively cut and fed while rotating the cutting tool at a rotational speed of 20000 to 40000 rpm. However, cutting with a cutting device cannot increase the processing speed, and is not always satisfactory in terms of productivity.

  Also, as a method of dividing the wafer along the street, a method of applying an external force along the street and then breaking it after applying a scratch (scribe line) along the street with a point scriber has been put into practical use. . However, although this method has a high processing speed, there are cases where the flaws (scribe lines) formed on the point scriber are shallow and cannot be reliably broken along the street.

On the other hand, in recent years, as a method of dividing the wafer along the street, there is a method of forming a laser processing groove by irradiating a pulse laser beam along the street formed on the wafer and breaking along the laser processing groove. Proposed. (For example, refer to Patent Document 1.)
JP-A-10-305420

  According to the laser processing method described above, the laser processing groove can be formed at a relatively high processing speed. However, since the wall surface of the laser processing groove formed along the street is rough, there is a problem that the brightness is lowered when the device to be individually divided is a laser diode.

  Therefore, when a wafer on which a laser diode is formed as a device is divided, a laser processing groove is formed on the street formed in one direction that does not affect the brightness using a laser processing device, and the brightness is affected. There has been proposed a method of making a scribe line on a street formed in the other direction using a point scriber.

  Thus, it has been found that when the laser processing groove is formed at the intersection with the street where the scratch (scribe line) is made by the point scriber, the brightness of the laser diode is lowered.

  The present invention has been made in view of the above facts, and the main technical problem thereof is that laser processing grooves can be accurately formed in a plurality of processing regions along a predetermined street formed on a workpiece. A laser processing method and a laser processing apparatus are provided.

In order to solve the main technical problem, according to the present invention, a laser processing method for forming laser processing grooves in a plurality of processing regions set along a predetermined street formed on a workpiece,
A processing hole forming step of forming a laser processing hole by irradiating a pulse laser beam to each start point position and end point position in a plurality of processing regions set along the street of the workpiece,
A processing groove forming step of forming a laser processing groove by irradiating a pulsed laser beam between the laser processing holes formed at the start point position and the end point position in the processing hole forming step,
A wafer laser processing method is provided.

Further, according to the present invention, according to the present invention, a laser beam irradiation means comprising a chuck table for holding a workpiece, and a condenser for irradiating a pulse laser beam to the workpiece held on the chuck table; In the laser processing apparatus comprising the chuck table and the processing feed means for moving the laser beam irradiation means relative to the processing feed direction,
A processing feed amount detecting means for detecting a relative processing feed amount between the chuck table and the laser beam irradiation means;
Storage means for storing the X and Y coordinate values of the start point position and the end point position in a plurality of machining areas set on the workpiece, the X and Y of the start point position and the end point position stored in the storage means Control means for controlling the laser beam irradiation means and the processing feed means based on a coordinate value and a detection signal from the processing feed amount detection means,
The control means stops the operation of the processing feeding means and activates the laser beam irradiation means when the X and Y coordinate values of the start point position and the end point position are positioned at positions corresponding to the condenser. Then, a laser processing hole is formed by irradiating the start point position and the end point position with a pulsed laser beam, and the laser processing hole formed at the start point position and the end point position corresponds to the condenser. Actuating the feed means and actuating the laser beam irradiation means to form a laser machining groove between the laser machining holes formed at the start position and the end position;
A laser processing apparatus is provided.

  According to the present invention, after performing the processing hole forming step of forming a laser processing hole by irradiating a pulse laser beam to the start point position and the end point position in a plurality of processing regions set along the street of the workpiece, the start point Since the processing groove forming process is performed to form a laser processing groove by irradiating a pulse laser beam between the laser processing holes formed at the position and the end point position, the irradiation position of the pulse laser beam irradiated in the processing groove forming process is slightly Even if an error occurs, it is not processed beyond the processing region between the laser processing holes.

  The wafer laser processing method and laser processing apparatus according to the present invention will be described below in more detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a laser processing apparatus constructed according to the present invention. A laser processing apparatus shown in FIG. 1 includes a stationary base 2, a chuck table mechanism 3 that is disposed on the stationary base 2 so as to be movable in a machining feed direction indicated by an arrow X, and holds a workpiece. The laser beam irradiation unit support mechanism 4 is movably disposed in the indexing feed direction indicated by the arrow Y perpendicular to the direction indicated by the arrow X in FIG. 2, and is movable in the direction indicated by the arrow Z to the laser beam irradiation unit support mechanism 4 And a laser beam irradiation unit 5 disposed in the.

  The chuck table mechanism 3 includes a pair of guide rails 31, 31 arranged in parallel along the machining feed direction indicated by the arrow X on the stationary base 2, and the arrow X on the guide rails 31, 31. A first slide block 32 movably disposed in the processing feed direction; a second slide block 33 disposed on the first slide block 32 movably in the index feed direction indicated by an arrow Y; A support table 35 supported by a cylindrical member 34 on the second sliding block 33 and a chuck table 36 as a workpiece holding means are provided. The chuck table 36 includes a suction chuck 361 formed of a porous material, and holds, for example, a disk-shaped semiconductor wafer, which is a workpiece, on the suction chuck 361 by suction means (not shown). . The chuck table 36 configured as described above is rotated by a pulse motor (not shown) disposed in the cylindrical member 34. The chuck table 36 is provided with a clamp 362 for fixing an annular frame described later.

  The first sliding block 32 is provided with a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on the lower surface thereof, and in the index feed direction indicated by an arrow Y on the upper surface thereof. A pair of guide rails 322 and 322 formed in parallel with each other are provided. The first sliding block 32 configured in this way is processed by the arrow X along the pair of guide rails 31, 31 when the guided grooves 321, 321 are fitted into the pair of guide rails 31, 31. It is configured to be movable in the feed direction. The chuck table mechanism 3 in the illustrated embodiment includes a machining feed means 37 for moving the first sliding block 32 along the pair of guide rails 31 and 31 in the machining feed direction indicated by the arrow X. The processing feed means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31, and a drive source such as a pulse motor 372 for rotationally driving the male screw rod 371. One end of the male screw rod 371 is rotatably supported by a bearing block 373 fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 372 by transmission. The male screw rod 371 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the first sliding block 32. Therefore, when the male screw rod 371 is driven to rotate forward and backward by the pulse motor 372, the first sliding block 32 is moved along the guide rails 31, 31 in the machining feed direction indicated by the arrow X.

  The laser processing apparatus in the illustrated embodiment includes a processing feed amount detecting means 374 for detecting the processing feed amount of the chuck table 36. The processing feed amount detection means 374 includes a linear scale 374a disposed along the guide rail 31, and a read head disposed along the linear scale 374a along with the first sliding block 32 disposed along the first sliding block 32. 374b. In the illustrated embodiment, the reading head 374b of the feed amount detecting means 374 sends a pulse signal of one pulse every 1 μm to the control means described later. Then, the control means to be described later detects the machining feed amount of the chuck table 36 by counting the input pulse signals. When the pulse motor 372 is used as the drive source of the machining feed means 37, the machining feed amount of the chuck table 36 is counted by counting the drive pulses of the control means to be described later that outputs a drive signal to the pulse motor 372. Can also be detected. When a servo motor is used as a drive source for the machining feed means 37, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to a control means described later, and the pulse signal input by the control means. By counting, the machining feed amount of the chuck table 36 can also be detected.

  The second sliding block 33 is provided with a pair of guided grooves 331 and 331 which are fitted to a pair of guide rails 322 and 322 provided on the upper surface of the first sliding block 32 on the lower surface thereof. By fitting the guided grooves 331 and 331 to the pair of guide rails 322 and 322, the guided grooves 331 and 331 are configured to be movable in the indexing and feeding direction indicated by the arrow Y. The chuck table mechanism 3 in the illustrated embodiment is for moving the second slide block 33 along the pair of guide rails 322 and 322 provided in the first slide block 32 in the index feed direction indicated by the arrow Y. First index feeding means 38 is provided. The first index feed means 38 includes a male screw rod 381 disposed in parallel between the pair of guide rails 322 and 322, and a drive source such as a pulse motor 382 for rotationally driving the male screw rod 381. It is out. One end of the male screw rod 381 is rotatably supported by a bearing block 383 fixed to the upper surface of the first sliding block 32, and the other end is connected to the output shaft of the pulse motor 382. The male screw rod 381 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the second sliding block 33. Therefore, when the male screw rod 381 is driven to rotate forward and reversely by the pulse motor 382, the second slide block 33 is moved along the guide rails 322 and 322 in the index feed direction indicated by the arrow Y.

  The laser beam irradiation unit support mechanism 4 includes a pair of guide rails 41, 41 arranged in parallel along the indexing feed direction indicated by the arrow Y on the stationary base 2, and the arrow Y on the guide rails 41, 41. The movable support base 42 is provided so as to be movable in the direction indicated by. The movable support base 42 includes a movement support portion 421 that is movably disposed on the guide rails 41, 41, and a mounting portion 422 that is attached to the movement support portion 421. The mounting portion 422 is provided with a pair of guide rails 423 and 423 extending in the direction indicated by the arrow Z on one side surface in parallel. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment includes a second index feed means 43 for moving the movable support base 42 along the pair of guide rails 41, 41 in the index feed direction indicated by the arrow Y. is doing. The second index feed means 43 includes a male screw rod 431 disposed in parallel between the pair of guide rails 41, 41, and a drive source such as a pulse motor 432 for rotationally driving the male screw rod 431. It is out. One end of the male screw rod 431 is rotatably supported by a bearing block (not shown) fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 432. The male screw rod 431 is screwed into a female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the moving support portion 421 constituting the movable support base 42. For this reason, when the male screw rod 431 is driven to rotate forward and backward by the pulse motor 432, the movable support base 42 is moved along the guide rails 41, 41 in the index feed direction indicated by the arrow Y.

  The laser processing apparatus in the illustrated embodiment includes index feed amount detection means 433 for detecting the index feed amount of the movable support base 42 of the laser beam irradiation unit support mechanism 4. The index feed amount detecting means 433 includes a linear scale 433a disposed along the guide rail 41 and a read head 433b disposed on the movable support base 42 and moving along the linear scale 433a. In the illustrated embodiment, the read head 433b of the feed amount detection means 433 sends a pulse signal of one pulse every 1 μm to the control means described later. And the control means mentioned later detects the index feed amount of the laser beam irradiation unit 5 by counting the input pulse signal. In the case where the pulse motor 432 is used as the drive source of the second index sending means 43, the laser beam irradiation unit 5 is counted by counting the drive pulses of the control means described later that outputs a drive signal to the pulse motor 432. It is also possible to detect the index feed amount. Further, when a servo motor is used as the drive source of the second index sending means 43, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to the control means described later, and the control means inputs it. The index feed amount of the laser beam irradiation unit 5 can also be detected by counting the number of pulse signals.

  The laser beam irradiation unit 5 in the illustrated embodiment includes a unit holder 51 and laser beam irradiation means 52 attached to the unit holder 51. The unit holder 51 is provided with a pair of guided grooves 511 and 511 that are slidably fitted to a pair of guide rails 423 and 423 provided in the mounting portion 422. By being fitted to the guide rails 423 and 423, the guide rails 423 and 423 are supported so as to be movable in the direction indicated by the arrow Z.

  As shown in FIG. 2, the laser beam irradiation means 52 is oscillated by the pulse laser beam oscillation means 522 disposed at the tip of the casing 521 and the pulse laser beam oscillation means 522 and the transmission optical system 523 disposed in the casing 521. A condenser 53 for irradiating a workpiece held on the chuck table 36 with a pulsed laser beam is provided. The pulse laser beam oscillation means 522 is composed of a pulse laser beam oscillator 522a composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 522b attached thereto. This repetition frequency setting means 522b is controlled by the control means described later. The transmission optical system 523 includes an appropriate optical element such as a beam splitter.

  The condenser 53 condenses the pulse laser beam oscillated by the pulse laser beam oscillation means 522 into an elliptical spot S as shown in FIG. 3, and irradiates the workpiece held on the chuck table 36. . The elliptical spot S is irradiated so that the long axis (d) is directed in the machining feed direction indicated by X in FIG. In the illustrated embodiment, the spot S has a major axis (d) of 200 μm and a minor axis (e) of 5 μm. Note that the elliptical spot S is formed by arranging, for example, two cylindrical lenses in series so that the optical axes cross each other on the upstream side of an objective condenser lens (not shown) in the condenser 53, and the two cylindrical lenses. By adjusting the distance between the spots, the lengths of the major and minor axes of the spots can be appropriately adjusted to make the spot shape elliptical or circular.

  An imaging means 6 for detecting a processing region to be laser processed by the laser beam irradiation means 52 is disposed at the front end of the casing 521 constituting the laser beam irradiation means 52. The imaging unit 6 includes an illuminating unit that illuminates the workpiece, an optical system that captures an area illuminated by the illuminating unit, an imaging device (CCD) that captures an image captured by the optical system, and the like. The captured image signal is sent to a control means (not shown).

  The laser beam irradiation unit 5 in the illustrated embodiment includes a moving means 53 for moving the unit holder 51 along the pair of guide rails 423 and 423 in the direction indicated by the arrow Z. The moving means 53 includes a male screw rod (not shown) disposed between the pair of guide rails 423 and 423, and a drive source such as a pulse motor 532 for rotationally driving the male screw rod. By driving the male screw rod (not shown) in the forward and reverse directions by the motor 532, the unit holder 51 and the laser beam irradiation means 52 are moved along the guide rails 423 and 423 in the direction indicated by the arrow Z. In the illustrated embodiment, the laser beam irradiation means 52 is moved upward by driving the pulse motor 532 forward, and the laser beam irradiation means 52 is moved downward by driving the pulse motor 532 in reverse. Yes.

  The laser processing apparatus in the illustrated embodiment includes a control means 10. The control means 10 is constituted by a computer, and a central processing unit (CPU) 101 that performs arithmetic processing according to a control program, a read-only memory (ROM) 102 that stores a control program and the like, and a pulse laser beam on a workpiece to be described later. A readable / writable random access memory (RAM) 103 that stores data of X and Y coordinate values of the irradiation start point and end point, calculation results, and the like, a counter 104, an input interface 105, and an output interface 106 are provided. Detection signals from the machining feed amount detection means 374, the index feed amount detection means 433, the imaging means 6 and the like are input to the input interface 105 of the control means 10. A control signal is output from the output interface 106 of the control means 10 to the pulse motor 372, pulse motor 382, pulse motor 432, pulse motor 532, laser beam irradiation means 52, and the like. The random access memory (RAM) 103 includes a first storage area 103a for storing data of X and Y coordinate values of a start point and an end point of a processing area on a workpiece to be described later, and a detection value to be described later. A second storage area 103b for storing data and another storage area are provided.

The laser processing apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
In FIG. 4, an optical device wafer 20 as a workpiece to be laser-processed is attached to a protective tape 22 made of a synthetic resin sheet such as polyolefin mounted on an annular frame 21 with the surface 200a facing upward. The state is shown. The optical device wafer 20 includes a plurality of first streets 201 formed in a first direction on a surface 200 a of a gallium nitride (GaN) substrate 200 and a plurality of first streets formed in a direction orthogonal to the first streets 201. A plurality of regions are partitioned by two streets 202, and an optical device 203 made of a laser diode is formed in the partitioned regions. Each optical device 203 has the same configuration. The optical device wafer 20 configured as described above does not affect the luminance of the optical device 203 even if the laser processing groove is formed along the first street 201 using the laser processing apparatus described above. When the laser processing groove is formed along the street 202, the brightness of the optical device 203 is lowered. Accordingly, the illustrated optical device wafer 20 is formed with a laser processing groove along the first street 201 and a scratch (scribe line) is formed along the second street 202 using a point scriber. The optical device 203 is divided into individual optical devices 203 by applying an external force along the both streets.

  In the optical device wafer 20 formed as described above, as shown in FIG. 5, the start point position (B) and the end point of the processing region for each row (A1, A2, A3, A4, A5) of the first street 201. Position (C) is set on both sides of the second street 202. The X and Y coordinate values of each start point position (B) and end point position (C) and the distance (L) between the start point position (B) and end point position (C) (processing area) are the values of the design values above. First stored in the storage area 103 a of the random access memory (RAM) 103 of the control means 10. In FIG. 5, the X and Y coordinate values of the first street 201 other than the A1 and A5 lines are omitted except for both ends.

Laser that forms a laser processing groove between the start point position (B) and the end point position (C) (processing region) along the first street 201 formed on the optical device wafer 20 using the laser processing apparatus described above. An embodiment of processing will be described.
The optical device wafer 20 configured as described above has the laser processing shown in FIG. 1 in a state where the surface 200a is attached to the protective tape 22 attached to the annular frame 21 as shown in FIG. The protective tape 22 is placed on the chuck table 36 of the apparatus. Then, by operating a suction means (not shown), the optical device wafer 20 is sucked and held on the chuck table 36 via the protective tape 22. The annular frame 21 is fixed by a clamp 362.

  As described above, the chuck table 36 that sucks and holds the optical device wafer 20 is positioned directly below the imaging unit 6 by the processing feeding unit 37. When the chuck table 36 is positioned directly below the imaging means 6, the optical device wafer 20 on the chuck table 36 is positioned at the coordinate position shown in FIG. In this state, an alignment operation is performed to determine whether or not the first street 201 and the second street 202 formed on the optical device wafer 20 held on the chuck table 36 are arranged parallel to the X direction and the Y direction. carry out. In other words, the optical device wafer 20 held on the chuck table 36 is imaged by the imaging means 6 and image processing such as pattern matching is executed to perform alignment work. The X and Y coordinate values of the start point position (B) and the end point position (C) are detected by the image pickup means 6 while holding the optical device wafer 20 on the chuck table 36, and the X and Y coordinates thereof are detected. The detected value may be stored in the first storage area 103a of the random access memory (RAM) 103 of the control means 10 instead of the design value described above.

  Next, the machining feed means 37 is operated to move the chuck table 36, and the first start point position B1 at the leftmost end in FIG. 5 of the uppermost A1 row in the first street 201 formed in the optical device wafer 20 is shown. (x1, y1) is positioned below the condenser 53 of the laser beam irradiation means 52 as shown in FIG. At this time, in the illustrated embodiment, the condensing spot S (see FIG. 3) of the pulse laser beam irradiated from the condensing device 53 is set to have a long axis (d) of 200 μm. In order for the left end of the axis (d) to correspond to the first start point position B1 (x1, y1) at the leftmost end, the position on the right side of 100 μm from the first start point position B1 (x1, y1) at the left end is collected. Position it so that it is directly under the optical device 53. Then, the condensing spot S of the pulse laser beam irradiated from the condenser 53 is matched with the vicinity of the surface 20 a (upper surface) of the optical device wafer 20. Next, in a state where the operation of the processing feed unit 37 is stopped, a pulsating laser beam having an absorptive wavelength (for example, 355 nm) is applied to the gallium nitride (GaN) substrate 200 from the condenser 53 of the laser beam irradiation unit 52 ( Machining hole forming process). The number of pulses of the pulse laser beam irradiated at this time may be several pulses. As a result, a laser processing hole 210 is formed on the right side in FIG. 6B from the first start position B1 (x1, y1).

  As described above, if the machining hole forming step is performed at the first start point position B1 (x1, y1) to form the laser machining hole 210, the machining feed means 37 is operated to move the chuck table 36, The first end point position C1 (x2, y1) of the uppermost A1 row in the first street 201 formed on the optical device wafer 20 is positioned below the condenser 53 of the laser beam irradiation means 52. At this time, in the illustrated embodiment, as described above, the focused spot S (see FIG. 3) of the pulse laser beam irradiated from the collector 53 is set to have a long axis (d) of 200 μm. In order for the right end portion of the long axis (d) in the spot S to correspond to the first end point position C1 (x2, y1), the position to the left of 100 μm from the first end point position C1 (x2, y1) is the condenser 53. Position it so that it is directly below. And the process hole formation process mentioned above is implemented. Thereafter, the second start point B2 (x3, y1), the second end point C2 (x4, y1), the third start point B3 (x5, y1), the third end point C3 (x6, y1), the fourth start point The machining hole forming step is also performed on B4 (x7, y1) and the fourth end point C4x8, y1).

  As described above, when the processing hole forming step is performed on the uppermost A1 row in the first street 201 formed in the optical device wafer 20, the control unit 10 performs the processing feeding unit 37 and the second feeding unit 37. The index sending means 43 is operated, and the first start point B1 (x1, y2) of the A2 row in the first street 201 formed in the optical device wafer 20 shown in FIG. The above-described drilling hole forming step is also performed for each start point position and end point position that are positioned below and set in line A2 in the first street 201. Further, the above-described machining hole forming step is similarly performed for each of the start point position and the end point position set in the A3 line, the A4 line, and the A5 line in the first street 201 formed in the optical device wafer 20. To do.

  As described above, if the processing hole forming step is performed on each start point position and end point position set on all the first streets 201 formed on the optical device wafer 20, the control unit 10 will process the processing feed unit 37. And the second index feed means 43 is operated to move the chuck table 36, and the first start position at the leftmost end in FIG. 5 of the uppermost A1 row in the first street 201 formed in the optical device wafer 20 B1 (x1, y1) (laser machining hole 210 is formed) is positioned below the condenser 53 of the laser beam irradiation means 52 as shown in FIG. At this time, in the illustrated embodiment, the condensing spot S (see FIG. 3) of the pulsed laser beam irradiated from the concentrator 53 has the major axis (d) set to 200 μm, so the first starting point position B1 From (x1, y1) to (a) in FIG. 7, for example, the position on the right side of 130 μm is positioned directly below the condenser 53, that is, the center position of the focused spot S. Accordingly, the focused spot S of the pulse laser beam irradiated at this position has a rear end located on the right side of 30 μm in FIG. 7A from the first start position B1 (x1, y1). Then, the condensing spot S of the pulse laser beam irradiated from the condenser 53 is matched with the vicinity of the surface 20 a (upper surface) of the optical device wafer 20. Next, the control means 10 operates the processing feed means 37 while irradiating the gallium nitride (GaN) substrate 21 with a pulsed laser beam having an absorptive wavelength (for example, 355 nm) from the condenser 53 of the laser beam irradiation means 52. Then, the chuck table 31 is moved at a predetermined processing feed speed in the direction indicated by the arrow X1 in FIG. 7A (processing groove forming step). Then, based on the detection signal from the machining feed amount detection means 374, the control means 10 determines that the position on the left side of, for example, 130 μm from the first end point position C1 (x2, y1) in FIG. When the center position of the focused spot S is reached, the laser beam irradiation means 52 is controlled to stop the irradiation of the pulsed laser beam. Accordingly, the focused spot S of the pulse laser beam irradiated at this position is 30 μm to the left of the front end of the first end position C1 (x2, y1) in FIG. As a result, as shown in FIG. 7B, the optical device wafer 20 includes the first laser processing hole 210 formed in the first start position B1 (x1, y1) along the first street 201 and the first laser processing hole 210. A laser processing groove 220 is formed between the laser processing hole 210 formed at the starting point position B1 (x1, y2) (processing groove forming step).

In addition, the said process groove formation process is performed on the following process conditions, for example.
Laser light source: YVO4 laser or YAG laser Wavelength: 355 nm
Average output: 3W
Repetition frequency: 10 kHz
Processing feed rate: 300 mm / sec

  Since the energy of the pulse laser beam irradiated in the process groove forming process described above has a Gaussian distribution, both ends of the laser process groove 220 formed by the first irradiation pulse and the last irradiation pulse are deep. Becomes shallower. For this reason, when the optical device wafer 20 is broken along the first street 201 in which the laser processing groove 220 is formed, the breaking becomes difficult. However, in the above-described embodiment, the laser processing groove 210 is formed in each of the first end point C1 (x2, y1) position and the first start point position B1 (x1, y2). Therefore, the optical device wafer 20 can be easily broken along the first street 201 in which the laser processing grooves 220 are formed. Further, in the above-described embodiment, the laser processing holes 210 respectively formed at the first start point position B1 (x1, y1) and the first end point position C1 (x2, y1) are 200 μm long in the processing feed direction. Therefore, even if a slight error occurs in the irradiation position of the pulse laser beam irradiated in the above-described processing groove forming step, the pulse laser beam is not irradiated outside the laser processing hole 210.

As described above, if the machining groove forming step is performed between the first start point position B1 (x1, y1) and the first end point position C1 (x2, y1), the control means 10 detects the machining feed amount detection means. Based on the detection signal from 374, the second start point B2 (x3, y1) in FIG.
For example, when the position on the right side of 130 μm reaches the position immediately below the condenser 53, that is, the center position of the condensing spot S, the laser beam irradiation means 52 is controlled to irradiate the pulse laser beam. Then, based on the detection signal from the machining feed amount detection means 374, the control means 10 is, for example, a position 130 μm before the second end point C2 (x4, y1) in FIG. 7A (FIG. 7A). When the laser beam irradiation means 52 is controlled, the irradiation of the pulsed laser beam is stopped. Hereinafter, the third start point B3 (x5, y1) to the third end point C3 (x6, y1) and the fourth start point B4 (x7, y1) to the fourth end point C4x8, y1) shown in FIG. The process groove forming step is performed in the same manner as described above. As a result, the optical device wafer 20 is formed in the uppermost A1 row of the first street 201 with the laser processing hole 210 formed at each starting point position and at each starting point position as shown in FIG. The laser processing hole 210 is surely formed. Therefore, the laser processing groove 210 is not formed across the second street 202.

  As described above, when the laser beam irradiation process is performed on the uppermost A1 row in the first street 201 formed in the optical device wafer 20, the control means 10 performs the processing feeding means 37 and the second indexing. The feeding means 43 is operated, and the first starting point B1 (x1, y2) of the A2 line in the first street 201 formed in the optical device wafer 20 shown in FIG. In the first street 201, the above-described processed groove forming step is performed on the A2 row. Further, the above-described process groove forming step is similarly performed on A3, A4, and A5 on the first street 201 formed on the optical device wafer 20.

  A plurality of second streets formed on the optical device wafer 20 before or after the above-described processing hole forming step and processing groove forming step are performed on the first street 201 formed on the optical device wafer 20. A scribe line is formed along a point scriber 202. An external force is applied to the optical device wafer 20 along the plurality of first streets 201 in which the laser processing holes 210 and the laser processing grooves 220 are formed and the plurality of second streets 202 in which scribe lines are formed. Thus, the optical device wafer 20 is divided into individual optical devices 203. Since the optical device 203 divided in this way is broken by forming a scribe line with respect to the second street 202 having an influence on the luminance, the luminance is not lowered. On the other hand, the laser beam irradiation process is performed on the first street 201 having little influence on the luminance to form the laser grooves 210, so that the processing speed can be increased and the productivity can be improved. In the laser beam irradiation step, since the laser processing groove 210 is accurately formed between each start point and the end point in the first street 201, the laser processing groove 210 is formed across the second street 202. The brightness of the optical device 203 is not lowered.

  Although the present invention has been described based on the illustrated embodiment, the present invention is not limited to the embodiment, and various modifications are possible within the scope of the gist of the present invention. For example, in the above-described embodiment, an example in which the shape of the focused spot of the pulse laser beam is an ellipse is shown, but the focused spot of the pulse laser beam may be circular. Further, the laser processing holes formed at the start point position and the end point position in the processing region may be formed by a circular focused spot, and the laser processed groove may be formed by an elliptical focused spot.

The perspective view of the laser processing apparatus comprised according to this invention. The block diagram of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. Explanatory drawing which shows the shape of the condensing spot of the pulse laser beam irradiated from the laser beam irradiation means shown in FIG. The perspective view which shows the state which affixed the optical device wafer processed by the laser processing method by this invention to the protective tape with which the cyclic | annular flame | frame was mounted | worn. Explanatory drawing which shows the X and Y coordinate value of the starting point position and end point position which are set to the optical device wafer shown in FIG. Explanatory drawing which shows the process hole formation process in the laser processing method by this invention. Explanatory drawing which shows the process groove | channel formation process in the laser processing method by this invention.

Explanation of symbols

2: Stationary base 3: Chuck table mechanism 31: Guide rail 36: Chuck table 37: Work feed means 374: Work feed amount detection means 38: First index feed means
4: Laser beam irradiation unit support mechanism 41: Guide rail 42: Movable support base 43: Second index feed means 433: Index feed amount detection means 5: Laser beam irradiation unit 51: Unit holder 52: Laser beam processing means 53: Light collection Device 6: Imaging means 10: Control means 20: Optical device wafer 201: First street 202: Second street 203: Device 210: Laser processing hole 220: Laser processing groove 21: Ring frame 22: Protective tape

Claims (2)

A laser processing method for forming laser processing grooves in a plurality of processing regions set along a predetermined street formed in a workpiece,
A processing hole forming step of forming a laser processing hole by irradiating a pulse laser beam to each start point position and end point position in a plurality of processing regions set along the street of the workpiece,
A processing groove forming step of forming a laser processing groove by irradiating a pulsed laser beam between the laser processing holes formed at the start point position and the end point position in the processing hole forming step,
A wafer laser processing method characterized by the above. A chuck table for holding a workpiece, a laser beam irradiation means having a condenser for irradiating a workpiece held on the chuck table with a pulsed laser beam, and the chuck table and the laser beam irradiation means in the processing feed direction In a laser processing apparatus comprising a processing feed means for relatively moving,
A processing feed amount detecting means for detecting a relative processing feed amount between the chuck table and the laser beam irradiation means;
Storage means for storing the X and Y coordinate values of the start point position and the end point position in a plurality of machining areas set on the workpiece, the X and Y of the start point position and the end point position stored in the storage means Control means for controlling the laser beam irradiation means and the processing feed means based on a coordinate value and a detection signal from the processing feed amount detection means,
The control means stops the operation of the processing feeding means and activates the laser beam irradiation means when the X and Y coordinate values of the start point position and the end point position are positioned at positions corresponding to the condenser. Then, a laser processing hole is formed by irradiating the start point position and the end point position with a pulsed laser beam, and the laser processing hole formed at the start point position and the end point position corresponds to the condenser. Actuating the feed means and actuating the laser beam irradiation means to form a laser machining groove between the laser machining holes formed at the start position and the end position;
Laser processing equipment characterized by that.

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