JP2010158691A - Laser beam machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus capable of executing laser beam machining of a wafer along the scheduled division line without damaging the surface of the wafer by emitting the laser beam from the back side of the wafer along the scheduled division line. <P>SOLUTION: In the laser beam machining apparatus for irradiating a workpiece held by a chuck table with the laser beam, a laser beam irradiation means comprises: a pulse laser beam oscillating means for oscillating the linearly polarized pulse laser beam; an electrooptic effect device for generating a first wave and a second wave in the direction orthogonal to that of the first wave by bending a part of each pulse of the pulse laser beam oscillated from the pulse laser beam oscillating means; a polarized beam splitter for separating the first wave and the second wave generated by the electrooptic effect device from each other; a damper for absorbing one wave separated by the polarized beam splitter; a condenser for condensing the other wave separated by the polarized beam splitter; and a control means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus for performing laser processing on a wafer such as a semiconductor wafer or an optical device wafer along a predetermined division line.

  In the semiconductor device manufacturing process, a plurality of regions are defined by dividing lines arranged in a lattice pattern on the surface of a substantially disk-shaped silicon substrate, and devices such as ICs and LSIs are formed in the partitioned regions. . The semiconductor wafer formed in this way is cut along a predetermined division line to divide the region where the circuit is formed to manufacture individual devices. In addition, optical device wafers with gallium nitride compound semiconductors laminated on the surface of sapphire substrates are also divided into individual optical devices such as light-emitting diodes and laser diodes by cutting along the planned division lines, and are widely used in electrical equipment. It's being used.

As a method for dividing a wafer such as a semiconductor wafer or an optical device wafer, a laser is irradiated by irradiating a pulse laser beam having a wavelength (for example, 355 nm) having an absorptivity with respect to the wafer along a predetermined division line formed on the wafer. There has been proposed a method in which a machining groove is formed and cleaved by a mechanical braking device along the laser machining groove. (For example, refer to Patent Document 1.)
JP 2004-9139 A

In addition, as a method of dividing the wafer, the pulsed laser beam having a wavelength (for example, 1064 nm) having transparency with respect to the wafer is irradiated along the planned dividing line and the wafer is divided into the wafer. There has also been proposed a method of dividing a wafer by continuously forming a deteriorated layer along a predetermined line and applying an external force along a predetermined divided line whose strength is reduced by forming the deteriorated layer. (For example, see Patent Document 2.)
Japanese Patent No. 3408805

  The above-mentioned devices such as IC and LSI and optical devices are formed by laminating a device layer on the surface of a silicon substrate or sapphire substrate, so that the device layer is not damaged by laser beam irradiation. Irradiate with laser beam. However, not all of the energy of the irradiated laser beam contributes to processing, and there is a problem that part of the energy that does not contribute to processing passes through the substrate and damages the device layer formed on the surface of the substrate.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is to irradiate a laser beam along the planned dividing line from the back side of the wafer and to divide the wafer without damaging the surface of the wafer. To provide a laser processing apparatus capable of performing laser processing along a line.

In order to solve the above-mentioned main technical problem, according to the present invention, laser processing comprising: a chuck table for holding a workpiece; and a laser beam irradiation means for irradiating the workpiece held on the chuck table with a laser beam. In the device
The laser beam irradiating means includes a pulse laser beam oscillating means including a laser oscillator that oscillates a linearly polarized laser beam and a pulse generator that outputs a pulse signal to the laser oscillator, and a pulse laser beam oscillated from the pulse laser beam oscillating means. An electro-optic effect element that generates a first wave and a second wave in a direction orthogonal to the first wave by bending a part of the wave of each pulse, and a first wave generated by the electro-optic effect element A polarization beam splitter that separates the wave and the second wave, a damper that absorbs one of the waves separated by the polarization beam splitter, and a collector that collects the other wave separated by the polarization beam splitter; And a control means for controlling the electro-optic effect element,
The control means is configured to make at least the rising part and the other part of the rising and falling parts of the energy distribution in the wave of each pulse of the pulse laser beam oscillated from the pulse laser beam oscillating means relatively the first wave. Controlling the electro-optic effect element to generate a second wave;
The polarizing beam splitter directs the first wave to the damper and directs the second wave to the collector;
A laser processing apparatus is provided.

  The laser beam irradiation means includes synchronization means for synchronizing the time when the pulse laser beam oscillated from the pulse laser beam oscillation means reaches the electro-optic effect element and the time when the control signal output from the control means reaches the electro-optic effect element. It is desirable that

  Since the laser beam irradiation means of the laser processing apparatus according to the present invention is configured as described above, each pulse wave of the pulse laser beam oscillated from the pulse laser beam oscillation means is caused to rise and fall by the electro-optic effect element. Among the portions, at least the rising portion is generated in the first wave and the second wave relatively with the other portions. The first wave at the rising portion is separated by the polarization beam splitter and discarded by the damper. The energy distribution of the second wave in each pulse wave of the pulse laser beam that is separated by the polarization beam splitter and irradiated from the condenser has a steep waveform because the rising part that does not contribute to the processing is removed and the energy distribution is Only a high-density laser beam is applied to the back surface of the wafer, which is a workpiece held on the chuck table. Therefore, since all energy of the pulse laser beam applied to the back surface of the wafer contributes to the processing, the device layer formed on the surface of the substrate is not damaged by being transmitted through the substrate of the wafer.

The perspective view of the laser processing apparatus comprised according to this invention. The block diagram which shows 1st Embodiment of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. Explanatory drawing which shows energy distribution of each pulse of the pulse laser beam oscillated from the pulse laser beam oscillation means which comprises the laser beam irradiation means shown in FIG. Explanatory drawing which shows the effect | action of the electro-optic effect element which comprises the laser beam irradiation means shown in FIG. The block diagram which shows 2nd Embodiment of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. The perspective view of the optical device wafer as a to-be-processed object. The principal part expanded sectional view of the optical device wafer shown in FIG. The perspective view which shows the state which affixed the protective tape on the surface of the optical device wafer shown in FIG. Explanatory drawing of the laser processing groove | channel formation process implemented using the laser processing apparatus shown in FIG. The principal part expanded sectional view of the optical device wafer laser-processed by the laser processing groove | channel formation process shown in FIG. Explanatory drawing of the deteriorated layer formation process implemented using the laser processing apparatus shown in FIG.

DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a laser processing apparatus configured according to the present invention will be described in 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 and a chuck table mechanism 3 that is disposed on the stationary base 2 so as to be movable in a machining feed direction (X-axis direction) indicated by an arrow X and holds a workpiece. A laser beam irradiation unit support mechanism 4 disposed on the stationary base 2 so as to be movable in an indexing direction (Y axis direction) indicated by an arrow Y perpendicular to the X axis direction, and an arrow Z on the laser beam unit support mechanism 4 And a laser beam irradiation unit 5 disposed so as to be movable in the focus position adjustment direction (Z-axis direction).

  The chuck table mechanism 3 includes a pair of guide rails 31 and 31 disposed in parallel along the X-axis direction on the stationary base 2, and is arranged on the guide rails 31 and 31 so as to be movable in the X-axis direction. A first sliding block 32 provided; a second sliding block 33 movably disposed on the first sliding block 32 in the Y-axis direction; and a cylindrical member on the second sliding block 33 And a chuck table 36 as a workpiece holding means. The chuck table 36 is made of a porous material and has a workpiece holding surface 361. A wafer as a workpiece is held on the chuck table 36 by suction means (not shown). Further, the chuck table 36 is rotated by a pulse motor (not shown) disposed in the cylindrical member 34.

  The first sliding block 32 has a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on the lower surface thereof, and is parallel to the upper surface along the Y-axis direction. A pair of formed guide rails 322 and 322 are provided. The first sliding block 32 configured in this manner moves in the X-axis direction along the pair of guide rails 31, 31 when the guided grooves 321, 321 are fitted into the pair of guide rails 31, 31. Configured to be possible. The chuck table mechanism 3 in the illustrated embodiment includes a processing feed means 37 for moving the first slide block 32 along the pair of guide rails 31, 31 in the X-axis direction. 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, the first sliding block 32 is moved along the guide rails 31 and 31 in the X-axis direction by driving the male screw rod 371 forward and backward by the pulse motor 372.

  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 Y-axis direction. The chuck table mechanism 3 in the illustrated embodiment has a first index for moving the second sliding block 33 in the Y-axis direction along a pair of guide rails 322 and 322 provided in the first sliding block 32. A 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, by driving the male screw rod 381 forward and backward by the pulse motor 382, the second slide block 33 is moved along the guide rails 322 and 322 in the Y-axis direction.

  The laser beam irradiation unit support mechanism 4 is movable in the Y-axis direction on a pair of guide rails 41, 41 arranged in parallel along the Y-axis direction on the stationary base 2. The movable support base 42 is provided. 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 Z-axis direction 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 and 41 in the Y-axis direction. 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. Therefore, the movable support base 42 is moved in the Y-axis direction along the guide rails 41 and 41 by driving the male screw rod 431 forward and reversely by the pulse motor 432.

  The laser beam irradiation unit 5 in the illustrated embodiment includes a unit holder 51 and laser beam irradiation means 6 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 Z-axis direction.

  The illustrated laser beam application means 6 includes a cylindrical casing 61 that is fixed to the unit holder 51 and extends substantially horizontally. A first embodiment of the laser beam irradiation means 6 will be described with reference to FIG. The laser beam irradiating means 6 shown in FIG. 2 includes a pulse laser beam oscillating means 62 disposed in a casing 61, and a first portion of a pulse laser beam oscillated from the pulse laser beam oscillating means 62 by bending a part of the pulse wave. And an electro-optic effect element (electro-optical device: EOD) 63 for generating a second wave in a direction orthogonal to the first wave, and a first wave generated by the electro-optic effect element (EOD) 63 A polarizing beam splitter 64 that separates the first wave and the second wave, a damper 65 that absorbs one of the waves separated by the polarizing beam splitter 64, and the other wave that is separated by the polarizing beam splitter 64 And a control means 67 for controlling the pulse laser beam oscillation means 62 and the electro-optic effect element (EOD) 63. .

  The pulse laser beam oscillating means 62 includes a laser oscillator 621 that oscillates a linearly polarized laser beam and a pulse generator 622. Based on the pulse signal generated by the pulse generator 622, a predetermined repetition frequency is generated from the laser oscillator 621. Oscillates a pulsed laser beam. The laser oscillator 621 and the pulse generator 622 are controlled by the control means 67. The pulse laser beam oscillated from the pulse laser beam oscillation means 62 will be described with reference to FIG. In FIG. 3, the horizontal axis represents time and the vertical axis represents output. The pulse width B of the pulse laser beam having a predetermined repetition frequency oscillated from the pulse laser beam oscillation means 62 is set to 100 ns, for example. The energy distribution (time waveform) of the pulse of the pulse laser beam does not have a rectangular shape, but forms a Gaussian distribution that has a peak output at the center of the pulse width B. Therefore, the output of 20 ns at the rising and falling portions in the pulse energy distribution (time waveform) of the pulse laser beam is considerably lower than the peak output and does not have energy contributing to the processing of the wafer substrate described later. There is a problem that part of the energy that does not contribute to the processing of the workpiece permeates the wafer substrate and damages the device layer formed on the surface of the wafer substrate.

  In the illustrated embodiment, the electro-optic effect element (EOD) 63 is 20 ns in each of the rising and falling portions of the energy distribution of the pulse energy S in the pulse wave of the pulse laser beam as shown in FIG. In the meantime, magnetic fields 63a and 63b are generated, and the rising and falling waves are bent 90 degrees. As a result, the energy distribution of the first wave composed of the bent rising portion and falling portion is the energy distribution indicated by S2 and S3 in FIG. 4B. On the other hand, the energy distribution of the second wave composed of other parts other than the rising and falling parts is a steep energy distribution S1 with the rising and falling parts removed as shown in FIG. Become.

  Returning to FIG. 2, the description is continued. In the illustrated embodiment, the polarization beam splitter 64 allows the second wave (energy distribution is S1) to pass, and the first wave (energy distribution is S2 and S2). Reflect and separate S3). The pulse laser beam composed of the second wave (energy distribution S1) that has passed through the polarization beam splitter 64 is guided to the condenser 66, and is reflected and separated by the polarization beam splitter 64 (energy distribution). The pulse laser beam consisting of S2 and S3) is absorbed by the damper 65.

  In the above-described embodiment, the example in which the rising and falling waves of the energy distribution of the pulse energy S in the pulse wave of the pulsed laser beam are bent by 90 degrees has been described, but other than the rising and falling parts Alternatively, the electro-optic effect element (EOD) 63 may generate a magnetic field to bend the wave (energy distribution is S1) other than the rising and falling portions by 90 degrees. In this case, the polarization beam splitter 64 passes the waves (energy distribution is S1) other than the rising part and the falling part bent by 90 degrees and guides them to the condenser 66, and the rising part and the falling part The waves (energy distributions S2 and S3) are separated and guided to the damper 65.

  The condenser 66 includes a direction changing mirror 661 that changes the direction of the pulse laser beam composed of the second wave (energy distribution S1) that has passed through the polarizing beam splitter 64, and a direction changed by the direction changing mirror 661. A condenser lens 662 for condensing the converted pulse laser beam and irradiating the workpiece W held on the chuck table 36 is provided. The concentrator 66 configured in this way is disposed at the tip of a cylindrical casing 61 as shown in FIG.

  The laser beam irradiation means 6 in the embodiment shown in FIG. 2 includes a delay circuit 68 that delays the pulse signal generated by the pulse generator 622 of the pulse laser beam oscillation means 62 and outputs it to the control means 67. The delay circuit 68 generates the pulse laser beam oscillated from the laser oscillator 62 based on the pulse signal generated by the pulse generator 622 when the pulse laser beam reaches the electro-optic effect element (EOD) 63 and the pulse generator 622. It functions as a synchronizing means for synchronizing the control signal output from the control means 67 based on the pulse signal thus obtained with the time when the control signal reaches the electro-optic effect element (EOD) 63.

Next, a second embodiment of the laser beam application means 6 will be described with reference to FIG.
The laser beam irradiating means 6 in the second embodiment shown in FIG. 5 includes a point in time when the pulse laser beam oscillated from the laser oscillator 62 in the laser beam irradiating means 6 shown in FIG. 2 reaches the electro-optic effect element (EOD) 63. The configuration is substantially the same as that of the laser beam irradiation means 6 shown in FIG. 2 except that the synchronization means for synchronizing the time point when the control signal output from the control means 67 reaches the electro-optic effect element (EOD) 63 is different. The same members are denoted by the same reference numerals, and the description thereof is omitted.
In the laser beam irradiation means 6 in the second embodiment shown in FIG. 5, the pulse laser beam oscillated from the laser oscillator 621 of the pulse laser beam oscillation means 62 is transmitted through an electro-optic effect element (EOD) via a direction changing mirror 69a and a delay means 69b. ) 63. On the other hand, a detection signal from a photodetector 69c that detects a slight pulse laser beam oscillated from the laser oscillator 62 and transmitted through the direction changing mirror 69a is sent to the control means 67. In such a configuration, the direction from which the pulsed laser beam oscillated from the laser oscillator 621 of the pulsed laser beam oscillation means 62 is oscillated from the laser oscillator 62 and reaches the electro-optic effect element (EOD) 63 via the direction changing mirror 69a. Since the time at which the control signal output from the control means 67 reaches the electro-optic effect element (EOD) 63 is delayed based on the signal from the photodetector 69c that detects a slight pulse laser beam transmitted through the conversion mirror 69a, the direction conversion mirror Delay means 69b is disposed between 69a and electro-optic effect element (EOD) 63. The delay means 69b can be constituted by an optical fiber or the like that adjusts the optical path length. In this way, by arranging the delay means 69b between the direction conversion mirror 69a and the electro-optic effect element (EOD) 63, the pulse laser beam oscillated from the laser oscillator 621 of the pulse laser beam oscillation means 62 is converted into the direction conversion mirror 69a. And based on the signal from the photodetector 69c that detects the slight pulsed laser beam that has been oscillated from the laser oscillator 62 and transmitted through the direction changing mirror 69a, and reaching the electro-optic effect element (EOD) 63 via the delay means 69b. The time when the control signal output from the control means 67 reaches the electro-optic effect element (EOD) 63 can be synchronized.

  Returning to FIG. 1, the description is continued. At the front end portion of the casing 61 constituting the laser beam irradiation means 6, an imaging means 7 for detecting a processing region to be laser processed by the laser beam irradiation means 6 is disposed. In the illustrated embodiment, the imaging unit 7 includes an infrared illumination unit that irradiates a workpiece with infrared rays, and an infrared ray that is emitted by the infrared illumination unit, in addition to a normal imaging device (CCD) that captures visible light. And an imaging device (infrared CCD) that outputs an electrical signal corresponding to the infrared rays captured by the optical system, and sends the captured image signal to a controller (not shown) or the control means 67. .

  The laser beam irradiation unit 5 in the illustrated embodiment includes a focal position adjusting means 53 for moving the unit holder 51 along the pair of guide rails 423 and 423 in the Z-axis direction. The focal position adjusting 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. Then, the male screw rod (not shown) is driven to rotate forward or reverse by the pulse motor 532, thereby moving the unit holder 51 and the laser beam irradiation means 6 along the pair of guide rails 423 and 423 in the Z-axis direction. In the illustrated embodiment, the laser beam irradiation means 6 is moved upward by driving the pulse motor 532 forward, and the laser beam irradiation means 6 is moved downward by driving the pulse motor 532 in the reverse direction. ing.

The laser processing apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
Here, an optical device wafer as a wafer to be processed by the laser processing apparatus will be described with reference to FIGS. 6 shows a perspective view of the optical device wafer, and FIG. 7 shows an enlarged cross-sectional view of the main part of the optical device wafer shown in FIG.
An optical device wafer 10 shown in FIGS. 6 and 7 includes a plurality of devices by a device layer 12 in which a film made of gallium nitride (GaN), aluminum nitride gallium (AlGaN), or the like is laminated on the surface of a substrate 11 made of sapphire. 13 is formed in a matrix. Each device 13 is partitioned by division lines 14 formed in a lattice shape.
In order to perform laser processing on the back surface 10b of the optical device wafer 10 thus configured, the surface 10a of the optical device wafer 10 is applied to the surface of the protective tape T mounted on the annular frame F as shown in FIG. Wear (wafer support process).

  If the wafer support step described above is performed, a laser processing groove forming step for forming a laser processing groove on the back surface 10b of the optical device wafer 10 along the planned division line 14 is performed. In this laser processing groove forming step, first, the protective tape T side of the optical device wafer 10 is placed on the chuck table 36 of the laser processing apparatus shown in FIG. 1 and the semiconductor wafer 10 is sucked and held on the chuck table 36. To do. Therefore, the optical device wafer 10 is held with the back surface 10b facing upward.

  As described above, the chuck table 36 that sucks and holds the optical device wafer 10 is positioned immediately below the imaging unit 7 by the processing feeding unit 37. When the chuck table 36 is positioned immediately below the image pickup means 7, the image pickup means 7 and a controller (not shown) or the control means 67 performs an alignment operation for detecting a processing region to be laser processed on the semiconductor wafer 10. That is, the image pickup means 7 and the controller (not shown) or the control means 67 include the division line 14 formed in a predetermined direction of the optical device wafer 10 and the laser beam irradiation means 6 that irradiates the laser beam along the division line 14. Image processing such as pattern matching for alignment with the condenser 66 is performed, and alignment of the laser beam irradiation position is performed. Similarly, the alignment of the laser beam irradiation position is performed on the division line 14 formed in the optical device wafer 10 and extending in a direction orthogonal to the predetermined direction. At this time, the surface 10a on which the division line 14 of the semiconductor wafer 10 is formed is located on the lower side. However, the imaging unit 7 corresponds to the infrared illumination unit, the optical system for capturing infrared rays, and infrared rays as described above. Since an image pickup unit configured with an image pickup device (infrared CCD) or the like that outputs an electric signal is provided, the planned division line 14 can be picked up through the back surface 10b.

  If the division line 14 formed on the optical device wafer 10 held on the chuck table 36 as described above is detected and the laser beam irradiation position is aligned, as shown in FIG. Then, the chuck table 36 is moved to the laser beam irradiation area where the condenser 66 of the laser beam application means 6 is located, and the predetermined street 14 is positioned directly below the collector 66. At this time, as shown in FIG. 9A, the optical device wafer 10 is positioned such that one end of the planned dividing line 14 (the left end in FIG. 9A) is located directly below the condenser 66. Next, while irradiating the sapphire substrate 11 with a pulsed laser beam having an absorptive wavelength from the condenser 66, the chuck table 36, that is, the optical device wafer 10 is moved in a direction indicated by an arrow X1 in FIG. Move at machining feed rate. Then, as shown in FIG. 9B, when the other end of the planned dividing line 14 (the right end in FIG. 9B) reaches a position directly below the condenser 66, the irradiation of the pulse laser beam is stopped and the chuck table is stopped. That is, the movement of the optical device wafer 10 is stopped. In this laser processing groove forming step, the condensing point P of the pulse laser beam is matched with the vicinity of the upper surface of the street 10. As a result, a laser processed groove 15 is formed on the back surface 10b of the optical device wafer 10 along a predetermined division line 14 as shown in FIG.

The processing conditions in the laser processing groove forming step are set as follows, for example.
Laser light source: YVO4 pulse laser Wavelength: 355 nm
Repetition frequency: 90 kHz
Average output: 1.2W
Pulse width: 200ns
Condensing spot diameter: φ2-3μm
Processing feed rate: 120 mm / sec

Here, the action of the pulse laser beam applied to the back surface 10b of the optical device wafer 10 in the laser processing groove forming step will be described.
Each pulse wave of the pulse laser beam oscillated from the pulse laser beam oscillating means 62 of the laser beam irradiating means 6 shown in FIGS. 2 and 5 is converted into energy at each pulse energy S by the electro-optic effect element (EOD) 63 as described above. The rising part S2 and the falling part S3 (see FIG. 4C) of the distribution are bent by 90 degrees, and the waves of the rising part S2 and the falling part S3 are separated by the polarization beam splitter 64 and discarded to the damper 65. Then, the energy distribution S1 of each pulse of the pulse laser beam irradiated from the condenser 66 through the polarization beam splitter 64 has a rising portion S2 and a falling portion S3 that do not contribute to the processing as shown in FIG. 4B. Therefore, only the laser beam having a high energy density is irradiated on the back surface 10b of the optical device wafer 10. Therefore, since all energy of the pulse laser beam applied to the back surface 10b of the optical device wafer 10 contributes to the processing, the device layer 12 formed on the surface of the substrate 11 is not damaged by being transmitted through the substrate 11. The rising portion S2 and the falling portion S3 of the falling portion S3 that do not contribute to the processing in each pulse energy of the pulsed laser beam are irradiated in the processing state following the processing by the energy of the energy distribution S1, Since all energy contributes to processing, it does not pass through the substrate 11 and reach the device layer 12 formed on the surface of the substrate 11. Therefore, the electro-optic effect element (EOD) 63 may be configured to bend the rising portion S2 at least in each pulse of the pulse laser beam by 90 degrees.

  If the above-described laser processing groove forming step is performed along all the planned division lines 14 formed in the optical device wafer 10 in a predetermined direction, the chuck table 36 and thus the optical device wafer 10 are rotated by 90 degrees. Then, the above-described laser processing groove forming step is performed along all the planned division lines 14 formed in the optical device wafer 10 in the direction orthogonal to the predetermined direction.

  If the above-described laser processing groove forming step is performed along all the planned division lines 14 formed on the optical device wafer 10 as described above, the optical device wafer 10 is transferred to the next division step. . In the dividing step, the laser processed groove 15 formed along the planned dividing line 14 of the optical device wafer 10 is formed to a depth that can be easily divided, so that it can be easily divided by mechanical braking. it can.

Next, refer to FIG. 11 for an example in which a deteriorated layer is formed inside a wafer along a predetermined dividing line of the wafer in which a plurality of devices are formed in a matrix by a device layer formed on the surface of the silicon substrate. To explain. FIG. 11 shows a state corresponding to FIG. 9 described above, and the same reference numerals are used for the members.
In order to form a deteriorated layer inside the wafer 10, the chuck table 36 is moved to a laser beam irradiation region where the condenser 66 of the laser beam irradiation means 6 is located as shown in FIG. Is positioned directly below the condenser 66. At this time, as shown in FIG. 11A, the wafer 10 is positioned so that one end of the scheduled division line 14 (the left end in FIG. 11A) is located directly below the condenser 66. Next, the condensing point P of the pulse laser beam irradiated from the condenser 66 is set to the middle position in the thickness direction of the wafer 10. Then, while irradiating a pulse laser beam having a wavelength that is transmissive to the silicon substrate from the condenser 66, the chuck table 36, that is, the wafer 10 is moved in the direction indicated by the arrow X1 in FIG. Move it. Then, as shown in FIG. 11B, when the other end of the planned dividing line 14 (the right end in FIG. 11B) reaches a position immediately below the condenser 66, the irradiation of the pulse laser beam is stopped and the chuck table is stopped. 36, that is, the movement of the wafer 10 is stopped. As a result, the altered layer 16 is formed along the predetermined division line 14 as shown in FIG. 11B inside the wafer 10 (modified layer forming step).

The processing conditions in the deteriorated layer forming step are set as follows, for example.
Laser light source: YVO4 pulse laser Wavelength: 1342 nm
Repetition frequency: 100 kHz
Average output: 1W
Pulse width: 200ns
Condensing spot diameter: φ1μm
Processing feed rate: 300 mm / sec

  Also in the deteriorated layer forming step, as in the above-described embodiment, the rising portion and the falling portion that do not contribute to the processing of the energy distribution in each pulse energy of the pulse laser beam irradiated from the condenser 66 are removed, and a steep waveform is obtained. Therefore, only the laser beam having a high energy density is irradiated on the wafer 10. Accordingly, since all energy of the pulse laser beam applied to the wafer 10 contributes to the processing, the device layer formed on the surface of the silicon substrate is not damaged by being transmitted through the silicon substrate.

2: stationary base 3: chuck table mechanism 36: chuck table 37: processing feed means 38: first index feed means 4: laser beam irradiation unit support mechanism 43: second index feed means 5: laser beam irradiation unit 51: unit Holder 53: Focus position adjusting means 6: Laser beam irradiation means 62: Pulse laser beam oscillation means 621: Laser oscillator 622: Pulse generator 63: Electro-optic effect element (EOD)
64: Polarizing beam splitter 65: Damper 66: Condenser 661: Direction conversion mirror 662: Condensing lens 67: Control means 68: Delay circuit 69a: Direction conversion mirror 69b: Delay means 69c: Photo detector 7: Imaging means 10: Optical device wafer 11: Sapphire substrate 12: Device layer 13: Device 14: Planned division line 15: Laser processing groove 16: Altered layer

Claims (2)

In a laser processing apparatus comprising: a chuck table for holding a workpiece; and a laser beam irradiation means for irradiating a workpiece with a laser beam to the workpiece held on the chuck table.
The laser beam irradiating means includes a pulse laser beam oscillating means including a laser oscillator that oscillates a linearly polarized laser beam and a pulse generator that outputs a pulse signal to the laser oscillator, and a pulse laser beam oscillated from the pulse laser beam oscillating means. An electro-optic effect element that generates a first wave and a second wave in a direction orthogonal to the first wave by bending a part of the wave of each pulse, and a first wave generated by the electro-optic effect element A polarization beam splitter that separates the wave and the second wave, a damper that absorbs one of the waves separated by the polarization beam splitter, and a collector that collects the other wave separated by the polarization beam splitter; And a control means for controlling the electro-optic effect element,
The control means is configured to make at least the rising part and the other part of the rising and falling parts of the energy distribution in the wave of each pulse of the pulse laser beam oscillated from the pulse laser beam oscillating means relatively the first wave. Controlling the electro-optic effect element to generate a second wave;
The polarizing beam splitter directs the first wave to the damper and directs the second wave to the collector;
Laser processing equipment characterized by that.   The laser beam irradiating means synchronizes the time when the pulse laser beam oscillated from the pulse laser beam oscillating means reaches the electro-optic effect element and the time when the control signal output from the control means reaches the electro-optic effect element. The laser processing apparatus according to claim 1, comprising means.

Images