JP2016140914A - Laser processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser processing apparatus capable of forming holes at multiple positions at a time without generating a crack.SOLUTION: The laser processing apparatus includes: workpiece holding means for holding a workpiece on an XY plane; and laser beam irradiation means for irradiating the workpiece held by the workpiece holding means, with a laser beam. The laser beam irradiation means includes: pulsed laser beam oscillation means for emitting a pulsed laser beam at a repetition frequency M; a light collector for collecting the pulsed laser beam emitted by the pulsed laser beam oscillation means, and irradiating the workpiece held by the workpiece holding means, with the pulsed laser beam; and pulse dispersion means provided between the pulsed laser beam oscillation means and the light collector, for dispersing the pulsed laser beam onto multiple X coordinates and Y coordinates. The pulse dispersion means includes a scanner which has a mirror for reflecting the pulsed laser beam emitted at the repetition frequency M, and oscillates at a repetition frequency M1 lower than the repetition frequency M, thereby dispersing the pulsed laser beam onto (M/M1) coordinates.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a laser processing apparatus that performs laser processing on a workpiece such as a semiconductor wafer.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by division lines arranged in a lattice pattern on the surface of a substantially disc-shaped semiconductor wafer, and devices such as ICs and LSIs are formed in the partitioned regions. . Then, the semiconductor wafer is cut along the planned division line to divide the region where the device is formed to manufacture individual semiconductor devices.

  In order to reduce the size and increase the functionality of an apparatus, a module structure in which a plurality of semiconductor chips are stacked and electrodes of the stacked semiconductor devices are connected has been put into practical use. This module structure irradiates a laser beam from the back surface corresponding to the location where the electrode is formed on the semiconductor wafer, forms a through hole (via hole) in which the electrode is embedded, and connects the copper or the copper connected to the electrode into this through hole (via hole). A conductive material such as aluminum is embedded (for example, Patent Document 1).

JP 2008-62261 A

Thus, as described above, in order to form a through hole (via hole) by laser processing, it is necessary to irradiate a plurality of pulse laser beams at one place (through hole drilling position). It is desirable to improve productivity by increasing the value.
However, when a pulsed laser beam is irradiated several times at one place with a high repetition frequency, there is a problem that a heat accumulation crack occurs and the quality of the device is lowered.
According to the experiments by the present inventors, it has been found that the maximum repetition frequency at which no crack is generated when forming a through hole (via hole) is 10 kHz.

  This invention is made | formed in view of the said fact, The main technical subject is providing the laser processing apparatus which can form a hole simultaneously in several positions, without generating a crack.

In order to solve the above-mentioned main technical problem, according to the present invention, a workpiece holding means for holding a workpiece on the XY plane, and a laser beam for irradiating the workpiece held on the workpiece holding means with a laser beam An irradiation means, and a laser processing apparatus comprising:
The laser beam irradiating means includes: a pulse laser beam oscillating means that oscillates a pulse laser beam at a repetition frequency M; and a workpiece that is collected by the pulse laser beam oscillating means and held by the workpiece holding means. A light collector that irradiates the light source, and a pulse dispersion means that is disposed between the pulse laser beam oscillation means and the light collector to disperse the pulse laser light into a plurality of X coordinates and Y coordinates,
The pulse dispersion means has a mirror that reflects the pulse laser beam oscillated at the repetition frequency M, and oscillates at a repetition frequency M1 lower than the repetition frequency M to disperse the pulse laser beam in (M / M1) coordinates. Equipped with a scanner,
A laser processing apparatus is provided.

The pulse dispersion means comprises Y coordinate dispersion means for dispersing the pulse laser beam into a plurality of Y coordinates and X coordinate dispersion means for dispersion into a plurality of X coordinates,
The Y coordinate dispersion means includes a main scanner that oscillates at a repetition frequency M1 and an auxiliary scanner that oscillates at a repetition frequency that is an integral multiple of the repetition frequency M1 to disperse a pulsed laser beam. Specify the Y coordinate where the pulse laser beam is irradiated by shifting the phase of the repetition frequency,
The X coordinate dispersion means includes a main scanner that oscillates at a repetition frequency M1 and an auxiliary scanner that oscillates at a repetition frequency that is an integral multiple of the repetition frequency M1 to disperse a pulsed laser beam. The X coordinate on which the pulse laser beam is irradiated is specified by shifting the phase of the repetition frequency.

  In the laser processing apparatus according to the present invention, the laser beam irradiation means for irradiating the workpiece held by the workpiece holding means held in the XY plane with the laser beam irradiation means oscillates the pulse laser beam at the repetition frequency M; and A condenser for condensing the pulse laser beam oscillated by the pulse laser beam oscillating means and irradiating the workpiece held by the workpiece holding means, and disposed between the pulse laser beam oscillating means and the condenser Pulse dispersion means for dispersing the pulse laser beam into a plurality of X-coordinates and Y-coordinates, and the pulse dispersion means has a mirror for reflecting the pulse laser beam oscillated at the repetition frequency M and has a repetition frequency M1 lower than the repetition frequency M. It is equipped with a scanner that oscillates and disperses the pulse laser beam to (M / M1) coordinates, so When forming communication holes at the X and Y coordinate positions corresponding to the coordinates set to, multiple laser pulses can be irradiated simultaneously at the maximum repetition frequency that does not cause cracks, improving productivity. To do.

The perspective view of the laser processing apparatus comprised according to this invention. The block block diagram of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. The block block diagram which shows the Y coordinate dispersion | distribution means which comprises the laser beam irradiation means shown in FIG. The repetition frequency M01 (30 kHz) of the first complementary resonant scanner, the repetition frequency M02 (20 kHz) of the second complementary resonant scanner, and the repetition frequency M1 (10 kHz) of the main resonant scanner constituting the Y coordinate dispersion means shown in FIG. ), And a graph showing the combined repetition frequency MY obtained by adding the repetition frequencies M01 (30 kHz), M02 (20 kHz), and M1 (10 kHz). The block block diagram which shows the X coordinate dispersion | distribution means which comprises the laser beam irradiation means shown in FIG. The repetition frequency M01 (30 kHz) of the first complementary resonant scanner, the repetition frequency M02 (20 kHz) of the second complementary resonant scanner, and the repetition frequency M1 (10 kHz) of the main resonant scanner constituting the X coordinate dispersion means shown in FIG. ), And each repetition frequency M01 (30 kHz), M02 (20 kHz), and M1 (10 kHz), a graph showing the combined repetition frequency MX. Explanatory drawing which shows the coordinate which irradiates the pulse laser beam oscillated from the pulse laser beam oscillation means by the pulse dispersion means which consists of the Y coordinate dispersion means shown in FIG. 3 and the X coordinate dispersion means shown in FIG. The block block diagram of the control means with which the laser processing apparatus shown in FIG. 1 is equipped. The perspective view of the semiconductor wafer as a to-be-processed object. The perspective view which shows the state which affixed the semiconductor wafer shown in FIG. 9 on the adhesive tape with which the cyclic | annular flame | frame was mounted | worn. Explanatory drawing of the laser processing process implemented by 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 the X-axis direction, which is a machining feed direction indicated by an arrow X, and holds a workpiece. And a laser beam irradiation unit 4 as a laser beam irradiation means disposed on the base 2.

  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 slide block 32 provided, and a second slide arranged on the first slide block 32 so as to be movable in the Y-axis direction which is an indexing feed direction indicated by an arrow Y orthogonal to the X-axis direction. A block 33, 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 for holding the workpiece in the XY plane are provided. The chuck table 36 includes a suction chuck 361 made of a porous material, and holds, for example, a circular semiconductor wafer as a workpiece on a holding surface which is the upper surface of the suction chuck 361 by suction means (not shown). It is supposed to be. 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 that supports a workpiece such as a semiconductor wafer via a protective tape.

  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 X-axis direction moving means 37 for moving the first slide block 32 in the X-axis direction along the pair of guide rails 31, 31. The X-axis direction moving 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. Yes. 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 slide block 32 is moved in the X-axis direction along the guide rails 31 and 31 by driving the male screw rod 371 forward and backward by the pulse motor 372.

  The laser processing apparatus in the illustrated embodiment includes X-axis direction position detection means 374 for detecting the X-axis direction position of the chuck table 36. The X-axis direction position detecting means 374 is a linear scale 374a disposed along the guide rail 31, and a reading that is disposed along the linear scale 374a together with the first sliding block 32 disposed along the first sliding block 32. It consists of a head 374b. In the illustrated embodiment, the reading head 374b of the X-axis direction position detecting means 374 sends a pulse signal of one pulse every 1 μm to the control means described later. The control means described later detects the position of the chuck table 36 in the X-axis direction by counting the input pulse signals. When a pulse motor 372 is used as a drive source for the machining feed means 37, the drive pulse of a control means, which will be described later, that outputs a drive signal to the pulse motor 372 is counted, whereby the chuck table 36 is moved in the X-axis direction. The position can also be detected. When a servo motor is used as a drive source for the X-axis direction moving means 37, 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 position of the chuck table 36 in the X-axis direction can also be detected by counting the pulse signals.

  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 Y-axis direction movement for moving the second sliding block 33 along the pair of guide rails 322 and 322 provided in the first sliding block 32 in the Y-axis direction. Means 38 are provided. The Y-axis direction moving 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. Yes. 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 processing apparatus in the illustrated embodiment includes Y-axis direction position detecting means 384 for detecting the Y-axis direction position of the second sliding block 33. The Y-axis direction position detecting means 384 is a linear scale 384a disposed along the guide rail 322, and a reading which is disposed along the linear scale 384a together with the second sliding block 33 disposed along the second sliding block 33. And a head 384b. In the illustrated embodiment, the reading head 384b of the Y-axis direction position detecting means 384 sends a pulse signal of one pulse every 1 μm to the control means described later. The control means described later detects the position of the chuck table 36 in the Y-axis direction by counting the input pulse signals. When a pulse motor 382 is used as a drive source for the Y-axis direction moving means 38, the Y 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 382. An axial position can also be detected. When a servo motor is used as the drive source of the Y-axis direction moving means 38, 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. By counting the pulse signal, the position of the chuck table 36 in the Y-axis direction can also be detected.

  The laser beam irradiation unit 4 includes a support member 41 disposed on the base 2, a casing 42 supported by the support member 41 and extending substantially horizontally, and a laser beam irradiation disposed on the casing 42. Means 5 and an imaging means 50 disposed at the front end of the casing 42 for detecting a processing region to be laser processed are provided. The imaging unit 50 includes an illuminating unit that illuminates the workpiece, an optical system that captures an area illuminated by the illuminating unit, and an imaging device (CCD) that captures an image captured by the optical system. Then, the captured image signal is sent to the control means described later.

The laser beam irradiation means 5 will be described with reference to FIG.
As shown in FIG. 2, the laser beam irradiation means 5 condenses the pulse laser beam oscillation means 51 and the workpiece W held on the chuck table 36 by condensing the pulse laser beam oscillated from the pulse laser beam oscillation means 51. A condenser 52; a pulse dispersion means 6 disposed between the pulse laser beam oscillating means 51 and the condenser 52 for dispersing the pulse laser beam oscillated from the pulse laser beam oscillating means 51 into a plurality of Y coordinates and X coordinates; The optical axis deflecting unit 9 deflects the pulse laser beam dispersed by the pulse dispersing unit 6 in the X-axis direction. The pulse laser beam oscillating means 51 includes a pulse laser beam oscillator 511 and a repetition frequency setting means 512 attached thereto. The pulse laser beam oscillator 511 of the pulse laser beam oscillation means 51 oscillates a pulse laser beam LB having a wavelength of 355 nm in the illustrated embodiment. The repetition frequency M of the pulse laser beam LB oscillated by the pulse laser beam oscillation means 51 is set to 40 kHz in the illustrated embodiment. The condenser 52 includes an fθ lens that condenses the pulse laser beam LB oscillated from the pulse laser beam oscillation unit 51 and guided through the Y coordinate dispersion unit 7, the X coordinate dispersion unit 8, and the optical axis deflection unit 9. A condenser lens 521 is provided.

  The pulse dispersion means 6 disposed between the pulse laser beam oscillation means 51 and the condenser 52 disperses the pulse laser beam LB oscillated from the pulse laser beam oscillation means 51 into a plurality of Y coordinates in the illustrated embodiment. Y coordinate dispersion means 7 and X coordinate dispersion means 8 for dispersing the pulse laser beam LB dispersed in the Y coordinate by the Y coordinate dispersion means 7 into a plurality of X coordinates. As shown in FIG. 3, the Y-coordinate dispersing means 7 includes a first complementary resonant scanner 71 having a reflecting mirror 711, a second complementary resonant scanner 72 having a reflecting mirror 721, and a main mirror having a reflecting mirror 731. And a resonant scanner 73.

  The first complementary resonant scanner 71 swings corresponding to the repetition frequency set by the frequency setting unit 712, and the second complementary resonant scanner 72 swings corresponding to the repetition frequency set by the frequency setting unit 722. The main resonant scanner 73 is configured to swing according to the repetition frequency set by the frequency setting unit 732. The frequency setting unit 712 sets the repetition frequency M01 of the first complementary resonant scanner 71 to 30 kHz, the frequency setting unit 722 sets the repetition frequency M02 of the second complementary resonant scanner 72 to 20 kHz, and the frequency setting unit 732 The repetition frequency M1 of the resonant scanner 73 is set to 10 kHz. The repetition frequency M01 of the first complementary resonant scanner 71 and the repetition frequency M02 of the second complementary resonant scanner 72 are set to an integral multiple of the repetition frequency M1 of the main resonant scanner 73.

  The main resonant scanner 73 oscillating at the repetition frequency M1 disperses the pulse laser beam LB oscillated at the repetition frequency M by the pulse laser beam oscillation means 51 into (M / M1) Y coordinates. In the illustrated embodiment, the repetition frequency M of the pulse laser beam LB oscillated by the pulse laser beam oscillation means 51 is set to 40 kHz, and the repetition frequency M1 of the main resonant scanner 73 is set to 10 kHz. Dispersed in Y coordinates (40/10) every (1/4) × (1 / 10k) seconds. Note that the interval between the four Y coordinates distributed by the main resonant scanner 73 corresponds to the interval between the Y coordinates of bonding pads provided on a semiconductor wafer device to be described later in the illustrated embodiment. Is set to

The Y coordinate dispersion means 7 in the embodiment shown in FIG. 3 is configured as described above, and the pulse laser beam LB oscillated from the pulse laser beam oscillation means 51 enters the reflection mirror 711 of the first complementary resonant scanner 71. . The pulse laser beam LB incident on the reflection mirror 711 of the first auxiliary resonant scanner 71 is emitted through the reflection mirror 721 of the second auxiliary resonant scanner 72 and the reflection mirror 731 of the main resonant scanner 73.
In FIG. 4, the repetition frequency M01 (30 kHz) of the first auxiliary resonant scanner 71, the repetition frequency M02 (20 kHz) of the second auxiliary resonant scanner 72, the repetition frequency M1 (10 kHz) of the main resonant scanner 73, and A graph showing the combined repetition frequency MY obtained by adding the repetition frequencies M01 (30 kHz), M02 (20 kHz) and M1 (10 kHz) is shown. In FIG. 4, the horizontal axis represents time (1/10 k) second, and the vertical axis represents the Y coordinate. The pulsed laser beam LB oscillated from the pulsed laser beam oscillating means 51 has a Y coordinate corresponding to the combined repetition frequency MY added from the reflecting mirror 731 of the main resonant scanner 73 every (1/4) × (1 / 10k) seconds. Four (I II III IV) are emitted. The four Y-coordinates (I II III IV) of the pulse laser beam LB emitted from the reflecting mirror 731 of the main resonant scanner 73 are the repetition frequency M1 (10 kHz) of the main resonant scanner 73 and the first complementary resonant scanner 71. Can be specified by shifting the phase of the repetition frequency M01 (30 kHz) and the repetition frequency M02 (20 kHz) of the second complementary resonant scanner 72.

Next, the X coordinate dispersion means 8 constituting the pulse dispersion means 6 will be described with reference to FIG.
In the illustrated embodiment, the X-coordinate dispersing means 8 has a configuration in which the Y-coordinate dispersing means 7 is disposed in a state of being rotated 90 degrees about the optical axis as a rotation axis. A supplementary resonant scanner 81, a second complementary resonant scanner 82 provided with a reflective mirror 821, and a main resonant scanner 83 provided with a reflective mirror 831 are provided.

  The first complementary resonant scanner 81 swings corresponding to the repetition frequency set by the frequency setting unit 812, and the second auxiliary resonant scanner 82 swings corresponding to the repetition frequency set by the frequency setting unit 822. The main resonant scanner 83 is configured to be swung in accordance with the repetition frequency set by the frequency setting unit 832. The frequency setting unit 812 sets the repetition frequency M01 of the first complementary resonant scanner 81 to 30 kHz, the frequency setting unit 822 sets the repetition frequency M02 of the second complementary resonant scanner 82 to 20 kHz, and the frequency setting unit 832 The repetition frequency M1 of the resonant scanner 83 is set to 10 kHz. The repetition frequency M01 of the first complementary resonant scanner 81 and the repetition frequency M02 of the second complementary resonant scanner 82 are set to an integral multiple of the repetition frequency M1 of the main resonant scanner 83.

  In the main resonant scanner 83 that oscillates at the repetition frequency M1, the pulse laser beam oscillation means 51 disperses the pulse laser beam LB oscillated at the repetition frequency M into (M / M1) X coordinates. In the illustrated embodiment, the repetition frequency M of the pulse laser beam LB oscillated by the pulse laser beam oscillation means 51 is set to 40 kHz, and the repetition frequency M1 of the main resonant scanner 83 is set to 10 kHz. It is distributed every (1/4) × (1/10 k) seconds on the X coordinates of 40 (40/10) pieces. Note that the interval between the four X coordinates dispersed by the main resonant scanner 83 corresponds to the interval between the X coordinates of bonding pads provided in a semiconductor wafer device to be described later in the illustrated embodiment. Is set to

The X coordinate dispersion means 8 in the embodiment shown in FIG. 5 is configured as described above, and the pulse laser beam LB emitted from the Y coordinate dispersion means 7 enters the reflection mirror 811 of the first complementary resonant scanner 81. To do. The pulse laser beam LB incident on the reflection mirror 811 of the first complementary resonant scanner 81 is emitted through the reflection mirror 821 of the second complementary resonant scanner 82 and the reflection mirror 831 of the main resonant scanner 83.
In FIG. 6, the repetition frequency M01 (30 kHz) of the first complementary resonant scanner 81, the repetition frequency M02 (20 kHz) of the second complementary resonant scanner 82, the repetition frequency M1 (10 kHz) of the main resonant scanner 83, and A graph showing a combined repetition frequency MX obtained by adding up each repetition frequency M01 (30 kHz), M02 (20 kHz) and M1 (10 kHz) is shown. In FIG. 6, the horizontal axis represents time (1/10 k) seconds, and the vertical axis represents the X coordinate. The pulse laser beam LB oscillated from the pulse laser beam oscillating means 51 has an X coordinate corresponding to the combined repetition frequency MX, which is added from the reflection mirror 831 of the main resonant scanner 83 every (1/4) × (1 / 10k) seconds. Four (I II III IV) are emitted. The four X coordinates (I II III IV) of the pulse laser beam LB emitted from the reflecting mirror 831 of the main resonant scanner 83 are the repetition frequency M1 (10 kHz) of the main resonant scanner 83 and the first complementary resonant scanner 81. Can be specified by shifting the phase of the repetition frequency M01 (30 kHz) and the repetition frequency M02 (20 kHz) of the second complementary resonant scanner 82.

  The pulse dispersion means 6 including the Y coordinate dispersion means 7 and the X coordinate dispersion means 8 described above is configured as described above, and the pulse laser beam LB oscillated from the pulse laser beam oscillation means 51 is converted into the optical axis deflection means 9 and the condenser. 4 (I II III IV) are irradiated onto the XY coordinates shown in FIG.

  Returning to FIG. 2 and continuing the description, the optical axis deflecting means 9 comprises a galvano scanner 91 in the illustrated embodiment. By displacing the galvano scanner 91 from the position indicated by the solid line to the position indicated by the broken line, the pulse laser beam is deflected in the X-axis direction from the position indicated by the solid line to the position indicated by the broken line, and is applied to the condenser lens 521 of the condenser 52. Lead. Accordingly, by synchronizing the displacement speed from the position indicated by the solid line of the galvano scanner 91 to the position indicated by the broken line with the moving speed of the chuck table 36 to the left in FIG. 2, the chuck table 36 is processed to the left in FIG. In the state shown in FIG. 2, the pulse laser beam can be continuously irradiated to the irradiation position indicated by the solid line and the broken line in the embodiment shown in FIG.

  The laser processing apparatus in the illustrated embodiment includes a control means 10 shown in FIG. 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 readable and writable data that stores arithmetic results and the like. A random access memory (RAM) 103, an input interface 104 and an output interface 105 are provided. Detection signals from the X-axis direction position detection unit 374, the Y-axis direction position detection unit 384, the imaging unit 50, and the like are input to the input interface 104 of the control unit 10. The output interface 105 of the control means 10 constitutes the X-axis direction moving means 37, the Y-axis direction moving means 38, the pulse laser beam oscillation means 51 of the laser beam irradiation means 5, and the Y coordinate dispersion means 7 of the pulse dispersion means 6. A frequency setting unit 712 for setting the frequency of the first complementary resonant scanner 71, a frequency setting unit 722 for setting the frequency of the second complementary resonant scanner 72, a frequency setting unit 732 for setting the frequency of the main resonant scanner 73, and a pulse. The frequency setting unit 812 that sets the frequency of the first complementary resonant scanner 81 that constitutes the X coordinate dispersing unit 8 of the dispersing unit 6, the frequency setting unit 822 that sets the frequency of the second complementary resonant scanner 82, and the main resonant scanner 83. A frequency setter 832 for setting the frequency of the optical axis deflection means 9; A control signal is output to the galvano scanner 91 or the like.

The laser processing apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
FIG. 9 shows a perspective view of a semiconductor wafer 20 as a workpiece to be processed by the laser processing apparatus described above. A semiconductor wafer 20 shown in FIG. 10 is made of a silicon wafer, and a plurality of division lines 201 are formed in a lattice shape on the surface 20a, and a plurality of areas partitioned by the plurality of division lines 201 are formed. A device 202 such as an IC or LSI is formed. Each device 202 has the same configuration. Four bonding pads 203 are formed on the surface of the device 202, respectively. The four bonding pads 203 are made of copper in the illustrated embodiment. Communication holes (via holes) reaching the bonding pads 203 from the back surface 20b are formed at positions corresponding to the four bonding pads 203, respectively. As for the coordinates of the four bonding pads 203 in each device 202, design value data is stored in the random access memory (RAM) 103. Incidentally, in correspondence with the coordinates of the four bonding pads 203 in the device 202, the pulse dispersion means 6 including the Y coordinate dispersion means 7 and the X coordinate dispersion means 8 in the illustrated embodiment has four light outputs (I II III XY coordinates of the pulsed laser beam are set.

  In order to form communication holes (via holes) reaching the bonding pads from the back surface 20b at positions corresponding to the four bonding pads 203 of the semiconductor wafer 20 described above, as shown in FIG. The surface 20a of the semiconductor wafer 20 is adhered to the surface of the adhesive tape T on which the outer peripheral portion is mounted so as to cover the portion. The adhesive tape T is formed of a vinyl chloride (PVC) sheet in the illustrated embodiment.

  If the workpiece support process described above is performed, the adhesive tape T side of the semiconductor wafer 20 is placed on the chuck table 36 of the laser processing apparatus shown in FIG. Then, by operating a suction means (not shown), the semiconductor wafer 20 is sucked and held on the chuck table 36 via the adhesive tape T (workpiece holding step). Accordingly, the back surface 20b of the semiconductor wafer 20 held on the chuck table 36 via the adhesive tape T is on the upper side. The annular frame F that supports the semiconductor wafer 20 via the adhesive tape T is fixed by a clamp 362 disposed on the chuck table 36.

  When the above-described workpiece holding step is performed, the chuck table 36 that sucks and holds the semiconductor wafer 20 by operating the X-axis direction moving unit 37 is positioned immediately below the imaging unit 50. When the chuck table 36 is positioned immediately below the image pickup means 50, the image pickup means 50 and the control means 10 execute an alignment operation for detecting a processing region to be laser processed on the semiconductor wafer 20. That is, the imaging unit 50 and the control unit 10 are used for alignment with the condenser 52 of the laser beam irradiation unit 5 that irradiates the laser beam along the planned division line 201 formed in the predetermined direction of the semiconductor wafer 20. Image processing such as pattern matching is executed to align the laser beam irradiation position. At this time, the surface 20a on which the division line 201 of the semiconductor wafer 20 is formed is positioned on the lower side. However, as described above, the imaging unit 50 corresponds to the infrared illumination unit, the optical system for capturing infrared rays, and infrared rays. Since an image pickup unit configured with an image pickup device (infrared CCD) or the like that outputs an electric signal is provided, it is possible to pick up an image of the planned division line 201 through the back surface 20b.

  As described above, when the division line formed on the semiconductor wafer 20 held on the chuck table 36 is detected and the laser beam irradiation position is aligned, the chuck table 36 is moved as shown in FIG. The laser beam irradiation means 5 moves to the laser beam irradiation region where the condenser 52 is located, and positions the intermediate position of the device 202 between the predetermined division line 201 and the predetermined division line 201 directly below the condenser 52. Then, the focal point of the pulse laser beam irradiated from the condenser 52 is positioned near the back surface (upper surface) of the semiconductor wafer 20. The pulse laser beam oscillation means 51 of the laser beam irradiation means 5, the pulse dispersion means 6, and the galvano scanner 91 as the optical axis deflection means 9 are operated, and the X-axis direction moving means 37 is operated to move the chuck table 36 to the arrow X 1 in FIG. Is moved at a predetermined moving speed in the direction indicated by. Note that the XY coordinates of four (I II III IV) pulse laser beams emitted from the pulse dispersion means 6 comprising the Y coordinate dispersion means 7 and the X coordinate dispersion means 8 are in the device 202 formed on the semiconductor wafer 20. Since it is set corresponding to the coordinates of the four bonding pads 203, the pulse laser beam oscillated from the pulse laser beam oscillation means 51 is irradiated to the position corresponding to the four bonding pads 203. Then, the galvano scanner 91 operates as described above while the chuck table 36 moves by a predetermined amount, so that a predetermined number of pulse laser beams are irradiated to the positions corresponding to the four bonding pads 203 to the semiconductor wafer 20. Communication holes (via holes) reaching the four bonding pads 203 are formed. In this way, the laser processing step of forming communication holes (via holes) at positions corresponding to the four bonding pads 203 provided in all the devices 202 formed in the same row in the X-axis direction is performed. This laser processing step is performed at positions corresponding to the four bonding pads 203 provided in all the devices 202 formed on the semiconductor wafer 20.

The laser processing step is performed under the following processing conditions.
Laser light source: YVO4 laser or YAG laser Wavelength: 355 nm
Repetition frequency: 40 kHz
Average output: 4W
Condensing spot diameter: φ10μm
Processing feed rate: 100 mm / second Repetitive frequency of the first complementary resonant scanner: 30 kHz
Repetitive frequency of the second complementary resonant scanner: 20 kHz
Repetitive frequency of main resonant scanner: 10 kHz

  As described above, in the laser processing apparatus in the illustrated embodiment, communication holes (via holes) are formed at the X and Y coordinate positions corresponding to the coordinates of the plurality of bonding pads 203 provided on the device 202 formed on the semiconductor wafer 20. ), A plurality of coordinates can be simultaneously irradiated with a pulse laser beam at a maximum repetition frequency (10 kHz) that does not cause cracks, and productivity is improved.

2: stationary base 3: chuck table mechanism 36: chuck table 37: X-axis direction moving means 38: Y-axis direction moving means 4: laser beam irradiation unit 5: laser beam irradiation means 51: pulsed laser beam oscillation means 52: condenser 6 : Pulse dispersion means 7: Y coordinate dispersion means 71: first complementary resonant scanner 72: second complementary resonant scanner 73: main resonant scanner 8: X coordinate dispersion means 81: first complementary resonant scanner 82: second Supplementary resonant scanner 83: Main resonant scanner 9: Optical axis deflecting means 10: Control means 20: Semiconductor wafer

Claims (2)

A laser processing apparatus comprising: a workpiece holding means for holding a workpiece in an XY plane; and a laser beam irradiation means for irradiating a workpiece with a laser beam to the workpiece held by the workpiece holding means,
The laser beam irradiating means includes: a pulse laser beam oscillating means that oscillates a pulse laser beam at a repetition frequency M; and a workpiece that is collected by the pulse laser beam oscillating means and held by the workpiece holding means. A light collector that irradiates the light source, and a pulse dispersion means that is disposed between the pulse laser beam oscillation means and the light collector to disperse the pulse laser light into a plurality of X coordinates and Y coordinates,
The pulse dispersion means has a mirror that reflects the pulse laser beam oscillated at the repetition frequency M, and oscillates at a repetition frequency M1 lower than the repetition frequency M to disperse the pulse laser beam in (M / M1) coordinates. Equipped with a scanner,
Laser processing equipment characterized by that. The pulse dispersion means comprises Y coordinate dispersion means for dispersing the pulse laser beam into a plurality of Y coordinates and X coordinate dispersion means for dispersion into a plurality of X coordinates,
The Y coordinate dispersion means includes a main scanner that oscillates at a repetition frequency M1 and an auxiliary scanner that oscillates at a repetition frequency that is an integral multiple of the repetition frequency M1 to disperse a pulsed laser beam. Specify the Y coordinate where the pulse laser beam is irradiated by shifting the phase of the repetition frequency,
The X coordinate dispersion means includes a main scanner that oscillates at a repetition frequency M1 and an auxiliary scanner that oscillates at a repetition frequency that is an integral multiple of the repetition frequency M1 to disperse a pulsed laser beam. The laser processing apparatus according to claim 1, wherein the X coordinate to be irradiated with the pulse laser beam is specified by shifting the phase of the repetition frequency.