JP6510829B2 - Laser processing equipment - Google Patents

Description

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

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by planned dividing lines arranged in a lattice on the surface of a semiconductor wafer having a substantially disk shape, and devices such as IC and LSI are formed in the partitioned regions. . Then, the semiconductor wafer is cut along the dividing lines to divide the area where the devices are formed, thereby manufacturing individual semiconductor devices.

  In order to miniaturize the device and enhance the function, a module structure in which a plurality of semiconductor chips are stacked and electrodes of stacked semiconductor devices are connected has been put to practical use. In this module structure, a laser beam is irradiated from the back surface corresponding to the portion on the semiconductor wafer where the electrode is formed, a through hole (via hole) for embedding the electrode is formed, and copper or the like connected to the electrode in this through hole (via hole) It is the structure which embeds conductive materials, such as aluminum, (for example, patent documents 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 to one place (through hole drilling position), so the repetition frequency of the pulse laser beam To improve productivity.
However, when the pulse laser beam is irradiated to a single location multiple times at a high repetition frequency, there is a problem that heat buildup cracks occur to degrade the quality of the device.
According to the experiment of the inventor of the present invention, it was found that the maximum repetition frequency at which a crack is not generated when forming a through hole (via hole) is 10 kHz.

  The present invention has been made in view of the above-described facts, and a main technical problem thereof is to provide a laser processing apparatus capable of simultaneously forming holes at a plurality of positions without generating a crack.

In order to solve the above-mentioned main technical problems, according to the present invention, a workpiece holding means for holding a workpiece on an XY plane, and a laser beam for irradiating a laser beam to the workpiece held by the workpiece holding means. A laser processing apparatus comprising: irradiation means;
The laser beam application means comprises a pulse laser beam oscillation means for oscillating a pulse laser beam at a repetition frequency M, and a workpiece to be processed held by the workpiece holding means by condensing the pulse laser beam oscillated by the pulse laser beam oscillation means. And a pulse dispersion means disposed between the pulse laser beam oscillation means and the condenser for dispersing the pulse laser beam into a plurality of X coordinates and Y coordinates,
The pulse dispersion means has a mirror for reflecting 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 light at (M / M1) coordinates. A scanner , Y coordinate dispersing means for dispersing the pulse laser beam into a plurality of Y coordinates, and X coordinate dispersing means for dispersing the plurality of X coordinates;
The Y coordinate dispersing means includes a main scanner swinging at a repetition frequency M1 and a complementary scanner swinging at a repetition frequency that is an integral multiple of the repetition frequency M1 to disperse the pulse laser beam, the main scanner and the complementary scanner Shift the phase of the repetition frequency to identify the Y coordinate to which the pulsed laser beam is emitted,
The X coordinate dispersing means includes a main scanner swinging at a repetition frequency M1 and a complementary scanner swinging at a repetition frequency that is an integral multiple of the repetition frequency M1 to disperse a pulse laser beam; A laser processing apparatus is provided that shifts the phase of the repetition frequency to specify the X coordinate to which the pulsed laser beam is irradiated.

In the laser processing apparatus according to the present invention, a laser beam application means for applying a laser beam to a workpiece held by a workpiece holding means for holding on an XY plane, a pulse laser beam oscillation means for oscillating pulse laser beams at a repetition frequency M; A condenser which condenses the pulsed laser beam oscillated by the pulsed laser beam oscillating means and irradiates the workpiece held by the workpiece holding means, and is disposed between the pulsed laser beam oscillating means and the condenser And pulse dispersion means for dispersing the pulse laser beam into a plurality of X coordinates and Y coordinates, the pulse dispersion means having a mirror for reflecting the pulse laser beam oscillated at the repetition frequency M and having the repetition frequency M1 lower than the repetition frequency M swung (M / M1) and a scanner for distributing the pulse laser beam to a number of coordinates, Pal The apparatus comprises a Y coordinate dispersing means for dispersing a laser beam into a plurality of Y coordinates and an X coordinate dispersing means for dispersing a plurality of X coordinates, the Y coordinate dispersing means comprising: a main scanner oscillating at a repetition frequency M1 and the repetition frequency A supplementary scanner is provided which disperses the pulse laser beam by oscillating at a repetition frequency of an integer multiple of M1, and the Y coordinate of the pulse laser beam to be irradiated is specified by shifting the phase of the repetition frequency of the main scanner and the supplementary scanner The X coordinate dispersion means comprises a main scanner oscillating at a repetition frequency M1 and a supplementary scanner oscillating at a repetition frequency of an integral multiple of the repetition frequency M1 to disperse the pulse laser beam, and the repetition of the main scanner and the supplementary scanner setting Runode, the workpiece to identify the X coordinate of the pulse laser beam is irradiated by shifting the phase of the frequency X coordinates corresponding to the coordinates, when forming a communication hole in the Y-coordinate position, a crack can simultaneously applying a pulse laser beam to a plurality of coordinates at a maximum repetition frequency not causing, the productivity is improved.

FIG. 1 is a perspective view of a laser processing apparatus configured in accordance with the present invention. FIG. 2 is a block diagram of laser beam irradiation means provided in the laser processing apparatus shown in FIG. 1; FIG. 3 is a block diagram showing a Y coordinate dispersing means that constitutes the laser beam irradiating means shown in FIG. 2; The repetition frequency M01 (30 kHz) of the first complementary resonance scanner constituting the Y coordinate dispersion means shown in FIG. 3, the repetition frequency M02 (20 kHz) of the second complementary resonance scanner, and the repetition frequency M1 (10 kHz) of the main resonance scanner. And a graph showing a combined repetition frequency MY obtained by adding each repetition frequency M01 (30 kHz) to M02 (20 kHz) and M1 (10 kHz). FIG. 3 is a block diagram showing an X-coordinate dispersing means that constitutes the laser beam irradiating means shown in FIG. 2; The repetition frequency M01 (30 kHz) of the first complementary resonance scanner constituting the X coordinate dispersion means shown in FIG. 5, the repetition frequency M02 (20 kHz) of the second complementary resonance scanner, and the repetition frequency M1 (10 kHz) of the main resonance scanner. And a graph showing a combined repetition frequency MX obtained by adding each of the repetition frequencies M01 (30 kHz) and M02 (20 kHz) and M1 (10 kHz). Explanatory drawing which shows the coordinate which irradiates the pulse laser beam oscillated from pulse laser beam oscillation means by the pulse dispersion means which consists of Y coordinate dispersion means shown in FIG. 3, and X coordinate dispersion means shown in FIG. FIG. 2 is a block diagram of control means provided in the laser processing apparatus shown in FIG. 1; The perspective view of the semiconductor wafer as a to-be-processed object. FIG. 10 is a perspective view showing a state in which the semiconductor wafer shown in FIG. 9 is attached to an adhesive tape mounted on an annular frame; Explanatory drawing of the laser processing process implemented by the laser processing apparatus shown in FIG.

  Hereinafter, preferred embodiments of a laser processing apparatus configured in accordance with the present invention will be described in detail with reference to the attached drawings.

  Referring to FIG. 1, a perspective view of a laser processing apparatus constructed in accordance with the present invention is shown. The laser processing apparatus shown in FIG. 1 includes a stationary base 2 and a chuck table mechanism 3 disposed on the stationary base 2 so as to be movable in the X-axis direction, which is a processing feed direction indicated by arrow X, and holding a workpiece. And a laser beam irradiation unit 4 disposed on the base 2 as a laser beam irradiation means.

  The chuck table mechanism 3 is disposed on the stationary base 2 so as to be movable in the X-axis direction on the pair of guide rails 31 arranged in parallel along the X-axis direction, and the guide rails 31. A first sliding block 32 provided, and a second sliding block movably disposed on the first sliding block 32 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 the cylindrical member 34 on the second slide 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 has a suction chuck 361 formed of a porous material, and holds, for example, a circular semiconductor wafer as a workpiece on a holding surface which is an upper surface of the suction chuck 361 by suction means (not shown). It is supposed to The chuck table 36 configured in this manner 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 for supporting a workpiece such as a semiconductor wafer through a protective tape.

  The first slide block 32 is provided with a pair of guided grooves 321, 321 fitted to the pair of guide rails 31, 31 on its lower surface, and is parallel to the upper surface along the Y-axis direction A pair of guide rails 322, 322 are provided. The first slide block 32 configured in this manner moves in the X-axis direction along the pair of guide rails 31, 31 by the guided grooves 321, 321 being fitted to the pair of guide rails 31, 31. Configured to be possible. The chuck table mechanism 3 in the illustrated embodiment comprises 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 drive source such as a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31 and a pulse motor 372 for driving the male screw rod 371 to rotate. There is. The externally threaded rod 371 is rotatably supported at one end thereof on 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. The male screw rod 371 is screwed into a through female screw hole formed in a female screw block (not shown) provided protruding 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 by driving the externally threaded rod 371 forward and reversely by the pulse motor 372.

  The laser processing apparatus in the illustrated embodiment is provided with an X-axis direction position detection means 374 for detecting the position of the chuck table 36 in the X-axis direction. The X-axis direction position detection means 374 is a reading that is disposed along the linear scale 374a disposed along the guide rail 31 and the first sliding block 32 and moves along the linear scale 374a along with the first sliding block 32. It consists of a head 374b. The read head 374b of the X-axis direction position detection means 374 sends a pulse signal of one pulse every 1 μm to the control means described later in the illustrated embodiment. 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 the pulse motor 372 is used as a drive source of the processing feed means 37, the X axis direction of the chuck table 36 is counted by counting the drive pulses of the control means described later which outputs a drive signal to the pulse motor 372. The position can also be detected. When a servomotor is used as a drive source of the X-axis direction moving means 37, a pulse signal output from a rotary encoder for detecting the number of rotations of the servomotor is sent to the control means described later, and the control means inputs The X axis direction position of the chuck table 36 can also be detected by counting the pulse signal.

  The second slide block 33 is provided at its lower surface with a pair of guided grooves 331, 331 fitted with a pair of guide rails 322, 322 provided at the upper surface of the first slide block 32, By fitting the guided grooves 331, 331 to the pair of guide rails 322, 322, the guide grooves can be moved in the Y-axis direction. The chuck table mechanism 3 in the illustrated embodiment moves in the Y-axis direction for moving the second slide block 33 along the pair of guide rails 322 provided on the first slide block 32 in the Y-axis direction. Means 38 are provided. The Y-axis direction moving means 38 includes an externally threaded 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 externally threaded rod 381. There is. The externally threaded rod 381 is rotatably supported by a bearing block 383 fixed at one end to the upper surface of the first sliding block 32, and the other end is connected by transmission to the output shaft of the pulse motor 382. The male screw rod 381 is screwed into a through female screw hole formed in a female screw block (not shown) provided protruding on the lower surface of the central portion of the second sliding block 33. Therefore, by driving the externally threaded rod 381 forward and reverse by the pulse motor 382, the second sliding block 33 is moved in the Y-axis direction along the guide rails 322, 322.

  The laser processing apparatus in the illustrated embodiment is provided with Y-axis direction position detection means 384 for detecting the Y-axis direction position of the second sliding block 33. The Y-axis direction position detection means 384 is a reading that moves along the linear scale 384a along with the second slide block 33 and is disposed on the linear scale 384a disposed along the guide rail 322 and the second slide block 33. It consists of a head 384b. The read head 384b of the Y-axis direction position detection means 384 sends a pulse signal of one pulse every 1 μm to the control means described later in the illustrated embodiment. And the control means mentioned later detects the Y-axis direction position of the chuck table 36 by counting the input pulse signal. When the pulse motor 382 is used as a drive source of the Y-axis direction moving unit 38, Y of the chuck table 36 is counted by counting drive pulses of a control unit described later that outputs a drive signal to the pulse motor 382. The axial position can also be detected. When a servomotor is used as a drive source of the Y-axis direction moving means 38, a pulse signal output from a rotary encoder for detecting the number of revolutions of the servomotor is sent to the control means described later, and the control means inputs The Y-axis direction position of the chuck table 36 can also be detected by counting the pulse signals.

  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 area to be laser-processed are provided. The imaging unit 50 includes an illumination unit for illuminating a workpiece, an optical system for capturing an area illuminated by the illumination unit, and an imaging device (CCD) for capturing an image captured by the optical system. , The picked up image signal is sent to the control means mentioned later.

The laser beam application means 5 will be described with reference to FIG.
The laser beam application means 5 condenses the pulse laser beam oscillated from the pulse laser beam oscillation means 51 and the pulse laser beam oscillation means 51 as shown in FIG. 2 and irradiates the workpiece W held on the chuck table 36 A condenser 52, and a pulse dispersion means 6 disposed between the pulse laser beam oscillation means 51 and the condenser 52 for dispersing the pulse laser beam oscillated from the pulse laser beam oscillation means 51 into a plurality of Y coordinates and X coordinates An optical axis deflection means 9 is provided for deflecting the pulse laser beam dispersed by the pulse dispersion means 6 in the X-axis direction. The pulse laser beam oscillation means 51 is composed of 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 pulsed laser beam LB oscillated by the pulsed laser beam oscillating means 51 is set to 40 kHz in the illustrated embodiment. The condenser 52 comprises an fθ lens for condensing the pulsed laser beam LB oscillated from the pulsed laser beam oscillating means 51 and guided through the Y coordinate dispersing means 7, the X coordinate dispersing means 8 and the optical axis deflecting means 9. A condenser lens 521 is provided.

  The pulse dispersion means 6 disposed between the pulse laser beam oscillation means 51 and the light collector 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. The X coordinate dispersing means 8 disperses the pulse laser beam LB dispersed into the Y coordinate by the Y coordinate dispersing means 7 into a plurality of X coordinates. As shown in FIG. 3, the Y coordinate dispersing means 7 mainly 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 reflecting mirror 731. A resonant scanner 73 is provided.

  The first complementary resonance scanner 71 swings in response to the repetition frequency set by the frequency setting unit 712, and the second complementary resonance scanner 72 swings in response to the repetition frequency set by the frequency setting unit 722. The main resonant scanner 73 is configured to be swung 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 resonance scanner 71 to 30 kHz, the frequency setting unit 722 sets the repetition frequency M02 of the second complementary resonance 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 resonance scanner 71 and the repetition frequency M02 of the second complementary resonance scanner 72 are set to integral multiples of the repetition frequency M1 of the main resonance scanner 73.

  The main resonant scanner 73 oscillating at the repetitive frequency M1 disperses the pulsed laser beam LB oscillated at the repetitive frequency M by the pulsed laser beam oscillating 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. It disperses to (40/10) Y coordinates every (1/4) × (1/10 k) seconds. In the illustrated embodiment, the distance between the four Y coordinates dispersed by the main resonant scanner 73 corresponds to the distance between the Y coordinates of the bonding pad provided on the semiconductor wafer device which is a workpiece to be described later. Is set as.

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 complementary resonance scanner 71 is emitted through the reflection mirror 721 of the second complementary resonance scanner 72 and the reflection mirror 731 of the main resonance scanner 73.
4, the repetition frequency M01 (30 kHz) of the first complementary resonance scanner 71, the repetition frequency M02 (20 kHz) of the second complementary resonance scanner 72, the repetition frequency M1 (10 kHz) of the main resonance scanner 73, and A graph showing a combined repetition frequency MY obtained by adding up each repetition frequency M01 (30 kHz), M02 (20 kHz) and M1 (10 kHz) is shown. In FIG. 4, the horizontal axis represents time (1/10 k) seconds, and the vertical axis represents Y coordinates. The pulse laser beam LB oscillated from the pulse laser beam oscillation means 51 is added to the Y coordinate corresponding to the addition repetition frequency MY added up every (1/4) × (1/10 k) seconds from the reflection mirror 731 of the main resonance scanner 73. 4 pieces (I II III IV) are emitted. The Y coordinates of the four (I II III IV) pulse laser beams LB emitted from the reflection mirror 731 of the main resonant scanner 73 have a repetition frequency M1 (10 kHz) of the main resonant scanner 73 and the first complementary resonant scanner 71. Of the repetition frequency M01 (30 kHz) of the second complementary resonance scanner 72 and the repetition frequency M02 (20 kHz) of the second complementary resonance scanner 72.

Next, the X coordinate dispersing means 8 constituting the pulse dispersing means 6 will be described with reference to FIG.
In the illustrated embodiment, the X-coordinate dispersing unit 8 is arranged in a state where the Y-coordinate dispersing unit 7 is rotated by 90 degrees about the optical axis, and the first X-coordinate dispersing unit 8 includes the reflecting mirror 811. A complementary resonant scanner 81, a second complementary resonant scanner 82 having a reflecting mirror 821, and a main resonant scanner 83 having a reflecting mirror 831 are provided.

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

  The main resonant scanner 83 oscillating at the repetitive frequency M1 disperses the pulsed laser beam LB oscillated at the repetitive frequency M by the pulsed laser beam oscillating means 51 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 disperses to (40/10) X coordinates every (1/4) × (1/10 k) seconds. In the illustrated embodiment, the distance between the four X coordinates dispersed by the main resonant scanner 83 corresponds to the distance between the X coordinates of the bonding pads provided on the device of the semiconductor wafer which is a workpiece to be described later. Is set as.

The X coordinate dispersing 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 dispersing means 7 enters the reflection mirror 811 of the first complementary resonator scanner 81. Do. The pulse laser beam LB incident on the reflection mirror 811 of the first complementary resonance scanner 81 is emitted through the reflection mirror 821 of the second complementary resonance scanner 82 and the reflection mirror 831 of the main resonance scanner 83.
6, the repetition frequency M01 (30 kHz) of the first complementary resonance scanner 81, the repetition frequency M02 (20 kHz) of the second complementary resonance scanner 82, the repetition frequency M1 (10 kHz) of the main resonant scanner 83, and A graph is shown showing a summed repetition frequency MX obtained by summing each of the repetition frequencies M01 (30 kHz), M02 (20 kHz) and M1 (10 kHz). 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 oscillation means 51 is added to the X coordinate corresponding to the addition repetition frequency MX added from the reflection mirror 831 of the main resonance scanner 83 every (1/4) × (1/10 k) seconds. 4 pieces (I II III IV) are emitted. The X coordinates of the four (I II III IV) pulse laser beams LB emitted from the reflection 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. Of the repetition frequency M01 (30 kHz) of the second complementary resonance scanner 82 and the repetition frequency M02 (20 kHz) of the second complementary resonance 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 optical axis deflection means 9 and the light collector of the pulse laser beam LB oscillated from the pulse laser beam oscillation means 51 Four (I II III IV) irradiations are applied to the XY coordinates shown in FIG. 7 every 52 seconds (1/10 k) seconds.

  Returning to FIG. 2 and continuing the description, the optical axis deflection means 9 comprises a galvano scanner 91 in the illustrated embodiment. By displacing the galvano scanner 91 from the position shown by the solid line to the position shown by the broken line, the pulse laser beam is deflected in the X axis direction from the position shown by the solid line to the position shown by the broken line Lead. Therefore, the displacement speed from the position shown by the solid line of the galvano scanner 91 to the position shown by the broken line is synchronized with the moving speed of the chuck table 36 to the left in FIG. In the fed state, the pulse laser beam can be irradiated continuously to the irradiation position shown by the solid line and the broken line in the embodiment shown in FIG.

  The laser processing apparatus in the illustrated embodiment comprises 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 control programs and the like, and read / write that stores arithmetic results and the like. A random access memory (RAM) 103 and an input interface 104 and an output interface 105 are provided. Detection signals from the X-axis direction position detection means 374, the Y-axis direction position detection means 384, the imaging means 50 and the like are input to the input interface 104 of the control means 10. From the output interface 105 of the control means 10, 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 application means 5, and the Y coordinate dispersion means 7 of the pulse dispersion means 6 are configured. Frequency setting unit 712 for setting the frequency of the first complementary resonance scanner 71, frequency setting unit 722 for setting the frequency of the second complementary resonance scanner 72, frequency setting unit 732 for setting the frequency of the main resonant scanner 73, pulse A frequency setting unit 812 for setting the frequency of the first complementary resonator scanner 81 constituting the X coordinate dispersing unit 8 of the dispersing unit 6, a frequency setting unit 822 for setting the frequency of the second complementary resonator scanner 82, a main resonant scanner 83 Frequency setting unit 832 for setting the frequency of The control signal is output to the next 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 above-described laser processing apparatus. The semiconductor wafer 20 shown in FIG. 10 is made of a silicon wafer, and has a plurality of planned division lines 201 formed in a lattice shape on the surface 20 a and a plurality of areas divided by the plurality of planned division lines 201. A device 202 such as an IC or LSI is formed. The devices 202 all have the same configuration. Four bonding pads 203 are formed on the surface of the device 202, respectively. The four bonding pads 203 are formed of copper in the illustrated embodiment. Communication holes (via holes) reaching the bonding pads 203 from the back surface 20 b are formed at positions corresponding to the four bonding pads 203. The coordinates of the four bonding pads 203 in each device 202 have design value data stored in the random access memory (RAM) 103. The four pulse dispersion means 6 consisting of the Y coordinate dispersion means 7 and the X coordinate dispersion means 8 in the illustrated embodiment correspond to the coordinates of the four bonding pads 203 in the device 202. The XY coordinates of the pulsed laser beam of III IV) 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, the inner opening of the annular frame F as shown in FIG. The surface 20a of the semiconductor wafer 20 is attached to the surface of the adhesive tape T having the outer peripheral portion attached thereto so as to cover the portion. The adhesive tape T is formed of a polyvinyl chloride (PVC) sheet in the illustrated embodiment.

  After carrying out the above-described workpiece supporting step, 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, the semiconductor wafer 20 is suctioned and held on the chuck table 36 through the adhesive tape T by operating suction means (not shown) (workpiece holding step). Therefore, the back surface 20 b 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 supporting the semiconductor wafer 20 via the adhesive tape T is fixed by a clamp 362 disposed on the chuck table 36.

  After performing the above-described workpiece holding process, the X-axis direction moving means 37 is operated to position the chuck table 36 holding the semiconductor wafer 20 under suction directly below the imaging means 50. When the chuck table 36 is positioned directly below the imaging means 50, the imaging means 50 and the control means 10 execute an alignment operation for detecting the processing area of the semiconductor wafer 20 to be laser-processed. That is, the imaging unit 50 and the control unit 10 perform alignment with the light collector 52 of the laser beam application unit 5 that applies the laser beam along the planned dividing line 201 formed in the predetermined direction of the semiconductor wafer 20. Image processing such as pattern matching is performed to perform alignment of the laser beam irradiation position. At this time, the surface 20a on which the planned dividing line 201 of the semiconductor wafer 20 is formed is located on the lower side, but as described above, the imaging means 50 corresponds to an infrared illumination means, an optical system for capturing infrared rays, and infrared rays. Since the image pickup means constituted by an image pickup element (infrared CCD) or the like for outputting an electric signal is provided, it is possible to image the planned division line 201 by watermarking from the back surface 20b.

  As described above, when the planned dividing line formed on the semiconductor wafer 20 held on the chuck table 36 is detected and alignment of the laser beam irradiation position is performed, as shown in FIG. It moves to the laser beam irradiation area where the condenser 52 of the laser beam irradiation means 5 is located, and positions the middle position of the device 202 between the predetermined planned dividing line 201 and the planned dividing line 201 directly below the condenser 52. Then, the focusing point of the pulse laser beam emitted from the light collector 52 is positioned in the vicinity of the back surface (upper surface) of the semiconductor wafer 20. Pulse laser beam oscillating means 51 and pulse dispersing means 6 of laser beam irradiating means 5 and galvano scanner 91 as optical axis deflecting means 9 are operated, and X axis direction moving means 37 is operated to move chuck table 36 to arrow X1 in FIG. It moves at a predetermined moving speed in the direction indicated by. The XY coordinates of the four (I II III IV) pulse laser beams emitted from the pulse dispersion means 6 consisting of the Y coordinate dispersion means 7 and the X coordinate dispersion means 8 in the device 202 formed on the semiconductor wafer 20 The setting is made corresponding to the coordinates of the four bonding pads 203, so the pulse laser beam oscillated from the pulse laser beam oscillating means 51 is irradiated to the position corresponding to the four bonding pads 203. Then, while the chuck table 36 moves by a predetermined amount, the galvano scanner 91 operates as described above, so that the position corresponding to the four bonding pads 203 is irradiated with a predetermined number of pulse laser beams, and the semiconductor wafer 20 is irradiated. Communication holes (via holes) reaching the four bonding pads 203 are formed. In this manner, the laser processing step of forming the communication holes (via holes) at the positions corresponding to the four bonding pads 203 provided on all the formed devices 202 in the same row in the X-axis direction is performed. This laser processing step is performed at the positions corresponding to the four bonding pads 203 provided on all the devices 202 formed on the semiconductor wafer 20.

The said laser processing process is performed on the following processing conditions.
Laser beam source: YVO4 laser or YAG laser Wavelength: 355 nm
Repetition frequency: 40kHz
Average power: 4W
Focus spot diameter: φ10 μm
Processing feed rate: 100 mm / s Repetition frequency of the first complementary resonance scanner: 30 kHz
Repetition frequency of second complementary resonance scanner: 20 kHz
Repetitive frequency of main resonant scanner: 10kHz

  As described above, in the laser processing apparatus in the illustrated embodiment, the communication holes (via holes (via holes) at 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 At the time of forming (1), the pulse laser beam can be simultaneously irradiated to a plurality of coordinates at the maximum repetition frequency (10 kHz) which does not cause a crack, and the 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 dispersing means 7: Y coordinate dispersing means 71: first complementary resonant scanner 72: second complementary resonant scanner 73: main resonant scanner 8: X coordinate dispersing means 81: first complementary resonant scanner 82: second Complementary resonant scanner 83: Main resonant scanner 9: Optical axis deflection means 10: Control means 20: Semiconductor wafer

Claims (1)

A laser processing apparatus comprising: workpiece holding means for holding a workpiece on an XY plane; and laser beam irradiation means for irradiating a workpiece held by the workpiece holding means with a laser beam,
The laser beam application means comprises a pulse laser beam oscillation means for oscillating a pulse laser beam at a repetition frequency M, and a workpiece to be processed held by the workpiece holding means by condensing the pulse laser beam oscillated by the pulse laser beam oscillation means. And a pulse dispersion means disposed between the pulse laser beam oscillation means and the condenser for dispersing the pulse laser beam into a plurality of X coordinates and Y coordinates,
The pulse dispersion means has a mirror for reflecting 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 light at (M / M1) coordinates. A scanner , Y coordinate dispersing means for dispersing the pulse laser beam into a plurality of Y coordinates, and X coordinate dispersing means for dispersing the plurality of X coordinates;
The Y coordinate dispersing means includes a main scanner swinging at a repetition frequency M1 and a complementary scanner swinging at a repetition frequency that is an integral multiple of the repetition frequency M1 to disperse the pulse laser beam, the main scanner and the complementary scanner Shift the phase of the repetition frequency to identify the Y coordinate to which the pulsed laser beam is emitted,
The X coordinate dispersing means includes a main scanner swinging at a repetition frequency M1 and a complementary scanner swinging at a repetition frequency that is an integral multiple of the repetition frequency M1 to disperse a pulse laser beam; A laser processing device that shifts the phase of the repetition frequency to specify the X coordinate to which the pulsed laser beam is emitted .