JP7537894B2 - Laser processing equipment - Google Patents

Description

The present invention relates to a laser processing device that includes a holding means for holding a workpiece, a laser beam application means for applying a laser beam to the workpiece held by the holding means, and a feed means for feeding the holding means and the laser beam application means relative to each other for processing.

Wafer surfaces are divided into ICs, LSIs, and other devices along planned dividing lines, and are then divided into individual device chips using a dicing machine and laser processing machine. Each device chip is then used in electrical equipment such as mobile phones and personal computers.

The laser processing device includes a holding means for holding the workpiece, a laser beam application means for applying a laser beam to the workpiece held by the holding means, and a feed means for feeding the holding means and the laser beam application means relatively for processing, and can perform the desired processing on the workpiece (see, for example, Patent Document 1).

JP 2011-60862 A

However, the oscillator that emits the laser beam installed in the laser processing device has the pulse width of the laser beam set to a predetermined value according to the workpiece or the processing conditions. Therefore, when processing multiple types of workpieces or processing under multiple processing conditions, the user of the laser processing device must prepare many laser processing devices corresponding to each workpiece or each processing condition, which results in high equipment costs.

In light of the above, the objective of the present invention is to provide a laser processing device that can reduce equipment costs.

In order to solve the above problems, the present invention provides the following laser processing apparatus: That is, the laser processing apparatus includes a holding means for holding a workpiece, a laser beam application means for applying a laser beam to the workpiece held by the holding means, and a feed means for relatively feeding the holding means and the laser beam application means for processing, the laser beam application means including at least an oscillator for oscillating a laser beam and a condenser for focusing the laser beam oscillated by the oscillator on the workpiece held by the holding means, and a pulse width expander for expanding the pulse width of the laser beam is disposed between the oscillator and the condenser, and the pulse width expander is provided with a plurality of VBG crystals spaced apart in the circumferential direction for expanding the pulse width of the incident laser beam. The present invention provides a laser processing apparatus which includes a rotating body having a plurality of VBG crystals attached thereto at intervals in the circumferential direction, and a rotation mechanism which rotates the rotating body to position any one of the plurality of VBG crystals on the optical axis of the laser beam , and a pulse width reducer which reduces the pulse width of the laser beam is disposed between the pulse width expander and the collector, and the pulse width reducer includes a rotating body having a plurality of VBG crystals attached thereto at intervals in the circumferential direction, which reduce the pulse width of the incident laser beam, and a rotation mechanism which rotates the rotating body to position any one of the plurality of VBG crystals on the optical axis of the laser beam, and the pulse width expander can set the pulse width of the laser beam to a desired value by combining the pulse width expander and the pulse width reducer.

The laser processing apparatus of the present invention includes a holding means for holding a workpiece, a laser beam application means for applying a laser beam to the workpiece held by the holding means, and a feed means for relatively feeding the holding means and the laser beam application means for processing, and the laser beam application means includes at least an oscillator for emitting a laser beam, and a condenser for focusing the laser beam oscillated by the oscillator on the workpiece held by the holding means, and a pulse width stretcher for expanding the pulse width of the laser beam is disposed between the oscillator and the condenser , and the pulse width stretcher includes a rotor on which a plurality of VBG crystals for expanding the pulse width of the incident laser beam are mounted at intervals in the circumferential direction, and a rotor is rotated to focus the plurality of VBG crystals. and a rotation mechanism for positioning one of the VBG crystals on the optical axis of the laser beam, and a pulse width reducer for reducing the pulse width of the laser beam is disposed between the pulse width expander and the collector, and the pulse width reducer includes a rotor on which a plurality of VBG crystals for reducing the pulse width of the incident laser beam are mounted at intervals in the circumferential direction, and a rotation mechanism for rotating the rotor to position one of the plurality of VBG crystals on the optical axis of the laser beam, and the pulse width of the laser beam can be set to a desired value by the combination of the pulse width expander and the pulse width reducer, so that a user can perform desired processing by appropriately setting the pulse width of the laser beam in accordance with the workpiece or processing conditions, and equipment costs can be reduced.

1 is a perspective view of a laser processing apparatus configured according to the present invention; FIG. 2 is a block diagram of the laser beam application means shown in FIG. 1 . FIG. 3 is a perspective view of the pulse width stretcher shown in FIG. 2 . FIG. 3 is a perspective view of the pulse width reducer shown in FIG. 2 . FIG. 11 is a block diagram showing another embodiment of the laser beam application means.

Below, a preferred embodiment of a laser processing device constructed according to the present invention will be described with reference to the drawings.

The laser processing device 2 shown in FIG. 1 includes a holding means 4 for holding a workpiece, a laser beam application means 6 for applying a laser beam to the workpiece held by the holding means 4, and a feed means 8 for feeding the holding means 4 and the laser beam application means 6 relatively for processing.

The holding means 4 includes an X-axis movable plate 12 attached to the upper surface of the base 10 so as to be movable in the X-axis direction indicated by the arrow X in Fig. 1, a Y-axis movable plate 14 attached to the upper surface of the X-axis movable plate 12 so as to be movable in the Y-axis direction (direction indicated by the arrow Y in Fig. 1) perpendicular to the X-axis direction, a support 16 fixed to the upper surface of the Y-axis movable plate 14, and a cover plate 18 fixed to the upper end of the support 16. The XY plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

The cover plate 18 is formed with a long hole 18a extending in the Y-axis direction, and the chuck table 20, which extends upward through the long hole 18a, is rotatably attached to the upper end of the support 16. The chuck table 20 is rotated by a rotating means (not shown) built into the support 16. A porous circular suction chuck 22 connected to a suction means (not shown) is disposed at the upper end of the chuck table 20, and the suction means generates a suction force on the upper surface of the suction chuck 22, thereby suction-holding the workpiece placed on the upper surface of the suction chuck 22. In addition, a plurality of clamps 24 are disposed at intervals around the periphery of the chuck table 20.

As shown in FIG. 1, the laser beam application means 6 of the illustrated embodiment includes a housing 26 that extends upward from the upper surface of the base 10 and then extends substantially horizontally. Inside the housing 26, an oscillator 28 (see FIG. 2) that oscillates a laser beam LB is disposed. The oscillator 28 oscillates a laser beam LB (so-called seed light) with a repetition frequency of about several tens of MHz, an output of about several watts, and a pulse width of about several hundred fs.

As shown in FIG. 1, a condenser 30 is attached to the underside of the tip of the housing 26, which focuses the laser beam LB emitted by the oscillator 28 onto the workpiece held on the chuck table 20 of the holding means 4, and an imaging means 32 is attached to capture an image of the workpiece held on the chuck table 20 to detect the area to be laser processed. For convenience, in FIG. 2, the condenser 30 is shown in the form of a focusing lens.

With reference to FIG. 2, between the oscillator 28 and the condenser 30, there is provided an optical system 34 for adjusting the laser beam LB oscillated by the oscillator 28, and a first fixed mirror 36 for reflecting the laser beam LB that has passed through the optical system 34 and directing it to the condenser 30. The optical system 34 includes, for example, a relay lens, a mirror, and a beam splitter for directing the laser beam LB oscillated by the oscillator 28, a repetition frequency conversion means (not shown) for converting the repetition frequency of the laser beam LB oscillated by the oscillator 28 to an appropriate repetition frequency (for example, about several hundreds of kHz), an output amplification means (not shown) for amplifying the output of the laser beam LB oscillated by the oscillator 28 to an appropriate output (for example, about several tens of W), an output adjustment means (not shown) for adjusting the output of the laser beam LB amplified by the output amplification means to an appropriate output, and a wavelength conversion means (not shown) for converting the wavelength of the laser beam LB oscillated by the oscillator 28 to an appropriate wavelength.

As shown in FIG. 2, between the oscillator 28 and the collector 30 (between the oscillator 28 and the optical system 34 in the illustrated embodiment), there are disposed a pulse width expander 38 that expands the pulse width of the laser beam LB, a first movable mirror 40 that reflects the laser beam LB oscillated by the oscillator 28 and guides it to the pulse width expander 38, and a second fixed mirror 42 that reflects the laser beam LB that has passed through the pulse width expander 38 and guides it to the optical system 34.

As shown in FIG. 3, the pulse width expander 38 of the illustrated embodiment includes a cylindrical rotor 44 and a rotation mechanism 46 that rotates the rotor 44. Three VBG (Volume Bragg Grating) crystals 48a, 48b, and 48c that expand the pulse width of the incident laser beam LB are mounted on the rotor 44 at equal intervals in the circumferential direction.

In the illustrated embodiment, VBG crystal 48a expands the pulse width by 10 times, VBG crystal 48b expands the pulse width by 100 times, and VBG crystal 48c expands the pulse width by 1000 times. The pulse width expander 38 positions the VBG crystal 48a, 48b, or 48c on the optical axis of the laser beam LB by rotating the rotor 44 using the rotation mechanism 46.

The number of VBG crystals in the pulse width expander 38 is not limited to three and may be set arbitrarily. The expansion coefficient of the pulse width in the pulse width expander 38 is not limited to the above-mentioned 10 times, 100 times, and 1000 times, and may be any expansion coefficient. In addition, a known grating method having a grating mirror may be used as the pulse width expander 38.

As shown in FIG. 2, the first moving mirror 40 is positioned by the first moving mechanism 50 at a distanced position (position shown by a solid line in FIG. 2) away from the optical axis of the laser beam LB oscillated by the oscillator 28, and at a reflection position (position shown by a dashed line in FIG. 2) where the first moving mirror 40 reflects the laser beam LB oscillated by the oscillator 28.

When the first movable mirror 40 is positioned at the separated position, the laser beam LB generated by the oscillator 28 is guided to the optical system 34. On the other hand, when the first movable mirror 40 is positioned at the reflecting position, the laser beam LB generated by the oscillator 28 is reflected by the first movable mirror 40 and guided to the pulse width expander 38, enters the VBG crystal 48a, 48b or 48c, and has its pulse width expanded by 10 times, 100 times or 1000 times, and is then reflected by the second fixed mirror 42 and guided to the optical system 34.

In this way, in the laser beam application means 6, the pulse width (e.g., 100 fs) of the laser beam LB can be expanded to the desired value (1 ps, 10 ps, or 100 ps) by the VBG crystals 48a to 48c of the pulse width expander 38.

Continuing with the explanation with reference to FIG. 2, in the illustrated embodiment, between the pulse width expander 38 and the condenser 30 (specifically, between the pulse width expander 38 and the optical system 34) are disposed a pulse width reducer 52 that reduces the pulse width of the laser beam LB, a second movable mirror 54 that reflects the laser beam LB that has passed through the pulse width expander 38 and directs it to the pulse width reducer 52, and a third fixed mirror 56 that reflects the laser beam LB that has passed through the pulse width reducer 52 and directs it to the optical system 34.

As shown in FIG. 4, the pulse width reducer 52 of the illustrated embodiment includes a cylindrical rotor 58 and a rotation mechanism 60 that rotates the rotor 58. Eight VBG crystals 62a to 62h that reduce the pulse width of the incident laser beam LB are mounted on the rotor 58 at equal intervals in the circumferential direction.

In the illustrated embodiment, the VBG crystal 62a reduces the pulse width by 2/10, the VBG crystal 62b reduces the pulse width by 3/10, the VBG crystal 62c reduces the pulse width by 4/10, the VBG crystal 62d reduces the pulse width by 5/10, the VBG crystal 62e reduces the pulse width by 6/10, the VBG crystal 62f reduces the pulse width by 7/10, the VBG crystal 62g reduces the pulse width by 8/10, and the VBG crystal 62h reduces the pulse width by 9/10. The pulse width reducer 52 positions any one of the VBG crystals 62a to 62h on the optical axis of the laser beam LB by rotating the rotor 58 with the rotating mechanism 60.

The number of VBG crystals in the pulse width reducer 52 is not limited to eight and may be set arbitrarily. The pulse width reduction coefficient in the pulse width reducer 52 is not limited to the above-mentioned 2/10 to 9/10, and may be any reduction coefficient. In addition, a known grating method having a transmission grating may be used as the pulse width reducer 52.

As shown in FIG. 2, the second moving mirror 54 is positioned by the second moving mechanism 64 at a distanced position (position shown by a solid line in FIG. 2) away from the optical axis of the laser beam LB that has passed through the pulse width expander 38, and at a reflection position (position shown by a two-dot chain line in FIG. 2) at which the second moving mirror 54 reflects the laser beam LB that has passed through the pulse width expander 38.

When the second movable mirror 54 is positioned at the separated position, the laser beam LB that has passed through the pulse width expander 38 is reflected by the second fixed mirror 42 and guided to the optical system 34. On the other hand, when the second movable mirror 54 is positioned at the reflecting position, the laser beam LB that has passed through the pulse width expander 38 is reflected by the second movable mirror 54 and guided to the pulse width reducer 52, enters one of the VBG crystals 62a to 62h, and has its pulse width reduced to anywhere from 2/10 times to 9/10 times, and is then reflected by the third fixed mirror 56 and guided to the optical system 34.

In the laser beam application means 6 of the illustrated embodiment, the pulse width of the laser beam LB can be expanded to a desired value such as 10 times, 100 times, 1000 times, etc. by the VBG crystals 48a to 48c of the pulse width expander 38, and in addition, the pulse width of the laser beam LB can be set to a desired value such as 2 times, 3 times, 4 times, ..., 700 times, 800 times, 900 times, etc. by combining the VBG crystals 48a to 48c of the pulse width expander 38 with the VBG crystals 62a to 62h of the pulse width reducer 52.

The laser beam application means 6 is not limited to the above-mentioned form, and may be, for example, the form shown in FIG. 5. The laser beam application means 6 shown in FIG. 5 includes a first half-wave plate 66 arranged between the oscillator 28 and the optical system 34, a first motor 68 for rotating the first half-wave plate 66, a first polarizing beam splitter 70 for directing the laser beam LB that has passed through the first half-wave plate 66 to the optical system 34 or the pulse width expander 38, a second half-wave plate 72 arranged between the pulse width expander 38 and the second fixed mirror 42, a second motor 74 for rotating the second half-wave plate 72, and a second polarizing beam splitter 76 for directing the laser beam LB that has passed through the second half-wave plate 72 to the second fixed mirror 42 or the pulse width reducer 52.

The first half-wave plate 66 is positioned by the first motor 68 to a P-polarization position that adjusts the polarization plane of the laser beam LB relative to the first polarizing beam splitter 70 to P-polarization, and an S-polarization position that adjusts the polarization plane of the laser beam LB relative to the first polarizing beam splitter 70 to S-polarization.

When the first half-wave plate 66 is positioned in the P polarization position, the laser beam LB emitted by the oscillator 28 has its polarization plane adjusted to P polarization with respect to the first polarizing beam splitter 70 by the first half-wave plate 66, and then passes through the first polarizing beam splitter 70 and is guided to the optical system 34.

On the other hand, when the first half-wave plate 66 is positioned at the S-polarization position, the laser beam LB emitted by the oscillator 28 has its polarization plane adjusted to S-polarization relative to the first polarizing beam splitter 70 by the first half-wave plate 66, and is then reflected by the first polarizing beam splitter 70 and guided to the pulse width expander 38, where it enters the VBG crystal 48a, 48b or 48c and has its pulse width expanded by 10 times, 100 times or 1000 times.

The second half-wave plate 72 is positioned by the second motor 74 to a P-polarization position that adjusts the polarization plane of the laser beam LB relative to the second polarizing beam splitter 76 to P-polarization, and an S-polarization position that adjusts the polarization plane of the laser beam LB relative to the second polarizing beam splitter 76 to S-polarization.

When the second half-wave plate 72 is positioned in the P polarization position, the laser beam LB that passes through the pulse width expander 38 has its polarization plane adjusted to P polarization by the second half-wave plate 72 with respect to the second polarizing beam splitter 76, and then passes through the second polarizing beam splitter 76, is reflected by the second fixed mirror 42, and is directed to the optical system 34.

On the other hand, when the second half-wave plate 72 is positioned at the S-polarization position, the laser beam LB that has passed through the pulse width expander 38 is adjusted by the second half-wave plate 72 to have its polarization plane adjusted to S-polarization relative to the second polarizing beam splitter 76, and is then reflected by the second polarizing beam splitter 76 and guided to the pulse width reducer 52, where it enters one of the VBG crystals 62a to 62h and has its pulse width reduced to anywhere between 2/10 and 9/10 times, and is then reflected by the third fixed mirror 56 and guided to the optical system 34.

Therefore, even in the configuration shown in FIG. 5, the pulse width of the laser beam LB can be expanded to a desired value by the VBG crystals 48a to 48c of the pulse width expander 38, and the pulse width of the laser beam LB can be set to a desired value by combining the VBG crystals 48a to 48c of the pulse width expander 38 with the VBG crystals 62a to 62h of the pulse width reducer 52.

The feed means 8 will be described with reference to FIG. 1. The feed means 8 in the illustrated embodiment includes an X-axis feed means 78 that feeds the holding means 4 and the laser beam application means 6 relatively in the X-axis direction, and a Y-axis feed means 80 that indexes and feeds the holding means 4 and the laser beam application means 6 relatively in the Y-axis direction.

The X-axis feed means 78 has a ball screw 82 that extends in the X-axis direction along the top surface of the base 10, and a motor 84 that rotates the ball screw 82. A nut portion (not shown) of the ball screw 82 is connected to the X-axis movable plate 12. The X-axis feed means 78 converts the rotational motion of the motor 84 into linear motion using the ball screw 82 and transmits it to the X-axis movable plate 12, and feeds the X-axis movable plate 12 in the X-axis direction along the guide rail 10a on the base 10 relative to the laser beam application means 6.

The Y-axis feed means 80 has a ball screw 86 that extends in the Y-axis direction along the upper surface of the Y-axis movable plate 14, and a motor 88 that rotates the ball screw 86. A nut portion (not shown) of the ball screw 86 is connected to the Y-axis movable plate 14. The Y-axis feed means 80 converts the rotational motion of the motor 88 into linear motion using the ball screw 86 and transmits it to the Y-axis movable plate 14, indexing and feeding the Y-axis movable plate 14 in the Y-axis direction relative to the laser beam application means 6 along the guide rail 12a on the X-axis movable plate 12.

Figure 1 shows a wafer 90 as a workpiece to be processed using a laser processing device 2. The disk-shaped wafer 90 may be made of, for example, silicon. The front surface 90a of the wafer 90 is partitioned into a plurality of rectangular regions by lattice-shaped division lines 92, and a plurality of devices 94 such as ICs and LSIs are formed in each of the rectangular regions. In the illustrated embodiment, the back surface 90b of the wafer 90 is attached to an adhesive tape 98 whose periphery is fixed to an annular frame 96.

When performing laser processing on the wafer 90 using the laser processing device 2 as described above, first, the wafer 90 is suction-held on the upper surface of the chuck table 20. In addition, the annular frame 96 is fixed with a plurality of clamps 24. Next, the wafer 90 is imaged from above by the imaging means 32, and based on the image of the wafer 90 captured by the imaging means 32, the planned division line 92 is aligned in the X-axis direction, and the light collector 30 is positioned above the planned division line 92 aligned in the X-axis direction.

Next, the first and second movable mirrors 40, 54 are moved to set the optical path of the laser beam LB from the oscillator 28 to the optical system 34, and the pulse width of the laser beam LB irradiated to the wafer 90 is set to the desired value by appropriately selecting the combination of the VBG crystals 48a to 48c of the pulse width expander 38 and the VBG crystals 62a to 62h of the pulse width reducer 52.

Then, while the chuck table 20 is moved relative to the collector 30 in the X-axis direction at a predetermined feed rate, the pulse width is set to a desired value by the combination of the pulse width expander 38 and the pulse width reducer 52, and the laser beam LB, which has been converted to an appropriate repetition frequency, output, and wavelength by the optical system 34, is irradiated onto the wafer 90 along the intended division line 92 to perform laser processing.

Examples of laser processing performed on the wafer 90 include modified layer formation processing, in which a focal point of a laser beam having a wavelength that is transparent to the wafer 90 is positioned inside the wafer 90 and the laser beam is irradiated onto the wafer 90 to form a modified layer inside the wafer 90 along the intended division line 92, and ablation processing, in which a focal point of a laser beam having a wavelength that is absorbent to the wafer 90 is positioned on the surface 90a of the wafer 90 and the laser beam is irradiated onto the wafer 90 to form a groove along the intended division line 92.

Next, the chuck table 20 is indexed and fed in the Y-axis direction relative to the collector 30 by an amount equal to the spacing of the planned division lines 92 in the Y-axis direction. By alternately repeating laser processing and indexing, all of the planned division lines 92 aligned in the X-axis direction are laser processed. Then, the chuck table 20 is rotated 90 degrees, and by alternately repeating laser processing and indexing, all of the planned division lines 92 that are perpendicular to the planned division lines 92 that were previously laser processed are also laser processed.

As described above, in the laser processing device 2 of the illustrated embodiment, the pulse width of the laser beam LB can be set to a desired value, so that the user can perform the desired processing by appropriately setting the pulse width of the laser beam LB according to the workpiece or processing conditions. Therefore, with the laser processing device 2 of the illustrated embodiment, it is not necessary to prepare many laser processing devices corresponding to each workpiece or each processing condition, so equipment costs can be reduced.

2: Laser processing device 4: Holding means 6: Laser beam application means 8: Feed means 28: Oscillator 30: Condenser 38: Pulse width expander 52: Pulse width reducer

Claims (1)

A laser processing apparatus including a holding means for holding a workpiece, a laser beam application means for applying a laser beam to the workpiece held by the holding means, and a feed means for relatively feeding the holding means and the laser beam application means for processing,
the laser beam application means includes at least an oscillator that oscillates a laser beam, and a condenser that condenses the laser beam oscillated by the oscillator onto the workpiece held by the holding means;
A pulse width stretcher for expanding the pulse width of the laser beam is disposed between the oscillator and the condenser, and the pulse width stretcher includes a rotor on which a plurality of VBG crystals for expanding the pulse width of the incident laser beam are mounted at intervals in the circumferential direction, and a rotation mechanism for rotating the rotor to position any one of the plurality of VBG crystals on the optical axis of the laser beam,
A pulse width reducer for reducing the pulse width of the laser beam is disposed between the pulse width expander and the condenser, and the pulse width reducer includes a rotor on which a plurality of VBG crystals for reducing the pulse width of the incident laser beam are mounted at intervals in the circumferential direction, and a rotation mechanism for rotating the rotor to position any one of the plurality of VBG crystals on the optical axis of the laser beam,
A laser processing device capable of setting the pulse width of a laser beam to a desired value by combining the pulse width expander and the pulse width reducer.