JP2007237210A - Laser beam machining method and apparatus - Google Patents

Laser beam machining method and apparatus Download PDF

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JP2007237210A
JP2007237210A JP2006061364A JP2006061364A JP2007237210A JP 2007237210 A JP2007237210 A JP 2007237210A JP 2006061364 A JP2006061364 A JP 2006061364A JP 2006061364 A JP2006061364 A JP 2006061364A JP 2007237210 A JP2007237210 A JP 2007237210A
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fluence
laser beam
irradiating
pulse
workpiece
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Masayuki Fujita
Yusaku Izawa
Hiroyuki Nagai
Ryuichiro Sasaki
Mutsumi Yoshida
友策 井澤
睦 吉田
裕之 永井
隆一郎 笹木
雅之 藤田
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Aisin Seiki Co Ltd
Laser Gijutsu Sogo Kenkyusho
アイシン精機株式会社
財団法人レーザー技術総合研究所
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Abstract

To provide a laser processing method and apparatus for removing a brittle material such as a semiconductor crystal while suppressing generation of chipping and cracking.
SOLUTION: A low fluence irradiating means 2 for irradiating a surface of a crystalline workpiece 6 with a pulsed laser beam at a predetermined low fluence, and a pulsed laser beam on an irradiation area of the workpiece radiated by the low fluence irradiating means 2. And a high fluence irradiating means 2 for irradiating with a predetermined high fluence that changes the surface shape of the workpiece 6.
[Selection] Figure 1

Description

  The present invention relates to a laser processing method and apparatus, and more particularly to a laser processing method and apparatus for removing a brittle material such as a semiconductor crystal while suppressing the occurrence of chipping and cracking (drilling, grooving, scribing, etc.).

  Drilling, grooving, and cutting can be performed by focusing and irradiating a workpiece with pulsed laser light or cw laser light with a pulse time width (hereinafter simply referred to as pulse width) of nanoseconds or more. Has been known for a long time (for example, see Non-Patent Document 1).

  Recently, when a workpiece is irradiated with a short pulse laser beam having a pulse width on the order of femtoseconds to picoseconds, the irradiation region may be ablated and removed when the fluence is equal to or greater than the ablation threshold of the workpiece. It is known (see, for example, Non-Patent Document 2). Removal processing such as grooving and cutting can be performed by scanning the laser beam or scanning the workpiece.

Further, in order to assemble semiconductor elements formed on a semiconductor wafer into individual semiconductor devices, it is necessary to divide the wafer into semiconductor chips. Conventionally, the wafer has been cut and cut with a blade.
Fumio Inaba, other edition "Laser Handbook" published by Asakura Shoten, February 20, 1973, p. 695-699 J. Bovatsek, et. Al. "Laser Ablation Threshold and Etch Rate Comparison Between the Ultrafast Yb Fiber-based FCPA Laser and a Ti: Sapphire Laser for Various Materials" Proceedings of the 5th International Symposium on Laser Precision Microfabrication, 2004.

  However, in the conventional laser processing using laser light and mechanical processing using a blade or the like, when the workpiece is a crystalline brittle material, due to thermal or / and mechanical stress due to removal processing, for example, in the case of groove cutting, Cracks and chipping occur on the side walls and bottom. As a result, for example, in the case of manufacturing a semiconductor chip, as the chip size becomes smaller, cracks and chipping cause the performance of the semiconductor device to deteriorate, and the defect rate increases.

  The present invention has been made in view of the problems of the conventional laser processing method and machining, and provides a laser processing method and apparatus for removing brittle materials such as semiconductor crystals while suppressing the occurrence of chipping and cracking. The challenge is to do.

  The invention according to claim 1 made to solve the problem comprises an amorphization step of amorphizing the irradiated region by irradiating the surface of a crystalline workpiece with a pulsed laser beam at a predetermined low fluence, and the amorphous And a removing step of irradiating the irradiation region made amorphous in the forming step with a predetermined high fluence to remove the irradiation region.

  Since removal processing is performed after the crystalline workpiece is made amorphous to reduce brittleness, occurrence of chipping and cracking can be suppressed.

  The invention according to claim 2 to solve the problem includes an amorphization step of amorphizing the irradiated region by irradiating a surface of a crystalline workpiece with a pulsed laser beam at a predetermined low fluence, and the amorphous And a machining process for machining the irradiation region that has been made amorphous in the forming process.

  Since the removal process is performed by machining, the processing cost can be reduced.

  The invention according to claim 3 made to solve the problem comprises an amorphization step of amorphizing the irradiated region by irradiating the surface of the crystalline workpiece with a first pulse laser beam at a predetermined low fluence, And a removal step of irradiating the irradiation region amorphousized in the amorphization step with a second pulse laser beam at a predetermined high fluence to remove the irradiation region.

  Since separate pulse laser beams are used for amorphization and removal, laser characteristics (pulse width, wavelength) suitable for amorphization and laser characteristics suitable for removal can be selected.

  The invention according to claim 4 is the laser processing method according to any one of claims 1 to 3, wherein the object to be processed is a semiconductor, and the photon energy of the pulse laser light or the first pulse laser light. Is smaller than the band gap of the semiconductor.

  The range of low fluence that causes amorphization is wide, and it becomes easy to set the fluence in the amorphization process.

  The invention according to claim 5 made to solve the problem is a low fluence irradiating means for irradiating a surface of a crystalline workpiece with a pulsed laser beam at a predetermined low fluence, and the low fluence irradiating means. A laser processing apparatus, comprising: a high fluence irradiation unit configured to irradiate the irradiation region of the processing object with the pulsed laser light at a predetermined high fluence that changes the surface shape of the processing object.

  The irradiated region can be made amorphous by irradiating the pulsed laser beam with a predetermined low fluence where the crystalline workpiece is made amorphous by the low fluence irradiating means, and the amorphous irradiated region is made by the high fluence irradiating means. Since removal processing is performed, occurrence of cracking and chipping can be suppressed.

  The invention according to claim 6 is the laser processing apparatus according to claim 5, wherein the low fluence irradiating means and the high fluence irradiating means apply the pulse laser beam to the surface of the object to be processed. It is characterized by sharing a condensing optical system for controlling a spot diameter formed by condensing.

  Since the low fluence irradiation means and the high fluence irradiation means share the condensing optical system, the laser processing apparatus can be reduced in size.

  The invention according to claim 7 is the laser processing apparatus according to claim 6, wherein the low fluence irradiating means and the high fluence irradiating means are pulses for controlling a time-axis pulse shape of the pulse laser light. It is characterized by including shape control means.

  With the pulse shape control means, the intensity distribution at the rising and falling parts of the pulse is set to a predetermined low fluence, and the intensity distribution at the peak is set to a predetermined high fluence, so that it becomes amorphous by single shot (single pulse irradiation). Removal processing can be performed.

  The invention according to claim 8 made to solve the problem is a low fluence irradiating means for irradiating a surface of a crystalline workpiece with a pulsed laser beam at a predetermined low fluence, and the low fluence irradiating means. And a machining means for machining an irradiation area of the workpiece.

  Since removal processing is performed by machining means, the processing cost can be reduced.

  The invention according to claim 9 made to solve the problem includes a low fluence irradiating means for irradiating a surface of a crystalline workpiece with a first pulse laser beam at a predetermined low fluence, and irradiating with the low fluence irradiating means. And a high fluence irradiating means for irradiating a second pulsed laser beam at a predetermined high fluence that changes the surface shape of the object to be processed on the irradiated region of the object to be processed. It is.

  Since the pulse laser beams of the low fluence irradiation means and the high fluence irradiation means are different, laser characteristics (pulse width, wavelength) suitable for amorphization and laser characteristics suitable for removal can be selected.

  The invention according to claim 10 is the laser processing apparatus according to any one of claims 5, 8, and 9, wherein the object to be processed is a semiconductor, and the pulse laser beam or the first pulse laser beam is used. The photon energy is smaller than the band gap of the semiconductor.

  The range of low fluence causing amorphization is wide, and it becomes easy to set the fluence with the low fluence irradiation means.

  Since removal processing is performed after the crystalline workpiece is made amorphous to reduce brittleness, occurrence of chipping and cracking can be suppressed.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
The laser processing apparatus of this embodiment is a type that sequentially irradiates the same pulsed laser beam. As shown in FIG. 1, the xyz three-axis movement that moves the pulse laser light source 1, the fluence control means 2, and the workpiece 6 is performed. And a stage 5.

  As the pulse laser light source 1, for example, a fiber chirped pulse amplification (FCPA) light source can be used. The FCPA light source is a light source that combines a mode-locked fiber laser and a chirped pulse amplifier, and outputs, for example, laser light having a center wavelength of 1558 nm, a typical pulse width of 870 fs, and a repetition frequency of 172.9 kHz. The spatial beam profile is Gaussian.

  The fluence control means 2 includes a pulse laser light energy adjuster 21 and a condensing optical system 22, and is also a low fluence irradiation means and a high fluence irradiation means. For example, when condensing optical system 22 is fixed by adjusting the position in the z-axis direction so that the position of the beam waist coincides with the surface of workpiece 6 when the condensing optical system 22 condenses laser light. When the energy is reduced by the energy adjuster 21, it functions as a low fluence irradiation means. On the other hand, when energy is increased by the energy regulator 21, it functions as a high fluence irradiation means. As the energy adjuster 21, for example, an ND filter or a combination of a λ / 2 plate and a polarizer can be used. As the condensing optical system 22, a single lens or a microscope objective lens can be used. Incidentally, in the present embodiment, a combination of a λ / 2 plate and a polarizing beam splitter is used for the energy adjuster 21 and a 100 × objective lens of NA 0.8 is used for the condensing optical system 23.

  As described above, the fluence control means 2 that is also the low fluence irradiation means and the high fluence irradiation means includes the energy adjuster 21 and the condensing optical system 22, but omits the energy adjuster 21 and collects the condensing optics. Only system 23 can be used. As a result, the processing apparatus can be reduced in size. When the condensing optical system 22 is moved in the z-axis direction as indicated by the dotted arrow A, or the workpiece 6 is moved in the z-axis direction by the moving stage 5, the condensing spot diameter on the surface of the workpiece 6 is increased. Because it changes, you can change the fluence. That is, as shown in FIG. 2A, when the condensing point p of the condensing optical system 22 is adjusted to a position D above the surface 6a of the workpiece 6, the condensing spot diameter on the surface 6a increases. , Decrease fluence. Since the focused spot diameter depends on D, by changing D, the fluence can be set to a predetermined low fluence. If D is made small, that is, D = 0, the focused spot diameter is minimized (see FIG. 2B), and the fluence is maximized. Therefore, by reducing D, the fluence can be set to a predetermined high fluence.

  Reference numeral 3 denotes a polarization controller, for example, a λ / 4 plate. When the laser light is linearly polarized light, polarization dependency can be eliminated by changing to circularly polarized light. Reference numeral 4 denotes a bending mirror.

  In order for an object to be processed to be amorphous without being removed, the fluence must be made equal to or less than the removal threshold. Since the removal processing threshold (including the ablation threshold) is related to the material of the workpiece, the wavelength of the laser beam, the pulse width, etc., the range of low fluence to be amorphized is the material of the workpiece, the wavelength of the laser beam It depends on the pulse width of the laser beam and needs to be determined experimentally.

  Therefore, first, experiments and results performed for obtaining a predetermined low fluence value to be amorphized by the laser processing apparatus of the present embodiment will be described. The workpiece 6 is a Si (100) wafer having a thickness of 545 μm, the pulse laser light source 1 is the FCPA light source having a center wavelength of 1558 nm, a pulse width of 870 fs, and a repetition frequency of 172.9 kHz, and the fluence control means 2 changes the fluence. The relationship between fluence and amorphization was investigated. Since the repetition frequency is 172.9 kHz, the workpiece 6 was scanned with the moving stage 5 in the x-axis direction at a speed of 750 mm / s so as to obtain a single shot. The reason why the single shot is used is that the fluence cannot be made extremely small in the laser processing apparatus of the present embodiment. Therefore, when the double shot is used, the fluence doubles and ablation occurs.

  When D = 0 and the fluence is changed from low to high with the energy adjuster 21 alone and the pulsed laser light is irradiated to the Si wafer, if the fluence is too low, the inside and of course the surface will not change, but the fluence is high. Then, as shown in FIG. 3A, a whitish circular pattern close to the focused spot diameter is observed. When the fluence is further increased, a crater due to ablation is observed in a whitish circular pattern as shown in FIG. The white color appears to be due to the change in the refractive index of the pulse laser irradiation region. FIG. 4 is a cross-sectional TEM photograph of the circular pattern of FIG. 3A. From FIG. 4A, it can be seen that the depth of the whitish altered layer is about 0.05 μm. FIG. 4B is a TEM photograph in which the vicinity of the center of FIG. It can be seen that a regular pattern is observed in the layer below the whitish alteration layer, whereas no observation is observed in the whitish alteration layer, and the whitish alteration layer is amorphous.

  In order to obtain the range of the predetermined low fluence value to be amorphized, as described above, if TEM observation is performed one by one, it becomes an enormous amount of experiment. Therefore, TEM observation was stopped appropriately. Instead, the lower limit of the predetermined low fluence was determined from the relationship between the size of the circular pattern that changed to whitish and the fluence, and the upper limit of the predetermined low fluence was determined from the relationship between the ablation depth and the fluence as follows.

The diameter of the circular pattern that changes to whitish is D, the diameter of the focused spot is 2ω, the peak fluence at the focused spot is F 0 , the lower limit of the fluence that changes to whitish, that is, the lower limit of the predetermined low fluence value to be amorphized is F l th , Then, the following relationship is established.

D 2 = (2ω) 2 ln (F 0 / F l th ) (1)
Ablation depth is L, multiphoton absorption order is n, multiphoton absorption coefficient is α n , ablation threshold, that is, upper limit of predetermined low fluence value to be amorphized, F u th , focused spot fluence is F, pulse When the width is τ, the following relationship is established.

L = {1 / (n−1) α n } {(F u th / τ) 1−n − (F / τ) 1−n } (2)
Figure 5 takes the square namely D 2 diameter of the circular pattern alteration whitish vertical axis is a plot of experimental values taking a peak fluence F 0 on the horizontal axis. The straight line connecting the experimental data is obtained by fitting the equation (1), and it can be seen from this that the lower limit F l th = 0.53 J / cm 2 of the predetermined low fluence value to be amorphized.

FIG. 6 is a graph in which experimental values are plotted with the ablation depth L on the vertical axis and the fluence F on the horizontal axis. The curve connecting the experimental data is obtained by fitting the equation (2). From this, it can be seen that the upper limit F u th = 0.73 J / cm 2 of the predetermined low fluence value to be amorphized.

From the above, in the case of an FCPA light source with a wavelength of 1558 nm, the range of the predetermined low fluence value to be amorphized is 0.53 to 0.73 J / cm 2 .

On the other hand, when the same experiment was performed using the pulse laser light source 1 as a pulse laser light source having a wavelength that is significantly different from 800 nm, the range of a predetermined low fluence value for amorphization is 0.26 to 0.29 J / cm 2. Met. Therefore, in the case of Si, the range of a predetermined low fluence that is made amorphous by irradiation with a pulse laser having a wavelength of 1558 nm is wide and easy to control. The reason why the range is wide is that the photon energy of a pulse laser with a wavelength of 1558 nm is as small as 0.79 eV while the band gap of Si is 1.15 eV.

  Next, the experiment and result performed in order to obtain | require the predetermined | prescribed low fluence value amorphousized with the laser processing apparatus of this embodiment and its laser pulse width dependence are demonstrated.

  The workpiece 6 is a Si (100) wafer having a thickness of 545 μm, the pulse laser light source 1 is a titanium sapphire laser light source having a central wavelength of 800 nm and a repetition frequency of 1 kHz, and a pulse compressor with a built-in laser light source is adjusted to a pulse width of 100 fs. The fluence control means 2 was used to change the fluence, and the relationship between the pulse width, the fluence, and the amorphization was examined.

  After setting the pulse width, the laser beam was irradiated to the same point a plurality of times, the region that was whitishly altered in the laser spot was measured, and the range of a predetermined low fluence was obtained by equation (1). When laser light with a wavelength of 800 nm was irradiated, the region that was whitishly changed to a ring-shaped pattern. Therefore, it can be seen that whether the region that changes to whitish becomes a ring shape or a circle differs depending on the laser wavelength. Increasing the number of irradiations increased the width of the ring and confirmed the growth of the amorphous region. Ablation occurred above a certain number of irradiations.

  The narrowest ring that was observed was named the S-ring, and the widest ring just before the ablation was named the L-ring, and the inner and outer diameters of each ring were measured. The irradiation fluence at the location to be evaluated was evaluated by the equation (1). A similar experiment was performed with the pulse widths changed to 100 fs, 400 fs, 1 ps, and 4 ps. The number of times of irradiation leading to ablation varies depending on the pulse width.

  FIG. 7 is a graph in which experimental values are plotted by taking the fluence of the portion corresponding to the inner diameter and outer diameter of the ring-shaped pattern generated by whitening due to amorphization on the vertical axis and taking the pulse width on the horizontal axis. FIG. 7 is a log-log graph display. The straight lines connecting the data points intersect at a pulse width of 8 ps (8000 fs).

  Therefore, it can be seen that the range of the predetermined low fluence value for amorphization becomes narrower as the pulse width becomes longer, and stable amorphization cannot be realized when the pulse width is 8 ps or more. The upper limit of the pulse width varies depending on the wavelength of the laser beam and the physical property value of the workpiece.

  From the above experiment, the wavelength of the laser light is preferably in the range of 200 to 2000 nm. When the object to be processed is a semiconductor material, the range of 400 to 1600 nm is more desirable. Further, the pulse width of the laser light is preferably in the range of 10 fs to 8 ps. Therefore, short pulse laser light is desirable as the pulse laser light to be amorphized.

  Next, each process when the workpiece 6 is a Si (100) wafer having a thickness of 545 μm and the pulse laser light source 1 is the FCPA light source having a center wavelength of 1558 nm, a pulse width of 870 fs, and a repetition frequency of 172.9 kHz. explain.

<Preparation process>
The workpiece 6 (Si wafer) is set on the moving stage 5 and the surface is adjusted so that the surface becomes the beam waist position of the objective lens 22 of 100 times.

<Amorphization process>
First, the energy adjuster 21 is adjusted so that the fluence at the position of the beam waist (waist diameter 2ω) of the objective lens 22 becomes a predetermined low fluence, for example, 0.6 J / cm 2 , and a shutter (not shown). Turn off. Next, by moving the moving stage 5 and turning on the shutter and irradiating the pulse laser beam with a fluence of 0.6 J / cm 2 , an elongated region having a width of about 2ω, a length h, and a depth δ is made amorphous. Is done. The length h depends on the moving speed of the moving stage 5 and the time during which the shutter is on. The depth δ is about 0.05 μm according to experiments.

<Removal process>
First, the moving stage 5 is returned to the initial stage of the amorphization process. Next, a predetermined high fluence for ablating the fluence at the position of the beam waist of the objective lens 22, for example, 0.9 J / cm 2 (in this case, the predetermined high fluence is equal to or greater than the ablation threshold). The energy adjuster 21 is adjusted to turn off a shutter (not shown). Next, the moving stage 5 is moved, the shutter is turned on, and pulsed laser light is applied to the region that has been amorphized in the amorphization process with a fluence of 0.9 J / cm 2 in an overlapping manner, thereby obtaining a width 2ω ′ (ω > Ω ′), a long groove having a length h and a depth δ ′ (δ> δ ′) is formed.

  In the present embodiment, since the crystalline workpiece is made amorphous to reduce brittleness and then removed, chipping and cracking can be suppressed.

  The predetermined high fluence is preferably set close to the ablation threshold. If the ablation threshold value is greatly exceeded, ω <ω ′ and δ <δ ′, and the ablation region becomes larger than the amorphized region. As a result, cracks and chipping are likely to occur around the groove.

  In order to cut deep grooves while suppressing cracks and chipping, the above <amorphization step> and <removal step> may be repeated.

  Next, a modification of this embodiment will be described with reference to FIG. In FIG. 8, the same components as those of the laser processing apparatus of the first embodiment shown in FIG. For example, 23 is a partially reflecting mirror that reflects 20% and transmits 80%. Reference numeral 23 'denotes a total reflection mirror. The workpiece 6 is moved in the direction of arrow C by the moving stage 6 and is first irradiated with pulsed laser light at a predetermined low fluence by the condensing optical system 22. Next, when the workpiece 6 moves to the position indicated by the dotted line, the condensing optical system 22 'irradiates the pulse laser beam with a predetermined high fluence.

<Preparation process>
The condensing spot areas on the surface of the object 6 to be processed by the condensing optical systems 22 and 22 ′ are S and S ′, respectively. Assuming that the energy of the pulse laser beam is E, the fluences of the focused irradiation region of the workpiece 6 by the focusing optical systems 22 and 22 ′ are ER / S and ET / S ′, respectively. Therefore, first, the energy adjuster 21 and the position of the condensing optical system 22 'are adjusted so that ET / S' is equal to a predetermined high fluence, that is, 0.9 J / cm 2 or more equal to or greater than the ablation threshold of Si. To be. Next, the condensing optical system 22 is adjusted so that ER / S becomes equal to a predetermined low fluence, for example, 0.6 J / cm 2 .

<Amorphization process>
As shown in FIG. 8, the workpiece 6 indicated by the solid line is first irradiated with a pulsed laser beam with a fluence of 0.6 J / cm 2 by the condensing optical system 22 while moving in the arrow C direction. The formed region is made amorphous.

<Removal process>
When the workpiece 6 moves in the direction of arrow C and reaches the condensing spot area of the condensing optical system 22 ', the pulse laser beam is 0.9 J / cm 2 fluence in the amorphized area in the amorphization process. It is irradiated with and the groove is cut.

  In this modification, since the amorphization and the removal processing are sequentially performed only by moving the processing object, it is not necessary to return the processing object one by one as in the first embodiment. As a result, the processing time can be shortened.

(Embodiment 2)
The laser processing apparatus of this embodiment is the same as the laser processing apparatus of Embodiment 1 shown in FIG. The fluence control means 2 which is also the low fluence irradiation means and the high fluence irradiation means in the first embodiment is a pulse shape control means for controlling the time-axis pulse shape of the pulse laser light in the second embodiment.

The pulse traveling in the direction of arrow B in FIG. 1 reaches the workpiece 6, but FIG. 9 schematically shows the pulse that arrives with time on the horizontal axis and intensity on the vertical axis. is there. That is, first, the rising edge E r of the pulse arrives, then the peak E m arrives, and finally the falling edge E f arrives. E r and E f are the hatched area, E m is the hatched area, and E r , E m , and E f are energy (J). Dividing by S (cm 2 ) gives fluence. Therefore, the condensing spot of the workpiece 6 first becomes a fluence of E r / S, and then becomes a fluence of E m / S and E f / S. By appropriately adjusting the energy with the energy adjuster 21, the predetermined low fluence for amorphizing E r / S and the predetermined high fluence for ablating E m / S (above the ablation threshold of the workpiece) By doing so, amorphization with a single shot and subsequent ablation can be performed continuously.

There is a limit to using the energy regulator 21 alone to achieve a predetermined low fluence for amorphizing E r / S and a predetermined high fluence for ablating E m / S. For example, the FCPA light source used in Embodiment 1 can change the average output by changing the pump power, and can change the energy of one pulse by changing the average output. Therefore, the limit can be relaxed by changing the average output of the FCPA light source 1 and adjusting the energy by the energy adjuster 21. By the way, in the FCPA light source, a laser pulse from a mode-locked fiber laser is extended by an expander, then amplified by a fiber amplifier, and compressed by a compressor. When the pump power of the fiber amplifier is increased, nonlinear effects such as self-phase modulation and stimulated Raman scattering become significant, and a pedestal component is generated as shown in FIG. FIG. 10A shows a pedestal-free pulse when the pumping power is optimal, and FIG. 10B shows a pulse having a pedestal component by increasing the pumping power. Therefore, the limit can be further relaxed by changing the pumping power. As can be understood from the above description, the pulse shape control means of claim 7 includes, for example, the FCPA light source 1 and the energy adjuster 21.

  In this embodiment, the pulse shape control means sets the intensity distribution of the rising and falling parts of the pulse to a predetermined low fluence and the intensity distribution of the peak to a predetermined high fluence so that a single shot (single pulse irradiation) ) Can be amorphized and removed.

(Embodiment 3)
The laser processing apparatus of this embodiment is a type that performs machining after irradiating a pulse laser beam to make it amorphous, and as shown in FIG. 11, a pulse laser light source 1, a fluence control means 2, and a workpiece 6 are provided. An xyz triaxial moving stage 5 to be moved and a dicing blade 7 are provided.

  Next, each process of this embodiment is demonstrated.

<Amorphization process>
Since the amorphization process is the same as that of the first embodiment, the description thereof is omitted.

<Machining process>
Grooves are cut by cutting the region amorphized in the amorphization step with a dicing blade.

  In the present embodiment, since the removal process is performed by machining, the processing cost can be reduced.

(Embodiment 4)
The laser processing apparatus according to the present embodiment is a type that sequentially irradiates different pulse laser beams. As shown in FIG. High fluence irradiation means 2 for irradiating the irradiation region of the workpiece 6 irradiated by the fluence irradiation means 2 and the low fluence irradiation means with a predetermined high fluence in which the surface shape of the workpiece 6 changes. 'And a switching mirror 4' for switching between the first pulsed laser beam and the second pulsed laser beam.

  Reference numeral 1 denotes a pulse laser light source that outputs a first pulse laser beam. For example, a laser beam having a center wavelength of 1558 nm, a typical pulse width of 870 fs, and a repetition frequency of 172.9 kHz is output. The low fluence irradiation means 2 includes an energy adjuster 21 and a condensing optical system 22, and adjusts the first pulse laser light output from the pulse laser light source 1 to a predetermined low fluence to irradiate the workpiece 6. .

  Reference numeral 1 ′ denotes a pulse laser light source that outputs a second pulse laser beam, which is, for example, a third harmonic generator of a Q-switched Nd: YAG laser. For example, the light source 1 'outputs laser light having a wavelength of 355 nm, a pulse width of 30 ns, and a repetition frequency of 50 kHz. The high fluence irradiating means 2 ′ includes an energy adjuster 22 ′ and a condensing optical system 22 ′, and adjusts the second pulse laser beam output from the pulse laser light source 1 ′ to a predetermined high fluence so as to process the workpiece 6. Irradiate.

  In this embodiment, since separate pulse laser beams are used for amorphization and removal, laser characteristics (pulse width, wavelength) suitable for amorphization and laser characteristics suitable for removal can be selected.

  In particular, it is highly likely to be used for manufacturing semiconductor devices in the electrical industry.

It is a block diagram of the laser processing apparatus which concerns on Embodiment 1 of this invention. It is a figure explaining the change of the condensing spot diameter by the distance between a condensing optical system and a workpiece. It is a surface micrograph after changing a fluence on a Si wafer and irradiating a pulse laser. It is a cross-sectional TEM photograph of the circular pattern of FIG. It is a diagram showing the relationship between the square D 2 and peak fluence F 0 of the diameter of the circular pattern whitish alteration. It is a figure which shows the relationship between the ablation depth L and fluence F. FIG. It is a figure which shows the relationship between the fluence of the location corresponding to the internal diameter and outer diameter of a ring-shaped pattern, and pulse width. It is a block diagram of the laser processing apparatus which concerns on the deformation | transformation aspect of Embodiment 1. It is a schematic diagram of the time-axis pulse shape of a laser beam. It is a figure which shows the laser pulse shape which has a pedestal component, and the pedestal free laser pulse shape. It is a block diagram of the laser processing apparatus which concerns on Embodiment 3 of this invention. It is a block diagram of the laser processing apparatus which concerns on Embodiment 4 of this invention.

Explanation of symbols

2... Low fluence irradiation means 2, 2 ′... High fluence irradiation means 22, 22 ′.・ Pulse shape control means 7 ... Machining means

Claims (10)

  1. An amorphization step of amorphizing the irradiated region by irradiating the surface of the crystalline workpiece with a pulsed laser beam at a predetermined low fluence;
    And a removing step of irradiating the irradiation region amorphousized in the amorphization step with the pulsed laser light at a predetermined high fluence to remove the irradiation region.
  2. An amorphization step of amorphizing the irradiated region by irradiating the surface of the crystalline workpiece with a pulsed laser beam at a predetermined low fluence;
    And a machining process for machining the irradiated region that has been amorphized in the amorphization process.
  3. Amorphization step of amorphizing the irradiated region by irradiating the surface of the crystalline workpiece with a first pulsed laser beam at a predetermined low fluence;
    A laser processing method comprising: a removing step of irradiating the irradiation region amorphousized in the amorphization step with a second pulse laser beam at a predetermined high fluence to remove the irradiation region.
  4.   The laser processing method according to claim 1, wherein the object to be processed is a semiconductor, and a photon energy of the pulse laser beam or the first pulse laser beam is smaller than a band gap of the semiconductor.
  5. A low fluence irradiation means for irradiating the surface of the crystalline workpiece with a pulsed laser beam at a predetermined low fluence;
    A high fluence irradiating means for irradiating the pulsed laser beam at a predetermined high fluence that changes the surface shape of the object to be processed, in an irradiation region of the object to be processed irradiated by the low fluence irradiating means; A featured laser processing apparatus.
  6.   The low fluence irradiating means and the high fluence irradiating means share a condensing optical system that controls a spot diameter formed by condensing the pulsed laser light on the surface of the workpiece. Item 7. The laser processing apparatus according to Item 6.
  7.   The laser processing apparatus according to claim 6, wherein the low fluence irradiation unit and the high fluence irradiation unit include a pulse shape control unit that controls a time-axis pulse shape of the pulse laser beam.
  8. A low fluence irradiation means for irradiating the surface of the crystalline workpiece with a pulsed laser beam at a predetermined low fluence;
    And a machining means for machining an irradiation region of the workpiece irradiated by the low fluence irradiation means.
  9. Low fluence irradiation means for irradiating the surface of the crystalline workpiece with the first pulse laser beam at a predetermined low fluence;
    High fluence irradiation means for irradiating a second pulse laser beam at a predetermined high fluence that changes the surface shape of the object to be processed, on an irradiation region of the object to be processed irradiated by the low fluence irradiation means. A laser processing apparatus characterized by the above.
  10.   10. The laser processing according to claim 5, wherein the object to be processed is a semiconductor, and a photon energy of the pulse laser beam or the first pulse laser beam is smaller than a band gap of the semiconductor. apparatus.
JP2006061364A 2006-03-07 2006-03-07 Laser beam machining method and apparatus Pending JP2007237210A (en)

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JP2014014848A (en) * 2012-07-10 2014-01-30 Disco Abrasive Syst Ltd Laser processing method
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JP2004351466A (en) * 2003-05-29 2004-12-16 Aisin Seiki Co Ltd Laser beam machining method and laser beam machining apparatus
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WO2009091020A1 (en) * 2008-01-17 2009-07-23 Honda Motor Co., Ltd. Laser working apparatus, and laser working method
US8258429B2 (en) 2008-01-17 2012-09-04 Honda Motor Co., Ltd. Laser working apparatus, and laser working method
JP2014147974A (en) * 2008-03-21 2014-08-21 Imra America Inc Laser-based material processing method and system
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JP2010247189A (en) * 2009-04-16 2010-11-04 Shin Etsu Polymer Co Ltd Method of manufacturing semiconductor wafer and apparatus therefor
JP2011245774A (en) * 2010-05-28 2011-12-08 Mitsuboshi Diamond Industrial Co Ltd Laser processing method
CN102689092A (en) * 2012-06-15 2012-09-26 合肥知常光电科技有限公司 Solar wafer precision machining method and device using double laser beams
JP2014014848A (en) * 2012-07-10 2014-01-30 Disco Abrasive Syst Ltd Laser processing method
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