U.S. patent application number 13/322301 was filed with the patent office on 2012-03-15 for laser machining device and laser machining method.
This patent application is currently assigned to HAMAMATSU PHOTONICS K.K.. Invention is credited to Kenshi Fukumitsu.
Application Number | 20120061356 13/322301 |
Document ID | / |
Family ID | 43586166 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120061356 |
Kind Code |
A1 |
Fukumitsu; Kenshi |
March 15, 2012 |
LASER MACHINING DEVICE AND LASER MACHINING METHOD
Abstract
The controllability of modified spots is improved. A laser
processing apparatus 100 comprises a first laser light source 101
for emitting a first pulsed laser light L1, a second laser light
source 102 for emitting a second pulsed laser light L2, half-wave
plates 104, 105 for respectively changing directions of
polarization of the pulsed laser light L1, L2, polarization beam
splitters 106, 107 for respectively polarization-separating the
pulsed laser light L1, L2 having changed the directions of
polarization, and a condenser lens 112 for converging the
polarization-separated pulsed laser light L1, L2 at an object to be
processed 1. When the directions of polarization of the pulsed
laser light L1, L2 changed by the half-wave plates 104, 105 are
varied by a light intensity controller 121 in the laser processing
apparatus 100, the ratios of the pulsed laser light L1, L2
polarization-separated by the polarization beam splitters 106, 107
are altered, whereby the respective intensities of the pulsed laser
light L1, L2 are adjusted.
Inventors: |
Fukumitsu; Kenshi;
(Shizuoka, JP) |
Assignee: |
HAMAMATSU PHOTONICS K.K.
Hamamatsu-shi
JP
|
Family ID: |
43586166 |
Appl. No.: |
13/322301 |
Filed: |
August 6, 2010 |
PCT Filed: |
August 6, 2010 |
PCT NO: |
PCT/JP10/63352 |
371 Date: |
November 23, 2011 |
Current U.S.
Class: |
219/121.61 |
Current CPC
Class: |
B28D 5/0005 20130101;
B28D 5/0011 20130101; B23K 26/0604 20130101; B23K 26/0622 20151001;
B23K 26/0624 20151001; B23K 2101/40 20180801; B23K 26/0006
20130101; B23K 26/53 20151001; C03B 33/0222 20130101; B23K 26/0613
20130101; B23K 2103/56 20180801; B23K 2103/54 20180801 |
Class at
Publication: |
219/121.61 |
International
Class: |
B23K 26/38 20060101
B23K026/38 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 11, 2009 |
JP |
2009-186586 |
Claims
1. A laser processing apparatus for converging a plurality of
pulsed laser light at an object to be processed, so as to form a
plurality of modified spots within the object along a line to cut
and cause the plurality of modified spots to produce a modified
region, the apparatus comprising: a first laser light source for
emitting a first pulsed laser light having a first wavelength; a
second laser light source for emitting a second pulsed laser light
having a second wavelength different from the first wavelength; a
first half-wave plate for changing a direction of polarization of
the first pulsed laser light; a second half-wave plate for changing
a direction of polarization of the second pulsed laser light;
polarization separation portion for polarization-separating the
first pulsed laser light having the direction of polarization
changed by the first half-wave plate and the second pulsed laser
light having the direction of polarization changed by the second
half-wave plate; a condenser lens for converging at the object the
first and second pulsed laser light polarization-separated by the
polarization separation portion; and light intensity control
portion for controlling an intensity of the first and second pulsed
laser light by varying the directions of polarization of the first
and second pulsed laser light changed by the first and second
half-wave plates.
2. A laser processing apparatus for converging a plurality of
pulsed laser light at an object to be processed, so as to form a
plurality of modified spots within the object along a line to cut
and cause the plurality of modified spots to produce a modified
region, the apparatus comprising: a first laser light source for
emitting a first pulsed laser light having a first wavelength; a
nonlinear optical crystal for receiving the first pulsed laser
light and emitting the first pulsed laser light and a second pulsed
laser light having a second wavelength different from the first
wavelength; a first half-wave plate for changing a direction of
polarization of the first pulsed laser light; a second half-wave
plate for changing a direction of polarization of the second pulsed
laser light; polarization separation portion for
polarization-separating the first pulsed laser light having the
direction of polarization changed by the first half-wave plate and
the second pulsed laser light having the direction of polarization
changed by the second half-wave plate; a condenser lens for
converging at the object the first and second pulsed laser light
polarization-separated by the polarization separation portion; and
light intensity control portion for controlling an intensity of the
first and second pulsed laser light by varying the directions of
polarization of the first and second pulsed laser light changed by
the first and second half-wave plates.
3. A laser processing apparatus according to claim 2, further
comprising pulse width control portion for controlling a pulse
width of the first pulsed laser light emitted from the first laser
light source; wherein the pulse width control portion changes the
pulse width of the first pulsed laser light so as to lower a
harmonic conversion efficiency of the nonlinear optical crystal
such that the nonlinear optical crystal emits no second pulsed
laser light.
4. A laser processing apparatus according to claim 1, further
comprising concentering portion for making the first and second
pulsed laser light concentric with each other.
5. A laser processing apparatus according to claim 1, wherein the
polarization separation portion includes: a first polarization beam
splitter for polarization-separating the first pulsed laser light
having the direction of polarization changed by the first half-wave
plate; and a second polarization beam splitter for
polarization-separating the second pulsed laser light having the
direction of polarization changed by the second half-wave
plate.
6. A laser processing apparatus according to claim 1, wherein the
light intensity control portion has a greater width of
controllability for the first pulsed laser light than for the
second pulsed laser light.
7. A laser processing apparatus according to claim 1, wherein the
light intensity control portion makes the intensity of the first
pulsed laser light lower than an intensity threshold at which the
modified spots are formed when the first pulsed laser light is
converged alone at the object.
8. A laser processing apparatus for converging a plurality of
pulsed laser light at an object to be processed, so as to form a
plurality of modified spots within the object along a line to cut
and cause the plurality of modified spots to produce a modified
region, the apparatus comprising: a first laser light source for
emitting a first pulsed laser light having a first wavelength; a
second laser light source for emitting a second pulsed laser light
having a second wavelength different from the first wavelength; and
a condenser lens for converging the first and second pulsed laser
light at the object; wherein the first pulsed laser light has an
intensity made lower than an intensity threshold at which the
modified spots are formed when the first pulsed laser light is
converged alone at the object.
9. A laser processing apparatus for converging a plurality of
pulsed laser light at an object to be processed, so as to form a
plurality of modified spots within the object along a line to cut
and cause the plurality of modified spots to produce a modified
region, the apparatus comprising: a first laser light source for
emitting a first pulsed laser light having a first wavelength; a
nonlinear optical crystal for receiving the first pulsed laser
light and emitting the first pulsed laser light and a second pulsed
laser light having a second wavelength different from the first
wavelength; and a condenser lens for converging the first and
second pulsed laser light at the object; wherein the first pulsed
laser light has an intensity made lower than an intensity threshold
at which the modified spots are formed when the first pulsed laser
light is converged alone at the object.
10. A laser processing apparatus according to claim 1, wherein the
first pulsed laser light has a wavelength longer than that of the
second pulsed laser light.
11. A laser processing method of converging a plurality of pulsed
laser light at an object to be processed, so as to form a plurality
of modified spots within the object along a line to cut and cause
the plurality of modified spots to produce a modified region; the
method comprising the step of converging a first pulsed laser light
having a first wavelength and a second pulsed laser light having a
second wavelength different from the first wavelength at the object
through a condenser lens; wherein the step makes the first pulsed
laser light have an intensity lower than an intensity threshold at
which the modified spots are formed when the first pulsed laser
light is converged alone at the object.
12. A laser processing method according to claim 11, wherein the
first pulsed laser light has a wavelength longer than that of the
second pulsed laser light.
13. A laser processing apparatus according to claim 2, further
comprising concentering portion for making the first and second
pulsed laser light concentric with each other.
14. A laser processing apparatus according to claim 2, wherein the
polarization separation portion includes: a first polarization beam
splitter for polarization-separating the first pulsed laser light
having the direction of polarization changed by the first half-wave
plate; and a second polarization beam splitter for
polarization-separating the second pulsed laser light having the
direction of polarization changed by the second half-wave
plate.
15. A laser processing apparatus according to claim 2, wherein the
light intensity control portion has a greater width of
controllability for the first pulsed laser light than for the
second pulsed laser light.
16. A laser processing apparatus according to claim 2, wherein the
light intensity control portion makes the intensity of the first
pulsed laser light lower than an intensity threshold at which the
modified spots are formed when the first pulsed laser light is
converged alone at the object.
17. A laser processing apparatus according to claim 2, wherein the
first pulsed laser light has a wavelength longer than that of the
second pulsed laser light.
18. A laser processing apparatus according to claim 8, wherein the
first pulsed laser light has a wavelength longer than that of the
second pulsed laser light.
19. A laser processing apparatus according to claim 9, wherein the
first pulsed laser light has a wavelength longer than that of the
second pulsed laser light.
Description
TECHNICAL FIELD
[0001] The present invention relates to a laser processing
apparatus and laser processing method for forming a modified region
in an object to be processed.
BACKGROUND ART
[0002] Known as a conventional laser processing apparatus is one
which converges first and second laser light having wavelengths
different from each other at an object to be processed, so as to
cut the object. For example, the following Patent Literature 1
discloses a laser processing apparatus which ablates a portion of a
substrate by using a first radiation pulse of a first ultraviolet
wavelength and a second radiation pulse of a second ultraviolet
wavelength longer than the first ultraviolet wavelength. For
example, the following Patent Literature 2 discloses a laser
processing apparatus which cuts an object to be processed by using
an oscillated wave of laser light and its harmonic.
[0003] On the other hand, a laser processing apparatus has recently
been developed, which converges pulsed laser light at an object to
be processed, so as to form a plurality of modified spots within
the object along a line to cut and cause the plurality of modified
spots to produce a modified region as disclosed in the following
Patent Literature 3, for example.
CITATION LIST
Patent Literature
[0004] Patent Literature 1: Japanese Patent Application Laid-Open
No. 2-182389
[0005] Patent Literature 2: Japanese Patent Publication No.
2604395
[0006] Patent Literature 3: Japanese Patent Application Laid-Open
No. 2004-337903
SUMMARY OF INVENTION
Technical Problem
[0007] Laser processing apparatus such as those mentioned above
have been required to improve their controllability of modified
spots. That is, it has been desired for them to accurately control
the size of modified spots and the length of fractures generated
from the modified spots (hereinafter simply referred to as
"fracture length") according to the thickness, material, and the
like of the object, for example.
[0008] It is therefore an object of the present invention to
provide a laser processing apparatus and laser processing method
which can improve the controllability of modified spots.
Solution to Problem
[0009] For achieving the above-mentioned object, the laser
processing apparatus in accordance with one aspect of the present
invention is a laser processing apparatus for converging a
plurality of pulsed laser light at an object to be processed, so as
to form a plurality of modified spots within the object along a
line to cut and cause the plurality of modified spots to produce a
modified region, the apparatus comprising a first laser light
source for emitting a first pulsed laser light having a first
wavelength, a second laser light source for emitting a second
pulsed laser light having a second wavelength different from the
first wavelength, a first half-wave plate for changing a direction
of polarization of the first pulsed laser light, a second half-wave
plate for changing a direction of polarization of the second pulsed
laser light, polarization separation means for
polarization-separating the first pulsed laser light having the
direction of polarization changed by the first half-wave plate and
the second pulsed laser light having the direction of polarization
changed by the second half-wave plate, a condenser lens for
converging at the object the first and second pulsed laser light
polarization-separated by the polarization separation means, and
light intensity control means for controlling an intensity of the
first and second pulsed laser light by varying the directions of
polarization of the first and second pulsed laser light changed by
the first and second half-wave plates.
[0010] The laser processing apparatus in accordance with another
aspect of the present invention is a laser processing apparatus for
converging a plurality of pulsed laser light at an object to be
processed, so as to form a plurality of modified spots within the
object along a line to cut and cause the plurality of modified
spots to produce a modified region, the apparatus comprising a
first laser light source for emitting a first pulsed laser light
having a first wavelength, a nonlinear optical crystal for
receiving the first pulsed laser light and emitting the first
pulsed laser light and a second pulsed laser light having a second
wavelength different from the first wavelength, a first half-wave
plate for changing a direction of polarization of the first pulsed
laser light, a second half-wave plate for changing a direction of
polarization of the second pulsed laser light, polarization
separation means for polarization-separating the first pulsed laser
light having the direction of polarization changed by the first
half-wave plate and the second pulsed laser light having the
direction of polarization changed by the second half-wave plate, a
condenser lens for converging at the object the first and second
pulsed laser light polarization-separated by the polarization
separation means, and light intensity control means for controlling
an intensity of the first and second pulsed laser light by varying
the directions of polarization of the first and second pulsed laser
light changed by the first and second half-wave plates.
[0011] In these aspects of the present invention, when the
directions of polarization of the first and second pulsed laser
light changed by the first and second half-wave plates are varied
by the light intensity control means, the ratios of the first and
second pulsed laser light polarization-separated by the
polarization separation means are altered. As a result, the
respective intensities of the first and second pulsed laser light
can be adjusted. Therefore, the respective intensities of the first
and second pulsed laser light can be controlled desirably without
greatly changing the pulse widths of the first and second pulsed
laser light, for example. Hence, high-quality modified spots having
favorable sizes and fracture lengths can be formed accurately. That
is, the present invention can improve the controllability of
modified spots.
[0012] Preferably, the laser processing apparatus further comprises
pulse width control means for controlling a pulse width of the
first pulsed laser light emitted from the first laser light source,
while the pulse width control means changes the pulse width of the
first pulsed laser light, so as to lower a harmonic conversion
efficiency of the nonlinear optical crystal such that the nonlinear
optical crystal emits no second pulsed laser light. This makes it
possible to converge the first pulsed laser light alone at the
object, so as to form the modified spots.
[0013] Preferably, the laser processing apparatus further comprises
concentering means for making the first and second pulsed laser
light concentric with each other. This can simplify the structure
of optical systems concerning the first and second pulsed laser
light.
[0014] The polarization separation means may include a first
polarization beam splitter for polarization-separating the first
pulsed laser light having the direction of polarization changed by
the first half-wave plate and a second polarization beam splitter
for polarization-separating the second pulsed laser light having
the direction of polarization changed by the second half-wave
plate.
[0015] Preferably, the light intensity control means has a greater
width of controllability for the first pulsed laser light than for
the second pulsed laser light. This can favorably form high-quality
modified spots in the object.
[0016] Preferably, the light intensity control means makes the
intensity of the first pulsed laser light lower than an intensity
threshold at which the modified spots are formed when the first
pulsed laser light is converged alone at the object. In this case,
for forming the modified spots, the first and second pulsed laser
light act as auxiliary and main pulsed laser light, respectively.
In addition, the first pulsed laser light acts favorably so as not
to affect the second pulsed laser light. As a result, high-quality
modified spots can be formed in the object.
[0017] The laser processing apparatus in accordance with still
another aspect of the present invention is a laser processing
apparatus for converging a plurality of pulsed laser light at an
object to be processed, so as to form a plurality of modified spots
within the object along a line to cut and cause the plurality of
modified spots to produce a modified region, the apparatus
comprising a first laser light source for emitting a first pulsed
laser light having a first wavelength, a second laser light source
for emitting a second pulsed laser light having a second wavelength
different from the first wavelength, and a condenser lens for
converging the first and second pulsed laser light at the object;
wherein the first pulsed laser light has an intensity made lower
than an intensity threshold at which the modified spots are formed
when the first pulsed laser light is converged alone at the
object.
[0018] The laser processing apparatus in accordance with a further
aspect of the present invention is a laser processing apparatus for
converging a plurality of pulsed laser light at an object to be
processed, so as to form a plurality of modified spots within the
object along a line to cut and cause the plurality of modified
spots to produce a modified region, the apparatus comprising a
first laser light source for emitting a first pulsed laser light
having a first wavelength, a nonlinear optical crystal for
receiving the first pulsed laser light and emitting the first
pulsed laser light and a second pulsed laser light having a second
wavelength different from the first wavelength, and a condenser
lens for converging the first and second pulsed laser light at the
object; wherein the first pulsed laser light has an intensity made
lower than an intensity threshold at which the modified spots are
formed when the first pulsed laser light is converged alone at the
object.
[0019] The laser processing method in accordance with a still
further aspect of the present invention is a laser processing
method of converging a plurality of pulsed laser light at an object
to be processed, so as to form a plurality of modified spots within
the object along a line to cut and cause the plurality of modified
spots to produce a modified region; the method comprising the step
of converging a first pulsed laser light having a first wavelength
and a second pulsed laser light having a second wavelength
different from the first wavelength at the object through a
condenser lens; wherein the step makes the first pulsed laser light
have an intensity lower than an intensity threshold at which the
modified spots are formed when the first pulsed laser light is
converged alone at the object.
[0020] In these aspects of the present invention, the first and
second pulsed laser light are converged at the object, so as to
form a plurality of modified spots and cause the modified spots to
produce a modified region. Here, the intensity of the first pulsed
laser light is lower than the intensity threshold at which the
modified spots are formed when the first pulsed laser light is
converged alone at the object. Hence, for forming the modified
spots in this case, the first and second pulsed laser light act as
auxiliary and main pulsed laser light, respectively. In addition,
the first pulsed laser light acts favorably so as not to affect the
second pulsed laser light. As a result, high-quality modified spots
can be formed in the object.
[0021] The first pulsed laser light may have a wavelength longer
than that of the second pulsed laser light.
ADVANTAGEOUS EFFECTS OF INVENTION
[0022] The present invention can improve the controllability of
modified spots.
BRIEF DESCRIPTION OF DRAWINGS
[0023] FIG. 1 is a plan view illustrating an example of an object
to be processed for which a modified region is formed;
[0024] FIG. 2 is a sectional view of the object taken along the
line of FIG. 1;
[0025] FIG. 3 is a plan view of the object after laser
processing;
[0026] FIG. 4 is a sectional view of the object taken along the
line IV-IV of FIG. 3;
[0027] FIG. 5 is a sectional view of the object taken along the
line V-V of FIG. 3;
[0028] FIG. 6 is a chart for explaining relationships between the
intensity of pulsed laser light and modified spots;
[0029] FIG. 7 is a chart illustrating examples of modified spots
formed in the object by using first and second laser light;
[0030] FIG. 8 is a schematic structural diagram illustrating the
laser processing apparatus in accordance with a first embodiment of
the present invention;
[0031] FIG. 9 is a schematic structural diagram illustrating a main
part of the laser processing apparatus of FIG. 8;
[0032] FIG. 10 is a flowchart illustrating operations of a laser
processing method using the laser processing apparatus of FIG.
8;
[0033] FIG. 11 is a schematic structural diagram illustrating a
main part of the laser processing apparatus in accordance with a
second embodiment of the present invention;
[0034] FIG. 12 is a schematic structural diagram illustrating a
main part of the laser processing apparatus in accordance with a
third embodiment of the present invention; and
[0035] FIG. 13 is a schematic structural diagram illustrating a
main part of the laser processing apparatus in accordance with a
fourth embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0036] In the following, preferred embodiments of the present
invention will be explained in detail with reference to the
drawings. In the drawings, the same or equivalent constituents will
be referred to with the same signs while omitting their overlapping
descriptions.
[0037] In the laser processing apparatus and laser processing
method in accordance with the embodiments, a plurality of pulsed
laser light are simultaneously converged at an object to be
processed, so as to form a plurality of modified spots within the
object and cause the plurality of modified spots to produce a
modified region which becomes a cutting start point. Therefore, the
forming of the modified region will firstly be explained with
reference to FIGS. 1 to 5.
[0038] As illustrated in FIG. 1, an object to be processed 1 has a
line to cut 5 set for cutting the object 1. The line 5 is a virtual
line extending straight. When forming a modified region within the
object 1, the laser light L is relatively moved along the line 5
(i.e., in the direction of arrow A in FIG. 1) while locating a
converging point P within the object 1 as illustrated in FIG. 2.
This forms a modified region 7 within the object 1 along the line 5
as illustrated in FIGS. 3 to 5, whereby the modified region 7
formed along the line 5 becomes a cutting start region 8.
[0039] A glass substrate is used as the object 1, for which a
semiconductor material, a piezoelectric material, or the like is
employable. The converging point P is a position at which the laser
light L is converged. The line 5 may be curved instead of being
straight and may be a line actually drawn on the front face 3 of
the object 1 without being restricted to the virtual line. The
modified region 7 may be formed either continuously or
intermittently. The modified region 7 may also be formed into rows
or dots. It will be sufficient if the modified region 7 is formed
at least within the object 1. There are cases where fractures are
formed from the modified region 7 acting as a start point, and the
fractures and modified region 7 may be exposed at outer surfaces
(the front face, rear face, and outer peripheral face) of the
object 1.
[0040] Here, the laser light L is absorbed in particular in the
vicinity of the converging point within the object 1 while being
transmitted therethrough, whereby the modified region 7 is formed
in the object 1 (internal absorption type laser processing).
Therefore, the front face 3 of the object 1 hardly absorbs the
laser light L and thus does not melt. In the case of forming a
removing part such as a hole or groove by melting it away from the
front face 3, the processing region gradually progresses from the
front face 3 side to the rear face side in general (surface
absorption type laser processing).
[0041] The modified region formed in this embodiment means regions
whose physical characteristics such as density, refractive index,
and mechanical strength have attained states different from those
of their surroundings. Examples of the modified region include
molten processed regions, crack regions, dielectric breakdown
regions, refractive index changed regions, and their mixed regions.
Further examples of the modified region include an area where the
density of the modified region has changed from that of an
unmodified region in the material of the object and an area formed
with a lattice defect (which can collectively be referred to as a
high-density transitional region).
[0042] The molten processed regions, refractive index changed
regions, areas where the modified region has a density different
from that of the unmodified region, and areas formed with a lattice
defect may further incorporate a fracture (cut or microcrack)
therewithin or at an interface between the modified and unmodified
regions. The incorporated fracture may be formed over the whole
surface of the modified region or in only a part or a plurality of
parts thereof.
[0043] This embodiment produces the modified region 7 by forming a
plurality of modified spots (processing scars) along the line 5. A
plurality of modified spots, each of which is a modified part
formed by a shot of one pulse of the pulsed laser light (i.e., one
pulse of laser irradiation), gather to form the modified region 7.
Examples of the modified spot include crack spots, molten processed
spots, refractive index changed spots, and those mixed with at
least one of them.
[0044] For the modified spots, it is preferred to control their
size and the length of fractures occurring therefrom (hereinafter
also referred to as "fracture length") appropriately in view of the
required cutting accuracy, flatness of cut sections, thickness,
kind, and crystal orientation of the object, and the like.
[0045] That is, when the modified spots are too large or the
fracture length is too long, fluctuations in the size of modified
spots and fracture length become greater, thereby lowering the
accuracy in cutting the object 1 along the line 5. This also
enhances irregularities on a cut section of the object 1, thereby
worsening the flatness of the cut section. When the modified spots
are too small, on the other hand, the object is harder to cut.
[0046] When the size of modified spots and fracture length are made
appropriate, they can be formed uniformly, while deviations from
the line 5 can be suppressed. This can also improve the accuracy in
cutting the object 1 along the line 5 and the flatness of the cut
section.
[0047] FIG. 6 is a chart for explaining relationships between the
intensity of pulsed laser light and modified spots. As illustrated
in FIG. 6, modified spots S can be controlled by regulating the
intensity (power) of pulsed laser light. Specifically, the size of
modified spots S and the length of fractures C can be made smaller
when the intensity of the pulsed laser light is lowered. On the
other hand, the size of modified spots S and the length of
fractures C can be made greater when the intensity of the pulsed
laser light is enhanced. The intensity of pulsed laser light can be
represented by the peak power density per pulse, the energy (J) per
pulse, or the average output (W) determined by multiplying the
energy per pulse by the frequency of the pulsed laser light, for
example.
[0048] In the case where pulsed laser light (hereinafter referred
to as first pulsed laser light) having a wavelength of 1064 nm is
converged alone at the object 1 here, a modified spot S1 is formed
when the intensity of the first pulsed laser light is at an
intensity threshold a or greater. In the case where pulsed laser
light (hereinafter referred to as second pulsed laser light) having
a wavelength of 532 nm which is shorter than the wavelength of the
first pulsed laser light is converged alone at the object 1, a
modified spot S2 is formed when the intensity of the second pulsed
laser light is at an intensity threshold .beta. or greater, for
example.
[0049] For example, there is a case where the intensity thresholds
a and .beta. are 15 .mu.J and 6 .mu.J, respectively. The intensity
threshold is an intensity of laser light at which a modified region
is formed in the object 1. Here, forming the modified spots S is
meant to appropriately form modified spots constituting a modified
region to become a cutting start region (ditto in the
following).
[0050] In the case where the first and second pulsed laser light
are simultaneously converged at the object 1, a modified spot S3 is
also formed at an intensity lower than any of the respective
intensities at which the first and second pulsed laser light are
converged alone. This modified spot S3 has a characteristic feature
similar to that of a modified spot formed by converging pulsed
laser light having an ultrashort pulse (e.g., of several psec),
i.e., the fractures C attain an appropriate length (a half cut or
full cut occurs) with a relatively small modified spot.
[0051] FIG. 7 is a chart illustrating examples of modified spots
formed in the object by using the first and second laser light.
Each photograph in the chart is an enlarged plan view illustrating
the object 1 formed with the modified spots S. Here, the first and
second pulsed laser light each have a pulse pitch of 50 .mu.m,
while their directions of polarization lie in their scanning
direction (the vertical direction on the chart). The first pulsed
laser light at the intensity of 0 .mu.J means that it is not
converged at the object 1 (i.e., the object is irradiated with the
second pulsed laser light alone). The second pulsed laser light at
the intensity of 0 .mu.J means that it is not converged at the
object 1 (i.e., the object is irradiated with the first pulsed
laser light alone). As the object 1, a glass slide is employed.
[0052] When the intensity of the second pulsed laser light is 0
.mu.J, as illustrated in FIG. 7, no modified spots S are formed in
the object, whereby processing is impossible. When the intensity of
the second pulsed laser light is 6 .mu.J or less, the modified
spots S cannot be formed continuously with a favorable accuracy,
whereby a so-called shot miss phenomenon occurs. When the intensity
of the second pulsed laser light is 4 .mu.J in particular, the shot
miss phenomenon occurs greatly depending on the intensity of the
first pulsed laser light (when the intensity of the first pulsed
laser light is 0 to 10 .mu.J). This shows that controlling the
intensity of the second pulsed laser light can suppress the shot
miss phenomenon in particular. That is, the second pulsed laser
light having a wavelength shorter than that of the first pulsed
laser light is used as a main element concerning the forming of the
modified spots S.
[0053] It is also seen that, as the intensity of the first pulsed
laser light is higher, the size of modified spots S becomes
greater, a greater number of fractures C occur, and the fracture
length increases. Hence, it is seen that controlling the intensity
of the first pulsed laser light can adjust the size of modified
spots S in particular. Using the first pulsed laser light within a
range where its laser intensity is lower than the intensity
threshold of the object 1 for this laser light (i.e., the intensity
threshold of the object 1 when irradiated with this laser light
alone) makes it easier to control the size of modified spots S.
First Embodiment
[0054] The first embodiment of the present invention will now be
explained. FIG. 8 is a schematic structural diagram illustrating
the laser processing apparatus in accordance with the first
embodiment of the present invention. As illustrated in FIG. 8, the
laser processing apparatus 100 comprises a housing 111 for
accommodating optical systems concerning the first and second
pulsed laser light, a condenser lens 112 for converging the first
and second pulsed laser light at the object 1, a support table 113
for supporting the object 1 irradiated with the pulsed laser light
L1, L2 converged by the condenser lens 112, a stage 114 for moving
the support table 113 along X, Y, and Z axes, and a stage
controller 115 for controlling the movement of the stage 114.
[0055] The laser processing apparatus 100 also comprises an
autofocus unit 116 in order to converge the pulsed laser light L1,
L2 accurately at a predetermined position within the object 1, so
as to form the modified region 7. This allows the laser processing
apparatus 100 to control the pulsed laser light L1, L2 accurately
such that they converge at a fixed position from the front face 3
or rear face of the object 1, for example.
[0056] FIG. 9 is a schematic structural diagram illustrating a main
part of the laser processing apparatus of FIG. 8. As illustrated in
FIG. 9, the laser processing apparatus 100 comprises first and
second pulsed laser light sources 101, 102, a laser light source
controller 103, half-wave plates 104, 105, and polarization beam
splitters 106, 107.
[0057] The first pulsed laser light source (first laser light
source) 101 emits the first pulsed laser light L1 having a
wavelength of 1064 nm with a pulse width of 23 nsec, for example.
The second pulsed laser light source (second laser light source)
102 emits the second pulsed laser light L2 having a wavelength of
532 nm with a pulse width of 15 nsec, for example, as a pulsed
laser light having a wavelength shorter than that of the first
pulsed laser light L1. Here, the pulsed laser light sources 101,
102 respectively emit the pulsed laser light L1, L2 whose
directions of polarization lie in the vertical direction on the
drawing sheet. Fiber lasers, for example, can be used as the pulsed
laser light sources 101, 102.
[0058] The laser light source controller 103 is connected to the
first pulsed laser light source 101, so as to adjust the pulse
width, pulse timing, and the like of the pulsed laser light L1
emitted from the first pulsed laser light source 101. The laser
light source controller 103 is also connected to the second pulsed
laser light source 102, so as to adjust the pulse timing and the
like of the pulsed laser light L2. The laser light source
controller 103 regulates the adjustment of the respective pulse
timings of the pulsed laser light sources 101, 102.
[0059] The half-wave plates 104, 105 are arranged behind the pulsed
laser light sources 101, 102 on the optical axes (optical paths) of
the pulsed laser light L1, L2, respectively. The half-wave plate
(first half-wave plate) 104 changes the direction of polarization
of the first pulsed laser light L1 emitted from the first pulsed
laser light source 101. The half-wave plate (second half-wave
plate) 105 changes the direction of polarization of the second
pulsed laser light L2 emitted from the second pulsed laser light
source 102.
[0060] The polarization beam splitter (first polarization beam
splitter) 106 is arranged behind the half-wave plate 104 on the
optical axis of the first pulsed laser light L1. The polarization
beam splitter 106 polarization-separates the first pulsed laser
light L1 having the direction of polarization changed by the
half-wave plate 104. Specifically, in the first pulsed laser light
L1, the polarization beam splitter 106 transmits therethrough a
constituent polarized in the vertical direction on the drawing
sheet, but reflects a constituent polarized in the direction normal
to the drawing sheet.
[0061] The polarization beam splitter (second polarization beam
splitter) 107 is arranged behind the half-wave plate 105 on the
optical axis of the second pulsed laser light L2. The polarization
beam splitter 107 polarization-separates the second pulsed laser
light L2 having the direction of polarization changed by the
half-wave plate 105. Specifically, in the second pulsed laser light
L2, the polarization beam splitter 107 transmits therethrough a
constituent polarized in the vertical direction on the drawing
sheet, but reflects a constituent polarized in the direction normal
to the drawing sheet.
[0062] The laser processing apparatus 100 further comprises a light
intensity controller 121. The light intensity controller 121
controls the angles of rotation of the half-wave plates 104, 105 by
actuators and the like, so as to vary the directions of
polarization of the pulsed laser light L1, L2 changed by the
half-wave plates 104, 105.
[0063] In the light intensity controller 121, the range in which
the direction of polarization of the first pulsed laser light L1
changed by the half-wave plate 104 is variable is greater than the
range in which the direction of polarization of the second pulsed
laser light L2 changed by the half-wave plate 105 is variable.
Therefore, in the light intensity controller 121, the width by
which the intensity of the first pulsed laser light L1 is
controllable is greater than the width by which the intensity of
the second pulsed laser light L2 is controllable.
[0064] A laser processing method using thus constructed laser
processing apparatus 100 will now be explained with reference to a
flowchart illustrated in FIG. 10.
[0065] In the laser processing apparatus 100 of this embodiment, as
illustrated in FIGS. 8 and 9, the object 1, which is a glass
substrate or sapphire substrate, having an expandable tape attached
to the rear face 21 thereof, is mounted on the stage 114 at first.
Subsequently, the object 1 is simultaneously irradiated with the
pulsed laser light L1, L2 from the respective pulsed laser light
sources 101, 102, while using the front face 3 as a laser light
irradiation surface and locating the converging point P within the
object 1. Here, the laser light source controller 103 regulates the
pulse timings such that the respective pulses of the pulsed laser
light L1, L2 overlap each other at least partly.
[0066] The first pulsed laser light L1 emitted from the first
pulsed laser light source 101 passes through the half-wave plate
104, so as to be adjusted in terms of polarization, and then is
polarization-separated by the polarization beam splitter 106 (S2,
S3). Subsequently, the first pulsed laser light L1 transmitted
through the polarization beam splitter 106 is reflected by dichroic
mirrors 108 to 110 in sequence, so as to be made incident on the
condenser lens 112.
[0067] The second pulsed laser light L2 emitted from the second
pulsed laser light source 102 passes through the half-wave plate
105, so as to be adjusted in terms of polarization, and then is
polarization-separated by the polarization beam splitter 107 (S2,
S3). Subsequently, the second pulsed laser light L2 transmitted
through the polarization beam splitter 107 passes through the
dichroic mirror 109, so as to become concentric with the first
pulsed laser light L1, and is reflected by the dichroic mirror 110
while in this concentric state, so as to be made incident on the
condenser lens 112. This converges the pulsed laser light L1, L2
into the object 1, while their directions of polarization lie in
the scanning direction (S4). The dichroic mirror 110 is desired to
be used for transmitting therethrough the light reflected by the
object 1 so as to observe it with a camera device (not depicted) in
order to study the object 1. When there is no camera device, a
simple reflecting mirror may be used.
[0068] Together with such irradiation with the pulsed laser light
L1, L2, the stage 114 is driven, so as to move (scan) the object 1
along the line 5 relative to the pulsed laser light L1, L2, thereby
forming a plurality of modified spots S within the object 1 along
the line 5 and producing the modified region 7 by the modified
spots S (S5, S6). Thereafter, the expandable tape is expanded, so
as to cut the object 1 along the line 5 from the modified region 7
acting as a cutting start region.
[0069] Here, the laser processing apparatus 100 of this embodiment
is equipped with the light intensity controller 121. Therefore, by
actuating the light intensity controller 121, so as to vary the
directions of polarization of the pulsed laser light L1, L2
transmitted through the half-wave plates 104, 105, the laser
processing apparatus 100 can change the ratios of the pulsed laser
light L1, L2 polarization-separated by the polarization beam
splitters 106, 107. As a result, in the pulsed laser light L1, L2,
the ratios of polarization direction constituents transmitted
through the polarization beam splitters 106, 107 are adjusted
appropriately. Hence, the respective intensities of the pulsed
laser light L1, L2 converged by the condenser lens 112 are adjusted
as desired.
[0070] In this regard, when controlling the intensities of the
pulsed laser light L1, L2 by adjusting their inputs, for example,
as in the conventional laser processing apparatus, their input
ranges are hard to adjust greatly because of structures of the
pulsed laser light sources 101, 102.
[0071] By contrast, as mentioned above, this embodiment can control
the respective intensities of the pulsed laser light L1, L2 as
desired without greatly changing the input ranges of the pulsed
laser light L1, L2. Therefore, this embodiment can accurately form
high-quality modified spots S having favorable sizes and fracture
lengths in the object 1, thereby improving the controllability of
modified spots S.
[0072] In particular, as mentioned above, this embodiment forms the
modified spots S by simultaneously converging the two pulsed laser
light L1, L2 having different wavelengths. This can make the total
intensity of pulsed laser light lower than that in the case where
the modified spots S are formed by converging one of the pulsed
laser light L1, L2 alone (see FIG. 6).
[0073] For forming the modified spots S by converging one of the
pulsed laser light L1, L2 alone, it has conventionally been
necessary for them to have an ultrashort pulse width (e.g., several
psec), which may need special laser light sources for the pulsed
laser light sources. By contrast, this embodiment can reduce not
only the necessity for minimizing the pulse widths of the pulsed
laser light L1, L2, but also the need for special laser light
sources, whereby typical common laser light sources can be used.
This can lower the cost and enhance the reliability and
versatility.
[0074] In general, for accurately forming the modified spots S by
simultaneously converging the pulsed laser light L1, L2, it is
preferred to change the intensity of the first pulsed laser light
L1 more greatly than the intensity of the second pulsed laser light
L2 (see FIG. 7). In this regard, the controllable width of
intensity of the first pulsed laser light L1 is greater than the
controllable width of intensity of the second pulsed laser light L2
in this embodiment as mentioned above. This can perform favorable
laser processing in conformity to the relationship between the
intensities of the pulsed laser light L1, L2 at the time of forming
the modified spots S, thereby favorably producing high-quality
modified spots S in the object 1.
[0075] Since the pulsed laser light L1, L2 are made concentric with
each other as mentioned above, this embodiment can simplify the
structure of optical systems concerning the pulsed laser light L1,
L2.
[0076] Since the second pulsed laser light L2 is used as a main
element for forming the modified spots S as mentioned above, it is
preferred for the second pulsed laser light L2 to have a pulse
width shorter than that of the first pulsed laser light L1 as in
this embodiment.
[0077] When converging the pulsed laser light L1, L2 at the object
1 upon irradiation in this embodiment, at least one of the light
intensity controller 121 and laser light source controller 103 may
be actuated such that the intensity of the first pulsed laser light
L1 is lower than the intensity threshold a (see FIG. 6).
[0078] Specifically, the intensity of the first pulsed laser light
L1 may be made lower than the intensity threshold a at which the
modified spots S are formed when the first pulsed laser light L1 is
converged alone at the object 1. In other words, the intensity of
the first pulsed laser light L1 may be within a predetermined
intensity range where the modified spots S are not formed when the
first pulsed laser light L1 is converged alone at the object 1.
[0079] For forming the modified spots S in this case, the first and
second pulsed laser light L1, L2 act as auxiliary and main pulsed
laser light, respectively. In addition, the first pulsed laser
light L1 acts favorably so as not to affect the second pulsed laser
light L2. As a result, high-quality modified spots S can be formed
in the object 1. That is, this enables excellent laser processing
under multi-wavelength simultaneous irradiation with the pulsed
laser light L1, L2 cooperating with each other.
[0080] In general, the wavelength, pulse width, peak power, and the
like of pulsed laser light required for forming the modified spots
S within the object 1 by converging the pulsed laser light vary
depending on the kind of the object 1 and the like. When forming
the modified spots S in the object 1 that is a silicon substrate,
for example, it is preferred for the pulsed laser light to have a
wavelength of 1064 nm and a relatively long pulse width (100 to 200
nsec). When forming the modified spots S in the object 1 that is a
glass substrate or sapphire substrate as in this embodiment, it is
preferred for the pulsed laser light to have a shorter pulse width
so as to enhance the intensity (peak energy).
[0081] In this regard, the laser processing apparatus 100 of this
embodiment can accurately form the modified spots S not only in the
object 1 that is a glass substrate or sapphire substrate as
mentioned above, but also in the object 1 that is a silicon
substrate. Specifically, a filter or the like is placed on the
optical axis of the second pulsed laser light L2 so that the second
pulsed laser light L2 is not converged at the object 1. At the same
time, the first pulsed laser light L1 having a pulse width of 200
nsec, for example, is converged at the object 1.
[0082] Therefore, this embodiment allows the single laser
processing apparatus 100 to be used as a processing apparatus for
various substrates. The single laser processing apparatus 100 can
also easily handle the object 1 such as a bonded substrate
constituted by silicon and glass substrates.
[0083] In this embodiment, as in the foregoing, the polarization
beam splitters 106, 107 constitute the polarization separation
means, while the light intensity controller 121 does the light
intensity control means. The dichroic mirrors 108, 109 constitute
the concentering means, while the laser light source controller 103
does the pulse width control means.
Second Embodiment
[0084] The second embodiment of the present invention will now be
explained. This embodiment will be explained mainly in terms of
differences from the above-mentioned first embodiment.
[0085] FIG. 11 is a schematic structural diagram illustrating a
main part of the laser processing apparatus in accordance with the
second embodiment of the present invention. As illustrated in FIG.
11, the laser processing apparatus 200 of this embodiment differs
from the above-mentioned laser processing apparatus 100 in that it
has a polarization beam splitter 201 in place of the polarization
beam splitters 106, 107 (see FIG. 9) and further comprises a
half-wave plate 202.
[0086] The polarization beam splitter (first and second
polarization beam splitter) 201 is arranged behind the half-wave
plate 104 on the optical axis of the first pulsed laser light L1
and behind the half-wave plate 105 on the optical axis of the
second pulsed laser light L2. The polarization beam splitter 201 is
adapted to handle two wavelengths, so as to polarization-separate
the first pulsed laser light L1 having the direction of
polarization changed by the half-wave plate 104 and the second
pulsed laser light L2 having the direction of polarization changed
by the half-wave plate 105.
[0087] Specifically, in the first pulsed laser light L1, the
polarization beam splitter 201 transmits therethrough a constituent
polarized in the vertical direction on the drawing sheet as it is,
but reflects a constituent polarized in the direction normal to the
drawing sheet. In the second pulsed laser light L2, the
polarization beam splitter 201 transmits therethrough a constituent
polarized in the vertical direction on the drawing sheet as it is,
while making it concentric with the first pulsed laser light L1,
but reflects a constituent polarized in the direction normal to the
drawing sheet.
[0088] The half-wave plate 202 is arranged behind the polarization
beam splitter 201 on the optical axis of the first pulsed laser
light L1. The half-wave plate 202 changes the direction of
polarization of the first pulsed laser light L1 reflected by the
polarization beam splitter 201 but transmits therethrough the
second pulsed laser light L2 passed through the polarization beam
splitter 201 as it is. Here, the half-wave plate 202 changes the
direction of polarization of the first pulsed laser light L1 from
the direction normal to the drawing sheet to the vertical direction
on the drawing sheet.
[0089] In thus constructed laser processing apparatus 200, the
first pulsed laser light L1 emitted from the first pulsed laser
light source 101 is transmitted through the half-wave plate 104,
where its polarization is adjusted, and then reflected by the
dichroic mirror 203, so as to be polarization-separated by the
polarization beam splitter 201. The first pulsed laser light L1
reflected by the polarization beam splitter 201 is transmitted
through the half-wave plate 202, where its polarization is
adjusted, and then reflected by the dichroic mirror 110, so as to
be made incident on the condenser lens 112.
[0090] The second pulsed laser light L2 emitted from the second
pulsed laser light source 102 is transmitted through the half-wave
plate 105, where its polarization is adjusted, and then
polarization-separated by the polarization beam splitter 201. The
second pulsed laser light L2 transmitted through the polarization
beam splitter 201 is made concentric with the first pulsed laser
light L1 and passes through the half-wave plate 202 as it is while
in this concentric state. Thereafter, the second pulsed laser light
L2 is reflected by the dichroic mirror 110, so as to be made
incident on the condenser lens 112. As a consequence, the pulsed
laser light L1, L2 are converged into the object 1, while their
directions of polarization lie in the scanning direction.
[0091] As in the foregoing, this embodiment is effective in
improving the controllability of the modified spots S as with the
one mentioned above. This embodiment also allows the single laser
processing apparatus 200 to be used as a processing apparatus for
various substrates as in the above-mentioned first embodiment.
[0092] In this embodiment, as in the foregoing, the polarization
beam splitter 201 constitutes the polarization separation means,
while the polarization beam splitter 201 and dichroic mirror 203 do
the concentering means.
Third Embodiment
[0093] The third embodiment of the present invention will now be
explained. This embodiment will be explained mainly in terms of
differences from the above-mentioned first embodiment.
[0094] FIG. 12 is a schematic structural diagram illustrating a
main part of the laser processing apparatus in accordance with the
third embodiment of the present invention. As illustrated in FIG.
12, the laser processing apparatus 300 of this embodiment mainly
differs from the above-mentioned laser processing apparatus 100
equipped with the two pulsed laser light sources 101, 102 in that
it has one pulsed laser light source. Specifically, the laser
processing apparatus 300 is not equipped with the second pulsed
laser light source 102 but further comprises a nonlinear optical
crystal 301.
[0095] The nonlinear optical crystal 301, for which a KTP crystal
as a second harmonic generator (SHG crystal) for generating an
optical harmonic is used here, performs a wavelength conversion of
the pulsed laser light L1.
[0096] Specifically, when the first pulsed laser light L1 having a
wavelength of 1064 nm as a fundamental wave is incident on the
nonlinear optical crystal 301, the latter emits the second pulsed
laser light L2 having a wavelength of 532 nm as a second harmonic
concentrically with the first pulsed laser light L1. Here, the
first pulsed laser light L1 whose direction of polarization tilts
by 45.degree. from the vertical direction of the drawing sheet is
made incident on the nonlinear optical crystal 301, whereby the
first pulsed laser light L1 and the second pulsed laser light L2
whose direction of polarization lies in the direction normal to the
drawing sheet are emitted concentrically with each other.
[0097] A half-wave plate 302 for changing the direction of
polarization of the first pulsed laser light L1 is disposed in
front of the nonlinear optical crystal 301 on the optical axis of
the first pulsed laser light L1. The half-wave plate 302 changes
the direction of polarization of the first pulsed laser light L1
incident on the half-wave plate 302 from the vertical direction on
the drawing sheet to the direction tilted by 45.degree. from the
vertical direction of the drawing sheet.
[0098] When forming the modified spots S within the object 1 that
is a glass substrate or sapphire substrate by the laser processing
apparatus 300, the first pulsed laser light L1 emitted from the
first pulsed laser light source 101 is transmitted through the
half-wave plate 302, where its polarization is adjusted, and then
made incident on the nonlinear optical crystal 301, so as to be
wavelength-converted. Subsequently, the nonlinear optical crystal
301 emits the pulsed laser light L1, L2 concentrically with each
other.
[0099] The first pulsed laser light L1 emitted from the nonlinear
optical crystal 301 is transmitted through a dichroic mirror 303, a
quarter-wave plate 144, where elliptical polarization is turned
into linear polarization, and the half-wave plate 104, where the
polarization is adjusted, and then polarization-separated by the
polarization beam splitter 106. The first pulsed laser light L1
transmitted through the polarization beam splitter 106 is reflected
by the dichroic mirrors 108, 109 in sequence, so as to be made
incident on the condenser lens 112.
[0100] The second pulsed laser light L2 emitted from the nonlinear
optical crystal 301 is reflected by the dichroic mirrors 303, 304
in sequence and transmitted through the half-wave plate 105, where
its polarization is adjusted, and then polarization-separated by
the polarization beam splitter 107. The second pulsed laser light
L2 transmitted through the polarization beam splitter 201 passes
through the dichroic mirror 109, so as to become concentric with
the first pulsed laser light L1, and is reflected by the dichroic
mirror 110 while in this concentric state, so as to be made
incident on the condenser lens 112. As a consequence, the pulsed
laser light L1, L2 are converged into the object 1, while their
directions of polarization lie in the scanning direction.
[0101] As in the foregoing, this embodiment is effective in
improving the controllability of the modified spots S as with those
mentioned above. Since the pulsed laser light L1, L2 are converged
at the object 1 by using the single first pulsed laser light source
101, this embodiment makes it easier to set pulse timings such that
the respective pulses of the pulsed laser light L1, L2 overlap each
other.
[0102] The laser processing apparatus 300 of this embodiment can
accurately form the modified spots S not only in the object 1 that
is a glass substrate or sapphire substrate, but also in the object
1 that is a silicon substrate.
[0103] Specifically, the laser light source controller 103 changes
the pulse width of the first pulsed laser light L1 emitted from the
first pulsed laser light source 101. Here, the first pulsed laser
light L1 has a pulse width (e.g., 20 nsec) longer than that in the
case of forming the modified spots S in the object 1 such as a
glass or sapphire substrate. This lowers the harmonic conversion
efficiency of the nonlinear optical crystal 301 so that only the
first pulsed laser light L1 is emitted from the nonlinear optical
crystal 301 (i.e., the second pulsed laser light L2 is not
substantially emitted therefrom). As a result, the pulsed laser
light L1 is converged alone into the object 1, so as to form the
modified spots S.
[0104] Therefore, this embodiment allows the single laser
processing apparatus 300 to be used as a processing apparatus for
various substrates. The single laser processing apparatus 300 can
also easily handle the object 1 such as a bonded substrate
constituted by silicon and glass substrates.
[0105] In this embodiment, as in the foregoing, the nonlinear
optical crystal 301 and dichroic mirrors 108, 109 constitute the
concentering means.
Fourth Embodiment
[0106] The fourth embodiment of the present invention will now be
explained. This embodiment will be explained mainly in terms of
differences from the above-mentioned third embodiment.
[0107] FIG. 13 is a schematic structural diagram illustrating a
main part of the laser processing apparatus in accordance with the
fourth embodiment of the present invention. As illustrated in FIG.
13, the laser processing apparatus 400 of this embodiment mainly
differs from the above-mentioned laser processing apparatus 300 in
that the optical axes of the pulsed laser light L1, L2 are kept
concentric (completely concentric) with each other. Specifically,
the laser processing apparatus 400 comprises a nonlinear optical
crystal 401 in place of the nonlinear optical crystal 301 (see FIG.
12), and a polarization beam splitter 402 in place of the
polarization beam splitters 106, 107 (see FIG. 12).
[0108] The nonlinear optical crystal 401, for which a BBO crystal
is used here, performs a wavelength conversion of the pulsed laser
light L1. When the first pulsed laser light L1 is made incident on
the nonlinear optical crystal 401, the latter emits the first and
second pulsed laser light L1, L2 concentrically with each other.
When the first pulsed laser light L1 whose direction of
polarization lies in the vertical direction on the drawing sheet is
made incident on the nonlinear optical crystal 401 here, the latter
emits the first pulsed laser light L1 and the second pulsed laser
light L2 whose direction of polarization lies in the direction
normal to the drawing sheet concentrically with each other.
[0109] The polarization beam splitter (first and second
polarization beam splitter) 402, which is adapted to handle two
wavelengths, is arranged behind the half-wave plates 104, 105 on
the optical axis of the pulsed laser light L1, L2. The polarization
beam splitter 402 polarization-separates each of the pulsed laser
light L1, L2 having their directions of polarization changed by the
half-wave plates 104, 105. Specifically, in each of the pulsed
laser light L1, L2, the polarization beam splitter 402 transmits
therethrough a constituent polarized in the vertical direction on
the drawing sheet as it is, but reflects a constituent polarized in
the direction normal to the drawing sheet.
[0110] In thus constructed laser processing apparatus 400, the
first pulsed laser light L1 emitted from the first pulsed laser
light source 101 is made incident on the nonlinear optical crystal
401, so as to be wavelength-converted, and the nonlinear optical
crystal 401 emits the pulsed laser light L1, L2 concentrically with
each other.
[0111] The first pulsed laser light L1 emitted from the nonlinear
optical crystal 401 is transmitted through the half-wave plate 104,
where its polarization is adjusted, and then the half-wave plate
105 as it is, so as to be polarization-separated by the
polarization beam splitter 402. On the other hand, the second
pulsed laser light L2 emitted from the nonlinear optical crystal
401 is transmitted through the half-wave plate 104 as it is and
then the half-wave plate 105, where its polarization is adjusted,
so as to be polarization-separated by the polarization beam
splitter 402. The pulsed laser light L1, L2 transmitted through the
polarization beam splitter 402 are reflected by the dichroic mirror
110, so as to be made incident on the condenser lens 112. As a
consequence, the pulsed laser light L1, L2 are converged into the
object 1, while their directions of polarization lie in the
scanning direction.
[0112] As in the foregoing, this embodiment is effective in
improving the controllability of the modified spots S as with those
mentioned above. This embodiment also allows the single laser
processing apparatus 400 to be used as a laser processing apparatus
for various substrates as with the above-mentioned third
embodiment.
[0113] Since this embodiment is constructed such that the optical
axes of the pulsed laser light L1, L2 are kept concentric with each
other as mentioned above, the structure of optical systems
concerning the pulsed laser light L1, L2 can be made much simpler,
while it becomes further easier to set pulse timings such that the
respective pulses of the pulsed laser light L1, L2 overlap each
other.
[0114] In this embodiment, as in the foregoing, the polarization
beam splitter 402 and nonlinear optical crystal 401 constitute the
polarization separation means and concentering means,
respectively.
[0115] While preferred embodiments of the present invention have
been explained in the foregoing, the laser processing apparatus in
accordance with the present invention is not limited to the
above-mentioned laser processing apparatus 100, 200, 300, 400 in
accordance with the embodiments, and the laser processing method is
not restricted to the above-mentioned laser processing methods in
accordance with the embodiments. The present invention may also be
those modified or applied to others within the scope not deviating
from gist set forth in each claim.
INDUSTRIAL APPLICABILITY
[0116] The present invention can improve the controllability of
modified spots.
REFERENCE SIGNS LIST
[0117] 1 . . . object to be processed; 5 . . . line to cut; 7 . . .
modified region; 100, 200, 300, 400 . . . laser processing
apparatus; 101 . . . first pulsed laser light source (first laser
light source); 102 . . . second pulsed laser light source (second
laser light source); 103 . . . laser light source controller (pulse
width control means); 104 . . . half-wave plate (first half-wave
plate); 105 . . . half-wave plate (second half-wave plate); 106 . .
. polarization beam splitter (first polarization beam splitter,
polarization separation means); 107 . . . polarization beam
splitter (second polarization beam splitter, polarization
separation means); 112 . . . condenser lens; 108, 109, 203 . . .
dichroic mirror (concentering means); 121 . . . light intensity
controller (light intensity control means); 201 . . . polarization
beam splitter (first and second polarization beam splitter,
polarization separation means, concentering means); 301, 401 . . .
nonlinear optical crystal (concentering means); 402 . . .
polarization beam splitter (first and second polarization beam
splitter, polarization separation means); L1 . . . first pulsed
laser light; L2 . . . second pulsed laser light; S . . . modified
spot; .alpha. . . . intensity threshold
* * * * *