U.S. patent application number 11/065589 was filed with the patent office on 2005-07-21 for laser processing method and processing device.
This patent application is currently assigned to Sumitomo Heavy Industries, Ltd.. Invention is credited to Hamada, Shiro, Yamaguchi, Tomoyuki, Yamamoto, Jiro.
Application Number | 20050155956 11/065589 |
Document ID | / |
Family ID | 34752001 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050155956 |
Kind Code |
A1 |
Hamada, Shiro ; et
al. |
July 21, 2005 |
Laser processing method and processing device
Abstract
Laser beam is irradiated to a surface of a processing target
after reforming a cross section of the laser beam with a mask
having a pierced hole by concentrating the laser beam passing
through the pierced hole by a lens to foreman image of the pierced
hole of the mask on the surface of the processing target. The laser
beam passing through the lens is scanned to move an irradiating
position of the laser beam on the surface of the processing target,
and the image of the pierced hole of the mask is formed on the
surface of the processing target during the scanning for processing
the processing target. A high quality laser process can be carried
out.
Inventors: |
Hamada, Shiro; (Yokosuka,
JP) ; Yamamoto, Jiro; (Yokosuka, JP) ;
Yamaguchi, Tomoyuki; (Yokosuka, JP) |
Correspondence
Address: |
SQUIRE, SANDERS & DEMPSEY L.L.P.
14TH FLOOR
8000 TOWERS CRESCENT
TYSONS CORNER
VA
22182
US
|
Assignee: |
Sumitomo Heavy Industries,
Ltd.
|
Family ID: |
34752001 |
Appl. No.: |
11/065589 |
Filed: |
February 25, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11065589 |
Feb 25, 2005 |
|
|
|
PCT/JP03/11126 |
Aug 29, 2003 |
|
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Current U.S.
Class: |
219/121.69 ;
219/121.68 |
Current CPC
Class: |
B23K 2101/40 20180801;
B23K 26/082 20151001; B23K 26/0853 20130101; B23K 26/382 20151001;
B23K 26/60 20151001; B23K 26/0648 20130101; B23K 26/0732 20130101;
B23K 26/0622 20151001; B23K 2103/50 20180801; B23K 26/40 20130101;
B23K 26/066 20151001; B23K 26/0626 20130101; B23K 26/364 20151001;
B23K 26/0652 20130101; B23K 2103/42 20180801 |
Class at
Publication: |
219/121.69 ;
219/121.68 |
International
Class: |
B23K 026/38; B23K
026/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 30, 2002 |
JP |
2002-254015 |
Claims
What are claimed are:
1. A laser processing method, comprising the steps of: (a)
irradiating laser beam from a laser source through an optical
system onto a surface of a processing target; and (b) scanning said
laser beam on the surface of the processing target by the optical
system and so controlling at least one parameter among those of
said laser source and said optical system that variation of an
irradiating condition of the laser beam on the processing target
caused by the scanning is suppressed.
2. The laser processing method according to claim 1, wherein said
step (a) shapes a cross section of the laser beam with a mask
having a pierced hole, and collects light of the laser beam passed
through the pierced hole and focuses the pierced hole of the mask
on the surface of the processing target by a lens, and said step
(b) controls the optical system so that the pierced hole of the
mask is focused on the surface of the processing target during the
scanning of the laser beam.
3. The laser processing method according to claim 2, wherein said
step (b) controls the optical system so that an optical length
between the mask and the lens and an optical length between the
lens and the surface of the processing target are fixed.
4. The laser processing method according to claim 2, wherein said
step (b) comprises the step of moving the lens along a direction
parallel to a direction of the laser beam passing through the lens
and moving the mask along a direction parallel to a direction of
the laser beam passing through the mask.
5. The laser processing method according to claim 2, wherein said
step (a) shapes a beam spot on the surface of the processing target
in a shape having a pair of parallel sides, and said step (b) moves
the beam spot along a direction parallel to the pair of parallel
sides.
6. The laser processing method according to claim 2, wherein the
laser beam on the surface of the processing target has density
distribution in which strength in a peripheral area of the beam
spot is greater than strength in a central part of the beam
spot.
7. The laser processing method according to claim 2, wherein the
laser beam is pulsed laser beam, and said step (b) comprises the
step of increasing pulse energy of the laser beam when an incident
angle of the laser beam to the surface of the processing target
becomes large.
8. The laser processing method according to claim 2, wherein said
step (b) moves the mask and the lens to decrease a variation in an
area of the beam spot on the surface of the processing target when
an incident angle of the laser beam on the surface of the
processing target is varied.
9. The laser processing method according to claim 1, wherein said
step (a) condenses the laser beam by a lens, and said step (b)
controls the optical system so that change in optical length
between the lens and the surface of the processing target is
suppressed.
10. The laser processing method according to claim 9, wherein said
step (b) comprises the step of moving the lens along a direction of
the laser beam passing through the lens.
11. The laser processing method according to claim 9, wherein the
laser beam irradiating on the lens is collimated beam, and an
optical length between the lens and the surface of the processing
target is same as a focal length of the lens.
12. The laser processing method according to claim 1, wherein said
step (a) condenses the laser beam by a lens, and said step (b)
controls at least one of the laser source and the optical system so
that variation in pulse energy density or power density of the
laser beam on the surface of the processing target caused by shift
of an incident point is suppressed when the incident point of the
laser beam on the processing target is moved.
13. The laser processing method according to claim 12, wherein said
step (b) comprises the step of moving the lens along a direction of
the laser beam passing through the lens.
14. The laser processing method according to claim 13, wherein said
step (b) so moves the lens along the direction of the laser beam
that a focal point of the laser beam goes away from the incident
point on the target when increase in the pulse energy density or
power density of the laser beam on the surface of the processing
target is suppressed, and so moves the lens along the direction of
the laser beam that a focal point of the laser beam comes closer to
the incident point on the target when decrease in the pulse energy
density or power density of the laser beam on the surface of the
processing target is suppressed.
15. The laser processing method according to claim 12, wherein said
step (b) adjusts power of the laser beam by using a variable
attenuator.
16. The laser processing method according to claim 1, wherein said
step (a) condenses the laser beam by a lens, and said step (b)
suppresses a variation in an area of a beam spot of the laser beam
on the surface of the processing target caused by motion of an
incident point when the incident point of the laser beam on the
processing target is moved.
17. The laser processing method according to claim 16, wherein said
step (b) comprises the step of moving the lens along a direction of
the laser beam passing through the lens.
18. A laser processing method, comprising the steps of: (c)
obtaining a spread angle of laser beam and a distance between
proximity mask and a surface of a processing target in accordance
with a relationship among a spread angle of the laser beam passing
through the proximity mask having a pierced hole, a distance
between the proximity mask and the surface of the processing target
and precision of transferring the pierced hole of the proximity
mask on the surface of the processing target; and (d) transferring
the pierced hole on the surface of the processing target by
irradiating the laser beam of which spread angle is adjusted by a
value obtained in said step (c) and passing through the pierced
hole of the proximity mask of which distance to the surface of the
processing target is adjusted by a value obtained in said step (c)
onto the surface of the processing target, while sweeping the laser
beam.
19. A laser processing method, comprising the steps of: (e)
irradiating continuous-wave laser beam from a laser source through
an optical system which can be switched over between a first
configuration in which the laser beam is emitted and a second
configuration in which the laser beam is not emitted; (f)
projecting the laser beam emitted from the optical system on a mask
having a rectangle-shaped pierced hole to shape a cross section,
condensing the laser beam by a lens, and focusing an image of the
pierced hole on a surface of a processing target; and (g) moving
the image of the pierced hole along a direction parallel to a side
of the rectangle image on the surface of the processing target
wherein said step (e) emits the laser beam from the optical system
intermittently when discrete dotted pattern is to be formed on the
surface of the processing target, and said step (e) emits the laser
beam from the optical system continuously when a linear pattern is
to be formed on the surface of the processing target.
20. The laser processing method according to claim 19, further
comprising, after the step (g), the steps of: (h) rotating the mask
around an axis parallel to a direction of the laser beam so that
the image of the pierced hole rotates on the surface of the
processing target; and (i) moving the image of the rotated pierced
hole on the surface of the processing target along a direction
parallel to a side of the rotated image of the rectangle pierced
hole.
21. A laser processing method, comprising the steps of: (j)
emitting pulsed laser beam from a first laser source and
continuous-wave laser beam from a second laser source; (k)
preheating a target spot defined on a surface of a processing
target having abase layer and a surface layer formed of a material
that is harder to be processed by laser irradiation than the base
layer, with the continuous-wave laser beam from the second laser
source, and thereafter irradiating the pulsed laser beam from the
first laser source to the target spot to form a hole in the surface
layer of the processing target.
22. The laser processing method according to claim 21, wherein said
step (k) preheats the processing, target while keeping a
temperature of the base layer not higher than a melting point of
the base layer by irradiating the continuous-wave laser beam from
the second laser source.
23. The laser processing method according to claim 21, wherein said
step (k) scans the continuous-wave laser beam and pulsed laser beam
on the surface of the processing target wherein a beam spot of the
pulsed laser beam is included inside of a beam spot of the
continuous-wave laser beam.
24. The laser processing method according to claim 23, wherein a
shape of the beam spot of the continuous-wave laser beam on the
surface of the processing target is a circle, and the beam spot of
the pulsed laser beam is positioned at a center of the circle.
25. A laser processing apparatus, comprising: a laser source that
emits laser beam; a holder that holds a processing-target; an
optical system comprising a lens that condenses the laser beam from
the laser source, and a beam scanner that sweeps the laser beam
passed through the lens, to scan an incident point of the laser
beam on a surface of the processing target held by the holder; and
a controller which so controls at least one parameter among those
of said laser source and said optical system that variation of an
irradiating condition of the laser beam on the processing target
caused by scanning is suppressed.
26. The laser processing apparatus according to claim 26, wherein
said optical system further comprises a mask disposed on a light
path between the laser source is and the lens and having a pierced
hole for shaping a cross section of the laser beam, the lens
condenses the laser beam of which cross section is shaped by the
mask and forms an image of the pierced hole on the surface of the
processing target held by the holder, and the controller comprises
a moving mechanism that moves the mask and the lens, and a
synchronizer that synchronizes scanning by the beam scanner with
motion of the mask and the lens by the moving mechanism.
27. The laser processing apparatus according to claim 26, wherein
the moving mechanism keeps an optical length between the mask and
the lens fixed and between the lens and the surface of the
processing target fixed, by moving the lens along a direction of
the laser beam passing through the lens and moving the mask along a
direction of the laser beam passing through the mask.
28. The laser processing apparatus according to claim 26, wherein
the moving mechanism moves the mask and the lens to decrease a
variation in an area of the image of the pierced hole formed on the
surface of the processing target when an incident angle of the
laser beam on the surface of the processing target is varied.
29. The laser processing apparatus according to claim 26, wherein
the controller further comprises a variable attenuator that adjusts
pulse energy of the laser beam irradiated from the laser source
wherein an attenuation rate of the pulse energy is decreased when
the incident angle of the laser beam on the surface of the
processing target becomes large.
30. The laser processing apparatus according to claim 26, wherein
said controller further comprises a pulse energy density changer
that increases the pulse energy density in a peripheral area of a
cross section of the pulsed laser beam compared to a central
part.
31. The laser processing apparatus according to claim 26, wherein
the pierced hole of the mask has a shape having a pair of sides
parallel to each other.
32. The laser processing apparatus according to claim 31, wherein,
when an X-direction and a Y-direction which are crossing with each
other at a right angle are defined on the surface of the processing
target held by the holder, the beam scanner comprises an
X-direction scanner for scanning the laser beam along the
X-direction and a Y-direction scanner for scanning the laser beam
along the Y-direction on the surface of the processing target, and
the lens forms an image of the pair of the parallel sides of the
pierced hole on the surface of the processing target in the
X-direction.
33. The laser processing apparatus according to claim 25 wherein
the controller comprises a moving mechanism that moves the lens,
and an adjuster so adjusts the moving mechanism that a variation in
pulse energy density or power density of the laser beam on the
surface of the processing target is suppressed when the beam
scanner moves an incident position of the laser beam on the surface
of the processing target.
34. The laser processing apparatus according to claim 33, wherein
the adjuster adjusts the moving mechanism to so move the lens along
the direction of the laser beam that a focal point of the laser
beam goes away from the incident point on the target when increase
in the pulse energy density or power density of the laser beam on
the surface of the processing target is to be suppressed, and so to
move the lens along the direction of the laser beam that a focal
point of the laser beam comes closer to the incident point on the
target when decrease in the pulse energy density or power density
of the laser beam on the surface of the processing target is to be
suppressed.
35. The laser processing apparatus according to claim 25, wherein
the controller comprises a moving mechanism that moves the lens,
and an adjuster that adjusts the moving mechanism to so move the
lens that variation in an area of a beam spot on the surface of the
processing target is suppressed when the beam scanner moves an
incident position of the laser beam on the surface of the
processing target.
36. The laser processing apparatus according to claim 25, wherein
the controller further comprises a variable attenuator that
attenuates power of the laser beam at a variable attenuation rate,
and an adjuster that so adjusts the variable attenuator that
variation in pulse energy density or power density of the laser
beam on the surface of the processing target is suppressed when the
beam scanner moves an incident position of the laser beam on the
surface of the processing target.
37. A laser processing apparatus, comprising: a laser source that
emits laser beam; a holder that holds a processing target; a first
lens that converges or diverges the laser beam from the laser
source; a second lens that condenses the laser beam passed through
the first lens; a beam scanner that sweeps the laser beam passed
through the second lens, to scan an incident point of the laser
beam on a surface of the processing target held by the holder; a
moving mechanism that moves the first lens; and a controller that
controls the moving mechanism to so move the first lens that
variation in pulse energy density or power density of the laser
beam on the surface of the processing target is suppressed when the
beam scanner moves an incident position of the laser beam on the
surface of the processing target, and wherein NA1/NA2 is not less
than 2 when a numerical aperture of the first lens for the laser
beam irradiated on the first lens is NA1, and a numerical aperture
of the;second lens for the laser beam irradiated on the second lens
is NA2.
38. A laser processing apparatus, comprising: a laser source that
emits laser beam; a holder that holds a processing target; a beam
cross section shaper that has a pierced hole through which the
laser beam from the laser source passes and can change a length in
one direction of a cross section of the laser beam passing through
the pierced hole upon reception of an external signal; a lens that
condenses the laser beam from the beam cross section shaper; a beam
scanner that sweeps the laser beam passed through the lens, to scan
an incident point of the laser beam on a surface of the processing
target held by the holder; and a controller that so controls the
beam cross section shaper that variation in a shape of a beam spot
on the surface of the processing target is suppressed when the beam
scanner moves an incident position of the laser beam on the surface
of the processing target.
39. The laser processing apparatus according to claim 38, wherein
said controller inclines said beam cross section shaper from a
surface vertical to a direction of the laser beam when the cross
section of the laser beam is to be shaped into a shape of which one
direction is longer than another.
40. The laser processing apparatus according to claim 39, wherein
the beam cross section shaper can rotate the pierced hole around an
axis parallel to the direction of the laser beam.
41. A laser processing apparatus, comprising: a laser source that
emits laser beam; a holder that holds a processing target; a lens
that condenses the laser beam from the laser source; a beam scanner
that sweeps the laser beam passed through the lens, to scan an
incident point of the laser beam on a surface of the processing
target held by the holder; and a proximity mask disposed on a path
of the laser beam directed to the processing target from the beam
scanner and has a pierced hole through which the laser beam is
allowed to pass to be irradiated on the processing target.
42. The laser processing apparatus according to claim 41, further
comprising: a moving mechanism that moves the lens; and a
controller that controls the moving mechanism to so move the lens
that variation in pulse energy density or power density of the
laser beam on the surface of the processing target is suppressed
when the beam scanner moves an incident position of the laser beam
on the surface of the processing target.
43. A laser processing apparatus, comprising: a laser source that
emits continuous-wave laser beam; a holder that holds a processing
target; an optical system receiving the laser beam from the laser
source, which can switched over between a first configuration in
which the laser beam is emitted and a second configuration in which
the laser beam is not emitted; a mask that has a rectangle-shaped
pierced hole which allows the laser beam from the optical system to
pass and be shaped; a lens that condenses the laser beam from the
mask and forms an image of the rectangle-shaped pierced hole on a
surface of the processing target held by the holder; a moving
mechanism that moves the holder and can move an incident position
of the laser beam from the lens on the surface of the processing
target; a mask rotating mechanism that rotates the mask around an
axis parallel to an optical axis of the laser beam passing through
the pierced hole of the mask; and a controller that controls the
first or second configuration of the optical system, controls the
moving mechanism to move the incident position of the laser beam on
the processing target along a first direction and controls the mask
rotating mechanism to rotate the mask to make a certain side of the
image of the rectangle-shaped pierced hole on the surface of the
processing target parallel to the first direction before the moving
mechanism moves the incident position of the laser beam on the
processing target along the first direction.
44. A laser processing apparatus, comprising: a holder that holds a
processing target; a first laser source that emits pulsed laser
beam; a second laser source that emits continuous-wave laser beam;
an optical system that transmits the pulsed laser beam from the
first laser source and the continuous-wave laser beam from the
second laser source on a surface of the processing target held by
the holder in such a manner that a beam spot of the pulsed laser
beam is included inside a beam spot of the continuous-wave laser
beam; and a moving mechanism that moves the beam spots of the
pulsed laser beam and the continuous-wave laser beam on the surface
of the processing target.
45. The laser processing apparatus according to claim 44, wherein
the optical system joins the pulsed laser beam from the first laser
source and the continuous-wave laser beam from the second laser
source, and transmits the laser beams on the surface of the
processing target along same optical path.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation application of
PCT/JP03/011126, filed on Aug. 29, 2003, which claims priority on
Japanese patent application 2002-254015, filed on Aug. 30, 2002,
which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] A) Field of the Invention
[0003] This invention relates to a laser processing method and a
laser processing apparatus processes by irradiating laser beam on a
processing target.
[0004] B) Description of the Related Art
[0005] FIG. 9 is a schematic view showing a conventional laser
processing apparatus that forms a groove. Pulsed laser beam is
radiated from a light source 51, for example, at frequency of 1
kHz. After pulse energy density of a beam cross section is
uniformed (flat-topped) by a homogenizer 52, the cross section of
the laser beam is formed to be a circular shape. The laser beam of
which the cross section has been formed is reflected by a
reflection mirror, 54 and irradiates to a substrate 56 via a focus
lens 55. The substrate 56 is, for example, a substrate wherein an
indium-tin-oxide (ITO) film is formed on a glass basic material.
The laser beam irradiates to the ITO film on the substrate 56. A
beam spot of the laser beam irradiated onto a surface of the ITO
film is, for example, a circle with diameter of 0.2 mm. The
substrate 56 is loaded on an XY stage 57. By moving the substrate
56 in a two dimensional plane, an irradiation position of the
pulsed laser beam can be moved in the surface of the substrate
56.
[0006] First, tin order o form groove on the ITO film on the
substrate 56, the XY stage 57 is moved so that the pulsed laser
beam is irradiated with a 50% redundancy rate. The redundancy rate
means that a rate of a moving distance to a direction of a radius
of a circle by one shot of the pulsed laser beam to the
diameter.
[0007] FIG. 10A is a schematic plan view of the substrate 56
wherein a groove is formed on the ITO film by opening continuous
holes by the laser beam irradiated with 50% redundancy rate. The
openings of the groove are indicated with thick lines. As a result
that the holes with a shape depending on the beam spot of the laser
beam irradiated onto the ITO film are continuously excavated, the
groove is formed. Therefore, edges of the openings; along the
direction of the groove length have bumps by a part of a perimeter
of the circular beam spot. Also, when the frequency of the laser
beam to be irradiated is 1 kHz, and the beam spot of the laser beam
on the ITO film on the substrate 56 is a circle of diameter of 0.2
mm, processing velocity becomes 100 m/s. Mainly, the processing
velocity is controlled by the moving velocity of the XY stage;
therefore, the processing velocity cannot be increased more than.
100 mm/s considering uniformity of the processed form.
[0008] In order to make the edges of the openings of the groove
formed on the ITO film close to a straight line, a method for
increasing the redundancy rate will be used. For example, the XY
stage 57 is moved so that the pulsed laser beam is irradiated with
90% redundancy rate onto the ITO film of the substrate 56 to form
the groove.
[0009] FIG. 10B is a schematic plan view of the substrate 56 on
which the groove is formed on the ITO film by opening continuous
holes with the laser beam irradiated with 90% redundancy rate.
Similar to FIG. 10A, the openings of the groove are indicated with
the thick lines. The edges of the openings along the length
direction of the grooves become closer to a straight line. However,
the processing velocity is 1/5 of the case that the 50%, redundancy
rate is used, that is, 20 mm/s because the laser beam is irradiated
with 90% redundancy rate. Although the forms of the opening can be
improved, time efficiency of the process becomes worse.
[0010] FIG. 11 is a schematic cross sectional view of the substrate
56. The groove is formed on the ITO film formed on the glass basic
material. The sidewalls of the groove are inclined to the surface
of the substrate 56. It is preferable that the groove has a sheer
sidewall shape.
SUMMARY OF THE INVENTION
[0011] It is an object of the present invention to provide a laser
processing method and a laser processing apparatus that can execute
a high quality laser process.
[0012] According to one aspect of the present invention, there is
provided a laser processing method, comprising the steps of: (a)
irradiating laser beam from a laser source through an optical
system onto a surface of a processing target; and (b) scanning said
laser beam on the surface of the processing target by the optical
system and so controlling at least one parameter among those of
said laser source and said optical system that variation of an
irradiating condition of the laser beam on the processing target
caused by the scanning is suppressed.
[0013] According to another aspect of the present invention, there
is provided a laser processing apparatus, comprising: a laser
source that emits laser beam; a holder that holds a processing
target; an optical system comprising a lens that condenses the
laser beam from the laser source, and a beam scanner that sweeps
the laser beam passed through the lens, to scan an incident point
of the laser beam on a surface of the processing target held by the
holder; and a controller which so controls at least one parameter
among those of said laser source and said optical system that
variation of an irradiating condition of the laser beam on the
processing target caused by scanning is suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic view of a laser processing apparatus
according to the first embodiment of the present invention.
[0015] FIG. 2 is a schematic view showing a light path of laser
beam in the laser processing apparatus according to the first
embodiment of the present invention.
[0016] FIG. 3A and FIG. 3B are schematic plan views of a substrate
processed by the laser beam irradiation.
[0017] FIG. 4A is an example of a pierced hole of a mask, and FIG.
4B is a schematic view showing a hole to be opened on the substrate
when the pierced hole shown in FIG. 4A are focused on the
substrate.
[0018] FIG. 5A is a schematic graph showing energy density for one
pulse in the cross section of the pulsed laser beam radiated from
the laser source. FIG. 5B is a schematic graph showing energy
density for one pulse in the cross section of the pulsed laser beam
of which the pulse energy density distribution is converted by a
cone optical system. FIG. 5C is a schematic cross sectional view of
the hole processed by the pulsed laser beam having the pulse energy
density distribution shown in FIG. 5B.
[0019] FIG. 6 is a schematic view of the laser processing apparatus
according to a modified example of the first,embodiment of the
present invention.
[0020] FIG. 7 is a schematic view showing a light path adjusting
mechanism.
[0021] FIG. 8A and FIG. 8B are schematic views showing a career
mechanism.
[0022] FIG. 9 is a schematic view of a conventional laser scribing
apparatus.
[0023] FIG. 10A and FIG. 10B are schematic plan views of a
substrate processed by the conventional laser scribing
apparatus.
[0024] FIG. 11 is a schematic cross sectional view of the substrate
processed by the conventional laser scribing apparatus.
[0025] FIG. 12A is a schematic view of a laser processing apparatus
according to the second embodiment of the present invention. FIG.
12B is a schematic view of a laser processing apparatus according
to a modified example of the second embodiment of the present
invention.
[0026] FIG. 13 is a schematic view showing a light path of the
laser beam in the laser processing apparatus according to the
second embodiment of the present invention.
[0027] FIG. 14 is a schematic view showing a light path of the
laser beam in the laser processing apparatus according to a
modified example of the second embodiment of the present
invention.
[0028] FIG. 15A its a schematic view of the laser processing
apparatus according to the third embodiment of the present
invention. FIG. 15B is a schematic view showing other structural
example of a primary concentrating lens according to the third
embodiment of the present invention
[0029] FIG. 16 is a schematic view showing structural example of a
secondary concentrating lens.
[0030] FIG. 17 is a schematic view of the laser processing
apparatus according to the fourth embodiment of the present
invention.
[0031] FIG. 18A is schematic view looked at from a direction of the
axis of rotation of an aperture inclining mechanism that is rotated
by the aperture inclining mechanism. FIG. 18B is a schematic view
looked at from a direction of an optical axis of the laser beam of
the aperture rotated by the aperture inclining mechanism.
[0032] FIG. 19 is a schematic view of the laser processing
apparatus according to the fifth embodiment of the present
invention.
[0033] FIG. 20 is a plan view of the substrate, which an image of
the pierced hole is projected, showing a result of a simulation
concerning to transcription precision in a laser processing method
using a proximity mask.
[0034] FIG. 21 is a graph that schematically shows a relationship
between an extent angle of the laser beam and a proximity gap when
the process is executed at a certain transcription precision.
[0035] FIG. 22A is a schematic view of the laser processing
apparatus according to the sixth embodiment of the present
invention, and FIG. 22B is a schematic cross sectional view of the
substrate.
[0036] FIG. 23 is an example of a timing chart of a trigger signal
and the laser beam when the laser processing is executed by using
the laser processing apparatus according to the sixth embodiment of
the present invention.
[0037] FIG. 24A is a schematic plan view of the substrate on which
a line is formed. FIG. 24B is a schematic plan view of the
substrate on which a dot is formed.
[0038] FIG. 25 is a schematic view showing a mask rotation
mechanism holding a mask.
[0039] FIG. 26 is a schematic plan view of the substrate on which a
line is formed by using the mask rotation mechanism.
[0040] FIG. 27A is a schematic view of the laser processing
apparatus according to the seventh embodiment of the present
invention, and FIG. 27B is a schematic cross sectional view of the
substrate.
[0041] FIG. 28A, FIG. 28B and FIG. 28C are plan views of the
substrate for explaining a positional relationship between a
processing target point and a beam spot.
[0042] FIG. 29 is a schematic plan view of the substrate formed a
line without the mask rotation mechanism.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] FIG. 1 is a schematic view of a laser processing apparatus
according to the first embodiment of the present invention.
[0044] A high frequency (a wave length of 355 nm) that is three
times of Nd:YAG laser is radiated (or emitted) with a pulse energy
1 mJ/pulse and a pulse width 50 ns from a laser source 1, for
example, Nd:yttrium-alminum-garnet (YAG) laser oscillator including
a wave-length conversion unit. The laser beam passes through a
variable attenuator 2 that adjusts the pulse energy, and then
through an expander 3 that enlarges diameter and emits an expanded
collimated beam, and is incident on a cone optical system 4. The
cone optical system 4 is formed of one pair of cone lenses 4a and
4b. The pair of the cone lenses 4a and 4b are, for example, in the
same shape and are positioned so that the bottoms counter to each
other. The laser beam is irradiates from the direction of a right
cone axis to the cone lens 4a so that the center of the beam cross
section overlaps the top of the right cone part and radiated from
the cone lens 4b. The cone optical system 4 converts beam profile
of the laser beam to irradiate in order to be weak in the central
part of the beam cross section and to be powerful in the peripheral
part. This will be explained later. Moreover, as for the cone
optical system 4, a convex lens instead of the cone lens 4b at the
laser beam radiation side can be used.
[0045] The laser beam radiated from (or passed through) the cone
optical system 4 passes an object lens 6 that focuses the
rectangular pierced hole of the mask 5 on the substrate 12. The
mask 5 and the object lens 6 can move to a parallel direction to
the moving direction of the laser beam by the each of voice coil
mechanisms 9 and 10 (it can be replaced by a driver mechanism such
as a piezo driver mechanism). The voice coil mechanisms 9 and 10
are driven by a signal transmitted from a controller 11. Moreover,
the substrate 12 is fixed on a holding stand (or holder) 8.
[0046] The laser beam concentrated (or condensed) by the object
lens 6 irradiated to a galvano scanner 7. The galvano scanner 7 is
formed of a scanner for X 7a and a scanner for Y 7b, and scans the
laser beam at high velocity in a two dimensional direction. The
scanner for X 7a and the scanner for Y 7b are formed of a
reflection mirror that is oscillatable. When an X direction and a Y
direction which cross each other are decided on the substrate 12 to
be held on the holding stand 8, the scanner for X 7a and the
scanner for Y 7b scan the laser beam so that each of the
irradiation positions of the laser beam concentrated by the object
lens 6 moves toward the X direction and the Y direction on the
surface of the substrate 12. The galvano scanner 7 can scan the
laser beam in a two dimensional direction by combining the scanner
for X 7a and the scanner for Y 7b.
[0047] The substrate 12 that is a processing target is, for
example, a substrate wherein the indium-tin-oxide (ITO) film is
formed on a glass base material, and the laser beam irradiates to
the ITO film of the substrate 12 at a processing energy of about 1
J/cm.sup.2.
[0048] FIG. 2 is a schematic view showing a light path of laser
beam that scans on the substrate 12 via the mask 5, the object lens
6 and the galvano scanner 7.
[0049] When the laser beam is irradiating to an irradiating
position (which is the position of the laser beam spot on the
target to be processed) M on the substrate 12, a pierced hole of
the mask 5 is focused at M. Also, when an optical length from the
mask 5 to the object lens 6 is a, and when an optical length from
the object lens 6 to the irradiating position (or incident
position) on the substrate 12 is b, and when a focal length of the
object lens is f, it is necessary to satisfy the following equation
in order to focus the pierced hole of the mask on the substrate
12.
(1/a)+(1/b)=1/f (1)
[0050] By the operation of the galvano scanner 7, the irradiating
position of the laser beam is changed from the irradiation position
M on the substrate 12 to N. If incident angles to the irradiating
position M and an incident angle to the irradiating position N are
different, and if the mask 5 and the object lens 6 are fixed, the
optical length from the object lens 6 to the irradiating position M
and the optical length from the object lens 6 to the irradiating
position N are different. (the difference is expressed as
.DELTA.b). Therefore, the pierced hole of the mask 5 is not focused
on the N.
[0051] In the laser processing apparatus shown in FIG. 1, the
controller 11 is synchronized with the movement of the galvano
scanner 7 and a signal to move the mask 5 and the object lens e to
each of the voice coil mechanisms 9 and 10. This signal is a signal
for moving the mask 5 and the object lens 6 in order to maintain a
fixed optical length from the mask 5 to the object lens 6 and from
the object lens 6 to the irradiating position on the substrate 12.
The voice coil mechanisms 9 and 10 receive the signal from the
controller 11 and move each of the mask 5 and the object lens 6
toward a parallel direction to the moving direction of the laser
beam.
[0052] As shown in FIG. 2, when the irradiating position M is
changed to N, a moving distance of the mask 5 and the object lens 6
by the voice coil mechanisms 9 and 10 is .DELTA.b. The mask 5 and
the object lens 6 are displaced by the same length .DELTA.b to the
same direction. By doing this, the above equation (1) is satisfied,
and the pierced hole of the mask 5 is focused at the irradiating
position N.
[0053] Not only in the two points of the irradiating positions M
and N, for example, when the optical length a from the mask 5 to
the object lens 6 and the optical length b from the object lens 6
to the irradiating position on the substrate 12 are always fixed
during scanning the laser beam, the pierced hole of the mask 5 is
focused on the surface of the substrate 12. The mask 5 and the
object lens. 6 are synchronized with the scanning of the laser beam
by the galvano scanner 7, and are moved so that the optical length
a and the optical length b are always fixed. In this case, focus
magnification (a reduction rate) of the pieced hole of the mask 5
is always fixed.
[0054] For example, when the focal length f of the object lens 46
is 833 mm, and when the optical length a from the mask 5 to the
object lens 6 is 5000 mm, and when the optical length b from the
object lens 6 to the irradiating position on the substrate 12 is
fixed 1000 mm, focus magnification (a reduction rate) of the
pierced hole of the mask 5 is 1/5.
[0055] FIG. 3A is a schematic plan view of a substrate 12 wherein a
hole is formed at a focus position by irradiating one shot of the
laser beam in order to focus a rectangular pierced hole of the mask
5 on the surface of the substrate 12. On the substrate 12, a
rectangular beam spot which the pierced hole is focused is formed,
and a hole is opened at the position on the ITO film.
[0056] FIG. 3B is a plan view of the substrate 12 on which a groove
is formed at the irradiating position. In FIG. 3B, the irradiation
position of the beam is moved focusing the rectangular pierced hole
of the mask 5 at a fixed focus magnification (a reduction rate),
and the groove is formed at the irradiating position by irradiating
the four-shots pulsed laser beam. The pulsed laser beam is scanned
toward a long side direction: of the beam spot focus in a rectangle
by the galvano scanner 7. Also, the beam is irradiated at the 50%
redundancy rate, and the opened holes, are continued at each shot
to form the groove.
[0057] A fixed sized rectangular beam spot is formed, and the laser
beam is scanned toward a parallel direction to a pair of parallel
sides (long sides in FIG. 3B). By doing this, a groove with a fixed
width can be formed. As the embodiment of the present invention,
when the pulsed laser beam is used, the laser beam is scanned so
that a part of a pair of sides (long sides in FIG. 3B) that has
parallel beam spot overlaps with a part of a pair of the sides that
has parallel beam spot of the last shot. Since the edge of the
groove opening is formed by a straight line part of the rectangular
beam spot, it becomes a straight line without bumps.
[0058] From a point of easiness of control, in the substrate 12, it
is preferable that the beam spot is formed so that a direction of a
pair of sides of which beam spot is parallel is parallel to the X
direction and the Y direction.
[0059] Moreover, the pierced hole of the mask 5 that is focused on
the substrate 12 is not necessary to be rectangle. When the beam
spot is formed in a shape having a parallel pair of sides and the
laser beam is scanned toward a parallel direction to the parallel
pair of sides, the groove with a fixed groove without bumps at the
edge of the opening can be processed.
[0060] FIG. 4A is an example of a pierced hole of a mask. The
pierced hole of the mask 5 is formed to be a shape having a
parallel pair of sides. Other pair of sides connected the above
pair of sides each other is bending toward inside. When the cross
section of the laser beam is reformed or shaped by using the mask
having the above pierced hole, a beam spot with a shape having a
parallel pair of sides can be formed.
[0061] FIG. 4B is a schematic view showing a hole to be opened on
the substrate when the pierced hole shown in FIG. 4A is focused on
the substrate. By forming the same holes as the above hole
continuously in a parallel direction to the parallel pair of sides,
a groove with a fixed width that does not have bumps at the edge of
the opening can be processed. Moreover, since an accumulated energy
density of the laser beam that irradiates to a peripheral of the
edge of the groove is larger than an accumulated energy density of
the laser beam that irradiates in the center of the groove, the
side of the groove can become closer to verticality.
[0062] Moreover, when only a groove that extends to one direction
is firmed by the laser process as shown in FIG. 3B, one dimensional
galvano scanner and a polygon scanner having an oscillating mirror
may be used. At that time, scanning direction of the scanner and a
direction of one pair of sides with parallel beam spot are
agreed.
[0063] The cone optical system 4 will be explained with reference
to FIGS. 5A to 5C. As described above, the cone optical system 4
converts the beam profile of the incoming laser beam in order to
make the cross section of the beam weak in the central part and to
make it strong in the peripheral.
[0064] FIG. 5A is a schematic graph showing energy density for one
pulse in the cross section of the pulsed laser beam radiated from
the laser source 1. Generally, the pulsed laser beam is high in
pulse energy density in the central part of the cross section, and
becomes low in pulse energy density as close to the peripheral
area. The cone optical system 4 reverses the central part and the
peripheral area of the irradiated laser beam by two cone lenses 4a
and 4b before the radiation. Therefore, the beam profile of the
laser beam to be radiated from the cone optical system 4 has a weak
distribution in the central part of the beam cross section and a
strong distribution in the peripheral area.
[0065] FIG. 5B is a schematic graph showing energy density for one
pulse in the cross section of the pulsed laser beam after the
radiation from the cone optical system 4 and reforming with the
mask 5. The beam has a weak distribution in the central part of the
beam cross section and a strong pulse energy density distribution
in the peripheral area.
[0066] FIG. 5C is a schematic cross sectional view of the substrate
12 cut along C5-C5 line in FIG. 3B. The laser beam having the beam
profile shown in FIG. 5B is concentrated by the object lens 6 to be
irradiated to the substrate 12. By that, an inclination angle of
the sides can be close to 90 degree on the ITO film of the
substrate 12. Therefore, the groove shown in FIG. 3 is not only
formed to have the opening edge of straight line, but also has
sheer side walls.
[0067] Moreover, synchronizing with the movement of the galvano
scanner, the pulse energy of the pulsed laser beam is adjusted, and
a better process can be executed. When the incident angle of the
laser beam which irradiates to the substrate 12 becomes large, a
beam spot area at the irradiating position becomes large.
Therefore, when the pulse energy of the laser beam scanned by the
galvano scanner is fixed at a fixed value, the pulse energy density
of the laser beam at the irradiating position becomes small as the
incident angle becomes large, and change in processitivity is
generated. In order to keep a fixed processitivity. There are some
cases to keep a fixed value of the pulse energy density of the
laser beam at the irradiating position.
[0068] A variable attenuator 2, with synchronization to the
movement of the galvano scanner 7, changes the pulse energy of the
laser beam radiated from the laser source 1. Based on the
synchronization signal transmitted from the controller 11, when the
laser beam is irradiated to the substrate 12 at a large incident
angle, an attenuation rate of the pulse energy makes small, and the
pulse energy of the beam radiated from the variable attenuator 2 is
increased. By doing that, the pulse energy density at the
irradiating position of the laser beam can be kept the fixed
value.
[0069] Moreover, it is not necessary to keep the fixed value of the
pulse energy density. When the incident angle of the laser beam to
the substrate 12 changes, as the change in pulse energy density at
the irradiating position makes small, the processing quality can be
improved when the attenuation rate of the pulse energy by the
variable attenuator 2.
[0070] Moreover, when the laser beam is irradiated on the substrate
12 to scan, synchronizing with the movement of the galvano scanner
7 and changing the focus magnification rate (reduction rate) of the
pierced holes of the mask 5, the pulse energy density at the
irradiating position of the laser beam can be kept the fixed
value.
.DELTA..sub.2=f.sup.2.times..DELTA..sub.1/(b-f-.DELTA..sub.1)/(b-f)
(2)
[(a+.DELTA..sub.2)/(b-.DELTA..sub.2)].sup.2=(a/b).sup.2/cos .theta.
(3)
[0071] In order to satisfy the both of the above equations,
.DELTA..sub.1 and .DELTA..sub.2 are determined with corresponding
to the incident angle .theta. to the substrate 12 (an angle made by
a normal and the angle of incidence), and in order to the optical
length from the mask 5 to the object lens 6 be a+.DELTA..sub.2, and
in order to the optical length from the object lens 6 to the
irradiating position on the substrate 12 be b-.DELTA..sub.2, the
mask 5 and the object lens e may be moved corresponding to the
incident angle .theta.. Here, a is the optical length from the mask
5 to the object lens 6 when the incident angle .theta. is 0, and b
is the optical length from the object lens 6 to the irradiating
position on the substrate 12. Also, f is the focus point distance
of the object lens 6. Although the equations (2) and (3) are not
strictly satisfied, the quality of the laser process can be
improved by changing the focus magnification rate in order to make
the change in beam spot area smaller when the incident angle
changes. When the incident angle becomes large, the focus
magnification rate (reduction rate) may be made smaller.
[0072] FIG. 6 is a schematic view of the laser processing apparatus
that equips a light path adjustment mechanism 20 that changes the
optical length b from the object lens 6 to the irradiating position
on the substrate 12 according to a modified example of the first
embodiment of the present invention. The voice coil mechanisms 9
and 10 are removed from the laser processing apparatus shown in
FIG. 1, and a light path adjustment mechanism 20 is added. Other
structure is the same as the structure of the laser processing
apparatus shown in FIG. 1. In the laser processing apparatus shown
in FIG. 6, the optical length a from the mask 5 to the lens 6 is
fixed. By the light path adjustment mechanism, for example,
synchronizing with the movement of the galvano scanner 7, the
optical length b from the object lens 6 to the irradiating position
on the substrate 12 can be kept fixed during scanning the laser
beam. By doing that, the pierced hole of the mask 5 is always
focused at a fixed focus magnification rate (reduction rate), and a
groove shown in FIG. 3B can be processed.
[0073] FIG. 7 is a schematic view showing the light path adjusting
mechanism 20. The light path adjustment mechanism 20 is formed of
four reflective mirrors 21a to 21d. Each of the four mirrors change
a moving direction of the incoming laser beam, for example at 90
degree, and the light path adjustment mechanism 20 radiates the
laser beam to a parallel direction to the moving direction of the
irradiated laser beam. The reflective mirrors 21a and 21b form a
moving part 22. The moving part 22 can move to a direction of an
arrow in the drawing. The optical length b from the object lens 6
to the substrate 12 is adjusted by displacing the moving part 22.
When the incident angle of the laser beam to the substrate 12
becomes large, the moving part 22 moves to upward in FIG. 7. By
shortening the optical length of the laser beam in the light path
adjustment mechanism 20, the light path b is kept fixed. The
movement of the moving part 22 is executed after receiving the
signal from the controller 11. The controller 11 keeps the optical
length b from the object lens 6 to the substrate 12 shown in FIG. 6
fixed by synchronizing the movement of the galvano scanner to the
movement of the moving part 22.
[0074] In the laser processing apparatus shown in FIG. 6, although
the light path adjustment mechanism 20 is added for adjusting the
optical length b, it also can be inserted between the mask 5 and
the object lens 6 for adjusting the light path a. By using two
light path adjustment mechanisms 20, the optical length a and the
optical length b can be adjusted during scanning the laser beam,
for example, in order to satisfy the equation (1).
[0075] Moreover, depending on the process to be executed, either
one of the mask 5 and the object lens 6 may be moved. For example,
with fixing the object lens 6, only the mask 5 can be moved in
order to satisfy the equation (1).
[0076] Although the substrate wherein the ITO film is formed on the
glass substrate is considered as the processing target, a substrate
wherein a polyimide film is formed on a silicon substrate and the
polyimide film part may be processed may be used. These are used as
a solar battery substrate and a liquid-crystal substrate Moreover,
a touch panel which the ITO film is formed on the polyimide film,
moreover, a semiconductor film or the like can be processed. Also,
a film-type processing target can be processed.
[0077] FIG. 8A is a schematic view of a carrier mechanism 31 for
carrying a film 30. The film 30 is carried by the carrier mechanism
31. A vacuum chuck 32 fixes a predetermined processing position on
the film 30 and determines a surface to be processed. By
irradiating the laser beam scanned by the galvano scanner to the
film 30 fixed by the vacuum chuck 32, the process at the
predetermined process position is executed. When the process at the
predetermined process position terminates, the carrier mechanism 31
carries the film 30, and other process position is fixed by the
vacuum chuck to be processed.
[0078] Conventionally, the process is executed by moving the film
30 fixed by the vacuum chuck 32 at the XY stage and irradiating the
beam by using a fixed optics. In the embodiments of the present
invention, the process is executed by scanning the beam by the
galvano scanner, and executing the process by irradiating the beam
at the process position. Therefore, the processing velocity can be
faster.
[0079] FIG. 8B is a schematic view of the carrier mechanism 31
equipped with the rotary encoder 33. The rotary encoder 33 detects
the velocity of the film 30 carried by the carrier mechanism 31. A
detected result is transmitted to the controller 11, and the
controller 11 calculates carried amount of the film 30 from the
carrying velocity of the film 30. A control signal formed from the
carrying velocity of the film 30, the carried amount and the data
at the designated processing position determined on the film 30 is
transmitted from the controller 11 to the galvano scanner 7. The
galvano scanner 7 scans the laser beam after receiving the control
signal and the process is executed by irradiating the beam at the
predetermined processing position on the film 30.
[0080] Since the XY stage is not necessary, and the process can be
executed carrying the film 30, the processing velocity can be
faster.
[0081] By using the laser processing apparatus of which the cone
optical system 4, the mask 5 and the voice coil mechanism 9 are
removed from the laser processing apparatus shown in FIG. 1, a
focus process can be executed. The laser beam is focused by the
object lens 6 on the substrate 12. By the movement of the galvano
scanner, the laser beam scans on the substrate 12. When the
irradiating position of the beam on the substrate 12 is changed,
the object lens 6 is moved to a parallel direction to the moving
direction of the beam which passes through the object lens by the
voice coil mechanism 10 so that the laser beam optical length b
from the object lens 6 to the substrate 12 is kept to be fixed. By
this move, the laser beam is always focused on the substrate 12.
Therefore, the process in good quality can be realized.
[0082] Although the pulsed laser beam is used in the embodiments of
the present invention, a continuous-wave laser beam may be used
depending on the process to be executed. Although in the
embodiments of the present invention, an Nd:YAG laser oscillator
including a wave-length conversion unit is used, and a high
frequency wave of three times of the Nd:YAG laser is radiated, a
basic wave of the solid laser to, five-times high frequency wave
can be used. Also, a CO.sub.2 laser and the like can be used.
[0083] Also, in the embodiments of the present invention, although
the galvano scanner is used as a fast scanning optical system, a
fast scanning optical system using a polygon mirror can be used. By
moving the processing target at the XY stage, the beam is scanned
by using the fast scanning optical systems without changing the
irradiating position of the laser beam. Then the processing
velocity can be improved since the irradiating position of the
laser beam is changed.
[0084] In the focus processing method described in the above, the
laser beam is always focused on the surface of the substrate. Next,
a method for executing a high quality process by adjusting the
positioning relationship between the focus of the laser beam and
the surface of the substrate corresponding to the irradiating
position of the laser beam to the surface of the substrate will be
explained.
[0085] In a laser processing apparatus according to the second
embodiment of the present invention shown in FIG. 12A, the cone
optical system 4, the mask 5 and the voice coil mechanism 9 are
removed from the laser processing apparatus shown in FIG 1.
Moreover, a variable attenuator 2 is removed, and it equips a
circular pierced hole between the expander 3 and the object lens 6,
and an aperture 5a that adjusts a beam radius is positioned. It is
not necessary to focus the pierced hole of the aperture 5a on the
surface of the substrate 12.
[0086] By using the voice coil mechanism 10, pulse energy density
of the laser beam irradiated on the surface of the substrate is
adjusted by moving the object lens 6 to the parallel direction to
the moving direction of the laser beam that passes through the
object lens 6 and making the laser beam focus be close to and away
from the surface of the substrate.
[0087] By the control signal transmitted from the controller 11,
the galvano scanner 7 swings the laser beam to a desired moving
direction at a desired timing. By the control signal transmitted
from the controller 11, the voice coil mechanism 10 is synchronized
with the galvano scanner 7 to move, and the laser can be irradiated
to the substrate 12 at desired pulse energy density corresponding
to the irradiating position of the laser beam.
[0088] With reference to FIG. 13, an example of a laser processing
method using the laser processing apparatus in FIG. 12A will be
explained. An upper part in FIG. 13 schematically shows a light
path of the pulsed laser beam scanning on the substrate 12 via the
galvano scanner 7.
[0089] A laser beam L1b irradiates to an irradiating position M1
vertical to the surface of the substrate. Laser beams L1a and L1c
irradiate to irradiating positions N1a and N1c at incident angle
.alpha.1. The irradiating position M is positioned at a center of a
line between the edge of the irradiating position. N1a and the edge
of the irradiating position N1c.
[0090] A lower part in FIG. 13 shows a surface of the substrate
looked at from the galvano scanner 7. Each of beam spots 91a, 91b
and 91c shows either one of beam spots on the surface of the
substrate (that is, the irradiating positions N1a, M1 and N1c) of
the laser beams L1a, L1b and L1c.
[0091] Swinging the moving direction of the laser beam from the
light path of the laser beam L1a to the light path of the laser
beam L1c, irradiation of the pulsed laser beam is repeated. Then,
as same as those shown in FIGS. 10A and 10B, a groove 101 is formed
on the surface of the substrate so that the holes formed at the
irradiating position of each laser continue.
[0092] First, when the laser beam L1 a that forms a starting point
of the groove 101 is irradiated, the position of the object lens 6
is set so that the laser beam L1a is focused at the irradiating
position N1a. Moreover, a point where the size of the beam, spot
becomes minimum is called a focus of the laser beam.
[0093] Then, when the laser beam L1c that forms the ending point of
the groove 101 is irradiated, the position of the object lens 6 is
so controlled that the laser beam L1c is focused at the irradiating
position N1c. Since the optical length from the object lens 6 to
the irradiating positions N1a and N1c is almost the same, the
position of the object lens 6 at a time of starting and finishing
of the groove process may be considered to be the same. Moreover,
the incident angles of the laser beam L1a and L1c are the same, and
areas of the beam spots 91a and 91c are considered to be the
same.
[0094] First, it will be explained what kind of problem arises when
the groove is formed by scanning the laser beam in a state that the
object lens 6 is fixed at this position.
[0095] When the object lens 6 is fixed at a position where the
laser beam L1a is focused at the irradiating position N1a (or the
laser beam L1c is focused at the irradiating position N1c), a
virtual surface which a locus of the focus of the laser beam that
is assigned the moving direction by the galvano scanner 7 draws is
a light concentrating surface 81a. A point R on the light
concentrating surface 81a shows a focus position of the laser beam
L1b.
[0096] At the irradiating position other than the irradiating
positions Na1 and N1c, the laser beam irradiates to the substrate
on the way of focusing. As the distance from the irradiating
position to the focus point becomes long, the beam radius at the
irradiating position becomes larger than the beam radius at the
focus point.
[0097] The pulse energy density of the laser beam is normally
higher than the peripheral of the outer circumference of the beam
cross section. When the beam radius becomes large, the pulse
density at each position in the beam cross section becomes low.
Therefore, a region that has the pulse energy density equal to or
more than a threshold value that can process the substrate is
limited to around the center of the beam cross section, although
the beam radius becomes large.
[0098] In the peripheral area of the irradiating position N1a and
N1c, a wide groove is formed by irradiating the laser beam with a
small diameter and having the pulse energy density equal to or more
than a threshold value from the center to the outer circumference
of the beam cross section at the high pulse energy density. On the
other hand, in the peripheral area of the irradiating position M1,
a narrow groove is formed by irradiating the laser beam with a
large diameter and having the pulse energy density equal to or more
than a threshold value only at the small center area of the beam
cross section at the low pulse energy density. As described above,
the widths of the grooves are varied depending on the positions
they are formed.
[0099] Moreover, the distance from the irradiating position M1 of
the laser beam L1b to the point R on the light concentrating
surface 81a becomes longer as the incident angle .alpha.1 becomes
large. Therefore, as the incident angle .alpha.1 becomes large, the
difference between the beam radius of the laser irradiated to the
N1c and the beam radius of the laser irradiate at the irradiating
position M1 becomes large. That is, the difference of the width
between the edge and the center of the groove becomes clear. Since
the incident angle .alpha.1 is incident angle of the laser beam to
form the edge of the groove, for example, it becomes large when a
long groove is to be formed on a large substrate.
[0100] Next, a method for forming a groove by scanning the laser
beam adjusting the focus position by moving the position of the
object lens 6 will be explained. When the focus position of the
laser beam is adjusted, the beam radius of the laser beam
irradiated on the substrate is adjusted, and the pulse energy
density on the surface of the substrate is adjusted.
[0101] It is considered where to focus the laser beam L1b that
irradiates to the irradiating position M1. By setting the focus
closer to the irradiating position M1 than the point R on the light
concentrating surface 81a, the beam radius becomes small, and it
can be corrected in order to increase the pulse energy density of
the irradiating position M1. When the focus comes closer to the
irradiating position M1, the pulse energy density at the
irradiating position M1 becomes higher than the pulse energy
density at the irradiating positions N1a and N1c.
[0102] Since the laser beam L1b irradiates to the surface of the
substrate vertically, the beam spot at the irradiating position M1
is circular. On the other hand, since the laser beams L1a and L1c
irradiate to the surface of the substrate from slant at the
incident angle .alpha.1, the beam spots 91a and 91c are shapes of
spread ellipse. That is, the pulse energy density at the beam spot
91b when the laser beam L1b is focused at the irradiating position
M1 is higher than the pulse energy density at the beam spots 91a
and 91c.
[0103] Then, the focus point of the laser beam L1b is set to a
little deeper (far from the irradiating position M1 toward inside
the substrate) position than the irradiating position M1, and area
of the beam spot 91b its made to be the same as the area of the
beam spots 91a and 91c. By doing that, the laser can be irradiated
to execute the process at the same pulse energy density as the
irradiating position N1a, N1c or M1.
[0104] At other irradiating position on the groove 101, the pulse
energy density is made to be equal so that the area of the beam
spot is kept to be fixed, and the process may be executed. Track of
the focus at a time of scanning on the groove 101 in a condition
without changing the area of the beam spot is a light concentrating
surface 81b. The focus position of the laser beam L1b is a point Q
on the light concentrating surface 81b.
[0105] It will be explained how to adjust the position of the
object lens 6 when the focus is moved along the flight
concentrating surface 81b first, when the laser beam L1a is
irradiated, the position of the object lens 6 is so controlled that
the laser beam is focused at the irradiating position N1a. This
positions called a standard position.
[0106] When the laser beam is scanned from the irradiating position
N1a to M1, the object lens 6 is gradually moved from the standard
position to the direction of the laser source. Then, the focus is
moved along the light concentrating surface 81b that is closer to
the surface of the substrate than the light concentrating surface
81a, and the area of the beam spot becomes large, and it is
controlled that the pulse energy density becomes low. A moving
distance from the standard position of the object lens is zero for
the laser beam L1a that irradiates to the irradiating position N1a.
The moving distance is set to increase as the laser moves to the
irradiating position M1, and the moving distance of the laser beam
L1b that irradiates to the irradiating position M1 is maximum.
[0107] When the laser beam is continuously scanned from the
irradiating position M1 to N1c, the object lens 6 may gradually
close to the standard position. The moving distance from the
standard position of the object lens is made to decrease as the
laser moves to the irradiating position N1c, and the moving
distance of the laser beam L1c that irradiates to the irradiating
position N1c is made to be zero.
[0108] As described in the above, by scanning the laser with
adjusting the position of the object lens 6 in order to move along
the light concentrating surface 81b, it is controlled that the
width changes depending on the position, and the groove can be
formed.
[0109] Next, it is summarized how to move the object lens. When the
scan continues without moving the position of the object lens, and
when the pulse energy density on the surface of the substrate
becomes low, the object lens is moved so that the focus of the
laser beam becomes close to the irradiating position along the
moving direction of the laser beam to control the decline of the
pulse energy density. When the scan continues without moving the
position of the object lens, and when the pulse energy density on
the surface of the substrate becomes high, the object lens is moved
so that the focus of the laser beam becomes far from the
irradiating position along the moving direction of the laser beam
to control the rise of the pulse energy density.
[0110] Although the method for focusing on the surface of the
substrate at the irradiating position of both sides of the groove
has been explained as an example of the process, the focus point
may be set at any other irradiating position. When the area of the
beam spot at each irradiating position is made to be fixed, the
process can be executed with equal pulse energy density, and a
fixed processitivity can be kept to any irradiating position.
[0111] Moreover, although the pulse energy:density of the laser
beam to be irradiated is not kept to be strictly fixed at each
irradiating position, a high quality process can be executed by
suppressing a variation of the pulse energy density at the
irradiating position at a time of changing the irradiating
position.
[0112] Although the example of the groove process (the scribing
process) has been explained, a piercing process may be executed.
Although the example of scan the galvano scanner to the
one-dimensional direction has been explained, a process all over
the surface of the substrate may be executed by scanning to the
laser beam in two-dimensional directions. Although the example of
the process to use the pulsed laser beam has been explained, the
laser beam may be a continuous-wave. When the process is executed
by the continuous-wave laser beam, it is controlled that power
density at a surface to be processed changes by the irradiating
position.
[0113] The pulse energy density of the laser beam to be irradiated
to the substrate can be adjusted by the variable attenuator instead
of moving the object lens 6.
[0114] In the laser processing apparatus according to the modified
example of the second embodiment of the present invention shown in
FIG. 12B, a variable attenuator 2 is added to the laser processing
apparatus shown in FIG. 12A. The variable attenuator 2 synchronizes
with the movement of the galvano scanner based on the control
signal transmitted from the controller 11, and the power of the
pulsed laser beam to be irradiated to the substrate 12 can be
attenuated at desired attenuation rate.
[0115] With reference to FIG. 14, an example of a laser processing
method used the variable attenuator will be explained. FIG. 14
schematically shows a light path of the pulsed laser beam that
scans on the substrate 12 via the object lens 6 and the galvano
scanner 7.
[0116] Laser beam L2b irradiates to an irradiating position M2
vertical to the surface of the substrate. Laser beams L2a and L2c
irradiate to irradiating positions N2a and N2c. Irradiating
position M2 is positioned at the center of a line between the
irradating position N2a and irradiating position N2c.
[0117] The object lens 6 is fixed to a position to focus the laser
beam L2b at the irradiating position M2. A track of the focus of
the laser beam altering the moving direction by the galvano scanner
7 draws a virtual surface, and it is a light concentrating surface
82.
[0118] As same as the explanation with reference to FIG. 13,
swinging the moving direction of the laser beam from the light path
of the laser beam L2a to the direction of the light path of the
laser beam L2c, irradiation of the pulsed laser beam is repeated to
form a groove on the surface of the substrate.
[0119] As the irradiating position of the laser beam goes away from
the irradiating position M2, a distance from the position where the
laser beam focuses to the position to irradiate to the substrate
becomes long. Since the laser beam after passing through the focal
point is divergent pencil of rays, the beam spot of the surface of
the substrate becomes large as the distance from the focal point to
the irradiating position becomes long.
[0120] Also, as the irradiating position goes away from the
irradiating position M2, the incident angle of the laser beam to
the substrate becomes large. Also, in a case that the laser beam
that has same sizes beam radius is irradiated, the beam spot of the
surface of the substrate becomes large as the incident angle
becomes large.
[0121] As explained with reference to FIG. 13, the pulse energy
density in a large beam spot declines all over the beam section, a
region that can process the substrate and that is equal to or more
than a threshold value is limited to around the center of the beam
cross section. Therefore, the width of the groove formed by the
irradiation of large beam spot becomes narrow.
[0122] When the groove is formed by irradiating the laser at a
fixed pulse energy to any irradiating position, the width of the
groove around the center becomes wide, and the width of the groove
at the edge becomes narrow.
[0123] Here, the power is adjusted by the variable attenuator 2
corresponding to the irradiating position so that the pulse energy
density on the surface of the substrate at any irradiating position
is fixed. The attenuation rate of the power is minimum when the
edge of the groove is processed. Then, as the processing point
moves toward the center of the groove, the attenuation rate is
increased, and it will be maximum when the irradiating position M2
where is the center of the groove is irradiated. By doing that, it
is controlled that the width changes depending on the position, and
the groove is formed.
[0124] Moreover, in order to uniform the pulse energy density of
the laser beam to be irradiated to the substrate, it may be
combination of that the focal point is moved by moving the object
lens 6 in the voice coil mechanism 10 and that the power of the
pulsed laser beam is attenuated by the variable attenuator 2.
[0125] Moreover, the laser beam may be a continuous wave. When the
process is executed by the continuous wave laser beam, the power of
the continuous-wave laser beam is controlled by the variable
attenuator in order to suppress the power density at the surface to
be processed to change depending on the irradiating position.
[0126] For example, in the process of the glass basic material
formed the ITO film on the surface, the size of the substrate tends
to be large. When the substrate becomes large, and the area to be
processed becomes large, a case that the moving amount of the
object lens 6 becomes large occurs in the process to execute by
moving the object lens corresponding to the irradiating position of
the laser beam as explained with reference to FIG. 13. From a view
point of easiness of the control, it is preferable that the moving
amount of the object lens 6 can be made to be small.
[0127] Next, a laser processing apparatus according to the third
embodiment of the present invention that can make the moving,
distance of the focal point of the laser beam long in a state that
the moving distance of the object lens 6 is controlled to be short
will be explained.
[0128] In the laser processing apparatus shown in FIG. 15A, a
second light concentrating lens 71 is added between the object lens
6 and the galvano scanner 7 in the laser processing apparatus shown
in FIG. 12A. Moreover, the object lens 6 is called a first light
concentrating lens 6 in the explanation of FIG. 15A.
[0129] The laser beam radiated from the aperture 5a irradiates to
the first light concentrating lens 6. The first light concentrating
lens 6 concentrates the laser beam on a virtual first light
concentrating surface 83. The laser beam passed through the first
light concentrating surface 83 becomes divergent pencil of rays to
irradiates to the second light concentrating lens 71. The laser
beam concentrated by the second light concentrating lens 71 swings
the moving direction to the galvano scanner to irradiate to the
substrate 12.
[0130] Next, the moving amount of the first light concentrating
lens 6 will be explained. When the first light concentrating
surface 83 is made to be close to the second light concentrating
lens 71, the focal point of the laser beam concentrated by the
second light concentrating lens 71 moves to a direction that the
laser beam moves. The moving distance of the first light
concentrating surface 83 is d1, and the moving distance of the
focal point of the laser beam is d2. Also, the number of the
openings of the second light concentrating lens 71 to the laser
beam that irradiates to the second light concentrating lens 71 is
NA1, and the number of the openings of the second light
concentrating lens to the concentrated beam passed through the
second light concentrating lens 71 is NA2. If the magnification P
is defined to the following equation:
P=NA1/NA2
[0131] The, the following equation can be obtained:
d2=d1.times.P.sup.2
[0132] As obvious from the above equation, the magnification P is
made to be large, the moving distance d2 of the focus can be
lengthened, although the moving distance d1 of the first light
concentrating surface 83 is shortened. For example, when the
magnification P is 2, the focus point of the laser beam can be
moved by 8 mm to the moving direction of the laser beam by making
the first light concentrating surface 83 be closer by 2 mm to the
second light concentrating lens 71.
[0133] The movement of the first light concentrating surface 53 is
opened by moving the first light concentrating lens 6 to the
optical axis direction. When the laser beam to irradiate to the
first light concentrating lens 6 is parallel pencil of rays, the
moving distance of the first light concentrating lens 6 and the
moving distance of the first light concentrating surface is same.
If the distance to move the first light concentrating lens 6 is
equal to or less than about 2 mm, a linear actuator used the piezo
driver mechanism can be used. By using the linear actuator used the
piezo driver mechanism instead of the voice coil mechanism 10, the
first concentrating lens 6 can be moved fast and precisely.
[0134] FIG. 16 shows an example of a structure of the second light
concentrating lens 71. The second light concentrating leans 71 is
consisted of plurality of lenses. An object focal point So and an
image focal point Si are in a relationship of conjugate. This
object focal point So is equal to the position of the beam spot on
the first light concentrating surface 83 shown in FIG. 15A. This
focus optical system is considered to be an optical system of
infinity conjugate. The second light concentrating lens 71 is
divided into front side lenses group 71a and back side lenses group
71b. The pencil of rays is made to be the parallel pencil of rays
by the front side lenses group 71a. This parallel pencil of rays
focuses on the image focal point Si by the back side lenses group
71b. Moreover, although there is a case that the second light
concentrating lens 71 cannot be divided physically, it is
considered that it can virtually be divided.
[0135] The front focal length of the front side lenses group 71a is
Ff, and the back focal length of the back side lenses group 71b is
Fr. At this time, the magnification defined, with the
above-described equation can be expressed as following:
P=Fr/Ff
[0136] Although in the laser processing apparatus shown in FIG.
15A, the first light concentrating lens 6 is consisted of a convex
lens, as shown in FIG. 15B, it may be consisted of a concave lens.
At this time, the first light concentrating surface 83a becomes a
virtual image and appears closer to the laser source side than the
concave lens 6a.
[0137] By making the magnification P large, the focus point
position of the laser beam to be irradiated to the substrate can
largely changed being the moving distance of the first light
concentrating lens 6 controlled to be short. To obtain a
significant effect, it is preferable that the magnification P
equals or more than 2, and 4 or more is more preferable.
[0138] Since the beam spots 91a and 01c shown in FIG. 13 are the
beam spots of the laser beam that irradiates obliquely to the
substrate, they are ellipse. On the other hand, since the beam spot
91b is the beam spot of the laser that irradiates to the substrate
vertically, it is circular. As described in the above, the incident
angle is different depending on the irradiating position of the
laser beam, and the shapes of the beam spot on the substrate
differ.
[0139] With reference to FIG. 17 the laser processing apparatus
according to the fourth embodiment that can correct the shape of
the beam spot corresponding to the irradiating position will be
explained.
[0140] In the laser processing apparatus shown in FIG. 17, an
aperture inclining mechanism 60a that rotates the aperture 5a
around the axis that is vertical to the optical axis of the laser
beam and an aperture rotation mechanism 61a that rotates the
aperture 5a around the axis that is parallel to the optical axis of
the laser beam are added to the laser processing apparatus shown in
FIG. 12A. Moreover, components (paraxial components) in the
peripheral of paraxial of the optical system is called an optical
axis of the laser beam.
[0141] Moreover, the aperture rotation mechanism 61a is the same
mechanism as that a mask rotation mechanism rotates the mask, and
the aperture rotation mechanism rotates the aperture 5a around the
axis parallel to the optical axis of the laser beam. The laser
processing apparatus explained later with reference to FIG. 22A has
the mask rotation mechanism.
[0142] The aperture inclining mechanism 60a and the, aperture
inclining mechanism 61a synchronizes with the movement of the
galvano scanner 7 based on the control signal transmitted from the
controller 11 and change the inclining angle surrounding the axis
that is vertical to the optical axis of the laser beam and the
rotation angle surrounding the axis that is parallel to the optical
axis of the laser beam.
[0143] The shape of the beam cross section that is vertical to the
optical axis and the shape of the beam cross section on the surface
of the substrate at a time that the laser beam obliquely,
irradiates to the surface of the substrate are compared. The shape
of the beam cross section on the surface of the substrate is a
shape that the shape of the beam cross section that is vertical to
the optical axis is expanded to the cross lines between the surface
of the substrate and the irradiating surface. For example, when the
laser beam with a circular cross section irradiates obliquely to
the surface of the substrate, the beam cross section on the surface
of the substrate becomes a ellipse that is long to the cross
lines.
[0144] Therefore, by irradiating the laser beam formed to be oval
of which a cross section cut in a vertical direction of the optical
axis at a proper ratio of a minor axis and a major axis onto the
surface of the substrate with an inclination by making the major
axis vertical to the irradiating surface, the beam spot on the
surface of the substrate will be circle.
[0145] FIG. 18A schematically shows a diagram of the aperture 5a
rotated around the axis that is vertical to the optical axis of the
laser beam by the aperture inclining mechanism 60a looked along a
direction of the rotation axis of the aperture inclining mechanism
60a. The laser beam 1b irradiated from left in the diagram is
reformed or shaped its cross section by the aperture 5a to radiate
to right in the drawing.
[0146] As shown in FIG. 18B, the circular pierced hole 62a of the
aperture 5a rotated by the aperture inclining mechanism 60a looks
ellipse when it is looked along the optical axis of the laser beam.
That is, the cross section of the laser beam is reformed to
ellipse.
[0147] Further, when a surface where the two different diameters of
the circle-shaped pierced hole of the aperture 5a are placed
crosses with the optical axis of the laser beam at a right angle, a
cross section of the laser beam will be formed to a circle-shape.
As inclining the aperture 5a and enlarging the angle between the
central axis of the rotation of the circle-shaped pierced hole and
the optical; axis of the laser beam, a minor axis of an oval of the
cross section of the beam after the reformation. The aperture
inclining mechanism 60a can change a ratio of length and width of
the cross section of the laser beam.
[0148] As shown in FIG. 18C, the aperture 5a is rotated around the
axis that is parallel to the optical axis of the laser beam by
using the aperture rotation mechanism 61a.
[0149] The shape of the beam cross section at a position where the
beam spot of the laser beam becomes minimum (it is called a focus
of the laser beam) is ellipse. The long axis direction of the beam
cross section at the focus point is corresponding to the short axis
direction of the beam cross section at a pierced hole position of
the aperture 5a.
[0150] Therefore, the aperture 5a is rotated by the aperture
rotation mechanism 61a so that the long axis direction which the
beam cross section is ellipse at the pierced hole position matches
with the cross line direction. By doing that, the shape of the beam
spot on the substrate can be kept to be circle at any irradiating
position.
[0151] Moreover, although the process by the light concentrating
method in which it is unnecessary to focus the pierced hole of the
aperture on the surface of the substrate has been explained, the
shape of the beam spot on the substrate can be corrected in a case
that a process by a mask projecting method wherein the image of the
pierced hole is focused on the surface of the substrate can be
executed. In the case of the mask projecting method, the long axis
direction of the image of the pierced hole formed on the surface of
the substrate is corresponding to the long axis direction of the
beam cross section at the pierced hole position of the mask.
[0152] It is the same as that the mask having the circular pierced
hole is inclined around the axis that is vertical to the optical
axis of the laser beam. When the mask is rotated around the axis
that is parallel to the optical axis of the laser beam, it is
rotated so that the short axis direction of the ellipse of the beam
cross line at a time of radiating the pierced hole matches with the
cross line direction between the irradiating surface and the
surface of the substrate.
[0153] Although the case that the shape of the pierced hole is a
circle has been explained, the shape of the beam spot of the laser
beam reformed by the pierced hole in any other shapes can be
corrected.
[0154] Next, a laser processing apparatus according to the fifth
embodiment of the present invention that executes the laser
processing method using the proximity mask will be explained with
reference to FIG. 19. In the laser processing apparatus shown in
FIG. 19, a proximity mask 63 is added to the laser processing
apparatus shown in FIG. 12A.
[0155] The proximity mask 63 is held by a proximity mask holding
mechanism (a proximity mask holder) 64, and is configured to (or
disposed at) a position right on the substrate 12 in a parallel to
the surface of the substrate 12. A pierced hole having the same
shape as a desired shape to be processed on the surface of the
substrate is formed on the proximity mask 63. The distance dg (a
proximity gap) from the proximity mask 63 to the surface of the
substrate 12 is adjusted by the proximity mask holding mechanism
64.
[0156] An expander 3 enlarges the beam radius of the laser beam
radiated from the laser source 1 to radiate the laser beam of
parallel light. The laser beam that is radiated from the expander 3
has a spread angle (or beam divergence angle) .beta.. By the
expander 3, for example, when the beam radius of the laser beam is
expanded by 10 times, the spread angle falls by {fraction (1/10)}.
By the expander 3, the spread angle of the laser beams can be
adjusted.
[0157] Scanning on the proximity mask 63 by the galvano scanner 7,
the radiation of the laser beam is executed. The laser beam is
passed through the pierced hole of the proximity mask 63 to
irradiate to the substrate 12, and the substrate 12 is processed.
In the part other than the pierced hole through which the laser
beam did not pass, the substrate 12 is not processed. As described
in the above, the shape of the pierced hole that is formed in the
proximity mask 63 is transcribed or transferred to the surface of
the substrate, and the surface of the substrate can be
processed.
[0158] At this time, although the irradiating position of the laser
beam is changed, the laser radiation can be executed moving the
position of the object lens 6 corresponding to the irradiating
position of the laser beam to the substrate so that the variation
of pulse energy at the surface of the substrate is suppressed.
Moreover, the laser source 1 may be a laser source that radiates
the continuous-wave laser beam. In that case, a variation of the
power density at the surface of the substrate is suppressed.
[0159] In order to execute a precise process, it is necessary that
the shape of the pierced hole that is formed in the proximity mask
63 is accurately transcribed to the substrate. The precision of the
transcript is depending on the spread angle of the laser beam
irradiated to the proximity mask. It may be considered that the
spread angle of the laser beam irradiated to the proximity mask is
same as the spread angle .beta. of the laser beam at a tome of
passing the expander.
[0160] FIG. 20 shows a result of simulation how the precision of
the transcript changes depending on proximity gap and the spread
angle of the laser beam. A pierced hole image 97 with T-shape in a
case that the proximity gap and the spread angle of the laser beam
is variously changed. In each drawing, the spread angle of the
laser beam is smaller as being positioned on the right side, and
the proximity gap is smaller as being positioned on the lower
side.
[0161] As an edge of the image 97 is clearer, the precision of the
transcript will be higher. As obvious from the drawing, when the
spread angles are the same, the precision of the transcript
declines as the proximity gap becomes larger. Also, at a time of
the same proximity gaps, the precision of the transcript declines
as the spread angles becomes large. As making the proximity gap and
the spread angle be smaller, the precision of the transcript can be
higher.
[0162] FIG. 21 schematically shows a graph showing a relationship
that the proximity gap and the spread angle of the laser beam
should satisfy when a certain precision of the transcript is
secured. When a certain precision of the transcript is secured, the
spread angle should be small when the proximity gap is large, and
the proximity gap should be small when the spread angle is
large.
[0163] If the relationships between the proximity gap and the
spread angle of the laser beam should satisfy for the various
transcript precisionsare obtained in advance as shown in FIG. 21,
the proximity gap and the spread angle can easily selected when the
process is executed at the desired transcript precision.
[0164] In the laser processing method using the proximity mask,
there is an advantage that the process can be executed at high
transcript precision by setting the proximity gap and the spread
angle small. Also, by executing the process by positioning the
pierced hole of the proximity mask right on the position of the
substrate to be processed, high positioning precision can be
obtained. Since the surface of the substrate other than the
position to be processed is covered by the proximity mask, there is
an advantage that scattered material generated by scraping the
substrate at the time of the process is hard to stick on the
surface of the substrate.
[0165] Moreover, when the process for irradiating the laser beam
that passed through the pierced hole of the proximity mask to the
substrate is executed, the irradiating position to the substrate of
the laser beam is moved by swinging the moving direction of the
laser beam by the galvano scanner. Therefore, high-speeding of the
process can be realized than the case of moving the irradiating
position by moving the XY stage that loads on the substrate.
[0166] Next, with reference to FIG. 22A, the laser processing
apparatus according to the sixth embodiment of the present
invention that has the laser source that oscillates the
continuous-wave laser beam will be explained. As a laser source 1
that oscillates the continuous-wave laser beam, for example, a
semiconductor laser that oscillates the laser beam having a
wavelength in an infrared light region can be used.
[0167] Laser beam 1b0 irradiated from the laser source 1 is
irradiated to a dividing optical system 65. The dividing optical
system 65 divides the laser beam 1b0 to laser beam 1b1 moving along
a certain optical axis during a certain time and to laser beam 1b2
moving along other optical axis during other time.
[0168] The dividing optical system 65 is, for example, consisted of
a half wave plate 65a, an electronic optical element 65b that
indicates Pockels effect, and a polarizing plate 65c. The
polarizing plate 65c polarizes the laser beam 1b0 radiated from the
laser source 1 to make it linearly polarized light such as
p-polarized light to the polarizing plate 65c. The p-polarized
light is irradiated to the electronic optical element 65b.
[0169] The electronic optical element 65b revolves the polarization
surface of the laser beam based on a trigger signal sig transmitted
from the controller 11. When the electronic optical element 65b is
in a condition that no voltage is imposed, the irradiated
P-polarized light is radiated without a change. The electronic
optical element 65b is in a condition that voltage is imposed, the
electronic optical element 65b revolves the polarization surface of
the P-polarized light at 90 degree. By that, the laser beam
radiated from the electronic optical element 65b becomes
s-polarized light to the polarizing plate 65c.
[0170] The polarizing plate 65c has the P-polarized light pass
through without a change and reflects the S-polarized light. The
laser beam 1b1 of the S-polarized light that is reflected by the
polarization plate 65c irradiates to a beam dumper 66 that will be
a terminator of the laser beam 1b1. The laser beam 1b2 of the
P-polarized light that penetrates the polarization plate 65c
irradiated to the expander 3.
[0171] The beam radius is enlarged by the expander 3, and the laser
beam 1b2 made to be a parallel light irradiates to the mask 5
having a rectangular pierced hole. Here, an example of a process by
the mask projection method will be explained. That is, the image of
the pierced hole of the mask 5 is focused on the surface of the
substrate 12 to execute the process.
[0172] The mask rotation mechanism 61 is used for rotating around
the parallel axis to the optical axis of the laser beam. The mask
rotation mechanism 61 is consisted of, for example, a goniometer,
and rotates the mask only by a desired angle at a desired timing
based on the control signal transmitted from the controller 11.
Details of the mask rotation mechanism 61 will be explained later.
The voice coil mechanism 9 moves the position of the mask 5 in
parallel to the moving direction of the laser beam.
[0173] The laser beam 1b2 radiated from the mask 5 is concentrated
by the object lens 6. The voice coil mechanism 10 moves the
position of the object lens 6 in parallel to the moving direction
of the laser beam. The laser beam radiated from the object lens 6
irradiates to the surface of the substrate 12 after passing the
galvano scanner.
[0174] With reference to FIG. 22B, the substrate 12 that is a
processing target will be explained. A transcript layer 111 is
positioned on the surface of a base layer 110. This transcript
layer 111 has a property to be adhered to the surface of the base
layer 110 when it is heated.
[0175] For example, a part 111a of the transcript layer 111 is
heated by the irradiation and the heating makes the part 111a
adhered to the base layer 110. When a part 111b where a part is not
heated on the transcript layer 111 is removed, the only heated part
111a remains on the surface of the base layer 110. This is, for
example, the similar to that only a heated part of ink on an ink
ribbon is transcribed to a sheet of a paper when thermal transfer
printing is executed.
[0176] Back to FIG. 22A, the explanation will be continued. An XY
stage 8a is used as a holding stand of the substrate 12. The XY
stage 8a can move the substrate 12 on a two-dimensional surface
that is parallel to the surface of the substrate 12. The XY stage
8a is controlled by the controller 11, and the substrate 12 is
moved to a desired position at a desired timing.
[0177] In an example of the laser processing method explained here,
the scanner 7a for X and the scanner for Y of the galvano scanner
is fixed to a position where the laser beam radiated from the
galvano scanner 7 vertically irradiates to the substrate 12. By
moving the substrate 12 at the XY stage 8a, the irradiation
position of the laser beam to the substrate 12 will be moved.
[0178] By using the voice coil mechanisms 9 and 10, the length of
the light path from the mask 5 to the object lens 6 and the length
of the light path from the object lens 6 to the substrate 12 are
set so that the image of the pierced hole of the mask 5 is focused
on the surface of the substrate 12 at a desired focus magnification
(a reduction rate).
[0179] With reference to FIG. 23, a control method of the dividing
optical system will be explained. FIG. 23 shows an example of a
timing chart of the trigger signal sig and the laser beam 1b0, 1b1
and 1b2. The radiation of the laser beam 1b0 is started at a time
0.
[0180] During the time 0 to the time 1, the trigger signal is not
transmitted from the controller. Voltage is not imposed on the
electro-optical element during that time, and the laser beam 1b2 is
continuously radiated from the dividing optical system. The laser
beam 1b1 is not radiated. The laser beam during that time is the
continuous-wave.
[0181] During the time t1 to the time t2, the controller
synchronizes with the trigger signal sig periodically transmitted
from the controller, and voltage is imposed on the electro-optical
element of the dividing optical system.
[0182] The electro-optical element is in a condition that voltage
is imposed during the trigger signal sig is being transmitted, and
the laser beam 1b0 is divided into the laser beam 1b1. On the other
hand, the electro-optical element is in a condition that no voltage
is imposed during the trigger signal sig is not being transmitted,
the laser beam 1b0 is divided into the laser beam 1b2. The laser
beam 1b2 from the time t1 to the time t2 becomes the laser beam
which oscillation and pause are periodically repeated.
[0183] In the laser beam intermittently radiated during that time,
by adjusting the trigger signal sig, pulse width w1 and period w2
can be set to an arbitral length. For example, the pulse width w1
is 10 .mu.s to a few 10 .mu.s, and the period w2 is 10 .mu.s.
[0184] As described in the above, when the trigger signal is not
input to the dividing, optical system, the laser beam 1b2 that
continuously radiates can be obtained. When the trigger signal is
intermittently input to the dividing optical system, the laser beam
1b2 that intermittently radiates can be obtained.
[0185] Since the laser beam 1b2 continuously radiated can be
continuously irradiated to the substrate, for example, it is
suitable for the process for forming a line (a process leaving the
transcript layer in a line shape on the base layer). On the other
hand, since the laser beam 1b2 intermittently radiated can be
irradiated intermittently to the substrate, for example, it is
suitable for the process for forming a dot (a process leaving the
transcript layer on the base layer in a dot shape).
[0186] With reference to FIG. 24A, a line processing method will be
explained. The laser irradiation to the substrate 12 is started,
and the process is started. At the beginning of the process, a full
region at the edge of the line 103 is irradiated by the rectangular
beam spot 93. Then, continuously irradiating the laser, the XY
stage is moved to one direction so that the beam spot approaches
other edge of the line 103. The moving direction of the XY stage is
parallel to one side of the rectangular beam spot 93. Moreover, the
moving direction of the beam spot on the substrate is indicated
with an arrow.
[0187] When the beam spot reaches other edge of the line 103, the
laser irradiation to the substrate is stopped, and the process will
be finished. By doing that, by heating the region in lines on the
surface of the substrate with the laser irradiation, the line 103
that is a linear-shaped remaining part of the transcript layer on
the surface of the base layer will be formed.
[0188] A side of the long direction of the formed line 103 is
parallel to one side of the beam spot 93, and an external shape of
the line 103 is a rectangle of which the sides of width direction
are parallel to the side crossing with one side of the beam spot
93. The width of the line 103 is the same as the length of the side
crossing with one side of the beam spot 93.
[0189] With reference to FIG. 24B, a method of the dot process will
be explained. In the dot process, irradiating the laser beam
intermittently on the substrate 12, the XY stage is moved to one
direction. The moving direction of the XY stage is parallel to one
side (called a side p) of the rectangular beam spot 94a.
[0190] First, at the beginning of the first pulsed laser beam
irradiation, a whole region at one edge of a dot 104a is irradiated
by the rectangular beam spot 94a. Since the XY stage is moved, the
beam spot moves on the substrate until the laser irradiation of the
first pulse terminates. The moving direction of the beam spot in
indicated with an arrow.
[0191] By doing that, dotted region of the surface of the substrate
is heated, and the dot 104a remaining the transcript layer in dots
on the surface of the base layer is formed.
[0192] Thereafter, each of dots 104b, 104c, 104d and 104e is
respectively formed by each of the laser irradiation of the second
pulse, third pulse, fourth pulse and fifth pulse. Moreover, the
region on the surface of the substrate irradiated by each of the
beam spot 94b, 94c, 94d and 94e at the beginning of the irradiation
of the second pulse, third pulse, fourth pulse and the fifth pulse
is agreed with the region where the region of the surface of the
substrate irradiated by the beam spot 94a is moved in parallel to
the moving direction of the XY stage. Each dot stands in a parallel
straight line to the moving direction of the XY stage.
[0193] An external shape of each dot is a rectangle having a
parallel side to the side (called a side q) crossing with the side
p of the beam spot 94a.
[0194] The length of the side crossing with the moving direction of
the XY stage of each dot is same as the length of the side q, for
example, 20 .mu.m when the length of the side q is 20 .mu.m.
[0195] The length of the side parallel to the moving direction of
the XY stage of each dot is depending on the length of the side p
of the beam spot, the moving velocity of the XY stage and the
irradiating time (pulse width) of the pulse.
[0196] For example, it is assumed that the length of the side p of
the beam spot is 12 .mu.m, that the moving velocity of the XY stage
is 800 mm/s and that the pulse width is 10 .mu.s. Since the moving
distance (that is, the distance which the substrate moves) of the
XY stage in the pulse width 10 .mu.s is 8 .mu.m, the length of the
side parallel to the moving direction of the XY stage of the dots
is 20 .mu.m that is added the moving distance 8 .mu.m on the length
of the side p of the beam spot 12 .mu.m.
[0197] A pitch d between adjusting dots agrees with the distance
that the XY stage moves during one period of the pulse. For
example, when the pulse period is 375 .mu.s, and when the moving
velocity of the XY stage is 8 mm/s, the pitch d is 300 .mu.m.
[0198] The above explanation is summarized that the 20 .mu.m dot
can be formed at a pitch of 300 .mu.m in a case that the size of
the beam spot is set to be the length of the sides of 12 .mu.m and
the length of the side q of 20 .mu.m, and that the laser beam is
oscillated with the pulse 10 .mu.s at the period 375 .mu.s to move
the XY stage at 800 mm/s.
[0199] There is a case that process of a plurality of the lines
having different directions on the substrate is desired. Although
when the lines with different directions are formed in a state the
direction of the beam spot on the substrate is fixed, problems such
as that the line width changes depending on the line direction
arise.
[0200] With reference to FIG. 29, an example of the above situation
will be explained. By the method explained with reference to FIG.
24A, the line 109a is formed first. Next, the line 109b having a
different direction from the line 109a is formed without changing
the direction of the beam spot. At the beginning of the
irradiation, the beam spot 99 is irradiated at one end of the line
109b. Moving the XY stage to the longitudinal direction of the line
109b, the beam spot is moved to other end of the line 109b to form
the line 109b.
[0201] As shown in the diagram, although the width of the line 109a
is same as the length of the long side of the beam spot 99, the
width of the line 109b is not always same as the length of the long
side. Moreover, the end side of the line 109b cannot be formed in
order to right cross to the longitudinal direction of the line. By
using the mask rotation mechanism 61 shown in FIG. 22A such problem
can be avoided.
[0202] FIG. 25 is a schematic view showing the mask rotation
mechanism 61 holding the mask 5 having the rectangle pierced hole
62. A surface where the two diagonal lines of the rectangle pierced
hole 62 are drawn is vertical to the optical axis of the laser
beam. The mask rotation mechanism 61 rotates the mask 5 around the
axis parallel to the optical axis of the laser beam as the cross
point of the rectangular diagonal of the pierced hole 62 to be the
center of the rotation.
[0203] In correspondence to the rotation of the mask 5, the image
of the pierced hole 62 is rotated on the surface of the substrate
12. The side of the rectangular image of the pierced hole 62 on the
substrate can be parallel to the arbitrary direction on the surface
of the substrate.
[0204] As explained next, the mask 5 can be rotated by the mask
rotation mechanism 61 in order to change the direction of the line
to be processed before changing the moving direction of the
irradiating position of the laser beam on the substrate.
[0205] With reference to FIG. 26, the method for processing a line
using the mask rotation mechanism will be explained. By the method
explained with reference to FIG. 24A, the line 103a is 15 formed.
It is assumed that the length of the long side of the beam spot 931
is the same as the width of the line 103a, and the direction of the
short side of the beam spot 93a is parallel to the longitudinal
direction of the line 103a.
[0206] Before starting the process of the line 103b having the
different direction from the line 103a, the mask is rotated by the
mask rotation mechanism so that the short side of the beam spot 93b
becomes parallel to the longitudinal direction of the line 103b.
Then, the substrate is moved by the XY stage so that the beam spot
is irradiated on the whole end of the line 103b.
[0207] The irradiation of the laser beam is started, and by the
same process as the process explained with reference to FIG. 24,
the line 103b is formed moving the XY stage to the longitudinal
direction of the line 103b. Also, the width of the line 103b is
same as the length of the long side of the beam spot 93b.
[0208] By doing that, the plurality of the lines having different
directions can be formed so that each of lines has the same width.
Moreover, in order to form the plurality of dots having different
direction without changing the size and the shape, the mask
rotation mechanism can be used.
[0209] Although the example for making the laser beam a pulse by
controlling the dividing optical system by the periodical trigger
signal has been explained, it is not necessary that the trigger
signal is periodical. For example, when the dots are formed at the
different pitches, the trigger signal that is not periodic can be
used. Moreover, the pulse width of the laser beam may not be fixed.
It may be properly set corresponding to the size of the dots to be
formed.
[0210] By changing the shape and the size of the beam spot on the
substrate, the line width and the dot size can be adjusted. By the
change of the mask, the shape and the size of the beam spot can be
changed. Also, by changing the focus magnification (reduction
rate), the size of the beam spot can be changed.
[0211] Although the example of the process leaving the transcript
layer in lines or in dots on the substrate has been explained, it
may be a process that the surface of the substrate is dug in lines
or in dots by the laser irradiation.
[0212] The shape of the pierced hole of the mask is not limited to
a rectangle, and it is selected corresponding to the shape of the
dots and lines desired to be formed.
[0213] Although the example moving the irradiation position of the
laser beam on the substrate by the XY stage has been explained, the
irradiating position can be moved by changing or swinging or
sweeping the moving direction of the laser beam with the galvano
scanner.
[0214] Next, with reference to FIG. 27A, the laser processing
apparatus according to the seventh embodiment of the present
invention will be explained. In FIG. 27A, the laser processing
apparatus has two laser sources, and one laser source radiates the
pulsed laser beam, and another laser source radiates the continuous
laser beam.
[0215] Laser source 1a is, for example, a Nd:YAG laser oscillator
including a wave-length conversion unit, and radiates the pulsed
laser beam of the fourth high-frequency wave (wave length of 266
nm) of the Nd:YAG laser. The pulse width is, for example, 10 ns The
pulsed laser beam that is radiated by the laser source 1a
irradiates to the half-wave plate 69a to be a straight polarization
in order to be the p-polarized light to the polarization plate
67.
[0216] The laser source 1b is, for example, a semiconductor laser
oscillator, and radiates the continuous-wave laser beam of
wavelength of 808 nm. The continuous-wave laser beam radiated from
the laser source 1b irradiates to the half-wave plate 69b to be a
straight polarization in order to be the s-polarized light to the
polarization plate 67.
[0217] The pulsed laser beam radiated from the half-wave plate 69a
passes through an expander 3a that enlarges the bear diameter and
makes the beam parallel light and a mask 5 having a pierced hole
in, for example, a rectangle shape. Thereafter, the pulsed laser
beam is irradiated to the surface of the polarization plate 67 at
45 degree incident angle.
[0218] The continuous-wave laser beam radiated from the half-wave
plate 69b passes through an expander 3b that enlarges the beam
diameter and makes the beam parallel light and is reflected by a
turning mirror 68. Thereafter, the continuous-wave laser beam is
irradiated to the back surface of the polarization plate 67 at 45
degree incident angle.
[0219] The polarization plate 67 penetrates the pulsed laser beam
that is the p-polarized light and reflects the continuous-wave
laser beam that is the s-polarized light. The pulsed laser beam
radiated from the laser source 1a and the continuous-wave laser
beam radiated from the laser source 1b are combined by the
polarization plate 67, and both laser beams move along with the
same optical axis.
[0220] The pulsed laser beam passed through the polarization plate
67 and continuous-wave laser beam reflected by the polarization
plate 67 are concentrated by the object lens 6, pass through the
galvano scanner 7, and are irradiated to the substrate 12.
[0221] The XY stage 8a used as the holding stand of the substrate
12 can move the substrate 12 in a two dimensional surface that is
parallel to the surface of the substrate 12. The XY-stage 8a is
controlled by the controller 11, and the substrate 12 is moved to a
desired position at a desired timing. In the example of the laser
processing method explained here, the scanner for X 7a and the
scanner for Y 7b of the galvano scanner 7 are fixed at a position
where the laser beam radiated from the galvano scanner 7 irradiates
to the substrate 12 in vertical. By moving the substrate 12 at the
XY stage 8a, the irradiation position of the laser beam to the
substrate 12 is moved.
[0222] The voice coil mechanisms 9 and 10 move each position of the
mask 5 and the object lens 6 parallel to the moving direction of
the pulsed laser beam radiated from the laser source 1a. The image
of the pierced hole of the mask 5 is focused on the surface of the
substrate 12 at a desired focus magnification (reduction rate) by
adjusting the position of the mask 5 and the object lens 6.
[0223] With reference to FIG. 27B, the substrate 12 that is a
processing target will be explained. A surface layer 121 is formed
on the surface of a base layer 120. The base layer 120 is, for
example, a color filter of a liquid-crystal display device, and is
a resin layer consisted of a polyimide group resin and an acryl
group resin with thickness of 1 .mu.m. The surface layer 121 is,
for example, ITO film with thickness of 0.5 .mu.m.
[0224] When only the surface layer 121 is removed, by the laser
irradiation, it is difficult that only the surface layer 121 is
processed because it is easier to process the base layer 120 than
the surface layer 121. For example, when the laser is irradiated on
the substrate, the base layer is explosively scattered under The
influence of the heat conducted to the base layer 120 and the
surface layer may be blown off.
[0225] The inventors of the present invention found out that the
process for only the surface layer 121 becomes easy by executing
the laser irradiation after preheating of the substrate. In the
laser processing apparatus shown in FIG. 27A, the substrate 12 is
preheated by the continuous-wave laser beam radiated from the laser
source 1b, and the process of the holes or the like is executed by
the pulsed laser beam radiated from the laser source 1a.
[0226] Next, with reference to FIGS. 28A to 28C, an example of a
method for forming a hole irradiating the pulsed laser after
preheating a processing target point on the substrate by the
continuous-wave laser.
[0227] As shown in FIG. 28A, on the surface of the substrate 12 to
be irradiated the continuous wave laser beam (as indicated with
circular beam spot 95), points 105a, 105b and 105c to be processed
are defined. The center of the beam spot 95 will be positioned on a
straight line connecting the points 105a, 105b and 105c to be
processed. The XY stage is moved parallel to this straight line,
and the points 105a to 105c to be processed are moved to the
direction of the beam spot 95.
[0228] As shown in FIG. 28B when the point 105a to be processed
reaches at the edge of the beam spot 95, the continuous-wave laser
is irradiated the point 105a to be processed, and the preheat
supply is started.
[0229] As shown in FIG. 28C, when the processing target point 105a
reaches the edge of the beam spot 95, one shot of the pulsed laser
is irradiated to the center of the beam spot 95. The beam spot of
the pulsed laser is indicated with beam spot 96.
[0230] The processing target point is preheated during moving from
the edge to the center of the beam spot 95. By irradiating the
pulsed laser on the preheated processing target point 105a, it is
controlled that the base layer is processed, and a hole can be
formed on the surface layer of the substrate.
[0231] The substrate 12 is continuously moved, as same as the
processing target point 105a, holes are formed at the points 105b
and 105c.
[0232] The irradiation condition of the continuous laser beam used
for preheating is that, for example, the beam spot is a circular
shape with a diameter of 20 mm, and the power density at the
surface of the substrate is 0.1 w/cm.sup.2. The irradiation
condition of the pulsed laser beam used for processing is that, for
example, the beam spot is a square of 10 .mu.m, and the pulse
energy density at the surface of the substrate is 0.1 to 0.4
J/cm.sup.2.
[0233] Moreover, the time the processing target point is preheated
is almost same as the time that the processing target point moves
for the length of the radius of the beam spot of the
continuous-wave laser. For example, when the beam spot radius is 10
mm, and when the moving velocity of the XY stage is 800 mm/s, the
time will be about 0.13 seconds. By irradiating at the center of
the beam spot of the continuous-wave laser beam, it becomes easy to
execute the process arranging preheating time, although the moving
direction of the XY stage is variously changed.
[0234] Since the preheating given on the surface of the substrate
by the continuous-wave laser irradiation conducts to the base
layer, the base layer is processed when there is much preheat.
Therefore, it is necessary that the preheating is given in order to
be at a temperature at which the base layer is not processed or
less than that temperature. For example, it is necessary that the
temperature of the base layer is or less than a fusing point of the
materials of the base layer.
[0235] Although the ITO film is transparent to a visible light, for
example, absorption coefficient to near-infrared radiation with
wavelength of 808 nm is not "0". Therefore, the light of this
wavelength can be used for preheating the ITO film. When the light
with the wavelength (for example, wave length of about 1064 nm)
that the absorption coefficient of the ITO is larger, preheating
efficiency is expected to be improved.
[0236] Although the example for irradiating the pulsed laser beam
and the continuous-wave laser beam to the substrate by overlapping
them on the same optical axis has been explained, both laser beams
may not be on the same optical axis. By irradiating both laser
beams to the substrate with the beam spot of the pulsed laser beam
included inside of the beam spot of the continuous-wave laser beam,
pre-heat can be supplied to the spot to be processed from that the
spot to be processed reaches to the edge of the beam spot of the
continuous-wave laser beam to the position of the beam spot of the
pulsed laser beam.
[0237] In order to give preheat, it is necessary that the
processing target point reaches the irradiating position of the
pulsed laser beam after passing inside of the beam spot of the
continuous laser beam. Therefore, it is necessary the irradiating
position of the pulsed laser beam is where the processing target
point does not agree with the position of the processing target
point at a time of contacting with perimeter of the beam spot of
the continuous laser beam.
[0238] Although the example of forming a hole has been explained,
the plurality of holes may be continuously formed so that a groove
may be formed.
[0239] Although the example of moving the irradiating position on
the substrate by the XY stage has been explained, the irradiating
position can be moved by swinging the moving direction of the laser
beam by the galvano scanner.
[0240] The present invention has been described in connection with
the preferred embodiments. The invention is not limited only to the
above embodiments. It is apparent that various modifications,
improvements, combinations, and the like can be made by those
skilled in the art.
* * * * *