U.S. patent application number 13/307204 was filed with the patent office on 2012-03-22 for laser irradiation apparatus, laser irradiation method, fabrication method for thin film semiconductor device and fabrication method for display apparatus.
This patent application is currently assigned to Sony Corporation. Invention is credited to Masatoshi Inagaki, Minoru Nakajima, Keisuke Omoto.
Application Number | 20120067856 13/307204 |
Document ID | / |
Family ID | 39150069 |
Filed Date | 2012-03-22 |
United States Patent
Application |
20120067856 |
Kind Code |
A1 |
Omoto; Keisuke ; et
al. |
March 22, 2012 |
LASER IRRADIATION APPARATUS, LASER IRRADIATION METHOD, FABRICATION
METHOD FOR THIN FILM SEMICONDUCTOR DEVICE AND FABRICATION METHOD
FOR DISPLAY APPARATUS
Abstract
A laser irradiation apparatus, including: an optical system
configured to form laser light of a linear cross section to be
irradiated on an irradiation object; and a cutting member having a
light blocking portion configured to block the laser light formed
in the linear cross section by the optical system to cut the laser
light so as to have a predetermined length along a line
longitudinal direction; the light blocking portion having a
plurality of fins provided on the light blocking portion thereof so
as to fetch and absorb the laser light.
Inventors: |
Omoto; Keisuke; (Aichi,
JP) ; Nakajima; Minoru; (Aichi, JP) ; Inagaki;
Masatoshi; (Aichi, JP) |
Assignee: |
Sony Corporation
Tokyo
JP
|
Family ID: |
39150069 |
Appl. No.: |
13/307204 |
Filed: |
November 30, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11844502 |
Aug 24, 2007 |
8084707 |
|
|
13307204 |
|
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Current U.S.
Class: |
219/121.72 |
Current CPC
Class: |
B23K 26/066 20151001;
H01S 3/005 20130101; B23K 26/0738 20130101 |
Class at
Publication: |
219/121.72 |
International
Class: |
B23K 26/00 20060101
B23K026/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 29, 2006 |
JP |
2006-231506 |
Claims
1. A for making a thin film semiconductor device, the method
comprising the steps of: forming laser light of a linear cross
section; cutting the laser light of the linear cross section so as
to have a predetermined length in a line longitudinal direction
using a cutting member which has a light blocking portion
configured to block the laser light; and irradiating the laser
light of the predetermined length in the line longitudinal
direction on a semiconductor film to crystallize the semiconductor
film, wherein, the cutting member has a plurality of fins on the
light blocking portion, and the fins are configured to fetch and
absorb the laser light.
2. A for making a display apparatus, the method comprising the
steps of: forming laser light of a linear cross section; cutting
the laser light of the linear cross section so as to have a
predetermined length in a line longitudinal direction using a
cutting member which has a light blocking portion configured to
block the laser light; and irradiating the laser light of the
predetermined length in the line longitudinal direction on a
semiconductor film to crystallize the semiconductor film, wherein,
the cutting member has a plurality of fins on the light blocking
portion thereof, and the fins are configured to fetch and absorb
the laser light.
Description
RELATED APPLICATION DATA
[0001] This application is a division of U.S. patent application
Ser. No. 11/844,502, filed Aug. 24, 2007, the entirety of which is
incorporated herein by reference to the extent permitted by law.
The present application claims the benefit of priority to Japanese
Patent Application No. JP 2006-231506 filed in the Japan Patent
Office on Aug. 29, 2006, the entirety of which is incorporated by
reference herein to the extent permitted by law.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a laser irradiation apparatus and
a laser irradiation method for irradiating linear laser light on an
irradiation object, and further relates to a fabrication method for
a thin film semiconductor device and a fabrication method for a
display apparatus for crystallizing a semiconductor film by
irradiating linear laser light.
[0003] In recent years, a thin film transistor (hereinafter
referred to simply as TFT) for which a crystalline semiconductor
film represented by a polycrystalline silicon film is used as a
device for forming a driving circuit for controlling pixels or a
switching device for pixels for a display apparatus such as a
liquid crystal display apparatus, an organic EL (Electro
Luminescence) display apparatus and so forth.
[0004] As a method for crystallizing an amorphous semiconductor
film such as an amorphous silicon film, a method which uses laser
light (laser beam) is known and disclosed, for example, in Japanese
Patent Laid-Open No. 2001-156017. In this method, linear laser
light is irradiated on an amorphous semiconductor film using a
laser irradiation apparatus to heat the semiconductor film so as to
be crystallized. Normally, the laser light used for the
crystallization is pulse laser light, and by the semiconductor film
is momentarily heated by the pulse laser light so as to be
crystallized to obtain a crystalline semiconductor film.
[0005] FIGS. 5A and 5B schematically show an example of a
configuration of an existing laser irradiation apparatus. Refer to
FIGS. 5A and 5B, the laser irradiation apparatus includes an
optical system 51, a pair of cutting members 52 and a table 53.
[0006] The optical system 51 forms laser light outputted from a
laser light source not shown so as to have a linear cross section
(cross section perpendicular to an optical axis). The cutting
members 52 cut the laser light (linear beam) LB formed so as to
have a linear form by the optical system 51 in a predetermined
length in an X direction along a line longitudinal direction of the
laser light LB, which is a left and right direction in FIG. 5.
[0007] The table 53 supports a substrate 54 on which a
semiconductor film which is an irradiation object is formed. On a
main face (top face) of the substrate 54, an amorphous
semiconductor film 55 is formed at a stage before laser
irradiation. Further, the table 53 is supported for movement by a
table moving mechanism not shown.
[0008] In order to crystallize the semiconductor film 55 in a laser
light irradiation target region 56 using the laser irradiation
apparatus having the configuration described above, the substrate
54, on which the semiconductor film 55 which is the irradiation
object is placed, is placed on the table 53 so as to be supported
by the table 53. Then, the cross sectional shape of the laser light
outputted from the laser light source not shown is converted into a
linear form by the optical system 51, and then the linear laser
light LB is irradiated from the optical system 51 on the substrate
54. At this time, part of the linear laser light LB, that is, the
opposite end portions of the linear laser light LB, are block by
the cutting members 52 to cut the laser light LB so as to have a
predetermined length conforming to the size of the laser light
irradiation target region 56 of the substrate 54.
[0009] Further, in order to irradiate the laser light on a wide
area on the substrate 54, the table 53 is successively moved in a
Y-direction at a fixed pitch in synchronism with a timing at which
the laser light LB is irradiated. As a result, the semiconductor
film 55 is crystallized by irradiation of the laser light LB.
SUMMARY OF THE INVENTION
[0010] However, the existing laser irradiation apparatus has a
problem that, when the laser light LB is cut by the cutting members
52, the laser light is reflected upwardly by the surface or top
face of the cutting members 52, and the reflected light has a
harmful influence on the crystallization step of the semiconductor
film.
[0011] Particular examples of the influence are described below.
(1) The reflected light from the cutting members 52 returns to the
laser light source and varies the output of the laser light. (2)
The reflected light from the cutting members 52 returns to the
optical path and interferes with the laser light thereby to vary
the intensity of the laser light or give rise to local intensity
non-uniformity of the laser light. (3) An optical device of the
optical system 51 is heated by the reflected light from the cutting
members 52 and thermally expanded thereby to vary the optical path
of the laser light and the intensity of the laser light or make the
intensity distribution of the laser light non-uniform.
[0012] According to an embodiment of the present invention, there
is provided a laser irradiation apparatus including an optical
system configured to form laser light of a linear cross section to
be irradiated on an irradiation object, and a cutting member having
a light blocking portion configured to block the laser light formed
in the linear cross section by the optical system to cut the laser
light so as to have a predetermined length along a line
longitudinal direction, the light blocking portion having a
plurality of fins provided thereon so as to fetch and absorb the
laser light.
[0013] According to another embodiment of the present invention,
there is provided a laser irradiation method including the steps of
forming laser light of a linear cross section, cutting the laser
light of the linear cross section so as to have a predetermined
length in a line longitudinal direction using a cutting member
which has a light blocking portion configured to block the laser
light, and irradiating the laser light of the predetermined length
in the line longitudinal direction on an irradiation object, the
cutting member having a plurality of fins provided on the light
blocking portion thereof and configured to fetch and absorb the
laser light.
[0014] In the laser irradiation apparatus and the laser irradiation
method, a plurality of fins are provided on a light blocking
portion of a cutting member configured to cut laser light, and the
laser light is fetched and absorbed by the fins. As a result,
different from the existing technique, the laser light blocked for
cutting can be prevented from being reflected by the surface of the
cutting member. Consequently, the harmful influence of the laser
light reflected by the cutting member can be prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIGS. 1A and 1B are a schematic side elevational view and a
schematic top plan view, respectively, showing an example of a
configuration of a laser irradiation apparatus to which the present
invention is applied;
[0016] FIG. 2 is an enlarged view of a portion denoted by C in FIG.
1;
[0017] FIG. 3 is a diagram illustrating a result of an experiment
in which the variation of a laser output is examined;
[0018] FIGS. 4A and 4B are diagrams illustrating a result of an
experiment in which the position variation of laser light is
examined; and
[0019] FIGS. 5A and 5B are schematic views showing an example of a
configuration of an existing laser irradiation apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] FIGS. 1A and 1B schematically show an example of a
configuration of a laser irradiation apparatus to which the present
invention is applied. Referring to FIGS. 1A and 1B, the laser
irradiation apparatus shown includes an optical system 1, a pair of
cutting members 2 and a table 3.
[0021] The optical system 1 forms laser light outputted from a
laser light source not shown so as to have a linear cross section
perpendicular to an optical axis. The laser light source outputs
laser light in the form of pulse laser light using, for example, a
pulse oscillation type excimer laser as an oscillation source. The
optical system 1 is configured using an optical device such as, for
example, a cylindrical lens. In the optical system 1, the laser
light outputted from the laser light source is converted into
linear laser light LB which typically has a line length or
longitudinal dimension of 300 mm and a line width or lateral
directional dimension of approximately 100 to 500 .mu.m.
[0022] The paired cutting members 2 cut the laser light or linear
beam LB formed in a linear form by the optical system 1 to a
predetermined length in an X-direction along the line longitudinal
direction, which is a left and right direction in FIG. 1, of the
laser light LB. The cutting members 2 are plate-formed members
formed from a metal material such as aluminum and mounted at a
position spaced upwardly by a predetermined distance from the table
3 using, for example, a mounting member such as a bracket not
shown. The cutting members 2 are arranged in a state opposed to
each other in a predetermined spaced relationship on the same line
parallel to the X-direction. The cutting length of the laser light
LB depends upon the distance (opposing distance) between the
cutting members 2. Therefore, the cutting members 2 are provided
for movement in directions toward and away from each other along
the line longitudinal direction (X-direction) of the laser light LB
such that the cutting length of the laser light LB can be adjusted
to a laser light irradiation target region hereinafter
described.
[0023] The table 3 supports a substrate 4 on which a semiconductor
film which is an irradiation object is formed. For the substrate 4,
for example, a glass substrate, a semiconductor substrate (silicon
substrate or the like) or a plastic substrate is used. On the main
face (top face) of the substrate 4, amorphous semiconductor film 5
formed from, for example, an amorphous silicon film is formed at a
stage prior to laser irradiation. Further, the table 3 is supported
for movement by a table movement mechanism not shown. The movement
of the table 3 by the table movement mechanism is performed in
order to irradiate the laser light LB on an entire laser light
irradiation target region 6 set on the substrate 4 in a state
wherein the irradiation position of the laser light is fixed in the
Y-direction perpendicular to the line longitudinal direction.
[0024] Further, the cutting members 2 described above individually
include a plurality of fins 7. The fins 7 are provided on a light
blocking portion (portion at which the laser light LB which need
not be irradiated on the irradiation object is irradiated) for
cutting the laser light LB on the top face side of the cutting
members 2.
[0025] FIG. 2 is an enlarged view of a portion denoted by C in FIG.
1. As can be recognized from FIG. 2, the fins 7 are mounted on the
top face of each of the cutting members 2 in an inclined state with
respect to the optical axis of the laser light LB. The fins 7 are
thin plate-formed members formed from a metal material such as
aluminum, and are bent so that the inside angle thereof is an
obtuse angle. Where each of the fins 7 is divided into a first
portion 7A and a second portion 7B with respect to the bent
portion, the first portion 7A is fixed to the cutting member 2
using a fixing member such as a screw not shown, and the second
portion 7B is disposed so as to stand obliquely from the top face
of the cutting member 2.
[0026] The second portion 7B of the fin 7 is inclined such that,
when the laser light LB inputted to the light blocking portion for
cutting is reflected on the surface (inclined face) of the second
portion 7B, the reflected laser light is directed outwardly along
the line longitudinal direction, that is, the X-direction. The
outward direction described here indicates a direction away from
the central position of the length of the laser light LB along the
line longitudinal direction. By disposing the second portion 7B of
the fin 7 in such an inclined direction as described above, the
laser light reflected by the second portion 7B can be prevented
with certainty from returning to the optical path of the laser
light LB for crystallization which passes the space between the
cutting members 2.
[0027] Further, if the top face (mounting face for the fins 7) of
the cutting member 2 defines the right angle with respect to the
optical axis of the laser light LB, then the inclination angle
.theta. of the second portion 7B of the fin 7 is set, for example,
within a range of .theta.=45.degree. to 75.degree. with respect to
the top face of the cutting member 2. It is to be noted that the
direction and the angle of the fin 7 is set commonly to all of the
fins 7 mounted on one of the cutting members 2. Further, where the
left and right cutting members 2 are compared with each other, the
inclination angle .theta. of the fin 7 is commonly set, but the
inclination direction of the fin 7 is opposite between the cutting
members 2. Further, the front and rear faces of the first portion
7A of the fin 7 are preferably formed as roughened faces by a
roughening process such as a sand blasting process, and the front
and rear faces of the second portion 7B of the fin 7 are preferably
formed as mirror faces by mirror finish such as a polishing
process.
[0028] Further, the fins 7 are arranged linearly along the
X-direction (line longitudinal direction of the laser light) such
that at least a portion thereon on which the laser light LB is to
be irradiated is covered fully. By arranging the fins 7 in this
manner, the cutting member 2 can be covered in a wide range in the
X-direction with the fins 7. In the arrangement of the fins 7, the
relationship between the length L1 from the bent portion of the fin
7 to the end of the second portion 7B in the X-direction and the
length L2 from the bent portion of the fin 7 to the end of the
first portion 7A of another fin 7 adjacent in the X-direction is
set to L1.gtoreq.L2 such that the first portion 7A of the fin 7 is
entirely hidden by the second portion 7B of the adjacent fin 7 when
the fins 7 are viewed from the optical axis direction, that is,
from above, of the laser light LB.
[0029] Further, each of the end portions of the cutting members 2
opposed to each other adjacent the cut ends of the laser light LB
is formed in an acute-angled or sharp knife edge form and is
inclined obliquely in an upward direction with the knife edge
portion thereof directed upwardly with respect to the optical axis
of the laser light LB similarly to the second portion 7B of the
fins 7. The end portion 2A forms part of the arrangement of the
fins 7. The reason why the end portion 2A of the cutting member 2
is formed in a sharp knife edge form is that it is intended to
prevent the laser light reflected by the end portion 2A of the
cutting member 2 from returning upwardly toward the optical system
1.
[0030] Now, a laser irradiation method, a fabrication method for a
thin film semiconductor device and a fabrication method for a
display apparatus to which the present invention is applied are
described. In the laser irradiation method, laser light of a linear
cross section is formed, and the laser light of the linear cross
section is cut so as to have a predetermined length in a line
longitudinal direction using a cutting member 2 which has a light
blocking portion configured to block the laser light. Then, the
laser light of the predetermined length in the line longitudinal
direction is irradiated on an irradiation object. The cutting
member 2 has a plurality of fins 7 provided on the light blocking
portion thereof and configured to fetch and absorb the laser light
LB.
[0031] Meanwhile, in the fabrication method for a thin film
semiconductor device, laser light of a linear cross section is
formed, and the laser light of the linear cross section is cut so
as to have a predetermined length in a line longitudinal direction
using a cutting member 2 which has a light blocking portion
configured to block the laser light. Then, the laser light of the
predetermined length in the line longitudinal direction is
irradiated on a semiconductor film to crystallize the semiconductor
film. The cutting member 2 has a plurality of fins 7 provided on
the light blocking portion thereof and configured to fetch and
absorb the laser light LB. Thus, the laser irradiation method
described above is applied to the fabrication method for a thin
film semiconductor device in which the laser light cut so as to
have the predetermined length in the line longitudinal direction is
used for the crystallization of a semiconductor film. The
fabrication method for a thin film semiconductor device can be
applied, for example, as a fabrication method for a TFT array in
which a glass substrate is used.
[0032] Further, in the fabrication method for a display apparatus,
laser light of a linear cross section is formed, and the laser
light of the linear cross section is cut so as to have a
predetermined length in a line longitudinal direction using a
cutting member 2 which has a light blocking portion configured to
block the laser light. Then, the laser light of the predetermined
length in the line longitudinal direction is irradiated on a
semiconductor film to crystallize the semiconductor film. The
cutting member 2 has a plurality of fins 7 provided on the light
blocking portion thereof and configured to fetch and absorb the
laser light LB. Thus, the laser irradiation method described above
is applied to the fabrication method for a display apparatus in
which the laser light cut so as to have the predetermined length in
the line longitudinal direction is used for the crystallization of
a semiconductor film. The fabrication method for a display
apparatus can be applied, for example, as a fabrication method for
a liquid crystal display apparatus or an organic EL display
apparatus in which a TFT array is used, for example, as a switching
element for use with pixels or as an element which forms a driving
circuit for controlling pixels.
[0033] Details of the laser irradiation method are described below.
First, where a semiconductor film 5 in a laser light irradiation
target region 6 is to be crystallized using the laser irradiation
apparatus having the configuration described above, the substrate 4
on which the semiconductor film 5 which is an irradiation object is
placed is placed on and supported by the table 3 and the sectional
shape of the laser light (pulse laser or the like) outputted from
the laser light source not shown is converted into a linear form by
the optical system 1 so that the linear-formed laser light LB is
irradiated from the optical system 1 on the substrate 4.
[0034] Thereupon, part of the linear-formed laser light LB, that
is, the opposite end portions of the linear-formed laser light LB
in the line longitudinal direction are intercepted by the paired
cutting members 2 to cut the laser light LB in a predetermined
length conforming to the size of the laser light irradiation target
region 6 of the substrate 4. Generally, linear laser light to be
used for crystallization of a semiconductor film is parallel light,
and therefore, the cut length of the laser light LB, that is, the
length of the laser light LB in the X-direction by the cutting
member 2 is adjusted before laser irradiation so as to conform to
the length of the laser light irradiation target region 6 of the
substrate 4, that is, to the length of the laser light irradiation
target region 6 in the X-direction.
[0035] Further, in order to irradiate the laser light over a wide
area of the substrate 4, the table 3 is moved successively in the
Y-direction at a fixed pitch in synchronism with the irradiation
timing of the laser light LB. More particularly, the table 3 is
moved successively in the Y-direction at intervals of a pitch
smaller than the width (size in the Y-direction) of the
linear-formed laser light LB so that the laser light LB is
irradiated on the semiconductor film 5 on the substrate 4 at each
of the movement positions to irradiate the laser light LB on the
semiconductor film 5 in the laser light irradiation target region 6
by a plural number of times. As a result, the semiconductor film 5
is instantaneously heated and melted by irradiation of the laser
light LB and is crystallized upon cooling solidification. Here,
while the table 3 is moved in the Y-direction, alternatively the
laser light LB may be scanned in the Y-direction in place of the
movement of the table 3.
[0036] Further, where the laser light LB is cut by the cutting
members 2, the fins 7 are provided on the light blocking portions
of the cutting members 2 for cutting the laser light LB as
described above. Consequently, the laser light LB blocked by the
cutting member 2 without being irradiated on the substrate 4 on
which the semiconductor film 5 which is an irradiation object is
placed is inputted to the light blocking portions for cutting on
the top face side of the cutting member 2. The fins 7 are provided
on the light blocking portions, which are portion on which the
laser light LB which need not be irradiated on the substrate 4 is
irradiated, as described above. Therefore, the laser light LB
inputted to the light blocking portion is fetched between the fins
7 adjacent to each other in the X-direction as shown in FIG. 2.
[0037] The laser light LB fetched in this manner gradually advances
to the interior portion, that is, in the direction toward the first
portion 7A, of the fins 7 while reflected repetitively many times
between the front and rear faces each in the form of a mirror face,
as the reflection faces, of the second portions 7B opposed to each
other of the fins 7 adjacent to each other in the X-direction.
Then, the laser light LB is attenuated within a period of time
within which the reflection occurs repetitively between the fins 7,
and finally, the laser light LB is absorbed in the inside of the
fins 7, that is, in the spaces between the fins 7 adjacent to each
other in the X-direction. Therefore, where the laser light LB is
cut by the cutting members 2, the laser light is prevented from
being reflected upwardly by the surface or top face of the cutting
members, different from the related art. Accordingly, a harmful
influence of the laser light LB reflected by the cutting members 2
can be prevented.
[0038] In particular, since the reflected light from the cutting
members 2 can be prevented from returning to the laser light
source, the output variation of the laser light can be prevented.
Further, since the reflected light from the cutting members 2 can
be prevented from returning to the optical path and interfering
with the laser light, the intensity variation of the laser light
and the local intensity non-uniformity of the laser light can be
eliminated. Further, since an optical device of the optical system
1 can be prevented from being heated by the reflected light from
the cutting member 2, the optical path variation and the intensity
variation of the laser light caused by the temperature variation of
the optical device and non-uniformity of the intensity distribution
can be eliminated. Therefore, the laser light LB can be irradiated
uniformly on the entire laser light irradiation target region 6 set
on the substrate 4.
[0039] Further, since, if the laser irradiation method of the
present invention is applied to the fabrication method for a thin
film semiconductor device, then the laser light can be accurately
irradiated on the aimed portion with the stabilized laser output,
the semiconductor film 5 on the substrate 4 can be crystallized
uniformly. Therefore, the characteristic dispersion among TFTs can
be reduced.
[0040] Further, particularly in an organic EL display apparatus
among various display apparatus, if the crystallinity becomes
non-uniform from influences of the output variation and the optical
path variation of the laser light and the output profile variation
in a crystallization process of a semiconductor film by irradiation
of laser light, then the influences are easily manifested as
dispersion of luminance of a display screen. Therefore, if the
laser irradiation method of the present invention is applied to the
fabrication method for an organic EL display apparatus, then the
dispersion of the luminance can be suppressed to enhance the
picture quality.
[0041] Further, while it is considered that, if the laser light LB
is fetched and absorbed by the fins 7 as described above, then the
fins 7 generate heat as a result of absorption of the laser light
LB, the fins 7 are formed originally from a material having a high
thermal conductivity such as a metal material such as aluminum and
readily radiate the heat also from the structure thereof.
Therefore, the heat generated by the absorption of the laser light
LB can be radiated effectively from the fins 7. As a result,
thermal deformation of the fins 7 and the cutting members 2 formed
from metal plates can be prevented effectively.
[0042] FIG. 3 illustrates a result of an experiment which was
conducted to check the variation of the laser output per one pulse.
Referring to FIG. 3, the axis of ordinate indicates the laser
output (intensity) and the axis of abscissa indicates time. As
recognized from FIG. 3, where the results in a case (with fins)
wherein the fins 7 are provided and another case (with no fins)
wherein no fins 7 are provided are compared with each other, a high
laser output is obtained in the former case rather than in the
latter case. The difference between the laser outputs in the former
and latter cases indicates that the laser light reflected upwardly
from the surface of the cutting member 2 comes as returning light
to the laser light source and causes variation of the laser output,
which results in loss of the output, from an influence of the
returning light.
[0043] FIGS. 4A and 4B illustrate results of an experiment which
was conducted to check the variation of the laser light across
laser irradiation. Particularly, FIG. 4A indicates a result of the
experiment where no fins are provided and FIG. 4B indicates results
of the experiment where the fins are provided. In FIGS. 4A and 4B,
the axis of ordinate indicates the laser output and the axis of
abscissa indicates the position of laser light in a line lateral
direction or widthwise direction. As recognized from FIGS. 4A and
4B, where no fins are provided, deviation (optical path variation)
of the position of the laser light appears across the laser
irradiation and a little variation is confirmed also in the profile
(top hat type form) of the laser output. On the other hand, where
the fins are provided, deviation of the position of the laser light
does not appear across the laser irradiation and no variation is
confirmed also in the profile of the laser output.
[0044] It is to be noted that, even if the fins 7 to be provided on
the paired cutting members 2 are inclined in directions opposite to
those in the embodiment described above, a remarkable effect can be
expected when compared with an alternative case wherein no fins 7
are provided. Further, as the configuration of each fin 7, the
second portion 7B may be formed in a vertical direction from the
first portion 7A once while only an upper portion of the second
portion 7B is inclined.
[0045] While a preferred embodiment of the present invention has
been described using specific terms, such description is for
illustrative purposes only, and it is to be understood that changes
and variations may be made without departing from the spirit or
scope of the following claims.
* * * * *