U.S. patent application number 12/494416 was filed with the patent office on 2010-07-08 for laser annealing apparatus and semiconductor device manufacturing method.
This patent application is currently assigned to SEMICONDUCTOR ENERGY LABORATORY CO., LTD.. Invention is credited to Masaaki Hiroki, Koichiro Tanaka, Shunpei Yamazaki.
Application Number | 20100173480 12/494416 |
Document ID | / |
Family ID | 19074912 |
Filed Date | 2010-07-08 |
United States Patent
Application |
20100173480 |
Kind Code |
A1 |
Yamazaki; Shunpei ; et
al. |
July 8, 2010 |
LASER ANNEALING APPARATUS AND SEMICONDUCTOR DEVICE MANUFACTURING
METHOD
Abstract
This invention is intended to provide a laser annealing method
by employing a laser annealer lower in running cost so as to deal
with a large-sized substrate, for preventing or decreasing the
generation of a concentric pattern and to provide a semiconductor
device manufacturing method including a step using the laser
annealing method. While moving a substrate at a constant rate
between 20 and 200 cm/s, a laser beam is radiated aslant to a
semiconductor film on a surface of the semiconductor substrate.
Therefore, it is possible to radiate a uniform laser beam to even a
semiconductor film on a large-sized substrate and to thereby
manufacture a semiconductor device for which the generation of a
concentric pattern is prevented or decreased. By condensing a
plurality of laser beams into one flux, it is possible to prevent
or decrease the generation of a concentric pattern and to thereby
improve the reliability of the semiconductor device.
Inventors: |
Yamazaki; Shunpei; (Tokyo,
JP) ; Tanaka; Koichiro; (Kanagawa, JP) ;
Hiroki; Masaaki; (Kanagawa, JP) |
Correspondence
Address: |
NIXON PEABODY, LLP
401 9TH STREET, NW, SUITE 900
WASHINGTON
DC
20004-2128
US
|
Assignee: |
SEMICONDUCTOR ENERGY LABORATORY
CO., LTD.
Atsugi-shi
JP
|
Family ID: |
19074912 |
Appl. No.: |
12/494416 |
Filed: |
June 30, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10944000 |
Sep 20, 2004 |
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12494416 |
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10212773 |
Aug 7, 2002 |
6847006 |
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10944000 |
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Current U.S.
Class: |
438/487 ;
257/E21.134; 257/E21.347; 438/795 |
Current CPC
Class: |
H01L 21/02691 20130101;
H01L 21/2026 20130101; B23K 26/0838 20130101; C21D 1/34 20130101;
H01L 21/02686 20130101 |
Class at
Publication: |
438/487 ;
438/795; 257/E21.347; 257/E21.134 |
International
Class: |
H01L 21/268 20060101
H01L021/268; H01L 21/20 20060101 H01L021/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2001 |
JP |
2001-245095 |
Claims
1. A method of manufacturing a semiconductor device comprising:
emitting a plurality of laser beams from a plurality of
oscillators; making the plurality of laser beams pass through a
fiber array; condensing the plurality of laser beams having passed
through the fiber array to form a condensed laser beam; and
irradiating a semiconductor film with the condensed laser beam in
order to increase crystallinity of the semiconductor film.
2. The method of manufacturing a semiconductor device according to
claim 1, wherein the step of irradiating the semiconductor film
with the condensed laser beam includes: changing a relative
position of the semiconductor film with respect to the condensed
laser beam in a first direction; changing the relative position of
the semiconductor film in a second direction perpendicular to the
first direction by a distance equal to or smaller than a length of
the condensed laser beam in the second direction; and then changing
the relative position of the semiconductor film with respect to the
condensed laser beam in a third direction parallel and opposite to
the first direction.
3. The method of manufacturing a semiconductor device according to
claim 2, wherein the steps of changing the relative position
includes a step of changing a position of the semiconductor
film.
4. The method of manufacturing a semiconductor device according to
claim 1, wherein the semiconductor film is irradiated with the
condensed laser beam aslant to the semiconductor film.
5. The method of manufacturing a semiconductor device according to
claim 1, wherein the semiconductor film is crystallized by the
irradiation of the condensed laser beam.
6. The method of manufacturing a semiconductor device according to
claim 1, wherein the plurality of laser beams is condensed by a
waveguide.
7. The method of manufacturing a semiconductor device according to
claim 1, wherein each of the plurality of oscillators is one
selected from a group consisting of a Nd: YAG laser, an Nd: YLF
laser, an Nd: YVO.sub.4 laser and an Nd: YAlO.sub.3 laser.
8. The method of manufacturing a semiconductor device according to
claim 1, wherein each of the plurality of laser beams is a CW laser
beam.
9. The method of manufacturing a semiconductor device according to
claim 1, wherein each of the plurality of laser beams is a pulsed
laser beam.
10. A method of manufacturing a semiconductor device comprising:
emitting a plurality of laser beams from a plurality of
oscillators; making the plurality of laser beams proximate to one
another by a fiber array; irradiating a semiconductor film with a
laser beam passed through the fiber array in order to increase
crystallinity of the semiconductor film while moving a laser-light
irradiation position relative to the semiconductor film in a first
direction; moving the laser-light irradiation position relative to
the semiconductor film in a second direction perpendicular to the
first direction by a distance equal to or smaller than a length of
the laser beam in the second direction; irradiating the
semiconductor film with the laser beam while moving the laser-light
irradiation position relative to the semiconductor film in a third
direction parallel and opposite to the first direction after moving
the laser-light irradiation position relative to the semiconductor
film in the second direction; and then moving the laser-light
irradiation position relative to the semiconductor film in the
second direction by a distance equal to or smaller than the length
of the laser beam in the second direction.
11. The method of manufacturing a semiconductor device according to
claim 10, wherein the steps of irradiating the semiconductor film
with the laser beam while moving the laser-light irradiation
position relative to the semiconductor film in the first direction,
moving the laser-light irradiation position relative to the
semiconductor film in the second direction, irradiating the
semiconductor film with the laser beam while moving the laser-light
irradiation position relative to the semiconductor film in the
third direction, and moving the laser-light irradiation position
relative to the semiconductor film in the second direction are
continuously repeated.
12. The method of manufacturing a semiconductor device according to
claim 10, further comprising modulating the plurality of laser
beams by a plurality of nonlinear optical elements after emitting
the plurality of laser beams from the plurality of oscillators.
13. The method of manufacturing a semiconductor device according to
claim 10, wherein the semiconductor film is irradiated with the
laser beam aslant to the semiconductor film.
14. The method of manufacturing a semiconductor device according to
claim 10, wherein the semiconductor film is crystallized by the
irradiation of the laser beam.
15. The of manufacturing a semiconductor device according to claim
10, wherein the plurality of laser beams is condensed by a
waveguide.
16. The method of manufacturing a semiconductor device according to
claim 10, wherein each of the plurality of oscillators is one
selected from a group consisting of a Nd: YAG laser, an Nd: YLF
laser, an Nd: YVO.sub.4 laser and an Nd: YAlO.sub.3 laser.
17. The method of manufacturing a semiconductor device according to
claim 10, wherein each of the plurality of laser beams is a CW
laser beam.
18. The method of manufacturing a semiconductor device according to
claim 10, wherein each of the plurality of laser beams is a pulsed
laser beam.
19. A method of manufacturing a semiconductor device comprising:
forming a semiconductor film over a substrate having an insulating
surface; emitting a plurality of laser beams from a plurality of
oscillators; making the plurality of laser beams proximate to one
another by a fiber array; irradiating the semiconductor film with a
laser beam passed through the fiber array in order to increase
crystallinity of the semiconductor film while moving a laser-light
irradiation position relative to the semiconductor film in a first
direction; moving the laser-light irradiation position relative to
the semiconductor film in a second direction perpendicular to the
first direction by a distance equal to or smaller than a length of
the laser beam in the second direction; irradiating the
semiconductor film with the laser beam while moving the laser-light
irradiation position relative to the semiconductor film in a third
direction parallel and opposite to the first direction after moving
the laser-light irradiation position relative to the semiconductor
film in the second direction; and then moving the laser-light
irradiation position relative to the semiconductor film in the
second direction by a distance equal to or smaller than the length
of the laser beam in the second direction.
20. The method of manufacturing a semiconductor device according to
claim 19, wherein the steps of irradiating the semiconductor film
with the laser beam while moving the laser-light irradiation
position relative to the semiconductor film in the first direction,
moving the laser-light irradiation position relative to the
semiconductor film in the second direction, irradiating the
semiconductor film with the laser beam while moving the laser-light
irradiation position relative to the semiconductor film in the
third direction, and moving the laser-light irradiation position
relative to the semiconductor film in the second direction are
continuously repeated.
21. The method of manufacturing a semiconductor device according to
claim 19, further comprising modulating the plurality of laser
beams by a plurality of nonlinear optical elements after emitting
the plurality of laser beams from the plurality of oscillators.
22. The method of manufacturing a semiconductor device according to
claim 19, wherein the semiconductor film is irradiated with the
laser beam aslant to the semiconductor film.
23. The method of manufacturing a semiconductor device according to
claim 19, wherein the semiconductor film is crystallized by the
irradiation of the laser beam.
24. The method of manufacturing a semiconductor device according to
claim 19, wherein the plurality of laser beams is condensed by a
waveguide.
25. The method of manufacturing a semiconductor device according to
claim 19, wherein each of the plurality of oscillators is one
selected from a group consisting of a Nd: YAG laser, an Nd: YLF
laser, an Nd: YVO.sub.4 laser and an Nd: YAlO.sub.3 laser.
26. The method of manufacturing a semiconductor device according to
claim 19, wherein each of the plurality of laser beams is a CW
laser beam.
27. The method of manufacturing a semiconductor device according to
claim 19, wherein each of the plurality of laser beams is a pulsed
laser beam.
28. A method of manufacturing a semiconductor device comprising:
emitting a plurality of laser beams from a plurality of
oscillators; making the plurality of laser beams proximate to one
another by a fiber array; irradiating a semiconductor film with a
laser beam passed through the fiber array in order to increase
crystallinity of the semiconductor film while moving a laser-light
irradiation position relative to the semiconductor film in a first
direction; moving the laser-light irradiation position relative to
the semiconductor film in a second direction perpendicular to the
first direction by a distance equal to or smaller than a length of
the laser beam in the second direction; irradiating the
semiconductor film with the laser beam while moving the laser-light
irradiation position relative to the semiconductor film in a third
direction parallel and opposite to the first direction after moving
the laser-light irradiation position relative to the semiconductor
film in the second direction; and then moving the laser-light
irradiation position relative to the semiconductor film in the
second direction by a distance equal to or smaller than the length
of the laser beam in the second direction, wherein the laser-light
irradiation position relative to the semiconductor film is moved
while being accelerated before irradiating with the laser beam, and
is moved at a constant rate during the irradiation, and is moved
while being decelerated during the laser-light irradiation position
relative to the semiconductor film being outside of the
semiconductor film.
29. The method of manufacturing a semiconductor device according to
claim 28, wherein the steps of irradiating the semiconductor film
with the laser beam while moving the laser-light irradiation
position relative to the semiconductor film in the first direction,
moving the laser-light irradiation position relative to the
semiconductor film in the second direction, irradiating the
semiconductor film with the laser beam while moving the laser-light
irradiation position relative to the semiconductor film in the
third direction, and moving the laser-light irradiation position
relative to the semiconductor film in the second direction are
continuously repeated.
30. The method of manufacturing a semiconductor device according to
claim 28, further comprising modulating the plurality of laser
beams by a plurality of nonlinear optical elements after emitting
the plurality of laser beams from the plurality of oscillators.
31. The method of manufacturing a semiconductor device according to
claim 28, wherein the semiconductor film is irradiated with the
laser beam aslant to the semiconductor film.
32. The method of manufacturing a semiconductor device according to
claim 28, wherein the semiconductor film is crystallized by the
irradiation of the laser beam.
33. The method of manufacturing a semiconductor device according to
claim 28, wherein the plurality of laser beams is condensed by a
waveguide.
34. The method of manufacturing a semiconductor device according to
claim 28, wherein each of the plurality of oscillators is one
selected from a group consisting of a Nd: YAG laser, an Nd: YLF
laser, an Nd: YVO.sub.4 laser and an Nd: YAlO.sub.3 laser.
35. The method of manufacturing a semiconductor device according to
claim 28, wherein each of the plurality of laser beams is a CW
laser beam.
36. The method of manufacturing a semiconductor device according to
claim 28, wherein each of the plurality of laser beams is a pulsed
laser beam.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a laser annealer employing
a laser beam. The present invention also relates to a semiconductor
device manufacturing method for manufacturing a semiconductor
device through steps including a step using a laser annealing
method. The semiconductor device means herein one of a general
device which can function by employing semiconductor characteristic
and which involve an electro-optic device such as a liquid crystal
display and a light emitting device, and an electronic device which
has the electro-optic device incorporated therein as a
component.
[0003] In recent years, study has been broadly made on the art to
carry out laser anneal on a semiconductor film formed over an
insulating substrate of glass or the like in order for
crystallization or improving crystallinity. Such semiconductor
films often use silicon. In the present description, the means for
crystallizing a semiconductor film by using a laser beam and
obtaining a crystalline semiconductor film is referred to as laser
crystallization.
[0004] The glass substrate is cheap in price and excellent in
workability as compared to the conventionally often used synthetic
quartz glass substrate, having a merit to easily prepare a
large-area substrate. This is the reason of the studies noted
above. Meanwhile, the laser is used, by preference, in
crystallization because the glass substrate is low in melting
point. The laser can deliver high energy only to the semiconductor
film without substantially increasing in substrate temperature.
Furthermore, throughput is by far high as compared to the heating
means using an electric furnace.
[0005] Crystalline semiconductor films are formed from many crystal
grains, and therefore they are also referred to as polycrystalline
semiconductor films. Because the crystalline semiconductor film
formed through laser anneal has high mobility, thin film
transistors (TFTs) can be formed using the crystalline
semiconductor film. They are broadly utilized, e.g. in a monolithic
liquid-crystal electrooptical device having pixel-driving and
drive-circuit TFTs formed on one glass substrate.
[0006] Meanwhile, there is preferential use of a method for laser
anneal that the high-output pulse laser light, of an excimer laser
or the like, is formed through an optical system into a square spot
in several-centimeter square or a linear form having a length of 10
centimeters or longer on an irradiation plane in order to scan the
laser light (or moving a laser-light irradiation position
relatively to the irradiated plane), because of high producibility
and industrial superiority. By the way, to form the laser light to
linear shape means that the laser light is formed to linear shape
at the irradiated plane. It means that the cross-sectional shape of
laser light forms linear shape. Further, the "linear shape"
referred herein is not strictly means for "line" but means for the
rectangular which aspect is large or oval shape. For example, the
aspect ratio is 10 or more. (Preferably 100-10000).
[0007] Particularly, the use of a linear beam can realize laser
irradiation over the entire irradiation surface by scanning only in
the direction perpendicular to a lengthwise direction of the linear
beam, differently from the case using the laser light in a spot
form requiring scanning, providing high production efficiency. The
scanning in a direction perpendicular to the lengthwise direction
is carried out because the direction of scanning is the highest in
efficiency. Due to the high production efficiency, the use of a
linear beam formed of pulse-oscillated excimer laser light through
a proper optical system in the current laser anneal process is in
the mainstream of the technology to manufacture liquid crystal
display devices using TFTs.
[0008] 2. Related Art
[0009] To form an excimer laser beam, KrF (wavelength: 248 nm) or
XeCl (wavelength: 308 nm) is used as excitation gas. However, such
gases as Kr (krypton) and Xe (xenon) are quite expensive. Due to
this, if Kr or Xe is employed and gas exchange is conducted more
frequently, manufacturing cost is disadvantageously pushed up.
[0010] In addition, attachments such as a laser tube for laser
oscillation and a gas purifier for removing unnecessary compounds
generated during oscillation are required to be replaced once in
two or three years. Most of these attachments are expensive, which
again disadvantageously pushes up manufacturing cost.
[0011] As described above, a laser irradiation device employing an
excimer laser beam exhibits high performance. However, the laser
irradiation device of this type takes much labor for maintenance
and the running cost (which means herein cost entailed by the
operation of the device) thereof is disadvantageously high if used
as a mass-production laser irradiation device.
[0012] Therefore, to realize a laser lower in running cost than the
excimer laser and a laser annealing method employing the laser,
there is proposed a method of using a solid-state laser (which
outputs a laser beam with a crystal rod set as a resonant
cavity).
[0013] Using a YAG laser which is one of the typical solid-state
lasers, a laser beam is irradiated to a semiconductor film.
According to the YAG laser, a laser beam (wavelength: 532 nm) which
is modulated to a second harmonic by a nonlinear optical element is
processed into a linear beam, which has a linear shape on an
irradiation surface, by an optical system. The semiconductor film
is an amorphous silicon film which has a thickness of 55 nm and
which is formed on a substrate ("1737 substrate" manufactured by
Corning Inc.) by a plasma CVD method. However, on a crystalline
silicon film obtained by executing steps including a step using a
laser annealing method to the amorphous silicon film, a concentric
pattern is formed. This pattern indicates that the material
property of the crystalline silicon film in the plane is not
uniform. Due to this, if a TFT is manufactured using a crystalline
semiconductor on which a concentric pattern is formed, the pattern
adversely influences the electrical characteristic of the TFT.
Here, a pattern of concentric circles is described as concentric
pattern.
[0014] Further, as the screen of the electro-optic device is made
large in size, the area of mother glass increases. Following this,
demand for irradiating a laser beam to a semiconductor layer
provided on the mother glass serving as a substrate at high rate
rises for the laser annealing method.
[0015] In addition, demand for compensating for the poor power of a
laser beam which is employed to temporarily melt a semiconductor
layer in the crystallization of the semiconductor layer rises for
the laser annealing method.
SUMMARY OF THE INVENTION
[0016] It is, therefore, an object of the present invention to
provide a laser annealing method for a laser irradiation device
which requires low running cost, capable of preventing the
generation of a concentric pattern or decreasing the formation
thereof and to provide a semiconductor device manufacturing method
including a step using the laser annealing method.
[0017] A cause for generating the concentric pattern will be
considered. A laser beam irradiated to an amorphous silicon film is
a linear beam which has a linear shape on an irradiation surface.
Due to this, even if some pattern is formed on a crystalline
silicon film which is obtained after the irradiation of the laser
beam, the pattern should be parallel or vertical to the linear beam
as long as a semiconductor film, a substrate and a substrate stage
are completely flat. However, an observed pattern is a concentric
pattern. From this, it is considered that the generation of the
concentric pattern is not derived from the linear beam. Namely, it
can be estimated that the thickness of the semiconductor film, the
laser beam absorption coefficient of the semiconductor film, the
substrate or the substrate stage, or a combination thereof causes
the generation of the concentric pattern.
[0018] The laser beam absorption coefficient of the semiconductor
film among the causes for generating the concentric pattern will be
considered. The reflectance and transmittance of the amorphous
silicon film (thickness: 55 nm) relative to wavelength are obtained
and the results are shown in FIGS. 10A and 10B, respectively. It is
noted that the amorphous silicon film is formed on the 1737
substrate by the plasma CVD method. FIGS. 10A and 10B show that the
reflectance and transmittance of the amorphous silicon film for the
second harmonic (wavelength: 532 nm) of the YAG laser are 26% and
38%, respectively. It is considered that reflected light from the
surface of the amorphous silicon film interferes with the laser
beam transmitted by the amorphous silicon film on a certain
surface. It can be estimated that this causes the concentric
pattern.
[0019] To prevent or decrease the generation of the concentric
pattern, therefore, it is considered that it is necessary to
prevent such interference. To prevent the interference, a plurality
of laser beams are condensed, the condensed laser beams are
irradiated to the semiconductor film on the surface of the
substrate and the semiconductor film is thereby crystallized.
[0020] Accordingly, a laser annealer according to the present
invention is a laser annealer comprising: a laser light source
outputting a laser beam; and a moving mechanism for moving a
substrate irradiated with the laser beam aslant, and characterized
in that the moving mechanism has a function of reciprocating by a
distance equal to or larger than a length of one edge of the
substrate, and of moving in a direction perpendicular to the
reciprocating direction by a distance equal to or smaller than a
length of the laser beam in a Y axis direction in a region in which
the laser beam is irradiated to the substrate, As a result, by
employing the laser annealer according to the present invention, it
is possible to prevent or decrease the generation of a concentric
pattern, which has been disadvantageously generated by the
irradiation of a laser beam and to improve the reliability of a
resultant semiconductor device. It is also possible to uniformly
irradiate a laser beam to even a semiconductor film on a
large-sized substrate.
[0021] Further, a laser annealer according to the present invention
is a laser annealer comprising: a laser light source outputting a
laser beam; a nonlinear optical element modulating the laser beam;
a waveguide condensing the modulated laser beam; and a moving
mechanism for moving a substrate irradiated with the condensed
laser beam aslant, and characterized in that the moving mechanism
has a function of reciprocating by a distance equal to or larger
than a length of one edge of the substrate, and of moving in a
direction perpendicular to the reciprocating direction by a
distance equal to or smaller than a length of the laser beam in a Y
axis direction in a region in which the laser beam is irradiated to
the substrate. As a result, by employing the laser annealer
according to the present invention, it is possible to prevent or
decrease the generation of a concentric pattern, which has been
disadvantageously generated by the irradiation of a laser beam and
to improve the reliability of a resultant semiconductor device. It
is also possible to uniformly irradiate a laser beam to even a
semiconductor film on a large-sized substrate.
[0022] A semiconductor device manufacturing method according to the
present invention is a semiconductor device manufacturing method
comprising the steps of: forming a semiconductor film on a
substrate; and irradiating a plurality of laser beams to the
semiconductor film, and characterized in that a step of irradiating
the laser beams aslant to the semiconductor film while moving the
substrate at a constant rate, and a step of moving the substrate in
a direction perpendicular to the moving direction by a distance
equal to or smaller than a width of the laser beams are
continuously repeated. As a result, by employing the laser annealer
according to the present invention, it is possible to prevent or
decrease the generation of a concentric pattern, which has been
disadvantageously generated by the irradiation of a laser beam and
to improve the reliability of a resultant semiconductor device. It
is also possible to uniformly irradiate a laser beam to even a
semiconductor film on a large-sized substrate.
[0023] A semiconductor device manufacturing method according to the
present invention is a semiconductor device manufacturing method
comprising the steps of: forming a semiconductor film on a
substrate; and irradiating a plurality of laser beams to the
semiconductor film, and characterized in that a step of modulating
the plurality of laser beams by a plurality of nonlinear optical
elements, respectively, a step of causing the modulated laser beams
to pass through a waveguide and thereby condensing the modulated
laser beams, and a step of irradiating the condensed laser beams
aslant to the semiconductor film while moving the substrate at a
constant rate, and moving the substrate in a direction
perpendicular to the moving direction by a distance equal to or
smaller than the laser beam, are continuously repeated. As a
result, by employing the laser annealer according to the present
invention, it is possible to prevent or decrease the generation of
a concentric pattern, which has been disadvantageously generated by
the irradiation of a laser beam and to improve the reliability of a
resultant semiconductor device. It is also possible to uniformly
irradiate a laser beam to even a semiconductor film on a
large-sized substrate.
[0024] Further, a semiconductor device manufacturing method
according to the present invention is a semiconductor device
manufacturing method characterized in that the constant rate falls
within a range of 20 to 200 cm/s. As a result, it is possible to
irradiate a laser beam to a semiconductor layer provided on a
large-sized substrate at high rate.
[0025] In addition, the laser beams employed in the present
invention may be processed into elliptic shape by an optical
system.
[0026] Furthermore, a semiconductor device manufacturing method
according to the present invention is a semiconductor device
manufacturing method characterized in that the laser beam is
incident on the semiconductor film at an aslant angle of 5 to
10.degree. with respect to a normal line direction of a front
surface of the substrate or a normal line direction of a rear
surface of the substrate. This method has been contrived from the
fact that if a step using a laser annealing method is executed
while inclining the substrate, no concentric pattern appears, and
characterized by irradiating a laser beam to the substrate with an
angle with respect to the substrate. By applying the present
invention, it is possible to remove or decrease the irregularity of
the material property of a crystalline semiconductor film caused by
the interference of the laser beam. If a TFT is manufactured using
such a crystalline semiconductor film, the electrical
characteristic of the TFT is improved.
[0027] Moreover, semiconductor device manufacturing method
according to the present invention is a semiconductor device
manufacturing method characterized in that crystallization of the
semiconductor substrate is progressed in a direction parallel to
the substrate and closer to an end face of the substrate. By
employing the semiconductor device manufacturing method according
to the present invention, it is possible to manufacture a
semiconductor device in which the surface of a semiconductor layer
is flat and which has high electrical mobility.
[0028] Additionally, the laser beam may be irradiated to the
semiconductor film from a rear surface side of the substrate (an
opposite side of the surface where semiconductor film is
formed).
[0029] As for the laser beam, an ordinary known laser such as a YAG
laser (which normally indicates an Nd: YAG laser), an Nd: YLF
laser, an Nd: YVO.sub.4 laser, an Nd: YAlO.sub.3 laser, a ruby
laser, a Ti: sapphire laser or a glass laser can be employed. The
YAG laser which is excellent in coherency and pulse energy is
particularly preferable.
[0030] If the YAG laser is employed, for example, it is preferable
to use a second harmonic (wavelength: 532 nm). This is because the
wavelength of the fundamental harmonic of the YAG laser (first
harmonic) is as long as 1064 nm. The first harmonic can be
modulated to the second, third or fourth harmonic by a wavelength
modulator which includes a nonlinear element. The respective
harmonics can be formed according to a well-known technique. In
this specification, it is assumed that "a laser beam from a
solid-state laser" includes not only the first harmonic but also
harmonics the wavelength of which is modulated halfway.
[0031] It is also possible to employ a Q switch method (Q
modulation switch method) which is well utilized for the YAG laser.
This method is to suddenly increase the Q factor of a laser
resonator from a state of a sufficiently low Q factor to thereby
output a quite steep pulse laser beam with quite high energy
level.
[0032] The solid-state laser employed in the present invention can
basically output a laser beam if a resonant mirror or a light
source for exciting solid-state crystal is provided. Due to this,
compared with the excimer laser, it does not take much labor for
maintenance. That is, since the solid-state laser is far lower in
running cost than the excimer laser, it is possible to greatly
reduce semiconductor device manufacturing cost. In addition, if the
frequency of the maintenance decreases, the operatively of a
mass-production line improves and the overall throughput of the
manufacturing process improves, which also greatly contributes to
the reduction of the semiconductor device manufacturing cost.
Besides, the area occupied by the solid-state laser is smaller than
that of the excimer laser, it is advantageously effective for the
design of a manufacturing line.
[0033] If the power of the laser beam is not lower than 10 W,
uniform laser annealing can be performed even with a single laser
beam. The laser beam having a power of not lower than 10 W suffices
to melt the semiconductor layer in the crystallization of the
semiconductor layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a view which shows an example of laser beam
irradiation;
[0035] FIG. 2 is a view which shows an example of a laser
annealer;
[0036] FIG. 3 is a view which shows the example of the laser
annealer;
[0037] FIG. 4 is an explanatory view for the X and Y directions of
a processing target substrate;
[0038] FIG. 5 is a graph showing the relationship between
processing target substrate moving time and rate;
[0039] FIG. 6 is a view which shows an example of a laser annealer
according to the present invention;
[0040] FIGS. 7A to 7D show semiconductor device manufacturing
steps;
[0041] FIG. 8 is a view which shows a semiconductor device
according to the present invention;
[0042] FIG. 9A is a schematic diagram of a TFT of a pixel section,
and FIG. 9B is a schematic diagram of a TFT of a driving
circuit;
[0043] FIG. 10A is a graph showing the reflectance of an amorphous
silicon film (thickness: 55 nm) relative to wavelength, and FIG.
10B is a graph showing the transmittance of the amorphous silicon
film (thickness of 55 nm) relative to wavelength;
[0044] FIG. 11 is a view which shows an example of a laser
annealer;
[0045] FIG. 12 is a view which shows an example of a laser
annealer; and
[0046] FIGS. 13A to 13C are views which show an example of a laser
annealer.
EMBODIMENT MODE
[0047] A laser beam irradiation method in one embodiment of the
present invention will first be described with reference to FIG.
1.
[0048] Through a crystallization step by irradiating a laser beam
to an amorphous silicon layer, a crystalline silicon layer is
formed. This crystallization is conducted in a laser annealing
chamber 602 in which a transparent window 601 is provided.
[0049] First, a light transmitting substrate made of barium or
aluminum borosilicate glass as borosilicate glass represented by
#7059 glass or #1737 glass manufactured by Corning Inc. is employed
as a substrate. Alternatively, a quartz substrate or a silicon
substrate may be employed as the substrate. In this embodiment, a
glass substrate of a size of 680 mm.times.880 mm and a thickness of
1.1 mm is employed. In this specification, a substrate on which a
foundation film and a semiconductor film are formed in this order
is referred to as "processing target substrate".
[0050] Inside of the laser annealing chamber 602, a stand 603, a
stage 604 provided on the stand 603, and a moving mechanism 605 for
moving the stand 603 are disposed. Outside of the laser annealing
chamber 602, an evacuation pump 630, a gas supply tube 607 and a
gate valve 608 are disposed.
[0051] The stand 603 is provided so that the base 603 is moved in
directions at right angle (X axis direction and Y axis direction)
to the normal line direction of a processing target substrate 606
by the moving mechanism 605 for moving the stand 603 to thereby
irradiate a laser beam to the upper surface of the processing
target substrate 606. A laser beam irradiation direction is aslant
with respect to the normal line direction of the processing target
substrate 606 by 5 to 10.degree..
[0052] In this specification, a semiconductor manufacturing device
which includes the stage 604 and the moving mechanism 605 is
referred to as a laser annealer. The base 603 may be provided
between the stage 604 and the moving mechanism 605. The laser
annealer may include a laser oscillator 609, an optical system 610
and a mirror 611 in addition to the above-stated constituent
elements. An amorphous silicon layer is crystallized by a
combination of the laser annealing chamber 602 in which the laser
annealer and the transparent window 601 are disposed, the
evacuation pump 630, the gas supply tube 607 and the gate valve
608. FIG. 2 shows the laser annealer of FIG. 1 from the Y axis
direction. FIG. 3 shows the laser annealer viewed from a mirror
side (upward of the processing target substrate 606). The moving
mechanism 605 can move by a distance equal to or larger than the
length of one edge of the processing target substrate 606 in the X
axis direction and can move by a distance equal to or smaller than
the width of a laser beam in the Y axis direction perpendicular to
the X direction. It is to be noted that the width of the laser beam
is a width of the laser beam in a direction perpendicular to a
moving direction by the moving mechanism.
[0053] As shown in FIG. 1, a laser beam 600 is emitted from the
laser oscillator 609, processed to have an elliptic cross section
by the optical system 610, reflected by the mirror 611, caused to
pass through the transparent window 601 and irradiated to the
processing target substrate 606. The irradiation light beam may be
a rectangular light beam.
[0054] FIG. 4 is a view which shows the processing target substrate
606 from the normal line direction. The processing target substrate
606 is provided so that the end portion of the processing target
substrate 606 is located at a position away from a laser beam
irradiated position by 100 mm. Next, the moving mechanism 605 is
moved while being accelerated so as to move the processing target
substrate 606 in a direction of an arrow {circle around (1)}. After
0.05 seconds, the laser beam 600 is irradiated to the processing
target substrate 606 at a constant rate (20 cm/s in this
embodiment). If the laser beam irradiated position is outside of
the processing target substrate 606, the moving rate is decelerated
(FIG. 5). Next, the same step as that in the arrow {circle around
(1)} direction is executed in a direction of an arrow {circle
around (2)} which is opposite to the arrow {circle around (1)}
direction, to thereby crystallize the substrate. To execute a step
in a direction of an arrow {circle around (3)} and that in a
direction of an arrow {circle around (4)}, the step in the arrow
{circle around (1)} direction and that in the arrow {circle around
(2)} direction may be repeated, respectively. If necessary, these
steps may be repeatedly executed to irradiate the entire surface of
the processing target substrate 606 with the laser beam. The
semiconductor film in the processing target substrate 606 is
crystallized in a direction which is parallel to the processing
target substrate 606 and which is closer to the end face of the
processing target substrate 606.
[0055] The rate of moving the processing target substrate 606 may
be set at a constant rate which falls within a range of 20 to 200
cm/s.
[0056] In the crystallization, the processing target substrate 606
may be disposed on the stage 604 to keep the temperature of the
processing target substrate 606 to be a predetermined temperature
by a heater provided in the stand 603. If the amorphous silicon
layer is crystallized at a temperature of 450.degree. C., the grain
diameter of crystals increases.
[0057] As the laser oscillator 609, a laser oscillator which
oscillates a CW laser beam as the laser beam 600 is employed.
[0058] The atmosphere of the laser annealing chamber 602 may be
controlled by the evacuation pump 630 which is provided as a
pressure reduction and evacuation means. A gas supply tube 607a
which is connected to a hydrogen gas cylinder through a valve and a
gas supply tube 607b which is connected to a nitrogen or the other
gas cylinder through a valve are provided as the gas supply tube
607 which serves as a gas supply means. In this embodiment, the
laser beam is irradiated at ordinary temperature at ordinary
pressure.
[0059] In this embodiment, the laser beam is irradiated to the
semiconductor film on the surface of the substrate while moving the
substrate at a constant rate between 20 and 200 cm/s. Due to this,
a uniform laser beam can be irradiated to even the semiconductor
film on a large-sized substrate.
[0060] In this embodiment, power is set at 10 W. However, if the
power is set at not lower than 10 W, uniform laser annealing can be
performed even with a single laser beam. The laser beam having a
power of not lower than 10 W suffices to melt the semiconductor
layer in the crystallization of the semiconductor layer.
[0061] In this embodiment, a laser beam is emitted from one laser
oscillator. Alternatively, a plurality of laser beams may be
condensed using a plurality of laser oscillators so as to increase
beam intensity. By thus condensing the laser beams, it is possible
to decrease the generation of the concentric pattern and to thereby
improve the reliability of a resultant semiconductor device. If
necessary, a plurality of optical systems, a plurality of mirrors,
a fiber and the like may be employed.
[0062] According to the present invention, the laser beam is
processed to have an elliptic cross section in the step using the
laser annealing method to thereby improve throughput. Besides, by
using a solid-state laser easy to maintain, higher throughput than
that by laser annealing employing a conventional excimer laser can
be attained. Consequently, it is possible to decrease the
manufacturing cost of a TFT and the semiconductor device such as a
display formed out of the TFT.
[0063] Moreover, by irradiating the laser beam aslant to the
semiconductor film, it is possible to remove or decrease the
concentric pattern generated on the semiconductor film and to
thereby make the material property of the semiconductor film after
the step using the laser annealing method uniform. If a
semiconductor device is manufactured using such a semiconductor
film, it is possible to greatly improve the performance of the
semiconductor device.
DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
Embodiment 1
[0064] An optical system will be described below with reference to
FIG. 6 in this embodiment.
[0065] As a laser oscillator 201, it is desirable to use a
high-power laser (a YAG laser, a YVO.sub.4 laser or the like). Of
course, a gas laser, a glass laser or the like may also be used as
long as it has high power. The laser light generated from the laser
oscillator 201 is formed into a linear beam whose irradiation plane
has a linear shape, by using the optical system. The optical system
uses, for example, a long focal length cylindrical lens 205 for
enlarging a laser beam into a long beam, and a cylindrical lens 206
for converging a laser beam into a thin beam. By using such long
focal length cylindrical lenses, it is possible to obtain a laser
beam which is reduced in aberration and is uniform in energy
distribution at or near the irradiation plane. In addition, the
long focal length cylindrical lenses are effective in restraining a
remarkable difference from occurring between the beam width of a
beam incident on the semiconductor film and the beam width of a
beam reflected from the back surface of the substrate. Experiments
of the present inventor showed that when a cylindrical lens having
a focal length of 500 mm or more was used, the influence of
aberration was able to be drastically reduced.
[0066] A reflecting mirror 207 is provided in front of the
cylindrical lens 206 so that the traveling direction of the laser
beam can be changed. The angle at which the laser beam is made
incident on the irradiation plane can be adjusted to the desired
angle .theta. by the reflecting mirror 207. If the angle of the
cylindrical lens 206 is changed according to the angle of the
reflecting mirror 207, a laser beam having far higher symmetry can
be formed on the irradiation plane.
[0067] In addition, when linear beams are to be irradiated onto a
semiconductor film, the irradiation is carried out with a scanning
overlapping ration of 0 to 80% of the laser beam (laser beam in the
Y-axis direction in the present Embodiment) during the scanning. It
is to be noted that in case of a pulsed laser, the irradiation can
be carried out with an overlapping ratio of 50 to 98% between the
successively irradiated laser beams, and alternatively with no
overlapping. Since optimum conditions differ according to the
states of semiconductor films or the delay periods of laser beams,
it is preferable that an operator appropriately determine the
optimum conditions.
[0068] In Embodiment 1, a pulsed laser (Output 20 W, frequency 30
Hz, YAG) was used as the laser oscillator 201. The pulsed laser
beam was modulated to a second harmonic by a non-linear optical
element 202 and was then formed into a linear beam of width 130 mm
and length 0.4 mm by using the optical system, and the linear beam
was irradiated onto the semiconductor film. At this time, the
linear beam was irradiated with an angular deviation of 5 to 10
degrees from the direction perpendicular to the substrate 204.
[0069] Stand 208 is provided under a stage 203, and moving
mechanism 209 is provided under the stand 208. A substrate 204 can
be moved in the X axis direction and Y axis direction by moving
mechanism 209. A ball, a barrel, a motor and the like may be
provided below the moving mechanism 209.
[0070] The semiconductor film in the processing target substrate
204 is crystallized in a direction which is parallel to the
processing target substrate 204 and witch is closer to the end face
of the processing target substrate 606.
[0071] Moreover, by irradiating the laser beam aslant to the
semiconductor film of the processing target substrate 204, it is
possible to remove or decrease the concentric pattern generated on
the semiconductor film and to thereby make the material property of
the semiconductor film after the step using the laser annealing
method uniform. If a semiconductor device is manufactured using
such a semiconductor film, it is possible to greatly improve the
performance of the semiconductor device.
Embodiment 2
[0072] This embodiment describes the method of crystalline for the
laser anneal device.
[0073] First, a glass substrate (Corning 1737 with a glass
distortion temperature of 667.degree. C.) was prepared as a
substrate 1000. Then, a protective film 1001 is formed on the
substrate 1000, and a tantalum nitride film 1002a (50 nm thick) and
tantalum film 1002a (250 nm thick) were formed successively in the
form of a multilayer configuration on the protective film 1000 by
sputtering. (FIG. 7A) Then, the gate electrode 1002 having a multi
layer configuration formed by photolisography, which is
conventional patterning method.
[0074] Subsequently, the gate insulating film and the amorphous
semiconductor film 1004 were formed successively in the form of a
multilayer configuration without being exposed to the atmosphere
(FIG. 7C). In this embodiment, in order to prevent impurities from
diffusing from the gate wiring to the semiconductor film and the
gate insulating film during fabrication, the silicon nitride film
1003a (50 nm in thickness) and the silicon oxide film 1003b (125 nm
in thickness) were formed in the form of a multilayer configuration
by means of the plasma CVD method to allow the layer to serve as a
gate insulating film of a multilayer configuration. In this
embodiment, a two layer insulating film is employed as the gate
insulating film, however, the gate insulating film may be of a
single layer or of a multilayer configuration with three layers or
more. In addition, in this embodiment, an amorphous silicon film
1004 54 nm in thickness was formed on the gate insulating film as
the amorphous semiconductor film 104 by means of the plasma CVD
method. Furthermore, the formation in the form of a multilayer
configuration was carried out successively without exposure to the
atmosphere so that each interface of the layers does not have
contaminants adhered thereto from the atmosphere.
[0075] Thereafter, heating treatment was carried out (at a
temperature of 500.degree. C. for one hour) in order to reduce the
concentration of hydrogen, which prevents the crystallization of
the semiconductor film, in the amorphous silicon film.
[0076] After the state shown in FIG. 7C has been obtained, the
amorphous semiconductor film 1004 was irradiated with infrared
light or ultraviolet light (laser annealing) to be crystallized
(laser crystallization) in order to form the crystalline
semiconductor film 1005 (semiconductor film including crystals)
(FIG. 7D). The amorphous semiconductor film 1004 is crystallized in
a direction which is parallel to the substrate 1000 and which is
closer to the end face of the substrate 1000.
[0077] In the case of using ultraviolet light as the
crystallization technique, laser light or intensified light emitted
from an ultraviolet light lamp can be used, while in the case of
using infrared light, infrared laser light or an intensified light
emitted from an infrared light lamp can be used. In this
Embodiment, The YVO.sub.4 CW laser beam is shaped oval and
irradiated on the semiconductor film at an aslant angle of 5 to
10.degree. with a scanning overlapping ratio of 0 to 80.degree. A)
of the laser beam (laser beam in the Y-axis direction in the
present embodiment) during the scanning.
[0078] Furthermore, one can determine the conditions for laser
crystallization (such as the wavelength of the laser light, the
intensity of irradiation, the frequency of repetition, and the time
of irradiation) as appropriate in consideration of the thickness of
the amorphous semiconductor film 1004, the temperature of the
substrate and so forth.
[0079] Furthermore, some conditions for laser crystallization may
cause the semiconductor film to crystallize after passing through a
melting state, or the semiconductor film to crystallize in a solid
phase without being melted or in an intermittent state between the
solid phase and liquid phase. This process allows the amorphous
semiconductor film 1004 to crystallize and change into the
crystalline semiconductor film 1005. In this embodiment, the
crystalline semiconductor film is a poly-crystalline silicon film
(poly-silicon film).
Embodiment 3
[0080] The structure of the active matrix liquid crystal display
device obtained by using Embodiment 1 and 2 will be described with
reference to the top view of FIGS. 8 to 9.
[0081] In the top view of active matrix display device shown in
FIG. 8A, the pixel portion 811, the driver circuit (general name of
gate driving circuit 805 and source driving circuit 807), an
external input terminal 803 to which an FPC (Flexible Printed
Circuit) is bonded, a wiring 804 for connecting the external input
terminal 803 with input sections of the respective circuits, and
the like are formed on an active matrix substrate 801. The active
matrix substrate 801 and an opposing substrate 802, on which a
color filter and the like are formed, are bonded with each other,
sandwiching an end-sealing material 809 therebetween.
[0082] A gate driving circuit has the function to input the signal
to selected gate wiring 806. The gate wiring 806 is the wiring that
connects to gate electrode electrically. And the selected gate
wirings are selected one by one. Of course, an insulating film is
provided on the gate wiring. On the other way, a source driving
circuit has the function to receive the image data signal and apply
the signal to the pixel electrode, which connected to the selected
gate wiring. The source driving circuit 807 moves with matching the
timing of gate driving circuit 805. Then, an image of active matrix
type display device can be obtained by selecting the switching
element (not shown) of each gate wiring and by applying the desired
voltage through source wiring 808.
[0083] A color filter formed on the surface of the pixel portion
811 facing the counter substrate is provided so that each of red
(R), green (G) and blue (B) color filters corresponds to each
pixel. For practical display, color display is realized by color
filters of three colors, i.e., a red color filter, a green color
filter and a blue color filter. The arrangement of color filters of
these three colors is arbitrary.
[0084] When the direction of grain growth caused by the irradiation
of laser light (FIG. 8) is the same direction of arrow, if that
direction and the flowing direction of carrier (channel direction)
in a semiconductor layer 810 showed in FIG. 9A (Figure of TFT at
pixel portion) are the same, electric mobility are not lowered. 806
indicate gate wiring and 811 indicates contact-hall. As the same
way, if the direction of grain growth caused by the irradiation of
laser light of FIG. 8 and the direction of carrier flow in
semiconductor layer 910 showed in FIG. 9B (figure of TFT at driving
circuit) are the same, electric mobility are not lowered. 906
indicate gate wiring and 911 indicates contact hall.
Embodiment 4
[0085] A laser annealer different from that in the first embodiment
will be described. The laser annealer in this embodiment is
characterized by providing a plurality of laser oscillators, a
plurality of optical systems and a plurality of mirrors, condensing
laser beams oscillated by the laser oscillators and processed by
the optical systems, respectively and irradiating the condensed
light beams to a substrate.
[0086] As shown in FIG. 11, laser beams 1100a to 1100c are emitted
from laser oscillators 1109a to 1109c, processed by optical systems
1110a to 1110c, and reflected by mirrors 1111a to 1111c,
respectively. The reflected laser beams are condensed and
irradiated to a processing target substrate 1113 which is mounted
on a stage 1104. Using a moving mechanism 1105 which is provided
below the stage 1104, the processing target substrate 1113 can be
moved in the X axis direction and the Y-axis direction. A ball, a
barrel, a motor and the like may be provided below the moving
mechanism 1105.
[0087] In this embodiment, it is possible to prevent or decrease
the generation of a concentric pattern which has been
disadvantageously generated by the irradiation of a laser beam or
laser beams. It is, therefore, possible to improve the reliability
of a resultant semiconductor device.
Embodiment 5
[0088] A laser annealer different from those in the first and
second embodiments will be described. The laser annealer in this
embodiment is characterized by providing a plurality of laser
oscillators, a plurality of nonlinear optical elements and a
waveguide, emitting laser beams from the respective laser
oscillators, modulating the laser beams by the respective nonlinear
optical elements, condensing the modulated laser beams by the
waveguide and irradiating the condensed laser beams to a
substrate.
[0089] As shown in FIG. 12, laser beams are emitted from laser
oscillators 100a to 100c, the laser beams 112a to 112c modulated by
nonlinear optical elements 101a to 101c are incident on a fiber
array 103 and condensed by a waveguide 104. The laser beams emitted
from a fiber array 105 are irradiated to a processing target
substrate 113 on a stage 110. It is noted that the fiber array 103
is a means for making the laser beams 112a to 112c proximate to one
another.
[0090] A stand 106 is provided below a stage 110 and a moving
mechanism 107 is provided below the stand 106. Using the moving
mechanism 107, the processing target substrate 113 can be moved in
the X axis direction and the Y axis direction (not shown). A ball,
a barrel, a motor and the like may be disposed below the moving
mechanism 107.
[0091] In this embodiment, it is possible to prevent or decrease
the generation of a concentric pattern which has been
disadvantageously generated by the irradiation of a laser beam. It
is, therefore, possible to improve the reliability of a resultant
semiconductor device.
Embodiment 6
[0092] A laser annealer different from those in the first to third
embodiments will be described, while particularly referring to an
example of a moving mechanism for moving a stage with reference to
FIG. 13.
[0093] Normally, a stage on which a processing target to be
irradiated with a laser beam is mounted is moved along a guide rail
which is provided in either the X axis direction or the Y axis
direction. A curved object referred to as ball (bearing) is put
between the guide rail and a section (slider) which fixes the
stage. Therefore, a mechanism which can decrease load caused by
friction and can smoothly move the stage is realized.
[0094] Since the ball (bearing) is worn by the repetitive movement
of the stage, it is necessary to replace the ball by periodical
maintenance. In addition, to move the stage more smoothly, it is
necessary to decrease abrasion caused by the movement of the
stage.
[0095] A moving mechanism for moving the stage in this embodiment
is shown in FIG. 13A. In FIG. 13A, reference symbol 1300 denotes a
guide rail on which irregularities are formed in one direction to
move the stage in a fixed direction. Reference symbol 1301 denotes
a section, referred to as a slider, which fixes the stage. The
slider 1301 can be moved along the guide rail 1300. Alternatively,
a plurality of sliders may be provided to be fixed at predetermined
intervals. A reference symbol 1302 denotes a rod which penetrates a
hole formed in the slider 1301 and is provided in a direction along
the guide rail 1300. The rod 1302 is fixed to the guide rail 1300
by an end plate 1304.
[0096] A power supply voltage and the air are fed to the slider
1301 through a cable 1303. FIG. 13B is an enlarged view of the
slider 1301. A magnetic field which attracts the slider 1301 and
the guide rail 1300 to each other is generated by the power supply
voltage. In addition, a magnetic field in a direction in which the
slider 1301 is away from and out of contact with the rod 1302 in
the hole provided in the slider 1301, is generated by the power
supply voltage. Using the principle of a linear motor force, the
slider 1301 moves in a direction indicated by an arrow. On the
other hand, a force acts on the slider 1301 and the guide rail 1300
so that the slider 1301 and the guide rail 1300 are attracted to
each other by this magnetic field. The air fed to the slider 1300
is discharged to a region between the slider 1301 and the guide
rail 1300 from an air hole 1305. Since a force acts in a direction
in which the slider 1301 is away from rod 1302 by the attracting
force of the magnetic field and the discharge of the air, a fixed
distance is maintained between the slider 1301 and the guide rail
1300.
[0097] Alternatively, instead of generating magnetic field by the
power supply voltage applied through the cable, one of the guide
rail 1300 and the slider 1301 may be formed out of a magnetic
member and the other one of the guide rail 1300 and the slider 1301
may be formed out of a material attracted by the magnetic member to
thereby generate a magnetic field. Alternatively, the guide rail
1300 and the slider 1301 may be formed out of magnetic members,
respectively.
[0098] Further, instead of generating the magnetic field by the
power supply voltage applied through the cable, one of the rod 1302
and the slider 1301 may be formed out of a magnetic member and the
other one of the rod 1302 and the slider 1301 may be formed out of
a material which tends to be away from the magnetic member to
thereby generate a magnetic field. Alternatively, the rod 1302 and
the slider 1301 may be formed out of magnetic members,
respectively.
[0099] Using the stage moving mechanism shown in this embodiment,
it is possible to move the stage along the guide rail in a
non-contact manner, to dispense with the regular replacement of the
ball (bearing) and to thereby facilitate maintenance. In addition,
because of the non-contact movement, abrasion hardly occurs and the
stage can be moved more smoothly than a case where a ball is
employed.
[0100] FIG. 13C shows a state in which a processing target 1311 to
be irradiated with a laser beam is mounted on a stage 1310 fixed
onto the slider 1301. In this embodiment, the stage moving means
enables the stage to be moved more smoothly, making it possible to
irradiate the laser beam to the processing target 1311 more
uniformly.
[0101] As described so far, by employing the laser annealer
according to the present invention, a plurality of laser beams are
condensed to one laser flux to thereby prevent or decrease the
generation of a concentric pattern, which has been
disadvantageously generated by the irradiation of a laser flux and
to make it possible to improve the reliability of a resultant
semiconductor device. If the laser annealer according to the
present invention is employed, it is possible to uniformly
irradiate a laser beam or laser beams to even a semiconductor film
on a large-sized substrate.
[0102] Further, according to the present invention, the laser beam
is processed to have an elliptic cross section in the step using
the laser annealing method to thereby improve throughput. Besides,
by using a solid-state laser maintenance of which is easy, higher
throughput than that by laser annealing employing a conventional
excimer laser can be attained. Consequently, it is possible to
decrease the manufacturing cost of a TFT and the semiconductor
device such as a display formed out of the TFT.
[0103] Moreover, by irradiating the laser beam aslant to the
semiconductor film, it is possible to remove or decrease the
concentric pattern generated on the semiconductor film and to
thereby make the material property of the semiconductor film after
the step using the laser annealing method, uniform. If a
semiconductor device is manufactured using such a semiconductor
film, it is possible to greatly improve the performance of the
semiconductor device.
* * * * *