U.S. patent application number 12/490236 was filed with the patent office on 2009-11-05 for method of manufacturing polysilicon thin film and method of manufacturing thin film transistor having the same.
Invention is credited to Se-Jin CHUNG, Ui-Jin Chung, Chi-Woo Kim, Dong-Byum Kim.
Application Number | 20090275178 12/490236 |
Document ID | / |
Family ID | 37083673 |
Filed Date | 2009-11-05 |
United States Patent
Application |
20090275178 |
Kind Code |
A1 |
CHUNG; Se-Jin ; et
al. |
November 5, 2009 |
METHOD OF MANUFACTURING POLYSILICON THIN FILM AND METHOD OF
MANUFACTURING THIN FILM TRANSISTOR HAVING THE SAME
Abstract
In a method of manufacturing a polysilicon thin film and a
method of manufacturing a TFT having the thin film, a laser beam is
irradiated on a portion of an amorphous silicon thin film to
liquefy the portion of the amorphous silicon thin film. The
amorphous silicon thin film is on a first end portion of a
substrate. The liquefied silicon is crystallized to form silicon
grains. The laser beam is shifted from the first end portion
towards a second end portion of the substrate opposite the first
end portion by an interval in a first direction. The laser beam is
then irradiated onto a portion of the amorphous silicon thin film
adjacent to the silicon grains to form a first polysilicon thin
film. Therefore, electrical characteristics of the amorphous
silicon thin film may be improved.
Inventors: |
CHUNG; Se-Jin; (Yongin-si,
KR) ; Kim; Chi-Woo; (Seoul, KR) ; Chung;
Ui-Jin; (Suwon-si, KR) ; Kim; Dong-Byum;
(Seoul, KR) |
Correspondence
Address: |
HAYNES AND BOONE, LLP;IP Section
2323 Victory Avenue, Suite 700
Dallas
TX
75219
US
|
Family ID: |
37083673 |
Appl. No.: |
12/490236 |
Filed: |
June 23, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11234609 |
Sep 23, 2005 |
7557050 |
|
|
12490236 |
|
|
|
|
Current U.S.
Class: |
438/166 ;
257/E21.347; 257/E21.412; 438/487 |
Current CPC
Class: |
H01L 29/78606 20130101;
H01L 21/02691 20130101; H01L 21/02532 20130101; H01L 29/78675
20130101; H01L 29/04 20130101; H01L 29/66757 20130101; H01L 21/2026
20130101; H01L 27/1285 20130101; H01L 21/02686 20130101 |
Class at
Publication: |
438/166 ;
438/487; 257/E21.347; 257/E21.412 |
International
Class: |
H01L 21/336 20060101
H01L021/336; H01L 21/268 20060101 H01L021/268 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2005 |
KR |
2005-28628 |
Jun 4, 2005 |
KR |
2005-28629 |
Jun 4, 2005 |
KR |
2005-28632 |
Claims
1. A method of manufacturing a polysilicon thin film comprising:
irradiating a laser beam generated from a laser unit onto a first
portion of an amorphous silicon thin film to liquefy the first
portion of the amorphous silicon thin film, the laser beam having a
beam shape including a first width substantially in parallel with a
first direction and a second width substantially in parallel with a
second direction substantially perpendicular to the first
direction; transporting the substrate or the laser beam for
shifting the laser beam in the first direction to form a first
polysilicon thin film; rotating the substrate or the laser beam by
a predetermined angle after forming the first polysilicon thin
film; and transporting the substrate or the laser beam for shifting
the laser beam in the second direction to liquefy the first
polysilicon thin film and to form a second polysilicon film.
2. The method of claim 1, wherein the second width is greater than
the first width, the beam shape of the laser unit is substantially
the same shape as a shape of the laser beam irradiated onto the
first portion.
3. The method of claim 2, wherein the amorphous silicon thin film
is formed on the substrate and the second width of the beam is
substantially same to a side of the substrate.
4. The method of claim 3, wherein the first width of the beam is
about 3 um to about 10 um.
5. The method of claim 1, wherein the amorphous silicon thin film
is formed on the substrate and the second width of the beam is
substantially same to a side of the substrate.
6. The method of claim 5, wherein the first width of the beam is
about 3 um to about 10 um.
7. The method of claim 1, the shifting of the laser beam in the
first direction is discrete.
8. The method of claim 7, the discretion interval is same to or
less than half of the first width of the laser beam.
9. The method of claim 7, the discretion interval is bigger than
half and less than the first with of the laser beam.
10. The method of claim 7, wherein the second width is greater than
the first width, the beam shape of the laser unit is substantially
the same shape as a shape of the laser beam irradiated onto the
first portion.
11. The method of claim 10, wherein the amorphous silicon thin film
is formed on the substrate and the second width of the beam is
substantially same to a side of the substrate.
12. The method of claim 11, wherein the first width of the beam is
about 3 um to about 10 um.
13. The method of claim 7, wherein the amorphous silicon thin film
is formed on the substrate and the second width of the beam is
substantially same to a side of the substrate.
14. The method of claim 13, wherein the first width of the beam is
about 3 um to about 10 um.
15. A method of manufacturing a thin film transistor comprising:
forming an amorphous silicon thin film on a substrate; irradiating
a laser beam generated from a laser unit onto the amorphous silicon
thin film to change the amorphous silicon thin film into a
polysilicon thin film; partially etching the polysilicon thin film
to form a polysilicon pattern; forming a first insulating layer on
the substrate having the polysilicon pattern; forming a gate
electrode on the first insulating layer overlapping a portion of
the polysilicon pattern; forming a second insulating layer on the
first insulating layer and the gate electrode; partially etching
the first and second insulating layers to form contact holes; and
forming a source electrode and a drain electrode on the second
insulating layer, the source electrode being spaced apart from the
drain electrode, the source and drain electrodes being electrically
connected to the polysilicon pattern through the contact holes,
wherein the laser beam irradiation scans a first direction to
change the amorphous silicon thin film into a first polysilicon
thin film, and the laser beam irradiation scans a second direction
to change the first polysilicon thin film into a second polysilicon
thin film.
16. The method of claim 15, the first direction and the second
direction are different from each other.
17. The method of claim 16, the first direction and the second
direction are substantially perpendicular.
18. The method of claim 16, wherein the beam shape of the laser
unit is elongated and substantially the same shape as a shape of
the laser beam irradiated onto the first portion.
19. The method of claim 18, wherein the length of the beam is
substantially same to a side of the substrate.
20. The method of claim 19, wherein the width of the beam is about
3 um to about 10 um.
21. The method of claim 16, the scanning of the laser beam in the
first direction is discrete.
22. The method of claim 21, the discretion interval is same to or
less than half of the first width of the laser beam.
23. The method of claim 21, the discretion interval is bigger than
half and less than the first with of the laser beam.
24. The method of claim 21, wherein the beam shape of the laser
unit is elongated substantially the same shape as a shape of the
laser beam irradiated onto the first portion.
25. The method of claim 24, wherein the length of the beam is
substantially same to a side of the substrate.
26. The method of claim 25, wherein the width of the beam is about
3 um to about 10 um.
27. The method of claim 21, wherein the beam is elongated and the
length of the beam is substantially same to a side of the
substrate.
28. The method of claim 27, wherein the width of the beam is about
3 um to about 10 um.
29. A method of manufacturing a polysilicon thin film comprising:
irradiating a laser beam generated from a laser unit onto a first
portion of an amorphous silicon thin film to liquefy the first
portion of the amorphous silicon thin film, the laser beam having a
beam shape including a first width substantially in parallel with a
first direction and a second width substantially in parallel with a
second direction substantially perpendicular to the first
direction; transporting the substrate or the laser beam for
scanning the laser beam in the first direction to form a first
polysilicon thin film; rotating the substrate or the laser beam by
a predetermined angle after forming the first polysilicon thin
film; and transporting the substrate or the laser beam for scanning
the laser beam in the second direction to liquefy the first
polysilicon thin film and to form a second polysilicon film.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation application of U.S. patent
application Ser. No. 11/234,609, filed on Sep. 23, 2005 and relies
for priority upon Korean Patent Application No. 2005-28628 filed on
Apr. 6, 2005, Korean Patent Application No. 2005-28629 filed on
Apr. 6, 2005, and Korean Patent Application No. 2005-28632 filed on
Apr. 6, 2005, the contents of which are incorporated herein by
reference in their entireties.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of manufacturing a
polysilicon thin film and a method of manufacturing a thin film
transistor (TFT) having the thin film. More particularly, the
present invention relates to a method of manufacturing a
polysilicon thin film having improved electrical characteristics
and a method of manufacturing a TFT having the thin film.
[0004] 2. Description of the Related Art
[0005] A liquid crystal display (LCD) device includes a switching
element. The switching element includes an amorphous silicon thin
film transistor (a-Si TFT) or a polysilicon thin film transistor
(poly-Si TFT). The LCD device having the poly-Si TFT has a faster
operating speed than the LCD device having the a-Si TFT, thereby
providing better image display quality than the LCD device having
the a-Si TFT.
[0006] The poly-Si TFT is directly formed on a substrate, or an
amorphous silicon thin film is crystallized to form the poly-Si TFT
through heat treatment.
[0007] When a temperature of a glass substrate to be used for the
LCD device rises above about 600.degree. C., the glass substrate is
deformed. This avoid this deformation, the amorphous silicon thin
film is crystallized using an excimer laser. In the excimer laser
annealing (ELA) process, a laser beam having a high energy is
irradiated onto the amorphous silicon thin film for a period of
tens of nanoseconds to crystallize the amorphous silicon thin film
so that the glass substrate is not deformed.
[0008] When the amorphous silicon thin film is treated by the ELA
process, silicon atoms in the amorphous silicon thin film are
rearranged in a grain form to provide the poly-Si TFT with high
electrical mobility. In the ELA process, the amorphous silicon thin
film is melted and then solidified to form the poly-Si TFT. That
is, the poly-Si TFT formed through the ELA process has high
operating speed in a switched-on state.
[0009] However, a leakage current flows through an interface
between polysilicon grains in a switched-off state. That is,
silicon atoms at the interface are not securely combined with one
another, causing an electron-hole to be formed at the interface,
thereby generating a leakage current.
SUMMARY
[0010] In accordance with the present invention, a method of
manufacturing a polysilicon thin film having improved electrical
characteristics is provided.
[0011] In accordance with the present invention, a method of
manufacturing a thin film transistor (TFT) having the
above-mentioned thin film is also provided.
[0012] A method of manufacturing a polysilicon thin film in
accordance with an embodiment of the present invention is provided
as follows. A laser beam is irradiated on a first portion of an
amorphous silicon thin film to liquefy the portion of the amorphous
silicon thin film. The first portion of the amorphous silicon thin
film is on a first end portion of a substrate. The liquefied
silicon is crystallized to form silicon grains. The laser beam is
shifted from the first end portion to a second end portion of the
substrate opposite the first end portion by an interval in a first
direction. The laser beam is then irradiated onto a second portion
of the amorphous silicon thin film adjacent to the silicon grains
to form a first polysilicon thin film.
[0013] A method of manufacturing a thin film transistor in
accordance with an embodiment of the present invention is provided
as follows. An amorphous silicon thin film is formed on a
substrate. A laser beam is irradiated onto the amorphous silicon
thin film to change the amorphous silicon thin film into a
polysilicon thin film. The polysilicon thin film is partially
etched to form a polysilicon pattern. A first insulating layer is
formed on the substrate having the polysilicon pattern to protect
the polysilicon pattern. A gate electrode is formed on the first
insulating layer corresponding to the polysilicon pattern. A second
insulating layer is formed on the first insulating layer and the
gate electrode. The first and second insulating layers are
partially etched to form contact holes. A source electrode and a
drain electrode are formed on the second insulating layer. The
source electrode is spaced apart from the drain electrode. The
source and drain electrodes are electrically connected to the
polysilicon pattern through the contact holes, respectively.
[0014] In accordance with the present invention, the laser beam is
repetitively irradiated onto the substrate from the first end
portion toward the second end portion to increase a grain size to
form the poly-Si thin film having improved electrical
characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above and other advantages of the present invention will
become readily apparent by reference to the following detailed
description when considered in conjunction with the accompanying
drawings wherein:
[0016] FIG. 1 is a cross-sectional view showing a method of
manufacturing a polysilicon (poly-Si) thin film in accordance with
one embodiment of the present invention;
[0017] FIG. 2 is a plan view showing the method of manufacturing
the poly-Si thin film shown in FIG. 1;
[0018] FIG. 3 is an enlarged cross-sectional view showing a portion
`A` shown in FIG. 1;
[0019] FIGS. 4A to 4F are cross-sectional views showing the growth
of the poly-Si shown in FIG. 2;
[0020] FIGS. 5A to 5C are plan views showing the growth of the
poly-Si shown in FIG. 2;
[0021] FIG. 6 is a plan view showing a poly-Si thin film shown in
FIG. 2;
[0022] FIG. 7 is a graph showing a relationship between an
intensity of a laser beam and a location;
[0023] FIG. 8 is a graph showing a portion `B` of FIG. 7;
[0024] FIGS. 9A to 9C are plan views showing a growth of a poly-Si
formed by a method of manufacturing a thin film in accordance with
another embodiment of the present invention;
[0025] FIG. 10 is a plan view showing a poly-Si thin film formed by
the method shown in FIGS. 9A to 9C;
[0026] FIG. 11 is a plan view showing a method of manufacturing a
poly-Si thin film in accordance with another embodiment of the
present invention;
[0027] FIGS. 12A to 12C are plan views showing the method shown in
FIG. 11;
[0028] FIG. 13 is a plan view showing the poly-Si thin film formed
by the method shown in FIG. 11; and
[0029] FIGS. 14A to 14D are cross-sectional views showing a method
of manufacturing a poly-Si thin film in accordance with one
embodiment of the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0030] The invention is described more fully hereinafter with
reference to the accompanying drawings, in which embodiments of the
invention are shown. This invention may, however, be embodied in
many different forms and should not be construed as limited to the
embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the scope of the invention to those skilled in
the art. In the drawings, the size and relative sizes of layers and
regions may be exaggerated for clarity.
[0031] It will be understood that when an element or layer is
referred to as being "on", "connected to" or "coupled to" another
element or layer, it can be directly on, connected or coupled to
the other element or layer, or intervening elements or layers may
be present. In contrast, when an element is referred to as being
"directly on," "directly connected to" or "directly coupled to"
another element or layer, there are no intervening elements or
layers present. Like numbers refer to like elements throughout. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items.
[0032] It will be understood that, although the terms first,
second, third etc. may be used herein to describe various elements,
components, regions, layers and/or sections, these elements,
components, regions, layers and/or sections should not be limited
by these terms. These terms are only used to distinguish one
element, component, region, layer or section from another region,
layer or section. Thus, a first element, component, region, layer
or section discussed below could be termed a second element,
component, region, layer or section without departing from the
teachings of the present invention.
[0033] Spatially relative terms, such as "beneath", "below",
"lower", "above", "upper" and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if the device in the figures is turned over, elements
described as "below" or "beneath" other elements or features would
then be oriented "above" the other elements or features. Thus, the
exemplary term "below" can encompass both an orientation of above
and below. The device may be otherwise oriented (rotated ninety
degrees or at other orientations) and the spatially relative
descriptors used herein interpreted accordingly.
[0034] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0035] Embodiments of the invention are described herein with
reference to cross-sectional illustrations that are schematic
illustrations of idealized embodiments (and intermediate
structures) of the invention. As such, variations from the shapes
of the illustrations as a result, for example, of manufacturing
techniques and/or tolerances, are to be expected. Thus, embodiments
of the invention should not be construed as limited to the
particular shapes of regions illustrated herein but are to include
deviations in shapes that result, for example, from manufacturing.
For example, an implanted region illustrated as a rectangle will,
typically, have rounded or curved features and/or a gradient of
implant concentration at its edges rather than a binary change from
implanted to non-implanted region. Likewise, a buried region formed
by implantation may result in some implantation in the region
between the buried region and the surface through which the
implantation takes place. Thus, the regions illustrated in the
figures are schematic in nature and their shapes are not intended
to illustrate the actual shape of a region of a device and are not
intended to limit the scope of the invention.
[0036] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0037] FIG. 1 is a cross-sectional view showing a method of
manufacturing a polysilicon (poly-Si) thin film in accordance with
one embodiment of the present invention. FIG. 2 is a plan view
showing the method of manufacturing the poly-Si thin film shown in
FIG. 1. FIG. 3 is an enlarged cross-sectional view showing a
portion `A` shown in FIG. 1.
[0038] Referring to FIGS. 1 to 3, an apparatus for manufacturing
the poly-Si thin film 140 includes a laser unit 10, an XY-stage 20
and a substrate 100.
[0039] The laser unit 10 generates a laser beam 200 to
intermittently irradiate the laser beam 200 onto the substrate 100.
In the method shown in FIGS. 1 to 3, the laser unit 10 comprising
an excimer laser that has various characteristics such as short
wavelength, high output, high efficiency, etc. The excimer laser
may comprise an inert gas excimer laser, an inert gas halide
excimer laser, a mercury halide excimer laser, an inert gas oxide
excimer laser or a polyatomic excimer laser. Examples of the inert
gas include Ar.sub.2, Kr.sub.2, Xe.sub.2, etc. Examples of the
inert gas halide include ArF, ArCl, KrF, KrCl, XeF, XeCl, etc.
Examples of the mercury halide include HgCl, HgBr, Hgl, etc.
Examples of the inert gas oxide include ArO, KrO, XeO, etc.
Examples of the polyatomic material include Kr.sub.2F, Xe.sub.2F,
etc.
[0040] A wavelength of the laser beam 200 generated from the laser
unit 10 is about 200 nm to about 400 nm. In the method shown in
FIGS. 1 to 3, the wavelength of the laser beam 200 generated from
the laser unit 10 is about 250 nm to about 308 nm. A frequency of
the laser beam 200 is about 300 Hz to about 6,000 Hz. In the method
shown in FIGS. 1 to 3, the frequency of the laser beam 200 is about
4,000 Hz to about 6,000 Hz.
[0041] The XY-stage 20 supports the substrate 100, and repeatedly
transports the substrate 100 in a first direction with respect to
the substrate 100 by a first interval. In the method shown in FIGS.
1 to 3, the XY-stage 20 transports the substrate 100 from right to
left, and the XY-stage 20 is shifted by the first interval in a
first direction substantially perpendicular to the second direction
with respect to the substrate 100.
[0042] As the XY-stage 20 transports the substrate 100, the laser
beam 200 generated from the laser unit 10 is irradiated onto the
substrate 100 from a first end portion 102 of the substrate 100 to
a second end portion 104 of the substrate 100. The second end
portion 104, which is adjacent to a right side of the substrate
100, is opposite the first end portion 102, which is adjacent to a
left side of the substrate 100. Alternatively, the XY-stage 20 may
transport the substrate 100 from left to right, and the XY-stage 20
may be shifted by the first interval in the first direction.
[0043] The substrate 100 is positioned on the XY-stage 20, and
comprises a transparent substrate 110, an oxide layer 120 and an
amorphous silicon (a-Si) thin film 130. In the method shown in
FIGS. 1 to 3, a size of the substrate 100 is about 470 mm.times.360
mm.
[0044] The transparent substrate 110 is positioned on the XY-stage
20. The transparent substrate 110 comprises glass or quartz to
transmit light. The oxide layer 120 is provided on the transparent
substrate 110, and improves interfacial characteristics between the
transparent substrate 110 and the a-Si thin film 130. The a-Si thin
film 130 is deposited on the oxide layer 120 through a chemical
vapor deposition (CVD) process. The a-Si thin film 130 comprises
amorphous silicon.
[0045] The laser beam 200 generated from the laser 10 is irradiated
onto the a-Si thin film 130 so that the a-Si thin film 130 is
rapidly melted. In FIGS. 1 to 3, the a-Si thin film 130 onto which
the laser beam 200 is irradiated is fully melted, while remaining
portions of the a-Si thin film 130 onto which the laser beam 200 is
not irradiated remain in a solid state. The melted a-Si thin film
130 is rapidly crystallized through a solid phase crystallization
to form a polysilicon (poly-Si) thin film 140.
[0046] FIGS. 4A to 4F are cross-sectional views showing a growth of
the poly-Si shown in FIG. 2. In particular, FIG. 4A is a
cross-sectional view showing a first liquefaction of a portion of
the a-Si thin film.
[0047] Referring to FIG. 4A, the laser unit 10 that generates the
laser beam 200 is prepared on the a-Si thin film 130 that is
provided on the substrate 100. The substrate 100 is positioned on
the XY-stage 20. The laser beam 200 may have a beam shape such as
an elliptical shape, a quadrangular shape, etc. A first width of
the beam shape of the laser beam 200 is shorter than a second width
of the beam shape of the laser beam 200. The second width of the
beam shape of the laser beam 200 may be substantially equal to a
side length of the substrate 100. In FIG. 4A, the first width of
the beam shape of the laser beam 200 is more than twice the width
of a unit poly-Si crystal formed by each of transportations of the
substrate 100.
[0048] The laser beam 200 generated from the laser unit 10 is
firstly irradiated onto a portion of the a-Si thin film 130
adjacent to the first end portion 102 of the substrate to firstly
liquefy the portion of the a-Si thin film 130, thereby forming the
liquefied silicon region 134. That is, a phase of the a-Si thin
film 130 is changed from an amorphous solid phase to a liquid
phase. The portion of the a-Si thin film 130 onto which the laser
beam 200 is firstly irradiated is fully liquefied. Remaining
portions of the a-Si thin film 130 remain in the amorphous solid
phase.
[0049] In FIG. 4A, an intensity of a unit shot of the laser beam
200 is enough to fully liquefy the a-Si thin film 130.
Alternatively, the intensity of the unit shot of the laser beam 200
may be smaller than that for liquefying the a-Si thin film 130, and
a plurality of shots of the laser beam 200 may be irradiated onto
the portion of the a-Si thin film 130 to fully liquefy the a-Si
thin film 130.
[0050] FIG. 4B is a cross-sectional view showing a crystal growth
adjacent to sides of the firstly liquefied silicon region.
[0051] Referring to FIG. 4B, the firstly liquefied silicon region
134 is firstly crystallized from the sides of the firstly liquefied
silicon region 134 through solid phase crystallization. The firstly
crystallized poly-Si 142 adjacent to the sides that are interfaces
between the remaining portion of the a-Si thin film 132 and the
firstly liquefied silicon region 134 functions as a core of the
crystal growth. That is, the remaining portion of the a-Si 132
functions as the core of the crystal growth so that the liquefied
silicon region 134 is firstly crystallized from sides of the
firstly liquefied silicon region 134 to a center of the firstly
liquefied silicon region 134 by a lateral growth width of about a
half of the first width of the beam shape of the laser beam 200. In
FIG. 4B, the lateral growth width is about 1 .mu.m to about 5
.mu.m. For example, the lateral growth width may be about 2 .mu.m
to about 4 .mu.m.
[0052] FIG. 4C is a cross-sectional view showing a protruding
portion in the center of the firstly crystallized poly-Si.
[0053] Referring to FIG. 4C, when the first crystallization of the
firstly liquefied silicon region 134 is completed, the protruding
portion 146 is formed on the center of the firstly crystallized
poly-Si 142. The lateral growths from the sides meet at the center
of the firstly crystallized poly-Si 142. An electrical mobility of
the protruding portion 146 is lower than remaining portion of the
firstly crystallized poly-Si 142. In order to make the electrical
mobility of the poly-Si thin film more uniform, the protruding
portion 146 is removed by following the processes.
[0054] FIG. 4D is a cross-sectional view showing a secondly
liquefying of another portion of the a-Si thin film adjacent to the
firstly liquefied silicon region.
[0055] Referring to FIG. 4D, the laser unit 10 is shifted by the
first interval from the first end portion 102 toward the second end
portion 104. The laser beam 200 generated from the laser unit 10 is
secondly irradiated onto a portion of the a-Si thin film 130, a
portion of the firstly crystallized poly-Si 142 and the firstly
protruding portion 146 adjacent to the first end portion 102 of the
substrate 100. The irradiation by the laser beam 200 secondly
liquefies the portion of the a-Si thin film 130, the portion of the
firstly crystallized poly-Si 142 and the firstly protruding portion
146 to form the secondly liquefied silicon region 134'. The portion
of the a-Si thin film 130 onto which the laser beam 200 is secondly
irradiated is fully liquefied. The melting of the firstly
protruding portion 146 causes the surface of the firstly
crystallized poly-Si 142 to planarize, thereby eliminating the
protruding portion 146. In FIG. 4D, the first interval is more than
the half of the width of the firstly crystallized poly-Si 132.
[0056] FIG. 4E is a cross-sectional view showing a crystal growth
adjacent to sides of the secondly liquefied silicon region
134'.
[0057] Referring to FIG. 4E, the secondly liquefied silicon region
134' is secondly crystallized from the sides of the secondly
liquefied silicon region 134' through solid phase crystallization.
The secondly crystallized poly-Si 142' adjacent to the sides that
are interfaces between the remaining portion of the firstly
crystallized poly-Si 142 and the secondly liquefied silicon region
134' and an interface between the remaining portion of the a-Si
thin film 132 and the secondly liquefied silicon region 134'
functions as a core of the crystal growth. That is, along a first
side, crystal growth is formed from the firstly crystallized
poly-Si 142 so that the secondly liquefied silicon region 134' is
secondly crystallized from the interface between the remaining
portion of the firstly crystallized poly-Si 142 and the secondly
liquefied silicon region 134'. Along a second side opposite the
first side, the a-Si thin film 132 functions as the core of the
crystal growth so that the secondly liquefied silicon region 134'
is secondly crystallized from the interface between the remaining
portion of the a-Si thin film 132 and the secondly liquefied
silicon region 134' by a lateral growth width of about a half of
the first width of the beam shape of the laser beam 200.
[0058] FIG. 4F is a cross-sectional view showing a protruding
portion on a center of the secondly liquefied silicon region.
[0059] Referring to FIG. 4F, when the second crystallization of the
secondly liquefied silicon region 134' is completed, the second
protruding portion 146' is formed on the secondly crystallized
poly-Si 142'.
[0060] The laser unit 10 is again shifted to irradiate the laser
beam 200 onto a portion of the a-Si thin film 130, a portion of the
secondly crystallized poly-Si (not shown) and the second protruding
portion 146' to thirdly liquefy the portion of the a-Si thin film
130 and the portion of the secondly crystallized poly-Si 142' to
form the liquefied silicon region 134, and eliminate the second
protruding portion 146'. The portion of the a-Si thin film 130 onto
which the laser beam 200 is thirdly irradiated is fully liquefied.
The above-described processes are repeated across the surface of
the substrate 100 to form the poly-Si thin film 140 having
increased electrical mobility.
[0061] FIGS. 5A to 5C are plan views showing the growth of the
poly-Si shown in FIG. 2. In particular, FIG. 5A is a plan view
showing the poly-Si thin film formed by the first irradiation of
the laser beam.
[0062] Referring to FIG. 5A, the laser beam 200 generated from the
laser unit 10 is irradiated onto the portion of the a-Si thin film
130. The portion of the a-Si thin film 130 is rapidly liquefied to
form the liquefied silicon region 134, and crystallized from the
sides of the liquefied silicon region 134 through the solid phase
crystallization.
[0063] In the solid phase crystallization, the a-Si thin film 130
at the sides of the liquefied silicon region 134 functions as the
core of the crystal growth. The firstly crystallized poly-Si 142
grows from the core to form a plurality of silicon grains 143.
Silicon grain boundaries 144 are defined by adjacent silicon grains
143.
[0064] When the silicon grains 143 grow through the solid phase
crystallization, the firstly protruding portion 146 is formed on
the center of the firstly crystallized poly-Si 142. In FIG. 5A, the
firstly protruding portion 146 extends in the second direction.
[0065] FIG. 5B is a plan view showing the poly-Si thin film formed
by the second irradiation of the laser beam.
[0066] Referring to FIGS. 4D and 5B, the laser unit 10 is shifted
by the first interval D1 in the first direction from the first end
portion 102 toward the second end portion 104. The laser beam 200
generated from the laser unit 10 is secondly irradiated onto the
portion of the a-Si thin film 130, the portion of the firstly
crystallized poly-Si 142 and the firstly protruding portion 146 to
secondly liquefy the portion of the a-Si thin film 130, the portion
of the firstly crystallized poly-Si 142 and the firstly protruding
portion 146 to form the secondly liquefied silicon region, and
eliminate the firstly protruding portion 146. The portion of the
a-Si thin film 130 onto which the laser beam 200 is secondly
irradiated is fully liquefied. In FIGS. 4D and 5B, the first
interval D1 is no more than the half of the first width of the beam
shape of the laser beam 200, which ensures that the laser beam 200
will fully liquefy the protruding portion formed by the previous
irradiation. For example, the first interval D1 of the laser beam
200 is about 1 .mu.m to about 4 .mu.m.
[0067] When the laser beam 200 is overly irradiated onto the a-Si
thin film 130, the a-Si thin film 130 separate from the oxide layer
120. In order to prevent the separation of the a-Si thin film 130,
an overlapped area between the firstly irradiated laser beam and
the secondly irradiated laser beam is no more than about 90% of an
area of the laser beam 200.
[0068] When the laser beam 200 generated from the laser unit 10 is
secondly irradiated onto the portion of the a-Si thin film 130, the
portion of the firstly crystallized poly-Si 142, the portion of the
a-Si thin film 130, the portion of the firstly crystallized poly-Si
142 and the firstly protruding portion 146 are secondly liquefied
to form the secondly liquefied silicon region 134'. In addition,
the firstly protruding portion 146 is eliminated by the melting of
the a-Si thin film 130. The portion of the a-Si thin film 130 is on
a right side of the laser beam 200, and the portion of the firstly
crystallized poly-Si 142 is on a left side of the laser beam
200.
[0069] The secondly liquefied silicon region 134' is secondly
crystallized from the interface between the remaining portion of
the firstly crystallized poly-Si 142 and the secondly liquefied
silicon region 134' so that the silicon grains 143 grow toward a
central portion of the laser beam 200. In addition, the secondly
liquefied silicon region 134' is secondly crystallized from the
interface between the remaining portion of the a-Si thin film 132
and the secondly liquefied silicon region 134'. When the second
crystallization of the secondly liquefied silicon region 134' is
completed, the second protruding portion 146' is formed on the
secondly crystallized poly-Si 142' along the center of the laser
beam 200.
[0070] FIG. 5C is a plan view showing the poly-Si thin film formed
by the third irradiation of the laser beam.
[0071] Referring to FIG. 5C, the laser unit 10 is shifted by a
second interval D2 in the first direction from the first end
portion 102 toward the second end portion 104. The laser beam 200
generated from the laser unit 10 is thirdly irradiated onto a
portion of the a-Si thin film 130 shown in FIG. 4D, a portion of
the secondly crystallized poly-Si 142' and the secondly protruding
portion 146' to thirdly liquefy the portion of the a-Si thin film
130 shown in FIG. 4D, the portion of the secondly crystallized
poly-Si 142' and the secondly protruding portion 146' to form the
thirdly liquefied silicon region (not shown), and eliminate the
secondly protruding portion 146'. The portion of the a-Si thin film
130 shown in FIG. 4D onto which the laser beam 200 is thirdly
irradiated is fully liquefied. The second interval D2 is no more
than the half of the first width of the beam shape of the laser
beam 200. In FIG. 5C, the second interval D2 is substantially equal
to the first interval D1.
[0072] When the laser beam 200 generated from the laser unit 10 is
thirdly irradiated onto the portion of the a-Si thin film 130 shown
in FIG. 4D, the portion of the secondly crystallized poly-Si 142',
the portion of the a-Si thin film 130 shown in FIG. 4D, the portion
of the secondly crystallized poly-Si 142' and the secondly
protruding portion 146' are thirdly liquefied to form the thirdly
liquefied silicon region (not shown). In addition, the secondly
protruding portion 146' is eliminated. The portion of the a-Si thin
film 130 shown in FIG. 4D is on a right side of the laser beam 200,
and the portion of the secondly crystallized poly-Si 142' is on a
left side of the laser beam 200. The thirdly liquefied silicon
region (not shown) is thirdly crystallized from the interface
between the remaining portion of the secondly crystallized poly-Si
142' and the thirdly liquefied silicon region (not shown) so that
the silicon grains 143 grow toward a central portion of the laser
beam 200. In addition, the thirdly liquefied silicon region (not
shown) is thirdly crystallized from the interface between the
remaining portion of the a-Si thin film 132 shown in FIG. 4D and
the thirdly liquefied silicon region (not shown). When the third
crystallization of the thirdly liquefied silicon region (not shown)
is completed, the third protruding portion 146'' is formed on the
thirdly crystallized poly-Si 142'' along the center of the laser
beam 200.
[0073] The generation and elimination of the protruding portions
146, 146' and 146'' are repeated so that the silicon grains 143
grow in the first direction across the surface of the substrate
100. Therefore, the poly-Si thin film 140 having increased
electrical mobility is formed.
[0074] FIG. 6 is a plan view showing a poly-Si thin film shown in
FIG. 2.
[0075] Referring to FIG. 6, the poly-Si thin film 140 includes the
silicon grains 143 and the silicon grain boundaries 144.
[0076] The silicon grains 143 extend in the first direction from a
left side to a right side of the substrate. The silicon grain
boundaries 144 also extend in a direction that is substantially in
parallel with the silicon grains 143. Electrons may not flow
through the silicon grain boundaries 144 so that an electrical
mobility of the poly-Si thin film 140 in the first direction is
greater than an electrical mobility of the poly-Si thin film 140 in
the second direction. That is, the electrons or holes may be
trapped at the silicon grain boundaries 144.
[0077] FIG. 7 is a graph showing a relationship between an energy
intensity of a laser beam and a location. The location is a
horizontal length of a predetermined point on a surface on which
the laser beam is irradiated. FIG. 8 is a graph showing a portion
`B` of FIG. 7.
[0078] Referring to FIGS. 7 and 8, an energy profile of the laser
beam 200 generated from the laser unit 10 includes a flat portion
220 and two inclined portions 210. The flat portion 220 has a
substantially constant energy distribution. Each of the inclined
portions 210 has an inclined energy distribution. The flat portion
220 is between the inclined portions 210.
[0079] The second width of the beam shape of the laser beam 200 is
substantially equal to the side length of the substrate 100. For
example, when the size of the substrate 100 is about 470
mm.times.360 mm, the second width of the beam shape of the laser
beam 200 may be about 470 mm or about 360 mm.
[0080] When the first width L of the beam shape of the laser beam
200 is shorter than about 3 .mu.m, the laser beam 200 may be
incontrollable. In addition, when the first width L of the beam
shape of the laser beam 200 is too wide, the width of the liquefied
silicon region 134 is too wide to form micro-crystals in the
silicon grains. The first width L of the beam shape of the laser
beam 200 is about 3 .mu.m to about 10 .mu.m.
[0081] The energy intensity of the flat portion is about 400
mJ/cm.sup.2 to about 1,000 mJ/cm.sup.2. When the energy intensity
of the flat portion is less than about 400 mJ/cm.sup.2, the laser
beam 200 may be unable to liquefy the a-Si thin film 130. When the
energy intensity of the flat portion is more than about 1,000
mJ/cm.sup.2, the laser beam 200 melts too large portion of the a-Si
thin film 130 so that the a-Si thin film 130 may be separated from
the oxide layer 120.
[0082] An inclination S of the inclined portion is no more than
about 10 .mu.m. The inclination S of the inclined portion is no
more than about 3 .mu.m. The inclination S is a horizontal width
between about 10% of the energy intensity of the flat portion 220
and about 90% of the energy intensity of the flat portion 220. The
inclination S of the inclined portion 210 is a ratio of the energy
intensity of the laser beam 200 to a width of the inclined portion
210. The inclination S is determined between about 10% of the
energy intensity of the flat portion 220 and about 90% of the
energy intensity of the flat portion 220. A maximum energy
intensity H corresponds to the energy intensity of the flat portion
220. When the inclination S of the inclined portion 210 is more
than about 10 .mu.m, a uniformity of the energy intensity of the
laser beam 200 is decreased so that a crystal growth of the silicon
grains may be deteriorated.
[0083] A variation F of the energy intensity of the flat portion
210 is no more than about 5% of a maximum energy intensity 222 of
the flat portion 210. That is, a difference between the maximum
energy intensity 222 of the flat portion 210 and a minimum energy
intensity 224 of the flat portion 210 is no more than about 5%.
When the variation F of the energy intensity is more than about 5%,
the uniformity of the energy intensity of the laser beam 200 is
deteriorated, and micro-crystals may remain in the liquefied
silicon region.
[0084] The laser beam 200 is repetitively irradiated onto the a-Si
thin film 130, and is shifted by the interval to form the poly-Si
thin film 140 having silicon grains 143 of increased sizes.
[0085] FIGS. 9A to 9C are plan views showing a growth of a poly-Si
formed by a method of manufacturing a thin film in accordance with
another embodiment of the present invention. The method of
manufacturing the thin film of FIGS. 9A to 9C is substantially the
same as in FIGS. 1 to 8, except for the poly-Si thin film. Thus,
the same reference numerals will be used to refer to the same or
like parts as those described in FIGS. 1 to 8 and any further
explanation concerning the above elements will be omitted.
[0086] FIG. 9A is a plan view showing the poly-Si thin film formed
by a first irradiation of a laser beam.
[0087] Referring to FIG. 9A, the laser beam 200 generated from a
laser unit 10 is irradiated onto a portion of an a-Si thin film
(not shown). The a-Si thin film (not shown) is provided on a
substrate. The portion of the a-Si thin film (not shown) is rapidly
liquefied to form a liquefied silicon region (not shown), and
crystallized from sides of the liquefied silicon region (not shown)
through solid phase crystallization. The portion of the a-Si thin
film (not shown) onto which the laser beam 200 is firstly
irradiated is fully liquefied.
[0088] In the solid phase crystallization, the a-Si thin film (not
shown) at the sides of the liquefied silicon region (not shown)
functions as a core of the crystal growth. The firstly crystallized
poly-Si 152 grows from the core to form a plurality of silicon
grains 153. The silicon grain boundaries 154 are defined by
adjacent silicon grains 153.
[0089] When the silicon grains 153 grow through the solid phase
crystallization, a firstly protruding portion 156 is formed on a
center of the firstly crystallized poly-Si 152. In FIG. 9A, the
firstly protruding portion 156 extends in the second direction.
[0090] FIG. 9B is a plan view showing the poly-Si thin film formed
by a second irradiation of the laser beam.
[0091] Referring to FIG. 9B, the laser unit 10 is shifted by a
third interval B1 from a second end portion of the substrate toward
a first end portion of the substrate. When the laser unit 10 is
shifted in the opposite direction to the direction of FIG. 2, sizes
of the poly-Si crystals may be uniformized, and mobility of
electrons in various directions may also be uniformized. The laser
beam 200 generated from the laser unit 10 is secondly irradiated
onto a portion of the a-Si thin film (not shown) and a portion of
the firstly crystallized poly-Si 152 to secondly liquefy the
portion of the a-Si thin film (not shown) and the portion of the
firstly crystallized poly-Si 152 to form a secondly liquefied
silicon region (not shown). In this embodiment, the firstly
protruding portion 156 remains. The portion of the a-Si thin film
(not shown) onto which the laser beam 200 is secondly irradiated is
fully liquefied. In FIG. 9B, the third interval B1 is more than a
half of a first width of a beam shape of the laser beam 200.
[0092] When the laser beam 200 generated from the laser unit 10 is
secondly irradiated onto the portion of the a-Si thin film (not
shown) and the portion of the firstly crystallized poly-Si 152, the
portion of the a-Si thin film (not shown) and the portion of the
firstly crystallized poly-Si 152 are secondly liquefied to form the
secondly liquefied silicon region (not shown). The firstly
protruding portion 156 is not eliminated. The portion of the a-Si
thin film (not shown) is on one side of the laser beam 200, and the
portion of the firstly crystallized poly-Si 152 is on an opposite
side of the laser beam 200. The one side and the opposite side of
the laser beam 200 corresponds to a left side and a right side of
the laser beam, as viewed in the perspective shown in FIG. 1.
[0093] The secondly liquefied silicon region (not shown) is
secondly crystallized from an interface between a remaining portion
of the firstly crystallized poly-Si 152 and the secondly liquefied
silicon region (not shown) so that the silicon grains 153 grow
toward a central portion of the laser beam 200. In addition, the
secondly liquefied silicon region (not shown) is secondly
crystallized from the interface between the remaining portion of
the a-Si thin film (not shown) and the secondly liquefied silicon
region (not shown). When the second crystallization of the secondly
liquefied silicon region (not shown) is completed, the second
protruding portion 156' is formed on the secondly crystallized
poly-Si 152' along a center of the laser beam 200. In FIG. 9B, the
second protruding portion 156' is substantially in parallel with
the first protruding portion 156.
[0094] FIG. 9C is a plan view showing the poly-Si thin film formed
by a third irradiation of the laser beam.
[0095] Referring to FIG. 9C, the laser unit 10 is shifted by a
fourth interval B2 from the second end portion toward the first end
portion. The laser beam 200 generated from the laser unit 10 is
thirdly irradiated onto a portion of the a-Si thin film (not shown)
and a portion of the secondly crystallized poly-Si 152' to thirdly
liquefy the portion of the a-Si thin film (not shown) and the
portion of the secondly crystallized poly-Si 152'. This forms a
thirdly liquefied silicon region (not shown), while the secondly
protruding portion 156' remains. The fourth interval B2 is more
than the half of the first width of the beam shape of the laser
beam 200. In FIG. 9C, the fourth interval B2 is substantially equal
to the third interval B1.
[0096] When the laser beam 200 generated from the laser unit 10 is
thirdly irradiated onto the portion of the a-Si thin film (not
shown) and the portion of the secondly crystallized poly-Si 152',
the portion of the a-Si thin film (not shown) and the portion of
the secondly crystallized poly-Si 152' are thirdly liquefied to
form a thirdly liquefied silicon region (not shown). In addition,
the secondly protruding portion 156' is not eliminated. The portion
of the a-Si thin film (not shown) is on a left side of the laser
beam 200, and the portion of the secondly crystallized poly-Si 152'
is on a right side of the laser beam 200, as viewed in the
perspective shown in FIG. 1. The thirdly liquefied silicon region
(not shown) is thirdly crystallized from the interface between the
remaining portion of the secondly crystallized poly-Si 152' and the
thirdly liquefied silicon region (not shown) so that the silicon
grains 153 grow toward a central portion of the laser beam 200. In
addition, the thirdly liquefied silicon region (not shown) is
thirdly crystallized from the interface between the remaining
portion of the a-Si thin film (not shown) and the thirdly liquefied
silicon region (not shown). When the third crystallization of the
thirdly liquefied silicon region (not shown) is completed, the
third protruding portion 156'' is formed on the thirdly
crystallized poly-Si 152'' along the center of the laser beam 200.
In FIG. 9C, the first, second and third protruding portions 156,
156' and 156'' are substantially in parallel with one another.
[0097] The laser unit 10 is shifted by the interval that is greater
than the half of the first width of the beam shape of the laser
beam 200 so that the protruding portions 156, 156' and 156'' are
not liquefied in subsequent irradiation steps. Accordingly, the
protruding portions 156, 156' and 156'' are not eliminated.
Therefore, a manufacturing time of the poly-Si thin film 150 is
decreased.
[0098] FIG. 10 is a plan view showing a poly-Si thin film formed by
the method shown in FIGS. 9A to 9C.
[0099] Referring to FIG. 10, the poly-Si thin film 150 includes the
silicon grains 153, the silicon grain boundaries 154 and the
protruding portions 156, 156' and 156'' shown in FIGS. 9A to
9C.
[0100] The protruding portions 156, 156' and 156'' shown in FIGS.
9A to 9C are substantially in parallel with one another. The
silicon grains 153 extend between the protruding portions 156, 156'
and 156'' shown in FIGS. 9A to 9C. Generally, the silicon grain
boundaries 154 are inclined with respect to the protruding portions
156, 156' and 156''. In addition, the silicon grains 153 are also
formed adjacent to sides of the poly-Si thin film 150.
[0101] The poly-Si thin film 150 including the protruding portions
156, 156' and 156'' provider lower electrical mobility than a
poly-Si thin film without protruding portions. The poly-Si thin
film 150 having low electrical mobility can be used for a P-channel
metal oxide semiconductor (PMOS) element.
[0102] FIG. 11 is a plan view showing a method of manufacturing a
poly-Si thin film in accordance with another embodiment of the
present invention. The method of manufacturing the thin film of
FIG. 11 is substantially the same as in FIGS. 1 to 8 except for the
poly-Si thin film. Thus, the same reference numerals will be used
to refer to the same or like parts as those described in FIGS. 1 to
8 and any further explanation concerning the above elements will be
omitted.
[0103] Referring to FIG. 11, a laser unit that generates a laser
beam 200 is prepared on an a-Si thin film 130 that is formed on a
substrate 100. The substrate 100 is positioned on an XY-stage 20.
The XY-stage 20 transports and rotates the substrate 100. The laser
beam 200 has a beam shape such as an elliptical shape, a
quadrangular shape, etc. A first width of the beam shape of the
laser beam 200 is shorter than a second width of the beam shape of
the laser beam 200. The second width of the beam shape of the laser
beam 200 is controlled by an optical controller (not shown) of the
laser unit 10 shown in FIG. 1.
[0104] The substrate 100 includes a first end portion 102 that is
adjacent to a left side of the substrate 100, a second end portion
104 that is adjacent to a right side of the substrate 100, a third
end portion 106 that is adjacent to an upper side of the substrate
100, and a fourth end portion 108 that is adjacent to a lower side
of the substrate 100, as viewed from the perspective shown in FIG.
11. The laser beam 200 includes a first laser beam 200a and a
second laser beam 200b. The second width of the beam shape of the
first laser beam 200a is substantially equal to a side length of
each of the first and second end portions 102 and 104. The second
width of the beam shape of the second laser beam 200b is
substantially equal to a side length of each of the third and
fourth end portions 106 and 108.
[0105] The first laser beam 200a generated from the laser unit is
irradiated onto a portion of the a-Si thin film adjacent to the
first end portion 102 of the substrate to liquefy the portion of
the a-Si thin film to form the liquefied silicon region. The
portion of the a-Si thin film onto which the first laser beam 200a
is irradiated is fully liquefied. That is, a phase of the a-Si thin
film is changed from an amorphous solid phase to a liquid
phase.
[0106] The liquefied silicon region is crystallized from sides of
the liquefied silicon region through a solid phase crystallization.
That is, the remaining portion of the a-Si functions as the core of
the crystal growth so that the liquefied silicon region is
crystallized from interfaces between the remaining portion of the
a-Si and the liquefied silicon region to a center of the liquefied
silicon region by a lateral growth. When the first crystallization
of the liquefied silicon region is completed, a protruding portion
is formed in the center of the crystallized poly-Si.
[0107] The laser unit is repetitively shifted by an interval from
the first end portion 102 toward the second end portion 104, and
the first laser beam 200a generated from the laser unit is
repetitively irradiated onto a portion of the a-Si thin film, a
portion of the crystallized poly-Si and the protruding portion to
fully liquefy the portion of the a-Si thin film, the portion of the
crystallized poly-Si and the protruding portion to form the
liquefied silicon region, and eliminate the protruding portion. In
FIG. 11, the interval of the first laser beam 200a is less than a
half of a first width of the beam shape of the first laser beam
200a. The crystallized poly-Si forms first silicon grains, and the
first silicon grains grow to form a first poly-Si thin film. The
first poly-Si thin film includes the first silicon grains and the
first silicon grain boundaries. The first silicon grains and the
first silicon grain boundaries extend in a first direction.
[0108] When the first poly-Si thin film is completed, the XY-stage
20 is rotated by about ninety degrees so that the substrate 100 is
rotated by about ninety degrees. The second width of the beam shape
of the laser beam 200 is changed from the length of each of the
first and second end portions 102 and 104 to the length of each of
the third and fourth end portions 106 and 108. That is, the first
laser beam 200a is changed into the second laser beam 200b.
[0109] The second laser beam 200b generated from the laser unit is
irradiated onto a portion of the first poly-Si thin film adjacent
to the third end portion 106 of the substrate 100 to fully liquefy
the portion of the first poly-Si thin film to form the liquefied
silicon region. Alternatively, the first poly-Si thin film may be
partially melted to form a partially liquefied silicon region. The
liquefied silicon region is then crystallized through the solid
phase crystallization, and a protruding portion that extending in
the first direction is formed. The laser unit is repetitively
shifted by an interval from the third end portion 106 toward the
fourth end portion 108, and the second laser beam 200b generated
from the laser unit is repetitively irradiated onto a portion of
the first poly-Si thin film, a portion of the crystallized poly-Si
and a protruding portion to fully liquefy the portion of the a-Si
thin film, the portion of the crystallized poly-Si and the
protruding portion to form the liquefied silicon region, and
eliminate the protruding portion. In FIG. 11, the interval of the
second laser beam 200b is more than a half of a first width of the
beam shape of the second laser beam 200b. The interval of the
second laser beam 200b may be substantially equal to the interval
of the first laser beam 200a.
[0110] The crystallized poly-Si forms second silicon grains, and
the second silicon grains grow to form a second poly-Si thin film.
The second poly-Si thin film includes the second silicon grains and
second silicon grain boundaries. In FIG. 11, the second silicon
grains are formed by a growth of the first silicon grains in the
first direction so that the second silicon grains have a larger
size than the first silicon grains.
[0111] FIGS. 12A to 12C are plan views showing the method shown in
FIG. 11.
[0112] Referring to FIG. 12A, the first laser beam 200a is
repetitively irradiated onto the a-Si thin film, and shifted by an
interval from the first end portion 102 toward the second end
portion 104 so that the first poly-Si thin film 140 without
protruding portions is formed. The first poly-Si thin film 140
includes the first silicon grains 143 and the first silicon grain
boundaries 144 that extend in the first direction.
[0113] Referring to FIG. 12B, in order to grow the first silicon
grains 143 in the second direction, the second laser beam 200b
generated from the laser unit is irradiated onto a portion of the
first poly-Si thin film 140 adjacent to the third end portion 106
of the substrate 100 to fully liquefy the portion of the first
poly-Si thin film 140, thus forming the liquefied silicon region.
Alternatively, the portion of the first poly-Si thin film 140 onto
which the second laser beam 200b is irradiated may be partially
liquefied to form a partially liquefied silicon region. The first
silicon grain boundaries 144 are eliminated by the liquefaction.
Therefore, the first silicon grains 143 grow in the second
direction to form the second silicon grains 162.
[0114] Referring to FIG. 12C, the laser unit is repetitively
shifted by an interval `I` from the third end portion 106 toward
the fourth end portion 108, and the second laser beam 200b
generated from the laser unit is repetitively irradiated onto the
portion of the first poly-Si thin film 140 so that the first
silicon grains 143 repetitively grow in a second direction with
respect to the substrate. Therefore, the second silicon grains 162
have greater size than the first silicon grains 143. Alternatively,
the second silicon grains 162 may be pseudo mono-crystalline
grains.
[0115] FIG. 13 is a plan view showing the poly-Si thin film formed
by the method shown in FIG. 11.
[0116] Referring to FIG. 13, the second poly-Si thin film 160
includes the second silicon grains 162 and second silicon grain
boundaries 164. Each of the second silicon grains 162 extends in
the first and second directions. The second silicon grain
boundaries 164 are positioned between adjacent second silicon
grains 162. In FIG. 13, the second silicon grain boundaries 164
have a roughly circular shape. As the size of the second silicon
grains 162 is increased, the electrical mobility of the second
poly-Si thin film 160 is also increased.
[0117] In addition, as the size of the second silicon grains 162 is
increased, a density of the silicon grain boundaries 164 is
decreased to decrease a leakage current that may be formed through
the silicon grain boundaries 164 when a TFT is turned off.
[0118] The substrate 100 is rotated by the ninety degrees, and the
first and second laser beams 200 are irradiated onto the a-Si thin
film 130 in the first and second directions to maximize the size of
the second poly-Si grains 162, thereby increasing the electrical
mobility.
[0119] FIGS. 14A to 14D are cross-sectional views showing a method
of manufacturing a poly-Si thin film in accordance with one
embodiment. In particular, FIG. 14A is a cross-sectional view
showing a poly-Si pattern on a transparent substrate.
[0120] Referring to FIG. 14a, an oxide layer 320 is formed on a
transparent substrate 310. An a-Si thin film is formed on the oxide
layer 320.
[0121] The a-Si thin film is converted into a poly-Si thin film
using a laser beam. In particular, a laser unit that generates the
laser beam is prepared on the transparent substrate 310 having the
a-Si thin film. The laser beam has a beam shape such as an
elliptical shape, a quadrangular shape, etc. A second width of the
beam shape of the laser beam is greater than a first width of the
beam shape of the laser beam. The laser beam is irradiated onto a
portion of the a-Si thin film adjacent to a first end portion of
the transparent substrate 310 to fully liquefy a portion of the
a-Si thin film. Alternatively, the portion of the a-Si thin film
adjacent to a first end portion of the transparent substrate 310
may be partially liquefied. Silicon grains grow in the liquefied
silicon region through a solid phase crystallization. The laser
beam is repetitively irradiated onto the a-Si thin film, and
shifted from the first end portion to a second end portion of the
transparent substrate 310 to form a poly-Si thin film.
[0122] The poly-Si thin film is partially etched through an etching
process such as a plasma etching, a wet etching, etc., to form a
poly-Si pattern 330.
[0123] Referring to FIG. 14B, a first insulating layer 340 is
formed on the poly-Si pattern 330 to protect the poly-Si pattern
330. In FIG. 14B, the first insulating layer 340 is formed through
a plasma enhanced chemical vapor deposition (PECVD) process.
[0124] A gate electrode G is formed on the first insulating layer
340. In FIG. 14B, the gate electrode G is positioned at the center
of the poly-Si pattern 330. In particular, a metal is deposited on
the first insulating layer 340, and partially etched to form the
gate electrode G.
[0125] Referring to FIG. 14C, a second insulating layer 350 is
formed on the gate electrode G and the first insulating layer 340.
The second insulating layer 350 may be formed through a PECVD
process. A thickness of the second insulating layer 350 is more
than a predetermined thickness to improve credibility and
reliability of the TFT 300 and to prevent a cross-talk. In FIG.
14C, the thickness of the second insulating layer 350 is more than
about 6,000 .ANG..
[0126] The first and second insulating layers 340 and 350 are
partially etched to form a first contact hole 352 and a second
contact hole 354. The first contact hole 352 is adjacent to a right
side of the gate electrode G, and the second contact hole 354 is
adjacent to a left side of the gate electrode G. The second contact
hole 354 is spaced apart from the first contact hole 352.
[0127] Referring to FIG. 14D, a source electrode S and a drain
electrode D are formed on the second insulating layer 350. The
source electrode S is electrically connected to the poly-Si pattern
340 through the first contact hole 352, and the drain electrode D
is electrically connected to the poly-Si pattern 340 through the
second contact hole 354.
[0128] A protecting layer 360 is formed on the second insulating
layer 350 having the source electrode S and the drain electrode D.
The protecting layer 360 is partially etched to form a pixel
contact hole 362. A pixel electrode 370 is formed on the protecting
layer 360. The pixel electrode 370 is transparent. The pixel
electrode 370 is electrically connected to the drain electrode D
through the pixel contact hole 362.
[0129] The poly-Si pattern 340 having high electrically mobility is
formed by the laser beam to improve electrical characteristics of
the TFT 300.
[0130] The TFT 300 is a top gate type TFT. Alternatively, the TFT
may be a bottom gate type TFT that has a poly-Si pattern interposed
between a gate electrode and source/drain electrodes.
[0131] In accordance with the present invention, the laser beam is
repetitively irradiated onto the substrate, and shifted from the
first end portion toward the second end portion to form a poly-Si
thin film having increased grain size and improved electrical
characteristics.
[0132] In addition, the interval of the shift of the laser unit is
controlled to control a manufacturing time of the poly-Si thin
film.
[0133] The laser unit may be rotated by about ninety degrees so
that the laser beam is firstly and secondly irradiated onto the
a-Si thin film. The size of the silicon grains is maximized to
increase the electrical mobility.
[0134] The poly-Si pattern has high electrical mobility so that the
TFT has improved electrical characteristics.
[0135] Although the exemplary embodiments of the present invention
have been described, it is understood that the present invention
should not be limited to these exemplary embodiments but various
changes and modifications can be made by one of ordinary skill in
the art within the spirit and scope of the present invention as
hereinafter claimed.
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