KR101886862B1 - Crystallization method and method of fabricating thin film transistor using thereof - Google Patents

Abstract

The crystallization method of the present invention and the method of manufacturing a thin film transistor using the same can be applied to the crystallization using a green laser by using two scans having different energy of the laser beam or using a laser beam having a step profile Forming an amorphous silicon thin film on a substrate; And scanning the amorphous silicon thin film with a green laser beam having a step profile to proceed crystallization.

Description

TECHNICAL FIELD [0001] The present invention relates to a crystallization method and a thin film transistor manufacturing method using the same,

The present invention relates to a crystallization method and a method of manufacturing a thin film transistor using the same, and more particularly, to a crystallization method using a green laser and a method of manufacturing a thin film transistor using the method.

Recently, interest in information display has increased, and a demand for using portable information media has increased, and a light-weight flat panel display (FPD) that replaces a cathode ray tube (CRT) And research and commercialization are being carried out. In recent years, a liquid crystal display device or an organic electroluminescent device has been developed as a flat panel display device having particularly excellent performance such as thinning, weight reduction, and low power consumption, thereby replacing existing CRTs.

The active matrix (AM) method, which is a driving method mainly used in the liquid crystal display device, is excellent in resolution and video realization capability and uses a thin film transistor (TFT) as a switching element, It controls the voltage on and off.

In addition, since the organic electroluminescent device has high luminance and low operating voltage characteristics and is a self-luminous device that emits light by itself, it has a high contrast ratio, can realize an ultra-thin display, So that it is easy to manufacture and design a driving circuit, and has recently attracted attention as a flat panel display device.

In such a liquid crystal display device and an organic electroluminescent device, a thin film transistor, which is a switching element, is essentially used for on / off control of each pixel region in common.

In general, the thin film transistor uses amorphous silicon as an active layer. However, since the amorphous silicon is disordered in its atomic arrangement, it changes into a metastable state upon irradiation with light or an electric field, This is becoming a problem. In addition, since the carrier mobility of the amorphous silicon thin film transistor is as low as 0.1 cm ² / Vs to 1.0 cm ² / Vs in the channel, it is difficult to use it as a driving circuit device.

In order to solve this problem, a polycrystalline silicon thin film transistor having a mobility higher than that of the amorphous silicon thin film transistor has been developed and a crystallization method using an excimer laser (EL) has been proposed as the crystallization of the amorphous silicon .

In the crystallization using the excimer laser, a laser beam having a wavelength of 308 nm is generated by a gas medium and used for crystallization. However, a laser beam having an optimum power for melting amorphous silicon using a gas as a source medium for generating a laser beam is generated. The substantially generated laser beam has a large error range of its energy density, The energy density of the laser beam irradiated to the amorphous silicon is different from that of the laser beam irradiated to the amorphous silicon. In addition, there is a disadvantage in that the maintenance cost is large, for example, an expensive gas medium must be replaced frequently.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a crystallization method using a green laser and a method of manufacturing a thin film transistor using the green laser.

It is another object of the present invention to provide a crystallization method with improved crystallization uniformity in a crystallization using a green laser and a method of manufacturing a thin film transistor using the crystallization method.

Other objects and features of the present invention will be described in the following description of the invention and claims.

According to an aspect of the present invention, there is provided a crystallization method comprising: forming an amorphous silicon thin film on a substrate; Scanning a green laser beam having a first energy density to the amorphous silicon thin film to progress a solid-phase crystallization so as to form a uniform grain; And scanning a green laser beam having a second energy density higher than the first energy density to the amorphous silicon thin film to recrystallize the grain as a seed.

In this case, the first energy density is characterized in that it is set to ^{300mJ / cm 2 ~ 450mJ / cm} 2.

The second energy density is characterized in that the set ^{500mJ / cm 2 ~ 800mJ / cm} 2.

Another crystallization method of the present invention includes: forming an amorphous silicon thin film on a substrate; And scanning the amorphous silicon thin film with a green laser beam having a step profile to advance the crystallization.

At this time, the laser beam has a different energy density from the two laser beams having a phase difference with respect to the beam width direction, thereby forming a step profile.

In this case, the green laser beam having the step profile is formed by adjusting the energy density of the two laser beams after giving a phase difference to the two laser sources through the optical system in the beam width direction.

 The energy density of the front laser beam located at the front side relative to the scanning direction is set low and the energy density of the rear laser beam at the rear side is set high.

At this time, the energy density of the laser beam over a portion matchumyeo crystallization starts, for example, characterized in that it is set to ^{300mJ / cm 2 ~ 350mJ / cm} 2.

At this time, the energy density of the laser beam back, uses the energy density region in which re-crystallization by a shot pulses overlap, for example, it characterized in that it is set to ^{500mJ / cm 2 ~ 800mJ / cm} 2.

A buffer layer is formed on the substrate, and an amorphous silicon thin film is formed thereon.

And then performing a dehydrogenation process on the amorphous silicon thin film after forming the amorphous silicon thin film.

A method of manufacturing a thin film transistor of the present invention includes: forming an amorphous silicon thin film on a substrate; Scanning a green laser beam having a step profile on the amorphous silicon thin film to proceed crystallization; And patterning the crystallized silicon thin film to form an active layer.

In this case, the laser beam has a different energy density from the two laser beams having a phase difference with respect to the beam width direction, thereby forming a step profile.

In this case, the green laser beam having the step profile is formed by adjusting the energy density of the two laser beams after giving a phase difference to the two laser sources through the optical system in the beam width direction.

The energy density of the front laser beam positioned at the front side relative to the scanning direction is set low and the energy density of the rear laser beam at the rear side is set high.

As described above, the crystallization method and the method of manufacturing a thin film transistor using the same according to the present invention can reduce the maintenance cost compared to the conventional excimer laser crystallization by crystallizing using the green laser, thereby ensuring high productivity and cost competitiveness Effect.

The crystallization method and the method of manufacturing a thin film transistor using the same according to the present invention are characterized in that crystallization using the green laser is performed by using two scans whose energy is different from each other or by using a laser beam having a step profile The crystallization uniformity can be improved. As a result, it provides an effect applicable to a large area display. Also, mura is suppressed due to improvement of grain size and crystallization uniformity, thereby improving the performance of the organic electroluminescent device.

1 and 2 are views showing a green laser crystallization apparatus according to the present invention as an example.
Fig. 3 is a graph showing the absorbance according to wavelength in amorphous silicon and polycrystalline silicon. Fig.
4A to 4D are sectional views sequentially showing the crystallization method according to the first embodiment of the present invention.
5A to 5C are sectional views sequentially showing the crystallization method according to the second embodiment of the present invention.
Figures 6A and 6B schematically illustrate the profiles of a first laser beam and a second laser beam.
FIGS. 7A, 7B and 8 schematically illustrate the profile of a laser beam used in the crystallization method according to the second embodiment of the present invention; FIGS.
9A to 9F are sectional views sequentially showing a method of manufacturing a thin film transistor according to the present invention.
10 and 11 are graphs showing electrical characteristics of the thin film transistor along various positions of the panel.

Hereinafter, preferred embodiments of a crystallization method and a method of manufacturing a thin film transistor using the same according to the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 are views showing a green laser crystallization apparatus according to an embodiment of the present invention.

1, the structure of the optical system is shown as an example in the green laser crystallization apparatus according to the present invention, but the present invention is not limited to the structure of the optical system.

Referring to the drawings, the green laser crystallization apparatus according to the present invention may include an optical system including a laser generator 150 and a beam splitter 185, The laser beam 155 is irradiated to the predetermined substrate 110 through the optical system in a scan manner.

The laser generator 150 includes a diode 152 for supplying light energy in the form of infrared rays and a YAG (Yttrium Aluminum) 150 for generating a substantial laser beam 155 by collecting light energy from the diode 152. [ A Garnet rod 151 and a Second-Harmonic Generation (SHG) optical system 153.

At this time, the diode 152 supplies the light energy to the YAG rod 151 in an infrared form, and the YAG rod 151 transmits the YAG rod 151 through the light energy incident therein. And the atoms are brought into a high energy state, and return to the original state, thereby generating a laser beam 155. The second harmonic generation optical system 153 doubles the wavelength of the laser beam 155 emitted from the YAG rod 151 and is incident on the YAG rod 151 from the diode 152, The laser beam 155 coming out through the second harmonic generation optical system 153 still has a wavelength of 1064 nm but another part of the laser beam 155 having a wavelength of 1064 nm still passes through the second harmonic generation optical system 153 by its action, A laser beam 155 having a wavelength of < / RTI >

The laser beam 155 passing through the second harmonic generation optical system 153 and having two wavelength bands is passed through a wavelength separation mirror 154 to a laser beam 155 having a wavelength of 532 nm and an infrared ray (IR) having a wavelength of 1064 nm .

The laser beam 155 having a wavelength of 532 nm has a plurality of reflection mirrors 171a, 171b and 171c, an attenuator and a shutter 181, a telescope lens 172, Is irradiated onto the substrate 110 via a homogenizer 182, a wavelength separation mirror 155, and a focusing lens 175.

The laser beam 155 separated by the wavelength separation mirror 185 is incident on a CCD 175, an imaging lens 173, an attenuator 177, And a beam profile / feedback control system 183 comprised of a beam profile controller 174.

However, the present invention is not limited to the configuration of the optical system.

In the case of the green laser crystallization apparatus having the above-described configuration, the diode 152 used as an energy source and the YAG rod 151, which is a solid medium for generating the laser beam 155, usually have a lifetime of about 15 to 18 hours It is about one year, assuming that it is used, which is three times longer than an excimer laser device that uses gas or liquid as the medium of laser beam generation.

In the laser crystallization apparatus using the solid as the source, the error of the energy density per unit area of the generated laser beam 155 is much smaller than the laser beam generated through the excimer laser device using the gas as the medium source, Which is caused by a difference in energy density between the positions of the laser beams 155, is hardly generated.

However, the crystallization method using the green laser has a disadvantage in that there is a difference in light absorption between amorphous silicon and polycrystalline silicon due to the laser wavelength.

Fig. 3 is a graph showing the degree of absorption according to wavelengths in amorphous silicon and polycrystalline silicon.

Referring to FIG. 3, it can be seen that the light absorption of the amorphous silicon and the polycrystalline silicon varies depending on the wavelength. In the case of the green laser having a wavelength of about 532 nm, there is a large difference in the light absorption between the amorphous silicon and the polycrystalline silicon .

As described above, the amorphous silicon and the polycrystalline silicon have different optical absorptions, and the green laser wavelength at which light absorption occurs at the entire depth of the silicon, resulting in non-uniform crystallization, and large and small grains are randomly distributed.

That is, due to the characteristic of the green laser wavelength, as the crystal grows with the fine grain of the shoulder region of the first shot as the seed when the laser beam overlaps, a uniform crystal growth This becomes difficult.

Accordingly, the first embodiment of the present invention proposes a crystallization method using two scans with different energy of the laser beam to improve such uneven crystallization.

4A to 4D are cross-sectional views sequentially illustrating the crystallization method according to the first embodiment of the present invention.

At this time, the first embodiment of the present invention describes amorphous silicon as a thin film to be crystallized, but the present invention is not limited thereto.

As shown in FIG. 4A, a buffer layer 111 having a predetermined thickness is formed on the entire surface of the substrate 110 made of a transparent insulating material such as glass.

The buffer layer 111 serves to prevent impurities such as sodium (Na) present in the substrate 110 from penetrating into the upper layer during the crystallization process.

Then, a predetermined amorphous silicon thin film 120 is formed by depositing amorphous silicon on the entire surface of the substrate 110 on which the buffer layer 111 is formed.

As a typical method for depositing the amorphous silicon thin film 120, there are a low pressure chemical vapor deposition (LPCVD) method and a plasma enhanced chemical vapor deposition (PECVD) method. When the amorphous silicon thin film 120 is deposited by the plasma chemical vapor deposition method, about 20% of the hydrogen atoms are included in the amorphous silicon thin film 120 although there is a difference depending on the temperature of the substrate during deposition.

4B, dehydrogenation is performed on the amorphous silicon thin film 120 to remove hydrogen contained in the amorphous silicon thin film 120, if necessary.

Then, the uniform scan of the laser generating apparatus 150, the amorphous silicon thin film 120, the laser beam (155 '), the low energy density of ^{300mJ / cm 2 ~ 450mJ / cm} 2 in the via, as shown in Figure 4c One proceeds to solid phase crystallization. At this time, for example, the solid-phase crystallization can form a first polycrystalline silicon thin film 130 'having a seed of a uniform grain by a first scan using a laser beam 155' of 350 mJ / cm ² region.

Then, as shown in Fig. 4d, by scanning the first polycrystalline silicon thin film ^{(130 ') 500mJ / cm 2} ~ 800mJ / cm 2 of the laser beam (155 ") of a high energy density in the formed of a first scan For example, the recrystallization may be carried out by using a laser beam of 650 mJ / cm ² area, using a uniform grain formed in the first scan as a seed, and then recrystallizing the seed using the uniform grain as a seed. The second polycrystalline silicon thin film 130 is formed.

In the crystallization method according to the first embodiment of the present invention, the crystallization uniformity is improved, but the productivity is somewhat lowered because two scans are required to proceed with seed formation and recrystallization.

Accordingly, the second embodiment of the present invention proposes a crystallization method using a laser beam having a step profile in order to improve such productivity deterioration.

In order to form a uniform and large grain, it is necessary to form a uniform seed at a low energy density and then recrystallize by a pulse overlap shot at a high energy density. In the case of the first embodiment of the present invention, the productivity is lowered. However, in order to overcome this limitation, it is possible to form a uniform and large size grain by one scan by changing the laser beam profile.

5A to 5C are sectional views sequentially showing the crystallization method according to the second embodiment of the present invention.

In this case, the amorphous silicon is described as a thin film to be crystallized in the second embodiment of the present invention, but the present invention is not limited thereto.

As shown in FIG. 5A, a buffer layer 211 having a predetermined thickness is formed on a front surface of a substrate 210 made of a transparent insulating material such as glass.

Then, a predetermined amorphous silicon thin film 220 is formed by depositing amorphous silicon on the entire surface of the substrate 210 on which the buffer layer 211 is formed.

As described above, typical methods for depositing the amorphous silicon thin film 220 include a low pressure chemical vapor deposition method and a plasma chemical vapor deposition method. When the amorphous silicon thin film 220 is deposited by the plasma CVD method, about 20% of hydrogen atoms are included in the amorphous silicon thin film 220 depending on the temperature of the substrate during deposition.

5B, a dehydrogenation process is performed on the amorphous silicon thin film 220 to remove hydrogen contained in the amorphous silicon thin film 220, if necessary.

5C, a laser beam 255 having a step profile is irradiated to the amorphous silicon thin film 220 through the laser generator 250 to form a polycrystalline silicon thin film 230 having a uniform and large grain, .

6A and 6B schematically show profiles of a first laser beam and a second laser beam.

7A, 7B, and 8 are views schematically showing the profile of the laser beam used in the crystallization method according to the second embodiment of the present invention.

Here, FIG. 7A schematically shows the lower surface of the laser beam having the step profile, and FIG. 7B schematically shows the side surface of the laser beam having the step profile.

Referring to the drawings, the laser beam 255 may have a step profile by differentiating the energy densities of the two laser beams 255a and 255b having a phase difference with respect to the beam width W direction.

The laser beam 255 having such a step profile can be formed by adjusting the energy density of the two laser beams 255a and 255b after giving a phase difference with respect to the beam width W direction through the optical system of the two laser sources . For example, the energy density of the front laser beam 255a located at the front side relative to the scanning direction can be lowered, and the energy density of the rear laser beam 255b at the rear side can be increased. The energy density of the front laser beam 255a corresponds to the portion where the crystallization starts, and may be set to, for example, about 300 mJ / cm ² to about 350 mJ / cm ² . The energy density of the back of the laser beam (255b) is used and the energy density region in which re-crystallization by a shot pulses overlap, for example, be about ^{500mJ / cm 2 ~ 800mJ / cm} 2.

For example, when the thickness of the amorphous silicon thin film 220 is 500Å about the energy density of the front laser beam (255a) it is and about 350mJ / cm ^2, the energy density of the back of the laser beam (255b) is 750mJ / cm ² ~ 800mJ / cm < ² >.

The energy density of the front laser beam 255a is about 300 mJ / cm ² and the energy density of the rear laser beam 255b is about 500 mJ / cm ² to 600 mJ / cm ² when the thickness of the amorphous silicon thin film 220 is about 600 Å. cm < ² >.

In this manner, a uniform seed is formed using the region having the low energy density of the front laser beam 255a with respect to the scanning direction, and then recrystallized in the region having the high energy density of the rear laser beam 255b, Can be formed by one scan.

The polycrystalline silicon thin film crystallized according to the present invention can be used for manufacturing semiconductor devices such as a thin film transistor, a solar cell, and an image sensor, and a method of manufacturing a thin film transistor using the polycrystalline silicon thin film crystallized by the crystallization method The following is a description.

9A to 9F are sectional views sequentially showing a method of manufacturing a thin film transistor according to the present invention.

First, as shown in FIG. 9A, a buffer layer 211 having a predetermined thickness is formed on a substrate 210 made of a transparent insulating material such as glass.

At this time, the buffer layer 211 is made of a silicon oxide (SiO ₂ ), and functions to prevent impurities such as sodium present in the substrate 210 from penetrating into the upper layer during the crystallization process.

After the amorphous silicon thin film is deposited to a predetermined thickness on the substrate 210 on which the buffer layer 211 is formed, the amorphous silicon thin film is crystallized using the crystallization method of the present invention to form a polycrystalline silicon thin film.

At this time, as a typical method for depositing the amorphous silicon thin film as described above, there are a low pressure chemical vapor deposition method and a plasma chemical vapor deposition method. When the amorphous silicon thin film is deposited by the above plasma chemical vapor deposition method, about 20% of hydrogen atoms are included in the amorphous silicon thin film although there is a difference depending on the substrate temperature during deposition.

If necessary, the amorphous silicon thin film is subjected to a dehydrogenation process to remove hydrogen contained in the amorphous silicon thin film.

Then, the amorphous silicon thin film is irradiated with a laser beam having a step profile to form a polycrystalline silicon thin film having uniform and large grain. In this case, for example, a uniform seed is formed using a region having a low energy density of the front laser beam with respect to the scanning direction, and then recrystallized in a region having a high energy density of the rear laser beam, Scan can be formed.

Thereafter, the polycrystalline silicon thin film is patterned through a photolithography process to form a predetermined active layer 224.

9B, a silicon oxide film or a silicon nitride film (SiNx) is deposited on the entire surface of the substrate 210 on which the active layer 224 is formed to form a gate insulating film 215a.

A gate line (not shown) extending in one direction is formed on the substrate 210 on which the gate insulating layer 215a is formed and a gate electrode 221 connected to the gate line is formed on the active layer 224 .

At this time, the gate electrode 221 and the gate line are formed by selectively depositing a first conductive film on the entire surface of the substrate 210 and then performing a photolithography process.

Here, the first conductive layer may be formed of aluminum (Al), aluminum alloy (Al alloy), tungsten (W), copper (Cu), chromium (Cr), molybdenum A low resistance opaque conductive material such as a molybdenum alloy can be used. The first conductive layer may have a multi-layer structure in which two or more low-resistance conductive materials are stacked.

For example, when an N-type thin film transistor is formed, high concentration n + ions are injected into a predetermined region of the active layer 224 using the gate electrode 221 as a mask to form a source region 224a and a drain region 224b. The gate electrode 221 functions as an ion stopper to prevent a dopant from penetrating into the channel region 224c of the active layer 224. [

9C, an interlayer insulating layer 215b is deposited on the entire surface of the substrate 210, and then a partial region of the gate insulating layer 215a and the interlayer insulating layer 215b is selectively formed by using a photolithography process. A first contact hole 240a and a second contact hole 240b are formed to expose portions of the source region 224a and the drain region 224b, respectively.

9D, the source electrode 222 and the drain electrode 224 are electrically connected to the source region 224a and the drain region 224b through the first contact hole 240a and the second contact hole 240b, respectively, And a drain electrode 223 are formed.

The source electrode 222, the drain electrode 223, and the data line are formed on the front surface of the substrate 210 to define a data line (not shown) crossing the gate line, And then selectively patterned through a photolithography process.

Here, as the second conductive film, a low-resistance opaque conductive material such as aluminum, an aluminum alloy, tungsten, copper, chromium, molybdenum, or molybdenum alloy may be used. The second conductive layer may be formed in a multi-layered structure in which two or more low-resistance conductive materials are stacked.

9E, a passivation layer 215c is deposited on the entire surface of the substrate 210, and then a portion of the passivation layer 215c is selectively patterned using a photolithography process to form the drain electrode 223 The second contact hole 240c exposes a part of the third contact hole 240c.

Then, as shown in FIG. 9F, a third conductive film is formed on the entire surface of the substrate 210. The third conductive layer includes a transparent conductive material having a high transmittance such as indium tin oxide (ITO) or indium zinc oxide (IZO) to form a pixel electrode.

Thereafter, the third conductive film is selectively removed through a photolithography process to form the third conductive film on the array substrate 210, and the third conductive film is electrically connected to the drain electrode 223 through the third contact hole 240c The pixel electrode 218 is formed.

Meanwhile, the thin film transistor thus manufactured can improve the uniformity of crystallization by using two scans whose energy is different from that of the laser beam or by using a laser beam having a step profile. As a result, the present invention can be applied to a large area display, and mura is suppressed due to improvement of grain size and crystallization uniformity, thereby improving the performance of a display device such as an organic electroluminescent device.

For reference, FIGS. 10 and 11 are graphs showing electrical characteristics of a thin film transistor according to various positions of a panel, and illustrate electric characteristics measured at eight points in a panel. FIG.

10 shows electrical characteristics of a thin film transistor crystallized through a green laser having a general gaussian flow profile. FIG. 11 is a graph showing the electrical characteristics of the step profile according to the second embodiment of the present invention. And shows the electrical characteristics of a thin film transistor crystallized through a green laser.

Referring to FIG. 10, the electrical characteristics of the thin film transistor crystallized through the Gaussian green laser having an energy density of 750 mJ / cm ² are not uniform. For example, the average mobility is about 55.9 cm ² / Vs, with a uniformity of about 69%.

Referring to FIG. 11, the energy density of the front is 350mJ / cm ² energy density of the back it can be seen that the electrical characteristics even if the thin film transistor crystallization through the green laser with 780mJ / cm ² in the step profile . For example, the average mobility is about 62.4 cm ² / Vs, with a uniformity of about 82%.

10, the mobility is increased by about 10%, and the uniformity is improved by about 13%.

While a great many are described in the foregoing description, it should be construed as an example of preferred embodiments rather than limiting the scope of the invention. Therefore, the invention should not be construed as limited to the embodiments described, but should be determined by equivalents to the appended claims and the claims.

110, 210: substrate 111, 211:
120, 220: Amorphous silicon thin film 130, 230: Polycrystalline silicon thin film
150, 250: laser generating device 155, 255: laser beam

Claims (15)

Forming an amorphous silicon thin film on a substrate;
Scanning a green laser beam having a first energy density to the amorphous silicon thin film to progress a solid-phase crystallization so as to form a uniform grain; And
And scanning the amorphous silicon thin film with a green laser beam having a second energy density higher than the first energy density to recrystallize the grain as a seed. Forming an amorphous silicon thin film on a substrate; And
And scanning the amorphous silicon thin film with a green laser beam having a step profile to proceed crystallization,
Wherein the laser beam has a different energy density from the two laser beams having a phase difference with respect to a width direction of the beam to form a step profile. The method of claim 1, wherein the first energy density of the crystallization method characterized in that it is set to ^{300mJ / cm 2 ~ 450mJ / cm} 2. The method of claim 1, wherein the second energy density of the crystallization method characterized in that the set ^{500mJ / cm 2 ~ 800mJ / cm} 2. delete 3. The method according to claim 2, wherein the green laser beam having the step profile is formed by adjusting the energy density of the two laser beams after giving a phase difference to the two laser sources through the optical system in the beam width direction . The crystallization method according to claim 2, wherein the energy density of the front laser beam positioned at the front side with respect to the scanning direction is set low and the energy density of the rear laser beam at the rear side is set high. The crystallization method according to claim 7, wherein the energy density of the front laser beam is adjusted to a portion where crystallization is started, and is set to, for example, 300 mJ / cm ² to 350 mJ / cm ² . 9. The method of claim 8 wherein the energy density of the back of the laser beam is a crystallization method characterized in that it uses an energy density region in which re-crystallization by a shot pulses overlap, for example, set to ^{500mJ / cm 2 ~ 800mJ / cm} 2 . The crystallization method according to any one of claims 1 and 2, wherein a buffer layer is formed on the substrate, and then an amorphous silicon thin film is formed thereon. The crystallization method according to claim 10, further comprising the step of performing a dehydrogenation process on the amorphous silicon thin film after forming the amorphous silicon thin film. Forming an amorphous silicon thin film on a substrate;
Scanning a green laser beam having a step profile on the amorphous silicon thin film to proceed crystallization; And
And patterning the crystallized silicon thin film to form an active layer,
Wherein the laser beam has a different energy density from the two laser beams having a phase difference with respect to the beam width direction, thereby forming a step profile.
delete 13. The method of claim 12, wherein the green laser beam having the step profile is formed by adjusting the energy density of two laser beams after giving a phase difference to the two laser sources through the optical system in the beam width direction. ≪ / RTI > The manufacturing method of a thin film transistor according to claim 12, wherein the energy density of the front laser beam positioned at the front side with respect to the scanning direction is set low and the energy density of the rear laser beam at the rear side is set high.

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