CRYSTALLIZATION METHOD OF AMORPHOUS SILICON

A crystallization method of amorphous silicon includes forming amorphous silicon on a substrate; first-irradiating a laser beam on the amorphous silicon while moving the substrate in a first direction; moving a position of the substrate in a second direction perpendicular to the first direction, and second-irradiating a laser beam on the amorphous silicon while moving the substrate in an opposite direction to the first direction.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to and benefits of Korean Patent Application No. 10-2021-0139370 under 35 U.S.C. § 119, filed in the Korean Intellectual Property Office (KIPO) on Oct. 19, 2021, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

The disclosure relates to a crystallization method of amorphous silicon.

2. Description of the Related Art

Generally, a display device such as a liquid crystal display device or an organic light emitting display device uses a thin film transistor to control light emission of each pixel. Since such a thin film transistor includes polysilicon, a step of forming a polysilicon layer on a substrate is performed in a process of manufacturing a display device. An amorphous silicon layer is formed on a substrate, and the amorphous silicon layer is crystallized to form the polysilicon layer. The crystallizing of the amorphous silicon layer may be performed by irradiating a laser beam on the amorphous silicon layer.

SUMMARY

Embodiments are to provide a crystallization method of amorphous silicon that may reduce visibility of a stain by adjusting a position of a substrate for each irradiation step of the laser beam.

An embodiment provides a crystallization method of amorphous silicon, including forming amorphous silicon on a substrate; first-irradiating a laser beam on the amorphous silicon while moving the substrate in a first direction; moving a position of the substrate in a second direction perpendicular to the first direction, second-irradiating a laser beam on the amorphous silicon while moving the substrate in an opposite direction to the first direction.

The laser beam may be emitted from a laser beam source. The laser beam emitted from the laser beam source may be reflected by a polygonal mirror that rotates around a rotation axis, and then may be irradiated onto the substrate.

The polygonal mirror may include a first reflective surface and a second reflective surface, and a moving distance of a laser beam reflected by the first reflective surface on the substrate and a moving distance of a laser beam reflected by the second reflective surface on the substrate may be equal to each other.

The laser beam reflected by the polygonal mirror may be sequentially reflected by a first mirror and a second mirror and then may be irradiated onto the substrate.

The first mirror may have a convex reflective surface, and the second mirror may have a concave reflective surface.

A moving distance of the substrate in the first direction in the first-irradiating of the laser beam and a moving distance of the substrate in the opposite direction to the first direction in the second-irradiating of the laser beam may be equal to each other.

The crystallization method of amorphous silicon may further include, moving the position of the substrate in an opposite direction to the second direction; and third-irradiating a laser beam on the amorphous silicon while moving the substrate in the first direction.

A moving distance in the first direction in the third-irradiating of the laser beam and a moving distance in the first direction in the first-irradiating of the laser beam may be equal to each other.

The crystallization method of amorphous silicon may further include, moving the position of the substrate in the second direction; fourth-irradiating a laser beam on the amorphous silicon while moving the substrate in the opposite direction to the first direction.

A moving distance in the opposite direction to the first direction in the fourth-irradiating of the laser beam and a moving distance in the first direction in the third-irradiating of the laser beam may be equal to each other.

In the second-irradiating of the laser beam, a moving distance of the substrate in the second direction may be in a range of about 1 cm to about 10 cm.

Another embodiment provides a crystallization method of amorphous silicon, including forming amorphous silicon on a substrate; vibrating, while moving the substrate in a first direction, vibrating the substrate in a second direction perpendicular to the first direction, and first-irradiating a laser beam on the amorphous silicon during the moving; moving a position of the substrate in the second direction; and vibrating the substrate in the second direction while moving the substrate in an opposite direction to the first direction, and second-irradiating a laser beam on the amorphous silicon during the moving.

A width of vibration in the second direction in the first-irradiating of the laser beam and a width of vibration in the second direction in the second-irradiating of the laser beam may be different from each other.

A moving distance of the substrate in the first direction in the first-irradiating of the laser beam and a moving distance of the substrate in the opposite direction to the first direction in the second-irradiating of the laser beam may be equal to each other.

The crystallization method of amorphous silicon may further include moving the position of the substrate in an opposite direction to the second direction; and vibrating the substrate in the second direction while moving the substrate in the first direction, and third-irradiating a laser beam on the amorphous silicon during the moving.

The crystallization method of amorphous silicon may further include moving the position of the substrate in the second direction; and vibrating the substrate in the second direction while moving the substrate in the opposite direction to the first direction, and fourth-irradiating a laser beam on the amorphous silicon during the moving.

A width of vibration in the second direction in the third-irradiating and a width of vibration in the second direction in the fourth-irradiating may be different from each other.

In the second-irradiating of the laser beam, a moving distance of the substrate in the second direction may be in a range of about 1 cm to about 10 cm.

The laser beam may be emitted from a laser beam source. The laser beam emitted from the laser beam source may be reflected by a polygonal mirror that rotates around a rotation axis, and then may be irradiated onto the substrate.

The laser beam reflected by the polygonal mirror may be sequentially reflected by a first mirror and a second mirror and then may be irradiated onto the substrate.

According to the embodiments, it is possible to provide a crystallization method of amorphous silicon that may reduce visibility of a stain by adjusting a position of a substrate for each irradiation step of the laser beam.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The use of cross-hatching and/or shading in the accompanying drawings is generally provided to clarify boundaries between adjacent elements. As such, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, dimensions, proportions, commonalities between illustrated elements, and/or any other characteristic, attribute, property, etc., of the elements, unless specified. Also, like reference numerals denote like elements.

Further, in the accompanying drawings, the size and relative sizes of elements may be exaggerated for clarity and/or descriptive purposes. When an embodiment may be implemented differently, a specific process order may be performed differently from the described order. For example, two consecutively described processes may be performed substantially at the same time or performed in an order opposite to the described order.

Further, in the specification, the phrase “in a plan view” or “on a plane” means when an object portion is viewed from above, and the phrase “in a cross-sectional view” or “on a cross-section” means when a cross-section taken by vertically cutting an object portion is viewed from the side.

Hereinafter, a laser crystallization apparatus and a laser crystallization method according to an embodiment is described in detail with reference to the accompanying drawings below.

FIG.1schematically illustrates a laser crystallization apparatus according to an embodiment of the disclosure. As shown inFIG.1, the laser crystallization apparatus according to the embodiment may include a laser beam source100, a polygonal mirror300, a first mirror400, and a second mirror500.

The laser beam source100may emit a linearly polarized laser beam. The laser beam source100may include a laser beam source and a linear polarizer. For example, the laser beam source100may use a fiber laser. The fiber laser may be advantageous in controlling output in a wide range, maintaining at a low maintenance cost, and operating at high efficiency.

The polygonal mirror300may reflect an incident laser beam from the laser beam source100. The polygonal mirror300may rotate around a rotation axis310. The laser beam emitted from the laser beam source100may be reflected by the polygonal mirror300and reach an amorphous silicon layer20on a substrate10. Accordingly, the amorphous silicon layer20may be crystallized to become a crystallization silicon layer.

In case that the polygonal mirror300rotates, the laser beam may be irradiated to all or most of an area of the amorphous silicon layer20. The laser beam reflected from the polygonal mirror300may be irradiated to the amorphous silicon layer20, and as the polygonal mirror300rotates, a point on the amorphous silicon layer20to which the laser beam reaches is changed (e.g., changed to be crystalized). As shown inFIG.1, in case that the laser beam emitted from the laser beam source100arrives on a first reflective surface320of the polygonal mirror300and in case that the polygonal mirror300rotates in a direction indicated by an arrow around the rotation axis310, the point on the amorphous silicon layer20where the laser beam reaches is moved in a +y direction. In the specification, the +y direction means a direction indicated by a y arrow on the illustrated direction axis, and a −y direction means an opposite direction to the y arrow.

For example, the laser beam emitted from the laser beam source100may move on the first reflective surface320of the polygonal mirror300, and the point on the amorphous silicon layer20to which the laser beam reaches may move in the +y direction. For example, the point on the amorphous silicon layer20may move in the +y direction during the moving of the laser beam on the first reflective surface320.

In case that the polygonal mirror300is further rotated and the laser beam emitted from the laser beam source100arrives on a second reflective surface330of the polygonal mirror300, the laser beam moves again in the +y direction on the amorphous silicon layer20. A moving length of the laser beam reflected by the second reflective surface330may be the same as a moving length of the laser beam reflected by the first reflective surface320.

For example, the amorphous silicon layer20is irradiated once in the y-direction for each reflective surface of the polygonal mirror300, and in case that the substrate10is moved in an x direction by using a stage while rotating the polygonal mirror300, all or most of the area of the amorphous silicon layer20may be irradiated with a laser beam. The x direction may intersect the y direction. For example, the x direction may be perpendicular to the y direction.

In other embodiments, the laser beam reflected from the polygonal mirror300may immediately reach the amorphous silicon layer20. However, in the embodiment, a path of the laser beam reflected from the polygonal mirror300may be adjusted by using the first mirror400and the second mirror500as shown inFIG.1, and then, it may allow the laser beam to reach the amorphous silicon layer20.

As shown inFIG.1, the first mirror400may have a convex reflective surface, and the second mirror500may have a concave reflective surface. Referring toFIG.1, in case that the laser beam is reflected from a point far from the second reflective surface330among points in the first reflective surface320of the polygonal mirror300, the laser beam may be irradiated to an edge of the amorphous silicon layer20in the −y direction. In case that the laser beam is reflected from a point adjacent to the second reflective surface330among the points in the first reflective surface320of the polygonal mirror300, the laser beam may be irradiated near the edge of the amorphous silicon layer20in the +y direction.

Accordingly, in case that the laser beam is reflected by the first reflective surface320and the polygonal mirror300rotates, a length of the laser beam irradiated area of the amorphous silicon layer20may correspond to a width of the amorphous silicon layer20in the y direction.

In case that the laser beam is irradiated in this way, the entire area of the amorphous silicon layer20may be uniformly crystallized, but in case that there is a defect410(e.g., refer toFIG.2) in the first mirror400, a line stain may occur in a scan direction due to overlap of a shadow caused by the defect410. Thus, the defect410may be (or may include) contamination or damage to the first mirror400.FIG.2schematically illustrates a crystallization silicon layer crystallized in case that there is the defect410in the first mirror400. As shown inFIG.2, the shadow overlaps due to the defect410of the first mirror400, and a stain21occurs due to a difference in crystallization characteristics in the shadow part.

FIG.3schematically illustrates the case in which the stain21occurs on the crystallization silicon layer25due to the defect410of the first mirror400. InFIG.3, the substrate10may move in the x direction, and the laser beam may be scanned in they direction. As shown inFIG.3, a degree of crystallization is changed in some areas due to the overlap of the shadow caused by the defect410of the first mirror400, which is viewed as the stain21as shown inFIG.3.FIG.4schematically illustrates an image of a line stain occurring in actual crystallized silicon.

As described above, since the laser beam moves the same distance every time the amorphous silicon layer20is scanned in the y-direction once, the stain21may be formed at the same position for each scan, and thus as shown inFIGS.3and4, the stain21may be viewed as a continuous line.

Accordingly, the crystallization method of amorphous silicon according to the embodiment may control the position and movement speed of the substrate during crystallization, so that the stains21may not overlap each other for each scan. Thus, the stains21may not be readily viewed. Description of removing the stains21is provided below.

FIGS.5to7schematically illustrate a crystallization process according to an embodiment step by step.FIG.8illustrates the crystallization silicon layer25crystallized through the crystallization ofFIGS.5to7.

Referring toFIG.5, the amorphous silicon layer is first crystallized while moving the substrate10in a +x direction. In the specification, the +x direction means a direction indicated by the x arrow on the directional axis shown in each drawing, and the −x direction means an opposite direction of the x arrow. Similarly, the +y direction means a direction indicated by the y arrow on the directional axis shown in each drawing, and the −y direction means an opposite direction of the y arrow.

FIG.5illustrates the crystallization silicon layer25crystallized by laser beam irradiation among the amorphous silicon. A movement speed in the x direction of the substrate10may be faster than a crystallization speed of the entire amorphous silicon layer by the movement of the substrate10. The crystallization speed of the entire amorphous silicon layer by the movement of the substrate10is referred to as a reference speed, and the movement speed of the substrate10may be three times the reference speed. Since the substrate10moves at the movement speed faster than the reference speed by three times, a degree of crystallization of the amorphous silicon layer after the movement of the substrate10may be the same as that shown inFIG.5. For example, since the substrate10rapidly moves, the crystallization may not be performed as a whole, but the crystallization may occur only in some areas of the crystallization silicon layer25.FIG.5illustrates the crystallization silicon layer25partially crystallized by irradiating the laser beam.

For better comprehension and ease of description,FIG.5illustrates the crystallization silicon layer25crystallized by irradiating the laser beam as a straight line, but the crystallization silicon layer25may be crystallized by irradiating the laser beam in a diagonal direction.FIG.5illustrates the stain21formed by the defect410of the first mirror400having different crystallinity from that of other areas. Comparing with the embodiment ofFIG.3, in the embodiment ofFIG.5, since the substrate10is quickly moved and the laser beam is irradiated, the stains21may not be continuous but are formed to be spaced apart from each other.

Referring toFIG.6, in case that the substrate10is moved again in the −x direction, the amorphous silicon layer may be crystallized by irradiating the laser beam thereon.FIG.6illustrates the crystallization silicon layer25crystallized by the irradiation with the laser beam and the stain21that is not sufficiently crystallized. In the step ofFIG.6, the substrate10may move in the −x direction in a state in which it further moves in the +y direction than a position (hereinafter, a reference position) of the substrate10inFIG.5. Accordingly, as shown inFIG.6, the formation position of the stain21may be lower in the y direction than the position of the stain21shown inFIG.5. For example, the position of the stain21formed in the step ofFIG.6may be shifted in the y direction (e.g., −y direction) from the position of the stain21formed in the step ofFIG.5. Since the substrate10moves in the +y direction from the reference position and the laser beam is irradiated, the position of the stain21formed in the step ofFIG.6may be lower than the position of the stain21formed in the step ofFIG.5. The moving distance (or shifted distance) of the stain21in they direction may be in a range of about 1 cm to about 10 cm. However, this is only an example, and the moving distance in the y direction may vary according to embodiments.

The distance (e.g., moving distance of substrate10) moved in the +x direction inFIG.5and the distance (e.g., moving distance of substrate10) moved in the −x direction inFIG.6may be the same. In the specification, the same distance means that the difference therebetween is less than 10%.

Referring toFIG.7, in case that the substrate10is moved again in the +x direction, the amorphous silicon layer may be crystallized by irradiating the laser beam thereon.FIG.7illustrates the crystallization silicon layer25crystallized by the irradiation with the laser beam and the stain21that is not sufficiently crystallized. The substrate10may move in the +x direction in a state in which it further moves in the −y direction than a position (hereinafter, a reference position) of the substrate10inFIG.5. Accordingly, as shown inFIG.7, the formation position of the stain21may be higher in the y direction than the position of the stain21shown inFIG.5. This is because the laser beam is irradiated in the state in which the substrate10moves in the −y direction. The moving distance (or shifted distance) of the stain21in they direction based on the reference position of the substrate may be in a range of about 1 cm to about 10 cm. However, this is only an example, and the moving distance in the y direction may vary according to embodiments. The moving distance of the substrate10in the +x direction inFIG.7may be the same as the moving distance of the substrate10in the +x direction inFIG.5.

FIG.8schematically illustrates the crystallization silicon layer25crystallized by irradiating the laser beam through the processes ofFIGS.5to7as described above. Referring toFIG.8, the stains21may be dispersed and positioned at various positions in the crystallization silicon layer25without being displayed as a line (or single line). In case that the laser beam is irradiated as shown inFIGS.5to7, the laser beam may be irradiated on different positions of the substrate10in the y direction for each irradiation process. Since the position of the substrate10varies for each irradiation, the position of the stains21also varies for each irradiation. Accordingly, the stains21formed during each irradiation do not overlap as one, but are dispersed from each other, so that visibility of the stains21may be lowered. For example, comparing the embodiments ofFIGS.3and8, in the embodiment ofFIG.3in which the entire amorphous silicon layer20is continuously crystallized at once, the stains21may overlap and be viewed as a single line. However, in the embodiment ofFIG.8, since the stains21are dispersed and positioned without overlapping each other as one, the stains21may be less visually recognized compared with the embodiment ofFIG.3.

For example, the crystallization method according to the embodiment may increase the movement speed of the substrate10and performs the crystallization by repeatedly irradiating the laser beam, and the position of the substrate10may move in the y direction in each irradiation process of the substrate10. Therefore, even if the stains21occur due to the defect410of the first mirror400, the stains21may not overlap each other as a single stain (or overlapped stain) and be dispersed in each irradiation process, thereby reducing the visibility of the stains21.

InFIGS.5to7, after moving the substrate10in the y direction in each irradiation step, the irradiation is performed while moving it in the x direction, but in each irradiation process, by vibrating it in the y direction while moving the substrate10in the x axis, it is possible to further disperse the formation positions of the stains21.

FIGS.9to11schematically illustrate an irradiation process of irradiating the laser beam on the substrate10and moving the substrate in both the x direction and the y directions, andFIG.12illustrates the crystallization silicon layer25crystallized through the laser beam irradiation ofFIGS.9to11.

Referring toFIG.9, the substrate10may move in the +x direction, and the substrate10may move simultaneously in the y direction as shown inFIG.9. InFIG.9, the movement of the substrate10in the y direction may be in a form of vibrating up and down in the y direction, and the vibration of the substrate10in they direction may be combined with the movement of the substrate10in the x direction. Thus, the movement trajectory of the substrate10may be as indicated by an arrow (e.g., waveform arrow) inFIG.9. The stains21may be dispersedly positioned in the crystallization silicon layer25crystallized by irradiating the laser beam. For example, compared with the embodiment ofFIG.5, the stains21ofFIG.5may appear at constant positions, but in the embodiment ofFIG.9, the stains21may dispersedly appear.

Referring toFIG.10, the substrate10may move in the −x direction, and the substrate10may move simultaneously in they direction as shown inFIG.10. InFIG.10, the movement of the substrate10in they direction may be in a form of vibrating up and down in they direction, and the vibration of the substrate10in they direction may be combined with the movement of the substrate10in the x direction. Thus, the movement trajectory of the substrate10may be as indicated by an arrow (e.g., waveform arrow) inFIG.10. The entire position of the substrate10may be in a state in which it further moves in the +y direction than a position (hereinafter, a reference position) of the substrate10inFIG.9. For example, the entire position of the substrate10may be shifted in the +y direction than the reference position of the substrate10inFIG.9. Referring toFIG.10, the stains21may be dispersedly positioned in the crystallization silicon layer25crystallized by irradiating the laser beam. Since the entire substrate10further moves (or is shifted) in the +y direction from the reference position, the stains21may be positioned in the −y direction as a whole compared to the embodiment ofFIG.9.

Referring toFIG.11, the substrate10may move in the +x direction, and the substrate10may move simultaneously in the y direction as shown inFIG.11. For example, the substrate10may move in the +x direction during the moving of the substrate10in the y direction as shown inFIG.11. InFIG.11, the movement of the substrate10in they direction may be in a form of vibrating up and down in the y direction, and the vibration in they direction may be combined with the movement in the x direction. Thus, the movement trajectory of the substrate10may be as indicated by an arrow (e.g., waveform arrow) inFIG.11. The entire position of the substrate10may be in a state in which it further moves in the −y direction than a position (hereinafter, a reference position) of the substrate10inFIG.9. Referring toFIG.11, the stains21may be dispersedly positioned in the crystallization silicon layer25crystallized by irradiating the laser beam. Since the entire substrate10further moves (or is shifted) in the −y direction from the reference position, the stains21may be positioned in the +y direction as a whole compared to the embodiment ofFIG.9.

FIG.12schematically illustrates the crystallization silicon layer25crystallized through the laser irradiation process ofFIGS.9to11as described above. Referring toFIG.12, the stains21may be dispersed and positioned at various positions in the crystallization silicon layer25without being displayed as a line (or single line). In case that the laser beam is irradiated as inFIGS.9to11above, the laser beam may be irradiated on different positions of the substrate10in the +y and −y directions based on the reference position. In case that the substrate10moves in the x direction, the laser beam may be irradiated during the vibrating of the substrate10in they direction. Therefore, as shown inFIG.12, the positions of the stains21may be dispersed in each irradiation process, and the stains21during each irradiation may not overlap each other as a single stain, but may be dispersed from each other to lower the visibility of the stains21. For example, comparing the embodiments ofFIGS.3and12, in the embodiment ofFIG.3that is continuously crystallized at once, the stains21may overlap and be viewed as a single line. However, in the embodiment ofFIG.12, since the stains21are dispersed and positioned without overlapping each other as one, the stains21may be less visually recognized compared with the embodiment ofFIG.3.

Comparing the embodiments ofFIGS.8and12, the stains21may be more dispersed, in the embodiment ofFIG.12in which the movement in the x direction and the movement in the y direction are simultaneously performed in each laser irradiation step, compared with the embodiment ofFIG.8in which only the movement in the x direction during the laser irradiation is performed.

InFIGS.9to11, the width of vibration in they direction in each irradiation step may be different for each step. For example, inFIGS.9to11, a path along which the substrate10moves is shown by the arrow (e.g., waveform arrow), and the size (e.g., amplitude) of the wavelength of each arrow (e.g., waveform arrow) may be different from each other. Thus, in case that the width of the vibration of the substrate10in the y direction is different in each irradiation step, the degree of overlap of the stains21may be reduced and the stains21may be dispersed, thereby reducing visibility thereof.

FIGS.5to12schematically illustrate configurations of crystallizing the amorphous silicon layer20by repeatedly irradiating the laser beam on the substrate10three times. However, this is only an example, and the number of repeatedly irradiating the substrate may vary according to embodiments. In case that the substrate10is irradiated n times, the movement speed of the substrate10in the x direction in each irradiation step may be n times faster than the reference speed.

FIGS.13to17schematically illustrate configurations of crystallizing the amorphous silicon layer20by repeatedly irradiating the laser beam on the substrate10four times. Referring toFIG.13, the amorphous silicon layer may be crystallized and the substrate10may move in the +x direction. For example, the amorphous silicon layer may be crystallized during the moving of the substrate10in the +x direction.FIG.13illustrates the crystallization silicon layer25in which amorphous silicon is crystallized and the stain21in which the crystallization is not sufficiently performed. The movement speed of the substrate10may be 4 times the reference speed.

Referring toFIG.14, the substrate10may move in the −x direction, and the amorphous silicon layer may be crystallized by irradiating the laser beam thereon. For example, the amorphous silicon layer may be crystallized by irradiating the laser beam on the substrate10during the moving of the substrate10in the −x direction.FIG.14schematically illustrates the crystallization silicon layer25crystallized by the irradiation with the laser beam and the stain21that is not sufficiently crystallized. The substrate10may move in the −x direction in a state in which it further moves in the +y direction than the position (hereinafter, the reference position) of the substrate10inFIG.13. Accordingly, as shown inFIG.14, the formation position of the stain21may be lower in the y direction than inFIG.13. The laser beam may be irradiated in the state in which the substrate10moves in the +y direction, and the formation position of the stain21may be lower in they direction than the reference position of the substrate10shown inFIG.13. The moving distance (or shifted distance) of the substrate10in the y direction based on the reference position may be in a range of about 1 cm to about 10 cm. However, this is only an example, and the moving distance in the y direction may vary according to embodiments.

Referring toFIG.15, the substrate10may move in the +x direction, and the amorphous silicon layer may be crystallized by irradiating the laser beam thereon. For example, the amorphous silicon layer may be crystallized by irradiating the laser beam on the substrate10during the moving of the substrate10in the +x direction.FIG.15illustrates the crystallization silicon layer25crystallized by the irradiation with the laser beam and the stain21that is not sufficiently crystallized. The substrate10may move in the +x direction in a state of moving in the −y direction from the reference position. Accordingly, as shown inFIG.15, the formation position of the stain21may be higher in the y direction than inFIG.13. This is because the laser beam is irradiated in the state in which the substrate10moves in the −y direction from the reference position. The moving distance (or shifted distance) of the substrate10in the y direction based on the reference position may be in a range of about 1 cm to about 10 cm. However, this is only an example, and the moving distance (or shifted distance) in the y direction may vary according to embodiments.

Referring toFIG.16, the substrate10may move again in the −x direction, and the amorphous silicon layer may be crystallized by irradiating the laser beam thereon. For example, the amorphous silicon layer may be crystallized by irradiating the laser beam on the substrate during the moving of the substrate10in the −x direction.FIG.16illustrates the crystallization silicon layer25crystallized by the irradiation with the laser beam and the stain21that is not sufficiently crystallized. The substrate10may move in the −x direction in a state of moving in the +y direction from the reference position. Accordingly, as shown inFIG.14, the formation position of the stain21may be lower in the y direction than inFIG.13. The substrate10may move (or be shifted) in the +y direction from the reference position, and the laser beam may be irradiated on the substrate10. The moving distance (or shifted distance) of the substrate10in they direction based on the reference position may be in a range of about 1 cm to about 10 cm. However, this is only an example, and the moving distance in the y direction may vary according to embodiments.

FIG.17schematically illustrates the crystallization silicon layer25crystallized by irradiating the laser beam as inFIGS.13to16. Referring toFIG.17, the stains21may be dispersed and positioned in the crystallization silicon layer25without being displayed as a line (or single line). In case that the laser beam is irradiated as inFIGS.13to16above, since the laser beam is irradiated on the substrate10with different positions from the reference position in the y direction, the position of the stain21may also be positioned at different positions for each irradiation. Accordingly, the stains21during each irradiation may not overlap as one (or single line), but may be dispersed from each other. Thus, visibility of the stains21may be lowered.

InFIGS.13to16, the movement speed of the substrate10in each irradiation step may be 4 times the reference speed. For example, in case that the amorphous silicon layer20is crystallized by irradiating the laser beam on the substrate10n times, the movement speed of the substrate10in the x direction in each irradiation step may be n times faster than the reference speed.

FIGS.18to20schematically illustrate configurations of crystallizing the amorphous silicon layer20by repeatedly irradiating the laser beam on the substrate10two times. Referring toFIG.18, the substrate10may move in the +x direction, and the amorphous silicon layer may be crystallized. For example, the amorphous silicon layer may be crystallized during the moving of the substrate10in the +x direction.FIG.18illustrates the crystallization silicon layer25crystallized by the irradiation with the laser beam and the stain21that is not sufficiently crystallized. The movement speed of the substrate10may be 2 times the reference speed.

Referring toFIG.19, the substrate10may move in the −x direction, and the amorphous silicon layer may be crystallized by irradiating the laser beam thereon. For example, the amorphous silicon layer may be crystallized by the irradiating of the laser beam thereon during the moving of the substrate10in the −x direction.FIG.19illustrates the crystallization silicon layer25crystallized by the irradiation with the laser beam and the stain21that is not sufficiently crystallized. The substrate10may move in the −x direction in a state in which it further moves in the +y direction than the position (hereinafter, the reference position) of the substrate10inFIG.18. Accordingly, as shown inFIG.19, the formation position of the stain21may be lower in the y direction than inFIG.13. This is because the laser beam is irradiated in the state in which the substrate10moves in the +y direction. The moving distance (or shifted distance) of the substrate10in they direction based on the reference position may be in a range of about 1 cm to about 10 cm. However, this is only an example, and the moving distance (or shifted distance) in the y direction may vary according to embodiments.

FIG.20schematically illustrates the crystallization silicon layer25crystallized by irradiating the laser beam as inFIGS.18and19. Referring toFIG.20, the stains21may be dispersed and positioned in the crystallization silicon layer25without being displayed as a line (or single line). In case that the laser beam is irradiated as inFIGS.18to19above, since the laser beam is irradiated on different positions of the substrate10in the y direction, the position of the stain21may also be positioned to be different for each irradiation. Accordingly, the stains21during each irradiation may not overlap as one (or single), but may be dispersed from each other. Thus, visibility of the stains21may be lowered. For example, comparing the embodiments ofFIGS.3and20, in the embodiment ofFIG.3that is continuously crystallized at once, the stains21may overlap and be viewed as a single line, but in the embodiment ofFIG.20, since the stains21are dispersed and positioned without overlapping each other as one, the stains21may be less visually recognized compared with the embodiment ofFIG.3.

In the previous embodiment, the configuration of repeatedly irradiating the laser beam 2 to 4 times has been described as examples, but the disclosure is not limited thereto, and the number of irradiations may vary. As described above, in case that the number of irradiations is n times, the movement speed of the substrate10in the x direction may be n times faster than the reference speed. The position of the substrate10may move (or be shifted) in the y direction for each irradiation, and/or the substrate10may vibrate in the y direction during the irradiation. Thus, the overlapping of the stains21may be prevented, and the visibility of the stains21may be reduced in the crystallization silicon layer25.

For example, in the crystallization method according to the embodiment, the movement speed of the substrate10may be increased, and the laser beam may be repeatedly irradiated. Thus, the crystallization may be performed, and the position of the substrate10may move (or be shifted) in the y and/or the substrate10may vibrate in the y direction, during the irradiation process of the substrate10. Therefore, even if the stains21occur due to the defect410of the first mirror400, the stains21may not overlap each other as a single stain (or overlapped stain) and be dispersed in the irradiation process, thereby reducing the visibility of the stains21.