KR20080077794A - Silicon crystallization apparatus and method for crystallizing silicon using the same - Google Patents

Abstract

An apparatus for crystallizing silicon and a method for crystallizing the silicon using the same are provided to minimize the surface roughness of a polysilicon thin film obtained by crystallizing an amorphous silicon thin film, and shorten a time for crystallizing the amorphous silicon thin film. A beam generation unit(110) generates a laser beam to emit the laser beam to a beam adjustment unit(120). The beam adjustment unit homogenizes the energy density of the laser beam, and emits the homogenized laser beam to a beam split unit(130). The beam split unit splits the laser beam in order to make the split laser beams advance on different paths. The beam split unit is composed of plural mirrors(132,134) distanced from each other so that the laser beam emitted from the beam adjustment unit is split by the mirrors. A stage(140) loads and moves a substrate(150) on which an amorphous silicon film(152) is formed. The split laser beams are respectively applied to the substrate in a scanning type while the substrate is moved by the stage.

Description

Silicon crystallization equipment and silicon crystallization method using the same {SILICON CRYSTALLIZATION APPARATUS AND METHOD FOR CRYSTALLIZING SILICON USING THE SAME}

1 is a view schematically illustrating the configuration of a silicon crystallization equipment according to an embodiment of the present invention.

FIG. 2 is a diagram for describing a width and a scan pitch of a laser beam divided by the beam splitter illustrated in FIG. 1.

FIG. 3 is a diagram for schematically describing an energy density according to a width of a laser beam divided by the beam splitter illustrated in FIG. 1.

{Description of symbols for main parts of the drawing}

100: silicon crystallization equipment 110: beam generation unit

120: beam adjuster 130: beam splitter

132: first mirror 134: second mirror

140: stage 150: substrate

152: amorphous silicon thin film 154: polysilicon thin film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of a flat panel display, and more particularly, to a silicon crystallization apparatus for crystallizing an amorphous silicon thin film formed on a substrate used for manufacturing a flat panel display and a silicon crystallization method using the same.

Flat panel displays (FPDs), such as liquid crystal displays (LCDs) and organic light emitting diodes (OLEDs), are switching devices for driving an active matrix (AM). It may include a thin film transistor substrate on which a thin film transistor (TFT) is formed.

The thin film transistor formed on the thin film transistor substrate may include a gate electrode, a source electrode, a drain electrode, an insulating layer, and a channel layer formed of a silicon thin film.

The thin film transistor having the above structure may be classified into an amorphous silicon (a-Si) thin film transistor and a polysilicon (p-Si) thin film transistor according to the silicon crystal state in the silicon thin film forming the channel layer. have.

The amorphous silicon thin film forming the channel layer of the amorphous silicon thin film transistor may be formed on the substrate through a low temperature deposition process. For this reason, when the channel layer is formed of an amorphous silicon thin film, there is an advantage that a substrate having a low melting point and a low cost glass or the like may be used as the substrate. However, since there is no regularity in the arrangement of silicon atoms in the amorphous silicon thin film, the amorphous silicon thin film transistor has a disadvantage in that its electrical characteristics are inferior.

On the other hand, the polysilicon thin film forming the channel layer of the polysilicon thin film transistor has considerably better electrical characteristics than the amorphous silicon thin film. For this reason, the polysilicon thin film transistor has an advantage that the device can be highly integrated.

The polysilicon thin film may be formed by crystallizing the amorphous silicon thin film formed on the substrate through a low temperature deposition process. At this time, as a method for crystallizing the amorphous silicon thin film to a polysilicon thin film (Solid Phase Crystallization (SPC) method, Metal Induced Crystallization (MIC) method, Excimer Laser Annealing (ELA) method, etc.) There is this. Among these, the excimer laser annealing method is most widely used. This is because the substrate is not thermally damaged by the excimer laser for a short time, so that the substrate may not be damaged.

Meanwhile, in order to crystallize the amorphous silicon thin film formed on the substrate into a polysilicon thin film by an excimer laser annealing method, a silicon crystallization apparatus including a beam generator, a beam control unit, and a stage is used.

Conventional crystallization processes of crystallizing an amorphous silicon thin film formed on a substrate using the silicon crystallization equipment into a polysilicon thin film may be performed as a primary and a secondary scan process. This will be outlined as follows.

First, a substrate on which an amorphous silicon thin film is formed is mounted on a stage, and then a laser beam is generated using a beam generator.

Then, the beam control unit is used to uniform the energy density of the laser beam generated by the beam generator.

Subsequently, when a laser beam having a uniform energy density is irradiated to a predetermined region on the substrate, the amorphous silicon of the predetermined region is crystallized to polysilicon while melting and cooling.

The stage is then moved so that the laser beam is irradiated across the substrate in a manner that scans other areas on the substrate. Accordingly, the entire amorphous silicon thin film may be crystallized into a polysilicon thin film. (1st scan process)

After the primary scanning process is finished, the stage moves back to the initial position and recrystallizes the polysilicon thin film formed by the primary scanning process in the same manner as the primary scanning process. (2nd scan process)

On the other hand, if the surface state of the polysilicon thin film is uneven, the interface characteristics between the polysilicon thin film and the insulating film formed to cover the same is worsened, there is a problem that the device characteristics of the polysilicon thin film transistor is reduced.

In order to prevent this, the conventional crystallization process consists of a primary and a secondary scan process, as described above. Specifically, since the laser beam having a high energy density is used to crystallize the amorphous silicon thin film during the primary scan process, the surface of the polysilicon thin film formed after the primary scan process may be somewhat rough. Accordingly, by performing the second scan process using a laser beam having a lower energy density than the first scan process, the surface roughness of the polysilicon thin film may be reduced by recrystallization of the polysilicon thin film.

However, since the secondary scan process is performed after the primary scan process is completed as described above, there is a problem in that the crystallization process time of the amorphous silicon thin film is increased. For this reason, productivity of a flat panel display device may deteriorate.

Therefore, the technical problem to be achieved by the present invention is to minimize the surface roughness of the polysilicon thin film formed through the crystallization process of the amorphous silicon thin film and to reduce the crystallization process time of the amorphous silicon thin film and silicon crystallization using the same To provide a way.

Further technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above are clearly understood by those skilled in the art from the following description. Can be understood.

Silicon crystallization equipment according to the present invention for achieving the above technical problem is a beam generator for generating a laser beam; A beam adjuster which makes the energy density of the generated laser beam uniform; A beam splitter configured to split the laser beam having the uniform energy density so that the laser beam having the uniform energy density travels in different paths; And a stage for seating and moving the substrate on which the amorphous silicon thin film crystallized by the divided laser beam is formed.

Here, the amorphous silicon thin film may be simultaneously crystallized in different regions on the substrate by the divided laser beam.

The beam splitter may include a plurality of mirrors disposed to be spaced apart from each other.

The plurality of mirrors may divide the laser beam having the uniform energy density by reflecting or transmitting the laser beam having the uniform energy density.

Here, the divided laser beams may have different beam widths.

Here, the generated laser beam may be an excimer laser beam.

On the other hand, the silicon crystallization method according to the present invention for achieving the above technical problem is a step of seating a substrate on which an amorphous silicon thin film is formed; Generating a laser beam for crystallizing the amorphous silicon thin film using a beam generator; Making the energy density of the generated laser beam uniform by using a beam control unit; Dividing the laser beam having a uniform energy density by using a beam splitter such that the laser beam having a uniform energy density travels in different paths; And crystallizing the amorphous silicon thin film using the split laser beam.

The method may further include moving the stage such that the divided laser beam is irradiated to the substrate in a manner of scanning the substrate.

Here, the amorphous silicon thin film may be simultaneously crystallized in different regions on the substrate by the divided laser beam.

Here, the generated laser beam may be an excimer laser beam.

The beam splitter may include a plurality of mirrors disposed to be spaced apart from each other.

The plurality of mirrors may divide the laser beam having the uniform energy density by reflecting or transmitting the laser beam having the uniform energy density.

Here, the divided laser beams may have different beam widths.

Specific details of other embodiments are included in the detailed description and the drawings. Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings.

Hereinafter, a silicon crystallization apparatus and a silicon crystallization method using the same according to an embodiment of the present invention with reference to the accompanying drawings will be described in detail.

1 is a view schematically illustrating the configuration of a silicon crystallization equipment according to an embodiment of the present invention.

Referring to FIG. 1, the silicon crystallization apparatus 100 according to an exemplary embodiment of the present invention includes a beam generator 110, a beam adjuster 120, a beam splitter 130, and a stage 140. Here, the silicon crystallization equipment 100 may be operated by a power source provided from the outside.

The beam generator 110 may generate the laser beam LB1, and may emit the generated laser beam LB1 to the beam adjuster 120. The laser beam LB1 generated by the beam generator 110 may be, for example, an excimer laser beam in the form of a pulse having a short irradiation period of several tens of ns and a frequency of several thousand Hz. Here, the medium of the excimer laser beam may be any one of dimer complexes excited in a halogenated inert gas. Specifically, the medium of the excimer laser beam may be any one of the dimer complexes ArF (193 nm), KrF (248 nm), XeCl (308 nm) and XeF (351 nm).

The beam adjuster 120 may uniform the energy density of the laser beam LB1 incident from the beam generator 110, and divide the laser beam LB2 uniformed by the beam adjuster 120 into a beam splitter. You can exit 130. Here, the laser beam LB2 having uniform energy density by the beam adjuster 120 may be a linear laser beam LB2 having a predetermined rectangular cross-sectional area.

The beam adjuster 120 may include an attenuator, a homogenizer, or the like in order to make the energy density of the laser beam LB1 incident from the beam generator 110 uniform. In addition, the beam adjuster 120 may further include an optical system composed of a plurality of lenses.

The beam splitter 130 may split the laser beam LB2 incident from the beam adjuster 120. This is to advance the laser beam LB2 incident from the beam adjuster 120 in different paths. In this case, since the laser beams LB3 and LB4, which are divided by the beam splitter 130 and travel in different paths, may be irradiated to different areas on the substrate 150, each of the different areas may be amorphous. The crystallization process of the silicon thin film 152 may be performed at the same time.

The beam splitter 130 may include a plurality of mirrors 132 and 134 disposed to be spaced apart from each other to split the laser beam LB2 incident from the beam adjuster 120. The number of mirrors is not limited because the number of mirrors may vary depending on the crystallinity of the amorphous silicon thin film 152 and the size of the substrate 150.

Hereinafter, for convenience of description, a case in which the beam splitter 130 includes two mirrors 132 and 134, that is, the first and second mirrors 132 and 134 will be described as an example.

The first and second mirrors 132 and 134 constituting the beam splitter 130 are incident from the beam adjuster 120 by reflecting and / or transmitting the laser beam LB2 incident from the beam adjuster 120. The laser beam LB2 may be divided. In this case, the ratio of the reflectance and the transmittance of each of the first and second mirrors 132 and 134 may be appropriately adjusted to adjust the split ratio of the laser beam LB2 incident from the beam adjuster 120.

For example, a ratio of reflectance and transmittance of the first mirror 132 to which the laser beam LB2 is directly incident from the beam adjuster 120 is set to 70:30, and is reflected by the first mirror 132. The ratio of the reflectance and the transmittance of the second mirror 134 to which the laser beam LB4 is incident may be set to 100: 0 (or a ratio close to that). Here, each of the laser beam LB3 transmitted through the first mirror 132 and the laser beam LB4 reflected by the second mirror 134 may be simultaneously irradiated to each of different regions on the substrate 150.

The stage 140 may seat and move the substrate 150 on which the amorphous silicon thin film 152 is formed. Here, the substrate 150 may be vacuum adsorbed on the stage 140.

Due to the movement of the stage 140, each of the laser beams LB3 and LB4 divided by the beam splitter 130 and traveling in different paths irradiates the substrate 150 in a manner that scans the substrate 150. Can be. At this time, the stage 140 may move minutely.

FIG. 2 is a diagram for describing a width and a scan pitch of a laser beam divided by the beam splitter illustrated in FIG. 1.

When the stage 140 moves slightly, as shown in FIG. 2, each of the laser beam LB3 having the first beam width BW1 and the laser beam LB4 having the second beam width BW2 is The laser beams LB3 and LB4 may be irradiated onto the substrate 150 while being overlapped and scanned. In this case, the degree of overlap of the laser beams LB3 and LB4 may be determined by the scan pitches SP1 and SP2 of the laser beams LB3 and LB4.

As such, the reason why the stage 140 is slightly moved to overlap each of the laser beams LB3 and LB4 with respect to each of the laser beams LB3 and LB4 is due to the characteristics of the excimer laser beam. This will be described with reference to FIGS. 2 and 3.

FIG. 3 is a diagram for schematically describing an energy density according to a width of a laser beam divided by the beam splitter illustrated in FIG. 1.

2 and 3, the profile of the excimer laser beam does not have a square wave shape like other laser beams, but has a trapezoidal shape. For this reason, crystallization of the amorphous silicon thin film 152 may not occur below a predetermined energy density E1. Accordingly, in consideration of this, the laser beams LB3 and LB4 are superposed on the laser beams LB3 and LB4 so that the amorphous silicon thin film 152 may be crystallized over the entire region of the substrate 150. .

Meanwhile, the polysilicon thin film 154 formed in a predetermined region on the substrate 150 by crystallization by the irradiation of the laser beam LB4 reflected by the second mirror 134 may have the first mirror as the stage 140 moves. Recrystallization may be performed by irradiation of the laser beam LB3 transmitted through 132. Since the stage 140 may proceed without moving back to the initial position, the crystallization process time of the amorphous silicon thin film 152 may be shortened. Here, the amorphous silicon thin film 152 may be crystallized into the polysilicon thin film 154 by the irradiation of the laser beam LB4 reflected by the second mirror 134, and the laser transmitted through the first mirror 132. Since the polysilicon thin film 154 may be recrystallized by the irradiation of the beam LB3, the first beam width BW1 may be smaller than the second beam width BW2.

Hereinafter, a method of crystallizing the amorphous silicon thin film 152 using the silicon crystallization apparatus 100 according to the embodiment of the present invention will be described in detail.

First, the substrate 150 on which the amorphous silicon thin film 152 is formed is mounted on the stage 140. Here, the amorphous silicon thin film 152 may be formed on the substrate through chemical vapor deposition (CVD).

Thereafter, the laser beam LB1 for crystallizing the amorphous silicon thin film 152 is generated using the beam generator 110. Here, the laser beam LB1 generated by the beam generator 110 may be an excimer laser beam.

Thereafter, the energy density of the laser beam LB1 generated by the beam generator 110 is uniformed using the beam adjuster 120.

Subsequently, the laser beam LB2 having the uniform energy density by the beam adjusting unit 120 is divided using the beam splitter 130, so that the energy beam has the uniform energy density by the beam adjusting unit 120. Proceed to different paths. The beam splitter 130 may include a plurality of mirrors 132 and 134 disposed to be spaced apart from each other.

Subsequently, each of the laser beams LB3 and LB4 divided by the beam splitter 130 and traveling in different paths is simultaneously irradiated onto each of the different regions on the substrate 150. As a result, crystallization of the amorphous silicon thin film 152 is performed in each of the different regions on the substrate 150.

Thereafter, the stage 140 is divided so that each of the laser beams LB3 and LB4 divided by the beam splitter 130 and propagates in different paths is irradiated onto the substrate 150 by scanning the substrate 150. While moving, the crystallization process is performed over the entire substrate 150.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains can realize that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. I can understand that.

Therefore, since the embodiments described above are provided to completely inform the scope of the invention to those skilled in the art, it should be understood that they are exemplary in all respects and not limited. The invention is only defined by the scope of the claims.

According to the present invention, the surface roughness of the polysilicon thin film formed through the crystallization process of the amorphous silicon thin film can be minimized and the crystallization process time can be shortened because the stage does not have to be moved to the initial position.

Claims (13)

A beam generator for generating a laser beam; A beam adjuster which makes the energy density of the generated laser beam uniform; A beam splitter configured to split the laser beam having the uniform energy density so that the laser beam having the uniform energy density travels in different paths; And A stage for seating and moving a substrate on which an amorphous silicon thin film crystallized by the divided laser beam is formed. Silicon crystallization equipment comprising a. The method of claim 1, And the amorphous silicon thin film is simultaneously crystallized in different regions on the substrate by the divided laser beam. The method of claim 1, And the beam splitter comprises a plurality of mirrors disposed to be spaced apart from each other. The method of claim 3, And said plurality of mirrors divide the laser beam with uniform energy density by reflecting or transmitting the laser beam with uniform energy density. The method of claim 1, And wherein said split laser beam has different beam widths. The method of claim 1, And the generated laser beam is an excimer laser beam. Mounting a substrate on which an amorphous silicon thin film is formed on a stage; Generating a laser beam for crystallizing the amorphous silicon thin film using a beam generator; Making the energy density of the generated laser beam uniform by using a beam control unit; Dividing the laser beam having a uniform energy density by using a beam splitter such that the laser beam having a uniform energy density travels in different paths; And Crystallizing the amorphous silicon thin film using the split laser beam Silicon crystallization method comprising a. The method of claim 7, wherein Moving the stage such that the split laser beam is irradiated to the substrate in a manner that scans the substrate Silicon crystallization method further comprising. The method of claim 7, wherein And the amorphous silicon thin film is simultaneously crystallized in different regions on the substrate by the divided laser beam. The method of claim 7, wherein Wherein the generated laser beam is an excimer laser beam. The method of claim 7, wherein And the beam splitter comprises a plurality of mirrors disposed to be spaced apart from each other. The method of claim 11, And said plurality of mirrors divide the laser beam with uniform energy density by reflecting or transmitting the laser beam with uniform energy density. The method of claim 7, wherein And wherein said divided laser beams have different beam widths.

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