KR20070072200A - Apparatus for crstallization and method for crystallizing silicon - Google Patents

Abstract

A silicon crystallizing apparatus and a silicon crystallizing method using the same are provided to enhance the uniformity of silicon crystallization at an overlap region by using a triangle type structure of both end portions of a mask pattern. A silicon crystallizing apparatus includes a laser beam generating unit for generating a laser beam, a substrate stage, a mask, a reduction lens, a mask moving stage. The substrate stage is arranged opposite to the laser beam generating unit. The substrate stage moves in X and Y directions. The mask(100) is arranged between the substrate stage and the laser beam generating unit. The reduction lens is used for reducing the laser beam. The mask moving stage is connected with the mask in order to move the mask. An edge portion(131a) of a mask pattern(131) of the mask is formed like a triangle type structure.

Description

Silicon crystallization apparatus and silicon crystallization method using the same {APPARATUS FOR CRSTALLIZATION AND METHOD FOR CRYSTALLIZING SILICON}

1 to 3 are diagrams for explaining silicon crystallization using a sequential side-solidification technique.

4 illustrates a mask used for silicon crystallization according to a prior art example.

5 is a view showing a mask for silicon crystallization according to another embodiment of the prior art.

FIG. 6 is a view showing the shape of a silicon film during laser beam irradiation using a silicon crystallization mask according to another embodiment of the prior art of FIG. 5;

Figure 7 is a photograph showing the distortion of the edge shape due to the interference of the pattern obtained by Figure 6;

8 schematically illustrates a silicon crystallization apparatus according to the present invention.

9 is a view showing a silicon crystallization mask according to the present invention.

FIG. 10 is a view showing the form of a silicon film at the time of laser beam irradiation using the silicon crystallization mask of FIG. 9; FIG.

FIG. 11 is a photograph showing a crystallization state of the silicon film of FIG. 10.

12 is a view showing a crystallization form of a silicon film during laser beam irradiation while moving the silicon crystallization mask stage according to the present invention.

-Code description of main parts of drawing-

50 crystallization apparatus 53 laser beam

55 laser beam generator 57 reduction lens

100: crystallization mask 110: mask moving stage

120: substrate 131: mask pattern

131a: edge portion 140: amorphous thin film

141: Irradiated amorphous thin film 141a: edge portion

143: non-irradiated amorphous thin film 150: substrate stage

133, 145: baseline

The present invention relates to a crystallization apparatus and a silicon crystallization method used, and more particularly, to a crystallization apparatus for crystallizing a silicon film by sequential lateral solidification (SLS) technology and a silicon crystallization method using the same. .

Sequential lateral solidification (SLS) is a technique used for laser crystallization, in which silicon grain grows perpendicularly to the interface at the interface between the liquid and solid silicon regions. Use

In this regard, the crystallization method of the silicon thin film by the SLS technique will be described with reference to the drawings.

1 to 3 are views for explaining a process of crystallizing an amorphous silicon thin film by using the SLS technology, and shows a simplified state of growth of silicon grain according to the number of laser irradiation times.

Referring to FIG. 1, the amorphous silicon thin film (the whole drawing) is first irradiated with a straight laser beam having a predetermined size. At this time, the laser of sufficient energy to melt the silicon part 11 irradiated with the laser beam is supplied.

In addition, the silicon portion 11 exposed to the laser beam is solidified soon after melting. In this process, silicon grains 11a are laterally grown from both interfaces 11b of the solid silicon region not irradiated with the laser beam and the liquid silicon region irradiated with the laser beam.

The growth length of silicon grains (hereinafter referred to as the growth length of silicon grains per laser pulse) formed by one laser beam irradiation is determined according to the size of the laser energy and the thickness of the silicon thin film.

The solidification of the silicon region melted by the laser beam is divided into the following aspects.

When the width W of the silicon melting region is smaller than twice the growth length of silicon grain per laser pulse, as shown in FIG. 1, the silicon grain 11a grown at both interfaces 11b collides at the center of the silicon melting region. Crystallization occurs in such a way that growth stops.

Here, reference numeral 11c denotes a grain boundary formed by collision of silicon grains 11a laterally grown at both interfaces 11b of the molten silicon portion by primary irradiation of the laser beam.

In addition, when the width W of the silicon melting region is larger than twice the growth length of silicon grains per laser pulse, although not shown in the figure, the silicon grains 11a grown at both interfaces 11b are the central portion of the silicon melting region. Crystallization occurs in such a way that growth stops as it collides with the fine silicon grains generated by cooling.

2, the laser beam is secondarily irradiated after moving the amorphous silicon thin film to a degree smaller than the growth length of silicon grain per laser pulse. At this time, the laser of sufficient energy to melt all the silicon part irradiated with the laser beam is supplied. As a result, the silicon part exposed to the laser beam is solidified soon after melting.

In this process, silicon grains 11a and 13a grow laterally from both interfaces 13b of the molten silicon portion by secondary irradiation of the laser beam. At this time, the silicon grains 11a formed by the primary irradiation of the laser beam continue to grow laterally by acting as seeds of crystallization at the interface 13b. Thus, the silicon grain 13a has a result of growing in the direction in which the laser beam moves as shown in the figure.

Reference numeral 13c denotes a grain boundary formed by collision of silicon grains 11a and 13a laterally grown at both interfaces 13b of the molten silicon portion by secondary irradiation of the laser beam.

Referring to FIG. 3, the silicon crystal film 11a is moved to an amorphous silicon thin film as described above, and the silicon crystal 11a is repeatedly n-times irradiated with a laser beam to melt and solidify the silicon thin film to obtain a desired size of the silicon grain 11a. To grow. The silicon grain 11a is laterally grown in the laser scanning direction at the initial formation position.

As described above, when using the SLS technology, it is possible to dramatically increase the size of the silicon grain.

When the SLS technology is applied to a large-area silicon thin film, silicon crystallization is performed by simultaneously irradiating a large-area silicon substrate with a plurality of laser beams to improve yield.

Fig. 4 shows a mask used in the crystallization process of a large area silicon thin film in the prior art.

Referring to FIG. 4, in order to pattern one laser beam into a plurality of laser beams, a silicon crystallization process may be performed using a mask in which a plurality of rectangular mask patterns are formed.

As shown in Fig. 4, in the case of using the mask 20 having a plurality of linearly shaped light transmissive areas 21a arranged in the light non-transmissive area 21b, the shape is as many as the number of the light transmissive areas 21a. As many laser beams can be provided and used simultaneously.

Silicon crystallization by SLS technology is performed using a plurality of straight laser beams obtained by passing through a plurality of mask patterns shown in FIG.

Meanwhile, a method of crystallizing silicon according to the prior art will be described with reference to FIGS. 5 to 7.

5 is a view showing a mask for silicon crystallization according to another embodiment of the prior art.

FIG. 6 is a diagram illustrating the shape of a silicon film during laser beam irradiation using a silicon crystallization mask according to another exemplary embodiment of FIG. 5.

FIG. 7 is a photograph showing distortion of an edge shape caused by interference of the pattern obtained by FIG. 6.

Referring to FIG. 5, after preparing a crystallization mask 30 in which a plurality of rectangular mask patterns 31 are formed, the crystallization mask 30 is formed on a silicon film (not shown) formed on a substrate (not shown). Place it in

Next, referring to FIG. 6, the laser beam is irradiated to the silicon film 41 through the crystallization mask 30, and the laser beam is irradiated to the mask-shaped silicon film 41. In this case, the laser beam is irradiated only to the silicon film 41a portion, and the silicon film 41a portion means a complete melting region due to the laser beam irradiation. In addition, the edge portion of the completely melting region is formed to be round, as shown in Figure 7, because the edge shape (edge shape) due to interference appears distorted.

Therefore, non-uniform crystallization region is generated in the overlapping region of the silicon film, thereby deteriorating device characteristics.

Accordingly, the present invention has been made to solve the above problems of the prior art, a silicon crystallization apparatus and silicon using the same that can improve the uniformity of silicon crystallization of the overlap region by changing the mask shape to a triangular form during laser crystallization The purpose is to provide a crystallization method.

Silicon crystallization apparatus according to the present invention for achieving the above object, the laser beam generating device for generating a laser beam; A substrate stage disposed corresponding to the laser beam generator and moving in an X direction or a Y direction; A mask disposed between the X-Y stage and the laser generator, the edges of the plurality of mask patterns passing through the laser beam overlap each other with respect to a reference line; A reduction lens for reducing the laser beam passing through the mask to a predetermined ratio; And a mask moving stage connected to the mask and moving the mask minutely.

In addition, the silicon crystallization method according to the present invention for achieving the above object comprises the steps of preparing a substrate on which an amorphous silicon thin film is deposited; Securing the substrate to a substrate stage; Positioning a mask on the substrate, the mask having edges of a plurality of mask patterns overlapping with respect to a reference line; Irradiating a laser beam through a plurality of mask patterns of the mask; Crystallizing a plurality of regions of the amorphous silicon thin film corresponding to the position of the mask pattern with a first silicon crystal; Moving the mask by a small distance using the mask moving stage and irradiating a laser beam to crystallize an amorphous silicon region proximate to the first silicon crystal; And repeating this crystallization process to crystallize the amorphous silicon thin film.

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

8 is a view schematically showing a silicon crystallization apparatus according to the present invention.

9 is a view showing a mask for silicon crystallization according to the present invention.

FIG. 10 is a view showing the form of a silicon film during laser beam irradiation using the silicon crystallization mask of FIG. 9.

FIG. 11 is a photograph showing a crystallization state of the silicon film of FIG. 10.

12 is a view showing a crystallization form of a silicon film during laser beam irradiation while moving the silicon crystallization mask stage according to the present invention.

Referring to FIG. 8, the crystallization apparatus 50 used for silicon crystallization includes a laser generator 55 generating a laser beam 53, and a laser beam 53 emitted through the laser apparatus 55. A focusing lens 55 for focusing the light, a mask 100 dividing the laser beam 53 through a slit, that is, a mask pattern, and a laser beam positioned below the mask 100 and passing through the mask 100. And a reduction lens 57 for reducing the size of the 53 to a predetermined ratio.

In addition, the X-Y stage 150 to which the substrate 120 on which the amorphous silicon thin film 140 is formed is fixed is positioned at a position corresponding to the mask 100.

In addition, the mask 100 is fixed to the mask movement stage 110 by a predetermined method, and may move a minute distance of several μm under the control of the mask movement stage 110. Since the mask stage 110 is small in size, the time for moving and stopping is significantly shorter than that of the X-Y stage 150.

Therefore, in the process of crystallizing the amorphous silicon thin film 140 in units of blocks, the micro distance movement of the laser beam 53 in one block is controlled by the movement of the mask 100 using the mask stage 110. That is, the area to which the laser beam 53 is irradiated within one block is defined as the movement of the mask, not the movement of the specimen.

In this case, since the movement range of the mask stage 110 is limited, the X-Y stage 150 is used only when the crystal region of the substrate is moved in units of blocks.

When the mask stage 110 is used as described above, the time required for crystallization of the thin film can be shortened more than when only the X-Y stage 150 is used.

A method of crystallizing a silicon thin film using the silicon crystallization apparatus according to the present invention having the above configuration will be described below with reference to the accompanying drawings.

Referring to FIG. 9, a mask 100 for silicon crystallization having a plurality of mask patterns 131 having edges formed in a triangular shape instead of a conventional rectangular shape is manufactured. In this case, the plurality of mask patterns 131 are formed such that the edge portions of the mask patterns 131 in the form of triangles overlap each other by a predetermined width about the reference line 133.

Next, as shown in FIG. 8, after fixing the substrate 120 on which the amorphous silicon thin film 140 is deposited to the X-Y stage 150, the mask 100 for silicon crystallization is positioned on the substrate 120.

Subsequently, a laser beam is irradiated onto the amorphous silicon thin film 140 formed on the substrate 120 through the crystallization mask 100. In this case, the laser beam 53 is divided through a plurality of mask patterns 131 formed on the mask 100 to partially melt the amorphous silicon thin film 141 in one block to form a liquid silicon state. That is, the part of the amorphous silicon thin film 141 partially melted thus represents a complete melting region due to the laser beam irradiation. In addition, as shown in FIG. 10, the edge portion 131a of the overlapping mask pattern 131 causes diffraction to occur due to light interference of the laser beam between the upper and lower sides, thereby causing the edge of the amorphous thin film 141 to which the laser beam is irradiated. Near complete melting region is created at 141a.

Then, when the laser beam irradiation is stopped, the liquid silicon rapidly cools and grain grows at the boundary between the amorphous silicon and the liquid silicon. In this case, the size of the grain may be controlled according to the width A of the mask pattern 131.

Subsequently, the mask 131 is moved by a number μm corresponding to a distance equal to or smaller than the width of the grain using the mask stage 110 of FIG. 8.

As such, the mask pattern 131 of the mask 100 is positioned close to the crystallized region 141 of the amorphous silicon thin film, thereby obtaining a result as if the substrate is moved.

When the laser beam is irradiated to the mask 100 moved by the minute distance, the laser beam passes through the mask pattern 131 moved by the mask, and thus the portion of the crystal region in the first irradiation and the region adjacent to the laser beam is moved. The amorphous silicon thin film 143 is dissolved.

When the laser beam irradiation is stopped again, the grain formed during the first irradiation acts as a seed to obtain a laterally grown crystal.

As described above, the process as described above is repeated to complete growth of one block of silicon crystal.

Then, after the crystallization of one block is finished, the crystal growth process of the next block without crystal growth of silicon is started. In this case, when the blocks are moved, the crystallization process may be performed by moving the substrate stage (not shown) larger than the mask stage (not shown) to the X axis or the Y axis. That is, as shown in FIG. 11, the mask pattern overlapped around the reference line 133 by irradiating a laser beam through the mask 100 having the plurality of mask patterns 131 while continuously moving the stage on which the substrate is disposed. The edge portion 141a of the silicon thin film 141 irradiated in a triangular shape of the edge portion 131a of the mask pattern 131 by causing diffraction phenomenon by light interference of the laser beam to occur at the edge portion 131a of 131. The uniformity of silicon crystallization in) is improved.

Therefore, as shown in FIG. 12, which is a photograph showing a cross section of the “C” portion of FIG. 11, it can be seen that the uniformity is improved without the occurrence of a non-uniform hook-like form as before.

As described above, according to the silicon crystallization mask and the silicon crystallization method using the same according to the present invention has the following effects.

When designing a mask for a two-shot SLS process, the edge shape is changed from a rectangular shape to a triangular shape, thereby improving uniformity in overlapping laser beams.

In addition, by changing the edge portion to a triangular shape when designing the mask, a part of the edge portion of the mask pattern arranged up and down is overlapped around the reference line, so that the completely melted area caused by diffraction phenomenon artificially due to the interference between the top and bottom edges of the edge portion is designed. By generating a near complete melting region, non-uniformity can be eliminated during laser beam overlap due to stage movement of the substrate which proceeds for crystallization of the silicon thin film formed on the substrate.

On the other hand, while described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications of the present invention without departing from the spirit and scope of the invention described in the claims below And can be changed.

Claims (5)

A laser beam generator for generating a laser beam; A substrate stage disposed corresponding to the laser beam generator and moving in an X direction or a Y direction; A mask disposed between the X-Y stage and the laser generator, the edges of the plurality of mask patterns passing through the laser beam overlap each other with respect to a reference line; A reduction lens for reducing the laser beam passing through the mask to a predetermined ratio; And And a mask moving stage connected to the mask and moving the mask minutely. The silicon crystallization apparatus of claim 1, wherein edge portions of both sides of the mask pattern are formed in a triangular shape. Preparing a substrate on which an amorphous silicon thin film is deposited; Securing the substrate to a substrate stage; Positioning a mask on the substrate, the mask having edges of a plurality of mask patterns overlapping with respect to a reference line; Irradiating a laser beam through a plurality of mask patterns of the mask; Crystallizing a plurality of regions of the amorphous silicon thin film corresponding to the position of the mask pattern with a first silicon crystal; Moving the mask by a small distance using the mask moving stage and irradiating a laser beam to crystallize an amorphous silicon region proximate to the first silicon crystal; And Repeating this crystallization process to crystallize the amorphous silicon thin film. The silicon crystallization method of claim 3, wherein edge portions of both sides of the mask pattern are formed in a triangular shape. The silicon crystallization method of claim 3, wherein diffraction occurs due to laser beam interference at edge portions of the mask pattern overlapping each other about the reference line.

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