KR100542990B1 - Method for crystalizing armophous silicon, mask pattern and flat panel display device using polysilicon thin film fabricated by the same method - Google Patents

Abstract

The present invention relates to a method of crystallizing an amorphous silicon thin film, a mask pattern, and a flat panel display device using a polycrystalline silicon thin film manufactured using the same. A first mask pattern for crystallizing amorphous silicon in one mask by irradiating the same laser. And a crystallization method of an amorphous silicon thin film, characterized in that a mask having a second mask pattern for performing a dehydrogenation process and a mask pattern used therein and a flat panel display using a polycrystalline silicon thin film manufactured by the method Providing the device can reduce the process time and cost, and can provide a flat panel display device with excellent current characteristics.

Polycrystalline Silicon, Dehydrogenation, Mask Pattern

Description

Crystallization method of amorphous silicon thin film, mask pattern and flat panel display device using polycrystalline silicon thin film manufactured using the same.

1A and 1B are diagrams showing a SLS crystallization method and a schematic form of polycrystalline silicon manufactured by the method according to a conventional embodiment.

FIG. 2A is a diagram illustrating a mask pattern according to an embodiment of the present invention, and FIG. 2B is a graph showing a change in energy density when scanning with a laser having a constant energy from X to Y of FIG. 2A.

3 is a diagram illustrating a mask pattern according to another exemplary embodiment of the present invention.

[Industrial use]

The present invention relates to a method for crystallizing an amorphous silicon thin film, a mask pattern, and a flat panel display device using a polycrystalline silicon thin film manufactured by using the same. A crystal display method of a thin film, a mask pattern, and a flat panel display device using a polycrystalline silicon thin film manufactured using the same.

[Prior art]

Using SLS crystallization technology, polycrystalline or monocrystalline particles can form large silicon grains on a substrate, and when TFTs are manufactured, they exhibit characteristics similar to those of TFTs made of monocrystalline silicon. It is reported that it can be obtained.

As a method of implementing this, as disclosed in PCT International Patent WO 97/45827 and US Pat. No. 6,322,625, after deposition of amorphous silicon, SLS technology converts amorphous silicon on the entire substrate into polycrystalline silicon, or select regions on the substrate. Techniques for crystallizing bays are disclosed.

As such, in the technique of crystallization, the amorphous silicon layer is energy treated with a laser or the like to crystallize, and during the process the silicon layer is crystallized by melting and continuing cooling. Crystallization occurs through the crystal growth process where small crystal seeds that are not dissolved by laser energy grow to form large crystals. When a plurality of seeds are present at different locations in the unmelted silicon, the seeds grow to form polycrystalline silicon.

Each crystal of polycrystalline silicon formed by this process has its own boundary. When polycrystalline silicon is used as the channel region of a semiconductor device, the charge mobility is generally low due to the effect of grain boundaries.

In a liquid crystal display device having a TFT made of low temperature polycrystalline silicon, the active layer of the TFT is deposited by depositing an amorphous silicon layer by Plasma Enhanced Chemical Vapor Deposition (PECVD) and then annealing or crystallizing the amorphous silicon layer using laser annealing technology. Is formed.

For processes using PECVD, amorphous silicon containing about 15% hydrogen is allowed to deposit. Therefore, it is necessary to heat-treat the amorphous silicon layer containing hydrogen at a temperature of 400 ° C. or higher before the laser annealing process. That is, when the amorphous silicon layer contains a large amount of hydrogen, the silicon thin film layer is separated by the ablation phenomenon during laser irradiation, and the surface of the polycrystalline silicon layer is roughened, thereby deteriorating current characteristics.

Therefore, when the amorphous silicon foil using PECVD is laminated, dehydrogenation is performed by high temperature heating in a furnace or CVD chamber. In particular, dehydrogenation requires efficient heat treatment for a long time at a high temperature of 450 ° C. or higher in a furnace, which may cause warpage and shrinkage of the substrate, which takes a lot of time.

On the other hand, when the amorphous silicon layer is formed by low pressure CVD (LPCVD), since it contains relatively low hydrogen, laser annealing is possible without the need for a dehydrogenation process. In addition, since the concentration of hydrogen contained is low, the surface of the polycrystalline silicon layer formed by crystallization becomes small.

However, this method has a problem of low production efficiency.

Therefore, US Patent No. 6,174,790 discloses dehydrogenation by irradiating a laser of lower energy density than crystallization to provide a method for simultaneously dehydrogenation and crystallization, and then crystallizing by irradiating a laser of higher energy density. Is done. However, this method also has the disadvantage of high process time and cost.

The present invention has been made to solve the problems described above, an object of the present invention is to provide a mask pattern and an amorphous silicon thin film manufacturing method that can proceed simultaneously with dehydrogenation and crystallization of amorphous silicon.

In addition, it is to provide a flat panel display device using a polycrystalline silicon thin film manufactured using such a method.

The present invention to achieve the above object,

The present invention

It provides a crystallization method of an amorphous silicon thin film characterized by using a mask having a first mask pattern for crystallizing the amorphous silicon to a single mask to irradiate the same laser and a second mask pattern for performing a dehydrogenation process. do.

In addition, the present invention

It provides a flat panel display device characterized in that using the polycrystalline silicon thin film manufactured by the above manufacturing method.

In addition, the present invention

A crystallization mask pattern is provided which satisfies the conditions of the following formula so that crystallization and dehydrogenation can be simultaneously performed using the same laser in crystallization of amorphous silicon.

[expression]

a + b <2 μm,

Here, a represents the size of the pattern region through which the laser transmits, and b represents the size of the pattern region through which the laser does not transmit.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

1A and 1B illustrate a conventional SLS crystallization method and a schematic form of polycrystalline silicon produced by the method.

As shown in FIG. 1A, a mask used in a method of crystallizing amorphous silicon by a sequential lateral solidification (SLS) method includes a region in which a laser beam is transmitted (width: a) and a region that is not able to transmit (width: b) are continuously arranged. Has a form.

The widths a and b are defined as areas where light is transmitted and areas that are not transmitted by the mask when measured at a straight length in a direction perpendicular to the primary grain boundaries.

When the laser beam is irradiated to the amorphous silicon thin film layer through the mask as described above, the polycrystalline silicon crystal grains are prevented from lateral growth due to the dissolution and solidification of the amorphous silicon in the region where the laser beam is transmitted. The branched polycrystalline silicon thin film layer is formed, and amorphous silicon remains in the region where the laser beam does not transmit.

As shown in FIG. 1B, when the mask is moved by the stage movement, the amorphous silicon thin film layer and a portion of the already crystallized polycrystalline silicon layer are overlapped so that the laser beam is irradiated, the amorphous silicon and the crystalline silicon are dissolved and then cooled to cover the mask. Silicon atoms are attached to the undissolved preformed polycrystalline silicon crystal grains so that the crystal grains grow to have elongated columnar crystal grains in one direction having a width W.

On the other hand, when the laser beam is superimposed again, the preformed crystal grains of the overlapped portions are dissolved again and the width W of the crystallized polycrystalline silicon grains is changed by the width o of the region in which the laser beam is dissolved.

FIG. 2A is a diagram illustrating a mask pattern according to an embodiment of the present invention, and FIG. 2B is a graph showing a change in energy density when scanning with a laser having a constant energy from A to B of FIG. 2A.

Referring to FIG. 2A, a mask pattern according to an exemplary embodiment of the present invention includes a mask pattern region A for crystallizing amorphous silicon and a mask pattern region B for dehydrogenation.

In the mask pattern, the size of the laser penetrating region is larger in the case of A and b = 3a + 4 in the case of A or B, and the size of the laser transmission region of the mask pattern is increased. In this case, it can be seen that the laser energy density changes as shown in FIG. 2B when proceeding while scanning the laser from X to Y while irradiating the same laser. That is, it can be seen that when the size of the region where the laser is transmitted is small, energy scattering occurs due to scattering of light. The above relation is not particularly meaningful and is merely a b size that can be used in the crystallization process.

Therefore, the amorphous silicon of the portion irradiated by the laser irradiation must be completely dissolved, but in the case of B region, the amorphous silicon is not completely dissolved but only partially dissolved, so that only the dehydrogenation process is performed.

Therefore, when irradiating a laser while moving a mask from X to Y direction, amorphous silicon first crystallizes and then dehydrogenation occurs. On the other hand, in the case of irradiating a laser while moving the mask from Y to X direction, dehydrogenation occurs first and then crystallization proceeds, so that crystallization and dehydrogenation may proceed simultaneously.

As the laser crystallization method used in the present invention, a sequential lateral solidification (SLS) method is used.

In general, when the SLS crystallization method is used, the energy density required for crystallization is about 500 mJ / cm 2 or more because the amorphous silicon thin film must be completely dissolved when the thickness of the amorphous silicon thin film is approximately 500 to 1,000 Å, whereas the dehydrogenation treatment is required. For this reason, relatively low energy of about 300 mJ / cm 2 or less is required.

In the present invention, the mask pattern for crystallization and the mask pattern for dehydrogenation are simultaneously formed in one mask pattern and scanned to dehydrogenation using laser scattering in the dehydrogenation process.

At this time, the pattern region where dehydrogenation occurs, that is, the B region has a mask pattern that satisfies the following equation.

[expression]

a + b <2 μm,

Here, a represents the size of the pattern region through which the laser transmits, and b represents the size of the pattern region through which the laser does not transmit.

As such, by controlling the size of the pattern region through which the laser penetrates and the size of the pattern region through which the laser does not transmit, even when using a laser having an energy density of 500 mJ / cm 2 using laser scattering, the laser density can be lowered. It becomes possible.

In this case, the shape of the pattern region through which the laser beam of the region B where dehydrogenation occurs may be in the form of a line. In addition, the shape of the pattern region through which the laser beam of the region B where dehydrogenation occurs may not be transmitted may be a dot or a polygon.

2 is a diagram illustrating a mask pattern according to another exemplary embodiment of the present invention. Also in FIG. 3, crystallization and dehydrogenation of amorphous silicon can be simultaneously performed by using a mask pattern having both a mask pattern region A in which crystallization occurs and a mask pattern region in which dehydrogenation B occurs.

In the case of the mask pattern region A in which crystallization takes place, the size c of the region through which the laser is transmitted and the size d of the region in which the laser does not penetrate are determined. It can be seen that the size (a), compared with the size (b) of the area where the laser can not transmit.

Also in this embodiment, a and b of the mask pattern region B where dehydrogenation occurs must satisfy the above equation.

That is, it should be a + b <2 mu m.

On the other hand, in the mask pattern region A where crystallization takes place, c and d need to be larger than a and b, and there is no need to satisfy a special relational expression. That is, what is necessary is just to be able to melt | dissolve amorphous silicon completely.

On the other hand, the polycrystalline silicon thin film manufactured as described above can provide a thin film transistor having good electrical characteristics since dehydrogenation is simultaneously performed, so that the surface roughness of the film is not large.

In the present invention, a flat panel display device can be manufactured using a thin film transistor using a polycrystalline silicon thin film manufactured by the above manufacturing method.

The flat panel display device is preferably an organic electroluminescent element or a liquid crystal display device.

As described above, in the present invention, the crystallization and dehydrogenation of amorphous silicon are simultaneously performed, resulting in the process simplification and reduction of the tact time, and the process is required at a much lower temperature than the case where the substrate is glass. Plastic substrates can also be used.

Claims (12)

A method of crystallizing an amorphous silicon thin film, characterized in that a mask having a first mask pattern for crystallizing amorphous silicon to a single mask by irradiating the same laser and a second mask pattern for performing a dehydrogenation process are used. The method of claim 1, A method of crystallizing an amorphous silicon thin film, wherein a first mask pattern is first applied during laser irradiation, and then a second mask pattern is applied. The method of claim 1, A method of crystallizing an amorphous silicon thin film, wherein a second mask pattern is first applied during laser irradiation, and then a first mask pattern is applied. The method of claim 1, Wherein the second mask pattern satisfies the following equation: [expression] a + b <2 μm, Here, a represents the size of the pattern region through which the laser transmits, and b represents the size of the pattern region through which the laser does not transmit. The method of claim 1, The crystallization method of the amorphous silicon thin film, wherein the pattern region through which the laser beam of the second mask pattern passes is in the form of a line. The method of claim 1, The pattern region in which the laser beam of the second mask pattern does not transmit is a crystallization method of an amorphous silicon thin film. The method of claim 1, The crystallization method is SLS crystallization method of the amorphous silicon thin film crystallization method. delete delete In the laser crystallization for crystallizing the amorphous silicon, the same laser is used to simultaneously provide a mask pattern for crystallization and a mask pattern for dehydrogenation, and the mask pattern for dehydrogenation satisfies the following formula. Crystallization Mask Pattern: [expression] a + b <2 μm, Here, a represents the size of the pattern region through which the laser transmits, and b represents the size of the pattern region through which the laser does not transmit. The method of claim 10, The crystallization mask pattern having a line shape of a pattern region through which the laser beam of the mask pattern for dehydrogenation is transmitted. The method of claim 10, The crystal region mask pattern of the pattern region that the laser of the mask pattern for dehydrogenation is not transmitted is a dot or a polygon.

Images