KR100686332B1 - A polycrystalline silicone thin film and the method for forming the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycrystalline silicon thin film and a method of forming the same, wherein the polycrystalline silicon film includes a substrate 1, an amorphous silicon film layer 2 disposed on the substrate, and a microcrystalline silicon film layer 3 disposed on the amorphous silicon film. By providing a thin film and a method of forming the same, not only can the carrier mobility between the polycrystalline silicon and the gate oxide film required for manufacturing a display device including TFT-LCD, TFT-OLED, etc. be improved, but also in the reproducibility and image quality of the manufacturing process thereof. You can expect an improvement.

Excimer laser, polycrystalline silicon thin film, amorphous silicon, microcrystalline silicon

Description

A polycrystalline silicon thin film and the method for forming the same}

1A and 1B are diagrams illustrating a laminated structure of a polycrystalline silicon thin film according to the prior art.

2 is a view showing the volume% of the crystals according to the laser energy density when forming the polycrystalline silicon thin film (□: when only the amorphous silicon layer is used, the thickness of the layer is 50 nm, △: 35 nm thick amorphous silicon When a 15 nm thick microcrystalline silicon layer is deposited on the layer, ◇: when a 35 nm thick amorphous silicon layer is deposited on the 15 nm thick microcrystalline silicon layer).

3 is a diagram showing surface roughness according to laser energy density when forming a polycrystalline silicon thin film (□: when only an amorphous silicon layer is used, and when the thickness of the layer is 50 nm, Δ: on an amorphous silicon layer having a thickness of 35 nm When a 15 nm thick microcrystalline silicon layer is deposited, ○: When a 35 nm thick microcrystalline silicon layer is deposited on a 15 nm thick amorphous silicon layer, ◇: 35 nm thick on a 15 nm thick microcrystalline silicon layer Deposited an amorphous silicon layer).

4 is an atomic force microscopy (AFM) photograph showing non-uniformity observed on the surface of a polycrystalline silicon thin film crystallized with an excimer laser according to the prior art.

5 is a view showing a laminated structure of a polycrystalline silicon thin film formed according to an embodiment of the present invention.

6 is a view showing the crystal size according to the laser energy density when forming a polycrystalline silicon thin film (□: when only 50 nm thick amorphous silicon layer, △: 15 nm thick fine on a 35 nm thick amorphous silicon layer A crystalline silicon layer is deposited).

FIG. 7A is a SEM photograph showing the surface of a polycrystalline silicon thin film crystallized at a laser energy density of 280 mJ / cm ² after stacking 15 nm of amorphous silicon and 35 nm of amorphous silicon, and FIG. 7B is 340 mJ of silicon having the same structure. SEM image showing the surface of the polycrystalline silicon thin film crystallized at / cm ² , Figure 7c is a SEM image showing the surface of the polycrystalline silicon thin film crystallized after laminating the amorphous silicon to a thickness of 50 nm.

8A is a graph showing XRD peaks of a polycrystalline silicon thin film crystallized after laminating amorphous silicon to a thickness of 50 nm, and FIG. 8B is a XRD of a polycrystalline silicon thin film crystallized after laminating 15 nm of amorphous silicon 35 nm / microcrystalline silicon. Graph showing peaks.

FIG. 9 is a diagram illustrating that amorphous silicon is sandwiched and laminated between microcrystalline silicon layers according to another exemplary embodiment of the present invention.

[Industrial use]

The present invention relates to a polycrystalline silicon thin film and a method of forming the same, and more particularly, to a polycrystalline silicon thin film used in a display device including a TFT-LCD, a TFT-OLED and the like.

[Prior art]

Sufficient to obtain thin film properties (field effect mobility, etc.) required for a TFT device when forming a polycrystalline thin film from an amorphous silicon film by the Eximer Laser Annealing method used in the prior art disclosed in US Pat. No. 4,409,724. Crystal size and crystallization must be achieved, and sufficient laser energy must be applied for this.

For example, 50 nm thick amorphous silicon deposited by PECVD has an average crystal size of 0.3 μm or more when polycrystalline by ELA, and at least 90% of the crystal volume% (determined from the Raman spectrum) of the entire silicon thin film. The energy density of the excimer laser to be irradiated should be at least 280 mJ / cm 2 (see FIGS. 2 and 6), and the surface roughness (RMS) of silicon crystallized in this energy density range is It can increase from a minimum of 3 nm to 15 nm (see FIG. 3).

1A and 1B show a laminated structure of a polycrystalline silicon thin film according to the prior art, and FIG. 1A shows a laminated structure of an initial amorphous silicon thin film before excimer laser crystals, and FIG. 1B shows a microcrystalline silicon film layer ( 3) is laminated below the amorphous silicon film layer 2, and the lamination structure after crystallization with an excimer laser is shown.

1A and 1B, it can be seen that the surface roughness after crystallization becomes more rough than before crystallization. Referring to FIG. 3, which is a graph showing the relationship between the excimer laser and the crystallized surface roughness, It can be seen that the surface roughness increases with the increase.

At this time, the peak to valley height at the surface after laser crystallization of the 50 nm thick initial amorphous silicon ranges from 20 nm to 50 nm, and such large surface roughness or peak to valley height is increased in the TFT manufacturing process. This results in almost the same roughness in all films deposited by CVD or sputtering on the silicon film, and the resulting defects in the device result in overall degradation of the performance of the display such as TFT OLED or TFT LCD using polycrystalline silicon. It is expected to cause an effect.

Another problem with crystallization by ELA is that it is often observed on the polycrystalline silicon surface after the underlying nonuniformity crystallinity and surface roughness by the laser beam scan method is crystallized (see FIG. 4). .

In another conventional US Pat. No. 5,827,773, in order to improve the size and crystallinity of silicon crystals, microcrystalline silicon may be deposited by CVD and then amorphous silicon may be deposited thereon to improve laser efficiency. .

However, there is a problem that polycrystalline formation in this manner can result in greater surface roughness and peak to valley height compared to amorphous silicon single film.

For example, when a 35 nm thick amorphous silicon film was deposited on 15 nm thick microcrystalline silicon and crystallized by ELA, the surface roughness varied from about 15 nm to 60 nm as the laser energy density changed (FIG. 2 and FIG. 3), and thus the peak-to-valley height was observed to vary with a wide variation from about 5 nm to 250 nm.

In another prior art, US Pat. No. 5,970,369, polycrystalline silicon thin films are obtained by repeating the steps of depositing amorphous silicon, crystallizing with an excimer laser, and then depositing and crystallizing amorphous silicon again to obtain excellent crystallinity at high energy density. The problem is that the surface is non-uniform and the crystal orientation cannot be controlled.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems described above, and an object of the present invention is to provide a polycrystalline silicon thin film having an extremely oriented crystal structure and a uniform crystal size and a method of forming the same.

The present invention to achieve the above object, the present invention

Substrate 1;

An amorphous silicon film layer (2) disposed on the substrate; And

A microcrystalline silicon film layer 3 disposed on the amorphous silicon film

It provides a polycrystalline silicon thin film comprising a.

In addition, the present invention

Stacking an amorphous silicon film layer (2) on the substrate (1);

Laminating a fine crystalline silicon film layer (3) after the laminating step; And

And laminating the microcrystalline silicon film layer 3 and crystallizing the silicon film layer 3 by excimer laser annealing.

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

FIG. 5 is a diagram illustrating a lamination structure of a polycrystalline silicon thin film formed according to an embodiment of the present invention, in which amorphous silicon 2 is laminated on a substrate 1, and microcrystalline silicon 3 is disposed on the amorphous silicon 2. ), And a lamination structure of a polycrystalline silicon thin film crystallized by excimer laser annealing (ELA).

The amorphous silicon 2 is deposited by chemical vapor deposition (CVD) and the microcrystalline silicon 3 is deposited thereon in the same manner.

It is then crystallized with an excimer laser having a laser energy density of 280 mJ / cm 2 to 340 mJ / cm 2.

The crystallized polycrystalline silicon thin film does not deteriorate in crystallinity as compared with the case of using only amorphous silicon, has excellent uniformity in crystal size, and is extremely crystallographically oriented.

This is presumably because the fine crystalline silicon stacked on the upper layer is not completely melted during laser annealing, but nucleates and crystallizes using the remaining seeds.

It is also speculated that the microcrystals of the microcrystalline silicon layer of the upper layer exposed to the vacuum during crystallization during the crystallization can grow with sufficient directivity due to the slow heat loss.

At this time, it is preferable that the thickness of the microcrystalline silicon (3) layer of an upper layer part is 5-35 nm.

When the thickness of the microcrystalline silicon (3) layer is 35 nm or more, the surface roughness is extremely excellent, but the crystallinity of the entire silicon film is lowered, which is not preferable.

Meanwhile, the microcrystalline silicon film layer 3 deposited by the same method after CVD deposition of the amorphous silicon film layer 2 is deposited by diluting a gas containing silicon with hydrogen or by diluting a gas containing silicon with argon gas. It is preferable.

In addition, the present invention provides a multilayer silicon thin film as shown in FIG.

The multilayer silicon thin film shown in FIG. 9 has a structure in which a microcrystalline silicon film layer 3 is first laminated on a substrate 1, and an amorphous silicon film layer 2 and a microcrystalline silicon film layer 3 are successively stacked.

The amorphous silicon film layer 2 and the microcrystalline silicon film layer 3 are preferably laminated by CVD.

It is then crystallized with an excimer laser having a laser energy density of 280 mJ / cm 2 to 340 mJ / cm 2.

Forming a polycrystalline silicon thin film with such a structure solves the high surface roughness or narrow laser energy density range of the prior art in the TFT manufacturing process and the difficulty of forming a reproducible polycrystalline silicon thin film due to the instability of the laser energy. Can be.

This means that when crystallized by ELA, the first microcrystalline silicon film layer 2 acts as a seed for the crystallization of the amorphous silicon film layer, thereby forming a silicon film having a high crystallinity and a large crystal size. It is presumed that the microcrystalline silicon film is continuously grown under the influence of crystal nucleation and growth of the amorphous silicon, which is a lower film, during ELA crystallization, and at the same time suppresses an increase in surface roughness.

In addition, an amorphous silicon film layer may be successively laminated to the lower microcrystalline silicon film layer, followed by further laminating a microcrystalline silicon film layer, followed by successively laminating an amorphous silicon film layer and a microcrystalline silicon film layer.

In this case, the number of the microcrystalline silicon film layer and the amorphous silicon film layer is not limited, but the first layer on the substrate should be a microcrystalline silicon layer and the top layer should also be a microcrystalline silicon layer.

The thickness of the microcrystalline silicon layer, which is the top layer, is preferably 5 to 35 nm.

When the thickness of the fine crystalline silicon (3) layer is 35 nm or more, crystallization does not occur well and crystallinity is lowered, which is not preferable.

Meanwhile, the microcrystalline silicon film layer 3 deposited by the same method after CVD deposition of the amorphous silicon film layer 2 is deposited by diluting a gas containing silicon with hydrogen or by diluting a gas containing silicon with argon gas. It is preferable.

The polycrystalline silicon thin film formed of the structure as described above has a surface roughness of 3 nm to 10 nm of the fine crystal silicon film layer 3 of the uppermost layer.

The polycrystalline silicon thin film thus formed can be used for this purpose because it can greatly reduce the defects of the display such as TFT-LCD and TFT-OLED due to the surface roughness.

Hereinafter, a preferred embodiment of the present invention. However, the following examples are only presented to better understand the present invention, but the present invention is not limited to the following examples.

Example 1

Crystals measured from Raman Spectroscopy when 35 nm thick amorphous silicon was deposited by CVD and then 15 nm of fine crystalline silicon was deposited thereon and crystallized by ELA at a total thickness of 50 nm. The volume percent of is about 95% and 90% (laser energy density) for laser energy density of 340 mJ / cm2 to 340 mJ / cm2. The properties are excellent (see FIGS. 7A and 7B) and show (111) crystal orientations for both samples of 50 nm of amorphous silicon and 15 nm of amorphous silicon 35 nm of amorphous silicon when subjected to XRD analysis under the same analysis conditions. , Especially for microcrystalline silicon 15 nm / amorphous silicon 35 nm samples, the peak intensity is increased by about three times that of amorphous silicon monolayer silicon. It can be seen that it is scientifically oriented (see FIGS. 8A and 8B).

In addition, due to the surface roughness inhibitory effect of the fine crystalline silicon, it was possible to obtain a surface having a low roughness even at a high energy density (see FIG. 3).

In particular, when crystallized by ELA using an amorphous silicon film, the volume percentage of the crystal was high at about 280 mJ / cm 2 to about 96%, while the surface roughness was bad (see FIG. 3), and as the laser energy density increased, FIG. 7C. As can be seen, as the crystal grows, the grain size non-uniformity increases.

On the other hand, the crystallinity of the two-layer silicon of 15 nm microcrystalline silicon / 35 nm of amorphous silicon is inferior, but the roughness is relatively small, and even the high laser energy density shows a very uniform crystal size.

It can be seen that by depositing the microcrystalline layer into the top layer, even during short laser pulse periods of 22 nanoseconds, the microcrystals exposed to vacuum were able to grow with sufficient orientation due to slow heat loss.

Example 2

Deposition of 35 nm of microcrystalline silicon on 15 nm of amorphous silicon to a total thickness of 50 nm, the volume% of the crystal measured from Raman spectroscopy when crystallized by ELA is 240 mJ / 78% to 83% for the laser energy density of cm 2 to 340 mJ / cm 2, which was lower than that of ELA crystallization after amorphous silicon or microcrystalline silicon as a lower film and deposition of amorphous silicon, but the surface roughness was lower. It could have a very small value from 2 nm to 3 nm (peak to valley 6 nm to 20 nm) (see FIG. 3).

Therefore, based on the results of the experiments described above, after depositing microcrystalline silicon on a substrate by CVD, subsequently the amorphous silicon and then again the microcrystalline silicon film act as seeds for the crystallization of the amorphous silicon, thereby crystallinity and crystallization. It enables the formation of large size silicon film, and the second microcrystalline silicon film will be continuously grown under the influence of crystal nucleation and growth of amorphous silicon, the underlying film during ELA crystallization, and at the same time suppress the increase of surface roughness. It is expected to have an effect.

Forming a silicon film with such a structure to form a polycrystalline silicon film makes it difficult to form a reproducible polycrystalline silicon thin film due to the high surface roughness or narrow laser energy density range for improving crystallinity and the instability of laser energy in the TFT manufacturing process. I was able to solve all the problems.

 As described above, the surface roughness of the crystal according to the present invention can be maintained at 3 nm to 10 nm or less, and the crystal size uniformity, crystal orientation and high field effect mobility are superior to polycrystalline silicon using only amorphous silicon. mobility, at least 100 cm 2 / V · sec) can be obtained reproducibly, and the defects of the TFTs due to the surface roughness of the polycrystalline silicon can be greatly reduced.

Claims (13)

Substrate 1; An amorphous silicon film layer (2) disposed on the substrate (1); And A microcrystalline silicon film layer 3 disposed on the amorphous silicon film Silicon thin film comprising a. The method of claim 1, A silicon thin film further comprising a microcrystalline silicon film layer (3) between the substrate (1) and the amorphous silicon film layer (2). The method according to claim 1 or 2, The thickness of the microcrystalline silicon film layer (3) is 5 to 35 nm silicon thin film. The method according to claim 1 or 2, A silicon thin film having a surface roughness of 3 to 10 nm of the microcrystalline silicon film layer (3). The method of claim 2, The silicon thin film is a silicon thin film, wherein the amorphous silicon thin film layer (2) and the microcrystalline silicon thin film layer (3) on the lower microcrystalline silicon thin film layer (3) are alternately stacked so that the top layer is a microcrystalline silicon film layer (3). Stacking an amorphous silicon film layer (2) on the substrate (1); Laminating a fine crystalline silicon film layer (3) after the laminating step; And And laminating the microcrystalline silicon film layer (3) and crystallizing the microcrystalline silicon film layer (3) by excimer laser annealing. The method of claim 6, And laminating a microcrystalline silicon film layer (3) on the substrate prior to laminating an amorphous silicon film layer (2) on the substrate (1). The method of claim 7, wherein In the method of forming the polycrystalline silicon thin film, a microcrystalline silicon film layer 3 is laminated on the substrate 1, an amorphous silicon film layer 2 is laminated on the microcrystalline silicon film layer 3, and the microcrystal A method of forming a polycrystalline silicon thin film which is crystallized by excimer laser annealing after repeatedly performing the step of forming the silicon film (3). The method of claim 6, Method of forming a polycrystalline silicon thin film having an energy density of the excimer laser is 240 to 340 mJ / ㎠ in the crystallization step. The method according to claim 6 or 7, A method of forming a polycrystalline silicon thin film, wherein the microcrystalline silicon film layer (3), which is the top layer of the polycrystalline silicon thin film, is laminated at a thickness of 5 to 35 nm. The method according to claim 6 or 7, The method of laminating the silicon film layers is chemical vapor deposition (CVD). The method of claim 11, The chemical vapor deposition method (CVD) is a method of forming a polycrystalline silicon thin film which dilutes a gas containing silicon with hydrogen. The method of claim 11, The chemical vapor deposition method (CVD) is a method of forming a polycrystalline silicon thin film to dilute a gas containing silicon with argon.

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