KR100544143B1 - Method of fabricating thin film transistor, the TFT using the same method, and flat panel display device with the TFT - Google Patents

Abstract

The present invention comprises two or more laser irradiation steps for forming an amorphous silicon layer into a polycrystalline silicon layer; A thin film transistor manufacturing method further comprising an etching step for reducing the surface roughness of the silicon layer increased by laser irradiation between each laser irradiation step, wherein the etching step is performed by a dry etching method and a laser is performed after the etching step The irradiating step is irradiated with an energy density such that the crystallinity of the silicon layer is increased by 20% or more than the crystallinity after the etching step, and eventually the crystallinity of the silicon layer is 60% or more. A method of manufacturing a thin film transistor, a thin film transistor using the method, and a flat panel display device having the same are provided.

Description

Method of manufacturing a thin film transistor, a thin film transistor and a flat panel display device having the same {Method of fabricating thin film transistor, the TFT using the same method, and flat panel display device with the TFT}

1 is a flowchart illustrating a method of forming an amorphous silicon layer into a polycrystalline silicon layer as an embodiment of the present invention.

2 is a diagram illustrating a laser processing apparatus.

3 is a diagram illustrating a sputter etching apparatus of an ion shower type.

4 is a diagram illustrating the surface roughness after laser irradiation and argon sputter etching according to an embodiment of the present invention.

5 is a view showing the degree of crystallization according to the laser energy density in the second laser irradiation step according to an embodiment of the present invention.

6 is a schematic partial cross-sectional view of a flat panel display device having a thin film transistor according to the present invention.

The present invention relates to a thin film transistor manufacturing method including a polycrystalline silicon layer, and more particularly a thin film transistor which reduces the surface roughness of the silicon layer increased by laser irradiation in the thin film transistor manufacturing method of making the amorphous silicon layer into the polycrystalline silicon layer. The present invention relates to a manufacturing method, a thin film transistor, and a flat panel display device having the same.

In displaying an image, many kinds of display apparatuses are used. In recent years, various flat panel display apparatuses are used to replace conventional cathode ray tubes, that is, cathode ray tubes (CRTs). Such flat panel display devices can be classified into self-emissive and non-emissive types according to the light emission type. Representative self-emissive display devices are plasma display devices and organic electroluminescence. A display device (organic electroluminescent display device) and the like, and a typical non-luminescent display device is a liquid crystal display (liquid crystal device).

In the case of a liquid crystal display and an organic electroluminescent display, an active driving liquid crystal display (AMLCD) and an active driving organic electroluminescent display in which a driving element, that is, a thin film transistor (TFT), adjusts a voltage or a current applied to a pixel (AMOLED), and so on. Amorphous silicon and polycrystalline silicon are used for the thin film transistor as a driving element, and since the polycrystalline silicon, especially polycrystalline silicon having a large particle diameter, has better field effect mobility than amorphous silicon or polycrystalline silicon having a small particle diameter, Polycrystalline silicon is mainly used as an element forming the.

Methods for producing polycrystalline materials, for example polycrystalline silicon, are classified into low temperature processes and high temperature processes depending on the production temperature. In the case of a high temperature process, there is a problem that the film thickness becomes uneven due to high surface roughness during film formation. In the low temperature process, laser processing, that is, laser annealing that irradiates a laser beam onto a thin film substrate, is typically used. Since crystallization of amorphous silicon by the laser beam is performed in nanosecond units, a substrate under the thin film is used. It has the advantage of minimizing the damage to it.

Meanwhile, various methods for enhancing the crystallinity of a semiconductor active layer such as a silicon layer through laser annealing have been studied. One of the methods is to irradiate a laser to the semiconductor active layer.

Japanese Patent Laid-Open No. 2001-297983 discloses a laser annealing method through laser beam multiple irradiation to improve the quality of a polycrystalline silicon layer.

However, this polycrystalline silicon layer according to the prior art has the advantage that the degree of crystallinity is increased, but at the same time accompanied by the problem that the surface roughness of the silicon layer is significantly increased. This increase in surface roughness is due to grain boundaries, which may cause significant problems in the reliability of the product, which may subsequently impair the insulation of the silicon layer, that is, the insulating layer formed on one side of the semiconductor active layer. It may be.

 SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a method for manufacturing a thin film transistor which increases the crystallinity by laser irradiation and improves the surface roughness of the polycrystalline silicon layer.

In order to achieve the above object, the present invention comprises two or more laser irradiation steps for forming an amorphous silicon layer into a polycrystalline silicon layer; There is provided a thin film transistor manufacturing method further comprising an etching step for reducing the surface roughness of the silicon layer increased by the laser irradiation between each laser irradiation step.

According to another aspect of the present invention, the etching step may be performed by a dry etching method.

According to another aspect of the present invention, the laser irradiation step performed after the etching step may be irradiated with an energy density such that the crystallinity of the silicon layer is increased by 20% or more than the crystallinity after the etching step.

According to another aspect of the present invention, the laser irradiation step performed after the etching step may be such that the crystallinity of the silicon layer is 60% or more.

The present invention also provides at least two laser irradiation steps for forming an amorphous silicon layer into a polycrystalline silicon layer to achieve the above object; There is provided a thin film transistor further comprising an etching step for reducing the surface roughness of the silicon layer increased by the laser irradiation between each laser irradiation step.

The present invention also provides at least two laser irradiation steps for forming an amorphous silicon layer into a polycrystalline silicon layer to achieve the above object; Provided is a flat panel display device having a thin film transistor manufactured by further comprising an etching step for reducing the surface roughness of the silicon layer increased by laser irradiation between each laser irradiation step.

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart illustrating a method of forming an amorphous silicon layer into a polycrystalline silicon layer as an embodiment of the present invention, FIG. 2 is a diagram illustrating a laser processing apparatus, and FIG. 3 is an ion shower method. It is a figure which shows the sputter etching apparatus of this.

First, as shown in FIG. 1, after amorphous silicon is inserted into a laser processing apparatus, a first laser irradiation step S102 is performed. The first laser irradiation step (S102) is carried out with the laser processing apparatus shown in FIG. 2, firstly the substrate 207 is seated on the stage on the support 209, which is disposed in the chamber 215 through the substrate window 213. do. The support 209 is transferable by a support transfer device, the support transfer device is a transfer bar fixing portion 211 fixed to one side of the chamber 215, a transfer bar 210 supported by the transfer bar fixing portion 211, It is mounted to the support 209 is composed of a transfer drive device 220 to move along the transfer bar (210). The upper side of the chamber 215 is disposed with a gas transfer system 214 for introducing a gas to create an atmosphere in the chamber 215, the lower side of the chamber 215 is a pump system 212 for discharging the gas This is arranged. An amorphous material, for example, an amorphous silicon layer 207 ′, is formed on one surface of the substrate 207. The laser beam generated by the laser oscillator 201 passes through the slit 202 to the controller 203, partly to feed back the state of the laser beam and the other part to the optical system 204 to transmit the laser beam. The energy distribution and size are adjusted. The laser beam passing through the optical system 204 is irradiated onto the substrate via a fixed reflection mirror 205 through a modification window 206 disposed on top of the chamber 215. The crystallinity of the amorphous silicon layer is increased by laser irradiation to form a polycrystalline silicon layer.

After the first laser irradiation step S102 is performed, the etching step S104 proceeds. Various etching methods may be performed as the etching step, and it is preferable to use a dry etching method having anisotropy so as to minimize surface damage in areas other than desired areas. 3 illustrates an ion etching apparatus 300 as an example of a dry etching apparatus for performing an etching step S104 according to the present invention. The ion etching apparatus 300 includes a chamber 320, a substrate holder 316 in which a substrate 318 having a semiconductor active layer is disposed in the chamber 320, and a gas inlet 302 for flowing in and out of the atmospheric gas into the chamber 320. ) And gas discharge part 322, filament 304 for forming plasma, anode 306 and electromagnet 308, acceleration electrode 310 for forming ion beam and neutralizing electron 314, electrospinning for neutralization It consists of a filament 312. First, a substrate 318 having a polycrystalline silicon layer on one surface is introduced into the chamber 320 and seated on one surface of the substrate holder 316. An inert gas such as argon (Ar), krypton (Kr), xenon (Xe), or the like, which is not reactive as an ion source, is introduced into the gas inlet 302, and in one embodiment of the present invention, argon (Ar) is used. At this time, the chamber 320 is maintained at a reduced pressure. Thereafter, a plasma is formed in the chamber 320 by the filament 304, the anode 306, and the electromagnet 308, and an argon ion beam is generated from the acceleration electrode 310 and the neutralizing electrospinning filament 312. And neutralization electrons 314 are formed and incident on the substrate 318 on one surface of the substrate holder 316. The incident Ar Ion beam and the neutralizing electrons 314 strike the surface of the polycrystalline silicon layer on one surface of the substrate 316 to mitigate surface roughness of the polycrystalline silicon layer by removing surface protrusions such as grain boundary protrusions. .

Thereafter, a second laser irradiation step S106 is performed, and the second laser irradiation step goes through the same process as the first laser irradiation step. This second laser irradiation step (S106) can increase the degree of crystallinity reduced by the etching step (S104).

4 shows the surface roughness of the silicon layer after the first laser irradiation step, the argon sputter etching step and the second laser irradiation step according to an embodiment of the present invention, respectively.

In this embodiment, a silicon layer having a thickness of 500 mW was used as the semiconductor active layer, an XeCl excimer laser of 308 nm wavelength was irradiated to the silicon layer, and argon sputter etching was performed.

After the first laser irradiation step is carried out at an optimal energy density, for example 300 mJ / cm ² , the RMS value of the surface roughness is about 200, while argon sputter etching When subjected to the dry etching step, the RMS value of the surface roughness is reduced to approximately 150. When the second laser irradiation step after the dry etching step is performed, it can be confirmed that the surface roughness does not increase by the laser irradiation again performed.

5 is a view showing the degree of crystallinity according to the laser energy density in the second laser irradiation step.

In this case, a silicon layer having a thickness of 500 mW was used as the semiconductor active layer, and an XeCl excimer laser having a wavelength of 308 nm was used as the irradiated laser.

5 shows the crystallinity of the semiconductor active layer obtained after each step.

Crystallinity is determined by the Raman spectral ratio for the polycrystalline and residual amorphous silicon layers.

The crystallinity of the semiconductor active layer became approximately 75% after the first laser irradiation step of laser irradiation at the optimum energy density, for example, 300 mJ / cm ² , for the semiconductor active layer of the amorphous silicon layer. On the other hand, after the dry etching step such as ar sputter etching, the crystallinity of the semiconductor active layer was reduced to 51%. On the other hand, the dry after the etching step in the second laser irradiation step, the case where the laser energy density is increased from 200mJ / cm ² to 300mJ / cm ^2, the crystallinity is 240mJ / cm ² to 300mJ / cm ^2, crystallinity of 51 after the etching step in the range of It has a crystallinity greater than%, and the crystallinity increases with energy density, and then decreases to the point where the energy density is 280 mJ / cm ² .

On the other hand, in the laser irradiation step performed after the etching step, the laser beam is preferably irradiated to the semiconductor active layer so that the crystallinity of the semiconductor active layer is 60% or more. In other words, the semiconductor active layer may be used in a thin film transistor of a display device such as an organic electroluminescent display device. In this case, the semiconductor active layer increases the operability of the thin film transistor by securing an appropriate electron mobility of 40 cm ² / Vs or more, thereby providing a display area. The crystallinity of the silicon layer as the semiconductor active layer during the laser irradiation step after the etching step is 60, so that the size of the device, the compactness of the device due to the built-in driving circuit, etc., and the screen quality, such as the brightness uniformity over the display area, can be achieved. It is preferable to make it more than%.

In one embodiment of the present invention, the second laser irradiation can be performed to have a 20% increase in the crystallinity of the silicon layer after the etching step, it is most preferable that the crystallinity of the silicon layer is 60% or more.

As can be seen in one embodiment, by performing the dry etching step between the laser irradiation steps, the surface roughness of the silicon layer can be reduced by the dry etching step, and in the laser irradiation step after the dry etching step With proper laser irradiation density energy, it is possible to restore the crystallinity of the silicon layer, which is reduced due to surface roughness. Therefore, high crystallinity of the silicon layer and reduction of surface roughness can be simultaneously obtained.

Meanwhile, according to another embodiment of the present invention, the flat panel display device may include a thin film transistor manufactured by the present invention. 6 is a schematic partial cross-sectional view of an electroluminescent display device as a flat panel display device having a thin film transistor according to the present invention. The thin film transistor according to the present invention is disposed between the buffer layer 620 formed on one surface of the substrate 610, and the semiconductor active layer 630, the gate electrode layer 650, and the source / drain electrode layers 670a and 670b, respectively. The TFT layer may be formed of an insulating layer such as a gate insulating layer 640 or an intermediate layer 660. The protective layer 680 is formed on one surface of the source / drain electrode layers 670a and 670b, and the first electrode layer 690 is disposed through the via hole 681 formed on one side of the protective layer 680. The pixel defining layer 691 may be formed on the passivation layer 680, and an opening region 694 is disposed in a corresponding region of the first electrode layer 690. An electroluminescent part 692 including a light emitting layer or the like may be formed on one surface of the first electrode layer 690 through the opening region 694, and a second electrode layer 693 may be deposited on the entire surface thereof. In the electroluminescent display device, the semiconductor active layer 630 through which the channel is energized by an electrical signal applied to the gate electrode 650 may be formed of a polycrystalline thin film according to the present invention.

6 shows an example of the present invention, and the present invention is not limited to the organic / inorganic electroluminescent display device, but within the limits provided with the semiconductor active layer manufactured according to the method of the present invention. It can also be applied to a liquid crystal display device. In addition, the thin film transistor manufacturing method shown in FIG. 1 is an example for explaining the present invention, and may comprise several laser irradiation steps within a range including an etching step, particularly a dry etching step, between the laser irradiation steps. Various modifications are possible.

According to the method of manufacturing a thin film transistor having a polycrystalline silicon layer according to the present invention, the surface roughness is improved by performing a dry etching step, and the crystallinity reduced by the dry etching step is recovered by laser irradiation after the dry etching step.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (6)

A thin film transistor manufacturing method comprising a polycrystalline silicon layer, At least two laser irradiation steps for forming an amorphous silicon layer into the polycrystalline silicon layer, further comprising an etching step between each laser irradiation step to reduce the surface roughness of the polycrystalline silicon layer. Thin film transistor manufacturing method. The method of claim 1, wherein the etching step, A method of manufacturing a thin film transistor, characterized in that it is carried out by a dry etching method. The method of claim 1, wherein the laser irradiation step performed after the etching step, And irradiating at an energy density such that the crystallinity of the silicon layer is increased by 20% or more than the crystallinity after the etching step. The method of claim 3, wherein the laser irradiation step performed after the etching step, And a crystallinity of 60% or more of the silicon layer. A thin film transistor manufactured using the method of any one of claims 1 to 4. A flat panel display device comprising a thin film transistor manufactured using the method of any one of claims 1 to 4.

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