KR20080000299A - Poly-silicon thin film transistor liquid crystal display device and the method of fabricating thereof - Google Patents

Abstract

A poly-silicon thin film transistor LCD and a fabrication method thereof are provided to manufacture poly-silicon with an excellent crystallization characteristic by reducing a time for solid-phase crystallization through a plasma surface-treating process. An amorphous silicon layer is formed on a substrate(200). A plasma-treating is performed on the amorphous silicon layer. The amorphous silicon layer which is plasma-treated is thermally treated to form a poly silicon layer. Before the amorphous silicon layer is formed, a buffer layer(220) is formed on the substrate. The plasma treatment uses a gas such as oxygen, helium and argon. The plasma treatment time is 60 to 120 sec.

Description

Poly-silicon thin film transistor liquid crystal display device and the method of fabricating

1A to 1C are cross-sectional views showing a conventional method of crystallizing an amorphous silicon layer into a polysilicon layer in a process sequence.

2A through 2D are cross-sectional views illustrating a method of crystallizing an amorphous silicon layer into a polysilicon layer according to the present invention in a process sequence.

3A and 3B show a detail of FIG. 2C;

4 is a flow chart showing a process of the present embodiment.

5A to 5C are cross-sectional views of polysilicon thin film transistor liquid crystal displays using polysilicon formed by the crystallization method of the present invention, in order of process.

* Explanation of symbols for the main parts of the drawings *

200: glass substrate 220: buffer layer

225 gate insulating film 240a pure silicon layer

240b, 240c: impurity silicon layer 240: semiconductor layer

245 interlayer insulating film 250 gate electrode

254: source electrode 258: drain electrode

260: protective film 270: pixel electrode

CH3: Drain contact hole

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polysilicon thin film transistor liquid crystal display device, and more particularly, to a polysilicon forming method capable of shortening the crystallization time by adding a plasma surface treatment step in an intermediate step in crystallizing an amorphous silicon layer by a solid phase crystallization method. will be.

Recently, with increasing interest in information display and increasing demand for the use of portable information media, research and commercialization of lightweight thin-film flat panel display devices, which replace the existing display device, the Cathode Ray Tube (CRT) It is done.

In particular, active driving liquid crystal display devices have become mainstream in such flat panel displays. In an active driving liquid crystal display device, a thin film transistor is used as a switching element to change the transmittance of a pixel by adjusting a voltage applied to a liquid crystal of one unit pixel.

Among them, Liquid Crystal Display Device (LCD) is the most widely used, replacing the cathode ray tube (CRT) for mobile image display devices because of its excellent image quality, light weight, thinness, and low power consumption. It is being developed in various ways such as a monitor of a notebook computer.

A general liquid crystal display device may be largely divided into a liquid crystal panel displaying an image and a driving unit for applying a driving signal to the liquid crystal panel. The liquid crystal panel may include a color filter array substrate and a thin film transistor array substrate which are bonded to each other with a predetermined space. And a liquid crystal layer injected between the two substrates.

In this case, the thin film transistor array substrate has a plurality of gate wires arranged in one direction at a predetermined interval, a plurality of data wires crossing in a direction perpendicular to the respective gate wires, and each of the gate wires and data wires intersect with each other. A plurality of pixel electrodes formed in a matrix form in each defined pixel region, and a plurality of thin film transistors switched by signals of the gate lines to transfer the signals of the data lines to each pixel electrode, are provided.

Here, it may be classified according to the silicon layer used as the active layer of the thin film transistor, which may be divided into a method of using amorphous silicon as an active layer and a polysilicon as an active layer.

The active layer using polysilicon has a carrier mobility of about 10 to 100 times faster than amorphous silicon, so that a driving circuit can be made on a substrate, and thus it is advantageous to use it as a switching element of a high resolution panel.

Accordingly, liquid crystal display devices using polysilicon as the active layer have been recognized as a technology for realizing next generation high performance intelligent display systems.

The method of forming the polysilicon may be classified into three types.

In general, in order to form a polysilicon thin film, pure amorphous silicon is deposited on a predetermined method, that is, by depositing an amorphous silicon thin film by plasma chemical vapor deposition (PECVD) or low pressure chemical vapor deposition (LPCVD) with a thickness of 500 kV on an insulating substrate. Use the method of crystallization.

First, the solid phase crystallization method is a method of forming polysilicon by heat-treating amorphous silicon for a long time at a high temperature.

Secondly, the metal-induced crystallization method is a method of forming polysilicon by depositing a metal on amorphous silicon, which has the advantage of manufacturing a large-area glass substrate.

Third, the laser heat treatment method is a method of growing a polysilicon by irradiating a laser on a substrate on which an amorphous silicon thin film is deposited.

However, the third method, which is a heat treatment method using a laser, has the advantage of forming polysilicon at low temperature, but in organic EL (electro-luminescence), many stains are generated due to laser pulse instability.

Therefore, although it is inferior to polysilicon through the laser heat treatment method in terms of crystal characteristics, many studies have been made on solid crystallization method, which is the first method because it is superior in terms of staining and device uniformity.

Here, in the solid phase crystallization method using heat, since the reaction rate is very sensitive to temperature, it is possible to increase the temperature and to obtain better crystal characteristics as the time is increased.

However, in the manufacturing process using the glass substrate, there is a fear that the glass is deformed at a high temperature and requires a long heat treatment time at 600 ^° C or less, which has the disadvantage of low productivity.

Hereinafter, a general solid crystallization method will be described with reference to the accompanying drawings.

1A to 1C are cross-sectional views illustrating a method of crystallizing general amorphous silicon into polysilicon according to a process sequence.

As shown in FIG. 1A, a buffer layer 20 is formed on the substrate 10 as one selected from a group of inorganic insulating materials including silicon oxide (SiO ₂ ) and silicon nitride (SiNx).

Subsequently, an amorphous silicon layer 30 is formed on the buffer layer 20.

In this case, the buffer layer 20 is formed for the purpose of preventing foreign substances of the substrate 10 from penetrating the silicon layer 30 and damaging the silicon layer 30 in the process of crystallizing the silicon layer 30. .

As shown in FIG. 1B, the substrate 100 on which the amorphous silicon layer 30 is formed is subjected to a long heat treatment process in a furnace.

However, in the case of the glass substrate 10, heat treatment is performed at 600 ^° C. or less due to deformation of glass at a high temperature. As a result of the process, the amorphous silicon gradually crystallizes into polysilicon.

In this case, the mixed layer 35 in which the amorphous silicon and the polysilicon are mixed is formed.

As shown in FIG. 1C, when the process is performed for a long time, complete crystallization proceeds in the mixed layer 35 in which amorphous silicon and polysilicon are mixed to form the polysilicon layer 40.

Therefore, the polysilicon layer may be formed through the solid phase crystallization method described above.

However, the above-described solid-phase crystallization method using heat has the advantage that the reaction rate is very sensitive to temperature, thereby obtaining silicon having excellent crystal characteristics as the temperature is increased and the time is increased, but the productivity decreases with the increase of time. Caused.

Accordingly, the polysilicon thin film transistor liquid crystal display device according to the present invention has been devised to solve the problems as described above, and is a dangling bond, void or interstitial type through a plasma surface treatment process. By increasing the disorder of the silicon array by making a lot of silicon bonds, such as), as the crystallization proceeds, it can be easily combined with the next amorphous silicon, which reduces the activation energy and reduces the crystallization time. have.

A polysilicon liquid crystal display according to the present invention comprises the steps of forming an amorphous silicon layer on a substrate, and plasma processing the amorphous silicon layer;

And heat treating the plasma-treated amorphous silicon layer to form a polysilicon layer.

The method may further include forming a buffer layer on the substrate before forming the amorphous silicon layer.

The plasma treatment uses gases such as oxygen (O) ₂ , helium (He), argon (Ar), and the like, and the plasma treatment time is performed under a condition of 60 to 120 sec.

The plasma treatment temperature is carried out at 300 ~ 500 ^° C., the plasma treatment process is characterized in that the pressure is carried out at 20 ~ 200mTorr, power 1000 ~ 15000W, gas flow rate 500 ~ 1000sccm.

Polycrystalline silicon formation method in which a large amount of silicon bonds, such as dangling bonds, voids or interstitial through the plasma treatment.

A method of manufacturing a polysilicon liquid crystal display according to the present invention may include forming a buffer layer on a substrate, forming an amorphous silicon layer on the buffer layer, and performing a plasma treatment on the amorphous silicon layer;

Forming the plasma-treated amorphous silicon layer into a polysilicon layer through a high temperature heat treatment process, and forming a gate insulating film on the polysilicon layer;

Forming a gate electrode on the gate insulating layer, doping the polysilicon layer using the gate electrode as a doping mask, and an interlayer insulating layer including first and second semiconductor contact holes on the gate electrode Forming a;

Forming a source and a drain electrode on the interlayer insulating layer, the source and drain electrodes contacting the doped polysilicon layer through the first and second semiconductor contact holes, and a protective layer including a drain contact hole on the source and drain electrodes. Forming;

And forming a pixel electrode on the passivation layer, the pixel electrode contacting the drain electrode through the drain contact hole.

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

--- First Embodiment ---

The polysilicon thin film transistor liquid crystal display according to the present invention can shorten the crystallization time by adding the plasma surface treatment process to the intermediate step in the process of crystallizing the amorphous silicon into polysilicon, and the crystallization characteristics by reducing the crystallization time It is possible to produce this excellent polysilicon.

2A to 2D are cross-sectional views illustrating a first embodiment according to the present invention, and FIGS. 3A and 3B are detailed views of FIG. 2C and show only portions corresponding to the switching regions.

As shown in FIG. 2A, a buffer layer 120 is formed on the substrate 100 with one selected from a group of inorganic insulating materials including silicon oxide (SiO ₂ ) and silicon nitride (SiNx).

Subsequently, an amorphous silicon layer 130 is formed on the buffer layer 120.

In this case, the buffer layer 120 is formed for the purpose of preventing foreign substances of the substrate 100 from penetrating the silicon layer 130 and damaging the silicon layer 130 during the crystallization of the silicon layer 130. .

As shown in FIG. 2B, a plasma surface treatment process is performed on the substrate 100 on which the amorphous silicon layer 130 is formed.

At this time, the process conditions during the plasma surface treatment power (power) 1000 ~ 1500W, the gas is He, O ₂ , Ar, etc., the pressure is 50 ~ 200mTorr, the gas flow rate (gas flow rate) 500 ~ 1000sccm The time is 60 ~ 120sec, the temperature proceeds around 400 ^° C.

In this case, the amorphous silicon layer 130 increases the disorder of the silicon array by making a large number of silicon bonds such as dangling bonds, voids, or interstitial through a plasma surface treatment process.

Here, in the plasma surface treatment process, when a light gas such as helium (He), oxygen (O ₂ ) or argon (Ar) is used, it is easy to move to an interface, thereby facilitating the formation of the dangling bond at the interface. Crystallization time can be reduced.

As shown in FIG. 2C, the substrate 100 subjected to the plasma surface treatment process is subjected to a heat treatment process at a high temperature.

At this time, the heat treatment process is performed within 600 ^° C near the temperature at which the glass is not deformed in the furnace (furnace) or RTA (Rapid Thermal Annealing) equipment.

In this case, as shown in FIGS. 3A and 3B, the crystallization may proceed from an interface directly above the buffer layer 120 by the heat treatment process, or may be performed inside the amorphous silicon layer, and is generally an electron buffer layer 120. Crystallization takes place at the top interface.

2C, as the crystallization proceeds from the interface above the buffer layer 120 through the above-described process, a portion of the amorphous silicon is gradually crystallized into polysilicon to form a mixed layer 135 in which amorphous silicon and polysilicon are mixed. do.

As shown in FIG. 2D, as time passes, all of the amorphous silicon is crystallized to form the polysilicon layer 140.

Through the above-described process, the amorphous silicon is crystallized to polysilicon to form the polysilicon layer 140.

4 is a flow chart of the above-described process.

As shown, 1. a step of preparing a substrate 2. a step of depositing a buffer layer on the substrate 3. a step of depositing an amorphous silicon layer on the buffer layer 4. performing a plasma treatment process on the amorphous silicon layer Step 5. Generating a large amount of silicon bonds such as dangling bonds, vacancy, penetration type, etc. by the plasma treatment process 6. Forming a polysilicon layer.

Therefore, in the step of crystallizing amorphous silicon into polysilicon through the above-described process, by adding the plasma surface treatment process to the intermediate step, silicon such as dangling bonds, voids or interstitial, etc. As the crystallization progresses by increasing the disorder of the silicon array by making a lot of bonds, the crystallization time can be shortened due to the reduction of activation energy due to the reduction of the latency period for nucleation. In addition, it becomes possible to manufacture a polysilicon excellent in crystallinity according to the reduction of the crystallization time.

--- Second Embodiment ---

A second embodiment of a polysilicon thin film transistor liquid crystal display device according to the present invention relates to a polysilicon liquid crystal display device to which the polysilicon formed in the first embodiment is applied.

5A to 5C are cross-sectional views illustrating a polysilicon liquid crystal display device according to a second embodiment according to a process sequence.

As shown in FIG. 5A, the buffer layer 220 is formed on the substrate 200 with one selected from a group of inorganic insulating materials including silicon oxide (SiO ₂ ) and silicon nitride (SiNx), and the buffer layer 220 is formed on the substrate 200. The polysilicon layer formed according to the first embodiment is formed on the substrate, and the polysilicon layer 240 is formed by patterning the polysilicon layer by a photolithography process.

Subsequently, a gate insulating layer 225 is formed on the semiconductor layer 240, and a gate metal layer (not shown) is successively deposited on the gate insulating layer 225, and the pattern is formed to form a gate wiring in one direction. ) And a gate electrode 250 extending from the gate line.

As shown in FIG. 5B, the semiconductor layer 240 is formed of a pure silicon layer 240a corresponding to the gate electrode 250 by doping the gate electrode 250 as an ion stopper. In addition, n-type or p-type ions are doped on both sides of the pure silicon layer 240a to be divided into impurity silicon layers 240b and 240c.

In this case, the pure silicon layer 240a is not doped to maintain a polycrystalline phase, and the impurity silicon layers 240b and 240c are doped to become an amorphous phase.

Subsequently, an interlayer insulating layer 245 including first and second semiconductor contact holes CH1 and CH2 is formed on the gate electrode 250, and the first and second semiconductors are formed on the interlayer insulating layer 245. The source and drain electrodes 254 and 258 corresponding to the respective regions are formed by connecting to the contact holes CH1 and CH2.

As shown in FIG. 5C, after the passivation layer 260 including the drain contact hole CH3 is formed on the source and drain electrodes 254 and 258, the drain electrode 258 and the drain contact hole CH3 are formed. The pixel electrode 270 is connected to each other.

Through the above-described process, the array substrate of the polysilicon thin film transistor liquid crystal display device can be manufactured.

Accordingly, the polysilicon thin film transistor liquid crystal display according to the present invention increases the silicon bonds such as dangling bonds, voids, or interstitial through a plasma surface treatment process, and thus crystallization proceeds. Since it is easier to bond with the side amorphous silicon, the crystallization time can be shortened due to the reduction of the activation energy due to the reduction of the latent period for nucleation, and excellent crystal characteristics through the shortening of the aforementioned crystallization time. It is possible to produce polysilicon.

Therefore, the polysilicon thin film transistor liquid crystal display device according to the present invention can reduce the solid crystallization time through the plasma surface treatment process, thereby making it possible to produce polysilicon having excellent crystal characteristics.

Claims (8)

Forming an amorphous silicon layer on the substrate; Plasma treating the amorphous silicon layer; Heat treating the plasma-treated amorphous silicon layer to form a polysilicon layer; Polycrystalline silicon crystallization method comprising a. The method of claim 1, And forming a buffer layer on the substrate before forming the amorphous silicon layer. The method of claim 1, The plasma treatment is a method of forming polycrystalline silicon using a gas such as oxygen (O) ₂ , helium (He), argon (Ar) and the like. The method according to claim 1 or 3, The plasma treatment time is a polycrystalline silicon formation method is performed under the condition of 60 ~ 120sec. The method of claim 1 or 3, The plasma treatment temperature is a polycrystalline silicon formation method that proceeds at 300 ~ 500 ^° C. The method according to claim 1 or 3, The plasma treatment process is a polycrystalline silicon forming method is performed at a pressure of 20 ~ 200mTorr, power 1000 ~ 15000W, gas flow rate 500 ~ 1000sccm. The method of claim 1, And a large amount of silicon bonds such as dangling bonds, voids, or interstitial are generated by the plasma treatment. Forming a buffer layer on the substrate; Forming an amorphous silicon layer on the buffer layer; Performing a plasma treatment on the amorphous silicon layer; Forming the plasma-treated amorphous silicon layer into a polysilicon layer through a high temperature heat treatment process; Forming a gate insulating film on the polysilicon layer; Forming a gate electrode on the gate insulating film; Doping the polysilicon layer using the gate electrode as a doping mask; Forming an interlayer insulating film including first and second semiconductor contact holes on the gate electrode; Forming source and drain electrodes on the interlayer insulating layer, the source and drain electrodes contacting the doped polysilicon layer through the first and second semiconductor contact holes; Forming a protective film including a drain contact hole on the source and drain electrodes; Forming a pixel electrode on the passivation layer, the pixel electrode contacting the drain electrode through the drain contact hole; Polysilicon liquid crystal display device manufacturing method comprising a.

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