KR20080067910A - Thin film transistor and manufacutring method thereof - Google Patents

Abstract

A thin film transistor and a manufacturing method thereof are provided to deposit readily a gate electrode by forming a capping layer on an upper surface of a gate insulating layer. A buffer layer(110) is formed on an upper surface of a substrate(100). A source electrode(121) and a drain electrode(122) are formed on an upper surface of the buffer layer. An active layer(130) is formed on the upper surface of the buffer layer to cover partially the source electrode and the drain electrode. A gate insulating layer(140) is formed on an upper surface of the active layer. A capping layer(150) is formed on an upper surface of the gate insulating layer. A gate electrode(160) is formed on an upper surface of the capping layer.

Description

 Thin film transistor and its manufacturing method {Thin film transistor and manufacutring method

1 is a cross-sectional view showing a schematic structure of a typical top gate active drive device

2 is a cross-sectional view of a thin film transistor according to the present invention.

3A to 3F are cross-sectional views illustrating a manufacturing process of a thin film transistor according to the present invention.

4 is a view for explaining the formation of a capping layer by O ₂ plasma treatment the gate insulating film in accordance with the present invention

5 is a graph measuring binding energy of a gate insulating film and a capping layer according to the present invention.

<Description of the symbols for the main parts of the drawings>

100 substrate 110 buffer layer

121: source electrode 122: drain electrode

130: active layer 140: gate insulating film

150: capping layer 160: gate electrode

200: chamber

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor and a method for manufacturing the same, and more particularly, to a thin film transistor and a method for manufacturing the same, which can block gas and moisture from penetrating into the gate insulating film from the outside, thereby preventing deterioration in gate insulating film properties. It is about.

Recently, with the rapid development of the information society, various types of display devices such as liquid crystal display (PDP), plasma display panel (PDP), electro luminescent display (ELD), vacuum fluorescent display (VFD), and organic light emitting display are being introduced. Developed.

Among them, liquid crystal display (LCD) panels are excellent in resolution, color display, and image quality, and are being actively applied to notebooks and desktop monitors.

On the other hand, as the display panel is enlarged according to consumer demand, various process facilities are being developed, and facilities using new construction methods are being developed.

Here, the liquid crystal display device is in a trend that its application range is gradually widening due to the characteristics such as light weight, thinness, low power consumption driving.

In accordance with this trend, liquid crystal displays are used in office automation equipment, audio, video equipment, computer monitors, broadcast reception monitors, and the like.

In order to use the liquid crystal display as a general screen display device in various parts, it is a matter of how high quality images such as high definition, high brightness, and large area can be realized while maintaining the characteristics of light weight, thinness, and low power consumption. can do.

A normal liquid crystal display device displays an image by adjusting the light transmittance of the liquid crystal using an electric field.

To this end, the liquid crystal display includes a liquid crystal panel in which liquid crystal cells are arranged in a matrix and a driving circuit for driving the liquid crystal panel.

Therefore, the liquid crystal display device is comprised from the 1st board | substrate and the 2nd board | substrate which were bonded by the fixed space, and the liquid crystal layer injected between the said 1st board | substrate and the 2nd board | substrate.

In more detail, the first substrate has a plurality of gate lines in one direction and a plurality of data lines at regular intervals in a direction perpendicular to the gate line to define a pixel area.

In addition, a pixel electrode is formed in the pixel region, and a thin film transistor is formed at a portion where the gate line and the data line cross each other, and a data signal of the data line is applied to each pixel electrode according to a signal applied to the gate line. Is authorized.

In addition, a black matrix layer is formed on the second substrate to block light in portions other than the pixel region, and portions corresponding to each pixel region are R, G, B, and color filter layers for expressing color. A common electrode for realizing an image is formed on the color filter layer.

In the liquid crystal display as described above, the liquid crystal of the liquid crystal layer formed between the first and second substrates is aligned by an electric field between the pixel electrode and the common electrode, and the light passes through the liquid crystal layer according to the degree of alignment of the liquid crystal layer. Adjust the amount of to express the image.

On the other hand, a display such as a liquid crystal display device may be divided into a passive matrix (PM) display and an active matrix (AM) display according to a driving method.

In the passive driving display structure, the anode and the cathode are arranged so as to be orthogonal to each other to drive the light when current flows in the pixels orthogonal to each other.

In this method, pixel brightness is controlled by time division driving. At this time, image information is input from the opposite electrode according to one line electrode which is turned on.

Therefore, this type of driving generates the momentary high luminance because the brightness decreases by the inverse of the number to be scanned.

In addition, the active driving display has a fundamental principle similar to that of a thin film transistor-liquid crystal display (TFT-LCD), and generally, amorphous silicon (a-Si) or polysilicon (poly-Si) is used as an active layer ( It is used as an active layer to control the current or voltage in the pixel.

In addition, the active driving device not only regulates the current or voltage of each pixel, but also has a merit of minimizing the external area of the driving device in terms of design since the driving circuit is used as a back plane in design.

Currently, display active thin film transistors have made many advances with liquid crystal displays and organic ELs.

However, the active thin film transistor uses poly-Si or amorphous silicon (a-Si) as a channel material.

 The use of the channel as polysilicon increases hole mobility, whereas the use of amorphous silicon has a disadvantage in that the mobility is lowered, thereby limiting its application.

Recently, various researches have been conducted on the problems of overcoming the low mobility of amorphous silicon and channel materials for realizing low temperature process. Among them, the organic materials and inorganic materials are used. Can be.

The representative of the field using organic materials is pentacene (Pentacene) as a channel material, which is suitable for low temperature process, but has not been commercialized due to various problems such as the stability of organic matter and the application of gate insulator.

A typical field using inorganic materials is thin film transistors using ZnO and Indium Gallium Zinc Oxide (IGZO).

ZnO and IGZO can be used as n-type metal oxide semiconductors (NMOS) as the n-channel material of the thin film transistor while showing the n-type characteristics of the semiconductor.

1 is a cross-sectional view illustrating a schematic structure of a general top gate active driving device, in which a buffer layer 11 and an active layer 12 are sequentially formed on a substrate 10, and the active layer 12 is formed. The gate insulating layer 15 and the gate electrode 16 are sequentially formed on the upper side of the gate insulating layer, and the source and drain electrodes 13 and 14 are formed on the active layers 12 on both sides of the gate insulating layer 15.

In the top gate active driving device, when a voltage is applied to the gate electrode 16, a channel is formed in the active layer 12 so that a current flows between the source and drain electrodes 13 and 14.

Therefore, the transistor functions.

At this time, SiNx is used as the gate insulating film, which is deposited at low temperature using PE-CVD.

However, the disadvantage of PE-CVD is a problem of using a low temperature process, and after the gate insulating film is formed, many defects are formed in the gate insulating film. In particular, N and H which are not bonded with Si are typical examples.

The defects disappear when raised to a high temperature. When ZnO and IGZO are used as the active layer, the materials processed at a low temperature have a heat effect, and thus the characteristics of the gate insulating layer are changed.

In addition, the gate insulating film that is not stable reacts with external moisture or gas, and the characteristics thereof change during the process.

In order to solve the problems described above, the present invention can form a capping layer on the gate insulating film to block the gas and moisture penetrating into the gate insulating film from the outside, thereby preventing the deterioration of the gate insulating film properties An object of the present invention is to provide a thin film transistor and a method of manufacturing the same.

Another object of the present invention is to provide a thin film transistor capable of smoothly depositing a gate electrode by forming a capping layer on the gate insulating film by surface treating the gate insulating film using an O ₂ plasma, and a method of manufacturing the same.

A preferred aspect for achieving the above objects of the present invention,

A substrate having a buffer layer formed thereon;

Source and drain electrodes formed on the buffer layer;

An active layer surrounding a portion of each of the source and drain electrodes and formed on the buffer layer;

A gate insulating film formed over the active layer; A capping layer formed on the gate insulating layer;

A thin film transistor including a gate electrode formed on the capping layer is provided.

Another preferred aspect for achieving the above object of the present invention,

Forming a buffer layer over the substrate;

Forming a source and a drain electrode on the buffer layer;

Enclosing a portion of each of the source and drain electrodes and forming an active layer on the buffer layer;

Forming a gate insulating film on the active layer;

Forming a capping layer on the gate insulating layer;

Provided is a method of manufacturing a thin film transistor, the method comprising forming a gate electrode on the capping layer.

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

2 is a cross-sectional view of a thin film transistor according to the present invention, the substrate 100 having a buffer layer 110 formed thereon; Source and drain electrodes 121 and 122 formed on the buffer layer 110; An active layer 130 formed around the buffer layer and covering a portion of each of the source and drain electrodes 121 and 122; A gate insulating layer 140 formed on the active layer 130; A capping layer 150 formed on the gate insulating layer 140; The gate electrode 160 is formed on the capping layer 150.

The capping layer 150 may be a layer formed by performing O ₂ plasma treatment on the gate insulating layer 140.

In this case, when the gate insulating layer 140 is a silicon-based compound, the capping layer is formed of one of a SiN _x film, a SiO film, and a SiON film combined with the silicon.

The active layer 130 is a layer in which a current flow channel is formed between the source and drain electrodes by the voltage applied to the gate electrode 160.

In addition, the thickness of the capping layer 150 is preferably 1nm ~ 10nm.

When the capping layer 150 is formed on the gate insulating layer 140 in this manner, the capping layer 150 may block gas and moisture from penetrating into the gate insulating layer 140 from the outside, thereby preventing the characteristics of the gate insulating layer 140. It can prevent a fall.

Accordingly, the present invention is to form a capping layer on the gate insulating film, it is possible to reduce the external influence of the gate insulating film.

3A to 3F are cross-sectional views illustrating a process of manufacturing a thin film transistor according to the present invention. First, a buffer layer 110 is formed on a substrate 100 (FIG. 3A).

Thereafter, source and drain electrodes 121 and 122 are formed on the buffer layer 110 (FIG. 3B).

Subsequently, a portion of each of the source and drain electrodes 121 and 122 is wrapped to form an active layer 130 on the buffer layer 110 (FIG. 3C).

Subsequently, a gate insulating layer 140 is formed on the active layer 130 (FIG. 3D).

Next, a capping layer 150 is formed on the gate insulating layer 140 (FIG. 3E).

In this case, the capping layer 150 may be formed by performing O ₂ plasma treatment on the gate insulating layer to form the capping layer.

Finally, the gate electrode 160 is formed on the capping layer 150 (FIG. 3F).

4 is a view for explaining the formation of a capping layer by O ₂ plasma treatment of the gate insulating film according to the present invention, in the above-described process of Figure 3d, after forming the gate insulating film on the active layer, in the chamber 200 In the O ₂ plasma treatment, a capping layer 150 is formed on the gate insulating layer 140.

That is, when the gate insulating film is a silicon-based compound, the capping layer is formed of a SiN _x film, an SiO film, and a SiON film bonded to the silicon.

Therefore, in the present invention, a silica-like material is formed by using O ₂ plasma, which is a surface treatment method, for capping the gate insulating film in a top gate type low temperature thin film transistor, thereby reducing external influences. .

In addition, since the capping layer formed by surface treatment using O ₂ plasma has improved wettability, metal for forming the gate electrode is well deposited on the capping layer.

5 is a graph measuring binding energy between the gate insulating film and the capping layer according to the present invention. When the gate insulating film is a silicon-based compound, the capping layer is formed by O ₂ plasma treatment of the gate insulating film according to the present invention. Is formed.

Referring to the measurement graph of FIG. 5, it can be seen that the binding energy of the capping layer B is higher than the binding energy of the gate insulating layer A before the O ₂ plasma treatment.

From the binding energy, it can be seen that the silicon-based compound state is changed from the silicon-based compound state.

Therefore, since the binding energy of the capping layer is higher than that of the gate insulating film, the metal for forming the gate electrode can be better deposited on the capping layer than the gate insulating film.

As described above, the present invention has the effect of forming a capping layer on the gate insulating film to block the gas and moisture penetrating into the gate insulating film from the outside, thereby preventing the deterioration of the gate insulating film properties have.

In addition, the present invention has an effect that the deposition of the gate electrode can be facilitated by forming a capping layer on the gate insulating film by surface-treating the gate insulating film using O ₂ plasma.

Although the invention has been described in detail only with respect to specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (6)

A substrate having a buffer layer formed thereon; Source and drain electrodes formed on the buffer layer; An active layer surrounding a portion of each of the source and drain electrodes and formed on the buffer layer; A gate insulating film formed over the active layer; A capping layer formed on the gate insulating layer; A thin film transistor comprising a gate electrode formed on the capping layer. The method of claim 1, The capping layer, And a layer formed by performing O ₂ plasma treatment on the gate insulating layer. The method of claim 1, The gate insulating film is a silicon-based compound, The capping layer is a thin film transistor, characterized in that one of the SiN _x film, SiO film and SiON film. The method of claim 1, The thickness of the capping layer, A thin film transistor, which is 1 nm to 10 nm. Forming a buffer layer over the substrate; Forming a source and a drain electrode on the buffer layer; Enclosing a portion of each of the source and drain electrodes and forming an active layer on the buffer layer; Forming a gate insulating film on the active layer; Forming a capping layer on the gate insulating layer; And forming a gate electrode on the capping layer. The method of claim 5, wherein Forming a capping layer on the gate insulating film, And forming the capping layer by performing O ₂ plasma treatment on the gate insulating layer.

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