KR101200879B1 - Thin film transistor substrate for hybrid liquid crystal display and method for fabricating thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor substrate for a hybrid liquid crystal display device and a manufacturing method thereof, and includes a pixel semiconductor layer and a driving semiconductor layer. At least a driving semiconductor layer of the semiconductor layers includes germanium.

Hybrid liquid crystal display, flat band voltage, germanium

Description

Thin film transistor substrate for hybrid liquid crystal display device and manufacturing method thereof

1 is a schematic diagram illustrating a hybrid liquid crystal display device according to an exemplary embodiment of the present invention.

2 is a cross-sectional view of a thin film transistor substrate for a hybrid liquid crystal display according to an exemplary embodiment of the present invention.

3A and 3B are graphs of voltage and current characteristics according to changes in germanium content of the thin film transistor of FIG. 2.

4A to 4H are cross-sectional views of steps of a manufacturing process of a thin film transistor substrate for a hybrid liquid crystal display according to an exemplary embodiment of the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS (S)

111: pixel gate electrode 112: pixel gate insulating film

113: pixel semiconductor layer 131: driving gate electrode

133: driving semiconductor layer 134: buffer layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor (TFT) substrate for a hybrid liquid crystal display (LCD) and a method of manufacturing the same. More particularly, the present invention relates to a method for reducing standby power and reducing power consumption. A thin film transistor substrate for a hybrid liquid crystal display device capable of increasing a contrast ratio and a method of manufacturing the same.

In today's information society, the role of electronic displays has become very important, and various electronic displays have been widely used in various industrial fields. In the field of electronic display devices, electronic display devices having new functions suitable for the needs of the information society have been continuously developed. In general, an electronic display device refers to a device that transmits various pieces of information to a human through vision. That is, an electronic display device refers to an electronic device that converts an electronic information signal output from various electronic devices into an optical information signal that can be recognized by a human eye, and is a device that plays a role of a bridge between humans and electronic devices. It can be said.

In such an electronic display device, when an optical information signal is displayed by a light emitting phenomenon, it is referred to as a light emitting display device, and when it is displayed by light modulation due to reflection, scattering, or interference phenomenon, it is called a light receiving display device. Light emitting displays, also called active display devices, include cathode ray tube (CRT), plasma display panel (PDP), organic electroluminescent display (OLD), and light emitting diodes (LED). Light Emitting Diode (LED) etc. can be mentioned. The light receiving display device, which is called a passive display device, may include a liquid crystal display (LCD) and an electrophoretic image display (EPID).

Cathode ray tube display device, which is used for television and computer monitor, and has the longest history, has the highest market share in terms of economy, but has many disadvantages such as heavy weight, large volume and high power consumption. .

Recently, due to the rapid progress of semiconductor technology, there is a demand for a flat panel display device as an electronic display device suitable for a new environment in accordance with the trend of lowering and lowering power of various electronic devices and miniaturization, thinning, and lightening of electronic devices. It is rapidly increasing. Accordingly, flat panel display devices such as a liquid crystal display (LCD), a plasma display device (PDP), an organic EL display device (OELD), and the like have been developed, and among these flat panel display devices, it is easy to miniaturize, light weight, and thinner. In particular, liquid crystal display devices having low power consumption and low driving voltage are drawing attention.

A liquid crystal display device injects a liquid crystal material having anisotropic dielectric constant between a color filter substrate having a common electrode, a color filter, a black matrix, and the like, and a thin film transistor substrate having a thin film transistor, a pixel electrode, or the like formed thereon. A display device expressing a desired image by adjusting the intensity of an electric field formed in the liquid crystal material by applying different potentials to the common electrode to change the molecular arrangement of the liquid crystal material, and thereby controlling the amount of light transmitted through the transparent insulating substrate. to be. The thin film transistor of the liquid crystal display device may be classified into a driving thin film transistor constituting a gate driver or a data driver and a pixel thin film transistor constituting a liquid crystal panel.

Both the driving thin film transistor and the pixel thin film transistor may be formed of amorphous silicon, and when formed of amorphous silicon, the mobility of the thin film transistor is reduced, and thus the integration degree of the gate driver or data driver composed of the driving thin film transistor is reduced. There is a problem of being lowered.

Both the driving thin film transistor and the pixel thin film transistor may be formed of polycrystalline silicon, and when formed of polycrystalline silicon, the performance and reliability of the thin film transistor may be improved, but the manufacturing process is complicated, thereby increasing the manufacturing cost of the liquid crystal display device. Let's do it.

In order to overcome this disadvantage, a hybrid liquid crystal display device in which the driving thin film transistor is formed of polycrystalline silicon and the pixel thin film transistor is formed of amorphous silicon has been proposed.

The driving thin film transistor of the conventional hybrid liquid crystal display uses a silicon nitride film (SiNx) as a gate insulating film, and a plurality of fixed charges are present in the gate insulating film of the silicon nitride. The fixed charge causes a negative shift in the flat band voltage of the driving thin film transistor. This negative transition of the flat band voltage increases the standby current flowing in the inactive state of the thin film transistor, which causes a problem of increased power consumption and reduced contrast ratio.

An object of the present invention is to provide a thin film transistor substrate for a hybrid liquid crystal display device and a method of manufacturing the same, which can increase contrast ratio while effectively reducing standby current.

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The technical objects to be achieved by the present invention are not limited to the technical matters mentioned above, and other technical subjects which are not mentioned can be clearly understood by those skilled in the art from the following description. There will be.

A thin film transistor substrate for a hybrid liquid crystal display according to an exemplary embodiment of the present invention includes a pixel gate electrode formed on a transparent insulating substrate, a pixel gate insulating film covering the pixel gate electrode, a pixel semiconductor layer formed on the pixel gate insulating film, and the pixel. A pixel thin film transistor including a pixel source electrode and a pixel drain electrode formed on the semiconductor layer; And a driving gate electrode formed on the transparent insulating substrate, a driving gate insulating film covering the driving gate electrode, a driving semiconductor layer formed on the driving gate insulating film, a buffer layer formed on the driving semiconductor layer, and a driving formed on the buffer layer. And a driving thin film transistor including a source electrode and a driving drain electrode.
The pixel semiconductor layer includes amorphous silicon and germanium, and the driving semiconductor layer includes polycrystalline silicon and germanium.
The germanium is contained in each of the driving semiconductor layers greater than 0 and less than 10 atm%.
The method of manufacturing a thin film transistor substrate for a hybrid liquid crystal display device includes forming a pixel gate electrode and a driving gate electrode on a transparent insulating substrate; Forming a pixel gate insulating film and a driving gate insulating film on the pixel gate electrode and the driving gate electrode; Forming a first amorphous semiconductor film of silicon and germanium on the pixel gate insulating film and the driving gate insulating film; Crystallizing a first amorphous semiconductor film formed on the driving gate electrode to form a polycrystalline semiconductor film; Forming a second amorphous semiconductor film of silicon on the first amorphous semiconductor film and the polycrystalline semiconductor film; Forming an electrode film with a conductive material on the second amorphous semiconductor film; And etching the first amorphous semiconductor film, the polycrystalline semiconductor film, the second amorphous semiconductor film, and the electrode film to form a pixel semiconductor layer, a pixel source electrode, a pixel drain electrode, a driving semiconductor layer, a buffer layer, a driving source electrode, and a driving drain electrode. Forming a step.
The first amorphous semiconductor film contains germanium that is greater than 0 and less than 10 atm%.
In the forming of the first amorphous semiconductor film, the silicon source gas and the germanium source gas are provided at 4000: 1 to 100: 1.

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Specific details of other embodiments are included in the detailed description and the drawings. Advantages and features of the present invention, and methods of achieving the same will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. Like reference numerals refer to like elements throughout.

Hereinafter, a thin film transistor substrate for a hybrid liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3B. 1 is a schematic diagram illustrating a hybrid liquid crystal display device according to an exemplary embodiment of the present invention. 2 is a cross-sectional view of a thin film transistor substrate for a hybrid liquid crystal display according to an exemplary embodiment of the present invention. 3A and 3B are graphs of voltage and current characteristics according to changes in germanium content of the thin film transistor of FIG. 2.

Referring to FIG. 1, a hybrid liquid crystal display according to the present invention includes a gate driver 200, a data driver 300, and a liquid crystal panel 400 formed on a transparent insulating substrate 100. The gate driver 200 includes a plurality of driving thin film transistors formed of polycrystalline silicon in a portion of the transparent insulating substrate 100, and sequentially outputs scan signals to the gate lines GL of the liquid crystal panel 400. The data driver 300 includes a plurality of driving thin film transistors formed of polycrystalline silicon in another portion of the transparent insulating substrate 100, and outputs an image signal to the data lines DL of the liquid crystal panel 400. The liquid crystal panel 400 extends in another direction on the transparent insulation substrate 100 in the horizontal direction, is arranged in the vertical direction, and extends in the vertical direction with a gate line GL for transmitting a scan signal. Of the pixel thin film transistor TFT and the pixel thin film transistor TFT formed in a region defined by the data line DL for transmitting an image signal, and defined by the gate line GL and the data line DL. The liquid crystal capacitor Clc is connected between the drain and the common voltage Vcom, and the storage capacitor Cst is connected to the drain of the pixel thin film transistor TFT.

As illustrated in FIG. 2, a pixel thin film transistor (a-Si TFT) and a driving thin film transistor (poly-Si TFT) are formed on a thin film transistor substrate for a hybrid liquid crystal display according to an exemplary embodiment of the present invention. The pixel thin film transistor (a-Si TFT) includes a pixel gate electrode 111, a pixel gate insulating layer 112, a pixel semiconductor layer 113, a pixel source electrode 116, and a transparent insulating substrate 100. The pixel drain electrode 117 is included. The driving thin film transistor (poly-Si TFT) may include a driving gate electrode 131, a driving gate insulating layer 112, a driving semiconductor layer 133, and a buffer layer formed of amorphous silicon on the driving semiconductor layer 133 ( 134 and a driving source electrode 137 and a driving drain electrode 138.

Here, the pixel gate electrode 111 is formed of a metal material including aluminum or the like on the transparent insulating substrate 100, and the pixel gate insulating layer 112 is formed of a silicon nitride film (R) in a region covering the pixel gate electrode 111. And an insulating material such as SiNx) and silicon oxide film (SiOx).

The pixel semiconductor layer 113 is formed of amorphous silicon and germanium at a position covering the pixel gate electrode 111 on the pixel gate insulating layer 112, and the pixel source electrode 116 and the pixel drain electrode 117 are made of aluminum. And a metal material including chromium and the like, and are disposed to be spaced apart from each other while exposing the pixel semiconductor layer 113 in a region corresponding to the pixel gate electrode 111. In addition, the ohmic contact layers 114 and 115 are formed of amorphous silicon doped with a high concentration of n-type impurities at an interface between the pixel source electrode 116 and the pixel drain electrode 117 and the pixel semiconductor layer 113.

Meanwhile, the driving gate electrode 131 is formed of a metal material including aluminum on the transparent insulating substrate 100, and the driving gate insulating layer 112 is formed of a silicon nitride film (SiNx) in a region covering the driving gate electrode 131. ) And a silicon oxide film (SiOx).

The driving semiconductor layer 133 is formed of polycrystalline silicon and germanium at a position covering the driving gate electrode 131 on the driving gate insulating layer 112, and the buffer layer 134 is formed of amorphous silicon on the driving semiconductor layer 133. The driving source electrode 137 and the driving drain electrode 138 are metal materials including aluminum and chromium, and are spaced apart from each other by exposing the buffer layer 134 to a region corresponding to the driving gate electrode 131. It is located and formed. In addition, the ohmic contact layers 135 and 136 are formed of amorphous silicon doped with a high concentration of n-type impurities at the interface between the driving source electrode 137, the driving drain electrode 138, and the buffer layer 134.

The driving semiconductor layer 133 is formed of polycrystalline silicon and germanium. Germanium may be contained in the driving semiconductor layer 133 in an amount ratio of greater than 0 and less than or equal to 10 atm%. Germanium may effectively reduce the standby current flowing when the driving thin film transistor (poly-Si TFT) is not activated by adjusting the flat band voltage. Germanium may be contained in the pixel semiconductor layer 113 in the same content ratio.

3A is a graph of voltage and current characteristics according to the germanium content change of the driving thin film transistor (poly-Si TFT). Referring to FIG. 3A, the driving thin film transistor pol0y increases as the germanium content of the driving semiconductor layer 133 increases. It can be seen that the standby current flowing in the state where -Si TFT) is not activated is reduced. FIG. 3B is a graph of voltage and current characteristics according to a change in germanium content of a pixel thin film transistor (a-Si TFT). Referring to FIG. 3B, a pixel thin film transistor (a-Si TFT) may be included even if germanium is included in the pixel semiconductor layer 113. It can be seen that the standby current flowing in the state where) is not activated is hardly changed.

The intermediate insulating layer 118 is formed of an organic insulating material on the pixel source electrode 116, the pixel drain electrode 117, the driving source electrode 137, and the driving drain electrode 138. The passivation layer 119 is formed on the passivation layer, and the passivation layer 119 is formed on the passivation layer 119. The passivation layer 119 is connected to the pixel drain electrode 117 or the driving drain electrode 138. have.

Hereinafter, a method of manufacturing a thin film transistor substrate for a hybrid liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 4A to 4H. 4A to 4H are cross-sectional views of steps of a manufacturing process of a thin film transistor substrate for a hybrid liquid crystal display according to an exemplary embodiment of the present invention.

First, a gate electrode material is deposited on the transparent insulating substrate 100, and the pixel gate electrode 111 and the driving gate electrode 131 are formed as shown in FIG. 4A by using a photo process and an etching process. The material of the pixel gate electrode 111 and the driving gate electrode 131 is selected from a metal material having a low resistivity value, and preferably selected from a metal material such as aluminum.

Next, as illustrated in FIG. 4B, the pixel gate insulating layer 112 and the driving gate insulating layer 112 are formed on the pixel gate electrode 111 and the driving gate electrode 131. The pixel gate insulating film 112 and the driving gate insulating film 112 may be formed of a silicon nitride film, a silicon oxide film, or the like.

Next, as shown in FIG. 4C, the first amorphous semiconductor film 151 is formed of silicon and germanium on the pixel gate insulating film 112 and the driving gate insulating film 112. Here, it is preferable that the 1st amorphous semiconductor film 151 contains germanium larger than 0 and 10 atm% or less. Specifically, silicon source gas (eg, SiH 4, Si 2 H 6) and germanium source gas (eg, GeH 4, GeF 4) are provided at 4000: 1 to 100: 1.

Next, as illustrated in FIG. 4D, the first amorphous semiconductor film 151 formed on the driving gate electrode 131 is crystallized by an excimer laser annealing process to form a polycrystalline semiconductor film 152. .

Next, as shown in FIG. 4E, the second amorphous semiconductor film 153 is formed of silicon on the first semiconductor film and the polycrystalline semiconductor film 152.

Next, as illustrated in FIG. 4F, the third amorphous semiconductor film 154 and the electrode material 155 are formed of a conductive material on the second amorphous semiconductor film 153 with silicon heavily doped with n-type impurities. do. Here, the electrode film 155 is selected from a metal material having a low specific resistance value, and preferably selected from a metal material including aluminum, chromium, and the like.

Next, as shown in FIG. 4G, the first amorphous semiconductor film 151, the polycrystalline semiconductor film 152, the second amorphous semiconductor film 153, the third amorphous semiconductor film 154, and the electrode film 155 are disposed. Etching forms the pixel semiconductor layer 113, the pixel source electrode 116, the pixel drain electrode 117, the driving semiconductor layer 133, the buffer layer 134, the driving source electrode 137, and the driving drain electrode 138. do.

Next, as shown in FIG. 4H, an intermediate insulating layer 118 is formed on the pixel source electrode 116, the pixel drain electrode 117, the driving source electrode 137, and the driving drain electrode 138 with an organic insulating material. And a passivation layer 119 formed of an inorganic insulating material on the intermediate insulating layer 118, and connected to the pixel drain electrode 117 or the driving drain electrode 138 with a transparent insulating material on the passivation layer 119. Electrodes 120 and 140 are formed.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

Therefore, it should be understood that the above-described embodiments are provided so that those skilled in the art can fully understand the scope of the present invention. Therefore, it should be understood that the embodiments are to be considered in all respects as illustrative and not restrictive, The invention is only defined by the scope of the claims.

In the thin film transistor substrate for a hybrid liquid crystal display according to the exemplary embodiment of the present invention, the driving semiconductor layer is formed of polycrystalline silicon and germanium, and the germanium is contained at 10% or less, thereby preventing the driving thin film transistor from being activated. Since the standby current flowing in the non-active state can be effectively reduced, the contrast ratio can be increased while reducing the power consumption.

In addition, the method for manufacturing a thin film transistor substrate for a hybrid liquid crystal display according to an exemplary embodiment of the present invention can effectively manufacture the thin film transistor substrate described above.

Claims (5)

A pixel thin film including a pixel gate electrode formed on a transparent insulating substrate, a pixel gate insulating film covering the pixel gate electrode, a pixel semiconductor layer formed on the pixel gate insulating film, a pixel source electrode and a pixel drain electrode formed on the pixel semiconductor layer transistor; And A driving gate electrode formed on the transparent insulating substrate, a driving gate insulating film covering the driving gate electrode, a driving semiconductor layer formed on the driving gate insulating film, a buffer layer formed on the driving semiconductor layer, and a driving source formed on the buffer layer A driving thin film transistor including an electrode and a driving drain electrode, The pixel semiconductor layer includes amorphous silicon and germanium, The driving semiconductor layer is a thin film transistor substrate for a hybrid liquid crystal display, characterized in that the polycrystalline silicon and germanium. The method of claim 1, And the germanium is contained in each of the driving semiconductor layers greater than 0 and less than 10 atm%. Forming a pixel gate electrode and a driving gate electrode on the transparent insulating substrate; Forming a pixel gate insulating film and a driving gate insulating film on the pixel gate electrode and the driving gate electrode; Forming a first amorphous semiconductor film of silicon and germanium on the pixel gate insulating film and the driving gate insulating film; Crystallizing a first amorphous semiconductor film formed on the driving gate electrode to form a polycrystalline semiconductor film; Forming a second amorphous semiconductor film of silicon on the first amorphous semiconductor film and the polycrystalline semiconductor film; Forming an electrode film with a conductive material on the second amorphous semiconductor film; And The first amorphous semiconductor film, the polycrystalline semiconductor film, the second amorphous semiconductor film, and the electrode film are etched to form a pixel semiconductor layer, a pixel source electrode, a pixel drain electrode, a driving semiconductor layer, a buffer layer, a driving source electrode, and a driving drain electrode. A method of manufacturing a thin film transistor substrate for a hybrid liquid crystal display device comprising the step of forming. The method of claim 3, And wherein the first amorphous semiconductor film contains germanium of greater than 0 and less than 10 atm%. 5. The method of claim 4, In the forming of the first amorphous semiconductor film, a silicon source gas and a germanium source gas are provided in a range of 4000: 1 to 100: 1.

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