KR20110061419A - Method of fabricating oxide thin film transistor - Google Patents

Abstract

PURPOSE: A method for manufacturing an oxide thin film transistor is provided to prevent a carrier concentration change of a channel area by using an etch stopper, thereby preventing an oxide semiconductor from being deteriorated. CONSTITUTION: A gate insulating film(115a), an oxide semiconductor layer, and an insulating layer are successively formed on a substrate(110). The insulating layer is selectively patterned so that an etch stopper(125) is formed on a gate electrode. The oxide semiconductor layer is selectively patterned to form an active layer in the lower part of the etch stopper. Source/drain electrodes are electrically connected to the source/drain areas of the active layer. A protection layer is formed on the substrate on which the source/drain electrodes are formed. A pixel electrode is electrically connected to the drain electrode through a contact hole.

Description

Manufacturing Method of Oxide Thin Film Transistor {METHOD OF FABRICATING OXIDE THIN FILM TRANSISTOR}

The present invention relates to a method for manufacturing an oxide thin film transistor, and more particularly, in the combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr; x, y, z> 0). The present invention relates to a method for manufacturing an oxide thin film transistor using an integrative quarter- or tetracomponent oxide semiconductor as an active layer.

Recently, with increasing interest in information display and increasing demand for using a portable information carrier, a lightweight flat panel display (FPD), which replaces a conventional display device, a cathode ray tube (CRT), is used. The research and commercialization of Korea is focused on. In particular, the liquid crystal display (LCD) of the flat panel display device is an image representing the image using the optical anisotropy of the liquid crystal, is excellent in resolution, color display and image quality, and is actively applied to notebooks or desktop monitors have.

The liquid crystal display is largely composed of a color filter substrate and an array substrate, and a liquid crystal layer formed between the color filter substrate and the array substrate.

The active matrix (AM) method, which is a driving method mainly used in the liquid crystal display device, uses an amorphous silicon thin film transistor (a-Si TFT) as a switching device to drive the liquid crystal in the pixel portion. to be.

Hereinafter, a structure of a general liquid crystal display device will be described in detail with reference to FIG. 1.

1 is an exploded perspective view schematically illustrating a general liquid crystal display.

As shown in the figure, the liquid crystal display device is largely a liquid crystal layer (liquid crystal layer) formed between the color filter substrate 5 and the array substrate 10 and the color filter substrate 5 and the array substrate 10 ( 30).

The color filter substrate 5 includes a color filter C composed of a plurality of sub-color filters 7 for implementing colors of red (R), green (G), and blue (B); A black matrix 6 that separates the sub-color filters 7 and blocks light passing through the liquid crystal layer 30, and a transparent common electrode that applies a voltage to the liquid crystal layer 30. 8)

In addition, the array substrate 10 may be arranged vertically and horizontally to define a plurality of gate lines 16 and data lines 17 defining a plurality of pixel regions P. The thin film transistor T, which is a switching element formed in the cross region, and the pixel electrode 18 formed on the pixel region P, are formed.

The color filter substrate 5 and the array substrate 10 are joined to face each other by a sealant (not shown) formed on the outer side of the image display area to form a liquid crystal display panel, and the color filter substrate 5 And the bonding of the array substrate 10 is made through a bonding key (not shown) formed in the color filter substrate 5 or the array substrate 10.

On the other hand, the above-mentioned liquid crystal display device has been the most attracting display device until now because of the light weight and low power consumption, but the liquid crystal display device is not a light emitting device but a light receiving device and because of the technical limitations such as brightness, contrast ratio and viewing angle, Development of new display devices that can overcome the disadvantages is actively being developed.

Organic Light Emitting Diode (OLED), one of the new flat panel displays, is self-luminous, so it has better viewing angle and contrast ratio than liquid crystal displays, and it is lightweight because it does not require backlight. It is also advantageous in terms of power consumption. In addition, there is an advantage that the DC low-voltage drive is possible and the response speed is fast, in particular, it has an advantage in terms of manufacturing cost.

Recently, studies on the large area of the organic light emitting display have been actively conducted, and in order to achieve this, there is a demand for developing a transistor having stable operation and durability by securing a constant current characteristic as a driving transistor of the organic light emitting display.

Amorphous silicon thin film transistors used in the above-described liquid crystal display device can be fabricated in a low temperature process, but have very low mobility and do not satisfy the constant current bias condition. Polycrystalline silicon thin film transistors, on the other hand, have high mobility and satisfactory constant current test conditions, and are difficult to obtain uniform characteristics, making it difficult to large area and require high temperature processes.

Accordingly, an oxide thin film transistor having an active layer formed of an oxide semiconductor has been developed. In this case, when the oxide semiconductor is applied to a thin film transistor having a bottom gate structure, an etching process of a source / drain electrode, in particular, plasma is used. There is a problem that the oxide semiconductor is damaged during dry etching and causes denaturation.

In order to prevent this, an etch stopper may be additionally formed on the active layer as a barrier layer. In this case, the back channel region of the active layer may form the active layer and the etch stopper. Exposure to chemicals such as photoresist film and stripper and ultraviolet light (UV) used in the photolithography process (hereinafter referred to as photo process) to change the characteristics of the semiconductor thin film causing deterioration of device characteristics Done.

2 is a cross-sectional view schematically illustrating a structure of a general oxide thin film transistor.

As shown in the drawing, a general oxide thin film transistor includes a gate electrode 21 formed on a predetermined substrate 10, a gate insulating film 15a formed on the gate electrode 21, and an oxide semiconductor on the gate insulating film 15a. An etch stopper 25 formed of an active layer 24 formed of a predetermined insulating material, source / drain electrodes 22 and 23 electrically connected to a predetermined region of the active layer 24, and the source / drain electrodes ( 22 and 23, and a pixel electrode 18 electrically connected to the drain electrode 23. The passivation layer 15b is formed on the passivation layer 15b.

3A through 3F are cross-sectional views sequentially illustrating a manufacturing process of the general oxide thin film transistor illustrated in FIG. 2.

As shown in FIG. 3A, a first conductive film is deposited on the entire surface of a predetermined substrate 10, and then selectively patterned through a photo process to form a gate electrode 21 formed of the first conductive film on the substrate 10. To form.

Next, as illustrated in FIG. 3B, an oxide semiconductor layer including a gate insulating film 15a and a predetermined oxide semiconductor is sequentially deposited on the entire surface of the substrate 10 to cover the gate electrode 21. By selectively patterning using a process, an active layer 24 made of the oxide semiconductor is formed on the gate electrode 21.

As shown in FIG. 3C, an insulating layer made of a predetermined insulating material is deposited on the entire surface of the substrate 10, and then selectively patterned by using a photo process to form the insulating material on the active layer 24. Form an etch stopper 25 made of.

Next, as illustrated in FIG. 3D, a second conductive film is formed on the entire surface of the substrate 10 on which the etch stopper 25 is formed, and then selectively patterned through the photo process to etch the active layer 24. Source / drain electrodes 22 and 23 made of the second conductive layer and electrically connected to the source / drain regions of the active layer 24 are formed on the top of the stopper 25.

Next, as shown in FIG. 3E, a predetermined protective layer 15b is formed on the entire surface of the substrate 10 on which the source / drain electrodes 22 and 23 are formed, and then selectively patterned through a photo process. The contact hole 40 exposing a part of the drain electrode 23 is formed.

As shown in FIG. 3F, a third conductive film is formed on the entire surface of the substrate 10 and then selectively patterned through a photo process to electrically connect the drain electrode 23 through the contact hole. The electrode 18 is formed.

That is, in the prior art, after the deposition of the oxide semiconductor layer, an active layer is formed through a photo process, and then an insulating layer for forming an etch stopper is deposited. The etch stopper is formed by patterning the insulating layer through another photo process.

At this time, the patterning of the active layer and the deposition of the insulating layer are performed while the vacuum of the vacuum chamber is released, and the oxide semiconductor is exposed to the atmosphere, and the photosensitive film is subjected to a photo process for forming the active layer and the etch stopper. Exposure to chemicals such as and strippers and UV damages the back channel region. As a result, the device characteristics are deteriorated, and the tact time is increased by the movement between the chamber equipment during the deposition of the insulating layer.

In general, an oxide semiconductor has both characteristics of a conductor and a semiconductor, and can be transferred by controlling a carrier concentration in a thin film. The main mechanism for controlling the carrier concentration is due to the electrons produced by the generation of oxygen vacancy points, and the generation of oxygen attack points results in damage of oxide semiconductors in various processes. Is generated by). As a result, oxide semiconductors are thought to be damaged by solvents of basic materials in addition to commonly known acids.

The present invention is to solve the above problems, a ternary system consisting of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr; x, y, z ≥ 0) It is an object to provide a method for producing an oxide thin film transistor using a component oxide semiconductor as an active layer.

Another object of the present invention is to form an etch stopper by depositing an insulating layer immediately after depositing an oxide semiconductor layer to prevent damage to the back channel of the active layer during patterning of the active layer and the etch stopper. To provide a method of manufacturing.

It is still another object of the present invention to provide a method of manufacturing an oxide thin film transistor in which a resistance of an oxide semiconductor layer exposed through etching of the insulating layer is reduced to form a contact region with a source / drain electrode.

Other objects and features of the present invention will be described in the configuration and claims of the invention described below.

In order to achieve the above object, the manufacturing method of the oxide thin film transistor of the present invention comprises the steps of forming a gate electrode on the substrate; Continuously forming a gate insulating film, an oxide semiconductor layer, and an insulating layer on the substrate; Selectively patterning the insulating layer to form an etch stopper on the gate electrode; Selectively patterning the oxide semiconductor layer to form an active layer under the etch stopper; Forming a source / drain electrode electrically connected to a source / drain region of the active layer on the substrate on which the active layer and the etch stopper are formed; Forming a protective layer on the substrate on which the source / drain electrodes are formed; Removing a portion of the protective layer to form a contact hole exposing a portion of the drain electrode; And forming a pixel electrode electrically connected to the drain electrode through the contact hole, wherein the oxide semiconductor layer includes AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr). It is characterized by consisting of ternary or tetracomponent oxide semiconductor consisting of a combination of x, y, z ≥ 0).

As described above, the method of manufacturing the oxide thin film transistor according to the present invention has an excellent uniformity by using an amorphous oxide semiconductor as an active layer, thereby providing an effect applicable to a large area display.

In this case, the amorphous oxide semiconductor reacts to the plasma in a subsequent process to change the carrier concentration of the channel region. In the method of manufacturing an oxide thin film transistor according to the present invention, an etch stopper is used to By preventing the carrier concentration change, it provides an effect of preventing the deterioration of the oxide semiconductor.

In particular, the method of manufacturing an oxide thin film transistor according to the present invention forms an etch stopper by depositing an insulating layer immediately after depositing an oxide semiconductor layer to completely prevent the exposure of the back channel region, while By preventing the back channel of the active layer from being damaged during patterning, the device characteristics are improved.

Hereinafter, exemplary embodiments of an oxide thin film transistor and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

4 is a cross-sectional view schematically illustrating a structure of an oxide thin film transistor according to an exemplary embodiment of the present invention, wherein AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr; x, y, z ≥ The structure of an oxide thin film transistor using a ternary or tetracomponent oxide semiconductor composed of a combination of 0) as an active layer is schematically shown.

As shown in the figure, the oxide thin film transistor according to the embodiment of the present invention is a gate electrode 121 formed on a predetermined substrate 110, a gate insulating film 115a formed on the gate electrode 121, the gate electrode ( 121 The source / drain electrodes 122 electrically connected to the active layer 124 formed of an oxide semiconductor on the top, the etch stopper 125 formed of a predetermined insulating material, and the source / drain regions of the active layer 124. 123).

In addition, the oxide thin film transistor according to the exemplary embodiment of the present invention may include a passivation layer 115b formed on the substrate 110 on which the source / drain electrodes 122 and 123 are formed and a contact hole formed in the passivation layer 115b. And a pixel electrode 118 electrically connected to the drain electrode 123.

In this case, although not shown in the drawing, the gate electrode 121 is connected to a predetermined gate line, and a portion of the source electrode 122 extends in one direction to be connected to a data line, and the gate line and the data line are connected to a substrate ( 110 is arranged vertically and horizontally to define the pixel region.

Here, the oxide thin film transistor according to the embodiment of the present invention is a ternary system consisting of a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr; x, y, z ≥ 0) Alternatively, as the active layer 124 is formed by using a four-component oxide semiconductor, high mobility and constant current test conditions are satisfied, and uniform characteristics are secured, and thus it is applicable to a large area display including a liquid crystal display and an organic light emitting display. It has advantages

In addition, recently, a tremendous interest and activity has been focused on transparent electronic circuits, and oxide thin film transistors using the oxide semiconductor as an active layer have high mobility and can be manufactured at low temperatures, and thus can be used in the transparent electronic circuits. There is this.

In addition, since the oxide semiconductor may have a wide band gap, it is possible to manufacture UV light emitting diodes (LEDs), white LEDs, and other components having high color purity, and may be processed at low temperatures to produce light and flexible products. It has features that can be.

The oxide thin film transistor according to the embodiment of the present invention having the above characteristics has the etch made of a predetermined insulating material between the source electrode 122 and the drain electrode 123 on the channel region of the active layer 124. A stopper 125 is formed, and the etch stopper 125 serves to prevent the carrier concentration of the channel region from being changed by the plasma treatment in the post process.

In addition, the oxide thin film transistor according to the exemplary embodiment of the present invention forms an etch stopper 125 by depositing an insulating layer immediately after the oxide semiconductor layer is deposited, thereby forming the active layer 124 and the etch stopper 125. When patterning, the back channel of the active layer 124 may be prevented from being damaged by chemicals or UV, which will be described in detail through the following method of manufacturing an oxide thin film transistor.

5A through 5G are cross-sectional views sequentially illustrating a manufacturing process of an oxide thin film transistor according to an exemplary embodiment of the present invention illustrated in FIG. 4.

As shown in FIG. 5A, a predetermined gate electrode 121 is formed on a substrate 110 made of a transparent insulating material.

At this time, the oxide semiconductor applied to the oxide thin film transistor of the present invention can be deposited at a low temperature, it is possible to use a substrate 110 that can be applied to low-temperature processes such as plastic substrate, soda lime glass. In addition, because of the amorphous properties, it is possible to use the large-area display substrate 110.

In addition, the gate electrode 121 is formed by depositing a first conductive layer on the entire surface of the substrate 110 and then selectively patterning the same through a photo process.

The first conductive layer may include aluminum (Al), aluminum alloy (Al alloy), tungsten (W), copper (Cu), nickel (Ni), chromium (Cr), Low resistance opaque conductive materials such as molybdenum (Mo), titanium (Ti), platinum (platinum; Pt), tantalum (Ta), and the like may be used. In addition, the first conductive layer may be a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), and the conductive material may be stacked in two or more kinds. It can also be formed into a multi-layered structure.

Next, as illustrated in FIG. 5B, an oxide semiconductor layer 120 made of a gate insulating film 115a, a predetermined oxide semiconductor, and a predetermined insulating material are sequentially disposed on the entire surface of the substrate 110 on which the gate electrode 121 is formed. An insulating layer 115 is formed.

In this case, an inorganic insulating film such as silicon nitride film (SiNx) or a silicon oxide film (SiO ₂ ) or a highly dielectric oxide film such as hafnium (Hf) oxide or aluminum oxide may be used as the gate insulating film 115a and the insulating layer 115. have.

In addition, the oxide semiconductor layer 120 is, for example, a ternary system made of a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr; x, y, z ≥ 0) or It can be formed from a tetracomponent oxide semiconductor.

In addition, the gate insulating film 115a and the insulating layer 115 may be formed by a chemical vapor deposition method such as plasma enhanced chemical vapor deposition (PECVD), and physical vapor deposition (sputtering) It may be formed by a physical vapor deposition (PVD) method.

Next, as shown in FIG. 5C, when the insulating layer is selectively patterned through a photo process, an etch stopper 125 made of the insulating material is formed on the gate electrode 121 of the substrate 110. Will be formed.

In this case, dry etching, such as oxygen plasma treatment, may be used for etching the insulating layer, and the oxide semiconductor layer 120 below the etching stopper 125, that is, the active layer will be described below, while the insulating layer is etched. The back channel region of the layer is completely prevented from exposing, thereby eliminating instability caused by the exposure and preventing damage caused by patterning of the etch stopper 125.

In addition, the oxide semiconductor layer 120 exposed when the insulating layer is etched through oxygen plasma treatment to form the etch stopper 125 has a resistance reduced by oxygen plasma, thereby exposing the exposed oxide semiconductor layer 120. ), A source / drain region, which is a contact region with a source / drain electrode to be described later, is formed. However, the present invention is not limited thereto, and after forming the etch stopper 125, the resistance of the oxide semiconductor layer 120 exposed through surface treatment or heat treatment such as oxygen plasma is reduced so as to provide a source / contact area. A drain region can also be formed.

As described above, in the exemplary embodiment of the present invention, the gate insulating film 115a, the oxide semiconductor layer 120, and the insulating layer 115 are successively deposited, and then the etch stopper 125 is first formed to form the back channel region of the active layer. While the exposure is completely prevented, the instability caused by the exposure can be eliminated and the loss of the gate insulating film 115a can be prevented.

Next, as shown in FIG. 5D, the oxide semiconductor layer is selectively patterned on the substrate 110 on which the etch stopper 125 is formed through a photo process to form the oxide semiconductor on the gate electrode 121. The active layer 124 is formed.

In this case, as the back channel region of the active layer 124 is prevented by the etch stopper 125 previously formed, the back channel region may be prevented from being damaged by the patterning of the active layer 124. .

Next, as shown in FIG. 5E, a second conductive layer is formed on the entire surface of the substrate 110 on which the active layer 124 and the etch stopper 125 are formed.

In this case, the second conductive layer may use a low resistance opaque conductive material such as aluminum, aluminum alloy, tungsten, copper, nickel, chromium, molybdenum, titanium, platinum, tantalum, etc. to form a source electrode and a drain electrode. In addition, the second conductive layer may be formed of a transparent conductive material such as indium tin oxide, indium zinc oxide, or a multilayer structure in which two or more conductive materials are stacked.

The second conductive film is selectively patterned through a photo process to form a source electrode 122 and a drain electrode 123 electrically connected to the source and drain regions of the active layer 124.

In this case, in the embodiment of the present invention, the active layer 124 and the source / drain electrodes 122 and 123 are formed through two mask processes, for example, but the present invention is limited thereto. The active layer 124 and the source / drain electrodes 122 and 123 may be simultaneously formed in one mask process.

Next, as shown in FIG. 5F, the protective film 115b is formed on the entire surface of the substrate 110 on which the source / drain electrodes 122 and 123 are formed, and then selectively removed through the photo process. Contact hole 140 exposing a portion of the drain electrode 123.

As shown in FIG. 5G, after forming the third conductive film on the entire surface of the substrate 110 on which the protective film 115b is formed, the third conductive film is formed on the substrate 110 by selectively removing the same. The pixel electrode 118 is formed to be electrically connected to the drain electrode 123 through the contact hole 140.

In this case, the third conductive layer includes a transparent conductive material having excellent transmittance such as indium tin oxide or indium zinc oxide to form the pixel electrode 118.

6A and 6B are graphs illustrating transfer characteristics of an oxide thin film transistor, and FIG. 6A illustrates transfer characteristics of a general oxide thin film transistor, and FIG. 6B illustrates transfer characteristics of an oxide thin film transistor according to an embodiment of the present invention. have.

6A and 6B illustrate results of measuring transfer characteristics of thin film transistors of various positions in a panel having a size of 370 mm × 470 mm.

As shown in the figure, a general oxide thin film transistor has a smoother slop of the transfer curve and a lower on current than the oxide thin film transistor according to an embodiment of the present invention, and according to the position of the panel. The measured transfer characteristics are also uneven, which means that the back channel region of the active layer is damaged to some extent by the photo process for forming the active layer and the etch stopper, and the back channel region of the active layer is damaged depending on the position of the panel. It can be seen that the degree received is not constant.

On the other hand, the oxide thin film transistor according to the embodiment of the present invention shows that the slope of the transfer curve is steep and the on-current is also improved, and thus the transfer characteristics are improved. It can be seen that.

As described above, the present invention can be used not only in a liquid crystal display device but also in another display device manufactured using a thin film transistor, for example, an organic light emitting display device in which an organic light emitting element is connected to a driving transistor.

In addition, the present invention has an advantage that it can be used in a transparent electronic circuit or a flexible display by applying an amorphous oxide semiconductor material capable of processing at low temperature while having high mobility as an active layer.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the invention should not be defined by the described embodiments, but should be defined by the claims and their equivalents.

1 is an exploded perspective view schematically showing a general liquid crystal display device.

2 is a cross-sectional view schematically showing the structure of a typical oxide thin film transistor.

3A to 3F are cross-sectional views sequentially illustrating a process of manufacturing the general oxide thin film transistor illustrated in FIG. 2.

4 is a cross-sectional view schematically showing the structure of an oxide thin film transistor according to an embodiment of the present invention.

5A through 5G are cross-sectional views sequentially illustrating a manufacturing process of an oxide thin film transistor according to an exemplary embodiment of the present invention illustrated in FIG. 4.

6A and 6B are graphs showing transfer characteristics of oxide thin film transistors.

DESCRIPTION OF REFERENCE NUMERALS

110: array substrate 118: pixel electrode

121: gate electrode 122: source electrode

123: drain electrode 124: active layer

125: etch stopper

Claims (6)

Forming a gate electrode on the substrate; Continuously forming a gate insulating film, an oxide semiconductor layer, and an insulating layer on the substrate; Selectively patterning the insulating layer to form an etch stopper on the gate electrode; Selectively patterning the oxide semiconductor layer to form an active layer under the etch stopper; Forming a source / drain electrode electrically connected to a source / drain region of the active layer on the substrate on which the active layer and the etch stopper are formed; Forming a protective layer on the substrate on which the source / drain electrodes are formed; Removing a portion of the protective layer to form a contact hole exposing a portion of the drain electrode; And Forming a pixel electrode electrically connected to the drain electrode through the contact hole, wherein the oxide semiconductor layer comprises AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr; A method of manufacturing an oxide thin film transistor, characterized in that it comprises a ternary or quaternary oxide semiconductor composed of a combination of x, y, z ≥ 0). The method of claim 1, wherein the oxide semiconductor layer is formed of an amorphous zinc oxide semiconductor. The method of claim 1, wherein the substrate is formed of a glass substrate or a plastic substrate. The method of claim 1, wherein the insulating layer is patterned using dry etching such as oxygen plasma treatment. 5. The source / drain region of claim 4, wherein the oxide semiconductor layer that is not covered by the etch stopper when the insulating layer is patterned has a resistance reduced by oxygen plasma, and is a contact region with the source / drain electrodes. Forming an oxide thin film transistor, characterized in that forming. 5. The method of claim 4, further comprising reducing the resistance of the exposed oxide semiconductor layer by performing surface treatment or heat treatment after the formation of the etch stopper.

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