KR20090065269A - Transparent thin transistor with polymer passivation layer and method for manufacturing the same - Google Patents

Abstract

A transparent thin film transistor having a polymer protection layer and a manufacturing method thereof are provided to prevent a change of characteristics caused by external environment and to prevent a change of characteristics of an active layer caused by a low-temperature process. A gate electrode(122) is formed on an upper surface of a substrate. A gate insulating layer(120) is formed on an upper surface of the gate electrode. A semiconductor active layer(130) is formed on an upper surface of the gate insulating layer. A source electrode and a drain electrode are formed at both ends of the semiconductor active layer, respectively. A protective layer of the polymer material is formed to cover the semiconductor active layer, the source electrode, and the drain electrode.

Description

Transparent thin film transistor having a polymer protective film and a method of manufacturing the same {TRANSPARENT THIN TRANSISTOR WITH POLYMER PASSIVATION LAYER AND METHOD FOR MANUFACTURING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent thin film transistor and a method of manufacturing the same, and more particularly, to a transparent thin film transistor having a lower gate structure having a protective film and a method of manufacturing the same.

The present invention is derived from the research conducted as part of the IT source technology development project of the Ministry of Information and Communication and the Ministry of Information and Telecommunications Research and Development. .

The transparent thin film transistor is a thin film transistor in which an active layer is formed using a transparent semiconductor. The transparent thin film transistor is recently provided in a pixel area of a flat panel display device such as an organic light emitting display device and the like to allow light to be extracted to the outside through the thin film transistor. Research is actively underway.

The thin film transistor may be divided into a top gate structure and a bottom gate structure according to its structure.

The upper gate structure has a structure in which a source / drain electrode and a semiconductor active layer are below and a gate insulating layer and a gate electrode are mounted thereon, so that the semiconductor active layer is naturally sealed and protected by the gate insulating layer.

However, the upper gate structure thin film transistor has a disadvantage in that the semiconductor active layer undergoes various changes in the process of depositing the upper structure such as the gate insulating layer and the gate electrode.

On the other hand, the lower gate structure has a structure including a gate insulating layer formed on the gate electrode, a source / drain electrode formed on the gate insulating layer, and a semiconductor active layer. The lower gate structure has the advantage of not having to go through other processes affecting the characteristics of the active layer since the semiconductor active layer can be formed last, but the disadvantage is that the semiconductor active layer is exposed to the external environment and is not protected. Therefore, in general, a thin film transistor having a lower gate structure requires a protective film for protecting a semiconductor active layer.

On the other hand, since the transparent oxide semiconductor used in the manufacture of the thin film transistor is sensitively changed according to temperature or chemical change of the surface, a lower gate structure in which the semiconductor active layer process is last performed is preferable if possible.

However, in the process of forming the protective film, it is not preferable that the semiconductor active layer is deteriorated or a change that adversely affects the transistor characteristics occurs. In the conventional silicon-based thin film transistor, a protective film is formed by using an inorganic thin film such as silicon oxide, silicon nitride, and aluminum oxide, and has characteristics due to high temperature and plasma or active chemicals experienced in the process of depositing an inorganic thin film. There is a problem that is likely to change.

Accordingly, an object of the present invention is to form a protective film of a polymer material in a relatively low temperature process in order to ensure long-term stability of the transparent thin film transistor of the bottom gate structure, to minimize changes in characteristics during the process, and to maintain transparency of the thin film transistor. To provide a way.

To this end, the transparent thin film transistor formed with a polymer protective film according to an embodiment of the present invention, a substrate; A gate electrode formed on the substrate; A gate insulating layer formed on the gate electrode; A semiconductor active layer formed on the gate insulating layer; Source and drain electrodes formed on both ends of the semiconductor active layer; And a protective film of a polymer material covering the semiconductor active layer, the source electrode, and the drain electrode.

In addition, for this purpose, a method of manufacturing a transparent thin film transistor having a polymer protective film according to an embodiment of the present invention, (a) sequentially stacking a gate electrode, a gate insulating layer and a semiconductor active layer on a substrate; (b) forming source and drain electrodes on both ends of the semiconductor active layer, respectively; And (c) forming a protective film of a polymer material covering the semiconductor active layer, the source electrode, and the drain electrode.

As described above, according to the present invention, by forming a polymer protective film on a transparent thin film transistor having a lower gate structure, it is possible to prevent the transistor characteristics from being changed by an external environment and to use a low temperature process. The characteristic can be prevented from changing.

In addition, by forming a protective film using a polymer material, there is an advantage of ensuring long-term stability of the device and maintaining transparency, which is an important characteristic of the transparent thin film transistor.

In addition, when a transparent semiconductor thin film transistor array having a bottom gate structure is used as a backplane of an organic light emitting diode display panel, a polymer passivation layer may be used as a bank layer, and a separate bank process may be omitted, and most polymers absorb ultraviolet rays. Therefore, it is possible to bring about a UV blocking effect by the thin film transistor without forming a separate UV blocking film.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

As described above, it is preferable that the transparent thin film transistor has a lower gate structure that does not need to go through other processes affecting the active layer properties when the active layer is formed. However, in the lower gate structure, the active layer is exposed to air, and thus there is a problem due to the long-term stability of the device and the influence of the external environment. In order to solve the above problems, the present invention provides a method for forming a protective film on the semiconductor active layer and the source / drain electrode. At this time, a protective film is formed of a polymer material by a low temperature process due to the characteristics of the transparent oxide semiconductor whose properties are easily changed by high temperature, plasma or active chemicals.

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

First, the structure of a thin film transistor having a lower gate structure will be described with reference to FIG. 1 to assist in understanding the invention.

FIG. 1A is a schematic diagram illustrating a thin film transistor having an inverse coplanar lower gate structure. Referring to FIG. 1A, a substrate 110, a gate electrode 122, and a gate insulating layer 120 are sequentially stacked from below, and a source / drain electrode 132 is disposed on the gate insulating layer 120. , 134 is formed, and the semiconductor active layer 130 covering both the source / drain electrodes 132 and 134 is formed. As such, the structure in which both ends of the semiconductor active layer 130 cover the source / drain electrodes 132 and 134 is called an inverse coplanar structure.

On the other hand, Figure 1 (b) is a schematic diagram showing a thin film transistor of the reverse-stagger bottom gate structure. Referring to FIG. 1B, it can be seen that the substrate 110, the gate electrode 122, and the gate insulating layer 120 are sequentially stacked from below, like the inverse coplanar lower gate structure. However, it can be seen that the source / drain electrodes 132 and 134 cover both ends of the semiconductor active layer 130 as opposed to the reverse coplanar lower gate structure. As such, the structure in which the source / drain electrodes 132 and 134 cover both ends of the semiconductor active layer 130 is referred to as an inverse stagger structure.

The transparent thin film transistor to be provided in the present invention may be applied to both the reverse coplanar bottom gate structure and the reverse stagger bottom gate structure. However, for convenience of description, hereinafter, the features of the present invention applied to the inverse coplanar lower gate structure will be described.

2 is an exemplary view showing a transparent thin film transistor having a polymer protective film according to an embodiment of the present invention. Referring to FIG. 2, a transparent thin film transistor having a polymer protective film according to an embodiment of the present invention may include a substrate 110, a gate electrode 122 formed on the substrate, and a gate insulating layer covering the gate electrode 122. (120), the source / drain electrodes 132 and 134 formed at intervals on the gate insulating layer 120, the semiconductor active layer 130 and the source / drain formed between the source / drain electrodes 132 and 134. And a polymer protective layer 140 covering the drain electrodes 132 and 134 and the semiconductor active layer 130.

The substrate 110 may be a glass substrate, a plastic substrate, or the like, and any substrate may be used as long as the substrate 110 is made of a transparent material. As the plastic substrate, a flexible substrate may be used.

The gate electrode 122 is formed of a transparent conductive material. Transparent conductive materials include indium tin oxide (hereinafter referred to as ITO), indium zinc oxide (hereinafter referred to as IZO), and indium tin zinc oxide (hereinafter referred to as ITZO). Etc.) may be used.

The gate electrode 122 may be formed on the entire surface of the substrate 110 and then patterned. Alternatively, the gate electrode 122 may be deposited on a desired region of the substrate 110 using a mask. The gate electrode 122 may be formed using an inkjet printing method. It may be deposited in the region.

The gate insulating layer 120 is formed on the substrate 110 to cover the gate electrode 122 to form the source / drain electrodes 132 and 134 and the semiconductor active layer 130 to be formed on the gate insulating layer 120. It serves to insulate from the gate electrode 122 and is formed of a transparent insulating material. As the insulating material having transparency, silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), or the like may be used.

The source / drain electrodes 132 and 134 are formed on the gate insulating layer 120, and like the gate electrode 122, a transparent conductive material, that is, ITO, IZO, ITZO, or the like may be used.

The semiconductor active layer 130 is formed between the source / drain electrodes 132 and 134 and is made of a transparent oxide. Transparent oxides that may be used in the semiconductor active layer 130 include zinc oxide (ZnO), indium zinc oxide (InZnO), indium gallium zinc oxide (InGaZnO), tin oxide (SnO ₂ ), cadmium tin oxide (CdSnO), and the material. Substances containing these may be used.

The polymer passivation layer 140 is formed on the gate insulating layer 120 to cover the source / drain electrodes 132 and 134 and the semiconductor active layer 130. The material used as the polymer passivation layer 140 should be able to block various materials affecting the characteristics of the semiconductor active layer 130 including moisture and carbon dioxide contained in the air, and visible light to maintain transparency, which is a characteristic of the transparent thin film transistor. The transmittance must be high. Polymer materials having such properties include epoxy resins, polyvinylacetate (PVA), polyvinylphenol (PVP), perylene resins, polyethylene resins, polyether resins, and polycarbonate resins.

As described above, when the protective layer is formed using the polymer material, the semiconductor active layer may be protected while maintaining the advantages of the lower gate structure. In other words, unlike the conventional technology which affects the characteristics of the semiconductor active layer by using a high temperature process of the plasma process including sputtering or chemical vapor deposition during the formation of the protective film, it is possible to protect the device by forming a protective film of the polymer material in a low temperature process. There is an advantage to that.

As the low temperature process, a spin coating method, a dip coating method, a spray coating method, or the like may be used. The thermal evaporation method or the electron beam evaporation method may be used. Vacuum vapor deposition methods, such as a method, can also be used.

On the other hand, by combining the transparent thin film transistor as described above with the organic light emitting diode device can be produced a transparent display panel. This will be described below with reference to FIG. 3.

3 is a diagram illustrating a structure of an organic light emitting display pixel using a transparent thin film transistor according to an exemplary embodiment of the present invention.

In order to form such a display pixel, first, a through hole is formed on the drain electrode of the transparent thin film transistor formed as shown in FIG. 2, and the formed through hole is filled with a conductive material to form the anode electrode 152. Thereafter, the organic light emitting diode layer 154 and the cathode electrode 156 are formed on the anode electrode 152.

The through hole, the anode electrode 152, the organic light emitting diode layer 154, and the cathode electrode 156 may be formed by a method used in a manufacturing process of a general display.

As described above, when the transparent thin film transistor according to the exemplary embodiment of the present invention is applied to an organic light emitting diode display panel, the organic light emitting diode is not easily formed because a process of forming a bank, which is a planarization insulating layer, for forming the anode electrode 152 on the transistor is not required. There is an advantage that can be used in the manufacture of diode display panels.

On the other hand, in general, the transparent oxide semiconductor thin film has its electrical and optical properties changed by ultraviolet light, and most polymer materials have the property of blocking ultraviolet light. Therefore, there is an advantage that it is not necessary to form a separate UV blocking film after manufacturing the display panel as described above.

Meanwhile, among the materials constituting the semiconductor active layer 130, there are materials whose properties are deteriorated under the influence of a photoresist, a photoresist stripper, various etching solutions, and the like, which are contacted during the patterning process.

Therefore, when fabricating a lower gate structure transparent thin film transistor using such a material, an inorganic protective film such as aluminum oxide or silicon oxide may be formed on the semiconductor active layer 130.

In general, the inorganic passivation layer 136 is formed to be thin in order to secure the etching selectivity of the lower source / drain electrodes 132 and 134 and the gate insulating layer 120 in the semiconductor active layer 130 patterning process, and the semiconductor active layer 130 And are etched together to have the same width as the semiconductor active layer 130. 4 is a view illustrating a structure of a thin film transistor in which a polymer passivation layer is formed on an inorganic passivation layer as described above. Even when the inorganic passivation layer 136 is formed, the transparent passivation layer may be formed by forming the polymer passivation layer 140 according to the present invention. Can be.

On the other hand, while the above has been shown and described with respect to the preferred embodiments of the present invention, the present invention is not limited to the specific embodiments described above, the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

1 (a) is a schematic diagram showing a thin film transistor having an inverse coplanar lower gate structure,

Figure 1 (b) is a schematic diagram showing a thin film transistor of the reverse-stagger bottom gate structure,

2 is an exemplary view showing a transparent thin film transistor having a polymer protective film according to an embodiment of the present invention;

3 is a view showing the structure of an organic light emitting display pixel using a transparent thin film transistor according to an embodiment of the present invention,

4 is a view showing a structure of a thin film transistor in which a polymer protective film is formed on an inorganic protective film.

Claims (10)

Board; A gate electrode formed on the substrate; A gate insulating layer formed on the gate electrode; A semiconductor active layer formed on the gate insulating layer; Source and drain electrodes formed on both ends of the semiconductor active layer; And A protective film of a polymer material covering the semiconductor active layer, the source electrode, and the drain electrode Transparent thin film transistor formed with a polymer protective film comprising a. The method of claim 1, The protective film is made of any one of an epoxy resin, polyvinylacetate, polyvinylphenol, perylene resin, polyethylene resin, polyether resin, and polycarbonate resin. Transparent thin film transistor with a polymer protective film. The method of claim 1, The gate electrode, the source electrode, and the drain electrode are made of any one material of ITO, IZO, and ITZO. Transparent thin film transistor with a polymer protective film. The method of claim 1, The gate insulating layer is made of silicon oxide or aluminum oxide Transparent thin film transistor with a polymer protective film. The method of claim 1, The semiconductor active layer is made of ZnO, InZnO, InGaZnO, SnO ₂ , CdSnO and a material containing any one of the above materials. Transparent thin film transistor with a polymer protective film. The method of claim 1, Inorganic protective film formed on the semiconductor active layer Transparent thin film transistor formed with a polymer protective film further comprising. (a) sequentially depositing a gate electrode, a gate insulating layer, and a semiconductor active layer on the substrate; (b) forming source and drain electrodes on both ends of the semiconductor active layer, respectively; And (c) forming a protective film of a polymer material covering the semiconductor active layer, the source electrode, and the drain electrode; Method of manufacturing a transparent thin film transistor formed with a polymer protective film comprising a. The method of claim 7, wherein The protective film is formed by any one of spin coating, dip coating, spray coating, thermal evaporation and electron beam evaporation. The manufacturing method of the transparent thin film transistor in which the polymer protective film was formed. The method of claim 7, wherein The protective film is formed of any one of an epoxy resin, polyvinylacetate, polyvinylphenol, perylene resin, polyethylene resin, polyether resin, and polycarbonate resin. The manufacturing method of the transparent thin film transistor in which the polymer protective film was formed. The method of claim 7, wherein step (b), Forming an inorganic protective film on the semiconductor active layer Method of manufacturing a transparent thin film transistor formed with a polymer protective film further comprising.

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