Thin film transistor and its manufacturing method

Abstract

The present invention relates to a thin film transistor comprising a gate electrode, an active layer spaced apart from the gate electrode, a source electrode provided on one side of the active layer, a drain electrode provided on the other side of the active layer, and a contact layer provided at least either between the active layer and the source electrode or between the active layer and the drain electrode, wherein the contact layer comprises at least one first metal oxide selected from the group consisting of Zn, In, and Ga, and a method for manufacturing the thin film transistor.

Description

[Technical Field]

[0001] The present invention relates to a thin film transistor and a method for manufacturing the same, and more particularly to an oxide thin film transistor and a method for manufacturing the same. [Background technology]

[0002] 2. Description of the Related Art Thin film transistors are used as circuit elements for independently driving each pixel in semiconductor devices, liquid crystal displays (LCDs), organic electroluminescence (EL) display devices, and the like.

[0003] Such a thin film transistor comprises a gate electrode, an active layer used as a channel, a source electrode, and a drain electrode. When a metal oxide is used as the material of the active layer, the thin film transistor is called an oxide thin film transistor.

[0004] In the manufacturing process of an oxide thin film transistor, the active layer is exposed to an etching gas during an etching process for patterning. When the active layer is exposed to the etching gas, the exposed surface is damaged by the etching gas, and oxygen contained therein is lost. When oxygen deficiency occurs in the active layer, the electrical conductivity of the active layer increases, making it conductive, which causes a device short circuit and prevents stable operation of the thin film transistor. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been devised to solve the above-mentioned conventional problems, and an object of the present invention is to provide a thin film transistor and a manufacturing method thereof that can prevent oxygen deficiency in the active layer and improve stability. [Means for solving the problem]

[0006] To achieve the above object, the present invention provides a thin film transistor comprising: a gate electrode; an active layer spaced apart from the gate electrode; a source electrode provided on one side of the active layer; a drain electrode provided on the other side of the active layer; and a contact layer provided at least one between the active layer and the source electrode and between the active layer and the drain electrode, wherein the contact layer comprises an oxide of at least one first metal selected from the group consisting of Zn, In, and Ga.

[0007] The contact layer may include a first contact layer provided between the active layer and the source electrode, and a second contact layer provided between the active layer and the drain electrode.

[0008] The active layer may include the second metal oxide, and the second metal oxide included in the active layer and the first metal oxide included in the contact layer may be different from each other.

[0009] The metal contained in the first metal oxide may be different from the metal contained in the second metal oxide.

[0010] The composition ratio of the metal and oxygen contained in the first metal oxide may be different from the composition ratio of the metal and oxygen contained in the second metal oxide.

[0011] The content of oxygen contained in the first metal oxide may be less than the content of oxygen contained in the second metal oxide.

[0012] The thickness of the contact layer may range from 30 Å to 100 Å.

[0013] The pattern of the contact layer may be different from the pattern of the active layer.

[0014] The semiconductor device may further include an interlayer insulating layer provided between the active layer and the source electrode, the interlayer insulating layer having a contact hole that exposes the source electrode, and the contact layer may be provided in the contact hole.

[0015] The semiconductor device may further include a gate insulating layer disposed between the gate electrode and the active layer, and the source electrode may extend from an upper surface of the contact layer to an upper surface of the gate insulating layer.

[0016] The present invention also provides a method for manufacturing a thin film transistor, comprising the steps of forming an active layer on a substrate, forming a gate insulating film and a gate electrode on the active layer, forming an interlayer insulating layer on the gate electrode, forming contact holes in the interlayer insulating layer and exposing the active layer through the contact holes, forming a contact layer containing an oxide of at least one first metal selected from Zn, In, and Ga on an upper surface of the exposed active layer in the contact holes, and forming a source electrode or a drain electrode on the contact layer.

[0017] The interlayer insulating layer is made of nitride, and the contact layer can be formed by a selective deposition process without a patterning process.

[0018] The present invention also provides a method for manufacturing a thin film transistor, comprising the steps of forming a gate electrode on a substrate, forming a gate insulating film on the gate electrode, forming an active layer on the gate insulating film, forming a contact layer containing an oxide of at least one first metal selected from Zn, In, and Ga on an upper surface of the active layer, and forming a source electrode or a drain electrode on the contact layer.

[0019] The active layer may include the second metal oxide, and the second metal oxide included in the active layer may be different from the first metal oxide included in the contact layer.

[0020] The metal contained in the first metal oxide may be different from the metal contained in the second metal oxide.

[0021] The composition ratio of the metal and oxygen contained in the first metal oxide may be different from the composition ratio of the metal and oxygen contained in the second metal oxide.

[0022] The content of oxygen contained in the first metal oxide may be less than the content of oxygen contained in the second metal oxide.

[0023] The thickness of the contact layer may range from 30 Å to 100 Å. [Effects of the Invention]

[0024] According to the present invention as described above, the following effects are obtained.

[0025] According to one embodiment of the present invention, contact layers made of metal oxide are formed between the active layer and the source electrode and between the active layer and the drain electrode, so that oxygen contained in the contact layers can fill the spaces where oxygen has escaped from the active layer, thereby preventing the active layer from becoming conductive due to the oxygen contained in the contact layers diffusing into the spaces where oxygen has escaped from the active layer. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic cross-sectional view of a thin film transistor according to an embodiment of the present invention; [Figure 2] 1 is a schematic cross-sectional view of a thin film transistor according to another embodiment of the present invention; [Figure 3A] 2A to 2C are cross-sectional views illustrating a manufacturing process of a thin film transistor according to an embodiment of the present invention. [Figure 3B] 2A to 2C are cross-sectional views illustrating a manufacturing process of a thin film transistor according to an embodiment of the present invention. [Figure 3C]2A to 2C are cross-sectional views illustrating a manufacturing process of a thin film transistor according to an embodiment of the present invention. [Figure 4A] 5A to 5C are cross-sectional views illustrating a manufacturing process of a thin film transistor according to another embodiment of the present invention. [Figure 4B] 5A to 5C are cross-sectional views illustrating a manufacturing process of a thin film transistor according to another embodiment of the present invention. [Figure 4C] 5A to 5C are cross-sectional views illustrating a manufacturing process of a thin film transistor according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The advantages and features of the present invention, as well as methods for achieving them, will become more apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully convey the scope of the invention to those skilled in the art. The present invention is defined only by the scope of the claims.

[0028] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for illustrating the embodiments of the present invention are merely examples, and the present invention is not limited to the details shown in the drawings. The same reference numerals refer to the same elements throughout the specification. Furthermore, in describing the present invention, if a detailed description of related prior art is deemed to unnecessarily obscure the gist of the present invention, such a detailed description will be omitted. When "comprises," "has," "consists of," etc. are used in the present invention, other parts may be added unless "only" is used. When an element is expressed in the singular, it also includes the plural unless otherwise explicitly stated.

[0029] When interpreting elements, they are interpreted as including a margin of error unless otherwise expressly stated.

[0030] In the case of a description of a positional relationship, for example, when the positional relationship of two parts is described using "above," "on top," "below," or "beside," one or more other parts may be located between the two parts, unless the words "immediately" or "directly" are used.

[0031] When describing a temporal relationship, for example, when the temporal precedence relationship is described using "after," "following," "next to," or "before," it can also include cases where the relationship is not consecutive, unless the words "immediately" or "directly" are used.

[0032] Although terms such as "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another. Therefore, a first component referred to below may also be a second component within the technical concept of the present invention.

[0033] The features of the various embodiments of the present invention may be partially or fully combined or combined with each other, and may be technically interlocked and driven in various ways, and each embodiment may be implemented independently of the others or may be implemented together in a linked relationship.

[0034] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0035] FIG. 1 is a schematic cross-sectional view of a thin film transistor according to an embodiment of the present invention.

[0036] FIG. 1 relates to a thin film transistor of a top gate structure in which a gate electrode 150 is provided above an active layer 130 .

[0037] As can be seen from FIG. 1, a thin film transistor according to one embodiment of the present invention comprises a substrate 110, a buffer layer 120, an active layer 130, a gate insulating layer 140, a gate electrode 150, an interlayer insulating layer 160, contact layers 170a and 170b, a source electrode 180, and a drain electrode 180b.

[0038] The substrate 110 may be made of various materials known in the art, such as glass, plastic, or a semiconductor substrate. The substrate 110 may be a transparent substrate or an opaque substrate. The substrate 110 may also be a reflective substrate made of a metal material, such as stainless steel (SUS), titanium (Ti), molybdenum (Mo), or an alloy thereof.

[0039] The buffer layer 120 is formed on the substrate 110. Specifically, the buffer layer 120 is formed between the substrate 110 and the active layer 130 and serves to prevent materials contained in the substrate 110 from diffusing into the active layer 130 during the deposition process of the active layer 130. In addition, the buffer layer 120 serves to prevent external moisture or oxygen from penetrating into the active layer 130 through the substrate 110.

[0040] The buffer layer 120 may include, but is not necessarily limited to, silicon oxide.

[0041] The active layer 130 is patterned on the buffer layer 120 .

[0042] The active layer 130 may be made of a metal oxide. The active layer 130 may be made of a single layer of metal oxide or a plurality of layers of metal oxide.

[0043] The active layer 130 may include, for example, a metal oxide doped with impurities, such as zinc oxide, and the impurities may include at least one of indium (In), gallium (Ga), and tungsten (W).

[0044] Indium (In) is a metal with a relatively small bandgap, and when the active layer 130 contains indium, the charge concentration increases, improving mobility. Gallium (Ga) is a metal with a relatively large bandgap, and when the active layer 130 contains gallium, the charge concentration decreases, improving device stability. Therefore, the electrical conductivity of the active layer 130 can be adjusted by controlling the content of impurities contained in the metal oxide. In addition, the electrical conductivity of the active layer 130 can be reduced as the proportion of oxygen in the active layer 130 made of a metal oxide increases.

[0045] The gate insulating layer 140 is patterned on the active layer 130 .

[0046] The gate insulating layer 140 is formed between the active layer 130 and the gate electrode 150 to provide insulation between the active layer 130 and the gate electrode 150 .

[0047] The gate insulating layer 140 may be made of an inorganic insulating material such as, but not limited to, silicon oxide (SiO2), silicon nitride (SiNx), alumina (Al2O3), or zirconia (ZrO2).

[0048] The gate insulating layer 140 may be patterned in the same pattern as the gate electrode 150, but is not limited thereto.

[0049] The gate electrode 150 is patterned on the gate insulating layer 140. The gate electrode 150 is formed to overlap the active layer .

[0050] The gate electrode 150 and the gate insulating layer 140 are patterned to expose a portion of the top surface of the active layer 130 .

[0051] The gate electrode 150 may be made of at least one metal selected from the group consisting of aluminum (Al), neodymium (Nd), silver (Ag), chromium (Cr), titanium (Ti), tantalum (Ta), molybdenum (Mo), and copper (Cu), or an alloy containing any of these metals, but is not limited thereto. The gate electrode 150 may be made of a single layer or multiple layers of the metals or alloys. For example, the gate electrode 150 may be made of a double layer including a metal layer selected from the group consisting of chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum (Mo), which has excellent physicochemical properties, and an aluminum (Al), silver (Ag), or copper (Cu) metal layer, which has low resistivity.

[0052] The interlayer insulating layer 160 is formed on the gate electrode 150 and covers the active layer 130 and the gate electrode 150. The interlayer insulating layer 160 has a first contact hole CH1 and a second contact hole CH2, and predetermined regions of the active layer 130 are exposed through the first contact hole CH1 and the second contact hole CH2.

[0053] The interlayer insulating layer 160 may be made of an inorganic insulating material such as, but not limited to, silicon oxide (SiO2), silicon nitride (SiNx), alumina (Al2O3), or zirconia (ZrO2).

[0054] The source electrode 180a and the drain electrode 180b are formed on the interlayer insulating layer 160. The source electrode 180a and the drain electrode 180b are spaced apart from each other with the gate electrode 150 interposed therebetween.

[0055] The source electrode 180a and the drain electrode 180b may be formed of the same material and process. For example, the source electrode 180a and the drain electrode 180b may be formed of a single layer or multiple layers of at least one metal selected from the group consisting of aluminum (Al), neodymium (Nd), silver (Ag), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum (Mo), or an alloy containing any of these metals.

[0056] The source electrode 180a is electrically connected to one side of the upper surface of the active layer 130 through the first contact hole (CH1), and the drain electrode 180b is electrically connected to the other side of the upper surface of the active layer 130 through the second contact hole (CH2).

[0057] The contact layers 170a and 170b include a first contact layer 170a and a second contact layer 170b. The first contact layer 170a is provided in the first contact hole (CH1), and the second contact layer 170b is provided in the second contact hole (CH2). Therefore, the contact layers 170a and 170b have a different pattern from the active layer 130.

[0058] The first contact layer 170a is provided between the source electrode 180a and one side of the upper surface of the active layer 130, and electrically connects the source electrode 180a to one side of the upper surface of the active layer 130. Therefore, the upper surface of the first contact layer 170a contacts the lower surface of the source electrode 180a, and the lower surface of the first contact layer 170a contacts one side of the upper surface of the active layer 130.

[0059] The second contact layer 170b is disposed between the drain electrode 180b and the other side of the upper surface of the active layer 130, and electrically connects the drain electrode 180b to the other side of the upper surface of the active layer 130. Therefore, the upper surface of the second contact layer 170b contacts the lower surface of the drain electrode 180b, and the lower surface of the second contact layer 170b contacts the other side of the upper surface of the active layer 130.

[0060] Each of the first contact layer 170a and the second contact layer 170b may be made of a metal oxide. Each of the first contact layer 170a and the second contact layer 170b may be made of a single layer of metal oxide or multiple layers of metal oxide.

[0061] In particular, each of the first contact layer 170a and the second contact layer 170b may be made of a single layer or multiple layers of at least one metal oxide selected from Zn, In, and Ga. For example, each of the first contact layer 170a and the second contact layer 170b may be made of a single layer or multiple layers of a metal oxide selected from ZnO, InO, GaO, IZO, IGO, GZO, and IGZO.

[0062] The first contact layer 170a and the second contact layer 170b may each be made of a metal oxide different from that of the active layer 130. For example, if the metal oxide forming the active layer 130 is a first metal oxide and the metal oxide forming the contact layers 170a and 170b is a second metal oxide, the metals constituting the second metal oxide and the metals constituting the first metal oxide may be different from each other. In some cases, the metals constituting the second metal oxide and the metals constituting the first metal oxide may be the same, in which case the composition ratio of metal to oxygen constituting the second metal oxide may be different from the composition ratio of metal to oxygen constituting the first metal oxide. In particular, the second metal oxide may have a lower oxygen content and a higher metal content than the first metal oxide.

[0063] The first contact layer 170a and the second contact layer 170b may serve to prevent one side and the other side of the active layer 130 exposed by the first contact hole CH1 from being made conductive during processing.

[0064] If the source electrode 180a and the drain electrode 180b are formed directly on the active layer 130 without forming the contact layers 170a and 170b, the upper surface of the active layer 130 is exposed to the etching gas during the process of forming the first and second contact holes (CH1 and CH2) in the interlayer insulating film 160 to form the source electrode 180a and the drain electrode 180b. When the active layer 130 is exposed to the etching gas, the active layer 130 is damaged by the etching gas from its upper surface to a certain depth, losing oxygen and becoming oxygen-deficient. When oxygen deficiency occurs in the active layer 130, the electrical conductivity of the active layer 130 increases, making it conductive, which can cause a device short circuit and prevent the thin film transistor from operating stably.

[0065] In contrast, according to an embodiment of the present invention, contact layers 170a and 170b made of metal oxide are formed between the active layer 130 and the source electrode 180a and between the active layer 130 and the drain electrode 180b, so that oxygen contained in the contact layers 170a and 170b can fill the spaces where oxygen has escaped from the active layer 130. Therefore, it is possible to prevent the active layer 130 from becoming conductive due to the oxygen contained in the contact layers 170a and 170b diffusing into the spaces where oxygen has escaped from the active layer 130.

[0066] Here, the contact layers 170a and 170b may be formed to a thickness (D) of 30 Å to 100 Å. If the contact layers 170a and 170b are formed to a thickness of less than 30 Å, oxygen may not diffuse sufficiently into the active layer 130, and if the contact layers 170a and 170b are formed to a thickness of more than 100 Å, the process time may increase excessively, which may hinder miniaturization of the thin film transistor.

[0067] FIG. 2 is a schematic cross-sectional view of a thin film transistor according to another embodiment of the present invention.

[0068] FIG. 2 relates to a thin film transistor having a bottom gate structure in which the gate electrode 150 is provided below the active layer 130.

[0069] 2, a thin film transistor according to another embodiment of the present invention includes a substrate 110, a buffer layer 120, an active layer 130, a gate insulating layer 140, a gate electrode 150, contact layers 170a and 170b, a source electrode 180a, and a drain electrode 180b. Since the materials of each component are the same as those in FIG. 1, a repeated description thereof will be omitted, and only different structures will be described below.

[0070] The substrate 110 and the buffer layer 120 are the same as those in Fig. 1, and therefore, a repeated description will be omitted. The buffer layer 120 may be omitted.

[0071] The gate electrode 150 is patterned on the buffer layer 120 .

[0072] The gate insulating layer 140 is formed on the gate electrode 150. The gate insulating layer 140 may be formed on the entire surface of the substrate 110.

[0073] The active layer 130 is patterned on the gate insulating layer 140 , and a portion of the active layer 130 overlaps the gate electrode 150 .

[0074] The first contact layer 170 a is provided on one side of the upper surface of the active layer 130 and electrically connects the source electrode 180 a to one side of the upper surface of the active layer 130 .

[0075] The second contact layer 170b is provided on the other side of the upper surface of the active layer 130 and electrically connects the drain electrode 180b to the other side of the upper surface of the active layer 130.

[0076] If oxygen deficiency occurs on the upper surface of the active layer 130 due to an etching gas during patterning of the active layer 130, the first contact layer 170a and the second contact layer 170b can supply additional oxygen to prevent the active layer 130 from becoming conductive.

[0077] The source electrode 180a may extend to one side of the upper surface of the gate insulating layer 140 on the first contact layer 170a, and the drain electrode 180b may extend to the other side of the upper surface of the gate insulating layer 140 on the second contact layer 170b.

[0078] 3A to 3C are schematic cross-sectional views of a thin film transistor according to an embodiment of the present invention, which relate to the manufacturing process of the thin film transistor according to FIG. 1 described above.

[0079] First, as can be seen from FIG. 3A, a buffer layer 120 is formed on a substrate 110, an active layer 130 is patterned on the buffer layer 120, a gate insulating layer 140 and a gate electrode 150 are patterned on the active layer 130, an interlayer insulating layer 160 is formed on the gate electrode 150, and a first contact hole (CH1) and a second contact hole (CH2) are formed in the interlayer insulating layer 160 to expose one side of the upper surface of the active layer 130 and the other side of the upper surface.

[0080] When the first contact hole CH1 and the second contact hole CH2 are formed, oxygen deficiency may occur on one side of the upper surface of the active layer 130 and on the other side of the upper surface.

[0081] Next, as can be seen from FIG. 3B, a first contact layer 170a is patterned on one side of the upper surface of the active layer 130 exposed by the first contact hole (CH1), and a second contact layer 170b is patterned on the other side of the upper surface of the active layer 130 exposed by the second contact hole (CH2).

[0082] The oxygen contained in the first contact layer 170a can fill the area where oxygen has escaped from one side of the upper surface of the active layer 130, and the oxygen contained in the second contact layer 170b can fill the area where oxygen has escaped from the other side of the upper surface of the active layer 130.

[0083] Here, the contact layers 170a and 170b may be formed to a thickness (D) of 30 to 100 Å.

[0084] If the interlayer insulating layer 160 is made of a nitride such as silicon nitride rather than an oxide such as silicon oxide, the metal oxide constituting the contact layers 170a and 170b may be deposited only on the upper surface of the active layer 130 in the contact holes CH1 and CH2, rather than on the interlayer insulating layer 160. Therefore, if the interlayer insulating layer 160 is made of a nitride, a separate patterning process for forming the contact holes 170a and 170b is not required, and selective deposition is possible.

[0085] The first contact layer 170a and the second contact layer 170b can be formed by atomic layer deposition (ALD), which involves repeating a process cycle multiple times, the process cycle including a step of supplying a source gas containing a metal, a step of purging the source gas, a step of supplying a reactive gas containing oxygen, and a step of purging the reactive gas.

[0086] The process of supplying the raw material gas may include at least one of the following processes: a process of supplying a gas containing zinc (Zn), a process of supplying a gas containing indium (In), a process of supplying a gas containing gallium (Ga), a process of supplying a gas containing indium (In) and zinc (Zn), a process of supplying a gas containing indium (In) and gallium (Ga), a process of supplying a gas containing zinc (Zn) and gallium (Ga), and a process of supplying a gas containing indium (In), zinc (Zn) and gallium (Ga).

[0087] As an example, the first contact layer 170a and the second contact layer 170b may be made of zinc oxide (ZnO) formed by repeating a process cycle multiple times, the process cycle including a step of supplying a source gas containing zinc (Zn) into a chamber, a step of purging the source gas, a step of supplying a reactive gas containing oxygen into the chamber, and a step of purging the reactive gas.

[0088] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of indium oxide (InO) formed by repeating a process cycle multiple times, the process cycle including a step of supplying a source gas containing indium (In) into a chamber, a step of purging the source gas, a step of supplying a reactive gas containing oxygen into the chamber, and a step of purging the reactive gas.

[0089] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of gallium oxide (GaO) formed by repeating a process cycle multiple times, the process cycle including a step of supplying a source gas containing gallium (Ga) into a chamber, a step of purging the source gas, a step of supplying a reactive gas containing oxygen into the chamber, and a step of purging the reactive gas.

[0090] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of indium zinc oxide (IZO) formed by repeating a process cycle including a step of supplying a source gas containing indium (In) and zinc (Zn) into a chamber, a step of purging the source gas, a step of supplying a reaction gas containing oxygen into the chamber, and a step of purging the reaction gas multiple times.

[0091] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of indium zinc oxide (IZO) formed by repeating a process cycle including a step of supplying a first source gas containing indium (In) into a chamber, a step of purging the first source gas, a step of supplying a first reactive gas containing oxygen into the chamber, a step of purging the first reactive gas, a step of supplying a second source gas containing zinc (Zn) into the chamber, a step of purging the second source gas, a step of supplying a reactive gas containing oxygen into the chamber, and a step of purging the second reactive gas multiple times.

[0092] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of indium gallium oxide (IGO) formed by repeating a process cycle including a step of supplying a source gas containing indium (In) and gallium (Ga) into a chamber, a step of purging the source gas, a step of supplying a reaction gas containing oxygen into the chamber, and a step of purging the reaction gas multiple times.

[0093] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of indium gallium oxide (IGO) formed by repeating a process cycle including the steps of: supplying a first source gas containing indium (In) into a chamber; purging the first source gas; supplying a first reactive gas containing oxygen into the chamber; purging the first reactive gas; supplying a second source gas containing gallium (Ga) into the chamber; purging the second source gas; supplying a second reactive gas containing oxygen into the chamber; and purging the second reactive gas.

[0094] The first contact layer 170a and the second contact layer 170b may be made of gallium zinc oxide (GZO) formed by repeating a process cycle including a step of supplying a source gas containing gallium (Ga) and zinc (Zn) into a chamber, a step of purging the source gas, a step of supplying a reaction gas containing oxygen into the chamber, and a step of purging the reaction gas multiple times.

[0095] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of gallium zinc oxide (GZO) formed by repeating a process cycle including the steps of: supplying a first source gas containing gallium (Ga) into a chamber; purging the first source gas; supplying a first reactive gas containing oxygen into the chamber; purging the first reactive gas; supplying a second source gas containing zinc (Zn) into the chamber; purging the second source gas; supplying a second reactive gas containing oxygen into the chamber; and purging the second reactive gas.

[0096] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of indium gallium zinc oxide (IGZO) formed by repeating a process cycle multiple times, the process cycle including: supplying a first source gas containing gallium (Ga) into the chamber; purging the first source gas; supplying a first reactive gas containing oxygen into the chamber; purging the first reactive gas; supplying a second source gas containing indium (In) and zinc (Zn) into the chamber; purging the second source gas; supplying a second reactive gas containing oxygen into the chamber; and purging the second reactive gas.

[0097] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of indium gallium zinc oxide (IGZO) formed by repeating a process cycle including a step of supplying a first source gas containing indium (In) into the chamber, a step of purging the first source gas, a step of supplying a first reactive gas containing oxygen into the chamber, a step of purging the first reactive gas, a step of supplying a second source gas containing gallium (Ga) and zinc (Zn) into the chamber, a step of purging the second source gas, a step of supplying a second reactive gas containing oxygen into the chamber, and a step of purging the second reactive gas multiple times.

[0098] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of indium gallium zinc oxide (IGZO) formed by repeating a process cycle multiple times, the process cycle including: supplying a first source gas containing zinc (Zn) into the chamber; purging the first source gas; supplying a first reactive gas containing oxygen into the chamber; purging the first reactive gas; supplying a second source gas containing gallium (Ga) and indium (In) into the chamber; purging the second source gas; supplying a second reactive gas containing oxygen into the chamber; and purging the second reactive gas.

[0099] Alternatively, the first contact layer 170a and the second contact layer 170b may be made of indium gallium zinc oxide (IGZO) formed by repeating a process cycle including the following steps: supplying a first source gas containing zinc (Zn) into the chamber, purging the first source gas, supplying a first reactive gas containing oxygen into the chamber, purging the first reactive gas, supplying a second source gas containing gallium (Ga) into the chamber, purging the second source gas, supplying a second reactive gas containing oxygen into the chamber, purging the second reactive gas, supplying a third source gas containing indium (In) into the chamber, purging the third source gas, supplying a third reactive gas containing oxygen into the chamber, and purging the third reactive gas. The supply of the first, second, and third source gases is not in any particular order.

[0100] Next, as shown in FIG. 3C, a source electrode 180a is formed on the first contact layer 170a, and a drain electrode 180b is formed on the second contact layer 170b.

[0101] The source electrode 180a extends into the first contact hole CH1 to contact the first contact layer 170a, and the drain electrode 180b extends into the second contact hole CH2 to contact the second contact layer 170b.

[0102] 4A to 4C are schematic cross-sectional views of a thin film transistor according to another embodiment of the present invention, which relate to the manufacturing process of the thin film transistor according to FIG. 2 described above.

[0103] First, as can be seen from FIG. 4A, a buffer layer 120 is formed on a substrate 110, a gate electrode 150 is patterned on the buffer layer 120, a gate insulating layer 140 is formed on the gate electrode 150, and an active layer 130 is formed on the gate insulating layer 140.

[0104] Next, as can be seen from FIG. 4B, a first contact layer 170a is patterned on one side of the upper surface of the active layer 130, and a second contact layer 170b is patterned on the other side of the upper surface of the active layer 130.

[0105] The first contact layer 170a and the second contact layer 170b are formed by the same methods as those described above, and therefore, a repeated description will be omitted.

[0106] Next, as shown in FIG. 4C, a source electrode 180a is patterned on the first contact layer 170a, and a drain electrode 180b is patterned on the second contact layer 170b.

[0107] Although the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments and can be embodied in various modifications without departing from the technical spirit of the present invention. Therefore, the embodiments disclosed herein are intended to illustrate, rather than limit, the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not limiting. The scope of protection of the present invention should be interpreted by the scope of the claims, and all technical spirits within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims

1. gate electrode an active layer spaced apart from the gate electrode; a source electrode provided on one side of the active layer; a drain electrode provided on the other side of the active layer; and a contact layer provided at least one of between the active layer and the source electrode and between the active layer and the drain electrode; The contact layer comprises an oxide of at least one first metal selected from the group consisting of Zn, In, and Ga.

2. 2. The thin film transistor of claim 1, wherein the contact layers include a first contact layer provided between the active layer and the source electrode, and a second contact layer provided between the active layer and the drain electrode.

3. the active layer comprises a second metal oxide; The thin film transistor of claim 1 , wherein the second metal oxide contained in the active layer and the first metal oxide contained in the contact layer are different from each other.

4. The thin film transistor of claim 3 , wherein the metal contained in the first metal oxide is different from the metal contained in the second metal oxide.

5. The thin film transistor of claim 3 , wherein a composition ratio of the metal to oxygen contained in the first metal oxide is different from a composition ratio of the metal to oxygen contained in the second metal oxide.

6. The thin film transistor of claim 3 , wherein the content of oxygen contained in the first metal oxide is less than the content of oxygen contained in the second metal oxide.

7. 2. The thin film transistor of claim 1, wherein the contact layer has a thickness in the range of 30 Å to 100 Å.

8. 10. The thin film transistor of claim 1, wherein the pattern of the contact layer is different from the pattern of the active layer.

9. further comprising an interlayer insulating layer disposed between the active layer and the source electrode; the interlayer insulating layer is provided with a contact hole through which the source electrode is exposed; 2. The thin film transistor according to claim 1, wherein the contact layer is provided in the contact hole.

10. The gate insulating layer may further include a gate insulating layer disposed between the gate electrode and the active layer. The thin film transistor of claim 1 , wherein the source electrode extends from the top surface of the contact layer to the top surface of the gate insulating layer.

11. forming an active layer on a substrate, forming a gate insulating film and a gate electrode on the active layer, and forming an interlayer insulating layer on the gate electrode; forming a contact hole in the interlayer insulating layer and exposing the active layer through the contact hole; forming a contact layer in the contact hole on the exposed upper surface of the active layer, the contact layer including an oxide of at least one first metal selected from Zn, In, and Ga; A method for manufacturing a thin film transistor, comprising the step of forming a source electrode or a drain electrode on the contact layer.

12. The method of claim 11, wherein the interlayer insulating layer is made of nitride, and the contact layer is formed by a selective deposition process without a patterning process.

13. forming a gate electrode on a substrate, forming a gate insulating film on the gate electrode, and forming an active layer on the gate insulating film; forming a contact layer containing an oxide of at least one of the first metals selected from Zn, In, and Ga on the upper surface of the active layer; A method for manufacturing a thin film transistor, comprising the step of forming a source electrode or a drain electrode on the contact layer.

14. the active layer comprises a second metal oxide; 14. The method for manufacturing a thin film transistor according to claim 11, wherein the second metal oxide contained in the active layer and the first metal oxide contained in the contact layer are different from each other.

15. The method of claim 14 , wherein the metal contained in the first metal oxide is different from the metal contained in the second metal oxide.

16. The method of claim 14 , wherein a composition ratio of the metal to oxygen contained in the first metal oxide is different from a composition ratio of the metal to oxygen contained in the second metal oxide.

17. The method for manufacturing a thin film transistor according to claim 14 , wherein the content of oxygen contained in the first metal oxide is less than the content of oxygen contained in the second metal oxide.

18. 15. The method for manufacturing a thin film transistor according to claim 14, wherein the contact layer has a thickness in the range of 30 Å to 100 Å.

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