OXIDE SEMICONDUCTOR-BASED TRANSISTOR AND METHOD OF MANUFACTURING THE SAME

Abstract

Disclosed are an oxide semiconductor-based transistor and a method of manufacturing the same. The oxide semiconductor-based transistor includes: a substrate provided with a bottom electrode; an insulator layer formed on the substrate; an active layer formed on the insulator layer; an electron transport layer formed on the active layer; and a top electrode formed on the electron transport layer. Since the oxide semiconductor-based transistor has a hybrid channel of PBD formed along with indium-zinc oxide (IZO), it is possible to improve mobility of electric charges and stability of electric devices and control a threshold value.

Claims

1. An oxide semiconductor-based transistor comprising: a substrate provided with a bottom electrode; an insulator layer formed on the substrate; an active layer formed on the insulator layer, the active layer formed of an indium-zinc oxide (IZO) thin film; an electron transport layer formed on the active layer, the electron transport layer formed of a [2-(4-T-BUTYLPHENYL)-5-(4-BIPHENYLYL)-1,3] (PBD) powder deposited on the IZO thin film; and a top electrode formed on the electron transport layer.

2. The oxide semiconductor-based transistor according to claim 1, wherein the substrate is an n-type silicon substrate.

3. The oxide semiconductor-based transistor according to claim 2, wherein the insulator layer is formed by growing silicon oxide (SiO.sub.2) from the silicon substrate through thermal oxidization.

4-5. (canceled)

6. The oxide semiconductor-based transistor according to claim 3, wherein the top electrode is formed of aluminum (Al).

7. The oxide semiconductor-based transistor according to claim 6, wherein the active layer is formed by manufacturing an IZO thin film based on a solution process using a reagent containing [In(NO.sub.3).sub.3xH.sub.2O] and [Zn(CH.sub.3COO).sub.22H.sub.2O].

8. (canceled)

9. The oxide semiconductor-based transistor according to claim 7, wherein the top electrode is formed by depositing aluminum pellets in vacuum using a metal evaporator.

10. The oxide semiconductor-based transistor according to claim 1, wherein the bottom electrode is used as a gate electrode, and the top electrode is divided into a pair of pieces used as a source electrode and a drain electrode.

11. A method of manufacturing an oxide semiconductor-based transistor, comprising: fabricating a substrate provided with a bottom electrode; forming an insulator layer on the substrate; forming an active layer on the insulator layer, the active layer formed of an indium-zinc oxide (IZO) thin film; forming an electron transport layer on the active layer, the electron transport layer formed of a [2-(4-T-BUTYLPHENYL)-5-(4-BIPHENYLYL)-1,3] (PBD) powder deposited on the IZO thin film; and forming a top electrode on the electron transport layer.

12. The method according to claim 11, wherein, in the fabrication of the substrate, the substrate is an n-type silicon substrate.

13. The method according to claim 12, wherein, in the formation of the insulator layer, the insulator layer is formed by growing silicon oxide (SiO.sub.2) from the silicon substrate through thermal oxidation.

14-15. (canceled)

16. The method according to claim 13, wherein, in the formation of the top electrode, the top electrode is formed of aluminum (Al).

17. The method according to claim 16, wherein, in the formation of the active layer, the active layer is formed by manufacturing an IZO thin film based on a solution process using a reagent containing [In(NO.sub.3).sub.3xH.sub.2O] and [Zn(CH.sub.3COO).sub.22H.sub.2O].

18. (canceled)

19. The method according to claim 17, wherein, in the formation of the top electrode, the top electrode is formed by depositing aluminum pellets in vacuum using a metal evaporator.

20. The method according to claim 11, wherein the bottom gate is used as a gate electrode, and the top electrode is divided into a pair of pieces used as a source electrode and a drain electrode.

21. The oxide semiconductor-based transistor according to claim 1, wherein the IZO thin film has a thickness between 20 and 30 nm.

22. The oxide semiconductor-based transistor according to claim 1, wherein the PBD has a thickness between 0 and 20 nm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:

[0037] FIG. 1 illustrates a layer structure of an oxide semiconductor-based transistor according to an embodiment of the invention;

[0038] FIG. 2 illustrates energy band levels of elements of the oxide semiconductor-based transistor according to an embodiment of the invention;

[0039] FIG. 3 illustrates a chemical expression of PBD according to an embodiment of the invention;

[0040] FIG. 4 is a flowchart illustrating a method of manufacturing an oxide semiconductor-based transistor according to an embodiment of the invention;

[0041] FIG. 5 illustrates transfer characteristics depending on a thickness of the PBD in an indium-zinc oxide thin-film transistor according to an embodiment of the invention;

[0042] FIG. 6 illustrates a result of a stress test depending on a thickness of the PBD in an indium-zinc oxide transistor according to an embodiment of the invention; and

[0043] FIG. 7 shows scanning optical microscopic images obtained by capturing a surface of an oxide transistor depending on a deposition thickness of the PBD according to an embodiment of the invention.

DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. It is noted that like reference numerals denote like elements throughout overall drawings. In addition, descriptions of well-known apparatus and methods may be omitted so as to not obscure the description of the representative embodiments, and such methods and apparatus are clearly within the scope and spirit of the present disclosure.

[0045] The terminology used herein is only for the purpose of describing particular embodiments and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. It is further to be noted that, as used herein, the terms “comprises”, “comprising”, “include”, and “including” indicate the presence of stated features, integers, steps, operations, units, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, units, and/or components, and/or combination thereof.

[0046] Unless specified otherwise, all terminologies used herein including technical or scientific terminologies have the same meanings as those generally appreciated by a person ordinarily skill in the art to which the present invention pertains. Terminologies defined in typical dictionaries should be construed to have meanings matching those described in the context of the related art, and should not be construed as being abnormal or excessively formal unless defined apparently herein.

[0047] The present invention will now be described with reference to the accompanying drawings, in which like reference numerals denote like elements throughout the entire specification, and they will not be repeatedly described intentionally. In the following description, any specific word or sentence for the related art will not be provided for simplicity purposes if it unnecessarily obscures the subject matter of the invention.

[0048] FIG. 1 illustrates a layer structure of an oxide semiconductor-based transistor according to an embodiment of the invention.

[0049] Referring to FIG. 1, the oxide semiconductor-based transistor according to an embodiment of the invention includes a substrate 110, an insulator layer 120, an active layer 130, an electron transport layer 140, and top electrodes 150 and 160.

[0050] The substrate 110 is fabricated to include a bottom layer. According to an embodiment of the invention, the substrate 110 may be a heavily doped n-type (n.sup.++) silicon substrate.

[0051] The insulator layer 120 is formed on the substrate 110. According to an embodiment of the invention, the insulator layer 120 may be formed by growing silicon oxide (SiO.sub.2) from the silicon substrate through thermal oxidization.

[0052] The active layer 130 is formed on the insulator layer 120. According to an embodiment of the invention, the active layer 130 may be formed of indium-zinc oxide (IZO).

[0053] According to an embodiment of the invention, the active layer 130 may be formed by manufacturing an IZO thin film based on a solution process using a reagent containing [In(NO.sub.3).sub.3xH.sub.2O] and [Zn(CH.sub.3COO).sub.22H.sub.2O].

[0054] The electron transport layer 140 is formed on the active layer 130.

[0055] The electron transport layer 140 according to an embodiment of the invention may be formed by depositing [2-(4-T-BUTYLPHENYL)-5-(4-BIPHENYLYL)-1,3] (PBD) on the IZO thin film.

[0056] According to an embodiment of the invention, the electron transport layer 140 may be formed of PBD. FIG. 3 illustrates a chemical expression of the PBD according to an embodiment of the invention.

[0057] The top electrodes 150 and 160 are formed on the electron transport layer 140. According to an embodiment of the invention, the top electrodes 150 and 160 may be formed of aluminum (Al). In this case, the top electrodes 150 and 160 may be formed by depositing aluminum pellets in vacuum using a metal evaporator.

[0058] According to the present invention, the bottom electrode may be used as a gate electrode, and a pair of top electrodes may be used as source and drain electrodes 150 and 160.

[0059] FIG. 2 illustrates energy band levels of elements in the oxide semiconductor-based transistor according to an embodiment of the invention.

[0060] Referring to the energy band levels of FIG. 2, it is recognized that electrons moving from aluminum can be more easily moved to the IZO thin film due to the PBD.

[0061] However, as illustrated in FIG. 6, it is recognized that a positive shift of the threshold voltage Vth is generated, and electric stability is degraded if the PBD having a thickness of 10 nm or larger is deposited.

[0062] FIG. 4 is a flowchart illustrating a method of manufacturing an oxide semiconductor-based transistor according to an embodiment of the invention.

[0063] Referring to FIG. 4, in the method of manufacturing an oxide semiconductor-based transistor according to an embodiment of the invention, first, a substrate provided with a bottom electrode may be formed of an n-type silicon substrate.

[0064] Then, an insulator layer 120 is formed on the substrate 110 (S420). In the process (S420) of forming the insulator layer, the insulator layer 120 may be formed by growing silicon oxide (SiO.sub.2) on the silicon substrate through thermal oxidization.

[0065] Then, an active layer 130 is formed on the insulator layer 120.

[0066] Then, an electron transport layer 140 is formed on the active layer 130 (S440). In the process (S430) of forming the active layer, the active layer may be formed of indium-zinc oxide (IZO).

[0067] Then, top electrodes 150 and 160 are formed on the electron transport layer 140 (S450). In the process (S440) of forming the electron transport layer, the electron transport layer may be formed of PBD.

[0068] In the process (S450) of forming the top electrodes, the top electrodes may be formed of aluminum (Al).

[0069] According to an embodiment of the invention, in the process (S430) of forming the active layer 130, the active layer 130 may be formed by manufacturing an IZO thin film based on a solution process using a reagent containing [In(NO.sub.3).sub.3xH.sub.2O] and [Zn(CH.sub.3COO).sub.22H.sub.2O].

[0070] In the process (S440) of forming the electron transport layer 140 according to an embodiment of the invention, the electron transport layer 140 may be formed by depositing PBD on the IZO thin film.

[0071] In the process (S450) of forming the top electrode 150 according to an embodiment of the invention, the top electrodes 150 and 160 may be formed by depositing aluminum pellets in vacuum using a metal evaporator.

[0072] An exemplary process of manufacturing an oxide transistor according to the present invention will now be described.

[0073] First, a substrate provided with a bottom electrode is formed from a heavily doped n-type silicon substrate at a thickness of 600 μm.

[0074] Silicon oxide (SiO.sub.2) having a thickness of 100 nm is grown through thermal oxidization to form an insulator layer.

[0075] In order to fabricate an IZO oxide thin film based on a solution process, indium nitrate hydrate [In(NO.sub.3).sub.3xH.sub.2O] and zinc acetate dihydrate [Zn(CH.sub.3COO).sub.22H.sub.2O] are employed as a reagent.

[0076] As a solvent for producing indium and zinc solutions of 0.1 M (molar concentration), 2-methoxyethanol is employed. Acetylacetone serving as a stabilizer for dissolving the reagent is added to the indium solution. For expediting reaction, ammonia (NH3) as a catalyst is added. In addition, only acetylacetone as a stabilizer is added to the zinc solution. Then, the indium solution and the zinc solution are stirred for an hour under a temperature of 60° C.

[0077] Then, the indium (In) solution and the zinc (Zn) solution are mixed at a mixing ratio of 7:3, and stirring is performed for two hours under a temperature of 27° C.

[0078] In order to form an IZO channel, spin coating is performed at a rotation speed of 1,500 rpm, and then annealing is performed. As a result, an IZO thin film having a thickness of 20 to 30 nm is formed.

[0079] The PBD used as a material of the electron transport layer is deposited on the IZO thin film at a thickness of 0 to 20 nm. According to an embodiment of the invention, a PBD powder is deposited on the IZO thin film using an organic evaporator at thicknesses of 0, 5, 10, and 20 nm.

[0080] Finally, for forming source and drain electrodes, aluminum pellets are deposited at a thickness of 100 nm in vacuum using a metal evaporator.

[0081] Electric characteristics of the resulting oxide semiconductor device are measured under a room environment using a semiconductor device analyzer AGILENT® B1500. The measurement results are shown in FIG. 5.

EXPERIMENTAL EXAMPLES

[0082] FIG. 5 illustrates transfer characteristics depending on a thickness of the PBD in an indium-zinc oxide thin-film transistor according to an embodiment of the invention.

[0083] Referring to FIG. 5, transfer characteristics of the transistor device are plotted when the PBD thin film has thicknesses of “0, 5, 10, and 20 nm.” In the measurement of the transistor device, a drain is grounded, and voltages are applied to a source and a gate. A drain current is measured by applying a voltage of −10 to 30 V to the gate. As a result, it is recognized that excellent transistor characteristics are obtained when the PBD has a thickness of 5 nm. In addition, power consumption and efficiency in a digital circuit can be improved by controlling the threshold voltage depending on a variation of the thickness.

[0084] FIG. 6 illustrates a result of an electrical stress test as a function of the time depending on a thickness of the PBD in an indium-zinc oxide transistor according to an embodiment of the invention.

[0085] Referring to FIG. 6, it is recognized that performance of the transistor is unsatisfactory when the PBD has a thickness equal to or larger than “10 nm.” In addition, electrical stability is highest when the PBD has a thickness of “5 nm.” Furthermore, the drain current becomes unstable as time elapses when the PBD has a thickness equal to or larger than “5 nm.”

[0086] FIG. 7 shows optical microscopic images obtained by capturing a surface of an oxide transistor depending on a deposition thickness of the PBD according to an embodiment of the invention.

[0087] Referring to FIG. 7, the optical images (a), (b), (c), and (d) show surfaces of the oxide transistors having PBD deposition thicknesses of 0, 5, 10, and 20 nm, respectively.

[0088] The IZO thin-film transistor (TFT) using an oxide semiconductor material is fabricated as a high-quality PLED display driving backplane device. According to the present invention, since the electron transport layer (ETL) capable of improving electron mobility forms a hybrid channel along with the oxide semiconductor layer, it is possible to improve important device parameters such as electric charge mobility or an ON/OFF ratio and implement a faster and more accurate device. Finally, the present invention is expected to be used as a core technology for improving performance of a next-generation display.

[0089] Although exemplary embodiments of the present invention have been shown and described, it will be apparent to those having ordinary skill in the art that a number of changes, modifications, or alterations to the invention as described herein may be made, none of which depart from the spirit of the present invention. All such changes, modifications and alterations should therefore be seen as within the scope of the present invention.