Manganese tin oxide based transparent conducting oxide and transparent conductive film and method for fabricating transparent conductive film using the same

Abstract

Disclosed is a manganese tin oxide-based transparent conducting oxide (TCO) with an optimized composition, which has low surface roughness, low sheet resistance and high transmittance even when deposited at room temperature, a multilayer transparent conductive film using the same and a method for fabricating the same. The manganese tin oxide-based transparent conducting oxide has a composition of Mn.sub.xSn.sub.1-xO (0<x0.055), and the multilayer transparent conductive film includes: a manganese tin oxide-based transparent conducting oxide having a composition of Mn.sub.xSn.sub.1-xO (0<x0.055); a metal thin film deposited on the manganese tin oxide-based transparent conducting oxide; and a manganese tin oxide-based transparent conducting oxide having a composition of Mn.sub.xSn.sub.1-xO (0<x0.055) deposited on the metal thin film.

Claims

1. A manganese tin oxide-based transparent conducting oxide film, wherein the manganese tin oxide has a composition Mn.sub.xSn.sub.1-xO (0<x0.055), and has an amorphous phase.

2. The manganese tin oxide-based transparent conducting oxide film according to claim 1, wherein x is 0.0350.055.

3. The manganese tin oxide-based transparent conducting oxide film according to claim 1, wherein x is 0.045.

4. The manganese tin oxide-based transparent conducting oxide film according to claim 1, wherein a Root Mean Square surface roughness of the manganese tin oxide-based transparent conducting oxide film is 0.60.85 nm.

5. The manganese tin oxide-based transparent conducting oxide film according to claim 1, wherein a sheet resistance of the manganese tin oxide-based transparent conducting oxide film is 6.610.4 /cm.sup.2.

6. The manganese tin oxide-based transparent conducting oxide film according to claim 1, wherein a transmittance of the manganese tin oxide-based transparent conducting oxide film is 8286% for visible light.

7. The manganese tin oxide-based transparent conducting oxide according to claim 1, wherein the manganese tin oxide-based transparent conducting oxide is capable of being deposited on a substrate at room temperature.

8. The manganese tin oxide-based transparent conducting oxide film according to claim 7, wherein the substrate is a glass substrate or a polymer substrate.

9. The manganese tin oxide-based transparent conducting oxide film according to claim 8, wherein the polymer substrate is made of at least one selected from a group consisting of polyester, polyethylene, polycarbonate or polyethylene terephthalate.

10. A multilayer transparent conductive film, comprising: a first manganese tin oxide-based transparent conducting oxide film, wherein the first manganese tin oxide-based transparent conducting oxide has an amorphous phase and has a composition of Mn.sub.xSn.sub.1-xO (0<x0.055); a metal thin film deposited on the manganese tin oxide-based transparent conducting oxide film; and a second manganese tin oxide-based transparent conducting oxide film, wherein the second manganese tin oxide-based transparent conducting oxide has an amorphous phase and has a composition of Mn.sub.xSn.sub.1-xO (0<x0.055) deposited on the metal thin film, wherein the metal thin film has a thickness less than 100 nm.

11. The multilayer transparent conductive film according to claim 10, wherein x is 0.035-0.055.

12. The multilayer transparent conductive film according to claim 10, wherein x is 0.045.

13. The multilayer transparent conductive film according to claim 10, wherein the metal thin film is at least one selected from a group consisting of Ag, Au, Cu, Pd, Pt, Ni, Al, Y, La, Mg, Ca, Fe, Pb and Zn or an alloy thereof.

14. The multilayer transparent conductive film according to claim 10, wherein either of the first and the second manganese tin oxide-based transparent conducting oxide film has a thickness of 20-200 nm and the metal thin film has a thickness of 5-50 nm.

15. A method of manufacturing a manganese tin oxide film, the method comprising: obtaining a tin dioxide deposition target; obtaining a manganese dioxide deposition target; and simultaneously removing material from the tin dioxide deposition target and the manganese dioxide deposition target so as to deposit a film of manganese tin oxide on a substrate physically separated from the tin dioxide deposition target and the manganese dioxide deposition target, wherein the manganese tin oxide film has a composition of Mn.sub.xSn.sub.1-xO (0<x0.055), and has an amorphous phase.

16. The method of claim 15, wherein the simultaneously removing material comprises providing radio frequency power to the tin dioxide deposition target and the manganese dioxide deposition target in a vacuum environment.

17. The method of claim 16, wherein the radio frequency power provided to the tin dioxide deposition target is greater than the radio frequency power provided to the manganese dioxide deposition target.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view for explaining a surface roughness of a transparent conducting oxide in crystalline and amorphous phases.

(2) FIG. 2 is a schematic view of a multilayer transparent conductive film according to an example of the present disclosure.

(3) FIG. 3 shows a sheet resistance graph of a MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition.

(4) FIG. 4a shows a surface roughness of a MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition at three points.

(5) FIG. 4b shows a sheet resistance graph of a MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition where the three points are indicated.

(6) FIG. 5 shows a sheet resistance graph of pure SnO.sub.2 and a Mn-doped SnO.sub.2 multilayer transparent conductive film.

(7) FIG. 6 shows a transmittance graph of pure SnO.sub.2 and a Mn-doped SnO.sub.2 multilayer transparent conductive film.

DETAILED DESCRIPTION

(8) The example embodiments of the present disclosure provides a transparent conducting oxide (TCO) having a composition of Mn.sub.xSn.sub.1-xO (0<x0.055) and a multilayer transparent conductive film with a TCO/metal thin film/TCO structure in which the transparent conducting oxide (TCO) having the composition and a metal thin film are deposited alternately.

(9) The transparent conducting oxide (TCO) having a composition of Mn.sub.xSn.sub.1-xO (0<x0.055) according to the example embodiments of the present disclosure has low surface roughness even when deposited at room temperature, not to speak of at high temperature, and exhibits superior electrical properties due to the low surface roughness. The low surface roughness improves electron mobility at the interface between the transparent conducting oxide (TCO) and the metal thin film, thereby improving the electrical properties of the multilayer transparent conductive film having the TCO/metal thin film/TCO structure.

(10) The transparent conducting oxide (TCO) according to the example embodiments of the present disclosure has a composition of Mn.sub.xSn.sub.1-xO (0<x0.055). As seen from 0<x0.055, the composition is obtained as a trace amount of Sn in SnO.sub.2 is replaced by Mn.

(11) The electrical and optical properties of the transparent conducting oxide (TCO) are secured when it has a composition of Mn.sub.xSn.sub.1-xO (0<x0.055). When the compositional ratio of Mn exceeds 0.055, the electrical and optical properties may worsen due to an increased surface roughness.

(12) In an example embodiment of the present disclosure, a RMS (Root Mean Square) surface roughness of the transparent conducting oxide (TCO) thin film having the composition of Mn.sub.xSn.sub.1-xO (0<x0.055), for example, may be 0.6-0.85 nm, preferably 0.6-0.8 nm.

(13) In an example embodiment of the present disclosure, a sheet resistance of the transparent conducting oxide (TCO) thin film having the composition of Mn.sub.xSn.sub.1-xO (0<x0.055), for example, may be 6.610.4 /cm.sup.2.

(14) In an example embodiment of the present disclosure, a transmittance of the transparent conducting oxide (TCO) thin film having the composition of Mn.sub.xSn.sub.1-xO (0<x0.055), for example, may be 8286%.

(15) From the experiments of the present disclosure, it has been found out that optimum electrical and optical properties are achieved when the compositional ratio of Mn is 0.035-0.055, in particular 0.045, with a transmittance of 86% and a sheet resistance of 6.6 /cm.sup.2. For reference, when the compositional ratio of Mn is 0.045, Mn accounts for 2.59 wt % in the Mn.sub.xSn.sub.1-xO.

(16) In the embodiments of the present disclosure, the optimized composition of Mn.sub.xSn.sub.1-xO (0<x0.055) was determined by forming a MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition (Mn.sub.xSn.sub.1-xO (0x1)), and comparting the thin film layer into plural zones, and then measuring the electrical and optical properties of the each zones of the thin film layer.

(17) The multilayer transparent conductive film having a TCO/metal thin film/TCO structure, wherein the transparent conducting oxide (TCO) having a composition of Mn.sub.xSn.sub.1-xO (0<x0.055) according to the embodiments of the present disclosure has been applied (see FIG. 2), may exhibit superior electrical and optical properties. Because the transparent conducting oxide (TCO) having a composition of Mn.sub.xSn.sub.1-xO (0<x0.055) of the embodiments of the present disclosure has low surface roughness and high transmittance even with a small thickness of 20-200 nm, the multilayer transparent conductive film having the TCO/metal thin film/TCO structure may secure superior electrical and optical properties.

(18) The multilayer transparent conductive film having the TCO/metal thin film/TCO structure is designed such that the transparent conducting oxide (TCO) has a thickness of 20-200 nm and the metal thin film has a thickness of 5-50 nm. When the thickness of the metal thin film is less than 5 nm, it is difficult to form a uniform film. And, when it exceeds 50 nm, transmittance may decrease. The metal thin film may reflect most of incident light and hardly transmit it due to low refractive index and large extinction coefficient when it exists as a single layer. But, when it is disposed between the transparent conducting oxides (TCO), light reflection is reduced since the traveling properties of light changes in the medium. As the metal thin film, one of Ag, Au, Cu, Pd, Pt, Ni, Al, Y, La, Mg, Ca, Fe, Pb and Zn or an alloy thereof may be used.

(19) Because the transparent conducting oxide (TCO) having a composition of Mn.sub.xSn.sub.1-xO (0<x0.055) according to the embodiments of the present disclosure can be deposited at room temperature as described above, it can be applied onto a polymer substrate made of polycarbonate (PC), polyethylene terephthalate (PET), polyester, polyethylene, etc. Accordingly, it can be used as a transparent electrode of a flexible device. The transparent conducting oxide (TCO) or the multilayer transparent conductive film having the TCO/metal thin film/TCO structure can be deposited through various deposition processes such as sputtering, CVD, PVD, etc.

(20) The manganese tin oxide-based transparent conducting oxide (TCO) according to embodiments of the present disclosure, the multilayer transparent conductive film using the same and the fabrication method thereof are described in more detail through the following examples.

Example 1: Determination of Optimized Composition by Continuous Composition Spread Method

(21) A 75 mm15 mm glass substrate was positioned in an off-axis continuous composition spread sputtering device wherein two sputter gun were arranged with an angle of 90 degrees. 2-inch SnO.sub.2 target and MnO.sub.2 target were mounted for each sputter gun. After creating a high-vacuum atmosphere of about 210.sup.6 Torr using a rotary pump and a turbomolecular pump, argon (Ar) gas was injected and sputtering was conducted at a pressure of 45 mTorr. The SnO.sub.2 target was sputtered at 40 W and the MnO.sub.2 target was sputtered at 10 W, for 1 hour, respectively. Before the thin film deposition, pre-sputtering was conducted for 15 minutes.

(22) Through the sputtering, a thin film layer was formed on the glass substrate. The SnO.sub.2 target and the MnO.sub.2 target were used, and a MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition of Mn.sub.xSn.sub.1-xO (0x1) was formed. In the formed MnO.sub.2SnO.sub.2-based thin film layer, the substrate portion close to the MnO.sub.2 target was relatively rich in MnO.sub.2 and the substrate portion close to the SnO.sub.2 was relatively rich in SnO.sub.2. Also, the thickness of the thin film layer formed on the substrate portions close to the each targets were relatively thicker than that of the thin film formed on the middle portion of the substrate.

(23) The sheet resistance of the MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition was measured. As seen from FIG. 3, the sheet resistance increased as the content of MnO.sub.2 increase, and the electrical properties were improved as the SnO.sub.2 content increases. It can be seen that the MnO.sub.2SnO.sub.2-based thin film layer exhibits low sheet resistance in a broad range. Of the total width 75 mm of the thin film layer, the zone corresponding to 10-55 mm showed sheet resistance of about 6.6 /cm.sup.2. In the zone past 55 mm (i.e., in the zone where Mn content was 3.17 wt % or more), the sheet resistance increased rapidly.

(24) In addition, the surface roughness of the MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition was analyzed by atomic force microscopy (AFM). From FIG. 4a, the MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition had an amorphous phase. When RMS was measured for three points (Point 1, Point 2 and Point 3 in FIGS. 4a and 4b) randomly chosen from the 10-55 mm zone of overall 75 mm thin film layer, the RMS value was very low as 0.644-0.838 nm. Also, the MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition had a transmittance of 80% or higher in the visible region.

(25) From the experimental results on the MnO.sub.2SnO.sub.2-based thin film layer having a continuous composition, the most superior properties were observed when the composition was Mn.sub.0.045Sn.sub.0.955O. The composition Mn.sub.0.045Sn.sub.0.955O corresponds to SnO.sub.2 containing 2.59 wt % of Mn.

Example 2: Deposition and Characterization of Multilayer Transparent Conductive Film

(26) A transparent conducting oxide (TCO), a metal thin film and a transparent conducting oxide (TCO) were deposited sequentially on a glass substrate. The transparent conducting oxide (TCO) was Mn-doped SnO.sub.2 and the metal thin film was Ag. That is to say, a multilayer transparent conductive film with a Mn-doped SnO.sub.2/Ag/Mn-doped SnO.sub.2 structure was formed on a glass substrate through sputtering deposition at room temperature.

(27) The Mn-doped SnO.sub.2 was deposited using a SnO.sub.2 target containing 2.59 wt % of Mn. For comparison, three different multilayer transparent conductive films of 2.59 wt % Mn-doped SnO.sub.2/Ag/2.59 wt % Mn-doped SnO.sub.2, 10 wt % Mn-doped SnO.sub.2/Ag/10 wt % Mn-doped SnO.sub.2 and SnO.sub.2/Ag/SnO.sub.2 were formed by depositing 2.59 wt % Mn-doped SnO.sub.2, 10 wt % Mn-doped SnO.sub.2 and SnO.sub.2, respectively.

(28) An on-axis sputtering device was used and the deposition was conducted under an argon (Ar) atmosphere at a pressure of 5 mTorr. The target power was 30 W. The top and bottom TCOs were deposited to a thickness of 50 nm and the Ag was deposited to a thickness of 12 nm. The total thickness of the multilayer transparent conductive film was 112 nm.

(29) The electrical properties of the deposited three multilayer transparent conductive films were analyzed by the four-point probe method, hall measurement and UV/Vis spectrometry.

(30) The sheet resistance of the 2.59 wt % Mn-doped SnO.sub.2/Ag/2.59 wt % Mn-doped SnO.sub.2, the 10 wt % Mn-doped SnO.sub.2/Ag/10 wt % Mn-doped SnO.sub.2 and the SnO.sub.2/Ag/SnO.sub.2 was 6.6 /cm.sup.2, 10.4 /cm.sup.2 and 14.7 /cm.sup.2, respectively. The sheet resistance was superior for the Mn-doped SnO.sub.2 to the pure SnO.sub.2. But, when Mn was doped in excess (10 wt %), the electrical property of the thin film worsened (see FIG. 5).

(31) The transmittance of the multilayer transparent conductive films was 86%, 81% and 82% for the 2.59 wt % Mn-doped SnO.sub.2/Ag/2.59 wt % Mn-doped SnO.sub.2, the 10 wt % Mn-doped SnO.sub.2/Ag/10 wt % Mn-doped SnO.sub.2 and the SnO.sub.2/Ag/SnO.sub.2, respectively. The multilayer transparent conductive film wherein the 2.59 wt % Mn-doped SnO.sub.2 was used showed the most superior transmittance property (see FIG. 6). Based on these results, it can be concluded that the multilayer transparent conductive film wherein the 2.59 wt % Mn-doped SnO.sub.2 is used exhibits low sheet resistance and high transmittance in the visible region even with a relatively small thickness and is applicable to various display devices including flexible devices.