KR102741597B1 - Oxide semiconductor and semiconductor device comprising the same - Google Patents

Abstract

The present invention relates to an oxide semiconductor and a semiconductor device including the same. Specifically, according to one embodiment of the present invention, the oxide semiconductor includes an oxide doped with ytterbium (Yb) and containing indium (In) and zinc (Zn), thereby having excellent electrical characteristics and safety.

Description

Oxide semiconductor and semiconductor device comprising the same {OXIDE SEMICONDUCTOR AND SEMICONDUCTOR DEVICE COMPRISING THE SAME}

The present invention relates to an oxide semiconductor and a semiconductor device including the same.

TFT (Thin Film Transistor), a display semiconductor, is a transistor with a thin film stacked on it. TFT, a type of semiconductor, acts as an electrical switch that controls the brightness of light in a display composed of multiple pixels, and can control light emission by turning the light on/off by controlling the electrical signal.

TFT can be classified according to the forming material of the oxide layer, and physical properties such as electron mobility can be secured depending on the material used. Conventionally, a-Si TFT using amorphous silicon or LTPS TFT using polycrystalline silicon were used. However, since a crystalline silicon thin film requires a high temperature of 800℃ or higher during manufacturing, it must be formed on an expensive substrate with high heat resistance, such as a silicon wafer or quartz, rather than a glass substrate or an organic substrate, and there is a problem that it is difficult to reduce the cost because it is limited to the top gate configuration of the TFT. In addition, although an amorphous silicon thin film can be formed at a relatively low temperature, there are problems such as slow switching speed, conductivity or leakage current when visible light is irradiated to the semiconductor active layer, and therefore, a light-blocking layer that blocks visible light must be additionally configured.

Recently, interest in amorphous oxide semiconductors (AOS) that are inexpensive, have high electron mobility, low off current, and excellent transmittance in the visible light region has increased. Such AOS include IZO (indium zinc oxide), IZTO (indium zinc tin oxide), IGTO (indium gallium tin oxide), and IGZO (indium gallium zinc oxide). However, oxide semiconductors can have defects due to impurities such as metal hydroxyl groups and carbon, which can deteriorate their electrical characteristics and lower their stability under various operating conditions such as gate, illumination, and thermal bias stress. Therefore, there has been an attempt to increase the stability using terbium (Tb), but there was a problem that the electrical characteristics deteriorated as the Tb content increased. In addition, there were attempts to improve stability by controlling the composition ratio of IGZO, but there was a problem that mobility and stability decreased as the content of Ga increased. Therefore, research is ongoing to improve stability without deteriorating mobility and electrical characteristics that can secure the performance of oxide semiconductors.

Japanese Patent Publication No. 2013-0056579

Accordingly, the present invention aims to provide an oxide semiconductor having excellent electrical characteristics and stability and a semiconductor device including the same.

According to one embodiment of the present invention, an oxide semiconductor is provided, which includes an oxide doped with ytterbium (Yb) and containing indium (In) and zinc (Zn).

According to another embodiment of the present invention, a semiconductor device is provided, including: a substrate; a dielectric layer formed on the substrate; a semiconductor layer including the oxide semiconductor formed on the dielectric layer; and an electrode formed on the semiconductor layer.

According to another embodiment of the present invention, a thin film transistor including the semiconductor element is provided.

According to another embodiment of the present invention, a display device including the thin film transistor is provided.

An oxide semiconductor according to one embodiment of the present invention includes an oxide doped with ytterbium (Yb) and containing indium (In) and zinc (Zn), thereby having excellent electrical characteristics and safety without deterioration of characteristics such as mobility.

Specifically, the present invention relates to an oxide semiconductor having a new composition by doping Yb, which is the most abundant rare earth element, into IZO. Yb has a standard electrode potential of -2.19 V, which is significantly lower than that of In (0.34 V) and Zn (0.76 V), and also has an electronegativity of 1.1, which is lower than that of In (1.78) and Zn (1.65). In addition, the dissociation energy of Yb-O metal oxide is 397.9 kJ/mol, which is higher than that of In-O (360 kJ/mol) and Zn-O (284.1 kJ/mol). Therefore, it can effectively reduce oxygen vacancies (Vo), which are the biggest cause of low stability of amorphous oxide semiconductors.

Furthermore, under various conditions such as negative bias stress (NBS), positive bias stress (PBS), negative bias illumination stress (NBIS), positive bias illumination stress (PBIS), negative bias temperature stress (NBTS), and positive bias temperature stress (PBTS), the TFT including IYZO according to the present invention has a threshold voltage (V _th ) variation (△V _th ) reduced by 15% or more compared to a TFT including IGZO used in the related art, and thus has excellent stability under various conditions.

In addition, while the mobility of the TFT (10.13 cm ² /Vs) including the conventional IGZO is generally reduced by about 13% compared to that of the IZO (11.63 cm ² /Vs), the TFT (11.86 cm ² /Vs) including the IYZO according to the present invention has almost no change in mobility. Therefore, since the oxide semiconductor according to the present invention has excellent electrical characteristics and stability without a decrease in mobility, it can exhibit excellent performance when applied to semiconductor devices, thin film transistors, and displays.

Figure 1 shows the transfer characteristics of an IZO TFT and an IGZO TFT (Ga doping concentration: 1 mol%, 3 mol%, 5 mol%) (a), and the transfer characteristics of an IZO TFT and an IYZO TFT (Yb doping concentration: 1 mol%, 3 mol%, 5 mol%) (b).
Figure 2 shows the Hall measurement characteristics of an IZO TFT and an IGZO TFT (Ga doping concentration: 1 mol%, 3 mol%, 5 mol%) (a), and the Hall measurement characteristics of an IZO TFT and an IYZO TFT (Yb doping concentration: 1 mol%, 3 mol%, 5 mol%) (b).
Figure 3 shows the stability evaluation of an IZO TFT (a), an IGZO TFT (Ga doping concentration: 3 mol%) (b), and an IYZO TFT (Yb doping concentration: 3 mol%) (c) under PBS conditions, and the stability evaluation of an IZO TFT (d), an IGZO TFT (Ga doping concentration: 3 mol%) (e), and an IYZO TFT (Yb doping concentration: 3 mol%) (f) under NBS conditions.
Figure 4 shows the stability evaluation of IZO TFT (g), IGZO TFT (Ga doping concentration: 3 mol%) (h), and IYZO TFT (Yb doping concentration: 3 mol%) (i) under PBTS conditions, and the stability evaluation of IZO TFT (j), IGZO TFT (Ga doping concentration: 3 mol%) (k), and IYZO TFT (Yb doping concentration: 3 mol%) (l) under NBTS conditions.
Figure 5 shows the stability evaluation of IZO TFT (m), IGZO TFT (Ga doping concentration: 3 mol%) (n), and IYZO TFT (Yb doping concentration: 3 mol%) (o) under PBIS conditions, and the stability evaluation of IZO TFT (p), IGZO TFT (Ga doping concentration: 3 mol%) (q), and IYZO TFT (Yb doping concentration: 3 mol%) (r) under NBIS conditions.
Figure 6 shows the evaluation of the optical response characteristics of an IZO TFT (a), an IGZO TFT (doping concentration of Ga: 1 mol%) (b), an IGZO TFT (doping concentration of Ga: 3 mol%) (c), an IGZO TFT (doping concentration of Ga: 5 mol%) (d), an IYZO TFT (doping concentration of Yb: 1 mol%) (e), an IYZO TFT (doping concentration of Yb: 3 mol%) (f), and an IYZO TFT (doping concentration of Yb: 5 mol%) (g).
Figure 7 shows O1s spectra of IZO (a), IGZO (doping concentration of Ga: 1 mol%) (b), IYZO (doping concentration of Yb: 1 mol%) (c), IYZO (doping concentration of Yb: 3 mol%) (d), and IYZO (doping concentration of Yb: 5 mol%) (e) films.
Figure 8 shows the optical band gaps of IZO and IGZO (doping concentration of Ga: 1 mol%, 3 mol%, 5 mol%) (a), the band edge state of the IZO film (b), the band edge state of the IGZO (doping concentration of Ga: 1 mol%) film (c), the band edge state of the IGZO (doping concentration of Ga: 3 mol%) film (d), the band edge state of the IGZO (doping concentration of Ga: 5 mol%) film (e), the optical band gaps of IZO and IYZO (doping concentration of Yb: 1 mol%, 3 mol%, 5 mol%) (f), the band edge state of the IYZO (doping concentration of Yb: 1 mol%) film (g), the band edge state of the IYZO (doping concentration of Yb: 3 mol%) film (h), and the optical band gaps of the IZO and IYZO (doping concentration of Yb: 5 mol%) shows the band edge state (i) of the film.
Figure 9 shows the contact resistance of an IZO TFT (a), the contact resistance of an IGZO (Ga doping concentration: 3 mol%) (b), and the contact resistance of an IYZO (Yb doping concentration: 3 mol%) (c) measured using TLM (Transmission Line Measurement).
Figure 10 shows scanning probe microscope (AFM) images and their RMS roughnesses of IZO TFT (a), IGZO (doping concentration of Ga: 1 mol%) (b), IGZO (doping concentration of Ga: 3 mol%) (c), IGZO (doping concentration of Ga: 5 mol%) (d), IYZO (doping concentration of Yb: 1 mol%) (e), IYZO (doping concentration of Yb: 3 mol%) (f), and IYZO (doping concentration of Yb: 5 mol%) (g), and X-ray diffraction (XRD) patterns of IZO, IGZO (doping concentration of Ga: 3 mol%), IYZO (doping concentration of Yb: 1 mol%), IYZO (doping concentration of Yb: 3 mol%), and IYZO (doping concentration of Yb: 5 mol%). This shows the pattern (h).
Figure 11 shows the transfer characteristics and output characteristics of IYZO (Yb doping concentration: 7 mol%) (a), IYZO (Yb doping concentration: 9 mol%) (b), IGZO (Ga doping concentration: 7 mol%) (c), and IGZO (Ga doping concentration: 9 mol%) (d), and the results of evaluating the electrical characteristics derived therefrom.
Figure 12 shows the transfer characteristics and output characteristics of IYZO (Yb doping concentrations: 2 mol%, 5 mol%, 13 mol%, 19 mol%, and 24 mol%, respectively) and the mobility characteristics derived therefrom when the drain voltage is 20.1 V.
Figure 13 shows the transfer characteristics and output characteristics of IYZO (Yb doping concentrations: 5 mol%, 10 mol%, 15 mol%, 20 mol%, and 25 mol%, respectively) and the mobility characteristics derived therefrom when the drain voltage is 20.1 V.

Hereinafter, the present invention will be described in detail. The present invention is not limited to the contents disclosed below, and may be modified in various forms as long as the gist of the invention is not changed.

In this specification, when a part is said to "include" a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated.

All numbers and expressions indicating the amounts of ingredients, reaction conditions, etc. described in this specification should be understood as being modified by the term "about" in all cases unless otherwise specified.

When it is described in this specification that one component is formed on or below another component, it includes both that one component is formed directly on or below the other component, or indirectly through the interposition of another component.

In the numerical ranges that limit the size, physical properties, etc. of the components described in this specification, if a numerical range limited only to an upper limit and a numerical range limited only to a lower limit are separately exemplified, it should be understood that a numerical range in which these upper and lower limits are combined is also included in the exemplary range of the present invention.

An oxide semiconductor according to one embodiment of the present invention includes an oxide doped with ytterbium (Yb) and containing indium (In) and zinc (Zn).

IZO, a representative amorphous oxide semiconductor (AOS), has been studied extensively due to its advantage of high electron mobility, but has the disadvantage of low reliability and stability under various bias stress conditions. Therefore, attempts have been made to improve both electrical characteristics and stability through an annealing process, but when the annealing temperature increases above 400℃, there is a problem that V _th moves in the negative direction due to the increase in carrier concentration, which deteriorates stability.

Accordingly, IGZO with Ga introduced is being used to improve both electrical characteristics and stability, but there is a problem that the price of Ga fluctuates greatly, making it difficult to secure a stable supply. In addition, as the content of Ga increases, mobility and stability may decrease.

The oxide semiconductor according to the present invention is IZO doped with Yb, which is the most abundant rare earth element, and thus has a stable supply compared to Ga, and can further improve electrical characteristics and stability compared to the case of Ga doping.

According to one embodiment of the present invention, the doping concentration of Yb may be 1 mol% to 10 mol%. For example, the doping concentration of Yb may be 1 mol% to 9 mol%, 2 mol% to 10 mol%, or 3 mol% to 9 mol%. The doping concentration of Yb may be calculated as a percentage (mol%) of the molar number of Yb to the sum of the molar numbers of all metal components (In, Yb, Zn).

The molar ratio of the In and the Yb may be 1:0.001 to 0.8. For example, the molar ratio of the In and the Yb may be 1:0.001 to 0.7, 1:0.001 to 0.6, 1:0.001 to 0.5, 1:0.001 to 0.3, 1:0.001 to 0.1, 1:0.001 to 0.05, or 1:0.001 to 0.02.

According to one specific example, the atomic ratio of In, Yb and Zn can satisfy the following formulas A1 to A3.

[Formula A1]

0.2 ≤ In/(In + Zn) ≤ 0.99

[Formula A2]

0.29 ≤ In/(In + Yb) ≤ 0.99

[Formula A3]

0.1 ≤ Zn/(Yb + Zn) ≤ 0.99

According to another specific example, the atomic ratio of In, Yb and Zn can satisfy the following formulas B1 to B3.

[Formula B1]

0.2 ≤ In/(In + Zn) ≤ 0.8

[Formula B2]

0.29 ≤ In/(In + Yb) ≤ 0.99

[Formula B3]

0.29 ≤ Zn/(Yb + Zn) ≤ 0.99

According to another specific example, the atomic ratio of In, Yb and Zn can satisfy the following formulas C1 to C3.

[Formula C1]

0.8 ≤ In/(In + Zn) ≤ 0.99

[Formula C2]

0.59 ≤ In/(In + Yb) ≤ 0.99

[Formula C3]

0.1 ≤ Zn/(Yb + Zn) ≤ 0.98

According to one embodiment of the present invention, the oxide semiconductor can have a hall mobility of 1.3 cm ² /Vs or more. For example, the oxide semiconductor can have a hall mobility of 1.35 cm ² /Vs or more, 1.4 cm ² /Vs or more, or 1.42 cm ² /Vs or more.

The oxide semiconductor may have a carrier concentration of 1.2 × 10 ¹⁶ cm ^-3 or more. For example, the oxide semiconductor may have a carrier concentration of 1.21 × 10 ¹⁶ cm ^-3 or more, 1.22 × 10 ¹⁶ cm ^-3 or more, or 1.24 × 10 ¹⁶ cm ^-3 or more.

The oxide semiconductor may have a threshold voltage (V _th ) of -40 V to 40 V. For example, the oxide semiconductor may have a threshold voltage of -40 V to 40 V, -30 V to 30 V, -20 V to 25 V, -10 V to 20 V, -10 V to 15 V, -5 V to 15 V, -5 V to 10 V, or 0 V to 5 V.

Additionally, the oxide semiconductor can have a threshold voltage variation (Δthreshold voltage, ΔV _th ) of -6 V to 3 V.

In one specific example, the oxide semiconductor can have a hall mobility of 1.3 cm ² /Vs or more, a carrier concentration of 1.2 × 10 ¹⁶ cm ^-3 or more, and a threshold voltage (ΔV _th ) of -6 V to 3 V.

In one specific example, the threshold voltage variation (ΔV _th ) of the oxide semiconductor can be -3 V to 2.8 V under conditions of positive bias stress (PBS) and negative bias stress (NBS), can be -5 V to 4 V under conditions of positive bias temperature stress (PBTS) and negative bias temperature stress (NBTS), and can be -6 V to 1.5 V under conditions of positive bias illumination stress (PBIS) and negative bias illumination stress (NBIS).

More specifically, the threshold voltage variation (ΔV _th ) of the oxide semiconductor can be -3 V to 2.6 V, -2.8 V to 2.5 V or -2.6 V to 2.4 V under the conditions of PBS and NBS, -4.5 V to 4 V, -4 V to 3.5 V or -3.5 V to 3 V under the conditions of PBTS and NBTS, and -5.8 V to 1.5 V, -5.5 V to 1.3 V or -5.2 V to 1.2 V under the conditions of PBIS and NBIS.

The oxide semiconductor may have an electron mobility of 1 cm ² /Vs to 120 cm ² /Vs. For example, the electron mobility of the oxide semiconductor may be 1 cm ² /Vs or more, 5 cm ² /Vs or more, or 10 cm ² /Vs or more, and may also be 120 cm ² /Vs or less, 100 cm ² /Vs or less, 80 cm ² /Vs or less, 60 cm ² /Vs or less, 40 cm ² /Vs or less, or 30 cm ² /Vs or less. Specifically ^, the electron mobility of the oxide semiconductor may be 1 cm ² /Vs to 120 cm ² /Vs, 5 cm ² /Vs to 110 cm ² /Vs, 5 cm ² /Vs to 100 cm ² /Vs, 10 cm ² /Vs to 90 cm ² /Vs, 15 cm ² /Vs to 80 cm ² /Vs, 25 cm ² /Vs to 70 cm ² /Vs, 30 cm ² /Vs to 60 cm 2 /Vs, 35 cm ² /Vs to 50 cm ² /Vs, or 1 cm ² /Vs to 40 cm ² /Vs. In one specific example, the oxide semiconductor may have an electron mobility of 1 cm ² /Vs to 40 cm ² /Vs.

The oxide semiconductor can have a subthreshold swing (SS) of 0.06 V/decade to 2 V/decade. For example, the oxide semiconductor can have a SS of 0.06 V/decade to 1.8 V/decade, 0.1 V/decade to 1.6 V/decade, 0.12 V/decade to 1.4 V/decade, 0.16 V/decade to 1.2 V/decade, 0.2 V/decade to 1.0 V/decade, 0.24 V/decade to 0.8 V/decade, 0.3 V/decade to 0.7 V/decade, or 0.4 V/decade to 0.55 V/decade.

The oxide semiconductor can have an interface trap density (D _it ) of 1x10 ¹² cm ^-2 eV ^-1 to 5x10 ¹² cm ^-2 eV ^-1 . For example, the oxide semiconductor can have D _it of 1.5x10 ¹² cm ^-2 eV ^-1 to 5.0x10 ¹² cm ^-2 eV ^-1 , 2.0x10 ¹² cm ^-2 eV ^-1 to 4.5x10 ¹² cm ^-2 eV ^-1 , 2.51x10 ¹² cm ^-2 eV ^-1 to 4.0x10 ¹² cm ^-2 eV ^-1 , or 3.0x10 ¹² cm ^-2 eV ^-1 to 3.5x10 ¹² cm ^-2 eV ^-1 .

The oxide semiconductor has an on/off ratio of 1.0x10 ⁶ to 5.0x10 ⁶ . For example, the oxide semiconductor may have an on/off ratio of 1.5x10 ⁶ to 5.0x10 ⁶ , 2.0x10 ⁶ to 4.5x10 ⁶ , 2.5x10 ⁶ to 4.0x10 ⁶ , 3.0x10 ⁶ to 4.0x10 ⁶ , or 3.0x10 ⁶ to 3.5x10 ⁶ .

The oxide semiconductor may have an M-O bonding ratio of 45% to 70% when analyzed by XPS. For example, the oxide semiconductor may have an M-O bonding ratio of 50% to 70%, 50% to 65%, 55% to 65%, or 55% to 60%. Furthermore, the oxide semiconductor may have an oxygen vacancy (Vo) ratio of 15% to 50% when analyzed by XPS. For example, the oxide semiconductor may have an oxygen vacancy ratio of 15% to 45%, 20% to 40%, 25% to 40%, 25% to 35%, or 25% to 30%. In one specific example, the oxide semiconductor may have an M-O bonding ratio of 45% to 70% and an oxygen vacancy ratio of 15% to 50%.

The oxide semiconductor can have a root mean square (RMS) surface roughness of 0.1 nm to 0.5 nm. For example, the oxide semiconductor can have an RMS surface roughness of 0.15 nm to 0.50 nm, 0.20 nm to 0.45 nm, 0.25 nm to 0.40 nm, or 0.30 nm to 0.35 nm.

The above oxide semiconductor can have a contact resistance of 5000Ω to 200000Ω. For example, the oxide semiconductor can have a contact resistance of 5000Ω to 190000Ω, 10000Ω to 180000Ω, 20000Ω to 170000Ω, 30000Ω to 160000Ω, 40000Ω to 150000Ω, 50000Ω to 140000Ω, 60000Ω to 130000Ω, 70000Ω to 120000Ω, 80000Ω to 110000Ω, or 90000Ω to 100000Ω.

According to another embodiment of the present invention, a semiconductor device includes: a substrate; a dielectric layer formed on the substrate; a semiconductor layer including the oxide semiconductor formed on the dielectric layer; and an electrode formed on the semiconductor layer.

The above substrate is a base for forming a semiconductor element, and is not particularly limited in terms of material, but may include, for example, silicon, glass, plastic, metal foil, etc. The substrate may have a plate shape, or may be formed to have a specific pattern by depositing and patterning a metal material such as molybdenum (Mo) or aluminum (Al) on the substrate. Alternatively, the substrate may include a metal or metal oxide that is a conductive material to be used as a gate electrode, and specifically, may include at least one of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), and silver (Ag). The thickness of the above-mentioned substrate is not particularly limited, and may be, for example, 0.0001 mm or more, 0.0005 mm or more, 0.001 mm or more, 0.005 mm or more, 0.01 mm or more, 0.05 mm or more, 0.1 mm or more, 0.5 mm or more, or 1 mm or more, and may also be 10 mm or less, 5 mm or less, 3 mm or less, or 2 mm or less.

The dielectric layer is formed on a substrate and serves to insulate the substrate, the semiconductor layer, and the electrode. The dielectric layer may include an insulating material used in a general semiconductor process. For example, the dielectric layer may include at least one of a dielectric selected from the group consisting of silicon oxide (SiO ₂ ), hafnium oxide (HfO ₂ ), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), and silicon nitride (Si ₃ N ₄ ). The dielectric layer may be formed using a method such as vacuum deposition, chemical vapor deposition, physical vapor deposition, atomic layer deposition, metalorganic chemical vapor deposition, plasma enhanced chemical vapor deposition, molecular beam epitaxy, hydride vapor deposition, sputtering, spin coating, or dip coating. The thickness of the dielectric layer may be 10 nm or more, 20 nm or more, 30 nm or more, or 50 nm or more, and may also be 500 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less. As a specific example, the thickness of the dielectric layer may be 50 nm to 200 nm.

The semiconductor layer may be composed of the oxide semiconductor described above. The semiconductor layer may be formed by a solution process or a deposition process, but is not limited thereto. In particular, while a thin film transistor (TFT) using a conventional oxide semiconductor may be manufactured only by a solution process such as spin coating, the oxide semiconductor according to the present invention can be applied to other thin film processes such as sputtering, atomic layer deposition (ALD), and chemical vapor deposition (CVD), and therefore, it is useful as a material for memory semiconductors for artificial intelligence (AI) as well as displays in the future.

The thickness of the semiconductor layer can be 1 nm or more, 5 nm or more, 10 nm or more, 20 nm or more, or 30 nm or more, and can also be 500 nm or less, 300 nm or less, 200 nm or less, 100 nm or less, or 50 nm or less. For example, the thickness of the semiconductor layer can be 5 nm to 50 nm, 10 nm to 100 nm, 10 nm to 50 nm, 10 nm to 40 nm, 10 nm to 25 nm, 20 nm to 100 nm, 20 nm to 50 nm, 20 nm to 40 nm, 40 nm to 100 nm, or 20 nm to 40 nm. In one specific example, the thickness of the semiconductor layer can be 5 nm to 50 nm.

The above electrode may include a source electrode and a drain electrode, which are arranged to be spaced apart from each other and may be electrically connected to the semiconductor layer. The electrode may be formed of a metal material, and may include at least one selected from the group consisting of, for example, molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), copper (Cu), indium tin oxide (ITO), indium zinc oxide (IZO), and indium tin zinc oxide (ITZO), but is not limited thereto. The electrode may be obtained by depositing a conductive film on the semiconductor layer, forming a photoresist pattern thereon, and then patterning the conductive film using the photoresist pattern as a mask. The above-mentioned conductive film can be formed using a method such as vacuum deposition, chemical vapor deposition, physical vapor deposition, atomic layer deposition, organic metal chemical vapor deposition, plasma chemical vapor deposition, molecular beam epitaxy, hydride vapor deposition, sputtering, spin coating, or deep coating.

The thickness of the electrode may be 5 nm or more, 10 nm or more, 30 nm or more, or 50 nm or more, and may also be 500 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less. As an example, the thickness of the electrode may be 10 nm to 200 nm.

A thin film transistor according to another embodiment of the present invention includes the semiconductor element. Specifically, the semiconductor element of the present invention can be used as a field effect transistor (FET) applied to a display device, and more specifically, can be used as a thin film transistor (TFT).

The ratio (R _{C1 /R C0 ) of the contact resistance (R C0 ) of the IZO measured using TLM (Transmission Line Measurement) and the contact resistance (R C1 ) of the thin film transistor may be 5 or less. For example, the ratio (R C1 /R C0 ) of the contact} resistance (R _C0 ) of the IZO measured using TLM and the contact resistance (R _C1 ) of the thin film transistor may be 4.5 or less, 4 or less, 3.5 or less, 3 or less, 2.5 or less, or 2 or less.

A display device according to another embodiment of the present invention includes the thin film transistor. Specifically, the semiconductor element is used as a transistor used as a pixel driving element in a liquid crystal display (LCD) or an organic light emitting display (OLED) device.

The above contents are explained in more detail by the following examples. However, the following examples are only intended to illustrate the present invention, and the scope of the examples is not limited to these examples.

Manufacturing of oxide semiconductors

Example 1

A SiO ₂ substrate having a 100 nm SiO ₂ layer grown by wet oxidation on a P-type doped Si wafer was used. Here, the Si layer was used as a gate, and the SiO ₂ layer was used as a gate insulator. The substrate was washed successively in an ultrasonic cleaner with detergent, deionized water, isopropanol, and acetone for 10 min each, and then dried on a hot plate at 150 °C for 10 min. The SiO ₂ /Si wafer was irradiated with deep ultraviolet (DUV) rays of 185 nm and 265 nm for 10 min using an ultraviolet-ozone cleaner (AC-16, Ahtech), spin-coated with an IYZO solution, and annealed in an electric furnace in air at 550 °C for 60 min to deposit a 40 nm thin film. The IYZO solution was synthesized by dissolving indium chloride (Sigma Aldrich) and zinc acetate dihydrate (Sigma Aldrich) in 2-methoxyethanol (Sigma Aldrich) at 0.1 M each and adding ytterbium chloride dihydrate (Sigma Aldrich) at a doping concentration of 1 mol%. A pattern was formed on the IYZO thin film through a photolithography process, which served as the active layer of the device. A 100 nm thick ITO electrode was deposited on the patterned active layer through a lift-off process to manufacture an IYZO oxide semiconductor with a Yb doping concentration of 1 mol%.

Example 2

An IYZO oxide semiconductor was manufactured in the same manner as in Example 1, except that the doping concentration of Yb was set to 3 mol%.

Example 3

An IYZO oxide semiconductor was manufactured in the same manner as in Example 1, except that the doping concentration of Yb was set to 5 mol%.

Comparative Example 1

An IZO oxide semiconductor was manufactured in the same manner as in Example 1, except that ytterbium chloride dihydrate was not added.

Comparative Example 2

An IGZO oxide semiconductor was manufactured in the same manner as in Example 1, except that gallium nitrate (Sigma Aldrich) was used instead of ytterbium chloride dihydrate.

Comparative Example 3

An IGZO oxide semiconductor was manufactured using the same method as in Comparative Example 2, except that the doping concentration of Ga was set to 3 mol%.

Comparative Example 4

An IGZO oxide semiconductor was manufactured using the same method as in Comparative Example 2, except that the doping concentration of Ga was set to 5 mol%.

Experimental Example 1: Electrical Characteristics Evaluation (1)

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the electrical characteristics were evaluated by measuring the transfer characteristics in a darkroom using an HP 4145B semiconductor parameter analyzer (Hewlett-Packard).

Figure 1 shows the transfer characteristics of an IZO TFT and an IGZO TFT (Ga doping concentration: 1 mol%, 3 mol%, 5 mol%) (a), and the transfer characteristics of an IZO TFT and an IYZO TFT (Yb doping concentration: 1 mol%, 3 mol%, 5 mol%) (b).

As shown in Fig. 1, as the doping concentration of Ga increased from 1 mol% to 5 mol%, V _th shifted in the positive direction and the on current decreased (a), and as the doping concentration of Yb increased from 1 mol% to 5 mol%, V _th shifted in the positive direction and the on current increased at the doping concentration of 1 mol% and then decreased at the doping concentrations of 3 mol% and 5 mol% (b). However, in the case of the IGZO TFT (Ga doping concentration: 3 mol%), the on current greatly decreased by 35% compared to the IZO TFT, which deteriorated the electrical characteristics, whereas in the case of the IYZO TFT (Yb doping concentration: 3 mol%), the on current decreased more than that of the IYZO TFT (Yb doping concentration: 1 mol%), but the electrical characteristics were improved because it had a higher value than that of the IZO TFT.

Experimental Example 2: Electrical Characteristics Evaluation (2)

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, electrical characteristic parameters were extracted and evaluated through the transfer characteristics measured in a darkroom using an HP 4145B semiconductor parameter analyzer (Hewlett-Packard).

Table 1 shows the electrical characteristic parameters of IZO TFTs, IGZO TFTs (Ga doping concentration: 1 mol%, 3 mol%, 5 mol%), and IYZO TFTs (Yb doping concentration: 1 mol%, 3 mol%, 5 mol%).

As shown in Table 1, the subthreshold swing and interface trap density (Dit) of the IZO TFT were 1.08 V/decade and 3.83×10 ¹² cm ^-2 eV ^-1, respectively, while those of the IGZO TFT (Ga doping concentration: 3 mol%) were reduced to 0.63 V/decade and 2.15×10 ¹² cm ^-2 eV ^-1 , respectively. In the case of IYZO TFT (Yb doping concentration: 3 mol%), the switching characteristics were reduced to 0.51 V/decade and 1.69×10 ¹² cm ^-2 eV ^-1 , respectively. Switching characteristics were improved by reducing interface defects and traps through doping.

division Electron mobility
(cm ² /Vs) Threshold voltage (V _th )(V) SS
(V/decade) D _it
(x10 ¹² cm ^-2 eV ^-1 ) On/Off Rain (x10 ⁶ ) IZO 11.63 -7.4 1.08 3.83 2.92 IGZO 1mol% 11.58 -2.8 0.68 2.31 2.70 3mol% 10.13 -0.4 0.63 2.14 2.22 5mol% 9.49 1 1.07 3.77 1.90 IYZO 1mol% 12.43 -2.8 0.65 2.20 3.06 3mol% 11.86 0 0.51 1.69 3.00 5mol% 10.88 1.6 0.58 1.94 2.32

Experimental Example 3: Electrical Characteristics Evaluation (3)

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the characteristics of carrier concentration, Hall mobility, and resistivity were evaluated using a Hall measurement system (HMS-5000, Ecopia) at room temperature.

Figure 2 shows the Hall measurement characteristics of an IZO TFT and an IGZO TFT (Ga doping concentration: 1 mol%, 3 mol%, 5 mol%) (a), and the Hall measurement characteristics of an IZO TFT and an IYZO TFT (Yb doping concentration: 1 mol%, 3 mol%, 5 mol%) (b).

As shown in Fig. 2, the hall mobility and carrier concentration were 1.88 cm ² /Vs and 1.59 × 10 ¹⁶ cm ^-3 in IZO, while those in IGZO (Ga doping concentration: 3 mol%) were 1.21 cm ² /Vs and 1.29 × 10 ¹⁶ cm ^-3 (a), and those in IYZO (Yb doping concentration: 3 mol%) were 1.45 cm ² /Vs and 1.24 × 10 ¹⁶ cm ^-3 (b). Although the electrical properties tend to decrease somewhat with doping, the degree of deterioration in the electrical properties of Yb was less than that of Ga.

Experimental Example 4: Bias Stability Evaluation

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the bias stability was evaluated by measuring the change in transfer characteristics according to the gate bias stress using an HP 4145B semiconductor parameter analyzer (Hewlett-Packard).

Figure 3 shows the stability evaluation of an IZO TFT (a), an IGZO TFT (Ga doping concentration: 3 mol%) (b), and an IYZO TFT (Yb doping concentration: 3 mol%) (c) under PBS conditions, and the stability evaluation of an IZO TFT (d), an IGZO TFT (Ga doping concentration: 3 mol%) (e), and an IYZO TFT (Yb doping concentration: 3 mol%) (f) under NBS conditions.

As shown in Fig. 3, IZO had low stability under the conditions of PBS and NBS, and when doped with Ga and Yb, the stability was improved compared to IZO. In addition, the stability was even better when doped with Yb than with Ga.

Experimental Example 5: Evaluation of thermal bias stability

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the thermal bias stability was evaluated by measuring the change in transfer characteristics according to the gate bias and temperature stress using an HP 4145B semiconductor parameter analyzer (Hewlett-Packard).

Figure 4 shows the stability evaluation of IZO TFT (g), IGZO TFT (Ga doping concentration: 3 mol%) (h), and IYZO TFT (Yb doping concentration: 3 mol%) (i) under PBTS conditions, and the stability evaluation of IZO TFT (j), IGZO TFT (Ga doping concentration: 3 mol%) (k), and IYZO TFT (Yb doping concentration: 3 mol%) (l) under NBTS conditions.

As shown in Fig. 4, IZO had low stability under the conditions of PBTS and NBTS, and when doped with Ga and Yb, the stability was improved compared to IZO. In particular, when doped with Yb, the thermal stability was better than that of Ga.

Experimental Example 6: Evaluation of Optical Bias Stability

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the optical bias stability was evaluated by measuring the change in transfer characteristics according to the gate bias and optical stress using an HP 4145B semiconductor parameter analyzer (Hewlett-Packard).

Figure 5 shows the stability evaluation of IZO TFT (m), IGZO TFT (Ga doping concentration: 3 mol%) (n), and IYZO TFT (Yb doping concentration: 3 mol%) (o) under PBIS conditions, and the stability evaluation of IZO TFT (p), IGZO TFT (Ga doping concentration: 3 mol%) (q), and IYZO TFT (Yb doping concentration: 3 mol%) (r) under NBIS conditions.

As shown in Fig. 5, IZO had very low stability under the conditions of PBIS and NBIS, and when doped with Ga and Yb, the stability was improved compared to IZO. In particular, when doped with Yb, the optical stability was more excellent than when doped with Ga. Specifically, it can be seen that Yb effectively reduced oxygen vacancies (Vo), which cause low stability of amorphous oxide semiconductors, as a dopant of IZO TFTs.

Experimental Example 7: Evaluation of Light Response Characteristics

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the thermal bias stability was evaluated by comparing the changes in the transfer characteristics measured in a dark room and a bright room, respectively, using an HP 4145B semiconductor parameter analyzer (Hewlett-Packard).

Figure 6 shows the evaluation of the optical response characteristics of an IZO TFT (a), an IGZO TFT (doping concentration of Ga: 1 mol%) (b), an IGZO TFT (doping concentration of Ga: 3 mol%) (c), an IGZO TFT (doping concentration of Ga: 5 mol%) (d), an IYZO TFT (doping concentration of Yb: 1 mol%) (e), an IYZO TFT (doping concentration of Yb: 3 mol%) (f), and an IYZO TFT (doping concentration of Yb: 5 mol%) (g).

As shown in Fig. 6, IZO showed a negative V _th shift of -2.6 V when measured under 1000 lux, while IGZO and IYZO showed improved light response characteristics as the doping concentration increased. In particular, when the doping concentration of IYZO was 5 mol%, it was significantly improved to -0.4 V. This is because Yb effectively suppressed Vo when doped compared to Ga.

Experimental Example 8: Changes in chemical bonding properties (XPS)

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the chemical bonding characteristics were evaluated by measuring the kinetic energy due to photoelectron emission within the thin film using an X-ray photoelectron spectroscopy (XPS, NEXSA XPS, Thermo Fisher Scientific) using an Al Ka (1486.68 eV) X-ray source.

Figure 7 shows O1s spectra of IZO (a), IGZO (doping concentration of Ga: 1 mol%) (b), IYZO (doping concentration of Yb: 1 mol%) (c), IYZO (doping concentration of Yb: 3 mol%) (d), and IYZO (doping concentration of Yb: 5 mol%) (e) films.

As shown in Fig. 7, Vo tends to decrease as Ga and Yb are doped. A decrease in Vo reduces the carrier concentration, which may decrease the mobility. Specifically, doping causes an increase in O _Ⅰ (MO) and O _Ⅲ (impurities) peaks, and in particular, the ratio of the O _Ⅲ peak was higher in the case of IGZO (Ga doping concentration: 3 mol%) than in IYZO (Yb doping concentration: 3 mol%). An increase in the O _Ⅲ peak causes scattering, which induces a decrease in mobility and stability. In addition, the ratio of the O _Ⅰ peak was higher and the ratio of the O _Ⅱ peak was lower in the case of IYZO (Yb doping concentration: 3 mol%) than in IGZO (Ga doping concentration: 3 mol%). This shows that IYZO effectively suppresses Vo by promoting MO bonding compared to IGZO, thereby contributing to the improvement of stability.

Experimental Example 9: Comparison of Band Edge States

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the absorption coefficient was measured using UV-visible spectroscopy (V-670, Jasco) to compare the band edge states.

Figure 8 shows the optical band gaps of IZO and IGZO (doping concentration of Ga: 1 mol%, 3 mol%, 5 mol%) (a), the band edge state of the IZO film (b), the band edge state of the IGZO (doping concentration of Ga: 1 mol%) film (c), the band edge state of the IGZO (doping concentration of Ga: 3 mol%) film (d), the band edge state of the IGZO (doping concentration of Ga: 5 mol%) film (e), the optical band gaps of IZO and IYZO (doping concentration of Yb: 1 mol%, 3 mol%, 5 mol%) (f), the band edge state of the IYZO (doping concentration of Yb: 1 mol%) film (g), the band edge state of the IYZO (doping concentration of Yb: 3 mol%) film (h), and the optical band gaps of the IZO and IYZO (doping concentration of Yb: 5 mol%) shows the band edge state (i) of the film.

As shown in Fig. 8, both IGZO and IYZO showed an increase in the optical band gap depending on the doping. Specifically, in IGZO, the area of the deep band edge state increased as the doping concentration increased, and the area of the shallow band edge state decreased. On the other hand, in IYZO, the area of the shallow band edge state increased when the doping concentration was 1 mol%, and then gradually decreased when the doping concentration was 3 mol%. Since the area of the shallow band edge state is proportional to the carrier concentration by Vo, and the area of the deep band edge state is proportional to the scattering, it can be seen that the stability is further improved in the case of IYZO.

Experimental Example 10: Contact Resistance Comparison

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the output characteristics were measured using the TLM (transmission line method) using an HP 4145B semiconductor parameter analyzer (Hewlett-Packard), and the contact resistance was compared.

Figure 9 shows the contact resistance of an IZO TFT (a), the contact resistance of an IGZO (Ga doping concentration: 3 mol%) (b), and the contact resistance of an IYZO (Yb doping concentration: 3 mol%) (c) measured using TLM (Transmission Line Measurement).

As shown in Fig. 9, the contact resistance increased when Ga and Yb were doped compared to IZO. Specifically, the contact resistance of IGZO (Ga doping concentration: 3 mol%) increased by about 7 times compared to IZO, while that of IYZO (Ya doping concentration: 3 mol%) increased by about 1.75 times. Therefore, it can be seen that IYZO (Ya doping concentration: 3 mol%) has a much lower contact resistance than IGZO (Ga doping concentration: 3 mol%), and thus very effectively suppresses the deterioration of electrical properties.

Experimental Example 11: Comparison of Crystallinity and Surface Morphology of Thin Films

For the oxide semiconductors of Examples 1 to 3 and Comparative Examples 1 to 4, the crystallinity and surface morphology of the thin films were measured and compared using GI-XRD (D8 Advance A25 Plus, Bruker) and atomic force microscopy (AFM, XE-100, Park Systems).

Figure 10 shows scanning probe microscope (AFM) images and their RMS roughnesses of IZO TFT (a), IGZO (doping concentration of Ga: 1 mol%) (b), IGZO (doping concentration of Ga: 3 mol%) (c), IGZO (doping concentration of Ga: 5 mol%) (d), IYZO (doping concentration of Yb: 1 mol%) (e), IYZO (doping concentration of Yb: 3 mol%) (f), and IYZO (doping concentration of Yb: 5 mol%) (g), and X-ray diffraction (XRD) patterns of IZO, IGZO (doping concentration of Ga: 3 mol%), IYZO (doping concentration of Yb: 1 mol%), IYZO (doping concentration of Yb: 3 mol%), and IYZO (doping concentration of Yb: 5 mol%). This shows the pattern (h).

As shown in Fig. 10, IGZO and IYZO were amorphous like IZO, and compared to IZO, when doped with Ga and Yb, more specifically, the RMS value tended to decrease as the doping concentration of Ga and Yb increased. In particular, the RMS value of IYZO with a doping concentration of 3 mol% decreased significantly compared to that of IGZO with a doping concentration of 3 mol%.

Example 4

An IYZO oxide semiconductor was manufactured in the same manner as in Example 1, except that the doping concentration of Yb was set to 7 mol%.

Example 5

An IYZO oxide semiconductor was manufactured in the same manner as in Example 1, except that the doping concentration of Yb was set to 9 mol%.

Comparative Example 5

An IGZO oxide semiconductor was manufactured using the same method as in Comparative Example 2, except that the doping concentration of Ga was set to 7 mol%.

Comparative Example 6

An IGZO oxide semiconductor was manufactured using the same method as in Comparative Example 2, except that the doping concentration of Ga was set to 9 mol%.

Experimental Example 10: Electrical Characteristics Evaluation (2)

For the oxide semiconductors of Examples 4 and 5 and Comparative Examples 5 and 6, the electrical characteristics were evaluated by measuring the transfer characteristics and output characteristics in a darkroom using an HP 4145B semiconductor parameter analyzer (Hewlett-Packard).

Figure 11 shows the results of evaluating the electrical characteristics of IYZO (doping concentration of Yb: 7 mol%) (a), IYZO (doping concentration of Yb: 9 mol%) (b), IGZO (doping concentration of Ga: 7 mol%) (c), and IGZO (doping concentration of Ga: 9 mol%) (d).

As shown in Fig. 11, as the doping concentration of Ga and Yb increases, V _th shifts in the positive direction, electron mobility decreases, and subthreshold swing increases. However, in the case of IYZO doped with Yb, it can be seen that it is superior to IGZO in terms of mobility and subthreshold swing.

Examples 6 to 10

An oxide semiconductor was manufactured in the same manner as in Example 1, except that the molar ratio of In:Zn:Yb was changed as described in Fig. 12 and the active layer was applied to the entire surface.

Examples 11 to 15

An oxide semiconductor was manufactured in the same manner as in Example 1, except that the molar ratio of In:Zn:Yb was changed as described in Fig. 13 and the active layer was applied to the entire surface.

Experimental Example 11: Electrical Characteristics Evaluation (3)

For the oxide semiconductors of Examples 6 to 15, the electrical characteristics were evaluated by measuring the transfer characteristics and output characteristics in a darkroom using an HP 4145B semiconductor parameter analyzer (Hewlett-Packard).

Figures 12 and 13 show the transfer characteristics and output characteristics according to various compositions of IYZO and the mobility at a drain voltage of 20.1 V.

As shown in Fig. 12, it can be seen that the off current is high and the mobility is high as the ratio of In and Zn is high. It can be seen that the off current decreases and the mobility decreases as the doping concentration of In decreases and the doping concentration of Yb increases. In addition, as shown in Fig. 13, it can be seen that the off current decreases and the mobility decreases as the doping concentration of In decreases and the doping concentration of Yb increases while fixing the doping concentration of Zn to 1.5 mol%.

Claims (19)

Ytterbium (Yb) is doped,
Contains an oxide composed of indium (In) and zinc (Zn),
An oxide semiconductor in which the atomic ratios of In, Yb and Zn satisfy the following formulas A1 to A3:
[Formula A1] 0.2 ≤ In/(In + Zn) ≤ 0.99
[Formula A2] 0.29 ≤ In/(In + Yb) ≤ 0.99
[Formula A3] 0.1 ≤ Zn/(Yb + Zn) ≤ 0.99
In paragraph 1,
An oxide semiconductor having a doping concentration of Yb of 1 mol% to 10 mol%.
In paragraph 1,
An oxide semiconductor having a molar ratio of indium (In) and ytterbium (Yb) of 1:0.001 to 0.8.
delete In paragraph 1,
An oxide semiconductor having a hall mobility of 1.3 cm ² /Vs or more, a carrier concentration of 1.2 × 10 ¹⁶ cm ^-3 or more, and a threshold voltage (ΔV _th ) of -6 V to 3 V.
In paragraph 5,
The above threshold voltage change amount (ΔV _th ) is
-3 V to 2.8 V under positive bias stress (PBS) and negative bias stress (NBS) conditions,
-5 V to 4 V under positive bias temperature stress (PBTS) and negative bias temperature stress (NBTS) conditions,
An oxide semiconductor having a voltage range of -6 V to 1.5 V under positive bias illumination stress (PBIS) and negative bias illumination stress (NBIS).
In paragraph 1,
An oxide semiconductor having an electron mobility of 1 cm ² /Vs to 40 cm ² /Vs.
In paragraph 1,
An oxide semiconductor having a threshold voltage (V _th ) of -40 V to 40 V.
In paragraph 1,
An oxide semiconductor having a subthreshold swing (SS) of 0.06 V/decade to 2 V/decade.
In paragraph 1,
An oxide semiconductor having an interface trap density (D _it ) of 1x10 ¹² cm ^-2 eV ^-1 to 5x10 ¹² cm ^-2 eV ^-1 .
In paragraph 1,
An oxide semiconductor having an on/off ratio of 1.0x10 ⁶ to 5.0x10 ⁶ .
In paragraph 1,
An oxide semiconductor having a MO bonding ratio of 45% to 70% and an oxygen vacancy ratio of 15% to 50% when analyzed by XPS.
In paragraph 1,
An oxide semiconductor having an RMS (root mean square) surface roughness of 0.1 nm to 0.5 nm.
In paragraph 1,
An oxide semiconductor having a contact resistance of 5000Ω to 200000Ω.
write;
A dielectric layer formed on the above substrate;
A semiconductor layer including the oxide semiconductor of claim 1 formed on the dielectric layer, and
A semiconductor device comprising an electrode formed on the semiconductor layer.
In Article 15,
A semiconductor device, wherein the thickness of the semiconductor layer is 5 nm to 50 nm.
A thin film transistor comprising a semiconductor device according to claim 15.
In Article 17,
A thin film transistor, wherein the ratio (R _c1 /R _c0 ) of the contact resistance (R _c0 ) of the IZO and the contact resistance (R _c1 ) of the thin film transistor measured using TLM (Transmission Line Measurement) is 5 or less.
A display device comprising a thin film transistor according to claim 17.