KR101040138B1 - Method for forming zinc oxide based thin films doped with silver and group II elements and thin films formed using the same - Google Patents

Abstract

The thin film forming method comprises: forming a thin film comprising zinc oxide doped with silver and a group III element on a substrate; And heating the thin film in a gas atmosphere to reduce oxygen vacancy in the thin film. The forming of the thin film may include providing a target material and a substrate including zinc oxide doped with silver and a group III element; Irradiating and vaporizing the target material with a laser; And depositing the vaporized target material in a thin film on the substrate. The thin film forming method may improve the p-type conductivity by reducing the oxygen vacancy in the thin film by heat-treating the thin film doped with silver and group III elements.

p-type, zinc oxide, thin film, silver, aluminum, mutual doping

Description

Method for forming ZnO based thin film co-doped with silver and group III element and thin film formed using the same}

Embodiments relate to a method for forming a zinc oxide based thin film co-doped with silver and a group III element, and a thin film formed using the same.

Zinc oxide (ZnO) is a II-VI compound semiconductor having a hexagonal structure. In addition to having a bandgap of 3.37 electron volts (eV) at room temperature, zinc oxide has an exciton binding energy of 60 mV, which is relatively greater than 24 mV of thermal energy at room temperature, resulting in ultraviolet radiation by excitons. The light emission of the region is easy.

In the case of zinc oxide, high quality single crystal growth is easier than gallium nitride (GaN), and electrical conductivity can be controlled. In addition, it is suitable for the implementation of the blue and ultraviolet region light emitting devices due to the excellent optical properties showing high light emission characteristics by excitons even with low excitation energy. Zinc oxide has also been widely used in various fields such as high temperature and / or high voltage electric and electronic devices, surface acoustic wave devices, piezoelectric devices, sensing devices, or transparent conductive films.

Due to the various applications of zinc oxide, extensive research on zinc oxide is under way. Among them, researches related to the production of zinc oxide having p-type conducting properties have been actively conducted. However, zinc oxide is a compound that exhibits intrinsic n-type conductivity due to natural oxygen vacancies or invasive zinc defects in its manufacture. Due to such self-compensation of impurity defects, it is difficult for zinc oxide to realize p-type conduction characteristics through doping of p-type dopants.

According to an aspect of the present invention, a method of forming a p-type zinc oxide based thin film co-doped with silver and a group III element, and compensated for n-type conduction by oxygen vacancies, and formed using the same It can provide a thin film that can be.

According to one or more exemplary embodiments, a method of forming a thin film includes: forming a thin film including zinc oxide doped with silver and a group III element on a substrate; And heating the thin film in a gas atmosphere to reduce oxygen vacancy in the thin film.

The heating of the thin film may include heating the thin film in any one or two or more atmospheres thereof selected from the group consisting of oxygen and an inert gas.

The heating of the thin film may include heating the thin film to a temperature of 50 ° C to 1500 ° C.

The heating of the thin film may include heating the thin film for 1 second to 600 minutes.

The forming of the thin film may include providing a target material and a substrate including zinc oxide doped with silver and a group III element; Irradiating and vaporizing the target material with a laser; And depositing the vaporized target material in a thin film on the substrate.

In addition, the forming of the thin film may further include heating the substrate and the target material to a temperature of 10 ° C to 1200 ° C.

The thin film according to the exemplary embodiment may be formed of zinc oxide, which is doped with each other by silver and group III elements, and has reduced oxygen vacancies by heat treatment in a gas atmosphere.

The Group III element may include any one selected from the group consisting of boron element, aluminum element, gallium element, indium element and thallium element or two or more thereof.

According to an aspect of the present invention, it is possible to form a thin film including zinc oxide in which silver (Ag) and group III elements are co-doped with each other. In addition, by heat-treating the thin film, oxygen vacancies in the thin film can be reduced to improve the p-type conductivity of the thin film.

The thin film forming method can implement an excellent film quality and is easy to process. The p-type zinc oxide thin film thus formed can be applied to various devices such as transparent oxide thin film transistors, energy devices such as solar cells, light emitting devices such as LEDs, sensing devices such as chemical sensors and biosensors, and transparent conductive electrodes. .

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

1 is a flowchart of a thin film forming method according to an embodiment.

Referring to FIG. 1, first, a thin film including zinc oxide (ZnO) co-doped with silver (Ag) and a group III element may be formed on a substrate (S1). The Group III element may be, for example, an aluminum (Al), boron (B), gallium (Ga), indium (In) or thallium (Tl) elements, and may include a combination of two or more thereof.

A zinc oxide (ZnO) based thin film doped with silver (Ag) and a group III element may be formed by various methods. For example, chemistry such as physical vapor deposition, thermal chemical vapor deposition, or metal organic chemical vapor deposition, such as sputtering or pulsed laser deposition. The thin film by vapor deposition, solution-based synthesis using a source selected from the group consisting of a water-soluble reaction raw material containing silver (Ag) and a water-soluble reaction raw material containing a Group III element, or other suitable process Can be formed.

Silver (Ag) doped with zinc oxide (ZnO) can act as a source for diffusion of the p-type semiconductor while substituting zinc (Zn). In this case, the group III elements doped with silver (Ag) may facilitate the doping of other dopants by causing a structural change in the lattice structure of zinc oxide (ZnO) as a parent material. That is, the group III element lowers the activation energy of the thin film, thereby making it easier to substitute zinc (Zn) by silver (Ag).

Next, a thin film including zinc oxide (ZnO) doped with silver (Ag) and a group III element may be heat-treated in a gas atmosphere (S2). For example, the thin film may be heat-treated by heating the thin film in an atmosphere containing at least one of oxygen and an inert gas. As the inert gas, for example, helium (He), argon (Ar) and the like can be used. When the heat treatment is performed in an oxygen atmosphere, it is possible to induce a decrease in oxygen vacancies due to an increase in oxygen partial pressure.

In one embodiment, the thin film may be heated to a temperature of about 50 ° C to about 1500 ° C to perform heat treatment. In addition, during the heat treatment, the thin film may be heated by heating for about 1 second to about 600 minutes. Furthermore, the thin film may be heated for about 10 seconds to about 300 minutes.

The heat treatment process described above serves to diffuse the dopants existing in the doped lattice of zinc oxide (ZnO) into the substituted lattice. As a result, the oxygen vacancy present in the zinc oxide can be reduced. Since oxygen vacancies are n-type charge carriers, reducing oxygen vacancies may reduce self-compensation due to oxygen vacancies, thereby improving p-type conduction characteristics of doped zinc oxide (ZnO).

2 is a schematic diagram of an exemplary apparatus for performing a thin film forming method according to one embodiment, and FIG. 3 is a flowchart of a thin film forming method that may be performed using the apparatus of FIG. 2.

2 and 3, first, the substrate 20 and the target material 30 may be provided (S11). The substrate 20 and the target material 30 may be located adjacent to each other in the chamber 10. As a non-limiting example, the separation distance between the substrate 20 and the target material 30 may be about several cm. The chamber 10 may include supports 120 and 130 for supporting each of the substrate 20 and the target material 30. Each support 120, 130 may be made of a material that is relatively stable even at high temperatures, such as molybdenum (Mo) or other suitable material.

The substrate 20 may be formed of c-sapphire or other suitable material as a part where a thin film will be formed later. Meanwhile, the target material 30 may be made of zinc oxide (ZnO) doped with silver (Ag) and a group III element. As group III elements mutually doped with silver (Ag), aluminum (Al), boron (B), gallium (Ga), indium (In), or thallium (Tl) elements may be used, and two or more of them may be used together. Can also be used.

The target material 30 may be in various forms such as powder or lumps. Since the method for forming the target material 30 doped with one or more dopants is well known to those skilled in the art through a pulse laser deposition method, a detailed description thereof will be omitted.

The amount of dopants doped in the target material 30 may be appropriately adjusted according to the semiconductor characteristics to be realized in the final thin film. For example, in one embodiment, the target material 30 may be comprised of zinc oxide (ZnO) doped with silver (Ag) and aluminum (Al) in an amount of about 1 wt% (wt%) to about 5 wt%. have.

Chamber 10 may be a sphere, cylinder, or other suitable shape. The pressure in the chamber 10 may be appropriately adjusted, and the chamber 10 may be in a vacuum state. The chamber 10 may include an outlet 100 for discharging the gas in the chamber 10 to the outside using a pump or the like, and an inlet 110 for injecting the gas into the chamber 10. The pressure in the chamber 10 may be adjusted while introducing gas into the chamber 10 through the injection port 110.

For example, in one embodiment, a thin film may be formed on the substrate 20 under the condition that the pressure in the chamber 10 is about 350 mTorr while injecting about 80 sccm of oxygen into the chamber 10.

Next, the target material 30 and the substrate 20 may be heated (S12). The target material 30 and the substrate 20 may be heated to a temperature of about 10 ° C to about 1200 ° C. For example, by using the heater 40 positioned in contact with the outside of the chamber 40 so that the chamber 10 has a hot wall, the target material 30 and the substrate 20 are heated to form a thin film. A suitable environment can be created. However, this is merely illustrative, and in other embodiments, the processes described below at room temperature may be performed without the above-described heating process.

Next, the target material 30 may be vaporized by irradiating a laser on the target material 30 (S13). When the laser is irradiated onto the target material 30, thermal and / or non-thermal decomposition of the target material 30 may occur due to the interaction of the laser and the target material 30. In this case, the chamber 10 may include a transmission window 140 for partially passing the laser, and the laser generator 50 may irradiate the laser to the target material 30 through the transmission window 140. . For example, the transmission window 140 may be made of glass.

The laser generator 50 may be a fluoride krypton (KrF) laser having a wavelength of about 248 nm, an argon fluoride (ArF) laser having a wavelength of about 193 nm, or a xenon chloride (XeCl) laser having a wavelength of about 308 nm. It may include an excimer laser generator. The laser generator 50 may also include neodymium-yttrium, aluminum, garnet lasers (Nd: YAG lasers) or other suitable laser generators having a wavelength of about 355 nm. have.

The laser generator 50 may irradiate a pulsed laser. In this case, the frequency of the pulse laser may be about 1 to about 20 Hz. In addition, the lens 500 is positioned between the laser generator 50 and the chamber 10 to focus the laser beam such that the energy transmitted to the unit area of the target material 30 is several J / cm ² per pulse. It may be. For example, an excimer laser having an energy density of about 1.5 J / cm ² may be irradiated to the target material 30 for about 10 minutes.

In one embodiment, the laser may be irradiated while rotating the target material 30. For example, the support 130 may be connected to the motor 300 or the like to rotate at revolutions per minute of 0 to about 20 rpm. As the support 130 rotates, the position where the laser is irradiated onto the target material 30 is moved, thereby preventing the laser from being continuously irradiated to the same area, and as a result, the respective areas of the target material 30 are relatively Can be consumed uniformly. In addition, partial thermal oxidation of the target material 30 or formation of a temperature difference can be prevented, so that abnormal deposition such as lumps can be prevented from occurring on the substrate 20.

Meanwhile, in another embodiment, the target material 30 may be irradiated with the laser while rotating the substrate 20 instead of the target material 30 or rotating both the target material 30 and the substrate 20.

Next, the target material 30 vaporized by the laser may be deposited as the thin film 200 on the substrate 20 positioned adjacent to the laser beam (S14). Therefore, the thin film 200 formed on the substrate 20 has the same composition as the target material 30. When the thin film 200 is formed by using the target material 30 made of silver (Ag) and group III elements mutually doped with zinc oxide (ZnO), the thin film may be formed of silver (Ag) and the like. Group III elements are composed of zinc oxide (ZnO) doped with each other, and thus have p-type semiconductor properties.

Next, in order to reduce oxygen vacancies in the thin film 200, the thin film 200 may be heat treated in a gas atmosphere (S15). For example, the thin film 200 may be heated while injecting one or more of oxygen and an inert gas into the chamber 10. In one embodiment, the thin film may be heated to a temperature of about 50 ° C to about 1500 ° C. In addition, the thin film may be heated for about 1 second to about 600 minutes. Furthermore, the thin film may be heated for about 10 seconds to about 300 minutes.

According to the above-described embodiment, the thin film 200 may be formed on the substrate 20 by using the chamber 10 having the warm wall and the laser generator 50 by physical vapor deposition. The target material 30 is made of a material doped with silver (Ag) and a group III element, and the thin film 200 has the same composition as the target material 30, and as a result, the silver (Ag) and group III elements are The mutually doped thin film 200 may be formed. In addition, by reducing the oxygen vacancy in the thin film 200 by heat treatment after forming the thin film 200, it is possible to improve the p-type conduction characteristics of the thin film 200.

Table 1 below shows the hole measurement results of the zinc oxide (ZnO) based thin film formed by doping silver (Ag) and aluminum (Al) according to the thin film forming method according to the embodiments. As shown, it can be seen that the p-type conduction properties appear in all the thin films formed according to the embodiments.

Zinc Oxide Target Material Silver / Aluminum Content (wt%) Thin film formation temperature (℃) Hall concentration Hall mobility
(cm ² V ^-1 s ^-1 ) Resistance (Ωcm) One 300 1.19 × 10 ¹⁸ 0.46 11.26 One 400 2.55 × 10 ¹⁸ 0.67 3.67 3 300 5.11 × 10 ¹⁸ 0.4 3.08 3 400 8.31 × 10 ¹⁷ 1.66 4.5 5 300 7.8 × 10 ²⁰ 0.0021 3.87 5 400 8.98 × 10 ¹⁸ 0.14 4.87

Although the present invention described above has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and variations may be made therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a flowchart of a thin film forming method according to an embodiment.

2 is a schematic diagram of an exemplary apparatus for performing a thin film forming method according to one embodiment.

3 is a flow chart of a thin film forming method according to one embodiment that may be performed using the apparatus of FIG. 2.

Claims (8)

Forming a thin film comprising zinc oxide doped with silver and a group III element on the substrate; And Reducing the oxygen vacancies in the thin film by heating the thin film in a gaseous atmosphere containing oxygen. The method of claim 1, The gas atmosphere is a thin film forming method further comprises an inert gas. The method of claim 1, Reducing the oxygen vacancies in the thin film comprises heating the thin film to a temperature of 50 ° C to 1500 ° C. The method of claim 1, Reducing the oxygen vacancies in the thin film, the thin film forming method comprising the step of heating the thin film for 1 second to 600 minutes. The method of claim 1, Forming the thin film, Providing a target material and a substrate comprising zinc oxide doped with silver and a Group III element; Irradiating and vaporizing the target material with a laser; And Depositing the vaporized target material on the substrate as a thin film. The method of claim 5, Forming the thin film, And heating the substrate and the target material to a temperature of 10 ° C to 1200 ° C. delete delete

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