KR20140120663A - Preparation method of ZnO:Al thin film - Google Patents

Abstract

The present invention relates to a method for manufacturing an aluminum-doped zinc oxide (ZnO:Al) thin film in which aluminum is doped and, more specifically, to a method for manufacturing an aluminum-doped zinc oxide thin film with high conductivity and mobility and high thermoelectric effect by processing an aluminum-doped zinc oxide thin film with low conductivity and mobility and low thermoelectric effect through various heat treatment methods. The aluminum-doped zinc oxide thin film manufactured according to the present invention can improve the structural, electrical, and thermal characteristics of the thin film to be efficiently used as a transparent conducting semiconductor thin film instead of a relatively expensive ITO thin film in a solar cell and a thermoelectric element.

Description

Preparation method of ZnO: Al thin film [

The present invention relates to a method of manufacturing an aluminum-doped aluminum oxide (ZnO: Al) thin film, and more particularly to a method of manufacturing an aluminum- The present invention relates to a method for producing an aluminum zinc thin film having high electrical conductivity, mobility and high thermoelectric effect characteristics through various heat treatment methods.

The transparent conductive film is an essential material that ensures conductivity and transparency by coating on a panel used for a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting device, and a solar cell. The method of forming the transparent conductive film is usually carried out by means of a physical vapor deposition method such as a vacuum deposition method or a sputtering method. In particular, as a method capable of mass production of a uniform thin film having a large area, most of them are formed by DC magnetron sputtering because of operability and stability of the film.

In recent years, a flat panel display (FPD) market has been rapidly expanding mainly in liquid crystal displays (LCDs) and plasma display panels (PDPs), and a transparent conductive film having conductivity and being transparent to visible light has been essentially adopted.

Transparent conductive film materials, which are mainly used today, have been widely applied to most applications due to their excellent electrical and optical properties as indium tin oxide (ITO). However, due to the scarcity of indium, (ZnO) thin films doped with Group 3 elements (Al, Ga, In) as impurities have attracted attention as alternative materials because they have the disadvantage that they are degraded. In order to grow the zinc oxide thin film, a fabrication technique such as molecular beam epitaxy, pulse laser deposition, and radio frequency sputtering is used. In particular, the radiofrequency magnetron sputtering The cost is economical, the physical properties of the thin film are easily manipulated, and the deposition is easy in a large area. However, when grown in a low-temperature environment, it is not easy to obtain an oxide thin film having high-quality single crystal characteristics. In addition, when grown at a high temperature, it is grown in an oxygen atmosphere, which is a disadvantage of growing into a polycrystalline thin film.

Conventional methods to overcome this disadvantage are, for example, changing the factors such as working pressure, the amount of aluminum dopant, the substrate temperature, the ratio of argon / oxygen, Research has been intensively conducted. In the case of the heat treatment process, changes in grain size, crystal structure and optical transmittance have been reported.

However, despite these efforts, the study on the heat treatment process of aluminum-doped zinc oxide thin films has not been studied until now, and most of the heat treatment fields being studied are focused on structural changes of polycrystalline materials. On the other hand, a thermoelectric device is a future-oriented field capable of producing clean energy as well as generating electricity using solar energy. According to recent researches, when aluminum-doped zinc oxide is manufactured into nano-form, bulk form, as described in Journal of Materials Chemistry 22 (2012) 14633, Nano letters 11 (2011), 4337). However, no study has been made on the thermoelectric effect of the aluminum oxide thin film, which is a transparent conductive thin film, through the heat treatment process.

Korean Patent Laid-Open No. 10-2012-011040

Accordingly, it is an object of the present invention to provide an aluminum oxide thin film having excellent properties in structural, electrical and thermal properties by improving the characteristics of aluminum oxide (ZnO: Al) thin film grown by a radio wave sputtering method at a low temperature.

In order to achieve the above object,

Low-temperature deposition of a zinc oxide thin film on a substrate using a sputtering method (step 1);

Heat treating the aluminum zinc oxide thin film deposited in Step 1 under vacuum at 250 to 350 ° C for 30 minutes to 1 hour and 30 minutes (Step 2); And

(3) heat-treating the aluminum zinc oxide thin film heat-treated in step 2 under a high purity nitrogen or hydrogen atmosphere at 200-500 ° C for 30 minutes to 1 hour 30 minutes under vacuum, Of the present invention.

According to the present invention, single crystal growth can be promoted through a heat treatment process to obtain a thin film of aluminum oxide thin film semiconductor which is excellent in structural, electrical and thermal properties. The present invention provides a high quality oxide semiconductor thin film which is superior in structural, optical, electrical and thermal characteristics and provides a high quality aluminum oxide thin film which is a transparent conductive semiconductor thin film which can replace the ITO thin film with a relatively high price, The commercialization of the zinc oxide semiconductor can be accelerated. Further, the present invention can improve the characteristics of a solar cell and a thermoelectric device by implementing an aluminum oxide thin film having excellent optical, electrical and thermal characteristics due to a heat treatment process. Furthermore, it is possible to reduce the defects present in aluminum oxide using high purity hydrogen or nitrogen gas, thereby increasing the efficiency of the device.

1 is a schematic view of a zinc oxide thin film structure formed by the method of an embodiment of the present invention.
FIG. 2 is a photoluminescence spectrum of an aluminum oxide thin film according to an embodiment of the present invention, according to a heat treatment condition. FIG.
FIG. 3 is an X-ray spectral distribution chart of the aluminum oxide thin film according to an embodiment of the present invention, according to heat treatment conditions. FIG.
4 is a distribution diagram of electrical resistivity, carrier concentration, and mobility of an aluminum zinc oxide thin-film semiconductor according to a heat treatment condition in an aluminum oxide zinc thin film according to an embodiment of the present invention.
5 is a graph showing a Seebeck coefficient (S) according to heat treatment conditions in the zinc oxide thin film according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

The present invention

Low-temperature deposition of a zinc oxide thin film on a substrate using a sputtering method (step 1);

Heat treating the aluminum zinc oxide thin film deposited in Step 1 under vacuum at 250 to 350 ° C for 30 minutes to 1 hour and 30 minutes (Step 2); And

(3) heat-treating the aluminum zinc oxide thin film heat-treated in step 2 under a high purity nitrogen or hydrogen atmosphere at 200-500 ° C for 30 minutes to 1 hour 30 minutes under vacuum, Of the present invention.

First, Step 1 is a step of depositing a zinc oxide thin film on a substrate by a sputtering method at a low temperature.

In the manufacturing method according to the present invention, the aluminum oxide zinc thin film is preferably a single crystalline thin film having a unidirectionality. In order to obtain a high-quality thin film through a heat treatment process, the formed film must have the characteristics of a single crystal since it can basically have a single directionality on the substrate to promote the dominant direction growth.

In the manufacturing method according to the present invention, the substrate is preferably a transparent substrate made of glass or plastic. In the case of a glass substrate, excellent characteristics in environmental resistance can be secured owing to excellent thin film crystallinity. Plastic substrates can be deposited at lower temperatures than glass substrates, and flexible substrates for plastic substrates deposited with excellent transparent conductive films can be widely used for flexible displays.

In the manufacturing method according to the present invention, the sputtering method is preferably a radio wave sputtering method, but is not limited thereto, and other sputtering methods commonly used in the art can be used.

Next, Step 2 is a step of heat-treating the aluminum zinc oxide thin film deposited in Step 1 under vacuum.

In the production process according to the invention, the vacuum is 760 ~ 1 × 10 ^-3 Torr together preferably having a degree of vacuum, and if the case falls outside this range, the range of the initial degree of vacuum higher than 10 ^-3 torr vacuum days , The amount of residual gas is insufficient during the heat treatment, which can not help to improve the properties of the oxide thin film. When the degree of vacuum is too low, the impurity such as oxygen is adsorbed at a temperature higher than 760 torr, There is a problem that it can be brought .

In the manufacturing method according to the present invention, it is preferable that the heat treatment is performed at 250 to 350 ° C for 30 minutes to 1 hour and 30 minutes.

Further, step 3 is a step of heat-treating the aluminum zinc oxide thin film heat-treated in step 2 under a high-purity nitrogen or hydrogen atmosphere under vacuum.

In the production process according to the invention, the vacuum is 760 ~ 1 × 10 ^-3 Torr together preferably having a degree of vacuum, and if the case falls outside this range, the range of the initial degree of vacuum higher than 10 ^-3 torr vacuum days The amount of the residual gas is insufficient during the heat treatment, so that it can not significantly improve the properties of the oxide thin film. When the degree of vacuum is too low, the impurity such as oxygen is adsorbed at a temperature higher than 760 torr, There is a problem that it can be brought.

In the production method according to the present invention, it is preferable to use a high purity gas of 99.9% or more in the above step. The zinc oxide thin film grown by the sputtering method does not have a stoichiometric composition ratio of zinc: oxygen = 1: 1 and oxygen vacancies exist. These oxygen defects weaken the increase of resistivity and light transmittance, which is a factor that hinders the physical properties of the thin film. In order to reduce such oxygen defects, the characteristics of the aluminum zinc oxide thin film can be improved by heat treatment using a high purity gas of 99.9% or more.

In the manufacturing method according to the present invention, it is preferable that the heat treatment is performed at 200 to 500 ° C for 30 minutes to 1 hour and 30 minutes.

As shown in FIGS. 2 to 5, the aluminum zinc oxide thin film produced according to the above method has improved structural, electrical, and thermal thin film characteristics, and is superior in transparency to a relatively expensive ITO thin film in solar cells and thermoelectric devices It can be usefully used as a semiconductor thin film.

Hereinafter, the present invention will be described in more detail by way of examples. The following Examples illustrate the present invention, and the contents of the present invention are not limited by Examples.

< Example  1>

Improved optical, electrical and thermal properties Aluminum oxide zinc  Manufacture of thin films

1, a ZnO: Al single crystal thin film was deposited on a soda lime glass substrate using a high purity zinc oxide target doped with 2 wt% of aluminum by a radio wave sputtering method at room temperature .

Specifically, the distance between the sputtering gun and the substrate was fixed to about 11 cm, and the soda ash substrate was immersed in an etching solution containing HNO ₃ : K ₂ CrO ₄ : H ₂ O ₂ at a ratio of 1: 1: 20 for 30 minutes High purity distilled water, acetone and methanol were washed with ultrasonic wave for 3 minutes each in order. Residual impurities were removed with high purity nitrogen gas. Also, in order to remove moisture on the surface of the substrate, the substrate was subjected to heat treatment at a temperature of 400 ° C for 30 minutes in a growth chamber, and then slowly cooled to room temperature, which is a growth temperature. The initial vacuum level before the thin film deposition was maintained at ~ 1 × 10 ^-7 Torr, and the amount of argon gas was constantly injected at 20 sccm (Standard Cubic Centimeter per Minute) to grow the thin film under a vacuum of ~ 1 × 10 ^-3 Torr.

Then, the aluminum oxide thin film grown at a low temperature by the radio wave sputtering method was heat treated in an electric furnace maintained in a vacuum. Specifically, vacuum exhaust was performed using a high temperature furnace in which a quartz tube having a vacuum degree of ~ 1 × 10 ^-3 Torr was sealed. Thereafter, heat treatment is performed at 300 ° C. for one hour under vacuum, and high purity nitrogen (purity 99.999%) or high purity hydrogen (purity 99.999%) gas is introduced into the quartz tube equipped with the sample under vacuum, The zinc oxide thin films were fabricated by annealing for one hour at.

< Experimental Example  1>

Heat treatment Aluminum oxide zinc  Thin film properties

The following experiment was carried out to investigate the change of the thin film characteristics of aluminum oxide (ZnO: Al) thin films deposited by radio wave sputtering at low temperatures.

The ZnO thin films grown by RF sputtering at low temperatures were annealed at room temperature for 1 hour at 200, 300, 500 ℃ and for 1 hour. The change in the photoluminescence spectrum was measured and shown in Fig.

As shown in FIG. 2, the ZnO (Al) thin film exhibits a decrease in oxygen defects and an increase in photoluminescence intensity as the annealing temperature increases in a high purity hydrogen atmosphere.

In order to investigate the change of the characteristics of the thin film according to the annealing atmosphere, the X-ray spectral distribution of the zinc oxide thin film annealed for 1 hour in a vacuum, nitrogen atmosphere or hydrogen atmosphere without annealing is shown in FIG. 3, The distributions of resistivity, carrier concentration and mobility are shown in Fig. 4, and Seebeck coefficient (S) is shown in Fig.

3A is a graph showing the X-ray spectrum of the zinc oxide thin film grown by the sputtering method, FIG. 3B is a graph showing the X-ray spectra of the ZnO thin film grown by sputtering, FIG. FIG. 3D shows a case where heat treatment is performed under a 500 DEG C hydrogen atmosphere. As shown in FIG. 3, the zinc oxide thin film grown on the glass substrate has a structure of zinc oxide (ZnO) and shows a unidirectionality of (002) plane and (004) plane on the c-axis. Further, as shown in Figs. 3B, 3C and 3D, the relative intensity of the (002) plane and the (004) plane was increased by the heat treatment process.

FIG. 4 is a graph showing the electrical resistivity, carrier concentration, and mobility of the aluminum oxide thin film semiconductor according to the heat treatment conditions of the present invention. Mobility and carrier concentration increase. This means that the heat treatment has an important influence on the characteristics of the solar cell and the thermoelectric device, and it is understood that the improvement of the optical characteristics and the change of the transport characteristics are also improved.

5B is a graph showing the Seebeck coefficient (S) of zinc oxide which is not subjected to the heat treatment process, and FIGS. 5B, 5C and 5D are graphs showing the heat transfer effect of the zinc oxide thin film according to the present invention. , Nitrogen, and vacuum annealed aluminum zinc oxide thin films. It can be seen that the anti-Seebeck coefficient of aluminum oxide after heat treatment is increasing. In order to obtain excellent thin film characteristics, a high Seebeck coefficient S and an electric conductivity σ are required, and it can be seen that the ZnS thin film subjected to the heat treatment process of the present invention improves the Seebeck coefficient S and the electric conductivity σ.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (7)

Low-temperature deposition of a zinc oxide thin film on a substrate using a sputtering method (step 1);
Heat treating the aluminum oxide thin film deposited in step 1 under vacuum at a temperature of 250 to 350 DEG C for 30 minutes to 1 hour and 30 minutes (step 2); And
Heat treating the aluminum zinc oxide thin film heat-treated in step 2 under a high-purity nitrogen or hydrogen atmosphere at a temperature of 200 to 500 ° C for 30 minutes to 1 hour and 30 minutes under vacuum (step 3) A method for producing an aluminum zinc thin film. The method according to claim 1,
Wherein the aluminum oxide zinc thin film is a single crystalline thin film having a unidirectional property. The method according to claim 1,
Wherein the substrate is a transparent substrate made of glass or plastic. The method according to claim 1,
Wherein the sputtering method is a radio-wave sputtering method. The method according to claim 1,
Wherein the vacuum has a vacuum degree of 760 to 1 x 10 &lt; ^-3 &gt; Torr. The method according to claim 1,
Wherein the high purity is 99.9% or more. An aluminum oxide thin film improved in thin film characteristics produced by the method of claim 1.

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