KR20150019623A - Method of depositing zinc oxide based thin film - Google Patents

Abstract

Provided is a method for depositing a zinc oxide-based thin film including: a step of mixing at least two first organic solvents with a zinc oxide precursor; a step of evaporating the mixed solution of the first organic solvents and the zinc oxide precursor; and a step of depositing a zinc oxide-based thin film on the substrate by supplying an oxidizing agent and air obtained by evaporating the mixed solution of the first organic solvents and the zinc oxide precursor to a deposition chamber in which a substrate is installed. Preferably, the method for depositing the zinc oxide-based thin film, wherein the zinc oxide-based thin film is coated with gallium, includes: a step of mixing at least two second organic solvents with a gallium precursor; a step of evaporating the mixed solution of the second organic solvents and the gallium precursor; and a step of depositing a zinc oxide-based thin film coated with gallium on the substrate by supplying the air obtained by evaporating the mixed solution of the second organic solvents of the gallium precursor to the deposition chamber.

Description

[0001] METHOD OF DEPOSITING ZINC OXIDE BASED THIN FILM [0002]

The present invention relates to a method for depositing a zinc oxide thin film using a mixed solution obtained by mixing a zinc oxide precursor with at least two organic solvents other than a single solvent.

Flat panel displays such as TFT-LCD, PDP, FED, and OLED; A solar cell using a photoelectric effect; touch screen; A transparent conductive film (Transparent Conducting Electrode) is required. The transparent conductive film is one of the materials that is indispensable for flat panel displays and solar cells. It protects the internal electronic devices from external influences and transmits electric signals and currents to electronic devices while transmitting the light from the electronic devices without resistance. , There is a condition that light transmittance and electric conductivity should be excellent. Materials used as transparent conductive films should have low resistivity values (10 ^-3 to 10 ^-4 ohm · cm) and high light transmittance in the visible light range. In addition, there is little change in the characteristics of the electronic devices inside the display due to the heat received during the manufacturing process.

The most widely used transparent electrode material is ITO (In _1-x Sn _x O ₃ ), which has excellent optical and electrical properties. However, the production cost of In, which is one of the raw materials, ITO has the disadvantage that when plasma is exposed to the plasma, the characteristics are severely changed due to heat. On the other hand, ZnO having a band gap of about 3.4 eV has a very good transmittance of infrared rays and visible light, and is excellent in electrical conductivity and plasma durability. In addition, it can be grown at low temperatures, and the production cost is also relatively low, which is emerging as a promising material for transparent electrodes and functional windows of area displays.

However, ZnO-based thin films as transparent conductive oxide films have a change in electrical properties as a result of changes in the quantitative ratios of Zn and O due to the influence of oxygen in the case of ZnO-based thin films in which no impurities are added for a long time in the atmosphere, There is a drawback that it is not stable. Therefore, in order to overcome this problem, many researchers have conducted studies on using a zinc oxide thin film doped with an n-type dopant as a transparent conductive oxide film by a group III element such as aluminum, indium, gallium, or boron. (Thin Solid Films, 427, 401-405, 2003, Thin Solid Films, 392, 334, 2001, Thin Solid Films, 442, 121-126, 2003)

Among them, the resistance of gallium to oxidation is larger than that of aluminum, and the covalent bond lengths of gallium-oxygen and zinc-oxygen are 1.92 Å and 1.97 Å, respectively. The gallium-oxygen bond length is slightly smaller, Gallium is mainly used as an n-type impurity because it can minimize the strain of the zinc oxide lattice, and the effect of gallium oxide on the electrical and optical properties of the zinc oxide doped with gallium Research has also been conducted. (J. KIEEME, Vol. 23, No. 9, pp. 685-690, September 2010)

The zinc oxide based thin film can be deposited on a substrate through a physical vapor deposition method. When a sputtering process is used in a physical vapor deposition method, a zinc oxide (ZnO) based target is used as a target material (Publication Number: 10-2008-0064269).

As precursors for preparing zinc oxide, zinc complexes mainly composed of organic ligands are mainly used. Among the well-known complexes (Zn (O ₂ CMe) ₂ , Zn ₄ O (O ₂ CNEt ₂ ) _6, etc.) are volatilized at relatively low temperatures but have the disadvantage of causing carbon contamination in the film (Andrew ,; Johnson In addition, metal halide compounds are also widely used as precursors for the production of zinc oxide (see, for example, L. Hollingsworth, N. Kociok-K, G. Kieran, C .; Molloy. (Kaiya, K., Takahashi, N., Nakamura, T., Okamoto, S., Yamamoto, H., Thin Solid Film, 2002, 409, 116.)

In addition, research has been carried out to deposit a zinc oxide thin film on a substrate through chemical vapor deposition using diethyl zinc and a diethyl zinc octane solution as raw materials. 10-2007-0053617, 10-2006-0125500).

1 is a schematic view of a conventional PECVD apparatus for depositing a zinc oxide based thin film using diethyl zinc or dimethyl zinc as a raw material.

Figure 1 illustrates a PECVD apparatus for depositing undoped zinc oxide and fluorine-, gallium- or boron-doped zinc oxide. The PECVD apparatus of Fig. 1 is a system in which a volatile organometallic zinc compound, such as diethylzinc or dimethylzinc; Argon or helium as the carrier gas; Carbon dioxide as an oxidizing agent; And triethylboron, trimethylgallium or nitrogen trifluoride as a dopant to form a reaction composition, introducing the reaction composition into the deposition chamber 1, and depositing a zinc oxide thin film on the substrate 5.

6 is an opening, 7 is a power source, 8, 9, 10, 11, 12 and 13 are lines, 14, 15, 16, 17 and 18 And 19 denote flow control devices, and 20 denote heat retaining devices.

FIG. 2 is a schematic view of a conventional deposition chamber for depositing a gallium-doped zinc oxide thin film using a solution prepared by dissolving diethyl zinc and trimethyl gallium in an organic solvent as a raw material.

A solution prepared by dissolving dimethyl zinc or diethyl zinc in an organic solvent (ether, ketone, ester, hydrocarbon, or alcohol) and a solution prepared by dissolving trimethyl gallium in an organic solvent (hydrocarbon) (Oxygen gas, ozone gas, nitrogen oxide gas or vapor) is supplied to the deposition chamber through the supply pipe 25 at the same time.

Reference numeral 21 denotes a substrate, 22 denotes a susceptor, 23 denotes a heater, 26 denotes a rotating shaft, 27 denotes a reaction gas discharging portion, and 29 denotes a reaction chamber.

As shown in Fig. 1, when diethyl zinc or dimethyl zinc is used as the zinc oxide precursor and when trimethyl gallium is used as the dopant, the vapor pressure is too high, the risk of flammability due to high reactivity is great, There are disadvantages. In particular, due to the risk of ignition due to high reactivity, trimethylgallium is added as a dopant so that the deposition of a zinc oxide thin film using a precursor such as diethylzinc or dimethylzig must be performed at low pressure, and atmospheric chemical vapor deposition is not available There were disadvantages.

A method has been proposed in which dimethyl zinc or diethyl zinc is dissolved in an organic solvent to suppress spontaneous ignitability and explosiveness and to form a high purity zinc oxide film. (Patent Document 10-2006-0125500).

However, since the vapor pressure of the precursor and the diluted solvent are different from each other in order to use the above-described method, there is a disadvantage that chemical vapor deposition is required to vaporize the raw material after supplying the raw material to the vaporizer. However, in the case of incomplete vaporization of the raw material in this method, impurities in the vaporizer are deposited due to incomplete decomposition of the raw material, so that the vaporization device is clogged and the reproducibility of the thin film due to this is extremely bad.

SUMMARY OF THE INVENTION The present invention has been conceived to solve the problems described above, and it is an object of the present invention to provide a high-quality and high-purity zinc oxide thin film by mixing a mixed solvent in which two or more solvents other than a single solvent are mixed at a predetermined ratio, But it is an object of the invention.

In order to accomplish the above object, the present invention provides a method of manufacturing a semiconductor device, comprising: mixing at least two first organic solvents and a zinc oxide precursor; Vaporizing a mixture of the at least two first organic solvents and the zinc oxide precursor; And supplying a gas obtained by vaporizing the mixture of the at least two first organic solvents and the zinc oxide precursor and an oxidizing agent to a deposition chamber in which the substrate is embedded to deposit a zinc oxide thin film on the substrate. Thereby providing a method of forming a thin film.

Preferably, the zinc oxide based thin film is a gallium-doped zinc oxide based thin film, and the zinc oxide based thin film deposition method includes: mixing at least two second organic solvents and a gallium precursor; Vaporizing a mixture of the at least two second organic solvents and the gallium precursor; And a gas obtained by vaporizing a mixture of the at least two second organic solvents and the gallium precursor is supplied to the deposition chamber to deposit the gallium-doped zinc oxide thin film on the substrate.

According to the present invention, it is possible to obtain a high-quality and high-purity zinc oxide thin film by mixing a mixed solvent in which two or more solvents other than a single solvent are mixed at a certain ratio with zinc oxide precursor .

1 is a schematic view of a conventional PECVD apparatus for depositing gallium-doped zinc oxide thin film using diethyl zinc or dimethyl zinc and trimethyl gallium as raw materials.
FIG. 2 is a schematic view showing another conventional deposition chamber for depositing a gallium-doped zinc oxide thin film using a solution prepared by dissolving diethyl zinc and trimethyl gallium in an organic solvent as a raw material.
FIGS. 3 and 4 are diagrams showing the vapor pressures of diethylzinc, octane, heptane, hexane, pentane, and the vapor pressures of trimethylgallium, isohexane, dimethylbutane, and cyclopentane.
5 is a schematic view of a CVD apparatus according to an embodiment of the present invention.
Figures 6 and 7 are views schematically showing examples of canisters.
FIGS. 8 to 10 are views showing the results of analysis of a zinc oxide thin film deposited according to Example 1. FIG.
FIGS. 11 to 13 are views showing the results of analysis of the zinc oxide-based thin film deposited according to Example 2. FIG.

According to an embodiment of the present invention, as a precursor to be used for depositing a zinc oxide thin film by using a CVD method using a bubbler instead of a CVD method using a vaporizer, dimethyl zinc or diethyl zinc is used as a raw material do. By diluting this raw material in two or more solvents, stability is achieved, and the vapor pressure of the raw material and the solvent are almost equal to each other. Thus, the solvent and the raw material are uniformly vaporized by using a bubbler without using a vaporizer to deposit a reproducible zinc oxide- do.

As the first organic solvent for diluting the zinc oxide precursor, hydrocarbons are used, and as the hydrocarbons, paraffinic hydrocarbons represented by C _n H _{2n + 2} or cycloparaffin hydrocarbons represented by the general formula C _n H _2n (n: 5 To 12) are preferable. Also particularly preferred are heptane and octane. The content of dimethyl zinc and diethyl zinc used as raw materials is preferably 0.1 to 2 mol / L.

In addition, according to one embodiment of the present invention, trimethylgallium, which is a doping material used for increasing the electric conductivity, is also produced by a method such as dimethylzinc, diethylzinc, etc., and has a high deposition rate and high productivity, It is possible to mass-produce a gallium-doped zinc oxide thin film through atmospheric vapor deposition suitable for the process.

The second organic solvent used for the trimethyl gallium used as a dopant is also a hydrocarbon. Examples of the hydrocarbon include paraffinic hydrocarbons represented by C _n H _{2n + 2} or cycloparaffin hydrocarbons represented by the general formula C _n H _2n (n: 5 To 12) are preferable. Particularly preferred are isohexane, dimethylbutane and cyclopentane. The amount of trimethyl gallium used as a raw material is also preferably from 0.1 to 2 mol / L.

According to another aspect of the present invention, there is provided a method for depositing gallium-doped oxide-based thin film on a substrate, the method including: depositing a substrate in a deposition chamber; supplying a trimethylgallium precursor, which is a zinc oxide precursor, And a method for depositing a zinc oxide-based thin film.

Preferably, a gallium-doped zinc oxide based thin film is deposited on the substrate by atmospheric pressure chemical vapor deposition.

Trimethylgallium used as a dopant with dimethyl zinc or diethyl zinc is particularly difficult to handle because it has a chemical characteristic of igniting in air and exploding in oxygen. In the present invention, the raw material is diluted in an organic solvent to suppress pyrophoricity and explosiveness, thereby forming gallium-doped gallium oxide-doped thin film of high quality and high purity.

In the present invention, the previously used zinc oxide precursor such as dimethyl zinc, diethyl zinc and the like and the trimethyl gallium as the dopant are diluted in two or more organic solvents to stabilize the precursor, and the vapor pressures of the precursor and the organic solvent are almost the same (Preferably within ± 0.03 torr within a tolerance range) and then applied to chemical vapor deposition (CVD) using a bubbler to deposit gallium-doped zinc oxide thin film.

Preferably, the gas obtained by vaporizing the mixed liquid of the first organic solvent and the zinc oxide precursor is carried into the deposition chamber by the inert carrier gas.

5 is a view showing a schematic structure of a CVD apparatus according to an embodiment of the present invention.

In the CVD apparatus, dimethylzinc, diethylzinc, or the like is diluted in at least two first organic solvents, and trimethylgallium is diluted in at least two second organic solvents. A dip-tube, or a canister 113, 118 with a tube as in FIG. i) supplying gas from the gas supply section 111 to the canisters 113 and 118 through a dip-tube or tube to aid vaporization of the zinc oxide precursor and the gallium precursor, which is a dopant, or ii) A gaseous zinc oxide precursor and a gallium precursor are supplied together with an inert carrier gas.

At this time, oxidant gas (oxygen gas, ozone gas, nitrogen oxide gas, vapor of steam or alcohol) is supplied from the oxidant supply units 115 and 117 to the deposition chamber 100 together.

The upper electrode 102 has the form of a showerhead. The showerhead refers to a chamber, plenum, or other structure having a plurality of openings for discharging precursors and the like to the deposition chamber 100.

The substrate 105 may be a silicon substrate, a sapphire substrate, a ceramics substrate, a glass substrate, a metal oxide substrate, a metal substrate, or the like. In order to efficiently form gallium-doped zinc oxide thin film, the temperature of the substrate can be set at 100 to 400 ° C, preferably 250 to 350 ° C. The zinc oxide precursor and the gallium precursor supplied may be chemically vapor-deposited on the substrate heated to the temperature to form a reproducible gallium-doped zinc oxide thin film.

In order to obtain a gallium-doped gallium oxide-based thin film dopant, a dopant may be introduced into the deposition chamber 100 and deposited together, or a doping process may be performed in a subsequent process.

?

(Production of raw materials)

An inert argon is supplied in a canister having an inner diameter of 70 cm and a height of 50 cm to make the inside of the container into an argon atmosphere. In this vessel, diethylzinc and pre-diluted organic solvent (octane + heptane) were charged into the vessel, and the mixed solution was stirred at room temperature and atmospheric pressure to prepare a raw material. Trimethylgallium was also added to the organic solvent (isohexane, Cyclopentane) was charged into a container, and this mixed solution was stirred at room temperature and atmospheric pressure to prepare a raw material. Here, a solution of 0.3 mol / L of diethylzinc and trimethylgallium was prepared to prepare 1 L of raw material necessary for the examples. The two diluted organic solvents were roughly matched to the diethylzinc and trimethylgallium vapor pressures by temperature, using Raoul and Dalton 's law. The chart for the preparation of the mixed solution is given as follows.

0.3M diethylzinc solution octane
Injection amount (mol / l) Heptane
Injection amount (mol / l) Octane and heptane
Mixed solvent vapor pressure Diethylzinc
Vapor pressure 24 ℃ 5.622 0.381 15.09 torr 15.10 torr 40 ℃ 5.633 0.368 34.83 torr 34.83 torr 80 ℃ 5.383 0.646 202.05 torr 202.07 torr

0.3M trimethylgallium solution Iso-hexane
Injection amount (mol / l) Cyclopentane
Injection amount (mol / l) Iso-hexane and cyclopentane
Mixed solvent vapor pressure Trimethyl gallium
Vapor pressure 24 ℃ 6.812 1.048 216.76 torr 216.77 torr 40 ℃ 6.016 2.140 425.70 torr 425.70 torr 80 ℃ 2.335 7.189 1760.50 torr 1760.51 torr

(deposition)

[Example 1]

The glass substrate was set in the heating section of the CVD chamber of the CVD apparatus, and the degree of vacuum in the deposition chamber was set at normal pressure. Then, the temperature inside the canister was set to room temperature and the temperature of the substrate was maintained at 350 占 폚. The gas was supplied to the raw material at a flow rate of 20 sccm / min using a gas flow controller to assist in vaporization of the raw material, and argon gas was supplied at a flow rate of 50 sccm / min through a carrier gas supply line heated to 80 캜, Was supplied at a flow rate of 5 sccm / min to form a zinc oxide-based thin film on the glass substrate for several minutes.

The ZnO thin film thus obtained was analyzed by a scanning electron microscope to show crystallinity grown in a c-axis direction of a 90 nm thin film columnar structure (FIGS. 8 and 9). As a result of X-ray diffraction analysis, (002) crystal planes in the c-axis direction appeared at around 2θ (degress) value of 34.4 (FIG. 10). As a result of analyzing with a sheet resistance meter, 2.222 × 10 ³ Ω / sq (specific resistance 2 × 10 ^-3 ΩCm) appeared. In addition, infrared spectroscopic analysis showed that it has a transmittance of 80% or more in visible light region.

As a result, a transparent conductive oxide-zinc oxide thin film having a (002) crystal face in the c-axis direction which is superior in carrier mobility and having high light transmittance and low resistance was obtained.

[Example 2]

The glass substrate was set in the heating section of the CVD apparatus, and the CVD apparatus was set at the atmospheric pressure. Then, the temperature inside the canister was set at 40 占 폚, and the temperature of the substrate was maintained at 350 占 폚. The gas was supplied to the raw material at a flow rate of 500 sccm / min using a gas flow controller to assist vaporization of the raw material, and argon gas was supplied at a flow rate of 200 sccm / min through a carrier gas supply line heated to 80 캜, Was supplied at a flow rate of 300 sccm / min to form a zinc oxide thin film on the glass substrate for 20 minutes.

The thus-obtained zinc oxide thin film was analyzed by a scanning electron microscope to show crystallinity grown in a c-axis direction of a columnar structure with a thickness of 140 nm (FIGS. 11 and 12). As a result of X-ray diffraction analysis, (002) crystal planes in the c-axis direction appeared at around 2θ (degress) value of 34.4 (FIG. 13). As a result of analyzing with sheet resistance meter, 4.28 × 10 ³ Ω / sq (specific resistance 6 × 10 ^-3 ΩCm) appeared. In addition, infrared spectroscopic analysis showed that it has a transmittance of 80% or more in visible light region.

As a result, a transparent conductive oxide-zinc oxide thin film having a (002) crystal face in the c-axis direction which is superior in carrier mobility and having high light transmittance and low resistance was obtained.

100: deposition chamber, 102: upper electrode
103: lower electrode, 105: substrate
111: carrier gas supply unit, 113, 118: canister
115, 117: oxidant supplier

Claims (17)

Mixing at least two first organic solvents and a zinc oxide precursor;
Vaporizing a mixture of the at least two first organic solvents and the zinc oxide precursor; And
Supplying a gas mixture obtained by vaporizing the mixed liquid of the at least two first organic solvents and the zinc oxide precursor and an oxidizing agent to a deposition chamber in which the substrate is embedded to deposit a zinc oxide thin film on the substrate, Thin film deposition method. The method according to claim 1,
The zinc oxide thin film is a gallium-doped zinc oxide thin film,
In the above-described zinc oxide-based deposition method,
Mixing at least two second organic solvents and a gallium precursor;
Vaporizing a mixture of the at least two second organic solvents and the gallium precursor; And
Supplying a gas obtained by vaporizing a mixture of the at least two second organic solvents and the gallium precursor to the deposition chamber to deposit the gallium-doped zinc oxide thin film on the substrate, Deposition method. 3. The method of claim 2,
Wherein the gallium precursor comprises trimethyl gallium. 3. The method of claim 2,
Wherein the gallium precursor is mixed with the second organic solvent at a concentration of 0.1 to 2 mol / L. 3. The method of claim 2,
Wherein the second organic solvent comprises at least one of paraffinic hydrocarbons represented by the general formula C _n H _{2n + 2} or cycloparaffin hydrocarbons represented by the general formula C _n H _2n (n = 5 to 12) A method for depositing zinc-based thin films. 6. The method of claim 5,
Wherein the second organic solvent comprises at least one of isohexane, dimethylbutane, and cyclopentane. The method according to claim 1,
Wherein the zinc oxide precursor comprises at least one of diethylzinc and dimethylzinc. The method according to claim 1,
Wherein the zinc oxide precursor is mixed with the first organic solvent at a concentration of 0.1 to 2 mol / L. The method according to claim 1,
Wherein the first organic solvent comprises at least one of paraffinic hydrocarbons represented by the general formula C _n H _{2n + 2} or cycloparaffin hydrocarbons represented by the general formula C _n H _2n (n = 5 to 12) A method for depositing zinc-based thin films. 10. The method of claim 9,
Wherein the second organic solvent comprises at least one of heptane and octane. The method according to claim 1,
Wherein the zinc oxide based thin film is deposited by chemical vapor deposition. 12. The method of claim 11,
Wherein the chemical vapor deposition is an atmospheric pressure chemical vapor deposition. The method according to claim 1,
Wherein the gas obtained by vaporizing the mixture of the first organic solvent and the zinc oxide precursor is transported into the deposition chamber by an inert carrier gas. The method according to claim 1,
Wherein the oxidizing agent comprises at least one of oxygen gas, ozone gas, nitrogen oxide gas, steam, and alcohol vapor. The method according to claim 1,
Wherein the substrate is at least one of a silicon substrate, a sapphire substrate, a ceramics substrate, a glass substrate, a metal oxide substrate, and a metal substrate. The method according to claim 1,
Wherein a gas is blown into a mixed solution of the first organic solvent and the zinc oxide precursor to vaporize the mixture. The method according to claim 1,
Wherein the vapor pressure of the mixed solvent in which the at least two first organic solvents are mixed and the vapor pressure of the zinc oxide precursor coincide within an error range of +/- 0.03 torr.

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