KR100644163B1 - Process for preparing zinc oxide thin film - Google Patents

Abstract

A method for manufacturing a zinc oxide thin film is provided to improve the qualities without an additional oxygen source by performing a metal organic chemical deposition using amino alkyl acid alkyl zinc as a thin film precursor material. Amino alkyl acid alkyl zinc is vaporized. A zinc oxide thin film is formed on a base member by using the vaporized amino alkyl acid alkyl zinc. The base member is made of one selected from a group consisting of a silicon substrate, a sapphire substrate and a zinc oxide substrate. The base member is performed with a surface oxidation. When the zinc oxide thin film is formed on the base member, the temperature of the base member is in a predetermined range of 250 to 400 ‹C.

Description

Production method of zinc oxide thin film {PROCESS FOR PREPARING ZINC OXIDE THIN FILM}

1 is a graph showing the results of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) of methyl (1-dimethylamino-2-methyl-2-propoxy) zinc (II) prepared in Preparation Example 1;

2 is a graph showing the results of X-ray diffraction analysis of the zinc oxide thin film prepared in Example 1,

3 is a graph showing the results of X-ray diffraction analysis of the zinc oxide thin film prepared in Example 2,

4 is a graph showing the results of X-ray diffraction analysis of the zinc oxide thin film prepared in Example 3,

5 to 8 are scanning electron micrographs of the zinc oxide thin films prepared in Examples 2, 3, 5, and 7.

The present invention relates to a method for producing a zinc oxide thin film, and more particularly, to a method for producing a high quality crystalline zinc oxide thin film by performing metal organic chemical vapor deposition (MOCVD) under milder process conditions without separately supplying an oxygen source. will be.

Zinc oxide is a transparent semiconductor with a band gap of about 3.4 eV, and can be applied to optical devices such as light emitting diodes and laser diodes, piezoelectric devices, and transparent conductive films. (Ohta etc., "Current injection emission from a transparent pn junction composed of p- SrCu ₂ O ₂ / n- ZnO, " Appl. Phys. Lett., 2000 , 77, 475-477; Bagnall etc., " Optically pumped lasing of ZnO at room temperature, " Appl. Phys Lett., 1997 , 70, 2230-2232; Wacogne etc., "Effective piezoelectric activity of zinc oxide films grown by radio-frequency planar magnetron sputtering," Appl. Phys. Lett., 1995 , 67, 1674-1676; Jiang etc., "Aluminum-doped zinc oxide films as transparent conductive electrode for organic light emitting," Appl. Phys. Lett., 2003 , 83, 1875-1877).

Among the methods of forming a zinc oxide thin film on a substrate, a chemical method using a zinc compound may be classified into metal organic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD).

In general, metal organic chemical vapor deposition is a method of depositing a thin film using a solid or liquid source in the form of a metal organic material. As a raw material for forming a zinc oxide film, a metal chloride or a zinc complex compounded with an organic ligand is mainly used. come.

However, zinc chloride, a representative metal chloride, has a high sublimation temperature, making it difficult to use in processes (Kaiya etc., "Epitaxial growth of ZnO thin films exhibiting room-temperature ultraviolet emission by atmospheric pressure chemical vapor deposition," Thin Solid Films , 2002). , 409, 116-119), zinc complexes combined with organic ligands have a lower sublimation temperature than zinc chloride, but have the disadvantage of causing carbon contamination in thin films (Ayouchi etc., "Preparation and characterization of transparent ZnO thin films obtained by spray pyrolysis , " Thin Solid Films , 2003 , 426, 68-77).

On the other hand, dialkyl zinc is known as a precursor suitable for use in the production of zinc oxide thin films due to its high volatility and low decomposition temperature.However, the precursor itself is unstable and difficult to handle and before vaporized dialkyl zinc reaches the substrate. There is a problem in that it reacts easily with an oxygen source and produces powdered zinc oxide (Li etc., "Growth of stoichiometric (002) ZnO thin films on Si (001) substrate by using plasma enhanced chemical vapor deposition," J. Vac . Sci. Techonol. A, 2002 , 20, 1779-1783).

In addition, in order to manufacture a zinc oxide thin film by performing the MOCVD process using the precursor materials, an oxygen source must be separately supplied. Most precursor materials have high reactivity with oxygen sources, so these two raw materials (zinc source and oxygen source) are highly reactive. The device is complicated because the devices must be configured so that they do not contact each other until they reach the substrate.

Therefore, a recent research has been conducted to prepare a zinc oxide thin film using a single precursor containing oxygen in the precursor. Such precursors include alkyl zinc alkylate containing one alkyl group and one alkyl acid group ligand (Auld etc., "Growth of ZnO by MOCVD using Alkylzinc Alkoxides as Single-source Precursors", J. Mater. Chem., 1994, 4, 1249-1253) and hexamethylene kiss [μ- (diethyl bar Mato _{-O: O '] - μ 4} - oxo zinc tetra (Petrella etc., "Single-Source Chemical Vapor Deposition Growth of ZnO Thin Films Using Zn ₄ O (CO ₂ NEt) ₆ ", Chem. Mater. , 2002 , 14, 4339-4342), etc. For example, when preparing a zinc oxide thin film using a single precursor, the precursor is Since it contains oxygen, there is an advantage that a zinc oxide thin film can be manufactured at low temperature by chemical decomposition reaction without receiving an oxygen source separately.

However, since alkyl zinc alkylate is present as a tetramer and hexakis [μ- (diethylcarbamato-O: O ']-μ ₄ -oxotetra zinc has a high molecular weight, all of these precursors Vaporization characteristics are not good.

Accordingly, the inventors of the present invention use zinc alkylaminoalkylate having a dimer structure, which has excellent vaporization properties and can act as a single precursor, as a precursor for producing zinc oxide thin films, thereby providing excellent zinc oxide without supplying an oxygen source. It was confirmed that the thin film can be prepared and completed the present invention.

It is an object of the present invention to provide a method for producing a high quality zinc oxide thin film which is uniform, has good coverage, and has a uniform orientation in milder conditions without separately supplying an oxygen source.

In order to achieve the above object, the present invention provides a method for producing a zinc oxide thin film comprising vaporizing an alkyl zinc alkylaminoalkyl acid and then depositing a zinc oxide thin film on the substrate by contacting the resulting vapor with a substrate.

Hereinafter, the present invention will be described in more detail.

A feature of the present invention is that when preparing a zinc oxide thin film using a metal organic chemical vapor deposition (MOCVD) process, a thin film of dialkyl aminoalkyl acid alkyl acid having excellent vaporization characteristics and capable of acting as a single precursor material It is used as a precursor material for manufacturing.

The zinc oxide thin film manufacturing process according to the present invention may be performed by vaporizing a metal precursor alkyl zinc alkylamino acid and then contacting the substrate. More specifically, the pressure inside the reactor may be increased after mounting the substrate in the reactor. A zinc oxide thin film can be deposited on a substrate by maintaining a temperature of 10 ^-2 to 1 Torr and injecting a zinc oxide thin film precursor of alkyl zinc alkylalkylate into the reactor together with a carrier gas while maintaining the temperature of the substrate at 250 to 400 ° C. have.

Examples of the alkyl zinc alkylalkyl used in the present invention include methyl (1-dimethylamino-2-methyl-2-propoxy) zinc (II) and ethyl (1-dimethylamino-2-methyl-2-propoxy) zinc. (II), methyl (1-dimethylamino-2-ethyl-2-butoxy) zinc (II), and the like, and alkyl zinc aminoalkyl acid not only contains an oxygen atom in the molecule, but also as a dimer. Since present, the sublimation temperature is lowered to 60 to 90 ° C., so the vaporization characteristics are excellent.

Therefore, when producing zinc oxide thin film by using MOCVD process, alkyl zinc alkyl alkylate having excellent vaporization properties is used as a precursor for thin film production, which is much more than conventional MOCVD process (600 to 800 ℃) without supplying oxygen source. The thin film deposition process can be carried out at a low temperature of 250 to 400 ° C.

Alkyl alkylaminoalkylates can be prepared by conventional manufacturing processes for reacting dialkylzinc and aminoalcohols in organic solvents (Kitamura etc., "Self and Nonself Recognition of Asymmetric Catalysts.Nonlinear Effects in the Amino Alcohol-Promoted Enantioselective Addition of Dialkylzincs to Aldehydes ", J. Am. Chem. Soc. , 1995 , 117, 4832-4842).

As the reactor used in the present invention, a reactor made of stainless steel is preferable, and as a substrate for forming a zinc oxide thin film, a substrate for forming a thin film, for example, silicon (111), sapphire (0001), zinc oxide ( A substrate such as 0001) can be used.

The substrate may be used by itself without surface treatment or may be used after forming an oxide film on the surface by oxidation treatment.

In addition, in the present invention, an inert gas such as argon may be used as a carrier gas to facilitate the injection of the precursor for forming a thin film into the reactor, and the carrier gas may be injected at a flow rate of 10 to 15 cc / min. Do.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are only for illustrating the present invention and the scope of the present invention is not limited thereto.

Preparation Example 1 Preparation of Methyl (1-dimethylamino-2-methyl-2-propoxy) zinc (II)

ZnMe ₂ (1.0 M heptane solution, 5 mL, 5.0 mmol) and 30 mL of hexane were added to a 125 mL Schlenk flask, and 0.59 g (5.0 mmol) of 1-dimethylamino-2-methyl-2-propanol (dmampH) was added slowly. Was added. The reaction solution was stirred at room temperature for 12 hours. After completion of the reaction, the solvent was removed under reduced pressure to obtain a white solid compound, which was then sublimed under reduced pressure (sublimation conditions: 45 DEG C and 10 ^-2 Torr) to obtain 0.71 g (yield 72.0%) of the title compound in the form of white crystals.

Melting Point: 123-125 ℃

¹ H-NMR (CDCl ₃ , 300.13 MHz): δ 0.31 (s, 3H, Zn (C H ₃ )), 1.25 (s, 6H, C (C H ₃ ) ₂ ), 2.12 (s, 2H, NC H ₂ C), 2.15 (s, N (C H ₃ ) ₂ ).

Results of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) of the prepared precursors are shown in FIG. 1. From FIG. 1, methyl (1-dimethylamino-2-methyl-2-propoxy) zinc (II) begins to sublimate rapidly at about 120 ° C. and completes sublimation at about 200 ° C. with little residue. T ₁ It can be seen that _{/ 2} (the temperature at which the sample weight is half the original weight) is 185 ° C.

Example 1 Preparation of Zinc Oxide Thin Film

The MOCVD process was performed using the material obtained in Preparation Example 1 as a precursor material.

Specifically, the surface of the silicon substrate is washed with distilled water or acetone, and then oxidized in a piranha solution (solution having a ratio of sulfuric acid to hydrogen peroxide 1: 1) heated to 80 ° C. for 30 minutes to form an oxide film, and then again. A substrate for thin film formation was prepared by washing with distilled water and drying the surface with nitrogen. After the prepared substrate was mounted on the heater inside the stainless steel reactor, the vacuum pump was operated so that the pressure inside the reactor was 10 ^-5 Torr. Subsequently, the thin film precursor obtained in Preparation Example 1 was injected into the reactor at a flow rate of 14 cc / min with argon as a carrier gas while maintaining the sublimation at 90 ° C to deposit a thin film on the silicon substrate for 1 hour. The substrate temperature was maintained at 275 ° C. and the reactor pressure was 6 × 10 ⁻¹ Torr when the thin film was deposited.

The X-ray diffraction analysis of the thin film thus prepared is shown in FIG. 2. From Fig. 2, it can be seen that only peaks corresponding to the (0002) plane of zinc oxide are observed at the position 2θ = 34.5 °, indicating that zinc oxide first grew in the [0001] direction (see JCPDS 36-). 1451). In addition, as a result of measuring the full-width at half maximum (FWHM) from the X-ray diffraction pattern of Figure 2, the value is about 0.2 °, it can be seen that the crystallinity of the prepared film is very excellent.

Example 2: Preparation of Zinc Oxide Thin Film

A zinc oxide thin film was deposited on the substrate by following the same process as Example 1 except that the temperature of the substrate was maintained at 250 ° C. when the thin film was deposited.

Example 3-7 Preparation of Zinc Oxide Thin Film

 The zinc oxide thin film was deposited on the substrate by the same process as in Example 1 except that the temperature of the substrate was maintained at 300, 325, 350, 375, and 400 ° C. when the thin film was deposited.

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면으로도 성장하였음을 보여 주는 것이다.X-ray diffraction patterns of the thin films prepared in Examples 2 and 3 of the thin films thus prepared are shown in FIGS. 3 and 4, respectively. From Figs. 3 and 4, the peaks were observed at 2θ = 31.8 °, 34.5 °, 36.3 ° and 56.6 ° in thin films grown at temperatures of 250 ° C. and 300 ° C., respectively.

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It also shows that it grew in cotton.

In addition, scanning electron micrographs of the zinc oxide thin films prepared in Examples 2, 3, 5, and 7 are shown in FIGS. 5 to 8, respectively. 5 to 8, when the thin film growth temperature is 250 ° C. (Example 2), the surface of the grown thin film is very smooth and tens of nanometer-sized particles are evenly distributed, and as the growth temperature is higher than 250 ° C. It can be seen that the surface of the thin film gradually becomes rough and the average particle size also increases.

As described above, according to the present invention, when the metal organic chemical vapor deposition process is performed using alkyl zinc alkylaminoalkyl as a thin film precursor, a high quality grown in a constant orientation at a lower temperature than a conventional method without supplying an oxygen source separately Zinc oxide thin films can be prepared.

Claims (6)

A method for producing a zinc oxide thin film, comprising depositing a zinc oxide thin film on a substrate by vaporizing the alkylzinc aminoalkyl acid zinc and then producing the vapor. In claim 1, Alkyl zinc aminoalkyl acid is methyl (1-dimethylamino-2-methyl-2-propoxy) zinc (II), ethyl (1-dimethylamino-2-methyl-2-propoxy) zinc (II) and methyl ( 1-dimethylamino-2-ethyl-2-butoxy) zinc (II). In claim 1, Wherein the substrate is selected from a silicon (111) substrate, a sapphire (0001) substrate and a zinc oxide (0001) substrate. The method of claim 1 or 3, Wherein the substrate is surface oxidized. In claim 1, Wherein the substrate temperature ranges from 250 to 400 ° C. when depositing the thin film. In claim 1, Alkyl zinc aminoalkyl acid is vaporized at 60 to 90 캜.

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