KR100704914B1 - Process for preparing nickel oxide thin film by metal organic chemical vapor deposition using nickelii aminoalkoxide - Google Patents

Abstract

The present invention relates to a method for preparing a nickel oxide thin film by metal organic chemical vapor deposition (MOCVD) using a nickel aminoalkoxide precursor of Formula 1 as a raw material of nickel, according to the method of the present invention. Compared to the conventional metal organic chemical vapor deposition method, a high quality nickel oxide thin film can be obtained under milder process conditions.

[Formula 1]

Wherein m is an integer ranging from 1 to 3, and R ¹ , R ² , R ³ and R ⁴ are independently C ₁ -C ₄ linear or branched alkyl groups.

Nickel Oxide Thin Films, MOCVD, Nickel Aminoalkoxides

Description

PROCESS FOR PREPARING NICKEL OXIDE THIN FILM BY METAL ORGANIC CHEMICAL VAPOR DEPOSITION USING NICKEL (II) AMINOALKOXIDE}

1 is an X-ray diffraction pattern of the nickel oxide thin film prepared in Example 1,

2 is an X-ray diffraction pattern of the nickel oxide thin film prepared in Example 2,

3 is a scanning electron micrograph of the nickel oxide thin film prepared in Example 2, and the substrate temperature is 230 ° C., FIG. 3B is 285 ° C., FIG. 3C is 360 ° C., 3D is 377 ° C., and FIG. 3E is 410 ° C. ego,

4 is an X-ray photoelectron spectroscopy spectrum of the nickel oxide thin film prepared in Example 3. FIG.

The present invention relates to a method for manufacturing a nickel oxide thin film, and more particularly, a substrate using metal organic chemical vapor deposition (MOCVD) using nickel aminoalkoxide as a nickel source and oxygen gas as an oxygen source. The present invention relates to a method for producing a nickel oxide thin film having excellent characteristics.

Nickel oxide is currently a p -type transparent conductive thin film, chemical sensor, electrochromic display, antiferromagnetic layer of spin-valve thin film, and coating of lithium ion battery due to its excellent electrical, magnetic and optical properties. Its applications vary from materials to high-k materials by doping lithium and aluminum (H. Sato et al., "Transparent conducting p-type NiO thin films prepared by magnetron sputtering," Thin Solid Films , 1993 , 236, 27 -31; I. Hotovy et al., "Preparation and characterization of NiO thin films for gas sensor applications," Vacuum , 2000 , 58, 300-307; SA Makhlouf et al., "Humidity sensing properties of NiO / Al ₂ O ₃ nanocomposite materials, " Solid State Ionic , 2003 , 164, 97-106; JSEM Svensson et al.," Electrochromic hydrated nickel oxide coatings for energy efficient windows: Optical properties and coloration mechanism, " Appl . Phys. Lett . , 1986 , 49, 1566-1568; S. Yamada et al., "Electrochromic proper ties of sputtered nickel-oxide films " J. Appl . Phys. , 1988 , 63, 2116-2119; H. Yamane et al.," Differential type giant magnetoresistive memory using spin-valve film with a NiO pinning layer, " J. Appl . Phys. , 1998 , 83, 4862-4868; SS Lee et al., "Field sensitivity in spin-valve sandwiches with antiferromagnetic NiO films," IEEE Tran . Magn . , " 1996 , 32, 3416-3418 and Y. Lin et al.," High permittivity Li and Al doped NiO ceramics, " Appl . Phys. Lett . , 2004 , 85, 5664-5666). resistance switching has been reported for a long time (see JF Gibbons et al., "Switching properties of thin NiO films," Solid-State Electron. , 1964 , 7 , 785-790). As the necessity of memory devices arises, various studies have been conducted for the purpose of resistance RAM (RRAM) device formation using resistance switching or conductivity switching of metal oxide thin films. Compared with the excellent resistance switching characteristics such as relatively high on / off ratio, the NiO thin film is known to have the highest potential for device demagnetization (S. Seo et al., “Reproducible resistance switching in polycrystalline NiO films, " Appl . Phys. Lett . , 2004 , 85, 5655-5657; S. Seo et al.," Conductivity switching characteristics and reset currents in NiO films, " Appl . Phys. Lett . , 2005 , 86, 093509 Attention is focused on the production of excellent nickel oxide thin films.

A method of forming a nickel oxide thin film on a substrate may be classified into physical deposition methods such as sputtering and chemical deposition methods such as metal organic chemical vapor deposition (MOCVD).

Chemical vapor deposition is easier to grow thin films with a smaller surface roughness and relatively uniform to large area substrates as compared to physical vapor deposition. In particular, the MOCVD method is capable of larger area deposition than the sputtering method, has excellent step coverage in a complicated structure having a three-dimensional shape, and has a small surface roughness.

The most important factor for the growth of high quality thin film by MOCVD is the selection of good precursors that can be properly applied to the process. Therefore, for the chemical deposition of nickel oxide, the synthesis of excellent precursor materials and the development of a suitable thin film manufacturing process have become important research subjects.

Only a few studies have been reported so far to apply the MOCVD method to the production of nickel oxide thin films (W.-c. Yeh et al., "Chemical Vapor Deposition of Nickel Oxide Films from Bis-π-Cyclopentadienyl-Nickel , " Jpn . J. Appl . Phys. Part 1 , 1997 , 36, 6884-6887; and J.-K. Kang et al.," Chemical vapor deposition of nickel oxide films from Ni (C ₅ H ₅ ) ₂ / O ₂ , " Thin Solid Films , 2001 , 391, 57-61).

As nickel compounds applied to MOCVD, several compounds such as Ni (acac) ₂ (acac = acetylacetonato) and Ni (C ₅ H ₅ ) ₂ have been introduced. Among them, it is reported that Ni (acac) ₂ is not able to deposit NiO thin films without plasma assistance, and many defects due to plasma are formed inside the deposited thin films. (W.-c. Yeh et al., "Chemical Vapor Deposition of Nickel Oxide Films from Bis-π-Cyclopentadienyl-Nickel," Jpn . J. Appl . Phys. Part 1 , 1997 , 36, 6884-6887). In addition, since Ni (C ₅ H ₅ ) ₂ has a high manufacturing cost and a strong bonding force of C ₅ H ₅ ⁻ ions decomposed during deposition, the Ni (C ₅ H ₅ ) ₂ may be easily incorporated into the thin film to act as a carbon pollutant.

Therefore, in order to alleviate the above-mentioned disadvantages, it is necessary to develop a nickel source having a moderate reactivity to an oxygen source, capable of depositing at a low temperature, and low carbon pollution, and developing a suitable thin film manufacturing process using the same.

Accordingly, the present invention is to provide a nickel oxide thin film having a good surface uniformity, good coverage, good carbon contamination and good quality by the MOCVD method using a nickel nickel alkoxide, a new precursor for nickel.

In order to achieve the above technical problem, the present invention provides a method for producing a nickel oxide thin film by the MOCVD method using a nickel aminoalkoxide represented by the following formula (1) together with an oxygen source as a nickel precursor.

[Formula 1]

Where

m is an integer ranging from 1 to 3, preferably 1 or 2, and R ¹ , R ² , R ³ and R ⁴ are independently C ₁ -C ₄ linear or branched alkyl groups.

Nickel according to the present invention in comparison to Ni (acac) ₂ and Ni (C ₅ H ₅ ) ₂ compounds, which are not capable of depositing nickel oxide without the aid of plasma or which cause carbon contamination in the nickel oxide thin film due to decomposing during deposition The aminoalkoxide compound has a higher reactivity with respect to the oxygen source, so that the MOCVD process can be performed even at a low temperature, and when the nickel oxide thin film is manufactured using the nickel aminoalkoxide compound, there are few impurities such as carbon and the surface roughness of the thin film is small. And it was possible to prepare a nickel oxide thin film with uniform crystal grains.

Particularly, in the nickel aminoalkoxide compound, bis (dimethylamino-2-methyl-2-butoxy) nickel (II) [Ni (dmamb) ₂ ] of the following Chemical Formula 2 is a liquid at room temperature, and the compound is used as a nickel source. When used, it is not necessary to heat a bubbler (bubbler) for storing the nickel source, and does not condense when transported to the reactor using a carrier gas, there is an advantage that can maintain a constant amount flowing into the reactor.

[Formula 2]

The nickel oxide thin film manufacturing process according to the present invention specifically includes the following steps:

1) simultaneously supplying a gas containing nickel aminoalkoxide as a nickel source and an oxygen element as an oxygen source to a MOCVD reactor to form a nickel oxide thin film by pyrolysis on a substrate,

2) controlling the structural, chemical and electrical properties of the growing nickel oxide thin film by controlling the deposition temperature and deposition pressure.

The present invention is explained in more detail below.

In the method for forming a nickel oxide thin film by the MOCVD method, a nickel oxide thin film is formed by simultaneously supplying a nickel source and an oxygen source to the substrate while maintaining a constant temperature of the substrate to induce thermal decomposition of the nickel source and reaction with the oxygen source. Form.

In the method of the present invention, a silicon (Si) wafer and a silicon wafer in which SiO ₂ , platinum (Pt), ruthenium (Ru), ruthenium oxide (RuO ₂ ), and iridium (Ir) are deposited may be used as a substrate. . More preferably, a silicon wafer deposited with platinum is used.

The precursor of nickel used in the present invention is represented by Ni [OCR ¹ R ² (CH ₂ ) _m NR ³ R ⁴ ] ₂ , which is nickel hexaammine dichloride [Ni (NH ₃ ) ₆ as shown in Scheme 1 below. Cl ₂ ] compounds and 2 equivalents of alkali metal salts of MOCR ¹ R ² (CH ₂ ) _m NR ³ R ⁴ , where M is Li or Na, can be obtained by refluxing in toluene to induce a ligand substitution reaction ( See Korean Patent Application No. 2003-0069585).

Scheme 1

[Ni (NH ₃ ) ₆ Cl ₂ ] + 2 Na [OCR ¹ R ² (CH ₂ ) _m NR ³ R ⁴ ] →

Ni [OCR ¹ R ² (CH ₂ ) _m NR ³ R ⁴ ] ₂ + 2 NaCl + 6 NH ₃

As the gas containing oxygen element as the oxygen source, one selected from oxygen (O ₂ ), water (H ₂ O), ozone (O ₃ ), NO, NO ₂ is used, but the ease of production, economics and In view of safety, oxygen gas is most preferred.

In the method for producing a nickel oxide thin film according to the present invention, the temperature of the substrate varies depending on the nickel aminoalkoxide, but is selected within the range of 200 ° C. to 500 ° C., and when [Ni (dmamb) ₂ ] is used, the preferred range is 230 ° C. To 380 ° C.

The temperature of the nickel source is determined according to the characteristics of the nickel source, but it is better to select and maintain it in a range from room temperature to 100 ° C.

The synthesis experiment is carried out in an inert argon or nitrogen atmosphere using a glove box or Schlenk line, and the structure and physical properties of the reaction product obtained in the synthesis are characterized by ¹ H nuclear magnetic resonance (NMR), Can be identified using carbon nuclear magnetic resonance ( ¹³ C NMR), elemental analysis (EA), mass spectroscopy, thermogravimetric / differential thermal analysis (TG / DTA) have.

The present invention will be described in more detail with reference to the following Examples. However, the following examples are merely examples of the present invention, and the claims of the present invention are not limited thereto.

Formation of Nickel Oxide Thin Films by Metal Organic Chemical Vapor Deposition

A silicon wafer and a silicon wafer coated with platinum were used as the substrate. [Ni (dmamb) ₂ ] was used as the nickel source. The nickel source temperature was 30 ° C., the substrate temperature was 230 ° C. to 430 ° C., and the deposition pressure was 500 mTorr. A thin film was prepared.

<Example 1>

The platinum / silicon substrate on which the nickel oxide thin film was to be deposited was washed sequentially with acetone, ethanol and deionized water. After the prepared substrate was mounted on a heater inside the reactor made of stainless steel, the reactor was evacuated using a vacuum pump so that the internal pressure was 10 ⁻³ Torr. As a nickel source, bis (dimethylamino-2-methyl-2-butoxy) nickel (II) [Ni (dmamb) ₂ ] prepared according to the method described in Korean Patent Application No. 2003-69585 was maintained at 30 ° C. And then injected into the reactor at a flow rate of 10 cc / min with carrier gas argon. High purity oxygen gas (99.999%) was flowed into the oxygen source at a flow rate of 100 cc / min and the nickel source and oxygen source were just above the substrate to deposit a thin film for 30 minutes. At this time, the substrate temperature was maintained at 330 ℃, the pressure of the reactor was maintained at 5 × 10 ^-1 Torr.

The X-ray diffraction pattern of the thin film thus prepared is shown in FIG. 1. The peaks seen near 2θ = 37 °, 80 ° in FIG. 1 are all peaks corresponding to the (111) plane of NiO (see JCPDS 36-1451). From this result, it can be seen that the nickel oxide thin film prepared in Example 1 is nickel monoxide (NiO).

<Example 2>

Nickel oxide thin films were deposited at various platinum substrate temperatures under the same conditions as in Example 1. The supply time of Ni (dmamb) ₂ and oxygen gas was fixed at 30 minutes. According to the X-ray diffraction pattern of FIG. 2, only peaks corresponding to the (111) plane of NiO appear in the region of the substrate temperature 230 to 450 ° C. in the same manner.

3 is a scanning electron microscopy (SEM) photograph of the nickel oxide thin film prepared at each substrate temperature in Example 2. FIG. On the surface of the thin film obtained by varying the substrate temperature from 230 ° C to 377 ° C, there is little difference in grain size, but it can be seen that the crystallization proceeds gradually. However, in the substrate of 400 ° C. or higher, the surface is rough and partially three-dimensional crystal phases are observed (see FIG. 3 (e)). From this result, it can be seen that a uniform nickel oxide thin film is formed in the temperature range of the substrate temperature of 230 to 380 ° C. .

<Example 3>

Under the same conditions as in Example 1, a nickel oxide thin film was deposited using only a substrate as a Si wafer. 4 is an X-ray photoelectron spectroscopy spectrum of a nickel oxide thin film of about 360 A thickness formed by depositing the substrate at 300 ° C. for 30 minutes in Example 3. FIG. Spectra were obtained after the surface was cleaned by argon ion sputtering for 5 minutes to remove carbon contamination on the sample surface. Only the characteristic optoelectronic peaks of nickel and oxygen were observed in this spectrum, and the ratio of nickel and oxygen was measured to be about 1: 1. In addition, the shape and binding energy values of the Ni 2p cabinet level spectrum show typical NiO (Ni monoxide) formation. In particular, near 284 eV, there are few C 1s peaks indicating carbon contamination. The contamination of carbon adversely affects the properties of the nickel oxide thin film. From this, it was confirmed that the nickel oxide thin film having almost no carbon contamination was produced due to almost complete surface reaction under the conditions of Example 3.

In Examples 1, 2, and 3, a silicon wafer with platinum or a natural oxide film was used as a substrate, but a wafer including a metal such as iridium (Ir) and ruthenium (Ru) or a metal oxide such as RuO ₂ was used. The growth rate is only slightly different and the overall trend is the same.

As described above, the MOCVD method of manufacturing a nickel oxide thin film using nickel aminoalkoxide according to the present invention includes Ni (acac) ₂ and Ni (C ₅ H ₅ ) ₂ compounds having high carbon contamination, which can be deposited using plasma. Compared with the MOCVD process, the surface roughness of the thin film is smaller and the crystal grains of nickel oxide are more uniform. In addition, since the contamination of carbon that adversely affects the electrical properties in the thin film is negligible and the vaporization temperature of the precursor is much lower than that of using other precursors, it is possible to produce a nickel oxide thin film having a relatively simple quality.

Claims (9)

In the method for producing a nickel oxide thin film on a substrate using a nickel source and an oxygen source, a nickel aminoalkoxide represented by the following formula (1) is used as the nickel source, and oxygen gas (O ₂ ), water (H ₂ O) as the oxygen source. , Ozone (O ₃ ), NO, or NO ₂ using, the method for producing a nickel oxide thin film, characterized in that the temperature of the substrate is kept constant in the range of 200 to 500 ℃. [Formula 1]

(Wherein m is an integer ranging from 1 to 3 and R ¹ , R ² , R ³ and R ⁴ are independently C ₁ -C ₄ linear or branched alkyl groups). In claim 1, Method of producing a nickel oxide thin film, characterized in that m in formula (1) 1 or 2. In claim 2, Nickel aminoalkoxide is a method for producing a nickel oxide thin film, characterized in that the compound of formula (2). [Formula 2]

delete In claim 1, A method for producing a nickel oxide thin film, which uses oxygen gas (O ₂ ) as an oxygen source. In claim 1, A method for producing a nickel oxide thin film, wherein the temperature of the nickel source is kept constant in the range from room temperature to 100 ° C. delete In claim 1, A method for producing a nickel oxide thin film, characterized in that a silicon wafer is used as a substrate or a silicon wafer is deposited on a material selected from SiO ₂ , RuO ₂ , platinum (Pt), iridium (Ir) or ruthenium (Ru). In claim 8, A method for producing a nickel oxide thin film, comprising using a silicon wafer on which platinum is deposited as a substrate.

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