KR19990008863A - Deposition Method of Titanium Dioxide Using Titanium Butyrate - Google Patents

Abstract

The present invention relates to a method for chemically depositing titanium dioxide using titanium-butyrate. The titanium dioxide film prepared by the method of the present invention has a low carbon content and can form a rutile phase structure even at a low temperature of about 400 ° C.

Description

Deposition Method of Titanium Dioxide Using Titanium Butyrate

The present invention relates to a method for depositing titanium dioxide onto a substrate using titanium thi-butyl acid ( tert -butyl acid).

Titanium dioxide has a high refractive index, and titanium dioxide films are used as optical materials for multilayer interference filters, antireflective coatings, optical waveguides, and the like. Its high dielectric constant can also be used in thin film capacitors. It is also used to purify air and water using photocatalytic effects or to remove contaminants from coating surfaces [A. Heller and JR Brock, Materials and methods for photocatalyzing oxidation of organic compounds on water, US Patent No. 5,256,616; And T. Watanabe, A. Kitamura, E. Kojima, C. Nakayama, K. Hashimoto and A. Fujishima, Photocatalytic activity of TiO ₂ thin film under room light, Photocatalytic Purification and Treatment of Water and Air , DF Ollis and H. Al-Ekabi eds., Elsevier (1993) pp 747-751].

Chemical vapor deposition of titanium dioxide using titanium chloride, titanium isopropyl acid or ethyl acetate as a raw material of titanium is well known [HO Pierson, Handbook of Chemical Vapor Deposition (CVD) , Noyes Publications (Park Ridge, New Jersey, USA, 1992), pp 236-237. However, since titanium chloride is extremely sensitive to moisture to form a powder, it is difficult to handle and there is a problem in that an oxygen source must be used together. Titanium ethylate is inconvenient to use for chemical vapor deposition because it is a solid at room temperature. Titanium isopropyl acid is a liquid at room temperature and atmospheric pressure and has the highest vapor pressure among known titanium alkylate compounds, but a large amount of carbon tends to be contained in the titanium dioxide film chemically deposited using titanium isopropyl acid as a raw material. The boiling point of titanium isopropyl acid is 91.3 ^o C at 5 mmHg and the boiling point of titanium titanyl titanate is 93.8 ^o C at 5 mmHg [DC Bradley, RC Mehrotra, and PD Gaur, Metal Alkoxides , Academic Press, (London, 1978 )]. Therefore, tert -butyrate is also easily vaporized at room temperature and can be used for chemical vapor deposition. However, there have been no reports of synthesizing titanium dioxide using tert -butyrate as a raw material.

The inventors have found that the titanium dioxide film chemically deposited using titanium-butyl butylate contains much less carbon than the titanium dioxide film chemically deposited using titanium isopropyl acid as a raw material under the same conditions.

When the titanium dioxide film is coated on a substrate, an amorphous phase or ananatase phase is generally formed at low temperatures, and a rutile phase is formed at high temperatures. Among these, the rutile phase has a higher refractive index than the anatas phase having a density of 4.26 g / cm 3 and 3.84 g / cm 3, which is advantageous for use as an optical material. have.

In the case of chemical vapor deposition using titanium isopropyl acid as a raw material, only the Anatha phase appears when the temperature of the substrate is less than 600 ^o C. In the case of plasma assisted chemical vapor deposition, the anatase phase and the rutile phase appear to be mixed. ^o It is known to heat above C [HLM Chang, TJ Zhang, H. Zhang, J. Guo, HK Kim, and DJ Lam, Epitaxy, microstructure, and processing-structure relationships of TiO ₂ thin films grown on sapphire (0001 ) by MOCVD, Journal of Material Research , 8 , 2634 (1993); H.-Y. Lee and H.-G. Kim, The role of gas-phase nucleation in the preparation of TiO ₂ films by chemical vapor deposition, Thin Solid Films , 229 , 187 (1993); GA Battiston, R. Gerbasi, M. Porchia, and A. Marigo, Influence of substrate on structural properties of TiO ₂ thin films obtained via MOCVD, Thin Solid Films , 239 , 186 (1994); YH Lee, KK Chan, and MJ Brady, Plasma enhanced chemical vapor deposition of TiO ₂ in microwave-radio frequency hybrid plasma reactor, Journal of Vacuum Science and Technology A, 13 , 596 (1995); And J. Yan, DC Gilmer, SA Campbell, WL Gladfelter, and PG Schmid, Structural and electrical characterization of TiO ₂ grown from titanium tetrakis-isopropoxide (TTIP) and TTIP / H ₂ O ambients, Journal of Vacuum Science and Technology B , 14 , 1706 (1996). However, the present inventors were able to chemically deposit a titanium dioxide film on rutile even when the substrate temperature was 400 ^° C. when tert -titanium butylate was used as a raw material.

An object of the present invention is to provide a method for depositing titanium dioxide using titanium thi-butylate.

1 is an X-ray diffraction spectrum of a titanium dioxide film obtained in Examples and Comparative Examples of the present invention (a: Example 1; b: Example 2; c: Comparative Example 1; and d: Comparative Example 2).

In order to achieve the above object, the present invention provides a method of chemically depositing a titanium dioxide film on a substrate by vaporizing titanium thi-butyl acid.

Hereinafter, the present invention will be described in detail.

Substrates used for depositing the titanium dioxide film of the present invention include, but are not limited to, silicon single crystal, glass, and the like.

Titanium butyrate used in the present invention can be obtained by reacting titanium chloride with 4 equivalents of potassium thi-butylate in hexane or ethyl ether and distillation under reduced pressure as in the following scheme. It can also be purchased commercially.

TiCl ₄ + 4KOBu ^t → Ti (OBu ^t ) ₄ + 4KCl

The method of depositing titanium dioxide on a substrate using titanium-butyrate is as follows.

Titanium butyrate is vaporized at room temperature to deposit a titanium dioxide film on a substrate heated to 250-400 ° C. without using a carrier gas. The temperature where the vaporized titanium-butyrate passes is maintained at room temperature. The pressure inside the reactor before vaporizing the titanium titanium butyrate is several tens of mbar. The pressure increases several times to ten times when titanium thibutylate is introduced into the reactor to start chemical vapor deposition.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited only to the following examples. The elemental composition and phase structure of the titanium dioxide films prepared in Examples and Comparative Examples of the present invention can be known from Auger spectrum and X-ray diffraction pattern, respectively.

Example 1

Titanium butyrate was vaporized at room temperature and subjected to chemical vapor deposition on a Si (100) substrate heated to 250 ° C. without carrier gas for 2 hours. While the deposition continued, interference colors by the transparent oxide thin film appeared in turn on the substrate surface. The elemental composition of the film calculated from the signal of the Auger spectrum obtained after sputtering the surface of the deposited titanium dioxide film with Ar ⁺ ions for 60 seconds was titanium: oxygen: carbon = 0.34: 0.61: 0.05. As can be seen in 1 (a), X-ray diffraction pattern, the 2θ = 25.3, it showed diffraction peaks corresponding to 38.6, respectively Ana ^o Tasman on the (101), (112) crystal plane in the obtained titanium dioxide film.

Example 2

Titanium butyrate was vaporized at room temperature and subjected to chemical vapor deposition on a Si (100) substrate heated to 400 ° C. without a carrier gas for 2 hours. While the deposition continued, interference colors by the transparent oxide thin film appeared in turn on the substrate surface. The elemental composition of the film calculated from the signal of Auger spectrum obtained after sputtering the surface of the deposited film with Ar + ions for 60 seconds was titanium: oxygen: carbon = 0.33: 0.56: 0.11. As can be seen in FIG. 1 (b), the X-ray diffraction pattern obtained from the titanium dioxide film includes (110), (101), (211), and (002) at 2θ = 27.5, 36.1, 54.3, and 62.7 ^o , respectively. A small diffraction peak due to the (101) crystal plane of the anatas phase was observed at 2θ = 25.3 ^o along with the diffraction peak due to the crystal plane).

Comparative Example 1

Titanium isopropyl acid was vaporized at room temperature and subjected to chemical vapor deposition on a Si (100) substrate heated to 250 ° C. without carrier gas for 2 hours. While the deposition continued, interference colors by the transparent oxide thin film appeared in turn on the substrate surface. The elemental composition of the film calculated from the signals of Auger spectrum obtained after sputtering the surface of the deposited film with Ar ⁺ ions for 60 seconds was titanium: oxygen: carbon = 0.32: 0.58: 0.10. As can be seen in FIG. 1 (c), the X-ray diffraction pattern obtained from the titanium dioxide film includes 2101 = 25.3, 38.6, 55.1, and 95.2 ^o at (101), (112), (211), ( 321) Diffraction peaks due to the crystal plane appeared.

Comparative Example 2

Titanium isopropyl acid was vaporized at room temperature and subjected to chemical vapor deposition on a Si (100) substrate heated to 400 ° C. without a carrier gas for 2 hours. While the deposition continued, interference colors by the transparent oxide thin film appeared in turn on the substrate surface. After the deposition was completed, the film formed on the substrate was black in color. The elemental composition of the film calculated from the signal of Auger spectrum obtained after sputtering the surface of the deposited film with Ar ⁺ ions for 60 seconds was titanium: oxygen: carbon = 0.30: 0.54: 0.16. As can be seen from Fig. 1 (d), the X-ray diffraction pattern obtained from the titanium dioxide film showed large diffraction peaks due to (101) and (224) crystal planes on the anatase phase at 2θ = 38.6 and 82.7 ^o , respectively.

The method of the present invention using titanium-butyrate as a raw material of titanium dioxide can not only obtain a titanium dioxide film containing less carbon than the conventional method using titanium isopropyl acid as a raw material, but also a low temperature of about 400 ° C. Also has the advantage that the rutile phase can be obtained.

Claims (4)

A method of vaporizing titanium thi-butyl carbonate to form a titanium dioxide film on a substrate by chemical vapor deposition. The method of claim 1, Characterized in that the temperature of the substrate is in the range of 250 to 400 ℃. The method of claim 1, And wherein said substrate forms a rutile titanium dioxide film at < RTI ID = 0.0 > 400 C. < / RTI > The method of claim 1, The substrate is silicon single crystal.