RU2436727C2 - Method to produce nanocrystalline films of rutile - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to a technology of production of nanocrystalline films of rutile and may be used to develop semiconductor instruments, and also in production of protective and other functional coatings. The method includes formation of a nanocrystalline film of titanium by method of magnetron spraying or electron-beam evaporation on the oxidated surface of a plate from silicon and film oxidation. Oxidation is carried out in an oxidising gas medium during pulse irradiation of the titanium film by photons using pulse xenon bulbs with the radiation range of 0.2-1.2 mcm for 1.6-1.8 s with pulse duration of 10^-2 s and a dose of radiation arriving to the film equal to 230 - 260 J·cm^-2 .

EFFECT: increased rate of oxidation, reduced thermal load at substrate, increased density of produced film.

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Description

The invention relates to a technology for producing films of semiconductor and dielectric materials and can be used to create semiconductor devices, protective and functional coatings.

The relevance of developing promising methods for producing films of titanium dioxide (rutile) remains due to the fact that it is a wide-gap semiconductor and one of the most effective catalysts (Fujishima A., Zhang X. Tryk DA TiO ₂ photocatalysis and related surface phenomena // Surface Science Reports . 2008. Vol.63. No. 12. P.515-582). Rutile nanocrystalline films are also promising for creating storage devices that use the phenomenon of resistive switching (Sawa A. Resistive switching in transition metal oxides // Materialstoday. 2008. Vol.11; No. 6. P.28-36).

Known methods for producing films of titanium oxides on substrates of various types: oxidation of a metal surface activated by heat treatment at high temperatures in an oxidizing environment (patent RU 2369663, IPC С23С 8/10, 2009; Bai A.S., Liner D.I., Slesareva E.N., Tsypin M.I. Oxidation of titanium and its alloys (Moscow: Metallurgy, 1970), thermal oxidation of Ti films obtained by thermal evaporation and cathodic atomization (Zhang Y., Ma X., Chen P., Yang D Crystallization behaviors of TiO ₂ films derived from thermal oxidation of evaporated and sputtered titanium films // J. of Alloys and Compounds. 2009. Vol.480. No. 2. P.938-941), anodirova (patent SU 1156409, IPC C25D 11/26, 1996), chemical vapor deposition (CVD process) (patent RU 2351688, IPC C23C 16/40, C03C 17/245, 2004), combined isothermal and laser processing ( photon energy 1.96 eV) of Ti films in a vacuum of 3 · 10 ^-4 Pa (Chaplanov AM, Shibko AN The influence of laser radiation on the kinetics of oxidation of titanium films during heat treatment // Quantum Electronics. - 1993.- t.20. - No. 2. - S.191-193), ion implantation of oxygen, followed by heat treatment (patent RU 2340038, IPC H01L 21/265, 2008), irradiation of Ti films with IR radiation (photon energy 1.17-1.24 eV) together with heat treatment (Pribytkov D.M., Malevskaya L.A., Khoviv AM Influence of IR radiation on the oxidation of thin films of the Cu-Ti system on a Si substrate at reduced oxygen pressure // Inorganic Materials. 2004. V. 40. No. 10. 1220 -1223; Barsukova L.V., Anokhin V.Z., Khoviv AM Thermal and laser-thermal oxidation of titanium in the temperature range 773-973K // Known RAS. Inorganic Materials. T. 28. No. 5. 1992. C .1019 -1021).

The main disadvantage of these methods is the long duration of the process and the high thermal load on the substrate. It is known that the oxidation process at elevated temperatures is accompanied by the formation and growth of structural disturbances, violation of the substrate composition (Dvurechensky A.V., Kachurin G.A., Nidaev E.V., Smirnov L.S. Pulse annealing of semiconductor materials. M: Science. - 1982. - 208 p .; Borisenko V.E. Solid-state processes in semiconductors under pulsed heating / Mn .: Navuka i tehnika. - 1992. - 248 p .; Labunov V.A., Borisenko V.E., Gribkovsky VV Pulse heat treatment of materials of semiconductor electronics with incoherent light // Foreign Electr constant prices Appliances -. 1983. -. №1 S.3-57).

The closest analogue to the claimed solution is the method for producing oxide films proposed in the work (Pribytkov D.M., Malevskaya L.A., Khoviv AM Influence of IR radiation on the oxidation of thin films of the Cu-Ti system on a Si substrate under reduced oxygen pressure // Inorganic materials. 2004. T. 40. No. 10. 1220-1223). It includes the following stages:

applying a metal film by magnetron sputtering onto a silicon substrate; placing an oxidizable heterostructure in the reactor chamber;

creating a vacuum (p = 10 ^-3 Pa) in the reactor chamber;

creating an oxygen stream in a vacuum chamber (p = 0.4 Pa);

synthesis of the oxide film occurs as a result of irradiation of the substrate with LG-1000 halogen lamps (maximum radiation intensity at a wavelength of 1 μm), together with thermal annealing at a temperature of 400 ° C for 10-60 min.

The disadvantage of this method is the long duration of the process, which makes it equivalent to the classical thermal oxidation.

The technical result is an increase in the rate of the oxidation process, a decrease in the thermal load on the substrate due to localization of radiation in the metal (in the skin layer), an increase in the density of the oxide and the formation of a nanocrystalline structure.

The technical result is achieved in that a method for producing a rutile nanocrystalline film includes magnetron sputtering or electron beam evaporation of a titanium nanocrystalline film on an oxidized surface of a silicon wafer and oxidizing the film in an oxidizing gas medium when it is pulsed by photons using pulsed xenon lamps with a radiation range 0.2-1.2 μm, while the pulsed irradiation of the film is carried out for 1.6-1.8 s with a pulse duration of 10 ^-2 s and the dose of radiation entering the film from 230 to 260 J · cm ^-2 .

The nanocrystalline structure of the initial titanium film is necessary in order to activate oxidation not only on the surface, but also in the bulk of the film; this leads to a significant increase in the speed of the process, controlled by the rapid diffusion of oxygen along grain boundaries over the entire thickness of the film. The absence of a concentration gradient across the thickness precludes the formation of concomitant lower oxides.

Reducing the temperature load on the heterostructure is achieved by a short processing time (pulse duration 10 ^-2 s, pulse duration 1.6-1.8 s).

The method is implemented as follows.

A titanium film is deposited on an unheated substrate from an oxidized silicon wafer by magnetron sputtering or electron beam evaporation in ultrahigh vacuum (no worse than 10 ^-7 Pa), in the second case the film is more compact. To prevent carbidization of the film during application in both versions, the vacuum chamber of the installation is pumped out using oil-free means.

Oxidation of the film is carried out on a modernized installation of pulsed photonic processing of VOLP - 1 (AS USSR, No. 1228716, CL 21/268, 1984). The installation consists of a working chamber, in the frontal plane of which xenon lamps INP 16 / 250A are installed (spectrum in the wavelength range 0.2-1.2 microns); systems for filling the gas mixture into the working chamber; control unit. The oxidized sample is placed in the working chamber parallel to the plane in which the lamps are located. In the working chamber using a gas inlet system creates a stream of gas oxidizing agent (oxygen or air). Pulse photon processing (IFO) is carried out by pulse packets with a duration of 10 ^-2 s for 1.6-1.8 s. In this case, the energy flux density of the radiation entering the sample (E _AND ) varies in the range of 230-260 J · cm ^-2 .

The effect of irradiation with photons in addition to thermal is to generate an excess concentration of vacancies in the metal film, which leads to an additional acceleration of diffusion processes and, as a result, to an increase in the rate of the oxidation reaction.

Example 1

The initial Ti films with a thickness of up to 0.5 μm were deposited on the surface of thermally oxidized KDB-10 (111) silicon wafers by magnetron sputtering of a VT-1-00 grade titanium target in an argon atmosphere (p = 0.5 Pa) at room temperature of the substrate on the setup Oratorio-29. Working pressure was achieved using oil-free pumping means (cryogenic pump), the magnetron power was 2 kW.

The thickness of the films was varied by the speed of movement of the plates along the conveyor under the magnetron. The surface of the Si wafers before being placed in a vacuum unit was treated in a peroxide-ammonia mixture H ₂ O ₂ : NH ₄ OH = 6: 1 and washed in deionized water, followed by drying in a centrifuge. IFO in the air atmosphere was carried out by pulse packets with a duration of 10 ^-2 s for 1.6-1.8 s. In this case, the energy flux density of the radiation entering the sample (E _AND ) varies in the range of 110-260 J · cm ^-2 .

The phase composition of the films after IFR was studied by X-ray diffraction on an ARL X-TRA instrument from Termo-techno, the surface morphology of transverse cleaved heterostructures was studied by SEM using a JEOL JSM-6380 instrument, and also by AFM using a Solver P47 scanning probe microscope. The thickness of oxide films was measured by ellipsometry on an LEF-3M-1 device.

Figure 1 - characteristic of the phase composition of the initial film (a), the thickness of the layers of SiO ₂ and Ti (b), the surface relief (c) and the substructure (insert) of the initial heterostructure Ti / SiO ₂ / Si.

The calculation of the X-ray diffraction patterns showed that the starting films did not contain oxide phases. The thickness of the initial Ti films is 0.53 μm (Fig.1B). From diffraction and from the TEM image fragment (FIG. 1 c), it follows that the Ti films have a nanocrystalline structure.

Figure 2 shows x-ray diffraction patterns characterizing the phase composition of Ti films that have passed IFR in air at various values of the light flux energy density E _AND . IFO at Е _И = 110-170 J · cm ^-2 led to the formation of a two-phase oxide (Ti ₂ O ₃ with a rhombohedral lattice (а = 0.542 nm) (JCPDS-International Center for Diffraction Data. - 1998) and TiO ₂ with a tetragonal lattice (a = 0.4593 nm, c = 0.2959 nm (rutile)) with partial preservation of the metal phase (Fig.2A). Further increase in E _And to 260 J · cm ^-2 leads to the formation of single-phase films containing only the higher phase oxide - TiO ₂ (rutile) (figb).

Figure 3 shows microphotographs of the transverse cleavage (a) and the surface topography (b) of the heterostructure that underwent an IFR at E _И = 260 J · cm ^-2 .

From the data of ellipsometry (the thickness of the oxide film was 1.08 μm) and from a comparison of the images of the cleaved surfaces (Figs. 1b and 3a), it follows that the process of oxidation of the film is complete.

As can be seen from fig.3b, as a result of IFI there is an increase in surface roughness; the dimensions of the lateral heterogeneities of the relief increase from 0.1 to 0.5 μm, respectively, at 170 and 230 J / cm ² .

A study of the structure showed that the films are continuous. Thereby, an article is obtained which is an oxidized silicon wafer with a titanium dioxide film with a rutile structure on its surface.

Implementation of the proposed method allows to obtain products consisting of a substrate and a single-phase nanocrystalline rutile film formed on its surface. In comparison with known methods, the proposed technical solution provides a simplification of the technology and a significant reduction in the manufacturing time of the product.

Claims (1)

A method of producing a rutile nanocrystalline film, comprising the formation of a nanocrystalline titanium film on an oxidized surface of a silicon wafer by magnetron sputtering or electron beam evaporation and oxidizing the film in an oxidizing gas medium when it is pulsed by photons using pulsed xenon lamps with a radiation range of 0.2-1.2 μm, while pulsed irradiation of the film is carried out for 1.6-1.8 s with a pulse duration of 10 ^-2 s and a dose of radiation entering the film from 230 to 260 J cm ^-2 .

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