CN101235484A - Method for preparing semi-metal ferroferric oxide thin film - Google Patents

Abstract

The invention relates to a method for preparing semimetal ferroferric oxide thin film, which belongs to the technical field of preparing magnetic film. The method which is provided by the invention comprises: utilizing magnetron sputtering equipment, adopting ceramic Fe2O3 as target material, heating a substrate to 500-700DEG C, supplying mixed gas of H2 and Ar to a vacuum chamber as working gas, utilizing a mass flowmeter to keep the mass ratio between the H2 and the Ar to be 0.1-0.15, keeping the sputtering pressure to be 0.5-1Pa after discharging, keeping the sputtering power to be 100W, and controlling the film thickness through controlling the depositing time according to the demands. The method of the invention has the advantages that the cost is low, high temperature is not needed, and the requirements for sintering equipment are comparatively low, which is beneficial for Fe3O4 large scale production, and the like.

Description

A kind of preparation method of semi-metal ferroferric oxide thin film

Technical field

The invention belongs to the thin magnetic film preparing technical field, be specifically related to a kind of magnetically controlled sputter method of in reducing atmosphere, using and prepare Fe₃O ₄The method of film.

Background technology

As a kind of novel electronic self-rotation material, semi-metallic obtains international extensive concern in recent years because of its huge applications potentiality on non-volatile magnetic memory (MRAM), magneto-dependent sensor, hard disk playback head isospin electronic device. Semi-metallic is a kind of magnetic material, and for a certain spin direction, its band structure is metallic character, and certain density of states is arranged near the Fermi surface; And to another spin direction, the band structure of material is the insulator characteristic, and the density of states is zero near the Fermi surface, so has the spin polarizability up to 100% near the Fermi surface. Calculate and experimental result Fe according to being with₃O ₄Be a kind of semi-metallic, have 100% spin polarizability and far above the Curie temperature (858K) of room temperature, thereby become the most potential candidate material of spin electric device of room-temperature applications, therefore paid close attention to widely and study.

At present, people utilized the method successes such as molecular beam epitaxy (MBE), pulsed laser deposition (PLD) and magnetron sputtering preparation Fe₃O ₄Film. But MBE equipment is extremely expensive, there is the shortcoming of the spatial distribution inequality of the nonlinear change of the limitation in plumage brightness zone and evaporation particle temperature and quality in PLD, make it be only suitable for depositing the film of small size, and in deposition process with the phenomenon of droplet deposition, cause easily the inhomogeneous of membrane structure, have a strong impact on the performance that transports of electronics, therefore, low-cost, high-quality and be easy to existing microelectronic technique mutually the exploitation of compatible method for manufacturing thin film to Fe₃O ₄The suitability for industrialized production of film and large-scale application have vital meaning. Magnetron sputtering is to use very widely a kind of method for manufacturing thin film in the microelectronics industry, and is with low cost, is fit to the deposition of large area film. People utilize the magnetron sputtering method plated film all to adopt high-purity Fe or ceramic Fe at present₃O ₄As target. High-purity Fe target cost is high, and it is low to compare sputter rate than oxide target, and Fe₃O ₄Target must fire in vacuum drying oven or inert atmosphere protection in case oxidation, and needs the high temperature more than 1200 ℃, and is therefore higher to equipment requirement.

Summary of the invention

The object of the invention is to solve the problems of the prior art and a kind of low cost, high-quality are provided, have large-scale production potential with Fe₂O ₃Fe as target₃O ₄Method for manufacturing thin film.

Method provided by the present invention may further comprise the steps:

1) preparation Fe₂O ₃Target: will analyze pure Fe₂O ₃Powder oven dry, after PVA (polyvinyl alcohol) granulation, 100Mpa is dry-pressing formed, 500 ℃ of binder removals 12 hours, then with sample 1000 ℃ of lower sintering 2 hours, make Fe₂O ₃Target;

2) with step 1) the middle Fe for preparing₂O ₃Target places the magnetron sputtering apparatus vacuum chamber, vacuumizes, and substrate is heated to 500～700 ℃, behind the temperature stabilization, passes into H in vacuum chamber₂With the mist of Ar, utilize mass flowmenter to keep H₂With the mass ratio of Ar be 0.1～0.15, after the build-up of luminance, sputtering power is transferred to 100W, keep stable gas pressure at 0.5～1Pa, open baffle plate, the beginning sputter, when treating that desired thickness is arrived in film growth, stop sputter after, treat that sample naturally cools to below 50 ℃, stop vavuum pump, open vacuum chamber, sample is taken out.

Adopt method of the present invention can prepare pure phase, semi-metal ferroferric oxide thin film that electromagnetic property is good, can be as required, by control sedimentation time control film thickness.

Compared with prior art, the present invention has following beneficial effect:

1) the present invention is at wider H₂/ Ar quality is prepared pure phase Fe than in the scope (0.1～0.15)₃O ₄Film has very large process tolerance, and experimental repeatability is good, need not very accurate control and can obtain high-quality film, is conducive to large-scale industrial production.

2) the present invention adopts Fe₂O ₃As target, with Fe used in the prior art₃O ₄Target is compared, and its sintering procedure can carry out in air, need not inert gas shielding, and do not need higher temperature, agglomerating plant is required lower, and be conducive to Fe₃O ₄The large-scale production of film.

3) the prepared film of the inventive method, its saturation magnetization is close to Fe₃O ₄Block materials, Saturation field is low, and the APBs defect concentration of film inside is lower, and electromagnetic property is good.

Description of drawings

Fig. 1. the Fe of the inventive method preparation₃O ₄The X-ray diffractogram of film;

Fig. 2. the Fe of the inventive method preparation₃O ₄The x-ray photoelectron power spectrum of film;

Fig. 3. the Fe of the inventive method preparation₃O ₄The change curve (R-T) of the electrical resistance temperature of film, wherein illustration is the 1nR-T of data^-1/4Matched curve;

Fig. 4. the Fe of the inventive method preparation₃O ₄The hysteresis curve that film records under 300K and 10K temperature.

The specific embodiment

Adopt conventional ceramic target technology of preparing to prepare Fe₂O ₃Target: will analyze pure Fe₂O ₃Powder oven dry, through after the PVA granulation dry-pressing formed (100Mpa), 500 ℃ of lower binder removals 12 hours, then with sample 1000 ℃ of lower sintering 2 hours, make Fe₂O ₃Target, for subsequent use, target diameter 50mm, thick 3mm.

Embodiment 1

With Fe₂O ₃Target places vacuum chamber, and start vacuumizes, and substrate is heated to 500 ℃, behind the temperature stabilization, passes into H in vacuum chamber₂/ Ar mass ratio is 0.1 mist, by the flow of mass flowmenter control gas, after the build-up of luminance, sputtering power is transferred to 100W, keep stable gas pressure at 0.5Pa, open baffle plate, the beginning sputter, after 1 hour, stop sputter, treat that sample naturally cools to below 50 ℃, stops vavuum pump, open vacuum chamber, sample is taken out. The thickness of sample is 180nm.

Embodiment 2

With Fe₂O ₃Target places vacuum chamber, and start vacuumizes, and substrate is heated to 500 ℃, behind the temperature stabilization, passes into H in vacuum chamber₂/ Ar mass ratio is 0.125 mist, by the flow of mass flowmenter control gas, after the build-up of luminance, sputtering power is transferred to 100W, keep stable gas pressure at 0.5Pa, open baffle plate, the beginning sputter, after 1 hour, stop sputter, treat that sample naturally cools to below 50 ℃, stops vavuum pump, open vacuum chamber, sample is taken out. The thickness of sample is 180nm.

Embodiment 3

With Fe₂O ₃Target places vacuum chamber, and start vacuumizes, and substrate is heated to 500 ℃, behind the temperature stabilization, passes into H in vacuum chamber₂/ Ar mass ratio is 0.15 mist, by the flow of mass flowmenter control gas, after the build-up of luminance, sputtering power is transferred to 100W, keep stable gas pressure at 0.5Pa, open baffle plate, the beginning sputter, after 1 hour, stop sputter, treat that sample naturally cools to below 50 ℃, stops vavuum pump, open vacuum chamber, sample is taken out. The thickness of sample is 180nm.

Embodiment 4

With Fe₂O ₃Target places vacuum chamber, and start vacuumizes, and substrate is heated to 600 ℃, behind the temperature stabilization, passes into H in vacuum chamber₂/ Ar mass ratio is 0.1 mist, by the flow of mass flowmenter control gas, after the build-up of luminance, sputtering power is transferred to 100W, keep stable gas pressure at 1Pa, open baffle plate, the beginning sputter, after 1 hour, stop sputter, treat that sample naturally cools to below 50 ℃, stops vavuum pump, open vacuum chamber, sample is taken out. The thickness of sample is 190nm.

Embodiment 5

With Fe₂O ₃Target places vacuum chamber, and start vacuumizes, and substrate is heated to 700 ℃, behind the temperature stabilization, passes into H in vacuum chamber₂/ Ar mass ratio is 0.1 mist, by the flow of mass flowmenter control gas, after the build-up of luminance, sputtering power is transferred to 100W, keep stable gas pressure at 1Pa, open baffle plate, the beginning sputter, after 1 hour, stop sputter, treat that sample naturally cools to below 50 ℃, stops vavuum pump, open vacuum chamber, sample is taken out. The thickness of sample is 190nm.

Utilize Surfcom 480A type surface roughness analysis instrument to measure the thickness of the semi-metal ferroferric oxide thin film for preparing in the embodiment of the invention; Adopt X-ray diffraction analysis instrument (BRUKER-AXS D8 Cu k α, λ=0.154056nm) film is carried out structural characterization; The chemical valence that adopts x-ray photoelectron power spectrum (VG MK II) to carry out the Fe element characterizes; The measurement of hysteresis curve is finished by the VSM in PPMS (Quantum Design) system; Carrying out electrical properties with Agilent E5273 and the Lakeshore 340 common alternating temperature electric measuring systems that form measures.

The XRD test result shows that adopting the prepared film of the inventive method is pure phase Fe₃O ₄, have (111) orientation; The x-ray photoelectron power spectrum of film is the Fe of standard₃O ₄Sign γ-Fe does not appear in the film power spectrum₂O ₃The satellite peak of the 718eV vicinity that dephasign exists; In the electrical resistance temperature variation curve of sample, obvious Verwey phase transformation appears in the 115K place, and resistance increases suddenly; The relation of resistance and temperature meets range transition (VRH) conductive mechanism of electronics: $\mathrm{\ρ}={\mathrm{\ρ}}_{\∞}\exp \left[{\left(\frac{T_0}{T}\right)}^{1/4}\right];$ Under the room temperature, the saturation magnetization of film is 410emu/cm³, near the saturation magnetization of body material; The Saturation field of film is 5kOe only, shows that the APBs defect concentration of film inside is lower.

Claims (1)

1, a kind of preparation method of semi-metal ferroferric oxide thin film is characterized in that, may further comprise the steps:

1) preparation Fe₂O ₃Target: will analyze pure Fe₂O ₃Powder oven dry, after the PVA granulation, 100Mpa is dry-pressing formed, 500 ℃ of binder removals 12 hours, then with sample 1000 ℃ of lower sintering 2 hours, make Fe₂O ₃Target;

2) with step 1) the middle Fe for preparing₂O ₃Target places the magnetron sputtering apparatus vacuum chamber, vacuumizes, and substrate is heated to 500～700 ℃, behind the temperature stabilization, passes into H in vacuum chamber₂With the mist of Ar, wherein H₂With the Ar mass ratio be 0.1～0.15, after the build-up of luminance, sputtering power is transferred to 100W, keep stable gas pressure at 0.5～1Pa, open baffle plate, the beginning sputter, when treating that desired thickness is arrived in film growth, stop sputter, treat that sample naturally cools to below 50 ℃, stop vavuum pump, obtain ferriferrous oxide film.

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