阅读说明：本技术 一种制备晶片级均匀六方氮化硼薄膜的方法 (Method for preparing wafer-level uniform hexagonal boron nitride film ) 是由 武斌 姚文乾 刘云圻 于 2019-04-15 设计创作，主要内容包括：本发明公开了一种制备晶片级均匀六方氮化硼薄膜的方法。该方法采用化学气相沉积法,利用大单晶铜基底预先进行电化学抛光,而后放入高温管式炉进行生长六方氮化硼,即可得到晶片级六方氮化硼薄膜。在不同的晶面上氮化硼会形成三角、六方等多种晶型,在同一晶面上六方氮化硼会实现单晶晶型的无缝拼接,最终形成均匀连续晶片级六方氮化硼薄膜,六方氮化硼作为优异的介电材料在光电材料、微电子器件等方面都有极高的潜在应用价值,本发明为六方氮化硼材料的产业化应用提供了进一步可能。(The invention discloses a method for preparing a uniform hexagonal boron nitride film at a wafer level. The method adopts a chemical vapor deposition method, utilizes a large single crystal copper substrate to carry out electrochemical polishing in advance, and then the large single crystal copper substrate is put into a high-temperature tube furnace to grow hexagonal boron nitride, so that the wafer-level hexagonal boron nitride film can be obtained. The hexagonal boron nitride can form various crystal forms such as triangle, hexagonal and the like on different crystal faces, the seamless splicing of single crystal forms can be realized on the hexagonal boron nitride on the same crystal face, and finally a uniform continuous wafer-level hexagonal boron nitride film is formed, and the hexagonal boron nitride as an excellent dielectric material has extremely high potential application value in the aspects of photoelectric materials, microelectronic devices and the like, so that the invention provides further possibility for the industrial application of the hexagonal boron nitride material.)

1. A method of preparing a continuous wafer-level uniform hexagonal boron nitride film, comprising: and (3) performing electrochemical polishing on the monocrystalline metal surface, and then performing boron nitride growth by using a chemical vapor deposition method to obtain the boron nitride-based material.

2. The method of claim 1, wherein: the single crystal metal is single crystal copper;

the crystal face of the continuous wafer-level uniform hexagonal boron nitride film grown by the single crystal metal is a (111) face or a (110) face;

the thickness of the single crystal metal is 50-100 μm.

3. The method according to claim 1 or 2, characterized in that: in the electrochemical polishing step, the polishing solution consists of water, phosphoric acid, ethanol, isopropanol and urea;

the dosage ratio of the water, the phosphoric acid, the ethanol, the isopropanol and the urea is specifically 250 mL: 125 mL: 125 mL: 25mL of: 4g of the total weight.

4. A method according to any one of claims 1-3, characterized in that: in the electrochemical polishing step, the voltage is 3V-5V; in particular 3.5V;

the current is 2A-4A; specifically 2.4A;

polishing for 2-5 min; specifically 3 min.

5. The method according to any one of claims 1-4, wherein: in the growth step, the temperature is 950-;

heating to 1000-1050 ℃ at the heating rate of 30-35 min;

the time is 1min-60 min; specifically 30-60 min; more specifically 20 min;

the flow ratio of the inert gas and the hydrogen is 0-500: 50-300 parts of; in particular 200: 100, respectively;

the inert gas is specifically argon;

the flow rate of the inert gas is 0-500 sccm;

the flow rate of the hydrogen is 50-300 sccm.

6. The method according to any one of claims 1-4, wherein: in the growth step, the boron nitrogen source is a solid borane ammonia complex; in particular ammonia borane;

the ratio of the amount of the boron nitrogen source to the area of the continuous wafer-level uniform hexagonal boron nitride film was 5 mg: 4 x 10cm²。

7. A continuous wafer-scale uniform hexagonal boron nitride film produced by the method of any one of claims 1-6.

Technical Field

The invention belongs to the field of materials, and relates to a method for preparing a wafer-level uniform hexagonal boron nitride film.

Background

Since the discovery of graphene in 2004, research related to the field of two-dimensional materials has been vigorously developed. Hexagonal boron nitride is formed by nitrogen atoms and boron atoms sp²Hybrid formation, the structure of which is a hexagonal honeycomb like plane similar to graphene, is also calledBeing white graphene, the band gap is about 6eV, which is only 1.7% lattice mismatched with graphene, but unlike graphene, boron nitride is an excellent insulator. The hexagonal boron nitride has the advantages of good electrical and thermal stability, high surface flatness, wide band gap and the like, so that the hexagonal boron nitride can be used as an ideal insulating substrate to be applied to the fields of electronics, optoelectronics, photovoltaics and the like. The document shows that the hexagonal boron nitride can be used as a high-quality graphene dielectric substrate and applied to a graphene device to greatly improve the electrical property of graphene, and the charge mobility of the graphene film which is placed on the hexagonal boron nitride film is far higher than that of a silicon substrate. Therefore, the control synthesis of the hexagonal boron nitride film with large area, high quality and uniformity has important significance for the basic research and commercial application of two-dimensional materials.

Disclosure of Invention

It is an object of the present invention to provide a method of preparing a uniform hexagonal boron nitride film at the wafer level.

The invention provides a method for preparing a continuous wafer-level uniform hexagonal boron nitride film, which comprises the following steps: and (3) performing electrochemical polishing on the monocrystalline metal surface, and then performing boron nitride growth by using a chemical vapor deposition method to obtain the boron nitride-based material.

In the above method, the single-crystal metal is single-crystal copper;

the crystal face of the continuous wafer-level uniform hexagonal boron nitride film grown by the single crystal metal is a (111) face or a (110) face.

The thickness of the single crystal metal is 50 μm to 100 μm, preferably 100 μm.

In the electrochemical polishing step, the polishing solution consists of water, phosphoric acid, ethanol, isopropanol and urea;

the dosage ratio of the water, the phosphoric acid, the ethanol, the isopropanol and the urea is specifically 250 mL: 125 mL: 125 mL: 25mL of: 4g of the total weight of the mixture; a typical polishing liquid volume may be 525 ml.

The voltage is 3V-5V; specifically 3.5V.

The current is 2A-4A; specifically 2.4A.

Polishing for 2-5 min; specifically 3 min.

The purpose of the electrochemical polishing is to remove surface contaminants and attachments;

in the growth step, the temperature is 950-;

heating to 1000-1050 ℃ at the heating rate of 30-35 min; specifically, the temperature can be raised to 1000 ℃ within 30 min;

the time is 1min-60 min; specifically 30-60 min; more specifically 20-30 min;

the flow ratio of the inert gas and the hydrogen is 0-500: 50-300 parts of; in particular 200: 100, respectively;

the inert gas is specifically argon;

the flow rate of the inert gas is 0-500 sccm; specifically 100-; more specifically 200 sccm; the inert gas is specifically argon;

the flow rate of the hydrogen is 50-300 sccm; specifically 10-100 sccm; more specifically 10-25sccm, such as 20 sccm.

In the growth step, the boron nitrogen source is a solid borane ammonia complex; in particular ammonia borane, i.e. NH₃·BH₃. The ratio of the amount of the boron nitrogen source to the area of the continuous wafer-level uniform hexagonal boron nitride film was 5 mg: 4 x 10cm²。

The method further comprises the following steps: after the growth is finished, quickly cooling the obtained growth system to 100 ℃, then closing hydrogen, cooling to room temperature, and then closing inert gas.

The method further comprises the following steps: before the growth step, when the temperature of the precursor and the tube furnace reaches the growth temperature, the flow rate of hydrogen is changed to 20sccm, the heating band is switched on, the temperature of the heating band is controlled to be 140 ℃ by a constant temperature controller, the flow rate of hydrogen is adjusted to 10-25sccm, preferably 20sccm, and a boron nitrogen source which is placed in the test tube in advance is sent to the region of the heating band under the drive of magnetons.

In the above method, the single crystal copper having a crystal plane of (111) or (110) can be produced by various conventional methods, for example, by a method comprising the steps of: processing the polycrystalline copper foil for a plurality of times to obtain single crystal copper with a crystal face being a (111) face;

each treatment includes polishing and annealing.

In the method, each treatment is polishing and annealing;

the number of times is at least 3 times; specifically 3 times or 4 times.

In the polishing step, the polishing method is electrochemical polishing.

In the electrochemical polishing step, the polishing solution consists of water, phosphoric acid, ethanol, isopropanol and urea;

the voltage is 3V-5V;

the current is 2A-4A;

polishing for 2-5 min; specifically 3 min.

In the polishing solution, the dosage ratio of water, phosphoric acid, ethanol, isopropanol and urea is 250 mL: 125 mL: 125 mL: 25mL of: 4g of the total weight.

The annealing is carried out in the presence of an inert gas and a reducing gas;

the flow rate of the inert gas is 100sccm-400 sccm;

the flow rate of the reducing gas is 50sccm-200 sccm;

the annealing temperature is 1070-1083 ℃;

the annealing time is 30min-180 min.

The inert gas is argon or nitrogen;

the reducing gas is hydrogen.

The method further comprises the steps of: after each annealing, the copper foil was naturally cooled to room temperature.

More specifically, the single crystal Cu (111) can be produced as follows:

and performing electrochemical polishing on the cut copper foil (7cm multiplied by 5cm) in an ethanol/phosphoric acid system for 3min (wherein the specific composition of a polishing solution is that deionized water (mL), phosphoric acid (mL), ethanol (mL), isopropanol (mL) and urea (g) are mixed according to the proportion of 250: 125: 125: 25: 4, the conditions of the electrochemical polishing are that the voltage is kept at 5V, the current is 2A, the polishing time is 3min, the copper foil is cleaned and dried, then the copper foil is placed in a high-temperature tube furnace, 100-400sccm inert gas (such as argon, nitrogen and the like) and 50-200sccm hydrogen are introduced, heating is started, annealing is performed for 1-1083 h when the temperature is slightly lower than the melting point (5 ℃) of the metal copper, and the copper foil is cooled to room temperature under the same conditions and then taken out.

And secondly, carrying out electrochemical polishing on the taken copper foil again, wherein the operation condition is not changed.

And thirdly, carrying out high-temperature annealing, electrochemical polishing and other steps on the copper foil in the second step again, wherein all conditions are the same as the above. The number of cycles should not be less than three until the entire surface of the copper foil is converted to a single crystal copper (111) plane.

In addition, the continuous wafer-level uniform hexagonal boron nitride film prepared by the method also belongs to the protection scope of the invention. In the method for preparing the wafer-level uniform hexagonal boron nitride film, the crystal boundary and crystal face existing on the surface of commercially available copper are eliminated by the single crystal copper, and the highly oriented boron nitride single crystal can be obtained when the boron nitride grows, so that the uniform hexagonal boron nitride film is formed by seamless splicing. The characterization of a Scanning Electron Microscope (SEM) shows that a typical triangular hexagonal boron nitride single crystal and a uniform hexagonal boron nitride film under an optical microscope and the SEM grow on the prepared large single crystal copper surface, and the corresponding Raman spectrogram and the ultraviolet-visible light absorption spectrogram indicate that the material is the uniform hexagonal boron nitride film material. As can be seen from the Transmission Electron Microscope (TEM) results, the diffraction spots exhibited a high degree of orientation, and it was confirmed that the film was a large single-crystal continuous uniform hexagonal boron nitride film having a high degree of orientation.

Drawings

FIG. 1 is a Raman spectrum of a uniform hexagonal boron nitride film transferred to a silicon wafer prepared in example 1.

FIG. 2 is a graph showing an ultraviolet-visible light absorption spectrum of a uniform hexagonal boron nitride film prepared in example 1 transferred onto a glass slide.

FIG. 3 is a photo of an optical image of a large single-crystal copper sheet after high-temperature thermal oxidation of hexagonal boron nitride grown in example 1.

FIG. 4 is a photographic image of a continuous uniform hexagonal boron nitride film transferred to a silicon wafer substrate in example 1.

FIG. 5 is a photograph taken by means of a scanning electron microscope showing the hexagonal boron nitride film transferred to a silicon wafer in example 1.

FIG. 6 is a scanning electron micrograph of a highly oriented hexagonal boron nitride single crystal according to example 2.

FIG. 7 is a scanning electron micrograph of a highly oriented hexagonal boron nitride single crystal seamlessly spliced into a uniform boron nitride film in example 2.

FIG. 8 is a transmission microscope diffraction spot plot of a continuous uniform hexagonal boron nitride film as in example 2.

FIG. 9 is a scanning electron micrograph of the continuous uniform hexagonal boron nitride film on the substrate etched in the direction of the hexagonal boron nitride film in example 2.

FIG. 10 is a photomicrograph of a continuous uniform hexagonal boron nitride film at the wafer level of example 2.

Detailed Description

The present invention will be further illustrated with reference to the following specific examples, but the present invention is not limited to the following examples. The method is a conventional method unless otherwise specified. The starting materials are commercially available from the open literature unless otherwise specified.

The single crystal copper (111) planes used in the following examples were prepared as follows:

firstly, electrochemically polishing copper foil (with the purity of 99.9%) with the thickness of 100 mu m in polishing solution (containing phosphoric acid, ethanol, isopropanol and urea) for 3min, cleaning with deionized water, and performing N-ion cleaning₂And (5) drying.

And secondly, placing the copper foil on a quartz substrate and in the middle of a clean quartz tube, placing the quartz tube in a high-temperature tube furnace to enable the middle of the quartz tube to be positioned in the central area of the tube furnace, introducing 200sccm argon and 100sccm hydrogen into the quartz tube, starting the tube furnace to heat, and annealing for 60min after the temperature reaches 1075 ℃. The tube furnace was closed and allowed to cool to room temperature.

And thirdly, carrying out electrochemical polishing treatment and high-temperature annealing on the copper foil obtained in the second step again until the surface of the sample is completely converted into a single crystal copper (111) surface.