CN112962082A

CN112962082A - Two-dimensional hBN film with magnetron sputtering Cu film as buffer layer and preparation method thereof

Info

Publication number: CN112962082A
Application number: CN202110273353.9A
Authority: CN
Inventors: 陈占国; 赵泽利; 陈曦; 赵纪红; 刘秀环; 侯丽新; 高延军
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2021-03-15
Filing date: 2021-03-15
Publication date: 2021-06-15

Abstract

A two-dimensional hBN film with a magnetron sputtering Cu film as a buffer layer and a preparation method thereof belong to the technical field of epitaxial growth of semiconductor materials. The invention utilizes magnetron sputtering technology to grow a Cu film on a sapphire or quartz substrate and the like as a buffer layer, and then adopts low-pressure chemical vapor deposition technology to epitaxially grow a two-dimensional hBN film on the Cu buffer layer. Compared with the metal foil used in the prior art, the surface of the Cu buffer layer is smoother and smoother, the Cu (111) crystal face is matched with the hBN crystal lattice, the Cu buffer layer is more suitable for the growth of a two-dimensional hBN film, and the thickness of the Cu buffer layer can be adjusted by the sputtering technological parameters of the Cu target. The two-dimensional hBN film prepared by the method has larger size and higher quality, and the Cu film buffer layer can be directly used as a bottom electrode of an hBN device with a vertical structure.

Description

Two-dimensional hBN film with magnetron sputtering Cu film as buffer layer and preparation method thereof

Technical Field

The invention belongs to the technical field of epitaxial growth of semiconductor materials, and particularly relates to a two-dimensional hBN film taking a magnetron sputtering Cu film as a buffer layer and a preparation method thereof.

Background

In recent years, two-dimensional materials have been developed rapidly, and each of the two-dimensional materials has attracted much attention of related researchers. Among them, hexagonal boron nitride (hBN) is favored by many researchers because of its excellent properties such as high thermal stability, corrosion resistance, high insulation, and high thermal conductivity, and two-dimensional hBN is very similar to graphene in structure, and is also called "white graphite". In recent years, researchers have confirmed that the two-dimensional hBN film has a wide application prospect, can be used as a good substrate of a semiconductor device, greatly improves the performance of the device, can be used as a protective coating, can be used for manufacturing an ultraviolet photoelectric device and the like, and therefore, the preparation of the large-area high-quality two-dimensional hBN film becomes a key content and a research hotspot in the field. At present, the preparation of two-dimensional hBN film mostly adopts a Chemical Vapor Deposition (CVD) method, and the method has the advantages of low cost, controllability and the like. The choice of the substrate is mostly based on transition metal foil at present, because the transition metal tends to play a certain catalytic role in the growth of hBN, and in addition, the crystal lattice of the transition metal tends to be matched with the hBN very well. However, the metal foil available on the market at present has a rough surface due to its industrial production process, has a dense rolling line, and the surface of the metal foil tends to be in a polycrystalline state, which is not suitable for the growth of large-sized thin films.

In order to obtain a two-dimensional hBN film with large size and good quality, the roughness of the surface of the substrate and the crystal orientation of the surface are very important prerequisites, so that the search for an ideal buffer layer becomes the key for preparing the two-dimensional hBN film.

Disclosure of Invention

The invention aims to provide a two-dimensional hBN film taking a magnetron sputtering Cu film as a buffer layer and a preparation method thereof. The method adopts magnetron sputtering to plate a Cu film with a smooth surface and tending to a single crystal surface on a sapphire, quartz and other substrates with two polished surfaces as a buffer layer, and then adopts a low-pressure chemical vapor deposition (LPCVD) technology to grow the two-dimensional hBN film on the Cu film buffer layer.

The invention relates to a two-dimensional hBN film taking a magnetron sputtering Cu film as a buffer layer and a preparation method thereof, which comprises the following steps:

(1) ultrasonically cleaning a Sapphire (Sapphire) or Quartz plate (Quartz) substrate with two polished surfaces for 10-20 minutes by using acetone, ethanol and deionized water in sequence, drying, and then placing a high-purity (more than 99.9995 percent) Cu target and the cleaned substrate in a magnetron sputtering equipment growth chamber; the distance between the Cu target and the substrate is 4-8 cm, and the Cu target is connected with a 13.56MHz radio frequency source (the maximum output power is more than 300W);

(2) vacuumizing the growth chamber of the magnetron sputtering equipment to 1 × 10^-3Heating the substrate to 300-800 ℃ below Pa; introducing high-purity argon (Ar, the purity is more than 99.9995%), wherein the flow is 50-100 sccm, and the pressure of the growth chamber is kept at 3-6 Pa; starting a radio frequency source, wherein the sputtering power is 60-80W, so that argon is ionized to glow; then adjusting the pressure of the growth chamber to 1-3 Pa, sputtering the copper target at the power of 100-200W for 2-3 h; after the sputtering is finished, the growth chamber is cooled to room temperature and then the substrate is taken out, thereby obtaining a Cu film on the substrateA buffer layer;

(3) ultrasonically cleaning the substrate obtained in the step (2) by using acetone, ethanol and deionized water for 10-20 minutes in sequence, drying the substrate, then placing the substrate into a quartz tube deposition cavity of LPCVD equipment, and weighing 40-100 mg of ammonia borane to place the ammonia borane into a source heating vessel of the LPCVD equipment;

(4) vacuumizing a deposition cavity of LPCVD equipment to below 10Pa, and filling high-purity argon to normal pressure (the normal pressure refers to atmospheric pressure); repeating the operations of vacuumizing to below 10Pa and filling high-purity argon to normal pressure for more than 2 times; then the deposition cavity is vacuumized to below 10Pa again, and high-purity argon and high-purity hydrogen (H) are introduced₂And the purity is more than 99.9995 percent), the flow of high-purity argon is 100-300 sccm, the flow of high-purity hydrogen is 50-100 sccm, the temperature is raised under normal pressure, the temperature raising process lasts for 120-140 min, the temperature is raised to 1030-1070 ℃, the substrate is annealed for 1-2 h at the temperature, and after the annealing is finished, the temperature of the deposition cavity is reduced to 950-1020 ℃ and is kept stable;

(5) adjusting the flow of high-purity argon gas to be 50-100 sccm, adjusting the pressure in a deposition chamber to be 50-100 Pa under the protection of the high-purity argon gas, and then heating ammonia borane to 60-80 ℃ to deposit an hBN film, wherein the deposition time is 0.5-2 h; and naturally cooling to room temperature after the deposition of the hBN film is finished, thereby obtaining the two-dimensional hBN film on the substrate by taking the magnetron sputtering Cu film as a buffer layer.

The invention has the advantages that: (1) the surface of the obtained Cu film buffer layer is smooth and flat, and the roughness is obviously superior to that of a Cu foil; (2) the surface of the Cu film buffer layer is a Cu (111) crystal face which is matched with the hBN crystal lattice, so that the Cu film buffer layer is more suitable for the growth of a two-dimensional hBN film; (3) the thickness of the Cu film buffer layer can be controlled by adjusting magnetron sputtering parameters according to requirements.

Drawings

FIG. 1: the invention relates to a process flow chart for preparing a two-dimensional hBN film on a magnetron sputtering Cu film buffer layer. The device comprises a sapphire or quartz substrate 1, a magnetron sputtering Cu thin film buffer layer 2 and a two-dimensional hBN thin film 3. The first step is to obtain a Cu film buffer layer 2 on a sapphire or quartz substrate 1 through magnetron sputtering, and the second step is to obtain a two-dimensional hBN film 3 through epitaxial growth on the Cu film buffer layer 2.

FIG. 2: SEM pictures (a) of a Cu thin film buffer layer prepared by the method of the invention and SEM pictures (b) of a commercially available high-purity metal Cu foil.

FIG. 3: SEM photograph of the section of the Cu film buffer layer prepared by the method.

FIG. 4: the XRD diffraction pattern (a) of the Cu film buffer layer prepared by the method of the invention and the XRD diffraction pattern (b) of the commercially available high-purity metal Cu foil.

FIG. 5: XPS narrow scan spectra of the B1s orbital (a) and the N1s orbital (B) of two-dimensional hBN films prepared by the method of the invention.

Detailed Description

Example 1:

(1) ultrasonically cleaning a Sapphire (Sapphire) substrate with two polished surfaces for 10 minutes by using acetone, ethanol and deionized water in sequence, drying, and then placing a high-purity Cu target and a cleaned substrate slice in a magnetron sputtering growth chamber;

(2) setting the target distance of magnetron sputtering equipment to be 5cm, connecting a Cu target holder with a 13.56MHz radio frequency source, starting a mechanical pump to vacuumize a growth chamber to 8Pa, and then starting a molecular pump to vacuumize a cavity to 5 multiplied by 10^-4Pa, starting a heating power supply to heat the substrate to 400 ℃, then starting an air inlet valve, introducing high-purity Ar gas with the flow of 100sccm, adjusting a gate valve, keeping the pressure of a cavity at 3Pa, starting a radio frequency source, setting the power to be 75W, starting the radio frequency source, adjusting the gate valve to adjust the pressure of the cavity to 1Pa after glowing, adjusting the sputtering power to 100W, sputtering a Cu target for 2 hours, sequentially closing the air inlet valve, the gate valve, a molecular pump and a mechanical pump after sputtering is finished, opening the cavity after cooling to room temperature, and taking out the substrate, thereby obtaining a Cu thin film buffer layer on the substrate;

(3) ultrasonically cleaning the substrate obtained in the step (2) for 10 minutes by sequentially using acetone, ethanol and deionized water, drying, placing the substrate into a quartz tube deposition chamber of LPCVD equipment, weighing 50mg of ammonia borane, and placing the ammonia borane into a source heating vessel;

(4) and (3) screwing valves at two sides of the quartz tube, opening a mechanical pump to pump the quartz tube to 3Pa, closing the mechanical pump to fill argon (Ar) to normal pressure, repeating the process for 3 times, and pumping the quartz tube to 3Pa again. However, the device is not suitable for use in a kitchenThen the mechanical pump is closed, Ar and H are introduced₂Ar flow rate of 200sccm, H₂Opening a tail gas valve with the flow of 50sccm, heating in a normal pressure atmosphere for 130min, heating to 1050 ℃ and maintaining, annealing the substrate for 1h, and after the annealing is finished, reducing the temperature of the cavity to 1000 ℃ and maintaining the temperature stably;

(5) close H₂The carrier gas is changed into pure Ar, the flow rate of Ar is 50sccm, a tail gas valve is closed, a mechanical pump valve is opened, the air pressure in a quartz tube is always controlled at 50Pa, an ammonia borane heating power supply is opened, the source heating temperature is set to be 70 ℃, the film deposition process lasts for 1h, after the film deposition is finished, the heating power supply, the mechanical pump and the carrier gas flowmeter are sequentially closed, then the cavity is filled to normal pressure by Ar, the substrate is taken out after the film deposition is naturally cooled to room temperature under the protective atmosphere of Ar, and therefore the two-dimensional hBN film with the magnetron sputtering Cu film as the buffer layer is obtained on the substrate.

As shown in fig. 2(a), the surface topography of the Cu film buffer layer is very flat and smooth, which is greatly improved compared to the conventional Cu foil of fig. 2(b), and it can be seen from fig. 3 that the Cu film buffer layer obtained by magnetron sputtering has a thickness of 0.8 μm. As shown in fig. 4(b), the conventional metallic Cu foil surface exhibits a polycrystalline state of Cu (111), Cu (200) and Cu (220), which is not matched with the lattice of hBN, and is not suitable for large-area epitaxial growth of two-dimensional hBN thin films, while as shown in fig. 4(a), the XRD diffractogram shows that the surface of the Cu thin film buffer layer obtained by magnetron sputtering tends to be Cu (111) single crystal, which is less mismatched with the lattice of hBN.

The X-ray photoelectron spectrum of the two-dimensional hBN film grown on the magnetron sputtered Cu film buffer layer, as shown in fig. 5, the peak positions of B1s and N1s correspond to 189.7eV and 397.6eV, respectively, and match with the peak position of standard boron nitride, where B1s has a weak small peak in the high energy region due to the adsorption of trace O on the sample surface during the test. The two-dimensional hBN film prepared by the method can be characterized without being transferred to other substrates, and the Cu film buffer layer can be directly used as a bottom electrode of an hBN device with a vertical structure.

Claims

1. A preparation method of a two-dimensional hBN film with a magnetron sputtering Cu film as a buffer layer comprises the following steps:

(1) cleaning and drying a substrate, then placing a high-purity Cu target and the cleaned substrate in a growth chamber of magnetron sputtering equipment, wherein the distance between the Cu target and the substrate is 4-8 cm, and then connecting the Cu target with a radio frequency source;

(2) vacuumizing the growth chamber of the magnetron sputtering equipment to 1 × 10^-3Heating the substrate to 300-800 ℃ below Pa; introducing high-purity argon, and keeping the pressure of the growth chamber at 3-6 Pa; starting a radio frequency source, wherein the sputtering power is 60-80W, so that argon is ionized to glow; then adjusting the pressure of the growth chamber to 1-3 Pa, sputtering the Cu target for 2-3 h at the sputtering power of 100-200W; after the sputtering is finished, cooling the growth chamber to room temperature, and then taking out the substrate, thereby obtaining a Cu thin film buffer layer on the substrate;

(3) cleaning and drying the substrate obtained in the step (2), then placing the substrate into a quartz tube deposition cavity of low-pressure chemical vapor deposition equipment, and placing ammonia borane into a source heating vessel of the low-pressure chemical vapor deposition equipment;

(4) vacuumizing a deposition cavity of low-pressure chemical vapor deposition equipment to below 10Pa, and filling high-purity argon to normal pressure; repeating the operations of vacuumizing to below 10Pa and filling high-purity argon to normal pressure for more than 2 times; then vacuumizing the deposition cavity to below 10Pa again, introducing a mixed gas of high-purity argon and high-purity hydrogen, heating to 1030-1070 ℃ under normal pressure, annealing the substrate for 1-2 hours at the temperature, and after the annealing is finished, reducing the temperature of the deposition cavity to 950-1020 ℃ and maintaining the temperature stably;

(5) adjusting the pressure in the deposition chamber to 50-100 Pa under the protection of high-purity argon, and then heating ammonia borane to 60-80 ℃ for hBN film deposition, wherein the deposition time is 0.5-2 h; and naturally cooling to room temperature after the deposition of the hBN film is finished, thereby obtaining the two-dimensional hBN film on the substrate by taking the magnetron sputtering Cu film as a buffer layer.

2. The method for preparing the two-dimensional hBN film by taking the magnetron sputtering Cu film as the buffer layer according to claim 1, wherein the method comprises the following steps: the substrate in the step (1) is a sapphire or quartz plate with two polished surfaces.

3. The method for preparing the two-dimensional hBN film by taking the magnetron sputtering Cu film as the buffer layer according to claim 1, wherein the method comprises the following steps: and in the step (1) and the step (3), the substrate is ultrasonically cleaned for 10-20 minutes by sequentially using acetone, ethanol and deionized water, and then dried.

4. The method for preparing the two-dimensional hBN film by taking the magnetron sputtering Cu film as the buffer layer according to claim 1, wherein the method comprises the following steps: in the step (1), the frequency of the radio frequency source is 13.56MHz, and the maximum output power is more than 300W.

5. The method for preparing the two-dimensional hBN film by taking the magnetron sputtering Cu film as the buffer layer according to claim 1, wherein the method comprises the following steps: the purity of the high-purity Cu target in the step (1) is more than 99.9995%, the purity of the high-purity argon in the steps (2) and (4) is more than 99.9995%, and the purity of the high-purity hydrogen in the step (4) is more than 99.9995%.

6. The method for preparing the two-dimensional hBN film by taking the magnetron sputtering Cu film as the buffer layer according to claim 1, wherein the method comprises the following steps: the surface of the Cu film buffer layer in the step (2) is flat and smooth and is a Cu (111) crystal face.

7. The method for preparing the two-dimensional hBN film by taking the magnetron sputtering Cu film as the buffer layer according to claim 1, wherein the method comprises the following steps: the flow rate of the high-purity argon in the step (2) is 50-100 sccm, the flow rate of the high-purity argon in the step (4) is 100-300 sccm, the flow rate of the high-purity hydrogen is 50-100 sccm, and the flow rate of the high-purity argon in the step (5) is 50-100 sccm.

8. The method for preparing the two-dimensional hBN film by taking the magnetron sputtering Cu film as the buffer layer according to claim 1, wherein the method comprises the following steps: and (4) keeping the temperature rise process for 120-140 min.

9. A two-dimensional hBN film with a magnetron sputtering Cu film as a buffer layer is characterized in that: is prepared by the method of any one of claims 1 to 8.