CN115323475B - A kind of preparation method of hexagonal boron nitride thin film with high index crystal plane - Google Patents

Abstract

The invention discloses a preparation method of a hexagonal boron nitride film with a high-index crystal face. The invention forms a monocrystalline AlN template layer on the high-index crystal face substrate to form the high-index crystal face substrate, and forms oxygen enriched Al on the monocrystalline AlN template layer _x O _y A thin layer; at Al _x O _y Formation of B on the thin layer _m N _n A film, a composite structure is obtained; physically pressing a low-index crystal face substrate with an AlN film and a composite structure, and reconstructing at a high temperature to form h-B _k N _l A film; disruption of oxygen enrichment of Al _x O _y Thin layer, give a film with h-B _k N _l A low-index crystal face AlN template of the film; h-B _k N _l The film has the same crystal face orientation as the high-index crystal face substrate, can have the designated crystal face orientation, and breaks the bottleneck of the existing preparation technology; the high-index crystal face substrate can be reused; the h-BN film is prepared by adopting the deposition and high-temperature reconstruction modes, so that the process difficulty can be reduced, expensive high-temperature equipment is avoided, the yield is improved, and the cost is reduced.

Description

A kind of preparation method of hexagonal boron nitride thin film with high index crystal plane

technical field

The invention relates to a two-dimensional material preparation technology, in particular to a preparation method of a high-index crystal plane hexagonal boron nitride (h-BN) film.

Background technique

The boron (B) atoms and nitrogen (N) atoms in the layered h-BN layer are covalently bonded, and the van der Waals force is used between the layers. The band gap is greater than 5.0eV. It is a new type of high-efficiency ultraviolet light source and detector device. Preferred ultra-wide bandgap semiconductor materials for microelectronics and optoelectronic devices. At present, chemical vapor deposition technology is mainly used at home and abroad to prepare h-BN thin films on metal substrates such as copper and nickel with (111) crystal plane orientation, and metal organic chemical vapor deposition technology is used to prepare h-BN thin films on (0001) crystal plane oriented sapphire and other non-metal substrates. h-BN thin films were prepared on metal substrates. The h-BN films prepared by the above method all have a low-index (0001) crystal plane orientation, and the growth direction is the [0001] crystal orientation. The low-index (0001) crystal plane h-BN thin film has strong intralayer electricity, light, and heat transport capabilities, but poor interlayer electricity, light, and heat transportation capabilities (about 1/100 to 1/100 of the inner layer). 1/10). In order to improve the electricity, light, heat and other transport capabilities of h-BN films along the growth direction and meet the material requirements of high-power semiconductor optoelectronic devices, it is necessary to prepare h-BN with a high-index crystal plane whose growth direction deviates from the [0001] crystal direction. single crystal film.

Contents of the invention

In order to overcome the above deficiencies in the prior art, the present invention proposes a method for preparing a high-index crystal plane hexagonal boron nitride film.

The preparation method of the high-index crystal plane hexagonal boron nitride thin film of the present invention comprises the following steps:

1) Provide a high-index crystal plane substrate. The high-index crystal plane substrate is a high-temperature-resistant hexagonal structure sapphire (Al ₂ O ₃ ) or silicon carbide (SiC) with non-(0001) and (000-1) crystal plane orientations. , the upper surface of the high-index crystal plane substrate is polished to form a polished surface, and AlN is deposited on the polished surface of the high-index crystal plane substrate to form a single crystal AlN template layer with a high-index crystal plane, and the high-index crystal plane lining The bottom and the single crystal AlN template layer constitute a high-index crystal plane customized AlN template, and the high-index crystal plane customized AlN template has non-(0001) and (000-1) crystal plane orientations;

2) Use a plasma oxygen (O) source or an ozone generator to treat the upper surface of the AlN template with a high-index crystal plane, that is, the single-crystal AlN template layer, and control the oxygen flow rate and processing time to form oxygen-enriched _AlxO on its surface _y thin layer, where x is the stoichiometry of Al in the Al _x O _y thin layer, and y is the stoichiometry of O in the Al _x O _y thin layer. By controlling the oxygen flow rate and processing time, the Al _x O _y thin layer The stoichiometric ratio x/y of Al to O is less than 2/3;

3) Deposit a B _m N _n film on the upper surface of the Al _x O _y thin layer to obtain a composite structure of B _m N _n thin film, Al _x O _y thin layer and high-index crystal plane customized AlN template, where m is B _m The stoichiometry of boron (B) in the N _n film, n is the stoichiometry of nitrogen (N) in the B _m N _n film, adjust the deposition temperature and the stoichiometric ratio of boron and nitrogen, so that the boron and nitrogen in the B _m N _n film The stoichiometric ratio m/n is less than 0.7;

4) Provide a low-index crystal plane substrate. The low-index crystal plane substrate is a high-temperature-resistant hexagonal structure sapphire or silicon carbide with (0001) or (000-1) crystal plane orientation. For low-index crystal plane substrates The upper surface is polished to form a polished surface, and an AlN film is deposited on the polished surface of the low-index crystal plane substrate. The low-index crystal plane substrate and the AlN film form a low-index crystal plane AlN template, and the low-index crystal plane AlN template has (0001) Or (000-1) crystal plane orientation;

5) Lay the AlN thin film side of the low-index crystal plane AlN template and the B _m N _n film side of the composite structure, and the low-index crystal plane substrate side of the low-index crystal plane AlN template and the high-index composite structure Place a gravity plate on one side of the crystal plane substrate, use the gravity plate to physically press the low-index crystal plane AlN template and the composite structure, and reconstruct it under a high-temperature nitrogen atmosphere to remove the excess nitrogen atoms in the B _m N _n film from the AlN film and the composite structure. Interfacial discharge of B _m N _n films to form single-crystal hB _k N _l films with low vacancy density while maintaining the integrity of the low-index facet AlN template and composite structure to form low-index facet AlN template/hB _k N _l films Overall structure of /Al _x O _y thin layer/high index crystal plane substrate; single crystal hB _k N _l film has a hexagonal lattice structure with the same crystal plane index as the high index crystal plane substrate, k is hB _k N _l The stoichiometry of B in the film, l is the stoichiometry of N in the hB _k N _l film, the annealing time and annealing temperature are controlled so that the stoichiometric ratio of B and N in the hB _k N _l film satisfies: 0.9<k/l<1.1 ;

6) Destroying the AlN template with low-index crystal plane/hB _k N _l thin film/Al _x O _y thin layer/high-index crystal plane to customize the overall structure of AlN template with oxygen-enriched Al x O _y thin layer, and separating the Al _x O y layer with hB _k Low-index facet AlN templates for _Nl thin films.

Wherein, in step 1), the high-index crystal plane is a crystal plane other than (0001) and (000-1) crystal plane, the low-index crystal plane is (0001) or (000-1) crystal plane, and the polished surface The surface roughness is less than 1nm. The thickness of the single crystal AlN template layer is 50-500nm.

In step 2), a plasma O source configured by magnetron sputtering, physical vapor deposition, or molecular beam epitaxy bombards the single-crystal AlN template layer of the high-index facet custom-made AlN template, and the thickness of _{the AlxOy} thin layer is 1 ~5nm. The ozone generator activates oxygen molecules to form ozone molecules, and the ozone molecules chemically react with the _{surface of the single crystal AlN template layer to form a dense Al x O y thin} layer with a thickness of 1-5nm. In the above two approaches, the oxygen flow rate and processing time are positively correlated with the stoichiometric ratio y/x of Al and O in the Al _x O _y thin layer.

In step 3), the deposition method adopts magnetron sputtering, physical vapor deposition or molecular beam epitaxy; the B _m N _n thin film has a polycrystalline structure, the thickness is 20-300 nm, and the boron (B) vacancy density exceeds 1.0×10 ¹⁹ cm ^-3 . During the deposition process, the temperature rises, which inhibits the incorporation of N atoms, resulting in an increase in the B/N ratio in the BN film; the deposition temperature and the stoichiometric ratio of the B source and the nitrogen source provided during the deposition are related to the B _m N _n film The stoichiometric ratio m/n of B and N is positively correlated.

In step 4), the thickness of the low-index crystal plane substrate is 100-500 microns.

In step 5), the material of the gravity plate is selected as one of corundum, silicon carbide, metal tungsten and molybdenum; the high temperature range is 1200-1400 ° C; the boron (B) vacancy density of the single crystal hB _k N _l film is formed less than 5.0×10 ¹⁶ cm ^-3 .

In step 6), the oxygen-enriched Al _x O _y thin layer is etched by acid solution or hydrogen atmosphere annealing method.

Advantages of the present invention:

In the present invention, a single-crystal AlN template layer is formed on a high-index crystal plane substrate to form a high-index crystal plane substrate, and an oxygen-enriched Al _x O _y thin layer is formed on the single crystal AlN template layer; on the Al _x O _y thin layer Form a B _m N _n film on the substrate to obtain a composite structure; physically press the low-index crystal plane substrate with an AlN film and the composite structure, and restructure at high temperature to form a hB _k N _l film; destroy the oxygen-enriched Al _x O _y film layer to obtain a low-index AlN template with a hB _k N _l film; the hB _k N _l film has the same crystal plane orientation as the high-index crystal plane substrate, and h-BN with a specified crystal plane orientation can be prepared, breaking the existing There are preparation technology bottlenecks; high-index crystal plane substrates can be reused; the preparation of h-BN thin films by deposition and high-temperature reconstruction can reduce process difficulty, avoid the use of expensive high-temperature equipment, increase productivity and reduce costs.

Description of drawings

Fig _. 1 obtains the sectional view of _AlxOy thin layer according to an embodiment of the preparation method of high-index crystal plane hexagonal boron nitride thin film of the present invention;

Fig. 2 obtains the sectional view of the B _m N _n film according to an embodiment of the preparation method of the high-index crystal plane hexagonal boron nitride film of the present invention;

Fig. 3 obtains the sectional view of single crystal hB _k N _l thin film according to an embodiment of the preparation method of high index crystal plane hexagonal boron nitride thin film of the present invention;

Fig. 4 is a cross-sectional view of a low-index AlN template with a hB _k N _l film separated from one embodiment of the method for preparing a high-index crystal plane hexagonal boron nitride film according to the present invention.

Detailed ways

The present invention will be further elaborated below through specific embodiments in conjunction with the accompanying drawings.

As shown in Figure 1, the preparation method of the high-index crystal plane hexagonal boron nitride film of this embodiment includes the following steps:

1) Provide a high-index crystal plane substrate with a high-temperature resistant hexagonal structure. The high-index crystal plane substrate is sapphire (Al ₂ O ₃ ) with a (11-22) crystal plane orientation. For the upper surface of the high-index crystal plane substrate Polishing is performed to form a polished surface, and 300nm thick AlN is deposited on the polished surface of the high-index crystal plane substrate to form a single-crystal AlN template layer with a high-index crystal plane. The high-index crystal plane substrate and the single-crystal AlN template layer consist of High-index crystal plane customized AlN template 1, high-index crystal plane customized AlN template with non-(0001) and (000-1) crystal plane orientation;

2) Use plasma oxygen (O) source to bombard the high-index crystal plane to customize the upper surface of the AlN template, that is, the single crystal AlN template layer, and control the oxygen flow rate and processing time to form an oxygen-enriched 3nm-thick Al _x O _y on its surface Thin layer 2, wherein, x is the stoichiometry of Al in _{the AlxOy thin} layer, y is the stoichiometry of O in _{the AlxOy} thin layer, x/y=0.5, as shown in Figure 1;

3) Deposit a 100nm-thick B _m N _n film 3 on the upper surface of the Al _x O _y thin layer by magnetron sputtering technology to obtain a B _m N _n thin film, Al _x O _y thin layer and a high-index crystal plane customized AlN template The composite structure of , wherein, m is the stoichiometry of boron (B) in the B _m N _n film, n is the stoichiometry of nitrogen (N) in the B _m N _n film, adjust the deposition temperature and B/N stoichiometric ratio, m /n=0.6, B vacancy density is greater than 5.0×10 ¹⁹ cm ^-3 , as shown in Figure 2;

4) A low-index crystal plane substrate 5 is provided. The low-index crystal plane substrate is a SiC substrate with a (0001) crystal plane orientation, and the upper surface of the low-index crystal plane substrate is polished to form a polished surface. An AlN film 4 is deposited on the polished surface of the surface substrate, the low-index crystal plane substrate and the AlN film form a low-index crystal plane AlN template, and the low-index crystal plane AlN template has a (0001) crystal plane orientation;

5) Lay the AlN thin film side of the low-index crystal plane AlN template and the B _m N _n film side of the composite structure, and the low-index crystal plane substrate side of the low-index crystal plane AlN template and the high-index composite structure A gravity plate is placed on one side of the crystal surface substrate, and the gravity plate is a corundum plate with a thickness of 300 microns. The gravity plate is used to physically press the low-index crystal surface AlN template and the composite structure, and treat it at 1350 ° C for 30 minutes in a nitrogen atmosphere. The excess nitrogen atoms in the B _m N _n film are expelled from the interface between the AlN film and the B _m N _n film to form a single-crystal hB _k N _l film6 with low vacancy density, while maintaining the low-index crystal plane AlN template and the composite structure Integrity, forming the overall structure of low-index crystal plane AlN template/hB _k N _l thin film/Al _x O _y thin layer/high-index crystal plane substrate; single crystal hB _k N _l film has a hexagonal lattice structure, with high Indices of the crystal plane index of the same substrate, k is the stoichiometry of B in the hB _k N _l film, l is the stoichiometry of N in the hB _k N _l film, the annealing time and annealing temperature are controlled so that in the hB _k N _l film The stoichiometric ratio of B and N satisfies k/l=0.95, and the thickness is reduced to 80nm, as shown in Figure 3;

6) Use acid solution to destroy the oxygen _- enriched Al x O _y thin layer in the overall structure of the low-index crystal plane AlN template/hB _k N _l thin film/Al _x O _y thin layer/high-index crystal plane customized AlN template, and isolate A low-index AlN template with hB _k N _l thin film, and a reusable high-index substrate 1, as shown in Figure 4.

Finally, it should be noted that the purpose of the disclosed embodiments is to help further understand the present invention, but those skilled in the art can understand that various replacements and modifications can be made without departing from the spirit and scope of the present invention and the appended claims. It is possible. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the protection scope of the present invention is subject to the scope defined in the claims.

Claims (8)

1. a preparation method of high-index crystal plane hexagonal boron nitride thin film, is characterized in that, described preparation method comprises the following steps: 1) Provide high-index crystal plane substrates. High-index crystal plane substrates are high-temperature-resistant hexagonal sapphire or silicon carbide with non-(0001) and non-(000-1) crystal plane orientations. For high-index crystal plane substrates The upper surface of the upper surface is polished to form a polished surface, and AlN is deposited on the polished surface of the high-index crystal plane substrate to form a single-crystal AlN template layer with a high-index crystal plane. The high-index crystal plane substrate and the single-crystal AlN template layer consist of High-index crystal plane customized AlN template, high-index crystal plane customized AlN template with non-(0001) and non-(000-1) crystal plane orientation; 2) Use a plasma oxygen source or an ozone generator to treat the upper surface of the AlN template with a high-index crystal plane, that is, the single-crystal AlN template layer, and control the oxygen flow rate and treatment time to form an oxygen-enriched Al _x O _y thin layer on the surface , where x is the stoichiometry of Al in the Al _x O _y thin layer, y is the stoichiometry of O in the Al _x O _y thin layer, by controlling the oxygen flow rate and processing time, the Al and O in the Al _x O _y thin layer The stoichiometric ratio x/y is less than 2/3; 3) Deposit a B _m N _n film on the upper surface of the Al _x O _y thin layer to obtain a composite structure of B _m N _n thin film, Al _x O _y thin layer and high-index crystal plane customized AlN template, where m is B _m The stoichiometry of boron in the N _n film, n is the stoichiometry of nitrogen in the B _m N _n film, adjust the deposition temperature and the stoichiometric ratio of boron and nitrogen, so that the stoichiometric ratio of boron and nitrogen in the B _m N _n film m/ n is less than 0.7; 4) Provide a low-index crystal plane substrate. The low-index crystal plane substrate is a high-temperature-resistant hexagonal structure sapphire or silicon carbide with (0001) or (000-1) crystal plane orientation. For low-index crystal plane substrates The upper surface is polished to form a polished surface, and an AlN film is deposited on the polished surface of the low-index crystal plane substrate. The low-index crystal plane substrate and the AlN film form a low-index crystal plane AlN template, and the low-index crystal plane AlN template has (0001) Or (000-1) crystal plane orientation; 5) Lay the AlN thin film side of the low-index crystal plane AlN template and the B _m N _n film side of the composite structure, and the low-index crystal plane substrate side of the low-index crystal plane AlN template and the high-index composite structure Place a gravity plate on one side of the crystal plane substrate, use the gravity plate to physically press the low-index crystal plane AlN template and the composite structure, and reconstruct it under a high-temperature nitrogen atmosphere to remove the excess nitrogen atoms in the B _m N _n film from the AlN film and the composite structure. Interfacial discharge of B _m N _n films to form single-crystal hB _k N _l films with low vacancy density while maintaining the integrity of the low-index facet AlN template and composite structure to form low-index facet AlN template/hB _k N _l films /Al _x O _y thin layer/high-index crystal planes customize the overall structure of the AlN template; single-crystal hB _k N _l films have a hexagonal lattice structure and have the same crystal plane index as the high-index crystal plane substrate, k is hB _k The stoichiometry of boron in the N _l film, l is the stoichiometry of nitrogen in the hB _k N _l film, the annealing time and annealing temperature are controlled so that the stoichiometric ratio of boron and nitrogen in the hB _k N _l film satisfies: 0.9<k/l<1.1; 6) Destroying the AlN template with low-index crystal plane/hB _k N _l thin film/Al _x O _y thin layer/high-index crystal plane to customize the overall structure of AlN template with oxygen-enriched Al x O _y thin layer, and separating the Al _x O y layer with hB _k Low-index facet AlN templates for _Nl thin films. 2. The preparation method according to claim 1, characterized in that, in step 1), the surface roughness of the polished surface is less than 1 nm. 3. preparation method as claimed in claim 1, is characterized in that, in step 2) in, by the plasma O source bombardment high-index crystal face custom-made AlN template of magnetron sputtering, physical vapor deposition or molecular beam epitaxy configuration The thickness of the single crystal AlN template layer and the Al _x O _y thin layer is 1-5 nm. 4. preparation method as claimed in claim 1 is characterized in that, in step 3) in, deposition method adopts magnetron sputtering, physical vapor deposition or molecular beam epitaxy; B _m N _n film has polycrystalline structure, and thickness is 20-300nm, the boron vacancy density exceeds 1.0×10 ¹⁹ cm ^-3 . 5. The preparation method according to claim 1, characterized in that, in step 4), the thickness of the low-index crystal plane substrate is 100-500 microns. 6. The preparation method according to claim 1, characterized in that, in step 5), the material of the gravity plate is selected as one of corundum, silicon carbide, metal tungsten and molybdenum. 7. The preparation method according to claim 1, characterized in that, in step 5), the range of high temperature is 1200-1400°C; The boron vacancy density for forming single crystal hB _k N _l films is lower than 5.0×10 ¹⁶ cm ^-3 . 8. The preparation method according to claim 1, characterized in that, in step 6), the oxygen-enriched Al _x O _y thin layer is etched by acid solution or hydrogen atmosphere annealing method.

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