WO2021233305A1 - 氮化物外延片及其制备方法和半导体器件 - Google Patents

氮化物外延片及其制备方法和半导体器件 Download PDF

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WO2021233305A1
WO2021233305A1 PCT/CN2021/094407 CN2021094407W WO2021233305A1 WO 2021233305 A1 WO2021233305 A1 WO 2021233305A1 CN 2021094407 W CN2021094407 W CN 2021094407W WO 2021233305 A1 WO2021233305 A1 WO 2021233305A1
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layer
dimensional material
nitride
substrate
epitaxial wafer
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French (fr)
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陈智斌
黄伯宁
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华为技术有限公司
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Definitions

  • This application relates to the field of semiconductor technology, in particular to a nitride epitaxial wafer, a preparation method thereof, and a semiconductor device.
  • Gallium nitride (GaN) materials are widely used in power devices, radio frequency devices and optoelectronic devices due to the advantages of large band gap and high mobility.
  • GaN gallium nitride
  • gallium nitride materials are usually epitaxially grown on silicon substrates.
  • silicon-based gallium nitride due to the large lattice mismatch and thermal expansion coefficient mismatch of more than 17% between GaN and silicon, there will be huge stresses in silicon-based gallium nitride. These stresses will cause warpage in the epitaxy and affect GaN. Uniformity and reliability of epitaxial wafers. And as the size of the substrate increases and the thickness of the epitaxial layer increases, the problem of warpage will become more and more serious. Therefore, it is necessary to find a gallium nitride epitaxial growth method that can effectively relieve stress and reduce warpage.
  • the embodiment of the present application provides a nitride epitaxial wafer, a preparation method thereof, and a semiconductor device.
  • a nucleation layer on a substrate, and forming a two-dimensional material layer on the nucleation layer by splicing or in-situ growth, It can effectively relieve the stress caused by lattice mismatch and thermal mismatch between the substrate and the epitaxial layer, reduce the warpage during and after the epitaxy, improve the uniformity and reliability of the nitride epitaxial wafer, and improve the semiconductor device performance.
  • the first aspect of the embodiments of the present application provides a nitride epitaxial wafer, including:
  • a nucleation layer is formed on the substrate, and the nucleation layer is an aluminum nitride (AlN) layer or a gallium nitride layer;
  • a two-dimensional material layer is formed on the nucleation layer; the two-dimensional material layer is formed by splicing multiple small-size two-dimensional material films, or the two-dimensional material layer is formed by a two-dimensional material on the nucleation layer In-situ growth and formation;
  • the epitaxial layer is formed on the two-dimensional material layer, and the material of the epitaxial layer includes the third main group metal nitride.
  • the nucleation layer can provide a nucleation center for the subsequent growth of the nitride epitaxial layer, alleviate the lattice mismatch between the substrate and the epitaxial layer, and can effectively block the impurities brought by the substrate from the subsequent nitride epitaxial layer growth.
  • the two-dimensional material layer can directly release the stress by using lattice slip, significantly reducing the occurrence of epitaxial warping, and improving the uniformity and crystal quality of the nitride epitaxial layer.
  • the two-dimensional material layer formed by the splicing method can effectively reduce the warpage of the nitride epitaxial layer of large size (6 inches and above) and thick film (5 ⁇ m and above), and obtain large size, large thickness and high quality.
  • the two-dimensional material layer formed by the in-situ growth method can effectively avoid the damage that may occur during the two-dimensional material transfer process, and can be prepared by the deposition process like the epitaxial layer.
  • the two-dimensional material layer is formed by splicing multiple small-size two-dimensional material films.
  • a high-quality two-dimensional material layer can be obtained, and stress relief can be achieved, so as to smoothly prepare a high-quality 6-inch Large-size nitride epitaxial wafers and above.
  • a splicing gap between some or any two adjacent small-size two-dimensional material films.
  • the setting of the splicing gap can prevent the two-dimensional material layer from being laminated at the splicing place.
  • the width of the splicing gap is greater than or equal to 0.1 ⁇ m and less than or equal to 1/2 of the distance between the largest two points on the small-sized two-dimensional material film.
  • Reasonable control of the size of the splicing gap can not only prevent the appearance of two-dimensional material stacking, but also better ensure that the two-dimensional material layer has a certain area ratio on the nucleation layer, which is beneficial to exert its stress relief effect.
  • the proportion of the area occupied by the two-dimensional material layer on the nucleation layer is not less than 50%.
  • the two-dimensional material layer has a certain area ratio on the nucleation layer, which is beneficial to exert its stress relief effect.
  • the shape of the small-sized two-dimensional material film may be a polygon.
  • the polygonal structure film has a linear side length, which can better implement the splicing process and better control the uniformity of the gap width between two adjacent small-sized two-dimensional material films.
  • the shape of the small-sized two-dimensional material film is an equilateral triangle, a right-angled triangle, a regular hexagon, a square, a rectangle, or a rhombus.
  • the shape of the small-sized two-dimensional material film in the embodiments of the present application is not limited to polygons, and other shapes that can be spliced are also possible, such as circles.
  • the two-dimensional material layer is formed by in-situ growth of a two-dimensional material on the nucleation layer.
  • In-situ growth can directly prepare a relatively complete two-dimensional material thin film by one-time deposition, and the process operation is convenient.
  • the material of the two-dimensional material layer includes graphene, boron nitride, silylene, germanene, phosphorene, boronene, tinene, transition metal sulfide, transition metal carbide, and transition metal nitrogen. At least one of the compounds.
  • the thickness of the two-dimensional material layer is less than or equal to 1 nm.
  • the two-dimensional material layer is a single-layer graphene.
  • the material of the epitaxial layer is a group III metal nitride, which may specifically include one or more of GaN, AlN, InN, AlGaN, InGaN, InAlN, and InAlGaN.
  • the thickness of the epitaxial layer is greater than or equal to 300 nm.
  • the thickness of the existing gallium nitride epitaxial layer is limited by stress, and the thickness is generally small.
  • the nitride epitaxial wafer of the embodiment of the present application can eliminate the stress well, so theoretically, the thickness can be unlimited.
  • the thickness of the epitaxial layer may be greater than or equal to 5 ⁇ m, and may also be greater than or equal to 10 ⁇ m.
  • the substrate includes a silicon substrate, a sapphire substrate, a silicon-on-insulator substrate (SOI substrate), a gallium nitride substrate, a gallium arsenide substrate, an indium phosphide substrate, and a nitride Aluminum substrate, silicon carbide substrate, quartz substrate or diamond substrate.
  • SOI substrate silicon-on-insulator substrate
  • GaN substrate gallium nitride substrate
  • gallium arsenide substrate an indium phosphide substrate
  • Aluminum substrate silicon carbide substrate, quartz substrate or diamond substrate.
  • the thickness of the nucleation layer is 10 nm to 300 nm.
  • the nitride epitaxial wafer further includes a transition layer disposed between the two-dimensional material layer and the epitaxial layer, and the transition layer is an aluminum nitride layer or a gallium nitride layer.
  • the transition layer and the nucleation layer are made of the same material.
  • the thickness of the transition layer is 10 nm-300 nm.
  • the second aspect of the embodiments of the present application provides a method for preparing a nitride epitaxial wafer, including:
  • nucleation layer Forming a nucleation layer on the substrate, the nucleation layer being an aluminum nitride layer or a gallium nitride layer;
  • the third group metal nitride is epitaxially grown on the two-dimensional material layer to form an epitaxial layer.
  • the nucleation layer is prepared by means of physical vapor deposition or metal organic chemical vapor deposition.
  • a two-dimensional material is grown in situ on the nucleation layer by chemical vapor deposition to form the two-dimensional material layer.
  • the preparation method further includes forming a transition layer between the two-dimensional material layer and the epitaxial layer, and the transition layer is an aluminum nitride layer or a gallium nitride layer.
  • a third aspect of the embodiments of the present application provides a semiconductor device, including the nitride epitaxial wafer described in the first aspect of the embodiments of the present application.
  • the semiconductor device may be a power device, a radio frequency device or an optoelectronic device. Specific examples are field effect transistors, light emitting diodes, laser diodes, and the like.
  • the nucleation layer and the two-dimensional material layer are sequentially arranged between the substrate and the nitride epitaxial layer, and the lattice slip of the two-dimensional material is used to directly release the stress and reduce
  • a nitride epitaxial layer with high uniformity and high crystal quality was obtained by epitaxially on the substrate.
  • the nitride epitaxial wafer of the embodiment of the present application has a high temperature external delay time, which can also effectively reduce the occurrence of warpage.
  • large-size single-layer two-dimensional material films usually have some pores (nano-level pores that are inevitable in the preparation process), resulting in film coverage The rate is low, and polycrystalline is easy to grow in the pores, which affects the crystal quality of the subsequent epitaxial layer.
  • a small-sized, high-quality two-dimensional material film is transferred and spliced to the nucleation layer to form a two-dimensional material layer, which can improve the overall film quality of the two-dimensional material layer and obtain a higher single-layer coverage.
  • the preparation method provided in the embodiments of the present application has a simple process and can meet the needs of large-scale production of high-quality main group III metal nitride materials and industrialized devices.
  • the semiconductor device provided by the embodiment of the present application due to the nitride epitaxial wafer provided by the embodiment of the present application, can obtain a large-size and thick nitride epitaxial layer device, which can effectively reduce the cost of the device and improve the performance of the device.
  • FIG. 1 is a schematic diagram of the structure of a nitride epitaxial wafer 100 provided in an embodiment of the present application;
  • FIGS. 2a to 2e are schematic diagrams of different splicing modes of two-dimensional material layers provided in the embodiments of the present application;
  • FIG. 3 is a schematic structural diagram of a nitride epitaxial wafer 100 provided in another embodiment of the present application.
  • Example 5 is a Raman scattering pattern of the epitaxial layer surface of the nitride epitaxial wafer prepared in Example 1 of the present application;
  • Example 6 is an Atomic Force Microscope (AFM) picture of the surface of the epitaxial layer of the nitride epitaxial wafer prepared in Example 1 of the present application.
  • AFM Atomic Force Microscope
  • the embodiments of the present application provide a nitride epitaxial wafer, which has a nitride epitaxial layer with high uniformity and high crystal quality, and can be applied to semiconductor devices to improve device performance.
  • the nitride epitaxial wafer may have a nitride epitaxial layer with a large size of 6 inches or more and a thickness of 5 microns or more.
  • the nitride epitaxial wafer 100 provided by the embodiment of the present application includes a substrate 10, a nucleation layer 20, a two-dimensional material layer 30, and an epitaxial layer 40.
  • the nucleation layer 20 is an AlN layer or a GaN layer, Formed on the substrate 10, the two-dimensional material layer 30 is formed on the nucleation layer 20, and the epitaxial layer 40 is formed on the two-dimensional material layer 30.
  • the material of the epitaxial layer 40 includes the third main group metal nitride.
  • the substrate 10 may be a silicon substrate, a sapphire substrate, a silicon-on-insulator substrate (SOI substrate), a gallium nitride substrate, a gallium arsenide substrate, an indium phosphide substrate, and a silicon nitride substrate.
  • the aluminum substrate, silicon carbide substrate, quartz substrate or diamond substrate can also be any of the currently known substrates that can be used to prepare the third group metal nitride film.
  • the crystal orientation of the silicon substrate is not limited. For example, it can be a silicon substrate with a (111) crystal face index, a silicon substrate with a (100) crystal face index, or a silicon substrate with other crystal face indexes. .
  • the nucleation layer 20 is a layer of aluminum nitride or gallium nitride film, and the nucleation layer 20 completely covers the substrate 10.
  • the nucleation layer 20 can provide a nucleation center for the subsequent growth of nitride epitaxial layers
  • the nucleation layer 20 can relieve the stress caused by the lattice mismatch between the substrate 10 and the epitaxial layer 40, and can also effectively block the impurities brought by the substrate 10 from the subsequent growth of the nitride epitaxial layer. Influence, reduce lattice defects, reduce dislocation density, and improve the crystal quality of the nitride epitaxial layer.
  • the nucleation layer 20 is relatively thin and is single crystal or quasi-single crystal, so the stress caused by the lattice mismatch between the substrate 10 and the epitaxial layer 40 can be relieved, and the crystal quality of the subsequent nitride epitaxial layer will not be affected. It can also effectively control costs.
  • the thickness of the nucleation layer 20 may be 10 nm to 300 nm. In other embodiments of the present application, the thickness of the nucleation layer 20 may be 20 nm-200 nm. In some other embodiments of the present application, the thickness of the nucleation layer 20 may also be 50 nm-150 nm.
  • the nucleation layer 20 may be prepared by physical vapor deposition, or may be prepared by metal organic chemical vapor deposition.
  • physical vapor deposition (Physical Vapor Deposition) is a process that uses a physical process to achieve material transfer and transfer atoms or molecules to the surface of a substrate.
  • the basic methods of PVD include vacuum evaporation, sputtering, ion plating (hollow cathode ion plating, hot cathode ion plating, arc ion plating, active reactive ion plating, radio frequency ion plating, DC discharge ion plating) and so on.
  • Metal-organic chemical vapor deposition is a chemical vapor deposition technology that uses the thermal decomposition reaction of organometallic compounds to grow thin films by vapor phase epitaxy.
  • the organic compound and the hydride of V and VI elements are used as crystal growth source materials to grow III-V and II-VI compound films on the substrate by means of thermal decomposition reaction.
  • the metal-organic chemical vapor deposition method can improve the crystal quality of the subsequent epitaxial layer nitrides, while the physical vapor deposition method is simple in process.
  • the entire nitride epitaxial wafer can be prepared by only one epitaxy, without the need for secondary epitaxy. Reduce the cost of epitaxy.
  • the material of the two-dimensional material layer 30 may specifically include graphene, boron nitride, silylene, germanene, phosphorene, boronene, stanene, transition metal sulfide, transition metal carbide, and transition metal carbide. At least one of metal nitrides.
  • the two-dimensional material layer 30 is formed on the nucleation layer 20, and van der Waals epitaxy can be used to release stress, and the subsequent growth of the epitaxial layer 40 does not require re-nucleation. Van der Waals epitaxy is the force between atoms, that is, atoms do not form bonds with each other.
  • Inserting the two-dimensional material layer 30 between the two nitride layers of the nucleation layer 20 and the epitaxial layer 40 can make the two-dimensional material of the two-dimensional material layer 30 and the two nitride layers of the nucleation layer 20 and the epitaxial layer 40 not directly Bonded, there will be no stress. The stress caused by the lattice mismatch will be eliminated by the tensile slip of the two-dimensional material.
  • the thickness of the two-dimensional material layer 30 is less than or equal to 1 nm.
  • the two-dimensional material layer is a single-layer two-dimensional material, such as a single-layer graphene, a single-layer boron nitride, a single-layer transition metal sulfide, and a single-layer blue phosphorus.
  • the single-layer two-dimensional material can better obtain the epitaxial layer with higher crystal quality, and improve the uniformity of the nitride film of the epitaxial layer.
  • the two-dimensional material layer 30 may not be a single layer at every location, and there may be a small amount of two or more regions.
  • the two-dimensional material layer 30 may also be a doped two-dimensional material, the doping element may be various elements known to be doped with a two-dimensional material, and the doped two-dimensional material may be, for example, nitrogen-doped graphene.
  • the thickness of the two-dimensional material layer 30 when the thickness of the two-dimensional material layer 30 is less than or equal to 1 nm, that is, when the distance between the upper and lower nitride layers of the nucleation layer 20 and the epitaxial layer 40 is less than or equal to 1 nm, it will be in a kind of remote epitaxy. That is, the atoms of the lower nucleation layer still have a weak force on the upper atoms, so that the upper atoms will still grow according to the arrangement of the lower atoms, so as to avoid the degradation of crystal quality and obtain a high-quality epitaxial layer.
  • the upper layer nitride When the two-dimensional material layer is too thick, the upper layer nitride will completely lose the force of the lower layer nitride, and it is easy to form polycrystalline.
  • the single-layer two-dimensional material has a relatively thinner thickness, so the atoms of the nucleation layer can form a relatively stronger force on the atoms of the epitaxial layer, which is more conducive to improving the crystal quality of the epitaxial layer.
  • there are voids in the two-dimensional material layer including splicing gaps and pores), that is, the area with a thickness of 0, force will be generated between the upper and lower nitride layers to introduce stress, but as a whole, as long as the void ratio is within a certain range , Can still play a role in reducing stress.
  • the lamination will greatly affect the stress release, and will also cause the loss of force between the epitaxial layer and the nucleation layer, resulting in polycrystalline formation, and reducing the crystal quality of the epitaxial layer. Therefore, the impact of the two-dimensional material lamination is much greater than the void.
  • the two-dimensional material layer 30 is formed by transferring multiple small-size two-dimensional material films onto the nucleation layer 20 and splicing together.
  • the two-dimensional material layer is formed by splicing, and small-size, high-quality (no laminate or very few laminates, less pores) two-dimensional material films can be selected to be transferred and spliced to the nucleation layer to form a two-dimensional material layer. It can improve the quality of the two-dimensional material layer, reduce the area ratio of the laminated area, and at the same time, reduce the pores to obtain a higher single-layer coverage, so as to better use the two-dimensional material layer to release stress and improve the crystal of the nitride epitaxial layer quality.
  • the specific shape and size of the small-size two-dimensional material film used for splicing are not limited, and can be any shape.
  • the shape of the small-sized two-dimensional material film is a polygon.
  • the polygonal structure film has a linear side length, which can better implement the splicing process and better control the uniformity of the gap width between two adjacent small-sized two-dimensional material films.
  • the polygon has an internal angle that can be divisible by 360°, which can better adapt to a circular substrate. In order to better realize the splicing, small-size two-dimensional material films cut into regular shapes can be selected for splicing.
  • the more regular and symmetrical the shape is it is more conducive to cutting and splicing, and it can also make the outer contour of the finally formed two-dimensional material layer more regular, so as to better control the growth and preparation of the epitaxial layer, and can Reduce material loss during final cutting (generally, the edges of the epitaxial layer and subsequent functional layers will be cut off after preparation).
  • the shape of the small-sized two-dimensional material film may be, but not limited to, an equilateral triangle, a right-angled triangle, a regular hexagon, a square, a rectangle, or a rhombus.
  • the small-size two-dimensional material film 301 has a rectangular shape, and a plurality of rectangular small-size two-dimensional material films 301 are arranged in order to form a two-dimensional material layer 30 with a rectangular outer contour.
  • the shape of the small-sized two-dimensional material film 301 is a regular hexagon.
  • the shape of the small-sized two-dimensional material film 301 is a rhombus. As shown in FIG.
  • the shape of the small-sized two-dimensional material film 301 is a regular triangle. As shown in FIG. 2e, the shape of the small-sized two-dimensional material film 301 is a right triangle. It should be noted that FIGS. 2a-2e are only schematic views of the splicing of the small-sized two-dimensional material film 301 in some embodiments of the present application. The specific splicing form, the shape and quantity of the small-sized two-dimensional material film, and the two-dimensional The outer contour of the material layer is not limited to what is shown in the figure. The size of the small-size two-dimensional material film 301 can be reasonably selected according to the size of the substrate and the quality of the two-dimensional material film.
  • the size of the small-size two-dimensional material film may be 1 mm-100 mm.
  • the use of small-size, high-quality two-dimensional material film transfer and splicing to the nucleation layer to form a two-dimensional material layer can improve the quality of the two-dimensional material layer, obtain a higher single-layer coverage, and effectively avoid the self-contained single-layer two-dimensional material. Some have shortcomings such as small size and insufficient coverage.
  • the solution of this application to form a two-dimensional material layer by splicing is particularly suitable for the preparation of large-size nitride epitaxial wafers of 6 inches, 8 inches and above.
  • the multiple small-sized two-dimensional material films 301 that are spliced to form the two-dimensional material layer 30 may not all have the same shape.
  • the two-dimensional material layer 30 may include two or more different The small-sized two-dimensional material film 301 in the shape, for example, contains both a rectangle and a triangle.
  • the two-dimensional material layer 30 formed by splicing can be clearly seen as a discontinuous film.
  • the two-dimensional material layer 30 does not completely cover the nucleation layer 20, and a certain distance may be left between the outer edge of the two-dimensional material layer 30 and the outer edge of the nucleation layer 20.
  • the two-dimensional material can be prevented from forming a stack at the splicing point, which is beneficial to the subsequent nitrides.
  • the growth of the epitaxial layer improves the crystal quality.
  • the width of the splicing gap is greater than or equal to 0.1 ⁇ m and less than or equal to 1/2 of the distance between the largest two points on the small-sized two-dimensional material film. Taking the small-size two-dimensional material film shape as a square as an example, the width of the splicing gap is smaller than the radius of the circumscribed circle of the square. Reasonable control of the size of the splicing gap can not only prevent the appearance of two-dimensional material stacks, but also better ensure that the two-dimensional material layer has a certain area ratio on the nucleation layer, which is beneficial to exert its stress relief effect. To facilitate operation and control, in some embodiments of the present application, the splicing gap may be greater than or equal to 0.5 mm, for example, specifically 1 mm-20 mm.
  • the proportion of the area occupied by the two-dimensional material layer 30 on the nucleation layer 20 is not less than 50%.
  • the two-dimensional material layer 30 has a certain area ratio on the nucleation layer 20, which is beneficial to exert its stress relief effect. In some other embodiments of the present application, the area ratio of the two-dimensional material layer 30 on the nucleation layer 20 is greater than 70%.
  • the two-dimensional material layer 30 is grown and formed in situ on the nucleation layer 20.
  • the entire two-dimensional material layer 30 is generally a continuous film.
  • a discontinuous film may also be formed due to process operation problems.
  • the two-dimensional material layer 30 may be grown in situ by chemical vapor deposition.
  • the growth process of two-dimensional materials generally includes the process of nucleation point formation-expansion-merging.
  • the in-situ growth method in the embodiments of the application is particularly suitable for two-dimensional nitride materials, such as boron nitride. Since the two-dimensional material layer and the epitaxial layer are both nitrides, it can also be prepared by metal organic chemical vapor deposition like the epitaxial layer. , Thereby simplifying the process operation of the entire epitaxial film layer.
  • the material of the epitaxial layer 40 includes a third group metal nitride, specifically, for example, it may be one or more of GaN, AlN, InN, AlGaN, InGaN, InAlN, and InAlGaN.
  • the thickness of the epitaxial layer 40 is greater than or equal to 300 nm.
  • the thickness of the existing gallium nitride epitaxial layer is limited by stress, and the thickness is generally small.
  • the nitride epitaxial wafer of the embodiment of the present application can eliminate stress well, so it can be applied to the preparation of thick film epitaxial layer, which can theoretically be unlimited thickness.
  • the thickness of the epitaxial layer may be greater than or equal to 5 ⁇ m, or greater than or equal to 10 ⁇ m, for example, 15 ⁇ m-100 ⁇ m.
  • the surface of the epitaxial layer 40 is flat as a whole, and the splicing gap of the two-dimensional material does not affect the continuous film formation of the nitride of the epitaxial layer.
  • the epitaxial layer 40 may completely cover the nucleation layer 20 or partially cover the nucleation layer 20, which is basically consistent with the outer contour of the two-dimensional material layer 30.
  • different nitride epitaxial layers can be applied to different semiconductor devices, for example, GaN, AlGaN, and AlN can be applied to power devices, and In-containing nitride epitaxial layers can be applied to optoelectronic devices.
  • other elements may also be added to the epitaxial layer 40.
  • carbon may be added to form high resistance and improve the voltage resistance.
  • the epitaxial layer 40 is easily peeled off and transferred to other target substrates, which can be used to realize the reuse of the original substrate 10. It can also be used to make gallium nitride self-supporting substrates and flexible devices.
  • the nitride epitaxial wafer 100 further includes a transition layer 50 disposed between the two-dimensional material layer 30 and the epitaxial layer 40.
  • the transition layer 50 may be an AlN layer or a GaN layer. Floor.
  • the thickness of the transition layer can be 10nm-300nm.
  • the arrangement of the transition layer 50 can effectively block the impurities introduced by the two-dimensional material layer 30 and improve the crystal quality of the nitride epitaxial layer.
  • due to the existence of certain splicing gaps and pores in the two-dimensional material layer (nano-level pores unavoidable in the preparation process, Generally, the size is tens or hundreds of nanometers).
  • the transition layer 50 After the transition layer 50 is set, a better crystal quality can be formed in the uncovered area of the two-dimensional material layer.
  • the transition layer 50 and the nucleation layer 20 are made of the same material, that is, the transition layer 50 and the nucleation layer 20 are both AlN layers, or both are GaN layers. In this way, the two-dimensional material layer 30 can be located in the middle of the homogeneous layer, thereby improving the crystal quality of the subsequent nitride epitaxial layer 40.
  • the transition layer 50 is peeled away from the two-dimensional material layer 30 along with the epitaxial layer 40.
  • a nucleation layer and a two-dimensional material layer are sequentially arranged between the substrate and the nitride epitaxial layer, the nucleation layer is used to relieve the stress caused by lattice mismatch, and the two-dimensional The lattice slip of the material directly releases the stress, which can reduce the occurrence of epitaxial warpage, and obtain a nitride epitaxial layer with high uniformity and high crystal quality.
  • the nucleation layer can provide a nucleation center for the subsequent growth of the nitride epitaxial layer, alleviate the lattice mismatch between the substrate and the epitaxial layer, and can effectively block the impurities brought by the substrate from the subsequent nitride epitaxial layer growth.
  • the two-dimensional material layer can directly release the stress by using lattice slip, significantly reducing the occurrence of epitaxial warping, and improving the uniformity and crystal quality of the nitride epitaxial layer.
  • the two-dimensional material layer formed by the splicing method can effectively reduce the warpage of the nitride epitaxial layer of large size (6 inches and above) and thick film (5 ⁇ m and above), and obtain large size, large thickness and high quality.
  • the two-dimensional material layer formed by the in-situ growth method can effectively avoid the damage that may occur during the two-dimensional material transfer process, and can be prepared by the deposition process like the epitaxial layer.
  • an embodiment of the present application also provides a method for preparing a nitride epitaxial wafer, including:
  • a nucleation layer is formed on the substrate, and the nucleation layer is an AlN layer or a GaN layer.
  • the nucleation layer 20 may be prepared on the substrate 10 by physical vapor deposition or metal organic chemical vapor deposition. Before preparing the nucleation layer 20, the substrate 10 may be subjected to a conventional cleaning process.
  • the nucleation layer 20 is prepared on the substrate 10 by means of magnetron sputtering.
  • the substrate 10 may be placed in a magnetron sputtering system, and the pressure of the reaction chamber is 0.8 Pa -1Pa, pass nitrogen and oxygen for 3min-5min to obtain the processed substrate 10, and then use 99.999% pure aluminum or gallium as the target, magnetron sputtering aluminum nitride or nitrogen on the processed substrate 10 Gallium is obtained, and the nucleation layer 20 is obtained.
  • the operating parameters in the magnetron sputtering process can be set according to actual needs, and the embodiments of the present application are not particularly limited, nor are they limited to the foregoing range. In some other embodiments of the present application, other physical vapor deposition methods may also be used to prepare the nucleation layer 20.
  • the nucleation layer 20 is prepared on the substrate 10 by metal-organic chemical vapor deposition.
  • the substrate 10 may be placed in a metal-organic chemical vapor deposition reaction chamber at 900 At a temperature of -1100°C and a pressure of 30-60 Torr, hydrogen and ammonia gas are introduced for 3 minutes to 5 minutes to obtain a processed substrate 10, and then hydrogen, ammonia, and an aluminum source or a gallium source are introduced.
  • Aluminum nitride or gallium nitride is deposited on the substrate 10 to obtain the nucleation layer 20.
  • each parameter in the deposition process is not limited to the above range.
  • Gallium sources include, but are not limited to, trimethylgallium and triethylgallium.
  • the aluminum source includes, but is not limited to, trimethylaluminum and triethylaluminum.
  • the method for forming the two-dimensional material layer 30 on the nucleation layer 20 is: transferring multiple small-sized two-dimensional material films to the nucleation layer 20 and splicing to form the two-dimensional material layer 30.
  • graphene it can be, but not limited to, using chemical vapor deposition to grow graphene on a metal substrate (such as copper foil).
  • a metal substrate such as copper foil
  • carbon is introduced into the reaction chamber.
  • the carbon source can be a carbon-containing gas, such as methane, ethylene, acetylene, etc.; the metal substrate on which graphene is grown is placed in a mixed solution of 1mol/L iron oxide and 2mol/L hydrochloric acid for 12 hours to remove the metal substrate, Obtain the graphene from which the metal substrate is removed, and then select the high-quality part of the graphene to cut to obtain multiple high-quality and small-size graphene films, transfer multiple small-size graphene films to the nucleation layer 20, and splice them into the target Dimensions of the two-dimensional material layer.
  • graphene films can be prepared multiple times to obtain multiple high-quality and small-size graphene films.
  • multiple high-quality and small-size graphene films can be cut into the same regular shape.
  • the two-dimensional material layer formed by splicing is a discontinuous film, and a splicing gap is formed between adjacent small-size graphene films 301. The setting of the splicing gap is specifically as described above.
  • the method for forming the two-dimensional material layer 30 on the nucleation layer 20 is to grow the two-dimensional material in situ on the nucleation layer 20 to form the two-dimensional material layer 30.
  • the two-dimensional material can be grown in situ by chemical vapor deposition.
  • the in-situ growth of boron nitride can be carried out in a metal organic chemical vapor deposition reaction chamber, so that single-step epitaxy can be realized, the process is simplified, and the cost is reduced.
  • the specific operation of the in-situ growth of various two-dimensional materials can adopt existing known methods, which are not specifically limited in this application.
  • the epitaxial layer 40 may be prepared by metal organic chemical vapor deposition. Specifically, the substrate 10 obtained after step S02 is placed in a metal organic chemical vapor deposition reaction chamber, and hydrogen and ammonia are blown in for 3-5 minutes at a temperature of 900-1100° C. and a pressure of 30-60 Torr to obtain The treated substrate 10 is then fed with hydrogen gas, ammonia gas, and a source of the third main group metal, and the third main group metal nitride is epitaxially grown on the two-dimensional material layer 30 to form the epitaxial layer 40.
  • the metal nitride of the third main group may be specifically, for example, one or more of GaN, AlN, InN, AlGaN, InGaN, InAlN, and InAlGaN.
  • the third group metal source is an organic compound containing a third group metal element, such as trimethylgallium, triethylgallium, trimethylaluminum, and triethylaluminum.
  • the above-mentioned preparation method may further include forming a transition layer 50 between the two-dimensional material layer 30 and the epitaxial layer 40. That is, before step S03, a transition layer 50 is first prepared on the two-dimensional material layer 30, and then the epitaxial layer 40 is grown on the transition layer 50.
  • the material of the transition layer 50 can be an AlN layer or a GaN layer.
  • the material of the transition layer 50 is the same as the material of the nucleation layer 20.
  • the transition layer 50 may specifically be a high temperature aluminum nitride layer or a high temperature gallium nitride layer, and the transition layer 50 may be an AlN layer or a GaN layer with a high V/III ratio.
  • the provision of the transition layer 50 can avoid the risk of leakage caused by the introduction of more impurities in the two-dimensional material.
  • the transition layer 50 can act as an impurity barrier layer to improve the crystal quality of the subsequent nitride epitaxial layer.
  • the transition layer 50 can be used as an impurity barrier layer on the one hand, and on the other hand, by doping a certain amount of carbon in the transition layer 50, a high resistance can be formed, thereby improving the nitride epitaxy.
  • the pressure resistance of the layer can be used as an impurity barrier layer on the one hand, and on the other hand, by doping a certain amount of carbon in the transition layer 50, a high resistance can be formed, thereby improving the nitride epitaxy.
  • the embodiment of the application also provides a semiconductor device, including the nitride epitaxial wafer provided in the embodiment of the application.
  • the nitride epitaxial wafer of the embodiment of the application can be directly used as a part of the semiconductor device, or the epitaxial layer can be peeled off and applied to In semiconductor devices.
  • the semiconductor device includes, but is not limited to, a power device, a radio frequency device, or an optoelectronic device.
  • the power devices and radio frequency devices may be transistors, specifically field effect transistors, such as High Electron Mobility Transistor (HEMT).
  • HEMT High Electron Mobility Transistor
  • the optoelectronic device is, for example, a light emitting diode (Light Emitting Diode, LED) and a laser diode (Laser diode, LD). Specifically, it can be a nitride-based light-emitting diode or a nitride-based quantum well laser diode.
  • the semiconductor device is a light emitting diode
  • the light emitting diode includes the nitride epitaxial wafer provided above in the embodiment of the present application, and the quantum well active region that continues epitaxial growth on the epitaxial layer, etc., and P, N Electrodes etc.
  • a method for preparing a nitride epitaxial wafer includes:
  • the silicon substrate with the graphene layer is placed in a metal organic chemical vapor deposition reaction chamber, and hydrogen, ammonia, and a source of gallium are introduced at a temperature of 1100°C and a pressure of 50 Torr.
  • a 10nm aluminum nitride transition layer and a 5 ⁇ m gallium nitride epitaxial layer were sequentially grown on the top.
  • a method for preparing a nitride epitaxial wafer includes:
  • the silicon substrate on which the graphene layer is formed is placed in a metal organic chemical vapor deposition reaction chamber, and hydrogen, ammonia, and trimethylgallium are introduced at a temperature of 1100°C and a pressure of 50 Torr.
  • a gallium nitride epitaxial layer with a thickness of 2 ⁇ m is grown on the graphene layer.
  • a method for preparing a nitride epitaxial wafer includes:
  • a method for preparing a nitride epitaxial wafer includes:
  • the thickness of the graphene is not more than 1nm
  • Example 1 The obtained gallium nitride epitaxial substrate for Raman spectroscopy Raman detection, the surface of the epitaxial layer Raman scattering spectra shown in Figure 5, it can be seen from FIG. 5, Raman peak E2 (E2 Hight) located 568cm - It is about 1, which is basically consistent with the standard Raman peak of gallium nitride, indicating that the gallium nitride epitaxial layer is basically in a stress-free state.
  • E2 is the GaN Raman peak that is strongly related to the stress. By comparing its offset from the standard peak, the type and magnitude of the stress can be judged (left shift is tensile stress, right shift is compressive stress).
  • Fig. 6 is an Atomic Force Microscope (AFM) picture of the epitaxial layer of the gallium nitride epitaxial wafer obtained in Example 1.
  • AFM Atomic Force Microscope

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Abstract

本申请实施例提供一种氮化物外延片，包括衬底；成核层，形成于所述衬底上，所述成核层为氮化铝层或氮化镓层；二维材料层，形成于所述成核层上，所述二维材料层由多块小尺寸二维材料薄膜拼接形成，或者所述二维材料层由二维材料在所述成核层上原位生长形成；外延层，形成于所述二维材料层上，所述外延层的材质包括第三主族金属氮化物。通过在衬底上设置成核层，并通过拼接或原位生长的方式在成核层上形成二维材料层，能够有效缓解衬底和外延层之间由于晶格失配和热失配产生的应力，降低外延翘曲的发生，提高氮化物外延片的均匀性和可靠性。本申请实施例还提供一种氮化物外延片的制备方法和包含该氮化物外延片的半导体器件。

Description

氮化物外延片及其制备方法和半导体器件
本申请要求于2020年5月18日提交中国专利局、申请号为202010418395.2、申请名称为“氮化物外延片及其制备方法和半导体器件”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及半导体技术领域，尤其涉及一种氮化物外延片及其制备方法和半导体器件。
背景技术
氮化镓(GaN)材料由于禁带宽度大、迁移率高等优势，被广泛用于功率器件、射频器件和光电器件中。目前，氮化镓材料通常是在硅衬底上外延生长得到。然而，由于GaN与硅之间存在超过17％的大晶格失配和热膨胀系数失配，因此在硅基氮化镓中会存在巨大应力，这些应力会导致外延中产生翘曲，从而影响GaN外延片的均匀性和可靠性。而且随着衬底尺寸的增大，以及外延层厚度的增加，翘曲的问题将变得越来越严重。因此，有必要寻求一种可以有效缓解应力，降低翘曲发生的氮化镓外延生长方法。
发明内容
本申请实施例提供一种氮化物外延片及其制备方法和半导体器件，通过在衬底上设置成核层，并通过拼接或原位生长的方式在成核层上形成二维材料层，能够有效缓解释放衬底和外延层之间由于晶格失配和热失配产生的应力，降低外延过程中和外延后翘曲，提升氮化物外延片的均匀性和可靠性，进而提升半导体器件的性能。
本申请实施例第一方面提供一种氮化物外延片，包括：
衬底；
成核层，形成于所述衬底上，所述成核层为氮化铝(AlN)层或氮化镓层；
二维材料层，形成于所述成核层上；所述二维材料层由多块小尺寸二维材料薄膜拼接形成，或者所述二维材料层由二维材料在所述成核层上原位生长形成；
外延层，形成于所述二维材料层上，所述外延层的材质包括第三主族金属氮化物。
其中，成核层可为后续生长氮化物外延层提供成核中心，缓解衬底与外延层的晶格失配，同时还可以有效阻挡衬底带来的杂质对后续氮化物外延层的生长产生的影响，提高外延层的晶体质量。而二维材料层可利用晶格滑移直接释放应力，显著降低外延翘曲的发生，提高氮化物外延层的均匀性和晶体质量。其中，通过拼接方式形成的二维材料层，尤其可以有效降低大尺寸(6英寸及以上)、厚膜(5μm及以上)氮化物外延层的翘曲发生，获得大尺寸、大厚度、高质量氮化物外延片。而通过原位生长的方式形成的二维材料层能够有效避免二维材料转移过程可能产生的破损，可与外延层一样采用沉积工艺制备。
本申请一实施方式中，所述二维材料层由多块小尺寸二维材料薄膜拼接形成。通过有目的地选择多块高质量的小尺寸二维材料薄膜拼接形成二维材料层，可以获得整体质量较高的二维材料层，很好地实现应力释放，从而顺利制备获得高质量6英寸及以上的大尺寸 氮化物外延片。
本申请实施方式中，部分或任意相邻两块所述小尺寸二维材料薄膜之间具有拼接缝隙。拼接缝隙的设置可以避免二维材料层在拼接处出现叠层现象。
本申请一些实施方式中，所述拼接缝隙宽度大于或等于0.1μm，且小于或等于所述小尺寸二维材料薄膜上最大两点间距离的1/2。合理控制拼接缝隙尺寸，既能防止二维材料叠层的出现，又能较好地保证二维材料层在成核层上具有一定的面积占比，有利于发挥其应力释放作用。
本申请一些实施方式中，所述二维材料层在所述成核层上所占的面积比例不低于50％。二维材料层在成核层上具有一定的面积占比，有利于发挥其应力释放作用。
本申请一些实施方式中，所述小尺寸二维材料薄膜的形状可为多边形。多边形结构薄膜具有直线型边长，可较好地实施拼接工艺，更好地控制相邻两块小尺寸二维材料薄膜之间的缝隙宽度的均匀性。具体地，本申请一些实施方式中，小尺寸二维材料薄膜的形状为等边三角形、直角三角形、正六边形、正方形、矩形或菱形。当然，本申请实施例中小尺寸二维材料薄膜的形状并不局限于多边形，其他可实现拼接的形状也可以，如圆形等。
本申请另一实施方式中，所述二维材料层由二维材料在所述成核层上原位生长形成。原位生长能够直接一次沉积制备获得较完整的二维材料薄膜，工艺操作方便。
本申请实施方式中，所述二维材料层的材质包括石墨烯、氮化硼、硅烯、锗烯、磷烯、硼烯、锡烯、过渡金属硫化物、过渡金属碳化物和过渡金属氮化物中的至少一种。
本申请实施方式中，所述二维材料层的厚度小于或等于1nm。
本申请实施方式中，所述二维材料层为单层石墨烯。
本申请实施方式中，所述外延层的材质为第三主族金属氮化物，具体地可包括GaN、AlN、InN、AlGaN、InGaN、InAlN、InAlGaN中的一种或多种。
本申请实施方式中，所述外延层的厚度大于或等于300nm。现有氮化镓外延层的厚度受应力所限一般厚度较小，而本申请实施例的氮化物外延片可以很好地消除应力，因此理论上可以做到无限厚度。在本申请一些实施方式中，外延层的厚度可以是大于或等于5μm，也可以是大于或等于10μm。
本申请实施方式中，所述衬底包括硅衬底、蓝宝石衬底、绝缘体上硅衬底(SOI衬底)、氮化镓衬底、砷化镓衬底、磷化铟衬底、氮化铝衬底、碳化硅衬底、石英衬底或金刚石衬底。
本申请实施方式中，所述成核层的厚度为10nm-300nm。
本申请实施方式中，所述的氮化物外延片还包括设置于所述二维材料层与所述外延层之间的过渡层，所述过渡层为氮化铝层或氮化镓层。
本申请实施方式中，所述过渡层与所述成核层的材质相同。
本申请实施方式中，所述过渡层的厚度为10nm-300nm。
本申请实施例第二方面提供一种氮化物外延片的制备方法，包括：
在衬底上形成成核层，所述成核层为氮化铝层或氮化镓层；
将多块小尺寸二维材料薄膜转移至所述成核层上拼接形成所述二维材料层；或者在所述成核层上原位生长二维材料形成二维材料层；
在所述二维材料层上外延生长第三主族金属氮化物，形成外延层。
本申请实施方式中，采用物理气相沉积或金属有机化学气相沉积的方式制备所述成核层。
本申请实施方式中，采用化学气相沉积的方式在所述成核层上原位生长二维材料形成所述二维材料层。
本申请实施方式中，所述的制备方法还包括在二维材料层与所述外延层之间形成过渡层，所述过渡层为氮化铝层或氮化镓层。
本申请实施例第三方面提供一种半导体器件，包括本申请实施例第一方面所述的氮化物外延片。所述半导体器件可以是功率器件、射频器件或光电器件。具体例如为场效应晶体管、发光二极管、激光二极管等。
本申请实施例提供的氮化物外延片和制备方法，通过在衬底与氮化物外延层之间依次设置成核层和二维材料层，利用二维材料的晶格滑移直接释放应力，降低了外延翘曲的发生，在衬底上外延获得了高均匀性、高晶体质量的氮化物外延层。本申请实施例氮化物外延片在高温外延时，也能够有效降低翘曲的发生。同时，由于目前大尺寸、高质量单层二维材料薄膜制备存在一定困难，大尺寸单层二维材料薄膜通常会存在一些孔隙(制备工艺过程不可避免存在的纳米级孔隙)，导致膜层覆盖率较低，孔隙处易生长多晶，影响后续外延层晶体质量。本申请实施例通过利用小尺寸、高质量的二维材料薄膜转移拼接至成核层上形成二维材料层，可以提高二维材料层的整体膜层质量，获得更高的单层覆盖率，从而更好地利用二维材料层释放应力，提升氮化物外延层的晶体质量。本申请实施例提供的制备方法，工艺简单，可以满足大规模生产高质量第三主族金属氮化物材料和工业化器件的需求。本申请实施例提供的半导体器件，由于采用本申请实施例提供的氮化物外延片，可以获得大尺寸，厚氮化物外延层器件，可有效降低器件成本，提高器件性能。
附图说明
图1是本申请一实施方式中提供的氮化物外延片100的结构示意图；
图2a至图2e是本申请实施方式中提供的二维材料层不同拼接方式的示意图；
图3是本申请另一实施方式中提供的氮化物外延片100的结构示意图；
图4是本申请实施方式中提供的氮化物外延片的制备工艺流程图；
图5是本申请实施例1制备的氮化物外延片的外延层表面拉曼散射图谱；
图6是本申请实施例1制备的氮化物外延片的外延层表面的原子力显微镜(Atomic Force Microscope，AFM)图片。
具体实施方式
下面结合本申请实施例中的附图对本申请实施例进行描述。
本申请实施例提供一种氮化物外延片，其具有高均匀性、高晶体质量氮化物外延层，可应用于半导体器件中，以提高器件性能。而且该氮化物外延片可具有6英寸以上大尺寸、5微米及以上厚度的氮化物外延层。
如图1所示，本申请实施例提供的氮化物外延片100，包括衬底10、成核层20、二维 材料层30、以及外延层40，成核层20为AlN层或GaN层，形成于衬底10上，二维材料层30形成于成核层20上，外延层40形成于二维材料层30上，外延层40的材质包括第三主族金属氮化物。
本申请实施方式中，衬底10可以是硅衬底、蓝宝石衬底、绝缘体上硅衬底(SOI衬底)、氮化镓衬底、砷化镓衬底、磷化铟衬底、氮化铝衬底、碳化硅衬底、石英衬底或金刚石衬底，还可以是现有已知的任意一种可用于制备第三主族金属氮化物薄膜的衬底。其中，硅衬底的晶体取向不限，例如可以是(111)晶面指数的硅衬底，也可以是(100)晶面指数的硅衬底，还可以是其他晶面指数的硅衬底。
本申请实施方式中，成核层20为一层氮化铝或氮化镓薄膜，成核层20完全覆盖衬底10，成核层20一方面可为后续生长氮化物外延层提供成核中心，另一方面成核层20可以缓解衬底10与外延层40之间由于晶格失配产生的应力，同时还可以有效阻挡衬底10带来的杂质给后续氮化物外延层的生长产生的影响，减少晶格缺陷，降低位错密度，提高氮化物外延层的晶体质量。另外，成核层20较薄，为单晶、准单晶，因此可缓解衬底10与外延层40之间晶格失配产生的应力，不会给后续氮化物外延层的晶体质量带来影响，还可以有效控制成本。本申请一些实施方式中，成核层20的厚度可以为10nm-300nm。本申请另一些实施方式中，成核层20的厚度可以为20nm-200nm。本申请其他一些实施方式中，成核层20的厚度也可以为50nm-150nm。
本申请实施方式中，成核层20可以是采用物理气相沉积的方式制备得到，也可以是采用金属有机化学气相沉积的方式制备得到。其中，物理气相沉积PVD(Physical Vapor Deposition)是利用物理过程实现物质转移，将原子或分子转移到基材表面上的过程。PVD的基本方法包括真空蒸发、溅射、离子镀(空心阴极离子镀、热阴极离子镀、电弧离子镀、活性反应离子镀、射频离子镀、直流放电离子镀)等。金属有机化学气相沉积(MOCVD,Metal-organic Chemical Vapor Deposition)是一种利用有机金属化合物热分解反应进行气相外延生长薄膜的化学气相沉积技术，具体地可将金属有机化合物以Ⅲ族、Ⅱ族元素的有机化合物和V、Ⅵ族元素的氢化物等作为晶体生长源材料，以热分解反应方式在衬底上生长Ⅲ-V族、Ⅱ-Ⅵ族化合物薄膜。其中，金属有机化学气相沉积的方式可以提升后续外延层氮化物的晶体质量，而物理气相沉积的方式工艺简单，整个氮化物外延片的制备仅需要一次外延即可完成，无需二次外延，可降低外延成本。
本申请实施方式中，二维材料层30的材质具体可以是包括石墨烯、氮化硼、硅烯、锗烯、磷烯、硼烯、锡烯、过渡金属硫化物、过渡金属碳化物和过渡金属氮化物中的至少一种。二维材料层30形成于成核层20上，可利用范德华外延释放应力，后续外延层40的生长也不需要重新成核。范德华外延即原子间作用力，就是原子相互之间没有成键。在成核层20和外延层40两层氮化物之间***二维材料层30，可以使得二维材料层30的二维材料与成核层20和外延层40两层氮化物之间没有直接成键，也就不会有应力。晶格失配造成的应力将会由二维材料的拉伸滑移而消除。
本申请实施方式中，二维材料层30的厚度小于或等于1nm。本申请一具体实施方式中，二维材料层为单层二维材料，例如为单层石墨烯、单层氮化硼、单层过渡金属硫化物和单层蓝磷等。单层二维材料能够更好地获得晶体质量较高的外延层，提升外延层氮化物薄膜 的均匀性。但需要说明的是，由于目前二维材料薄膜的制备工艺限制，二维材料层30可能并非每一处均为单层，也可能存在少量两层或两层以上的区域，本申请实施方式中，二维材料层30也可以是掺杂二维材料，掺杂元素可以是已知可掺杂二维材料的各种元素，掺杂二维材料例如可以是掺氮石墨烯。
本申请实施方式中，当二维材料层30的厚度小于或等于1nm，即成核层20和外延层40上下两层氮化物之间的间距在小于或等于1nm时，会处于一种远程外延的状态，即下层成核层原子依然对上层原子存在较弱的作用力，使得上层原子仍会按照下层原子的排列进行生长，从而避免晶体质量下降，获得高质量外延层。当二维材料层过厚时会使得上层氮化物完全失去下层氮化物的作用力，容易形成多晶。单层二维材料相对具有更薄的厚度，因此可以使成核层原子对外延层原子形成相对更强的作用力，更有利于提高外延层晶体质量。而如果二维材料层存在空隙(包括拼接缝隙与孔隙)，即厚度为0的区域，上下层氮化物之间会产生作用力而引入应力，但就整体而言，只要空隙比例在一定范围内，依然能起到降低应力的作用。而叠层会较大影响应力释放，也会使外延层与成核层间失去作用力导致多晶生成，降低外延层晶体质量，因此二维材料叠层的影响远大于空隙。
而且目前，大尺寸单层二维材料薄膜制备存在一定困难，难以获得高质量，通常膜层会存在一些叠层区域和孔隙区域，叠层和孔隙区域都容易导致多晶的生成。本申请一实施方式中，为了获得大尺寸高质量的氮化物外延片，二维材料层30采用多块小尺寸二维材料薄膜转移至成核层20上拼接形成。采用拼接方式形成二维材料层，可以有目的地选择小尺寸、高质量(无叠层或极少叠层、少孔隙)的二维材料薄膜转移拼接至成核层上形成二维材料层，可以提高二维材料层的质量，减少叠层区域面积占比，同时少孔隙也能获得更高的单层覆盖率，从而更好地利用二维材料层释放应力，提升氮化物外延层的晶体质量。
本申请实施方式中，用来拼接的小尺寸二维材料薄膜的具体形状和尺寸不限，可以是任意形状。本申请一些实施方式中，小尺寸二维材料薄膜的形状为多边形。多边形结构薄膜具有直线型边长，可较好地实施拼接工艺，更好地控制相邻两块小尺寸二维材料薄膜之间的缝隙宽度的均匀性。本申请一些实施方式中，多边形具有可被360°整除的内角角度，可以更好地适应圆形衬底。为了更好地实现拼接，可以是选择裁切成规则形状的小尺寸二维材料薄膜进行拼接。可以理解地，形状越规则、越对称，则更有利于裁切和拼接，也能使得最终形成的二维材料层的***轮廓更加规整，从而能够更好地控制外延层的生长制备，而且可以在最后裁剪时减少材料损耗(一般外延层及后续功能层制备好后会裁切掉边缘)。
本申请实施方式中，小尺寸二维材料薄膜的形状具体可以是但不限于是等边三角形、直角三角形、正六边形、正方形、矩形或菱形。如图2a所示，小尺寸二维材料薄膜301的形状为矩形，多个矩形小尺寸二维材料薄膜301按顺序排列形成***轮廓为矩形的二维材料层30。如图2b所示，小尺寸二维材料薄膜301的形状为正六边形。如图2c所示，小尺寸二维材料薄膜301的形状为菱形。如图2d所示，小尺寸二维材料薄膜301的形状为正三角形。如图2e所示，小尺寸二维材料薄膜301的形状为直角三角形。需要说明的是，图2a-图2e仅为本申请一些实施方式中小尺寸二维材料薄膜301的拼接示意图，本申请实施例具体的拼接形式、小尺寸二维材料薄膜的形状和数量、二维材料层的***轮廓均不限于图中所示。小尺寸二维材料薄膜301的尺寸可根据衬底尺寸和二维材料薄膜质量进行合理选择， 本申请一些实施方式中，小尺寸二维材料薄膜的尺寸可以是1mm-100mm。采用小尺寸、高质量的二维材料薄膜转移拼接至成核层上形成二维材料层，可以提高二维材料层的质量，获得更高的单层覆盖率，有效避免单层二维材料自有的尺寸小、覆盖率不足等缺点。本申请采用拼接方式形成二维材料层的方案尤其适用于6英寸、8英寸及以上的大尺寸氮化物外延片的制备。
本申请一些实施方式中，拼接构成二维材料层30的多块小尺寸二维材料薄膜301，也可以不都是相同形状，例如，二维材料层30可同时包含两种或两种以上不同形状的小尺寸二维材料薄膜301，例如同时包含矩形和三角形。
本申请实施方式中，拼接形成的二维材料层30可以明显看出为非连续薄膜。二维材料层30不完全覆盖成核层20，二维材料层30的外边缘与成核层20的外边缘之间可保留一定距离。
本申请实施方式中，部分或任意相邻两块小尺寸二维材料薄膜301之间留有拼接缝隙，通过设置一定拼接缝隙可以避免二维材料在拼接处形成叠层，从而有利于后续氮化物外延层的生长，提高晶体质量。
本申请一些实施方式中，拼接缝隙宽度大于或等于0.1μm，且小于或等于小尺寸二维材料薄膜上最大两点间距离的1/2。以小尺寸二维材料薄膜形状是正方形为例，拼接缝隙的宽度小于正方形外接圆半径。合理控制拼接缝隙尺寸，既能防止二维材料叠层的出现，又能较好地保证二维材料层在成核层上具有一定的面积占比，有利于发挥其应力释放作用。为方便操作控制，本申请一些实施方式中，拼接缝隙可以是大于或等于0.5mm，例如具体为1mm-20mm。
本申请一些实施方式中，二维材料层30在成核层20上所占的面积比例不低于50％。二维材料层30在成核层20上具有一定的面积占比，有利于发挥其应力释放作用。本申请其他一些实施方式中，二维材料层30在成核层20上所占的面积比例大于70％。
本申请另一实施方式中，二维材料层30在成核层20上原位生长形成。该实施方式中，二维材料层30整体一般为连续式薄膜，在某些实施方式中，因工艺操作问题也可能形成非连续薄膜。二维材料层30可以是采用化学气相沉积的方式原位生长获得。二维材料的生长过程一般包括成核点形成-扩张-合并的过程。本申请实施例原位生长方式尤其适用于氮化物二维材料，例如氮化硼，由于二维材料层与外延层同为氮化物，其也可同外延层一样通过金属有机化学气相沉积方式制备，从而可简化整个外延片膜层的工艺操作。
本申请实施方式中，外延层40的材质包括第三主族金属氮化物，具体地例如可以是GaN、AlN、InN、AlGaN、InGaN、InAlN、InAlGaN中的一种或多种。外延层40的厚度大于或等于300nm。现有氮化镓外延层的厚度受应力所限一般厚度较小，而本申请实施例的氮化物外延片可以很好地消除应力，因此可适用于厚膜外延层的制备，理论上可以无限厚度。在本申请一些实施方式中，外延层的厚度可以是大于或等于5μm，也可以是大于或等于10μm，例如15μm-100μm。本申请实施例中，外延层40表面整体平整，二维材料的拼接缝隙不影响外延层氮化物连续成膜。外延层40可以是完全覆盖成核层20，也可以是部分覆盖成核层20，与二维材料层30***轮廓基本一致。
本申请实施方式中，不同氮化物外延层可以适用不同半导体器件，如GaN、AlGaN、 AlN可适用功率器件，而含In的氮化物外延层可适用于光电器件。
本申请实施方式中，为配合使用性能要求，外延层40中也可掺入其他元素，例如为了提升绝缘性，可掺入碳，形成高电阻，提高耐压性能。
本申请实施方式中，由于外延层40和二维材料层30之间存在较弱范德华力，因此外延层40易于被剥离并转移至其他目标衬底，可用于实现原衬底10的重复利用，也可用于制作氮化镓自支撑衬底和柔性器件。
本申请一些实施方式中，如图3所示，氮化物外延片100还包括设置于二维材料层30与外延层40之间的过渡层50，过渡层50可以是AlN层，也可以是GaN层。过渡层的厚度可以是10nm-300nm。过渡层50的设置可以有效阻挡二维材料层30引入的杂质，提升氮化物外延层的晶体质量，同时由于二维材料层存在一定拼接缝隙和孔隙(制备工艺过程不可避免存在的纳米级孔隙，一般尺寸为几十或几百纳米)，过渡层50设置后可以使二维材料层未覆盖处也形成较好的晶体质量。进一步地，过渡层50与成核层20的材质相同，即过渡层50与成核层20同为AlN层，或同为GaN层。这样可使得二维材料层30位于同质层中间，从而提高后续氮化物外延层40的晶体质量。
本申请实施方式中，当需要将外延层40剥离下来使用时，过渡层50随外延层40一同与二维材料层30剥离开来。
本申请实施例提供的氮化物外延片，通过在衬底与氮化物外延层之间依次设置成核层和二维材料层，利用成核层缓解晶格失配产生的应力，以及利用二维材料的晶格滑移直接释放应力，可降低外延翘曲的发生，获得高均匀性、高晶体质量的氮化物外延层。其中，成核层可为后续生长氮化物外延层提供成核中心，缓解衬底与外延层的晶格失配，同时还可以有效阻挡衬底带来的杂质对后续氮化物外延层的生长产生的影响，提高外延层的晶体质量。而二维材料层可利用晶格滑移直接释放应力，显著降低外延翘曲的发生，提高氮化物外延层的均匀性和晶体质量。其中，通过拼接方式形成的二维材料层，尤其可以有效降低大尺寸(6英寸及以上)、厚膜(5μm及以上)氮化物外延层的翘曲发生，获得大尺寸、大厚度、高质量氮化物外延片。而通过原位生长的方式形成的二维材料层能够有效避免二维材料转移过程可能产生的破损，可与外延层一样采用沉积工艺制备。
相应地，如图4所示，本申请实施例还提供一种氮化物外延片的制备方法，包括：
S01、在衬底上形成成核层，所述成核层为AlN层或GaN层。
其中，具体可以是采用物理气相沉积或金属有机化学气相沉积的方式在衬底10上制备成核层20。在制备成核层20之前，可以先对衬底10进行常规的清洁处理。
本申请一具体实施方式中，采用磁控溅射的方式在衬底10上制备成核层20，具体地可以是，将衬底10置于磁控溅射***中，反应室压力为0.8Pa-1Pa，通入氮气和氧气3min-5min，得到处理后的衬底10，然后以99.999％纯度的铝或镓为靶材，在处理后的衬底10上磁控溅射氮化铝或氮化镓，得到成核层20。其中，磁控溅射过程中的操作参数可以根据实际需要进行设定，本申请实施例不作特殊限定，也不局限于上述的范围。在本申请其他一些实施方式中，还可以是采用其他的物理气相沉积方式制备成核层20。
本申请另一具体实施方式中，采用金属有机化学气相沉积的方式在衬底10上制备成核层20，具体地可以是，将衬底10置于金属有机化学气相沉积反应室中，于900-1100℃的 温度和30-60Torr的压力下，通入氢气和氨气3min-5min，得到处理后的衬底10，然后通入氢气、氨气、以及铝源或镓源，在处理后的衬底10上沉积得到氮化铝或氮化镓，即得到成核层20。本申请实施方式中，沉积过程中的各参数并不局限于上述范围。镓源包括但不限于为三甲基镓、三乙基镓。铝源包括但不限于为三甲基铝、三乙基铝。
S02、在成核层上形成二维材料层。
本申请一实施方式中，在成核层20上形成二维材料层30的方法为：将多块小尺寸二维材料薄膜转移至成核层20上拼接形成二维材料层30。
以石墨烯为例，可以是但不限于采用化学气相沉积法在金属衬底(如铜箔)上生长石墨烯，具体地，于800～1000℃的反应室中，向反应室中通入碳源，碳源可以为含碳气体，如甲烷、乙烯、乙炔等；将生长有石墨烯的金属衬底置于1mol/L氧化铁和2mol/L盐酸的混合溶液中12小时去除金属衬底，得到去除金属衬底的石墨烯，然后选取石墨烯高质量部分裁取获得多块高质量小尺寸的石墨烯薄膜，将多块小尺寸石墨烯薄膜转移至成核层20上，并拼接成目标尺寸的二维材料层。由于目前较大尺寸的高质量石墨烯薄膜制备困难，为了能够拼接成较大目标尺寸的二维材料层，可多次制备石墨烯薄膜裁取获得多块高质量小尺寸的石墨烯薄膜。为了更好地实现拼接，可将多块高质量小尺寸的石墨烯薄膜裁切成相同的规则形状。拼接形成的二维材料层为非连续薄膜，相邻的小尺寸石墨烯薄膜301之间形成有拼接缝隙。拼接缝隙的设置具体如前文所述。
本申请另一实施方式中，在成核层20上形成二维材料层30的方法为：在成核层20上原位生长二维材料形成二维材料层30。具体可以是采用化学气相沉积的方式原位生长二维材料。其中，氮化硼的原位生长可以是在金属有机化学气相沉积反应室中进行，从而可实现单步外延，简化工艺，降低成本。各种二维材料的原位生长的具体操作可采用现有已知的方式，本申请不做特殊限定。
S03、在二维材料层上外延生长第三主族金属氮化物，形成外延层。
本申请实施方式中，外延层40可以是通过金属有机化学气相沉积的方式制备得到。具体地，将经步骤S02后获得的衬底10置于金属有机化学气相沉积反应室中，于900-1100℃的温度和30-60Torr的压力下，通入氢气和氨气3-5min，得到处理后的衬底10，然后通入氢气、氨气、以及第三主族金属源，在二维材料层30上外延生长得到第三主族金属氮化物，形成外延层40。其中，第三主族金属氮化物具体地例如可以是GaN、AlN、InN、AlGaN、InGaN、InAlN、InAlGaN中的一种或多种。第三主族金属源为含第三主族金属元素的有机化合物，如三甲基镓、三乙基镓、三甲基铝、三乙基铝等。
本申请实施方式中，上述制备方法还可以包括在二维材料层30与外延层40之间形成过渡层50。即在步骤S03之前，先在二维材料层30上制备一层过渡层50，再在过渡层50上生长外延层40。过渡层50的材质可为AlN层或GaN层。为提高拼接缝隙处外延层晶体质量，可选地，过渡层50的材质与成核层20的材质相同。过渡层50具体可以是高温氮化铝层或高温氮化镓层，过渡层50可以是具有高V/Ⅲ比的AlN层或GaN层。
对于转移拼接方式形成二维材料层的方案，过渡层50的设置可避免二维材料引入较多杂质引发的漏电风险，过渡层50可以充当杂质阻挡层，提高后续氮化物外延层的晶体质量。
而对于原位生长方式形成二维材料层的方案，过渡层50一方面可以作为杂质阻挡层， 另一方面，通过在过渡层50中掺杂一定碳，可以形成高电阻，从而提升氮化物外延层的耐压能力。
本申请实施例还提供一种半导体器件，包括本申请实施例上述提供的氮化物外延片，本申请实施例氮化物外延片可以直接作为半导体器件的一部分，也可以是将外延层剥离下来应用于半导体器件中。该半导体器件包括但不限于为功率器件、射频器件或光电器件。其中功率器件、射频器件可以是晶体管，具体可为场效应晶体管，如高电子迁移率晶体管(High Electron Mobility Transistor，HEMT)。光电器件例如为发光二极管(Light Emitting Diode，LED)，激光二极管(Laser diode，LD)。具体可为氮化物基发光二极管，氮化物基量子阱激光二极管。
例如，本申请一实施方式中，半导体器件为发光二极管，发光二极管包括本申请实施例上述提供的氮化物外延片，以及在外延层上继续外延生长的量子阱有源区等，以及P、N电极等。
下面分多个实施例对本申请方案进行进一步描述。
实施例1
一种氮化物外延片的制备方法，包括：
(1)将尺寸为8英寸的硅衬底置于磁控溅射***中，反应室压力为1Pa，通入氮气和氧气5min，然后以99.999％纯度的铝为靶材，在硅衬底上磁控溅射氮化铝，得到厚度为25nm的氮化铝成核层；
(2)采用化学气相沉积法在铜箔上生长单层石墨烯，选取质量较高的部分裁切成正方形，腐蚀除去铜箔得到小尺寸高质量单层石墨烯薄膜，按上述方法获得所需要尺寸的多块小尺寸高质量单层石墨烯薄膜后，将所得多块小尺寸高质量单层石墨烯薄膜转移至氮化铝成核层上，并按图2a的方式依次拼接形成单层石墨烯层，每块小尺寸石墨烯的尺寸为1cm*1cm，任意相邻两块小尺寸单层石墨烯薄膜之间的拼接缝隙控制在0.2cm以内；石墨烯层在整个氮化铝成核层上所占的面积比例约为80％。
(3)将形成有石墨烯层的硅衬底置于金属有机化学气相沉积反应室中，于1100℃的温度和50Torr的压力下，通入氢气、氨气、以及镓源，在石墨烯层上依次生长10nm的氮化铝过渡层和5μm的氮化镓外延层。
实施例2
一种氮化物外延片的制备方法，包括：
(1)将尺寸为8英寸的硅衬底置于金属有机化学气相沉积反应室中，于900-1100℃的温度和30-60Torr的压力下，通入氢气、氨气、以及三甲基铝，在衬底上沉积得到厚度为150nm的氮化铝成核层；
(2)从金属有机化学气相沉积反应室中取出硅衬底，采用化学气相沉积法在成核层上原位生长单层石墨烯；
(3)将形成有石墨烯层的硅衬底再置于金属有机化学气相沉积反应室中，于1100℃的温度和50Torr的压力下，通入氢气、氨气、以及三甲基镓，在石墨烯层上生长得到厚度为 2μm的氮化镓外延层。
实施例3
一种氮化物外延片的制备方法，包括：
(1)将尺寸为8英寸的硅衬底置于金属有机化学气相沉积反应室中，在硅衬底上外延氮化铝，得到厚度为200nm的氮化铝成核层；
(2)在氮化铝成核层上外延一层厚度小于1nm的二维氮化硼；
(3)将形成有氮化硼的硅衬底在1100℃的温度和50Torr的压力下，通入氢气、氨气、以及铝源，在氮化硼层上沉积得到厚度为10nm的氮化铝过渡层；
(4)继续于1100℃的温度和50Torr的压力下，向金属有机化学气相沉积反应室通入氢气、氨气、以及镓源，在氮化铝过渡层上生长得到厚度为2-6μm的氮化镓外延层。
实施例4
一种氮化物外延片的制备方法，包括：
(1)将尺寸为8英寸的硅衬底置于金属有机化学气相沉积反应室中，在硅衬底上外延氮化铝，得到厚度为200nm的氮化铝成核层；
(2)采用化学气相沉积法在氮化铝成核层上生长单层石墨烯，石墨烯厚度不大于1nm；
(3)将形成有石墨烯的硅衬底放入金属有机化学气相沉积反应室中，在1100℃的温度和50Torr的压力下，通入氢气和氨气4min，然后通入氢气、氨气、以及铝源，在石墨烯层上沉积得到厚度为10nm的氮化铝过渡层；
(4)继续于1100℃的温度和50Torr的压力下，向金属有机化学气相沉积反应室通入氢气、氨气、以及镓源，在氮化铝过渡层上生长得到厚度为2-6μm的氮化镓外延层。
将实施例1所得氮化镓外延片采用拉曼光谱仪进行拉曼检测，外延层表面拉曼散射图谱如图5所示，从图5可以看出，拉曼峰E2(E2 Hight)位于568cm -1左右，其与氮化镓标准拉曼峰基本一致，表明氮化镓外延层基本处于无应力状态。E2是与应力强相关的氮化镓拉曼峰，通过比较其与标准峰的偏移量可判断应力类型(左移为张应力，右移为压应力)和大小。
另外，图6是实施例1所得氮化镓外延片外延层的原子力显微镜(Atomic Force Microscope，AFM)图片，从图6中可以看到，氮化镓外延层表面呈现明显的台阶流，表明晶体质量较好；RMS(均方根粗糙度)仅为0.176nm，说明平整度良好。

Claims (23)

  1. 一种氮化物外延片，其特征在于，包括：
    衬底；
    成核层，形成于所述衬底上，所述成核层为氮化铝层或氮化镓层；
    二维材料层，形成于所述成核层上；所述二维材料层由多块小尺寸二维材料薄膜拼接形成，或者所述二维材料层由二维材料在所述成核层上原位生长形成；
    外延层，形成于所述二维材料层上，所述外延层的材质包括第三主族金属氮化物。
  2. 如权利要求1所述的氮化物外延片，其特征在于，部分或任意相邻两块所述小尺寸二维材料薄膜之间具有拼接缝隙。
  3. 如权利要求2所述的氮化物外延片，其特征在于，所述拼接缝隙宽度大于或等于0.1μm，且小于或等于所述小尺寸二维材料薄膜上最大两点间距离的1/2。
  4. 如权利要求1-3任一项所述的氮化物外延片，其特征在于，所述二维材料层在所述成核层上所占的面积比例不低于50％。
  5. 如权利要求1所述的氮化物外延片，其特征在于，所述小尺寸二维材料薄膜的形状为多边形。
  6. 如权利要求5所述的氮化物外延片，其特征在于，所述小尺寸二维材料薄膜的形状为等边三角形、直角三角形、正六边形、正方形、矩形或菱形。
  7. 如权利要求1-6任一项所述的氮化物外延片，其特征在于，所述二维材料层的材质包括石墨烯、氮化硼、硅烯、锗烯、磷烯、硼烯、锡烯、过渡金属硫化物、过渡金属碳化物和过渡金属氮化物中的至少一种。
  8. 如权利要求1-7任一项所述的氮化物外延片，其特征在于，所述二维材料层的厚度小于或等于1nm。
  9. 如权利要求1-8任一项所述的氮化物外延片，其特征在于，所述二维材料层为单层二维材料。
  10. 如权利要求1所述的氮化物外延片，其特征在于，所述外延层的材质包括GaN、AlN、InN、AlGaN、InGaN、InAlN、InAlGaN中的一种或多种。
  11. 如权利要求1所述的氮化物外延片，其特征在于，所述外延层的厚度大于或等于300nm。
  12. 如权利要求1所述的氮化物外延片，其特征在于，所述衬底包括硅衬底、蓝宝石衬底、绝缘体上硅衬底、氮化镓衬底、砷化镓衬底、磷化铟衬底、氮化铝衬底、碳化硅衬底、石英衬底或金刚石衬底。
  13. 如权利要求1所述的氮化物外延片，其特征在于，所述成核层的厚度为10nm-300nm。
  14. 如权利要求1所述的氮化物外延片，其特征在于，还包括设置于所述二维材料层与所述外延层之间的过渡层，所述过渡层为氮化铝层或氮化镓层。
  15. 如权利要求14所述的氮化物外延片，其特征在于，所述过渡层与所述成核层的材质相同。
  16. 如权利要求14所述的氮化物外延片，其特征在于，所述过渡层的厚度为1nm-300nm。
  17. 一种氮化物外延片的制备方法，其特征在于，包括：
    在衬底上形成成核层，所述成核层为氮化铝层或氮化镓层；
    将多块小尺寸二维材料薄膜转移至所述成核层上拼接形成所述二维材料层；或者在所述成核层上原位生长二维材料形成二维材料层；
    在所述二维材料层上外延生长第三主族金属氮化物，形成外延层。
  18. 如权利要求17所述的制备方法，其特征在于，采用物理气相沉积或金属有机化学气相沉积的方式制备所述成核层。
  19. 如权利要求17所述的制备方法，其特征在于，采用化学气相沉积的方式在所述成核层上原位生长二维材料形成所述二维材料层。
  20. 如权利要求17-19任一项所述的制备方法，其特征在于，还包括在所述二维材料层与所述外延层之间形成过渡层，所述过渡层为氮化铝层或氮化镓层。
  21. 一种半导体器件，其特征在于，包括如权利要求1-16任一项所述的氮化物外延片。
  22. 如权利要求21所述的半导体器件，其特征在于，所述半导体器件包括功率器件、射频器件或光电器件。
  23. 如权利要求22所述的半导体器件，其特征在于，所述半导体器件包括场效应晶体管、发光二极管或激光二极管。
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