WO2020207234A1 - 采用2d材料磊晶去疵单晶基板及其制备方法和制作组件 - Google Patents

采用2d材料磊晶去疵单晶基板及其制备方法和制作组件 Download PDF

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WO2020207234A1
WO2020207234A1 PCT/CN2020/080585 CN2020080585W WO2020207234A1 WO 2020207234 A1 WO2020207234 A1 WO 2020207234A1 CN 2020080585 W CN2020080585 W CN 2020080585W WO 2020207234 A1 WO2020207234 A1 WO 2020207234A1
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layer
single crystal
gan
epitaxy
crystal substrate
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王晓靁
刘家桓
宋高梅
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王晓靁
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/0206—Substrates, e.g. growth, shape, material, removal or bonding

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  • the present invention relates to the technical field of LEDs, in particular to a single crystal substrate that uses 2D material ultra-thin intermediate layer homogeneity or quasi-homogenous epitaxy to remove defects, as well as a preparation method and components thereof.
  • epitaxy has an important influence on the quality of products.
  • the influence on quality even includes luminous efficiency and durability.
  • the reason is that light-emitting diodes particularly require electrons and holes to cooperate with each other when the crystal is excited to generate photons smoothly.
  • the main luminescent material of light-emitting diodes is gallium nitride (GaN), which is usually grown on a substrate by an epitaxial method.
  • the crystalline structure and structure of gallium nitride produced are largely affected by the substrate used.
  • this technical field usually considers several conditions when selecting a suitable substrate material.
  • the substrate material is hoped to be a single crystal material that can minimize the defect density.
  • the crystal structure, lattice constant (lattice constant), coefficient of thermal expansion (CTE, coefficient of thermal expansion) and the epitaxial material can be matched to avoid the epitaxial process as much as possible. Affect the crystal quality of light-emitting diodes.
  • the most commonly used substrate material is single crystal sapphire (Sapphire), which mainly considers its advantages such as good chemical stability and mature manufacturing technology; and due to the increase in production capacity in recent years, sapphire substrates are compared with other alternatives, such as: nitrogen Aluminum (AlN) and even gallium nitride (GaN) substrates are more in line with economic requirements.
  • SiN single crystal sapphire
  • GaN gallium nitride
  • the defect density of GaN or AlGaN epitaxial layer is too high, which affects the laser diode (
  • LD laser diode
  • CTE coefficient of thermal expansion
  • UV LED ultraviolet light emitting diodes
  • the UVC LED luminous wavelength belonging to the deep ultraviolet range has the most disinfection and sterilization effect, except that it will effectively replace the current low-efficiency energy consumption and harmful
  • the current aluminum nitride substrate mass production technology most suitable for UV LEDs has a bottleneck. The development of UVC LEDs is still focused on matching Poor sapphire substrates cause great obstacles to performance improvement.
  • the melting points of aluminum nitride and gallium nitride are both above 2,500 degrees Celsius and there is a problem of high vapor pressure.
  • the current growth of gallium nitride is based on the Hydride Vapor Phase Epitaxy (HVPE) method to produce monocrystalline GaN substrates. Due to the constraints of production costs and yield conditions, mass production is currently The technology reaches a 4-inch substrate and the cost is extremely high.
  • HVPE Hydride Vapor Phase Epitaxy
  • the defect density of the above-mentioned gas phase method is still higher than that of other liquid phase crystal growth processes, but it is limited by the slow crystal growth rate of other processes, and the mass production cost is higher.
  • the mainstream business is still limited to the HVPE method.
  • the literature points out that the growth rate of vapor phase GaN is still possible to increase several times and maintain good crystallinity. However, due to the deterioration of defect density, it is not currently used as an orientation to reduce the cost of GaN substrates.
  • PVT physical vapor transport
  • one of the vapor phase methods is used to produce single crystal aluminum nitride substrates.
  • Zinc oxide (ZnO) single crystal material is a more suitable substrate material choice in the previous item in terms of crystalline structure, thermal properties and lattice constant, so it has attracted technology developers to invest in research.
  • zinc oxide is not widely used in the technical field today. The main reason is that zinc oxide has high chemical activity and is easily corroded by hydrogen-containing substances in the subsequent epitaxy process, resulting in poor epitaxial layer quality, as shown in Figure 1.
  • hydrogen etches the zinc oxide substrate while zinc rapidly diffuses into the epitaxial layer, resulting in poor epitaxial quality. Adjusting the process to improve the epitaxial quality still occurs diffusion of zinc and oxygen and doping into the light-emitting diode crystal grains, causing light emission The characteristics do not meet expectations, making this structure unable to meet actual market demand.
  • Two-dimensional materials (two-dimensional (2D) materials) is a rapidly developing emerging field.
  • 2D materials family the first and most well-known material that attracted a large amount of R&D investment is graphene. Its two-dimensional layered structure has special or Excellent physical/chemical/mechanical/optical properties. There is no strong bond between the layers, only Van der Waals forces are combined, which also means that there are no dangling bonds on the surface of the layered structure.
  • graphene has It has been confirmed to have a wide range and excellent application potential; graphene research and development work is generally carried out around the world, and it also drives the research and development of more 2D materials, including hexagonal boron nitride hBN (hexagonal Boron Nitride), transition metal dichalcogenides TMDs (transition Metal dichalcogenides) and black phosphorus are also among the 2D material families that have accumulated more research and development results. As shown in Figures 2 and 3, the above-mentioned materials have their own specific material properties and application potentials. The development of related materials is also Continue to actively promote.
  • graphene, hBN, and MoS 2 which is one of the TMDs materials, are all considered to have excellent diffusion barrier properties, as well as varying degrees of high temperature stability, especially hBN has excellent chemical passivation Inertness and high temperature oxidation resistance.
  • FIGS 4a and 4b are schematic diagrams of mechanical composition lamination, as shown in Figures 5a and 5b. It is a schematic diagram of physical or chemical vapor deposition.
  • van der Waals epitaxy may be beneficial to heterogeneous epitaxy comes from the direct chemical bond of the traditional epitaxial interface is replaced by van der Waals force bonding, which will relieve the stress or strain energy from the lattice and thermal expansion mismatch in the epitaxial process to a certain extent. , So that the quality of the epitaxial layer is improved, or the introduction of 2D materials and van der Waals epitaxy can make some hetero-epitaxial technologies that were previously impossible to be practical.
  • the above-mentioned 2D layered material has a hexagonal or honeycomb structure, and is considered structurally compatible with Wurtzite and Zinc-Blende structural materials in external delay.
  • the related fields of the present invention are mainly Epitaxial materials belong to this type of structure.
  • the substrate material used is one of the vapor phase methods (Hydride Vapor Phase Epitaxy, HVPE) produced monocrystalline gallium nitride (GaN) substrates
  • HVPE Hydride Vapor Phase Epitaxy
  • GaN gallium nitride
  • GaN epitaxial growth with high crystallinity has been successfully achieved on the surface of 2D materials; the barrier properties of the 2D material layer itself and the combination of van der Waals forces with 3D materials will be effective.
  • the purpose of the present invention is to provide a single crystal substrate using 2D material epitaxy to remove defects.
  • the present invention also provides a method for preparing the above-mentioned single crystal substrate and a manufacturing component of the above-mentioned single crystal substrate.
  • the solution of the present invention is:
  • GaN quasi-homogeneous material single crystal substrate for example: ZnO and other materials
  • VDWE Van der Waals epitaxy
  • high-quality (ie high crystallinity, XRD FWHM can be lower than 400arcsec)
  • GaN or GaN-based epitaxial layer 2D material ultra-thin layer is composed of a single material or formed by stacking more than one material, quasi-homogeneous material single crystal substrate
  • condition range of Quasi-homogeneous epitaxy is: lattice constant mis
  • the thickness of the ultra-thin 2D material layer ranges from 0.5 nm to 1000 nm.
  • the ultra-thin 2D material layer is a single material with good barrier effect, such as hexagonal boron nitride hBN and graphene.
  • the 2D material ultra-thin layer is a composite layer structure.
  • the top layer adopts a 2D material with good lattice matching with GaN or high surface energy which is favorable for epitaxy, such as WS 2 or MoS 2
  • the bottom layer adopts a 2D material with good barrier effect, such as Hexagon Boron nitride hBN, graphene (graphene).
  • a metal catalyst layer is added between the substrate and the intermediate layer.
  • the total thickness of the metal catalyst layer ranges from 0.5 nm to 3000 nm.
  • the metal catalyst layer includes Fe, Co, Ni, Au, Ag, Cu, W, Mo, Ru, or Pt.
  • the method for preparing a single crystal substrate using 2D material epitaxy to remove defects is as follows:
  • the substrate material is subjected to epitaxial growth grade polishing as the starting material, and appropriate pre-treatment (including chip cleaning) as the preparation for the subsequent manufacturing process;
  • the second step is to use van der Waals Epitaxy or Quasi van der Waals Epitaxy technology to cover the surface of the substrate with a 2D material with good barrier effect as an intermediary layer;
  • the third step is to use van der Waals Epitaxy or Quasi van der Waals Epitaxy technology to grow high-quality GaN or GaN-based epitaxy on the interposer.
  • a single layer or a composite layer of 2D material is covered on the surface of the substrate material.
  • the 2D material covering the surface of the substrate material adopts growth, deposition, transfer or coating processes, and the total thickness of a single layer or multiple layers ranges from 0.5 nm to 1000 nm .
  • a metal catalyst layer and other manufacturing processes are added at an appropriate time.
  • the total thickness of the metal catalyst layer ranges from 0.5 nm to 3000 nm.
  • the growth or deposition process of the 2D material covering the surface of the substrate material may require a metal catalyst layer including Fe, Co, Ni, Au, Ag, Cu, W, Mo, Ru, or Pt to be grown or deposited on the surface of the substrate first. A heat treatment process is required.
  • the present invention can use the aforementioned method to directly produce a finished GaN template (GaN template) with a high-quality GaN epitaxial layer on the surface; or peel off the original substrate from the surface high-quality GaN epitaxial layer produced by the aforementioned method, and then attach it to other substrate materials Afterwards, the necessary steps are performed to make components or bond with other substrate materials to become the finished GaN template.
  • GaN template GaN template
  • the present invention uses a 2D material with good barrier effect to cover the surface of the substrate material as an intermediary layer for high-quality GaN epitaxy, for van der Waals epitaxy or quasi-van der Waals epitaxy technology applications, and an ultra-thin 2D material layer as a barrier layer to block the substrate
  • the defects in the material cause damage to the quality of the epitaxial layer and component performance.
  • the defects in the substrate include point defects (such as oxygen ions or other impurities) and line defects (such as dislocations).
  • a high-quality GaN single crystal substrate can be obtained.
  • the simplification of the assembly process makes the choice of substrate materials wider, and the manufacturing cost is greatly reduced, which is conducive to market promotion and application.
  • Figure 1 is a schematic diagram of a conventional zinc oxide substrate being eroded during the epitaxy process
  • FIG. 2 is a schematic diagram of the structure of a conventional two-dimensional material transition metal dichalcogenide TMDs
  • FIG. 3 is a schematic diagram of the structure of the conventional two-dimensional material hexagonal boron nitride hBN;
  • 4a and 4b are schematic diagrams of conventional mechanical composition lamination
  • Figures 5a and 5b are schematic diagrams of conventional physical and chemical vapor deposition
  • Fig. 6 is a schematic diagram of the growth of an existing GaN single crystal substrate
  • Figure 7 is a schematic structural diagram of Embodiment 1 of this creation.
  • Figure 8 is a schematic structural diagram of the second embodiment of the creation.
  • Figure 9 is a schematic diagram of the authoring component.
  • Substrate 1 epitaxial layer 2, ultra-thin 2D material layer 3, top layer 31, bottom layer 32, and metal catalytic layer 4.
  • the single crystal substrate using 2D epitaxy to remove defects disclosed in the present invention is used on a low-cost GaN single crystal substrate 1 or other low-cost GaN quasi-homogeneous single crystal substrate 1 2D material van der Waals epitaxy (VDWE) with good barrier effect grows a 2D material ultra-thin layer 3 as an intermediate layer, and van der Waals epitaxially grows a high-quality GaN or GaN-based epitaxial layer 2 on the 2D material ultra-thin layer 3.
  • VDWE van der Waals epitaxy
  • the so-called low-cost GaN single crystal substrate 1 refers to a GaN single crystal substrate obtained by relaxing restrictions on crystal growth conditions to improve production efficiency, such as a GaN single crystal substrate obtained by increasing the crystal growth rate by the HVPE method.
  • the so-called other low-cost GaN quasi-homogeneous material single crystal substrate 1 refers to materials such as ZnO whose manufacturing cost is lower than the current HVPE GaN.
  • the range of conditions for epitaxy of the quasi-homogeneous material single crystal substrate 1 is: the lattice constant mismatch is not more than 5% and the thermal expansion coefficient difference is not more than 1.5 ⁇ 10 -6 °C -1 .
  • the ultra-thin 2D material layer is composed of a single material or formed by stacking more than one material.
  • the so-called high-quality GaN or GaN-based epitaxial layer 2 refers to high crystallinity, and the XRD FWHM (XRD pattern full width at half maximum) can be less than 400 arcsec (radian seconds).
  • the thickness of a single layer or multiple layers of the ultra-thin 2D material layer 3 ranges from 0.5 nm to 1000 nm.
  • the ultra-thin 2D material layer 3 shown in FIG. 7 is a single material with good barrier effect, such as hexagonal boron nitride hBN and graphene.
  • the 2D material ultra-thin layer 3 shown in FIG. 8 is a composite interposer.
  • the top layer 31 uses a 2D material that has a good lattice match with GaN or a high surface energy that is favorable for epitaxy, such as WS 2 or MoS 2
  • the bottom layer 32 uses a good barrier effect 2D materials, such as hexagonal boron nitride hBN, graphene (graphene).
  • the lattice constants of various materials are shown in Table 3.
  • the present invention uses the 2D material ultra-thin layer 3 or the bottom layer 32 with good barrier effect as a barrier layer (barrier) to prevent defects in the substrate material from causing damage to the quality of the epitaxial layer and the performance of the components.
  • the defects in the substrate include point defects (such as oxygen). Ions or other impurities) and line defects (such as dislocations) can obtain high-quality GaN single crystal substrates, simplifying the epitaxy and component processes, making the choice of substrate materials wider and reducing manufacturing costs, which is beneficial to market promotion application.
  • the present invention can add a metal catalytic layer 4 on the surface of the 2D material covering the substrate 1, and the metal catalytic layer 4 can include Fe, Co, Ni, Au, Ag, Cu, W, Mo, Ru or Pt. Etc., the metal catalytic layer 4 is grown or deposited on the surface of the substrate 1, and a heat treatment process may also be required.
  • the total thickness of the metal catalytic layer 4 ranges from 0.5 nm to 3000 nm.
  • the present invention also discloses a method for preparing a single crystal substrate using 2D material epitaxy to remove defects, and the steps are as follows:
  • the substrate 1 (chip) material is subjected to epitaxial growth grade polishing as a starting material, and appropriate pre-treatment (including chip cleaning) is used as a preparation for subsequent manufacturing procedures.
  • manufacturing processes such as the metal catalyst layer 4 can be added in due course according to the growth requirements of the 2D material.
  • the growth or deposition process of the 2D material covering the surface of the substrate 1 may require a metal catalyst layer 4 including Fe, Co, Ni, Au, Ag, Cu, W, Mo, Ru, or Pt to be grown or deposited on the surface of the substrate 1. , May also need heat treatment process.
  • the total thickness of the metal catalytic layer 4 ranges from 0.5 nm to 3000 nm.
  • the second step is to use van der Waals epitaxy or quasi-van der Waals epitaxy technology to cover the surface of the substrate 1 with a 2D material with good barrier effect as an intermediate layer; it can be a single layer or a composite layer 2D material ultra-thin layer 2 covering.
  • the 2D material covering the surface of the substrate 1 can adopt existing processes, including growth, deposition, transfer, coating, etc., and related necessary pre-treatment and post-treatment processes.
  • the total thickness of single layer or multiple layers ranges from 0.5 nm to 1000 nm.
  • the third step is to use van der Waals epitaxy or quasi Van der Waals epitaxy technology to grow a high-quality GaN or GaN-based epitaxial layer 2 on the interposer.
  • the various optoelectronic semiconductor component products produced by the method of the present invention can be directly made into a finished GaN template with a high-quality GaN epitaxial layer using the aforementioned method; or the aforementioned method can be made
  • the high-quality GaN epitaxial layer on the surface is peeled off the original substrate, and then bonded with other substrate materials and then subjected to the necessary processes to form components or bonded with other substrate materials to become the finished GaN template.

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Abstract

本发明公开了采用2D材料磊晶去疵单晶基板，在低成本GaN单晶基板或其他低成本的GaN准同质材料单晶基板上采用阻隔效果的2D材料范德华外延生长2D材料超薄层作为中介层，在2D材料超薄层上范德华外延生长高质量GaN或GaN基外延层，2D材料超薄层由单一材料构成或者一种以上材料迭层形成，准同质材料单晶基板外延的条件范围为：晶格常数不匹配度不大于5％以及热膨胀系数差异不大于1.5×10-6℃-1。本发明还公开了制备方法以及其制作组件。本发明可获得高质量GaN单晶基板，将外延及组件工序简化，使得采用的基板材料选择可能性更为宽广，制造成本大大降低，有利于市场推广应用。

Description

采用2D材料磊晶去疵单晶基板及其制备方法和制作组件 技术领域
本发明涉及LED的技术领域，特别涉及采用2D材料超薄中间层同质或准同质磊晶去疵单晶基板，以及制备方法，和其制作组件。
背景技术
在发光二极管或雷射二极管(LD,laser diode)的组件制造过程中，磊晶对产品的质量有重要的影响。其中对质量的影响甚至包含发光效率、耐久度等。原因在于发光二极管尤其要求构成晶体激发时电子与电洞彼此配合才可以顺利产生光子。相对地，如果在材料结构或组织上产生缺陷，电子与电洞的相互结合过程中被缺陷阻碍的可能性就会增加，导致发光效果的劣化。发光二极管主要的发光材料选用氮化镓(GaN)，通常是以外延的方法生长在基板上，而所生产出的氮化镓结晶结构和组织则很大部分受所采用的基板影响。为了增进上述发光二极管的发光效率、耐久度以及其他关于发光二极管质量相关的特性，此技术领域通常在选择合适基板材料时考虑几种条件。通常，基板的材料希望是能尽量减少缺陷密度的单晶材料，在晶体结构、晶格常数(lattice constant)、热膨胀系数(CTE,coefficient of thermal expansion)与外延材料匹配才能尽可能避免在外延过程中影响发光二极管的晶体质量。
依照目前技术，最常采用的基板材料是单晶的蓝宝石(Sapphire)，主要是考虑其化学稳定性好、制造技术成熟等优点；并且由于近年产能增加，蓝宝石基板相对其他替代品，如：氮化铝(AlN)，甚至氮化镓(GaN)基板等，更符合经济要求。但由于蓝宝石在晶体结构、晶格常数(lattice constant)、热膨胀系数(CTE,coefficient of thermal expansion)与外延材料匹配上不尽理想，导致GaN或AlGaN外延层缺陷密度偏高影响了雷射二极管(LD,laser diode)方面的应用以及紫外光发光二极管(UV LED)的性能提升；其中属于深紫外光范围的UVC LED发光波长最具有消毒杀菌的效能，除将有效取代现行低效耗能并有害环境的汞灯之外，更将在民生及日常消毒杀菌应用中有 极大发展潜能，但目前最适于UV LED的氮化铝基板量产技术存在瓶颈，UVC LED开发主要仍着力于匹配度不佳的蓝宝石基板，导致性能提升存在极大障碍。
氮化铝和氮化镓的熔点均在摄氏两千五百度以上且存在蒸气压高问题，换言之，若想要直接以熔融长晶的方法制作前述两种材料的单晶基板，则不只制造成本更高，也相对会产生更多废热，对环境造成不可避免的污染。气相法长晶部分，目前氮化镓长晶采用的是氢化物气相外延法(Hydride Vapor Phase Epitaxy,HVPE)来生产单晶氮化镓基板，由于生产成本及产率条件等限制，目前量产技术达到4英寸基板同时成本极高。事实上，上述气相法缺陷密度仍然偏高于其他液相长晶工序，但受限于其余工序长晶速率过于缓慢，量产成本更为高昂，在市场需求、组件性能以及基板成本与供应量折衷考虑之下，商转主流仍限于HVPE法。文献指出气相法GaN长晶速率仍有提高数倍的可能并维持良好结晶性，但受限于缺陷密度劣化，目前并未能作为降低GaN基板成本的取向。至于氮化铝长晶技术，采用的是气相法之一的物理气相传输法(Physical Vapor Transport,PVT)来生产单晶氮化铝基板，由于生产技术及良率限制，全球仅两家厂家有量产能力，目前量产技术仅达到2英寸基板同时成本极高，而产能全由少数厂商占有无法广泛供应市场。由于氮化铝本身化学特性以及物理气相传输法硬件零组件限制，单晶成品中一定程度的碳(C)与氧(O)杂质存在为不可避免，也一定程度影响组件特性。
表1
Figure PCTCN2020080585-appb-000001
Figure PCTCN2020080585-appb-000002
氧化锌(ZnO)单晶材料就结晶构造、热性质和晶格常数而言，都是前项中较为合适的基板材料选择，因此吸引了技术开发者投入研究。不过氧化锌今日在技术领域中并不被广泛采用，其中主要的原因包括氧化锌的化学活性高，容易在随后的外延过程中受到含氢物质的侵蚀导致外延层质量低劣，如图1所示，在外延工序时会发生氢蚀刻氧化锌基板同时锌快速扩散进入外延层导致外延品质不佳，调整制程改善外延质量却仍然发生锌与氧扩散、掺杂入发光二极管的晶粒中，造成发光特性不符合预期，使得该种结构无法符合实际市场需求。
同样的情形，也可能存在于目前使用中的其他光电组件基板-外延组合中，例如碳化硅(SiC)或砷化镓(GaAs)等；其中单晶碳化硅基板是目前高性能功率半导体以及高端发光二极管的基板材料，单晶长晶工序为气相法中的物理气相传输法(Physical Vapor Transport,PVT)，高质量大尺寸碳化硅单晶成长技术难度高，高端量产技术掌握在少数厂商手中，影响所及应用成本仍有很大进步空间。
二维材料(two-dimensional(2D)materials)是一个快速发展的新兴领域，2D材料家族中最早吸引大量研发投入也最知名的材料为石墨烯(graphene),其二维层状结构具备特殊或优异的物理/化学/机械/光电特性，层与层间则没有强力的键结存在，仅以范德华力结合，这也表示层状结构表面没有空悬键(dangling bond)存在，目前石墨烯已被确认具有广泛而优异的应用潜能；石墨烯研发工作于全球普遍开展，同时也带动更多2D材料的研发，包括六方氮化硼hBN(hexagonal Boron Nitride)、过渡金属二硫族化物TMDs(transition metal dichalcogenides)以及黑磷black phosphorus等也是2D材料家族中累积较多研发成果者,如图2和图3所示，上述材料均各自具备特异的材料特性与应用潜能,相关材料的制造技术开发也持续积极推展中。除了优异的光电特性之外,石墨烯、hBN 以及TMDs材料之一的MoS 2都被视为具有优异的扩散阻障特性,也有程度不一的高温稳定性,尤其hBN更具有绝佳的化学钝性(inertness)以及高温耐氧化性。
由于具备上述层状结构本质以及层间范德华力结合特性,将2D材料家族中两种或多种材料制作成层状堆栈异质结构(hetero-structures)技术可行性大开,异质结构除了结合不同特性更创造出新的应用特性或制作出新的组件成为可能,目前光电及半导体领域的研发相当积极，如图4a、4b所示是机械性组成迭层的示意图，图5a、5b所示是物理或化学气相沉积的示意图。
2D材料的范德华力结合特性也获得应用于传统3D材料的外延基板用途的关注，其着眼点在于外延技术中外延材料在晶体结构、晶格常数(lattice constant)、热膨胀系数(CTE,coefficient of thermal expansion)必须与基板材料匹配非常良好，但现实上常遭遇如本发明主题欠缺适合基板材料，或者是理想的基板材料成本偏高或不容易取得等情形，此时2D材料对于异质外延基板提供了另一种解决方案，也就是所谓的范德华外延(van der Waals Epitaxy)。范德华外延可能有利于异质外延的机制来自于传统外延接口直接的化学键改由范德华力结合所取代，将使得来自于外延工序中晶格以及热膨胀不匹配的应力或应变能因此获得一定程度的舒缓，从而使得外延层质量获得改善,或者说藉由2D材料以及范德华外延导入可以使某些原先无法实用化的异质外延技术成为可能。相关研究也指出,当上述2D材料相互迭层异质结构时,相互间作用力以范德华力为主；而在2D材料上进行3D材料的外延时，由于接口上3D材料的空悬键(dangling bond)存在同时对接口的结合力有贡献，这种外延实质上并非纯粹范德华外延(van der Waals Epitaxy)或者更精确地可视为准范德华外延(Quasi van der Waals Epitaxy)；不论何种情形，晶格与热膨胀的匹配程度，无疑地仍对最终的外延质量起了一定的作用，2D材料中介层与基板材料都对整体的匹配度有所贡献。上述2D层状材料具有六角形或蜂巢状(hexagon or honeycomb)结构，与纤锌矿(Wurtzite)和闪锌矿(Zinc-Blende)结构材料在外延时被视为结构兼容，本发明相关领域主要外延材料均属此类结构。
以蓝光雷射二极管量产为例，由于雷射二极管组件特性对外延主 动层缺陷密度非常敏感，依照目前技术，采用的基板材料为气相法之一的氢化物气相外延法(Hydride Vapor Phase Epitaxy，HVPE)生产的单晶氮化镓(GaN)基板，由于生产成本及产率条件等限制，目前量产技术达到4英寸基板同时成本极高。事实上，上述气相法缺陷密度仍然偏高于其他液相长晶工序，但受限于其余工序长晶速率过于缓慢，量产成本更为高昂，在市场需求、组件性能以及基板成本与供应量折衷考虑之下，商转主流仍限于HVPE法。
表2是不同条件下，各种GaN晶体生长方法的对比(1atm＝1.01325×10 5Pa，1inch＝2.54cm)。
Figure PCTCN2020080585-appb-000003
如图6所示，是现有工艺在高质量GaN单晶基板直接外延成长高质量GaN或GaN基外延层，但目前在GaN单晶基板成本极高的前提之下，商转主流折衷采用HVPE法GaN单晶基板,缺陷密度相较于其他液相长晶工序GaN单晶或蓝宝石单晶基板高了约10 2到10 4倍。
如前所述，HVPE等气相法GaN长晶速率仍有提高数倍的可能并维持良好结晶性，但受限于缺陷密度劣化，目前并未能作为降低GaN基板成本的取向。如果能放宽长晶条件限制以提升产效，所产制的GaN单晶基板成本将可有效降低，成为高缺陷密度但相对低成本的GaN单晶基板。实际上，在2D材料表面已成功实现高结晶性(XRD FWHM可达～200arcsec)的GaN外延成长；而2D材料层本身具有的阻障特性以及与3D材料间主要由范德华力结合，均将有效阻隔基板材料中的缺陷(错位、杂质等)对外延层质量的损害；外延基板的主体与外延层仍为同质GaN时，晶格热性质的匹配也获得保证，维系了同质外延的有利基础。
发明内容
为了解决上述问题，本发明的目的在于提供一种采用2D材料磊晶去疵单晶基板。
本发明还提供了上述单晶基板的制备方法，和上述单晶基板的制作组件。
为了达成上述目的，本发明的解决方案是：
采用2D材料磊晶去疵单晶基板，在低成本GaN单晶基板(例如来自于放宽长晶条件限制以提升产效，如HVPE法提高长晶速率)或其他低成本(即制造成本低于现行HVPE GaN)的GaN准同质材料单晶基板(例如：ZnO等材料)上采用阻隔效果佳的2D材料范德华外延(VDWE)生长2D材料超薄层作为中介层，在2D材料超薄层上范德华外延生长高质量(即高结晶性，XRD FWHM可低于400arcsec)GaN或GaN基外延层，2D材料超薄层由单一材料构成或者一种以上材料迭层形成，准同质材料单晶基板外延(Quasi-homogeneous epitaxy)的条件范围为：晶格常数不匹配度(lattice constant misfit)不大于5％以及热膨胀系数(CTE,coefficient of thermal expansion)差异不大于1.5×10 -6℃ -1。
所述2D材料超薄层的厚度范围在0.5nm到1000nm。
所述2D材料超薄层为阻隔效果佳的单一材料，如六方氮化硼hBN、石墨烯(graphene)。
所述2D材料超薄层为复合层结构，顶层采用与GaN晶格匹配佳或高表面能有利于外延的2D材料，如WS 2或MoS 2，而底层采用阻隔效果佳的2D材料，如六方氮化硼hBN、石墨烯(graphene)。
所述基板和中介层之间加入金属催化层，金属催化层总厚度范围在0.5nm到3000nm，金属催化层包括Fe、Co、Ni、Au、Ag、Cu、W、Mo、Ru或Pt等。
采用2D材料磊晶去疵单晶基板的制备方法，步骤如下：
第一步，对基板材料进行外延成长等级抛光作为起始材料，并经由适当前处理(含芯片清洗)作为后续制造程序的准备；
第二步，利用范德华外延(van der Waals Epitaxy)或准范德华外延(Quasi van der Waals Epitaxy)技术，将阻隔效果佳的2D材料覆盖在基板材料表面作为中介层；
第三步，利用范德华外延(van der Waals Epitaxy)或准范德华外延(Quasi van der Waals Epitaxy)技术，在中介层上成长高质量GaN或GaN基外延层。
所述第二步，在基板材料表面进行单层或复合层2D材料覆盖。
所述第二步，2D材料覆盖基板材料表面是采用成长(growth)、沉积(deposition)、转移(transfer)或涂覆(coating)等工序，单层或多层总厚度范围在0.5nm到1000nm。
所述第一步和第二步之间，根据2D材料成长需求，在适时加入金属催化层等制造工序。金属催化层总厚度范围在0.5nm到3000nm。所述2D材料覆盖基板材料表面的成长或沉积工序可能需要有包括Fe、Co、Ni、Au、Ag、Cu、W、Mo、Ru或Pt等金属催化层先行成长或沉积在基板表面，也可能需要热处理工序。
本发明可以使用前述方法直接制成表面为高质量GaN外延层的GaN模板(GaN template)成品；也可以将前述方法制成的表面高质量GaN外延层剥离原基板，再与其他基板材料贴合后进行必要工序制成组件或与其他基板材料贴合后成为GaN模板成品。
采用上述方案后，本发明采用阻隔效果佳的2D材料覆盖基板材料表面作为高质量GaN外延的中介层，进行范德华外延或准范德华外延技术应用，2D材料超薄层作为阻障层，来阻隔基板材料中的缺陷对外延层质量以及组件性能造成的损害，基板中的缺陷包括点缺陷(如氧离子或其他杂质)和线缺陷(如错位)，可获得高质量GaN单晶基板，将外延及组件工序简化，使得采用的基板材料选择可能性更为宽广，制造成本大大降低，有利于市场推广应用。
附图说明
图1是习知氧化锌基板在外延过程中受侵蚀示意图；
图2是习知二维材料过渡金属二硫族化物TMDs的结构示意图；
图3是习知二维材料六方氮化硼hBN的结构示意图；
图4a、4b是习知机械性组成迭层的示意图；
图5a、5b是习知物理和化学气相沉积的示意图；
图6是现有GaN单晶基板生长示意图；
图7是本创作的实施例一结构示意图；
图8是本创作的实施例二结构示意图；
图9是本创作制作组件的示意图。
标号说明
基板1，外延层2，2D材料超薄层3，顶层31，底层32，金属催化层4。
具体实施方式
下面结合附图和具体实施例对本发明作进一步详细说明。
如图7和图8所示，本发明揭示的采用2D材料磊晶去疵单晶基板，是在低成本GaN单晶基板1或其他低成本的GaN准同质材料单晶基板1上，采用阻隔效果佳的2D材料范德华外延(VDWE)生长2D材料超薄层3作为中介层，在2D材料超薄层3上范德华外延生长高质量GaN或GaN基外延层2。
其中，所谓低成本GaN单晶基板1是指来自于放宽长晶条件限制以提升产效获得的GaN单晶基板，如HVPE法提高长晶速率获得的GaN单晶基板。所谓其他低成本的GaN准同质材料单晶基板1是指ZnO等制造成本低于现行HVPE GaN的材料。准同质材料单晶基板1外延的条件范围为：晶格常数不匹配度不大于5％以及热膨胀系数差异不大于1.5×10 -6℃ -1。2D材料超薄层由单一材料构成或者一种以上材料迭层形成。所谓高质量GaN或GaN基外延层2是指高结晶性，XRD FWHM(XRD图谱半峰全宽)可低于400arcsec(弧度秒)。2D材料超薄层3的单层或多层厚度范围在0.5nm到1000nm。图7所示的2D材料超薄层3为阻隔效果佳的单一材料，如六方氮化硼hBN、石墨烯(graphene)。图8所示的2D材料超薄层3为复合中介层，顶层31采用与GaN晶格匹配佳或高表面能有利于外延的2D材料，如WS 2或MoS 2，而底层32采用阻隔效果佳的2D材料，如六方氮化硼hBN、石墨烯(graphene)。各种材料晶格常数如表3。
表3
材料 晶格常数a(nm)
六方氮化硼hBN 0.25
石墨烯graphene 0.246
WS 2 0.318
MoS 2 0.3161
WSe 2 0.3297
MoSe 2 0.3283
本发明采用阻隔效果佳的2D材料超薄层3或底层32作为阻障层 (barrier)来阻隔基板材料中的缺陷对外延层质量以及组件性能造成损害，基板中的缺陷包括点缺陷(如氧离子或其它杂质)和线缺陷(如错位)，可获得高质量GaN单晶基板，将外延及组件工序简化，使得采用的基板材料选择可能性更为宽广，制造成本大大降低，有利于市场推广应用。
为了获得更佳的结构，本发明可在2D材料覆盖基板1材料的表面增加金属催化层4，金属催化层4可以包括Fe、Co、Ni、Au、Ag、Cu、W、Mo、Ru或Pt等，金属催化层4先行成长或沉积在基板1表面,也可能需要热处理工序，金属催化层4总厚度范围在0.5nm到3000nm。
本发明还揭示了采用2D材料磊晶去疵单晶基板的制备方法，步骤如下：
第一步，对基板1(芯片)材料进行外延成长等级抛光作为起始材料，并经由适当前处理(含芯片清洗)作为后续制造程序的准备。
第一步之后，第二步之前，可根据2D材料成长需求，在适时加入金属催化层4等制造工序。所述2D材料覆盖基板1材料表面的成长或沉积工序可能需要有包括Fe、Co、Ni、Au、Ag、Cu、W、Mo、Ru或Pt等金属催化层4先行成长或沉积在基板1表面，也可能需要热处理工序。金属催化层4总厚度范围在0.5nm到3000nm。
第二步，利用范德华外延或准范德华外延技术，将阻隔效果佳的2D材料覆盖在基板1材料表面作为中介层；可以是单层或复合层2D材料超薄层2覆盖。2D材料覆盖基板1材料表面可以采用既存的工序,包括成长、沉积、转移、涂覆等，以及相关必要的前处理与后处理工序。单层或多层总厚度范围在0.5nm到1000nm。
第三步，利用范德华外延或准范德华外延技术，在中介层上成长高质量GaN或GaN基外延层2。
使用本发明方法所制作的各种光电半导体组件产品，如图9所示，可以使用前述方法直接制成表面为高质量GaN外延层的GaN模板(GaN template)成品；也可以将前述方法制成的表面高质量GaN外延层剥离原基板，再与其他基板材料贴合后进行必要工序制成组件或与其他基板材料贴合后成为GaN模板成品。
以上所述仅为本发明的较佳实施例，并非对本发明的限制。应当 指出，本领域的技术人员在阅读完本说明书后，依本案的设计思路所做的等同变化，均落入本案的保护范围。

Claims (10)

  1. 采用2D材料磊晶去疵单晶基板，其特征在于：在GaN单晶基板或GaN准同质材料单晶基板上采用阻隔效果的2D材料范德华外延生长2D材料超薄层作为中介层，在2D材料超薄层上范德华外延生长GaN或GaN基外延层，2D材料超薄层由单一材料构成或者一种以上材料迭层形成，准同质材料单晶基板外延的条件范围为：晶格常数不匹配度不大于5％以及热膨胀系数差异不大于1.5×10 -6℃ -1。
  2. 如权利要求1所述的采用2D材料磊晶去疵单晶基板，其特征在于：所述2D材料超薄层的厚度范围在0.5nm到1000nm。
  3. 如权利要求1所述的采用2D材料磊晶去疵单晶基板，其特征在于：所述2D材料超薄层为具阻隔效果的单一材料；或者所述2D材料超薄层为复合层结构，顶层采用与GaN晶格匹配或高表面能的2D材料，而底层具采用阻隔效果的2D材料。
  4. 如权利要求1所述的采用2D材料磊晶去疵单晶基板，其特征在于：所述GaN或GaN基外延层是指高结晶性，XRD FWHM低于400arcsec。
  5. 如权利要求1所述的采用2D材料磊晶去疵单晶基板，其特征在于：所述基板和中介层之间加入金属催化层，金属催化层总厚度范围在0.5nm到3000nm，金属催化层包括Fe、Co、Ni、Au、Ag、Cu、W、Mo、Ru或Pt。
  6. 如权利要求1至5任一项所述的采用2D材料磊晶去疵单晶基板，其特征在于制备方法的步骤如下：
    第一步，对基板材料进行外延成长等级抛光作为起始材料，并经由适当前处理作为后续制造程序的准备；
    第二步，利用范德华外延或准范德华外延技术，将具阻隔效果的2D材料覆盖在基板材料表面作为中介层；
    第三步，利用范德华外延或准范德华外延技术，在中介层上成长GaN或GaN基外延层。
  7. 如权利要求6所述的采用2D材料磊晶去疵单晶基板，其特征在于所述第二步，在基板材料表面进行单层或复合层2D材料覆盖，单层或多层总厚度范围在0.5nm到1000nm。
  8. 如权利要求6所述的采用2D材料磊晶去疵单晶基板，其特征在于所述第一步和第二步之间，根据2D材料成长需求，加入金属催化层制造工序，金属催化层总厚度范围在0.5nm到3000nm，所述金属催化层先行成长或沉积在基板表面。
  9. 应用如权利要求1至5任一项所述的采用2D材料磊晶去疵单晶基板，直接制成表面为GaN外延层的GaN模板成品。
  10. 应用如权利要求1至5任一项所述的采用2D材料磊晶去疵单晶基板，将制成的表面GaN外延层剥离原基板，再与其他基板材料贴合后进行必要工序制成组件或与其他基板材料贴合后成为GaN模板成品。
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