WO2019127422A1 - 一种led结构及其制备方法 - Google Patents

一种led结构及其制备方法 Download PDF

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Publication number
WO2019127422A1
WO2019127422A1 PCT/CN2017/119983 CN2017119983W WO2019127422A1 WO 2019127422 A1 WO2019127422 A1 WO 2019127422A1 CN 2017119983 W CN2017119983 W CN 2017119983W WO 2019127422 A1 WO2019127422 A1 WO 2019127422A1
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Prior art keywords
substrate
patterned
led structure
mask layer
colloid
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PCT/CN2017/119983
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English (en)
French (fr)
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何宗江
贾志强
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深圳前海小有技术有限公司
深圳佑荟半导体有限公司
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Priority to PCT/CN2017/119983 priority Critical patent/WO2019127422A1/zh
Publication of WO2019127422A1 publication Critical patent/WO2019127422A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof

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  • the present invention relates to the field of semiconductor technology, and more particularly to an LED structure and a method of fabricating the same.
  • a substrate supporting the growth of a semiconductor material is required.
  • the nature of the substrate is critical to the quality of the epitaxially grown semiconductor layer.
  • the currently widely used substrate materials are mainly sapphire, silicon and silicon carbide. These materials have many advantages as substrates.
  • the patterned sapphire substrate (PSS) technology can improve the light extraction efficiency of the LED chip and increase the lifetime of the LED by reducing the reverse leakage current.
  • sapphire has a thermal expansion coefficient of 8.5*10 -6 /K
  • various commonly used semiconductor epitaxial materials such as gallium nitride (coefficient of thermal expansion is 5.8*10 -6).
  • /K has a large difference in thermal expansion coefficient, and the difference between the epitaxial material and the substrate material in the thermal expansion coefficient is not only likely to degrade the quality of the epitaxial film, but also cause damage to the device due to heat generation during the operation of the device, and It is also difficult to completely eliminate the adverse effects of lattice mismatch with the epitaxial material.
  • Figure 1 shows the structure of a currently common LED chip. Due to the crystal characteristics of AlGaN, it is necessary to grow an AlN layer on sapphire to grow a better quality AlGaN epitaxial layer. Due to the presence of AlN, the laser or Other methods are very difficult to remove sapphire, and removing sapphire is very beneficial for light efficiency.
  • the present invention is directed to providing a patterned substrate by using a conventional substrate material and then stripping off the conventional liner.
  • the bottom LED chip solves many defects caused by the conventional substrate, such as poor heat dissipation performance and low light extraction efficiency.
  • an aspect of the present invention provides a method of fabricating an LED structure, the method comprising the steps of:
  • the first substrate is peeled off, or the release layer and the first substrate are peeled off.
  • the patterned first substrate means: a plurality of concave structures are arranged on the substrate, and an upper plane is between two adjacent concave structures, the concave structure is from top to bottom
  • the concave structure is from top to bottom
  • the transition surface extending upward along the lower surface edge and forming a recess together with the lower surface, the transition surface extending obliquely upward along the end of the side wall, one end of the transition surface
  • the side wall is connected and the other end is connected to the upper plane.
  • the side wall is inclined and the angle between the side wall and the lower surface is ⁇ , ⁇ is between 100° and 120°; the angle between the transition surface and the upper surface is ⁇ , ⁇ is between 120° and 150°.
  • the "forming the patterned first substrate” further comprises the following steps:
  • the colloid is etched by oxygen plasma to form a vacancy having a hexagonal hole shape or a circular hole shape, and at the end of the colloid away from the mask layer An inclined surface is formed.
  • the inclined surface has a ⁇ angle with the direction of the mask layer, and ⁇ ranges between 45° and 80°.
  • a mask layer and spin-on-colloid on a substrate depositing a mask layer on the substrate, the mask layer being SiO 2 and having a thickness between 80-120 nm; Then, a colloid is spin-coated on the mask layer.
  • the release layer material may be graphene or boron nitride.
  • the "stripping the first substrate, or peeling off the release layer and the first substrate” is peeled off by tape bonding.
  • Another aspect of the present invention provides an LED structure having a patterned substrate and an LED epitaxial growth on the substrate, the patterned substrate being: arranged on the substrate Having a plurality of convex structures, an upper plane between the two adjacent convex structures, the convex structures including a transition surface, a side wall and a lower surface in order from top to bottom, the side walls extending upward along the lower surface edge and Forming a protrusion together with the lower surface, the transition surface extending obliquely upward along the end of the side wall, one end of the transition surface connecting the side wall and the other end connecting the upper plane.
  • the side wall is inclined and the angle between the side wall and the lower surface is ⁇ , ⁇ is between 100° and 120°; the angle between the transition surface and the upper plane is ⁇ . , ⁇ is between 120 ° - 150 °.
  • the method for preparing the LED structure of the present application after forming a patterned substrate by using a conventional substrate (for example, sapphire or the like), forming a buffer layer and an LED epitaxial layer by forming a peeling layer which is easily peeled off, and peeling off the conventional substrate, thereby forming
  • a conventional substrate for example, sapphire or the like
  • the prepared LED structure is formed by using a suitable material
  • the substrate is a patterned substrate composed of a special convex structure, which can form a photonic crystal, thereby greatly improving the LED chip. Light output efficiency.
  • FIG. 1 is a schematic view of a prior art LED structure
  • FIG. 2 is a flow chart showing a method of fabricating an LED structure according to an embodiment of the present invention
  • FIG. 3 is a flow chart of a method of forming a patterned first substrate in a method of fabricating an LED structure according to an embodiment of the present invention
  • FIG. 4 is a schematic view showing a state in which a mask layer and a spin-on colloid are deposited on a substrate in the first embodiment of the present invention
  • FIG. 5 is a schematic view showing a state of a step of etching a colloid by oxygen plasma in the first embodiment of the present invention
  • FIG. 6 is a schematic view showing a state of a step of etching a mask layer in the first embodiment of the present invention
  • FIG. 7 and FIG. 8 are schematic views showing a state in which a step of etching a substrate to form a concave structure in the first embodiment of the present invention
  • FIG. 9 is a schematic view showing a state of a step of removing a mask layer in the first embodiment of the present invention.
  • Figure 10 is a schematic view showing a state in which a step of depositing a peeling layer material to form a patterned peeling layer in the first embodiment of the present invention
  • Figure 11 is a schematic view showing a state in which a buffer layer is formed on a peeling layer in the first embodiment of the present invention
  • FIG. 12 is a schematic view showing a state of a step of growing an LED epitaxial layer on a buffer layer in the first embodiment of the present invention
  • Figure 13 is a schematic view showing the state of the step of peeling off the sapphire substrate and the peeling layer in the first embodiment of the present invention
  • Figure 14 shows a schematic diagram of a raised structure in a patterned substrate of an LED structure in accordance with one embodiment of the present invention.
  • One aspect of the present invention provides a method of fabricating an LED structure. As shown in FIG. 2, the method includes the following steps:
  • the first substrate is peeled off, or the release layer and the first substrate are peeled off.
  • the patterned first substrate may be formed using a conventional substrate material, for example, may be formed using conventional sapphire, silicon carbide, or the like.
  • the patterned first substrate can be formed as follows:
  • FIGS. 4 to 9 a process of forming a patterned first substrate according to a first embodiment of the present invention is shown.
  • a sapphire substrate is used as an example in this embodiment.
  • a mask layer 27 and a spin-on colloid 28 are deposited on the substrate 21.
  • a mask layer 27 of a certain thickness is deposited on the sapphire substrate 21, and the mask layer 27 is made of SiO 2 or other hard material having a thickness of between 80 and 120 nm, more preferably 100 nm.
  • the hexagonal aperture array is transferred to the mask layer 27 by nanoimprinting or photolithography in a hexagonal or circular aperture shape.
  • the period of the hexagonal hole pattern ie, the distance between the geometric centers of the adjacent two hexagonal pattern
  • the optimum value is 1.2 ⁇ m
  • the radius of the circumcircle of the hexagonal pattern is 0.5-1.2 ⁇ m
  • the optimum value is 1 ⁇ m.
  • the colloid 28 is etched by an oxygen plasma, and an inclined surface 281 is formed at an end of the colloid 28 away from the mask layer 27 by utilizing a difference in speed of mass transfer between the etching precursor and the product at the surface and the bottom of the colloid 28. 281 causes the upper end of the colloid 28 to have a trapezoidal shape.
  • the inclined surface 281 and the mask layer 27 have a ⁇ angle, and the ⁇ range is between 45° and 80°, and the optimum value is 60°.
  • the step of etching the mask layer is illustrated.
  • the hard mask layer 27 at the vacancy 29 is etched by an etching gas such as a fluorine-based gas.
  • an etching gas such as a fluorine-based gas.
  • the colloid 28 is highly lowered by the etching of the gas, and the inclination of the inclined surface 281 is constant.
  • the step of etching the substrate to form a concave structure is carried out in two steps.
  • the etching gas BCl3, Cl2, Ar, etc., mixed in a certain ratio, for example, the ratio of BCl3, Cl2 is 7:2
  • the sapphire substrate 21 is etched, and a recess 220 is formed at a position where the substrate 21 is located at the vacancy 29.
  • the recess 220 has a trapezoidal shape in cross section, and the trapezoid is located on the surface of the substrate 21 with a side length a.
  • the side length inside the substrate 21 is b, a>b.
  • the trapezoidal groove 220 includes two oblique sides 2201 and a lower bottom edge 2202. While etching the sapphire substrate 21, the colloid 28 is highly lowered by the etching of the gas, and the inclination of the inclined surface 281 is constant; at this time, the mask layer 27 is an independent rectangular body.
  • the sapphire substrate 21 located at the vacancy 29 is further etched by etching gas (BCl3, Cl2, Ar, etc., in a certain ratio, for example, the ratio of BCl3, Cl2 is 8:1), as shown in FIG.
  • etching gas BCl3, Cl2, Ar, etc., in a certain ratio, for example, the ratio of BCl3, Cl2 is 8:1
  • the colloid 28 is highly lowered under the etching action of the gas, and the side surface thereof and the side surface of the mask layer 27 are etched, and the side surface of the colloid 28 is located at the same side as the side surface of the corresponding mask layer 27.
  • a straight line forms a slope 287 on the sides of the two.
  • the effect of the two on the etched shape on the sapphire substrate 21 during the etching process is guided by the difference in the shape of the longitudinal direction of the colloid 28 and the mask layer 27, in the process, the groove 220 on the sapphire substrate 21
  • the two beveled edges 2201 are etched from the edge straight shape to include two segments, a transition surface 222 and a sidewall 221, and the two are at an angle to each other.
  • the solution includes concentrated sulfuric acid and hydrogen peroxide, wherein the ratio of concentrated sulfuric acid to hydrogen peroxide is 5:1, and the hydrogen peroxide can decompose oxygen by heating, and the colloid 28 and the mask layer 27 can be removed by washing with a mixture of concentrated sulfuric acid and oxygen.
  • a plurality of array-arranged concave structures 22 are left on the sapphire substrate 21, i.e., a patterned first substrate is formed, wherein the two adjacent concave structures 22 are in an upper plane
  • the concave structure includes, in order from top to bottom, a transition surface, a side wall and a lower surface, the side wall extending upward along the lower surface edge and forming a recess together with the lower surface, the transition surface being obliquely upward along the end of the side wall Extending, one end of the transition surface is connected to the side wall, and the other end is connected to the upper plane. More preferably, the side wall is inclined and the angle between the side wall and the lower surface is ⁇ , ⁇ is between 100° and 120°; the angle between the transition surface and the upper surface is ⁇ , ⁇ is between 120° and 150°.
  • the end of the colloid is etched into a shape having an inclined surface by using an oxygen plasma etching, so that the gas etching process in the subsequent step gradually produces a colloid and a mask layer having a certain inclination.
  • the side surface and the concave structure on the sapphire substrate, the inclined surface of the colloidal end portion determines the formation of the transition surface and the side wall in the concave structure, so that the specially patterned first substrate can be formed.
  • a release layer material can be deposited on the sapphire substrate.
  • a release layer material can be deposited on the sapphire substrate.
  • the step of depositing a release layer material on a patterned first substrate to form a patterned release layer is illustrated.
  • a patterned release layer 23 is deposited on the sapphire substrate 21 .
  • the release layer material may preferably be graphene or boron nitride, and may be deposited by a conventional method such as chemical vapor deposition.
  • the setting of the peeling layer can solve the problem that the sapphire needs laser stripping, high cost and complicated operation.
  • a peeling layer formed of graphene or boron nitride can be easily peeled off.
  • a step of depositing a buffer layer on the lift-off layer is shown.
  • a buffer layer 24 is formed on the peeling layer 23.
  • the formation of the buffer layer can be advantageous for the epitaxial growth of the LED, and preferably can be formed using an aluminum nitride or aluminum gallium nitride material.
  • the step of growing the LED epitaxial on the buffer layer is illustrated. As shown in FIG. 12, after the buffer layer 24 is formed, the LED epitaxy 25 is grown thereon, and conventional LED epitaxial growth can be performed by a conventional method.
  • the step of stripping is shown.
  • the sapphire substrate 21 and the peeling layer 23 are peeled off.
  • the peeling can be carried out by tape bonding.
  • the release layer may be peeled off together with the first substrate, or only the first substrate layer may be peeled off as needed.
  • the peeled first substrate such as the sapphire substrate or the release layer can be reused, which improves the utilization ratio of the material and reduces the production cost.
  • an LED structure having a patterned substrate 24 i.e., the buffer layer 24
  • an LED epitaxial growth on the substrate is formed. 25 wherein a plurality of convex structures are arranged on the patterned substrate 24 (the convex structures correspond to the concave structures formed on the first substrate), and the upper adjacent planes are upper planes .
  • An enlarged structure of the illustrated raised structure is shown in FIG.
  • each raised structure 12 includes a transition surface 122, a sidewall 121 and a lower surface 123 that extend upward along the edge of the lower surface 123 and with the lower portion
  • the surface 123 together form a protrusion; the transition surface 122 extends obliquely upward along the upper end of the side wall 121, and the transition surface 122 is connected between the side wall 121 and the upper plane 124.
  • the side wall 121 has an oblique direction and an angle between the side wall 121 and the lower surface 123 is ⁇ , ⁇ is between 100° and 120°, and the optimum value is 110°.
  • the angle between the transition surface 122 and the upper plane 124 is ⁇ , ⁇ is between 120° and 150°, and the optimum value is 140°.
  • the incident angle when more light passing through the convex structure 12 is emitted to the outside is less than full
  • the critical angle of reflection is emitted to the outside, which greatly improves the light extraction efficiency of the LED, thereby improving the light extraction efficiency of the LED chip.
  • the lower surface 123 has a circular shape
  • the convex structure 12 is viewed from the bottom to the top
  • the convex structure 12 has a hexagonal hole shape or a circular hole shape.
  • the lower surface of the patterned substrate 24 formed by the buffer layer can form a structure of a photonic crystal, which can further improve the light extraction efficiency of the LED chip.

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Abstract

一种LED结构的制备方法以及由此制备的LED结构。该方法包括如下步骤：形成图形化的第一衬底（21）；在图形化的第一衬底（21）上沉积剥离层材料形成图形化的剥离层（23）；在剥离层（23）上沉积形成缓冲层（24）；在缓冲层（24）上生长LED的外延（25）；剥离第一衬底（21），或者剥离剥离层（23）和第一衬底（21）。该申请的方法利用常规衬底(例如蓝宝石等)形成图形化衬底后，通过形成容易剥离的剥离层（23）后再形成缓冲层（24）和LED外延（25），并剥离掉常规衬底，形成具有特定图形化衬底的LED结构，所制备的LED结构采用合适的材料形成衬底，同时该衬底为特殊凸起结构构成的图形化衬底，可以形成光子晶体，从而极大地提高了LED芯片的出光效率。

Description

一种LED结构及其制备方法 技术领域
本发明涉及半导体技术领域，更具体而言涉及一种LED结构及其制备方法。
背景技术
在半导体结构和器件的外延生长中，需要支撑半导体材料生长的衬底。衬底的性质对外延生长的半导体层的质量非常关键。目前广泛使用的衬底材料主要有蓝宝石、硅和碳化硅。这些材料作为衬底有诸多优点，尤其是，图形化的蓝宝石衬底(PSS)技术，既可以提高LED芯片的出光效率，也可以通过减小反向漏电流提升LED寿命。
然而，这些材料作为衬底也有一些问题，以蓝宝石为例，其热膨胀系数为8.5＊10 -6/K，与常用的各种半导体外延材料，例如氮化镓(热膨胀系数为5.8＊10 -6/K)等有较大的热膨胀系数差，外延材料与衬底材料在热膨胀系数上相差过大不仅可能使外延膜质量下降，还会在器件工作过程中，由于发热而造成器件的损坏，而且也很难完全消除与外延材料之间的晶格失配的不利影响。
图1示出了一种目前常见的LED芯片的结构，由于AlGaN的晶体特点，需要在蓝宝石上生长一层AlN层才能生长一层质量较好的AlGaN外延层，由于AlN的存在，使得激光或者其他方法非常难去掉蓝宝石，去掉蓝宝石对于出光效率是有很大好处的。
发明内容
针对现有LED芯片常用的衬底材料带来的诸如散热性能差、晶格失配等等问题，本发明旨在提供了一种利用常规衬底材料形成图形化衬底后再剥离掉常规衬底的LED芯片，从而解决了常规衬底带来的诸多缺陷，例如散热性能差、出光效率低等缺点。
鉴于上述问题，本发明一方面提供了一种LED结构的制备方法，所述方法包括如下步骤：
形成图形化的第一衬底；
在所述图形化的第一衬底上沉积剥离层材料形成图形化的剥离层；
在所述剥离层上沉积形成缓冲层；
在缓冲层上生长LED的外延；
剥离所述第一衬底，或者剥离所述剥离层和第一衬底。
优选地，所述图形化的第一衬底是指：在所述衬底上排布多个凹形结构，两相邻凹形结构之间为上平面，所述凹形结构自上而下依次包括过渡面、侧壁和下表面，所述侧壁沿下表面边缘向上延伸且与所述下表面共同形成凹陷，所述过渡面沿侧壁端部向斜上方延伸，该过渡面的一端连接所述侧壁、另一端连接所述上平面。
更优选地，所述侧壁呈倾斜方向且该侧壁与下表面之间的夹角为α，α介于100°-120°之间；所述过渡面与上平面之间的夹角为β，β介于120°-150°之间。
优选地，所述“形成图形化的第一衬底”进一步包括如下步骤：
在衬底上沉积掩膜层及旋涂胶体；
氧等离子体刻蚀所述胶体；
刻蚀掩膜层；
刻蚀衬底，形成凹形结构；
去除掩膜层。
进一步地，在所述“氧等离子体刻蚀所述胶体”步骤中，通过氧等离子体将胶体刻蚀，形成具有六边孔形或者圆孔形的空位，并在胶体远离掩膜层的一端形成倾斜面。
更优选地，所述倾斜面与掩膜层的方向呈γ角，γ的范围介于45°-80°之间。
优选地，在所述“在衬底上沉积掩膜层及旋涂胶体”步骤中，在衬底上沉积掩膜层，该掩膜层为SiO 2，其厚度介于80-120nm之间；然后，在所述掩膜层上旋涂胶体。
优选地，所述剥离层材料可以为石墨烯或者氮化硼。
所述“剥离所述第一衬底，或者剥离所述剥离层和第一衬底”通过胶带粘贴进行剥离。
本发明另一方面提供了一种LED结构，所述LED结构具有图形化的衬底以及在该衬底上生长的LED外延，所述图形化的衬底是指：在所述衬底上排布多个凸形结构，两相邻凸形结构之间为上平面，所述凸形结构自上而下依次包括过渡面、侧壁和下表面，所述侧壁沿下表面边缘向上延伸且与所述下表面共同形成凸起，所述过渡面沿侧壁端部向斜上方延伸，该过渡面的一端连接所述侧壁、另一端连接所述上平面。
优选地，所述侧壁呈倾斜方向且该侧壁与下表面之间的夹角为α，α介于100°-120°之间；所述过渡面与上平面之间的夹角为β，β介于120°-150°之间。
有益效果
本申请的LED结构的制备方法，利用常规衬底(例如蓝宝石等)形成图形化衬底后，通过形成容易剥离的剥离层后再形成缓冲层和LED外延，并剥离掉常规衬底，形成具有特定图形化衬底的LED结构，所制备的LED结构采用合适的材料形成衬底，同时该衬底为特殊凸起结构构成的图形化衬底，可以形成光子晶体，从而极大地提高了LED芯片的出光效率。
附图说明
从下面结合附图的详细描述中，将会更加清楚的理解本发明的上述及其他目的、特征和其他优点，其中，
图1为一种现有技术的LED结构的示意图
图2为本发明一个实施方案的LED结构的制备方法的流程图；
图3为本发明一个实施方案的LED结构的制备方法中，形成图形化第一衬底的方法的流程图；
图4为本发明第一实施例中在衬底上沉积掩膜层及旋涂胶体的步骤的状态示意图；
图5为本发明第一实施例中氧等离子体刻蚀胶体的步骤的状态示意图；
图6为本发明第一实施例中刻蚀掩膜层的步骤的状态示意图；
图7和图8为本发明第一实施例中刻蚀衬底形成凹形结构的步骤的状态 示意图；
图9为本发明第一实施例中去除掩膜层的步骤的状态示意图；
图10为本发明第一实施例中沉积剥离层材料形成图形化的剥离层的步骤的状态示意图；
图11为本发明第一实施例中在剥离层上沉积形成缓冲层的步骤的状态示意图；
图12为本发明第一实施例中在缓冲层上生长LED外延的步骤的状态示意图；
图13为本发明第一实施例中剥离蓝宝石衬底和剥离层的步骤的状态示意图；
图14示出了根据本发明一个实施方案的LED结构的图形化衬底中一个凸起结构的示意图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及具体实施方案，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施方案仅用以解释本发明，并不用于限定本发明。
本发明一方面提供了一种LED结构的制备方法，如图2所示，所述方法包括如下步骤：
形成图形化的第一衬底；
在所述图形化的第一衬底上沉积剥离层材料形成图形化的剥离层；
在所述剥离层上沉积形成缓冲层；
在缓冲层上生长LED的外延；
剥离所述第一衬底，或者剥离所述剥离层和第一衬底。
其中，图形化的第一衬底可以采用常规的衬底材料形成，例如，可以采用常用的蓝宝石、碳化硅等形成。
优选地，如图3所示，图形化的第一衬底可以如下形成：
在衬底上沉积掩膜层及旋涂胶体；
氧等离子体刻蚀所述胶体；
刻蚀掩膜层；
刻蚀衬底，形成凹形结构；
去除掩膜层。
更具体地，如图4-图9，示出了根据本发明第一实施例的图形化第一衬底的形成过程。该实施例中采用蓝宝石衬底作为示例。
请参阅图4，示出了在衬底上沉积掩膜层及旋涂胶体的步骤。如图4所示，在衬底21上沉积掩膜层27及旋涂胶体28。在蓝宝石衬底21上沉积一定厚度的掩膜层27，该掩膜层27为SiO 2或者其他硬质材质，其厚度为介于80-120nm之间，更优选为100nm。在所述掩膜层27上旋涂一定厚度的纳米压印或者光刻胶，即所述胶体28，该胶体28在掩膜层27上以阵列排布且在胶体28上形成的空位29形状为六边孔形或者圆孔形，通过纳米压印或者光刻方式将六边孔型阵列转移到掩膜层27上。所述六边孔型图形的周期(即相邻两六边孔型图形的几何中心之间的距离)为0.8-2μm，最佳值为1.2μm，该六边孔型图形的外接圆半径为0.5-1.2μm，最佳值为1μm。
请参阅图5，示出了氧等离子体刻蚀胶体的步骤。通过氧等离子体将胶体28刻蚀，利用刻蚀前体和生成物在所述胶体28表面和底部质量传输的速度差异，在胶体28远离掩膜层27的一端形成倾斜面281，该倾斜面281使胶体28上端呈梯形形状。在本实施例中，所述倾斜面281与掩膜层27的方向呈γ角，γ的范围介于45°-80°之间，最佳值为60°。
请参阅图6，示出了刻蚀掩膜层的步骤。通过刻蚀气体(例如氟基气体)将位于空位29处的硬质掩膜层27刻蚀。与此同时，所述胶体28在气体的刻蚀作用下高度降低，其倾斜面281的倾斜度不变。
请参阅图7和图8，示出了刻蚀衬底，形成凹形结构的步骤。该步骤分两步进行，首先如图7所示，通过刻蚀气体(BCl3、Cl2、Ar等气体按一定比例混合，例如可以是BCl3、Cl2的比例是7∶2)将位于空位29处的蓝宝石衬底21刻蚀，在衬底21位于空位29的位置处形成向下凹陷的凹槽220，该凹槽220的截面呈梯形形状，该梯形位于衬底21表面的边长为a、位于衬底21内部的边长为b，a＞b。所述梯形凹槽220包括两斜边2201和下底边2202。在刻蚀蓝宝石衬底21的同时，所述胶体28在气体的刻蚀作用下高度降低，其 倾斜面281的倾度不变；此时，所述掩膜层27为独立的矩形体。
接着，再通过刻蚀气体(BCl3、Cl2、Ar等气体按一定比例混合，例如可以是BCl3、Cl2的比例是8∶1)继续将位于空位29处的蓝宝石衬底21刻蚀，如图8所示，此时，所述胶体28在气体的刻蚀作用下高度降低，同时其侧面以及掩膜层27侧面被刻蚀，所述胶体28的侧面与对应的掩膜层27的侧面位于同一直线，在该两者的侧面形成一斜面287。与此同时，通过胶体28和掩膜层27纵向的形状差异，引导刻蚀过程中该两者对蓝宝石衬底21上刻蚀形状的影响，在此过程中，蓝宝石衬底21上凹槽220的两斜边2201从边缘直线形状刻蚀成包括两段，即过渡面222和侧壁221且该两者之间互成角度。
请参阅图9，示出了去除掩膜层的步骤。配备包括浓硫酸和双氧水的溶液，其中，浓硫酸和双氧水的比例为5∶1，双氧水通过升温可分解出氧气，通过浓硫酸和氧气的混合体可以将胶体28和掩膜层27清洗去除。由此，蓝宝石衬底21上留下多个阵列排布的凹形结构22，即，形成了图形化的第一衬底，其中，两相邻凹形结构22之间为上平面，所述凹形结构自上而下依次包括过渡面、侧壁和下表面，所述侧壁沿下表面边缘向上延伸且与所述下表面共同形成凹陷，所述过渡面沿侧壁端部向斜上方延伸，该过渡面的一端连接所述侧壁、另一端连接所述上平面。更优选地，所述侧壁呈倾斜方向且该侧壁与下表面之间的夹角为α，α介于100°-120°之间；所述过渡面与上平面之间的夹角为β，β介于120°-150°之间。
上述方法中，通过采用氧等离子体刻蚀，将胶体的端部刻蚀呈具有倾斜面的形状，从而使其之后的步骤中气体刻蚀的过程逐渐产生具有一定倾斜度的胶体和掩膜层侧面以及蓝宝石衬底上的凹形结构，所述胶体端部的倾斜面决定了所述凹形结构中过渡面和侧壁的生成，从而可以形成经特殊图形化的第一衬底。
形成该图形化的蓝宝石衬底后，可以在该蓝宝石衬底上沉积剥离层材料。请参阅图10，示出了在图形化的第一衬底上沉积剥离层材料形成图形化的剥离层的步骤。如图10所示，在蓝宝石衬底21上，沉积形成图形化的剥离层23。剥离层材料优选可以为石墨烯或者氮化硼，可以通过例如化学气相沉积等常规方法进行沉积。剥离层的设置，可以解决蓝宝石需要激光剥离，成本高且操作复杂的问题。尤其是石墨烯或者氮化硼形成的剥离层，可以容易地 进行剥离。
接着，请参阅图11，示出了在剥离层上沉积形成缓冲层的步骤。如图11所示，在剥离层23上形成缓冲层24。该缓冲层的形成，可以有利于在LED外延的生长，优选可以采用氮化铝或者氮化铝镓材料形成。
请参阅图12，示出了在缓冲层上生长LED外延的步骤。如图12所示，形成缓冲层24后，在其上生长LED外延25，可以采用常规的方法进行常规LED外延的生长。
最后，请参阅图13，示出了剥离的步骤。如图13所示，剥离了蓝宝石衬底21和剥离层23。本申请中，剥离可以通过胶带粘贴进行。而且，可以将剥离层和第一衬底一起剥离，或者也可以根据需要，只剥离第一衬底层。另外，通过胶带剥离后，所剥离的第一衬底例如蓝宝石衬底或者剥离层均可以重复利用，提高了材料的利用率，降低了生产成本。
由此，在剥离了蓝宝石衬底21和剥离层23后，形成了一种LED结构，该LED结构具有图形化的衬底24(即，缓冲层24)以及在该衬底上生长的LED外延25，其中，在图形化的衬底24上排布多个凸形结构(该凸起结构与前文第一衬底上形成的凹形结构对应)，两相邻凸起结构之间为上平面。所示凸起结构的放大结构如图14所示，每个凸起结构12包括过渡面122、侧壁121和下表面123，所述侧壁121沿下表面123边缘向上延伸且与所述下表面123共同形成一凸起；所述过渡面122沿侧壁121上端部向斜上方延伸，该过渡面122连接在所述侧壁121和所述上平面124之间。所述侧壁121呈倾斜方向且该侧壁121与下表面123之间的夹角为α，α介于100°-120°之间，最佳值为110°。所述过渡面122与上平面124之间的夹角为β，β介于120°-150°之间，最佳值为140°。通过将凸起结构12设置成倾斜的侧壁121且该倾斜的侧壁121与上平面124之间设置过渡面122，使更多经过凸起结构12的光线出射到外界时的入射角小于全反射临界角而出射至外界，大大提高了LED的光提取效率，从而提高LED芯片的出光效率。在本实施例中，所述下表面123呈圆形，而从下到上仰视所述凸起结构12，该凸起结构12呈六边孔形或者呈圆孔形排列。
通过该多个凸起结构的阵列排布，该缓冲层构成的图形化衬底24下表面可以形成光子晶体的结构，可以进一步提高LED芯片的出光效率。
以上所述仅为本发明的较佳实施方式而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (11)

  1. 一种LED结构的制备方法，所述方法包括如下步骤：
    形成图形化的第一衬底；
    在所述图形化的第一衬底上沉积剥离层材料形成图形化的剥离层；
    在所述剥离层上沉积形成缓冲层；
    在缓冲层上生长LED的外延；
    剥离所述第一衬底，或者剥离所述剥离层和第一衬底。
  2. 如权利要求1所述的LED结构的制备方法，其中，所述图形化的第一衬底是指：在所述衬底上排布多个凹形结构，两相邻凹形结构之间为上平面，所述凹形结构自上而下依次包括过渡面、侧壁和下表面，所述侧壁沿下表面边缘向上延伸且与所述下表面共同形成凹陷，所述过渡面沿侧壁端部向斜上方延伸，该过渡面的一端连接所述侧壁、另一端连接所述上平面。
  3. 如权利要求2所述的LED结构的制备方法，其中，所述侧壁呈倾斜方向且该侧壁与下表面之间的夹角为α，α介于100°-120°之间；所述过渡面与上平面之间的夹角为β，β介于120°-150°之间。
  4. 如权利要求1-3中任一项所述的LED结构的制备方法，其中，所述“形成图形化的第一衬底”进一步包括如下步骤：
    在衬底上沉积掩膜层及旋涂胶体；
    氧等离子体刻蚀所述胶体；
    刻蚀掩膜层；
    刻蚀衬底，形成凹形结构；
    去除掩膜层。
  5. 如权利要求4所述的LED结构的制备方法，其中，在所述“氧等离子体刻蚀所述胶体”步骤中，通过氧等离子体将胶体刻蚀，形成具有六边孔形或者圆孔形的空位，并在胶体远离掩膜层的一端形成倾斜面。
  6. 如权利要求4所述的LED结构的制备方法，其中，在所述“在衬底上沉积掩膜层及旋涂胶体”步骤中，在衬底上沉积掩膜层，该掩膜层为SiO 2，其厚度介于80-120nm之间；然后，在所述掩膜层上旋涂胶体。
  7. 如权利要求5所述的LED结构的制备方法，其中，所述倾斜面与掩 膜层的方向呈γ角，γ的范围介于45°-80°之间。
  8. 如权利要求1所述的LED结构的制备方法，其中，所述剥离层材料为石墨烯或者氮化硼。
  9. 如权利要求1所述的LED结构的制备方法，其中，所述“剥离所述第一衬底，或者剥离所述剥离层和第一衬底”通过胶带粘贴进行剥离。
  10. 一种LED结构，所述LED结构具有图形化的衬底以及在该衬底上生长的LED外延，所述图形化的衬底是指：在所述衬底上排布多个凸形结构，两相邻凸形结构之间为上平面，所述凸形结构自上而下依次包括过渡面、侧壁和下表面，所述侧壁沿下表面边缘向上延伸且与所述下表面共同形成凸起，所述过渡面沿侧壁端部向斜上方延伸，该过渡面的一端连接所述侧壁、另一端连接所述上平面。
  11. 如权利要求10所述的LED结构，其中，所述侧壁呈倾斜方向且该侧壁与下表面之间的夹角为α，α介于100°-120°之间；所述过渡面与上平面之间的夹角为β，β介于120°-150°之间。
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