WO2021203500A1 - 一种发光二极管芯片及其制作方法 - Google Patents

一种发光二极管芯片及其制作方法 Download PDF

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Publication number
WO2021203500A1
WO2021203500A1 PCT/CN2020/088747 CN2020088747W WO2021203500A1 WO 2021203500 A1 WO2021203500 A1 WO 2021203500A1 CN 2020088747 W CN2020088747 W CN 2020088747W WO 2021203500 A1 WO2021203500 A1 WO 2021203500A1
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laser
layer
reflection layer
emitting diode
chip
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PCT/CN2020/088747
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English (en)
French (fr)
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林宗民
黄苡叡
张中英
邓有财
陈艳萍
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厦门三安光电有限公司
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Priority to CN202080004935.0A priority Critical patent/CN112840467A/zh
Publication of WO2021203500A1 publication Critical patent/WO2021203500A1/zh

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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

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  • the invention relates to the field of light-emitting diode chips, in particular to a light-emitting diode chip and a manufacturing method thereof.
  • the process of cutting and separating the LED wafer into individual LED chips usually adopts laser cutting or laser stealth cutting.
  • the laser cutting process due to the limitation of the minimum size of the laser beam and the tolerance of the machine's alignment accuracy, and the design of the cutting path between the chip and the chip is too narrow, the laser beam will burn the chip functional area. Defective problems such as chip leakage. Especially the smaller the chip size, the more obvious its influence, such as mini-LED and Micro-LED.
  • the invention aims to provide a light-emitting diode chip and a manufacturing method thereof, so as to solve the problem of easy damage to the epitaxial structure in the existing laser cutting process.
  • a method for manufacturing a light-emitting diode chip includes the following process steps:
  • the LED wafer includes a substrate and a plurality of LED units located on the substrate, and there is a cutting channel between two adjacent LED units;
  • a laser reflection layer that has the ability to reflect the laser wavelength of the laser is formed on the outer surface of the LED unit, and the laser reflection layer covers at least the side wall area of the LED unit at the edge of the cutting lane;
  • the present invention also provides a light emitting diode chip, including: a substrate and an epitaxial structure on the substrate, a laser reflective layer is provided on the side surface of the epitaxial structure, and the laser reflective layer is used for the substrate.
  • the cutting laser beam has reflective ability.
  • the reflectivity of the laser reflective layer to the laser beam is more than 80%, more preferably more than 90%, so that the width of the cutting lane can be reduced to less than 20 ⁇ m, or even less than 15 ⁇ m, to ensure that the epitaxial structure is No damage during cutting.
  • the wavelength of the laser beam used for substrate cutting is 1064 ⁇ 100 nm.
  • the laser reflective layer only has the ability to reflect the laser wavelength of the laser.
  • the laser reflection layer includes a Bragg reflection layer, a photonic crystal reflection layer, or a reflection layer structure that is a mixture of both the Bragg reflection layer and the photonic crystal reflection layer designed for the laser wavelength of the laser.
  • the laser reflection layer is formed on the outer surface of the LED unit using electron beam evaporation or ion beam sputtering technology.
  • the laser reflective layer also covers the edge area of the top surface of the LED unit on the side facing away from the substrate.
  • the outer surface of the LED unit is further provided with a chip reflection layer that has the ability to reflect the wavelength of light emitted by the LED unit, and the laser reflection layer is formed on the chip reflection layer.
  • the laser reflection layer and the chip reflection layer can be completely overlapped or partially overlapped.
  • the laser reflective layer has the ability to reflect the wavelength of light emitted by the LED unit.
  • the laser reflection layer is a Bragg reflection layer
  • the Bragg reflection layer is formed by alternately stacking a first material layer and a second material layer.
  • the thickness of the first substance layer and the second substance layer are different with the number of layers.
  • the thicknesses of the first substance layer and the second substance layer both decrease as the number of layers increases.
  • the thickness of the first substance layer and the second substance layer both increase as the number of layers increases.
  • the thickness of the first substance layer and the second substance layer varies randomly with the number of layers.
  • the number of Bragg reflective layers is greater than 3 layers and less than 61 layers.
  • the number of pairs of the Bragg reflective layer is n, wherein the thickness of the first material layer of the first pair is D1, and the thickness of the first material layer of the second pair and the third pair is (75% ⁇ 90%)*D1, the thickness of each layer of the first substance layer from the fourth pair to the n/2th pair is (30%-50%)*D1, the first substance from the n/2+1 pair to the nth pair The thickness of each layer of the layer is (20%-30%)*D1, where n ⁇ 8.
  • the number of pairs of the Bragg reflective layer is n, wherein the thickness of the second material layer of the first pair is D2, and the thickness of the second material layer of the second pair and the third pair is (75% ⁇ 90%)*D2, the thickness of each layer of the first substance layer from the fourth pair to the n/2th pair is (30%-50%)*D11, the first substance from the n/2+1 pair to the nth pair The thickness of each layer of the layer is (20%-30%)*D2, where n ⁇ 8.
  • the manufacturing method of the light-emitting diode chip provided by the present invention has the following advantages:
  • the laser reflective layer Since the outer surface of the functional area of the LED unit forms a laser reflective layer that has the ability to reflect the laser wavelength, during laser cutting, when the laser beam is irradiated on the side wall of the LED unit, the laser reflective layer is The laser is reflected, so that the laser beam will not affect the epitaxial structure of the LED unit during the cutting process, so the LED chip will not cause defects such as leakage due to damage to the epitaxial structure.
  • the width of the cutting lane can be minimized, thereby increasing the number of chips per LED wafer.
  • Figure 1 shows a schematic cross-sectional view of an LED wafer.
  • Fig. 2 shows a schematic diagram after a laser reflection layer is formed on the side wall of the LED unit.
  • FIG. 3 shows a schematic diagram after a laser reflection layer is formed on the sidewall of a single LED unit.
  • FIG. 4 shows a schematic diagram after the chip reflection layer and the laser reflection layer are formed on the sidewall of the light-emitting diode chip with the flip-chip structure.
  • FIG. 5 shows a schematic diagram after forming a chip reflection layer and a laser reflection layer on the sidewall of a light-emitting diode chip with a front-mounted structure.
  • Fig. 6 shows the relational graph of the reflectivity of the Bragg reflective layer to the wavelength of each band.
  • This embodiment provides a method for manufacturing a light-emitting diode chip, which includes the following process steps:
  • the LED wafer includes a substrate 10 and a plurality of LED units 20 on the substrate.
  • a dicing lane 30 is provided between two adjacent LED units 20.
  • Each LED unit includes an epitaxial structure 21 formed on the substrate by an epitaxial process and an electrode 22 formed on the epitaxial structure by a chip process.
  • the substrate may be a sapphire substrate, a silicon carbide substrate, a gallium nitride substrate, or the like.
  • a sapphire substrate is selected as the substrate, and the epitaxial structure is formed on the c-plane surface of the sapphire substrate.
  • the c-plane surface of the sapphire substrate is defined as the front side, and the opposite side is the back side.
  • FIG. 1 is a schematic diagram of the cross-sectional structure of the LED wafer in this embodiment.
  • the epitaxial structure at least includes a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer sequentially stacked on the front surface of the substrate.
  • the first conductivity type semiconductor layer is an N-type GaN layer
  • the active layer is a GaN-based multiple quantum well layer
  • the second conductivity type semiconductor layer is a P-type GaN layer.
  • the N-type gallium nitride layer, the multi-quantum well layer and the P-type gallium nitride layer are the basic building blocks of the epitaxial structure of the LED chip.
  • the epitaxial structure can also include other components that optimize the performance of the LED chip.
  • Functional structure layer The epitaxial structure can be formed on the substrate by means of Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), Epitaxy Growth Technology and Atomic Layer Deposition (ALD). superior.
  • PVD Physical Vapor Deposition
  • CVD Chemical Vapor Deposition
  • ALD Atomic Layer Deposition
  • the chip manufacturing process at least the P electrode and the N electrode are formed on the above-mentioned epitaxial structure, and the dicing line 30 is etched. Since the specific process of completing the chip manufacturing process on the epitaxial structure to obtain multiple LED units is well known to those skilled in the art, it will not be repeated here in this application. And on this basis, the chip manufacturing process can also form functional structure layers that optimize the performance of the LED chip on the epitaxial structure, such as a current spreading layer, a Bragg reflector layer (DBR), etc.
  • DBR Bragg reflector layer
  • a laser reflection layer 23 having the ability to reflect the laser wavelength is formed on the outer surface of the LED unit 20.
  • the laser reflection layer 23 may be a Bragg reflection layer (DBR), a photonic crystal (PhCs) reflection layer or a mixed reflection layer structure of both the Bragg reflection layer and the photonic crystal reflection layer (DBR/PhCs) designed for the laser wavelength.
  • the laser reflection The layer 23 covers at least the sidewall area of the LED unit 20 at the edge of the cutting lane 30.
  • the laser reflective layer 23 may be formed on the outer surface of the LED unit by using techniques such as electron beam evaporation or ion beam sputtering.
  • the outer surface of the functional area of the LED unit 20 has a laser reflection layer 23 that can reflect the laser wavelength, and there is no laser reflection layer structure in the cutting lane 30, when the laser beam irradiates the LED unit When on the sidewall of the LED unit 20, the laser reflective layer 23 reflects the laser light irradiated on the LED unit 20, so that the laser beam only acts on the cutting lane 30 for cutting, without affecting the epitaxial structure of the LED unit 20. Therefore, the LED The chip will not cause defects such as leakage due to damage to the epitaxial structure.
  • the problems of chipping and missing corners of the LED chip cutting edge are not easy to occur, and the cutting edge can be made close to vertical. LED chip.
  • the width design of the dicing lane can be minimized, thereby increasing the number of chips produced on a single LED wafer.
  • the laser reflection layer 23 adopts a DBR reflection layer, which has a reflectivity of more than 80% for the laser beam. More preferably, the DBR reflection layer can be alternately stacked by n pairs of high refractive index materials and low refractive index materials.
  • the high refractive index material can be TiO 2 , NB 2 O 5 , TA 2 O 5 , H f O 2 , ZrO 2, etc.; the low refractive index material can be SiO 2 , MgF 2 , Al 2 O 5 , SiON, SiN Wait.
  • the laser cutting mentioned here can use a laser to perform laser tangent to the substrate along the cutting path from the epitaxial side; it can also use the method of laser stealth cutting, that is, the laser beam exits from the epitaxial side and focuses on the substrate Invisible cutting is performed internally. Since the outer surface of the functional area of the LED unit has a laser reflective layer that can reflect the laser wavelength, the laser beam will not affect the epitaxial structure of the LED unit during laser invisible cutting.
  • the difference between this embodiment and Embodiment 1 is that the laser reflective layer 23 not only covers the sidewall area of the LED unit 20 at the edge of the cutting lane 30, but also covers the edge area of the top surface of the LED unit 20.
  • the top surface of the LED unit 20 described here is the surface of the epitaxial structure facing away from the substrate.
  • the laser reflective layer 23 on the edge area of the top surface of the LED unit 20 will also be aligned
  • the laser irradiated on the LED unit 20 is reflected, so that the laser beam will not affect the chip structure of the LED unit 20 during the cutting process, and the performance of the produced light-emitting diode chip is ensured.
  • the laser reflection layer 23 only reflects the laser light at the wavelength of the laser.
  • the light emitted by the manufactured light-emitting diode chip is blue light (445-475 nm) or green light (510-535 nm).
  • the laser is a fiber laser, and its laser wavelength is infrared (940 ⁇ 1100nm).
  • the laser reflection layer 23 only reflects the light of the laser wavelength (infrared), and does not reflect blue or green light, so it does not affect the light-emitting diodes.
  • the emission of light from the chip For example, the sidewall area of a light-emitting diode chip with a front-mounted structure is covered with the laser reflection layer 23.
  • the laser reflection layer 23 reflects the laser beam to protect the chip structure; when the light-emitting diode chip is working, the laser reflection layer 23 does not block the emission of light (blue or green light) from the LED chip, so that the LED chip can still have a large light-emitting angle.
  • the difference between this embodiment and Embodiment 1 is that the LED chip obtained by cutting the LED wafer is a flip-chip LED chip, that is, the light of the LED chip is emitted from the substrate side.
  • the sidewall area of the light-emitting diode chip and other areas on the top surface where the electrode is located except for the electrode have a chip reflective layer 24 that can reflect the wavelength of the light emitted from the light-emitting diode chip.
  • the chip reflective layer 24 can improve the light-emitting diode chip.
  • the laser reflection layer 23 covers the chip reflection layer 24.
  • the laser reflection layer 23 is formed on the chip reflection layer 24, and the chip reflection layer 24 and the laser reflection layer 23 can share a set of masks during the manufacturing process, so as to achieve the purpose of saving cost and shortening the process time.
  • the difference between this embodiment and Embodiment 1 is that the LED chip obtained by cutting the LED wafer is a LED chip with a front-mounted structure, that is, the light from the LED chip is emitted from the electrode side.
  • the sidewall area of the light-emitting diode chip is provided with a chip reflection layer 24 that has the ability to reflect the wavelength of light emitted by the light-emitting diode chip, and the chip reflection layer 24 can improve the light-emitting efficiency of the light-emitting diode chip.
  • the laser reflection layer 23 covers the chip reflection layer 24.
  • the laser reflection layer 23 is formed on the chip reflection layer 24, and the chip reflection layer 24 and the laser reflection layer 23 can share a set of masks during the manufacturing process, so as to achieve the purpose of saving cost and shortening the process time.
  • the laser reflection layer 23 not only has the ability to reflect the laser wavelength, but also has the ability to reflect the wavelength of the light emitted from the light-emitting diode chip, so that the laser reflection layer 23 also has the embodiment 4.
  • the laser reflective layer 23 is preferably a Bragg reflective layer.
  • the Bragg reflective layer is formed by alternately stacking a first material layer and a second material layer, and the thickness of the first material layer and the second material layer varies with each other.
  • the number of layers varies.
  • the first substance layer and the second substance layer can be made of two of SiO 2, TiO 2 , HfO 2 , ZnO 2 , ZrO 2 , Cu 2 O 3 and other materials.
  • the number of pairs of the laser reflection layer 23 is n
  • the thickness of each material layer can be set according to the following: the thickness of the first material layer of the first pair is D1, and the thickness of the first material layer of the second pair and the third pair is D1.
  • the thickness is (75% ⁇ 90%)*D1
  • the thickness of each layer of the first material layer from the fourth pair to the n/2th pair is (30% ⁇ 50%)*D1
  • the n/2+1 pair to The thickness of each layer of the first substance layer of the nth pair is (20%-30%)*D1
  • the thickness of the second substance layer of the first pair is D2
  • the thickness of the second substance layer of the second and third pairs Is (75% ⁇ 90%)*D2
  • the thickness of each layer of the first material layer from the fourth pair to the n/2th pair is (30% ⁇ 50%)*D11, the n/2+1 pair to the nth
  • the thickness of each layer of the first material layer is (20%-30%)*D2, where n ⁇ 8.
  • the first material layer and the second material layer in the Bragg reflective layer are respectively made of SiO 2 and TiO 2 as an example for description.
  • the Bragg reflective layer has 24 layers (12 pairs), each layer Refer to the following table for the material and thickness:
  • the relationship diagram of the reflectance of the Bragg reflective layer to the wavelengths of each band is shown in Fig. 6.
  • the Bragg reflective layer has good reflectivity for wavelengths around 440-590nm and 900-1100nm Greater than 90%), so the Bragg reflective layer has good reflectivity to the emitted light (blue, green) and laser wavelength of the light-emitting diode chip, and has the ability to reflect both the laser wavelength and the wavelength of the emitted light of the light-emitting diode chip .
  • the first material layer and the second material layer decrease with the increase in the number of layers in the present embodiment, they are not limited to this.
  • the thickness of the first material layer and the second material layer can also vary with the number of layers. The number of layers increases; or the thickness of the first material layer and the second material layer varies randomly with the number of layers.

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Abstract

本发明涉及一种发光二极管芯片及其制作方法，该制作方法在LED晶圆上的LED单元的功能区外表面形成对激光波长具有反射能力的激光反射层，该激光反射层在激光切割时，对照射于LED单元上的激光产生反射, 使激光束在进行切割的工艺过程中不会对LED单元的外延结构造成影响，解决了现有激光切割过程中易损伤外延结构的问题。

Description

一种发光二极管芯片及其制作方法 技术领域
本发明涉及发光二极管芯片领域，具体是涉及一种发光二极管芯片及其制作方法。
背景技术
现有发光二极管芯片制程中，将LED晶圆切割分离成单颗的LED芯片的工艺通常采用激光切割或激光隐切的方式。在激光切割过程中，因激光束最小尺寸的限制以及机台的对位精度的公差存在，并且芯片与芯片之间的切割道设计过狭窄的关系，会出现激光束灼烧芯片功能区而造成芯片的漏电等不良问题。尤其是在芯片尺寸越小时其影响越明显，如mini-LED与Micro-LED。
而在激光隐切过程中，由于激光精度偏差，以及劈裂时存在斜裂的问题，使得切割道的尺寸难以缩小(通常在20μm以上，以保证外延结构在切割时不受损伤)。
发明概述
技术问题
问题的解决方案
技术解决方案
本发明旨在提供一种发光二极管芯片及其制作制作方法，以解决现有激光切割过程中易损伤外延结构的问题。
具体方案如下：一种发光二极管芯片的制作方法，包括以下工艺步骤：
(1)提供LED晶圆以及激光器，该LED晶圆包括衬底以及位于衬底上的多个LED单元，相邻两LED单元之间具有一切割道；
(2)在LED单元的外表面上形成对激光器的激光波长具有反射能力的激光反射层，该激光反射层至少将LED单元位于切割道边缘的侧壁区域覆盖住；
(3)沿切割道进行激光正切或者激光束从LED单元一侧入射衬底进行激光隐切，得到发光二极管芯片。
本发明还提供了一种发光二极管芯片，包括：衬底及位于该衬底之上的外延结构，所述外延结构的侧表面上设置有激光反射层，该激光反射层对一用于衬底切割的激光束具有反射能力。
优选地，所述激光反射层对于该激光束的反射率为80％以上，更佳的为90％以上，使得所述切割道的宽度缩小可以到20μm以下，甚至为15μm以下，保证外延结构在切割时不受损伤。具体的，所述用于衬底切割的激光束的波长为1064±100nm。
在一些实施例中，所述激光反射层仅对激光器的激光波长具有反射能力。
在一些实施例中，所述激光反射层包含针对激光器的激光波长设计的布拉格反射层、光子晶体反射层或者布拉格反射层和光子晶体反射层两者混和的反射层结构。
在一些实施例中，所述激光反射层采用电子束蒸镀或者离子束溅射技术形成于LED单元的外表面上。
在一些实施例中，所述激光反射层还覆盖所述LED单元背离衬底一侧的顶面边沿区域。
在一些实施例中，所述LED单元的外表面上还设置有对该LED单元出射光线波长具有反射能力的芯片反射层，所述激光反射层形成于芯片反射层上。所述激光反射层与芯片反射层可以完全重叠设置，也可以部分重叠设置。
在一些实施例中，所述激光反射层对所述LED单元出射光线波长具有反射能力。
在一些实施例中，所述激光反射层为布拉格反射层，该布拉格反射层由第一物质层和第二物质层交替层叠设置而成。
优选地，第一物质层和第二物质层的厚度随层数的不同而不同。在一些实施例中，所述第一物质层和第二物质层的厚度均随层数增加而减小。在一些实施例中，所述第一物质层和第二物质层的厚度均随层数增加而增加。在一些实施例中，所述第一物质层和第二物质层的厚度随层数随机变化。
在一些实施例中，所述布拉格反射层的层数大于3层且小于61层。
在一些实施例中，所述布拉格反射层的对数为n，其中第一对的第一物质层的 厚度为D1，第二对和第三对的第一物质层的厚度为(75％～90％)*D1，第四对至第n/2对的第一物质层的各层厚度为(30％～50％)*D1，第n/2+1对至第n对的第一物质层的各层厚度为(20％～30％)*D1，其中n≥8。
在一些实施例中，所述布拉格反射层的对数为n，其中第一对的第二物质层的厚度为D2，第二对和第三对的第二物质层的厚度为(75％～90％)*D2，第四对至第n/2对的第一物质层的各层厚度为(30％～50％)*D11，第n/2+1对至第n对的第一物质层的各层厚度为(20％～30％)*D2，其中n≥8。
发明的有益效果
有益效果
本发明提供的发光二极管芯片的制作方法与现有技术相比较具有以下优点：
1、由于LED单元功能区的外表面形成对激光波长具有反射能力的激光反射层，因此在激光切割时，激光束照射在LED单元的侧壁上时，激光反射层对照射于LED单元上的激光产生反射，使激光束在进行切割的工艺过程中不会对LED单元的外延结构造成影响，因此LED芯片不会因外延结构损伤而导致漏电等缺陷。
2、通过反射层与激光束尺寸的搭配，在对mini-LED与micro-LED进行切割的过程中，也不容易发生LED芯片切割边缘崩边、缺角的问题，能够制得切割边缘接近垂直的LED芯片。
3、通过反射层与激光束尺寸的搭配，可将切割道的宽度设计最小化，从而增加单片LED晶圆的芯片数产出。
对附图的简要说明
附图说明
图1示出了LED晶圆的具备剖面示意图。
图2示出了在LED单元的侧壁上形成激光反射层后的示意图。
图3示出了单个LED单元的侧壁上形成激光反射层后的示意图。
图4示出了倒装结构的发光二极管芯片的侧壁上形成芯片反射层和激光反射层后的示意图。
图5示出了正装结构的发光二极管芯片的侧壁上形成芯片反射层和激光反射层后的示意图。
图6示出了布拉格反射层对各波段波长的反射率的关系图。
发明实施例
本发明的实施方式
为进一步说明各实施例，本发明提供有附图。这些附图为本发明揭露内容的一部分，其主要用以说明实施例，并可配合说明书的相关描述来解释实施例的运作原理。配合参考这些内容，本领域普通技术人员应能理解其他可能的实施方式以及本发明的优点。图中的组件并未按比例绘制，而类似的组件符号通常用来表示类似的组件。
现结合附图和具体实施方式对本发明进一步说明。
实施例1
本实施例提供一种发光二极管芯片的制作方法，其包括以下工艺步骤：
(1)提供LED晶圆(wafer)以及激光器，该LED晶圆包括衬底10以及位于衬底上的多个LED单元20，相邻两LED单元20之间具有一切割道30。
每一LED单元都包括由外延制程形成于衬底上的外延结构21和由芯片制程形成于外延结构上的电极22。其中，衬底可以为蓝宝石衬底、碳化硅衬底、氮化镓衬底等。在本实施例中，衬底选用蓝宝石衬底，外延结构形成于蓝宝石衬底的c-plane面上，定义蓝宝石衬底的c-plane面为正面，相对的另一面为背面。
参考图1，图1为本实施例中的LED晶圆的剖面结构示意图。外延结构至少包括位于衬底正面上依次层叠的第一导电型半导体层、有源层以及第二导电型半导体层。例如，本实施例中的第一导电型半导体层为N型GaN层，有源层为GaN基多量子阱层，第二导电型半导体层为P型GaN层。其中N型氮化镓层、多量子阱层和P型氮化镓层为LED芯片的外延结构的基本构成单元，在此基础上，外延结构还可以包括其他对LED芯片的性能具有优化作用的功能结构层。外延结构可以通过物理气相沉积(Physical Vapor Deposition，PVD)、化学气相沉积(Chemical Vapor Deposition，CVD)、外延生长(Epitaxy Growth Technology)和原子束沉积(Atomic Layer Deposition，ALD)等方式形成在衬底上。
芯片制程则在上述的外延结构上至少形成P电极和N电极，并且刻蚀出切割道30。由于在外延结构上完成芯片制程，以获得多个LED单元的具体过程为本领域 技术人员所熟知，本申请在此不做赘述。且在此基础上，芯片制程还可以在外延结构上形成对LED芯片的性能具有优化作用的功能结构层，例如电流扩展层、布拉格反射层(DBR)等。
(2)参考图2，在LED单元20的外表面上形成对激光波长具有反射能力的激光反射层23。该激光反射层23可以是针对激光波长设计的布拉格反射层(DBR)、光子晶体(PhCs)反射层或布拉格反射层和光子晶体反射层(DBR/PhCs)两者混和反射层结构，该激光反射层23至少将LED单元20位于切割道30边缘的侧壁区域都覆盖住。激光反射层23可以采用诸如电子束蒸镀或者离子束溅射等技术形成于LED单元的外表面上。
(3)沿切割道进行激光切割并劈裂，得到发光二极管芯片。
在进行激光切割的时候，由于LED单元20功能区的外表面上具有对激光波长具有反射能力的激光反射层23，而切割道30内无此激光反射层结构，因此当激光束照射在LED单元20的侧壁上时，激光反射层23对照射于LED单元20上的激光产生反射，使激光束仅作用于切割道30进行切割，而不会对LED单元20的外延结构造成影响，因此LED芯片不会因外延结构损伤而导致漏电等缺陷。并且通过反射层23与激光束尺寸的搭配，在对mini-LED与micro-LED进行切割的过程中，也不容易发生LED芯片切割边缘崩边、缺角的问题，能够制得切割边缘接近垂直的LED芯片。另外，通过反射层23与激光束尺寸的搭配，可将切割道的宽度设计最小化，从而增加单片LED晶圆的芯片数产出。
在本实施例中，该激光反射层23采用DBR反射层，其对激光束的反射率为80％以上，更佳该DBR反射层可以由n对高折射率材料和低折射率材料交替堆叠而成，其中高折射率材料可以为TiO 2、NB 2O 5、TA 2O 5、H fO 2、ZrO 2等；低折射材料可以为SiO 2、MgF 2、Al 2O 5、SiON、SiN等。这里需明确的是，这里所说的激光切割可以是采用激光从外延侧沿切割道对衬底进行激光正切；也可以采用激光隐切的方式，即激光束从外延侧出射并聚焦于衬底内部而进行隐切，由于LED单元功能区的外表面上具有对激光波长具有反射能力的激光反射层，因此在激光隐切时，激光束不会对LED单元的外延结构造成影响。
实施例2
参考图3，本实施例与实施例1区别的是，激光反射层23除了将LED单元20位于切割道30边缘的侧壁区域都覆盖住外，还将LED单元20顶面的边沿区域覆盖。这里所述的LED单元20的顶面为外延结构背离衬底一侧的表面。在激光切割时，当激光束大于切割道的宽度或者对位偏差而导致激光束照射在LED单元20顶面的边沿区域上时，LED单元20顶面的边沿区域的激光反射层23也会对照射于LED单元20上的激光产生反射，使激光束在进行切割的工艺过程中不会对LED单元20的芯片结构造成影响，确保了制得的发光二极管芯片的性能。
实施例3
本实施例与实施例1区别的是，激光反射层23只针对激光波长进行激光反射，例如，制得的发光二极管芯片出射的光线为蓝光(445～475nm)或者绿光(510～535nm)，而激光器为光纤激光器，其激光波长为红外(940～1100nm)，该激光反射层23只针对激光波长(红外)的光线进行反射，而不会反射蓝光或者绿光，因而并不会影响发光二极管芯片光线的出射。例如，正装结构的发光二极管芯片的侧壁区域覆盖有该激光反射层23，在激光切割过程中，该激光反射层23反射激光束而保护芯片结构；在发光二极管芯片工作时，该激光反射层23并不阻挡发光二极管芯片光线(蓝光或者绿光)的出射，使得该发光二极管芯片仍然能够具有大出光角度。
实施例4
参考图4，本实施例与实施例1区别的是，LED晶圆经切割得到的发光二极管芯片为倒装结构的发光二极管芯片，即该发光二极管芯片的光线是从衬底侧出射的。
该发光二极管芯片的侧壁区域、以及电极所在的顶面除电极外的其它区域上具有对发光二极管芯片的出射光线波长具有反射能力的芯片反射层24，芯片反射层24能够提高该发光二极管芯片的出光效率。而激光反射层23覆盖在芯片反射层24上。在芯片反射层24上形成激光反射层23，可以在制程中芯片反射层24和激光反射层23共用一套掩模，达到节约成本以及缩减制程时间的目的。
实施例5
参考图5，本实施例与实施例1区别的是，LED晶圆经切割得到的发光二极管芯 片为正装结构的发光二极管芯片，即该发光二极管芯片的光线是从电极侧出射的。
该发光二极管芯片的侧壁区域上具有对发光二极管芯片的出射光线波长具有反射能力的芯片反射层24，芯片反射层24能够提高该发光二极管芯片的出光效率。而激光反射层23覆盖在芯片反射层24上。在芯片反射层24上形成激光反射层23，可以在制程中芯片反射层24和激光反射层23共用一套掩模，达到节约成本以及缩减制程时间的目的。
实施例6
本实施例与实施例1区别的是，激光反射层23不仅对激光波长具有反射能力而且对发光二极管芯片的出射光线波长也具有反射能力，从而使得该激光反射层23还兼具了实施例4、实施例5中芯片反射层的功能，但该激光反射层23可通过一次制程工艺完成。
在本实施例中，激光反射层23优选为布拉格反射层，该布拉格反射层由第一物质层和第二物质层交替层叠设置而成，且第一物质层与第二物质层的厚度为随层数的不同而不同。其中，第一物质层与第二物质层可以由SiO 2、TiO 2、HfO 2，ZnO 2，ZrO 2，Cu 2O 3等材料中的其中两种制成。具体的，该激光反射层23的对数为n，各物质层的厚度可以根据下面进行设置：第一对的第一物质层的厚度为D1，第二对和第三对的第一物质层的厚度为(75％～90％)*D1，第四对至第n/2对的第一物质层的各层厚度为(30％～50％)*D1，第n/2+1对至第n对的第一物质层的各层厚度为(20％～30％)*D1，第一对的第二物质层的厚度为D2，第二对和第三对的第二物质层的厚度为(75％～90％)*D2，第四对至第n/2对的第一物质层的各层厚度为(30％～50％)*D11，第n/2+1对至第n对的第一物质层的各层厚度为(20％～30％)*D2，其中n≥8。通过如此设计，可以使得激光反射层23可以同时高反射用于衬底切割的激光束及LED芯片出射的光线。
在本实施例中，以该布拉格反射层中的第一物质层与第二物质层分别由SiO 2和TiO 2制成为例来进行说明，该布拉格反射层共有24层(12对)，各层的材料以及厚度参考下表：
Figure PCTCN2020088747-appb-000001
该布拉格反射层对各波段波长的反射率的关系图如图6所示，从图6中可以看出，该布拉格反射层对440～590nm、900～1100nm左右的波长都具有良好的反射率(大于90％)，因此该布拉格反射层对发光二极管芯片的出射光线(蓝光、绿光)以及激光波长都具有良好的反射率，同时兼具对激光波长以及发光二极管芯片的出射光线波长的反射能力。虽然本实施例中以第一物质层与第二物质层随层数的增加而减小为例来进行说明，但并不仅限定于此，第一物质层和第二物质层的厚度也可随层数增加而增加；或者第一物质层和第二物质层的厚度随层数随机变化。
尽管结合优选实施方案具体展示和介绍了本发明，但所属领域的技术人员应该明白，在不脱离所附权利要求书所限定的本发明的精神和范围内，在形式上和细节上可以对本发明做出各种变化，均为本发明的保护范围。

Claims (22)

  1. 一种发光二极管芯片的制作方法，其特征在于，包括以下工艺步骤：
    (1)提供LED晶圆以及激光器，该LED晶圆包括衬底以及位于衬底上的多个LED单元，相邻两LED单元之间具有一切割道；
    (2)在LED单元的外表面上形成对激光器的激光波长具有反射能力的激光反射层，该激光反射层至少将LED单元位于切割道边缘的侧壁区域覆盖住；
    (3)沿切割道进行激光正切或者激光束从LED单元侧入射进行激光隐切，得到发光二极管芯片。
  2. 根据权利要求1所述的制作方法，其特征在于：所述激光反射层对激光器的激光波长反射率为80％以上。
  3. 根据权利要求1所述的制作方法，其特征在于：所述激光反射层包含针对激光器的激光波长设计的布拉格反射层、光子晶体反射层或者布拉格反射层和光子晶体反射层两者混和的反射层结构。
  4. 根据权利要求1所述的制作方法，其特征在于：所述激光反射层采用电子束蒸镀或者离子束溅射技术形成于LED单元的外表面上。
  5. 根据权利要求1所述的制作方法，其特征在于：所述激光反射层还将LED单元背离衬底一侧的顶面边沿区域覆盖住。
  6. 根据权利要求1所述的制作方法，其特征在于：所述LED单元的外表面上具有对该LED单元出射光线波长具有反射能力的芯片反射层，所述激光反射层形成于芯片反射层上。
  7. 根据权利要求1所述的制作方法，其特征在于：所述激光反射层对LED单元出射的光线波长具有反射能力。
  8. 根据权利要求7所述的制作方法，其特征在于：所述激光反射层包含布拉格反射层，该布拉格反射层由第一物质层和第二物质层交替层叠设置而成。
  9. 根据权利要求8所述的制作方法，其特征在于：所述第一物质层和 第二物质层的厚度均随层数增加而减小。
  10. 根据权利要求8所述的制作方法，其特征在于：所述第一物质层和第二物质层的厚度均随层数增加而增加。
  11. 根据权利要求8所述的制作方法，其特征在于：所述第一物质层和第二物质层的厚度随层数随机变化。
  12. 根据权利要求8所述的制作方法，其特征在于：所述布拉格反射层的层数大于3层且小于61层。
  13. 一种发光二极管芯片，其特征在于，包括：衬底及位于该衬底之上的外延结构，所述外延结构的侧表面上设置有激光反射层，该激光反射层对一用于衬底切割的激光束具有反射能力。
  14. 根据权利要求13所述的发光二极管芯片，其特征在于：所述激光反射层对该激光束的反射率为80％以上。
  15. 根据权利要求13所述的发光二极管芯片，其特征在于：所述用于衬底切割的激光束的波长为1064±100nm。
  16. 根据权利要求13所述的发光二极管芯片，其特征在于：所述激光反射层为针对所述激光束设计的布拉格反射层、光子晶体反射层或者布拉格反射层和光子晶体反射层两者混和的反射层结构。
  17. 根据权利要求13所述的发光二极管芯片，其特征在于：所述激光反射层还覆盖所述外延结构背离衬底一侧的顶面边沿区域。
  18. 根据权利要求13所述的发光二极管芯片，其特征在于：所述外延结构的外表面上设置有芯片反射层，该芯片反射层对该LED芯片出射的光线具有反射能力，所述激光反射层形成于芯片反射层上。
  19. 根据权利要求13所述的发光二极管芯片，其特征在于：所述激光反射层对外延结构出射光线波长具有反射能力。
  20. 根据权利要求19所述的发光二极管芯片，其特征在于：所述激光反射层包含布拉格反射层，该布拉格反射层由第一物质层和第二物质层交替层叠设置而成。
  21. 根据权利要求20所述的发光二极管芯片，其特征在于：所述第一物质层和第二物质层的厚度均随层数增加而减小。
  22. 根据权利要求21所述的发光二极管芯片，其特征在于：所述第一物质层和第二物质层的厚度均随层数增加而增加。
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CN109671822A (zh) * 2019-01-10 2019-04-23 佛山市国星半导体技术有限公司 一种防激光切割损伤的led晶圆及其制作方法、切割方法
CN110299472A (zh) * 2019-06-28 2019-10-01 京东方科技集团股份有限公司 一种阵列基板、显示面板及显示装置

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