CN103165780A - Manufacturing method of GaN-based LED chip with improved brightness - Google Patents

一种提高亮度的GaN基LED芯片的制作方法，包括如下步骤：步骤1：取一半导体衬底；步骤2：采用金属有机化学气相沉积的方法，在半导体衬底上依次生长低温GaN缓冲层、不掺杂GaN层、N-GaN层、多量子阱发光层和P-GaN层，形成GaN外延片；步骤3：在GaN外延片表面的一侧向下刻蚀，刻蚀深度到达N-GaN层，在N-GaN层的一侧形成台面；步骤4：在GaN外延片的上表面蒸镀ITO薄膜；步骤5：在P-GaN层上的ITO薄膜上光刻腐蚀出一凹槽；腐蚀掉多量子阱发光层和P-GaN层侧壁上的ITO薄膜，保留台面上的ITO薄膜；步骤6：在ITO薄膜上的凹槽内制作P电极，在台面上的ITO薄膜上制作N电极，完成制备。

A method for manufacturing a GaN-based LED chip with improved brightness, comprising the following steps: step 1: taking a semiconductor substrate; step 2: adopting a metal-organic chemical vapor deposition method to sequentially grow a low-temperature GaN buffer layer, Undoped GaN layer, N-GaN layer, multi-quantum well light-emitting layer and P-GaN layer to form a GaN epitaxial wafer; Step 3: Etching down one side of the GaN epitaxial wafer surface, and the etching depth reaches N-GaN layer, forming a mesa on one side of the N-GaN layer; Step 4: Evaporate an ITO film on the upper surface of the GaN epitaxial wafer; Step 5: Etch a groove on the ITO film on the P-GaN layer; etch Remove the ITO film on the sidewall of the multi-quantum well light-emitting layer and the P-GaN layer, and keep the ITO film on the mesa; step 6: make a P electrode in the groove on the ITO film, and make an N electrode on the ITO film on the mesa , to complete the preparation.

提高亮度的GaN基LED芯片的制作方法Manufacturing method of GaN-based LED chip with improved brightness

技术领域technical field

本发明涉及光电器件领域，具体涉及一种提高亮度的GaN基LED芯片的制作方法。The invention relates to the field of photoelectric devices, in particular to a method for manufacturing a GaN-based LED chip with improved brightness.

背景技术Background technique

发光二极管(LED)是一种能将电信号转换成光信号的结型电致发光半导体器件。GaN基LED作为固态光源一经出现便以其高效、长寿命、环保等优点广受好评，用LED作为新光源的固态照明灯，将有机会逐渐取代传统的照明灯而进入寻常百姓家。A light emitting diode (LED) is a junction electroluminescent semiconductor device that converts electrical signals into optical signals. Once GaN-based LEDs appeared as solid-state light sources, they were widely praised for their high efficiency, long life, and environmental protection. Solid-state lighting using LEDs as new light sources will have the opportunity to gradually replace traditional lighting and enter the homes of ordinary people.

一般采用蓝宝石衬底的外延片来制备高亮度的GaN基LED。如何提高GaN基LED的发光效率是一直以来的研究重点(参阅图5，图5为常规GaN基LED的结构示意图)。目前蓝光GaN基的LED内量子效率可达70％以上，大功率LED芯片的外量子效率通常只有40％左右，大功率LED芯片的光提取效率较低影响了外量子效率的提高。影响LED光提取效率的因素主要有两方面：1.由于GaN材料的折射率(n＝2.5)与空气(n＝1)和蓝宝石衬底(n＝1.75)相差较大，导致GaN有源区产生的光只有少数逃逸到材料体外。2.通常LEDP、N金属电极为CrAu，Cr和Au对光的吸收很严重，从GaN材料内部出射的部分光被P、N金属电极所吸收，无法有效提取出来。尤其是对于1023尺寸以下的小芯片，电极的面积占发光区15％以上，这部分光的损失很严重。对于前者，目前国内外采用的主要技术方案为P-GaN表面粗化技术和光子晶体技术等，可以提高大功率LED芯片的光提取效率，LED的光功率提高20％以上。对于后者，有人尝试在P电极下制作光学膜反射镜，通过反射镜膜层，将光反射回GaN材料。但光学膜反射镜需要增加溅射多层介质膜工艺，工艺复杂、成本较高。此外离子溅射对P-GaN表面有损伤，造成器件工作电压升高。Epitaxial wafers of sapphire substrates are generally used to prepare high-brightness GaN-based LEDs. How to improve the luminous efficiency of GaN-based LEDs has always been the focus of research (see FIG. 5, which is a schematic structural diagram of a conventional GaN-based LED). At present, the internal quantum efficiency of blue GaN-based LEDs can reach more than 70%, and the external quantum efficiency of high-power LED chips is usually only about 40%. The low light extraction efficiency of high-power LED chips affects the improvement of external quantum efficiency. There are two main factors affecting the light extraction efficiency of LEDs: 1. Due to the large difference between the refractive index of GaN material (n=2.5) and air (n=1) and sapphire substrate (n=1.75), the GaN active region Only a small amount of the generated light escapes outside the material. 2. Usually, the LED P and N metal electrodes are CrAu, and Cr and Au absorb light very seriously. Part of the light emitted from the inside of the GaN material is absorbed by the P and N metal electrodes and cannot be effectively extracted. Especially for small chips with a size below 1023, the area of the electrodes accounts for more than 15% of the light-emitting area, and the loss of light in this part is very serious. For the former, the main technical solutions currently adopted at home and abroad are P-GaN surface roughening technology and photonic crystal technology, etc., which can improve the light extraction efficiency of high-power LED chips, and the optical power of LEDs can be increased by more than 20%. For the latter, some people try to make an optical film mirror under the P electrode, and reflect light back to the GaN material through the mirror film layer. However, the optical film mirror needs to add a sputtering multi-layer dielectric film process, which is complicated and costly. In addition, ion sputtering will damage the surface of P-GaN, which will increase the operating voltage of the device.

发明内容Contents of the invention

本发明的目的在于，提供了一种提高亮度的GaN基LED芯片的制作方法。该方法在制备P、N电极时，同时制作了P电极金属反射镜，将从LED有源区发出的射向P电极的光大部分反射回材料内部。此外，在制作ITO透明电极时，将ITO同时作为与P-GaN和N-GaN的欧姆接触金属层，解决了由于P、N金属体系的变更，N电极与N-GaN的欧姆接触问题。本发明方法没有增加新的工艺步骤，具有工艺简单，成本低，光提取效率高等特点。经此方法制备出的LED芯片(10*23mil)亮度比原来提高4％以上，工作电压不变。The object of the present invention is to provide a method for manufacturing a GaN-based LED chip with improved brightness. In this method, when P and N electrodes are prepared, a P electrode metal reflector is produced at the same time, and most of the light emitted from the LED active area to the P electrode is reflected back to the inside of the material. In addition, when making ITO transparent electrodes, ITO is used as the ohmic contact metal layer with P-GaN and N-GaN at the same time, which solves the problem of ohmic contact between N electrodes and N-GaN due to the change of P and N metal systems. The method of the invention does not add new process steps, and has the characteristics of simple process, low cost, high light extraction efficiency and the like. The brightness of the LED chip (10*23mil) prepared by the method is increased by more than 4% compared with the original one, and the working voltage remains unchanged.

本发明提供一种提高亮度的GaN基LED芯片的制作方法，包括如下步骤：The invention provides a method for manufacturing a GaN-based LED chip with improved brightness, comprising the following steps:

步骤1：取一半导体衬底；Step 1: Take a semiconductor substrate;

步骤2：采用金属有机化学气相沉积的方法，在半导体衬底上依次生长低温GaN缓冲层、不掺杂GaN层、N-GaN层、多量子阱发光层和P-GaN层，形成GaN外延片；Step 2: Using metal-organic chemical vapor deposition, sequentially grow a low-temperature GaN buffer layer, undoped GaN layer, N-GaN layer, multi-quantum well light-emitting layer and P-GaN layer on the semiconductor substrate to form a GaN epitaxial wafer ;

步骤3：在GaN外延片表面的一侧向下刻蚀，刻蚀深度到达N-GaN层，在N-GaN层的一侧形成台面；Step 3: Etching downward on one side of the surface of the GaN epitaxial wafer, the etching depth reaches the N-GaN layer, and forming a mesa on one side of the N-GaN layer;

步骤4：在GaN外延片的上表面蒸镀ITO薄膜；Step 4: Evaporating an ITO film on the upper surface of the GaN epitaxial wafer;

步骤5：在P-GaN层上的ITO薄膜上光刻腐蚀出一凹槽；腐蚀掉多量子阱发光层和P-GaN层侧壁上的ITO薄膜，保留台面上的ITO薄膜；Step 5: etching a groove on the ITO thin film on the P-GaN layer; etching away the ITO thin film on the sidewall of the multi-quantum well light-emitting layer and the P-GaN layer, and retaining the ITO thin film on the mesa;

步骤6：在ITO薄膜上的凹槽内制作P电极，在台面上的ITO薄膜上制作N电极，完成制备。Step 6: Make a P electrode in the groove on the ITO film, make an N electrode on the ITO film on the table, and complete the preparation.

附图说明Description of drawings

为进一步说明本发明的具体技术内容，以下结合实施例和附图详细说明如后，其中：In order to further illustrate the specific technical content of the present invention, below in conjunction with embodiment and accompanying drawing detailed description as follows, wherein:

图1是本发明的制备流程图；Fig. 1 is a preparation flow chart of the present invention;

图2是本发明GaN基LED的结构的示意图；Fig. 2 is the schematic diagram of the structure of GaN-based LED of the present invention;

图3是常规工艺和本发明工艺的I-V曲线对比图；Fig. 3 is the I-V curve contrast figure of conventional technology and technology of the present invention;

图4是常规工艺和本发明工艺的P-I曲线对比图；Fig. 4 is the P-I curve contrast figure of conventional technology and technology of the present invention;

图5是常规GaN基LED的结构示意图。Fig. 5 is a schematic structural diagram of a conventional GaN-based LED.

具体实施方式Detailed ways

请参阅图1和图2所示，本发明提供一种提高亮度的GaN基LED芯片的制作方法，包括如下步骤：Please refer to Fig. 1 and Fig. 2, the present invention provides a method for manufacturing a GaN-based LED chip with improved brightness, comprising the following steps:

步骤1：取一半导体衬底1，所述半导体衬底1的材料为蓝宝石、硅、碳化硅或金属；Step 1: Take a semiconductor substrate 1, the material of the semiconductor substrate 1 is sapphire, silicon, silicon carbide or metal;

步骤2：采用金属有机化学气相沉积(MOCVD)的方法，在半导体衬底1上依次生长低温GaN缓冲层2(厚度为1μm)、不掺杂GaN层3(厚度为1μm)、N-GaN层4(厚度为3μm)、多量子阱发光层5(厚度为150nm)和mP-GaN层6(厚度为300n)，形成GaN外延片，其中所述半导体衬底1为蓝宝石、硅、碳化硅或金属；Step 2: Using metal-organic chemical vapor deposition (MOCVD), sequentially grow a low-temperature GaN buffer layer 2 (with a thickness of 1 μm), an undoped GaN layer 3 (with a thickness of 1 μm), and an N-GaN layer on the semiconductor substrate 1 4 (thickness is 3 μm), multi-quantum well light-emitting layer 5 (thickness is 150nm) and mP-GaN layer 6 (thickness is 300n), forms GaN epitaxial wafer, wherein said semiconductor substrate 1 is sapphire, silicon, silicon carbide or Metal;

步骤3：在GaN外延片表面的一侧向下刻蚀，刻蚀深度到达N-GaN层4，在N-GaN层4的一侧形成台面41。该台面41的刻蚀深度1500nm-2000nm。使用Cl₂、BCl₃、Ar₂作为刻蚀气体，其中Cl₂的流量为30-100sccm，BCl3流量为10-20sccm，Ar₂的流量为15-25sccm；刻蚀功率为400-700W；射频功率为100-200W；刻蚀时间为10-15min；Step 3: Etching downward on one side of the surface of the GaN epitaxial wafer, the etching depth reaches the N-GaN layer 4 , and forming a mesa 41 on one side of the N-GaN layer 4 . The etching depth of the mesa 41 is 1500nm-2000nm. Use Cl ₂ , BCl ₃ , Ar ₂ as etching gas, wherein the flow rate of Cl ₂ is 30-100 sccm, the flow rate of BCl3 is 10-20 sccm, and the flow rate of Ar ₂ is 15-25 sccm; the etching power is 400-700W; the RF power 100-200W; etching time 10-15min;

步骤4：在GaN外延片的上表面蒸镀ITO薄膜7；厚度为

Step 4: Evaporate an ITO thin film 7 on the upper surface of the GaN epitaxial wafer; the thickness is

步骤5：选用AZ6130光刻胶和小王水(3HCl:HNO₃)光刻腐蚀出ITO图形，在P-GaN层6上的ITO薄膜7上光刻腐蚀出一凹槽71；腐蚀掉多量子阱发光层5和P-GaN层6侧壁上的ITO薄膜7，保留台面41上的ITO薄膜7。ITO透明电极不仅与P-GaN形成良好的欧姆接触，还可与N-GaN形成良好的欧姆接触，降低接触电压，从而降低器件的工作电压。Step 5: Select AZ6130 photoresist and aqua regia (3HCl:HNO ₃ ) to etch out the ITO pattern by photolithography, etch a groove 71 on the ITO film 7 on the P-GaN layer 6; etch away the multi-quantum The ITO thin film 7 on the side walls of the light-emitting layer 5 and the P-GaN layer 6 in the well, and the ITO thin film 7 on the mesa 41 remain. The ITO transparent electrode not only forms a good ohmic contact with P-GaN, but also forms a good ohmic contact with N-GaN, reducing the contact voltage, thereby reducing the operating voltage of the device.

步骤6：在ITO薄膜7上的凹槽71内制作P电极8，在台面41上的ITO薄膜7上制作N电极9。其中P电极8和N电极9的材料为Al/Pt/Au、Ag/Pt/Au、Ni/Ag/Pt/Au、Ti/Ag/Pt/Au、Ni/Al/Pt/Au或Ti/Al/Pt/Au。其中P电极8和N电极9中的最下面一层的的材料为Al或Ag时，其厚度为

当最下面一层的的材料为Ni或Ti时，其厚度为

Al和Ag是金属反射镜，可以将从有源区发出的射向P电极的光大部分反射回材料内部，再经其它路径发射出来。如果需要进一步增加AL或Ag与P-GaN之间的粘附性，可以在AL或Ag的下面蒸镀薄层金属Ni或Ti作为粘附层，薄层的Ni或Ti对光的吸收很小，可以保证大部分光透过此薄层被金属Al或Ag反射回材料内部。Step 6: making a P electrode 8 in the groove 71 on the ITO film 7 , and making an N electrode 9 on the ITO film 7 on the mesa 41 . Wherein the material of P electrode 8 and N electrode 9 is Al/Pt/Au, Ag/Pt/Au, Ni/Ag/Pt/Au, Ti/Ag/Pt/Au, Ni/Al/Pt/Au or Ti/Al /Pt/Au. Wherein when the material of the bottom layer in the P electrode 8 and the N electrode 9 is Al or Ag, its thickness is

When the material of the bottom layer is Ni or Ti, its thickness is

Al and Ag are metal mirrors, which can reflect most of the light emitted from the active area to the P electrode back to the inside of the material, and then emit it through other paths. If it is necessary to further increase the adhesion between AL or Ag and P-GaN, a thin layer of metal Ni or Ti can be evaporated under AL or Ag as an adhesion layer, and the thin layer of Ni or Ti has little light absorption , it can ensure that most of the light passes through this thin layer and is reflected back to the interior of the material by the metal Al or Ag.

步骤7：将片子的蓝宝石衬底减薄至150um，划裂成单独芯片，进行器件的I-V特性测试和P-I特性测试。Step 7: Thin the sapphire substrate of the chip to 150um, split it into individual chips, and conduct the I-V characteristic test and P-I characteristic test of the device.

请参阅图3，图3给出了本发明工艺和原工艺制作的LED器件的电流-电压特性对比图。从图3可知，本发明工艺的LED器件的工作电压与原工艺相差无几。Please refer to FIG. 3 . FIG. 3 shows a comparison chart of current-voltage characteristics of LED devices manufactured by the process of the present invention and the original process. It can be seen from FIG. 3 that the operating voltage of the LED device of the inventive process is almost the same as that of the original process.

请参阅图4，图4给出了本发明工艺和原工艺制作的LED器件的光功率-电流特性对比图。从图4可知，本发明工艺的LED器件的光功率比原工艺增加4％(20mA)。Please refer to FIG. 4 . FIG. 4 shows a comparison chart of optical power-current characteristics of LED devices manufactured by the process of the present invention and the original process. It can be seen from FIG. 4 that the optical power of the LED device of the inventive process is increased by 4% (20mA) compared with the original process.

以上所述，仅是本发明的实施例而已，并非对本发明作任何形式上的的限制，凡是依据本发明技术实质对以上实施例所作的任何简单修改、等同变化与修饰，均仍属于本发明技术方案范围之内，因此本发明的保护范围当以权利要求书为准。The above description is only an embodiment of the present invention, and does not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still belong to the present invention. Within the scope of the technical solution, the protection scope of the present invention should be determined by the claims.