Micro-LED芯片制备及其基于铟焊料的倒装焊技术研究

FABRICATION OF MICRO-LED CHIP AND STUDY ON ITS FLIP-CHIP BONDING TECHNOLOGY BASED ON INDIUM SOLDER

王浩

11930594

硕士

材料工程

邱成峰

2021-05-20

2021-06-07

南方科技大学

深圳

基于第三代半导体材料GaN制作的Micro-LED是一种自发光显示器件，具有结构简单、亮度高、解析力强、能耗低、响应速度快、寿命长和稳定性好等特点，相较于LCD和OLED拥有明显的技术优势，被誉为完美的下一代显示技术。Micro-LED可用于高像素密度平板显示、柔性屏、医学光疗和可见光通信等领域，拥有广阔的应用前景和重要的研究价值。相较于水平结构和垂直结构，倒装结构的Micro-LED不仅热阻小、电极不占出光面积、光利用率高，而且能够实现超高密度集成。而倒装焊技术是实现倒装结构Micro-LED芯片与驱动基板互相连接的重要技术手段。本论文采用熔点低，质地软，能实现不同膨胀系数材料之间较好的非匹配性连接的金属铟作为焊接材料。针对提高Micro-LED芯片和驱动基板之间倒装焊接的有效性和可靠性，本文做了一些列研究内容。包括：对Micro-LED芯片的制备工艺进行了一定的优化，将金属电极的槽型结构改进为凸起结构，凸起结构有效解决了铟回流过程中铟球偏移和液态铟渗透至金属-钝化层界面的问题；优化了Micro-LED芯片的回流焊工艺流程，通过在回流前进行稀盐酸浸泡预处理和回流中营造通甲酸的还原性气体环境，有效降低了氧化层对铟回流的影响，并在合适的温度曲线下，得到了形状统一、无偏移的铟焊料回流缩球效果；优化了Micro-LED芯片的倒装焊工艺，根据芯片像素点的个数和取一定的铟球压缩范围，结合使用光学显微镜和扫描电子显微镜观测铟球焊接形貌的手段，得到了适用于不同像素间距和尺寸的Micro-LED芯片倒装焊参数即温度、键合压力和键合时间的范围；选择将Micro-LED芯片和图案化金属引线基板进行倒装的显示方案，实现了Micro-LED芯片特定图案的发光显示，又通过归类倒装芯片的显示效果和测定相应的I-V曲线，分析了Micro-LED倒装芯片可能的失效原因，为前述工艺的进一步优化提供实践依据。

Micro-LED based on the third generation semiconductor material GaN is a kind of self-luminous display device, which has the characteristics of simple structure, high brightness, high resolution, low energy consumption, fast response, long life and good stability. Compared with LCD and OLED, it has obvious technical advantages and is known as the perfect next generation display technology. Micro-LED can be used in high pixel density flat panel display, flexible screen, medical phototherapy, visible light communication and other fields, and has broad application prospects and important research value. Compared with the horizontal structure and vertical structure, flip-chip structure Micro-LED not only has small thermal resistance, no light area occupied by the electrode, high light utilization, but also can achieve ultra-high density integration. Flip-chip bonding is an important technology to realize the interconnection between flip-chip structure Micro-LED chips and driving substrates.In this paper, Indium is used as the bonding material, which has low melting point, soft texture and can achieve better unmatched connection between different thermal expansion coefficient materials. In order to improve the effectiveness and reliability of flip-chip bonding between Micro-LED chips and driver substrates, this paper has done a series of research work: We have Optimized the fabrication process of Micro-LED chips. The groove structure of metal electrode was improved to convex structure which effectively solved the problems of indium ball deviation and liquid indium penetrating into the metal-passivation interface in the process of indium reflow; We have Optimized the reflow process. The bad effect of In2O3 on indium reflow was effectively reduced by soaking the chip in dilute hydrochloric acid before reflow and creating reducing gas environment with formic acid during reflow. Under the appropriate temperature curve, the reflow shrinkage effect with uniform shape and no indium ball deviation was obtained; We have Optimized the flip-chip bonding process of Micro-LED chips. According to the number of pixels in the chip and a certain range of indium ball compression, and combining the bonding quality of indium ball observed by microscope or SEM after flip-chip bonding experiment, the bonding parameters, such as temperature, bonding pressure and bonding time, were obtained for different chips. Finally we chose the display scheme that bonding the Micro-LED chips and patterned metal lead substrates together, and realized the display of specific pattern in Micro-LED chips. By classifying the display effect and measuring the I-V curve, the possible failure causes of the Micro-LED flip chips were analyzed, which could provide a practical basis for the further optimization of the above process.

Micro-LED 铟焊料 电极结构 回流焊 倒装焊

Micro-LED indium solder electrode structure reflow flip-chip bonding

中文

独立培养

南方科技大学

王浩. Micro-LED芯片制备及其基于铟焊料的倒装焊技术研究[D]. 深圳. 南方科技大学,2021.