【作者】 金曦；

【导师】 刘劲松； 朱大庆；

【作者基本信息】 华中科技大学 ， 物理电子学， 2009， 博士

【摘要】 随着多媒体业务和高端计算机等技术的发展,人们对数据处理速率的需求日益增加。传统电互连在高速传输时面临高传输损耗、EMI和信号完整性差等缺点,光互连技术能够很好的解决高速互连发展的瓶颈。为了与成熟的PCB技术兼容,通常采用将光波导嵌入PCB中实现互连,其中聚合物光波导材料及其制作工艺成为关系到该技术实现并投入实用的重要因素之一。本文主要研究了氟化聚酰亚胺的合成、光学性能及其光波导的制作工艺。聚合物光波导材料具有明显的综合性能优势,加工简单,成本低廉,光学损耗低,易实现功能化。其中,氟化聚酰亚胺的热稳定性高,而且通过调节含氟量可实现折射率的精确可调,在光波导器件上得到广泛应用。鉴于氟化聚酰亚胺薄膜的性能受合成和制备等工艺条件的影响,本文采用“两步法”合成6FDA/ODA氟化聚酰亚胺及其共聚物,优化了其合成工艺,测试其热稳定性能,并利用Metricon2010棱镜耦合薄膜测试系统和FT-IR光谱仪,重点研究了热亚胺化及后续热处理过程中,聚酰胺酸-聚酰亚胺薄膜的折射率、双折射、热光系数、传输损耗等光学性能随热处理温度的变化,发现薄膜的折射率、双折射、红外吸收强度、光学损耗随最高热处理温度的升高出现极值,从IR光谱结果推测其原因在于热处理过程中导致其分子结构和聚集态发生了改变,由此确定氟化聚酰亚胺的最优热处理条件。氟化聚酰亚胺光波导的直写工艺是本文的另一重点内容。第一种方法是利用CO₂激光的热作用,通过聚酰胺酸的热亚胺化直写氟化聚酰亚胺光波导。文中首先介绍了CO₂激光直写氟化聚酰亚胺光波导的设备、工艺流程及机理,通过对直写区域进行微区红外光谱分析,发现激光作用后聚酰胺酸仅部分亚胺化,且亚胺环的特征吸收峰发生蓝移,所得聚酰亚胺表现部分结晶性。接着利用ANSYS软件分析了直写速率和激光过滤对波导宽度的影响,并从实验上研究了预处理温度、激光功率、直写速率、光阑和离焦量等工艺条件对波导形貌（波导宽度、陡直度、光滑度）的影响,优化了工艺参数,通过截断法测试光波导损耗在5.6dB/cm以上。另一种方法是利用微细笔直写聚酰亚胺光波导。文中首先介绍了直写光波导的装置、工艺流程,并实验研究了直写速率、气体压力、聚酰胺酸溶液的润湿行为等工艺条件对波导高宽比的影响,采用截断法测试波导的传输损耗,最小可达0.11dB/cm,并从环境条件、溶液粘度和热处理过程分析了损耗测试结果存在较大差异的原因。更多还原

【Abstract】 Next generation internet switches and high-end computers are expected to process aggregate data rates in the order of Tbit/s and the interconnection between the processing units will have to handle data rates in the order of 10-40Gbit/s. Based on basic physical law the copper based electrical interconections will suffer from high transmission losses, severe signal integrity, and electro magnetic interference（EMI） problems at such data rates. In order to overcome the evident high-speed interconnection bottle-neck, optical interconnects are considered the prefered option. The integration of optical waveguides in printed circuit board or backplane is considered more economical for board- or chip-interconnection. And the materials and processes of waveguides have to meet the severe requirements compatible with PCB industry.Following the development of integrated optics, the advantages of polymer waveguide materials, performances reqirements for electro-optical printed circuit board, and the methods for waveguide fabrication are reviewed. The reaction mechanisms of "two-step" synthsis of polyimide were also analyzed to find out the factors that influence the properties of final products.In order heighten the molecular weight of fluorinated polyimide, the process of synthesis were optimized through modified molecular ratio of dianhydride and diamine, the order of adding reactant, reaction temperature, solvents. And the products were characterized by IR, TGA and DSC, when the differences in molecular aggregation between the chemical imidized polyimides and thermal imidized ones.Moreover, the relationship between thermal and optical properties of fluorinated polyimides （FPI） with their repeat units were discussed based on the structure-properties relationship of polymers. Then the influences of curing temperature on the optical properties （refractive index, birefringence, optical loss and thermo-optical coefficient） of FPI were demonstrated by IR spectrum and optical measurements through Metricon 2010 prism coupler. The optical properties of FPI thin films have their extremum at 240-270℃duo to the changing aggregation structure of FPI after thermal curing. And the optimized curing process was proposed.Two kinds of waveguide process were demonstrated, including CO₂ laser direct-writing and micropen direct-writing. The heat transfer during fabricating FPI waveguide by CO₂ laser direct writing was simulated through ANSYS. Then the effects of processes such as writing speed, the power of laser, pre-curing temperature on the profiles of waveguide were investigated experimentally, and the optical loss of FPI waveguide fabricated was measured by cut-off method, which can be larger than 5.6dB/cm. Furthermore, the processes of micro-pen direct-writing FPI waveguide were implemented after well understanding the viscous flow characteristics of poly（amide acid）s solution and its wetting behaviours on SiO₂ films. And the optical loss of FPI waveguide was also measured by cut-off method, which can reach about 0.1dB/cm.更多还原