KrF激光辐照SOI热效应及在纳米光波导光整加工中的应用

发布时间：2017-12-28 10:33

本文关键词：KrF激光辐照SOI热效应及在纳米光波导光整加工中的应用　出处：《中北大学》2017年硕士论文　论文类型：学位论文

【摘要】：绝缘体上硅(Silicon-on-insulator,SOI)材料因在微电子、光电子领域表现出的无与伦比的优势而成为微光机电系统的重要材料之一,其在光通信、光互联计算、数字图像处理以及军事领域具有广阔应用前景。其中,基于SOI材料的纳米光波导利用Si波导层与SiO2限制层大折射率差的优势,具备了较强的局域光场能力,有望成为光量子通信的基本导波元件。目前,实现基于SOI材料器件的批量生产和低成本是先进制造追求的目标。紫外激光对微结构的加工不仅具有高精度、可实现柔性生产等优势,在SOI基光电子器件加工中因具有光斑尺寸小、吸收系数大、加工无需掩膜等优点而获得了广泛应用。特别地,采用紫外激光表面熔凝技术降低纳米光波导侧壁粗糙度,制造超低损耗纳米光波导成为光通信、生化传感、高灵敏探测等诸多领域发展的关键。本文基于激光与物质相互作用基本机理和传热学理论,研究了KrF准分子激光辐照SOI材料的熔融损伤阈值、汽化损伤阈值和温度场分布规律,探讨了KrF准分子激光辐照SOI材料热影响区域较小的特点和在微加工领域的应用,同时对SOI材料的自加热效应进行了分析;在此基础上将KrF准分子激光应用于SOI纳米光波导粗糙侧壁的光整加工,并进行了理论分析和有限元数值模拟,在获得温度场分布规律的基础上,通过控制激光的工艺参数,对波导熔池形貌进行了精确控制,结合波导粗糙侧壁光整加工的相关知识,提出了新的工艺流程,优化了工艺参数。为明确KrF准分子激光辐照下SOI材料温度场演化规律,考虑材料相变潜热和较大范围温度变化对材料参数的影响,在分析激光能量的时间、空间分布的基础上,建立了激光辐照下SOI材料的热响应模型;在不同能量密度激光作用下,得到SOI材料的熔融和汽化损伤阈值分别为0.362 J/cm2、1.285 J/cm2;材料温度的径向分布表明,纳秒激光辐照下的高温区域只存在于激光光斑一定范围内,远离辐照区域温度下降较快;轴向温度分布表明,热量多沉积在表面Si层而SiO2层温度较低,这主要是由SiO2的热导率远远小于表面单晶硅热导率导致的。针对SOI纳米光波导侧壁较大的表面粗糙度引起的光传输散射损耗过大的问题,利用有限元数值模拟了KrF准分子激光对波导侧壁的熔凝光整加工温度场,研究了波导侧壁熔池温度场的演化规律,优化了工艺参数。结果表明,熔池形成于波导上表面与迎光侧壁夹角处;激光入射角度一定时,熔池熔深与平均能量密度正相关;熔池形貌受控于激光入射角度:随着入射角度的减小,熔池形貌由单边U形过渡为单边V形最终呈带钝角单边V形。分析表明,较大激光入射角对应的熔池形貌更有利于波导侧壁的光整加工;据此提出先确定激光入射角度以优化熔池形貌,再选取合适平均能量密度以获得足够熔化深度的工艺方法。本文的研究结果可为紫外激光加工SOI基光电子器件和SOI材料的激光损伤效应提供理论依据,也有助于促进KrF准分子激光在SOI纳米光波导粗糙侧壁光滑化中的进一步发展和应用。
[Abstract]:Silicon on insulator (Silicon-on-insulator, SOI) materials because of performance in the field of microelectronics and Optoelectronics incomparable advantages and become one of the important materials in the micro electromechanical system, optical communication, optical interconnect computing, digital image processing and military fields has a broad application prospect. Among them, the nano waveguide based on SOI material has strong local optical field capability, which takes advantage of the large refractive index difference between the Si waveguide layer and the SiO2 limiting layer, and is expected to become the basic guided wave element in the optical quantum communication. At present, the realization of mass production and low cost based on SOI material devices is the goal of advanced manufacturing. UV laser processing of microstructures not only has the advantages of high accuracy and flexible production, but also has wide applications in the processing of SOI based optoelectronic devices due to its advantages of small spot size, large absorption coefficient and no mask processing. Especially, ultraviolet laser surface melting technology has been applied to reduce the roughness of nano optical waveguide sidewall, and the fabrication of ultra-low loss nanoscale optical waveguides has become the key to the development of optical communication, biochemical sensing, high sensitive detection and many other fields. In this paper, the basic mechanism of interaction between laser and material and heat transfer theory based on the melting damage threshold and damage threshold of vaporization and temperature distribution of KrF excimer laser irradiation of SOI materials, discusses the characteristics of the small area of KrF excimer laser irradiation SOI thermal effects and applications in the field of micro machining, the material from SOI the heating effect is analyzed; on the basis of KrF excimer laser used in the finishing of SOI nano optical waveguide sidewall roughness, and carried out theoretical analysis and FEM simulation, based on the temperature field distribution, by controlling the technical parameters of the laser, the precise control of the waveguide pool morphology combined with knowledge of the rough side wall waveguide finishing, puts forward a new process flow, process parameters have been optimized. Clear KrF excimer laser irradiation temperature field of SOI material evolution, considering the effect of material latent heat and a wide range of temperature on material parameters, based on the analysis of the spatial distribution of the laser energy, the time, established a model of thermal response of SOI materials under laser irradiation; under different laser energy density, obtained SOI material of melting and vaporization damage threshold were 0.362 J/cm2, 1.285 J/cm2; the radial distribution of temperature shows that the high temperature region under nanosecond laser irradiation of the laser spot exists only in a certain range, away from the irradiated area temperature decreased rapidly; the axial temperature distribution showed that more heat deposited on the surface of Si layer and SiO2 layer at low temperature this is far less than the surface, silicon thermal conductivity caused by SiO2 thermal conductivity. For SOI nano optical waveguide surface of the larger side wall roughness light scattering loss caused by the transmission of big problems, using the finite element numerical simulation of KrF excimer laser melting on the waveguide side wall of the finishing temperature, to study the evolution of temperature field in molten pool side wall waveguide, optimization of process parameters. The results show that the weld pool is formed on the upper surface of the waveguide side wall facing the light angle; laser incident angle is fixed, weld pool penetration is positively correlated with the average energy density; the weld shape is controlled by the laser incident angle, with the decrease of the angle, the weld shape by unilateral U shape unilateral V shaped end. With unilateral V obtuse angle shape. The analysis shows that the weld pool morphology corresponding to the larger laser incidence angle is more conducive to the finishing of the side wall of the waveguide. Based on this, a method for determining the laser incidence angle to optimize the pool shape and selecting the suitable average energy density to obtain enough melting depth is put forward. The research results in this paper can provide a theoretical basis for laser damage effect of SOI based optoelectronic devices and SOI materials, and further promote the further development and application of KrF excimer laser in the smooth side wall of SOI nanomaterials.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN252;TN249

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