【作者】 李云飞；

【导师】 吴传贵；

【作者基本信息】 电子科技大学 ， 工程硕士（专业学位）， 2022， 硕士

【摘要】 随着信息通信以及光通信技术的飞速发展,集成光子学因其在光通信系统中发挥着关键作用而受到广泛关注。单晶铌酸锂(Lithium Niobate,LN)凭借其优异的电光特性以及非线性光学性能,无疑成为具有光明前景的光子平台。Si和LN的异质集成可以兼容Si光子平台的成熟工艺和LN优异的光学性能,为实现低成本、高质量的集成光电子器件提供了新的解决方案。本文选择以苯并环丁烯(Benzocyclobutene,BCB)作为中间层,通过实验对基于BCB的Si和LN块材的异质键合工艺进行详细的研究,并将该工艺应用于LN薄膜微环谐振器和Si衬底的异质集成,使用光学测试平台探究集成对器件性能的影响。论文中主要研究内容和实验成果如下:(1)采用聚合物键合的方式,以BCB作为中间层,通过工艺参数的调整实现了BCB键合层厚度的控制。传统的BCB键合,BCB键合层的厚度通常在微米级别,较厚的中间层厚度在集成光学器件中不利于光学耦合,会导致器件性能受到影响。为获得亚微米级别的BCB中间层厚度,本文通过使用均三甲苯(Mesitylene)对BCB进行稀释,调整旋涂转速,利用SEM等表征手段得到了厚度与稀释参数和旋涂参数的规律,实现了BCB层厚度的控制,在较高的稀释比以及旋涂转速参数下得到了150nm厚的BCB键合层。通过控制BCB中间层厚度,可针对具体的器件结构尺寸灵活地调整工艺参数,进行LN光学器件和Si的键合集成。(2)利用等离子体活化技术以及固化温度的控制保证了Si和LN键合样品的键合强度。为降低BCB中间层厚度,BCB的旋涂以及预键合过程会受到影响,从而影响键合质量,Si和LN热失配的影响也更加显著。本文利用等离子体活化技术对Si衬底表面和BCB界面层进行处理,用接触角测试表征键合表界面的润湿性能以及黏附性能,改善了高转速和稀释比参数下BCB在衬底表面的旋涂效果以及预键合效果。在此基础上,通过调整退火温度曲线,解决了热失配导致的LN碎裂问题。利用拉伸测试表征不同参数下键合样品的键合强度,并均保持在3MPa以上,验证了工艺的可靠性。(3)仿真设计并加工制备得到了LN薄膜微环谐振器,利用光学测试平台对键合前后的器件性能进行了测试分析。使用COMSOL仿真设计了20GHz的微环谐振器的结构尺寸,利用微纳加工技术制备得到LN薄膜微环谐振器。采用光学平台测试得到微环谐振器的消光比ER为6.981d B,Q值为86123.63,计算得到传输损耗为0.4150d B/cm。基于上述工艺将制备得到的LN薄膜微环谐振器与Si衬底进行了异质集成,再次通过光学平台进行测试,得到微环谐振器的Q值减小为43060.56,传输损耗变为1.3511d B/cm,但消光比ER增加至11.383d B,验证了LN光学器件基于BCB的Si基异质集成的可行性。更多还原

【Abstract】 With the rapid development of information communication and optical communication technology,integrated photonics plays a key role in optical communication system,which has attracted extensive attention.Single crystal Lithium Niobate(LN),with excellent electro-optic properties and nonlinear optical properties,has undoubtedly become a promising photonic platform.The heterogeneous integration of Si and LN is compatible with the mature process of Si photons and the excellent optical properties of LN,providing a new solution for the realization of low-cost,high-quality integrated optoelectronic devices.In this thesis,Benzocyclobutene(BCB)was selected as the intermediate layer,and the heterogeneous bonding process of BCB based Si and LN block material was explored in detail through experiments,and the process was applied to the heterogeneous integration between Si substrate and LN thin film microring resonator.The effect of device’s performance after integration was explored using the optical test platform.The main research contents and experimental results are as follows:(1)BCB was taken as the middle layer,and the thickness of BCB bonding was controlled by adjusting the process parameters.In traditional BCB bonding,the thickness of BCB bonding layer is usually in the micron level,and the thick middle layer thickness is not conducive to optical coupling in integrated optical devices,which will affect the performance of device.In order to make sure the thickness of BCB intermediate layer is at sub-micron level,BCB was diluted with Mesitylene and speed of spin coating was adjusted.SEM and other characterization methods were used to obtain the relationship between the thickness of BCB and parameters,the rule of BCB layer thickness was controlled.BCB bonding layer’s thickness of 150 nm was obtained at high dilution ratio and rotational speed.By controlling the thickness of BCB intermediate layer,the bonding of LN optical device and Si can be flexibly assembled according to the specific structure size of device.(2)Plasma activation technology and curing temperature ensured the strength of Si and LN bonded samples.In order to reduce the thickness of BCB intermediate layer,the spin coating and pre-bonding process of BCB would be affected,thus the bonding quality would be influenced,and the influence of thermal mismatch would be more significant.In this thesis,plasma activation technology was used to treat the Si substrate surface and BCB interface layer.Contact Angle measurement was used to characterize the wettability and adhesion properties of the interface of the bonding surface,and the spin-coating effect and pre-bonding effect of BCB on the substrate surface were improved under high rotational speed and dilution ratio parameters.On this basis,fragmentation of LN caused by thermal mismatch was solved by adjusting annealing temperature curve.Tensile test was used to characterize the bonding strength of bonded samples with different parameters,and the bonding strength remained above 3MPa,which verified the reliability of the process.(3)Simulation design and fabrication of LN thin film microring resonator,optical testing platform was used to test and analyze the device performance before and after bonding.The structure size of 20 GHz microring resonator was designed by COMSOL simulation.LN thin film microring resonator was prepared by micro-nano machining technology.The Extinction ratio of the microring resonator is 6.981 d B,the Q value is86123.63 and the transmission loss is 0.4150 d B/cm.Based on the above process,the heterointegration of LN thin film microring resonator and Si substrate was realized,and the test was carried out on the optical platform again.The Q value of the microring resonator was reduced to 43060.56 and the transmission loss was changed to1.3511 d B/cm,but the extinction ratio increases to 11.383 d B,which verified the feasibility of heterointegration of LN optical device with Si based on BCB.更多还原