【作者】 尉伟；

【导师】 裴元吉；

【作者基本信息】 中国科学技术大学 ， 核技术及应用， 2007， 博士

【摘要】 光谐振腔内的光的不断循环，使得在谐振腔频率附近的光能量的储存成为可能，光学微谐振腔的场的作用和反作用之间的相互作用可以成为一些基础研究领域的关键，例如腔量子电动力学实验，自发发射控制，非线性光学，生物化学探测以及量子信息处理。以回音壁模式工作的高性能光学微腔（包括微柱、微盘以及微球体）以其所具有的超高品质系数，小模式体积，以及相对简单的制作过程，使得它们成为FP型微腔以外的最有前途的腔量子电动力学研究手段。基于腔量子电动力学的量子运算的实现，是一种非常有前途及希望实现的量子计算方式，而构成量子计算机的基础是量子门，运用高性能微腔可实现量子门。本文主要对采用光刻以及干法刻蚀进行微盘谐振腔制作工艺进行研究，并给出得到了通过光刻、反应离子束刻蚀、XeF₂刻蚀得到高Q值光微谐振腔的研制结果。论文主要工作和创新之处包括：1)在国内首先通过光刻方法以及干法刻蚀方法得到高Q值微盘谐振腔，微盘腔的Q值达到约1×10⁵。光刻法制作微盘谐振腔的制作步骤为：光刻，包括基片处理，甩胶，曝光，显影以及光刻胶的处理等；对二氧化硅层的刻蚀，以形成微谐振腔图形；对二氧化硅层下硅层的选择性刻蚀，形成微谐振腔支撑。采用光刻工艺方法制作高Q值微盘腔，不但可以避免滴状和球体状的一些不良特性，同时制作工艺保证了高Q值微盘腔制作的几何尺寸可控性以及制作的重复性，作为随后在量子信息和量子逻辑器件方面的实验研究工作的技术基础。2)对制作过程中光刻工艺进行了实验研究。基片处理、涂胶、光刻胶的前烘和后烘、曝光参数、显影参数等许多方面都影响着作为随后刻蚀工艺掩模的光刻胶浮雕图形质量，并最终影响微谐振腔的性能。通过实验，我们的到了适宜的光刻工艺参数。3)制作SiO₂微盘谐振腔腔体的研究。使用CHF₃与Ar的混合气体反应离子束刻蚀RIBE进行SiO₂盘成型是可行的，反应气体CHF₃的引入，可提高光刻胶掩模与SiO₂的选择比，并通过调整离子能量、束流密度以及入射角度，得到较快的SiO₂刻蚀速率以及一定范围内可控的侧壁陡直度，可用于制作符合要求的SiO₂微盘谐振腔图形。在微谐振腔制作实验中使用2∶1的CHF₃／Ar混合气体作为工作气体的RIBE制作的SiO₂微谐振腔，得到了边缘清晰、光滑，具有近似垂直侧壁的SiO₂微谐振腔腔体。实验证明，此种刻蚀方法制作SiO₂微谐振腔腔体具有精度高和易于进行刻蚀控制的优点，对保证微谐振腔的几何特征和物理特性是有利的。在国际上首次通过RIBE得到具有垂直侧壁的SiO₂微谐振腔。4)对采用适宜的Si刻蚀方法得到SiO₂微盘谐振腔支撑进行实验研究。XeF₂对Si进行的刻蚀是一种各向同性的刻蚀，各方向的刻蚀速率与晶向或者硅掺杂物无关，而且此反应不需要进行气体电离，在室温下即可进行，使用的刻蚀系统结构简单，刻蚀条件易于控制。刻蚀后的硅表面粗糙度与刻蚀时的XeF₂气体压强有直接的关系。针对这种刻蚀，我们研制了一种简单的刻蚀系统，并成功地以光刻胶和SiO₂作为掩模层，实现了硅的深度刻蚀和侧面掏空的刻蚀，其刻蚀选择比大于1000∶1；在XeF₂对硅所进行的刻蚀过程中，不会对已经成型的SiO₂微腔造成明显的几何形状影响，以此保证其物理特性；此刻蚀手段应用于微盘谐振腔制造过程中，得到了“蘑菇状”的SiO₂／Si结构的微盘谐振腔，为后续的微腔激光和量子信息逻辑器件的研制奠定了基础。更多还原

【Abstract】 Re-circulation of light within optical microresonators’ volumes enables the storage of optical power near specific resonant frequencies, The interaction of active or reactive material with the modal fields of optical microresonators provides key physical models for basic research such as cavity quantum electrodynamics （QED） experiments, spontaneous emission control, nonlinear optics, bio chemical sensing and quantum information processing. Optical high quality optical microresonators which work in the form of whispering gallery mode （WGM）, such as microcylinders, microdisks, and microspheres have been achieved. The combination of their ultrahigh quality factor, very small mode volume, and relatively easy fabrication process, makes them potential means for cavity QED experiments. The proposal based on cavity quantum electrodynamics （QED） is one of the most potential ones to realize quantum gates, which are the most pivotal devices in the experimental schemes to realize quantum computation and quantum computer. In this paper, we research the technics to fabricate microdisk optical resonators with photolithography and etching, and the high Q（about 1×10⁵） microdisk optical resonators have been achieved with standard UV photolithography, reactive ion beam etching（RIBE）, and silicon etching with XeF₂. The most significant advance of the work described in this thesis is as follow.1) The silica microdisk optical resonator which exhibit whispering-gallery-type modes with quality factors （Q） 1×10⁵ have been fabricated firstly with standard photolithographic techniques and dry etching in China. The following fabrication steps have been adopted: silicon wafers coated with certain thickness silicon dioxide （SiO₂） are painted with photoresistant （PR）; mask graphics is transferred to PR over silica with standard photolithograph; PR graphics is transferred to silica layer with ion beam etching （IBE）; silicon under the silica disk is etched with isotropic silicon etching to form mushroom like microresonators. The microdisk optical resonators are free form negative character of microsphere cavity, fabrication process with standard photolithography and dry etching can achieve geometry control and the repeatable fabrication of high Q microdisk cavity; the repeatable and controllable microresonators fabrication process can provide the favorable prophase technical fundament of development of quantum gates.2) The research of photolithography technics in this fabrication process. The wafer cleaning, photoresist painting, pre-bake and latter-bake of PR, exposal, developing all can affect the PR figures, which are the masks of latter etching and define the microresonators’ capability. These technics parameters have been optimized with experiments.3) Research of fabrication of the SiO₂ microresonators. The reactive ion beam etching with Ar/CHF₃ mixed work gas has been used to form the SiO₂ microdisks,, the PR to SiO₂ etching selectivity has been improved with the addition of CHF₃, and the controllable sidewall angle can been achieved with suitable ion energy, gas composition and incident angle. In the fabrication process of microdisk resonators, the SiO₂ microdisk cavity has been achieved with RIBE with 2:1 CHF₃/Ar mixture with smooth edge and vertical sidewall. This etching method has favorable transfer precision and controllability, which is important to keep microcavity’s geometrical and physical character. The SiO₂ microdisk resonators with vertical sidewall have been achieved with RIBE in the world. 4) Research of the silicon etching. This silicon etching is used to fabricate the silicon pillar under the SiO₂ microdisk, which support the microresonators. XeF₂ can react with silicon in room temperature and be used as silicon dry etching gas, it is a kind of isotropic dry etching. A XeF₂ pulse etching system with simple structure and easy operating has been constructed to perform SiO₂/Si etching. With this system, the mushroom-like SiO₂/Si structure has been fabricated, and the etching selectivity between silicon and silica mask exceed 1000. SiO₂ microdisk resonators have been fabricated by this etching, which are the fundament of the future quantum computation research.更多还原