【作者】 李小丽；

【导师】 钮晓鸣； 王庆康；

【作者基本信息】 上海交通大学 ， 微电子学与固体电子学， 2009， 博士

【摘要】 作为最有影响力的纳米结构加工技术之一,纳米压印技术因具有高分辨率、低成本、可大规模生产等优势,在国际半导体技术蓝图(ITRS)中被列为下一代32nm、22nm和16nm节点光刻技术的重要代表。自1995年华裔科学家周郁(Stephen Chou)教授在Appl. Phys. Lett.上首次提出纳米压印概念以后,引起了业界的广泛重视和研究热潮。国外半导体设备制造商、材料商以及工艺商纷纷开始涉足这一领域的研究工作,短短十多年来,已经发展了热压印、紫外压印以及微接触印刷等多种压印形式。但是,和光学曝光技术不同,纳米压印技术是一种接触式工艺,纳米尺度下的材料性能、高精度压印制程、脱膜、尺寸效应等关键问题尚在研究之中,尤其是和现有半导体工艺的兼容性尚没有妥善的解决方案。因此,纳米压印技术目前还处于实验室研究水平,国际上只有少数半导体集成电路制造领先企业在尝试进行工业化试验。本论文工作研究利用紫外纳米压印技术制作二维平面光子晶体结构及其应用。深入研究了紫外纳米压印的关键工艺过程。针对技术瓶颈,研究了大面积低成本纳米压印模板的制备技术、功能化光刻胶的制备技术以及模板表面抗粘连修饰技术。最后,以二维平面光子晶体提高半导体发光二极管(LED)光抽取效率作为应用方向,研究了平面光子晶体提高半导体照明器件光抽取效率的理论设计和工艺兼容实现。通过这些研究工作的开展,促进了我国对纳米压印技术核心知识产权的掌握,推动了纳米压印技术的工业化应用步伐。论文内容主要包括以下几个方面:首先,针对电子束光刻技术直接加工纳米压印模板存在高成本、低效率的瓶颈问题,发明了一种利用湿法刻蚀工艺将凹模转换为凸模的低成本、大面积紫外纳米压印模板的制作方法。利用该方法获得了100 nm以下的光子晶体纳米阵列结构。通过对紫外纳米压印光刻胶AMONIL进行功能改性,制备了具有光致发光特性的氧化锌量子点(ZnO QDs)复合的纳米压印光刻胶,该光刻胶增强了ZnO QDs的荧光特性,并且保持了良好的紫外纳米压印特性,拓展了纳米压印技术在LED等光电器件领域的应用。深入研究了紫外纳米压印过程中基底和模板的清洗、模板的表面修饰、光刻胶薄膜制备技术、高精度纳米压印制程控制技术以及图形衬底转移技术等关键工艺。开发出了一套气相法表面处理装置,研究了碳氟气相表面处理技术。修饰后的纳米压印模板对水的接触角由修饰前的33°提高到113°,有效的降低了纳米结构模板的表面能,解决了纳米压印过程中脱模难的问题。最终利用紫外纳米压印技术实现了对二维平面光子晶体结构的制造技术,复型精度在10 nm以内。最后结合光子晶体在提高LED光抽取效率中的实际应用,基于等效折射率理论和薄膜光学增透理论,设计了在氮化镓基蓝光LED外延片表面构建光子晶体的厚膜结构,提出了一组实验可行的光子晶体结构参数。研究了紫外纳米压印技术与LED半导体制作工艺有效集成的关键技术,成功制备出了光子晶体LED器件。经封装后初步测试结果表明,有光子晶体结构的比没有光子晶体结构的LED器件在光通量、光效率以及光辐射功率等方面最高分别提高了22.3%、36.65%、14.23%。实验测试与理论设计方案比较结果表明,高占空比(2r/a)的平面光子晶体结构有利于使局限在LED芯片内的光能量向自由空间耦合,从而提高光波的输出效率。同样的占空比条件下,不同的周期和刻蚀深度对出光效率也有影响,周期越小,刻蚀深度要求越高。这一结论为后续进一步优化理论设计方案,提高加工工艺具有指导意义。本论文的部分研究工作是和LED芯片制造商共同合作完成,器件制作部分完全通过工业流水线进行流片,封装测试均按照目前厂商统一标准执行,工艺过程与现有半导体工艺具有完全相兼容性。因此,本论文的研究工作为纳米压印技术尽早实现工业化应用,推动更小、更冷、更快的纳电子半导体产业发展具有更加现实的意义。更多还原

【Abstract】 As one of the most promising nanostructure processing technologies, nanoimprint lithography (NIL) has the advantages of high-resolution, low-cost and large-scale production. Therefore, NIL was classified as one of the important representatives of next generation lithography (NGL) for the 32nm, 22m and 16nm nodes in the International Technology Roadmap for Semiconductors (ITRS). Since 1995, Chinese scientist, Professor Stephen Chou, put forward the concept of“nanoimprint”for the first time in the journal of Appl. Phys. Lett., it has aroused more and more attention and the research boom from the academic and industrial circles. Foreign manufacturers of semiconductor equipment, materials, and technology providers have begun to set foot in this area of research work. In the last more than a decade, NIL has developed with some types of imprinting methods, such as Hot Embossing Lithography (HEL), UV-based Nanoimprint Lithography(UV-NIL) andμ-Contact Print(μCP), etc.. Nevertheless, as a contact processing technology of nanostructure fabrication, some key issues of the NIL technology, such as nano-scale material properties, high precision imprinting process, demolding, are still being investigated up to now, and in particular compatibility with the current semiconductor industrial process is still not unavailable, which is different from the non-contact process of optical lithography. That is the reason why NIL is still at the level of laboratory research and only several semiconductor Integrated Circuit (IC) pioneers are in the attempt to carry out industrial tests.In this paper, the aim is to fabricate two-dimensional photonic crystal (2D-PC) structure and develop its applications. The key technologies in the process of UV-NIL were deeply investigated. Researches on large-area and low-cast UV-NIL stamp fabrication technologies, functional nanoimprint resist preparation and stamp surface anti-stick modification were carried out to solve the bottlenecks in the process. For the application, the optimized 2D-PC structure for improving the light extraction efficiency of LED were theoretically designed and finally fabricated via combing UV-NIL and semiconductor manufacturing processes. These research works are necessary for mastering the core intellectual property rights, and promoting the industrialization of NIL technologies. Paper mainly include the following contents.First, for the disadvantages of high-cost and low-efficiency of fabricating UV-NIL stamp directly by EBL, a new process was invented to fabricate 2D-PC nano-arrays with the critical dimension of below 100 nm by transferring a concave pattern to a convex nanosize stamp via wet etching technology, which is low-cost and large-area process available. Meanwhile, A new kind of UV-NIL resist with photoluminescent properties was prepared by modifying the imported nanoimprint resist, AMONIL, with ZnO quantum dots (QDs). The new functional UV-NIL resist not only enhancing the photoluminescent properties of ZnO QDs but also preserving the nanoimpint capabilities, which explores the promising applications in the optoelectronic devices.The key technologies in UV-NIL process including substrate and stamp cleaning, stamp anti-stick modification, preparation of the resist film, high precision nanoimprint process controlling and pattern transferring to the substrate were studied in detail. A vapor deposition set was developed for the stamp surface anti-stick treatment. The contact angle of the stamp surface was enhanced from 33°before modified to 113°after modified, which resolved the problem of demoulding difficulty in the UV-NIL process. Ultimately, the 2D-PC structure was fabricated by UV-NIL successfully with the accuracy within 10 nm.Finally, for the actual application to enhance the light extraction efficiency of LED, using the equivalent refractive index theory and antireflective optical film theory, the 2D-PC structures on the surface of gallium nitride (GaN) of LED epitaxial wafer were designed. A set of 2D-PC parameters was put forward. With the effective integration of UV-NIL and LED semiconductor manufacturing process, PC-LEDs were manufactured successfully. After chip packages, the initial test results indicated that PC-LEDs had clearly improvement than that without PC structures in the flux, light efficiency and light radiation with the highest increases by 22.3%, 36.65%, 14.23% respectively. Comparing the experimental results with the theoretical designs, it was shown that the 2D-PC structure with high duty ratio (2r / a) was conducive to the light energy limited into the LED chip to be coupled out to the free-space, thereby enhancing the efficiency of light output. Different periods and etching depths of 2D-PC structures also have influences on the light extraction efficiency under the same duty cycle. The smaller the period, the higher the etching depth was required. This conclusion has great significance for the further theoretical optimization and process improvement.Part of the studies in this paper was carried out cooperating with the LED chip manufacturer. The device production process was completed through the industrial line and the packaging and testing were in accordance with the current standard. Therefore, implementation process has completely compatibility with the existing semiconductor technology. Accordingly, the present research work in this paper show more practical significance for the industrial applications of NIL in the development of the nanoelectronic semiconductor industry to the aim of smaller, colder, faster nanodevices.更多还原