【作者】 方庆玲；

【导师】 李效东； 金东杓；

【作者基本信息】 国防科学技术大学 ， 材料科学与工程， 2011， 博士

【摘要】 作为微机电系统(MEMS)、集成电路(IC)和芯片实验室(LOC)等领域的基本组件,微/纳米图形结构在现代工业社会中处于一个举足轻重的地位。本文合成了可光固化的聚硅氮烷先驱体材料,使之能利用各种先进光学成型技术制备出微/纳米图形结构,并结合硅表面加工、微流控器件、压印技术等应用背景,通过进一步的无机化处理,采用更快捷的路径制备出符合不同领域需求的高性能微/纳米图形结构。首先,本文用光敏分子ICMA分别和低分子量的聚乙烯基硅氮烷(PVSZ)和全氢聚硅氮烷(PHPS)反应,获得具有光固化性能的甲基丙烯酸酯化的聚硅氮烷,对应的产物分别记为MPVSZ和MPHPS。经FT-IR,1H-NMR,13C-NMR等手段表征了产物和中间体的化学结构。基于MPVSZ,本文首次通过光刻和水解转化路径制备了一种新型的高选择性硅刻蚀掩膜。以甲苯为溶剂,混合光引发剂Irgacure 369和热引发剂Luperox 231配制不同浓度的MPVSZ光固化体系,在6英寸的硅片基底上可获得的最大的涂层厚度~ 6μm。以50 wt%的MPVSZ光固化体系为原料,通过旋涂获得平整涂层,然后经过前烘、I-line光刻、IPA显影、后烘等工艺,制备出了最小特征尺寸1μm的MPVSZ微结构,形态有圆形、方形和线形等。氨气催化下,微结构在80°C可水解转化为silicate陶瓷结构,采用FT-IR,XPS等手段研究了其水解机理。将水解前后的微结构作为硅刻蚀掩膜进行干法刻蚀研究,以SF6/Cl2/Ar为刻蚀剂,发现silicate微结构比MPVSZ微结构表现出更好的抗蚀性能,对硅基底的刻蚀选择性达8-16,并在SF6/Cl2/Ar = 10/0/10时达到最高。另外,通过纳米压印技术,从MPVSZ光固化体系可以制备Sub-100 nm的纳米结构。基于MPVSZ刻蚀掩膜的制备可以和传统MEMS工艺有效结合,同时又能避免传统高选择性刻蚀掩膜材料复杂的多步成型过程,所以该研究工作可以降低硅表面微加工的成本,从而具有较大价值。另外,基于MPVSZ本文还开发了一种耐溶剂的刚性微混合器的制备新路径。配制75 wt%的MPVSZ光固化体系,注入经MPTMS表面处理的玻璃模具,通过新型的静态液相光刻方法一步获得通道内包埋P-SHM微混合结构的MPVSZ敞口芯片。讨论了该过程的MPVSZ的光聚合机理。通过80°C水解处理将MPVSZ芯片转化为silicate陶瓷芯片,并与PHPS涂层的PDMSO微通道封接,常温氨气催化水解处理将PHPS涂层转化为Si-O结构,最终获得具有优良的耐溶剂性和机械性能的P-SHM微流控系统。将两支5μL/min流体注入该系统,2.3 cm后实现混合,远小于相同尺寸空白微通道的理论混合长度101.6 cm。基于MPVSZ转化的silicate陶瓷微流控系统拥有良好的机械性能但是制备成本却比传统刚性材料制备微流控芯片低,具有优良的耐溶剂性使它可以作为PDMSO微流控芯片的有效补充,这两点使得该制备路径在LOC领域具有重要意义。基于首次合成的MPHPS,制备可用作压印模板的透明高硬微/纳米图形结构。Irgacure500为光引发剂配制MPHPS光固化体系,采用自制的hard-PDMSO微结构压印模板通过紫外压印获得MPHPS微结构。MPHPS的sub-100 nm结构则是从自制的FP模板压印获得,特征尺寸为70 nm和90 nm。在碱性条件下室温水解10 h,MPHPS固化样品原子构成由SiN0.33O0.40C0.57转变为SiO1.5,化学结构从聚合物转变为Si-O无机结构。获得的Si-O微/纳米图形结构为无色透明,硬度提高到4.5 GPa,弹性模量提高到115.1 GPa,机械性能符合实验室和生产实践对高硬压印模板的要求。该路线制备高硬模板的成本远低于传统MEMS路线。在本文的MPVSZ光刻法制备微结构及其水解制备Silicate微结构的研究基础上,本文进一步开展了对这些微结构的CNT改性研究。首先,设计了可批量生产适合表面修饰的高纯度高长径比CNT的CVD立式反应炉,对获得的CNT进行化学修饰实现它们在MPVSZ溶液的稳定均匀分散。然后配制CNT含量为0.1 wt%,0.3 wt%,0.5 wt%的MPVSZ光固化混合液,在6英寸硅片上获得平整涂层后,经前烘、I-line非接触模式光刻、显影、后烘等工艺步骤,可以获得CNT/MPVSZ微结构。进一步水解处理获得CNT/silicate复合陶瓷微结构。CNT无论在MPVSZ聚合物基体中还是在MPVSZ转化的silicate陶瓷基体中都起到了增强的作用,且它们的机械性能都随着CNT含量提高而增强。更多还原

【Abstract】 As the basic blocks in micro-electromechanical systems(MEMS), integrated circuit(IC) and lab on a chip(LOC) fields, micro/nano- patterned structures play a key role in the modern industry society. Towards the application in silicon patterning, microfluidics devices, imprinting lithography etc., this dissertation fabricated micro/nano- structures with good properties from as-synthesized photocurable polysilazane precursors by novel rapid routes using optics lithography techniques and hydrolysis treatment.Two photocurable polysilazanes-based resins were obtaind by adding methacrylated units onto the polyvinylsilazane and perhydropolysilazane, whose products were donated MPVSZ and MPHPS respectively. Therein, MPHPS was firstly synthesized and characterized by FT-IR, 1H-NMR, 13C-NMR methods.Based on MPVSZ, a novel etch mask with high selectivity for silicon was fabricated in one step photolithography and hydrolytic conversion route. Photocurable MPVSZ mixture liquid containing photo-initiator Irgacure 369 and thermal-initiator Luperox 231 could be spin-coated to smooth films with the thickness up to ~ 6μm. MPVSZ mixture with 50 wt% concentration was spin-coated upon a 6 inches silicon wafer, followed by pre-baking, UV-exposure, developing, post-baking steps, then, the photolithographic MPVSZ microstructures with various shape(dot, square, line, etc.) were obtained, with the smallest feature size of 1μm. A hydrolysis treatment by exposing the MPVSZ microstructures in a 80°C ammonia ambience was taken here to acquire the silicate ceramic microstructures with a denser physical structure. Its hydrolytic conversion mechanism was investigated by FT-IR, XPS methods. SF6/Cl2/Ar mixture gas as the dry plasma etching etchant was used to investigate both of the cured and hydrolyzed MPVSZ patterns as the etch mask. The MPVSZ-derived silicate structure showed a better etching resistance than the microstructues before hydrolysis, its etching selectivity over silicon was achieved 8-16, and attained the highest at SF6/Cl2/Ar = 10/0/10. Besides, sub-100 nm nanostructures were fabricated by nano-imprinting lithography. MPVSZ patterning could be combined well with the conventional MEMS lithography technique, at the same time, the complex multi-steps patterning those conventional etch masks with high selectivities was avoided, thus it largely decreased the fabricating cost for the silicon patterning.Besides, based on MPVSZ, a novel technique to fabricate a rigid and chemically resistant micromixer system was developed. MPVSZ photocurable mixture liquid with a concentration of 75 wt% was injected into a MPTMS surface-treated glass mold and followed by a static liquid photolithography(SLP) step, which resulted in a cured MPVSZ open microchip with a built-in protrudent staggered herringbone mixer(P-SHM) structure. Its photo-polymerization mechanism was discussed. The cured-MPVSZ chip was converted to silicate ceramic chip by hydrolyzing in the vaporized ammonia ambiance at 80°C, and binded with the matched PHPS coated PDMSO micro-channel. Then another hydrolysis treatment at room temperature was taken to convert the PHPS coating to silica, resulting in a rigid and chemically resistant P-SHM microfluidics system being obtained. Two fluids were injected into this system, and realized mixing in 2.3 cm which was much shorter than the blank micro-channel at the same dimension of 101.6 cm. The MPVSZ-derived silicate based microfluidics chip owned good mechanical properties but lower fabricating cost compared to the chips from the conventional rigid materials, moreover, due to its good chemically resistance it could be as an effective complementarity of the widely used PDMSO chip, all these advantages make this it valuable in LOC field.Based on the firstly synthesized MPHPS, a new route to fabricate transparent and rigid micro/nano- structures towards using as the imprint mold was developed. Photocurable MPVSZ mixture liquid mixed with Irgacure 500 as photo-initiator was UV-imprinted to microstructure by using an as-prepared hard-PDMSO mold. The sub-100 nm cured-MPVSZ nanostructure was fabricated by using an as-prepared FP mold, with the feature size of 70 nm and 90 nm. By exposing the cured MPHPS in basic ambience for 10 h at room temperature, the chemical component was converted from SiN0.33O0.40C0.57 to SiO1.5, and the chemical structure was converted from polymer phase to Si-O inorganic phase. The obtained hydrolyzed micro/nano- structures was transparent, with an increased hardness of 4.5 GPa and an increased elastic elastic modulus of 115.1 GPa, which could meet with the requirement of the hard imprint mold used in both lab and industry, moreover, its fabrication cost was much lower than those conventional rigid materials mold made by MEMS routes.Based on the above researches on MPVSZ microstructures and their derived silicate microstructures, this paper made a further investigation on their modified microstructures using carbon nanotubes (CNT). A vertical CVD reactor was firstly designed to fabricate CNT in large scale. The as-prepared CNT with good quality was well dispersed in the photocurable MPVSZ mixture liquid through a designed chemical modification. CNT/MPVSZ solution with series CNT content of 0.1wt%, 0.3wt%, 0.5wt% was fabricated and spin-coated to be smooth film on a 6 inch silicon wafer. After going pre-baking, I-line photolithography, developing steps, MPVSZ microstructures modified by CNT were obtained. The CNT/MPVSZ microstructures were converted to CNT/silicate composite ceramic microstructures by a further hydrolysis treatment. It was concluded that the additive CNT strengthened both of the silicate ceramic matrix and MPVSZ polymer matrix, and the mechanical properties were increased by the increase of the CNT content.更多还原