高密度深刻蚀熔融石英光栅的设计与制作
文献类型：学位论文
| 作者 | 王顺权 |
| 学位类别 | 博士 |
| 答辩日期 | 2006 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 周常河 |
| 关键词 | 微光学 感应耦合等离子体 石英光栅 密集波分复用系统 |
| 其他题名 | Design ang fabrication of high-density deep-etched fused silica transmission gratings |
| 中文摘要 | 微结构光学是一门属于多门前沿学科交叉领域的新兴学科。近年来，成熟的微电子工艺技术也被用于微光学元件的加工中，并且取得了很大的成功。感应耦合等离子刻蚀工艺是微电子工艺中用来在半导体，介质膜和金属导电层上得到各种图形的一种高效的刻蚀技术。同样它也能用来在石英等各种光学材料上形成各种图形，从而用来生产微光学元件。熔融石英材料的损伤域值很高，热膨胀系数很小，能够在高强激光和对稳定性要求严格的环境中工作。深刻蚀熔融石英光栅采用了先进的微电子加工工艺，在合适深宽比的情况下，一级衍射效率能够达到98％，在一定程度上还起到了减小光学表面反射率，增加透射率的作用。所以用熔融石英制作的深刻蚀高密度光栅是非常有用的光学元件。不同密度的深刻蚀石英光栅，存在着相应的优化深度，其中包括了密集波分复用系统中采用的600l/mm高密度深刻蚀石英光栅等等。但是制作高密度深刻蚀熔融石英光栅在工艺上存在很多难点，其中最为突出的就是如何在小线宽的情况下得到很深的刻蚀深度，从而得到高的深宽比和高效率；还有一个难点是刻蚀过程中如何很好地避免微光学元件表面聚合物沉积。本论文旨在研究和讨论如何很好地解决这两个问题，并制作出高品质的高密度熔融石英深刻蚀光栅。主要内容包括： 1. 深刻蚀工艺技术的优化研究。在利用微电子ICP干法刻蚀工艺制作熔融石英微光学光栅时遇到的两个主要问题：一．如何避免刻蚀时光栅表面的聚合物沉积；二．如何在高密度的情况下得到较深的刻蚀深度（深刻蚀）。我们在实验中主要采用了三种措施来解决如上所述刻蚀中的难点：㈠在反应气体中通入适量的氧气。在反应气体中通入适量的氧气，能够通过氧气产生的等离子体来燃烧分解刻蚀过程中产生的聚合物，使得最后得到的光栅表面没有聚合物沉积；㈡采用铬膜作为刻蚀掩蔽。由于铬膜在等离子环境中能更好的抵抗物理腐蚀和化学腐蚀，所以用铬膜取代传统的光刻胶掩膜作为刻蚀掩蔽，能取得较高的熔融石英对铬膜的刻蚀选择比，从而得到更深的刻蚀深度；㈢降低刻蚀过程中基片的温度。使用冰水混合物作为冷却液体能有效地降低基片刻蚀时的温度，减小基片侧蚀速率，从而提高刻蚀深度。另外我们还采用了其它一些技术，例如增加气体流速以减少气体滞留时间，来抑制聚合物沉积等等。在有效实施这些措施的基础上，我们提出了ICP刻蚀熔融石英的优化条件。实验证明，所报道的优化参数和深刻蚀工艺途径很好地解决了上述问题。 2. 高密度深刻蚀光栅在DWDM系统中的应用。光栅由于衍射效率高，近年来受到DWDM领域的广泛关注。据我们所知，没有人针对光纤通信的1.55微米波段给出高密度深刻蚀矩形光栅的设计参数。我们用Moharam等人提出的严格耦合波理论计算分析了适用于1550nm光通讯波段的高效率熔融石英光栅的各种结构参数。理论证明当石英光栅的密度在650～700l/mm，刻蚀深度在2.5～3微米的范围内时，光栅的理论衍射效率能达到95％以上。光栅结构参数的设计结果很好地指导了光栅的制作。 3. 高密度石英光栅的制作流程和测试。在文章的后半部分，我们给出了使用微电子工艺技术和ICP刻蚀技术，制作了适用于DWDM系统的密度为674 l/mm，深度为2.5微米的高密度深刻蚀石英光栅的具体流程，并对最终制作出的光栅样品做了光学测试。光栅的实测效率为87.1％，在考虑了光栅背面反射，表面散射，和占空比误差后，和理论值能很好吻合。实验证明了ICP刻蚀优化条件的适用性和优化结构设计的正确性。 |
| 英文摘要 | Micro-optics has received great interest in recent years, and microoptical elements are becoming more and more widely used in optical systems. In recent years, microelectronics processing technology has been successfully used in the fabrication of micro-optics elements. Inductively coupled plasma etching technology is the technology that can effectively produce various patterns on semiconductors, dielectric layers, and metal films. Nowadays, it is used to form patterns on optical materials, such as fused silica micro-optical elements. Fused silica is a material with high laser-power threshold value, and low heat-induced expansion value, which can stand well in environment with high power laser or fluctuating temperature. Fabrication of deep-etched fused silica grating takes advantage of microelectronics processing technology, which is widely used now. The grating can reach a diffraction efficiency as high as 98% when the garting parameters are optimized. The optimized ethed depth is related with the grating density. For example, grating with density of 650~700 l/mm and a depth of 2.5~3 microns can reach an efficiency of above 95%. So it can be easily used in DWDM system for (de)multiplexing. But there are many difficulties in fabricating gratings with inductively coupled plasma etching technology. Two most obvious difficulties are how to get a deep etched depth for a high efficiency, and how to avoid polymer deposition on the surface of the grating for good optical transmission. This thesis addresses these two problems, and the fabrication process of deep-etched high-density fused silica gratings. The details are listed as follows: 1. Research of the optimization of the deep etching process with ICP etching technology. There are two main problems when we use ICP etching technology to fabricate fused silica grating. One is how to avoid polymer deposition on the surface of the grating. The other is how to get a deep etched depth when high density fused silica grating is etched. In experiments, we increase the gas flow rate to reduce the gas resident time, we use oxygen as an additive. By these two means, we successfully avoid the polymer deposition in the etch process. For deep etching purpose, Cr is used as the sacrificial layer instead of the traditional photoresist mask. Besides, we use low temperature water to cool the substrate to maintain a low rate sidewall-etch. With the help of these measures, we find an optimized etching condition. Following experiments indicate that the measures and the reported etching condition works very well. 2. Application of the high-density deep-etched fused silica gratings for DWDM system. High-density deep-etched fused silica gratings aroused great interest in DWDM demultiplxing field for its high efficiency and some other advantages. But as we know, no one has presented the optimized design and fabrication of the deep etched binary-phase fused silica transmission grating for wavelength of 1550nm in DWDM system. We obtained all the structure parameters of a high efficiency grating for use in DWDM system by the rigorous coupled-wave theory. Numeriacal result indicates that if a fused silica grating has the density of 650~700 l/mm, and the etched depth of 2.5~3 microns, it can reach a diffraction efficiency of above 95%. The calculated structure parameters provide an useful guide for the following fabrication process. 3. Detailed fabrication and testing process of high-density deep-etched fused silica gratings. In the rear part of the thesis, we present the detailed fabrication process of the fused silica grating with density of 674 l/mm, and etched depth of 2.5 microns. Efficiency of the fabricated grating is measured to be 87.1%. Considering the unavoidable experimental errors such as surface reflection and surface scattering, the measured efficiency matches theoretical results very well. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15588]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 王顺权. 高密度深刻蚀熔融石英光栅的设计与制作[D]. 中国科学院上海光学精密机械研究所. 2006. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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