基于非晶硅薄膜的红外吸收层膜系设计、仿真与实验研究

【作者】 傅俊威；

【导师】 李伟；

【作者基本信息】 电子科技大学 ， 光学工程， 2011， 硕士

【摘要】 非晶硅（a-Si）薄膜由于具有良好的红外吸收性能、与标准硅集成电路兼容性好、能实现大规模生产等优点,而成为微测辐射热计研究的热点之一。在微测辐射热计的制备中采用非晶硅薄膜作热敏层,可以采用自支撑结构而省去氮化硅（Si₃N₄）等支撑层,简化制备工艺。此外,非晶硅薄膜还具有较小的热导率和优良的热绝缘性能,因而可采用短桥腿和后桥腿设计,提高微桥结构的占空比及机械强度,可承受高强度的振动及冲击。本文简要介绍了基于非晶硅薄膜的微测辐射热计的微桥结构、工作原理及主要性能,重点采用Matlab软件对微桥热敏面的光学吸收性能进行了设计、仿真和优化。具体方法是从单层膜系仿真向多层膜系仿真发展,从薄膜的吸收层仿真过渡到整体器件的仿真,最终从理论上得到最佳和优化的设计方案。进行仿真实验时,主要选取了氧化硅（SiO₂）、氮化硅（Si₃N₄）、氧化钛（TiO₂）及氮化钛（TiN）四种红外吸收材料。仿真研究表明,TiN是一种非常适合用于增强微桥热敏面红外吸收的薄膜材料;当微桥结构的各部分取恰当的参数值时,在8～14μm波长范围内,多层薄膜的红外吸收率可以达到90%以上。这一结果对实际微桥制备和应用具有积极的指导意义。在仿真的基础上,我们分别制备了Si₃N₄、TiO₂及TiN薄膜,用傅里叶变换红外吸收光谱方法研究了不同薄膜的红外吸收率情况,并与仿真结果进行对比研究,发现红外吸收实测结果与仿真结果基本一致,从而在一定程度上验证了仿真结果的正确性。同时,也发现实验研究与仿真研究之间存在着一定的偏差,这可能与沉积的薄膜厚度偏高有关。但是,TiN薄膜在仿真中表现出来的优良红外吸收特性,在实验验证中并没有完全展示出来。更多还原

【Abstract】 Amorphous silicon （a-Si） thin film has many excellent characteristics such as good infrared absorption, compatible with semiconductor technology and is able to be used in large scale production. It had become one of the hottest subjects in the research of microbolometers. During the preparation of microbolometers, a-Si thin film can be used as the thermal-sensitive layer, and is able to support itself and other layers using its so called self-supporting structure. We can omit other layers like Si₃N₄ and simplify the whole preparation processess. Besides, a-Si thin film had lower thermal conductivity and greater thermal insulation, so we can increase the fill factor and mechanical strength of the microbridge structure. It can make the microbolometers endure high-intensity vibrations and strong mechanical shocks.Firstly, the microbridge structure, operation principles and primary performance of the microbolometers were introduced based on a-Si thin film. Secondly, focusing on optical absorption characteristic of the thermal-sensitive surface on the microbridge structure, we had carried out lots of analysis, simulation and optimization by using MatLab software. We started the simulations from single film to multi-layer film, from the absorption layer films to the whole device. And finally, we had theoretically obtained an optimal design.Before simulation, we chose SiO₂、Si₃N₄、TiO₂ and TiN as the infrared absorption films. The results of simulation showed that TiN is a kind of suitable film to enhance the infrared absorption of thermal-sensitive surface of the microbridge. When we set up some appropriate parameters of each part of the microbridge structure, the infrared absorptivity of the multi-layer films can reach over 90% from 8μm to 14μm. The results had a positive guiding significance to the practical preparation and application of the microbridge structure based on a-Si thin films.Based on the simulation, we had prepared some Si₃N₄, TiO₂ and TiN thin films. And we had measured the infrared absorption of these films by means of Fourier Transform Infrared Spectroscopy （FTIR）. Compared with the simulation, it can be seen that the results of the infrared absorption were basically the same as those of simulations. It means that the simulation results can be verified by experiments in a certain extent. Meanwhile, there were also some differences between simulations and experiments. These might be related to the thicker thickness of the films used in FTIR test. However, the excellent infrared absorption characteristic of TiN thin film demonstrated in simulations has not been realised yet in the following FTIR experiments.更多还原