MEMS 红外气体传感器关键芯片与系统集成研究

The traditional infrared gas sensors with mass in volume and high-cost are hard to realize the miniaturization and smart. Based on the research work on MEMS modulating IR photonic crystals (PCs) emitters, which is supported by young scientist project of natural science foundation of China (NSFC), a low-cost and high-integrated infrared System-in-Package (SiP) is developed. A novel mid-infrared hollow fiber with high couple efficiency and low loss is fabricated as a cell for the integrated infrared gas SiP system. Then, we explore to integrate PCs-based infrared modulating emitter with narrow-passband, infrared pyroelectric detector with PCs structure and an ASIC (Application Specific Integrated Circuit）SOC (System On Chip) with low power dissipation and multi-channel for gas annlysis, into a TO packaging to form a completely novel infrared SiP system. The volume of the packaging with optical multi-reflection structure is about tens of cubic centimeter. Firstly, pyroelectric thin film IR detector with PCs structure is emphatically researched based on the photonic band gap (PBG)，which means the light cannot transmit in the photonic crystal when light's frequency locates in the PBG. As we all known, the thermal isolative structure of the substrate and its infrared radiation is the major factors that limit the resolution of infrared pyroelectric thin film IR detector．If the photonic band gap is designed at the mid-infrared wavelength，the layer with PCs can be used as an excellent thermal isolative substrate, The thermal conductivity is near to zero because of the resistance to the radiation. Therefore，the introduction of the PCs will enhance the sensitivity of pyroelectric thin film IR detector and break through the difficulty in the low detecting efficiency. Meanwhile, we focus on the study of ASIC SOC with low consumption and multi-channel input for the gas analysis. As a mix-mode chip，the application-specific controller chip including analog signal and digital signal processing block can be applied to receiving，amplifying，processing，controlling signals of pyroelectric thin film IR detector，and offer a wide application in gas analysis fields. The SOC chip can greatly decrease system noise and detect weak signals with low power and high sensitivity using . The MEMS gas infrared SiP system featuring high selectivity, high sensitivity, fast response and low cost is able to compatible with IC process and be easy to further integrate. It would be a promising production with mass production, and emerge as a great innovator.

本项目探索发展一种高度集成化的MEMS红外气体传感器集成系统。该系统以高耦合、低损耗传输特性的中红外空心光纤为吸收腔，将窄带电调制MEMS红外辐射源、光子晶体热释电红外探测器，低功耗多通道专用SOC系统处理芯片，通过MEMS系统集成技术，封装在体积仅为十几立方厘米带有多次反射结构的TO封装体内。重点研究光子晶体结构的热释电红外探测器，尝试利用光子晶体的光子频率禁带特性，实现对特定波段光辐射的全反射，得到热绝缘衬底导热率趋于O的光子晶体支撑结构。通过新技术的尝试，提高探测灵敏度，突破传统热释电探测器探测效率低的难点。同时，专注于专用低功耗多通道红外气体分析专用SOC集成芯片的研究，通过SOC技术进一步降低系统噪声，实现对微弱信号的低功耗高灵敏检测。 该微传感器集成系统具有体积小、集成度高、功耗低、响应快和价格低等优点，具有很大的技术拓展天地和巨大的应用市场，是典型的系统集成创新。

针对传统的化学、电化学、光谱等技术的环境监测仪器存在体积大、使用条件受限、灵敏度低、检测指标单一、不能现场实时、快速直观和多参数监测等问题，本项目以CO、CO2、CH4等有毒有害气体为具体监测对象，利用先进的MEMS和IC集成技术，研究高集成度的MEMS化红外气体传感器系统。该微传感器集成系统具有体积小、集成度高、功耗低、响应快和价格低等优点，具有很大的技术拓展天地和巨大的应用市场，是典型的系统集成创新。.系统以高耦合、低损耗传输特性的中红外空心光纤为吸收腔，将窄带电调制MEMS红外辐射源、光子晶体热释电红外探测器，低功耗多通道专用SOC系统处理芯片，通过MEMS系统集成技术，封装成SIP核心探测模组。该系统突破了光子晶体红外辐射源和红外阵列探测器结构设计和MEMS制作、一体化系统集成、微弱信号采集处理等关键技术，实现红外辐射源100Hz的调制频率，小于0.35μm 的FWHM （半高全宽）；通过对小尺寸光栅器件的制作工艺的摸索，获得了较好的工艺参数。成功制备出周期为6μm，8μm，10μm，16μm，24μm 和 36μm光栅结构器件，其对红外光的吸收效率均高于等面积的非光栅结构器件，证明光栅结构可以提高器件对红外光的吸收效率；采用0.35umCMOS工艺设计研制了3通道专用低功耗多通道红外气体分析专用SOC集成芯片，实现传感器微弱信号接收、放大、调理电路，A/D转化，通过SOC技术进一步降低系统噪声，实现对微弱信号的低功耗高灵敏检测。最后，完成红外探测器阵列及MEMS红外光源嵌入式探测功能模块的研制，利用所研制的嵌入式多气体检测系统，准确实现气体的定性定量分析等功能，实现对CO2、CO和氟利昂气体的测试验证，测试精度与测试响应时间分别达到±3 F.S与30秒以内，检测限达到1ppm，满足指标要求。.项目的研究成果可提升关键部件的自主化水平，打破国外关于此类产品的技术壁垒，开发出可产品化的新型传感器芯片。