基于MEMS叠层微结构的SO2毒气传感器

Sulfur dioxide poison gas sensor based on MEMS laminated microstructure

利用多孔上电极叠层微结构，以真空镀膜技术形成气敏膜，采用MEMS微加工技术研制了气体传感器。依据等效电路和工艺边界条件，通过电导公式推导出传感器的输出电导提高了10^3倍，解决了有机半导体的信号采集问题。通过SEM微观形貌，确认蒸发电流100～120A、蒸发时间8～12s为电极成膜最佳条件；气敏膜表面呈现二次化学反应融合的200nm左右“米粒状”活性颗粒状态，均匀一致，孔隙有序。测试结果表明：比例系数为0．15～0．35的硫酸掺杂CuPcxPANI1-x对SO2有最佳的灵敏度；考虑到减少H2S气体干扰，选择CuPc0.35PANI0.65为气敏材料，在加热电压VH为1～2．5V时提高了传感器的灵敏度特性和响应恢复特性，响应时间为30s；传感器输出特性为单对数线性关系，检测范围为0～200×10^-6；经6个月的稳定性考核，其输出阻抗漂移≤±5％，灵敏度漂移≤10％。

Aimed at the technical difficulty of low electric conductivity of novel organic semiconductor, a kind of laminated microstructure on porous upper electrode was brought forward. A gas sensitive film was formed using vacuum deposition,then, a gas sensor was developed by MEMS micro-fabrication. According to the equivalent circuit and the technologic boundary condition, the output conductance of the sensor has increased by 1 000 times derived by a conductance formula,which solves the signal gathering problem of organic semiconductor. SEM microcosmic pattern indicates that the best condition is the evaporating electric current of 100-120 A,and evaporating time of 8-12 s. On that condition, the surface of gas sensitive film is covered with activated granules inosculated by the secondary chemical reaction,like rice grain in uniform distribution and ordered holes. The testing result indicates that vitriol doped CuPcxPANI1-x with proportionality coefficient of 0.15-0.35 has the best sensitivity to SO2. The CuPc0.35 PANI0.65 is selected in order to reduce the interference of H2S. When heating voltage VH is 1-2. 5 V, sensitivity and responsive restorability will be enhanced and responsive time is 30 s. The output characteristic of sensor is single linear logarithmic, the detecting range is 0-200×10^-6. Through stability examination for six months, output impedance shift and sensitivity are less than or equal to ±5% and 10%, respectively.