基于3ω法的微测辐射热计像元薄膜热导率测试

Thermal Conductivity Testing of Microbolometer Pixel Films Based on 3ωMethod

热导是微测辐射热计像元的重要参数之一,其大小直接影响像元的响应高低。热导与组成像元的薄膜材料的热导率相关,薄膜的特征尺寸、温度和淀积工艺皆会影响热导率。监控工艺线上薄膜的热导率,对像元的设计具有重要意义。根据3ω谐波探测技术,搭建了薄膜热导率的测试系统,测试了厚度为20~100 nm的氮化硅(SiN x)及二氧化硅(SiO 2)薄膜的热导率,包括温度特性和尺寸特性。根据尺寸特性计算得到SiN x的本征热导率为0.747 W/(m·K),SiO 2的本征热导率为1.085 W/(m·K)。测得厚度为100 nm的钛(Ti)金属薄膜的热导率为6.708 W/(m·K)。与基于光热法的测试系统相比,基于3ω法的测试台架搭建更简单。该方法利用微机电系统(Micro-Electromechanical Systems,MEMS)制造工艺制备测试样品,是MEMS产品设计与制造中表征微纳尺度薄膜热导率的理想方案。

Thermal conductivity is one of the important parameters of microbolometer pixels,and its magnitude directly affects the response of the pixel.Thermal conductivity is related to the thermal conductivity of the thin film materials that make up the pixels.The characteristic size,temperature,and deposition process of the thin film all affect the thermal conductivity.Monitoring the thermal conductivity of thin films on the production line is of great significance for the design of pixels.Based on the 3ωharmonic detection technology,a testing system for the thermal conductivity of thin films was built,and the thermal conductivity of SiN x and SiO 2 thin films with a thickness of 20~100 nm was tested,including temperature and dimensional characteristics.According to the dimensional characteristics,the intrinsic thermal conductivity of SiN x is 0.747 W/(m·K),and that of SiO 2 is 1.085 W/(m·K).The thermal conductivity of a titanium film with a thickness of 100 nm was tested to be 6.708 W/(m·K).Compared with the testing system based on photo-thermal method,the construction of the 3ωmethod testing system is simpler.This method utilizes the manufacturing process of micro-electromechanical systems(MEMS)to prepare test samples,which is an ideal solution for characterizing the thermal conductivity of micro-nano scale thin films in MEMS product design and manufacturing.