高灵敏度石墨烯纳晶碳膜压阻机理及其MEMS传感器关键技术研究

High sensitivity MEMS sensors have wide application prospect in intelligent manufacturing and high-end equipment. For traditional MEMS piezoresistive sensors, there are some problems, for example, the piezoresistive coefficient of silicon is limited, sensitivity is restricted by elastic sensitive structures, the technological process is complex and so on. As a result, in this research new types of MEMS sensors based on graphene nanocrystalline embedded carbon film are proposed. Combined with molecular dynamics, quantum mechanical calculation, experimental test and analysis methods, this study conducts a layer-by-layer revelations of basic science problems about the piezoresistive principle of graphene nanocrystalline embedded carbon film and carbon membrane–Si substrate bonding mechanism, and a novel material with high gauge factor and reliable membrane-based bonding is obtained. Replacing traditional doped silicon, this material is deposited on silicon surface as pressure-sensing element by only one step to improve the sensitivity of sensors. Based on pressure and acceleration sensors, in order to apply graphene nanocrystalline embedded carbon film to MEMS sensors, the key technology research is carried out. The stess and strain of Si elastic structures are analyzed. According to the electrical and mechanical properties of graphene nanocrystalline embedded carbon film, the circuit and the resistance layout are designed, electrode material optimization and MEMS process compatibility are studied. Then the production of the sensors are finished, and a performance testing is carried on to verify its high sensitivity, also the temperature drift property is measured. In this study it is both included the development of high gauge factor material and matching of elastic structures, so that the sensitivity of sensors will be improved greatly. This research will provide theory and technology foundation to the development of novel high sensitive MEMS sensors.

高灵敏度MEMS传感器在智能制造及高端装备等领域具有广泛的应用前景。针对传统MEMS压阻式传感器硅压阻系数有限、灵敏度受弹性结构制约、工艺繁复等问题，本研究提出了基于石墨烯纳晶碳膜的新型MEMS传感器。结合分子动力学量子力学计算和实验测试手段，逐层揭示石墨烯纳晶碳膜的压阻原理和碳膜-硅基结合机理的基础科学问题，获得高压阻因子且膜基结合可靠的新型材料，替代传统掺杂硅将其一步沉积形成压敏元件，提高传感器灵敏度。以压力和加速度传感器为主，开展石墨烯纳晶碳膜应用于MEMS传感器的关键技术研究。分析硅基弹性结构的应力应变，根据石墨烯纳晶碳膜的电学力学特性，设计相应的电路和电阻布局方式，研究电极材料优选和MEMS工艺兼容性。完成传感器制作封装，对其高灵敏度、温漂特性验证测试。从高压阻因子材料开发和弹性结构匹配双向研究，大幅提高传感器的灵敏度，为开发新型高灵敏度MEMS传感器奠定理论和技术基础。

针对传统MEMS压阻式传感器硅压阻系数有限、灵敏度受弹性结构制约、工艺繁复等问题，本研究提出了基于石墨烯纳晶碳膜的新型MEMS传感器。采用直流磁控溅射技术与高离化脉冲式等离子磁控溅射(HIPMS)在硅衬底上原位沉积了具有应变敏感特性的石墨烯纳晶碳膜。研究了薄膜的电导率和压阻系数随sp2团簇尺寸的变化规律。通过在0~400 V范围内调节负偏压，使压阻因子GF (gauge factor, GF)在3.3~30范围内进行调节，GF与sp2簇大小呈明显的负相关关系。电导率和GF具有类似的趋势。结合分子动力学量子力学计算和实验测试手段，逐层揭示石墨烯纳晶碳膜的压阻原理和碳膜-硅基结合机理的基础科学问题，获得高压阻因子且膜基结合可靠的新型材料，替代传统掺杂硅将其一步沉积形成压敏元件，提高传感器灵敏度。以压力和加速度传感器为主，开展石墨烯纳晶碳膜应用于MEMS传感器的关键技术研究。分析硅基弹性结构的应力应变，根据石墨烯纳晶碳膜的电学力学特性，设计相应的电路和电阻布局方式，研究电极材料优选和MEMS工艺兼容性。完成传感器制作封装，对其高灵敏度、温漂特性验证测试。其中，成功地将薄膜制成惠斯通全桥，并与微机电系统(MEMS)压阻力传感器集成。该力传感器的灵敏度达到9.8 μV/V/mN，在0~210 mN的测试范围内，非线性度约为2.0% FS，具有良好的重复性。碳膜压阻传感器因其经济、简单、绿色的压阻材料制造工艺和吸引人的性能而成为潜在的选择。