【作者】 陆学斌；

【导师】 刘晓为；

【作者基本信息】 哈尔滨工业大学 ， 微电子学与固体电子学， 2010， 博士

【摘要】 多晶硅薄膜良好的压阻特性使其在压阻式传感器中得到了广泛应用。已有研究结果表明,多晶硅纳米薄膜与普通多晶硅薄膜相比具有更加优越的压阻特性,因此有着广阔的应用前景。本文对多晶硅纳米薄膜的压阻特性进行研究,主要包括工艺条件对压阻特性的影响和多晶硅纳米薄膜杨氏模量的研究。在对压阻特性进行研究的基础上,进行多晶硅纳米薄膜的压力传感器应用研究。在工艺条件对压阻特性的影响研究中,利用LPCVD方法在不同工艺条件下制备了多晶硅纳米薄膜,研究了工艺条件对多晶硅纳米薄膜电阻、应变系数及其温度系数的影响,选取了优化工艺条件。此时,多晶硅纳米薄膜的应变系数达到34,比相同掺杂浓度的普通多晶硅薄膜高25%以上;应变系数的温度系数在1×10-3/℃附近,比普通多晶硅薄膜小近一倍;电阻的温度系数小于1×10-4/℃,比普通多晶硅薄膜小近一个数量级。优化工艺条件的选取,为多晶硅纳米薄膜的压力传感器应用研究提供了必要的设计依据。此外,还研究了掺杂浓度与压阻非线性的关系。对多晶硅纳米薄膜的压阻非线性进行了分析,发现多晶硅纳米薄膜的压阻非线性主要来源于晶界。对于多晶硅纳米薄膜,晶粒度很小,随着掺杂浓度的变化,晶界宽度发生变化,同时晶界压阻效应在多晶硅压阻效应中占据的比重也发生变化,因此晶界对多晶硅压阻非线性的影响随着掺杂浓度的变化而变化。掺杂浓度与压阻非线性关系的研究同样为研制多晶硅纳米膜压力传感器提供了设计依据。在压阻特性的研究中,对多晶硅纳米薄膜的杨氏模量进行了研究。在隧道压阻理论中,多晶硅纳米薄膜的杨氏模量是采用单晶硅的杨氏模量与一修正系数相乘而来,而对该修正系数的取值并没有给出合理的解释。在传感器的结构设计中,为了使有限元仿真结果与实际情况更加接近,需要多晶硅纳米薄膜的杨氏模量作为仿真参数。本文利用扫描电镜和透射电镜对多晶硅纳米薄膜的微观结构进行表征,根据多晶硅纳米薄膜的生长、结构特点,建立了晶粒模型。以该模型为基础,提出了用于计算多晶材料纳米薄膜杨氏模量的方法,并计算了多晶硅纳米薄膜的杨氏模量。利用原位纳米力学测试系统对多晶硅纳米薄膜的杨氏模量进行了测试。理论计算结果与测试结果进行比较,二者吻合。多晶硅纳米薄膜杨氏模量的研究完善了隧道压阻理论,同时为后续压力传感器的结构设计提供了依据。在对多晶硅纳米薄膜压阻特性进行研究的基础上,进行了多晶硅纳米薄膜的压力传感器应用研究。对多晶硅纳米膜压力传感器进行有限元仿真,根据仿真结果对传感器的结构进行了优化设计。利用多晶硅纳米薄膜作为传感器压敏电阻的制作材料,制定完整工艺流程,解决了传感器研制过程中的关键工艺,完成压力传感器的研制。该压力传感器的量程为0~0.6MPa。多晶硅纳米薄膜具有良好的高温压阻特性,在0~200℃的温度范围内,对所研制传感器的性能进行了测试。将研制的多晶硅纳米膜压力传感器和普通多晶硅压力传感器以及其他类型高温压力传感器进行比较,多晶硅纳米膜压力传感器具有高灵敏度、低温度系数以及工艺简单等优点。本文为将多晶硅纳米薄膜应用于压阻式传感器的研究奠定了基础,同时实现了多晶硅纳米膜压力传感器的研制。更多还原

【Abstract】 Polysilicon film, due to its favorable piezoresistive properties, has been widely used in piezoresistive sensors. The previous researches have shown that the polysilicon nanofilm have better piezoresistive properties than common polysilicon film, and have promising future of application.In this paper, the piezoresistive characteristics of polysilicon nanofilm are investigated, including the influence of process on piezoresistive properties and theoretical calculation of Young’s modulus of the film. Based on the studies, application of the film on pressure sensor is investigated.The influences of the process on piezoresistive properties of the film were studied. The optimized process parameters for best piezoresistive properties were obtained. Here, the piezoresistive properties of the film are followed: gauge factor can reach 34 which is higher about 25% than that of common polysilicon film under same high doping concentration; temperature coefficient of resistance is less than 1×10-4/℃which is almost an order lower than that of common polysilicon film; temperature coefficient of gauge factor is about 1×10-3/℃which is about half of that of common polysilicon film. The optimized process parameters provide the necessary design rules of polysilicon nanofilm pressure sensor. The influence of process on piezoresistive nonlinearity is investigated also. The piezoresistive nonlinearity of the film is analyzed; the results show that the piezoresistive nonlinearity of the film is mainly influcened by piezoresistive nonlinearity of grain boundary. The relation between piezoresistive nonlinearity and doping concentration was studied, and the results provide the design rules of the sensor too.The Young’s modulus of the film is studied. The Young’s modulus is a parameter which associate piezoresistive coefficient and gauge factor, and is an important parameter in structure design of the sensor. In tunneling piezoresistive theory, the Young’s modulus is obtained by Young’s modulus of single silicon multiply a modified factor which is not explained reasonably. In structure design of the sensor, to make the results of finite element analyses(FEA)simulation are more close to reality, the Young’s modulus is necessary as simulation parameter. The microstructures of the film were observed by scanning electron microscope and transmission electron microscope, the grain model of the film was built according to characters of growth and structure. Based on the grain model, the method to calculate the Young’s modulus was presented, and the Young’s modulus was theoretically calculated. The Young’s modulus of the film was measured by in-situ Nano mechanical test system. The comparision between theory results and experimental results is conducted, and theory results agree with experimental results. The grain model can analyze the Young’s modulus and the calculation method is valid. The studies of Young’s modulus complement the tunneling piezoresistive theory, and provide simulation parameter in structure design of the sensor.Based on the studies of piezoresistive properities, application of the film on pressure sensor is investigated.The FEA of the sensor was performed; the sensors’s structure is optimized designed according to the results of FEA. Utilizing the film as piezoresistors of sensor, the complete process of the sensor was described, and the key technology in sensor’s fabrication was solved, finally the sensor was developed. The measured range of the sensor is 0-0.6MPa. Because of the better high temperature piezoresistive properties of the film, the input-output characteristics of the sensor were tested from 0℃to 200℃. The comaprision between polysilicon nanofilm pressure sensor and common polysilicon film pressure sensor, other high temperature pressure sensor were made, the polysilicon nanofilm pressure sensor provide advantages of high sensitivity, low temperature drift and simple fabrication process.The study of the sensor is completed, and the study results lay a foundation for application of the film to piezoresistive sensor.更多还原