面向MEMS压力传感器的硅纳米线压阻特性研究

With the development of sensors in direction of miniaturization, low power consumption, high integration, intelligence, silicon nanowire piezoresistors with easy integration and high sensitivity will be extensively utilized. However, there are mutually contradictory opinions in studying piezoresistive characteristics of silicon nanowires. Some papers indicated that the piezoresistive coefficient of silicon nanowire has been increased two orders of magnitude compared with the bulk one. But some papers reported that the piezoresistive coefficient of silicon nanowire could not change with size of nanowire and the giant piezoresistive effect was resulted from measuring error. Herein, silicon nanowire piezoresistors with different sizes, crystal orientations, doping concentrations will be fabricated with high concentration boron doped silicon which could be self-restrained etching in base solution. Meanwhile, silicon nanowire piezoresistors were integrated into MEMS pressure sensors. Through measuring the output features of pressure sensing structure, the quantitative relationship between piezoresistive coefficient of silicon nanowire and sizes, crystal orientations, doping concentrations and temperature will be figured out. After optimizing the performance of silicon nanowire piezoresistors, a prototype MEMS pressure senor will be fabricated and characterized its properties. The special features of this project were that silicon nanowire piezoresistors with varied parameters were fabricated with high concentration boron doped silicon and integrated into MEMS pressure sensor. With the help of the elastic force analysis, several characteristics of silicon nanowire piezoresistance could be accurately obtained. The implementation of this project will classify the characteristics of silicon nanowire piezoresistor which were ambiguous in present research, and can accumulate valuable data for application of silicon nanowire piezoresistors in MEMS pressure sensors.

随着传感器向微型化、低功耗、高集成、智能化发展，可集成高灵敏的硅纳米线压阻条具有广泛应用潜力。但是，对硅纳米线压阻性能的研究还有异议：有报道指出硅纳米线的压阻系数较相应块体材料提高2个量级，也有报道认为硅纳米线的压阻系数并不随尺寸改变，巨压阻效应可能来自测量误差。本项目利用腐蚀自停止的浓硼掺杂硅层，制作具有不同尺寸、取向、掺杂的硅纳米线压阻，同时集成到MEMS压力传感器中。通过测量感压结构的输出特性，掌握硅纳米线压阻系数与尺寸、取向、掺杂及温度的定量关系，优化硅纳米线压阻性能，制作出以硅纳米线压阻为换能单元的MEMS压力传感器原型器件并测试其性能。本项目特色在于用浓硼掺杂硅制作出多参量变化的硅纳米线压阻，集成到MEMS压力传感器中，结合弹性力学分析，准确获得硅纳米线压阻各项性能。项目实施将解决目前对硅纳米线压阻特性研究中所存异议，为构建基于硅纳米线压阻的MEMS压力传感器夯实理论基础。

随着MEMS压力传感器向微型化、高集成、低功耗、智能化发展，硅纳米线压敏电阻的使用会越来越多。但目前，对硅纳米线压阻的特性还没有全面掌握，急需解决的问题有：硅纳米线尺寸、取向、掺杂与压阻系数的定量关系；硅纳米线压阻如何与MEMS压力传感器可靠集成；在MEMS压力传感器中，硅纳米线压阻性能与温度的关系；影响硅纳米线压阻性能的主要因素（尺寸、取向、掺杂、温度）之间的相互影响及性能优化。本项目针对目前的主要问题，利用浓硼扩散硅自停止腐蚀层，制作具有多参量变化的硅纳米线压阻，并集成到MEMS压力传感器中，系统研究硅纳米线尺寸、取向、掺杂与压阻系数的定量关系，揭示硅纳米线压阻性能与温度的定量关系，经过优化硅纳米线压阻性能，制备出基于硅纳米线压阻的MEMS压力传感器的原型器件，并系统测试传感器性能。项目的实施揭示出硅纳米线压阻系数受纳米线尺寸和掺杂浓度影响较小，纳米线晶格取向从[110]向[100]变化时，压阻系数逐渐减小。芯片尺寸减小到1.3 mm ×1.3 mm×0.9 mm，量程0-1 Mpa输出120 mv，满量程精度优于1%，灵敏度温度系数最大为3%，电阻温度系数最大为2.5%，芯片响应时间约10秒，一周零点漂移量为满量程的1%，芯片级的器件总功耗约1微瓦。项目执行过程中，发表论文5篇，其中3篇SCI论文影响因子大于3，申请发明专利7项，培养硕士研究生2名。该项目的实施，为构建基于硅纳米线压阻的MEMS压力传感器积累了丰富经验。