基于MEMS工艺的微热加速度计和微热陀螺仪的制备

Preparation of Micro-Thermal Accelerometer and Micro-Thermal Gyroscope Based on MEMS Process

微热加速度计和微热陀螺仪两者传感芯片结构相似,并且制备工艺完全兼容,在同一块绝缘体上硅(SOI)基板上运用同一工艺流程同时制备出了微热陀螺仪传感芯片和微热加速度计传感芯片。为了准确地创建微尺度的图案和结构,设计了四块光刻掩模版来制作该微热加速度计芯片和微热陀螺仪芯片,分别对应于接触孔开口、热敏电阻、互连布线和背面空腔。轻掺杂硅热敏电阻的可控电阻温度系数(TCR)大于传统金属丝,因此选择p型硅作为热敏电阻材料。TCR由硅片的掺杂浓度决定,使用了三种不同掺杂浓度的硅片进行对比实验,从而选定硅片的掺杂浓度为1×10^(17)cm^(-3),对应的TCR为3500×10^(-6)/℃。选择SOI作为衬底材料,显著增强了微热陀螺仪和微热加速度计的耐高温性,并且提高了其灵敏度。在电感耦合等离子体-反应离子刻蚀(ICP-RIE)和氢氟酸(HF)蒸气工艺过程中,通过光刻胶和聚酰亚胺层成功保护了非常薄和易碎的热敏电阻,在4英寸(1英寸=2.54 cm)SOI基板上一次最多可以成功制备出180个微热陀螺仪传感芯片和108个微热加速度计传感芯片,制备的微热加速度计传感芯片尺寸为2 mm×2 mm×0.4 mm,微热陀螺仪传感芯片尺寸为5.8 mm×5.8 mm×0.4 mm。分别对制备的微热加速度计和微热陀螺仪进行了测试,微热陀螺仪x轴灵敏度为0.107 mV/(°/s),y轴灵敏度为0.102 mV/(°/s),微热加速度计灵敏度为13 mV/g。通过一次工艺流程制备出两种热流体惯性传感器,极大地缩短了制备时间,降低了制备成本,成功实现了高精度的批量生产。

The sensing chip structures of the micro-thermal accelerometer and the micro-thermal gyroscope are similar,and the preparation processes are completely compatible.The microthermal gyroscope sensing chip and micro-thermal accelerometer sensing chip were simultaneously prepared on the same silicon on insulator(SOI)substrate using the same process flow.In order to accurately create microscale patterns and structures,four photolithography masks were designed to fabricate the micro-thermal accelerometer chip and micro-thermal gyroscope chip,corresponding to the contact hole openings,thermistors,interconnect wiring and back cavity,respectively.The controllable resistance temperature coefficient(TCR)of lightly doped silicon thermistors is greater than that of traditional metal wires.Therefore,p-type silicon was chosen as the material for the thermistor.The TCR is determined by the doping concentration of the silicon wafer.Three silicon wafers with different doping concentrations were used for comparative experiments,and the doping concentration of the silicon wafer is selected as 1×10^(17)cm^(-3),and the corresponding TCR is 3500×10^(6)/℃.Choosing SOI as the substrate material significantly enhances the high temperature resistant of micro-thermal gyroscopes and micro-thermal accelerometers and improves their sensitivities.In the inductively coupled plasmareactive ion etching(ICP-RIE)and HF steam processes,very thin and fragile thermistors were successfully protected by the photoresist and polyimide layers.Up to 180 micro-thermal gyroscope sensing chips and 108 micro-thermal accelerometer sensing chips can be successfully fabricated at one time on the 4-inch(1 inch=2.54 cm)SOI substrate.The size of the fabricated micro-thermal accelerometer sensing chip is 2 mm×2 mm×0.4 mm,and the size of the microthermal gyroscope sensing chip is 5.8 mm×5.8 mm×0.4 mm.Tests were conducted on the prepared micro-thermal accelerometers and micro-thermal gyroscopes,respectively.The sensitivity of the micro-thermal gyroscope on the x-axis is 0.107 mV/(°/s),the sensitivity on the y-axis is 0.102 mV/(°/s),and the sensitivity of the micro-thermal accelerometer is 13 mV/g.Two types of thermal fluid inertial sensors were prepared through a process flow,which greatly shortened the preparation time,reduced preparation costs and successfully achieved high-precision batch production.