摘要
从理论和实验上系统地讨论了压阻输出微传感器的噪声 .选用了单晶硅、非晶硅、多晶硅和微晶硅四种材料作为压阻材料 ,设计了 16种不同尺寸的力敏 Wheastone电桥 ,并对器件分别进行了两种不同浓度的掺杂和两种不同条件的退火 ,共获得 2 5 6种压阻输出的微传感器 .测量所有器件的噪声 ,并对噪声谱进行理论分析 ,实验结果表明单晶硅具有最低的 1/ f 噪声和 Hooge因子 (α)的值 ,而非晶硅略好于微晶硅和多晶硅 .几何尺寸大的力敏电阻具有低的 1/ f 噪声 ,但 α值不受器件尺寸的影响 .掺杂浓度增加 10倍时 ,不同器件的 1/ f 噪声降低介于35 %— 5 0 %之间 .相比 95 0℃、10 m in退火条件 ,10 5 0℃、30 m in的高温长时间退火的器件 ,其 1/ f 噪声降低约 6 5 % .
1/f noise is investigated in silicon-based piezoresistive microsensors as a function of the geometry and material of the pizeoresistors.A series of differently sized piezoresistive Wheastone bridges have been fabricated using single crystal silicon,LPCVD amorphous silicon,LPCVD poly-crystalline silicon and LPCVD micro-crystalline silicon as piezoresistive layers.The resistor layers are boron ion-implanted with two different doping doses,and then annealed at two different temperatures.The measurement results show that single crystal silicon is the best material for low noise microsensor.Compared with LPCVD piezoresistive devices,the Hooge factor (α) of single crystal silicon can be reduced more than two magnitude orders.Among the three LPCVD silicon materials,amorphous silicon is a little better than the other two LPCVD piezoresistive materials.The α value is independent of the device geometry though the bigger sized resistors have lower 1/f noise.The 1/f noise will be decreased 35%-50% if the doping dose increases 10 times.But the α values keep unchanged for the piezoresistive devices of different doping concentrations.That means the 1/f noise arises from lattice scattering,but not from impurity scattering for the piezoresistors.Compared with 950℃ 10min annealing,1050℃ 30min annealing decreases noise level about 65%.
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