1/F noise considerations for the design and process optimization of piezoresistive cantilevers

被引:175
作者
Harley, JA [1 ]
Kenny, TW [1 ]
机构
[1] Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA
基金
美国国家科学基金会;
关键词
D O I
10.1109/84.846703
中图分类号
TM [电工技术]; TN [电子技术、通信技术];
学科分类号
0808 ; 0809 ;
摘要
Piezoresistive cantilevers are limited by two major noise sources: Johnson noise, which is independent of frequency, and conductance fluctuation noise, which has a 1/f spectrum. The 1/f fluctuations of piezoresistive cantilevers are shown to vary inversely with the total number of carriers in the piezoresistor, as formulated by Hooge in 1969, Therefore, while 1/f noise is reduced for large heavily doped cantilevers, sensitivity considerations favor thin lightly doped cantilevers. Balancing these conflicting constraints produces optima for many design and processing parameters. For a cantilever with specified spring constant and bandwidth requirements, optima are identified far the beam thickness and Length, and it is shown that the legs should be between 1/3 and 2/3 of the total length with a doping depth that is 1/3 of the beam thickness. Additionally, an optimal doping concentration is identified as a function of the cantilever volume and the measurement bandwidth. Annealing reduces 1/f noise, but causes a loss in sensitivity due to dopant diffusion, and an optimal anneal is computed with a typical diffusion length 10(-6) cm, The analysis, methods, and some of the conclusions of this paper are also applicable to other types of piezoresistive sensors.
引用
收藏
页码:226 / 235
页数:10
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