NOISE AND SENSITIVITY IN POLYSILICON PIEZORESISTIVE CANTILEVERS
Yu Xiao-mei (于晓梅)a, Jiang Xing-liu (江兴流)a, J. Thaysenb, O. Hansenb, A. Boisenb
a Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100083, China; b Mikroelektronik Centret, Bldg.345 E, Technical University of Denmark, DK-2800, Lyngby, Denmark
Abstract Piezoresistive cantilevers with dimensions of 200×50×1.8μm3 have been fabricated from polycrystalline silicon using reactive ion etching (RIE) and back etching processes. Full Wheatstone bridges have been designed symmetrically on-chip, with two resistors placed on the cantilevers and two resistors on the substrate. The differential measurements of the two cantilevers can reduce the thermal shift of the signal in the system and the external noise in the laboratory. The characteristics of the fabricated cantilevers have been analysed by measuring the noise and the sensitivity. The measured noise spectra show that the 1/f noise is the dominant noise source at low frequencies. With the linear relation between 1/f noise and bias voltages, the Hooge factor ($\alpha$) was calculated to be 0.0067. The 1/f noise was explained in terms of a lattice scattering model, which occurs in the depletion region of the grains. The displacement sensitivity of the cantilevers $(\frac{\Delta R}{R}z^{-1})$ was calculated to be 1×10-6nm-1 by measuring the resistance change and the vertical deflection of the cantilever. The gauge factor of the piezoresistive cantilever was calculated to be 19. At a 3 V bias voltage and 1000 Hz measurement bandwidth, 1 nm of minimum detectable deflection has been obtained.
Received: 30 March 2001
Revised: 09 May 2001
Accepted manuscript online:
PACS:
84.32.Ff
(Conductors, resistors (including thermistors, varistors, and photoresistors))
Fund: Project supported by the Foundation of State Overseas Scholarship Council of China.
Cite this article:
Yu Xiao-mei (于晓梅), Jiang Xing-liu (江兴流), J. Thaysen, O. Hansen, A. Boisen NOISE AND SENSITIVITY IN POLYSILICON PIEZORESISTIVE CANTILEVERS 2001 Chinese Physics 10 918
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