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鄭博倫 (Po-Lun Cheng)
鄭博倫 (Po-Lun Cheng)
Design and Fabrication of A Strain-Type Atomic Force Microscopy
Design and Fabrication of A Strain-Type Atomic Force Microscopy
應變式原子力探測計之設計與製作
應變式原子力探測計之設計與製作
Atomic force microscopy (AFM) is a popular device for inspecting topography of the sample surface. Here we propose a novel process to fabricate a strain-type atomic force microscopy, which is different from other AFM, like the optical, tunneling, and capacitive type. It incorporates strain gauge and Wheatstone bridge circuit into the cantilever with a sensing tip. In this design, the tip is fabricated on the bottom of the cantilever and the gauge circuit is fabricated on the top of the cantilever.
Atomic force microscopy (AFM) is a popular device for inspecting topography of the sample surface. Here we propose a novel process to fabricate a strain-type atomic force microscopy, which is different from other AFM, like the optical, tunneling, and capacitive type. It incorporates strain gauge and Wheatstone bridge circuit into the cantilever with a sensing tip. In this design, the tip is fabricated on the bottom of the cantilever and the gauge circuit is fabricated on the top of the cantilever.
First the analytical expressions of the strain and the deflection of the cantilever beam are derived and verified by the finite element method. We also perform sensitivity analysis in the resistance design. Then the gauge circuit using Wheatstone bridge is analyzed to compensate temperature effect. Finally the relation of the deflection of the cantilever beam and output voltage is obtained.
First the analytical expressions of the strain and the deflection of the cantilever beam are derived and verified by the finite element method. We also perform sensitivity analysis in the resistance design. Then the gauge circuit using Wheatstone bridge is analyzed to compensate temperature effect. Finally the relation of the deflection of the cantilever beam and output voltage is obtained.
In the fabrication process, the polysilicon acts as the resistor, and a 5μm tip is made. The 2μm thick Si-rich nitride forms the main structure including the 200μm×40μm cantilever beam, which is fabricated by etching the silicon from the back side of the wafer. In the back etching process, the thinner Si3N4 is shown to be able to protect the strain gauge on the front side. The testing results on resistance change and output voltage show good agreement with simulation results.
In the fabrication process, the polysilicon acts as the resistor, and a 5μm tip is made. The 2μm thick Si-rich nitride forms the main structure including the 200μm×40μm cantilever beam, which is fabricated by etching the silicon from the back side of the wafer. In the back etching process, the thinner Si3N4 is shown to be able to protect the strain gauge on the front side. The testing results on resistance change and output voltage show good agreement with simulation results.
[1] P.-L. Cheng, C.-I. Liao, H.-R. Wu, Y.-C. Chen, C.-C. Chien, C.-L. Yang, S.-F. Tzou, J. Tang, R. Kodali, L. Washington, Y. Cho, V.-C. Chang, T. Fu, and W. Hsu, "Effective surface treatments for selective epitaxial SiGe growth in locally strained pMOSFETs." Journal of Semiconductor Science and Technology 2007, 22, 140-143.
[2] P.-L. Cheng, C.-I. Liao, C.-C. Chien, C.-L. Yang, S.-F. Ting, L.-S. Jeng, C.-T. Huang, O. Cheng, S.-F. Tzou, W. Hsu, "Effectiveness of Si thin buffer layer for selective SiGe epitaxial growth in recessed source and drain for pMOS." Materials Chemistry and Physics 2008, 107, 471-475.
[2] P.-L. Cheng, C.-I. Liao, C.-C. Chien, C.-L. Yang, S.-F. Ting, L.-S. Jeng, C.-T. Huang, O. Cheng, S.-F. Tzou, W. Hsu, "Effectiveness of Si thin buffer layer for selective SiGe epitaxial growth in recessed source and drain for pMOS." Materials Chemistry and Physics 2008, 107, 471-475.
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