Design and fabrication of a strain-type scanning probe for atomic force microscopy

Po Lun Cheng*, Cheng Chang Lee, Wen-Syang Hsu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

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 scanning probe for atomic force microscopy, which is different from other scanning probe in 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. In the fabrication process, the polysilicon acts as the resistor, and a 5 μm tip is made. The 2 μm thick Si-rich nitride forms the main structure including the 200 μm × 40 μm 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 size of the pyramid apex is about 36 nm. The testing results on resistance change and output voltage show good agreement with simulation results.

Original languageEnglish
Pages (from-to)1-9
Number of pages9
JournalJournal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao
Volume20
Issue number1
StatePublished - 1 Jan 1999

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