Evaluation of mechanical properties of Si(001) and SiO2 nanobeams using an atomic force microscope

Sriram Sundararajan and Bharat Bhushan

Computer Microtribology and Contamination Laboratory
The Ohio State University,

206 W. 18th Ave
Columbus, OH 43210-1107, USA

Takahiro Namazu and Yoshitada Isono

Department of Mechanical Engineering
Faculty of Science and Engineering
Ritsumeikan University

1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan

Measurement and evaluation of mechanical properties of micro/nanoscale structures is essential to help address reliability issues in microelectromechanical systems (MEMS). This paper describes a quasi-static bending test of nanometer scale fixed beams with trapezoidal cross section (width ratio of about 1.5) using an atomic force microscope (AFM). This technique is used to evaluate bending strength of beams made from single-crystal silicon [Si(001)] and silicon dioxide (SiO2), with a length of 6 mm, widths ranging from 200 to 800 nm and a thickness of about 255 nm. The Si beams were fabricated from an Si diaphragm by field-enhanced anodization using an AFM followed by wet etching. SiO2 beams were fabricated by thermal oxidation of the Si beams after the final wet etching step. Elastic moduli of the materials are evaluated using the results of the bending tests. The fracture surfaces are observed using an SEM to identify failure modes. Fracture toughness values are also evaluated by fracture mechanics considerations. Effects of length scales and materials on mechanical properties are discussed.