Development of AFM tensile test technique for evaluating mechanical properties of sub-micron thick DLC films

• Published in: Journal of microelectromechanical systems Vol. 15; no. 1; pp. 169 - 180
• Main Authors: Isono, Y., Namazu, T., Terayama, N.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Atomic force microscope (AFM); Atomic force microscopy; Atomic measurements; Deposition; Diamond-like carbon; diamond-like carbon (DLC); Diamond-like carbon films; Elastic constants; Exact sciences and technology; Film thickness; Finite element analysis; Force measurement; Fracture strength; Hydrogen; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical factors; Mechanical instruments, equipment and techniques; Mechanical properties; Microelectromechanical devices; Micromechanical devices and systems; nano-indentation test; Physics; Plasma measurements; Poisson's ratio; Poissons ratio; Raman spectroscopy; Spectrum analysis; Studies; Surface cracks; tensile test; Testing; Vacuum apparatus and techniques; Vacuum gauges; Young's modulus; fracture strength; Atomic force microscopy; Surface treatments; Diamond-like carbon; Coatings; Poisson's ratio; Finite element method; Young's modulus; diamond-like carbon (DLC); tensile test; Modelling; Silicon; Ionization level; PECVD; Elastic properties; Microelectromechanical device; Elastic constants; Ruptures; Deformation modulus; Measurement sensor; Tensile tests; Mechanical properties; Mechanical tests; Experimental study; Raman spectroscopy; Layer thickness; Young modulus; Thick film devices; Monocrystals; Poisson ratio; Atomic force microscope (AFM); nano-indentation test
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2005.859196

This paper describes mechanical properties of submicron thick diamond-like carbon (DLC) films used for surface modification in MEMS devices. A new compact tensile tester operating under an atomic force microscope (AFM) is developed to measure Young's modulus, Poisson's ratio and fracture strength of single crystal silicon (SCS) and DLC coated SCS (DLC/SCS) specimens. DLC films with a thickness ranging from 0.11 /spl mu/m to 0.58 /spl mu/m are deposited on 19-/spl mu/m-thick SCS substrate by plasma-enhanced chemical vapor deposition using a hot cathode penning ionization gauge discharge. Young's moduli of the DLC films deposited at bias voltages of -100 V and -300 V are found to be constant at 102 GPa and 121 GPa, respectively, regardless of film thickness. Poisson's ratio of DLC film is also independent of film thickness, whereas fracture strength of DLC/SCS specimens is inversely proportional to thickness. Raman spectroscopy analyses are performed to examine the effect of hydrogen content in DLC films on elastic properties. Raman spectra reveal that a reduction in hydrogen content in the films leads to better elastic properties. Finally, the proposed evaluation techniques are shown to be applicable to sub-micron thick DLC films by finite element analyses.