Processing vs. Properties of MEMS

Post processing conditions of MEMS structures are very important for device reliability and mechanical properties. Depending on the processing conditions, intergranular or transgranular fracture may occur (see images of delaminated MEMS samples and intergranualr failure).

Images should not be adopted or used without the explicit permission by this group

We have shown that the mechanical strength of MUMPS polysilcion decreases by 0.1 GPa for very minute of exposure in 49% HF. (See plot.)

Locally inhomogenous deformations occur because the film surface integrity is compromised by HF. The local deformations in figure are due to loosely held grains after the grain boundaries were attacked by HF.

RELEVANT PUBLICATIONS

  1. I. Chasiotis, W.G. Knauss, "The Mechanical Strength of Polysilicon Films: 1. The Influence of  Fabrication Governed Surface Conditions", J. of the Mechanics and Physics of Solids 51 (8) pp. 1533-1550, (2003).
     
  2. I. Chasiotis, and W.G. Knauss, "Experimentation at the Micron- Submicron Scale", Comprehensive Structural Integrity Vol. 8. Interfacial and Nanoscale Failure. Volume Editors: W. Gerberich and W. Yang, Elsevier Science, pp. 41-87, (2003).

College of Engineering   University of Illinois at Urbana-Champaign