Crystal Orientation and Specimen Size Dependences of Creep Properties of Micron-Thick Silicon for 3d Microstructured Mems

This study clarified the crystal orientation dependence of steady-state creep properties at elevated temperatures for 5 μm-thick single-crystal silicon (Si) films by punch creep-forming tests and their finite element analyses (FEA), for designing three-dimensional (3D) microstructured MEMS. The creep coefficient, α, and the creep exponent, ß, in the power-law creep constitutive equation [1] were quantitatively evaluated for Si films with {100}, {111}, and {110} surfaces at temperatures ranging from 1223 K to 1323 K. The crystal orientation dependence of the creep activation energy, Q, could be caused by the size of the activation area of dislocation in each specimen. There was also a specimen size dependence of the creep deformation behavior of Si since the frequency factor of dislocation slip differs between micron- and sub-millimeter-thick Si specimens.