Tensor‐resolved stress analysis in silicon MEMS device by polarized Raman spectroscopy

Abstract

AbstractA polarized Raman method is described to measure the tensor elements of the residual stress state (induced upon fabrication) in a thin silicon plate, a suspended structure belonging to the test element group (TEG) chip of a microelectromechanical system (MEMS). The residual stress data experimentally retrieved by the Raman methodology are compared to those calculated according to a finite element model (FEM) of the MEMS. While FEM required the input of the thermal history experienced by the suspended bridge silicon structure, experimental Raman data directly revealed the stress tensor components without any assumption needed. An improved analytical procedure is shown that enables retrieving individual stress tensor components from polarized Raman light. Tensor‐resolved Raman analysis, capable of de‐coupling the hydrostatic and the deviatoric parts of the stress tensor, represents a key‐point in rationalizing the role of thermal history as well as of other processing parameters on the development of internal stress in MEMS devices made of silicon.