Experimental investigation of MEMS DRIE etching dimensional loss

In this paper, a general approach to evaluate the DRIE etching dimensional loss on a Micro Electro Mechanical (MEM) structure is presented. MEM movable elements are generally fabricated by an anisotropic etching of the structural layer with high aspect ratio. The part to part difference introduced by technological process spreads directly affects the electromechanical response of the devices generating disagreement between simulation model and actual part behaviours. The process variability was evaluated through a set of vibrating test structures in which the flexural elements that define the structural stiffness are shielded by dummy silicon elements of different geometry and number. Results show that the average dimensional loss and the etching reproducibility are directly affected by the local exposed area and etched structure homogeneity.