Wafer level sealing characterization method using Si micro cantilevers

Abstract

In this study, a wafer level sealing characterization method using the pressure dependence of the mechanical quality factor of Si micro cantilevers has been developed. Since the equation for design of a cantilever near fixed walls in free molecular flow regime has not been derived, a new equation has been proposed. We determine that the minimum measurable pressure necessary for the characterization of MEMS sealing is 0.1 Pa, and the suitable sensor type is the resonant type using the optical measurement method. The devices are fabricated from silicon-on-insulator (SOI) and pyrex glass wafers and have many cavities in which there are three cantilever structures. A measurable pressure range of 10 −2 to 10 3 Pa is achieved. The errors in the quality factors calculated by the proposed equation are influenced by the cantilever dimensions; the energy dissipation of the cantilever (180 μm × 40 μm × 5 μm) is calculated with an error of less than 22%.