Failure analysis from microcracks to a dominant crack in MEMS thin films using combined damage and fracture mechanics

Reliability issues in MEMS devices are generally rooted in the evolution of microdefects in materials. Although the failure occurs at the top level of the device (macroscopic function), the root cause of the functional failure can be traced back to the bottom level (material micro defects). Therefore, it is crucial to consider the influence of material damage in the stress-strain constitutive equations to calculate the magnitude of crack propagation force. In this paper, a combined method of damage and fracture is considered for calculating the stress of crack tip of MEMS thin films. To calculate the initiations and growths of microcracks, continuum damage mechanics (CDM) is used. Based on the CDM method, a relationship between material degradation and the increase of electrical resistance is established. Through the established computational methods, we can perform a calculation analysis on the failure of MEMS caused by cracks. A multiscale quantification result establishes pairwise connections between material degradation characterization (damage D), crack propagation (tip stress K), and macroscopic performance (resistance R). This article provides a valuable theoretical basis for investigating the failure mechanisms of MEMS.