Fracture analysis of anodically bonded silicon substrates during the CMP process

In this paper, a stress and fracture study, occurring during the chemical mechanical polishing (CMP) of anodically bonded substrates is presented. The samples contain glass pillars, used to form the glass cavities and a silicon substrate sealing the glass structure, the samples are fabricated using the anodic bonding process. The mechanical stresses of the bonded silicon substrate are simulated using the COMSOL software. The fracture strength after post-processing is investigated based on the criterion value, which is the ratio of the anodically bonded area over the cavity area. It is found that the bonded area and the distribution of pillars are related to the mechanical stability of the bonded substrate during the CMP process. Studies on the stability of subsequent processes, like CMP after anodic bonding, plays an important role in improving the fabrication yield of anodic bonded devices.