Collapse of microchannels during anodic bonding: Theory and experiments

By fabricating a large number of microchannels with different aspect ratios using anodic bonding, we demonstrate that a channel collapse can occur during anodic bonding as a result of the high electric field inside the channels. A theory is developed to establish a criterion for the collapse. This theory shows that the collapse can be avoided as long as the condition εaV2a/Eeffd3<1 is satisfied, where εa is the permittivity of air, V is the applied voltage for anodic bonding, Eeff is a material constant which characterizes the elastic stiffness of the materials, a is the half width of the channel, and d is the channel depth. The validity of this theory is checked by comparing with experimental results.