Microfluidic platforms realized by micromachining and anodic bonding of Si and glass substrates

Presented work focuses mainly on issues accompanied with defect free anodic bonding of multilayer glass-Si-glass microfluidic structures. The problems associated with prefabricated structures which included micromachined or patterned topography on one or both of the mating surfaces and bonding to SiO₂ terminated Si were investigated. In this study, Pyrex 7740 and Borofloat 33 glass wafers were bonded to bare Si and Si/SiO₂ terminated structures in the temperature range 350-400°C in the air ambient under applied anodic voltages between 800-1200V. Appropriate configuration of bonding electrodes was found mandatory to avoid debonding effects in multilayer bonding process. Wet etching of glass was used to fabricate microchannels and recessed structures in glass, which were subsequently anodically bonded to the cover glass via different intermediate layers. Thin intermediate Al layer was found to provide very uniform and stable bond between two glass wafers.