A novel approach to fabricate glass micro-objects for MEMS application

A novel foaming process to fabricate wafer-level micro glass objects including bubbles and runners for MEMS packaging was studied. Firstly shallow cavities were wet etched fast on the surface of a silicon wafer. CaCO₃ powders were placed in the silicon cavities. Then the cavities were sealed with a glass wafer by anodic bonding. The bonded wafers were then heated up, and the gas released by CaCO3 foamed the glass into cylindrical channels or spherical bubbles according to the pattern in silicon substrate. Results show that the wafer level glass spherical cavities and glass channels by hot forming process are fabricated successfully. The objects on silicon wafer are from 2000 μ m to 100 μ m in diameter. After hot-forming process the diameter of micro glass spherical objects are approximately from 3500 μ m to 130 μ m in diameter. A theoretical model of the foaming process was discussed as well as the potential applications of the micro glass objects. This process was used to fabricate low-cost micro glass cavities including channels and bubbles with a cylindrical or spherical shape and a smooth internal surface for applications of micro reactors, analytical and bioanalytical applications, and MEMS packaging.