Micromachining of Pyrex 7740 Glass by Silicon Molding and Vacuum Anodic Bonding

A wafer-level processing technology that is used to precisely fabricate regular arrays of deep cavities in a Pyrex 7740 glass wafer is presented by silicon molding and vacuum anodic bonding. The fabrication process is based on etching cavities in silicon, followed by vacuum anodic bonding of a glass wafer to the etched silicon wafer. The bonded wafers are then heated inside a furnace at a temperature above the softening point of the glass, and the glass is shaped into cavities. The processing parameters are obtained by a series of experiments. The array of square glass cavities with 10-μm side length is accurately fabricated. Finally, a wafer-level hermetic packaging process is demonstrated after the second anodic bonding process. A diced single chip has been tested for leakage rate and bonding strength, which shows that the presented fabrication process is appropriate for the wafer-level packaging of MEMS devices.