A new approach to fabricate deep cavities in Pyrex7740 glass for vacuum packaging of sensors

In the field of manufacturing of micro-system, the Pyrex7740 glass is a widely-used material since its coefficient of thermal expansion is similar to that of silicon and it has good optical performance for optical sensors and actuators. The use of Pyrex7740 glass is limited by its isotropic etching characteristic. In this paper, a new wafer-level process to precisely fabricate deep cavities on the Pyrex7740 glass is presented. The process is based on the anodic bonding, and the Si substrate is employed as a mold layer to form the shape of the cavity. Finally the cavities were formed by the atmospheric pressure after the special heat treatment. The Pyrex7740 glass substrate with cavities could be used for high density packaging of micro-system by anodic bonding or adhesive bonding, and may also benefit the application in the micro flow channel system. This new micro-machining process could be described as a basic wafer-level process to the MEMS technology.