Fabrication of low cost spherical alkali atom vapor cells by combining a low temperature anodic bonding and a Chemical Foaming Process (CFP)

Abstract

In this presentation, a novel fabrication process, based on our previous research [4-5], used to manufacture spherical alkali atom vapor cells for miniaturized atomic clock application will be presented, allowing low-cost wafer level batch fabrication and assembly. This method combines low temperature anodic bonding technique and Chemical Foaming Process (CFP) for producing spherical alkali atom vapor cells. The Rb (Rubidium) vapor cell, which consists of two cavities, has been carefully designed. The smaller one which taken as reaction chamber connected to the larger one which served as a working chamber with micro-channel can prevent reactant from entering into working chamber improves the purity of Rb in the working chamber. The fabrication is based on UV laser equipment, and then a thin Pyrex7740 glass wafer is anodic bonded to the patterned silicon wafer. Subsequently, the bonded wafer is heated over the softening point of the glass (Tg=821°C) and hydrogen gas released by TiH2 blowing the glass into spherical shells. During this process the reaction take place and produce rubidium vapor which through microchannel to enter working chamber. The Rb vapor cell is characterized by EDS (Energy Dispersive Spectroscopy) and ultraviolet spectrophotometer. Results show that during fabrication process the rubidium produced and Rb vapor cell is fabricated successfully.