The vapor cells, which contain the simple substrate of alkali metals, are usually the key part of MEMS atomic devices. Alkali metal is extremely active with oxygen and water, making it incompatible with some necessary MEMS process since the instruments are not oxygen-proof. By using paraffin to packet the simple substrate of alkali metals, rubidium for example, the oxidation and deterioration of the metal can be avoided, making it easier to transfer Alkali metals into the vapor cells. It has also been reported that paraffin can serve as a wall-coating material to improve the Q-factor and the long-term frequency stability of the atomic devices. A mold method of manufacturing the package is introduced along with the related key technologies. Laser beam method and needle mold method are discussed to make blind holes on the paraffin wax layer. Paraffin packages containing rubidium simple substrate has been achieved, ranging from 0.9mm3 to 1.6mm3 in size, with the smallest one containing 0.2μL of rubidium inside. The sealing performance of the package has been tested in a one-month (30 days) test and proves to work well by judging from the color of the sealed metal. A low-temperature anodic bonding process is introduced for the fabrication, and absorption spectrum of the vapor cell is obtained, proving that alkali metal simple substrate has been transferred to the vapor cells.
High quality anti-relaxation coating material for alkali atom vapor cells