MEMS Thin-Film Vacuum Package Utilizing Glow Discharge Getter

This work demonstrates a thin-film encapsulated MEMS package integrated with a low-temperature plasma getter on the package lid. The thin-film encapsulated package was fabricated using anodized porous alumina as a capping layer and PECVD silicon dioxide as the sacrificial layer. A Silicon Pirani gauge was used to monitor the pressure changes inside the sealed cavity. The two titanium-gold film electrodes were separated by ∼300 μm and placed above the capping layer. The package was sealed at 50 μTorr pressure using evaporated aluminum oxide. A glow discharge is formed in the cavity when a voltage >800V is applied at room temperature. The sputtered titanium from the discharge reacts with available reactive gas molecules and reduces the vacuum of the micro package. After the glow discharge getter activation, a decrease in the pressure of 50 μTorr from 2 μTorr was observed for the volume of 1.65x10-6cm3. The pressure in the micro package might be below the reported one since the limiting sensitivity of the MEMS Pirani gauge. The use of a glow discharge getter integrated with the package saves device space as well as avoids the use of high voltages near the device. EDX results indicate that the sputtered material is not deposited underneath the wafer.