Characterization of the activation of yttrium-based getter films by electrical measurements and ion-beam analyses

Gettering properties of thin films of pure yttrium and yttrium-based alloys have been studied for application to MEMS vacuum packaging at the wafer level. Thin films of Y, Zr-Y, Ti-Y and V-Y were co-evaporated under ultra-high vacuum. It is demonstrated that the sheet resistance measured by 4-probes technique before and after activation at 250°C gives a good estimation of the oxygen sorption ability determined by NRA. Pure yttrium has been found to be highly reactive after deposition (sheet resistance increases by 40% after 1 month in air) but poorly efficient in oxygen trapping after activation. Conversely, the sorption ability of Y-V, Y-Zr and Y-Ti alloys is extremely high and increases with the yttrium content in the film. The bests results for sorption are obtained with Y-V (2.7 1022 atom/cm3 for Y44V56).