Chemical treatment of getter films on wafers prior to vacuum packaging

The patterned getter film at wafer level has been proven to be the viable technical solution to integrate a getter film in vacuum packaged MEMS. The different MEMS vacuum bonding technologies such as eutectic, direct fusion and anodic bonding guarantee a suitable combination of time and temperature to properly activate the getter film. However, before any MEMS vacuum bonding process it has been discovered that a caustic chemical treatment of the getter film both cleans the film and enhances its performance without measurable degradation of its structural integrity. For example, caustic chemical treatment with SC1 with NH4OH and SC2 with HCl did not affect the morphology and the sorption capacities of the getter film and significantly increased the sorption capacity. The getter film at wafer level can withstand also treatment with a highly aggressive HNO3 process. Therefore, we demonstrated the full compatibility of the getter film towards both temperature and chemical treatment with regards to the activation and capacity of the getter film.