Activation Model of Nano Getter for MEMS Devices Based on Sandwich Structures of Au-Porous Ti-Dense Ti Film

Abstract

Ti-based nano Nonevaporable getters (NEGs) have become essential materials for maintaining a long-term high vacuum in Micro-Electro-Mechanical System (MEMS) devices. However, it is still a confusing issue how to select the annealing temperature and time for the getter activation on the basis of the required activation level, excessive temperature and time will damage the MEMS devices inside the package. Therefore, the relationship between the activation temperature, activation time and activation level gains more attention since it can give guidance for the vacuum packaging process, which currently lacks an effective quantitative model to be followed. This paper introduces a simple and efficacious model for determining the activation parameters according to Fick’s diffusion law and reports a sandwich getter with an ‘Au-Porous Ti-Dense Ti’ structure based on this model to improve the getter performances. Experimental results indicate that ~50% activation level is achieved for a 3mm $\times 3$ mm sandwich-style getter with 2 hours of 300°C annealing, which is expected to enable a high vacuum for a $1\mu $ L microcavity up to 12 years. These results show close agreement with the model, proving to be valuable for optimizing the recipe of getter activation and providing an efficient way to prevent MEMS device failures.[2024-0165]