Optimization of etch-hole design for the thin film packaging

Abstract

This paper reports the effect of the etch hole size, their distribution on cap layer and their quantity on the release time, down deformation of encapsulation after sealing. Uniform distribution of the etch hole in the centre of cap layer helps in reducing the release time. However, it results in a mass loading. Etch holes distributed at the edge of the Thin Film Encapsulation (TFE) help in protecting of the mass loading. However, it increases the release time of the TFE. So it is required to carefully arrange the etch holes on the cap layer in such way that mass loading on the MEMS device can be avoided and release time can also be minimized. The other aspect of this study is to check the downward deformation after sealing with a function of number of etch holes and their distribution of the cap layer. It is observed that a uniform distribution of etch hole in the cap layer helps in minimizing the stress and downward deformation of the encapsulation after the sealing process. For demonstrating the TFE, amorphous Si and SiO2 were used as a sacrificial layer and the cap layer, respectively. The etching of amorphous-Si (a-Si) sacrificial layer was performed with help of XeF2.