Characterization of Vapor HF Sacrificial Etching Through Submicron Relase Holes for Wafer-Level Vacuum Packaging Based on Silicon Migration Seal

Vapor hydrogen fluoride (vHF) sacrificial SiO2 etching is a crucial process for wafer-level packaging based on silicon migration seal (SMS) technology. In this study, the characteristics of vHF etching through release holes with a diameter of 0.5 μm were investigated by using a series of test patterns and structures. The etch rate shows some dependence on the number of release hole array, distance from the release hole, and dimension of sealed cavity. This work also reveals the role of the water as both a by-product and catalyst during through-hole vHF etching. The results of this study provide important design guidelines for SMS-based MEMS packaging as well as other similar vacuum packaging technology and improve the understanding of vHF etching mechanisms.