Investigation of Vapor HF Sacrificial Etching Characteristics Through Submicron Release Holes for Wafer-Level Vacuum Packaging Based on Silicon Migration Seal

Vapor hydrogen fluoride (vHF) sacrificial SiO
₂
etching is a crucial process for wafer-level packaging based on silicon migration seal (SMS) technology. In this study, by using test samples with several kinds of test patterns and structures, the characteristics of vHF etching through release holes with a diameter of
$0.5 \mu \text{m}$
were investigated. The results showed that through-hole etch rate had some dependence on the number and distribution of release holes, distance from the release holes, and dimension of sealed cavity, which is much different from normal vHF etching. The stiction problem in such a special case was also tested by releasing cantilever structures of different length. They were more likely to bend during through-hole etching than during normal etching. This work 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. [2023-0065]