Thick THB sacrificial layer and metal encapsulation process

Here, THB as a sacrificial layer has been characterized and used to develop a metal encapsulating process. The idea in combination with conventional thin film processes is vey helpful for thick monolithic wafer-level packaging of RF MEMS devices allowing a vertical space of as large as 100 µm for the devices to freely actuate. In this method, a very thick layer of THB 151N photo resist (100µm) in combination of thin films (1 µm–5 µm) is employed to serve as encapsulation. This thick layer is removed at the end of the process leaving a very spacious cavity. The proposed technique helps in advancing monolithic packaging field and increasing the thickness considerably.