New release technique of a thick sacrificial layer and residue effects on novel half-coaxial transmission line filters

Abstract

This paper presents a new release technique for efficient and complete removal of the thick sacrificial layer applicable to surface-micromachined devices and compares this with other conventional release methods. A fully surface-micromachined half-coaxial transmission line filter having a large air-filled gap of 100 mu m in thickness is successfully demonstrated using the proposed release technique. The effects of the sacrificial layer residue on the RF responses of the filters, completed by a conventional oxygen plasma ashing process, are analyzed with the aid of x-ray photoelectron spectroscopy (XPS). Experiments show that the proposed new release technique makes it possible to completely remove the thick sacrificial layer, shorten the process time, increase the after-fabrication yield and improve the process reproducibility of the large air-filled gap filters compared to the conventional oxygen plasma ashing method.