Microwave Characteristics of Thin-Film Passivation on Ceramic Substrate by Using DC Reactive Magnetron Sputtering

This paper presents a novel method to change the dielectric constant and enhance the average power-handling capability (APHC) to a thin-film coplanar waveguide (CPW) line through dc reactive magnetron sputtering. This paper discusses the effects of material properties, microwave characteristics, and APHC on the thin-film CPW line. An aluminum nitride (AlN) thin film can be deposited on the surface of a ceramic substrate to provide a substrate with a smooth surface. Using the proposed thin-film passivation on the ceramic substrate can effectively improve the thermal conductivity and enhance the APHC of a thin-film CPW line. In a physical experiment, a thin-film CPW line with a 3-μm-thick AlN thin film was deposited on a 1000-μm-thick ceramic substrate. Microwave losses (including conductor loss α
_c
(f) and dielectric loss α
_d
(f)) dielectric constant and APHC were extracted from S-parameters that were measured up to 10 GHz. The method can be applied in ceramic fabrication processes, particularly in low-temperature cofired ceramic techniques.