Thin-film bandpass filter and manufacturing method thereof

Abstract

A thin-film bandpass filter is provided. The thin-film bandpass filter includes a substrate, a plurality of first capacitors formed on the substrate, each being electrically connected in series, at least one second capacitor electrically connected to branch terminals positioned between the plurality of first capacitors, an inductor electrically connected in parallel to the second capacitor, and a plurality of supports for propping up the inductor so that the inductor is separated a predetermined space above the substrate and/or the second capacitor. The first and second capacitors, respectively, include a first metal layer, a dielectric layer, and a second metal layer, all of which are sequentially formed on the substrate. The inductor is comprised of a predetermined pattern of a thin-film metal layer propped by the plurality of supports, to both ends of which are electrically connected to the first and second metal layers of the second capacitor, and suspended by the substrate and/or the second capacitor. Due to a structure in which the inductor is suspended by the substrate and/or the capacitor that the thin-film bandpass filter has, the parasitic capacitance can be minimized, thereby enhancing the Q factor and minimizing the insertion loss of the filter. Furthermore, the overall size of the filter is significantly reduced by forming at least a portion of an inductor on the capacitor.