Improved coupled resonator filter performance using a carbon-doped oxide de-coupling layer

We describe a newly developed de-coupling material SiOCH for coupled resonator filter applications. The SiOCH films belong to a general class of low-k dielectrics often referred to as carbon-doped oxides (CDO). In this work, CDO replaces SiLK, significantly improving the performance of the resulting filters. In contrast to the spin-on and curing process used to deposit SiLK, the CDO films are deposited using plasma enhanced chemical vapor deposition. The resulting films possess a low acoustic impedance that can be varied over a range greater than 2:1 through a choice of deposition conditions. The new filters possess several key advantages over the SiLK-based devices reported previously, including decreased filter insertion loss, a passband free of spurious notches, and a dramatically lower temperature coefficient of frequency.