Bandpass and bandstop filters using CMOS-compatible micromachined edge-suspended coplanar waveguides

This paper reports the on-chip CPW transmission lines and microwave filters fabricated on CMOS-grade silicon substrates using micromachined edge-suspended CPW structures. A full wave simulation of the electromagnetic (EM) fields distribution in the CPW structures reveals that at high frequency most of the fields are concentrated in the areas along and underneath the edges of the metal lines. The CPW´s and CPW-based filters´ performance can be greatly improved after we remove the lossy silicon in these parts. Moreover, the silicon under the center of the metal lines is kept untouched to provide strong mechanical support to the filters, eliminating the need for high-cost MEMS packaging techniques. A bandpass filter with a passband insertion loss of -3.5dB and a bandstop filter with stopband insertion loss -17.5dB are demonstrated in this work.