Micromachined 22 GHz PI filter by CMOS compatible ICP deep trench technology

A K-band second-order bandpass filter with planar inductive pi-network using CMOS technology is demonstrated for the first time. To reduce the substrate loss of the filter, the CMOS process compatible backside inductively-coupled-plasma (ICP) deep trench technology is used to selectively remove the silicon underneath the filter. After the ICP etching, a 55.5-92.2% improvement in quality factor is achieved for the inductors in the filter. In addition, a 1.1 dB improvement in maximum available power gain (G_Amax) in K-band is achieved for the filter after the ICP etching. These results show that the micromachined pi (PI) filter is very promising for microwave/millimetre-wave RFIC applications