Micromachined 50 GHz/60 GHz Phi filters by CMOS compatible ICP deep trench technology

Micromachined 50 and 60 GHz millimeter-wave filters were implemented by using a 0.18 μm CMOS technology. The CMOS-compatible inductively coupled-plasma (ICP) deep trench technology is used to selectively remove the silicon underneath the filters completely, and so the substrate loss of the filters can be significantly reduced. The results show that 3.2, 2.6, and 2.1. dB improvements in S₁₁, S₂₁, and G_Amax, respectively, are achieved for the 60 GHz filter after the backside ICP etching. Besides, for the 50 GHz filter, a 295.8% (from 9.6 to 38) improvement in Q-factor of its inductors is achieved. These results show that the backside ICP etching is effective to reduce the substrate loss and parasitic capacitance in the millimeter-wave frequency bands, and hence is very promising for millimeter-wave CMOS RFIC applications.