Layout optimization techniques for (r_{g}) and, (f_{max}) of Cascode devices for mm wave applications

A common-source cascode device is commonly used in amplifier designs at RF/mmWave frequencies. In addition to intrinsic parasitic components, extrinsic components due to wiring and layout effects, also play an important role towards performance and accurate modelling of the devices. In this work, a comparison of two different layout techniques for cascode devices is presented, to reduce the extrinsic parasitic elements, such as gate resistance. A multi-gate or multi-port layout technique is proposed for optimizing the gate resistance \(r_{g}\). Two separate structures are designed and fabricated using 45nm CMOS SOI technology. Extracted values from measurement results show reduction of 10% in \(r_{g}\) of multi-gate layout technique compared to a conventional gate-above-device layout for cascode devices. However, conventional layout exhibits smaller gate to source and gate-to-drain capacitances which leads to better performance in terms of speed, i.e. \(f_{max}\).