CMOS RF circuit design and reliability for wireless communications

Front-end circuits are the most difficult to be designed in wireless transceivers. They determine the selectivity and the sensitivity of the transceiver. With the explosive growth of the wireless communication market and the continuous increase of the working frequency, the front-end RF circuit design is becoming a big challenge for wireless communications. As CMOS technology advances, fully integrated CMOS transceivers are possible.; As CMOS device sizes shrink, the channel electric field becomes higher and the hot carrier (HC) effect becomes more significant. When the oxide is scaled down to less than 5 nm, soft-breakdown (SBD) often takes place. As a result, oxide trapping and interface generation cause long term performance drift and related reliability problems in devices and circuits.; The RF front-end circuits include low noise amplifier (LNA), local oscillator (LO) and mixer. It is desirable for a LNA to achieve high gain with low noise figure, a LO to generate low noise signal with sufficient output power, wide tuning range, and high stability, and a mixer to up-convert or down-convert the signal with good linearity. However, the RF front-end circuit performance is very sensitive to the variation of device parameters. The experimental results show that device performance is degraded significantly subject to HC stress and SBD. Therefore, RF front-end performance is degraded by HC and SBD effects.; This dissertation focuses on the following aspects: (1) The methodologies for evaluating RF circuit reliability have been proposed. The device performance drifts due to HC and SBD are examined experimentally by measuring threshold voltage, mobility and transconductance before and after stress for 0.16 μm CMOS technology. And then the aged model files are used to simulate RF circuit degradations. (2) VCO performance degradations due to HC and SBD effects will be studied systematically. Analytical equations for phase noise and timing jitter in terms of main circuit parameters will be derived and be used to predict the VCO performance degradations. Comparison between analytical prediction and SpectraRF simulation results is given. (3) LNA performance degradations due to HC and SBD are studied. Analytical equations of noise figure for different LNA structures are derived. (4) Design techniques for improving RF front-end circuit stability are proposed and verified.