Effect of gate poly-silicon depletion on MOSFET input impedance

• Published in: IEEE microwave and wireless components letters Vol. 16; no. 5; pp. 290 - 292
• Main Authors: Bandi, S.P.R., Washburn, C., Mukund, P.R., Kolnik, J., Paradis, K., Howard, S., Burleson, J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-05-2006; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Depletion; Devices; Electronics; Exact sciences and technology; Frequency measurement; Frequency ranges; Gate depletion effect; Gates; Impedance measurement; Input impedance; input impedance model; Large scale integration; Length measurement; Mathematical models; Microwave and submillimeter wave devices, electron transfer devices; Microwave circuits; Microwaves; MOSFET circuits; MOSFETs; Noise measurement; Quantum capacitance; Radio frequency; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Testing; Input impedance; MOS technology; MOSFET; Frequency dependence; Gate depletion effect; Simulation; Polycrystal; Active component; Microwave transistor; Input output equipment; input impedance model
• ISSN: 1531-1309; 1558-1764
• DOI: 10.1109/LMWC.2006.873454

One of the most challenging problems encountered in developing RF circuits is accurate prediction of MOS behavior at microwave signal and data frequencies. An attempt is made in this work to accurately model the device input impedance for the 1-20-GHz frequency range. The effect of device length and single-leg width on the input impedance is studied with the aid of extensive measured data obtained from devices built in 0.11-μm and 0.18-μm technologies. The measured data illustrates that the device input impedance has a nonlinear frequency dependency. It is also shown that this variation in input impedance is a result of gate poly-silicon depletion, which can be modeled by an external RC network connected at the gate of the device. Excellent agreement between the simulation results and the measured data validates the model in the device active region.