Electrical Characterization of Bulk Mosfets in Terms of Backscattering Coefficients

Rumsey, D.W. M.S., Purdue University, December 2001, Electrical Characterization of Bulk MOSFETS in Terms of Backscattering Coefficients. Major Professor: Mark S. Lundstrom As the end of the roadmap for semiconductor devices is approached, channel lengths are shrinking, and drain current demands are remaining high. Current day devices operate in a quasi-ballistic regime. In order to assess device performance and to aid in the design of future devices, it will be necessary to characterize devices in terms of their backscattering coefficients. A brief overview of the ballistic MOSFET theory is presented. The method to calculate a ballistic current vs. voltage curve is presented as well as a discussion of how scattering is accounted for. A technique is presented for extracting the backscattering coefficients from measured data. The technique was first verified using a device simulator then applied to a technology whose target device has a gate length of 0.25 μm. The target NMOS device, for this technology, operates at ~30% of the ballistic limit while the PMOS device operates at about ~20% of the ballistic limit. The relationship the backscattering coefficient has with gate voltage is explored along with the significance of the ballistic channel resistance. Finally the technique presented in this thesis is compared to other techniques which have been published.