MOSFET Performance Scaling—Part I: Historical Trends

A simple analytical model that describes MOSFET operation in saturation from subthreshold to strong inversion is used to derive a new formulation of the intrinsic switching delay of the transistor. The proposed model follows the scaling trend of experimental ring-oscillator data better than the conventional CV/I metric. The historical trend of MOSFET performance scaling is examined, and it is shown that the continuous increase of the carrier velocity in the channel has been the main driver for the improved transistor performance with scaling. The dependence of velocity and mobility in recent strain-engineered devices is studied based on published experimental data, and a theory is proposed to justify this dependence. It is shown that the virtual-source velocity depends on low-field mobility more strongly than what was previously believed, in spite of the fact that state-of-the-art MOSFETs operate at 60%-65% of their ballistic limit. These observations will be used in Part II of this paper to explore the tradeoffs between key device parameters in order for the commensurate scaling of the device performance with its dimensional scaling to continue in the future high-performance CMOS generations.