2 The scaling of MOSFETs, Moore's law, and ITRS

The scaling of MOSFETs, Moore’s law, and ITRS Chapter 22.4 Chapter SummaryIn this chapter we have reviewed Moore’s law and the International TechnologyRoadmap for Semiconductor Technology. Both Moore’s law and the ITRS have playeda significant role in the advancement of the CMOS technology. In particular the roadmap has been an important guiding document that gives the direction for research anddevelopment for next generation devices. Apart from their role as a driving force behindthe development of semiconductor technology as a whole, our emphasis was on theirinfluence on MOSFETs scalingThe two most important scaling rules, ‘constant field’ and the ‘generalisedscaling,’ have been discussed in detail. Based on the physical properties of shortchannel MOSFETs, the generalised scaling rule has been adopted for this work. It takesinto account the 2D properties of the electric field and the retarded reduction of thesupply voltage during the scaling process.The limiting factors that hinder the progress of MOSFET scaling have also beendiscussed. Application dependant power constraints (including the leakage currents), theintrinsic parameter fluctuations, and the issue of the reliability of ultra-thin gatedielectric material are among the major scaling limiting factors that jeopardise Moore’slaw in the near future.The main ultimate limitation to the scaling of transistors is the atomic structureof matter. A MOSFET cannot be smaller than an atom. The transistor post 2025,according to the IBM roadmap, will be reaching these limitations.In the next chapter the simulation strategy and overall methodology used toinvestigate the scaling and intrinsic parameter fluctuation in nano CMOS devices arepresented.39