ABSTRACT
The invention of the transistor in 1947 represented the starting point for a fast-paced development of semiconductor technology, thus setting the grounds for the electronics industry toward continuously improved functionalities. Related technological progress supported a steady trend toward more and more compact and complex integrated circuits, which has been achieved, in particular, by the reduction of transistor’s critical dimensions, as predicted by Moore’s law.1 Recently, however, it can be foreseen that fundamental limitations will seriously hinder further device miniaturization. In fact, today, commercial transistors have channel dimensions on the
8.1 Introduction .................................................................................................. 181 8.1.1Role of Discrete Dopants in Scaled-Down Devices ......................... 181 8.1.2 Doping Techniques for Nanoscale Devices ...................................... 183
8.1.2.1Uncontrolled (Random) Doping ........................................ 184 8.1.2.2 Controlled Doping ............................................................. 185
8.1.3 Guidelines for Dopant-Atom Devices............................................... 186 8.2Observation of Individual Dopants by LT-KPFM ........................................ 187
8.2.1 Techniques for Dopant Detection ..................................................... 187 8.2.2KPFM Setup for Dopant Detection in Devices under Normal
Operation .......................................................................................... 189 8.2.3 Observation of Individual Dopant Potentials and
Single-Electron Charging ................................................................. 189 8.2.4 Correlation with Electrical Characteristics ...................................... 191
8.3Single-Electron Tunneling via Dopants in Nanoscale Transistors ............... 193 8.3.1 Tunneling via Individual Dopants in Nanoscale Transistors ............ 193 8.3.2 Effect of Channel Pattern and Dielectric Confinement on the
Properties of Individual Dopants...................................................... 194 8.3.3Interacting Dopants in Silicon Nanotransistors ................................ 198
8.4 Conclusions ................................................................................................... 201 Acknowledgments ..................................................................................................202 References ..............................................................................................................202
order of 10-20 nanometers. At such a small scale, fluctuations of device fabrication become significant and pose serious concerns in terms of device yield for industrial applications. Among such fluctuations, uncontrollability in dopant distribution starts to be dominant. The diagram shown in Figure 8.1 illustrates the role of individual dopants in different aspects of research.
