Transmission Electron Microscopy in Micro-nanoelectronics

Chapter 2

Dopant Distribution Quantitative Analysis Using STEM-EELS/EDX Spectroscopy Techniques

2.1. Introduction

2.1.1. Dopant analysis challenges in the silicon industry

As mentioned in the general introduction of this book, the MOS transistor is the key component driving the electronic logic revolution for the last 50 years. However, strong problems can be predicted for MOS with a length less than 20 nm (i.e. four elemental silicon cells). Among the various phenomena, susceptible to limit the MOS, are the instabilities due to the statistical fluctuation of the number of dopant atoms inside small devices [BOI 88, PAC 00, HOE 72, THO 98]. This consideration is of primary importance because, for each new technology node, the definition of the doping architecture is one of the most challenging steps [DEN 74]. For the doped areas optimization, technologists have benefited from a previous knowledge in ions implantation, induced defects distribution, dopant diffusion, interaction with defects, furnace and rapid thermal annealing processes, recrystallization, dopant activation, simulation and electrical tests. Finally, complex doping architecture were always successfully developed pushing the limits of the MOS performances to their maximum. For each generation of technology, the CMOS transistors are smaller but give better switching performances in term of speed and I-on (I-off) currents. During the early developments, it was not possible to detect at the nanometer-scale the dopant ...