Transmission Electron Microscopy in Micro-nanoelectronics

Chapter 6

Interdiffusion and Chemical Reaction at Interfaces by TEM/EELS

6.1. Introduction

The purpose of this chapter is to show how research on interdiffusion and chemical reactions in thin films and their interface with semiconductor substrates can be conducted using the transmission electron microscopy (TEM) based method and their coupling with electron energy-loss spectroscopy (EELS). Analytical TEMs commonly installed nowadays in most materials science laboratories are mainly considered in this study. The discussion will be illustrated in the context of the developments of new gate oxides (commonly called high-k or HK) for the replacement of SiO₂ in metal oxide semiconductor field-effect transistors (MOSFETs). Literature data from HfO₂, which is already integrated in MOSFET production since end of 2007 [BOH 07] and of rare earth-based oxides (REO), will be particularly discussed together with results obtained at CEMES.

6.2. Importance of interfaces in MOSFETs

For several decades, the microelectronics industry succeeded in reducing the size of the components with an outstanding efficiency and regularity. The gate length of the key component, the MOSFETs, has scaled down from several microns in 1971 to some tens of nanometers nowadays. The Si/SiO₂ couple, the heart of microelectronics devices, was the chosen ally for the successful scaling because it is a system that presents several intrinsic qualities unrivaled to date. First, an amorphous SiO₂ layer can be thermally grown ...