Transmission Electron Microscopy in Micro-nanoelectronics

Chapter 1

Active Dopant Profiling in the TEM by Off-Axis Electron Holography

1.1. Introduction

Electron holography is a powerful transmission electron microscopy (TEM)-based technique that can be used to measure the phase change of an electron wave that has passed through a region of interest compared to the phase of an electron wave that has passed through only a vacuum. As the phase of an electron is sensitive to the magnetic, electrostatic and strain fields that can be found in and around a specimen, electron holography is a unique method that can be used to recover all of these properties with nanometer-scale resolution. The electrostatic potential in semiconductor materials is modified by the presence of active dopants. At this time, when only a few dopant atoms can affect the properties of an electronic device, electron holography provides a unique opportunity to look inside these devices and to learn about the activity of the dopant atoms. Characterization techniques such as secondary ion mass spectrometry and atom probe tomography cannot differentiate between active and inactive dopants. Other techniques such as scanning capacitance microscopy and scanning spreading resistance microscopy, which are capable of measuring the active dopants at the surface of specimens, may well have problems adapting to the latest generations of semiconductor materials that can consist of doped nanowires and three-dimensional structures. Therefore, electron holography is unique in that it ...