Transmission Electron Microscopy in Micro-nanoelectronics

Chapter 7

Characterization of Process-Induced Defects

We cannot think of a book dealing with transmission electron microscopy TEM and microelectronics that did not address the difficult field of “defects”. Defects in crystalline silicon are often detrimental for devices notably affecting dopant diffusion during processing and finally causing leakage. A “good process” is often a process that creates fewer defects than others. In general, defects are created as a “reaction” of the crystals to strong “out-of-equilibrium” conditions generated by the processes used to fabricate the devices. More precisely, they provide a solution to the system to lower its energy, to relax, from a (too) high-energy state toward a lower energy configuration. Thus, it is important to know the crystallographic characteristics of the defects to understand their origin. Knowledge of their characteristics is also required to determine the image contrast rules to which they obey. This is a prerequisite condition to compare, on a quantitative basis, the effect of process options (e.g. annealing conditions) onto their sizes and densities, guiding the search for optimized process conditions. While classical techniques such as “weak-beam dark field” (WBDF) and “Fresnel contrast” imaging have been at the core of defect characterization for decades, new techniques making use of geometric phase analysis (GPA) of high resolution transmission electron microscopy (HRTEM) images or electron holography can provide complementary ...