Atomic layer deposition

Atomic layer deposition (ALD), also referred to historically as atomic layer epitaxy, is a vapor-phase deposition technique for preparing ultra-thin films with precise growth control. ALD is currently rapidly evolving, mostly driven by the continuous trend in the miniaturization of electronic devices. In addition, many other innovative technologies are increasingly benefitting from the high-quality thin films. This chapter describes—on an elementary level—the key features of ALD. A standard ALD process scheme is used to discuss the relevant concepts of the technique. Materials that can be deposited by ALD are discussed, including typical precursors and co-reactants that can be used. Several example chemistries, specifically for ALD of Al2O3, HfO2, TiN, and Pt, are presented to illustrate the variety in surface chemistry. ALD reactor types are described and, finally, some cases are addressed to illustrate the virtues and practicalities of ALD that are important to advancing present day and emerging thin-film applications.