Atomic Layer Deposition

Atomic layer deposition (ALD) for thin film deposition is one of the most important techniques that is enabling the continuous miniaturization of semiconductor devices. ALD film growth is obtained by repeating a sequence of two or more self-limiting surface reactions wherein the respective reactants are periodically introduced onto the substrate with intermediate reactor purging. The self-limiting nature of ALD reactions provides a precise sub-nanometer control over deposition thickness. Uniform distribution of surface active sites ensures that the introduced reactants uniformly react on the entire substrate surface including any non-planar features, hence ALD provides excellent thickness uniformity and step coverage. In ALD process development, the selection of reactants and deposition cycle parameters are made based on the thermodynamics and kinetics of the involved surface reactions. This chapter provides a brief survey on the present status of ALD in semiconductor device fabrication, and outlines few of the major challenges in the application of ALD in large-volume fabrication.