Very high frequency plasma reactant for atomic layer deposition

Although plasma-enhanced atomic layer deposition (PE-ALD) results in several benefits in the formation of high-k dielectrics, including a low processing temperature and improved film properties compared to conventional thermal ALD, energetic radicals and ions in the plasma cause damage to layer stacks, leading to the deterioration of electrical properties. In this study, the growth characteristics and film properties of PE-ALD Al ₂ O ₃ were investigated using a very-high-frequency (VHF) plasma reactant. Because VHF plasma features a lower electron temperature and higher plasma density than conventional radio frequency (RF) plasma, it has a larger number of less energetic reaction species, such as radicals and ions. VHF PE-ALD Al ₂ O ₃ shows superior physical and electrical properties over RF PE-ALD Al ₂ O ₃ , including high growth per cycle, excellent conformality, low roughness, high dielectric constant, low leakage current, and low interface trap density. In addition, interlayer-free Al ₂ O ₃ on Si was achieved in VHF PE-ALD via a significant reduction in plasma damage. VHF PE-ALD will be an essential process to realize nanoscale devices that require precise control of interfaces and electrical properties.