Reactive sputtering for highly oriented HfN film growth on Si (100) substrate

Highly oriented cubic (100) HfN films were grown on Si (100) substrates by direct current magnetron reactive sputtering of a metallic Hf target in an Ar/N₂ gas environment. The influence of N₂ flow ratio on the (100) preferred orientation and crystallinity of the HfN films is investigated. X-ray diffraction shows that not only HfN but also orthorhombic HfSi₂ forms in the sputtered films. Increasing the N₂ flow ratio is unfavorable for the formation of HfSi₂ while the deposition rate of HfN is decreased. X-ray diffraction and cross-sectional scanning transmission electron microscopy (STEM) reveal that epitaxial orthorhombic HfSi₂ can form on the Si substrate, and (100) HfN is in epitaxy with the epitaxial HfSi₂. As a result, a (100) oriented HfN film can grow on Si. The epitaxial relationships are shown to be HfN (100)[011¯] // HfSi₂ (020)[001] // Si (100)[011¯] and HfN (100)[011¯] // HfSi₂ (020)[100] // Si (100)[011¯]. Atomically resolved STEM images also show the bonding characteristics across the HfN/HfSi₂ and HfSi₂/Si interfaces.