Nucleation studies of high-κ aluminum oxide and hafnium oxide thin films on silicon carbide by plasma-enhanced atomic layer deposition

Nucleation phenomena occurring on hexagonal silicon carbide (4H-SiC) surface during the early stages of plasma-enhanced atomic layer deposition (PE-ALD) of high-κ aluminum oxide (Al2O3) and hafnium oxide (HfO2) were systematically studied. Atomic force microscopy (AFM) and conductive AFM analyses revealed the evolution of the film morphology and the uniformity of the insulating behavior upon increasing the number of PE-ALD cycles. In particular, a nonuniform insulating behavior was observed after the early nucleation stages. The use of in situ spectroscopic ellipsometry (SE) to determine the dielectric thickness during the deposition on 4H-SiC was demonstrated, and results were correlated to the observed evolution of the dielectric behavior during deposition. Moreover, a comparison has been carried out with analogous in situ SE analyses of identical PE-ALD processes on silicon substrates, and optical model fitting was elaborated to evaluate the nucleation delay on the SiC surface with respect to silicon substrates due to different chemical features of the two surfaces. This study provides a valuable method to future optimization of high-κ growth on 4H-SiC.