Interfacial Properties of HfO2/ SiN/Si Gate Structures

High-k stacks composed of a silicon nitride interfacial layer and a hafnium oxide layer on top have been fabricated and analyzed. In this paper, we propose the introduction of the SiN layer between the high-k dielectric and the silicon substrate as a barrier to prevent the uncontrollable SiO₂ growth during sputtering. The SiN films were deposited by electron cyclotron resonance chemical vapour deposition (ECR-CVD) using N₂ and SiH₄ as precursor gases. The HfO₂ thin films were grown by high pressure sputtering (HPS) in Ar inert atmosphere. The bonds present in the SiN_x films, both prior and after the HfO₂ deposition, were studied by Fourier transform infrared spectroscopy. We observed that the sputtering of the HfO₂ film in Ar does not affect significantly the SiN layer. TEM measurements also showed that the bonding properties of the buffer SiN film are preserved during the high-k sputtering in Ar atmosphere, demonstrating the suitability of this approach. Finally, metal oxide semiconductor (MOS) devices were fabricated to determine the interface trap distribution (Dit) using the high-low frequency capacitance method, obtaining values in the low 10¹¹ eV^-1cm^-2 range.