Interfacial Properties of HfO2/ SiN/Si Gate Structures

摘要

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 SiNx 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.