Effect of hydrogen participation on the improvement in electrical characteristics of HfO_2 gate dielectrics by post-deposition remote N_2, N_2/H_2, and NH_3 plasma treatments

摘要

The structural and electrical characteristics of hafnium oxide (HfO2) gate dielectrics treated by a variety of post-deposition nitridation processes, including remote N2, N2/H2 and NH3 plasma, are presented by the x-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy and electrical measurements. The XPS measurement reveals that the nitrogen content in the HfO2 thin film treated by remote nitrogen and hydrogen plasma is higher than that treated only by remote nitrogen plasma, suggesting that the hydrogen has the capability to facilitate nitrogen dissociation. An ultra-thin interfacial layer (IL) thickness (～0.3 nm), a high dielectric constant (20), an acceptable gate leakage current density (～9 × 10~-6 A cm~-2), and a low capacitance equivalent thickness (1.9 nm) of the HfO2 gate dielectric were achieved by the post-deposition remote NH3 plasma nitridation treatment. However, an IL layer as thick as 1.5 nm was observed in the sample treated only by remote N2 plasma. The results indicate that the participation of hydrogen in the nitridation process is a promising way to improve the electrical properties of HfO2 gate dielectrics.