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A low temperature remote plasma assisted oxidation (RPAO) process for interface formation and passivation has been extended from Si and SiC to GaN. The process, which can be applied to nanoscale structures including quantum dots and wires, provides excellent control of ultra-thin interfacial layers which passivate the GaN substrate, preventing a parasitic or subcutaneous oxidation of the substrate during plasma deposition of SiO 2 . This remote plasma processing for GaN-dielectric heterostructures includes: (i) an in situ nitrogen plasma surface clean, (ii) RPAO for formation of an interfacial GaO x transition region between the GaN and deposited dielectric, and (iii) a remote plasma enhanced chemical vapor deposition of an SiO 2 dielectric.

In previous studies, device-quality Si–SiO2 interfaces and dielectric bulk films (SiO2) were prepared using a two-step process; (i) remote plasma-assisted oxidation (RPAO) to form a superficially interfacial oxide (∼0.6 nm) and (ii) remote plasma enhanced chemical vapor deposition (RPECVD) to deposit the oxide film. The same approach has been applied to GaN–SiO2 system. Low-temperature (300 °C) remote N2/He plasma cleaning of the GaN surface, and the kinetics of GaN oxidation using RPAO process and subcutaneous oxidation during the SiO2 deposition using an RPECVD process have been investigated from analysis of on-line Auger electron spectroscopy (AES) features associated N and O. Compared to single-step SiO2 deposition, significantly reduced defect state densities are obtained at the GaN–dielectric interfaces by independent control of GaN–GaOx (x∼1.5) interface formation by RPAO, and SiO2 deposition by RPECVD.

Three different buffer layers on a Si substrate were grown to investigate the interfacial layer effect during HfO 2 deposition and thermal annealing. The three different buffer layers were the very thin Al 2 O 3 , remote plasma nitridation (RPN)-treated Al 2 O 3 , and RPN-treated HfO 2 films. HfO 2 films were then grown on these three different buffer layers by a remote plasma atomic layer deposition method. The HfO 2 films with RPN-treated buffer layers retarded silicate formation or growth of an interfacial layer more effectively than those without RPN treatment. The HfO 2 films with an RPN-treated HfO 2 buffer layer showed the lowest effective oxide thickness and those with an RPN-treated buffer layer exhibited low leakage current density. The effective fixed-oxide charge density of the HfO 2 film with an RPN-treated HfO 2 buffer layer showed the lowest value of 3.60 X 10 11 /cm 2 compared to the other films. As the annealing temperature increased, the flatband voltage (V FB ) for the HfO 2 films was shifted and became close to the ideal V FB . The interface stability of HfO 2 with a nitrided buffer layer formed by RPN treatments resulted in the improvement of the electrical properties of HfO 2 films.

We investigated the physical and electrical characteristics of a HfO 2 /ultrathin SiO 2 (∼0.5 nm)/Si structure grown by a remote plasma atomic layer deposition (RPALD). The HF-cleaned Si substrate was oxidized by a remote plasma oxidation (RPO) process and yielded a ∼0.5 nm thick SiO 2 layer. HfO 2 films were deposited on both H-terminated and RPO-treated Si substrates by the RPALD. During HfO 2 film deposition, the RPO-treated sample showed more effectively retarded formation of initial Hf silicate layers than the sample on H-terminated Si. RPO treatment also improves electrical properties including hysteresis, effective fixed oxide charge density (Q f,eff ) and equivalent oxide thickness (EOT).