M.-H. Cho

Suppression of phase separation in Hf-silicate films using NH3 annealing treatment

The structural characteristics of Hf-silicate films and nitrogen incorporated Hf-silicate films, prepared using a NH3 annealing treatment, were investigated by various measurements. Hf-silicate films annealed in a N2 ambient at 900°C show the evidence of crystallization in local regions, resulting in the phase separation of HfO2 and SiO2. In addition, a SiO2 overlayer is formed on the Hf-silicate films, due to the diffusion of Si by postannealing in an ambient of N2 at 900°C. However, in nitrogen incorporated Hf-silicate films, prepared using a NH3 annealing treatment, phase separation is effectively suppressed and no SiO2 overlayer is present. The incorporated N is distributed into the film and interfacial layer, and obstructs the diffusion of Si from the substrate as well as the film. Structural changes in films affect electrical characteristics such as the dielectric constant and flatband voltage.

Effects of N2+ ion implantation on phase transition in Ge2Sb2Te5 films

The phase transitions of Ge2Sb2Te5 (GST) films after bombardment with 40keV N2+ ions were investigated. Comparing the nitrogen incorporated GST films with a pure GST film, the suppression of a crystalline grain growth was more effective in the N2+ implanted GST film than in a nitrogen codeposited GST film, i.e., x-ray diffraction data showed that the intensities of the crystalline diffraction peaks were decreased and the full widths at half maximum were broader than that of a pure GST film. This suppression of crystallization owing to the incorporation of nitrogen drastically reduced the roughness of surface morphology and decreased the electrical conductivity of the crystalline film. A near edge x-ray absorption fine structure experiment and x-ray photoemission spectroscopy data demonstrated that the suppression of crystalline grain growth is due to the formation of Ge3N4 and interstitial N2 molecules. In N2+ implanted GST films, in particular, interstitial N2 molecules played a major role in the suppres...

Initial nucleation and growth of atomic layer deposited HfO2 gate dielectric layers on Si surfaces with the various surface conditions using in situ medium energy ion scattering analysis

The initial nucleation and growth of atomic layer deposited HfO2 films under various surface conditions were investigated by in situ medium energy ion scattering analysis. The influences of an O–H terminated surface on the initial growth stage were investigated in detail using the atomic density of Hf that reacted on the surface. The measured growth rate of HfO2 per cycle was applied to a mathematical model based on classical chemical kinetics. A parabolic initial growth with an extremely low rate at the initial stage of growth was observed for the film with a hydrogen-terminated surface. However, linear growth, with a value of 1.41×1014Hfatoms∕cm2cycle, was maintained for films grown on an O–H terminated surface. The ∼1∕6 steric hindrance factor extracted from a phenomenological model was related to the size of the tetrahedral HfCl4 molecule and the possible attachment sites. Moreover, the surface roughness and electrical properties of the atomic layer deposited HfO2 films show a strong dependence on the initial nucleation and growth on the different surface conditions.The initial nucleation and growth of atomic layer deposited HfO2 films under various surface conditions were investigated by in situ medium energy ion scattering analysis. The influences of an O–H terminated surface on the initial growth stage were investigated in detail using the atomic density of Hf that reacted on the surface. The measured growth rate of HfO2 per cycle was applied to a mathematical model based on classical chemical kinetics. A parabolic initial growth with an extremely low rate at the initial stage of growth was observed for the film with a hydrogen-terminated surface. However, linear growth, with a value of 1.41×1014Hfatoms∕cm2cycle, was maintained for films grown on an O–H terminated surface. The ∼1∕6 steric hindrance factor extracted from a phenomenological model was related to the size of the tetrahedral HfCl4 molecule and the possible attachment sites. Moreover, the surface roughness and electrical properties of the atomic layer deposited HfO2 films show a strong dependence on the...

Change in phase separation and electronic structure of nitrided Hf-silicate films as a function of composition and post-nitridation anneal

The thermal stability and electronic structure of nitrided xHfO2∙(100−x)SiO2 (HfSiO) (x=25%, 50%, and 75%), prepared using an NH3 annealing treatment, were investigated. The quantity of N incorporated into the Hf-silicate film was dependent on the mole fraction of SiO2 in the film: i.e., a silicate film containing a high mole fraction of SiO2 contained a higher quantity of N, resulting in the suppression of phase separation. In particular, the incorporated N easily diffuses out through a silicate film that contains a small quantity of SiO2 during the post-nitridation anneal, while in a film with a high quantity of SiO2, it is relatively stable. The phase separation effect in the nitrided film with a low SiO2 mole fraction was significantly influenced by the stability of N in the film and interface.

Structural and stoichiometric change in nitrided HfO2 grown on Ge(100) by atomic layer deposition

The electronic structure and stoichiometric characteristics of postnitrided HfO2 grown on Ge(100) were investigated by various physical measurements. N incorporation in HfO2 grown on Ge was strongly related to the diffusion of Ge from Ge substrate into the film by the postannealing treatment in an NH3 ambient. The diffusion of Ge into the HfO2 film was influenced by the formation of GeOx and GeOxNy in the interfacial region. The small amount of N was incorporated into the film at a nitrided temperature of 600°C, while much larger amounts of N atoms were incorporated into the interfacial layer to form GeON at a temperature of 700°C, resulting in the suppression of the diffusion of Ge into the film. However, the interfacial nitrided layer was not stably maintained during the postnitridation anneal, resulting in an enhanced interdiffusion of Ge and Hf into the film.