Lee A. Walsh

A combined hard x-ray photoelectron spectroscopy and electrical characterisation study of metal/SiO2/Si(100) metal-oxide-semiconductor structures

Combined hard x-ray photoelectron spectroscopy (HAXPES) and electrical characterisation measurements on identical Si based metal-oxide-semiconductor structures have been performed. The results obtained indicate that surface potential changes at the Si/SiO2 interface due to the presence of a thin Al or Ni gate layer can be detected with HAXPES. Changes in the Si/SiO2 band bending at zero gate voltage and the flat band voltage for the case of Al and Ni gate layers derived from the silicon core levels shifts observed in the HAXPES spectra are in agreement with values derived from capacitance-voltage measurements.

The impact of porosity on the formation of manganese based copper diffusion barrier layers on low- κ dielectric materials

This work investigates the impact of porosity in low-κ dielectric materials on the chemical and structural properties of deposited Mn thin films for copper diffusion barrier layer applications. X-ray photoelectron spectrscopy (XPS) results highlight the difficulty in distinguishing between the various Mn oxidation states which form at the interlayer dielectric (ILD)/Mn interface. The presence of MnSiO3 and MnO were identified using x-ray absorption spectroscopy (XAS) measurements on both porous and non-porous dielectric materials with evidence of Mn2O3 and Mn3O4 in the deposited film on the latter surface. It is shown that a higher proportion of deposited Mn converts to Mn silicate on an ILD film which has 50% porosity compared with the same dielectric material with no porosity, which is attributed to an enhanced chemical interaction with the effective larger surface area of porous dielectric materials. Transmission electron microscopy (TEM) and energy-dispersive x-ray spectroscopy (EDX) data shows that the Mn overlayer remains predominately surface localised on both porous and non-porous materials.

Investigation of the thermal stability of Mo-In0.45Ga0.47As for applications as source/drain contacts

The electrical and chemical stability of Mo-InGaAs films for source-drain applications in transistor structures has been investigated. It was found that for 5 nm thick Mo films, the sheet resistance remains approximately constant with increasing anneal temperatures up to 500 °C. A combined hard x-ray photoelectron spectroscopy and x-ray absorption spectroscopy analysis of the chemical structure of the Mo-InGaAs alloy system as a function of annealing temperature showed that the interface is chemically abrupt with no evidence of inter-diffusion between the Mo and InGaAs layers. These results indicate the suitability of Mo as a thermally stable, low resistance source-drain contact metal for InGaAs-channel devices.

A combined capacitance-voltage and hard x-ray photoelectron spectroscopy characterisation of metal/Al2O3/In0.53Ga0.47As capacitor structures

Capacitance-Voltage (C-V) characterization and hard x-ray photoelectron spectroscopy (HAXPES) measurements have been used to study metal/Al2O3/In0.53Ga0.47As capacitor structures with high (Ni) and low (Al) work function metals. The HAXPES measurements observe a band bending occurring prior to metal deposition, which is attributed to a combination of fixed oxide charges and interface states of donor-type. Following metal deposition, the Fermi level positions at the Al2O3/In0.53Ga0.47As interface move towards the expected direction as observed from HAXPES measurements. The In0.53Ga0.47As surface Fermi level positions determined from both the C-V analysis at zero gate bias and HAXPES measurements are in reasonable agreement. The results are consistent with the presence of electrically active interface states at the Al2O3/In0.53Ga0.47As interface and suggest an interface state density increasing towards the In0.53Ga0.47As valence band edge.