Thermal oxidation of nickel disilicide

Abstract

The thermal oxidation characteristics of nickel disilicide on Si substrates have been investigated in the temperature range of 700-900°C in dry oxygen and wet oxygen. A surface layer of SiO2 grows parabolically in time. The growth rate is independent on the crystalline structure (epitaxial or polycrystalline) and thickness of the NiSi2 layer. We surmise that the oxidation mechanism is dominated by oxygen diffusion through the growing SiO2. Activation energies for the dry and wet oxidation are 1.0±0.1 eV and 1.5±0.1 eV, respectively. NiSi2 layers on SiO2 oxidize with the same rate - resulting with progressively Ni-rich NiSi2. Preliminary measurements of the oxide quality yield dielectric strength of 2.1×106 V cm-1, and a pinhole density of about 100 per cm2. A survey of oxidation data for Si and other refractory metal silicides shows that their oxidation does not draw similar kinetics to that of NiSi2.