Chemical and kinetic insights into the Thermal Decomposition of an Oxide Layer on Si(111) from Millisecond Photoelectron Spectroscopy

Kinetics formulation for Two-Dimensional Growth Behavior of Water/Ice Interface on Si Substrate

Sublimation drying is used in the drying process of semiconductor device manufacturing. However, the solidification behavior mechanics of sublimation agents on substrates has not been clarified. Therefore, the properties of solidified films within substrate surfaces can become nonuniform, leading to their collapse. This study aimed to analyze the interface growth behavior during the cooling and solidification of a water/ice system as a basic case and to clarify the dynamic mechanism of the solidification behavior of liquid films on Si substrates. The solidification behavior of a water/ice system on Si substrates was captured on a video at different cooling rates. The recorded video was subjected to a digital image analysis to examine the crystal morphology and quantify the interface growth rate. The least-squares method with kinetic formulas was used to evaluate the feasibility of fitting the temperature variation to the interface growth rate. A visual examination of the morphology of interfacial growth revealed that it can be classified into four morphologies. The proposed kinetic equation describes the experimental results regarding the temperature dependence of the interfacial growth rate. Through image analysis, the interface growth rate of water and ice was quantified, and an evaluation formula was proposed.

Thermodynamic insights into Henry's constant in hyperthermal oxidation of silicon for fabricating optical waveguides

Hyperthermal oxidation of silicon is envisaged to be an alternative to silicon-on-insulator (SOI) waveguide fabrication for photonic integrated circuit (PIC) devices, and thus the local oxidation of silicon (LOCOS) technique has attracted attention. In this article, starting with the thermodynamic insights into the Deal-Grove model for defining the thermal oxidation, we model the Henry's law constant in the silicon oxidation process with the ensemble contributions of thermodynamic and chemical energies, and extract an empirical model with the published statistical data. Then, the simulations show the dramatic temperature/time dependences of Henry's constant, and the different effects of the thermodynamic and chemical energies. Systematic simulations of the temperature/time dependences of both the growth rate and thickness of oxide are carried out where the temperature dependence of the oxidant diffusivity is also considered. Consequently, the simulation results from the two models astonishingly agree with each other. Typically, at 1100 °C, with a 3 h oxidation time, 2.10 and 1.34 μm SiO₂ layers can be grown with the thermodynamic model under two diffusivity models, while with the empirical one, the two extreme cases can grow 2.10 and 1.28 μm SiO₂ layers, respectively.

Ni-mediated reactions in nanocrystalline diamond on Si substrates: the role of the oxide barrier

Nanocrystalline diamond (NCD) films grown on Si substrates by microwave plasma enhanced chemical vapor deposition (MWPECVD) were subjected to Ni-mediated graphitization to cover them with a conductive layer. Results of transmission electron microscopy including electron energy-loss spectroscopy of cross-sectional samples demonstrate that the oxide layer on Si substrates (∼5 nm native SiO₂) has been damaged by microwave plasma during the early stage of NCD growth. During the heat treatment for graphitizing the NCD layer, the permeability or absence of the oxide barrier allow Ni nanoparticles to diffuse into the Si substrate and cause additional solid-state reactions producing pyramidal crystals of NiSi₂ and SiC nanocrystals. The latter are found impinged into the NiSi₂ pyramids but only when the interfacial oxide layer is absent, replaced by amorphous SiC. The complex phase morphology of the samples is also reflected in the temperature dependence of electrical conductivity, where multiple pathways of the electronic transport dominate in different temperature regions. We present models explaining the observed cascade of solid-state reactions and resulting electronic transport properties of such heterostructures.

Nanocrystalline diamond films grown on Si/native oxide substrates were subjected to Ni-mediated graphitization. Transmission electron microscopy study revealed crystals of NiSi₂ and SiC across the carbon/silicon interface in addition.