Oxygen-induced atomic desorptions in oxynitrides: Density functional calculations

Abstract

The role of atomic oxygen, ${\mathrm{O}}_{2}$, and NO molecules in the nitrogen and oxygen removal processes observed during the thermal growth of oxynitride $({\mathrm{SiO}}_{x}{\mathrm{N}}_{y})$ films is addressed by spin density functional calculations. Our results show that the energetically most favorable N-desorption mechanism would be induced by ${\mathrm{O}}_{2}$ reacting with the Si-[NO]-Si structure in ${\mathrm{SiO}}_{2}$, where nitrogen is released from the network as an interstitial NO molecule, leaving a peroxy linkage (Si-O-O-Si) in its place. Atomic O diffusing via peroxy linkage also removes nitrogen from the Si-[NO]-Si structure. However, this reaction has an occurrence rate of about ${10}^{4}$ times smaller that the most favorable one. We also identify an oxygen exchange mechanism occurring through the annihilation of two peroxyl O atoms when they approach each other, where oxygen is released from the network as an ${\mathrm{O}}_{2}$ molecule leaving a perfect ${\mathrm{SiO}}_{2}$ structure. The energetics of other possible scenarios for atomic desorptions in ${\mathrm{SiO}}_{x}{\mathrm{N}}_{y}$ are also discussed.