Stress in silicon at Si3N4/SiO2 film edges and viscoelastic behavior of SiO2 films

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Abstract
Dislocation generation in silicon substrates at Si3N4/SiO2 film edges is investigated after thermal treatment at 900–1200 °C for 2 h in a N2 atmosphere. In order to explain the obtained experimental results, we propose a model to calculate stresses in silicon at the film edge. In the present model, it is assumed that the SiO2 film is a Maxwell viscoelastic solid, and stress values are obtained using the finite element method and analytical solutions under plain strain conditions. The calculated results show that the shape of the stress distribution at the Si3N4/SiO2 film edge is different from that at the Si3N4 film edge, and that stress in the former is small in comparison with that at the latter. As a result, it is proved that the present model gives a physical interpretation for the suppression of dislocation generation with Si3N4/SiO2 films.