Due to the fast development of microelectronics, quite an important
number of the chemical aspects of component formation has been occulted. In
particular just a few studies are related to thin film formation in the scope of
chemical reactions and modelisation. Thermodynamics itself has been
implemented rather ponctually and in an incomplete way. One of the Mayn
reasons for this is that thin films are considered as standingly non equilibrium
systems and that. thermodynamics, as a macroscopic science, has Maynly been
considered as inadequate. Thus, we have decided to reconsider the problem of
thin films formation from a strictly chemical point of view.Using a simple
system (formation of silicon nitride on monocrystalline silicon), the chemical
reactions have been investigated.
Classical thermodynamics, though inaccurate and approximate for
such systems is necessary to develop the first steps of a thermodynamical model
describing the deposit formation. Using a computer program helping a global
treatment of several chemical reactions confirms the conclusions obtained by
classical thermodynamics. We have discussed the insufficiency of the classical
model, and shown that, with respect to what was experimentally observed, it
was nevertheless globally valid, and that the nitride formation should be
regarded as a superposition of classical chemical reactions that occurred in
"close to the equilibrium" states and globally following the classical laws of
thermodynamics. Thus, we propose a model of formation for the first mono
layer of Si3N4 on monocrystalline silicon which is in total agreement to
experimental observations.