THE ROLE OF HYDROGEN IN THE FORMATION, REACTIVITY AND STABILITY OF SILICON (OXY)NITRIDE FILMS

In the last decennium it has become clear how hydrogen and hydrogenated gases are involved in the formation of thin dielectric nitride and oxynitride films As a consequence hydrogen is incorporated in the deposited or grown films, where it plays a role in their physical, chemical and electrical reactivity and stability. Hydrogen is able to migrate in and desorb from the films via several mechanisms. These mechanisms are concisely reviewed. We consider the processes of wet oxidation and nitridation in the Si-O-N system as two manifestations of a single chemical reaction system. In this system hydrogen stabilizes intermediate reaction products, allowing multi-step reactions to proceed. Interruption of the process or, more specifically, isolation of the intermediate species from the reactants results in incorporation of these hydrogenated intermediates in the material. It appears that the reactivity of oxynitrides strongly increases for increasing 0/N concentration ratio of the material. The use of isotope-sensitive high-energy ion beam methods is emphasized.