Properties of plasma-deposited Si-rich silicon nitride films in current enhancement injectors

Abstract

Si-rich silicon nitride (SiNx:H) film deposited on top of thermal SiO2 has been found to give rise to current enhancement through the double-layer sandwich structure similar to the injector device based on Si-rich SiO2 [DiMaria et al., J. Appl. Phys. 51, 2722 (1980)]. In this paper, the properties of the SiNx:H film, deposited by the plasma-enhanced chemical vapor deposition technique and its injector structure, are reported. It has been found that the as-deposited film is amorphous, but subsequent annealing done at 900–1100 °C leads to the crystallization of the excess Si in the material. For injector structures made of moderately Si-rich films, the current enhancement effect does not depend strongly on the film composition and the subsequent heat treatment. For samples made of very Si-rich films, however, the post-metallization anneal step (at 400 °C) causes the as-deposited SiNx:H film to react strongly with the gate Al. This lowers the crystallization temperature of the excess Si very significantly, and also supresses the current enhancement in the corresponding injector structure. Possible mechanisms are discussed. The cyclability of the injector structure, in particular, charge trapping and degradation of the underlying SiO2 layer as a result of current injection, is also discussed.