Dependences of nitrogen incorporation behaviors on the crystallinity and phase distribution of atomic layer deposited Hf-silicate films with various Si concentrations

Abstract

This study examined the nitrogen incorporation behavior of atomic layer deposited HfO2 and Hf-silicate films with various Si concentrations during thermal annealing under a NH3 atmosphere. The level of crystallization and the phase distribution of the films (crystalline HfO2 and amorphous Hf-silicate and SiO2) had a significant effect on extent of nitrogen incorporation. There was virtually no nitrogen incorporation in the crystallized HfO2. Under the condition that the Hf-silicate films were not phase-separated and crystallized during thermal nitridation, the excess HfO2 and SiO2 phases that did not contribute to the amorphous HfSiO4 phase were easily nitrided. On the other hand, the amorphous HfSiO4 phase was barely nitrided. Therefore, it was concluded that the level of nitrogen concentration in the Hf-silicate films decreased with increasing Si concentration in the films. The changes in the capacitance equivalent thickness, gate leakage current density, and flatband voltage shift of the various films after thermal nitridation were consistent with the nitrogen concentration in the films.