Effect of reactive gases (NH₃/N₂) on silicon–nitride thin films deposited with diiodosilane (SiH₂I₂) precursors

Abstract

A more in-depth study was conducted on silicon nitride thin films deposited using the space-divided plasma enhance atomic layer deposition (PE-ALD) method. Existing silicon nitride thin films are fabricated using thermal chemical vapor deposition (CVD) at high temperatures of 700 °C or higher with carbon (C)- and chlorine (Cl)-based precursors. However, the high process temperature and the high concentration of C and Cl in films cause a slew of issues for semiconductor integration. In this study, the silicon–nitride thin films have been deposited using the PE-ALD method and an iodine-based precursor to solve these problems. NH₃ and N₂ gases were used as the reactant gases. When N₂ was used as the reactant gas instead of NH₃, the concentration of the hydrogen (H) impurity was reduced from 19 to 15%. A plasma treatment was used to improve the density and remove the impurities in the thin films; the density of the thin films was confirmed to be 3.21 g/cm³, and the H concentration was 11%, indicating that the properties had improved. When a small amount of He gas was added to N₂, the step coverage properties were improved up to 99.2%. The results of this study confirmed that silicon nitride thin films having superior properties can be produced using iodine-based precursors.