DEPOSITION OF SILICON NITRIDE THIN FILM VIA REMOTE PLASMA-ENHANCED ATOMIC LAYER DEPOSITION

Abstract

The silicon nitride (SiNx) using 1,3-di-isopropylamino-2,4dimethylcyclosilazane (CSN-2) and N2 remote plasma was investigated. The growth rate of SiNx thin films was saturated at 200 - 500 ℃, which has a wide range of process window region, and the growth rate was approximately 0.38 Å/cycle. The physical and chemical properties of the SiNx were investigated as a function of deposition temperature. We were able to obtain the stoichiometric SiNx thin film at 500 ℃, and thin film with more conformal and good etching characteristics could be confirmed by transmission electron microscopy (TEM) and wet etch rate test as the temperature increased. However, it is necessary to further improve the characteristics of the thin film at 350 ℃, which is a low process temperature for depositing a gate spacer in logic device. Therefore, we developed 3 step process which is the H2 plasma step was introduced before the N2 plasma step. When the H2 plasma step was introduced between the precursor and reactant, the H radical acts as a precursor ligand removing and the N2 plasma breaks H atoms and deposited. In order to investigate the effect of H2 plasma, we evaluated the growth rate, step coverage and wet etch rate according to H2 plasma exposure time (10 – 30 sec). As a result, the side step coverage increased from 82 % to 105 % for the narrow pattern (AR : 2.7) and the bottom step coverages increased from 90 % to 110 % maximum. By increasing the H2 plasma (30 sec), the wet etch rate was 32 Å/min, which is much lower than the case of only N2 plasma (43 Å/min).