Methods for forming a silicon nitride film

A method for forming a silicon nitride film by a plasma enhanced atomic layer deposition (PEALD) process, the method comprising:

• providing a substrate into a reaction chamber;
• and
• performing at least one unit deposition cycle of a PEALD process, wherein a unit cycle comprises:
• contacting the substrate with a vapor phase reactant comprising a silicon precursor;
• and
• contacting the substrate with a reactive species generated from a plasma produced from a gas mixture comprising a nitrogen precursor and an additional gas, wherein the additional gas comprises at least one of helium or neon and the gas mixture is introduced into the reaction chamber at a flow rate ratio of additional gas to nitrogen precursor greater than 4:1.