Method of forming insulation film by modified PEALD

A method of forming an insulation film by plasma enhanced atomic layer deposition (PEALD), comprising in the following sequence:

• (i) introducing a precursor without a reactant gas into a reaction space where a substrate is placed, which precursor is an aminosilane compound;
• (ii) exciting the precursor in the reaction space with a plasma by applying a first RF power to the reaction space for adsorbing the precursor on a surface of the substrate;
• (iii) adsorbing the plasma-treated precursor onto the surface of the substrate;
• (iiia) purging the reaction space between steps (iii) and (iv) without RF power;
• (iv) introducing a reactant gas without a precursor to the reaction space and exciting the reactant gas with a plasma by applying a second RF power to the reaction space to treat the precursor-adsorbed surface with the excited reactant gas to form and fix a film on the surface, wherein the reactant gas is NO2, O2, H2, CO2, N2O, N2 and/or NH3,
• wherein steps (i) to (iv) constitute one cycle of PEALD, wherein the first RF power is lower than the second RF power wherein the first RF power is less than 50 W so as to maintain a step coverage of the film at 90% or higher as measured for an aspect ratio (depth/opening width) of 3, and the second RF power is 100 W or more;
• and
• (v) repeating the one cycle multiple times until an atomic layer of a desired thickness is obtained.