Substrate processing method

A method of processing a substrate in a reaction chamber, comprising:

• providing the substrate into the reaction chamber;
• forming a stack layer comprising an insulation layer and a first sacrificial layer on the substrate;
• forming a stepped structure on the stack layer, wherein the stepped structure comprises an upper surface, a lower surface and a side surface connecting the upper surface and the lower surface;
• forming a second sacrificial layer on the stepped structure;
• forming a third sacrificial layer on the second sacrificial layer;
• and
• performing a wet etching to remove the second sacrificial layer and the third sacrificial layer from the side surface, so that the second sacrificial layer and the third sacrificial layer remain on the upper surface and the lower surface,
• wherein a wet etch rate of the third sacrificial layer is modulated by supplying a nitrogen source during forming the third sacrificial layer, and
• wherein the insulation layer is a SiO2 layer and the first sacrificial layer is a SiN layer, and
• wherein the third sacrificial layer is a SiCN layer formed by repeating a cycle comprising:
• supplying a second silicon source and the nitrogen source to the substrate simultaneously to form the SiCN layer while applying a second power to the reaction chamber,
• wherein the second silicon source comprises a carbon constituent, and a wet etch rate of the SiCN layer is modulated by reducing a carbon constituent by supplying the nitrogen source, and
• performing a post treatment by applying a third power to the reaction chamber,
• wherein the nitrogen source is further supplied during the post treatment.