Chemical treatment method

A method of chemically treating a substrate held by a substrate-holding means by contacting a surface of the substrate with an etching liquid or a plating liquid, the method comprising the steps of:

• supplying the etching liquid or the plating liquid from a cylindrical inner cell by a chemical supply means disposed over the substrate-holding means;
• filling a space defined by the substrate-holding means as a bottom surface and a cylindrical outer cell with open ends disposed at an outer circumference of the cylindrical inner cell as a side surface with the etching liquid or the plating liquid;
• and
• performing a chemical treatment of the surface of the substrate using the etching liquid or the plating liquid while axially moving the outer cell to vary a width of a slit, which is formed between a bottom end of the outer cell and a top surface of the substrate-holding means, for exhausting the etching liquid or the plating liquid and thereby changing a pressure of the etching liquid or the plating liquid in the space,
• wherein the method further comprises varying the width of the slit intermittently at least in three levels to adjust a discharge rate of the etching liquid or the plating liquid, thereby controlling the pressure of the etching liquid or the plating liquid in the space.