US Patent 7419614 Method of etching and cleaning objects

A method of etching and cleaning objects contained in a vessel, includes etching the objects by providing etching solution into the vessel, forcing out the etching solution from the vessel by providing pressurized gas into the vessel; cleaning the objects by providing cleaning solution into the vessel; and draining the cleaning solution from the vessel. By forcing out the etching solution with a pressurized gas such as nitrogen gas, there is no density difference of the etching solution in contact with the objects, leading to uniform etching of the objects.