Method of high pressure treatment

A high-pressure processing method for removing an unnecessary substance on the surface of a workpiece by bringing the surface of the workpiece into contact with supercritical carbon dioxide and additives in a high-pressure processing chamber, said method comprising the steps of:

• sealing said high-pressure processing chamber after loading said workpiece in said high-pressure processing chamber;
• pressurizing said high-pressure processing chamber with pressurized carbon dioxide supplied to said high-pressure processing chamber to a predetermined pressure and a predetermined temperature higher than the critical pressure and critical temperature thereof respectively;
• dissolving said additives and a co-solvent in supercritical carbon dioxide by mixing said additives and said co-solvent with said supercritical carbon dioxide in the upstream of said high-pressure processing chamber;
• removing an unnecessary substance on said workpiece while maintaining the inside of said high-pressure processing chamber higher than the critical pressure and critical temperature of carbon dioxide, by supplying continuously a predetermined amount of a mixture fluid of said additives, said co-solvent and said supercritical carbon dioxide to said high-pressure processing and ejecting a substantially equal amount of the high-pressure fluid to the predetermined supply amount from said high-pressure processing chamber;
• obtaining a first rinse fluid in which said co-solvent is dissolved in said supercritical carbon dioxide, by stopping feed of said additives and mixing said co-solvent with said supercritical carbon dioxide in the upstream of said high-pressure processing chamber;
• performing a first rinsing process for replacing the mixture fluid of said additives, said co-solvent and said supercritical carbon dioxide in said high-pressure processing chamber with said first rinse fluid while maintaining the inside of said high-pressure processing chamber higher than the critical pressure and critical temperature of carbon dioxide, by supplying continuously a predetermined amount of said first rinse fluid to said high-pressure processing chamber and ejecting a substantially equal amount of the high-pressure fluid to the predetermined supply amount from said high-pressure processing chamber;
• performing a second rinsing process for replacing said first rinse fluid in said high-pressure processing chamber with said supercritical carbon dioxide while maintaining the inside of said high-pressure processing chamber higher than the critical pressure and critical temperature of carbon dioxide, by stopping supply of said co-solvent, supplying continuously only supercritical carbon dioxide by a predetermined amount to said high-pressure processing chamber and ejecting a substantially equal amount of the high-pressure fluid to the predetermined supply amount from the high-pressure processing chamber;
• stopping feed of carbon dioxide to said high-temperature processing chamber;
• decompressing said high-pressure processing chamber to atmospheric pressure;
• and
• unloading said workpiece from said high-pressure processing chamber.