Apparatus and method for treating a workpiece using plasma generated from microwave radiation

A method of plasma treating a surface of a workpiece at atmospheric pressure, said method comprising the steps of:

• providing a plasma generating apparatus comprising a chamber for containing a plasma, a first inlet having a first inlet orifice for admitting a plasma gas into said chamber, a second inlet having a second inlet orifice for admitting a working gas into said chamber, plural plasma concentrators spaced apart from one another and being disposed in said chamber for varying the density of the plasma within said chamber, an outlet from said chamber allowing a gaseous species to exit said chamber, and a microwave power supply for providing microwave radiation to said chamber and generating plasma from said plasma gas, whereby said plasma excites said working gas to create an excited species which exits said outlet to treat the surface;
• supplying plasma gas through said first inlet and into said chamber;
• providing microwave radiation from said microwave power supply to said plasma gas;
• generating a plasma from the plasma gas using said microwave radiation, the plasma being concentrated near the plasma concentrators;
• supplying working gas through said second inlet to said chamber, wherein said working gas bypasses said first inlet orifice;
• exciting said working gas using the plasma to create an excited gaseous species;
• juxtaposing said outlet with the workpiece to treat a surface of the workpiece;
• and
• applying a treatment of the excited species to the surface of the workpiece at approximately atmospheric pressure.