Patent ID: 6036878
Filing Date: 2000-03-14
Classification: H01J,H01L

Abstract:
In an inductively coupled plasma reactor for processing a semiconductor wafer, the reactor comprising a vacuum chamber for containing said wafer, a process gas source, a semiconductor window electrode facing an interior portion of said chamber, an inductive power radiator on an exterior side of said semiconductor window electrode, said RF field having a skin depth generally decreasing with the frequency of said RF field and with the density of the plasma in said chamber and generally increasing with the pressure inside said vacuum chamber, the inductive coupling of said RF field tending to approach extinguishment as said skin depth approaches the spacing between said wafer and said window electrode, a method for maintaining an intermediate plasma density inside said chamber less than a high plasma density without extinguishing said inductive coupling of said RF field, said method comprising:operating said reactor at a selected flow rate of said process gas, a selected chamber pressure and a selected plasma source power level corresponding to said intermediate plasma density;maintaining the frequency of said RF field at least at a level sufficient to limit said skin depth to a depth less than the electrode-to-wafer spacing, whereby to maintain said inductive coupling of said RF field.