Patent ID: 7232506

Claim:
In a sputter coating system comprising: a vacuum chamber having a coating station; substrate mounting and moving means adapted for passing one or more substrates to be coated through said coating station; means for introducing a reactive gas into said vacuum chamber at a predetermined rate; a target operating at a predetermined power level sufficient to create a reactive atmosphere in said coating station and to plasma sputter a selected material onto substrates when passed through said coating station by said substrate mounting and moving means; and a plasma generator operating at a predetermined power level for increasing the area, density and reactivity of the reactive atmosphere in said coating station, a method of reactive sputtering comprising the steps of: (1) operating the plasma generator at a power level at which (a) the partial pressure of the reactive gas required to convert substantially all of the material sputtered onto the substrates into a different chemical species is below (b) the partial pressure of the reactive gas required for substantially poisoning the target, so that there is a range of reactive gas partial pressures between (a) the partial pressure of the reactive gas required to convert substantially all of the material sputtered onto the substrates into a different chemical species and (b) the partial pressure of the reactive gas, over which it is feasible to monitor the reactive gas partial pressure and to effect control of the reactive gas partial pressure within a predetermined range by feedback control means; (2) monitoring the partial pressure of the reactive gas; (3) monitoring a system operating parameter; and (4) automatically controlling the partial pressure of the reactive gas responsive to variance in (i) the partial pressure of the reactive gas and/or (ii) the system operating parameter by actively controlling the rate of introduction of reactive gas into the chamber to maintain the partial pressure of the reactive gas in the predetermined range of reactive gas partial pressures, wherein the partial pressure of the reactive gas is automatically controlled responsive to variance in the system operating parameter by feedforward control.