Method and apparatus for sputter coating stepped wafers

Abstract

A magnetron sputtering method and apparatus employing a one-piece annular target having a concave continuously smooth surface with an inwardly facing portion close to and surrounding the outer edge of a stepped wafer provides a sputtering surface with areas facing the differently facing surfaces of the wafer steps. Two concentric erosion zones on the target surface are independently energized at different electrical parameter values by synchronizing the power applied to the single target with switched activation of plasmas overlying the respective target regions which define the erosion zones. The electrical parameters and the geometry are established so as to uniformly coat the differently facing surfaces of the stepped wafer. During part of the duty cycle during which each target region is energized, parameters may be measured. Such parameters may be those which vary with changes in geometry as for example may be due to target erosion. The operation of different target regions, such as the duty cycles or power levels for such regions, may be separately varied in response to the measurements or otherwise, to maintain uniform substrate coating as the target erodes. The target is thicker under the outer region and has an annular pole piece embedded to reduce the space separating the target erosion regions, and includes means to cool the target and reinforce it against thermal expansion.