Patent ID: 8721847

Claim:
A control mechanism for controlling the movement of a magnet assembly in a sputter chamber, comprising: a magnet assembly; a scanning mechanism including a first arm rotatable about a central axis and a second arm mounted on the first arm and rotatable about a pivot axis located on the first arm and supporting the magnet assembly at a position on the second arm thereby allowing azimuthal and radial movement of the magnet assembly about the central axis; two motors differentially and mechanically coupled to the two arms; a first reflector disposed on the first arm and a second reflector disposed on the second arm away from the pivot axis; a first optical sensor positioned at a first radial distance from the central axis and operatively associated with the first reflector; a second optical sensor positioned at a second radial distance from the central axis different than the first radial distance and operatively associated with the second reflector; and a controller responsive to outputs of the first and second optical sensors and controlling the two motors to control relative angular positions of the first and second arms to thereby control a path of the radial and azimuthal movement of the magnet assembly according to a selected one of a plurality of such paths, wherein at least the second sensor is operative during execution of the selected one of the paths and the controller responsive to the second sensor flags an invalid rotation condition of the first and second arms and the first and second sensors are used to rehome the positions of the first and second arms.