A substrate handler is provided. In one embodiment, the substrate handler includes a first and second carriage coupled to a rail. A first robot having at least two grippers is attached to the first carrier. A second robot having at least one gripper is coupled to the second carriage. The first carriage is independently positionable along the rail relative to the second carriage. As each carriage has a separate actuator, the movements of the first and second robot are decoupled, thereby allowing increased throughput. The substrate handler is particularly suitable for using in a planarization system having an integrated substrate cleaner.