A wafer processing apparatus may be presented. The apparatus comprising a first loadlock and a second loadlock, at least one extra chambers for preprocessing or postprocessing the wafers, at least one reaction chambers configured to process the wafers, a first wafer handling chamber comprising a first robot, the first robot configured to move wafers between the first and second loadlocks and the extra chambers, a second wafer handling chamber comprising a second robot, the second robot configured to move wafers between the reaction chambers and a pass-through chamber, a pass-through chamber configured to stack wafers from both the first wafer handling chamber and the second wafer handling chamber; and a scheduling unit configured to schedule movements of the plurality of wafers by the first robot and the second robot.