1. A method for wafer processing comprising: loading a first plurality of wafers into a wafer cluster tool, wherein the first plurality of wafers are loaded into the cluster tool individually at intervals delimited by a first sending period, and each wafer of the first plurality of wafers is processed according to a first recipe, the first recipe including a first sequence of process steps a first plurality of process times, wherein each process step in the first sequence of process steps has a corresponding process time in the first plurality of process times; loading a second plurality of wafers into a wafer cluster tool, wherein the second plurality of wafers are loaded into the cluster tool individually at intervals delimited by a second sending period, and each wafer in the second plurality of wafers is processed according to a second recipe, the second recipe including a second sequence of process steps; a second plurality of process times, wherein each process step in the second sequence of process steps has a corresponding process time in the second plurality of process times; wherein the cluster tool has a transition period, during which the cluster tool processes one or more wafers from the first plurality of wafers according to the first recipe and one or more wafers from the second plurality of wafers according to the second recipe.