The invention includes a method and apparatus for scheduling packet transmissions on a data channel from a base transceiver station to a plurality of wireless terminals. During the wafer cleaning process the rate monitor can monitor a rate at which changes are being made to a portion of the wafer, as the wafer is covered with a liquid, and predict an endpoint in time to the wet cleaning process. The wafer including the first-generation seed is sliced thicker than the other wafers so that the wafer including the first-generation seed does not break.