Abstract: A wafer cleaning apparatus provides two opposed brushes for brushing a vertically disposed wafer in a tank which can contain a process liquid. A pressure controller adaptively controls the pressure exerted by the brushes on the wafer to compensate for brush wear. Rim driving wheels engage the wafer periphery with a porous jacket coupled to a fluid delivery system, thereby simultaneously rotating and cleaning the periphery of the wafer. The apparatus includes a fluid delivery system for separately and independently delivering a plurality of constituents of a cleaning solution to the brushes, thereby ensuring that a freshly mixed cleaning solution reaches the wafer. The tank can be filled with a process liquid through which megasonic waves provided by a transducer can propagate and impinge upon the wafer thereby enhancing the cleaning of the wafer or the brushes.