A centrifugal spray processor for processing semiconductor wafers uses larger numbers of spray nozzles. Each spray nozzle delivers a reduced volume of liquid, to reduce consumption of liquid process chemicals. The nozzles operate at a higher back pressure. The increased number of nozzles, offset nozzle patterns and groupings of nozzles, lower nozzle flow rates, and higher nozzle back pressures, provide improved processing results. The improved spray system may be provided as a retrofit kit.