A processor for making porous silicon or processing other substrates has first and second chamber assemblies. The first and second chamber assemblies include first and second seals for sealing against a wafer, and first and second electrodes, respectively. The second seal is moveable towards and away from a wafer in the processor, to move between a wafer load/unload position, and a wafer process position. The second electrode may move with the second seal. A light source shines light onto the first side of the wafer. The processor may be pivotable from a substantially horizontal orientation, for loading and unloading a wafer, to a substantially vertical orientation, for processing a wafer.