NOVELTY - The method involves epitaxially growing a film of silicon of a conductivity type on a thin porous silicon layer (102) formed in silicon wafer (100) during deposition process. Another film of silicon of another conductivity type is epitaxially grown on the film during another deposition process to form P-N junction (203) while the films are attached to the porous layer. A set of electrical contacts (990) is formed to a layer during forming process, where another set of electrical contacts (991) is formed to another layer during another forming process.    USE - Method for fabricating a thin interdigitated backside contact photovoltaic solar cell on a thick silicon wafer.    ADVANTAGE - The method enables providing epitaxial deposition of multiple semiconductor layers of the solar cell on a porous layer of a mother wafer and subsequent exfoliation of the epitaxial layer so as to reduce use of silicon compared with the thick wafer process, so that the epitaxial deposition on porous silicon for the formation of very thin silicon wafers avoids multiple energy-intensive steps characteristic of the process of slicing a thick solar cell wafer from an ingot, thus providing improved control of dopant profiles within the photo voltaic cell by in situ formation of P plus-P and N plus-P junctions during epitaxial deposition processes. The method enables allowing processing the cell with a limited number of steps so as to reduce the number of processing steps, thus lowering manufacturing costs of the cell. The method enables creating a porous layer on a surface of a thick silicon wafer on a surface by an electrochemical etching process, so that the wafer is heated to cause sufficient thermal reflow or redistribution of silicon at the upper surface of the porous layer to enable high quality epitaxial growth of subsequent films after creation of the porous layer. The method enables allowing auto-doping process to diffuse a dopant from a thicker heavily doped mother wafer through the porous layer into the portion of the wafer destined to form the thin photo voltaic cell so as to create a heavily doped front layer to reflect electrons back towards the backside contacts.    DETAILED DESCRIPTION - The method involves etching an aluminum conducting layer to remove portions not overlying the contact regions.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic side cross-sectional view of a wafer attached to a chuck illustrating a laser ablation trimming operation of wafer edges.    Silicon wafer (100)    Thin porous silicon layer (102)    P-N junction (203)    Electrical contacts (990, 991)    Chuck (1000)