A semiconductor system includes a silicon substrate and a porous silicon region disposed on the silicon substrate. The porous silicon region is configured to passivate the surface of the silicon substrate via a field effect and to reduce reflection loss on the silicon substrate via an appropriate refractive index. The porous silicon region is manufactured by a stain etching process, which retrofits existing tools for junction isolation and Phosphorus Silicon Glass (PSG) etch in solar cell manufacturing. The retrofitted tools for junction isolation and PSG etch achieves multiple purposes in a single step, including etch-back, PSG etch, antireflection coating, and passivation of the front surface of the solar cell.