NOVELTY - A porous layer (2) is formed on silicon substrate (3) by etching surface of silicon substrate. Mixed aqueous solution contains metal ions. Surface of silicon substrate is texturized by etching holes on porous layer with mixed acid comprising hydrofluoric acid and nitric acid. Texturized surface of silicon substrate is etching using alkaline chemical liquid, and processed with water containing ozone (4). Metal and organic impurities in holes (2a) are removed by generating air bubbles (7) within holes formed on silicon substrate. Thus, silicon substrate is cleaned.    USE - Cleaning of silicon substrate used for manufacturing solar cell (claimed).    ADVANTAGE - The method efficiently and economically cleans silicon substrate. The solar cell manufactured using silicon substrate has high photoelectric conversion efficiency.    DETAILED DESCRIPTION - A porous layer is formed on the surface of a silicon substrate by etching surface of silicon substrate using a mixed aqueous solution of an oxidant and hydrofluoric acid. The mixed aqueous solution contains metal ions. The surface of the silicon substrate is texturized by etching the holes on the porous layer with a mixed acid comprising hydrofluoric acid and nitric acid. The texturized surface of silicon substrate is etching using an alkaline chemical liquid, and processed with water containing ozone. Metal and organic impurities in the holes are removed by generating air bubbles within holes formed on the silicon substrate. Thus, silicon substrate is cleaned. An INDEPENDENT CLAIM is included for manufacture of solar cell, which involves cleaning silicon substrate after forming texture in one surface of primary conductivity-type silicon substrate, diffusing secondary conductivity-type impurity element in one surface side of silicon substrate, forming impurity diffused layer, forming electrode in one surface side of silicon substrate and other surface side of silicon substrate.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view explaining removal process of metal catalyst inside the porous layer by ozone water washing.    Metal catalyst (1)    Porous layer (2)    Hole (2a)    Silicon substrate (3)    Water containing ozone (4)    Bubbles (7)