NOVELTY - Multicrystalline silicon substrate (1) comprises a substrate of multicrystalline silicon having large irregularities formed on a surface by etching with an alkaline aqueous solution, and fine textures formed by dry etching over the large irregularities.    USE - The substrate is used in solar cell useful for converting light energy incident on its surface such as sunlight into electric energy. The solar cell can be crystalline silicon, amorphous silicon or compound based solar cell.    ADVANTAGE - The invention effectively improves the solar cell performance even in a condition of removal of the damaged layer by alkaline etching prior to reaction ion etching for forming fine textures. The substrate allows fine textures to be formed uniformly with even height, thus efficiently reducing reflectance in solar cell. Solar cell with high conversion efficiency can thus be fabricated.    DETAILED DESCRIPTION - Multicrystalline silicon substrate comprises a substrate of multicrystalline silicon having large irregularities formed on a surface by etching with an alkaline aqueous solution, and fine textures formed by dry etching over the large irregularities. A ratio r expressed as r = a/b, which is the ratio between the length a of a virtual line connecting individual peaks of the fine textures at a vertical cross-section and the length b of a straight line connecting the endpoints of the virtual line, is greater than or equal to1 and smaller than 1.1.    An INDEPENDENT CLAIM is also included for a process for roughening a surface of a multicrystalline silicon substrate, comprising etching a surface of a substrate with an alkaline aqueous solution for forming large textures having a surface area-to-planar surface area ratio of larger than 1 and smaller than 1.1; and a dry etching step for forming fine textures over the large irregularities.    DESCRIPTION OF DRAWING(S) - The figure illustrates a reactive ion etching device used in a process for roughening a surface of a multicrystalline silicon substrate.    Silicon substrate (1)    Mass-flow controller (8)    Radio frequency electrode (9)    Pressure regulator (10)    Vacuum pump (11)