NOVELTY - Etching a wafer (100) comprises selectively etching only a single side of the wafer and asymmetrically etching both sides of the wafer with different etching rates. Etching only the single side of wafer comprises closely adhering sides of two wafers that face each other having no gap, simultaneously etching sides of closely adhered wafers exposed to the external, and separating closely adhered wafers. Asymmetrically etching both sides of wafer comprises overlapping wafers to have predetermined gaps between the respective wafers, etching overlapped wafers, and separating overlapped wafers.    USE - Wafer etching for manufacture of bulk silicon solar cell (claimed).    ADVANTAGE - The reflectivity of light receiving surface of silicon substrate may be lower than that of non-light receiving surface such that the rate that light incident on light receiving surface that is reflected again on outer surface to be lost is low, thus making it possible to provide a solar cell having an excellent light trapping effect. The bulk silicon solar cell can manufacture and provide the wafer used in silicon substrate to have economically high yields, thus making it possible to reduce entire manufacturing costs of solar cell. Two wafers are overlapped and the etching is performed on it, thus making it possible to simultaneously obtain two wafers for a solar cell that have a single-sided etching structure or asymmetric etching structure. Unnecessary wafer back surface etching can be removed by selectively etching only the light receiving surface, thus making it possible to simplify and reduce work manpower by half compared to conventional technique and to reduce manufacturing costs.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a solar cell which is a bulk silicon solar cell; and    (2) manufacture of bulk silicon solar cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view explaining a method of etching a wafer using a discontinuous process.    Wafer (100)