Abstract: The invention relates to the field of method of etching a substrate (W), in particular a wafer, in order to produce a grid of micro-protrusion. Such grid of micro-protrusion is generally made using UV photolithography followed by wet and chemical engraving with an etching solution. Most of the currently available methods do not lead to an even attack of the wafer surface by the etching solution because the reaction produces a release of micro-bubbles which, if not properly evacuated, disturb the etching process. In the present invention, substrate(s) (W) are disposed on a magnetic supporting device (1) which is driven in rotation in the etching solution via a magnetic agitator external to the etching solution, so that the magnetic supporting device (1) causes the substrate to rotate at least in a same direction the magnetic supporting device (1). The present invention makes it possible to obtain substrates with good homogeneity.