NOVELTY - The method comprises contacting a disc or plate-shaped silicon semiconductor substrate (10) having a lower side surface (12), an upper side surface and side surface (14, 18, 20) to an aqueous chemical process medium. The substrate is moved relative to the process medium in simultaneous formation of a triplet line between the substrate, the substrate medium and surrounding atmosphere. The relative movement is carried out under avoiding the contacting of the process medium with the upper side area of the substrate.    USE - Method for chemical treatment of a disc or plate-shaped silicon semiconductor substrate for the production of solar cells.    ADVANTAGE - The method ensures chemical treatment of a disc or plate-shaped silicon semiconductor substrate without cracks, micro cracks or surface roughness.    DETAILED DESCRIPTION - The method comprises contacting a disc or plate-shaped silicon semiconductor substrate (10) having a lower side surface (12), an upper side surface and side surface (14, 18, 20) to an aqueous chemical process medium. The substrate is moved relative to the process medium in simultaneous formation of a triplet line between the substrate, the substrate medium and surrounding atmosphere. The relative movement is carried out under avoiding the contacting of the process medium with the upper side area of the substrate. The triplet line is formed related to the relative movement between the substrate and the process medium on desired height at the side surface turned away the process medium flow side and/or the atmosphere is adjusted related to partial pressure of the components available in the process medium in such a way that the upper side surface is formed with hydrophobic characteristics. The triplet line is formed at the edge turned away the process medium flow side between the upper side surface and side surface of the substrate. The substrate is moved relative to the process medium in simultaneous formation of a stern wave existing from the substrate from the process medium. The substrate is turned during the relative movement to the process medium in a circumference that goes out from each edge passing between the upper side surface and side surface or in the area of the side surface during the chemical treatment of the triplet line. The chemical treatment is carried out at 5 degrees C in a circumference and the substrate has smooth lower side and side area after the treatment, where a layer thickness of 1-100 mu m is worn-out through the chemical treatment. The doped silicon substrate with pn-transition is used in the lower surface side and/or in the side surface as substrate. The doped area is removed through the chemical treatment. The substrate has a quadratic, pseudo-quadratic, rectangular or circular geometry. The substrate has a thickness of 100-200 mu m and is used with a square geometry in top view, with edges, from which each edge has a length of 125-156 mm. The substrate is moved areawisely under wetting of the side area through the process medium relative to the side area. The substrate is equipped in its surface side with hydrophobic characteristics before the chemical treatment. The surface side is equipped with a structure causing a lotus blossom effect and is oxide free and/or smooth. The substrate is pre-treated with an aqueous solution of hydrofluoric acid with a concentration of 1-10 wt.% and interacts after the pre-treatment with the process medium over a time of 5-60 seconds. The pre-treatment is carried out at 20-40 degrees C. The chemical treatment is carried out at a relative speed between the substrate and the process medium of o.5-5 m/min. The substrate is moved to the process medium. The atmosphere surrounding the upper side of the substrate is adjusted during the chemical treatment in such a way that the partial pressure of the acid with oxidizing effect is same or less than the partial pressure of the acid with complexing effect. The atmosphere is changed through targeted supply of inactive and/or reactive gas components during the chemical treatment in such a way that an etching effect arises itself from the atmosphere influencing on the surface side. The atmosphere is exchanged by the supply of hydrogen fluoride steam of 100-1000 mg/m3, nitric acid steam of 100-3000 mg/m3, inert gas such as nitrogen or argon and/or air with an exchange rate of 10-100 times per hour.    DESCRIPTION OF DRAWING(S) - The figure shows a principle representation of a reaction area for chemical treatment of substrates.    Substrate (10)    Lower side surface (12)    Side surface (14, 18, 20)    Process area (22)    Housing. (24)