NOVELTY - The treatment chamber (20, 21) such as a cooling chamber and a heat treatment chamber for thermally processing a planar substrate (10), comprises a transport unit for conveying and supporting the substrate during thermal processing, a gas flow unit (30) for convection-heating or convection-cooling the substrate, and a discharge unit (33), through which the gases introduced into the treatment chamber via the gas flow unit is discharged in a controlled manner. The gas flow unit comprises outlet openings (32) in an area turned towards the substrate for the gas.    USE - Treatment chamber such as a cooling chamber and a heat treatment chamber for thermally processing a planar substrate, which is useful for manufacturing flat panel displays and solar cells.    ADVANTAGE - The treatment chamber is capable of economically, rapidly and efficiently processing the planar substrate with less effort and less energy consumption without causing damage to the substrate or coatings.    DETAILED DESCRIPTION - The treatment chamber (20, 21) such as a cooling chamber and a heat treatment chamber for thermally processing a planar substrate (10), comprises a transport unit for conveying and supporting the substrate during thermal processing, a gas flow unit (30) for convection-heating or convection-cooling the substrate, and a discharge unit (33), through which the gases introduced into the treatment chamber via the gas flow unit is discharged in a controlled manner. The gas flow unit comprises outlet openings (32) in an area turned towards the substrate for the gas. The treatment chamber includes discharge caps arranged to some of the outlet openings for targeted discharge of the gases flowing from the outlet opening. The gas flow unit comprises a tubular gas distributor with nozzle sections, at whose ends outlet openings are arranged, aligned on the substrate. The gas distributor and/or the nozzle sections have controllable valve for controlling the gas flow. The cross-section of the nozzle section tapers in direction to the outlet openings. The substrate flatly lies on the transport unit. The gas distributor is arranged parallel to the substrate surface. The nozzle sections protrude out vertically from the tube sections in the direction of the substrate surface. The discharge unit is arranged as elongated discharge caps arranged along the tube sections. The treatment chamber forms a closed space during the thermal processing of the substrate. The gas flow unit forms a part of a closed gas guiding circuit. The gas flow unit contains a pump, a heat exchanger for heating or cooling the gases conducted to the substrate surface, a drying device and/or a filtering device for drying and/or cleaning the gases conducted to the substrate surface, and a control device for power control of the pump and/or for flow control in the tubular gas distributor and/or nozzle sections. The treatment chamber comprises closable openings for introducing and discharging the substrate, and a thermal insulation shield, which is formed as gas-tight closable outer chamber that surrounds a gas-tight closable inner chamber and which is formed by a tempering device arranged in the area of the wall of the treatment chamber. The tempering device is formed by a system of cooling channels and/or heating channels, and forms a part of a heating circuit and/or a cooling circuit, in which a liquid medium circulates. The gas flow unit contains an electrically operatable heating device for heating the gases. A heating unit is arranged in the inner chamber for delivering the thermal energy. The inner wall of the treatment chamber consists of a reflecting material in a section-wise manner. INDEPENDENT CLAIMS are included for:    (1) a device for thermally processing a planar substrate; and    (2) a method for thermally processing a planar substrate.    DESCRIPTION OF DRAWING(S) - The diagram shows a sectional view of a heat treatment chamber.    Treatment chamber (20, 21)    Planar substrate (10)    Gas flow unit (30)    Outlet openings (32)    Discharge unit. (33)