Heater surface of a plurality of heating segments

The invention relates to a sheet heater composed of a plurality of heating segments, which is provided for radiation heating of a thermal process plant and to a transport plane for to be transported through a conditioning chamber of the process tool in a transport direction along a transport path large area substrates. With the invention, a surface heater is to be provided with a plurality of heating segments for radiation heating of a thermal process plant, with good homogenization of the heat distribution is achieved even with the failure of individual heating segments and which allows to control the distributed over the surface radiant heating targeted to total to achieve a homogenization of the heat distribution. characterized that a plurality of heating segments (3) form in a row alongside each other, a heater group (7) and that each heating segment (3) is reached, the are that the heating segments (3) oriented transversely to the transport direction and arranged in rows one behind the other, in such a way with is connected to an electrical power source.