Abstract: Disclosed herein is a method for operating a light-radiant heating furnace which includes a main heater capable of irradiating light onto an object to heat it up and a subsidiary heater adapted principally to additionally heat a peripheral portion of said object, which method includes actuating said main heater and subsidiary heater repeated in accordance with their respective actuation curves, which have in advance been prepared, in synchronization with intermittent transportation of objects into said light-radiant heating furnace. The light-radiant heating furnace permits a uniform heat treatment of objects always with high efficiency but without development of slip line or warping, even when they are semiconductor wafers and are heated up in short time periods.

Abstract: When heating a semiconductor wafer by means of application of radiated light, subsidiary heating means which elongates along the circumference of the wafer is employed to additionally heat or to preheat the circumferential portion of the wafer so as to make the temperature of the wafer uniform at the entire surface thereof. Use of such subsidiary heating means is effective to prevent the occurrence of such a damage as slip line or the like in the wafer.

Abstract: When heating a semiconductor wafer by means of application of radiated light, it is effective to employ subsidiary heating means whose temperature rises upon exposure to the radiated light so that the circumferential portion of the wafer is additionally heated to compensate radiation of heat therefrom. The subsidiary heating means is arranged to elongate along the circumference of the wafer. It is important to limit the ratio of the characteristics, whose definition will be given below, of the subsidiary heating means to that of the wafer to 0.6-1.4 in order to avoid the occurrence of such a damage as slip line or the like in the wafer. The characteristics are expressed by the following formula: ##EQU1## wherein .eta.: reflectivity;.rho.: specific gravity (g/cm.sup.3);d: thickness (cm); andC: specific heat (joule/g.multidot..degree.C.).