Patent ID: 8324530

Claim:
A method for heating a wafer by at least one light flux pulse, wherein the wafer has at least one layer to be heated and a sub-layer adjacent the layer to be heated, which comprises: selecting a light flux having a wavelength such that the absorption coefficient of the light flux by the layer to be heated is low as long as the temperature of the layer to be heated is in a low temperature range (PBT) but wherein the absorption coefficient increases significantly when the temperature of the layer to be heated enters a high temperature range (PHT) situated approximately above the low temperature range, wherein pulse intensity and duration are such that, in the absence of the sub-layer, the temperature of the layer to be heated remains within the low temperature range; selecting a sub-layer having an absorption coefficient of the light flux at the selected wavelength which is high in the low temperature range (PBT), wherein the temperature of the sub-layer enters the high temperature range (PHT) when the sub-layer is subject to the light flux; and applying the light flux to the wafer, at least locally, via the front face of the layer to be heated opposite the sub-layer, for a sufficient time to heat, in a first phase, the sub-layer from its initial temperature to a temperature at least situated in the temperature range (PHT), and, in a second phase, to heat, by thermal diffusion from the heated sub-layer, an adjacent portion of the layer to be heated to a temperature situated in the high temperature range (PHT), and further, in a third phase, to render absorbent the adjacent portion, thus generating, in the layer to be heated, an absorbent thermal front wherein the temperature is situated in the high temperature range (PHT), with the absorbent thermal front progressing towards the front face under the combined or dual effect of forward thermal diffusion of the thermal front and thermal energy supplied by the light flux which reaches the thermal front via the not yet absorbent remainder of the layer to be heated.