Method for laser thermal processing using thermally induced reflectivity switch

A method for controlling the amount of heat transferred to a process region of a semiconductor workpiece when exposed to laser radiation, comprising the steps of:

• covering one or more process regions of the workpiece with an absorber layer of one or more of the materials titanium, titanium nitride, tantalum and tungsten nitride all in a thickness range of 10 nm to 1000 nm and silicon dioxide and silicon nitride in the thickness range of 1 nm to 30 nm;
• forming, atop the absorber layer, a reflectivity switch layer, the reflectivity switch layer changing reflectivity at a melting temperature of silicon;
• irradiating the workpiece with laser radiation that is absorbed in the absorber layer;
• and
• stripping the reflectivity switch and absorber layers from the workpiece.

A method for controlling the amount of heat transferred to a process region of a semiconductor substrate when exposed to laser radiation, comprising the steps of:

• providing a substrate with one or more process regions;
• covering the one or more process regions with an absorber layer;
• covering the absorber layer with a reflectivity switch layer that changes reflectivity from a low-reflectivity state to a high-reflectivity state when the workpiece process region reaches a critical temperature;
• and
• laser irradiating the reflectivity switch layer to bring the workpiece process region to the critical temperature;
• wherein the amount of heat absorbed by the absorber layer is from laser radiation incident the absorber layer coming through the reflectivity switch layer, and the heat transferred to the one or more process regions and the reflectivity switch layer is limited when the reflectivity switch layer changes to the high-reflectivity state.