Surface temperature rise in multilayer solids induced by a focused laser beam

Abstract

Surface temperatures of a laser-heated structure consisting of intersecting gold and nickel lines on a Si substrate with a SiO2 surface layer were determined experimentally and theoretically. Temperatures were measured with micron-sized thin-film thermocouples formed from intersecting gold and nickel lines. Temperature profiles were calculated using a finite difference method which took into account the optical and physical properties of the thermocouple metal lines, the silicon dioxide layer, and the silicon substrate. For a 0.2-μm SiO2 layer, maximum surface temperatures were much higher with the metal lines than without because of the lower reflectivity of the gold relative to the silicon and the limited ability of the thin metal lines to conduct heat away from the irradiated region. Calculated maximum temperatures on the metal lines depended strongly on the thicknesses of the insulating SiO2 layer and the metal lines. Application of these results to the dynamics of laser-induced chemical vapor deposition is discussed.