Patent ID: 7302034

Claim:
A method for establishing an areal density of an elemental constituent of a plurality of layers of material in a multilayer structure comprising a plurality of layers of material, the method comprising: irradiating a calibration sample of known elemental composition with penetrating radiation; calibrating absolute intensities of at least a first and a second x-ray characteristic fluorescence lines emitted by the calibration sample from a single element or two elements present in at least a layer of the multilayer structure; irradiating the multilayer structure with penetrating radiation; detecting fluorescent radiation emanating from the layer; determining a fluorescence intensity at each of the first and second characteristic fluorescence lines; solving separately for the areal densities of the elemental constituents of the layer and absorption due to overlayers on the basis of known differential functional dependence of absorption at energies of the first and second characteristic fluorescence lines; and repeating the step of solving with respect to a second layer of the multilayer structure.