A new micro-spot XRF metrology tool has been developed that enables on-product production control of films and stacks used in the semiconductor and data storage industry. The tool has been evaluated using several thin films and stacks and the initial results verify the suitability of this micro-spot XRF method as an in-line metrology technique. Both the classical XRF analysis method as well as the fundamental parameter approach proved to be applicable. The successful combination of micro-spot excitation and fundamental parameter analysis makes the technique a powerful method for on-product characterization of single films and multi-layers. (C) 2003 Elsevier B.V. All rights reserved.