Abstract: Systems and methods for performing inspection and metrology operations on metallization processes such as on back-end-of-line (BEOL) metallization thickness and step coverage are disclosed. Specific examples include measurements of thickness and uniformity of barrier layers, including tantalum for example, and seed layers, including copper for example, in Damascene, including dual-Damascene, trenches during the interconnect fabrication steps of integrated circuit production. The invention also relates to the detection and measurement of void formation during and after copper electroplating. The invention utilizes x-ray fluorescence to measure the absolute thicknesses and the thickness uniformity of the barrier layers in the trenches, the copper seed layers for electroplating, and the final copper interconnects.

Abstract: An element-specific imaging technique utilizes the element-specific fluorescence X-rays that are induced by primary ionizing radiation. The fluorescence X-rays from an element of interest are then preferentially imaged onto a detector using an optical train. The preferential imaging of the optical train is achieved using a chromatic lens in a suitably configured imaging system. A zone plate is an example of such a chromatic lens; its focal length is inversely proportional to the X-ray wavelength. Enhancement of preferential imaging of a given element in the test sample can be obtained if the zone plate lens itself is made of a compound containing substantially the same element. For example, when imaging copper using the Cu La spectral line, a copper zone plate lens is used.