Thickness determination of ultra-thin foils in the EUV spectrum

The method of EUV transmission spectroscopy provides a fast thickness characterization for thin foils and is based on a laser induced plasma source which emits light in the EUV. The laser is focused on a molybdenum target and creates a characteristic plasma emission. The filtered and monochromatized plasma emission in the EUV range encounters the ultra-thin foil. To measure the transmission values, which is dependent upon the thickness of the foil, a highly sensitive camera with a very low readout noise is required. Using the camera GE 2048 512 BI UVI at the Max-Born-Institute Berlin, the standard deviation is lower than 0.005 and enables foils thickness characterization with nanometer accuracy.