Spatial coherence in electron-beam patterning

The authors demonstrate a simple method to identify noise sources in electron-beam systems and accurately quantify the resulting errors in feature placement. Line gratings with a 46 nm average pitch were patterned with electron-beam lithography and measured with transmission x-ray diffraction (XRD) and scanning electron microscopy (SEM). All SEM micrographs were analyzed in Fourier space to facilitate comparison with the XRD data. Diffraction profiles and Fourier transforms of SEM micrographs contained numerous “satellite” peaks, meaning weak peaks adjacent to the strong primary nodes, that are characteristic of periodic extensions and compressions in the grating pitch. The wavelength and amplitude of these pitch variations were calculated with a simple scaling law by comparing the positions and intensities of satellite peaks relative to their neighboring primary nodes. This approach is remarkably easy to implement because it does not require any modeling of electron density profiles. Data were used to ca...