Extreme ultraviolet (EUV) lithography is growing in demand as device feature sizes shrink. With shrinking sizes, reducing line edge roughness (LER) and line width roughness (LWR) becomes critical. While several processes contribute to the LER/LWR of the final structure, understanding the stochastic effects arising from the discrete interaction of photons with the photo-active components in the EUV resist will aid in designing resists and optimizing processes. Infrared photo-induced force microscopy (IR PiFM) is a technique that combines non-contact AFM and IR spectroscopy to non-destructively analyze local chemical bonds on extremely thin samples (~ 1 nm thick) with sub-5 nm spatial resolution. In addition to local IR spectra with high spectral resolution (~ 3 cm-1), it can also generate absorption maps (PiFM images at different wavenumbers associated with chemical components) for visualizing a chemical interface between the exposed and unexposed regions of a resist, providing an unprecedented opportunity to perform chemical metrology. This paper will present IR PiFM data on metal oxide EUV resists, both patterned and un-patterned, that are exposed at different conditions. PiF-IR spectra acquired on exposed but undeveloped resists clearly follow the chemical changes associated with changing dosage, even on a low dose of 10 mJ/cm2. On patterned samples, LER and LWR on chemical images are calculated for different exposure conditions and compared to the values derived from topographical data. The chemical sensitivity and the mapping capability at ultrahigh resolution afforded by IR PiFM will help greatly in developing and optimizing EUV resist composition and processing steps.
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