Coherent anti-Stokes Raman scattering (CARS) microscopy is demonstrated to be a powerful imaging technique with chemical specificity for studying chemically amplified polymer photoresists. Samples of poly(tertbutyloxycarbonyloxystyrene) (PTBOCST) resist imprinted by interferometric lithography with a pattern of lines/spaces of 400 nm/400 nm and 200 nm/200 nm were used to test CARS imaging capabilities. Chemical contrast in the image is obtained by probing the carbonyl stretching vibration of the tert-butoxyl carbonyl group of PTBOCST. The experimental images demonstrate high spatial resolution (≈270 nm) and strong signal, which allows short acquisition times. Advantages and limitations of CARS in comparison with other imaging techniques with chemical specificity, such as infrared near field scanning optical microscopy (IR NSOM), are discussed.

Scanning transmission x-ray microscopy (STXM) is shown to be a powerful imaging technique that provides chemical selectivity and high spatial resolution (∼35nm) for studying chemically amplified photoresists. Samples of poly(4-t-butoxycarbonyloxystyrene) PTBOCST resist, imprinted by deep ultraviolet lithography with a line∕space pattern of 1.10μm∕0.87μm followed by a post-exposure bake, are used to demonstrate STXM imaging capabilities to extract photoresist latent images. Chemical contrast is obtained by measuring the x-ray absorption at an energy of 290.5 eV, corresponding to a carbon K shell electronic transition to the unoccupied π* molecular orbital of the PTBOCST carbonyl group. A quantitative analysis provides the spatial distribution of the fraction of the unexposed and deprotected polymers remaining after the post-exposure bake stage as well as the thickness of both regions. Both chemical and topographical contributions to the total contrast are estimated. Advantages and limitations of STXM in comparison with other imaging techniques with chemical specificity are discussed.

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