XAS photoresists electron/quantum yields study with synchrotron light

The main roadblock for EUV lithography to be successfully adopted for high-volume manufacturing is the current lack of source power. One way to help mitigate this problem is to optimize the photoresist by increasing both absorbance and quantum yield. The latter represents the ratio between the sums of generated acids and absorbed photons. Yield is also thought to be limited by the number of generated electrons per absorbed photon, or electron yield, that may be generated after a photo absorption event. While absorbance is relatively easy to measure, yields are extremely difficult to quantify, and the debate on upper limits is far from settled. In this paper, we present how, using synchrotron light with tunable energy, we directly measured dispersion curves and electron yield for ArF, KrF and EUV photoresists using X-ray Absorption Spectroscopy. Knowing the electron yield allowed us to better model organic EUV materials: stochastic simulations show how both electron yield and blur are very similar for organic materials, and how the electron blur is not a fixed property of the material, but may vary spatially, depending on a combination of photoresist formulation and local photon absorption density.