Secondary electrons play critical roles in several imaging technologies, including extreme ultraviolet (EUV) lithography. At longer wavelengths of light (e.g. 193 and 248 nm), the photons are directly involved in the photochemistry occurring during photolysis. EUV light (13.5 nm, 92 eV), however, first creates a photoelectron, and this electron, or its subsequent daughter electrons create most of the chemical changes that occur during exposure. Despite the importance of these electrons, the details surrounding the chemical events leading to acid production remain poorly understood. Previously reported experimental results using high PAG-loaded resists have demonstrated that up to five or six photoacids can be generated per incident photon. Until recently, only electron recombination events were thought to play a role in acid generation, requiring that at least as many secondary electrons are produced to yield a given number of acid molecules. However, the initial results we have obtained using a Monte Carlo-based modeling program, LESiS, demonstrate that only two to three secondary electrons are made per absorbed EUV photon. A more comprehensive understanding of EUVinduced acid generation is therefore needed for the development of higher performance resists.

One of the obstacles hindering the transition from 193 nm to extreme ultraviolet (EUV) photolithography is photoresist performance. However, design of next generation chemicallyamplified EUV resists necessitates that we fully understand the mechanisms underlying photoacid generation. In particular, we would like to determine the effective distance the lowenergy electrons generated during EUV exposure travel within resists while continuing to induce photoacid generator (PAG) decomposition, since diffusion length carries important implications for resolution and line edge roughness. Here, we demonstrate two novel experimental approaches for obtaining electron diffusion length in resists using top-down electron beam exposure: thickness loss experiments and in situ mass spectrometry.