Comparison of resist outgassing at wavelengths from 193nm to 13nm

Corresponding to the ITRS roadmap, EUV Lithography will in the not-too-far future reach the point, where critical resist dimensions are in the same order of magnitude as polymer chains and acid diffusion lengths, while photon energies will largely exceed the binding energies of all organic molecules. Especially in EUV, where secondary electron side reactions may lead to a higher outgassing of polymer fragments than in 157nm and 193nm lithography, outgassing is agreed to be a critical issue for resist development. In this paper EUV, 193nm and 157nm outgassing is characterized using an online mass spectrometer attached to several different outgassing setups (i.e. synchrotron, laser). The total outgassing and the time dependent outgassing of resist fragments has been characterized for a number of resist polymer platforms. The results are compared and discussed in terms of the applied photon energies and differences in EUV, 157nm and 193nm exposures. Time dependent scanning of selected mass channels was used to differentiate if an outgassing fragment had its origin from the photoacid generator (PAG) or from a photolytic or a photochemical reaction of the polymer matrix. For EUV, correlations are given between resist outcassing and high dose crosslinking and scissioning behaviour of EUV resists.